Enhanced dispersion and stability of gold nanoparticles on stoichiometric and reduced TiO2(1 1 0) surface in the presence of molybdenum

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Abstract

Mo, Au and their coadsorbed layers were produced on nearly stoichiometric and oxygen-deficient titania surfaces by physical vapor deposition (PVD) and characterized by low energy ion scattering (LEIS), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and scanning tunnelling microscopy (STM). The behavior of Au/Mo bimetallic layers was studied at different relative metal coverages and sample temperatures. STM data indicated clearly that the deposition of Au on the Mo-covered stoichiometric TiO2(1 1 0) surface results in an enhanced dispersion of gold at 300 K. The mean size of the Au nanoparticles formed at 300 K on the Mo-covered TiO2(1 1 0) was significantly less than on the Mo-free titania surface (2 ± 0.5 nm and 4 ± 1 nm, respectively). Interestingly, the deposition of Mo at 300 K onto the stoichiometric TiO2(1 1 0) surface covered by Au nanoparticles of 3-4 nm (0.5 ML) also resulted in an increased dispersity of gold. The driving force for the enhanced wetting at 300 K is that the Au-Mo bond energy is larger than the Au-Au bond energy in 3D gold particles formed on stoichiometric titania. In contrast, 2D gold nanoparticles produced on ion-sputtered titania were not disrupted in the presence of Mo at 300 K, indicating a considerable kinetic hindrance for breaking of the strong Au-TiOx bond. The annealing of the coadsorbed layer formed on a strongly reduced surface to 740 K did not cause a decrease in the wetting of titania surface by gold. The preserved dispersion of Au at higher temperatures is attributed to the presence of the oxygen-deficient sites of titania, which were retained through the reaction of molybdenum with the substrate. Our results suggest that using a Mo-load to titania, Au nanoparticles can be produced with high dispersion and high thermal stability, which offers the fabrication of an effective Au catalyst.

Original languageEnglish
Pages (from-to)1650-1658
Number of pages9
JournalSurface Science
Volume602
Issue number9
DOIs
Publication statusPublished - May 1 2008

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Keywords

  • Au
  • Bimetallic system
  • Enhanced dispersion
  • Mo
  • Nanoparticles
  • Oxygen-deficient
  • Thermal stability
  • TiO(1 1 0) surface

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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