(Abstract)

Photocatalytic properties of TiO₂ aqueous suspension were analyzed by means of the chemiluminescent probe method, which enables us to monitor superoxide ions (O₂^-) and hydrogen peroxide (H₂O₂) in the reaction system. The amount of produced O₂^- is independent on the surface properties of TiO₂, while H₂O₂ is formed significantly for smaller particles with large amount of surface hydroxyl groups. The amount of produced OH radicals was estimated from the effect of Cl^- ions on the O₂^- formation and found to be large for the TiO₂ having a large amount of surface hydroxyl groups. This difference is explained to originate from the different structure of hole intermediates, based on the ESR measurements for these powders at 77K.