Highly selective two-electron electrocatalytic CO₂ reduction on single‐atom Cu catalysts

Abstract

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–N₄–NG) is developed for highly selective electrocatalytic reduction of CO₂ to CO. The single‐atom structure and coordination environment of Cu–N₄–NG are identified by synchrotron‐based characterization. Compared to a conventional bulk Cu catalyst, Cu–N₄–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–N₄ 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–N₄–NG compared to the competing hydrogen evolution reaction (HER) due to their limiting potential differences. Therefore, the highest CO selectivity is observed on Cu–N₄–NG over the bulk Cu catalyst due to more favorable kinetics and thermodynamics.