以水熱合及表面改良之二氧化鈦奈米管光催化降解廢水中染料

本研究利用水熱合成法，將商業型二氧化鈦(P-25)於氫氧化鈉溶液中加熱反應並以鹽酸酸洗，製備成二氧化鈦奈米管(TNT)，分析其結構特性與評估其光催化活性。本研究分別探討(1)不同酸洗濃度(0.1 N、0.5 N、1.0 N)製成之TNT；(2)固定酸洗濃度(0.5 N)添加5 ~ 20 wt.% SnO2改質；及(3)固定酸洗濃度(0.1 N)添加5 wt.% SnO2、Al2O3、FeCl2改質。所合成之樣品利用X射線繞射光譜(XRD)、氮氣等溫吸脫附、掃描式電子顯微鏡(SEM)、穿透式及高解析穿透式電子顯微鏡(TEM and HR-TEM)、紫外光-可見光分光光譜(UV-vis)、化學分析電子光譜儀(ESCA)、傅立葉轉換紅外線光譜(FTIR)及光激發螢光光譜(PL)，分析其物化特性。合成樣品光催化活性，利用UV光激發光觸媒，並以亞甲基藍(MB)、剛果紅(CR)、結晶紫(CV)染料，進行脫色反應評估。製成之二氧化鈦奈米管比表面積約為300 ~ 400 m2/g，與起始材料P-25相比，面積增加6 ~ 7倍，二氧化鈦奈米管為中空兩端開口具多層管壁且管長可達100 ~ 200 nm 之管狀結構。0.1 N、0.5 N、1.0 N-TNT對亞甲基藍光催化去除效果約為60 ~ 80% 。 UV光激發TNT產生之電子-電洞對具有再結合之特性，然而，在TNT添加入SnO2製備成複合材料後，以PL(Photoluminescence)分析其電子-電洞對複合率，其SnO2/TNT複合材料確實可達到降低電子-電洞對複合率之效果，此是由於SnO2/TNT彼此產生異質結構之特性，適量添加SnO2的複合材料對亞甲基藍去除效果可高達96%。另外，亞甲基藍光催化活性評估中，TNT之光催化反應動力學，皆符合一階反應動力式。

關鍵字

二氧化鈦奈米管；水熱合成法；異質結構；光催化；染料；光激發螢光光譜

並列摘要

In this study, TNT was synthesized by a hydrothermal method from commercial Degussa P-25 TiO2 nanoparticles. Moreover, SnO2, Al2O3, FeCl2, were utilized as precursors to modify the surface of TNT. Various TNT composites were synthesized by three stages：(1)after the hydrothermal process, the sample was washed with DI water and 0.1 N, 0.5 N or 1.0 N HCl, respectively, (2)different content (5, 10, 20 wt.%) SnO2 mixed P-25 as precursors for producing SnO2/TNT composites, which HCl 0.5 N as acid washing concentration, and (3) 5 wt.% SnO2, Al2O3, FeCl2 and P-25 as precursors for synthesizing Sn-TNT, Al-TNT, and Fe-TNT respectively under 0.1 N HCl treatment. The physical and chemical properties of all prepared samples were analyzed by X-ray diffraction spectra (XRD), nitrogen adsorption-desorption isotherm, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (TEM, HR-TEM), UV-visible spectrometry (UV-vis), electron spectroscopy for chemical analysis (ESCA), fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL). The photocatalytic performance of sample was evaluated through degradation of organic dyes comprised of methylene blue (MB), Congo red (CR), crystal violet (CV). After hydrothermal treatment, the BET surface area of TNT series samples significantly grew from 55 m2/g (raw P-25) to around 300 ~ 400 m2/g, with an increase of 6 ~ 7 times. The TNT exhibited a hollow tubular shapethat both sides open with a diameter around 5 nm and length 100 ~ 200 nm. The MB photodegradation efficiencies of basic TNT samples were around 60% ~ 80% under UV irradiation. In contrast, Sn5-TNT possessed the highest photodegradation efficiency in this study, which was approximately 96% removal. PL analysis result indicated that the rate of recombination of e-/h+ pair was decreased with the presence of SnO2 as precursors. This was due to the hetero junction relation between SnO2 and TNT which was formed during hydrothermal treatment. Furthermore, the MB photodegradation conformed the first-order reactions equation.

並列關鍵字

titanium dioxide nanotubes ； hydrothermal method ； heterostructures ； photocatalysis ； dyes ； photoluminescence

參考文獻

Bavykin, D. V.; Parmon, V. N.; Lapkin, A. A.; Walsh, F. C. (2004) "The effect of hydrothermal conditions on the mesoporous structure of TiO2 nanotubes." Journal of Materials Chemistry 14(22): 3370-3377.

Borges, M. E.; Alvarez-Galvan, M. C.; Esparza, P.; Medina, E.; Martin-Zarza, P.; Fierro, J. L. G. (2008) "Ti-containing volcanic ash as photocatalyst for degradation of phenol." Energy&Environmental Science 1(3): 364-369.

Dagan, G.; Tomkiewicz, M. (1993) "TiO2 aerogels for photocatalytic decontamination of aquatic environments." Journal of Physical Chemistry 97(49): 12651-12655.

Diebold, U. (2003) "The surface science of titanium dioxide." Surface Science Reports 48(5-8): 53-229.

Garnweitner, G.; Antonietti, M.; Niederberger, M. (2005) "Nonaqueous synthesis of crystalline anatase nanoparticles in simple ketones and aldehydes as oxygen-supplying agents." Chemical Communications (3): 397-399.

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以水熱合及表面改良之二氧化鈦奈米管光催化降解廢水中染料

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