SACRIFICIAL PHOTOLYSIS OF WATER ON TIO2 FINE POWDERS PREPARED BY THE HYDROTHERMAL METHOD

The often discussed role of surface hydroxylation of TiO//2 particles as an essential characteristic for their photocatalytic activity can be verified by preparing TiO//2 powders by a hydrothermal method, since hydroxylated surface layers will be better retained on these particles formed in superheated water. Thus, fine powders of TiO//2 (rutile) with high degree of crystallinity are formed from titanium oxychloride in a mixed solvent of water and 2-propanol at 160-230 degree C and 20-120 atm. The anatase phase is produced from the same medium when sulfate ion impurity is present, with left bracket SO//4**2** minus right bracket / left bracket Cl** minus right bracket greater than 0. 03. Aqueous suspensions of both forms of TiO//2, either as such or after Pt-loading, do not produce H//2 on band gap illumination, whereas H//2 is generated in the presence of hole scavengers such as EDTA, TEOA, sulfite or hypophosphite. The effects of hole scavenger concentration, Pt:TiO//2 ratio, particulate suspension density and the nature of hole scavengers on H//2 production are presented.