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1.
Visible-light-driven heterostructure Ag/Bi2WO6 nanocomposites were prepared by transforming Ag+ ions into metallic Ag0 nanoparticles loaded on top of Bi2WO6 nanoplates under visible light irradiation for 1 h. XRD, XPS, SEM and TEM analyses indicated that spherical metallic Ag nanoparticles were uniformly dispersed on top of orthorhombic Bi2WO6 thin nanoplates. Rhodamine B (RhB) was used as a dye model for investigation of photocatalytic performance of Bi2WO6 nanoplates with different weight contents of Ag nanoparticles illuminated by visible radiation. In this research, 10% Ag/Bi2WO6 nanocomposites have the highest photocatalytic activity in the degradation of RhB at 94.21% within 210 min because of the rapid diffusion of electronic charge through the Schottky barrier between metallic Ag nanoparticles and Bi2WO6 thin nanoplates, good electrical conductivity of metallic Ag nanoparticles, inhibited recombination of charge carriers and enhanced photocatalytic activity of Ag/Bi2WO6 nanocomposites. Main active species of the photocatalysis and stability of the photocatalyst were also evaluated. 相似文献
2.
Pure orthorhombic phase Bi 2WO 6 powders were synthesized by a microwave hydrothermal method in the absence of surfactants and templates, using Bi(NO 3) 3·5H 2O and Na 2WO 4·2H 2O as raw materials. Photocatalytic properties of the samples prepared at different reaction temperatures were also studied with Rhodamine B (RhB) solution as the target catabolite under visible light. The results indicate that flower-like Bi 2WO 6 powders can be obtained by controlling the microwave reaction temperatures in the absence of any additives. The growth of flower-like Bi 2WO 6 powders is a multistage layer assembly process, in which the flower-like Bi 2WO 6 self-assembling with the uniform size about 2 μm is synthesized at 180 °C. At the same time, the photocatalytic reaction rate constant ( k) gets up to 0.04167/min and the degradation rate of RhB solution is more than 96 % after being irradiated under visible light for 70 min. 相似文献
3.
Polythermic studies of Bi 2WO 6–Bi 2UO 6 system revealed existence of a broad Bi 2W 1?xU xO 6 solid solution with the Aurivillius-type structure. Below 750 °C, the homogeneity area is narrow ( x ≤ 0.12) but extends significantly at higher temperatures (up to ca. 75% Bi 2UO 6 at 1025 °C). The solid solution retains orthorhombic symmetry over the entire compositional range, but substitution of U for W results in significant lowering of second harmonic intensity and Curie point suggesting, at high substitution degrees, a very close approach to the archetypic body-centered tetragonal centrosymmetric structure. The known Bi 2WO 6-based solid solutions are discussed in terms of thermal stability, and a general geometrical explanation is suggested. Incorporation of large cations into the B perovskitic positions of [Bi 2O 2][ An?1BnO 3n+1] Aurivillius structures seems yet to be restricted by the n = 1 case. 相似文献
4.
通过两步水热法合成了一种新型的还原氧化石墨烯(RGO)修饰的Bi 2WO 6(Bi 2WO 6-RGO), 结果表明其在可见光下的光催化性能得到了显著的提高. 研究了RGO在Bi 2WO 6-RGO中的含量对其光催化性能的影响, 从而确定出RGO相对于Bi 2WO 6的最佳掺杂质量比值为1%. 通过扫描电镜(SEM)研究发现, RGO并没有改变Bi 2WO 6光催化剂的结构和形貌. Bi 2WO 6-RGO在可见光下的光催化性能得以提高可以归功于RGO. 其可能的机理是石墨烯的存在有利于光生载流子(激子)的分离, 从而导致产生更多的O 2·-用于有机染料污染物(如罗丹明B (RhB))的降解. RhB分子在石墨烯上的有效吸附可能也是导致Bi 2WO 6-RGO光催化性能提高的另一原因. 相似文献
5.
以TiO 2纳米管为模板,采用多组分自组装结合水热法制备Bi 2WO 6/TiO 2纳米管异质结构复合材料。通过多种技术如X射线衍射(XRD),X射线光电子能谱(XPS),N 2吸附-脱附,扫描电镜(SEM),高分辨透射电镜(HRTEM)和紫外可见漫反射吸收光谱(UV-Vis DRS)考察所制备样品的组成、结构、形貌、光吸收和电子性质。Bi 2WO 6纳米片或纳米粒子分布在TiO 2纳米管上,形成异质结构。随后,通过在紫外、可见和微波辅助光催化模式下降解染料罗丹明B(RhB)来评价复合催化剂的光催化活性。与TiO 2纳米管和Bi 2WO 6相比,Bi 2WO 6/TiO 2-35纳米管在多模式下表现出更优异的光催化活性。与紫外和可见降解模式相比,Bi 2WO 6/TiO 2-35纳米管在微波辅助光催化模式下对RhB的降解效率最高。这种增强的光催化活性源于适量Bi 2WO 6的引入、纳米管独特的形貌特征和降解模式所引起的增强的量子效率。降解过程中的活性物种被证明是h +,·OH和·O 2-自由基。而且,在微波辅助光催化模式下,可产生更多的·OH和·O 2-自由基。 相似文献
6.
The compound Bi 3W 2O 10.5 was synthesized by the solid-state technique from Bi 2O 3 and WO 3 in stoichiometric quantities. Single crystals were grown by the melt-cooling technique and the crystal structure was solved
in the tetragonal I4/ m space group with a = 3.839 (1) ?, c = 16.382 (5) ?, V = 241.4 (1) ? 3, Z = 4 and was refined to an R inde x of 0.0672. The structure represents a modification of the Aurivillius phase and consists of [Bi 2O 2] 2+ units separated by WO 8 polyhedra. a.c. impedance studies indicate oxide ion conductivity of 2.91 10 −5 Scm −1 at 600°C.
Dedicated to Prof J Gopalakrishnan on his 62nd birthday. 相似文献
7.
Y 2O 3:Bi 3+ phosphor thin films were prepared by pulsed laser deposition in the presence of oxygen (O 2) gas. The microstructure and photoluminescence (PL) of these films were found to be highly dependent on the substrate temperature. X-ray diffraction analysis showed that the Y 2O 3:Bi 3+ films transformed from amorphous to cubic and monoclinic phases when the substrate temperature was increased up to 600 °C. At the higher substrate temperature of 600 °C, the cubic phase became dominant. The crystallinity of the thin films, therefore, increased with increasing substrate temperatures. Surface morphology results obtained by atomic force microscopy showed a decrease in the surface roughness with an increase in substrate temperature. The increase in the PL intensities was attributed to the crystallinity improvement and surface roughness decrease. The main PL emission peak position of the thin films prepared at substrate temperatures of 450 °C and 600 °C showed a shift to shorter wavelengths of 460 and 480 nm respectively, if compared to the main PL peak position of the powder at 495 nm. The shift was attributed to a different Bi 3+ ion environment in the monoclinic and cubic phases. 相似文献
8.
Bi2WO6/UiO-66-NH2 photocatalysts were fabricated through solvothermal method using acetic acid as template. The photocatalytic performance of as-fabricated composites was highly improved under simulated visible light due to the addition of UiO-66-NH2. The structural and chemical properties of the composites were characterized through FTIR, XRD, XPS, SEM, BET, UV–vis DRS and PL. After 90 min of visible light irradiation, the RhB at an initial concentration of 10 mg·L?1 in the solution was degraded by 99.4% due to the addition of 10 mg of the composite. There was no significant decrease in the photocatalytic activity even after four rounds of cycles. The free radical capture experiments indicate that the photogenerated holes (h+) were the main active sites. The possible photocatalytic degradation mechanism was proposed as the specific surface area of the composite was enlarged due to the uniform distribution of UiO-66-NH2 on the surface of Bi2WO6. The electron–hole pairs recombination rate was decreased due to the photogenerated electrons (e?) on the CB of Bi2WO6 which can be rapidly transferred to the CB of UiO-66-NH2 and the photogenerated holes of UiO-66-NH2 transferred to the VB of Bi2WO6. Meanwhile, the RhB was directly oxidized to H2O and CO2 by h+ to achieve the purification effect. 相似文献
9.
The phases Pb 5Bi 17P 5O 43 and Pb 5Bi 18P 4O 42 are among many recent new oxyphosphates discovered in the ternary system PbO–Bi 2O 3–P 2O 5. The syntheses of the vanadates and arsenates led to isostructural compounds. Both series display a distorted 3×3×3 superstructure of the tetragonal δ-Bi 2O 3 polymorph. These types of phases display interesting anion conductivities and measurements were performed from 300 °C to 800 °C on the phosphates, arsenates and vanadates of the two families. The Pb 5Bi 18X 4O 42 phases have higher conductivity values than those of Pb 5Bi 17X 5O 43. Of the three homologues the vanadates always have the highest conductivities, i.e., at 800 °C: 1.6×10 −2 Siemens·cm −1 for Pb 5Bi 18V 4O 42 and 1.6×10 −3 Siemens·cm −1 for Pb 5Bi 17V 5O 43. An increase of the volume of the unit cell due to the increasing radius of the pentavalent cations from P, As to V, 0.34 Å, 0.47 Å, 0.59 Å respectively, helps the anion migration through the structure. 相似文献
10.
Two kinds of bismuth tungsten oxide nanocrystals were prepared by microwave hydrothermal method. The morphology modulation of nanocrystals synthesized with precursor suspension's pH varied from 0.25 (strong acid) to 10.05 (base) was studied. The 3D flower like aggregation of Bi 2WO 6 nanoflakes was synthesized in acid precursor suspension and the nanooctahedron crystals of Bi 3.84W 0.16O 6.24 were synthesized in alkalescent precursor. The dominant crystal is changed from Bi 2WO 6 to Bi 3.84W 0.16O 6.24 when the precursor suspension changes from acid to alkalescence. The growth mechanisms of Bi 2WO 6 and Bi 3.84W 0.16O 6.24 were attributed to the different solubility of WO 42− and [Bi 2O 2] 2+ in precursor suspensions with various pH. For the decomposition of Rhodamine B (RhB) under visible light irradiation ( λ>400 nm), different morphology of Bi 2WO 6 crystal samples obtained by microwavesolvothermal process showed different photocatalytic activity. 相似文献
11.
Bi 2WO 6 multilayer films have been fabricated successfully by a layer-by-layer (LbL) technique from Bi 2WO 6 nanoplates, which show higher visible-light photoactivity ( λ>420 nm) than that of Bi 2WO 6 nanoplate powders and P25 TiO 2 films. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and UV-visible absorption spectroscopy. Photocatalytic activities of the films were evaluated by the rhodamine B (RhB) decomposition under UV and visible-light irradiation. Thickness and photoactivity of the film can be modified easily by changing the deposition cycles. Bi 2WO 6 films have the spectral selectivity of the photocatalytic degradation of RhB. Under the wavelength greater than 300 nm, the RhB molecules tend to be transformed to rhodamine over Bi 2WO 6 films selectively. However, in the case of shorter wavelength ( λ=254 nm) light irradiation, the RhB molecules can be photodegraded completely. 相似文献
12.
The Bi 2WO 6/α-Fe 2O 3 composite photocatalyst was synthesized by using goethite as a precursor through hydrothermal-calcination method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis reflection spectrometer (DRS), X-ray photoelectron spectroscopy (XPS) and N 2 adsorption-desorption measurement (BET). These results indicated that the self-made composite photocatalysts had excellent catalytic performance of degradation of gaseous benzene. When benzene initial concentration at 50 mg/m 3, over the α-FeOOH/Bi 2WO 6 with molar mass of 0.8:1, calcined at 350 °C for 2 h and the pH of precursor solution was 3, the benzene degradation rate reached 71.9% and the mineralization efficiency reached 67.7% after 220 min UV irradiation, respectively. The h + and O 2− generated in the photocatalytic system should be played a pivotal role for the enhanced photodegradation performance of gaseous benzene. 相似文献
13.
The visible-light-driven photocatalyst Bi 2WO 6 nanoparticles have been prepared by calcining amorphous complex precursor at a relatively low temperature of above 450 oC. The effects of calcination temperature and time on the structures and properties of Bi 2WO 6 nanoparticles have been investigated in detail. The photocatalytic activity of the Bi 2WO 6 powders were evaluated by degradation of RhB molecules in water under visible light irradiation ( λ>400 nm). The results showed that the particle size and grain size of Bi 2WO 6 increased with the calcination temperature and time. The photocatalytic activity of the best sample was about 8.8 times higher than that of the sample prepared by traditional solid state reaction and the photo-degradations was a zero-order reaction. The best route to enhance the photocatalytic activity of Bi 2WO 6 was to prepare the sample at a lower temperature for a longer time, due to the samples with better crystallization and smaller particle size. 相似文献
14.
Pd nanoparticles supported on Bi2WO6 nanoplates used for visible-light-driven photocatalyst were successfully synthesized by photoreduction deposition method under visible-light irradiation. Different analytical techniques including X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and photoluminescence spectroscopy revealed that face-centered cubic metallic Pd nanoparticles were uniformly loaded on top of orthorhombic Bi2WO6 nanoplates to form heterostructure Pd/Bi2WO6 nanocomposites. Photocatalytic activities of pure Bi2WO6 sample and heterostructure Pd/Bi2WO6 nanocomposites were studied through the photodegradation of rhodamine B (RhB) under visible-light irradiation. The photocatalytic efficiency of Bi2WO6 was increased to the highest by being loaded with 5 wt% Pd and then decreased by being loaded with 10 wt% Pd. The improved photocatalytic efficiency caused by high-efficiency diffusion and separation of photo-generated charge carriers was explained and can lead to superior photodegradation of RhB under visible-light irradiation. 相似文献
15.
Uniform Bi 2WO 6 pancakes were prepared via a solvothermal route in a solvent mixture of glycerol (Gly) and water ( V/ V = 1). A variety of techniques including scanning electron microscopy, transmission electron micrographs, X-ray powder diffraction, Brunauer–Emmett–Teller, FT-IR spectra, and UV–Vis diffuse reflectance spectra, were employed to characterize the structure and properties of the as-obtained Bi 2WO 6. It was found that Bi 2WO 6 pancakes showed prominent photocatalytic performance for the degradation of rhodamine B (RhB) under visible light ( λ ≥ 420 nm) irradiation, which can be attributed to its good crystallization, large surface area, unique morphology and structural features. 相似文献
16.
The vanadium pentoxide (V 2O 5) films were deposited on silicon wafer by DC magnetron sputtering. By Raman scattering measurements, the microstructure properties of the V 2O 5 films prepared with different O 2–Ar gas flow ratios and annealed at different temperatures were studied, respectively. The results revealed that the increase of O 2–Ar gas flow ratio during sputtering was of advantage to prepare the V 2O 5 film with desired layer structure. A high post-annealing temperature (below 500 °C) induced the crystallization and the formation of the integrated structure of V 2O 5 film. However, it was found that both intensities of Raman scattering peaks at 146 cm ?1 and 994 cm ?1, respectively, decreased for samples annealed at a temperature of 550 °C. The peak at 146 cm ?1 was attributed to skeleton bent vibration and that at 994 cm ?1 was due to the stretching vibration of vanadyl V=O A bond. It showed that the high-temperature annealing was believed to have distorted the microstructure of V 2O 5 films. The oxygen vacancies were, therefore, induced, which benefited the formation of V-O A-V bonds between layers. The result of X-ray diffraction measurements was in good agreement with that of Raman scattering spectra. 相似文献
17.
以Bi(NO 3) 3·5H 2O和Na 2WO 4·2H 2O为主要原料,采用水热法合成了纯相Bi 2WO 6,并对其进行非金属离子Br -掺杂改性。采用XRD、SEM、TEM、XPS、Raman、PL和DRS研究了Br -掺杂对Bi 2WO 6的物相结构、形貌和可见光催化性能的影响。结果表明,Br -掺杂可有效提高Bi 2WO 6的可见光催化性能,当掺杂量(物质的量百分数)为8%时,溴掺杂Bi 2WO 6的光催化性能最好,可见光照射40 min后,可降解96.73%的罗丹明-B,与未掺杂Bi 2WO 6相比,其降解率提高了36.32%。 相似文献
18.
以Bi(NO_3)_3·5H_2O和Na_2WO_4·2H_2O为主要原料,采用水热法合成了纯相Bi_2WO_6,并对其进行非金属离子Br-掺杂改性。采用XRD、SEM、TEM、XPS、Raman、PL和DRS研究了Br~-掺杂对Bi_2WO_6的物相结构、形貌和可见光催化性能的影响。结果表明,Br-掺杂可有效提高Bi_2WO_6的可见光催化性能,当掺杂量(物质的量百分数)为8%时,溴掺杂Bi_2WO_6的光催化性能最好,可见光照射40 min后,可降解96.73%的罗丹明-B,与未掺杂Bi_2WO_6相比,其降解率提高了36.32%。 相似文献
19.
Transparent thin films were prepared by a sol–gel method starting from precursor formation in solution, subsequent spin coating followed by a heating ramp up to a maximum of 700 °C. Starting from a Bi 2MoO 6 synthesis route, the phase formation and thin film processing of the bismuth containing materials Bi 2WO 6, Bi 3Ti 4O 12 and additionally of the tungsten–bronze structure Sr 0.75Ba 0.25Nb 2O 6 were studied. Spin coating was used to adjust the film thickness in a wide range from 6 to 200 nm. All films were obtained as multicrystalline pure phases according to X-ray diffraction analyses. Scanning electron micrographs revealed homogeneous coatings composed of nanoparticles with a crystallite size varying between 20 and 100 nm, furthermore the UV–VIS spectra demonstrated a high transparency of the films, 80–90% at 600 nm. 相似文献
20.
Novel Bi 2WO 6‐coupled Fe 3O 4 magnetic photocatalysts with excellent and stable photocatalytic activity for degrading tetracycline hydrochloride and RhB were successfully synthesized via a facile solvothermal route. Through the characterization of the as‐prepared magnetic photocatalysts by X‐ray diffractometry, scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy, UV–Vis diffuse reflectance spectra, it was found that the as‐prepared magnetic photocatalysts were synthesized by the coupling of Bi 2WO 6 and Fe 3O 4, and introduction of appropriated Fe 3O 4 can improve nanospheres morphology and visible‐light response. Among them, BFe2 (0.16% Fe 3O 4) exhibited the best photocatalytic activity for degradation of tetracycline hydrochloride (TCH), reaching 81.53% after 90 min. Meanwhile, the as‐prepared magnetic photocatalysts showed great separation and recycle property. Moreover, the results of electrochemical impedance spectroscopy demonstrated that the well conductivity of Fe 3O 4 can promote photogenerated charge carriers transfer and inhibit recombination of electron–hole pairs, so that Bi 2WO 6/Fe 3O 4 exhibited enhanced photocatalytic activity on degradation of TCH and RhB. Hence, this work provides a principle method to synthesize Bi 2WO 6/Fe 3O 4 with excellent photocatalytic performance for actual application, in addition, it showed that introduction of Fe 3O 4 not only can provide magnetism, but also can enhance photocatalytic activity of Bi 2WO 6/Fe 3O 4 magnetic photocatalysts. 相似文献
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