Chemistry Department, INSTM & Centre of Excellence for Nanostructured Materials

1. Embedded metal nanoparticles: an intriguing approach to the design of active and stable catalyst for hydrogen production P. Fornasiero, M.F. Casula, L. De Rogatis, V. Gombac, M. Graziani, B. Lorenzut, T. Montini Chemistry Department, INSTM & Centre of Excellence for Nanostructured Materials University of Trieste Chemistry Department, University of Cagliari VI Convegno Nazionale sulla Scienza e Tecnologia dei Materiali Perugia, 12-15 June 2007

2. Outline 1.Aim of the work 2. Catalysts Design 3. Activity a.Methane Partial Oxidation b.Ethanol Steam Reforming c.PRefential OXidation 4.Perspectives/Conclusions

3. Current Global H2 Coal 4% Electrolysis 4% Oil 7% Misc. 5% Methanol 5% Methane 85% 500 billion Nm3/year Refining 37% Ammonia 50%

4. Refuelling station Dewar Truck Delivery Large reformer LH2 LH2 Pump dispenser compressed H2 NG H2 H2 vehicle Large reformer Dewar Truck Delivery dispenser liquid H2 NG H2 H2 vehicle Large reformer compressor storage dispenser Pipeline Delivery NG compressed H2 H2 H2 vehicle On-line reformer compressor storage dispenser compressed H2 H2 vehicle Electrolyser compressor storage dispenser compressed H2 H2 vehicle H2 Economy: Infrastructures requirements

5. H2 vehicles: technical requirements Storage Hydrogen Storage in MicroporousMetal-Organic Frameworks (MOFs) Omar M. Yaghi et co-workers,SCIENCE VOL 300 16 MAY 2003 Fuel Cell Stability and durability (membrane, electrode) Cost, stability durability.. (technical requirements and costs)

6. Miniaturization

7. Miniaturization Fuel cell

8. Catalyst Design ... toincorporate the nanoparticles into an “open shell” of SiO2 that willlimit the sinteringof the particles at high temperaturewhilepreventing a total occlusion of the particlesand consequentlyfavoring accessibility of the catalytic sitesto the reactants. Schematic representation of Au nanoparticles capped with 1-dodecanethiol (DT) and 3-mercaptopropyltrimethoxysilane and the AuNP-organic-SiO2 structure. METHOD: modified sol-gel approach A.Corma et al., Angew.Chem.Int.Ed.45(2006) 3328

9. Support/ Promoters Reactants Products Active Site Metal cluster CATALYST DESIGN: our approach ENCAPSULATION of pre-formed metal nanoparticles into porous oxide layers METHOD: simple and low cost Synthesis by co-precipitation Appl.Catal.B: Environmental 71 (2007) 125

10. A 0.53 B 0.26 C 0.11 TEM image nanoparticles obtained at 0.53 Rh / surfactant molar ratio CATALYST DESIGN: our approach 1. Preparation of a stable suspension of protected metal nanoparticles HEAC16Br surfactant Schulz et al. Chem. - A Eur.J.6 (2000), 618 J. Alloys Compd. (2007)

11. Calcination 900°C x 5h Precipitation of theSupportin hydroxide form Protected - metal nanoparticles CATALYST DESIGN: our approach 2. Deposition and growth of the porous oxide layers around metal nanoparticles in two steps Appl.Catal.B: Environmental 71 (2007) 125

12. H production from CH Partial Oxidation 2 4

13. Impregnated Protected STABILITY 1% Rh impregnated v.s. 1% Rh embedded @Al2O3 Temperature 750 °C Appl.Catal.B: Environmental 73 (2007) 84

14. O2 (5%) / Ar MPO 850°C 750°C CO2 Deactivation (I) 2 nm Appl.Catal.B: Environmental 73 (2007) 84

15. Deactivation (II) 2 nm Appl.Catal.B: Environmental 73 (2007) 84

16. H production from Ethanol Steam Reforming 2

17. SAMPLES Rh(1%)@Al2O3 vsRh(1%)@CexZr1-xO2(Y%)-Al2O3 What is the effect of promoters on ...? • reactionmechanism • (in terms of yields and selectivity of products) • operative temperature • nature of carbonaceous deposits

18. Conversion/Yield (%) CH3COCH3 -H2 Temperature (°C) CH3CHO CH4 + CO + H2O C2H5OH CO + H2 CO2 + H2 -H2O CH2CH2 Coke Rh(1%)@Al2O3 EtOH + H2O 1 : 5 GHSV = 150000 mL g-1 h-1 Appl.Catal.B: Environmental 71 (2007) 125

19. Conversion/Yield (%) CH3COCH3 -H2 Temperature (°C) CH3CHO CH4 + CO + H2O C2H5OH CO + H2 CO2 + H2 -H2O CH2CH2 Coke Rh(1%)@Ce0.2Zr0.8O2(40%)-Al2O3 EtOH + H2O 1 : 5 GHSV = 150000 mL g-1 h-1 Appl.Catal.B: Environmental 71 (2007) 125

20. O2/Ar SR-EtOH 600 °C 160 hrs Coke DEPOSITION TPO:Temperature Programmed OxidationExperiment Rh@Al2O3 EtOH + H2O 1 : 5 GHSV = 150000 mL g-1 h-1 Rh@CexZr1-xO2-Al2O3 Ce/Zr mixed oxide leads to a significantly reduction of the amount of coke deposits Appl.Catal.B: Environmental 71 (2007) 125

21. Perspectives: Ni Nanoparticles Synthesis Problems to control the size and size distribution a. to obtain a stable colloidal suspension b. metal nanoparticles are easily oxidized c.

22. T = 25 °C Ar HDA + NaBH4 NaBH4/Ni = 3/5 Ni Precursor Perspectives: Ni Nanoparticles Synthesis Reducing agent =NaBH4 Protective agent = HDA Solvent = THF Tetrahydrofuran

23. Perspectives: Ni Nanoparticles Synthesis Ni(NO3)2· 6 H2O HDA/Ni= 15 NaBH4/Ni = 5 Nanoparticle SIZE: 2-4 nm

24. PReferential OXidation Of CO (PROX)

25. Other Metals: PReferential OXidation • Thiols protected gold nanoparticles CO (1%) + O2 (1%) CO (1%) + O2 (1%) + H2 (50%) CO (1%) + O2 (1%) + H2 (50%) + CO2 (20%) CO conversion / % CO (1%) + O2 (1%) + H2 (50%) + CO2 (5%) + H2O (5%) Au (1%)/CeO2 Temperature / °C Collaboration with L. Pasquato, University of Trieste Chem.Mater. 19 (2007) 650

26. Other Metals: PReferential OXidation • Thiols protected gold nanoparticles Aged Fresh Collaboration with S. Polizzi, University of Venezia Chem.Mater. 19 (2007) 650

27. CONCLUSIONS Active and stable catalyst can be obtained by • Encapsulation of metal nanoparticles in porous oxides; • Modulation of the dimension of the nanoparticles; • Design of the support composition.

28. ACKNOWLEDGEMENTS University of Trieste INSTM FISR 2002 FIRB 2001

29. END Thank you for your attention !