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.