Hollow Porous Carbon Nanofibers with Fe–N–C Modified by Fe3O4 Nanoparticles for Enhancing Mass Transfer for Boosting the Oxygen Reduction Reaction

Designing low-cost and high-efficiency non-noble metal electrocatalysts for the oxygen reduction reaction (ORR) is critical for the development of renewable and sustainable energy devices. It is of essential importance to precisely design and rationally adjust the porous morphology and nanostructure of catalysts to improve mass transfer and the accessibility of active sites. Herein, we elaborately designed a unique hollow hierarchical porous carbon nanofiber with Fe3O4/Fe–N–C sites anchored as a high-efficiency electrocatalyst for ORR. The hollow porous carbon nanofibers (HPCNFs) were prepared via a facile convenient coaxial electrospinning technology to fabricate the hollow carbon nanofibers and through zinc nitrate-assisted pyrolysis to form a hierarchical porous structure. Benefiting from its unique hollow porous construction, facilitated mass transfer, and highly accessible active sites, the optimized Fe-HPCNFs catalyst exhibited significant ORR performance and stability, with a half-wave potential of 0.89 V outperforming the commercial catalyst (20% Pt/C). Remarkably, Zn–air batteries assembled with Fe-HPCNFs achieved excellent activity with a robust peak power density of 172 mW·cm–2 and a high specific capacity of 905.4 mAh·gZn–1. Furthermore, the ORR mechanism was investigated by density functional theory calculations, demonstrating that the synergistic effect of Fe3O4 nanoparticles and Fe–N–C active sites can effectively boost the electrocatalytic activity for ORR.