FeNi Dual-Metal Dimer Embedded in Nitrogen-Doped Graphene for Enhanced Oxygen Reduction Catalysis: A Density Functional Theory Study.

Developing highly effective single-atom catalysts for oxygen reduction reaction (ORR) is critical to improve fuel cell efficiency. Hence, this study systematically investigates ORR performance of single-metal (FeN4-G, NiN4-G) and dual-metal (FeNiN3-G) catalysts embedded in nitrogen-doped graphene through density functional theory (DFT) calculations. Through analysis of ORR intermediates adsorption on M-N-C surfaces, the Gibbs free energy changes, density of states, and electron transfer profiles of catalytic systems are investigated. DFT calculations reveal that while the over-binding of FeN4-G and intermediates impedes desorption kinetics and weak interactions of NiN4-G favor the less efficient 2e- pathway, FeNiN3-G addresses these limitations through synergistic Fe-Ni electronic coupling. By optimizing d-band alignment and charge redistribution, FeNiN3-G lowers the rate-determining step energy barrier and reduces overpotential. Moreover, the dual-metal configuration promotes selective 4e- ORR via efficient OO bond cleavage. This work provides mechanistic insights for designing high-efficiency M-N-C electrocatalysts for energy conversion technologies.