FTIR Study of CO Oxidation on Au/TiO<sub>2</sub> at 90 K and Room Temperature. An Insight into the Nature of the Reaction Centers

and, Flora Boccuzzi; Chiorino, A.

doi:10.1021/jp000749w

Cited by 180 publications

(152 citation statements)

References 18 publications

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“…The perpendicular orientation is preferred than the parallel ones for Au 2 , Au 3 and Au 4 clusters, whereas for Au 5 , Au 6 and Au 7 , the situation is quite the contrary. Charge analysis suggests that the adsorption strength is mainly due to the electrostatic interactions between the clusters and support.…”

Section: Discussionmentioning

confidence: 86%

“…That is, the odd-numbered Au n clusters are favoring bridge adsorption of O 2 whereas even-numbered ones are favoring end-on adsorption mode. It should be noticed that for Au 2 , Au 6 and Au 8 clusters, the O 2 molecule could not adsorb on their bridge sites due to the adsorption energy is close to zero. Similarly, the O 2 molecule could also not adsorb on the surfaces of the planar Au 6 , Au 8 and Au 10 clusters.…”

Section: O 2 Adsorption Energiesmentioning

confidence: 99%

“…It should be noticed that for Au 2 , Au 6 and Au 8 clusters, the O 2 molecule could not adsorb on their bridge sites due to the adsorption energy is close to zero. Similarly, the O 2 molecule could also not adsorb on the surfaces of the planar Au 6 , Au 8 and Au 10 clusters. The odd-even oscillation of adsorption energies for Au n O 2 clusters is clear evidence based on the analysis above.…”

Section: O 2 Adsorption Energiesmentioning

confidence: 99%

“…The adsorption energies (E 3 ) obtained with Equation (3) indicate that the perpendicular orientation is preferred than the parallel one for Au 2 , Au 3 and Au 4 clusters. However, for Au 5 , Au 6 and Au 7 clusters, the most stable orientation is parallel due to their larger adsorption energies. The largest adsorption energy for the studied system is observed in Au 7 cluster, which value is -1.15 eV.…”

Section: Pure Au N Clusters On N-graphenementioning

confidence: 99%

“…As a new kind of catalyst to catalyze CO oxidation reactions at low temperatures, nanosized gold clusters have recently attracted considerable interest from both the industrial and academic communities due to their unique physical and chemical properties [1][2][3][4][5][6]. It is well known that gold in its bulk form has little or no catalytic activity.…”

Section: Introductionmentioning

confidence: 99%

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The Interactions of Oxygen with Small Gold Clusters on Nitrogen-Doped Graphene

Chen

Sun

et al. 2013

Molecules

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By means of density functional theory, the adsorption properties of O 2 molecule on both isolated and N-graphene supported gold clusters have been studied. The N-graphene is modeled by a C 65 NH 22 cluster of finite size. The results indicate that the catalytic activity and the O 2 adsorption energies of odd-numbered Au clusters are larger than those of adjacent even-numbered ones. The O 2 molecule is in favor of bonding to the bridge sites of odd-numbered Au clusters, whereas for odd-numbered ones, the end-on adsorption mode is favored. The perpendicular adsorption orientation on N-graphene is preferred than the parallel one for Au 2 , Au 3 and Au 4 clusters, while for Au 5 , Au 6 and Au 7 , the parallel ones are favored. When O 2 is adsorbed on N-graphene supported Au clusters, the adsorption energies are largely increased compared with those on gas-phase ones. The increased adsorption energies would significantly facilitate the electron transfer from Au d-orbital to π* orbital of O 2 , which would further weakening the O-O bond and therefore enhancing the catalytic activity. The carbon atoms on N-graphene could anchor the clusters, which could make them more difficult to structural distortion, therefore enhance their stability.

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Section: Discussionmentioning

confidence: 86%

Section: O 2 Adsorption Energiesmentioning

confidence: 99%

Section: O 2 Adsorption Energiesmentioning

confidence: 99%

Section: Pure Au N Clusters On N-graphenementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Interactions of Oxygen with Small Gold Clusters on Nitrogen-Doped Graphene

Chen

Sun

et al. 2013

Molecules

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Nanocrystalline CeO₂ Increases the Activity of Au for CO Oxidation by Two Orders of Magnitude

et al. 2004

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More than twenty years ago it was shown that gold, despite its limited adsorption properties, catalyzes reactions such as CO oxidation, [1] alkene hydrogenation, [2] and ethylene hydrochlorination.[3] However, strong interest in gold for catalysis emerged only recently owing to the seminal work of Haruta et al. [4] These authors showed that when gold is deposited on a metal-oxide support by a coprecipitation method, the metal exhibits high catalytic activity for CO oxidation at low temperatures. Moreover, they found that the distinctive behavior of the gold catalysts was due to the presence of nanosized Au particles.In a recent review, Bond and Thompson [5] showed that, in the case of Au-supported catalysts, factors such as Au particle size, preparation method, pretreatment conditions, and choice of the support play an important role in the CO oxidation activity of the final catalyst. Indeed, when nanoparticles of Au are deposited on TiO 2 , [4b, 6a] Co 3 O 4 , [4b, 6b] ZnO, [7] Fe 2 O 3 , [4b, 6a] or MgO, [8] the catalysts are particularly active for the above-mentioned reaction. In contrast, nanoparticles of Au were much less active when other supports were used. [5,9] These results suggest that a synergetic effect between the metal oxide support and Au may exist at the interface such that the metal oxide does not simply act as an inert carrier, but intervenes in the catalytic process.We thought that if gold nanoparticles on the order of 3 to 5 nm were essential for the catalysis (owing to the presence of a large number of surface gold atoms with properties different from those of bulk gold) and if a synergetic mechanism occurs at the gold and metal oxide interface, the characteristics of the metal oxide surface should be of paramount importance. In other words, if the support could be prepared in the form of discrete, well-defined nanoparticles, this should have an influence on the surface electronic properties and consequently on the gold-support interaction.

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Mechanism and Active Sites of the Oxidation of CO over Au/TiO₂

Fujitani¹,

Nakamura²

2011

Angewandte Chemie

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Dedicated to the Fritz Haber Institute, Berlin, on the occasion of its 100th anniversary Gold nanoparticles supported on titanium oxides are highly active catalysts for the oxidation of CO even at low temperature. [1,2] Despite extensive research to determine the reaction mechanism and the active sites on a molecular scale, there is still no consensus about 1) the the active sites and the mechanism of activation of O 2 molecules and 2) the role of moisture and its influence on the activity of the catalysts.For instance, although most research groups agree that small Au 0 nanoparticles are the predominant catalytic species, [3][4][5] other groups have proposed that cationic gold species, [6][7][8] undercoordinated sites on the gold nanoparticles, [9][10][11] or electron-rich gold nanoparticles play an essential role in the reaction. [12] Furthermore, dissociation of O 2 has been reported to occur when undercoordinated gold atoms are present on extended gold surfaces under model conditions. [13,14] On the basis of high-intensity in situ X-ray absorption near-edge structure analysis, van Bokhoven and coworkers indicated that O 2 molecules can dissociate on gold nanoparticles supported on Al 2 O 3 and TiO 2 substrates. [15] In contrast, Liu et al. calculated that the barrier to dissociation of O 2 on unsupported gold is > 2 eV and that even at the Au/ TiO 2 interface, the dissociation barrier is still 0.52 eV. [16] These values indicate that O 2 interacts weakly with gold, and thus spontaneous dissociation of O 2 molecules on the gold surface is not energetically favorable. Recently, Behm and co-workers found that the amount of active oxygen species on the Au/ TiO 2 surface is linearly related to the number of perimeter sites at the interface between the oxide support and the gold nanoparticles, indicating that the gold-support interface plays a dominant role in O 2 activation. [17] Furthermore, the oxidation of CO is greatly influenced by moisture in the reactant gas. [18][19][20][21] Date et al. proposed on the basis of their research and that of others that moisture has two effects: it activates O 2 molecules, and it decomposes a carbonate species. [20] However, the mechanistic details of the promotional effect of moisture are not fully understood. Here, we describe the reaction mechanism and active sites for the oxidation of CO over Au/TiO 2 , along with the role of moisture, on a molecular scale.First, we investigated the effect of moisture on the oxidation of CO over Au/TiO 2 (110) (Figure 1). The gold coverage of all samples was fixed at one monolayer equivalent (MLE). The reaction was carried out at a typical reaction temperature of 300 K and the features for the oxidation of CO appeared remarkably. We used quadrupole mass spectrometry to monitor the CO 2 signal at m/q = 44. In the absence of moisture, formation of CO 2 was not observed, indicating that the oxidation of CO did not proceed under these reaction conditions. However, in the presence of H 2 O, formation of CO 2 increased linearly with the reaction...

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FTIR Study of CO Oxidation on Au/TiO₂ at 90 K and Room Temperature. An Insight into the Nature of the Reaction Centers

Cited by 180 publications

References 18 publications

The Interactions of Oxygen with Small Gold Clusters on Nitrogen-Doped Graphene

The Interactions of Oxygen with Small Gold Clusters on Nitrogen-Doped Graphene

Nanocrystalline CeO₂ Increases the Activity of Au for CO Oxidation by Two Orders of Magnitude

Mechanism and Active Sites of the Oxidation of CO over Au/TiO₂

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FTIR Study of CO Oxidation on Au/TiO2 at 90 K and Room Temperature. An Insight into the Nature of the Reaction Centers

Cited by 180 publications

References 18 publications

The Interactions of Oxygen with Small Gold Clusters on Nitrogen-Doped Graphene

The Interactions of Oxygen with Small Gold Clusters on Nitrogen-Doped Graphene

Nanocrystalline CeO2 Increases the Activity of Au for CO Oxidation by Two Orders of Magnitude

Mechanism and Active Sites of the Oxidation of CO over Au/TiO2

Contact Info

Product

Resources

About

FTIR Study of CO Oxidation on Au/TiO₂ at 90 K and Room Temperature. An Insight into the Nature of the Reaction Centers

Nanocrystalline CeO₂ Increases the Activity of Au for CO Oxidation by Two Orders of Magnitude

Mechanism and Active Sites of the Oxidation of CO over Au/TiO₂