Reactivity studies with gold-supported molybdenum nanoparticles

Potapenko, Denis V.; Horn, Jillian M.; Beuhler, R. J.; Song, Zhen; White, Michael G.

doi:10.1016/j.susc.2004.10.035

Cited by 21 publications

(17 citation statements)

References 56 publications

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“…We do not consider a sintering process to be the likely explanation for the changes in basal plane to edge ratio, since STM investigations have shown that the initial size of the MoS 2 triangles are unaffected by extensive hydrogen exposure (hours) at 10 –6 mbar and 450 °C. It should be noted that the overall process also results in a drop of the total Mo 3d spectral area, which likely reflects a loss of Mo due to accelerated alloying between the gold substrate and the molybdenum atoms exposed by the reducing conditions . As a result of the intense desulfurization which occurred in the experiment without a balancing source of S ( e.g.…”

Section: Resultsmentioning

confidence: 99%

In Situ Detection of Active Edge Sites in Single-Layer MoS₂ Catalysts

et al. 2015

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MoS2 nanoparticles are proven catalysts for processes such as hydrodesulfurization and hydrogen evolution, but unravelling their atomic-scale structure under catalytic working conditions has remained significantly challenging. Ambient pressure X-ray Photoelectron Spectroscopy (AP-XPS) allows us to follow in situ the formation of the catalytically relevant MoS2 edge sites in their active state. The XPS fingerprint is described by independent contributions to the Mo 3d core level spectrum whose relative intensity is sensitive to the thermodynamic conditions. Density Functional Theory (DFT) is used to model the triangular MoS2 particles on Au(111) and identify the particular sulphidation state of the edge sites. A consistent picture emerges in which the core level shifts for the edge Mo atoms evolve counterintuitively toward higher binding energies when the active edges are reduced. The shift is explained by a surprising alteration in the metallic character of the edge sites, which is a distinct spectroscopic signature of the MoS2 edges under working conditions.

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Section: Resultsmentioning

confidence: 99%

In Situ Detection of Active Edge Sites in Single-Layer MoS₂ Catalysts

et al. 2015

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“…It can be assumed that the diffusion of Au atoms of a nanoparticle is activated by the impinging Mo atoms due to different reasons: (i) the decrease in Au-Au bond strength owing to the formation of Mo-Au bond, resulting even in Mo-Au exchange and surface alloying [19], (ii) the reaction heat generated by the oxidation of Mo at the perimeter of Au nanoparticles. In terms of thermodynamic parameters it is well established that gold has lower surface free energy than molybdenum [20] and Au/Mo has larger binding energy than Au/TiO 2 [5]. Although Mo is rather reactive and it is partially oxidized during the deposition by the Ocontent of titania [13], the adsorbing Mo atoms may cause structural changes in the deposited gold [20] and the wetting of oxidized and unoxidized molybdenum may occur [5,16,20].…”

Section: Deposition Of Mo On Tio 2 (1 1 0) Surface Doped With Aumentioning

confidence: 99%

“…In terms of thermodynamic parameters it is well established that gold has lower surface free energy than molybdenum [20] and Au/Mo has larger binding energy than Au/TiO 2 [5]. Although Mo is rather reactive and it is partially oxidized during the deposition by the Ocontent of titania [13], the adsorbing Mo atoms may cause structural changes in the deposited gold [20] and the wetting of oxidized and unoxidized molybdenum may occur [5,16,20]. In the case of low gold coverages where the formation of 2D particles on sputtered titania was also found by others [36], the Mo deposition caused a decrease in Au LEIS signals (Fig.…”

Section: Deposition Of Mo On Tio 2 (1 1 0) Surface Doped With Aumentioning

confidence: 99%

“…Mo nanoparticles formed through physical vapor deposition (PVD) was found to be encapsulated by gold after thermal activation, what was explained with the lower surface energy of Au compared to that of Mo [20]. In the study of the electronic interaction between Mo(1 1 0) crystal plane and Au atoms, it was found that molybdenum induced a decrease in the population of Au 5d electron orbital [21].…”

Section: Introductionmentioning

confidence: 99%

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Enhanced dispersion and stability of gold nanoparticles on stoichiometric and reduced TiO2(1 1 0) surface in the presence of molybdenum

et al. 2008

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a b s t r a c tMo, Au and their coadsorbed layers were produced on nearly stoichiometric and oxygen-deficient titania surfaces by physical vapor deposition (PVD) and characterized by low energy ion scattering (LEIS), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and scanning tunnelling microscopy (STM). The behavior of Au/Mo bimetallic layers was studied at different relative metal coverages and sample temperatures. STM data indicated clearly that the deposition of Au on the Mo-covered stoichiometric TiO 2 (1 1 0) surface results in an enhanced dispersion of gold at 300 K. The mean size of the Au nanoparticles formed at 300 K on the Mo-covered TiO 2 (1 1 0) was significantly less than on the Mo-free titania surface (2 ± 0.5 nm and 4 ± 1 nm, respectively). Interestingly, the deposition of Mo at 300 K onto the stoichiometric TiO 2 (1 1 0) surface covered by Au nanoparticles of 3-4 nm (0.5 ML) also resulted in an increased dispersity of gold. The driving force for the enhanced wetting at 300 K is that the Au-Mo bond energy is larger than the Au-Au bond energy in 3D gold particles formed on stoichiometric titania. In contrast, 2D gold nanoparticles produced on ion-sputtered titania were not disrupted in the presence of Mo at 300 K, indicating a considerable kinetic hindrance for breaking of the strong Au-TiO x bond. The annealing of the coadsorbed layer formed on a strongly reduced surface to 740 K did not cause a decrease in the wetting of titania surface by gold. The preserved dispersion of Au at higher temperatures is attributed to the presence of the oxygen-deficient sites of titania, which were retained through the reaction of molybdenum with the substrate. Our results suggest that using a Mo-load to titania, Au nanoparticles can be produced with high dispersion and high thermal stability, which offers the fabrication of an effective Au catalyst.

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“…In an effort to obtain sulfides catalysts with better efficiency, one approach is to optimizing the interaction between the active sulfides and the supports surface [10,89,96]. However, characterization techniques almost reach their limits at this stage.…”

Section: Synthetic Fabrication Of Molybdenum Sulfide With Inorganimentioning

confidence: 99%

Synthetic Fabrication of Nanoscale MoS2-Based Transition Metal Sulfides

Wang

Yuan

2010

Materials

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Transition metal sulfides are scientifically and technologically important materials. This review summarizes recent progress on the synthetic fabrication of transition metal sulfides nanocrystals with controlled shape, size, and surface functionality. Special attention is paid to the case of MoS2 nanoparticles, where organic (surfactant, polymer), inorganic (support, promoter, doping) compounds and intercalation chemistry are applied.

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Reactivity studies with gold-supported molybdenum nanoparticles

Cited by 21 publications

References 56 publications

In Situ Detection of Active Edge Sites in Single-Layer MoS₂ Catalysts

In Situ Detection of Active Edge Sites in Single-Layer MoS₂ Catalysts

Enhanced dispersion and stability of gold nanoparticles on stoichiometric and reduced TiO2(1 1 0) surface in the presence of molybdenum

Synthetic Fabrication of Nanoscale MoS2-Based Transition Metal Sulfides

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Reactivity studies with gold-supported molybdenum nanoparticles

Cited by 21 publications

References 56 publications

In Situ Detection of Active Edge Sites in Single-Layer MoS2 Catalysts

In Situ Detection of Active Edge Sites in Single-Layer MoS2 Catalysts

Enhanced dispersion and stability of gold nanoparticles on stoichiometric and reduced TiO2(1 1 0) surface in the presence of molybdenum

Synthetic Fabrication of Nanoscale MoS2-Based Transition Metal Sulfides

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In Situ Detection of Active Edge Sites in Single-Layer MoS₂ Catalysts

In Situ Detection of Active Edge Sites in Single-Layer MoS₂ Catalysts