• Analytical Science and Technology
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• v.8 no.4
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• pp.683-689
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• 1995

Electrochemical reduction of carbon dioxide under high pressure on Fe electrodes and a gas diffusion electrode containing Pt catalyst (Pt-GDE) had been investigated. Formic acid was formed on Fe electrode with a faradaic efficiency of 60% at a current density of $120mA\;cm^{-2}$ under 30 atm of $CO_2$. Hydrocarbons such as $CH_4$, $C_2H_6$, $C_3H_6$, $1-C_4H_8$, and $n-C_5H_{12}$ are also formed. The distribution of hydrocarbons followed well the Schultz-Flory distribution. $CH_4$ was formed efficiently as the main reduction product on Pt-GDE.

• Journal of Electrochemical Science and Technology
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• v.6 no.4
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• pp.121-130
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• 2015

The micro emulsion method has been successfully used for preparing perovskite LaCoO₃ with uniform, fine-shaped nanoparticles showing high activity as electro catalysts in oxygen reduction reactions (ORRs). They are, therefore, promising candidates for the air-cathode in metal-air rechargeable batteries. Since the activity of a catalyst is highly dependent on its specific surface area, nanoparticles of the perovskite catalyst are desirable for catalyzing both oxygen reduction and evolution reactions. Herein, LaCoO₃ powder was also prepared by sol-gel method for comparison, with a broad particle distribution and high agglomeration. The electro catalytic properties of LaCoO₃ and LaCoO₃-carbon Super P mixture layers toward the ORR were studied comparatively using the rotating disk electrode technique in 0.1 M KOH electrolyte to elucidate the effect of carbon Super P. Koutecky-Levich theory was applied to acquire the overall electron transfer number (n) during the ORR, calculated to be ~3.74 for the LaCoO₃-Super P mixture, quite close to the theoretical value (4.0), and ~2.7 for carbon-free LaCoO₃. A synergistic effect toward the ORR is observed when carbon is present in the LaCoO₃ layer. Carbon is assumed to be more than an additive, enhancing the electronic conductivity of the oxide catalyst. It is suggested that ORRs, catalyzed by the LaCoO₃-Super P mixture, are dominated by a 2+2-electron transfer pathway to form the final, hydroxyl ion product.

• Journal of the Korean Ceramic Society
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• v.55 no.1
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• pp.50-54
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• 2018

This study investigated the long-term durability of catalyst(Pd or Fe)-infiltrated solid oxide cells for $CO_2$/steam co-electrolysis. Fuel-electrode supported solid oxide cells with dimensions of $5{\times}5cm^2$ were fabricated, and palladium or iron was subsequently introduced via wet infiltration (as a form of PdO or FeO solution). The metallic catalysts were employed in the fuel-electrode to promote $CO_2$ reduction via reverse water gas shift reactions. The metal-precursor particles were well-dispersed on the fuel-electrode substrate, which formed a bimetallic alloy with Ni embedded on the substrate during high-temperature reduction processes. These planar cells were tested using a mixture of $H_2O$ and $CO_2$ to measure the electrochemical and gas-production stabilities during 350 h of co-electrolysis operations. The results confirmed that compared to the Fe-infiltrated cell, the Pd-infiltrated cell had higher stabilities for both electrochemical reactions and gas-production given its resistance to carbon deposition.

• Journal of the Korean Electrochemical Society
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• v.21 no.1
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• pp.1-5
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• 2018

In this study, boron - doped carbon was prepared by reducing carbon dioxide ($CO_2$) at high temperature by using sodium borohydride ($NaBH_4$). The boron - doped carbon was coated on carbon felt and applied as an electrode for a vanadium redox battery cell. As a result of electrochemical performance evaluation, reversibility of carbon felt coated with boron doped carbon compared to pure carbon felt was improved by about 20% and charge transfer resistance was reduced by 60%. In the charge / discharge results, energy density and energy efficiency were improved by 21% and 12.4%, respectively. These results show that carbon produced by reduction of $CO_2$ can be used as electrode material for redox flow battery.

• Journal of Electrochemical Science and Technology
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• v.8 no.1
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• pp.61-68
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• 2017

Electrochemical conversion of $CO_2$ and production of $H_2$ were attempted on a three-dimensionally ordered, porous metal organic framework (MOF-74) in which transition metals (Co, Ni, and Zn) were impregnated. A lab-scale proton exchange membrane-based electrolyzer was fabricated and used for the reduction of $CO_2$. Real-time gas chromatography enabled the instantaneous measurement of the amount of carbon monoxide and hydrogen produced. Comprehensive calculations, based on electrochemical measurements and gaseous product analysis, presented a time-dependent selectivity of the produced gases. M-MOF-74 samples with different central metals were successfully obtained because of the simple synthetic process. It was revealed that Co- and Ni-MOF-74 selectively produce hydrogen gas, while Zn-MOF-74 successfully generates a mixture of carbon monoxide and hydrogen. The results indicated that M-MOF-74 can be used as an electrocatalyst to selectively convert $CO_2$ into useful chemicals.

• Journal of the Korean Electrochemical Society
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• v.22 no.1
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• pp.1-12
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• 2019

The reduction of nitrogen to produce ammonia has been attracting much attention as a renewable energy technology. Ammonia is the basis for many fertilizers and is also considered an energy carrier that can power internal combustion engines, diesel engines, gas turbines, and fuel cells. Traditionally, ammonia has been produced through the Haber-Bosch process, in which atmospheric nitrogen combines with hydrogen at high temperature ($350-550^{\circ}C$) and high pressure (150-300 bar). This process consumes 1-2% of current global energy production and relies on fossil fuels as an energy source. Reducing the energy input required for this process will reduce $CO_2$ emissions and the corresponding environmental impact. For this reason, developing electrochemical ammonia-production methods under ambient temperature and pressure conditions should significantly reduce the energy input required to produce ammonia. In this review, we introduce the electrochemical nitrogen reduction reaction at ambient condition. Numerical studies on the electrochemical nitrogen reduction mechanism have been carried out through the computation of density function theory. Electrodes such as nanowires and porous electrodes have been also actively studied for further participation in electrochemical reactions.

• Bulletin of the Korean Chemical Society
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• v.19 no.2
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• pp.183-188
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• 1998

Incorporation of metalloporphyrins into polypyrrole (PPy) film was achieved either by electropolymerization of pyrrole in the presence of metal-tetra(sulfonatophenyl)porphyrin anion (MTSPP, M=Co, Fe) or by metalizing hydrogenated tetra(4-sulfonatophenyl)porphyrin anion (H2TSPP) doped into PPy through ion-exchange. Electrochemical reduction of oxygen on the PPy doped with metallo porphyrin (PPy-MTSPP) was studied in acidic and basic solutions. Oxygen reduction on PPy-MTSPP electrodes appeared to proceed through a 4-electron pathway as well as a 2-electron path. In acidic solutions, the overpotential for O2 reduction on PPy-CoTSPP electrode was smaller than that on gold by about 0.2 V. In basic solutions the overpotential of the PPy-CoTSPP electrode in the activation range was close to those of Au and Pt. The limiting current was close to that of Au. However, polypyrrole doped with cobalt-tetra(sulfonatophenyl)porphyrin anion (PPy-CoTSPP) or with iron-tetra(sulfonatophenyl)porphyrin anion (PPy-FeTSPP) was found to have limited potential windows at high temperatures (above 50 ℃), and hence the electrode could not be held at the oxygen reduction potentials in basic solutions (pH 13) without degradation of the polymer.

• Journal of Electrochemical Science and Technology
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• v.2 no.2
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• pp.85-90
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• 2011

Active oxygen species or free radicals are considered to cause extensive oxidative damage to biological macromolecules, which brings about a variety of diseases as well as aging. Electrolyzed reduced water(ERW) has been regarded as a ideal antioxidative agent in recent years. ERW is produced by passing a diluted salt solution through an electrolytic cell, within which the anode and cathode are separated by membrane. It can be produced reactive materials in ERW near the cathode during the electrolysis of water. ERW have the following advantages over other traditional cleaning agents: effective antioxidative agent, easy preparation, inexpensive, and environmentally friendly. The main advantage of ERW is its safety and antioxidative effect. ERW with strong reducing potential can be used to remove dirt and grease from items such as cutting boards and other kitchen utensils. The primary aim of this study is the activation mechanism of oxidation reduction potentials, ion conductivity, pH, and electrochemical properties with reactive materials in ERW.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.112-119
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• 2022

Molten carbonate fuel cells (MCFCs) are environmentally friendly, large-capacity power generation devices operated at approximately 650℃. If MCFCs are to be commercialized by improving their competitiveness, their cell life should be increased by operating them at lower temperatures. However, a decrease in the operating temperature causes a reduction in the cell performance because of the reduction in the electrochemical reaction rate. The cell performance can be improved by introducing a coating on the cathode of the cell. A coating with a high surface area expands the triple phase boundaries (TPBs) where the gas and electrolyte meet on the electrode surface. And the expansion of TPBs enhances the oxygen reduction reaction of the cathode. Therefore, the cell performance can be improved by increasing the reaction area, which can be achieved by coating nanosized LiCoO₂ particles on the cathode. However, although a coating improves the cell performance, a thick coating makes gas difficult to diffuse into the pore of the coating and thus reduces the cell performance. In addition, LiCoO₂-coated cathode cell exhibits stable cell performance because the coating layer maintains a uniform thickness under MCFC operating conditions. Therefore, the performance and stability of MCFCs can be improved by applying a LiCoO₂ coating with an appropriate thickness on the cathode.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.1
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• pp.37-44
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• 2023

Transition metal (Me = Cu, Fe, Ni) doped (Pr, Ba)Co₂O_5+𝛿 (PBCO) material were investigated in terms of electronic structure change and electrochemical properties. It was confirmed that (Pr, Ba)(Co, Cu)O_5+𝛿 (PBCCu) and (Pr, Ba)(Co, Fe)O_5+𝛿 (PBCFe) showed cubic and orthorhombic structures, respectively, but (Pr, Ba)(Co, Ni)O_5+𝛿 (PBCNi) showed secondary phases. PBCCu has an average particle diameter of 1093 nm, and PBCO and PBCFe have an average particle diameter of 495.1 nm and 728 nm, respectively. The average oxidation values of B site ions in PBCMe were calculated to be 3.26 (PBCO), 2.48 (PBCCu), 3.32 (PBCFe), and valence band maximum (VBM) was -0.42 eV (PBCO), -0.58 eV (PBCCu), -0.11 eV (PBCFe). It is expected that PBCCu easily interacts with adsorbed oxygen due to the lowest oxidation value and the highest VBM. The polarization resistance was 0.91 Ω cm² (PBCO), 0.77 Ω cm² (PBCCu), 1.06 Ω cm² (PBCFe) at 600℃, showing the lowest polarization resistance of PBCCu.