Controllable Synthesis of Bi_xO_yBr_z/TiO₂ Heterojunctions with Excellent Visible‐Light‐Driven Photocatalytic Activities for Phenol

Abstract Bi x O y Br z /TiO 2 composites have been synthesized by hydrothermal method, with TiO 2 nanoparticles being employed as substrate. During the process of hydrothermal reaction, both temperature and pH have been utilized to effectively regulate the Bi/Br atomic ratio of Bi x O y Br z /TiO 2 composites. In essence, the competitive reaction between OH − and Br − in the solution is the key factor to form Bi x O y Br z with different Bi/Br atomic ratios. Under visible light, the prepared Bi 4 O 5 Br 2 /TiO 2 heterojunction demonstrates higher photocatalytic activity than other Bi x O y Br z /TiO 2 composites for phenol and Rh B. The removal rate of phenol with Bi 4 O 5 Br 2 /TiO 2 heterojunction is up to 92.1% after irradiation for 75 min. The excellent photocatalytic activities of Bi 4 O 5 Br 2 /TiO 2 heterojunction are mainly attributed to its optimized microstructure and the matching band energy structure, whereby TiO 2 nanoparticles with ≈10 nm diameter uniformly arranged on ≈10.2 nm thick Bi 4 O 5 Br 2 nanosheets. Moreover, the heterojunction structure promotes the separation of photo‐generated electrons and holes in Bi 4 O 5 Br 2 /TiO 2 , while and h + are the main active species during its photocatalytic processes.