Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 51: Frontiers of Electronic-Structure Theory: Focus on the Interface Challenge V (joint session O/CPP/DS/TT)

O 51.7: Vortrag

Mittwoch, 3. April 2019, 12:30–12:45, H9

Transition metal oxide nanoparticles as efficient catalysts for proton exchange membrane electrolyzers: morphology, activity and stability — •Daniel Opalka, Yonghyuk Lee, Jakob Timmermann, Christoph Scheurer, and Karsten Reuter — Technische Universität München

Transition metal oxides such as RuO₂ and IrO₂ are currently the best known electrocatalysts for the oxygen evolution reaction from liquid water in proton exchange membrane (PEM) electrolyzers. However, dynamic load operation of PEM cells induces transformations of the catalyst morphology leading to metal dissolution and catalyst degradation. We present a computational model to predict the morphology, activity and stability from ab initio electronic structure theory and fundamental thermodynamic principles. Based on this model, we have explored novel strategies to reduce material expenses and improve catalyst stability while preserving high catalytic activity via nanoparticles with a core-shell design. From an analysis of different surface coverages with oxygen, hydroxyl and hydroxo species, voltage-dependent phase diagrams for catalyst surfaces are presented which correlate with characteristic features observed in cyclovoltammetric measurements. Results from atomistic models of selected nanoparticles on the basis of Wulff’s Theorem show negligible size effects, but a strong influence of the facet terminations on the surface relaxation.