Trace amounts of Carbon Monoxide (CO) adversely affect the performance of PEM Fuel Cell. CO is adsorbed and stuck at the active sites of Platinum electrodes causing reduction in power output of the Fuel Cell. Since, CO can pass through the proton-exchange membrane , even less than 10 ppm of CO in air can cause irreversible poisoning of not only cathode but also anode. The present cathode air filters do not have the ability to remove CO from air. Further, catalysts available for CO oxidation at ambient temperatures (e.g. Hopcalite) become inactive in presence of moisture.

A novel catalyst has been developed for ambient temperature CO oxidation in the presence of moisture. This novel catalyst comprises a precious metal, a metal oxide on an inert catalyst support such as silica or alumina. The catalyst was prepared by incipient wetness impregnation. The catalyst yielded a steady CO conversion (>99%) in the presence of moisture (RH 50 - 90%) for more than 8 hours at ambient temperature (230C). The catalyst was evaluated at various face velocities, CO challenge concentrations at ambient temperature with RH of 0-100%. The catalyst demonstrated an extremely high activity for CO oxidation. In a thin bed test, a challenge gas (RH 50%) containing 250 ppmv CO was passed through a packed bed of the catalyst particles (150 µm) with a bed thickness of 1.5 cm at a gas face velocity of 1.0 m/s. The catalyst successfully reduced the CO concentration to below 0.1 ppmv for 8 hours without any deactivation.

The performance of microfibrous entrapped catalyst is also studied. Polymer fiber entrapped catalyst significantly improved CO oxidation performance. Microfibrous entrapment substantially reduced the bed thickness and pressure drop over the bed, for achieving the same CO conversion. Therefore, this novel catalyst composition entrapped in microfibrous media can effectively be used in a cathode air filter for PEM Fuel cell.

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