Regensburg 2022 – scientific programme

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O: Fachverband Oberflächenphysik

O 10: Focus Session: Single Atom Catalysis 2

O 10.4: Topical Talk

Monday, September 5, 2022, 16:00–16:30, H4

Design of Model Single-Atom Catalysts: Metal Adatoms, Monomeric Oxide Units, and Mixed Surface Layers on Oxide Surfaces — •Zdenek Dohnalek — Physical and Computational Sciences Directorate and Institute for Interfacial Catalysis, Pacific Northwest National Laboratory, Richland, WA 99354, USA

Single-atom catalysts have attracted significant attention due to their ultimate metal efficiency and the promise of novel properties. The sublimation of oxides and metals is employed to design monodispersed model systems with supported metal adatoms, monomeric oxide units, and ordered mixed oxide surfaces. Scanning tunneling microscopy, ensemble-averaged electron spectroscopies, and density functional theory are employed to achieve an atomic-level understanding. Specifically, the deposition of (MgO)1 monomers and (MoO3)n oligomers is studied on anatase TiO2(101) via direct evaporation of MgO and MoO3 powders. While gas phase (MgO)1 is readily immobilized at room temperature, (MoO3)n transiently diffuse, agglomerate, and spontaneously decompose into the (MoO3)1 monomers. The transient mobility of the oligomers is the key to the self-assembly of the ordered overlayers of (MoO3)1. Metal adatoms and mixed oxide surfaces are synthesized by the sublimation of Rh onto Fe3O4(001). Higher substrate temperatures facilitate Rh incorporation into the surface, leading to ordered mixed Rh-Fe3O4(001). Cryogenic deposition temperatures stabilize Rh on the surface and allow for the preparation of the pure Rh adatom phase. The effect of temperature and adsorbates on the stability of such model catalysts is explored.