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 Gn(I)/Ga(0) couple 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 x 10(-4) cm s(-1). respectively, at tungsten, and 0.14 and 1.82 x 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 x 10(-7) and 9.12 x 10(-7) cm(2) s(-1), respectively. (C) 1999 The Electrochemical Society. S0013-4651(98)12-073-6. All rights reserved.