ELECTROCHEMICAL INVESTIGATIONS IN THE IONIC LIQUID 1-BUTYL-3-METHYLIMIDAZOLIUMHEXAFLUOROPHOSPHATE

摘要

The electrochemical properties of 1-butyl-3-methylimidazolium hexafluorophosphate solutions of lithium, sodium and potassium hexafluorophosphate and of ferrocene were investigated. 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. An apparent anomaly in the rotating disk voltammograms for ferrocene oxidation in this ionic liquid was found to be due to the high value of the Schmidt number, 3.5 x 10~7. Analysis of the current transient resulting from application of a voltage step to the rotating disk can be used to determine the associated Schmidt number without prior knowledge of the viscosity and density of the solvent, or diffusion coefficient of the reacting species.