Investigation on Speek-Porphyrin Interaction for Polymer Electrolyte Membranes Portable Applications

The polyaromatic membranes can be considered as an alternative to PFSA based membranes, for portable fuel cell applications. In this context, the sulphonated polyetheretherketone (sPEEK) due to its properties such as high thermo-oxidative stability, high solvent resistance, excellent mechanical properties, proton conductivity comparable to Nafion depending on the sulphonation degree and low cost (about 1/40 if compared to Nafion) is a good candidate. In order to guarantee a good proton conduction in operative conditions useful for portable applications (room temperature and low pressure) a sulphonation degree of about 65% was selected. To improve the characteristics of membranes based on bare sulphonated polymer, composite membranes based on sPEEK and porphyrins with different substituents in the periphery of the macrocycle were studied. A screening of different weight percentages (in the range 0-5) was carried out in order to identify the best composition as a function of the interactions between porphyrins and polymeric matrix. With the aim to better understand the influence of the aggregation state of porphyrins embedded into polymeric matrix, physico-chemical characterizations such as UV-Vis and Fluorescence emission, ion exchange capacity, water retention, dimensional variations and swelling, structural and morphological analyses were carried out. Moreover, proton conductivity measurements at low temperatures were performed to understand the influence of the interactions on the proton transport mechanism. Finally, electrochemical tests in a PEFC fed by hydrogen and air were performed on the developed membranes to verify the performance in the selected operative conditions.