Superior Oxygen Reduction on Curved Fe-N4 Sites Enabled by Molecular Infiltration within Self-Assembled Fullerene Microbelts

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-Nx 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 C60s act as molecular metal chelator and nitrogen source, 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 an 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.