Fast diffusion in a room temperature ionic liquid confined in mesoporous carbon

We report a quasielastic neutron scattering study in the temperature range of 290 to 350 K of a room temperature ionic liquid, [bmim ⁺][Tf ₂N ^-], in the bulk form and confined in the 8.82.1 nm diameter pores of a mesoporous carbon matrix. In both bulk and confined liquids, our measurements, which are sensitive to the dynamics of the hydrogen-bearing cations, detect two distinct relaxation processes related to the diffusion of the cations. We have found that the cations that do not become immobilized near the pore walls exhibit an enhanced rather than suppressed diffusivity compared to the cation diffusivity in bulk liquid. Our results provide first experimental observation of molecular diffusion in a room temperature ionic liquid in confinement which is faster than diffusion in the bulk liquid.