Influence of the exchange current density and overpotential for hydrogen evolution reaction on the shape of electrolytically produced disperse forms - Review

Abstract

<p class="PaperAbstract">In this study, comprehensive survey of formation of disperse forms by the electrolysis from aqueous electrolytes and molten salt electrolysis has been presented. The shape of electrolitically formed disperse forms primarily depends on the nature of metals, determined by the exchange current density (j<sub>0</sub>) and overpotential for hydrogen evolution reaction as a parallel reaction to metal electrolysis. The decrease of the j<sub>0 </sub>value leads to a change of shape of dendrites from the needle-like and the 2D fern-like dendrites (metals characterized by high j<sub>0 </sub>values) to the 3D pine-like dendrites (metals characterized by medium j<sub>0 </sub>values). The appearing of a strong hydrogen evolution leads to formation of cauliflower-like and spongy-like forms (metals characterized by medium and low j<sub>0 </sub>values). The other disperse forms, such as regular and irregular crystals, granules, cobweb-like, filaments, mossy and boulders, usually feature metals characterized by the high j<sub>0 </sub>values. The globules and the carrot-like forms are a characteristic of metals with the medium j<sub>0 </sub>values. The very long needles were a product of molten salt electrolysis of magnesium nitrate hexahydrate. Depending on the shape of the disperse forms, i.e. whether they are formed without and with vigorous hydrogen evolution, formation of all disperse forms can be explained by either application of the general theory of disperse deposits formation or the concept of "effective overpotential". With the decrease of j<sub>0</sub> value, the preferred orientation of the disperse forms changed from the strong (111) in the needle-like and the fern-like dendrites to randomly oriented crystallites in the 3D pine-like dendrites and the cauliflower-like and the spongy-like forms.</p>

Hydrogen Bubble Templated Metal Foams as Efficient Catalysts of CO2 Electroreduction

“…We thus produced mesoporous, large surface area copper foams, shown in Figure 19. Several procedures for the potentiostatic (Figures 3 and 4) and galvanostatic (Figure 5) means of copper foam preparation were reported by the works of Nikolić et al [31–36] . and of Zhang et al [52] .…”

“…Starting with the advent of the 21st century, the method experienced a boom, as it turned out to be quite useful for the creation of high surface area electrocatalyst materials – not necessarily platinum based ones. Among recent works directed at the development of tailored electrocatalyst materials using the DHBT method, the works of Chialvo and Marozzi, [27,28] Shin et al ., [29,30] Nikolić et al ., [31–36] Cherevko et al ., [37–43] as well as the works of the Bhargava group, [44–47] including a review [22] deserve further attention.…”

Metal powder electrolysis: The shape of powder particles as a function of the exchange current density and overpotential for hydrogen evolution reaction

“…Aside from very thin needles, holes formed from detached hydrogen bubbles can be also formed by this molten salt electrolysis process. 4,11 There is no any difference in the shape of thin needlelike forms between those obtained by potentiostatic and galvanostatic regimes of electrolysis.…”

“…For the group of normal metals, the exchange current density decreases in the following row: Pb < Ag < Zn. 4 Pb and Zn represent the limiting cases for this group of metals, since the estimated value of j 0 for Pb tends to infinity, while the j 0 value for Zn brings it closer to the group of the intermediate metals. The needle-like and the 2D (two-dimensional) fern-like dendrites are the typical shapes of powder particles characterizing this group of metals ( Fig.…”

Correlation of Morphology and Crystal Structure of Metal Powders Produced by Electrolysis Processes

“…These metal low j0 values, high Tm, and low overpotentials for hydrogen ev Figure 1 gives a schematic presentation of the position of the of metals from each of these groups in a function of electrochemic j0 value. A schematic position of metals on a scale of the exchange curren represents silver electrodeposited from the ammonium electrolyte [15].…”