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.     

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.     

DBD-CVD法制备掺氮二氧化钛薄膜及其结构性能

采用介质阻挡放电化学气相沉积(DBD-CVD)法制备TiO2透明自清洁功能薄膜,选用四异丙醇钛(TTIP)、NH3作为反应先驱体,另外再加入一定量的N2、Ar或者He作为稀释气体控制气体的流量和流速。通过对其进行X射线衍射、紫外-可见光谱、X光电子能谱、场发射扫描电镜、光催化性质、光亲水性质等测试表明,过DBD-CVD方法制备TiO2薄膜,只存在锐钛矿相,氮掺杂改变了薄膜中锐钛矿相晶粒生长的取向,从而影响薄膜的表面微观结构,促使光吸收限红移,提高了薄膜在可见光照射下的光催化效率,并改善了薄膜表面的亲水性能。     

Recyclable and high-sensitivity electrochemical biosensing platform composed of carbon-doped TiO2 nanotube arrays

Electrode fouling and passivation are the main reasons for attenuated signals as well as reduced sensitivity and selectivity over time in electrochemical analysis. We report here a refreshable electrode composed of carbon-doped TiO(2) nanotube arrays (C-doped TiO(2)-NTAs), which not only has excellent electrochemical activity for simultaneous determination of 5-hydroxytryptamine and ascorbic acid but also can be easily photocatalytically refreshed to maintain the high selectivity and sensitivity. The C-doped TiO(2)-NTAs are fabricated by rapid annealing of as-anodized TiO(2)-NTAs in argon. The residual ethylene glycol absorbed on the nanotube wall acts as the carbon source and no foreign carbon precursor is thus needed. The morphology, structure, and composition the C-doped TiO(2)-NTAs are determined, and the corresponding doping mechanism is investigated by thermal analysis and in situ mass spectroscopy. Because of the high photocatalytic activity of the C-doped TiO(2)-NTAs electrode, the electrode surface can be readily regenerated by ultraviolet or visible light irradiation. This photoassisted regenerating technique does not damage the electrode microstructure while rendering high reproducibility and stability.     

Photocatalytic Property of TiO2 Films Deposited by Pulsed DC Magnetron Sputtering

TiO2 thin films were prepared by DC magnetron sputtering with the oxygen flow rate higher than the threshold. The film deposited for 5 h was of anatase phase with a preferred orientation along the <220> direction, but the films deposited for 2 and 3 h were amorphous. The transmittance and photocatalytic activity of the TiO2 films increased constantly with increasing film thickness. When the annealing temperature was lower than 700℃, only anatase grew in the TiO2 film. TiO2 phase changed from anatase to rutile when the annealing temperature was above 800℃. The photocatalytic activity decreased with increasing annealing temperature.     

Synthesis of photocatalytic TiO2 thin films via the high-pressure crystallization process at low temperatures

TiO2 thin films with a monophasic anatase structure were synthesized via a high-pressure crystallization (HPC) process which successfully lowered the crystallization temperature of TiO2 films from 350 to 150 degrees C. The thermal budget and energy consumption during the crystallization process were markedly reduced and dense films without cracks were obtained. During the HPC process, crystallization took place throughout the films and TiO2 films with uniform crystallinity were obtained. The HPC process also led to an enhancement in the wettability of TiO2 thin films. The hydrophilicity of the films increased with heating temperatures via high-pressure annealing. In comparison with the conventional annealing, the HPC process not only produced TiO2 films with superior photo-induced super-hydrophilicity, but also led to higher photocatalytic activity of the films. The HPC process was confirmed to provide a new route for synthesizing well-crystallized anatase TiO2 thin films with high photocatalytic activity and good wettability at low temperatures.     

Room temperature one-step synthesis of microarrays of N-doped flower-like anatase TiO2 composed of well-defined multilayer nanoflakes by Ti anodization

Microarrays of N-doped flower-like TiO(2) composed of well-defined multilayer nanoflakes were synthesized at room temperature by electrochemical anodization of Ti in NH(4)F aqueous solution. The TiO(2) flowers were of good anatase crystallinity. The effects of anodizing time, applied voltage and NH(4)F concentration on the flower-like morphology were systematically examined. It was found that the morphologies of the anodized Ti were related to the anodizing time and NH(4)F concentration. The size and density of the TiO(2) flowers could be tuned by changing the applied voltage. The obtained N-doped flower-like TiO(2) microarrays exhibited intense absorption in wavelengths ranging from 320 to 800 nm. Under both UV and visible light irradiation, the photocatalytic activity of the N-doped flower-like TiO(2) microarrays in the oxidation of methyl orange showed a significant increase compared with that of commercial P25 TiO(2) film.     

Enhanced photocatalytic activity of C-N-codoped TiO2 films prepared via an organic-free approach

An organic-free sol-gel method was developed to synthesize crack-free, high surface roughness and visible-light-active C-N-codoped TiO(2) films. These films were subsequently evaluated for its photodegradation efficient using stearic acid as the model pollutant compound. The current approach avoids the use of hazardous organic solvents and employs carbon black as the carbon source as well as a template to increase the surface roughness. The presence of carbon and nitrogen species in TiO(2) was studied and discussed. The concentrations of carbon and nitrogen dopants in the TiO(2) films were affected by calcination temperature and the concentration of carbon black. Optimal visible light photocatalytic activity was observed for C-N-codoped TiO(2) film at 10.0 wt.% C, which was more than double that of the N-doped TiO(2) film. The enhancement in visible light photocatalytic activities of the C-N-codoped TiO(2) films was attributed to the synergistic effects of carbon and nitrogen dopants, and high surface roughness of the prepared films.     

Ce3+掺杂钛酸钡纳米管薄膜的制备与性能

以阳极氧化制备的TiO_2纳米管薄膜为模版,通过水热法制备了Ba_(1-x)Ce_xTiO_3(0≤x≤0.08)纳米管薄膜,研究了Ba_(1-x)Ce_xTiO_3的结构、表面形貌及其电性能。采用X射线衍射仪表征其晶体结构,采用扫描电子显微镜和透射电子显微镜观察其表面及断口形貌,采用宽频介电阻抗谱仪测试其介电性能。结果表明,在较为温和的条件下用水热法成功制备出立方相结构的Ba_(1-x)Ce_xTiO_3纳米管薄膜,纳米管孔径在80~95nm之间;将制备的Ba_(1-x)Ce_xTiO_3经退火后生成多晶的Ba1-xCexTiO3纳米管薄膜,且样品的管外径尺寸在90~100nm之间,管壁的厚度为25~30nm,介电常数在1kHz下最高可达472,介电损耗为0.41。     

Effects of calcination temperatures on photocatalytic activity of SnO2/TiO2 composite films prepared by an EPD method

SnO2/TiO2 composite films were fabricated on transparent electro-conductive glass substrates (F-doped SnO2-coated glass:FTO glass) via an electrophoretic deposition (EPD) method using Degussa P25 as raw materials, and were further characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), UV-vis diffuse reflectance spectra and Photoluminescence spectra (PL). XRD and XPS results confirmed that the films were composed of TiO2 and SnO2. FESEM images indicated that the as-prepared TiO2 films had roughness surfaces, which consisted of nano-sized particles. The effects of calcination temperatures on the surface morphology, microstructures and photocatalytic activity of SnO2/TiO2 composite films were further investigated. All the prepared SnO2/TiO2 composite films exhibited high photocatalytic activities for photocatalytic decolorization of Rhodamine-B aqueous solution. At 400 degrees C, the SnO2/TiO2 composite films showed the highest photocatalytic activity due to synergetic effects of low sodium content, good crystallization, appropriate phase composition and slower recombination rate of photogenerated charge carriers.     

Fast fabrication of long TiO2 nanotube array with high photoelectrochemical property on flexible stainless steel

Oriented highly ordered long TiO2 nanotube array films with nanopore structure and high photoelectrochemical property were fabricated on flexible stainless steel substrate (50 microm) by anodization treatment of titanium thin films in a short time. The samples were characterized by means of field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and photoelectrochemical methods, respectively. The results showed that Ti films deposited at the condition of 0.7 Pa Ar pressure and 96 W sputtering power at room temperature was uniform and dense with good homogeneity and high crystallinity. The voltage and the anodization time both played significant roles in the formation of TiO2 nanopore-nanotube array film. The optimal voltage was 60 V and the anodization time is less than 30 min by anodizing Ti films in ethylene glycerol containing 0.5% (w) NH4F and 3% (w) H2O. The growth rate of TiO2 nanotube array was as high as 340 nm/min. Moreover, the photocurrent-potential curves, photocurrent response curves and electrochemical impedance spectra results indicated that the TiO2 nanotube array film with the nanoporous structure exhibited a better photo-response ability and photoelectrochemical performance than the ordinary TiO2 nanotube array film. The reason is that the nanoporous structure on the surface of the nanotube array can separate the photo electron-hole pairs more efficiently and completely than the tubular structure.     

Layer-by-layer assembly of TiO2 nanowire/carbon nanotube films and characterization of their photocatalytic activity

We report on the layer-by-layer (LbL) formation of TiO(2)-MWNT-TiO(2) coatings on quartz with either trititanate derived TiO(2) nanowires or Degussa P25 as the photocatalytically active material. The optimized deposition sequence is discussed in detail and the morphology of the prepared coatings is analyzed by SEM and XRD. The heterogeneous photocatalytic performance of the coatings was tested in the methyl orange oxidation reaction. The apparent first order rate constant fell in the 0.01-0.20 h(-1) range over a 2.5 × 2.5 cm(2) film depending on the type and the thickness of the titanate coating. Building a multiwall carbon nanotube layer into the middle of the layer improved the photocatalytic activity for each material for all of the studied thicknesses. P25 based films performed 2-5 times better than TiO(2) nanowire films; however, the pores in the P25 based films were largely blocked because the isotropic P25 nanoparticles form closely packed layers by themselves and even more so with the comparably sized multiwall carbon nanotubes. Therefore, films derived from titanate nanowires appear to be more suitable for use as multifunctional, photocatalytically active filtration media.     

Sol-gel assisted ZnO nanorod array template to synthesize TiO(2) nanotube arrays

A TiO(2) nanotube array with a large surface area is fabricated on a glass substrate using a ZnO nanorod array and sol-gel process, and the structural characteristics of the TiO(2) nanotube array are investigated. The well-aligned ZnO nanorod array, which is deposited on ZnO seed layer coated glass substrates by the wet-chemical route, is used as a template to synthesize TiO(2)/ZnO composite nanostructures through the sol-gel process. Then, by selectively removing the ZnO template, a TiO(2) nanotube with contours of the ZnO nanorods is fabricated on the ZnO seed layer coated glass. The resultant TiO(2) nanotubes are 1.5?μm long and 100-120?nm in inner diameter, with a wall thickness of ～10?nm. In addition, by adjusting the experimental parameters, such as the dip-coating cycle number or heating rate, porous TiO(2) thick films can also be obtained.     

TiO2纳米管阵列薄膜的水热晶化

首先在KF和乙二醇的混合溶液中利用阳极氧化技术在钛基底表面制得了一层排列整齐、形貌均一的TiO₂纳米管阵列薄膜,然后将制得的薄膜进行水热处理,通过扫描电子显微镜、X射线衍射仪等表征手段研究了水热处理温度和时间对TiO₂纳米管阵列薄膜表面形貌、结晶度以及管状结构的影响。结果表明:水热处理即使在较短的时间内（如3 h）也可在较低温度下（如210℃）使TiO₂纳米管阵列薄膜由无定形转变为锐钛矿型结构;提高水热处理温度或延长水热处理时间均可提高薄膜的结晶度,但同时纳米管管壁结晶度增加会使管内径变小甚至堵塞,从而破坏管状结构。     

溶胶凝胶法制备的TiO2薄膜结构对光催化活性的影响

TiO2多孔纳米薄膜采用溶胶－凝胶法在普通载玻片上制得。薄膜的结构如孔径、孔分布和厚度可控制。通过稀醋酸的分解来测定锐钛矿TiO2多孔薄膜的结构对光催化活性的影响。     

泡沫镍负载TiO2和TiO2/Al2O3薄膜的光催化性能研究

以泡沫镍为载体，Al2O3作为过渡中间层，用溶胶-凝胶法在泡沫镍上负载锐钛矿相的TiO2薄膜，制成泡沫金属基的TiO2和TiO2／Al2O3光催化剂，利用XRD和FE-SEM等测试手段对其性质进行表征，用乙醛气体的光催化降解测试其活性．研究表明：泡沫镍负载的TiO2和TiO2／Al2O3薄膜具有良好的光催化活性，特别是TiO2／Al2O3薄膜具有更高的催化活性．这是由于负载的Al2O3过渡中间层增大了载体的比表面积，具有吸附浓缩作用，同时也增加了负载光催化剂的活性位数量．实验表明：TiO2／Al2O3薄膜的光催化活性和稳定性较单一的TiO2薄膜有非常显著的提高．     

P-type Cu--Ti--O nanotube arrays and their use in self-biased heterojunction photoelectrochemical diodes for hydrogen generation

Copper and titanium remain relatively plentiful in the earth's crust; hence, their use for large-scale solar energy conversion technologies is of significant interest. We describe fabrication of vertically oriented p-type Cu-Ti-O nanotube array films by anodization of copper rich (60% to 74%) Ti metal films cosputtered onto fluorine doped tin oxide (FTO) coated glass. Cu-Ti-O nanotube array films 1 mum thick exhibit external quantum efficiencies up to 11%, with a spectral photoresponse indicating that the complete visible spectrum, 380 to 885 nm, contributes significantly to the photocurrent generation. Water-splitting photoelectrochemical pn-junction diodes are fabricated using p-type Cu-Ti-O nanotube array films in combination with n-type TiO 2 nanotube array films. With the glass substrates oriented back-to-back, light is incident upon the UV absorbing n-TiO 2 side, with the visible light passing to the p-Cu-Ti-O side. In a manner analogous to photosynthesis, photocatalytic reactions are powered only by the incident light to generate fuel with oxygen evolved from the n-TiO 2 side of the diode and hydrogen from the p-Cu-Ti-O side. To date, we find under global AM 1.5 illumination that such photocorrosion-stable diodes generate a photocurrent of approximately 0.25 mA/cm (2), at a photoconversion efficiency of 0.30%.     

A new precursor for the preparation of nanocrystalline TiO2 films and their photocatalytic properties

In this work, we present a new precursor for the preparation of thin and transparent nanocrystalline TiO2 films, which involves the use of Titanium(IV) bis(ammonium lactato) dihydroxide as Ti(IV) source and Triton X-100 as surfactant template. The films were heated at various temperatures in order to optimize their nanostructure and their photocatalytic activity. The morphology and the nanostructure of the films were characterized by SEM and AFM. Crystallinity of the films was examined by XRD and their light absorption with UV-Vis spectroscopy. The photocatalytic activity of the films was investigated by using an azo dye: Basic Blue 41. Excitation of the samples was made by low intensity black light tubes emitting in the Near-UV. The photodegradation of the dye was studied as a function of the quality of the deposited TiO2 films and the calcination temperature in comparison with similar films made by standard procedures.     

氮掺杂改性TiO_2多孔薄膜光催化降解4-硝基苯酚

本文采用溶胶-凝胶法制备了N掺杂TiO_2光催化剂,并对N掺杂TiO_2进行了改性,分别以P25、N掺杂TiO_2、改性的N掺杂TiO_2为原料,通过逐步研磨、旋转涂膜以及高温煅烧制得三种多孔薄膜,并对其进行了表征。场发射扫描电子显微镜(FESEM)观察结果显示,煅烧后薄膜呈现显著的多孔结构。以4-硝基苯酚(4-NP)溶液为目标污染物,研究紫外光下TiO_2多孔薄膜的光催化性能,确定最佳降解条件,并研究了薄膜耐用性以及三种薄膜对4-NP的光催化性能的比较。结果表明,三种多孔薄膜中,改性N掺杂TiO_2多孔薄膜光催化性能最佳,10mg/L的4-NP溶液吸附30min,在pH=2条件下180min,降解率达到了90%以上,改性N掺杂TiO_2多孔薄膜单次降解180min,循环使用4次的降解率仍接近80%,显示了薄膜具有较好的可耐用性。     

Effect of MWCNT Inclusion in TiO2 Nanowire Array Film on the Photoelectrochemical Performance

Rutile TiO2 nanowire array films with multi-walled carbon nanotube(MWCNT) inclusion perpendicularly grown on fluorine-doped tin oxide(FTO) substrate were prepared by a facile hydrothermal method.The absorption edges of the TiO2 nanowire array films are blue-shifted with increasing MWCNT content.The resistance of the TiO2 nanowire array film is decreased by MWCNT inclusion.The optimum TiO2 /MWCNT molar ratio in the feedstock is 1:0.1.For the TiO2 nanowire array film with MWCNT inclusion served as electrode in dye-sensitized solar cell(DSSC),an overall 194% increase of photoelectric conversion efficiency has been achieved.