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.