Pt nanoparticles were successfully deposited onto SiO2 nanoparticles sulfonated by different chemical sources such as H2SO4, CH3SO3H, Na2SO4, and HSO3Cl and denoted as Pt-HS/SiO2, Pt-CS/SiO2, Pt-NS/SiO2 and Pt-SS/SiO2, respectively. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) analyses for Pt-containing sulfonated SiO2 nanoparticles were conducted to identify the phase, oxidation state of Pt incorporated and the existence of -SO3+ on SiO2 nanoparticles. Transmission electron microscope analysis shows 2-4 nm of Pt nanoparticles on the surface of SiO2 nanoparticle. The proton conductivities of various membranes are highly consistent with metallic Pt and -SO3+ contents based on XPS analysis. The membrane electrolyte assembly (MEA) fabricated with Nafion/Pt-NS/SiO2 composite membrane showing the smallest Pt particle size and excellent dispersion shows the best cell performance under zero humidity, following the order of Pt-NS/SiO2 > Pt-HS/SiO2 > Pt-CS/SiO2 > Pt-SS/SiO2. It also shows that the MEA fabricated with Nafion/Pt-NS/SiO2 composite membrane shows the least decrease by 5.7% in open circuit voltage with relative humidity while that for Nafion/Pt-CS/SiO2 composite membrane is the largest by 15.3%. The results suggest that Pt particle size, its dispersion, metallic Pt and -SO3 contents are critical and quite different with chemical source for sulfonation, affecting the cell performance. (C) 2013 Elsevier B.V. All rights reserved.