Simulation of 3D Electrochemical Phase Formation: Mixed Growth Control

Processes of nucleation and growth largely determine the structure and properties of thin films obtained by electrodeposition on foreign substrates. Theoretical aspects of the initial stages of electrochemical phase formation under constant and variable overpotentials are considered in this work. Simulation of multiple nucleation with mixed (charge transfer, and diffusion) controlled growth was performed for three cases (cyclic voltammetry, potentiostatic electrodeposition, and galvanostatic electrodeposition). The influence of the bulk concentration of depositing ions and the exchange current density at the electrolyte/nucleus interface on cyclic voltammograms (CVs), transients of current and overpotential, as well as the number and size of non-interacting new-phase nuclei was analyzed. It is found that, under galvanostatic conditions, the number of nuclei decreases as the concentration of depositing ions increases due to a more rapid decrease in overpotential. The proposed model was applied to determine the diffusion coefficient, exchange current density, and transfer coefficient considering the experimental CV.

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

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.

Revisiting Trends in the Exchange Current for Hydrogen Evolution

Nørskov and collaborators proposed a simple kinetic model to explain the volcano relation for the hydrogen evolution reaction on transition metal surfaces in such that j_0= k_0 f(ΔG_H) where j_0...

Avoiding Dendrite Formation by Confining Lithium Deposition Underneath Li-Sn Coatings

<p>The use of interfacial layers to stabilize the lithium surface is a popular research direction for improving the morphology of deposited lithium and suppressing lithium dendrite formation. This work considers a different approach to controlling dendrite formation where lithium is plated underneath an interfacial coating. In the present research, a Li-Sn intermetallic was chosen as a model system due to its lithium-rich intermetallic phases and high Li diffusivity. These coatings also exhibit a significantly higher Li exchange current than bare Li thus leading to better charge transfer kinetics. The exchange current is instrumental in determining whether lithium deposition occurs above or below the Li-Sn coating. High-resolution transmission electron microscopy and cryogenic focused ion beam scanning electron microscopy were used to identify the features associated with Li deposition. Atomic scale simulations provide insight as to the adsorption energies determining the deposition of lithium below the Li-Sn coating. </p>