Co nanoparticles embedded in wheat-like porous carbon nanofibers as bifunctional electrocatalysts for rechargeable zinc-air batteries

Abstract

Developing high-efficiency, low-cost and durable bifunctional catalysts for oxygen evolution and reduction reaction (OER and ORR) is paramount yet challenging for the application of rechargeable Zn-air batteries (ZABs). Herein, we prepared an unique wheat-like porous carbon nanofibers embedded with Co nanoparticles as a bifunctional oxygen electrocatalyst for ORR and OER, which was obtained by carbonizing the zeolitic imidazolate frameworks-Co and polyacrylonitrile electrospun nanofibers. The unique wheat-like porous structure not only provides a large specific surface area for the catalyst, but also facilitates the transport of electrolyte and oxygen during the electrocatalytic process, improving its catalytic activity. Meanwhile, the unique wheat-like structure with metal nanoparticles wrapped into the carbon nanofibers can avoid corrosion caused by alkaline electrolyte. The bifunctional catalyst displays excellent electrocatalytic performance for OER with a positive overpotential of 440 mV at 10 mA·cm−2 and ORR with a positive half-wave potential of 825 mV. Furthermore, the maximum power density of the assembled ZABs with catalyst Co@N-PCNF-1.0 serving as the air electrode is 118.41 mW·cm−2, and this ZABs are able to cycle 200 h in galvanostatic discharge test. This work can offer some interesting design concepts for the construction of outstanding bifunctional catalysts toward rechargeable Zn-air batteries.