Hierarchical mesoporous γ-Fe2O3/carbon nanocomposites derived from metal organic frameworks as a cathode electrocatalyst for rechargeable Li-O2 batteries

Hierarchical mesoporous gamma-Fe2O3/carbon nanocomposites were prepared from metal organic frameworks (MOFs) MIL-100(Fe). The gamma-Fe2O3/carbon nanocomposites and its precursor MIL-100(Fe) was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra (Raman), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry analysis (TGA) and N-2 adsorption/desorption measurements. It is found that the as-prepared materials possess a hierarchical mesoporous nanostructure between the carbon and gamma-Fe203 nanoparticles. When applied as cathode catalysts in rechargeable Li-O-2 batteries, it is demonstrated from the galvanostatic discharge-charge process and cyclicvoltammetry (CV) that the electrode with gamma-Fe2O3/carbon nanocomposites exhibits a lower charge and discharge over-potential, higher discharge capacity and better cycling stability than the pure Super P electrode, indicating its potential as a promising catalyst for Li-O-2 batteries. The electrode with gamma-Fe2O3/carbon nanocomposites shows a discharge capacity up to similar to 5970 mAh g(carbon+catalyst)(-1) at 0.1 mA cm(-2) and a high C-rate performance, and exhibits a very stable discharge voltage plateau of 2.7 V and a charge voltage plateau of similar to 3.75 V. With the addition of gamma-Fe2O3/carbon nanocomposites, the Li-O-2 batteries can obtain good cycle performance over 30 cycles as confining the discharge/charge capacities to 600 mA h g(carbon+catalyst)(-1). (C) 2014 Elsevier Ltd. All rights reserved.