High charge/discharge rate polypyrrole films prepared by pulse current polymerization

Polypyrrole (PPy) films doped by p-toluenesulfonic (PTS) ion were prepared by pulse current polymerization (PCP PPy) and direct current polymerization (DCP PPy) in aqueous solution. During polymerization of DCP PPy films, the sustained high anodic potentials can result in overoxidation and -CH₂- formation at pyrrole rings, which was confirmed by the FTIR spectroscopy. PCP PPy films exhibited more homogeneous and smoother appearance than DCP PPy films. The apparent diffusion coefficient of PCP PPy films was one order of magnitude bigger than that of DCP PPy films, which was closely correlated with the more ordered structure of PCP PPy films confirmed by XRD. When the scanning rate reached up to 500 mV s^-1, the CV curves of PCP PPy films showed rectangular shape within voltage range of -0.8 V to +0.8 V. High charge/discharge rate of PCP PPy films can be attributed to well wettability, very small charge transfer resistance, high electronic conductivity and ions apparent diffusion coefficient. After 50,000 charge/discharge cycles, the specific capacitance of PCP PPy films only decreased by 14% at a charge/discharge current of 20 A g^-1 within voltage range of 0-0.4 V.