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 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 (lambda >= 420 nm) 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, transfer to the valance band of BiVO4 which furthet 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. (C) 2016 Elsevier B.V. All rights reserved.