Abstract: The porous nanocrystalline TiO2 doped with La was synthesized by sol-gel method. The combination of the photoacoustic (PA) and the surface photovoltage (SPV) techniques was proved to be a promising experimental method to probe the photogenic electron behaviors and electron structure on the surface. Results showed that active oxygen and hydroxy were formed on the donor-type active centers produced by the La-O-Ti compounds enriched on the surfaces, which resulted in the sensitized photoreaction of charge transfer transitions on the surface after adsorbing oxygen and H2O. It was experimentally confirmed that doping an appropriate amount of La not only enhanced the surface photovoltage characters of the sample, but also suppressed effectivly the nonradiative transitions, leading to the increased photon efficiency. The charge transfer transitions were dependent closely on the nonradiative transitions, while the formation of active oxygen and hydroxy on the adsorptive surface was independent of the nonradiative transitions.

Key words: Nanocrystalline TiO2 doped with La, Photoacoustic spectroscopy, Surface photovoltaic spectroscopy, Surface electronic structure