Photocatalytic remote oxidation with various photocatalysts and enhancement of its activity

Abstract

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 O₂ 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.