Photoelectrochemical Solar Fuel Production (eBook)

Prof. Juan Bisquert and Prof. Sixto Giménez are faculty members at Universitat Jaume I de Castelló in Spain.

Preface 8
Contents 14
List of Acronyms 16
Contributors 20
Part I: Fundamentals 23
Chapter 1: Semiconductor Electrochemistry 24
1.1 Introduction 24
1.2 A Brief Summary of Semiconductor Physics 25
1.2.1 Energy Bands and the Fermi-Dirac Distribution 25
1.2.2 Doped Semiconductors and the Fermi Energy 26
1.2.3 Fermi Energy and Electrochemical Potential 27
1.2.4 The Illuminated Semiconductor and Quasi-Fermi Energies 28
1.2.5 Semiconductor Junctions and Energy Scales 30
1.2.6 Electron Transfer at the Semiconductor/Electrolyte Interface 33
1.2.7 Potential Distribution Across the Semiconductor/Electrolyte Junction 36
1.2.8 Surface States and Fermi Level Pinning 40
1.2.9 Current-Voltage Characteristics of the Semiconductor/Electrolyte Junction in the Dark 43
1.3 Photoelectrochemical Processes 44
1.3.1 The Gärtner Equation 44
1.3.2 Recombination in the Space Charge Region and at the Surface 47
1.3.3 Rates and Rate Constants of Photoelectrochemical Processes 50
1.3.4 Quasi Fermi Levels and the Concept of Overpotential 52
1.4 Nanostructured Semiconductor Electrodes 54
1.4.1 Photocatalysis and Photosynthesis at Dispersed Semiconductor Particles 54
1.4.2 Potential Distribution for Nanospheres and Nanorods in an Electrolyte 55
1.4.3 Mesoporous Semiconductor Electrodes 57
1.5 Conclusions 58
References 59
Chapter 2: The Oxygen Evolution Reaction: Mechanistic Concepts and Catalyst Design 62
2.1 Introduction 62
2.2 Electrochemical Perspectives 66
2.2.1 The Tafel Slope 66
2.2.2 Electrochemical Reaction Orders 73
2.2.3 Mechanistic Analysis 75
2.3 Thermochemical Perspectives 83
2.3.1 The Potential-Determining Step 83
2.3.2 Reaction Pathways and Surface Effects 87
2.4 Trends in Activity 90
2.4.1 Bulk Thermochemistry 91
2.4.2 Binding Energies and Scaling Relations 93
2.4.3 Electronic Structure and Activity 95
2.5 Tailoring Activity 99
2.5.1 Catalyst Synergy 99
2.5.2 Activity-Stability Relations 104
2.5.3 Conductivity Effects 106
2.5.4 The Active Site 109
2.6 Conclusion 115
References 116
Chapter 3: Hydrogen and CO2 Reduction Reactions: Mechanisms and Catalysts 126
3.1 Introduction 126
3.2 Theory: Storage of Fuel from PEC Water Splitting 127
3.3 Hydrogen Evolution Reaction (HER) 129
3.3.1 Historical Background and Theory of HER 130
3.3.2 Metal Sulfides Based HER Catalysts 134
3.3.3 Metal Phosphide Based HER Catalysts 147
3.3.4 Metal Carbide Based HER Catalysts 149
3.3.5 Nitride Based HER Catalysts 151
3.4 CO2 Reduction 153
3.4.1 Selecting Ideal Photocatalyst for CO2 Reduction 155
3.4.2 Theory of Photocatalytic CO2 Reduction 156
3.4.3 Dye Sensitized TiO2 for CO2 Reduction 159
3.4.4 Photocatalytic Dyads 159
3.4.5 TiO2-Noble Metal Nanoparticle Doping 161
3.4.6 TiO2-Noble Metal-Metal Oxide Doping 161
3.4.7 Heterogeneous Semiconductors as Photocatalysts 163
3.4.8 Graphene-Based Photocatalysts 163
3.4.9 Graphene: Based Photoelectrocatalysts 165
3.5 Conclusions 171
References 171
Part II: Methods 182
Chapter 4: Photoelectrochemical Cell Design, Efficiency, Definitions, Standards, and Protocols 183
4.1 Introduction 183
4.2 The Photoelectrochemical Cell 185
4.2.1 Cell Design 185
4.2.2 Electrodes 188
4.2.2.1 General Considerations 189
4.2.2.2 Photovoltaic Cell + Electrocatalyst (PV + EC) 191
4.2.2.3 Photovoltaic Cell + Photoelectrode (PV + PEC) 196
4.2.2.4 Dual Photoelectrodes (Photoanode + Photocathode, i.e. PEC) 198
4.2.3 The Electrolyte 199
4.2.4 Ion Exchange Membranes 201
4.2.4.1 Proton Exchange Membranes 201
4.2.4.2 Anion Exchange Membranes 202
4.2.4.3 Bipolar Membranes 202
4.2.4.4 Membrane-Less Systems 203
4.3 Measurement Protocols 203
4.3.1 Simulated Solar Irradiation Measurements 203
4.3.2 Determining the Flatband Potential 207
4.3.3 Evolved Gas Quantification 208
4.4 Efficiency Definitions 209
4.4.1 Solar-to-Hydrogen (STH) Conversion Efficiency 209
4.4.2 Applied Bias Photon to Current Conversion Efficiency (ABPE) 211
4.4.3 Spectral Response Measurements 211
4.4.3.1 Incident Photon to Current Conversion Efficiency (IPCE) 212
4.4.3.2 Absorbed Photon to Current Conversion Efficiency (APCE) 213
4.5 Summary and Conclusions 214
References 214
Chapter 5: Interface Engineering of Semiconductor Electrodes for Photoelectrochemical Water Splitting: Application of Surface ... 218
5.1 Introduction 218
5.2 Theoretical Considerations on Photovoltaic and Photoelectrochemical Cells 221
5.3 Energetic Conditions of PEC Based Water Splitting 225
5.4 Promising Integrated PV/PEC Device Structures 231
5.5 A Survey of Semiconductor Junctions Incorporated in PEC Cells 236
5.5.1 Formation of Semiconductor Junctions: Metal Contact 237
5.5.2 Formation of Semiconductor Junctions: Electrolyte Contact 242
5.5.3 Fermi Level Pinning and Surface (Interface) States 249
5.5.4 Interface Engineering: Formation of Semiconductor-Passivation Layer-Cocatalyst-Electrolyte Interfaces 255
5.6 Fundamentals and Applications of Photoelectron Spectroscopy 257
5.6.1 Experimental Procedure 258
5.6.1.1 Basic Setup and Operation Principle 258
5.6.1.2 Sample Preparation: Vacuum Conditions 261
5.6.1.3 Preparation of Solid Surfaces for Photoemission Experiments 262
5.6.1.4 Analysis of Solid-Solid Interfaces Using Photoemission 264
5.6.1.5 Study of Solid-Liquid Interfaces Using Photoemission 265
5.6.2 Information Available from XPS 268
5.6.2.1 Analysis of Peak Lines and Intensities 268
Elemental Analysis 268
Compositional Analysis 268
5.6.2.2 Analysis of Energy Shifts 270
Chemical Shifts 270
Surface Potential Changes 270
5.6.3 Interface Analysis 275
5.6.4 Information from Valence Band Spectra 278
5.7 Case Study: Si Based Photoelectrochemical Cells 280
5.7.1 Water Splitting with Si Based Photoelectrodes 280
5.7.2 Tandem Solar Cell as a Buried Junction Photoelectrode 282
5.7.3 Si Photoelectrode Interface Analysis 285
5.7.4 Interface Studies on p-i-n Tandem Cell Photoelectrodes 287
5.8 Summary and Conclusion 289
References 291
Chapter 6: Analysis of Photoelectrochemical Systems by Impedance Spectroscopy 300
6.1 Introduction 300
6.2 Steady-State Operation of PEC Systems 304
6.3 Resistances and Capacitances in PEC Systems 306
6.4 Total Resistance Rdc and the Connection to jV Curves 309
6.5 Charge TransferCharge Transfer via Surface States 313
6.5.1 Properties of Surface States 313
6.5.2 Theory of Charge Transfer via Surface States and Valence or Conduction Band 314
6.5.3 Types of Analysis of IS Results 321
6.5.4 Experimental Results 321
6.6 Band Edge Movement 325
6.7 Modification of Charge Transfer Rate 326
6.8 Transport and Reaction in Nanostructures 330
6.8.1 Transport and Charge Transfer 333
6.8.2 Determination of Band Edge Shift by Displacement of the Chemical Capacitance 335
6.9 Conclusions 337
References 337
Chapter 7: Advanced Photoelectrochemical Characterization: Principles and Applications of Dual-Working-Electrode Photoelectroc... 341
7.1 Background 341
7.2 Single-Working-Electrode Photoelectrochemistry 344
7.3 Dual-Working-Electrode PhotoelectrochemistryDual-Working-Electrode (DWE) Photoelectrochemistry 346
7.3.1 Dual-Working-Electrode Setup in Electrochemistry 346
7.3.2 Energy Diagram of the DWE PEC Setup 347
7.3.3 Instrumentation and Samples for DWE PEC 348
7.3.4 Information Accessible Through DWE PEC 349
7.4 Applications of DWE PEC 349
7.4.1 The ``Adaptive´´ SCEC Junction Hypothesis 349
7.4.2 Tracking the Path of Photogenerated Holes 352
7.4.3 In Situ Measurement of the EC Potential 354
7.4.4 Open-Circuit Photovoltage Measurement 357
7.4.5 Dark Junction J-V Behavior as a Function of Vcat 359
7.4.6 Summary of DWE PEC Results 360
7.5 Outlook 361
Appendix: Experimental Details 362
Au Thin-Film Contact 362
Sample Viability Tests 363
Test Cell and Measurement Setup 363
Impact of the Au Contact 363
Verifying the Independence of the Two WEs 365
References 366
Part III: Materials and Devices 370
Chapter 8: Multinary Metal Oxide Photoelectrodes 371
8.1 Introduction 371
8.2 Limitations of Binary Metal Oxides 373
8.3 n-Type Multinary Metal Oxidesn-Type Multinary Metal Oxides 374
8.3.1 Bismuth Vanadate (BiVO4Bismuth Vanadate (BiVO4)) 374
8.3.1.1 Crystal Structure 374
8.3.1.2 Electronic Structure and Optical Properties 376
8.3.1.3 Photoelectrochemical Properties 377
8.3.1.4 Future Outlook 381
8.3.2 Copper Tungstate (CuWO4) 382
8.3.2.1 Crystal Structure 382
8.3.2.2 Electronic Structure and Optical Properties 383
8.3.2.3 Photoelectrochemical Properties 383
8.3.2.4 Future Outlook 385
8.3.3 Iron Tungstate (Fe2WO6) 385
8.3.3.1 Crystal Structure 385
8.3.3.2 Electronic Structure and Optical Properties 386
8.3.3.3 Photoelectrochemical Properties 386
8.3.3.4 Future Outlook 387
8.4 p-Type Multinary Metal Oxides 387
8.4.1 Copper Bismuth Oxide (CuBi2O4) 388
8.4.2 Delafossite (CuFeO2) 389
8.4.3 Iron Spinels (AFe2O4) and Cobalt Spinels (CoB2O4) 390
8.5 Tandem Devices with Multinary Oxides 391
8.6 Challenges for Multinary Oxides 393
8.6.1 Crystallinity and Stoichiometry 394
8.6.2 High-Temperature Stability 395
8.6.3 Doping and Alloying 396
8.7 Conclusions and Future Outlook 398
References 400
Chapter 9: Non-Oxide Materials (Nitrides, Chalcogenides, and Arsenides) 408
9.1 General Perspective 408
9.1.1 General Semiconductor Properties 408
9.1.2 Band Edge and Flatband Potentials 409
9.1.3 Photocurrent 411
9.1.4 Stability and Corrosion 413
9.2 Elemental Semiconductors (Si, Ge, and C (Diamond)) 414
9.2.1 Semiconductor Properties 414
9.2.2 Flatband and Band Edge Potentials 414
9.2.3 Photocurrent-Voltage Characteristics 416
9.2.4 Stability Improvements by Catalysts and Protection Layers 416
9.3 III-V Semiconductors (Phosphide and Arsenide) 417
9.3.1 Semiconductor Properties 417
9.3.2 Flatband and Band Edge Potentials 417
9.3.3 Photo-corrosion and Stability Improvements by Catalysts and Protection Layers 420
9.3.4 Ternary Materials 421
9.4 Nitrides (GaN, AlN, and InN) 422
9.4.1 Semiconductor Properties 422
9.4.2 Flatband and Band Edge Potentials 423
9.4.3 Photocurrent-Voltage Characteristics 425
9.4.4 Stability Improvements by Catalysts and Protection Layers 427
9.4.5 Other Properties 429
9.5 Chalcogenides (Sulfide, Selenide, and Telluride) and Others 430
9.5.1 Semiconductor Properties 430
9.5.2 Flatband and Band Edge Potentials 431
9.5.3 Photo-corrosion and Stability Improvements by Catalysts and Protection Layers 432
9.6 Tandem Structures 434
9.7 Concluding Remarks 436
References 436
Chapter 10: Combinatorial Synthesis and Screening of Oxide Materials for Photoelectrochemical Energy Conversion 442
10.1 The Combinatorial Approach for Developing New Materials 442
10.2 Materials for Photoelectrochemical Water Splitting 443
10.3 The Preparation and Characterization of Libraries 445
10.4 Library Design 445
10.5 Substrates 446
10.6 Methods for Preparing Libraries 448
10.6.1 Preparation Methods in Ambient Air 448
10.6.2 Preparation Under Reduced Pressure 450
10.7 Pyrolysis and Annealing 453
10.8 Screening Libraries 454
10.8.1 Measuring (Photo)electrochemical Properties 454
10.8.1.1 Screening with the Whole Library Immersed into an Electrochemical Cell 455
10.8.1.2 Screening Using Independent Electrochemical Cells 457
10.8.1.3 Scanning Droplet Cells for Photoelectrochemical Screening 458
10.8.2 Detecting the Changes in Optical Properties Due to Evolution of the Products 462
10.8.3 Detection of Products 462
10.9 Data Processing 464
10.10 Combinatorial Studies of Mixed Metal Oxide Photoelectrodes and Electrocatalysts 464
10.11 Libraries Prepared with Combinatorial Methods 464
10.11.1 Photocathodes for the HER 466
10.11.2 Photoanodes for the OER 467
10.11.3 Electrocatalysts 469
10.12 Theoretical Approaches 470
10.13 Distributed Searches in an Outreach Environment 471
10.14 Outlook 471
References 472
Chapter 11: Nanostructured Materials 478
11.1 A Brief History of Nanoscale Photoelectrochemistry 478
11.2 Pros and Cons of Nanostructured Photoelectrodes 479
11.2.1 Shorter Pathway for Charge Carrier Collection 479
11.2.2 Higher Light Absorption 480
11.2.3 Increased Surface Area 481
11.2.4 Reduced Depletion Layer Thickness 481
11.3 Different Morphologies of Nanostructures 481
11.3.1 Zero-Dimensional Nanoparticles 482
11.3.2 One-Dimensional Nanostructures for Water Splitting 482
11.3.3 Two/Three-Dimensional Nanostructures for Water Splitting 483
11.3.4 Heteronanostructures for Water Splitting 484
11.4 Synthesis Methods 484
11.4.1 Solution Phase Methods 485
11.4.2 Electrochemical Anodization 486
11.4.3 Gas Phase Methods 488
11.4.4 Template Induced Synthesis 490
11.5 Explored Nanostructured Materials 491
11.5.1 Titanium Dioxide 492
11.5.2 Zinc Oxide 493
11.5.3 Tungsten Trioxide 494
11.5.4 Iron Oxide 494
11.5.5 Bismuth Vanadate 495
11.5.6 Cuprous Oxide 496
11.5.7 Manganese Dioxide 497
11.5.8 Metal Nitrides 498
11.5.9 Silicon 498
11.5.10 Metal Chalcogenides 499
11.6 Heteronanostructures 500
11.7 Conclusions and Outlook 501
References 502
Chapter 12: Advanced Device Architectures and Tandem Devices 508
12.1 Introduction 508
12.2 Harvesting the Solar Spectrum and Developing Photopotential 509
12.3 Employing thin Semiconductor Layers in Tandem Cells 515
12.4 Photoelectrode Configurations and Device Design Considerations 517
12.5 Demonstrations of Operational Tandem Cells for Solar Hydrogen Production 521
12.6 Economic Considerations 524
12.7 Summary and Conclusion 525
References 526
Chapter 13: Dye Sensitized Photoelectrosynthesis Cells for Making Solar Fuels: From Basic Science to Prototype Devices 528
13.1 Water Oxidation 529
13.2 Dye-Sensitized Photoelectrosynthesis Cells (DSPECs) 532
13.3 The Elements of a DSPEC 534
13.4 Chromophore-Catalyst Assemblies 535
13.5 Interfacial Dynamics 538
13.6 Molecular Catalysis: Water Oxidation 540
13.7 The Role of Atom-Proton Transfer in Water Oxidation Catalysis 541
13.8 BDA-Catalysts 542
13.9 Water Oxidation in Propylene Carbonate 543
13.10 First Row Transition Metal Complex Catalysts for Water Oxidation 544
13.11 Water Oxidation on Oxide Surfaces 545
13.12 Molecular Catalysis: CO2 Reduction 547
13.13 CO2 Reduction to Formate 547
13.14 CO2 Reduction to Syngas 549
13.15 Catalysis of CO2 Splitting into CO and O2 551
13.16 Stabilization of Surface Binding 551
13.17 DSPEC Water Splitting 553
13.18 Core/Shell Electrodes 554
13.19 DSPEC: Design Strategies 556
13.20 Looking Ahead: Challenges for the Future 558
References 559
Index 564