Synergetic effects of Cu cluster-doped g-C3N4 with multiple active sites for CO2 reduction to C2 products: A DFT study

The photocatalytic reduction of CO2 is a promising strategy for converting this greenhouse gas into valuable products. However, developing highly efficient photocatalysts remains a challenging task. In this study, we investigated the properties of Cu4 and Cu5-doped g-C3N4 photocatalysts using density functional theory. Our findings revealed that Cu clusters can form an Ohmic contact with C3N4, promoting the separation and transfer of photo-generated electrons and holes, and reducing the reaction barrier. We optimized the adsorption models of gas-phase intermediate molecules and identified the most stable configuration with the lowest adsorption energy. The results indicated that Cu clusters and C3N4 can work synergistically to provide active sites for the adsorption of gas-phase molecules, revealing the mechanism for lowering the activation energy. Cu4-doped C3N4 was identified as the most promising photocatalyst through the comparison of the Gibbs free energy change in CO2 reduction and the HER energy barrier. Further research found that the co-adsorption of *CO on the Cu clusters effectively suppressed the hydrogen evolution reaction, providing insights into the potential mechanism un-derlying the high selectivity of Cu clusters for the production of C2 products through CO2 reduction.