MOF-Superstructure-Derived 2D Fe2O3/Fe-N-C Nanosheets as Catalysts for Zn-Air Batteries: Synergistically Enhanced Mass Transport and Electrocatalytic Activity.

Metal-organic framework (MOF)-derived single-atom Fe-N-C catalysts exhibit promising oxygen reduction reaction (ORR) activity. However, their practical performance in zinc-air batteries (ZABs) is hindered by low active site utilization efficiency and excessively strong adsorption of ORR intermediates. Herein, we fabricate a catalyst featuring atomically dispersed Fe and Fe2O3 nanoparticles anchored on large-scale two-dimensional (2D) carbon nanosheets via pyrolysis of MOF superstructure precursors. A dual Fe-source strategy enhances Fe/N contents while creating abundant Fe-Nx and N-doped carbon active sites. Experimental and theoretical results reveal that the 2D nanosheet architecture provides high O2 storage capacity and rapid mass transfer channels, significantly improving Fe-Nx site utilization. Meanwhile, Fe2O3 modulates Fe's d-p orbital hybridization and enhances outermost electron delocalization, weakening excessive binding of ORR intermediates. Consequently, the Fe2O3/Fe-N-C nanosheet catalyst demonstrates superior ORR performance and enhanced ZABs performance compared to conventional Fe-N-C nanoparticle catalysts. This study offers new insights into developing high-performance ORR catalysts through synergistic optimization of single-atom active site electronic structures and support architecture.