Preparation And Optimization Of PANI: Electrochemical Perfrmance

Conducting polymers are always the areas of research focus since the discovery in 1970s, which mainly depend on their excellent properties. However, PANI is the most prominent one among the conducting polymers. Nowadays, the energy problems have attracted much attention in the world, it is necessary to develop sustainable and renewable energy and the high-efficiency energy storage system. Supercapacitor is exactly the one, which can charge quickly and possess high energy/power density. Therefore, much attention have been payed to the fabrication of PANI-based supercapacitor electrode materials, and nanostructured PANI electrode materials have been prepared in order to improve the electrochemical performance and then to realize the potential application of PANI. Chemical oxidative polymerization is a convenient and practical method for the synthesis of PANI, and the polymerization condition would affect the properties of the resulting polymers, so it is significant to study the effect of process on the performance. What’s more, the poor cyclic stability of PANI is the core issues that scientist intend to work it out eagerly, thus study on the reason that led to the deterioration of cyclic stability would helpful to understand the properties of PANI and to prepare high-performance PANI electrode materials. In this dissertation, the variation of properties of PANI depend on different polymerization condition and process were studied just by changing the oxidant/monomer ration, washing process and oxidant. Additionally, PANI electrode was fabricated by a dip and coating method, and XPS was applied to study the surface element content changes before and after the CV cycling, indicating some chemical or physical process might be ascribed to the reason of the deterioration of PANI.The specific contents were shown as follows:Firstly, a series of PANI and PPy have been prepared through traditional chemical oxidative polymerization using different mole ratio of APS/monomer. The change of the yield, conductivity, thermal stability, capacitance and cyclic stability with different APS/monomer have been studied, and the effect of washing process also have been considered. It was found that electrical conductivities and specific capacitances were depend on the APS/monomer mole ratio. The capacitance achieved the maximum for both polymers when the APS/monomer mole ratio was set at 0.5, in addition, the cyclic stability also better than the others, so the 0.5 was considered as the optimal O/M ratio.Secondly, the nanostructured PANI have been prepared by rapidly mixed polymerization via using three kinds of oxidants. Namely, ammonium peroxydisulfate (APS), H2O2/Fe2+ and FeCl3. The variation of morphologies, yield, electrical conductivity and electrochemical performance with the changing of oxidants and reaction times were investigated. As a result, PANI prepared with APS or FeCl3 were all nanofibers while the one prepared with H2O2/Fe2+ was nanorods. At the same time, the reaction times have little effect on the morphology of PANI prepared with APS and the length of PANI nanofibers prepared with FeCl3 would prolong with the extension of reaction times. The electrochemical test showed that the capacitance of PANI prepared with APS was the highest than that of the PANI prepared with the other two oxidants, not only the capacitance but also the yield, conductivity were also the highest, indicating that the APS is suitable for the polymerization of aniline.Thirdly, PANI have been prepared by rapid mixing polymerization using FeCl3 as oxidant. The obtained product was subjected to dedoping-doping process and coated onto a stainless steel mesh via a dip and coating method, then the electrode was test through CV cycling in a three electrode system, finally the surface of the electrode was characterized by XPS to investigate the change of elements content. The result showed that the electrolyte ion would exchange with the dopant during the charge-discharge process because the sulfur content increased with the increasing of cycle numbers, while the chlorine content decreased. In addition, the PANI chains might be oxidized or hydrolyzed at the same time, since the oxygen content increased after cycling. Therefore, the deterioration of PANI might be ascribed to the ion exchange and oxidation-hydrolysis process.