Supporting Information

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1 Supporting Information Copyright Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2012 Design of a Highly Nanodispersed Pd MgO/SiO 2 Composite Catalyst with Multifunctional Activity for CH 4 Reforming Hyun You Kim, [b] Jung-Nam Park,* [a] Graeme Henkelman, [b] and Ji Man Kim [a] cssc_ _sm_miscellaneous_information.pdf

2 Table S1. The physical properties of studied catalysts Samples Metal loading contents [a] (wt%) Pd Mg Pd crystalline size [b] (nm) assynthesized after reaction BET surface area [c] (m 2 g -1 ) Pore volume [c] (cm 3 g -1 ) Pd/SiO 2 (Imp) Pd/SiO 2 (ME) Pd-MgO/SiO 2 (Imp) Pd-MgO/SiO 2 (ME) [a] Pd metal contents is analyzed by ICP method. [b] Pd crystalline size was calculated by Scherrer equation. [c] BET surface areas and Pore volume were calculated from the N 2 adsorption. 1

3 Table S2. Energy of the reaction of the initial reaction steps: CO 2 adsorption and CH 4 dissociation Reaction Energy of reaction (ev) CO 2 activation by MgO [a] CO 2 (gas) MgO-CO 2 * CH 4 adsorption and subsequent dissociation by Pd nanoparticle [b] CH 4 (gas) Pd-CH 4 * 0.41 Pd-CH * 4 Pd-CH * 3 + Pd-H * Pd-CH * 3 Pd-CH * 2 + Pd-H * Pd-CH * 2 Pd-CH * + Pd-H * Pd-CH * Pd-C * + Pd-H* [a] MgO strongly binds CO 2 and converts into MgO-CO * 2 carbonate [b] Pd nanoparticles completely dissociate CH 4 into Pd-C * and four Pd-H * 2

4 Quantity absorbed (m 2 /g) Pd/SiO 2 (ME) 2 ME Pd/SiO 2 (Imp) Pd/SiO Pd-MgO/SiO 2 IMP 2 (ME) Pd-MgO/SiO Pd-Mg/SiO 2 (Imp) ME Pd-Mg/SiO 2 IMP P/P 0 Figure S1. N 2 adsorption-desorption isotherms for as-synthesized catalysts. 3

5 Figure S2. XPS of Pd 3d 5/2 measured under identical conditions for Pd-MgO/SiO 2 catalysts. (a) As synthesized Pd-Mg/SiO 2 (ME), (b) as synthesized Pd-Mg/SiO 2 (Imp), (c) Pd-Mg/SiO 2 (ME) after reaction, (d) Pd-Mg/SiO 2 (Imp) after reaction. 4

6 Figure S3. Sinter resistance of catalysts synthesized with ME method. The SiO 2 shell prevents agglomeration of the Pd nanoparticles. TEM images of as-synthesized catalysts; (a) Pd/SiO 2 (ME), (b) Pd/SiO 2 (Imp). TEM images of catalysts exposed to CO 2 and CH 4 for 15 hours at 700 o C; (c) Pd/SiO 2 (ME), (d) Pd/SiO 2 (Imp). 5

7 Figure S4. Thermogravimetric (TG)/TPO analysis of studied catalysts. Catalysts were tested after 15 hours of reaction at 700 o C. The Mg loading of each catalyst was 3.6 wt%. 6

8 Figure S5. CO 2 Temperature programmed oxidation (TPO) analysis on studied catalysts. TPO was performed after CH 4 reforming at 700 o C for 15 hours, under temperature programmed oxidation in 50% O 2 in N 2. The amount of CO 2 produced is proportional to the amount of residual carbon on the catalyst surface after CH 4 reforming. Catalysts synthesized by ME method which encapsulated with SiO 2, show improved coke resistance. MgO improves coke resistance as well. The Mg loading of Pd- MgO/SiO 2 (Imp) and Pd-MgO/SiO 2 (ME) catalysts is 3.6 wt%. 7

9 Figure S6. Comparison of H 2 /Ar and CO/Ar production of MgO/SiO 2 (ME), Pd/SiO 2 (ME), and Pd-MgO/SiO 2 (ME) catalysts at low temperature region. All catalysts were synthesized with ME method. CO and H 2 production is highly related with the interplay between Pd and MgO. The Mg loading of each catalyst was 3.6 wt%. CH 4 conversion over Pd/SiO 2 (ME) and Pd-MgO/SiO 2 (ME) at 450 o C is 9.6 and 14.4%, respectively. 8

10 Figure S7. H 2 TPR profile of studied catalysts. The Mg loading of Pd-MgO/SiO 2 (Imp) and Pd-MgO/SiO 2 (ME) catalysts is 3.6 wt%. 9

11 Figure S8. CH 4 dissociation on the Pd(111) facet. Dissociated H atom from the prior step was not considered in the next step. CH 4 was complete dissociated on the Pt(111). We examined further catalytic pathways in the presence of C * and H * on the Pt(111) facet. 10

12 Figure S9. CO 2 -TPD profile of studied catalysts. Peaks at low temperature region confirm that MgO strongly binds CO 2. High temperature peak observed in Imp catalysts is due to the associative desorption of CO 2 from CO * and O *. [1] The Mg loading of Pd- MgO/SiO 2 (Imp) and Pd-MgO/SiO 2 (ME) catalysts is 3.6 wt%. 11

13 Figure S10. CO 2 adsorption and activation on MgO. Header number represents the corresponding reaction step presented in Figure 6a. Oxygen atom of the Mg-CO * 2 can be transferred to the Pd-C *. Step 4 and 5 show that the CO desorption from the catalyst is a two-step process; CO spillover from Pd to MgO and subsequent desorption from the MgO-CO *. 12

14 Figure S11. H 2 O adsorption and dissociation on Pd nanoparticle. Header number represents the corresponding reaction step presented in Figure 6b. H 2 O was dissociated into Pd-OH * and Pd-H *. Pd-OH * and Pd-C * were associated into Pd-COH *, which provides a low-energy pathway for the H 2 production. 13

15 Figure S12. Low-temperature CH 4 reforming activity over Pd-MgO/SiO 2 (ME) and Ni/SiO 2 (ME) catalyst. 14

16 Figure S13. Pd-MgO interface model for DFT calculations. To describe the transfer of reaction intermediates between Pd and MgO the Pd 24 linear nanoparticle which covered with two (111) faces was softly landed on the MgO(110) slab. 15

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