Fundamental Concepts in Heterogeneous Catalysis E-Book

Jens K. Nørskov

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 345

Veröffentlichungsjahr: 2014

Beschreibung

This book is based on a graduate course and suitable as a primer for any newcomer to the field, this book is a detailed introduction to the experimental and computational methods that are used to study how solid surfaces act as catalysts. Features include: * First comprehensive description of modern theory of heterogeneous catalysis * Basis for understanding and designing experiments in the field * Allows reader to understand catalyst design principles * Introduction to important elements of energy transformation technology * Test driven at Stanford University over several semesters

Leseprobe

CONTENTS

Cover

Title page

Copyright page

Preface

1 Heterogeneous Catalysis and a Sustainable Future

References

Further Reading

2 The Potential Energy Diagram

2.1 Adsorption

2.2 Surface Reactions

2.3 Diffusion

2.4 Adsorbate–Adsorbate Interactions

2.5 Structure Dependence

2.6 Quantum and Thermal Corrections to the Ground-State Potential Energy

References

Further Reading

3 Surface Equilibria

3.1 Chemical Equilibria in Gases, Solids, and Solutions

3.2 The Adsorption Entropy

3.3 Adsorption Equilibria: Adsorption Isotherms

3.4 Free Energy Diagrams for Surface Chemical Reactions

Appendix 3.1 The Law of Mass Action and the Equilibrium Constant

Appendix 3.2 Counting the Number of Adsorbate Configurations

Appendix 3.3 Configurational Entropy of Adsorbates

References

Further Reading

4 Rate Constants

4.1 The Timescale Problem in Simulating Rare Events

4.2 Transition State Theory

4.3 Recrossings and Variational Transition State Theory

4.4 Harmonic Transition State Theory

Reference

Further Reading

5 Kinetics

5.1 Microkinetic Modeling

5.2 Microkinetics of Elementary Surface Processes

5.3 The Microkinetics of Several Coupled Elementary Surface Processes

5.4 Ammonia Synthesis

Reference

Further Reading

6 Energy Trends in Catalysis

6.1 Energy Correlations for Physisorbed Systems

6.2 Chemisorption Energy Scaling Relations

6.3 Transition State Energy Scaling Relations in Heterogeneous Catalysis

6.4 Universality of Transition State Scaling Relations

References

Further Reading

7 Activity and Selectivity Maps

7.1 Dissociation Rate-Determined Model

7.2 Variations in the Activity Maximum with Reaction Conditions

7.3 Sabatier Analysis

7.4 Examples of Activity Maps for Important Catalytic Reactions

7.5 Selectivity Maps

References

Further Reading

8 The Electronic Factor in Heterogeneous Catalysis

8.1 The

d

-Band Model of Chemical Bonding at Transition Metal Surfaces

8.2 Changing the

d

-Band Center: Ligand Effects

8.3 Ensemble Effects in Adsorption

8.4 Trends in Activation Energies

8.5 Ligand Effects for Transition Metal Oxides

References

Further Reading

9 Catalyst Structure

9.1 Structure of Real Catalysts

9.2 Intrinsic Structure Dependence

9.3 The Active Site in High Surface Area Catalysts

9.4 Support and Structural Promoter Effects

References

Further Reading

10 Poisoning and Promotion of Catalysts

References

Further Reading

11 Surface Electrocatalysis

11.1 The Electrified Solid–Electrolyte Interface

11.2 Electron Transfer Processes at Surfaces

11.3 The Hydrogen Electrode

11.4 Adsorption Equilibria at the Electrified Surface–Electrolyte Interface

11.5 Activation Energies in Surface Electron Transfer Reactions

11.6 The Potential Dependence of the Rate

11.7 The Overpotential in Electrocatalytic Processes

11.8 Trends in Electrocatalytic Activity: The Limiting Potential Map

References

Further Reading

12 Relation of Activity to Surface Electronic Structure

12.1 Electronic Structure of Solids

12.2 The Band Structure of Solids

12.3 The Newns–Anderson Model

12.4 Bond-Energy Trends

12.5 Binding Energies Using the Newns–Anderson Model

Further Reading

Index

End User License Agreement

List of Tables

Chapter 02

Table 2.1 ZPE correction for selected hydrogenation reactions

List of Illustrations

Chapter 01

Figure 1.1 Illustration of the role of catalysis in providing sustainable routes to fuels and base chemicals. Whether the energy flux from sunlight is harvested through biomass, through intermediate electricity production from photovoltaics or wind turbines, or directly through a photoelectrochemical reaction, the process always requires an efficient catalyst, preferably made of earth-abundant materials.

Figure 1.2 High-resolution transmission electron microscopy image of a supported Ru catalyst for ammonia synthesis recorded at 552°C and 5.2 mbar in a gas composition of 3:1 H

2

/N

2

. A Ru particle with a well-formed lattice and surface facets is seen on an amorphous support consisting of BN. A Ba–O promoter phase is observed on top of the Ru particle.

Chapter 02

Figure 2.1

Left

: PED for the physisorption of Ar in the threefold position of the Cu(111) surface. The potential energy is shown as a function of the distance between the Cu surface and the adsorbate. The energy of the adsorbate at a distance of 6 Å is chosen as a reference. Due to the filled outermost electronic shell on the Ar atom, this species does not chemisorb to the surface at all, and the shallow physisorption minimum is clearly visible.

Right

: PED for the chemisorption of H on Cu(111) in ontop, bridge, and threefold position.

Figure 2.2

Left

: PES for H

2

dissociation over Cu(111). The potential energy of the system is shown as a function of the Cu–H

2

and H–H distance, respectively. H

2

far from the Cu surface has been chosen as a reference. The lowest potential energy path for H

2

splitting is marked with black crosses.

Right

: PED for H

2

dissociation where the lowest potential energy (from the figure on the left) is plotted as a function of the reaction path. The PES is calculated without relaxations of the hydrogen and copper atoms. If these are taken into account, a slightly lower barrier of 0.78 eV is found (see CatApp).

Figure 2.3 Measured dissociation probability for a monoenergetic beam of H

2

molecules impinging on a Cu(111) surface as a function of their kinetic energy.

Figure 2.4 Illustration of the elementary reaction steps on surfaces.

Figure 2.5 These screenshots from the CatApp (http://suncat.slac.stanford.edu/catapp/) show examples of elementary reaction PEDs that can be obtained from this tool.

Left

and

center

: N

2

splitting on close-packed and stepped Ru(0001), respectively.

Right

: select view of the CatApp. Here, the user can choose the reaction and surface parameters from drop-down menus.

Figure 2.6 PED for ammonia synthesis on the stepped Ru(0001). The numbers correspond to the six different reaction steps that are defined earlier. The data for the six reaction steps has been obtained from CatApp and “glued” together to yield the reaction diagram.