Effects of Pt loading in the anode on the durability of a membrane-electrode assembly for polymer electrolyte membrane fuel cells during startup/shutdown cycling

Abstract

A polymer electrolyte membrane fuel cell (PEMFC) stack of a fuel cell vehicle (FCV) is inevitably exposed to reverse current conditions, which are formed by the oxygen reduction reaction (ORR) induced at the anode with a hydrogen/air boundary during startup/shutdown processes. With an increase in the reverse current, the degradation rate of the cathode that experiences a highly corrosive condition (locally high potential) increases. In this work, the anode Pt loading is decreased from 0.4 to 0.1 mg cm(-2) to decrease the reverse current. The decrease in the anode Pt loading is found to decrease the hydrogen oxidation rates (HOR) during normal operation, but this loading decrease barely affected the cell performance. However, a decrease in the anode Pt loading can significantly decrease the reverse current, leading to a diminished cathode degradation rate during startup/shutdown cycling. It is revealed by slow decreases in the cell performance (i-V curves) and electrochemical active surface area (EAS), and a slow increase in the charge-transfer resistance (R-ct), which can be attributed to corrosion of the carbon support and dissolution/migration/agglomeration of the platinum catalyst.