Photocatalytic degradation of methylene blue over Co3O4/Bi2WO6 composite under visible light irradiation

Bi2WO6 powders are synthesized through hydrothermal process and Co3O4/Bi2WO6 composites with p-n heterojunction structure are prepared by the impregnation method. Co3O4/Bi2WO6 composites are characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), UV-Vis absorption spectrum, and photo luminescence spectrum. After Co3O4 is loaded, the ability of visible light absorption of Co3O4/Bi2WO6 composite is enhanced greatly. The PL intensity of Co3O4/Bi2WO6 composite is lower than that of pure Bi2WO6, which clearly indicates that the recombination of photogenerated charge carrier between the hybrid orbital of Bi-6s and O-2p.(VB) to the empty W-5d orbital is inhibited greatly in the composite semiconductors. The presence of Co3O4 leads to an increase in photocatalytic activity. The highest efficiency is observed when calcined at 300 degrees C with 0.2 wt% cobalt content. On the basis of the calculated energy band positions and PL spectra, the mechanism of enhanced photocatalytic activity has been discussed. In addition, the effects of H2O2 concentration and pH value on photocatalytic activity were also presented. (C) 2007 Elsevier B.V. All rights reserved.