Electrochemical thin film deposition of polypyrrole on different substrates
Introduction
Since polypyrrole was first electrochemically synthesized more than two decades ago by Diaz et al. [1], it has been intensively investigated. Polypyrrole is an intrinsically conducting polymer, and its thin and plastic film has many possible applications [2] such as capacitors [3], electrochromic devices [4], anti-corrosive coatings [4], batteries [5], actuators [6] and sensors [7]. The advantages of electrochemical deposition of polypyrrole are that films can be prepared simply with one-step procedure and exact control of thickness. There have been many works dealing with preparation of thin polypyrrole films [8] and influence of the preparation conditions on the properties of electrochemically polymerized polypyrrole. The preparation conditions studied include deposition current, deposition potential, and composition of deposition solutions. However, there are needs to further investigate effects of different substrate electrode materials on properties of polypyrrole films. Moreover, some important applications of polypyrrole such as batteries, chemical and biological sensors are used in aqueous solutions experienced instability problems [9], [10], and also require development of robust polypyrrole films stable in aqueous solution.
In this study, we investigated electrochemical deposition of polypyrrole with different substrate electrode materials. The screen-printing microfabrication technology has advantages of flexibility, low cost, high reproducibility and high-throughput mass production, and thus is widely used in electronic components, energy storage systems and electrochemical sensors. Carbon inks are preferred materials for screen-printed electrodes due to their extremely low cost. Screen-printed carbon electrodes were evaluated for polypyrrole deposition in this report. We particularly addressed the problem of polymer instability in aqueous solutions and identified the influence of substrate materials on polypyrrole stability.
Section snippets
Experimental
EG&G PAR-273A potentiostat was used to conduct cyclovoltammetry and electrolysis experiments for polypyrrole deposition. Solartron 1260+1287 were used for impedance and cyclic voltammetry measurements. Glassy carbon electrode (3-mm diameter, CHI), gold electrode (3 mm, CHI) and homemade carbon composite electrodes, fabrication method is described later, were used as working electrodes. The working, reference (Ag/AgCl) and auxiliary electrodes (Pt sheet) were placed in 10 ml beaker cell for
Effect of deposition methods on polypyrrole films
CV, galvanostatic and potentiostatic depositions were carried out to investigate the effects of deposition methods on properties of polypyrrole thin films. The thickness of polypyrrole is determined by the electric charge passed during the electrochemical polymerization [8]. The film thickness was made identical to each other for comparison by controlling the same electric deposition charge of 0.42 C/cm2. All investigation works on deposition methods were done with glassy carbon electrodes. The
Conclusion
The results show that galvanostatic deposition of polypyrrole film could produce highest electrochemical reactivity in comparison to cyclic voltammetry and potentiostatic deposition methods, the conductive films on all substrates exhibited p-type conjugate polymer characteristics, and different electrode substrate materials have influences on stability of electrochemical polypyrrole thin films deposited on different substrates. The results also demonstrate that instability might be caused by
References (11)
- et al.
J. Power Sources
(1994) - et al.
Synth. Met.
(1980) Synth. Met.
(1995)- et al.
Chem. Rev.
(1997)