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 gZn –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.

Exploring cost-effective and durable bifunctional oxygen electrocatalysts for oxygen reduction and oxygen evolution reactions (ORR and OER) is critical for the commercial implementation of rechargeable Zn–air batteries but remains as an immense challenge. Herein, CoNi nanoalloys wrapped with N-doped graphene embedded into N-doped carbon nanotubes (CN@NC) have been prepared by a universal two-step pyrolysis method. The optimal CN@NC–2–800 affords a positive half-wave potential of 0.83 V for ORR and a small overpotential of 400 mV at 10 mA cm–2 for OER, outperforming most of the current non-precious bifunctional oxygen electrocatalysts. Expectedly, the liquid Zn–air battery based on CN@NC–2–800 displays a high open-circuit voltage of 1.52 V, a large peak power density of 172 mW cm–2, and a long cycle life of 300 h. Furthermore, the developed all-solid-state Zn–air battery also shows remarkable stability with various degrees of bending. This work offers a simple and effective way to explore highly efficient and durable electrocatalysts for renewable energy applications.

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Exploring high-performance, stable, and economical noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER) in alkaline media is an urgent mission. Herein, the graphenewrapped Co-WC heterojunction nanoparticle embedded in porous carbon nanospheres (Co-WC@G/PCSs) is fabricated via calcination of a CoWO 4 /PCSs precursor. With an optimized PCSs amount and carbonization temperature, sphere-like Co-WC@G/PCSs exhibit superior alkaline HER activity with a small overpotential (67 mV at a current density of 10 mA cm −2 ), a low Tafel slope (56 mV dec −1 ), and a high exchange current density (0.48 mA cm −2 ). Moreover, the Co-WC@G/PCSs also exhibit high stability in alkaline solution, showing no significant degradation after 10 000 cycles. The excellent HER performance is mainly attributed to abundant heterointerface interfaces between Co and WC, which can tailor the electronic configuration and enlarge exposed active sites. Our work suggests a facile and large-scale strategy to synthesize abundant heterointerface interfaces and graphene-coated electrocatalysts for designing an efficient noble-metal-free electrocatalyst.