Supporting Information

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1 Supporting Information High Performance Au Pd Supported on 3D Hybrid Strontium-Substituted Lanthanum Manganite Perovskite Catalyst for Methane Combustion Yuan Wang, Hamidreza Arandiyan, * Jason Scott, * Mandana Akia, Hongxing Dai, * Jiguang Deng, Kondo-Francois Aguey-Zinsou and Rose Amal Yuan Wang, Dr. Hamidreza Arandiyan, Dr. Jason Scott, Prof. Rose Amal Particles and Catalysis Research Group, School of Chemical Engineering, The University of New South Wales, Sydney, NSW 2052, Australia * address: h.arandiyan@unsw.edu.au * address: jason.scott@unsw.edu.au Prof. Kondo-Francois Aguey-Zinsou MERL in Group, School of Chemical Engineering, The University of New South Wales, Sydney, NSW 2052, Australia Dr. Mandana Akia Mechanical Engineering Department, University of Texas-Rio Grande Valley, 1201 West University Drive, Edinburg, TX 78539, USA. Prof. Hongxing Dai, Dr. Jiguang Deng, Beijing Key Laboratory for Green Catalysis and Separation, and Laboratory of Catalysis Chemistry and Nanoscience, Beijing University of Technology, Beijing , China * address: hxdai@bjut.edu.cn S-1

2 Contents Item Page Experimental section S-3 Figure S1 S-3 Scheme S1 S-4 Figure S2 S-5 Figure S3 S-9 Figure S4 S-10 Figure S5 S-11 Figure S6 S-12 Figure S7 S-13 Figure S8 S-14 Figure S9 S-15 Figure S10 S-16 Figure S11 S-16 Figure S12 S-17 Figure S13 S-18 Figure S14 S-19 Figure S15 S-20 Figure S16 S-21 Figure S17 S-21 Figure S18 S-22 Figure S19 Table S1 Table S2 S-23 S-24 S-25 S-2

3 1. EXPERIMENTAL SECTION 1.1 Synthesis of PMMA microsphere Well-arrayed monodispersed polymethyl methacrylate (PMMA) microspheres were prepared using a modified emulsifier-free emulsion polymerization technique with water-oil biphase double initiators ml distilled water was added in a three-necked round-bottomed flask (2000 ml) and placed in 70 ºC water bath, stirring for 30 min to reach thermal equilibrium. Methyl methacrylate (MMA, 115 ml), as monomer, was added to the water and N 2 (Flow rate = 50 ml/min) was introduced to the system for 2 h. In a separate polyethylene bottle, 0.40 g of potassium persulfate was dissolved into 50 ml of water and added to the flask. Under a constant stirring rate (1100 r/min) and the protection of N 2, the mixture was kept at 70 ºC for min. At the end of the reaction period, the flask was immediately placed in an ice bath to stop the reaction. The obtained PMMA suspension was centrifuged and dissolved in 3000 ml distilled water to remove the K and S ions, with the homogeneous latex with nearly monodispersed PMMA microspheres then obtained by moisture removal in an 80 ºC water bath. In the present study, the average diameter of the obtained microspheres was 210 nm which was estimated using the Zetasizer Nano Z system and SEM image (Figure S1). (A) (B) Figure S1. (A) SEM image of PMMA and (B) size distribution of PMMA microspheres. S-3

4 Scheme S1. Schematic illustration of the preparation of bimetallic AuPd/3DOM LSMO catalysts; (a) PMMA hard template, (b) 3DOM LSMO and (c) 1Pd/3DOM LSMO. 1.2 Synthesis of 3DOM LSMO catalysts Well-arrayed colloidal crystal template PMMA microspheres with an average diameter of ca. 200 nm were synthesized according to the procedures described in our previous work 1. 3DOM LSMO catalysts were prepared by a L-lysine-assisted PMMA hard-templating method adopting nitrates of La, Sr and Mn as the metal source. The typical procedure is as follows: desired amounts of La(NO 3 ) 3 6H 2 O, Sr(NO 3 ) 2 and Mn(NO 3 ) 2 (50%) were dissolved in a 7 ml distilled water: 3mL ethylene glycol: 3mL methanol solution at room temperature (RT). After stirring for 4h to obtain a transparent solution, ca g of the PMMA colloidal crystal template was added to the precursor solution and impregnated for 4 h. After filtering and drying at RT for 24 h, the obtained solid was first calcined in an N 2 flow (90 ml/min) at a ramp rate of 1 C/min from RT to 300 C, kept for 3 h, cooled to RT, and then further calcined in an air flow (90 ml/min) at the same heating rate from RT to 750 C where it was maintained at this temperature for 4 h. For comparison purposes, a onedimensionally disordered nonporous (1DDN) LSMO was prepared using a citrate method descried elsewhere 2. In a typical process, lanthanum, strontium and manganese nitrate and citric acid with S-4

5 molar ratio of 1 were dissolved in distilled water and stirred 2 h for full mixing. Then the mixture was dried at 80 C for 12 h. The obtained powder was calcined at 750 C for 4 h. 1.3 Synthesis of bimetallic z wt% Au x Pd y /3DOM LSMO Scheme S1 illustrates the preparation process of bimetallic AuPd/3DOM LSMO catalysts. The zau x Pd y /1DDN LSMO (molar ratio Au/Pd: x:y=1:1, 1:2, 1:3, z=1 wt%) and zau x Pd y /3DOM LSMO (z=1, 2 and 3 wt%, molar ratio Au/Pd: x:y=1:2) catalysts were synthesized by modifying the method in reference 3. The method, known as the gas-bubble-assisted reduction process, involves the reduction of a dual noble metal chloride solution under N 2 gas, using poly(vinyl)alcohol (PVA) as a capping agent. Figure S2. Synthesis process of zau x Pd y /3DOM LSMO (z=1, 2 and 3 wt%, molar ratio Au/Pd: x:y=1:2) samples. To prepare Au-Pd bimetallic catalysts, 1 g of 3DOM (or 1DDN) LSMO was added into a certain volume of 4 g/l metal precursor solution containing both HAuCl 4 and Na 2 PdCl 4 with desired Au S-5

6 and Pd loadings. A desired amount of PVA (Au: PVA mass ratio=1:1.5) was added into the solution and stirred for 20 min. After replacing the stirring system with the N 2 bubble system, a 0.1 M NaBH 4 aqueous solution (Au: NaBH 4 molar ratio=1:5) was introduced to the solution to form a brown suspension. The bubbling was maintained for 8 h so all the metal particles could be loaded onto the perovskite carrier, as indicated by a colorless filtrate. The Au-Pd bimetallic catalysts were then recovered by filtration and washing with distilled water, followed by drying at 100 C for 12 h and calcining at 450 C for 3 h. The typical synthesis process is detailed in Figure S Catalyst characterization The actual loading of Au and Pd on the LSMO supports was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). X-ray powder diffraction (XRD) experiments were performed on a PANalytical Empyrean II diffractometer with Cu Kα radiation (λ = nm) at 45 kv and 40 ma to identify the crystal phases and to analyze lattice parameters. Scattering intensity was recorded in the range of 8 o < 2θ < 90 o for all of the samples with a 2θ step of 0.03 o and a count time of 2 s per step. The diffraction patterns were indexed to JCPDS (Joint Committee on Powder Diffraction Standards) files. The size distribution of the PMMA microspheres was measured by a Zetasizer Nano ZS system. Textural properties, such as BET surface area, pore volume and pore size of the catalysts were determined from the adsorption and desorption isotherms of nitrogen at 196 o C on a Micrometric Tristar 3000 adsorption analyzer. Before measurement, the samples were degassed at 150 o C for 3 h. Morphologies and the macromesoporous structure, as well as noble metal size and dispersion on the supports, were analyzed by scanning electron microscopy 4 and field-emission high resolution scanning electron microscopy (FE-HRSEM) using a FEI Nova Nano SEM 450 FE-SEM microscope at an S-6

7 accelerating voltage of 5 kv, with a work distance (WD) between 5 and 8 mm and magnifications in the range of HRSEM images and morphologies of the surface structures can be seen by using the back-scattered electron detector (BSED) and secondary electron detector (SED), respectively. Field-emission high resolution transmission electron microscopic (FE-HRTEM) images of the samples were obtained on a Philips CM200 apparatus. For identifying chemical compositions of the crystal phases, high-angle annular dark-field -scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (HAADF-STEM-EDS) was employed using a JEOL JEM-ARM200F STEM to obtain the EDS spectra. Samples were prepared by dispersing them in ethanol before being deposited onto copper-coated grids. Hydrogen temperatureprogrammed reduction (H 2 -TPR) and ammonium temperature-programmed desorption (NH 3 - TPD) experiments were carried out on a Micromeritics Autochem II apparatus equipped with a thermal conductivity detector (TCD) detector. For H 2 -TPR analysis, the sample (approximately 20 mg) was pre-treated under an Argon flow of 40 ml/min as the temperature was increased at a ramp rate of 10 o C/min to 150 o C, where it was kept at this temperature for 30 min to remove water. Then, a reducing gas (10% H 2 in Ar) was introduced at a flow rate of 40 ml/min with a ramp of 10 o C/min from RT to 900 o C. The variation in H 2 concentration of the effluent stream was monitored online by the thermal conductivity detector. For the NH 3 -TPD analysis, 20 mg of sample was first pretreated under 20 ml/min He flow as the temperature increased at a ramp rate of 10 o C/min to 500 o C where it was kept at this temperature for 60 min. A 5% NH 3 with N 2 as the balance (20 ml/min) was introduced at RT for 30min, followed by He at 20 ml/min for 60 min. A temperature-program from RT to 950 o C with a ramp rate of 10 o C/min was conducted as the NH 3 concentration in the effluent stream was recorded using the TCD. X-ray photoelectron spectroscopy (XPS, Thermo Scientific, UK, model ESCALAB250Xi) was used to probe the La S-7

8 3d, Sr 3d, Mn 2p, O 1s, Au, Pd 1s and C 1s binding energies 5 of surface species with Mg Kα (hν = ev) as the excitation source. So as to remove adsorbed water and carbonate species from the Au/Pd LSMO surface, the sample was pre-treated in an O 2 flow of 20 ml/min at 200 o C for 1 h. After being cooled to RT, the pre-treated sample was transferred to a holder in a Glove Bag (Instruments for Research and Industry, USA) filled with helium, and then the holder was transferred into the spectrometer chamber under helium. The pre-treated sample was outgassed (0.5 h) in the preparation chamber before being analyzed in the analysis chamber. The C is signal at ev was taken as a reference for BE calculation. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was undertaken using a Brüker VERTEX 70v FTIR spectrometer, equipped with a liquid N 2 cooled MIR source, KBr optics, and a RockSolid interferometer. For each analysis, approximately 30 mg of catalyst was placed in a commercial insitu DRIFTS cell (HVC-DRM-5, Harrick's Scientific, USA) possessing ZnS windows. The sample was treated in O 2 at 300 o C for 2h to remove residual organics on the catalyst surface before being cooled to room temperature (RT) for DRIFTS analysis. Initially, the catalyst was exposed to a 10 ml/min mixed gas of 1 vol% CH 4 : 6 vol% O 2 (N 2 as balance) for 90 min to saturate the catalyst surface with the reactants. DRIFTS spectra were recorded at temperatures of 50, 100, 200, 300, 350, 400, 450, 500 and 550 o C under the continued reaction gas flow. Desorption spectra of the samples were recorded at 500 o C to assess reaction intermediate bonding with the catalyst surface,, initially when the reaction was stopped (i.e. 0 min corresponding to when the reaction gas mix was no longer passed over the catalyst) up to 10 min under an Ar flow (20 ml/min). 1.5 Catalytic activity measurements Catalytic methane combustion was performed in a continuous-flow, fixed-bed quartz tube microreactor (i.d. =6.0 mm) using a catalyst sample of 20 mg (Figure S3). Each sample was S-8

9 initially oxidized in a flow of O 2 at 300 C for 2h, followed by purging in a flow of N 2 for 30min at this temperature. After cooling to 200 C, the reactant gas containing 5 vol% CH vol% O vol% N 2 was passed through the reactor bed with a total flow rate of 42.8 ml/min, giving a GHSV of ca. 50,000 ml/(g h). The outlet gases from the microreactor were analyzed online by a gas chromatograph (Young Lin 6500) equipped with a TCD detector and a Carboxen-1010 PLOT column. The catalytic activities of the samples were evaluated using the temperatures (T 10%, T 50% and T 90% ) required for methane conversions of 10%, 50% and 90%, respectively. The total conversion of methane (Conv.) was determined as follows: Conv. % 100 Figure S3. Photographs of the experimental set-up used for catalyst activity assessment. S-9

10 LSMO perovskite No (f) Intensity (a.u.) (e) (d) (c) (b) (a) Theta (Deg.) Figure S4. XRD profile of (a) 3DOM LSMO, (b) 1Au/3DOM LSMO, (c) 1Pd/3DOM LSMO, (d) 1AuPd/3DOM LSMO, (e) 2AuPd/3DOM LSMO and (f) 3AuPd/3DOM LSMO. S-10

11 Volume Adsorbed (cm 3 /g, STP) (A) (f) (e) (d) (c) (b) (a) Relative Pressure (P/P 0 ) (B) (C) (f) d V/d (log D) (e) (d) (c) (b) d V/d (log D) (f) (e) (d) (c) (b) (a) (a) Pore diameter (nm) Pore diameter (nm) Figure S5. (A) N 2 adsorption-desorption isotherms; (B) and (C) pore size distributions of (a) 3DOM LSMO, (b) 1Au/3DOM LSMO, (c) 1Pd/3DOM LSMO, (d) 1AuPd/3DOM LSMO, (e) 2AuPd/3DOM LSMO and (f) 3AuPd/3DOM LSMO. S-11

12 Figure S6. Pictures of PMMA products with different colors synthesized by different strategies and associated SEM images of PMMA-1. S-12

13 Figure S7. SEM images of 3DOM LSMO synthesized with different surfactant agents: (a) and (b): PMMA-2, PEG 8000, L-lysine and nitric acid, (c) and (d) PMMA-2, PEG400, L-lysine and nitric acid. S-13

14 Figure S8. SEM images of 3DOM LSMO synthesized with different acids: (a) and (b): PMMA-1, ethylene glycol, methanol, L-lysine and nitric acid, (c) and (d) PMMA-1, ethylene glycol, methanol, L-lysine and citric acid. S-14

15 Figure S9. HAADF-STEM images and EDS elemental maps of the 1AuPd/3DOM LSMO sample. S-15

16 Figure S10. HRTEM images and size distribution of fresh and aged 1AuPd/3DOM LSMO (after 5.0 vol.% water treatment at 380 C for 9 h). Figure S11. HRTEM images and Au size distribution of fresh and aged 1Au/3DOM LSMO (after 5.0 vol.% water treatment at 380 C for 9 h). S-16

17 Figure S12. HRTEM images and Pd size distribution of fresh and aged 1Pd/3DOM LSMO (after 5.0 vol.% water treatment at 380 C for 9 h). S-17

18 (A) 1Au/3DOM LSMO 1AuPd/3DOM LSMO 2AuPd/3DOM LSMO 3AuPd/3DOM LSMO Intensity (a.u.) Intensity (a.u.) shifted 0.3 ev Binding energy (ev) (B) 1Pd/3DOM LSMO 1AuPd/3DOM LSMO 2AuPd/3DOM LSMO 3AuPd/3DOM LSMO Shifted 0.5 ev Figure S13. (A) Au 4f and (B) Pd 3d XPS spectra of the supported monometallic and bimetallic Au-Pd catalysts Binding energy (ev) S-18

19 Methane conversion (%) (A) (d) (c) (b) (a) (B) 3DOM LSMO Temperature ( C) Au atom Pd atom Au atom Pd atom Pd atom Au atom 3DOM LSMO 3DOM LSMO 3DOM LSMO 3DOM LSMO 1.8 Methane conversion (%) DOM LSMO 1AuPd/1DDN LSMO 1AuPd/3DOM LSMO 2AuPd/3DOM LSMO 3AuPd/3DOM LSMO Reaction rate (10-6 mol/(g cat s)) Temperature ( C) Figure S14. (A) Methane conversion versus reaction temperature of (a) 1Au/3DOM LSMO, (b) 1Pd/3DOM LSMO, (c) physical mixture of 1Pd/3DOM LSMO and 1Au/3DOM LSMO, (d) 1AuPd/3DOM LSMO; (B) methane conversion and reaction rate versus reaction temperature. S-19

20 (A) % Au mole ratio TOF noble metal (s -1 ) Ea (kj/mol) (B) % Pd mole ratio Temperature ( C) Fresh Catalyst 0 H 2 Pretreatment O 2 Pretreatment T 10% T 50% T 90% Figure S15. (A) TOF and E a for 1 wt% Au x Pd y /1DDN LSMO catalysts at 270 C with GHSV=50,000 ml/(g h) and (B) T 10%, T 50% and T 90% methane conversion temperatures for 1Au 1 Pd 2 /1DDN LSMO catalyst with either H 2, or O 2 pretreatment at 300 C for 2 h as well as the fresh catalyst. S-20

21 100 5 vol.% 5 vol.% 5 vol.% Methane conversion (%) C 550 C Tim e on stream (min) Figure S16. Effect of 5 vol% water vapor concentration at 380 and 550 C on the methane combustion activity of 3AuPd/3DOM LSMO. CO Au/3DOM LSMO O CH C-H CH 3 - C-O C=O CH Absorbance (a.u.) Temperature ( C) Wavenumber (cm -1 ) Figure S17. In-situ DRIFTS spectra of methane oxidation over Au/3DOM LSMO. S-21

22 Absorbance (a.u.) O C-H CH 4 C-H CH C-O 1550 C=O CO (A) 3DOM LSMO CH min 1 min 5 min 10 min Absorbance (a.u.) Wavenumber (cm -1 ) O C-H CH 4 C-H CH C=O C-O CO (B) Pd/3DOM LSMO CH min 1 min 5 min 10 min Wavenumber (cm -1 ) 2360 (C) Au-Pd/3DOM LSMO CO 2 Absorbance (a.u.) O 2 - CO 3 2- CH CH C-O C=O CH min 1 min 5 min 10 min Wavenumber (cm -1 ) Figure S18. In-situ DRIFTS spectra of desorption of intermediates and reactants at 500 C under a 20 ml/min Ar flow from 0 min to 10 min. S-22

23 (A) 1DDN LSMO CH 4 Absorbance (a.u.) (B) 3DOM LSMO CH 4 Absorbance (a.u.) CH min 3 min 5 min 10 min Wavenumber (cm -1 ) CH min 3 min 5 min 10 min Wavenumber (cm -1 ) Figure S19. In-situ DRIFTS spectra of CH 4 adsorption at 50 C from 1 min to 10 min. S-23

24 Figure S19 shows the in-situ DRIFTS spectra of CH 4 adsorbed on the 3DOM LSMO and 1DDN LSMO at 50 C from 1min to 10min. Two peaks at 1300 and 3014 cm-1 are observed which are attributed to CH 4. It is apparent that the 3DOM LSMO surface is rapidly saturated with methane molecules (within 1min) while the 1DDN LSMO has not been saturated with CH 4 after 10 min exposure. The result correlates with the NH 3 -TPD result which indicated the elevated Brønsted acid site presence on the 3DOM LSMO surface. It has been reported that a high electron density around Brønsted acid sites facilitates the adsorption and activation of reactant molecules 6. Table S1 Surface element composition, H 2 consumption and catalytic activities of the 3DOM, AuPd/3DOM LSMO and 1AuPd/1DDN LSMO samples. Surface element composition a Reducibility Methane conversion ( C) Sample Mn 4+ /Mn 3+ molar ratio O ads /O latt molar ratio Au δ+ /Au 0 molar ratio Pd 2+ /Pd 0 molar ratio H 2 consumption rate (mmol/(g cat s)) b T 10% T 50% T 90% 3DOM LSMO Au/3DOM LSMO Pd/3DOM LSMO AuPd/3DOM LSMO AuPd/3DOM LSMO AuPd/3DOM LSMO AuPd/1DDN LSMO a Estimated by quantitatively analyzing the XPS spectra of the samples; b Calculated based on the H 2 -TPR profiles of the samples; S-24

25 Table S2 Comparison of methane oxidation activity by various catalysts as reported by literature. Catalyst Reaction condition T 50% (ºC) T 90% (ºC) reaction rate at T 50% (µmol/(gcat s)) reaction rate at T 90% (µmol/(gcat s)) Ref. 3.0 wt%aupd/3dom LSMO 5% CH 4, GHSV = 50,000 ml/(g h) 1.1 wt% Pt/3DOM Ce 0.6 Zr 0.3 Y 0.1 O 2 2% CH 4, GHSV = 30,000 ml/(g h) 1.5 wt% Pd/LaMnO 3 1% CH 4, GHSV = 32,000 ml/(g h) 0.1 Pd 0.25 wt% Co /γ-al 2 O 3 1 % CH 4, GHSV = 20,000 ml/(g h) Pd@CeO 2 /H-Al 2 O 3 0.5% CH 4, GHSV = 200,000 ml/(g h) Pd 0.4 Au 0.2 /SiC 1 % CH 4, GHSV = 12,500 ml/(g h) 2.9 Au 0.50 Pd/meso-Co 3 O % CH 4, GHSV = 20,000 ml/(g h) La 0.9 Ce 0.1 CoO % CH 4, GHSV = 1,2000 ml/(g h) La 0.7 Ag 0.3 MnO 3 1 % CH 4, GHSV = 10,000 ml/(g h) La 0.7 Sr 0.3 MnO 3 1 % CH 4, GHSV = 10,000 ml/(g h) La 0.7 Ce 0.3 MnO 3 1 % CH 4, GHSV = 10,000 ml/(g h) La 0.7 MnO 3 1 % CH 4, GHSV = 10,000 ml/(g h) Sr 0.8 La 0.2 MnAl 11 O 19 2 % CH 4, GHSV = 24,000 ml/(g h) 1.0 wt% Pd/Al 2 O 3 5 % CH 4, GHSV = 30,000mL/(g h) 1.0 wt% Pd/ZrO 2 5 % CH 4, GHSV = 30,000mL/(g h) 1 mol% Pd, LaMnPd 1 % CH 4, GHSV = 5,000 ml/(g h) 2 mol% Rh, LaMnRh 1 % CH 4, GHSV = 5,000 ml/(g h) Present work S-25

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