Fundamental Concepts in Heterogeneous Catalysis (eBook)

JENS K. NØRSKOV, PHD, is the Leland T. Edwards Professor of Engineering at Stanford University, USA. He is the founding director of the SUNCAT Center for Interface Science and Catalysis at Stanford University and SLAC National Accelerator Laboratory, USA. He has pioneered the development of a set of concepts allowing a molecular level understanding of surface chemical processes and heterogeneous catalysis. FELIX STUDT, PHD, is a Staff Scientist at the SLAC National Accelerator Laboratory, USA. His SUNCAT research group focuses on understanding catalytic processes for efficient energy conversion and using this as a basis for design of new catalysts. FRANK ABILD-PEDERSEN, PHD, is a Staff Scientist at the SUNCAT Center at SLAC National Accelerator Laboratory, USA, where his group focuses on the development of theoretical models of molecule surface interactions and models describing ultrafast surface processes measured in X-ray free electron lasers. THOMAS BLIGAARD, PHD, is a Senior Staff Scientist at at SLAC National Accelerator Laboratory, USA and the deputy director for theory at the SUNCAT Center, USA. His research group focuses on the development of electronic structure methods, kinetics tools, and data mining in catalysis.

Preface viii

1 Heterogeneous Catalysis and a Sustainable Future 1

2 The Potential Energy Diagram 6

2.1 Adsorption, 7

2.2 Surface Reactions, 11

2.3 Diffusion, 13

2.4 Adsorbate-Adsorbate Interactions, 15

2.5 Structure Dependence, 17

2.6 Quantum and Thermal Corrections to the Ground-State Potential Energy, 20

3 Surface Equilibria 26

3.1 Chemical Equilibria in Gases, Solids, and Solutions, 26

3.2 The Adsorption Entropy, 31

3.3 Adsorption Equilibria: Adsorption Isotherms, 34

3.4 Free Energy Diagrams for Surface Chemical Reactions, 40

Appendix 3.1 The Law of Mass Action and the Equilibrium Constant, 42

Appendix 3.2 Counting the Number of Adsorbate Configurations, 44

Appendix 3.3 Configurational Entropy of Adsorbates, 44

4 Rate Constants 47

4.1 The Timescale Problem in Simulating Rare Events, 48

4.2 Transition State Theory, 49

4.3 Recrossings and Variational Transition State Theory, 59

4.4 Harmonic Transition State Theory, 61

5 Kinetics 68

5.1 Microkinetic Modeling, 68

5.2 Microkinetics of Elementary Surface Processes, 69

5.3 The Microkinetics of Several Coupled Elementary Surface Processes, 74

5.4 Ammonia Synthesis, 79

6 Energy Trends in Catalysis 85

6.1 Energy Correlations for Physisorbed Systems, 85

6.2 Chemisorption Energy Scaling Relations, 87

6.3 Transition State Energy Scaling Relations in Heterogeneous Catalysis, 90

6.4 Universality of Transition State Scaling Relations, 93

7 Activity and Selectivity Maps 97

7.1 Dissociation Rate-Determined Model, 97

7.2 Variations in the Activity Maximum with Reaction Conditions, 101

7.3 Sabatier Analysis, 103

7.4 Examples of Activity Maps for Important Catalytic Reactions, 105

7.4.1 Ammonia Synthesis, 105

7.4.2 The Methanation Reaction, 107

7.5 Selectivity Maps, 112

8 The Electronic Factor in Heterogeneous Catalysis 114

8.1 The d-Band Model of Chemical Bonding at Transition Metal Surfaces, 114

8.2 Changing the d-Band Center: Ligand Effects, 125

8.3 Ensemble Effects in Adsorption, 130

8.4 Trends in Activation Energies, 131

8.5 Ligand Effects for Transition Metal Oxides, 134

9 Catalyst Structure: Nature of the Active Site 138

9.1 Structure of Real Catalysts, 138

9.2 Intrinsic Structure Dependence, 139

9.3 The Active Site in High Surface Area Catalysts, 143

9.4 Support and Structural Promoter Effects, 146

10 Poisoning and Promotion of Catalysts 150

11 Surface Electrocatalysis 155

11.1 The Electrified Solid-Electrolyte Interface, 156

11.2 Electron Transfer Processes at Surfaces, 158

11.3 The Hydrogen Electrode, 161

11.4 Adsorption Equilibria at the Electrified Surface-Electrolyte Interface, 161

11.5 Activation Energies in Surface Electron Transfer Reactions, 162

11.6 The Potential Dependence of the Rate, 164

11.7 The Overpotential in Electrocatalytic Processes, 167

11.8 Trends in Electrocatalytic Activity: The Limiting Potential Map, 169

12 Relation of Activity to Surface Electronic Structure 175

12.1 Electronic Structure of Solids, 175

12.2 The Band Structure of Solids, 179

12.3 The Newns-Anderson Model, 184

12.4 Bond-Energy Trends, 186

12.5 Binding Energies Using the Newns-Anderson Model, 193

Index 195