- 學位論文
以電化學陽極氧化法自丙三醇水溶液中產製二氧化鈦奈米管陣列及其光電化學作用
Array of TiO2 nanotube prepared by electrochemical anodization from aqueous glycerol solution and its photo-electrochemical characteristic
摘要
本研究採用三極式電化學陽極氧化法，以拋光之鈦箔為工作電極，白金鈦網為相對電極，飽和甘汞電極為參考電極，在含氟離子(0.08 M~0.36 M)之丙三醇水溶液中(丙三醇含量在25 vol. %~100 vol. %)，在10 V~30 V 電位下製備二氧化鈦奈米管，討論實驗參數對奈米管形貌之影響。結果顯示：在不含丙三醇之含氟水溶液中，適合二氧化鈦奈米管的成長電位範圍在10~20 V。在此電位範圍內，若水溶液中加入丙三醇，則所得奈米管的管徑會隨著丙三醇濃度之增加而縮小，丙三醇含量超過80 vol. %，則生成奈米孔薄膜取代奈米管，當丙三醇含量達100 vol. %，則僅出現氧化層，沒有奈米孔、奈米管的生成。 若溶液中丙三醇含量在90 vol. %，在20 V下進行定電位氧化反應，氟離子濃度由0.17 M增加至0.36 M，則由奈米孔轉變為奈米管結構。若在水溶液中丙三醇含量在90 vol. %，氟離子濃度0.27 M，控制陽極氧化電位在10 V~30 V範圍內，均能獲得二氧化鈦奈米管結構，且隨電位由10 增加至 30 V時，奈米管之管徑由41 增大至 100 nm。在此系統中，尤其在20 V定電位下，獲得之奈米結構形貌最佳。 鈦箔在含0.27 M 氟離子及90 vol. %丙三醇之水溶液中，施加20 V定電位處理2小時後，具有相同管徑之二氧化鈦奈米管試樣，經X ii 光繞射 (XRD)分析為非晶質(amorphous)結構。這些非晶質結構，經高溫爐在400、450 與500 ℃ 持溫1小時後，XRD的分析顯示: 經400 ℃加熱出現少量銳鈦礦之結晶；經450 ℃加熱後銳鈦礦結晶量大增;而在500 ℃加熱後，出現部份之金紅石結晶。若將加熱前後之二氧化鈦奈米管試樣放入 1.0 M 之KOH溶液中測量光電化學電流，結果光電化學電流由大而小之次序如: 450 ℃ > 400 ℃ > 500 ℃ 試片。 鈦箔在含0.27 M 氟離子及90 vol.%丙三醇之水溶液中，經施加10~30 V五組定電位處理2小時後，得到具有不同管徑之二氧化鈦奈米管試樣，經450 ℃加熱1小時後，同樣條件檢測光電化學電流，結果顯示:定電位在20 V所產製的二氧化鈦奈米管(管徑約77 nm)於450 ℃加熱後之試片，其光電化學電流最高 (約0.12 mA/cm2)約為定電位在10 V所產製的奈米管(管徑約41 nm，光電化學電流為0.03 mA/cm2)之四倍。光電化學電流的大小與奈米管管徑大小有關，但沒有比例關係。
並列摘要
Thin films of self-organized titanium dioxide nanotubes were fabricated by three-electrode electrochemical anodization on polished Ti-foil in 0.08 M~0.36 M fluoride aqueous solution containing 25 vol. %~100 vol. % glycerol under potentials ranging from 10 V to 30 V at room temperature. The effect of experimental parameters on the morphology of thin films was of interest. It was found that a film of nantubes could be fabricated at potentials in the range 10~20 V in an aqueous solution of 0.08 M fluoride without glycerol. In the presence of glycerol, films of nanotubes were fabricated but the diameter of the tubes decreases with increasing the concentration of glycerol. As the glycerol concentration beyond 80 vol. %, a porous film formed instead. Moreover, for the glycerol up to 100 vol. %, only a dense oxide film was formed rather than porous film or films consisting of nanotubes. As the anodization conducted potentiostatically at 20 V in a mixed solution containing 90 vol. % glycerol and 0.17 – 0.36 M fluoride, a porous film or films consisting of nanotubes could. If one conducting anodization under the potential at 10~30 V in 0.27 M fluoride solution iv containing 90 vol. % glycerol, would obtain a film with well organized nanotubes. The diameter of the tubes increases from 41 to 100 with increasing the potential from 10 to 30 V. The films with nanotubes fabricated under these conditions revealed good structure. The films fabricated at 20 V in 0.27 M fluoride solution containing 90 vol. % glycerol for 2 h revealed similar magnitude in diameters. Analysis by x-ray diffraction (XRD), the nanotubes in the as-anodised film were amorphous. Annealing in an atmospheric furnace for 1 h at 400 – 500 ℃, phase transformation may happen. A little of anatase crystals were present in the film annealed at 400 ℃ ; a major amount of anatases in the film annealed at 450 ℃ and a mixing phases consisting of anatase and rutile in the film annealed at 500 ℃. The photocatalytic activity of the annealed TiO2 nanotube was determined in 1 M KOH solution to measure the photo-electrochemical current. The current decreases in the order 450 ℃ > 400 ℃> 500 ℃ annealed specimens. For Ti-foil conducted potentiostatic anodization at 10 - 30 V in 0.27 M fluoride solution containing 90 vol. % glycerol for 2 h, films consisting nanotubes differed in diameters was obtained. All the specimens were annealed at 450 ℃for 1 h and subject to determine the photocatalytic v activity. The photo-electrochemical current is the highest for specimen anodized at 20 V(0.12 mA/cm2) in contrast to that anodized at 10V(0.03 mA/cm2). The diameter of the nanotubes is greater (77 nm)for that anodized at 20 V that at 10 V (41 nm).
參考文獻
延伸閱讀
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