Iridium Oxidation-State Dynamics during Transient Operation under PEM Water Electrolysis Single-Cell Conditions Revealed by Time-Resolved Operando XAS
Abstract
Resolving the oxidation-state dynamics of Ir oxide anode catalysts during individual potential transients in proton exchange membrane water electrolysis (PEMWE) single cells remains challenging. Here, we developed an operando X-ray absorption spectroscopy (XAS) cell based on a modified lab-scale single-cell design and performed super quick XAS (SQXAS) measurements with a time resolution of ca. 200 ms. The cell enabled evaluation of catalyst-coated membranes (CCMs) with an active area of 1 cm 2 and exhibited current-voltage performance comparable to that of conventional single cells at an elevated temperature (45 °C), indicating that a realistic electrochemical environment was established. Operando Ir L 3 -edge SQXAS measurements were performed using this cell for two CCMs, one with crystalline IrO 2 and the other with amorphous IrO x anode catalysts. Operando SQXAS during cyclic voltammetry indicated continuous oxidation of Ir above certain potentials and an oxidation-state plateau below them, with the behavior being more pronounced for amorphous IrO x . These results are consistent with previous half-cell-based operando XAS studies, suggesting that their fundamental findings may extend to more realistic environments. Operando SQXAS was also performed during transient potential changes simulating PEMWE startup and shutdown. In both cases, changes in the Ir oxidation state rapidly followed the applied potential for rutile IrO 2 as well as amorphous IrO x . These results not only reveal the dynamics of Ir oxidation states under such transient operations but also provide guidance for designing effective accelerated stress tests for Ir oxide catalysts.
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BibTeX
@misc{hayashi2026iridium,
title = {{Iridium Oxidation-State Dynamics during Transient Operation under PEM Water Electrolysis Single-Cell Conditions Revealed by Time-Resolved Operando XAS}},
author = {Kenta Hayashi and Shuji Takahashi and Masanori Inaba and Sumiya Ando and Takamasa Nonaka and Wataru Yoshimune},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008392/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008392/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Iridium Oxidation-State Dynamics during Transient Operation under PEM Water Electrolysis Single-Cell Conditions Revealed by Time-Resolved Operando XAS
AU - Kenta Hayashi
AU - Shuji Takahashi
AU - Masanori Inaba
AU - Sumiya Ando
AU - Takamasa Nonaka
AU - Wataru Yoshimune
PY - 2026
DA - 2026/09/07
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008392/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008392/v1
AB - Resolving the oxidation-state dynamics of Ir oxide anode catalysts during individual potential transients in proton exchange membrane water electrolysis (PEMWE) single cells remains challenging. Here, we developed an operando X-ray absorption spectroscopy (XAS) cell based on a modified lab-scale single-cell design and performed super quick XAS (SQXAS) measurements with a time resolution of ca. 200 ms. The cell enabled evaluation of catalyst-coated membranes (CCMs) with an active area of 1 cm 2 and exhibited current-voltage performance comparable to that of conventional single cells at an elevated temperature (45 °C), indicating that a realistic electrochemical environment was established. Operando Ir L 3 -edge SQXAS measurements were performed using this cell for two CCMs, one with crystalline IrO 2 and the other with amorphous IrO x anode catalysts. Operando SQXAS during cyclic voltammetry indicated continuous oxidation of Ir above certain potentials and an oxidation-state plateau below them, with the behavior being more pronounced for amorphous IrO x . These results are consistent with previous half-cell-based operando XAS studies, suggesting that their fundamental findings may extend to more realistic environments. Operando SQXAS was also performed during transient potential changes simulating PEMWE startup and shutdown. In both cases, changes in the Ir oxidation state rapidly followed the applied potential for rutile IrO 2 as well as amorphous IrO x . These results not only reveal the dynamics of Ir oxidation states under such transient operations but also provide guidance for designing effective accelerated stress tests for Ir oxide catalysts.
ER -