Title Page
Contents
Abstract 11
I. Introduction 13
II. Experimental 19
II-1. Hydrogen permeability measurement using GC 19
II-2. Measurement of fluoride ion concentration 21
II-3. Fenton test 24
II-4. Analysis 25
II-5. Fuel cell operation 26
II-6. Accelerated stress test method of the membrane 28
III. Results and discussion 29
III-1. Ionic conductivity interpretation of the polymer membrane 29
III-1.1. Model 29
III-1.2. Effect of the relative humidity and current density on the water content in the membrane 34
III-1.3. Effect of the water content, relative humidity and current density on the ionic conductivity 38
III-1.4. Effect of Temperature on the water content and ionic conductivity 47
III-2. Chemical degradation by the Fenton test 49
III-3. Performance and durability according to the membrane thickness 57
III-4. Accelerated stress test of the polymer electrolyte membrane 72
III-4.1. Comparison of the accelerated stress test techniques 72
III-4.2. Mechanical durability test 75
III-4.3. Membrane durability test (OCV holding + Humidity cycling) 81
IV. Conclusion 117
V. References 119
초록 126
Table 1. Comparison of the AST protocol with the DOE and NEDO 17
Table 2. Parameter values in the simulation 31
Table 3. Comparison of the AST protocol with the SCNU protocol 74
Table 4. Test values after the SCNU AST protocol 97
Fig. 1. H₂ on-line measurements of the PEMFC cathode outlet using... 19
Fig. 2. Calibration curves of the gas chromatography for the hydrogen... 20
Fig. 3. Fluoride ion calibration using an ISE (Ion Selective... 23
Fig. 4. Schematic diagram of the SCNU AST protocol 28
Fig. 5. Schematic diagram of the transport of protons and water in... 29
Fig. 6. Flow chart of the calculation steps in the developed membrane... 33
Fig. 7. Comparison of the water content in the membrane as a function... 35
Fig. 8. Water content in the membrane as a function of the current density 37
Fig. 9. Comparison of the ionic conductivity as a function of the... 39
Fig. 10. (a) Ionic conductivity and (b) error as a function of the... 42
Fig. 11. Variation of the ion conductivity as a function of the current density 43
Fig. 12. Membrane resistance as a function of the current density at... 45
Fig. 13. Ionic conductivity as a function of the relative humidity 46
Fig. 14. Variation of the ionic conductivity as a function of the temperature 47
Fig. 15. Comparison of the ionic conductivity as a function of the... 48
Fig. 16. FT-IR spectrum results after experiment under various ion... 50
Fig. 17. Comparison of the fluoride ion concentration 51
Fig. 18. Comparison of the hydrogen peak at GC before and after the... 52
Fig. 19. (a) Fluoride emission rate (b) hydrogen permeability as a function... 54
Fig. 20. Crossover hydrogen concentration vs. FER 55
Fig. 21. Lifetime vs. FER 56
Fig. 22. Performance results of the various membrane thickness 62
Fig. 23. (a) OCV (b) current density at 0.6V as a function of the... 64
Fig. 24. (a) High frequency resistance (b) charge transport resistance... 66
Fig. 25. Electrochemical surface area as a function of the membrane thickness 67
Fig. 26. Hydrogen crossover current density as a function of the... 68
Fig. 27. Hydrogen permeability measured gas chromatography as a... 69
Fig. 28. Lifetime vs. membrane thickness 70
Fig. 29. Performance - Lifetime as a function of the membrane thickness 71
Fig. 30. Photograph of the destroyed membrane after humidity... 77
Fig. 31. Photograph of Nafion® 211 MEA after humidity cycling(이미지참조) 79
Fig. 32. SEM image of Nafion® 211 MEA after H₂/Ar humidity cycling at...(이미지참조) 80
Fig. 33. OCV as a function of time during the SCNU AST protocol 83
Fig. 34. Performance results during the SCNU AST protocol 87
Fig. 35. (a) OCV (b) current density at 0.6V as a function of the... 89
Fig. 36. (a) High frequency resistance (b) charge transport resistance... 91
Fig. 37. Hydrogen crossover current density as a function of the... 92
Fig. 38. Hydrogen concentration of the cathode outlet as a function of... 93
Fig. 39. Electrochemical surface area as a function of the accelerated... 94
Fig. 40. Number of moles of fluoride and change in OCV during the... 95
Fig. 41. Hydrogen crossover current density after 5,000hr standard... 96
Fig. 42. TEM images of the catalyst from the Gore™ MEA samples (a)... 100
Fig. 43. TEM images of the catalyst from the Gore™ MEA samples... 101
Fig. 44. FT-IR spectra of degraded membrane during the SCNU AST... 104
Fig. 45. (a) Hydrogen crossover current density (b) hydrogen peak at... 107
Fig. 46. FT-IR spectra of degraded membrane during SCNU AST... 108
Fig. 47. Total FT-IR spectra wavenumbers range from 1,400 to 1,500 cm-1.(이미지참조) 109
Fig. 48. Raman spectroscopy initial and after degradation using the SCNU AST protocol 111
Fig. 49. SEM image of the membrane surface after degradation in the... 114
Fig. 50. SEM image of pin-hole on the membrane surface after... 115
Fig. 51. EDS elemental mapping of C, O, F, S and Pt 116