Bi-rich BixOyBrz-based photocatalysts for energy conversion and environmental remediation: A review

Recently, BiOX-based (X = F, Cl, Br, I, etc.) photocatalysts have been discovered and used in many energy and environmental applications. However, inadequate reduction activities and positive conduction band minimum (CBM) potential are the main bottlenecks of BiOX. Therefore, a potential solution to addressing such constraints is to adopt a Bi-rich strategy with BiOX photocatalyst. The comprehensive features of Bi-rich BixOyBrz led us to select them over all other BiOX. These photocatalysts exhibit perfect band gap in the visible region ≅ 2.8 eV, account top portion of visible light (43–45%), and have rich atomic composition and layered crystal structure (providing large surface area for charge transfer), making them ideal photocatalysts. With their unique properties, the modified Bi-rich BixOyBrz is more favorable to addressing environmental and energy conversion concerns. However, fast charge recombination and more positive conduction band of some of the Bi-rich BixOyBrz reduce their photocatalytic activity. As a result, the current review offers an in-depth overview of numerous strategies for modifying Bi-rich BixOyBrz photocatalysts, such as employing co-catalysts, doping, heterojunction, microstructure regulation, etc. The detailed characteristics of Bi-rich BixOyBrz and their synthesis processes are also briefly presented in the proposed review paper. Also, various applications of Bi-rich BixOyBrz photocatalysts for pollutant degradation, hydrogen generation, solar fuel conversion, CO2 reduction, and nitrogen fixation have been presented with their proposed photocatalytic mechanism. Finally, following in-depth analysis and reasoned discussion, the article concludes with key findings and future research directions that provide new advancements in other rapidly evolving disciplines that can find application in the energy and environmental areas.