Dc Proton Conductivity At Low-Frequency In Nafion Conductivity Spectrum Probed By Time-Resolved Saxs Measurements And Impedance Spectroscopy

The electric transport properties of Nafion membranes are investigated by impedance spectroscopy (IS) and correlated with small angle X-ray scattering (SAXS). Detailed IS measurements in a wide range of temperature and frequencies (f) allowed separating contributions from different charge carriers in Nafion. At controlled relative humidity and temperature, Nafion IS spectrum exhibits at T>160 degrees C two distinct frequency-independent conductivities occurring at high f approximate to 10(6) Hz and low f<10(-2) Hz. Such IS measurements were combined with time-dependent SAXS measurements under applied dc electric potential, which provided compelling evidence that the low-f dc conductivity is related to the motion of protons via ion-hopping in hydrated Nafion membranes. (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 822-828