engleski

Reduced graphene oxide/α-Fe2O3 fibres as active material for supercapacitor application

The supercapacitors are an attractive alternative to batteries because they can provide higher power density and longer cycle life but suffer from lower energy density. For successful application of supercapacitors in hybrid electric vehicles, both high power and energy densities are required. Therefore, much effort has been made to achieve these demands. One approach includes a development of new active materials based on the different material combinations, morphology and particle size.3 A promising strategy would be a combination of a capacitive material (carbon nanotubes, graphene) with an earth-abundant, nontoxic and low-cost metal oxide (RuO2, MnO2, IrO2, MoO2, V2O5 , SnO2, Fe2O3, or Fe3O4). Such a combination provides good conductivity which is attributed to the carbon structures and high energy densities which are attributed to the pseudocapacitive effects of metal oxides. In this work the composite hydrogel, composed of reduced graphene oxide and hematite fibres (rGO/hematite), was successfully prepared by the hydrothermal procedure starting from GO and hematite nanofibres. Morphological and structural characteristics of the composite hydrogel were investigated by using SEM and XRD techniques. According to the results, hematite fibres are distributed between rGO sheets increasing the inter-sheet space and decreasing the rGO restacking. The composite was tested as an active material in supercapacitor and therefore, two different symmetric supercapacitors were prepared, one containing pure rGO and the other composite hydrogel. The electrochemical charge storage characteristics of prepared supercapacitors were investigated in 0.5 mol dm-3 Na2SO4 by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The obtained results confirmed a positive effect of the hematite addition on electrochemical properties of the new composite material: (i) specific capacitance values of supercapacitor were increased from 17.5 F g-1 (bare rGO) to 26.2 F g-1(composite rGO/hematite) and (ii) restructuring of the active material, that takes place during charging/discharging, is minimized.

Reduced Graphene Oxide ; Hematite Nanofibres ; Supercapacitors ; CV ; EIS ; Charging/Discharging

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