In-situ reduction synthesis of La2O3/NiM-NCNTs (M = Fe, Co) as efficient bifunctional electrocatalysts for oxygen reduction and evolution reactions

Highly active and stable bifunctional catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play a vital role in rechargeable zinc-air batteries. In this work, La2O3 and alloy nanoparticles (NiFe and NiCo) decorated nitrogen doped carbon nanotubes hybrids (denoted as La2O3/NiFe-NCNTs and La2O3/NiCo-NCNTs) were successfully prepared by the in-situ reduction procedure. The crystalline structure and morphology of hybrids were characterized by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). La2O3/NiFe-NCNTs revealed desirable bifunctional catalytic activities towards both oxygen reduction reaction (5.1 mA cm(-2) at 0.3 V vs. RHE) and oxygen evolution reaction (1.69 V vs. RHE at 10 mA cm(-2)) in alkaline media. Furthermore, rechargeable zinc-air batteries fabricated with La2O3/NiFe-NCNTs as the bifunctional catalyst demonstrated a small charge-discharge voltage gap (1.04 V) and long-term stability after charge-discharge cycling for 100 cycles. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.