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

•The metallic nanoparticles wrapped in the wheat-like porous carbon nanofibers as bifunctional electrocatalysts were prepared by electrospinning.•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.•The bifunctional catalyst displays excellent electrocatalytic performance for ORR with a positive half-wave potential of 825 mV and OER with a positive overpotential of 440 mV at 10 mA·cm−2. 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. [Display omitted]