Regulating the coordination environment of Co single atoms for achieving efficient electrocatalytic activity in CO2 reduction

Regulating the coordination environment of Co single-atom catalysts represents a powerful strategy to enhance its catalytic performance for CO2 electrochemical reduction. Herein, we adopt metal-organic frameworks (MOFs) to assist the preparation of Co single-atom catalysts with four-coordinated N and four-coordinated N/C on N-doped porous carbon. The atomic dispersion of Co atoms species on the N-doped porous carbon were confirmed using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure (XAFS) analysis. XAFS results revealed that the coordination number of the N binding to the Co single atom was strongly dependent on the pyrolysis temperature. The Co atoms with four-coordinated N on N-doped porous carbon (Co-1 -N-4) exhibited a Faradaic efficiency of 82% and a current density of -15.8 mA cm(-2) for CO production in CO2 electrochemical reduction. Moreover, the Co-1-N-4 catalytic site also held remarkable stability for 10-hour potentiostatic test towards CO2 electrochemical reduction. Mechanistic study further revealed that the Co-1-N-4 active site promotes the binding strength of CO2 and facilitates CO2 activation, which was responsible for its excellent CO2 electrochemical reduction performance.