ZIF‐67‐Derived Co 1− x S Nanoparticles Encapsulated in N‐Doped Carbon Nanotubes as Bifunctional Oxygen Electrocatalysts for High‐Performance Rechargeable Zn‐Air Batteries

Abstract

The development of efficient and durable bifunctional oxygen electrocatalysts is crucial for high‐performance rechargeable Zn‐air batteries. Herein, a hierarchical Co 1− x S@C/NCNTs heterostructure composed of Co‐deficient Co 1− x S nanoparticles encapsulated by carbon layers and coupled with N‐doped carbon nanotubes is constructed through melamine‐assisted pyrolysis followed by vapor‐phase sulfuration. During this process, ZIF‐67‐derived Co nanoparticles catalyze the in situ growth of NCNTs, while subsequent sulfuration converts metallic Co into defect‐rich Co 1− x S and partially incorporates sulfur into the carbon/NCNT framework. The resulting hierarchical porous structure, interconnected conductive NCNT network, N,S‐doped carbon environment, carbon‐layer confinement, and nonstoichiometric Co 1− x S phase synergistically promote electron transfer, oxygen diffusion, electrolyte penetration, and the adsorption/conversion of oxygen‐containing intermediates. Consequently, Co 1− x S@C/NCNTs exhibits favorable bifunctional ORR/OER activity, with an ORR half‐wave potential of 0.83 V, an OER overpotential of 340 mV at 10 mA cm −2 , and a low‐potential gap of 0.74 V. The assembled rechargeable Zn‐air battery delivers an open‐circuit voltage of 1.46 V, a peak power density of 120.7 mW cm −2 , a specific capacity of 581.43 mAh g Zn −1 , and stable cycling for 60 h. This work provides a rational strategy for designing defect‐rich sulfide/carbon heterostructures for rechargeable Zn‐air batteries.