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.