Investigation of chemical and electrochemical behaviour of graphene/manganese oxide/tin oxide ternary nanocomposite

Abstract

Graphene based nanocomposites show many intriguing physical and chemical properties. Dye removal capacity and higher electrochemical capacitance with longer cyclic performance are two prominent arena of them. Binary nanocomposites of Mn-oxide and Sn-oxide with graphene, offering low cost, environmental benignity and easy synthesis procedure, constitute some of the ideal examples in this regard. Consequently, the graphene based ternary nanocomposites of these metal oxides could be an alternative material with greater potential, to serve the same purposes. Hence, in our present work, a ternary nanocomposite consist of graphene, Mn-oxide and Sn-oxide was synthesized by following a three step method. Graphene oxide (GO), obtained from graphite flake following Hummers method was introduced, first with Mn(CH3COO)2 and then with KMnO4 in water-isopropyl alcohol system to obtain GO/Mn-oxide nanocomposite. It was further stirred with SnCl2 in aqueous media furnishing a graphene/Mn-oxide/Sn-oxide ternary nanocomposite. The obtained mass was dried and then annealed under N2 inert atmosphere to achieve better crystallinity of nanoparticles and better reduction of GO. The synthesized materials were characterized using FTIR, FESEM, EDX, XRD and TGA. Dye removal capacity of the materials synthesized, were investigated with visible spectroscopy using MB as a model dye. After 75 minutes of interaction, with 5 mg sample in 5 ppm solution at pH 3, the ternary nanocomposite showed a specific adsorption capacity of 17.7 mg/g, while that of graphene/Mn-oxide and graphene/Sn-oxide binary nanocomposites, under same conditions, was 17.5 mg/g and 17.4 mg/g respectively; suggesting that, the binary and the ternary nanocomposites have almost same amount of surface area. It was also explored that, the ternary nanocomposite is more effective at its lower dose and in low pH solution. Electrochemical capacitive behaviour was investigated with CV, CP and EIS. As a capacitive material, at the current density of 0.5 A/g, it showed a specific capacitance of 145.6 F/g, while under the same conditions, the graphene/Mn-oxide and the graphene/Sn-oxide binary nanocomposites showed 463.8 and 178.3 F/g specific capacitance respectively. The low specific capaciatance of the ternary nanocomposite in comparison to the binaries was attributed to the different ratio of the oxide forms of metals on graphene and their nature. However, the ternary nanocomposite showed a higher discharging/charging time ratio, lower charge transfer resistance and after 500 cycles, it retained almost 84% of its electrochemical charge storage capacity.