An organically-modified ceramic material (TiO2-RSO3H) to be used as filler in Nafion-based composite membranes was synthesized by covalently grafting propylsulfonic acid groups on the surface of TiO2 nanoparticles. Higher ion exchange capacity (IEC) and proton conductivity of the hybrid material (one order of magnitude higher for the functionalized filler) reflected in superior performance of Nafion/TiO2-RSO3H composite membranes compared to Nafion. The highest conductivity value was obtained for the composite membrane containing 10 wt. % TiO2-RSO3H (sigma = 0.08 S cm(-1) at 140 degrees C). The membranes were tested in a DMFC single cell. The presence of the filler resulted in a general enhancement in the cell response, in terms of both higher power density (PD) delivered and lower methanol crossover with respect to unfilled Nafion membrane. The DMFC containing N_10TiO(2)-RSO3H membrane showed the best performance at 110 degrees C with a PD of 64 mW cm(-2), corresponding to a PD improvement of about 40% with respect to that of Nafion membrane. (c) 2013 Elsevier B.V. All rights reserved.