Direct growth of vertically aligned single-walled carbon nanotubes on conducting substrate and its electrochemical performance in ionic liquid

We report fabrication of vertically-aligned single-walled carbon nanotube (VA-SWCNT) electrodes for a symmetric electrochemical capacitor using a simple, low-cost ethanol-based SWCNT growth system. From the CNT direct growth technique, the electrode was easily prepared and consequently assembled with an electrochemically-stable ionic liquid as electrolyte. VA-SWCNTs were directly grown on conducting SUS 310S foils in which the binder material was not incorporate in the capacitor structure. The morphology of as-grown CNTs was investigated using scanning and transmission electron microscopy. This capacitor demonstrated gravimetric capacitance of up to 584 F g-1 (at 1 mV s-1 scan rate) and a high rate capability, with up to 1,000 mV s-1 scan rate being obtained. From the cyclic voltammetric analysis, the capacitance was contributed not only from the ideal double layer capacitance, but also from faradaic/redox processes that might have occurred during charge-discharge. Other than the capacitance, the VA-SWCNT capacitor electrochemical performance was also measured by using frequency response (electrochemical impedance) and charge-discharge analyses