Photocatalytic Characterizations for TiO₂ Sol Containing Transition Metal Elements by Hydrothermal Treatment

抄録

The photocatalytic performance of TiO₂ thin films coated on porous alumina balls using various aqueous TiOCl₂ solutions as starting precursors, to which 1.0 mol% transition metal (Ni²⁺, Cr³⁺, Fe³⁺, Nb³⁺, and V⁵⁺) chlorides had been already added, has been investigated, together with characterizations for TiO₂ sols synthesized simultaneously in the same autoclave through hydrothermal method. The synthesized TiO₂ sols were all formed with an anatase phase, and their particle size was between several nm ∼ 30 nm showing ζ-potential of -25 ∼ -35 mV, being maintained stable for over 6 months. However, the TiO₂ sol added with Cr had a much lower value of ζ-potential and larger particle sizes. The coated TiO₂ thin films had almost the same shape and size as those of the sol. The pure TiO₂ sol showed the highest optical absorption in the ultraviolet light region, and other TiO₂ sols containing Cr³⁺, Fe³⁺ and Ni²⁺ showed higher optical absorption than pure sol in the visible light region. According to experiments for removal of a gas-phase benzene, the pure TiO₂ film showed the highest photo dissociation rate in the ultraviolet light region, but in artificial sunlight the photo dissociation rate of TiO₂ coated films containing Cr³⁺, Fe³⁺ and Ni²⁺ measured higher together with the increase of optical absorption by doping.