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17–19 Sept 2018
Fakultät für Maschinenwesen der Technischen Universität München
Europe/Berlin timezone

Characterization of nanostructured iridium oxide-based electrocatalysts using advanced x-ray analytics

19 Sept 2018, 11:45
15m
MW 2001 (Fakultät für Maschinenwesen)

MW 2001

Fakultät für Maschinenwesen

Talk P10 Others Parallel session 9

Speaker

Dr Raul Garcia-Diez (Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB))

Description

Iridium oxide (IrO$_2$) has been suggested as a promising candidate for efficient water oxidation, and thus catalyst materials based on nanostructured iridium (hydr)oxide have recently been developed and commercialized. In this work, we present a comprehensive spectroscopic study of commercially available iridium oxide-based electrocatalysts (“nano-IrO$_2$” and “IrO$_2$@TiO$_2$”) using advanced x-ray analytics at the synchrotron sources BESSY II and ALS.

The spectroscopic study of these materials at the oxygen K-edge revealed a high-resolution fingerprint related to the reorganization of local electronic states presumably due to a varying degree of crystallinity, as suggested by the comparison with an extensively characterized rutile-like IrO$_2$ and an amorphous iridium oxide. Furthermore, detailed information about the hybridization of electronic states in the valence band was obtained combining the atom specificity of soft x-ray absorption (XAS) and emission spectroscopy (XES) with the surface sensitivity of x-ray photoelectron spectroscopy (XPS).
The study was completed comparing the spectroscopic results with diffraction and microscopy measurements, in which the heterogeneous nature of the nanostructured iridium oxide-based materials is confirmed, discerning contributions from a rutile-type structure and an amorphous phase. The latter phase has been implicated in the high catalytic activity of these materials in the sluggish oxygen evolution reaction.

Primary authors

Dr Raul Garcia-Diez (Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB)) Dr Regan G. Wilks (Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB)) Prof. Marcus Bär (Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB))

Co-authors

Dr Armin Siebel (Technische Universität München, Chair of Technical Electrochemistry, Department of Chemistry and Catalysis Research Center) Mrs Alexandra Weiß (Technische Universität München, Chair of Technical Electrochemistry, Department of Chemistry and Catalysis Research Center) Mr Maximilian Bernt (Technische Universität München, Chair of Technical Electrochemistry, Department of Chemistry and Catalysis Research Center) Dr Wanli Yang (Advanced Light Source (ALS), Lawrence Berkeley National Laboratory) Prof. Hubert A Gasteiger (TUM)

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