Factors enabling high mobility of protons and water in perfluorosulfonate membranes under low hydration conditions1

This work describes new features describing the mechanism of proton and water transport in ion conducting membranes used in Proton Exchange Membrane Fuel Cells. A combination of NMR diffusion measurements and AC conductivity measurements as a function of water content reveal enhanced mobility of protons and water in low equivalent weight 3M perfluorosulfonic acid membranes at low water content. It is proposed that this is a result of the close proximity of adjacent acid-bearing sidechains in the lower equivalent weight ionomers. This proximity allows more facile exchange of species from group to group.