Spatially Resolved and Atom Specific Microscopy and Spectroscopy “New Characterization Tools” What can we do now that we could not do before and how will it change the world

Complementarity of techniques Broad beam: good statistics average over sites Local probe: poor statistics probes individual sites Time resolutionSpatial resolution Species specificSite specific Insight  N N where N = number of tools We want everything at once!

“Real-time” surface imaging methods Nanoscale [“atomic” resolution] –Fast Scanning Tunneling Microscopy (STM) –Field Ion Microscopy (FIM/FEM) Mesoscale [chemically sensitive] –Low Energy Electron Microscopy (LEEM) –Photoemission Electron Microscopy (PEEM) –Ellipsomicroscopy for Surface Imaging (EMSI) –Imaging FT-IR spectroscopy

Pattern formation on catalysts J. Lauterbach, et al., Surface Science 294 (1993) 116

Ellipsomicroscopy for Surface Imaging (EMSI)

P > mbar -> EMSI T = 540 K, CO/O 2 = Image size:1mm x 1.25 mm, dt = 0.33 s Lele, T. and J. Lauterbach, Chaos 12(1) (2002) Video

Low Energy Electron Microscopy & Synchrotron-based Photoemission Electron Microscopy Sample -20 keV Image Electron emitter Photons (uv, x-rays) 777°C 761°C 755°C 0.5  m 755°C Dark field TiO2 surface structure - LEEM RuO 2 growth

Probing of Valence Electrons with X-rays Atom specific Orbital symmetry selective Experiment--Theory

Catalytic Chemistry with Orbitals Theoretical simulations, Mats Nyberg, Stockholm University Probe pulse at different delay time  t Both N atoms New Ru Catalyst Active site at steps Hansen et.al. Science 294, 1508 (2001) Haber-Bosch N 2 + 3H 2 2NH 3

XASpectroelectrochemistry Element specific Resolves multiple redox sites Perfect for fuel cells

New Tools for Neutron Scattering: Determination of Chloroform Adsorption site in Faujasite From H pair distribution function. (J. Eckert, C. Mellot-Draznieks and A. K. Cheetham, J. Am. Chem. Soc. 2002, 124, 170 ) Parallel detectors offer more sensitivity Vibrational spectroscopy without selection rules

Paraboloid: Height h 0 = 3.1 nm ± 0.1 nm radius r 0 = 24 nm +2 nm(tip) Volume V = pi/2 h 0 r 0 2 = 2800 nm 3 density [PE] = 25 molecules/nm 3 TOF = 19 ± 2 molecules / s AFM image 100 x 100 nm heigth 3 nm AFM image of polyethylene formed by a single catalytic site: Cr on SiO 2 / Si(100) Peter Thüne, Joachim Loos, Piet Lemstra, Hans Niemantsverdriet, Macromol Symposia 2001

Laegsgaard, Osterlund, Thostrup, Rasmussen, Stensgaard and Besenbacher, Rev. Sci. Instrum. 72 (2001), Pressure-induced reconstructions on Cu(110) exposed to H bar (before) 1 bar H 2 (during) bar (after) Atomic Resolution Images Under High Pressure Conditions In-situ HRTEM offers defect analysis - identification of active sites in vanadyl pyrophosphate catalysts

Ga EELS 1.4Å As Z-contrast STEM Z=31 Z=33

EELS profile across a single particle 2nm Co L 2,3 -edges Ni L 2,3 -edges Energy Loss (eV) Intensity (a.u.) Co Ni Co/Ni Concentration profile

Pt on  -alumina 1.3 Å probe Pt on  -alumina 0.5 Å probe Imaging of Active Catalyst Atom Configurations Pt atoms sit in surface vacancies [001] [110]