Effects of Mo Replacement on the Structure and Visible-Light-Induced Photocatalytic Performances of Bi2WO6 Photocatalyst

Phase-pure Bi2MoxW1-xO6 (0 <= x <= 1) photocatalysts were synthesized via a hydrothermal method. The as-prepared Bi2MoxW1-xO6 photocatalysts had an Aurivillius crystal structure and showed special anisotropic growth. The optical absorption spectra of Bi2MoxW1-xO6 were red-shifted monotonically as the value of x increased. On the basis of theoretical calculations, the introduction of Mo atom into Bi2WO6 could reduce the conduction band level of Bi2WO6, so the band gap energy was reduced. The curvature of the conduction band became smaller with an increase in the Mo content due to the different electronegativities of Mo 4d and W 5d. The photocatalytic activities determined by rhodamine B degradation under visible light irradiation (lambda > 420 nm) of Bi2MoxW1-xO6 photocatalysts were significantly improved as compared with Bi2MoO6. The higher efficiency of Bi2WO6 was attributed to more effective photoelectron transfer in the conduction band with larger curvature. The photocatalytic activities under visible light irradiation (lambda > 450 nm) of Bi2MoxW1-xO6 photocatalysts were much higher than that of Bi2WO6. The mechanism was discussed on the basis of the cystal structure, morphology, and electronic stucture. This work provides a strategy for developing active photocatalysts with more utilization of visible light.