- 學位論文
直接成長Ni-Fe LDH催化劑於石墨烯與矽之蕭特基接面之高效能光電化學產氧反應
High Performance Graphene/Si Schottky Junction Photoanode for Water Oxidation by In-situ Growth of Ni-Fe LDH catalyst
摘要
化石燃料對地球所造成的汙染日益嚴重，迫使人類尋求對環境無害、可再生的替代能源以求永續發展。近年來，結合電化學與太陽能的光電化學於水分解的應用廣大的受到科學家的關注，希望能直接將太陽能轉換為容易儲存之化學能。本論文主要利用能隙較小、地球含量較多的矽作為光電化學水分解的電極材料，並以水分解主要能量反應步驟，即「產氧反應」為研究方向。 首先，由於二維材料單原子層石墨烯具有出眾的物理及化學特性，能夠與矽接觸形成肖特基接面，提高載子分離率，並具有惰性保護的能力。因此，我們利用低壓化學氣象沉積法，有效的成長一定面積且均勻的石墨烯薄膜，利用傳統PMMA轉印法，將在可見光範圍內具有高穿透率的單層石墨烯轉印至n-type矽基板上。接著，我們使用各種方式包括旋塗、水熱法以及電化學沉積等方式嘗試將具有良好電催化活性的Ni-Fe LDH 催化劑直接沉積於石墨烯/矽基板上。結果顯示，石墨烯/矽基板之異質結構有利於電沉積法，能夠有效地將大量的Ni-Fe LDH 催化劑直接成長於石墨烯/矽基板上。之後，我們使用X射線光電子能譜(XPS)、X射線射線繞射儀(XRD)、歐傑電子能譜儀(AES)以及選區電子繞射(SAED) 做Ni-Fe LDH 催化劑的元素成分價態與晶體結構的分析。並以掃描電子顯微鏡(SEM)、穿透式電子顯微鏡(TEM) 觀察Ni-Fe LDH 催化劑表面形態、晶向以及整體元件結構。 最後，利用線性掃描伏安法（LSV）、電化學阻抗分析（EIS）以及莫特-肖特基圖(Mott-Schottky plot) 等方式，量測電化學沉積之Ni-Fe LDH於石墨烯/矽基板上的元件特性。實驗結果顯示大量的Ni-Fe LDH 催化劑沉積於石墨烯與矽的肖特基異質接面，促使產氧反應之起始電壓相較於理論值左移0.47 VRHE並達到飽和電流35 mA/cm2，展現出極佳的產氧效率。
並列摘要
To develop the alternative energy which is eco-friendly, the photoelectrochemistry water splitting has attracted a lot of attention in recent years. In this thesis, silicon which gets a large amount of earth content and with a small energy gap is used as the photoelectrochemical water splitting electrode material and the energy control step of the water splitting, namely "oxygen evolution reaction (OER)", is the main research direction. First, the superior physical and chemical characteristics of the two-dimensional material graphene form Schottky junction when contacting with silicon, improve the carrier separation, and protect silicon from corrosion. We used PMMA to transfer the chemical vapor deposition synthesized graphene on n-type silicon. Next, the heterostructure of graphene/n-type silicon is beneficial for in-situ synthesizing highly electrocatalytic activity Ni-Fe LDH catalyst by electrodeposition method. X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), Auger electron spectroscopy (AES) and selected area electron diffraction (SAED) is used to confirm the elemental composition, electronics states and crystal structure of Ni-Fe LDH. The surface morphology and crystal orientation of Ni-Fe LDH are observed with scanning electron microscope (SEM) and transmission electron microscope (TEM). Finally, using linear scanning voltammetry (LSV), electrochemical impedance analysis (EIS), and Mott-Schottky plot to measure the photoelectrochemical behavior. Large amount of Ni-Fe LDH catalyst deposited on the heterostructure of graphene/silicon displays excellent OER efficiency with negatively shifted about 0.47 VRHE relative to the theoretical value in the OER on-set potential and the saturation current about 35 mA /cm2.