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-Fe 2 P/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 Fe 2 P nanoparticles embedded in ZIF-derived N,P-codoped carbon nanoboxes. Consequently, the obtained CZIF-PA-Fe 2 P/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 Fe 2 P 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. The selective etching of phytic acid not only endows the material with abundant pore diameters to enhance mass transfer but also serves as an in-situ phosphorus source to promote the uniform nucleation of highly active Fe 2 P nanoparticles. By employing PA-induced etching, shell-in-shell carbon catalysts were successfully fabricated to exhibit satisfactory oxygen reduction. Download: Download high-res image (196KB) Download: Download full-size image