• Journal of Electrochemical Science and Technology
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• 제13권4호
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• pp.462-471
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• 2022

In this study, the electrochemical impedance characteristics of CO₂/H₂O co-reduction to produce CO/H₂ syngas were investigated in a low-temperature single cell. The effect of the operating conditions on the single-cell performance was evaluated at different feed concentrations and cell voltages, and the corresponding electrochemical impedance spectroscopy (EIS) data were collected and analyzed. The Nyquist plots exhibited two semicircles with separated characteristic frequencies of approximately 1 kHz and tens of Hz. The high-frequency semicircles, which depend only on the catholyte concentration, could be correlated to the charge transfer processes in competitive CO₂ reduction and hydrogen evolution reactions at the cathodes. The EIS characteristics of the CO₂/H₂O co-reduction single cell could be explained by the equivalent circuit suggested in this study. In this circuit, the cathodic mass transfer and anodic charge transfer processes are collectively represented by a parallel combination of resistance and a constant phase element to show low-frequency semicircles. Through nonlinear fitting using the equivalent circuit, the parameters for each electrochemical element, such as polarization resistances for high- and low-frequency processes, could be quantified as functions of feed concentration and cell voltage.

• KEPCO Journal on Electric Power and Energy
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• 제5권4호
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• pp.331-335
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• 2019

In this study we investigate catalytic activity and selectivity of mixture of Ag and ketjenblack according to their ratios by product analysis and electrochemical experiments, such as cyclic voltammetry, linear sweep voltammetry and chronoamperometry. We reveal that catalytic activity toward CO₂ reduction to CO is improved by simple mixing Ag nanoparticle and ketjenblack because addition of ketjenblack suppresses aggregation of Ag nanoparticles and brings increase in electrochemical active surface area. However, excess amount of ketjenblack rather inhibit the CO₂ reduction to CO. These observations provide clues to develop highly active Ag catalyst or electrode toward electrochemical reduction of CO₂.

• 한국재료학회지
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• 제33권2호
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• pp.29-46
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• 2023

The electrochemical reduction of carbon dioxide (CO₂) to value-added products is a remarkable approach for mitigating CO₂ emissions caused by the excessive consumption of fossil fuels. However, achieving the electrocatalytic reduction of CO₂ still faces some bottlenecks, including the large overpotential, undesirable selectivity, and slow electron transfer kinetics. Various electrocatalysts including metals, metals oxides, alloys, and single-atom catalysts have been widely researched to suppress HER performance, reduce overpotential and enhance the selectivity of CO₂RR over the last few decades. Among them, single-atom catalysts (SACs) have attracted a great deal of interest because of their advantages over traditional electrocatalysts such as maximized atomic utilization, tunable coordination environments and unique electronic structures. Herein, we discuss the mechanisms involved in the electroreduction of CO₂ to carbon monoxide (CO) and the fundamental concepts related to electrocatalysis. Then, we present an overview of recent advances in the design of high-performance noble and non-noble singleatom catalysts for the CO₂ reduction reaction.

• 신재생에너지
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• 제19권4호
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• pp.20-26
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• 2023

Emitted CO₂ is an attractive material for microbial electrochemical CO₂ reduction. Microbial electrochemical CO₂ reduction (i.e., microbial electrosynthesis, MES) using biocatalysts has advantages compared to conventional CO₂ reduction using electrocatalysts. However, MES has several challenges, including electrode performance, biocatalysts, and reactor optimization. In this study, an MES system was investigated for optimizing reactor types, counter electrode materials, and CO₂-converting microorganisms to achieve effective CO₂ upcycling. In autotrophic cultivation (supplementation of CO₂ and H₂), CO₂ consumption of Rhodobacter sphaeroides was observed to be four times higher than that with heterotrophic cultivation (supplementation of succinic acid). The bacterial growth in an MES reactor with a single-chambered shape was two times higher than that with a double chamber (H-type MES reactor). Moreover, a single-chambered MES reactor equipped with titanium mesh as the counter electrode (anode) showed markedly increased current density in the graphite felt as a working electrode (cathode) compared to that with a graphite felt counter electrode (anode). These results demonstrate that the optimized conditions of a single chamber and titanium mesh for the counter electrode have a positive effect on microbial electrochemical CO₂ reduction.

• 마이크로전자및패키징학회지
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• 제27권4호
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• pp.11-17
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• 2020

Copper has been proved to be the best catalyst for electrochemical CO2 reduction reaction, however, for optimal efficiency and selectivity, its performance requires improvements. Electrochemical CO2 reduction reaction (RR) using CuO nanowire electrode was performed with different concentrations of KHCO3 electrolyte (0.1 M, 0.5 M, and 1 M). Cu(OH)2 was formed on Cu foil, followed by thermal-treatment at 200℃ under the air atmosphere for 2 hrs to transform it to the crystalline phase of CuO. We evaluated the effects of different KHCO3 electrolyte concentrations on electrochemical CO2 reduction reaction (RR) using the CuO nanowire electrode. At a constant current (5mA), low concentrated bicarbonate exhibited a more negative potential -0.77 V vs. Reversible Hydrogen Electrode (RHE) (briefly abbreviated as VRHE), while the negative potential reduced to -0.33 VRHE in the high concentration of bicarbonate solution. Production of H2 and CH4 increased with an increased concentration of electrolyte (KHCO3). CH4 production efficiency was high at low negative potential whereas HCOOH was not influenced by bicarbonate concentration. Our study provides insights into efficient, economically viable, and sustainable methods of mitigating the harmful environmental effects of CO2 emission.

• 마이크로전자및패키징학회지
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• 제31권2호
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• pp.78-84
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• 2024

이산화탄소 (CO₂)의 전기화학적 환원은 CO₂를 고부가가치 탄소화합물로 변환하는 효과적인 방법으로 주목받고 있다. 본 논문에서는 e-beam 증착법과 양극 산화법을 이용하여 전기화학적 CO₂ 환원용 g-C₃N₄가 도입된 다공성 Au(pAu) 전극을 합성하는 손쉬운 방법과 그 특성에 대해 보고한다. 제작된 pAu@g-C₃N₄ 전극 (@ -0.9 VRHE)은 pAu 전극대비 더 우수한 전기화학적 성능을 보였다. CO₂ 환원 성능을 확인해 보았을 때, 두 전극 모두 CO 생성물에 대해 100%의 패러데이 효율 (FE)을 기록하였으며, pAu@g-C₃N₄ 전극은 최대 9.94 mg/s의 CO 생산량을 나타내어 pAu 전극에 비해 최대 2.2배 많은 CO를 생산하였다. 본 연구는 CO₂ 배출로 인한 기후 변화에 대응하는 경제적이며 지속 가능한 방법을 제공할 뿐만 아니라, 전기화학적 CO₂ 환원용 전극 개발에 크게 기여할 것으로 예상된다.

• Bulletin of the Korean Chemical Society
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• 제21권4호
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• pp.405-411
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• 2000

Electrochemical and spectroelectrochemical studies of cobalt-Schiff (Co-SB) base complexes, Co(salen) [N-N'-bis(salicylaldehyde)-ethylenediimino cobalt(II)] and Co(salophen) [N-N'-bis(salicylaldehyde)-1,2-pheny-lenediimino cobalt(II)], have been c arried out to test them as oxygen reduction catalysts. Both compounds were found to form an adduct with oxygen and exhibit catalytic activities for oxygen reduction. Comparison of spec-tra obtained from electrooxidized complexes with those from Co-SB complexes equilibrated with oxygen in-dicates that the latter are consistent with the postulated complex formed with oxygen occupying the coaxial ligand position, namely, Co(III)-SB·O2 - .The catalysis of oxygen reduction is thus achieved by reducing Co(III) in the oxygen-Co-SB adduct, releasing the oxygen reduction product, e.g., O2 - ., from the Co(II)-SB complex.

• Bulletin of the Korean Chemical Society
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• 제28권11호
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• pp.1996-2002
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• 2007

The redox behavior of a [Ni6(μ3-Se)2(μ4-Se)3(Fe(η 5-C5H4P-Ph2)2)3] (= [Ni-Se-dppf], dppf = 1,1-bis(diphenylphosphino) ferrocene) cluster was studied using platinum (Pt) and glassy carbon electrodes (GCE) in nonaqueous media. The cluster showed electrochemical activity at the potential range between +1.6 and ?1.6 V. In the negative region (0 to ?1.6 V), the cluster exhibited two-step reductions. The first step was one-electron reversible, while the second step was a five-electron quasi-reversible process. On the other hand, in the positive region (0 to +1.6 V), the first step involved one-electron quasi-reversible process. The applicability of the cluster was found towards the electrocatalytic reduction of CO2 and was evaluated by experiments using rotating ring disc electrode (RRDE). RRDE experiments demonstrated that two electrons were involved in the electrocatalytic reduction of CO2 to CO at the Se-Ni-dppf-modified electrode.

• Journal of Electrochemical Science and Technology
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• 제13권1호
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• pp.148-158
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• 2022

The electrochemical CO₂ reduction (ECR) to produce value-added fuels and chemicals using clean energy sources (like solar and wind) is a promising technology to neutralize the carbon cycle and reproduce the fuels. Presently, the ECR has been the most attractive route to produce carbon-building blocks that have growing global production and high market demand. The electrochemical CO₂ reduction could be extensively implemented if it produces valuable products at those costs which are financially competitive with the present market prices. Herein, the electrochemical conversion of CO₂ obtained from flue gases of a power plant to produce diesel and formic acid using a consistent techno-economic approach is presented. The first scenario analyzed the production of diesel fuel which was formed through Fischer-Tropsch processing of CO (obtained through electroreduction of CO₂) and hydrogen, while in the second scenario, direct electrochemical CO₂ reduction to formic acid was considered. As per the base case assumptions extracted from the previous outstanding research studies, both processes weren't competitive with the existing fuel prices, indicating that high electrochemical (EC) cell capital cost was the main limiting component. The diesel fuel production was predicted as the best route for the cost-effective production of fuels under conceivable optimistic case assumptions, and the formic acid was found to be costly in terms of stored energy contents and has a facile production mechanism at those costs which are financially competitive with its bulk market price. In both processes, the liquid product cost was greatly affected by the parameters affecting the EC cell capital expenses, such as cost concerning the electrode area, faradaic efficiency, and current density.

• Journal of Electrochemical Science and Technology
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• 제12권4호
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• pp.406-414
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• 2021

Electrochemical devices are constructed for continuous syngas (CO + H₂) production with controlled selectivity between CO₂ and proton reduction reactions. The ratio of CO to H₂, or the faradaic efficiency toward CO generation, was mechanically manipulated by adjusting the space volume between the cathode and the polymer gas separator in the device. In particular, the area added between the cathode and the ion-conducting polymer using 0.5 M KHCO₃ catholyte regulated the solution acidity and proton reduction kinetics in the flow cell. The faradaic efficiency of CO production was controlled as a function of the distance between the polymer separator and cathode in addition to that manipulated by the electrode potential. Further, the electrochemical CO₂ reduction device using Au NPs presented a stable operation for more than 23 h at different H₂:CO production levels, demonstrating the functional stability of the flow cell utilizing the mechanical variable as an important operational factor.