Hybrid organic-inorganic membranes for a medium temperature fuel cell

Sulfonated polyetheretherketone has been used as polymer matrix for hybrid membrane formation with inorganic proton conductors. Membranes incorporatin g up to 40% w/w of inorganic proton conductor including amorphous silica, z irconium phosphate sulfophenylphosphonate and zirconium phosphate, have bee n prepared. The membranes have been characterised using powder X-ray diffra ction and MAS NMR spectroscopy where appropriate, and conductivity measurem ents performed as a function of relative humidity (RH) at 100 degrees C and as a function of temperature at 100% RH. In all cases, the presence of the inorganic particles leads to an increase in conductivity of the polymer me mbrane and is without detriment to its flexibility. For example, PEEK-S-bas ed membranes containing 10% amorphous silica, 30% zirconium phosphate or 40 % amorphous zirconium phosphate sulfophenylphosphonate present conductiviti es in the range 0.03 - 0.09 Scm(-1) at 100 degrees C/100 % RH. Polarisation characteristics for PEEK-S membranes containing 25 and 13% w/w of zirconiu m phosphate under conditions of hydrogen/ oxygen and hydrogen/air respectiv ely are reported up to 120 degrees C.