Effect of Nd3+ doping on photocatalytic activity of TiO2 nanoparticles for water decomposition to hydrogen

The undoped TiO2 and Nd3+-doped TiO2 samples were prepared by sol-gel method and characterized by XRD, UV-Vis, TEM and N-2 adsorption. The correlation between the photocatalytic activity for hydrogen evolution and the phase composition, BET surface area and intensity of light-absorption in UV region was investigated. For the undoped TiO2 samples, the particle size and agglomeration increased while its BET surface area and the intensity of light-absorption in UV region decreased with the increasing calcination temperature; the anatase to rutile phase transformation started at 600 degrees C and completed at: 800 degrees C; the photocatalytic activity of undoped TiO2 decreased with the increasing calcination temperature, and the sample calcined at 600 degrees C was the best because of the coexistence of a certain proportion of rutile/anatase mixed phase. For the Nd3+/TiO2 samples, Nd3+ doping inhibited the crystal phase transformation and the rutile phase began to appear at 800 degrees C; moreover, Nd3+ doping restrained the growth of grain size, improved the dispersivity of the particles, and raised BET surface area. The more the doping amount was, the larger the BET surface area was. As the calcination temperature increases, the decreasing extent of the light-absorption intensity of Nd3+/TiO2 in UV region was lower than that of undoped TiO2. Nd3+ raised the photocatalytic activity for hydrogen generation and the optimum amount of Nd3+ doping was 0.1%, at which the photocatalytic activity of Nd3+/TiO2 was 3.5 times higher than that of undoped TiO2.