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Heterogeneous Catalysis Opportunities and challenges

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Title: Heterogeneous Catalysis Opportunities and challenges


1
Heterogeneous CatalysisOpportunities and
challenges
J. K. Nørskov Center for Atomic-scale
Materials Physics Technical University of
Denmark norskov_at_fysik.dtu.dk
  • Challenges
  • Societal needs
  • Developing the basic understanding
  • Opportunities
  • Designing at the nano-scale

2
Challenges I
Dream reactions waiting for a catalyst
Jens Rostrup-Nielsen XVII Sympósio
Iberoamericano de Catálisis, July 16-21, 2000
3
Challenges II
  • Dreaming on .
  • Heterogeneous catalysts for assymmetric synthesis
  • Photolytic water splitting (hydrogen economy)
  • Biomimetics, synthetic enzymes
  • Non-thermal processes in general
  • (e.g. electro- and photocatalysis)

See E. Derouane, CATTECH 5, 226 (2001)
4
Challenges III
  • The science of heterogeneous catalysis
  • A comprehensive scientific basis
  • Much has been done
  • Much more is needed (oxides, size effects,
    photocatalysis, electrocatalysis, relation to
    homogeneous and enzyme catalysis )
  • Making the insight useful!
  • The ultimate test

5
Opportunities- design at the nano-scale
  • Rational catalyst design
  • Discovery on the basis of insight
  • Data-driven methods
  • - Accelerated discovery by access to
  • large amounts of data
  • Bio-inspired catalysis

6
Rational catalyst design
  • What determines the catalytic
  • activity/selectivity/lifetime ?
  • How can we affect it?
  • - We have tremendous new possibilities

7
Ammonia synthesisN23H2? 2NH3
Ozaki and Aika, Catalysis 1 (Anderson and
Boudart, Ed.)
8
Ammonia synthesis over Ru
Ru(0001)
step
Logadottir, Nørskov
9
Steps do everything
Au decorates steps Hwang, Schroder, Gunther,
Behm, Phys. Rev. Lett. 67, 3279 (1991)  
Dahl, Logadottir, Egeberg, Larsen, Chorkendorff,
Törnqvist, Nørskov, Phys.Rev.Lett. 83, 1814
(1999)
10
The Brønsted-Evans-Polanyi relation
Logatottir, Rod, Nørskov, Hammer, Dahl, Jacobsen,
J. Catal. 197, 229 (2001)
11
Calculated ammonia synthesis rates400 C, 50 bar,
H2N231, 5 NH3
Logatottir, Rod, Nørskov, Hammer, Dahl, Jacobsen,
J. Catal. 197, 229 (2001)
12
Interpolation in the periodic table
Jacobsen, Dahl, Clausen, Bahn, Logadottir,
Nørskov, JACS 123 (2001) 8404.
13
Interpolation in the periodic table
Jacobsen, Dahl, Clausen, Bahn, Logadottir,
Nørskov, JACS 123 (2001) 8404.
14
Measured ammonia synthesis rates 400 C, 50 bar,
H2N231
Jacobsen, Dahl, Clausen, Bahn, Logadottir,
Nørskov, JACS 123 (2001) 8404.
15
Data driven methods
  • High throughput screening
  • Direct testing of many catalysts, fast,
    efficiently
  • Data mining
  • Correlating catalytic activity/selectivity/
    durability to descriptors that can be tabulated

16
H. Toulhoat and P. Raybaud Workshop Catalysis
from First Principles Vienna 02/02
Using DFT calculations in the search of
prospective catalysts
  • The object of the game
  • Find sets of descriptors Dik of solid materials
    Mi , and a mathematical model F such that Aij
    being the Turn Over Frequency of Mi as catalyst
    for the reaction j at operationg conditions Cj
    one has
  • Identify ranges of Dik that maximize F
  • Screen Databases of Materials Properties before
    screening real materials
  • Better if one descriptor is sufficient, but do
    not take it for granted
  • Much better if F has a sound physical basis
  • Adsorbate/substrate bond strengths should provide
    good descriptors according to the Sabatier
    principle

17
H. Toulhoat and P. Raybaud Workshop Catalysis
from First Principles Vienna 02/02
Using DFT calculations in the search of
prospective catalysts
18
H. Toulhoat and P. Raybaud Workshop Catalysis
from First Principles Vienna 02/02
Using DFT calculations in the search of
prospective catalysts
  • E MC _at_ Fm-3m carbides is rather consistent with
    simple chemisorption models
  • Onset of dissociative chemisorption as MC bond
    strength increases

19
H. Toulhoat and P. Raybaud Workshop Catalysis
from First Principles Vienna 02/02
Using DFT calculations in the search of
prospective catalysts
  • The experimental Alloying effects is correctly
    predicted

20
Getting data/descriptors
  • Structure (in situ)
  • Spectroscopy (in situ)
  • Surface thermochemistry
  • Calculations
  • There is a large need for systematic data
  • - and for good descriptors

21
Structure-activity Correlation Hydrodesulfurizatio
n of thiophene
Topsøe, Clausen, Massoth Hydrotreating Catalysis,
Science and Technology (Anderson and Boudart
(Eds.), Springer (1996).
22
Descriptors from spectroscopy
23
Single crystal microcalorimerty
Larsen, Starr, Campbell, Chem.Thermodyn. 33, 333
(2001) Brown, Kose, King, Chem. Rev. 98, 797
(1998).
24
Descriptors from DFT
Correlation between adsorption energies and
activation barriers and the d-band center
Mavrikakis , Hammer, Nørskov Phys. Rev. Lett. 81,
2819 (1998)
25
CO tolerance of Pt alloy anodes for PEM fuel
cells
Pt
M
S. Gottesfeld et al., J. Electrochem. Soc. 148
(2001) A11.
   Christoffersen, Liu, Ruban, Skriver, Nørskov,
J.Catal. 199, 123 (2001)
26
How can the d-band center be changed?
Calculated d band shifts
Overlayer
Host
Ruban, Hammer, Stoltze, Skriver, Nørskov,
J.Mol.Catal. A 115, 421 (1997)
27
Methane activation
Transition state for CH4 dissociation on Ni(211)
b
Bengaard, Rostrup-Nielsen, Nørskov
28
Methane activation on Ni/Ru
Egeberg, Chorkendorff, Catal. Lett. 77, 207
(2001)
29
Lessons from biology
  • Catalysis at ambient temperature and pressure
  • Extreme selectivity
  • Direct coupling of energy into the important
    reaction coordinate (non-thermal catalysis)

30
Nitrogenase
nitrogenase
ATP
complex formation
Fe protein

4Fe-4S cluster
MoFe protein
P-cluster
nucleotide replacement
ATP cleavage electron transfer
FeMo cofactor
Fe protein
reduction

complex dissociation
Burgess, Lowe, Chem. Rev. 96, 2983
(1996) Schindelin, Kisker, Schlessman, Howard,
Rees, Nature 387, 370 (1997)
31
N2 hydrogenation on FeMoco
Rod, Nørskov JACS 122, 12751 (2000)
32
The Fe Protein cycle
E
MoFe protein
Fe protein
ATP
1)
4Fe-4S cluster
FeMoco
P-cluster
2)
E
3)
ADP
E
4)
See also Spee, Arendsen, Wassnik, Marrit, Hagen,
Haaker, FEBS Lett. 432, 55 (1998)
33
Comparing the FeMoco and Ru(0001)
Rod, Logadottir, Nørskov J.Chem.Phys.
112, 5343 (2000)
34
Status
  • Well developed basic understanding
    theory-experiment
  • Beginning to be able to use it directly in
    catalyst design
  • Some activity-descriptor correlations
  • Host of new in situ methods for catalyst
    characterization
  • New very powerful screening methods
  • We have a starting point which is radically
    different from the situation 5 or 10 years ago!

35
Moving forward
  • More basic understanding theory-experiment
  • Integration of the conceptual framework for
    heterogeneous, homogeneous and enzyme catalysis
  • More systematic data (descriptors)
  • Better synthesis methods
  • Better coupling of catalyst design and process
    engineering
  • INTEGRATION

36
Promoting development
An integrated approach
Experiments, models
Synthesis testing characterization
Theory
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