Electrodeposition of composite polypyrrole–carbon nanotube films

Polypyrrole (PPY) films were electrochemically deposited on stainless steel substrates from aqueous pyrrole solutions containing p-toluene sulphonic acid and 4,5-dihydroxy-1,3-benzenedisulphonic acid disodium salt (tiron). The deposition potential of PPY in the solutions containing tiron was 0·2 V lower than that in the solutions containing p-toluene sulphonic acid. It was found that tiron can be used for the dispersion of multiwalled carbon nanotubes (MWCNTs) and fabrication of composite PPY–MWCNT films. The deposition yield was studied under galvanostatic conditions. The mechanism of PPY–MWCNTs deposition in the presence of tiron was discussed. The incorporation of MWCNTs into the PPY during electropolymerisation resulted in the formation of porous films. The films were investigated for the application in electrodes of electrochemical supercapacitors. Cyclic voltammetry data for the films tested in the 0·5M Na₂SO₄ solutions showed a capacitive behaviour in a voltage window of −0·5 to +0·4 V versus a saturated calomel electrode. The composite PPY–MWCNT films showed improved capacitive behaviour and lower electrical resistance compared to the pure PPY films. A highest specific capacitance (SC) of 310 F g⁻¹ was obtained at a scan rate of 2 mV s⁻¹ for the composite films. The SC decreased with an increasing film thickness and scan rate. The cycling stability of the films was investigated. The results indicated that the PPY–MWCNT films deposited on the stainless steel substrates are promising electrode materials for electrochemical supercapacitors.