Polyaniline as cathodic material for electrochemical energy sources (original) (raw)
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About the capacitive currents in conducting polymers: the case of polyaniline
Journal of Solid State Electrochemistry, 2019
In the present work, we review the occurrence of capacitive currents in conducting polymer and, particularly, in the electrochemical response of polyaniline film-coated electrodes Firstly, we present and discuss the differences between the electrical double-layer capacitance and the so-called pseudocapacitance. Then, we discuss the capacitive behavior of Pani as studied by a variety of electrochemical (cyclic voltammetry, electrochemical impedance spectroscopy) and spectroscopic techniques (epr, UV-visible). Understanding the capacitive behavior of polyaniline (Pani) becomes essential not only from an academic point-of-view but also from a technological perspective, as Pani has been extensively employed for the construction of materials for supercapacitors.
2005
Polyaniline (PANI) films have been deposited on stainless steel (SS) substrate by galvanostatic, potentiostatic and potentiodynamic methods. Electrochemical impedance spectra of the electrodes have been analyzed using a transmission line model consisting of two rails of finite resistances. The impedance spectra of the galvanostatically prepared electrodes are similar in shape to those of potentiostatically grown electrodes. The resistance of aqueous pore (R aq) due to ionic doping-dedoping process is greater than the resistance (R p) of electronic chargetransfer on polymer chain. These parameters exhibit an increase in magnitude with thickness of PANI, as expected from the transmission line theory. The shape of impedance spectra of potentiodynamically grown PANI, however, is different and its R aq ≤ R p. The impedance parameters of potentiodynamically prepared PANI/SS electrodes have been found to depend on the sweep rate used for the deposition of PANI. Several possible explanations have been discussed to understand the influence of sweep rate during deposition on impedance parameters of the electrodes. In contrast to the behavior of PANI deposited by galvanostatic and potentiostatic methods, R p decreases with an increase in thickness of PANI deposited by the potentiodynamic method. The effect of concentration of aniline used for the deposition of PANI on impedance parameters has also been studied. The results of capacitance of PANI obtained from the ac impedance studies have been found to be comparable with those obtained from the cyclic voltammetric studies.
International Journal of Chemistry, 2018
The double layer capacitance of polyaniline (PANi)-coated electrode in acidic solution exhibited little frequency dispersion under the emeraldine (electrically conducting) state, while it showed large frequency dispersion under the insulating state. The former has a possibility of working as such an ideal capacitor that it may generate neither heat in iterative charge-discharge processes nor leakage of stored charge. The frequency dispersion is generally expressed by f-l for ac-frequency f and a constant l. This power law is ascribed to orientation of solvent dipoles rather than non-uniform distribution of ions. The value of l under the conducting state was close to zero, implying the orientation to be facilitated by less interaction of solvents. The less interaction was supported indirectly with strain-stress curves of PANi by atomic force microscopy. l-Values close to zero were retained even for thick PANi films.
Impedance and voltammetric studies of electrogenerated polyaniline conducting films
Synthetic Metals, 1994
Polyaniline thin films were electrochemically synthesized from aniline in three acids: sulfuric, hydrochloric and perchloric. Cyclic voltammetry was used in the electrosynthesis, and the relationship of voltammetric parameters and the properties of the conductive form of the films were investigated. The main tool for film characterization was impedance spectroscopy. Semiautomated plotting of three-dimensional Argand diagrams with a potential parameter was used for synoptic view of the system and nonlinear least-square data fitting was used for rigorous treatment. Charge storage capacity, resistance and changes in constant phase element parameters were analyzed in relation to the use of the three acidic media.
Electrochemical impedance spectroscopy (EIS) is an experimental method for characterizing electrochemical systems. This method measures the impedance of the concerned electrochemical system over a range of frequencies, and therefore the frequency response of the system is determined, including the energy storage and dissipation properties. The aim of this article is to review articles focusing on electrochemical impedance spectroscopic studies and equivalent electrical circuits of conducting polymers, such as polypyrrole, polycarbazole, polyaniline, polythiophene and their derivatives, on carbon surfaces. First, the conducting polymers are introduced. Second, the electrochemical impedance spectroscopic method is explained. Third, the results of EIS applications using equivalent electrical circuits for conducting polymers taken from the literature are reviewed.
Russian Journal of Electrochemistry, 2004
Electrochemical impedance spectroscopy is used to characterize thin p-doped polypyrrole (PPy) films in propylene carbonate (PC) solutions and poly(trifluorophenyl)thiophene (PTFPT), in solutions based on sulfolane (SF). It appears that the latter film is much less swelled compared to the former one. One consequence of this difference is that the PTFPT film shows a much higher bulk resistance compared to that for the PPy film. Another important consequence is that the swelling of the PTFPT film is essentially physically non-homogeneous. Two parallel, uncoupled paths, with different chemical diffusion coefficients, model the experimental results adequately. In order to quantify the impedance spectra for both polymer films, we use a model proposed by Rubinstein et al. explaining the difference in the diffusion coefficients of within a thin Nafion film. The model can also predict the impedance spectra for composite powdery electrodes containing different particle sizes, such as composite cathodes and graphite anodes used in lithium batteries.
In this study, aniline (ANI) was electropolymerized on three different electrodes; platinum (Pt), glassy carbon (GC), and carbon fiber micro electrodes (CFME) in acid aqueous solution (0.5 M H2SO4) by cyclic voltammetry (CV). Electrode / PANI / electrolyte system was studied by electrochemical impedance spectroscopy (EIS). The results indicate the choice of electrode has a little effect on anodic (Ea) and cathodic peak potentials (Ec) during electropolymerization process. An equivalent electrical circuit (R(Q(R(C(R(C(RW))))(CR)) was proposed for PANI on three different electrodes. The highest low frequency capacitance (Csp=120 mF / cm2) was obtained for PANI / Pt electrode compared to PANI / CFME (239.1 μF / cm2) and PANI / GC (38.9 μF / cm2) electrode. However, the highest double layer capacitance was obtained for PANI / CFME (Cdl = 190.9 mF / cm2) than Pt electrode (58.2 mF / cm2) and GC (24.3 mF / cm2).
Impedance spectroscopy in electrode/electrolyte interface investigations
Solid State Ionics, 1994
Electrochemical characteristics of two propylene carbonate-encapsulating polymer electrolytes based on a polyester of 3,3'thiodipropionic acid and tri-ethylene glycol, and on a bis-amino poly (ethyleneoxide) PEO-poly (propyleneoxide) (PPO) eopolymer, respectively, are compared to those of a polymer network based on PEO and a styrenic macromonomer of PEO, with particular emphasis on Li/polymer electrolyte interface stability.