ZIF-67 as Continuous Self-Sacrifice Template Derived NiCo₂O₄/Co,N-CNTs Nanocages as Efficient Bifunctional Electrocatalysts for Rechargeable Zn-Air Batteries

Probing competent bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) plays a crucial role in the development of energy conversion and storage systems. Herein, we introduce a continuous self-sacrifice template strategy for synthesis of the novel NiCo₂O₄/Co,N-CNTs nanocages (NCs) as an efficient ORR/OER bifunctional electrocatalyst for Zn-air batteries. The NiCo₂O₄ and Co,N-CNTs are derived from the external and internal self-sacrifice of ZIF-67, respectively. The as-prepared NiCo₂O₄/Co,N-CNTs NCs display remarkable electrocatalytic activity toward ORR (E_1/2 = 0.862 V) and OER (E_j10 = 1.569 V) simultaneously, outperforming the commercial catalysts like Pt/C and RuO₂, respectively. The reversible oxygen electrode index (Δ = E_j10 (OER) - E_1/2 (ORR)) is ∼0.707 V in alkaline electrolyte. Interestingly, NiCo₂O₄/Co,N-CNTs NCs act as a cathode electrocatalyst in a primary Zn-air battery system with a high power density of 173.7 mW cm^-2. Therefore, the continuous self-sacrifice template strategy proposed in this work is expected to inspire the design of high-performance bifunctional nonprecious electrocatalysts for application in sustainable energy conversion devices.