Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 72 , Issue 3
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  • Manabu ISHIFUNE, Yasumichi KOGAI, Hiroyuki IIJIMA, Yoshiya KERA, Natsu ...
    2004 Volume 72 Issue 3 Pages 159-164
    Published: March 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    The silylene-germylene copolymer with the SiSiGe ordered sequences was successufully synthesized in 49% yield by the electroreductive polymerization of bis(chlorodimethylsilyl)dibutylgermane, which was prepared by the electroreductive cross-coupling reaction of chlorodimethylsilane with dichlorodibutylgermane followed by the chlorination of the Si-H bonds. The resulting copolymer having 3900 of the number average molecular weight showed a characteristic strong UV absorption bands (λmax) at 300 nm, and the extinction coefficients (εmax) per dibutylgermylene and dimethylsilylene units were calculated to be 14000. On the other hand, the electroreductive homo- and copolymerization of dibutyldichlorosilane or dibutyldichlorogermane with dichlorodimethylsilane were also carried out using Mg electrodes to give the corresponding copolymers in 6-44% yield. The number average molecular weights were 3000-4600. The copolymers showed λmax at 308 and 286 nm. The εmax per dibutylsilylene, dibutylgermylene or dimethylsilylene units were calculated to be 6300 and 1600. The εmax value of copolymer with SiSiGe sequences was found to be much higher than those of copolymers having random sequences. A large difference of the εmax values between the silylene-germylene copolymers is probably due to the conformational difference of the polymer main chain.

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  • Young-Sun PARK, Moon-Yup JANG, Tom HATAE, Hiroki ITOH, Yohtaro YAMAZAK ...
    2004 Volume 72 Issue 3 Pages 165-170
    Published: March 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    High proton conducting Nafion/Calcium hydroxyphosphate (CHP) composite membranes were prepared using homogeneous dispersive homogenizing and solvent casting process for fuel cell applications. Crystallinity from decomposed X-ray diffractograms, increased whereas crystalline sizes gradually decreased in composite membranes with the CHP amounts. In X-ray profiles, new crystalline peaks were found in the original amorphous region of Nafion in composite membranes. It suggests that the incorporated CHP forms the crystalline structure within Nafion. It may allow composite membrane to have better thermal and mechanical stability by the virtue of a kind of nucleating agent in its crystallization process. In the analysis of water bending vibration at 1673 cm-1 by FT-IR, composite membranes showed lower water uptakes than in cast Nafion. It is also noteworthy that the disappearance of hydrated proton bending vibration at 1731 cm-1 might explain that less water is required for proton to transport in composite membranes. In FIB micrographs many holes, considering as clusters and channels in the surface of the all membranes, were shown. It is likely that these channels are connected three-dimensionally. The 5% composite membrane has not only higher conductivity but also lower activation energy than in the cast Nafion. We conclude that the structural modification in crystalline and cluster regions as well as the improvement of proton transport through three dimensional channels may cause higher conductivity and lower activation energy in composite membranes.

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  • Yi LI, Sadayuki ASAOKA, Takamichi YAMAGISHI, Tomokazu IYODA
    2004 Volume 72 Issue 3 Pages 171-174
    Published: March 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    Efficient and selective N-arylation of pyridine derivatives was demonstrated as nucleophilic substitution reaction of electrochemically generated π-radical cations such as pyrene and perylene. 1-Methylimidazole also worked as a nucleophile toward pyrene π-radical cation to give the imidazorium. This reaction provides a widely applicable and powerful method for pyridinium-conjugated assembly in which redox-active pyridinium moieties can be integrated through π-conjugated system. Preparative scale synthesis was demonstrated successfully by using perylene π-radical cation prepared by chemical oxidation with I2/AgClO4. The resulting pyridinium-conjugated assembly shows both one-electron reduction assigned to the pyridium moiety and one-electron oxidation of the pyrene and perylene moieties. UV-visible absorption and fluorescence spectra indicated intramolecular charge transfer character from the pyrenyl and perylenyl moieties to the pyridinium ones of the pyridinium-conjugated assembly.

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  • Daizo TAKAOKA, Mineo IKEMATSU, Masahiro ISEKI, Kikuo TAKIZAWA, Seiichi ...
    2004 Volume 72 Issue 3 Pages 175-182
    Published: March 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    Nitrogen and phosphorus in wastewater impose a burden on the environment and cause damages such as eutrophication in closed water bodies. In the former paper, we showed that a pair of iron cathodes is able to reduce nitrate to ammonia via nitrite and discussed the reduction mechanism by comparing with nitrate reduction by ferrous ions dissolved anodically. Here we showed that, in addition to nitrite reduction, nitrite re-oxidation can be caused by hypochlorous acid in the solution generated at anode and by electrically on anode. We also showed that the nitrite oxidation can be suppressed by reducing the size of anode by minimizing the cross section of the nitrite oxidation reaction on anode.

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