Theoretical Study on the Modulation of Oxygen Electrocatalysis in Co-Based Single-Atom Catalysts by N and S Co-Coordination

Understanding how local coordination environments influence oxygen electrocatalytic activity is essential for designing efficient non-precious metal catalysts. In this work, density functional theory (DFT) calculations were performed to systematically explore the impact of N/S co-coordination on the electronic structure and catalytic properties of graphene-supported cobalt single-atom catalysts (SACs). The results demonstrate that all Co–N–S configurations exhibit negative formation energies and positive dissolution potentials, suggesting favorable thermodynamic and electrochemical stability. Among these configurations, CoN₂S₂-pen shows a lower oxygen reduction reaction (ORR) overpotential of 0.53 V, while CoN₂S₂-hex exhibits superior oxygen evolution reaction (OER) performance with an overpotential of 0.42 V. Analyses of charge density differences and projected density of states (PDOS) reveal strong hybridization between Co 3d and O 2p orbitals, which facilitates O₂ activation and stabilizes intermediate adsorption. These findings underscore the potential of N/S co-coordination in modulating the electronic structure and enhancing the bifunctional oxygen electrocatalytic performance of Co-based SACs.