AVS 52nd International Symposium
    Surface Science Monday Sessions
       Session SS1-MoM

Paper SS1-MoM8
Reactivity Studies of Molybdenum Carbide Nanoparticles formed on Au(111) using Reactive-Layer Assisted Deposition

Monday, October 31, 2005, 10:40 am, Room 202

Session: Catalytic Chemistry of Hydrocarbons
Presenter: D.V. Potapenko, BNL
Authors: D.V. Potapenko, BNL
J.M. Horn, BNL and SUNY at Stony Brook
M.G. White, BNL and SUNY at Stony Brook
Correspondent: Click to Email
The chemical properties of MoC@sub x@ nanoparticles prepared by a novel method on the Au(111) support have been studied using cyclohexene, cyclohexane and benzene as test molecules. The surfaces have been prepared by depositing Mo by physical vapor deposition (PVD) on a reactive layer of ethylene, which was physisorbed on a Au(111) substrate at low temperatures (85 K). STM imaging shows that the resulting MoC@sub x@ particles have a narrow size distribution and preferentially nucleate near the 'elbow' sites on the reconstructed (22 x @sr@3)-Au(111) surface. Auger and XPS indicate that the MoC@sub x@ particles are near stoichiometric (x = 1). Also we have found that in the thermodynamically stable state MoC@sub x@ particles are partially encapsulated by gold from the support. Thermal programmed desorption (TPD) studies have shown that cyclohexene undergoes three different reactions on bare (not encapsulated by Au) MoC@sub x@ nanoparticles: hydrogenation to cyclohexane, partial dehydrogenation with benzene formation, and complete dehydrogenation with surface carbon deposition. In contract, interaction of cyclohexene with Au-encapsulated MoC@sub x@ nanoparticles exhibits a very high (at least 95 %) selectivity toward partial dehydrogenation to benzene. The found selectivity is higher than that for cyclohexene reactions on either C/Mo(110) or Pt(111) surfaces. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences under contract No. DE-AC02-98CH10886.