State of Water in Nafion 117 Proton Exchange Membranes Studied by Dielectric Relaxation Spectroscopy

Abstract

AbstractDynamics of water in Nafion 117 membranes, in the acid form, at two hydration levels and several temperatures were investigated by means of dielectric relaxation spectroscopy in both, low (10−2 to 107 Hz, 25 to −80 °C) and microwave (0.045-26 GHz, 35 °C) frequency regions by employing different experimental setups. Three states of water were identified: a) strongly bound to the sulfonic groups (in agreement with other investigations) forming the first hydration layer; b) loosely bound, surrounding the first layer and c) free water, having similar dynamics as in the bulk state.