Composite electrodes were fabricated for supercapacitor applications by depositing vanadium oxide onto multi-walled carbon nanotube (MWCNT) buckypaper using supercritical fluid deposition (SFD). The deposited thin vanadium oxide layer showed amorphous structure with excellent uniformity. In aqueous KCl electrolyte, the vanadium oxide exhibited a constant pseudo-capacitance of ∼ 1024 F g(-1), which was independent of the oxide material loading (up to 6.92 wt%) and voltage scan rate (up to 100 mV s(-1)). The highest specific electrode capacitance achieved was ∼ 85 F g(-1), which was almost four times that of the pristine buckypaper electrode.
Large-size composite carbon nanotubes/polyaniline as supercapacitor electrode material has been investigated for optimization of the areal specific capacitance. Polyaniline, as conductive polymer, is synthesized on the structure of carbon nanotubes by an in situ method. Thicker the composite electrode and higher polyaniline loading increase the gravimetric and volumetric specific capacitance. It is noticeable that this report's areal specific capacitance can reach approximately 6.5 F cm −2 .
Carbon nanotubes (CNTs) have attracted great attention because of their unique structural, electrical, mechanical and thermal properties. Then CNTs have potential application as electrode for batteries and supercapacitors, especially binder-free electrodes. The major challenge is to fabricate the large scale electrode with the uniform thickness, electrical property. The large scale CNTs buckypaper can be fabricated via vacuum filtration technique. The characteristics of CNT dispersion and buckypaper depend on variety of factor such as sonication power, sonication time, dispersant…. In this study, we investigate the multiwall carbon nanotubes (MW CNTs) in Isopropanol (IPA) solvent with different sonication conditions, membrane filter size for paper with areal density of 3 mg/cm2 with different sizes such as 4, 10, 20 cm in diameter and large scale of 30x30 cm2. It is observed that the dispersion of CNTs are good and the thickness, conductivity are uniform over whole sample for above sizes. We also can get the highest conductivity of buckypaper was 3.9x103 S/m in 30 mins. It is found that the higher sonication power and higher sonication time are better for buckypaper.
The synthesis of polyaniline (PANI) containing different carbon nanotubes (CNTs) by in situ electrochemical polymerization is reported in this study. The samples were characterized by scanning electron microscopy. Fourier transform infrared and ultraviolet– visible spectroscopy were used to determine the change in structure of the polymer/CNT composites. Thermogravimetric analysis showed that the composites had better thermal stability than the pure PANI. In addition, the electrochemical measurements such as cyclic voltametric (CV) curves showed that the conductivity of the obtained nanocomposite increased. The results of measuring cyclic voltammetry also showed that the specific capacitance of nanocomposite was much higher than the pure PANI and CNTs. This is due to the fact that the composites consisting of electroactive species and carbon materials with highly specific surface areas are significantly promote the energy density of supercapacitors. Such supercapacitors exhibit simultaneously both double layer capacitance and Faradic pseducapacitance in energy storage.
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