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Issue 3, 2017
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In situ observation of reactive oxygen species forming on oxygen-evolving iridium surfaces

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Abstract

Water splitting performed in acidic media relies on the exceptional performance of iridium-based materials to catalyze the oxygen evolution reaction (OER). In the present work, we use in situ X-ray photoemission and absorption spectroscopy to resolve the long-standing debate about surface species present in iridium-based catalysts during the OER. We find that the surface of an initially metallic iridium model electrode converts into a mixed-valent, conductive iridium oxide matrix during the OER, which contains OII− and electrophilic OI− species. We observe a positive correlation between the OI− concentration and the evolved oxygen, suggesting that these electrophilic oxygen sites may be involved in catalyzing the OER. We can understand this observation by analogy with photosystem II; their electrophilicity renders the OI− species active in O–O bond formation, i.e. the likely potential- and rate-determining step of the OER. The ability of amorphous iridium oxyhydroxides to easily host such reactive, electrophilic species can explain their superior performance when compared to plain iridium metal or crystalline rutile-type IrO2.

Graphical abstract: In situ observation of reactive oxygen species forming on oxygen-evolving iridium surfaces

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Publication details

The article was received on 16 Oct 2016, accepted on 30 Nov 2016 and first published on 01 Dec 2016


Article type: Edge Article
DOI: 10.1039/C6SC04622C
Chem. Sci., 2017,8, 2143-2149
  • Open access: Creative Commons BY license
    All publication charges for this article have been paid for by the Royal Society of Chemistry

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    In situ observation of reactive oxygen species forming on oxygen-evolving iridium surfaces

    V. Pfeifer, T. E. Jones, J. J. Velasco Vélez, R. Arrigo, S. Piccinin, M. Hävecker, A. Knop-Gericke and R. Schlögl, Chem. Sci., 2017, 8, 2143
    DOI: 10.1039/C6SC04622C

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