Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 69 , Issue 1
Showing 1-34 articles out of 34 articles from the selected issue
Vision
Communication
  • Yong-Ming LI, Mitsuhiro HIBINO, Masaru MIYAYAMA, Tetsuichi KUDO
    2001 Volume 69 Issue 1 Pages 2-5
    Published: January 05, 2001
    Released: September 25, 2019
    JOURNALS OPEN ACCESS

    Proton conductivity of some hydrated compounds such as ZrO2·nH2O, SnO2·nH2O, and Ce(HPO4)2·nH2O were investigated in the temperature range of 25°C∼150°C under saturated water vapor pressure (pH2O/ps=1, ps: equilibrium pressure). They showed high proton conductivity in the order of 10−2 S cm−1 at 150°C. The activation energies of conduction were small (0.16-0.19 eV), suggesting the surface adsorbed water mechanism. A composite of Ce (HPO4)2·nH2O with ethylene oxide/propylene oxide random copolymer (P(EO/PO)) was prepared and tested from a practical interest. It showed relatively high proton conductivity in the order of 10−3 S cm−1, though the fraction of Ce(HPO4)2·nH2O was as small as 7% in weight.

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Technical Papers
  • Kazuyuki NAGAYAMA, Kunikazu KAMIOKA, Eiichi IWATA, Hideyuki OKA, Yuji ...
    2001 Volume 69 Issue 1 Pages 6-9
    Published: January 05, 2001
    Released: September 25, 2019
    JOURNALS OPEN ACCESS

    Instability of the lithium-manganese oxide, which has the spinel structure, in nonaqueous electrolyte solution was investigated. The lithium-manganese oxide powder samples were soaked in various kinds of nonaqueous electrolyte solutions at 85°C for 4 days. The amount of manganese ions which were dissolved in the electrolyte solutions were analyzed by ICP-AES. The chemical state of the manganese ions in the solutions were identified by ESR. From the results of ESR, it had been shown that the manganese ions formed at least three different formes of Mn2+ complexes in the nonaqueous electrolyte solution. The hydrolysis of the lithium hexafluorophosphate electrolyte in the nonaqueous electrolyte solutions were followed by 31P-NMR. We suppose that the hydrofluoric acid, which was caused from the hydrolysis reaction of the lithium hexafluorophosphate electrolyte with trace amounts of water in the electrolyte solution or in lithium-manganese oxide powder, induced the solubility of manganese ions from lithium-manganese oxides.

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  • Mahito ATOBE, Kazuhito SATO, Tsutomu NONAKA
    2001 Volume 69 Issue 1 Pages 10-15
    Published: January 05, 2001
    Released: September 25, 2019
    JOURNALS OPEN ACCESS

    Ultrasonic effects on cathodic reduction and adsorption of p-methylbenzaldehyde in an acidic solution were investigated using a liquid mercury electrode. The reductions were also carried out on solid electrodes such as lead, amalgamated lead and cadmium under ultrasonic irradiation in comparison with the mercury electrode. Current efficiency for the galvanostatic electrolysis, leading to formation of the corresponding hydrodimeric (meso/dl-1, 2-di-p-methylphenyl-1, 2-dihydroxyethane; HD) and hydromonomeric (p-methylbenzyl alcohol; HM) products, was influenced by outlet power of ultrasounds at all the electrodes. In addition, product selectivities for HD/HM and meso/dl-HD were also increased and decreased, respectively, under the irradiation. However, these ultrasonic effects appeared quite different between the liquid and solid electrodes. A steady-state voltammogram of p-methylbenzaldehyde exhibited an unusual prewave with a maximum at −0.8 V vs. SCE on the liquid mercury electrode, while such a prewave could not be observed on the solid electrodes. The prewave disappeared under the irradiation as well as in the presence of a surfactant such as gelatin. The preparative scale electrolysis could be also potentiostatically carried out at −0.7 V vs. SCE in the prewave potential range in silence to give HD predominantly, while the electrolysis could not be carried out under the irradiation at such less negative potential. An electrocapillary curve in the solution of p-methylbenzaldehyde on the mercury electrode was drastically deformed from a parabola in a potential range of 0.2-0.9 V vs. SCE where the prewave was voltammetrically observed. These results suggested that the prewave might be as due to a self-catalytic reduction of p-methylbenzaldehyde adsorbed specifically on the mercury electrode.

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  • Akira KITAJIMA, Toshiharu TERANISHI, Mikio MIYAKE
    2001 Volume 69 Issue 1 Pages 16-20
    Published: January 05, 2001
    Released: September 25, 2019
    JOURNALS OPEN ACCESS

    To obtain basic information for the development of high performance electrochemical NO sensor for biological systems, performance of carbon electrodes (based on mechanical pencil leads) covered with three-layered films consisting of cationic polymer, a sieving material for NO (α-cyclodextrin, α-CD), and anionic polymer (Nafion) was investigated in vitro. We have anticipated that cationic and anionic polymer films effectively discriminate ionic species present in biological systems and that α-CD layer placed between ionic polymer films avoids charge neutralization of polymer films and concentrates NO near electrode surface by reversible sieving effects. Among cationic polymers investigated, poly(diallyldimethylammonium chloride) (PDDA) formed a film more stable than poly(ethyleneimine) (PEI) and poly(allylamine hydrochloride) (PAH). By cyclic voltammetry (CV) measurements, an electrode covered with PDDA /α-CD/ Nafion (typical thickness: 20, < 1, and 30 µm, respectively) showed higher NO oxidation current than a bare electrode, and little oxidation currents for materials present in living body, such as ascorbic acid, uric acid, dopamine hydrochloride, and sodium nitrite. Films prepared by drying solutions containing polymer and α-CD at 80°C for 5 min were stable at least for 80 min during differential pulse voltammetry (DPV) measurements with intermittent NO bubbling in a physiological saline solution called Krebs-Henseleit (KH).

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  • Xingjiang LIU, Yoshitsugu SONE, Saburo KUWAJIMA
    2001 Volume 69 Issue 1 Pages 21-26
    Published: January 05, 2001
    Released: September 25, 2019
    JOURNALS OPEN ACCESS

    For a thin film lithium-ion secondary battery, it is important to use a polymer or gel electrolyte with high ionic conductivity and good mechanical strength. In this work, two types of poly(vinylidene fluoride hexafluopropylene) (PVdF-HFP) were compared as preparing gel electrolyte for lithium-ion secondary battery. The PVdF-HFP copolymers polymerized by the emulsion method (PVdF-HFPe) and the suspension method (PVdF-HFPs), were applied in this study. The gel electrolyte was prepared by casting the THF solution of mixture of PVdF-HFP, ethylene carbonate (EC), propylene carbonate (PC) and LiClO4 salt. All of the gel electrolytes exhibited a typical arrhenius behavior in temperature dependence of ionic conductivity, and gave a high ionic conductivity of 1-3 mS cm−1 at ambient temperature when adding the 1.75 ml plasticizer to 1 g PVdF-HFP. Especially, the PVdF-HFPs gel showed a higher mechanical strength over 4 M Pa. With the cyclic voltammetry, the PVdF-HFPs gel electrolyte showed anodic stability up to above 4.0 V on Ni, Al, and stainless steel (SUS), and cathodic stability down to Li deposition potential on Cu, Ni and SUS. It was also suggested that the anode (MCMB) or cathode (LiCoO2) active material could work in the PVdF-HFPs gel electrolyte.

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  • Hiroshi MORITA, Yoshihiro MUGIKURA, Takao WATANABE, Takaaki MIZUKAMI, ...
    2001 Volume 69 Issue 1 Pages 27-33
    Published: January 05, 2001
    Released: September 25, 2019
    JOURNALS OPEN ACCESS

    The main electrode reaction of Molten Carbonate Fuel Cell (MCFC) is oxidation of hydrogen at anode and reduction of oxygen and CO2 at cathode. These gas would be supplied to MCFC through LNG reformer, compressor combined gas-turbine unit or CO2 recirculation by burning the H2 and CO of anode exhaust gas in a catalytic burner on MCFC power plant’s level. In case a unit for supplying gas to MCFC stack is in some trouble, it is perhaps possible to force the MCFC stack to generate electricity in spite of short reactive gas through inverter. In order to clarify the behavior of MCFC under such a situation, we carried out durability tests in keeping MCFC generating under no supply of respective gases (anode hydrogen, cathode oxygen or CO2) with bench-scale cells. As a result of the tests, 1) the reduction of cathode NiO to Ni (NiO + 2e → Ni + O2−) and subsequent CO product by reduction of carbonate ion (CO32− + 2e → CO + 2O2−) occur under no supply of cathode oxygen, 2) the reduction of oxygen and CO2 by dissociation of carbonate ion (CO32− → CO2 + O2− and 1/2O2 + CO2 + 2e → CO32−) occurs under no supply of cathode CO2 and 3) the oxidation of anode Ni to NiO (Ni + O2− → NiO + 2e) and subsequent oxygen and CO2 product by oxidation of carbonate ion (CO32− → 1/2 O2 + CO2 + 2e) occur under no supply of anode hydrogen.

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