Novel BiOBr/Bi2S3 high-low junction prepared by molten salt method for boosting photocatalytic degradation and H2O2 production

The molten salt method focuses on improving the crystallinity of synthetic materials and avoiding the high energy consumption of traditional synthesis processes. In this work, a novel BiOBr/Bi2S3 high-low junction with large contact area was constructed by the molten salt method combined with the ion exchange strategy. Its unique energy band structure and new charge transfer mechanism realize the rapid migration of photogenerated charges between different components. Specifically, Bi2S3 was grown on BiOBr in situ by a high-temperature molten salt reaction. Due to the deep valence band position of BiOBr and the narrow band gap of Bi2S3, an intrinsic internal electric field and band bending are produced at the interface, forming a high-low junction photocatalyst with an intimate interface. In addition, the BiOBr/Bi2S3 composite maintains a high oxidation potential and produces high and robust photocatalytic oxidation activity. In the molten state, the close binding of BiOBr and Bi2S3 can be promoted through the ion-exchange strategy, resulting in excellent photocatalytic degradation rates of bisphenol A and tetracycline and in-situ generation of H2O2. Finally, the mechanism of carriers separation and transfer in BiOBr/Bi2S3 high-low junction is also discussed. Density functional theory (DFT) results found that the improvement of O2 adsorption ability would promote the occurrence of oxygen reduction reaction (ORR), and make positive contributions to the enhanced H2O2 production activity. This study will provide a new perspective for broadening the spectral response range of Bi-based photocatalytic materials and preparing high-low junction photocatalysts with dense interface by the molten salt method.