INVESTIGATION OF PHOTOCATALYTIC DECOMPOSITION MECHANISM OF ORGANIC-COMPOUNDS ON PLATINIZED SEMICONDUCTOR CATALYST BY ROTATING-RING-DISK ELECTRODE TECHNIQUE

Rotating Pt-ring TiO2-disk electrodes were used to investigate the catalytic mechanism of Pt sites in platinized semiconductor catalysts. When a TiO2 disk electrode immersed in a methanol-water mixture was illuminated with chopped light, an anodic current was observed at the Pt ring electrode even at cathodic potentials at which reduction (cathodic) current was expected to flow. This peculiar phenomenon was enhanced by oxygen bubbling and could be observed only in solutions with pH < 8. The phenomenon was analyzed in terms of a HO2. radical which can promote a deprotonation reaction of organic compounds such as methanol. The decomposition (oxidation) of organic compounds also can occur at Pt sites in the presence of oxygen and hydrogen ions.