Recent progress on Bi₄O₅Br₂-based photocatalysts for environmental remediation and energy conversion

As a V-VI-VII visible light active compound, Bi4O5Br2 with a unique hierarchical crystal structure can generate an electrostatic field vertically within the crystal, providing tunable properties and a suitable band structure, and has been widely explored in solar energy conversion and environmental purification. However, the narrow band gap of Bi4O5Br2 seriously restricts the improvement of its photocatalytic performance. Great efforts have been made to increase the carrier mobility of Bi4O5Br2. Herein, we present a comprehensive review on the recent progress of Bi4O5Br2-based photocatalysts. First, we briefly introduce the crystal structure and photocatalytic mechanism of Bi4O5Br2. The synthesis processes of Bi4O5Br2-based photocatalysts are also presented, including the hydrothermal/solvothermal method, hydrolysis method, microwave irradiation method, and other synthesis methods. Then, we outline the modification strategies of Bi4O5Br2-based photocatalysts, such as non-metallic and metallic modifications, facet and morphology engineering, vacancy introduction, carbon materials modification, and heterojunction construction. Subsequently, the photocatalytic performance of Bi4O5Br2-based materials and their potential application in contaminant degradation, hydrogen evolution, CO2 reduction, and N-2 fixation are discussed. Consequently, we propose the challenges and prospects of Bi4O5Br2-based photocatalysts for broad application.