Studies On Preparation Of Co-doping TiO₂ With Rare Earth And Sulphur And Its Photocatalytic Properties

Pure TiO₂, S-doped TiO₂ and La³⁺, S co-doped TiO₂ nanoparticle photocatalysts were prepared by sol-gel method, and characterized by means of X-ray diffraction, XPS and UV-Vis diffuse reflectance spectra. The effects of S-doping content and calcinated temperature on the photocatalytic activity for hydrogen generation of photocatalysts under visible-light irradiation were investigated. The results show that an appropriate content of S-dopant could effectively enhance the photocatalytic activity of TiO₂ calcined at appropriate temperature. The XPS proved the valence state of doping S in S/TiO₂ was manily +6 (partly +4) and the S substituted for some of the lattice Ti⁴⁺. The phase transfer from anatase to rutile and the grain growth of TiO₂ were inhibited by doping S, and the absorption edge shifts remarkably toward longer wavelength.Rare earth ions(La³⁺,Eu³⁺,Nd³⁺,Tb³⁺,Er³⁺)-doped S/TiO₂ nanoparticle photocatalysts also were prepared by sol-gel method. The photocatalysts were characterized by means of X-ray diffraction and electrochemistry experiment. As a model reaction, photocatalytic hydrogen generation from water using EDTA as electron donor was investigated. It has been found that the activities of all earth doped S/TiO₂ samples have been increased compard to that of pure TiO₂ and S/TiO₂, and the order was＞Eu³⁺/S/TiO₂＞La³⁺/S/TiO₂>Nd³⁺/S/TiO₂＞Tb³⁺/S/TiO₂＞Er³⁺/S/TiO₂＞S/TiO₂＞TiO₂. The data of electrochemistry experiment showed that the flat-band potential of conduction of RE/S/S/TiO₂ has been shifted negatively. For the lattice distortion raised the Fermi level, which caused flat-band potential of the conduction band of TiO₂ to shift negatively. As a result, the photoinduced electrons of the conduction band had stronger reductive capability and the photocatalytic activity of hydrogen generation was improved.