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A rational synthesis of single-atom iron–nitrogen electrocatalysts for highly efficient oxygen reduction reaction

Developing low-cost nonprecious catalysts to replace Pt-based material is of great significance and importance for high-performance energy devices. Designing highly efficient, stable, and economic oxygen reaction electrocatalysts with atomically-dispersed metal–N–C active sites through an effective strategy is highly desired for the oxygen reduction reaction (ORR). Currently, the preparation of monoatomic catalysts with high loading and high activity, and the assurance of active sites fully exposed and participating in the reaction is challenging. Herein, atomically-dispersed Fe sites anchored to a porous carbon (Fe-SA/PC) hybrid synthesized via a facile dual-confinement route is reported. The experimental and theoretical simulations reveal that edge oxygen dopants facilitate the micropore trapping of the organic iron complex and the formation of isolated Fe atoms by subsequent pyrolysis. The optimized Fe-SA/PC catalyst exhibits outstanding electrocatalytic activity toward the ORR with a half-wave potential of 0.91 V, which is superior to most of the reported single-atom catalysts. DFT calculations proved that Fe–Nx sites with carbon defects can synergistically reduce the reaction barriers as compared to the intact Fe–Nx atomic configuration. This work provides a promising strategy for the design and construction of a series of high performance single-atom catalysts.