An investigation has been made on a high temperature polybenzimidazole (PBI) proton exchange membrane doped with phosphoric acid. Two and five percent concentrations of CO in the hydrogen were evaluated to determine the effect of high CO concentrations on the performance of the PBI membrane under conditions that are representative of reformed fuels. A 3 × 3 matrix of fuel composition, temperature and air stoichiometry was studied at two pressures: one atmosphere and one bar gage. A controlled experiment using hydrogen of 99.997% purity was used as a baseline fuel before and after the exposure to higher CO concentrations. A comparison between the pure hydrogen runs and those where CO was also present in the fuel showed a significant reduction in cell performance. Subsequent runs with pure hydrogen restored the cell performance. The mechanism that led to the cell recovery with pure hydrogen will be discussed.

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