BiOX(X=Cl, Br, I)-based S-scheme heterostructure photocatalysts for environmental remediation and energy conversion

Over the past decade, photocatalysis has gained recognition as a powerful tool for environmental remediation and sustainable energy production. Bismuth oxyhalides (BiOX, where X = Cl, Br, I) have attracted particular interest as efficient photocatalysts due to their excellent visible-light harvesting capabilities, straightforwardsynthesis, and high photostability. S-scheme heterojunctions have been developed to further improve their performance, which enhances electron-hole separation and significantly increases photocatalytic efficiency. This review examines recent advancements in BiOX-based S-scheme heterostructures, focusing on their diverse applications in pollutant degradation, CO₂ reduction, and H₂ production. An evaluation of the effectiveness, benefits, and limitations of various synthesis methods has been carried out in this article in addition to various strategies to improve the photocatalytic activity of BiOX. This study also compares the suitability of the synthesized methods for removing emerging organic and inorganic pollutants, including dyes, pharmaceuticals, and other contaminants of environmental concern. The performances of various BiOX catalysts for H₂ production and CO₂ conversion to chemicals and fuels were discussed to point out the strengths, weaknesses, and the need for high-performance BiOX catalysts for energy conversion. Also, an analysis of the specific mechanisms driving the photocatalytic activity and strategies to address current challenges have been presented in the article. Finally, this review identifies key knowledge gaps and presents recommendations for scaling BiOX photocatalysts toward large-scale and industrial applications.