Effects of Loading and Nafion Content on the Activity and Stability of Iridium Oxygen Evolution Reaction Catalysts

Zlatar M, Simon C, Przybysz JM, Rodríguez MG, Katsman J, Ayoub M, Khalakhan I, Cherevko S (2025)

Publication Type: Journal article

Publication year: 2025

Journal

Journal of The Electrochemical Society Electrochemical Society

Book Volume: 172

Article Number: 106506

Journal Issue: 10

DOI: 10.1149/1945-7111/ae1168

Abstract

Iridium (Ir) is the benchmark catalyst for the oxygen evolution reaction (OER) in proton-exchange-membrane water electrolyzers, yet its scarcity demands rigorous, reproducible benchmarking in aqueous model systems. We systematically vary catalyst loading and Nafion ionomer content to probe how ink formulation governs the activity–stability trade-off for two Ir phases: metallic Ir and IrO2. OER activity and Ir dissolution are monitored simultaneously using online inductively coupled plasma mass spectrometry, and the catalyst–ionomer interface is characterized by electron microscopy and X-ray photoelectron spectroscopy. Our results show that catalyst loading has no effect on Ir dissolution, while ionomer content is the dominant and phase-dependent parameter: on metallic Ir, increasing Nafion lowers activity with no effect on dissolution, while for IrO2, it increases both activity and dissolution. These opposing trends are consistent with ionomer-induced changes in interfacial structure, oxidation state, particle dispersion, and accessible active area. Our study shows that ionomer content and catalyst phase must be carefully controlled and reported when benchmarking Ir-based OER catalysts, and provides practical guidelines to balance performance while minimizing precious-metal loss.

Involved external institutions

Forschungszentrum Jülich / Research Centre Jülich (FZJ) DE Germany (DE) Univerzita Karlova v Praze / Charles University in Prague CZ Czech Republic (CZ)

How to cite

APA:

Zlatar, M., Simon, C., Przybysz, J.M., Rodríguez, M.G., Katsman, J., Ayoub, M.,... Cherevko, S. (2025). Effects of Loading and Nafion Content on the Activity and Stability of Iridium Oxygen Evolution Reaction Catalysts. Journal of The Electrochemical Society, 172(10). https://doi.org/10.1149/1945-7111/ae1168

MLA:

Zlatar, Matej, et al. "Effects of Loading and Nafion Content on the Activity and Stability of Iridium Oxygen Evolution Reaction Catalysts." Journal of The Electrochemical Society 172.10 (2025).

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