Electrochemical Growth of Vertically-Oriented High Aspect Ratio Titania Nanotubes by Rabid Anodization in Fluoride-Free Media
Electrochemical Growth of Vertically-Oriented High Aspect Ratio Titania Nanotubes by Rabid Anodization in Fluoride-Free Media
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DOI：
10.1166/jnn.2009.440
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发表时间：
2009-03-01
影响因子：
--
通讯作者：
Kusunose, Takafumi
中科院分区：
文献类型：
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作者：
Fahim, Narges Fathy;Sekino, Tohru;Kusunose, Takafumi
通过在无氟化物电解质中对钛片进行恒电位阳极氧化，可以生长出垂直取向的高纵横比二氧化钛纳米管束。针对在 HClO4 和 NaCl 电解液中合成二氧化钛纳米管，优化了施加电压等阳极氧化条件。在pH值接近1的0.1M高氯酸中，施加电压20V进行阳极氧化，得到的纳米管长度约为30μm，外径约为40nm，内孔径约为10nm，长径比为750:1。而对于在pH值为4.3的0.3M氯化钠中制备的纳米管，长度在50μm以上，长径比为1250:1。通过在阳极氧化之前用（4 wt% HF+5 M HNO3）溶液预处理钛片，证明了一种提高纳米管均匀性的方法。首次通过在 H2SO4 水溶液中阳极氧化制备了管长超过 500 nm 的二氧化钛纳米管。在 HClO4 电解质中生产的高纵横比二氧化钛纳米管层，在 300 至 550 摄氏度的温度范围内进行了退火研究。 XRD 图案和 TEM 数据证实了在 450 摄氏度退火后形成了具有完美纳米管状结构的单一锐钛矿相。虽然在约 500 摄氏度退火后金红石二氧化钛相开始出现，并且给出了由于纳米管/钛金属之间界面处的底层钛金属氧化而出现金红石相的证据。另一方面，如 SEM 图像所示，纳米管结构在大约 550 摄氏度的退火温度下开始因管变平和卷起特性丧失而被破坏。这些高纵横比纳米管的优异形态及其快速生长速度预示着其在染料敏化太阳能电池、水光解和纳米生物医学等广泛应用中的光明前景。
Vertically-oriented high aspect ratio titania nanotube bundles have been grown by a potentiostatic anodization of titanium sheet in fluoride-free electrolytes. The anodization conditions like the applied voltage were optimized for the synthesis of titania nanotubes in HClO4 and NaCl electrolyte. The resulting nanotubes have a length of about 30 mu m, outer diameter about 40 nm, inner pore size of about 10 nm and the aspect ratio was 750:1 by anodization in 0.1 M perchloric acid of pH similar to 1 at applied voltage of 20 V. While for nanotubes prepared in 0.3 M NaCl of pH 4.3, the length was above 50 mu m with the aspect ratio of 1250:1. A method to increase the uniformity of nanotube was demonstrated by pretreatment the titanium sheet by (4 wt% HF+5 M HNO3) solution prior to anodization. Titania nanotubes were prepared, for the first time, by anodization in aqueous H2SO4 electrolyte alone with tube length above 500 nm. Annealing studies were performed, on high aspect ratio Titania nanotube layers produced in HClO4 electrolyte, in the temperature interval of 300 to 550 degrees C. The XRD patterns and TEM data confirmed the formation of single anatase phase after annealing at 450 degrees C with perfect nanoubular structure. While the rutile titania phase starts to emerege after annealing at about 500 degrees C and the evidence for the appearance of rutile phase due to the oxidation of the underlying Ti metal at the interface between nanotube/Ti-metal was given. On the other hand, the nanotubular structure starts to destroy upon annealing temperature of approximate 550 degrees C by tube flattening and losing of roll-up characteristics as indicated in SEM images. The superior morphology of these high aspect ratio nanotubes and their rapid growth rate foreshadow a bright future in wide applications like dye-sensitized solar cells, water photolysis and nanobiomedical.