Monodispersed Eu₂O₃-Modified Fe₃O₄@NCG Composites as Highly Efficient and Ultra-stable Catalysts for Rechargeable Zn–Air Batteries

Constructing highly efficient cathode catalysts for Zn–air batteries (ZABs) is an attractive research topic in sustainable energy storage area. Herein, the rare-earth metal oxide modification strategy has been proposed to construct the highly efficient and ultra-stable catalysts for ZABs. Accordingly, a graphene oxide-doped carbon-supported Eu2O3-modified Fe3O4 (Fe3O4/Eu2O3@NCG) catalyst is developed with layered Fe–Eu-MOF/GO as a precursor. Detailed characterization reveals that Fe3O4/Eu2O3@NCG possesses unique structural properties, including carbon–metal–carbon configuration, plentiful oxygen vacancies, and variable metal-active sites, which endows the catalyst with strong conductivity, high activity, and ultra-long stability. The optimal Fe3O4/Eu2O3@NCG catalyst exhibits an outstanding electrochemical performance, and the potential difference (Egap) between oxygen reduction reaction and oxygen evolution reaction is merely 0.68 V at 0.1 M KOH condition. Moreover, density functional theory calculations are employed to investigate the reaction mechanism and the synergetic effect between Fe and Eu atoms. Most importantly, the Fe3O4/Eu2O3@NCG-based aqueous ZAB delivers a high power density (218 mW/cm2), specific capacity (854 mA h/g@5 mA/cm2), and an impressive ultra-long cycle property with more than 1000 h (>6000 cycles) charge–discharge cycle life. In addition, the Fe3O4/Eu2O3@NCG-based all-solid-state ZAB also exhibits an outstanding performance, achieving >460 h cycle life (>2760 cycles) and strong practical application capability.