tailieunhanh - Electrochemical study of electroactive poly (5-hydroxy-1,4-naphthoquinone-co-5-hydroxy-3-acetic acid-1,4-naphthoquinone) by impedance spectroscopy

The conducting polymer poly(5-hydroxy-1,4-naphthoquinone-co-5-hydroxy-3-acetic acid-1,4- naphthoquinone) with electroactive quinone group was investigated by Electrochemical Impedance Spectroscopy (EIS) in aqueous medium. The evaluations of parameters of equivalent circuit in term of applied potential were considered. The simulated EIS data presented a good agreement with the results obtained by other electrochemical methods. | Journal of Chemistry Vol. 42 4 P. 497 - 500 2004 ELECTROCHEMICAL STUDY OF CONDUCTING ELECTROACTIVE POLYMER POLY 5-HYDROXY-1 4-NAPHTHOQUINONE -CO- 5-hydroxy-3-Acetic ACID-1 4-NAPHTHOQUINONE by ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY Received 3rd 2003 TRAN ĐAI LAM Faculty of Chemical Technology Hanoi University of Technology SUMMARY The conducting polymer poly 5-hydroxy-1 4-naphthoquinone-co-5-hydroxy-3-acetic acid-1 4-napht ho quinone with electroactive quinone group was investigated by Electrochemical Impedance Spectroscopy EIS in aqueous medium. The evaluations of parameters of equivalent circuit in term of applied potential were considered. The simulated EIS data presented a good agreement with the results obtained by other Voltammetries. I - INTRODUCTION Electrochemical methods such as Cyclic Voltammetry CV Differential Pulse Voltammetry DPV Square Wave Voltammetry SWV through large perturbations by imposing potential steps or potential sweeps on the studied system lead the system to the state far from equilibrium. The obtained response is normally transient. The principle of EIS is to introduce a small perturbation by the means of sinusoidal signal of small amplitude in order to obtain the response in quasi- stationary state. This method has many advantages among them the most important one is the ability to have precise measurements because the response may be indefinitely steady and the ability to distinguish processes that may occur in one reaction especially when their time constants are well separated 1 2 . Randles equivalent circuit for electronically conducting polymers ECP In general an electrochemical cell can be represented in terms of an equivalent circuit. A methods such as Cyclic and Differential Pulse frequently used is Randles circuit 3 . For an ECP the behavior in the high frequency HF and in the low frequency LF regions are similar to that of simple redox system. However when the frequency is decreased to very low values mHz the .