On the nanosecond proton dynamics in phosphoric acid-benzimidazole and phosphoric acid-water mixtures.

The unique proton conduction mechanism of phosphoric acid is important for the functions of complex phosphate containing biological and technological systems (e.g. phospholipid membranes and polybenzimidazole phosphoric acid membranes for high-temperature PEM fuel cells). In neat phosphoric acid structural proton diffusion, i.e. proton hopping between phosphoric acid molecules, is superimposed onto hydrodynamic diffusion of the molecules in the viscous liquid. In this study we separate the two dynamic contributions on the nanosecond timescale for the model systems phosphoric acid-water and phosphoric acid-benzimidazole. We demonstrate that