Electrochemical deposition of copper on zinc and its alloys

Owing to unstable electrical energy generation from intermittent solar and wind energy sources, the development of efficient and durable nonnoble electrocatalysts is extremely desirable, in particular, those that can be used over a wide range of current densities for the hydrogen evolution reaction (HER), especially >1 A cm–2, which is extremely desirable for energy transformation in power systems. Here, a nanosponge-like NiMo solid solution based on a nanoscale Kirkendall effect is fabricated via a one-step high-temperature sintering method. A polycrystalline layer of NiMo oxyhydroxide is formed on the surface of the as-prepared electrode after aging, thus achieving a low overpotential and Tafel slope of 37 mV at 10 mA cm–2 and 39.2 mV dec–1, respectively. The electrode displays superior electrochemical stability over a wide range of current densities without compromising its electrocatalytic activity; in particular, it is durable for over 300 h at 2 A cm–2. This is attributed to the combination of the 3D-interconnected nanosponge structure, synergistic effect between the Ni and Mo species, lattice distortion of the solid solution, and its high conductivity. This work provides a possible commercialization for the fabrication of nonprecious electrocatalysts with high performance in large-scale energy conversion.

Test data is presented for one grade of copper graphite brush material, Morganite CMlS, over a wide range of surface velocities, atmospheres, and current densities that are expected for fast discharge (<l00 ms) homopolar generators. The brushes were run on a copper coated 7075-T6 aluminum disk at surface speeds up to 277 m/sec. One electroplated copper and three flame sprayed copper coatings were used during the tests. Significant differences in contact voltage drops and surface mechanical properties of the copper coatings were observed.

The possibility of obtaining smooth homogeneous copper coatings with good adhesion and homogeneous copper coatings with poor adhesion by electrochemical deposition of copper on steel from a solution of nontoxic copper(II) complex with the ligands, 1,3-propylenediamine-N,N′-diacetato-N,N′-di-3-propionic acid, was analyzed. For both types of coatings, the optimum composition of the solution and the optimum deposition conditions were determined.

Electrodeposition of lead dioxide from methanesulfonate solutions

Electrochemical behavior of the bare indium-tin oxide (ITO) electrode in 1 M NaOH electrolyte has been studied in a wide range of current density and applied charge in view of its possible application as a counterelectrode in rare earth optical windows. Nature and kinetics of both cathodic and anodic processes developed on ITO depend on electrolyte composition as well as on transformations occurring with the electrode. Contribution of oxygen vacancies and ions is crucial for the electrochemical behavior of ITO. At the cathodic polarization, the electrode components are deeply reduced so that ITO is gradually and irreversibly converted to a metallic mirror with a noticeable decrease of oxygen content. At high anodic current density, the ITO electrode undergoes modifications and its conductivity decreases probably also due to the change of oxygen content in the oxides lattice. A phenomenological description of all the processes involved in ITO electrochemical performance and their reversibility is proposed and discussed. A stable operation of ITO in electrochemical devices can be achieved only in the case of usage of external RedOx dissolved in the electrolyte or deposited on the ITO electrode. Such active components could be selected from the different systems studied for flat panel displays.

Anodization of molybdenum in glycol-borate electrolyte— A peculiar kinetics of insulating film formation

The effects of the bath composition and the plating conditions of gold plating using 5,5-dimethylhydantoin-gold complex on deposition were investigated.High current efficiency and bright films were obtained from the bath containing phosphate buffer in a wide range of current density in comparison with the citrate bath. In terms of the plating conditions, the plating temperature should be 60ºC to deposit with high current efficiency. The optimum pH value was 8.0 to increase the current efficiency to almost 100% in a wide range of current density. The optimum composition to obtain a bright yellow deposit film was 0.04mol/L of gold ion and 6 times that concentration of 5,5-dimethylhydantoin, even though the gold complex has four ligands in its molecular structure.Addition of thallium ion shifted the deposition potential to positive direction and increased current density, and accelerated depositing. Thallium played an important role to make deposited grains uniform, refine and dense. As a result, the appearances of the deposited films were bright yellow.

A theoretical and experimental study of the electrohydrodimerization process to produce adiponitrile is used to determine an appropriate reaction model. From numerical simulations of five proposed reaction schemes and subsequent comparison with experimental data, the most favoured route is via an anion, intermediate of acrylonitrile. This route, a five step reaction involving electrochemical and chemical reaction in a diffusion/reaction layer, gives good predictions of product distributions over a wide range of current densities and acrylonitrile concentrations of product distributions over a wide range of current densities and acrylonitrile concentrations.

Until now, perfluorinated proton exchange membrane (PEM) has been widely used as the electrolyte for PEMFC. As long as the perfluorinated PEM is used for the electrolyte, both the cell performance and durability of PEMFC strongly depends on the water content in its electrolyte, since the high conductivity of electrolyte is presented only at the sufficient hydrated state. On the other hand, pre-humidification of fuel and oxidant gases complicates the PEMFC system and prevents it from cost reduction. Therefore, in order to achieve simultaneously the high performance, durability and cost reduction of PEMFC, it is though to be a best way that both the anode and cathode catalyst layers will be highly humidified only by the water produced through an electrode reaction without pre-humidification of fuel and oxidant gases. Although the management of the vapor permeation rates through gas diffusion layers will be most effective for such a self-humidified PEMFC, it isn't so easy to achieve it in the wide range of current density. In this study, by using the cell simulation method for PEMFC, we calculated numerically the vapor permeation rates through anode and cathode gas diffusion layers which enabled the self-humidified PEMFC without pre-humidification or with low pre-humidification of fuel and oxidant gases.

Until now, perfluorinated proton exchange membrane (PEM) has been widely used as the electrolyte for PEMFC. As long as the perfluorinated OEM is used for the electrolyte, both the cell performance and durability of OEMFC strongly depends on the water content in its electrolyte, since the high conductivity of electrolyte is presented only at the sufficient hydrated state. On the other hand, pre-humidification of fuel and oxidant gases complicates the PEMFC system and prevents it from cost reduction. Therefore, in order to achieve simultaneously the high performance, durability and cost reduction of PEMFC, it is thought to be a best way that both the anode and cathode catalyst layers will be highly humidified only by the water produced through an electrode reaction without pre-humidification of fuel and oxidant gases. Although the management of the vapor permeation rate through gas diffusion layers will be most effective for such a self-humidified PEMFC, it isn't so easy to achieve it in the wide range of current density.

Energy-efficient capture technologies need to be deployed by 2050 to abate global warming caused by excessive carbon dioxide (CO2) emissions. CO2 capture using alkaline solutions and absorbent regeneration mediated through bipolar membrane electrodialysis (BMED) have been tested previously as a standalone technology. However, the continuous operation of an integrated system remains largely unclear. Here, a bench-scale study was conducted using an integrated prototype to analyze the performance of CO2 capture and electrochemical regeneration using potassium hydroxide (KOH) aqueous solution. A wide range of current densities from 150 to 1000 A/m2 was applied to demonstrate the continuous operation of the CO2 capture system emphasizing the stability in attainable high rich carbon loading and CO2 desorption. The electrochemical regeneration module achieved CO2 desorption efficiency of 70% and absorbent recovery up to 89% under industrial relevant current densities of 500–1000 A/m2. The absorbent recovery has been identified to be a result of the combined effect of load ratio and rich carbon loading. The observed inefficient CO2 separation indicates significant potential to enhance energy efficiency. These results represent a pivotal step forward in electrochemically mediated CO2 capture technology, with promising potential for rapid industrial scale-up in the near future.

The electrochemical deposition of copper has been extensively studied. In some experimental conditions, this electrodeposition represents the base of the calibration of the electrochemical quartz microbalances (EQCM). This technique allows the detection of intermediate species which are formed in the interfacial region, by measuring the F(dm/dq) function during electrochemical experiments. Furthermore, R-EQCM devices provides additional information on the deposited layers and the electrode/solution interfacial regions, by measuring instantaneously the motional resistance R of the equivalent Butterworth-Van-Dyke circuit. This resistance could be almost considered as the sum of three different contributions as a first approach: Ro, due to the electrode (quartz/Au/Cu) system, RCu related with the Cu phase, and the RCu/solution associated with the Cu / solution interface: R = Ro+RCu+RCu/solution This work explores the interpretation of this magnitude and its dependence on the nature of the interfacial region. For this purpose, the electrochemical deposition of copper as well as its anodic dissolution in acid sulfuric aqueous solutions were studied. . Generally, measuring the resonance frequency, it is concluded that in the deposition and the anodic dissolution of copper, the instantaneous values of F (dm /dq) and F (D m/Dq) (measured in an interval of time) approaching 32 g·.mol – 1. This means that the overall reaction involves the transfer of two electrons per atom of copper. This is useful from a practical perspective: Both deposition and anodic dissolution of copper are suitable to calibrate the microbalance and for correcting the theoretical factor between mass and frequency that provides the Sauerbrey equation. However, although both processes have an efficiency near to 100 %, there is always a little hydrogen evolution which is manifested by a small increase of pH solution during the experiments of copper electrodeposition . Since hydrogen gas at room temperature is slightly soluble in water, the production of hydrogen results in bubbles whose size depends on the medium composition and temperature which affect the surface tension. It is known that the rate of this process increases at higher cathodic overpotentials, which is able to generate superhydrophobic surfaces on metallic copper [2]. Due to the formation of hydrogen bubbles on the copper is the reason that the measure of the motional resistance shows periodic oscillations (Figure 1) and his period exceeds to the time of formation of successive copper layers during the electrochemical deposition. The relative maxima of these fluctuations should correspond to the hydrogen microbubbles leaving the electrode surface. The function dm/dt evolves parallel on time to the R value during the copper deposition. From the aforesaid results, it is inferred the great usefulness of the in situ measure of the motional resistance for obtaining information about the electrode/solution interfacial region. The F (dm/dq), dm/dt function, and the appropriate measure of the motional resistance are useful to explain the interfacial differences that occur between the deposition and anodic dissolution of copper. The results points to the fact that the calibration of the Sauerbrey equation perhaps is better during the anodic process of dissolution than by means of an electrodeposition process, since during this last process, hydrogen bubbles are produced, whose kinetics can be followed by the oscillations of the motional resistance.The aforesaid results are consistent with the spectroelectrochemical measurements. Figure 1. Oscillations of motional resistance R during a galvanostatic (I = - 2 mA) cooper deposition on Au (23,1 mm2) electrode in a 0.5 M CuSO4 diluted sulphuric aqueous solution (pH =1) at 298 K. REFERENCES [1] D. Giménez-Romero, C. Gabrielli, J.J. García-Jareño, H. Perrot, F. Vicente Electrochemical quartz crystal microbalance study of copper electrochemical reaction in acid medium containing chlorides,. J. Electrochem. Soc. 153 (2006)J32-J39. [2] Ying Li , Wen-Zhi Jia , Yan-Yan Song , and Xing-Hua Xia, Superhydrophobicity of 3D Porous Copper Films Prepared Using the Hydrogen Bubble Dynamic Template. Chem. Mater. 19 (23) (2007) 5758–5764. ACKNOWLEDGEMENTS Part of this work was supported by FEDER-CICyT CTQ2015-71794-R. Figure 1

We have developed high-quality epitaxial NbN/AlN/NbN Josephson tunnel junctions with a wide range of current density Jc. The junctions show excellent tunneling properties with a large gap voltage of 5.6 mV and a large IcRN product of 3.5 mV. The quality factor Rsg/RN is about 60 for the junctions with a Jc of 2.2 A/cm2, and above 10 for the junctions with a Jc of 25 kA/cm2. The crystal structures across the junction barrier are investigated using x-ray diffraction and cross-sectional scanning transmission electron microscopy, and demonstrate epitaxial growth of the NbN/AlN/NbN trilayers for the wide range of Jc.

The composite polymer electrolyte membranes were prepared from sulfonated poly (ether sulfone) (SPES), silicotungstic acid (STA) and fly ash (FA). Post sulfonation process was adopted to synthesize SPES using sulphuric and chlorosulfonic acid. The prepared electrolyte membranes were examined by water uptake capacity, swelling ratio, ion-exchange ability, proton conductivity, thermal stability and electrochemical performance for evaluating the pertinence of these membranes in fuel cell applications. As such the pristine membrane restricts with the proton conductivity of 0.042 S cm−1 at 30 °C and 0.060 S cm−1 at 90 °C while the polymer composite membrane, SP-STA-FA-10 reveals the maximum conductivity of 0.054 S cm−1 at 30 °C and 0.073 S cm−1 at 90 °C. It also exhibits good thermal stability than that of the pure membrane. The membrane electrode assemblies (MEAs) have been successfully developed from SPES as well as SP-STA-FA-10 membranes and their electrochemical performance were studied the wide range of current density. Herein, the composite membranes derived from SPES, STA and FA can be viable candidates for fuel cell applications.

Electrochemical deposition of copper on stepped platinum surfaces in the [0 1 [formula omitted]] zone vicinal to the (1 0 0) plane