Based On Carbon Nanotubes And Carbon Atoms Line Supercapacitor

The electrodes composed of multiwalled carbon nanotube(MWNT) array, polypyrrole(PPy) and multiwalled carbon nanotube array composite, and carbon atom wires applied to supercapacitors were studied. Various measurements including SEM, TEM, XRD and IR were carried out to characterize the morphology, structure and compositions of these materials respectively. The electrochemical performance of the electrodes were investigated by use of the cyclic voltammetric,galvanostatic charge/discharge and AC impedance methods. The experimental results from the materials mentioned above and those used currently for supercapacitors are compared with each other.The multiwalled carbon nanotube array was fabricated by chemical vapor deposition(CVD) in the template of porous alumina in the presence of a catalyst such as cobalt and the carbonaceous source of C2H2. The morphology examination by SEM and TEM showed that the carbon nanotubes were arranged in the array uniformly and paralleled, with smooth walls, the outside diameter of 120 nm and the inside diameter of 110 nm. From the cyclic voltammetry, the array electrodes in an acidic electrolytic solution had greater capacitance than the case in a neutral electrolytic solution. The specific capacitance of 365 F/g was achieved with the discharge current density of 210 mA/g in the solution of 1 mol/L H2SO4. The value was much higher than those of disordered carbon nanotubes or activated carbon electrodes. In addition, the carbon nanotube array electrode, was found to have low ESR and good cycling stability.To select a proper conducting polymer to form the composite electrode with MWNT arrays, poly(3-methylthiophene), polyaniline and polypyrrole coated on a Pt electrode were investigated respectively for their potential application in supercapacitors. After comprehensive consideration, we picked up the composite electrode of PPy and the MWNT array as the candidate to be studied in detail. It was fabricated by electro-oxidation of Py in the aqueous solution containing 0.025 mol/L Py and 0.1 mol/L LiClO4on theMWNT array electrode. The morphology of the composite electrode observed by SEM showed that PPy was uniformly coated on the MWNTs. From the measurements of cyclic voltammetry and galvanostatic charge/discharge, the composite electrode had higher specific capacitance (0.84F/cm2) than pure MWNT array electrode (0.38F/cm2) in the same experimental conditions.A kind of linear elementary carbon with the similar structure to carbyne was prepared by a new method. The sample appeared to be winding lines with the diameter of around 0.2 run in the magnified image of the high resolution transmission electron microscope (HRTEM). Considering its predominating composition of carbon (93%) and the comparable size in diameter to the bond length of C-C (0.154 nm), we term the linear elementary carbon as carbon atom wires (CAW). IR was used to characterize the structure of CAW before and after an acid-treatment with HNO3. The results showed that the acid-treatment with HNO3 could increase activated functional groups, such as -OH, -COOH. The electrodes made up of carbon atom wires had good capacitive performance. But from the results of cyclic voltammetric and galvanostatic charge/discharge experiments, we found that the specific capacitance of acid-treated CAW (256F/g) was much higher than the CAW without the acid treatment (122F/g). The CAW electrode was found to have low ESR and good cycling stability.