Reactions at solid surfaces: From atoms to complexity. Gerhard Ertl Fritz Haber Institut der Max Planck-Gesellschaft Berlin, Germany

Transcription

1 Reactions at solid surfaces: From atoms to complexity Gerhard Ertl Fritz Haber Institut der Max Planck-Gesellschaft Berlin, Germany

2 Jöns Jakob Berzelius

3 Wilhelm Ostwald Nobel Prize 1909

4 A + B C r = d[a] dt = k[a][b] k = k 0 e E*/RT

5 Progress of a chemical reaction Energy E without catalyst with catalyst ΔE

6 Heterogeneous catalysis dn i dt Reactor Steady-state reaction rate: dn i dt dn j dt i: reactants j: products dn j dt = r = f (p i, p j, T, catalyst)

7 Fritz Haber Nobel Prize 1918

8 N H 2 2 NH 3 Haber & LeRossignol, 1909

9 Carl Bosch Nobel Prize 1931

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11 World population and ammonia production Population / Population Production / 10 6 t/a N 1 Production Year M. Appl, Ammonia, Wiley VCH (1999)

12 P.H. Emmett (1974): The experimental work of the past 50 years leads to the conclusion that the rate-limiting step in ammonia synthesis over iron catalysts is the chemisorption of nitrogen. The question as to whether the nitrogen species involved is molecular or atomic is still not conclusively resolved, though, in my opinion, the direct participation of nitrogen in an atomic form seems more likely than in molecular form. The physical basis of heterogeneous catalysis (E. Drauglis & R.I. Jaffee, eds.), Plenum Press, New York, 1975, p. 3

13 alyticccatalytic synthesis of ammonia am ((Haber--Bosch process)process) Technical conditions: T 400 C, p 300 bar promoted iron catalyst BASF S6-10 catalyst (at. %) 100 nm Fe K Al Ca O Bulk composition Surface unreduced reduced cat. active spot G. Ertl, D. Prigge, R. Schlögl & D. Weiss, J.Catal. 79 (1983), 359

14 Irving Langmuir Nobel Prize 1932

15 Most finely divided catalysts must have structures of great complexity. In order to simplify our theoretical consideration of reactions at surfaces, let us confine our attention to reactions on plane surfaces. If the principles in this case are well understood, it should then be possible to extend the theory to the case of porous bodies. In general, we should look upon the surface as consisting of a checkerboard... I. Langmuir, Trans. Faraday Soc. 17 (1922), 607

16 AlAl (111)(111) 1.3 nm 0.9 nm 4.6 nm 7.1 nm

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18 O / Pt (111) J. Wintterlin, R. Schuster, and G. Ertl, Phys.Rev.Lett. 77 (1996), 123.

19 O/Ru (0001) T = 300 K QuickTime and a decompressor are needed to see this picture. J. Wintterlin & R. Schuster

20 N / Fe (100) Å R. Imbihl, R.J. Behm, G. Ertl, W. Moritz, Surface Sci. 123 (1982), 129.

21 Dissociative nitrogen adsorption on Fe single crystal surfaces y Fe (111) Fe (100), T=693K Fe (110) Fe (110) Fe (100) [L] N 2 exposure Fe (111) F. Bozso, G. Ertl, M. Grunze & M. Weiss, J. Catal. 49 (1977), 18; 50 (1977), 519

22 Mechanism of catalytic ammonia synthesis N + 3H 314 NH + 2H N 2 N 2 ad 2N ad 1 / 2 N / 2 H kj/mol ad + 3 / 2 H N ad + 3H ad ~960 NH ad + 2H ad 389 NH 2 + H ~21 50 ~33 ~41 1 / 2 N NH 2ad + H ad 460 ΔH=46 kj/mol NH 3 NH 3ad H 2 2H ad N ad + H ad NH ad + H ad NH ad NH 2 ad NH 2 ad + H ad NH 3 ad NH 3 G. Ertl, Catal.Rev.Sci.Eng. 21 (1980), 201

23 Catalytic synthesis of ammonia: Microkinetics C ammonia Calculated exit NH 3 mole fraction atm 150 atm 300 atm Experimental exit NH 3 mole fraction N H 2 2NH 3 promoted iron catalyst P. Stoltze and J.K. Nørskov, Phys. Rev. Lett. 55 (1985), 2502 J. Catal. 110 (1988), 1

24 mg/mile 150 Car exhaust emission (USA) CO HC NO x year

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26 Rh(111)-( 3 3)R30 -CO Rh(111)-(2 2)-O Rh(111)-(2 2)-(O+1 CO) S. Schwegmann, H. Over, V. De Renzi, G. Ertl, Surf Sci. 375 (1997), 91

27 Catalytic oxidation of CO O C Pt 1 CO + 2 O 2 2CO + O 2 2CO 2 CO + * CO ad O 2 + 2* O 2,ad 2O ad O ad + CO ad CO 2 + 2* 260 E LH = 100 I ΔH = 283 kj/mol CO ad +O ad CO 2ad ( Pt at low coverages) ~21 CO2

28 1 CO + 2 O 2 CO 2 / Pt(110) 300 R CO t [100sec] T = 470K; p CO = mbar; p O2 = mbar M. Eiswirth and G. Ertl, Surface Sci. 177 (1986), 90

29 160 Number (thousands) Year Hares Lynxes

30 Lotka-Volterra Model dx dt = α 1 x α 2 xy dy dt = β 1 xy β 2 y x,y x y t

31 CO / Pt(110) 1 2 missing row 0.2 ML θ CO 0.5 ML 1 1 θ CO 0.5 ML

32 1 CO + 2 O 2 CO 2 / Pt(110) K. Krischer, M.Eiswirth & G. Ertl, J.Chem.Phys. 96 (1992), 9161 (Theory) rate [ML s 1 ] coverage [ML] CO O t [s] T = 540K; p O2 = mbar; p CO = mbar

33 Heartbeats of ultra thin catalyst QuickTime and a decompressor are needed to see this picture. F. Cirak, J.E. Cisternas, A.M. Cuitino, G. Ertl, P.Holmes, I. Kevrekidis, M.Ortiz, H.H. Rotermund, M.Schunack, J. Wolff, Science 300 (2003), 1932 Ultra thin (200 nm thick) Pt(110) catalyst during CO oxidation, 5 mm sample diameter, T = 528 K, p O2 = 1 x 10-2 mbar, p CO = 1.85 x 10-3 mbar

34 [110] -- [110] 2 CO + O 2 2 CO 2 / Pt(110) Target patterns [001] QuickTime and a Sorenson Video decompressor are needed to see this picture. p O 2 = 3.2 x 10-4 mbar p CO = 3 x 10-5 mbar T = 427 K Ø = 500 μm

35 Spiral waves during CO-oxidation on Pt(110) QuickTime and a Sorenson Video decompressor are needed to see this picture. PEEM images with 500 µm diameter, steady-state conditions: p O2 =4x10-4 mbar, p CO =4.3x10-5 mbar, T = 448 K S. Nettesheim, A. von Oertzen, H.H. Rotermund, G. Ertl, J.Chem.Phys. 98 (1993), 9977

36 Chemical turbulence QuickTime and a Photo decompressor are needed to see this picture. Photoemission electron microscope (PEEM) imaging. Dark regions are predominantly oxygen covered, bright regions are mainly CO covered. Real time, image size 360 x 360 μm Temperature T = 548 K, oxygen partial pressure p o2 = 4 x 10-4 mbar, CO partial pressure p co = 1.2 x 10-4 mbar.

37 Global delayed feedback O 2 CO UHV Chamber PEEM sample Delay Amplifier Integrator M. Kim, M. Bertram, M. Pollmann, A. von Oertzen; A.S. Mikhailov, H.H. Rotermund, and G. Ertl, Science 292 ( 2001 ), 1357

38 CO oxidation reaction on Pt(110) QuickTime and a decompressor are needed to see this picture. Suppression of spiralwave turbulence and development of intermittent turbulence with cascades of reproducing bubbles

39 Retina 10μm

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