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Understanding Dynamic chemistry at the Catalytic Interface

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Title: Understanding Dynamic chemistry at the Catalytic Interface


1
Understanding Dynamic Chemistry at the Catalytic
Interfaces
NCU Student Topic Seminar
Debabrata Bagchi 17/01/2019
2
Outline
  • What is Catalytic Interface
  • Dynamic behavior at Catalytic Interface
  • Challenge in probing the dynamics at Catalytic
    Interface
  • Difficulty of using Conventional Spectroscopy
    Microscopy
  • In Situ Techniques to probe the Dynamics at
    Interface
  • Environmental Transmission Electron Microscopy
    (ETEM)
  • In Situ Scanning Tunneling Microscopy (HP STM)
  • Conclusion future aspects

3
What is Interface?
  • When different phases exist together, the
    boundary between two of them is called Interface.

Wenpei Gao et al. Acc. Chem. Res. 2017, 50,
787-795.
4
What is Catalysis?
5
Where is Catalytic Interface?
Yong Yang et al. Chem. 2018, 4, 2054-2083.
6
Dynamic chemistry happening in Catalytic Interface
  • Elementary Steps of Heterogeneous Catalysis

Jian Dou et al. Chem. Soc. Rev. 2017, 46,
2001-2027.
7
Changes occurred in the catalyst surface
Catalyst-Gas Interface
Jian Dou et al. Chem. Soc. Rev. 2017, 46,
2001-2027.
8
Changes occurred in the catalyst surface
Catalyst-Liquid Interface
Nejc Hodnik et al. Acc. Chem. Res. 2016, 49,
2015-2022
9
Time length scales for dynamic processes in
Catalytic Interface
  • Blue Molecular processes at the active site.
  • Green Processes involving solid state catalysts.
  • Yellow Transport processes of reactants and
    products.

Kai F. Kalz et al. ChemCatChem 2017, 9, 17-29.
10
How to probe dynamic processes in Catalysis?
In situ or Operando Studies Spectroscopic Study
Conducted in Reaction Condition (High pressure,
Temperature or at some specific condition)
Kai F. Kalz et al. ChemCatChem 2017, 9, 17-29.
11
In Situ Techniques to probe the dynamics
Photon based Spectroscopy
Electron based Microscopy
  • In Situ X-ray Absorption Spectroscopy (XAS)
  • Ambient Pressure X-Ray Photoelectron Spectroscopy
  • Surface Enhanced Raman
  • Spectroscopy (SERS)
  • In Situ Infrared (IR) Spectroscopy
  • In Situ Scanning Tunneling Microscopy (STM)
  • Environmental Transmission Electron
    Microscopy(ETEM)

Jian Dou et al. Chem. Soc. Rev. 2017, 46,
2001-2027.
12
In Situ X-Ray Absorption Spectroscopy(XAS)
In Situ XAS Evolution of the structure,
coordination oxidation state of metal centre
during catalysis.
Pd_at_ZrO2
Reduction of NO with H2
  • At 120C a Pdd species were detected from
    initial Pd metallic species. This process
    parallels the high production of N2O observed.
  • At 150C the selectivity shifts mainly toward N2
    (80) the Pd atoms aggregate again into metallic
    Pd NPs.

Kristof Paredis et al. J. Am. Chem. Soc. 2011,
133, 1345513464.
13
In Situ X-Ray Photoelectron Spectroscopy(XPS)
In Situ XPS measures the elemental composition,
empirical formula, chemical state electronic
state of the elements that exist within a
material.
Ceria (CeO2)
  • Oxygen vacancies on a CeO2 surface are active
    sites for dissociative or molecular adsorption
    during catalysis.
  • From XPS Spectra
  • At 400C in O2 Most of the cerium atoms exist in
    the form of Ce4
  • Upon purging hydrogen and then filling oxygen,
    the Ce4 is partially reduced to Ce3
  • Operando XPS of CeO2 shows the dynamic change of
    oxidation state of Ce.

Evolution of Ce 3d XPS spectra of CeO2 at
different reaction conditions
Franklin Tao et al. Chem. Commun., 2012, 48,
38123814.
14
In Situ Electron Microscopy
  • Conventional Electron Microscopy needs UHV
  • Electron must transit from the sample to a
    detector without scattering from any background
    gas over a flight path on the order of 1 m
  • Microchannel plates in detector do not tolerate
    moisture

T. W. Hansen et al. Catal. Lett. 2002, 84, 7-9.
15
Environmental Transmission Electron Microscopy
Main purpose
To confine the reactant to the vicinity of the
sample thus making the gas path length along the
direction of the electrons as short as possible.
T. W. Hansen et al. Mat. Sci. Technol. 2010, 26,
13381344.
16
Environmental TEM study
Ba-Ru/BN

Barium promoted ruthenium catalyst on a support
of boron nitride
Conventional TEM
The distance between the BN layers is 0.34 nm
corresponding to the (002) planes..
Emmanuel Auger et al. Science 2001, 294,
1508-1511.
17
Growth of CNF at Interface during catalysis
Ni/MgAl2O4 catalyst used for steam reforming
Carbon formation can destroy the catalyst pellets
causing blockage of the reactor with detrimental
result
  • Carbon Nano Fibres from methane decomposition was
    developed through reshaping of Ni nanocrystal.

G. Krinner at al. Nature 2004, 427, 426-429.
18
Sintering at the Catalytic Interface
  • Oxygen-induced Pt Nanoparticle Sintering
  • Pt/Al2O3/Si3N4 Catalyst
  • 10 mBar air at 650 C

Visualisation of Sintering by ETEM
S. B. Simonsen et al. J. Am. Chem.
Soc. 2010, 132,79687975.
19
Dynamics of Pt/CNT in O2 or H2O Using ETEM
Schematic Of ETEM Set Up
Langli Luo et al. ACS Catal. 2017, 7, 7658-7664.
20
Dynamics of Nafion/Pt/CNT on O2 H2O Using ETEM
  • Nafion is used as a membrane for PEMFC by
    permitting hydrogen ion transport.

Nafion/Pt/CNTs
Langli Luo et al. ACS Catal. 2017, 7, 7658-7664.
21
Probing Nano particle interface Challenge
J. A. Rodriguez et al. Science 2007, 318,
1757-1760.
22
Scanning Tunneling Microscope (STM)
Gerd Binning
Heinrich Rohrer
Nobel Prize in Physics in 1986 for inventing STM
STM image of Graphite
23
Basic Set-Up of STM
  • The basis of STM is the Quantum Tunneling theory
  • There is a finite probability that an electron
    will jump from one surface to the other of
    lower potential.

24
Tunneling Current in STM
  • If the distance(z) between tip and sample
    increases, It will decrease exponentially.
  • Atoms of different elements of a catalyst
    surface or of adsorbates can be
  • readily distinguished as It depends on local
    density of states rs (0, EF) of the sample
    surface.

25
Creating Reaction Condition in In Situ STM
The main feature is isolation of the gas
Environment from the UHV environment
Lets talk about application
Luan et al. Rev. Sci. Instrum. 2013, 84, 034101.
26
In Situ STM analysis of Restructuring of Metal
Surface Cu(111) CO interface
Cu (111), most compact lowest energy surface of
Cu, became unstable and formed cluster at the
terraces when exposed to CO gas
Restructuring Relatively weak metal-metal bond
(low cohesive energy of 3.5 eV) low coordinated
Cu atoms formation at the edges energy gained by
binding with CO.
Baran Eren et al. Science 2016, 351, 475478.
27
Effect of clustering on surface reactivity for
the Water Gas Shift reaction
APXPS experiments of H2O adsorption on Cu(111)
  • Water does not adsorb on the Cu(111) surface at
    room temperature.
  • The cluster-covered surface was very active in
    dissociating water, as shown by the increasing
    oxygen peak.
  • A key step in the water-gas i.e. dissociation of
    H2O shift reaction, becomes highly activated as a
    result of the CO-induced clustering.

Baran Eren et al. Science 2016, 351, 475478.
28
Gas enhanced mass transport at the surface
Cu2O-Cu(111) CO Interface
  • Cu2O(111)-like thin films grown on Cu(111) appear
    as rows.

A. E. Baber et al. J. Am. Chem. Soc. 2013, 135,
1678116784.
29
Formation of self assembled hydrocarbon at
Interface Co(0001)-Gas interface during reaction
Violeta Navarro et al. Nat. Chem. 2016, 8,
929934.
30
CO induced coalescence of isolated Pd adatoms at
the Fe3O4(001)
G. S. Parkinson et al. Nat. Mater. 2013, 12,
724728.
31
Effect of higher pressure of CO on the Pd/Fe3O4
G. S. Parkinson et al. Nat. Mater. 2013, 12,
724728.
32
In Situ STM ETEM for In Situ Studies of
Interface
In Situ STM
ETEM
Franklin. Tao et al. Chem. Rev. 2016, 116,
3487-3539.
33
Conclusion Future Aspects
  • Probing the transient phenomena happening in the
    interface is an issue.
  • Study of Solid Liquid interface is still
    challenging at reaction condition.
  • Thermal drift is always a unavoidable problem for
    high Temperature reaction dynamic study.
  • Deconvolution of beam effects (for ETEM).
  • Effects might be directly to sample or by
    ionization of gases.

34
Thank you
35
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36
Creating In Situ Condition in HP-STM
The main feature is isolation of the gas
Environment from the UHV environment
General Features
Lets talk about application
Luan et al. Rev. Sci. Instrum. 2013, 84, 034101.
37
Restructuring due to surface lattice strain
in Hex-Pt(100) CO Interface
CO molecules are bound to Pt nanoclusters through
a tilted on-top configuration with a separation
of 3.7-4.1 Ã…
The phenomenon of restructuring of metal catalyst
surfaces induced by adsorption
Feng Tao et al. Nano Lett. 2009, 9, 2167-2171.
38
Behaviour of stepped catalyst gas
interface Pt(557) CO
As CO coverage approaches 100, the flat terraces
of Pt(557) break up into nm-sized clusters the
process is reversible
Low-coordination Pt edge sites in nanoclusters
relieves the strong CO-CO repulsion in the highly
compressed adsorbate film
Feng Tao et al. Science, 2010, 327, 850853.
39
Dynamics in a Metal Alloy-gas Interface Au/Ni(111)
surface alloy CO

At high pressure surface is covered with small
irregular clusters, persisting even after the
high-pressure CO is pumped away
STM Image Analysis
STM images (1000x1000 Ã…2) taken from an STM movie.
  • Movie reveals that the Au cluster formation
    starts at the Ni steps. Ni atoms are removed and
    Au clusters are nucleated and left behind.

(1000x1000 Ã…2) Inset (60x60 Ã…2) reveals a
clean Ni(111) surface)
Scale (800x800 Ã…2) Inset (50x50 Ã…2)
Ni-carbonyl formation is responsible for the
removal of the Ni atoms in the surface layer.
E. K. Vestergaard et al. Phys. Rev. Lett. 2005,
95, 126101.
40
ETEM Study of (100)Au_at_CeO2 CO Interface
Au/CeO2 catalyst showed high catalytic activity
for the oxidation of CO at RT
At Vacuum
  • CO adsorption induces a reconstruction of a (100)
    surface facet to a(100)-hex facet on Au NPs.

Hideto Yoshida et al. Science 2012, 335, 317-319.
41
ETEM Study of (100)Au_at_CeO2 CO Interface
  • By combining ab initio calculations with image
    simulations, it is confirmed that CO molecules
    only bind with reconstructed hexagonal Au top
    layers on the (100) surface.
  • Such selective absorption implies dissimilar
    reaction rates on different surface facets can be
    applied to elucidate reaction mechanisms.

Hideto Yoshida et al. Science 2012, 335, 317-319.
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