Studies on electrochemical stability of room temperature ionic liquids

In this paper three air and water-stable room temperature ionic liquids (RTILs): N-butylpyridinium tetrafluoroborate(BPBF4), 1-butyl-3-methylimidazolium tetrafluoroborate(BMIBF4), and 1-ethyl-3-methylimidazolium ethyl sulfate(EMISE) were synthesized. Their electrochemical windows were measured by cyclic voltammetry at 303. 15-343. 15 K. The cyclic voltammograms show the order of windows which represent the electrochemical stability of RTIL is: BPBF4<BMIBF4<EMISE. When temperature increases the windows reduce, that is, the stability of RTIL reduces with the increase of temperature. The difference among the windows of the three RTILs is mainly dependent on the order of the reductive limits of the cations: EMI+ \ - 1.40 V \ >BMI+ \ - 0.95 V \ >BP+ \0.02 V \. It is very interesting that while the oxidative limit of anion BF4- and the reductive limit of all the cations reduce with the increase of temperature, but the oxidative limit of anion SE- increases.