MEIS investigations of adsorbate induced segregation at the bimetallic surfaces of single crystal alloys and supported nanoparticles
Lead Research Organisation:
University of St Andrews
Department Name: Chemistry
Abstract
Heterogeneously catalysed reactions using bimetallic catalysts are widespread and responsible for the production of large quantities of high value industrial chemicals. One example is the synthesis of vinyl acetate monomer (VAM) from the reaction of ethylene and acetic acid over supported Pd/Au catalysts. The promoting role of Au in this reaction has been investigated by a number of research groups worldwide in recent years. It has been proposed that the VAM forming reaction is extremely sensitive to the surface composition and the local atomic arrangement at the bimetallic surface. We have established that medium energy ion scattering (MEIS), unlike most other surface analytical techniques, is capable of quantifying the surface composition even under the influence of the adsorbate. We have recently used MEIS to show that the surface composition of Pd/Au surfaces is itself influenced by the adsorption of acetic acid. This phenomenon of adsorbate induced segregation has been largely ignored in previous studies of bimetallic catalysts despite the fact that such effects are predicted on thermodynamic grounds. In this project, we will use MEIS to quantify the temperature, composition and crystal face dependence of adsorbate induced segregation at single crystal PdAu surfaces. Furthermore, we will increase the relevance of our model systems by using MEIS to characterise alloying, sintering and adsorbate induced segregation at bimetallic Pd/Au nanoparticles grown on a planar oxide surface. We will utilise scanning tunnelling microscopy, reflection absorption infrared spectroscopy and temperature programmed desorption to provide complementary information on the size, shape and adsorption properties of the bimetallic nanoparticles.
Organisations
Publications
Gustafson J
(2011)
Depth-profiling the composition of bimetallic nanoparticles using medium energy ion scattering
in Surface Science
Haire A
(2011)
Influence of preparation conditions on the depth-dependent composition of AuPd nanoparticles grown on planar oxide surfaces
in Surface Science
Murdoch A
(2013)
Alloy formation in the Co/Pd{111} system - A study with medium energy ion scattering and scanning tunnelling microscopy
in Surface Science
Murdoch A
(2016)
The influence of CO adsorption on the surface composition of cobalt/palladium alloys
in Surface Science
Trant A
(2010)
Surface Chemistry Underpinning Enantioselective Heterogeneous Catalysis: Supramolecular Self-Assembly of Chiral Modifiers and Pro-Chiral Reagents on Ni{111}
in The Journal of Physical Chemistry C
Trant A
(2009)
Alloy formation in the Au{111}/Ni system - An investigation with scanning tunnelling microscopy and medium energy ion scattering
in Surface Science
Trant A
(2010)
Adsorption of (S)-glutamic acid induces segregation of Ni at bimetallic Au/Ni surfaces
in Surface Science
Trant AG
(2011)
Chiral recognition at one-dimensional metal-organic coordination networks initiates the ordering of prochiral catalytic reagent methylacetoacetate on Au{111}.
in Langmuir : the ACS journal of surfaces and colloids
Wilson K
(2011)
Interaction of the Pro-Chiral Molecule, Methylacetoacetate, with ( S )-Aspartic Acid Modified Ni{111}
in The Journal of Physical Chemistry C
Description | Many catalysts consist of metal or bimetallic nanoparticles dispersed on high surface area oxide supports. In order to understand the catalytic behaviour of bimetallic nanoparticles, we need a clear idea of the surface composition of the particles which is often different to the bulk. In addition, we would like to know how the surface composition is influenced by the gas phase. We developed a method using medium energy ion scattering to characterise the depth dependent composition of bimetallic nanoparticles even in the presence of an adsorbed molecular layer. |
Exploitation Route | bimetallic particles are used widely in catalysis and fuel cells. This method could be used to examine the composition of a range of bimetallic particles in each of these fields. |
Sectors | Environment |
Description | published the method for data analysis. The closing of the STFC MEIS facility has limited any follow up in the UK, but other groups worldwide are using similar approaches to analyse nanoparticles. |
First Year Of Impact | 2009 |