臺灣博碩士論文加值系統

本研究利用化學浴沉積法(chemical bath deposition)在透明導電FTO玻璃上直接生長與基材垂直排列的定向氧化鋅奈米棒陣列(ZNR)，再在其表面以連續離子層吸附反應法(SILAR)披覆硫化鎘(CdS)奈米顆粒。以FE-SEM和HR-TEM觀察其表面形貌、UV-Vis測其吸光性質、XRD確定氧化鋅與硫化鎘晶相。在太陽光電水分解之量測中，我們以製得之CdS/ZNR電極作為工作電極，金線為輔助電極，Ag/AgCl為參考電極，0.35 M Na2SO3與0.25 M Na2S的水溶液為電解液，AM 1.5模擬太陽光(100 mW/cm2 )為光源。在披覆CdS的製程中使用之溶劑與披覆次數會影響CdS粒子的特性，進而影響對太陽光電水分解之效率。研究結果顯示，以水作為溶劑進行CdS披覆，CdS會以顆粒狀附著於ZNR，又以披覆八次(CdS/ZNR-8w)測得的太陽光電水分解之光電轉換效率最高(4.14%)；以乙醇作為溶劑披覆CdS，CdS會以薄膜狀附著於ZNR，以披覆六次(CdS/ZNR-6e)測得的光電轉換效率最高(3.86%)。由此得知，在ZNR基材的溶劑選擇水比乙醇好。又在披覆六次的製程中，前三次以水溶劑披覆顆粒狀的CdS，後三次以乙醇溶劑披覆薄膜狀的CdS (CdS/ZNR-3w3e)，此披覆順序使CdS披覆更為緊密，減少漏電流發生機率，其光電轉換效率更提升至5.23%。
另外，再在ZNR表面以SILAR法披覆硒化鎘(CdSe)奈米顆粒，重複披覆次數製得不同CdSe含量之硒化鎘/氧化鋅奈米棒陣列電極(CdSe/ZNR)。當僅披覆CdSe奈米顆粒時，光電轉換效率為4.12%。再將CdS/ZNR與CdSe/ZNR兩電極的非導電面合併後照光，光先經CdS面穿透至CdSe面，使光譜中400-550 nm的波長被CdS奈米顆粒吸收，550-750 nm的波長被CdSe奈米顆粒吸收，充分利用可見光後，其太陽光電水分解之光電轉換效率更大幅提升至6.61%。

We fabricated CdS quantum dots sensitized ZnO nanorod arrays (CdS/ZNR) as photoanodes that used for solar water splitting. The vertically aligned ZNR was fabricated via a simple chemical bath deposition method (CBD), and the CdS quantum dots were coated on the ZNR by using successive ionic layer adsorption and reaction (SILAR). The prepared electrodes were characterized by FE-SEM, HR-TEM, XRD, UV-Vis, and photoelectrochemical measurements. All the photoelectrochemical measurements were carried out in a three-electrode cell with an Au wire as a counter electrode and an Ag/AgCl electrode as a reference. A mixture of 0.35 M Na2SO3 and 0.25 M Na2S aqueous solution was used as electrolyte. The working electrode was illuminated with a solar-simulated light source (AM 1.5 G filtered, 100 mW/cm2 ). In this study, we changed the solvent (water and ethanol) used in SILAR processes to fabricated various CdS/ZNR photoanodes, such as eight water-based SILAR cycles (CdS/ZNR-8w), six ethanol-based SILAR cycles (CdS/ZNR-6e), and three water-based as well as three ethanol-based SILAR cycles (CdS/ZNR-3w3e). After CdS sensitization, TEM images showed that ZnO nanorod were covered with nanoparticular forme in water solvent but with film form in ethanol solvent. The photoconversion efficiency of CdS/ZNR-8w for 4.14% was much higher than that of CdS/ZNR-6e for 3.86%, so the choice of solvent that water was better than ethanol. Further, the photoconversion efficiency of CdS/ZNR-3w3e had best performance of 5.23%. The photoconversion efficiency was enhanced because of the ZnO nanorod were covered with nanoparticle and then film. Such CdS composite was closely coated on the ZnO nanorod and could collect more excited photoelectrons.
Furthermore, we also fabricated CdSe quantum dots sensitized ZNR (CdSe/ZNR) as photoanode. The CdSe quantum dots were coated on the ZNR surface using SILAR methode. The photoconversion efficiency of the single sided CdSe/ZNR was 4.12%. In order to increase the light-harvesting in the full spectrum of visible light region, we used CdS to absorb the short wavelength region (400-550 nm), and CdSe to absorb the long wavelength region (550-750 nm). Therefore, we combined CdS/ZNR electrode with CdSe/ZNR electrode by their non-conductive sides (CdS//CdSe), and the incident light transmitted through the CdS/ZNR substrate to the CdSe/ZNR substrate, thus the light could be absorbed by both substrates. The best photoconversion efficiency of 6.61% was achieved by using the CdS//CdSe as photoelectrode in solar water splitting.

摘　要 …………………………………………………………………….. i

Abstract …………………………………………………………………….. iii

致謝 …………………………………………………………………….. v

目錄 …………………………………………………………………….. vi

表目錄 …………………………………………………………………….. viii

圖目錄 …………………………………………………………………….. ix

第一章 緒論……………………………………………………………….. 1
1.1 前言……………………………………………………………….. 1
1.2 再生能源與產氫研究之簡介………………………………….… 3
1.3 光觸媒催化原理……………………………………………….…. 8
1.4 太陽光電水分解反應………………………………………….…. 10
1.5 一維氧化鋅奈米棒…………………………………………….…. 12
1.6 量子點 (Quantum Dots)……………………………………….…. 16
1.6.1 量子點的特性……………………………………….…... 16
1.6.2 量子點合成與組裝技術…………………………….…... 21
1.6.3 量子點敏化氧化鋅奈米棒…………………………….... 22
1.7 研究動機與目的………………………………………………….. 23
第二章 實驗方法………………………………………………………….. 25
2.1 藥品及儀器……………………………………………………….. 25
2.2 樣品製備………………………………………………………….. 27
2.2.1 氧化鋅奈米棒陣列…………………………………….... 27
2.2.2 連續離子層吸附反應法披覆CdS奈米粒子………….. 27
2.2.3 連續離子層吸附反應法披覆CdSe奈米粒子……….... 31
2.3 材料特性分析…………………………………………………….. 32
2.3.1 場發射掃描式電子顯微鏡(Field Emission Scanning Electron Microscopy；FE-SEM)……………………..…32
2.3.2 高解析穿透式電子顯微鏡(High Resolution Transmission Electron Microscopy；HR-TEM)…….…..32
2.3.3 能量分散式X光能譜(Energy Dispersive X-ray Spectroscopy；EDS)……..…………………………....…..32
2.3.4 X-射線繞射圖譜(X-ray Diffraction Pattern；XRD)……………………………………………33
2.3.5 紫外光-可見光吸收光譜(Ultraviolet-Visible Spectrum）……..…………………………….………33
2.4 太陽光電水分解之組裝與測試………………………………….. 34
2.4.1 水分解反應設備裝置……………………..…………….. 34
2.4.2 測量方式…………..…………………………………….. 35
第三章 結果與討論……………………………………………………….. 40
3.1 氧化鋅奈米棒陣列…………………………………………….…. 40
3.2 以水(乙醇)作為溶劑將硫化鎘披覆於氧化鋅奈米棒陣列…….. 44
3.2.1 工作電極之特性鑑定……………..…………………….. 44
3.2.2 太陽光電水分解量測………………..………………….. 61
3.3 水和乙醇兩溶劑交換披覆硫化鎘於氧化鋅奈米棒陣列……… 67
3.3.1 工作電極之特性鑑定…………………..……………….. 67
3.3.2 太陽光電水分解量測………………………..………….. 72
3.4 電化學交流阻抗分析…………………………………………….. 77
3.5 雙面硫化鎘和硒化鎘敏化於氧化鋅奈米棒陣列………………. 78
3.5.1 工作電極之特性鑑定………………………..………….. 78
3.5.2 太陽光電水分解量測………………………..………….. 85
第四章 結論………………………………………………………………... 95
參考文獻 ……………………………………………………………………... 96

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