Visible-light-activated Ce-Si co-doped TiO2 photocatalyst

To enhance the visible photocatalytic activity and thermal stability of TiO₂, Ce-Si co-doped TiO₂ materials were synthesized through a nonaqueous method of which the purpose was to reduce the aggregation between TiO₂ particles. The obtained materials maintained anatase phase and large surface area of 103.3 m² g⁻¹ even after calcined at 800 °C. The XPS results also indicated that Si was weaved into the lattice of TiO₂, and Ce mainly existed as oxides on the surface of TiO₂ particles. The doped Si might enhance surface area and suppress transformation from anatase to rutile, while the doped Ce might cause visible absorption and inhibit crystallite growth during heat treatment. Evaluated by decomposing dye Rhodamine B, visible photocatalytic activity of Ce-Si co-doped TiO₂ was obviously higher than that of pure TiO₂ and reached the maximum at Ce and Si contents of 0.5 mol% and 10 mol%.     

Fabrication of nitrogen-doped TiO2 layer on titanium substrate

In this paper, macropores TiO₂ layer was fabricated on titanium substrates based on plasma based ion implantation (PBII). In order to increase the photodegradation efficiency of fabricated TiO₂ layer, two approaches are used: (1) preparation of macropores on TiO₂ layer to increase the total photodegradation area and (2) nitrogen doping (N-doping) to increase light absorption efficiency. The fabrication process of the N-doped macropores TiO₂ layer comprises four steps: firstly, helium plasma based ion implantation (He-PBII) is employed to generate He bubbles in substrate; secondly, oxygen plasma based ion implantation (O-PBII) and a followed annealing in air are executed to obtain rutile and anatase mixture TiO₂ phases; thirdly, He bubbles are exposed to the surface via an Ar ion sputter process; lastly, the samples are doped by nitrogen PBII (N-PBII). The photodegradation of Rhodamine B solution under Xe lamp indicates that the TiO₂ layer with surface macropores and N-doping has higher light photocatalysis efficiency.     

Oblique angle deposition of TiO2 thin films prepared by electron-beam evaporation

Optical, structural and photocatalytic properties of TiO₂ thin films obliquely deposited on quartz glass substrate using an electron-beam evaporation method were investigated. The photocatalytic activity of the films was evaluated by photodecomposition of methylene blue. An increase in incident deposition angle increased the porosity and surface roughness of the TiO₂ films. As a result, the photocatalytic activity was enhanced with incident deposition angle up to 60°. However, a further increase in incident deposition angle to 75° reduced the photocatalytic activity due to a lack of the crystalline phase.     

Visible-light photocatalysis of nitrogen-doped TiO2 nanoparticulate films prepared by low-energy ion implantation

Nitrogen-doped TiO₂ (N-TiO₂) films were prepared by low-energy implantation of nitrogen ions into pulsed laser deposited anatase TiO₂ films. The anatase phase of the films was not changed by the implantation with very low energy of 200 eV. XPS measurements revealed that the implanted nitrogen species were mainly interstitial ones. The nitrogen concentration was increased with increasing ion flux which could be controlled by adjusting the gas flow rate of the ion source. All the produced N-TiO₂ films exhibited visible-light photocatalytic activities in degradation of methylene blue in aqueous solutions, indicating that interstitial nitrogen could also be responsible for the photocatalysis in visible region. Higher visible-light photocatalytic efficiency was achieved with higher implanted nitrogen concentration.     

Magnetic iron oxide nanopowders produced by CO2 laser evaporation

Magnetic iron oxide nanopowders were produced with the laser evaporation technique under normal process gas pressure. In addition, the generated particles were coated in situ with stearic acid and separated on magnets. The methods and the used laboratory setup are briefly described. Influences of essential process conditions, particularly the use of continuous and pulsed laser radiation as well as the properties of the process gas, were experimentally investigated. The produced nanopowders were analysed with TEM, XRD, and magnetic measurements and confirmed the in-principle suitability of the presented method.     

Photocatalytic thin films containing TiO2:N nanopowders obtained by the layer-by-layer self-assembling method

In this work, TiO₂-N powders were synthesized by high-energy ball milling, using commercial titanium dioxide (TiO₂) in the anatase phase and urea to introduce nitrogen into TiO₂ in order to enhance their photocatalytic properties in the visible spectral region. Several samples were prepared by milling a mixture of TiO₂-urea during 2, 4, 8, 12 and 24 h and characterized by spectroscopic and analytical techniques. X-ray diffraction (XRD) results showed the coexistence of anatase and high-pressure srilankite TiO₂ crystalline phases in the samples. Scanning electron microscopy (SEM) revealed that the grain size of the powder samples decreases to 200 nm at 24 h milling time. UV-Vis diffuse reflectance spectroscopic data showed a clear red-shift in the onset of light absorption from 387 to 469 nm as consequence of nitrogen doping in the samples. The photocatalytic activity of the TiO₂-N samples was evaluated by methylene blue degradation under visible light irradiation. It was found that TiO₂-N samples had higher photocatalytic activity than undoped TiO₂ samples, which could be assigned to the effect of introducing N atoms and XPS results confirm it. Using polyethylenimine (PEI), transparent thin films of TiO₂-N nanoparticles were prepared by layer-by-layer self assembly method. UV-visible spectrophotometry was employed in a quantitative manner to monitor the adsorbed mass of TiO₂ and PEI after each dip cycle. The adsorption of both TiO₂ and PEI showed a saturation dip time of 15 min.     

Photo-induced surface charge separation of highly oriented TiO2 anatase and rutile thin films

Surface charge separation behavior of photo-generated carriers in highly oriented TiO₂ anatase and rutile films was investigated using a technique in which the transient surface charge is observed by laser pulse irradiation without metal contacts and an externally applied field. According to the measurements, the quantum efficiency of photo-generated holes transported toward the surface was determined as a function of incident laser energy. The photo-generated holes in anatase can be transported toward the surface for irradiation at the photon energy of its bandgap. The holes transported toward the rutile surface, however, were generated close to the surface for irradiation at the photon energy much higher than its bandgap.     

Synthesis and Characterization of TiO2 Doped ZnO Microtubes

以氯化锌和硫酸钛为原料,通过湿化学法成功制备了钛掺杂氧化锌微米管. 以粉末X射线衍射仪、场发射扫描电子显微镜、光致发光系统对样品进行了表征. 结果表明,未经掺杂的氧化锌微管具有良好的六方中空结构. 在TiO₂/ZnO比率小于5%时,钛掺杂和未掺杂氧化锌管具有相近的尺度,外表光滑,近于圆柱形. 当TiO₂/ZnO比率大于5%时,生成一种由ZnO, Ti₃O₅和TiO组成的多相混合物. 钛掺杂氧化锌在光催化降解甲基橙溶液效果明显.     

Preparation and photocatalytic properties of silver nanoparticles loaded on CNTs/TiO2 composite

In this study, new nanoscale photocatalyst based on silver and CNTs/TiO₂ was successfully prepared by photoreduction method. The prepared Ag-CNTs/TiO₂ was characterized by TEM, XRD and XPS. The photocatalytic activity was also evaluated by photocatalytic degradation of Reactive Brilliant Red X-3B dye. The results indicated that the photocatalytic efficiency of CNTs/TiO₂ increased in the presence of Ag nanoparticles and the photocatalysis reaction followed a first order kinetics. The kinetic constant of Ag-CNTs/TiO₂ for dye degradation was nearly 1.2 times than that of CNTs/TiO₂, which indicated decorating Ag nanoparticles on CNTs/TiO₂ could enhance the photocatalytic ability.     

H_3PW_(12)O_(40)/La-N-TiO_2复合催化剂可见光下光催化降解吡虫啉研究(英文)

制备出H3PW12O40/La-N-TiO2催化剂并采用红外光谱,N2吸附-脱附分析,透射电镜和紫外漫反射进行结构表征。红外光谱检测表明,复合催化剂中H3PW12O40保留了Keggin结构;掺杂La-N之后,复合催化剂的BET比表面积是母体TiO2的两倍;透射电镜检测表明,催化剂由相对均匀的球形颗粒组成,分散性良好;紫外漫反射检测表明,掺杂La和N元素后所制备的复合催化剂对可将光的光响应性能明显提高。对吡虫啉的光催化实验表明,所制备的不同负载量催化剂中30%H3PW12O40/0.3%La-1.0%N-TiO2具有最好的光催化活性(≥400nm),光照3h后吡虫啉降解率为91.57%,光照6h后吡虫啉降解率达98.89%,基本上完全降解。     

Al2O3/SiO2 films prepared by electron-beam evaporation as UV antireflection coatings on 4H-SiC

Al₂O₃/SiO₂ films have been deposited as UV antireflection coatings on 4H-SiC by electron-beam evaporation and characterized by reflection spectrum, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The reflectance of the Al₂O₃/SiO₂ films is 0.33% and 10 times lower than that of a thermally grown SiO₂ single layer at 276 nm. The films are amorphous in microstructure and characterize good adhesion to 4H-SiC substrate. XPS results indicate an abrupt interface between evaporated SiO₂ and 4H-SiC substrate free of Si-suboxides. These results make the possibility for 4H-SiC based high performance UV optoelectronic devices with Al₂O₃/SiO₂ films as antireflection coatings.     

Preparation, characterization and photocatalytic activity of the neodymium-doped TiO2 hollow spheres

Nd-doped titania hollow spheres were prepared using carbon spheres as template and Nd-doped titania nanoparticles as building blocks. The Nd-doped titania nanoparticles were synthesized at low temperature. The prepared hollow spheres were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectrum (DRS). The effects of Nd content on the physical structure and photocatalytic activities of doped titania hollow sphere samples were investigated. Results showed that there was an optimal Nd-doped content (3.9 at.%) for the photocatalytic degradation of dye X-3B (C.I. Reactive Red 2). The apparent rate constant of the best one was almost 9 times as that of P25 titania. The mechanism of photocatalytic degradation of dyes under visible light irradiation was also discussed.     

Low temperature deposition and characterization of TiO2 photocatalytic film through cold spray

Cold spray was employed as a novel low temperature approach to deposit titanium dioxide (TiO₂) photocatalytic film. The film microstructure was characterized using X-ray diffraction and scanning electron microscopy. The photocatalytic performance was examined through acetaldehyde degradation under ultraviolet illumination. Results showed that TiO₂ film was successfully deposited on substrate surface through cold spray. The film thickness reached up to 15 μm. The film presented a rough surface and porous structure. Owing to the low temperature of spray powder, no phase and particle size changes occurred to TiO₂ during deposition. It was found that the cold-sprayed TiO₂ film was active for photodegradation of acetaldehyde.     

Influence of oxygen-plasma posttreatment on the properties of SiO2 films prepared by the electron-beam evaporation method

SiO₂ films were deposited on K9 substrate by the electron-beam evaporation method. The influence of oxygen-plasma posttreatment on the properties of SiO₂ films was investigated. After oxygen-plasma treatment, it was found that the microdefect density of films reduced. We deduced that the absorption of films also reduced. The treated sample exhibited higher LIDT value compared with the as-deposited sample. However, this study is the preliminary work and optimization by this method will be discussed in our future work.     

The preparation of nitrogen-doped TiO2−xNx photocatalyst coated on hollow glass microbeads

In this paper, the effective method for nitrogen-doped TiO_2−xN_x photocatalyst coated on hollow glass microbeads is described, which uses titanium tetraisopropoxide [Ti(iso-OC₃H₇)₄] as the raw materials and gaseous ammonia as a heat treatment atmosphere. The effects of heat treatment temperature and time on the photocatalytic activity of TiO_2−xN_x/beads are studied. The photocatalyst is characterized by the UV-vis diffuse reflection spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis and scanning electron microscopy (SEM). The results show that when the TiO_2−xN_x/beads is heated at 650 °C for 5 h, the photocatalytic activity of the TiO_2−xN_x/beads is the best. Compared with TiO₂, the photoabsorption wavelength range of nitrogen-doped TiO_2−xN_x red shifts of about 60 nm, and the photoabsorption intensity increases as well. The photocatalytic activity of the TiO_2−xN_x/beads is higher than that of the TiO₂/beads under visible light irradiation. The presence of nitrogen neither influences on the transformation of anatase to rutile, nor creates new crystal phases. When the TiO_2−xN_x/beads is heated at 650 °C for 5 h, the amount of nitrogen-doped is 0.53 wt.% in the TiO_2−xN_x. As the density of TiO_2−xN_x/beads prepared is lower than 1.0 g/cm³, it may float on water surface and use broader sunlight spectrum directly.     

Effect of nano-titanium hydride on formation of multi-nanoporous TiO2 film on Ti

The effect of titanium hydride on the formation of nanoporous TiO₂ on Ti during anodization has been investigated by X-ray photoelectron spectroscopy, grazing incident X-ray diffraction, transmission electron microscopy and scanning electron microscopy. Titanium hydride (TiH₂) was formed after cathodization, profoundly impacting the formation of nanoporous TiO₂ on Ti by anodization. Oxide layer and nanocrystal structure were observed after anodization with cathodic pretreatments. A multi-nanoporous TiO₂ layer was formed on the titanium. The titanium hydride is a nanostructure. The nanostructure is directly changed to nanoporous TiO₂ by a dissolution reaction during anodization. The nanoporous layer is difficult to form without cathodization. The nanostructural TiH₂ is important in forming a nanoporous TiO₂ layer. Anodization treatment with cathodic pretreatment not only yields a titanium surface with a multi-nanostructure, but also transforms the titanium surface into a nanostructured titanium oxide surface.     

Synthesis and characterization of nitrogen-doped TiO2 coatings on reduced graphene oxide for enhancing the visible light photocatalytic activity

Nitrogen-doped TiO₂ coatings on reduced graphene oxide were prepared via a sonochemical synthesis and hydrothermal process. The nanocomposites showed improved photocatalytic activity due to their large specific surface areas (185–447 m²/g), the presence of TiO₂ in the anatase phase, and a quenched photoluminescence peak. In particular, GN3-TiO₂ (nitrogen-doped TiO₂ coatings on rGO with 3 ml of titanium (IV) isopropoxide) exhibited the best photocatalytic efficiency and degradation rate among the materials prepared. With nitrogen-doped on the reduced graphene oxide surface, the photocatalytic activity is enhanced approximately 17.8 times compared to that of the pristine TiO₂. The dramatic enhancement of activity is attributed to the nitrogen contents and rGO effectively promoting charge-separation efficiency and providing abundant catalytically active sites to enhance the reactivity. The composites also showed improved pollutant adsorption capacity, electron–hole pair lifetime, light absorption capability, and absorbance of visible light.     

Influence of the heating temperature on the properties of nickel doped TiO2 films prepared by sol-gel method

Formation and properties of nickel doped TiO₂ films prepared by sol-gel method were studied using X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy, and energy dispersive X-ray analysis. The results demonstrate that sizes of TiO₂ crystallites increase with increasing heating temperature. Also, at temperatures above 800 ° C diffusion of nickel onto the surfaces results in increased concentrations of nickel compounds on the surfaces. Similar to pure TiO₂ films the light-induced modification of hydrophilicity is observed also in the case of nickel doped TiO₂ films.     

Growth process of atomically flat anodic films on titanium under potentiostatical electrochemical treatment in H2SO4 solution

The as-deposited titanium film on silicon wafer was electrochemically treated in potential sweep and potential step modes in 0.1 M H₂SO₄ solution at 30 °C. Under the anodization conditions of potential sweep and properly modulated cyclic voltammetry (CV), nanoscale grains, step-terrace structure and atomic images were clearly observed on the surface of anodic oxide film on titanium. Under potential step conditions, if the anodization time was short (1 s), no grains could be found on the anodic oxide film surface, even though the potential was high up to 9000 mV. Moreover, whatever potential sweep or potential step mode was performed, sufficient time (low sweep rate means a prolonged anodization time) was needed for the formation of nanoscale grains, atomically flat surface and step-terrace structure on the anodized titanium film.