Impact of Operating Conditions on Degradation Behavior of a 500 kW-Class PEM Water Electrolysis System

Proton exchange membrane water electrolysis is a promising technology for renewable hydrogen production. However, its durability under dynamic operating conditions remains insufficiently understood. In this study, 500 kW-class PEMWE system was evaluated under constant-current operation, daily start and stop, and accelerated durability testing. Degradation rates were quantified from cell-voltage evolution and correlated with electrochemical impedance spectroscopy, gas analysis, water-quality analysis, and metal dissolution measurements. The degradation rate increased from 74 μV h −1 under rated-current DSS conditions to 262 μV h −1 under severe ADT conditions, demonstrating that dynamic operation accelerates degradation more significantly than current loading. Impedance analysis indicated that degradation was primarily governed by internal resistance increase, while charge-transfer resistance increased during prolonged ADT operation. Furthermore, a reproducible linear relationship between initial cell voltage and subsequent voltage increase was confirmed. These results provide fundamental data or an evaluation methodology for future lifetime prediction, and operational optimization of large-scale PEMWE systems.