Comprehensive resource covering hydrogen oxidation reaction, oxygen reduction reaction, classes of electrocatalytic materials, and characterization methods
Electrocatalysis for Membrane Fuel Cells focuses on all aspects of electrocatalysis for energy applications, covering perspectives as well as the low-temperature fuel systems principles, with main emphasis on hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR).
Following an introduction to basic principles of electrochemistry for electrocatalysis with attention to the methods to obtain the parameters crucial to characterize these systems, Electrocatalysis for Membrane Fuel Cells covers sample topics such as: - Electrocatalytic materials and electrode configurations, including precious versus non-precious metal centers, stability and the role of supports for catalytic nano-objects; - Fundamentals on characterization techniques of materials and the various classes of electrocatalytic materials; - Theoretical explanations of materials and systems using both Density Functional Theory (DFT) and molecular modelling; - Principles and methods in the analysis of fuel cells systems, fuel cells integration and subsystem design.
Electrocatalysis for Membrane Fuel Cells quickly and efficiently introduces the field of electrochemistry, along with synthesis and testing in prototypes of materials, to researchers and professionals interested in renewable energy and electrocatalysis for chemical energy conversion.
Table of Contents
Preface xv
Part I Overview of Systems 1
1 System-level Constraints on Fuel Cell Materials and Electrocatalysts 3
Elliot Padgett and Dimitrios Papageorgopoulos
1.1 Overview of Fuel Cell Applications and System Designs 3
1.1.1 System-level Fuel Cell Metrics 3
1.1.2 Fuel Cell Subsystems and Balance of Plant (BOP) Components 5
1.1.3 Comparison of Fuel Cell Systems for Different Applications 9
1.2 Application-derived Requirements and Constraints 10
1.2.1 Fuel Cell Performance and the Heat Rejection Constraint 10
1.2.2 Startup, Flexibility, and Robustness 13
1.2.3 Fuel Cell Durability 14
1.2.4 Cost 16
1.3 Material Pathways to Improved Fuel Cells 18
1.4 Note 19
Acronyms 20
Symbols 20
References 20
2 PEM Fuel Cell Design from the Atom to the Automobile 23
Andrew Haug and Michael Yandrasits
2.1 Introduction 23
2.2 The PEMFC Catalyst 27
2.3 The Electrode 32
2.4 Membrane 38
2.5 The GDL 42
2.6 CCM and MEA 46
2.7 Flowfield and Single Fuel Cell 50
2.8 Stack and System 55
Acronyms 57
References 58
Part II Basics - Fundamentals 69
3 Electrochemical Fundamentals 71
Vito Di Noto, Gioele Pagot, Keti Vezzù, Enrico Negro, and Paolo Sgarbossa
3.1 Principles of Electrochemistry 71
3.2 The Role of the First Faraday Law 71
3.3 Electric Double Layer and the Formation of a Potential Difference at the Interface 73
3.4 The Cell 74
3.5 The Spontaneous Processes and the Nernst Equation 75
3.6 Representation of an Electrochemical Cell and the Nernst Equation 77
3.7 The Electrochemical Series 79
3.8 Dependence of the E cell on Temperature and Pressure 82
3.9 Thermodynamic Efficiencies 83
3.10 Case Study - The Impact of Thermodynamics on the Corrosion of Low-T FC Electrodes 85
3.11 Reaction Kinetics and Fuel Cells 88
3.11.1 Correlation Between Current and Reaction Kinetics 88
3.11.2 The Concept of Exchange Current 89
3.12 Charge Transfer Theory Based on Distribution of Energy States 89
3.12.1 The Butler-Volmer Equation 96
3.12.2 The Tafel Equation 100
3.12.3 Interplay Between Exchange Current and Electrocatalyst Activity 101
3.13 Conclusions 103
Acronyms 104
Symbols 104
References 107
4 Quantifying the Kinetic Parameters of Fuel Cell Reactions 111
Viktoriia A. Saveleva, Juan Herranz, and Thomas J. Schmidt
4.1 Introduction 111
4.2 Electrochemical Active Surface Area (ECSA) Determination 114
4.2.1 ECSA Determination Using Underpotential Deposition 115
4.2.1.1 Hydrogen Underpotential Deposition (H UPD) 116
4.2.1.2 Copper Underpotential Deposition (Cu UPD) 117
4.2.2 ECSA Quantification Based on the Adsorption of Probe Molecules 118
4.2.2.1 CO Stripping 118
4.2.2.2 No -2 ∕NO Sorption 119
4.2.3 Double-layer Capacitance Measurements and Other Methods 120
4.2.4 ECSA Measurements in a PEFC: Which Method to Choose? 120
4.3 H 2 -Oxidation and Electrochemical Setups for the Quantification of Kinetic Parameters 121
4.3.1 Rotating Disc Electrodes (RDEs) 122
4.3.2 Hydrogen Pump (PEFC) Approach 124
4.3.3 Ultramicroelectrode Approach 125
4.3.4 Scanning Electrochemical Microscopy (SECM) Approach 125
4.3.5 Floating Electrode Method 127
4.3.6 Methods Summary 128
4.4 ORR Kinetics 129
4.4.1 ORR Mechanism Studies with RRDE Setups 129
4.4.2 ORR Pathway on Me/N/C ORR Catalysts 130
4.4.3 ORR Kinetics: Methods 132
4.4.3.1 Pt-based Electrodes 132
4.4.3.2 Pt-free Catalysts: RDE vs. PEFC Kinetic Studies 133
4.5 Concluding Remarks 133
Acronyms 134
Symbols 134
References 135
5 Adverse and Beneficial Functions of Surface Layers Formed on Fuel Cell Electrocatalysts 149
Shimshon Gottesfeld
5.1 Introduction 149
5.2 Catalyst Capping in Heterogeneous Catalysis and in Electrocatalysis 151
5.3 Passivation of PGM/TM and Non-PGM HOR Catalysts and Its Possible Prevention 156
5.4 Literature Reports on Fuel Cell Catalyst Protection by Capping 161
5.4.1 Protection of ORR Pt catalysts Against Agglomeration by an Ultrathin Overlayer of Mesoporous SiO 2 or Me-SiO 2 161
5.4.2 Protection by Carbon Caps Against Catalyst Detachment and Catalyst Passivation Under Ambient Conditions 162
5.5 Other Means for Improving the Performance Stability of Supported Electrocatalysts 166
5.5.1 Replacement of Carbon Supports by Ceramic Supports 166
5.5.2 Protection of Pt Catalysts by Enclosure in Mesopores 167
5.6 Conclusions 170
Abbreviations 171
References 171
Part III State of the Art 175
6 Design of PGM-free ORR Catalysts: From Molecular to the State of the Art 177
Naomi Levy and Lior Elbaz
6.1 Introduction 177
6.2 The Influence of Molecular Changes Within the Complex 179
6.2.1 The Role of the Metal Center 179
6.2.2 Addition of Substituents to MCs 183
6.2.2.1 Beta-substituents 184
6.2.3 Meso-substituents 186
6.2.4 Axial Ligands 187
6.3 Cooperative Effects Between Neighboring MCs 190
6.3.1 Bimetallic Cofacial Complexes - “Packman” Complexes 191
6.3.2 MC Polymers 191
6.4 The Physical and/or Chemical Interactions Between the Catalyst and Its Support Material 193
6.5 Effect of Pyrolysis 194
Acronyms 196
References 196
7 Recent Advances in Electrocatalysts for Hydrogen Oxidation Reaction in Alkaline Electrolytes 205
Indra N. Pulidindi and Meital Shviro
7.1 Introduction 205
7.2 Mechanism of the HOR in Alkaline Media 206
7.3 Electrocatalysts for Alkaline HOR 212
7.3.1 Platinum Group Metal HOR Electrocatalysts 212
7.3.2 Non-platinum Group Metal-based HOR Electrocatalysts 214
7.4 Conclusions 220
Acronyms 221
References 221
8 Membranes for Fuel Cells 227
Paolo Sgarbossa, Giovanni Crivellaro, Francesco Lanero, Gioele Pagot, Afaaf R. Alvi, Enrico Negro, Keti Vezzù, and Vito Di Noto
8.1 Introduction 227
8.2 Properties of the PE separators 228
8.2.1 Benchmarking of IEMs 229
8.2.2 Ion-exchange Capacity (IEC) 229
8.2.3 Water Uptake (WU), Swelling Ratio (SR), and Water Transport 231
8.2.4 Ionic Conductivity (σ) 233
8.2.5 Gas Permeability 234
8.2.6 Chemical Stability 235
8.2.7 Thermal and Mechanical Stability 237
8.2.8 Cost of the IEMs 239
8.3 Classification of Ion-exchange Membranes 240
8.3.1 Cation-exchange Membranes (CEMs) 240
8.3.1.1 Perfluorinated Membranes 240
8.3.1.2 Nonperfluorinated Membranes 245
8.3.2 Anion-exchange Membranes (AEMs) 246
8.3.2.1 Functionalized Polyketones 247
8.3.2.2 Poly(Vinyl Benzyl Trimethyl Ammonium) (PVBTMA) Polymers 248
8.3.2.3 Poly(sulfones) (PS) 249
8.3.3 Hybrid Ion-exchange Membranes 249
8.3.3.1 Hybrid Membranes with Single Ceramic Oxoclusters [P/(M X O Y) n ] 250
8.3.3.2 Hybrid Membranes Comprising Surface-functionalized Nanofillers 254
8.3.3.3 Hybrid Membranes Doped with hierarchical “Core-Shell” Nanofillers 254
8.3.4 Porous Membranes 257
8.3.4.1 Porous Membranes as Host Material 257
8.3.4.2 Porous Membranes as Support Layer 258
8.3.4.3 Porous Membranes as Unconventional Separators 259
8.4 Mechanism of Ion Conduction 259
8.5 Summary and Perspectives 268
Acronyms 271
Symbols 272
References 272
9 Supports for Oxygen Reduction Catalysts: Understanding and Improving Structure, Stability, and Activity 287
Iwona A. Rutkowska, Sylwia Zoladek, and Pawel J. Kulesza
9.1 Introduction 287
9.2 Carbon Black Supports 288
9.3 Decoration and Modification with Metal Oxide Nanostructures 289
9.4 Carbon Nanotube as Carriers 291
9.5 Doping, Modification, and Other Carbon Supports 293
9.6 Graphene as Catalytic Component 293
9.7 Metal Oxide-containing ORR Catalysts 296
9.8 Photodeposition of Pt on Various Oxide-Carbon Composites 299
9.9 Other Supports 301
9.10 Alkaline Medium 302
9.11 Toward More Complex Hybrid Systems 303
9.12 Stabilization Approaches 306
9.13 Conclusions and Perspectives 307
Acknowledgment 308
Acronyms 308
References 308
Part IV Physical-Chemical Characterization 319
10 Understanding the Electrocatalytic Reaction in the Fuel Cell by Tracking the Dynamics of the Catalyst by X-ray Absorption Spectroscopy 321
Ditty Dixon, Aiswarya Bhaskar, and Aswathi Thottungal
10.1 Introduction 321
10.2 A Short Introduction to XAS 323
10.3 Application of XAS in Electrocatalysis 325
10.3.1 Ex Situ Characterization of Electrocatalyst 325
10.3.2 Operando XAS Studies 330
10.4 Δμ XANES Analysis to Track Adsorbate 334
10.5 Time-resolved Operando XAS Measurements in Fuel Cells 338
10.6 Fourth-generation Synchrotron Facilities and Advanced Characterization Techniques 340
10.6.1 Total-reflection Fluorescence X-ray Absorption Spectroscopy 341
10.6.2 Resonant X-ray Emission Spectroscopy (RXES) 341
10.6.3 Combined XRD and XAS 342
10.7 Conclusions 342
Acronyms 343
References 344
Part V Modeling 349
11 Unraveling Local Electrocatalytic Conditions with Theory and Computation 351
Jun Huang, Mohammad J. Eslamibidgoli, and Michael H. Eikerling
11.1 Local Reaction Conditions: Why Bother? 351
11.2 From Electrochemical Cells to Interfaces: Basic Concepts 352
11.3 Characteristics of Electrocatalytic Interfaces 355
11.4 Multifaceted Effects of Surface Charging on the Local Reaction Conditions 356
11.5 The Challenges in Modeling Electrified Interfaces using First-principles Methods 358
11.5.1 Computational Hydrogen Electrode 359
11.5.2 Unit-cell Extrapolation, Explicit Solvated Protons, and Excess Electrons 360
11.5.3 Counter Charge and Reference Electrode 361
11.5.4 Effective Screening Medium and mPB Theory 361
11.5.5 Grand-canonical DFT 362
11.6 A Concerted Theoretical-Computational Framework 362
11.7 Case Study: Oxygen Reduction at Pt(111) 364
11.8 Outlook 367
Acronyms 367
Symbols 368
References 368
Part VI Protocols 375
12 Quantifying the Activity of Electrocatalysts 377
Karla Vega-Granados and Nicolas Alonso-Vante
12.1 Introduction: Toward a Systematic Protocol for Activity Measurements 377
12.2 Materials Consideration 378
12.2.1 PGM Group 378
12.2.2 Low PGM and PGM-free Approaches 379
12.2.3 Impact of Support Effects on Catalytic Sites 381
12.3 Electrochemical Cell Considerations 382
12.3.1 Cell Configuration and Material 382
12.3.2 Electrolyte 385
12.3.2.1 Purity 385
12.3.2.2 Protons vs. Hydroxide Ions 386
12.3.2.3 Influence of Counterions 388
12.3.3 Electrode Potential Measurements 388
12.3.4 Preparation of Electrodes 391
12.3.5 Well-defined and Nanoparticulated Objects 395
12.4 Parameters Diagnostic of Electrochemical Performance 396
12.4.1 Surface Area 396
12.4.2 Hydrogen Underpotential Deposition Integration 397
12.4.2.1 Surface Oxide Reduction 398
12.4.2.2 CO Monolayer Oxidation (CO Stripping) 400
12.4.2.3 Underpotential Deposition of Metals 401
12.4.2.4 Double-layer Capacitance 402
12.4.3 Electrocatalysts Site Density 402
12.4.4 Data Evaluation (Half-Cell Reactions) 404
12.4.5 The E 1/2 and E (j Pt (5%)) Parameters 405
12.5 Stability Tests 407
12.6 Data Evaluation (Auxiliary Techniques) 409
12.6.1 Surface Atoms vs. Bulk 410
12.7 Conclusions 411
Acknowledgments 412
Acronyms 412
Symbols 413
References 414
13 Durability of Fuel Cell Electrocatalysts and Methods for Performance Assessment 429
Bianca M. Ceballos and Piotr Zelenay
13.1 Introduction 429
13.2 Fuel Cell PGM-free Electrocatalysts for Low-temperature Applications 431
13.3 PGM-free Electrocatalyst Degradation Pathways 432
13.3.1 Demetallation 432
13.3.2 Carbon Oxidation 436
13.3.3 Micropore Flooding 439
13.3.4 Nitrogen Protonation and Anionic Adsorption 439
13.4 PGM-free Electrocatalyst Durability and Metrics 440
13.4.1 Performance and Durability Evaluation in Air-supplied Fuel Cell Cathode 440
13.4.2 Assessment of Carbon Corrosion in Nitrogen-purged Cathode 443
13.4.3 Determination of Performance Loss upon Cycling Cathode Catalyst in Nitrogen 443
13.4.4 Recommendations for ORR Electrocatalyst Evaluation in RRDE in O 2 and in an Inert Gas 446
13.4.5 Electrocatalyst Corrosion 447
13.5 Low-PGM Catalyst Degradation 447
13.5.1 Pt Dissolution 449
13.5.2 Carbon Support Corrosion 452
13.5.3 Pt Catalyst MEA Activity Assessment and Durability 454
13.5.4 PGM Electrocatalyst MEA Conditioning in H 2 /Air 454
13.5.5 Accelerated Stress Test of PGM Electrocatalyst Durability 456
13.6 Conclusion 457
Acronyms 459
References 460
Part VII Systems 471
14 Modeling of Polymer Electrolyte Membrane Fuel Cells 473
Andrea Baricci, Andrea Casalegno, Dario Maggiolo, Federico Moro, Matteo Zago, and Massimo Guarnieri
14.1 Introduction 473
14.2 General Equations for PEMFC Models 474
14.2.1 Analytical and Numerical Modeling 474
14.2.2 Reversible Electromotive Force 476
14.2.3 Fuel Cell Voltage 477
14.2.4 Activation Overpotential 478
14.2.5 Ohmic Overpotential - PEM Model 479
14.2.6 Concentration Overpotential 480
14.2.7 Examples of Fuel Cell Modeling 482
14.3 Multiphase Water Transport Model for PEMFCs 483
14.4 Fluid Mechanics in PEMFC Porous Media: From 3D Simulations to 1D Models 488
14.4.1 From Micro- to Macroscopic Models 490
14.4.2 Porous Medium Anisotropy 491
14.4.3 Fluid-Fluid Viscous Drag 492
14.4.4 Surface Tension and Capillary Pressure 492
14.5 Physical-based Modeling for Electrochemical Impedance Spectroscopy 496
14.5.1 Experimental Measurement and Modeling Approaches 496
14.5.2 Physical-based Modeling 497
14.5.2.1 Current Relaxation 497
14.5.2.2 Laplace Transform 498
14.5.3 Typical Impedance Features of PEMFC 498
14.5.4 Application of EIS Modeling to PEMFC Diagnostic 500
14.5.5 Approximations of 1D Approach 501
14.6 Conclusions and Perspectives 502
Acronyms 503
Symbols 504
References 507
15 Physics-based Modeling of Polymer Electrolyte Membrane Fuel Cells: From Cell to Automotive Systems 511
Andrea Baricci, Matteo Zago, Simone Buso, Marco Sorrentino, and Andrea Casalegno
15.1 Polymer Fuel Cell Model for Stack Simulation 511
15.1.1 General Characteristics of a Fuel Cell System for Automotive Applications 511
15.1.2 Analysis of the Channel Geometry for Stack Performance Modeling 514
15.1.3 Analysis of the Air and Hydrogen Utilization for Stack Performance Modeling 516
15.1.4 Introduction to Transient Stack Models 518
15.2 Auxiliary Subsystems Modeling 519
15.2.1 Air Management Subsystem 519
15.2.2 Hydrogen Management Subsystem 521
15.2.3 Thermal Management Subsystem 522
15.2.4 PEMFC System Simulation 522
15.3 Electronic Power Converters for Fuel Cell-powered Vehicles 525
15.3.1 Power Converter Architecture 527
15.3.2 Load Adaptability 527
15.3.3 Power Electronic System Components 528
15.3.3.1 Port Interface Converters 530
15.3.3.2 The PEMFC Interface Converter 530
15.3.3.3 The Motor Interface Converter 530
15.3.3.4 The Energy Storage Interface 531
15.3.3.5 Supervisory Control 531
15.4 Fuel Cell Powertrains for Mobility Use 532
15.4.1 Transport Application Scenarios 532
15.4.2 Tools for the Codesign of Transport Fuel Cell Systems and Energy Management Strategies 534
15.4.2.1 Automotive Case Study: Optimal Codesign of an LDV FCHV Powertrain 535
Acronyms 540
Symbols 541
References 541
Index 545
