High Performance Conducting Polymer Coatings for Enhanced Electrochemical Properties

Abstract

The dissertation focuses on performance of conducting polymer as a coating that can used as anticorrosive agent, ion-exchange membrane and electrodes for energy storage devices. There are mainly two ways to synthesize conducting polymers: chemical and electrochemical polymerization. The most commonly used method is chemical oxidative polymerization. However, the conducting polymer produced via chemical method can have impurities because of the presence of oxidants. This can affect the uniformity of the coating and as a result their performance. In this study, we adopted electrochemical polymerization to improve the purity of conducting polymer coating. Besides, the polymerization time can be reduced to few minutes instead of several hours. Moreover, we can control the thickness of the coating and can have in-situ deposition on any surface. There are several factors such as electrolyte composition, concentration of monomer, electrochemical technique and deposition potentials that affects formation of conducting polymer film that directly influences its homogeneity and compactness as a coating and its electrochemical performance. Adhesion is important for good coating thus cannot be overstated. There are four projects covered in this dissertation. The first project (chapter 2) discussed the effect of various acidic medium on passivation of steel and electropolymerization of polypyrrole. The coating morphology was compared when coating produced using various doping agents. Further, the integrity of the coating was evaluated by testing their adhesion and was enhanced. Additionally, the harsh bleach treatment was performed multiple times and thermal stability of the produced coating was tested. Moreover, the corrosion performance of the coating was investigated in salt solution (mimicking marine environment). The second project (chapter 3) focuses on the electropolymerization of polyaniline on stainless steel. The reversible change in oxidation states of polyaniline was used to study the electrochemical exchange of anion from the produced coating. Additionally, the coating adhesion was evaluated and enhanced using bio-adhesives. Further, this study was applied to study the anion transport from the solution to the coating to understand the electrochemical activity of the polyaniline. The third project discusses the use of sulfur based conducting polymers as anticorrosive coatings. The thiophene derivatives have limited work in the field of corrosion therefore, poly (3,4-ethylenedioxythiophene) was used to study its anticorrosive properties for steel. The electropolymerization potential was optimized for better corrosion performance. The effect of counter-ion used for poly (3,4-ethylenedioxythiophene) as anticorrosive coating was studied. The fourth project focused on the effect of various dopant acids on electrochemical performance of polyaniline as electrode material for pseudocapacitors. The electrochemical testing involves charge storage, cycling stability that can be affected by size of the dopant used.