Atomically dispersed metal and nitrogen codoped carbon (M-N-C) catalysts with N-coordinated metal (MN x ) sites have shown compelling performance in electrochemical CO 2 reduction (ECR). However, extra uncoordinated N species commonly coexist with MN x sites in M-N-C, which are impossible to ignore due to their inevitable interference in catalytic performance. Considering this, we developed high-performance Co-N-C for ECR by diminishing the uncoordinated N species. The resulting electrocatalyst displays a CO faradic efficiency (FE CO ) of 99.4% with a CO current density of −24.8 mA•cm −2 at a low overpotential of 0.49 V in an H-type cell, and a high FE CO over 90% is obtained in a flow cell within a wide current density window (50−600 mA•cm −2 ), exceeding all reported Co-N-C catalysts. Density functional theory calculations reveal that isolated CoN 4 sites can reduce the energy barrier required for the formation of COOH* and suppress the occurrence of hydrogen evolution compared with CoN 4 sites with extra uncoordinated N species, thus resulting in enhanced activity and selectivity in CO production.
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