Supporting Online Material for

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1 Supporting Online Material for Coordinatively Unsaturated Al 3+ Centers as Binding Sites for Active Catalyst Phases of Platinum on γ-al 2 O 3 Ja Hun Kwak,* Jianzhi Hu, Donghai Mei, Cheol-Woo Yi, Do Heui Kim, Charles H. F. Peden,* Lawrence F. Allard, Janos Szanyi* *To whom correspondence should be addressed. Kwak@pnl.gov (J.H.K.); chuck.peden@pnl.gov (C.H.F.P.); janos.szanyi@pnl.gov (J.S.) This PDF file includes: Materials and Methods SOM Text Fig. S1 References Published 25 September 2009, Science 325, 1670 (2009) DOI: /science

2 SUPPORTING ONLINE MATERIAL I. Materials and Experimental Methods: 1. Catalyst preparation: All catalysts were prepared by a conventional incipient wetness method using aqueous Pt(NH 3 ) 4 (NO 3 ) 2 solutions. After loading the support materials, γ-al 2 O 3 (Condea, 200 m 2 /g) and α-al 2 O 3 (Alfa Aesar, ~5 m 2 /g), with Pt to the desired level, the samples were dried at 393K overnight and then calcined at 573 K in dry air Al MAS NMR measurements: 27 Al MAS NMR measurements were performed at room temperature on a Varian-Inova MHz NMR spectrometer, operating at a magnetic field of 21.1 T. The corresponding 27 Al Larmor frequency is MHz. This instrument is located in the Environmental Molecular Sciences Laboratory at Pacific Northwest National Laboratory. All spectra were acquired at sample spinning rates of either 18 or 23 khz (± 5 Hz). A single pulse sequence with a pulse angle of ~77 was used, corresponding to a pulse width of 3 μs. Each spectrum was acquired using a total of 512 scans with a recycle delay time of 1 s and an acquisition time of 66 ms. All the spectra are externally referenced to 1.0 M aqueous Al(NO 3 ) 3 (0ppm). The advantages of both enhanced spectral resolution and sensitivity for acquiring 27 Al MAS NMR at ultrahigh field (21.1T) have been extensively discussed previously (Ref. 11 and S1). 3. HR-STEM measurements: Aberration-corrected high-angle annular dark-field (HA- ADF) images were obtained at the High Temperature Materials Laboratory located at Oak Ridge National Laboratory, using a JEOL 2200 FEF aberration-corrected STEM. 4. Pt XANES measurements: The Pt XANES measurements were carried out at beamline 18A at the National Synchrotron Light Source located at Brookhaven National Laboratory. II. DFT Calculations: The γ-al 2 O 3 support was represented by the (100) orientation where surface penta-coordinate Al 3+ sites were exposed. A 2 1 supercell of the γ-al 2 O 3 (100) surface model with eight atomic layers was used in the calculations. The model surface slab (11.16 Å 8.41 Å 8.37 Å) was symmetrical to avoid unphysical dipole-dipole interactions between the neighboring slabs. A height of 15 Å in the z direction was used to separate the surface slab and its images. We examined different 1

3 Pt x O y (PtO, α-pto 2, β-pto 2 and Pt 3 O 4 ) monolayer structures which were taken from the corresponding optimized Pt x O y bulk. The structure shown in Fig. 5 is the most stable structure of PtO layer on the γ-al 2 O 3 (100) surface. Periodic DFT slab calculations were performed using the Vienna ab-initio simulation package (VASP) (S2). The core and valence electrons were represented by the projector augmented wave (PAW) method and plane wave functions with a kinetic energy cutoff of 400 ev (S3). The generalized gradient approximation (GGA) combined with the Perdew-Burke-Ernzerhof (PBE) functional (S4) was used in the calculations. Ground-state atomic geometries were obtained by minimizing the forces on each atom to below 0.05 ev/å. For the Pt x O y /γ-al 2 O 3 (100) systems, all atoms of the Pt x O y layer and the top four atomic layers were allowed to relax while other atoms in the model surface slabs were fixed during optimization. After testing different k-point grid schedules along with the system size, a Monkhorst Pack grid of size of was used to sample the surface Brilliouin zone to assure accuracy. Further details of DFT calculations can be found in our previous publications (S5). 2

4 Figures: Figure S1: Pt L III XANES spectra for 10% Pt/γ-Al 2 O 3 and 1% Pt/γ-Al 2 O 3 after calcination at 573K. 3

5 References: S1. J. H. Kwak, J. Hu, A. Lukaski, D. H. Kim, J. Szanyi and C. H. F. Peden, J. Phys. Chem. C 112, 9486 (2008). S2. G. Kresse and J. Furthmuller, Phys. Rev. B 54, (1996); G. Kresse and J. Furthmuller, Comput. Mater. Sci. 6, 15 (1996); G. Kresse and J. Hafner, Phys. Rev. B 49, (1994). S3. P. E. Blochl, Phys. Rev. B 50, (1994); G. Kresse and D. Joubert, Phys. Rev. B 59, 1758 (1999). S4. J. P. Perdew, K. Burke and M. Ernzerhof, Phys. Rev. Lett. 77, 3865 (1996). S5. D. Mei, Q. Ge, J. H. Kwak, D. H. Kim, J. Szanyi and C. H. F. Peden, J. Phys. Chem. C, 112, (2008); J. H. Kwak, D. Mei, C. W. Yi, D. H. Kim, C. H. F. Peden, L. Allard and J. Szanyi, J. Catal. 261, 17 (2009). 4