Effects of Rhodium Doping on the Microstructures and Photocatalytic Performances of TiO 2 Powders

Abstract

Rh-doped TiO₂ powder was synthesised by the sol-gel method, and its structure and performance were characterised using a variety of techniques. When calcined between 673 K and 873 K, the TiO₂ in the 1 at% Rh/TiO₂ powders was mainly present as the anatase form. In contrast, at calcination temperatures of 973 K, most of the TiO₂ existed in the rutile structure. At a given calcination temperature, increasing the doping amounts of Rh decreases the anatase content and cell volume but increases the crystal size. Compared with pure TiO₂ powders synthesised under the same conditions, the temperature for the phase transition of TiO₂ from the anatase structure to the rutile structure was lower by 146.8 K in the Rh/TiO₂ powders; however, the excitation wavelength of the Rh/TiO₂ powders was broadened to the visible light region. Unfortunately, the particles of the Rh/TiO₂ powders aggregated resulting in reduced Brunauer–Emmett–Teller surface area, and a decrease in the photocatalytic activity.