A novel composite (FMC) to serve as a durable 3D-clam-shaped bifunctional cathode catalyst for both primary and rechargeable zinc-air batteries

Novel and highly durable air cathode electrocatalyst with three dimensional (3D)-clam-shaped structure, MnO2 nanotubes-supported Fe2O3 (Fe2O3/MnO2) composited by carbon nanotubes (CNTs) ((Fe2O3/MnO2)(3/4)-(CNTs)(1/4)) is synthesized using a facile hydrothermal process and a following direct heattreatment in the air. The morphology and composition of this catalyst are analyzed using scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). The morphology characteristics reveal that flower-like Fe2O3 particles are highly dispersed on both MnO2 nanotubes and CNT surfaces, coupling all three components firmly. Electrochemical measurements indicate that the synergy of catalyst exhibit superior bifunctional catalytic activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) as well as stability than Pt/C and IrO2 catalysts. Using these catalysts for air-cathodes, both primary and rechargeable zinc-air batteries (ZABs) are assembled for performance validation. In a primary ZAB, this 3D-clamed catalyst shows a decent open circuit voltage (OCV, similar to 1.48 V) and a high discharge peak power density (349 mW cm(-2)), corresponding to a coulombic efficiency of 92%. In a rechargeable ZABs with this bifunctional catalyst, high OCV (> 1.3 V) and small charge-discharge voltage gap (< 1.1 V) are achieved along with high specific capacity (780 mAh g(-1) at 30 mA cm(-2)) and robust cycle-life (1,390 cycles at cycle profile of 20 mA/10 min). (C) 2017 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.