二氧化鈦為良好的光觸媒材料,其光催化活性與比表面積大小有直接的關係,本研究將商業用的二氧化鈦(Degussa P-25)和溶膠-水熱法製備的銳鈦礦相二氧化鈦(Anatase)分別利用水熱法製備二氧化鈦奈米管,期望能提高二氧化鈦的比表面積,進而提升其光催化效率。在樣品製備部分,首先將TiO2在NaOH鹼液中充分的攪拌,再用110℃水熱反應,出來先經由水洗,及鹽酸溶液洗濯至不同酸鹼值(pH=10、9、8、7、6、5、4)、烘乾得到二氧化鈦奈米管。 利用穿透式電子顯微鏡(TEM)觀察其粒徑大小及外觀形狀;以X光繞射儀(XRD)分析粉體的結晶相、結晶強度及各相所佔比例﹔以氮氣吸附儀(BET)量測粉體的比表面積大小;最後利用紫外光(254nm)的光源照射,使亞甲基藍(methylene)產生光裂解反應,作為產物二氧化鈦光催化活性分析的指標。 結果顯示所製備的奈米管大幅提升了二氧化鈦的比表面積,且隨清洗的pH值降低,比表面積逐漸增加。二氧化鈦奈米管平均內徑約8-11 nm,平均外徑約10-13 nm,平均長度約80-150 nm,二氧化鈦奈米管的結晶形態與晶格和原二氧化鈦奈米粒有明顯不同,除了銳鈦礦和金紅石的繞射峰外還有代表鈦管的繞射峰被發現。最後藉由亞甲基藍光降解反應發現所製備之二氧化鈦奈米管具有高光催化活性。
One of the important ways to enhance photocatalytic efficiency is to prepare catalyst with high surface area. In this work, by dissolving the commercial titanium dioxide (Degussa-P25) and hydrothermal-prepared TiO2 under the alkali condition, followed by hydrothermal treatment at 110 °C for 48 hr, the titanium dioxide nanotubes were successfully made. The products were characterized by transmission electron microscopy (TEM) for morphology, dimensions and size distribution; by X-ray diffraction (XRD) for crystalline phase; and by Brunauer-Emmett-Teller (BET) for surface area. Based on TEM, the as-prepared TiO2 were observed to be tube-shape with inner diameters of 8-11 nm, outer diameters of 10-13 nm, and average length of 80-150 nm. The BET measurement shows large enhancement in the specific surface area from 40-50 m2/g (DP-25) to 110-330 m2/g. From the XRD result, we observe the disappearance of titanium oxide anatase phase and rutile phase.The photocatalytic activity of as-prepared TiO2 was tested in the reaction of methylene blue photodegradation in aqueous solution.