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

DOI: 10.1039/D0CP00217H DOI Help

Authors: Anita Hamar Reksten (Norwegian University of Science and Technology (NTNU)) , Andrea Russell (University of Southampton) , Peter W. Richardson (University of Southampton) , Stephen J. Thompson (University of Southampton) , Karina Mathisen (Norwegian University of Science and Technology (NTNU)) , Frode Seland (Norwegian University of Science and Technology (NTNU)) , Svein Sunde (Norwegian University of Science and Technology (NTNU))
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Chemistry Chemical Physics

State: Published (Approved)
Published: March 2020
Diamond Proposal Number(s): 8591

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.

Subject Areas: Chemistry, Materials

Instruments: B18-Core EXAFS