Capacitive characteristics of nanocomposites of conducting polypyrrole and functionalized carbon nanotubes: effects of in situ dopant and film thickness

The nanocomposites of functionalized single-walled carbon nanotubes (FSWNTs) and conducting polypyrrole (PPy) doped by FSWNTs, Cl − , toluenesulfonate (TOS − ), and dodecylbenzenesulfonate (DBS − ), respectively, were electrochemically co-deposited to evaluate their applicability in supercapacitors. The effects of the dopants, with focus on their mass, size and surfactivity, and film thickness on the capacitive characteristics were investigated in 3 M KCl aqueous solution. Although the nanostructure of composites can admittedly improve the capacitive properties, dopant anion was demonstrated to be a more essential factor. The specific capacitance of PPy-TOS/FSWNT nanocomposites was greater than that of pristine PPy/FSWNT nanocomposites and PPy-DBS/FSWNT nanocomposites by ten and 100 times, respectively. Furthermore, PPy-TOS/FSWNT nanocomposites exhibited the lowest dependence of capacitance on the charging–discharging rate and composite thickness due to its high electronic and ionic conductivity resulting from the appropriate doping level and size of TOS - as well as the synergic effect of PPy-TOS and FSWNTs. In addition, PPy-TOS/FSWNT nanocomposites presented a remarkably stable cycling performance.