# Presentation: 349347

## Heterogeneous CatalysisOpportunities 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 Denmark
- norskov@fysik.dtu.dk

## 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)
 ...

- 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

- What determines the catalytic
- 	activity/selectivity/lifetime ?
- How can we affect it?
- - We have tremendous new possibilities

## Ammonia synthesisN2+3H2 2NH3

- Ozaki and Aika, *Catalysis ***1 **(Anderson and Boudart, Ed.)

## Ammonia synthesis over Ru

- Ammonia synthesis over Ru

**Ru(0001)**

**step**

- Logadottir, Nørskov

## 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)

## The Brønsted-Evans-Polanyi relation 

- Logatottir, Rod, Nørskov, Hammer, Dahl, Jacobsen, J. Catal. **197**, 229 (2001)

- The Brønsted-Evans-Polanyi relation

## Calculated ammonia synthesis rates400 C, 50 bar, H2:N2=3:1, 5% NH3

**Calculated ammonia synthesis rates**400 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.

## 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

- 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 {D******ik******} of solid materials M******i  ******, and a mathematical model F such that A******ij ******being the Turn Over Frequency of Mi as catalyst for the reaction ******j ******at operationg conditions C******j ******one has:***
***Identify ranges of D******ik****** 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***

***Using DFT calculations ***
***in the search of prospective catalysts***

***H. Toulhoat and P. Raybaud***
***Workshop Catalysis from First Principles Vienna  02/02***

## Using DFT calculations 

***Using DFT calculations ***
***in the search of prospective catalysts***

***H. Toulhoat and P. Raybaud***
***Workshop Catalysis from First Principles Vienna  02/02***

## Using DFT calculations 

***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***

## Using DFT calculations 

***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 Correlation

- Hydrodesulfurization of thiophene

- Topsøe, Clausen, Massoth
- Hydrotreating Catalysis, Science and Technology
- (Anderson and Boudart (Eds.), Springer (1996).

## Descriptors from spectroscopy

## Single crystal microcalorimerty

- Larsen, Starr, Campbell, Chem.Thermodyn. **33**, 333 (2001)
- Brown, Kose, King, Chem. Rev. **98**, 797 (1998).

## Descriptors from DFT

- Correlation between adsorption
- energies and activation barriers
- and the d-band center

- Mavrikakis , Hammer, Nørskov
- Phys. Rev. Lett. **81**, 2819 (1998)

##  CO tolerance of Pt alloy anodes for PEM fuel cells

-  Pt

-   M

- 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

- b

- Transition state for CH4
- dissociation on Ni(211)

## Methane activation on Ni/Ru

-  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

- nitrogenase

- ATP

- +

- nucleotide
- replacement

- ATP cleavage
- electron transfer

- +

- reduction

- complex formation

- complex dissociation

- 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)

## N2 hydrogenation on FeMoco

- N2 hydrogenation on FeMoco

-  Rod, Nørskov
-   JACS **122**,  12751 (2000)

## The Fe Protein cycle

- 1)

- 2)

- 3)

- 4)

- E

- E

- E

- MoFe protein

- FeMoco

- P-cluster

- Fe protein

- 4Fe-4S cluster

- ATP

- ADP

- See also: Spee, Arendsen, Wassnik, Marrit, Hagen, Haaker, FEBS Lett. **432**, 55 (1998)

## Comparing the FeMoco and Ru(0001)

-     Rod, Logadottir, Nørskov
*      *J.Chem.Phys. **112**, 5343 (2000)

## 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

## Promoting development

- Synthesis
- testing
- characterization

- Experiments, models

- Theory

- An integrated approach: