Title: Understanding Dynamic chemistry at the Catalytic Interface
1Understanding Dynamic Chemistry at the Catalytic
Interfaces
NCU Student Topic Seminar
Debabrata Bagchi 17/01/2019
2Outline
- 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
3What 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.
4What is Catalysis?
5Where is Catalytic Interface?
Yong Yang et al. Chem. 2018, 4, 2054-2083.
6Dynamic chemistry happening in Catalytic Interface
- Elementary Steps of Heterogeneous Catalysis
Jian Dou et al. Chem. Soc. Rev. 2017, 46,
2001-2027.
7Changes occurred in the catalyst surface
Catalyst-Gas Interface
Jian Dou et al. Chem. Soc. Rev. 2017, 46,
2001-2027.
8Changes 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.
11In 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.
12In 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.
13In 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.
- 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.
14In 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.
15Environmental 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.
16Environmental 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.
17Growth 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.
18Sintering 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.
19Dynamics of Pt/CNT in O2 or H2O Using ETEM
Schematic Of ETEM Set Up
Langli Luo et al. ACS Catal. 2017, 7, 7658-7664.
20Dynamics 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.
21Probing Nano particle interface Challenge
J. A. Rodriguez et al. Science 2007, 318,
1757-1760.
22Scanning Tunneling Microscope (STM)
Gerd Binning
Heinrich Rohrer
Nobel Prize in Physics in 1986 for inventing STM
STM image of Graphite
23Basic 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.
24Tunneling 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.
25Creating 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.
26In 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.
28Gas 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.
29Formation of self assembled hydrocarbon at
Interface Co(0001)-Gas interface during reaction
Violeta Navarro et al. Nat. Chem. 2016, 8,
929934.
30CO induced coalescence of isolated Pd adatoms at
the Fe3O4(001)
G. S. Parkinson et al. Nat. Mater. 2013, 12,
724728.
31Effect of higher pressure of CO on the Pd/Fe3O4
G. S. Parkinson et al. Nat. Mater. 2013, 12,
724728.
32In Situ STM ETEM for In Situ Studies of
Interface
In Situ STM
ETEM
Franklin. Tao et al. Chem. Rev. 2016, 116,
3487-3539.
33Conclusion 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.
34Thank you
35(No Transcript)
36Creating 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.
37Restructuring 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.
38Behaviour 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.
39Dynamics 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.
40ETEM 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.
41ETEM 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.