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PreprintCC BYChemRxiv

Facet-Dependent Redox Reversibility Governs the Stability of IrO2 Surfaces under Dynamic Electrochemical Potentials

  • Yuto Okayama1,2
  • Tomohiro Yoshinaga1,2
  • Naomi Naraki1,2
  • Arata Umehara1,2
  • Taichi Hama1,2
  • Haruto Fuse1,2
  • Yao Fangyi1,2
  • Wenxiong Zhang3
  • Hiroshi Ando3
  • Yoshihisa Harada3
  • Takeshi Watanabe4
  • Tomoki Uchiyama5,2
1 more authors
  • Naoto Todoroki1,2
5 affiliations
  1. 1Graduate School of Environmental Studies
  2. 2Tohoku University
  3. 3Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, Japan, 277-8581
  4. 4Japan Synchrotron Radiation Research Institute, Kouto, Sayo-cho
  5. 5Graduate School of Engineering
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Abstract

Understanding catalyst stability under fluctuating potentials is essential for renewable-powered water electrolysis, yet the surface processes governing degradation remain unclear. Here, we investigate IrO2(110) and IrO2(100) single-crystal thin films under potential cycling relevant to renewable-powered proton-exchange membrane water electrolysis. The activity of IrO2(110) increased after cycling, whereas IrO2(100) deactivated. X-ray photoelectron spectroscopy indicated higher Ir valence on both facets, accompanied by a pronounced increase in surface OH species only on (110). O K-edge X-ray absorption spectroscopy revealed larger oxidation-induced changes on (100), while in situ X-ray absorption fine-structure measurements showed reversible electronic and local structural responses on (110) but irreversible structural evolution on (100). These contrasting responses demonstrate that surface stability under fluctuating potentials cannot be inferred from oxidation state alone. Rather, it depends on whether the facet-specific coordination environment can reversibly accommodate coupled redox and structural perturbations. These results identify redox accommodation as a mechanistic descriptor for oxide electrocatalyst durability under dynamic operation.

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Cite

BibTeXRIS
BibTeX
@misc{okayama2026facetdependent,
  title = {{Facet-Dependent Redox Reversibility Governs the Stability of IrO2 Surfaces under Dynamic Electrochemical Potentials}},
  author = {Yuto Okayama and Tomohiro Yoshinaga and Naomi Naraki and Arata Umehara and Taichi Hama and Haruto Fuse and Yao Fangyi and Wenxiong Zhang and Hiroshi Ando and Yoshihisa Harada and Takeshi Watanabe and Tomoki Uchiyama and Naoto Todoroki},
  howpublished = {ChemRxiv},
  year = {2026},
  month = sep,
  doi = {10.26434/chemrxiv.15008297/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008297/v1},
  note = {CC BY},
}
RIS
TY  - UNPB
TI  - Facet-Dependent Redox Reversibility Governs the Stability of IrO2 Surfaces under Dynamic Electrochemical Potentials
AU  - Yuto Okayama
AU  - Tomohiro Yoshinaga
AU  - Naomi Naraki
AU  - Arata Umehara
AU  - Taichi Hama
AU  - Haruto Fuse
AU  - Yao Fangyi
AU  - Wenxiong Zhang
AU  - Hiroshi Ando
AU  - Yoshihisa Harada
AU  - Takeshi Watanabe
AU  - Tomoki Uchiyama
AU  - Naoto Todoroki
PY  - 2026
DA  - 2026/09/04
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15008297/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008297/v1
AB  - Understanding catalyst stability under fluctuating potentials is essential for renewable-powered water electrolysis, yet the surface processes governing degradation remain unclear. Here, we investigate IrO2(110) and IrO2(100) single-crystal thin films under potential cycling relevant to renewable-powered proton-exchange membrane water electrolysis. The activity of IrO2(110) increased after cycling, whereas IrO2(100) deactivated. X-ray photoelectron spectroscopy indicated higher Ir valence on both facets, accompanied by a pronounced increase in surface OH species only on (110). O K-edge X-ray absorption spectroscopy revealed larger oxidation-induced changes on (100), while in situ X-ray absorption fine-structure measurements showed reversible electronic and local structural responses on (110) but irreversible structural evolution on (100). These contrasting responses demonstrate that surface stability under fluctuating potentials cannot be inferred from oxidation state alone. Rather, it depends on whether the facet-specific coordination environment can reversibly accommodate coupled redox and structural perturbations. These results identify redox accommodation as a mechanistic descriptor for oxide electrocatalyst durability under dynamic operation.
ER  -