Hierarchical catalytic electrodes of cobalt-embedded carbon nanotubeicarbon flakes arrays for flexible solid-state zinc-air batteries

Flexible air cathodes, with active and stable catalytic activities for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), are key components and urgently required for realizing wearable metal-air batteries. Herein, a facile solution impregnation strategy to construct metal-organic frameworks on electrospun nanofibers following melamine-assisted carbonization synthetic approach is reported to prepare low-cost, scalable, and efficient bifunctional air electrodes. The flexible electrode comprises carbon nanofibers as the backbone that supports nitrogen-doped, cobalt embedded carbon nanotubes/porous carbon flakes arrays hierarchical structures (CoNCNTF/CNFs). The combined advantages of optimized chemical compositions and CNT/carbon flakes morphology endow CoNCNTF/CNFs with a promising reversible oxygen overpotential of 0.76 V. The flexible solid-state zinc-air battery using CoNCNTF/CNEs film as the additive-free air electrode exhibit favorable battery capacity and power density, durable stability and good bendability, surpassing that of the precious metal-based air electrodes. (C) 2018 Elsevier Ltd. All rights reserved.