Nano-scale TiO2 photocatalysts co-doped by rare earth ions (La3+, Ce3+) and heteropolyacids were designed and prepared by sol-gel method to probe synergistic effect on photocatalytic elimination of organic compounds, and their physicochemical properties were characterized by X-ray diffraction (XRD), specific surface area and porosity (BET and BJH), high resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), and X-ray photoelectron spectroscopy (XPS) as well as Raman spectroscopy. The photocatalytic activity of prepared catalysts was evaluated by the degradation of methylene blue (MB) in water under UV-light irradiation. The results showed that the co-doping of the rare earth ions and heteropolyacids can significantly improve the photocatalytic activity of prepared composite photocatalysts due to the efficient inhibition of the recombination of photogenerated electron-hole pairs. The enhancement mechanism of co-doping of the rare earth ions and heteropolyacids on TiO2 is also discussed. (C) 2012 Elsevier Inc. All rights reserved.