1. Spectroscopic and related techniques in surface science for unravelling heterogeneously catalyzed reaction mechanisms
Ludo Juurlink, Ph.D.
Leiden Institute of Chemistry
Leiden University, Leiden, the Netherlands
Office: Gorlaeus Laboratories DE0.01
phone
Course objectives: 
At the this short course students
can explain how surface science attempts to understand heterogeneous catalysis
can outline how common experimental (spectroscopic) techniques reveal information on surfaces, adsorbates, and chemical reactions
Understand why and how (supersonic) molecular beams are useful herein
are informed on some recent examples in the field of gas-surface dynamics

2. Surface Science and Gas-Surface Reaction Dynamics
Schedule
Date
Time
Topics
14-Dec-17
11:00 – 11:50
Introduction: Surface Science for Catalysis
Surface Crystallography
Low Energy Electron Diffraction
Scanning Tunneling Microscopy
12:00 – 12:50
Introduction to spectroscopic techniques
Auger Electron Spectroscopy
X-ray photoelectron spectroscopy
Reflection Absorption InfraRed Spectroscopy
Temperature Programmed Desorption
15-Dec-17
Controlling molecular impact: supersonic molecular beams
Examples of combined use of SMB and Surface Science
Examples from the recent literature on CH4
State-selected dissociation
Mode-selected dissociation
Bond-selected dissociation
Stereodynamical effects

3. Surface Science and Gas-Surface Reaction Dynamics
Schedule
Date
Time
Topics
14-Dec-17
11:00 – 11:50
Introduction: Surface Science for Catalysis
Surface Crystallography
Low Energy Electron Diffraction
Scanning Tunneling Microscopy
12:00 – 12:50
Introduction to spectroscopic techniques
Auger Electron Spectroscopy
X-ray photoelectron spectroscopy
Reflection Absorption InfraRed Spectroscopy
Temperature Programmed Desorption
15-Dec-17
Controlling molecular impact: supersonic molecular beams
Examples of combined use of SMB and Surface Science
Examples from the recent literature on CH4
State-selected dissociation
Mode-selected dissociation
Bond-selected dissociation
Stereodynamical effects

4. Heterogeneous Catalysis
Surface Science
to help understand
Heterogeneous Catalysis

5. Heterogeneous Catalysis: example MSR
CH4 + H2O
3H2 + CO
CH4 + H2O  3H2 + CO
~1000 °C
30 bar
Simple cubic crystal.
Every atom represented by cube or sphere.

6. Heterogeneous Catalysis: example MSR
Al2O3
pellets
Also promotors and other chemical to stabilize particles!
Simple cubic crystal.
Every atom represented by cube or sphere.

7. Heterogeneous Catalysis: example MSR
CH4 + H2O  3H2 + CO
Simple cubic crystal.
Every atom represented by cube or sphere. Ni Ni Ni

8. Heterogeneous Catalysis: example MSR
CH4 + H2O  3H2 + CO
Too much energy required -- reactants don’t react.
Intermediate blocks surface – no product formation
Simple cubic crystal.
Every atom represented by cube or sphere.
G. Jones et al. Journal of Catalysis 259, 147 (2008)

9. Heterogeneous Catalysis: Fischer-Tropsch
Simple cubic crystal.
Every atom represented by cube or sphere.

10. Surface Science approach using single crystals
1970’s onward: Single crystal surfaces:
Macroscopic pieces of pure metals, alloys, semiconductors, oxides, …. with a polished surface exposing a single type of ordering of atoms.
2000’s onward: Well-defined particles grown on crystal surfaces:
Microscopic single crystalline particles of pure metals, alloys, oxides, …. grown by vapor deposition onto a well-ordered oxide support.
Simple cubic crystal.
Every atom represented by cube or sphere.

11. Single crystals Ta single crystal Re single crystal polishing
cutting by spark erosion
polishing
Simple cubic crystal.
Every atom represented by cube or sphere.

12. Single crystals Ag single crystal with a curved surface
Simple cubic crystal.
Every atom represented by cube or sphere.

13. Basics of two-dimensional crystallography

14. Bulk crystal structures
1. triclinic
2. monoclinic
3. orthorhombic
4. rhombohedral
5. tetragonal
6. hexagonal
7 lattice systems
14 Bravais lattices
simple
base-centered
simple
base-centered
body-centered
face-centered
7. cubic
simple
simple
body-centered
face-centered
body-centered

15. Bulk crystal structures

16. Bulk crystal structures
examples
Body centered cubic (bcc) Fe, W
Face centered cubic (fcc) Ni, Cu, Pt
Hexagonal close packed (hcp) Ru, Co
Diamond lattice Cdiamond, Si, Ge
Zinc blende structure ZnS, GaAs, InP
Rock salt NaCl, NiO

17. Atomically flat surfaces as bulk truncations
surface layer normal to [100]
Example: fcc
[100]
[010]
[001]
[111]
surface layer normal to [111]

18. A real single crystal surface on a manipulator
Ru(0001)
10 mm
2 mm
LN2
LN2

19. Vicinal surfaces (001) Families of planes e.g. {100}, {111}, {110}
(1-11)
(001)
(1-11)
(1-10)
[110]
[110]
(1-10)
[111]
[001]
[110]
54.7°
35.3°
54.7°

20. Vicinal surfaces
stepped
stepped and kinked

21. Do these surfaces represent the surface of particles?
Helveg et al., Nature 427, 426 (2004)
Behrens et al., Science 336, 893 (2012)

22. Do these surfaces represent the surface of particles?
R.A. Olsen and L.B.F. Juurlink, Hydrogen dissociation on stepped Pt surfaces, in Dynamics of Gas-Surface Interactions: Atomic-level Understanding of scatttering processes at surfaces, Ed. Busnengo and Diez-Muiño, Springer Series in Surface Science, Springer (Berlin, 2013)
Honkala et al., Science 307, 555 (2005)

23. Referring to surfaces: Miller indices
Plane with Miller indices h, k and l is (hkl). It is orthogonal to reciprocal lattice vector [hkl].
Determine intercept plane on axes a1, a2, and a3
Take reciprocal of obtained numbers: 1/a1, ….
Reduce to smallest integers with same ratio
(321) a3 a3
h = 1 / (1/3)
k = 1 / (1/2)
l = 1 / 1
1/2 of a2 a2
1/3 of a1 a1

24. Miller indices
Plane with Miller indices h, k and l is (hkl). It is orthogonal to reciprocal lattice vector [hkl].
Determine intercept plane on axes a1, a2, and a3
Take reciprocal of obtained numbers: 1/a1, ….
Reduce to smallest integers with same ratio

25. Some important crystal structures

26. Some important crystal structures

27. Imaging surface in reciprocal space Low Energy Electron Diffraction

28. Reciprocal lattice Reciprocal lattice:
where h and k are integers and ….
Reciprocal lattice vectors:
real space lattice
reciprocal space lattice

29. Bragg’s law and the Ewald sphere
3-D crystals: conservation of 3D momentum and (3D) energy

30. Low Energy Electron Diffraction (LEED)
Wavelength, , must be close to interatomic distance, “a”
For example:
Ekin = 20 eV,  = 2.7 Å
Ekin = 200 eV,  = 0.87 Å 
Inverse relation between the ‘position’ of the diffraction spot and the distance between atoms
= n  for diffraction ‘hot spot’

31. Low Energy Electron Diffraction (LEED)

32. Interpretation of a LEED pattern
Sharpness: well-ordered surface shows bright, sharp spots
Geometry: gives information on crystallographic structure
Spot profile: intensity distribution across width of spot -> surface imperfections cause weakening of spot
I-V analysis: evaluation of atom positions

33. Surface and overlayer structures (superstructure)

34. Notation for surface and overlayer structures
Matrix notation:
Wood’s notation:
Primitive and centered: ‘p’ and ‘c’

35. Low Energy Electron Diffraction (LEED)
Ogletree et al, Surf. Sci. 173, 351 (1986)

36. Diffraction techniques
Electron-based techniques
Low energy electron diffraction (LEED: typically 50 eV)
Reflection high-energy electron diffraction (RHEED: typically 20 keV)
Transmission electron diffraction (TED: typically 200 keV)
Auger electron diffraction (AED)
X-ray based techniques
Grazing-incidence X-ray diffraction (GIXRD; typically 15 keV)
Surface X-ray diffraction (SXRD; typically 15 keV)
Grazing-incidence small-angle X-ray scattering (GISAXS)
Other techniques
Photo-electron diffraction (PED)
Thermal-energy atom diffraction (typically 15 meV He atoms)

37. Imaging surface in real space Scanning Tunneling Microscopy

38. Scanning Tunneling MicroscopyF d E
sample tip
vacuum EF
Evac
EF + eV

39. Scanning Tunneling MicroscopyV
tip
specimen
piezo
element
trajectory

40. Scanning Tunneling Microscopy
Forschungszentrum Jülich, Germany

41. Scanning Tunneling Microscopy
Au(111)
Leiden Probe Microscopy BV

42. STM images of adsorbates
H2O ‘double strands’ along a Pt(553) edge
Diffusion of In atoms in a Cu(100) surface
Kolb et al., Phys. Rev. Lett. 116, , (2016)
Gastel et al, Phys. Rev. Lett. 86, 1562 (2001)

43. STM images of adsorbates