The ionic resistance of a nanostructured membrane electrode assembly under nonequilibrium conditions

The ionic resistance of the membrane electrode assembly (MEA) of O$_{2}$/H$_{2}$ fuel cells is studied in situ in a broad range of MEA compositions by using electrochemical impedance spectroscopy and polarization measurements. The MEAs are composed of platinum on carbon, carbon nanotubes, and Nafion, a proton- conducting polymer. We investigate atypical growth of the MEA resistance with the increasing Nafion content and spatial nonuniformity in the MEA ionic resistivity. A mechanism underlying this phenomenon is proposed.