Perfluorinated ionomers, specifically Nafion, are the most widely used ion exchange membranes for fuel cell applications. Nafion is typically incorporated into the catalyst ink layer as a binder and proton conductor, where it is confined to films on the nanometer size-scale. Therefore, developing a deeper understanding of the fundamental water transport mechanisms in thin films is critical. In this study, the diffusion of water vapor into Nafion thin films was measured using time-resolved, in situ polarization modulation infrared reflection adsorption spectroscopy (PM-IRRAS). Specifically, diffusion of both H2O and D2O in dry and hydrated Nafion films was captured by obtaining molecular-level resolution of the water adsorbed in the thin film in real time. The effective diffusion coefficient of water in the Nafion thin films was many orders of magnitude less than those reported in bulk films and was dependent on the initial hydration state. However, little difference was observed between the diffusion coefficient for H2O and D2O. Moreover, our results indicate that water-induced swelling (polymer relaxation) of the Nafion films was orders of magnitude slower than those calculated for bulk films.

Water transport in Nafion thin film membranes using time-resolved polarization modulation infrared reflection adsorption spectroscopy (PM-IRRAS)

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.