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Dynamic Activation of Adsorped Intermediates via Axial Traction for the Promoted Electrochemical CO2 Reduction.

Regulating the local environment and structure of metal center coordinated by nitrogen ligands (e.g., M-N4) to accelerate overall reaction dynamics of electrochemical CO2 reduction reaction (CO2RR) has attracted extensive attention. Herein, we develop an axial traction strategy to optimize the electronic structure of M-N4 moiety and construct atomically dispersed nickel sites coordinated with four nitrogen atoms and one axial oxygen atom, which are embedded within the carbon matrix (Ni-N4-O/C). The Ni-N4-O/C electrocatalyst exhibited excellent CO2RR performance with a maximum CO Faradic efficiency (FE) close to 100% at -0.9 V. The CO FE could be maintained above 90% in a wide range of potential window from -0.5 to -1.1 V. The superior CO2RR activity is due to the Ni-N4-O active moiety composed of a Ni-N4 site with an additional oxygen ligand that induces an axial traction effect. The unique structure was evidenced by aberration-corrected scanning transmission electron microscopy and synchrotron radiation X-ray absorption spectroscopy. Theoretical calculations elucidate that the introduction of axial oxygen atom could optimize surface states of Ni-N4 moieties and enhance the charge polarization effect, therefore decreasing the potential barrier of intermediate COOH* formation, a key factor to accelerate the reaction kinetics and boost the CO2RR performance.