Tangential and normal conductivities of Nafion® membranes used in polymer electrolyte fuel cells

Conductivity measurements of Nafion® 112, 115 and 117 membranes in the normal direction are reported in this paper. The measurements were made by means of impedance spectroscopy as a function of temperature. The conductivity was measured directly on hot-pressed carbon paper/membrane/carbon paper samples fully immersed in deionized water. The data show that Nafion® membranes are really isotropic and that tangential and normal direction conductivity measurements gave the same results when the same hydration level was utilized.