In-situ growth of CoFeS_2 on metal-organic frameworks-derived Co-NC polyhedron enables high-performance oxygen electrocatalysis for rechargeable zinc-air batteries

摘要

The development of efficient and cost-effective bi-functional electrocatalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is promising for high-performance rechargeable metal-air batteries. In this article, a bi-functional catalyst (Co-NC@CoFeS2) towards ORR and OER is synthesized via the simple insitu growing of cobalt-iron sulfide on cobalt and nitrogen co-doped polyhedral carbon (Co-NC). The combination of cobalt-iron sulfide and Co-NC substrate not only enlarges accessible channels for the reaction but also promotes electron transfer in the catalytic process. Benefiting from the synergy of the Co-NC substrate and the supported cobalt-iron sulfide in regulating the electrochemical interfaces, the electrical conductivity and the electronic structure, a narrow voltage gap of 0.646 V between the OER potential at 10 mA cm-2 and the halfwave potential of the ORR is observed for Co-NC@CoFeS2, showing an enhanced catalytic capability than that of the standard Pt/C + RuO2 composite. Moreover, a rechargeable Zn-air battery with Co-NC@CoFeS2 as an air electrode exhibits a large open-circuit voltage (1.44 V), high peak power density (174.4 mW cm-2), and long cycle life (over 400 cycles). Therefore, this work provides a new vision for the design and preparation of promising functional electrocatalysts for Zn-air batteries.