Enhancing Zinc-Air Flow Batteries: Single-Atom Catalysis within Cobalt-Encapsulated Carbon Nanotubes for Superior Efficiency.

Amid the world's escalating energy needs, rechargeable zinc-air batteries stand out because of their environmental sustainability, with their performance being critically dependent on the oxygen reduction reaction (ORR). The inherent slow kinetics of the ORR at air electrodes frequently constrains their operational efficiency. Here, we develop a new self-catalytic approach for in situ growth of carbon nanotubes with new cathode material Co@CoN 3 /CNTs-800 without external additives. Density functional theory calculation reveals this method integrates nonprecious single-atom catalysis with spatial confinement, facilitating large-scale, in situ fabrication of CNTs, which can support dispersed atomic CoN 3 sites and enforce spatial confinement on Co nanoparticles. The Co@CoN 3 /CNTs-800 electrode achieves an electron transfer number close to ideal (3.9 out of 4.0). In rechargeable zinc-air flow batteries, it achieves a peak power density of 169.5 mW cm -2 and a voltage gap that is only 1.6% larger than the original after 700 h. This work surmounts critical challenges in the ORR kinetics for zinc-air batteries.