Novel Polymeric Composite TPPS/s-PEEK Membranes for Low Relative Humidity PEFC

Composite membranes based on different wt percentages of meso-tetrakis-(4-sulfonatophenyl)porphyrin (TPPS) embedded in a medium sulfonation degree (50%) sulfonated poly(etheretherketone)(s-PEEK) were investigated. The successful introduction of porphyrin into the membranes andthe characterization of its dierent species into the membrane ionic domains were carried out byspectroscopic techniques. Moreover, the eect of TPPS arrangement was investigated in terms ofwater retention, proton conductivity and fuel cell performance at low relative humidity (RH). It wasfound that the introduction of this porphyrin induces a variation of the chemical-physical parameters,such as ion exchange capacity (IEC), water up-take (Wup %) and proton concentration ([H+]),attributable to the interactions that occur between the sulfonic groups of the polymer and the nitrogensites of TPPS. The TPPS, in its J-aggregated form, actively participates in the proton conductionmechanism, also maintaining the adequate water content in more drastic conditions (80 C and 50%RH). A maximum power density value of 462 mW cm?2 was obtained for the s-PEEK membrane,with a 0.77 wt % content of TPPS. This evidence suggests that the presence of J-aggregates in theproton conduction channels maintains a good hydration, even if a drastic reduction of the RH of thereactant gases occurs, preventing the membrane from a dry-out eect.