Construction of Cu-Modified g-C3N4 Nanosheets for Photoinduced CO2 Reduction to CO and Selectivity Mechanism Insight

Graphite polymeric carbon nitride (PCN) has been extensively applied to photocatalytic CO2 reduction reactions, which are expected to enhance the reaction activity and improve product selectivity by introducing transition metals. In this work, we successfully prepared Cu-modified PCN (Cu-PCN) by a thermal polymerization approach and conducted a systematic and comprehensive exploration of the photocatalytic reduction of CO2 and selective generation of CO reactions. A series of experiments and DFT results attest that a tiny amount of Cu anchor on PCN, forming an active site for activating CO2, can significantly mediate the electron transport to absorbed CO2 molecul0065s through the Cu sites and improve the efficiency of the light-driven CO2 reduction reaction. As-designed photocatalysts exhibit excellent photocatalytic reduction of CO2 to a CO selectivity close to 100%. Detection of intermediates using in situ FT-IR reveals that *COOH is the critical intermediate and is a rate-limiting step in the overall reaction, which is consistent with DFT results. Our work makes up for these deficiencies in previous related research and provides a good reference for exploring the product selectivity of photocatalytic reduction of CO2.