Zinc-air batteries (ZABs) can be useful systems for power storage due to their high energy density and safety, as well as low costs and the natural abundance of zinc. However, this type of battery suffers from slow kinetics of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) at the air cathodes during charging and discharging. Low-cost, highly active, stable, bifunctional electrocatalysts for the OER and the ORR would, thus, be useful. Single-atom catalysts can be promising in this context, but usually require a polymer binder to affix them to the cathode. This decreases the activity of the catalyst and the lifespan of the battery.

Rufan Zhang, Tsinghua University, Beijing, China, and colleagues have developed cobalt single-atom catalysts on flexible carbon supports for binder-free zinc-air batteries. The team used electrospinning to create fiber mats from multi-walled carbon nanotubes (MWCNTs), zinc acetate and 2-methylimidazole (to form zeolite nanoparticles), polyacrylonitrile (PAN), and Co(NO₃)₂·6H₂O. The material was then carbonized, which transformed the zeolite nanoparticles and excess zinc acetate into N-doped porous carbon structures, while the carbon nanotubes remained. The resulting flexible material acts as a support for well-dispersed Co single atoms.

The prepared catalyst can be used as a binder-free air cathode and showed good electrocatalytic activity for oxygen reduction and evolution. The porous structure provides good accessibility to the active sites of the catalyst. The catalyst also showed excellent durability.

• Stabilizing Cobalt Single Atoms via Flexible Carbon Membranes as Bifunctional Electrocatalysts for Binder-Free Zinc–Air Batteries,
  Ying Han, Hengli Duan, Chenhui Zhou, Haibing Meng, Qinyuan Jiang, Baoshun Wang, Wensheng Yan, Rufan Zhang,
  Nano Lett. 2022.
  https://doi.org/10.1021/acs.nanolett.2c00278