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

Abstract Novel and highly durable air cathode electrocatalyst with three dimensional (3D)-clam-shaped structure, MnO 2 nanotubes-supported Fe 2 O 3 (Fe 2 O 3 /MnO 2 ) composited by carbon nanotubes (CNTs) ((Fe 2 O 3 /MnO 2 ) 3/4 -(CNTs) 1/4 ) is synthesized using a facile hydrothermal process and a following direct heat-treatment 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 Fe 2 O 3 particles are highly dispersed on both MnO 2 nanotubes and CNT surfaces, coupling all three components firmly. Electrochemical measurements indicate that the synergy of catalyst exhibit superior bi-functional catalytic activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) as well as stability than Pt/C and IrO 2 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, ∼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 at 30 mA cm −2 ) and robust cycle-life (1,390 cycles at cycle profile of 20 mA/10 min).