Initial open circuit voltage response as a practical diagnostic approach in proton exchange membrane water electrolysis

Proton exchange membrane water electrolysis is a promising technology for sustainable hydrogen production yet transferable diagnostics across systems, especially in early operation remain as a key challenge for a reproducible operation. Despite being an easily accessible metric, transient open circuit voltage behavior in proton exchange membrane water electrolysis remains less explored than in proton exchange membrane fuel cells. In this work, early post conditioning open circuit voltage behavior is evaluated as an empirical indicator of transient instability during operation. The results reveal clear differences between open circuit voltage behavior and subsequent operational performance for catalyst coated membranes incorporating nominally identical membranes from different manufacturers. These findings highlight the potential of simple diagnostic strategies for early-stage material assessment in proton exchange membrane water electrolysis, suggesting differences in manufacturing while exposing limitations in the reproducibility of the metric across nominally identical material and operational conditions. Additionally, material properties were investigated after conditioning step, using fluoride ion and total fluorine measurements as two closely related metrics and their potential link to open circuit voltage performance. No clear correlation between these metrics and open circuit voltage behavior was observed.