On Solar Hydrogen & Nanotechnology

ON SOLAR HYDROGEN & NANOTECHNOLOGY......Page 5
Contents......Page 7
List of Contributors......Page 19
Preface......Page 21
Editor Biography......Page 25
Part One: Fundamentals, Modeling, and Experimental Investigation of Photocatalytic Reactions for Direct Solar Hydrogen Generation......Page 27
1.1 Introduction......Page 29
1.2 Hydrogen or Hype?......Page 30
1.3.1 The Solar Resource......Page 31
1.3.2 Converting Sunlight......Page 32
1.3.3 Solar-Thermal Conversion......Page 33
1.3.4 Solar-Potential Conversion......Page 34
1.3.5 Pathways to Hydrogen......Page 35
1.4.2 PEC Water-Splitting Reactions......Page 36
1.4.3 Solar-to-Hydrogen Conversion Efficiency......Page 39
1.5.1 Rectifying Junctions......Page 40
1.5.2 A Solid-State Analogy: The np + Junction......Page 41
1.5.3 PEC Junction Formation......Page 43
1.5.4 Illuminated Characteristics......Page 45
1.5.5 Fundamental Process Steps......Page 46
1.6.1 Single-Junction Performance Limits......Page 49
1.6.2 Multijunction Performance Limits......Page 50
1.6.3 A Shining Example......Page 53
1.7.1 What’s Needed, Really?......Page 54
1.8 Facing the Challenge: Current PEC Materials Research......Page 55
References......Page 58
2.1 Importance of Theoretical Studies on TiO2 Systems......Page 63
2.2.1 First-Principle Calculations on TiO2......Page 65
2.2.2 C-Doped TiO2......Page 67
2.2.3 Nb-Doped TiO2......Page 71
2.3.2 Theoretical Calculations of TiO2 Surfaces and Adsorbents......Page 77
2.3.3 Surface Hydroxyl Groups and Photoinduced Hydrophilic Conversion......Page 79
2.4.1 Conventional Sensitizers: Ruthenium Compounds and Organic Dyes......Page 84
2.4.2 Multiexciton Generation in Quantum Dots: A Novel Sensitizer for a DSSC......Page 85
2.4.3 Theoretical Estimation of the Decoherence Time between the Electronic States in PbSe QDs......Page 86
2.5 Future Directions: Ab Initio Simulations and the Local Excited States on TiO2......Page 89
2.5.1 Improvement of the DFT Functional......Page 90
2.5.2 Molecular Mechanics and Ab Initio Molecular Dynamics......Page 91
2.5.3 Description of Local Excited States......Page 92
2.5.4 Nonadiabatic Behavior of a System and Interfacial Electron Transfer......Page 93
References......Page 94
3 Photocatalytic Reactions on Model Single Crystal TiO2 Surfaces......Page 103
3.1 TiO2 Single-Crystal Surfaces......Page 104
3.2 Photoreactions Over Semiconductor Surfaces......Page 106
3.3 Ethanol Reactions Over TiO2(110) Surface......Page 107
3.4 Photocatalysis and Structure Sensitivity......Page 109
3.5 Hydrogen Production from Ethanol Over Au/TiO2 Catalysts......Page 110
References......Page 113
4.1 Introduction......Page 117
4.2 Geometric Structure and Defects of the Rutile TiO2 (110) Surface......Page 119
4.3 Reactions of Water with Oxygen Vacancies......Page 122
4.4 Splitting of Paired H Adatoms and Other Reactions Observed on Partly Water Covered TiO2(110)......Page 124
4.5 O2 Dissociation and the Role of Ti Interstitials......Page 127
4.6 Intermediate Steps of the Reaction Between O2 and H Adatoms and the Role of Coadsorbed Water......Page 132
4.7 Bonding of Gold Nanoparticles on TiO2(110) in Different Oxidation States......Page 138
4.8 Summary and Outlook......Page 141
References......Page 143
Part Two: Electronic Structure, Energetics, and Transport Dynamics of Photocatalyst Nanostructures......Page 149
5.1 Introduction......Page 151
5.2.1 Soft X-Ray Absorption and Emission Spectroscopy......Page 152
5.3 Experiment Set-Up......Page 153
5.3.1 Beamline......Page 154
5.3.2 Spectrometer and Endstation......Page 155
5.3.3 Sample Arrangements......Page 157
5.4 Results and Discussion......Page 158
References......Page 165
6.1 Introduction......Page 169
6.2 Soft X-Ray and Electron Spectroscopies......Page 171
6.3.2 Sample Handling and the Influence of X-Rays, UV-Light and Low-Energy Electrons on the Properties of the WO3 Surface......Page 173
6.3.3 Surface Band Edge Positions in Vacuum – Determination with UPS/IPES......Page 175
6.3.4 Estimated Surface Band-Edge Positions in Electrolyte......Page 177
6.3.5 Conclusions......Page 179
6.4.2 The O K XES Spectrum of ZnO:N Thin Films – Determination of the Valence Band Maximum......Page 180
6.4.3 The Impact of Air Exposure on the Chemical Structure of ZnO:N Thin Films......Page 181
6.4.4 Conclusions......Page 183
6.6 Summary......Page 184
References......Page 185
7.1 Introduction......Page 189
7.2 X-Ray Transient Absorption Spectroscopy (XTA)......Page 191
7.3 Tracking Electronic and Nuclear Configurations in Photoexcited Metalloporphyrins......Page 197
7.4 Tracking Metal-Center Oxidation States in the MLCT State of Metal Complexes......Page 202
7.5 Tracking Transient Metal Oxidation States During Hydrogen Generation......Page 204
7.6 Prospects and Challenges in Future Studies......Page 206
References......Page 207
8.1 Introduction......Page 215
8.2 Vibrational Spectroscopy on TiO2 Photocatalysts: Experimental Considerations......Page 217
8.3 Raman Spectroscopy of Pure and Doped TiO2 Nanoparticles......Page 221
8.4 Gas–Solid Photocatalytic Reactions Probed by FTIR Spectroscopy......Page 225
8.5.1 Reactions with Formic Acid......Page 231
8.5.2 Reactions with Acetone......Page 247
8.6 Summary and Concluding Remarks......Page 255
References......Page 256
9.1 Introduction......Page 265
9.2.1 Semiconductor Quantum Dots......Page 266
9.2.2 Metal Oxide Nanocrystalline Semiconductor Films......Page 267
9.2.3 QD Sensitized Metal Oxide Semiconductor Films......Page 268
9.3.2 Calculation of Absorption Difference......Page 271
9.3.3 System Arrangement......Page 272
9.4 Controlling Interfacial Electron Transfer Reactions by Nanomaterial Design......Page 273
9.4.1 QD/Metal-Oxide Interface......Page 274
9.4.2 QD/Electrolyte Interface......Page 276
9.4.3 Conducting Glass/Electrolyte Interface......Page 278
9.5 Application of QD-Sensitized Metal-Oxide Semiconductors to Solar Hydrogen Production......Page 284
References......Page 286
Part Three: Development of Advanced Nanostructures for Efficient Solar Hydrogen Production from Classical Large Bandgap Semiconductors......Page 291
10.1 Introduction......Page 293
10.2 Crystal Structure of TiO2......Page 294
10.2.1 Electronic and Defect Structure of TiO2......Page 295
10.2.2 Preparation of TiO2 Nanotubes......Page 298
10.2.3 Energetics of Photodecomposition of Water on TiO2......Page 305
References......Page 314
11.1 Introduction......Page 317
11.2 Fundamentals of Electrochemical Deposition......Page 318
11.3 Electrodeposition of Metal Oxides and Other Compounds......Page 320
11.4.1 Electrodeposition of Pure ZnO......Page 321
11.4.2 Electrodeposition of Doped ZnO......Page 323
11.5.1 ZnO Nanorods......Page 324
11.5.2 ZnO Nanotubes......Page 327
11.5.3 Two-Dimensional ZnO Nanostructures......Page 328
11.6.1 Dye Molecules as Structure-Directing Additives......Page 329
11.6.2 ZnO Electrodeposition with Surfactants......Page 333
11.6.3 Other Additives......Page 337
11.7.1 Dye-Sensitized Solar Cells (DSSCs)......Page 338
11.7.2 Photoelectrochemical Investigation of the Electron Transport in Porous ZnO Films......Page 342
11.7.3 Performance of Nanoporous Electrodeposited ZnO Films in DSSCs......Page 346
11.7.4 Use of ZnO Nanorods in Photovoltaics......Page 347
11.8 Photocatalytic Properties......Page 348
References......Page 349
12.1 Historical Context......Page 359
12.2 Macrocrystalline WO3 Films......Page 360
12.4 Nanostructured Films......Page 362
12.5 Tailoring WO3 Films Through a Modified Chimie Douce Synthetic Route......Page 365
12.6 Surface Reactions at Nanocrystalline WO3 Electrodes......Page 368
12.7 Conclusions and Outlook......Page 371
References......Page 372
13.1 Introduction......Page 375
13.2.1 Structural and Electrical/Electronic Properties......Page 376
13.2.2 α-Fe2O3 in PEC Splitting of Water......Page 377
13.3 Nanostructured α-Fe2O3 Photoelectrodes......Page 378
13.3.1 Preparation Techniques and Photoelectrochemical Response......Page 379
13.3.2 Flatband Potential and Donor Density......Page 391
13.4.1 Doping......Page 394
13.4.2 Choice of Electrolytes......Page 399
13.4.3 Dye Sensitizers......Page 400
13.4.5 Forward/Backward Illumination......Page 401
13.4.7 Layered Structures......Page 403
13.4.8 Deposition of Zn Islands......Page 406
13.4.9 Swift Heavy Ion (SHI) Irradiation......Page 408
13.4.10 p/n Assemblies......Page 411
13.5 Efficiency and Hydrogen Production......Page 412
13.6 Concluding Remarks......Page 414
References......Page 419
Part Four: New Design and Approaches to Bandgap Profiling and Visible-Light-Active Nanostructures......Page 425
14.1 Introduction......Page 427
14.2.1 The Use of High-Throughput and Combinatorial Methods in Materials Science......Page 428
14.2.2 HTE Applications to PEC Discovery......Page 431
14.2.3 Absorbers......Page 434
14.2.4 Bulk Carrier Transport......Page 437
14.2.6 Morphology and Material System......Page 438
14.2.7 Library Format, Data Management and Analysis......Page 440
14.3 Practical Methods of High-Throughput Synthesis of Photoelectrocatalysts......Page 441
14.3.1 Vapor Deposition......Page 442
14.3.2 Liquid Phase Synthesis......Page 443
14.3.3 Electrochemical Synthesis......Page 445
14.3.4 Spray Pyrolysis......Page 448
14.4 Photocatalyst Screening and Characterization......Page 449
14.4.1 High-Throughput Screening......Page 450
14.4.2 Secondary Screening and Quantitative Characterization......Page 458
14.5.1 Solar Absorbers......Page 463
14.5.2 Improving Charge-Transfer Efficiency......Page 469
14.5.3 Improved PEC Electrocatalysts......Page 474
14.5.4 Design and Assembly of a Complete Nanostructured Photocatalytic Unit......Page 477
14.6 Summary and Outlook......Page 479
References......Page 480
15.1.1 Introduction......Page 485
15.1.3 Metal-Oxide PEC Cells......Page 486
15.1.5 Deposition Techniques for Metal Oxides......Page 488
15.2.1 Colloidal Nanoparticles......Page 489
15.2.2 TiO2 Sol-Gel Synthesis......Page 490
15.2.3 TiO2 Hydrothermal Synthesis......Page 491
15.2.4 TiO2 Solvothermal and Sonochemical Synthesis......Page 492
15.2.5 TiO2 Template-Driven Synthesis......Page 494
15.2.8 WO3 Solvothermal and Sonochemical Synthesis......Page 496
15.2.9 WO3 Template Driven Synthesis......Page 497
15.2.10 ZnO Sol-Gel Nanoparticle Synthesis......Page 499
15.2.11 ZnO Hydrothermal Synthesis......Page 500
15.2.12 ZnO Solvothermal and Sonochemical Synthesis......Page 501
15.2.13 ZnO Template-Driven Synthesis......Page 505
15.3.2 Synthesis and Fabrication of 1D TiO2 Nanostructures......Page 507
15.3.3 Colloidal Synthesis and Fabrication of 1D WO3 Nanostructures......Page 512
15.3.4 Colloidal Synthesis and Fabrication of 1D ZnO Nanostructures......Page 513
15.4.1 Colloidal Synthesis of 2D TiO2 Nanostructures......Page 514
15.4.2 Colloidal Synthesis of 2D WO3 Nanostructures......Page 516
15.4.3 Colloidal Synthesis of 2D ZnO Nanostructures......Page 517
15.5 Conclusion......Page 518
References......Page 519
16.1 Introduction......Page 533
16.2.1 Synthetic and Structural Aspects......Page 535
16.2.2 Photocatalytic Hydrogen Evolution......Page 537
16.2.3 Peroxide Formation......Page 539
16.2.4 Water Electrolysis......Page 541
16.3 CdSe Nanoribbons as a Quantum-Confined Water-Splitting Catalyst......Page 542
16.4 Conclusion and Outlook......Page 544
References......Page 545
17.1 Introduction......Page 549
17.2.1 Concepts and Experimental Set-Up of Aqueous Chemical Growth......Page 550
17.2.2 Achievements in Aqueous Design of Highly Oriented Metal-Oxide Arrays......Page 554
17.3 Quantum Confinement Effects for Photovoltaics and Solar Hydrogen Generation......Page 555
17.3.1 Multiple Exciton Generation......Page 556
17.3.3 Intermediate Band Materials......Page 557
17.4.1 Iron-Oxide Quantum-Rod Arrays......Page 559
17.4.2 Doped Iron-Oxide Quantum-Rod Arrays......Page 567
17.4.3 Quantum-Dot–Quantum-Rod Iron-Oxide Heteronanostructure Arrays......Page 571
17.4.4 Iron Oxide Oriented Porous Nanostructures......Page 572
References......Page 574
18.1 Introduction......Page 585
18.3.1 Sr2+ Ion-Doped CeO2......Page 587
18.3.2 Metal-Ion Doped GaN......Page 590
18.4 Effects of Metal-Ion Removal......Page 595
18.5.1 YxIn2-xO3......Page 599
18.5.2 ScxIn2-xO3......Page 606
18.5.3 YxIn2-xGe2O7......Page 608
18.6 Effects of Zn Addition to Indate and Stannate......Page 609
18.6.2 Ba3Zn5In2O11......Page 610
18.7 Conclusions......Page 611
References......Page 612
19.1.1 Solar Water Splitting......Page 615
19.1.2 Supramolecular Complexes and Photochemical Molecular Devices......Page 616
19.1.3 Polyazine Light Absorbers......Page 617
19.1.4 Polyazine Bridging Ligands to Construct Photochemical Molecular Devices......Page 620
19.1.5 Multi-Component System for Visible Light Reduction of Water......Page 621
19.1.6 Photoinitiated Charge Separation......Page 622
19.2.1 Photoinitiated Electron Collection on a Bridging Ligand......Page 624
19.2.2 Ruthenium Polyazine Light Absorbers Coupled Through an Aromatic Bridging Ligand......Page 626
19.2.3 Photoinitiated Electron Collection on a Platinum Metal......Page 628
19.2.4 Two-Electron Mixed-Valence Complexes for Multielectron Photochemistry......Page 630
19.2.5 Rhodium-Centered Electron Collectors......Page 631
19.2.6 Mixed-Metal Systems for Solar Hydrogen Production......Page 639
19.3 Conclusions......Page 640
Acknowledgments......Page 642
References......Page 643
Part Five: New Devices for Solar Thermal Hydrogen Generation......Page 647
20.1.1 Energy Production and Nanotechnology......Page 649
20.2 Solar Hydrogen Production......Page 650
20.2.1 Solar Hydrogen Production: Thermochemical Processes......Page 651
20.2.2 Solar Chemical Reactors......Page 652
20.3.2 Redox Materials......Page 653
20.3.3 Water Splitting: Laboratory Tests......Page 655
20.3.4 HYDROSOL Reactors......Page 656
20.3.5 Solar Testing......Page 657
20.3.6 Simulation......Page 659
20.4 HYDROSOL Process......Page 662
20.5 Conclusions......Page 663
References......Page 664
21.1 Comparison of Solar Hydrogen Processes......Page 667
21.2 STEP (Solar Thermal Electrochemical Photo) Generation of H2......Page 672
21.3 STEP Theory......Page 674
21.4 STEP Experiment: Efficient Solar Water Splitting......Page 679
21.5.1 Direct Solar Thermal Hydrogen Generation......Page 683
21.5.2 Indirect (Multistep) Solar Thermal H2 Generation......Page 685
21.6 Conclusions......Page 686
References......Page 687
Index......Page 691