Structural Study of Zirconium Phosphate−Nafion Hybrid Membranes for High-Temperature Proton Exchange Membrane Fuel Cell Applications

The structure of inorganic fillers dispersed in proton exchange membranes for fuel cell (PEMFC) was investigated by X-ray scattering and electron microscopy. The hybrid membranes have been obtained by an in situ precipitation of zirconium phosphate (α-ZrP) particles within a perfluorosulfonated ionomer membrane (Nafion). An extended angular range in the scattering experiments was covered in order to analyze simultaneously the crystalline structure of the particles, their shape and their size. At wide angles, the scattering peaks characteristic of the presence of α-ZrP have been observed and the width analysis of the scattering peak corresponding to the stacking of α-ZrP layers suggests a packing of 10−13 α-ZrP layers. The small angle spectra reveal that the structure of the membrane is not modified by the introduction of inorganic species and the excess of scattering intensity due to inorganic particles is well reproduced by the form factor of oblate ellipsoids, with a semimajor axis length of about 280 Å and a semiminor axis length of about 35 Å. These results are confirmed by high-resolution scanning electron microscopy.