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Depth-Profiling Cation Location and Oxidation States of Ni Foam Electrodes in Fe/Co-Enriched Electrolytes under Alkaline Water Oxidation Conditions

Chalil Oglou, Ramadan ; Ceccato, Marcel ; Frederiksen, Morten Linding ; Shavorskiy, Andrey LU ; Bentien, Anders and Lauritsen, Jeppe V. (2025) In ACS Catalysis 15. p.17122-17132
Abstract

This study investigates the surface transformations of nickel foam (NF) electrodes induced by Fe and Co cation incorporation from the electrolyte following activation in the oxygen evolution reaction (OER), using both ex situ time-of-flight secondary ion mass spectrometry (TOF-SIMS) and in situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). Electrochemical measurements demonstrate that Fe enhances OER kinetics as expected, while the copresence of Co improves electrode conductivity and electrochemically active surface area. Our surface analyses with depth resolution on cation location and corresponding oxidation states interestingly reveal the formation of a chemically distinct Ni-based layered structures following OER... (More)

This study investigates the surface transformations of nickel foam (NF) electrodes induced by Fe and Co cation incorporation from the electrolyte following activation in the oxygen evolution reaction (OER), using both ex situ time-of-flight secondary ion mass spectrometry (TOF-SIMS) and in situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). Electrochemical measurements demonstrate that Fe enhances OER kinetics as expected, while the copresence of Co improves electrode conductivity and electrochemically active surface area. Our surface analyses with depth resolution on cation location and corresponding oxidation states interestingly reveal the formation of a chemically distinct Ni-based layered structures following OER conditions, with a preferential Ni2+M3+O(OH) topmost composition (M = Fe or Co) and a Ni3+M2+O(OH)/Ni metal subsurface layer. These layers evolve through a proposed mechanism involving two-proton, one-electron transfer, which specifically generates Fe3+and Co3+sites in the Ni2+topmost layer that are more active than single Ni3+sites. Upon air exposure, the layered phases become chemically homogeneous, though their signatures remain detectable in TOF-SIMS. This study shows that Fe and Co incorporation from the electrolyte leads to the formation of chemically distinct surface layers on NF electrodes, which are associated with improved OER performance. These findings clarify how secondary metals modify the surface chemistry of Ni electrodes in alkaline electrolysis conditions.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
NAP-XPS, surface analysis, synchrotron, trace metals, water electrolysis
in
ACS Catalysis
volume
15
pages
11 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:105017374582
ISSN
2155-5435
DOI
10.1021/acscatal.5c04791
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2025 American Chemical Society
id
8a1b4df6-553a-4eed-b957-427e2e8ee5b0
date added to LUP
2025-12-08 13:00:33
date last changed
2025-12-08 13:01:43
@article{8a1b4df6-553a-4eed-b957-427e2e8ee5b0,
  abstract     = {{<p>This study investigates the surface transformations of nickel foam (NF) electrodes induced by Fe and Co cation incorporation from the electrolyte following activation in the oxygen evolution reaction (OER), using both ex situ time-of-flight secondary ion mass spectrometry (TOF-SIMS) and in situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). Electrochemical measurements demonstrate that Fe enhances OER kinetics as expected, while the copresence of Co improves electrode conductivity and electrochemically active surface area. Our surface analyses with depth resolution on cation location and corresponding oxidation states interestingly reveal the formation of a chemically distinct Ni-based layered structures following OER conditions, with a preferential Ni<sup>2+</sup>M<sup>3+</sup>O(OH) topmost composition (M = Fe or Co) and a Ni<sup>3+</sup>M<sup>2+</sup>O(OH)/Ni metal subsurface layer. These layers evolve through a proposed mechanism involving two-proton, one-electron transfer, which specifically generates Fe<sup>3+</sup>and Co<sup>3+</sup>sites in the Ni<sup>2+</sup>topmost layer that are more active than single Ni<sup>3+</sup>sites. Upon air exposure, the layered phases become chemically homogeneous, though their signatures remain detectable in TOF-SIMS. This study shows that Fe and Co incorporation from the electrolyte leads to the formation of chemically distinct surface layers on NF electrodes, which are associated with improved OER performance. These findings clarify how secondary metals modify the surface chemistry of Ni electrodes in alkaline electrolysis conditions.</p>}},
  author       = {{Chalil Oglou, Ramadan and Ceccato, Marcel and Frederiksen, Morten Linding and Shavorskiy, Andrey and Bentien, Anders and Lauritsen, Jeppe V.}},
  issn         = {{2155-5435}},
  keywords     = {{NAP-XPS; surface analysis; synchrotron; trace metals; water electrolysis}},
  language     = {{eng}},
  pages        = {{17122--17132}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{ACS Catalysis}},
  title        = {{Depth-Profiling Cation Location and Oxidation States of Ni Foam Electrodes in Fe/Co-Enriched Electrolytes under Alkaline Water Oxidation Conditions}},
  url          = {{http://dx.doi.org/10.1021/acscatal.5c04791}},
  doi          = {{10.1021/acscatal.5c04791}},
  volume       = {{15}},
  year         = {{2025}},
}