Studies On Preparation Of Rare Earth Doping TiO₂ And Its Photocatalytic Properties

Eu/TiO₂/SiO₂ composite photocatalysts were prepared by sol-gel- impregnation process and characterized by means of XRD, FT-IR and EPR. When TiO₂ was doped with Si⁴⁺ and Eu³⁺, the particle diameter of Eu/TiO₂/SiO₂ photocatalysts decreased and the crystal transformation of titania from anatase to rutile was prevented. The incorporation of Si⁴⁺ into the matrix of the TiO₂ was promoted owing to the co-doping of Si⁴⁺ and Eu³⁺. As a model reaction, the photocatalytic degradation of methyl orange was investigated.The adsorption constants of methyl orange over catalysts were evaluated and the adsorption mechanism was also discussed. Optimal doping amounts for Si⁴⁺ and Eu³⁺ were 39.06 wt% and 0.03 wt% respectively, and the co-doping of them showed a synergistic effect for photoreaction activity of titanium dioxide.Rare earth ions (La³⁺, Sm³⁺, Eu³⁺, Dy³⁺, Er³⁺)-doped TiO₂ photocatalysts were also prepared by sol-gel-impregnation and the platinum was deposited on photocatalysts by photodepositon process. The photocatalysts were characterized by means of X-ray diffraction, electrochemistry experiment. As a model reaction, photocatalytic hydrogen generation from water using formaldehyde as electron donor was investigated .It has been found that the activities of all rare earth doped TiO₂ samples have been increased compared to that of pure TiO₂, and the order was La/TiO₂ >Sm/TiO₂>Eu/TiO₂>Dy/TiO₂>Er/TiO₂. The data of lattice distortion implied that Ti⁴⁺ could enter into rare earth oxide that existed on the surface of titanium dioxide. The data of electrochemistry experiment showed that the flat-band potential of conduction of RE/TiO₂ has been shifted negatively. For n-type semiconductor, the lattice distortion raised the Fermi level, which caused flat-band potential of the conduction band of TiO₂ to shifted negatively. As a result, the photoinduced electrons of the conduction band had stronger reductive capability and the photocatalytic activity of hydrogen generation was improved.