Photocatalytic Properties of the Transition Metal Doped TiO_2 Powder Prepared by Sol-Gel Process

摘要

Transition metal-doped TiO_2 powders as a photocatalyst were prepared by sol-gel process and Sb, Bi and Nb were introduced into them as dopants. The photocatalytic behaviors of the doped TiO_2 powder were studied as a function of dopant, doping concentration and preparation conditions. X-ray diffraction, FT-Raman, B.E.T. and scanning electron microscopy were applied for structural and microstructural studies. Optical properties of the doped TiO_2 powders were studied by UV-Visible Spectrometer and photocatalytic activity of the doped TiO_2 was characterized in terms of the degradation of 1,4-dichlorobenzene. X-ray difraction analysis showed that doping with a transition metal ion suppresses anatase-to-rutile phase transition compared with the pure TiO_2. The Sb and Nb-doped TiO_2 powders did not exhibit any other diffraction peaks except those belonging to TiO_2. On the other hand, a diffraction peak of Bi_4Ti_3O_(12) appears for 5 at.% Bi-doped samples. All of the doped TiO_2 powders had higher specific surface area than undoped TiO_2. Surface area increased with increasing dopant concentration depending on the dopant, from 33.9 m~2/g to 55.4m~2/g. The UV-visible absorption spectra of doped samples were red-shifted by 20～50nm according to the doping level. Also transition metal doped TiO_2 powders exhibited better photocatalytic activity than the undoped TiO_2. The increase in photoactivity is probably due to the increase in the interfacial electron transfer, red shifts, and better crystallinity.