Electrodeposition of thin solid films on gold from a choline chloride-urea electrolyte

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A Finite Element Simulation of the Electrochemical Growth of a Single Hemispherical Silver Nucleus

Understanding the early stages of electrochemical nucleation and growth is the cornerstone for nanoscale electrodeposition. Although studied since decades, the process is not yet fully understood. In this paper, we introduce a new modelling approach to study the growth of a single hemispherical nucleus: Multi-Ion Transport and Reaction Model (MITReM). This approach takes into account the transport driven by diffusion and migration of all species in the electrolyte together with the electrochemical reactions at the electrode boundary. A Finite Element Method (FEM) is used to solve the balance equations for the concentration of all the active species and the electrolyte potential. In contrast to analytical models or discrete scale modelling techniques, the strength of this approach is that no assumptions on the diffusional or kinetic limitations have to be made. In addition, this novel platform allows to add further levels of complexity, such as multiple nuclei, adatom surface diffusion, aggregation, particle detachment, etc. The simulation results prove that, the initial growth stage of a 10 nm single hemispherical silver nucleus always starts under kinetic control, regardless of concentration and electrode potential. Later on, a transition from kinetic to diffusion control takes place. The time of transition depends on the imposed concentration and electrode potential. Moreover, the simulations clearly show that the growth rate is strongly affected by the imposed concentration and electrode potential, as it has been proven experimentally in countless occasions. Numerical simulation by MITReM proves to be of great interest to gain knowledge towards unravelling the early stages of electrochemical nucleation and growth processes.info:eu-repo/semantics/publishe

On the Control and Effect of Water Content during the Electrodeposition of Ni Nanostructures from Deep Eutectic Solvents

textcopyright 2018 American Chemical Society. The electrodeposition of nickel nanostructures on glassy carbon was investigated in 1:2 choline chloride-urea deep eutectic solvent (DES) containing different amounts of water. By combining electrochemical techniques, with ex situ field emission scanning electron microscopy, high-angle annular dark field scanning transmission electron microscopy, and energy-dispersive X-ray spectroscopy, the effect of water content on the electrochemical processes occurring during nickel deposition was better understood. At highly negative potentials and depending on water content, Ni growth is halted due to water splitting and formation of a mixed layer of Ni/NiO x (OH) 2(1-x)(ads) .Moreover, under certain conditions, the DES components can also be (electro)chemically reduced at the electrode surface, blocking further three-dimensional growth of the Ni NPs. Hence, a two-dimensional crystalline Ni-containing network can be formed in the interparticle region.info:eu-repo/semantics/publishe

Water distribution at the electrified interface of deep eutectic solvents

Preferential asymmetric electrosorption of water onto a moderately polarized electrode surface.info:eu-repo/semantics/publishe

Influence of water content and applied potential on the electrodeposition of Ni coatings from deep eutectic solvents

Ni coatings were electrodeposited from 1:2 choline chloride (ChCl) - urea (U) deep eutectic solvents (DESs) on low carbon steel. We report on the inter-related influence of water content in the electrolyte and applied potential on the formation of Ni films and their chemical composition and morphology. This was investigated by cyclic voltammetry (CV) and chronoamperometry (CA) in combination with ex-situ characterization techniques (FE-SEM, EDS, XPS and Raman spectroscopy). Ni electrodeposition from DES is shown to be highly complex: Ni+2 reduction is followed by water reduction, which triggers electrolyte decomposition. A water content higher than 4.5%wt and/or performing electrodeposition at potentials more negative than Einfo:eu-repo/semantics/publishe

Electrochemical formation and stability of copper selenide thin films in the choline chloride-urea deep eutectic solvent at gold electrode

The electrodeposition of copper-selenium binary compounds on gold electrode was investigated in the choline chloride – urea (ChCl-U) deep eutectic solvent at 110 °C. Cyclic voltammetry and potentiostatic deposition followed by stripping voltammetries were employed to gain thermodynamic insights pointing to the formation of Cu2Se, which is supported by X-Ray Photoelectron Spectroscopy. The electrochemical stability domain of the compound is about 900 mV (from ≈−0.81 V to ≈+0.07 V vs. a silver quasi-reference electrode) and is consistent with the thermodynamics of induced co-deposition. The domain is limited at positive potentials by the oxidation to Se(0) and at negative potentials by the reduction to Cu(0). While copper is readily deposited on the gold electrode, the electrodeposition of selenium requires a significant overpotential. As a consequence, copper is kinetically favoured in the co-deposition and is present in its pure form at short deposition times. This is circumvented by using longer deposition times or more negative potentials. Photoelectrochemical measurements show that the as-deposited compound behaves as a p-type semiconductor.info:eu-repo/semantics/publishe

Comprehensive Study of the Electrodeposition of Nickel Nanostructures from Deep Eutectic Solvents: Self-Limiting Growth by Electrolysis of Residual Water

The electrodeposition of nickel nanostructures on glassy carbon was investigated in 1:2 choline chloride-urea (1:2 ChCl-U) deep eutectic solvent (DES). By combining electrochemical techniques with ex situ FE-SEM, XPS, HAADF-STEM, and EDX, the electrochemical processes occurring during nickel deposition were better understood. Special attention was given to the interaction between the solvent and the growing nickel nanoparticles. The application of sufficiently negative potential results in the electrocatlytic hydrolysis of residual water in the DES, which leads to the formation of a mixed layer of Ni/Ni­(OH)_2(ads). In addition, hydrogen bonds between hydroxide species and the DES components could be formed, quenching the growth of the nickel clusters favoring their aggregation. Due to these processes, a highly dense distribution of nickel nanostructures can be obtained within a wide potential range. Understanding the role of residual water and the interactions at the interface during metal electrodeposition from DESs is essential to produce supported nanostructures in a controllable way for a broad range of applications and technologies

An in-situ XANES investigation of the interactions between iron, manganese and antimony in silicate melts

International audienceThe analysis of iron, manganese and antimony in silicate glass is of great interest in chemistry, materials science, earth sciences and archaeological sciences. Yet, conclusions from different fields appear to be contradictory and many questions about redox reactions in glass remain. The purpose of this study is thus to discuss whether and how these multivalent elements interact in glass. Soda-lime silicate melts containing iron along with manganese and/or antimony have been analysed at different high temperatures under argon atmosphere. Using in-situ XANES at the Fe K-edge, redox thermodynamics, kinetics and diffusivities have been assessed for the different compositions. The data obtained show that antimony is more efficient at oxidising iron compared to manganese at all temperatures. The oxidising power trend would thus be Sb > Sb + Mn > Mn. Furthermore, hypotheses on the formation of Fe-Mn complexes are also reported in glasses with stoichiometric proportions of iron and manganese. Based on the determination of redox diffusivities, it appears that presence of other multivalent elements does not significantly affect the iron redox mechanisms and that diffusivity is essentially controlled by the mobility of calcium