Issue 11, 2016

Reactive oxygen species in iridium-based OER catalysts


Tremendous effort has been devoted towards elucidating the fundamental reasons for the higher activity of hydrated amorphous IrIII/IV oxyhydroxides (IrOx) in the oxygen evolution reaction (OER) in comparison with their crystalline counterpart, rutile-type IrO2, by focusing on the metal oxidation state. Here we demonstrate that, through an analogy to photosystem II, the nature of this reactive species is not solely a property of the metal but is intimately tied to the electronic structure of oxygen. We use a combination of synchrotron-based X-ray photoemission and absorption spectroscopies, ab initio calculations, and microcalorimetry to show that holes in the O 2p states in amorphous IrOx give rise to a weakly bound oxygen that is extremely susceptible to nucleophilic attack, reacting stoichiometrically with CO already at room temperature. As such, we expect this species to play the critical role of the electrophilic oxygen involved in O–O bond formation in the electrocatalytic OER on IrOx. We propose that the dynamic nature of the Ir framework in amorphous IrOx imparts the flexibility in Ir oxidation state required for the formation of this active electrophilic oxygen.

Graphical abstract: Reactive oxygen species in iridium-based OER catalysts

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Article information

Article type
Edge Article
28 Apr 2016
18 Jul 2016
First published
19 Jul 2016
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2016,7, 6791-6795

Reactive oxygen species in iridium-based OER catalysts

V. Pfeifer, T. E. Jones, S. Wrabetz, C. Massué, J. J. Velasco Vélez, R. Arrigo, M. Scherzer, S. Piccinin, M. Hävecker, A. Knop-Gericke and R. Schlögl, Chem. Sci., 2016, 7, 6791 DOI: 10.1039/C6SC01860B

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