M. A. Vorotyntsev

University of Burgundy | UB · Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB)

The passage of cathodic current through the acidized aqueous bromate solution (catholyte) leads to a negative shift of the average oxidation degree of Br atoms. It means a distribution of Br-containing species in various oxidation states between 􀀀1 and +5, which are mutually transformed via numerous protonation/deprotonation, chemical, and redox/el...

Oligopyrrole-acceptor (BF4 or PF6) complexes, i.e., positively charged oligopyrrole (OPy) clusters with BF4⁻ or PF6⁻ doping anions, represent a model of a charged region of the polymer chain inside a polypyrrole film deposited on the electrode surface via electropolymerization of the pyrrole monomer in a non-aqueous electrolyte containing BF4⁻ or P...

The passage of cathodic current through the acidized aqueous bromate solution (catholyte) leads to a negative shift of the average oxidation degree of Br atoms. It means a distribution of Br-containing species in various oxidation states between −1 and +5, which are mutually transformed via numerous protonation/deprotonation, chemical, and redox/el...

The hydrogen-bromate flow battery represents one of the promising variants for hybrid power sources. Its membrane-electrode assembly (MEA) combines a hydrogen gas diffusion anode and a porous flow-through cathode where bromate reduction takes place from its acidized aqueous solution: BrO3− + 6 H+ + 6 e− = Br− + 3 H2O (*). The process of electric cu...

Shunting currents are among the main problems of all-vanadium redox flow battery stacks since, in addition to capacity losses, they cause negative effects associated with the local destruction of electrodes and bipolar plates. The values of both the shunting currents and their destructive effects on materials can be reduced at the battery developme...

A novel method has been proposed for rapid determination of principal transmembrane transport parameters for solute electroactive co-ions/molecules, in relation to the crossover problem in power sources. It is based on direct measurements of current for the electrode, separated from solution by an ion-exchange membrane, under voltammetric and chron...

Theoretical analysis of changes in the composition of the system in the course of electrolysis of acidic aqueous chloride solution + P. A. Zader1,*, D. V. Konev1,2, J. Gun3, O. Lev3, M. A. Vorotyntsev1,* 1 Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences, Moscow, Russia 2 Institute for Problems of Che...

A power source based on the current-generating reaction of aqueous chlorate-to-chloride reduction by molecular hydrogen would provide as much as 1150 Wh per 1 L of reagent storage (for a combination of 700 atm compressed hydrogen and saturated aqueous solution of lithium chlorate) at room temperature, but direct electroreduction of chlorate only pr...

We measured the ring collection coefficient of bromide anion oxidation products in a neutral and slightly alkaline medium on a rotating ring-disk electrode (glassy carbon disk, platinum ring) varying the following parameters: disk electrode rotation velocity, sodium bromide concentration, pH of the medium (in the range of 6–12), anode current on th...

Quantum chemical approach has been applied for modeling the change in the conformation of the polypyrrole (PPy) chain both in its neutral and positively charged (doped) states due to its interaction with incorporated counterions. Polymer has been modeled by oligopyrrole molecule of 9–15 monomer units. It is shown that it is energetically favorable...

We measured the ring collection coefficient of bromide anion oxidation products in a neutral and slightly alkaline medium on a rotating ring-disk electrode (glassy carbon disk, platinum ring) varying the following parameters: disk electrode rotation velocity, sodium bromide concentration, pH of the medium (in the range of 6 – 12), anode current on...

Theoretical analysis of electrochemically inactive halate-anion (XO3−, X = halogen) electroreduction at rotating disk electrode (RDE) under steady-state conditions via autocatalytic mediator cycle based on X2/X− redox couple in acidic aqueous medium has been performed in relation to prospects to use this reaction as cathodic process of high energy...

Theoretical studies of the shape of the linear potential sweep voltammogram for a reversible electron-transfer reaction have been overviewed. Two different expressions for the current–potential dependences have been proposed therein. Our analysis has shown that this divergency originates from the implicit difference of the assumptions on the pretre...

Thin polypyrrole films (thickness: about 30 nm) have been deposited at electrode surface via potentiostatic oxidation of dilute (1 mM) pyrrole solution in acetonitrile (AN). It has been shown that their subsequent treatment by means of multi-cycle voltammetry within a broad potential range (up to -2.0 V vs. Ag/Ag⁺ in AN) leads to their "activation"...

Temporal evolution of the process of reduction of the electrochemically-inactive halate anion, XO3⁻ (X is halogen), via autocatalytic redox mediator cycle based on the X2/X⁻ couple, after a large-amplitude stepwise potential change has been studied theoretically for the first time via numerical and analytical methods. This analysis has been perform...

In recent years, the key principles of the electric power industry have radically changed and the number of studies on the development of devices for electrical energy storage in a different form such as mechanical or chemical energy has rapidly increased. This review gives a brief description of these devices. The attention is focused on redox flo...

A theory was developed to explain how charge selectivity is reversed in tight junctions (TJs) between epithelial cells when the sign of the TJ fixed charge changes. An original method that allows for the ion cavity effect was used to calculate the changes in ion solvation energies that occur upon ion transfer in TJs. An equation was derived to desc...

Развита теория инверсии зарядовой селективности плотных контактов между эпителиальными клетками при изменении знака фиксированного в них заряда. На основе метода нашей работы, учитывающей эффект полости иона, рассчитаны изменения энергий сольватации ионов при их переходе в плотных контактах. Выведена формула для определения зависимостей отношения п...

A new variant of the theory of charging processes for electroactive polymer films on electrode surfaces was recently developed for conducting polymers containing cation-radicals (polarons) of identical sizes. Compared with the previously proposed models, the new approach explicitly takes into account the polaron charge delocalization over several m...

Material and charge balances in the course of the electropolymerization process of the non-substituted Mg(II) porphine (MgP) at a low oxidation potential from its acetonitrile solutions of various concentrations have been studied via the in situ electrochemical quartz crystal microbalance method (EQCM). Thus, registered electrode mass increase due...

Changes in the indicator electrode potential (at zero current) E and (quasi) equilibrium composition of aqueous solution in the anode chamber of the model electrolyzer, which initially contained 0.5 M concentration of bromide anions, provided that the solution was kept at a constant pH and constant (together with the gas phase above it) total numbe...

A great deal of research has been dedicated to improving the performance of vanadium redox flow battery (VRFB). In this work, we propose the design of a cell for testing membrane electrode assembly of VRFB, which enables the optimization of the flow field, conditions of charge‐discharge tests, and the nature of components (electrodes, membrane) wit...

Tight junctions (TJs) of epithelial cells play a key role in regulation of the ion exchange between NaCl solutions separated by the layer of these cells. Their functioning is based on a strong difference in the permeabilities of these channels for Na⁺ and Cl⁻ ion migrational fluxes owing to specific properties of the protein network inside TJs. It...

Palladium-polypyrrole (Pd-PPy) composites synthesized via one-step and one-pot redox procedure have been tested as electrocatalysts for formaldehyde oxidation in aqueous solution under both inert and oxygen atmospheres. It has clearly been shown that inert electrode coated by the Pd-PPy composites demonstrates a high catalytic activity. Electrochem...

The vanadium redox flow battery (VRFB) is the most promising type of rechargeable power sources for medium- and large-scale energy storage devices for modern power systems. The intensive research and development activity of leading world centers aimed at optimizing the key element of the VRFB—the membrane electrode assembly (MEA)—necessarily includ...

The paper presents three datasets obtained by electrochemical quartz microbalance technique which was applied to studies of conducting polymer film in contact with non-aqueous electrolyte solution. The first dataset describes the calibration procedure of gold-coated quartz crystal, immersed in acetonitrile silver ion-containing electrolyte, by mean...

Hydrogen-bromate flow battery is a promising hybrid current source for air-deficient environment that functions by electrocatalyzed reactions of hydrogen oxidation and aqueous LiBrO3 reduction. The flow cell consists of porous carbonaceous cathode, platinum catalyzed hydrogen oxidation gas diffusion anode, and separating proton exchange membrane. P...

The changes in indicator-electrode potential and (quasi)equilibrium solution composition in the anodic compartment of a model electrolyzer initially filled with aqueous electrolyte containing 0.5 M concentration of bromide anions are calculated under the condition that pH 2 is maintained constant in this compartment. The theoretical analysis is car...

In view of applied prospects of the bromate electroreduction in acidic medium this process has been analyzed for the solution flow through a channel filled in with porous conducting material playing the role of 3D electrode. The process passes via mediator redox cycle where the bromine is reduced at the electrode surface to bromide which is subject...

CELL FOR SPECTROPHOTOMETRY OF ELECTROLYTES IN THE PROCESS ELECTROCHEMICAL RESEARCH Abstract: Usage: for holding electrochemical tests with simultaneous registration of the spectra of the studied electrolyte. The essence of the utility model is that the cell for spectrophotometry of electrolytes in the process of electrochemical research includes...

Acidic aqueous solutions of bromic acid salts (bromates) are promising electrolytes for redox flow batteries due to their record high power capacity and the rate of electrode reactions proceeding in the autocatalytic regime. The paper gives a comparison of the results of mathematical modeling and experimental measurements of steady-state currents o...

Till now, calculation of the electrostatic potential distribution and other electric properties of a nonlocal polar medium occupying a restricted spatial region has been carried out within the framework of two different approaches. One of them (which may be called “unrestricted medium approximation” UMA) disregards the existence of “external region...

The article contains results of numerical analysis of convective-diffusion transport equations for the components of the bromate anion electrochemical reduction process at rotating disk electrode via the redox-mediator autocatalysis (EC″) mechanism. The problem is solved taking into account the difference in the diffusion coefficients of the compon...

Acidic aqueous solutions of bromic acid salts (bromates) are promising electrolytes for redox flow batteries due to their record high power capacity and the rate of electrode reactions proceeding in the autocatalytic regime. The paper gives a comparison of the results of mathematical modeling and experimental measurements of steady state currents o...

There exist numerous Br-containing species in various oxidation states between −1 and +5 (Br⁻, Br3⁻, Br5⁻, Br2 in the solute and liquid states, BrO⁻, HBrO, BrO3⁻, etc.), which are mutually transformed via numerous protonation/deprotonation, chemical and redox/electrochemical processes. Composition of their aqueous solutions has been analyzed under...

Novel approach to synthesis of conjugated oligomers/polymers is proposed. This approach combines all advantages of electrochemical methods: variation of the oxidation potential in wide range with high precision, direct control of the process rate and product yield, variation of both the doping anion/cation nature and the composition of polymerizati...

A new method (AA approximation) is proposed for obtaining approximate analytical solutions of a system of equations describing the transport of the basic reagents for the electroreduction process of the BrO\(_{3}^{ - }\) anion on a rotating disc electrode in an acid medium in the presence of very small additions of molecular bromine. This process i...

The oxidation of a 10 mM aqueous solution of sodium bromide in a sulfuric acid medium on the surface of a platinum electrode in a cell with separated spaces was studied. The process is important in view of the use of the bromine–bromide redox couple in redox flow batteries. The study was performed by cyclic voltammetry, potentiostatic chronoamperom...

The electrooxidative polymerization of pyrrole on the surface of a glassy carbon electrode was studied, while varying the solvent, the type and concentration of supporting electrolyte, redox mediator addition to the polymerization medium, and hydrodynamic conditions. The efficiency of polymerization was determined as the ratio of the charge of the...

A new method for the calculation of electric field distributions in the systems with spatiallyrestricted regions filled with polar media with nonlocal dielectric characteristics is proposed. The presence of regions with different dielectric properties in the system (as exemplified by the presence of an ion-filled cavity in which there is no polar m...

Palladium nanoparticles–polypyrrole composite (Pd/PPy) catalyzes the addition of perfluoroalkyl halides to olefins to produce a variety of products with good yields. An effective fluoroalkylation technique tested with various olefins, fluoroalkyl halides and Pd/PPy was developed. The reaction proceeds highly efficient under mild phosphine-free reac...

Theoretical description of the BrO3⁻ anion reduction from aqueous acidic solution at RDE under steady-state conditions requires to solve a set of ordinary differential transport-kinetic equations for the concentrations of the components of this system (BrO3⁻, Br⁻, Br2, H⁺) supplemented with boundary conditions at the electrode surface and in the bu...

A composite material in the form of powder is synthesized by a redox reaction in mixed aqueous solution of Pd(NH3)4Cl2 + pyrrole. The composite consists of polypyrrole globules with palladium nanoparticles uniformly distributed inside the latter. Being applied as a film on the electrode surface, both components of this material exhibit redox activi...

Novel member of polymetalloporphines, namely manganese polymetalloporphine of type I (pMnP-I) obtained by ion exchange from magnesium polyporphine of type I (pMgP-I) is reported for the first time and compared to its cobalt analogue (pCoP-I). Both polymer films have been obtained via two-step procedure: demetalation of the pMgP-I electrode film via...

An efficient cyanation of vinyl bromides, activated chlorides and mesylates with K4Fe(CN)6 has been performed using palladium polypyrrole nanocomposite. The reactions are clean and high yielding. They are highly stereoselective furnishing (E)‐nitriles from (E)‐halides and Z‐nitriles from Z‐halides. Chemoselective cyanation of sp2(vinyl)‐Br bond in...

Process of bromate anion reduction at rotating disk electrode in steady state occurring owing to catalytic cycle is analyzed theoretically. The cycle consists of bromine/bromide reversible redox-couple and comproportionation irreversible reaction. Because of the cycle autocatalytic character (EC''-mechanism: Electrochim. Acta, 2015, 173, 779), the...

The reduction of the bromate anion on a rotating disk electrode (RDE) in a steady-state mode due to the catalytic cycle consisting of a reversible bromine/bromide redox pair and irreversible counter-proportionation reaction was studied theoretically. As the cycle is autocatalytic (EC″ mechanism: Electrochim. Acta, 2015, vol. 173, p. 779), at high v...

Process of bromate reduction from aqueous acidic medium at (hemi)spherical microelectrode under steady-state conditions has been analyzed theoretically. Since bromate anion is non-electroactive within the potential range under consideration its transformation is based on the electroreduction of bromine which is present in bulk solution in small (ev...

Theory of the convective-diffusion transport for the steady-state electroreduction of bromate-anion at rotating disk electrode has been developed for the first time for the compositions of the bulk solution where the bromate concentration is much higher than the proton one. Because of the non-electroactivity of the bromate anions and protons the pr...

Our recent theoretical analysis of the bromate reduction from acidic media at rotating disk electrode (RDE) under steady-state conditions gave astonishing predictions for the current at the plateau of the voltammogram (called “the maximal current”, jmax) which deviated cardinally from those for the previously known mechanisms of electrochemical pro...

Bromate reduction from strongly acidic solutions under steady-state conditions in the presence of a very small amount of bromine has been studied voltammetrically at disk microelectrodes of various radii. In conformity with theoretical predictions the intensity of the average current density depends on the electrode size in a non-monotonous manner,...

The process of electroreduction of bromate anion BrO3⁻ from aqueous solutions on catalytically inactive (e.g., carbon) electrodes is theoretically described in the framework of the generalized Nernst layer model in which the Nernst-layer thickness is chosen independently for each system’s component according to the Levich formula. For this system,...

Theoretical study of the bromate anion reduction under steady-state conditions is performed for rotating disk electrode. Transport of the components in solution is described within the framework of the Nernst stagnant layer model. Numerical calculations carried out recently for the same system confirmed the validity of our previous approximate anal...

The fundamental scientific areas founded and developed by V.G. Levich and his school, and their importance in contemporary theoretical electrochemistry have been overviewed.

A concept of high energy density (ED) hydrogen-bromate flow battery was supported by experiments with flow cells with 0.1 cm2 to 50 cm2 apparent area. H2/NaBrO3 flow cells with H2 gas diffusion anode, proton exchange membrane (PEM) and carbonaceous flow-by or flow-through cathodes were employed. Estimates show that theoretical ED of H2/bromate flow...

The use of a solution-phase redox mediator presents an opportunity to perform the slow oxygen reduction reaction in the bulk of a solution rather than on a surface of a precious metal electrocatalyst. Specific details of several potential mediator chemistries (Br 2 /2Br-, V(V)/V(VI) etc.), the current status of the development, and the potential fo...

Theory of the steady-state electroreduction of bromate-anion at rotating disk electrode has been developed. Bulk solution contains high concentrations of bromate anion and a strong acid (which are non-electroactive at the electrode) as well as a tracer amount of bromine. The current passes owing to bromine which is reduced to bromide ion that parti...

In the presence of carbon nanotubes (CNTs), palladium (Pd)–polypyrrole (PPy)@CNT nanocomposites have been synthesized by way of one-pot and one-step colloidal synthesis from a solution of a palladium inorganic salt and organic pyrrole as monomeric precursor to PPy. This efficient method leads to the growth of nanoparticles of the palladium inorgani...

Recent theoretical studies of the bromate electroreduction from strongly acidic solution have been overviewed in view of very high redox-charge and energy densities of this process making it attractive for electric energy sources. Keeping in mind non-electroactivity of the bromate ion the possibility to ensure its rapid transformation via a redox-m...

Three alternative methods were developed for the synthesis of modifying palladium–polypyrrole layers on the surface of an inert electrode. Their electrocatalytic activity toward formaldehyde under inert atmosphere was checked. All the suggested methods are one-stage and allow synthesis of a film on the electrode surface from a solution containing a...

The process of electroxidative polymerization of magnesium 5,15-di(n-methoxyphenyl)porphine MgP(MeOPh)2 is studied. The presence of substituents in positions 5 and 15 of the porphine macroring makes reactive two of its four meso positions, which allows new bonds to be formed only in the opposite positions 10 and 20. As a result, the process of elec...

Novel synthetic route towards electroactive films of Co(II) polyporphine has been elaborated. It is based on the electrochemical transformation of the metal-free polyporphine film with replacement of protons inside the macrocycles by Co(II) cations. Compared to the conventional procedure of such ion exchange based on extended thermal treatment of m...

Theoretical analysis has been developed for the reduction reaction of the non-electroactive bromate anion from its aqueous solution at a thin-layer porous electrode on the surface of a membrane transporting protons from anode under steady-state 1D conditions. The cathodic process is realized via a cycle composed of the reversible Br2 to 2 Br⁻ trans...

The reduction of nonelectroactive bromate anion BrO3⁻ from acidic solutions while limiting the maximum current by diffusion transport of protons was studied by methods of numerical integration of transport equations. The calculation was performed based on a generalization of the Nernst steady diffusion layer model, in which the choice of the layer...

A method for modification of the inert electrode surface with an electroactive polymeric film containing the CoN4 catalytic site has been suggested and approved. The described approach affords the maximal content of the metal porphine moiety per unit weight of the coating. The classical method of introduction of an ion into the porphine macrocycle...

Theoretical analysis has been developed for the reduction process of the non-electroactive bromate anion through an autocatalytic cycle composed of the reversible Br2-to-Br− transformation and the irreversible (owing to high acidity of the solution) comproportionation reaction. Owing to the autocatalytic character of this redox-mediating cycle (EC′...

The study is devoted to analyzing the electroreduction of bromate anion BrO 3⁻ on catalytically inactive (e.g., carbon) electrodes by numerical methods. This process is realized due to the combination of the reversible mediator pair Br2/Br⁻ and the process of comproportionation (reaction of bromate and bromide anions) in solution phase. These react...

A new member of the polyporphine series—cobalt polyporphine of type I (pCoP-I)—was prepared from the starting magnesium polyporphine of type I (pMgP-I) by ion exchange, i.e. by sequential processing of the pMgP-I polymer film on the electrode surface with solutions of trifluoroacetic acid (forming metalfree polyporphine of type I, pH2P-I) and cobal...