Effect of activation and surface modification on the properties of carbon nanotubes supercapacitors

To increase the specific capacitance of supercapacitors based on carbon nanotubes (CNTs), activation and surface modification were carried out by using KOH and concentrated nitric acid respectively. The materials were analyzed by transmission electron microscopy (TEM), N-2 adsorption and infra-red spectra (IR). The effect of activation and surface modification on the performance of the CNTs supercapacitors was also studied by cyclic voltammetry and galvanostatic charge/discharge. The results showed that activation enlarged the BET specific surface area of the CNTs and hence increased the specific capacitance of the supercapacitors from 43 F (.) g(-1) to 73 F (.) g(-1). By surface modification, large quantities of electroactive functional groups were adsorbed on the surface of the CNTs, thus pseudocapacitance was induced and the specific capacitance was further increased to 94 F (.) g(-1).