Preparation and characterization of cerium oxide doped TiO2 nanoparticles

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 nanosized 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 800degreesC, 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. (C) 2004 Elsevier Ltd. All rights reserved.