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

Phase-pure Bi 2 Mo x W 1– x O 6 (0 ≤ x ≤ 1) photocatalysts were synthesized via a hydrothermal method. The as-prepared Bi 2 Mo x W 1– x O 6 photocatalysts had an Aurivillius crystal structure and showed special anisotropic growth. The optical absorption spectra of Bi 2 Mo x W 1– x O 6 were red-shifted monotonically as the value of x increased. On the basis of theoretical calculations, the introduction of Mo atom into Bi 2 WO 6 could reduce the conduction band level of Bi 2 WO 6, 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 (λ > 420 nm) of Bi 2 Mo x W 1– x O 6 photocatalysts were significantly improved as compared with Bi 2 MoO 6 . The higher efficiency of Bi 2 WO 6 was attributed to more effective photoelectron transfer in the conduction band with larger curvature. The photocatalytic activities under visible light irradiation (λ > 450 nm) of Bi 2 Mo x W 1– x O 6 photocatalysts were much higher than that of Bi 2 WO 6 . 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.