Effects of Rhodium Doping on the Microstructures and Photocatalytic Performances of TiO2 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.