• Title, Summary, Keyword: Electrochemical reaction

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Effects of the Polarization Resistance on Cyclic Voltammograms for an Electrochemical-Chemical Reaction

  • Chang, Byoung-Yong
    • 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.

Electrochemical Effectiveness Factors for Butler-Volmer Reaction Kinetics in Active Electrode Layers of Solid Oxide Fuel Cells

  • Nam, Jin Hyun
    • Journal of Electrochemical Science and Technology
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    • v.8 no.4
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    • pp.344-355
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    • 2017
  • In this study, a numerical approach is adopted to investigate the effectiveness factors for distributed electrochemical reactions in thin active reaction layers of solid oxide fuel cells (SOFCs), taking into account the Butler-Volmer reaction kinetics. The mathematical equations for the electrochemical reaction and charge conduction process were formulated by assuming that the active reaction layer has a small thickness, homogeneous microstructure, and high effective electronic conductivity. The effectiveness factor is defined as the ratio of the actual reaction rate (or equivalently, current generation rate) in the active reaction layer to the nominal reaction rate. From extensive numerical calculations, the effectiveness factors were obtained for various charge transfer coefficients of 0.3-0.8. These effectiveness data were then fitted to simple correlation equations, and the resulting correlation coefficients are presented along with estimated magnitude of error.

Probing of Electrochemical Reactions for Battery Applications by Atomic Force Microscopy

  • Kim, Yun-Seok
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.98.2-98.2
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    • 2013
  • Electrochemical phenomena underpin a broad spectrum of energy, chemical, and information technologies such as resistive memories and secondary batteries. The optimization of functionalities in these devices requires understanding electrochemical mechanisms on the nanoscale. Even though the nanoscale electrochemical phenomena have been studied by electron microscopies, these methods are limited for analyzing dynamic electrochemical behavior and there is still lack of information on the nanoscale electrochemical mechanisms. The alternative way can be an atomic force microscopy (AFM) because AFM allows nanoscale measurements and, furthermore, electrochemical reaction can be controlled by an application of electric field through AFM tip. Here, I will summarize recent studies to probe nanoscale electrochemical reaction in battery applications by AFM. In particular, we have recently developed electromechanical based AFM techniques for exploring reversible and irreversible electrochemical phenomena on the nanoscale. The present work suggests new strategies to explore fundamental electrochemical mechanisms using the AFM approach and eventually will provide a powerful paradigm for probing spatially resolved electrochemical information for energy applications.

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Micro Groove Machining for Electrochemical Micro-Machining (전기화학 가공을 이용한 마이크로 홈 가공)

  • 김영민;이은상
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.1844-1847
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    • 2003
  • Electrochemical micro-machining(EMM) is used to achieve a desired workpiece surface by dissolving the metal workpiece with an electrochemical reaction. This machining method can be applied to metal that is difficult to machining using other methods. The workpiece dissolves when it is positioned close to the tool electrode in electrolyte and current is applied. This aim of this work is to develop electrochemical micro-machining(EMM) technique for micro groove shape by establishing appropriate electrochemical parameters of machining

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Electrochemical Promotion of Pt Catalyst for The Oxidation of Carbon Monoxide

  • Shin, Seock-Jae;Kang, An-Soo
    • Journal of the Korea Safety Management & Science
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    • v.2 no.4
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    • pp.187-195
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    • 2000
  • Electrochemical promotion of the reaction rate was investigated for CO oxidation in a solid electrolyte catalytic reactor where a thin film of Pt was deposited on the yttria stabilized zirconia as an electrode as well as a catalyst. It was shown under open circuit condition that potential was a mixed potential of $O_2$exchange reaction and electrochemical reaction induced by CO. The effect of electrochemical modification on the CO oxidation rate was studied at various overpotentials and $P_{CO}$$P_{O2}$.

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Regulation of Electrochemical Oxidation of Glucose by lonic Strength-Controlled Virtual Area of Nanoporous Platinum Electrode

  • Kim, Jong-Won;Park, Se-Jin
    • Journal of the Korean Electrochemical Society
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    • v.10 no.3
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    • pp.203-206
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    • 2007
  • Electrochemical reaction of glucose was regulated by the electrochemically active area of nanoporous platinum, which is controlled by ionic strength. The profile of the oxidation current of glucose vs. ionic strength was identical with that of the electrochemically active area. This result confirms that the nanopores are virtually opened for the electrochemical reaction of glucose when the ionic strength climbs over a specific concentration and implies that the electrochemical reactions on nanoporous electrode surfaces can be controlled by concentration of electrolyte.

A Study on the Electrochemical Hydrogenation Reaction Mechanism of the Laves Phase Hydrogen Storage Alloys (Laves phase계 수소저장합금의 전기화학적 수소화 반응 매카니즘에 관한 연구)

  • Lee, Ji-Youl;Kim, Chan-Jung;Kim, Dai-Ryong
    • Transactions of the Korean hydrogen and new energy society
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    • v.8 no.1
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    • pp.31-41
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    • 1997
  • In order to investigate the mechanism of electrochemical hydrogenation reaction on Zr-based Laves phase hydrogen storage alloy electrodes, electrochemical charge/discharge characteristics, potentiostatic/dynamic polarizations and electrocehmical impedance spectroscopy(EIS) of Zr-Ti-Mn-Ni and Zr-Ti-Mn-Ni-M(M=Fe, Co, Al) alloys were examined. Electrochemical discharge capacities of the alloys were quite different with gas charge capacities. Therefore, it was considered that discharge capacities of the alloys depend on electrochemical kinetic factors rather then thermodynamic ones. Discharge efficiencies were increased linearly with exchange current densities. The results of potentiostatic/dynamic polarization measurements showed that electrochemical charge and discharge reaction of Zr-based Laves phase hydrogen storage alloys is controlled by charge transfer process at the electrode surface. The EIS measurements also confirmed this result.

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A Comparative Study on Electrochemical Impedance Analysis of Solid Carbon Fuels in Direct Carbon Fuel Cell (직접탄소 연료전지에서 고체 탄소 연료에 따른 전기화학 임피던스 비교 연구)

  • Cho, Jaemin;Eom, Seongyong;Lee, Gwangseob;Ahn, Seongyool;Kim, Duckjool;Choi, Gyungmin
    • Transactions of the Korean hydrogen and new energy society
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    • v.25 no.6
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    • pp.620-628
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    • 2014
  • Direct Carbon Fuel Cell(DCFC) is one of new power generation that the chemical energy of solid carbon can be converted into electrical energy directly. At the high temperature, the electrochemical reaction of the carbon takes place and the carbon reacts with oxygen to produce carbon dioxide as followed overall reaction ($C+O_2{\rightarrow}CO_2$). However, in case of using the raw coals as a fuel of DCFC, the volatile matter containing carbon, hydrogen, and oxygen produces at operating temperature. In this study, the electrochemical reaction of Adaro coal was compared with Graphite. This work focused on the electrochemical reaction of two kinds of solid carbon by Electrochemical Impedance Spectroscopy(EIS). The EIS results were estimated by equivalent circuit analysis. The constant phase element(CPE) was applied in Randle circuit to explain an electrode and fuel interface. The correlation between the fuel characteristic and electrochemical results was discussed by elements of equivalent circuit of each fuel.

Treatment of Industrial Wastewater including 1,4-Dioxane by Fenton Process and Electrochemical Iron Redox Reaction Process (Fenton공정과 철 이온의 전기적 산화·환원 반응을 이용한 공정에서 1,4-Dioxane을 포함하는 산업폐수 처리에 관한 연구)

  • Lee, Sang Ho;Kim, Pan Soo
    • Journal of Korean Society of Water and Wastewater
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    • v.21 no.4
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    • pp.375-383
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    • 2007
  • Treatment efficiency research was performed using Fenton process and the electrochemical process in the presence of ferrous ion and hydrogen peroxide for the industrial wastewater including 1,4-Dioxane produced during polymerization of polyester. The Fenton process and the electrochemical Iron Redox Reaction (IRR) process were applied for this research to use hydroxyl radical as the powerful oxidant which is continuously produced during the redox reaction with iron ion and hydrogen peroxide. The results of $COD_{Cr}$ and the concentration of 1,4-Dioxane were compared with time interval during the both processes. The rapid removal efficiency was obtained for Fenton process whereas the slow removal efficiency was occurred for the electrochemical IRR process. The removal efficiency of $COD_{Cr}$ for 310 minutes was 84% in the electrochemical IRR process with 1,000 mg/L of iron ion concentration, whereas it was 91% with 2,000 mg/L of iron ion concentration. The lap time to remove all of 1,4-Dioxane, 330 mg/L in the wastewater took 150 minutes with 1,000 mg/L of iron ion concentration, however it took 120 minutes with 2,000 mg/L of iron ion concentration in the electrochemical IRR process.

Electrochemical Removal Efficiency of Pollutants on ACF Electrodes

  • Oh, Won-Chun;Park, Joung-Sung;Lee, Ho-Jin;Yum, Min-Hyung
    • Carbon letters
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    • v.5 no.4
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    • pp.191-196
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    • 2004
  • The electrochemical removal (ECR) of water pollutants by activated carbon fiber (ACF) electrodes from wastewater was investigated over wide range of electrochemical reaction time. The ECR capacities of ACF electrodes were associated with their internal porosity and were related to physical properties and to reaction time. And, surface morphologies and elemental analysis for the ACFs after electrochemical reaction are investigated by SEM and EDX to explain the changes in adsorption properties. The FT-IR spectra of ACFs for the investigation of functional groups show that the electrochemical treatment is consequently associated with the homogeneous removal of pollutants with the increasing surface reactivity of the activated carbon fiber surfaces. The ACFs were electrochemically reacted to waste water to investigate the removal efficiency for the COD, T-N and T-P. From these removal results of pollutants using ACFs substrate, satisfactory removal performance was obtained. The outstanding removal effects of the ACFs substrate were determined by the properties of the material for adsorption and trapping of organics, and catalytic effects.

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