The effect of platinum on free radical generation and membrane degradation in proton exchange membrane (PEM) fuel cells is investigated using three typical cell configurations. Examinations of the fluoride emission rates (FERs) under different testing conditions indicate that platinum deposited in the membrane plays an important role as a catalytic center for the formation of H2O2 and HO center dot free radicals, leading to PEM degradation. The chemical durability of the membranes is tested in accelerated Fenton tests. It confirms the formation of free radicals in the presence of platinum in the decomposition of H2O2 by colorimetric method with dimethyl sulfoxide (DMSO) as the trapping agent. In addition, structural and morphological changes of the membranes are characterized using FT-IR spectroscopy and scanning electron microscopy (SEM). Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.