Repulsive interactions between Au and S on Mo(110) and Rh(111): An experimental and theoretical study

Journal Article · Thu Feb 29 04:00:00 EST 1996 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/jp952861d· OSTI ID:226740

Rodriguez, J A; Kuhn, M; Hrbek, J ^[1]

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1. Brookhaven National Lab., Upton, NY (United States)

The coadsorption of Au and S on Mo(110) and Rh(111) has been examined using thermal desorption mass spectroscopy, photoemission, and ab initio self-consistent-field calculations. On both surfaces, the interactions between Au and S are repulsive. S reduces the adsorption energy of Au. In some cases, the weakening of the Mo-Au and Rh-Au bonds is so large (5-7 kcal/mol) that the Au adatoms `ball up` on the surface instead of `wetting` the Mo(110) and Rh(111) substrates. The ab initio SCF calculations show that an S adatom modifies the chemical behavior of adjacent Mo and Rh sites by reducing their contribution to the density of states around the Fermi level of the system, weakening in this way their ability to form strong bonds with Au. In the Au/S/Mo(110) and Au/S/Rh(111) surfaces. Au and S compete for the electrons of the transition-metal substrate. Gold produces dramatic changes in the reaction pathways for the removal of sulfur from the Mo and Rh surfaces. In the Au/S/Rh(111) system, S{sub 2} desorbs at much lower temperatures (100-250 K) than in S/Rh(111). For Au/S/Mo(110), the presence of Au favors desorption of S{sub 2} instead of migration of S into the bulk of Mo. These results are consistent with a model in which Au compresses the S overlayer into islands of high local coverage, reducing in this way its stability and favoring the `pairing` of sulfur atoms and desorption of S{sub 2}. 52 refs., 15 figs., 1 tab.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 226740
• Journal Information: Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 9 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
36 MATERIALS SCIENCE
40 CHEMISTRY
ADSORPTION
BIMETALS
CATALYSIS
CATALYSTS
CHEMICAL REACTIONS
DESORPTION
GOLD
MASS SPECTRA
MOLYBDENUM
PHOTOEMISSION
RHODIUM
SULFUR