Ultraviolet light induced oxygen vacancy-rich BiPO4−x/Bi2S3 nanorods with enhanced photocatalytic activity and mechanism

The vacancy defects of different elements generated in nanocrystals play a very important role in the photocatalytic reduction reactions. In this study, novel oxygen vacancy-rich BiPO4−x/B2S3 heterostructure nanorods (OV-BPO/BS) are successfully prepared by introducing UV light irradiation. Subsequently, a variety of characteristic data, including ESR, XPS and HRTEM unveil the formation of heterojunction and oxygen vacancies. Further, density functional calculations reveal that the newly formed oxygen vacancies bring a defect level, which results in the enhanced photocatalytic activity. The photocatalytic reduction results of MB degradation indicate that the oxygen vacancies contribute to the faster separation of photo-generated charge carriers. The co-existence of the heterostructure and induced oxygen vacancies exhibit an improved photoreduction efficiency. Through adjusting the ratio of S and P, we further obtain BiPO4/B2S3 (denotes as BPO/BS in this paper), 50% BiPO4/B2S3 (denotes as 50% BPO/BS in this paper), and 25% BiPO4/B2S3 (denotes as 25% BPO/BS in this paper). After UV light irradiation, different vacancies types can be introduced into BPO/BS. The photocatalytic mechanism of these materials reveals that the synergistic effect between heterojunction and vacancies greatly promotes the photoinduced carriers separation efficiency, which is tested by electrochemical impedance spectroscopy and photocurrent response. This study brings a new method to rational design of new photocatalysts and a new perspective to study the relationship between the nanocrystal defects and their properties.