Sulfonated poly(ether ether ketone) (sPEEK)/mesoporous benzene-silica electrolyte composite membranes were prepared using a solvent casting method. The two components were mixed thoroughly in N,N-dimethyl acetamide, at various concentrations up to 20 wt% of the mesoporous benzene-silica powder. The degree of sulfonation was 65% for sPEEK, and the ion-exchange capacity of mesoporous benzene-silica was 0.60 mequiv./g. The mesoporous benzene-silica material had a 2D hexagonal (p6mm) mesostructure with a pore diameter of 2.7 nm. The composite membranes exhibited higher proton conductivities than a pristine sPEEK membrane, and the proton conductivity increased with temperature. However, the sPEEK-based composite membranes showed very low methanol crossover below 5 x 10(-7) cm(2)/s, but this value was still in the same range as the pristine sPEEK membrane. A maximum proton conductivity of 0.079 S/cm was obtained for the sPEEK-OMB15 membrane at 80 degrees C, and the highest DMFC cell performance was at 56 mW/cm(2), which were approximately 119 and 37% increases compared to the pristine sPEEK membrane, respectively. (C) 2010 Elsevier B.V. All rights reserved.