표제지

목차

약기호표 10

국문요약 11

1. 서론 12

1.1. 연구 배경 12

1.2. 연구 동향 21

1.3. 연구 목적 24

2. 실험 방법 25

2.1. 고내구 전극 코팅 장비 제작 25

2.2. 촉매 슬러리 및 PDMS 용액 준비 29

2.3. 막-전극 접합체 제작 29

2.4. 특성 분석 30

2.5. 전기화학 성능 분석 및 내구 평가 32

2.5.1. 전기화학 평가 조건 32

2.5.2. 담지체 내구 평가 조건 32

3. 실험 결과 및 고찰 36

3.1. 고내구 전극 코팅 36

3.2. PDMS 로딩양 최적화 39

3.2.1. 촉매 및 막-전극 접합체 특성 분석 39

3.2.2. 전기화학 분석 및 담지체 내구 평가 47

3.3. 고결정성 탄소 담지체 촉매 코팅 66

3.3.1. 고결정성 촉매 및 막-전극 접합체 특성 분석 66

3.3.2. 전기화학 분석 및 내구 평가 70

4. 결론 82

참고문헌 84

Abstract 90

Table 3-1. Atomic percentages of C and Si using SEM and EDX mapping cross-sectional images. 45

Table 3-2. Porosity values for cathodes with experimental porosimeter measurement and theoretical calculation. 46

Table 3-3. Summary of proton transport resistance value for 100% RH and 50% RH of Reference and PDMS coated MEAs with PDMS loading of 0.05, 0.1, and 0.2 mg PDMS/cm² . 61

Table 3-4. Summary of solubility, diffusivity and permeability parameters of oxygen gas in PDMS and Nafion ionomer. 62

Table 3-5. Rate of increase in porosity from initial theoretical value after carbon degradation protocol. 63

Table 3-6. Summary of R Ohm and R LF-HF of all MEAs before and after carbon degradation protocol from EIS spectra in Figure 3-9. 64

Table 3-7. Summary of peak power density and ECSA values for all MEAs before and after carbon degradation protocol (3k and 6k cycles). 65

Table 3-8. Summary of peak power density and ECSA values for all MEAs before and after SU/SD protocol. 80

Table 3-9. Summary of peak power density and ECSA values for all MEAs before and after FS protocol. 81

Figure 1-1. Schematic illustration of single cell composition and principle of PEMFCs. 15

Figure 1-2. Price trends for fuel cell stacks. 16

Figure 1-3. U.S. Department of Energy's heavy-duty fuel cell cost targets. 17

Figure 1-4. Potential changes by reaction during SU/SD protocol. 18

Figure 1-5. Potential distribution during SU/SD condition. 19

Figure 1-6. Potential changes over time under FS condition. 20

Figure 2-1. Developed parallel 2-nozzle spray system set-up. 26

Figure 2-2. 3-D modeling image of a jig for mounting to parallel 2-nozzle spray system. 27

Figure 2-3. Schematics of (a) the travel path of a serpentine pattern and (b) flattening through a center shift of △w (0.5 mm). 28

Figure 2-4. Schematic of the U.S. Department of Energy's carbon degradation protocol. 34

Figure 2-5. Schematic of a self-designed tube for SU/SD durability test. 35

Figure 3-1. Schematic of experimental set-up for a laboratory-made two-nozzle spray system and MEA with the PDMS-coated electrode. 37

Figure 3-2. Photographs of the (a) catalyst slurry, (b) suspension that mixed catalyst slurry with PDMS based on n-Hexane, and (c) PDMS solution based on n-Hexane. 38

Figure 3-3. (a-c) The TEM images of PDMS coated Pt/C catalyst layer at various loadings: 0.05, 0.1, and 0.2 mg PDMS/cm² and (d-f) Corresponding EDX mapping images of Si. 41

Figure 3-4. (a) XPS wide spectra and (b) Si 2p spectra of Reference and PDMS coated electrodes. (c-f) Contact angles for (c) Reference, PDMS loading (d) 0.05, (e) 0.1, and (f) 0.2 mg PDMS/cm²... 42

Figure 3-5. (a-d) Cross-sectional SEM images and corresponding EDX-mapping images of Si for cathodes of MEAs: (a) Reference and PDMS loading of (b) 0.05, (c) 0.1, and (d) 0.2 mg PDMS/cm², respectively. 43

Figure 3-6. (a) Pore volume and (b) cumulative pore volume distribution of electrodes through mercury intrusion porosimetry measurement. 44

Figure 3-7. (a-b) Schematics of the cross-sectional 2-dimensional Pt/C particle with (a) Nafion ionomer and (b) Pt/C particles with Nafion ionomer and PDMS. (c) Comparison of oxygen transport capacity for... 52

Figure 3-8. EIS spectra in H₂/N₂ conditions for (a-d) 100% RH and (e-h) 50% RH of (a, e) Reference and PDMS coated MEAs with PDMS loading of (b, f) 0.05, (c, g) 0.1, and (d, h) 0.2 mgPDMS/cm², respectively.[이미지참조] 53

Figure 3-9. (a-c) Performance curves before and after carbon degradation protocol (3k and 6k cycles) for MEAs, and (d-f) Corresponding EIS spectra at 0.6V. 54

Figure 3-10. Corresponding enlargements of ohmic resistance part of Figure 3-9 for (a) Initial, (b) after carbon degradation protocol 3k cycles, and (c) 6k cycles, respectively. 55

Figure 3-11. HFR spectra for all the MEAs at a fully humidified condition. 56

Figure 3-12. CV measurements before and after carbon degradation protocol (3k and 6k cycles) of MEAs with (a) Reference, (b) PDMS 0.05, (c) PDMS 0.1, and (d) PDMS 0.2 mgPDMS/cm².[이미지참조] 57

Figure 3-13. (a-d) Cross-sectional SEM images of cathodes and (e-h) TEM images of Pt/C catalyst after carbon degradation protocol 6k cycles of MEAs; (a, e) Reference and PDMS loading of (b, f) 0.05, (c,... 58

Figure 3-14. Schematic illustration of carbon corrosion phenomenon for PDMS coated and conventional electrode. 59

Figure 3-15. (a) Performance curve and (b) EIS spectra at 0.6V at low relative humidity (50% RH) with flow rate (H₂/Air＝150/800 ml/min). 60

Figure 3-16. (a) XPS wide spectra of Vulcan XC-72 and LaC, deconvolution analysis of (b) LaC and (c) Vulcan XC-72 C 1s peak. (d) Raman spectra and (e) XRD pattern of Vulcan XC-72 and LaC. (f) TEM... 68

Figure 3-17. TEM images of Pt/LaC (a) w/o and (b) w/ PDMS, and (c) Corresponding EDX mapping images of C, Pt, and Si. (d) XPS wide spectra and (e) Si 2p spectra of Pt/LaC and Pt/LaC with PDMS. 69

Figure 3-18. Schematic of carbon deterioration mechanisms during (a) SU/SD and (b) FS protocol. 73

Figure 3-19. (a) Flowchart of SU/SD protocol with corresponding electrode markings. (yellow dashed line) Performance curves of (b) Initial, after SU/SD (c) 5 cycles and (d) 10 cycles, respectively. 74

Figure 3-20. EIS spectra at 0.8V and 0.6V of (a, d) initial, after SU/SD (b, e) 5 cycles and (c, f) 10 cycles, respectively. 75

Figure 3-21. CV measurements before and after SU/SD 10 cycles of (a) Pt/C, (b) Pt/C+PDMS 0.1, (c) Pt/LaC, and (d) Pt/LaC+PDMS 0.1 at cathode. 76

Figure 3-22. SEM cross-sectional images of cathode electrode (a-d) before and (e-h) after SU/SD protocol of (a, e) Pt/C, (b, f) Pt/C+PDMS 0.1, (c, g) Pt/LaC, and (d, h) Pt/LaC+PDMS 0.1, respectively. 77

Figure 3-23. (a) Flowchart of FS protocol with corresponding electrode markings. (red dashed line) (b) Behaviors of cell potential under FS protocol. (c) Performance curves of initial and after FS protocol,... 78

Figure 3-24. CV measurements at electrode before and after FS protocol of (a) Pt/C and (b) Pt/LaC+PDMS 0.1. 79