Shiro Yoshizawa

Gas Permeation in SPE Method I . Oxygen Permeation Through Nafion and NEOSEPTA

The permeation of oxygen at atmospheric pressure through Nafion® 120 and NEOSEPTA® ACH‐45T ion‐exchange membranes was investigated by an electrochemical monitoring technique, which utilizes SPE composite electrodes prepared by an electroless plating method. The oxygen diffusion coefficients were almost the same for each material, but the oxygen solubility was much higher in Nafion than in NEOSEPTA. The oxygen solubility in NEOSEPTA could be explained in terms of dissolution in the aqueous component of the membrane, but the oxygen solubility in Nafion was too high for such an explanation, and was postulated to involve the role of the polytetrafluoroethylene backbone.

Nonaqueous lithium/titanium dioxide cell

The cell performance and the reaction mechanism of the Li/1 M LiClO4 propylene carbonate/TiO2 cell, which has an open circuit voltage of 2.85–2.90 V and 950 Wh/kg of theoretical energy density, are presented. The open circuit voltage and the working voltage exceeded the theoretical open circuit voltage (1.1 V) predicted from thermodynamic data assuming 1 electron transfer per molecule of TiO2 and the products to be Ti2O3 and Li2O. The working voltage of Li/anatase TiO2 cell is higher than that of Li/rutile TiO2 cell. The reaction mechanism has been shown by the electrochemical and X-ray diffractional examination to be The self-discharge test was also done and proved the capacity loss to be negligible during a month of storage. storage.

Application of the spe method to organic electrochemistry—II. Electrochemical hydrogenation of olefinic double bonds

The electrochemical hydrogenation of some olefinic compounds in both polar and non-polar solvent was undertaken to confirm the feasibility of the spe electrolysis method. The olefinic double bonds of cyclo-octene, α-methyl stylene and diethyl maleate were electrochemically hydrogenated on spe composite electrodes in n-hexane without the need to add supporting electrolyte. The location of the hydrogenation reaction sites was also discussed by using Auspe, AuPtspe, Ptspe and PtAuspe composite electrodes and it was revealed that the reaction took place on the solution side of the spe composite.

Application of the solid polymer electrolyte (SPE) method to organic electrochemistry—III. Kolbe type reactions on Pt-SPE

Abstract The feasibility of a solid polymer electrolyte (SPE) method for Kolbe type reactions was investigated by using Pt-SPE composed with Nafion 415 and platinum. The Kolbe reaction of acetic acid proceeded effectively on one side and both sides Pt-SPE composites. The lower current efficiency was observed on the latter than on the former. Neat acetic acid could also be electrolysed on both sides SPE though the cell voltage was fairly high. A methanolic solution of monomethyl adipate was electrolysed to give dimethyl sebacate on both sides Pt-SPE according to the Brown-Walker reaction. The current efficiency and the terminal voltage increased with the concentration of monomethyl adipate. Pt-SPE behaved as an active electrode of a high roughness factor, eg about 6, for the Kolbe reaction of acetate.

Discharge mechanism of the manganese dioxide electrode

Abstract The discharge overpotential of manganese dioxide electrode was measured in various electrolyte solutions, with the following results: 1. (1) The overpotential in neutral solution is much higher than in acidic or alkaline solution. 2. (2) In alkalde or neutral solution, the overpotential of a heat-treated manganese dioxide electrode was higher than that of an unheated one. In acidic solution, however, both electrodes showed the same polarization behaviour. The following explanation is proposed: The primary product of the discharge reaction is MnOOH, which is removed from the surface of electrode. The overpotential of manganese dioxide electrode is caused by the slowness of the removal processes of MnOOH. Such processes are: 1. (i) in acidic solution, MnOOH reaction with the solution, which produces Mn 2+ and MnO 2 ; 2. (ii) in alkaline solution, diffusion of H + into MnO 2 ; and 3. (iii) in neutral solution, simultaneous occurrence of (i) and (ii). In the case of diffusion, the diffusion resistance is closely related to the concentration of OH − ion in the solution and also dependent upon the amount of combined water in the manganese dioxide crystal lattice.

Nonaqueous lithium/pyromellitic dianhydride cell

Abstract The new lithium/1 M LiClO 4 propylene carbonate/pyromellitic dianhydride (PDA) cell and the improved Li/PDA cell are presented. The Li/PDA cell system has an open circuit voltage of 3.1–3.2 V, and 0.246 Ah g −1 theoretical capacity, which is based on two-electron transfer. When the pyromellitic acid (PA), which is insoluble in the electrolyte, is added in PDA cathode as proton donor, the specific capacity is roughly two times than that of PDA. The cathode of such improved Li/PDA cell consists of 42 wt% of PDA, 18 wt% of PA and 40 wt% of acetylene black. Such improved Li/PDA cell has about 1300 Wh kg −1 of energy density. The cell performance of the improved Li/PDA cell is examined, and the self-discharge test is also done and proved the capacity loss to be negligible during two weeks of storage in spite of the solubility of PDA (0.07 mol l −1 ) in an electrolyte solution.

Mass Transfer and Current Distribution under Free Convection Conditions

Correlation of mass transfer with current distribution, for deposition and dissolution of metals, on vertical electrodes, under free convection conditions, is discussed. The equation of mass transfer and the Laplace equation, determining the concentration and potential distributions, respectively, are solved simultaneously. The results explain most features of observed current distributions.

Electrode Heat Balances of Electrochemical Cells Application to Water Electrolysis

This paper deals with a method of estimating single electrode heat balances during the electrolysis of molten NaCl-ZnCl2 in a cell using aβ-alumina diaphragm. By measuring the thermoelectric power of the thermogalvanic cells: (T) Na/β-alumina/NaCl-ZnCl2/β-alumina/Na(T+dT) and (T) C,Cl2/NaCl-ZnCl2/Cl2,C(T+dT) the single electrode Peltier heat for sodium deposition and for chlorine evolution at 370° C were estimated to be −0.026±0.001 JC−1 and+0.614±0.096 J C−1, respectively.

Anodic oxidation of silver in alkaline solution

Abstract A silver electrode prepared by electrolytic deposition on a platinum wire was oxidized anodically in alkaline solution at constant cd. The impedance change and the potential change after opening the circuit in the course of anodic oxidation were observed and analysed. In the anodic oxidation, crystalline Ag 2 O was formed during the first step and then a potential peak appeared; crystalline AgO was formed during the second step. The impedance increased exponentially in the course of anodic oxidation and then decrease gradually with the formation of AgO, resulting in a maximum impedance. The potential decay after opening of the circuit consisted of a rapid change of ms order and a successive slow change of s order. From these results the rate-determining step in the oxidation process is considered to diffusion process of Ag + and/or O 2− in the oxide layer during the first step, and the crystallization process of AgO on the oxide surface during the second step.

Electrode kinetics of nickel hydroxide in alkaline solution

The electrode kinetics of a nickel hydroxide electrode and effects of Li+ ions and rare-earth compounds were studied by the means of observation of decay and growth of polarization and measurement of electrode impedance. From the experimental results, the rate-determining step of the charge and discharge reaction is considered to be the diffusion process of protons and/or defects in the hydroxide layer. The values of ∐D/φ or ∐D. L in the hydroxide layer can be obtained from theoretical treatment of the observed data. These values may be used as the measured of activity of the nickel-hydroxide electrode. By addition of Li+ ions in the electrolyte, the values of ∐D. L were increased for charge, but slightly decreased for the discharge. Such phenomena may be explained as the effect of the Li+ ion, which has lower valency than the nickel ion in nickel hydroxide, an n-type semiconductor during charge and p-type semiconductor during discharge. And then, by addition of rare-earth compounds to the electrolyte solution, the values of ∐D. L were slightly increased for charge and discharge, probably due to the increase of active centres on the electrode surface.