Synthesis of multifunctional nanostructured zinc-iron mixed oxide photocatalyst by a simple solution-combustion technique

A series of nanostructure zinc-iron mixed oxide photocatalysts have been fabricated by solution-combustion method using urea as the fuel, and nitrate salts of both iron and zinc as the metal source. Different characterization tools, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV-visible spectra (DRUV-vis), electron microscopy, and photoelectrochemical measurement were employed to establish the structural, electronic, and optical properties of the material. Electron microscopy confirmed the nanostructure of the photocatalyst. The synthesized photocatalysts were examined towards photodegradation of 4-chloro-2-nitro phenol (CNP), rhodamine 6G (R6G), and photocatalytic hydrogen production under visible light (λ ≥ 400 nm). The photocatalyst having zinc to iron ratio of 50:50 showed best photocatalytic activity among all the synthesized photocatalysts.     

Synthesis and photochemical performance of CdS nanoparticles photocatalysts for photodegradation of organic dye

Large scale CdS nanoparticles are synthesized by a facile and effective route. The as-prepared CdS product was characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electronmicroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy and UV–Vis diffuse reflectance spectroscopy. The CdS nanoparticles showed higher photocatalytic activity for the discoloration of methyl orange under UV light irradiation for 90 min. Significantly, the stability and recycling of the photocatalyst was also investigated. This study may provide a new insight into the design and prepared of visible-light photocatalytic materials.     

Fabrication of TiO<Subscript>2</Subscript>/ZnO composite nanofibers with enhanced photocatalytic activity

TiO₂/ZnO composite nanofibers have been successfully prepared by electrospinning technique. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, Raman spectrum, X-ray photoelectron spectroscopy and UV–Vis diffuse reflectance spectroscopy, were used to characterize the as-synthesized nanofibers. The photocatalytic studies revealed that the TiO₂/ZnO nanofibers exhibited enhanced photocatalytic efficiency of photodegradation. Additionally, the recycling experiment of TiO₂/ZnO nanofibers had been done, demonstrating that TiO₂/ZnO nanofibers have high efficiency and stability.     

水热合成的MoS2/石墨烯/N-TiO2复合材料的可见光催化性能

以氧化石墨烯(GO)、钼酸、硫脲和TiN为原料,成功制备了MoS_2/石墨烯/N-TiO_2(MGNT)复合材料。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HR-TEM)、X射线光电子能谱(XPS)及紫外-可见漫反射光谱(UV-Vis DRS)等手段测试分析了样品的物相组成、形貌、成分和光吸收性能。紫外-可见漫反射测试结果表明,MoS_2、石墨烯共同修饰及氮掺杂使得TiO_2的吸收带边发生红移,且其可见光吸收性能明显提高。可见光照射下降解亚甲基蓝溶液的实验结果表明,MoS_2/石墨烯共同修饰的氮掺杂TiO_2的光催化降解性能分别是氮掺杂TiO_2(NT)和石墨烯修饰氮掺杂TiO_2(GNT)的1.82倍和1.59倍,其吸附性分别为氮掺杂TiO_2、石墨烯修饰氮掺杂TiO_2的11.14倍和4.77倍。     

Ultrasonic-assisted synthesis of ZnO/NiO nanocomposites and kinetic study of their photocatalytic activity

In the present study, a facile ultrasonic-assisted method was developed for the synthesis of ZnO/NiO nanocomposites. The X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, diffuse reflectance spectroscopy and Fourier transform infrared spectroscopy techniques was applied for characterization of structure, purity, morphology and optical properties of the resultant samples. The photocatalytic performance of the synthesized ZnO/NiO nanocomposites was evaluated by monitoring the photodegradation of Rhodamine B (RhB) under UV light irradiation. Moreover, the influence of various parameters, such as molar percentage of NiO to ZnO, initial RhB concentration, pH of solution and photocatalyst weight was studied. The results show that the photocatalytic activity of the ZnO/NiO nanocomposite was higher than that of pure ZnO and NiO.     

Synthesis and photocatalytic activity of stable nanocrystalline TiO(2) with high crystallinity and large surface area

Superior photoactive TiO(2) nanopowders with high crystallinity and large surface area were synthesized by a hydrothermal process in the presence of cetyltrimethylammonium bromide and a post-treatment with ammonia. The prepared photocatalysts were characterized by X-ray diffraction (XRD), Raman spectroscopy, N(2) adsorption-desorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectra (DRS) and surface photovoltage spectroscopy (SPS). The prepared nanocrystallites were highly resistant to thermal sintering, and the calcinations up to 900 degrees C were shown to enhance the crystallinity of the anatase phase without any rutile phase and the separation rate of photoinduced charges of TiO(2) particles. It remained as large as 196 and 125 m(2)/g even after calcinations at 700 and 800 degrees C, respectively. The photocatalytic activity of prepared photocatalysts was obviously higher than that of commercial Degussa P25 on the photodegradation of methylene blue and phenol in water under ultraviolet-light irradiation, and the sample calcined at 800 degrees C afforded the highest photocatalytic activity.     

TiO2 supported on rod-like mesoporous silica SBA-15: Preparation, characterization and photocatalytic behaviour

TiO₂ nanoparticles have been successfully incorporated in the pores of mesoporous silica SBA-15 with different morphologies by a wet impregnation method. The composites were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma (ICP) emission spectroscopy, transmission electron microscopy (TEM), N₂-sorption and UV-Vis diffuse reflectance spectroscopy. The photodegradation of methyl orange (MO) was used to study their photocatalytic property. It is indicated that the morphology of SBA-15 had a great influence on the photocatalytic activity of the composites. When TiO₂/SBA-15 composite was prepared by loading TiO₂ nanoparticles on uniform rod-like SBA-15 of 1 μm length, it showed higher photocatalytic degradation rate than that on less regular but much larger SBA-15 support. This difference was rationalized in terms of the homogeneously distributed and shorter channels of rod-like SBA-15, which favored mass transport and improved the efficient utilization of the pore surface.     

Synthesis and photocatalytic properties of TiO2 nanostructures

TiO₂ particles, rods, flowers and sheets were prepared by hydrothermal method via adjusting the temperature, the pressure and the concentration of TiCl₄. The as-prepared TiO₂ powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra and N₂ adsorption–desorption measurements. It was found that pressure is the most important factor influencing the morphology of TiO₂. The photocatalytic activity of the products was evaluated by the photodegradation of aqueous brilliant red X-3B solution under UV light. Among the as-prepared nanostructures, the flower-like TiO₂ exhibited the highest photocatalytic activity.     

Preparation of Fe3+-doped TiO2 catalysts by controlled hydrolysis of titanium alkoxide and study on their photocatalytic activity for methyl orange degradation

Fe3+-doped TiO2 (Fe-TiO2) porous microspheres were prepared by controlled hydrolysis of Ti(OC4H9)4 with water generated "in situ" via an esterification reaction between acetic acid and ethanol, followed by hydrothermal treatment. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic absorption flame emission spectroscopy (AAS), electron paramagnetic resonance (EPR) spectrum, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), and nitrogen adsorption-desorption methods. All of the undoped TiO2 and Fe-TiO2 samples exclusively consist of primary anatase crystallites, which further form porous microspheres with diameters ranging from 150 to 500 nm. The photocatalytic activity of Fe-TiO2 catalysts was evaluated from the photodegradation of methyl orange (MO) aqueous solution both under UV and visible light irradiation. Fe3+ doping effectively improves the photocatalytic activity under both UV light irradiation and visible light irradiation with an optimal doping concentration of 0.1 and 0.2%, respectively. The photocatalytic mechanisms of Fe-TiO2 catalysts were tentatively discussed.     

Hydrothermal synthesis,characterisation and photocatalytic properties of BiOIO3 nanoplatelets

In this work, BiOIO₃ nanoplatelets were successfully prepared by a simple hydrothermal method. The as-prepared samples were characterised by energy-dispersive spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray powder diffraction and ultraviolet visible diffuse reflectance spectroscopy. The photocatalytic activities of the as-prepared BiOIO₃ nanoplatelets were evaluated by photodegradation of rhodamine B (RhB) under simulated solar light. The results showed that the change of temperature within a certain range has almost no influence on the morphology and size of BiOIO₃ nanoplatelets. However, it had an obvious effect on the photocatalytic performance of BiOIO₃ nanoplatelets. The results showed that the BiOIO₃ sample synthesised at 130 °C exhibited the highest photocatalytic activities compared to others, with RhB completely decomposed in 80 min. The products with proper crystallinity formed at 130 °C have the optimal rate of RhB photodegradation. It indicated that the most favourable crystallinity made it beneficial to improve the photocatalytic activity. The possible mechanism of the photocatalytic reaction based on deep analysis and the experimental results was discussed in detail.     

Effect of Ag loading on activated carbon doped ZnO for bisphenol A degradation under visible light

Silver modified activated carbon doped zinc oxide (Ag/AC-ZnO) was synthesized via a calcination-electroless deposition route. The samples were characterized by X-ray powder diffractometry, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of the Ag/AC-ZnO was evaluated for bisphenol A degradation in the presence of H₂O₂ under visible light irradiation. The archived results showed that the photocatalytic activity of the Ag/AC-ZnO was higher than that of AC-ZnO and pure ZnO. The cytotoxicity of the bisphenol A after photocatalysis under visible light irradiation was tested using L929 mouse fibroblast cells and the obtained results indicated that the treated bisphenol A solution exhibited no cytotoxicity against normal cells.     

浸渍-沉积法制备一维Au/TiO_2的光催化性能研究

以钛酸纳米管为载体、HAuCl4为金前驱体,通过浸渍-沉积法制备一维金修饰TiO2光催化剂(Au/TiO2)。通过X射线衍射和紫外-可见漫反射吸收光谱研究材料的结构和性质。以甲基橙溶液作为模拟废液,研究Au/TiO2材料在紫外光条件下的光催化活性。研究表明,由于金可以接受电子,从而促进光生电子和光生空穴的分离,使TiO2的光催化活性提高;Au/TiO2的光催化活性还与金的含量密切相关,金的最佳负载量为1%(质量分数)。     

CNTs-copper oxide nanocomposite photocatalyst with high visible light degradation efficiency

Cu_xO (x = 1 or 2)/Carbon nanotubes (CNTs) nanocomposite was prepared through a two-step process including copper electroless deposition on CNTs followed by chemical-thermal oxidation. The effect of electroless deposition time and hence copper oxide content on the photocatalytic activity was studied, and 30 min of deposition was optimal. X-ray diffraction (XRD) and Raman results confirm the formation of both crystalline CuO and Cu₂O phases. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images showed the dispersion of copper oxide nanoparticles onto the surface of CNTs. The diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) results showed that decreasing the copper oxide content decreases the bandgap and the electron-hole pairs recombination rate. The photocatalytic activity was investigated for the degradation of methyl orange (MO) and methylene blue (MB) under visible light irradiation. Relatively complete methylene blue (MB) degradation was obtained after 120 min for a 2 mg/L solution, while about 70% of methyl orange (MO) was degraded. The stability of the sample was also investigated, and the sample was able to maintain its performance after three cycles.     

钙钛矿型氧化合物AgNbO3的水热合成与表征

采用水热法制备了钙钛矿型化合物Ag-NbO3晶体,对化合物进行粉末X射线表征。Rietveld精修结果表明化合物AgNbO3属于三方晶系,空间群为R-3C。并对化合物进行了扫描电子显微镜(SEM)、BET法测定比表面积和对固体紫外漫反射光谱进行表征。对该化合物的光催化性质进行了测试,在可见光照射下降解染料龙胆紫。结果表明此化合物在室温下具有很高的光催化性质,在光催化性能方面具有潜在的应用价值。     

石墨/TiO2复合光催化剂的制备和性能

以石墨和纯的TiO₂为原料,采用球磨工艺制备了石墨/TiO₂复合光催化剂。使用XRD、SEM、TEM、XPS和DRS等手段对其性能进行了表征。以甲基橙为模拟污染物,研究了石墨掺入量、球磨时间对复合光催化剂光催化活性的影响。结果表明,石墨/TiO₂复合光催化剂具有锐钛矿结构,球磨后TiO₂(101)面的衍射峰宽化并右移,TiO₂成为200 nm左右的不规则球状颗粒,在其表面均匀分布着石墨。TiO₂晶粒的Ti-O键的结合能变高,且表面有缺陷产生,使其在可见光区具有显著的吸收。石墨掺入量为5%、球磨时间为12 h的石墨/TiO₂样品对甲基橙具有优异的光催化降解效果,在70 min的降解时间内甲基橙的降解去除率可达95.08%。石墨/TiO₂复合光催化剂的光催化反应速率常数k为0.043035 min^-1,是纯TiO₂的2.64倍。     

Rapid,simple and low-cost fabrication of BiOBr ultrathin nanocrystals with enhanced visible light photocatalytic activity

BiOBr ultrathin nanocrystals were prepared by a rapid, simple and low-cost route, and characterised by X-ray diffraction, scanning electron microscope, transmission electron microscopy, energy dispersive X-ray, UV–vis diffuse reflectance spectroscopy and electrochemical impedance spectroscopy analyses. The size of the resulting BiOBr ultrathin nanocrystals is about 60–100 nm in width and 15–20 nm in thickness. The photocatalytic activity of the samples was evaluated in terms of the degradation of RhB. Compared with BiOBr three-dimensional microspheres and P₂₅-TiO₂, the BiOBr ultrathin nanocrystals exhibited the best visible-light-induced photocatalytic activity.     

Photoactivity of brookite–rutile TiO2 nanocrystalline mixtures obtained by heat treatment of hydrothermally prepared brookite

Pure brookite phase was prepared by hydrothermal synthesis of titanium peroxo-complex in the presence of glycolic acid at 220 °C. The structure of prepared brookite samples was determined by X-ray powder diffraction (XRD) and selected area electron diffraction (SAED). The prepared brookite was studied by in situ high temperature XRD in air. The morphology and microstructure characteristics were also obtained by transmission electron microscopy (TEM). The nitrogen adsorption–desorption was used for determination of surface area (BET) and porosity. The method of UV–vis diffuse reflectance spectroscopy was employed to estimate band-gap energies of prepared brookite. The photocatalytic activity of the prepared titania samples were assessed by photocatalytic decomposition of Orange II dye in an aqueous slurry under UV irradiation at 365 nm wavelength. The photocatalytic activity of the prepared sample brookite heated to 800 °C in air was higher than nanocrystalline unheated brookite powder.     

Pd nanoparticle loaded TiO<Subscript>2</Subscript> semiconductor for photocatalytic degradation of Paraoxon pesticide under visible-light irradiation

Overuse of the organophosphorus pesticides such as Paraoxon in agriculture industry has raised significant threats to the environment by contamination of soils and groundwaters. Therefore, extensive studies have been carried out to develop an effective method for removing of these poisonous pollutants from contaminated resources. In the current study, Pd nanoparticle loaded TiO₂ nanocomposites with different weight percentages of Pd were prepared via a facile photoreduction method and for the first time, were used for photocatalytic degradation of Paraoxon under visible-light irradiation. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy techniques. In these nanocomposites, the presence of Pd nanoparticles enhances the photocatalytic activity of TiO₂ by their surface plasmon resonance effect and also by narrowing the band gap energy of TiO₂. The results of photocatalytic activity measurements indicate that the nanocomposite with 0.8 wt% content of Pd (PT0.8) has the best photocatalytic activity. The result of total organic carbon test shows that Paraoxon was completely mineralized by PT0.8 photocatalyst after 120 min, under visible-light irradiation.     

Fabrication of solar light induced Fe-TiO2 immobilized on glass-fiber and application for phenol photocatalytic degradation

Iron-doped anatase titanium dioxide catalysts coated on glass-fiber were successfully synthesized by a dip-coating sol–gel method. The prepared catalysts were characterized by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy to understand the synthesis mechanism, and their photocatalytic activities were evaluated by photodegradation of phenol under simulated solar irradiation. EDX analysis confirmed the existence of iron in the immobilized catalysts. XRD suggested that the phase transition of the catalysts from anatase to rutile were restrained, and almost pure anatase TiO₂ could retain even the calcination temperature reached 800 °C. The UV-Vis diffuse reflectance spectroscopy of the catalysts showed a red shift and increased photoabsorbance in the visible range for all the doped samples. Iron loading and calcination temperature have obvious influences on photocatalytic activity. In this study, the optimal doping dose and calcination temperature were around 0.005 wt% and 600 °C, respectively.     

One-pot synthesis of visible-light-driven plasmonic photocatalyst Ag/AgCl in ionic liquid

Plasmonic photocatalyst Ag/AgCl was prepared by in situ hydrothermal method with the contribution of 1-octyl-3-methylimidazolium chloride ([Omim]Cl), in which the [Omim]Cl ionic liquid acted not only as a precursor but also as a reducing reagent in the process of formation of Ag?. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and thermogravimetric and differential scanning calorimetry (TG-DSC). The photocatalytic activity of the composites were evaluated by degradation of methyl orange (MO) under visible light irradiation. The experimental results showed that the high activity and stability of Ag/AgCl photocatalysts under visible-light irradiation were due to their localized surface plasmon resonance (LSPR). Based on the characterization of the structure and photocatalytic performance, the LSPR was determined by synergetic effect of many factors, such as particle size of metallic Ag, contents of the Ag? nanoparticles, and the extent of metallic Ag dispersing. A photocatalytic mechanism of the Ag/AgCl photocatalyst was also proposed.