Water self-diffusion and ionic conductivity in perfluorinated sulfocationic membranes MF-4SK

Water self-diffusion and ion mobilities in various ionic forms (H⁺, Li⁺, Na⁺, Rb⁺, Cs⁺, and Ba²⁺) of perfluorinated sulfocationic membranes MF-4SK were studied by NMR and impedance spectroscopy. When degrees of hydration are low, the self-diffusion coefficients of water and ionic conductivities are considerably affected by the water content of the membrane. The self-diffusion coefficients decrease in the order H⁺ > Ba²⁺ > Cs⁺ > Rb⁺ > Na⁺ > Li⁺, whereas the ion mobility decreases in the order H⁺ > Li⁺ > Na⁺ > Cs⁺ > Ba²⁺.