铜掺杂TiO_2纳米管阵列的制备与光催化还原性能

以阳极氧化法制得的TiO2纳米管阵列为前驱体,用浸渍法制备了不同铜掺杂量的TiO2纳米管阵列。采用场发射扫描电镜(FE-SEM)、X射线衍射(XRD)、X光电子能谱(XPS)、荧光光谱(PL)对样品进行表征。以Cr6+水溶液为目标污染物,对比不同铜掺杂量TiO2纳米管阵列的光电催化还原效果。结果表明,掺杂前后TiO2纳米管阵列在形貌上没有明显变化;掺杂的铜是以Cu2+的形态存在;掺铜后TiO2纳米管阵列还原效果优于掺铜前;低剂量铜掺杂的TiO2纳米管阵列的还原效果优于高剂量铜掺杂的TiO2纳米管阵列。     

TiO2纳米管阵列的制备工艺对其光催化性能的影响

采用阳极氧化法,在醇(丙三醇、乙二醇)-水-NH4F电解液体系中制备高度有序的TiO2纳米管阵列。采用场发射扫描电子显微镜(SEM)、X射线衍射仪(XRD)对TiO2纳米管阵列的形貌和晶型结构进行表征,讨论了阳极氧化法制备工艺(阳极氧化电压、氧化时间、电解液)对TiO2纳米管的形貌、结构及其甲基橙光催化降解性能的影响;分析了退火温度对TiO2阵列的物相及其光催化性能的影响。研究结果表明,采用高电压、增加氧化时间有利于TiO2纳米管阵列光催化的提高,在其它参数相同的情况下,采用丙三醇作为电解液制备获得的TiO2纳米管阵列较乙二醇体系具有更加优异的光催化性能。     

不同制备条件对二氧化钛纳米管阵列及其结构的影响

采用阳极氧化法以NH4F/乙二醇为电解液制备高度有序的TiO2纳米管,研究了不同电解液浓度、电解电压、电解时间等参数对TiO2纳米管的影响.在不同温度下对TiO2纳米管进行退火处理.分别利用转靶X射线衍射仪(XRD)和场发射扫描电子显微镜(SEM)对TiO2纳米管阵列的物相结构和形貌变化进行表征.结合氧化过程电流密度变...     

TiO2纳米管阵列催化降解甲基橙的性能研究

采用阳极氧化法制备了TiO2纳米管阵列电极,以甲基橙为目标降解物研究了TiO2纳米管阵列电极的光催化和光电催化性能.此外,还进行了超声辐射替代紫外光照探索性研究.结果表明,阳极氧化时间和热处理温度对TiO2纳米管阵列电极的光催化性能具有显著影响;在光催化过程中,施加一定外加电压可有效提高电极的光催化活性.尽管与紫外光照相比,超声辐射在TiO2纳米管阵列电极的催化氧化甲基橙分子过程中的促进作用具有一定的差距,但仍显示出替代紫外光照的可行性.     

Amorphous and crystalline TiO2 nanotube arrays for enhanced Li-ion intercalation properties

We have employed a simple process of anodizing Ti foils to prepare TiO2 nanotube arrays which show enhanced electrochemical properties for applications as Li-ion battery electrode materials. The lengths and pore diameters of TiO2 nanotubes can be finely tuned by varying voltage, electrolyte composition, or anodization time. The as-prepared nanotubes are amorphous and can be converted into anatase nanotubes with heat treatment at 480 degrees C. Rutile crystallites emerge in the anatase nanotube when the annealing temperature is increased to 580 degrees C, resulting in TiO2 nanotubes of mixed phases. The morphological features of nanotubes remain unchanged after annealing. Li-ion insertion performance has been studied for amorphous and crystalline TiO2 nanotube arrays. Amorphous nanotubes with a length of 3.0 microm and an outer diameter of 125 nm deliver a capacity of 91.2 microA h cm(-2) at a current density of 400 microA cm(-2), while those with a length of 25 microm and an outer diameter of 158 nm display a capacity of 533 microA h cm-2. When the 3-microm long nanotubes become crystalline, they deliver lower capacities: the anatase nanotubes and nanotubes of mixed phases show capacities of 53.8 microA h cm-2 and 63.1 microA h cm(-2), respectively at the same current density. The amorphous nanotubes show excellent capacity retention ability over 50 cycles. The cycled nanotubes show little change in morphology compared to the nanotubes before electrochemical cycling. All the TiO2 nanotubes demonstrate higher capacities than amorphous TiO2 compact layer reported in literature. The amorphous TiO2 nanotubes with a length of 1.9 microm exhibit a capacity five times higher than that of TiO2 compact layer even when the nanotube array is cycled at a current density 80 times higher than that for the compact layer. These results suggest that anodic TiO2 nanotube arrays are promising electrode materials for rechargeable Li-ion batteries.     

Effects of structure of anodic TiO(2) nanotube arrays on photocatalytic activity for the degradation of 2,3-dichlorophenol in aqueous solution

In this study titanium dioxide nanotube (TNT) arrays were prepared by an anodic oxidation process with post-calcination. The morphology and structure of the TNT films were studied by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of the TNT films was evaluated in terms of the degradation of 2,3-dichlorophenol in aqueous solution under UV light irradiation. The effects of the nanotube structure including tube length and tube wall thickness, and crystallinity on the photocatalytic activity were investigated in detail. The results showed that the large specific surface area, high pore volume, thin tube wall, and optimal tube length would be important factors to achieve the good performance of TNT films. Moreover, the TNT films calcined at 500 degrees C for 1h with the higher degree of crystallinity exhibited the higher photocatalytic activity than other TNT films calcined at 300 and 800 degrees C. Consequently, these results indicate that the optimization of TiO(2) nanotube structures is critical to achieve the high performance of photocatalytic reaction.     

Influence of calcination parameters on the TiO2 photocatalytic properties

Nanocrystalline titanium dioxide (TiO₂) powders with different crystal phase composition were obtained by controlled hydrolysis and post-thermal treatments. The physicochemical properties of the powders were investigated by XRD, TEM/EDS, N₂ physic adsorption and DRS. The results obtained show that the particle size and crystalline structure are parameters strongly dependent on the calcination conditions, mainly temperature and heating rate. The influence of the TiO₂ phase composition on its photocatalytic activity, concerning the methylene blue photodegradation was studied. It was found that higher TiO₂ photocatalytic activity is related with the co-existence of the three TiO₂ polymorphs: anatase, brookite and rutile.     

Preparation and photocatalytic activity of N-doped TiO2 nanotube array films

The N-doped TiO₂ nanotube array films were fabricated directly by one-step electrochemical anodic oxidation of Ti foils in an HF electrolyte containing ammonium and nitrate ions. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDX), and ultraviolet–visible (UV–vis) absorption spectroscopy, respectively. The photocatalytic activities were evaluated by the degradation of methyl orange (MO) under visible light irradiation. The results showed that N dopant was successfully introduced into the TiO₂ nanotube array films. The N-doped TiO₂ nanotube array films showed a red shift and an enhancement of the absorption in the visible light region compared to the undoped sample. The photocatalytic activities of the N-doped TiO₂ samples were much higher than those of the undoped sample. A maximum enhancement of photocatalytic activity was achieved for the N-doped TiO₂ sample prepared in 0.07 M HF electrolyte containing 1.0 M NH₄NO₃, and 81% of MO was degraded in 150 min under visible light irradiation.     

TiO_2纳米管阵列热驱动掺银制备TiO_2-Ag复合涂层及其光催化性能

无定形结构TiO2纳米管阵列(titania nanotube arrays,TNA)在浸泡AgNO3溶液后,再经适当的热处理,不仅可使TNA的晶体结构转变为锐钛矿型或金红石型,还可以制得海绵状TiO2-Ag复合涂层。深入研究了AgNO3溶液浓度、热处理温度等对TiO2-Ag复合涂层结构和光催化制氢性能影响的影响。研究结果表明,AgNO3溶液浓度对TiO2-Ag复合涂层形貌结构和晶体结构具有重要影响。当AgNO3溶液浓度为0.1~0.5 mol/L、热处理温度为500℃时,可制得海绵状TiO2-Ag复合涂层,该涂层在紫外-可见光光照条件下,光催化制氢速率为2.14μmol/cm2·h。     

Hydrogenated TiO2 nanotube arrays for supercapacitors

We report a new and general strategy for improving the capacitive properties of TiO(2) materials for supercapacitors, involving the synthesis of hydrogenated TiO(2) nanotube arrays (NTAs). The hydrogenated TiO(2) (denoted as H-TiO(2)) were obtained by calcination of anodized TiO(2) NTAs in hydrogen atmosphere in a range of temperatures between 300 to 600 °C. The H-TiO(2) NTAs prepared at 400 °C yields the largest specific capacitance of 3.24 mF cm(-2) at a scan rate of 100 mV s(-1), which is 40 times higher than the capacitance obtained from air-annealed TiO(2) NTAs at the same conditions. Importantly, H-TiO(2) NTAs also show remarkable rate capability with 68% areal capacitance retained when the scan rate increase from 10 to 1000 mV s(-1), as well as outstanding long-term cycling stability with only 3.1% reduction of initial specific capacitance after 10,000 cycles. The prominent electrochemical capacitive properties of H-TiO(2) are attributed to the enhanced carrier density and increased density of hydroxyl group on TiO(2) surface, as a result of hydrogenation. Furthermore, we demonstrate that H-TiO(2) NTAs is a good scaffold to support MnO(2) nanoparticles. The capacitor electrodes made by electrochemical deposition of MnO(2) nanoparticles on H-TiO(2) NTAs achieve a remarkable specific capacitance of 912 F g(-1) at a scan rate of 10 mV s(-1) (based on the mass of MnO(2)). The ability to improve the capacitive properties of TiO(2) electrode materials should open up new opportunities for high-performance supercapacitors.     

阳极氧化法制备TiO2纳米管阵列

采用阳极氧化法在乙二醇体系电解液中制备TiO2纳米管阵列,获得了长度为15~20μm的底端纳米管与顶端纳米线的新型复合结构。讨论了电解液中不同含水量对该复合结构形成的影响,并采用两步阳极氧化法对该结构的形成机理进行了分析。结果表明,当乙二醇体系电解液含有0.4%(质量分数)NH4F和2%(体积分数)H2O时,电解液腐蚀速度适中,纳米管上端部分被选择性腐蚀,最终形成纳米管与纳米线的复合结构。     

The combination of rotating disk photocatalytic reactor and TiO2 nanotube arrays for environmental pollutants removal

A combined photocatalytic system on one single TiO(2)-nanotube (TNT)/Ti photocatalyst, which was indeed the functional combination of photon-efficient thin-film and conventional bulk-phase photocatalysis processes, was effectively developed in rotating disk photocatalytic reactor for environmental purification applications. The TNT/Ti rotating disk, of uniform size and well-aligned, was successfully prepared by direct anodic oxidation on a dominantly large surface area of 38 cm(2), compared to the typical 1 cm(2) in available literature. To estimate the potentials of combined photocatalytic system for environmental applications, the degradation of rhodamine B was carried out under the optimized conditions, a substrate removal efficiency of nearly 90% and a mineralization efficiency of 56% were observed for initial 20 mg/L solution after 3 h treatment. Compared with the combined photocatalytic system on TiO(2) nanoparticle disk, a significant improvement in substrate removal efficiency of about 25-40% was observed on TNT/Ti disk. It was confirmed that the main degradation of rhodamine B occurred on the upper half of TNT/Ti disk above the heavily colorized sample solution, which was attributed to the superior UV utilization efficiency and the resultant high interfacial photoactivity.     

Unexpected adsorption of oxygen on TiO2 nanotube arrays: influence of crystal structure

We present kinetics data of O2, n/iso-butane, CO2, and CO adsorbed at ultrahigh vacuum conditions on TiO2 nanotube (TiNTs) arrays produced by electrochemical anodization; amorphous and polycrystalline (anatase and mixed anatase/rutile) TiNTs have been studied addressing structure-activity relationships. Oxygen distinctly interacts with the TiNTs, whereas this process is not observed on fully oxidized TiO2 single crystals. Both molecularly and atomically bonded oxygen have been observed. Variations in the binding energies of alkanes were also detected.     

Influence of operational parameters on the TiO2 photocatalytic degradation of Methylene blue

Thin films of titanium oxide were obtained by dip-coating, using the sol–gel method. TiO₂ powder (Degussa, P25) and polyethylene glycol (PEG) were added to enhance the photocatalytic properties of resulting films. Effects of experimental variables on the photocatalytic properties of the coatings were evaluated based on the degradation efficiency of the reference dye (Methylene blue). The photocatalytic activity of resulting TiO₂ coatings was improved with the loading of TiO₂ powder (Degussa, P25) and PEG in the sols. The electron-hole pair photogeneration increases with the energy of irradiation and improves photocatalytic efficiency. Increasing coating thickness leads to a rough surface with more reaction sites. Photodegradation conversion of Methylene blue (Mb) decreases with an increase in the initial concentration of Mb.     

Fabrication of carbon-modified TiO2 nanotube arrays and their photocatalytic activity

TiO₂ nanotube (TN) arrays were fabricated by an anodic oxidation process. Through a heat treatment of the as-fabricated TN arrays under a continuous Ar and acetylene flux, carbon-modified TN (C-TN) arrays were obtained. The as-fabricated catalysts were characterized by FE-SEM, HRTEM, XPS, Raman and UV-Vis spectra. Moreover, photocatalytic activity of the C-TN arrays was evaluated through the photodegradation of aqueous methyl blue. The experiments demonstrated that the C-TN arrays display an excellent photocatalytic activity. Under sunlight irradiation, the C-TN arrays are able to almost completely decompose the methylene blue pollutant of 1 × 10^− 5 M within 300 min.     

Enhanced hydrogen production on porous TiO2 nanotube arrays

Well aligned TiO2 nanotube arrays have been synthesized via anodization in an NH4F and ethylene glycol electrolyte; the resulting carbon-entrained films were treated by oxygen and argon microwave plasma. It was found that as-prepared amorphous TiO2 nanotubes can be easily crystallized into anatase at temperature lower than 150 degrees C. Carbon can be effectively eliminated in oxygen plasma and a new secondary porosity was emerged. It was found such a porous film has obvious photovoltaic and hydrogen production enhancement under simulated solar irradiation compared with that crystallized in inert argon plasma. This phenomenon may be attributed to the improvement of light adsorption and its excellent capability of hole-electron separation derives from highly ordered nanoporous configurations.     

V掺杂TiO2纳米管阵列的制备及光催化研究

以钒钛合金为原料,应用阳极氧化法制备出高度致密、有序的V掺杂TiO2纳米管阵列。应用扫描电镜(SEM)和粉末X光衍射仪(XRD)表征分析纳米管阵列的形貌和结构,结果表明在浓度不同的HF电解液下制备出径向不同的纳米管阵列,电解液浓度(0.5%～1.5%(质量分数)),管径变化(39.7～72.7nm)。在室温、可见光照射条件下,以10mg/L的亚甲基蓝溶液为模拟污染物进行光催化降解试验,研究了其光催化性能。结果显示V掺杂TiO2纳米管阵列光催化性能优于纯TiO2纳米管,且在HF电解液浓度为1.0%(质量分数)时制备出来的TiO2纳米管光催化降解有机毒物性能最佳。     

Super-long aligned TiO2/carbon nanotube arrays

5?mm long aligned titanium oxide/carbon nanotube (TiO(2)/CNT) coaxial nanowire arrays have been prepared by electrochemically coating the constituent CNTs with a uniform layer of highly crystalline anatase TiO(2) nanoparticles. While the presence of the TiO(2) coating was confirmed by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and x-ray diffraction, the resultant TiO(2)/CNT coaxial arrays were demonstrated to exhibit minimized recombination of photoinduced electron-hole pairs and fast electron transfer from the long TiO(2)/CNT arrays to external circuits. This, in conjunction with the aligned macrostructure, facilitates the fabrication of TiO(2)/CNT arrays for various device applications, ranging from photodetectors to photocatalytic systems. Thus, the millimeter long TiO(2)/CNT arrays represent a significant advance in the development of new macroscopic photoelectronic nanomaterials attractive for a variety of device applications beyond those demonstrated in this study.     

合成条件对晶态介孔TiO2结构和性能的影响

采用sol-gel法合成了锐钛矿相介孔氧化钛，利用XRD、BET、TEM和PL对介孔TiO2的结构和光致发光性能进行了表征及分析。结果表明，采用预制TiO2溶胶为钛源，所得介孔氧化钛具有良好的锐钛矿晶型、较大的孔径和比表面积，具有高的光致发光活性。