Electrode materials for electrochemical capacitors based on poly(3,4 ethylenedioxythiophene) and functionalized multi-walled carbon nanotubes characterized in aqueous and aprotic electrolytes

Abstract

Within this work, we report a facile one-stage synthesis of nanocomposites based on functionalized carbon nanotubes (CNTs) and electroactive polymer poly(3,4-ethylenedioxythiophene). Three different composites are investigated as potential electrode materials for the electrochemical capacitors. Two of the composites contain carbon nanotubes (ox-CNTs), functionalized by acid oxidation process (65% HNO3, 120 °C). The third composite comprises of non-covalently functionalized carbon nanotubes, modified by surfactant addition. The functionalization process provides a uniform distribution of carbon nanotubes in water, what in turn helps to synthesize homogenous and reproducible composite materials. The composites are synthesized by chemical polymerization of EDOT in the solution of dispersed carbon nanotubes. The goal of such synthesis is to obtain polymer chains directly on CNTs. For comparison, one composite is prepared by simple dispersion of ox-CNTs in the commercially available pEDOT/polystyrene sulfonate (PSS) solution. The composite layers are tested electrochemically in aqueous and aprotic electrolytes for electrochemical capacitor application. The electrochemical results reveal that the presence of oxidized carbon nanotubes improves the conductivity and increases the capacitance values of the composites layers. The best electrochemical performance (capacitance of approx. 80 F g−1 in the aqueous and aprotic electrolyte) is exhibited by the composite obtained by chemical polymerization of EDOT in the solution of ox-CNTs.