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Issue 12, 2011
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X-Ray spectroscopy of electrochemically deposited iridium oxide films: detection of multiple sites through structural disorder

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Abstract

We report the results of X-ray absorption spectroscopy studies on electrochemically deposited iridium oxide films. The emphasis of the study is the correlation of X-ray derived structural data with electrochemically controlled charge state. Data were acquired for films subject to redox cycling in neutral and alkaline aqueous media. In both cases, cyclic voltammetric responses show two redox couples, coulometrically of roughly equal magnitude. Assays of the iridium population (based on the iridium L3 absorption edge amplitude) and the charge injected (based on integration of the voltammetric response) show that overall an average of ca. one electron per iridium atom is transferred. The absorption edge shifts indicate that the formal charge on the iridium changes, on average, from ca. 3.5+ to ca. 4.5+ across the entire process. EXAFS-derived changes in mean Ir–O distance and their mean square variation have been interpreted in terms of a two-site model, in which the two types of site have distinct redox potentials. Variations of local structure and disorder with potential are discussed and a generic model for structural disorder (parameterized via Debye–Waller factor) with diagnostic capability is developed.

Graphical abstract: X-Ray spectroscopy of electrochemically deposited iridium oxide films: detection of multiple sites through structural disorder

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Publication details

The article was received on 11 Aug 2010, accepted on 02 Nov 2010 and first published on 20 Dec 2010


Article type: Paper
DOI: 10.1039/C0CP01472A
Phys. Chem. Chem. Phys., 2011,13, 5252-5263

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    X-Ray spectroscopy of electrochemically deposited iridium oxide films: detection of multiple sites through structural disorder

    A. R. Hillman, M. A. Skopek and S. J. Gurman, Phys. Chem. Chem. Phys., 2011, 13, 5252
    DOI: 10.1039/C0CP01472A

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