Influence of dopants and carbon nanotubes on polypyrrole electropolymerization and capacitive behavior

In this work we demonstrate the feasibility of electropolymerization of polypyrrole (PPy) films on stainless steel substrates using alizarin red (AR) and anthraquinone-2-sulfonic acid sodium salt (AQ) as anionic dopants. The results indicate that AR offers the advantage of reduced electropolymerization potential. The comparison of experimental data for AR and AQ provides an insight into the influence of the dopant molecular structure on electropolymerization of PPy. The chelating properties of AR allow the fabrication of adherent films. Moreover, the use of AR allows the dispersion and charging of multiwalled carbon nanotubes (MWCNT) and their electrochemical incorporation into the PPy films during electropolymerization. Scanning electron microscopy observations show the formation of porous films, containing MWCNT, coated with PPy. The composite PPy-MWCNT films offer advantages, compared to pure PPy films, for application in electrodes of electrochemical supercapacitors (ES), due to higher specific capacitance (SC), improved SC retention with increasing film mass and lower impedance.