Highly Selective Two-Electron Electrocatalytic CO2 Reduction on Single-Atom Cu Catalysts

Cu-based electrocatalysts with high catalytic selectivity for the CO2 reduction reaction present a significant technological challenge. Herein, a catalyst comprised of Cu single atoms in a nitrogen-doped graphene matrix (Cu-N-4-NG) is developed for highly selective electrocatalytic reduction of CO2 to CO. The singleatom structure and coordination environment of Cu-N-4-NG are identified by synchrotron-based characterization. Compared to a conventional bulk Cu catalyst, Cu-N-4-NG achieves a Faradaic efficiency of 80.6% toward CO under a moderate applied potential of -1.0 V versus reversible hydrogen electrode (RHE). Kinetic experiments show that 1) the Cu-N-4 moiety favors the CO2 activation step and 2) the moiety-anchoring graphene facilitates water dissociation, which supplies protons for CO2 reduction. Moreover, density functional theory (DFT) calculations reveal that CO2 reduction is less hindered thermodynamically on Cu-N-4-NG compared to the competing hydrogen evolution reaction (HER) due to their limiting potential differences. Therefore, the highest CO selectivity is observed on Cu-N-4-NG over the bulk Cu catalyst due to more favorable kinetics and thermodynamics.

Automated summary

Cu-based electrocatalysts with high catalytic selectivity for the CO2 reduction reaction are a significant technological challenge. A Cu single atom catalyst, Cu-N-4-NG, has been developed for the selective electrocatalytic reduction of CO2 to CO, achieving an 80.6% Faradaic efficiency under moderate applied potential. The single-atom structure and coordination environment, along with moiety-anchoring graphene, contribute to the high selectivity and efficiency of CO production on Cu-N-4-NG compared to bulk Cu catalysts.