In situ induced growth strategy of Co2P nanocrystals encapsulated into stable 3D carbon network as a bifunctional electrocatalyst for Zn-air battery

Abstract

Rational design of inexpensive and robust carbon-based bifunctional catalysts is of considerable interest for practical application of rechargeable Zn-air battery (ZAB) technology. Herein, a facile in-situ induced growth strategy is developed to construct Co2P nanocrystals encapsulated into a stable 3D carbon nanotube-modified graphene network (Co2P@NPCNG). Specifically, cobalt tetranitrophthalocyanine (CoPc(NO2)4) is employed not only as the coupling agent to form and complex Co2P nanocrystals with graphene, but also as the inducer to catalyze the graphitization of melamine to grow the uniform Co2P nanocrystal-encapsulated CNTs on graphene in situ. Encouragingly, the as-synthesized Co2P@NPCNG exhibits favorable bifunctional oxygen electrocatalytic activity, fast reaction kinetics and excellent stability. Impressively, both liquid ZAB and all-solid-state ZABs used Co2P@NPCNG as air-cathode catalysts display considerable open-circuit voltage, charge-discharge property and long lifetime. Significantly, density functional theory (DFT) calculations demonstrate that the superior properties of Co2P@NPCNG originate to the synergetic contributions between the stable configuration of 3D conductive carbon network and high metallic density of Co2P. This work may provide feasible and facile avenues to strategically construct high-efficient 3D carbon-based bifunctional electrocatalysts for portable and even wearable devices.