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.