Abstract Nickel‐nitrogen‐carbon single‐atom catalysts have attracted widespread interest for CO2 electroreduction but they suffer from poor stability. Herein, we report on the preparation of Cl‐ and N‐doped porous carbon nanosheets with atomically dispersed NiN4Cl active sites (NiN4Cl‐ClNC) through a molten‐salt‐assisted pyrolysis strategy. The optimized NiN4Cl‐ClNC catalyst delivers exceptional CO2 conversion activity with outstanding stability for over 220 h at −0.7 V versus RHE and a high CO Faradaic efficiency of 98.7% at a CO partial current density of 12.4 mA cm‒2. Moreover, NiN4Cl‐ClNC displays a remarkable CO partial current density of approximately 349.4 mA cm−2 in flow‐cell, meeting the requirements of industrial applications. Operando attenuated total reflectance surface‐enhanced infrared absorption spectroscopy and density functional theory calculations are used to understand the outstanding activity and stability. Results reveal that the introduced axial Ni‐Cl bond on the Ni center and Cl─C bond on the carbon support synergetically induce electronic delocalization, which not only stabilizes Ni against leaching but also facilitates the formation of the COOH* intermediate that is found to be the rate‐determining step.
