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
-Al
2O
3 catalyst support material. The results
obtained show that coordinatively unsaturated pentacoordinate
Al
3+ (Al
3+penta) centers present on the (100) facets of the
-Al
2O
3 surface are anchoring Pt. At low loadings, the active
catalytic phase is atomically dispersed on the support surface
(Pt/Al
3+penta = 1), whereas two-dimensional Pt rafts form at
higher coverages.
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.
* To whom correspondence should be addressed. E-mail: Kwak{at}pnl.gov (J.H.K.); chuck.peden{at}pnl.gov (C.H.F.P.); janos.szanyi{at}pnl.gov (J.S.)
