Surface phase of TiO2 modified with La2O3 and its effect on the photocatalytic H2 evolution

TiO2 nanoparticles modified with La2O3 were prepared by an impregnation method using anatase TiO2 support (La2O3/TiO2) or amorphous Ti(OH)4 support (La2O3/Ti(OH)4). The bulk and surface crystalline phases of La2O3/TiO2 (or La2O3/Ti(OH)4) have been characterized by X-ray powder diffraction (XRD) and UV Raman spectroscopy. Besides, morphology and particle size of La2O3/TiO2 and La2O3/Ti(OH)4 samples have been determined by TEM (transmission electron microscope) and Brunauer–Emmett–Teller (BET), respectively. It is found that the phase transformation and increase of the particle size of TiO2 can be more effectively inhibited in the La2O3/TiO2 than in the La2O3/Ti(OH)4. Photocatalytic experiments indicated that the La2O3/TiO2 (or La2O3/Ti(OH)4) samples with surface anatase phase have the similar overall photocatalytic activities. Moreover, it is found that the high crystallinity of surface anatase phase is benefit for the high photocatalytic activity of TiO2 modified with La2O3.