Title Page
요약
ABSTRACT
Contents
1. Introduction 15
2. Theoretical background 18
2.1. Polymer electrolyte membrane fuel cells (PEMFCs) 18
2.2. Carbon corrosion 19
3. Experimental 20
3.1. Synthesis of electrocatalyst 20
3.1.1. preparation of Nb-doped TiO₂ and carbon nanotube hybrid support 20
3.1.2. Preparation of Pt electrocatalyst with as-prepared supports 22
3.2. Physical characterization 23
3.3. Electrochemical analysis 24
3.3.1. Half-cell tests 24
3.3.2. Single-cell tests 26
4. Results and discussion 27
4.1. Materials characterization 27
4.2. Electrochemical performence of catalysts 38
4.3. MEA performance and durability test 44
5. Conclusions 49
6. References 50
Figure 4.1.1. TEM images of (a) NbTO@CNT-N400, (b) Pt/ Nb TO@CNT-N400, (c) NbTO@CNT (d) Pt/ NbTO@CNT-N800, (e) NbTO@CNT-H800,... 28
Figure 4.1.2. (a) Thermogravimetric analysis of f-CNT, NbTO, and NbTO@CNT recorded in air from 50 ℃ to 950 ℃. The inset is enlarged... 29
Figure 4.1.3. (a) XRD patterns of NbTO@CNT with different Nb doping level and (b) a narrow range of 24° to 30°. (c) XRD... 32
Figure 4.1.4. XPS survey spectra of Ti 2p of NbTO@CNT (a) N400, (c) N800, and (e) H800 and Nb 3d of (b) N400, (d) N800,... 34
Figure 4.1.5. XPS survey spectra of Pt 4f (a) Pt/C and (b) Pt/NbTO@CNT-H800. 35
Figure 4.1.6. (a) Absorbance vs. wavelength, and (b) calculation of energy band gap of NbTO@CNT-H800 and TO@CNT-H800 using... 37
Figure 4.2.1. Electrocatalyst performance before and after ADT. CV curves of (a) Pt/NbTO@CNT-N400, (b) Pt/NbTO@CNT-... 41
Figure 4.2.2. Electrocatalyst performance before and after ADT. LSV curves of (a) Pt/NbTO@CNT-N400, (b) Pt/NbTO@CNT-... 42
Figure 4.2.3. Electrocatalyst performance of Pt/NbTO@CNT with different Nb doping level. (a) CV and (b) LSV curves.... 43
Figure 4.3.1. Polarization curves of Pt/NbTO@CNT with different ionomer content (5, 10, 20, and 30 wt%). 46
Figure 4.3.2. Single-cell performance before and after AST. I-V polarization curves of (a) Pt/NbTO@CNT and (b) Pt/C. (C) H₂/O₂... 47
Figure 4.3.3. Before and after ADT of single cell performance. CV curves of (a) Pt/NbTO@CNT and (b) Pt/C. Nyquist plot of (c)... 48