氧化鐵材料擁有價格便宜、在地球含量豐富、無毒及可於中性電解液中操作之優點，在近年來被認為是應用於超級電容器上，很有潛力之擬電容材料；其理想操作電位於負電位處，因此也為一很有潛力之非對稱電容器的陽極材料。但其有導電度較差之缺點，且在許多文獻中，其穩定性及高掃速表現並不是很理想。而碳材通常具有高的比表面積、良好的導電性以及電化學穩定性，因此常被用來做為金屬氧化物奈米材料之基材。如將金屬氧化物成長於其中，與之形成複合材料，可藉此彌補氧化金屬導電性及穩定性的不足。本研究利用簡單方便的定電位電沉積法，藉由不同電沉積電位的使用，將氧化鐵沉積於具有高比表面積(737 m2/g)及高導電度之石墨烯多孔膜中，期望利用兩者結合之協同效應，使電容表現更佳。
本研究製備出大小約5 nm之γ-Fe2O3奈米粒子，其均勻地分散於石墨烯多孔膜中，顏色為紅棕色。觀察其電化學表現，在電解液為1 M的亞硫酸鈉溶液中，以掃描速率25 mV/s、電位窗-0.8 V至0 V(vs. Ag/AgCl)進行循環伏安掃描。發現以電位-0.6 V進行電沉積所製備出之複合材料，有最佳之電化學表現。其氧化鐵所貢獻的比電容值，可高達223.5 F/g。並且經過一千圈的循環伏安掃描後，其比電容值沒有降低，反而還有上升的情形。除此之外，在高掃描速率500 mV/s下，經過40000圈的循環伏安掃描後，其比電容值也依然完全沒有衰退，反而有上升的情況發生，顯示本研究所製備出的複合材料，其電化學穩定性極佳。高掃描速率之表現的部分，將掃速提升至1000 mV/s時，其比電容值仍保有67 %(相較於以掃描速率25 mV/s所得到之比電容值)，且CV圖沒有變形歪斜；而利用充放電測試，將電流密度由1 A/g提高至20 A/g，其比電容值維持率為91 %，顯示本複合材料具有良好的高速性能 (high rate capability)。另外，於電流密度20 A/g時，其庫倫效率(Coulombic efficiency)可達95 %。
本研究認為利用定電位電沉積將氧化鐵奈米粒子與石墨烯結合，由於氧化鐵奈米粒子會均勻地分散於高比表面積、高導電度之石墨烯多孔膜中，彼此間較不易聚集堆積，因此能增加電解液與氧化鐵奈米粒子的接觸機會，使氧化鐵奈米粒子得到更有效的利用。除此之外，分散均勻、無聚集傾向的氧化鐵奈米粒子，會使電子傳導路徑降低，當電化學反應發生時，電解液與電極表面發生法拉第反應，電子能夠快速地通過氧化鐵到達高導電性的石墨烯表面，並迅速地傳達至電流收集器上，故使氧化鐵/石墨烯複合材料的電化學表現提升。
本研究所製備出之氧化鐵/石墨烯複合材料，能應用於需要高功率及高穩定性之超級電容器。其理想之操作電位於負電位處，且於此條件下其電化學表現穩定，因此本研究所製備出之氧化鐵/石墨烯複合材料，同時也為一具有潛力之非對稱電容器的陽極材料。

Iron oxides have been considered as one of the promising pseudocapacitor electrode materials in recent years, owing to their low cost, Earth abundance, and low toxicity. In addition, the suitable working potentials of iron oxides are below 0 V (vs. Ag/AgCl), and they are thus a promising candidate as an anode material. But their limited conductivities are disadvantageous, and many reports show that the high rate capability and cycling stability of iron oxides are not good enough. In this study, we develop a successful preparation method for γ-Fe2O3/graphene composites, which involves a simple cathodic electrodeposition of γ-Fe2O3 nanocrystals into a mesoporous graphene film of high conductivity and high specific surface area (737 m2/g). The synergistic effects between the γ-Fe2O3 and graphene drastically improve the capacitive performance of γ-Fe2O3.
γ-Fe2O3 nanoparticles with an average particle size of 5 nm are well-dispersed in the grapheme film. The electrochemical performance of the resulting γ-Fe2O3/graphene composite electrode is tested by cyclic voltammetry(CV) and galvanostatic charge-discharge in Na2SO3. The results show that when the γ-Fe2O3 is deposited potentiometrically at a potential of -0.6 V, the γ-Fe2O3/graphene electrode exhibits the highest specific capacitance, 223.5 F/g, within the potential window of -0.8 V to 0 V at a scan rate of 25 mV/s. The relevant cycling performance is excellent, with the specific capacitance even increasing after 1000 cycles. In addition, the increasing trend in specific capacitance is observed after 40000 cycles at the scan rate of 500 mV/s. The composite also shows an outstanding high rate capability, with a retention of 67 % in specific capacitance when operated at a high scan rate of 1000 mV/s as compared with the specific capacitance obtained at the scan rate of 25 mV/s. The specific capacitance maintains at a 91 % level when the charging/discharging rate increases from 1 to 20 A/g. At the high discharging rate of 20 A/g, the Coulombic efficiency can still maintain at 95 %.
The incorporation of γ-Fe2O3 nanoparticles into the graphene film reduces the aggregation of the nanoparticles, which makes possible the well-dispersed and thus better utilized γ-Fe2O3 nanoparticle. Here, graphene provides a highly conductive network for electron transport during the charge and discharge processes.

摘要 I
Abstract III
致謝 V
總目錄 VI
圖目錄 VIII
表目錄 XIII
第一章 緒論 1
1.1電化學原理 1
1.1.1電化學反應系統 1
1.1.2 影響電化學反應系統的因素 2
1.1.3 電極材料 2
1.2 超級電容器 3
1.2.1 超級電容器簡介 3
1.2.2擬電容器 6
1.2.3電容定義 7
第二章 文獻回顧 8
2.1 氧化鐵於超級電容器之應用 8
2.1.1 單純氧化鐵應用於超級電容器 8
2.1.2 結合氧化鐵與碳材應用於超級電容器 20
2.1.3 氧化鐵電極做為非對稱電容器之陽極的應用 29
第三章 研究方法 33
3.1 實驗藥品 33
3.2 實驗儀器 34
3.3 檢測儀器 35
3.4 實驗動機 37
3.5 實驗流程 39
3.5.1 石墨電極之製備及前處理 40
3.5.2 石墨烯/石墨工作電極之製備 40
3.5.3 利用電化學方法沉積氧化鐵於石墨烯基板骨架 41
3.5.4 電化學分析實驗 41
第四章 實驗結果與討論 44
4.1 氧化鐵沉積於石墨烯/石墨電極之製備 44
4.1.1 氧化鐵沉積於石墨烯/石墨電極之材料鑑定 45
4.2氧化鐵沉積於石墨烯/石墨電極之電化學實驗 56
4.2.1 無電沉積與電沉積之比較 67
4.2.2 不同電解液所造成之影響 69
第五章 結論 70
第六章 參考資料 72

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