Synergistically Coupled CoFe Core–Shell Nanoparticles and Fe–N x Motifs in N,S,P-Doped Hierarchical Carbon for Rechargeable Zinc–Air Batteries

Abstract Rechargeable zinc–air batteries (ZABs) require efficient and durable bifunctional oxygen electrocatalysts to accelerate both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, we report a hierarchical N, S, and P co-doped carbon catalyst (CoFe/NSP-HC) featuring CoFe core–shell alloy nanoparticles and Fe–Nx coordination motifs, synthesized through a pyrolysis strategy using heteroatom-enriched g-C3N4 as both template and dopant source. Structural characterization reveals a hierarchical porous architecture with uniformly distributed heteroatoms, strong metal–support interactions, and a well-defined Co-rich core/Fe-rich shell configuration. The synergistic integration of CoFe alloy interfaces, Fe–Nx coordination sites, and a defect-rich carbon framework effectively modulates the electronic structure and optimizes the adsorption/desorption behavior of oxygenated intermediates. Consequently, the optimized CoFe/NSP-HC catalyst exhibits bifunctional activity with an ORR half-wave potential of 0.82 V and an OER overpotential of 260 mV at 10 mA cm–2, delivering a low bifunctional potential gap (ΔE) of 0.67 V. Furthermore, the catalyst demonstrates robust electrochemical durability, maintaining stable ORR/OER performance after prolonged cycling. Density functional theory calculations reveal that Fe–Nx sites and Fe-based interfacial centers provide favorable reaction energetics for oxygen electrocatalysis, while Co species contribute to electronic modulation and kinetic enhancement. When employed as the air cathode in a rechargeable ZAB, CoFe/NSP-HC delivers a peak power density of 158.7 mW cm–2 and long-term cycling stability exceeding 350 h. This work provides an effective strategy for constructing multi-component electrocatalysts with synergistically engineered active sites for advanced metal–air energy storage systems.