Recent updates on controlled vacancies formation in defect-engineered in BiOCl: strategies, characterization techniques and enhanced photocatalytic activity

In the field of photocatalysis, precise defect engineering has emerged as a controlling strategy to improve the performance of semiconductor materials. Among them, bismuth oxychloride (BiOCl) stands out due to its different layered structure and built-in electric fields, which together facilitate efficient charge separation. This review provides a comprehensive overview of recent advancements in tailoring intrinsic defects, particularly oxygen vacancies, chloride vacancies, and bismuth-related defects, in BiOCl. Advanced characterization techniques such as density functional theory (DFT), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and electron paramagnetic resonance (EPR) are discussed for their role in identifying and quantifying these defect states. The weak interlayer interactions and distinctive stacking arrangement in BiOCl offer a flexible platform for defect modulation, enabling precise control over surface reactivity and catalytic selectivity. Particular emphasis is placed on metal and non-metal doping strategies that modify the band structure and enhance charge carrier dynamics. The construction of heterostructures, including type-II, Z -scheme, and S-scheme configurations, is also explored to further improve redox capability. BiOCl-based materials demonstrate outstanding photocatalytic activity in H 2 production, CO 2 reduction, and degradation of organic pollutants. This review highlights the strategic importance of defect engineering in optimizing BiOCl photocatalysts by elucidating the interplay between defect types and photocatalytic mechanisms. It offers valuable guidance for designing next-generation photocatalytic materials with high efficiency and sustainability to address global environmental and energy challenges. • Bismuth, oxygen, and chloride defects in BiOCl were explored. • Various characterization techniques to identify defects in BiOCl were highlighted. • The role of defects, doping, and heterojunctions in environmental and energy applications was discussed. • The predominant challenges and future outlooks are provided inclusively.