CO₂ Reduction Mechanism Based on a Partially Reduced Cu Single-Atom Catalyst: A First-Principles Study

Experimentally, CO can be generated as the main product at a lower negative potential. Since CO is the key intermediate of methanol synthesis and C–C coupling reactions, the catalyst should have a strong adsorption capacity for CO molecules. Theoretical computations, based on Cu–N4–C models, indicate that a significantly high-energy barrier needs to be for carboxylation of CO2, resulting primarily in formic acid formation and exhibits weak adsorption of CO. Given the abundance of N–H bonds involved in both the preparation of N@graphene and electrocatalytic reduction, a Cu–N4H–C structural model has been proposed, and the model can remain stable at 600 K up to 3 ps based on AIMD simulations. In the Cu–N4H–C model, the Cu+ ion is partially reduced and enhances the adsorption capacity of CO. The model effectively lowers the energy barrier for CO2 carboxylation to 0.23 eV, and the energy barrier for methanol synthesis is 0.50 eV. By doping with K atoms, the catalyst can also be reduced. The reduced catalyst shows an ideal reduction performance of CO2 to HCOOH. Based on ab initio simulations, this study will reveal the influence of the microenvironment on the CO2 reduction process in Cu single-atom catalysts and is helpful for the realization of efficient CO2 reduction in experiments.