In this study, the influence of micro-porous layers (MPL) on polymer electrolyte membrane fuel cell (PEMFC) durability was investigated. Two fuel cells were built, one with a micro-porous layer on the anode side, and a second cell with MPL on both sides. Experiments were conducted by varying operational parameters such as current density, reactant stoichiometry, and inlet relative humidity. Fuel cell degradation was evaluated by measuring fluoride release rates. The largest factor determining fluoride release rate was found to be the presence of MPL; the cell with MPLs on both sides exhibited significantly reduced fluoride release rates compared to that of cell with one MPL. Increasing the current density also reduced the fluoride release rate for cells with only one MPL whereas there was only a moderate effect on cells with two MPLs. Microscopy analysis showed small but significant changes in ionomer layer thickness. Polarization measurements indicated that there was little change in the performance for both cells over the test period. (c) 2008 Elsevier B.V. All rights reserved.