Conductive Polymer Composite Film Electrodes And Their Electrochemical Properties

Conductive polymers have been applied in many fields such as electrochemical catalysis, electrode materials, sensors, corrosion inhibition for metal and etc due to their excellent physical and chemical properties. Polyaniline and polypyrrole have been the most studied polymers because of their rich meterial sources, convenience of preparation, high conductivity and environmental stability. Recently the composite materials containing polyaniline and polypyrrole have been paid much attention to because of the poor mechanical properties of pure conductive polymers. On one hand the conductive polymer composite materials hold their primary properties, and on the other hand their mechanical properties have been improved at a certain extent. Thus preparing functional conductive polymer composite materials and studying the properties of their modified electrode are very meaningful.We use polysulfone as a basic material to prepare two kinds of polymer composite film electrodes by electrochemical method in this research: Several experimental methods are applied to test their structure and properties, their electrocatalytic activity, especially the electrocatalytic ability for methanol oxidation after platinum modification. This thesis consists five chapters as follows:Chapter one: The correlative content of conductive polymers, conductive polymer electrodes and direct methanol fuel cells(DMFC) are summarized.Chapter two: The conception, principium and the data analysis of Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy(EIS) which are referred in this research are summarized and discussed.Chapter three: Polypyrrole(PPY)/polysulfone(PSF) composite film electrodes were electropolymerized by cyclic voltammetry technique in hydrochloric acid aqueous solution. The morphology and chemical component of the composite films were characterized by SEM and FTIR respectively, and the electrochemical properties of the composite film electrodes were investigated by electrochemical methods. The results of SEM and FTIR show that the composite film has bi-layer structure with asymmetrical microstructure, where the inner layer (in contact with the working electrode) comprises conductive polypyrrole with smooth, dense, and less porous structure, while the outer layer(in contact with the electrolytic solution) is composed of non-conductive polysulfone with a lot of small pores. The data of electrochemical experiments indicate that the composite film electrode has wide electrochemical window and distinct electrocatalytic activity for hydroquinone(H2Q). The reaction of H₂Q on it is a kinetic limitation reaction, at the same time the oxidation peak currents have a linear relationship with the concentration of H₂Q in the range from 5mM to 30mM, this implies that the electrode has a potential to detect H2Q.Chapter four: Polyaniline/polysulfone(PAN/PSF) composite film electrodes were electropolymerized by cyclic voltammetry technique in sulfuric acid aqueous solution firstly, then the platinum(Pt) modified composite film electrodes were got by electrodepositing the Pt particles on it. The chemical component and morphology of composite films were characterized by FTIR and SEM respectively, EDS was applied to mensurate the Pt loading at the same time, then the electrochemical properties of the Pt modified PAN/PSF composite film electrodes were investigated by electrochemical methods. The results of FTIR, SEM and EDS show that the composite film has bi-layer structure with asymmetrical pores, and platinum particles are homogeneously dispersed in the porous polyaniline layer. The data of electrochemical experiments indicate that the platinum modified electrode has excellent electrocatalytic property for methanol oxidation, and the electrocatalytic property for methanol oxidation is very stable. The anodic oxidative peak currents of methanol about 0.65V are linearly proportional to the square root of scan rates between 10mVs^-1 and 100mVs^-1, which suggests that the electrocatalytic oxidation of methanol on modified electrode is a diffusion -controlled process.Chapter five: Polypyrrole/polysulfone(PPY/PSF) composite film electrodes with asymmetric bi-layer microstructure were prepared in pH=2.6 potassium chloride solutions firstly, then the platinum(Pt) modified composite film electrodes were got by electrodepositing the Pt particles on it. The electrocatalytic properties for methanol oxidation of the electrodes were investigated by electrochemical methods. The results show that the electrode has excellent electrocatalytic property for methanol oxidation, and the electrocatalytic property for methanol oxidation is very stable.