Research On Electrosynthesis And Property For Polyaniline And Polypyrrole

The conducting polyaniline(PAni) and polypyrrole(PPy) have the advantages of environmental stability, easy synthesis, redox reversibility and so on, there are widespread application prospect and reseachering values in domains of life science, sensor, battery, photoelectronic devices, and metal anticorrosion etc. In this thesis, PAni and PPy were prepared on stainless steel. Morphology was observed by scanning electron microscopy and structure was characterized by infrared spectroscopy. The electrochemical behavior of pyrrole synthesis was studied by cyclic voltammetry. The protection mechanism of PAni and PPy was investigated by methods such as linear sweep voltammetry curves, potentiodynamic polarization curves, open-circuit potential-time curves and electrochemistry impedance spectrum. The capacitive property of noble metal doped PAni was studied through cyclic voltammetry and charge-discharge curves.The PAni and Pt doped PAni films ware prepared by constant potential method in aniline+perchloric acid solusion with 1 mmol L-1 H2PtCl6 or not. Anti-corrosion performance of the two kinds of films for stainless steel was investigated in 2 mol L-1H2SO4. The capative properties of films were studied in 0.5 mol L-1H2SO4. The results show that generation of Pt reduces with number of cycles increasing, and it can be infered that Pt particles are distributed from the inside of composite film to the surface. Corrosion potential-time curves show that PAni film doped with Pt catalyzes reduction of oxygen and quickly adds the oxidation state of polyaniline for maintaining metal passivation. The potentiodynamic polarization curves indicated that in comparison with pure PAni, Pt doped PAni can provide protection for stainless steel during longer period. Electrochemistry impedance spectrum show that charge transfer resistance of Pt doped PAni has no obvious increase in 14 h and ion diffusion model is nearly the ideal capacitance type, indicating that the concentration of oxidation state of polyaniline in PAni/Pt complexes is great. In comparison with PAni, Cyclic voltammetry area of PAni/Pt is larger and its discharge time is also longer, stating that the storage capacity of PAni/Pt is better.PAni-Fe(CN)6 and PAni were prepared on stainless steel by constant potential method in aniline+sulfuric acid+potassium nitrate solution with 0.1 mol L-1 K3Fe(CN)6 or not. Corrosion preventing for stainless steel of PAni-K3Fe(CN)6 and PAni were studied. The results showed that K3Fe(CN)6 in the electrolyte solution is beneficial to the passivation of stainless steel. The current-time curves of potential step show that PAni film doped by Fe(CN)63- is capable of inhibiting metal's pitting corrosion in 0.1 mol L-1HC1+0.1 mol L-1H2SO4 solution. Open-circuit potential-time curve shows that PAni films doped with Fe(CN)63- maintain the stainless steel at more positive potentials than pure PAni all the time, and it also keeps the stainless steel at positive potential for a longer period, when they were immersed in 0.1 mol L-1HCl solution. The potentiodynamic polarization curves indicate that Fe(CN)63- doping in the PAni-Fe(CN)6 films with metal ions dissolved near the substrate surface forms a thin overcoating film of metal hexacyanoferrate leading to the stabilization of its passive layer. The corrosion potential was increased with immersion time in 0.02 mol L-1 HC1+0.04 mol L-1H2SO4, and its corrosion current decreases. And there was a diffusion controlled Warbury impedance in electrochemistry impedance spectrum in 0.02 mol L-1 HC1+0.04 mol L-1H2SO4 solution which indicated that PAni films doped with Fe(CN)63- are able to prevent penetration of Cl-.PPy-HTSO-AOT and PPy-HTSO were prepared on stainless steel by constant potential method in pyrrole+P-toluensulfonic acid solution with 0.02 mol L-1 bis(2-ethylhexyl) sulfosuccinate(AOT) or not. Corrosion preventing of PPy for stainless steel in NaCl solution was studied. Scanning electron microscope results show that the particles in PPy-HTSO film packs and is uneven, while a homogeneous and compact morphology is observed on PPy-HTSO-AOT film surface. Cyclic voltammetry in 1 mol L-1 NaNO3 shows that PPy films doped AOT can inhibit the anion exchange. When immersed in NaCl solution, the corrosion potential of SS/PPy-HTSO-AOT declined more slowly than SS/PPy-HTSO and the potential value of the former stayed more positive during the immersing time. After soaking in corrosion solution for 2 h, the corrosion current changes a little, indicating PPy-HTSO-AOT film can better prevent the penertration of etching solution. At low frequency, the greater impedance modulus of SS/PPy-HTSO-AOT and its better charge transfer resistance are indicative of improvement of the anticorrosion performance of PPy film doped with AOT.