(Invited) Degradation Mechanisms, Diagnostics, and Mitigation in Proton Exchange Membrane Water Electrolyzers
Authors: Alia Shaun M , Padgett Elliot , Chan Ai-Lin , Blair Sarah J. , Medina Samantha , Reeves Kimberly S. , Yu Haoran , Cullen David A. , Park Jaehyung , Kariuki Nancy N. , Kropf A. Jeremy , Ahluwalia Rajesh , Myers Deborah J. 
Published: December 2024

Hydrogen has unique advantages as an energy carrier, with a high energy density and abilities for long term storage and conversion between electricity and chemical bonds. Although hydrogen currently has a significant role in transportation and agriculture, its use in energy consumption overall has been limited. With decreasing electricity prices, electrolysis cost reductions can be achieved and allow for an opportunity for greater use. While load-following renewable power sources can reduce feedstock cost, further cost reductions can be achieved by decreasing stack and system cost.1 Proton exchange membrane (PEM) water electrolyzers rely on platinum group metal (PGM) catalysts due to the high anode potentials and low pH of proton conducting systems.2 While iridium (Ir) abundance is a potential concern for the ubiquitous deployment of PEM water electrolyzers,3,4 thrifting Ir while improving performance and durability is critical for reaching hydrogen cost targets.

Efforts are needed and underway to understand electrolyzer degradation and develop accelerated stress tests when accounting for lower PGM loadings and hydrogen cost reduction targets.5 In this presentation, studies correlating operational and shutdown strategies to performance losses, identifying degradation mechanisms, and evaluating their impact on electrolyzer lifetime will be discussed. Depending on catalyst/interfacial properties and operational parameters, processes including catalyst/transport layer migration, and catalyst reordering, segregation, and oxidation have been observed and linked between ex situ characterization and in situ diagnostics. Through these studies, shutdown processes and catalyst redox transitions have generally been found to increase loss rates; varying catalyst types and morphologies, however, can also present significant integration challenges particularly when focusing on low PGM loading and durability testing.

Mitigation options have further been explored that can address degradation processes, including catalyst development and electrode design strategies. Within catalysis, commercial screenings and development efforts have both modified materials properties and catalyst/ionomer/pore distribution throughout the catalyst layer. In some cases, electrode design efforts have also led to altered site utilization and changed the extent to which operational stressors utilize the entire catalyst layer, impacting performance losses over time. Catalysis of the oxygen evolution reaction by Ir will be discussed as it relates to current status in the tradeoff between electrolyzer cost, performance, and lifetime; particular challenges in PEM durability and accelerated stress test development will be also discussed as well as it relates to other low temperature electrolysis technologies.

[1] B. Pivovar, N. Rustagi and S. Satyapal, The Electrochemical Society Interface, 27, 47 (2018).

[2] K. Ayers, N. Danilovic, R. Ouimet, M. Carmo, B. Pivovar and M. Bornstein, Annual Review of Chemical and Biomolecular Engineering, 10, 219 (2019).

[3] Cortney Mittelsteadt, Esben Sorensen, and Qingying Jia, Ir Strangelove, or How to Learn to Stop Worrying and Love the PEM Water Electrolysis Energy Fuels 37, 12558 (2023).

[4] Mark Clapp, Christopher M. Zalitis, Margery Ryan, Perspectives on current and future iridium demand and iridium oxide catalysts for PEM water electrolysis, Catalysis Today 420, 114140 (2023).

[5] Pivovar, B. S.; Boardman, R., H2NEW: Hydrogen (H2) from Next-generation Electrolyzers of Water, 2023.

[6] Electron microscopy was performed at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

[7] X-ray spectroscopy and scattering performed at the Advanced Photon Source at Argonne National Laboratory, a DOE Office of Science User Facility.