Ion Mobility of 1-Ethyl-3-methylimidazolium Tetrafluoroborate and 1-Ethyl-3-methylimidazolium Bis(trifluorosulfonyl)amide Ionic Liquids

Abstract

The mobilities of the cation and anion species in 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquids were measured at four different temperatures from 298.2 to 313.2 K on the basis of electrophoretic NMR method. The comparison between the mobilities and the NMR diffusion coefficients showed that the cation and anion mobilities become larger as the diffusion coefficients increase and are almost equal to each other unlike in the case of the diffusion coefficients. Moreover, all the experimentally obtained mobilities are found to be appreciably higher than the calculated ones from the diffusion coefficients with the Einstein relation. The deviation of the experimental mobilities from the Einstein relation was discussed in terms of the ion transport mechanisms.