Effects of structure, morphology, and up-conversion on Nd-doped BiVO4 system with high photocatalytic activity

Nd-doped BiVO4 photocatalysts with high photocatalytic activities have been synthesized by the microwave hydrothermal method. The effects of Nd doping on structural transformation, morphology, chemical valence, optical properties, and photocatalytic activities of Nd-doped BiVO4 photocatalysts were investigated systematically. It is found that Nd doping and pH of the reaction precursor can induce the stabilization of tetragonal zircon BiVO4, and Nd3+ ions have been incorporated into the BiVO4 lattice. The structure and morphology of BiVO4 play a significant role in the photocatalytic activity. The UV–vis diffuse reflectance spectra of Nd-doped BiVO4 present four absorption peaks at 532, 590, 690 and 750 nm due to the excitation of Nd3+ species. The strong up-conversion fluorescence spectra of Nd-doped BiVO4 suggest the existence of up-conversion process, and the value of k/BET could reflect the effect of up-conversion lively and directly in Nd-doped BiVO4 system. The contribution of high photodegradation activities to Nd-doped BiVO4 catalysts under simulated sun-light is mainly from UV-light region. The mechanism of up-conversion upon sun-light excitation is proposed in favor of the improved photocatalytic activities of Nd-doped BiVO4.