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

Abstract

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.