Effect of heat treatment on the crystal phase composition, semiconducting properties and photoelectrocatalytic color removal efficiency of TiO2 nanotubes arrays
Effect of heat treatment on the crystal phase composition, semiconducting properties and photoelectrocatalytic color removal efficiency of TiO2 nanotubes arrays
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DOI：
10.1016/j.electacta.2014.06.056
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发表时间：
2014-09-10
影响因子：
6.6
通讯作者：
Gonzalez, Ignacio
中科院分区：
文献类型：
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作者：
Acevedo-Pena, Prospero;Carrera-Crespo, J. Edgar;Gonzalez, Ignacio
在0.05 M NH4F、0.05 M乙二醇（1%水）电解液中，30V恒电位阳极氧化2小时生长TiO2纳米管薄膜。TiO2阳极膜在不同温度下热处理0.5 h，在相同温度（600℃）下热处理不同时间长度。通过XRD测量表征薄膜的晶体结构，发现在325℃时出现锐钛矿相。在这些薄膜中形成的锐钛矿较好地向[001]方向取向，这似乎是其即使在800℃等高温下也能保持热稳定性的原因。另一方面，在高于或等于600℃的温度下检测到金红石，同时阻挡层增厚。透射角x射线衍射（GAXRD）结果表明，即使在700℃时，金红石相主要在薄膜的内部形成，而锐钛矿相仍存在于纳米管晶体（外层）中。提高热处理温度可以改善靛蓝胭脂红的脱色效果，从而使电子在薄膜中更好地传递；然而，金红石的出现大大降低了薄膜的光电化学性能。Mott-Schottky测量表明，含金红石的薄膜比仅由锐钛矿组成的薄膜具有更负的平带电位，这使我们提出，在管的底部通过热氧化形成的金红石薄膜作为光生电子向钛衬底传输的屏障，增加了薄膜中的复合。(C) 2014 Elsevier Ltd.版权所有。
TiO2 nanotube films were grown by potentiostatic anodization at 30V during 2 hours in 0.05 M NH4F in ethylene glycol (1% water) electrolyte. TiO2 anodic films were heat treated at different temperatures during 0.5 h, and during different time length at the same temperature (600 degrees C). Crystal structure of the film was characterized by XRD measurements showing the appearance of anatase phase at 325 degrees C. The anatase formed in these films was preferably oriented towards [001] direction, which seems to be the origin of its thermal stability even at elevated temperatures, such as 800 degrees C. On the other hand, rutile was detected at temperatures higher than or equal to 600 degrees C, simultaneously with the thickening of the barrier layer. Glancing angle X-ray diffraction (GAXRD) measurements showed that rutile is mainly formed in the inner part of the film, meanwhile anatase phase remains in nanotube crystals (outer part), even at 700 degrees C. Indigo carmine decoloration was improved by increasing the heat treatment temperature which provided a better electron transport through the film; however, the appearance of rutile in the film drastically decreased the photoelectrochemical performance. Mott-Schottky measurements showed that rutile containing films have a more negative flat band potential than those only composed of anatase, which allowed us to propose that rutile film formed in the base of the tubes by thermal oxidation acts as a barrier for the transport of photogenerated electrons towards titanium substrate increasing the recombination in the film. (C) 2014 Elsevier Ltd. All rights reserved.