Electrodeposition of polypyrrole–carbon nanotube composites for electrochemical supercapacitors

In this work we introduce a new electrochemical strategy for the fabrication of composite polypyrrole (PPY)–multiwalled carbon nanotube (MWCNT) composites for electrochemical supercapacitors (ES). The problem of low adhesion of PPY films on stainless steel and Ni substrates is addressed by the use of pyrocatechol violet (PV) dye as an anionic dopant. The experimental data indicates that strong adhesion of PPY films is attributed to catecholate type of PV bonding. We also find that PV strongly adsorbs on MWCNT and allows efficient dispersion, charging and controlled electrophoretic deposition (EPD) of MWCNT. The use of PV for electropolymerization of PPY and EPD of MWCNT allows the formation of composite films by combined electrodeposition method. Results show that Ni-plaque current collectors developed for high power battery applications can be electrochemically impregnated with PPY–MWCNT to form electrodes for ES. Ni plaque based electrodes offer advantages of significantly higher materials loading and superior capacitive behavior compared to thin film electrodes formed on stainless steel current collectors. The electrodes obtained by pulse impregnation show higher specific capacitance compared to the electrodes prepared by galvanostatic impregnation.