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Heterogeneous Catalysis Opportunities and challenges Challenges –Societal needs –Developing the basic understanding Opportunities –Designing at the nano-scale.

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Presentation on theme: "Heterogeneous Catalysis Opportunities and challenges Challenges –Societal needs –Developing the basic understanding Opportunities –Designing at the nano-scale."— Presentation transcript:

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

2 Challenges I Jens Rostrup-Nielsen: XVII Sympósio Iberoamericano de Catálisis, July 16-21, 2000 Dream reactions waiting for a catalyst:

3 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) Challenges II

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 1.What determines the catalytic activity/selectivity/lifetime ? 2.How can we affect it? - We have tremendous new possibilities

7 Ammonia synthesis N 2 +3H 2  2NH 3 Ozaki and Aika, Catalysis 1 (Anderson and Boudart, Ed.)

8 Ammonia synthesis over Ru Ru(0001) step Logadottir, Nørskov

9 Steps do everything Dahl, Logadottir, Egeberg, Larsen, Chorkendorff, Törnqvist, Nørskov, Phys.Rev.Lett. 83, 1814 (1999) Au decorates steps: Hwang, Schroder, Gunther, Behm, Phys. Rev. Lett. 67, 3279 (1991)

10 Logatottir, Rod, Nørskov, Hammer, Dahl, Jacobsen, J. Catal. 197, 229 (2001) The Brønsted-Evans-Polanyi relation

11 Calculated ammonia synthesis rates 400 C, 50 bar, H 2 :N 2 =3:1, 5% NH 3 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

14 Jacobsen, Dahl, Clausen, Bahn, Logadottir, Nørskov, JACS 123 (2001) Measured ammonia synthesis rates 400 C, 50 bar, H 2 :N 2 =3:1

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 The object of the game… Find sets of descriptors {D ik } of solid materials M i, and a mathematical model F such that A ij being the Turn Over Frequency of Mi as catalyst for the reaction j at operationg conditions C j one has: Identify ranges of D ik 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 Using DFT calculations in the search of prospective catalysts H. Toulhoat and P. Raybaud Workshop Catalysis from First Principles Vienna 02/02

17 Using DFT calculations in the search of prospective catalysts H. Toulhoat and P. Raybaud Workshop Catalysis from First Principles Vienna 02/02

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

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

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 Hydrodesulfurization of thiophene Number of Co edge atoms (x10 20 /g catalyst) HDS activity (x10 2 /mol/g/h) Topsøe, Clausen, Massoth Hydrotreating Catalysis, Science and Technology (Anderson and Boudart (Eds.), Springer (1996).

22 Descriptors from spectroscopy CO TPD shiftCore level shift Goodman and Rodriguez, Science 279 (1992) 897

23 Single crystal microcalorimerty Cu/MgO Ag/MgO Pb/MgO 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: Ruban, Hammer, Stoltze, Skriver, Nørskov, J.Mol.Catal. A 115, 421 (1997) Overlayer Host

27 Methane activation Bengaard, Rostrup-Nielsen, Nørskov b Transition state for CH 4 dissociation on Ni(211)

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 + nucleotide replacement ATP cleavage electron transfer + reduction complex formation complex dissociation Fe protein MoFe protein 4Fe-4S cluster P-cluster FeMo cofactor Burgess, Lowe, Chem. Rev. 96, 2983 (1996) Schindelin, Kisker, Schlessman, Howard, Rees, Nature 387, 370 (1997)

31 N 2 hydrogenation on FeMoco Rod, Nørskov JACS 122, (2000)

32 The Fe Protein cycle 1) 2) 3) 4) E E E MoFe protein FeMoco P-cluster Fe protein 4Fe-4S cluster ATP ADP 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 Synthesis testing characterization Experiments, models Theory An integrated approach:


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