V. V. Kondratiev

Spectroelectrochemical study of poly-3,4-ethylenedioxythiophene films in the presence of different supporting electrolytes

Steady-state absorption spectra of poly-3,4-ethylenedioxythiophene (PEDOT) films at different oxidation degrees and their differential cyclic voltabsorptograms are studied in 0.1 M LiClO4, Bu4NBF4, and Bu4NPF6 solutions in acetonitrile. Three major absorption bands are obtained in the film electronic spectra: a complex band with a pronounced maximum at λ = 600 nm that corresponds to π → π* electronic transitions in reduced fragments of a PEDOT film and two absorption bands (at λmax = 850 nm and λmax > 1100 nm) corresponding to two oxidized film fragments. It is shown that the position and shape of absorption bands are practically independent of the nature of dopant anions, which points to the absence of pronounced interactions with positively charged polymer fragments. An attempt is made to analyze the obtained spectroelectrochemical data qualitatively to estimate the extinction coefficients and concentrations of absorbing particles and their variation in the course of redox processes.

Composite electrode materials based on conducting polymers loaded with metal nanostructures

The electrochemical and chemical methods for synthesizing conducting polymer-metal nanocomposite materials are considered as well as the main factors affecting the structure and electrochemical properties of these composites. The experimental data on the catalytic activity of conducting polymer–metal electrodes are analyzed in respect to several electrochemical reactions. The approaches to theoretical description of electrochemical processes on heterogeneous conducting polymer–metal electrodes are discussed and examples of experimental testing of applicability of the proposed the theoretical models are shown. The bibliography includes 335 references.

Morphological changes in electrochemically deposited poly(3,4-ethylenedioxythiophene) films during overoxidation

Electrochemical and morphological properties of thin poly(3,4-ethylenedioxy-thiophene) (PEDOT) films deposited on gold were investigated in aqueous sulfuric acid solutions. X-ray diffraction and electron microscopy were used for monitoring the morphological changes and structure evolution caused by overoxidation. The diffraction peaks of PEDOT became sharper and more intensive during the subsequent oxidation cycles. This indicates that besides the degradation of the PEDOT film, its crystallinity was gradually improved with increasing the number of oxidation cycles. These changes may result in the appearance of novel properties that may be advantageous for specific applications.

Gold electroless deposition into poly-3,4-ethylenedioxythiophene films

By electroless deposition of gold into poly-3,4-ethylenedioxythiophene (PEDOT) films, the composite films (PEDOT-Au) are synthesized. Their electrochemical properties are studied by cyclic voltammetric (CVA) method. It is shown that in contrast to the original PEDOT film, the CVA curves of composite PEDOT-Au films measured in the presence of chloride ions reveal additional redox peaks associated with the presence of gold particles. The loading of metal gold particles by its chemical deposition into the polymer film is quantitatively assessed using quartz crystal microbalance method. The film mass is shown to depend on the time of gold loading and its original concentration in solution. The gold particles are shown to be oxidized by a reaction of the first order with respect to chloride ions. Based on the results of voltammetric and microbalance methods, the formation of a poorly soluble gold oxidation product Au(I)Cl in chloride-containing solutions was inferred.

Effect of addition of a conducting polymer on the properties of the LiFePO4-based cathode material for lithium-ion batteries

Effect of addition of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) conducting polymer on the structure and properties of a cathode material based on lithium iron phosphate was studied. The X-ray diffraction method was used to examine the structure of lithium iron phosphate in a freshly prepared C-LiFePO4/C/PEDOTS:PSS composite material and in that subjected to a prolonged cycling. The chargedischarge characteristics of the cathode material of the conventional composition, which contains carbon black and poly(vinylidene fluoride) binder, and a new composition with addition of PEDOT:PSS were compared. The specific capacity of C-LiFePO4/C/PEDOT:PSS was 165 mA h g−1 (at 0.2C current), which substantially exceeds the specific capacity of the LiFePO4 material in the conventional composition.

Structure and electrochemical properties of composite films based on poly-3,4-ethylenedioxythiophene with metallic palladium inclusions

The electrochemical behavior of PEDOT/Pd composite films obtained by the chemical deposition of ultradisperse Pd particles in the poly-3,4-ethylenedioxythiophene (PEDOT) polymer matrix was studied. The structure of the films was determined by electron microscopy and energy-dispersion X-ray fluorescence analysis. The electrochemical properties of PEDOT/Pd composite films in solutions containing hydrogen peroxide was also studied. Special attention was paid to the effect of the time of the chemical deposition of palladium in the polymer structure on the electroreduction of hydrogen peroxide in phosphate buffer solutions.

The electrochemical degradation of poly(3,4-ethylenedioxythiophene) films electrodeposited from aqueous solutions

Abstract In this review, results of recent studies on the electrochemical stability and degradation properties of poly(3,4-ethylenedioxythiophene) films are summarized, with particular emphasis on the structural changes induced by overoxidation and electrochemical degradation. The most important electrodeposition methods for the preparation of PEDOT films in surfactant free aqueous media have also been summarized, and several experimental techniques suitable for monitoring the degradation process have been discussed. Morphological changes in PEDOT films during overoxidation have been analyzed. Overoxidation mechanisms proposed in the literature have been surveyed.

Mass tranfer of ions and solvent at redox processes in poly-3,4-ethylenedioxythiophene films

The work presents the data on mass transfer at the interface of the poly-3,4-ethylenedioxythiophene film with different propylene carbonate electrolyte solutions (TBAPF6, LiClO4, NaClO4, TBAClO4, TBABF4) obtained using the quartz microgravimetry method in combination with cyclic voltammetry. It is shown that two parts of different nature can be observed in the region of electric activity of poly-3,4-ethylenedioxythiophene films on Δm, ΔQ curves. They evidence the change in mass transfer conditions at achieving different film oxidation degrees.

Synthesis and electrochemical properties of composite materials based on poly-3,4-ethylenedioxythiophene with manganese dioxide inclusions

The electrochemical behavior of PEDOT/MnO2 composite films obtained by chemical deposition of manganese dioxide into poly-3,4-ethylenedioxythiophene (PEDOT) films was studied. The structure of the composite films was characterized by scanning electron microscopy. The cyclic voltammograms of PEDOT/MnO2 films in 1 M lithium perchlorate solutions were studied at different synthesis times and potassium permanganate concentrations in solution. The specific capacitances of the materials and their dependence on the potential scan rate and the number of cycles were determined by cyclic voltammetry.

Synthesis and electrochemical properties of composite films based on poly-3,4-ethylenedioxythiophene with inclusions of silver particles

The electrochemical behavior of PEDOT/Ag composite films obtained by chemical deposition of ultrafine Ag particles into the poly-3,4-ethylenedioxythiophene (PEDOT) matrix was studied. The film morphology was characterized by transmission electron microscopy (TEM). The changes in the mass of the films during the chemical deposition of silver into the polymer structure were evaluated microgravimetrically. The mass of the included metallic silver particles depends on the synthesis time and the initial concentration of silver ions in solution. The cyclic voltammograms (CVs) of PEDOT/Ag films in sodium nitrate solutions and sodium nitrate solutions with additions of chloride ions were studied. The cyclic voltammograms of PEDOT/Ag films in chloride-containing solutions showed the peaks of the oxidation of silver and reduction of the oxidation product, which were absent on the CVs of the starting PEDOT film.