Peripheral Structure-Activity Relationships in N-Doped Single-Atom Catalysts Efficient for CO2 Electroreduction

Electrochemical CO2 reduction reaction (CO2RR) is a promising route for the conversion of CO2 into valuable carbon products. Nitrogen-carbon (NC)-supported single-atom catalysts (SACs), particularly those with peripheral coordination geometries, have attracted considerable attention. In the present work, we investigate two N-coordinating Co-SAC geometries, pyridinic (CoPriN4) and pyrrolic (CoProN4), constructed at the periphery of idealized graphene fragments for the CO2-to-CO conversion pathway. Our density functional theory (DFT) calculations, performed within the computational hydrogen electrode (CHE) framework, demonstrate that incorporating five- and six-membered NC ring structures in the outer shell modulates the inner-shell electronic properties of the N-doped systems, influencing electron transfer behavior and inducing d-p hybridization between the Co center and the coordinating N atoms. In particular, CoProN4 exhibits stronger d-p hybridization, resulting in weakened *CO desorption relative to CoPriN4. This electronic modulation optimizes the thermodynamic adsorption energies of key intermediates (*COOH and *CO) and thermodynamically disfavors the competing hydrogen evolution reaction, thereby lowering the predicted thermodynamic limiting potential for CO2RR. As the present study is based on static thermodynamic modeling of idealized graphene fragments and does not account for explicit kinetic barriers or solvent dynamics, the proposed peripheral design strategy offers a useful thermodynamic perspective for understanding structure-property relationships in NC-supported Co-SACs for electrochemical CO2 reduction.