Preparation, characterization of Mo, Ag-loaded BiVO4 and comparison of their degradation of methylene blue

Two types of metal-loaded visible-light-driven photocatalysts, Mo-BiVO4 and Ag-BiVO4, were synthesized by wet impregnation method. Material poperties were characterized by UV-vis diffuse reflectance spectroscopy, X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy and low temperature nitrogen adsorption-desorption. Photocatalytic activity of the obtained materials was investigated through degrading methylene blue (MB) solution under visible-light irradiation. The results reveal that both metal loaded-BiVO4 catalysts have monoclinic scheelite structure. Mo and Ag exist as oxides on the surface of the particles. The changes of absorption in visible-light region, band gap (E (g)) and specific surface area (A (BET)) caused by loading Ag are more obvious than those caused by loading Mo. But the isoelectric point of Ag-BiVO4 decreases less than that of Mo-BiVO4 does. Both catalysts show higher photocatalytic activity than pure BiVO4, resulting in the significantly improved efficiency of degradation of MB. And the degradation efficiency of these two metal-loaded BiVO4 photocatalysts is similar to each other. However, mechanisms of such enhancement are different. The decrease of isoelectric point helps Mo-BiVO4 improve the degradation efficiency. As for Ag-BiVO4, the augmentation of absorption in visible-light region as well as the abatement of E (g) plays more important roles.