Title Page
ABSTRACT
Contents
CHAPTER 1. INTRODUCTION 12
1.1. Ammonia 12
1.1.1. Physicochemical properties and uses 12
1.1.2. Applications in energy field 16
1.2. Ammonia electrochemical oxidation reaction 20
1.2.1. Noble metal based materials 27
1.2.2. Non-noble metal based materials 29
1.2.3. NiCu based materials 31
1.3. Research objectives 33
CHAPTER 2. EXPERIMENTS 34
2.1. Materials 34
2.2. Preparation methods 34
2.3. Characterization 35
2.4. Electrochemical activity tests 37
2.4.1. Ammonia removal test 37
2.4.2. Gas measurement and Faradaic efficiency calculation 39
CHAPTER 3. RESULTS AND DISCUSSION 41
3.1. Preparation and characterization of NiCu-D electrocatalysts 41
3.2. Electrochemical oxidation of ammonia 50
3.3. Effects of different precipitation agents on AOR activity of NiCu-electrocatalysts 58
3.4. Ammonia removal test and selectivity of the products 62
3.5. Unique synergistic effect of Ni and Cu in AOR[원문불량;p.55-56] 66
CHAPTER 4. CONCLUSION 73
REFERENCES 74
Table 1.1. Properties of NH₃ and H₂ 19
Table 1.2. Gerischer-Maueuer (G-M) mechanism of the AOR process 22
Table 1.3. Oswin-Salomon (O-S) mechanism of the AOR process 23
Table 3.1. AOR activities of different electrocatalysts 54
Table 3.2. Parameters of EIS measurements of NiCu-D-1:1/CP, NiCu-D-1:2/CP, NiCu-D-1:4/CP, and Ni-D-1:2/CP 56
Table 3.3. Double layer capacitance of the NiCu-D/CP and Ni-D-1:2/CP electrodes 56
Table 3.4. Double layer capacitance of the NiCu electrodes made from different precipitation agents 58
Table 3.5. Gibbs Free Energy of Adsorbed Intermediates at 0 V Relative to N₂(g), H₂O(g), and OH-(Reused with ACS permission) 68
Figure 1.1. Molecular structure of NH₃ 14
Figure 1.2. The growth of global NH₃ production from 1998 to 2023 (ammonia production unit: megaton) 15
Figure 2.1. Calibration curve of Nessler's reagent 38
Figure 2.2. GC-TCD system for N₂ and O₂ quantification. 40
Figure 3.1. Schematic diagram of NiCu-D electrocatalysts preparation 42
Figure 3.2. FE-SEM images of NiCu-based electrocatalysts with dodecylamine in different M:D, (a) and (b): NiCu-D-1:1, (c) and (d): NiCu-D-1:2, (e) and (f): NiCu-D-1:4, (g) to (j): elemental mapping of NiCu-D-1:2 catalyst 45
Figure 3.3. XRD patterns of NiCu-D and Ni-D-1:2 catalysts 47
Figure 3.4. XPS spectra of NiCu-D-1:2/CP electrode before and after AOR experiments, (a) and (a') Ni2p before and after AOR, (b) and (b') Cu2p before and after AOR, (c) and (c') O1s before and after AOR 49
Figure 3.5. (a) and (b) Cyclic voltammograms (CV) of dodecylamine-based electrodes in NaOH 0.5M without and with NH₄Cl 0.055M, (c) LSV curves of dodecylamine-based electrodes, (d) Tafel plots of NiCu-D/CP... 53
Figure 3.6. Stability test of NiCu-D at 0.6 V vs Hg/HgO. 55
Figure 3.7. CV measurements with different scan rates of dodecylamine-based electrodes 57
Figure 3.8. SEM images of NiCu-Urea, NiCu-TEA, NiCu-NaOH, and NiCu-NH3 59
Figure 3.9. Cyclic voltammetry of prepared catalysts in NaOH with and without NH₃, scan rate: 25mV/s 60
Figure 3.10. LSV and Tafel slopes of synthesized electrocatalysts 61
Figure 3.11. (a) NH₃ removal and (b), (c), (d) Faradaic efficiency of NiCu-D-1:2/CP, NiCu-Urea/CP, and Ni-D-1:2/CP at 0.6V vs Hg/HgO, respectively 65
Figure 3.12. Free-energy diagram of the minimum-energy pathway for ammonia electrooxidation on (a) Ni (111) and (b) Ni(111) with Cu(111) at 0 V vs. RHE. Zero energy corresponds to N2(g). The green and brown words represent the species... 69
Figure 3.13. Plausible AOR mechanism towards N₂ and NOₓ formation 72