The electrode with various contents of Nafion ionomer for inside and/or on the surface in the catalyst layer, respectively, was designed for proton exchange membrane fuel cell (PEMFC) electrode to investigate the effect of Nafion ionomer distribution in the catalyst layer on cell performance and improve electrode performance. The effect of Nafion ionomer on the electrode of each design was judged by a cyclic voltammetry measurement and the cell performance obtained through a single cell test using H-2/O-2 gases. Electrodes with different ionomer distributions for inside and on the surface in the catalyst layer, respectively, were examined. it is found that the electrode where the Nafion ionomer is impregnated on the surface of catalyst layer shows better cell performance than that where the Nafion ionomer is incorporated in the inside of catalyst layer. The best cell performance among the catalyst layers tested in this study was obtained for the electrode with 0.5 mgcm(-2) of Nafion ionomer inside the catalyst layer and 1.0 mg cm(-2) of Nafion ionomer on the surface of the catalyst layer together. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.