AN ELECTROCHEMICAL AND SPECTROSCOPIC STUDY OF CERIUM IN THE BASIC ALUMINUM CHLORIDE-1-METHYL-3-ETHYLIMIDAZOLIUM CHLORIDE MOLTEN-SALT

Ultraviolet-visible spectroscopic measurements indicated that cerium(III) and -(IV) are complexed as [CeCl6]x-(x = 3 and 2, respectively) anions in the basic aluminum chloride-1-methyl-3-ethylimidazolium chloride (AlCl3-MeEtimCl) molten salt. The [CeCl6]3-/2- electrode reaction is quasireversible at glassy carbon, platinum, and tungsten electrodes in this melt; k(s) and alpha values for this reaction at these electrodes are (4.3 +/- 0.6) x 10(-4) cm s-1 and 0.40 +/- 0.00; (10 +/- 1) x 10(-4) cm s-1 and 0.50 +/- 0.00; and (32 +/- 2) x 10(-4) cm s-1 and 0.56 +/- 0.04, respectively, at 40-degrees-C. The E1/2 of this reaction is 0.64 V [vs. Al in the 66.7-33.3 mole percent (m/o) melt], and the average diffusion coefficient and Stokes-Einstein product for [CeCl6]3-are (3.9 +/- 0.2) x 10(-7) cm2 s-1 and (1.7 +/- 0.1) x 10(-10) g cm s-2 K-1 at 40-degrees-C. Electrogenerated [CeCl6]2- exhibited greater kinetic stability in basic AlCl3-MeEtimCl than was expected based on previous results obtained in high-temperature chloride melts; however, it is eventually reduced to [CeCl6]3- by chloride ion. The half -life of electrogenerated [CeCl6]2- is approximately eight days.