Ag-TiO₂ catalysts with different contents of Ag were prepared by the sol-gel method in the absence of light. Through XRD, Raman, PL and XPS characterizations and activity evaluations of photocatalytic degradation of rhodamine B, it was found that the doped Ag promoted the phase transformation, but has a depression effect on the anatase grain growth. The PL intensity decreased with increasing of contents of Ag doping, suggesting that doped Ag inhibited recombination of photoinduced electrons and holes. In rather low doping concentration range (Ag/Ti atom3%) there are mainly migration and diffusion of Ag⁺ ions, and in rather high doping concentration range (Ag/Ti atom≥3%) migration and diffusion of Ag⁺ ions coexist with surface reductions. In the neighborhood of the shallow surface close to the diffusion threshold value (Ag/Ti atom=3%～5%), Ag-TiO₂ catalysts have abundant shallow superficial layer electron traps and are favorable for the derivation towards Ag of superficial reduced state, leading to effective inhibition of recombination of photoinduced electrons and holes which significantly elevates the photocatalytic efficiency. When the silver dopant exceeded threshold value, the catalytic activity of Ag-TiO₂ decreased.

Key words: photocatalysis, TiO₂, Ag, preparation