На главную              К списку выставок

Современные методы теоретической и экспериментальной электрохимии

Журнальные статьи

Balakai V.I., Sundukova N.G., Balakai K.V. Possibility of saving silver in deposition of a multilayer copper-nickel-silver coating // Russian Journal of Applied Chemistry. 2011. Vol. 84, № 1. P. 72–78.

Possibility of making thinner silver coatings on low-current sliding contacts in deposition of multilayer nickel-silver and copper-nickel-silver coatings from various electrolytes was studied.

Cachet-Vivier C. et al. Development of cavity microelectrode devices and their uses in various research fields // Journal of Electroanalytical Chemistry. 2013. Vol. 688. P. 12–19.

The cavity microelectrodes (CMEs) have been introduced in the 1990s and since then have been employed for the characterization of various types of materials ranging from materials used for energy storage, biological applications, catalysis characterization, or corrosion studies. This technique takes advantage of working on small amount of pure electroactive materials (few hundreds nanograms) using usual electrochemical techniques (cyclic voltammetry, electrochemical impedance spectroscopy, etc.) and allows a rapid screening of the electrochemical behavior of new materials. The CME development and its main applications for the electrochemistry of powder materials are reviewed and discussed.

Deconinck D., Van Damme S., Deconinck J. A temperature dependent multi-ion model for time accurate numerical simulation of the electrochemical machining process. Part I: Theoretical basis // Electrochimica Acta. 2012. Vol. 60. P. 321–328.

A new temperature dependent multi-domain model is presented for numerical simulation of the electrochemical machining process with a moving cathode tool. The method includes mass transfer as a consequence of diffusion, convection and migration, combined with the electroneutrality condition and linearized temperature dependent polarization relations at the electrolyte-electrode interface. Concentration and temperature dependent expressions are used for the diffusion coefficients and electrolyte viscosity. The electrolyte flow field is calculated using the laminar Navier-Stokes equations for viscous incompressible flow. Heat is generated in the bulk solution and in the electrical double layer. The electrodes are cooled by natural convection. The level set method is used for tracking the anode interface. The model is applied to the electrochemical machining of steel in a NaNO3 supporting electrolyte. Hydrogen is formed at the cathode, and metal dissolution and oxygen evolution reactions are considered at the anode. The effect of water depletion at the electrodes is modeled by limiting the oxygen and hydrogen evolution reaction rates depending on the local surface water concentration. The heat conduction through electrodes and the heat production by the electrode reactions are found to play an important role.

Economou D.J. Tailored ion energy distributions on plasma electrodes // Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films. 2013. Vol. 31, № 5. P. 050823.

As microelectronic device features continue to shrink approaching atomic dimensions, control of the ion energy distribution on the substrate during plasma etching and deposition becomes increasingly critical. The ion energy should be high enough to drive ion-assisted etching, but not too high to cause substrate damage or loss of selectivity. In many cases, a nearly monoenergetic ion energy distribution (IED) is desired to achieve highly selective etching. In this work, the author briefly reviews: (1) the fundamentals of development of the ion energy distribution in the sheath and (2) methods to control the IED on plasma electrodes. Such methods include the application of "tailored" voltage waveforms on an electrode in continuous wave plasmas, or the application of synchronous bias on a "boundary electrode" during a specified time window in the afterglow of pulsed plasmas.

Fang Y.-H., Liu Z.-P. Toward Anticorrosion Electrodes: Site-Selectivity and Self-Acceleration in the Electrochemical Corrosion of Platinum // The Journal of Physical Chemistry C. 2010. Vol. 114, № 9. P. 4057–4062.

As an important concern in both science and industry, metal corrosion at solid/liquid interfaces is not well understood at the atomic level. The challenge to investigators ties in the simultaneous consideration of the extended solid Surface, the electrochemical potential, and the water Solution. The work presented here represents the first theoretical attempt to elucidate the oxidation mechanism of the Pt electrode under electrochemical conditions by exploring the oxidation kinetics of differently Structured Pt Surfaces, including Pt(111), Pt(211), and Pt(100). We show that the most abundant and close-packed (111) surface in Pt metal can be oxidized because of the presence of surface OR The corrosion is self-accelerated kinetically once the defects are created, as demonstrated by the low kinetic barrier of oxidation on Pt(211). By contrast, the open Pt(100) facet is very inert toward surface Oxidation. Apart from the revealed surface-structure sensitivity, Pt corrosion is also strongly affected by the local oxygen coverage as pinned by the electrochemical potential. For Pt(111), the subsurface oxygen formation occurs Only above 0.5 ML oxygen coverage around 1.1 V. The kinetics model for the surface oxidation proposed in this work provides new insights for designing, the next generation of anticorrosion electrode materials in fuel cells.

Geiger W.E., Barriere F. Organometallic Electrochemistry Based on Electrolytes Containing Weakly-Coordinating Fluoroarylborate Anions // Accounts of Chemical Research. 2010. Vol. 43, № 7. P. 1030–1039.

A new generation of supporting electrolyte salts that incorporate a weakly coordinating anion (WCA) expands anodic applications by providing a dramatically different medium in which to generate positively charged electrolysis products. A chain of electrolyte anions is now available for the control of anodic reactions, beginning with weakly ion-pairing WCAs, progressing through the traditional anions, and culminating in halide ions. Although the electrochemical properties of a number of different WCAs have been reported, the most systematic work involves fluoro- or trifluoromethyl-substituted tetraphenylborate anions (fluoroarylborate anions). In this Account, we focus on tetrakis(perfluorophenyl)borate, [B(C(6)F(5))(4)](-), which has a significantly more positive anodic window than tetrakis[(3,5-bis(trifluoromethyl)phenyl)]borate, [BArF(24)](-), making it suitable in a larger range of anodic oxidations.

Gonzalez Perez O., Bisang J.M. Modelling of three-dimensional bipolar electrodes with irreversible reactions // Journal of Applied Electrochemistry. 2011. Vol. 41, № 5. P. 609–616.

The behaviour of an electrochemical reactor with three-dimensional bipolar electrodes for irreversible reactions is analysed. Copper deposition at the cathodic side and oxygen evolution at the anodic one were adopted as test reactions at the bipolar electrode, from an electrolyte solution with a copper concentration lower than 1000 mg dm(-3), pH 2 and 1 M Na(2)SO(4) as supporting electrolyte. A mathematical model considering the leakage current is proposed, which can represent the tendency observed in the experimental data related to cathodic thickness and potential at both ends of the bipolar electrode. High values of leakage current were determined, which restricts the faradaic processes to small thicknesses at both ends of the bipolar electrode. Likewise, the performance of the bipolar electrochemical reactor for the treatment of effluents is experimentally and theoretically examined. In this case, the conversion for copper removal was 90.1% after 480 min of operation with one bipolar electrode and 94.8% after 300 min of operation with two bipolar electrodes at a total current of 3 A.

Graham W.G., Stalder K.R. Plasmas in liquids and some of their applications in nanoscience // Journal of Physics D: Applied Physics. 2011. Vol. 44, № 17. P. 174037.

The range of applications for plasmas in liquids, plasmas in contact with liquid surfaces and plasmas containing liquid drops is growing rapidly across a range of technologies. Here the focus is on plasmas where the electrodes are immersed in liquids and their applications in nanoscience. The physical phenomena in both high voltage (tens of kilovolts) and low voltage (a few hundred volts) plasmas in liquid are described together with a discussion of the plasma-induced chemistry. Studies show that in water the plasmas are formed in water vapour created by Joule heating as either channels in the liquid or as layers on the electrodes. The chemistry in these water vapour plasmas and at their interface with the liquid is discussed in the context of the highly reactive radicals produced, such as H and OH. The current use of a variety of plasmas-in-liquid systems in the area of nanoscience is discussed, with an emphasis on nanoparticle growth.

Isakaev E.K. et al. Investigation of low-temperature plasma generator with divergent channel of the output electrode and some applications of this generator // High Temperature. 2010. Vol. 48, № 1. P. 97–125.

A review is made of experimental and theoretical investigations of processes occurring in low-temperature plasma generators (LTPG) with divergent channel of the output electrode, and the possibilities of utilizing these generators in new plasma technologies are analyzed. Comparison is made of the characteristics of discharge (including the current-voltage characteristic) in a divergent channel and in a cylindrical channel of uniform cross section. The effect of divergent channel of the output electrode and of its expansion ratio on the pattern of physical processes in LTPGs of different designs is studied. Investigations are performed of the distribution of electric current and heat flux density along a channel with a segmented output electrode. The voltaic equivalents of heat fluxes to cathode and anode are determined. The process of “shunting” of discharge is investigated, which causes fluctuations of electric arc-burning voltage. The investigations involving an LTPG with divergent channel reveal that the voltage amplitude in the case of shunting decreases with increasing current strength and, at high currents of argon arc, does not exceed 1–2 V. Results are given of spectral and visual investigations of LTPG. It is demonstrated that, in an LTPG with divergent channel, the plasma temperature in the region of energy input at currents of 300 A and higher exceeds 30 000 K. The significant part is found which is played by vacuum ultraviolet radiation in the process of closing the arc to anode. The mechanisms of erosion of the tungsten cathode tip are investigated, which play an important part in increasing the cathode service life by way of recirculation of tungsten atoms because of their ionization in the discharge gap. Results are given of using an LTPG with divergent channel of the output electrode in plasma technologies of surface hardening, cutting, and hard-facing of metals. The technology of plasma hardening of wheel pairs, adopted by the RZhD (Russian Railroads) Joint-Stock Company, provides for increasing the service life of railroad wheels by a factor of 1.5–2.

Keidar M. et al. Mechanism of carbon nanostructure synthesis in arc plasma // Physics of Plasmas. 2010. Vol. 17, № 5. P. 057101.

Plasma enhanced techniques are widely used for synthesis of carbon nanostructures. The primary focus of this paper is to summarize recent experimental and theoretical advances in understanding of single-wall carbon nanotube (SWNT) synthesis mechanism in arcs, and to describe methods of controlling arc plasma parameters. Fundamental issues related to synthesis of SWNTs, which is a relationship between plasma parameters and SWNT characteristics are considered. It is shown that characteristics of synthesized SWNTs can be altered by varying plasma parameters. Effects of electrical and magnetic fields applied during SWNT synthesis in arc plasma are explored. Magnetic field has a profound effect on the diameter, chirality, and length of a SWNT synthesized in the arc plasma. An average length of SWNT increases by a factor of 2 in discharge with magnetic field and an amount of long nanotubes with the length above 5 mu m also increases in comparison with that observed in the discharge without a magnetic field. In addition, synthesis of a few-layer graphene in a magnetic field presence is discovered. A coupled model of plasma-electrode phenomena in atmospheric-pressure anodic arc in helium is described. Calculations indicate that substantial fraction of the current at the cathode is conducted by ions (0.7-0.9 of the total current). It is shown that nonmonotonic behavior of the arc current-voltage characteristic can be reproduced taking into account the experimentally observed dependence of the arc radius on arc current.

Kraemer E. et al. Mechanism of Anodic Dissolution of the Aluminum Current Collector in 1 M LiTFSI EC:DEC 3:7 in Rechargeable Lithium Batteries // Journal of the Electrochemical Society. 2013. Vol. 160, № 2. P. A356–A360.

So-called "corrosion" of the aluminum current collector in the electrolyte 1 M LiTFSI in ethylene carbonate : diethyl carbonate, EC:DEC (3:7, by wt) has been investigated by electrochemical and analytical methods. In fact, Al "corrosion" in this electrolyte is actually an anodic Al dissolution reaction. In addition to Al dissolution various electrolyte degradation processes were identified. A combination of a specially developed on-line ICP-OES method and in situ EQCM measurements revealed that before the dissolution of aluminum starts, an "activation" process takes place for ca. 6 hours, which is accompanied by strong electrolyte oxidation. The electrolyte decomposition reactions were investigated by ex situ IC measurements which showed that the LiTFSI decomposed and that F- s the main decomposition product. ex situ GC-MS measurements revealed that also the solvent decomposes and CO2 as well as ethoxyethanol are formed as degradation products.

Liu X., Zweier J.L. Application of electrode methods in studies of nitric oxide metabolism and diffusion kinetics // Journal of Electroanalytical Chemistry. 2013. Vol. 688. P. 32–39.

Nitric oxide (NO) has many important physiological roles in the body. Since NO electrodes can directly measure NO concentration in the nM range and in real time, NO electrode methods have been generally used in laboratories for measuring NO concentration in vivo and in vitro. This review focuses on the application of electrode methods in studies of NO diffusion and metabolic kinetics. We have described the physical and chemical properties that need to be considered in the preparation of NO stock solution, discussed the effect of several interfering factors on the measured curves of NO concentration that need to be eliminated in the experimental setup for NO measurements, and provided an overview of the application of NO electrode methods in measuring NO diffusion and metabolic kinetics in solution and in biological systems. This overview covers NO metabolism by oxygen (O-2), superoxide, heme proteins, cells and tissues. Important conclusions and physiological implication of these studies are discussed.

Liu Y. et al. Theory of Electrochemistry for Nanometer-Sized Disk Electrodes // The Journal of Physical Chemistry C. 2010. Vol. 114, № 24. P. 10812–10822.

It has been shown previously that conventional voltammetric theories may become inapplicable at electrodes of nanometer scale due to enhanced effects of the diffuse double layer on the interfacial charge transport and transfer processes (Anal. Chem. 1993, 65, 3343; J. Phys. Chem. B 2006, 110, 3262). As well as the diffuse double layer effects, we show in present study that the voltammetric responses of nanometer-sized electrodes would differ from the macroscopic electrodes due to significant edge effects of dielectric screening and electron tunneling if the electrode has planar geometries. These nanoedge effects arise because of the comparable size of the electrode with the dipole molecules and the effective electron tunneling distance. Models for these nanoedge effects are developed and combined with Poisson-Nernst-Planck theory and Marcus electron-transfer theory to describe the voltammetric characteristics of nanometer-sized disk electrodes. Marcus theory instead of Butler-Volmer theory is used to describe the electrochemical electron transfer kinetics because the greatly increased mass transport rates at the nanoscale electrochemical interface would render most of the electron transfer reaction to become largely irreversible so that the kinetics-controlled voltammetric behavior would extend to very large overpotentials at which the Marcus inversion of the electron transfer rate may occur. The theoretical calculations based on present models show the pronounced radial heterogeneities of interfacial potential, concentrations, and rate constant of charge transfer at the electrochemical interface of nanodisk electrodes, which in turn can significantly alter the voltammetric responses of these electrodes. It is indicated that the radial extension of electron transfer at the nanodisk electrode overwhelmingly determines the limiting currents on the voltammetric responses of the nanodisk electrode, while the electrical double layer effects can severely impact the kinetic characteristics of voltammetric responses (e.g., half-wave potential).

Luo J. et al. Design and electrochemical characterization of ternary alloy electrocatalysts for oxygen reduction reaction // Journal of Electroanalytical Chemistry. 2013. Vol. 688. P. 196–206.

The ability to engineer the composition and structure of nanoalloy catalysts is important for developing active, robust and low-cost catalysts for fuel cell applications. The recognition of the importance of structural and chemical alloying effects of nanoalloy particles on the electrocatalytic properties has been an important driving force for the exploration of various binary and ternary platinum-based alloy catalysts. In comparison with the extensive studies of binary alloy catalysts for oxygen reduction reaction, the exploration of ternary nanoalloy catalysts in the past few years has led to many intriguing discoveries in terms of enhanced catalytic activities. In this article, we highlight recent progress of our work in the synthesis, processing and electrochemical characterization of molecularly-capped ternary nanoalloy catalysts, focusing on the enhanced electrocatalytic activity of Pt-based ternary nanoalloy catalysts for oxygen reduction reaction in fuel cells. Selected examples of ternary nanoparticle catalysts for electrocatalytic oxygen reduction reaction will be discussed. While important insights have been gained from studies of detailed structural aspects based a variety of techniques, this report summarizes some of the major findings in the studies of the electrochemical and electrocatalytic properties of the ternary nanoalloys to highlight the importance of ternary composition for the design and preparation of electrocatalysts.

Malyshev V.V., Gab A.I. High-temperature galvanic coatings of molybdenum, tungsten, and carbides thereof from ionic solutions. II. Physicochemical properties // Protection of Metals and Physical Chemistry of Surfaces. 2012. Vol. 48, № 2. P. 238–242.

Physicochemical (thickness, hardness, adhesion to support, wear resistance, abrasive resistance, porosity, corrosion stability) properties of high-temperature galvanic coatings of molybdenum, tungsten, and carbides thereof are studied.

Nguyen H.V.P. et al. A New Cathode for Reduced-Temperature Molten Carbonate Fuel Cells // Journal of the Electrochemical Society. 2014. Vol. 161, № 14. P. F1458–F1467.

Oxygen solubility is the rate-determining step (RDS) for the reduction reaction on the cathodes of molten carbonate fuel cells (MCFCs), especially at low operating temperatures below 600 degrees C. The poor wetting property of the mixed ionic and electronic conductor (MIEC) coating, such as BYS (Bi1.5Y0.3Sm0.2O3-delta) on the NiO cathode, to the liquid electrolyte creates openings where oxygen absorption and dissociation take place to provide more oxide ionic species to electrochemical reaction sites (ERSs). Therefore, poor wetting MIEC-coated cells showed a much higher power density compared to standard cells, with a factor of 1.4 at the low operating temperature of 550 degrees C. Long-term operation of 2500 hours with a low voltage loss of 9 mV suggests that BYS is a promising alternative cathode material for molten carbonate fuel cells.

Peckova K., Barek J. Boron Doped Diamond Microelectrodes and Microelectrode Arrays in Organic Electrochemistry // Current Organic Chemistry. 2011. Vol. 15, № 17. P. 3014–3028.

A review. Boron doped diamond (BDD) has been recognized as nearly ideal electrode material for many electrochem. applications due to the low and stable background current over a wide potential range, corrosion and fouling resistance, high thermal cond., and high current densities. Microelectrodes and microelectrode arrays possess numerous attractive features for electrochem. including reduced iR drop, low capacitive-?charging currents, and steady-?state diffusion currents. Coupling the advantages of the microelectrodes and their arrays with the usefulness of BDD is presented and discussed in this review on the examples of existing miniaturized BDD devices and their applications in org. electrochem. The varieties in their fabrication, construction, and applications in org. electrochem. are presented. The latter include mainly electroanal., where single BDD microelectrodes have been employed as amperometric sensors in capillary electrophoretic techniques including electrophoretic microchips and other liq. flow systems, and further for in vivo?/in vitro detection of biogenic compds. Applications of BDD microelectrode arrays are rather limited, as their construction is a very challenging task and recent studies are more concerned with their fabrication and structural and electrochem. characterization. Thus, the techniques for the fabrication of such arrays and their construction are reviewed and their possibilities and limitations in org. electrochem. based on existing results are discussed.

Rodrigues de Oliveira G. et al. Complementary Mechanism Model for the Electrochemical Mineralization // Current Organic Chemistry. 2012. Vol. 16, № 17. P. 1957–1959.

Comninellis and his research group have elucidated a theoretical model that permits us to predict the chemical oxygen demand (COD) and instantaneous current efficiency (ICE), during the electrochemical oxidation of organic pollutants on a synthetic boron-doped diamond thin film electrodes (BDD) in a batch recirculation system under galvanostatic conditions. Several studies highlight the good correlation between theoretical predictions and empirical data, but it was noted that some data, from some experiments, were not in agreement with the theoretical model, since it achieved efficiencies above 100%. Recently, few studies have reported phenomena that occur in electrocatalytic systems which were not deducted in the first models. Thus, we emphasize that the mineralization of organic compounds on BDD electrodes involves not only hydroxyl radicals but also the molecular oxygen present in air, in saturated aqueous solutions or strong oxidants generated from simultaneous reactions. Therefore, this highlights summarizes the results reported by other electrochemists until nowadays to understand the electrochemical oxidation mechanisms.

Rudnev V.S. et al. Plasma-electrolytic oxidation of valve metals in Zr(IV)-containing electrolytes // Protection of Metals and Physical Chemistry of Surfaces. 2010. Vol. 46, № 4. P. 456–462.

The studies devoted to the production of Zr-containing coatings on valve metals (Ti, Al, and Mg) using plasma-electrolytic oxidation are reviewed. The coatings are formed from aqueous electrolyte suspensions containing dispersed ZrO(2) particles, as well as Zr(IV) fluorocomplexes, polyphosphate, and tartrate complexes, and from Zr(SO(4))(2) electrolytes. The layers that contain both zirconium oxide in either monoclinic or tetragonal modification and zirconium pyrophosphate and layers containing simple and complex zirconium phosphates are obtained. The described approaches enable one to produce protective layers and can form the basis of the technique for obtaining surface structures with a complex chemical composition, as well as coatings that contain certain compounds with specific characteristics.

Stamate E. Discrete and modal focusing effects: principles and applications // Plasma Physics and Controlled Fusion. 2012. Vol. 54, № 12. P. 124048.

Charge flux distribution on the surface of biased electrodes of different geometries immersed in a plasma is investigated by three-dimensional simulations and experiments. It is demonstrated that the sheath surrounding the electrodes that interface insulators acts as an electrostatic lens, focusing the charges to distinct locations on the electrode surface depending on the entrance coordinates at the sheath edge. Two focusing effects are identified. Discrete focusing leads to the formation of a passive surface of no ion impact, near the edge of the electrodes interfacing insulators. Modal focusing results in the formation of certain 'modal spots' and/or 'modal lines'. Several phenomenological aspects and potential applications are reviewed and further discussed, including charge focusing by a three-dimensional plasma-sheath-lens, ion dose uniformity during plasma immersion ion implantation, mass spectrometry and plasma monitoring.

Stuve E.M. Ionization of water in interfacial electric fields: An electrochemical view // Chemical Physics Letters. 2012. Vol. 519-520. P. 1–17.

High electric fields promote ionization of water, yet relatively little is known about this topic due to the difficulty of generating such fields. The high field capability of field emitter tips enables study of ionization in water layers. Results from this work include ionization fields, water layer morphology, dielectric properties, coadsorbate interactions, cluster distributions of hydrated hydronium ions H+(H2O)(m), and field ionization images. These experimental results, combined with theoretical findings, are interpreted in the context of four examples from electrochemistry; double layer structure, hydrogen oxidation, CO oxidation, and oxygen reduction; to reveal the research frontier in interfacial ionization of water.

Svancara I., Zima J. Possibilities and Limitations of Carbon Paste Electrodes in Organic Electrochemistry // Current Organic Chemistry. 2011. Vol. 15, № 17. P. 3043–3058.

In this review (with 100 refs)?, applicability of carbon paste electrodes (CPEs) in org. electrochem. is of interest, when the authors cover the area in its entirety and over the whole period of the existence of carbon pastes in electrochem. and electroanal. The individual periods are retrospectively summarized, when particular attention is paid to the Adams' era (R.N. Adams) representing the most extensive research ever carried out with carbon paste-?based electrodes and org. compds. (namely: arom. amines, hydroquinones and catechols, aminophenols and catecholamines)?. The following activities are discussed and critically evaluated with the aid of table surveys or selected illustrative examples, when all the major trends and contemporary achievements are highlighted, including the recent years, the present time, and future prospects.

Van Soestbergen M., Biesheuvel P.M., Bazant M.Z. Diffuse-charge effects on the transient response of electrochemical cells // Physical Review E. 2010. Vol. 81, № 2. P. 021503-1 - 021503-13.

We present theoretical models for the time-dependent voltage of an electrochemical cell in response to a current step, including effects of diffuse charge (or "space charge") near the electrodes on Faradaic reaction kinetics. The full model is based on the classical Poisson-Nernst-Planck equations with generalized Frumkin-Butler-Volmer boundary conditions to describe electron-transfer reactions across the Stern layer at the electrode surface. In practical situations, diffuse charge is confined to thin diffuse layers (DLs), which poses numerical difficulties for the full model but allows simplification by asymptotic analysis. For a thin quasi-equilibrium DL, we derive effective boundary conditions on the quasi-neutral bulk electrolyte at the diffusion time scale, valid up to the transition time, where the bulk concentration vanishes due to diffusion limitation. We integrate the thin-DL problem analytically to obtain a set of algebraic equations, whose (numerical) solution compares favorably to the full model. In the Gouy-Chapman and Helmholtz limits, where the Stern layer is thin or thick compared to the DL, respectively, we derive simple analytical formulas for the cell voltage versus time. The full model also describes the fast initial capacitive charging of the DLs and superlimiting currents beyond the transition time, where the DL expands to a transient non-equilibrium structure. We extend the well-known Sand equation for the transition time to include all values of the superlimiting current beyond the diffusion-limiting current.

Vogt H. On the gas-evolution efficiency of electrodes I – Theoretical // Electrochimica Acta. 2011. Vol. 56, № 3. P. 1409–1416.

At gas-?evolving electrodes, the product of an electrochem. reaction, e.g. H2 or O2, does initially not exist as a gas but in dissolved form in the electrolyte liq. Its appearance as gas bubbles results from subsequent desorption. However, the process of desorption from the liq. phase into the gaseous phase is commonly not complete in the vicinity of the electrode or at all in the interelectrode space. The fraction of the product transferred into the gaseous phase of gas bubbles adhering to the electrode surface is termed the gas-?evolution efficiency. This quantity is one of the controlling parameters in estg. the rate of microconvective mass transfer, the industrially most important mechanism. A theor. study shows the impact of the bubble coverage - previously only derived from an anal. of exptl. data in combination with an unsubstantiated perception - and gives information on further controlling quantities: the mass transfer coeffs. of two competing mechanisms.

Weber A.Z. et al. A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells // Journal of the Electrochemical Society. 2014. Vol. 161, № 12. P. F1254–F1299.

Nitric oxide (NO) has many important physiological roles in the body. Since NO electrodes can directly measure NO concentration in the nM range and in real time, NO electrode methods have been generally used in laboratories for measuring NO concentration in vivo and in vitro. This review focuses on the application of electrode methods in studies of NO diffusion and metabolic kinetics. We have described the physical and chemical properties that need to be considered in the preparation of NO stock solution, discussed the effect of several interfering factors on the measured curves of NO concentration that need to be eliminated in the experimental setup for NO measurements, and provided an overview of the application of NO electrode methods in measuring NO diffusion and metabolic kinetics in solution and in biological systems. This overview covers NO metabolism by oxygen (O-2), superoxide, heme proteins, cells and tissues. Important conclusions and physiological implication of these studies are discussed.

Агеева Е.В., Агеев Е.В., Воробьев Е.А., Осьминина А.С. Получение износостойких покрытий с использованием электродов из твердосплавных электроэрозионных порошков и их исследование // Упрочняющие технологии и покрытия. 2014. Т. 112. № 4. С. 21–23.

The results of studies of the composition and properties of the electrodes of the powders obtained by dispersing electro discharge waste, and electrodes of them. Based on the studies noted the high efficiency of the powders obtained by dispersing waste electroerosive sintered carbide grade T15K6, as electrode materials fabricated by isostatic pressing and sintering, electro-spark alloying of the cutting tool.

Белый А.В., Ганавати Б., Кукареко В.А., Бекиш Ю.Н., Цыбульская Л.С. Структура и триботехнические свойства, обработанного ионами азота электроосажденного покрытия Fe-Ni // Трение и износ. 2014. Т. 35. № 3. С. 245-249.

Исследовано структурно-фазовое состояние, микротвердость и износостойкость обработанного ионами азота электроосажденного покрытия Fe 64Ni 36. Установлено, что ионно-лучевая обработка приводит к образованию в поверхностных слоях покрытия Fe 64Ni 36 твердого раствора азота в матричной g-фазе (g N), а также нитрида (Fe,Ni) 4N - g?-фазы. Микротвердость модифицированного ионами азота поверхностного слоя покрытия Fe 64Ni 36 возрастает до Н 0 ,24 = 7600 МПа. Показано, что ионно-лучевая обработка Fe-Ni покрытия приводит к существенному снижению интенсивности его изнашивания.

Будилов В.В., Агзамов Р.Д., Рамазанов К.Н., Рамазанов И.С. Технология ионного азотирования титанового сплава ВТ6 с применением эффекта полого катода // Упрочняющие технологии и покрытия. 2014. Т. 116. № 8. С. 37–39.

Рассмотрена технология ионного азотирования титанового сплава ВТ6 в тлеющем разряде с проявлением эффекта полого катода (ЭПК). Определено влияние ЭПК на параметры тлеющего разряда, структуру и микротвердость титанового сплава ВТ6. Получены вольтамперные характеристики, оценена микротвердость по глубине азотированного слоя, проанализирована структура азотированных образцов в тлеющем разряде с проявлением и без проявления ЭПК. Разработан технологический процесс ионного азотирования, основанный на фазовом модифицировании поверхностного слоя в тлеющем разряде с проявлением ЭПК титановых сплавов.

Графов Б.М. Фрактальная теория диффузионного электрохимического шума // Электрохимия. 2015. Т. 51. № 1. С. 3-9.

Выполнен стохастический анализ свойств равновесного шума в электрохимической цепи переменного тока, соответствующей электрохимической системе с диффузионным контролем за фарадеевским процессом. Показано, что адекватный учет шума импеданса Варбурга ведет к двух-фрактальному стохастическому уравнению Ланжевена, в которое входят фрактальные временные производные 1/2- и 1/4-го порядка. При этом фрактальная производная 1/4-го порядка характеризует цветность шумового источника. Проведена количественная оценка влияния шума импеданса Варбурга на релаксационный (переходный) режим установления равновесных флуктуаций электродного потенциала. Доказано, что в условиях диффузионного контроля за фарадеевским процессом электрохимическая стохастическая диффузия носит характер фрактальной ускоренной аномальной диффузии, асимптотически переходящей (при больших временах наблюдения) в режим нормальной стохастической диффузии.

Жачкин С.Ю., Болдырев А.И., Болдырев А.А., Михайлов В.В., Гедзенко Д.В., Пеньков Н.А. Антикоррозионная защита металла методом гальвоноконтактного осаждения // Упрочняющие технологии и покрытия. 2014. Т. 119. № 11. С. 29–31.

Представлены материалы по практическому применению метода гальваноконтактного осаждения покрытий в целях повышения коррозионной устойчивости стальных конструкционных материалов. Приведены практические режимы реализации метода.

Ляхов Б.Ф., Солодкова Л.Н., Ващенко С.В., Бардышев И.И. Применение тонких гальванических покрытий для создания барьера, препятствующего десорбции водорода из палладия // Коррозия: материалы, защита. 2012. №8. С.37-40.

Методами термодесорбции и хроноамперометрии исследовано влияние тонких (0,3-1 мкм) гальванических кадмиевых, цинковых, медных и двухслойных Cu/Cd покрытий на абсорбцию и десорбцию водорода палладиевой матрицей. Установлено, что все изученные покрытия обладают барьерными свойствами по отношению к водороду как при абсорбции, так и при его десорбции из Pd. Однако кадмиевые покрытия обладают лучшими барьерными свойствами для выхода водорода из Pd, чем цинковые покрытия. Барьерные свойства тонких кадмиевых покрытий усиливаются при нанесении на Pd подслоя электролитической меди, что особенно важно при изучении поведения малых количеств водорода в Pd.

Мозгов С.А., Саушкин Б.П., Моргунов Ю.А., Лобода А.А. Электрохимическая отделочная обработка изделий из сплава ЭП5741НП // Упрочняющие технологии и покрытия. 2014. Т. 110. № 2. С. 6–10.

Проведен анализ возможности электрохимической обработки изделий из сплава ЭП 741НП с точки зрения получения поверхностей с низкой шероховатостью и гарантированного удаления дефектного слоя после операции электроэрозии. Исследована динамика выравнивания исходной микрогеометрии поверхности. Подобраны состав электролита и параметры режима для электрохимической отделочной обработки изделий из сплава ЭП 741НП.

Нечипорук В.В., Юзькова В.Д., Ткачук М.М. Поведение окислительно-восстановительных систем с электростатической адсорбцией на электродах в отсутствие пассивации // Электрохимия. 2011. Т. 47. № 12. С. 1438-1450.

В работе проводится теоретическое исследование влияния электростатической адсорбции на устойчивость стационарных состояний и возникновение монотонной неустойчивости в электрохимических системах без пассивации при различных режимах проведения процесса (гальваностатическом, потенциостатическом и режиме постоянной разности потенциалов). Показано, что электростатическая адсорбция может быть причиной возникновения множественности стационарных состояний в гальваностатическом режиме и режиме постоянной разности потенциалов. Построены соответствующие диаграммы статической бифуркации в областях различных параметров системы. В потенциостатическом режиме рассматриваемая система стремится к устойчивому стационарному состоянию.

34. J01823
Перелыгин Ю.П., Киреев С.Ю., Виноградов С.Н.Износостойкость и антифрикционные свойства гальванических покрытий палладием, оловом, цинком и сплавами на их основе // Трение и смазка в машинах и механизмах. 2012. №10. С.13-16.

Проведены сравнительные испытания гальванических покрытий палладием, оловом, цинком и сплавами на их основе в целях определения их износостойкости и антифрикционных свойств. Из исследованных покрытий наибольшей износостойкостью обладает покрытие сплавом палладий-никель, лучшими антифрикционными свойствами – олово-цинк.

Печенкина И.А., Михельсон К.Н. Материалы мембран ионоселективных электродов на основе ионофоров: проблемы и достижения (обзор) // Электрохимия. 2015. Т. 51. № 2. С. 115-125.

Представлен обзор работ, посвященных материалам мембран ионоселективных электродов (ИСЭ) на основе ионофоров. Кратко рассмотрены основные сведения о таких мембранах. Исходя из того, что поливинилхлорид (ПВХ) до сих пор доминирует в качестве матрицы мембран ИСЭ на основе ионофоров, и ограниченные сроки жизни таких электродов обусловлены недостаточной липофильностью компонентов мембран, прежде всего их пластификаторов, обсуждаются полимеры, применяемые в качестве альтернативы ПВХ и ионофоры, иммобилизованные на цепи полимера. Приведены сведения об ИСЭ, компоненты мембран которых представляют собой перфторированные соединения, что может быть особенно важно для медико-биологических применений. Приведены краткие сведения о работах, где вместо замены ПВХ само-пластифицированными полимерами осуществлена замена низкомолекулярных пластификаторов их полимерными аналогами при сохранении ПВХ в качестве полимерной матрицы. Обсуждается применение ионных жидкостей в качестве компонентов мембран ИСЭ и интерпретация полученных в литературе закономерностей функционирования таких электродов. По ходу обзора привлекается внимание к электрохимическим аспектам вопросов, которые исследуются в литературе, главным образом, с точки зрения материаловедения.

Степанов И.Б., Прибытков Г.А., Фирсина И.А., Иванов Ю.Ф. Нитридные покрытия, полученные вакуумно-дуговым испарением порошковых катодов Ti–Al, Ti–Al–Si // Упрочняющие технологии и покрытия. 2014. Т. 110. № 2. С. 33–37.

Проведены исследования структуры и свойств покрытий, полученных вакуумно-дуговым испарением экспериментальных спеченных катодов Ti–Al и Ti–Al–Si. Установлено, что покрытия содержат нанокристаллические составляющие, обладают сверхвысокой твердостью, износостойкостью, имеют низкий коэффициент трения. Шероховатость поверхности покрытий, осажденных при испарении композиционных катодов, значительно меньше, чем у соответствующих композиционных покрытий, осажденных при совместном использовании одноэлементных титанового и алюминиевого катодов.

Сторублев М.Л. Повышение управляемости технологических процессов нанесения гальванических покрытий // Упрочняющие технологии и покрытия. 2014. Т. 112. № 4. С. 37–43.

Представлена методика повышения управляемости технологических процессов. Выполнено моделирование процессов электролитического хромирования и меднения в стационарной ванне, для которых определены управляющие параметры, назначены допуски на параметры процессов, выполнена оценка гибкости процессов по времени.

Толмачев Ю.В. Водород-галогенные электрохимические ячейки: обзор применений и технологий (обзор) // Электрохимия. 2014. Т. 50. № 4. С. 339-356.

В данном обзоре описываются традиционные и новые применения водород-галогенных прямых и регенеративных топливных элементов, такие как рекуперация энергии из избытка H2 и Cl2, образующихся в ходе хлор-щелочного электролиза, а также стационарное и мобильное хранение энергии. Из-за значительного сходствa между водород-галогенными топливными элементами и электролизерами, последние также обсуждаются в данной работе. Далее следует более детальное описание различных конструкций, классифицируемых по используемым электролитам: водные растворы, иономеры, допированный фосфорной кислотой полибензимидазол, галогенидные расплавы и другие. Делается вывод о том, что водород-хлорные и водород-бромные топливные элементы могут быть конкурентоспособными вариантами для применения в области стационарного и мобильного хранения энергии. Тем не менее выбор наиболее подходящего электролита для таких элементов не может быть сделан в настоящее время, и необходимы дальнейшие исследования полных систем, в особенности систем с иономерами и твердокислотными электролитами.

Толмачев Ю.В., Воротынцев М.А. Топливные элементы с химически регенеративными редокс-катодами (обзор) // Электрохимия. 2014. Т. 50. № 5. С. 451-461.

Использование редокс-медиаторов, находящихся в фазе раствора, позволяет осуществить медленную реакцию восстановления кислорода в объеме раствора, а не на поверхности электрокатализатора из дорогостоящего металла. В данной работе обсуждаются детали химических превращений нескольких потенциальных медиаторов (Br2/2Br–, V(V)/V(VI) и другие системы), статус этих разработок и перспективы дальнейшего развития топливных элементов с химически регенеративными редокс-катодами.

Щепочкин А.В. и др. Прямая нуклеофильная функционализация C(sp2)-H связей в аренах и гетероаренах электрохимическими методами // Успехи химии. 2013. Т. 82. № 8. С. 747-771.

Систематизирован и обобщен материал по основным электрохимическим методам и приемам, используемым для прямой функционализации связи С(sp 2)-H, которая протекает по механизмам нуклеофильного замещения водорода (S N H-реакции). Рассмотрены важные особенности препаративных электрохимических процессов. Особое внимание уделено синтетическим возможностям обсуждаемых превращений.

Ярославцев И.Ю. , Богданович Н.М., Вдовин Г.К., Демьяненко Т.А., Бронин Д.И., Исупова Л.А. Катоды на основе никелато-ферритов редкоземельных металлов, изготовленные с применением промышленного сырья, для твердооксидных топливных элементов // Электрохимия. 2014. Т. 50. № 6. С. 611-617.

Синтезированы порошки композитных материалов на основе никелато-феррита лантана с применением мишметалла Ln - Ni - Fe - O (LnNF), различающихся соотношением лантаноидов. Методом РФА определен фазовый состав порошков. Установлено, что кристаллическая структура основной фазы в LnNF, полученного с применением мишметалла с высоким содержанием лантана перовскитоподобна, а с высоким содержанием церия - флюоритоподобна. Методом дилатометрии определены температурные коэффициенты линейного расширения синтезированных материалов. Четырехзондовым методом на постоянном токе исследованы температурные зависимости электропроводности компактных образцов и пористых электродов из этих материалов. Электропроводность компактных образцов из материалов, изготовленных с применением мишметалла с перовскитоподобной структурой основной фазы, приблизительно на три порядка превосходит электропроводность материалов на основе мишметалла с высоким содержанием церия. Методом импедансной спектроскопии исследованы температурные зависимости поляризационной проводимости электродов в ячейках с Ce0.8Sm0.2O1.9 (SDC) электролитом при 600 - 900°С в воздушной среде. Установлено, что электроды из LnNF, имеющие перовскитоподобную кристаллическую структуру основной фазы, обладают высокой электрохимической активностью.

На главную              К списку выставок