Research On Electrosynthesis And Electrochemical Properties For Conducting Polypyrrole

Conductive polypyrrole?PPy?has the advantages of easy preparation,high stability and high conductivity.It has been widely studied in the fields of biomedicine,photoelectric materials,batteries,supercapacitors,sensors and metal corrosion protection.In this paper,a variety of PPy was prepared by electrodeposition on a stainless steel substrate,and the effects of different DN values of solvents and doped ions on the polymerization potential,conductivity,microstructure and corrosion resistance of PPy were studied.Stainless steel substrate surface observed by metallographic microscope and the scanning electron microscope to observe the microstructure of PPy film,the polymerization of pyrrole were studied with cyclic voltammetric curves potential and membrane REDOX active,PPy,prepared by potentiostatic method with four-probe electrical conductivity meter measuring the conductivity PPy,use the open circuit potential-time curve,potentiodynamic polarization curves and electrochemical impedance spectroscopy study of PP y anti-corrosion performance of stainless steel base.To investigate the effect of L-Leu doped PPy on corrosion resistance of stainless steel substrate.The effect of L-Leu concentration on corrosion inhibition efficiency of stainless steel substrate in 0.1mol/L H₂SO₄ was studied by using the electrodynamic polarization curve.Pyrrole+H₂SO₄ solution containing/without 0.1mol/L Leu was prepared by potentiostatic method on a stainless steel substrate.The particle size of PPy prepared in the solution containing L-Leu was uniform,compact,and the membrane surface was smooth.However,the PPy particles prepared in the solution without L-Leu had uneven distribution,loose accumulation,severe agglomeration and rough membrane surface.The open-circuit potential-time curve in 3.5wt%NaCl showed that at the beginning of soaking,the membrane potential of PPy doped/undoped l-leu had a small difference,but after soaking for 30min,the potential of PPy undoped L-Leu gradually decreased,and corrosion of the stainless steel base gradually occurred.When the L-Leu doped PPy is dedoped,the resulting L-Leu forms a hydrophobic corrosion inhibiting film on the stainless steel substrate,which makes it difficult for corrosive ions to reach the surface of the stainless steel s ubstrate and extends the protection time of the stainless steel substrate.To explore the relationship between the preparation of solvents with different DN values and corrosion resistance to PPy.Electrodeposition of PPy on stainless steel substrate was carried out by potentiostatic method in solution of water?H₂O?or acetonitrile?ACN?or nitromethane?CH₃NO₂?containing pyrrole+NaClO₄.The DN value of CH₃NO₂ was the smallest,the intermediate force with pyrrole polymerization was the weakest,the conductivity of prepared PPy was the highest,the membrane microstructure was the most uniform,the particle aggregation was the closest,and the structural defects were the least.The DN value of H₂O was the highest,the intermediate force with pyrrole polymerization was the strongest,the conductivity of the prepared PPy was the lowest,the membrane microstructure was the most uneven,and the structure defects were the most.The electrode potential of PPy prepared in CH₃NO₂ was maintained at a high value at 1mol/L H₂SO₄.After a long soak,the corrosive medium began to enter the PPy film,and the PPy prepared in CH₃NO₂ had the highest REDOX activity,and it was the easiest to release the inhibiting ion ClO ₄^-by dedoping,so as to maintain the stability of the passi vation film on the surface of the stainless steel substrate.Electrochemical impedance spectroscopy also showed that the corrosion charge transfer resistance(R_ct)of the PPy film prepared in CH₃NO₂ was the largest,the resistance to the movement of corrosive ions was the largest,and the protection time of the stainless steel substrate was the longest.To explore the influence of the concentration ratio of doped ions Na ₂MoO₄ and Na₂WO₄ on the preparation of PPy and the corrosion resistance of stainless stee l substrate.The effect of the concentration of Na₂MoO₄ and Na₂WO₄ on the corrosion inhibition efficiency of stainless steel substrate in 0.1mol/L citric acid?CA?was studied by using the electrodynamic polarization curve.The results showed that the self-corrosion current density of stainless steel was the lowest in the CA solution containing 0.024mol/L Na₂MoO₄+0.006mol/L Na₂WO₄.Cyclic voltampere curve indicates that the concentration of Na₂MoO₄ increases and the concentration of Na₂WO₄ decreases,which is more conducive to the formation of passivation film on the surface of stainless steel substrate.Potentiostatic method was used to prepare the PPy membrane,and doping of MoO₄^2-and WO₄^2-in the solution would reduce the polymerization rate of pyrrole.Cyclic voltammetry was used to study the REDOX activity of PPy in 3.5wt%NaCl and 0.1mol/L H₂SO₄.The results showed that SS/PPy?Na₂MoO₄:Na₂WO₄=4:1?membrane had the best stability and the highest membrane activity.The open-circuit potential-time curve in 3.5wt%NaCl showed that during immersion,the PPy prepared in pyrrole solution with different concentration ratios of MoO₄^2-and WO₄^2-could maintain a high electrode potential,but the SS/PPy?Na₂MoO₄:Na₂WO₄=4:1?membrane showed the slowest decrease in potential.The electrochemical impedance spectra in 3.5wt%NaCl showed that the film resistance and REDOX charge transfer resistance of SS/PPy?Na₂MoO₄:Na₂WO₄=4:1?were the highest,and did not change significantly with the increase of immersion time.The REDOX charge transfer resistors of SS/PPy?Na₂MoO₄:Na₂WO₄=1:1?and SS/PPy?Na₂MoO₄:Na₂WO₄=1:4?decreased with the immersion time.