Biochar-supported photocatalysts: Performance optimization and applications in emerging contaminant removal from wastewater

[Display omitted] •The properties of biochar supported photocatalysts (BSPs) for water treatment are discussed.•The effects of the synthesis methods, biochar properties, photocatalyst properties, and morphology are presented.•A comprehensive analysis of biochar feedstock and pyrolysis temperature effects on BSP performance is provided.•The research gaps and future directions for BSP applications for water treatment are highlighted. Biochar supported photocatalysts (BSPs) have attracted significant attention in recent years due to their excellent performances in many applications such as water splitting, hydrogen production, carbon dioxide sequestration, water treatment, and many more. While numerous review papers provide general overviews on the synergistic effects, synthesis, characterizations, and applications for contaminant removal, few explore the variables affecting the performance of these composites. This review identifies the key knowledge gaps in the existing literature, calling for more systematic research on the parameters that influence BSP performance. It emphasizes the importance of selecting suitable photocatalyst and biochar materials, with a focus on biochar adsorption and electron exchange capacities and their relationship to enhanced photocatalytic capabilities. This work highlights the crucial role of the inherent material properties, synthesis methods, and loading ratios in determining the morphology, crystal structure, and performance of photocatalysts, emphasizing the need for structured studies for the efficient optimization of BSPs. Overall, this work provides a comprehensive guide of the parameters that affect the performance of BSPs, paving the way for a systematic approach toward designing photocatalyst materials with optimal properties for wastewater treatment.