A kinetic model for describing effect of the external surface concentration of TiO_2 on the reactivity of egg-shell activated carbon supported TiO_2 photocatalys

The porous support supported TiO2 is considered to be the promising photocatalyst due to the fact that it is easily recovered from water and has high capacity to mineralize pollutants. Obviously, the expected structure of this kind of photocatalyst is egg-shell, that is, TiO2 is mainly on the external surface of the porous support. The reactivity of the supported photocatalyst strongly depends on the concentration of TiO2 on the external surface of the porous support. In this study, a kinetic model was developed to describe the effect of the external surface concentration of TiO2 (CESC) on the reactivity of egg-shell activated carbon (AC) supported TiO2 photocatalysts. It was found that the obtained model precisely described the effect of CESC, on the reactivity of TiO2/AC photocatalysts. This study can be used to deeply understand the performance of TiO2/AC catalysts and to provide valuable information on designing efficient supported TiO2 photocatalysts.     

TiO2/SiO2复合光催化剂制备工艺参数优化及其表征

先以无机钛盐、硅酸盐为原料制取聚合硅酸硫酸钛,再通过液相水解法制得TiO2/SiO2复合光催化剂,并用SEM、XRD、BET和甲基橙脱色率对复合光催化剂进行表征。结果表明,TiO2/SiO2复合光催化剂制备优化工艺参数为:Ti(SO4)2作钛源、Ti/Si摩尔比为12∶1、水解反应pH值为6、煅烧温度为650℃,以此条件制备的复合光催化剂对甲基橙脱色率可达98.6%以上;TiO2/SiO2复合光催化剂为一种分散均匀的纳米级球形颗粒,其成分为以锐钛矿为主的TiO2,SiO2的复合有效抑制了TiO2晶粒的生长,同时提高了TiO2的热稳定性。     

Carboxyl-modified hierarchical wrinkled mesoporous silica supported TiO2 nanocomposite particles with excellent photocatalytic performances

Titanium dioxide (TiO₂) is a common photocatalyst for organic pollutants degradation. However, in practical application, the poor adsorption capacity of pure TiO₂ seriously impeded its efficiency in the degradation of organic molecules. In this work, a series of hierarchical wrinkle mesoporous silica supported TiO₂ nano-composite particles (TiO₂ @WMS-COOH) were successfully prepared. Thanks to their high surface areas, large pore volumes and mesoporous structures, these materials showed high adsorption capacity and excellent photocatalytic performance towards dye molecules, which is comparable to or even better than commercial catalyst P25. Moreover, their photocatalytic efficiency can be further enhanced by increasing the calcination temperature during preparation process. Therefore it can be concluded that the TiO₂ @WMS-COOH particles may find promising applications in the photodegradation of organic pollutants.     

Synthesis of SnO2TiO2 nanocomposite photocatalysts by supercritical fluid combination technology

Acrylic acid, acrylic ester and their ramification have developed quickly in recent years. However, their pro duction process produces a mass of waste water, which when released into the aquatic ecosystem, becomes a source of dramatic disturbance of aquat…     

Ag/TiO_2/AC光催化氧化NO性能研究

以活性炭(AC)为载体,采用溶胶-凝胶法和浸渍法制备新型光催化剂Ag/TiO_2/AC,利用SEM、XRD、BET和UV-Vis光谱等手段对样品进行了表征,并以模拟烟气中的NO为对象,进行光催化氧化性能测试。结果表明,Ag/TiO_2/AC的比表面积为895.21 m~2/g,且对光响应波长已扩展到可见光区,该催化剂在光催化氧化NO反应中具有优异的活性,NO的氧化率高于60.5%。     

TiO2多孔性薄膜的制备及其环境净化性能研究

采用溶胶-凝胶工艺，以聚乙二醇（PEG）为造孔剂，不锈钢丝网为金属基底，制备了TiO₂多孔性薄膜。通过IR，SEM，BET，Raman光谱等测试方法对TiO₂多孔性薄膜进行了表征。实验结果表明,通过控制制备条件得到的TiO₂薄膜具有锐钛矿晶型和多孔性结构。TiO₂多孔性薄膜的光催化性能与煅烧温度和镀膜次数密切相关。450℃热处理、镀膜4次的TiO₂多孔性薄膜具有较高的活性和稳定性，其对气相甲醛的降解率比普通TiO₂薄膜高28.8%，在TiO₂多孔性薄膜连续使用4次后，甲醛的降解率仍维持在80%以上。     

Preparation and photo-catalytic activity of TiO2-coated medical stone-based porous ceramics

Medical stone-based porous ceramics as a carrier were prepared by ultra-fine grinding and low-temperature sintering method. Nano-TiO₂ thin films were loaded on the carrier by chemical liquid deposition method using titanium tetrachloride as a precursor. The micro-morphology and microstructure of the synthesized samples were characterized using X-ray diffraction, scanning electron microscopy with energy dispersive spectrometry, and mercury injection method. The photo-catalytic activity of the TiO₂ thin films was investigated by degrading formaldehyde. The main crystalline phase in the TiO₂ thin films calcined at 550°C is anatase with the average particle size about 10 nm. The specific surface area of the carrier-coated nano-TiO₂ increases from 3.68 to 5.32 m²/g. The formaldehyde removal rate of the TiO₂/medical stone-based porous ceramics irradiated under an ultraviolet lamp for 120 min reaches 85.6%.     

Preparation and characterization of in-site regenerated TiO<Subscript>2</Subscript>-ACFs photocatalyst

In-site regenerated titanium dioxide-activated carbon fibers (TiO₂-ACFs) photocatalyst was prepared by the sol-gel method. Detailed surface and structural characterization of the TiO₂-ACFs photocatalyst was carried out. The photoactivity of TiO₂-ACFs under ultraviolet irradiation was compared with original ACFs and pure TiO₂ by the degradation of methylene blue aqueous solution. The degradation efficiency by the TiO₂ (5wt%)-ACFs sample is much higher than that by TiO₂ and ACFs. The results show that the photocatalysis by TiO₂-ACFs is a six-step process. The adsorption-transfer-photocatalysis rate of TiO₂-ACFs is higher than the adsorption-photocatalysis rate of TiO₂, so the photocatalysis rate of the TiO₂-ACFs system is higher than that of TiO₂ photocatalyst.     

银掺杂多孔氧化钛光催化甲基橙降解反应条件的探究

利用溶胶-凝胶法结合光还原法制备Ag掺杂多孔TiO_2光催化剂,以甲基橙的降解效果为评价标准,考查了光照降解时间、光催化剂用量、甲基橙溶液初始浓度、溶液pH值对光催化剂催化降解甲基橙的影响。结果表明,本方法制备的光催化剂无论是在紫外光还是可见光下均具有优良的光催化性能:在浓度为10 mg/L的甲基橙溶液中,4 g/L光催化剂,紫外光照射80 min,甲基橙可实现100%完全降解;相同催化条件下,可见光照100 min,甲基橙完全降解;当反应溶液pH=2时,紫外光和可见光都可在20 min内实现甲基橙的完全降解。     

LaVO4/TiO2在分解甲基橙中的光催化性能研究

光催化剂TiO₂在污水有机物降解中有着巨大优势,但由于对光的利用率过低,需要在TiO₂的基础上进行掺杂来改善其光催化性能。本研究利用稀土镧元素对TiO₂进行了掺杂分别制备了LaVO₄/TiO₂和La(NO₃)₃/TiO₂复合光催化剂,并将它们应用于甲基橙的光催化降解反应,证实了LaVO₄对TiO₂的光催化效果有较明显的增强作用。另外还研究了不同pH条件制备和不同掺杂比例的LaVO₄/TiO₂光催化效果,pH在10.56左右制备出的LaVO₄和掺杂比例为5%的LaVO₄制得的LaVO₄/TiO₂复合光催化剂效果较好。     

Mechanochemical preparation of sulfur-doped nanosized TiO2 and its photocatalytic activity under visible light

In order to make nanosized TiO2 photocatalyst responsive to visible light and effectively utilize solar energy, we have, for the first time, prepared S-doped nanosized TiO2 by a mechanochemical method with hydrolysis of TiCl4. The as-prepared S-doped nanosized TiO2 possesses strong absorption for visible light of 400-650 nm and shows high photocatalytic activity for decomposition of methylene blue under irradiation of visible light. The oxidation states of the S atoms incorporated into TiO2 were determined to be S^6＋ and S^4＋. The comparative study of fluorescence emission spectra shows that S-doping has also improved the separation of electron-hole pairs.     

Chemical treatments of the nanocrystalline porous TiO2 electrodes

Two types of nanocrystalline porous TiO₂ electrodes were prepared by the hydrothermal and painting methods. The incident photon-to-current efficiency and photoelectrical conversion efficiency were both improved by chemical treatments of titanium tetrachloride and titanium isopropoxide. The surface roughness, quantities of adsorbed dye, photocurrent-voltage curves, IR spectra and UV-visible absorption spectra were measured, and the mechanism of chemical treatments was discussed.     

Dissolution and diffusion of TiO2 in the CaO-Al2O3-SiO2 slag

The dissolution of TiO2 in the CaO-Al2O3-SiO2 slag under static conditions was studied in the temperature range from 1643 K to 1703 K. After TiO2 dissolved, the microstructure of the interface between TiO2 and the slag was observed by scanning electron microscopy, and the concentration profiles of Ti4＋and other ions across the TiO2/slag interfaces were analyzed by energy-dispersive X-ray spectroscopy. On the basis of these results, the dissolution behavior of TiO2 was evaluated, and the diffusivity of Ti4＋in the bulk slag was estimated. Ac-cording to the Stokes-Einstein relation, the viscosity calculated by a previously reported model gave a diffusivity of Ti4＋ions greater than that estimated by the concentration profiles of Ti4＋ions. The mechanism of TiO2 dissolution in the CaO-Al2O3-SiO2 slag is discussed in de-tail.     

The hemocompatibility and the reabsorption function of TiO2 nanotubes biomembranes

A novel high-intensity TiO2 nanotubes array membrane was fabricated via electrochemical anodization of highly pure titanium foil and an open-ended TiO2 nanotubes array membrane was obtained by HF gas etching at the bottom of the nanotubes. Pig tubular epithelial cells (LLC-PK1) and vascular endothelial cells (ECV304) were cultivated on the open-ended TiO2 nanotubes surface through a mixing implantation method and TiO2 nanotubes biomembrane materials with physiological function were successfully produced. Hemocompatibility of glass slides, pure titanium, TiO2 nanotubes without cells and TiO2 nanotubes with culture cells were investigated by the plasma recalcification time method and reabsorption of sodium and potassium were measured by custom-designed devices. The results show that the hemocompatibility of the TiO2 nanotubes array membrane with culture cells was superior to the control group, and the biomembrane has an excellent reabsorption function. This demonstrates that a TiO2 nanotubes array membrane has excellent physiological function and is an ideal candidate material for biological dialysis.     

Enhanced photocatalytic degradation of tetracycline hydrochloride by molecular imprinted film modified TiO<Subscript>2</Subscript> nanotubes

To enhance the photocatalytic activity of TiO2 nanotubes,tetracycline hydrochloride(TC) molecularly imprinted titania modified TiO2 nanotubes(MIP-TiO2) was prepared by liquid phase deposition,which improved the molecular recognition ability of the photocatalyst toward template molecules.This MIP-TiO2 photocatalyst was characterized by ESEM and XRD,which showed that the imprinted titania was deposited on the nanotube uniformly and was of well-crystalized anatase-type.In the adsorption experiments,MIP-TiO2 exhibited a high adsorption capacity(about 1.6 times higher than that of TiO2 nanotubes) for TC mainly because of its imprinted sites and high surface area.Under UV irradiation MIP-TiO2 showed enhanced photocatalytic activity with an apparent first-order rate constant 1.9-fold that of TiO 2 nanotubes.     

Preparation of narrow band gap V2O5/TiO2 composite films by micro-arc oxidation

V₂O₅/TiO₂ composite films were prepared on pure titanium substrates via micro-arc oxidation (MAO) in electrolytes consisting of NaVO₃. Their morphology and elements were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis. Phase composition and valence states of species in the films were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS) were also employed to evaluate the photophysical property of the films. The V₂O₅/TiO₂ composite films show a sheet-like morphology. Not only V₂O₅ phase appears in the films when the NaVO₃ concentration of the electrolyte is higher than 6.10 g/L and is loaded at the surface of anatase, but also V⁴⁺ is incorporated into the crystal lattice of anatase. In comparison with pure TiO₂ films the V₂O₅/TiO₂ composite films exhibit significantly narrow band gap energy. The film prepared in an electrolyte consisting of NaVO₃ with a concentration of 8.54 g/L exhibits the narrowest band gap energy, which is approximately 1.89 eV. The V₂O₅/TiO₂ composite films also have the significantly enhanced visible light photocatalytic activity. The film prepared in an electrolyte consisting of NaVO₃ with a concentration of 8.54 g/L exhibits the best photocatalytic activity and about 93% of rhodamine is degraded after 14 h visible light radiation.     

Morphological structure and physicochemical properties of nanotube TiO2

Morphological structure and physicochemical properties of nanotube TiO₂ were investigated. It was found that the TiO₂ nanotube consisted of 2–5 monolayers of TiO₂ molecules, and its inner diameter was between 4.2 and 5.9 nm. The nanotube TiO₂ powder had high specific surface area and pore volume (379 m²/g and 1.431 cm³/g respectively) and its decolorization activity for Reactive Brilliant Red X-3B was 2 times higher than that of raw TiO₂ (p-25). This new type of TiO₂ was hopeful for application in photocatalysis and composite nanomaterial.     

Au@SiO2 core/shell nanoparticle-decorated TiO2 nanorod arrays for enhanced photoelectrochemical water splitting

To improve the separation efficiency of photoinduced charge carries,Au@SiO2nanoparticles(NPs)with core–shell structure were loaded onto the surface of TiO2nanorods grown on fluorine-doped tin oxide substrate by a facile two-step process.The resulted Au@SiO2/TiO2photoanodes were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,as well as photoelectrochemical measurements.Compared with pristine TiO2nanorod film,the Au@SiO2/TiO2films showed remarkable enhancement in photoelectrochemical water splitting,with incident photonto-current conversion efficiency increasing from 31%to37%at 380 nm at 0.7 V versus saturated calomel electrode.This could be interpreted by the effect of metallic surface plasmon resonance of Au@SiO2NPs,which would generate an intense electromagnetic field with spatially nonhomogenous distributed intensity.As a result,the charge carriers generated in the near-surface region of TiO2nanorods could be easily separated.This modification method based on the effect of metallic surface plasmon resonance for promoted charge carrier separation provides a promising way to develop semiconductor photoelectrodes with high solar water-splitting performance.     

Photocatalytic and electrochemical degradation of methylene blue by titanium dioxide

A photoanode structure for dye-sensitized solar cells has been applied into the photocatalytic/electro- chemical cooperative degradation of methylene blue solu- tions. The low eutectic point of titanium dioxide （TiO2） with a fluorine-doped tin dioxide （FTO） conductive layer results in a high reactivity of TiO2 for the photocatalytic process as well as a good electron transfer for the elec- trochemical process. The porous TiO2 layer maintains a large surface area for the degradations. Through the com- binational process, the degradation velocity was improved by - 36 %, compared to a pure photocatalytic process.     

A novel TiO2 with a large amount of bulk intrinsic defects-Visible-light-responded photocatalytic activity induced by foreign trap

A novel TiO2 (anatase) containing a large amount of single electron trapped oxygen vacancies (SETOV) was prepared by dehydration of titanic acid nanotubes. This novel TiO2 contains high concentration intrinsic defects in bulk structure, while its surface still remains the stoichiometric structure to protect them. And this novel TiO2 itself has the visible light absorption without any doping, so we call it as the third generation of TiO2 . However, it is regretted that this novel TiO2 (A) only has photocatalytic activity under UV light irradiation, and was inactive for the visible light. The true reasons for this phenomenon were investigated by the transient IR absorption and photoluminescence spectra. Through constructing the foreign electron traps (PdO, PtO2 ), the photocatalytic oxidation of propylene under visible light irradiation was successfully achieved. The removal yield of propylene (C3H6 ) reached 7.6% and 28% on 2 wt.% PtO2 /novel TiO2 and 2 wt.% PdO/novel TiO2 , respectively. By comparison with the noble metal electron traps (Pt, Pd), we found that the effective foreign electron traps need to satisfy two conditions: (1) its work function should situate in the range of Eg(TiO2 ); (2) O2 adsorbes on it undissociatively. This work opens up a new route for the investiga- tion of solar-energy-available TiO2 .