Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 70 , Issue 9
Showing 1-18 articles out of 18 articles from the selected issue
Vision
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Technical Papers
  • Toyohisa HOSHIKAWA, Ryuji KIKUCHI, Kazunari SASAKI, Koichi EGUCHI
    2002 Volume 70 Issue 9 Pages 675-680
    Published: September 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    The ac impedance spectroscopy was applied to dye-sensitized solar cells with TiO2 or Nb2O5 as the semiconductor electrode. It was found that the impedance spectra consisted of three or four semicircles in the Nyquist representation. The arc with a characteristic frequency of a few hundred Hz was attributable to the electron transport between the semiconductor particles or within the particles, the arc at a few Hz to the electron transport at the electrode/dye/electrolyte interface, and the arc at the frequency in the order of 10−1 Hz to the reduction of the electrolyte at the Pt electrode/electrolyte interface. The resistance of the arc at a few Hz decreased as the amount of the dye adsorbed on the TiO2 electrode and the irradiation intensity increased. When the Nb2O5 particles with large BET surface area were used as the electrode, the internal resistance of the solar cell was lowered; especially the shrinkage of the arcs in diameter at a few hundred Hz and a few Hz was significant.

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  • Takeshi NANAUMI, Yasuhiko OHSAWA, Koichi KOBAYAKAWA, Yuichi SATO
    2002 Volume 70 Issue 9 Pages 681-685
    Published: September 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    Activated carbon has high power density, but has limited specific capacity. To increase the capacity of activated carbon, ruthenium oxide was loaded into coal-based activated carbon by suspending the activated carbon in an aqueous RuCL solution followed by neutralization. Although the BET surface area of the activated carbon decreased upon ruthenium oxide loading compared to that of the starting material, its capacitance increased. The maximum capacity obtained in this study was 324 F g−1 for activated carbon loaded with 3.2 wt% ruthenium, an increase of about 25%. This unexpected large increase is considered to be due to an introduction of pseudocapacitance of ruthenium oxide and a new mesopore formation by oxidation of activated carbon during the heating process of the composite to improve the pore utility for double layer capacitance.

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  • Masayuki ITAGAKI, Makoto IGARASHI, Kunihiro WATANABE
    2002 Volume 70 Issue 9 Pages 686-691
    Published: September 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    The electrochemical impedance of various crevice electrodes has been calculated by a transmission line model using matrix. Inside of the crevice was divided into 300 parts, and the solution resistance, the charge transfer resistance, and the capacitance of electric double layer were assumed as the function of the position in the crevice. It takes approximately 10 min to calculate one spectrum of the impedance by the desk-top computer. The impedance shows frequency dispersion due to the current distribution in the high frequency range. The experimental impedance of artificial crevice electrodes was in agreement with the calculated results. The current distribution, which originates by the frequency and the position in the crevice, can be obtained in the course of the computer simulation.

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Technological Report
  • Kiyoteru OSAWA, Takahisa YAMASHIRO, Noriyuki KITAORI
    2002 Volume 70 Issue 9 Pages 692-696
    Published: September 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    The ultrasonic washing appliance used by professionals shows high cleaning performance in removing stains and spots from clothes. However, the machine system with high cleaning performance requires high electric power, and is large and heavy. We developed a portable ultrasonic washing machine for the common user. The conditions of the ultrasonic washing machine are as follows (1) the frequency of the oscillator (a bolt-clamped Langevin-type transducer) is 50 kHz, (2) the vibrator yields amplified vibration of the oscillator due to the unique shape of metal blocks (Al), (3) the oscillation circuit adjusts the phase to the waveform of voltage and electric current. Our product had the same cleaning effect as that of the professional washing appliance. It is powered by four dry batteries (size AA), and is very light in weight and compact.

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