2D Dual-Metal Zeolitic-Imidazolate-Framework-(ZIF)-Derived Bifunctional Air Electrodes with Ultrahigh Electrochemical Properties for Rechargeable Zinc-Air Batteries

Here first a 2D dual-metal (Co/Zn) and leaf-like zeolitic imidazolate framework (ZIF-L)-pyrolysis approach is reported for the low-cost and facile preparation of Co nanoparticles encapsulated into nitrogen-doped carbon nanotubes (Co-N-CNTs). Importantly, the reasonable Co/Zn molar ratio in the ZIF-L is the key to the emergence of the encapsulated microstructure. Specifically, high-dispersed cobalt nanoparticles are fully encapsulated in the tips of N-CNTs, leading to the full formation of highly active Co-N-C moieties for oxygen reduction and evolution reactions (ORR and OER). As a result, the obtained Co-N-CNTs present superior electrocatalytic activity and stability toward ORR and OER over the commercial Pt/C and IrO2 as well as most reported metal-organic-framework-derived catalysts, respectively. Remarkably, as bifunctional air electrodes of the Zn-air battery, it also shows extraordinary charge-discharge performance. The present concept will provide a guideline for screening novel 2D metal-organic frameworks as precursors to synthesize advanced multifunctional nanomaterials for cross-cutting applications.