Tailoring the Coordination Environment of Single-Atom Catalysts for Enhanced Electrochemical CO₂-to-CO Conversion Efficiency

Exploring the influence of the coordination environment of single-atom catalysts (SACs) on the electrochemical CO₂ reduction reaction is vital for assessing the reaction mechanism and structure-performance relationship. However, it is challenging to engineer the coordination configuration of isolated active metal atoms precisely. Herein, we strategically manipulate the coordination number of the Co–N_x configuration by simply changing the order of adding the metal precursor toward improved CO₂ electrolysis performance. Compared with the symmetric Co–N₄ coordination, the asymmetric Co–N₃ coordination leads to reinforced Co–N interaction and downshifted 3d orbital energy toward the Fermi level of the active Co sites, promoting the activation of CO₂ molecules and the formation of critical intermediate *COOH. The as-designed Co–N₃ SAC displays excellent Faradaic efficiency (FE) of 98.4% for CO₂-to-CO conversion at a low potential of −0.80 V, together with decent FE over a wide potential range (−0.50 V to −1.10 V) and high durability. This study presents an ideal platform to manipulate the coordination number of atomically dispersed metal catalysts and provides a fundamental understanding of coordination configuration-performance correlation for CO₂ electroreduction.