Comprehensive Review on g‐C ₃ N ₄ /BiOX Photocatalysts: Properties, Synthesis Methods, Photocatalytic Mechanisms, and Practical Application Challenges

Graphitic carbon nitride (g‐C 3 N 4 ) offers many advantages, such as chemical stability, suitable band gap, low cost, and simple preparation methods, positioning them as star materials in the field of photocatalysis. Bismuth oxyhalides (BiOX, where X = Cl, Br, or I) has a unique layered structure, good chemical stability, abundant surface‐active sites, and excellent light stability. It is a star material in the field of photocatalysis, and the combination of BiOX with other materials to form a composite catalyst has attracted much attention. This paper provides a systematic review of the properties of g‐C 3 N 4 /BiOX composites, its synthesis methods (hydrothermal/solvothermal method, precipitation method, in situ growth method, calcination method, self‐assembly method, and microwave‐assisted method), applications (degradation of pollutants, photocatalytic water splitting for hydrogen production, CO 2 reduction, nitrogen fixation, NO oxidation, and antibacterial activity), and photocatalytic mechanisms (Type II heterojunction, Z‐type heterojunction, S‐type heterojunction, and p–n heterojunction). Finally, the challenges faced by g‐C 3 N 4 /BiOX in practical applications are discussed, and effective suggestions are proposed for designing efficient, low‐cost, and environmentally friendly photocatalysts, thereby expanding their application prospects.