LAUSR

There is considerable interest in using ionic liquids (ILs) as protic electrolytes. However, the reported proton transfer rate in ILs is quite slow. In this study, we report functionalizing imidazolium ILs with alcohol hydroxyls, aiming at constructing hydrogen bonding networks in the electrolyte, can stimulate fast proton hopping transfer. For demonstration, the diffusion of proton and Cl− in 1-(3-hydroxypropyl)-3-methylimidazolium tetrafluoroboride (C3OHmimBF4) were studied using cyclic voltammetry and potentiostatic method at 30 °C. The diffusion coefficient of proton is about one order of magnitude higher than that of Cl− in the same electrolyte, and about 5 times that of proton in the non-hydydroxyl 1-(butyl)-3-methylimidazolium tetrafluoroboride (BmimBF4) when normalized to the diffusion coefficients of Cl− in respective ILs. In the meantime, 1H NMR spectra revealed a strong hydrogen bonding interaction between proton and C3OHmimBF4 which is absent between proton and BmimBF4, thus the significantly higher diffusion coefficient of proton in C3OHmimBF4 may suggest the formation of effective hydrogen bonding networks, enabling rapid proton hopping via the Grotthuss mechanism.