Reactivated Fe Nanoparticles on Carbon Nanotube Macro Film for High-Efficiency Rechargeable Zinc-Air Batteries

Rechargeable zinc-air batteries (ZABs) hold great potential in next-generation sustainable energy storage because of their high energy density, safety, and environmental friendliness. Nevertheless, the sluggish kinetics of the air cathode hinder their energy efficiency and cycling stability. Herein, we report a bridging strategy to fabricate a free-standing air cathode (NCNTs-Fe/CMF), consisting of the crosslinked and interconnected Fe nanoparticles (NPs) encapsulated on the N-doped carbon nanotubes (NCNTs-Fe), which are tightly bound to a carbon nanotube macro film (Fe/CMF) substrate to activate Fe NPs sites. The bridging effect of NCNTs-Fe/CMF endows excellent interfacial contact, a large specific surface area, and high electrical conductivity, accelerating electron transfer and promoting oxygen mass transfer/diffusion. In addition, the synergy between activated Fe NPs and N-doping enriches abundant nitrogen species, further facilitating the electrocatalytic process. As a result, the NCNTs-Fe/CMF exhibits excellent bifunctional catalytic activity, featuring a half-wave potential of 0.88 V and an overpotential of 340 mV at 10 mA cm -2 . Furthermore, the assembled rechargeable ZAB based on the NCNTs-Fe/CMF air cathode delivers a satisfactory power density of 130.0 mW cm -2 and outstanding cycling durability up to 200 h at 5 mA cm -2 . This work provides a bridging design strategy for developing highly efficient and stable free-standing air electrodes.