| Budget Amount *help |
¥6,000,000 (Direct Cost: ¥6,000,000)
Fiscal Year 1987: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1986: ¥5,500,000 (Direct Cost: ¥5,500,000)
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| Research Abstract |
The majn purpose of this research is to elucidate the molecular mechanism of the photooxidation reaction of water at n-type metal oxide semiconductor electrodes such as n-TiO2 and n-SrTiO_3, mainly by using a method of our recently developed surface luminescence spectroscopy. Through such research, new active electrode materials for electrochemical oxidation reaction of water will be found. We have focused our attention mainly on the mechanism of the photooxidation reaction at the n-TiO, electrode. Though it has often been assumed so far that this reaction proceeds via adsorbed OH radicals produced by the oxidation of adsorbed OH ions by photogenerated holes, it has been concluded in this re- search that this reaction proceeds via interstitial OH radicals produced in the n-TiO_2 bulk close to the surface. Theoretical considerations have sup- ported the latter new mechanism, showing that (1) OH^- ions can be assumed to penetrate into the n-TiO_2 (rutile) bulk through channels present parallel to the c-axis of this crystal, and (2) the resulting interstitial OH- ions in the n-TiO_2 bulk are energetically more easily oxidized than the adsorbed OH- ions, and can be assumed to be oxidized by the photogenerated holes, contrary to the adsorbed OH- ions. The above new mechanism is of great interest, proposing quite a new concept for the understanding of the mechanism of electrode reactions. This mechanism is also very interesting from a practical view-point, in that it indicates the possibility of finding new active electrode materials through the re-investigation of electrode materials on the basis of this new concept. Furthermore, the present finging of this new mechanism is of great value in that it clearly indicates that the surface luminescence spectroscopy is very effective for the in situ investigation of the molecular mechanism of the electrode reactions.
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