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 (Eg) and specific surface area (ABET) 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 Eg plays more important roles.