Atomically Defined Undercoordinated Active Sites for Highly Efficient CO2 Electroreduction

Abstract Electrocatalytic reduction of carbon dioxide (CO 2 ER) in rechargeable Zn–CO 2 battery still remains a great challenge. Herein, a highly efficient CO 2 ER electrocatalyst composed of coordinatively unsaturated single‐atom copper coordinated with nitrogen sites anchored into graphene matrix (Cu–N 2 /GN) is reported. Benefitting from the unsaturated coordination environment and atomic dispersion, the ultrathin Cu–N 2 /GN nanosheets exhibit a high CO 2 ER activity and selectivity for CO production with an onset potential of −0.33 V and the maximum Faradaic efficiency of 81% at a low potential of −0.50 V, superior to the previously reported atomically dispersed Cu–N anchored on carbon materials. Experimental results manifest the highly exposed and atomically dispersed Cu–N 2 active sites in graphene framework where the Cu species are coordinated by two N atoms. Theoretical calculations demonstrate that the optimized reaction free energy for Cu–N 2 sites to capture CO 2 promote the adsorption of CO 2 molecules on Cu–N 2 sites; meanwhile, the short bond lengths of Cu–N 2 sites accelerate the electron transfer from Cu–N 2 sites to *CO 2 , thus efficiently boosting the *COOH generation and CO 2 ER performance. A designed rechargeable Zn–CO 2 battery with Cu–N 2 /GN nanosheets deliver a peak power density of 0.6 mW cm −2 , and the charge process of battery can be driven by natural solar energy.