Research On Electrosynthesis And Property For Polypyrrole

The conducting polypyrrole?PPy? has the advantages of environmental stability, easy synthesis, redox reversibility and so on, there are widespread application prospect and reseachering values in domains of metal anticorrosion, sensor optoelectronic devices, life science, and battery etc. In this thesis, PPy were prepared on stainless steel. Morphology was observed by scanning electron microscopy, structure was characterized by infrared spectroscopy and conductivity was measured by four-probe conductivity measurement instrument. The electrochemical behavior of pyrrole synthesis was studied by cyclic voltammetry. Using the method of painting the lattice to research adhesion of PPy film on stainless steel. The protection mechanism of PPy was investigated by methods such as linear sweep voltammetry curves, potentiodynamic polarization curves, open-circuit potential-time curves and electrochemistry impedance spectrum.The PPy films ware prepared in the 0.1 mol L^-1 pyrrole that as the polymer monomer by galvanostatic method, and take water, acetonitrile and nitromethane as the solvents with 0.1 mol L^-1 NaCl O4 as the supports electrolyte. The effects of solvent nucleophile on PPy properties such as morphology, conductivity and anti-corrosion for stainless steel was investigated. The PPy film provided better protection properties for stainless steel, with higer corrosion potential, and smaller corrosion current density than bare stainless steel. Among the three solvents, water solvent was with the largest nucleophile. The PPy prepared in Water had the most defects, the lowest conductivity and had the worst protection among three solvent. The reason is that water had the most reaction with polymer intermediates which was easy to end the chain reactions, as a result, PPy film prepared in water possessed short conjugacy-length, large structure defects, low conductivity and worst corrosion-resistance. In order to study the protective function of the PPy membrane for the stainless steel in 1 mol L^-1 H₂SO₄, the potentiodynamic polarization curves and the electrochemistry impedance spectrum ware adopted. As it turned out, the PPy film prepared in nitromethane with the smallest nucleophile had the best protectation for stainless steel.PPy-C2O4-PFOS and PPy-C2O4 were prepared on stainless steel by galvanostatic method in pyrrole+oxalic acid solusion with 0.005 mol L^-1 KPFOS or not. Corrosion preventing for stainless steel of PPy-C2O4-PFOS and PPy-C2O4 were studied. The results showed that PPy-C2O4-PFOS had better adhesion than PPy-C2O4. The potentiodynamic polarization curves indicated that PPy films doped with PFOS^- had better protection effect on stainlee steel than undopped in 0.1 mol L^-1 HCl. Open-circuit potential-time curve showed that the potential of PPy films doped with PFOS^- maintained more positive potentials for more than 35 d, when they were immersed in 3.5%NaCl solution. And there was a diffusion controlled Warbury impedance in electrochemistry impedance spectrum in 0.58%NaCl solution which indicated that the rate of corrosion solusion among PPy doped with PFOS^- film was slower. In conclusion, perfluorooctanesulfonic acid potassium improved PPy film's adhesion on stainless steel. The PPy film doped with PFOS^- is compact with smaller pores, so PPy-C2O4-PFOS had better the mechanical isolation effect for corrosion solution and proecting effect for stainless steel.PPy-VO₃ and PPy were prepared on stainless steel by cyclic voltammetry method in pyrrole+oxalic acid+sodium oxalate solusion with 0.01 mol L^-1 NaVO₃ or not. To study corrosion preventing of PPy for stainless steel, linear sweep voltammetry curves, potentiodynamic polarization curves and electrochemistry impedance spectrum were adopted. The result showed that sodium metavanadate could inhibit the anodic dissolusion of stainless steel, improve the uniform and activity of PPy. VO₃^- can be released to slow corrosion rate of stainless steel by inhibiting the cathodic reaction. Although the two kinds of films could make the stainless steel form passivation film, PPy film doped with the VO₃^- had larger impedence resistance at low frequency, and it had a larger film resistance than the undoped films. Each impedance of PPy doped VO₃^- film has a diffusion controlled impedance Warbury. And as time went on, charge transfer resistance increased. Doping VO₃^- can improve corrosion resistance of PPy films.