Capacitance properties of poly(3,4-ethylenedioxythiophene)/carbon nanotubes composites

The electrochemical properties of composites prepared from an electrically conducting polymer poly(3,4-ethylenedioxythiophene), i.e. PEDOT and multiwalled carbon nanotubes (CNTs) have been investigated for supercapacitor application. The novel composite material was prepared by chemical or electrochemical polymerization of EDOT directly on the nanotubes or from a homogenous mixture of PEDOT and CNTs. Acetylene black (AB) has been also used as a composite component in order to evaluate whether nanotubes are giving improved properties or not. Electrodes prepared from such composites were used in supercapacitors operating in acidic (1 M H2SO4), alkaline (6M KOH) and organic (1 M TEABF4 in AN) electrolytic solutions. The capacitance values were estimated by galvanostatic, voltammetry and impedance spectroscopy techniques with two- or three-electrode cell configuration. Due to the open mesoporous network of nanotubes, the easily accessible electrode/electrolyte interface allows quick charge propagation in the composite material and an efficient reversible storage of energy in PEDOT during subsequent charging/discharging cycles. The composites with AB supply quite good capacitance results, however, nanotubes as electrode component gave definitively a more homogenous dispersion of PEDOT that should give a better charge propagation. The values of capacitance for PEDOT/carbon composites ranged from 60 to 160 F/g and such material has a good cycling performance with a high stability in all the electrolytes. Organic medium is especially interesting because of higher energy stored. Another quite important advantage of this composite is its significant volumetric energy because of the high density of PEDOT.