Tailoring local structures of atomically dispersed copper sites for highly selective CO2 electroreduction

Atomically-dispersed copper sites coordinated with nitrogen-doped carbon (Cu-N-C) can provide novel possibilities to enable highly selective and active electrochemical CO2 reduction reactions. However, the construction of optimal local electronic structures for nitrogen-coordinated Cu sites (Cu-N-4) on carbon remains challenging. Here, we synthesized the Cu-N-C catalysts with atomically-dispersed edge-hosted Cu-N-4 sites (Cu-N4C8) located in a micropore between two graphitic sheets via a facile method to control the concentration of metal precursor. Edge-hosted Cu-N4C8 catalysts outperformed the previously reported M-N-C catalysts for CO2-to-CO conversion, achieving a maximum CO Faradaic efficiency (FECO) of 96%, a CO current density of -8.97 mA cm(-2) at -0.8 V versus reversible hydrogen electrode (RHE), and over FECO of 90% from -0.6 to -1.0 V versus RHE. Computational studies revealed that the micropore of the graphitic layer in edge-hosted Cu-N4C8 sites causes the d-orbital energy level of the Cu atom to shift upward, which in return decreases the occupancy of antibonding states in the *COOH binding. This research suggests new insights into tailoring the locally coordinated structure of the electrocatalyst at the atomic scale to achieve highly selective electrocatalytic reactions.