Series Preface ............................................... xiii
Foreword ....................................................... xv
Foreword ..................................................... xvii
Preface ....................................................... xix
Notation .................................................... xxiii
Introduction ................................................ xxvii
Chapter 1 Solid-State Electrochemistry of Binary Metal Oxides .. 1
1.1 Structural Defects ......................................... 1
1.1.1 Thermodynamically Irreversible Defects .............. 1
1.1.2 Point Defects ....................................... 4
1.2 Nonstoichiometry ........................................... 4
1.3 Point Defects in Binary Metal Oxides ....................... 6
1.3.1 Types of Defects .................................... 6
1.3.2 Thermodynamic Approach .............................. 8
1.3.3 Defect Reactions .................................... 9
1.3.3.1 General Rules .............................. 9
1.3.3.2 Defect Equilibria .......................... 9
1.3.3.3 Stoichiometric Oxides ..................... 11
1.3.3.4 Nonstoichiometric Oxides .................. 12
1.3.3.5 Brouwer-Type Diagrams ..................... 15
1.3.3.6 Effect of Aliovalent Ions (Donors and
Acceptors) ................................ 16
1.3.4 Defects Aggregation ................................ 27
1.3.5 Dispersed Systems .................................. 29
1.4 Band Model ................................................ 31
1.5 Electrical Properties ..................................... 36
1.5.1 Electrical Conductivity ............................ 38
1.5.1.1 Effect of Oxygen Activity ................. 38
1.5.1.2 Effect of Temperature ..................... 42
1.5.1.3 Transference Numbers ...................... 44
1.5.1.4 Impedance Spectroscopy .................... 45
1.5.2 Thermoelectric Power ............................... 45
1.5.3 Electrical Conductivity versus Thermoelectric
Power Jonker Analysis .............................. 51
1.5.4 Work Function ...................................... 53
1.5.4.1 Basic Terms ............................... 53
1.5.4.2 Work Function at Elevated Temperatures .... 57
1.5.5 Surface Photovoltage Spectroscopy .................. 62
1.5.6 Hall Effect ........................................ 62
1.5.7 Coulometric Titration .............................. 63
1.6 Effect of Interfaces ...................................... 65
1.6.1 Surface Reactivity ................................. 65
1.6.2 Surface Sensitive Tools ............................ 67
1.6.3 Surface Segregation ................................ 69
1.6.3.1 Impurities ................................ 72
1.6.3.2 Low-Dimensional Structures ................ 72
1.6.3.3 Oxygen Activity ........................... 72
1.6.3.4 Segregation of Intrinsic Defects .......... 72
1.6.4 Surface versus Bulk Properties ..................... 73
1.6.4.1 Examples of NiO and CoO ................... 75
1.6.4.2 Examples of NiO and CoO Solid Solutions ... 78
1.6.4.3 Low-Dimensional Interface Structures ...... 86
1.7 Diffusion ................................................. 87
1.7.1 Diffusion Mechanisms ............................... 87
1.7.1.1 Vacancy Mechanism ......................... 87
1.7.1.2 Interstitial Mechanism .................... 87
1.7.1.3 Interstitialcy Mechanism (Collinear) ...... 88
1.7.1.4 Interstitialcy Mechanism (Noncollinear) ... 88
1.7.1.5 Interface Diffusion ....................... 88
1.7.2 Diffusion Kinetics ................................. 89
1.7.3 Grain Boundary Diffusion ........................... 93
1.7.4 Chemical Diffusion ................................. 95
1.7.4.1 Gas/Solid Equilibration ................... 95
1.7.4.2 Bulk Diffusion Controlled Kinetics ........ 99
1.7.4.3 Segregation-Induced Diffusive
Resistance ............................... 102
1.7.4.4 Monitoring of Gas/Solid Kinetics ......... 105
1.7.4.5 Relationships between Diffusion
Coefficients ............................. 108
1.8 Oxygen Ion Conductors .................................... 110
1.8.1 Electronic versus Ionic Conductors ................ 110
1.8.2 Electrochemical Cells ............................. 110
1.8.3 Oxidation Mechanism ............................... 114
1.9 Brief Survey on Selected Oxides .......................... 117
1.10 Concluding Remarks ....................................... 118
References ............................................... 119
Assignable Problems ...................................... 125
Chapter 2 Light-Induced Effects .............................. 127
2.1 Solar Radiation .......................................... 127
2.2 Solar Energy Spectrum .................................... 127
2.3 Light Source ............................................. 132
2.4 Light-Induced Effects in Semiconductors .................. 132
2.5 Data Reproducibility ..................................... 134
2.6 Energy Conversion Efficiency ............................. 135
2.6.1 Basic Relationships ............................... 135
2.6.2 Energy Losses ..................................... 138
2.6.2.1 Interdependence of Functional Properties .. 139
2.7 Light Measurements ....................................... 140
2.8 Concluding Remarks ....................................... 141
References ............................................... 141
Assignable Problems ...................................... 143
Chapter 3 Basic Properties of TiO2 ........................... 145
3.1 Titanium Oxides .......................................... 145
3.2 Titanium Dioxide ......................................... 145
3.2.1 Occurrence, Application, and Properties ........... 145
3.2.2 Nonstoichiometry .................................. 146
3.2.3 Production ........................................ 147
3.2.4 Structure ......................................... 148
3.2.5 Phase Diagram and Structures ...................... 151
3.2.6 Shear Structures .................................. 153
3.2.7 Electronic Structure .............................. 155
3.2.8 Anisotropy of Rutile .............................. 158
3.2.8.1 Electrical Resistivity ................... 159
3.2.8.2 Diffusion Kinetics ....................... 159
3.3 Concluding Remarks ....................................... 160
References ............................................... 160
Assignable Problems ...................................... 163
Chapter 4 Defect Chemistry ................................... 165
4.1 Undoped Titanium Dioxide ................................. 165
4.1.1 Point Defects in ТiO2 ............................. 165
4.1.2 Nonstoichiometry .................................. 166
4.1.3 Defect Reactions .................................. 167
4.1.4 Brouwer Defect Diagrams ........................... 171
4.1.5 Full Defect Diagram ............................... 175
4.1.6 Anomalies ......................................... 178
4.1.7 Effect of Cooling ................................. 179
4.1.8 Effect of Oxygen on Fermi Level ................... 180
4.2 Doping with Aliovalent Ions .............................. 183
4.2.1 Cations versus Anions ............................. 183
4.2.2 Donor-Doped TiO ................................... 184
4.2.3 Acceptor-Doped ТiO2 ............................... 186
4.3 Reactivity of Titanium Dioxide with Hydrogen ............. 193
4.4 Real Chemical Formula of ТiO2 ............................ 199
4.5 Concluding Remarks ....................................... 202
References ............................................... 203
Assignable Problems ...................................... 205
Chapter 5 Electrical Properties .............................. 207
5.1 Introduction ............................................. 207
5.2 Electrical Conductivity .................................. 207
5.2.1 General ........................................... 207
5.2.2 Undoped TiO ....................................... 208
5.2.2.1 Effect of Oxygen Activity ................ 210
5.2.2.2 Effect of Temperature .................... 216
5.2.2.3 Mobility Terms ........................... 222
5.2.2.4 Transference Numbers ..................... 224
5.2.2.5 Electrical Conductivity Components ....... 226
5.2.2.6 Effect of Impurities ..................... 229
5.2.2.7 Effect of Cooling ........................ 230
5.2.3 Donor-Doped ТiO2 .................................. 232
5.2.4 Acceptor-Doped ТiO2 ............................... 239
5.2.5 Heterogeneous Doping of ТiO2 ...................... 241
5.3 Thermoelectric Power ..................................... 242
5.4 Jonker Analysis .......................................... 255
5.5 Work Function ............................................ 259
5.6 Surface Photovoltage Spectroscopy ........................ 263
5.7 Hall Effect .............................................. 264
5.8 Coulometric Titration .................................... 265
5.9 Concluding Remarks ....................................... 266
References ............................................... 267
Assignable Problems ...................................... 272
Chapter 6 Diffusion .......................................... 275
6.1 Mass Transport Kinetics .................................. 275
6.2 Self-Diffusion ........................................... 275
6.3 Chemical Diffusion ....................................... 280
6.3.1 Equilibration Kinetics ............................ 280
6.3.2 Double Equilibration Kinetics ..................... 286
6.3.3 Nb-dopedTiO ....................................... 288
6.3.4 Alternative Diffusion Models ...................... 291
6.4 Concluding Remarks ....................................... 294
References ............................................... 295
Assignable Problems ...................................... 297
Chapter 7 Effect of Interfaces ............................... 299
7.1 Effect of Surface Properties on Reactivity ............... 299
7.1.1 Introduction ...................................... 299
7.1.2 Surface Science Approach .......................... 299
7.2 Segregation .............................................. 304
7.3 Reactivity ............................................... 309
7.3.1 Reactivity of ТiO2 with Light ..................... 309
7.3.2 Reactivity and Photoreactivity of ТiO2 with
Oxygen and Water .................................. 310
7.3.2.1 Oxygen ................................... 310
7.3.2.2 Water .................................... 311
7.3.3 Collective and Local Reactivity Factors ........... 312
7.4 Concluding Remarks ....................................... 318
References ............................................... 317
Assignable Problems ...................................... 322
Chapter 8 Applications ....................................... 323
8.1 Introduction ............................................. 323
8.2 Performance-Related Properties ........................... 324
8.2.1 Electronic Structure .............................. 325
8.2.2 Flat Band Potential ............................... 327
8.2.3 Charge Transport .................................. 330
8.2.4 Surface Active Sites .............................. 330
8.2.5 Surface versus Bulk Properties .................... 331
8.3 Solar Hydrogen ........................................... 332
8.3.1 Solar-to-Hydrogen Pathways ........................ 332
8.3.2 Solar Water Splitting in Nature ................... 334
8.3.3 Environmental Aspects ............................. 335
8.3.4 Cost-Related Aspects .............................. 338
8.4 Hydrogen Generation by Photoelectrochemical Water
Splitting ................................................ 338
8.4.1 General Concept ................................... 339
8.4.2 Reactions in Photoelectrochemical Cells ........... 342
8.4.3 Band Model of Photoelectrochemical Cells .......... 343
8.4.4 Photocell Structures .............................. 346
8.4.4.1 Photoelectrochemical Cell Equipped
with One Photoelectrode .................. 347
8.4.4.2 Hybrid-Type Cells ........................ 347
8.4.4.3 Photoelectrochemical Cell Equipped
with Two Photoelectrodes ................. 349
8.4.4.4 Alternative Solutions .................... 352
8.4.5 Simple Comparisons ................................ 353
8.4.6 Hurdles to Commercialization ...................... 354
8.4.6.1 Potential Market ......................... 354
8.4.6.2 Multidisciplinary Approach ............... 354
8.5 Solar Water Purification ................................. 356
8.5.1 Significance and Basic Concepts ................... 356
8.5.2 Photoreactivity of ТiO2 with Water ................ 358
8.5.2.1 Anodic Site .............................. 358
8.5.2.2 CathodicSite ............................. 360
8.5.3 Modification of Photocatalytic Properties ......... 361
8.5.3.1 Deposition of Noble Metals ............... 361
8.5.3.2 Doping with Aliovalent Ions .............. 362
8.5.4 Unresolved Problems ............................... 362
8.5.5 Oxidation of Microorganisms ....................... 365
8.6 Alternative Applications ................................. 371
8.7 Concluding Remarks ....................................... 372
8.7.1 Research Progress and Perspectives ................ 374
References ............................................... 375
Assignable Problems ...................................... 381
Appendix ...................................................... 383
Fundamental Constants ...................................... 383
Selected Conversion Factors ................................ 383
Selected Definitions ....................................... 383
Conversion Prefixes ........................................ 384
Index ......................................................... 385
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