Electrochemical doping of pure single-walled carbon nanotubes used as supercapacitor electrodes

Pure single-walled carbon nanotubes (SWCNTs) with little bundling show an excellent capacitor performance attributable to the intrinsic nature of the SWCNTs, and possess unusual electrochemical properties characterized by a butterfly shaped cyclic voltammogram which differs from those for conventional activated carbon electrodes. Electrochemical doping in semi-conductor nanotubes occurred at the interface between the electrolyte and the SWCNT surface. In situ measurements showed a remarkable increase of electric conductivity with the polarization from the flat band potential. Because of the potential dependence, the capacitance of the SWCNT electrodes was higher at the higher charging potentials.