TiO_2 composite nanotubes embedded with CdS and upconversion nanoparticles for near infrared light driven photocatalysis

We report a colloidal process to coat a layer of TiO2onto SiO2composite nanofibers containing embedded CdS and upconversion nanoparticles(UCNPs).The SiO2composite nanofibers were fabricated by electrospinning.To improve the energy transfer efficiency,UCNPs and CdS nanoparticles were bound in close proximity to each other within the SiO2matrix.β‐NaYF4:Yb(30%),Tm(0.5%)@NaYF4:Yb(20%),Er(2%)core–shell nanoparticles were used as nanotransducers for near infrared light.These nanoparticles exhibited enhanced upconversion fluorescence compared withβ‐NaYF4:Yb(30%),Tm(0.5%)orβ–NaYF4:Yb(30%),Tm(0.5%)@NaYF4nanoparticles.The morphologies,size and chemical compositions have been extensively investigated using field emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),X‐ray diffraction(XRD)and X‐ray photoelectron spectra(XPS),respectively.The TEM images showed that the TiO2composite nanotubes were embedded with a large amount of UCNPs and CdS nanoparticles.The composite TiO2nanotubes degraded more than90%of rhodamine B(RhB)dye during20min of irradiation by simulated solar light.In particular,more than50%of RhB was decomposed in70min,under irradiation of near infrared light(NIR).This high degradation was attributed to the full spectrum absorption of solar light,and the enhanced transfer efficiency for near infrared light.The as‐prepared nanostructures can harness solar energy,and provide an alternative to overcome energy shortages and environmental protection.

Photocatalytic Oxidation of Low Molecular Weight Hydrocarbon Gases over Pt-TiO2 Nanotubes

Pt-TiO2 nanotubes with tube diameter of -120 nm and uniformly dispersed Pt particles（size of -2 nm） were successfully synthesized via a carbon nanotube（CNT） templating method followed by a photo-deposition processing of Pt nanoparticles. The as-obtained Pt-TiO2 NTs possess both enhanced visible light absorption and reduced recombination of photogenerated electrons and holes. These merits boost the Pt-TiO2 NTs an excellent photocatalytic material toward photooxidation of a variety of low molecular hydrocarbons under atmospheric environment.

Enhanced Visible-Light-Induced Photoelectrocatalytic Degradation of Methyl Orange by CdS Sensitized TiO2 Nanotube Arrays Electrode

In this work, CdS sensitized TiO2 nanotube arrays （CdS/TiO2NTs） electrode was synthesized with the CdS deposition on the highly ordered titanium dioxide nanotube arrays （TiO2NTs） by sequential chemical bath deposition method （S-CBD）. The as-prepared CdS/TiO2NTs was characterized by field-emission scanning electron mi- croscopy （FE-SEM） and X-ray diffraction （XRD）. The results indicated that the CdS nanoparticles were effectively deposited on the surface of TiOeNTs. The amperometric I-t curve on the CdS/TiO2NTs electrode was also presented. It was found that the photocurrent density was enhanced significantly from 0.5 to 1.85 mA/cm2 upon illumination with applied potential of 0.5 V at the central wavelength of 253.7 nm. The photoelectrocatalytic （PEC） activity of the CdS/TiO2NTs electrode was investigated by degradation of methyl orange （MO） in aqueous solution. Compared with TiO2NTs electrode, the degradation efficiencies of CdS/TiO2NTs electrode increased from 78% to 99.2% under UV light in 2 h, and from 14% to 99.2% under visible light in 3 h, which was caused by effective separation of the electrons and holes due to the effect of CdS, hence inhibiting the recombination of electron/hole pairs of TiO2NTs.

Controllable incorporation of CdS nanoparticles into TiO_2 nanotubes for highly enhancing the photocatalytic response to visible light

A constant current electrochemical deposition was employed to incorporate CdS nanoparticles into the TiO2 nanotube arrays (TiO2NTs). The size and amount of CdS nanoparticles in TiO2NTs (CdS@TiO2NTs) were controllable via modulating current,deposition time and electrolyte concentration. It was revealed,from the scanning electron microscopy (SEM) images and X-ray photoelectron spectroscopy (XPS) in depth profile,that CdS nanoparticles were filled into TiO2 nanotubes. A shift of the absorption edge toward the visible region under the optimal electrodeposition condition was observed with the diffuse reflectance spectroscopy (DRS). A 5-fold enhancement in the photocurrent spectrum for TiO2NTs was observed and the photocurrent response range was significantly extended into the visible region because of the CdS incorporation. Compared with pure TiO2NTs,under a visible light irradiation,CdS@TiO2NTs exhibited a 3.5-fold improvement of photocatalytic activity,which was demonstrated by the photocatalytic decomposition of Rhodamine B (RhB).

Controllable synthesis of well-ordered TiO_2 nanotubes in a mixed organic electrolyte for high-efficiency photocatalysis

Well-ordered TiO 2 nanotube arrays (TNAs) were fabricated by electrochemical anodization in a mixed organic electrolyte consisting of ethylene glycol and glycerol. The morphology, structure, crystalline phase, and photocatalytic properties of TNAs were characterized by using TEM, SEM, XRD and photodegradation of methylene blue. It was found that the morphology and structure of TNAs could be significantly influenced by the anodization time and applied voltage. The obtained tube length was found to be proportional to anodization time, and the calculated growth rate of nanotubes was 0.6 m/h. The microstructure analysis demonstrated that the diameter and thickness of the nanotubes increased with the increase of anodization voltage. The growth mechanism of TNAs was also proposed according to the observed relationship between current density and time during anodization. As expected, the obtained TNAs showed a higher photocatalytic activity than the commercial TiO 2 P25 nanoparticles.

Effect of Anodization Parameters on Morphology and Photocatalysis Properties of TiO_2 Nanotube Arrays

Highly ordered TiO2 nanotube arrays were fabricated via electrochemical anodization of high purity Ti foil in fluoride-containing electrolyte. The effects of applied anodization potential, anodization time on the formation of TiO2 nanotube arrays and the photocatalytic degradation of methylene blue （MB） were discussed. The TiO2 nanotube arrays calcined at 500 ℃ for 2 h show pure anatase phase. The pore diameters of TiO2 nanotube arrays can be adjusted from 30 to 90 nm using a different anodization voltage. Anodization time mainly influenced TiO2 tube length, and by increasing the anodization time, the nanotube length became longer gradually. When the anodization potential was 40 V, the average growth rate of TiO2 nanotube was about 4.17 μm/h. Both anodization potential and time had important effects on the photocatalytic efficiency. The TiO2 nanotube arrays obtained at anodization potential of 40 V for I h showed the best photocatalytic degradation ratio of MB.

Visible Light Photocatalysis of Ni-Deposited TiO_(2) Nanotubes for Methyl Orange Degradation in Alkaline Medium

The photocatalysis of Ti O2nanotubes（Ti/TNT） and Ni-deposited Ti O2nanotubes（Ti/TNT–Ni） for methyl orange degradation was investigated.Methyl orange was selected as the model pollutant,and its photocatalytic degradation was determined in 1 mol/L KOH solution.Ti/TNT was produced by anodizing method,and the electrodeposition of nickel on TNT was performed galvanostatically.The characterization of electrodes was performed by scanning electron microscopy,energy-dispersive X-ray spectroscopy and X-ray diffraction analysis.The electrochemical behavior of the electrodes was determined by cyclic voltammetry and electrochemical impedance spectroscopy.The irradiation was applied by visible light source（k = 635 nm） for 48 h.UV/vis spectroscopy was used for determination of the concentration of methyl orange.Furthermore,after 48-h irradiation,the solutions were analyzed by Fourier transform infrared spectroscopy.Results showed that the concentration of methyl orange decreased from 100 ppm（10-6） to 16 ppm,after48-h irradiation with the photocatalysis of Ti/TNT–Ni.

TiO2 nanotube arrays decorated with Au and Bi2S3 nanoparticles for efficient Fe3+ ions detection and dye photocatalytic degradation

Due to increasingly serious environmental problems,many researchers are investigating green cleanenergy to solve the world’s energy supply issues.So the strategy that Au nanoparticles(Au NPs)and bismuth sulfide(Bi2S3)NPs are used to evenly decorate TiO2 nanotube arrays(TiO2 NTAs)was carried out.Composite materials demonstrated enhanced solar light absorption ability and excellent photoelectrochemical performance.This was attributed to the presence of Bi2S3 NPs with a narrow band gap and the decoration with noble metallic Au NPs which resulted in local surface plasmon resonance(LSPR)effects.The Au/Bi2S3@TiO2 NTAs composites exhibit improved photocatalytic activity for the degradation of methylene blue(MB)under irradiation of UV and visible light.Moreover,the Au/Bi2S3@TiO2 NTAs exhibits high fluorescence emission at 822 nm.Due to the better binding affinity between Bi2S3,TiO2 and Fe3+ions,the synthesized nanocomposites exhibit high selectivity to Fe3+ions.The number of binding sites for Au/Bi2S3@TiO2 NTAs was estimated to be 1.41 according to the double logarithmic regression method.The calculated value of"K"was 1862 M-1.Fluorescence emission intensity decreases with increasing concentration(30μM–5000μM).The detection limit of the synthesized sensor is 0.221μM.

Photo-degradation of Acid-red 3B dye catalyzed by TiO_2 nanotubes

TiO2 nanotube precursor was synthesized by the hydrothermal reaction of TiO2 powders with NaOH solution and the properties of the nanotube materials were tuned using different post-treatments. Transmission electron microscopic （TEM） observation revealed that the nanotube could be obtained by either a direct rinse with acid solution or rinse with distilled water followed by acid solution. The results of X-ray diffraction （XRD） and inductively coupled plasma （ICP） analysis indicated that the nanotube material was composed of H2Ti2O5·H2O. In addition, the photocatalytic activities of the resulting catalysts were found to be strongly dependent on the post-treatment. The results of the photocatalytic reaction showed that the degradation of Acid-red 3B dye fitted pseudo-zero-order kinetics and TiO2 nanotube prepared under direct rinse with acid solution exhibited a higher catalytic efficiency compared to other catalysts.

Photocatalytic decompositions of gaseous HCHO and methylene blue with highly ordered TiO_2 nanotube arrays

The highly ordered TiO2 nanotubes (NTs) were fabricated by the anodic oxidation method. Their morphology, structure and crystalline phase were characterized by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). The effects of morphology, specific surface area, pore structures and photo catalytic activity of the TiO2 NTs were investigated. UV-vis spectra analysis showed that its light absorption had been extended to the visible light range. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic oxidation of gaseous HCHO and MB aqueous solution. The samples had better adhesion strength in the dark and showed a higher photocatalytic activity than nanoparticles. Especially, with ultraviolet light pretreatment, the nanotubes exhibited more stable active for photocatalytic decomposition and the photodecomposition rate remained at high level after 3 cycles of the photocatalysis experiment. Thus, how the number of surface active group center dot OH increased and the mechanism for the great improvement for the photocatalytic activity are discussed. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Photocatalytic Property of TiO_2 Sensitized by Different Crystal Phase CdS

TiO2 samples sensitized by different crystal phase CdS （CT） are synthesized by hydrothermal process at different reaction temperature. The samples are characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and UV-Vis diffuse reflectance （UV-Vis）. The XRD result reveals that the crystal phase of CdS is transformed from cubic phase to hexagonal phase with the increase of hydrothermal reaction temperature （120-160℃）. The absorption edge of CT is extended from 498 nm to 546 nm. The photocatalytic degradation of rhodamin B （RhB） in aqueous solution is used to evaluate the photocatalytic activity of CT. With the increase of the preparation temperature, the photocatalytic activity of CT becomes stronger. The degradation rate of RhB by CdS/TiO2 at 160℃（CT-160℃） reaches 78%.

Enhanced hydrogen production activity over BiOX–TiO2 under solar irradiation:Improved charge transfer through bismuth oxide clusters

A series of titania nanoparticles and nanotubes deposited with various quantities of bismuth（Bi） were prepared via sol-gel and hydrothermal methods, respectively. They were then characterized using X-ray diffraction spectroscopy（XRD）, X-ray photo electron spectroscopy（XPS）, UV–Vis diffused reflectance spectra（DRS）, photoluminescence spectra（PLS）, transmission electron microscopy（TEM）, energy dispersive analysis of X-rays（EDAX）, and BET surface analysis. These catalysts were employed for the photocatalytic production of hydrogen from a mixture of pure water and glycerol under solar light irradiation. The presence of the Bispecies was found to play a vital role in enhancing activity while minimizing electron hole recombination（relative to bare TiO）. The nanotubes exhibited better activity than the nanoparticles of Bi-deposited TiO, showing the significance of the morphology; however, photocatalytic activity is predominantly dependent on the deposition of bismuth. The activity increased by approximately an order of magnitude at the optimum concentration of Bi deposited over TiO（2 wt%）. The presence of the Bispecies played a vital role in minimizing electron hole recombination, resulting in higher activity compared to bare TiO.

Photocatalytic Activity of TiO_2 Sensitized by CdS Quantum Dots under Visible-Light Irradiation

In this paper, CdS quantum dots sensitized TiO2 composite powders （QD-CdS/TiO2） were synthesized by impregnating TiO2 powder into CdS sol with different concentrations. X-ray diffraction pattern （XRD） shows the crystal structures of CdS and TiO2 are cubic phase and anatase phase separately in QD- CdS/TiO2 powder samples; the crystal size of CdS in QD- CdS/TiO2 is about 3-7 nm, while TiO2 crystal size is about 20 nm. With increasing CdS content in QD-CdS/TiO2 composite, the UV-Vis absorption spectrum shifted to the longer wavelength lines, exhibiting obvious quantum size effect. The fluorescence intensity of QD-CdS/TiO2 irradiated by blue light is weaker than that of pure CdS. When the molar ratio of CdS and TiO2 is about 1∶2, the QD-CdS/TiO2 powder has the best catalytic properties under visible-light irradiation, and the degradation rate of rhodamine B （RhB） is up to 92.2% within 60 min.

Nickel sulfide modified TiO_2 nanotubes with highly efficient photocatalytic H_2 evolution activity

TiO2 nanotubes（TNTs） with nickel sulfide（NiS） co-catalyst were prepared by a simple solvothermal method and characterized by X-ray diffraction, transmission electron microscope, N2-physisorption, UV–vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. Loading NiS nano-clusters can significantly enhance the photocatalytic H2 evolution performance of TNTs. The optimum NiS loading content was found to be 8 wt% and the corresponding hydrogen production rate is ca. 7486 μmol/h/g, being about 79 times higher than that of pure TNTs. This enhancement of photocatalytic H2 evolution was attributed to the synergistic effect between NiS and TNTs.

Two-Step Anodization of Maltilayer TiO_2 Nanotube and Its Photocatalytic Activity under UV Light

A double-layer TiO2 nanotube arrays were formed by two-step anodization of Ti foils in different electrolytes. First, Ti in 0.5 wt% HF was anodized to form thin nanotube layer. Afterwards a second anodization was conducted in a formamide based electrolyte, which allowed the second layer of nanotube growing directly underneath the first one. From FESEM investigation we found that the thickness of second layer corresponded to the anodization time, the increasing of which would lead to the excessive etching on the first layer. The first layer protected the lower one from fluoride corrosion during anodization process. The double layer TiO2 nanotube arrays showed no benefit to photodegradation effect in methyl orange degradation experiments.

Preparation of Polyaniline/TiO_2 Composite Nanotubes for Photodegradation of AZO Dyes

Polyaniline （PANI） composite nanotubes （90-130 nm in diameter） containing titanium dioxide （TiO2） nanoparticles （about 10 nm in diameter） were synthesized through a self-assembly process in the presence of a-naphthalenesulfonic acid （a-NSA） as the dopant. It was found that PANI-TiO2 composites and PANI nanotubes both behaved with significant photocatalytic activities towards AZO dyes, during 2 h photocatalytic processes under natural light, the degradation ratio was 94.2% and 97.2% respectively （methyl orange and orange II）. The morphology of such products was characterized by SEM. The specific surface area of such composite nanotubes was 14.7 m2/g compared to normal polyaniline which was 0.27 m2/g. IR and X-ray diffraction characterizations showed that the chemical chain of the composite nanotubes was identical to that of the doped PANI. It may provide a new way for photodegradation of organic contaminants by using conjugated polymer with dimensional structure.

Cd S/TiO2/ACFs光催化处理染料废水的试验研究

采用负载型CdS/TiO2/ACFs复合半导体材料对孔雀石绿染料废水进行光催化处理,分别考察了pH、反应时间、催化剂投加量等因素对处理效果的影响。结果表明:负载型CdS/TiO2/ACFs复合半导体对色度为250倍、COD为444mg/L的孔雀石绿染料废水,色度、COD去除率分别为97%和88%。

PbSe/TiO2同轴异质结纳米管的制备及光催化性能

通过溶液法合成了PbSe/TiO2复合纳米管,并对其进行了微观形貌、晶体结构等的表征。结果表明,制得的样品是由PbSe和TiO2两种材料构成的复合材料,致密、均匀的TiO2薄膜包覆在PbSe纳米管表面。以氙灯为模拟光源,通过对甲基橙的降解研究了PbSe/TiO2复合纳米管的光催化性能。结果显示,PbSe与TiO2之间形成的异质结使PbSe/TiO2复合纳米管具有较高的光催化性能,比纯PbSe纳米管的催化降解率提高了约4.5倍。另外,对PbSe/TiO2复合纳米管光催化稳定性也进行了研究。

TiO_2纳米管的光催化作用

以多孔氧化铝为模板制备出的锐钛矿型TiO2 纳米管管径均匀 ,管壁粗糙 ,由许多非常细小的TiO2 纳米粒子组成。在通空气条件下 ,该TiO2 纳米管对于十二烷基苯磺酸钠的光催化降解表现出很高的光催化活性 ,持续光照 2 0min可降解 3 0 %。紫外可见漫反射吸收光谱和结构表征的实验结果表明 ,TiO2 纳米管具有较宽的禁带和较小的电子 空穴复合几率 ,因此 ,其空穴 电子对具有强氧化 还原能力和高催化活性。

可见光响应的LaVO_4/TiO_2纳米管的合成、表征及对气相甲苯的光催化性能

通过水热方法合成了可见光响应的LaVO4/TiO2纳米管,采用XRD,TEM,氮气吸附-脱附以及表面光电压谱对样品进行了表征.以气相甲苯为典型污染物,研究了制备样品在可见光(λ>420 nm)条件下的光催化性能.实验结果表明,LaVO4的复合使TiO2的粒径减小,比表面积增大,光响应范围向可见光偏移.光催化实验结果表明,在可见光条件下,LaVO4/TiO2纳米管降解甲苯的效率比其它样品高,与纯TiO2纳米管相比,降解效率提高了47%.