Metal-organic framework-derived Fe/Cu-substituted Co nanoparticles embedded in CNTs-grafted carbon polyhedron for Zn-air batteries

Metal-organic frameworks (MOFs) and MOF-derived materials have attracted great attention as alternatives to noble-metal based electrocatalysts owing to their intriguing structure properties, especially for high efficiency and stable oxygen reduction reaction (ORR). Herein, we employed a one-pot reaction to make a multimetal (Fe, Co, Cu, and Zn) mixed zeolitic imidazolate framework (MM-ZIF) via adopting a simple in situ redox reaction. Further pyrolysis of the target MM-ZIF, a highly porous carbon polyhedron (FC-C@NC) grafted with abundant carbon nanotubes was obtained, in which ultrasmall Co nanoparticles with partial lattice sites substituted by Fe and Cu were embedded. The obtained FC-C@NC possessed large surface area, highly porous structure, widely-spread metal active sites, and conductive carbon frameworks, contributing to outstanding ORR activity and long-term stability. It displayed superior tolerance to methanol crossover and exceeded the commercial Pt/C catalyst and most previously reported non-noble-metal catalysts. Impressively, the as-produced FC-C@NC-based zinc-air battery afforded an open-circuit potential of 1.466 V, a large specific capacity of 659.5 mAh/g, and a high gravimetric energy density of 784.3 Wh/kg_Zn, significantly outperforming the Pt/C-based cathode.