Berlin 2018 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 71: Focus Session: Nanoscale Insights into Interfacial Electrochemistry II
O 71.1: Vortrag
Mittwoch, 14. März 2018, 15:00–15:15, HE 101
From nanoparticle shapes to mechanisms: modeling the oxygen evolution reaction at IrO2 nanoparticles from first-principles — •Daniel Opalka, Jakob Timmermann, Christoph Scheurer, and Karsten Reuter — Technische Universität München
The efficiency and commercial viability of proton-exchange membrane (PEM) electrolysers depends critically on the anode catalyst. Chemical stability requirements currently limit the available catalyst materials to iridium oxide based materials. Experiments identified the surface morphology and associated iridium hydroxo groups as important factors in the oxygen evolution reaction mechanism, but the relevant structural features in operating PEM cells remain elusive. In this contribution we develop an ab initio thermodynamics based scheme to predict the surface stoichiometry and composition of individual IrO2 facets as a function of the applied potential. Combined within a Wulff construction this yields the shape of IrO2 nanoparticle catalysts at operating conditions. The determined potential-dependent transformations of surface hydroxo groups furthermore allow to conclude on Faradaic charge transfer processes as observed in cyclovoltammetric experiments. From this atomistic picture we finally derive a mechanistic model which explains important reaction steps in the water oxidation reaction.