Control over Electrochemical CO₂ Reduction Selectivity by Coordination Engineering of Tin Single-Atom Catalysts

Carbon-based single-atom catalysts (SACs) with well-defined and homogeneously dispersed metal-N₄ moieties provide a great opportunity for CO₂ reduction. However, controlling the binding strength of various reactive intermediates on catalyst surface is necessary to enhance the selectivity to a desired product, and it is still a challenge. In this work, the authors prepared Sn SACs consisting of atomically dispersed SnN₃O₁ active sites supported on N-rich carbon matrix (Sn-NOC) for efficient electrochemical CO₂ reduction. Contrary to the classic Sn-N₄ configuration which gives HCOOH and H₂ as the predominant products, Sn-NOC with asymmetric atomic interface of SnN₃O₁ gives CO as the exclusive product. Experimental results and density functional theory calculations show that the atomic arrangement of SnN₃O₁ reduces the activation energy for *COO and *COOH formation, while increasing energy barrier for HCOO* formation significantly, thereby facilitating CO₂-to-CO conversion and suppressing HCOOH production. This work provides a new way for enhancing the selectivity to a specific product by controlling individually the binding strength of each reactive intermediate on catalyst surface.