Abstract
Trace iron (Fe) impurities pose a challenge in alkaline water electrolysis (AWE) and can significantly impact long-term performance, yet their comprehensive system-level effects remain poorly understood. Here, we present the mechanistic roles of Fe in AWE, using combined rotation disk electrode studies, zero-gap cell measurements, and durability tests up to 1,000 h. Fundamental electrochemistry shows that Fe deposition proceeds through a solution-mediated pathway, with dendritic growth triggered under specific mass-transport and potential conditions. In single-cell operation, Fe incorporation substantially enhances nickel (Ni)-based anode activity by forming highly active Ni-Fe oxyhydroxides, while cathodic Fe forms either thin films or dendrites, depending on potential, surface morphology, and electrolyte distribution. Although dendrites do not degrade hydrogen evolution performance up to 1,000 h, they reveal partial intrusion into the separator, indicating a potential durability risk. We identify five governing factors controlling Fe dendrite formation and provide design principles for impurity-resilient AWE systems.
| Original language | English |
|---|---|
| Article number | 102639 |
| Journal | Joule |
| DOIs | |
| State | Accepted/In press - 2026 |
Funding
This work was authored by the National Laboratory of the Rockies for the U.S. Department of Energy (DOE) , operated under contract no. DE-AC36-08GO28308 . This work was also authored by Argonne National Laboratory (“Argonne”), operated by UChicago Argonne, LLC , for the U.S. DOE under contract no. DE-AC02-06CH11357 . This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). This research used Beamline 8.3.2 and resources of the Advanced Light Source, a U.S. DOE Office of Science User Facility under contract no. DE-AC02-05CH11231 . Funding for this research was provided by TotalEnergies under project agreement CRD2323531 and by the Hydrogen from Next-generation Electrolyzers of Water (H2NEW) consortium, funded by the U.S. DOE Office of Energy Efficiency and Renewable Energy (EERE) Hydrogen and Fuel Cell Technologies Office (HFTO) award no. DE-EE0008836 . The views expressed herein do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). This work makes use of the E-XPS system at the Colorado School of Mines which was supported by the National Science Foundation under grant no. 1626619 . The Tescan SEM instrument at Mines was supported by the National Science Foundation under grant no. DMR-1828454 . We also acknowledge Mines’ Shared Instrumentation Facility for access and support of instruments used in this work. The authors would like to thank to Ellis Klein, Cole Delery, Alexis Palau, Melissa Kreider, and Florian Merlin Chabot for their technical support.
Keywords
- alkaline water electrolysis
- dendritic Fe deposition
- iron impurities
- Ni-based electrode
- Ni-Fe oxyhydroxides
- reference electrode
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