二氧化矽改質二氧化鈦粉體的製備與性質分析

Preparation and Characterization of Silica Modified Titanium Dioxide

林亞慧(Yai-Hui Lin)

指導教授 ： 蘇昭瑾

國立臺北科技大學/工程學院/有機高分子研究所/碩士(2006年)

摘要

本文研究方向有二，一為自製二氧化矽粉末負載於二氧化鈦製備二氧化矽/二氧化鈦( TiO2-SiO2 )，觀察其結晶是否能產生變化。另一為藉由二氧化矽的負載與洗除製備高比表面積的多孔性二氧化鈦( TiO2-SiO2-NaOH )。本研究以正四丁基氧化鈦為起始物，利用水熱法於不同反應階段中加入不同比例的二氧化矽奈米微粒，合成TiO2-SiO2混合粉末，再經熱濃氫氧化鈉溶液溶解二氧化矽，以製備TiO2-SiO2-NaOH粉末。將所得光觸媒粉末分別利用掃描式電子顯微鏡-能量散佈分析儀（SEM-EDS）分析元素種類與莫耳含量；化學分析能譜儀（ESCA）分析表面組成元素的狀態；穿透式電子顯微鏡(TEM) 測量粒徑大小及分佈；X光繞射儀(XRD)分析結晶相成份與不同晶相所佔比例；並以氮氣吸附儀(BET)量測粉末的表面積大小。
第一部份從EDS、ESCA得知成功的使用水熱法成功製備出二氧化矽/二氧化鈦粉末，從ESCA發現O 1s 的峰形分別由Si－O－Si中氧、Si－O－Ti中氧和Ti－O－Ti中氧產生，其中10 mol %自製二氧化矽負載於不同反應階段中加入所得的TiO2-SiO2，藉TEM發現二氧化矽可以提高其分散性，但晶相並無太大差異。隨著二氧化矽的莫耳比例大幅增加，粒徑大小約13.7 ~ 17.1 nm，直至加入50 mol %的二氧化矽，外觀形貌會形成模糊狀結構，晶相仍為純銳鈦礦(anatase)相結晶，由BET的測量可以得知二氧化矽負載於二氧化鈦的含量愈多，造成其比表面積有逐漸上升的趨勢，推測應是負載於表面的二氧化矽所造成。經亞甲基藍光催化降解反應的應證，其光催化效果最佳為鈦矽莫耳比6：4的二氧化矽/二氧化鈦粉末其對亞甲基藍的反應常數為k=0.092996（min-1），不同莫耳比例的二氧化矽/二氧化鈦光觸媒的光催化效果取決於適當的鈦矽比例。
第二部份觀察ESCA、EDS可以發現到矽元素的吸收訊號大部分減少甚至消失，得知以熱濃氫氧化鈉溶解二氧化矽成功製備出多孔性二氧化鈦，並於ESCA發現O 1s經過分峰後，可發現Si－O－Si中氧和Si－O－Ti中氧的吸收訊號下降。觀察自製二氧化矽洗除後的TiO2-SiO2-NaOH的晶相仍為純銳鈦礦(anatase)相，之後將不同莫耳比例二氧化矽洗除後的TiO2-SiO2-NaOH，晶相仍未改變，並藉由TEM可觀察到洗鹼後顆粒彼此間缝隙較洗鹼前大，粒徑大小約15.1 ~ 18.0 nm，但隨著二氧化矽莫耳比例增加會導致粉末其形貌仍呈模糊狀，從比表面積得知隨著二氧化矽莫耳比從10 mol %至比50 mol %有逐漸上升的趨勢，但隨著二氧化矽莫耳比從50 mol %至70 mol %其比表面積有明顯下降的趨勢，歸因於洗除二氧化矽後的表面呈凹凸不平狀增加進而使表面的孔洞變小，由氮氣等溫吸附脫附曲線的分析可得知多孔性二氧化鈦粉末的等溫吸附類型皆為中孔洞多孔性固體。並經亞甲基藍光催化裂解反應的應證，其光催化效果最佳為鈦矽莫耳比5：5的多孔性二氧化鈦粉末其對亞甲基藍的反應常數為k=0.150557（min-1），所得光催化結果為比表面積對光催化反應有極大的影響，顯示不同莫耳比例的多孔性二氧化鈦光觸媒的光催化效果受控於比表面積。

關鍵字

二氧化矽/二氧化鈦 ； 多孔性二氧化鈦 ； 亞甲基藍 ； 改質 ； 高比表面積

並列摘要

The purpose of this thesis is twofold：first, the titania/silica mixed oxide (TiO2-SiO2) mixed oxide has been made using the self-prepared SiO2 particles and to study the changes of TiO2 phases upon SiO2 loading. Second, TiO2 nanoparticles with enhanced surface area were synthesized under the interference followed by removal of SiO2. The mixed oxide, SiO2/TiO2 samples with various mol% Si at different reaction step, were prepared by a hydrothermal procedure using titanium tetra-n-butoxide as Ti-precursor. After condensation and calcination heat treatment, the SiO2/TiO2 nanoparticles (TiO2-SiO2) were obtained. To achieve the purpose of obtaining the high-surface-area TiO2 (TiO2-SiO2-NaOH), the SiO2 was removed subsequently using hot aqueous NaOH solution treatmemt at 60 ℃. The as-prepared TiO2 nanoparticles were characterized by energy dispersive spectrometer (SEM-EDS) for elemental content, by electron spectroscopy for chemical analysis (ESCA) for chemical state, by transmission electron microscopy (TEM) for dimensions and distribution, by X-ray diffraction (XRD) for the crystal structure, and by nitrogen gas adsorption/desorption isotherm for analysis of surface area and pore size distribution.
It is found that the obtained TiO2-SiO2 shows a broad O 2p ESCA peak which can be deconvoluted into three peaks corresponding to the formation of Ti-O-Ti, Si-O-Si, and Si-O-Ti bonds. The SiO2/TiO2 nanoparticles (10 mol%) show similar particle shape with loose and discrete structure, and it possess phases of anatase. Distribution of particle size of TiO2-SiO2 over a range was observed with the average size of 13.7 ~ 17.1 nm. When the silica content was about to 50 mol %, similar particle shape remained with agglomerated and blurred morphology. The BET measured surface area increased as well. The photocatalytic performance of TiO2-SiO2 is dependent on the silica content. At 60 mol% of silica content, the TiO2-SiO2 nanostructures exhibit the best photocatalytic performance in decomposition of methylene blue under the UV irradiation.
As show with second part, while the Si signal drops after NaOH treatment on the
results of EDS and ESCA. The such kind of high surface area and porous TiO2
significantly was confirmed after NaOH treatment by EDS and ESCA. The base TiO2 increases surface area of such-prepared. No significant change of XRD can be found within experimental error. Distribution of particle size of TiO2-SiO2 over a range was observed with the average size of 15.1 ~ 18.0 nm. The porous TiO2 nanostructures with enhanced surface area also exhibit enhanced photocatalytic performance in decomposition of methylene blue under the UV irradiation. At 50 mol% of silica content, the TiO2-SiO2-NaOH nanostructures exhibit the best photocatalytic performance in decomposition of methylene blue under the UV irradiation.

並列關鍵字

Titania/silica ； Porous titania ； Modified ； Methylene blue ； Specific surface

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