Berlin 2024 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 18: Solid-Liquid Interfaces I: Structure and Spectroscopy
O 18.5: Vortrag
Montag, 18. März 2024, 16:00–16:15, H 1012
Oxygen reduction reaction on adlayer covered surfaces: A case study on Ru(0001) in acid — •Albert K. Engstfeld1,2, Stephan Beckord1, Stefan Fuchs1, and R.Jürgen Behm1,3 — 1Institute of Surface Chemistry and Catalysis, Ulm, DE — 2Institute of Electrochemistry, Ulm, DE — 3Institute of Theoretical, Chemistry, Ulm, DE
On bare Ruthenium (Ru) electrodes, the oxygen reduction reaction (ORR) primarily leads to the formation of water. Depending on the electrode structure and availability of surface (hydr)oxides, in certain potential regions also H2O2 can be formed. Recently we have shown that the electrode surface is never free from adsorbates.[1]
In this work, we will show how such adlayers influence the ORR activity and discuss the limitations of the commonly accepted reaction pathway, which involves free surface sites. The electrodes are prepared under ultrahigh vacuum conditions and their structural integrity is determined by scanning tunnelling (STM) measurements performed before and after the electrocatalytic investigation. The electrocatalytic measurements are performed in O2-free and O2-saturated acid electrolytes (HClO4 and H2SO4). We will discuss the impact of bisulfate on the reactivity, which almost completely inhibits the reactivity of the surface. Furthermore, we illustrate that adsorbed OH plays a major role in the formation of H2O2 on such surfaces. Additional differential electrochemical mass spectrometry (DEMS) measurements allow disentangling the ORR from the hydrogen evolution reaction at high overpotentials.
[1] A.K. Engstfeld et al., Electrochimica Acta, 389 (2021) 138350
Keywords: Electrocatalysis; Single crystals; Oxygen reduction reaction; STM