Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 33: Teilchen und Cluster II

O 33.5: Vortrag

Montag, 7. März 2005, 11:45–12:00, TU EB107

Preparation and characterization of fully oxidized TiO₂ films on Ru (0001) and of Au/TiO₂/Ru(0001) model catalysts — •zhong zhao, T. Diemant, H. Rauscher, and R.J. Behm — Abt.Oberflächenchemie und Katalyse, Universität Ulm, 89069, Ulm

As part of an effort to study CO oxidation on Au/TiO₂ model catalyst, we investigated the growth, structure and chemical composition of completely oxidized TiO₂ films (thickness ca. 10 monolayers (ML)) on a Ru(0001) substrate, and Au/TiO₂ model catalysts prepared by Au evaporation on these films (catalytic properties of these model systems see [1]). Atomic resolution STM images show that after Ti deposition in O₂ (640 K) and annealing in O₂ , the TiO_x film is closed, relatively flat, and consists of TiO₂ (110). Upon room temperature Au evaporation and at lower Au coverages (≤0.2) ML Au nanoparticles nucleate preferentially at steps, a small fraction of them nucleates at defect sites on the TiO₂ terraces. With higher Au coverages, the Au particles grow increasingly on the whole surface. UHV annealing at 770 K (10 min) causes the Au clusters to grow, but different from Pt/TiO₂ [2] we find no encapsulation by TiO₂. The stability of the Au nanoparticles is discussed, comparing with recent findings for Au/TiO₂ (110) model catalysts [3]. [1] T. Diemant, Z. Zhao, H. Rauscher, and R.J. Behm, DPG Spring Meeting, AKF Surface Physics, Berlin (2005) [2] O. Dulub, W. Hebenstreit, and U. Diebold, Phys. Rev. Lett. 84, 3646 (2000) [3] S. Kielbassa, M. Kinne, and R.J. Behm, J. Phys. Chem. B, in press