New insight into indium electrochemistry in a Tf2N-based room-temperature ionic liquid

The electrodeposition of indium is reported in a new weakly hygroscopic piperidinium-based ionic liquid (1-butyl-1-ethyl-piperidinium bis(trifluoromethylsulfonyl)imide) that allows electrodeposition to be performed without a glove box. The electrochemistry of indium is thoroughly investigated and the drawbacks of using metal chloride precursors in Tf2N-based electrolytes are highlighted using cyclic voltammetry and stripping experiments. Voltammograms revealed complex electrochemical behaviour and several cathodic and anodic signals that could be attributed to the formation of indium chloro complexes during the scan, due to changes in the concentration ratio [Cl−]/[In(III)] of interfacial species during the In(III) reduction reaction. A procedure for the electrodeposition of indium avoiding the use of the indium chloride precursor is then proposed. It offers an improved morphology of the electrodeposit and an increase in faradic yield from 33% to 85% compared to chloride-containing RTILs.

► Synthesis and physicochemical properties of new piperidinium-based ionic liquids.
► Deep study of In electrochemistry and electrodeposition of In in ambient atmosphere. Troublesome aspects in using chloride metallic salts in Tf2N-based electrolytes.
► Improved deposit morphology and faradic yield using chloride-free electrolytes.