Factors Influencing the Voltage Decay Rates of High-Temperature Polymer Electrolyte Membrane Fuel Cells

Abstract

The voltage decay rates of two membrane electrode assemblies (MEAs) for high-temperature proton exchange membrane fuel cells were analyzed to investigate the causes of their degradation. The two MEAs were operated at a current density of 0.3 A cm−2 for 11,000 h at 150 °C, and I–V measurements were taken weekly for MEA 1 and daily for MEA 2. Initially, both MEAs showed a gradual voltage decay with decay rates under 8 μV h−1. The voltage decay rate in the gradual decay region was determined from the changes in the oxygen reduction reaction resistance in the cathode layer. In the later stages of operation, the voltage decay rates became exponential with respect to time, and the average rates increased in magnitude, yielding values over 30 μV h−1. The increase in the ohmic resistance of the membrane and proton transport resistance in the catalyst layer became the main factors in the later stages of cell operation. MEA 2, which was exposed to a daily high potential, showed an exponential decay sooner than MEA 1. The transition to exponential decay led to a rapid decay of the cell voltage and eventual MEA failure.