Seminars Archive

Fast X-ray photoelectron spectroscopy as an in-situ surface reaction probe

Abstract



Wednesday, July 10, 2002, 14:30


Seminar Room, ground floor, Building "T"



Sincrotrone Trieste, Basovizza




Fast X-ray photoelectron spectroscopy as an in-situ surface reaction probe










Adam F. Lee



(Department of Chemistry, University of Hull, UK)

ABSTRACT

Despite their immense socio-economic importance the discovery and optimisation
of new heterogeneous catalysts remains surprisingly inefficient. By studying
reactions on well-defined, single crystal surfaces, in conjunction with measurements
on the corresponding practical dispersed catalysts it is possible to obtain
fundamental insight into reaction mechanisms and to develop predictive capabilities.
However in order to further the rational design of catalytically active materials,
new in situ analytical techniques are required.

Here the application of time-resolved, Fast XPS as a chemically specific,
quantitative probe of reacting adsorbates over catalytically-active surfaces
is discussed. In alkyne coupling chemistry the threshold temperature and activation
barrier for ethyne cyclotrimerisation over Pd{111} have been determined. Coverage-dependent
configurational changes between the flat-lying and tilted benzene product
have also been followed by Fast XPS and NEXAFS. Coadsorbed NO suppresses
carbon deposition from hydrogenolysis side reactions and simultaneously accelerates
product desorption. Recent Fast XPS measurements examining sulphate-promoted
C3H6 combustion over Pt{111} are also reported, and evidence for a surface
alkyl-sulphate complex is presented.