Investigation of Polypyrrole Degradation Using Electrochemical Impedance Spectroscopy

Abstract

In this paper, the electrochemical degradation of polypyrrole film was studied by means of overpotential application. The overpotential was 0.58 V versus SCE, and after every 5 min of application of 0.58 V, a cyclic voltammogram was recorded in the range of -0.7 to 0.5 V as well as an electrochemical impedance spectroscopy and electrochemical quartz crystal microbalance (EIS and EQCM). The main characteristic is the huge increase in the charge transfer resistance (r(ct)), which indicates that the insertion process of ions in the polymer matrix is hindered by the electrochemical degradation. Once the process of insertion is damaged, the number of intercalated ions in the matrix should decrease, which is expressed by the low-frequency capacitance, which is proportional to the number of intercalated ions in the polymeric matrix. The decrease of intercalated ions has an influence in the mass variation of the polymer film, which is confirmed by EQCM measurements.

Structural changes during the overoxidation of electrochemically deposited poly(3,4-ethylenedioxythiophene) films

“…At higher frequencies an arc can be identified which can be observed more clearly in the spectra recorded after overoxidation (after repetitive cycling of the electrode potential between -0.3 and 1.5 V vs. SCE). The increase of the charge transfer resistance with the level of degradation is in accordance with the results for polypyrrole on Pt published in [57]. The decreasing capacitance and the increasing charge transfer resistance suggest that during (over)oxidation the electrochemical activity of the film decreases, and the charge transfer process at the metal/film interface becomes more hindered.…”

Photo-assisted electrodeposition of an electrochemically active polypyrrole layer on anatase type titanium dioxide nanotube arrays

“…From the 13 th scan, a rise of the current is observed as a function of the applied potential, and the shape of the voltammogram looks closer to the classical one observed on a conducting substrate during the electrochemical deposition of polypyrrole [18,19]. We must admit that the contribution of the photocurrent to the total current can now be neglected and In close agreement with the conclusion in Ref [14], we must admit that the PPy/TiO 2 -NTA junction shows higher electroactivity in a wide potential range, than uncovered TiO 2 -NTA layers.…”

“…8, red triangles). Between -0.6 V vs. SCE and 0.2 V vs. SCE, they exhibit the typical shape of the EIS diagram reported in [18,22,23] in the case of PPy deposited on a conducting surface, with a semi-circle in the high frequency range and a diffusion feature in the low frequency range. The capacitance associated with the HF semicircle was roughly estimated using the same equivalent circuit as for PPy electrodeposited in dark, and its evolution as a function of applied potential is also reported in Fig.…”

Complementary study on the electrical and structural properties of poly(3-alkylthiophene) and its copolymers synthesized on ITO by electrochemical impedance and Raman spectroscopy

“…In such cases, a second semicircle appeared at higher frequencies, probably related to the characteristics of interfacial processes in terms of resistance in the ITO/polymer interface, characteristics not found in these copolymers on platinum [3,23].…”

“…Marchesi et al [23] using CV and EIS techniques to understand the electrochemical degradation processes found, the decrease in the redox capacity of polymers with an increase in the number of voltammetric cycles and with the data from the Nyquist graph obtained by EIS, related to redox capacity variation with mobile ions along the polymer chain. Benedict et al [18] determined the variation in the resistivity values (R CT ) and double layer capacitance (C DL ) of P3MT and P3OT and their copolymers with the PDFA through the EIS in OCP and overpotential, and with Bode-phase diagram related to the two constants of the phase where the charge transfer processes occurred involving the radical and dication cation species.…”