The role of hydration in uncovering the OER activity of amorphous iridium oxide electrocatalysts
The role of hydration in uncovering the OER activity of amorphous iridium oxide electrocatalysts
Understanding the structural properties of iridium oxide electrocatalysts under operational conditions is critical for elucidating the structure–property relationships that enhance the catalytic activity for the oxygen evolution reaction. In this study, in situ X-ray absorption spectroscopy under realistic conditions was employed to investigate the potentiodynamic and time-resolved structural evolution of a commercial iridium oxide, alongside its fully hydrated and crystalline counterparts. Our findings reveal two distinct electrochemical regimes, a low potential plateau associated with a nonconductive Ir3+ state and a linear region where small potential variations induce reversible oxidation state and structural transformations. The structural changes were found to occur reversibly on the commercial material even after prolonged exposure to OER potentials. Notably, the hydrated IrOx exhibits extremely high OER activity, surpassing the commercial material by nearly an order of magnitude, yet it suffers from significant instability. In contrast, the crystalline IrO2 demonstrates poor activity as its catalytic performance appears to be confined to the surface. These findings highlight the critical role of hydration in modulating both activity and stability, offering valuable insights for the rational design of next generation iridium based OER catalysts.
IrO, OER, catalysts, electrochemistry, in situ XAS, water electrolysis
270-284
Sherwin, Connor Matthew
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Celorrio, Verónica
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Difilippo, Alessandro
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Rigg, Katie
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Clapp, Mark
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Ibraliu, Armando
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Luisman, Luke
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Wakelin, Thomas Simon Andrew
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Watson, Amber
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Zhelev, Nikolay
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McLeod, Lucy
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Zalitis, Christopher M.
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Russell, Andrea E.
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2 January 2026
Sherwin, Connor Matthew
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Celorrio, Verónica
7a8ccfa9-5d90-4502-8008-5e1bb15035c5
Difilippo, Alessandro
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Rigg, Katie
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Clapp, Mark
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Ibraliu, Armando
5fe3aa2c-a711-47bd-abd4-9ae0f01f4d92
Luisman, Luke
a26e1e4a-511a-403c-aab1-02434267fcdc
Wakelin, Thomas Simon Andrew
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Watson, Amber
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Zhelev, Nikolay
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McLeod, Lucy
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Zalitis, Christopher M.
be68c875-10fe-4b2c-90bc-4c41078640fa
Russell, Andrea E.
b6b7c748-efc1-4d5d-8a7a-8e4b69396169
Sherwin, Connor Matthew, Celorrio, Verónica, Difilippo, Alessandro, Rigg, Katie, Clapp, Mark, Ibraliu, Armando, Luisman, Luke, Wakelin, Thomas Simon Andrew, Watson, Amber, Zhelev, Nikolay, McLeod, Lucy, Zalitis, Christopher M. and Russell, Andrea E.
(2026)
The role of hydration in uncovering the OER activity of amorphous iridium oxide electrocatalysts.
ACS Catalysis, 16 (1), .
(doi:10.1021/acscatal.5c05765).
Abstract
Understanding the structural properties of iridium oxide electrocatalysts under operational conditions is critical for elucidating the structure–property relationships that enhance the catalytic activity for the oxygen evolution reaction. In this study, in situ X-ray absorption spectroscopy under realistic conditions was employed to investigate the potentiodynamic and time-resolved structural evolution of a commercial iridium oxide, alongside its fully hydrated and crystalline counterparts. Our findings reveal two distinct electrochemical regimes, a low potential plateau associated with a nonconductive Ir3+ state and a linear region where small potential variations induce reversible oxidation state and structural transformations. The structural changes were found to occur reversibly on the commercial material even after prolonged exposure to OER potentials. Notably, the hydrated IrOx exhibits extremely high OER activity, surpassing the commercial material by nearly an order of magnitude, yet it suffers from significant instability. In contrast, the crystalline IrO2 demonstrates poor activity as its catalytic performance appears to be confined to the surface. These findings highlight the critical role of hydration in modulating both activity and stability, offering valuable insights for the rational design of next generation iridium based OER catalysts.
Text
role-of-hydration-in-uncovering-the-oer-activity-of-amorphous-iridium-oxide-electrocatalysts
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Accepted/In Press date: 24 October 2025
e-pub ahead of print date: 19 December 2025
Published date: 2 January 2026
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Publisher Copyright:
© 2025 The Authors. Published by American Chemical Society
Keywords:
IrO, OER, catalysts, electrochemistry, in situ XAS, water electrolysis
Identifiers
Local EPrints ID: 508459
URI: http://eprints.soton.ac.uk/id/eprint/508459
ISSN: 2155-5435
PURE UUID: 2d6acf91-dc0b-4fb2-84b8-355b6afcd33e
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Date deposited: 22 Jan 2026 17:41
Last modified: 23 Jan 2026 02:58
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Contributors
Author:
Connor Matthew Sherwin
Author:
Verónica Celorrio
Author:
Alessandro Difilippo
Author:
Katie Rigg
Author:
Mark Clapp
Author:
Armando Ibraliu
Author:
Luke Luisman
Author:
Thomas Simon Andrew Wakelin
Author:
Amber Watson
Author:
Lucy McLeod
Author:
Christopher M. Zalitis
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