Fe/Fe3O4 heterostructures supported on N,O-doped hollow carbon spheres with high catalytic performance for oxygen reduction and zinc–air batteries

Abstract

The oxygen reduction reaction (ORR) is a crucial half-reaction in energy conversion and storage systems, playing a significant role in new energy devices such as fuel cells and metal–air batteries. Therefore, designing and constructing high-performance ORR catalysts holds substantial research significance. This study successfully constructed an Fe/Fe₃O₄ heterostructure (Fe/Fe₃O₄@NOC) on N,O-doped hollow mesoporous carbon spheres. The formation of this heterostructure effectively regulates the electronic structure of the interfacial active sites and optimizes the adsorption of oxygen-containing intermediates. Its ORR catalytic performance exhibits a high half-wave potential (0.89 V), significantly surpassing the catalytic activity of single-component ORR catalysts. In situ Raman spectroscopy and theoretical calculations reveal the tandem catalytic mechanism within the Fe/Fe₃O₄@NOC heterostructure: O₂ is preferentially adsorbed and activated by Fe₃O₄ and the resulting *OH/*O intermediates are subsequently transferred to adjacent Fe sites to complete the proton-coupled electron transfer steps. The Fe/Fe₃O₄@NOC-based zinc–air battery exhibits a peak power density of 245.6 mW cm⁻² and a specific capacity of 789.3 mAh g⁻¹, both surpassing those of the Pt/C-based zinc–air battery. These findings provide guidance for developing high-performance ORR electrocatalysts.