Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 72 , Issue 12
Showing 1-23 articles out of 23 articles from the selected issue
Visions
Headline
  • Hiroshi IRIE, Kayano SUNADA, Kazuhito HASHIMOTO
    2004 Volume 72 Issue 12 Pages 807-812
    Published: December 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    Although building materials coated with photoactive TiO2 show remarkable self-cleaning and anti-fogging effects outdoors by absorbing UV rays from the sun, they do not function indoors. This is because the UV light intensity indoors is too weak for a simple TiO2 coating to exhibit either photocatalysis or photo-induced hydrophilicity. In order to obtain interior photoactive building materials, herein we report three different types of materials based on TiO2, which can function even under room light conditions. First is a TiO2 film deposited with Cu that shows a remarkable antibacterial effect since the TiO2 photocatalytic reaction assists the intrusion of antibacterial copper ions into cells. Thus, even very weak UV light is sufficient to lower cell activity. Second is a layered TiO2/WO3 heterogeneous film, which becomes highly hydrophilic even under fluorescent light since the photo-generated holes produced in WO3 by UV light are transferred to the TiO2 side and then used for hydrophilic conversion. Third is a nitrogen doped TiO2 film, which can be highly hydrophilic by absorbing only visible light. In addition, we demonstrate a novel application of outdoor building materials coated with TiO2 to environmental technology using its photo-induced high hydrophilicity. By noting that a very thin water film can form on a highly hydrophilic surface and evaporation can effectively lower the temperature by robbing the latent heat from surroundings, we proposed a novel method for cooling the surfaces of buildings and their atmospheres, i.e., a small amount of water is continuously poured onto the surface of TiO2 coated materials. We show that this method can even reduce the temperature of a room, resulting in an energy conservation.

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Comprehensive Paper
  • Takashi OYABU, Ayako SAWADA, Tomoaki HASHIMOTO, Takayuki YOSHIOKA
    2004 Volume 72 Issue 12 Pages 813-817
    Published: December 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    Activated carbon has a high porous structure and it can absorb many kinds of chemical substances in an atmosphere. In this study, the capability was examined for formaldehyde, toluene and xylene using a tin oxide gas sensor, which are named as VOCs(volatile organic compounds). An interior plant pot was made of the activated carbon and was adopted as a subject. It had a high capability to remove those chemicals. The pot, which was installed in an experimental chamber, could absorb entirely the formaldehyde of about 6.5 ppm in five hours. It also had a removing capability to larger molecular weight chemicals, for example toluene and xylene. The sensor has higher sensitivity to the gases because there are a lot of free radicals on the sensor surface and many free electrons generate in the sensor bulk. Based on these results, the three pots were installed in a real office room and examined the removing capability. In the room, the formaldehyde was emitted continuously and the saturated concentration was almost constant. The concentration was decreased until 60% by installing the pots. They had a high removing capability to continuously emitting formaldehyde. The sensor output was sometimes calibrated by a formaldehyde measuring instrument. In the experimental room, temperature, humidity, light intensity, oxygen and carbon dioxide concentrations were also measured simultaneously. The characteristics had a correlation each other.

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Communications
Article
  • Yoshiki SHIMODAIRA, Toshiko MIURA, Tetsuyuki OKUMACHI, Tokio YAMABE, A ...
    2004 Volume 72 Issue 12 Pages 865-869
    Published: December 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    The density functional theory (DFT) calculation has been applied to investigate CO and H2 adsorption onto Pt-Ru, Pt-Rh, Pt-Pd, Pt-Ag alloys as well as Pt metal modeled by PtxM10−x (M = Ru, Rh, Pd, Ag, and x = 3, 5, 7) clusters. The most durable catalysts for CO poisoning were searched using the criteria that adsorption of CO should be weakened compared to pure Pt but adsorption of H2 should not be weakened, or activation energy for the H-H bond fission is not increased. Pt5Ru5 and Pt7Ru3 were the best catalyst in conformity with many experimental works. Slab calculation showed that Pt is more localized in the surface layer than the bulk content in Pt-Ru alloy. Energy profiles calculated for the two reactions, CO + OH → COOH and H2O → OH + H were compared between Pt and Pt-Ru alloy. No significant advantage for Pt-Ru alloy was found for the former reaction, but OH formation was more facile for the Ru site of Pt-Ru alloy.

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Technological Report
  • Kiyoshi KOBAYASHI, Shu YAMAGUCHI, Toru HIGUCHI, Shik SHIN, Takeyo TSUK ...
    2004 Volume 72 Issue 12 Pages 870-875
    Published: December 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    The electrical conductivity, thermoelectric power, and thermal conductivity of Ln0.9Sr0.1FeO3−δ (Ln = La and Nd) were measured as functions of temperature and oxygen partial pressure, and the electrical transport parameters were calculated using the defect model. It was found that the values of hole mobility, the equilibrium constant of the annihilation reaction for the oxide ion vacancy, thermal conductivity of La0.9Sr0.1FeO3−δ are larger than the values of Nd0.9Sr0.1FeO3−δ, while the thermoelectric power of La0.9Sr0.1FeO3−δ is smaller than those of Nd0.9Sr0.1FeO3−δ at the same hole concentration and temperature. Based on the X-ray absorption spectroscopy measurements, it is suggested that the thermoelectric properties of La0.9Sr0.1FeO3−δ and Nd0.9Sr0.1FeO3−δ are affected by the covalency of iron ions.

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Notes
  • Shigeomi TAKAI, Nobutaka HOSHIMI, Takao ESAKA
    2004 Volume 72 Issue 12 Pages 876-879
    Published: December 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    The oxide bronzes have been synthesized by the mechanochemical method. It was found that the deep-blue tungsten bronze was obtained by more than 12 hours milling with adding the non-polar liquid hydrocarbons. X-ray diffraction and TG-DTA measurements revealed that hydrogen content in the obtained bronzes can be controlled by milling time. Molybdenum and vanadium bronzes were also found to be formed by milling MoO3 and V2O5 powders milled with xylene. A self-supported membrane was prepared by casting the milled molybdenum bronze and ion exchange resin with acethilcellrose, which was electrolyzed to observe the elecrochromic behavior.

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  • Raghavan SUBASRI, Tadashi SHINOHARA
    2004 Volume 72 Issue 12 Pages 880-884
    Published: December 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    Photoelectrochemical characterization of copper specimens coated with a bilayer photoanode bearing the configuration Cu | Sb-SnO2 | SnO2 + TiO2 was carried out for verifying the suitability of such coatings for a cathodic protection of copper in presence of ultraviolet illumination. An optimization of the heat-treatment temperature of the coatings was accomplished which showed that a 200°C heat treatment was sufficient to obtain a desirable photoeffect. The results of the present investigation also showed that such bilayer photoanodes are functional for cathodic protection applications in the case of copper only under conditions of low oxygen potentials. A continued cathodic protection was possible even after cessation of ultraviolet illumination due to a charge storage of the photogenerated electrons transferred from TiO2 to SnO2, which could be slowly released to the metal substrate continuing to offer a cathodic protection under no illumination conditions.

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