Membrane durability was a key problem to the development of proton exchange membrane fuel cells (PEMFCs). A novel nanocomposite MnO2/SiO2-SO3H was prepared to mitigate the hydrogen peroxide attack to the membranes at fuel cell condition. The nanocomposites were synthesized by the wet chemical method and three-step functionalization. The crystal structure was characterized by X-ray powder diffraction (XRD), the crystallite size and the distribution of the nanocomposites were investigated by TEM. SEM-EDX was used to analyze the elemental distribution on the surface of the nanocomposite. And the surface functional groups (-SO3H) were evaluated by FT-IR. The amount of sulfonic acid groups introduced onto the silica surface was determined by titration method. The radical scavenging ability was estimated by UV-VIS spectroscopy using dimethyl sulfoxide (DMSO) as the trapping agent. The membrane durability was investigated via ex situ Fenton test and in situ open circuit voltage (OCV) accelerated test. In these tests, the fluoride emission rate (FER) reduced by nearly one order of magnitude with the dispersion of MnO2/SiO2-SO3H nanocomposites into Nafion membrane, suggesting that MnO2/SiO2-SO3H nanocomposites had a promising application to mitigate the degradation of the proton exchange membrane. (C) 2009 Elsevier B.V. All rights reserved.