Photocatalytic remote oxidation with various photocatalysts and enhancement of its activity

Photocatalytic remote oxidation with various photocatalysts, anatase TiO2, oxygen deficient TiO2, brookite TiO2, ZnO, WO3, metal (Au, Pt, Ag and Pd)-loaded anatase TiO2 and metal (Au, Pt and Ag)-loaded ZnO, were investigated. All these photocatalysts exhibited activities for remote oxidation. Among them, Pt-loaded TiO2 exhibited the highest activity; it took 2 min to make the octadecyltriethoxysilane-modified glass surfaces super-hydrophilic, while bare anatase TiO2 took 24 min. Since the remote oxidation activity of a TiO2 film that was prepared without organic compounds was almost the same as that of a normal TiO2 film, which contains organic impurities, the active species essential to the remote oxidation is not generated photocatalytically from the organic impurities but from ambient species such as O-2 and H2O. The photocatalytic remote oxidation by TiO2 and Pt-TiO2 could be applied to poly(vinylidenefluoride) and many other materials but not to Teflon. The same trend was observed for Fenton and H2O2-UV reactions, in which hydroxyl radical is generated, suggesting that an oxidizing species as strong as a hydroxyl radical is involved in the remote oxidation.