Publications

여러 단어 = 모두 포함(AND) · 정확한 문구는 큰따옴표: "Youngku Sohn" · 문구가 통째로 있는 논문이 먼저 나옵니다 · DOI로도 검색됩니다

2026

249

Laser-engineered Ag/Ag oxide interfaces for tunable CO₂ reduction: Mechanistic insights from experiment and theory

So Young Kim; Chae-Hyeon Lee; Ilsun Yoon; Choong Kyun Rhee; Hee-Joon Chun; Youngku Sohn

Mater. Today Energy 2026, 59, 102298. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

은(Ag) 전극의 계면 공학은 전기화학적 이산화탄소 환원(CO₂RR)의 활성과 선택성을 조절하는 효과적인 전략이다. 본 연구에서는 제어된 적외선(1064 nm) 레이저 처리로 Ag 및 산화 은(Ag/AgxO) 전극을 제조하고, KHCO₃ 전해질과 인산염 전해질에서 성능을 평가하였다. 레이저로 유도된 표면 재구성은 산화 상태, 결정학적 배향 및 계면 전자 특성을 변화시켜 전해질과 전위에 따른 생성물 분포의 변화를 일으켰다. KHCO₃ 전해질에서는 CO가 주생성물로 유지된 반면, 인산염 전해질에서는 레이저 처리 강도가 증가할수록 CO 선택성이 크게 향상되었다. 산화된 Ag 표면에서는 수소, 폼산염 및 C₂+ 탄화수소 생성이 억제되었다. 생성물 선택성은 뚜렷한 전위 의존성을 보였다. CO와 C₂+ 탄화수소는 중간 전위에서 최대값을 나타냈고, 폼산염 생성은 더 음의 전위에서 증가하였다. 장쇄 C₂+ 탄화수소는 Fischer-Tropsch형 성장 경향을 따랐다. 전기화학 임피던스 분광법을 통해 전하 전달 속도론과 계면 정전용량의 변화를 확인하였다. 밀도 범함수 이론 계산에서는 COOH* 중간체를 거치는 CO 생성이 Ag(111)과 Ag₂O(111)에서 유리한 반면, HCOO*를 거치는 폼산염 생성은 금속 Ag에서 더 유리한 것으로 나타났다. 이 결과는 Ag/산화 Ag 계면이 CO₂RR 경로를 조절하는 방식을 규명한다.

※ 연구실에서 옮긴 비공식 번역입니다. 정확한 표현은 원문·DOI를 확인해 주세요.

원문 (English) ▾

Interface engineering of silver (Ag) electrodes provides an effective strategy to tune activity and selectivity in electrochemical CO₂ reduction (CO₂RR). Here, Ag and Ag oxide (Ag/AgxO) electrodes were prepared via controlled infrared (1064 nm) laser treatment and evaluated in KHCO₃ and phosphate electrolytes. Laser-induced surface restructuring modified oxidation states, crystallographic orientations, and interfacial electronic properties, leading to electrolyte- and potential-dependent shifts in product distribution. In KHCO₃ electrolyte, CO remained the dominant product, whereas phosphate electrolyte significantly enhanced CO selectivity with increasing laser treatment. Oxidized Ag surfaces suppressed hydrogen, formate, and C₂+ hydrocarbons. Product selectivity showed clear potential dependence: CO and C₂+ hydrocarbons peaked at moderate potentials, while formate formation increased at more negative potentials. Long-chain C₂+ hydrocarbons followed a Fischer-Tropsch-like growth trend. Electrochemical impedance spectroscopy revealed changes in charge-transfer kinetics and interfacial capacitance. Density functional theory calculations indicate that CO formation via COOH intermediates is favored on Ag(111) and Ag₂O(111), whereas formate formation via HCOO* is more favorable on metallic Ag. These results clarify how Ag/Ag oxide interfaces regulate CO₂RR pathways.

248

Integration and Implementation of Machine Learning & Artificial Intelligence in Surface‐Enhanced Raman Spectroscopy

Netrapal Singh; Ba Thong Trinh; Sy Khiem Nguyen; Khanh Viet Nguyen; Changwook Kim; Byeonggwan Kim; Youngku Sohn; Ilsun Yoon

Advanced Sensor Research 2026, 5 (7), e70183. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

표면증강 라만 분광법(SERS)은 분자 식별과 미량 검출에 널리 사용되는 분석 기법으로, 최소한의 시료 전처리, 높은 감도, 분자 지문 정보 및 정량 분석 능력을 제공한다. 그러나 SERS 측정에서는 크고 복잡한 스펙트럼 데이터세트가 생성되므로, 이를 해석하는 데 많은 시간이 들고 전문 지식이 필요하다. 인공지능(AI)과 기계학습(ML)을 결합하면 데이터 처리, 특징 추출 및 패턴 인식을 자동화할 수 있어 지능형 SERS 감지 플랫폼의 새로운 세대를 구현할 수 있다. 기존 총설이 주로 응용 분야별 AI/ML-SERS 사례를 나열한 것과 달리, 본 연구는 네 가지 기여를 중심으로 비판적으로 종합하였다. 첫째, SERS 데이터의 특성과 알고리즘 선택을 연결하는 작업 흐름 수준의 분류 체계를 제시하였다. 둘째, 약 40편의 대표 연구를 정량 메타분석하여 보고된 정확도의 분포, 데이터세트 크기와 보고 성능의 관계, 고전적 화학계량학에서 딥러닝으로의 시간적 변화를 분석하였다. 셋째, 기판 배치 효과, 기술 반복 측정치의 데이터 누출, 스펙트럼 수준과 시료 수준 분할의 차이, 외부 검증 코호트의 부재 등 AI/ML-SERS에 특유한 검증상의 함정을 별도로 평가하였다. 넷째, 향후 AI/ML-SERS 연구를 위한 실용적인 보고 점검표를 제안하였다. 이 총설은 단순한 사례 나열보다 방법론적 엄밀성을 앞세워 AI/ML을 도입하려는 SERS 연구자와 분광 감지 분야에 진입하는 ML 연구자 모두를 지원하고자 한다.

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원문 (English) ▾

Surface-enhanced Raman spectroscopy (SERS) is an analytical technique widely used for molecular identification and trace detection, offering minimal sample preparation, high sensitivity, molecular fingerprinting, and quantitative capability. However, SERS measurements generate large, complex spectral datasets whose interpretation is time-consuming and requires specialized expertise. The integration of artificial intelligence (AI) and machine learning (ML) provides effective strategies for automated data processing, feature extraction, and pattern recognition, enabling a new generation of intelligent SERS sensing platforms. Unlike previous reviews, which have largely catalogued AI/ML-SERS applications by domain, this work provides a critical synthesis structured around four contributions: (i) a workflow-level taxonomy linking SERS data characteristics to algorithm selection; (ii) a quantitative meta-analysis of approximately 40 representative studies covering the distribution of reported accuracies, the relationship between dataset size and reported performance, and the temporal shift from classical chemometrics to deep learning; (iii) a dedicated assessment of validation pitfalls specific to AI/ML-SERS, including substrate batch effects, technical-replicate leakage, spectrum-level versus sample-level splitting, and the absence of external validation cohorts; and (iv) a practical reporting checklist for future AI/ML-SERS studies. By foregrounding methodological rigor rather than enumeration, the review aims to support both SERS practitioners adopting AI/ML and ML researchers entering spectroscopic sensing.

247

Switching CO₂ reduction pathways: Iron drives copper toward formate selectivity

Hyeonji Lee; So Young Kim; Gaeun Yun; Yunji Gwon; Sooyeon Bae; Huieun Shim; Jaehee Shin; Choong Kyun Rhee; Youngku Sohn

Appl. Surf. Sci. 2026, 731, 166390. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

구리(Cu)에서의 전기화학적 이산화탄소 환원(CO₂RR)은 일반적으로 매우 다양한 생성물을 만들기 때문에 원하는 화학물질을 선택적으로 얻기 어렵다. 본 연구에서는 미량의 철(Fe)을 Cu 전극에 도입하면 CO₂RR 경로를 상별로 선택적으로 조절할 수 있음을 보였다. 액상에서는 Fe 도입이 폼산염 선택성을 크게 높이는 동시에 에탄올과 프로판올 같은 다른 액상 생성물의 형성을 억제하였다. 기상에서는 Fe가 C₃+ 탄화수소 생성을 촉진하여 패러데이 효율을 높였고, 에틸렌과 같은 C₂ 화학종의 수율은 낮추었다. 구조 및 분광학적 특성 분석 결과, Fe는 결정면 재분포, 산화물 형성 및 국소 배위 변화 등을 통해 Cu 표면의 전자 구조와 형태를 재구성하는 것으로 나타났다. Fe 도핑을 통한 이러한 액상-기상 이중 선택성 제어는 CO₂RR의 생성물 분포를 조절하고 지속 가능한 탄소 전환 촉매 전략을 발전시키기 위한 새로운 설계 원리를 제시한다.

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원문 (English) ▾

Electrochemical CO₂ reduction (CO₂RR) on copper (Cu) typically produces a broad spectrum of products, making it difficult to selectively generate desired chemicals. Here, we show that incorporating trace amounts of iron (Fe) into Cu electrodes enables a phase-selective modulation of CO₂RR pathways. In the liquid phase, Fe incorporation significantly enhances formate selectivity, while concurrently suppressing the formation of other liquid products such as ethanol and propanol. In the gas phase, Fe promotes C₃+ hydrocarbon formation, increasing their Faradaic efficiency while diminishing the yields of C₂ species like ethylene. Structural and spectroscopic characterizations reveal that Fe induces electronic and morphological reconfiguration of the Cu surface, including facet redistribution, oxide formation, and local coordination changes. This dual-phase selectivity control via Fe doping offers a new design principle for tuning product distributions in CO₂RR and advancing catalytic strategies for sustainable carbon conversion.

246

Synergistic ligand–photon interactions for enhanced CO₂ electroreduction on Cu-based electrodes

Huieun Shim; Gaeun Yun; Yunji Gwon; Sooyeon Bae; Hyeonji Lee; Jaehee Shin; Hyojin Nam; Choong Kyun Rhee; Weixin Huang; Youngku Sohn

Surf. Sci. Technol. 2026, 4, 18. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

분자 배위와 광열 여기가 Cu 표면에서의 CO₂ 전기환원 선택성을 상승적으로 조절함을 보였다. 페난트롤린(Phen)으로 기능화하고 레이저 처리한 Cu 전극을 0.1 M KHCO₃ 전해질에서 다양한 조건으로 조사하였다. Phen–Cu는 총 탄화수소 패러데이 효율(FE) 19.2%와 사슬 성장 확률(α) 0.333을 나타내어 순수 Cu(9.17%, 0.224)를 능가하였다. 520 nm 조사는 국부적 광열 활성화를 일으켜 C₃+ 탄화수소 FE를 4배(0.076%)로 높였다. 최적 Phen 농도(0.25 μM)에서 다탄소 선택성이 최대였으며, 전위나 이온 환경이 이를 벗어나면 선택성은 C₁ 생성물 쪽으로 이동하였다. EIS 분석에서 Phen–Cu₅₂₀이 가장 낮은 전하전달 저항과 가장 높은 정전용량을 보여 계면 반응속도가 빨라졌음을 시사하였다. XPS와 원자가띠 스펙트럼은 Cu⁰/Cu⁺ 상태의 안정화, 지속적인 N–Cu 배위, 그리고 더 강한 전자적 결합과 연관된 원자가띠 시작점 이동을 확인해 주었다. 이 결과들은 리간드–광열 상승효과가 비평형 상태의 Cu⁰/Cu⁺ 풍부 계면을 만들어 CO 이량화와 사슬 성장을 촉진함을 보여주며, 전기화학적 Fischer–Tropsch 유사 반응을 유도하는 새로운 전략을 제시한다.

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원문 (English) ▾

We demonstrate that molecular coordination and photothermal excitation synergistically regulate CO₂ electroreduction selectivity on Cu. Phenanthroline (Phen)–functionalized and laser-treated Cu electrodes were investigated under 0.1 M KHCO₃ at various conditions. Phen–Cu exhibited a total hydrocarbon Faradaic efficiency (FE) of 19.2% and a chain-growth probability (α) of 0.333, surpassing bare Cu (9.17%, 0.224). Illumination at 520 nm triggered localized photothermal activation, quadrupling the C₃+ hydrocarbon FE (0.076%). The optimum Phen concentration (0.25 μM) maximized multicarbon selectivity, while deviations in potential or ionic environment shifted selectivity toward C₁ products. EIS analysis revealed the lowest charge-transfer resistance and highest capacitance for Phen–Cu₅₂₀, indicating accelerated interfacial kinetics. XPS and valence-band spectra confirmed Cu₀/Cu+ stabilization, persistent N−Cu coordination, and a VB onset shift associated with stronger electronic coupling. These results reveal that ligand-photothermal synergy creates a nonequilibrium, Cu₀/Cu+-rich interface that promotes CO dimerization and chain growth, providing a new strategy for directing electrochemical Fischer–Tropsch-like chemistry.

245

Nonequilibrium Photothermal Reactions Under Pulsed Laser Excitation: Mechanisms, Dynamics, and Applications

Huieun Shim; Sy Khiem Nguyen; Hyeonji Lee; Jaehee Shin; Ilsun Yoon; Youngku Sohn

ChemCatChem 2026, 18, e01870. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

펄스 레이저 여기는 에너지를 표면에 매우 국소적이면서도 시간이 제어된 방식으로 전달함으로써, 촉매반응에서 비평형 조건에 접근하는 유력한 방법이다. 연속파 조사와 달리 펄스 레이저는 펨토초에서 나노초에 이르는 극히 짧은 순간에 에너지를 집중시켜 급격한 온도 구배와 국부 가열, 나아가 전자계와 격자계의 부분적 비결합까지 유발할 수 있다. 이러한 효과는 표면 재구성, 중간체 결합 세기의 변화, 평상시에는 접근할 수 없던 반응 경로의 활성화로 이어지는 경우가 많다. 이와 같은 과도적 광열 환경은 열과 전하의 국재화가 생성물 선택성을 크게 좌우하는 CO₂ 환원, 수소 발생, 암모니아 합성 등에서 상당한 가능성을 보여 왔다. 본 총설은 성장하고 있는 펄스 광열 촉매 분야를 조망하여 레이저–물질 상호작용의 기본 메커니즘, 열적 영역과 비열적 영역의 구분, 그리고 주요 레이저 변수가 표면 반응성에 미치는 영향을 정리한다. 아울러 대표적인 반응계들을 살펴보고, 시간분해 분광법과 전산 모델링의 최근 발전이 그 기저의 동역학을 규명하고 차세대 촉매 플랫폼의 합리적 설계에 어떻게 기여하는지 논의한다.

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원문 (English) ▾

Pulsed laser excitation offers a compelling approach for accessing nonequilibrium conditions in catalysis by delivering energy to surfaces in a highly localized and time‐controlled manner. In contrast to continuous‐wave irradiation, pulsed lasers concentrate energy into extremely short bursts—ranging from femtoseconds to nanoseconds—which can induce steep thermal gradients, localized heating, and even partial decoupling between electronic and lattice subsystems. These effects often lead to surface restructuring, altered binding of intermediates, or activation of otherwise inaccessible pathways. Such transient photothermal environments have shown considerable promise in driving reactions like CO 2 reduction, hydrogen evolution, and ammonia synthesis, where heat and charge localization strongly influence product selectivity. This review examines the growing field of pulsed photothermal catalysis, highlighting the fundamental mechanisms of laser–matter interactions, the distinction between thermal and nonthermal regimes, and how key laser parameters affect surface reactivity. We also survey selected reaction systems and discuss how recent developments in time‐resolved spectroscopy and computational modeling are helping to unravel the underlying dynamics and inform the rational design of next‐generation catalytic platforms.

244

Progress in Advanced Photocatalysis and Photoelectrocatalysis

Youngku Sohn; Mohammad Mansoob Khan

J. Saudi Chem. Soc. 2026, 30, 5. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

진보된 광촉매 및 광전기촉매 분야의 최근 발전은 태양에너지 변환과 환경 정화의 지평을 크게 넓혔다. 지속가능한 에너지와 친환경 화학공정에 대한 시급한 요구에 따라, 더 넓은 태양 스펙트럼을 활용하면서 전하 분리와 표면 반응 속도를 함께 향상시키는 효율적인 반도체 기반 시스템 설계에 많은 노력이 집중되어 왔다. 이종접합 공학, 원소 도핑, 조촉매 담지, 결함 조절 등의 전략이 밴드 구조를 조절하고 재결합 손실을 억제하는 효과적인 수단으로 부상하였다. 이와 병행하여 광활성 물질을 전기화학 구조에 통합함으로써 광자와 전기의 구동력을 결합해 더 높은 반응 속도와 선택성을 달성하는 광전기촉매가 등장하였다. 첨단 분석 기법과 전산 모델링은 전하 이동 동역학과 활성점의 역할에 대한 메커니즘적 이해를 가능하게 한다. 이러한 진전에도 불구하고 안정성, 규모 확장성, 경제적인 합성 측면의 과제는 여전히 남아 있다. 소재 설계, 계면 공학, 시스템 통합에서의 지속적인 혁신이 광촉매·광전기촉매 기술을 실험실 연구에서 에너지 변환, 수소 생산, 환경 정화의 실용 단계로 앞당길 것으로 기대된다.

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원문 (English) ▾

Recent progress in advanced photocatalysis and photoelectrocatalysis has significantly expanded the frontier of solar energy conversion and environmental remediation. Driven by the urgent need for sustainable energy and green chemical processes, extensive efforts have focused on designing efficient semiconductor-based systems that can utilize a broader solar spectrum while enhancing charge separation and surface reaction kinetics. Strategies such as heterojunction engineering, elemental doping, cocatalyst loading, and defect modulation have emerged as effective means to tune band structures and suppress recombination losses. In parallel, the integration of photoactive materials into electrochemical architectures has given rise to photoelectrocatalysis, which couples photonic and electrical driving forces to achieve superior reaction rates and selectivity. Advanced characterization tools and computational modeling further enable mechanistic insights into charge transfer dynamics and active site functionality. Despite these advances, challenges persist regarding stability, scalability, and cost-effective synthesis. Continued innovations in material design, interfacial engineering, and system integration are anticipated to accelerate the transition of photocatalytic and photoelectrocatalytic technologies from laboratory research to practical applications in energy conversion, hydrogen production, and environmental remediation.

2025

243

Laser-engineered interfacial modulation of In, Sn, and InSn electrodes for enhanced electrochemical CO₂ reduction

So Young Kim; Gaeun Yun; Yunji Gwon; Sooyeon Bae; Seon Young Hwang; Choong Kyun Rhee; Youngku Sohn

Appl. Surf. Sci. 2025, 713, 164324. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

인듐(In), 주석(Sn) 및 이들의 합금(InSn)과 같은 p-블록 금속에서의 전기화학적 이산화탄소 환원(EC CO₂RR)은 폼산염 생산을 위한 유망한 경로이다. 본 연구에서는 레이저로 산화 상태와 표면 구조를 계면 수준에서 조절할 때 CO₂RR 성능이 어떻게 달라지는지 조사하였다. 1064 nm 레이저 어블레이션으로 금속/금속 산화물 계면을 제어하고, 서로 다른 레이저 세기에서 활성, 선택성 및 반응 속도론에 미치는 영향을 평가하였다. 중간 세기의 레이저 처리는 전기화학적 표면적을 늘리고 수소 발생을 억제하며 전하 전달 특성을 최적화하여 폼산염 패러데이 효율을 최대 87.5%까지 향상시켰다. 전기화학 임피던스 분광 분석에서는 레이저 처리 전극, 특히 CO₂ 포화 조건에서 전하 전달 저항이 낮고 전기 이중층 정전용량이 큰 것으로 나타났다. Ar 조건에서는 느린 수소 흡착 동역학을 나타내는 유도성 고리가 나타났으나, CO₂ 조건에서는 경쟁적인 *OCHO 결합으로 이 고리가 억제되었다. X선 광전자 분광법(XPS) 깊이 방향 분석은 CO₂RR 중 표면 산화 상태가 동적으로 변함을 보여주었으며, InSn은 가장 안정적이고 선택적인 계면을 나타냈다. 이 연구는 계면의 산화물-금속 화학과 표면 재구성이 CO₂RR 경로 및 속도론을 결정하는 핵심 요소임을 밝히고, 고효율 폼산염 선택적 전기촉매의 설계 전략을 제시한다.

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원문 (English) ▾

Electrochemical CO₂ reduction (EC CO₂RR) on p-block metals such as indium (In), tin (Sn), and their alloy (InSn) is a promising route for formate production. Here, we investigate how laser-induced interfacial tuning of oxidation states and surface structures modulates CO₂RR performance. Using 1064 nm laser ablation, we controlled the metal/metal oxide interface and evaluated its impact on activity, selectivity, and reaction kinetics across different laser intensities. Moderate laser treatment enhanced formate Faradaic efficiency up to 87.5% by increasing electrochemical surface area, suppressing hydrogen evolution, and optimizing charge transfer properties. Electrochemical impedance spectroscopy revealed lower charge transfer resistance and higher double-layer capacitance for laser-treated electrodes, particularly under CO₂-saturated conditions. Under Ar condition, inductive loops emerged, indicating sluggish hydrogen adsorption dynamics, which were suppressed under CO₂ due to competitive *OCHO binding. XPS depth profiling showed dynamic modulation of surface oxidation states during CO₂RR, with InSn exhibiting the most stable and selective interface. This study highlights the crucial role of interfacial oxide–metal chemistry and surface restructuring in dictating CO₂RR pathways and kinetics, providing a design strategy for efficient formate-selective electrocatalysts.

242

Photon–ligand–surface coupling drives C–C bond chain growth in electrochemical CO₂ and CO reduction

Huieun Shim; Gaeun Yun; Yunji Gwon; Sooyeon Bae; Choong Kyun Rhee; Ilsun Yoon; Youngku Sohn

Mater. Today Energy 2025, 54, 102116. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

이산화탄소와 일산화탄소를 전기화학적으로 환원하여 장쇄 탄화수소로 전환하는 방법은 지속 가능한 탄소 고부가가치화를 위한 유망한 경로이지만, 느린 C-C 결합과 경쟁적인 수소 발생 때문에 제한을 받는다. 본 연구에서는 금 전극의 4-아미노싸이오페놀(ATP) 기능화와 520 nm 광조사를 결합하여 상온·상압에서 Fischer-Tropsch형 탄화수소 합성을 촉진하는 하이브리드 전기촉매 플랫폼을 제시하였다. ATP 리간드는 싸이올-Au 결합을 통해 화학흡착되어 *CO 중간체를 안정화하고 C₂+ 생성물로의 결합을 촉진한다. CO₂ 및 CO 포화 환경 모두에서 ATP-Au₅₂₀ 계면은 탄화수소 선택성을 크게 높였으며, 무처리 Au에 비해 C₂+ 패러데이 효율이 3배 이상 증가하였다. 전기화학 임피던스 분광 분석에서 ATP-Au₅₂₀은 가장 낮은 계면 저항과 가장 높은 전기 이중층 정전용량을 보여, 향상된 전하 전달과 중간체 체류를 뒷받침하였다. 특히 광증강 효과는 전해질에 의존하였다. KHCO₃에서는 약한 전기장 구속과 제한적인 *CO 생성으로 개선 효과가 거의 없었지만, 인산염 완충용액에서는 더 조밀한 전기 이중층 형성과 향상된 플라스몬-전해질-표면 결합이 가능해져 광보조 반응성이 증폭되었다. 이 결과는 리간드 배위, 플라스몬 들뜸 및 전해질 구조화가 협동적으로 다탄소 생성물을 유도하는 설계 틀을 확립하며, CO₂/CO를 고부가가치 탄화수소 연료로 효율적으로 전환하는 광반응성 전기촉매 계면 공학에 새로운 통찰을 제공한다.

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원문 (English) ▾

Electrochemical reduction of CO₂ and CO into long-chain hydrocarbons offers a promising route for sustainable carbon valorization, but remains limited by sluggish C–C coupling and competing hydrogen evolution. Here, we report a hybrid electrocatalyst platform that integrates 4-aminothiophenol (ATP) functionalization of gold electrodes with 520 nm light irradiation to promote Fischer-Tropsch-like hydrocarbon synthesis under ambient conditions. The ATP ligand chemisorbs via thiol–Au bonding, stabilizing *CO intermediates and facilitating their coupling into C₂+ products. Under both CO₂- and CO-saturated environments, the ATP–Au₅₂₀ interface exhibits significantly enhanced hydrocarbon selectivity—achieving over threefold increases in C₂+ Faradaic efficiency compared to bare Au. Electrochemical impedance spectroscopy reveals the lowest interfacial resistance and highest double-layer capacitance for ATP–Au₅₂₀, reflecting improved charge transfer and intermediate retention. Notably, the photo-enhancement is electrolyte-dependent: while KHCO₃ shows negligible improvement due to poor field confinement and limited *CO generation, phosphate buffers support tighter electric double-layer formation and enhanced plasmon–electrolyte–surface coupling, amplifying light-assisted reactivity. These findings establish a design framework in which ligand coordination, plasmonic excitation, and electrolyte structuring cooperatively direct multicarbon formation. This approach provides new insight into interface engineering for light-responsive electrocatalytic platforms targeting efficient CO₂/CO upgrading to high-value hydrocarbon fuels.

241

Selective CO₂ and CO electroreduction to C₂–C₇ hydrocarbons on Pd–Au electrodes: Role of interfacial impedance and CO adsorption modulation

Hyeonji Lee; Seon Young Hwang; Gaeun Yun; So Young Kim; Hui Eun Shim; Choong Kyun Rhee; Youngku Sohn

Appl. Surf. Sci. 2025, 710, 163939. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

전극 조성과 전해질 환경이 생성물 선택성과 반응 속도론에 미치는 영향을 규명하기 위해 KHCO₃ 및 인산염 전해질에서 무처리 Pd 전극과 Au로 개질한 Pd 전극을 사용하여 CO₂와 CO의 전기화학적 환원을 체계적으로 조사하였다. 주된 기체 생성물은 CO와 H₂였고, 소량의 CH₄ 및 C₂+ 탄화수소도 검출되었다. 폼산염과 메탄올은 CO₂ 조건에서만 관찰되었다. Pd에 Au를 도입하면 특히 인산염 전해질에서 CO 결합이 약해지고 중간체 탈착이 촉진되어 탄화수소 생성량이 10배 이상 크게 증가하였다. 인산염 전해질을 사용했을 때 C₂+ 패러데이 효율은 KHCO₃에 비해 8배 이상 높아졌다. 앤더슨-슐츠-플로리 분석은 C₇ 탄화수소까지 Fischer-Tropsch형 거동이 나타남을 확인하였고, 알켄의 사슬 성장 확률은 알케인보다 높았다. 전기화학 임피던스 분광 분석 결과, KHCO₃에서는 강한 CO 흡착 때문에 전하 전달 저항과 계면 저항이 더 커지는 반면, 인산염에서는 계면 속도론이 더 유리해졌다. Au 증착은 계면 저항을 추가로 낮추고 전해질 pH와 인가 전위에 따라 전기 이중층 정전용량을 조절하였다. 분광학적 분석에서는 Au가 Pd의 전자 구조를 변화시켜 환원 조건에서 활성 표면을 안정화함을 확인하였다. 이 결과는 장쇄 탄화수소 생성을 지향하는 CO₂/CO 전기환원에서 Au 합금화와 인산염 전해질의 상승 효과를 보여준다.

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원문 (English) ▾

Electrochemical reduction of CO₂ and CO was systematically studied using bare Pd and Au-modified Pd electrodes in KHCO₃ and phosphate electrolytes to explore the impact of electrode composition and electrolyte environment on product selectivity and reaction kinetics. CO and H₂ were the dominant gaseous products, with minor CH₄ and C₂+ hydrocarbons detected. Formate and methanol were observed only under CO₂ conditions. Au incorporation into Pd significantly enhanced hydrocarbon formation—by more than 10 times—particularly in phosphate electrolyte, by weakening CO binding and promoting intermediate desorption. The use of phosphate electrolyte increased the C₂+ Faradaic efficiency by over 8-fold compared to KHCO₃. Anderson–Schulz–Flory analysis confirmed Fischer-Tropsch-like behavior up to C₇ hydrocarbons, with alkenes showing higher chain growth probability than alkanes. Electrochemical impedance spectroscopy revealed that KHCO₃ induces higher charge transfer and interfacial resistance, likely due to strong CO adsorption, whereas phosphate promotes more favorable interfacial kinetics. Au deposition further reduced interfacial resistance and modulated double-layer capacitance, depending on electrolyte pH and applied potential. Spectroscopic characterization confirmed that Au modified the electronic structure of Pd, stabilizing the active surface under reductive conditions. These findings highlight the synergistic effects of Au alloying and phosphate electrolytes in optimizing CO₂/CO electroreduction toward long-chain hydrocarbon production.

240

Electrochemical reduction of CO₂ and CO over Au on molybdenum: Insights into interfacial reaction kinetics and electronic structures

Jihye Lee; Huieun Shim; Gaeun Yun; Hyeonji Lee; Yunji Gwon; Choong Kyun Rhee; Youngku Sohn

Electrochim. Acta 2025, 540, 147245. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

상온·상압에서 Fischer-Tropsch(F-T) 화학을 모사할 수 있는 전기화학 플랫폼의 개발은 이산화탄소 활용 분야의 핵심 과제이다. 본 연구에서는 금이 코팅된 몰리브데넘(Au/Mo) 전극에서 전기화학적 CO₂ 및 CO 환원(CO₂RR 및 CORR)을 체계적으로 조사하였다. 인산염 완충용액에서 Au/Mo는 C₃+ 장쇄 탄화수소에 높은 선택성을 보였으며, 총 탄화수소 패러데이 효율은 0.251%, 사슬 성장 확률(α)은 약 0.30으로 고전적 F-T 거동과 일치하였다. 반대로 KHCO₃에서는 에틸렌 글리콜을 비롯한 산소화합물 생성이 유리했고, 패러데이 효율은 0.732%에 도달하였다. 전위, pH 및 알칼리 금속 양이온 효과를 분석한 결과, 인산염은 *CO 축적과 수소화를 촉진하는 반면 탄산수소염은 C-O 결합 형성을 촉진하였다. 450 nm 광조사 하의 광보조 CO₂RR과 CORR은 서로 다른 효과를 보였다. CO₂ 조건에서는 탄화수소 생성이 억제되고 CO 조건에서는 향상되었으며, 이는 *CO/*H 동역학과 계면 전하 조절로 설명되었다. 전기화학 임피던스 분광법은 기체 종류와 전위에 따라 속도론적 저항이 변함을 보여주어 수소 발생 반응과 CO₂RR의 경쟁 관계를 드러냈다. X선 광전자 분광법은 계면 조건에 따라 Mo 산화 상태와 Au 전자 구조가 조절되고 부분 산화된 Mo가 *CO 결합 활성점을 안정화함을 확인하였다. 이 결과는 Au/Mo 이종계면이 전자-양성자 결합 전달과 표면 재구성을 통해 다탄소 생성물을 조절할 수 있는 플랫폼임을 보여주며, 선택적 CO₂/CO 전기전환용 고급 이종구조 설계의 기반을 마련한다.

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원문 (English) ▾

The development of electrochemical platforms capable of mimicking Fischer-Tropsch (F-T) chemistry under ambient conditions remains a key challenge in CO₂ utilization. Here, we present a systematic study of electro chemical CO₂ and CO reduction (CO₂RR and CORR) over Au-coated molybdenum (Au/Mo) electrodes. In phosphate buffer, Au/Mo achieves high selectivity toward C₃+ long-chain hydrocarbons, with a total hydrocarbon faradaic efficiency (FE) of 0.251% and a chain growth probability (α) of ~0.30, consistent with classical F-T behavior. In contrast, KHCO₃ favors oxygenate production, notably ethylene glycol, with FE reaching 0.732%. Analysis of potential, pH, and alkali cation effects reveals that phosphate enhances *CO accumulation and hydrogenation, whereas bicarbonate promotes C–O bond formation. Photo-assisted CO₂RR and CORR under 450 nm illumination show divergent effects: hydrocarbon suppression under CO₂ and enhancement under CO, attributed to *CO/*H dynamics and interfacial charge modulation. Electrochemical impedance spectroscopy reveals gas- and potential-dependent evolution of the kinetic resistance, highlighting HER/CO₂RR competition. X-ray photoelectron spectroscopy confirms that Mo oxidation states and Au electronic structure are modulated by interfacial conditions, with partially oxidized Mo stabilizing active *CO-binding sites. Together, these results demonstrate that Au/Mo heterointerfaces offer a tunable platform for multi-carbon product formation via coupled electron–proton transfer and surface reconstruction. This work lays the groundwork for designing advanced heterostructures for selective CO₂/CO electroconversion.

239

Ag on Ni supports: In situ impedance analysis and Fischer–Tropsch mimicry via electrochemical CO₂ and CO reduction

Wookyeong Kang; Jaehee Shin; Yunji Gwon; Sooyeon Bae; Choong Kyun Rhee; Youngku Sohn

Mater. Today Energy 2025, 53, 102005. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

CO₂/CO를 부가가치 탄화수소로 전기화학적으로 환원하는 방법은 지속 가능한 연료 합성을 위한 유망한 경로이다. 본 연구에서는 은이 코팅된 니켈(Ag/Ni) 전극을 전기화학적 CO₂/CO 환원으로 Fischer-Tropsch(FT)형 화학을 모사할 수 있는 조절 가능한 플랫폼으로 조사하였다. Ag 표면층 두께를 체계적으로 변화시키고 X선 광전자 분광법, 전기화학 임피던스 분광법(EIS) 및 생성물 분석을 적용하여 표면 변환, 계면 전자 구조 및 촉매 성능에 관한 상세한 반응 기작을 규명하였다. 얇은 Ag 코팅에서는 Ni 표면이 일부 노출되어 수소 발생이 유리해지고 *CO 체류가 제한되므로 효과적인 C-C 결합이 억제되었다. 반면 두꺼운 Ag 막은 전자적으로 안정화된 금속 표면을 형성하여 *CO의 지속적인 축적과 FT형 경로를 통한 장쇄 탄화수소 생성을 촉진하였다. EIS 분석에서 CO는 일시적인 CO 피독 때문에 중간체 흡착 저항을 증가시킨 반면, CO₂는 더 안정적인 계면 속도론을 유지하였다. 탄화수소 선택성, 사슬 성장 확률 및 알켄/알케인 비는 모두 인가 전위와 Ag 피복률에 강하게 의존하여, C-C 결합 형성에 *CO-*H 균형이 핵심임을 보여주었다. 이 결과는 Ag/Ni 전극을 CO₂ 전기전환을 위한 견고하고 조절 가능한 시스템으로 확립하고, 하이브리드 전기화학 촉매의 계면 반응 동역학, 중간체 변화 및 구조-기능 관계에 관한 기초 통찰을 제공한다.

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원문 (English) ▾

Electrochemical reduction of CO₂/CO to value-added hydrocarbons represents a promising route toward sustainable fuel synthesis. In this work, we investigate Ag-coated Ni electrodes as tunable platforms for mimicking Fischer-Tropsch (FT)-like chemistry via electrochemical CO₂/CO reduction. By systematically varying Ag overlayer thickness and employing X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy (EIS), and product analysis, we uncover detailed mechanistic insights into surface transformation, interfacial electronic structure, and catalytic performance. Thin Ag coatings permit partial exposure of the Ni surface, favoring hydrogen evolution and resulting in limited *CO retention, which suppresses effective C–C coupling. In contrast, thicker Ag films yield electronically stabilized metallic surfaces that support sustained *CO accumulation and promote long-chain hydrocarbon formation through FT-like pathways. EIS reveals that CO increases intermediate adsorption resistance because of transient CO poisoning, whereas CO₂ maintains more stable interfacial kinetics. Hydrocarbon selectivity, chain growth probability, and alkene/alkane ratios all display strong dependence on applied potential and Ag coverage, underscoring the critical role of *CO–*H balance in enabling C–C bond formation. These findings establish Ag/Ni electrodes as a robust and tunable system for CO₂ electroconversion and provide fundamental insights into interfacial reaction dynamics, intermediate evolution, and structure–function relationships in hybrid electrochemical catalysts.

238

Interface engineering of Pt-deposited Cu electrodes via laser ablation for enhanced electrochemical CO₂ reduction to multi-carbon products

Sooyeon Bae; Gaeun Yun; Yunji Gwon; So Young Kim; Youngku Sohn

Advances in Industrial and Engineering Chemistry 2025, 1, 19. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

구리 기반 전극은 다양한 생성물 스펙트럼과 높은 촉매 효율 덕분에 전기화학적 CO₂ 환원 연구의 주요 소재로 널리 사용되어 왔다. 본 연구에서는 Pt를 증착한 Cu 전극계를 선택하고 레이저 어블레이션을 이용해 전극 계면을 정밀하게 조절하였다. 이러한 계면 공학을 통해 생성물 형성에 영향을 주는 복잡한 관계를 상세히 규명할 수 있었다. 환원 생성물로는 H₂, CO, CH₄와 C₂ 이상의 탄화수소 같은 기체 화학종은 물론, 에탄올·아세트산·프로판올·이소프로판올·아세트알데하이드·글리콜알데하이드 등의 액상 생성물이 포함되었다. 레이저 처리로 전극 표면을 미세하게 조정하면서 이들 생성물을 체계적으로 연구하여, 산소를 포함하는 경로와 포함하지 않는 C–C 결합 경로를 모두 탐색하였다. 또한 설계된 Pt/Cu 계면에서 일어나는 전기화학적 Fischer–Tropsch 합성 메커니즘을 심층 분석하였다. 최종적으로 계면이 제어된 Pt/Cu 계는 독특한 생성물 분포를 나타냈으며, 이는 고효율 합금형 전극 개발에 중요한 통찰을 제공한다.

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원문 (English) ▾

Copper-based electrodes have been widely employed as primary materials in electrochemical CO 2 reduction studies due to their diverse product spectrum and high catalytic efficiency. In this work, we selected a Pt-deposited Cu electrode system and employed laser ablation to precisely tune the electrode interface. This interface engineering facilitated a detailed investigation of the complex relationships influencing product formation. The reduction products included gaseous species such as H 2 , CO, CH 4 , and hydrocarbons beyond C 2 , as well as liquid products including ethanol, acetic acid, propanol, isopropanol, acetaldehyde, and glycolaldehyde. These products were systematically studied by finely adjusting the electrode surface via laser treatment, allowing exploration of both oxygenated and non-oxygenated C–C coupling pathways. Additionally, we conducted an in-depth analysis of electrochemical Fischer–Tropsch synthesis mechanisms at the engineered Pt/Cu interface. Ultimately, the interface-controlled Pt/Cu system exhibited unique product distributions, which provide important insights for the development of highly efficient alloy-type electrodes.

237

Electrochemical Fischer–Tropsch chemistry

Seon Young Hwang; Gaeun Yun; Boon Siang Yeo; Youngku Sohn

Chem. Eng. J. 2025, 520, 165806. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

Fischer-Tropsch(F-T) 합성은 합성가스(CO와 H₂)로부터 장쇄 파라핀과 올레핀(CnH₂n+2 및 CnH₂n)을 생산하는 확립된 산업 공정으로, 전통적으로 고온, 고압 및 열촉매가 필요하다. 이러한 조건은 많은 에너지를 소비하고 환경 문제를 일으킨다. 보다 지속 가능하고 효율적인 대안을 개발하기 위해 열 공정과 전기화학(EC) 공정 모두에 공통으로 존재하는 *CO와 *H 등의 표면 중간체를 활용하는 전기화학적 접근법이 유망한 해결책으로 부상하였다. 그러나 CO와 CO₂의 전기화학적 환원으로 F-T 합성을 재현하는 연구는 아직 초기 단계이며 높은 수율과 효율을 달성하기가 매우 어렵다. 이 총설에서는 전기화학적 F-T 화학의 개념을 소개하고, 최근의 선도 연구를 요약하며, 이 신흥 분야의 전망과 향후 연구 방향을 논의한다.

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원문 (English) ▾

Fischer-Tropsch (F-T) synthesis is a well-established industrial process for producing long-chain paraffins and olefins (CnH₂n+2 and CnH₂n) from syngas (CO and H₂), traditionally requiring high temperatures, high pressures, and thermal catalysts. These conditions result in significant energy consumption and environmental challenges. To develop a more sustainable and efficient alternative, electrochemical (EC) approaches have emerged as a promising solution, utilizing common surface intermediates, such as *CO and *H, found in both thermal and EC processes. However, replicating the F-T synthesis through EC reduction of CO and CO₂ remains in its infancy and presents considerable challenges for achieving high yields and efficiency. In this review, we introduce the concept of EC F-T chemistry, summarizing recent pioneering research and discussing the future outlook and potential directions for this emerging field.

236

Electrochemical CO₂ and CO reduction on Au/NiCr electrodes: Fischer–Tropsch mimicry and kinetic insights from in situ impedance spectroscopy

Hyerin Shin; So Young Kim; Gaeun Yun; Hyeonji Lee; Huieun Shim; Yunji Gwon; Sooyeon Bae; Jaehee Shin; Choong Kyun Rhee; Youngku Sohn

J. Alloys Compd. 2025, 1039, 183407. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

전기화학적 CO₂ 및 CO 환원(EC CO₂RR 및 CORR)은 지속 가능한 탄화수소 연료 생산을 위한 유망한 경로이다. 본 연구에서는 Au 스퍼터링 시간을 20-300초로 변화시킨 Au 코팅 NiCr 합금 전극(Au/NiCr)을 사용하여 Au 두께와 계면 구조가 촉매 거동에 미치는 영향을 조사하였다. Au 피복률이 낮을 때(20초) 노출된 NiCr 활성점은 *CO와 강하게 결합하여 표면 피독을 일으키므로 탄화수소 생성이 제한되었다. 반대로 두꺼운 Au 층(120초 이상)은 연속적인 Au 막을 형성하여 *COOH 생성과 *CO 수소화를 향상시키고 C-C 결합을 촉진하였다. 실시간 전기화학 임피던스 분광법에서 Au(300초)/NiCr은 특히 CO₂ 조건에서 더 큰 전기 이중층 정전용량, 더 낮은 전하 전달 저항 및 더 넓은 전기화학적 표면적을 나타냈다. 이러한 특성은 *CO 중간체의 안정화와 전기화학적 Fischer-Tropsch형 기작을 통한 C₁-C₃+ 탄화수소 생성 향상과 상관관계를 보였다. X선 회절, 주사 전자 현미경 및 X선 광전자 분광법을 결합한 분석으로 표면 재구성과 Au 농축을 확인하였다. 이 연구는 Au 두께와 합금 계면 공학의 상승 작용이 CO₂/CO 환원 성능을 조절하는 방식을 밝히고, 온화한 수계 조건에서 효율적이고 조절 가능한 탄화수소 전기합성을 위한 설계 원리를 제시한다.

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원문 (English) ▾

Electrochemical CO₂ and CO reduction (EC CO₂RR and CORR) provide promising routes for sustainable hydrocarbon fuel production. Here, we investigate Au-coated NiCr alloy electrodes (Au/NiCr) with varied Au sputtering times (20–300 s) to study how Au thickness and interfacial structure affect catalytic behavior. At low Au coverage (20 s), exposed NiCr sites lead to strong *CO binding and limited hydrocarbon formation due to surface poisoning. In contrast, thicker Au layers (≥120 s) yield continuous Au films that enhance *COOH formation, *CO hydrogenation, and promote C–C coupling. In-situ electrochemical impedance spectroscopy shows that Au(300 s)/NiCr exhibits higher double-layer capacitance, lower charge transfer resistance, and greater electrochemical surface area, especially under CO₂. These properties correlate with improved stabilization of *CO intermediates and enhanced production of C₁–C₃+ hydrocarbons via an EC Fischer-Tropsch like mechanism. Combined X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy analyses confirm surface restructuring and Au enrichment. This study highlights the synergistic role of Au thickness and alloy interface engineering in tuning CO₂/CO reduction performance, offering design principles for efficient, tunable hydrocarbon electrosynthesis under mild aqueous conditions.

235

Electrocatalytic CO₂ reduction over Ag/CuSn Electrodes: Modulation of C₁, C₂, and C₃+ products

Yunji Gwon; Seon Young Hwang; Sooyeon Bae; Gaeun Yun; So Young Kim; Choong Kyun Rhee; Youngku Sohn

J. Ind. Eng. Chem. 2025, 146, 468-483. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

서로 다른 금속을 조합하는 방법은 전기화학적(EC) 이산화탄소 환원에서 생성물을 조절할 수 있는 전극을 제작하는 효과적인 전략이다. 본 연구에서는 CuSn 및 EC 처리 CuSn 표면을 스퍼터 증착으로 Ag 개질하였다. KHCO₃, K₂CO₃ 및 KOH 전해질에서 여러 인가 전위를 적용하여 EC CO₂ 환원을 수행하고, 양이온과 음이온이 생성물 변화에 미치는 영향을 조사하였다. 주된 환원 생성물은 H₂, C₁ 화합물(CO, CH₄, 폼산염) 및 C₂ 화합물(C₂H₄, 에탄올, 아세트산염)이었다. 소량 생성물로는 C₁ 화합물인 메탄올, C₂ 화합물인 아세트알데하이드와 글리콜알데하이드, C₃+ 화합물인 프로판올과 아이소프로판올, 그리고 C₂H₆ 및 C₃+ 탄화수소가 확인되었다. C₂+ 탄화수소의 변화는 Fischer-Tropsch(F-T) 화학으로 설명하였다. 깊이 방향 X선 광전자 분광법을 사용하여 EC CO₂ 환원 전후의 Cu와 Sn 산화 상태 및 Cu/Sn 비를 조사하였다. 촉매 조성, 인가 전위 및 전해질 조성이라는 실험 인자들은 상호작용하여 복잡한 반응 환경을 형성하였다. 이 통합적 접근법은 목표 생성물 선택성을 달성하기 위한 최적 조건을 찾는 데 유용한 통찰을 제공한다.

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원문 (English) ▾

Combining different metals has proven to be an effective methodology for fabricating electrodes that can manipulate reduction products in electrochemical (EC) CO₂ reduction. In this study, CuSn and EC treated CuSn were surface-modified with Ag via sputter deposition. EC CO₂ reduction was performed at various applied po tentials in KHCO₃, K₂CO₃, and KOH electrolytes. The effects of cations and anions were tested to examine the variation in reduction products. The major reduction products were H₂ and C₁ compounds (CO, CH₄, formate), as well as C₂ compounds (C₂H₄, ethanol, and acetate). Minor products included C₁ compounds (methanol), C₂ compounds (acetaldehyde and glycolaldehyde), and C₃+ compounds (propanol and isopropanol), along with C₂H₆ and C₃+ hydrocarbon products. The variation of C₂+ hydrocarbons was explained by Fischer-Tropsch (F-T) chemistry. The oxidation states of Cu and Sn, as well as the Cu/Sn ratios, were examined before and after EC CO₂ reduction using depth-profiled X-ray photoelectron spectroscopy. The experimental factors—catalyst composition, applied potential, and electrolyte composition—interacted to create a complex reaction environment. This combined approach provides valuable insights into identifying optimal conditions for achieving desired product selectivity.

234

Electrochemical Recycling of Poly(ethylene terephthalate): Controlling Ni/Cu Electrode Oxide Layers through Laser Treatment

Sooyeon Bae; Seon Young Hwang; Gaeun Yun; Yunji Gwon; So Young Kim; Choong Kyun Rhee; Youngku Sohn

ACS Appl. Energy Mater. 2025, 8, 9604-9616. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

레이저를 이용한 이원계 전기촉매 가공은 알칼리 산화 공정에서 표면 조성과 반응 선택성을 조절하는 유망한 전략이다. 본 연구에서는 레이저 처리 강도를 0~100%로 달리한 Ni/Cu 합금 박막 전극을 1.0 M KOH 용액에서 에틸렌글리콜(EG)을 포름산염으로 전기화학적으로 산화시키는 반응에 적용하여 조사하였다. 레이저 출력 50%로 처리한 전극(Ni/Cu, L=50%)은 0.55 V(Hg/HgO)에서 84.9%의 최고 포름산염 패러데이 효율을 보였으며, 이는 최적화된 표면 NiOx 상과 증가한 전기화학적 표면적에 기인한다. 체계적인 분광 분석 결과 레이저에 의해 Ni이 풍부한 표면층이 형성되고, 이 층이 전기화학 조건에서 동적으로 구조 변화를 겪음을 확인하였다. 전기화학 임피던스 분광법과 Tafel 분석은 레이저 처리가 전하전달 저항을 낮추고 반응 속도를 개선함을 뒷받침하였다. 또한 이 시스템은 가수분해된 폴리(에틸렌 테레프탈레이트)와 테레프탈산 유도체의 선택적 산화도 보여, 폐기물을 화학원료로 전환하는 플랫폼으로서의 의미를 시사한다. 본 연구는 펄스 또는 연속파 레이저 가공으로 Ni/Cu 촉매의 계면을 조절할 수 있음을 보이며, 선택적 EG 산화는 물론 다른 소분자 변환에도 적용 가능한 조절성과 확장성을 갖춘 접근법을 제시한다.

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원문 (English) ▾

Laser-assisted engineering of bimetallic electrocatalysts presents a promising strategy for tuning surface composition and reaction selectivity in alkaline oxidation processes. Herein, we investigate Ni/Cu alloy foil electrodes subjected to varying laser treatment intensities (0–100%) for the electrochemical oxidation of ethylene glycol (EG) to formate in 1.0 M KOH. The electrode treated at 50% laser power (Ni/Cu L =50% ) exhibited the highest formate Faradaic efficiency of 84.9% at 0.55 V Hg/HgO, attributed to optimized surface NiO x phases and enhanced electrochemical surface area. Systematic spectroscopic analyses revealed laser-induced formation of Ni-rich surface layers, which underwent dynamic structural evolution under electrochemical conditions. Electrochemical impedance spectroscopy and Tafel analysis confirmed that laser treatment reduced charge transfer resistance and improved reaction kinetics. The system also demonstrated selective oxidation of hydrolyzed poly(ethylene terephthalate) and terephthalic acid derivatives, highlighting the relevance of this platform for waste-to-chemical conversion. This study demonstrates that pulsed or continuous-wave laser processing enables interfacial modulation of Ni/Cu catalysts, providing a tunable and scalable approach for selective EG oxidation and potentially other small-molecule transformations.

233

Laser ablation-controlled Au/Cu interfaces for modulating C₁, C₂, and C₃+ chemistry in electrochemical CO₂ reduction

Hui Eun Shim; Gaeun Yun; Seon Young Hwang; So Young Kim; Choong Kyun Rhee; Youngku Sohn

Mater. Today Energy 2025, 49, 101842. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

전극 표면의 정밀한 조절은 전기화학적 이산화탄소 환원(EC CO₂R)의 최종 생성물과 선택성을 결정하는 데 핵심적이다. Cu 기반 전극에서는 C₁, C₂ 및 C₃+ 생성물이 복잡하게 연관된 분포로 나타난다. 본 연구에서는 계면 조절을 통해 이러한 상호관계를 더 깊이 조사하였다. Au/Cu 전극계를 선택하고 레이저 어블레이션으로 Cu 지지체 위의 Au 표면층을 제거하여 계면을 정밀하게 조절하였다. 생성물에는 H₂, CO, 폼산염, CH₄, C₂H₄, C₂H₆, 산소화 생성물(에탄올, 아세트산염, 프로판올 및 아이소프로판올)과 C₃+ 탄화수소가 포함되었다. 정밀하게 조절한 Au 피복률에서 이들 생성물을 체계적으로 분석하고 산소 함유 및 비산소계 C-C 결합 경로를 모두 탐색하였다. 또한 전기화학을 통한 Fischer-Tropsch 합성을 논의하였다. 생성물 분포는 페르미 준위 부근의 상태 밀도뿐 아니라 표면층 Au와 Cu 지지체 사이의 계면 전자 구조와 강한 상관관계를 보였다. 계면이 제어된 Au/Cu 시스템에서 C₁, C₂ 및 C₃+ 생성물을 얻은 이 독특한 결과는 계면에서 형성되는 고효율 이중금속 전극 개발에 핵심 통찰을 제공한다.

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원문 (English) ▾

The precise modulation of an electrode surface has proven instrumental in shaping the final products and their selectivities during electrochemical CO₂ reduction (EC CO₂R). In the case of Cu-based electrodes, the resulting products exhibit a diverse distribution spanning C₁, C₂, and C₃+ products, showcasing intricate interrelations. In this study, we delve into a more profound exploration of these interrelationships through interface tuning. Specifically, we selected the Au/Cu electrode system and refined the interface using a laser ablation method to remove the overlayer of Au on the Cu support. The reduction products encompassed H₂, CO, formate, CH₄, C₂H₄, C₂H₆, oxygenated products (ethanol, acetate, propanol, and isopropanol), and C₃+ hydrocarbons. These products were systematically investigated with a finely tuned Au coverage, exploring both oxygenated and nonoxygenated C-C coupling paths. The discussion further delved into Fischer-Tropsch synthesis via electrochemistry. The results revealed a strong correlation between the product outcomes and the density of states near the Fermi level, along with the interfacial electronic structures of the overlaid Au and Cu support. The very unique findings from the interface-controlled Au/Cu system, yielding C₁, C₂, and C₃+ products, offer crucial insights for advancing the development of highly efficient bimetallic electrodes formed at interfaces.

232

Modulating electrochemical CO₂ reduction products by precise tuning of CuZn surface oxidation states

Yunji Gwon; Seon Young Hwang; So Young Kim; Sooyeon Bae; Gaeun Yun; Choong Kyun Rhee; Youngku Sohn

Mater. Today Energy 2025, 49, 101831. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

표면 산화 상태와 원소 조성은 전기화학적 이산화탄소 환원 반응의 생성물 분포에 결정적인 영향을 미친다. 그러나 전극 표면 특성을 조절하여 생성물을 정밀하게 제어하는 일은 여전히 어렵다. 본 연구에서는 CuZn 전극을 사용하고 서로 다른 출력의 적외선 레이저 처리로 표면을 정밀하게 조절하였다. 이 방법은 CuZn 전극의 표면 특성을 변화시켜 환원 생성물을 효과적으로 제어하였다. 레이저 출력이 증가할수록 전기화학적 활성이 CO와 같은 C₁ 생성물 쪽으로 이동하고, 에틸렌, 에탄올 및 프로판올과 같은 C₂ 및 C₃+ 생성물의 형성은 감소하였다. 이러한 변화는 표면 산화 상태, 원소 조성 및 계면 전자 구조의 변화와 밀접하게 연관되어 있으며, 원하는 CO₂ 환원 경로에 대한 촉매의 선택성과 효율을 높이는 표면 공학의 잠재력을 보여준다.

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원문 (English) ▾

Surface oxidation states and elemental compositions critically influence the distribution of reduction products in electrochemical CO₂ reduction reactions. Demonstrating the precise modulation of these products by adjusting electrode surface properties remains challenging. This study utilized a CuZn electrode, whose surface was finely tuned using infrared laser treatment at varying power levels. This method effectively modulated the reduction products by altering the CuZn electrode’s surface characteristics. Our investigation shows that increasing laser power shifts the electrochemical activity towards the production of C₁ products like CO, while decreasing the formation of C₂ and C₃+ products such as ethylene, ethanol, and propanol. These changes, closely tied to modifications in surface oxidation states, elemental compositions, and interfacial electronic structures, highlight the potential of surface engineering in enhancing catalyst selectivity and efficiency for desired CO₂ reduction pathways.

231

Cellulose-Based SERS Substrate for Vapor-Phase Thiol Detection with PCA for Enhanced Chemical Selectivity

Ba-Thong Trinh; Sy Khiem Nguyen; Dayeon Kim; Huu-Quang Nguyen; Jaebeom Lee; Youngku Sohn; Ilsun Yoon

Chemosensors 2025, 13, 101. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

In this work, we present a low-cost, label-free cellulose-based paper SERS (Surface-Enhanced Raman Scattering) substrate for the sensitive detection of thiol compounds. Uniform silver nanoparticles (AgNPs) were synthesized on cellulose filter paper via in situ reduction of a silver precursor under UVC irradiation, achieving a high SERS enhancement factor of 8.5 × 106. The Ag-cellulose substrate demonstrated reliable detection of benzenethiol, capturing its characteristic SERS signals with remarkable sensitivity. Quantitative analysis was enabled by adjusting exposure times for accurate calibration. Furthermore, Principal Component Analysis (PCA) was successfully employed to distinguish mixed samples of benzenethiol, hexanethiol, and propanethiol, showcasing the substrate’s capability in separating complex mixtures. This cellulose-based AgNP platform offers a sustainable, cost-effective solution for rapid chemical detection, with significant potential for real-world applications such as environmental monitoring and food safety.

230

Insights into MXenes and MXene-based heterostructures for various photocatalytic applications

Shaikh Parwaiz; Youngku Sohn; Mohammad Mansoob Khan

Mater. Sci. Semicond. Process. 2025, 186, 109099. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

태양에너지를 화학에너지로 전환하는 광촉매 기술은 에너지 위기와 환경 문제를 해결할 수 있는 유망한 방법이다. 원자 수준으로 얇은 층상 구조에서 유래한 독특한 표면 특성과 물리화학적 성질을 지닌 맥신(MXene)은 다양한 광촉매 응용을 위한 유망한 후보로 부상하고 있다. 이 총설은 MAX 상과 맥신의 구조 및 분류를 간결하게 분석한다. 맥신 제조에 사용되는 전통적 HF 식각법, 무-HF 대안법, 첨가제 매개 합성 및 직접 합성 등 여러 합성 기술을 개괄한다. 또한 물 분해, CO₂ 환원, N₂ 고정, H₂O₂ 생성 및 오염물질 분해를 위한 광촉매로서 맥신과 관련 이종구조를 조명한다. 후속 절에서는 더 나은 이해를 위해 상호보완적인 두 접근법인 실시간 특성 분석법과 제일원리 계산을 다룬다. 마지막으로 광촉매 분야에서 맥신 및 맥신 기반 이종구조의 잠재적 응용을 간략히 정리하고 향후 연구 방향을 제시한다. 이 총설은 독특하고 유망한 맥신 기반 광촉매를 설계하고 제작하는 데 유용한 참고 자료가 될 수 있다.

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원문 (English) ▾

Photocatalytic conversion of solar energy into chemical energy is a prospective solution to the energy crisis and environmental challenges. MXenes, characterized by their unique surface features and physicochemical properties derived from their atomically thin layered structures, are becoming promising candidates for various photocatalytic applications. This review offers a concise analysis of the structure and categorization of MAX phases and MXenes. The discussion covers a succinct overview of different synthesis techniques employed in the preparation of MXenes, encompassing traditional HF etching methods, HF-free alternatives, additive-mediated synthesis, and direct synthesis. This study highlights MXenes and related heterostructures as photocatalysts for H₂O splitting, CO₂ reduction, N₂ fixation, H₂O₂ generation, and pollutant degradation. We incorporated two complementary approaches, in-situ characterization methods, and first-principles calculations, in the following section to provide a better understanding. We conclude this review by offering insights into future directions and a concise summary of the potential applications of MXenes and MXene-based heterostructures in photocatalysis. This review could serve as a valuable reference for the design and fabrication of unique and promising MXene-based photocatalysts.

229

Electrochemical CO₂ reduction chemistry of C₁ and C₂+ products on Cu/Zn electrodes via galvanic replacement

Jaehee Shin; Yunji Gwon; Seon Young Hwang; Sooyeon Bae; So Young Kim; Choong Kyun Rhee; Youngku Sohn

J. Alloys Compd. 2025, 1010, 177660. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

전기화학적(EC) 이산화탄소 환원은 특히 Cu 기반 전극을 이용하여 부가가치 생성물을 생산하는 기술로 큰 관심을 받고 있다. 본 연구에서는 갈바니 치환으로 Cu/Zn 전극을 제조하고 EC CO₂ 환원 중 C₁ 및 C₂+ 생성물 생산 효율을 평가하였다. 주요 실험 변수는 인가 전위, 전해질 농도, 광조사 및 전극 구성이었다. Cu/Zn 전극은 합성가스(CO와 H₂)를 생성하는 동시에 에탄올에 대해 특히 높은 선택성을 보였다. 에탄올과 CO 형성은 주로 인가 전위와 전해질 농도의 영향을 받았다. 반응 후 분석에서는 전극의 형태, 결정 구조, 산화 상태 및 Cu/Zn 비가 크게 변한 것으로 나타났다. 이 결과는 에탄올 생성 기작과 C₁/C₂+ 생성물 형성에 대한 이해를 높이고, CO₂ 환원을 위한 더욱 효과적인 이중금속 전극 개발에 기여한다.

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원문 (English) ▾

Electrochemical (EC) reduction of CO₂ has gained significant interest for producing value-added products, especially with Cu-based electrodes. In this study, a Cu/Zn electrode was prepared via galvanic replacement and evaluated for its efficiency in generating C₁ and C₂+ products during EC CO₂ reduction. Key experimental parameters included applied potentials, electrolyte concentrations, light irradiation, and electrode configurations. The Cu/Zn electrode demonstrated notably high selectivity for ethanol, alongside syngas (CO and H₂) production. The formation of ethanol and CO was primarily influenced by the applied potential and electrolyte concentration. Post-reaction analysis revealed substantial changes in the electrode’s morphology, crystal structure, oxidation states, and Cu/Zn ratios. These findings enhanced the understanding of ethanol production mechanisms and C₁/C₂+ product formation, contributing to the development of more effective bimetallic electrodes for CO₂ reduction.

2024

228

NiO@GaN nanorods-based core-shell heterostructure for enhanced photoelectrochemical water splitting via efficient charge separation

Kedhareswara Sairam Pasupuleti; Roshani Awanthika Jayarathna; Seon Young Hwang; Pham Thi Minh Thu; Devthade Vidyasagar; Yun-Hae Shim; Eui-Tae Kim; Youngku Sohn; Young Heon Kim; Moon-Deock Kim

J. Alloys Compd. 2024, 1009, 176882. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

III-V족 반도체, 특히 GaN 나노구조 기반 광전극의 뛰어난 특성은 넓은 밴드갭과 우수한 광전자 특성 덕분에 청정하고 지속 가능한 수소 생산을 위한 광전기화학적 물 분해(PEC-WS) 분야에서 큰 잠재력을 지닌다. 그러나 GaN 나노막대(NR)에 불가피하게 존재하는 표면 상태는 태양광-수소(STH) 전환 효율을 낮추고 안정성을 떨어뜨려 PEC-WS의 실제 응용을 심각하게 제한한다. 이 문제는 하이브리드 이종구조를 형성하여 완화할 수 있다. 본 연구에서는 n-GaN NR 광전극 위에 p-NiO 나노입자(NP)를 적재한 II형 코어-셸 이종구조의 계면 공학을 개발하였다. 코어 GaN NR 위 NiO NP 셸 밀도의 영향을 평가한 결과, 최적화된 NiO@GaN NR 광전극은 1.23 V 대 RHE에서 1.38 mA/cm₂의 광전류 밀도(Jph)와 약 0.39%의 우수한 인가 바이어스 광-전류 전환 효율(ABPE)을 나타냈다. 이는 1-Sun 조사에서 무처리 GaN NR 광양극보다 각각 3.8배(Jph)와 4.8배(ABPE) 높은 값이다. 코어-셸 NiO@GaN NR 광전극의 II형 p-n 이종접합 띠 정렬은 표면 상태를 부동태화하여 광생성 전하 운반자의 재결합 속도를 낮추고 빛의 흡수와 포집 능력을 향상시켰다. 이에 따라 광양극/전해질 계면의 전하 분리와 전달이 크게 촉진되어 산화환원 반응, PEC-WS 및 STH 성능이 향상되었다. 이 결과는 미래 PEC-WS 기반 녹색에너지 응용을 위한 고효율 III-V족 하이브리드 이종구조 광전극의 설계와 제작에 유망한 전략을 제시한다.

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원문 (English) ▾

Remarkable properties of III-V semiconductors, particularly GaN nanostructured based photoelectrodes offers a potential attention in the field of photoelectrochemical water splitting (PEC-WS) for clean and sustainable hydrogen production, due to its wide bandgap, magnificent optoelectrical properties. However, the presence of inevitable surface states in GaN nanorods (NRs) leads to low solar-to-hydrogen (STH) conversion efficiency with poor stability, thereby severely limiting their practical application in PEC-WS, which can be effectively alleviated by constructing a hybrid heterostructures. Herein, we present the development of interfacial engineering of a type-II core-shell heterostructure based on p-NiO nanoparticles (NPs) loaded on n-GaN NRs photoelectrodes for PEC-WS. We assessed the impact of the NiO NPs shell density on core GaN NRs, finding that the optimized NiO@GaN NRs photoelectrode achieved a photocurrent density (Jph) of 1.38 mA/cm₂ at 1.23 V versus RHE and an excellent applied bias photo-to-current conversion efficiency (ABPE) of ~0.39%, which was 3.8 (Jph) and 4.8 (ABPE)-fold times higher than the pristine GaN NRs photoanode under 1-Sun illumination. The type-II p-n heterojunction band alignment between core-shell NiO@GaN NRs photoelectrode effectively reduced the photogenerated carrier recombination rate through surface states passivation and boost the light absorption and harvesting capacity. This facilitates a significant charge separation and transfer at the photoanode/electrolyte interface leading to enhanced redox reactions, resulting in improved PEC-WS and STH performances. These findings offer a promising strategy to design and fabricate highly efficient III-V hybrid heterostructure photoelectrodes for futuristic PEC-WS-based green energy applications.

227

Exploring C₁-C₃ variations and Fischer–Tropsch chemistry via electrochemical CO₂ reduction on electrodeposited Cu/Ag and Ag/Cu electrodes

Seon Young Hwang; Gaeun Yun; So Young Kim; Yunji Gwon; Sooyeon Bae; Choong Kyun Rhee; Youngku Sohn

Electrochim. Acta 2024, 507, 145100. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

Ag와 Cu 이중금속 전극은 전기화학적 CO₂ 환원을 통해 C-C 결합된 C₂+ 환원 생성물을 생산하는 용도로 광범위하게 연구되고 있다. 본 연구에서는 전착법으로 Ag 지지체 위에 Cu를 전착한 전극(CuED/Ag)과 Cu 지지체 위에 Ag를 전착한 전극(AgED/Cu)을 제조하고, 여러 전기화학 조건에서 환원 생성물의 거동을 조사하였다. 생성물은 H₂, C₁(CO, CH₄, 폼산염, 메탄올), C₂(C₂H₄, 에탄올, 아세트산염, 아세트알데하이드, 글리콜알데하이드 및 에틸렌 글리콜), C₃(프로판올, 아이소프로판올), 그리고 Fischer-Tropsch(F-T) 합성 생성물(CnH₂n 및 CnH₂n+2, n≥2)로 분류하였다. 특히 에틸렌 글리콜은 AgED/Cu에서만 관찰되었다. 환원 생성물은 인가 전위와 전해질 농도에 따라 동적으로 변하였다. 반응 기작에는 표면 H* 흡착, CO₂ 흡착, C-C 결합, 수소화 및 탈수가 관여하는 것으로 해석하였다. 소수 경로로 나타난 F-T 합성 화학은 *CO와 *CH₂ 삽입에 의한 사슬 성장으로 설명하였다. CuED/Ag와 AgED/Cu 전극에서 나타난 서로 다른 생성물 거동은 CO₂ 활용을 통해 부가가치 탄소 생성물을 생산하는 전극 개발에 유용한 통찰을 제공한다.

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원문 (English) ▾

Ag and Cu bimetallic electrodes are extensively studied for producing C-C coupled C₂+ reduction products through electrochemical CO₂ reduction. In this study, we prepared electrodes with Cu electrodeposited on Ag supports (CuED/Ag) and Ag electrodeposited on Cu supports (AgED/Cu) via electrodeposition, demonstrating behaviors for reduction products under various electrochemical conditions. The products were categorized as H₂, C₁ (CO, CH₄, formate, methanol), C₂ (C₂H₄, ethanol, acetate, acetaldehyde, glycolaldehyde, and ethylene glycol), C₃ (propanol, isopropanol), and Fischer-Tropsch (F-T) synthesis products (CnH₂n and CnH₂n+2, n ≥ 2). Notably, ethylene glycol was only observed over AgED/Cu. The reduction products dynamically changed with applied potentials and electrolyte concentrations. The mechanism was understood to involve surface H* adsorption, CO₂ adsorption, C-C coupling, hydrogenation, and dehydration. Minor F-T synthesis chemistry was observed, explained by *CO and *CH₂ insertion chain growth. The distinct product behaviors over the CuED/Ag and AgED/Cu electrodes provide valuable insights into the development of electrodes for producing value-added carbon products via CO₂ utilization.

226

Advances in Artificial Photosynthesis: The Role of Chalcogenides and Chalcogenide‐Based Heterostructures

Ashmalina Rahman; Shaikh Parwaiz; Youngku Sohn; Mohammad Mansoob Khan

ChemPhotoChem 2024, 9, e202400234. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Artificial photosynthesis, encompassing the photocatalytic generation of H 2 and CO 2 reduction innovations, seems to be a highly promising approach. This is due to its ability to efficiently transform CO 2 into hydrocarbon fuel and valuable chemical products using solar energy as a direct energy source. This will simultaneously help to mitigate global warming and energy shortage issues. Chalcogenide‐based semiconductors have recently gotten a lot of attention as an important area of research for photocatalytic H 2 production and CO 2 conversion, owing to their low band gap energy, suitable band structures, and a great photoresponsivity spectrum. Modifying chalcogenides into their heterostructures could be a great way to solve problems like photo corrosion and carrier recombination. Therefore, this review summarized a series of different modifications of chalcogenides and recent developments in their photocatalytic and photo electrocatalytic performance, particularly in H 2 production and CO 2 conversion. Lastly, we discussed the challenges, limitations, areas for development, and future prospects of chalcogenides and their heterostructures capable of utilizing visible light to produce H 2 gas and reduce CO 2 .

225

Electrochemical reduction of nitrate to ammonia using Fe-based catalyst: Insights into N₂, CO₂, and CO environments

Seon Young Hwang; Gaeun Yun; So Young Kim; Choong Kyun Rhee; Youngku Sohn

J. Environ. Chem. Eng. 2024, 12, 114482. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Electrochemical (EC) reduction of nitrate/nitrite for ammonia production is a key area of research in the realm of nitrogen pollutant treatment and recycling efforts. In this study, we utilized a commercial Fe(Mn) alloy to investigate EC reductions of nitrate/nitrite ions under N 2 , CO, and CO 2 -saturated conditions, shedding light on the influences of different feeding gases. Under N 2 conditions, the ammonia production Faradaic efficiency (FE) reached 60 %; however, it significantly decreased under CO 2 conditions. The presence of CO as a feeding gas proved detrimental, resulting in no ammonia production. Surprisingly, the Fe(Mn) alloy demonstrated superior EC Fischer-Tropsch (F-T) synthesis chemistry under CO conditions, generating CH 4 and long-chain hydrocarbons (C n H 2n+2 and C n H 2n , where n=2–7). This contrasts with existing literature, where such alloys typically perform better under CO 2 conditions. Notably, alkanes were found to be more predominant than their corresponding alkenes . The Anderson-Schulz-Flory equation plots exhibited significant linearity, resembling the traditional Fischer-Tropsch chain growth mechanism. This original discovery introduces new possibilities for employing commercial-grade Fe alloy in the direct EC F-T synthesis using CO, facilitating the production of long-chain hydrocarbons. Moreover, it paves the way for nitrate/nitrite ion treatments in analogous processes within diverse gas environments.

224

Tailoring electrochemical CO₂ reduction selectivity over CuSn by modulating surface oxidation state with infrared laser treatment

Yunji Gwon; Seon Young Hwang; So Young Kim; Gaeun Yun; Sooyeon Bae; Choong Kyun Rhee; Youngku Sohn

Chem. Eng. J. 2024, 499, 156752. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

적외선 레이저 처리로 CuSn 전극의 표면 구조를 정밀하게 개질하여 환원 생성물의 선택성을 효과적으로 미세 조절하였다. 레이저 출력이 증가함에 따라 금속 Cu와 Sn 표면은 더 많이 산화되었고, 깊이에 따른 Sn/Cu 조성비도 변했으며 전기화학 반응 후에는 추가 변화가 나타났다. C₁(CO, CH₄ 및 폼산염), C₂(C₂H₄, 에탄올, 아세트산염, 아세트알데하이드 및 글리콜알데하이드), C₃(프로판올 및 아이소프로판올) 화합물로 이루어진 다양한 환원 생성물 분포는 C₁ 생성물(CO와 폼산염)의 선택적 생산 쪽으로 이동하였다. 이러한 거동은 계면 전자 구조, 산화 상태, 조성비, 그리고 페르미 준위 부근에서 CO₂와 Cu, O 및 Sn 상태 밀도 사이의 상호작용이 달라진 결과이다. 레이저 처리법은 전극 표면을 정밀하게 조절하고 환원 생성물을 제어하며 선택성을 높일 수 있다. 또한 이 기법은 CO₂ 환원용 전극 설계에 새로운 접근법을 제시하여 촉매 성능 최적화를 위한 새로운 길을 연다.

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원문 (English) ▾

Infrared laser treatment was used to precisely modify the surface structure of CuSn electrodes, effectively fine-tuning the selectivity of reduction products. With increasing laser power, the metallic Cu and Sn surfaces became more oxidized, and the Sn/Cu composition ratio varied with depth and further changed post-EC reaction. The diversity of reduction products, including C₁ (CO, CH₄, and formate), C₂ (C₂H₄, ethanol, acetate, acetaldehyde, and glycolaldehyde), and C₃ (propanol and isopropanol) compounds, shifted towards a more selective production of C₁ (CO and formate) products. These tailored behaviors are attributed to variations in interfacial electronic structures, oxidation states, composition ratios, and the interaction between CO₂ and the density of states (Cu, O, and Sn) near the Fermi level. The laser treatment method enables precise tuning of electrode surfaces, modulation of reduction products, and enhancement of selectivity. Moreover, this technique presents a novel approach for electrode design in the field of CO₂ reduction, offering new avenues for optimizing catalytic performance.

223

Dynamic recycling behavior of Cu/Zn-based electrodes in electrochemical CO₂ reduction

Seon Young Hwang; Gaeun Yun; So Young Kim; Choong Kyun Rhee; Youngku Sohn

Appl. Surf. Sci. 2024, 670, 160628. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

전기화학적 이산화탄소 환원(EC CO₂R)에서는 반복 사용 가능성과 전극 안정성이 중요하며, 특히 음의 환원 전위에서 전극 거동이 변하기 때문에 더욱 그렇다. 본 연구에서는 Cu, Zn 및 CuZn 금속과 이들의 산화물을 사용하여 여러 차례 반복 사용했을 때의 EC CO₂R 생성물을 조사하였다. 환원 생성물과 패러데이 효율(FE)은 전극 종류에 따라 크게 달라졌다. 초기에는 Cu와 그 산화물, CuZn 합금과 그 산화물이 서로 다른 FE를 보였으나 이후 반복 사용에서는 성능이 비슷해졌다. 반면 Zn과 그 산화물의 차이는 전체 반복 과정에서 일관되게 유지되었다. 반응 후 전극의 조성과 산화 상태는 깊이 방향 X선 광전자 분광법으로 분석하였다. 분석 결과, 특히 Zn/Cu 비에서 산화 상태와 금속 상태 및 산화 상태의 분포가 크게 변한 것으로 나타났다. 이러한 통찰은 에너지 및 환경 응용을 위한 안정한 전극을 개발하는 데 중요하다.

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원문 (English) ▾

Recycling and electrode stability are crucial in electrochemical CO₂ reduction (EC CO₂R), especially due to changes in electrode behavior under negative reduction potentials. This study investigates the EC CO₂R products over multiple recycling steps using Cu, Zn, and CuZn metals, along with their oxides. Our findings reveal significant variations in reduction products and their Faradaic efficiencies (FEs), dependent on the electrode type. Initially, Cu and its oxide, as well as the CuZn alloy and its oxide, displayed varying FEs, but their performance normalized in later recycles. Conversely, Zn and its oxide showed consistent differences throughout the recycles. Depth-profiling X-ray photoelectron spectroscopy was used to analyze the electrodes’ composition and oxidation states post-reaction. The analyses highlighted substantial changes in oxidation states and the distribution of metallic and oxidized states, particularly in the Zn/Cu ratio. These insights are essential for developing stable electrodes for energy and environmental applications.

222

Electrochemical Fischer-Tropsch chemistry across transition metals: A paradigm shift in sustainable liquid fuel production

Seon Young Hwang; Ju Young Maeng; Ilsun Yoon; Chang Woo Myung; Choong Kyun Rhee; Youngku Sohn

Nano Energy 2024, 128, 109881. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

본 연구는 전통적인 고에너지 소모 공정에서 벗어난 친환경 액체 연료 생산법으로 전기화학적 Fischer-Tropsch(EC F-T) 합성을 탐구하였다. 전기화학적 합성가스 생성은 충분히 연구되어 있지만, CO₂와 CO 공급 기체를 이용한 F-T 화학 합성은 상대적으로 연구가 부족하다. Ti, Zr, V, Mo, Fe, Co, Ni, Pd, Cu, Ag, Au, Zn 및 Cd를 포함한 여러 전이금속을 조사한 결과, Zn을 제외한 금속에서 장쇄 탄화수소(CnH₂n 및 CnH₂n+2, n=2-7)를 생성하는 F-T 화학의 명확한 증거를 제시하였다. 이 과정은 전통적 F-T 합성과 유사한 표면 C-C 결합 사슬 성장을 포함하며, *CO 및 *CHx 삽입 반응이 관여한다. 페르미 준위 부근의 상태 밀도와 에너지 준위도 분석하였다. 이 실험 체계는 C-C 결합 기작에 대한 이해를 높이고, 장쇄 탄화수소 생산을 위한 친환경 전기화학 방법에 통찰을 제공하며, 미래 에너지 해결책을 위한 지속 가능한 F-T 합성의 혁신 전략을 발전시킨다.

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원문 (English) ▾

This study explores electrochemical Fischer-Tropsch (EC F-T) synthesis as an eco-friendly approach for liquid fuel production, departing from conventional energy-intensive methods. While EC syngas generation is wellexplored, the synthesis of F-T chemistry using CO₂ and CO feed gases remains relatively unexplored. Investigating various transition metals, including Ti, Zr, V, Mo, Fe, Co, Ni, Pd, Cu, Ag, Au, Zn, and Cd, we present compelling evidence of F-T chemistry, yielding long-chain hydrocarbons (CnH₂n and CnH₂n+2, n=2–7), with Zn being an exception. This breakthrough involves surface C-C coupling chain growth, resembling traditional F-T synthesis, incorporating *CO and *CHx insertion reactions. Density of states and energy states near the Fermi level were analyzed. The experimental framework enhances our understanding of C-C coupling mechanisms, offering insights into environmentally friendly EC methods for long-chain hydrocarbon production and advancing innovative strategies in sustainable F-T synthesis for future energy solutions.

221

Exploring Pd-Ag/Cu electrodes in electrochemical CO₂ reduction: Insights into C₁, C₂, and C₃+ chemistry

Gaeun Yun; Seon Young Hwang; So Young Kim; Yunji Gwon; Sooyeon Bae; Choong Kyun Rhee; Youngku Sohn

Appl. Surf. Sci. 2024, 665, 160279. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

이중금속 합금 전극은 광범위하게 연구되어 왔으며, 전기화학적(EC) 이산화탄소 환원을 위한 실용 전극 개발 후보로 여러 금속 원소가 주목받고 있다. 이를 위해서는 C₁ 화학, C₂ 및 C₃+ 생성물로 이어지는 C-C 결합, 전극 개발에 대한 이해가 중요하다. 본 연구에서는 Pd와 Ag를 동시 스퍼터 증착하여 Pd-Ag/Cu 전극을 제조하였다. Pd-Ag 개질에 따른 C₁, C₂ 및 C₃+ 생성물과 이들의 상호관계를 조사하기 위해 EC CO₂ 환원 성능을 평가하였다. KHCO₃, 인산염 및 KOH의 세 전해질에서 표면층 금속은 CH₄, C₂H₄, C₃+ 탄화수소 및 프로판올 생성을 향상시키는 반면 에탄올과 폼산염 생성을 억제하였다. 이러한 결과는 인가 전위와 반복 사용 과정에 크게 의존하였다. CH₄ 및 C₂H₄의 생성 기작은 C₂H₆ 및 C₃+ 탄화수소와 달랐으며, 후자는 Fischer-Tropsch(FT) 화학과 앤더슨-슐츠-플로리 식 분석으로 설명하였다. EC CO 환원은 주로 FT 화학으로 이어졌다. 이 연구는 EC CO₂ 환원에서 서로 연결된 C₁, C₂ 및 C₃+ 화학을 더 깊이 이해하게 하고 합금 전극 개발의 발전 가능성을 제시한다.

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원문 (English) ▾

Bimetallic alloy electrodes have been extensively investigated, with multiple metal elements emerging as candidates for developing practical electrodes in electrochemical (EC) CO₂ reduction. Understanding C₁ chemistry, C–C coupling leading to C₂ and C₃+ products, and electrode development is crucial for this purpose. In this study, Pd-Ag/Cu electrodes were prepared through the co-sputter deposition of Pd and Ag. These electrodes were tested in EC CO₂ reduction to examine the products associated with C₁, C₂, and C₃+, along with exploring their relationships over the Pd-Ag modification. In three different electrolytes—KHCO₃, phosphate, and KOH—the presence of overlayer metals enhanced the production of CH₄, C₂H₄, C₃+ hydrocarbons, and propanol, while inhibiting ethanol and formate. These outcomes were found to be highly dependent on applied potential and recycling processes. The production mechanisms for CH₄ and C₂H₄ appeared distinct from those of C₂H₆ and C₃+ hydrocarbons, which were elucidated through Fischer-Tropsch (FT) chemistry and Anderson-Schulz-Flory equation analysis. EC CO reduction predominantly led to FT chemistry. These studies offer deeper insights into the interconnected C₁, C₂, and C₃+ chemistry in EC CO₂ reduction, contributing to enhanced understanding and potential advancements in alloy electrode development.

220

Exploring Direct Electrochemical Fischer–Tropsch Chemistry of C₁–C₇ Hydrocarbons via Perimeter Engineering of Au–SrTiO₃ Catalyst

Ju Hyun Yang; Gi Beom Sim; So Jeong Park; Choong Kyun Rhee; Chang Woo Myung; Youngku Sohn

Adv. Energy Mater. 2024, 14, 2402062. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Traditionally, Fischer–Tropsch (FT) synthesis is performed using thermal catalysts and syngas (CO and H 2 ) under high‐pressure and high‐temperature conditions. However, this study introduces an approach that relies on FT chemistry assisted by electrochemistry, referred to here as direct electrochemical (EC) FT chemistry, under ambient conditions. A series of CH 4 , C n H 2n , and C n H 2n+2 hydrocarbons (n = 1–7) is successfully produced over gold (Au) nanoparticle‐loaded perovskite strontium titanate (SrTiO 3 ) nanostructures grown on rutile TiO 2 supported on Ti. Au (1.0 nm)–SrTiO 3 shows the best interface formation, with the highest Faradaic efficiency for C 2+ hydrocarbons. This direct EC‐FT process proceeds via a C─C coupling chain growth reaction at the Au‐SrTiO 3 interface as evidenced by the hydrocarbon weight distribution analysis and density functional theory calculations. The robust combination of experimental and computational findings reveals that optimum conditions for producing surface hydrogenation and C─C coupling polymerization, initiated by surface * CO and * H are achieved by controlling the undercoordinated Au at the perimeter sites of supported Au nanoparticles and by ensuring a harmonized density of states between Au and SrTiO 3 . This EC‐FT process opens a promising avenue for the direct conversion of CO 2 and H 2 O into value‐added long‐chain hydrocarbons.

219

Electrochemical CO₂ and CO reduction using Au/TiO₂ model catalysts for syngas and Fischer-Tropsch chemistry

So Young Kim; Seon Young Hwang; Gaeun Yun; Yunji Gwon; Sooyeon Bae; Choong Kyun Rhee; Youngku Sohn

Int. J. Hydrogen Energy 2024, 80, 754-770. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

Au/TiO₂ 모델 촉매는 다양한 응용 분야에서 널리 연구되어 왔지만, 전기화학적 CO₂ 및 CO 환원(EC CO₂R 및 COR)에서의 활용은 충분히 탐구되지 않았다. 본 연구에서는 먼저 레이저 보조법으로 금속 Ti 위에 루타일 TiO₂를 형성하고 이어서 표면에 Au를 스퍼터링하는 2단계 공정으로 Au/TiO₂/Ti 시스템을 제조하였다. KHCO₃와 인산염의 농도, 인가 전위, Au 표면층 두께 및 Ti 기반 촉매의 레이저 처리 조건을 변화시켰다. 주생성물은 실험 조건에 따라 비율이 달라지는 합성가스(CO와 H₂)였으며, 액상 폼산염과 기타 탄화수소도 검출되었다. 또한 *CO 및 H*와 같은 표면 화학종이 C-C 결합을 촉진하는 역할을 조사하고 전통적 Fischer-Tropsch(FT) 합성과 비교하였다. X선 광전자 분광법(XPS)과 자외선 광전자 분광법(UPS)을 포함한 분광 분석을 이용하여 계면 전자 구조, 산화 상태 및 전기화학 처리 후 표면층 안정성을 조사하였다. 이 연구는 Au/Ti 전극에서 EC CO₂R 및 COR 기작에 대한 이해를 높이고, 합성가스 생산과 직접 F-T 화학의 촉매 효율을 향상시키기 위한 전극 설계 및 운전 조건 최적화에 유용한 통찰을 제공한다.

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원문 (English) ▾

The Au/TiO₂ model catalyst has been extensively studied across various applications, yet its utilization in electrochemical CO₂ and CO reduction (EC CO₂R and COR) remains underexplored. In this study, we employed the Au/TiO₂/Ti system, prepared via a two-step process: initially forming rutile TiO₂ on metallic Ti through laser-assisted methods, followed by sputtering Au onto the surface. The experimental conditions included varying concentrations of KHCO₃ and phosphate, applied potentials, Au overlayer thickness, and laser treatment parameters for the Ti-based catalysts. The major products detected were syngas (CO and H₂), which varied with experimental settings, along with liquid formate and other hydrocarbons. The study also examined the role of surface species like *CO and H* in facilitating C–C coupling, drawing parallels to traditional Fischer-Tropsch (FT) synthesis. Spectroscopic analyses, including XPS and UPS, were utilized to investigate interfacial electronic structures, oxidation states, and overlayer stability post-electrochemical processing. This research contributes to a deeper understanding of EC CO₂R and COR mechanisms on Au/Ti electrodes, providing valuable insights into optimizing electrode design and operational conditions for enhanced catalytic efficiency in syngas production and direct F-T chemistry.

218

Perovskite oxide nanoparticles: Dual role as supports for luminescent Eu(III) ions and photocatalysts for bisphenol degradation

So Young Kim; Ju Young Maeng; Seon Young Hwang; Hyojin Hwang; Soohoon Choi; Jeongkwon Kim; Mohammad Mansoob Khan; Youngku Sohn

Materials Chemistry and Physics 2024, 322, 129554. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

CaTiO₃, SrTiO₃ 및 BaTiO₃와 같은 페로브스카이트 산화물은 발광 지지체와 광촉매 물질의 두 역할로 큰 주목을 받고 있다. 본 연구에서는 열 소성법으로 페로브스카이트 산화물 나노입자(NP)를 합성하고, UVC 조사 하에서 비스페놀 S(BPS)와 비스페놀 AF(BPAF)를 분해하는 광촉매로 사용하였다. 합성한 광촉매의 광촉매 분해 과정을 면밀히 조사하고, 생성된 이차 생성물은 액체 크로마토그래피-고분해능 질량분석법으로 확인하였다. BPS는 BPAF보다 상대적으로 더 빠르게 광촉매 분해되었다. 페로브스카이트 산화물 가운데 SrTiO₃는 BPS 분해에서 가장 높은 촉매 활성을 보였고, BaTiO₃는 BPAF 분해에서 가장 우수하였다. 또한 페로브스카이트 산화물 NP를 Eu₃+ 이온 도핑용 지지체로 사용하여 형광체를 제조하였다. 5D₀→7FJ(J=0-4) 전이에 해당하는 Eu₃+ 이온의 발광이 관찰되었으며 지지체 물질에 따라 달라졌다. 특히 CaTiO₃ 나노입자에 도핑된 Eu₃+가 가장 높은 발광 효율을 보였다. 이 결과는 페로브스카이트 산화물 기반 물질이 형광체와 광촉매로 동시에 기능함을 보여주며, 발광 효율 향상과 비스페놀 처리에 활용할 수 있는 가능성에 유용한 통찰을 제공한다.

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원문 (English) ▾

Perovskite oxides, such as CaTiO₃, SrTiO₃, and BaTiO₃, have gained significant recognition for their dual role as luminescence supports and photocatalytic materials. In this study, we synthesized perovskite oxide nanoparticles (NPs) using the thermal calcination method and employed them as photocatalysts for the degradation of bisphenol S (BPS) and bisphenol AF (BPAF) under UVC irradiation. The as-synthesized photocatalysts were thoroughly examined for the photocatalytic degradation process and identified secondary products were identified using liquid chromatography in conjunction with high-resolution mass spectrometry. Our observations highlighted the relatively faster photocatalytic degradation of BPS compared to BPAF. Notably, among the perovskite oxide materials, SrTiO₃ exhibited the highest catalytic activity for BPS degradation, while BaTiO₃ outperformed in the case of BPAF degradation. Perovskite oxide NPs were also utilized as supports for doping with Eu₃+ ions to create phosphor supports. Luminescent emissions from the Eu₃+ ions, characterized by the 5D₀ → 7FJ = 0-4 transitions, were observed and varied depending on the support material. Notably, Eu₃+ doped in CaTiO₃ nanoparticles exhibited the highest luminescence efficiency. These results highlight the dual functionality of perovskite oxide-based materials in phosphor applications and photocatalysis, offering valuable insights into their potential for both enhancing luminescence efficiency and treating bisphenols.

217

Electrocatalytic CO₂ Reduction for Dynamic C₁, C₂, and C₃+ Chemistry over Electrodeposited Zn on Cu and CuZn Mesh Supports

Sooyeon Bae; Seon Young Hwang; Gaeun Yun; Yunji Gwon; So Young Kim; Choong Kyun Rhee; Youngku Sohn

Energy & Fuels 2024, 38, 15497-15514. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

The electrodeposition of Cu and Zn onto bare Cu and CuZn mesh supports offers a straightforward method for fabricating novel electrodes for electrochemical CO 2 reduction (EC CO 2 R). This study evaluates the performance of these modified electrodes by assessing their Faradaic efficiency (FE) under various conditions including different electrolytes, concentrations, applied potentials, recycling effects, and Nafion treatment. The reduction products were categorized into several groups: C 1 gaseous products (CO and CH 4 ), C 2 gaseous products (C 2 H 4 and C 2 H 6 ), C 3,4 hydrocarbons, major C 1 /C 2 /C 3 liquid products (formate, ethanol, and propanol), and minor C 1 /C 2 /C 3 liquid products (methanol, acetate, acetaldehyde, and isopropanol). We evaluated their dynamic FE variations under various experimental conditions. The production of C 2+ hydrocarbons through EC CO 2 R was found to be analogous to conventional Fischer–Tropsch synthesis, highlighting the pivotal roles of *CO and *CH x intermediates. This study’s insights into the dynamic variations of C 1, C 2, and C 3+ product chemistry aid in the further development of Zn and Cu-based electrocatalysts.

216

Gaseous ozone inactivation of Bacillus atrophaeus spores on ceramic and porcelain tiles

Dokyung Kwon; Yongju Jo; Youngku Sohn; Jeongkwon Kim

Journal of Analytical Science and Technology 2024, 15, 43. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

In this study, we investigated the ozone inactivation efficiency of Bacillus atrophaeus spores attached to various tile surfaces. Eight different types of tiles were employed, considering factors such as porosity (ceramic, porcelain), color (white, black), and glossiness (matte, glossy). Inactivation was performed by exposing the spore-loaded tiles to ozone gas for a specified duration. The inactivation efficiencies of ozone gas on different tile surfaces were compared by analyzing the colony-forming units of desorbed Bacillus atrophaeus cultured in a growth medium. Results revealed a reduction in colony counts with increasing ozone exposure time, indicating a proportional enhancement in inactivation effectiveness on ozone exposure time. After exposure to ozone gas for 30 min or longer, more than 90% of spores on each tile were inactivated. Regarding porosity, ceramic tiles exhibited slightly superior inactivation effects compared to porcelain tiles. Additionally, in terms of glossiness, glossy tiles demonstrated better inactivation effects than matte tiles. However, no significant differences were observed in inactivation effects based on the color of the tiles.

215

Electrochemical CO₂/CO reduction on Ag/Cu electrodes and exploring minor Fischer–Tropsch reaction pathways

Gaeun Yun; Seon Young Hwang; Ju Young Maeng; Young Jun Kim; Choong Kyun Rhee; Youngku Sohn

Appl. Surf. Sci. 2024, 649, 159179. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

Ag/Cu 하이브리드는 전기화학적(EC) CO₂ 환원에서 효율이 높고 우수한 C-C 결합 생성물을 만드는 촉매로 부상하였다. 본 연구에서는 스퍼터 증착으로 제조한 Ag/Cu 전극을 사용하여 EC CO₂ 및 CO 환원 가능성을 조사하였다. Ag 두께는 생성되는 기체 및 액체 생성물에 큰 영향을 미쳤으며, Ag/Cu 계면이 핵심 역할을 하였다. CO₂ 포화 조건에서는 CO, CH₄ 및 C₂H₄가 높은 패러데이 효율로 생성되었고, CO₂로 포화된 KHCO₃에서는 폼산염, 에탄올, 프로판올, 아이소프로판올, 아세트산염 및 아세톤이 생성되었다. 인산염 조건에서는 Fischer-Tropsch 화학의 전형적 생성물인 장쇄 탄화수소(CnH₂n 및 CnH₂n+2, n=2-7)로 이어지는 새로운 경로가 확인되었다. 또한 CO 수소화를 통해 CH₄ 및 C₂-7 탄화수소가 생성됨을 보였으며, 알케인/알켄 비는 전해질의 종류와 농도, 인가 전위 및 Ag로 개질된 Cu에 따라 달라졌다. 이 결과는 에너지와 환경 응용뿐 아니라 C-C 결합을 통한 EC CO₂ 및 CO 환원의 발전에 시사점을 제공한다.

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원문 (English) ▾

Ag/Cu hybrids have emerged as highly efficient catalysts for electrochemical (EC) CO₂ reduction, yielding impressive C–C coupling products. We investigate Ag/Cu electrodes prepared via sputter deposition to explore their potential in EC CO₂ and CO reductions. Our study highlights the significant impact of Ag thickness on resulting gas and liquid products, emphasizing the vital role of the Ag/Cu interface. Under CO₂-saturated conditions, CO, CH₄, and C₂H₄ are produced with high Faradaic efficiencies, while CO₂-saturated KHCO₃ generates formate, ethanol, propanol, isopropanol, acetate, and acetone. Experiments in phosphate conditions reveal new pathways for long-chain hydrocarbons (CnH₂n and CnH₂n+2, n = 2–7), typical products of Fischer-Tropsch chemistry. We also demonstrate CO hydrogenation to CH₄ and C₂-7 hydrocarbons, with alkane/alkene ratios influenced by electrolyte nature, concentration, applied potential, and Ag-modified Cu. These insights have implications for energy, environmental applications, and the future of EC CO₂ and CO reduction through C–C coupling.

214

Cadmium sulfides: Electrochemical CO₂ reduction and Fischer–Tropsch synthesis pathways

Ju Young Maeng; Seon Young Hwang; So Young Kim; Choong Kyun Rhee; Youngku Sohn

J. Environ. Chem. Eng. 2024, 12, 111645. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

전기촉매 개발은 전기화학적(EC) 이산화탄소 재활용 기술을 발전시키는 핵심 요소이다. 본 연구에서는 카드뮴(Cd) 지지체 위에 황화 카드뮴(CdS)을 도입하고, 이어서 스퍼터 증착으로 Au, Ag 및 Cu를 증착하여 촉매를 개질하였다. 개질 촉매의 EC CO₂ 환원 성능을 엄밀하게 평가한 결과, 주생성물은 폼산염, CO 및 H₂였다. 특히 CdS/Cd는 개질하지 않은 Cd 촉매보다 훨씬 우수한 EC CO₂ 환원 성능을 보였다. 전이금속 증착은 H₂ 생성을 크게 억제했으며, NaHCO₃ 조건에서 Ag와 Cu 증착은 CO 생성을 향상시켰다. 인산염 조건의 Au/CdS/Cd에서는 CH₄와 알케인 우세 C₂-7 탄화수소가 상당량 생성되었고, 이는 전통적인 Fischer-Tropsch 합성 경로로 설명하였다. EC CO₂ 환원 후 CdS/Cd 표면은 정육면체 형태의 CdCO₃로 재결정화되었다. CdS/Cd에서의 광촉매 CO₂ 환원은 CO, CH₄, CH₃OH 및 알켄 우세 C₂-6 탄화수소를 생성하였다. 또한 Zn 전극 위에 황화 아연(ZnS)을 제조하여 평가한 결과 H₂와 CO가 주생성물이었고 폼산염은 관찰되지 않았다.

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원문 (English) ▾

The development of electrocatalysts is a pivotal aspect of advancing electrochemical (EC) CO₂ recycling. In this research, we incorporated cadmium sulfide (CdS) onto a cadmium (Cd) support and subsequently enhanced it with the deposition of Au, Ag, and Cu using sputter deposition techniques. These modified catalysts were then rigorously evaluated for their performance in EC CO₂ reduction. The primary products were formate, CO, and H₂. Notably, CdS/Cd demonstrated significantly superior performance in EC CO₂ reduction compared to the unmodified Cd catalyst. Furthermore, the deposition of transition metals drastically suppressed H₂ production, while Ag and Cu deposition enhanced CO production in NaHCO₃ conditions. For Au/CdS/Cd in phosphate condition, CH₄ and alkane-dominant C₂–7 hydrocarbons were significantly produced and explained by the conventional Fischer-Tropsch synthesis paths. After EC CO₂ reduction, CdS/Cd surface was observed to be recrystallized to CdCO₃ with a morphology of cubes. Photocatalytic CO₂ reduction over CdS/Cd produced CO, CH₄, CH₃OH, and alkene-dominant C₂–6 hydrocarbons. Additionally, a zinc sulfide (ZnS) on Zn electrode was prepared and tested, which showed H₂ and CO as main products, but no formate was observed.

213

Ultraviolet Light‐Assisted Decontamination of Chemical Warfare Agent Simulant 2‐Chloroethyl Phenyl Sulfide on Metal‐Loaded TiO₂/Ti Surfaces

Hye Ji. Jang; Gaeun Yun; Huieun Shim; Seon Young Hwang; So Young Kim; Jeongkwon Kim; Heesoo Jung; Mohammad Mansoob Khan; Youngku Sohn

ChemistryOpen 2024, 13, e202300246. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

The application of ultraviolet (UV) light for the decontamination of chemical warfare agents (CWAs) has gained recognition as an effective method, especially for treating hard‐to‐reach areas where wet chemical methods are impractical. In this study, TiO 2 /Ti was employed as a model catalyst, which was contaminated with 2‐chloroethyl phenyl sulfide (CEPS), and subjected to photocatalytic decontamination using both UVB and UVC light. Additionally, photocatalytic decontamination efficiency by introducing Au, Pt, and Cu onto the TiO 2 /Ti surface was explored. During the photodecomposition process under UVC light, at least eight distinct secondary byproducts were identified. It was observed that the introduction of overlayer metals did not significantly enhance the photodecomposition under UVC light instead overlaid Au exhibited substantially improved activity under UVB light. Whereas, photodecomposition process under UVB light, only five secondary products were detected, including novel compounds with sulfoxide and sulfone functional groups. This novel study offers valuable insights into the generation of secondary products and sheds light on the roles of overlayer metals and photon wavelength in the photodecontamination process of CWA.

212

Opening Direct Electrochemical Fischer–Tropsch Synthesis Path by Interfacial Engineering of Cu Electrode with P-Block Elements

Ju Hyun Yang; Seon Young Hwang; Ju Young Maeng; Go Eun Park; Seo Young Yang; Choong Kyun Rhee; Youngku Sohn

ACS Applied Materials & Interfaces 2024, 16, 3368-3387. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

The electrochemical synthesis of syngas (CO and H 2 ) has garnered considerable attention in the context of Fischer–Tropsch (FT) synthesis employing thermal catalysts. Nonetheless, the need for a novel, cost-effective technique persists. In this investigation, we introduce a direct electrochemical (dEC) approach for FT synthesis that functions under ambient conditions by utilizing a p-block element (Sn and In) overlaid Cu electrode. Surface *CO and H* species were obtained in an electrolytic medium through the CO 2 + H + + e – → HOOC ad → *CO (or direct CO adsorption) and H + + e – → H* reactions, respectively. We have observed C 2–7 long-chain hydrocarbons with a C n H 2 n +2 /C n H 2 n ratio of 1–3, and this observation can be explained through the process of C–C coupling chain growth of the conventional FT synthesis, based on the linearity of the Anderson-Schulz–Flory equation plots. Thick Sn and In overlayers resulted in the dominant production of formate, while CO and C 2 H 4 production were found to be proportional and inversely correlated to H 2, C 2 H 6, and C 3–7 hydrocarbon production. The EC CO 2 /CO reduction used in dEC FT synthesis offers valuable insights into the mechanism of C 2+ production and holds promise as an eco-friendly approach to producing long-chain hydrocarbons for energy and environmental purposes.

211

CuNiZn vs CuZn Electrodes: Electrochemical CO₂ Reduction, Role of Metal Elements, and Insights for C–C Coupling Chemistry

Yunji Gwon; Seon Young Hwang; Go Eun Park; Sooyeon Bae; Gaeun Yun; Choong Kyun Rhee; Youngku Sohn

ACS Appl. Energy Mater. 2024, 7, 614-628. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Exploring bi- and trimetallic catalysts in electrochemical CO 2 reduction (EC CO 2 R) has been a focal point for discovering reduction products. This study investigates the distinct roles of metal elements in the CO 2 R using CuNiZn and CuZn electrodes. Bimetallic CuZn exhibits superior electrochemical activity, yielding substantial amounts of CO, CH 4, C 2 H 4, and various liquid products, including formate, ethanol, acetate, propanol, and isopropanol. The study on trimetallic CuNiZn suggests potential connections to Fischer–Tropsch (FT) synthesis, indicating their capability to produce long-chain hydrocarbons (C n H 2 n and C n H 2 n +2, n = 2–7) from CO 2 . EC CO reduction validated the FT process over the bi- and trimetallic catalysts. The discussion explores mechanisms for the formation of CO, CH 4, and C–C coupled C 2+ products, considering potential- and concentration-dependent Faradaic efficiencies (FEs). Recycling tests emphasize the influence of metal composition on FEs. Surface analyses reveal oxidation states and compositional changes, while the dissolution of metals during electrochemistry highlights dynamic surface characteristics. This work provides insights into the metal composition of bi- and trimetallic catalysts, surface states, and electrochemical conditions, advancing our understanding of these electrodes and their role in CO 2 recycling through electrochemistry.

210

Electrochemical syngas production over Au/SrTiO₃ and Fischer–Tropsch synthesis chemistry for long-chain hydrocarbons

So Young Kim; Seon Young Hwang; Ju Young Maeng; Choong Kyun Rhee; Youngku Sohn

Int. J. Hydrogen Energy 2024, 51, 571-587. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

합성가스(CO와 H₂의 혼합물)는 Fischer-Tropsch(F-T) 합성을 통한 액체 연료 생산에 산업적으로 사용되어 왔다. 전통적인 합성가스 생산법은 석탄, 천연가스 또는 바이오매스를 사용하는 에너지 집약적 공정이다. 보다 친환경적인 공정을 위해 전기화학이 대안으로 부상하였다. 본 연구에서는 Au를 담지한 페로브스카이트 타이타늄산 스트론튬(SrTiO₃) 촉매를 사용하여 전기화학적(EC) CO₂ 전환으로 합성가스를 효율적으로 생산할 수 있음을 보였다. Au 표면층 두께, 인가 전위, 전해질 종류 및 농도와 같은 여러 변수를 조절하여 CO/H₂ 비를 쉽게 제어할 수 있었다. 또한 전기화학이 F-T 합성 공정의 소수 경로를 직접 개시할 수 있음을 확인하였다. CO 포화 전해질에서도 EC F-T 공정이 나타났으며, CO 분자가 직접 흡착하여 표면 H와 반응해 탄화수소를 생성하였다. 앤더슨-슐츠-플로리 식 분석은 강한 선형 관계를 보여 EC F-T 합성이 전통적 F-T 합성 기작을 따름을 확인하였다. 이 새로운 실증은 EC 합성가스 생산 기술 개발에 유용한 통찰을 제공할 뿐 아니라 C₂+ 탄화수소 생성 기작에 대한 이해를 높인다.

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원문 (English) ▾

Syngas (a mixture of CO and H₂) has been utilized in industrial settings for the production of liquid fuels through Fischer-Tropsch (F-T) synthesis. The conventional methods of producing syngas involve energy-intensive processes utilizing coal, natural gas, or biomass. However, in order to promote more environmentally friendly practices, electrochemistry has emerged as an alternative approach. In this study, we demonstrate that syngas can be efficiently produced through electrochemical (EC) CO₂ conversion using Au-loaded perovskite strontium titanate (SrTiO₃) as a catalyst. By manipulating various parameters such as overlayer Au thickness, applied potential, electrolyte type, and concentration, we can easily control the ratio of CO to H₂. Moreover, our findings reveal that electrochemistry can directly initiate the minor channel of the F-T synthesis process. We also observe the occurrence of the EC F-T process in CO-saturated electrolyte, where CO molecules directly adsorb and interact with surface H to generate hydrocarbons. The analysis of the Anderson-Schulz-Flory equation demonstrates a strong linear relationship, confirming that the EC F-T synthesis follows the conventional F-T synthesis mechanism. This novel demonstration not only offers valuable insights into the development of EC syngas production but also enhances our understanding of the mechanism behind the formation of C₂+ hydrocarbon products.

2023

209

Electrochemical reduction of CO₂ and CO using interface-engineered Au/Ti electrodes for long-chain hydrocarbon production

Young Jun Kim; Ju Young Maeng; Seon Young Hwang; Choong Kyun Rhee; Youngku Sohn

Appl. Catal. B 2023, 338, 123017. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

본 연구는 계면 공학으로 제조한 Au/Ti 전극을 사용한 CO₂ 및 CO의 전기화학적 환원을 보여준다. 표면 CO 형성 경로로 CO의 직접 흡착과 CO₂ 조건에서의 간접 과정이 제안되었다. 표면 H는 H+/H₂O로부터 형성되었다. 표면 CO와 H 사이의 Fischer-Tropsch 합성을 모사하여 CH₄와 탄화수소(CnH₂n 및 CnH₂n+2, n=2-7)를 생산하였다. CO의 패러데이 효율은 Au 피복률이 증가할수록 높아져 38%에 도달하였다. CO₂로 포화된 KHCO₃에서는 Au 피복률이 낮은 Au/Ti 전극에서 장쇄 탄화수소가 생성되었다. CO₂ 및 CO로 포화된 인산염 전해질에서는 Au 피복률이 높을수록 장쇄 탄화수소 생산량이 증가하였다. 알케인/알켄 비는 Au 피복률이 증가할수록 높아졌지만 인가 전위가 커질수록 낮아졌다. 이 연구는 계면 공학, 전기화학적 장쇄 탄화수소 생산 및 C-C 결합 기작에 관한 통찰을 제공한다.

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원문 (English) ▾

This study demonstrates the electrochemical reduction of CO₂ and CO using interface-engineered Au/Ti electrodes. Direct adsorption of CO and indirect processes in CO₂ conditions were proposed to form surface CO. Surface H was formed from H+/H₂O. Mimicking Fischer-Tropsch synthesis between surface CO and H resulted in the production of CH₄ and hydrocarbons (CnH₂n and CnH₂n+2, n = 2–7). Faradaic efficiency of CO increased with increasing Au coverage and reached 38%. In CO₂-saturated KHCO₃, long-chain hydrocarbon production was observed on Au/Ti electrodes with low Au coverage. In CO₂ and CO-saturated phosphate electrolytes, higher Au coverage resulted in higher production of long-chain hydrocarbons. The ratio of alkanes to alkenes increased with increasing Au coverage but decreased with applied potential. The study provides insights into interface engineering, electrochemical long-chain hydrocarbon production, and C-C coupling mechanisms.

208

Unlocking long-chain hydrocarbons (C₂–7) via direct electrochemical CO₂ and CO reduction on balanced Au/Ni electrodes

Young Jun Kim; Ju Young Maeng; Seon Young Hwang; Ju Hyun Yang; Ilsun Yoon; Chang Woo Myung; Choong Kyun Rhee; Youngku Sohn

Nano Energy 2023, 118, 108995. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

전기화학적(EC) 이산화탄소 환원법은 녹색에너지 및 환경 문제 해결 전략으로 널리 활용되어 왔다. 본 연구에서는 직접 전기화학적 Fischer-Tropsch(dEC F-T) 합성 경로라는 새로운 개념을 보여주기 위해 Au/Ni 전극을 사용하였다. 이 경로는 EC CO₂ 환원 중 H₂와 CO, 즉 합성가스를 만드는 전극 특성을 결합한다. Ni 전극 표면에 Au를 도입하자 CO 생산은 증가하고 H₂ 생산은 점차 감소하였다. 계면의 균형이 맞았을 때 뚜렷한 F-T 합성 경로가 나타나 일련의 탄화수소(CnH₂n 및 CnH₂n+2, n=2-7)가 생성되었다. dEC F-T 합성은 전해질, 농도, 금속 지지체(Co와 Fe), 여러 표면층 금속(Ag와 Cu), 광조사 및 동위원소 효과 등 다양한 조건에서 평가하였다. 앤더슨-슐츠-플로리 질량 분포 분석을 바탕으로 표면 C-C 결합 중합 반응을 통해 공정을 설명하였다. 또한 CO와 H의 직접 흡착을 이용한 EC CO 환원에서도 F-T 합성을 입증하였다. dEC F-T 경로는 고부가가치 장쇄 탄화수소를 생산하여 에너지 및 환경 문제를 해결할 수 있는 새로운 전략을 제공한다.

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원문 (English) ▾

Electrochemical (EC) CO₂ reduction method has been widely used as a green energy and environmental solution strategy. The use of Au/Ni electrodes was introduced to showcase a new concept of the direct EC Fischer-Tropsch (dEC F-T) synthesis pathway. This pathway involves the combination of electrodes that produce H₂ and CO (syngas) during electrochemical CO₂ reduction. The introduction of Au on the Ni electrode surface led to an increase in CO production and a gradual decrease in H₂ production. When the interface was balanced, a pronounced F-T synthesis pathway was observed, resulting in the production of a series of hydrocarbons (CnH₂n and CnH₂n+2, n = 2–7). The dEC F-T synthesis was evaluated under different conditions, including electrolytes, concentrations, metal supports (Co and Fe), various overlayer metals (Ag and Cu), light irradiation, and isotope effects. The process was elucidated through surface C-C coupling polymerization reactions based on Anderson-Schulz-Flory weight distribution analysis. Additionally, the F-T synthesis was demonstrated through EC CO reduction via direct CO and H adsorption. The dEC F-T path provides a novel strategy for energy and environment by producing high-value long-chain hydrocarbons.

207

Ag–Sb/Cu by Galvanic Replacement: Electrochemical CO₂ Reduction and Unveiling C₃+ Hydrocarbon Pathways

Sooyeon Bae; Seon Young Hwang; Gaeun Yun; Yunji Gwon; So Young Kim; Choong Kyun Rhee; Youngku Sohn

J. Phys. Chem. C 2023, 127, 23601-23617. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Ag/Cu electrodes have garnered substantial attention as extensively explored bimetallic catalysts in electrochemical (EC) CO 2 reduction, demonstrating efficient C–C coupled production. In this study, we broaden the horizon by introducing antimony (Sb) through galvanic replacement, resulting in the formation of Ag–Sb–Cu mesh electrodes. We systematically investigate the synergistic effects of this ternary system on EC CO 2 reduction, delving into various experimental conditions such as applied potentials, electrolytes, concentrations, and diverse modifications to the electrodes. The primary reduction products identified include CO, formate, CH 4, C 2 H 4, ethanol, and propanol. The incorporation of Sb and Ag on Cu significantly enhances the yields of the C 1, C 2, and C 3 products. Additionally, we consistently identify and comprehend the reaction pathway leading to alkene-dominant C 3+ hydrocarbons through the conventional Fischer–Tropsch synthesis mechanism. These findings illuminate the intricate interplay among the three metals, offering valuable insights for optimizing the catalytic performance in enhanced CO 2 reduction.

206

Construction of type-II SnO₂/InGaN nanorods heterostructure toward high photoelectrochemical performance

C. Thota; S. Ramu; C. Gangadhara; G. Murali; J. H. Yang; D. P. Upare; N.-H. Bak; Y. K. Kshetri; Y. Sohn; M. Reddeppa; M.-D. Kim

Appl. Phys. Lett. 2023, 123, 203903. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Exploring highly efficient and stable photoelectrode material is essential for high-performance photoelectrochemical (PEC) water-splitting applications. III-nitride semiconductors, particularly InGaN, have been considered as prospective materials for PEC hydrogen evolution. However, their surface states and other recombination centers, which enhance the charge recombination kinetics, are bottlenecks for the high PEC performance. In this work, we report the construction of type-II heterojunction by sputter depositing SnO₂ on InGaN nanorods (NRs) to promote interfacial carrier transport and thereby enhance PEC performance. The energy band offsets at the SnO₂/InGaN NRs interface were analyzed by x-ray photoelectron spectroscopy. Type-II heterojunction was defined at the SnO₂/InGaN NRs interface with a valence band offset of 0.77 eV and conduction band offset of 0.25 eV. The photocurrent density of the SnO₂/InGaN NRs photoanode is 7.09 mA/cm₂ at 0.77 V vs Ag/AgCl electrode with 80 nm SnO₂ thickness, which is ∼14-fold higher than that of the pristine InGaN NRs photoanode. Furthermore, the applied bias photo-to-current efficiency of SnO₂/InGaN NRs photoanode records 3.36% at 0.77 V vs Ag/AgCl electrode. The enhanced PEC performance is mainly ascribed to the formation of high-quality SnO₂/InGaN NRs heterojunction that enforces the directional charge transfer and substantially boosts the separation of photogenerated electron–hole pairs at the interface of InGaN NRs and SnO₂. Overall, this work sheds light on the promising strategy to design and fabricate III-nitride nanostructures-based photoelectrodes for feasible PEC water-splitting applications.

205

New reaction path for long-chain hydrocarbons by electrochemical CO₂ and CO reduction over Au/stainless steel

Seon Young Hwang; Ju Young Maeng; Go Eun Park; Seo Young Yang; So Young Kim; Choong Kyun Rhee; Youngku Sohn

Chemosphere 2023, 338, 139616. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

The Fischer-Tropsch (F-T) synthesis is recognized for its ability to produce long-chain hydrocarbons. In this study, we aimed to replicate F-T synthesis using electrochemical CO₂ reduction and CO reduction reactions on a stainless steel (SS) support with a gold (Au) overlayer. Under CO₂-saturated conditions, the presence of Au on the SS surface led to the formation of CH₄ and a range of hydrocarbons (CnH₂n and CnH₂n+2, n = 2-7), while bare SS primarily produced hydrogen. The Au(10 nm)/SS exhibited the highest hydrocarbon production in CO₂-saturated phosphate, indicating a synergistic effect at the Au-SS interface. In CO-saturated conditions, bare SS also produced long-chain hydrocarbons, but increasing Au thickness resulted in decreased production due to poor CO adsorption. Hydrocarbons were formed through both direct and indirect CO adsorption pathways. Anderson-Schulz-Flory analysis confirmed surface CO hydrogenation and C-C coupling polymerization following conventional F-T synthesis. The C₂ hydrocarbons exhibited distinct behavior compared to C₃-5 hydrocarbons, suggesting different reaction pathways. Despite low reduction product levels, our EC method successfully replicated F-T synthesis using the Au/SS electrode, providing valuable insights into C-C coupling mechanisms and electrochemical production of long-chain hydrocarbons. Depth-profiling X-ray photoelectron spectroscopy revealed significant changes in surface elemental compositions before and after EC reduction.

204

Electrochemical CO₂ reduction on tin and its alloys: Insights from depth-profiling X-ray photoelectron spectroscopy

Seo Young Yang; Ju Young Maeng; Seon Young Hwang; Go Eun Park; Choong Kyun Rhee; Youngku Sohn

J. Alloys Compd. 2023, 960, 170903. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

주석(Sn)과 그 합금은 독특한 p-블록 원소 특성 때문에 전기화학적 이산화탄소 환원(EC CO₂R) 전극으로 널리 사용된다. 본 연구에서는 다양한 조건에서 Sn 및 Sn 합금(SnBi와 SnPb) 전극의 EC CO₂R 성능을 조사하였다. EC CO₂R 전후 전극의 원소 분포는 깊이 방향 X선 광전자 분광법(XPS)으로 분석하였다. Sn과 그 합금은 높은 패러데이 효율과 선택성으로 폼산염/폼산을 효율적으로 생산하였다. Sn, SnBi 및 SnPb 전극의 패러데이 효율은 각각 96%, 93% 및 92%였고, 폼산염 선택성은 99.7%까지 크게 증가하였다. 깊이 방향 XPS 분석에서는 EC CO₂R 후 원소 분포, 산화 상태 및 산화물 층 두께가 크게 변한 것으로 나타났다. 또한 원소 조성은 깊이에 따라 달라졌다. 새롭게 규명한 깊이별 표면 원소 조성과 EC CO₂R 성능은 반응 전후 전극의 계면 전자 구조에 중요한 통찰을 제공한다. 이 결과는 보다 현실적인 전극 이론 모델을 개발하고 실제 응용을 위한 전기화학 공정을 최적화하는 데 중요하다.

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원문 (English) ▾

Tin (Sn) and its alloys are widely used as electrodes for electrochemical CO₂ reduction (EC CO₂R) due to their unique p-block elemental character. In this study, we investigated the performance of Sn and Sn alloys (SnBi and SnPb) electrodes for EC CO₂R under various conditions. The elemental distributions of the electrodes were examined using depth-profiling X-ray photoelectron spectroscopy (XPS) before and after EC CO₂R. Our results demonstrate that Sn and its alloys can efficiently produce formate/formic acid with high Faradaic efficiency and selectivity. The Faradaic efficiency was found to be 96%, 93%, and 92% for Sn, SnBi, and SnPb electrodes, respectively, with a significant increase in formate selectivity to 99.7%. The depth profiling XPS analysis revealed substantial changes in elemental distribution, oxidation state, and oxide layer thickness after EC CO₂R. Additionally, the elemental composition was found to vary with depth. The newly revealed surface elemental composition with depth and the EC CO₂R performance provide valuable insights into the interfacial electronic structure of the electrodes before and after EC CO₂R. These findings are crucial for developing more realistic theoretical models of the electrode and optimizing the electrochemical process for practical applications.

203

Unlocking the potential of gallium for electrochemical CO₂ reduction and the role of overlayer nickel for C C coupling pathways

Young Jun Kim; Gaeun Yun; Ju Young Maeng; Hye Ji Jang; Ilsun Yoon; Chang Woo Myung; Choong Kyun Rhee; Youngku Sohn

J. Ind. Eng. Chem. 2023, 126, 317-326. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

순수 갈륨(Ga)은 녹는점이 실온에 가깝기 때문에 전기화학적 이산화탄소 환원(EC CO₂R) 연구에서 널리 다루어지지 않았다. 그러나 본 연구에서는 금속 Ga를 선택하여 인가 전위, 전해질, 농도 및 광조사 조건을 변화시키며 EC CO₂R을 수행하였다. 폼산염, CO 및 H₂가 주생성물이었으며 그 분포는 사용 조건에 따라 달라졌다. Ga 전극 위에 니켈(Ni)을 도입하자 장쇄 C-C 결합과 Fischer-Tropsch 합성 경로가 열려 C₂-6 장쇄 탄화수소가 생성되었다. 이 연구는 전기화학적 CO₂ 환원에서 Ga를 활용하고 CO₂ 재활용용 Ga 기반 전기촉매를 개발하는 데 새롭고 유용한 통찰을 제공한다.

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원문 (English) ▾

Pure gallium (Ga) is not widely studied for electrochemical CO₂ reduction (EC CO₂R) due to its low melting point near room temperature. However, in this study, metallic Ga was selected and subjected to EC CO₂R under varying conditions of applied potentials, electrolytes, concentrations, and photoirradiation. The results showed that formate, CO, and H₂ were the major products produced and were dependent on the conditions used. The introduction of nickel (Ni) on the Ga electrode was found to open up long chain C-C bond coupling Fischer-Tropsch synthesis pathways, resulting in the production of long-chain C₂-6 hydrocarbons. This research provides new and valuable insights into the use of Ga for electrochemical CO₂ reduction and the development of Ga-based electrocatalysts for CO₂ recycling.

202

Electrochemical CO₂ reduction over surface-modified Cd-based electrodes and reaction paths for long-chain hydrocarbons

Ju Young Maeng; Seon Young Hwang; Choong Kyun Rhee; Youngku Sohn

Appl. Surf. Sci. 2023, 631, 157576. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

전기촉매를 사용하여 CO₂를 유용한 화학물질로 전환하는 방법은 지속 가능한 에너지 및 환경 문제 해결을 위한 유망한 전략이다. 본 연구에서는 카드뮴(Cd)을 여러 전이금속(Ti, Zr, Au, Cu 및 Pt)으로 개질하여 전기화학적 CO₂ 환원 전극으로 사용하였다. CO, H₂ 및 폼산염과 같은 생성물은 인가 전위, 전해질 농도 및 표면층 금속을 포함한 여러 요인에 따라 달라졌다. NaHCO₃ 농도를 높이면 CO와 폼산염 생성은 감소했지만 장쇄 탄화수소(CnH₂n 및 CnH₂n+2, n=2-6)가 생성되었다. Cd 전극 위에 Zr와 Ti를 스퍼터 증착하면 이러한 탄화수소가 더욱 증가했으며, Fischer-Tropsch 합성 기작을 따랐다. 생산 효율은 낮았지만 C-C 결합과 장쇄 탄화수소의 전기화학적 생성 기작을 이해하는 데 중요한 통찰을 제공하였다. 다른 금속(Au, Cu 및 Pt)으로 Cd 표면을 개질하여 생성물을 비교하였고, 전기화학 반응 후 Cd는 직육면체/정육면체 형태의 CdCO₃로 재결정화되었다. 이 결과는 에너지 및 환경 분야를 위한 표면 개질 Cd 기반 전기촉매와 장쇄 탄화수소 생산 기술 개발에 유용한 통찰을 제공한다.

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원문 (English) ▾

Using an electrocatalyst to convert CO₂ into useful chemicals is a promising strategy for sustainable energy and environmental solutions. In this study, cadmium (Cd) was modified with different transition metals (Ti, Zr, Au, Cu, and Pt) and used as an electrode for electrochemical CO₂ reduction. The resulting chemicals produced, such as CO, H₂, and formate, were dependent on various factors, including the applied potential, electrolyte concentration, and overlayer metal. By increasing the NaHCO₃ concentration, the production of CO and formate decreased, but long-chain hydrocarbons (CnH₂n and CnH₂n+2, n = 2–6) were produced. These hydrocarbons were further increased by sputter deposition of Zr and Ti on the Cd electrode, which followed a Fischer-Tropsch synthesis mechanism. Despite the low production efficiency, the results obtained provide significant insights into the mechanisms underlying C–C coupling and the electrochemical generation of long-chain hydrocarbons. By modifying the Cd surface with other metals (Au, Cu, and Pt), the resulting chemicals were compared, and Cd was found to recrystallize to CdCO₃ cuboid/cube morphology after electrochemistry. These results provide valuable insights for the development of surface-modified Cd-based electrocatalysts and long-chain hydrocarbon productions for energy and the environment.

201

Electrochemical CO₂ reduction versus CO reduction over Au/Ti electrocatalyts in phosphate buffer condition

Ju Young Maeng; Seon Young Hwang; Young Jun Kim; Choong Kyun Rhee; Youngku Sohn

Chem. Eng. J. 2023, 470, 143970. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

Ti에 담지된 Au는 여러 분야에서 안정성과 효율이 높은 촉매로 주목받고 있다. 본 연구에서는 인산염 완충 전해질에서 전기화학적(EC) CO₂ 환원과 CO 환원 모두에 Au/Ti를 전기촉매로 사용하였다. 주된 기체 생성물이 CO, H₂ 및 CH₄임을 확인하였고, EC CO₂ 환원에서는 초기 CO₂ 흡착에서 유래한 장쇄 탄화수소(CnH₂n 및 CnH₂n+2, n=2-7)가 생성됨을 처음으로 보였다. 마찬가지로 EC CO 환원에서는 촉매 표면에 CO가 직접 흡착하여 CH₄와 장쇄 탄화수소가 상당량 생성되었다. 간접적인 CO₂ 흡착과 직접적인 CO 흡착을 모두 포함하는 Fischer-Tropsch 합성 모사 전기화학 방법도 입증하였다. 앤더슨-슐츠-플로리법으로 질량 분포를 분석하여 표면 중합 반응을 이해하였고, 이를 CO와 CHx 삽입에 의한 것으로 해석하였다. 이 결과는 장쇄 탄화수소 연료 생산용 전기화학 방법과 전기촉매 개발에서 중요한 진전을 이룬다.

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원문 (English) ▾

Au supported on Ti has gained popularity as a highly stable and efficient catalyst in various fields. In this study, we report the use of Au/Ti as electrocatalysts for both electrochemical (EC) CO₂ reduction and CO reduction in a phosphate buffer electrolyte. We demonstrate, for the first time, that the dominant gas products are CO, H₂, and CH₄, and that the EC CO₂ reduction process yields long-chain hydrocarbons (CnH₂n and CnH₂n+2, n = 2–7) resulting from initial CO₂ adsorption. Similarly, CH₄ and long-chain hydrocarbons are significantly produced by EC CO reduction via direct CO adsorption on the catalyst surface. We also demonstrate an EC method for mimicking Fischer-Tropsch synthesis, which involves both indirect CO₂ and direct CO adsorptions. By analyzing the weight distribution using the Anderson-Schulz-Flory method, we were able to understand the surface polymerization reaction, which we attributed to CO and CHx insertion. These findings are highly unique and represent a significant advancement in the development of electrochemical methods and electrocatalysts for producing long-chain hydrocarbon fuels.

200

Interfacial Electronic Structures and the Fischer–Tropsch Synthesis Path by Electrochemical CO₂/CO Reduction for Ternary CuNiZn Alloys

Go Eun Park; Hye Ji Jang; Ju Young Maeng; Seon Young Hwang; Seo Young Yang; Choong Kyun Rhee; Youngku Sohn

ACS Appl. Energy Mater. 2023, 6, 7258-7273. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Metal alloy electrocatalysts are commonly used in electrochemical (EC) CO 2 reduction. In this study, we demonstrate the application of a ternary CuNiZn alloy as an electrocatalyst for both CO 2 and CO reductions. Our results show that formate, CO, CH 4, and C 2–7 hydrocarbons were produced through the process of initial CO 2 adsorption followed by subsequent stepwise reactions. Interestingly, we also observed the production of CH 4 and C 2–7 hydrocarbons (C n H 2 n +2 and C n H 2 n ) through EC CO reduction, which occurred via direct CO adsorption, followed by hydrogenation reactions. Furthermore, we discovered an electrochemically-induced surface reaction that mimics the Fischer–Tropsch (F–T) synthesis, resulting in the formation of long-chain hydrocarbons through C–C coupling/polymerization. We utilized X-ray photoelectron spectroscopy with Ar + ion sputtering depth to investigate the interfacial electronic structures and surface elemental composition distributions of Cu, Ni, and Zn. Our results indicate that these properties are highly dependent on both the applied potential and the depth at which they are measured. These unique observation provides significant insights into the EC F–T synthesis process, C–C coupling mechanism, the design of efficient metal alloy electrodes, and the theoretical modeling of alloys in both electrochemical CO 2 reduction and CO reduction.

199

Electrochemical CO₂/CO Reduction and C–C Coupling Path for Mimicking Fischer–Tropsch Synthesis over Cadmium Electrodes

Ju Young Maeng; Seon Young Hwang; Young Jun Kim; Ilsun Yoon; Chang Woo Myung; Choong Kyun Rhee; Youngku Sohn

J. Phys. Chem. C 2023, 127, 11448-11461. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Converting CO 2 into C n >2 hydrocarbons has been a significant challenge, but recent research has shown that cadmium (Cd) can be used to produce C 2–7 hydrocarbons (C n H 2 n and C n H 2 n +2 ) directly through electrochemical CO 2 reduction in a K 2 HPO 4 /KH 2 PO 4 buffer. The production of hydrocarbons was found to be enhanced by engineering the interface of the Cd surface with other transition metals. This process imitates the Fischer–Tropsch (F–T) synthesis, which involves surface polymerization reactions that couple carbon atoms together, resulting in the formation of long-chain hydrocarbons via the insertion of CO and CH x molecules. While the formate path was almost completely suppressed, the CO path remained. While the current Faradaic efficiency may be low, this study highlights the potential of electrochemical CO reduction for Cd. The study demonstrates that CO and H can directly participate in F–T synthesis through electrochemistry. Furthermore, Cd was observed to recrystallize into stacked wall structures resembling flowers after the electrochemical process. As a result, this research provides crucial insights that can aid in a better understanding of C–C coupling paths via electrochemistry.

198

Electrochemical CO₂ Reduction over In Alloy Electrodes and Depth‐Profiled Interfacial Electronic Structures

Seo Young Yang; Ju Young Maeng; Seon Young Hwang; Go Eun Park; Choong Kyun Rhee; Youngku Sohn

ChemCatChem 2023, 15, e202300336. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Indium (In) in the p‐block of the periodic table has demonstrated a high Faradaic efficiency (FE) for formate production in electrochemical CO 2 reduction reaction (EC CO 2 RR). Therefore, In‐based alloys have been extensively employed to improve performance. However, the effects of alterations in surface elemental composition and interfacial electronic structure have not been investigated in detail. In this study, we introduced In and In‐based alloys (InGaAg, InSn, and InSnBi) electrodes for EC CO 2 RR. The experimental conditions employed in the demonstrated tests encompass various factors, such as applied potentials, electrolytes and their concentrations, as well as the effects of light, including UV and infrared light radiation. Nuclear magnetic resonance spectroscopy confirmed formate production with high FE (97.7 %) and selectivity (98.5 %). Minor amounts of CO, CH 4 , and H 2 were also detected by gas chromatography. Depth‐profiling X‐ray photoelectron spectroscopy was used to examine the effects of alloying, potential‐induced exposed surface elemental compositions, and interfacial electronic structures. The study found that the elemental distribution was substantially altered after EC CO 2 RR. These unique results provide valuable information for the improvement and theoretical modeling of In‐based alloy electrocatalysts for CO 2 recycling.

197

Electrochemical CO₂ Reduction over a MoS₂/Mo Electrode

Seon Young Hwang; Min Hee Joo; Ju Young Maeng; Go Eun Park; Seo Young Yang; Choong Kyun Rhee; Youngku Sohn

Applied Science and Convergence Technology 2023, 32, 48-53. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

이황화 몰리브데넘(MoS₂)은 에너지 및 환경 응용에 유망한 물질이다. 본 연구에서는 Mo 지지체 위에 MoS₂를 직접 수열 성장시키고, 아직 연구가 드문 전기화학적 이산화탄소 환원(EC CO₂R)에 적용하였다. 금속 표면층과 MoS₂ 지지체의 효과를 조사하기 위해 Au, Ag 및 Cu를 MoS₂ 전극 위에 스퍼터 증착하였다. 무처리 MoS₂에서 EC CO₂R을 수행했을 때 많은 양의 CH₄, C₂-3 탄화수소 및 폼산염이 생성되었다. MoS₂ 위에 Au 표면층을 도입하면 CO, 메탄올 및 폼산염 생성이 증가하였다. 또한 알케인(CnH₂n+2, n=2, 3)과 알켄(CnH₂n, n=2, 3)의 비는 인가 전위와 표면층 금속에 따라 달라졌다. 특히 광조사는 CO와 C₂H₄ 농도를 각각 28배와 10배로 크게 증가시켰다. 이 결과는 CO₂ 재활용용 MoS₂ 기반 물질의 개발에 유용한 통찰을 제공한다.

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원문 (English) ▾

Molybdenum disulfide (MoS₂) is a promising material for energy and environmental applications. In this paper, we report the direct hydrothermal growth of MoS₂ on a Mo support and its application in the rarely explored electrochemical CO₂ reduction (EC CO₂R) process. To investigate the effects of metal overlayers and the MoS₂ support, Au, Ag, and Cu were sputter-deposited on a MoS₂ electrode. Large amounts of CH₄, C₂-3 hydrocarbons, and formate were produced via EC CO₂R on bare MoS₂. The introduction of a Au overlayer on MoS₂ enhanced the production of CO, methanol, and formate. Furthermore, the alkanes (CnH₂n+2, n = 2, 3) to alkenes (CnH₂n, n = 2, 3) ratio was dependent on the applied potential and overlayer metals. Notably, photoirradiation remarkably increased the CO and C₂H₄ concentrations by 28-fold and 10-fold, respectively. These findings provide valuable insights for the development of MoS₂-based materials for CO₂ recycling.

196

The Ways for Bi on Pt to Enhance Formic Acid Oxidation

Hyein Lee; Young Jun Kim; Youngku Sohn; Choong Kyun Rhee

Journal of Electrochemical Science and Technology 2023, 14, 21-30. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

This work presents a correlation between the behavior of formic acid oxidation (FAO) on various Bi-modified Pt(poly) disk electrodes and their morphologies observed on Bi-modified Pt(111) disk electrodes using electrochemical scanning tunneling microscopy (EC-STM) to understand the effects of Bi on Pt. To distinguish the FAO activities of Bi on Pt and plain Pt around Bi, additional Pt was intentionally deposited using two different routes: direct route and iodine route. In direct route, Pt was directly deposited on Bi islands and plain Pt sites around Bi islands, while in iodine route, Pt was exclusively deposited on Bi islands by protecting plain Pt sites with adsorbed iodine. Thus, a comparison of FAO performances on the two Bi-modified Pt electrodes with additional Pt (deposited in the different ways) disclosed a difference in FAO performances on plain Pt sites and Bi islands. When Bi coverage was ~0.04, the Bi deposits were scattered Bi islands enhancing FAO on Pt(poly). The additional Pt deposits using direct route increased FAO efficiency, while the ones using iodine route slightly decreased FAO current. The EC-STM observations indicated that Pt deposits around Bi islands, not on Bi islands, were responsible for the FAO current increase on Bi-modified Pt(poly). The FAO efficiency on Bi-modified Pt(poly) with a Bi coverage of ~0.25 increased by a factor of 2. However, the additional Pt deposits using the two Pt deposition routes notably decreased the FAO current. The dependency of FAO on Bi coverage was discussed in terms of electronic effect and ensemble effect.

195

Electrocatalytic syngas and photocatalytic long-chain hydrocarbon productions by CO₂ reduction over ZnO and Zn-based electrodes

Ju Young Maeng; Ju Hyun Yang; Hye Ji Jang; Min Hee Joo; Young Jun Kim; Choong Kyun Rhee; Youngku Sohn

Appl. Surf. Sci. 2023, 609, 155349. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

CO와 H₂로 이루어진 합성가스를 직접 전기촉매적으로 생산하는 방법은 에너지 및 환경 문제 해결 전략으로 주목받고 있다. 본 연구에서는 Zn 및 산화 아연 나노막대(ZnO NR) 기반 촉매가 전기촉매적 CO₂ 환원을 통한 합성가스 생산에서 유망한 성능을 보임을 입증하였다. H₂/CO 비는 표면 개질, 인가 전위, 전해질 및 Pt 증착으로 최적 조절할 수 있었다. ZnO NR은 CO₂ 환원 중 표면 재구성과 함께 금속 Zn으로 환원되는 것이 일반적으로 관찰되었다. 광촉매 CO₂ 환원에서도 CO, CH₄, CH₃OH 및 일부 유기 화합물이 확인되었다. 본 연구에서는 직접 광촉매 CO₂ 환원을 통해 상온에서 Fischer-Tropsch(F-T) 합성을 모사하여 CnH₂n 및 CnH₂n+2 형태의 장쇄 탄화수소(C₇ 화합물까지)를 생산할 수 있음을 보고한다. 기존 문헌의 결과와 달리 알케인보다 알켄이 우세하게 생성되었다. 이 독특한 결과는 에너지 및 환경 분야의 CO₂ 환원 전기촉매와 광촉매 개발에 유용한 정보를 제공한다.

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원문 (English) ▾

Direct electrocatalytic syngas (CO and H₂) production has been attracted as a strategy for energy and environmental solution. Herein, Zn and ZnO nanorod (ZnONR)-based catalysts were demonstrated to show promising performance in syngas production by electrocatalytic CO₂ reduction. The H₂/CO ratio was optimally tuned by surface modification, applied potentials, electrolytes, and Pt-deposition. ZnONR was observed to be commonly reduced to metallic Zn accompanying surface reconstruction during CO₂ reduction. Photocatalytic CO₂ reduction was also tested to observe CO, CH₄, CH₃OH, and some organic compounds. We report here a mimic of Fischer-Tropsch (F-T) synthesis can be achieved at ambient temperature by direct photocatalytic CO₂ reduction to produce long chain hydrocarbons of CnH₂n and CnH₂n+2 (up to C₇ compounds). Alkenes were observed to be predominant, compared with alkanes unlike the results reported in the literatures. The very unique results provide valuable information on the development of CO₂ reduction electrocatalysts and photocatalysts for energy and environment.

194

Eu(III)–BaTiO₃ nanoparticles and BaTiO₃/TiO₂/Ti sheets; photocatalytic and electrocatalytic CO₂ reduction

Seon Young Hwang; Hye Ji Jang; Young Jun Kim; Ju Young Maeng; Choong Kyun Rhee; Youngku Sohn

Mater. Sci. Semicond. Process. 2023, 153, 107134. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

페로브스카이트 타이타늄산 바륨(BaTiO₃, BTO)은 촉매로서 높은 잠재력을 보인다. Eu(III) 이온은 금속 산화물 모체에서 독특한 적색 발광 활성제로 사용되어 왔다. 본 연구에서는 Eu(III)가 도핑된 BTO 나노입자(NP)를 합성하고 광촉매 CO₂ 환원 활성과 생성물을 조사하였다. 주된 CO₂ 환원 생성물은 CH₃OH, CO 및 CH₄였다. 도핑한 Eu(III) 이온을 추적자로 사용하여 광발광(PL) 특성과 PL 수명을 측정하고 도펀트의 역할을 논의하였다. TiO₂/Ti 판 위에 직접 성장시킨 BTO 전극과 Cu가 증착된 BTO 전극을 사용하여 전기촉매적 CO₂ 환원 성능을 평가하였다. H₂가 주생성물이었고 표면에 Cu를 증착하면 폼산염이 크게 증가하였다. 도펀트 농도와 표면층 Cu 금속에 따른 BTO 표면 산화 상태는 X선 광전자 분광법으로 상세히 분석하였다. 도핑과 금속 증착으로 표면 전자 구조가 변하여 CO₂ 환원의 선택성과 생산성도 달라졌다. 이 독특한 물리화학적 특성과 CO₂ 환원 실증 결과는 CO₂ 환원 기작의 이해와 에너지 및 환경용 BTO 기반 촉매 개발에 중요한 정보를 제공한다.

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원문 (English) ▾

Perovskite barium titanate (BaTiO₃, BTO) has shown a high potential as catalysts. Eu(III) ion has been employed as a unique red-luminescence activator in a host metal oxide. Herein, Eu(III)-doped BTO nanoparticles (NPs) were synthesized, and their photocatalytic CO₂ reduction activities and products were examined. Major CO₂ reduction products were observed to be CH₃OH, CO, and CH₄. Doped Eu(III) ions were used as a tracer to discuss the roles of dopants by measuring photoluminescence (PL) properties and PL lifetimes. Electrocatalytic CO₂ reduction performances were evaluated using BTO electrodes directly grown on a TiO₂/Ti sheet, and Cu-deposited BTO electrodes. H₂ was a major product and formate was significantly increased upon Cu deposition on the surface. Surface oxidation states of BTO with dopant concentration and overlayer Cu metal were fully discussed by X-ray photoelectron spectroscopy. The surface electronic structure was altered by doping and metal deposition, and thereby the selectivity and productivity for CO₂ reduction were varied. The unique physicochemical properties and CO₂ reduction demonstration tests provide significant information on understanding CO₂ reduction mechanism and the development of BTO-based catalysts for energy and environment.

2022

193

Electrocatalytic CO₂ reduction reaction over group 15 bismuth and antimony film electrodes: What makes difference?

Hye Ji Jang; Ju Young Maeng; Young Jun Kim; Ilsun Yoon; Chang Woo Myung; Choong Kyun Rhee; Youngku Sohn

J. CO2 Util. 2022, 64, 102202. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

전기촉매적 이산화탄소 환원 반응(EC CO₂RR)의 활성과 생성물은 전극 물질의 성질에 크게 좌우되는 것으로 알려져 있다. 본 연구에서는 15족에 속하고 n-1d₁₀ns₂np₃ 전자배치를 갖는 Bi와 Sb 전극을 선택하여 인가 전위, 전해질, 농도 및 자외선 조건을 달리하며 EC CO₂RR 성능을 평가하였다. 주생성물은 폼산염과 H₂였고 CO도 소량 생성되었다. Bi 박막 전극은 약 94%의 높은 패러데이 효율과 95%의 폼산염 선택성을 보였다. Bi 위에 바나듐 표면층을 도입하면 폼산염 패러데이 효율이 더욱 향상되었다. 반면 Sb 박막은 폼산염보다 H₂에 대해 훨씬 높은 패러데이 효율을 나타냈다. 자외선은 폼산염과 CO 생성을 촉진하였다. 폼산염 및 H₂의 패러데이 효율은 노출된 결정면과 페르미 준위 부근의 상태 밀도를 바탕으로 논의하였다. 이 상세하고 독특한 연구는 부가가치 탄소 생성물을 생산하는 EC CO₂RR용 Bi 및 Sb 기반 전극 개발에 유용한 정보를 제공한다.

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원문 (English) ▾

Electrocatalytic CO₂ reduction reaction (EC CO₂ RR) activities and products are known to be highly dependent on the nature of electrode materials. Herein, Bi and Sb (in group 15 with n-1d₁₀ns₂np₃) electrodes were chosen and evaluated for EC CO₂ RR under various conditions of different applied potentials, electrolytes, concentration, and UV light. Major products were observed to be formate and H₂, and minor products included CO. Bi film electrode showed high Faradaic efficiency (FE) of ~94% and the selectivity of 95% for formate. Overlayer vanadium on Bi further enhanced the FE of formate. However, Sb film exhibited much higher FE of H₂ than that of formate. UV light was observed to promote formate and CO productions. The FEs of formate and H₂ were discussed with exposed crystal facets and density of states near the Fermi level. The very unique detailed study provides valuable information on the development of Bi and Sb-based electrodes for EC CO₂ RR of producing value-added carbon products.

192

Electrochemical Performance of Layer-Structured Ni_0.8Co_0.1Mn_0.1O₂ Cathode Active Materials Synthesized by Carbonate Co-Precipitation

Byung Hyun Park; Taeseong Kim; Hyerim Park; Youngku Sohn; Jongmin Shin; Misook Kang

Nanomaterials 2022, 12, 3610. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

The layered Ni-rich NiCoMn (NCM)-based cathode active material Li[NixCo(1−x)/2Mn(1−x)/2]O₂ (x ≥ 0.6) has the advantages of high energy density and price competitiveness over an LiCoO₂-based material. Additionally, NCM is beneficial in terms of its increasing reversible discharge capacity with the increase in Ni content; however, stable electrochemical performance has not been readily achieved because of the cation mixing that occurs during its synthesis. In this study, various layer-structured Li_1.0[Ni_0.8Co_0.1Mn_0.1]O₂ materials were synthesized, and their electrochemical performances were investigated. A NiCoMnCO₃ precursor, prepared using carbonate co-precipitation with Li₂CO₃ as the lithium source and having a sintering temperature of 850 °C, sintering time of 25 h, and metal to Li molar ratio of 1.00–1.05 were found to be the optimal parameters/conditions for the preparation of Li_1.0[Ni_0.8Co_0.1Mn_0.1]O₂. The material exhibited a discharge capacity of 160 mAhg−1 and capacity recovery rate of 95.56% (from a 5.0–0.1 C-rate).

191

Synthesis and photophysical properties of thiophene-modified salicylate derivatives

Hwan Pyo Jeon; Jiyeon Ha; In Tae Kim; Hae Ji Jang; Youngku Sohn; Jun-Gill Kang

J. Lumin. 2022, 250, 119096. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

2-하이드록시-4-(5-메톡시싸이오펜-2-일)벤조산(HmoTBAH)과 메틸 2-하이드록시-4-(5-메톡시싸이오펜-2-일)벤조에이트(MHmoTB)의 광물리적 특성을 다이클로로메테인(MC), 메탄올(MeOH) 및 다이메틸 설폭사이드(DMSO)에서 조사하였다. 싸이오펜으로 개질한 살리실레이트 유도체를 자외선(UV)으로 들뜨게 하면 380-500 nm 영역에 걸친 강한 발광이 나타났으며, 스펙트럼 특성은 용매의 영향을 받지 않았다. 그러나 동일한 용매에서 HmoTBAH의 발광 양자 수율(Q)은 MHmoTB보다 높았다. DMSO/물 혼합 용매(90 부피%)에서 두 유도체의 발광 특성에 대한 pH 영향도 조사하였고, 염기 처리한 HmoTBAH가 복잡한 방출 및 들뜸 스펙트럼을 나타냄을 확인하였다. 관찰된 광물리적 특성을 해석하기 위해 구조 기하와 전자 전이에 대한 양자역학 계산을 각각 밀도 범함수 이론(DFT)과 시간 의존 밀도 범함수 이론(TDDFT)으로 수행하였다.

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원문 (English) ▾

The photophysical properties of 2-hydroxy-4-(5-methoxythiophen-2-yl)benzoic acid (HmoTBAH) and methyl 2-hydroxy-4-(5-methoxythiophen-2-yl)benzoate (MHmoTB) were investigated in methylenechloride (MC), methanol (MeOH) and dimethyl sulfoxide (DMSO). Ultraviolet (UV) excitation of the thiophene-modified salicylate derivatives produced strong luminescence spanning over the 380–500 nm region, and the spectral features were not affected by the solvent. However, the luminescence quantum yield (Q) of HmoTBAH was higher than that of MHmoTB in a given solvent. The effects of pH on the luminescence properties of the two derivatives were also examined in a DMSO/water mixed solvent (90 vol%), and it was found that the base-treated HmoTBAH produced complex emission and excitation spectra. Furthermore, to interpret the observed photophysical properties, quantum-mechanical calculations of the structural geometry and the electronic transitions were performed using the density functional theory (DFT) and the time-dependent DFT (TDDFT), respectively.

190

Interface Engineered V-Zn Hybrids: Electrocatalytic and Photocatalytic CO₂ Reductions

Seon Young Hwang; Hye Ji Jang; Young Jun Kim; Ju Young Maeng; Go Eun Park; Seo Young Yang; Choong Kyun Rhee; Youngku Sohn

Nanomaterials 2022, 12, 2758. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

V-Zn hybrids have widely been used as catalyst materials in the environment and as energy. Herein, V-Zn hybrid electrodes were prepared by the hydrothermal and sputter-deposition methods using a Zn foil support. Their electrocatalytic CO₂ reduction (EC CO₂ RR) performances were tested under various applied potentials, different electrolytes, and concentrations before and after thermal treatment of the demonstrated electrode. Gas and liquid products were confirmed by gas chromatography and nuclear magnetic resonance spectroscopy, respectively. For V-Zn electrode by hydrothermal method produced mainly syngas (CO and H₂) with tunable ratio by varying applied potential. Minor products include CH₄, C₂H₄, and C₂H₆. A liquid product of formate showed a Faradaic efficiency (FE) of 2%. EC CO₂ RR efficiency for CO, CH₄, and formate was best in 0.2 M KHCO₃ electrolyte condition. CO and formate were further increased by photoirradiation and Nafion-treated electrode. Formate and CH₄ productions were significantly increased by thermal treatment of the V-Zn electrode. CO production was diminished for the V-Zn electrode by sputter deposition but was recovered by thermal treatment. Photocatalytic CO₂ RR was tested to find that RR products include CH₃OH, CO, CH₄, C₂H₄, and C₂H₆. Interestingly long-chain hydrocarbons (CnH₂n and CnH₂n+2, where n = 3–6) were first observed under mild conditions. The long-chain formation was understood by Fisher-Tropsch (F-T) synthesis. Alkenes were observed to be more produced than alkanes unlike in the conventional F-T synthesis. The present new findings provide useful clues for the development of hybrid electro-and photo-catalysts tested under various experimental conditions in energy and environment.

189

Ignition study of facile spray drying prepared microspheres of nickel coated boron nanoparticles using a shock tube

Haneol Lee; Jong Hun Kim; P.R. Deshmukh; Hyung Soo Hyun; Youngku Sohn; Weon Gyu Shin

J. Alloys Compd. 2022, 910, 164678. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

붕소는 질량 및 부피 기준 에너지 함량이 매우 높아 고에너지 연료 첨가제로 널리 연구되고 있다. 그러나 붕소 입자 중심부에 형성되는 표면 산화물 층은 기화 온도가 높고 연소 및 점화 성능을 저하시켜 실제 적용을 방해한다. 붕소의 연소와 점화 성능을 향상시키기 위해 간단하고 독창적인 분무건조법으로 붕소 입자 표면에 니켈 나노입자를 코팅하였다. 붕소와 니켈 입자의 질량 백분율 비를 달리하여 여러 시료를 제조하였다. 표면 형태 분석 결과, 니켈이 코팅된 붕소 입자는 미세구를 형성하였다. 이 미세구의 크기 분포는 2-15 µm였고 평균 지름은 4.64 µm였다. 시료 제조에 사용한 니켈 비율이 증가할수록 붕소 표면의 결정성 니켈 나노입자 코팅 밀도도 높아졌다. X선 회절(XRD) 분석에서는 새로운 상 형성 없이 붕소 표면에 니켈 입자가 코팅되었음을 확인하였다. 전계방출 주사 전자 현미경(FE-SEM), 선 주사, 원소 매핑 및 에너지 분산 분광법(EDS) 분석은 붕소 입자 표면이 니켈 입자로 코팅되고 두 물질이 긴밀하게 접촉함을 확인하였다. 니켈, 붕소 및 니켈 코팅 붕소 입자의 산화 성능은 열중량 분석(TGA)으로 조사하였다. 니켈 코팅 후 순수 붕소의 산화 시작점과 발열 피크가 더 이른 온도에서 나타났고, 1000 °C에서는 니켈 코팅 붕소의 질량 증가량이 감소하였다. 충격파관 실험에서 니켈 코팅 붕소는 순수 붕소보다 점화 지연 시간이 짧았다. B:Ni=40:1 및 B:Ni=10:1 시료의 점화 지연 시간은 순수 붕소보다 각각 12%와 16% 감소하였다. 따라서 분무건조로 제조한 니켈 코팅 붕소 입자는 코팅하지 않은 붕소에 비해 점화 성능이 크게 향상되었다.

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원문 (English) ▾

Boron is being widely explored as a potential additive for high energy fuels because of its extraordinary gravimetric and volumetric energy content. However, its application is obstructed by the surface oxide layer which forms on the core boron particles, degrading its combustion and ignition performance. This oxide layer has a high vaporization temperature. To improve the combustion and ignition performance of boron, nickel nanoparticles were coated on the boron particle surface using a simple and unique spray drying technique. Numerous samples were prepared while varying the boron and nickel particles weight percent ratios. Surface morphological analyses showed that the nickel coated boron particles formed microspheres. These microspheres had a size distribution in the range of 2–15 µm and a mean diameter of 4.64 µm. The coating density of the crystalline nickel nanoparticles on the boron surface increased as the nickel percent used for the sample preparation was increased. X-ray diffraction (XRD) identifies the coating of nickel particles over the boron surface without any phase formation. Field emission scanning electron microscopy (FE-SEM), line scanning, elemental mapping and energy dispersive spectroscopy (EDS) studies provided an elemental analysis of the nickel coated boron particles that confirmed the surfaces of the boron particles were coated with nickel particles, and formed intimate contact between them. The oxidation performance of nickel, boron, and boron coated with nickel particles was studied by thermogravimetric analysis (TGA). The beginning of oxidation and the exothermic peaks of pure boron appeared earlier after the coating with nickel. Also, a decrease in weight gain was observed at 1000 °C in the boron coated with nickel. A shock tube experiment showed the nickel coated boron has a lower ignition delay time than the pure boron. The ignition delay times of the nickel coated boron samples, such as B:Ni= 40:1 and B:Ni= 10:1 samples decreased by 12% and 16%, respectively, compared to pure boron. Thus, spray drying prepared nickel coated boron particles demonstrated a substantial improvement in ignition performance versus uncoated boron.

188

CO₂ reduction by photocatalytic and photoelectrocatalytic approaches over Eu(III)-ZnGa₂O₄ nanoparticles and Eu(III)-ZnGa₂O₄/ZnO nanorods

Hye Ji Jang; Ju Hyun Yang; Ju Young Maeng; Min Hee Joo; Young Jun Kim; Sung-Min Hong; Choong Kyun Rhee; Youngku Sohn

J. CO2 Util. 2022, 60, 101994. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

개발된 여러 촉매를 이용하여 이산화탄소 환원으로 부가가치 생성물을 만드는 연구가 광범위하게 진행되어 왔다. 본 연구에서는 Eu(III)가 도핑된 ZnGa₂O₄(ZGO) 나노입자와 ZGO가 혼성화된 ZnO 나노막대(ZGO/ZnO NR)를 다양한 실험 조건에서 광촉매 및 광전기촉매 CO₂ 환원에 적용하였다. 광촉매 CO₂ 환원에서 CO/CH₃OH 생산비는 ZGO의 경우 1보다 컸지만 ZGO/ZnO NR에서는 1보다 작았다. 전기화학적 CO₂ 환원에서는 CO와 H₂가 주생성물이었고 폼산염이 소량 생성되었으며, 생성량은 Eu(III) 도핑을 포함한 변수에 따라 달라졌다. 인가 전위가 증가할수록 H₂와 폼산염이 증가했고, CO는 -1.6 V 대 Ag/AgCl에서 가장 높은 패러데이 효율을 보였다. 합성가스 비(H₂/CO)는 0.5-2.0 범위에서 효율적으로 조절할 수 있었다. 자외선은 H₂에는 거의 영향을 주지 않으면서 CO 생성을 크게 증가시켰고 폼산염도 증가시켰다. 이 연구는 혼성 ZGO/ZnO NR, 도핑 및 자외선을 활용하여 환원 생성물과 합성가스 비를 제어하는 전략을 제시한다.

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원문 (English) ▾

Value-added products by CO₂ reduction have extensively been researched using many developed catalysts. Herein, Eu(III)-doped ZnGa₂O₄ (ZGO) nanoparticles and ZGO hybridized ZnO nanorods (ZGO/ZnONR) were evaluated for photocatalytic and photoelectrocatalytic CO₂ reduction under diverse experimental conditions. For photocatalytic CO₂ reduction, the CO/CH₃OH production ratio was > 1 for ZGO, but < 1 for ZGO/ZnONR. For electrochemical CO₂ reduction, CO and H₂ were major products with minor formate, and dependent on the parameters including Eu(III)-doping. H₂ and formate were increased with increasing applied potential, and CO showed the highest Faradaic efficiency at -1.6 V (vs. Ag/AgCl). Syngas (H₂/CO) ratio was shown to be efficiently controlled from 0.5 to 2.0. UV light showed a dramatic effect on increasing CO production but not on H₂. Formate was also increased under UV light. Overall, the present study provides strategies of controlling reduction products and syngas ratio by employing hybridized ZGO/ZnONR, doping, and UV light.

187

Effective inactivation of Bacillus atrophaeus spores and Escherichia coli on disposable face masks using ultraviolet laser irradiation

My-Chi Thi Nguyen; Huu-Quang Nguyen; Hanbyeol Jang; Sojung Noh; Youngku Sohn; Kiju Yee; Heesoo Jung; Jeongkwon Kim

Journal of Analytical Science and Technology 2022, 13, 23. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Due to the widespread emergence of COVID-19, face masks have become a common tool for reducing transmission risk between people, increasing the need for sterilization methods against mask-contaminated microorganisms. In this study, we measured the efficacy of ultraviolet (UV) laser irradiation (266 nm) as a sterilization technique against Bacillus atrophaeus spores and Escherichia coli on three different types of face mask. The UV laser source demonstrated high penetration of inner mask layers, inactivating microorganisms in a short time while maintaining the particle filtration efficiency of the masks. This study demonstrates that UV laser irradiation is an efficient sterilization method for removing pathogens from face masks.

186

Electrochemical Ce₃+/Ce₄+ and Eu₂+/Eu₃+ interconversion, complexation, and electrochemical CO₂ reduction on thio-terpyridyl-derivatized Au electrodes

So Jeong Park; Min Hee Joo; Ju Young Maeng; Choong Kyun Rhee; Jun-Gill Kang; Youngku Sohn

Appl. Surf. Sci. 2022, 576, 151793. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

싸이오-터피리딜 유도체화 Au 전극(Au-STpy)을 처음으로 사용하여 순환 전압전류법(CV)으로 Ce₃+/Ce₄+ 및 Eu₂+/Eu₃+ 이온의 전기화학적 산화환원 거동을 조사하였다. H₂SO₄ 전해질의 Ce₃+/Ce₄+ 이온에 대해 실시간 전류법과 형광 분광법을 적용한 결과, 환원 과정이 산화 과정보다 용이했고 기능화 Au는 산화환원 속도를 높였다. KCl 전해질에서는 Eu₂+/Eu₃+ 이온에 대한 CV와 전류법을 수행하였다. X선 광전자 분광법(XPS)과 형광 데이터는 전착된 Eu 착물의 Eu₃+ 상태를 확인하였다. 밀도 범함수 이론을 사용하여 싸이오-터피리딜 기능화 Au와 Ce₃+/Ce₄+ 및 Eu₂+/Eu₃+ 이온 착물의 최적화 구조, 전자 에너지 준위 및 열역학을 계산하였다. 기능화의 역할은 CO와 H₂를 주생성물로 하는 전기화학적 CO₂ 환원에서도 확인되었다. 자외선 광전자 분광법은 Au와 STpy 계면에서 새롭게 정렬된 에너지 준위를 보여주었다. 이 독특한 결과는 란타넘족 원소의 처리·재활용뿐 아니라 촉매, 디스플레이 및 금속-유기 착물 분야에서 기능화 Au의 전기화학적 응용에 대한 심층 정보를 제공한다.

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원문 (English) ▾

Thio-terpyridyl derivatized Au electrodes (Au-STpy) were first employed to understand electrochemical redox behaviors of Ce₃+/Ce₄+ and Eu₂+/Eu₃+ ions by cyclic voltammetry (CV). For Ce₃+/Ce₄+ ions in H₂SO₄ electrolyte, real-time amperometry and fluorescence spectroscopy revealed that the reduction process was more facile than the oxidation process, and the functionalized Au showed enhanced redox rates. CV and amperometry of Eu₂+/Eu₃+ ions were performed in KCl electrolyte. X-ray photoelectron spectroscopy (XPS) and fluorescence data confirmed Eu₃+ state for electrodeposited Eu complexes. Density functional theory was employed for optimized geometry, electronic energy levels and thermodynamics of the complexation of thio-terpyridyl-functionalized Au with Ce₃+/Ce₄+ and Eu₂+/Eu₃+ ions. The role of functionalization was also shown in electrochemical CO₂ reduction with major products of CO and H₂. Ultraviolet photoelectron spectroscopy revealed the newly aligned energy level at the interface of Au and STpy. The present unique results provide deeper information on functionalized Au for electrochemical applications to the treatment/recycling of lanthanide elements, in addition to catalysts, displays, and metal-organic complexes.

185

Photoelectrochemical CO₂ Reduction Products Over Sandwiched Hybrid Ga₂O₃:ZnO/Indium/ZnO Nanorods

Hye Ji Jang; Ju Hyun Yang; Ju Young Maeng; Min Hee Joo; Young Jun Kim; Choong Kyun Rhee; Youngku Sohn

Frontiers in Chemistry 2022, 10, 814766. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Recycled valuable energy production by the electrochemical CO 2 reduction method has explosively researched using countless amounts of developed electrocatalysts. Herein, we have developed hybrid sandwiched Ga 2 O 3 :ZnO/indium/ZnO nanorods (GZO/In/ZnO NR ) and tested their photoelectrocatalytic CO 2 reduction performances. Gas chromatography and nuclear magnetic spectroscopy were employed to examine gas and liquid CO 2 reduction products, respectively. Major products were observed to be CO, H 2 , and formate whose Faradaic efficiencies were highly dependent on the relative amounts of overlayer GZO and In spacer, as well as applied potential and light irradiation. Overall, the present study provides a new strategy of controlling CO 2 reduction products by developing a sandwiched hybrid catalyst system for energy and environment.

184

X-ray micro computed tomography and efficient electrochemical recovery of lanthanides on porous carbon cylinder electrodes

Min Hee Joo; So Jeong Park; Sung-Min Hong; Choong Kyun Rhee; Dongsoo Kim; Gisu Ji; Sung Woo Lee; Youngku Sohn

Composites Part B: Engineering 2022, 231, 109590. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Porous carbon cylinder (PCC) electrodes were prepared by thermal treatment of used corn starch packaging materials at 800 °C under Ar condition. The recycled PCC electrodes were first used to successfully recover lanthanide (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) ions in a 0.1 M NaClO₄ electrolyte by amperometry electrodeposition. The electrodeposited materials were characterized by scanning electron microscopy, X-ray diffraction crystallography, energy dispersive X-ray spectroscopy, Raman spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, temperature programmed reaction spectrometry, fluorescence (FL) spectroscopy, and real-time FL measurement for electrodeposition kinetic analysis. X-ray Micro computed tomography (X-ray micro-CT) was first successfully employed to examine open and closed pore 3D images for PCC before and after electrodeposition. Hydrogen storage property of PCC was also demonstrated. The present study showed very unique information for the preparation of PCC by recycling of used corn starch packaging materials, hydrogen storage, electrochemical recovery of lanthanide elements using the PCC, and inner and exterior 3D image processing of PCC using X-ray micro-CT.

183

In-situ evolution of the NiO nanosheets on 3D-Ni-foam as a self-supported electrode for energy storage device applications

Rajneesh Kumar Mishra; Gyu Jin Choi; Hyeon Jong Choi; Huisu Shin; Youngku Sohn; Seung Hee Lee; Jin Seog Gwag

Mater. Lett. 2022, 308, 131052. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

본 연구는 슈퍼커패시터용 고성능 무바인더 자립형 전극으로서 3차원 Ni 폼 위에 NiO 나노시트를 제자리 성장시키는 저비용 합성법을 제시한다. NiO//NiO 슈퍼커패시터는 6.7 A g-1에서 159.3 F g-1의 높은 비정전용량, 22.1 Wh kg-1의 에너지 밀도 및 15,250 W kg-1의 우수한 출력 밀도를 나타냈다. 또한 10,000회의 정전류 충방전(GCD) 순환 후 93.9%, 14시간 전압 유지 시험(VHT) 후 95.4%의 뛰어난 안정성을 보였다. 2시간 VHT 동안의 누설 전류도 0.09 mA로 낮았다.

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원문 (English) ▾

This report shows the inexpensive synthesis of in-situ evolution of NiO nanosheets on 3D-Ni-foam as an outstanding binder-free and self-supported electrode for supercapacitors. The NiO//NiO supercapacitor shows a high specific capacitance (159.3 F g-1) at 6.7 A g-1, energy density (22.1 Wh kg-1), and excellent power density (15250 W kg-1). It unfolds superb stability (93.9%) after 10,000 GCD cycles and (95.4%) after 14 h voltage holding tests (VHTs). Also, it shows a low leakage current of 0.09 mA during 2 h VHTs.

182

Electrochemical Ce(III)/Ce(IV) interconversion, electrodeposition, and catalytic CO ↔ CO₂ interconversion over terpyridine-modified indium tin oxide electrodes

So Jeong Park; Ju Young Maeng; Min Hee Joo; Jun-Gill Kang; Choong Kyun Rhee; Youngku Sohn

J. Ind. Eng. Chem. 2022, 106, 520-536. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

인듐 주석 산화물(ITO)은 전기화학, 디스플레이, 광전지 및 촉매 등 다양한 분야에서 전극으로 널리 사용되어 왔다. 본 연구에서는 터피리딘 개질 ITO와 싸이오-터피리딘 기능화 Au 개질 ITO 전극을 제조하고, 새로 개발한 전극에서 Ce(III)/Ce(IV) 이온의 전기화학적 산화환원 거동, 전환 속도 및 재활용 회수율을 순환 전압전류법과 전류법으로 평가하였다. 전기화학 반응 전후 전극의 물리화학적 특성은 주사 전자 현미경, X선 광전자 분광법, 자외선 광전자 분광법, X선 회절 및 형광 분광법으로 분석하였다. ITO-Au와 ITO-Au-STpy의 계면 에너지 준위는 자외선 광전자 분광법으로 조사하였다. 기능화 리간드와 Ce(III)/Ce(IV) 이온의 착물 형성은 밀도 범함수 이론 계산으로 분자 궤도 에너지 준위와 열역학을 구해 분석하였다. Ce가 전착된 ITO 전극의 열적 CO 산화 촉매 활성을 평가하였다. 또한 싸이오-터피리딘 기능화 유무에 따른 Au 개질 ITO 전극의 전기화학적 CO₂ 환원 성능을 비교하였다.

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원문 (English) ▾

Indium tin oxide (ITO) has extensively used as an electrode in diverse application areas of electrochemistry, displays, photovoltaics, and catalysts. Herein, terpyridine-modified ITO and thio-terpyridine-functionalized Au-modified ITO electrodes were prepared and evaluated for electrochemical redox behaviors and conversion rates of Ce(III)/Ce(IV) ions, and recycling recovery rates on the newly developed electrode by cyclic voltammetry and amperometry. Scanning electron microscopy, X-ray photoelectron spectroscopy, Ultraviolet photoelectron spectroscopy, X-ray diffraction crystallography, and fluorescence spectroscopy were employed for the physiochemical properties of the demonstrated electrodes before and after electrochemistry. The interfacial energy level was examined by ultraviolet photoelectron spectroscopy for ITO-Au and ITO-Au-STpy. Density functional theory calculations were performed to examine complexation between the functionalized ligand and Ce(III)/Ce(IV) ions by obtaining molecular orbital energy levels and thermodynamics. Thermal CO oxidation catalytic activity was tested for Ce-electrodeposited ITO electrode. In addition, electrochemical CO₂ reduction performance was evaluated for Au-modified ITO electrode with and without thio-terpyridine functionalization.

181

Current status, research gaps, and future scope for nanomaterials toward visible light photocatalysis

So Jeong Park; Ju Hyun Yang; Min Hee Joo; Youngku Sohn

Nanostructured Materials for Visible Light Photocatalysis 2022, 569-608. DOI ↗ 📊 인용 ↗ 관리

📄 초록 ▾

에너지 및 환경 문제에 대한 지속적인 관심을 바탕으로, 이 장에서는 최근 총설 논문을 검토하여 가시광선 조사에서 작동하는 금속 산화물, 황화물, 질화물 및 탄소 기반 물질 등 다양한 광촉매의 현재 수준을 다룬다. 먼저 광촉매의 기초와 응용 분야를 논의하며, 주요 응용 분야로 물 분해, CO₂ 환원 및 오염물질 제거를 소개한다. 최근 광촉매 연구 동향으로는 (1) 광(전기)촉매 반응기 설계와 (2) 광촉매 효율 및 광촉매 개질을 다룬다. 개질 방법은 (i) 결정상·결정면·결정성·형태, (ii) 크기·결함·촉매 지지체, (iii) 이종접합 계면 공학, (iv) Z-스킴 계면 형성, (v) 플라스몬 광촉매, (vi) 금속·비금속 도핑 및 감응제로 분류한다. 마지막으로 비금속 기반 광촉매, 광전기화학 및 자연 모사에 대해 논의한다.

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원문 (English) ▾

Motivated by the ongoing energy and environmental issues, this chapter deals with the current status of diverse photocatalysts such as metal oxides, sulfides, nitrides, and carbon-based materials working under visible light irradiation by discussing recent review articles. The fundamentals and the application areas of photocatalysts are first discussed, and the application areas mainly include water splitting, CO₂ reduction, and pollutant removal. For current trends of photocatalysts, (1) the design of photo(electro)catalyst reactors and (2) photocatalyst efficiency and modification of photocatalysts are discussed. The modification methods are categorized into (i) crystal phase/facet/crystallinity/morphology; (ii) sizes/defects/catalyst supports; (iii) heterojunction interface engineering; (iv) Z-scheme interfacing; (v) plasmonic photocatalysts; and (vi) metal/nonmetal doping and sensitizers. Finally, nonmetallic-based photocatalysts, photoelectrochemistry, and mimicking nature are discussed.

2021

180

PT-BI Co-Deposit Shell on AU Nanoparticle Core: High Performance and Long Durability for Formic Acid Oxidation

Young Jun Kim; Hyein Lee; Hee-Suk Chung; Youngku Sohn; Choong Kyun Rhee

Catalysts 2021, 11, 1049. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

This work presents the catalysts of Pt-Bi shells on Au nanoparticle cores and Pt overlayers on the Pt-Bi shells toward formic acid oxidation (FAO). Pt and Bi were co-deposited on Au nanoparticles (Au NP) via the irreversible adsorption method using a mixed precursor solution of Pt and Bi ions, and the amount of the co-deposits was controlled with the repetition of the deposition cycle. Rinsing of the co-adsorbed ionic layers of Pt and Bi with a H₂SO₄ solution selectively removed the Bi ions to leave Pt-rich and Bi-lean ( 0.4 atomic %) co-deposits on Au NP (Pt-Bi/Au NP), conceptually similar to de-alloying. Additional Pt was deposited over Pt-Bi/Au NPs (Pt/Pt-Bi/Au NPs) to manipulate further the physicochemical properties of Pt-Bi/Au NPs. Transmission electron microscopy revealed the core–shell structures of Pt-Bi/Au NPs and Pt/Pt-Bi/Au NPs, whose shell thickness ranged from roughly four to six atomic layers. Moreover, the low crystallinity of the Pt-containing shells was confirmed with X-ray diffraction. Electrochemical studies showed that the surfaces of Pt-Bi/Au NPs were characterized by low hydrogen adsorption abilities, which increased after the deposition of additional Pt. Durability tests were carried out with 1000 voltammetric cycles between −0.26 and 0.4 V (versus Ag/AgCl) in a solution of 1.0 M HCOOH + 0.1 M H₂SO₄. The initial averaged FAO performance on Pt-Bi/Au NPs and Pt/Pt-Bi/Au NPs (0.11 ± 0.01 A/mg, normalized to the catalyst weight) was higher than that of a commercial Pt nanoparticle catalyst (Pt NP, 0.023 A/mg) by a factor of ~5, mainly due to enhancement of dehydrogenation and suppression of dehydration. The catalytic activity of Pt/Pt-Bi/Au NP (0.04 ± 0.01 A/mg) in the 1000th cycle was greater than that of Pt-Bi/Au NP (0.026 ± 0.003 A/mg) and that of Pt NP (0.006 A/mg). The reason for the higher durability was suggested to be the low mobility of surface Pt atoms on the investigated catalysts.

179

Photocatalytic and Electrocatalytic Properties of Cu-Loaded ZIF-67-Derivatized Bean Sprout-Like Co-TiO₂/Ti Nanostructures

Hye Ji Jang; So Jeong Park; Ju Hyun Yang; Sung-Min Hong; Choong Kyun Rhee; Youngku Sohn

Nanomaterials 2021, 11, 1904. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

ZIF-derivatized catalysts have shown high potential in catalysis. Herein, bean sprout-like Co-TiO₂/Ti nanostructures were first synthesized by thermal treatment at 800 °C under Ar-flow conditions using sacrificial ZIF-67 templated on Ti sheets. It was observed that ZIF-67 on Ti sheets started to thermally decompose at around 350 °C and was converted to the cubic phase Co₃O₄. The head of the bean sprout structure was observed to be Co₃O₄, while the stem showed a crystal structure of rutile TiO₂ grown from the metallic Ti support. Cu sputter-deposited Co-TiO₂/Ti nanostructures were also prepared for photocatalytic and electrocatalytic CO₂ reduction performances, as well as electrochemical oxygen reaction (OER). Gas chromatography results after photocatalytic CO₂ reduction showed that CH₃OH, CO and CH₄ were produced as major products with the highest MeOH selectivity of 64% and minor C₂ compounds of C₂H₂, C₂H₄ and C₂H₆. For electrocatalytic CO₂ reduction, CO, CH₄ and C₂H₄ were meaningfully detected, but H₂ was dominantly produced. The amounts were observed to be dependent on the Cu deposition amount. Electrochemical OER performances in 0.1 M KOH electrolyte exhibited onset overpotentials of 330–430 mV (vs. RHE) and Tafel slopes of 117–134 mV/dec that were dependent on Cu-loading thickness. The present unique results provide useful information for synthesis of bean sprout-like Co-TiO₂/Ti hybrid nanostructures and their applications to CO₂ reduction and electrochemical water splitting in energy and environmental fields.

178

Electrochemical Ce(III)/Ce(IV) Redox Behavior and Ce Oxide Nanostructure Recovery over Thio-Terpyridine-Functionalized Au/Carbon Paper Electrodes

So Jeong Park; Min Hee Joo; Ju Hyun Yang; Sung-Min Hong; Choong Kyun Rhee; Jun-Gill Kang; Youngku Sohn

ACS Applied Materials & Interfaces 2021, 13, 27594-27611. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Understanding the electrochemical behaviors of Ce(III)/Ce(IV) ions is essential for better treatment, separation, and recycling of lanthanide (Ln) and actinide (An) elements. Herein, electrochemical redox behavior and interconversion of Ce(III)/Ce(IV) ions and their recoveries were demonstrated over newly developed thio-terpyridine-functionalized Au-modified carbon paper electrodes in acidic and neutral electrolytes. Cyclic voltammetry and amperometry were performed for the electrodes with and without thio-terpyridine functionalization. Ce oxide nanostructure recovery was successfully conducted by amperometry, and the electrodeposited nanostructured Ce materials were fully characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction crystallography, and X-ray photoelectron spectroscopy. Geometry optimization and the electronic energy state calculations were conducted by density functional theory at the B₃LYP/GENECP level for the complexes of Ce(III) and Ce(IV) ions with the thio-terpyridine in an aqueous state. The present unique results provide valuable information on understanding redox behaviors of Ln and An ions for their recycling and treatment processes.

177

Electrochemical behaviors and electrodeposited materials of lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) on terpyridine-functionalized Ti sheets

Min Hee Joo; So Jeong Park; Sung-Min Hong; Choong Kyun Rhee; Youngku Sohn

Materials Today Communications 2021, 27, 102305. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Electrochemical recovery of lanthanide metals has been a very important process for the treatments of nuclear and electronic wastes. In the present study, we established a big data set of lanthanide (III) (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) ions on electrochemical behaviors and electrodeposition over bare and terpyridine-functionalized Ti sheets. Cyclic voltammetry and amperometry experiments were performed in a 0.1 M NaClO₄ supporting electrolyte. The electrodeposited films were fully examined by scanning electron microscopy, Fourier-transform infrared (FT-IR) spectroscopy, energy dispersive X-ray spectroscopy (EDXS), X-ray photoelectron spectroscopy, and photoluminescence. FT-IR and EDXS data confirmed that all the electrodeposited lanthanide materials were of a similar lanthanide complex. Photoluminescence imaging profiles were also obtained for selected Eu(III)-deposited films. The newly established data set could be very useful for understanding electrochemical behaviors of lanthanide ions, improvement of recovery method, and fabrication of catalyst electrode materials by electrodeposition.

176

Electrochemistry, Electrodeposition, and Photoluminescence of Eu (III)/Lanthanides (III) on Terpyridine-Functionalized Ti Nanospikes

Min Hee Joo; So Jeong Park; Hye Ji Jang; Sung-Min Hong; Choong Kyun Rhee; Youngku Sohn

Metals 2021, 11, 977. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Terpyridine-functionalized Ti nanospike electrodes (TiNS-SiTpy) were developed and applied to cyclic voltammetry and amperometry of Ln (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) ions and mixed Eu (III) + Ln (III) ions in a 0.1 M NaClO₄ electrolyte. Electrodeposition was successfully performed over TiNS-SiTpy electrodes, which were fully examined by scanning electron microscopy, X-ray diffraction crystallography, Fourier-transform infrared spectroscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, photoluminescence (PL), and PL decay kinetics. The Gd and Tb ions were found to increase PL intensities with 10× longer lifetimes of 1.32 μs and 1.03 μs, respectively, compared with that of the electrodeposited Eu sample. The crystal phase and the oxidation states were fully examined for the mixed Ln (Eu + Gd and Eu + Tb) complex structures.

175

Thermal CO Oxidation and Photocatalytic CO₂ Reduction over Bare and M-Al₂O₃ (M = Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au) Cotton-Like Nanosheets

Hee Jung Yoon; Ju Hyun Yang; So Jeong Park; Youngku Sohn

Nanomaterials 2021, 11, 1278. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Aluminum oxide (Al₂O₃) has abundantly been used as a catalyst, and its catalytic activity has been tailored by loading transition metals. Herein, γ-Al₂O₃ nanosheets were prepared by the solvothermal method, and transition metals (M = Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au) were loaded onto the nanosheets. Big data sets of thermal CO oxidation and photocatalytic CO₂ reduction activities were fully examined for the transition metal-loaded Al₂O₃ nanosheets. Their physicochemical properties were examined by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction crystallography, and X-ray photoelectron spectroscopy. It was found that Rh, Pd, Ir, and Pt-loading showed a great enhancement in CO oxidation activity while other metals negated the activity of bare Al₂O₃ nanosheets. Rh-Al₂O₃ showed the lowest CO oxidation onset temperature of 172 °C, 201 °C lower than that of bare γ-Al₂O₃. CO₂ reduction experiments were also performed to show that CO, CH₃OH, and CH₄ were common products. Ag-Al₂O₃ nanosheets showed the highest performances with yields of 237.3 ppm for CO, 36.3 ppm for CH₃OH, and 30.9 ppm for CH₄, 2.2×, 1.2×, and 1.6× enhancements, respectively, compared with those for bare Al₂O₃. Hydrogen production was found to be maximized to 20.7 ppm during CO₂ reduction for Rh-loaded Al₂O₃. The present unique pre-screening test results provided very useful information for the selection of transition metals on Al₂O₃-based energy and environmental catalysts.

174

Enhanced Photoluminescence of Electrodeposited Europium Complex on Bare and Terpyridine-Functionalized Porous Si Surfaces

Min Hee Joo; So Jeong Park; Hye Ji Jang; Sung-Min Hong; Choong Kyun Rhee; Youngku Sohn

Photochem 2021, 1, 38-52. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

The trivalent Eu(III) ion exhibits unique red luminescence and plays an significant role in the display industry. Herein, the amperometry electrodeposition method was employed to electrodeposit Eu(III) materials on porous Si and terpyridine-functionalized Si surfaces. The electrodeposited materials were fully characterized by scanning electron microscopy, X-ray diffraction crystallography, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Photoluminescence (PL) spectroscopy revealed that PL signals were substantially increased upon deposition on porous Si surfaces. PL signals were mainly due to direct excitation and charge-transfer-indirect excitations before and after thermal annealing, respectively. The as-electrodeposited materials were of a Eu(III) complex consisting of OH, H₂O, NO₃−, and CO₃₂− groups. The complex was transformed to Eu₂O₃ upon thermal annealing at 700 °C. The electrodeposition on porous surfaces provide invaluable information on the fabrication of thin films for displays, as well as photoelectrodes for catalyst applications.

173

Electrodeposition and Characterization of Lanthanide Elements on Carbon Sheets

Min Hee Joo; So Jeong Park; Sung-Min Hong; Choong Kyun Rhee; Dongsoo Kim; Youngku Sohn

Coatings 2021, 11, 100. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Electrochemical coating and recovery by electrodeposition have been invaluably employed for facial thin film fabrication and the recycling of used materials. Herein, we have established a full data set of lanthanide (Ln: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) elements electrodeposited on carbon sheets. Cyclic voltammetry was performed for 10 mM Ln(III) ions in a 0.1 M NaClO₄ electrolyte over a carbon sheet between +0.5 V and −1.7 V (vs. Ag/AgCl). Amperometry was performed at a given potential to electrodeposit the Ln element on the carbon sheet. Their physicochemical properties were fully investigated by scanning electron microscopy, Fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The newly established full data set for Ln(III) ions over carbon electrodes provides useful fundamental information for the development of coating and recovery methods of Ln elements.

172

Electrochemical Eu(iii) behaviours and Eu oxysulfate recovery over terpyridine-functionalized indium tin oxide electrodes

So Jeong Park; Min Hee Joo; Sung-Min Hong; Jun-Gill Kang; Choong Kyun Rhee; Sung Woo Lee; Youngku Sohn

Inorganic Chemistry Frontiers 2021, 8, 1175-1188. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

The Eu element was recovered as EuSO 4 over new terpyridine-functionalized ITO by an electrochemical method and luminescent Eu 2 O 2 SO 4 was obtained by post-thermal annealing.

2020

171

Electrochemical Recovery and Behaviors of Rare Earth (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) Ions on Ni Sheets

Min Hee Joo; So Jeong Park; Sung Min Hong; Choong Kyun Rhee; Youngku Sohn

Materials 2020, 13, 5314. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

The electrochemical behaviors of rare earth (RE) ions have extensively been studied because of their high potential applications to the reprocessing of used nuclear fuels and RE-containing materials. In the present study, we fully investigated the electrochemical behaviors of RE(III) (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) ions over a Ni sheet electrode in 0.1 M NaClO₄ electrolyte solution by cyclic voltammetry between +0.5 and −1.5 V (vs. Ag/AgCl). Amperometry electrodeposition experiments were performed between −1.2 and −0.9 V to recover RE elements over the Ni sheet. The successfully RE-recovered Ni sheets were fully characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. The newly reported recovery data for RE(III) ions over a metal electrode provide valuable information on the development of the treatment methods of RE elements.

170

Photocatalytic CO₂ Reduction and Electrocatalytic H₂ Evolution over Pt(0,II,IV)-Loaded Oxidized Ti Sheets

Ju Hyun Yang; So Jeong Park; Choong Kyun Rhee; Youngku Sohn

Nanomaterials 2020, 10, 1909. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Energy recycling and production using abundant atmospheric CO₂ and H₂O have increasingly attracted attention for solving energy and environmental problems. Herein, Pt-loaded Ti sheets were prepared by sputter-deposition and Pt₄+-reduction methods, and their catalytic activities on both photocatalytic CO₂ reduction and electrochemical hydrogen evolution were fully demonstrated. The surface chemical states were completely examined by X-ray photoelectron spectroscopy before and after CO₂ reduction. Gas chromatography confirmed that CO, CH₄, and CH₃OH were commonly produced as CO₂ reduction products with total yields up to 87.3, 26.9, and 88.0 μmol/mol, respectively for 700 °C-annealed Ti under UVC irradiation for 13 h. Pt-loading commonly negated the CO₂ reduction yields, but CH₄ selectivity was increased. Electrochemical hydrogen evolution reaction (HER) activity showed the highest activity for sputter-deposited Pt on 400 °C-annealed Ti with a HER current density of 10.5 mA/cm₂ at −0.5 V (vs. Ag/AgCl). The activities of CO₂ reduction and HER were found to be significantly dependent on both the nature of Ti support and the oxidation states (0,II,IV) of overlayer Pt. The present result could provide valuable information for designing efficient Pt/Ti-based CO₂ recycle photocatalysts and electrochemical hydrogen production catalysts.

169

Energy Storage and CO₂ Reduction Performances of Co/Co₂C/C Prepared by an Anaerobic Ethanol Oxidation Reaction Using Sacrificial SnO₂

Young In Choi; Ju Hyun Yang; So Jeong Park; Youngku Sohn

Catalysts 2020, 10, 1116. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Co/Co₂C/C hybrids were prepared employing a new synthetic route and demonstrated as materials for energy storage and CO₂ recycling application. Herein, an anaerobic ethanol oxidation reaction over Co₃O₄ nanoparticles (NPs) was first employed to fabricate Co/Co₂C/C hybrids using sacrificial SnO₂. In the absence of SnO₂, Co₃O₄ NPs were converted to alpha and beta metallic Co. On the other hand, using sacrificial SnO₂ resulted in the formation of Co₂C and Co embedded in the carbon matrix at approximately 450 °C, as determined by temperature-programmed mass spectrometry analysis. The newly developed materials were fully examined by X-ray diffraction crystallography, scanning electron microscopy, energy-dispersive X-ray analysis, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The Co/Co₂C/C hybrids showed a specific capacitance of 153 F/g at a current density of 0.5 A/g. Photocatalytic CO₂ reduction experiments were performed and generated CO, CH₄, and CH₃OH as reduction products with yields of 47.7, 11.0, and 23.4 μmol/g, respectively. The anaerobic ethanol oxidation reaction could be a very useful method for the development of carbon-supported metal carbides, which have not been achieved by other synthetic methods. Furthermore, the demonstration tests unveiled new application areas of Co carbide materials.

168

Co-deposits of Pt and Bi on Au disk toward formic acid oxidation

Hyein Lee; Young Jun Kim; Youngku Sohn; Choong Kyun Rhee

Journal of Solid State Electrochemistry 2020, 24, 2535-2542. DOI ↗ 📊 인용 ↗ 관리

167

Pt Deposits on Bi/Pt NP Catalyst for Formic Acid Oxidation: Catalytic Enhancement and Longer Lifetime

Hyein Lee; Youngku Sohn; Choong Kyun Rhee

Langmuir 2020, 36, 5359-5368. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

This work presents an improvement in the activity and catalytic lifetime of Pt deposits on Bi-modified Pt nanoparticles (Bi/Pt NP) toward formic acid oxidation (FAO). Using an irreversible adsorption method, Bi was deposited on Pt NP to form Bi/Pt NP and sequentially Pt was deposited on Bi/Pt NP to form Pt/Bi/Pt NP. Voltammetric studies of Pt NP, Bi/Pt NP, and Pt/Bi/Pt NPs supported that Pt deposits of Pt/Bi/Pt NPs provided quite a unique behavior: simultaneous surface oxidation of deposited Pt and Bi and significant resistance to the oxidative removal of Bi. Furthermore, combined spectroscopic investigations revealed that the concentration of the employed Pt precursor ion solution determined the amount of deposited Pt from ∼0.2 to ∼0.4 in coverage. The best Pt/Bi/Pt NP catalyst with a Pt coverage of ∼0.25 enhanced the dehydrogenation processes below ∼0.4 V by a factor of more than 2 and increased the FAO current at ∼0.8 V roughly by 15 times, referring to those of Bi/Pt NP. The lifetime measurement works revealed that after the 1000th voltammetric cycle to 0.4 V, the FAO currents of Pt/Bi/Pt NPs were 2 and 4 times higher than those of Bi/Pt NP and Pt NP, respectively. The Pt deposits on Bi/Pt NP were concluded to play two roles in FAO: the promotion of FAO processes to increase the activity and the retardation of Bi oxidative removal to maintain the activity much longer.

166

A novel RGO/N-RGO supercapacitor architecture for a wide voltage window, high energy density and long-life via voltage holding tests

Rajneesh Kumar Mishra; Gyu Jin Choi; Youngku Sohn; Seung Hee Lee; Jin Seog Gwag

Chem. Commun. 2020, 56, 2893-2896. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Here, we demonstrated a unique symmetric supercapacitor (SSC) device architecture based on reduced graphene oxide (RGO) and nitrogen-doped RGO (N-RGO) electrodes. The RGO/N-RGO SSC shows a wide voltage window (2.2 V), high energy density (106.3 W h kg-1), and ultra-high power density (15184.8 W kg-1). The RGO/N-RGO SSC also delivers outstanding stability of 95.5% over 10 000 galvanostatic charging-discharging tests and 90.5% over 8 h of voltage holding tests. Additionally, this work explores a better understanding of leakage current and self-discharge mechanisms, which justifies the excellent state of health of the RGO/N-RGO SSC device.

2019

165

Spray drying formation of metal oxide (TiO₂ or SnO₂) nanoparticle coated boron particles in the form of microspheres and their physicochemical properties

Haneol Lee; P.R. Deshmukh; Jong Hun Kim; Hyung Soo Hyun; Youngku Sohn; Weon Gyu Shin

J. Alloys Compd. 2019, 810, 151923. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

In the present study, metal oxide (TiO₂ or SnO₂) nanoparticles were coated on boron particles using a facile spray drying technique. The coating of metal oxide nanoparticles on the boron surface was varied by changing the weight ratio of metal oxide nanoparticles to boron particles. The crystalline structure of the metal oxide nanoparticles was mainly retained without any additional phase formation on the metal oxide coated boron particles, as identified by XRD. FIB-SEM images showed that the TiO₂ or SnO₂ coated boron particles formed microspheres with diameters between 5 and 10 μm. FIB-cross sectional images indicated the microspheres had a porous structure, and every individual boron particle was coated by metal oxide nanoparticles. The line scanning profile, elemental mapping and corresponding EDAX spectra results indicated the boron particles were well coated with metal oxide nanoparticles, and confirmed the presence of respective elements in the samples, respectively. TEM study showed the fine coating of metal oxide nanoparticles on the surface of the boron particles. The surface elemental composition was identified with XPS, and revealed the strong interaction between the metal oxide and boron particles. The thermal behavior of the boron, metal oxide and metal oxide nanoparticle coated boron particles was studied in the presence of nitrogen and air atmosphere using thermogravimetric analysis. The TGA of the metal oxide nanoparticle coated boron particles showed enhanced oxidation-resistance performance in the presence of air atmosphere.

164

Reduced graphene oxide based supercapacitors: Study of self-discharge mechanisms, leakage current and stability via voltage holding tests

Rajneesh Kumar Mishra; Gyu Jin Choi; Youngku Sohn; Seung Hee Lee; Jin Seog Gwag

Mater. Lett. 2019, 253, 250-254. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Herein, we report the electrochemical properties such as self-discharge, leakage current and voltage holding tests (VHTs) of reduced graphene oxide (RGO) based solid-state symmetric supercapacitors (SSCs). SSC device demonstrates wide potential window (1.2 V), high specific capacity of 110.3 mA h g−1 at 1 A g−1, high energy density of 22.1 W h kg−1 and ultra-high power density of 7304.5 W kg−1. Further, SSC device depicts the high stability of 89.4% after 10,000 galvanostatic charge/discharge (GCD) cycles and 82.3% after 20 h VHTs. It also shows the small leakage current of 0.029 mA. Furthermore, SSC device retains the voltage of 0.7 V of its initial voltage (1.2 V) after 1 h self-discharge test, which suggests good state of health of the SSC device.

163

Electrochemical hydrogen evolution and CO₂ reduction over hierarchical MoSxSe₂-x hybrid nanostructures

Hye In Lee; Hwanhee Yu; Choong Kyun Rhee; Youngku Sohn

Appl. Surf. Sci. 2019, 489, 976-982. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Hydrogen production and CO₂ energy conversion have increasingly attracted attention and developing electrochemical energy catalysts has widely been performed to achieve clean energy and energy-recycle goals. Herein, hierarchical MoSxSe₂-x hybrid nanostructures were synthesized by the hydrothermal method, and the fundamental physiochemical properties were fully characterized by X-ray diffraction crystallography, scanning electron microscopy, high-resolution transmission electron microscopy, elemental mapping, Raman, and X-ray photoelectron spectroscopy. Electrochemical hydrogen evolution reaction was tested in an acidic electrolyte to show a catalytic activity order of MoS₂

162

Photoluminescence imaging of europium (III)‐doped γ‐Al₂O₃ nanofiber structures

So Jeong Park; Choong Kyun Rhee; Youngku Sohn

Luminescence 2019, 34, 838-845. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Aluminium oxide (Al 2 O 3 ) has widely been used for catalysts, insulators, and composite materials for diverse applications. Herein, we demonstrated if γ‐Al 2 O 3 was useful as a luminescence support material for europium (Eu) (III) activator ion. The hydrothermal method and post‐thermal treatment at 800°C were employed to synthesize Eu(III)‐doped γ‐Al 2 O 3 nanofibre structures. Luminescence characteristics of Eu(III) ions in Al 2 O 3 matrix were fully understood by taking 2D and 3D‐photoluminescence imaging profiles. Various sharp emissions between 580 to 720 nm were assigned to the 5 D 0 → 7 F J (J = 0, 1, 2, 3, 4) transitions of Eu(III) activators. On the basis of X‐ray diffraction crystallography, Auger elemental mapping and the asymmetry ratio, Eu(III) ions were found to be well doped into the γ‐Al 2 O 3 matrix at a low (1 mol%) doping level. A broad emission at 460 nm was substantially increased upon higher (2 mol%) Eu(III) doping due to defect creation. The first 3D photoluminescence imaging profiles highlight detailed understanding of emission characteristics of Eu(III) ions in Al oxide‐based phosphor materials and their potential applications.

161

Nitrogen-doped reduced graphene oxide as excellent electrode materials for high performance energy storage device applications

Rajneesh Kumar Mishra; Gyu Jin Choi; Youngku Sohn; Seung Hee Lee; Jin Seog Gwag

Mater. Lett. 2019, 245, 192-195. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Herein, we studied the nitrogen-doped reduced graphene oxide (N-doped RGO) as an excellent electrode materials in energy storage applications. The N-doped RGO based solid-state symmetric supercapacitor (SSC) device shows high specific capacity (141.1 mA h g−1) and high energy density (28.2 W h kg−1). The N-doped RGO based SSC device illustrates the notable stabilities of ∼95.4% via 10,000 galvanostatic charging-discharging (GCD) cycles and ∼93.2% via 8 h voltage holding tests. Additionally, the N-doped RGO based SSC device shows outstanding self-discharge properties, which retains the voltages of 0.65 V, 0.69 V, 0.68 V and 0.70 V of its initial voltage (1.2 V) after each GCD cycling + 2 h voltage holding test + 2 h self-discharge test, respectively, which vindicates the excellent state of health of the supercapacitor device.

160

ZnO-TiO₂ core-shell nanowires decorated with Au nanoparticles for plasmon-enhanced photoelectrochemical water splitting

Jinse Park; P.R. Deshmukh; Youngku Sohn; Weon Gyu Shin

J. Alloys Compd. 2019, 787, 1310-1319. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

The present work reports the development of Au-nanoparticle decorated ZnO-TiO₂ core-shell nanowires on the Si-wafer. The developed Au-nanoparticle decorated ZnO-TiO₂ core-shell nanowires exhibit a unique structure with uniform sensitization of Au-nanoparticles with the diameter in the range of 5–9 nm on the ZnO-TiO₂ core-shell heterostructure. This unique structure of Au-nanoparticle decorated ZnO-TiO₂ core-shell nanowires demonstrates an enhanced photocurrent density of 1.63 mAcm−2 upon illumination by visible light unveiling high photoelectrochemical water splitting activity. This photocurrent density is higher than the pristine ZnO nanowires (0.51 mAcm−2) and ZnO-TiO₂ core-shell nanowires (1.23 mAcm−2). Furthermore, photoelectrochemical water splitting efficiency of Au-nanoparticle decorated ZnO-TiO₂ core-shell nanowires was found to be 0.70%, which is higher than the ZnO nanowires (0.22%) and ZnO-TiO₂ core-shell nanowires (0.53%) at the same applied potential of +0.8 VRHE. The improved photocurrent density and efficiency is due to the enhanced absorbance in the visible region owing to the surface plasmon resonance effect of Au-nanoparticle, effective withdrawal of hot electron from the Au-nanoparticle at the interface of metal/semiconductor due to Schottky barrier as well as excellent charge-separation and transportation originating from the core-shell nanowires.

159

Photoelectrochemical Hydrogen Evolution and CO₂ Reduction over MoS₂/Si and MoSe₂/Si Nanostructures by Combined Photoelectrochemical Deposition and Rapid-Thermal Annealing Process

Sungmin Hong; Choong Kyun Rhee; Youngku Sohn

Catalysts 2019, 9, 494. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Diverse methods have been employed to synthesize MoS₂ and MoSe₂ catalyst systems. Herein, a combined photoelectrochemical (PEC) deposition and rapid-thermal annealing process has first been employed to fabricate MoS₂ and MoSe₂ thin films on Si substrates. The newly developed transition-metal dichalcogenides were characterized by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. PEC hydrogen evolution reaction (HER) was demonstrated in an acidic condition to show a PEC catalytic performance order of MoOx/Si MoS₂/Si MoSe₂/Si under the visible light-on condition. The HER activity (4.5 mA/cm₂ at −1.0 V vs Ag/AgCl) of MoSe₂/Si was increased by 4.8× compared with that under the dark condition. For CO₂ reduction, the PEC activity was observed to be in the order of MoS₂/Si MoOx/Si MoSe₂/Si under the visible light-on condition. The reduction activity (0.127 mA/cm₂) of MoSe₂/Si was increased by 9.3× compared with that under the dark condition. The combined electrochemical deposition and rapid-thermal annealing method could be a very useful method for fabricating a thin film state catalytic system perusing hydrogen production and CO₂ energy conversion.

158

Enhanced electrochemical hydrogen evolution over defect-induced hybrid MoO₃/Mo₃O₉·H₂O microrods

Ja In Gu; Jisuk Lee; Choong Kyun Rhee; Youngku Sohn

Appl. Surf. Sci. 2019, 469, 348-356. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Defected surface modification of metal oxides and hybridization of two crystal phases have been a good strategy of improving a catalytic performance by creating more active sites. Herein, MoO₃, Mo₃O₉·H₂O and their hybrid microrods were synthesized by the hydrothermal method, and the corresponding defect induced structures were prepared by the post hydrothermal treatment. The fundamental physiochemical properties were fully elucidated by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction crystallography, Fourier transform infrared spectroscopy, Raman, UV–visible absorption spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy. It was demonstrated that the hydrogen evolution reaction (HER) activity of the defect-induced hybrid MoO₃/Mo₃O₉·H₂O microrods was dramatically enhanced by 100×, compared with other structures. On the basis of the experimental results, induced defects, coupled oxidation states of Mo₅+ and Mo₆+, and the hybrids were shown to play crucial roles in the enhancement. The present defect modification in the hybrid structure could be a very useful strategy of improving catalytic activity in various catalyst application fields.

157

Photoluminescence, electro- and thermal catalytic properties of bare and Eu(III)-doped GaOOH, α- and β-Ga₂O₃ nanorods

Sungmin Hong; Choong Kyun Rhee; Youngku Sohn

J. Alloys Compd. 2019, 774, 11-17. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Gallium oxide has extensively been applied to various areas of optoelectronic devices, catalysts and displays. Herein, bare and Eu(III)-doped GaOOH, α- and β-gallium oxide (Ga₂O₃) nanorods were synthesized by the hydrothermal method and post-thermal treatment process. The physicochemical properties were fully examined by scanning electron microscopy, X-ray diffraction crystallography, Fourier-transform infrared spectroscopy, and UV–visible absorption. For diverse applications, we first performed CO oxidation tests, 2D/3D photoluminescence image spectroscopy, and electrochemical hydrogen evolution reaction. The unique results provide valuable information for the development of Ga oxide-based materials.

156

Magnetic/catalytic properties and strain induced structural phase transformation from β-FeOOH to porous α-Fe₂O₃ nanorods

Sung Woo Lee; Srivathsava Surabhi; Rambabu Kuchi; Youngku Sohn; Jong-Ryul Jeong

J. Alloys Compd. 2019, 771, 131-139. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Revealing detailed catalytic and magnetic properties and the corresponding structural changes of Fe oxide materials are extremely important for their diverse applications. For this, magnetic properties of thermally phase transformed β-FeOOH nanorods (NRs) (to porous α-Fe₂O₃) were examined in the temperature up to 550 °C. The thermal treatment enhances the lattice strain (e) that facilitates in creating pore structures. Fundamental physicochemical properties were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), diffuse reflectance UV–visible absorption spectroscopy, and X-ray photoelectron spectroscopy (XPS). An average size of pores and pore-size distribution were characterized by Brunauer-Emmett-Teller (BET) surface area analysis. Temperature and field dependent magnetic properties of calcination samples were investigated by vibrating sample magnetometer (VSM) for understanding the morphology-dependent magnetic behavior of NRs. The phase transformation behavior of these thermally treated magnetic NRs was analyzed through magnetic property characterization by considering all possible relationships with lattice strain effects, oxygen vacancies, magnetic, and morphology anisotropy.

2018

155

Antimicrobial activity of ZnO nanoplates and its Ag nanocomposites: Insight into an ROS-mediated antibacterial mechanism under UV light

Ara Joe; Se-Ho Park; Da-Jung Kim; Yeong-Ju Lee; Kwang-Hwan Jhee; Youngku Sohn; Eue-Soon Jang

Journal of Solid State Chemistry 2018, 267, 124-133. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

We have previously shown that the bactericidal effect of ZnO nanoparticles in the absence of a light source originates from the released Zn₂+ ions. The purpose of this study was to explore antibacterial activity arising from photo-induced reactive oxygen species (ROS) of ZnO nanoparticles under UV-A light irradiation. To achieve this, S. aureus and K. pneumoniae bacteria were exposed to three different ZnO nanoparticles under UV-A light. The concentrations of the ZnO nanoparticles were low, such that the antibacterial effect of the dissolved Zn₂+ ions was negligible. From various empirical evidence, we found that the oxygen defects of the ZnO crystals enhanced the photogeneration of ROS and consequently, the ZnO nanoplates (NPs) with the polar facets exhibited the most pronounced antibacterial activity under UV-A stimulation. To enhance the antimicrobial activity of the NPs, we successfully synthesized silver-nanoparticle-decorated ZnO NPs and explored their antibacterial activity compared to that of the NPs.

154

Blue-Light-Emitting Photostable Hybrid Films for High-Efficiency Large-Area Light Converter and Photonic Applications

Jung-Soo Kang; Jun-Gill Kang; Youngku Sohn; Kam Tong Leung

ACS Applied Materials & Interfaces 2018, 10, 44768-44775. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

A blue fluorophore of Schiff base zinc complex is prepared by a hydrolysis-free solution-based synthetic method. Under ultraviolet (UV) excitation, the complex produces blue emission with a quantum yield ( Q) of 42.6% in methylene chloride and 24.0% in standalone powder form. Quantum mechanical calculations show that the blue emission is generated by the change in the chemical state of the ligand associated with the complexation with Zn cations. Thin films of Zn complexes incorporated in polymethylmethacrylate (PMMA) and cellulose acetate butyrate (CAB) polymers are also prepared by dispersing the complexes into the polymer matrices. These hybrid polymer films exhibit several notable features, particularly enhanced luminescence efficiency (with maximum Q of 85.8% for PMMA and 30.0% for CAB) and scalability for fabrication over a large area while retaining the original properties of the host polymers. Light-emitting diodes are also fabricated using the CAB hybrid thin films, and they show a Q of 43.2% with excellent photostability. The complex and its hybrid films demonstrate their great potential for such applications as UV-to-blue conversion devices in photoelectronics, solar-cell concentrators, solid-state lighting and display, and greenhouse agriculture.

153

Conical multiple-layered Pt deposits on Au and its adsorption stoichiometries of CO and hydrogen

Jaesung Lee; Jae Kwang Yoo; Jandee Kim; Youngku Sohn; Choong Kyun Rhee

Electrochim. Acta 2018, 290, 244-254. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

This work demonstrated a method, termed iodine route, to produce height-controllable Pt deposits on Au using irreversible adsorption. Characterization of Pt deposits was performed utilizing scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy and cyclic voltammetry. The iodine route sequentially utilized iodine adsorption, selective replacement of adsorbed iodine on Pt deposits with CO, and removal of adsorbed CO to produce adsorbate-free Pt deposit surfaces on iodine-covered Au surface. Execution of additional Pt deposition on the particular surface permitted selective growth of Pt on the existing Pt deposits to produce conical tall multiple-layered Pt deposits of height of 4–6 atomic layers without rim of single-layered Pt-Au alloy. A comparison of Pt deposits formed via iodine route with those produced via CO and conventional routes revealed that their physical and chemical properties depended on deposition route. Pt deposits of conventional route were double-layered plateau with wide rims of single-layered Pt-Au alloy, while CO route yielded single-layered Pt-Au alloyed deposits. The adsorption stoichiometries of CO and hydrogen on Pt deposits were evaluated using electrochemical coverages of the adsorbates and STM coverage of surface Pt. A strong correlation between adsorption stoichiometric values and physical shapes of Pt deposits was revealed. Adsorption of CO and hydrogen on single-layered Pt-Au alloy enhanced so that the adsorption stoichiometries were verified to be ∼2, ascribable to adsorption on Au atoms in the Pt-Au alloy. On multiple-layered Pt deposits the adsorption stoichiometry of CO was similar to that on polycrystalline Pt, while that of hydrogen was ∼0.5. The observation was discussed in terms of mutual interactions between Pt and Au and crystallographic effect of highly stepped surfaces of conical tall multiple-layered Pt deposits.

152

Facile synthesis of CuCo₂O₄ composite octahedrons for high performance supercapacitor application

Ashok Kumar Das; Nam Hoon Kim; Seung Hee Lee; Youngku Sohn; Joong Hee Lee

Composites Part B: Engineering 2018, 150, 269-276. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

Shape tailoring of active materials could alter the performance of supercapacitors. Herein, we report the ethylenediaminetetraacetic acid (EDTA) assisted hydrothermal approach for the synthesis of single crystalline CuCo₂O₄ octahedrons and their application in a supercapacitor. Morphology and BET surface area analysis demonstrates the formation of CuCo₂O₄ octahedrons with a surface area of 61.97 m₂ g−1. As an active material, the CuCo₂O₄ octahedrons exhibited a high specific capacity of 989 C g-1 at 5 mV s−1. In addition, a long-term cyclic stability with 87% of its initial specific capacity retention was achieved after 5000 cycles at 10 A g−1. This outstanding performance could be ascribed to its unique octahedron morphology. The electrochemical results demonstrate that CuCo₂O₄ with such a unique octahedron architecture could be a potential active material for the development of a high performance supercapacitor.

151

Facile synthesis of porous CuCo₂O₄ composite sheets and their supercapacitive performance

Ashok Kumar Das; Nam Hoon Kim; Seung Hee Lee; Youngku Sohn; Joong Hee Lee

Composites Part B: Engineering 2018, 150, 234-241. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

The synthesis of metal oxide composites with porous structures for supercapacitor application has drawn much attention owing to their high surface area and easy access of the electrolyte ions to the electrode surface through the pores of the active materials. A facile hydrothermal approach is suggested for the synthesis of porous CuCo₂O₄ composite sheets and their application as an active electrode material for supercapacitor application. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) measurements show the formation of porous CuCo₂O₄ composite sheets. BET surface area measurements show that the porous CuCo₂O₄ composite sheet has 69.44 m₂ g−1 surface area, which is 4.7 times higher than quasi-spherical CuCo₂O₄ nanoparticles. The porous CuCo₂O₄ composite sheet delivered 1037 C g−1 specific capacity at 5 mV s−1. Additionally, the porous CuCo₂O₄ composite sheet retained 94% of its initial specific capacity after 5000 charge-discharge cycles at 10 A g−1 indicating an excellent cyclic stability. This excellent supercapacitive performance is attributed to the high surface area and enhanced ion transport through the pores of the CuCo₂O₄ sheets. This high specific capacity and excellent cyclic stability of the porous CuCo₂O₄ composite sheets prove to be a promising candidate for supercapacitor application.

150

Preparation of ultrathin TiO₂ coating on boron particles by thermal chemical vapor deposition and their oxidation-resistance performance

Jinyeong Sung; Minsang Shin; P.R. Deshmukh; Hyung Soo Hyun; Youngku Sohn; Weon Gyu Shin

J. Alloys Compd. 2018, 767, 924-931. DOI ↗ 📊 인용 ↗ 관리

📄 초록 (English) ▾

In the present study, we have demonstrated an easy approach for the ultrathin TiO₂ coating on boron particles by simple chemical vapor deposition (CVD) method. Boron particles dispersed in ethanol and titanium tetra isopropoxide (TTIP) were delivered in the tube furnace held at 450 °C through the atomizer and bubbler, respectively where the formation of TiO₂ coated boron particles arises. The obtained TiO₂ coated boron particles were characterized with different characterization techniques, such as, transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and thermogravimetric analysis (TGA). TEM analysis shows that the boron particles are utterly covered by a thin layer TiO₂ particles and the thickness of TiO₂ layer on the surface of boron particles varies with respect to the bubbler flow rate. Moreover, TiO₂ coated boron particles represents the core-shell like structure. Amorphous nature of boron is observed from the XRD. Further, XPS and EDX analysis shows the presence of B, Ti and O elements in the obtained samples. TGA analysis demonstrate the enhanced oxidation-resistance performance of TiO₂ coated boron particles as compared to pristine boron particles, which is due to the effective protection of the boron by thin TiO₂ coating against oxidation in oxygen environment.