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Operating proton exchange membrane ͑PEM͒ fuel cells at relatively high temperatures provides benefits that include greater tolerance to CO, easier management of water, and improved efficiency of heat rejection. At the same time, the degradation of fuel cell components is accelerated at higher cell temperatures, resulting in shortened cell lifetimes. In this study, we investigated temperature effects on cathode Pt/C catalyst durability. Cathode degradation was accelerated using square-wave potential cycling between 0.87 and 1.2 V ͑vs reference hydrogen electrode͒. More rapid Pt/C degradation was observed at higher temperatures, resulting in lower performance, loss of Pt catalyst electrochemically active surface area, and deposition of Pt in the membrane. Each has been quantified at 40, 60, and 80°C. More durable catalysts with improved microstructures are needed for commercial applications of fuel cells, and alternative accelerated tests must be developed for catalyst systems operating at higher temperatures.Proton exchange membrane ͑PEM͒ fuel cells show promise as the power source in future transportation systems, offering high energy-conversion efficiency without greenhouse gas emissions. We expect that the best vehicle designs will use fuel cell and battery hybrid-power systems. The system architecture, its operation, and the approach to power management will affect the life of both the battery and the fuel cell. For systems operated continuously, the electrode potential is nearly constant and generally low enough so that dissolution of platinum is not a first-order concern. For hybrid systems, and particularly for transportation applications, the electrode potential is frequently cycled and platinum dissolution and migration is prevalent. In addition to the high number of potential cycles expected for fuel cell vehicles, two further research objectives that affect this mode of degradation have been identified: reduced precious metal loadings to lower system cost and higher temperatures of operation for improved heat rejection. With the relatively high loadings ͑0.5 mg/cm 2 ͒ of catalysts common today, substantial loss in electrochemically active platinum may be tolerable. In contrast, if platinum loadings are decreased an order of magnitude, the electrode will be much less robust. Thus, a more complete understanding of the physics and chemistry of platinum dissolution and migration and the development of more stable catalyst structures are indispensable.Through fundamental understanding of the mechanisms of degradation, the broader objective of our research is to guide the development of new materials and to identify strategies to mitigate these failure modes in vehicle systems. An essential element is the development of physics-based models. Therefore, our aim is to not only to quantify the effect of temperature on the rate of degradation but to provide data to validate mathematical modeling of platinum dissolution, diffusion, and deposition under cyclic conditions. These models will help solidify our underst...

Operating proton exchange membrane (PEM) fuel cells at relatively high temperatures provides benefits that include greater tolerance to CO, easier management of water and improved efficiency of heat rejection. However, the degradation of fuel cell components is accelerated at higher cell temperatures resulting in shortened cell lifetimes. In this study, we investigated temperature effects on cathode Pt/C catalyst durability. Cathode degradation was accelerated using square-wave potential cycling between 0.87 V and 1.2 V (vs. reference hydrogen electrode). More rapid Pt/C degradation was observed at higher temperatures, resulting in lower performance, loss of Pt catalyst electrochemically active surface area, and deposition of Pt in the membrane. Each has been quantified at 40, 60 and 80 C. More durable catalysts with improved microstructures are needed to meet the future fuel cell commercial applications, and alternative accelerated tests for higher temperatures are required.