High activity of novel Pd/TiO2 nanotube catalysts for methanol electro-oxidation

Electro-oxidation of methanol in sulfuric acid solution was studied using palladium well-dispersed on titanium nanotubes, in relation to methanol oxidation processes in the direct oxidation methanol fuel cell. Pd dispersed on titania nanotubes, which leads to high surface area substrates, showed excellent catalytic activities compared to those of pure Pd and Pd-TiO₂ nanoparticles. TEM results show a narrow distribution of TiO₂ nanoparticles whose particle size is about 10 nm, and uniform nano-sized TiO₂ nanotubes with 10 nm in diameters are seen from HRTEM . A homogeneous structure in the composite nanomaterials is indicated by XRD analysis. The composite electrode activities were measured by cyclic voltammetry (CV) and at 25 °C it was found that 3 wt% Pd in titania nanotubes had the best activity for methanol oxidation.     

Multiscale characterization of antimicrobial poly(vinyl butyral)/titania nanofibrous composites

Titania nanofillers were used to reinforce nanofibers in composite mats produced by electrospinning of poly(vinyl butyral) with two different concentrations of polymers. The titania nanoparticles and titania nanotubes were added into an acetic acid/ethanol solution in different contents of 3 and 1 wt%, respectively. The effect of the processing system on the morphology of the produced fibers was analyzed. The antimicrobial poly(vinyl butyral) composite fibers with titanium dioxide nanoparticles and titanium dioxide nanotubes were produced by single and multineedle electrospinning systems. This study reports fabrication of composite nanofibrous mats with significant mechanical and antimicrobial properties at a high production speed, which is promising for commercial applications (health care, photocatalysis, protective clothing, etc.). The reported result revealed an outstanding correlation between values of elastic modulus derived from nanoindentation and dynamic mechanical techniques. Copyright © 2017 John Wiley & Sons, Ltd.     

Enhanced photocatalytic activity in composites of TiO2 nanotubes and CdS nanoparticles

A new composite consisting of TiO(2) nanotubes and CdS nanoparticles, where CdS particles bind covalently to the titania surface through a bifunctional organic linker, was successfully fabricated; this titania nanotube-based composite shows enhanced photocatalytic activity under visible-light irradiation.     

Synthesis and characterization of ultrahigh crystalline TiO2 nanotubes

Ultrahigh crystalline TiO2 nanotubes were synthesized by hydrogen peroxide treatment of very low crystalline titania nanotubes (TiNT-as prepared), which were prepared with synthesized TiO2 nanoparticles by hydrothermal methods in an aqueous NaOH solution. Thus, prepared ultrahigh crystalline TiO2 nanotubes (TiNT-H2O2) showed comparable crystallinity with high crystalline TiO2 nanoparticles. The details of nanotubular structures were elucidated by high resolution-transmission electron microscopy (HR-TEM), field emission-scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis in transmission electron microscopy (TEM-EDX), X-ray diffraction (XRD), photoluminescence (PL), and BET surface area. TiNT-H2O2 was found to be a multiwalled anatase phase only with an average outer diameter of approximately 8 nm and an inner diameter of approximately 5 nm and grown along the [001] direction to 500-700 nm long with an interlayer fringe distance of ca. 0.78 nm. The photocatalytic activity of TiNT-H2O2 was about 2-fold higher than those of TiNT-as prepared, synthesized TiO2 nanoparticles, and TiO2-P25 (Degussa) in the photocatalytic oxidation of trimethylamine gas under UV irradiation.     

Titania nanotubes (TNTs) prepared through the complex compound of gallic acid with titanium; examining photocatalytic degradation of the obtained TNTs

It was for the first time that the complex compound of gallic acid with titanium (IV) salt was used as a precursor to synthesize titania nanotubes. The study was separated into four main sections; (I) synthesizing the complex of titanium with gallic acid, (II) synthesizing anatase and rutile phases through thermal decomposing of the complex, (III) investigating the possibility to synthesize titania nanotubes from the rutile and anatase phases, and (IV) photocatalytic ability of all the nanoparticles.Different methods were applied to analysis, including X-ray diffraction, 1H NMR, FT-IR spectroscopy, elemental analysis, quantum-chemical modeling, Raman spectroscopy, thermal analysis, photoluminescence, BET analysis (to investigate the specific surface activity, total pore volume), EDX, electron microscopy (SEM), acceleration voltages, electrical conductivity, BJH method (to determine average pore diameter), and UV-Vis spectroscopy.We illustrated the possibility of the synthesis of the titania nanotubes from the anatase phase, while rutile phase was not turned to a tube shape.The photocatalytic ability of the obtained nanoparticles was tested by degrading bromophenol blue, as an organic pollutant, under weak light. TiO₂ in the form of nanotubes could reduce the concentration of bromophenol blue to 82%, as well as the rutile phase - to 70%, and finally anatase as nan-spheres to 36%.     

Large oriented arrays and continuous films of TiO(2)-based nanotubes

We report for the first time a one-step, templateless method to directly prepare large arrays of oriented TiO2-based nanotubes and continuous films. These titania nanostructures can also be easily prepared as conformal coatings on a substrate. The nanostructured films were formed on a Ti substrate seeded with TiO2 nanoparticles. SEM and TEM results suggested that a folding mechanism of sheetlike structures was involved in the formation of the nanotubes. The oriented arrays of TiO2 nanotubes, continuous films, and coatings are expected to have potentials for applications in catalysis, filtration, sensing, photovoltaic cells, and high surface area electrodes.     

Distinct visible-light response of composite films with CdS electrodeposited on TiO2 nanorod and nanotube arrays

Thorough infiltration of CdS nanoparticles into spaces of titania nanorod and nanotube arrays was achieved by an ac electrodeposition technique to construct composite films of CdS over titania. The substrate affected not only the electrodeposition rate but also the oriented growth of CdS. A photocurrent much larger than the simple summation of those arising from the two component layers of CdS and titania was detected for both composite films under visible-light illumination. Such an enhancement in the photocurrent was even more prominent for the composite film based on the titania nanorod arrays, which was contributed to the higher charge separation rate arising from the nearly single-crystalline nanorods when compared with the polycrystalline nanotubes.     

Photoinduced charge separation in titania nanotubes

The photocatalytic one-electron oxidation reaction of an aromatic compound during UV light irradiation of titania nanotubes and nanoparticles was investigated using time-resolved diffuse reflectance spectroscopy. Remarkably long-lived radical cations of the aromatic compound and trapped electrons were observed for the nanotubes when compared to those for nanoparticles. The influences of the morphology on the one-electron oxidation process of an aromatic compound adsorbed on the surface were discussed in terms of the charge recombination dynamics between the radical cation and electrons in TiO2.     

Bioinspired Hierarchical Nanotubular Titania Immobilized with Platinum Nanoparticles for Photocatalytic Hydrogen Production

A bioinspired nanocomposite composed of platinum nanoparticles and nanotubular titania was fabricated in which the titania matter was templated by natural cellulose substance. The composite possesses three‐ dimensional hierarchical structures, and ultrafine metallic platinum particles with sizes of ca. 2 nm were immobilized uniformly on the surfaces of the titania nanotubes. Such a nanocomposite with 1.06 wt % of platinum content shows the optimal photocatalytic hydrogen production activity from water splitting of 16.44 mmol h^?1 g^?1, and excessive loading of platinum results in poorer photocatalytic performance. The structural integrity of the nanocomposite upon cyclic water‐splitting processes results in its sufficient photocatalytic stability.     

Titania nanotube supported tin anodes for lithium intercalation

A new type of nanostructured titania nanotube supported tin anode was prepared for lithium ion batteries. The as-prepared titania nanotubes are in the anatase phase with diameters of about 12 nm. Tin nanoparticles are dramatically decorated on the titania nanotubes and have a particle size of about 10 nm. This new structure promises good retention of reversible capacity on cycling for lithium intercalation. By charge/discharge measurements, the reversible capacity of the titania nanotubes supported tin anode for lithiation and de-lithiation was found to be 312 mA h/g (cycled between 0.05 and 2.0 V) and 203 mA h/g (cycled between 0.05 and 1.3 V) after 50 cycles with around 100% columbic efficiency.     

Preparation of optical active single-handed helical barium titanate nanotubes and characterization of dielectric properties

Left and right-handed helical barium titanate nanotubes are prepared with the impregnation of Ba(OH)_2 into single-handed helical titania nanotubes.Wide angle X-ray diffraction pattern and transmission electron microscopy image indicate that they are constructed by nanoparticles with a partially crystalline structure.The diffuse reflertance circular dichroism spectra indicate that they exhibit optical activity which was proposed to originate from chiral defects on the inner surfaces of the nanotubes.Both the dielectric constant and tanδ decrease with increasing the frequency.At 10 and 100 Hz,one dielectric constant peak at 9.6℃ and one tanδ peak at 5.0℃ are observed at -120℃ to 180℃.     

二氧化钛纳米粒子和纳米管的合成、表征及对硝基苯的光催化性能研究

采用水热合成法, 通过改变反应条件, 控制反应参数, 成功地合成了粒径可控的球形TiO2纳米粒子和长径比、比表面积均比较大的纳米管. 用XRD, TEM, SAED和BET等手段对产物进行了表征. 为了测试产物的光催化性能, 以高浓度的硝基苯(NB)溶液为模拟水样, 进行了一系列提高降解效率的优化实验和光催化降解的对比实验. 通过对硝基苯溶液初始浓度、TiO2加入量和降解体系pH值等条件的考察, 得出硝基苯溶液的质量浓度为300 mg/L, TiO2的加入量为0.4 g/L, 体系的pH值为6~7时, 降解效果最好; 通过对比实验发现, 由于纳米管的大比表面积, 使得其光催化性能明显优于球形纳米粒子, 3 h后的降解率达到90%以上, 3.5 h左右硝基苯几乎被完全降解.     

柔性TiO2纳米管薄膜电极的制备及其光电性能

采用水热合成法制备出TiO₂纳米管,通过XRD、TEM和氮气等温吸附-脱附仪等测试手段对TiO₂纳米管进行了表征.用烧结的TiO₂纳米管和P25粉末混合制成薄膜电极,并研究了薄膜电极的表面形貌、染料吸附量和光电性能.研究表明,加入TiO₂纳米管可以制备出机械稳定的薄膜;掺杂TiO₂纳米管的含量越多,薄膜电极的染料吸附量越大;掺杂5%烧结纳米管粉末的薄膜电极的光电性能最好,其短路电流可达3.25mA,光电转换效率达到1.67%.     

Gold nanocatalysts supported on protonic titanate nanotubes and titania nanocrystals

Gold nanoparticles were first supported on protonic titanate nanotubes with the formation of Au/titanate nanocomposites. They were further transformed to Au/titania nanocomposites via an acetic acid treatment at 70 °C for 60 h. The porosity, crystal structure and morphology of those composites have been studied by X-ray diffraction (XRD), High-resolution transmission electron microscope (HRTEM), and low-temperature nitrogen adsorption. Catalytic tests for CO oxidation show that the Au/titanate nanocomposites had a promising activity with complete conversion of CO at 70 °C and that of Au/titania was at room temperature (25 °C). Both catalysts exhibited good thermal and long-term stabilities. The influence of the crystal vacancies and surface properties of the titanate and titania supports on the catalytic activities were evaluated.     

Ag负载TiO2纳米管微波辅助水热法制备及其光催化性能

以微波辅助水热法制备了二氧化钛纳米管,然后通过浸渍法在其表面负载了银纳米颗粒.所得样品用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、氮吸附、X射线光电子能谱(XPS)、紫外-可见漫反射等测试方法表征.微波加热处理可以大大缩短反应时间,产物为无定型纳米管,经高温焙烧后转变成锐钛矿型二氧化钛.所得纳米管的外径为7-8 nm,内径为5-6 nm,管长约200 nm,比表面积可达371 m2·g-1.负载的银分散在纳米管的表面,对纳米管的结构与晶型没有影响,但是拓宽了二氧化钛的光吸收范围,使吸收边红移至可见光区,并且有效抑制了光生电子空穴的复合.在可见光降解罗丹明B的实验过程中,与Ag负载的P25及纯二氧化钛纳米管相比,Ag负载二氧化钛纳米管具有更高的可见光催化活性,并且当Ag/Ti 物质的量的比为0.5%时,可见光催化性能最好.     

Electrodeposited copolymer electrolyte into nanostructured titania electrodes for 3D Li-ion microbatteries

The electrochemical synthesis of a copolymer electrolyte (PEO-PMMA) into titania nanotubes is described and studied. Compared with the electrochemical systems based on solid electrolytes deposited by top-down techniques, the copolymer/titania nanotube material reveals high electrochemical performance, opening new perspectives for the fabrication of 3D all-solid-state microbatteries.     

有机电解液在阳极氧化法制备TiO2纳米管中的应用

二氧化钛纳米管由于其特殊的结构和优异的性能,在很多领域都有着重要的应用前景。阳极氧化法是制备二氧化钛纳米管的一种主要方法。近来,在阳极氧化法中使用有机电解液来制备二氧化钛纳米管取得了非常显著的效果。与传统的水溶性电解液相比,其深宽比和光电转换效率有了很大的提高。本文主要介绍了二氧化钛纳米管的阳极氧化原理以及有机电解液在阳极氧化法中对二氧化钛纳米管生长过程的影响。     

水热法合成掺杂铁离子的小管径TiO_2纳米管

碳纳米管这种一维结构的新材料的发现为物理、化学、材料科学和纳米科学开辟了全新的研究领域。近年来,非碳无机类富勒烯(InorganicFullerene-like,简称IF)纳米管也受到人们的广泛关注。迄今为止报道的无机类富勒烯纳米管主要有:过渡金属硫化物(MS2,M=W,Mo,Nb)犤1～3犦、V2O5犤4犦、Al2O3犤5犦纳米管等。其中金属氧化物纳米管在催化、吸附、单电子晶体管等方面有着潜在的应用前景。TiO2纳米粉体和纳米膜材料在太阳能的存储与利用、光电转换、光致变色及光催化降解大气和水中的污染物等方面具有广泛的应用。为了提高其光催化活性和对…     

Low‐Temperature Synthesis of Crystalline Inorganic/Metallic Nanocrystal‐Halloysite Composite Nanotubes

We have demonstrated a facile approach for the low‐temperature synthesis of crystalline inorganic/metallic nanocrystal‐halloysite composite nanotubes by employing the bulk controlled synthesis of inorganic/metallic nanocrystals on halloysite nanotubes. The halloysite clay nanotubes can adsorb the target precursor and induce inorganic/metallic nanocrystals to grow in situ. The crystalline phase and morphology of the composite clay nanotubes is tunable. By simply tuning the acidity of the titania sol, the crystalline titania‐clay nanotubes with tunable crystalline phases of anatase, a mixture of anatase and rutile or rutile are achieved. The approach is general and has been extended to synthesize the representative perovskite oxide (barium and strontium titanate)‐halloysite composite nanotubes. Metallic nickel nanocrystal can also be grown on the surface of halloysite nanotubes at low temperature. The traditional thermal treatment for crystallite transformation is not required, thus intact contour of halloysite nanotubes and the crystallinity structure of halloysite nanotubes can be guaranteed. The combined properties from inorganic/metallic nanocrystal (high refractive index, high dielectric constant and catalytic ability) and the halloysite clay nanotubes are promising for applications such as photonic crystals, high‐k‐gate dielectrics, photocatalysis and purification.     

Size- and shape-dependent transformation of nanosized titanate into analogous anatase titania nanostructures

A size- and shape-dependent morphological transformation was demonstrated during the hydrothermal soft chemical transformation, in neutral solution, of titanate nanostructures into their anatase titania counterparts. Specifically, lepidocrocite hydrogen titanate nanotubes with diameters of approximately 10 nm were transformed into anatase nanoparticles with an average size of 12 nm. Lepidocrocite hydrogen titanate nanowires with relatively small diameters (average diameter range of < or = 200 nm) were converted into single-crystalline anatase nanowires with relatively smooth surfaces. Larger diameter (>200 nm) titanate wires were transformed into analogous anatase submicron wire motifs, resembling clusters of adjoining anatase nanocrystals with perfectly parallel, oriented fringes. Our results indicate that as-synthesized TiO2 nanostructures possessed higher photocatalytic activity than the commercial titania precursors from whence they were derived.