热处理温度对TiO2/SiO2复合气凝胶光催化性能的影响

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刘朝辉, 侯根良, 苏勋家, 郭锋, 肖舟, 贾海鹏. 热处理温度对TiO₂/SiO₂复合气凝胶光催化性能的影响 . 无机材料学报, 2012, 27(10): 1079-1083
LIU Zhao-Hui, HOU Gen-Liang, SU Xun-Jia, GUO Feng, XIAO Zhou, JIA Hai-Peng. Effects of Heat Treatment Temperature on Photocatalytic Activity of TiO₂/SiO₂ Composite Aerogels . Journal of Inorganic Materials, 2012, 27(10): 1079-1083 复制到剪切板

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热处理温度对TiO₂/SiO₂复合气凝胶光催化性能的影响

刘朝辉, 侯根良, 苏勋家, 郭锋, 肖舟, 贾海鹏

第二炮兵工程大学, 西安 710025

刘朝辉(1982-), 男, 博士研究生. E-mail:lzh007901@163.com

摘要

采用溶胶-凝胶法在常压下经不同温度热处理制备了TiO₂/SiO₂复合气凝胶光催化剂, 利用XRD、TGA和BET等手段对其微观结构进行表征, 以甲基橙溶液光催化降解实验评价其光催化性能, 研究了热处理温度对TiO₂/SiO₂复合气凝胶的微观结构及光催化性能影响规律. 结果表明: 随着热处理温度升高, TiO₂/SiO₂复合气凝胶中锐钛矿结晶度升高, 晶粒尺寸增大, 比表面积减小, 使TiO₂/SiO₂复合气凝胶对甲基橙溶液的光催化降解活性呈现先升后降的变化趋势. 当热处理温度为700℃左右, 紫外光照20 min TiO₂/SiO₂复合气凝胶对甲基橙溶液的降解率达到95.4%.

关键词: TiO₂/SiO₂复合气凝胶; 热处理温度; 微观结构; 光催化性能

中图分类号:TB34 文献标志码:A 文章编号:1000-324X(2012)10-1079-05

Effects of Heat Treatment Temperature on Photocatalytic Activity of TiO₂/SiO₂ Composite Aerogels

LIU Zhao-Hui, HOU Gen-Liang, SU Xun-Jia, GUO Feng, XIAO Zhou, JIA Hai-Peng

The Second Artillery University, Xi#cod#x02019;an 710025, China

Abstract

TiO₂/SiO₂ composite aerogels were prepared by Sol-Gel method at ambient pressure and heat-treated at different temperatures. The microstructure of TiO₂/SiO₂ composite aerogels was characterized by X-ray diffraction (XRD), thermo gravimetric analyzer (TGA) and N₂ adsorption-desorption. The photocatalytic activity was evaluated by means of photocatalytic degradation of methyl orange under UV irradiation. The effects of heat treatment temperatures on microstructure and photocatalytic activity were investigated. With the increase of heat treatment temperature, the crystallization of anatase and the anatase grain size increase, however, the specific surface area decreases. As a result, the photocatalytic activity of TiO₂/SiO₂ composite aerogels is enhanced initially, then decreases with the increase of heat treatment temperature. When the heat treatment temperature is set at about 700℃, the degradation ratio of methyl orange on the TiO₂/SiO₂composite aerogels reaches 95.4% after irradiated by ultraviolet light for 20 min.

Keyword: TiO₂/SiO₂ composite aerogels; heat treatment temperature; microstructure; photocatalytic activity

Show Figures

纳米TiO₂具有光活性高、催化性能强、无毒、价格低廉等优点, 是一种优良的光催化剂材料, 在光催化领域得到广泛的应用^{[ 1, 2, 3]}, 其中TiO₂气凝胶比表面积高、吸附效率高受到人们的广泛关注^{[ 4, 5, 6]}. 研究者发现, 与SiO₂复合得到的TiO₂/SiO₂复合气凝胶光催化剂比TiO₂气凝胶具有更好的光催化性能^{[ 7, 8]}, 并进行了深入研究. 甘礼华等^{[ 9]}发现当SiO₂与TiO₂摩尔比在1~5之间, TiO₂/SiO₂气凝胶的光催化性能会随着SiO₂含量增加而增强; 本课题组研究也发现^{[ 10]}, 随SiO₂含量增加, TiO₂/SiO₂气凝胶的光催化降解活性呈现先升后降的变化趋势.

目前, TiO₂/SiO₂复合气凝胶的制备工艺研究已较为成熟, 不仅可以通过超临界干燥得到结构较好的TiO₂/SiO₂复合气凝胶^{[ 11]}, 而且可以通过改进工艺, 在常压下制备高比表面积的TiO₂/SiO₂复合气凝胶^{[ 9, 12]}, 从而大幅降低成本. TiO₂/SiO₂复合气凝胶在应用之前通常需要进行后续热处理, 而后续热处理会改变复合气凝胶的各方面性能, 尤其是会对光催化性能产生显著影响, 但是关于热处理产生影响的内在机理研究报道还较少. 本工作重点探索热处理温度对TiO₂/SiO₂气凝胶微观结构的影响规律, 探讨热处理温度对TiO₂/SiO₂复合气凝胶光催化性能的影响机理.

1 实验部分

1.1 TiO₂/SiO₂复合气凝胶的制备

TiO₂/SiO₂复合气凝胶的制备方法与文献[10]报道相同.

SiO₂溶胶制备: 将体积比为10:13:2.4的正硅酸乙酯、无水乙醇、去离子水均匀混合, 用硝酸调节溶液pH值为0.6, 353 K下搅拌30 min, 得到SiO₂溶胶, 室温下静置备用;

TiO₂溶胶制备: 将体积比为1:2的钛酸丁酯和无水乙醇均匀混合, 用硝酸调节pH值为1, 得到溶液A, 将体积比为4:1的无水乙醇和去离子水均匀混合, 用硝酸调节pH值为0.6, 得溶液B, 再将溶液A与溶液B按体积比4.8:1.0混合, 强烈搅拌20 min, 即得到TiO₂溶胶.

TiO₂/SiO₂复合气凝胶的制备: 在强搅拌下将SiO₂溶胶用滴管缓慢滴加到TiO₂溶胶中, 并加入适量甲酰胺, 室温下静置直至凝结, 得到复合醇凝胶, TiO₂溶胶、SiO₂溶胶与甲酰胺的体积比为43:12:1.醇凝胶陈化12 h, 再用无水乙醇浸泡48 h, 其间更换无水乙醇4次, 之后常温下自然干燥, 得到TiO₂/SiO₂复合气凝胶. 复合气凝胶分别在500℃、600℃、700℃、800℃及900℃下热处理3 h.

1.2 表征方法

利用D/max-rB型X射线衍射仪(Cu Kα, 40kV)分析气凝胶的晶型结构和晶粒尺寸, 利用TGA601热重分析仪分析气凝胶样品的热稳定性, ASAP2010吸附测定仪分析气凝胶的比表面积和孔结构.

1.3 光催化实验

分别向1 L pH值为3、浓度为20 mg/L的甲基橙溶液中加入2.5 g TiO₂/SiO₂复合气凝胶光催化剂, 并避光搅拌, 使催化剂在反应液中分散均匀且达到吸附平衡, 以型号为GGZ-300的300 W紫外高压汞灯作为光源, 期间每10 min取一次样, 用UV755紫外可见分光光度计在464 nm波长处测定甲基橙溶液样品的吸光度变化. 因甲基橙溶液在0~30 mg/L的低浓度范围内, 其浓度与吸光度呈现出较好线性关系, 故降解率可表示为 D%=[( A₀- A)/ A]×100%, 其中, A₀为甲基橙溶液达到吸附平衡时的初始吸光度; A为甲基橙溶液降解过程中的吸光度.

2 实验结果与讨论

2.1 XRD分析

图1是不同热处理温度的TiO₂/SiO₂复合气凝胶样品的XRD图谱, 从图中可知, 500℃热处理时衍射峰宽而平, 对应的全为锐钛矿相, 其结晶度较低. 随着热处理温度的升高, 锐钛矿相结晶度越来越高, 700℃热处理时已较为完全, 但800℃热处理时仍然没有金红石相出现, 900℃热处理时为锐钛矿相和金红石相共存, 且根据公式 W_A=1/(1+1.265 I_R/ I_A)^{[ 13]}( W_A为锐钛矿相的质量分数, I_A和 I_R分别为锐钛矿相和金红石相的最强衍射峰峰面积)计算出样品中锐钛矿相的质量分数为71%.

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	图1 不同温度热处理的TiO₂/SiO₂复合气凝胶的XRD图谱Fig. 1 XRD patterns of TiO₂/SiO₂ composite aerogels calcined at different temperatures

图2是根据谢乐公式计算得到的不同温度热处理的锐钛矿晶粒尺寸. 随着热处理温度升高, 锐钛矿的晶粒尺寸不断变大. 热处理温度从500→600℃、600→700℃、700→800℃和800→900℃, 锐钛矿相晶粒尺寸分别增大了0.76、5.76、1.26和12.02 nm. 这说明过高的煅烧温度会导致部分TiO₂纳米粒子在界面出现部分熔化而粘结, 并最终出现粒子团聚和长大, 温度达到900℃时表现尤为明显. 与热处理纯TiO₂气凝胶^{[ 14]}相比, TiO₂/SiO₂复合气凝胶中锐钛矿相转化为金红石相的相变温度提高了近400℃, 锐钛矿相晶粒尺寸经700℃热处理减小了75.4%, 而且经900℃热处理仍保持在较小尺寸. 这说明TiO₂由锐钛矿向金红石相转变是从团聚的锐钛矿粒子内部界面开始的, 并随着热处理温度升高, 逐渐从内部界面向周围扩展, 而SiO₂以Ti-O-Si化学键形式与TiO₂结合, 有效地阻碍了TiO₂纳米晶的团聚, 进而提高其相变温度, 使复合气凝胶具有较好的热稳定性.

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	图2 热处理温度对TiO₂/SiO₂复合气凝胶中锐钛矿晶粒尺寸的影响Fig. 2 Effects of heat treatment temperature on crystal size of anatase in TiO₂/SiO₂ composite aerogels

2.2 TGA分析

图3为TiO₂/SiO₂复合气凝胶的TGA曲线, 测试升温范围为0~800℃. 样品的失重分为三个阶段: 从室温~142.28℃, 失重速度较快, 在78.18℃处达到最快, 失重率为10.59%, 这主要由于凝胶中的吸附水和乙醇的脱附释放造成的; 从142.28~404.54℃, 失重速度也较快, 在263.97℃处达到最快, 失重率为29.16wt%, 主要由于部分残余的未水解的正硅酸乙酯等有机物的燃烧与热分解造成的; 从 404.54~799.27℃, 基本上不失重, 表明有机物已全部除去.

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	图3 TiO₂/SiO₂复合气凝胶的TGA曲线Fig. 3 TGA curves of TiO₂/SiO₂ composite aerogels

2.3 BET分析

图4是500℃、700℃和900℃煅烧处理的TiO₂/SiO₂复合气凝胶样品在77.35 K时的N₂吸附-脱附等温线. 依据IUPAC的分类标准, 它们都属于第IV类等温线, 存在迟滞环, 这类等温线主要出现在孔径为2~50 nm的介孔材料中. 图4的迟滞回线均属于H1型, 产生迟滞回线是毛细凝聚作用的结果. H1型迟滞回线表明不同温度热处理的复合气凝胶样品中的介孔主要是两端开口的管径分布均匀的圆筒状孔, 且孔径分布较均匀. 不同温度煅烧样品的孔径都集中在2.5~10 nm之间, 适宜作光催化剂.

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	图4 不同温度热处理得到TiO₂/SiO₂复合气凝胶的N₂吸附- 脱附等温线Fig. 4 N₂ adsorption-desorption isotherms of TiO₂/SiO₂ composite aerogels calcined at different temperatures

图5是不同煅烧温度对样品的比表面积及平均孔径的影响规律. 随着煅烧温度的升高, 样品的比表面积和平均孔径均逐渐减小, 与500℃煅烧的样品相比, 900℃煅烧样品的比表面积减小了60.9%, 平均孔径减小了44.8%, 这说明热处理温度对样品的比表面积和平均孔径产生的影响均较大. 这主要是由于高温热处理下TiO₂纳米晶发生烧结而团聚, 并且随温度升高烧结不断加剧, 使复合气凝胶的三维多孔结构发生严重坍塌, 导致比表面积和平均孔径显著减小.

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	图5 热处理温度对TiO₂/SiO₂复合气凝胶的比表面积、平均孔径的影响Fig. 5 Effects of heat treatment temperature on specific surface area and average pore diameter of TiO₂/SiO₂ composite aerogels

2.4 光催化性能分析

图6反映了在紫外光照10、20和30 min下, 热处理温度与甲基橙溶液降解率的关系. 样品热处理温度从500℃升高到900℃时, 甲基橙溶液降解率总体上先升后降, 在700℃处理达到最大; 900℃处理样品对应的降解率比800℃处理略高, 但比600℃处理要低, 这说明锐钛矿相和金红石共同存在时, 光催化性能会有一定程度提高, 与纯TiO₂气凝胶情况类似^{[ 14]}, 但这种影响不显著. 紫外光照10、20和30 min时, 500℃热处理样品对甲基橙溶液降解率分别为42.9%、67.1%和87.1%, 700℃热处理的对应的甲基橙溶液降解率上升为71.3%、95.4%和99.2%; 900℃热处理的又下降为63.5%、82%和90.4%. 由此可见, 适当热处理温度能显著提高TiO₂/SiO₂复合气凝胶的光催化性能, 最佳热处理温度在700℃左右, 此时TiO₂晶化程度较高, 而且晶粒较小, 比表面积降低幅度也不大.

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	图6 不同温度热处理的TiO₂/SiO₂复合气凝胶对甲基橙溶液的光催化降解率Fig. 6 Photocatalytic degradation ratio of methyl orange with TiO₂/SiO₂ composite aerogels calcined at different temperatures

分析热处理温度对TiO₂/SiO₂复合气凝胶的结构及光催化性能的影响结果可知, 热处理温度对TiO₂/SiO₂复合气凝胶的晶型、晶粒尺寸和比表面积影响程度较大, 从而导致光催化性能存在显著差异. 非晶态的TiO₂/SiO₂复合气凝胶不具有光催化性能, 当热处理温度从室温升高至700℃时, 复合气凝胶中锐钛矿结晶度越来越高, 结晶越来越完善, 使光催化性能不断提高. 但当热处理温度达到700℃以上时, 过高的热处理温度会使复合气凝胶的晶粒尺寸显著增大, 对于纳米TiO₂颗粒来说, 光生电子迁移到晶面的时间 τ可由下式估算^{[ 15]}:

τ = r/π² D (1)

式中: r为TiO₂纳米晶粒的半径; D为载流子的扩散系数.

由式(1)可知, 随着纳米TiO₂粒径的增大, 其受紫外光激发产生的光生电子由晶粒内部迁移到晶粒表面所需时间越长, 光生电子和光生空穴的复合几率就越高, 到达表面的光生电子就越少, 从而催化活性越低.

过高的热处理温度也会使比表面积显著减小, 降低光催化活性. 因为TiO₂/SiO₂复合气凝胶对甲基橙溶液的催化降解模式是吸附和光催化氧化共同作用, 比表面积的减小, 降低了样品与甲基橙的接触面积, 吸附在TiO₂/SiO₂复合气凝胶表面以及孔洞内部的甲基橙与·OH结合的几率降低, 不利于发挥TiO₂的光催化活性.

3 结论

1) 随着热处理温度升高, TiO₂/SiO₂复合气凝胶中锐钛矿结晶度升高, 有利于增强光催化活性, 700℃热处理时晶化已较为完全.

2) 随着热处理温度升高, TiO₂/SiO₂复合气凝胶中TiO₂晶粒尺寸增大, 比表面积减小, 热处理温度高于700℃时, 变化尤为明显, 导致光催化性能降低.

3) 热处理可通过改变结晶度、晶粒尺寸和比表面积来显著影响TiO₂/SiO₂复合气凝胶的光催化性能. 随着热处理温度升高, 复合气凝胶的光催化性能呈现出先升后降趋势, 热处理温度为700℃左右, 复合气凝胶的光催化性能最佳.

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[12]	WANG Yu-Dong, CHEN Long-Wu, GAN Li-Hua, et al. Preparation and characterizations of monolithic TiO₂/SiO₂ aerogels obtained by non-supercritical drying method. Chemical Journal of Chinese Universities, 2004, 25(2): 325-329. [本文引用:1] [JCR: 0.856] [CJCR: 0.949]
[13]	Surolia P K, Tayade R J, Jasra R V. Effect of anions on the photocatalytic activity of Fe(III) salts impregnated TiO₂. Ind. Eng. Chem. Res. , 2007, 46(19): 6196-6203. [本文引用:1] [JCR: 2.206]
[14]	LIU Zhao-Hui, SU Xun-Jia, HOU Gen-Liang, et al. Efect of calcination temperature on photocatalytic properties of titania aerogels. Journal of Functional Materials, 2007, 38(Suppl. ): 2489-2491. [本文引用:2] [CJCR: 0.588]
[15]	Zhang H P, Lü M K, Liu S W, et al. Preparation and photocatalytic property of perovskite Bi₄Ti₃O₁₂ films. Materials Chemistry and Physics, 2009, 114(2/3): 716-721. [本文引用:1] [JCR: 2.072]

2010

2.43

0.0

Building and Environment. 2010, 45(8):1747-1754 DOI:10.1016/j.buildenv.2010.01.024

Photocatalytic oxidation for antimicrobial control in built environment: a brief literature overview

Abstract

This paper presents a literature review of the status of research on indoor antimicrobial control by photocatalytic oxidation (PCO). The review and discussion concentrate on (a) the PCO disinfection mechanisms; (b) different kinetic experiments and models; (c) the dependence of inactivation rate on some key influencing factors; (d) an overview of various PCO reactors and their application performance reported in the literature. Major conclusions of the overview and recommendations for future work include (a) several reaction pathways of PCO antimicrobial process were reported, but the decomposition of cell after inactivation needs to be fully understood; (b) kinetic experiments were carried out to determine the dependence of antimicrobial reaction rate on some influencing factors. However, the results from different researchers were not comparable to each other, due to differences of reaction parameters and the empirical models used; (c) various types of reactors were adopted to determine the efficiency of PCO on the rate of biological aerosol removal from air flow. There is a need to develop an empirical model for PCO reactor combining the particle dynamics and photocatalytic oxidation for bioaerosols; (d) there is a need to develop more stable and reliable photocatalysts, and further develop performance assessment protocol in both laboratory and the field.

... 纳米TiO₂具有光活性高、催化性能强、无毒、价格低廉等优点, 是一种优良的光催化剂材料, 在光催化领域得到广泛的应用^[1,2,3], 其中TiO₂气凝胶比表面积高、吸附效率高受到人们的广泛关注^[4,5,6] ...

2009

5.228

0.0

Environ. Sci. Technol.. 2009, 43(14):5423-5428

Highly thermal stable and highly crystalline anatase TiO₂ for photocatalys

Li Wei , Bai Yang , Liu Chang

2010

4.814

0.0

J. Phys. Chem. C. 2010, 114(17):7940-7948

One-step synthesis of bifunctional TiO₂ catalysts and their photocatalytic activity

Fang Jun , Shi Fucheng , Bu Jing

1993

0.0

The Journal of Physical Chemistry. 1993, 97(49):12651-12655

TiO₂ aerogels for photocatalytic decontamination of aquatic environments

Dagan G , Tomkiewicz M

2001

0.856

0.949

Chemical Journal of Chinese Universities. 2001, 22(11):1916-1918

Preparation and characterization of monolithic TiO₂ aerogel

Department of Chemistry, Tongji University, Shanghai 200092, China

Monolithic TiO₂ aerogels have been prepared from titanium n butoxide by sol-gel process and supercritical drying technique, and the structural properties of the aerogel samples have been characterized by means of SEM, TEM, XRD, IR, BETand pore distribution analysis. The results indicated that the optimum condition for preparing monolithic TiO₂ aerogels was n-[Ti(OC₄H₉)₄]: n-(C₂H₅OH): n-(H₂O): n-(HNO₃)=1:18.3:3.75:0.14. The final aerogels which consist of colloidal particles with diameters of about 5 nm were found to be with coherent uniform size and low density solid inorganic materials with porosity of about 90%, and contained mesopore in the range of 10-20 nm. The monolithic TiO₂ aerogels were of the pure amorphous form at room temperature, which would be converted into anatase and then into rutile by increasing the temperature of heat treatment.

2001

0.531

1.106

Journal of Inorganic Materials. 2001, 16(5):846-852

Formation process of monolithic TiO₂ aerogels and its effect on aerogels#cod#x02019; properties

Department of Chemistry Tongji University; Shanghai 200092; China

Monolithic TiO₂ aerogels were prepared by the process of hydrolysis and condensation of tetrabutyl titanate as precursor, and following by supercritical
drying. The effect of the preparing conditions and gelation process on macroscopic properties of monolithic TiO₂ aerogels was studied. The results indicate
that the final aerogels, which consist of amorphous TiO₂ with particle sizes of about 4-6nm, are uniform continuous network structural superlight monolithic materials with high porosity. The monolithic TiO₂ aerogels with different densities
and properties can be prepared by controlling the conditions of gelation process vigorously.

研究了ＴｉＯ_２气凝胶形成过程中制备条件和凝胶化过程对块状ＴｉＯ_２气凝胶宏观性质的影响，结果表明所得气凝胶是由粒度约为４～６ｎｍ的ＴｉＯ_２非晶态微粒连结而成的具有均匀网络结构的多孔性超轻量级块状材料，通过严格控制制备过程中凝胶化过程的条件及状态，可以获得不同密度不同品质的ＴｉＯ_２气凝胶．

2006

3.607

0.0

J. Phys. Chem. B. 2006, 110(17):8587-8592

New route to synthesize highly active nanocrystalline sulfated titania-silica: synergetic effects between sulfate species and silica in enhancing the photocatalysis efficiency

Xie C , Yang Q J , Xu Z L

... 研究者发现, 与SiO₂复合得到的TiO₂/SiO₂复合气凝胶光催化剂比TiO₂气凝胶具有更好的光催化性能^[7,8], 并进行了深入研究 ...

1999

0.0

Nanostructured Materials. 1999, 11(8):1313-1318

Preparation and photocatalytic activity of TiO₂-SiO₂ binary aerogelsv

Deng Z S , Wang J , Zhang Y L

... 研究者发现, 与SiO₂复合得到的TiO₂/SiO₂复合气凝胶光催化剂比TiO₂气凝胶具有更好的光催化性能^[7,8], 并进行了深入研究 ...

2005

0.92

0.6477

Chinese J. Chem. Eng.. 2005, 13(6):758-763

Preparation of TiO₂/SiO₂ aerogels by non-supercritical drying method and their photocatalytic activity for degradation of pyridine

Department of Chemistry, Tongji University, Shanghai 200092, China

TiO2/SiO2 aerogels with different molar ratio of SiO2/TiO2 were prepared via non-supercritical method using tetrabutyl titanate and silica sols as raw materials. The samples were characterized by TEM, SEM, BET, IR, XRD and so on. The results indicate that the BET surface area of TiO2/SiO2 aerogels calcined at 550℃ which consisted of anatase structure of TiO2 with narrow distribution pores of 5-25 nm is as high as 357.89 m^2·g^-1. For the photocatallytic degradation of pyridine, the catalytic activities of TiO2/SiO2 aerogels are much higher than that of TiO2 powder. The photocatalytic activity of TiO2/SiO2 aerogels calcined at 800℃ is the optimum. The higher the content of SiO2, the higher the photocatalytic activity of TiO2/SiO2 aerogels. The cost for preparation of the aerogels is greatly reduced by using non-supercritical drying method, and the aerogels are hopefully applied in the treatment of industrial waste water such as coking effluent treatment.

... 甘礼华等^[9]发现当SiO₂与TiO₂摩尔比在1~5之间, TiO₂/SiO₂气凝胶的光催化性能会随着SiO₂含量增加而增强 ...

... 目前, TiO₂/SiO₂复合气凝胶的制备工艺研究已较为成熟, 不仅可以通过超临界干燥得到结构较好的TiO₂/SiO₂复合气凝胶^[11], 而且可以通过改进工艺, 在常压下制备高比表面积的TiO₂/SiO₂复合气凝胶^[9,12], 从而大幅降低成本 ...

2010

0.531

1.106

Journal of Inorganic Materials. 2010, 25(9):911-915 DOI:10.3724/SP.J.1077.2010.00911

Effects of silicon content on microstructure and photocatalytic activity of TiO₂/SiO₂ composite aerogels

(The Second Artillery Engineering College, Xi’an 710025, China)

TiO₂/SiO₂ composite aerogels with different silicon contents were prepared by Sol-Gel method. The microstructure of TiO₂/SiO₂composite aerogels was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), X-ray photoelectron spectroscope (XPS) and N₂ adsorption-desorption, the photocatalytic activity was evaluated by means of photocatalytic degradation of methyl orange under UV irradiation. The effects of silicon content on microstructure and photocatalytic activity were investigated. The results show that Ti-O-Ti bonds, Si-O-Si bonds and Ti-O-Si bonds all form in TiO₂/SiO₂composite aerogels, which make composite aerogels have smaller crystal size, higher specific surface area and better thermal stability. As the silicon content increases, the specific surface area increases, however the anatase grain size, the anatase content and the average pore diameter reduce. At higher silicon content level, the photocatalytic activity of composite aerogels for methyl orange is improved initially, then decreases with the increase of silicon content. Proper silicon content can refine the structure and improve photocatalytic activity of TiO₂/SiO₂composite aerogels dramatically, and the optimal silicon content is about 9wt%.

采用溶胶-凝胶法制备了不同Si含量的TiO₂/SiO₂复合气凝胶. 利用XRD、FTIR、XPS和BET等手段表征了复合气凝胶组织结构, 以甲基橙溶液光催化降解实验评价其光催化活性, 研究了Si含量对TiO₂/SiO₂复合气凝胶的结构及光催化性能影响规律. 结果表明: TiO₂/SiO₂复合气凝胶中Ti-O-Ti、Si-O-Si和Ti-O-Si键相互交织, 使复合气凝胶具有小晶粒尺寸、高比表面积和高热稳定性. 随着Si含量增大, TiO₂/SiO₂复合气凝胶中TiO₂晶粒尺寸减小, TiO₂结晶度降低, 比表面积增大, 平均孔径减小, 且TiO₂/SiO₂复合气凝胶对甲基橙溶液的光催化降解活性呈现先升后降的变化趋势. 适当Si含量能显著改善TiO₂/SiO₂复合气凝胶的结构和光催化性能, Si含量最佳值在9wt%附近.

... 本课题组研究也发现^[10], 随SiO₂含量增加, TiO₂/SiO₂气凝胶的光催化降解活性呈现先升后降的变化趋势 ...

2000

0.0

0.1322

2004

0.856

0.949

Chemical Journal of Chinese Universities. 2004, 25(2):325-329

Preparation and characterizations of monolithic TiO₂/SiO₂ aerogels obtained by non-supercritical drying method

Department of Chemistry, Tongji University, Shanghai 200092, China

TiO₂/SiO₂ aerogels, a special kind of mesoporous materials, is comprised of linked nano-sized pores which possess a high photocatalytic activity. In our work, sols of TiO₂ and SiO₂ were prepared separately and mixed to prepare TiO₂/SiO₂ gels. Formamide as the drying control chemical additive(DCCA) was added to stiffen the microstructure of TiO₂/SiO₂ gels. TiO₂/SiO₂ gels were immersed in the tetraethoxysilane/ethanol solutions, exchanged pore fluid with low surface tension solvent, aged and then dried in different stages to realize the preparation of TiO₂/SiO₂ aerogels by non-supercritical drying. The resultant aerogels were transparent or translucent, highly porous and low density foams with bulk densities in the range of 0.4—0.9 g/cm³ and porosity about 80%—95%. The TiO₂/SiO₂ aerogels were comprised of dispersed TiO₂ and SiO₂ particles. The average particle diameter is about 10 nm, and average pore diameter is tens of nanometers. The phase of SiO₂ is amorphous and TiO₂ remains anatase microcrystal until 800 ℃. The effects of molar ratio of TiO₂ to SiO₂ and amount of formamide on sol-gel process and aerogel properties were also discussed.

分别通过TiO₂和SiO₂的单独溶胶和TiO₂/SiO₂复合凝胶,并添加干燥控制化学添加剂甲酰胺,形成比较完善的凝胶网络结构,同时通过正硅酸乙酯的乙醇溶液浸泡,低表面张力溶剂替换和分级陈化以及干燥等步骤,实现了块状TiO₂/SiO₂复合气凝胶的非超临界干燥制备.所得TiO₂/SiO₂气凝胶为无色或乳白色轻质块状多孔固体,表观密度约0.4～0.9g/cm³,孔隙率约80%～95%.它由直径约10nm的TiO₂和SiO₂微粒相互分散复合而成,孔洞直径约几十纳米.其相态SiO₂为无定形,TiO₂为锐钛矿晶型.随着焙烧温度的升高,直到800℃不发生相变化.

2007

2.206

0.0

Ind. Eng. Chem. Res. 2007, 46(19):6196-6203

Effect of anions on the photocatalytic activity of Fe(III) salts impregnated TiO₂

Surolia P K , Tayade R J , Jasra R V

... 265I_R/I_A)^[13](W_A为锐钛矿相的质量分数, I_A和I_R分别为锐钛矿相和金红石相的最强衍射峰峰面积)计算出样品中锐钛矿相的质量分数为71% ...

2007

0.0

0.588

... 与热处理纯TiO₂气凝胶^[14]相比, TiO₂/SiO₂复合气凝胶中锐钛矿相转化为金红石相的相变温度提高了近400℃, 锐钛矿相晶粒尺寸经700℃热处理减小了75 ...

... 900℃处理样品对应的降解率比800℃处理略高, 但比600℃处理要低, 这说明锐钛矿相和金红石共同存在时, 光催化性能会有一定程度提高, 与纯TiO₂气凝胶情况类似^[14], 但这种影响不显著 ...

2009

2.072

0.0

Materials Chemistry and Physics. 2009, 114(2/3):716-721

Preparation and photocatalytic property of perovskite Bi₄Ti₃O₁₂ films

Zhang H P , L#cod#x000fc; M K , Liu S W

... 可由下式估算^[15]: ...