Theoretical exploration on the activity of copper single-atom catalysts for electrocatalytic reduction of CO2

Enhancing the activity of the carbon dioxide reduction reaction (CO2RR) by controlling the structure of single-atom catalysts (SACs) has recently been shown to be a rather promising strategy. The effect of the structure and coordination environment on electrocatalytic CO2RR activity of single-atom copper catalysts (Cu-N/C) was investigated by using density functional theory (DFT) calculations. The free energies of the adsorption of intermediates *CO and *COOH are linearly correlated, and among 11 kinds of Cu-N/C catalysts, CuN3V and CuN2V2 have better CO2RR activity with Delta G(*COOH) as the descriptor. The free energy analysis of the CO2 electrocatalytic reduction reaction shows that CuN3V and CuN2V2 have the lowest limiting potentials in 11 Cu-N/C catalysts (-0.86 V and -0.93 V) too. For saturated structure catalysts, the production of *COOH is the decisive step, while the desorption of *CO is the decisive step for unsaturated ones. CuN3V and CuN2V2 have a high CO2RR selectivity, and their activation energy barriers for the CO2RR (1.37 eV and 1.32 eV) are much lower than that for the hydrogen precipitation reaction (HER, 3.22 eV and 4.53 eV). The change in the catalyst structure can affect not only the adsorption properties, but also the potential-determining step of the CO2RR, and the unsaturated structure is more favorable for improvement of the catalyst activity. These results highlight the important influence of the structure and coordination environment on the activity and selectivity of single-atom copper catalysts for the CO2RR, and provide helpful information for design of other metal single-atom catalysts.