engleski

Supercapacitors based on reduced graphene oxide hydrogels

Graphene is a monolayer of carbon atoms which due to delocalized π electrons possesses a good electrical conductivity. Good electrical conductivity and large specific surface area of graphene enable its application in electrochemical energy storage devices. Physical and chemical properties of graphene, as well as, its sheet size depend on the synthesis method. In this work, graphene was chemically synthesized using graphite as precursors. In the first step of synthesis graphene oxide (GO) was obtained and in the next step it was reduced. The reduction of GO is a crucial step in which it is necessary to remove a variety of oxygen functional groups bonded to the graphene sheet. For the reduction process it is desirable to achieve a high degree of reduction and good electron conductivity and to prevent the graphene agglomeration. By using hydrothermal procedure it is possible to archive all these demands [1, 2]. In this work reduced graphene oxide (rGO) was prepared by hydrothermal procedure supported by olive leaf extract (OLE) at different pH values. Structural and morphological characteristics of the obtained materials were determined by Raman spectroscopy, X-ray diffraction analysis (XRD), Fourier-transformed infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). By using cyclic voltammetry and electrochemical impedance spectroscopy (EIS) methods it was shown that all prepared materials exhibited good capacitive properties in 0.5 mol dm-3 Na2SO4 supporting electrolyte. The prepared materials were used to assemble supercapacitors (Fig.1) that were tested by cyclic voltammetry and EIS methods. The stability of the supercapacitors was determined by charging/discharging at constant current during 1000 cycles.

graphene ; graphene oxide ; hydrogel ; supercapacitors

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