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標題: | 奈米結構之氫氧化鐵作為新穎負極材料於非對稱式電化學電容之應用 Nanostructured Iron Oxyhydroxide (FeOOH) as A Novel Anode Material for Asymmetric Electrochemical Capacitor |
作者: | Ying-Chu Chen 陳盈竹 |
指導教授: | 顏溪成(Shi-Chern Yen) |
關鍵字: | 氫氧化鐵,超級電容,曲撓,儲能,機制, Iron Oxyhydroxide,Supercapacitor,Flexible,Charge Storage,Mechanism, |
出版年 : | 2013 |
學位: | 碩士 |
摘要: | 氫氧化鐵(FeOOH)因其可逆之氧化還原反應電位處在低(負)電位區,被視為是相異於廣泛應用在超級電容負極之碳材料以外的另一選擇。其優異的能量與功率密度,以及寬廣的電位操作範圍,更保證了其應用於非對稱式超級電容器的可行性。此類結合氫氧化鐵負極的非對稱式金屬氧化物電容器,改善了過往結合碳材之非對稱式電容器之電容效能。
本研究中主要利用定電位陽極沉積法將奈米結構之氫氧化鐵直接沉積在可曲撓之碳布基材上,並透過添加不同濃度之包覆劑(氟化銨,NH4F)與控制不同沉積時間來觀察材料形貌的改變以及其對於電化學特性的影響。經由掃描式電子顯微鏡來觀察表面型態、X光電子能譜儀觀察其化學鍵結的組成以及利用X 光繞射儀等對材料作定性分析。並經由循環伏安法、不同掃描速率之充放電測試,比較不同形貌的氫氧化鐵其電化學電容效能。 再者,將氫氧化鐵與二氧化錳(MnO2)組合成非對稱式金屬氧化物電容器。利用In-situ X光吸收光譜探討此非對稱式電容器之氧化價數以及晶格鍵長隨充放電過程的變化,以及利用電化學交流阻抗圖譜法分析不同工作電壓下此元件各介面之電阻與電解液中離子擴散阻值的改變。結合上述實驗所得觀察與實際電容器充放電測試結果,有助於廣泛瞭解此元件之操作機制,並以此作日後為對元件效能改善之基礎。 The Iron Oxyhydroxide (FeOOH) has been considered as an alternative anode material other than the common carbon-based electrode for supercapacitor due to its negative reversible redox potential. Its superior specific energy, specific power and wide potential window made it an attractive candidate for negative electrode in asymmetric supercapacitor. Combination of FeOOH with other transition-metal oxide cathodes as asymmetric supercapacitor could get a better capacitive performance compared to those adopted in carbon-based anode. Herein, we adopt a potentiostatically anodic electrodeposition route to prepare nanostructured FeOOH with different morphologies on the flexible carbon cloth substrate. Different morphologies of FeOOH were obtained by controlling the growth rate of various facets of the deposited oxide using capping agent. The morphologies of the resulting FeOOH were characterized via the scanning electron microscope; the chemical bonding and the crystal structure of FeOOH were identified by x-ray photoelectron spectroscopy and X-ray diffractometer. The correlation between morphologies and the electrochemical performance were investigated through cyclic voltammogram and chronopotentiometric system at different current densities. Moreover, we combine the FeOOH anode and MnO2 cathode into an asymmetric supercapacitor. The change of its oxidation state and the variation of bond-length during the charge/discharge process were directly visualized by the in-situ X-ray absorption spectroscopy. The resistance along the carrier transport (including charge transfer resistance, diffusion resistance, etc.) under various working potential was also investigated using electrochemical impedance spectroscopy. Combining these two observations and the capacitive behavior of the asymmetric cell can provide a comprehensive understanding of its operating mechanism and provide insights for further performance enhancements. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/63139 |
全文授權: | 有償授權 |
顯示於系所單位: | 化學工程學系 |
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