Preparation and characterization of highly photoactive nanocrystalline TiO<Subscript>2</Subscript> powders by solvent evaporationinduced crystallization method

Highly photoactive bi-phase nanocrystalline TiO₂ photocatalyst was prepared by a solvent evaporation-induced crystallization (SEIC) method, and calcined at different temperatures. The obtained TiO₂ photocatalyst was characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results show that solvent evaporation can promote the crystallization and phase transformation of TiO₂ at 100°C. When calcination temperatures are below 600°C, the prepared TiO₂ powders show bimodal pore size distributions in the mesoporous region. At 700°C, the pore size distributions exhibit monomodal distribution of the inter-aggregated pores due to the collapse of the intra-aggregated pores. At 100°C, the obtained TiO₂ photocatalyst by this method shows good photocatalytic activity, and at 400°C, its photocatalytic activity exceeds that of Degussa P25. This may be attributed to the fact that the prepared TiO₂ photocatalyst has higher specific surface areas, smaller crystallite size and bimodal pore size distribution.     

Preparation of nanocrystalline anatase TiO2 using basic sol-gel method

Nanocrystalline titanium dioxide particles with anatase structure and high thermal stability have been synthesized using the basic sol-gel method. The particle size and morphology were refined under hydrothermal conditions in the presence of different concentrations of tetramethylammonium hydroxide (TMAH) at 210°C and 230°C. XRD and TEM analysis showed that the TiO₂ particles obtained were homogeneous and monodispersive at low contents of TMAH. All intense peaks, clearly observed in the XRD patterns, were assigned to the anatase phase and no rutile phase was observed. At high contents of TMAH, nanoscale small (10–30 nm) and larger (>100 nm) TiO₂ particles were one-pot synthesized. The nanocrystalline TiO₂ particles synthesized by this method have good thermal stability. With the sintering temperature of up to 650°C, all the XRD peaks maintained good agreement with the anatase reference data.     

Preparation and characterization of nanocrystalline ZnO by direct precipitation method

Nanocrystalline ZnO was prepared with ZnCl₂·2H₂O and (NH₄)₂CO₃ as raw materials by direct precipitation method. The precursor was proved to be [Zn₅(OH)₆(CO₃)₂] by TG-DTG-DTA and IR analysis. This precursor was calcined at 300°C for 1, 2 and 3 hours respectively, and then the nanocrystalline ZnO of different grain size were obtained. The nanocrystalline ZnO was characterized using X-ray diffraction (XRD), TEM and Brunner-Emmett-Teller method (BET). Experimental results for nanocrystalline ZnO showed that the minimum size was about 8nm, the maximum was about 15 nm and the mean grain size was 12 nm, the surface area was 80.56 m²/g and the purity was 99.9% when the precursor was calcined at 300°C for 2 h. __________ Translated from Journal of Inner Mongolia Normal University (Natural Science Edition), 2006, 35(1) (in Chinese)     

Preparation of the TiO2 Thin Film Photocatalyst by the Dip-Coating Process

Titanium dioxide (TiO2) coated glass-plate thin film photocatalysts for elimination of air pollutants, were prepared by the dip-coating process with titanium alkoxide including polyethylene glycol (PEG). The surface structure of these thin films changed drastically with the size of the PEG. They were either transparent or opaque. Nitrogen oxides (NOx), one of the most hazardous of air pollutants, were found to be efficiently eliminated by the thin film photocatalyst. The photocatalytic activities of the transparent and opaque thin films were found to be almost equal. This may be due to the two films having the same surface area. The highest activity was obtained for thin films around 1 m.     

Low Temperature Solvent Evaporation-induced Crystallization Synthesis of Nanocrystalline TiO2 Photocatalyst

A novel and efficient methodology for obtaining highly active photocatalyst of bi-phase TiO2 with small particle size and high specific surface area was developed by solvent evaporation-in-duced crystallization (SEIC) method at low temperature. The prepared TiO2 powder was characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET surface areas. The photocatalyfic activity was evaluated by the photocatalyflc oxidation of acetone in air. The results showed that the photocatalytic activity of the TiO2 powder preDared by this method approached that of Degnssa P25. This may be atotributed to the fact that the predated TiO2 powder had larzer specific surface areas (265 m2. g- 1 ) and smaller crystallite size (about 5 nm), but relatively low crystallinity, as compared with Degussa P25.     

碳纳米管/TiO_2复合材料的制备及表征研究

采用溶胶-凝胶法和水热合成法,制备出碳纳米管/TiO2(CNTs/TiO2)复合材料。通过X-射线衍射仪(XRD)、扫描电子显微镜(SEM),紫外-可见漫反射光谱(UV-Vis),荧光光谱(LS)检测CNTs/TiO2的晶型及形貌。结果表明:锐钛矿相TiO2纳米颗粒负载在碳纳米管的管壁上,CNTs/TiO2在紫外-可见光波长范围均有较好的吸收性能。在灭菌灯照射下,以甲基橙溶液为降解目标,CNTs/TiO2复合材料对甲基橙溶液的降解有高的光催化活性,180 min内降解率达到85%以上。     

中孔TiO2的制备与表征

以聚氧乙烯十二烷基醚为模板剂,钛酸四丁酯为钛源制备了中孔TiO2,探讨了焙烧温度和掺杂对中孔TiO2结构的影响。利用XRD,TEM,FT-IR和N2吸附等对其结构进行了表征。结果表明,中孔TiO2具有较大的孔径和较高的热稳定性;钇掺杂使中孔TiO2的比表面积和孔体积增大及热稳定性提高。以噻吩加氢脱硫为探针反应,考察了以中孔TiO2为载体的Ni基催化剂的催化活性,钇掺杂能提高其催化活性。     

不同方法制备Ni-WO_3/TiO_2-ZrO_2催化剂及其性能研究

考察了Ti O2-Zr O2载体制备方法对Ni-WO3/Ti O2-Zr O2催化正庚烷异构化反应性能的影响.通过BET、XRD、SEM和NH3-TPD的表征结果表明,以模板-溶胶-凝胶法制备Ti O2-Zr O2载体时,Ni-WO3/Ti O2-Zr O2催化剂晶相结晶度较好,具有较适宜的表面酸性和比表面积,从而在正庚烷异构化反应中表现出较高的催化活性和选择性,正庚烷的转化率和异庚烷的选择性分别为72.62%和80.81%.实验结果还表明,Ti O2-Zr O2比Zr O2、Si O2-Zr O2和Al2O3-Zr O2更适宜作为载体制备催化剂应用于正庚烷异构化的反应中.     

高效光催化活性钠米农药制剂的制备

采用钛酸丁酯水解法制备出直径约为20 nm的纳米TiO2,并用钛酸丁酯对其进行改性。研究表明TiO2与硬脂酸事实上通过化学键键合,由亲水性变为亲油性。文中还提出了三种制备TiO2复合纳米农药制剂的方案,并探讨了几种TiO2复合纳米农药制剂在不同条件下的光催化降解率。结果表明,采用钛酸丁酯为原料直接在农药乳油中原位生成的TiO2复合纳米农药制剂与原农药性状保持基本一致,光催化降解率最大。     

溶胶-凝胶法制备二氧化钛溶胶

以钛酸丁脂为前驱体,乙醇为溶剂,采用溶胶-凝胶法制备了二氧化钛(TiO2)溶胶.最佳制备条件为:钛酸丁脂29 mmol,n(水):n(钛酸丁脂)=5:1,n(乙醇):n(钛酸丁脂)=15:1,pH 3～4,聚乙烯醇2 mL,于室温剧烈搅拌下缓慢加料制得透明度较好,可长时间放置,粘度适于涂膜的TiO2溶胶.     

Preparation and characterization of natural zeolite supported nano TiO2 photocatalysts by a modified electrostatic self‐assembly method

Natural zeolite supported nano TiO₂ photocatalysts were prepared by a modified electrostatic self‐assembly (ESA) method. First, γ‐mercaptopropyltrimethoxysilane with sulfhydryl (―SH) functional groups was modified on the zeolite powders by using a ‘dry process’. Second, silane with ―SH functional groups was oxidized to sulfonate (―SO₃H) groups by using a hydrogen peroxide/glacial acetic acid mixed solution, and the surface of ―SO₃H silane–zeolite was electronegative charged due to the ionization of ―SO₃H. Third, the hydrolytic titanium polycation from TiCl₄ solution assembled onto the electronegative charged zeolite under electrostatic attraction in the reaction solutions. Finally, zeolite supported nano TiO₂ photocatalysts can be obtained after the above compounds calcined at certain temperature. The samples were characterized by X‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface areas, Fourier transform infrared spectroscopy (FT‐IR), X‐ray photoelectron spectroscopy (XPS) and X‐ray fluorescence (XRF). The photocatalytic activities of the samples were evaluated by the degradation of methyl orange in aqueous solution. The results showed that ESA method effectively improved the composite efficiency of zeolite with TiO₂. The photocatalysts prepared by ESA method exhibited higher photocatalytic and recycling activities than that of traditional method. Copyright © 2014 John Wiley & Sons, Ltd.     

Preparation of Magnetic Photocatalyst TiO2 Supported on NiFe2O4 and Effect of Magnetic Carrier on Photocatalytic Activity

A magnetic photocatalyst TiO₂/NiFe₂O₄ (TN) with typical ferromagnetic hysteresis was prepared by a sol‐gel method, which is easy to be separated from a slurry‐type photoreactor under the application of an external magnetic field, being one of promising photocatalysts for wastewater treatment. The analysis of XRD indicated that the highly dispersed NiFe₂O₄ nanoparticles prevented the formation of rutile phase to some extent. A transmission electron microscope (TEM) was used to characterize the structure of the photocatalyst, indicating that the NiFe₂O₄ nanoparticles highly dispersed among TiO₂ nanoparticles. The prepared photocatalyst showed high photocatalytic activity for the degradation of methyl orange in water. The degradation results revealed that the NiFe₂O₄ nanoparticles played the role of recombination centre of photogenerated electrons and holes for the TN photocatalyst, which gave rise to the decrease in photocatalytic activity. Moreover, the experiment on recycled use of TN demonstrated a good repeatability of the photocatalytic activity.     

TiO_2/ACF光催化剂的超声波制备及其光催化活性

本文以超声波为晶化方法在低温下制得了炭纤维负载的Ti O2光催化剂(Ti O2/ACF)。通过X衍射、扫描电镜、液氮吸附等对晶化中所得催化剂Ti O2的晶型、形貌和织构进行了考察,并以甲基橙为降解物考察了催化剂活性。结果表明:在超声波作用下,Ti O2前驱体先被均匀负载到炭纤维表面,然后被晶化为14.2 nm的锐钛矿粒子;所得催化剂晶粒在炭纤维表面形成了1.1nm左右的微孔,其介孔体积比炭纤维高;超声晶化时间对晶粒大小无明显影响,但对催化剂活性有重要活性影响:60分钟的晶化活性最好,过长时间会使负载的Ti O2脱落,降低催化剂活性。实验结果还表明,Ti O2/ACF催化剂在重复使用中活性基本稳定,且对甲基橙吸附比原炭纤维高,其原因在于催化剂介孔体积的增加。     

异质结型AgI/AgBr/TiO2催化剂的制备及其光催化性能

首先以沉积-沉淀法制备AgBr/TiO₂复合催化剂,然后采用离子交换法制备出新型的异质结型AgI/AgBr/TiO₂光催化剂.利用XRD和UV-Vis对AgI/AgBr/TiO₂光催化剂进行了表征.以甲基橙为染料模型,在可见光条件下(500 W、λ>420 nm)研究了AgI的含量对AgI/AgBr/TiO₂催化活性的影响.结果表明,AgI拓展了催化剂的吸收光谱范围;AgI生成量为AgBr的5%时,AgI/AgBr/TiO₂的催化活性最高.AgI/AgBr异质结的形成有利于光生电子和空穴的分离,提高AgI/AgBr/TiO₂的催化活性.     

复合光催化剂CeO2/TiO2的制备及性能研究

采用溶胶-凝胶-浸渍法制备了CeO2／TiO2二元复合纳米光催化剂,用XRD、FTIR等对其进行了表征。以紫外灯为光源,直接耐晒兰(DFB)的脱色为模型反应,研究了CeO2／TiO2的光催化活性。结果表明：掺杂摩尔百分比x(CeO2)=1．44％、600℃煅烧2h时,该催化剂的催化活性最高,比纯TiO2高近1倍。DFB脱色的最佳条件为：pH9．0～10．0,投加量200mg／50mL,空气流量200mL／min。     

Photothermal characterization of highly porous,polycrystalline TiO2 electrodes fabricated by chemical synthesis

We report the optical absorption characteristics of highly porous, polycrystalline TiO₂electrodes and the influence of hydrolysis period for the preparation processes by photoacoustic (PA) spectroscopy together with photoelectrochemical (PEC) current ones. The PA spectra show peaks which are attributed to the lowest transition energy due to the quantum confinement effect. The peak intensity decreases with the increase of hydrolysis periods, indicating the possibilities of the changes in the thermal properties and the densities due to hydrolysis processes. The PEC spectra indicate that the photocurrent intensity also show peak and that of the longer hydrolysis periods is somewhat smaller than others, indicating the increase of interface states due to the formation of grain boundaries with the increase of hydrolysis processes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mo掺杂TiO2/AC负载膜的制备及光催化活性

溶胶-凝胶法;Mo掺杂TiO2/AC负载膜的制备及光催化活性     

AgBr/TiO2异质结型复合可见光催化剂的制备及其光催化活性

以钛酸四丁酯、KBr、AgNO3为前体,合成了具有异质结结构的纳米AgBr/Ti O2复合可见光催化剂.利用XRD、TEM、HRTEM和UV-Vis等方法对催化剂的晶相组成、形貌、粒度、微观结构、吸光性能等进行了表征.光催化降解亚甲基蓝活性结果表明,复合与单组分催化剂的光催化活性顺序为:AgBr/Ti O2AgBrAg-Br/P25P25Ti O2.含光敏剂AgBr的复合及单组份催化剂由于具有对可见光的良好吸收性能而具有较高的光催化活性.对于AgBr/Ti O2光催化剂,随mAgNO3/mTi O2比的增加,光催化活性先增强后减弱,当mAgNO3/mTi O2=3.35时光催化活性最高,分析结果表明,该复合催化剂粒径约15 nm,分散均匀且形成了紧密接触的AgBr/Ti O2异质结微结构,在紫外可见区(250～800 nm)都具有最强的光吸收.     

H2O2络合凝胶法制备纳米TiO2/SiO2复合催化剂及其光催化性能

采用H2O2络合凝胶法获得钛的络合物[TiO(H2O2)]2 水溶胶,并与SiO2水溶胶包覆复合,制备了纳米TiO2/SiO2复合半导体催化剂,其结构经XRD和BET表征。以含阳离子艳红染料模拟废水降解为模型反应,考察了复合催化剂的光催化性能。实验结果表明:经650℃焙烧后的复合催化剂中TiO2粒径为9.8 nm,光催化活性最好,SiO2的最佳掺杂量为25%。     

TiO2膜光催化剂的改进及表征

提出用粉末-溶胶法制备TiO2薄膜型光催化剂,介绍了粉溶法的制备工艺及改变pH值对催化活性的影响.研究结果表明, 利用粉溶法或添加浓HNO3后制备的TiO2薄膜光催化剂表现出了较高的光催化活性.结合结构表征详细分析了其中的原因.认为粉溶法制备的催化剂表面更粗糙,比表面积增大,膜厚度减小,这些都可能是其催化活性提高的原因.而加酸后膜催化活性提高主要是因为酸性条件下表面几乎没有Ti3+表面态,利于光生电子与光生空穴的分离.