Electrical Performance And Application Of Polypyrrole Films Prepared By Electrochemical Method

Polypyrrole (PPy) has been extensively investigated and was considered as the promising Electronically Conductive polymers (ECP), due to its excellent properties and advantages including environmentally friendly feature, low cost and facile synthesis.In the studies, the high density PPy films (HD-PPy), doped by p-toluenesulfonate (TOS-), were prepared on tatanum electrodes at the current density of 10 mA?cm-2 at 0℃. Its density was up to 1.42 g?cm-3, which was slightly larger than the maximum reported value abtained on glass carbon electrodes by 0.02～0.05 mA?cm-2 at -40℃. The method in the studies was of more practical value from the view of application, because it is easy to perform, low cost, time saving, and especially independent of the electrode surface. Its high density was resulted from the formation of plane-type two dimensional (2D) structure of molecular chains. The conductivity of HD-PPy was up to 200 S?cm-1. Furthermore, the thermal stability of HD-PPy films was significantly superior to that of conventional PPy films. In additional, HD-PPy could hinder ions insertion more effectively. It can be concluded that HD-PPy would be an excellent electrode material and anticorrosion material.Aiming to explore free-template method to relize micro/nano-PPy, the effects of pH and current density of polymerization on the morphology and structure of PPy were investigated. The horn-like PPy films (h-PPy) with horns in micro/nano size were obtained at pH=9 with current density larger than 3mA?cm-2. The horn might be a kind of non-plane 2D structure of molecure chains resulted from high current density in polymerizaiton. Furthermore, h-PPy was characterized as great specific area, highly ordering, and attractive conductivity up to 90 S?cm-1.To improve the charge/discharge rate and cycling stability of PPy-based electode of supercapacitor, the PEDOT/h-PPy composites and the composites of PPy and functionalized single-walled carbon nanotubes (F-SWNTs) were prepared by electrochemical methods. The two kinds of composites were characterized with highly porous structure, which leads to their specific capacitance up to 290 and 230 F?g-1 in 1M KCl aqueous solutions, respectively. Furthermore, they have very fast charge/ discharge rate and good cycle stability at potential window of 1V and 0.8 V, respectively.The porous PPy films were also obtained in the optimized conditions, whose electrochemical properties can be tailored by doping ions. By trying several ions, PPy-Cl had high specific capacitance up to 270 F?g-1, while PPy-TOS had very rapid charge/discharge ability. To achieve PPy with high area specific capacitance, we proposed the multi-step method to prepare porous thick PPy films. The results showed that two kinds of even porous PPy films, PPy-Cl and PPy-TOS with area specific capacitance up to 5 F?cm-2 were obtained by the method. Moreover, their mass specific capacitance could reach 330 F?g-1 and 191 F?g-1 at discharge current of 1 mA?cm-2. In concusion, PEDOT/h-PPy, PPy/F-SWNTs, PPy-Cl and PPy-TOS will be promissing electrode materials for supercapacitors.HD-PPy and PPy doped with dodecylbenzenesulfonate (PPy-DBS) were prepared on an underlayer of PPy doped with oxalate (PPy-C2O4) by galvanostatical method for effective copper protection, because PPy-TOS and PPy-DBS could not be obtained directly on copper surface by electrochemical methods. Their anticorrosion performance in 3.5% NaCl solution was signifanctly superior to that of conventional PPy-TOS and the bilayer PPy-C2O4, coatings with equal thickness. The reason is that HD-PPy and PPy-DBS could obstruct the corrosion ions (Cl-) from penetrating the PPy films and hinder the oxalate from escaping so that the healing ability of PPy could be maintained for a long term. The results demonstrate that HD-PPy and PPy-DBS films on an underlayer of PPy-C2O4 have potential application to protect copper.The PPy aluminum solid electrolytic capacitors (PA-Cap) were realized by electropolymerization of PPy on the underlayer of PPy/MnO2 prepared by chemical method. The leakage current can be effectively decreased by using coating silicon rubber and shortening polymerization, and can be further dereased by thermal treatment during pilot production. The aluminum electrolytic capacitors with high performance were achieved by optimizing oxidant concentration, dip numbers and current density of polymerization, and had been put into manufacture.