Cathodic Electrodeposition of In–Sn from a Choline Chloride–Glycerol (1:2) Deep Eutectic Solvent

Abstract

The feasibility of cathodic co-deposition of indium and tin was investigated in a type III deep eutectic solvent consisting of choline chloride and glycerol at a 1:2 molar ratio. The electrochemical bath contained indium(III) chloride (InCl₃) and tin(IV) chloride pentahydrate (SnCl₄·5H₂O), each at 10 mmolal, and experiments were performed on a glassy carbon electrode at 100 °C. Cyclic voltammetry was used to compare the electrochemical responses of the individual precursors with those of their mixture, while changes in switching potential and scan rate were examined to characterise the deposition process. The mixed electrolyte exhibited distinct cathodic and anodic responses, indicating that the presence of both metal species influenced their electrochemical behaviour. The dependence of cathodic peak current density on the square root of scan rate was consistent with diffusion-controlled reduction. Potentiostatic deposition followed by anodic stripping showed increasing peak intensities between 30 and 180 s, followed by decreases at longer deposition times. Chronoamperometric transients indicated three-dimensional nucleation and growth, with behaviour approaching the instantaneous nucleation model at longer times but deviating from simple theoretical profiles at shorter times. Scanning electron microscopy revealed irregular, granular deposits with local agglomeration, while energy-dispersive X-ray spectroscopy detected both indium and tin. These results support the feasibility of obtaining In–Sn-containing deposits from the choline chloride–glycerol electrolyte under the investigated conditions, although the crystalline phases and precise deposit composition remain to be established.