ZnO 나노구-MWCNT 복합 광전극을 이용한 광전기화학 및 광촉매 수소 생산 성능 향상 연구 = A Study on Enhanced Photoelectrochemical and Photocatalytic Hydrogen Production Using ZnO Nanosphere-MWCNT Composite Photoelectrodes

다국어 초록 (Multilingual Abstract)

Photoelectrochemical (PEC) water splitting represents a promising route toward sustainable solar-to-hydrogen energy conversion. Zinc oxide (ZnO), with its wide bandgap (~3.37 eV), high electron mobility and optical transparency has been intensively investigated as a photoanode material. However, its practical utilization remains limited by insufficient visible-light absorption and photocorrosion-induced instability. Here, we present a rationally engineered composite photoanode comprising ZnO nanospheres electrostatically integrated with surface-functionalized multi-walled carbon nanotube (MWCNT), forming a highly conductive and robust interfacial network. The ZnO nanospheres, assembled from quantum dots, ensure high surface area and efficient light harvesting, while the MWCNT network facilitates rapid charge transport and suppresses electron-hole recombination, as evidenced by pronounced photoluminescence quenching. This architecture delivers a remarkable photocurrent density of 417 µA/cm2 at 1.23 VRHE, corresponding to a 29.7-fold enhancement compared with pristine ZnO. In addition, the composite achieves a hydrogen yield of 3.44 µmol/cm2 (12.3 times higher) and accelerates pollutant degradation kinetics by 21-fold, demonstrating multifunctional performance. The synergistic interplay between ZnO nanostructures and MWCNTs not only enhances charge transfer dynamics but also imparts superior photostability. These findings highlight a scalable materials design strategy for developing high-efficiency, durable photoanodes, offering broad implications for next-generation solar fuel production and environmental remediation technologies.

목차 (Table of Contents)

• Chapter 1. Introduction 1
• Chapter 2. Theoretical Background 4
• 2.1. Water splitting for Hydrogen Production 4
• 2.2. Photocatalyst 8
• 2.3. Photoelectrochemical cell 12
• 2.4 Zinc Oxide 16
• 2.5. Carbon Nanotubes 19
• Chapter 3. Experimental Details 22
• 3.1. Functionalization of MWCNT 22
• 3.2. Synthesis of ZnO-MWCNT Nanocomposite 23
• 3.3. Preparation of Photoanode 24
• 3.4. Materials characterizations 25
• 3.5. Photocatalytic Experiment 27
• 3.6. Photoelectrochemical Measurements 28
• Chapter 4. Results and Discussion 29
• 4.1 Fabrication of ZnO-MWCNT nanocomposite photoanode 29
• 4.2 Characteristics of ZnO-MWCNT nanocomposite 37
• 4.3 PEC performance 54
• 4.4 Photodegradation & Hydrogen Production 65
• Chapter 5. Conclusions 73
• References 75
• Abstract (Korean) 81
• Acknowledgements 84