OER highly active encapsulants to improve the electrochemical anticorrosion of Fe–N–C for ultralong-lifespan and high-rate rechargeable zinc–air batteries

Abstract

Fe–N–C has been exploited as a promising oxygen reduction reaction (ORR) electrocatalyst. However, carbon corrosion and corresponding coordination structure destruction inevitably happen upon exposure at high potentials. Even under low potentials, the byproduct peroxide generated in 2-electron ORR processes produces radicals such as ˙OH and ˙OOH with Fe-center allies via Fenton-like reactions to destroy catalyst structures. In this work, we designed a composite, wherein each N-doped carbon nanotube with Fe nanoparticles encapsulated in the Fe-NCNT is uniformly and tightly wrapped by vertically grown NiFe-layered double hydroxide (LDH) nanosheets. During the charging process of Zn–air batteries (ZABs), the external NiFe-LDH preferentially catalyzes oxygen evolution reactions (OERs), and thus the internal Fe-NCNT could simply act as a carbon skeleton to transfer electrons. Moreover, the Fe-NCNT@NiFe-LDH displays a strikingly high peroxide disproportionation rate and superior electrocatalytic activities towards peroxide reduction and oxidation reactions. Thus, the radical corrosion is enormously reduced. The Fe-NCNT@NiFe-LDH delivers a record-refresh overpotential difference of 0.52 V, surpassing that of recently reported state-of-the-art bifunctional oxygen electrocatalysts. The composite-based ZABs demonstrate long discharging/charging lifespans and excellent rate performances, e.g. over 5000 cycles (near 1743 h) at 50 mA cm⁻².