Proton Diffusivity in the Protic Ionic Liquid Triethylammonium Triflate Probed by Quasielastic Neutron Scattering

Quasielastic neutron scattering (QENS) in combination with deuterium labeling allows for studying protonated "highlighted" species and extracting detailed information about tangled stochastic processes. This approach has been applied to examine proton dynamics in the protic ionic liquid, triethylammonium triflate. The temperature range covered during the experiments (2-440 K) included two melting transitions correspondingly reflected in the global and localized dynamics of the cation. To focus on the dynamics of the acidic proton, QENS spectra of the sample with the deuterated alkyl side chains were analyzed. The remaining hydrogen atom served as a tagged particle for investigating both global long-range motion of the cation and specific dynamics of the proton and, thus, provided insight into the transport properties of triethylammonium triflate, which is important for designing electrochemical devices.