Evidencing the formation of Pt nano-islands on Cr2O3/Ag(111)

Abstract

The present work reports on a comprehensive surface atomic structure investigation on a Pt/Cr₂O₃/Ag(111) model catalyst. Molecular beam epitaxy (MBE) was applied to achieve the Pt/Cr₂O₃ model system, and in situ characterization via X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED) and X-ray photoelectron diffraction (XPD) allowed for probing its outermost layers' properties. XPD provided valuable element-specific short-range information from the Pt/Cr₂O₃/Ag(111) surface, and the results were compared to a precise and systematic multiple scattering simulation approach. The experiments, characterizations and simulations suggest strong evidence of Pt nanoisland formation on the Cr₂O₃/Ag(111) surface. The results indicated that these nanoislands typically consist of three Pt monolayer thick clusters with considerable structural variations in their interatomic layer distances. Such an atomic rearrangement could clarify the high reactivity observed in heterogeneous catalysts containing Pt nanoparticles coalesced or dispersed on oxide substrates.