(63c) Selective Co Oxidation in the Presence of Excess Hydrogen over Promoted Pt Catalyst

The poisoning of a PEM fuel cell electrode by a trace amount of CO contaminating in fuel gases lowers the performance of PEM fuel cells. To eliminate this amount of CO, we can use the method of selective CO oxidation by adding oxygen into gas stream containing the suitable catalyst. The amount of CO contamination should be reduced to less than 10 ppm before the fuel gas enters the PEM fuel cell. This catalyst should be selectively active to CO oxidation reaction but not active to H2 oxidation reaction. In this work, we developed platinum based catalyst by promoted it with ceria which has an oxygen storage property. We prepared our catalyst by sol gel method. Then, we tested the activity of a 5%Pt/15%CeO2/Al2O3 to selective CO oxidation with the simulated reformed gas composition (1%CO, 20%CO2, 60%H2, 10%H2O and balance with He). We studied the effects of H2O and CO2 to the activity of the catalyst. We found that the presence of CeO2 in a platinum based catalyst dramatically enhanced the performance of the catalyst to CO oxidation. Water has a positive effect to the performance of this catalyst to CO oxidation. CO nearly completely converted to CO2 at 150 degree celcius with the selectivity of 52%. On the other hand, the presence of 20%CO2 in the gas stream has a negative effect to the activity of the catalyst. This caused by the reverse water gas shift reaction and the formation of carbonate species over ceria sites.

Keywords: selective CO oxidation, platinum, ceria, sol-gel, PEM fuel cells