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

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 859
Author(s):  
Nebojša D. Nikolić ◽  
Vesna M. Maksimović ◽  
Ljiljana Avramović
Keyword(s):  
Crystal Structure ◽  
Hydrogen Evolution ◽  
Current Density ◽  
Deep Eutectic Solvents ◽  
Electrochemical Process ◽  
Exchange Current ◽  
Exchange Current Density ◽  
Metal Powders ◽  
Molten Salt Electrolysis ◽  
Powder Particles

In this review paper, morphologies of metal powders produced by the constant (potentiostatic and galvanostatic) regimes of electrolysis from aqueous electrolytes are correlated with their crystal structure at the semiquantitative level. The main parameters affecting the shape of powder particles are the exchange current density (rate of electrochemical process) and overpotential for hydrogen evolution reaction. Depending on them, various shapes of dendrites (the needles, the two-dimensional (2D) fern-like, and the three-dimensional (3D) pine-like dendrites), and the particles formed under vigorous hydrogen evolution (cauliflower-like and spongy-like particles) are produced by these regimes of electrolysis. By decreasing the exchange current density value, the crystal structure of the powder particles is changed from the strong (111) preferred orientation obtained for the needle-like (silver) and the 2D (lead) dendrites to the randomly orientated crystallites in particles with the spherical morphology (the 3D dendrites and the cauliflower-like and the spongy-like particles). The formation of metal powders by molten salt electrolysis and by electrolysis in deep eutectic solvents (DESs) and the crystallographic aspects of dendritic growth are also mentioned in this review.

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

2020 ◽  
Vol 85 (3) ◽  
pp. 347-352
Author(s):  
Nebojsa Nikolic
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Current Density ◽  
Dendritic Growth ◽  
Three Dimensional ◽  
Exchange Current ◽  
Exchange Current Density ◽  
Two Dimensional ◽  
Molten Salt Electrolysis ◽  
Powder Particles

The short survey of the dependence of the shape of electrolytically produced powder particles on the exchange current density for metal deposition and overpotential for hydrogen evolution reaction is presented. The decrease of the exchange current density leads to a branching of dendrites and their transformation from needle-like and the two-dimensional (2D) fern-like to the three-dimensional (3D) pine-like shapes. Vigorous hydrogen evolution inhibits the dendritic growth leading to a formation of cauliflower-like and the spongy-like particles. The very thin needles were obtained by molten salt electrolysis. Mechanisms responsible for the formation of both the dendritic (the general theory of disperse deposits formation) and the cauliflower-like and the spongy-like particles (the concept of ?effective overpotential?) were also mentioned.

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

2020 ◽  
Vol 10 (2) ◽  
pp. 111-126
Author(s):  
Nebojša D. Nikolić
Keyword(s):  
Molten Salt ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Current Density ◽  
Magnesium Nitrate ◽  
Exchange Current ◽  
Exchange Current Density ◽  
Nitrate Hexahydrate ◽  
Molten Salt Electrolysis ◽  
Magnesium Nitrate Hexahydrate

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 (j0) and overpotential for hydrogen evolution reaction as a parallel reaction to metal electrolysis. The decrease of the j0 value leads to a change of shape of dendrites from the needle-like and the 2D fern-like dendrites (metals characterized by high j0 values) to the 3D pine-like dendrites (metals characterized by medium j0 values). The appearing of a strong hydrogen evolution leads to formation of cauliflower-like and spongy-like forms (metals characterized by medium and low j0 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 j0 values. The globules and the carrot-like forms are a characteristic of metals with the medium j0 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 j0 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.

Correlation of Exchange Current Density j₀ and the Standard Potential of the Metal Electrodes EM⁰ for the Hydrogen Evolution Reaction (HER)

2020 ◽  
Vol MA2020-01 (46) ◽  
pp. 2604-2604
Author(s):  
Daniel Lee Parr ◽  
Kasun Dadallagei ◽  
Sidney J. DeBie ◽  
Joshua R Coduto ◽  
Christian D Haas ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Current Density ◽  
Exchange Current ◽  
Exchange Current Density ◽  
Standard Potential ◽  
Metal Electrodes

Study on Hydrogen Evolution Properties of Carbon Supported PtCu-LaOx Membrane Electrode Materials

2011 ◽  
Vol 311-313 ◽  
pp. 2344-2347
Author(s):  
Bin Yang ◽  
Tao Xu
Keyword(s):  
Hydrogen Evolution ◽  
Double Layer ◽  
Current Density ◽  
Electrode Materials ◽  
Layer Structure ◽  
Ion Beam ◽  
Exchange Current ◽  
Exchange Current Density ◽  
Membrane Electrode ◽  
Membrane Electrodes

In order to reduce production cost of making H2, one of the key points was to reduce Pt loading in Pt/C catalytic electrode. In our study, a new type of Pt/C membrane electrodes, PtCu-LaOx/C (abbr. PCL) and LaOx-PtCu/C (abbr. LPC) double-layer structure, in which Pt nanometer particles homogeneously dispersed on the surface of carbonaceous substrates were manufactured by Ion Beam Sputtering (IBS) technology. The hydrogen evolution polarization curves of these double-layer membrane electrodes were tested by three-electrode system, and the optimal sample was selected by the calculation results of their exchange current density (i0) and decomposition voltage (Ed). It was found that PCL with Pt loading less than 0.05mg/cm2 (the electrode area) whose decomposition voltage and exchange current density was -0.204(V vs SCE) and 147.0μA/cm2 respectively in balanced condition.

Correlation of Exchange Current Density j₀ and the Standard Potential of the Metal Electrodes E0 M : A Different View of the Hydrogen Evolution Reaction (HER)

2021 ◽  
Vol MA2021-01 (46) ◽  
pp. 1864-1864
Author(s):  
Daniel Parr ◽  
Kasun Saweendra Rathnatunga Dadallagei ◽  
Sidney Debie ◽  
Joshua Richard Coduto ◽  
Christian D Haas ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Current Density ◽  
Exchange Current ◽  
Exchange Current Density ◽  
Standard Potential ◽  
Metal Electrodes

Molybdenum carbide nanocrystal embedded N-doped carbon nanotubes as electrocatalysts for hydrogen generation

2015 ◽  
Vol 3 (11) ◽  
pp. 5783-5788 ◽  
Author(s):  
Kai Zhang ◽  
Yang Zhao ◽  
Diyu Fu ◽  
Yujin Chen
Keyword(s):  
Carbon Nanotubes ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Current Density ◽  
Molybdenum Carbide ◽  
Hydrogen Generation ◽  
Cathodic Current Density ◽  
Exchange Current ◽  
Exchange Current Density ◽  
Cathodic Current

Highly conductive N-doped carbon nanotubes embedded with molybdenum carbide nanocrystals with a size less than 3 nm exhibit superior activity for the hydrogen evolution reaction, including small overpotential, large cathodic current density and high exchange current density.

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