Synchrotron-Radiation Photoemission Study of Growth and Stability of Au Clusters on Rutile TiO2(110)-1 1

Abstract

The growth and thermal stability of Au clusters on a partially-reduced rutile TiO2(110)-1 1 surface were investigated by high-resolution photoelectron spectroscopy using synchrotron-radiation-light. The valence-band photoelectron spectroscopy results demonstrate that the Ti3+3d feature attenuates quickly with the initial deposition of Au clusters, implying that Au clusters nucleate at the oxygen vacancy sites. The Au4f core-level photoelectron spectroscopy results directly prove the existence of charge transfer from oxygen vacancies to Au clusters. The thermal stability of Au clusters on the partially-reduced and stoichiometric TiO2(110) surfaces was also comparatively investigated by the annealing experiments. With the same film thickness, Au clusters are more thermally stable on the partially-reduced TiO2(110) surface than on the stoichiometric TiO2(110) surface. Meanwhile, large Au nanoparticles are more thermally stable than fine Au nanoparticles.

Morphology-Dependent Evolutions of Sizes, Structures, and Catalytic Activity of Au Nanoparticles on Anatase TiO2 Nanocrystals

“…12,13 Au nanoparticles prepared by Au vapor deposition were observed to preferentially nucleate at surface oxygen vacancy sites of the reduced rutile TiO 2 (110) surface with charge transfer from the substrate to the Au clusters, and such a charge transfer effect strongly modulates the electronic structure of supported Au nanoparticles and greatly enhances their stability. 14,15 It was also reported that an oxidized rutile TiO 2 (110) surface with oxygen adatoms adheres Au clusters more strongly than a reduced rutile TiO 2 (110) surface with surface oxygen vacancy sites. 16 However, studies of growth and structures of Au nanoparticles on other TiO 2 single-crystal surfaces are quite limited, although the TiO 2 surface structures strongly depend on the crystal planes.…”

“…Au/TiO 2 catalysts are one of the earliest and most extensively studied systems of Au catalysis. A volcano-shape dependence of their catalytic activity in low-temperature CO oxidation on the Au particle size has inspired many fundamental studies to understand the growth and structures of Au nanoparticles on TiO 2 that mostly use a rutile TiO 2 (110) single crystal as a model surface for TiO 2 . − The catalytic activity of Au nanoparticles supported on the rutile TiO 2 (110) surface also exhibited a volcano shape-dependent catalytic activity in low-temperature CO oxidation on the Au particle size. , Au nanoparticles prepared by Au vapor deposition were observed to preferentially nucleate at surface oxygen vacancy sites of the reduced rutile TiO 2 (110) surface with charge transfer from the substrate to the Au clusters, and such a charge transfer effect strongly modulates the electronic structure of supported Au nanoparticles and greatly enhances their stability. , It was also reported that an oxidized rutile TiO 2 (110) surface with oxygen adatoms adheres Au clusters more strongly than a reduced rutile TiO 2 (110) surface with surface oxygen vacancy sites . However, studies of growth and structures of Au nanoparticles on other TiO 2 single-crystal surfaces are quite limited, although the TiO 2 surface structures strongly depend on the crystal planes.…”

A Low-Energy Ion Scattering Approach for Studying Au Nanoclusters Grown on an H2O Buffer Layer

“…For scattering from metal nanoclusters adsorbed on insulating substrates, it has been shown that the NF directly correlates with the size of the nanoclusters. , Small clusters have quantum-confined electronic states, and the clusters are generally thought to be negatively charged, , so that electrons from these filled states efficiently neutralize the scattered alkali ions. In contrast, solid Au has a rather large work function compared to the Na and K ionization energies, so that the neutralization probability of Na + and K + in scattering from bulk Au is near zero. , Thus, the NF decreases as more Au is deposited and the size of the clusters increases so that the Au becomes more bulk-like.…”

Adsorption of Br2 onto Small Au Nanoclusters

“…A recent report from our group 22 agrees with work from the literature in that the clusters contain positively charged Au atoms, [55][56][57][58][59] although others have concluded that the clusters are overall negatively charged. [60][61][62][63] It was calculated from density functional theory (DFT) that the edge atoms of a nanocluster are the ones that are positively charged 59,64 and upward pointing dipoles are thus created at those sites. These upward pointing dipoles create a lower LEP, as with alkali adatoms, which raises the NF of the projectiles scattered from the edge atoms.…”