Synthesis and properties of ceramics-polymer composite membranes as high temperature proton conducting electrolytes

Proton-conducting inorganic/organic composite membranes, which were mechanically flexible, were fabricated, and their conduction properties were characterised for use as polymer electrolyte fuel cells (PEFCs) operating at relatively higher temperatures (100-150°C). SiO₂/PEO (polyethylene oxide) membranes doped with acidic molecules (monododecylphosphate) were fabricated by using the sol-gel route, and the proton conductivities were measured using impedance spectroscopy. The composite electrolytes showed reasonable electrical-conductivity values (10^-3-10^-4 S/cm) up to 150° C and differential thermal analysis and thermogravimetric analysis (DTA/TG) data showed that the membranes were thermally stable up to 350°C, possibly due to the SiO₂ backbone framework.