Nano Platinum Decorated Graphene Wrapped a-MnO2 Nanocomposite Lithium Air Breathing Cathode for Li-O2 Batteries
In this study, nano platinum decorated Graphene wrapped a-MnO2 nanocomposite cathode was produced to increase cycle life and the capacity of the Li-O2 batteries. Before production of the composite cathodes, Graphene Oxide (GO) was synthesized by Hummers Method and a-MnO2 nanowires was synthesized using microwave hydrothermal synthesis method. To production of the composite cathodes, GO and a-MnO2 dispersed in the distilled water and homogenously mixed using ultrasonication for 1 h. After then H2PtCl6 was added in the suspension under stirring. After then, NaBH4 solution was slowly added in the suspension to reduce H2PtCl6 and GO into platinum and Graphene, respectively. After centrifugation and drying of the products, Graphene/a-MnO2/Pt nanocomposite was obtained. Using this composite, Graphene/a-MnO2/Pt nanocomposite cathode was prepared. To prepare Graphene/a-MnO2/Pt nanocomposite cathode, 15wt.% PVDF dissolved in NMP solution and 85 wt.% Graphene/a-MnO2/Pt nanocomposite were mixed and obtained slurry cast on the nickel foam. After drying of the samples in vacuum oven, Graphene/a-MnO2/Pt nanocomposite cathode was obtained. The structure of the composite was characterized using X-ray diffraction pattern, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. Electrochemical characterization of the Graphene/a-MnO2/Pt nanocomposite cathode was performed between 2.15 V and 4.25 V at a constant current density of 0.1 mAcm-2 in ECC-Air test cell (purchased from EL-Cell Company in Germany). In order to investigate electrochemical reaction of the cathode with electrolyte, cyclic voltammetry test was carried out at a scan rate of 0.1 mV s-1. For further electrochemical characterization, electrochemical impedance spectroscopy of the cathode was investigated after selected cycles in the frequency range of 1000 kHz to 0.1 Hz with AC amplitude of 10 mV.
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