The Route to Better Catalysts:From Surface Science to Nanotechnology

by Francisco Zaera

Department of ChemistryUniversity of California

Riverside, CA 92521, USAPhone: 1 (951) 827-5498

Fax: 1 (951) 827-3962Email: zaera@ucr.edu

http://www.zaera.chem.ucr.edu

Haldor Topsøe Catalysis ForumMunkerupgaard, Denmark

August 27, 2015

1

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

F. Zaera, J. Phys. Chem. B, 106(16), 4043-4052 (2002).F. Zaera, Catal. Lett., 142(5), 501-516 (2012).

A selective process:• Consumes less reactants

• Avoids separation problems• Produces less polluting byproducts

2

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

IntroductionKey Issues in Catalysis

∆G°

Reactant

Product 1 Product 2

Selectivity Stability

T, Gases

Sintering:• Reduces surface area

• modifies surface structure• Requires priodic catalyst recycling

F. Zaera, Chem. Soc. Rev., 42(7), 2746-2762 (2013).F. Zaera, ChemSusChem, 6(10), 1797-1820 (2013).

F. Zaera, Prog. Surf. Sci., 69(1-3), 1-98 (2001).F. Zaera, Int. Rev. Phys. Chem., 21(3), 433-471 (2002).

F. Zaera, J. Phys. Chem. Lett., 1(3), 621-627 (2010).

Surface Science withModel Systems

3

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

IntroductionExperimental Approach

• Well-defined samples• Controlled environments

• Multiple techniques

Nanotechnology toPrepare Real Catalysts

1 nm

Outline

4

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

1. Surface Science of Olefin Hydrogenation

2. Shape Selectivity

3. Catalyst Nano-Architectures

A

B

Outline

5

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

1. Surface Science of Olefin Hydrogenation

2. Shape Selectivity

3. Catalyst Nano-Architectures

Surface Chemistry of Olefin ConversionHydrogenation, Isomerization, and H-D Exchange

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

H3C CH3C=CHH

cis-2-buteneH3C

CH3C=CH

H

trans-2-butene

C–C

butane

CH3H

H

H3CH

H

HC2H5C=CH

H

1-butene

2-butyl (ads)

H3C CH3C HH CH

Hydrogenation

Cis-TransIsomerization

Double BondMigration

Horiuti-Polanyi mechanism. Does not account for:effect of coadsorbed H, carbonaceous layers, stereoselectivity.

M. Polanyi, J. Horiuti, Trans. Faraday Soc., 30, 1164-1172 (1934).F. Zaera, Catal. Lett., 91(1-2), 1-10 (2003).

6

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

F. Zaera, Langmuir, 12(1), 88-94 (1996).

Surface Chemistry of Olefin ConversionHydrogenation under UHV: TPD

Olefin hydrogenation and H-D Exchange easily detected by

temperature programmed

desorption (TPD).

Not catalytic.

7

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

F. Zaera, T. V. W. Janssens and H. Öfner, Surf. Sci., 368(1-3), 371-376 (1996).H. Öfner and F. Zaera, J. Phys. Chem. B, 101(3), 396-408 (1997).

Surface Chemistry of Olefin ConversionHydrogenation under UHV: Molecular Beam

Ethylene can be hydrogenated with H2-rich molecular beams,

but not catalytically.

8

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Surface Chemistry of Olefin ConversionModel of Working Catalyst Surface

F. Zaera, Isr. J. Chem., 38, 293-311 (1998).F. Zaera, Catal. Lett., 91(1-2), 1-10 (2003).

Olefin hydrogenation takes place not on clean metalsbut in the presence of a carbonaceous layer (alkylidynes).

Ethylidyne

-Ethylene

Ethylene Hydrogenation

9

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

A. Tillekartne, J. P. Simonovis, M. F. López Fagúndez, M. Ebrahimi, F. Zaera, ACS Catal. 2, 2259-2268 (2012).

Ethylidyne is present on the surface during

ethylene hydrogenation.

Surface Chemistry of Olefin ConversionRAIRS Detection of Alkylidynes In Situ

H H

CH C

s(CH3)Ethylidyne (ads)

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A. Tillekartne, J. P. Simonovis, M. F. López Fagúndez, M. Ebrahimi, F. Zaera, ACS Catal. 2, 2259-2268 (2012). Francisco Zaera

Department of ChemistryUniversity of California, Riverside

Surface Chemistry of Olefin ConversionKinetics of Hydrogenation and H-D Exchange Catalysis

Fast and extensive ethylene

hydrogenation and H-D exchange catalysis in the presence of the

alkylidyne surface layer.

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-2 -4 -6 -80

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

F. Zaera, Phys. Chem. Chem. Phys., 29, 11988-12003 (2013).

Surface Chemistry of Olefin ConversionIntermediate Hydrogenation Regime

Log[P/Torr]

-10 -8 -6 -4 -2 0 2 4

UHV

Non catalytic

Rate (-C2H4)1

On clean Pt

Atmospheric P

Catalytic

Rate P(C2H4)0

On alkylidyne/Pt

TOF ~ 1 - 10

PressureGap(???)

Log[Reaction Probability]???

Log[Impinging Rate/ML s-1]

-4 -2 0 2 4 6 8 10

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Francisco ZaeraDepartment of Chemistry

University of California, Riverside

M. Ebrahimi, J. P. Simonovis, F. Zaera, J. Phys. Chem. Lett., 5, 2121-2125 (2014).

Surface Chemistry of Olefin ConversionHigh-Flux Molecular Beam Kinetics

Indeed, reaction probabilities are high (~70%) in the intermediate pressure range.

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M. Ebrahimi, J. P. Simonovis, F. Zaera, J. Phys. Chem. Lett., 5, 2121-2125 (2014).Francisco Zaera

Department of ChemistryUniversity of California, Riverside

Less surface alkylidyne at the high H2:HC ratios that display high TOFs:Olefin hydrogenation rate may be limited by carbonaceous layer.

Surface Chemistry of Olefin ConversionCarbonaceous Layer at High TOFs

14

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

A. Tillekartne, J. P. Simonovis, F. Zaera (2015).

Olefin hydrogenation rate may depend on the nature of thecarbonaceous deposits present on the surface.

Surface Chemistry of Olefin ConversionHydrogenation Rate vs. Nature of Alkylidyne

15

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

J. P. Simonovis, F. Zaera (2015).

H-D exchange used to evaluate H2 ads as possible rls.Slower under reaction conditions, alkylidyne vs. clean Pt.

Switchover in H-D exchange TOF at intermediate conversion.

Surface Chemistry of Olefin ConversionHydrogenation vs. H-D Exchange

Switchover inH-D exchange

TOF

End of C2H4Hydrogenation

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Outline

17

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

1. Surface Science of Olefin Hydrogenation

2. Shape Selectivity

3. Catalyst Nano-Architectures

Shape SelectivityStereoselectivity of Cis-Trans Isomerization

CH3HH CH3

H

CH3H

H3CH

H

H3C CH3C=CHH

cis-2-buteneH3C

CH3C=CH

H

trans-2-butene

cis-2-butene (ads)

H3C CH3C–C HH H

trans-2-butene (ads)

HH3C H

C–C CH3H

2-butyl (ads)

H3C CH3C HH CH

I. Lee and F. Zaera, J. Am. Chem. Soc., 127, 12174-12175 (2005).I. Lee, F. Zaera, Top. Catal., 56(15-17), 1284-1298 (2013).F. Zaera, Phys. Chem. Chem. Phys., 15(29), 11988-12003 (2013).

Isomerization depends on stereoselectivity of -H

elimination step from the alkyl intermediate.

18

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

998, 1200, 1376, 1460 cm-1 peaks

indicatecis-2-butene.

Trans-to-cisisomerization.

I. Lee and F. Zaera, J. Am. Chem. Soc., 127, 12174-12175 (2005).I. Lee, F. Zaera, J. Phys. Chem. C, 111, 10062-10072 (2007).

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Shape SelectivityTrans-to-Cis Conversion on Pt(111): IR Evidence

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1 nm

T. S. Ahmadi, Z. L. Wang, T. C. Green, A. Hanglein, M. A. El-Sayed, Science, 272, 1924-1926 (1996).I. Lee, R. Morales, M. A. Albiter, and F. Zaera, Proc. Nat. Acad. Sci., 105, 15241-15246 (2008).

(111)facets

Tetrahedral Pt Particles

Pt(111)

Pt(111)

Pt(100)

1 nm

Cubic Pt Particles(100)facets

20

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Shape SelectivityPreparation of Shape-Selected Pt Nanoparticles

H2H2PtCl6

PVP

Pt ColloidalParticle Preparation

+ SiO2

Sonication

Rinsing

Drying

Dispersion onSilica Xerogel

Calcination

Oxidation/Reduction

CatalystPretreatment

I. Lee, R. Morales, M. A. Albiter, and F. Zaera, Proc. Nat. Acad. Sci., 105, 15241-15246 (2008).

Shape SelectivitySupported Shape-Selected Pt Catalysts: Preparation

21

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

I. Lee, F. Delbecq, R. Morales, M. A. Albiter, and F. Zaera, Nature Mater., 8, 132-138 (2009).I. Lee, R. Morales, M. A. Albiter, and F. Zaera, Proc. Nat. Acad. Sci., 105, 15241-15246 (2008).

10 nm

Shape SelectivityPreservation of Nanoparticle Shape during Treatment

3 oxidation-reduction cycles at 475 K

10 nm

3 oxidation-reduction cycles at 575 K

22

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

H3CCH3C=CH

H

trans-2-butene

H3C CH3C=CHH

cis-2-butene

Shape SelectivityButene Cis-Trans Catalytic Selectivity

I. Lee, F. Delbecq, R. Morales, M. A. Albiter, and F. Zaera, Nature Mater., 8, 132-138 (2009).I. Lee, R. Morales, M. A. Albiter, and F. Zaera, Proc. Nat. Acad. Sci., 105, 15241-15246 (2008).

23

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Trans fats in partially hydrogenated oils have been linked to a variety of free radical and degenerative conditions such as cancer, arthritis, and

cardiovascular disease.

24

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Shape SelectivityOlefin Cis-Trans Isomerization Relevance

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Y. Zhu, F. Zaera, Catal. Sci. Technol., 4, 955-962 (2014).Y. Li, F. Zaera, J. Catal., 326, 116-126 (2015).

Size and shape sensitivity also seen in:• Unsaturated aldehyde (cinammonaldehyde) hydrogenation

• Glycerol oxidation

Shape SelectivityOther Reactions

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Outline

26

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

1. Surface Science of Olefin Hydrogenation

2. Shape Selectivity

3. Catalyst Nano-Architectures

A

B

Metal Particle StabilizationIn-Situ Growth of Support Around Metal Particles

Q. Zhang, I. Lee, J. Ge, F. Zaera, Y. Yin, Adv. Funct. Mater., 20(14), 2201–2214 (2010).I. Lee, J. Ge, Q. Zhang, Y. Yin, F. Zaera, Nano Research, 4(1), 115-123 (2011).

EtchingMeso-SiO2 CoatingPt-Deposition

Pt TEOS NaOH

TEOS NaOH

27

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Metal Particle StabilizationXPS and CO-IR Titration Characterization

74.2

73.8

PtO

CO/SiO2

2116

2089

2085

CO/BeadTEOS

NaOH

Pt surface becomes available again after etching.

28

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Q. Zhang, I. Lee, J. Ge, F. Zaera, Y. Yin, Adv. Funct. Mater., 20(14), 2201–2214 (2010).I. Lee, J. Ge, Q. Zhang, Y. Yin, F. Zaera, Nano Research, 4(1), 115-123 (2011).

29

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Q. Zhang, I. Lee, J. Ge, F. Zaera, Y. Yin, Adv. Funct. Mater., 20(14), 2201–2214 (2010).I. Lee, J. Ge, Q. Zhang, Y. Yin, F. Zaera, Nano Research, 4(1), 115-123 (2011).

Metal Particle StabilizationStability and Reactivity

Stable toward CO adsorptionHigher reactivity after etching.

TEM after CO ads

60 min

40 min

No etching

NaOH

NaOH

Metal Particle StabilizationThermal Stability

Mesoporous layer stops Pt sintering.

300 K 875 K 975 K 1075 KN

aked

Cov

ered

30

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Q. Zhang, I. Lee, J. Ge, F. Zaera, Y. Yin, Adv. Funct. Mater., 20(14), 2201–2214 (2010).I. Lee, J. Ge, Q. Zhang, Y. Yin, F. Zaera, Nano Research, 4(1), 115-123 (2011).

Yolk-ShellNanostructures

Shaped Nanoparticles

Catalysts fromDendrimers

31

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Catalyst Nano-ArchitecturesTandem Catalysis

Self-AssembledMonolayers

Tethering of MolecularFunctionality

Atomic LayerDeposition

Yolk-ShellNanostructures

Shaped Nanoparticles

Catalysts fromDendrimers

32

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Catalyst Nano-ArchitecturesTandem Catalysis

Self-AssembledMonolayers

Tethering of MolecularFunctionality

Atomic LayerDeposition

I. Lee, M. A. Albiter, Q. Zhang, J. Ge, Y. Yin, F. Zaera, PCCP, 13(7), 2449-2456 (2011).I. Lee, J.-B Joo, Y. Yin, F. Zaera, Angew. Chem., Int. Ed., 50(43), 10208-10211 (2011).

AuTiO2

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

33

Catalyst Nano-ArchitecturesAu@Void@TiO2 Yolk-Shell Synthetic Strategy

Au

TiO2

Advantages:• Structural stability, prevents sintering.

• Selective percolation to and from inside.

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

34

50 nm 50 nm

50 nm 50 nm

Au@TiO2

Au/TiO2-P25

As Prepared Calcined, 775K

I. Lee, J. B. Joo, Y. Yin and F. Zaera, Angew. Chem., Int. Ed., 43, 10208-10211 (2011).

Catalyst Nano-ArchitecturesAu@Void@TiO2 Thermal Stability

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

TiO2

TiO2

Pt

TiO2

PtTiO2

CO-TiO2

CO-Pt

• CO, in gas phase or dissolved in a liquid, can reach the metal inside.

• Also works with larger molecules (Cd, Zn-TPP)

and other solvents (EtOH)

35

Catalyst Nano-ArchitecturesAu@Void@TiO2 Shell Porosity

I. Lee, J.-B. Joo, Y. Yin, F. Zaera, Angew. Chem. Int. Ed., 50, 10208-10211 (2011).J. Liang, I. Lee, J.-B. Joo, A. Gutierrez, A. Tillekaratne, I. Lee, Y. Yin, F. Zaera, Angew. Chem. Int. Ed., 51, 8034-8036 (2012).J. Li, J. Liang, J.-B. Joo, I. Lee, Y. Yin, F. Zaera, J. Phys. Chem. C, 117, 20043–20053 (2013).

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

I. Lee, J.-B. Joo, Y. Yin, F. Zaera, Angew. Chem., Int. Ed., 50(43), 10208-10211 (2011).

36

Catalyst Nano-ArchitecturesAu@Void@TiO2 for CO Oxidation

CO oxidation at room temperature with Au@Void@TiO2 comparable to with Au/TiO2-P25.

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

New cryogenic T CO oxidation channel also with Au@Void@TiO2.

37

I. Lee, J. B. Joo, Y. Yin and F. Zaera, Angew. Chem., Int. Ed., 43, 10208-10211 (2011).I. Lee, J.-B. Joo, Y. Yin, F. Zaera, Surf. Sci., (2015).

Catalyst Nano-ArchitecturesAu@Void@TiO2 for CO Oxidation

CryoOxidation

RTOxidation

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Way to combine two or more functionalities in one single catalyst:• Bring together incompatible functionalities (i.e., acid + base)

• Can be used to convert short lived intermediates• Solve homogeneous catalyst solubility problems

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Catalyst Nano-ArchitecturesTandem Catalysis

Francisco ZaeraDepartment of Chemistry

University of California, Riverside39

Catalyst Nano-ArchitecturesTandem Catalysis

Only acid + base produces

nitrostyrene (3).

Conclusions

Catalyst synthesiswith new

nanotechnology

HighlySelectiveCatalysts

Reaction mechanisms from

surface science

Catalytic site structure from

theory

40

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

F. Zaera, J. Phys. Chem. Lett., 1, 621-627 (2010).I. Lee, M. A. Albiter, Q. Zhang, J. Ge, Y. Yin, F. Zaera,

PCCP, 13(7), 2449-2456 (2011).F. Zaera, Catal. Lett., 142, 501-516 (2012).

F. Zaera, Chem. Soc. Rev., 42 2746-2762 (2013).F. Zaera, ChemSusChem, 6, 1797-1820 (2013).

Acknowledgements

Prof. Yadong Yin

41

Francisco ZaeraDepartment of Chemistry

University of California, Riverside

Ilkeun Lee

Juan SimonovisYujung Dong

A

B

Alejandro NegreteZhihuan Weng