Formation of hollow frameworks of dual-sided Fe/Fe3C@N-doped carbon nanotubes as bifunctional oxygen electrocatalyst for Zn-air batteries

Rational design of effective bifunctional inexpensive oxygen electrocatalyst is highly important for Zn-air bat-teries (ZABs), which can accelerate both oxygen reduction/evolution reactions at the oxygen electrode. Herein, we present the formation of hierarchical hollow frameworks of dual-sided Fe/Fe3C@N-doped carbon nanotubes (FNCHFs) through a template-engaged method. Benefitting from the synergistic effect between the robust hollow frameworks and in-situ grown dual-sided N-doped carbon nanotubes, the FNCHF electrocatalyst presents enhanced mass/electron transport with high structural stability. As a result, the FNCHFs based bifunctional oxygen electrode demonstrates a desirable oxygen electrocatalytic activity and stability with a half-wave po-tential of 0.863 V for oxygen reduction and an overpotential of 340 mV to reach the current density of 10 mA cm(-2) for oxygen evolution. The corresponding ZAB exhibits a high peak power density of 206 mW cm(-2), a high specific capacity of 781 mAh gZ(n)(-1), and a good cycling stability more than 300 h.