1990 Fiscal Year Final Research Report Summary
Electrochemical Oxidation of O-Containing Substances and Energy Conversion
| Project/Area Number |
01470075
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
工業物理化学
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| Research Institution | Hokkaido University |
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Principal Investigator |
KITA Hideaki Hokkaido University, Faculty of Science Professor, 理学部, 教授 (30001712)
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| Co-Investigator(Kenkyū-buntansha) |
SHIMAZU Katsuaki Hokkaido University, Associate Prof., 理学部, 助教授 (30109417)
NAKAJIMA Hiroshi Hokkaido University, Associate Prof., 理学部, 助教授 (00000852)
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| Project Period (FY) |
1989 – 1990
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| Keywords | Reaction mechanism of electrooxidation of methanol / Analysis of time-dependent kinetics / Methanol fuel cell / Adsorbed hydrogen on Pt single crystal planes / Hydrogen electrode reaction and adsoarbed hydrogen / Solid polymer electrolyte membrane electrode / Molybdenum pomoter in methanol oxidation / (6) Effects of adsorbed carbon monoxide on electrode reactions |
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| Research Abstract |
1. Reaction Mechanism of Methanol Electrooxidation The reaction kinetics for the oxidation of methanol on a platinum electrode have been examined under precisely controlled conditions. The Tafel relations at constant surface coverages of the strongly adsorbed species show the existence of two potential regions where the predominant reaction path is different. The surface reaction of the strongly adsorbed species with OH (a) is rate determining at E>ca. 0.55 V, while the oxidative adsorption of methanol to form a reactive intermediate becomes the rate-determining step at E<ca. 0.55 V. In the latter potential region, the strongly adsorbed species is not oxidized so that its accumulation on the surface decreases the rate of the oxidative adsorption and thereby the total oxidation rate.
2. Preparation ofSingle Crystal Electrode and its Electrochemical Behavior The electrochemical behavior of hydrogen and oxygen adsorption on platinum low- and high-index planes was examined in acid and alkal
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i solutions. The features varied systematically with the surface structure and the pH of solution and are discussed in terms of steps and terraces of the respective surfaces. With respect to adsorbed hydrogen, Pt (111) provides mainly a long-range ordered adsorption site, Pt (100) mainly short-range ordered site, respectively. These adsorbed hydrogens do not take part in the hydrogen evolution reaction. The reaction intermediate is the on-top hydrogen atom. Electrochemical behavior of adsorbed CO is also examined.
3. Methanol Oxidation at Pt-SPE Electrode Modification of Pt-SPE electrode with molybdenum reduces the oxidation potential of methanol by ca. 0.15 V (ca. 10^2 times higher reaction rate). The redox couple of Mo (III) / Mo (IV) plays a key role in the enhancement of the catalytic activity of the Pt electrode. An extended analysis of voltammograms of the electrode coadsorbed with molybdenum and methanol species showed that the highest oxidation current is obtained at an equal coverage of the molybdenum and methanol species. The bifunctional mechanism was discussed. Less
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