AVS 51st International Symposium
    Surface Science Thursday Sessions
       Session SS1-ThM

Paper SS1-ThM10
Chemistry of Sulfur Compounds on Au(111)-Supported Mo Nanoparticles.

Thursday, November 18, 2004, 11:20 am, Room 210B

Session: Metal Oxide and Clusters III: Supported Cluster Formation and Reactivity
Presenter: D.V. Potapenko, Brookhaven National Laboratory
Authors: D.V. Potapenko, Brookhaven National Laboratory
J.M. Horn, BNL and SUNY at Stony Brook
M.G. White, BNL and SUNY at Stony Brook
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We are using the reconstructed (21 x @sr@3)-Au(111) surface as a template and inert support for depositing Mo nanoparticles for subsequent reactivity studies of desulfurization and the formation of Mo sulfide nanoparticles. Bulk molybdenum sulfide is the basis for commercial hydrodesulfurization (HDS) catalysts and this work is focused on exploring the modification of activity for nanostructured Mo and molybdenum sulfide on various supports. Nanoparticles of Mo were prepared on the Au(111) substrate by two methods: physical vapor deposition of Mo and chemical vapor deposition through the Mo(CO)@sub 6@ precursor. STM studies have shown that Mo nanoparticles are thermodynamically unstable on the Au(111) surface and that gold encapsulates Mo at temperatures > 300 K. It follows from TPD/AES experiments that bare Mo nanoparticles are very reactive: they cause complete dissociation of all the S-containing compounds tried and H@sub 2@ was the only major desorption product observed. Au-encapsulated Mo nanoparticles, on the other hand, are much less reactive. They do not chemically interact with thiophene (C@sub 4@H@sub 4@S). Surprisingly, Au-encapsulated Mo nanoparticles react with both H@sub 2@S and CH@sub 3@SH. The latter compound in this case dissociates only partially, causing S deposition and desorption of CH@sub 4@. We believe that interaction of X-SH compounds with Au-encapsulated Mo nanoparticles proceeds through intermediacy of surface gold thiolates.