Various Pt-containing silica nanoparticles were successfully synthesized and adopted in the fabrication of Nafion/silica and Nafion/Pt-containing silica composite membranes. X-ray diffraction and X-ray photoelectron spectroscopy analyses for Pt-containing silica nanoparticle were conducted to identify the phase and oxidation state of Pt incorporated onto silica nanoparticles. Transmission electron micrograph analysis shows 2-3 nm of Pt nanoparticles on the surface of silica nanoparticle. Water uptakes of Nafion/Pt-containing silicas and Nafion/silica composite membranes were measured. All these composite membranes show higher water uptakes than that of casting Nation membrane. In addition, S-Pt/SiO2 and Pt-S/SiO2 composite membranes show a little higher water uptake than that of Nafion/Pt/SiO2 composite membrane due to hydrophilic sulfonic group. The cell test using various MEAs shows that under zero humidity, Nafion/S-Pt/SiO2 composite membrane shows OAS A/cm(2) at 0.6 V and even comparable to that of casting Nation membrane under 100% humidity. It is seen that the cell performance was rather decreased with the increase of Pt-containing silica content due to water flooding and/or electron loss due to the electrical conduction transfer network formed by too much Pt within the membrane. Finally, in case of sulfonation, the order of sulfonation seems to be critical. (C) 2012 Elsevier B.V. All rights reserved.