STUDY OF POLYPYRROLE FILMS MODIFIED WITH COPPER AND SILVER MICROPARTICLES BY ELECTROCHEMICAL CEMENTATION PROCESS

Abstract

ABSTRACT Electroactive polypyrrole (PPy) films obtained under potentiostatic electropolimerization from aqueous solutions of pyrrole doped with sulfate (SO 42- ) anions were modified by incorporation of copper (Cu) and silver (Ag) microparticles using electrochemical cementation process. The electrochemically deposited and dissolving processes metals (Cu and Ag) onto and from polypyrrole were investigated. The PPy-Cu and PPy-Ag electrodes were characterized by electrochemical techniques and scanning electron microscopy (SEM) analysis and the electrochemical response of these modified electrodes was compared to that of the unmodified polypyrrole electrode. The results indicate that two forms of metal, valence and elemental ones, can be formed on polypyrrole at a constant cathodic potential. However, only the valence metal can be left on polypyrrole at the anodic potential. The copper and silver particles interact with polypyrrole films involving a strong complex formation affecting its electrochemical behavior. Scanning electron microscopy measurements show that dendritic-like metal aggregates are formed on the film surface. The electrochemical experiments reveal that metal deposition on conducting polymer can be envisaged as an attractive method for the electrodes fabrication. Keywords: Polypyrrole, Electrochemical cementation, Copper and Silver microparticles.e-mail: alvaroangel@upbmonteria.edu.co1. 2. INTRODUCTIONThere have been many advances in the application of conducting polymer and it is certain that this tendency will continue, inevitably encouraging research to find improved properties. Conducting polymers have been investigated for use as the electrode materials for a number of applications, including rechargeable batteries, electrochemical sensors, etc. [1,2]. Among the conjugating conducting polymers, polypyrrole is the most representative one for its easy polymerization and controllable property of switching it between conducting and insulating states by doping and undoping counterions into polymer matrix, as well as its chemical and thermal stabilities. These characteristics make it widely used in microelectronic devices, batteries, and sensors [3,4]. In recent years, several developments in polymer coated electrodes that incorporate metal have been carried out. Composite materials consisting of metal aggregates and conducting polymers attract considerable interest for basic research because of their technological applications in heterogeneous catalysis, environmental science, microelectronics and magnetism. Moreover, it has also been found that the conducting and the sensing behavior of conducting polymers could be further improved by imbedding metal particles into the polymer matrix to form a metal polymer complex [5-7]. The polymer serves as a conducting matrix which supports, separates and stabilizes the metal clusters. Deposition of metal particles onto polymer modified films has been found to be useful in the field of electrocatalysis [8,9] and the electrodes have enhanced the selectivity and the sensibility of many interesting electroanalytical reaction and improved the function of amperometric biosensor and potentiometric sensor [10,11]. The incorporation of metal microparticles into polymer films can be accomplished by electrolysis (applied potential or applied current). Since the cementation process seems to be promising in the polymer modification concept [12-14] because its convenience, good economy, and the wealth of current plating knowledge [15]. In this process, the composite material is synthesized by the oxidation of the respective monomer and further deposition of the metallic species from an aqueous solution of the suited cation. The metal particles usually used for the modification of polypyrrole films are platinum, nickel complexes, rhodium and cobalt complexes [16-19]. Although several researchers had focused their studies on the modification of conductive polymers with metals and the characteristics of the prepared complexes [20-22]. Nevertheless, a detailed understanding of the electrodeposition process of metals onto the conductive polymers and the effect of the interaction of metal-conducting polymer about the polymer properties has yet to be developed. It is important to know the effects of the modification by incorporation of metals microparticles by cementation process on the electrochemical behaviour of the conducting polymers films. Hence, in the present work, we study the electrochemical behaviour of PPy modified with copper and silver microparticles by cementation process. The PPy electrodeposition was performed using sulfate anion as doping agent and after that the PPy films was formed in the electrodes surface, this was immersed in aqueous sulfate acid solution containing Cu