Electrodeposition of tin, selenium, and tin-selenium compound in the choline chloride-glycerol deep eutectic solvent

The electrochemistry of Sn(II), Sn(IV), and Se(IV) in the choline chloride-glycerol deep eutectic solvent was investigated on glassy carbon at 110 °C by various electrochemical methods including cyclic voltammetry, chronopotentiometry, and chronoamperometry. The Sn(IV)/Sn(II) couple displays very slow electrochemical kinetics, so that the reduction of Sn(IV) essentially proceeds directly to Sn(0) through a 4 e⁻ process, even if the potential of the Sn(IV)/Sn(II) couple is more positive than the Sn(II)/Sn(0) couple. Because of this sequence of potentials, the comproportionation reaction Sn(IV) + Sn(0) → 2Sn(II) takes place when elemental tin is deposited from the Sn(IV) solution. The electrodeposition of tin proceeds through an instantaneous nucleation process with Sn(II) whereas a progressive nucleation mechanism is observed with Sn(IV). In the presence of both Sn(IV) and Se(IV) in solution, voltammetric features associated with the formation of a Sn-Se compound are clearly identified and the suitable potential range where the compound can be deposited without co-deposition of elemental tin is determined, as confirmed by SEM images and EDX analyses.