• Journal of the Korean Electrochemical Society
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• v.8 no.2
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• pp.99-105
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• 2005

In this study, the $PPy/CLO_4$ and PPy/PVS composite electrodes were prepared at various polymerization potential by incorporating electrolyte anions of different anion size during constant potential polymerization. The reulting Polypyrrole surfaces were inspected by SEM, and their electrochemical Properties were investigated with CV and ac impedance method. The results of electrochemical analysis were suggested that anion for $PPy/CLO_4$ electrode and cation fir PPy/PVS electrode were transferred during redox reaction. As constant potential of polymerization was increased, the charge transfer resistance of $PPy/CLO_4$ and PPy/PVS was decreased and the electric double layer capacitances of $PPy/CLO_4$ was higher than that of PPy/PVS. The change of PPy/PVS surface was relatively smaller than that of $PPy/CLO_4$ according to electropolymerization potential.

• Journal of Electrochemical Science and Technology
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• v.6 no.4
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• pp.146-151
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• 2015

Here I report an electrochemical simulation work that compares voltammetric current and resistance of a complex electrochemical reaction over a potential scan. For this work, the finite element method is employed which are frequently used for voltammetry but rarely for impedance spectroscopy. Specifically, this method is used for simulation of a complex reaction where a heterogeneous faradaic reaction is followed by a homogeneous chemical reaction. By tracing the current and its polarization resistance, I learn that their relationship can be explained in terms of rate constants of charge transfer and chemical change. An unexpected observation is that even though the resistance is increased by the rate of the following chemical reaction, the current can be increased due to the potential shift of the resistance made by the proceeding faradaic reaction. This report envisions a possibility of the FEM-based resistance simulation to be applied to understand a complex electrochemical reaction. Until now, resistance simulations are mostly based on equivalent circuits or complete mathematical equations and have limitations to find proper models. However, this method is based on the first-principles, and is expected to be complementary to the other simulation methods.

• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.8-13
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• 1998

This work presents the way how to evaluate the degree of reversibility of the discharging process undergone by the nickel hydroxide film cathodically deposited on pure nickel as a positive electrode for electrochemical capacitor using the combined cyclic voltammetry and potential drop method, supplemented by galvanostatic discharge and open-circuit potential transient methods. The time interval necessary just to establish the current reversal of anodic to cathodic direction from the moment just after applying the potential inversion of anodic to cathodic direction, was obtained on cyclic voltammogram. The cathodic charge density passed upon dropping the applied potential, was calculated on potentiostatic current density-time curve. Both the time interval and the cathodic charge density in magnitude can be regarded as being measures of the degree of reversibility of the discharging process undergone by the positive active material for supercapacitor, i.e. , the longer the time interval is, the lower is the degree of reversibility and the greater the cathodic charge density is, the higher is the degree of reversibility. From the applied potential dependences of the time interval and cathodic charge density, discharge at $0.42 V_{SCE}$ was determined to be the most reversible.

• Journal of Microbiology and Biotechnology
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• v.20 no.1
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• pp.94-100
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• 2010

Zymomonas mobilis was immobilized in a modified graphite felt cathode with neutral red (NR-cathode) and Saccharomyces cerevisiae was cultivated on a platinum plate anode. An electrochemical redox reaction was induced by 3 volts of electric potential charged to the cathode and anode. The Z. mobilis produced 1.3-1.5 M of ethanol in the cathode compartment, whereas the S. cerevisiae produced 1.7-1.9 M in the anode compartment after 96 h. The ethanol produced by the Z. mobilis immobilized in the NR-cathode and S. cerevisiae cultivated on the platinum plate was 1.5-1.6 times higher than that produced under conventional conditions. The electrochemical oxidation potential inhibited Z. mobilis, but activated S. cerevisiae. The SDS-PAGE pattern of the total soluble proteins extracted from the Z. mobilis cultivated under the electrochemical oxidation conditions was gradually simplified in proportion to the potential intensity. Z. mobilis and S. cerevisiae were cultivated in the cathode and anode compartments, respectively, of an electrochemical redox combination system. The Z. mobilis culture cultivated in the cathode compartment for 24 h was continuously transferred to the S. cerevisiae culture in the anode compartment at a rate of 300 ml/day. Approx. 1.0-1.2 M of ethanol was produced by the Z. mobilis in the cathode compartment within 24 h, and an additional 0.8-0.9 M produced by the S. cerevisiae in the anode compartment within another 24 h. Thus, a total of 2.0-2.1 M of ethanol was produced by the electrochemical redox combination of Z. mobilis and S. cerevisiae within 48 h.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1867-1870
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• 2014

• Journal of Electrochemical Science and Technology
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• v.11 no.4
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• pp.379-383
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• 2020

The novel voltammetry using a semi-circular potential wave for quasi-reversible charge transfer system on electrode is theoretically investigated. Compared with conventional voltammetry based on linear sweep such as linear sweep voltammetry (LSV), semi-circular potential sweep voltammetry (SCV) may decrease the charging current outside the center of potential range and increase the faradaic current at the midpoint due to variable scan rate. In this paper, we investigate the system based on macroelectrode where simple 1 dimensional (1 D) diffusion system is valid with various charge transfer rate constant (k₀). In order to observe the amplification at midpoint, voltammetric response with different midpoint ranging from -200 mV to 200 mV are studied. SCVs shows both the shift of peak potential and the amplification of peak current for quasi-reversible electrode reaction while only higher peak current is observed for reversible reaction. Moreover, the higher current at midpoint enable the amplification of current at low overpotential region which may assist the determination of onset potential as a figure-of-merit in electrocatalyst.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.301-306
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• 2000

This paper describes on the fabrication of a SOI substrate by SDB technology and electrochemical etch-stop. The surface of the thinned SDB SOI substrate is more uniform than that of grinding or polishing by mechanical method, and this process was found to be a very accurate method for SOI thickness control. During electrochemical etch-stop, leakage current versus voltage curves were measured for analysis of the open current potential(OCP) point, the passivation potential(PP) point and anodic passivation potential. The surface roughness and the controlled thickness selectivity of the fabricated a SDB SOI substrate were evaluated by using AFM and SEM, respectively.

• Bulletin of the Korean Chemical Society
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• v.26 no.6
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• pp.899-902
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• 2005

Indirect electrochemical oxidation of phenol by $Ce^{4+}$ was investigated in sulfuric acid solutions. It was found that electrode fouling during oxidation of phenol can be controlled by adjusting the time interval (TI) of double potential steps (DPSs). While the electroactivity was greatly decreased after several DPSs of a relatively long TI, repeated DPSs with a short potential pulse showed substantial amounts of electroactivity after a few hundreds or thousands DPS, suggesting that the formation of an insulating layer can be controlled by adjusting a potential program. Effectiveness of the consecutive application of DPSs for phenol decomposition was confirmed by GC-MS.

• Journal of Electrochemical Science and Technology
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• v.10 no.2
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• pp.99-103
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• 2019

A derivative of 1,4-Naphthoquinone coded HBU671 was synthesized and used in addition to activated carbon as composite electrode for supercapacitor application. From the electrochemical properties analysis, a specific capacitance of about $300F\;g^{-1}$ exhibited almost two times of that of activated carbon at a scan rate of $100mV\;s^{-1}$ and a potential window of - 0.2 - 1V. This improvement is due to the inherent redox reaction in HBU671. Cycle test also proved that this composite is still stable even after 1000 cycle within the applied potential window and it is highly recommended for practical application.

• Nuclear Engineering and Technology
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• v.55 no.10
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• pp.3659-3664
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• 2023

The electrochemical behavior of dissolved hydrogen (H₂) was investigated at a Pt electrode in a high temperature LiOH-H₃BO₃ solution. The diffusion current of the H₂ oxidation was proportional to the concentration of the dissolved H₂ as well as the reciprocal of the temperature. In the polarization curve, a potential region in which the oxidation current decreases despite an increase in the applied potential between the H₂ oxidation and the water oxidation regions was observed. This potential region was interpreted as being caused by the formation of a Pt oxide layer. Using the properties of the Cl^- ion that reduces the growth rate of the Pt oxide layer, it was confirmed that there is a correlation between the Cl^- ion concentration and the transient current of the H₂ oxidation.