Stationary Electrolysis Research Articles

Cobalt-vanadium coating deposition via programmed electrolysis mode

In the current work, the co-deposition of cobalt with vanadium from a complex citrate electrolyte via stationary and pulse electrolysis modes was investigated. The process was carried out at a current density of 1–15 Adm–2 in stationary electrolysis mode and 2–10 Adm–2 in pulse electrolysis mode, with variable ratio of pulse time to pause time at a temperature range of 35–400С and pH 3.0–3.5. According to the results of X-ray fluorescence spectrometry, the maximum content of vanadium in the coating obtained via the programmed electrolysis mode is 1.20–1.45%, which is tens of times higher than in the coating deposited by the stationary electrolysis mode (vanadium content of 0.007–0.017%) under similar conditions. The obtained results may confirm the hypothesis of additional vanadium reduction from oxo-anions by adsorbed hydrogen atoms formed on the cathode surface during the pause period. Based on the results of the analysis of 3D graphs, the optimal parameters of the process for fabricating a cobalt-vanadium coating with the maximum vanadium content in the alloy and a coating current efficiency of 80% have been established.

ELECTROLYSIS CONDITIONS EFFECT ON THE VANADIUM-CONTAINING COATINGS COMPOSITION

The development of functional materials with predictable properties is one of the priority directions in modern research. Obtaining new energy-saving materials for reducing the cost of hydrogen production in an electrochemical way is relevant for the hydrogen energy industry. Such electrode materials should have catalytic activity for the hydrogen evolution reaction. Catalytic properties can be predicted for coating alloys of the iron subgroup metals with vanadium, molybdenum, and tungsten. The aforementioned metals can be co-deposited from aqueous solutions with iron subgroup metal catalysts through the formation of cluster intermetallic compounds with Me-V, Mo, W bond adsorbed on the cathode surface. The induced co-deposition of cobalt with vanadium from the complex citrate electrolyte via stationary and pulse electrolysis modes was investigated in the current work. As a result of the research, it was found that the uniform microcrystalline light-gray high-quality cobalt-vanadium alloy coating is possible to be deposed from a citrate electrolyte with content of 0,1 mol/dm3 vanadium (in terms of metal) as a citrate complex The process was carried out at a current density of 1–15 A/dm2 by stationary electrolysis mode and 2–10 A/dm2 by pulse electrolysis mode, with a different ratio of pulse time to pause time, at a temperature range of 35–40°С and pH = 3,0–3,5. According to the results of the X-ray fluorescence (XRF) spectrometry, the maximum content of vanadium in the coating obtained via the programmable electrolysis mode is 1.20–1.45%, which is tens of times more than in the coating deposited by the stationary electrolysis mode (vanadium content 0.007-0.017%) under similar conditions. The obtained result may be a confirmation of the hypothesis of vanadium additional reduction from oxo-anions by adsorbed hydrogen atoms that formed on the cathode surface during the pause period. According to the results of the analysis of 2D graphs, the optimal parameters of the process for obtaining a cobalt-vanadium coating with the vanadium maximum content in the alloy and the coating current yield of 80% have been established.

The Effect of Organic Acids in the Presence of Cyclic Lactams on Kinetics of Electrodeposition and Morphology of Nickel Coatings Modified with Polymer

Using stationary electrolysis, the effect of the structure and concentration of some organic acids on kinetic parameters of electrodeposition of nickel from sulfate electrolytes containing cyclic lactams, such as e-caprolactam (CL) and N-methylpyrrolidone (MP), microstructure, mean grain size, and crystallite orientation has been studied. Integrated analysis of the data of polarization, adsorption, and spectral investigations has shown that enhancement of adsorption of amino acids in the presence of lactams leads not only to an increase in the polarization of the process, but also to significant changes of surface morphology. According to X-ray phase analysis and SEM data, the surface becomes smoother in the presence of amino acids, the grain size decreases, and a predominant orientation of crystallites appears in some cases. The formation of metal–polymer sharp-edged grains in the coatings prepared in the presence of CL and glycine has resulted in the formation of continuous smoothed layer and appearance of mirror shine of the deposits.

Performance and degradation of an SOEC stack with different cell components

High temperature water electrolysis with solid oxide electrolysis cells (SOECs) is a promising method for hydrogen production. In order to study the performance and degradation behavior of cells with different cell components in electrolysis mode, a four-cell stack was assembled that used JÜLICH's F10 design with two types of air electrodes based on La0.6Sr0.4CoO3−δ (LSC) and La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF). A PVD-prepared GDC layer was applied to LSCF cells while a screen-printing GDC layer was used in the LSC cells. The performance of the stack was first characterized with IV-curve measurements in both SOFC and SOEC modes within the temperature range of 700–800 °C. The durability of the stack was investigated by conducting a long-term stationary electrolysis operation with a constant current density of −0.5 Acm−2 and steam conversion rate of 50% at 800 °C. Electrochemical Impedance Spectroscopy (EIS) was used to study the electrochemical performance of the stack, as well as the degradation behavior during long-term electrolysis operation. The method “Distribution of Relaxation Times” (DRT) was applied for the further analysis of the EIS data, and the DRT results have successfully supported the stack degradation analysis.

Methods for controlling the composition and morphology of electrodeposited Fe–Mo and Fe–Co–Mo coatings

The effect of the electrolyte composition and the stationary electrolysis parameters on the composition and morphology of Fe–Mo and Fe–Co–Mo coatings deposited from complex citrate electrolytes based on Fe(III) is studied. It is shown that, at a constant component ratio of с(Fe3+): с(Co2+): с(MoO2− 4): с(Cit3–) = 2: 2: 1: 4, an increase in the electrolyte concentration leads to a decrease in the pH of the solution in a range of 4.85–4.30 and in the molybdenum content in the coating. An increase in the current density contributes to the molybdenum enrichment of the electrodeposited alloy in the entire range of electrolyte concentrations. The Fe–Mo alloy coatings have a rough microporous surface; an increase in the current density does not lead to significant changes in the surface topography. It is found that the formation of ternary coatings is characterized by the competitive reduction of iron and cobalt in the alloy; the molybdenum content depends on the current density. At a metal ratio of 3: 2: 1 and a molybdenum content of up to 17 at % in the Fe–Co–Mo alloy, the surface has a fine-grained needlelike structure typical of cobalt. With an increase in i c, the atomic fraction of molybdenum increases, while the surface becomes microglobular. The Fe–Co–Mo electrodeposits with a metal ratio of 2.5: 1.5: 1.0 and a molybdenum content of 19–20 at % have a more developed surface with a high density of spheroids.

Intensification of processes of electrodeposition of metals by use of various modes of pulse electrolysis

Investigations of the influence of various modes of electrolysis on the speed of processes of electrodeposition of metals are conducted. On the basis of theoretical investigations, the main potential opportunities for process intensification when using an pulsed current for processes whose speed is defined by mass transfer and charge transfer are defined. Weakly toxic electrolytes based on lactic acid are developed for formation of electroplatings by nickel, zinc, and tin; optimum parameters of stationary, galvanostatic, and potentsiostatic pulse electrolysis are determined. Investigations of kinetic regularities of the process of electrodeposition of metals are conducted, and the limiting stages of processes are defined. It is established that the greatest impact on the speed of electrodeposition of metals is exerted by potentiostatic pulse electrolysis. It is revealed that, to a greater degree, the intensification when using a pulsed current is characteristic of processes whose speed is limited by mass transfer.

Effect of H2O2 on Pt electrode dissolution in H2SO4 solution based on electrochemical quartz crystal microbalance study

The effect of H2O2 on the Pt dissolution in 0.5 mol dm−3 H2SO4 was investigated using an electrochemical quartz crystal microbalance (EQCM). For the potential cycling at 50 mV s−1, the Pt weight irreversibly decreases in a N2 atmosphere with H2O2, while only a negligible Pt weight-loss is observed in the N2 and O2 atmospheres without H2O2. The EQCM data measured by the potential step showed that the Pt dissolution in the presence of H2O2 depends on the electrode potential and the H2O2 concentration. For the stationary electrolysis, the Pt dissolution occurs at 0.61–1.06 and 1.06–1.36 V vs. RHE. It should be noted that the Pt dissolution phenomenon in the presence of H2O2 is also affected by the potential scanning time. Based on these results, H2O2 is considered not only to contribute to the formation of Pt-oxide causing the cathodic Pt dissolution, but also to participate in the anodic Pt dissolution and the chemical Pt dissolution.

Theoretical and experimental investigations on relationship between Kohlrausch regulating function/inequality and moving reaction boundary in electrophoresis

Kohlrausch regulating function (KRF) has been well defined from a moving boundary system for over 50 years. Recently, a series of theoretical and experimental studies were carried out on the concept of moving reaction boundary (MRB), including moving precipitate boundary, moving neutralization boundary and moving chelation boundaries (MCB). However, there has not been any direct evidence to show whether the KRF has validity for a MRB or not. In this paper, the KRF is derived from the equation of MRB under condition of nonzero boundary velocity. The result directly shows the relation between the KRF and a MRB. The relation is verified by some experimental and simulation results on MCB and moving neutralization boundary as well as Svensson's classic IEF. Furthermore, a Kohlrausch inequality was defined from the equation of MRB and was further proved by numerous data. The results show that we can use the KRF for the investigation on a MRB under the condition of nonzero boundary velocity, whereas we ought to notice with great attention that the KRF does possibly have invalidity under some special cases, such as stationary electrolysis and IEF. The findings hold an evident significance to the study of a MRB with the KRF.

The Alpher, Bethe, Gamow of isoelectric focusing, the alpha‐Centaury of electrokinetic methodologies. Part I

The birth and evolution of IEF in conventional carrier ampholyte buffers is reviewed here, from a shaky start during World War II, via desperate attempts of Svensson to create pH gradients by stationary electrolysis of salts, to the development of the IEF theory and the solution of the steady-state equation. The remarkable synthetic process of Ampholines, as ingeniously devised by Vesterberg, is additionally recalled, with a thorough description of the fundamental properties of these amphoteric buffers, creating and maintaining the pH gradient under strong electric fields. The review ends with a mention of the major contributions of B. J. Radola to this field, namely analytical and preparative IEF in granulated Sephadex layers and the development of ultrathin IEF, in polyacrylamide gels as thin as 20-100 mum. The latter technique paved the way to DNA sequencing gels and to CZE. The symptoms of decay are here presented through the simulations of Mosher and Thormann, clearly indicating an isotachophoretic mechanism for pH gradient decay with time. The decay of IEF was the birth of IPGs.

The unvalidity of Kohlrausch’ regulating function for Svensson’s isoelectric focusing and stationary electrolysis at steady state

Kohlrausch’ regulating function is of important significance in the field of electrophoresis. In this paper, the relative regulating function is defined from Kohlrausch’ regulating function. The relative values, including the limited values, of the regulating function for the stationary electrolysis of salt, on which the classic isoelectric focusing (IEF) is based, are computed and compared with the computer program of the QBASIC written by us. The results directly demonstrate that, (1) in a few cases the regulating function is valid for the stationary electrolysis and IEF, whereas (2) the function is, in most of cases, not valid for the stationary electrolysis and IEF at steady-state. Those findings may be useful for the studies on the relationships between Kohlrausch’ regulating function and IEF and for the classification of numerous electrophoretic techniques.

Steady-state electrolysis of a solution of nonamphotheric compounds.

The problem of stationary electrolysis of a solution of nonamphotheric compounds (acids or bases) is considered. The analysis is performed by taking into account the mobility dependence on pH. The properties of such a system are also compared with the ones pertaining to the solution of an amphoteric substance. It is anticipated that steady-state electrolysis of free acids and bases, in a convection-free system, might be useful for creating narrow pH gradients in rather acidic and alkaline milieus, which might be adopted for focusing without resorting to conventional carrier ampholytes or immobilized pH gradients.

Steady-state electrolysis of an ampholyte solution and possibility of violation of the "law of pH monotony".

The problem of stationary electrolysis of a single-component ampholyte solution is analyzed. The effect of nonconstant relative mobility is taken into account. It is demonstrated that an incorrect dissociation model (i.e., expressing the resulting ampholyte flux by the arithmetic sum of the fluxes for "cationic" and "anionic" species) may lead to the violation of the so-called "law of pH monotony".

Moving chemical reaction boundary and isoelectric focusing: II. Existence of quasi/equal fluxes (or transference numbers) of hydrogen and hydroxyl ions in stationary electrolysis and Svensson's isoelectric focusing

By using some basic physico-chemical data, the fluxes (or transference numbers) of proton and hydroxyl ion in the stationary electrolysis are compared with the relative judgment expressions which were defined from moving chemical reaction boundary equations. The results reveal that the quasi/equal fluxes of hydrogen and hydroxyl ions are present in the neutralization reaction boundary formed with pure acid and base, in stationary electrolysis and in Svensson's isoelectric focusing (IEF). Thus, the findings are completely in agreement with the inference–the existence of quasi/equal fluxes of proton and hydroxyl ion in stationary electrolysis and Svensson's IEF–which is based upon the conditional equations for the anolyte and catholyte (equivalently, stationary neutralization reaction boundary equations) and upon the facts that the pH gradients in Svensson's IEF are quasi-stable, but not complete stable.

Moving chemical reaction boundary and isoelectric focusing: I. Conditional equations for Svensson–Tiselius' differential equation of solute concentration distribution in idealized isoelectric focusing at steady state

In this paper, the differential equation, which is formulated by Svensson–Tiselius for the concentration distribution of protolytes in idealized isoelectric focusing (IEF) at steady state, is discussed. The general condition equations are formulated for Svensson–Tiselius' differential equation, and from the general conditional equations, the conditional equations for the acidic anolyte and alkaline catholyte used in Svensson's IEF are derived. It is theoretically shown that the condition equations for the anolyte and catholyte are the same as the stationary neutralization reaction boundary equations (SNRBEs) that can be deduced from the moving chemical reaction boundary equations (MCRBEs) in special cases. The conditional equations for the anolyte and catholyte reveal that an idealized IEF, viz., a stable pH gradient in IEF, can be achieved, if the fluxes of protons and hydroxyl ions migrating in opposite directions are equal to each other. According to the conditional equations for the anolyte and catholyte and the fact that the pH gradient in Svensson's IEF is quasi-stable, but not completely stable (due to the drifts and plateau of the pH gradient in IEF), one can infer that the quasi/equal fluxes of hydrogen and hydroxyl ions must be present in Svensson's IEF. As shown in the accompanying paper, this inference coincides with important findings, i.e. the existence of quasi/equal fluxes of hydrogen and hydroxyl ions in stationary electrolysis, on which Svensson's IEF is based.

Energy balance of D 2O electrolysis with a palladium cathode : Part I. Theoretical relations

On the basis of reliable thermochemical data, the relations for the calculation of the thermoneutral voltage, E tn, of the D 2O electrolysis from an approx. 0.1 M LiOD+D 2O solution with a Pd cathode with PdD n formation have been derived for stationary and non-stationary courses of electrolysis, as a function of reaction temperature, total pressure and current efficiencies of 0 2(g) and D 2(g) evolution. Due to the lack of thermochemical data for PdD n formation with n > 0.8, the accuracy of the calculated thermoneutral voltage with PdD n formation under non-stationary conditions is lower than for the case of stationary electrolysis.

Steady state electrolysis and isoelectric focusing

The properties of pH gradients formed by stationary electrolysis of weak mobile or fixed electrolytes are analyzed. The model uses the appropriate balance equations and those of chemical equilibria. It is shown how the equation of the current density has to be modified for considering that fraction of current that is associated with the diffusion of neutral buffer molecules within a pH gradient. Furthermore it is shown that the pH gradients themselves give rise to water production within the gradient and that essential properties of the steady state are related to chemical reactions between the electrolyte constituents. The differential equations describing the gradients of the concentration of a given component, the pH, conductivity and potential are explicitly formulated in relation to those reactions. The equations are solved numerically and the significance of the results for isoelectric focusing is discussed. The experimental conditions to reach shallow and smooth pH gradients exhibiting sufficient ionic strength are formulated.

Prospects and problems of electrochemically induced cold nuclear fusion

Experiments by Fleischmann, Pons and Jones stimulated the imagination of electrochemists. Now, concepts have to be discussed in detail. At first, the correlation between hot fusion muon catalyzed cold fusion and electrochemically and fracture induced cold fusion is explained. In Pd dueterons can be treated as delocalized bosons which are squeezed together in octahedral sites. The Coulomb barrier between the nuclei may be screened by the electron gas. Hence, deuteron tunneling may be enhanced. Experiments are discussed with respect to deuteron concentration and current-potential curves of relevant processes, i.e. deuteron or water discharge. In various experiments the surface state of the electrode is modified. Electrochemical calorimetry has to be carried out only for the limiting cases of complete electrolysis and recombination, respectively. Difficulties arise for stationary electrolysis. Radiochemical detection of fusion rates presumes careful elimination of background radiation, absorption phenomena (self and foreign), backscattering, etc. Experimental conditions to measure the tritium production, the γ-rays and neutrons are described. Three months after the first paper various interesting experiments have been presented. But there is no certain evidence and many doubts occurred. Independent of the estimated fusion rates, most results are near to the background level (neutron rates of 0.04 n/s) or to the experimental error (fusion heats corresponding to 10 13 s −1, similar to chemical reaction enthalpies). Experiments are complex for various reasons. To compare results of different authors, more experimental data have to be checked in detail. A distinction between a volume- or surface phenomenon is not yet possible. Neutron production at grain boundaries is discussed.

Isoelectric Focusing of Proteins in Gel Media

Abstract Separation of proteins according to their isoelectric point can be performed in a pH gradient formed by stationary electrolysis of carrier ampholytes. The pH gradient is stabilized by the use of polyacrylamide, agarose, and Sephadex gels. Separated proteins can be detected by fixation with trichloroacetic acid followed by nonspecific staining, by specific staining, or through immunodiffusion techniques. Isoelectric focusing of proteins in gel media can be carried out in gel columns or on thin-layer plates by using conventional electrophoresis apparatus. Electrofocusing can be followed by electrophoresis in gel media for more complete separation of components. Multiple samples of microgram quantities can be analyzed simultaneously by simple and rapid procedures. These methods have both analytical and preparative applications in protein fractionation work.

Isoelectric Characterization of Clostridium Botulinum Type C Toxin

The physico-chemical laws controlling natural pH gradients that have been developed by stationary electrolysis have been described in earlier papers by Svensson (2, 3). As demonstrated by Svensson (4) the resolving power attained by this method is better than 0.2 pH unit. In a later paper (5) the same author described the use of synthetic carrier ampholytes, and it was shown that a still better resolving power could be produced.