Structure and oxidation state of gold on different supports under various CO oxidation conditions

Weiher, Norbert; Bus, Eveline; Delannoy, Laurent; Louis, Catherine; Ramaker, David E.; Miller, Jeffrey T.; Bokhoven, Jeroen A. van

doi:10.1016/j.jcat.2006.03.010

Cited by 162 publications

(137 citation statements)

References 56 publications

Supporting

Mentioning

123

Contrasting

Order By: Relevance

“…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

View full text Add to dashboard Cite

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.

show abstract

Section: -9mentioning

confidence: 99%

Surface oxygen vacancies in gold based catalysts for CO oxidation

et al. 2014

View full text Add to dashboard Cite

show abstract

“…For example, Gates and co-workers use X-ray absorption techniques (XANES, EXAFS) and infrared spectroscopy to monitor the oxidation states of Au in CO oxidation and ethylene hydrogenation reactions over Au/MgO [16]. A similar approach has been recently used by Kung and co-workers [17] for studies of the CO oxidation reaction over Au/TiO 2 , by Wang et al [18] on Au/CeO 2 catalysts for water gas-shift reaction, Overbury et al [19] on Au/TiO 2 catalysts of CO oxidation and Wieher et al [20] of different gold catalysts. A recent paper by Hutchings et al [21] reports on complementary studies performed in different groups on the same Au/Fe 2 O 3 catalysts, in particular showing good potentia ls for using Au 197 Mössbauer spectroscopy to elucidate the role of cationic species in reactions.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2007

View full text Add to dashboard Cite

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.

show abstract

“…Gold nanoparticles supported on metal oxides can indeed catalyze low-temperature complete oxidation of hydrocarbons and CO, but also epoxidation reactions and hydrogenations, the NO reduction, and several other reactions as has been reviewed in the recent literature [2,3]. Perhaps the most intensively studied reaction to date is the CO oxidation on gold supported on oxides, such as iron oxide and titania [1,[4][5][6][7], and ceria [8][9][10][11], but also on non-reducible oxides, such as alumina [12][13][14][15] and silica [12]. Activity of nanoparticles of gold on non-oxide supports has also been reported [16].…”

Section: Introductionmentioning

confidence: 99%

“…There is conflicting information in the literature about the oxidation state of gold during the dry CO oxidation reaction [4,11,14,15,[25][26][27][28][29][30][31][32][33]. There is also an unresolved issue of the importance of gold particle size for this reaction [5,34,35], while a recent theoretical study finds no effect of the type of oxide support if gold clusters with a large number of cus sites are used [36].…”

Section: Introductionmentioning

confidence: 99%

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

et al. 2007

View full text Add to dashboard Cite

We compare the activity and relevant gold species of nanostructured gold-cerium oxide and gold-iron oxide catalysts for the CO oxidation by dioxygen and water. Well dispersed gold nanoparticles in reduced form provide the active sites for the CO oxidation reaction on both oxide supports. On the other hand, oxidized gold species, strongly bound on the support catalyze the water-gas shift reaction. Gold species weakly bound to ceria (doped with lanthana) or iron oxide can be removed by sodium cyanide at pH ‡12. Both parent and leached catalysts were investigated. The activity of the leached gold-iron oxide catalyst in CO oxidation is approximately two orders of magnitude lower than that of the parent material. However, after exposure to H 2 up to 400°C gold diffuses out and is in reduced form on the surface, a process accompanied by a dramatic enhancement of the CO oxidation activity. Similar results were found with the gold-ceria catalysts. On the other hand, pre-reduction of the calcined leached catalyst samples did not promote their water-gas shift activity. UV-Vis, XANES and XPS were used to probe the oxidation state of the catalysts after various treatments.

show abstract

Structure and oxidation state of gold on different supports under various CO oxidation conditions

Cited by 162 publications

References 56 publications

Surface oxygen vacancies in gold based catalysts for CO oxidation

Surface oxygen vacancies in gold based catalysts for CO oxidation

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

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

Contact Info

Product

Resources

About