Mechanism-Informed Breakdown: Understanding Degradation by Controlling Voltage-Hold Patterns in Proton Exchange
Ai-Lin Chan1, Steven C Hayden2, Steven P Harvey2
1Chemical and Material Sciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States.
ACS Applied Energy Materials
|January 30, 2026
Summary
Proton exchange membrane (PEM) water electrolysis stability is challenged by low catalyst loadings. Constant voltage holds improve catalyst durability compared to potential cycling, which degrades performance by damaging catalyst layers and ionomers.
Area of Science:
- Electrochemistry
- Materials Science
- Catalysis
Background:
- Proton exchange membrane (PEM) water electrolysis is crucial for green hydrogen production.
- Low catalyst loadings in PEM electrolyzers lead to performance instability and degradation over time.
- Understanding degradation mechanisms is vital for enhancing long-term operational stability.
Purpose of the Study:
- To investigate the impact of different stress conditions on the degradation mechanisms and voltage loss rates in PEM water electrolyzers.
- To compare the effects of potential cycling versus constant voltage holds on catalyst stability and performance.
- To elucidate the role of iridium (Ir) migration and catalyst layer (CL) integrity in PEM electrolyzer durability.
Main Methods:
- Application of distinct stress tests (potential cycling and constant 2 V hold) to membrane electrode assemblies.
- Analysis of iridium oxide crystallization, ionomer degradation, and catalyst layer thinning.
- Evaluation of kinetic loss rates, including Tafel slope, polarization kinetics, and charge transfer resistance.
Main Results:
- Potential cycling induced significant iridium oxide crystallization, ionomer degradation, and CL thinning, leading to higher kinetic losses.
- A constant 2 V hold resulted in a more uniform iridium band formation, maintaining catalytic activity and improving kinetic durability.
- Potential cycling caused disconnected iridium agglomerate migration, increased charge transfer resistance, and substantial ionomer damage, reducing active sites.
Conclusions:
- Distinct degradation pathways exist for load holds versus potential cycling in PEM water electrolysis.
- Constant voltage holds can enhance kinetic durability and stability compared to potential cycling.
- Optimizing operational strategies based on catalyst-ionomer interactions is key for long-term PEM electrolyzer performance, especially with intermittent energy sources.
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