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An in situ XAS study of high surface-area IrO2 produced by the polymeric precursor synthesis

An in situ XAS study of high surface-area IrO2 produced by the polymeric precursor synthesis
An in situ XAS study of high surface-area IrO2 produced by the polymeric precursor synthesis

Iridium oxide powders with a surface area of more than 1 m2 g −1 (4 m2 g −1 from the H-UPD charge) and iridium-oxide crystallites less than 10 nm across were synthesized by heat treating gels formed from citric acid, ethylene glycol and dihydrogen hexachloroiridate(IV) in air. The characteristics of the resulting material was found to be strongly dependent on the heat-treatment step in the synthesis. A single heat-treatment of the gel resulted in a material with a substantial fraction of elemental iridium metal, i.e. iridium in oxidation state zero (Ir0 ). Post-synthesis modification of the powder by potential cycling resulted in oxidation peaks consistent with the conversion of the metal phase to iridium oxide. Linear combination of the near-edge part of the X-ray absorption data (X-ray absorbtion near-edge spectroscopy, XANES) collected in situ during potential cycling and an analysis of the extended X-ray fine-structure (EXAFS) part of the spectrum showed that the overall metal fraction was not significantly affected by the cycling. The oxidation of the metal phase is therefore limited to a thin layer of oxide at the metal surface, and a significant part of the iridium is left inactive. A modification of the heat treatment procedure of the sample resulted in iridium oxide containing only insignificant amounts of elemental iridium metal.

1463-9076
18868-18881
Hamar Reksten, Anita
7536e96c-4a84-4deb-9495-9ec887cce78f
Russell, Andrea E.
b6b7c748-efc1-4d5d-8a7a-8e4b69396169
Richardson, Peter
a4a96907-f8ed-41c1-b641-1d19a587ddda
Thompson, Stephen
46677911-01d9-478e-ad98-87ac37cd56a6
Mathisen, Karina
aed0f945-dc58-434d-a950-95337a050b56
Seland, Frode
138bf72a-fddf-492d-9ca9-ad467f2a4ad3
Sunde, Svein
26a99ca7-aedc-4e58-ac3b-cdf865e1a53e
Hamar Reksten, Anita
7536e96c-4a84-4deb-9495-9ec887cce78f
Russell, Andrea E.
b6b7c748-efc1-4d5d-8a7a-8e4b69396169
Richardson, Peter
a4a96907-f8ed-41c1-b641-1d19a587ddda
Thompson, Stephen
46677911-01d9-478e-ad98-87ac37cd56a6
Mathisen, Karina
aed0f945-dc58-434d-a950-95337a050b56
Seland, Frode
138bf72a-fddf-492d-9ca9-ad467f2a4ad3
Sunde, Svein
26a99ca7-aedc-4e58-ac3b-cdf865e1a53e

Hamar Reksten, Anita, Russell, Andrea E., Richardson, Peter, Thompson, Stephen, Mathisen, Karina, Seland, Frode and Sunde, Svein (2020) An in situ XAS study of high surface-area IrO2 produced by the polymeric precursor synthesis. Physical Chemistry Chemical Physics, 22 (34), 18868-18881. (doi:10.1039/D0CP00217H).

Record type: Article

Abstract

Iridium oxide powders with a surface area of more than 1 m2 g −1 (4 m2 g −1 from the H-UPD charge) and iridium-oxide crystallites less than 10 nm across were synthesized by heat treating gels formed from citric acid, ethylene glycol and dihydrogen hexachloroiridate(IV) in air. The characteristics of the resulting material was found to be strongly dependent on the heat-treatment step in the synthesis. A single heat-treatment of the gel resulted in a material with a substantial fraction of elemental iridium metal, i.e. iridium in oxidation state zero (Ir0 ). Post-synthesis modification of the powder by potential cycling resulted in oxidation peaks consistent with the conversion of the metal phase to iridium oxide. Linear combination of the near-edge part of the X-ray absorption data (X-ray absorbtion near-edge spectroscopy, XANES) collected in situ during potential cycling and an analysis of the extended X-ray fine-structure (EXAFS) part of the spectrum showed that the overall metal fraction was not significantly affected by the cycling. The oxidation of the metal phase is therefore limited to a thin layer of oxide at the metal surface, and a significant part of the iridium is left inactive. A modification of the heat treatment procedure of the sample resulted in iridium oxide containing only insignificant amounts of elemental iridium metal.

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Accepted/In Press date: 27 March 2020
e-pub ahead of print date: 30 March 2020

Identifiers

Local EPrints ID: 439113
URI: http://eprints.soton.ac.uk/id/eprint/439113
ISSN: 1463-9076
PURE UUID: 3764cac2-dbbf-48fa-a1a1-8e5d5b689a70
ORCID for Andrea E. Russell: ORCID iD orcid.org/0000-0002-8382-6443

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Date deposited: 03 Apr 2020 16:30
Last modified: 15 Sep 2021 05:13

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