Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 70 , Issue 6
Showing 1-24 articles out of 24 articles from the selected issue
Vision
Headline
Comprehensive Paper
  • Keita IKEUE, Hiromi YAMASHITA, Masakazu ANPO
    2002 Volume 70 Issue 6 Pages 402-408
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    Unique titanium oxide photocatalysts incorporated within the cavities and frameworks of zeolites and mesoporous molecular sieves were prepared and their reactivity for the photocatalytic reduction of CO2 with H2O were investigated. UV-irradiation of these titanium oxide photocatalysts in the presence of CO2 and H2O at 323 K led to the formation of CH4 and CH3OH along with a minor formation of CO and O2. The isolated tetrahedrally coordinated titanium oxide highly dispersed within the zeolite frameworks exhibited a characteristic reactivity for the selective formation of CH3OH. The photocatalytic reactivity for the formation of CH3OH was found to be closely associated with the concentration of charge transfer excited triplet state, (Ti3+—O)*, of the highly dispersed tetrahedrally coordinated titanium oxide species and the selectivity for the photocatalytic formation of CH3OH was controlled by the hydrophobic and hydrophilic properties of these photocatalysts.

    Download PDF (684K)
Communications
  • Tatsuo ERABI, Takayuki OHTSUKI, Eiko OSAKI, Yohko ISHIKAWA, Tomomitsu ...
    2002 Volume 70 Issue 6 Pages 409-411
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    Photoelectrochemical behavior of triarylmethylium salts ([Φ3C]ClO4 and [Φ′Φb2C] ClO4 [Φ and Φ′ represent 2,4,6-trimethoxyphenyl, 2,6-dimethoxyphenyl, 2-methoxyphenyl, 4-methoxyphenyl, and phenyl groups]), expected as a novel photosensitizer, was studied at an ITO electrode in 1,2-dichloroethane under potentiostatic conditions. The slow increase in a cathodic current was observed upon illumination. The observed photocurrent depended on the applied potential, and the half-wave potential was close to the redox potential based on methylium-methyl radical redox couples. The photocurrent also depended on the concentration of the salts, and the illuminance of the incident light.

    Download PDF (249K)
  • Suzuko YAMAZAKI, Kensuke ARAKI
    2002 Volume 70 Issue 6 Pages 412-415
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    The photo-assisted catalytic degradations of trichloroethylene (TCE) and tetrachloroethylene (PCE) were studied in a tubular photoreactor packed with TiO2 pellets prepared by sol-gel method. The experiments were performed at 32°C in a non-circulating mode. Comparison with the ethylene degradation reveals that TCE and PCE were degraded more efficiently than ethylene. However, only 48% of TCE or 57% of PCE was converted to HCl and CO2 whereas 95% of ethylene was mineralized. Phosgene, CHCl3 and dichloroacetic acid were detected from the photodegradation of TCE while that of PCE yielded phosgene, CCl4 and trichlroacetic acid. Phosgene in the effluent gas stream was completely removed by passing through water. The reaction mechanism to form these chlorinated products is discussed.

    Download PDF (455K)
  • Kara MOCHIZUKI, Noriyuki ASAKURA, Toshiaki KAMACHI, Ichiro OKURA
    2002 Volume 70 Issue 6 Pages 416-417
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    A photochemical new oxygen sensor using continuous wave Nd-YAG laser (CW laser) as an excitation light has been developed, which is based on the stationary state quenching of triplet-triplet (T-T) absorption of zinc 5,10,15,20-tetrakis-(pentafluorophenyl)-porphyrin (ZnTFPP) by oxygen. The intensity of ZnTFPP T-T absorption decreases with oxygen concentration, indicating the applicability for oxygen sensor.

    Download PDF (183K)
  • Satoshi UCHIDA, Ryoji CHIBA, Miho TOMIHA, Naruhiko MASAKI, Masayuki SH ...
    2002 Volume 70 Issue 6 Pages 418-420
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    Titania nano tube was successfully obtained by hydrothermal treatment of nano size TiO2 fine powder in 10 M NaOH solution for 20 h at 110°C. The morphology of product was 8-10 nm in width and about 100 nm in length with tubular shape. The specific surface area was 270 m2 g−1, much higher than that of starting material titania powder with 50 m2 g−1. Photovoltaic properties of these titania film was also examined. The results were VOC = 0.704, ISC = 1.26 mA, η = 2.9%, FF = 0.66 for titania nano tube, and VOC = 0.767, ISC = 1.20 mA, η = 3.0%, FF = 0.72 for titania nano powder (P-25).

    Download PDF (431K)
  • Shigeko OZAKI, Lian-hua ZHAO, Kiminori ITOH, Masayuki MURABAYASHI
    2002 Volume 70 Issue 6 Pages 421-424
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    The gas-phase photocatalytic decomposition of individual- and two-component mixtures of chloroethylenes using near-UV-illuminated TiO2 was studied. The apparent quantum efficiencies for the degradation of cis-1,2-dichloro- (0.42), trichloro- (9.6), and tetrachloroethylene (10.6) were found to increase with the number of chlorine substituents. cis-1,2-Dichloro- and trichloroethylene in the presence of tetrachloroethylene decomposed with higher quantum efficiency, specifically, 1.6 and 11.7, respectively. The decomposition of cis-1,2-dichloroethylene in the mixtures was remarkably promoted, while the apparent quantum efficiency of tetrachloroethylene to function as an accelerator showed a decrease for the decomposition with cis-1,2-dichloroethylene (3.6) or with trichloroethylene (9.1). These findings were explained in terms of the presence of chlorine atoms in photochemical and photocatalytic reactions.

    Download PDF (364K)
  • Shin YAMAMOTO, Kiminori ITOH, Masayuki MURABAYASHI
    2002 Volume 70 Issue 6 Pages 425-428
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    The effect of Cl radical on direct photodegradation rates of phosgene was investigated using the circulation-type apparatus. Cl radical was hardly formed from molecular chlorine using a low-pressure mercury lamp, which had been employed for direct photodegradation of phosgene, because the spectrum of low-pressure mercury lamp is hardly absorbed by molecular chlorine. It was observed that Cl radical was formed from molecular chlorine by the irradiation from black-lights. Under presence of molecular chlorine and the irradiation from black-lights, significant increase in the rate constant of photodegradation of phosgene using low-pressure mercury lamp was observed. In addition small effect of increase of residence time in the reactor was observed.

    Download PDF (405K)
  • Hyun-Jeong NAM, Kiminori ITOH, Masayuki MURABAYASHI
    2002 Volume 70 Issue 6 Pages 429-431
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    TiO2 thin films on borosilicate glass and quartz glass substrates were prepared in order to investigate the influence of the substrate on photocatalytic activity. The preparation of TiO2 thin film was performed by sol-gel method. The influence of the substrate on TiO2 crystallization was examined at different TiO2 thin film sintering temperatures. The TiO2 thin film was irradiated with black-light fluorescent lamps. Photocatalytic activity was compared using trichloroethylene (TCE). The photocatalytic activity of the TiO2 thin film was confirmed to vary with the substrate. The crystal structures of the TiO2 thin films prepared on the glass substrates were examined using X-ray diffraction analysis, and the UV absorption of the thin film was measured by means of a spectrophotometer.

    Download PDF (384K)
  • Akinori KONNO, Gamaralalage R.A. KUMARA, Ryosuke HATA, Kirthi TENNAKON ...
    2002 Volume 70 Issue 6 Pages 432-434
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    A promising and cheaper alternative to the silicon solar cell, is the dye-sensitized photoelectrochemical cell and a solid-state dye-sensitized cells using p-CuI as the hole-conductor has advantages to conventional wet-type cells for practical use. However, this n-type semiconductor/Dye/p-type semiconductor device has problem of the long-term photostability. In this paper, the results of addition of several l-ethyl-3-methylimidazolium (Im) salts and the effect of their counter anions on the performance of the cell are described. We improved the performance and stability of the solid-state dye-sensitized solar cell using CuI with ImSCN whereas other Im salts showed only slight effect except for ImI.

    Download PDF (287K)
  • Hisashi HARADA, Koji SUDA
    2002 Volume 70 Issue 6 Pages 435-437
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    This paper deals with solid-solid photocatalysis; i.e. photocatalytic reaction for a solid substrate using Pt/TiO2 powdered photocatalyst (solid) under illumination. Malonic acid reacts to CO2 and a small amount of other minor products in an aqueous suspension of powdered photocatalyst under Ar atmosphere. In the case of the solid-solid system, CH4 was also produced from malonic acid as a major product together with CO2. The change of products distribution was observed and the changing behavior of products distribution with an addition of water was examined. Our result showed that the allowed limit amount of water to change the selectivity could be determined. Scheme of product switching was also discussed.

    Download PDF (303K)
  • Tsukasa TORIMOTO, Shihui SI, Bunsho OHTANI
    2002 Volume 70 Issue 6 Pages 438-441
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    Photoelectrochemical quartz crystal microbalance measurements were used for in situ monitoring of the photoelectrochemical deposition of PbO2 onto a TiO2 nanoparticulate film electrode. It was found that the photodeposition behavior of PbO2 was influenced by pH of solution. At pH 3.8, the mass of the TiO2 film electrode decreased in the initial stage of irradiation due to the desorption of Pb2+ from the TiO2 surface and then linearly increased due to PbO2 deposition with an increase in the charge flowing as a photocurrent, while the initial decrease of the mass was much smaller at pH 1.8.

    Download PDF (376K)
  • Shigeru IKEDA, Chigusa ABE, Tsukasa TORIMOTO, Bunsho OHTANI
    2002 Volume 70 Issue 6 Pages 442-445
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    The reaction between titanium(IV) oxide (TiO2) powders and 1,1′-binaphthalene-2,2′-diol (bn(OH)2), both of which are originally colorless, led to the formation of surface TiO2-bn(OH)2 complexes giving a broad absorption in the visible-light region below ca. 550 nm. When the surface complex was made on TiO2 loaded with platinum deposits, the powder exhibited photocatalytic activity for H2 evolution from deaerated triethanolamine solution under visible-light irradiation (>430 nm). On the basis of the experimental results, the reaction mechanism seems to involve visible-light excitation of the surface complexes, electron injection to TiO2, and its migration to platinum deposits, where reduction of H+ takes place.

    Download PDF (414K)
  • Toshihiko MATSUDA, Hajime MATSUMOTO
    2002 Volume 70 Issue 6 Pages 446-448
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    A liquid polyiodide, composed of 1-hexyl-3-methylimidazolium iodide and iodine without any solvent, was used as a redox mediator in cis-Ru(4,4′-dicalboxyl-2,2′-bipyridine)2(thiocyanato)2-sensitized porous TiO2 solar cells with varying iodine mole fractions. For iodine mole fractions below 0.5, short-circuit anodic photocurrents were observed. However, for iodine mole fractions above 0.5, short-circuit cathodic photocurrents were observed. A mechanism of the photocurrents was discussed, and it is shown that a high concentration of I3 promotes the back reaction of electrons with I3 on transparent conducting oxide substrates under illumination, as well as acting as a filter of incident light into solar cells.

    Download PDF (299K)
  • Motonari ADACHI, Issei OKADA, Supachai NGAMSINLAPASATHIAN, Yusuke MURA ...
    2002 Volume 70 Issue 6 Pages 449-452
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    Over two times higher short-circuit photocurrent density was attained in the dye-sensitized solar cells by using titania nanotubes as a semiconductor thin film in the thin film thickness region in comparison with that made of P-25. Titania nanotubes were synthesized by a surfactant-assisted templating mechanism using a laurylamine hydrochloride/tetraisopropylorthotitanate with acetylacetone system.1) Nanotubes have a mono-crystalline structure of anatase and showed the highest photocatalytic activity among the commercially available nano-crystalline titania. The dye-sensitized solar cell system using the mono-crystalline titania nanotubes showed about 5% sunlight-electricity conversion.

    Download PDF (345K)
  • Tsukasa YOSHIDA, Atsushi SHINADA, Torsten OEKERMANN, Takashi SUGIURA, ...
    2002 Volume 70 Issue 6 Pages 453-456
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    Time- and frequency-resolved photoelectrochemical studies have been performed on nano-honeycomb porous TiO2 electrode prepared by photoelectrochemical etching of single crystal TiO2, both for its bare surface and when sensitized by cis-di(thiocyanato)-N,N-bis(2,2’-bipyridyl-4,4’-dicalboxylate)ruthenium(II). Since the remaining wall in the porous layer become as thin as the double thickness of the space charge layer by photoetching, electron diffusion comes to play the main role in the charge transport rather than field-driven migration. Intensity modulated photocurrent spectroscopy revealed much faster electron diffusion in the honeycomb electrode than that in colloid based porous electrode, because of the smaller electron trap density in the nano-honeycomb structure owing to the nonexistence of grain boundaries.

    Download PDF (411K)
  • Akira TSUJIKO, Yuichiro SAJI, Kei MURAKOSHI, Yoshihiro NAKATO
    2002 Volume 70 Issue 6 Pages 457-459
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    The surface structure of TiO2 particles was changed by illumination in a sulfuric acid solution. Small dimples with a size less than a few tens of nm were formed when the surface of the particles was modified by platinum. Particles without the platinum modification did not show any change in their surface structure. A structural change was also observed when the particles were positively polarized in a sulfuric acid solution under illumination on an optically transparent glass electrode. The results suggest that the density of the photogenerated holes in the particles play an important role in inducing the photoetching reaction of TiO2 particles.

    Download PDF (360K)
  • Yoshihisa OHKO, Shuichi SAITOH, Tetsu TATSUMA, Akira FUJISHIMA
    2002 Volume 70 Issue 6 Pages 460-462
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    SrTiO3 photocatalyst was combined with an energy storage material, WO3, to fabricate a new photocatalysis system, envisaging application to, e.g., protection of metals from corrosion. The SrTiO3-WO3 composite system stores reductive energy under UV irradiation, as does the TiO2-WO3 system. Since SrTiO3 exhibits more negative photopotential (ca. −0.5 V vs Ag | AgCl) than TiO2 (ca. −0.4 V), the SrTiO3-WO3 system can be charged more rapidly. In addition, self-discharging of the SrTiO3-WO3 system on the basis of aerobic re-oxidation of the system is slower than that of the TiO2-WO3 system.

    Download PDF (329K)
  • Go HITOKI, Tsuyoshi TAKATA, Junko N. KONDO, Michikazu HARA, Hisayoshi ...
    2002 Volume 70 Issue 6 Pages 463-465
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    A range of transition-metal oxynitrides and a nitride were examined as potential photocatalysts active under visible light. (Oxy)nitrides based on tantalum, niobium and titanium are found to absorb visible light (λ ≤ 600 nm), and some of them are found to evolve H2 or O2 from aqueous solutions containing a sacrificial electron donor (CH3OH) or acceptor (Ag+), respectively, via band gap excitation without noticeable photo-degradation of the catalyst itself.

    Download PDF (310K)
Technical Papers
  • Satoshi UCHIDA, Miho TOMIHA, Naruhiko MASAKI
    2002 Volume 70 Issue 6 Pages 466-469
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    Preparation of titania/water paste for the electrode of dye-sensitized solar cell was examined. The dispersion mechanism of titania powder was related to both pH and viscosity of the paste in view of rheology. It can be concluded that lower pH than that of pzc (point zero charge) is necessary to keep on the highly dispersed state of titania powder in the paste. In the meanwhile, such a well-dispersed paste has very low viscosity, which are unsuitable for making a thick titania film. Therefore various kinds of additives as a thickener have also been studied.

    Download PDF (340K)
  • Tsukasa YOSHIDA, Torsten OEKERMANN, Kenji OKABE, Derek SCHLETTWEIN, Ka ...
    2002 Volume 70 Issue 6 Pages 470-487
    Published: June 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    A comprehensive study has been conducted on the cathodic electrodeposition of ZnO/eosinY hybrid thin films from aqueous mixed solutions containing Zn(NO3)2 and eosinY, as well as their photoelectrochemical characteristics. Adsorption of eosinY molecules on the growing surface of ZnO leads to the automatic formation of a nano-porous hybrid structure consisting of interconnected nano-sized ZnO crystals. The dye molecules are loaded into the film at a very high amount as orderly packed layer, being chemically attached to the internal surface of ZnO through their carboxylic acid group, and a major part of them could be desorbed by alkaline treatment without dissolving ZnO. Under the conditions of film preparation, electrochemical reduction of an eosinY molecule coupled with stable complex formation with a Zn2+ ion has been observed and is supposed to play a key role in the process of “self-assembly” of the three dimensional ZnO/eosinY hybrid structures. The electrodeposited ZnO/eosinY hybrid thin films exhibit a high performance as sensitized photoelectrodes. Intensity modulated photocurrent and photovoltage spectroscopies have shown a fast diffusion and a long lifetime of electrons injected from photoexcited eosinY into the conduction band of ZnO, indicating an almost barrier-free transport in the porous network of ZnO grown from solution. A high incident photon to current conversion efficiency of 47% was obtained in the absorption maximum of the loaded dye following a mild heat treatment of the film at 150°C, making the present material applicable to conductive plastic substrates for realization of flexible dye-sensitized solar cells.

    Download PDF (2231K)
Note
feedback
Top