Abstract: TiO2 catalysts doped with different rare earth ions were prepared by the sol-gel method and characterized by X-ray diffraction, transmission electron microscopy, and N2 adsorption. The photocatalytic activity for hydrogen evolution from water decomposition under UV light irradiation was investigated. Doping with rare earth ions restrained the growth of TiO2 particles, improved the particle dispersion, increased the BET surface area, and thus significantly enhanced the photocatalytic activity of TiO2 for H2 evolution. Among the catalysts, Gd3+/TiO2 had the smallest particle size, the best particle dispersion, and the highest BET surface area (35 times higher than that of the undoped TiO2). The gelling time varied with different rare earth ions. The longer the gelling time, the larger the BET surface area. A comparison between La3+/TiO2 and Gd3+/TiO2 indicated that the photocatalytic activity was not linear with the surface area. Moreover, the electronic configuration of rare earth ions had a significant effect on the photocatalytic activity of RE3+/TiO2. TiO2 samples doped with La3+ having a full-empty electronic configuration and Gd3+having a half-filled electronic configuration had higher photocatalytic activity for hydrogen evolution (3.69 and 3.72 times higher) than that of the undoped TiO2.

Key words: rare earth ion, titania, photocatalysis, hydrogen evolution, electronic configuration