Electronic coupling engineering of the FeF2@FeNC heterostructure for highly efficient and robust alkaline oxygen reduction

Abstract

The development of non-precious metal catalysts with both high activity and exceptional durability for the oxygen reduction reaction (ORR) remains a critical challenge. We propose an electronic coupling engineering strategy via constructing a heterostructure of iron fluoride (FeF₂) nanocrystals and atomically dispersed Fe–N₄ sites (denoted as FeF₂@FeNC), which is among the highest reported ORR activity and ultrahigh durability in alkaline media. FeF₂@FeNC achieves a half-wave potential of 0.96 V in alkaline electrolyte, surpassing commercial Pt/C and state of the art Fe based catalysts. Remarkably, it sustains this performance over 300 000 accelerated durability test cycles with negligible decay. Experimental characterization and density functional theory calculations show that the FeF₂/FeNC heterointerface induces significant charge redistribution, downshifting the d-band center of the Fe–N₄ sites and substantially reducing the *OH desorption barrier. Meanwhile, the strong electronic coupling at the interface reinforces Fe–N bonding and elevates the Fe dissolution barrier, effectively suppressing metal leaching during long-term cycling. The exceptional catalytic performance is further validated in rechargeable zinc–air batteries, where the FeF₂@FeNC-based device delivers a high peak power density of 253 mW cm⁻² and operates stably for over 500 hours. This work establishes a promising strategy for synchronously boosting the activity and stability of single-atom catalysts, holding great promise for practical energy conversion applications.