TiO<Subscript>2</Subscript>/TiO<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>N<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> nanocomposite and its acetaldehyde photodecomposition ability

Nitrogen-doped titania was coupled with the commercial titania nanoparticles by mechanical milling in liquid medium. The as-prepared nanocomposites (TiO₂/TiO_2−x N _y ) were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) specific surface area, UV–Vis spectroscopy, chemiluminescence, and acetaldehyde decomposition activity techniques. When a small amount of nitrogen-doped titania was added into the commercial titania, higher intensity and longer lifetime of ¹O₂ was observed, and the photocatalytic activity was efficiently improved. The TiO_2−x N _y acts as the acceptor of photoinduced holes. The recombination of the electron-hole was effectively depressed by the heterogeneous electron transfer. This could be an effective way to obtain highly active photocatalysts.     

Surface properties and photocatalytic activity of nanocrystalline titania films

In this work the efficiency and physicochemical details of a thin film produced by help of a microwave assisted sol gel technique is compared to different commercial powders (Degussa P25 and Hombikat UV100) deposited on glass substrates. Furthermore, a supercritical produced TiO₂ powder (SC 134) was included in the comparison.The prepared TiO₂ films were characterized using XRD, XPS, AFM, DSC and DLS. The photocatalytic activity was determined using stearic acid as a model compound. Investigation of the prepared films showed that the Degussa P25 film and the sol–gel film were the most photocatalytic active films. The activity of the films was found to be related to the crystallinity of the TiO₂ film and the amount of surface area and surface hydroxyl groups. Based on the XPS investigation of the films before and after UV irradiation it was suggested that the photocatalytic destruction of organic matter on TiO₂ films proceeds partly through formation of hydroxyl radicals which are formed from surface hydroxyl groups created by interactions between adsorbed water and vacancies on the TiO₂ surface. Furthermore a correlation between the amount of OH groups on the surface of the different TiO₂ films and the photocatalytic activity was found.     

Photocatalytic Activity of Titanium Dioxide Nanoparticles Immobilized in the Polymer Network of Polyacrylamide Hydrogel

Composite hydrogels based on polyacrylamide immobilized nanoparticles of commercial (P25 brand) titanium dioxide and of titanium dioxide nanoparticles prepared by electric explosion of a wire were synthesized. The enthalpy of interaction at the polyacrylamide/TiO₂ interface was determined by microcalorimetry using the thermochemical cycle method. Interaction of polyacrylamide polymer chains with the surface of TiO₂ nanoparticles is energetically unfavorable. The absence of interactions between the hydrogel polymer network and surface of TiO₂ nanoparticles favors manifestation of the UV-induced photocatalytic activity of TiO₂ nanoparticles immobilized in the hydrogel. Immobilization in the polyacrylamide hydrogel matrix decreases the photocatalytic activity of P25 brand TiO₂ nanoparticles, but does not affect the photocatalytic activity of titanium dioxide nanoparticles prepared by the electric explosion method. The photocatalytic activity of TiO₂ nanoparticles immobilized in the bulk of polyacrylamide hydrogel evaluated by the decomposition of Methyl Orange dye is controlled by the diffusion rate of the dye molecules into the bulk of the hydrogel and depends also on the aggregation of TiO₂ nanoparticles in the hydrogel matrix.

     

Synthesis and photocatalytic activity for water-splitting reaction of nanocrystalline mesoporous titania prepared by hydrothermal method

Nanocrystalline mesoporous TiO₂ was synthesized by hydrothermal method using titanium butoxide as starting material. XRD, SEM, and TEM analyses revealed that the synthesized TiO₂ had anatase structure with crystalline size of about 8 nm. Moreover, the synthesized titania possessed a narrow pore size distribution with average pore diameter and high specific surface area of 215 m²/g. The photocatalytic activity of synthesized TiO₂ was evaluated with photocatalytic H₂ production from water-splitting reaction. The photocatalytic activity of synthesized TiO₂ treated with appropriate calcination temperature was considerably higher than that of commercial TiO₂ (Ishihara ST-01). The utilization of mesoporous TiO₂ photocatalyst with high crystallinity of anatase phase promoted great H₂ production. Furthermore, the reaction temperature significantly influences the water-splitting reaction.     

掺氮TiO2可见光降解有机污染物的比较研究

用溶胶-凝胶法制备了不同掺杂量的N/TiO₂复合纳米粉末, 采用X射线衍射(XRD)、扫描透镜(TEM)、紫外-可见反射吸收光谱(UV-vis)对催化剂进行了初步表征. 通过X射线光电子能谱(XPS)、元素分析仪(EA)测定其含氮量. XPS分析结果显示TiO₂晶格中的氧被氮原子取代, N/TiO₂表面存在Ti^3＋离子; 紫外-可见反射吸收光谱测得不同掺杂量的N/TiO₂的禁带宽度(E_g), 推测在TiO₂价带上方生成了由N诱导产生的中间带, 当氮、钛摩尔比为0.0880时N/TiO₂的E_g最小, 为2.50 eV. 在可见光下, 以酸性桃红(SRB)和无色小分子对氯苯酚(4-CP)作为可见光活性实验的探针反应, 确定了最佳掺杂比为n_N/n_Ti＝0.0880. 结果表明, 最佳掺杂量下N/TiO₂能显著降解SRB和4-CP, 通过测定ESR, IR, TOC, COD, 重点比较了TiO₂在掺杂N前后在降解SRB和4-CP时的差异, 包括氧化物种、矿化率、最终产物等, 证明在可见光下, N/TiO₂的降解机理为电子从独立的N 2p轨道激发到Ti 3d轨道, 产生羟基自由基等氧化物种, 达到降解有机物的目的.     

Comparison between the performance of an immobilized impinging jet stream reactor and a slurry impinging jet stream reactor for photocatalytic phenol degradation

A new immobilized photocatalytic impinging jet stream reactor was designed, and the influences of the effective parameters like jet flow rate, TiO₂ coating disc diameter, nozzle-to-disc distance, and initial concentration on phenol removal were investigated. The reactor was also used as a slurry reactor, and degradation efficiencies in both reactors were compared based on their catalyst loading. The results indicated that the slurry reactor has a higher degradation efficiency than the immobilized reactor at the same TiO₂ loading and other operational conditions. The slurry reactor needs to separate and recover the TiO₂ nanoparticles from the reaction medium which increases the overall process complexity and cost, while the immobilized reactor could be reused at least 4times without any significant decrease in removal efficiency. RTD result indicates that the tank in series model (N?=?5) could properly predict the reactors hydrodynamic behavior.     

Removal of cationic Rhodamine-B dye using nano-titania with anatase crystalline structure and kinetic analysis of the photocatalytic reaction

Heterogeneous photocatalytic removal of Rhodamine-B (RhB) dye from liquid phase was done using anatase-phase nanocrystalline TiO₂ synthesized via a modified sol-gel process. The anatase-phase nanocrystalline TiO₂ was characterized using various analytical techniques including XRD, UV-vis DRS, PL, and FTIR to investigate its phase composition and structure, nanocrystalline size, band gap energy, photoluminescence and surface properties of the prepared systems. The photocatalytic discoloration efficiency of anatase-phase nanocrystalline titania was investigated by monitoring the decomposition of RhB dye as target compounds in an aqueous solution. The results showed that the as-prepared anatase-phase nanocrystalline TiO₂ was excellent for degradation of RhB molecule, and the crystallite size, excitonic PL and surface hydroxyl content have intimate relationship with the decomposition efficiency of RhB. The reaction mechanism was proposed and the results demonstrate that the role of direct photolysis on RhB dye degradation can be neglected. Meanwhile, the Langmuir-Hinshelwood kinetic model describes the photodecay date of RhB in consistent with a first order powder law and thus photocatalytic oxidation reaction followed a pseudo-first-order kinetics.     

Photoactive Polythiophene:Titania Hybrids with Excellent Miscibility for Use in Polymer Photovoltaic Cells

A series of poly{(3‐hexylthiophene)‐co‐[3‐(6‐hydroxyhexyl)thiophene]}:titania (P3HT‐OH:TiO₂) hybrids were synthesized via the in situ polycondensation of titanium (IV) n‐butoxide in the presence of P3HT‐OH. Introducing a hydroxyl moiety onto the side‐chain of poly(3‐hexylthiophene) (P3HT) significantly promotes the polymer‐titania interaction, resulting in the formation of homogeneous hybrid colloids. The UV‐vis spectra of P3HT‐OH:TiO₂ films demonstrate that TiO₂ markedly affects the stacking structure and the chain conformation of P3HT‐OH. The maximum absorption wavelength of these hybrid materials can be tailor‐made by merely varying the weight percentage of TiO₂. Moreover, P3HT‐OH:TiO₂ can be further utilized as an efficient compatibilizer in preparing photoactive P3HT:P3HT‐OH:TiO₂ films with excellent miscibility. The photovoltaic cell based on such a hybrid exhibited a 2.4‐fold higher value of power‐conversion efficiency compared to the cell based on P3HT:TiO₂.

     

Facile preparation of extremely photoactive boron-doped TiO2 nanotubes arrays

Doping of TiO₂ nanotube arrays with boron was realized via electrochemical treatment of as-anodized titania immersed in electrolyte containing boric acid. The photoactivity of doped and pure titania was examined by means of photoelectrochemical and photocatalytic response under UV–vis irradiation. The results showed that photocurrent density of B-TNTs is remarkably higher (7.5 times) than density of pure TiO₂ nanotube arrays. Furthermore, the usage of doped samples as a catalytic material leads to a significant improvement in decomposition efficiency of methylene blue and in the efficient formation of hydroxyl radicals than is the case in the presence of titania.     

Accelerated Photo-Induced Degradation of Benzidine-p-Aminothiophenolate Immobilized at Light-Enhancing TiO2 Nanotube Electrodes

Herein, the enhanced visible-light-induced degradation of the azo-dye benzidine-p-aminothiophenolate immobilized on TiO₂ nanotube electrodes is reported. Exploiting the reported photonic properties of the TiO₂ support and the strong electronic absorption of the dye allowed for employing surface-enhanced resonance Raman spectroscopy at 413 nm to simultaneously trigger the photoreaction and follow the time-dependent decay process. Degradation rate constants of up to 25 s⁻¹ were observed, which stand among the highest reported values for laser-induced degradation of immobilized dyes on photonically active supports. Contrast experiments with two differently light-enhancing TiO₂ nanotube electrodes establish the direct correlation of the material's optical response, that is, electromagnetic field enhancement, on the interfacial photocatalytic reaction.     

Influence of Pt promoter on the photo-oxidative degradation by visible-light plasmonic Pt-titania catalyst

Nanometer platinum-deposited titania particles were prepared through a soft chemical reduction method. The physico-chemical properties of the obtained products are analyzed by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, and photoluminescence spectra. The as-prepared metal-TiO₂ nanohybrid was found to show excellent photocatalytic reactivity toward rhodamine-B decomposition. In the current case, chemical reduction of hydrogen hexachloroplatinate by glucose results in the intercalation of metallic platinum into the titania matrix. The deposited platinum atoms were featured by surface-plasmon resonance under visible-light excitation and electrons from platinum nanoparticles would transfer to the conduction band of titania and accelerate the formation O₂^*− to degrade dye molecule. As a consequence, platinum deposition onto TiO₂ surface is confirmed to yield a superior photocatalytic performance over the naked titania.     

Visible-light-driven Oxygen Vacancy and Carbon Doping of C@TiO2-x Photocatalyst for Enhanced Pollutants Degradation Performance

Oxygen Vacancy (OVs) and carbon doping of the photocatalyst body will significantly enhance the photocatalytic efficiency. However, synchronous regulation of these two aspects is challenging. In this paper, a novel C@TiO_2-x photocatalyst was designed by coupling the surface defect and doping engineering of titania, which can effectively remove rhodamine B (RhB) and has a relatively high performance with wide pH range, high photocatalytic activity and good stability. Within 90 minutes, the photocatalytic degradation rate of RhB by C@TiO_2-x (94.1 % at 20 mg/L) is 28 times higher than that of pure TiO₂. Free radical trapping experiments and electron spin resonance techniques reveal that superoxide radicals (⋅O²⁻) and photogenerated holes (h⁺) play key roles in the photocatalytic degradation of RhB. This study demonstrates the possibility of regulating photocatalysts to degrade pollutants in wastewater based on an integrated strategy.     

Synthesis and Comparative Study of Nano-TiO2 Over Degussa P-25 in Disinfection of Water

Nanostructured TiO₂ crystals were synthesized by gel to crystalline conversion. The crystals obtained were anatase form of titania averaging in 30 nm particles with an intrinsic band gap of 3.1 eV. The photocatalytic behavior was evaluated for the bactericidal effect in water, contaminated with the indicator organism Escherichia coli. The 100% photoinactivation of E. coli was achieved within 60 min with suspended nano-TiO₂. The catalytic activity of synthesized nanosample was observed to be 2.6 times more than that of commercial TiO₂ sample referred to as Degussa P-25. The photoinactivation of E. coli was tested with irradiation source of different wavelengths to substantiate the influence of particle size and nano crystallinity on electronic band structure. The photoactivity of nano titania enhanced to 1.625 times when the source of irradiation shifted from 360 to 400 nm while Degussa P-25 showed no change.     

Ag3PO4的可见光光催化性能及机理分析

采用沉淀置换法制备了可见光光催化剂Ag3PO4,利用XRD、UV-Vis及XPS等对其进行了结构特性分析,以水中微污染有机物的降解评价了Ag3PO4的光催化活性,并通过活性物种及能带结构的分析对催化剂的光催化机理进行了推测。结果表明,Ag3PO4的带隙能约为1.9 eV、催化剂表面存在的Ag+可捕获光生e-、催化剂的价带电位较低,这有利于Ag3PO4在可见光照射下产生的e--h+的分离及活性物种.OH的形成。经60 min可见光光催化反应,15 mg.L-1的甲基橙和腐殖酸的降解率分别达97%和82%,比同等条件下TiO2-P25的降解率还高40%和25%,光催化剂Ag3PO4的用量为0.6 g.L-1。     

Enhanced and suppressed effects of ionic liquid on the photocatalytic activity of TiO2

The effects of a room temperature ionic liquid, 1-butyl-3-methylimidazolium terafluoroborate ([Bmim]BF₄), on the photocatalytic performance of Degussa P25 TiO₂ were investigated. Also, the photocatalysis mechanism was systematically analyzed by conducting different reactive radical trapping experiments. The results showed that photogenerated electrons were the main reactive species involved in the photocatalytic degradation of methyl orange (MO), while ?OH radicals and photogenerated holes played an important role in the photocatalytic decomposition of rhodamine B (RhB). The addition of ionic liquid (IL) could slightly enhance the photocatalytic degradation rate of MO because adsorption of [Bmim]⁺ ions on the TiO₂ surface not only enhanced traping and transfer of photogenerated electrons, but also facilitated adsorption of negatively charged MO. On the contrary, IL suppressed the degradation rate of RhB because [Bmim]⁺ on the TiO₂ surface not only hindered the access of positively charged RhB to TiO₂, but also restricted the diffusion of positively charged holes to the TiO₂/solution interface.     

原位红外光谱法研究Gd3+掺杂TiO2光催化降解乙烯性能

随着环境污染的日益严重,寻求环境友好、节能、高效的污染治理技术已成为各国科学研究者致力的目标。以TiO2半导体为主的多相光催化氧化技术因与传统污染处理技术相比具有许多优点而倍受青睐,但是,目前以TiO2为基础的光催化技术还存在量子效率低、太阳能利用率低等技术难题[1,2     

Microwave‐Hydrothermal Preparation and Visible‐Light Photoactivity of Plasmonic Photocatalyst Ag‐TiO2 Nanocomposite Hollow Spheres

Visible‐light‐driven plasmonic photocatalyst Ag‐TiO₂ nanocomposite hollow spheres are prepared by a template‐free chemically‐induced self‐transformation strategy under microwave‐hydrothermal conditions, followed by a photochemical reduction process under xenon lamp irradiation. The prepared samples are characterized by using scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, N₂ adsorption‐desorption isotherms, X‐ray photoelectron spectroscopy, UV/Vis and Raman spectroscopy. Production of ?OH radicals on the surface of visible‐light illuminated TiO₂ was detected by using a photoluminescence method with terephthalic acid as the probe molecule. The photocatalytic activity of as‐prepared samples was evaluated by photocatalytic decolorization of Rhodamine B (RhB) aqueous solution at ambient temperature under visible‐light irradiation. The results show that the surface plasmon absorption band of the silver nanoparticles supported on the TiO₂ hollow spheres was red shifted, and a strong surface enhanced Raman scattering effect for the Ag‐TiO₂ nanocomposite sample was observed. The prepared nanocomposite hollow spheres exhibits a highly visible‐light photocatalytic activity for photocatalytic degradation of RhB in water, and their photocatalytic activity is higher than that of pure TiO₂ and commercial Degussa P25 (P25) powders. Especially, the as‐prepared Ag‐TiO₂ nanocomposite hollow spheres at the nominal atomic ratio of silver to titanium ( R ) of 2 showed the highest photocatalytic activity, which exceeds that of P25 by a factor of more than 2.     

Preparation of Anatase Hollow TiO2 Spheres and Their Photocatalytic Activity in the Photodegradation of Chlorpyrifos

Hollow anatase titania (TiO₂) spheres were synthesized using fructose and tetrabutyl titanate (Ti(OC₄H₉)₄, TBT) as the precursors via the conventional hard template method. The morphological, structural and thermal properties of the products were characterized using scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG‐DTA), Brunauer? Emmett? Teller (BET) surface area analysis and diffuse reflectance ultraviolet visible (DR UV? Vis) spectroscopy. XRD revealed that the hollow TiO₂ prepared was in the anatase phase and the BET surface area measured was about 22 m² g^?1. The photocatalytic activity of the synthesized hollow anatase TiO₂ in the photodecomposition of chlorpyrifos was 18.67 % higher than that obtained using commercial TiO₂.     

Preparation and characterization of low-amount Yb3+-doped TiO2 photocatalyst

The nanoparticles of Yb³⁺-doped (0.125 wt.%) and pure TiO₂ were prepared by an acid-catalyzed sol-gel method and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy, and surface photovoltage spectroscopy; the specific surface of the samples was measured using the Brunauer-Emmett-Teller (BET) method. The photocatalytic degradation of methylene blue in aqueous solution was used as a probe reaction to estimate the photocatalytic activity of the prepared nanoparticles. The photocatalytic activity of Yb³⁺/TiO₂ composite nanoparticles is much higher than that of pure TiO₂. A low amount of Yb³⁺ in TiO₂ can inhibit the anatase-rutile phase transformation of TiO₂, prevent grain growth increasing the specific surface area, and favor the high-temperature stabilization of the pores. According to the surface voltage spectroscopy data, Tb³⁺-doping prevents recombination of photoinduced electrons and holes and improves the light absorption capacity of the particle surface. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1680–1685, October, 2006.     

Effects of urea on the microstructure and photocatalytic activity of bimodal mesoporous titania microspheres

Bimodal mesoporous TiO₂ microspheres with high photocatalytic activity were prepared by a hydrothermal method using titanium sulfate as precursor in the presence of urea. The results indicate that all prepared samples show bimodal pore-size distributions in the mesoporous region: smaller intra-aggregated pores with peak pore diameter of ca. 2 nm and larger inter-aggregated pores with peak pore diameter of ca. 12.5 nm. The molar ratio of urea to Ti(SO₄)₂ (R_u) has an obvious influence on the morphology, microstructure and photocatalytic activity of TiO₂. With increasing R_u, specific surface areas and porosity increase, contrarily, the crystallite size and relative anatase crystallinity decrease. The photocatalytic activity first increases with R_u. At R_u = 2.0, the photocatalytic activity reaches the highest and is obviously higher than that of Degussa P25. With further increasing R_u, the photocatalytic activity decreases. The formation rate of hydroxyl radicals during photocatalysis has a positive correlation with the photocatalytic activity.