Tuning the Microenvironment of Co‐N4 in Co Single‐Atom Catalysts for Electrocatalytic CO2 Reduction

Single‐atom catalysts (SACs), with their well‐defined structure, serve as an efficient catalyst model for studying the structure‐performance relation in the electrocatalytic CO2 reduction reaction (CO2RR). Current CO2RR research primarily focus on the coordination interactions between metal single atoms and coordinated ligands, while the impact of the metal SAC's microenvironment remains largely unexplored. Herein, we generate three microenvironments for a CoN4 ensemble by using different nitrogen sources to prepare Co SACs, i.e. pyridine‐type Co‐N4 (Co‐N4 SACPhen), the pyrrole‐type Co‐N4 (Co‐N4 SACDp) and the mixed‐type Co‐N4(Co‐N4 SACMm). It reveals that the Co‐N4 SACPhen contributes to CO generation with 99.5% selectivity at ‐0.76 vs RHE, whereas the Co‐N4 SACDp accelerates a severe hydrogen evolution reaction. Experimental studies confirmed that the Co‐N4 SACPhen possesses distinctive electrochemical properties and electronic structure, facilitating the generation of CO. This study deepens our understanding of the cobalt SAC's microenvironment's influence on CO2RR.