| Research Abstract |
This project has been made to clarify the excited states of the metal oxides and the intermediate species of photo-induced and/or photocatalytic reactions on the metal oxide catalysts, in oder to understand the true nature of photocatalysis, especially, in the primary processes. With the transition metal oxide catalysts supported onto <SiO_2> or porous Vycor glass, the charge transfer excited triplet state, <(Me ((n-1)+)]- O^-)^*> plays a significant role in the photo-induced and/or photocatalytic reactions on them. It has been found that the olefin metathesis reaction is photo-induced on supported Mo oxides with much higher quantum yield than 1.0, the mechanism involving a charge transfer excited triplet of the tetrahedrally co-ordinated Mo species being proposed. Mo and Ti oxide catalysts anchored onto <SiO_2> or porous Vycor glass were found to exhibit much higher photocatalytic activities than those the catalysts prepared by the conventional impregnation method, due to much higher dispersion of metal ions. On MgO oxide catalysts with co-ordinatvely unsaturated surface ions, charge transfer excited complexes were also found to play a significant role in the photocatalysed isomerization reaction of 2-butenes. With synthesized extremely samll particle <TiO_2> catalysts, the size quantization effect has been observed first for the photocatalysed hydrogenolysis of unsaturated hydrocarbons with <H_2O> . The yields of the photocatalytic reaction increase with decreasing the particle size of <TiO_2> , especually less than 100 <Ang> . Potential utilization of binary metal oxides involving Ti ions as photocatalysts has been investigated, the enhancement of the photocatalytic activity of <TiO_2> species being found in Te-Si and Ti-Al binary metal oxide catalysts.
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