SIMS study of Cs/MoS2(0001)

Karolewski, M.A.; Cavell, Ronald G.

doi:10.1016/0039-6028(89)90212-4

Cited by 23 publications

(8 citation statements)

References 36 publications

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“…The SIMS spectra in Figure 5 confirm that sulfidation at relatively low temperatures, 25 residual MoO intensity is probably due to the intimate contact of the MoS2 particles with the oxidic support.…”

Section: Resultsmentioning

confidence: 61%

“…Here a clear SIMS sensitivity effect is apparent: MoS," clusters have much lower intensities than MoO," clusters. 25 Nevertheless, the relative intensities of the MoO," clusters decrease clearly with increasing sulfidation temperature, indicating that the original oxygen coordination of Mo is disrupted by the sulfidation. Direct evidence for Mo-S contact is given by the relative increase in the intensities of the (Mo + 32)" and (Mo + 64)" clusters.…”

Section: Resultsmentioning

confidence: 99%

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Sulfidation mechanism by molybdenum catalysts supported on silica/silicon(100) model support studied by surface spectroscopy

Jong¹,

Borg²,

IJzendoorn³

et al. 1993

J. Phys. Chem.

138

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The sulfidation of disk-shaped MOO, particles with a thickness of 5-10 nm supported on a 5-nm-thick layer of Si02 on Si(100) in a mixture of 10% H2S in H2 at atmospheric pressure has been studied as a function of temperature. XPS and SIMS indicate the formation of Mo4+OS, at the surface and Mo(1V) oxides (probably H1.6Mo03 or MOO?) in the interior of the particles at temperatures between 20 and 100 OC, whereas MoS2 forms at temperatures of 125 OC and higher. Sulfur is present in two forms, as S2-and in a second form which is most probably Sz2-or SH-, but not elemental sulfur. The additional sulfur species disappear at temperatures between 150 and 200 OC. Rutherford backscattering analysis indicates S:Moatomicratios of 1-1.5 at sulfidation temperatures below 100 OC and of 2-2.5 above 100 OC. It is concluded that the sulfidation of Moo3 to MoS2 proceeds through a Mo(1V) oxysulfide, formed initially at the outside of the particle, and Mo(1V) oxide in the interior of the particle. Sulfidic species are believed to facilitate the reduction of Moo3 to Mo(1V) species at low temperatures.

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Section: Resultsmentioning

confidence: 61%

Section: Resultsmentioning

confidence: 99%

Sulfidation mechanism by molybdenum catalysts supported on silica/silicon(100) model support studied by surface spectroscopy

Jong¹,

Borg²,

IJzendoorn³

et al. 1993

J. Phys. Chem.

138

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show abstract

“…Despite the importance of the MoS 2 -based catalysts, only a limited number of studies have been published of these catalysts on the interpretation of reaction mechanisms − as well as on characterization of the alkali-doped MoS 2 surface. − In an effort to understand the fundamental chemistry involved in the MoS 2 -based catalysts, we investigated the surface atomic structures of a clean and Cs-covered MoS 2 (0002). The study was carried out using high-resolution X-ray photoemission spectroscopy (HRXPS), where HRXPS routinely achieves an energy resolution better than 0.3 eV and at the same time permits an angle-resolved X-ray photoemission spectroscopy (ARXPS) examination of the system with the purpose of determining surface structure and location of the electrons that are subject to photoemission.…”

Section: Introductionmentioning

confidence: 99%

Surface Structure of Single-Crystal MoS₂(0002) and Cs/MoS₂(0002) by X-ray Photoelectron Diffraction

et al. 1996

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The surface structure of a clean MoS 2 (0002) and an in situ Cs surface-doped MoS 2 (0002) has been studied using high-resolution X-ray photoemission spectroscopy. The X-ray photoelectron diffraction (XPD) patterns of the Mo 3d 5/2 and S 2p core levels from a clean, well-ordered MoS 2 (0002) show forward focusing intensity maxima along the directions of nearest neighbors in MoS 2 in both the polar and azimuthal angle scans. The XPD patterns in the azimuthal angle scan exhibit a pronounced photoelectron intensity maximum at every 60°, reflecting the 6-fold rotational symmetry of the basal plane. In addition, because of the finite electron escape depth and the short-range order of the scattered photoelectrons, the azimuthal scans of both the Mo 3d 5/2 and the S 2p core levels further display the 3-fold rotational symmetry of the trigonal prismatic local structure, which MoS 2 (0002) possesses. The deposition of Cs onto the MoS 2 (0002) surface at room temperature did not introduce any significant changes either in the low-energy electron diffraction or in the XPD patterns, indicating the absence of Cs-induced surface relaxation, but a new photoemission was observed 1.6 eV above the valence band edge of MoS 2 , which corresponds to the Cs 6s photoelectron shared with the MoS 2 lattice. Thus Cs/MoS 2 represents an electron donor-acceptor (EDA) surface complex.

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“…This apparent contradiction is resolved by considering that NO does not absorb solely on exposed molybdenum atoms in MoS 2 , but also on potassium cations, as indicated by several studies concerning the chemisorption of oxygen‐containing compounds on alkali‐doped MoS 2 29. 32, 33 This explains that NO adsorbs on potassium‐doped MoS 2 even after flowing COS in the absence of H 2 , which would block the Mo‐CUS, as described elsewhere 19. Furthermore, the assignment of potassium cations as adsorption centers implies that they can be part of the active sites responsible for the COS disproportionation, which is enhanced in the potassium‐decorated MoS 2 phase.…”

Section: Discussionmentioning

confidence: 99%

Influence of Potassium on the Synthesis of Methanethiol from Carbonyl Sulfide on Sulfided Mo/Al₂O₃ Catalyst

2011

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Potassium‐doped MoS2 catalysts supported on Al2O3 were synthesized, characterized by using atomic absorption spectroscopy, N2 physisorption, NO adsorption, X‐ray diffraction, temperature‐programmed sulfidation, and Raman spectroscopy, and tested in the synthesis of methanethiol from carbonyl sulfide (COS) and H2. The results revealed that two phases, pure MoS2 and potassium‐decorated MoS2 (formed at high potassium loadings), were present in the active catalysts. The main effect of potassium during sulfidation and during the catalytic reaction was to increase the mobility of surface oxygen or sulfur atoms. Thus, potassium promoted the disproportionation of COS to CO2 and CS2 and the production of CO from CO2. Additionally, potassium cations hindered the reductive decomposition of COS to CO and H2S and the hydrogenolysis of methanethiol to methane. Mars–van Krevelen‐type mechanisms were proposed to explain the disproportionation of COS on alumina and on the MoS2 phases. The catalytic site in the potassium‐decorated MoS2 phase was proposed to include a potassium cation as adsorption site.

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SIMS study of Cs/MoS2(0001)

Cited by 23 publications

References 36 publications

Sulfidation mechanism by molybdenum catalysts supported on silica/silicon(100) model support studied by surface spectroscopy

Sulfidation mechanism by molybdenum catalysts supported on silica/silicon(100) model support studied by surface spectroscopy

Surface Structure of Single-Crystal MoS₂(0002) and Cs/MoS₂(0002) by X-ray Photoelectron Diffraction

Influence of Potassium on the Synthesis of Methanethiol from Carbonyl Sulfide on Sulfided Mo/Al₂O₃ Catalyst

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SIMS study of Cs/MoS2(0001)

Cited by 23 publications

References 36 publications

Sulfidation mechanism by molybdenum catalysts supported on silica/silicon(100) model support studied by surface spectroscopy

Sulfidation mechanism by molybdenum catalysts supported on silica/silicon(100) model support studied by surface spectroscopy

Surface Structure of Single-Crystal MoS2(0002) and Cs/MoS2(0002) by X-ray Photoelectron Diffraction

Influence of Potassium on the Synthesis of Methanethiol from Carbonyl Sulfide on Sulfided Mo/Al2O3 Catalyst

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Product

Resources

About

Surface Structure of Single-Crystal MoS₂(0002) and Cs/MoS₂(0002) by X-ray Photoelectron Diffraction

Influence of Potassium on the Synthesis of Methanethiol from Carbonyl Sulfide on Sulfided Mo/Al₂O₃ Catalyst