BiVO₄/Bi₂O₃heterojunction deposited on graphene for an enhanced visible-light photocatalytic activity

Herein, a series of novel BiVO₄/graphene (GR)/Bi₂O₃heterojunction composites with different GR loading were prepared via a facile chemical bath deposition method, followed by a calcination treatment in N₂atmosphere. The resultant composites possess well-defined heterojunction, favorable band structures, and relatively high BET surface areas, leading to superior visible-light photocatalytic performances for degrading bisphenol-A (BPA). The effect of GR content on the photocatalytic reaction kinetics was investigated. We found that the maximum pseudo first-order degradation rate constant (3.1 × 10⁻³min⁻¹) was obtained when the GR content is 5.5 wt%, which is 3.6 times higher than that of the pristine BiVO₄/Bi₂O₃photocatalyst (8.5 × 10⁻⁴min⁻¹). More importantly, the power intensity normalized kinetic constant (2.5 × 10⁻⁴ min⁻¹ mW⁻¹cm²) was obviously higher than that of most of the previously reported bismuth based visible-light active photocatalysts for the degradation of BPA (1.06 × 10⁻⁵∼ 2.55 × 10⁻⁴ min⁻¹ mW⁻¹cm²). The remarkable performance was benefited from (1) the enhanced surface adsorption ability of the composites resulted from the π-π stacking interaction between GR and BPA molecule, and (2) the improved separation of photo-generated charge carriers achieved by using GR to accelerate the interfacial electron-transfer rate. Moreover, the examination of reactive species trapping experiments reveals that the photocatalytic degradation of BPA is dominated by both hole and hydroxyl radical oxidation process, which is consistent with the energy band structures. We believe that our results provide a valuable insight into the development of an efficient visible-light responsive photocatalyst for degrading organic pollutants.