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Heterogeneous Catalysis Opportunities and challenges. J. K. Nørskov Center for Atomic-scale Materials Physics Technical University of Denmark [email protected]. Challenges Societal needs Developing the basic understanding Opportunities Designing at the nano-scale. Challenges I. - PowerPoint PPT Presentation
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Heterogeneous CatalysisOpportunities 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 [email protected]
Challenges I
Jens Rostrup-Nielsen: XVII Sympósio Iberoamericano de Catálisis, July 16-21, 2000
Dream reactions waiting for a catalyst:
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
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
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
Rational catalyst design
1. What determines the catalytic activity/selectivity/lifetime ?
2. How can we affect it?
- We have tremendous new possibilities
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)
Logatottir, Rod, Nørskov, Hammer, Dahl, Jacobsen, J. Catal. 197, 229 (2001)
The Brønsted-Evans-Polanyi relation
-0.8 -0.4 0.0 0.4 0.8[E-E(Ru)](eV/N2)
10-5
10-4
10-3
10-2
10-1
100
101
TO
F(s
-1)
Fe
Mo
Ru
Co
Ni
Os
Calculated ammonia synthesis rates400 C, 50 bar, H2:N2=3:1, 5% NH3
Logatottir, Rod, Nørskov, Hammer, Dahl, Jacobsen, J. Catal. 197, 229 (2001)
Interpolation in the periodic table
Jacobsen, Dahl, Clausen, Bahn, Logadottir, Nørskov, JACS 123 (2001) 8404.
Jacobsen, Dahl, Clausen, Bahn, Logadottir, Nørskov, JACS 123 (2001) 8404.
Interpolation in the periodic table
Jacobsen, Dahl, Clausen, Bahn, Logadottir, Nørskov, JACS 123 (2001) 8404.
Measured ammonia synthesis rates 400 C, 50 bar, H2:N2=3:1
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
The object of the game…
• Find sets of descriptors {Dik} of solid materials Mi , and a mathematical model F such that Aij being the Turn Over Frequency of Mi as catalyst for the reaction j at operationg conditions Cj one has:
• Identify ranges of Dik 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
jikjiij CDFCMA ,,
Using DFT calculations
in the search of prospective catalysts
H. Toulhoat and P. Raybaud
Workshop Catalysis from First Principles Vienna 02/02
Periodic Trends for E MC in Fm-3m (NaCl) carbides
ScCr
VMn
CoNi
Y
Zr
TcRu
Rh
Pd
Ta
ReOs
Ir
Ti
Fe
Cu
NbMo
La
Hf
W
Pt
AuAg
0
20
40
60
80
100
120
140
160
E M
C Y
Y/P
AW
/GG
A/S
P (
kJ
/mo
l)
Using DFT calculations
in the search of prospective catalysts
H. Toulhoat and P. Raybaud
Workshop Catalysis from First Principles Vienna 02/02
Adsorption of C2H4 100K
: di-s bound : p bound
: No ads.
Sc Ti V Cr Mn Fe Co Ni Cu
Y Zr Nb Mo Tc Ru Rh Pd Ag
La Hf Ta W Re Os Ir Pt Au
Ru
Rh
Fe
CrW
Ni
Ta
Pt (Diss.)
Ag
AuCu Pt(molec)
Pd
y = 6,267x - 287,99
R2 = 0,894
y = 1,9625x - 29,758
R2 = 0,791
0
100
200
300
400
500
600
0 20 40 60 80 100 120 140
E MC YY (@NaCl/PAW/GGA/SP) (kJ/mol)
Qa
ds
ex
p. C
2H
4/M
(k
J/m
ol)
• E MC @ 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
Re3Ir
Ir3Re
Ir3Cu
Cu3Ir
Cu
Pd
Ru
IrPt
Os
Re
Co
Ni
1,E+00
1,E+01
1,E+02
1,E+03
1,E+04
1,E+05
10 12 14 16 18 20 22 24 26 28 30E MC YY (kCal.mol-1)
Ra
te i
n H
yd
rog
en
ati
on
of
C6
H6
(s
-1) TOF@30°C (M/Al2O3
Brunelle et al., 1977)
V théor.
• 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
Getting data/descriptors
• Structure (in situ)
• Spectroscopy (in situ)
• Surface thermochemistry
• Calculations
• …
There is a large need for systematic data
- and for good descriptors
Structure-activity CorrelationHydrodesulfurization of thiophene
1.5
10
0.5
00 1 2 3Number of Co edge atoms
(x1020/g catalyst)
HD
S a
cti
vit
y
(x10
2/m
ol/g
/h)
Topsøe, Clausen, MassothHydrotreating Catalysis, Science and Technology(Anderson and Boudart (Eds.), Springer (1996).
Descriptors from spectroscopyCO TPD shift Core level shift
Goodman and Rodriguez, Science 279 (1992) 897
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).
Descriptors from
DFT
Correlation between adsorptionenergies and activation barriersand the d-band center
Mavrikakis , Hammer, NørskovPhys. Rev. Lett. 81, 2819 (1998)
CO tolerance of Pt alloy anodes for PEM fuel cells
Pt
M
-0,5
0,0
0,5
1,0
1,5
2,0
Au Ir Ag Pd Rh Ru Cu Ni Co Fe Pt
EC
O ,
eV
- d,
eV
Substrate M
-0,2
0,0
0,2
0,4
0,6
0,8
1,0
0,0
0,2
0,4
0,6
0,8
1,0
Measured overages of CO on the alloy electrodes with 100 ppm CO/H2
M. Watanabe et al., Phys. Chem. Chem. Phys. 3 (2001) 306
1- co
Calculated changes in CO adsorption energy
S. Gottesfeld et al., J. Electrochem. Soc. 148 (2001) A11.
Christoffersen, Liu, Ruban, Skriver, Nørskov, J.Catal. 199, 123 (2001)
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
Methane activation
Bengaard, Rostrup-Nielsen, Nørskov
bTransition state for CH4
dissociation on Ni(211)
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-7
Thermal dissociation of CH4 at T = 530 K
Egeberg, Chorkendorff, Catal. Lett. 77, 207 (2001)
Lessons from biology
• Catalysis at ambient temperature and pressure
• Extreme selectivity
• Direct coupling of energy into the important reaction coordinate (non-thermal catalysis)
Nitrogenase 8e8HN2 23 H2NH
nitrogenase
ATP
FeP +2(MgATP) MoFeP 1k
1-kFeP 2(MgATP) MoFeP
4k 2knucleotidereplacement
ATP cleavageelectron transfer
oxFeP 2(MgADP) + MoFeP 3k
3-k oxFeP 2i )P(MgADP, MoFeP
reduction
complex formation
complex dissociation
-4AlFADP
Fe protein
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)
The Fe Protein cycle
1)
2)
3)
4)
E
E
E
MoFe protein
FeMoco P-cluster
Fe protein
4Fe-4S cluster
ATP
ADP 24HPO
See also: Spee, Arendsen, Wassnik, Marrit, Hagen, Haaker, FEBS Lett. 432, 55 (1998)
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!
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