Recent progress of cocatalysts loaded on carbon nitride for selective photoreduction of CO 2 to CH 4 .

A photocatalytic system driven by solar light is one of the promising strategies for converting CO 2 into valuable energy. The reduction of CO 2 to CH 4 is widely studied since CH 4 has a high energy density as the main component of nonrenewable natural gas. Therefore, it is necessary to develop semiconductor materials with high photocatalytic activity and CH 4 selectivity. Graphitic carbon nitride (g-C 3 N 4 /CN) has attracted widespread attention for photocatalytic CO 2 reduction due to its excellent redox ability and visible light response. A hybrid system constructed by loading cocatalysts on g-C 3 N 4 can significantly improve the yield of target products, and serve as a general platform to explore the mechanism of the CO 2 reduction reaction. Herein, we briefly introduce the theory of selective CO 2 photoreduction and the basic properties of cocatalysts. Then, several typical configurations and modification strategies of cocatalyst/CN systems for promoting CH 4 selective production are presented in detail. In particular, we systematically summarize the application of cocatalyst/CN composite photocatalysts in the selective reduction of CO 2 to methane, according to the classification of cocatalysts (monometal, bimetal, metal-based compound, and nanocarbon materials). Finally, the challenges and perspectives for developing cocatalyst/g-C 3 N 4 systems with high CH 4 selectivity are presented to guide the rational design of catalysts with high performance in the future.