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Title: Probing the influence of bimetallic composition on the Pd/Au catalysed synthesis of vinyl acetate monomer
Author: Haire, Andrew Richard
ISNI:       0000 0004 2719 2372
Awarding Body: University of St Andrews
Current Institution: University of St Andrews
Date of Award: 2010
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Scanning Tunnelling Microscopy (STM) was utilised together with the high resolution depth-profiling capabilities of Medium Energy Ion Scattering (MEIS), a technique traditionally associated with single crystal substrates, to probe the mean size and depth dependent composition profile of bimetallic PdAu nanoparticles on planar oxide surfaces as functions of the starting composition and annealing temperature. In order to fit composition profiles to experimental MEIS data, a new analysis tool has been designed that models the particles as flat-topped structures with a hexagonal base which can be divided into a number of shells, each shell corresponding to a particular ion pathlength inside the material. The reliability of this method will be discussed in detail. Fitting results show that the surface layers are always significantly enriched in Au compared to the bulk alloy composition. By comparing MEIS data for clean surfaces data for modified surfaces it was found that Pd generally segregates towards the particle surface on adsorption of acetic acid. The interaction of potassium acetate with Au/Pd{111} alloy surfaces of varying composition has been investigated using Temperature Programmed Desorption (TPD) and Reflection Absorption Infra Red Spectroscopy (RAIRS). At lower coverage, potassium acetate reacts reversibly with the surface to form CO and carbonate. Formation of surface acetate is observed on Pd-rich surfaces only. At higher coverage, acetate is the major surface species formed on all samples examined.
Supervisor: Baddeley, C. J. Sponsor: Engineering and Physical Sciences Research Council ; BP Chemicals Ltd
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Vinyl acetate ; MEIS ; Nanoparticles ; Pd/Au alloy ; TP1180.V48H2 ; Vinyl acetate--Synthesis ; Metal catalysts ; Surfaces (Technology)--Analysis ; Palladium alloys ; Gold alloys ; Nanoparticles