Rational design of positive-hexagon-shaped two-dimensional ZIF-derived materials as improved bifunctional oxygen electrocatalysts for use as long-lasting rechargeable Zn–Air batteries

Herein, a bottom-up method, i.e., a surfactant-assisted synthetic method to synthesize a novel dual-metal (Co/Zn) zeolitic-imidazolate framework (ZIF) that could maintain its positive-hexagon-shaped morphology after high-temperature thermal treatment, has been developed. As a bifunctional electrocatalyst, the Co nanoparticles encapsulated into both nitrogen-doped positive-hexagon-shaped carbon nanosheets and carbon nanotubes distributed over the nanosheet surface (Co-N-PHCNTs) show excellent electrocatalytic performance, superior to that of state-of-the-art benchmark noble-metal electrocatalysts. Remarkably, in a practical demonstration, the Co-N-PHCNTs serve as bifunctional air electrodes for Zn–air batteries, exhibiting a high peak power density of ≈125.41 mW cm−2 at a current density of ≈130 mA cm−2 with an extraordinary charge-discharge cyclability of over 673 h at 5 mA cm−2. This strategy not only provides guidance for the synthesis of 2D ZIF-derived materials but also for other 2D materials in cross-cutting applications.