DFT insights into single-atom Fe-anchored N-doped multilayer graphene for ORR and OER bifunctional catalysis

Abstract The electrocatalytic performance of FeNₓ sites embedded in multilayer graphene (FeNx/MLG) for the oxygen reduction (ORR) and oxygen evolution (OER) reactions was systematically investigated using density functional theory within an electrochemical thermodynamic framework. FeNx supported on bilayer graphene (FeNx/BLG) exhibits superior thermodynamic, electrochemical, and dynamic stability compared to single-layer graphene, arising from stronger Fe–N bonding, enhanced electron localization, and significant interlayer charge transfer. The presence of a second graphene layer induces interlayer π–d confinement, stabilizing Fe centers, strengthening Fe–N hybridization, and optimizing adsorption of oxygenated intermediates. Electrolyte effects further modulate activity, where pH influences proton–electron transfer energetics and shifts potential-determining steps, while solvation stabilizes polar intermediates and lowers free energy barriers. Increasing nitrogen coordination enhances Fe–N bonding and electronic structure, with FeN4–6 configurations showing optimal performance. Key descriptors, including OH* adsorption energy, d-band center, and Fe magnetic moment, exhibit strong linear correlations with activity (R² ≈ 0.94). FeN4–6/BLG sites achieve low overpotentials (0.45–0.50 V for ORR and 0.42–0.55 V for OER), comparable to state-of-the-art catalysts, highlighting BLG-supported FeNx as a promising platform for efficient bifunctional electrocatalysis.