In this work a three-dimensional non-isothermal and two-phase computational fluid dynamics model of a proton exchange membrane (PEM) fuel cell with straight flow field channel is developed and validated The model is used to predict the performance of the PEM fuel cell with changing parameters of the cathode catalyst layer which was usually assumed to be composed of spherical agglomerates The effect of cathode catalyst layer parameters such as catalyst layer thickness ionomer film thickness agglomerate size and porosity on the current density and power output of the PEM fuel cell is investigated The numerical results reveal that competitive influence of resistances to transport of species electron and proton within the cathode catalyst layer determines the performance of the PEM fuel cell in terms of area specific power density (W cm(-2)) and mass specific power density (kW g(Pt)(-1)) (c) 2010 Elsevier B V All rights reserved