Pure and Ce-doped nano-TiO_2 particles were prepared by a sol-gel process and characterized and explained by UV-Vis and XRD spectra. Being a model reaction,the photocatalytic degradation of methyl orange aqueous solution in the present of CeO_2/TiO_2 nano-particles was investigated with a high pressure mercury lamp as the light source. The results show that rare-earth Ce doped makes the reflective spectral characteristic of nano-TiO_2 move to the visible region with a red shift to 500?nm,and is favorable to...