Self-supported N-doped CNT arrays for flexible Zn-air batteries

The exploitation of flexible and rechargeable energy storage devices is crucial for meeting the requirements of the next generation of electronic products. Herein, we report a novel method to grow N-doped carbon nanotube (NCNT) arrays with encapsulated CoFe alloy nanoparticles on carbon fiber cloth (CFC) as a self-supported air cathode for flexible ZABs. The optimized electrode exhibits superior bifunctional activities with a half-wave potential of 0.873 V for the oxygen reduction reaction (ORR) and a potential of 1.506 V for the oxygen evolution reaction (OER) at 10 mA cm(-2), greatly superior to that of 20% Pt/C for the ORR and IrO(2)for the OER, respectively. The experimental results demonstrate that the atomically dispersed Co(Fe) dual-sites formed in the NCNT walls are key to the excellent activities of the self-supported electrode. When the self-supported electrode is applied as an air cathode for flexible solid-state ZABs, a large open-circuit voltage of 1.426 V, a high initial energy efficiency of 69% and a large power density of 37.7 mW cm(-2)as well as robust stability are achieved. Furthermore, the solid-state ZABs with the self-supported electrode exhibit excellent flexibility even under extreme bending conditions. Our strategy presented here opens a new way for bifunctional catalysts for high-performance flexible ZABs.