Properties of electropolymerized high density polypyrrole films

The high density PPy films (HD-PPy，ρ>1.4g/cm3) doped with p-toluenesulfonate (TOS-) counterions were electropolymerized by a facile approach in H2O and acetonitrile (AN) mixed solvent. The structure and electrochemical properties of the HD-PPy films were measured by X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) analysis, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that appropriate ratio of AN/H2O (99/1) could be favorable to increase the density of PPy films. Further enhancement of the density could be obtained by using higher current density (such as 10mA/cm2), as it favors the formation of two-dimensional structure. Generally, low temperature of polymerization, Tp (e.g. -20℃), is advantageous to the enhancement of density and conductance of PPy films. But if Tp is too low, it beesmes disadvantageous in case of the high current density of polymerization. The HD-PPy films (1.42g/cm3) were obtained at 0 ℃ with 10mA/cm2 in AN/H2O(99/1) solution. Furthermore, HD-PPy films were characterized not only by high electronic conductivity (～220S/cm) and high thermal stability, but also by low electrochemical activity. It was indicated that the HD-PPy would be not only an excellent electrode material but also a promising corrosion protection material.