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

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 h 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 h⁻¹ decay rate observed in a 4000 h durability test of a cell using 0.5 mg cm⁻² total PGM catalyst loading (0.4 mg_Ir cm⁻² anode, 0.1 mg_Pt cm⁻² cathode) and 3 A cm⁻² current density. We also analyze a comparative series of 1000 h tests under different conditions. These results provide valuable insights into anode catalyst degradation processes, as well as transferrable methodology for PEMWE durability research.