CoNi Nanoalloys @ N-Doped Graphene Encapsulated in N-Doped Carbon Nanotubes for Rechargeable Zn–Air Batteries

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.