The use of deep eutectic solvents for the dissolution and electrochemical recovery of indium from water insoluble In2O3 was evaluated. While In2O3 did not dissolve appreciably in choline chloride/ethylene glycol (molar ratio 1:2) and choline chloride/urea (molar ratio 1:2), it dissolved well in choline chloride/malonic acid (molar ratio 1:2) up to 0.1 M at 373 K. Cyclic voltammograms recorded on several types of electrode including GC, Cu, and Mo indicated that the reduction of In(III) to In on Cu and Mo substrates was complicated by hydrogen evolution reaction (HER) but not so seriously on GC due to the higher overpotential required for HER on GC electrode. Because of the HER, the current efficiency of the electrodeposition of In on Cu Mo electrodes was lower than on carbon electrode. Chronoamperometry results indicated that the deposition of In was possibly involved with the three-dimensional (3D) progressive nucleation on the Cu electrode, and 3D instantaneous nucleation on the GC electrode, respectively. Images taken by scanning electron microscopy (SEM) revealed the surface morphology of In electrodeposits was dependent on the electrode materials and applied potential. Crystalline In deposits on these substrates was confirmed by X-ray powder diffraction (XRD) patterns.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry