NANOCATALYSIS ON NOVEL SUPPORTS GRAPHENE SHEETS AND HIGHLY POROUS COORDINATION POLYMERS

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1 NANOCATALYSIS ON NOVEL SUPPORTS GRAPHENE SHEETS AND HIGHLY POROUS COORDINATION POLYMERS M. Samy El-Shall Department of Chemistry Virginia Commonwealth University Richmond, Virginia IWAM-09, February 22-24, 2009

2 Clusters Ionic Polymerization Structure Kinetics Binding Energy Nd:YAG Laser The CNN Laboratory Nucleation W(n) RT Particle-induced W* n* n Nanoparticles Catalysis Quantum Dots Rods Wires Ion-induced J. Am. Chem. Soc. 128, (2006) J. Am. Chem. Soc. 127, 7053 (2005) J. Chem. Phys. 126, (2007) 10 nm J. Phys. Chem. B. 109, (2005)

3 Nano Catalysis Catalysis is an integral part of Nanotechnology Synthetic Heterogeneous Catalysts Metal or Metal Oxide Nanoparticles Supported on Oxides are the Foundation of the Chemical Industry Biological Catalysts Enzymes are the Foundation of Biological Systems

4 Nano Catalysis Innovative Solutions to Real Problems Catalytic Oxidation of CO Conversion of CO and H 2 to higher molecular weight hydrocarbons (FTT) Hydrogen Production via partial oxidation of hydrocarbons to synthesis gas (H 2 and CO)

5 Catalysis On Nanoparticles Low Temperature Efficient Catalysts for CO Oxidation & Removal of Volatile Chemical Contaminants Carbon Monoxide Colorless, Odorless Gas, Product of Incomplete Combustion Highly Toxic due to its High Affinity towards Hemoglobin (replaces O 2 )

6 Nano Catalysts On Oxide Nanoparticles On Oxide Nanocubes & Nanobelts From Microwave Synthesis On Graphene Sheets On Porous Coordination Polymers MIL-101

7 Catalyst Systems Investigated Active Metal Au Pd Cu Catalyst Support CeO 2 ZrO 2 TiO 2 Fe 2 O 3 SiO 2 Al 2 O 3

8 Dispersing Small Au Nanoparticles On Larger CeO 2 Nanoparticles O 2 adsorbed on CeO 2 Large Nanoparticle CO adsorbed on small Au nanoparticle

9 LASER VAPORIZATION CONTROLLED CONDENSATION (LVCC) Sample Collection Surface Cold Plate ( C C) He or Ar ( torr) Convection 4-8 x 10 9 W/cm 2 Nd:YAG laser 532 nm 1-40 mj/pulse 10 ns Silicon Target Heated Plate ( C) J. Phys. Chem. 98, 3067 (1994); US Patents:5,580,655 99, (1995); 101, 1794 (1997) 5,695, , 59 (2001); 105, 2085 (2001) 6,136, , 2882 (2003) 6,368,406

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11 Synthesis of Au/CeO 2 Nanoparticles From a Micron size Powder Mixture Target Prepared by Pressing a Mixture of Au and CeO 2 Powders μm 500MPa Laser Ablation Au / CeO 2 Nanoparticles 1-5% Au + CeO 2 Powder Mixture Powder Pellet

12 G. Glaspell et al. Topics in Catalysis, 47, 22 (2008). N. R. E. Radwan et al.applied Catalysis A, 331, 8-18 (2007).

13 Pd/CeO 2 and Au/CeO 2 Nanoparticle Catalysts

14 Nanoparticle Catalysts Supported on MgO Cubes and ZnO Belts How important is the Shape of the Support? G. Glaspell et al. Topics in Catalysis, 2008, 47, 22 O. Fouad et al. Topics in Catalysis, 2008, 47, 84 G. Glaspell et al. J. Phys. Chem. B 2006, 110, 21387

15 100% O 2 convection Vacuum Evaporation of Mg in O 2 at 1200 C

16 Evaporation of Mg in O 2 atmosphere at Higher Temperatures (1200 C) Produces MgO Cubes Exclusively Pressure = 760 Torr O 2 Pressure = 100 Torr O 2

17 Evaporation of Zn in O 2 atmosphere at 850 C Produces ZnO Belts Exclusively 300 Torr O 2 Belts grow from tetrapods

18 Deposition-Precipitation of Au & Pd Nanoparticles on MgO Cubes and ZnO Belts

19 Catalytic Activities of Au/CeO 2 Nanoparticles Deposited on MgO Cubes 100 CO Conversion ( % ) MgO Cubes 5% Au / MgO Cubes 5% Au / CeO 2 Au (0.01) / CeO 2(0.24) / MgO Cubes (0.75) Catalyst Temperature ( 0 C) 1% Au / 24% CeO 2 / MgO NanoCubes show 70% CO CO 2 Conversion at Room Temperature

20 Microwave Synthesis Ultrastable Au/TiO 2 Catalysts Microwave Ti(OH) 4 TiO 2 + 2H 2 O Microwave TiO 2 + HNO 3 + HAuCl Au/TiO 4 2

21 HRTEM of 5% Au/TiO2

22 Au/TiO 2 : Different % Gold % Au / TiO 2 T 100% ( o C): -73 CO Conversion ( % ) % Au / TiO 2 T 100% ( o C): -26 T 50% ( o C): -52 1% Au / TiO 2 T 100% ( o C): -6 0 T 50% ( o C): Catalyst Temperature ( 0 C)

23 5%Au/TiO 2 :Calcination at different Temperatures CO Con (%) after 300 After Calcination at 700 o C After calcination at 500 o C Cat. Temp

24 CO Oxidation on 5% Au/TiO 2 After Calcination at 500 C 100 CO Conversion (%) time (hr) Conversion at -40 C

25 Microwave Synthesis of Surface Passivated Nanostructures Quantum Dots Nanorods, Nanowires, Nanoplates & Nanostars A. B. Panda, G. Glaspell, M. S. El-Shall, J. Phys. Chem. C. 111, 1861 (2007) J. Am. Chem. Soc. 128, 2790 (2006)

26 Microwave Synthesis of Nanostructures In conventional thermal heating considerable energy loss and sharp thermal gradients throughout the bulk solution may result in poor control of the nucleation process, inefficient and non uniform reaction conditions. In Microwave Dielectric heating energy is transferred directly to the reactants. Energy is supplied to the molecules faster than they are able to relax, creating high instantaneous temperatures which increase the yield and quality of product.

27 MWI CdS ZnS (a) PbS (c) 20 nm 50 nm (b) (e) 50 nm (f) (d) 50 nm 50 nm 20 nm

28 CdSe Shape Control by Surface Coatings and Microwave Reaction Times (a) (b) (c) MWI time (min) CdSe:HDA (mol) 1:9 1:9 1:18

29 PL of CdSe Nanocrystals of Different Shapes CdSe/HDA QDs Rods Cubes Intensity (a.u.) Wavelength (nm)

30 PL of CdSe Nanorods of Different sizes Intensity (a.u.) CdSe/HDA (C 16 ) Microwave Time 1 min 2 min 3 min 4 min 5 min Wavelength (nm)

31 Nanorods of Rare Earth Oxides Sm 2 O 3 Sm 2 O 3 Nd 2 O 3 Gd 2 O 3 Gd 2 O 3 Nanowire

32 The Rise of Graphene Graphene, a single hexagonally flat layer of graphite, has the highest intrinsic carrier mobility at room temperature of all known materials combined with very high mechanical strength & thermal stability Graphene holds great promise for the development of new composite materials, emissive displays, ultrasensitive detectors and micromechanical resonators The combination of highest mobility, thermal, chemical and mechanical stability with the high surface area offers excellent supports for heterogeneous catalysis where metallic and bimetallic nanoparticle catalysts can be efficiently dispersed on the graphene sheets

33 Microwave Synthesis of Graphene Sheets Supporting Metal Nanocrystals Hydrazine Graphene Microwaves (2.45 GHz) 0.8 nm G-Cu Nanoparticles Graphite Oxide 30 sec.- 2 min. Hydrazine/Cu(NO 3 ) 2 El-Shall, M. S. et al Nano Letters, 2009

34 0.34 nm 0.8 nm Graphite KMnO 4 /H 2 SO 4 Exfoliated Graphite Oxide Hummers and Offeman, J. Am. Chem. Soc. 1958, 80, 1339

35 Microwave Synthesis of Graphene Graphite GO EDA Am HZ Intensity (a.u.) GO Graphene Images of the graphite oxide (GO) suspension in water before and after MWI in the presence of the reducing agents ethylenediamine (EDA), ammonium hydroxide (Am) and hydrazine hydrate (Hz) θ XRD patterns of graphite, GO and graphene

36 SEM & TEM Images of Chemically Converted Graphene Sheets 50 nm

37 Raman Spectroscopy Graphite 2D Intensity (a.u.) GO Graphene Intensity (a.u.) Raman Shift (cm -1 ) Raman Shift (cm -1 )

38 AFM images and cross-section analysis of the as prepared chemically converted graphene sheets (a) nm (b) 4.07 nm (c) 6.89 nm

39 Comparison of the TGA plots of the graphite oxide and the chemically converted graphene sheets Weight (%) Graphene Graphene Oxide Temperature ( o C)

40 Metallic & Bimetallic Nanocatalysts Supported on Graphene Sheets (a) (b) (c) 50 nm 50 nm 20 nm Pd Cu CuPd Simultaneous Reduction of GO and Metal Salts in Water using Hydrazine Hydrate under MWI

41 Gold on Graphene Intensity (a.u.) Ag Au Cu UV-Vis absorptions of the toluene suspensions of the graphene sheets containing Ag, Au and Cu nanoparticles prepared by the simultaneous reduction of GO and the metal salt using oleyl amine as a reducing agent under MWI Wavelength (nm)

42 CO Oxidation on Pd, Cu, PdCu nanocatalysts Supported on Graphene 100 CO Conversion % PdCu/G Pd/G Cu/G 20 G Catalyst Temperature / o C

43 Microwave Synthesis of Metallic & Bimetallic Nanocatalysts Supported on the Highly Porous Coordination Polymers MIL-101 H. M. El-Kaderi, M. S. El-Shall, et al J. Am. Chem. Soc. 2009

44 Building Blocks for Coordination Polymers Inorganic Units SBUs Organic linkers Yaghi, O. M. et al, Nature 2003, 423, 705

45 Routes to High Surface Area Materials MOF-177 SA = 5640 m 2 /g; H 2 uptake ~7.5 wt% Chae, H. K. at al, Nature 2004, 427, 523.

46 MIL-101 Chromium-based MOF with the molecular formula (F,OH)-(H 2 O) 2 O[(O 2 C)-C 6 H 4 -(CO 2 )] 3 nh 2 O (n 25) Ferey, G. Chem. Soc. Rev 2008, 37, 191 Henschel, A. et al Chem. Comm. 2008, 4192

47 (b) MIL-101 (a) MIL μm 200 nm (c) Pd@MIL-101 (d) PdCu@MIL nm 20 nm Simultaneous Activation of the Pores of MIL-101 and the Rapid Chemical Reduction of the Metal Precursors using Hydrazine in a Microwave oven for 1-2 min

48 Microwave Activation of MIL-101 Langmuir Surface Area increases from 1610 to 3670 m 2 /g after MWI in the presence of Hydrazine

49 Nitrogen adsorption isotherms at 77.3 K for MIL-101 and metaldoped materials. Filled circles (adsorption), empty (desorption)

50 CO Oxidation on Metal Nanoparticles-Doped MIL % Pd-2%Cu-MIL-101 5% Pd-MIL-101 2% Cu-MIL-101 2% Pd-MIL-101 MIL CO Conversion % Catalyst Temperature ( o C)

51 The observed catalytic activities towards CO oxidation of the Pd, Pd-Cu and Cu nanocatalysts supported on the MIL-101 are significantly higher than any other reported metal clusters supported on MOFs. A significant number of oxygen vacancies may exist on the metal nanoparticle/mil- 101 interface. These vacancies are probably created as a result of the MWI process.

52 Conclusions & Outlook *** The significant increase in the concentration of corner and edge sites in MgO nanocubes make them well-defined supports to study the Shape-Control mechanism of the catalytic activity enhancement *** Au/TiO 2 Nanoparticle catalysts result in 100% CO oxidation at -73 C

53 *** A chemical reduction method assisted by microwave irradiation has been developed for the synthesis of chemically converted graphene sheets and metal nanoparticles dispersed on the graphene sheets ***A facile, general and effective approach based on microwave irradiation for the incorporation of a variety of metallic and bimetallic nanoparticle catalysts within porous coordination polymers

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55 Acknowledgment PRF-ACS Afton Chemical Philip Morris USA