The Effect of Redox Electrolyte on the Electrochemical Characteristics of a PEDOT–(Sodium 1,2-Naphthoquinone-4-sulfonate)/WMNT Nanocomposite Electrode

The methods of cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy were used to study the effect of electrolyte redox on the electrochemical characteristics of a composite based on a poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymer and multiwalled carbon nanotubes (MWCNTs). To form a uniform thin layer of PEDOT on the surface of nanotubes, an enzymatic polymerization of the monomer was used. The electrochemically active compound sodium 1,2‑naphthoquinone-4-sulfonate (NQS) was a dopant in the main PEDOT chain and, at the same time, a component of the electrolyte. The addition of 12.5 mM NQS to the electrolyte increased the specific capacitance of the PEDOT–NQS/MWCNT composite electrode from 390 to 800 F/g at a potential sweep rate of 10 mV/s. In a 1 M H 2 SO 4 + 12.5 mM NQS redox electrolyte, the composite electrode exhibited higher cyclic stability and lower charge transfer resistance compared to 1 M H 2 SO 4 . After 1000 cycles of potential scanning in the range from –0.1 to 0.8 V at a rate of 100 mV/s, the specific capacitance of the composite electrode in a solution of 1 M H 2 SO 4 decreased by 8%, and in a solution of 1 M H 2 SO 4 + 12.5 mm NQS increased by approximately 9%.