| The purpose of this work was to study the effects of varying the amounts of carbon monoxide in the feed stream on the performance of polymer electrolyte membrane fuel cells containing platinum and platinum alloy anode catalysts. To understand these effects, step changes in CO inlet concentration were introduced into fuel cell anodes under varying conditions. It took several minutes for fuel cell performance to be completely depressed by CO poisoning. Additionally, it was shown that upon removal of the CO source, the cell immediately began to recover. Within several minutes, the cell had attained its original performance, even though the anode still contained a large amount of catalyst sites blocked by CO. A kinetic model, based upon data generated with a segmented anode fuel cell, was modified to show that during transient excursions from steady state, the CO can be described as moving down the channel as a front, poisoning the entrance and then moving down the flow field until the entire cell is poisoned. Platinum-ruthenium alloyed anode catalysts showed less of a CO poisoning effect than did unalloyed Pt, and Platinum-molybdenum alloys showed even less. The same kinetic model was applied to anodes with alloyed platinum catalysts to see what kinetic parameters might give rise to the increased CO tolerance. |
