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Microwave-assisted synthesis of graphene/SnO2 composite material and its supercapacitive properties

Supercapacitors attract significant attention due to their promising properties for the energy storage and power supply. Charge storage mechanism in supercapacitors is based on the electrochemical double layer charging/discharging and therefore the capacitance is usually limited by the active surface area. To overcome this limitation there are efforts to increase capacitance by using the metal oxides or the conductive polymers where the charging/discharging mechanism includes fast redox reaction of the material and, as a result, much higher specific capacitance is obtained [1]. Considering the charge storage mechanism of metal oxide these materials are classified as ˝pseudocapacitors˝. The aim of this work was to study capacitive property of graphene/SnO2 composite material. Metal oxides electrochemical behaviour can be significantly improved by the presence of graphene due to its properties, such as high electrical conductivity, high surface area and flexibility. On the other hand SnO2 prevents agglomeration of the graphene sheets that results in graphene with high surface area. Therefore, synergistic effect of these two constituents is expected to enhance overall capacitive properties and improve these materials for supercapacitor application [2, 3]. In this work simple simultaneous synthesis of the SnO2 and reduction of the graphene oxide (GO) was carried out by using microwave- assisted hydrothermal synthesis. This method was selected due to its effects such as rapid volumetric heating, increased reaction rates and shortened reaction time. Hydrothermal synthesis and microwave assisted hydrothermal synthesis are useful for accelerating the de- protonation reaction of Sn(H2O)x(OH−)y(4−y)+ to SnO2 x nH2O offering good control of both particle size and particle distribution [4]. By using cyclic voltammetry it was shown that obtained material had good capacitive/pseudocapacitive properties suitable for supercapacitor application and specific capacitance values up to 93 F g-1 were determined. Obtained materials were additionally characterised by scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy (FTIR) that revealed presence of SnO2 and successful reduction of GO to reduced form (rGO).

Supercapacitors, graphene oxide, graphene, SnO2

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