Synthesis and photocatalytic characterization of porous cuprous oxide octahedra

Porous cuprous oxide octahedra with a mean diameter of 1 μm have been successfully prepared with high yield via a hydrothermal reduction process at a low temperature. The growth mechanism and the influences of the poly(vinylpyrrolidone) (PVP) and citric acid have been discussed. And then, the samples were used as photocatalytic in the degradation of methyl red (MR). Thanks to the 3D architecture of the product, the photocatalytic performance has been significantly improved. We believe that the present work will open up to systematically explore ways to fabricate porous nanostructures and thus find use in a variety of applications.     

Synthesis, characterization and photocatalytic activity of mesoporous titania nanorod/titanate nanotube composites

Mesoporous titania nanorod/titanate nanotube composites were prepared using TiF4 and H(3)BO(3) as the precursors. The prepared samples were characterized with TEM, SEM, XRD, HRTEM, and nitrogen adsorption-desorption isotherms. The photocatalytic activities were evaluated by photocatalytic oxidation of acetone in a gas phase and photocatalytic discolorization of methyl orange aqueous solution in an aqueous phase, respectively. The results indicated that the photocatalytic activity of the mesoporous titania nanorod/titanate nanotube composites exceeded that of P25 by a factor of about 2.5 times for the photocatalytic oxidation of acetone. This could be attributed to the fact that the former had a larger specific surface area and a higher pore volume. Moreover, the mesoporous titania nanorod/titanate nanotube composites, which could be readily separated after photocatalytic reaction in an aqueous phase, exhibited highly photocatalytic activity for the degradation of methyl orange aqueous solution.     

Synthesis, characterization and photocatalytic reactions of phosphated mesoporous titania

Mesoporous titania nanoparticles with a well-defined mesostructure was prepared by hydrothermal process, using nonionic triblock copolymer P123 as surfactant template, modified with phosphoric acid and followed by calcination at 600°C. The sol–gel titania was modified by in situ phosphorylation using phosphoric acid and thereby incorporating phosphorous directly into the framework of TiO₂. The resulting materials were characterized by XRD, SEM, TEM, nitrogen adsorption, TGA and DRS. It was found that the structural and optical properties of titania samples are strongly influenced by their phosphate modification. In case of calcined samples a positive effect on the specific surface area for the in situ phosphated sample was found. Mesoporous structure of phosphated titania did not collapse even after calcination at 600°C. The enhanced photocatalytic activity of the synthesized phosphate nanomaterials were evaluated through a study of the decomposition of fluorescein under UV light excitation and compared with undoped titania nanomaterial as well as with commercial titania.     

Synthesis of porous micro-sized titania cages and their photocatalytic property

Micro-sized TiO₂ cage consisted of anatase nanoparticles on the edges of each cube, was synthesized using TTIP as the reagent and NaF submicrometer sized cubes as the template. When a salt of cube was adopted as the template, the reactants prefer to grow on the active sites, edges and corners of the cube, after removing the NaF template, the skeleton of the cube remain as the cage-shaped materials. The hierarchical structures with nano-sized anatase particles and micro scaled cage architecture markedly enlarge the surface area and enhance the light harvesting by light scattering of TiO₂ frame, resulting in great photo-catalytic performance, which leads to the photo-degradation of methylene blue by 40% higher than that was achieved by crushed nanoparticles.     

Preparation, characterization and photocatalytic activity of manganese doped TiO(2) immobilized on silica gel

A series of Mn-TiO(2)/SiO(2) (silica gel loaded with manganese doped TiO(2)) photocatalysts have been prepared by sol-gel method, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Photocatalytic activities were enhanced in photocatalytic degradation of methyl orange over Mn-TiO(2)/SiO(2). XPS analysis shows that a Ti-O-Si or Ti-O-Mn bond is formed on the surface of photocatalyst. Mn is doped as a mixture of Mn(2+) and Mn(3+) on the surface of 1.0mol% Mn-TiO(2)/SiO(2). Mn(3+) appears to trap electrons and prohibit the electron-hole recombination. The electrons trapped in Mn(3+) site are subsequently transferred to the adsorbed O(2). As a result, the combination of the electron-hole pair was reduced.     

Synthesis of nano titania particles embedded in mesoporous SBA-15: characterization and photocatalytic activity

Supported nanocrystalline titanium dioxide (TiO2) has been prepared by a post-synthesis step via Ti-alkoxide hydrolysis through the use of mesoporous SBA-15 silica. TiO2/SBA-15 composites with various TiO2 loading have been prepared and characterized by X-ray diffraction, nitrogen adsorption, Fourier transform infrared spectroscopy and diffusive reflective UV-vis spectroscopy. The addition of mesoporous SBA-15 prevents the anatase to rutile phase transformation and the growth of crystal grain. TiO2 did not block the SBA-15 pores, and their surface was fully accessible for nitrogen adsorption. Calcination in air of the composites up to 800 degrees C did not change the nanocrystal phase and slightly increased the domain size from 5.0 to 7.5 nm, indicating that the anatase TiO2 grains in the mesostructures have a relatively high thermal stability and proper pore diameter allows controlling the size of obtained titania particles. The TiO2/SBA-15 composites prepared by this study showed much higher photodegradation ability for methylene blue (MB) than commercial pure TiO2 nanoparticles P-25. Experimental results indicate that the photocatalytic activity of titania/silica mixed materials depends on the adsorption ability of composite and the photocatalytic activity of the titania, and there is an optimal ratio of Ti:Si, too high or low Ti:Si ratio will lower the photodegradation ability of the composites.     

Synthesis and photocatalytic activity of titania microspheres with hierarchical structures

A combined sol-gel and solvothermal process was introduced to fabricate the titania microspheres with hierarchical structures by using lauryl alcohol as the structure-directing agent. Scanning electron microscope, high-resolution transmission electron microscope, Fourier transform infrared spectrograph and powder X-ray powder diffraction indicated that the molar ratio of lauryl alcohol, water and tetra-n-butyl titanate was the key factor for the formation of the mono-dispersed titania with anatase phase and the optimal ratio was 1.2:4:1. The diameter of the end-product was 523 ± 74 nm and it was composed of smaller nanoparticles with about 6.8 nm size in diameter. Photocatalytic activity of the end-product was investigated by employing Rhodamine B and Methylene blue as the model compounds. The target microspheres exhibited the higher photocatalytic efficiency compared with commercial Degussa P25 titania and this result might be due to the hierarchical structures of microspheres according to the analysis of Brunauer-Emmett-Teller specific surface areas.     

Synthesis, characterization and its visible-light-induced photocatalytic property of carbon doped ZnO

Carbon-doped ZnO was prepared by calcination of organic zinc compound synthesized by the reaction between ZnCl₂ and glycol. It was characterized by thermal analysis, XPS, XRD, DRUV-vis, and PL. The results show that substitution of lattice oxygen by carbon in ZnO results in significantly extending for its optical response from UV to visible region. The photocatalytic test shows that it efficiently photomineralize formaldehyde to CO₂ under irradiation of indoor fluorescent lamp and its photocatalytic activity is much better than nitrogen-doped TiO₂.     

Synthesis,defect characterization and photocatalytic degradation efficiency of Tb doped CuO nanoparticles

Monoclinic undoped and Tb doped CuO are prepared by solution combustion method and annealed at different temperatures. The effect of annealing and doping on their structural and optical properties of CuO are examined using XRD, FTIR and DRS. The surface and lattice defects in CuO and Tb doped CuO is analyzed qualitatively and quantitatively using positron lifetime and Doppler broadening spectroscopy. The average positron lifetime and electron momentum (energy) S parameter increases owing to the number of vacancies in the CuO lattice upon doping and decreases with increasing temperature. The migration of vacancies from grain to grain boundary region is observed at 600 °C annealed samples. At 800 °C, the overall behavior of lifetime value denotes that the vacancy type defect is recovered, cluster vacancy and microvoids exists with reducing size. The photocatalytic performance of undoped and Tb doped CuO on degradation of methylene blue (MB) and methyl orange (MO) is investigated under visible light for two different lamp power and dye concentration. The influence of annealing temperature and dopant ion on the efficiency is also elaborated. Enhanced photocatalytic efficiency in Tb doped CuO is observed upon annealing. X-ray photoelectron spectroscopy (XPS) result indicates that the valence states of Cu, O and Tb ions exist at the surface of the particles. Brunauer–Emmett–Teller N₂ adsorption–desorption analyses were employed to characterize specific surface area and porosity of Tb doped CuO. The doped CuO with pore size of about ～34 nm have a surface area of 16–28 m²/g. The surface area effect plays an important role in the enhanced catalytic performance on Tb doped catalysts.     

Preparation, characterization, and photocatalytic activity of Gd3+ doped TiO2 nanoparticles

TiO2 and Gd3+ doped TiO2 nanoparticles were prepared by sol-gel method and the materials were characterized by XRD, TEM, SEM-EDX, BET, FT-IR, UV-Vis absorption, and Raman spectral analysis. The photocatalytic activity of nano TiO2 and Gd/TiO2 nanoparticles was evaluated using a model pollutant propoxur, a carbamate pesticide, in a batch type UV photoreactor. The results revealed higher photocatalytic activity for Gd/TiO2 nanoparticles than both TiO2 nanoparticles and commercial TiO2 (Degussa P-25). The enhanced photocatalytic activity of Gd/TiO2 relative to TiO2 is attributed to its increased band gap energy as evidenced from the blue shift to shorter wavelength observed in the UV-Vis abso4ption spectra. The recombination rate of photogenerated electron-hole pair decreased due to increase in the band gap, which enhanced the charge transfer efficiency of Gd/TiO2 nanoparticles. Gd3+ with its half filled 7 f subshell facilitated rapid electron transfer at solid-liquid interface by shallowly trapping the electrons. Among the various dopant level of gadolinium, 0.3 wt% Gd/TiO2 nanoparticles showed higher activity than others due to its higher surface area.     

Synthesis, characterization and photocatalytic activity of nanotitania loaded W-MCM-41

Nanocrystalline titanium oxide (TiO(2)) is a promising material as a photocatalyst for photodecomposition of hazardous organic pollutants under illumination, because it is cheap, safe, environmentally benign, and chemically stable. However, the control of particle size and monodispersity of TiO(2) is a challenging task. The use of MCM-41, an inorganic template of uniform pore size (2-10?nm), can overcome this difficulty and produce stable nanoparticles of uniform size and shape. In an attempt to extend light absorption of the TiO(2)-based photocatalyst towards the visible light range and eliminate the rapid recombination of excited electrons/holes during photoreaction, a new photocatalyst (25%TiO(2)-loaded W-MCM-41) powder was prepared. W-MCM-41, with different ratios of Si to W (Si/W = 25, 50, 75), was synthesized by a hydrothermal method and loaded with 25?wt% TiO(2) utilizing a sol-gel method. In order to compare the photocatalytic activity of our sample, titania-loaded plain MCM-41 was also prepared. These materials were characterized by various physiochemical techniques such as UV-visible absorption spectroscopy, x-ray diffraction, nitrogen adsorption-desorption isotherm measurement, Fourier transform infrared (FT-IR) spectroscopy, and transmission electron microscopy. The photocatalytic activity of the prepared samples was evaluated using methyl orange as a model organic compound. It was found that the photodegradation ability of 25% TiO(2)-loaded W-MCM-41 was highly related to the amount of W atoms present in the sample; the optimum atomic ratio of Si to W was 25. It has been confirmed that the recombination rate of electrons/holes in 25%TiO(2)/W-MCM-41 declined due to the existence of W atoms in the sample.     

W doped vanadium oxide nanotubes: Synthesis and characterization

W doped vanadium oxide nanotubes (VONTs) were prepared via a rheological phase reaction followed by self-assembling process. The nanotubes were characterized by elemental analysis, IR, XRD, SEM, TEM, HRTEM, SAED and XPS. Elemental analysis, IR, XRD, SAED and XPS could confirm the crystalline characteristic of the W doped VONTs, while the SEM, TEM, and HRTEM confirmed their morphology and microstructure.     

Synthesis of manganese vanadate nanobelts and their visible light photocatalytic activity for methylene blue

Manganese vanadate nanobelts have been synthesised by a simple hydrothermal process using polymer polyvinyl pyrrolidone as the surfactant by adjusting the pH value. The X-ray diffraction, selected area electron diffraction and the high-resolution transmission electron microscopy (TEM) show that the manganese vanadate nanobelts are composed of a single crystalline monoclinic Mn₂V₂O₇ phase. Scanning electron microscopy and TEM observations show that the thickness, width and length of the nanobelts are 20 nm, 350 nm–1 μm and several dozens to several hundreds of micrometres, respectively. The photocatalytic activities of the manganese vanadate nanobelts have been evaluated by the photocatalytic degradation of methylene blue (MB) in an aqueous solution as a model pollutant under the solar light irradiation. After 4 h of the irradiation by the solar light, the MB solution with the volume of 10 mL and the concentration of 10 mg·mL^?1 can be totally degraded using 10 mg manganese vanadate nanobelts.     

Preparation, characterization and photocatalytic performance of Nd-doped titania nanoparticles with mesostructure

Nd³⁺-doped titania nanoparticles with mesostructures were synthesized via hydrothermal process by using cetyltrimethylammonium bromide (CTAB) as directing and pore-forming agent. The obtained materials were characterized by XRD, nitrogen adsorption-desorption, TEM and DRS. The existence of neodymium ion affect significantly the phase transition of the amorphous to anatase, and the band-gap energy was reduced because of the defect energy level induced by the 4f atomic orbital of Nd³⁺ with the optimal content of 1.5 at.% Nd. Density functional theory calculations can explain the band-gap narrowing. The maximum photocatalytic activity corresponds to the 0.5 at.% Nd³⁺-doped anatase nanopowders with mesostructures, which is higher than that of undoped samples.     

Synthesis and photocatalytic oxidation properties of titania hollow spheres

The hollow spheres of anatase TiO₂ with higher photocatalytic activity have been fabricated by spherical CaCO₃ nanoparticles as a template, and titanium sulfate (Ti(SO₄)₂) as a precursor, and the CaCO₃ templates were dissolved subsequently in dilute HNO₃ solution. The TiO₂ hollow spheres samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and N₂ adsorption-desorption isotherms. The characterization results indicate that as prepared TiO₂ hollow spheres sample was transformed to anatase phase in calcined at 400 °C, and the anatase TiO₂ hollow spheres have a higher specific surface area and show much better photocatalytic activity than commercial P25 in the photodegradation of Rhodamine B under the UV irradiation.     

Synthesis, characterization, and photocatalytic activities of titanate nanotubes surface-decorated by zinc oxide nanoparticles

Nanoscaled zinc oxide (ZnO) particles with different amounts are coated on titanate nanotubes (TNTs) by a facile chemical method at room temperature. The characterizations of XPS, TEM, XRD and UV-vis spectra confirm that pure hexagonal wurtzite ZnO nanoparticles with an average size of about 9nm are distributed on the surfaces of TNTs evenly and attached strongly. The photocatalytic activities of the ZnO-TNTs nanocomposite are superior to those of P25, ZnO, TNTs and ZnO-anatase TiO2 (TNP) nanocomposite in the oxidation of rhodamine B under UV light irradiation. A comparison of the photocatalytic activities between different catalysts is discussed. Furthermore, we also find that the ZnO-TNT nanocomposite shows very favorable recycle use potential, because they have a high sedimentation rate and their photocatalytic activity is only slightly decreased even after five times of repeated uses.     

无机酸刻蚀多孔氮化碳的合成及光催化性能

通过合理的形貌调控使石墨相氮化碳(g-C_3N_4)低维化和多孔化,是提高其光催化活性的有效途径.采用高温煅烧方法制备了HCl、HNO_3和H_2SO_4刻蚀的g-C_3N_4,并对它们进行了结构形貌表征、形成机理探究和光催化降解罗丹明B测试,还给出了活性增强机理.结果显示:酸刻蚀g-C_3N_4具有和g-C_3N_4相同的基本晶体结构,但是呈薄片状,且表面出现了大量纳米孔,这些孔是由无机酸阻碍前驱体中N—H键参与热缩聚反应所致,按照HCl、HNO_3、H_2SO_4的顺序阻碍作用依次增强,对应的孔径依次增大,结构边缘(C)_2—N—H基团的XPS特征峰强度也依次增加;经过40 min光反应,g-C_3N_4和HCl、HNO_3、H_2SO_4刻蚀的g-C_3N_4对罗丹明B的降解率分别为45%、 56%、 52%和95%,H_2SO_4刻蚀的g-C_3N_4光催化活性最高;酸刻蚀引起的薄片和多孔结构不仅增加了g-C_3N_4的比表面积,促进了暗条件下对罗丹明B的吸附,还通过量子限域效应提高了其光吸收能力,拓宽了禁带宽度,有效促进了光生电荷的分离.因此,酸刻蚀克服了g-C_3N_4的缺点,为探寻其光催化活性的提高方法提供了有价值的启发.     

Synthesis,characterization, and its photocatalytic activity of double-walled carbon nanotubes-TiO2 hybrid

Double-walled carbon nanotube (DWCNT)-TiO₂ hybrid was prepared by hydrothermal method and characterized by X-ray diffraction, electron microscopy, N₂-adsorption analysis, Raman spectroscopy, Fourier transform infrared spectroscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of DWCNT-TiO₂ hybrid was tested by the photocatalytic degradation of sulfathiazole. The experimental results showed that the introduction of the DWCNTs provides DWCNT-TiO₂ hybrid with visible light-induced photoactivity and a large surface area. The DWCNTs were coated with TiO₂ nanoparticles, which generated an intimate contact between the DWCNTs and TiO₂. The DWCNT-TiO₂ hybrid showed an excellent visible-light-induced activity, compared with multi-walled carbon nanotube-TiO₂ and single-walled carbon nanotube-TiO₂ hybrids, which can be attributed to the unique electronic structure of the DWCNTs that can work well as not only a photosensitizer but also an electron conductor. In addition, DWCNT-TiO₂ hybrid with the DWCNTs of long length showed higher degradation efficiency than that with the short length.     

Synthesis,characterization and photocatalytic activity of ZnO-SnO2 nanocomposites

Nanocomposites of coupled ZnO-SnO₂ photocatalysts were synthesized by the coprecipitation method and were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, surface area analyzer and scanning electron microscopy. Their photocatalytic activity was investigated under UV, visible and solar light and evaluated using methylene blue (MB) as a model pollutant. The performance of the coupled ZnO-SnO₂ photocatalysts was found to be related to the Zn/Sn molar ratio and to the calcination conditions. The photocatalyst with a Zn/Sn molar ratio of 1:0.05 calcined at 600 °C for 2 h showed the maximum degradation rate of MB under different lights used. Its photocatalytic activity was found to be about two times that of ZnO and about 10 times that of SnO₂ which can be explained by the heterojunction effect. Charge separation mechanism has been studied.