In this study, gas diffusion layers (GDLs) for proton exchange membrane fuel cell (PEMFC) were subjected to accelerated stress tests to investigate the progression of mechanical degradation of micro porous layers (MPLs) over a short period of time, and crack-free MPL was prepared to enhance the mechanical durability of the MPL A dummy cell was designed for the mechanical degradation of MPLs. There was no catalyst layer in the dummy cell and only air was supplied into the dummy cell to avoid electrochemical degradation of the MPL In the MPL degradation experiments, several puddle-shape defects were formed only around the cracks in the surface of the MPL, and these defects negatively affected the performance of the PEMFC. The single cell performance dramatically decreased at a high current density due to the puddle-shape defects. Thus, crack-free MPL was manufactured to reduce mechanical damage on the surface of MPL by adding a water-soluble polymer binder to the MPL slurry. The puddle-shape defects were not detected on the surface of the home-made crack-free MPL, and the decrease in the single cell performance after mechanical degradation of MPL was insignificant when the home-made crack-free MPL was used in the cathode. (C) 2012 Elsevier Ltd. All rights reserved.