Anhydrous proton conducting materials based on sulfonated dimethylphenethylchlorosilane grafted mesoporous silica/ionic liquid composite

Efficient membrane proton conductivity at elevated temperatures (>100 C) and reduced humidification conditions is a critical issue hindering fuel cell commercialization. Herein, proton conducting materials consisting of high surface area acid catalyzed mesoporous silica functionalized with sulfonated dimethylphenethylchlorosilane was investigated under anhydrous conditions. The organic moiety covalently bonded to the silica substrate via active hydroxyl groups on the silica pore surface. The structure and dynamic phases of the attached organic molecule were characterized and qualitatively determined by XRD, TEM, FT-IR, and solid state NMR. The amount of grafted organic molecules was estimated to be 2.45 μmol m^-2 by carbon elemental analysis. The so-formed composite materials showed adequate thermal stability up to 300 C as determined by TGA. Under anhydrous conditions, ionic conductivity of the composite material upon ionic liquid impregnation reaches a peak value of 1.14 × 10^-2 S cm^-1 at 160 C associated with the activation energy of 9.24 kJ mol^-1 for proton transport.