Electrochemistry of gallium in the Lewis acidic aluminum chloride-1-methyl-3-ethylimidazolium chloride room-temperature molten salt

The electrochemistry of gallium at tungsten and glassy carbon was investigated in the 60.0/40.0 mol % aluminum chloride-1-methyl-3-ethylimidazolium chloride molten salt. The electrodissolution of gallium produces a gallium(I) solution, which can be electrochemically oxidized to Ga(III). The formal potential for the Ga(III)/Ga(I) and Ga(I)/Ga(0) couples are 0.655 and 0.437 V, respectively. The Ga(I)/Ga(III) electrode reaction exhibits slow-charge transfer kinetics with an anodic transfer coefficient and a standard heterogeneous rate constant of 0.24 and 3.16×10^-4 cm s^-1, respectively, at tungsten, and 0.14 and 1.82×10^-9 cm s^-1, respectively, at glassy carbon. The electrodeposition of gallium at glassy carbon from solutions of Ga(I) exhibits instantaneous three-dimensional nucleation with diffusion-controlled growth of the nuclei. The Ga(III) species can react with gallium metal to form Ga(I). The diffusion coefficients for Ga(III) and Ga(I) species are 2.28×10^-7 and 9.12×10^-7 cm² s^-1, respectively.