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

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

2 Hydrogen production strategies Reforming of hydrocarbons Reforming of biomass Electrolysis Photolytic conversion Biological conversion..

3 CH 4 +H 2 O 3H 2 +CO Steam reforming DH= +206 kj/mol Ni catalyst Rostrup-Nielsen, Sehested, Nørskov Adv. Catal. 47, 65 (2002)

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

5 Problems 1. Carbon formation 2. Metal dusting 3. Too much CO

6 In situ (high temperature and pressure) Transmission Electron Microscopy (TEM) Formation of Carbon Nano-fibers The movies: Helveg, Cartes, Sehested, Hansen, Clausen, Rostrup-Nielsen, Abild-Pedersen, Nørskov Nature 327, 426 (2004)

7 The role of steps Helveg, Cartes, Sehested, Hansen, Clausen, Rostrup-Nielsen, Abild-Pedersen, Nørskov Nature 327, 426 (2004)

8 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)

9 Step blocking MD simulation Au/Ni Molenbroek, Nørskov, Clausen J. Phys. Chem. B 105, 5450 (2001)

10 Catalyst design at the nano-scale Besenbacher, Chorkendorff, Clausen, Hammer, Molenbroek, Nørskov, Stensgaard, Science 279, 1913 (1998)

11 Too much CO CO is a product: CO poisons PEM fuel cell: CH 4 +H 2 O 3H 2 +CO Possible solutions: Make fuel cell less CO poisoned Remove CO S. Gottesfeld et al., J. Electrochem. Soc. 148 (2001) A11.

12 CO blocks for hydrogen adsorption at the anode H coverage in the presence of CO: Θ H x10 4 T=80 o C E CO =-1.4 ev E H2 =-0.5 ev ppm CO in 1 bar H 2 Christoffersen, Liu, Ruban, Skriver, Nørskov: J.Catal. 199, 123 (2001)

13 New 3-component alloys from DFT Measure of competition Between CO and H: DE CO -1/2 DE H2 M Pt DE CO -1/2 DE H2 (ev) 0,18 0,15 0,12 0,09 0,06 0,03 PtRuCo PtRuNi PtRu Ru 0,00 Pure Fe Co Rh Ir Ni Pd Pt Cu Ag Au Sn Pt M Strasser, Fan, Devenney, Weinberg, Liu, Nørskov, J. Phys. Chem.B, 107, (2003)

14 Combinatorial Electrochemistry Electrochemical Multi-electrode array 64 addressable electrodes Photolitographic Fabrication Symyx Technologies proprietary US Patent No 6,187,164; 5,985,356; 6,004,617. Additional US and foreign patents pending

15 Results from parallel screening experiments Strasser, Fan, Devenney, Weinberg Symyx Technologies Relative area-normalized activity Log [ (I alloy /A alloy,real ) / (I Pt /A Pt,real )] Pt 20 Co 60 Ru 20 Pt 40 Co 40 Ru 20 Pt 60 Ni 20 Ru 20 Pt 60 Co 20 Ru 20 Pt 60 Ru 40 Pt 40 Ni 40 Ru 20 Pt20 Ni 60 Ru 20 Pt Strasser, Fan, Devenney, Weinberg, Liu, Nørskov J. Phys. Chem.B 107, (2003)

16 3 2 Water gas shift: Thermochemistry Disproportionation : OH* + OH* H 2 O* + O* CO(a)+2H(a) +2OH(a) Au Ag 1 Energy (ev) 0-1 CO(g)+2H 2 O(g) Cu Pt CO 2 (g)+h 2 (g)+ H 2 O(g) CO(a)+2H 2 O(g) Complete Dissociation : OH* +* O* + H* CO(a)+H(a) +OH(a)+ H CO(a)+2H 2 O(a) 2 O(a) Pd Ir Rh Co Ni Ru CO(a)+ 2H(a) +O(a) +H 2 O(a) CO2(a)+2H(a) +H 2 O(a) Courtesy of M. Mavrikakis UW Madison CO 2 (a)+h 2 (g) +H 2 O(a)

17 Nano effects in catalysis CO oxidation on Au particles supported on TiO 2 Valden, Lai, Goodman, Science 281, 1647 (1998) Wahlström, Lopez, Schaub, Thostrup, Rønnau, Africh, Lægsgaard, Nørskov, Besenbacher, PRL 90, (2003) No generally accepted explanation yet!

18 Reforming of biomass Reforming of oxygenated hydrocarbons over Raney-NiSn. Huber, Shabaker, Dumesic, Science 300, (2003).

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

20 The overpotential Ni-based electrolyzer: U = U 0 + h cathode + h anode + I R Efficiency: U0 U ( i) V ~ 1. 9 V ~ 65% Wendt, Imarisio, J. Appl. Electrochem. 17, 1 (1988)

21 Photovoltaics+electrolyzer 12% x 65% = 7.8%

22 The origin of the overpotential Even larger barriers at the anode! Kitchin, Bligaard, Stimming, Nørskov

23 A Pt/Pt cell Khaselev, Bansal, Turner, Int. J. Hydrogen Energy 26, 127 (2001)

24 Biomimetic hydrogen production Hydrogenase catalyses The active site H + +e - ½H 2 Add active site to electrode? Or make structure with similar properties? Gloaguen, Lawrence, Rauchfuss, JACS 123, 9476 (2001) Siegbahn, Blomberg, Wirstam, Crabtree J. Biological Inorganic Chemistry. 6, 460 (2001) Lamle, Vincent, Halliwell, Albracht, Armstrong, Dalton Trans

25 Biomimetic hydrogen production II Nitrogenase: Hinnemann, Nørskov, JACS 126, 3920 (2004)

26 The grand challenge Understand relationship between surface structure and catalytic properties Use insight for rational (atomic-scale) design of new catalysts Theory Model experiments Synthesis of new nano particle catalysts Testing and characterization

27 Thanks to B. Hinnemann, K. Honkala, T. Bligaard, H. Beengaard, F. Abild-Pedersen, P. Liu, A. Logadottir, I. Chorkendorff 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. Helveg, B. S. Clausen, J. Rostrup-Nielsen, J. Sehested, A. Molenbroek Haldor Topsøe J. R. Kitchin, M. A. Barteau, J. G. Chen University of Delaware P. Strasser, H. Weinberg Symyx U. Stimming Technical University Munich M. Mavrikakis University of Wisconsin, Madison