The room temperature ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate: Electrochemical couples and physical properties

The room temperature ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMLBF4) was demonstrated,as a versatile electrolyte by examining three representative electrochemical couples: ferrocene and tetrathiafulvalene oxidations and lithium ion reduction. Square-wave voltammetric data for ferrocene oxidation were fit to a reversible one-electron process using the COOL11 algorithm to give a half-wave potential of 0.490 V vs. Al/Al(III) and a diffusion coefficient of 5.1 x 10(-7) cm(2) s(-1). The two-electron oxidation of tetrathiafulvalene was reversible and proceeded through two consecutive one-electron steps; although data collected at lower square-wave frequencies indicated a slow precipitation of the TTF+ species. Lithium ion was reduced to lithium metal at a Pt electrode following the addition of water to the EMLBF4 electrolyte, whereas Lithium ion reduction at an Al wire produced-the beta-LiAl alloy. Conductivities and kinematic viscosities of EMIBF4 were measured from 20 to 100 degrees C and had values of 14 mS cm(-1) and 0.275 cm(2) s(-1), respectively, at 25 degrees C.