Monday, September 28, 2009

Science, v325

Some nice 27Al SSNMR spectra can be seen here:

Science, v325, page 1670

Coordinatively Unsaturated Al3+ Centers as Binding Sites for Active Catalyst Phases of Platinum on -Al2O3

Ja Hun Kwak,1,* Jianzhi Hu,1 Donghai Mei,1 Cheol-Woo Yi,2 Do Heui Kim,1 Charles H. F. Peden,1,* Lawrence F. Allard,3 Janos Szanyi1,*

In many heterogeneous catalysts, the interaction of metal particles with their oxide support can alter the electronic properties of the metal and can play a critical role in determining particle morphology and maintaining dispersion. We used a combination of ultrahigh magnetic field, solid-state magic-angle spinning nuclear magnetic resonance spectroscopy, and high-angle annular dark-field scanning transmission electron microscopy coupled with density functional theory calculations to reveal the nature of anchoring sites of a catalytically active phase of platinum on the surface of a -Al2O3 catalyst support material. The results obtained show that coordinatively unsaturated pentacoordinate Al3+ (Al3+penta) centers present on the (100) facets of the -Al2O3 surface are anchoring Pt. At low loadings, the active catalytic phase is atomically dispersed on the support surface (Pt/Al3+penta = 1), whereas two-dimensional Pt rafts form at higher coverages.
1 Institute for Interfacial Catalysis, Pacific Northwest National Laboratory, Post Office Box 999, MSIN K8-87, Richland, WA 99352, USA.2 Department of Chemistry and Institute of Basic Science, Sungshin Women’s University, Seoul 136-742, Repulic of Korea.3 Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.

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