Proton-conducting composite membranes based on polybenzimidazole and sulfonated mesoporous organosilicate

Sulfonated mesoporous organosilicate (s-MPOs) was synthesized by the one-step sol–gel method as a novel inorganic additive derived for use in the fuel cell. TEM observations revealed that the s-MPOs has well-ordered structure and many SO3H groups on the inner surface of the mesopores. The s-MPOs was added to the proton-conductive polymer matrix, polybenzimidazole (PBI) in the presence of H3PO4, and the proton conductivities were measured at 60–100 °C under controlled humidity. The PBI composites filled with only 1 wt% of s-MPOs gave proton conductivity more than 10-times higher than the original PBI/H3PO4 membrane. The s-MPOs possessing many SO3H groups were able to form effective proton conductive pathways via its periodic structure and to improve the conductivity. The greatest conductivity was estimated to be 0.21 S cm−1 at 80 °C and 98 %RH in case of a PBI/s-MPOs20 (incl. approx. 20 mol% of the SO3H units in MPS) composite.