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1.
In this study, mechanochemical processing has been used to manufacture a nanoparticulate powder of ZnO with a controlled particle size and minimal hard agglomeration. The suitability of this ZnO powder for use as either a photocatalyst or an optically transparent UV-filter was evaluated by comparing its optical and photocatalytic properties with those of three commercially available powders that were synthesised by chemical precipitation and flame pyrolysis. The ZnO powder synthesised by mechanochemical processing was found to exhibit high optical transparency and low photocatalytic activity per unit of surface area, which indicates that it is suitable for use in optically transparent UV-filters. 相似文献
2.
Bimodal nanocrystalline mesoporous TiO 2 powders with highly photocatalytic activity were prepared by a hydrothermal method using tetrabutylorthotitanate as precursor, and then dried in microwave oven. The prepared samples were characterized by XRD, SEM, TEM, HRTEM and N 2 adsorption-desorption measurement. The photocatalytic activity was evaluated by the photocatalytic degradation of acetone in air under UV light irradiation at room temperature. The effects of microwave drying on the microstructures and photocatalytic activity of the TiO 2 powders were investigated and discussed. The results show that microwave drying not only promotes the growth of the pores but also greatly reduces the state of agglomeration within the powders. All the microwave-dried TiO 2 powders show higher photocatalytic activity than Degussa P-25 (P25) and the TiO 2 powders dried by conventional method. 相似文献
3.
Anatase-type TiO 2 nanopowders less than 10 nm in average diameter were synthesized by a chemical vapor synthesis method. The TiO 2 nanopowders showed very poor photocatalytic properties, in spite of their large surface area. With subsequent heat treatment of the TiO 2 powders, their photocatalytic properties determined by measuring the degradation of 2-propanol were improved at temperatures up to 600 °C and then diminished along with formation of a rutile phase. This improvement in the photocatalytic properties of TiO 2 nanopowders was attributed to both a morphology change and a change in the electronic surface characteristics of TiO 2 particles during heat treatment. 相似文献
4.
Two kinds of vanadium-doped TiO 2 powders photocatalysts were prepared by sol-gel method in even doping and uneven doping modes, and were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of TiO 2 photocatalysts doped by vanadium evenly with lower dopant level up to 0.002 mol.% is better than that of undoped TiO 2, while with higher dopant level the activity is worse. TiO 2 photocatalysts doped by vanadium unevenly with a p-n junction semiconductor structure, was shown to have a much higher photocatalytic destruction rate than that of TiO 2 photocatalysts doped by vanadium evenly and undoped TiO 2, which is ascribed mainly to the electrostatic-field-driven electron-hole separation in TiO 2 particles doped by vanadium unevenly. 相似文献
5.
TiO 2 microspheres with mesoporous textural microstructures and high photocatalytic activity were prepared by hydrothermal treatment of mixed solution of titanium sulfate and urea with designed time. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N 2 adsorption-desorption measurements. The photocatalytic activity was evaluated via the photocatalytic oxidation of acetone in air at room temperature. The results show that the hydrothermal time significantly influences on the morphology, microstructure and photocatalytic activity of the as-prepared samples. With increasing hydrothermal time, specific surface areas and pore volumes decrease, contrarily, the crystallite size and relative anatase crystallinity increase. The photocatalytic efficiency of the as-prepared samples is obviously higher than that of commercial Degussa P25 (P25) powders. Especially, the as-prepared TiO 2 powders by hydrothermal treatment for 7 h shows the highest photocatalytic activity, which exceeds that of P25 by a factor of more than 2 times. 相似文献
6.
Eu 3+:NaGdF 4 samples were obtained via co-precipitation in aqueous solution (CP), reversed micelle (RM) method, reaction between solid GdF 3 and NaF solution (SR) as well as a solid-state reaction at high temperatures (SS). The synthesised materials were characterised using X-ray powder diffractometry, TEM microscopy, infrared spectroscopy and TGA analysis. For discussion of optical properties excitation and emission spectra were recorded and emission decay times were measured. The CP and RM methods allow to obtain powders with crystallite size of ∼10 nm, which may be smoothly increased to about 1 μm during post-fabrication heat treatment. Differences in structural and especially in optical properties of phosphors prepared by different techniques are emphasised and applicability of wet-chemistry routes for synthesis of fluoride powders is argued. 相似文献
7.
Ag/TiO 2 sol with narrow particle size distribution was synthesized using TiCl 4 as the starting material. TiCl 4 was converted to Ti(OH) 4 gel. The Ag/TiO 2 sol was prepared by a process where H 2O 2 was added and then heated at 90–97 °C. After condensation reaction and crystallization, a transparent sol with suspended Ag/TiO 2 was formed. Ag/TiO 2 was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, contact angle analysis, and X-ray photoelectron spectroscopy. The photocatalytic properties of Ag/TiO 2 film were evaluated by degradation of methylene blue in aqueous solution under UV light irradiation. The suspended Ag/TiO 2 particles were rhombus primary particles with the major axis ca. 40 nm and the minor axis ca. 10 nm. Ag nanoparticles were well dispersed on TiO 2 and the particle size was only 1–2 nm. Ag could restrain the recombination of photo-generated electrons and holes effectively. Transparent thin films could be obtained through dip-coating glass substrate in the sol. The thin film had strong hydrophilicity after being illuminated by UV light. Ag/TiO 2 film showed a significant increase in photocatalytic activity compared to the TiO 2 film. The high amount of surface hydroxyls on Ag/TiO 2 film also played an important role in its photocatalytic activity. 相似文献
8.
The pure SrNb 2O 6 powders were prepared at 1400 °C by a conventional solid-state method and characterized by X-ray powder diffraction and UV-vis diffuse reflection spectrum. The powders of Nb 2O 5 and SrNb 2O 6 were ball-milled together and annealed to form the Nb 2O 5/SrNb 2O 6 composite. Photocatalytic activities of the composites were investigated on the degradation of methyl orange. The results show that the proportion of Nb 2O 5 to SrNb 2O 6 and the annealing temperature greatly influence the photocatalytic activities of the composites. The best photocatalytic activity occurs when the weight proportion of Nb 2O 5 to SrNb 2O 6 is 30% and the annealing temperature is 600 °C. The tremendously enhanced photocatalytic activity of the Nb 2O 5/SrNb 2O 6 composite compared to Nb 2O 5 or SrNb 2O 6 is ascribed to the heterojunction effect taking place at the interface between particles of Nb 2O 5 and SrNb 2O 6. The powders also show a higher photocatalytic activity than commercial anatase TiO 2. 相似文献
9.
Fe 2O 3/SrTiO 3 composite powders have been prepared and their photocatalytic activities were investigated by photooxidizing methanol. These powders were characterized by ultraviolet (UV)-visible diffuse reflectance spectra, scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that the Fe 2O 3/SrTiO 3 composite powders with optimum proportion exhibited higher photocatalytic activity than pure SrTiO 3, Fe 2O 3 and TiO 2 (P25) under visible light ( λ>440 nm) irradiation. The SEM image of the composite powders showed that SrTiO 3 and Fe 2O 3 particles contacted well. Further research revealed that the calcination temperature is an important factor in the preparation of the composite powder with relatively high photocatalytic ability. 相似文献
10.
Anatase/rutile mixed-phase titanium dioxide (TiO 2) photocatalysts in the form of nanostructured powders with different primary particle size, specific surface area, and rutile content were produced from the gas-phase by flame spray pyrolysis (FSP) starting from an organic solution containing titanium (IV) isopropoxide as Ti precursor. Flame spray-produced TiO 2 powders were characterized by means of X-ray diffraction, Raman spectroscopy, and BET measurements. As-prepared powders were mainly composed of anatase crystallites with size ranging from 7 to 15 nm according to the synthesis conditions. TiO 2 powders were embedded in a multilayered fluoropolymeric matrix to immobilize the nanoparticles into freestanding photocatalytic membranes. The photocatalytic activity of the TiO 2-embedded membranes toward the abatement of hydrosoluble organic pollutants was evaluated employing the photodegradation of rhodamine B in aqueous solution as test reaction. The photoabatement rate of best performing membranes significantly overcomes that of membranes produced by the same method and incorporating commercial P25-TiO 2. 相似文献
11.
Novel graphene–TiO 2 (GR–TiO 2) composite photocatalysts were synthesized by hydrothermal method. During the hydrothermal process, both the reduction of graphene oxide and loading of TiO 2 nanoparticles on graphene were achieved. The structure, surface morphology, chemical composition and optical properties of composites were studied using XRD, TEM, XPS, DRS and PL spectroscopy. The absorption edge of TiO 2 shifted to visible-light region with increasing amount of graphene in the composite samples. The photocatalytic degradation of methyl orange (MO) was carried out using graphene–TiO 2 composite catalysts in order to study the photocatalytic efficiency. The results showed that GR–TiO 2 composites can efficiently photodegrade MO, showing an enhanced photocatalytic activity over pure TiO 2 under visible-light irradiation. The enhanced photocatalytic activity of the composite catalysts might be attributed to great adsorptivity of dyes, extended light absorption range and efficient charge separation due to giant π-conjugation system and two-dimensional planar structure of graphene. 相似文献
12.
Fe-, Ni-, Co- and Ag- loaded NaNbO 3 catalysts were prepared and their activities have been investigated in the reaction of photocatalytic hydrogen generation. Me/NaNbO 3 were synthesized by impregnation of NaNbO 3 in an aqueous solution of metal nitrates and then by calcination at the temperature of 400 °C. The crystallographic phases and optical and vibronic properties were examined by X-ray diffraction (XRD) and diffuse reflectance (DR) UV-vis and resonance Raman spectroscopic methods, respectively. Morphology and chemical composition of the produced samples were studied using a high-resolution transmission electron microscope (HR-TEM) and an energy dispersive X-Ray spectrometer (EDX) as its mode. The detailed analysis has revealed that all the investigated catalysts exhibit high crystallinity and the presence of Fe 2O 3, NiO, Co 3O 4 and Ag 2O oxides on Me/NaNbO 3 was confirmed. Finally, the influence of different metal loadings (Fe, Ni, Co and Ag) on the photocatalytic activity of NaNbO 3 for photocatalytic hydrogen generation has been investigated. Here we report that among all the Me/NaNbO 3 photocatalysts Ag-loaded NaNbO 3 exhibited higher photocatalytic efficiency for photocatalytic hydrogen generation than NaNbO 3. 相似文献
13.
In order to get photocatalysts with desired morphologies and enhanced visible light responses, the Fe-doped TiO 2 nanorod clusters and monodispersed nanoparticles were prepared by modified hydrothermal and solvothermal method, respectively. The microstructures and morphologies of TiO 2 crystals can be controlled by restraining the hydrolytic reaction rates. The Fe-doped photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectroscopy (UV-vis), N 2 adsorption-desorption measurement (BET), and photoluminescence spectroscopy (PL). The refinements of the microstructures and morphologies result in the enhancement of the specific surface areas. The Fe 3+-dopants in TiO 2 lattices not only lead to the significantly extending of the optical responses from UV to visible region but also diminish the recombination rates of the electrons and holes. The photocatalytic activities were evaluated by photocatalytic decomposition of formaldehyde in air under visible light illumination. Compared with P25 (TiO 2) and N-doped TiO 2 nanoparticles, the Fe-doped photocatalysts show high photocatalytic activities under visible light. 相似文献
14.
Bi 2O 3/SrTiO 3 composite powders have been prepared and their photocatalytic activities were investigated by photooxidation of methanol. These powders were characterized by UV-Visible diffuse reflectance spectra, SEM and X-ray diffraction (XRD). The results revealed that all the Bi 2O 3/SrTiO 3 composite powders exhibited higher photocatalytic activity than pure SrTiO 3, Bi 2O 3 and TiO 2 (P25) under visible light irradiation ( λ>440 nm). The effects of the Bi 2O 3 contents on the photocatalytic activities of the composite powders were examined, the photocatalytic activities increased with the content of Bi 2O 3 increasing to a maximum of 83% and then decreased under visible light irradiation. The effects of the calcination temperatures on the photocatalytic activities of the composite powders were also investigated. 相似文献
15.
Sintered ceramic powders of calcium-doped lead titanate [Pb 1−xCa xTiO 3] ceramics with different Ca dopant concentration in the range ( x=0-0.35) have been prepared using a sol-gel chemical route. The sol-gel technique is known to offer better purity and homogeneity, and can yield stoichiometric powders with improved properties at relatively lower processing temperature in comparison to conventional solid-state reaction. X-ray diffraction (XRD) and Raman spectroscopy studies have been carried out to identify the crystallographic structure and phase formation. The infrared absorption spectra in the mid-IR region (400-4000 cm −1) show the band corresponding to the Ti-O bond at ∼576 cm −1 and is found to shift to a higher wave number 592 cm −1 with increasing Ca content. The dielectric properties as a function of frequency, and phase transition studies on sintered ceramic Pb 0.65Ca 0.35TiO 3 has been investigated in detail over a wide temperature range 30-600 °C and the results are discussed. 相似文献
16.
An overall comparative study was carried out on Li-doped, F-doped, and Li-F-codoped TiO 2 powders in order to elucidate the roles of Li + and F − ions in photocatalyst. The characteristic data were based on the analysis of XRD, XPS, and PL spectra. The effects of atomic ratio of Li/Ti and F/Ti on the photocatalytic activity were also investigated. As the results, Li doping accelerated the phase formation of rutile in lower temperature while F doping prevented the phase transition from anatase to rutile. Li doping inducted a large amount of O OH on the surface of TiO 2, while F doping consumed much of O OH. Li + ions acted as the roles of recombination center of electron-hole pairs while F doping could restrain the recombination of electron-hole pairs on the center of Li + ions. The roles of Li + and F − ions were also confirmed in the experimental section, where the photocatalytic activity of TiO 2 was improved greatly by synergistic reaction of Li + and F − ions. 相似文献
17.
Sol-gel nanostructured titania materials have been reported to have applications in areas ranging from optics via solar energy to gas sensors. In order to enhance the photocatalytic activity, there are many studies regarding the doping of titanium dioxide (TiO 2) material with either non-metals (S, C, N, P) or metals (Ag, Pt, Nd, Fe). The present work has studied some un-doped and Pd-doped sol-gel TiO 2 materials (films and gels), with various surface morphologies and structures, obtained by simultaneous gelation of both precursors Ti(OEt) 4 and Pd(acac) 2. Their structural evaluation and crystallization behavior with thermal treatment were followed by DTA/TG analysis, infrared (IR) spectroscopy, Fourier transform infrared (FTIR), spectroellipsometry (SE), X-ray diffraction (XRD) and atomic force microscope (AFM). The influence of Pd on TiO 2 crystallization for both supported and un-supported materials was studied (lattice parameters, crystallite sizes, internal microstrains). The changes in the optical properties of the TiO 2-based vitreous materials were correlated with the changes of the structure. The hydrophilic properties of the films were also connected with their structure, composition and surface morphology. 相似文献
18.
Several chemical compounds based lithium niobate have been tested in the reaction for the photocatalytic hydrogen generation. The photocatalysts have been prepared by impregnation of Nb 2O 5 in the aqueous solution of lithium hydroxide and then the calcination at the temperature range of 400-650 °C. In this report, we present the interesting study showing that the most active catalyst for the photocatalytic generation of hydrogen is the one containing two lithium niobate phases such as LiNbO 3 and LiNb 3O 8. It means that the lithium niobates based catalyst without any further modification or doping can be applied as a novel material for this process. 相似文献
19.
Two kinds of plate-like NaNbO 3 were separately prepared by the one- and two-step molten salt processes via topochemical micro-crystal conversion methods. Meanwhile, the composite photocatalysts were obtained via heating the mixture of corresponding NaNbO 3 powders and urea. Their photocatalytic activities were evaluated from the photodegradation of Rhodamine B under full arc and visible light irradiation of Xe lamp. The sample containing NaNbO 3 prepared by the one-step molten salt process and carbon nitride displays the highest activity. The enhancement of photocatalytic activity was attributed to the surface properties and the state of the carbon nitride. 相似文献
20.
The present study examined the photocatalytic reaction of titanium dioxide (TiO 2)-coated, phosphor composite particles. Nanocrystalline TiO 2 layers were directly coated on the alkaline earth aluminate phosphor (CaAl 2O 4:Eu 2+,Nd 3+) particles by a sol-gel processing method and their photocatalytic reaction was analyzed according to the degradation of
methylene blue aqueous solution under visible light irradiation. Compared with pure TiO 2, the TiO 2-coated phosphor powders showed a different photocatalytic mechanism and much faster photocatalytic reactivity under visible
irradiation than that of pure TiO 2, which was almost negligible. The mechanism of the photocatalytic reactivity for the TiO 2-phosphor composite was discussed in terms of the energy band structure and phosphorescence. In addition, the TiO 2-coated phosphor powders were characterized by X-ray diffraction and transmission electron microscopy. 相似文献
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