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

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 m(2) g(-1) and micro-/meso-/macropore structure, the optimal CoFe@NC/KB-800 catalyst exhibits a low reversible oxygen overpotential (Delta E) 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 (similar to 2.2 V), displaying tremendous potentials in portable devices.