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O: Fachverband Oberflächenphysik

O 73: Solid/liquid interfaces II (focussed session)

O 73.1: Hauptvortrag

Donnerstag, 25. März 2010, 15:00–15:30, H33

Theoretical studies on the electrocatalytic Oxygen reduction reaction on Pt — •Timo Jacob — Universität Ulm, Albert-Einstein-Allee 47, D-89069 Ulm

The oxygen reduction reaction (ORR) is one of the most important reactions in basic electrochemistry and for various applications such as fuel cells. However, due to the high complexity of this reaction the exact mechanisms is still unknown.

Using density functional theory, we investigated different mechanisms of the ORR on Pt electrodes [1]. Among the three main mechanisms (i.e., O₂^ad-Dissociation, OOH^ad-Formation, and HOOH^ad-Formation) we found that HOOH^ad-Formation is the preferred process in gas phase. When including water solvation as an environmental effect, the reaction paths were modified, leading to drastic changes in the energetics and a nearly identical preference for the O₂^ad-Dissociation and the OOH^ad-Formation mechanisms. Interestingly, inclusion of solvent as well as electrode potential effects resulted in a picture showing that both Langmuir–Hinshelwood and Eley–Rideal mechanisms could be at play, making the ORR a rather complex reaction, where rigorous evaluation of the kinetics of all paths coupled together under certain environmental parameters was required to further elucidate the complicated nature of the overall reaction process.

[1] S. Venkatachalam, T. Jacob, Handbook of Fuel Cells Vol. 5&6, W. Vielstich, H. A. Gasteiger, H. Yokokawa (Eds.), John Wiley & Sons Ltd., Chichester, UK (2009)