Surface chemistry of catalysis by gold

Meyer, Randall J.; Lemire, Céline; Shaikhutdinov, Shamil K.; Freund, Hans‐Joachim

doi:10.1007/bf03215519

Cited by 775 publications

(762 citation statements)

References 537 publications

(696 reference statements)

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“…The planar model catalysts allow one to 3 precisely control the structure of the systems and investigate the processes occurring on the catalyst surface by employing various surface sensitive techniques. Recent fundamental studies on gold surfaces have been reviewed by Meyer et al [15].…”

Section: Introductionmentioning

confidence: 99%

Gold supported on well-ordered ceria films: nucleation, growth and morphology in CO oxidation reaction

et al. 2007

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Abstract. Structure of gold nanoparticles formed by physical vapor deposition onto thin ceria films was studied by scanning tunneling microscopy (STM). Gold preferentially nucleates on point defects present on the terraces of the well-ordered, fully oxidized films to a low density. The nucleation expands to the terrace step edges, providing a large variety of low-coordinated sites. Only at high coverage, the Au particles grow homogeneously on the oxygen-terminated CeO 2 (111) terraces. The morphology of Au particles was further examined by STM in situ and ex situ at elevated (up to 20 mbar) pressures of O 2 , CO, and CO + O 2 at 300 K. The particles are found to be stable in O 2 ambient up to 10 mbar, meanwhile gold sintering emerges at CO pressures above ~ 1 mbar. Sintering of the Au particles, which mainly proceeds along the step edges of the CeO 2 (111) support, is observed in CO + O 2 (1:1) mixture at much lower pressure (~10 -3 mbar), thus indicating that the structural stability of the Au/ceria catalysts is intimately connected with its reactivity in the CO oxidation reaction.

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Section: Introductionmentioning

confidence: 99%

Gold supported on well-ordered ceria films: nucleation, growth and morphology in CO oxidation reaction

et al. 2007

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“…On the other hand, some chemists hardly study gold reactions, especially the gold self-assembled monolayer (SAM), and the gold-organic molecule junction using scanning tunnelling microscopy [3][4][5][6]. In addition, gold is now well known as a catalyst [7,8], even without any stable oxide (its absence is unique to gold). As epoxy-amine liquid prepolymers are extensively applied onto metallic substrates and cured to obtain painted materials or adhesively bonded structures, they were studied as coating on different metallic substrates (such as Al, Ti, Sn, Zn, Fe, Cr, Cu, Ag, Ni, Au), with a particular emphasis put on gold.…”

Section: Introductionmentioning

confidence: 99%

Is gold always chemically passive?

Aufray

Roche

2008

Applied Surface Science

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. AbstractWhen epoxy-amine liquid mixtures are applied onto metallic substrates (such as Al, Ti, Sn, Zn, Fe, Cr, Cu, Ag, Ni, and Au), concomitant amine chemisorption and metallic surface dissolution occur, leading to organo-metallic complex formation. The interphase formation was studied, using two different amines as hardener (IsoPhoroneDiAmine and DiEthyleneTriAmine). If the complex concentration within the liquid amine or epoxyamine prepolymer was higher than its solubility limit, the complexes will crystallize. Sharp needle-like crystals were only observed with metal-IPDA organo-metallic complexes. A lot of metals are widely used as reactive substrates with gold as a reference, which is considered chemically inert. It is misleading, since it will be shown in this article that gold reacts with amine, just as the other metals.

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“…The enhanced catalytic activity of small gold clusters has been ascribed to a number of effects: bilayer structures that exhibit metal-nonmetal transitions [1][2][3], the metal-support interface [4][5][6][7], uncoordinated step-and corner atoms [8][9][10][11], strain [11], charge transfer from the support [12,13], and metal cationic sites [14]. Early work on model Au clusters supported on TiO 2 (110) correlated the presence of Au bilayer cluster morphologies (figure 1) with catalytic activity for CO oxidation [1].…”

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confidence: 99%

?Catalytically active Au on Titania:? yet another example of a strong metal support interaction (SMSI)?

2005

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In light of the many similarities between previous studies of the so-called strong metal support interaction (SMSI) involving Gr. VIII metals, and catalytically active Au, it is apparent that these two phenomena must be closely related. That active Au on titania spreads to form a bilayer structure, is electron-rich as determined by theory and experiment, nucleates on reduced Ti defects created by annealing to temperatures >750 K, and is deactivated via sintering in oxygen, is convincing evidence that the same basic principles responsible for activation of Au on titania are operative for SMSI involving Gr. VIII metals.KEY WORDS: gold, titania, CO oxidation, strong metal support interaction, SMSI.The enhanced catalytic activity of small gold clusters has been ascribed to a number of effects: bilayer structures that exhibit metal-nonmetal transitions [1][2][3], the metal-support interface [4][5][6][7], uncoordinated step-and corner atoms [8][9][10][11], strain [11], charge transfer from the support [12,13], and metal cationic sites [14]. Early work on model Au clusters supported on TiO 2 (110) correlated the presence of Au bilayer cluster morphologies (figure 1) with catalytic activity for CO oxidation [1]. These bilayer Au structures have been shown to bind CO approximately 50% more strongly than bulk Au (figure 2) [15]. Furthermore oxygen either alone or in a reaction mixture has been shown to promote sintering of these bilayer Au structures (figure 3) [1]. A recent model study [16] of Au on a highly reduced TiO x ordered film grown on Mo(112) has demonstrated that a coordinatively unsaturated, continuous Au bilayer structure that precludes assess of the reactant to the support, exhibits an exceptional high activity for catalytic CO oxidation (figure 4). The activity of this Au bilayer film is more than an order of magnitude more active than any previous report on a per Au atom basis [16]. A key feature of Au grown on TiO x /Mo(112) is the strength of the interaction between the overlayer Au and the support comprised of strong bonding between Au and reduced Ti atoms of the TiO x support, yielding electron-rich Au [16]. These recent studies are entirely consistent with recent theoretical studies [17] that show the importance of reduced Ti defect sites at the boundary between Au clusters and a TiO 2 interface in determining the Au cluster shape and electronic properties via transfer of charge from the support to Au [18]. Finally a recent theoretical study [19] has shown that a Au-only reaction pathway for a TiO x supported Au bilayer cluster is energetically competitive with alternative pathways requiring reactant-support interactions.In summary the essential features of the interaction of Au with TiO 2 that lead to enhanced catalytic activity are: (1) wetting of the support by the cluster; (2) strong bonding between the Au atoms at the interface with surface defects (reduced Ti sites); (3) electron-rich Au; (4) annealing at temperatures in excess of 750 K, sufficient to create and mobilize surface and bulk defects...

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Surface chemistry of catalysis by gold

Cited by 775 publications

References 537 publications

Gold supported on well-ordered ceria films: nucleation, growth and morphology in CO oxidation reaction

Gold supported on well-ordered ceria films: nucleation, growth and morphology in CO oxidation reaction

Is gold always chemically passive?

?Catalytically active Au on Titania:? yet another example of a strong metal support interaction (SMSI)?

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