Studies of deposition of and charge storage in polypyrrole–chloride and polypyrrole–carbon nanotube composites with an electrochemical quartz crystal microbalance

Carbon nanotubes and their composites with conducting polymers are of interest for supercapacitor and other electrode applications. This paper reports the use of the electrochemical quartz crystal microbalance to investigate the deposition and intercalation behaviour of polypyrrole–carbon nanotube and polypyrrole–chloride thin layers. The standard plots of mass versus potential were converted to “massograms” by differentiating the mass with respect to time. As dm/dt is proportional to I, the plot is directly comparable to the voltammogram. Using these data, deposition potentials of 0.7 and 0.8 V were selected for polypyrrole–chloride and polypyrrole–carbon nanotube films, respectively. In polypyrrole–chloride deposits, anion uptake upon oxidation was observed. In the polypyrrole–nanotube layers, a mix of cation expulsion and anion uptake upon oxidation is observed when using 0.1 M KCl (aq) as the electrolyte. However, using 0.1 M tetrabutylammonium bromide, only uptake of bromide is observed, due to the bulkiness of the cation. In addition to this complex charge neutralisation behaviour, a redox pseudocapacitance was confirmed directly using the massogram data.