Surface science studies of cobalt overlayers on clean and sulfur covered Mo(100) single crystal surfaces

Knight, Colette C.; Somorjai, Gábor A.

doi:10.1016/0039-6028(90)90734-p

Cited by 26 publications

(3 citation statements)

References 27 publications

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“…In recent years, the interaction between sulfur and well-defined bimetallic surfaces has been the subject of a large series of studies. − In part, this interest is motivated by the important role that sulfur plays in several areas of heterogeneous catalysis. , Catalysts that combine noble and late-transition metals are very sensitive to sulfur poisoning, and there is a general desire to improve the sulfur tolerance of these systems. In addition, Mo- and W-based bimetallic sulfides are frequently used for hydrodesulfurization (HDS) processes in the petroleum industry, and there is a clear need to enhance the activity of these catalysts.…”

Section: Introductionsupporting

confidence: 55%

“…In recent years, the interaction between sulfur and welldefined bimetallic surfaces has been the subject of a large series of studies. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] In part, this interest is motivated by the important role that sulfur plays in several areas of heterogeneous catalysis. 15,16 Catalysts that combine noble and late-transition metals are very sensitive to sulfur poisoning, 15 and there is a general desire to improve the sulfur tolerance of these systems.…”

Section: Introductionmentioning

confidence: 99%

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Interaction of Sulfur with Au/Pt(111) and Ag/Pt(111) Surfaces: Photoemission Studies

Rodríguez

Kühn

1996

J. Phys. Chem.

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The reaction of sulfur with Au/Pt(111) and Ag/Pt(111) surfaces has been investigated using high-resolution photoemission spectroscopy with synchrotron radiation. The valence spectra of S/Au/Pt(111) and S/Ag/Pt-(111) surfaces display weak signals at binding energies between 1.8 and 0 eV. The adsorption of S induces a large decrease in the density of states displayed by the bimetallic surfaces around the Fermi level. This phenomenon may be responsible for the decrease in chemical and catalytic activity that accompanies sulfur poisoning. In S/Au/Pt(111) surfaces, sulfur does not form compounds with Au or Pt. Au forms threedimensional clusters, while S segregates into two-dimensional islands of high local coverage where it is bonded to hollow and bridge sites of the Pt substrate. In S/Ag/Pt(111) surfaces, silver reacts with sulfur and promotes the synthesis of platinum sulfides. The formation of silver and platinum sulfides makes possible the adsorption of large amounts of sulfur on Ag/Pt(111) surfaces. The S/Au/Pt(111) and S/Ag/Pt(111) systems illustrate different extremes of the phenomena that can occur when sulfur is present on a bimetallic surface. The differences in the behavior of the S/Au/Pt(111) and S/Ag/Pt(111) surfaces arise from variations in the nature of the admetal T S and admetal T Pt interactions.

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Section: Introductionsupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Interaction of Sulfur with Au/Pt(111) and Ag/Pt(111) Surfaces: Photoemission Studies

Rodríguez

Kühn

1996

J. Phys. Chem.

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“…This migration, however, did not significantly affect the thermal desorption of Co from the surface. 7 The studies of CO adsorption on S/Co/Mo(l 10) and Co/S/ Mo(110) surfaces presented in this work are an attempt to understand the Co-S-Mo interaction using a model single-crystal system. In the experiments on S/Co/Mo( 110) surfaces, S appears to act almost entirely as a site blocker.…”

Section: Introductionmentioning

confidence: 99%

IRAS study of carbon monoxide adsorption on mixed cobalt and sulfur overlayers on molybdenum (110)

Kühn¹,

He²,

Goodman³

1994

J. Phys. Chem.

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Infrared reflection absorption spectroscopy (IRAS) was used to study the adsorption of carbon monoxide on mixed S and Co overlayers on a Mo(l10) surface. The results of this study indicate that there is a migration/ segregation of the adatoms into 2-D and 3-D islands and that the different domains are distinguishable by the stretching frequency of the adsorbed CO. Clean Mo(l10) as well as sulfided Co, (8x2)Co, p(2X2)S, and ~( 2 x 2 ) s domains on the Mo ( 110) surface are all observable. In addition, sulfur was seen to act as both a site blocker and electron-withdrawing agent on these surfaces. Finally, data obtained in this study suggest that the active adsorption site in a Co-MoS2 catalyst could be a Co-promoted M0-S site.

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The frontiers of surface structure analysis

Somorjai

1992

Surface & Interface Analysis

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Lowenergy electrons have been used predominantly to determine surface structure: low-energy electron difiaction (LEED) surface crystallography to identify the location of surface atoms and molecules, their site symmetry, bond distances and bond angles; and high-resolution electron energy-loss spectroscopy (HREELS) to determine the vibrational spectra of atoms and molecules at surfaces. The key findings of research using LEED and HREELS will be discussed. The new directions of research using these two techniques for studies of disordered surface layers and more complex molecules will be reviewed.Scanning tunneling microscopy (STM) and atomic force microscopy are new techniques under rapid development for surface structure determination. The combination of STM and LEED crystallography permits the quantitative validation of STM findings. Atomic spatial resolution uncovered several unexpected surface structures. The use of STM during high-pressure catalytic reactions is at the frontier of surface structure studies.Extended x-ray adsorption fine structure (EXAFS) and photoelectron difbaction have been used to study the atomic structure and coordination of clusters. Laser sum frequency generation (SFG) is employed to obtain vibrational spectra of molecules at solidJiquid and solid/solid interfaces. These techniques expand the frontiers of surface structure analysis to new types of surface and interface systems.

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Surface science studies of cobalt overlayers on clean and sulfur covered Mo(100) single crystal surfaces

Cited by 26 publications

References 27 publications

Interaction of Sulfur with Au/Pt(111) and Ag/Pt(111) Surfaces: Photoemission Studies

Interaction of Sulfur with Au/Pt(111) and Ag/Pt(111) Surfaces: Photoemission Studies

IRAS study of carbon monoxide adsorption on mixed cobalt and sulfur overlayers on molybdenum (110)

The frontiers of surface structure analysis

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