The prospect of CuX (X=O, S, Se) co-catalysts in photocatalysis: From engineering heterostructural integrity towards enhanced photocatalytic activities – A concise review

Recent progress in photocatalytic degradation and hydrogen generation highlights the role of co-catalysts in the efficiency of semiconductors-based photocatalysts. Co-catalysts provide an adequate solution to boost photocatalytic performance. This review first covers the synthesis methods for CuX along with the loading method of the co-catalysts to the base catalyst. Because of cost-effectiveness, compositional flexibility, outstanding physiochemical stability, tunable crystal phase narrow band gap, non-toxicity, adjustable microstructure, etc., copper-based co-catalysts have stimulated immense attention as they can magnify photocatalytic performance. The fundamental principles of photocatalytic degradation of organic molecules and hydrogen production are highly outlined. Then, the co-catalytic activities of various Cu-based materials involving Cu oxides, Cu sulfides, and Cu selenide are thoroughly discussed when they are coupled with base semiconductor materials (metal oxides, metal sulfides, nitrides, etc.), to attain a rationally designed photocatalyst for enhancing photocatalytic reactions. This review is expected to upgrade research on efficient co-catalyst design to refine the charge carrier separation in photocatalytic systems for CO₂ adsorption ability, light harvesting, and acting as reactive sites for the reduction reaction.