Phosphoric acid containing polymer electrolyte membranes, such as polybenzimidazole (PBI), can serve as fast proton conductor operable at relatively high temperature (up to 200°C) without the need for humidification. High temperature operation greatly alleviates the poisoning issues associated with the trace impurities, such as CO. However, the development of high performance low platinum loading electrode for this type of fuel cell remains a challenging task. Known issues include the reduced activity of platinum catalyst due to specific surface absorption of phosphate groups and the low oxygen solubility in phosphoric acid surrounding the platinum catalysts. Practically, the mobile nature of phosphoric acid makes it a very tricky task to design and optimize three phase boundaries which are critical for fuel cell performance. High temperature operation also exacerbates carbon support corrosion in the cathode.
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