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

Abstract

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 BiVO4/TiO2−x heterojunction is built by engineering the electronic structure of TiO2 with Ti3+ self-doping via a two-step hydrothermal process to achieve a high photocatalytic performance. The presence of Ti3+ creates a defect energy level under the conduction band of TiO2, and thereby diminishes the interfacial energy barrier between BiVO4 and TiO2. The Ti3+ defect energy level promotes the electron transfer from BiVO4 to conduction band of TiO2−x. The test of phenol degradation under 300W Xenon lamp equipped with UV cut-off filter (λ≥420nm) demonstrates that BiVO4/TiO2−x heterojunction exhibits higher photocatalytic activity than its counter parts, pure BiVO4 and the physic mixture of BiVO4 and TiO2−x. The improved photocatalytic performance is mainly attributed to the heterojunction formed between BiVO4 and TiO2−x, which improves the separation of photogenerated charge carriers as support by comparative photocurrent and time-resolved PL spectral measurements. In addition, Ti3+ self-doping also narrows the bandgap of TiO2 and enhances the visible-light activity of TiO2. The holes of TiO2−x transfer to the valance band of BiVO4 which further significantly improves the separation of photogenerated charge carriers, further. Additionally, the high surface area caused by TiO2-x also contributes to the improved photocatalytic efficiency.