Alternative explanation of asymmetry in cyclic voltammograms for redox reaction of poly(3-methylthiophene) films in acetonitrile solutions (original) (raw)
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Journal of Applied Electrochemistry, 1988
Theory is presented for the interpretation of cyclic voltammetric and chronoamperometric measurements made on electrodes modified by being covered with an insoluble layer of a polymer containing electroactive pendant groups. It is assumed that the redox behaviour of the film is non-ideal and that the activity coefficients of the components of the redox couple can be reasonably modelled by regular solution theory. In this way non-ideal behaviour is interpreted in terms of a single 'interaction parameter'. It is found that a wide range of cyclic voltammograms for diverse polymer systems reported in the literature can be thus very satisfactorily described. We also report the synthesis of the novel polymer poly(4-vinyl-triphenylamine), PVTPA, and describe and interpret the behaviour of electrodes coated with this polymer during electro-oxidation in acetonitrile solution. Excellent agreement with the regular solution theory is found. Chronoamperometric data for the related polymer poly(4-vinyl-4',4"-dibromotriphenylamine) is also reported and found to give good agreement with the theory.
Journal of Applied Polymer Science, 2016
The effect of the electropolymerization of seven poly(3-methylthiophene) (P3MT) films in the same used monomer solution have been investigated. Cyclic voltammetry, UV-visible, scanning electron microscopy, and electrochemical impedance measurements were carried out to understand the effect of the solution reusing on the polymer electrochemical properties. The obtained results show that, as the solution is reused, the polymerization rate increase and the charge in of the cyclic voltammetry decrease. Besides, there are important changes in the sample's morphologies, with the increase of the synthesis number, the amount of fibers increase and this leads to lower the conductivity of the polymer film. In agreement to this, the impedance data analysis shown important changes in the interfacial electronic parameters, i.e., changer transfer resistance and double-layer capacitance, used to describe the films.
Cyclic spectrovoltammetry: a new method to study the redox processes in conductive polymers
Synthetic Metals, 1992
We describe a new spectroelectrochemical method called cyclic spectrovoltammetry. The essence of the method is the application of factor analysis to the spectra recorded during a voltammetric measurement. Factor analysis enables us to use all the information contained in the spectra, a considerable improvement to former techniques employing data at only some wavelengths. When applied to poly(3-methylthiophene), two successive oxidation processes can be observed during the single oxidation peak in the cyclic voltammogram. The usefulness of the method in cases where voltammetric measurements are difficult to interpret is also demonstrated.
Electrochimica Acta, 2013
This work characterises the electropolymerisation of 3-methoxythiophene and presents an electrochemical study of poly(3-methoxythiophene) by cyclic voltammetry using different electrolytes in solvent mixture of water-acetonitrile (3:1, v/v) at 25 • C. Simultaneous measurements of the mirage effect and the quartz microbalance were also performed. This study evaluated the influence of cations on the electrochemical properties of monomers and polymers and allowed us to observe an anomalous behaviour of the synthesised polymer in the presence of potassium ions (K + ) when compared with other cations. The reversibility of the polymers was also evaluated with respect to the various electrolytes and was observed the influence of the polymer film thickness (deposited mass) on its electrochemical properties.
Theoretical and Experimental Chemistry, 2010
An in situ spectroelectrochemical study was carried out on the formation of 3-methylthiophene oligomer radical-cations (monomer, dimer, and trimer) and the 3-methylthiophene dihydrocation in the solution bulk during the electrochemical synthesis of a poly-3-methylthiophene coating on a conducting glass electrode. A dependence of the concentration of products formed on the cation radius (Li + and Na + ) and nature of the anion (ClO 4 and BF 4 -) of the base electrolyte was established. The conversion of charged components into neutral dimers and tetramers of 3-methylthiophene after termination of the anodic polymerization was shown in accord with reported results on the electrochemical polymerization of thiophenes.
Electrochimica Acta, 2003
Poly(3,4-dialkoxythiophene) films with different length of alkyl chain (1,3 and 8 carbon atoms) were obtained on Pt and ITO electrodes from the monomer solutions in acetonitrile by cyclic voltammetry (CV). The properties of the resulting films were studied by electrochemical methods, UV Á/Vis, FTIR and NMR spectra. The CVs were correlated with differential cyclic voltabsorptograms (DCVA) recorded at the absorption maxima to explain the shape of the voltammograms of the polymers studied, dependent on the alkyl-chain length in alkoxy group. The presence of the zones of different crystallinity in the polymer film was postulated. Significant influence of the type of the solvent on asymmetry of the cyclic voltammograms for the polymer doping Á/undoping has been discussed in terms of the solvent interaction with radical cation (polaron) delocalized on the alkoxy side groups. The polaron delocalization was proved by 1 H-NMR spectra. Appearance of infrared activated vibrations (IRAVs) in the range 1500 Á/600 cm (1 and a characteristic electronic band at 3300 cm (1 at the polarization potential '/0.25 V versus Ag/Ag ' and their gradual changes upon further polymer oxidation were interpreted in terms of evolution of different charge carriers in lightly and heavily doped polymer.
Electrochimica Acta, 2014
Specific features of voltammetric studies with modified electrodes are subject of the consideration performed in the review. Basing on the approaches developed in preceding works, three groups of problems are discussed. The first one concerns a regular treatment of quasi-equilibrium cyclic voltammograms of modified electrodes. It is emphasized that singular points of such curves and their form depend on the system parameters (charges of immobile charge carriers, binding of counter-ions with the film fragments). As regards the second group of problems, its existence results from possible effects of the film porosity on the rates of reduction/oxidation processes with participation of particles capable to react on the film/solution interface. The main conclusion followed from the performed discussion is in the possibility of appearing the limiting currents not controlled with tested particles diffusion within the adjacent electrolyte. In scope of the third group of problems, the tested particles reactions on the electrodes covered with metal-containing polymer films are considered. As follows from the proper analysis, the current-voltage curves of these processes are described with the well-known equations of the electrochemical kinetics. Validity of the obtained conclusions is illustrated with the corresponding experimental results.
Electrochemical Properties of Overoxidized Poly-3,4-Ethylenedioxythiophene
Russian Journal of Electrochemistry, 2018
The properties of poly(3,4-ethylenedioxythiophene) (PEDOT) films were studied electrochemically at high positive potentials (from-0.3 to 1.5 V relative to the Ag/AgCl electrode). A cyclic voltammetry (CV) study revealed the range of potentials (up to 1.3-1.5 V) where the cycling leads to significant changes in the electrochemical, structural, and morphological properties of the polymer film due to overoxidation. When the upper cycling potential E up exceeded 1.4 V, the anodic current significantly increased during the first cycle and then decreased, which suggests a loss of the electroactivity of the polymer and degradation of its properties. In the high-frequency region of the impedance spectra of the PEDOT films, a semicircle appears after overoxidation, which indicates a notable increase of the charge transfer resistance in the system, in contrast to the films subjected to potentiodymanic processing in a limited range of potentials from-0.3 to 1.3 V. The effect of overoxidation on the polymer morphology was studied by scanning electron microscopy. The chemical state of elements in the structure of the polymer film was determined by X-ray photoelectron spectroscopy. The obtained data indicate that-S=O groups formed at the thiophene sulfur in the polymer.
Electrochimica Acta, 2003
Study by EQCM on the voltammetric electrogeneration of poly(neutral red). The effect of the pH and the nature of cations and anions on the electrochemistry of the films Abstract Generation of poly(neutral red) films has been studied by means of the simultaneous measurements of current Á/potential and mass Á/potential curves during cyclic voltammetry (CV) experiments. It has been proved that the presence of molecular oxygen in the solution increases the amount of polymer deposited on the electrode. Otherwise, using the mass/charge ratio it is possible to obtain quantitative information about the electrodeposition by different procedures. It is observed that this ratio decreases when the amount of polymer electrogenerated increases, except when the polymer is not reduced and oxidised after its electrogeneration. The study of poly(neutral red) by CV and quartz crystal microbalance in solutions without monomer allows to discern between the role of different charged species which are present in the solution: salt cations (Cs ' , Na ' and K ' ), salt anions (NO 3 ( , Cl ( , I ( and Br ( ) and hydrated protons that can compensate electrical charge within the film during electrochemical processes. #
Chemistry of Materials, 1998
The electrochemical doping and undoping processes of poly-(3,3′′-didodecyl-2,2′:5′,2′′terthiophene) (poly(33′′DDTT)) were studied by scanning electrochemical microscopy (SECM) to characterize the electron transfer of the polymer with a redox mediator in solution when the polymer was at different oxidation levels. SECM showed that electron exchange processes of oxidized poly(33′′DDTT) were localized at the polymer/solution interface rather than inside the film. Poly(33′′DDTT) in the neutral state did not allow the permeation of redox species to the underlying metal and behaved like a completely passivating film. A modified expression for the effective electron-transfer rate constant, k eff , was obtained by grouping the terms concerned with charge transport across the polymeric film, and the values of k eff were calculated from SECM approach curves. The values of k eff for the electron transfer between poly(33′′DDTT) film and methyl viologen (MV +/2+ ) as the redox couple ranged between 10 -5 and 10 -1 cm s -1 , depending on polymer thickness, substrate potential, and MV concentration. Under the proper experimental conditions, k eff could be directly correlated with the conductance of the polymer film, where poly(33′′DDTT) thin films in the conducting state showed a metallic character.