AVS 46th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS2-TuM

Paper SS2-TuM10
Improved Catalytic Activity and Selectivity by Photon Irradiation

Tuesday, October 26, 1999, 11:20 am, Room 607

Session: Model Catalysts
Presenter: B. Kasemo, Chalmers University of Technology and University of Göteborg, Sweden
Authors: D. Chakarov, Chalmers University of Technology and University of Göteborg, Sweden
S. Ljungström, Competence Centre for Catalysis, Sweden
J. Bergeld, Chalmers University of Technology and University of Göteborg, Sweden
D. Ingert, Chalmers University of Technology and University of Göteborg, Sweden
V.P. Zhdanov, Chalmers University of Technology and University of Göteborg, Sweden
B. Kasemo, Chalmers University of Technology and University of Göteborg, Sweden
Correspondent: Click to Email
Photo-catalysis is the enhancement of a chemical reaction by combined action of a catalyst and photons, on the reaction rate and/or selectivity. In heterogeneous photo-catalysis, the reaction occurs on a solid surface, with the reactants in gaseous or fluid state. The photons usually excite hot (photo) electrons that by transient attachment to one of the reactants enhance the reaction. In the present work, we explore the possibilities to increase the efficiency of catalytic emission cleaning by photo-catalysis. The approach includes both experimental and theoretical studies of the different parameters that may influence the photo-catalytic reactions, such as catalyst composition and wavelength dependence. The experiments are performed with conventional noble metal car exhaust catalysts at atmospheric pressure, nanofabricated model catalyst, and extended single crystals at UHV. Theoretical treatment includes studies of hot electron excitation-transport-attachment processes and Monte Carlo simulation. We present results concerning the reaction kinetics and light-off behavior for different CO + O2 and CO + NO mixtures on different catalysts. The main observations to date are: The light-off temperature can be reduced substantially (by up to 80 degrees) by photon irradiation at 365 nm. The single photon, non-thermal origin of this photocatalytic effect is confirmed by power- and wavelength- dependence measurements. The different characteristics of the photocatalysis on supported platinum, compared to single crystal Pt (111) in UHV, are discussed in terms of case specific adsorbate coverages, hot electron excitation, and reaction mechanisms.