Quantifying Sources of Voltage Decay in Long-Term Durability Testing for PEM Water Electrolysis

Abstract Meeting a competitive 1$/kg hydrogen cost target for polymer electrolyte membrane water electrolysis (PEMWE) will require advances to significantly reduce capital costs and precious metal catalyst usage, while simultaneously enabling 40,000-80,000 hour stack lifetimes under dynamic use conditions. Minimizing cell voltage decay rates is therefore a key goal for PEMWE, although the fundamental processes governing voltage decay are not yet well understood. Here we present a quantitative approach to analyze the contributions to voltage decay in long-term PEMWE testing using polarization curves, impedance spectroscopy, and post-mortem electron microscopy. We apply this approach to analyze a 28 μV/hr decay rate observed in a 4000-hour durability test of a cell using 0.5 mg/cm2 total PGM catalyst loading (0.4 mgIr/cm2 anode, 0.1 mgPt/cm2 cathode) and 3 A/cm2 current density. We also analyze a comparative series of 1000-hour tests under different conditions. These results provide valuable insights into anode catalyst degradation processes, as well as transferrable methodology for PEMWE durability research.