1981 年 39 巻 7 号 p. 589-602
The photocatalytic activity of powdered TiO2 was increased enormously by supporting various catalysts such as Pt and RuO2·Water was decomposed into hydrogen and oxygen by using such photocatalysts. Interestingly, hydrogen evolution rate was enhanced remarkably by adding solid carbon or various organic compounds such as alcohols, carbohydrates or various biomasses to the aqueous suspension of the photocatalyst. For the decomposition of methanol and ethanol the quantum yield of hydrogen evolution exceeds 40-50 %. Those organic compounds were found to work as reducing agents and to be oxidized into CO2. Water was reduced photocatalytically to produce hydrogen. In addition to TiO2, various semiconductors which have the band gap in the visible wave-length region were found to evolve hydrogen by the same method. In the photocatalytic reactions of a large molecule such as carbohydrates with water, simple organic comounds such as methane, ethane, and ethanol were produced, showing some similarities with fermentation by microorganisms. The possibility of the application to organic synthesis was suggested. A water splitting system to produce hydrogen by using sun light was proposed combining these photocatalytic reactions with the photosynthesis of green plants.