Title Page
Contents
Abstract 12
1. Introduction 15
2. Research 26
2.1. Synthesis of quantum dot graphene oxide 26
2.1.1. Introduction 26
2.1.2. Experimental 28
2.1.3. Method 29
2.1.4. Results and discussion 30
2.1.5. Conclusions 34
2.2. B-doped reduced graphene oxide. 35
2.2.1. Introduction 35
2.2.2. Experimental 37
2.2.3. Method 38
2.2.4. Results and discussion 40
2.2.5. Conclusions 55
2.3. Co(O)₄(N)-type single-atom-based electrochemical catalyst. 56
2.3.1. Introduction 56
2.3.2. Experimental 58
2.3.3. Method 61
2.3.4. Results and discussion 67
2.3.5. Conclusion 118
3. Conclusions and Perspective 119
4. References 121
Publications 132
Table 1. Characteristics of fuel cells. 18
Table 2. Atomsic amounts of QDG-3 and GO. 32
Table 3. Elemental amounts of graphite oxide, 3D-B-rG-O, 5D-B-rG-O and 7D-B-rG-O determined from XPS measurements. 46
Table 4. Electrocatalytic ORR properties of 3D-B-rG-O, 5D-B-rG-O, and 7D-B-rG-O samples. 53
Table 5. Elemental amounts of GO, NrGO, Co-NrGO-1, and Co-NrGO-2 measured by XPS. 73
Table 6. Co 2p data of Co-NrGO-1, Co-NrGO-2, Co1, and Co2. (△E : Co 2p₃/₂ - Co 2p₁/₂)[이미지참조] 79
Table 7. EXAFS fitting results data of Co foil, CoO, Co₃O₄, Co-NrGO-1, Co1, Co-NrGO-2, and Co2. 83
Table 8. Oxygen reduction reaction catalytic performance data of NrGO, Co-NrGO-1, Co-NrGO-2, and Pt/C measured by RRDE. (HO₂+ yields and... 92
Table 9. Comparison of onset-potentials and electron transfer numbers of Co-NrGO-1, Co-NrGO-2, and previously reported efficient Co-containing ORR electrocatalyst. 93
Table 10. EIS results of NrGO, Co-NrGO-1, Co-NrGO-2, and Pt/C measured by RDE. (EIS was measured at 0.8 V) 95
Table 11. Comparison of the literature data of the TOF, MA, production temperature performance. 98
Table 12. Comparison of HO₂⁻ yield and electron transfer number of Co-NrGO-1, Co-NrGO-2, and previously reported efficient Co-containing ORR electrocatalyst. 99
Table 13. Durability test data of Co-NrGO-1, Co-NrGO-2, and Pt/C. (△ : differences between initial cycle data and 10,000th cycle data).[이미지참조] 102
Table 14. Electrocatalytic ORR properties of Co-NrGO-1, Co-NrGO-2, Co-ReGO-1, and Co-ReGO-2 before and after addition of KCN. (△ : differences...[이미지참조] 110
Table 15. The percentage of occupied states, free energy (*O₂ → *OOH), bond length (*O₂) and overpotential of Co atoms in Co-NrGO-1 and Co-NrGO-2. 113
Figure 1. (a) International energy consumption ratio. (b) Fossil fuel combustion components. (c) Type of renewable energy. (d) Schematic... 15
Figure 2. (a) Summary of fuel-cell types. (b) Components of a single fuel cell. 18
Figure 3. (a) Scheme of this work. TEM images of (a) QDG-1, (b) QDG-3, and (c) QDG-5. 30
Figure 4. (a) Schematic illustration of graphite oxide. (b) SEM and (c) TEM images of graphite oxide. (d) XRD patterns of graphite and graphite oxide. 31
Figure 5. (a) FT-IR spectra of QDG-3 and GO. QDG-3 and GO XPS deconvoluted spectra of (b) C 1s and (c) O 1s. 32
Figure 6. A scheme for the production of B-doped reduced graphene oxide. 41
Figure 7. SEM images of (a) 3D-B-rG-O, (b) 5D-B-rG-O, and (C) 7D-B-rG-O and TEM images of (d) 3D-B-rG-O, (e) 5D-B-rG-O, and (f) 7D-B-rG-O. 43
Figure 8. TEM and elemental mapping images of (a) 3D-B-rG-O, (b) 5D-B-rG-O and (c) 7D-B-rG-O. 45
Figure 9. (a) Raman, (b) deconvoluted XPS C 1s, and (c) deconvoluted XPS O 1s spectra of graphite oxide, 3D-B-rG-O, 5D-B-rG-O and 7D-B-rG-O, and... 48
Figure 10. (a) FT-IR spectra and (b) XRD patterns of graphite oxide, 3D-B-rG-O, 5D-B-rG-O and 7D-B-rG-O. 50
Figure 11. Electrochemical performance of G-O, 3D-B-rG-O, 5D-B-rG-O and 7D-B-rG-O (a) LSV curves and (b) Tafel slopes, (c) EIS measurements of 3D-... 52
Figure 12. SEM images of (a) GO, (b) NrGO, and (c) ReGO and TEM images of (d) GO, (e) NrGO, and (f) ReGO. 67
Figure 13. (a) XRD patterns of graphite, GO, NrGO, and ReGO. (b) FT-IR spectra of GO, NrGO, and ReGO. (c) N₂ adsorption/desorption isotherm plots,... 68
Figure 14. Deconvoluted XPS spectra of GO, NrGO, and ReGO, (a) C 1s and (b) O 1s. Amounts of functional groups calculated from deconvoluted XPS (c)... 69
Figure 15. (a) Scheme for the preparation of Co-NrGO-1 and Co-NrGO-2 this work. SEM images of (b) Co-NrGO-1 and (c) Co-NrGO-2. TEM images of (d)... 70
Figure 16. TEM images of (a) Co-NrGO-1 and (b) Co-NrGO-2. 72
Figure 17. Deconvoluted XPS C 1s spectra of NrGO, Co-NrGO-1, and Co-NrGO-2. 74
Figure 18. TEM (left) and EDX mapping (right) images of Co element of (a) Co-NrGO-1 and (b) Co-NrGO-2. STEM images of (c) Co-NrGO-1 and (d) Co-NrGO-2. 75
Figure 19. TEM elemental mapping images of (a) Co-NrGO-1 and (b) Co-NrGO-2. 76
Figure 20. (a) XANES spectra of Co foil, CoO, Co₃O₄, Co-NrGO-1, Co1, Co-NrGO-2, and Co (an inset Fig. shows enlarged curves in pre-edge region of... 78
Figure 21. Deconvoluted XPS Co 3p spectra of Co-NrGO-1, Co1, Co-NrGO-2, and Co2. 81
Figure 22. (a) Reaction free energy and (b) binding energy of Co1 and Co2. (c) Stable binding sites at pyrrolic-N in NrGO of Co1 and Co2. 86
Figure 23. Stable binding site at ketone in NrGO of (a) Co1 and (b) Co2. 88
Figure 24. (a) RRDE polarization curves of NrGO, Co-NrGO-1, Co-NrGO-2, and Pt/C in O₂ saturated 0.1 M KOH solution performed by using a rotating... 90
Figure 25. (a) Electrochemical impedance spectroscopy and (b) double-layer capacitance measurement of determining electrochemically active surface... 95
Figure 26. CV conducted at non-faradaic region potential window from 0.925 to 1.20 V vs RHE at scan rate of 20, 40, 60, 80, 100, 120, 160 and 200 mV s⁻¹... 96
Figure 27. LSV polarization curves of (a) Co-NrGO-1 and (b) Pt/C. 100
Figure 28. (a) LSV polarization curves of Co-NrGO-2 for initial and after 10,000 cycles. (b) Methanol tolerance tests of Pt/C, Co-NrGO-1, and Co-after-cycle. 101
Figure 29. TPR spectra of NrGO, Co-NrGO-1, and Co-NrGO-2. 103
Figure 30. Dissolved Co amounts in the electrolyte solutions for Co-NrGO-1 and Co-NrGO-2 electrodes measured by ICP-MS. 105
Figure 31. TEM and EDX elemental mapping images of Co-NrGO-1-after-cycle. 107
Figure 32. TEM and EDX elemental mapping images of Co-NrGO-2-after-cycle. 107
Figure 33. Possible active species in Co-NrGO-1 and Co-NrGO-2 for the ORR. 109
Figure 34. LSV polarization curves before and after KCN test (a) Co-NrGO-1, Co-NrGO-2 and (b) Co-ReGO-1, Co-ReGO-2 were measured at 0.1 M... 109
Figure 35. Free energy diagram for oxygen reduction reaction at pyrrolic-N site of Co-NrGO-1 and Co-NrGO-2. 112
Figure 36. Free energy diagram for oxygen reduction reaction at ketone site of Co-NrGO-1 and Co-NrGO-2. 116