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

Paper SS2-TuM7
Flow Reactor Studies of Nanofabricated Model Catalysts; Activity and Reconstruction

Tuesday, October 26, 1999, 10:20 am, Room 607

Session: Model Catalysts
Presenter: S. Johansson, Chalmers University of Technology, Sweden
Authors: S. Johansson, Chalmers University of Technology, Sweden
E. Fridell, Chalmers University of Technology, Sweden
B. Kasemo, Chalmers University of Technology, Sweden
Correspondent: Click to Email
Nanofabrication of model catalysts using the electron-beam lithography technique offers a way to produce geometrically well-defined model catalysts. Component interaction, particle separation and particle size (in the 10 nm range) can be controlled. Multi-layer structures can be obtained by repeating the fabrication-process. Furthermore, re-structuring can be accomplished by heat treatment afterwards in different gas mixtures. These nanofabricated catalysts are well suited to study, e.g., spillover effects in catalytic systems. A micro-reactor for catalytic evaluation of these nanofabricated model catalysts has been designed. It operates at atmospheric pressure and allows samples with a small total active surface area (below 1 mm@super 2@). This implies small gas-flows in the order of approx. 1-10 mm@super 3@/s. The small active surface-area comes from a limitation in the electron-beam lithography process to make large numbers of small structures in a reasonable time, due to the serial processing. The minimum Pt-surface-area needed for catalytic activity evaluation has not yet been determined for this system. Differences in the CO-reaction rate in the kinetically controlled region is measured as a function of interaction length between Pt and CeO@sub x@, where the total surface area of Pt has been kept constant. Morphology changes of nanofabricated Pt-discs with diameters up to 700 nm has been studied. Structural changes occur in reactant mixtures, e.g., CO+O@sub 2@ in Ar, at elevated temperatures (500°C). Disintegration of the larger Pt-discs into several smaller crystalline Pt-particles is observed.