A proton exchange membrane fuel cell (PEMFC) using a controlled amount of phosphoric acid (PA) in a membrane-electrode assembly (MEA) is operated at 150 C without humidification of the cells. The effects on MEA performance of Pt loading and the amount of PA in the cathode are investigated. The catalyst utilization is maximized by optimizing the PA content in the cathodes and results in lowering of the Pt loading in the MEA. In-situ cyclic voltammetry is used to confirm that the highest value of the active electrochemical area is achieved with the optimum amount or PA in the cathode. The transient response of cell voltage during Current density-voltage experiments (I-V curve) is also found to be affected by the amount of PA in the electrodes. (C) 2008 Elsevier B.V. All rights reserved.