Regensburg 2022 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 31: Solid-Liquid Interfaces 3: Reactions and Electrochemistry

O 31.4: Vortrag

Dienstag, 6. September 2022, 11:30–11:45, S054

First step of the oxygen reduction reaction on Au(111): An ab initio molecular dynamics study of the electrified metal/water interface — •Alexandra M. Dudzinski, Elias Diesen, Hendrik H. Heenen, Vanessa J. Bukas, and Karsten Reuter — Fritz-Haber-Institut der MPG, Berlin, Germany

The oxygen reduction reaction (ORR) is a key electrocatalytic process for developing sustainable energy technologies. And yet, many aspects of the underlying reaction mechanism are still poorly understood at the molecular level. Especially at weak-binding electrode surfaces such as Au, even the ability to bind aqueous O2 species as a first mechanistic step remain unclear. Resolving these questions requires going beyond the simplified thermodynamic models of charge-neutral reaction intermediates that have been commonly used in computational electrocatalysis so far. Here, we perform molecular dynamics simulations based on periodic density-functional theory (DFT) to investigate O2 adsorption at an electrified Au(111)/water interface. We elucidate structural interfacial properties as a function of surface charge, and show that the latter can significantly alter the O2 binding energy. Adsorption is specifically enhanced under electric fields that are realistic for ORR operation, suggesting this as a very possible first electrochemical, rather than purely chemical step of the mechanism and showing that field effects in corresponding DFT models cannot be neglected. The resulting dependence on (absolute) electrostatic potential may further explain the superior activity measured experimentally for this catalyst in alkaline vs. acidic media.