O2 plasma activation of dendrimer-derived Pt/γ-Al2O3 catalysts

Platinum particles, approximately 1.6 nm in size, were formed on γ-Al2O3 following impregnation with a Pt40-dendrimer precursor solution. These Pt particles are not catalytically active, since they are covered by the dendrimer component. Treatment in O2 plasma at room temperature removes the dendrimer without affecting metal dispersion. Subsequent treatment in H2 at 300 °C leads to partial aggregation of Pt, although the degree of such aggregation is relatively small, as the average size of the Pt particles remains approximately 2 nm. In contrast, when a high temperature oxidation/reduction treatment is used to activate the Pt40-dendrimer/γ-Al2O3 material, sintering of Pt is observed and the average Pt particle size increases to approximately 4 nm. Kinetic data obtained with Pt/γ-Al2O3 catalysts activated under both protocols for the structure-insensitive CO oxidation and the structure-sensitive ethane hydrogenolysis reactions underline the differences in the sizes of the Pt particles in these materials, consistent with previous literature reports.