Regensburg 2019 – scientific programme
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O: Fachverband Oberflächenphysik
O 68: Poster Wednesday: Nanostructures
O 68.2: Poster
Wednesday, April 3, 2019, 17:45–20:00, Poster B2
Iridium dioxide catalysts for water electrolysis - From Wulff shape to atomic structure and beyond — •Jakob Timmermann, Daniel Opalka, Christoph Scheurer, and Karsten Reuter — Technische Universität München, Germany
Iridium oxide is currently the preferred material to develop highly active and chemically stable nanoparticle catalysts for the electrochemical oxygen evolution reaction (OER) in proton exchange membrane electrolyzers. Computational models provide important support for the rational design of novel nanoparticle catalysts with optimal size, shape and stability. While the Wulff construction is often adopted to model single-compound nanocrystals, little is known about the influence of edge and corner atoms on the dimensional stability of ultra small IrO2 nanoparticles as used in state-of-the art OER catalysts. In order to validate the inherent approximations of the Wulff construction, we compare relaxed, mono-facet IrO2 Wulff nanoparticles of varying shape, size and stoichiometry to respective slab models for extended facets in a comprehensive structure analysis. We demonstrate that the geometry relaxation of IrO2 nanoparticles strongly depends on the termination and, hence, thermodynamic parameters of the environment, prohibiting the application of the Wulff construction for certain IrO2 surfaces. We further present an analysis of the contributions of facets, edges and corners to the surface free energy for selected nanoparticle models.