AVS 46th International Symposium
    Surface Science Division Monday Sessions
       Session SS2-MoA

Paper SS2-MoA3
Investigations of the Role of Edges on the Reaction Kinetics on Nanometer-sized Catalyst Particles using Monte Carlo Simulations

Monday, October 25, 1999, 2:40 pm, Room 607

Session: Reactions on Metals
Presenter: H. Persson, Chalmers University, Sweden
Authors: H. Persson, Chalmers University, Sweden
P. Thormahlen, Chalmers University, Sweden
V.P. Zhdanov, Boreskov Institute of Catalysis, Russia
B. Kasemo, Chalmers University, Sweden
Correspondent: Click to Email
From basic research on single crystals of catalytic materials, it is today well established that the rate of a catalytic reaction may vary considerably from one crystal face to another@footnote 1@ and that defect sites such as steps, kinks, surface vacancies, adatoms etc, may have different catalytic activities than the perfect terrace sites.@footnote 2@ In addition, there are (for supported catalysts) additional types of sites located at the particle-support boundary. It is therefore not surprising that a wide variety of behaviours of catalytic activity versus particle size have been observed,@footnote 3@ sometimes differing considerably from single crystals. The collective set of such differences and the challenge to understand and explain them is referred to as the "structure gap" in catalysis. This presentation will be focussed on Monte Carlo simulations of the kinetics of supported nm catalyst particles, being large enough to have attained bulk-electronic properties.@footnote 4,5,6,7@ The basic underlying mechanisms for the phenomena we will analyse are: (i) the different catalytic activities on different facets of a small supported crystalline particle become coupled in a strongly non-linear fashion due to diffusion occuring over facet boundaries, (ii) different kinetic rate constants at the facet boundaries of a supported particle compared to those for the perfect facets give rise to new kinetics, (iii) and spillover by diffusion of reactants, between the particle and its support, also create new kinetics. The main focus will be on how edges may affect the reaction kinetics. @FootnoteText@ @footnote 1@ R. Imbihl and G. Ertl, Chem. Rev. 95 (1995) 697. @footnote 2@ J.T. Yates, J. Vac. Sci. Technol. A 13 (1995) 1359. @footnote 3@ P.L.J. Gunter et al Catal. Rev. Sci. Eng. 39 (1997)77 @footnote 4@ V.P. Zhdanov, B. Kasemo, Surf. Sci. 405 (1998) 27. @footnote 5@ V.P. Zhdanov, B. Kasemo, Phys. Rev. Lett. 81 (1998) 2482. @footnote 6@ H. Persson et al., J. Vac. Sci. Techn. A (1999), in press. @footnote 7@ H. Persson et al, Catal. Today (1999), in press.