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 nano-composites was greater than that of pristine PPy/FSWNT nanocomposites and PPy-DBS/FSWNT nano-composites by ten and 100 times, respectively. Furthe-rmore, 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.