Protic ionic liquids (PILs) are highly conductive fluids that have emerged as alternative solvents for electrochemical applications including fuel cells. In the present contribution, the transport properties for a set of triethylamine (TEA)-based PILs were explored with pulsed field gradient stimulated echo (PFG-STE) NMR spectroscopy to obtain the self-diffusion coefficient (D) of the individual molecular species that comprise each system. We report self-diffusion coefficients from measurements conducted in two different laboratories for PILs that were produced by two distinct synthetic routes, a conventional route and a strictly anhydrous route. The PILs of interest are comprised of TEA cations and different anions, methane sulfonate (MS), bis(trifluoromethylsulfonyl)imide (TFSI), tetrachloroaluminate (AlCl4-), and bis(perfluoroethylsulfonyl)imide (BETI). In contrast with previous reports, the PFG-STE diffusion measurements presented here show no proton decoupled (Grotthuss mechanism) mobility in these PILs. Additionally, it is shown that the presence of moderate amounts of water (∼1000 ppm) can have a marked influence on D of the acidic proton.
ASJC Scopus subject areas
- Materials Science(all)
- Physical and Theoretical Chemistry