Overpotential Of Electrodeposition Research Articles

A highly reversible sodium metal anode by mitigating electrodeposition overpotential

Herein, we successfully introduce a sodiophilic Na–Cu–P composites via in situ alloying reaction, which can greatly mitigate the tip/growth/nucleation overpotential during Na deposition, thereby to realize a stable Na plating/stripping behaviors.

Extraction of tellurium and high purity bismuth from processing residue of zinc anode slime by sulfation roasting-leaching-electrodeposition process

Anode slime and its processing residue contains a variety of valuable elements, which are the main source of tellurium and bismuth. A systematic study on the extraction of tellurium and bismuth from processing residue of zinc anode slime and electrodeposition to obtain high purity bismuth was carried out. Sulfation roasting thermodynamics, leaching thermodynamics, and reduction potential involved in the extraction were calculated and used as theoretical guidance for the experiment. In the process of extracting tellurium and bismuth: the minimum amount of sulfuric acid and the appropriate low temperature of sulfation roasting conditions for processing residue of zinc anode slime are explained that the ratio of sulfuric acid to anode slime was 0.54:1, and the temperature was 435 °C. The leaching process of the roasting product was optimized. The optimal water leaching conditions were a liquid to solid ratio of 6:1 and a reaction time of 0.5 h at 25 °C. The optimal alkali leaching condition is 10% NaOH liquid to solid ratio of 6:1 and reaction time of 0.5 h at 25 °C. Tellurium and bismuth were separated, and tellurium was enriched from a low content of anode slime raw materials. The recovery rate of tellurium and bismuth were 84.9% and 97.1%, respectively. The reduced deposition process of bismuth ions on the cathode was characterized by cyclic voltammetry in the nitric acid. In the stable deposition state, electrodeposition overpotential of the bismuth ion on the titanium plate was 0.1068 V. Tributyl phosphate (TBP) was used as extraction solvent and nitric acid solution was used as stripping solution to purify the impurities in the basic bismuth sulfate. After extraction process, the removal rates of tellurium (Te), arsenic (As), copper (Cu), and antimony (Sb) were 96.5%, 93.3%, 99.1% and 100%, respectively. The content of other impurity elements also reduced greatly. The electrical separation process further reduced the content of impurities in the electrolyte, in which the concentration of tellurium was reduced to less than 1 ppm. A standard-compliant high purity elemental bismuth was obtained by electrodeposition from purified electrolyte.

Electrodeposition Kinetics in Li-S Batteries: Effects of Low Electrolyte/Sulfur Ratios and Deposition Surface Composition

Lithium-sulfur batteries obtain most of their capacity from the electrodeposition of Li2S. This is often a slow process, limiting the rate capability of Li-S batteries. In this work, the kinetics of Li2S deposition from polysulfide solutions of 1–7 M S concentration onto carbon and two conductive oxides (indium tin oxide, ITO; and aluminum-doped zinc oxide, AZO) were characterized. Higher polysulfide concentrations were found to result in significantly slower electrodeposition, with island nucleation and growth rates up to 75% less than at low concentrations. Since Li-S batteries with low electrolyte/sulfur (E/S) ratios necessarily reach higher polysulfide concentrations during use, the present results explain why high polarization and low rate capability are observed under such conditions. Given that low E/S ratios are critical to reach high energy density, means to improve electrodeposition kinetics at high polysulfide concentrations are necessary. Towards this goal, coatings of ITO and AZO on carbon fiber current collectors were found to improve island growth rates at 5 M by up to ∼60%. Of the two oxides, AZO was found to be superior in reducing the electrodeposition overpotential. Its benefits were demonstrated for carbon fiber current collectors coated with AZO and for conductive suspensions incorporating carbon black and nanoparticle AZO.

Application of the general theory of disperse deposits formation in an investigation of mechanism of zinc electrodeposition from the alkaline electrolytes

In this study, mechanism of electrodeposition of zinc from the alkaline electrolytes has been investigated using the general theory of disperse deposits formation. The exchange current densities in the range 18.4–88mAcm−2 were determined using new method based on comparison of experimental and simulated polarization curves, and the excellent agreement with the values found in the literature has been attained. Correlation between the polarization characteristics and morphologies of zinc deposits characterized by the scanning electron microscopic (SEM) technique was established. The spongy-like particles constructed from nanofilaments and the large grains or boulders were formed in the zone of the fast increase of the current density with the overpotential before the plateau of the limiting diffusion current density was reached. The shape of dendrites, formed inside the plateau of the limiting diffusion current density and at the higher ones, strongly depended on overpotential of the electrodeposition. Mechanism of formation of all obtained forms was discussed by the consideration of the different rates of growth of surface protrusions in a function of the overpotential of electrodeposition through the analysis of the change of the ratio between the height and the radius of the protrusions. In order to confirm of the proposed mechanism, comparison with polarization and morphological characteristics of the other metals characterized by the different exchange current density values was made and discussed. Although zinc is classified in the group of the normal metals characterized by the high values of the exchange current density, it was found that the polarization and morphological characteristics of zinc show certain and strong similarities with those of copper, classifying zinc just at boundary between the normal and intermediate metals, that is confirmed by the estimation of the exchange current density value for zinc.

Nucleation and early stages of growth of lead onto copper electrodes from dilute electrolytes

The processes of nucleation and growth of lead from the dilute electrolytes on copper substrates were investigated by chronoamperometry and by scanning electron microscopic (SEM) analysis of the deposits obtained in the potentiostatic regime of electrolysis. In the dependence of electrodeposition conditions, the nucleation of Pb followed either progressive or instantaneous type. The type of nucleation changed from progressive to instantaneous one with increasing the concentration of Pb(II) ions and the overpotential of electrodeposition. Regardless of the type nucleation, a novel type of Pb particles like cobweb was formed by the potentiostatic electrodeposition in the moment of nucleation and at the early stages of growth. On the basis of the shape of cobweb-like particles and the electrodeposition conditions leading to their formation, these particles were situated in the group of spongy-like ones. Also, comparative morphological analysis of Pb deposits obtained in the conditions of progressive and instantaneous nucleation confirmed the existence of two limiting types of nucleation.

Electrochemical and Crystallographic Aspects of Lead Granular Growth

Lead granules synthesized by the potentiostatic regime of electrolysis were characterized by the scanning electron microscopy technique. Effect of the different parameters of electrolysis, such as solution composition, overpotential of electrodeposition, and quantity of the electricity, on lead granular growth has been systematically investigated. Aside from the electrochemical aspects of lead granular growth, crystallographic aspects of the obtained granules were also analyzed. In the dependence of the electrodeposition conditions, granules of various shapes were obtained. The granules, such as octahedrons and hexagons, as well as many various types of twinned particles: single-twinned, multiply-twinned, lamellar-twinned, and many other complicated shapes denoted as polyparticles, were synthesized through regulation of the parameters of electrolysis. Increasing both the concentration of Pb2+ ions and overpotential of the electrodeposition favored the formation of more complicated forms. Formation of granules of specified crystallographic characteristics was also correlated with the basic principle of metal electrocrystallization.

Effect of ethylene glycol on electrochemical and morphological features of platinum electrodeposits from chloroplatinic acid

The aim of this work was to investigate the morphology, average size, and the electrochemical behavior of platinum nanoparticles electrodeposited from water and mixed water–ethylene glycol solutions of the electrolyte of H2PtCl6 and H2SO4 at a rotating disk electrode coated with Vulcan XC-72 carbon powder. Cyclic voltammetry and linear sweep voltammetry were used to determine the electrochemically active surface area (ESA) and oxygen reduction reaction (ORR) activity of the prepared Pt/C materials, respectively. XRD and scanning electron microscopy were used to study the influence of the electrodeposition methods applied on the morphology of platinum particles deposited in water and mixed water–ethylene glycol solutions. The average size of Pt crystallites was in the range of ca. 6–10 nm, and the average size of deposited Pt particles was in the range of ca. 30–150 nm. It was found that the presence of ethylene glycol in the electrolyte solution increased the overpotential of electrodeposition and it also strongly affected the morphology of Pt deposits when constant current electrodeposition was employed. Moreover, it was shown that pulse current electrodeposition is a more effective method compared to constant current electrodeposition method for the preparation of the Pt/Vulcan electrode with high ESA of Pt and enhanced catalytic activity toward ORR. The results obtained concerning the morphology and the spatial distribution of platinum particles electrodeposited on the surface of carbon support at different conditions demonstrate new possibilities to improve synthesis of Pt/C by electrodeposition methods.

Morphological and crystallographic characteristics of electrodeposited lead from a concentrated electrolyte

Electrodeposition of lead from a concentrated nitrate solution was examined by scanning electron microscopy (SEM) and by X-ray diffraction (XRD) analysis of the obtained powder particles. Single crystals of the (111) preferred orientation were formed at a low overpotential by ohmic controlled electrodeposition. Irregular crystals, needle-like and fern-like dendrites, predominantly of the (111) preferred orientation, were formed at high overpotentials (the diffusion control of the electrodeposition). The ratio of Pb crystallites oriented in the (200), (220), (311) and (331) planes increased with increasing electrodeposition overpotential. The correlation between the morphologies and crystallographic structures of the lead deposits was discussed by the consideration of general characteristics of growth layers in electrodeposition processes.

Correlate between morphology of powder particles obtained by the different regimes of electrolysis and the quantity of evolved hydrogen

Morphologies of copper powder particles obtained by both potentiostatic and pulsating overpotential (PO) regimes of electrolysis were investigated by the technique of scanning electron microscopy (SEM). Particles of dendritic or cauliflower-like shape were formed in the dependence of the selected parameters of square-waves PO. The obtained particles were compared with those obtained in the constant potentiostatic regime from solutions of different CuSO4 and H2SO4 concentrations. It was shown that the effect of the decreasing deposition pulse was equivalent to the increasing CuSO4 concentration. Pause duration was equivalent to the used concentration of H2SO4, while the overpotential amplitude in the PO regime corresponded to the overpotential of electrodeposition in the constant potentiostatic mode. Morphologies of powdered deposits were grouped in the three hydrogen co-deposition ranges and their formation was discussed in the dependence of the quantity of hydrogen generated at the cathode surface during electrochemical deposition processes.

Effective electrodeposition of Co–Ni–Cu alloys nanoparticles in the presence of alkyl polyglucoside surfactant

The effect of alkyl polyglucoside (APG) surfactant on the electrodeposition Co–Ni–Cu alloys nanoparticles has been investigated. In a typical electrodeposition experiment, it was found that as prepared Co–Ni–Cu alloys nanoparticles characteristics, such as size homogeneity, density, dispersion on the electrode substrate and the chemicals composition, depended strongly on the concentration of APG used in the reaction as well as the applied deposition potential. For the case of chemicals composition, low APG concentration (below CMC) was found to be effective for the preparation of excellent composition of the nanoalloys. Meanwhile, for the case of size homogeneity, density, and dispersion on the surface, high APG concentration (above CMC) and high deposition potential were preferred. It was also found that, at concentration above the CMC, the APG surfactant showed a metals ions deposition inhibition characteristic that caused increasing in the electrodeposition overpotential of the entire metals ions, namely cobalt, nickel and copper. As the result the copper was found to place a high percentage in the nanoalloys deposits. Owing to its simple procedure in controlling the composition and the nanoalloys growth characteristic, present approach should find a potential application in preparing Co–Ni–Cu magnetic nanoparticles for used in currently existing applications.

Morphologies of electrochemically formed copper powder particles and their dependence on the quantity of evolved hydrogen

Copper powder particles formed by electrolysis under different quantities of evolved hydrogen were analyzed using the scanning electron microscopy (SEM) technique. It was found that the structure of the powder particles strongly depended on the quantity of evolved hydrogen — that is, two types of powder particles were formed, depending on the quantity of evolved hydrogen. One type of particle was formed during the electrodeposition of copper when the quantity of evolved hydrogen was insufficient to change the hydrodynamic conditions in the near-electrode layer. This particle type comprised dendrites constructed of corncob-like structures as the basic element. The other type of particle was cauliflower-like and was formed when the quantity of evolved hydrogen was sufficient to change the hydrodynamic conditions in the near-electrode layer. However, both types of particle consisted of agglomerates of copper grains. The only difference lay in the size of the copper grains of which the agglomerates were constituted. The size of the grains was a function of the electrodeposition overpotential and, consequently, the quantity of evolved hydrogen, with a tendency to attain a steady value when the electrodeposition overpotential was increased.

Morphologies of copper deposits obtained by the electrodeposition at high overpotentials

Morphologies of copper deposits obtained at overpotentials belonging to the plateau of the limiting diffusion current density and at higher overpotentials were examined by the scanning electron microscopy (SEM) technique. Copper dendrites are formed at overpotentials belonging to the plateau of the limiting diffusion current density. The shape of copper dendrites depends on the electrodeposition overpotential. At higher overpotentials (800 and 1000 mV) and larger values of current densities, porous and very disperse copper deposits were obtained. These morphologies were a consequence of a very vigorous hydrogen evolution at these electrodeposition overpotentials. Also, the obtained copper structures consisted of agglomerates of copper grains. The size of copper grains is a function of the overpotential of electrodeposition, thus approaching to nano-sized dimensions is achieved when the electrodeposition overpotential is increased.

Methanol electrooxidation on platinum microparticles electrodeposited on poly ( o-methoxyaniline) films

In this paper we have studied the electrooxidation of methanol on electrodes obtained through the electrodeposition of platinum microparticles on poly ( o-methoxyaniline) films. The dependence of the electroactivity on the electrodes preparation parameters has been detailed. It has been shown that the concentration of the monomer during the formation of the polymeric films influences the rate of polymer growth and the electrocatalytic activity. A maximum methanol electrooxidation peak current has been observed for polymers grown to an anodic voltammetric charge of approximately 75 mC cm −2. It has been observed that the electroactivity increases when the platinum deposition is carried out in several steps instead of a single potential electrolysis. The conditions that favour a slower deposition process, i.e., smaller H 2PtCl 6 concentrations and smaller electrodeposition overpotential, lead to an enhancement of the methanol electrooxidation currents. This enhancement is attributed to an increase in the platinum surface area as a consequence of a decrease in the platinum particle size.

Electrocatalytic parameters of the electrodeposition of copper with silicotungstic acid (STA)

The effect of silicotungstic acid (STA) on the electrodeposition of copper in sulphuric acid was investigated. It was shown that the effect of STA on the kinetic parameters of electrodeposition depends on the electrodeposition overpotential. In particular, the effect of STA on the potential region where the reversible electrodeposition occurred was determined. The variation of the electrodeposition efficiency with the electrodeposition overpotential was deduced. These various results are correlated to the chemical composition of the electrodeposits.

水素化物浴によるアルミニウム電着について

To study the mechanism of electrodeposition of aluminum from the hydride bath, the present experiment was carried out, and the result was as follows:1. The most suitable composition for obtaining the best deposition was as follows.AlCl3 2-3M/l LiH 0.5-1.0M/l in etherDK=5-40mA/cm2 at room temperature2. The conductivity of the ether solution of AlCl3, LiH, LiAlH4, LiCl, NaH or their mixture was measured, and it was found that the conductivity of the solution containing AlCl3 was greater than others, and NaH decreased the conductivity of AlCl3 solution, from which it might be concluded that AlCl3+LiH, LiCl or LiAlH4 would produce complex ions in ether.3. The electrodeposition overpotential was measured by the commutator method, and it was found that a Tafel equation held well in the bath from which electrodeposition of aluminum could be obtained, and that the rate-determinant was three electron reactions.From the above, it was supposed that for obtaining the electrodeposition of aluminum, a complex ion containing Al3+ of relatively small stability constant must exist in the bath, and Al3+ produced from this complexion would be discharged at the cathode.