Tuning nitrogen reduction reaction activity via controllable Fe magnetic moment: A computational study of single Fe atom supported on defective graphene

Highlights: • The catalytic performances of carbon-based Fe single-atom catalysts for nitrogen electroreduction are systematically investigated. • A linear relation between the adsorption energy of N atom and the Fe magnetic moment is revealed. • The magnetic moment of the supported Fe atom plays an important role in N₂ activation. The design and development of low-cost and highly efficient electrocatalysts for nitrogen reduction reaction is crucial for NH₃ synthesis. Herein, by means of comprehensive density functional theory (DFT) calculations and thermodynamic analysis, the catalytic mechanisms of N₂ to NH₃ conversion on single Fe atom embedded in single vacancy and N-doped graphene are systematically investigated. Significantly, the magnetic moment of Fe atom varies with the coordination of neighboring N atom. An approximately linear scaling is found between the adsorption energy of N atom ($\Delta {\text{E}}_{\text{N*}}$) and Fe magnetic moment. The increased magnetic moment of Fe atom can strengthen the ΔE_N*, and promote the charge transfer between the N₂ molecule and substrates, resulting in a substantially lower overpotential for N₂ electroreduction. Our results highlight an important role of Fe magnetism in N₂ activation, which offers a novel strategy for inspiring the rational design of highly efficient carbon-based materials for N₂ fixation and conversion.