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Monitoring the Structural Changes in Iridium Nanoparticles during Oxygen Evolution Electrocatalysis with Operando
Rebecca K Pittkowski1, Stefanie Punke1, Andy S Anker1
1Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
Journal of the American Chemical Society
|September 30, 2024
Summary
Investigating iridium nanoparticle structure during oxygen evolution reaction (OER) reveals that the active iridium oxide phase lacks crystalline order and undergoes contraction. Multitechnique operando studies are essential for understanding electrocatalyst structure-property relationships.
Area of Science:
- Materials Science
- Electrochemistry
- Nanotechnology
Background:
- Understanding nanoparticle structure under operating conditions is key to catalysis.
- Iridium nanoparticles are promising electrocatalysts for reactions like oxygen evolution.
Purpose of the Study:
- To elucidate the structural evolution of ultrasmall iridium nanoparticles during oxygen evolution reaction (OER) under electrochemical conditions.
- To establish structure-property relationships for iridium-based electrocatalysts.
Main Methods:
- Operando X-ray total scattering and pair distribution function (PDF) analysis.
- Operando small-angle X-ray scattering (SAXS) for particle size determination.
- Operando X-ray absorption spectroscopy (XAS) for structural confirmation.
Main Results:
- Metallic iridium nanoparticles exhibit a decahedral structure at reducing potentials.
- Electrochemically formed iridium oxide contains nanoscale rutile-like clusters (<1 nm).
- The OER-active iridium oxide phase is largely amorphous, with observed contraction under OER conditions.
Conclusions:
- The active iridium oxide phase in OER is predominantly disordered.
- Operando XAS confirms iridium oxide contraction during the reaction.
- Multitechnique operando investigations are critical for a comprehensive understanding of electrocatalyst behavior.
