The adsorption of sulfur on Rh(111) and Cu/Rh(111) surfaces
- Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973 (United States)
The reaction of S{sub 2} with Rh(111) and Cu/Rh(111) surfaces has been investigated using synchrotron-based high-resolution photoemission, thermal desorption mass spectroscopy and {ital ab initio} self-consistent-field calculations. At 100 K, the adsorption of S{sub 2} on Rh(111) produces multilayers of S{sub n} species (n=2{endash}8) that desorb between 300 and 400 K, leaving a film of RhS{sub x} on the sample. S{sub 2} dissociates upon adsorption on clean Rh(111) at 300 K. An adsorption complex in which S{sub 2} is bridge bonded to two adjacent Rh atoms (Rh{endash}S{endash}S{endash}Rh) is probably the precursor state for the dissociation of the molecule. The larger the electron transfer from Rh(111) into the S{sub 2}(2{pi}{sub g}) orbitals, the bigger the adsorption energy of the molecule and the easier the cleavage of the S{endash}S bond. On Rh(111) at 300 K, chemisorbed S is bonded to two dissimilar adsorption sites (hollow and probably bridge) that show well separated S 2p binding energies and different bonding interactions. Adsorption on bridge sites is observed only at S coverages above 0.5 ML, and precedes the formation of RhS{sub x} films. The bonding of S to Rh(111) induces a substantial decrease in the density of d states that the metal exhibits near the Fermi level, but the electronic perturbations are not as large as those found for S/Pt(111) and S/Pd(111). Cu adatoms significantly enhance the rate of sulfidation of Rh(111) through indirect Cu{leftrightarrow}Rh{leftrightarrow}S{sub 2} and direct Cu{leftrightarrow}S{endash}S{leftrightarrow}Rh interactions. In the presence of Cu there is an increase in the thermal stability of sulfur on Rh(111). The adsorption of S{sub 2} on Cu/Rh(111) surfaces produces CuS{sub y} and RhS{sub x} species that exhibit a distinctive band structure and decompose at temperatures between 900 and 1100 K: CuS{sub y}/RhS{sub x}/Rh(111){r_arrow}S{sub 2}(gas) +Cu(gas)+S/Rh(111). {copyright} {ital 1998 American Institute of Physics.}
- OSTI ID:
- 573955
- Journal Information:
- Journal of Chemical Physics, Vol. 108, Issue 7; Other Information: PBD: Feb 1998
- Country of Publication:
- United States
- Language:
- English
Similar Records
H{sub 2}S adsorption on chromium, chromia, and gold/chromia surfaces: Photoemission studies
Reaction of H{sub 2}S with MgO(100) and Cu/MgO(100) surfaces: Band-gap size and chemical reactivity