Atomically Dispersed Dual-Metal Site Catalysts for Enhanced CO 2 Reduction: Mechanistic Insight into Active Site Structures.

Carbon-supported nitrogen-coordinated single-metal site catalysts (i.e., M-N-C, M: Fe, Co, or Ni) are active for the electrochemical CO 2 reduction reaction (CO 2 RR) to CO. Further improving their intrinsic activity and selectivity by tuning their N-M bond structures and coordination is limited. Herein, we expand the coordination environments of M-N-C catalysts by designing dual-metal active sites. The Ni-Fe catalyst exhibited the most efficient CO2RR activity and promising stability compared to other combinations. Advanced structural characterization and theoretical prediction suggest that the most active N-coordinated dual-metal site configurations are 2N-bridged (Fe-Ni)N 6 , in which FeN 4 and NiN 4 moieties are shared with two N atoms. Two metals (i.e., Fe and Ni) in the dual-metal site likely generate a synergy to enable more optimal *COOH adsorption and *CO desorption than single-metal sites (FeN 4 or NiN 4 ) with improved intrinsic catalytic activity and selectivity.