Controlling Ethylene Hydrogenation Reactivity on Pt sub(13) Clusters by Varying the Stoichiometry of the Amorphous Silica Support

Ethylene hydrogenation was investigated on size-selected Pt sub(13) clusters supported on three amorphous silica (a-SiO sub(2)) thin films with different stoichiometries. Activity measurements of the reaction at 300K revealed that on a silicon-rich and a stoichiometric film, Pt sub(13) exhibits a similar activity to that of Pt(111), in line with the known structure insensitivity of the reaction. On an oxygen-rich film, a threefold increased rate was measured. Pulsing ethylene at 400K, then measuring the activity at 300K, resulted in complete loss of activity on the silicon-rich surface compared to only marginal losses on the other surfaces. The measured reactivity trends correlate with charging characteristics of a Pt sub(13) cluster on the SiO sub(2) films, predicted through first-principle calculations. The results reveal that the stoichiometry-dependent charging by the support can be used to tune the selectivity of reaction pathways during a catalytic hydrogenation reaction.Original Abstract: Duenne Filme mit genau kontrollierter Zusammensetzung wurden als Katalysatortraeger eingesetzt und hinsichtlich ihres Einflusses auf die Reaktivitaet untersucht. Werden Cluster einer bestimmten Grose (Pt sub(13)) als Katalysator verwendet, so lassen sich individuelle Kenngrosen fuer jeden stochiometrisch einzigartigen Film mithilfe von Rechnungen ableiten. Es wird gezeigt, wie sich der Traeger auf eine Kohlenwasserstoff-Modellreaktion auswirkt.