Optimizing Electronic Microenvironment on Nickel Single-Atom Catalyst via In Situ Template Replacement for Efficient Electrochemical CO2 reduction

Abstract

Optimizing the coordination environment of metal centers in M–N₄ complexes is critical for accelerating the reaction kinetics in electrochemical CO₂ reduction (CO₂RR). Herein, we report a facile strategy for regulating the atomic coordination microenvironment on nickel single-atom catalysts (Ni SACs) by in situ template replacement during synthesis. By implementing one-pot pyrolysis with dynamically sacrificial template replacement, Ni SACs with axial oxygen coordination at Ni–N₄ sites, anchored on a N, O-co-doped carbon nanosheet framework (Ni–N₄O–C) were successfully obtained. The optimized catalyst exhibits outstanding performance in the electrochemical conversion of CO₂ to CO, achieving a maximum Faraday efficiency of 95% within a wide potential window of −0.54 to −1.04 V (vs RHE). Notably, it maintains remarkable durability, retaining over 90% efficiency even after prolonged operation at −0.74 V for 90 h. Further mechanistic studies reveal that the oxygen coordination Ni–N₄O–C site by regulating the coordination microenvironment reduces the free energy barrier for key *COOH intermediates compared to conventional Ni–N₄ sites. Our findings establish a template-mediated coordination environment adjustment method for the SACs design.