Enhanced bifunctional electrocatalysis of Co@NC@NCNT derived from ZIF-67 for advanced rechargeable Zn-air batteries

The rational design of low-cost, efficient, and durable bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is critical for advancing next-generation energy storage systems. Here, a dodecahedral zeolitic imidazolate framework-67 (ZIF-67) is employed as a structural template to direct the formation of cobalt-tipped nitrogen-doped carbon nanotube arrays (Co@NC@NCNT). This hierarchical architecture integrates high electrical conductivity with abundant accessible active sites. By optimizing the calcination temperature and melamine content, the resulting Co@NC@NCNT-750-10 catalyst achieves a high ORR half-wave potential of 0.821   V and a low OER overpotential of 370   mV. When applied in rechargeable Zn-air batteries (RZABs), it delivers a peak power density of 136.4   mW   cm −2 and a specific capacity of 722.9 mAh g⁻¹, outperforming commercial Pt/C and RuO 2 benchmarks. The assembled RZAB exhibits excellent cycling stability and energy efficiency, underscoring the promise of this catalyst system for practical implementation in high-performance, metal-air energy storage technologies.