Photocatalytic degradation of methylene blue by MoO3 modified TiO2 under visible light

MoO3/P25 catalysts were prepared by an impregnation method. The catalysts were characterized by X-ray diffraction, ultraviolet-visible spectrophotometry, Fourier transform infrared spectroscopy, and laser Raman spectroscopy, and their photocatalytic activty was evaluated by the degradation of methylene blue dye under visible light. The monolayer dispersion threshold of MoO3 on P25 was around 0.1 g/g. The strong interaction between the monolayer-dispersed tetrahedral-coordinated molybdenum oxide species and P25 led to a decrease in the band gap of P25, thus increasing the visible light absorption of the catalyst. Crystalline MoO3 was formed on catalysts with a MoO3/P25 mass ratio above 0.1. In these cases, the visible light absorption of the catalysts decreased with increasing MoO3 content. The band gap of the catalyst was not the only factor affecting its photocatalytic activity for the degradation of methylene blue under visible light. MoO3/P25 with the MoO3 to P25 mass ratio of 0.25, which possessed not only suitable band gap but also a certain amount of crystalline MoO3, showed the best catalytic performance. (C) 2014, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.