Electrochemical AFM Investigations of Proton Conducting Membranes

Perfluorinated, s-peek and s-ppek polymer electrolyte fuel cell membranes are investigated using electrochemical atomic force microscopy. The proton conductivity and the topography are measured simultaneously at a nanoscale resolution. The results are compared with those of Nafion, and significant differences in the proton conductivity are revealed. The hydrocarbon membranes show a small overall conductivity and not the typical conductive and non-conductive regions as observed for Nafion. For the s-peek membrane an anti-correlation between the topography and the conductivity is observed. One type of the perfluorinated membranes in principle behaves similar to Nafion, whereas another type behaves more similar to the hydrocarbon membranes. This suggests that the manufacturing process plays an important role for the morphology of the polymers.