SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 3: Metal Substrates: Adsorption and Reaction of Small Molecules I

O 3.4: Vortrag

Montag, 27. März 2023, 11:15–11:30, CHE 91

Surface segregation of PdAu(111) in reactive gas environments from ab initio thermodynamics — •Olga V Vinogradova, Vanessa J Bukas, and Karsten Reuter — Fritz Haber Institute of the Max Planck Society, Berlin, Germany

Catalytic properties of alloys are largely determined by the specific chemical composition at the surface. Differences in composition between surface and bulk regions depend intricately on both the parent metals and surrounding gas-phase environment. While a non-reactive environment is expected to induce surface segregation of the more noble alloy component, a reactive environment such as oxygen often favors the more active component at the surface. Using ab initio thermodynamics, here we explore the structure and composition of the PdAu(111) alloy surface in oxygen, nitrogen, and carbon containing environments. An exhaustive, yet systematic, search of the available phase-space shows the segregation profile in an oxygen atmosphere to follow the anticipated picture described above. Unlike oxygen, however, carbon at low coverages burrows deeper into the alloy substrate without first the adsorbate-induced segregation of Pd at the surface. A nitrogen environment induces an intermediate behavior to oxygen and carbon where the nitrogen atoms first favor either surface or subsurface sites depending on the detailed metallic composition profile.