Advances in bismuth oxyhalide-based photocatalytic CO₂ reduction: from materials design to reaction mechanisms

Bismuth oxyhalides (BiOX, X = Cl, Br, I) show broad application prospects in the field of photocatalytic CO₂ reduction due to their unique layered crystal structure, suitable band position and good chemical stability. However, pure BiOX materials generally have problems such as high photogenerated carrier recombination rate, low visible light utilization rate and difficult activation of CO₂ molecules, which seriously restrict their practical application efficiency. This review summarizes the modification strategies and research progress for enhancing the photocatalytic CO₂ reduction performance of bismuth oxyhalide materials in recent years. Firstly, the structural characteristics of traditional BiOX, the mechanism of photocatalytic CO₂ reduction and the photoelectrochemical characterization methods were introduced. Subsequently, six major modification strategies were elaborated in detail: structural regulation, bismuth-rich bismuth oxyhalides, element doping, defect regulation, heterojunction construction, and addition of co-catalysts. Based on this, an in-depth analysis was conducted on the mechanism of action and synergistic effects of the above strategies in broadening the light response range, promoting photogenerated charge carrier separation, optimizing CO₂ adsorption and activation, regulating product selectivity, and enhancing stability. Finally, the main challenges currently faced in the field were summarized, and the future research directions were discussed, aiming to provide references for the rational design and practical application of efficient bismuth oxyhalide photocatalysts.