An Investigation Of Preparation And Properties Of Polyaniline Complex Film Modified Electrode Material

Polyaniline (PAn) and its complex film were used to modify a platinum (Pt) electrode. The preparation and properties of PAn film and complex film modified electrode material were studied in this paper. The influencing factors on the PAn film's physical character and cyclic voltammetry character were studied by selecting electrochemical methods to synthesize PAn film. These factors include upper scanning potential, scanning rate and polymerization electric quantity in cyclic voltammetry method; polymerization potential in potentiostatic method; current density in galvanostatic method; pulse anodic potential (Ea), monomer density, pulse numbers and different ta in the same synthesis time in pulse square wave method, and so on. The density of acid medium and the doping of chloride ions also had great effects on PAn film's proterties.In cyclic voltammetry polymerization, each peak potential varied with the change of polymerization electric quantity and upper scanning potential. The reversibility of the three couples of peak of the PAn film changed worse with the increase of polymerization electric quantity, upper scanning potential and scanning rate. When upper scanning potential was at 0.95V, the scanning rate was below 60mV/s. In the preparation of PAn film by potentiostatic method, each peak potential did not vary with the variation of polymerization potential, while each peak current density changed with the variation of polymerization potential. In order to get a PAn film with three couples of oxidation-reduction peak on CV curves at 180,480 and 720mV, respectively, the potentiostatic polymerization should be used and the best polymerization potential was 0.9 V. In galvanostatic polymerization, when at high current density, ρi>0.1 mA/cm2, there were three couples of oxidation-reduction peak appeared on CV curve of PAn film at about 180, 500 and 900mV, respectly. While at low current density, ρi≤0.1 mA/cm2, there were only two couples of oxidation-reduction peak appeared on CV curve at about 900 and 200mV, respectively. The PAn film was even ,fast and also had a stable property at low current density, ρi>0.1 mA/cm2, and the best polymerization current density was 0.042 mA/cm2.The chloride ions with a small radius were easily doped to molecule chain. This doping contributed to improvement of the PAn film's properties, and increased the catalyze current at half oxidized state(0.4～0.7V). The PAn film prepared in the same condition exhibited different properties in the media with different pH values. The polyaniline has a better oxidation-reduction property in acid environment. The reversible oxidation-reduction reactions might be occurred between the different oxidation state. With the increase of solution pH value, the PAn film's electrochemical activity decreased. When the pH value was greater than 3, its electrochemical activity disappeared gradually.In pulse square wave polymerization, when the PAn film prepared at the potential of Ea=0.8V, the peak current reach to maximum value, while ΔEp was minimum.In order to improve the mechanical strength of PAn film, Nafion film and PVC film were used as basement film to prepare Pt/ Nafion and Pt/PVC electrode by means of a "overlay" method. Polyaniline was prepared by potentiostatic method in the loose layer of Nafion and PVC surface. And then the Pt/Nafion/PAn and Pt/PVC/PAn complex electrodes were got. Basement film not only increased the mechanical strength of PAn film, but also improved the adherence between PAn film and Pt and increased the electrochemical activity of PAn film. The polymerization potential, the immersion time of supporting film in aniline solution, the thick of supporting film have great effect on the properties of complex electrode.