First stages of silver electrodeposition in a deep eutectic solvent. Comparative behavior in aqueous medium

Abstract

The aim of the present work was to study the viability of a deep eutectic solvent (DES) solvent (consisting in a eutectic mixture of 1 choline chloride: 2 urea) as electrolyte for the electrodeposition of silver (I), paying special attention to the influence of the liquid on the mechanism of nucleation process. As this DES solvent is rich in chloride anion, which can act as complexing agent of the silver cation, parallel analysis was made, as reference, in aqueous media, both in free-chloride solution and in excess of chloride.These studies were made to analyze the role of chloride anion on the first stages of silver electrodeposition, but also to compare as nucleation mechanism changes depending on the medium, especially when DES solvent was used. For all solutions, cyclic voltammetry was useful to establish the potential range at which silver electrodeposition occurred, while potentiostatic technique was used to study the mechanism of the process. In all media, the deposition follows a nucleation and three dimensional growth governed by diffusion. The viability of the nucleation mechanism by Scharifker-Hills model was demonstrated. The analysis of the rising parts of the j-t transients confirms the obtained results by the model. Diffusion coefficients of silver species present in the solution were calculated from linear regression of j vs t -1/2 at long deposition times. IntroductionIn the last decades, room temperature ionic liquids (RTIL) have been demonstrated as an interesting alternative to the aqueous solutions for metals electrodeposition due to their intrinsic ionic conductivity, low vapor pressure and wide electrochemical window [1,2]. However, eutectic mixtures obtained by mixing quaternary ammonium halides with hydrogen bond donors, as amides, carboxylic acids or alcohols [3-6], known as deep eutectic solvents (DES) are emerging as substitutes of RTIL because of its lower price and greater stability against oxygen and water. 2 urea [3] is the selected DES. In aqueous medium, both perchlorate and chloride solutions were used; Ag(I) solubilises easily in perchlorate medium and in concentrated chloride solution, the excess of chloride allows the solubilisation of low Ag(I) concentration by means of Ag(I) complexation [20,21]. This last situation is comparable to that found in the ionic liquid in which a rough calculation indicates that the chloride concentration would be the equivalent of about 5 M, higher than the sodium chloride in aqueous medium [22]. The silver deposition in DES and in aqueous solution containing or not chloride complexing anion is analysed and compared. ExperimentalChemicals used were silver nitrate from Panreac, sodium chloride and sodium perchlorate both from Merck, all of them of analytical grade. Aqueous solutions were prepared with water doubly distilled and then treated with a Millipore Milli-Q system and the pH was kept at 3. The DES solvent was prepared using choline chloride (from Across Organics) and urea (from Merck) of analytical grade. The solids, in the molar Aqueo...

Advances in Copper Electrodeposition in Chloride Excess. A Theoretical and Experimental Approach

“…Therefore, from the non-dimensional analysis, the effect of the solvent nature on the mechanism seems clear. The growth of the nucleus formed was slowed by DES even for moderate temperatures (40 C), effect observed previously for the deposition of other metals [32].…”

“…Once the process has been characterized, the surface concentration values of Cu(II), free Cu(I) and complexed Cu(I) at any experiment time are readily obtained. Afterwards, the non-dimensional Scharifker and Hills (S-H) model [29,30] has been used to analyze the nucleation and growth deposition processes, an approach that has already been applied recently to deposition processes in ionic liquids [26,[31][32][33][34]. As will be shown, the knowledge of surface concentration values allows the complete quantitative analysis to be accomplished.…”

Catalyst–Electrolyte Interactions in Aqueous Reline Solutions for Highly Selective Electrochemical CO2 Reduction

“…We attribute the change in surface morphology of the Ag foils used in reline solutions to (i) dissolution of Ag oxide in reline, followed by (ii) electrodeposition of Ag nanoparticles back on the Ag foil when potential is applied to the cell, as illustrated by the schematic in Figure D. We could not find other specific reports in the literature detailing experimental observation of Ag oxide dissolution in ChCl‐based DES, but our hypothesis is supported the reports by Abbott et al . that ChCl‐based DES can dissolve a large number of metal oxides (e.g., TiO 2 , V 2 O 5 , Fe 3 O 4 , and CuO) and by Sebastián et al . that reline solvents could be used to control electrodeposition of Ag nanoparticles on vitreous carbon substrates.…”

Latent Fingermarks Enhancement in Deep Eutectic Solvent by Co-electrodepositing Silver and Copper Particles on Metallic Substrates

“…In addition, the anodic peak at -0.30 V was the stripping peak of Cu depositing on the substrate. Another distinct reductive peak appeared at -0.97 V which stands for the reduction peak of Ag + and the anodic stripping peak of Ag occurred at 0.02 V [32]. Considering the reduction peak of Ag + and Cu 2+ , the potential range was investigated from -0.80 V to -1.0 V for the electrodeposition experiment of Ag and Cu particles.…”