Bismuth oxyhalide photocatalysts for water purification: Progress and challenges

The photocatalytic degradation of organic pollutants in water and wastewater has gained considerable attention in recent decades, as bismuth oxyhalides (BiOX, X = Cl, Br, or I) have emerged as proficient semiconductor photocatalysts for diverse environmental applications. Despite their intrinsic merits, the solar energy conversion and mineralization efficiency of BiOX, both essential for augmented photocatalytic activity, necessitate significant enhancement. This review systematically expounds upon the multifarious strategies employed to refine BiOX photocatalysts, targeting optimized performance in water purification processes. We present thorough examinations of the fundamental photocatalytic mechanisms and pollutant degradation pathways, thereby affording a comprehensive understanding of these pivotal factors. Furthermore, the review confronts two critical challenges demanding resolution in future investigations: the synthesis of synchronously enhanced BiOX in all aspects and the formulation of appropriate reactor designs. This review provides invaluable guidance for the rational design of high-performance BiOX photocatalysts, facilitating advancements in water and wastewater treatment applications.