Composite sPEEK-porphyrin membranes development for PEFC applications

Composite membranes based on sulphonated Polyetheretherketone (sPEEK) and porphyrins with different substituents in the periphery of the macrocycle were developed tor PEFC applications at low temperature. A sulphonation degree of 65% was selected far these operative conditions in order to guarantee a good proton conduction. An investigation on different percentages (in the range 0-5wt%) of each porphyrin was carried out to verify the interaction with the polymeric matrix. The membranes were realized with a standardized doctor-blade method, thermally and chemically treated. UV-Vis and Fluorescence emission were carried out to investigate the aggregation state of porphyrins embedded in the membranes. Ionie exchange capacity and water uptake measurements were performed to highlight the physico-chemical properties of membranes. lt was found that specific interactions between nitrogenous groups of porphyrin and sulphonic groups of polymer occurred. Moreover, proton conductivity measurements at low temperatures were performed to understand the influence of the interactions on the proton transport mechanism. The developed membranes were characterized in a PEFC 25cm2 single celi to verify the electrochemical performance at the selected operative conditions.