Iron-nickel alloy nanoparticles encapsulated in nitrogen-doped carbon nanotubes as efficient bifunctional electrocatalyst for rechargeable zinc-air batteries.

In this work, we present an efficient bifunctional electrocatalyst comprising iron-nickel (FeNi) alloy nanoparticles confined in nitrogen-doped carbon nanotubes (denoted FeNi-NCNT) for zinc-air batteries. The FeNi-NCNT electrocatalyst is fabricated by anion-exchange of nickel(II) ion/zinc(II) ion-2,4,6-tris-(di(pyridin-2-yl)amino)-1,3,5-triazine complex with ferricyanide anion followed by mixing with melamine and then carbonization. The resultant FeNi-NCNT electrocatalyst displays excellent bifunctional activity with a low reversible oxygen electrode index of 0.725 V. The rechargeable aqueous zinc-air battery fabricated with FeNi-NCNT air cathode manifests both high specific capacity (819 mAh g at 5.0 mA cm) and long cycle life (1500 cycles/1000 h at 10 mA cm, 600 cycles/400 h at 25 mA cm, and 165 cycles/110 h at 50 mA cm). Moreover, flexible solid-state zinc-air battery assembled with FeNi-NCNT air cathode can deliver a specific capacity of 765 mAh g at 5.0 mA cm, a power density of 84.8 mW cm, and a cycle life of 110 h (330 cycles) at 2.0 mA cm.