The durability of proton exchange membrane fuel cells has been extensively studied. The main aim of the present study was to elucidate membrane electrode assembly (MEA) degradation mechanisms using an accelerated degradation technique (ADT). An ADT experiment was performed by applying 1.5 V to an MEA with hydrogen and nitrogen feeding to the anode and cathode, respectively, to simulate the high voltage generated during fuel cell shutdown and restart. This study adopted in situ as well as ex situ techniques, such as polarization curves, AC impedance, cyclic voltammetry (CV), linear sweep voltammetry (LSV). SEM and TEM to analyze the MEA before and after ADT experiments. Results show that the ADT could dramatically reduce the duration of the experiment while still observing MEA degradation. Current output at 0.4 V decreased by 41% after performing ADT for 60 min. LSV showed unchanging hydrogen crossover through the MEA, implying membrane degradation could be ignored during ADT evaluation. An increase in charge transfer resistance seen by AC impedance, shifts in the electrochemical surface area and double layering suggested that the main degradation mechanism during ADT evaluation is degradation of the carbon supporting the catalyst layer. (C) 2012 Elsevier Ltd. All rights reserved.