纳米二氧化钛粉的水热合成与光催化性能研究

以钛酸四丁酯(TBOT)为钛源,NH4Cl为分散剂,不经高温煅烧,直接低温水热合成纳米TiO2粉。采用FT-IR,XRD,TEM等方法研究了低温高压水热条件和NH4Cl浓度对TiO2粉的相组成、组织形貌的影响,并研究了其对甲基橙光催化降解的性能。结果表明,纳米TiO2具有锐钛矿相结构且无有机物残留。晶粒尺寸随着水热合成温度增高(120~180℃)而增大,随着NH4Cl/TBOT的摩尔比(0.1~0.5)增加而减小,但纳米粉逐渐出现团聚现象。水热温度为160℃以及NH4Cl/TBOT=0.25条件下合成的锐钛矿相纳米TiO2具有良好的分散性,其颗粒尺寸约为14 nm,且有高的光催化降解甲基橙的能力。     

水热合成纳米二氧化钛及其光催化性能研究

以钛酸四丁酯为原料,在盐酸介质中水热合成二氧化钛粉体,通过XRD对所得二氧化钛粉体进行了表征,研究合成条件(如盐酸浓度、反应温度及反应时间等)对所得二氧化钛的相组成及晶粒尺寸的影响。结果表明:产物二氧化钛的相组成受盐酸浓度的影响,而与反应温度及反应时间无关。反应温度及反应时间只影响二氧化钛的晶粒尺寸。光催化降解甲基橙的研究表明,所得锐钛矿、金红石和板钛矿3种混晶中,二氧化钛的光催化活性随着锐钛矿含量的降低而降低;纯金红石型二氧化钛的光催化活性较差。     

Influence of synthesis parameters on morphology and phase composition of porous titania layers prepared via water based chemical solution deposition

In this work, thick nanocrystalline mesoporous titania layers are synthesized via chemical solution deposition using a water based citratoperoxo-Ti(IV)-precursor solution. The aqueous citratoperoxo-Ti(IV)-precursor solution is modified by the addition of polyvinyl alcohol (PVA), which acts as a thickener and pore forming agent. Layers are tape casted onto ITO-coated glass substrates and are thermally processed. The influence of process parameters like Ti(IV)-concentration, blade thickness, crystallization temperature and time on the film's phase composition, morphology and thickness are investigated by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), variable angle spectroscopic ellipsometry (VASE), atomic force microscopy (AFM) and profilometry.

It is shown that the Ti(IV)-concentration and heat treatment influence the size and shape of the grains of which the films are composed, the film morphology (porosity, surface roughness) and the layer thickness, but no influence on the phase formation is observed. In all cases phase pure anatase layers are obtained.     

离子液体辅助合成CdMoO_4微球体及其光催化性能

分别以1 mL 1-正丁基-3-甲基咪唑氯盐([Bmim]Cl)(离子液体Ⅰ)和1 mL 14,-双(N-甲基咪唑)丁烷溴盐([C4(Mim)2][Br]2)(离子液体Ⅱ)为辅助剂,CdCl2与Na2MoO4在60℃下反应1 h制备了单分散性较好的圆球状和椭球状的CdMoO4,并利用X射线衍射仪、扫描电子显微镜对产物的组成和形貌进行了表征。结果表明,在2种条件下制备的产物均为四方晶相的CdMoO4,但其大小有所差异。以紫外光灯为光源,2种不同离子液体合成的CdMoO4微球为光催化剂,对有机染料罗丹明B进行了光降解实验。研究发现,利用双阳离子液体合成的CdMoO4微椭球具有更高的光催化活性,经过60 min其光降解率达到了98.9%。     

液相法制备纳米TiO2的工艺及其光催化降解盐酸土霉素的研究

以钛酸丁酯为前驱体,分别采用水热沉淀法和溶胶-凝胶法制备纳米TiO2光催化剂,以氙灯为光源,盐酸土霉素为降解对象,考察2种方法下样品的光催化能力,并对水热沉淀法制备TiO2在不同煅烧温度、底物浓度、光照强度及催化剂用量条件下的光催化活性进行研究。结果表明,相比溶胶-凝胶法,水热沉淀法制备的TiO2的光催化反应速率常数较大,粒径小,分布均匀,分散性好,光吸收能力强。     

A novel synthesis of carbon-coated anatase nanocrystals showing high adsorption capacity and photocatalytic activity

Anatase nanocrystals coated with thin and uniform carbon layer have been prepared directly by using molecular precursors of titanium tetrachloride as a titanium source and fructose as a carbon source in benzyl alcohol. The anatase nanoparticles thus prepared possess high crystallinity, and the carbonaceous species from the dehydrated sugar coat the nanoparticles and transform to uniform and thin carbon layer with graphitic nature. The thus prepared carbon-coated anatase nanocrystals exhibit fast adsorption of methylene blue with high capacity, and they also catalyze the photodecomposition of the dye with greatly enhanced activity. The synthesis route provides rational control over the properties of carbon-coated anatase nanocatalysts for practical applications.     

溶胶-凝胶法制备TiO_2光催化剂及其表征

以钛酸四丁酯为钛源,碳酸铵为掺杂剂,采用溶胶-凝胶法制备了含氮的二氧化钛先催化剂,采用X-射线粉末衍射、扫描电镜,对其结构、形貌和光催化特征进行了表征.以罗丹明B水溶液的光催化降解为模型反应,评价了所制试样的光催化活性.结果表明,焙烧温度为400℃时,晶型为锐钛矿结构,样品的光催化效果最好.     

颜料二氧化钛光催化特性评价

采用悬浆外照式光催化反应器,研究了在紫外光照下低活性颜料二氧化钛光催化降解罗丹明B的反应动力学特性。考察了二氧化钛浓度、罗丹明B浓度、紫外线波长及光强对光催化反应速率的影响,确定了适合颜料二氧化钛光催化特性评价的优化检测条件。研究表明,颜料二氧化钛光催化降解罗丹明B具有一级反应动力学特性。确定颜料二氧化钛光催化特性检测方法的优化操作条件为二氧化钛浓度约为4 g·L^-1、罗丹明B浓度为2~10 mg·L^-1、紫外光源主发射波长为254 nm。实验检测了表面包硅二氧化钛样品的光催化特性,表明该检测方法能够对颜料二氧化钛及包膜二氧化钛的光催化特性进行快速定量的评价。     

Zirconia and titania composite membranes for liquid phase separation: preparation and characterization

Crack-free tubular TiO₂/ZrO₂ composite ceramic membranes on ZrO₂ supports have been successfully synthesized from colloidal titania sols by the sol-gel technique. The pore sizes of the prepared membrane were mainly controlled by the sol properties and the calcination conditions. The influence of different parameters such as additives and solvents on the hydrolysis and polycondensation properties of the sols was studied by DTA–TG and viscosity measurements. The TiO₂/ZrO₂ composite ceramic membranes were characterized by X-ray diffraction and scanning electron microscopy. Composite membrane permeability and rejection properties were also investigated. The results proved that the range of composite membrane flux and retention could be controlled by controlling the amount of polyethylene glycol (PEG). PEG in titania sol systems was suitable for use as an organic additive to fabricate crack-free composite membranes. The larger the amount of PEG added to the precursor solution, the larger the size and number of pores produced in the prepared membranes when the PEG was completely combusted during heat-treatment. By controlling the amount of PEG added to the precursor solution, TiO₂/ZrO₂ composite ceramic membranes with different pore sizes were prepared, which can be used in photocatalytic membrane reactors and applied in liquid–liquid or liquid–solid separation in future research.     

TiO2光催化剂掺杂改性的研究进展

TiO₂在利用光能和环保等领域具有重要应用前景。由于TiO₂具有较大禁带宽度，限制其对太阳光等可见光能的利用。通过对TiO₂掺杂改性，合成出具有较窄禁带宽度和稳定性好的光催化剂，促进光催化剂的实际应用。介绍了TiO₂光催化作用机理，从金属掺杂、非金属掺杂和共掺杂等方面总结TiO₂催化剂掺杂改性的研究现状。     

硫酸氧钛液相法制备纳米二氧化钛

以硫酸氧钛为原料，液相法在水醇体系中制备纳米二氧化钛。讨论了表面活性剂、硫酸氧钛浓度、反应温度、体系pH、煅烧温度等因素对纳米粒子生成及性能的影响，用X射线衍射仪和透射电镜检测，证明实验获得的产物为粒径20～40nm的锐钛型二氧化钛。研究表明，通过改变工艺条件可控制纳米二氧化钛粒径及尺寸分布。工艺流程简单，制备成本低，易实现工业化。     

Facile synthesis of hollow Cu2O octahedral and spherical nanocrystals and their morphology-dependent photocatalytic properties

ABSTRACT: Herein, we report that octahedral and spherical Cu2O samples with hollow structures are synthesized in high yield by reducing Cu(EDA)22+complex with hydrazine. A series of experiments are carried out to investigate the factors which impact on the morphology of the Cu2O samples. It is observed that ethylenediamine (EDA) serves as a molecular template in the formation of hollow structure. Octahedral Cu2O with solid structure is prepared without EDA. When EDA is added, Cu2O sample with hollow structure is formed. Different morphologies of Cu2O such as spherical and octahedral could be obtained by adjusting the concentration of EDA and NaOH. The temporal crystal growth mechanism is proposed. Furthermore, the photocatalytic activities of the as-prepared Cu2O nanoparticles are evaluated by monitoring two dyes (methyl orange and congo red) using UV-visible spectrophotometer. Results show that the order of photocatalytic activity of Cu2O with different morphologies is as follows: hollow octahedral morphology > hollow sphere morphology > solid octahedral morphology. The hollow octahedral Cu2O anoparticles would be a promising material on applications for photocatalytic degradation of organic pollutants.     

钴掺杂二氧化钛光催化剂制备及光催化活性

采用溶胶-凝胶法制备了纯二氧化钛和不同钴掺杂量的二氧化钛复合纳米粒子。并用XRD、UV-Vis对样品组织结构进行了表征。以甲基橙（OM）的光催化降解为探针反应,评价了可见光催化活性,研究了不同热处理温度、不同钴掺杂量对二氧化钛光催化性能的影响。确定了最佳钴掺杂量和热处理温度分别为1%（物质的量分数）和600  ℃。在此条件下,钴的掺杂对二氧化钛的相变有很大的抑制作用,并使其光谱响应范围向可见光区拓展。与未掺杂的二氧化钛相比较,经钴掺杂的二氧化钛具有更高的催化性能。     

液相合成纳米氧化锌及其光催化性能探讨

以硝酸锌和氢氧化钠为原料,分别以水和醇作为溶剂,采用液相直接沉淀法合成纳米氧化锌。在以水为反应溶剂条件下,研究了反应时间、反应温度、反应物浓度和反应物配比对纳米氧化锌中位径和形貌的影响,得到制备较小中位径及合适长径比纳米氧化锌的最优反应条件,即:反应时间为3 h、反应温度为70 ℃、锌离子浓度为0.5 mol/L、锌离子与氢氧根浓度比为1:2。在上述最优反应条件下,研究了不同醇溶剂对纳米氧化锌中位径、形貌及其光催化性能的影响。研究发现,随着溶剂碳链长度的增长,纳米氧化锌中位径呈现上下波动,无明显变化规律,形貌由球状向柱状发展,光催化性能总体不断减弱。     

Direct synthesis of nano titania on highly-ordered mesoporous SBA-15 framework for enhancing adsorption and photocatalytic activity

This paper reports the synthesis of TiO₂-containing mesoporous catalysts for effectively enhancing the adsorption and photocatalytic activity. The factors that affect the photocatalytic activity of catalyst composites, including types of silica support, TiO₂ content, calcination temperature, and catalyst mass, were examined in this study. The samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and surface area analysis. The experimental results showed that incorporating TiO₂ nanoparticles into silica gel or SBA-15 frameworks could enhance the photodegradation rate more effectively than pure TiO₂. The TiO₂/SBA-15 sample displayed much higher adsorption and photocatalytic activity levels than did TiO₂/silica-gel. The pore volume and pore size of TiO₂/SBA-15 were as high as 1.317 cm³/g and 7.51 nm, respectively, which exceeded those of TiO₂/silica-gel (0.437 cm³/g and 3.68 nm, respectively). The rate constants of photocatalysis were determined. The photodegradation rate of the catalyst increased with decreasing TiO₂ content and increasing calcination temperature. The proposed method of preparing mesoporous photocatalysts is simple and suitable for mass production.     

Enhanced photocatalytic degradation of tetramethylammonium on silica-loaded titania

Photocatalytic degradation (PCD) of tetramethylammonium (TMA) in water was studied using both pure TiO₂ and silica-loaded TiO₂ (Si–TiO₂). Use of Si–TiO₂ catalyst prepared from commercial TiO₂ powder by a simple method developed in this work enhanced the PCD rate of TMA considerably. The Si/Ti atomic ratio of 18% was found to be an optimum in photoactivity and the calcined sample was more efficient than the uncalcined one. Several factors were noted to be responsible for the higher photoefficiency of Si–TiO₂ catalyst. Si–TiO₂ calcined at 700 °C did not show any sign of change in the crystalline structure from that of uncalcined pure TiO₂. The increased thermal stability of Si–TiO₂ enabled the bulk defects to be removed at high temperatures without forming the inactive rutile phase, which may partly contribute to the higher photoactivity. The most outstanding characteristics of Si–TiO₂ is its surface charge modification. Loading silica on to a titania surface made the surface charge highly negative, which was confirmed by zeta potential measurements. The enhanced electrostatic attraction of cationic TMA onto the negatively charged Si–TiO₂ surface seems to be the main reason for the enhanced photoactivity of Si–TiO₂. As a result of this surface charge change, the TMA PCD rate with Si–TiO₂ exhibited a maximum around pH 7 whereas the PCD with pure TiO₂ was minimized at pH 7. The X-ray photoelectron spectroscopic analysis showed the formation of SiO_x on the TiO₂ surface but the diffuse reflectance UV spectra indicated no significant difference in the band gap transition between pure TiO₂ and Si–TiO₂. In addition, the diffuse reflectance IR spectra showed the presence of more surface OH groups on Si–TiO₂ than on pure TiO₂, which may also contribute to the higher photoactivity of Si–TiO₂ through generating more OH radicals upon UV illumination.     

Shape and phase control of CdS nanocrystals using cationic surfactant in noninjection synthesis

Monodispersed CdS nanocrystals with controllable shape and phase have been successfully synthesized in this study by adding cationic surfactant in noninjection synthesis system. With the increase of the amount of cetyltrimethylammonium chloride (CTAC) added, the shape of the CdS nanocrystals changed from spherical to multi-armed, and the phase changed from zinc-blende to wurtzite. It was found that halide ion Cl- plays a key role in the transformation, and other halide ions such as Br- can also induce similar transformation. We proposed that the strong binding between Cd2+ and halide ions reduced the reactivity of the precursors, decreased the nuclei formed in the nucleation stage, and led to the high concentration of precursor in the growth stage, resulting in the increase of size and phase transformation of CdS nanocrystals. In addition, it was found that the multi-armed CdS nanocrystals lost quantum confinement effect because of the increase of the size with the increase of the concentration of CTAC.     

液相沉淀法制备纳米TiO2及其光催化性能的研究

提出了一种以TiSO₄为前驱体的制备锐钛矿型纳米TiO₂的液相沉淀法。通过控制适宜的制备条件，可将Ti^4+的初始浓度提高到15 mol·L^-1。以丙烯酰胺的光催化降解为模型反应，考察了所制备TiO₂的光催化活性。与萃取沉淀法制备的TiO₂和工业催化剂相比，该法制备的TiO₂不仅产率高，而且催化活性较好。     

La掺杂纳米TiO2的制备及光催化性能研究

采用溶胶-凝胶法制备了纯TiO₂和不同La掺杂量的TiO₂纳米粒子，对样品进行了TG-DTA、XRD和UV-Vis 吸收光谱分析，并以染料废水甲基橙为目标降解物，考察了样品的光催化性能。结果发现，La的掺杂抑制了TiO₂粒径的长大，细化了晶粒；La掺入到TiO₂的晶格中，引起了晶格的畸变和膨胀；La的掺杂使TiO₂的吸收带边发生了红移；适量La的掺杂可提高TiO₂的光催化性能。试验条件下，最佳掺杂摩尔分数为0.1％。     

液相法甲醇合成的平衡收率

对液相法甲醇合成系统进行了热力学分析，建立了求解该系统相平衡和化学平衡问题的非线性方程组。在此基础上，分别对以四甘醇二甲醚和角鲨烷为液相介质的反应热力学平衡进行了计算，结果表明液相介质具有提高甲醇平衡收率的作用。研究了液相介质的性能、用量、温度、压力及原料气组成对甲醇平衡收率的影响。