Tuning the Inter-Metal Interaction between Ni and Fe Atoms in Dual-Atom Catalysts to Boost CO Electroreduction.

Dual-atom catalysts (DACs) are promising for applications in electrochemical CO reduction due to the enhanced flexibility of the catalytic sites and the synergistic effect between dual atoms. However, precisely controlling the atomic distance and identifying the dual-atom configuration of DACs to optimize the catalytic performance remains a challenge. Here, the Ni and Fe atomic pairs were constructed on nitrogen-doped carbon support in three different configurations: NiFe-isolate, NiFe-N bridge, and NiFe-bonding. It was found that the NiFe-N bridge catalyst with NiN and FeN sharing two N atoms exhibited superior CO reduction activity and promising stability when compared to the NiFe-isolate and NiFe-bonding catalysts. A series of characterizations and density functional theory calculations suggested that the N-bridged NiFe sites with an appropriate distance between Ni and Fe atoms can exert a more pronounced synergy. It not only regulated the suitable adsorption strength for the *COOH intermediate but also promoted the desorption of *CO, thus accelerating the CO electroreduction to CO. This work provides an important implication for the enhancement of catalysis by the tailoring of the coordination structure of DACs, with the identification of distance effect between neighboring dual atoms.