New, high temperature superacid zirconia-doped Nafion(TM) composite membranes

This study reports the synthesis and the characterization of composite, proton-conducting membranes prepared by dispersing in a Nafion matrix a highly functionalized inorganic filler, i. e. superacid zirconia. The results demonstrate that the surface properties of this unique ceramic filler play a key role in promoting high hydration level and enhanced acidity, which in turn reflect in improved thermal and transport properties of the composite membranes. We show that these membranes, with an optimum of 5% of superacid zirconia content, have a high conductivity which remains stable at temperature levels where the ionic transport of plain Nafion, as well as of conventional Nafion-based composite membranes, usually decays. These results suggest that this new type of Nafion composite membrane may be successfully used as an improved separator in polymer-electrolyte membrane fuel cells.