Novel MOF-derived hollow CoFe alloy coupled with N-doped Ketjen Black as boosted bifunctional oxygen catalysts for Zn–air batteries

Abstract

Rational design of highly effcient bifunctional oxygen catalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a significant challenge for rechargeable Zn–air battery (ZAB). Herein, a newly developed hybrid catalyst (denoted as CoFe@NC/KB-800) consisting of hollow CoFe alloy and nitrogen-doped Ketjen Black is synthesized by pyrolysis of a novel Fe-glucosamine coated cobalt-based metal–organic framework. By virtue of ultra-high specific surface area of 1318.8 m2 g−1 and micro-/meso-/macropore structure, the optimal CoFe@NC/KB-800 catalyst exhibits a low reversible oxygen overpotential (ΔE) of 0.77 V between ORR and OER. Density functional theory (DFT) calculations validate that the superior catalytic activity is ascribed to synergistic CoFe@NC structure. Impressively, liquid ZAB catalyzed by CoFe@NC/KB-800 displays a high peak power density of 160 mW cm−2 and a low voltage gap of 0.65 V after 600 cycles. Three all-solid-state ZABs in series can successfully light LED (~2.2 V), displaying tremendous potentials in portable devices.