SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 73: Metal Substrates: Adsorption and Reaction of Small Molecules II

O 73.3: Vortrag

Donnerstag, 30. März 2023, 11:00–11:15, CHE 91

Ab initio-based chemisorption and thermodynamic stability of atomic H and O on Pt-Ir alloy surfaces — •Tobias Wittemann, Thorsten Klüner, and Halil Ibrahim Sözen — Institute of Chemistry, Carl-von-Ossietzky University of Oldenburg, 26129 Oldenburg, Germany

Electric vehicles powered by proton-exchange membrane (PEM) fuel cells are a CO2 emission-free alternative to conventional fossil fuel vehicles. In this study, we report density functional theory (DFT) investigations of binary Pt-Ir surfaces, which are a promising candidate for bifunctional anode catalysts in PEM fuel cells that could enable higher long-term durability of the anode catalyst. The chemisorption behaviour of atomic H and O on bimetallic Pt3Ir(111) and PtIr(111) surfaces was investigated for different coverages and compared with the monometallic Pt(111) and Ir(111) surfaces. We found that in both cases the chemisorption on the alloys becomes more stable with increasing number of Ir atoms at the adsorption site. Using the ab initio thermodynamics approach, we calculated phase diagrams for the chemisorption of atomic H and O species on these metal surfaces in order to transfer our findings to finite temperature and pressure conditions prevailing in real PEMFCs. Our theoretical results can provide a fundamental understanding for subsequent studies of the hydrogen oxidation reaction (HOR) and oxygen evolution reaction (OER) on Pt-Ir alloy surfaces and are thus crucial for the rational development of new anode catalyst materials.