Title Page
Abstract
Contents
Chapter 1. Introduction 15
1.1. Photocatalytic Hydrogen Evolution Reaction 15
1.2. Graphene Quantum Dots 25
1.3. Purpose of Research 28
Bibliography 32
Chapter 2. Ethylenediamine functionalized graphene quantum dots as alkaline HER photocatalyst 36
2.1. Introduction 36
2.2. Experimental details 42
2.2.1. Chemical used 42
2.2.2. Synthesis of graphene oxide 42
2.2.3. Synthesis of GQD 43
2.2.4. Synthesis of GQD-EDA 44
2.2.5. Characterizations of the material 44
2.2.6. Photocatalytic HER measurements 46
2.2.7. Electrochemical measurements 46
2.3. Results and discussion 47
2.3.1. Structural analysis of the catalyst 47
2.3.2. Photocatalytic HER Activity and Mechanism 54
2.3.3. Electrochemical Measurements 61
2.3.4. Fluorescence Lifetime Measurement 63
2.3.5. Effect of Amine Sources with Different Chain Lengths on HER Performance of Functionalized GQD 64
2.4. Conclusion 65
Bibliography 67
Chapter 3. Amphiphilic graphene quantum dots as HER photocatalyst via encapsulation of TADF photosensitizer 71
3.1. Introduction 71
3.2. Experimental details 76
3.2.1. Chemical used 76
3.2.2. Synthesis of GO 76
3.2.3. Synthesis of GQD 77
3.2.4. Synthesis of GQD-HA 78
3.2.5. Synthesis of NAPTPA-2Br 78
3.2.6. Characterizations of the material 81
3.2.7. Photocatalytic HER experiments 82
3.2.8. Photoelectrochemical measurements 83
3.3. Results and discussion 83
3.3.1. Characterizations of GQD-HA 83
3.3.2. Structural analysis of the photocatalytic system 94
3.3.3. Photocatalytic HER performance 97
3.3.4. Electrochemical & photoelectrochemical measurements 100
3.4. Conclusion 106
Bibliography 109
Chapter 4. Dye-sensitized amphiphilic graphene quantum dots for visible-light-driven photocatalytic HER in seawater 114
4.1. Introduction 114
4.2. Experimental details 119
4.2.1. Chemicals used 119
4.2.2. Synthesis of graphene oxide (GO) 120
4.2.3. Characterization of the materials 126
4.2.4. Photocatalytic HER experiments 127
4.2.5. Electrochemical & photoelectrochemical measurements 128
4.3. Results & discussion 129
4.3.1. Characterization of the materials 129
4.3.2. Structural characterization of HER system 137
4.3.3. Photocatalytic HER performance 142
4.3.4. Electrochemical measurements 145
4.4. Conclusion 148
Bibliography 150
List of Publications 154
List of Presentations 155
List of Patents 156
초록 157
Table 1-1. HER mechanism under acid and alkaline condition. 19
Table 1-2. OER mechanism under acid and alkaline condition. 19
Table 1-3. The composition of standard seawater with salinity = 35 g/kg. 24
Figure 1-1. Scheme of photocatalytic overall water splitting system 17
Figure 1-2. Scheme of dye-sensitized HER system 23
Figure 1-3. Properties of graphene 26
Figure 1-4. Synthetic strategies for GQD. 28
Figure 1-5. An overview of chapter 1. 29
Figure 1-6. An overview of chapter 2. 30
Figure 1-7. An overview of chapter 3. 31
Figure 2-1. TEM image of our (a) synthesized GO and (b), (c) synthesized GQD 48
Figure 2-2. TEM images of GQD -EDA. (a) TEM image along with particle size distribution (inset) and (b) HRTEM image with lattice fringes. 49
Figure 2-3. Comparison of FTIR spectra of GQD and GQD-5EDA. 50
Figure 2-4. (a) Comparison of FTIR spectra of GQD and GQD-5EDA. (b) Comparison of low-resolution XPS spectra of GQD and GQD-5EDA. High-... 51
Figure 2-5. Calculated the weight percentage of attached EDA 53
Figure 2-6. (a) Raman spectrum of GO, bare GQD and GQD-5EDA. (b) XRD spectrum of GQD and GQD-5EDA. 54
Figure 2-7. (a) Photocatalytic HER efficie ncy of GQD-EDA at pH = 10 with different wt% of EDA after 10 h of irradiation; (b) comparison of hydrogen... 55
Figure 2-8. Change in FTIR spectrum of GQD-5EDA after 10 h of HER experiment 57
Figure 2-9. (a) low resolution XPS spectrum and (b) deconvoluted C1s spectrum of GQD-5EDA after 10 h of HER experiment under alkaline condition[이미지참조] 57
Figure 2-10. Image of water contact angles on (a) bare GQD film, (b) GQD-1EDA (5.9 wt%), (c) GQD-3EDA (11.5 wt%), (d) GQD-5EDA (16.2 wt%),... 60
Figure 2-11. Water contact angle dependent on weight percentage of EDA 60
Figure 2-12. (a) LSV curves of GQD and GQD-5EDA. (b) Tafel curves of GQD and GQD-5EDA. 62
Figure 2-13. Nyquist plots of GQD and GQD-5EDA at -0.4 V (a) in 0.1 M KPF6 aqueous solution and (b) in 0.1 M KOH aqueous solution.[이미지참조] 63
Figure 2-14. Comparison of fluorescence lifetimes between GQD and GQD-5EDA (a) under neutral conditions and (b) under alkaline conditions. 64
Figure 2-15. Photocatalytic HER performances of GQD-5EDA, GQD-BDA, and GQD-HAD after 10 h of irradiation. 65
Figure 3-1. TEM image of (a) synthesized GO and (b), (c) synthesized GQD. 84
Figure 3-2. TEM images of GQD-HA. (a) HR-TEM image with the crystal lattice and (b) TEM image with particle diameter distribution (inset). 85
Figure 3-3. FTIR spectra of GQD and GQD-HA 86
Figure 3-4. (a) Low-resolution XPS spectra of GQD and GQD-HA. High-resolution deconvoluted C1s XPS spectra of (b) GQD, (c) GQD-HA and (d)...[이미지참조] 88
Figure 3-5. Calculated weight percentage of attached HA 90
Figure 3-6. Raman spectrum of GO, bare GQD and GQD-HA 91
Figure 3-7. XRD spectra of GQD and GQD-HA 92
Figure 3-8. Image of water contact angles on (a) bare GQD film, (b) GQD-HA (3.1 wt%), (c) GQD-HA (5.0 wt%), (d) GQD-HA (6.8 wt%) and (e)... 93
Figure 3-9. Water contact angle dependent on weight percentage of HA 93
Figure 3-10. Size distribution of NAPTPA-2Br with GQD and GQD-HA 95
Figure 3-11. TEM images of NAPTPA-2Br (a) without GQD-HA and (b), (c) with GQD-HA on lacey carbon grid 96
Figure 3-12. SEM image of GQD-HA/ NAPTPA-2Br 96
Figure 3-13. (a) Comparison of HER performance between GQD/NAPTPA-2Br and GQD-HA/NAPTPA-2Br, (b) photocatalytic HER performance of the... 100
Figure 3-14. (a) LSV curves of GQD and GQD-HA. Mott-Sc hottky plots s of (b) GQD and (c) GQD-HA. (d) Nyquist plots of GQD and GQD-HA. (e) C-... 102
Figure 3-15. Change in photoluminescence of NAPTPA-2Br after addition of GQD-HA. 104
Figure 3-16. Change in photoluminescence of NAPTPA-2Br after gradual addition of TEA. 104
Figure 3-17. (a) Nyquist plots of GQD/NAPTPA-2Br and GQD-HA/NAPTPA-2Br nanoparticles. (b) Transient photocurrent response at... 106
Figure 4-1. TEM image of as-synthesized GO 130
Figure 4-2. TEM image of as-synthesized GQD 130
Figure 4-3. (a) High-resolution TEM image of GQD-HA. (b) TEM image with diameter distribution (inset) 131
Figure 4-4. FT-IR spectra of GQD and GQD-HA 132
Figure 4-5. (a) Low-resolution XPS spectra of GQD and GQD-HA. Deconvoluted C1s XPS spectrum of bare GQD. Deconvoluted (c) C1s and (d)...[이미지참조] 135
Figure 4-6. Raman spectrum of GO, bare GQD and GQD-HA 136
Figure 4-7. XRD spectra of GQD and GQD-HA 137
Figure 4-8. Size distribution data (a) before and (b) after 2 hours of visible light irradiation. 139
Figure 4-9. TEM image of TPATCS (a) without GQD-HA and (b) with GQD-HA before irradiation. (c) HRTEM image of TPA TCS with GQD-HA before... 140
Figure 4-10. Absorption spectra of TPATCS with GQD-HA (black line) and without GQD-HA (red line). 141
Figure 4-11. Photoluminescence spectra of TPATCS with GQD-HA (black line) and without GQD-HA (red line). 142
Figure 4-12. HER performance of TPATCS with GQD-HA (black line) and without GQD-HA (red line) (a) in pure water and (b) in simulated seawater.... 145
Figure 4-13. Mott-Schottky plots of (a) bare GQD and (b) GQD-HA 146
Figure 4-14. (a) LSV curve of GQD and GQD-HA. (b) Nyquist plots of GQD and GQD-HA. (c) C-V curve of TPATCS. (d) Electronic band structure of... 148
Scheme 3-1. Synthesis of NAPTPA-2Br 79
Scheme 4-1. Synthetic route of TPATCS 123