Penn State Castleman Group

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Updated August 14, 2012


Guided Ion Beam Mass Spectrometry
Chris Harmon

It is our present goal to uncover possible noble metal and transition metal oxide species responsible for increased activity and selectivity toward the oxidation of CO and chemical feedstocks such as methanol. Catalytic reactivity is a nanoscale phenomenon in which a reactant molecule interacts with an active site existing on a surface. Gas-phase clusters can model the reactions taking place on the surface of heterogeneous catalysts without the complications of condensed-phase research. Gas-phase clusters may serve as models to probe catalytic reaction steps and to elucidate the electronic characteristics underlying the reactivity of bulk phase catalysts. From these studies, information useful in the design of new catalytic materials may be realized. Utilizing a guided ion beam mass spectrometer, the reactivity of mass selected ionic clusters may be investigated as a function of size, stoichiometry, and ionic charge state.

Naomi Schematic
Naomi Diagram

Radical oxygen centers have been found to be catalytically active for oxidation due to their elongated metal oxygen bond. We have studied a series of cationic zirconium oxide clusters and found those of the stoichiometry ZrxO2x+ (x = 1-4) exhibit enhanced oxidation of CO, C2H2 and C2H4. Further studies will be performed on the spectrum of anionic zirconium oxide clusters to examine the influence charge state has on catalytic activity of radical oxygen centers. Theoretical calculations have shown that other cationic metal oxide clusters contain radical oxygen centers as well. We plan to investigate the influence variation of the metal species has on selectivity and reaction rate. The catalytic active sites revealed through our gas-phase reactivity experiments may be incorporated into cluster assembled materials that will be highly active for industrially important oxidation reactions.

Catalytic Cycle