The effect of pore volume on the catalyst layer durability of PEM fuel cell was simulated by soaking the catalyst coated membrane (CCM) into H(2)O(2)/Fe(2+) solution. Before this simulation, the CCM with various pore volumes in catalyst layer was fabricated. The structure of catalyst layers was optimized with an increase in pore volume, leading to an improvement of fuel cell performance. However, this treatment causes a negative effect on the lifetime of CCM especially when H(2)O(2)/Fe(2+) introduced. As a result, the catalyst layer with high pore volume has a higher detaching rate than that with low pore volume. The detaching of catalyst layers could be attributed to degradation of both the recast Nafion in catalyst layers and the Nation membrane. The catalyst layer with high pore volume accelerates the recast Nation degradation. Thus, the durability of membrane electrode assembly should be considered when the catalyst layer is optimized. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.