Preparation and characterization of cerium oxide doped TiO2 nanoparticles

Abstract

A mixed oxide consisting of TiO2 as the major phase and CeO2−y (0<y<0.5) as the dopant phase was prepared via the sol-gel reaction of Ti(i-OC3H7)3 in an aqueous solution of Ce(NO3)3. The resulting oxide powders with different CeO2−y contents were all composed of nano-sized spheres. The CeO2−y phase was identified to have retarding effect on the phase transition from anatase TiO2 to rutile TiO2 at calcinations temperature as high as 800°C, which would otherwise be a thorough conversion. The CeO2−y–TiO2 powders could apparently shift the UV-absorption band of TiO2 toward visible range, and there was an optimal CeO2−y content in association with the maximum absorbance. This effect is interpreted as the existence of an n-type impurity band, due to the substitution of Ti4+ for Ce3+/4+ at the interface between the two oxides, in the gap of TiO2. According to X-ray photoelectron spectroscopy (XPS) investigation, the Ti element mainly existed as the chemical state of Ti4+ and the Ce oxide doping did not affect the peak position of Ti 2p. The Ce 3d spectrum of CeO2−y-doped TiO2 sample basically denotes a mixture of Ce3+/4+ oxidation states giving rise to a myriad of peaks.