Electrodeposition of indium on W and Cu electrodes in the deep eutectic solvent choline chloride-ethylene glycol (1:2)

Abstract

A B S T R A C TA procedure for drying the deep eutectic solvent (DES) choline chloride -ethylene glycol, ChCl-EG (1:2), based on the use of molecular sieves has been developed, being the final water content of the electrolyte 145 ± 5 ppm. In this dried DES, the stability of InCl and InCl 3 as well as the electrochemical behaviour of their solutions has been investigated using electrochemical techniques, X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Experiments performed under a N 2 atmosphere show that InCl 3 , dissolved in the rich chloride media as InCl p 3-p , is reduced on a tungsten electrode to indium metal via only one electrochemical step.Conversely, InCl undergoes the following disproportionation reaction when dissolved in the eutectic ChCl-EG (1:2)generating In(0) and giving place to identical electrochemical signals as those obtained after the addition of InCl 3 to the DES.On a tungsten electrode, nucleation and crystal growth of In plays an important role in the electrodeposition process. Chronoamperometric results were consistent with instantaneous three dimensional nucleation on a finite number of active sites with diffusion controlled growth of the nuclei, whatever the applied overpotential and temperature. Mass transport towards the electrode is a diffusion process, and the following empirical expression for the temperature dependence of the diffusion coefficient was calculated.= − ± ± − ( . . )-( ) 1 LnD 3 58 0 22 3665 76 TThe electro-reduction of In(III) solutions was also investigated at a copper substrate. The resulting cyclic voltammograms evidenced the formation of In-Cu intermetallic compounds. Hence, In-Cu alloy films were obtained by continuous potentiostatic electrolysis and intensiostatic pulse electrolysis. The obtained samples, characterized by XRD and SEM, revealed the formation of the metastable CuIn phase that could be transformed into Cu 11 In 9 by thermal annealing.

Electrodeposition of indium from non-aqueous electrolytes

“…1,2 Electrodeposition of indium from aqueous electrolytes has been extensively studied, but the co-evolution of hydrogen gas leads to low current efficiencies. [3][4][5] Electrodeposition of indium has also been investigated from non-aqueous electrolytes such as ionic liquids, [6][7][8][9] deepeutectic solvents [10][11][12][13] and molten salts 14,15 for electrowinning and formation of indium compounds. However, ionic liquids and deepeutectic solvents are often very viscous at ambient temperatures, whereas the use of high-temperature molten salts consumes a lot of energy.…”

Indium electrodeposition from indium(iii) methanesulfonate in DMSO

“…While indium(I) has been identified in a number of studies, the existence of indium(II) has not been reported. 11,16,18,19 Therefore, this species was not considered in our study. Because of the presence of a nucleation loop in the red CV in Fig.…”

“…Ionic liquids, deep-eutectic solvents (DES) and several organic electrolytes are more promising alternatives, as they have high (electro)chemical and thermal stabilities, but operate at lower temperatures. 11,[14][15][16][17][18][19] They support metal deposition in a broad potential and temperature range. However, ionic liquids and DES often have high viscosities, which hampers ion transport towards the electrode, lowering achievable current densities and thus deposition rates.…”

Electrodeposition of Sn–In Alloys Involving Deep Eutectic Solvents

“…Recently, the electrodeposition of In on Cu [34] and W [34,35] substrates was reported by using the deep eutectic solvent choline chloride-ethylene glycol (1:2).…”