A critical review of remaining useful life prediction for water Electrolyzers: From degradation mechanisms to prognostic models

With the increasing integration of electrolyzers in energy systems, operational durability has become a key concern. Achieving durability optimization requires effective performance indicators that capture degradation behavior and enable real-time monitoring. Remaining useful life (RUL) prediction, widely applied in batteries and fuel cells, offers a dynamic assessment of equipment health via degradation modeling. However, research on electrolyzer degradation mechanisms is still limited, and RUL lacks standardization and practical applicability in this context. For electrolyzers, DOE targets stack lifetimes of 40,000–80,000 h with degradation rates below 0.2 %/1000 h. However, in practice, the end of life is still commonly defined using an empirical criterion, typically defined as a 5–10 % increase in operating voltage relative to its initial value at a given current density. This study reviews degradation factors, synthesizes the current status of RUL research in electrochemical systems, and proposes a life prediction framework including data preprocessing, modeling, and evaluation. It also analyzes its applicability under electrolyzer conditions and outlines key challenges and future directions toward a reliable and interpretable RUL prediction system.