The composite film of polypyrrole and functionalized multi-walled carbon nanotubes as an electrode material for supercapacitors

The composite film of polypyrrole and functionalized multi-walled carbon nanotubes (PPy/F-MWNTs) was prepared by an optimized route according to our previous work. MWNTs were pretreated by sonicating with a concentrated H ₂SO ₄/HNO ₃ (3/1 volume ratio) solution in a water bath for 24 h, and were then co-electropolymerized with pyrrole to synthesize the PPy/F-MWNTs composite. MWNTs were cut into smaller nanorods and a lot of functional groups such as -COOH and -OH were produced during the pretreatment. After electropolymerization, MWNTs were coated by PPy via these functional groups resulting in a homogeneous, stable and porous composite film. When used as an electrode material for supercapacitors, PPy/F-MWNTs composite shows a specific capacitance of 243 F g ^-1 at the scanning rate of 10 mV s ^-1, and over 220 F g ^-1 at 200 mV s ^-1. It retains 94% of its initial capacitance after 1000 cycles of galvanostatic charge/discharge and the columbic efficiency is higher than 98.7% during cycling.