Reduction of methanol permeability in polyetherketone-heteropolyacid membranes

Organic-inorganic membranes for direct methanol fuel cell (DMFC) application were prepared, using an organic matrix of sulfonated polyetherketone (s-PEK), different heteropolyacids and an inorganic network of ZrO₂ or RSiO_3/2. The membranes were characterized concerning their methanol and water permeability by pervaporation and ionic conductivity by impedance spectrometry. The bleeding out of the heteropolyacid from the membrane was quantified. The presence of the ZrO₂ decreases the methanol and water permeability and reduces the bleeding out of the heteropolyacid. Molybdophosphoric acid (MoPA) was also investigated, showing a more pronounced bleeding out effect, which could be reduced by modifying the anion structure with the inclusion of Ni or Si. High conductivity values were obtained with membranes containing tungstophosphoric acid (TPA).