• Journal of the Korean Electrochemical Society
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• v.11 no.4
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• pp.227-241
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• 2008

This article involves a unified treatment of equilibrium thermodynamics of the chemical reaction coupled with other interfacial (phase boundary) reactions. The modified (restrictive) chemical potential ${\mu}_k^+$, such as electrochemical potential, hydrostatic-chemical (mechanochemical) potential (exceptionally in the presence of the pressure difference) and surface-chemical potential, was first introduced under the isothermal and isobaric conditions. This article then enlightened the equilibrium conditions in case where the release of chemical energy is counterbalanced by the supply of electrical energy, by the supply of hydrostatic work (exceptionally in the presence of ${\Delta}p$), and finally by the release of surface energy, respectively, at constant temperature T and pressure p in terms of the modified chemical potential ${\mu}_k^+$. Finally, this paper focussed on the difference between chemical and electrochemical equilibria based upon the fundamentals of the isothermal and isobaric equilibrium conditions described above.

• Journal of Hydrogen and New Energy
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• v.5 no.2
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• pp.65-71
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• 1994

Electrochemical and thermodynamic properties of $MmNi_5$ and the related alloys for nickel-metal hydride battery(Ni-MH) were studied in terms of the equilibrium hydrogen pressure. $MmNi_5$ alloy with high equilibrium hydrogen pressure(10~20atm at room temperature), which is usually difficult to charge, was substituted for Al in part. Partial substitution of Al made not only the equilibrium pressure to be reduced remarkably, but also the enthalpy change depending on the formation of metal hydride to be agreed to the value in gas phase reaction and electrochemical reaction. Besides the composition of Al which can be given the maximum discharge capacity was turned out to be between the 0.5~1.0 atoms of Al.

• Journal of Ocean Engineering and Technology
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• v.17 no.6
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• pp.77-82
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• 2003

The absorption of water into an anti-corrosive organic coating, such as alkyd and urethane resin coating, was investigated, using a quartz crystal microbalance (QCM). Anticorrosive properties of the coatings were also measured, by means of electrochemical impedance spectroscopy (EIS). The overall absorption of water in the coating is determined by the chemical nature of resin, and decreases with increasing thickness. The enhancement of anti-corrosive performance, through increase of coating thickness, was more remarkable in the case of the coating that hadlower equilibrium water absorption. The absorption kinetics curves were Fickian in nature. The EIS analysis confirmed that the resin, having lower equilibrium water absorption, shows higher anti-corrosive performan.

• Journal of the Korean Chemical Society
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• v.56 no.6
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• pp.731-738
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• 2012

The purpose of this study is to analyze the understandings of science high school students on the conception of chemical cell in relation to chemical equilibrium from the microscopic viewpoint at molecular level through questionnaires and follow-up interviews. The results show that they have high understandings on the chemical equilibrium states in the electrochemical cell and on the redox reaction taking place simultaneously when a metal electrode is immersed in the metal ion solution. However, they do not fully comprehend the development of electrical potential difference, electron movement, electrode potential measurement in the half-cells, and calculation of the net cell voltage between anode and cathode in the chemical cell because of difficulties in the microscopic understanding the interaction on the interface at the electrode and the electrolyte solution.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.6-6
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• 2001

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.482-483
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• 2006

Synthesis of iron nanopowder by room-temperature electrochemical reduction process of ${\alpha}-Fe_2O_3$ nanopowder was investigated in terms of phase evolution and microstructure. As process variables, reduction time and applied voltage were changed in the range of $1{\sim}20$ h and $30{\sim}40$ V, respectively. From XRD analyses, it was found that volume of Fe phase increased with increasing reduction time and applied voltage, respectively. The crystallite size of Fe phase in all powder samples was less than 30 nm, implying that particle growth was inhibited by the reaction at room temperature. Based on the distinct equilibrium shape of crystalline particle, phase composition of nanoparticles was identified by TEM observation.

• Bulletin of the Korean Chemical Society
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• v.28 no.9
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• pp.1523-1530
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• 2007

The first reduction peak of the cyclic voltammogram (CV) for sulfur reduction in dimethyl sulfoxide has been studied using time resolved Fourier transform electrochemical impedance spectroscopic (FTEIS) analysis of small potential step chronoamperometric currents. The FTEIS analysis results reveal that the impedance signals obtained during short potential steps can be resolved into electron transfer reactions of two different time constants in a high frequency region. The FTEIS method provides snap shots of impedance profiles during an earlier phase of the reaction, leading to time resolved EIS measurements. Our results obtained by the FTEIS analysis are consistent with a series of electron transfer and chemical equilibrium steps of a complex reaction, making up an ECE (electrochemical-chemical-electrochemical) mechanism postulated from the results of computer simulation.

• Journal of Hydrogen and New Energy
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• v.17 no.4
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• pp.440-447
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• 2006

Solid polymer electrolyte(SPE) membrane with electrodes embedded on both faces offer unique possibilities for the electrochemical cells like water electrolyzer with fuel cell. The Nafion 117 membrane was used as the SPE, and $Pt(NH_3)_4Cl_2$ and $NaBH_4$ as the electrocatalysts and reducing agent, respectively. The 'impregnation-reduction(I-R) method' has been investigated as a tool for the preparation of electrocatalysts for water electrolyzer by varying the concentration of reducing agent and reduction time at fixed concentration of platinum salt, 5 mmol/L. Pt-SPE electrocatalysts prepared by non-equilibrium I-R method showed the lowest cell voltage of 2.17 V at reduction time, 90 min and with concentration of reducing agent 0.8 mol/L and the cell voltage with those by equilibrium I-R method was 2.42 V at reduction time, 60 min and with concentration of reducing agent 0.8 mol/L. The cell voltage were obtained at a current density $1\;A/cm^2$ and $80^{\circ}C$. In water electrolysis, hydrogen production efficiency by Pt-SPE electrocatalyst is 68.2% in case of non-equilibrium I-R method and 61.2% at equilibrium I-R method.

• Journal of Hydrogen and New Energy
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• v.8 no.2
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• pp.51-56
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• 1997

The Zr-based Laves phase, $ZrV_2$ hydrogen storage alloy is not suited for the electrode of Ni-MH battery, because the binding strength of that with hydrogen is too strong although the storage capacity is high. For an application to electrode a part of V in alloys is substituted with Ni to make weaken the binding strength. The electrochemical and thermodynamic properties of Zr-V-Ni system alloys are investigated from the equilibrium potential and studied the possibility for the application to the rechargeable battery electrode.

• Bulletin of the Korean Chemical Society
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• v.26 no.11
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• pp.1783-1789
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• 2005

Modeling of a steam generator crevice in a nuclear power system needs to take into account both thermalhydraulic and chemical phenomena. As a first step towards developing a reliable model, a chemical equilibrium model was developed to predict chemical speciation in a magnetite-packed crevice by adopting the “tableau” method. The model was benchmarked with the available experimental data and the maximum deviation did not exceed two orders of magnitude. The developed model was applied to predict the chemical speciation in a magnetite-packed crevice. It was predicted that caustic environment was developed by the concentration of NaOH and the dissolution of magnetite. The model indicated that the dominant aqueous species of iron in the caustic crevice was $FeO_2\;^-$. The increase of electrochemical corrosion potential observed in the experiment was rationalized by the decrease of dissolved hydrogen concentration due to a boiling process. It was predicted that under the deaerated condition magnetite was oxidized to hematite.