Monodispersed Eu<sub>2</sub>O<sub>3</sub>-Modified Fe<sub>3</sub>O<sub>4</sub>@NCG Composites as Highly Efficient and Ultra-stable Catalysts for Rechargeable Zn–Air Batteries
Cheng Chen, Jilan Long, Kui Shen, Xiaohong Liu, Wei Zhang
Abstract
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.