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Free keywords:
Catalysis; Surface diffusion; Palladium; Carbon monoxide; Oxidation
Abstract:
Employing molecular beam methods, we have studied the angular distribution of products desorbing from oxide-supported Pd nanoparticles during catalytic oxidation of CO. A large range of particle sizes was covered by combining preparation techniques based on (1) metal evaporation and growth and (2) electron beam lithography. Whereas the CO2 distribution is symmetric and independent of the reaction conditions on small Pd aggregates, a strong influence of the reactant incidence angles and fluxes was observed for large particles. For the first time, these observations experimentally verify the existence of local reaction rate variations on a catalyst nanoparticle as a consequence of limited adsorbate mobility. Furthermore, the results allow us to extract in situ information about surface diffusion rates.
