The performance of a phosphoric acid doped polybenzimidazole (PBI) membrane, with Pt and Pt-Ni/C catalysts on the anode and cathode, respectively, was experimentally determined at 160 degrees C using neat H-2 and O-2. The resulting current voltage relation was then compared to a performance curve calculated from previously established values for the exchange current density and activation energy of the oxygen reduction reaction (ORR) on Pt-Ni/C. An overall voltage loss >200 mV, regardless of current density, was observed for the MEA relative to the predicted performance, implying about two orders of magnitude decrease in the exchange current density for the ORR. The reduction in exchange current density was attributed to anion (H2PO4-) adsorption. Published by Elsevier B.V.