Kinetics of Cathodic Processes of Deposition of Nickel–Molybdenum Alloys from an Ammonia–Citrate Electrolyte

Kinetics of cathodic processes in an ammonia–citrate electrolyte for depositing Ni–Mo alloys is studied. During electrolysis at potentials of up to –0.92 V (NHE) the cathode surface becomes covered by a film consisting of compounds of molybdenum of lower valencies. The beginning of the alloy deposition, which occurs at potentials more negative than –0.92 V, barely affects the partial density of the current of reduction of molybdate ions.     

Kinetics of cathodic reactions in the electrodeposition of cobalt-molybdenum alloy

Kinetics of cathodic reactions in the ammonia-citrate electrolyte for cobalt-molybdenum alloy deposition is studied using the method of quasi-steady-state polarization curves. The effect of concentration of sodium molybdate on the partial current densities of cobalt and molybdenum deposition is analyzed. The effect of hydrodynamic conditions on the kinetics of cathodic reactions in the cobalt-molybdenum alloy deposition is studied by the method of rotating disk electrode (RDE). In the system under investigation, the dependences of partial current densities of cobalt and molybdenum deposition on the square root of RDE angular velocity are rather complex. The experimental data are discussed under the assumption that various species are adsorbed on the cathode.     

Degradation mechanisms of MEA characteristics during water electrolysis in solid polymer electrolyte cells

The processes contributing to degradation of characteristics of membrane-electrode assemblies (MEA) of water electrolyzers with solid polymer electrolyte (SPE) are considered. Particularly, the life tests of an electrolysis cell with SPE reveal the migration of platinum from the cathodic active layer and its deposition in membrane’s near-cathode region. In addition to platinum, several other elements (Ti, Ir, Fe, Ni, Si) are detected in the membrane, carried there with the water-reagent from the structural elements of MEA, electrolysis cell, and its outer framing (anodic electrocatalytic layer, half-cells, tubes, water tank-separator, etc.). The observed considerable loss of platinum in the cathodic catalytic layer leads to a decrease in its activity (due to the decrease in concentration of platinum nanoparticles and the loss of their cohesion), while the appearance in the membrane of platinum and other ions that have the lower mobility as compared with hydrogen ions gives rise to modifications in the membrane structure thus increasing the electrolysis potential in the course of life tests.     

Electrodeposition of a cobalt-molybdenum alloy from an ammonia-citrate electrolyte

Kinetics of processes of electrochemical production of a cobalt-molybdenum alloy out of an ammonia-citrate electrolyte is studied. The electrolyte’s composition is similar to that used for depositing a nickel-molybdenum alloy. It is established that the cobalt-molybdenum alloy undergoes deposition at smaller values of pH (5.0–6.0) than the nickel-molybdenum alloy (7.0–9.0). The current efficiency for the cobalt-molybdenum alloy is substantially dependent on the electrolyte pH, whereas the chemical composition of the obtained deposits is practically independent of the electrolyte pH in the pH interval 5.0–8.0 at current densities of 0.025 to 0.100 A cm^?2. On the other hand, a change in the electrolyte pH produces a considerable effect on the morphology of the obtained deposits. At large values of pH (pH 8.0), one can obtain a powder-like deposit of the cobalt-molybdenum alloy with a small value of the current efficiency. The deposits that are obtained in the pH region 5.0–6.0 have some cracks, with the number of cracks increasing with the electrolyte pH.     

Electrochemical Formation of Al-Li Alloys by Codeposition of Al and Li from LiCl-KCl-AlF3 Melts at 853 K

The electrochemical behavior of Al(III) ions was studied in molten LiCl-KCl melts on a molybdenum electrode. Cyclic voltammetry, chronopotentiometry and chronoamperometry were used to explore the deposition mechanism of Al and Li. Cyclic voltammetry expriment indicates that under potential deposition(UPD) of lithium on pre-deposited aluminium led to the formation of liquid Al-Li alloys at 853 K. The diffusion coefficient of Al(III) ions at 853 K in LiCl-KCl-AlF₃(1%, mass fraction) melts was determined to be (2.79±0.05)×10^?5 cm²/s. Chronopotentiograms and chronoamperograms demonstrate that the codeposition of Al(III) and Li(I) ions formed Al-Li alloys at cathodic current densities higher than ?0.28 A/cm² or cathodic potentials more negative than ?2.20 V. X-Ray diffraction(XRD) pattern indicates that Al-Li alloys with different phases formed via galvanostatic electrolysis. Inductively coupled plasma(ICP) analyses of the samples obtained by electrolysis show that lithium and aluminium contents of Al-Li alloys could be controlled by AlF₃ concentration and current intensity.     

Ni–Mo alloy nanostructures as cathodic materials for hydrogen evolution reaction during seawater electrolysis

In the case of hydrogen production involving seawater electrolysis, one of the main targets is to develop more active cathodic materials, to optimize the efficiency of hydrogen evolution reaction (HER) and, by doing so, enhance the overall energy efficiency of electrolysis. Thus, to develop suitable HER electrocatalysts either an increase of the electrode active surface area or a design of a material having high intrinsic catalytic activity should be taken into consideration, both of them decreasing the HER overpotential. In the present work, various Ni–Mo alloy nanostructures (10–40 wt% Mo) have been prepared involving electrochemical deposition from aqueous and deep eutectic solvent (DES)-based electrolytes as potential cathodic materials suitable for hydrogen evolution reaction during water electrolysis. The electrocatalytic activity of the obtained layers has been investigated using real seawater electrolyte. The determined Tafel slopes suggested that the electrodeposited Ni–Mo alloy coatings follow an HER mechanism controlled by the Volmer reaction step. The EIS results indicated that the use of choline chloride-based ionic liquids as electrolytes facilitated Ni–Mo alloy coatings showing a significant increase in surface roughness. Studies of the intrinsic activity showed that the main contribution towards the apparent activity comes from the increase of the real surface area, although a slight increase of the intrinsic electrocatalytic activity in the case of Ni–Mo alloy coatings electrodeposited on Ni foam was also noticed. These results showed that Ni–Mo alloy coatings electrodeposited from the novel electrolytes based on choline chloride–urea–citric acid ternary mixtures associated with a porous substrate may represent a promising technological approach to build cathodic materials suitable for seawater electrolysis.     

Electrodeposition of Palladium-Zinc Alloy from the Ammonium Chloride-Na2EDTA Electrolyte

The influence of the electrolysis regime and electrolyte composition on the cathodic current efficiency by the palladium-zinc alloy and on the alloy composition was studied.     

Electrodeposition of Palladium-Zinc Alloy from Aminoacetic Electrolyte

The influence of the electrolysis conditions and electrolyte composition on the cathodic current efficiency by the alloy and on the alloy composition was studied for electrodeposition of the palladium-zinc alloy from an aminoacetic electrolyte.     

Recovery of Metals from Anodic Dissolution Slime of Waste from Electric and Electronic Equipment(WEEE) by Extraction in Ionic Liquids

The recovery of metals from a multi-component alloy obtained by crushing, melting and anodic dissolution of waste from electric and electronic equipment(WEEE) was investigated. The anodic dissolution of the alloy was carried out in an electrolysis cell with one copper cathode and a central cast anode, immersed in the electrolyte formed by choline chloride-ethylene glycol-iodine. The temperature of the electrolyte during the process was 343 K. Depending on the electrolysis parameters(current density and cell voltage), cathodic deposits of Sn, Pb and Zn of >99% purity were obtained. Cyclic voltammetry was used in order to determine the deposition potentials of the studied metals. The obtained metallic deposits were subject of determination of XRD, SEM/EDX and AFM in order to evidence the deposits structure and morphology. The experiments performed demonstrated the possibility of separating/selective recovery of metals from the multi-component alloy resulted from the waste from electrical and electronic equipment by anodic dissolution in ionic liquids.     

Electroreduction of Mo(VI) Compounds in Ammonium–Acetate Solutions

The kinetics of cathodic reactions in ammonium acetate solutions proposed for electrodeposition of metallic molybdenum was studied. The reduction of molybdenum compounds in the oxidation state +6 was found to occur stepwise according to the scheme Mo(VI) → Mo(V) → Mo(III). The waves observed on the polarograms are complicated by adsorption effects. The reduction of molybdenum to the metallic state is possible only at high negative potentials of the cathode; under the polarographic analysis conditions, this wave was not recorded. The deposit that formed on the surface of the solid cathode during cathodic polarization (i = 0.5 A cm^–2) contains both molybdenum in the metallic state and molybdenum oxides. The ratio between the electrolysis products depends on the temperature of solution: a decrease in the temperature leads to an increase in the amount of metallic molybdenum.

     

Continuous recovery of uranium oxides by electrolysis of M2MoO4-M2Mo2O7-UO2MoO4 melts (M = Li, Na, K, Cs)

Effect of the electrolyte composition and of the solvent-salt cation on the oxygen coefficient of the cathodic product (O/U atomic ratio) and basic characteristics of the potentiostatic electrodeposition of uranium dioxide in prolonged recovery of uranium oxides from electrolytes of the system M₂MoO₄-M₂Mo₂O₇-UO₂MoO₄ Melts (M = Li, Na, K, Cs) in air was analyzed. A decrease in the UO₂MoO₄ concentration and accumulation of M₂Mo₂O₇ in the electrolyte in the course of a prolonged electrolysis suppress the solvolysis of uranyl ions and make lower the oxygen coefficient of the cathodic product. Li₂MoO₄-based melts possessing pronounced oxygenacceptor properties exhibit an anomalous behavior in these experiments. The current efficiency, initial current density, and deposition rate of the product decrease as electrolytes are depleted of uranium. In discussions of numerical data, it is necessary to take into account the formation of lower valence forms of uranium due to the chemical corrosion of the cathodic product, and in the case of melts of the lithium system, the additional cathodic process in which the solvent is reduced.     

硫酸亚铁对化学沉积钴-铁-磷合金中的影响(英文)

在以次亚磷酸钠为还原剂、硼酸为缓冲剂和柠檬酸钠为络合剂的碱性介质中,化学沉积钴 铁 磷合金和钴 磷合金.研究了沉积工艺,如pH值和主盐CoSO4/FeSO4的摩尔比对沉积速率的影响.发现镀液中的硫酸亚铁对钴 铁 磷合金沉积有阻碍作用,以致其沉积速率比钴 磷的低.电化学极化实验表明,硫酸亚铁既影响阳极过程又影响阴极过程,它降低了两者的极化电流和极化电势.电化学实验结果与沉积速度测量结果基本相符.     

乙二胺在化学沉积Ni-B合金中的机理

研究乙二胺稳定剂对化学镀N i-B合金沉积速率和镀液稳定性的影响.实验表明,少量乙二胺可改善镀液的稳定性.镀液的电化学测试发现,乙二胺对体系的阳极过程和阴极过程均有影响,还原剂的氧化电流和合金的还原电流均随乙二胺加入量的增加而减少.红外光谱显示乙二胺附在镍基体表面发生化学吸附,从而抑制了还原剂的氧化,降低N i-B化学沉积速率(稳定了镀液).     

Electroreduction of molecular oxygen on carbon electrode modified by dispersed silver

Silver particles are formed by electrochemical deposition on the carbon electrode surface. It is found that the deposition process occurs according to the progressive nucleation mechanism, which results in formation of silver particles with the size of 95 to 190 nm as dependent on the electrodeposition time. The values of silver particle size and support surface coverage by metal obtained on the basis of microphotographs indicate that cathodic polarization in the presence of dissolved oxygen results in particle size redistribution due to the reaction of silver particle dissolution with further deposition simultaneously with oxygen electroreduction. The reaction of molecular oxygen electroreduction on a carbon electrode with deposited dispersed silver occurs via a mixed two- and four-electron mechanism. The observed limiting reaction current is of diffusion nature.     

Effect of Cathodic and Anodic Polarization in a Lithium Sulfate Solution on the Electrical Conductivity of Carbonized Fibrous Carbon Materials

The effect of cathodic and anodic polarization of carbonized fibrous carbon materials of the KNM and NT-1 types in a Li₂SO₄ solution on their properties: electrical conductivity, steady-state electrode potential, electrical conductivity profile across the electrode thickness in relation to the electrolysis time, current density, Li₂SO₄ concentration, electrode thickness, and current reversal, was studied. The stability of the resulting electrical conductivity profile across the electrode thickness with time and in the course of the subsequent electrolysis was assessed. The reduction of Fe³⁺ in the ferri-ferrocyanide system on electrically iso- and nonisoconducting fibrous carbon electrode was considered.     

Electrodeposition of nanocrystalline Ni–Cu alloy from environmentally friendly lactate bath

A new environmentally friendly electroplating bath for Ni–Cu alloy deposition was developed. Lactic acid was used as a complexing agent. The influence of bath composition, current density, pH and temperature on cathodic polarization, cathodic current efficiency and alloy composition was studied. Different proportions of the two metals were obtained by using different deposition parameters, but at all [Ni²⁺] / [Cu²⁺] ratios studied, preferential deposition of Cu occurred and regular co‐deposition took place. The Ni content of the deposit increased with Ni²⁺ content and current density and decreased with temperature. The surface morphology of the deposited Ni–Cu alloy was investigated using scanning electron microscopy. The crystal structure was examined using the X‐ray diffraction technique. The results showed that the deposits consisted of a single solid solution phase with a face‐centered cubic structure. The crystallite size lies in the range of 12 to 25 nm for as‐plated alloys. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of concentration of ammonia and citrate ions on the kinetics of cathodic reactions during electrodeposition of a nickel-molybdenum alloy

The effect of the concentration of ammonia and citrate ions on the kinetics of cathodic processes in electrolytes intended for depositing electrolytic coatings of a nickel-molybdenum alloy is studied. Conditions conducive to obtaining coatings of satisfactory quality are formulated. The effect of ammonia and citrate ions on the Mo content in the alloy is analyzed. The experimental data are explained by assuming that the intermediate products of reduction of nickel and molybdate ions are adsorbed on the electrode surface.To the Centennial of B.N. Kabanov.Translated from Elektrokhimiya, Vol. 41, No. 1, 2005, pp. 83–90.Original Russian Text Copyright © 2005 by Kuznetsov, Pavlov, Chepeleva, Kudryavtsev.     

Electroreduction of molybdenum(VI) at a prehydrogenated platinum electrode

The use of hydrogenated platinum electrodes allows observation of the electroreduction of some oxygenated ions, which is otherwise masked by the reduction of the hydrogen ion. The present paper deals with the reduction of molybdenum(VI) at a prehydrogenated platinum electrode in acid solutions. The experimental conditions for the electrode hydrogenation process are the following: 90 min at a cathodic current density of about 7 A/cm(2) for microelectrodes with an area of 0.02-0.03 cm(2); about 120 min at a current density of 1.5-2 A/cm(2) for microelectrodes with an area of 0.25-0.35 cm(2). The reduction of molybdenum(VI) in 0.8-1.6M H(2)SO(4) occurs in two consecutive steps: the more cathodic wave [Mo(V) to Mo(III)] is for the most part masked by the reduction of the solvent; the less cathodic wave [Mo(VI) to Mo(V)] takes place at E(1 2 ) values of about +0.07 V, is well shaped, diffusion-controlled and usable for the determination of molybdenum down to 4 x 10(-5)M or 6 x 10(-5)M if a rotating disk electrode is used. Interferences from diverse ions have been studied. A generalization of the effect of electrode hydrogenation on the reduction of those oxygenated ions so far studied [i.e., vanadium(IV), uranium(VI) and molybdenum(VI)] is presented.     

On-line electrolytic dissolution of solid metal samples and determination of copper in aluminium alloys by flame atomic absorption spectrometry

A flow-injection system was developed in which alloy metal samples are electrolytically dissolved and the dissolved samples are analysed by flame atomic absorption spectrometry (FAAS). The effects of electrolyte composition and electrolysis parameters on the dissolution of the sample were studied. The method was used for the determination of copper in aluminium alloys. Electrolyte solutions consisting of 0.2–1.0 M nitric acid are better than other electrolytes tested with regard to both alloy sample dissolution and determination of copper by FAAS. The peak height increases linearly with the electrolysis time or current within a certain range. The detection limit depends on the sensitivity of the detector used, and can be improved by increasing the electrolysis time or current. Generally, aluminium alloys containing 0.5–10% copper can give suitable signals for FAAS determination. The reproducibility of electrolysis and determination is about 4% for the same sampling points and 5% for different sampling points on the alloy sample.     

Preparation of Amorphous Film on Ni-S Alloy by Electroplating Method

IntroductionRecently,amorphousalloyshaveattTactedconsiderableattentionasnewfunctionalmaterial.Theycanbeattainedbyelectroplating,suchasplatingNi-P,Ni-B,Fe-W,Ni-Mo,Fe-P,etc..ThestructureofcodepositednickelandsulfurwasfirststudiedbyBrilllwithXRD.He,however,didnotdiscussthemethodofcodepositingnickelandsulfur.Afterwards,thereweresomereportsonNi-Sdeposit.Ingeneral,aNi-SdepositcanbeobtainedbyelectroplatingfromaWattsbathcontainingsuchsulfursourcesasthiocyanateKCNS',thioureaNH,CSNH,',andso…