Nafion/titania-based fillers composites are prepared by casting and tested in proton exchange membrane fuel cells (PEMFCs) operating at elevated temperatures (130 degrees C). Three types of titania-based fillers are studied: nanoparticles with nearly spherical shape, mesoporous particles with high surface area, and hydrogen titanate nanotubes. Properties of composites related to PEMFC operation, such as water absorption/retention and proton conductivity, are determined and correlated with microstructural data obtained by small-angle X-ray scattering. The addition of titanate nanotubes changes more markedly the physical properties of the composite electrolytes as compared to titanium oxide nanoparticles with different surface area, a feature probably related to the intrinsic hydration and proton conductivity of the nanotubes. Polarization curves of H-2/O-2 PEMFCs using composite electrolytes indicate that composite electrolytes contribute to a significant boost of H-2/O-2 PEMFC performance at 130 degrees C. (C) 2010 Elsevier B.V. All rights reserved.