Preparation And Electrocatalytic Activity Of Conducting Polymers

Conducting polymers, which exhibit a wide range of novel electrochemical and chemical properities, have been employed in a variety of applications, such as batteries, sensors, antistatic coatings, electrocatalysts and so on. Conducing polymers, such as polyaniline (PAN) and polypyrrole (PPy), are cheap and can be easily prepared. One of the most important properties of the conducting polymers is their ability to catalyze some electrochemical reactions. In this paper, electrocatalytic activity of conducting polymers on electrooxidation of small organic molecules and amino-acids has been studied, including the following five parts.A novel copolymer of polyaniline-poly(propylene oxide) (PAN-PPO) film is prepared by cyclic voltammetry in this paper. The electrochemical copolymerization mechanism of PAN-PPO has been discussed. PAN-PPO is characterized with SEM and thermogravimetric analysis. In addition, the electrocatalytic activity of PAN-PPO for electrooxidation of methanol and formic acid has been investigated. Results show that under the samilar conditions, polymerization rate and conductivities of PAN-PPO are higher than those of PAN. The structure of PAN-PPO is a cross-linked network, composed of many uniform and regular nano-fibers with diameter less than 70 nm. The degradation temperature of PAN-PPO is a little lower than that of PAN. In comparison with PAN, PAN-PPO shows a high electrocatalytic activity for electrooxidation of methanol and formic acid.The paper has demonstrated the preparation and electrocatalytic activity of PAN and PAN-PPO prepared in ionic liquids, such as HEImTfa, BMImHSO₄ and BMImH₂PO₄. PAN and PAN-PPO are characterized with SEM. In comparison to PAN prepared in H2SO4 solution, PAN prepared in HEImTfa (PAN-HEImTfa) is composed of significantly regular nano-particles and shows a high electrocatalytic activity on electrooxidation of formic acid, formaldehyde and oxalic acid. PAN-PPO can be prepared in BMImHSO₄ by cyclic voltammetry (PAN-PPO-BMImHSO₄). It is composed of nanofibers with diameter less than 80 nm and can electrolyze the electrooxidation of oxalic acid. PAN-PPO can also been synthesized in ionic liquid BMImH₂PO₄ (PAN-PPO-BMImH₂PO₄). It is dense and composed of the nano-fibers about 100 nm. The electrocatalytic activity of PAN-PPO-BMImH₂PO₄ on oxidation of oxalic acid is also high and stable. Electropolymerization of conducting polymers in ionic liquids is related to the viscosity of ionic liquids. The viscosity order of ionic liquids is BMImH₂PO₄＞BMIHSO₄＞HEImTfa, and the easiness order of electropolymerization in ionic liquid is HEImTfa＞BMIHSO₄＞BMImH₂PO₄. The diameter order of conducting polymers prepared in the ionic liquids is PAN-PPO-BMIH₂PO₄＞PAN-PPO-BMIHSO₄＞PAN-HEImTfa, and the electrocatalytic activity order is PAN-HEImTfa＞PAN-PPO-BMIHSO₄ PAN-PPO-BMIH₂PO₄.Conducting polymers can be used as supports for platinum catalyst panicles deposition. With the synergistic effect of conducting polymers and platinum panicles, the electrocatalytic activity can be greatly improved and use of platinum can be decreased. In this paper, Pt/PAN-PPO is prepared by Pt deposition onto a pre-synthesized PAN-PPO film (Pt/PAN-PPO). The diameter of Pt panicles on PAN-PPO is about 60 nm. The electrocatalytic activity of Pt/PAN-PPO has been studied on the electrooxidation performance of lysine and glycine in sulfuric acid solution. Pt/PAN-PPO shows high electrocatalytic activity on electro-oxidation of lysine and glycine, and the cycling number of Pt on PAN-PPO should be less than 9.PPy has been prepared in ionic liquid HEImTfa (PPy-HEImTfa). The influences of polymerization method and support electrode on polymerization rate, morphological structure and electrocatalytic activity of PPy-HEImTfa are investigated. Polymerization rate and the electrocatalytic activity of PPy-HEImTfa by cyclic voitammetry on Pt are higher than those on stainless steel, and the particle diameter of PPy-HEImTfa on Pt is less than that on stainless steel. In addition, on the same Pt support electrode, the panicle diameter of PPy-HEImTfa prepared galvanostatically is much less than that by cyclic voltammetry,Carbon nanotube (CNT) owns excellent conductivity, high stability and good mechanical properties. Electropolymerization of PPy/CNT composite is carded out using cyclic voltammetry. The electrocatalytic activity of PPy/CNT composite has been studied in this paper. Results show: PPy/CNT prepared on Pt exhibited excellent electrocatalytic activity for electro-oxidation of oxalic acid. In addition, electrocatalytic activity of PPy/CNT on Pt is better than that on stainless steel.