Gas diffusion electrodes (GDEs) incorporating zirconium hydrogen phosphate (ZHP) and Nafion ionomer are investigated in order to examine the influence of ZHP on the properties of catalyst layers (CL) for high temperature polymer electrolyte fuel cells (PEMFCs). ZHP/Naflon-GDEs contained 20 wt% ZHP based on Nafion. GDEs were characterized by SEM, TEM, and FT-IR. Fuel cell polarization curves for ZHP/Nafion-GDE cathodes and anodes were evaluated at temperatures ranging from 80 to 120 degrees C and relative humidities of 100% to 35%. ZHP/Nafion-containing anodes gave similar polarization curves to Nafion-GDEs below 100 degrees C but provided higher fuel cell performance above 100 degrees C. Thermal gravimetric analysis indicated that the presence of ZHP marginally increased the water content in the catalyst layer above 100 degrees C and EIS analysis indicated that ZHP increased protonic conductivity of the catalyst layer. In contrast, no such increase in performance was observed for ZHP/Nafion-GDE cathodes compared to Nafion-GDEs. (c) 2006 Elsevier B.V. All rights reserved.