Mechanism of deposition of gold precursors onto TiO2 during the preparation by cation adsorption and deposition–precipitation with NaOH and urea

Zanella, Rodolfo; Delannoy, Laurent; Louis, Catherine

doi:10.1016/j.apcata.2005.02.045

Cited by 345 publications

(294 citation statements)

References 47 publications

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“…Active catalysts are typically prepared by a coprecipitation process. For example for TiO 2 -supported catalysts, deposition precipitation is used where the TiO 2 is stirred in an aqueous solution of a gold salt and base is added to precipitate the gold, [78][79][80][81][82] whereas Fe 2 O 3 -supported catalysts are prepared by coprecipitation from an aqueous solution of gold and iron salts. [83][84][85] These methods tend to synthesize a very broad range of gold nano-structures and until recently particles in the 2-5 nm range were considered to be the active species in these catalysts.…”

Section: Designing Supported Gold and Gold Palladium Catalystsmentioning

confidence: 99%

“…These Au clusters, the majority of which were 0.2-0.5 nm in diameter, contain at most only a few Au atoms, but this study shows clearly that it is these very small species that are active in gold catalysis for CO oxidation. In a subsequent part of this study 81 we demonstrated that it is the bi-layer nanoclusters containing around 10 atoms, rather than the smaller monolayer structures, that are the active species. This study provides a valuable link with model catalyst studies which have previously demonstrated that extended bi-layer Au structures supported on a titanium dioxide substrate are exceptionally active for low temperature CO oxidation.…”

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confidence: 99%

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Heterogeneous catalysts—discovery and design

Hutchings

2009

J. Mater. Chem.

148

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Heterogeneous catalysis plays a key role in the manufacture of essential products in key areas of agriculture and pharmaceuticals, but also in the production of polymers and numerous essential materials. Our understanding of heterogeneous catalysts is advancing rapidly, especially by using the latest characterisation methods on these relatively complex effect materials. At the heart of these catalytic processes, both selective oxidation and hydrogenation play a key role. Both oxidation and hydrogenation exhibit similar requirements since often a partial reaction product is required, rather than the products of total hydrogenation or oxidation, in the latter case this being typically carbon dioxide and water. This Feature Article considers the approaches available for catalyst discovery and design for heterogeneous catalysts. Three catalysts are considered in detail, two exemplifying oxidation and the other selective hydrogenation. The design of vanadium phosphates for the selective oxidation of butane to maleic anhydride is described in terms of the search for advanced materials with superior activity. This is achieved through the synthesis of wholly amorphous vanadium phosphates. The design of supported gold and gold palladium alloy catalysts for the oxidation of carbon monoxide and the direct hydrogenation of oxygen to form hydrogen peroxide is described and the problems concerning selectivity control are discussed.

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Section: Designing Supported Gold and Gold Palladium Catalystsmentioning

confidence: 99%

mentioning

confidence: 99%

Heterogeneous catalysts—discovery and design

Hutchings

2009

J. Mater. Chem.

148

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“…This is a sign of more uniform distribution of Au particles on the W-modified sample surfaces most likely due to the increased gold uptake. The reason for the formation of metallic gold without additional reduction step is the low thermal stability of the [Au(en) 2 ] 3+ precursor complex when adsorbed on oxide surfaces [10,11,37]. The initial color of the samples was light yellow, however, during the drying at 80 • C the samples became gray-black.…”

Section: Xps Analysismentioning

confidence: 99%

Spectroscopic characterization of gold supported on tungstated zirconia

Kantcheva¹,

Milanova²,

Avramova³

et al. 2012

Catalysis Today

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Keywords:Gold supported on tungstated zirconia XRD DR-UV-vis spectroscopy XPS In situ FT-IR spectroscopy of adsorbed CO and CO + O2 a b s t r a c t Gold catalysts supported on tungstated zirconia (containing 5-20 wt% WO 3 ) are prepared by cationic adsorption from aqueous solution of [Au(en) 2 ]Cl 3 complex. The materials are characterized by XRD, DR-UV-vis spectroscopy and XPS. The nature of the deposited gold species is studied by FT-IR spectroscopy of adsorbed CO. It is concluded that the gold particles occupy preferentially the WO x -free zirconia surface and the dispersion of gold depends on the amount of coodinatively unsaturated (cus) Zr 4+ ions. Modification of zirconia by tungsten increases the gold uptake but at the same time causes decrease in the concentration of (cus) Zr 4+ ions thus lowering the dispersion of gold clusters. According to the results of in situ FT-IR spectroscopy, the Au/WO x ZrO 2 catalysts display higher activity in the CO oxidation in the low-temperature range (up to 150• C) than the WO x -free Au/ZrO 2 sample. The low-temperature activity of the W-containing catalysts could be associated with decreased basicity of the support oxide ions resulting in reduced accumulation of stable carbonate species.

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“…This is shown in Figure 1 representing the growing trend in term of publications per year involving gold-based catalytic materials and the use of environmental microscopies. Regarding the evolution of the number of studies using gold-based catalysts, the major part of the scientific publications concern the methods used for the deposition of gold nanoparticles with very narrow and well-defined sizes [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]. Besides conflicting papers on the influence of the support materials, the effect of the size on the reactivity of gold catalysts for environmental reactions is well established.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Processes on Gold-Based Catalysts Followed by Environmental Microscopies

et al. 2017

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Abstract:Since the early discovery of the catalytic activity of gold at low temperature, there has been a growing interest in Au and Au-based catalysis for a new class of applications. The complexity of the catalysts currently used ranges from single crystal to 3D structured materials. To improve the efficiency of such catalysts, a better understanding of the catalytic process is required, from both the kinetic and material viewpoints. The understanding of such processes can be achieved using environmental imaging techniques allowing the observation of catalytic processes under reaction conditions, so as to study the systems in conditions as close as possible to industrial conditions. This review focuses on the description of catalytic processes occurring on Au-based catalysts with selected in situ imaging techniques, i.e., PEEM/LEEM, FIM/FEM and E-TEM, allowing a wide range of pressure and material complexity to be covered. These techniques, among others, are applied to unravel the presence of spatiotemporal behaviours, study mass transport and phase separation, determine activation energies of elementary steps, observe the morphological changes of supported nanoparticles, and finally correlate the surface composition with the catalytic reactivity.

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Mechanism of deposition of gold precursors onto TiO2 during the preparation by cation adsorption and deposition–precipitation with NaOH and urea

Cited by 345 publications

References 47 publications

Heterogeneous catalysts—discovery and design

Heterogeneous catalysts—discovery and design

Spectroscopic characterization of gold supported on tungstated zirconia

Dynamic Processes on Gold-Based Catalysts Followed by Environmental Microscopies

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