Catalytic and biological hydrogen production

J. K. NørskovCenter for Atomic-scale Materials Physics

Technical University of Denmarknorskov@fysik.dtu.dk

Why make hydrogen?Sulfur emissions DK

Year

• Ammonia synthesis(N2+3H2 2NH3)

• Methanol synthesis (CO+2H2 CH3OH)

polymers …

• Hydrogenation

• …..

• Energy carrier???

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?

Steam reformingCH4+H2O 3H2+CO

Supported Ni catalyst

Rostrup-Nielsen, Sehested, NørskovAdv. Catal. 47, 65 (2002)

The atomic-scale picture

Ni(111)

Ni(211)

Bengaard, Nørskov, Sehested, Clausen, Nielsen, Molenbroek, Rostrup-Nielsen: J. Catal. 209, 365 (2002)

What determines the reactivity?

Bengaard, Nørskov

bBarrier for CH4 dissociation:

Ni(111)

Ni(211)

Ni Adatom(111)

Ni(100)

Nano-scale effects in catalysis

Lopez, Janssens, Clausen, Xu, Mavrikakis, Bligaard, Nørskov, J. Catal. 223, 232 (2004)

Au as catalyst for CO oxidation:Experimental data:

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).

Makinggold reactive:

Lopez, Janssens, Clausen, Xu, Mavrikakis, Bligaard, NørskovJ. Catal. 223, 232 (2004)

The main nano-effect: many low coordinates sites

# lowest coordinated atoms:~ 1 per particle

# atoms total:~ d3

=>

Activity~ 1/d3

Steam reforming – the main problem:Formation of Carbon Nano-fibers

In situ (high temperatureand pressure) TransmissionElectron Microscopy (TEM)

Helveg, Cartes, Sehested, Hansen, Clausen, Rostrup-Nielsen, Abild-Pedersen, NørskovNature 327, 426 (2004)

Carbon nucleation at steps

Ni(211)

Bengaard, Nørskov, Sehested, Clausen, Nielsen, Molenbroek, Rostrup-Nielsen: J. Catal. 209, 365 (2002)

Extra bonding at step

Ni(111)

Direct observation

Helveg, Cartes, Sehested, Hansen, Clausen, Rostrup-Nielsen, Abild-Pedersen, NørskovNature 327, 426 (2004)

C2H4 dissociation Ni(111)DFT: STM:

Ni(211)

Ni(111)

Vang, Vestergaard, Besenbacher, Dahl, Clausen, Honkala, Nørskov Nature Mat. (2004)

Step blocking ISTM – Ag/Ni(111)

Vang, Vestergaard, Besenbacher, Dahl, Clausen, Honkala, Nørskov Nature Mat. (2004)

Step blocking II

1

10

100

1000

1.5 1.6 1.7 1.8 1.9

1000/T (K-1)

k (m

mol

/(g·s

·bar

0.5 ) Ni 1wt%

Ag/Ni 0.1wt%/0.9wt% Cu/Ni 0.1wt%/1wt%

Step blocking changes rate constant for ethane hydrogenolysis:

Vang, Vestergaard, Besenbacher, Dahl, Clausen, Honkala, Nørskov Nature Mat. (2004)

Sinfelt

Step blocking III

Besenbacher, Chorkendorff, Clausen, Hammer, Molenbroek, Nørskov, Stensgaard, Science 279, 1913 (1998)

Electrolysis

Cathode: 2(H++e-) H2

Anode: H2O ½ O2 +2 H+____________________________________

Total: H2O ½ O2 +H2

∆G0 =2.46 eV (1.23 eV/electron)

Electrolysis

Cathode: 2(H++e-) H2

Anode: H2O ½ O2 +2 H+____________________________________

Total: H2O ½ O2 +H2

∆G0 =2.46 eV (1.23 eV/electron)

The hydrogen evolution process

Nørskov, Bligaard, Logadottir, Kitchin, Chen, Pandelov, Stimming, JES (2004)

The (new) volcano

)/exp()1( *00 kTGkei H∆−−−= θ)1(00 θ−−= kei

)/exp(1)/exp(

*

*

kTGkTG

H

H

∆−+∆−

=θ

Biological Hydrogen Production

– Purple bacteria – “photofermentation” using sunlight and oxidizing organic compounds

– Microalgae and cyanobacteria – “directbiophotolysis” resulting in water splitting

Purple BacteriaC2H4O2 + 2H2O → 2CO2 + 4H2

hν

Antenna

ReactionCenter

CytochromeComplexbc 1

ProtonChannel

ATPSynthase

hν

Energy

Q

QH2

H+H+

H+nH+

nH+

e-

C2

e- e-

ADP + Pi

ATP

H+

H2

e-

Fd

Nitrogenase

e-ATP

ATP

Organic acids CO + H + e2+ -

Biological analog of steam reformingD. Gust, Arizona State U.

Microalgae and cyanobacteriaH2O → H2 + ½O2

Antenna

PS IIReactionCenter Cytochrome

Complexb f 6

hν hν

Energy

Q

QH 2

H+

H+

H2

e -

e-

PCe-

ProtonChannel

ATPSynthase

nH+

nH+

ADP + Pi

ATP

PS IReactionCenter

H O2H + + O2

H+ H+Fd

Hydrogenase

Biological analog of electrolysisD. Gust, Arizona State U.

The active sites of the enzymes

Einsle, Teczan, Andrade, Schmid, Yoshida, Howard, Rees, Science 2002, 297, 1696.

Hinnemann, Nørskov, JACS 126, 3920 (2004)

Vollbeda, Fontecilla-Camps, Dalton Trans.4030-3048 (2003).

Siegbahn, Blomberg, Wirstam, Crabtree Biol. Inorg. Chem. 6, 460 (2001)

Biological hydrogen evolution

Hinnemann, Moses, Bonde, Chorkendorff , Nørskov (2004)

Biological hydrogen evolution

Hinnemann, Moses, Bonde, Chorkendorff , Nørskov

pH=7

U=430 mV

([4S-4Fe]1+/2+ )

Biomimetics Nitrogenase:

MoS2:

Hinnemann, Moses, NørskovBonde, Chorkendorff (2004)

MoS2 nanoparticles are metallicNanoparticles:1-layer slab:

Bollinger, Lauritsen, Jacobsen, Nørskov, Helveg, Besenbacher, Phys. Rev. Lett. 87, 196803 (2001).

Biomimetics II

Hinnemann, Moses, NørskovBonde, Chorkendorff (2004)

Electrolysis

Cathode: 2(H++e-) H2

Anode: H2O ½ O2 +2 H+____________________________________

Total: H2O ½ O2 +H2

∆G0 =2.46 eV (1.23 eV/electron)

Electro-thermo chemistry I

Example: H2O + * OH* +H++e-

1. Get ∆E for H2O + * OH* + 1/2H2 from DFT

2. Include the effect of water surroundings: ∆Ew

3. Calculate ∆G0 = ∆E +∆Ew+∆Ezpe-T∆S0

The effect of water I

Water layer

Ogasawara, Brena, Nordlund, Nyberg, Pelmenschikov, Petterson and Nilsson.PRL, 89, 2002, 276102

The effect of water IIMixed O+H2O∆Gw ~ .0 eV

The effect of water IIIMixed OH+H2O∆Gw = -.33eV

Similar to Clay, Haq and Hodgon.PRL, 92, 2004, 46102

The effect of water IVMixed OOH+H2O∆Gw = -.22 eV

Electro-thermo chemistry II

4. Use definition of U=0 (SHE): 1/2H2 ↔ H++e- ,∆G(U=0,cH+=1M ) = 0

5. Calculate effects of potential and pH:∆G(U,cH+) = eU - kT ln(cH+)

6. Include effects of local fields (small here)

Two conventions:

• Use H2O(g) at 0.035 bar as referenceH2O(l)↔ H2O(g)(peq=0.035 bar at 300 K)

• Fix ∆Gtot(U=0, pH=0) = -2.46 eV for ½O2+2H++2e- H2O(avoids calculation for gas phase O2)

Water splitting

Direct route: Peroxy route:

H2O+* *OH+H++e- H2O+* *OH+H++e-

* OH *O+H++e- * OH *O+H++e-

2 *O *OO H2O+ *O *OOH+H++e-

*OOH *OO +H++e-

*OO O2+* *OO O2+*

Water splitting at three potentials

Rossmeisl, Logadottir, Nørskov

U4U3U2U

O2 associative desorption is not possible

Only one important energy in problem:

Only one important energy in problem:

The overpotential for water splittingU=1.23V, pH=0, T=300 K

Rossmeisl, Logadottir, Nørskov

• Steam reforming– detailed picture

• Electrolysis – emerging understanding

• Enzymatic processes– new inspiration

Hydrogen production

Thanks toB. Hinnemann, K. Honkala, T. Bligaard, J. Rossmeisl, H. Bengaard,

A. Logadottir, I. Remediakis, A. Hellman, P. G. Moses

I. Chorkendorff, O. Lytken, J. BondeCenter for Atomic scale Materials Physics, Technical University of Denmark

F. Besenbacher, E. Vestergaard, R. VangCenter for Atomic scale Materials Physics, University of Aarhus

S. Dahl, S. Helveg, B. S. Clausen, J. Rostrup-Nielsen, J. Sehested, J. HyldtroftHaldor Topsøe A/S

J. R. Kitchin, J. G. ChenUniversity of Delaware

U. Stimming, PandelovTechnical University Munich

The old volcanos

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

Nudging the reactivity by alloyingCalculated d band shifts:

Overlayer

Host

Ruban, Hammer, Stoltze, Skriver, Nørskov, J.Mol.Catal. A 115, 421 (1997)

Methane activation on Ni/Ru

Ni Coverage [ML]0 1 2

Initi

alst

icki

ngpr

obab

ility

0

1e-7

2e-7

3e-7

4e-7

5e-7Thermal dissociation of CH4 at T = 530 K

Egeberg, Chorkendorff, Catal. Lett. 77, 207 (2001)