Investigation of the electronic interaction between TiO2(110) surfaces and Au clusters by PES and STM

Minato, Taketoshi; Susaki, Tomofumi; Shiraki, Susumu; Kato, Hiroyuki; Kawai, Maki; Aika, Ken‐ichi

doi:10.1016/j.susc.2004.06.047

Cited by 108 publications

(125 citation statements)

References 29 publications

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“…23 However, in situ studies showed that metallic gold is the only species on the catalyst surface under reactive conditions. 24 According to Minato et al, 25 the presence of sites with high electronic density on the surface is essential to the occurrence of the CO oxidation since the electronic transfer from these sites to the oxygen 2p* antibonding orbital is necessary for its activation (rate-determining step). These authors observed the presence of gold species in different oxidation states and the modication of them during the reaction.…”

Section: -9mentioning

confidence: 99%

Surface oxygen vacancies in gold based catalysts for CO oxidation

et al. 2014

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Experimental catalytic activity measurements, diffuse reflectance infrared Fourier spectroscopy, and density functional theory calculations are used to investigate the role and dynamics of surface oxygen vacancies in CO oxidation with O 2 catalyzed by Au nanoparticles supported on a Y-doped TiO 2 catalyst. Catalytic activity measurements show that the CO conversion is improved in a second cycle of reaction if the reactive flow is composed by CO and O 2 (and inert) while if water is present in the flow, the catalyst shows a similar behaviour in two successive cycles. DRIFTS-MS studies indicate the occurrence of two simultaneous phenomena during the first cycle in dry conditions: the surface is dehydroxylated and a band at 2194 cm À1 increases (proportionally to the number of surface oxygen vacancies). Theoretical calculations were conducted in order to explain these observations. On one hand, the calculations show that there is a competition between gold nanoparticles and OH to occupy the surface oxygen vacancies and that the adsorption energy of gold on these sites increases as the surface is being dehydroxylated. On the other hand, these results evidence that a strong electronic transfer from the surface to the O 2 molecule is produced after its adsorption on the Au/TiO 2 perimeter interface (activation step), leaving the gold particle in a high oxidation state. This explains the appearance of a band at a wavenumber unusually high for the CO adsorbed on oxidized gold particles (2194 cm À1 ) when O 2 is present in the reactive flow.These simultaneous phenomena indicate that a gold redispersion on the surface occurs under reactive flow in dry conditions generating small gold particles which are very active at low temperature. This fact is notably favoured by the presence of surface oxygen vacancies that improve the surface dynamics. The obtained results suggest that the reaction mechanism proceeds through the formation of a peroxo-like complex formed after the electronic transfer from the surface to the gas molecule.

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Section: -9mentioning

confidence: 99%

Surface oxygen vacancies in gold based catalysts for CO oxidation

et al. 2014

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“…2,31,64,65 Electron transfer to Au nanoparticles has been probed by laser excitation of TiO 2 nanoparticles coated with Au nanoparticles, 66 by photoemission spectroscopy (PES), and by STM. 67 As shown in Figure 7, ν CO frequencies are reported at 2120-2100 cm -1 for CO on Au particles supported on TiO 2 , 45,60 ∼2088 cm -1 for Au on Fe 2 O 3 (reduced FeO), 61 and 2050 cm -1 on very small Au particles supported on defect-rich MgO. 57 Electron-rich Au nanoparticles are reported to adsorb O 2 more strongly and to activate the O-O bond via charge transfer from Au by forming a superoxo-like species 48 and also to facilitate activation of CO. 19,30,45,68 Furthermore molecularly chemisorbed oxygen on Au/TiO 2 is found to be stable at the surface 48,51 and to react directly with CO to form CO 2 without O 2 dissociation.…”

Section: Origins Of Exceptionally High Catalytic Activities For Nanosmentioning

confidence: 99%

Catalytically Active Gold: From Nanoparticles to Ultrathin Films

Chen

Goodman

2006

ChemInform

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Ordered gold (Au) mono-and bilayer structures have been synthesized on a highly reduced titania surface. The Au bilayer exhibits a significantly higher catalytic activity for carbon monoxide oxidation than does the Au monolayer structure. This is the first report of Au completely wetting an oxide surface and demonstrates that ultrathin Au films on an oxide surface have exceptionally high catalytic activity, comparable to the activity observed for Au nanoparticles. This discovery is a key to understanding the nature of the active site of supported Au catalysts.

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“…20,21,30) Recent STM (scanning tunneling microscopy) observations 31,32) have found that reduced Ti-rich TiO 2 surfaces have strong interactions with Au clusters and prevent their migration as compared with the stoichiometric surface. STM observations 33,34) also clarified that O vacancies (Ti-rich defects) on TiO 2 (110) surfaces are preferential nucleation sites for Au clusters. Recent surface science experiments 35,36) also indicated that reduced Ti-rich TiO 2 surfaces have stronger adhesive interactions with deposited Au particles with charge transfer than the stoichiometric surface.…”

Section: Au/tio 2 Interfacesmentioning

confidence: 94%

“…Our theoretical results are consistent with or in good agreement with experimental observations by our group or others. [28][29][30][31][32][33][34][35][36][37][38][39] We discuss how the interface stoichiometry and configuration affect the adhesive, mechanical, chemical and electronic properties, including Schottky-barrier heights (SBH). We also discuss our recent electron microscopy observation of peculiar structural changes of a Au/CeO 2 system [40][41][42] from the view point of strong interfacial interactions.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Studies of the Atomic and Electronic Structure of Nano-Hetero Metal/Inorganic Material Interfaces in Collaboration with Electron Microscopy Observations

et al. 2007

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First-principles calculations based on density-functional theory have been applied to the energies and atomic and electronic structures of various metal/inorganic material interfaces such as metal/Al 2 O 3 , Au/TiO 2 and metal/SiC interfaces used in thermal barrier coatings, gold catalysts, and high-power electronic devices, respectively, in collaboration with electron microscopy observations. In each system, it has been shown that the interface stoichiometry, namely the features of interfacial termination species of inorganic materials, as well as the metal species, is one of the most important factors to design the interfacial structure and the adhesive, mechanical, chemical and electronic properties. Recent electron microscopy observations of peculiar dynamical structural changes in Au/CeO 2 systems are discussed from this view point.

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Investigation of the electronic interaction between TiO2(110) surfaces and Au clusters by PES and STM

Cited by 108 publications

References 29 publications

Surface oxygen vacancies in gold based catalysts for CO oxidation

Surface oxygen vacancies in gold based catalysts for CO oxidation

Catalytically Active Gold: From Nanoparticles to Ultrathin Films

Theoretical Studies of the Atomic and Electronic Structure of Nano-Hetero Metal/Inorganic Material Interfaces in Collaboration with Electron Microscopy Observations

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