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1.
以钛酸丁酯和季铵盐改性有机蒙脱石为原料,采用原位水解法和原位脱羟法制备了TiO2/蒙脱石纳米复合物。采用X射线衍射(XRD)、拉曼光谱(Raman)表征了不同焙烧温度下TiO2/蒙脱石纳米复合物中TiO2的结构相变,并与不同焙烧温度下纯TiO2的结构相变进行对比。结果发现TiO2/蒙脱石纳米复合物中TiO2从锐钛矿相开始转变为金红石的最低温度要比纯TiO2从锐钛矿开始相转变为金红石的最低温度高200℃,且在焙烧温度1 200℃时还存在锐钛矿相,而纯TiO2在焙烧温度800℃时就全部转换为金红石相。TiO2/蒙脱石纳米复合物中TiO2和纯TiO2的平均晶粒度都随焙烧温度升高而增大,但TiO2/蒙脱石纳米复合物中TiO2的平均晶粒度要小于相同温度下焙烧纯TiO2的平均晶粒度。表明蒙脱石结构层的硅氧结构抑制了TiO2晶型由锐钛矿相向金红石相的转变,进而使相变温度升高,同时阻碍了晶体的生长。  相似文献   

2.
TiO2纳米粒子制备方法对其光催化活性的影响   总被引:20,自引:0,他引:20  
尚静  徐自力等 《分子催化》2001,15(4):282-286
分别用胶溶法、金属醇盐水解法和低温水解法制备了TiO2纳米粒子;采用XRD和BET技术,测试了TiO2粒子的粒径、晶型及表面积。以庚烷的气相光催化氧化为探针反应,考察了不同方法、不同温度处理的TiO2粒子的光催化活性。结果表明,以胶溶法和金属醇盐水解法制备的TiO2粒子,随焙烧温度的增加TiO2粒子长大,晶型由锐钛矿向金红石型转变,光催化活性降低。用低温水解法,可在低温下制得金红石型TiO2粒子,但其催化活性很低。说明由原料和制备方法所决定的TiO2粒子的物理化学性质,影响其光催化行为。锐钛矿型TiO2粒子催化活性较金红石型TiO2好。这是由于前者的表面羟基含量较高且带隙能较大的缘故。  相似文献   

3.
方形锐钛矿TiO2纳米晶的合成及表征   总被引:3,自引:0,他引:3  
在不添加任何模板剂或形状控制剂的条件下,以TiCl4为前体,经氨水沉淀、乙醇洗涤和超临界干燥(AS制备法)选择性地合成了方形锐钛矿Ti02纳米单晶.热稳定性研究结果表明,当焙烧温度不超过650℃时,方形锐钛矿TiO2纳米晶的表面积、孔容、晶粒/颗粒尺寸基本保持不变,XRD和拉曼光谱分析表明,方形锐钛矿TiO2纳米晶在800℃下焙烧后仍能保持晶相不变,表现出很强的抗晶相转变能力.但在1000℃焙烧后,样品可以完全转变成金红石相TiO2。  相似文献   

4.
纳米TiO2混晶的形成及其对光催化性能的影响   总被引:20,自引:4,他引:20  
用溶胶-凝胶法通过改变晶型调节剂2-甲基-2,4戊二醇的添加量制备了金红石相和锐钛矿相比例不同的纳米TiO2混晶.以膨胀珍珠岩为载体,制备珍珠岩负载纳米TiO2混晶催化剂,以X射线衍射(XRD)、紫外-可见吸收光谱(UV-visiblespectrum)、BET、Raman光谱等方法对纳米TiO2混晶和负载型纳米TiO2催化剂进行表征和性能测定,研究了催化剂的混晶效应对光催化降解甲基橙催化性能的影响.结果表明:晶型调节剂的含量及制备条件对混晶中金红石和锐钛矿相TiO2的比率有较大的影响.对于负载型纳米TiO2催化剂,混晶比影响催化剂的光催化降解效率,当混晶比为6.1时光催化效率最高,这一结果对光催化剂的制备和应用都具有重要的意义.  相似文献   

5.
TiO2-SnO2复合纳米膜的制备及其光催化降解甲苯的活性   总被引:32,自引:1,他引:31  
彭峰  任艳群 《催化学报》2003,24(4):243-247
 采用溶胶-凝胶法制备了nano-TiO2-SnO2复合溶胶,经一次镀膜就能在玻璃上得到没有缺陷、结构紧密均匀的nano-TiO2-SnO2复合膜.通过扫描电镜观察到复合膜颗粒为球形,比纯TiO2膜的颗粒小,平均粒径为15nm,且粒径分布非常均匀.以空气中的有机挥发物甲苯模拟污染物,测定了nano-TiO2-SnO2复合膜的光催化降解性能.结果表明,n(SnO2)/n(TiO2)=0.05的nano-TiO2-SnO2复合膜催化剂具有最高的光催化活性,且比纯TiO2膜的活性高;甲苯初始浓度为920mg/m3时,反应5h甲苯完全降解.XRD分析表明,此复合物具有锐钛矿和金红石两种TiO2晶相,没有检测到SnO2的特征峰.  相似文献   

6.
光电化学电池(如染料敏化太阳能电池、量子点敏化太阳能电池以及光电化学水分解电池)是实现太阳能转化及存储的有效手段之一.其中,光电极是光电化学电池的核心组成部分,它集光吸收、光生电荷输运及转移等决定光转化效率的关键过程于一身,因此构筑高活性半导体光电极以实现高效太阳能转化利用引起研究者广泛关注.多孔TiO2纳米颗粒堆垛薄膜光阳极因具有大的比表面积,可提供更多的染料(量子点)担载和反应活性位点,在光电化学电池中表现出优异活性而被广泛研究.然而, TiO2纳米颗粒间大量存在的晶界对光生电荷有较强的散射作用,降低了光生电荷的收集效率.英国牛津大学Snaith研究小组利用模板辅助水热过程首次获得了(001)晶面占优的多孔单晶锐钛矿TiO2微米颗粒,这种多孔单晶TiO2微米颗粒在具有大比表面积的同时,其单晶结构还能有效去除晶界对电荷的散射作用,因而具有优异的电荷输运特性.利用这种多孔单晶TiO2微米颗粒组建的光阳极用于染料敏化太阳能电池中,展现出优异的太阳能光电转化性能.受该工作启发,各种形貌的多孔单晶TiO2微米颗粒作为光催化剂和光电化学分解水用光阳极材料被广泛研究,并表现出优异活性.在单晶微米颗粒堆垛成的薄膜光电极中,虽然单个单晶微米颗粒中晶界对电荷的散射作用被有效抑制,但是单晶颗粒间的晶界仍然存在并影响光生电荷的收集效率.为了彻底抑制晶界对光生电荷的散射作用,每个单晶颗粒都应该贯穿整个薄膜,例如一维TiO2纳米棒单晶阵列薄膜.虽然一维单晶阵列薄膜能够有效提高光生电荷的收集效率,但相对于多孔薄膜具有较小的比表面积,限制了担载染料(量子点)和反应位点的数量.为了增大TiO2单晶纳米棒阵列薄膜的比表面积,目前主要的手段包括调控纳米棒长径比、表面修饰TiO2纳米颗粒以及二次生长构建TiO2枝晶阵列.本文首次提出通过制备多孔单晶TiO2纳米棒单晶阵列薄膜来获得高比表面积和高光生电荷收集效率的光阳极,提高光电化学电池的效率.在透明导电薄膜(FTO)表面利用水热生长TiO2纳米棒阵列薄膜之前,预先在FTO基体上沉积一层SiO2球密堆模板, TiO2纳米棒单晶阵列在从FTO表面向上生长过程中,会将SiO2球模板包裹进TiO2纳米棒中,再通过碱溶液将SiO2球模板溶解,首次在FTO基体上原位生长出多孔单晶TiO2纳米棒阵列薄膜.将所得多孔单晶金红石TiO2纳米棒阵列薄膜作为光电化学分解水电池光阳极,其光电化学分解水活性相对于实心单晶金红石TiO2纳米棒阵列提高了2.6倍.多孔单晶金红石TiO2纳米棒阵列光阳极性能的提升可归因于:(1)多孔结构赋予多孔单晶金红石TiO2纳米棒阵列薄膜更大的比表面积,可提供更多的反应活性位点;(2)多孔结构能够有效缩短单晶金红石TiO2纳米棒中光生电荷体相输运距离,提高光生电荷的收集效率;(3)多孔结构通过对光多次反射吸收可有效增强光吸收,产生更多光生电荷参与水分解反应;(4)在制备过程中引入Si掺杂,导致多孔单晶金红石TiO2纳米棒带隙扩大了0.1 eV,带隙增大归因于导带位置负移0.1 eV,光生电子具有更强的还原能力,光电流起始电位相应负移约0.1 V.  相似文献   

7.
TiO2具有很高的光催化活性,同时TiO2纳米粒子具有耐酸碱和耐光化学腐蚀、低成本、无毒等性质,在许多领域引起广泛关注.据报道,TiO2的锐钛矿晶型比金红石晶型具有更好的光催化活性.由于金红石是TiO2的热力学稳定相,而锐钛矿是亚稳相,通常锐钛矿相在550-800℃温度范围内形成金红石相,从而降低其催化活性,限制了其应用.  相似文献   

8.
La2O3掺杂TiO2光催化剂的制备和性能   总被引:24,自引:2,他引:24  
采用溶胶-凝胶法制备了La2O3掺杂TiO2纳米光催化剂,并通过XRD、TEM、BET和XPS等手段进行了表征.掺入La2O3后,阻止了TiO2从锐钛矿晶型向金红石晶型的转变,使TiO2的粒径减小,比表面积增大.以甲基橙为光催化降解反应模型化合物,考察了光催化剂的活性.测定了甲基橙在纯TiO2和La2O3掺杂TiO2光催化剂上的吸附常数.考察了pH、H2O2对降解性能的影响.讨论了光催化活性与催化剂性质的关系.  相似文献   

9.
二氧化钛多相催化是一种极具前途的环境污染深度净化技术。 本文以钛酸四丁酯和四氯化锡为原料,无水乙醇为溶剂,采用溶胶-凝胶法制备了掺杂二氧化锡的二氧化钛薄膜和复合氧化物粉体。通过测量薄膜的吸收光谱推算光学能隙,结果发现掺杂样品的光学能隙比纯二氧化钛样品有所变小。随着热处理温度的提高,掺杂和纯二氧化钛样品的光学能隙都略微降低。X-射线衍射分析表明,复合氧化物粉体的热处理温度对样品的晶体结构和光催化性能有重要影响。以掺杂二氧化锡5 % 摩尔比的样品与纯二氧化钛对照,500 ℃以下热处理样品以锐钛矿结构为主,600 ℃热处理样品为锐钛矿与金红石相共存,并显示了较好的光催化性能。透射电子显微镜观察显示,同样600 ℃热处理,掺杂样品要比纯二氧化钛具有更小的颗粒尺寸。在700 ℃热处理的样品中,掺杂样品只存在金红石相而纯二氧化钛样品中仍存有锐钛矿相。用阿伦尼乌斯经验关系式推测的晶粒生长的活化能,纯二氧化钛47.486 kJ.mol, 掺杂5 % 摩尔比的复合氧化物样品33.103 kJ.mol。以亚甲基蓝为降解物质,考察了掺杂量和热处理温度对样品的光催化性能。  相似文献   

10.
微波载银对纳米二氧化钛相变及光催化性能的增效作用   总被引:4,自引:1,他引:3  
用微波法制备系列载Ag纳米TiO2,发现微波载Ag对纳米TiO2的相变和光催化活性具有增效作用。采用X-射线粉末衍射(XRD),透射电镜(TEM),X-射线光电子能谱仪(XPS),激光Raman光谱及漫反射光谱(DRS)方法对比研究纳米TiO2与载Ag纳米TiO2的性质。结果表明,所制得载Ag纳米TiO2是以锐钛矿为主相的混晶,平均粒径约为10 nm,负载Ag促进纳米TiO2中锐钛矿相转化金红石相相变,减小纳米晶尺寸,并使纳米TiO2光响应范围向可见光区移动 6 nm。在低浓度范围,微波法能均匀地将Ag负载于纳米TiO2表面,并以Ag0/Ag+的形式存在,抑制光生电子与光生空穴复合,大大地提高了纳米TiO2光催化活性。在近紫外-可见光照射下,载Ag量为0.05 mol %的纳米TiO2对罗丹明B的光催化降解效果最好。  相似文献   

11.
Phase transformation of TiO2 from anatase to rutile is studied by UV Raman spectroscopy excited by 325 and 244 nm lasers, visible Raman spectroscopy excited by 532 nm laser, X-ray diffraction (XRD), and transmission electron microscopy (TEM). UV Raman spectroscopy is found to be more sensitive to the surface region of TiO2 than visible Raman spectroscopy and XRD because TiO2 strongly absorbs UV light. The anatase phase is detected by UV Raman spectroscopy for the sample calcined at higher temperatures than when it is detected by visible Raman spectroscopy and XRD. The inconsistency in the results from the above three techniques suggests that the anatase phase of TiO2 at the surface region can remain at relatively higher calcination temperatures than that in the bulk during the phase transformation. The TEM results show that small particles agglomerate into big particles when the TiO2 sample is calcined at elevated temperatures and the agglomeration of the TiO2 particles is along with the phase transformation from anatase to rutile. It is suggested that the rutile phase starts to form at the interfaces between the anatase particles in the agglomerated TiO2 particles; namely, the anatase phase in the inner region of the agglomerated TiO2 particles turns out to change into the rutile phase more easily than that in the outer surface region of the agglomerated TiO2 particles. When the anatase particles of TiO2 are covered with highly dispersed La2O3, the phase transformation in both the bulk and surface regions is significantly retarded, owing to avoiding direct contact of the anatase particles and occupying the surface defect sites of the anatase particles by La2O3.  相似文献   

12.
氯化铵对TiO2纳米晶的形成、 结构及性能的影响   总被引:2,自引:0,他引:2  
以四氯化钛为原料, 通过氯化铵诱导晶化和热挥发分解法制备了二氧化钛纳米晶, 经粉末XRD, TEM, IR和比表面积及热重分析等手段进行了表征. 通过对粒子生长动力学分析, 在700 ℃以下存在两种生长势, 400 ℃时出现转折, 400 ℃以下粒子生长所需活化能为8.23 kJ/mol; 400 ℃以上粒子生长需活化能为45.71 kJ/mol. 于200 ℃时灼烧样品的表面积最大, 对甲基橙光催化降解活性最高.  相似文献   

13.
Photoexcited TiO(2) has been found to generate reactive oxygen species, yet the precise mechanism and chemical nature of the generated oxy species especially regarding the different crystal phases remain to be elucidated. Visible light-induced reactions of a suspension of titanium dioxide (TiO(2)) in water were investigated using electron paramagnetic resonance (EPR) coupled with the spin-trapping technique. Increased levels of both hydroxyl (˙OH) and superoxide anion (˙O(2)(-)) radicals were detected in TiO(2) rutile and anatase nanoparticles (50 nm). The intensity of signals assigned to the ˙OH and ˙O(2)(-) radicals was larger for the anatase phase than that originating from rutile. Moreover, illumination with visible (nonUV) light enhanced ˙O(2)(-) formation in the rutile phase. Singlet oxygen was not detected in water suspension of TiO(2) neither in rutile nor in anatase nanoparticles, but irradiation of the rutile phase with visible light revealed a signal, which could be attributed to singlet oxygen formation. The blue part of visible spectrum (400-500 nm) was found to be responsible for the light-induced ROS in TiO(2) nanoparticles. The characterization of the mechanism of visible light-induced oxy radicals formation by TiO(2) nanoparticles could contribute to its use as a sterilization agent.  相似文献   

14.
微乳法制备纳米TiO2 /SiO2的结构及光催化研究   总被引:1,自引:0,他引:1  
Nanosized TiO2 and TiO2/SiO2 particles were prepared by hydrolysis of tetrabutyl titanate (TBOT) and tetraethyl orthosilicate (TEOS) in the TX-100 reverse microemulsion. These particles were characterized by TG-DSC, XRD, FTIR, TEM,N2 adsorption-desorption. Their photocatalytic activity was tested by degradation of methyl orange. The result shows that TiO2/SiO2 nanoparticles are with a monodispersed spherical phase and a uniform size distribution,and TiO2 particles are dispersed on the surface of SiO2. The band for Ti-O-Si vibration in FTIR was observed, the Ti-O-Si bond increased the stability of anatase TiO2, suppressed the phase transformation of titania from anatase to rutile. And due to the addition of SiO2, the average size of titania decreased from 38 nm in pure TiO2 to 5 nm in TiO2/SiO2. It was found, under UV light irradiation, TiO2/SiO2 particles showed higher activity than pure TiO2, and TiO2/SiO2(1/1) particles showed the highest photocatalytic activity on the photocatalytic decomposition of methyl orange, which was influenced by crystal structure, particle size, crystallinity and Surface area Characteristics.  相似文献   

15.
TiO2纳米晶光催化降解铬酸根离子的研究   总被引:19,自引:0,他引:19  
以二氧化钛为光催化剂,研究了溶液的pH值、铬酸根离子的初始浓度、通入的气体种类、氧化钛的载量等因素对铬酸根离子降解率的影响。同时合成了粒径小于10nm的锐钛矿相和金红石相氧化钛纳米晶来考察晶相和尺寸效应对降解率的影响。结果表明,锐钛矿的催化活性高于金红石相,两者的催化活性均大大高于市售的氧化钛微粉。  相似文献   

16.
This study investigated the sedimentation and aggregation kinetics of titanium dioxide (TiO(2)) nanoparticles with varying material properties (i.e., crystallinity, morphology, and chemical composition). Used in the study were various types of commercially available TiO(2) nanoparticles: three spherical anatase (nominal diameters of 5, 10, and 50 nm) and two rutile nanoparticles (10×40 and 30×40 nm). The 50 nm anatase and 10×40 nm rutile showed higher stability in deionized water and 5 mM NaCl solutions at pH 7 than the 5, and 10 nm anatase nanoparticles in sedimentation experiments. In aggregation experiments, critical coagulation concentration values for the 50 nm anatase were the highest, followed by the 10×40 nm rutile and the 5 nm anatase nanoparticles in NaCl and CaCl(2) solutions. The aggregation kinetics was fitted reasonably well with the Derjaguin-Landau-Verwey-Overbeek (DLVO) equations for the TiO(2) nanoparticles tested. Results showed that crystallinity and morphology are not influential factors in determining the stability of TiO(2) nanoparticle suspensions; however, the differences in their chemical compositions, notably, the varying concentrations of impurities (i.e., silicon and phosphorus) in the pristine materials, determined the surface charge and therefore the sedimentation and aggregation of TiO(2) nanoparticles in the aqueous phase.  相似文献   

17.
微乳法合成纳米SiO2/TiO2及其光催化性能   总被引:1,自引:0,他引:1  
采用聚乙二醇辛基苯基醚(Triton X-100)/正己醇/环己烷/氨水微乳体系合成了纳米TiO2和SiO2/TiO2复合物,用X射线衍射、红外光谱和透射电镜对其结构进行了表征,并以甲基橙降解评价了其光催化性能,讨论了SiO2/TiO2摩尔比、晶相组成及粒径与光催化活性的关系.结果表明,SiO2/TiO2催化剂中形成了新的Ti-O-Si键和无定形SiO2;在纳米TiO2中复合SiO2能有效抑制锐钛矿向金红石的转变,增加锐钛矿的稳定性,并阻止TiO2晶粒的聚集生长.催化剂的光催化活性随金红石含量的增加而降低,加入适量SiO2能明显提高TiO2的光催化活性,其中摩尔比为1/7的SiO2/TiO2光催化活性最高.  相似文献   

18.
Zhu H  Shen M  Wu Y  Li X  Hong J  Liu B  Wu X  Dong L  Chen Y 《The journal of physical chemistry. B》2005,109(23):11720-11726
Raman and FT-IR spectra were employed to investigate the dispersion of molybdena on mixed TiO2 (rutile and anatase, signed as R and A) with different BET surface ratios of rutile/TiO2(R + A). The results showed that (1) molybdena would preferentially disperse on the rutile surface in mixed TiO2; (2) for MoO3/rutile with low molybdena loading (e.g., 0.20 mmol/100 m2 rutile), a dispersed molybdena species existed on the rutile surface in an isolated tetrahedral coordination environment, while for MoO3/rutile with high molybdena loading (e.g. 0.82 mmol/100 m2 rutile), a polymeric molybdena species could be detected on the rutile surface; (3) for the MoO3/anatase sample, a dispersed molybdena species existed on the anatase surface in a polymeric coordination environment; and (4) the formation of the Bronsted acid site on the surface of rutile and anatase should be related to the polymeric molybdena species. All these results have been discussed via the interaction between OH groups of molybdena and OH groups of rutile and anatase, and it seems reasonable to suggest that, for the lower molybdena loading, the different states of the dispersed molybdena species should result from the different dehydration orders of OH groups of the molybdena and surface OH groups of rutile and anatase.  相似文献   

19.
The simultaneous phase- and size-controlled synthesis of TiO(2) nanorods was achieved via the non-hydrolytic sol-gel reaction of continuously delivered two titanium precursors using two separate syringe pumps. As the injection rate was decreased, the length of the TiO(2) nanorods was increased and their crystalline phase was simultaneously transformed from anatase to rutile. When the reaction was performed by injecting titanium precursors contained in two separate syringes into a hot oleylamine surfactant solution with an injection rate of 30 mL/h, anatase TiO(2) nanorods with dimensions of 6 nm (thickness) x 50 nm (length) were produced. When the injection rate was decreased to 2.5 mL/h, star-shaped rutile TiO(2) nanorods with dimensions of 25 nm x 200 nm and a small fraction of rod-shaped anatase TiO(2) nanorods with dimensions of 9 nm x 100 nm were synthesized. Pure star-shaped rutile TiO(2) nanorods with dimensions of 25 nm x 450 nm were synthesized when the injection rate was further decreased to 1.25 mL/h. The simultaneous phase transformation and length elongation of the TiO(2) nanorods were achieved. Under optimized reaction conditions, as much as 3.5 g of TiO(2) nanorods were produced. The TiO(2) nanorods were used to produce dye-sensitized solar cells, and the photoconversion efficiency of the mixture composed of star-shaped rutile TiO(2) nanorods and a small fraction of anatase nanorods were comparable to that of Degussa P-25.  相似文献   

20.
Y掺杂纳米TiO2的合成及晶型转变过程   总被引:11,自引:0,他引:11  
溶胶-凝胶;锐钛型;金红石型;Y掺杂纳米TiO2的合成及晶型转变过程  相似文献   

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