| Preface | 6 |
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| Contents | 8 |
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| List of Contributors, MAE 49 | 15 |
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| Modern Aspects of Electrochemistry | 18 |
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| 1 Durability of PEM Fuel Cell Membranes | 19 |
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| 1 Summary | 19 |
| 2 Review of PEM Fuel Cell Degradation Phenomena and Mechanisms | 20 |
| 3 Membrane Degradation | 24 |
| 3.1. Stress in Membrane and MEAs | 25 |
| 3.2. Mechanical Characterization of Membranes | 29 |
| 3.3. Chemical Degradation Processes | 33 |
| 3.4. Mechanical Degradation Processes | 36 |
| 3.5. Interactions of Chemical and Mechanical Degradation | 44 |
| 4 Accelerated Testing and Life Prediction | 49 |
| 4.1. Accelerated Degradation Testing and Degradation Metrics | 49 |
| 4.2. Progressive Degradation Model of Combined Effects | 53 |
| 5 Mitigation | 57 |
| Acknowledgments | 60 |
| References | 60 |
| 2 Modeling of Membrane-Electrode-Assembly Degradation in Proton-Exchange-Membrane Fuel Cells -- Local H2 Starvation and Start--Stop Induced Carbon-Support Corrosion | 63 |
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| 1 Introduction | 63 |
| 2 Kinetic Model | 67 |
| 2.1. Electrode Kinetics | 67 |
| 2.2. Local H2 Starvation Model | 72 |
| 2.3. Start--Stop Model | 75 |
| 3 Coupled Kinetic and Transport Model | 78 |
| 3.1. Model Description | 78 |
| 3.2. Local H2 Starvation Simulation | 81 |
| 3.3. Start--Stop Simulation | 90 |
| 4 Pseudo-Capacitance Model | 94 |
| 4.1. Mechanism Description | 94 |
| 4.2. Model Description | 96 |
| 4.3. The Pseudo-capacitive Effect | 98 |
| 5 Summary and Outlook | 99 |
| Acknowledgments | 101 |
| List of Symbols | 101 |
| References | 103 |
| 3 Cold Start of Polymer Electrolyte Fuel Cells | 107 |
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| 1 Introduction | 107 |
| 2 Equilibrium Purge Cold Start | 113 |
| 2.1. Equilibrium Purge | 114 |
| 2.2. Isothermal Cold Start | 115 |
| 2.3. Proton Conductivity at Low Temperature | 115 |
| 2.4. Effects of Key Parameters | 118 |
| 2.4.1. Initial Membrane Water Content | 118 |
| 2.4.2. Startup Current Density | 121 |
| 2.4.3. Startup Temperature | 124 |
| 2.5. ORR Kinetics at Low Temperatures | 125 |
| 2.6. Short-Purge Cold Start | 128 |
| 3 Water Removal During Gas Purge | 129 |
| 3.1. Introduction | 130 |
| 3.2. Purge Curve | 132 |
| 3.3. Two Characteristic Parameters for Water Removal | 133 |
| 3.4. Stages of Purge | 135 |
| 3.5. Effect of Key Parameters | 136 |
| 3.5.1. Purge Cell Temperature | 136 |
| 3.5.2. Purge Gas Flow Rate | 139 |
| 3.5.3. Matching Two Parameters | 141 |
| 3.6. HFR Relaxation | 142 |
| 4 Concluding Remarks | 144 |
| References | 145 |
| 4 Species, Temperature, and Current Distribution Mapping in Polymer Electrolyte Membrane Fuel Cells | 147 |
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| 1 Introduction | 147 |
| 2 Species Distribution Mapping | 148 |
| 2.1. Species and Properties of Interest | 148 |
| 2.1.1. Hydrogen | 148 |
| 2.1.2. Oxygen | 148 |
| 2.1.3. Water | 148 |
| 2.1.4. Contaminants and Diluents | 149 |
| 2.1.5. Pressure Drop | 149 |
| 2.1.6. Flow Distribution | 150 |
| 2.2. Methodology and Results | 150 |
| 2.2.1. Pressure Drop Measurement | 150 |
| 2.2.2. Gas Composition Analysis | 151 |
| 2.2.3. Neutron Imaging | 153 |
| 2.2.4. Magnetic Resonance Imaging | 156 |
| 2.2.5. X-ray Imaging | 158 |
| 2.2.6. Optically Transparent Fuel Cells | 159 |
| 2.2.7. Embedded Sensors | 165 |
| 2.2.8. Other Methods | 166 |
| 2.3. Design Implications | 167 |
| 3 Temperature Distribution Mapping | 170 |
| 3.1. Methodology and Results | 171 |
| 3.1.1. IR Transparent Fuel Cells | 171 |
| 3.1.2. Embedded Sensors | 172 |
| 3.2. Design Implications | 173 |
| 4 Current Distribution Mapping | 174 |
| 4.1. Methodology and Results | 174 |
| 4.1.1. Partial MEA | 174 |
| 4.1.2. Segmented Cells | 175 |
| 4.1.3. Other Methods | 181 |
| 4.2. Design Implications | 183 |
| 5 Concluding Remarks | 184 |
| References | 185 |
| 5 High-Resolution Neutron Radiography Analysis of Proton Exchange Membrane Fuel Cells | 193 |
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| 1 Introduction | 193 |
| 2 Neutron Radiography Facility Layout And Detectors | 195 |
| 2.1. Neutron Sources and Radiography Beamlines | 195 |
| 2.2. Neutron Imaging Detectors | 199 |
| 3 Water Metrology with Neutron Radiography | 202 |
| 3.1. Neutron Attenuation Coefficient of Water, µw | 202 |
| 3.2. Sources of Uncertainties in Neutron Radiography | 205 |
| 3.2.1. Counting Statistics | 206 |
| 3.2.2. Beam Hardening | 208 |
| 3.2.3. Background Subtraction | 208 |
| 3.2.4. Changes in the Total Neutron Scattering from Water Absorbed in the Membrane | 209 |
| 3.2.5. Image Spatial Resolution | 210 |
| 4 Recent In Situ High-Resolution Neutron Radiography Experiments of PEMFCs | 213 |
| 4.1. Proof-of-Principle Experiments | 213 |
| 4.2. In Situ, Steady-State Through-Plane Water Content | 214 |
| 4.3. Dynamic Through-Plane Mass Transport Measurements | 215 |
| 5 Conclusions | 216 |
| Acknowledgments | 217 |
| References | 217 |
| 6 Magnetic Resonance Imaging and Tunable Diode Laser Absorption Spectroscopy for In-Situ Water Diagnostics in Polymer Electrolyte Membrane Fuel Cells | 219 |
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| 1 Introduction | 219 |
| 2 Magnetic Resonance Imaging (MRI): As a Diagnostic Tool for In-Situ Visualization of Water Content Distribution in PEMFC s | 220 |
| 2.1. Basic Principle of MRI | 220 |
| 2.2. MRI System Hardware for PEMFC Visualization | 224 |
| 2.3. MRI Signal Calibration for Water Content in PEM | 227 |
| 2.4. In Situ Visualization of Water in PEMFC Using MRI | 227 |
| 3 Tunable Diode Laser Absorption Spectroscopy (TDLAS): As a Diagnostic Tool for In-Situ Detection of Water Vapor Concentration in PEMFC s | 231 |
| 3.1. Basic Principle of TDLAS | 231 |
| 3.2. TDLAS System Hardware for Water Vapor Measurement | 232 |
| 3.3. TDLAS Signal Calibration for Measurement of Water Vapor Concentration | 234 |
| 3.4. In Situ Measurement of Water Vapor in PEMFC Using TDLAS | 237 |
| 4 Summary | 240 |
| References | 240 |
| 7 Characterization of the Capillary Properties of Gas Diffusion Media | 243 |
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| 1 Introduction | 243 |
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