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Degradation of iridium oxides via oxygen evolution from the lattice: correlating atomic scale structure with reaction mechanisms

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Abstract

Understanding the fundamentals of iridium degradation during the oxygen evolution reaction is of importance for the development of efficient and durable water electrolysis systems. The degradation mechanism is complex and it is under intense discussion whether the oxygen molecule can be directly released from the oxide lattice. Here, we define the extent of lattice oxygen participation in the oxygen evolution and associated degradation of rutile and hydrous iridium oxide catalysts, and correlate this mechanism with the atomic-scale structures of the catalytic surfaces. We combine isotope labelling with atom probe tomography, online electrochemical and inductively coupled plasma mass spectrometry. Our data reveal that, unlike rutile IrO2, Ir hydrous oxide contains –IrIIIOOH species which directly contribute to the oxygen evolution from the lattice. This oxygen evolution mechanism results in faster degradation and dissolution of Ir. In addition, near surface bulk regions of hydrous oxide are involved in the oxygen catalysis and dissolution, while only the topmost atomic layers of rutile IrO2 participate in both reactions. Overall our data provide a contribution to the fundamental understanding of the exceptional stability of Ir-oxides towards the oxygen evolution reaction. The proposed approach to a quantitative assessment of the degree of lattice oxygen participation in the oxygen evolution reaction can be further applied to other oxide catalyst systems.

Graphical abstract: Degradation of iridium oxides via oxygen evolution from the lattice: correlating atomic scale structure with reaction mechanisms

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Publication details

The article was received on 12 Jun 2019, accepted on 18 Oct 2019 and first published on 18 Oct 2019


Article type: Paper
DOI: 10.1039/C9EE01872G
Energy Environ. Sci., 2019, Advance Article
  • Open access: Creative Commons BY-NC license
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    Degradation of iridium oxides via oxygen evolution from the lattice: correlating atomic scale structure with reaction mechanisms

    O. Kasian, S. Geiger, T. Li, J. Grote, K. Schweinar, S. Zhang, C. Scheu, D. Raabe, S. Cherevko, B. Gault and K. J. J. Mayrhofer, Energy Environ. Sci., 2019, Advance Article , DOI: 10.1039/C9EE01872G

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