Confinement Phosphorization Strategy Unlocks FeP–N–C Catalysts for Highly Stable Zinc-Air Batteries

Abstract

Rechargeable zinc-air batteries (RZABs) are promising next-generation energy storage systems due to their high theoretical energy density. However, their practical application is hindered by the slow reaction kinetics of oxygen reduction/evolution (ORR/OER) at air cathodes. Herein, an innovative N-rich copolymer-confined phosphorization strategy for synthesizing FeP nanoparticles encapsulated in carbon matrix (FeP–NPC) has been developed. The methodology employs an iron-phytic acid/aniline/pyrrole ternary copolymer precursor, achieving atomic-level interfacial coupling between FeP nanocrystals and carbon substrate through precisely controlled phosphating thermodynamics. Electrochemical characterization reveals exceptional bifunctional activity with ORR onset potential of 1.04 V versus RHE (0.85 V half-wave potential) and OER overpotential of 1.66 V at 10 mA cm⁻² in 0.1 M KOH electrolyte, comparable to commercial Pt/C-RuO₂ benchmarks. The assembled RZAB demonstrates a peak power density of 185.0 mW cm⁻² with remarkable durability maintaining 53.5% round-trip efficiency over 530 h cycling. Advanced spectroscopic analysis and DFT calculations elucidate that the N-rich carbon matrix induces the formation of FeP–N–C active sites which facilitates d-band center downshifting of FeP via interfacial charge redistribution, thereby optimizing oxygen intermediate adsorption/desorption energetics. Furthermore, the conductive carbon network acts as an electron reservoir to facilitate charge transfer kinetics during bifunctional catalysis. This interface engineering strategy provides a paradigm for developing cost-effective transition metal phosphide catalysts, advancing the practical implementation of metal-air battery technologies in energy storage systems.