A flexible phosphosilicate-based intermediate temperature composite electrolyte membrane with proton conductivity at temperatures of up to 250 °C

Phosphosilicate sol/sulfonated poly(ether ether ketone) (PSi/SPEEK) composite membranes are fabricated by a simple mechanical mixing process. SPEEK provided the PSi/SPEEK membranes with satisfactory mechanical properties even when inorganic components made up 50% of their weight. Membrane proton conductivity was evaluated in the 180-250 °C range under ambient conditions of humidification from 100 °C water vapor and without humidity. A proton conductivity of 1.1 mS cm−1 was reached from the composite membrane 5P5Si5/5SPEEK at 250 °C with 100 °C water vapor, because of its improved hygroscopicity and functional groups. The conductivity of the 5P5Si5/5SPEEK membrane in ambient conditions with humidity from 100 °C water vapor was higher than in ambient conditions without humidity. This disparity was especially apparent above 200 °C.