Abstract
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.
