Surface Science Models of Heterogeneous Catalysts

The development of new heterogeneous catalysts is aided by the fundamental understanding of how reactant molecules, intermediates and products interact with the catalyst surface. Achieving such a level of understanding by investigating highly complex supported metal catalysts is extremely difficult. The application of surface analytical techniques can effectively address this question. However there is a limit to the relevance of data acquired under UHV conditions on single crystal surfaces. My research seeks to use the high resolution capabilities of surface analytical techniques to investigate well defined model catalyst surfaces; concentrating on the development of in situ probes (STM and PM-RAIRS) and the use of more realistic model surfaces.

Chirally Modified Surfaces

Much recent research has been aimed at the development of heterogeneous catalytic processes for the production of chiral molecules. This potentially offers a much cheaper route to important pharmaceutical products than the current processes that are catalysed by enzymes or homogeneous routes. One of the factors which has prevented the diversification of the current limited range of enantioselective heterogeneous reactions is the lack of a molecular level understanding of the mechanism of the surface reaction. My research focuses on the investigation of the chiral modification of supported Ni catalysts by a-hydroxy acids (e.g. R,R-tartaric acid, Figure 1) and a-amino acids. Such catalysts are known to achieve asymmetric hydrogenation of b-keto esters. In addition, we investigate the interaction of typical pro-chiral reagents such as methylacetoacetate (MAA) with chirally modified surfaces (Figure 2).

We are building facilities for STM/AFM and PM-RAIRS measurements at the liquid solid interface to investigate effects such as pH and the nature of the solvent on the chiral modification of metal surfaces. In addition, the predictions made from these investigations as to the mechanism of enantioselective promotion will be tested by carrying out catalytic measurements on well-defined model catalysts in a high pressure cell attached to our UHV system.

The Structure and Chemistry of Bimetallic Surfaces

Often bimetallic catalysts are more active and/or selective than their monometallic counterparts. My research concentrates on using surface analysis to understand how to optimise the composition and structure of bimetallic catalysts.

We have used STM, Medium Energy Ion Scattering (CLRC Daresbury Laboratory (http://www.dl.ac.uk/MEIS)), RAIRS and TPD to investigate the structure, composition and surface chemistry of ultra-thin surface alloy films grown on metal substrates. In particular, we are interested in quantifying the phenomenon of adsorbate induced segregation and to utilise this phenomenon to design novel enantioselective catalysts – for example by colloidal preparative routes (e.g. Figure 3).

Creating More Realistic Models of Heterogeneous Catalysts

Single crystal metal surfaces are good models of the crystalline facets of metal nanoparticles, but fail to model adequately the properties of the edges and corners of such particles thought to play important roles in heterogeneous catalysis. In addition, understanding the interaction between the metal nanoparticle and the support may be crucial in explaining catalytic behaviour. For example, using MAC-mode AFM, we have investigated the growth of metal nanoparticles (and their subsequent chiral modification) on planar oxide supports (Figure 4).

Current Group Members:

Dr Samson Patole (EPSRC PDRA – joint with Professor Neville Richardson)

Dr Johan Gustafson (Knut and Alice Wallenberg Foundation Fellow)

Aoife Trant (PhD student)

Andrew Haire (PhD student)

Sean Jensen (PhD student)

Financial Support:

EPSRC (GR/N01514; GR/R16198; GR/S86402; GR/T18585, EP/E047580/1)

EPSRC (Basic Technology)

BP Chemicals

SASOL

Selected Publications

Thermal treatment of glutamic acid modified Ni nanoclusters on Au{111} leads to the formation of 1-D metal organic co-ordination networks

AG Trant, TE Jones and CJ Baddeley;

Journal of Physical Chemistry C (in press)

The influence of modification pH and temperature on the interaction of methylacetoacetate with (S)-glutamic acid modified Ni{111}

TE Jones, AE Rekatas and CJ Baddeley

Journal of Physical Chemistry C 111 (2007) 5500

The effects of gold and co-adsorbed carbon on the adsorption and thermal decomposition of acetic acid on Pd{111}

TG Owens, TE Jones, TCQ Noakes, P Bailey and CJ Baddeley

Journal of Physical Chemistry B 110 (2006) 21152

Investigating the Mechanism of Chiral Surface Reactions: The Interaction of Methylacetoacetate with (S)-Glutamic Acid Modified Ni{111}

TE Jones and CJ Baddeley

Langmuir 22 (2006) 142

The growth of ultrathin Au films on Ni{1 1 1}: A study with medium energy ion scattering

TE Jones, TCQ Noakes, P Bailey and CJ Baddeley

Surface Science 600 (2006) 2129

Molecular ordering and adsorbate induced faceting in the Ag{110}-(S)-glutamic acid system

TE Jones, CJ Baddeley, A Gerbi, L Savio, M Rocca and L Vattuone

Langmuir; 21 (2005) 9468