Polymer electrolyte membrane degradation and mobility in fuel cells [Elektronische Ressource] : a solid-state NMR investigation / vorgelegt von Lida Ghassemzadeh Khoshkroodi
153 pages

Polymer electrolyte membrane degradation and mobility in fuel cells [Elektronische Ressource] : a solid-state NMR investigation / vorgelegt von Lida Ghassemzadeh Khoshkroodi

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Publié par
Publié le 01 janvier 2010
Nombre de lectures 27
Poids de l'ouvrage 10 Mo

Extrait




Polymer Electrolyte Membrane Degradation and
Mobility in Fuel Cells:
a Solid-state NMR Investigation




Von der Fakultät für Chemie der Universität Stuttgart
zur Erlangung der Würde eines
Doktors der Naturwissenschaften (Dr. rer. nat.)
genehmigte Abhandlung





Vorgelegt von
Lida Ghassemzadeh Khoshkroodi
aus Teheran, Iran






Hauptberichter: Prof. Dr. K. Müller
Mitberichter: Prof. Dr. J. Maier
Mitprüfer: Prof. Dr. E. Roduner
Tag der Einreichung: 19.05.2010
Tag der mündlichen Prüfung: 15.07.2010



Max-Planck-Institut für Festkörperforschung Stuttgart
und Institut für Physikalische Chemie der Universität Stuttgart
2010

Contents

CONTENTS ...........................................................................................................................3
ABBREVIATIONS AND SYMBOLS ..................................................................................7
1. INTRODUCTION....................................................................................................13
2. INTRODUCTION TO POLYMER ELECTROLYTE MEMBRANES..................15
2.1. PEM FUEL CELLS.................................................................................................................. 15
2.2. PEM FUEL CELL COMPONENTS............................................................................................. 18
2.3. NAFION MEMBRANE ............................................................................................................. 18
2.3.1. SYNTHESIS OF NAFION..................................................................................................... 19
2.3.2. NAFION MORPHOLOGY..................................................................................................... 20
2.3.3. WATER CONTENT AND CONDUCTIVITY............................................................................ 22
2.4. LIMITATIONS OF NAFION AS A FUEL CELL MEMBRANE........................................................ 23
2.4.1. LOW TEMPERATURE OPERATION PROBLEMS.................................................................... 23
2.4.2. DURABILITY AND DEGRADATION ISSUE........................................................................... 24
2.5. NAFION ALTERNATIVES........................................................................................................ 27
2.5.1. SHORT SIDE CHAIN PERFLUOROSULFONIC ACID IONOMERS............................................. 28
2.5.2. NAFION/OXIDE COMPOSITE MEMBRANES........................................................................ 28
2.6. OPEN QUESTIONS AND MISSING INVESTIGATIONS................................................................ 30
2.7. WHY TO CHOOSE SOLID-STATE NMR SPECTROSCOPY?....................................................... 31
2.8. LITERATURE REVIEW ON NMR STUDIES OF NAFION ........................................................... 32
1 22.8.1. H & H NMR .................................................................................................................. 32
192.8.2. F NMR........................................................................................................................... 33
2.8.3. OTHER NMR TECHNIQUES............................................................................................... 34
2.8.4. NMR STUDIES ON DEGRADED NAFION ............................................................................ 35
2.8.5. NMR STUDIES ON NAFION/OXIDE COMPOSITE MEMBRANES........................................... 36
3. BASICS OF NMR SPECTROSCOPY ....................................................................37
3.1. INTERACTION WITH EXTERNAL MAGNETIC FIELDS .............................................................. 37
3.2. INTERNAL INTERACTIONS..................................................................................................... 40
3.2.1. CHEMICAL SHIELDING...................................................................................................... 42

3.2.2. THE DIPOLAR INTERACTION............................................................................................. 45
3.3. SINGLE-PULSE EXCITATION.................................................................................................. 46
3.4. METHODS FOR IMPROVING RESOLUTION ............................................................................. 46
3.4.1. MAGIC ANGLE SPINNING (MAS)...................................................................................... 47
3.4.2. CROSS POLARIZATION (CP)............................................................................................. 49
3.4.3. DECOUPLING.................................................................................................................... 52
3.5. NUCLEAR SPIN RELAXATION................................................................................................ 54
3.5.1. INVERSION RECOVERY: MEASUREMENT OF T ................................................................. 57 1
3.5.2. SPIN LOCKING: MEASUREMENT OF T ............................................................................. 58 1 Ρ
4. FUEL CELL DEGRADATION TESTS ..................................................................61
4.1. INTRODUCTION..................................................................................................................... 61
4.2. EXPERIMENTAL .................................................................................................................... 61
4.2.1. MATERIALS...................................................................................................................... 61
4.2.2. MEMBRANE PRE-CONDITIONING...................................................................................... 61
4.2.3. FUEL CELL TESTS ............................................................................................................. 62
4.2.4. NMR SPECTROSCOPY ...................................................................................................... 63
4.3. RESULTS ............................................................................................................................... 63
4.4. DISCUSSION.......................................................................................................................... 68
4.5. CONCLUSIONS ...................................................................................................................... 69
5. EX-SITU DEGRADATION UNDER MIMIC FUEL CELL CONDITIONS.........71
5.1. INTRODUCTION..................................................................................................................... 71
5.2. EXPERIMENTAL .................................................................................................................... 71
5.2.1. MATERIALS AND SAMPLE PREPARATION ......................................................................... 71
5.2.2. NMR SPECTROSCOPY ...................................................................................................... 75
5.2.3. EQUIVALENT WEIGHT (EW)............................................................................................. 76
5.3. RESULTS ............................................................................................................................... 76
5.4. DISCUSSION.......................................................................................................................... 85
5.5. CONCLUSION ........................................................................................................................ 93
6. FENTON DEGRADATION TESTS.......................................................................95
6.1. INTRODUCTION..................................................................................................................... 95
6.2. EXPERIMENTAL .................................................................................................................... 96
6.2.1. SAMPLE PREPARATION AND FENTON TEST ...................................................................... 96
6.2.2. NMR SPECTROSCOPY ...................................................................................................... 98
6.2.3. ATR-FTIR SPECTROSCOPY ............................................................................................. 99
6.3. RESULTS ............................................................................................................................... 99

6.4. DISCUSSION........................................................................................................................ 107
6.5. CONCLUSIONS .................................................................................................................... 109
7. DYNAMICS IN COMPOSITE MEMBRANES....................................................111
7.1. INTRODUCTION................................................................................................................... 111
7.2. EXPERIMENTAL .................................................................................................................. 111
7.2.1. SAMPLE PREPARATION................................................................................................... 111
7.2.2. NMR SPECTRO

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