自從1970年代以來，隨著石化燃料的枯竭與環保意識的抬頭，對再生能源的需求越來越急迫。除了太陽能、風力發電….等，氫能一直被視為是下個世代最重要的能源之一。本實驗設計了硫化鎘-氧化鋅與硫化鎘-硫化亞銅殼層結構奈米線作為光催化劑以進行產氫之應用。首先，使用三區加熱的擴散爐成長出單晶的硫化鎘奈米線，再利用交流濺鍍的方式成長出氧化鋅的外殼。另一方面，利用陽離子交換的方法將硫化鎘奈米線的外層置換成硫化亞銅。使用以上兩種方法成功製備出硫化鎘-氧化鋅與硫化鎘-硫化亞銅殼層結構奈米線。上述奈米線使用了掃描式電子顯微鏡、穿透式電子顯微鏡、X光繞射儀與能量色散X-射線光譜來確定其結構；使用了光致發光譜與紫外光-可見光譜儀來分析其能隙與光學性質；使用了Shimadzu GC-2014氣相沈積儀來分析其氫氣的產量。相較於硫化鎘奈米線，硫化鎘-氧化鋅殼層結構奈米線與硫化鎘-硫化亞銅殼層結構奈米線之氫氣產率分別提升約100倍與10倍。本實驗展現了能階的編排對載子傳遞的重要性，同時為光催化產氫的領域開闢了一個新的方向。

With the increasing awareness of environmental issues, the renewable energy production has become urgent. Hydrogen is considered to be the promising fuel for the next generation. In this work, we construct novel nano-structures for hydrogen generation. CdS-ZnO core-shell nanowires and CdS-Cu2S core-shell nanowires were synthesized. First, crystalline CdS nanowires were synthesized in a three heating zone diffusion furnace through a VLS growth method. The ZnO shell was deposited with RF sputtering, and the Cu2S shell was achieved with cation exchange method. The core-shell nanowires have been examined by scanning electron microcopy, transmission electron microcopy, X-ray diffraction and energy dispersive spectroscopy to confirm their crystal structure. Photoluminescence and UV-visible analysis were used to examine their band gap and optical properties. A Shimadzu GC-2014 was used to identify and measure the amount of hydrogen gas produced by CdS-ZnO core-shell nanowires and CdS-Cu2S core-shell nanowires. Compared to CdS nanowires, the hydrogen generating activity of CdS-ZnO and CdS-Cu2S core-shell nanowires improved more than 2 orders and 1 order in magnitude, respectively. This experiment verifies the importance and usefulness of band alignment in structure design and opens up a new path for photocatalyst for hydrogen generation.

Chapter 1 Introduction 1
1.1 Hydrogen Energy 1
1.2 Photocatalysis Water Splitting 2
1.3 Heterogeneous Photocatalysts 3
1.3.1 Metal/Semiconductor Heterogeneous Photocatalysts 4
1.3.1.2 Local Surface Plasmon Resonance 5
1.3.1.2.1 SPR-mediated Charge Injection From Metal to Semiconductor 6
1.3.1.2.2 Near-field Electromagnetic Mechanism 6
1.3.1.2.3 Scattering Mechanism 7
1.3.2. Semiconductor/Semiconductor Heterogeneous Photocatalysts 7
1.4 CdS Nanowire 8
1.4.1 Property of CdS 8
1.4.2 Utilizing CdS Nanowires for Water Splitting 9
1.5 Heterojunction 10
1.5.1 Type 1 Heterojunction 11
1.5.2 Type II Heterojunction 11
1.5.3 Type III Heterojunction 12
1.6 Core-Shell Structure Nanowires 13
1.6.1 CdS/ ZnO Core-Shell Nanowires 13
1.6.1 CdS-Cu2S Core-Shell Nanowires 14

Chapter 2 Experimental Procedures 15
2.1 Preparation of Substrate 15
2.2 Vapor-Liquid-Solid Growth Mechanism 16
2.3 RF Sputter Deposition 17
2.4 Cation Exchange Method 18
2.5 Scanning Electron Microscope Observation 19
2.6 Transmission Electron Microscope Observation 20
2.7 Energy Dispersive Spectrometer ( EDS ) Analysis 21
2.8 Photoluminescence Measurement 21
2.9 UV-Vis Observation 21
2.10 X-Ray Diffractometry 22
2.11 GC Measurement 22
Chapter 3 Results and Discussion 24
3.1 Synthesis of CdS Nanowires 24
3.2 CdS-ZnO Core-Shell Nanowires 26
3.2.1 Synthesis of CdS-ZnO Core-Shell Nanowires 26
3.2.2 Structure and Morphology 27
3.2.2.1 SEM Observation 28
3.2.2.2 TEM Observation 29
3.2.2.3 X-ray Diffraction Analysis 30
3.2.2.4 Photoluminescence Measurement 31
3.2.2.5 UV-Vis Observation 32
3.2.3 Effects of CdS-ZnO Core-Shell Structure on Hydrogen Generation 33
3.2.4 Effects of Thickness of ZnO Shell on Hydrogen Generation 35
3.3 CdS-Cu2S Core-Shell Nanowires 37
3.3.1 Synthesis of CdS-Cu2S Core-Shell Nanowires and Cu2S Nanowires 37
3.3.2 Structure and Morphology 38
3.3.2.1 SEM Observation of CdS-Cu2S Core-Shell Nanowires 38
3.3.2.2 TEM Observation of CdS-Cu2S Core-Shell Nanowires 40
3.3.2.3 Photoluminescence Measurement of CdS-Cu2S Core-Shell Nanowires 41
3.3.2.4 SEM Observation of Cu2S Nanowires 43
3.3.2.5 TEM Observation of Cu2S Nanowires 44
3.3.3 Comparison between CdS-Cu2S Core-Shell Nanowires and Cu2S Nanowires on Hydrogen Generation 44
3.4 Comparison between CdS-ZnO Nanowires, CdS-Cu2S Core-Shell Nanowires on Hydrogen Generation 46
Chapter 4 Summary and Conclusions 48
Chapter 5 Future Prospects 50
5.1 Time-Resolved Photoluminescence Measurement of Electron Lifetime in ZnO Layer 50
5.2 CdS Nanowire Array for Hydrogen Generation by Applying LSPR 51
5.2.1 PS Spheres Arrangement 51
5.2.2 Growth of Gold Nanoparticle Array 53
5.2.3 Growth of CdS Nanowire Array 53
References 54

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