Cadiz-Paris Train Line; Catalysts, Nanostructures and EELS Spectroscopy. Susana Trasobares

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1 Cadiz-Paris Train Line; Catalysts, Nanostructures and EELS Spectroscopy Susana Trasobares

2 2010 Paris Odile Stéphan Mathieu Kociak Christian Colliex 1997 Cadiz Miguel López-Haro Juan C. Hernandez Jose A. Pérez-Omil Jose J Calvino

3 (Scanning) Transmission Electron Microscopy EELS Spectroscopy STEM VG-HB501 NION Ultra-STEM 100kV

4 Since 1997 Different nanostructures different questions to answer.

5 EELS Applications in biomedicine Iron Removal Mechanism EELS Applications in Environmental Catalysis Catalist deactivation Support-Metal Interaction (Ce oxidation state at interfase) Atomic Chemical Structure of the catalytic support

6 Determination of the Fe removal mechanism on ferritine Ferritin, the major intracellular storage form of Fe Ferritin iron core composition is different between physiological and pathological (especially Alzheimer s) brain ferritins Studying the Process of iron release from ferritin could help to understand neurodegenerations diseases Ft 2200 Ft 1200 Ft 500 Ft nm Journal of American Chemical Society, 130, 8062 (2008) In Collaboration with Granada University

7 L 3 Journal of American Chemical Society, 130, 8062 (2008) 709eV 710.5eV L 2 Ft kV 0.5nm probe size nA converge semi-angle 15mrad collection angle 24mrad EELS-SL 64 spectra HAADF Distance (nm) magnetite Fe 2+ Energy Loss(eV) Iron (II) enriched shell, not evident for the Ft 2000 Magnetite is the predominately phase at Ft 500 Fe is removed from the ferrihydrite phase no from magnetite apoferritin ferrihydrite hematite

8 EELS Applications in biomedicine Iron Removal Mechanism EELS Applications in Environmental Catalysis Catalist deactivation Support-Metal Interaction (Ce oxidation state at interfase) Atomic Chemical Structure of the catalytic support

9 Nanoparticles with Applications in Catalysis. 3 nm Complex structures 0.34 nm Pt M / Ce mixed oxides M=Au, Pt, Rh; Zr, Tb, Pr

10 Nanoparticles with applications in Catalysis Three Way Catalyst H 2 Production, Fuel Cell Bio-diesel, Water Depuration Objecitve; M / Ce mixed oxides M=Au, Pt, Rh; Zr, Tb, Pr TWC; Cold start Stable at high Temperature

11 Metal Nanoparticle (metal distribution, morphology, chemistry etc ) Metal-Support Interface Metal Support Interaction, epitaxial growth Active Catalytic Support; Oxygen Exchange between the chemical environment and the REDUCIBLE support. Ce 4+ Ce 3+ Zr and/or Tb doping improves the catalytic properties O 2- ½ O 2 + V O (oxygen vacancies) The Chemical Structure at atomic scale Catalytic Surface Modifications; before, during and after.

12 Catalyst Deactivation (particle decoration) Pt/Ce x Tb y O 2 Cadiz University Chem. Mater. 1999, 11,

13 Catalyst Deactivation (particle decoration) Rh/Ce x Pr y O 2 Ce M 5Ce M4 Intensity (a.u.) Pr M 5 Pr M Support 1 1 Rh CePr Cu Rh particle 2 Surface Rh particle Energy Loss (ev) 960 Combining EELS/EDS at University Cadiz Energy Energía (kev) Ce references Ce M 5 Ce M 4 Ce +4 Ce nm nm nm nm Oxidation state variation in individual nanocrystals VG HB501 Orsay J Phys Chem C 112, 5900, Energy Loss(eV) Energy Loss(eV)

14 Catalyst Deactivation (intermetallic formation) LnPt 5 particle T=973K T=1173K support Ce-M 5 Ce-M 4 Tb-M 5 Tb-M 4 Energy Loss (ev) Preferencial incorporation of Ce into the LnPt5 intermetallic LnPt 5 particle support Perez-Omil, Calvino et al Chem Mat 11, 12, 1999

15 Active Catalytic Support; Oxygen Exchange between the chemical environment and the REDUCIBLE support. Ce 4+ Ce 3+ Zr and/or Tb doping improve the catalytic properties O 2- ½ O 2 + V O (oxygen vacancies) The Chemical Structure at atomic scale Catalytic Surface Is there any structure modification. During catalyst preparation? During catalytic reaction?

16 Support modification during catalyst preparation process The support can be submitted to several experimental conditions (ph, T etc ) and reactions in order to deposit and disperse the metal nanoparticles 5 nm Is the chemical and electronic structure of the support modified?

17 Support Segregation (during catalytic preparation) Ce 0.8 Pr 0.2 O 2 Rh / Ce 0.5 Pr 0.5 O 2 Ce map Pr map Pr/Ce map Pr/Ce ratio nm nominal composition Distance (nm) Uniform composition at the bulk sample, having a higher content of Pr at the firstsurface layers (3-4 nm) Energy Loss(eV) Strong composition variations Experimental evidence of Pr Leaching J Phys Chem C 112,

18 Support Modification during catalytic reaction or treatment Ce x Zr 1-x O 2 Severe Reduction Mild Oxidation Ce Ce/Zr Zr Ce Zr Zr Ce HREM/HAADF Image and simulation Perez-Omil et al Chem. Mater. 17(17) (2005) 4282 Super-cell of the Ce x Zr 1-x O 2 crystal structure projected through the [110] direction

19 Now let s move to the Nion Ultra-STEM Microscope.

20 EELS Spectrum Imaging Mode Ce-N Zr-M 2,3 O-K Ce-M 4,5 SI EELS Image 45x40 Acquisition time 0.02s/spectrum 0.05nm step Edispersion=1eV Principal Component Analysis (PCA) to increase signal/noise ratio

21 Atomic Resolved Chemical Maps Combined with EELS Map simulations Ce Ce/Zr Ce/Zr Zr Ce/Zr Ce Experimental Chemical Evidence of Cationic Orden in Ce 0.5 Zr 0.5 O 2 -SRMO Compositional variation at the unit cell level In collaboration with Les Allen s Group at Melbourne University

22 Thank You Merci Gracias December 2001 February 2010

23 Thanks Christian Septiembre 2001

24 Nanoanalysis 2000 Cargese

25 2005 Round Table TEM / STEM 2006

26 EELS on the Nature; HAADF profile across a Carbon Nanotube ES4FUN project, peapod pattern made by High School Students

27 ESTEEM Project, European Union under the Framework 6 program Spanish MICINN/FEDER-EU (Project MAT NAN and CSD ) Junta de Andalucía (Proyecto de Excelencia FQM ) ES4FUN project