Superior oxygen reduction on curved Fe–N4 sites enabled by molecular infiltration within self-assembled fullerene microbelts

Abstract

The development of Fe–N–C electrocatalysts for the oxygen reduction reaction (ORR) is crucial for sustainable energy technologies, yet achieving a high density of atomically dispersed Fe–N_x sites remains a challenge. Herein, we proposed a novel spatial confinement strategy based on the molecular-level infiltration of iron-coordinated, water-soluble fullerene (Fe/wsC₆₀) into self-assembled fullerene microbelts (FMB). The –NH₂/–OH functionalized C₆₀ molecules act as molecular metal chelators and nitrogen sources, while the flexible FMB framework facilitates their effective permeation. This nanoscale confinement effectively mitigates Fe aggregation during pyrolysis, yielding a catalyst with abundant atomically dispersed curved Fe–N₄ sites alongside fine Fe₃C nanoparticles. The resultant (Fe/N@FMB) catalyst demonstrates exceptional ORR activity and stability in alkaline media with a half-wave potential of 0.891 V, surpassing Pt/C and control samples derived solely from wsC₆₀ or FMB. When integrated into a zinc–air battery, it also achieves a higher open-circuit voltage and power density than Pt/C. Theoretical calculations reveal that the curved carbon matrix and adjacent Fe₃C synergistically modulate the electronic structure of the Fe–N₄ moiety, thereby boosting the ORR kinetics. This work highlights the importance of nanoscale architectural design for precise precursor confinement in developing advanced electrocatalysts.