Reaction of S{sub 2} with NM/Mo(110) (NM = Cu or Ag) surfaces. Poisoning of bimetallic bonding and noble-metal-promoted sulfidation of Mo
- Brookhaven National Lab., Upton, NY (United States)
TDS, XPS, and XAES were used to examine the reaction of S{sub 2} gas with NMn/Mo(110) (NM = Cu or Ag). On these surfaces S{sub 2} dissociates into atomic S at 300 K. At submonolayer coverages ({theta}{sub s} + {theta}{sub NM} < 1 ML), S and Cu or Ag do not react to form noble-metal sulfides on top of Mo(110). Instead, the S and noble-metal adatoms compete for making bonds with the Mo(110) substrate. On the average, each S adatom diminishes the ability for bimetallic bonding of a minimum of three Mo surface atoms. At 0.4 < {theta}{sub s} < 0.8 ML, the weakening of the Mo-Cu and Mo-Ag bonds is very significant (>5 kcal/mol), and the noble-metal adatoms form 3D clusters on the Mo(110) surface. The exposure of NM/Mo(110) surfaces to large amounts of S{sub 2} gas ({theta}{sub s} > 1 ML) at 300 K produces noble-metal sulfides (CuS{sub x} or AgS{sub y}) and chemisorbed sulfur, without forming molybdenum sulfides. The sulfidation of molybdenum occurs after exposing NM/Mo(110) surfaces to S{sub 2} at 600-700 K. Cu and Ag promote (or catalyze) the formation of molybdenum sulfides. By comparing the results for the S{sub 2}/NM/Mo(110) systems with those reported for S{sub 2}/NM/Pt(111) systems, it is found that the `promotional effect` of a noble metal on the rate of sulfidation of a transition metal depends on three factors. 44 refs., 12 figs.
- Research Organization:
- Brookhaven National Laboratory (BNL), Upton, NY
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 70358
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 23 Vol. 99; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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