Construction of Asymmetric Fe-N3P1 Sites on Freestanding Nitrogen/Phosphorus Co-Doped Carbon Nanofibers for Boosting Oxygen Electrocatalysis and Zinc–Air Batteries

Abstract

The construction of freestanding carbon nanofiber membrane with single-atomic metal active sites and interconnected microchannels as air electrodes is vital for boosting the performance of zinc–air batteries (ZABs). Herein, single-atomic Fe sites is prepared on freestanding hierarchical nitrogen/phosphorus co-doped carbon nanofibers (Fe SACs@PNCNFs) by loading Fe-doped zeolitic imidazolate framework-8 with leaf-like structures on electrospun polyacrylonitrile (PAN) nanofibers with subsequent multi-step pyrolysis in the presence of sodium monophosphate, which are confirmed to be in the form of Fe-N₃P₁ by X-ray adsorption spectra. The asymmetric N/P coordinated Fe sites is theoretically demonstrated to boost the ORR performance with a half-wave potential of 0.89 V due to the weakened ^*O adsorption while stabilizing ^*OOH adsorption arising from the increased charge density of Fe sites compared to symmetric N coordinated Fe sites with Fe-N₄. Moreover, when liquid and quasi-solid ZABs are assembled, excellent battery performance is also achieved with peak power density of 163 and 72 mW cm⁻² as well as good stability for more than 190 and 65 h, respectively.