A series of Ce-TiO2/SiO2 (Ce-TiO2 coatings on SiO2) were prepared by the sol-gel process and characterized by TG-DTA, XRD, SEM, XPS and DRS. The photocatalytic activities of Ce-TiO2/SiO2 for the oxidation of formaldehyde irradiated by 250 W high-pressure mercury lamp were investigated. According to XPS investigation, the Ti element mainly existed as the chemical state of Ti4+, and Ce is present mainly in the +4 oxidation state and a little in the +3 oxidation state. The effect of cerium content on the photocatalytic activities was studied, and the result reveals that 0.10%Ce-TiO2/SiO2 exhibits highest photoactivity. The light absorption of Ce-TiO2/SiO2 increases with increasing cerium content, and cerium doping causes absorption spectra of Ce-TiO2/SiO2 to shift to the visible region. The high photocatalytic activity of Ce-TiO2/SiO2 can be explained by the effective separation of photogenerated electron-hole pairs, which are trapped by Ce4+ and hydroxyl groups balancing the positive charge generated by the incorporation of Si in a Ti matrix, respectively. (c) 2007 Published by Elsevier B.V.