Catalytic and biological hydrogen production

Transcription

1 Catalytic and biological hydrogen production J. K. Nørskov Center for Atomic-scale Materials Physics Technical University of Denmark

2 Why make hydrogen? Ammonia synthesis (N 2 +3H 2 2NH 3 ) Sulfur emissions DK Methanol synthesis (CO+2H 2 CH 3 OH) polymers Hydrogenation Year.. Energy carrier???

3 Catalytic and biological hydrogen production Heterogeneous gas phase processes - Steam reforming Electrolysis - An atomistic view - Problems overpotentials and Pt Biological hydrogen evolution - Hydrogenases - Nitrogenases Biomimetic hydrogen evolution?

4 CH 4 +H 2 O 3H 2 +CO Supported Ni catalyst Steam reforming Rostrup-Nielsen, Sehested, Nørskov Adv. Catal. 47, 65 (2002)

5 The atomic-scale picture Ni(111) Ni(211) Bengaard, Nørskov, Sehested, Clausen, Nielsen, Molenbroek, Rostrup-Nielsen: J. Catal. 209, 365 (2002)

6 What determines the reactivity? Ni(111) Barrier for CH 4 dissociation: b Ni(100) Ni(211) Bengaard, Nørskov Ni Adatom (111)

7 Nano-scale effects in catalysis Experimental data: Au as catalyst for CO oxidation: Schubert et al. J. Catal. 197, 113 (2001). Okamura et al. Catal. Lett. 51, 53 (1998). Lin et al. Catal. Lett. 17, 245 (1993). Haruta et al. J. Catal. 115, 301 (1989). Lee et al. J. Catal. 206, 305 (2002). Schimpf et al. Catal. Today 72, 63 (2002). Yuan et al. Catal. Lett. 42, 15 (1996). Haruta Stud. Surf. Sci. Catal. 110, 123 (1997) Haruta Catal. Today 36, 153 (1997). Lopez, Janssens, Clausen, Xu, Mavrikakis, Bligaard, Nørskov, J. Catal. 223, 232 (2004)

8 Making gold reactive: Lopez, Janssens, Clausen, Xu, Mavrikakis, Bligaard, Nørskov J. Catal. 223, 232 (2004)

9 The main nano-effect: many low coordinates sites # lowest coordinated atoms: ~ 1 per particle # atoms total: ~ d 3 => Activity ~ 1/d 3

10 Steam reforming the main problem: Formation of Carbon Nano-fibers In situ (high temperature and pressure) Transmission Electron Microscopy (TEM) Helveg, Cartes, Sehested, Hansen, Clausen, Rostrup-Nielsen, Abild-Pedersen, Nørskov Nature 327, 426 (2004)

11 Carbon nucleation at steps Ni(111) Ni(211) Extra bonding at step Bengaard, Nørskov, Sehested, Clausen, Nielsen, Molenbroek, Rostrup-Nielsen: J. Catal. 209, 365 (2002)

12 Direct observation Helveg, Cartes, Sehested, Hansen, Clausen, Rostrup-Nielsen, Abild-Pedersen, Nørskov Nature 327, 426 (2004)

13 C 2 H 4 dissociation Ni(111) DFT: STM: Ni(111) Ni(211) Vang, Vestergaard, Besenbacher, Dahl, Clausen, Honkala, Nørskov Nature Mat. (2004)

14 STM Ag/Ni(111) Step blocking I Vang, Vestergaard, Besenbacher, Dahl, Clausen, Honkala, Nørskov Nature Mat. (2004)

15 Step blocking II Step blocking changes rate constant for ethane hydrogenolysis: 1000 k (mmol/(g s bar 0.5 ) Ag/Ni 0.1wt%/0.9wt% Ni 1wt% Cu/Ni 0.1wt%/1wt% Sinfelt /T (K -1 ) Vang, Vestergaard, Besenbacher, Dahl, Clausen, Honkala, Nørskov Nature Mat. (2004)

16 Step blocking III Besenbacher, Chorkendorff, Clausen, Hammer, Molenbroek, Nørskov, Stensgaard, Science 279, 1913 (1998)

17 Electrolysis Cathode: 2(H + +e - ) H 2 Anode: H 2 O ½O 2 +2 H + Total: H 2 O ½O 2 +H 2 G 0 =2.46 ev (1.23 ev/electron)

18 Electrolysis Cathode: 2(H + +e - ) H 2 Anode: H 2 O ½O 2 +2 H + Total: H 2 O ½O 2 +H 2 G 0 =2.46 ev (1.23 ev/electron)

19 The hydrogen evolution process Nørskov, Bligaard, Logadottir, Kitchin, Chen, Pandelov, Stimming, JES (2004)

20 The (new) volcano i (1 0 = e k0 θ ) i ( 0 = ek0 1 θ)exp( GH * / kt) θ = exp( GH 1+ exp( G * / kt ) / kt ) H*

21 Biological Hydrogen Production Purple bacteria photofermentation using sunlight and oxidizing organic compounds Microalgae and cyanobacteria direct biophotolysis resulting in water splitting

22 Purple Bacteria hν C 2 H 4 O 2 + 2H 2 O 2CO 2 + 4H 2 Organic acids + - CO 2 + H + e hν e - e - C 2 H + nh + Antenna Energy Reaction Center e - QH 2 Q Cytochrome bc Complex 1 Proton Channel ATP H + H + Fd Nitrogenase e - e - H + ATP ADP + Pi ATP Synthase D. Gust, Arizona State U. H 2 nh + ATP Biological analog of steam reforming

23 Microalgae and cyanobacteria H 2 O H 2 + ½O 2 hν + H + HO 2 O 2 H + e - PC hν nh + Antenna Energy PS II Reaction Center e - QH 2 Q Cytochrome bf Complex 6 PS I Reaction Center Proton Channel H + H + Fd Hydrogenase e - H + ADP + Pi nh + ATP Synthase ATP D. Gust, Arizona State U. H 2 Biological analog of electrolysis

24 The active sites of the enzymes Einsle, Teczan, Andrade, Schmid, Yoshida, Howard, Rees, Science 2002, 297, Hinnemann, Nørskov, JACS 126, 3920 (2004) Vollbeda, Fontecilla-Camps, Dalton Trans (2003). Siegbahn, Blomberg, Wirstam, Crabtree Biol. Inorg. Chem. 6, 460 (2001)

25 Biological hydrogen evolution Hinnemann, Moses, Bonde, Chorkendorff, Nørskov (2004)

26 Biological hydrogen evolution U=430 mv ph=7 ([4S-4Fe] 1+/2+ ) Hinnemann, Moses, Bonde, Chorkendorff, Nørskov

27 Biomimetics Nitrogenase: MoS 2 : Hinnemann, Moses, Nørskov Bonde, Chorkendorff (2004)

28 MoS2 nanoparticles are metallic 1-layer slab: Nanoparticles: Bollinger, Lauritsen, Jacobsen, Nørskov, Helveg, Besenbacher, Phys. Rev. Lett. 87, (2001).

29 Biomimetics II Hinnemann, Moses, Nørskov Bonde, Chorkendorff (2004)

30 Electrolysis Cathode: 2(H + +e - ) H 2 Anode: H 2 O ½O 2 +2 H + Total: H 2 O ½O 2 +H 2 G 0 =2.46 ev (1.23 ev/electron)

31 Electro-thermo chemistry I Example: H 2 O + * OH* +H + +e - 1. Get E for H 2 O + * OH* + 1/2H 2 from DFT 2. Include the effect of water surroundings: E w 3. Calculate G 0 = E + E w + E zpe -T S 0

32 The effect of water I Water layer Ogasawara, Brena, Nordlund, Nyberg, Pelmenschikov, Petterson and Nilsson. PRL, 89, 2002,

33 The effect of water II Mixed O+H 2 O G w ~.0 ev

34 The effect of water III Mixed OH+H 2 O G w = -.33eV Similar to Clay, Haq and Hodgon. PRL, 92, 2004, 46102

35 The effect of water IV Mixed OOH+H 2 O G w = -.22 ev

36 Electro-thermo chemistry II 4. Use definition of U=0 (SHE): 1/2H 2 H + +e -, G(U=0,c H+ =1M ) = 0 5. Calculate effects of potential and ph: G(U,c H+ ) = eu - kt ln(c H+ ) 6. Include effects of local fields (small here)

37 Two conventions: Use H 2 O(g) at bar as reference H 2 O(l) H 2 O(g) (p eq =0.035 bar at 300 K) Fix G tot (U=0, ph=0) = ev for ½O 2 +2H + +2e - H 2 O (avoids calculation for gas phase O 2 )

38 Water splitting Direct route: Peroxy route: H 2 O+* *OH+H + +e - H 2 O+* *OH+H + +e - * OH *O+H + +e - * OH *O+H + +e - 2 *O *OO H 2 O+ *O *OOH+H + +e - *OOH *OO +H + +e - *OO O 2 +* *OO O 2 +*

39 Water splitting at three potentials U 2U 3U 4U Rossmeisl, Logadottir, Nørskov

40 O 2 associative desorption is not possible

41 Only one important energy in problem:

42 Only one important energy in problem:

43 The overpotential for water splitting U=1.23V, ph=0, T=300 K Rossmeisl, Logadottir, Nørskov

44 Hydrogen production Steam reforming detailed picture Electrolysis emerging understanding Enzymatic processes new inspiration

45 Thanks to B. Hinnemann, K. Honkala, T. Bligaard, J. Rossmeisl, H. Bengaard, A. Logadottir, I. Remediakis, A. Hellman, P. G. Moses I. Chorkendorff, O. Lytken, J. Bonde Center for Atomic scale Materials Physics, Technical University of Denmark F. Besenbacher, E. Vestergaard, R. Vang Center for Atomic scale Materials Physics, University of Aarhus S. Dahl, S. Helveg, B. S. Clausen, J. Rostrup-Nielsen, J. Sehested, J. Hyldtroft Haldor Topsøe A/S J. R. Kitchin, J. G. Chen University of Delaware U. Stimming, Pandelov Technical University Munich

46 The old volcanos Trasatti, J. Electroanal. Chem., 39, 163 (1972) O M Bockris, Reddy, Gamboa-Aldeco, Modern Electrochemistry 2A (2000).

47 Nudging the reactivity by alloying Calculated d band shifts: Overlayer Host Ruban, Hammer, Stoltze, Skriver, Nørskov, J.Mol.Catal. A 115, 421 (1997)

48 Initial sticking probability Methane activation on Ni/Ru 5e-7 Thermal dissociation of CH 4 at T = 530 K 4e-7 3e-7 2e-7 1e Ni Coverage [ML] Egeberg, Chorkendorff, Catal. Lett. 77, 207 (2001)

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