Fundamental Concepts in Heterogeneous 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-StatePotential 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 Constant42
Appendix 3.2 Counting the Number of Adsorbate Configurations44
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 SurfaceProcesses 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 HeterogeneousCatalysis 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 Conditions101
7.3 Sabatier Analysis 103
7.4 Examples of Activity Maps for Important Catalytic Reactions105
7.4.1 Ammonia Synthesis 105
7.4.2 The Methanation Reaction 107
7.5 Selectivity Maps 112
8 The Electronic Factor in Heterogeneous Catalysis114
8.1 The d-Band Model of Chemical Bonding at Transition MetalSurfaces 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 ElectrifiedSurface-Electrolyte Interface 161
11.5 Activation Energies in Surface Electron Transfer Reactions162
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 PotentialMap 169
12 Relation of Activity to Surface Electronic Structure175
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 Model193
Index 195