Nonnitrogen Coordination Environment Steering Electrochemical CO2-to-CO Conversion over Single-Atom Tin Catalysts in a Wide Potential Window

Replacing conventional metal–N4 moieties with different coordination structures is a promising strategy to tailor the activity and selectivity of single-atom catalysts (SACs). However, for CO2 electroreduction driven by metals that may produce diverse chemical species, such as Tin (Sn), the influences of nonnitrogen coordination environments on the CO2 reduction pathways are unclear. Herein, we report an Sn SAC with a special coordination structure of Sn-C2O2F, which delivers CO as an exclusive CO2 reduction product with a faradaic efficiency higher than 90.0% over a wide potential window (−0.2 to −0.6 V vs the reversible hydrogen electrode) and a peak value of up to 95.2%. The resulting cathodic energy efficiency and current density achieve 70.7% and 186 mA cm–2, respectively. In contrast, formate is predominantly formed on the Sn-N4 site. Theoretical calculations disclose that C and O coordination modulates the adsorption of intermediates, while an Sn-bonded F atom significantly suppresses the hydrogen evolution, thereby facilitating CO2-to-CO conversion. Meanwhile, the CO2-to-HCOO– conversion via O-bound intermediates or direct reaction of absorbed H and dissolved CO2 is prohibited.