自1972年Honda and Fujishima 提出以TiO¬2作為光電極材料，成為了半導體材料應用於光電極材料的先河，自此科學家已投入數十年時間研究相關領域。其中赤鐵礦也曾一度是光電極材料的人選，主要原因在於其能隙大小適中、溶液中穩定性良好、地殼含量高等等，然而其仍受限於本身特性造成電解水效率低弱，但目前已提出許多解決方法，例如摻雜其元素提高載子濃度、與其他材料結合形成異質接面等等。目前發展至今，赤鐵礦若欲與其他材料結合形成異質接面，大多需耗費高成本與複雜技術，本研究中試以合成磁鐵礦之共沉澱法，在不通保護氣氛的條件下反應，其產物主要為磁鐵礦與赤鐵礦以及少量不穩定鐵氧化合物，並且透過加入導電高分子(poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, PEDOT/PSS)將氧化鐵奈米粒子與其混合形成氧化鐵沉積薄膜，因而能夠直接塗抹於不同基板上，進行後續氧化鐵薄膜特性分析以及電化學相關測量。其中X-ray繞射圖譜發現到以共沉澱法合成之氧化鐵奈米粒子大多為磁鐵礦(Fe3O4)，僅有少量赤鐵礦(α-Fe2O3)出現，當加入PEDOT/PSS時，兩者間並無交互作用，PEDOT/PSS在2θ= 10°~30°間有非晶相峰出現。TEM影像中觀察到大多合成氧化鐵奈米粒子為磁鐵礦(Fe3O4)，與X-ray繞射圖譜結果一致，並且四種介面活性劑合成的氧化鐵奈米粒子尺寸約10 nm。UV/Vis 圖譜中顯示合成的氧化鐵奈米粒子並無明顯吸收峰，僅有介面活性劑本身溶出造成的吸收峰，當PEDOT/PSS加入時，顯示一樣結果，僅在245 nm有一吸收峰為PSS中的苯基造成。JV曲線中，ITO玻璃基板以甘胺酸合成之氧化鐵奈米粒子沉積薄膜光電流效率最大，但在矽基板則以貼附程度愈差有較大光電流效率，以單寧酸合成之氧化鐵奈米粒子沉積薄膜具有最大光電流效率。Mott-Schottky測試中,，四種介面活性劑合成的氧化鐵奈米粒子在ITO玻璃基板與矽基板中皆顯示正斜率，代表該合成材料具N-type性質，但計算平帶電位時，發現與水氧化還原電位有偏差，造成偏差原因為合成之氧化鐵奈米粒子大多為磁鐵礦(Fe3O4)，屬於類金屬材料，在Mott-Schottky測試中主要以半導體材料為主。EIS測試中顯示電極在反應中有兩因素主導，在高頻區以電荷轉移阻抗為主，而低頻區則屬於物質擴散阻抗，並且因電雙層非理想電容，選用R(QR)等效電路進行模擬。

In this research, we adopted conventional co-precipitation method to synthesize iron oxides. Numerous kinds of iron oxides were discovered in the results since the synthesis wasn’t carried out in a N2 atmosphere, which prevents magnetite from oxidizing. Within all the products, magnetite and hematite are the majorities. For characterization, crystal structure of the nanoparticles, surface morphology and optical properties of these iron oxides are examined. Furthermore, poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate was introduced to the nanoparticles and was then deposited into thin film. Finally, we deposited thin film on ITO glass and silicon wafer as photoelectrodes and JV curve measurement, Mott-Schottky and EIS measurement are brought out in order to obtain electrochemical properties of the electrodes.

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