Hierarchical 3D macrosheets composed of interconnected in situ cobalt catalyzed nitrogen doped carbon nanotubes as superior bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries

The oxygen reduction/evolution reactions (ORR/OER) are the cornerstone of metal-air batteries. The current central issue is to explore nonprecious metal based catalysts, especially bifunctional electrocatalysts with high activity for both ORR/OER processes with mild strategies. Herein, we report a facile yet scalable approach to fabricate hierarchical 3D macrosheets composed of interconnected in situ cobalt catalyzed nitrogen doped carbon nanotubes (denoted as Co@NCNT HMS) through the pyrolysis of g-C3N4@Co-glycolate microsheets, which exhibit outstanding oxygen catalysis performance. Specifically, a record low potential gap (Delta E = E-j10 - E-1/2) of 0.681 V can be achieved in 1 M KOH electrolyte. Impressively, a Zn-air battery based on a Co@NCNT HMS air cathode achieves a specific capacity of 675.8 mA h g(-1) and a peak power density of 159.83 mW cm(-2). More importantly, the cycling stability of the rechargeable Zn-air battery is outstanding with an excellent output voltage retention (97.3% after 150 h).