List of Contributors .......................................... XV
1 Chemical and Catalytic Properties of Size-Selected
Free and Supported Clusters
T.M. Bernhardt, U. Heiz. and U. Landman ................... 1
1.1 Introduction ............................................. 1
1.2 Experimental Techniques .................................. 2
1.2.1 Cluster Sources ................................... 3
1.2.2 Mass-Selection and Soft-Landing ................... 7
1.2.3 Gas-Phase Analysis Techniques .................... 18
1.2.4 Surface Analysis Techniques ...................... 46
1.3 Computational Techniques ................................ 71
1.3.1 Electronic Structure Calculations Via
Density Functional Theory ........................ 72
1.3.2 Computational Methods and Techniques ............. 87
1.4 Concepts for Understanding Chemical Reactions
and Catalytic Properties of Finite Systems .............. 90
1.4.1 Basic Mechanisms of Catalytic Reactions .......... 90
1.4.2 Cluster-Specific Mechanisms ...................... 95
1.5 Specific Examples ...................................... 100
1.5.1 Chemical Reactions on Point Defects of
Oxide Surfaces .................................. 101
1.5.2 The Oxidation of CO on Small Gold Clusters ...... 105
1.5.3 The Oxidation of CO on Small Platinum and
Palladium Clusters .............................. 137
1.5.4 The Reduction of NO by CO on Pd Clusters:
Cooler Cluster Catalysis ........................ 156
1.5.5 The Polymerization of Acetylene on Pd
Clusters ........................................ 165
References ................................................. 177
2 Theory of Metal Clusters on the MgO Surface: The Role of
Point Defects
G. Pacchioni ............................................ 193
2.1 Introduction ........................................... 193
2.1.1 Oxide Surfaces: Single Crystals, Powders,
Thin Films ...................................... 194
2.1.2 Metal Particles on Oxides ....................... 197
2.1.3 The Role of Defects in Nucleation and
Growth .......................................... 198
2.2 Theoretical Models ..................................... 199
2.2.1 Periodic Models ................................. 199
2.2.2 Local Cluster Models ............................ 200
2.2.3 Embedding Schemes ............................... 201
2.2.4 Electronic Structure Methods .................... 203
2.2.5 Density Functional Theory Versus Wave
Function Methods: Cu on MgO ..................... 207
2.3 Defects on MgO ......................................... 208
2.3.1 Low-Coordinated Cations ......................... 210
2.3.2 Low-Coordinated Anions .......................... 211
2.3.3 Hydroxyl Groups ................................. 212
2.3.4 Anion Vacancies ................................. 213
2.3.5 Cation Vacancies ................................ 215
2.3.6 Divacancies ..................................... 215
2.3.7 Impurity Atoms .................................. 216
2.3.8 0- Radical Anions ............................... 217
2.3.9 M Centers (Anion Vacancy Aggregates) ............ 218
2.3.10 Shallow Electron Traps .......................... 219
2.3.11 (M+)(e-) Centers ................................ 219
2.3.12 (111) Microfacets ............................... 221
2.4 Metal Deposition on MgO ................................ 222
2.4.1 Transition Metal Atoms on MgO(00l) .............. 222
2.4.2 Small Metal Clusters on MgO(00l) ................ 226
2.4.3 Metal Atoms on MgO: Where Are They? ............. 229
2.5 Reactivity of Supported Metal Atoms: The
Role of Defects ........................................ 233
2.6 Summary ................................................ 235
References ................................................. 237
3 Catalysis by Nanoparticles
C.R. Henry .............................................. 245
3.1 Introduction ........................................... 245
3.2 Specific Physical Properties of Free and
Supported Nanoparticles ................................ 249
3.2.1 Surface Energy and Surface Stress ............... 249
3.2.2 Lattice Parameter ............................... 250
3.2.3 Equilibrium Shape ............................... 251
3.2.4 Melting Temperature ............................. 254
3.2.5 Electronic Band Structure ....................... 255
3.3 Reactivity of Supported Metal Nanoparticles ............ 255
3.3.1 Support Effect: Reverse-spillover ............... 255
3.3.2 Morphology Effect ............................... 259
3.3.3 Effect of the Edges ............................. 260
3.3.4 The Peculiar Case of Gold Nanoparticles ......... 261
3.4 Conclusions and Future Prospects ....................... 264
References ................................................. 265
4 Lithographic Techniques in Nanocatalysis
L. Österlund, A.W. Grant, and B. Kasemo ................. 269
4.1 Introduction ........................................... 269
4.2 Methods to Make Model Nanocatalysts: A Brief
Overview ............................................... 275
4.2.1 Lithographic Techniques: An Introduction ........ 275
4.2.2 The Surface Science Approach: In Situ
Vapor Deposition Methods ........................ 276
4.2.3 Spin Coating .................................... 278
4.2.4 Self-Assembly ................................... 278
4.3 Fabrication of Supported Model Catalysts by
Lithography ............................................ 278
4.3.1 Electron-Beam Lithography ....................... 282
4.3.2 Colloidal Lithography ........................... 289
4.4 Microfabrication of TEM Membrane Windows ............... 304
4.4.1 Preparation Procedures .......................... 305
4.4.2 Chemical and Structural Characterization
of TEM Windows .................................. 308
4.4.3 Nanofabrication of Model Catalysts on
TEM Windows ..................................... 311
4.5 Experimental Case Studies with Nanofabricated
Model Catalysts: Catalytic Reactions and Reaction-
Induced Restructuring .................................. 314
4.5.1 Model Catalysts Fabricated by Electron-Beam
Lithography ..................................... 315
4.5.2 Catalytic Reaction Studies with Model
Catalysts Made by Colloidal Lithography ......... 326
4.6 Summary and Future Directions .......................... 333
References ................................................. 337
5 Nanometer and Subnanometer Thin Oxide Films at
Surfaces of Late Transition Metals
K. Reuter ............................................... 343
5.1 Introduction ........................................... 343
5.2 Initial Oxidation of Transition-Metal Surfaces ......... 345
5.2.1 Formation of Adlayers ........................... 345
5.2.2 Oxygen Accommodation Below the Top
Metal Layer ..................................... 348
5.2.3 Oxygen Accumulation in the Surface Region
and Surface Oxide Formation ..................... 352
5.2.4 Formation of the Bulk Oxide ..................... 354
5.3 Implications for Oxidation Catalysis ................... 357
5.3.1 The Role of the Gas Phase ....................... 357
5.3.2 Stability of Surface Oxides in an Oxygen
Environment ..................................... 358
5.3.3 Constrained Equilibrium ......................... 363
5.3.4 Kinetically Limited Film Thickness .............. 367
5.3.5 Surface Oxidation and Sabatier Principle ........ 369
5.4 Conclusions ............................................ 371
References ................................................. 374
6 Catalytic Applications for Gold Nanotechnology
Sania A.C., Carabineiro and David T. Thompson ........... 377
6.1 Introduction ........................................... 377
6.2 Preparative Methods .................................... 378
6.2.1 Naked Gold, Including Gold Single Crystals
and Colloidal Gold .............................. 378
6.2.2 Co-Precipitation ................................ 380
6.2.3 Deposition Precipitation ........................ 380
6.2.4 Impregnation .................................... 383
6.2.5 Vapour-Phase Methods and Grafting ............... 384
6.2.6 Ion-Exchange .................................... 386
6.2.7 Sol-Gel Method .................................. 387
6.2.8 Gold Alloy Catalysts ............................ 387
6.3 Properties of Nanoparticulate Gold
Catalysts .............................................. 388
6.3.1 Activity ........................................ 388
6.3.2 Selectivity ..................................... 390
6.3.3 Durability ...................................... 391
6.3.4 Poison Resistance ............................... 393
6.4 Reactions Catalysed by Nanocatalvtic
Gold and Gold Alloys ................................... 394
6.4.1 Water-Gas Shift ................................. 394
6.4.2 Vinyl Acetate Synthesis ......................... 398
6.4.3 Hydrochlorination of Ethync ..................... 400
6.4.4 Carbon Monoxide Oxidation ....................... 402
6.4.5 Selective Oxidation ............................. 412
6.4.6 Selective Hydrogenation ......................... 425
6.4.7 Hydrogen Peroxide Formation ..................... 432
6.4.8 Reduction of NO.r with Propene,
Carbon Monoxide or Hydrogen ..................... 434
6.4.9 Oxidative Decomposition of Dioxins and VOCs ..... 441
6.4.10 Catalytic Combustion of Hydrocarbons ............ 444
6.4.11 Ozone Decomposition ............................. 440
6.4.12 SO2 Removal ..................................... 447
6.4.13 Heck Reaction ................................... 449
6.4.14 CO2 Activation .................................. 450
6.4.15 Other Reactions ................................. 452
6.5 Potential Commercial Applications for Gold
Nanocatalysts .......................................... 457
6.5.1 Vinyl Acetate Synthesis ......................... 457
6.5.2 Methyl Glycolate Synthesis ...................... 458
6.5.3 Vinyl Chloride Synthesis ........................ 458
6.5.4 Gluconic Acid ................................... 458
6.5.5 Hydrogen Peroxide Production .................... 459
6.5.6 Air Cleaning .................................... 459
6.5.7 Autocatalysts ................................... 460
6.5.8 Fuel Cell Technology ............................ 463
6.5.9 Sensors ......................................... 464
6.6 Future Prospects ....................................... 467
References ................................................... 468
Index ........................................................ 491
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