Electrochemical Properties of Alkali Metals in 1-Butyl-3-methylimidazolium Hexafluorophosphate

Formal potentials and diffusion coefficients of the alkali metal couples of lithium, sodium, and potassium hexafluorophosphate salts dissolved in 1-butyl-3-methylimidazolium hexafluorophosphate were determined using a hanging mercury drop electrode as the working electrode. Chronoamperometry was used to determine the diffusion coefficients, which ranged from 1.4 X 10 -8 to 4.5 × 10 -8 cm 2 /s for the Na and K cations, respectively. Formal reduction potentials of -2.96 ± 0.01 V and -3.35 ± 0.01 V vs. the ferrocene/ferrocenium couple were obtained for sodium and potassium using normal pulse voltammetry. The presence of adsorption maxima in the lithium normal pulse voltammograms necessitated the use of chronopotentiometry to determine a lithium formal potential of -2.45 ± 0.02 V.