Transition metal-Nx doped graphene as an efficient oxygen reduction reaction catalyst: A theoretical perspective

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.

Evaluating the Oxygen Electrode Reactions of La Single-Atom Catalysts with the N/C Coordination Effect

There is a growing demand for bifunctional electrocatalysts for oxygen electrodes in rechargeable metal-air batteries. This article investigates the bifunctional activity of La single-atom catalysts with N/C coordination (LaNxC6-x@Gra) using density functional theory (DFT). The augmentation of N coordination will result in enhanced synthetic stability. The coordination between nitrogen and carbon (N/C) has a significant influence on the working stability of the system under consideration. In the context of active atoms, the coordination between nitrogen and carbon (N/C coordination) has a significant impact on the electronic structure. This, in turn, influences the adsorption performance and catalytic activity of the catalysts. In the case of stable coordination environments, a correlation exists between the f-orbital center (εf) and the overpotential (η) via the adsorption free energy of intermediates (ΔG*ads). This correlation serves as a useful tool for predicting catalytic performance. The LaNxC6-x@Gra exhibits remarkable bifunctional activity due to its complementary performance, with an overpotential for the oxygen reduction reaction (ηORR) of 0.66 V and an overpotential for the oxygen evolution reaction (ηOER) of 0.43 V. This makes it a promising candidate for use as a bifunctional electrocatalyst in oxygen electrodes.

Boron Coordination Effect in Ni-Nx Doped Graphene Catalysts on the ORR Performance Based on DFT Calculations

The coordination atoms of metal active site in transition metal N-doped carbon single atom electrocatalysts play a vital role in dominating the catalytic performance of oxygen reduction reaction (ORR) at the cathode of fuel cells or metal-air cells. In view of weak adsorption ability of Ni active site in NiN₄ -C catalysts to oxygen intermediate states, herein we introduce boron atoms with smaller electronegativity than N and C atoms to modulate the local coordination environment and electronic structures of Ni site. First-principles density functional calculations reveal that both B substitution for N atoms (NiN₂ B₂ -C) and B coordinating with N and C (NiN₄ B₈ -C) can effectively optimize the Gibbs free energy of oxygen intermediate states and hence improve the catalytic activity of the materials. In addition, we propose that the trend change in catalytic activity is mainly governed by the filling of antibonding orbitals between Ni-3d and O-2p states near the Fermi level.