Insight into the role of Ti3+ in photocatalytic performance of shuriken-shaped BiVO4/TiO2−x heterojunction

Heterojunction is recognized as an effective approach to improve photocatalytic performance, but a well-matched energy band alignment is critical therein. In this work, the shuriken-shaped BiVO 4 /TiO 2−x heterojunction is built by engineering the electronic structure of TiO 2 with Ti 3+ self-doping via a two-step hydrothermal process to achieve a high photocatalytic performance. The presence of Ti 3+ creates a defect energy level under the conduction band of TiO 2 , and thereby diminishes the interfacial energy barrier between BiVO 4 and TiO 2 . The Ti 3+ defect energy level promotes the electron transfer from BiVO 4 to conduction band of TiO 2−x . The test of phenol degradation under 300 W Xenon lamp equipped with UV cut-off filter (λ ≥ 420 nm) demonstrates that BiVO 4 /TiO 2−x heterojunction exhibits higher photocatalytic activity than its counter parts, pure BiVO 4 and the physic mixture of BiVO 4 and TiO 2−x . The improved photocatalytic performance is mainly attributed to the heterojunction formed between BiVO 4 and TiO 2−x , which improves the separation of photogenerated charge carriers as support by comparative photocurrent and time-resolved PL spectral measurements. In addition, Ti 3+ self-doping also narrows the bandgap of TiO 2 and enhances the visible-light activity of TiO 2 . The holes of TiO 2−x transfer to the valance band of BiVO 4 which further significantly improves the separation of photogenerated charge carriers, further. Additionally, the high surface area caused by TiO 2-x also contributes to the improved photocatalytic efficiency.