One step synthesis and characterization of copper doped sulfated titania and its enhanced photocatalytic activity in visible light by degradation of methyl orange

This paper reports on the synthesis of copper doped sulfated titania nano-crystalline powders with varying(2.0%–10.0%, by mass) by single step sol gel method. The synthesized photo catalyst has been characterized by employing various techniques like X-ray Diffraction(XRD), Ultraviolet–Visible Diffuse Reflection Spectroscopy(UV–Vis DRS), X-ray Photoelectron Spectroscopy(XPS), Scanning Electron Microscopy(SEM), Energy Dispersive Spectrometry(EDS), Fourier Transform Infrared Spectroscopic Studies(FT-IR), and Transmission Electron Microscopy(TEM). From the XRD and TEM results, all the samples were reported in anatase phase with reduction in particle size in the range of 7 to 12 nm. SEM indicated the change in morphology of the particles. The presence of copper in titania lattice was evidenced by XPS. From UV–Vis DRS and FT-IR studies indicated that prominent absorption shift is observed towards visible region(red shift), the entry of Cu2+into Ti O2 lattice as a substitutional dopant and SO42-ions were covalently bonded with Ti4 +on the surface of the copper doped titania respectively.The photocatalytic activity studies were investigated by considering methyl orange(MO) as dye pollutant in the presence of the visible light. The effect of various parameters like effect of dosage of the catalyst, dopant concentration, p H of the solution, and concentration of the dye was studied in detail.     

Efficient gas phase photodecomposition of acetone by Ru-doped Titania

Nanocrystalline titania particles doped with ruthenium oxide have been prepared by homogenous hydrolysis of TiOSO₄ in aqueous solutions in the presence of urea. The synthesized particles were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM), Selected Area Electron Diffraction (SAED) and surface area (BET) and porosity determination (BJH). The photocatalytic activity of Ru-doped titania samples was determined in the gas phase by decomposition of acetone during irradiation at 365 nm and 400 nm. The Ru-doped titania samples demonstrated enhanced photocatalytic activity under visible light. Ruthenium oxide causes the anatase to rutile transformation to occur at lower temperatures and decreasing of band-gap energy of Ru-doped samples.     

TiO2掺杂粉体的溶胶-凝胶和水热合成及其光降解甲醛

为了研究不同掺杂对二氧化钛光化学活性的影响,采用溶胶-凝胶,水热法,由TiOCl2成功制备了掺杂氮原子的二氧化钛样品,并制备了掺杂0.5%(摩尔分数)Fe3 ,Gu2 ,V5 ,Pd2 等金属离子的可见光响应型介孔材料.样品经由X射线衍射,透射电镜,Brunauer-Emmett-Teller(BET)比表面积,Barrett-Joyner-Halenda孔径分布,紫外可见光谱,光电子能谱和荧光光谱等表征;以荧光灯为光源(入射光波长λ≥410 nm),光催化降解甲醛为模式,评价了样品的催化活性.结果表明:掺杂Fe3 ,Cu2 ,V5 ,Pd2 的二氧化钛和单一掺氮的二氧化钛样品的粒径均为10 nm左右,BET比表面积为130 m2/g左右,均为锐钛矿相二氧化钛;Fe/TiO2,Cu/TiO2,V/TiO2,Pd/TiO2和TiO2/N样品的带隙能依次为:2.99,2.93,2.36,2.92 eV和2.87 eV,其在可见光下的光催化降解速率常数分别为:0.006 3,0.008 6,0.004 9,0.003 l/min和0.003 3/min.Cu/TiO2较高的荧光强度和较大的比表面积,导致了其较高的可见光光解活性.     

Photocatalytic performance of highly transparent and mesoporous molybdenum-doped titania films fabricated by templating cellulose nanocrystals

In this paper, the synthesis of mesoporous Mo-doped titania films templated by cellulose nanocrystals (CNCs) and their photocatalytic performance are reported for the first time. The prepared titania composite precursors containing the CNCs and molybdenum chloride were spin-coated on indium tin oxide (ITO) glass substrate, followed by calcining at 400?°C for 1?h. X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscope (SEM), and UV–vis spectrometer were employed to characterize the phase composition, pore structure, morphology, and optical property of the titania films in relation to CNCs templating and Mo doping. Photocatalytic performances of the titania films were also evaluated on the photodegradation of trichloroethylene under a fluorescent light source. The Mo-doped titania films with CNCs templating were highly transparent and mesoporous, exhibiting only anatase phase, high specific surface areas ranging in 135.4 – 149.0?m²/g, and small crystallite sizes of 9.5 – 11.1?nm. The results indicate that Mo ions were successfully doped by substituting for Ti ions in the titania lattice. The Mo doping stabilized the anatase phase and also increased the surface area of the CNCs-templated titania film while decreasing the mean pore width. Notably, the visible light absorption capacity and photocatalytic activity of the CNCs-templated titania films doped with Mo were dramatically greater than those of the pure and the CNCs-templated titania films, which is ascribed to the decreased recombination rate of photoexcited charges and the increased surface area with aids of the CNCs templating and the Mo doping.     

用水量对溶胶-凝胶法制备氮掺杂纳米二氧化钛的影响

采用两种用水量的溶胶-凝胶工艺制备了氮掺杂二氧化钛(N-TiO2)纳米颗粒粉末,对样品进行了X射线衍射、透射电子显微镜、X射线光电子能谱及紫外-可见漫反射谱分析,并以甲基橙的光催化降解实验研究了样品的可见光催化性能。结果表明:采用用水多的溶胶-凝胶工艺可获得可见光催化活性高的N-TiO2,且N-TiO2的颗粒粒径较小;由于溶胶中过量的N掺杂剂可在N-TiO2前驱体凝胶离心分离时被去除,可进行较低温度的煅烧,易于获得N掺杂浓度较高的N-TiO2。另外,采用用水多的工艺时,氮掺杂剂对TiO2颗粒的氮化及凝胶化过程也有很大的影响,有些含氮化合物作为掺杂剂可能会明显降低N-TiO2的可见光催化活性。     

Photocatalytic degradation of benzene,toluene, ethylbenzene,and xylene (BTEX) using transition metal-doped titanium dioxide immobilized on fiberglass cloth

Transition metal (Fe, V and W)-doped TiO₂ was synthesized via the solvothermal technique and immobilized onto fiberglass cloth (FGC) for uses in photocatalytic decomposition of gaseous volatile organic compounds—benzene, toluene, ethylbenzene and xylene (BTEX)—under visible light. Results were compared to that of the standard commercial pure TiO₂ (P25) coated FGC. All doped samples exhibit higher visible light catalytic activity than the pure TiO₂. The V-doped sample shows the highest photocatalytic activity followed by the W- and Fe-doped samples. The UV-Vis diffuse reflectance spectra reveal that the V-doped sample has the highest visible light absorption followed by the W- and Fe-doped samples. The X-ray diffraction (XRD) patterns indicate that all doped samples contain both anatase and rutile phases with the majority (>80%) being anatase. No new peaks associated with dopant oxides can be observed, suggesting that the transition metal (TM) dopants are well mixed into the TiO₂ lattice, or are below the detection limit of the XRD. The X-ray absorption near-edge structure spectra of the Ti K-edge transition indicate that most Ti ions are in a tetravalent state with octahedral coordination, but with increased lattice distortion from Fe- to V- and W-doped samples. Our results show that the TM-doped TiO₂ were successfully synthesized and immobilized onto flexible fiberglass cloth suitable for treatment of gaseous organic pollutants under visible light.     

TiCl4为原料掺碳二氧化钛的可见光催化活性

为拓展二氧化钛对可见光的响应,采用水解法和其它步骤制备了碳掺杂二氧化钛粉末。用X射线衍射和紫外-可见光漫反射吸收光谱以及X射线光电子能谱对制备的样品进行了表征,对可见光照射下的光催化活性进行了测试,并考察了光催化的重复性。结果表明：碳掺杂致使二氧化钛在可见光区的光吸收增强,在降解甲基橙的实验中表现出良好的可见光催化活性。     

镍掺杂对二氧化钛光催化性能影响的研究

采用溶胶-凝胶法制备了纳米二氧化钛以及不同掺镍量的TiO₂纳米粒子(原料中Ni∶TiO₂的摩尔分数为1%、3%、5%、7%、9%)。用紫外光照射甲基橙溶液的光催化降解实验研究了掺镍对二氧化钛光催化剂催化效率的影响，试验结果表明,当用n（Ni）∶n（TiO₂）＝5%的Ni(NO₃)₂溶液进行镍掺杂时，制得的TiO₂催化剂光催化效率最高，但与纯TiO₂相比，镍掺杂会减弱TiO₂的光催化效率。X射线衍射分析表明，未掺杂的TiO₂以锐钛矿和金红石两种晶型混合存在，镍掺杂后TiO₂的晶型几乎全为锐钛矿。镍掺杂后会减小TiO₂粒子的尺寸，增大其比表面积。     

Pure and (zinc or iron) doped titania powders prepared by sol-gel and used as photocatalyst

Pure and doped (zinc and iron) nanocrystalline titania powders were prepared by the sol-gel route. Doping tends to change the existing crystalline phases and their degree of crystallinity, but particle size distribution and morphology of the particles are also affected. In the pure titania system, the main crystalline phase is anatase but rutile is also present. The doped (Zn and Fe) titania crystallizes only as anatase. The undoped titania shows a bimodal distribution of particles size: fine (20-40 nm) and coarse (300-500 nm) grains. The doped TiO₂ powder also exhibits a much more uniform particle size distribution, with all grains under 40 nm.The photocatalytic efficiency of suspended powders was tested on the decolouration of Orange II aqueous solutions under visible artificial light irradiation. The maximum decolouration reached by the pure TiO₂ was 81% at a rate of 3.6 × 10⁻³ min⁻¹. Iron doping decreases the photocatalytic activity; the maximum dye degradation was only 43% at a rate of 1.3 × 10⁻³ min⁻¹. On the contrary, the performance of Zn-doped titania was better, having a decolouration rate of 17.7 × 10⁻³ min⁻¹.     

Li–Y doped and codoped TiO2 thin films: Enhancement of photocatalytic activity under visible light irradiation

Sol−gel synthesis based on the self-assembling template method has been applied to synthesize Li–Y doped and co-doped TiO₂ not only to improve simultaneously the structural and electronic properties of TiO₂ nanomaterials but also to achieve Li–Y doping of titania with high photocatalytic reactivity. The characterization of the samples was performed by GXRD, GSDR, FT-IR, and Raman spectroscopy. According to the GXRD patterns, all the observed reflections can be indexed using the anatase form of TiO₂, Which is confirmed by ground state diffuse reflectance and micro-Raman spectra. The Li–Y doped titania materials immobilized as nanostructured thin films on glass substrates exhibit high photocatalytic efficiency for the degradation of toluidine and benzoic acid under visible light irradiation. The development of these visible light-activated nanocatalysts has the potential of providing environmentally benign routes for water treatment.     

Synthesis and visible‐light‐derived photocatalysis of titania nanosphere stacking layers prepared by chemical vapor deposition

BACKGROUND: In this study, visible‐light‐derived photocatalytic activity of metal‐doped titanium dioxide nanosphere (TS) stacking layers, prepared by chemical vapor deposition (CVD), was investigated. The as‐grown TS spheres, having an average diameter of 100–300 nm, formed a layer‐by‐layer stacking layer on a glass substrate. The crystalline structures of the TS samples were of anatase‐type. RESULTS: Ultraviolet (UV) absorption confirmed that metallic doping (i.e. Co and Ni) shifted the light absorption of the spheres to the visible‐light region. With increasing dopant density, the optical band gap of the nanospheres became narrower, e.g. the smallest band gap of Co‐doped TS was 2.61 eV. Both Ni‐ and Co‐doped TS catalysts showed a photocatalytic capability in decomposing organic dyes under visible irradiation. In comparison, Co‐doped TiO₂ catalyst not only displays the adsorption capacity, but also the photocatalytic activity higher than the N‐doped TiO₂ catalyst. CONCLUSION: This result can be attributed to the fact that the narrower band gap easily generates electron–hole pairs over the TS catalysts under visible irradiation, thus, leading to the higher photocatalytic activity. Accordingly, this study shed some light on the one‐step efficient CVD approach to synthesize metal‐doped TS catalysts for decomposing dye compounds in aqueous solution. Copyright © 2010 Society of Chemical Industry     

Improvement in photocatalytic activity of morphologically controlled Pd-supporting TiO2 particles via sol–gel process using inkjet nozzle

The purpose of the present study is to prepare palladium-supporting porous titania particles via a sol–gel process using an inkjet nozzle and to improve the photocatalytic activity of the particles. The morphology of titania particles produced by the sol–gel process using an inkjet nozzle was evaluated by scanning electron microscopy and nitrogen physisorption measurements. The photocatalytic activity of the obtained titania particles was evaluated using the changes in the concentration of a methylene blue solution under UVC light irradiation and the effect of palladium supported on the inner and outer surfaces of the titania particles on the photocatalytic activity was investigated.The titania particles prepared by inkjet processing exhibited spherical porous structures. The particle and pore size distributions of the obtained titania particles were more uniform than those of the titania particles prepared using the non-inkjet nozzle. The titania particles supporting palladium on the inner and outer surfaces exhibited a faster rate of photocatalytic degradation than the titania particles supporting palladium on only the outer surface, with anatase titania particles exhibiting the highest rate of photocatalytic degradation. Thus, we have successfully improved the photocatalytic activity of titania particles by supporting palladium on the inner and outer titania surfaces. This sol–gel process using an inkjet nozzle is an effective method for the preparation of porous titania particles supporting palladium on their inner and outer surfaces.     

Fabrication of titanium doped BiVO4 as a novel visible light driven photocatalyst for degradation of residual tetracycline pollutant

In this study, titanium (Ti) was used as an active dopant to incorporate into BiVO₄ lattice using the hydrothermal method. The synthesized BiVO₄ and Ti–BiVO₄ with 1, 5 and 10 wt% of Ti dopants have been applied for photocatalytic decomposition of Tetracycline under visible light irradiation. The characterized results showed that this synthesized BiVO₄ and Ti–BiVO₄ materials existed in a form of spherical particles. The particle sizes of the Ti–BiVO₄ were much bigger than that of the BiVO₄. However, Ti dopants effectively enhanced visible light absorption, decreased band gap energy as well as prevented electron-hole recombination of the BiVO₄ leading to increase in photocatalytic activities of the doped materials. The obtained results from photocatalytic experiments indicated that the 5Ti–BiVO₄, whose weight ratio of Ti was 5%, was the best material for TC degradation (78.49%). Recycling tests were consecutively carried out in 4 runs to demonstrate the stability of the BiVO₄ photocatalyst with 5 wt% of Ti dopant.     

Processing of iron-doped titania powders in flame aerosol reactors

A flame aerosol reactor was used to synthesize Fe(III)-doped titania powders. The processing conditions were controlled to obtain varying ratios of Fe:Ti in the as processed powders. The iron was incorporated into the titania lattice and promoted the conversion of the anatase to the rutile phase. With an increase in the iron dopant concentration, a decrease in the crystal size of the resultant titania particles was observed, along with a conversion to the amorphous state. The defect structure was further explored by Raman spectroscopy, revealing an increased shift and broadening of the anatase peaks with an increasing iron dopant concentration, and was attributed to shrinkage in the grain size. Absorption spectra revealed a shift of the absorption band toward the visible frequencies. Powders with Fe:Ti ratio exceeding 0.8 resulted in a binary mixture that had superparamagnetic characteristics.     

不同方法制备硫掺杂TiO2及其可见光催化性能研究

采用水热法和焙烧法分别制备了硫掺杂纳米TiO₂,通过扫描电子显微镜、X射线光电子能谱和紫外可见漫反射光谱进行了表征,以水体中的甲基橙（MO）为模拟污染物,研究了硫掺杂纳米TiO₂ 的可见光光催化性能。结果表明,2种不同制备方法得到的硫元素掺杂TiO₂均表现出可见光活性。硫元素在TiO₂中分别取代了O₂和Ti的位置,改变了TiO₂原来的能带结构,形成新的杂质能级,从而使TiO₂ 的吸收区间由紫外拓展到可见光区。     

Flame synthesis of titania particles from titanium tetraisopropoxide in premixed flames

An experimental investigation of flame synthesis of titania particles was conducted in premixed flames. The titanium precursor and silicon dopant used in this study were titanium tetraisopropoxide (TTIP) and hexamethyldisiloxane (HMDS), respectively. The objective of this study was to investigate the influence of flame condition, TTIP concentration, and HMDS on the phase composition and particle morphology of titania synthesized in flames. It was found that the anatase content of titania particles made in flames was appreciably increased by the increase of oxygen concentration in the oxidizer. The increase of flame temperature results in the decrease of anatase content. A significant increase in rutile content of titania particles was observed by increasing the particle residence time at high temperatures. The doping of HMDS in flames inhibits the transformation of anatase to rutile phase and, therefore, reduces the rutile content of product particles. Under the flame doped with low concentrations of HMDS, titania particles with SiO₂ particle agglomerates attached were produced. Further increase of the HMDS concentration up to the Si to Ti molar ratio equal to 0.375 results in the formation of a large amount of SiO₂ agglomerates in the product.     

TiO2对聚氯乙烯紫外光稳定与催化降解的影响

综述了普通和纳米TiO_2对聚氯乙烯(PVC)的紫外光稳定和催化降解的机理及研究进展,以及包覆和掺杂改性对TiO_2光稳定和光催化性能的作用。金红石型纳米TiO_2具有优异的紫外光稳定特性,锐钛型纳米TiO_2表现出极强的光催化活性。无机包覆过的金红石型TiO_2对PVC有明显的保护作用。有机改性则能提高锐钛型TiO_2的分散性,从而提高其对聚合物的光催化效率。过渡金属离子掺杂可在TiO_2晶格中引入缺陷位置或改变结晶度,从而改变PVC的光降解速率。     

CdS/TiO2复合纳米粒子的制备及其产氢性能研究

采用化学沉淀法制备了CdS包覆TiO2（CdS/TiO2）复合纳米粒子,利用XRD、TEM、SEM、UV-vis吸收光谱等对其进行了表征分析,并以可见光分解水制氢为探针反应考察了复合纳米粒子的活性。结果表明,CdS/TiO2 复合纳米粒子的颗粒大小约为40nm,TiO2 以锐钛矿型存在,CdS以六方相存在;复合纳米粒子的吸收光谱较TiO2 发生“红移”,大幅拓宽了对可见光区的吸收范围。光解水制氢实验表明,CdS/TiO2 复合纳米粒子具有良好的可见光释氢活性和光学稳定性。     

Removal of methylene blue from aqueous solution by electrophoretically deposited titania‐halloysite nanotubes coatings

Two‐component suspensions of titania and halloysite nanotubes (HNTs) were prepared in ethanol with 0.5 g/L (optimum concentration) of polyethyleneimine (PEI) and different wt% of HNTs. Kinetics of Electrophoretic deposition (EPD) decreased with increasing the HNTs content in suspensions due to their less mobility compared with titania particles. HNTs reinforced the microstructure of coatings and reduced or completely prevented from cracking during drying and heat‐treatment steps. Removal of methylene blue (MB) via adsorption by HNTs coatings was faster than its photocatalytic degradation by titania coating. Dispersion of HNTs (up to ≈30 wt%) in the matrix of titania resulted in the synergistic catalytic effect in MB removal. The synergistic effect was because of the shorter traveling distance of MB molecules adsorbed on HNTs toward the photocatalytic active site of titania particles in composite coatings. However, the synergistic effect was destroyed with increasing the HNTs content in coating. Difference between the amount of MB removed by titania and composite coatings increased at longer times (≥60 minutes). Mass transfer of MB adsorbed on HNTs toward the photocatalytic active sites of adjacent titania particles can compensate the decline in the mass transfer from solution at longer times.     

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。