A study of polymer electrolyte fuel cell performance at high voltages. Dependence on cathode catalyst layer composition and on voltage conditioning

Abstract

We report polymer electrolyte fuel cell (PEFC) performances at high cell voltages (>0.7 V). We have tested various carbon supported PtM alloys (M: Cr, Ni, Rh, Sn) as cathode catalysts and compared performances with Pt/C. PtNi and PtCr provided the best results. Fuel cell performance at high constant voltages (>0.8 V) decreases rapidly with time. Within 1 h currents may drop to one half of their original value. Experiments strongly suggest that, at these voltages, there is an inherent Pt activity loss for oxygen reduction reaction (ORR) due to adsorption of oxygenated species from water. We also demonstrate that OH − species (from water oxidation), which block Pt active sites, adsorb at more positive voltages on PtM than on Pt surfaces. Thus, we conclude that the Pt surfaces of these alloys are more active for the ORR because of slower OH − species adsorption at high cell voltages. We have also found that short time cell voltage excursions from 0.8 to 0.5 V or lower at regular intervals, completely recovers the loss of performance. Consistent with our other results, pulsing to lower voltages reactivates the Pt surface by electrodesorption of OH − or other anions.