• Journal of Electrochemical Science and Technology
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• v.5 no.4
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• pp.95-104
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• 2014

Electrochemical performance of Li-ion cells with $LiMn_2O_4$ cathodes and graphite anodes with carbonates electrolytes containing quaternary ammonium-based room temperature ionic liquids (ILs) is investigated. Eight different ILs based on tetraalkylammonium, pyrrolidinium or piperidinium cations paired with bis(trifluoromethylsulfonyl)imide or tris(pentafluoroethyl)trifluorophosphate anions are examined in combination with dimethyl carbonate as a main solvent and fluoroethylene carbonate as a solid electrolyte interface forming agent. It is shown that cycling properties of the cells are strongly affected by the content of ILs in the electrolyte mixtures and its increase corresponds to lower discharge capacity retention. Since viscosity and conductivity of ILs are of a great importance for the electrolytes formulation, some kind of combined parameter should be used for the assessment of IL applicability and calculated values of Walden products for neat ILs represent one of the possible options. Besides, positive effect of ILs on reduction of flammability and enhancement of thermal stability of electrolytes in contact with charged electrodes have been demonstrated by means of self-extinguishing time test and differential scanning calorimetry respectively.

• Journal of Electrochemical Science and Technology
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• v.2 no.3
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• pp.163-167
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• 2011

Nicotinamide adenine dinucleotide, $NAD^+$, and its reduced form, NADH, play important roles as coenzymes in many enzymatic reactions. Electrochemical methods for $NAD^+$ or NADH detection or generation are drawn attention because it can provide the simple and low cost platform with fairly good sensitivity. In this study, the polysiloxane viologen polymer/diaphorase/hydrophilic polyurethane (PSV/DI/HPU) modified electrodes were simply prepared and demonstrated for bio-electrocatalytic $NAD^+$ sensors. The electrodes were co-immobilized with diaphorase and polysiloxane viologen polymer as an electron mediator followed by the overcoating with HPU membrane. The mixture of the enzyme and the electron mediator was well stabilized within HPU membrane and exhibited good reversibility and stability. The sensitivity was 0.2 $nA{\cdot}{\mu}M^{-1}$ and the detection limit was 28 ${\mu}M$ with a response time of 50 s ($t_{90%}$). The capability for NADH sensor was also observed on the PSV/DI/HPU electrode.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.677-684
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• 2016

Various commercially available gas diffusion layers (GDLs) from different manufacturers were used to prepare an air electrode using $La_{0.8}Sr_{0.2}CoO_3$ perovskite (LSCP) as the catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in an alkaline solution. Various GDLs have different physical properties, such as porosity, conductivity, hydrophobicity, etc. The ORR and OER of the resulting cathode were electrochemically evaluated in an alkaline solution. The electrochemical properties of the resulting cathodes were slightly different when compared to the physical properties of GDLs. Pore structure and conductivity of GDLs had a prominent effect and their hydrophobicities had a minor effect on the electrochemical performances of cathodes for ORR and OER.

• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.165-169
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• 2008

The effect of reduction of carbon dioxide by CODH(Carbon Monoxide Dehydrogenase) was compared on glassy carbon and gold working electrodes. In case of gold electrode, the choice of the optimum applied potential is very important since $H_2$ evolution can be mixed with $CO_2$ reduction. On the other hand, efficient $CO_2$ reduction was observed up to -650 mV vs. NHE on glassy carbon in neutral solution due to the larger overpotential for $H_2$ evolution on glassy carbon surface than that on gold surface. The optimum potential for $CO_2$ reduction was found to be $-570{\sim}600\;mV$ vs. NHE. The current efficiency of $CO_2$ to CO decreased dramatically at more negative potential according to the activity of enzyme decrease and the hydrogen evolution.

• Journal of the Korean Chemical Society
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• v.38 no.2
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• pp.136-145
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• 1994

Polymeric complexes such as M(Ⅱ)(PVPS)(SND), M(Ⅱ)(PVPS)(SOPD) have been prepared with monomeric complexes, M(Ⅱ)(SND) and M(Ⅱ)(SOPD)[M: Co(Ⅱ), Ni(Ⅱ), and Cu(Ⅱ)] and polymer PVPS. These complexes have been indentified by elemental analysis, spectroscopy, and T.G.A. From the results, it was found that M(Ⅱ)(PVPS)(SND), M(Ⅱ)(PVPS)(SOPD) complexes were penta-coordinated configuration. Electrochemical properties of these complexes studied by cyclic voltammetry and differential pulse polarography in 0.1 M TEAP-DMF solution at glassy carbon electrode. Co(Ⅱ)(PVPS)(SND) and Co(Ⅱ)(PVPS)(SOPD) showed irreversible two step reduction, such as Co(Ⅲ)/Co(Ⅱ) and Co(Ⅱ)/Co(Ⅰ), and Ni(Ⅱ)(PVPS)(SND), Ni(Ⅱ)(PVPS)(SOPD), Cu(Ⅱ)(PVPS)(SND), and Cu(Ⅱ)(PVPS)(SOPD) complexes showed irreversible one step reduction, such as Ni(Ⅱ)/Ni(Ⅰ) and Cu(Ⅱ)/Cu(Ⅰ), respectively.

• Clean Technology
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• v.29 no.1
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• pp.46-52
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• 2023

Oxalic acid has been traditionally obtained via the oxidation of carbohydrates using nitric acid and catalysts. However, this process produces a variety of nitrogen oxides during oxidation and requires a separation process due to its various intermediates. These products and additional steps increase the harmfulness and complexity of the process. Recently, the electrochemical reduction of carbon dioxide into oxalic acid has been suggested as an environmentally friendly and efficient technology for the production of oxalic acid. In this electrochemical conversion system, zinc oxalate (ZnC₂O₄) is obtained by the reaction of Zn²⁺ ions produced by Zn oxidation and oxalate ions produced by CO₂ reduction. ZnC₂O₄ can then be converted to form oxalic acid, but this requires the use of a strong acid and heat. In this study, a system was proposed that can easily convert ZnC₂O₄ to oxalic acid without the use of a strong acid while also allowing for easy separation. In addition, this proposed system can also further convert the products into glycolic acid which is a high-value-added chemical. ZnC₂O₄ was effectively separated into Zn(OH)₂ powder and oxalate solution through a chemical treatment and a vacuum filtration process. Then the Zn(OH)₂ and oxalate were electrochemically converted to zinc and glycolic acid, respectively.

• Journal of Electrochemical Science and Technology
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• v.9 no.2
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• pp.141-148
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• 2018

This study evaluated the performance characteristics of varied electrolyte species and amounts in a molten carbonate fuel cell (MCFC). Coin-type MCFCs were used at the condition of $650^{\circ}C$ and 1 atm. In order to measure the effects of varied electrolyte species and amounts, electrolytes of $(Li+K)_2CO_3$ and $(Li+Na)_2CO_3$ were selected and the amounts of 1.5 g, 2.0 g, 3.0 g, and 4.0 g were used. Insignificant performance differences were observed in the cell using different electrolytes, but the cell performance was sensitive to the amount of the electrolyte used. The pore-filling ratio (PFR), a ratio of pore filling in the components by the liquid carbonate electrolytes, was used to determine the optimum performance range. Consequently, 77% PFR demonstrated the optimum performance for both electrolytes. Thus, the MCFC had a permissible but narrow optimum performance range. The remaining amounts of electrolyte in the cells were determined using the weight reduction ratio (WRR) method after several hours of cell operation. The WRR used the relationship between the initial loaded amount of electrolyte and weight reduction of components in 10 wt% acetic acid. The relationships were linear and identical between the two electrolyte species.

• Journal of the Korean Electrochemical Society
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• v.10 no.3
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• pp.229-232
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• 2007

An amperometric immunosensor for the determination of rabbit IgG is proposed. The immunoassay utilizes a screen-printed carbon electrode on which osmium redox polymer is electrodeposited. This immunoassay detects 0.1 ng/ml of rabbit IgG, which is ${\sim}10^2$ fold higher than the most sensitive enzyme amplified amperometric immunoassay. The assay utilizes a screen-printed carbon electrode which was pre-coated by a co-electrodeposited film of an electron conducting redox hydrogel and a rabbit IgG. The rabbit IgG in the electron conducting film conjugates captures, when present, the anti-rabbit IgG. The captured anti-rabbit-IgG is labeled with horseradish peroxidase (HRP) which catalyzes the two-electron reduction of $H_2O_2$ to water. Because the redox hydrogel electrically connects HRP reaction centers to the electrode, completion of the sandwich converts the film from non-electrocatalytic to electro-catalytic for the reduction of $H_2O_2$ to $H_2O$ when the electrode is poised at 200 mV vs. Ag/AgCl.

• Journal of the Korean Chemical Society
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• v.33 no.2
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• pp.215-224
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• 1989

Electrochemical reductions of $trans-[Co(en)_2X_2](ClO_4)_n$ (where X is cyanide, nitrite, ammonia, and isothiocyanate) were investigated by cyclic voltammetry and polarography at mercury and glassy carbon electrode. $trans-[Co(en)_2(CN)_2]ClO_4$ was reduced to Co(II) complex followed by adsorption to the mercury electrode. Cyanide ion was not released from the reduced Co(II) complex but the cyanide and (en) were released after the reduction to metallic cobalt. The other complexes except $trans-[Co(en)_2(CN)_2]ClO_4$ were reduced to cobalt(II) complexes followed by release of monodendate ligand, and (en) was released at the reduction step to metallic cobalt. $trans-[Co(en)_2(NO_2)_2]ClO_4$ was reduced to cobalt(Ⅱ) complex, and $NO_2^-$ ion was released followed by electroreduction through ECE mechanism at pH 2. On glassy carbon electrode, all complexes of Co(III) were reduced to Co(II) complexes with irreversible one-electron diffusion controlled reaction in which (en) was not released at this step. Increasing absorption wave number of complexes caused to negative shift of peak potential.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.11
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• pp.727-734
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• 2017

The electrochemical conversion of $CO_2$ is one of the methods for reducing $CO_2$. Four materials (Ag, Ni, Pt, and Ir) were selected as the electrodes. The electrochemical conversion was performed under a cell voltage of 4.0 V at $600^{\circ}C$. The amounts of $CO_2$ reduction and carbon production were at the highest for Ag, followed by, Pt, Ni, and then Ir. The produced carbon samples were analyzed by thermogravimetric analysis and XRD. The thermogravimetric analysis results indicated that all the carbon produced at each electrode exhibited similar thermal reactivity. The XRD results showed that the crystallization of carbon was different depending on the electrode utilized. Although electrochemical conversion was the highest for the Ag electrode, a loss of material accompanied it. Therefore, for this study, the optimal electrode is Pt, taking into account reactivity and material losses.