Dual-role phytic acid etching induces shell-in-shell Fe₂P/N,P-codoped carbon nanoboxes for oxygen reduction

The rational design and facile synthesis of non‑platinum carbon catalysts with high energy conversion efficiency remain a core challenge in electrocatalysis. To address this, we successfully constructed a unique shell-in-shell catalyst through a phytic acid (PA) etching and secondary pyrolysis strategy, designated as CZIF-PA-Fe₂P/NC. In this process, PA not only drives the selective etching of cubic ZIF-8 nanocrystals but also serves as an in situ phosphorus source to induce the uniform nucleation of highly active Fe₂P nanoparticles embedded in ZIF-derived N,P-codoped carbon nanoboxes. Consequently, the obtained CZIF-PA-Fe₂P/NC catalyst achieves an excellent oxygen reduction reaction (ORR) half-wave potential of 0.914 V, and maintains a 96.73% current retention over a 30-h stability test. When assembled into zinc-air batteries, the device delivers a peak power density of 157.58 mW cm^-2, a specific capacity of 795.76 mAh g^-1, and long-term cycling stability surpassing that of 20 wt% Pt/C. Finally, density functional theory calculations reveal that the synergistic electronic modulation between the N,P-codoped carbon substrate and Fe₂P promotes an upward shift of the Fe d-band center, thereby optimizing the adsorption of key *OOH intermediates and significantly reducing the energy barrier of the rate-determining step. This work establishes a precise morphology design and interface engineering paradigm for developing cost-effective, high-performance metal-organic framework-derived non-noble-metal carbon electrocatalysts for energy conversion and storage applications.