in order to improve proton exchange membrane water electrolyzer (PEMWE) performance, some factors related to the processes of preparing the Membrane Electrode Assemblies (MEAs), such as iridium (Ir) electrocatalyst loading and Nafion (R) content at the anode, thicknesses of proton exchange membrane and gas diffusion layers (GDLs), were examined. in addition, a home-made supported Ir/titanium carbide (Ir/TiC, 20% Ir by weight) was developed for the anode. With best commercial Ir catalyst loading of 1.5 mg cm(-2) Ir at the anode, the cell's current densities of 1346 mA cm-2, 1820 mA cm(-2) and 2250 mA cm(-2) were achieved at the cell potentials of 1.80 V, 1.90 V and 2.00 V, respectively, A PEMWE with 0.3 mg cm(-2) Ir loading of Ir/TiC anode catalyst was comparatively stable and gave current densities of 840 mA cm(-2), 1130 mA cm(-2) and 1463 mA cm(-2) at the cell potentials of 1.80 V, 1.90 V and 2.00 V, respectively. Based on catalysis efficiency of Amperes per milligram of Ir, the Ir/TiC catalyst is found to be more active than unsupported It catalyst. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.