In this study, the effects of Nafion ionomer content in membrane electrode assemblies (MEAs) of polymer electrolyte membrane (PEM) water electrolyser were discussed. The MEAs were prepared with a catalyst coated membrane (CCM) method. The catalysts inks with Nafion ionomer could form uniform coatings deposited on the membrane surfaces. SEM and area EDX mapping demonstrated that anode catalyst coating was uniformly distributed, with a microporous structure. The contents of Nafion ionomer were optimized to 25% for the anode and 20% for cathode. A current density of 1 A cm(-2) was achieved at terminal voltage 1.586 V at 80 degrees C in a PEMWE single cell, with Nafion 117, Pt/C as cathode, and Ru(0.7)Ir(0.3)O(2) as anode. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.