Synthesis and structure analysis of La0.5SR0.5TiO3 nanoparticles prepared by thermal decomposition method

La0.5Sr0.5TiO3 (LSTO) nanoparticles were synthesized by thermal decomposition method using Cl3La, CI2Sr x 6H2O and C16H28O6Ti as starting materials. The obtained precursor in a powder form was calcined at 700, 900, 1100 and 1300 degrees C for 3, 6 and 9 h in air. The structures of all samples were analyzed by XRD and some of them were taken for SEM, TEM and VSM measurements. The results from SEM showed the parallelpipe like shape of the particles with sizes distributed between 80 and 180 nm and the sizes of these particles were increased with the increasing of calcination temperature and time. The XRD's results showed the perovskite structure with the lattice type of orthorhombic at the calcination temperature of 900, 1100 and 1300 degrees C for 3, 6 and 9 h. The TiO and others unknown phase were found at low calcination temperature and they were disappeared as the calcination temperature and time were increased. The results of TEM support the orthorhombic structure of LSTO nanoparticles with crystallite size less than 200 nm as revealed by SEM and XRD. The magnetic property of all samples was measured by VSM and revealed that those prepared at 700, 900, and 1100 degrees C exhibit diamagnetic behavior, whereas one at 1300 shows ferromagnetism at room temperature. In this work, it is found that the nano-LSTO of high crystalline phase and purity can be prepared by thermal decomposition method at calcination temperature of 900 to 1300 degrees C in air for 6-9 h.     

Effect of calcination temperature on the textural properties and photocatalytic activities of highly ordered cubic mesoporous WO3/TiO2 films

Highly organized cubic mesoporous WO3/TiO2 films were successfully prepared by evaporation-induced self-assembly (EISA) process, employing triblock copolymer as template. The characterization results by XRD, SEM, TEM, UV-Vis. spectrophotometry, and nitrogen adsorption-desorption isotherms reveal that the mesoporous films are made up of well-defined 3-D cubic (lm3m space group) mesoporous structure and nanocrystalline anatase frameworks with high surface area, uniform pore sizes and excellent optical transparency. Photocatalytic properties of the mesoporous WO3/TiO2 films in decomposing gaseous 2-propanol to CO2 were analyzed as a function of calcinations temperature. The highest photocatalytic activity was obtained for the films calcined at 450 degrees C, which possess an appropriate crystallinity and relevant ordering of mesoporous structure. It was found that that long-range ordering of mesopores is one of the important factors in determining the photocatalytic degradation of gaseous organics.     

Influence of structure parameters and crystalline phase on the photocatalytic activity of TiO2 nanotube arrays

Titanium oxide nanotube arrays (TiO2-NTAs) with different diameters and lengths are prepared by anodization of titanium foils in a water/ethylene glycol solution (5:95 V/V) containing 0.3 wt% NH4F. The effects of the diameters, lengths and crystalline phases of the NTAs on the photocatalytic (PC) activity are systematically evaluated. Larger pore diameter results in higher PC activity. The PC activity increases initially and then decreases with lengths for TiO2-NTAs and the optimal length that yields the highest PC activity is observed to be 6.2 microm. The crystalline phase and corresponding PC activity depend on the calcination temperature and their relationship is also investigated. The amorphous-to-anatase and anatase-to-rutile phase transitions initially occur at 300 and 500 degrees C, respectively. The PC activity of TiO2-NTAs initially increases with calcination temperature from 250 to 500 degrees C and then decreases at higher calcination temperature. The enhanced PC activity observed from the samples annealed at 250-450 degrees C is attributed to the better anatase crystalline structure at higher calcination temperature. The highest PC activity with regard to photodecomposition of methyl orange is observed from TiO2-NTAs calcined at 500 degrees C, which coincides with the anatse-to-rutile phase transformation. The synergistic effect of the anatase TiO2-NTAs and rutile barrier layers facilitate interfacial electron transfer consequently enhancing the PC activity. Further elevation of the calcination temperatures to 550 and 600 degrees C exhibits diminished PC activity because the NTs become shorter due to conversion of the bottom of anatase NTs into rutile film.     

Improved catalytic capability of mesoporous TiO2 microspheres and photodecomposition of toluene

A series of mesoporous titanium dioxide microspheres were calcined at various temperatures to improve their photocatalytic activity. The prepared catalysts were characterized by XRD, SEM, TEM, TG-DTA, UV-vis, and N(2) adsorption-desorption measurements, and their photocatalytic performances were investigated by photooxidation of gaseous toluene. As the results revealed, calcination temperatures obviously influenced the surface morphology and photocatalytic activity of the mesoporous TiO(2) microspheres. The noncalcined samples had a mesoporous structure of the anatase phase. The sample calcined at 400 °C showed a superior photocatalytic performance, which had a reaction rate constant 2-fold higher than that of P(25). The enhanced photoreactivity is possibly due to the synergetic effects of the mesoporous structure and light-transmittance ability of the catalysts. Two new reaction intermediates were discovered as well, and a tentative degradation pathway was proposed.     

H(2)O(2)-sensitized TiO(2)/SiO(2) composites with high photocatalytic activity under visible irradiation

TiO(2)/SiO(2) composite photocatalysts were prepared by depositing of TiO(2) onto nano-SiO(2) particles. X-ray diffraction (XRD), transmission electron micrograph (TEM), Raman spectrometer, UV-Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy (FT-IR) were employed to characterize the properties of the synthesized TiO(2)/SiO(2) composites. These results indicated that the products without calcination were amorphous, and calcination could enhance the crystallinity of TiO(2). Increases in the amount of TiO(2) would decrease the dispersion in the composites. H(2)O(2)-sensitized TiO(2)/SiO(2) composite photocatalysts could absorb visible light at wavelength below 550 nm. The photocatalytic activity of as-prepared catalysts was characterized by methyl-orange degradation. The results showed the uncalcined composite photocatalysts with amorphous TiO(2) exhibited higher photocatalytic activity under visible light, and the activity of catalysts with TiO(2) content over 30% decreased with increasing of TiO(2) content. Increases in the calcination temperature and TiO(2) content promote the formation of bulk TiO(2) and result in a decrease in activity.     

Synthesis of mesoporous titania nanoparticles with anatase frameworks and investigation of their photocatalytic performance

In this research paper, we synthesize various types of mesoporous titania nanoparticles (MTNs) with suitable surface area and pore size while creating anatase frameworks by applying hydrothermal treatment or calcination at different temperatures. Wide-angle XRD patterns and N2 adsorption-desorption isotherms reveal that the MTNs with crystallized anatase frameworks can be synthesized after an optimized hydrothermal treatment. In contrast, calcination of MTNs at high temperature caused the collapse of mesoporous structure, resulted in drastic reduction of the surface area of the MTNs. In addition, we investigate the photocatalytic activity of the prepared MTNs by measuring the degradation of methylene blue (MB). The results show that the reaction rates of the photocatalytic MB decomposition strongly depend on the degree of crystallinity in the MTNs frameworks and on the surface area of MTNs.     

煅烧温度对TiO_2中空微球光催化性能的影响

以分散聚合法制得的单分散阳离子聚苯乙烯（PS）微球为模板,钛酸丁酯为前驱体,采用溶胶-凝胶法在模板表面包覆TiO2壳层,并在不同煅烧温度下制备了晶相结构不同的微米级中空TiO2微球。采用TEM、SEM、FT-IR、XRD、UV-Vis DRS对样品的微观结构、相态组成及光催化性能进行了表征。结果表明TiO2中空微球平均粒径达到1.23μm,壳层厚度约为30nm;随着煅烧温度增加,锐钛矿晶粒尺寸会增加,并在700℃时出现混晶结构;在500℃煅烧得到的TiO2中空微球对甲基橙（MO）降解表现出比P25更好的光催化性能及光催化稳定性。     

Direct formation of reusable TiO2/CoFe2O4 heterogeneous photocatalytic fibers via two-spinneret electrospinning

A reusable photocatalytic TiO2/CoFe2O4 composite nanofiber was directly formed by using a vertical two-spinneret electrospinning process and sol-gel method, followed by heat treatment at 550 degrees C for 2 h. The high photocatalytic activity of the composite nanofibers depends on the good morphology of the fibers and the appropriate calcination temperature. The crystal structure and magnetic properties of the fibers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The photocatalytic activity of the TiO2/CoFe2O4 fibers was investigated through ultraviolet-visible absorbance following the photo-oxidative decomposition of phenol. Meanwhile, the presence of CoFe2O4 not only broadens the response region of visible light, but also enhances the absorbance of UV light. Furthermore, these fibers displayed photocatalytic activity associated with magnetic activity of CoFe2O4 ferrites, allowing easy separated of the photocatalysts after the photo-oxidative process and effectively avoided the secondary pollution of the treated water.     

晶粒尺寸可控的纳米二氧化钛的制备

采用微乳法和溶胶-凝胶法相结合的方法制备纳米二氧化钛,通过改变制备参数可以将纳米二氧化钛的晶粒尺寸控制在6~30 nm之间。采用X射线衍射、透射电镜等表征手段,对不同的制备条件与晶粒尺寸的关系进行研究。通过在可见光下对亚甲基蓝水溶液的降解测试其光催化活性。结果表明:补充结论纳米二氧化钛具有良好的光催化性能。     

Photocatalytic oxidation of nitric oxide with immobilized titanium dioxide films synthesized by hydrothermal method

Gas-phase photocatalytic oxidation (PCO) of nitric oxide (NO) with immobilized TiO2 films was studied in this paper. The immobilized TiO2 films were synthesized by hydrothermal method. The characterization for the physicochemical properties of catalysts prepared under different hydrothermal conditions were carried out by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), high resolution-transmission electron microscopy (HR-TEM), Brunauer-Emmett-Teller measurements (BET) and scanning electron micrograph (SEM). It was found that the PCO efficiency of the catalyst was mainly depended on the hydrothermal conditions. The optimal values of hydrothermal temperature and hydrothermal time were 200 degrees C and 24 h, respectively. Furthermore, it was also known that the photocatalytic efficiency would decrease remarkably when the calcination temperature was over than 450 degrees C. Under the optimal conditions (hydrothermal condition: 200 degrees C for 24 h; calcination temperature: 450 degrees C), the photocatalytic efficiency of catalyst could reach 60% higher than that of Degussa P25.     

Synthesis, characterization and photocatalytic H2 generation over ternary indium titanate nanoparticles

A low temperature surfactant-free solution-phase method has been successfully developed for the synthesis of ternary In2TiO5, nanoparticles using a solvothermal route. The mechanistic aspects of synthesis of In2TiO5 nanoparticles from precursors, In(acac)3 and Ti(IV) isopropoxide in benzyl alcohol at 220 degrees C under solvothermal conditions, were investigated by GC-MS and 13C{1H} NMR analysis. The N2-BET surface area of the 5-8 nm sized In2TiO5 nanoparticles was found to be 60 m2 g(-1), which decreased with increase in calcination temperature; 38 m2 g(-1) at 800 degrees C; 5 m2 g(-1) at 1200 degrees C. The High resolution transmission electron microscopy (HR-TEM) shows well-developed lattice fringes of the crystalline nanoparticles, and selected area electron diffraction (SAED), pattern was indexed to be orthorhombic In2TiO5. The nanoparticles show better photocatalytic hydrogen generation from water-methanol mixtures over bulk In2TiO5, anatase TiO2 nanoparticles prepared by identical route and commercial TiO2 photocatalyst (Degussa, P25) under UV-visible irradiation (16% UV + 84% visible). Photocatalytic properties as a function of crystallinity and surface area of indium titanate nanoparticles have also been investigated. The high photoactivity obtained is correlated with the electronic and crystal structure of In2TiO5.     

Synthesis of TiO2 supported on SBA-15 using chelating method and their photocatalytic decomposition of methylene blue

SBA-15 mesoporous materials were successfully prepared by the conventional hydrothermal method and used as the support for TiO2 loaded SBA-15 photocatalysts. The synthesized materials were characterized by XRD, PL, FT-IR, BET and TEM. We also examined the activity of these materials as photocatalysts for the decomposition of methylene blue. The loading of titanium dioxide on the framework of SBA-15 makes the pore diameter and the pore volume decrease and decreases the surface area compared to that of SBA-15. For the TiO2 loaded SBA-15 photocatalysts, the IR absorption at approximately 960 cm(-1) is commonly accepted as the characteristic vibration of the Ti-O-Si bond. The PL peaks appears at about 410 nm at a loading ratio of less than 5% but moves to 430 nm at higher loading ratios. It was also shown that the excitonic PL signal is proportional to the photocatalytic activity for the decomposition of methylene blue. The photocatalytic activity increases with increasing TiO2 loading ratio, shows a maximum value at 7% TiO2/SBA-15, and then decreases at 10% TiO2/SBA-15.     

Preparation and characterisation of TiO2 nanoparticle and titanate nanotube obtained from Ti-salt flocculated sludge with drinking water and seawater

This study aimed to prepare and characterise titanium dioxide (TiO2) nanoparticles and titanate nanotubes produced from Ti-sat flocculated sludge with drinking water (DW) and seawater (SW). The Ti-salt flocculated sludge from DW and SW was incinerated at 600 degrees C to produce TiO2 nanoparticles. XRD results showed that the anatase TiO2 structure was predominant for TiO2 from DW (TiO2-DW) and TiO2 from SW (TiO2-SW), which were mainly doped with carbon atoms. Titanate nanotubes (tiNT) were obtained when TiO2-DW and TiO2-SW were hydrothermally treated with NaOH solution. Structure phase, shape, crystallisation and photocatalytic activity of tiNT were affected by the incineration temperature and the amount of sodium present in different tiNT. The tiNT doped with thiourea incinerated at 600 degrees C presented anatase phase, showing a high increase of the degree of crystallisation with nanotube-like structures. The photocatalytic activity of these photocatalysts was evaluated using photooxidation of gaseous acetaldehyde. Thiourea doped tiNT-DW and tiNT-SW showed similar photocatalytic activity compared to commercially available TiO2-P25 under UV light and indicated a photocatalytic activity under visible light.     

Effect of filler types and calcination temperature on the microstructure and the nitric oxide photocatalytic activity of composite titanium dioxide films

The composite titanium dioxide (TiO(2)) films coating on the woven glass fabric were prepared by a modified sol-gel process, using pre-calcinated TiO(2) nanoparticle or silica gel as filler. The characterized physicochemical properties of the prepared catalyst films showed that the specific surface area, the microstructure and the crystal structure of the catalysts were greatly affected by the fillers and the calcination temperature. The physicochemical properties of composite films and the photocatalytic activity of nitric oxide (NO) show that the pre-calcinated TiO(2) nanoparticle is more favorable than silica gel as filler. The pre-calcinated TiO(2) nanoparticle filler can increase the photocatalytic activities of the catalysts by increasing the specific surface area, introducing a bimodal mesoporous structure, and creating a polymorphous crystal structure. And the TiO(2)-TiO(2) film calcinated at 400 degrees C exhibits the highest photocatalytic activity for NO oxidation and is more active than Degussa P25.     

溶胶-凝胶法制备TiO2粉体及其光催化性能研究

以钛酸丁酯为前驱物,无水乙醇为溶剂,采用溶胶-凝胶法制备了TiO2粉体,并采用紫外分光光度计、XRD等表征手段对TiO2的粒度、晶型结构进行了表征,分析了煅烧温度、TiO2晶型比例、溶液初始pH值等因素对TiO2结构性能及光催化活性的影响.结果表明:TiO2的锐钛矿晶型与金红石晶型的转相温度为700 ℃左右;采用溶胶-凝胶法制备TiO2时,控制溶液的pH值为4,煅烧温度为600 ℃,所得产物晶型全部为锐钛矿;当无水乙醇与钛酸丁酯的体积比为10:1时,产物的粒径为617 nm;且当配制溶液pH值为4,煅烧温度为600℃条件下,煅烧时间为40~60 min时,所制备TiO2的光催化效果较好,降解率较高;当光催化体系的pH值为9、以质量浓度为10 mg/L的亚甲基兰溶液浸泡2 h,TiO2的用量为0.25 g/L时,产物的降解率高达95.3%.     

Synthesis, characterization, and photocatalytic activity of TiO(2-x)N(x) nanocatalyst

Nitrogen-doped titanium dioxide powders were prepared by wet method, that is, the hydrolysis of acidic tetra-butyl titanate using aqueous ammonia solution, followed by calcination at temperatures about 350 degrees C. The catalysts exhibited photocatalytic activity in the visible light region owing to N-doping. The light absorption onset of TiO(2-x)N(x) was shifted to the visible region at 459 nm compared to 330 nm of pure TiO(2). An obvious decrease in the band gap was observed by the optical absorption spectroscopy, which resulted from N2p localized states above the valence band of TiO(2-x)N(x) (compared to TiO(2)). The TiO(2-x)N(x) catalyst was characterized to be anatase with oxygen-deficient stoichiometry by X-ray diffraction (XRD), surface photovoltage spectroscopy (SPS) and X-ray photoelectron spectroscopy (XPS). The binding energy of N1s measured by XPS characterization was 396.6 eV (TiN bonds, beta-N) and 400.9 eV (NN bonds, gamma-N(2)), respectively. The photocatalytic activity of TiO(2-x)N(x) under visible light was induced by the formation of beta-N in the structure. Photocatalytic decomposition of benzoic acid solutions was carried out in the ultraviolet and visible (UV-vis) light region, and the TiO(2-x)N(x) catalyst showed higher activity than pure TiO(2).     

介孔TiO2/WO3空心球的制备及其可见光光催化性能

以硫酸氧钛和偏钨酸铵为前驱体, 以柠檬酸作为络合剂, 采用喷雾干燥-高温煅烧两步法制备了介孔TiO₂/WO₃空心球复合材料。利用SEM、TEM、BET、XRD、UV-Vis DRS等手段对样品的形貌、微结构、比表面积、晶相组成和光学性能进行了表征和分析, 以亚甲基蓝为模拟降解物考察其光催化性能。结果表明: 复合材料为介孔空心球状结构, 球体分散好, 直径主要分布在1 μm左右; 球壁由纳米颗粒和空隙构成, 随着煅烧温度的升高, 颗粒粒径不断增大, 空隙孔径不断增大。性能研究结果表明, TiO₂与WO₃复合后, 样品对光的吸收范围扩展到了可见光区域, 这有利于提高太阳光的利用率; 当前驱体中WO₃含量为3mol%, 样品的煅烧温度为500℃时, 复合材料具有最好的光催化性能: 对亚甲基蓝降解率可达99.1%, 而P25的降解率仅为29.5%。     

Visible light active photocatalytic degradation of bisphenol-A using nitrogen doped TiO2

Nitrogen doped titania was prepared by low temperature sol-gel method using titanium precursor and nitrogen containing bases like triethylamine and tetramethyl ammonium hydroxide compounds. The materials were characterized by XRD, BET, SEM, XPS, DRS-UV, and FT-IR techniques. DRS-UV study substantially indicates shift of the absorption edge of TiO2 to lower energy region. The phase composition, crystallinity, specific surface area, and visible light activity of nitrogen doped titania depend upon the preparation conditions. Photocatalytic degradation of bisphenol-A in aqueous medium was investigated by TiO2 and nitrogen doped TiO2 under visible light irradiation in a batch photocatalytic reactor. The results indicate higher visible light activity for nitrogen doped TiO2 than commercial TiO2 (Degussa P25) for bisphenol-A degradation. The influence of various parameters such as initial concentration of bisphenol-A, catalyst loading and pH was examined for maximum degradation efficiency.     

Synthesis and photocatalytic activity of stable nanocrystalline TiO(2) with high crystallinity and large surface area

Superior photoactive TiO(2) nanopowders with high crystallinity and large surface area were synthesized by a hydrothermal process in the presence of cetyltrimethylammonium bromide and a post-treatment with ammonia. The prepared photocatalysts were characterized by X-ray diffraction (XRD), Raman spectroscopy, N(2) adsorption-desorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectra (DRS) and surface photovoltage spectroscopy (SPS). The prepared nanocrystallites were highly resistant to thermal sintering, and the calcinations up to 900 degrees C were shown to enhance the crystallinity of the anatase phase without any rutile phase and the separation rate of photoinduced charges of TiO(2) particles. It remained as large as 196 and 125 m(2)/g even after calcinations at 700 and 800 degrees C, respectively. The photocatalytic activity of prepared photocatalysts was obviously higher than that of commercial Degussa P25 on the photodegradation of methylene blue and phenol in water under ultraviolet-light irradiation, and the sample calcined at 800 degrees C afforded the highest photocatalytic activity.     

Mn、N共掺杂TiO_2负载竹质活性炭纤维的制备及可见光光催化性能

为研究Mn、N共掺杂TiO_2负载竹质活性炭纤维(Mn-N/TiO_2-BACF)的可见光光催化性能,首先,以MnSO_4·H_2O为锰源,尿素为氮源,采用溶胶-凝胶法制备了光催化复合材料Mn-N/TiO_2-BACF;然后,利用SEM、XRD及XPS等考察了煅烧温度对Mn-N/TiO_2-BACF结构和可见光光催化性能的影响。结果表明:Mn、N共掺杂使光催化复合材料的光响应范围由紫外光区域拓宽至可见光区域;随煅烧温度的提高,光催化复合材料表面的晶格氧含量逐渐降低,吸附氧含量先降低后增加,而羟基氧含量有所增加;光照400min后,350℃锻烧制备的Mn-N/TiO_2-BACF在可见光下对亚甲基蓝的光降解率达99.7%。同时,还发现Mn-N/TiO_2-BACF在可见光下的光降解率与煅烧温度没有相关性。