Durability and Degradation in High-Temperature Polymer Electrolyte Fuel Cells

Abstract

This work summarizes the major degradation modes observed in polymer electrolyte fuel cells with a strong emphasis on the modes observed in high temperature PEFCs based on PBI H3PO4 membranes. Some aspects are discussed in more detail, e.g., carbon corrosion, phosphoric acid evaporation rates, and the impact of high cathode potentials. Finally, a still ongoing durability test of a Celtec® P Series 1000 MEA is discussed in the light of cathode degradation. The MEA itself currently is running for more than 18,000 hours at constant current density. The overall degradation rate is only 6µV/h at the operation point of 0.2 A/cm². At this current density, the main part (55%) of the degradation is due to increased mass transport overpotentials and by reduced oxygen reduction kinetics (30%). The remaining 15% can be ascribed to a slight increase in ohmic cell resistance. The underlying processes leading to the different types of degradation are discussed.