The effect of current density on the regularities of nickel foam deposition processes has been studied. Porous nickel foams were obtained by electrochemical deposition in the galvanostatic mode at current densities of 0.3, 0.6, 0.9, and 1.2 A cm-2. The obtained deposits were characterized by high porosity and well adherence to the substrate material. The electrolytic foams had macro- and micropores. The features of the formation of the macropore system have been studied. It has been established that at low hydrogen evolution rates, a gradual formation of a porous structure occurs. While at higher rates, the formation of the matrix structure ends in the first minutes of electrolysis. It was shown that the log-normal distribution can be used to describe the formation of a hydrogen template as a system of macropores in electrolytic nickel foams over a wide range of current densities. A technique for the estimation of nickel foam macroporosity based on the data on the fraction of the surface occupied by macropores is proposed. The total porosity of deposits was calculated based on the data on the mass and volume of electrolytic foams. The catalytic activity of the obtained porous electrodes towards the hydrogen evolution reaction was analysed in an alkali solution. The value of depolarization at a current density of 0.3 A·cm–2 was used as a criterion for the efficiency of nickel foams. The value of depolarization for the obtained deposits varies in a wide range from 170 to 400 mV and strongly depends on the conditions of foam synthesis and their thickness. It has been established that nickel foams obtained at 1.2 A·cm–2 exhibit the best catalytic properties due to their uniform structure characterized by a large number of macropores evenly distributed throughout the foam volume. This ensures maximum access of the reacting particles to the electrode surface.

Porous nickel deposits were obtained by electrodeposition via dynamic hydrogen bubble template in a galvanostatic mode at a current density of 0.3, 0.6, 0.9 and 1.2 A & BULL;cm-2. Change of nickel foam morphology (dendrite particles, pore number and their sizes) with the applied current density was analyzed. It was found that at low hydrogen evolution rate, a gradual formation of a porous structure occurs, while at high ones, the formation of the template structure ends in the first minutes of electrolysis. It is shown that the log-normal distribution can be used to describe the formation of a hydrogen template as a system of nickel foam macropores. The catalytic activity of nickel foams toward hydrogen evolution was analyzed in an alkali solution. The Tafel slope for the obtained foams is in the range of 126-107 mV & BULL;dec-1. Nickel foams obtained at 1.2 A & BULL;cm-2 are the best candidates for hydrogen evolution electrodes due to their stable structure, providing maximum access of reacting particles to the inner surface of the electrode. & COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Porous nickel and nickel-cobalt alloy deposits were obtained by electrodeposition on a dynamic hydrogen bubble template. Deposition was carried out from chloride electrolytes in a galvanostatic mode at a current density of 0.3 A/cm2. The porosity of the obtained deposits is associated with the macro- and micropores. It was found that the nickel and nickel-cobalt alloy deposits feature by different porous layer structures. In case of nickel, a typical foam structure is formed, while the Ni–Co alloy deposit morphology is more like loose (powder) metals. The total porosity of the obtained structures calculated based on experimental data decreased with the deposit thickness: from 0.4 to 0.1 for nickel foams, and from 0.9 to 0.8 for the Ni–Co deposit. It was shown that the dependences of the macropore number and the fraction of the surface occupied by them can be approximated by lognormal distribution. The agreement between the experimental values and values calculated by approximating equations indicates the stochastic nature of the macropore system formation. The catalytic properties of the obtained porous deposits toward the hydrogen evolution reaction in alkali were investigated. It was found that the decrease in the hydrogen evolution potential in comparison with a smooth electrode reaches 370 mV for nickel foams, and 440 mV for porous Ni–Co alloy deposits. However, the high porosity of the Ni–Co alloy caused poor adhesion of the deposit to the substrate; therefore, the porous Ni–Co deposit cannot be used without further strengthening. The dependences of the depolarization value during hydrogen evolution on the average diameter of pores, their number, and the macropore fraction were analyzed. Optimal properties of foams that reduce the potential of hydrogen evolution in alkali are as follows: pore diameters from 30 to 50 μm and their quantity from 50 to 100 pcs/mm2.

Hydrogen used as an energy carrier can be obtained by water electrolysis. To improve the energy efficiency of this process porous nickel catalysts are often used. The paper investigates the electrodeposition regularities and the porous nickel deposits morphology and the properties of nickel foams toward the hydrogen evolution reaction. During electrodeposition at high current density, nickel deposits with macro-and micropores are formed. The dependence between the fraction of macropores on the deposit surface and the electrolysis time is described by the empirical equation. Total porosity of loose nickel deposits is much higher than the porosity of foams. However, the surface macropores fraction of deposits studied is approximately the same, while the microporosity of loose deposits is significantly higher. The values of nickel deposits total porosity calculated by the model agree with the values obtained by experimental data. The highest density of macropores on the surface is observed for the foam thickness of 100 mm. These data correlate with the results of polarization measurements. When the foam thickness increases up to 100 mm, hydrogen evolution overvoltage in the alkali solution decreases and the efficiency of nickel foam as a cathode material increases. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Features of hydrogen evolution during electrodeposition of dendritic copper, zinc and nickel deposits were studied in the present paper. Data on the changes in hydrogen current density and its differential current efficiency as well as porosity of copper, zinc and nickel deposits during electrolysis were obtained. It was shown that the potential during the formation of dendritic metal deposits is determined by the kinetic parameters of hydrogen reduction. Experimental data (the change in the electrode potential during electrodeposition and volume of evolved hydrogen) and hydrogen evolution kinetic parameters allowed to calculate the surface area available for hydrogen evolution during electrodeposition of loose metals. It was found that surface area available for hydrogen evolution increases during electrodeposition of loose metal under galvanostatic conditions. Morphology of dendrite particles and deposit growth rate are determined by metal nature, but properties of loose deposits (change in porosity along the deposit thickness) depend on the intensity of hydrogen evolution during electrolysis.

Abstract—Data on the most frequently mentioned systems consisting of bimetallic nanoparticles, one of the components of which are gold nanoparticles, are generalized and systematized. Methods of their preparation affecting their structural characteristics are described. Optical and other properties and advantages in their directed application in various fields are shown.

It is shown that the parameters of pulsed potential modes (pulse-on and pulse-off times) have a pronounced effect on the growth dynamics and properties of loose metal deposits in the cases that the process proceeds under the conditions of non-steady-state diffusion. It is proposed to use a ratio between the cathodic and anodic charges in a cycle as a parameter that characterizes the concentration changes. By varying the parameters of pulsed potential, zinc deposits of various morphology can be obtained: from compact deposits to highly porous deposits that consist of branched dendritic particles.

The four mostly frequently used gold nanoparticle species—nanospheres, nanorods, nanoshells, and nanocells—whose surface plasmonic resonance peaks lie in the visible to near-infrared range are considered. Their synthesis, optical properties, and some fields of practical application of the relevant materials are analyzed.