Cobalt Nanoparticles Embedded in N‑Doped Carbon Nanotubes on Reduced Graphene Oxide as Efficient Oxygen Catalysts for Zn-Air Batteries

The key point to developing green and environmentally friendly zinc-air batteries is exploring efficient bifunctional electrocatalysts for oxygen reduction and evolution reactions (ORR and OER) on an air electrode. Herein, we reported a facile and green method for fabricating a bifunctional electrocatalyst of Co@N-CNT/rGO, which is composed of cobalt nanoparticles wrapped into nitrogen-doped carbon nanotubes growing on reduced graphene oxide. It is obtained by pyrolyzing a GO-wrapped two-dimension leaf-like zeolitic imidazolate framework. The Co@N-CNT/rGO-0.1 exhibits efficient catalytic activities for ORR and OER with a small Tafel slope. It benefits from the synergistic effect of the Co nanoparticle and N-CNT, the high conductivity of reduced graphene oxide and highly graphitizing carbon nanotubes, the great specific surface area, and suitable aperture size. Moreover, the Co@N-CNT/rGO-0.1 catalyst assembled primary zinc-air battery shows a high open-circuit voltage (1.43 V), a large peak power density (122 mW cm^–2), and an excellent specific capacity (855 mA h g_Zn^–1). In addition, the Co@N-CNT/rGO-0.1 assembly rechargeable zinc-air battery also displays an excellent cycling durability of 120 h at 5 mA cm^–2. According to the above results, our work provides a cost-effective strategy to scale-up and commercialize the bifunctional electrocatalysts for zinc-air battery application.