Frequency response characteristic of single-walled carbon nanotubes as supercapacitor electrode material

Impedance analysis was employed to study the frequency response characteristics of supercapacitors utilizing single-walled carbon nanotubes (SWNTs) as electrode material. The knee frequency is around 631 Hz for the electrochemically oxidized SWNT supercapacitor, much higher than that of the as-prepared one (around 316 Hz) and the common activated carbon supercapacitor (< 1 Hz). The good frequency response observed in this work is due to the introduction of nanosized mesopores and oxygen-containing groups formed during the electrochemical oxidization of SWNTs. The capacitance of electrochemically oxidized SWNT supercapacitor is 113 F/g, which is much higher than the value of the as-prepared one (20 F/g). (C) 2008 American Institute of Physics.