Search

The effects of copper ion concentrations and electrolyte temperature on the morphologies and on the apparent densities of electrolytic copper powders deposited at high current densities under galvanostatic control were examined. These parameters were evaluated by the current efficiency of hydrogen evolution. In addition, scanning electron microscopy was employed for analyzing the morphology of the copper powders. It was found that the morphology was dependent on the copper ion concentration and electrolyte temperature under same current density (CD) conditions. At 150 mA cm-2 and a potential of 1000±20 mV (vs. SCE), porous and disperse copper powders were obtained at low concentrations of Cu ions (0.120 M Cu2+ in 0.50 M H2SO4). Under these conditions, a high rate of hydrogen evolution occurred parallel to copper electrodeposition. The morphology was changed from porous, disperse and cauliflower-like to coral-like, shrub-like and stalk--stock-like morphology with increasing Cu ion concentrations from 0.120, through 0.155, 0.315 and 0.475 to 0.630 M Cu2+ in 0.5 M H2SO4, respectively, at the same CD. Similarly, with increasing temperature, the powder morphology and the apparent density changed. The apparent density values of the copper powders were suitable for many powder metallurgy applications. [ABSTRACT FROM AUTHOR]

The effects of copper ion concentrations and electrolyte temperature on the morphologies and on the apparent densities of electrolytic copper powders at high current densities under galvanostatic regime were examined. These parameters were evaluated by the current efficiency of hydrogen evolution. In addition, scanning electron microscopy was used for analyzing the morphology of the copper powders. It was found that the morphology was dependent over the copper ion concentration and electrolyte temperature under same current density (CD) conditions. At 150 mA cm-2 and the potential of 1000±20 mV (vs. SCE), porous and disperse copper powders were obtained at low concentrations of Cu ions (0.120 M Cu2+ in 0.50 M H2SO4). Under this condition, high rate of hydrogen evolution reaction took place parallel to copper electrodeposition. The morphology was changed from porous, disperse and cauliflower-like to coral-like, shrub-like and stalk-stock like morphology with the increasing of Cu ion concentrations towards 0.120 M, 0.155 M, 0.315 M, 0.475 M and 0.630 M Cu2+ in 0.5 M H2SO4 respectively at the same CD. Similarly, as the temperature was increased, powder morphology and apparent density were observed to be changed. The apparent density values of copper powders were found to be suitable for many of the powder metallurgy applications. [ABSTRACT FROM AUTHOR]

In this paper, NiMo coatings were electrochemically deposited on a copper electrode (Cu/NiMo) and on an electrodeposited nickel onto copper plate (Cu/Ni/NiMo) in citrate solutions. Effects of electrolyte composition, pH value, and temperature on hydrogen-evolution reaction (HER) as well as the electrochemical stability in alkaline solution were investigated, and the electrochemical activation energy was determined for the NiMo alloys. This was evaluated by the determination of kinetic and mechanism of HER in alkali medium by the polarization measurements, cyclic voltammetry, and electrochemical impedance spectroscopy techniques. The morphology and chemical composition of the electrodeposited Ni-Mo were investigated using SEM and EDS analyses. The results showed that the corresponding HER overpotential of the Ni-Mo film depends on alloy composition and surface morphology. As the wt% of Mo content in the alloy is increased, the onset potential of electrode for HER shifted in the positive direction favoring hydrogen generation with lower overpotential. The overall experimental data indicated that the porous Ni-Mo coating on electrodeposited nickel plate was obtained when the molybdenum content was ca. 41 wt%. This electrodes exhibited high catalytic activity in the HER ( η = −48 mV at 100 mA cm and 80 °C), and their stability was tested by polarization measurements after different anodic and cathodic treatments in 1 M NaOH solution. Moreover, the corrosion behaviors of Ni and Cu/Ni/NiMo electrodes at open-circuit potential were also investigated, and their corrosion resistances were compared. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]