Synthesis, characterisation and electrochemical testing of multiwalled carbon nanotubes based nanocomposites for supercapacitor materials

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Date
2010-04
Authors
Valizadeh Kiamahalleh, Meisam
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Abstract
Electrochemical supercapacitors are becoming attractive energy storage devices and fill the gap between conventional capacitors and batteries because they have higher power density and a longer cycling life than batteries and have higher energy density than conventional dielectric capacitors. In this study, in order to take full of the capacitive behavior from different materials, hybrid supercapacitor electrodes made from multiwalled carbon nanotubes (MWCNTs), transition metal oxides and supported poly (3,4-ethylenedioxythiophene) (PEDOT) were investigated. Different transition metal oxides, such as CuO, Fe203, NiO and Mn02, were filled inside MWCNTs by wet chemical method. Transmission electron microscope (TEM) images revealed that metal oxides particles encapsulated in the cavities of MWCNTs. Energy-dispersive X-Ray (ED X) supported the chemical composition of metal oxideslMWCNTs nanocomposites indicating that the particles compositions comprised solely of carbon, metal and oxygen.The capacitive behaviour of the prepared nanocomposites were investigated by using cyclic voltammetery (CV) technique. It was found that the capacitive behaviour ofNiO and Mn02 filled in MWCNTs were higher than that of Fe203 and CuO. Hence, nanocomposites consisting ofNiO and Mn02 and MWCNTs were prepared in order to obtain higher capacitive behaviour. The obtained NiOIMn02IMWCNTs (NMOIMWCNTs) nanocomposite gave high capacitive behaviour. In addition, charge/discharge (CD) test for this nanocomposite demonstrated high specific capacitances (SC) value of 407.09 F/g due to the high pseudocapacitive behaviour of NiO and Mn02. Moreover, in order to further enhance the capacitive behaviour of the NMO/MWCNTs nanocomposite, it was coated with PEDOT as another type of pseudocapacitive material. The obtained NMO/MWCNTslPEDOT nanocomposite gave higher capacitive behaviour than NMO/MWCNTs nanocomposite and demonstrated greater SC value of 535.00 Fig due to adding PEDOT. The TEM images of NMO/MWCNTslPEDOT nanocomposite interestingly showed the successful filling NMO particles inside MWCNTs and confirmed the uniform coating of PEDOT layer on MWCNTs. EDX spectra and X-ray diffraction (XRD) pattern, confirmed the composition and crystal phase of NMO particles inside nanocomposite and the existence of PEDOT on NMO/MWCNTs nanocomposite. Thermal gravimetric analysis (TGA) on NMO/MWCNTslPEDOT nanocomposite showed that almost 20 wt% and 48 wt% of it were NMO particles and PEDOT, respectively. The maximum SC value predicted by design of experiment (DOE) from single response optimisation of NMO/MWCNTs and NMO/MWCNTslPEDOT nanocomposites were 453.12 and 545.36 Fig, respectively.
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Synthesis, characterisation and electrochemical testing of multiwalled carbon nanotubes based nanocomposites for supercapacitor materials , because they have higher power density and a longer cycling life
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