Title Page
ABSTRACT
Contents
CHAPTER 1. Introduction 22
1.1. Two-dimensional (2D) materials 23
1.1.1. Two-dimensional materials 23
1.1.2. MXenes 25
1.1.3. Molybdenum disulfide (MoS₂) 27
1.2. Supercapacitor for energy storage 27
1.3. Adsorbents for Radioisotope Removal 32
1.4. References 35
CHAPTER 2. Hybrid supercapacitors based on rGO/POM//MXene for high energy storage 41
2.1. Introduction 42
2.2. Experimental 44
2.2.1. Chemicals and reagents 44
2.2.2. Preparation of MXene and rGO-POM samples 44
2.2.3. Electrochemical measurements 45
2.2.4. Calculation of electrochemical parameters: 45
2.3. Results and discussion 47
2.3.1. Half-cell measurements 47
2.3.2. Full cell measurements 61
2.4. Conclusion 68
2.5. Reference 69
CHAPTER 3. High-performance supercapacitor based on nitrogen-doped carbon-coated molybdenum disulfide nanosheets 78
3.1. Introduction 79
3.2. Experimental 80
3.2.1. Materials 80
3.2.2. Synthesis of NC-MoS₂ 80
3.2.3. Structural characterization 81
3.2.4. Electrochemical characterization 81
3.3. Results and discussion 82
3.4. Conclusion 95
3.5. References 96
CHAPTER 4. Highly Efficient Removal of Radioactive Cesium and Strontium Ions Using Two-dimensional Titanium Carbide (Ti3C2Tx) MXene[이미지참조] 101
4.1. Introduction 102
4.2. Experimental 105
4.2.1. Chemicals 105
4.2.2. Synthesis of multi-layered Ti3C2Tx MXenes[이미지참조] 106
4.2.3. Synthesis of Ti3C2Tx/POSS-NH₂ composite[이미지참조] 106
4.2.4. Adsorption experiments 107
4.2.5. Characterization 107
4.2.6. Kinetics experiments 108
4.3. Results and Discussion 108
4.3.1. Effect of pH 120
4.3.2. Adsorption isotherm studies 122
4.3.3. Adsorption kinetics studies 130
4.3.4. Mechanism of Cs+ and Sr2+ adsorptions[이미지참조] 135
4.2.5. Effect of competitive cations 141
4.2.6. Absorbent regeneration 144
4.4. Conclusion 146
4.5. References 147
CHAPTER 5. Conclusions 157
5.1. Conclusions 158
Table 2-1. Comparative electrochemical parameters for the MXene and POMs based hybrid or asymmetric SCs 67
Table 4-1. Parameters of the Langmuir and Freundlich models for the adsorptions of Cs+ and Sr2+ by Ti₃C₂/POSS-NH₂.[이미지참조] 125
Table 4-2. Parameters of the Langmuir and Freundlich models for the adsorptions of Cs, and Sr by Ti3C2Tx.[이미지참조] 127
Table 4-3. Adsorption capacities of Cs+ and Sr2+ on Ti3C2Tx/POSS-NH₂ and other reported materials.[이미지참조] 129
Table 4-4. Kinetic parameters of the pseudo-first-order and pseudo-second-order models for Cs+ and Sr2+ adsorptions by Ti₃C₂/POSS-NH₂.[이미지참조] 132
Figure 1.1. Schematic diagram showing two-dimensional materials and their energy storage and selective radioactive removal applications. 24
Figure 1.2. Schematic showing charge storage mechanisms of EDLCs and pseudocapcitors. 29
Figure 2.1. Schematic of the synthesis approach used to prepare (a) MXene and (b) rGO-POM electrodes for assembling a HSC cell. 47
Figure 2.2. (a, b) SEM images and (c) TEM image of MXene, (d, e) SEM images and (f) TEM image for the rGO-POM sample. Inset shows the high-resolution TEM image for the rGO-... 50
Figure 2.3. (a) The broad scan XPS spectra for the rGO-POMs sample, (b) the narrow scan XPS spectra for the O1s of rGO-POMs sample, (c) the XRD and (d) Raman spectra for the... 51
Figure 2.4. XPS analysis for the MXene sample. (a) The broad scan XPS spectra, the core-level XPs spectra for the (b) Ti2p, (c) F1s, (d) O1s, and (e) C1s for the MXene sample. 52
Figure 2.5. CV curves for the (a) MXene and (b) rGO-POM electrodes at various scanning rates, (c) a plot of current density versus scan rate for the MXene and rGO-POM electrodes, (c)... 53
Figure 2.6. The plot of log (i) versus log (v) for the (a) rGO-POMs and (b) MXene electrodes, the plot of capacitive and diffusion-controlled contribution for the (c) rGO-POMs and (d)... 56
Figure 2.7. GCD curves for the (a) MXene and (b) rGO-POMs electrodes at various current densities, and capacitance plots for the (c) MXene and (d) rGO-POMs electrodes derived from... 57
Figure 2.8. The coulombic efficiency for the (a) MXene and (b) rGO-POMs electrodes derived from the charge-discharge curves, capacitance retention plot for the (c) MXene and (d) rGO-... 59
Figure 2.9. (a) Schematic procedure to assemble the rGO-PMO//MXene HSC cell. Digital photographs showing the flexibility of the assembled rGO-PMO//MXene HSC cell. (b) Three-... 60
Figure 2.10. (a) The capacitance and (b) coulombic efficiency for the HSC cell at various operating voltage window at current density of 14 A/g. 65
Figure 2.11. (a) Ragone plot for the rGO-PMO//MXene HSC cell and (b) Nyquist plot for the rGO-PMO//MXene HSC cell. The inset shows a magnified view of the Nyquist plot. (c)... 66
Figure 3.1. (a) SEM image of bulk MoS₂. (b) TEM image of PDA-MoS₂ sheet. (c) and (d) Low and high resolution TEM images of NC-MoS₂ sheets. 84
Figure 3.2. (a) HAADF-STEM image of NC-MoS₂ sheet. (b) EDX mapping images of Mo, S, N, and C signals. 85
Figure 3.3. (a) XRD patterns of bulk MoS₂ and NC-MoS₂. (b) XPS survey scan spectra of e-MoS₂ and NC-MoS₂. (c) C1s and (d) Mo3p and N1s spectra of NC-MoS₂. 86
Figure 3.4. CV curves of NC-MoS₂ and e-MoS₂ electrodes measured between -0.5 and +0.5 V at scan rate of 50 mV s-1 using 1 M Na₂SO₄.[이미지참조] 89
Figure 3.5. Galvanostatic charge/discharge curves (a) and specific capacitances (b) of NC-MoS₂(△) and e-MoS₂ (●) electrodes measured at different current densities. 91
Figure 3.6. Cycling performance of NC-MoS₂ (△) and e-MoS₂ (○) electrodes measured at constant current of 1 A g-1 during 1000 cycles.[이미지참조] 93
Figure 3.7. (a) Nyquist plots measured at a frequency range of 100 kHz to 10 mHz for NC-MoS₂ (△) and e-MoS₂ (○) electrodes. (b) Equivalent circuit model used for the fittings. 94
Figure 4.1. (a) Fourier transformation infrared spectra of Ti3C2Tx, POSS-NH₂, and Ti3C2Tx/POSS-NH₂, (b) X-ray diffraction spectra of Ti₃AlC₂, Ti3C2Tx, and Ti3C2Tx/POSS-NH₂,...[이미지참조] 110
Figure 4.2. X-ray photoelectron spectra of (a-d) Ti3C2Tx and (e-h) Ti3C2Tx/POSS-NH₂.[이미지참조] 114
Figure 4.3. High-resolution scanning electron microscopy (HR-SEM) images of (a) Ti₃AlC₂ MAX, (b) Ti3C2Tx MXene, and (c, d) Ti3C2Tx/POSS-NH₂.[이미지참조] 116
Figure 4.4. High-resolution transmission electron microscopy (HR-TEM) images of (a) Ti3C2Tx MXene and (b - d) Ti3C2Tx/POSS-NH₂. (e-f) Elemental mapping images of...[이미지참조] 118
Figure 4.5. (a, b) SEM-EDX analysis of Ti3C2Tx/POSS-NH₂. TEM (c) elemental mapping and (d) EDX of Ti3C2Tx/POSS-NH₂.[이미지참조] 119
Figure 4.6. (a) Equilibrium adsorption capacities of Cs+ and Sr2+ ions at various pH (between 5 and 11). (b) Zeta potential measurements of (i) Ti3C2Tx and (ii) Ti3C2Tx/POSS-NH₂.[이미지참조] 121
Figure 4.7. Langmuir and Freundlich isotherms for the adsorptions of (a) Cs+ and (b) Sr2+ by Ti3C2Tx/POSS-NH₂. (c) Adsorption kinetics, and (d) the pseudo-second-order kinetic model of...[이미지참조] 126
Figure 4.8. Langmuir linear isotherm plots of Cs+ and Sr2+ adsorption by (a, b) Ti3C2Tx/POSS-NH₂ and (c, d) Ti3C2Tx. (b) Freundlich linear isotherm plots of Cs+ and Sr2+ adsorption by (e,...[이미지참조] 127
Figure 4.9. Langmuir and Freundlich isotherm models for the adsorption of (a) Cs+ ions and (b) Sr2+ ions by Ti3C2Tx. (c) Adsorption kinetics and (d) pseudo-second-order kinetic model fit for...[이미지참조] 128
Figure 4.10. Pseudo-first-order kinetic model fit for the adsorption of Cs+/Sr2+ ions by (a, b) Ti3C2Tx/POSS-NH₂ and (c, d) Ti3C2Tx.[이미지참조] 133
Figure 4.11. (a) Survey spectra of Cs+ and Sr2+ ions-adsorbed Ti3C2Tx/POSS-NH₂, (b) Cs 3d spectrum of Cs+ ions-adsorbed Ti3C2Tx/POSS-NH₂, and (c) Sr 3d spectrum of Sr2+ ions-...[이미지참조] 138
Figure 4.12. X-ray photoelectron spectroscopy analysis of (a) Ti3C2Tx/POSS-NH₂, (b) Ti3C2Tx/POSS-NH₂-Cs+, and Ti3C2Tx/POSS-NH₂-Sr2+.[이미지참조] 139
Figure 4.13. Schematic diagram showing adsorption mechanism (surface complexation, ion exchange, electrostatic interaction, and encapsulation) of Cs+ and Sr2+ ions by Ti3C2Tx/POSS-NH₂[이미지참조] 140
Figure 4.14. Selectivity studies of (a) Cs+ ions among the coexisting monovalent K+ and Na+ cations by Ti3C2Tx, Ti3C2Tx/POSS-NH₂, and (b) Sr2+ ions among the coexisting divalent Ca2+,...[이미지참조] 143
Figure 4.15. (a) Regeneration test of Ti3C2Tx/POSS-NH₂ (Cs+=Sr2+= 50 mg L-1, pH 7.0, reaction time = 60 min). TEM morphology of (b) Cs+- and (c) Sr2+-adsorbed Ti3C2Tx/POSS-...[이미지참조] 145