Effect of oxygen-containing functional groups on specific capacitance of carbon nanotube electrochemical capacitors

Abstract

Electrochem. capacitors have numerous applications, ranging from large scale hybrid vehicles to small scale consumer electronics, with very high power d. at the cost of relatively low energy storage. A lot of works have been devoted to increase power and energy capacity as well as lifetime of such capacitors, and the use of functionalized carbon nanotube array is considered the most visible way to achieve that. We report here an approach to increase the specific capacitance of an electrochem. capacitor by simply increasing the no. of oxygenated functional groups that are attached to the carbon nanotubes. This finding shows an augmentation of nearly five orders of magnitude in the specific capacitance when the oxidn. level (oxygen /carbon at. ratio) of the nanotubes is increased from 2.5% to 7.5%. While this behavior was assessed in an aq. potassium hydroxide electrolyte, the totally opposite behavior with non polar and/or aprotic solvent is expected.