Construction of atomically dispersed Cu-N4 sites via engineered coordination environment for high-efficient CO2 electroreduction

Although considerable progress has been achieved by Cu nanoparticles for catalyzing CO2 reduction reaction (CO2RR), Cu single atom catalysts (Cu SACs) are generally suffered from inferior performance to that of widely investigated Fe, Co, Ni SACs. This phenomenon mainly ascribes to the lack of effective geometry and electronic engineering of copper active center from an atomic level. Herein, highly exposed atomically dispersed Cu-N-x (x denotes Cu-N coordination number) sites anchored on 3D porous carbon matrix are successfully synthesized through facile one step thermal activation, and Cu-N-4 sites exhibit boosted activity and selectivity compared to its nearly inert Cu-N-3 counterparts. Aided by density functional theory (DFT) calculations, the edge-hosted Cu-N-4 moieties are revealed as key active sites for efficient CO generation via optimized local coordination environment and electronic properties, which strongly interact with *COOH intermediate and facilitate the desorption of *CO. As a result, Cu-N-4 catalyst achieves high CO Faradaic efficiency (FECO) of over 90% from - 0.6 to -1.1 V vs. RHE with a maximum value of 98%, surpassing the previously reported Cu SACs for CO2-to-CO conversion. This work provides new insight into proper Cu SACs design and fundamental mechanism understanding to boost CO2RR.