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

Cu‐based electrocatalysts with high catalytic selectivity for the CO 2 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 CO 2 to CO. The single‐atom 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 CO 2 activation step and 2) the moiety‐anchoring graphene facilitates water dissociation, which supplies protons for CO 2 reduction. Moreover, density functional theory (DFT) calculations reveal that CO 2 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.