共查询到20条相似文献,搜索用时 46 毫秒
1.
Bismuth tungsten oxide and vanadium pentoxide (Bi 2WO 6/V 2O 5) heterostructures are produced by a green synthesis approach using Azadirachta indica extract for photocatalytic performance. The hydrothermal method at temperatures between 120 °C and 140 °C is used to synthesize Bi 2WO 6. Bi 2WO 6 and V 2O 5 phases are formed in pure orthorhombic wells according to the XRD pattern. The SEM displays V 2O 5 nanorods, Bi 2WO 6 hierarchical microspheres that resemble flowers at 120 °C, and particles with a particle-like character at 140 °C. In V 2O 5, the asymmetric stretching vibrations of the triplely coordinated oxygen (chain oxygen) bonds and the vibration of the doubly coordinated oxygen (bridge oxygen) bonds are responsible for a peak at 611 cm ?1. In FTIR spectra between 600 and 1600 cm ?1, the major absorption bands in Bi 2WO 6 are attributed to the W-O stretching, Bi-O stretching, and W-O-W bridging stretching modes. Bi 2WO 6@V 2O 5 at 120 °C has the lowest bandgap energy (2.32 eV) and optical electronegativity (0.62), as well as the highest refractive index (2.57), extinction coefficient (2.21), and dielectric constant (ε r = 0.72 and ε i = 11.4) among all samples, making it a suitable material for photocatalysis. Rhodamine blue (RhB) dye degradation is used to measure the photocatalytic activity (PCA) of certain materials. The results showed that heterostructure V 2O 5@Bi 2WO 6 synthesized at 120 °C is more attractive among all samples due to high degradation of RhB dye under sunlight irradiation in 90 min. 相似文献
2.
Pure WO_3 and Yb:WO_3 thin films have been synthesized by spray pyrolysis technique. Effect of Yb doping concentration on photoelectrochemical, structural, morphological and optical properties of thin films are studied. X-ray diffraction analysis shows that all thin films are polycrystalline nature and exhibit monoclinic crystal structure. The 3 at% Yb:WO_3 film shows superior photoelectrochemical(PEC) performance than that of pure WO_3 film and it shows maximum photocurrent density(Iph= 1090 μA/cm~2) having onset potentials around +0.3 V/SCE in 0.01 M HClO_4. The photoelectrocatalytic process is more effective than that of the photocatalytic process for degradation of methyl orange(MO) dye. Yb doping in WO_3 photocatalyst is greatly effective to degrade MO dye. The enhancement in photoelectrocatalytic activity is mainly due to the suppressing the recombination rate of photogenerated electron-hole pairs. The mineralization of MO dye in aqueous solution is studied by measuring chemical oxygen demand(COD) values. 相似文献
3.
The sensor based on WO 3-Cr 2O 3 nanocomposites show good selectivity to 2-butanone. 相似文献
4.
WO 3 nanoparticles were synthesized by the precipitation method varying the time employed in the formation of their precursor in aqueous media and the calcination temperature. The WO 3 crystallization process and morphology of the synthesized samples were followed by the XRD, TEM and SEM techniques. The effects of the calcination temperature on the surface area and optical properties of the WO 3 nanoparticles were also investigated. Nanoparticles with morphologies such as square and rectangular plates and ovoid forms were observed for the different experimental conditions. WO 3 nanoparticles with different morphologies were tested for the photocatalytic degradation of organic dyes. In general, the photocatalysts showed a capacity to bleach the dye solution in the following sequence: indigo carmine (IC) > rhodamine B (rhB) > congo red (CR). The extent of mineralization was determined by means of total organic carbon (TOC) measurements, which showed a satisfactory TOC reduction (93%, within 75 h) only for IC. This value was even better than the one concerning the P-25 Degussa reference. 相似文献
5.
Bi-layer WO 3–TiO 2 coatings have been synthesised on stainless steel (SS) substrates by consecutive cathodic electrodeposition of WO 3 (from peroxytungstate solutions) and TiO 2 electrosynthesis (from titanium oxosulfate solutions). The resulting TiO 2–WO 3/SS photoelectrodes have been screened for their photoresponse under ultraviolet (UV) and visible (vis) light illumination by photovoltammetry in supporting electrolyte (sodium sulfate) and malachite green (a typical dye) solutions. They were also evaluated for malachite green photooxidation during constant potential bulk photoelectrolysis. It was found that both photocurrent values and dye removal rates were higher at TiO 2–WO 3/SS than at plain WO 3/SS photoelectrodes, under both UV and vis illumination (up to 85% and 67% malachite green degradation has been achieved respectively from its 10 ppm solutions after 2 h). The enhancement of the UV and, as reported here for the first time, vis photocatalytic activity of WO 3 by the inclusion of TiO 2 is interpreted by reduced electron-hole recombination rates due to electron transfer from TiO 2 to WO 3 (during UV activation) and hole transfer from WO 3 to TiO 2 (during UV and vis light activation). 相似文献
6.
Ag/Bi 2WO 6 nanocomposites were successfully synthesized by a combination of hydrothermal method and ultrasonic vibration. The phases, vibration modes, constituents and morphologies were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The visible-light-driven photocatalytic activitiy of 0–10 wt% Ag/Bi 2WO 6 samples was studied by determining the photodegradation of rhodamine B under xenon lamp. In this research, 10 wt% Ag/Bi 2WO 6 nanocomposites exhibit the highest efficiency and have the promising photocatalytic properties for waste water treatment. 相似文献
7.
One‐dimensional (1D) CeO 2/Bi 2WO 6 heterostructured nanofibers with a diameter of about 300 nm were successfully synthesized by using a straightforward strategy combining an electrospinning technique with a sintering process. The acquired products were characterized by thermogravimetric and differential scanning calorimetric (TG‐DSC), Fourier transform infrared (FT‐IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area measurements, and UV/Vis spectroscopy. The obtained CeO 2/Bi 2WO 6 heterostructured nanofibers exhibited an excellent photocatalytic property for the degradation of Rhodamine B (RhB) dye driven by visible light due to the promoted separation of photoelectrons and holes and the large contact area between the photocatalyst and organic pollutant. 相似文献
8.
A Bi-based oxychloride Na 0.5Bi 1.5O 2Cl with a layered structure as a novel efficient photocatalyst was studied in the present paper. The powder was synthesized by a solid state reaction method. It was characterized by X-ray diffraction, scanning electron microscope and UV–vis diffuse reflectance spectrum. Degradation of methyl orange was used to evaluate the photocatalytic activity. The as-synthesized Na 0.5Bi 1.5O 2Cl has a smaller optical band gap of 3.04 eV than BiOCl ( Eg = 3.44 eV). It possesses a fair visible-light-response ability. The UV-induced photocatalytic activity follows the decreasing order of BiOCl > Na 0.5Bi 1.5O 2Cl > TiO 2, different from the order of Na 0.5Bi 1.5O 2Cl > TiO 2 > BiOCl under visible light irradiation. The dispersion of Pt over Na 0.5Bi 1.5O 2Cl leads to an obvious increase in the photocatalytic performance. The internal electric fields between [Na 0.5Bi 1.5O 2] and [Cl] slabs favor the efficient separation of photostimulated electron–hole pairs. 相似文献
9.
New fluorite-type solid solution domains have been evidenced in the system Y 6(W,Mo)(O,N) 12 using precursors prepared by the amorphous citrate route. The oxynitrides as well as the low temperature oxides (600 °C) crystallize in a cubic-type symmetry while the oxides annealed above 1200 °C exhibit a rhombohedral symmetry. Either cationic (W/Mo) or anionic (O/N) substitutions bring the possibility to tune the optical absorption of the yttrium tungstate Y 6WO 12, which potential as inorganic UV absorbers is discussed. 相似文献
10.
In this work, we report a novel AgBi(WO 4) 2–Bi 2WO 6 heterostructure, which was designed and synthesized by using a simple hydrothermal method. Methyl orange was used as a representative dye indicator to evaluate the visible‐light catalytic activity and the catalytic mechanism was investigated. The as‐synthesized AgBi(WO 4) 2–Bi 2WO 6 composite displayed a 43 times higher photocatalytic activity than Bi 2WO 6. Owing to the matched band gap and distinctive heterostructure, AgBi(WO 4) 2–Bi 2WO 6 reveals a high visible‐light response and high‐efficiency utilization of both photogenerated electrons and holes. AgBi(WO 4) 2 reveals a similar energy level to and good lattice match with Bi 2WO 6, which are favorable qualities for band bending and fluent electron transfer. Furthermore, the photoexcited electrons can produce oxygen to generate .O 2? radicals, which is vital for the overall utilization of both holes and electrons. This is the first example of AgBi(WO 4) 2 being used as photocatalytic material. 相似文献
11.
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
12.
Temperature-dependent Raman spectroscopy studies of K 2WO 4 and MgMoO 4 polycrystals were performed in order to obtain information about vibrational and structural changes in these materials as a function of temperature. The stability of the monoclinic phase for both K 2WO 4 and MgMoO 4 samples was assessed and our results indicated that this phase is stable in the 295–723 K and 300–770 K ranges for K 2WO 4 and MgMoO 4, respectively. It was observed that both samples underwent two phase transformations above room temperature. The first phase transformations which occur at about 633 K and 640 K for K 2WO 4 and MgMoO 4, respectively, is most likely connected with weak tilting and/or rotations of WO 4/MoO 4 tetrahedral units that lead to a disorder in the oxygen sublattice. Raman spectroscopy data also indicated that K 2WO 4 and MgMoO 4 exhibited a first-order phase transition at around 723 K and 770 K, respectively, changing from monoclinic to hexagonal symmetry. 相似文献
13.
The activities of Pt/WO 2, Ir/WO 2 and Pt–Ir/WO 2 toward the conversion of methylcyclopentane (MCP) were investigated. The catalysts were prepared using impregnation and co-impregnation methods and were characterized by SEM, XRD, N 2-sorption and TEM investigations. The most active catalyst toward the conversion of MCP, irrespective of the temperature, was Ir/WO 2. The order of the reactivity was Ir/WO 2 > Pt–Ir/WO 2 > Pt/WO 2. Strong metal–support interactions (SMSI) were observed for all the catalysts over the entire investigated temperature range. At 400 °C, the Pt and Pt–Ir showed 100% selectivity toward ring-enlargement reactions associated with the presence of electron-deficient adduct sites on the reducible acidic WO 2 support. Ring opening occurred over all the catalysts in three positions, resulting in the formation of 2-methylpentane (2-MP), 3-methylpentane (3-MP), and n-hexane ( n-H). Difficulty in breaking the secondary – tertiary carbon bonds was observed predominantly on the Ir catalyst, which opens the MCP ring via a selective mechanism. 相似文献
14.
以工业固体废弃物粉煤灰漂珠(fly ash cenospheres, FACs)为载体, 采用水热法制备了新颖的漂珠负载Bi 2WO 6复合材料(Bi 2WO 6/FACs), 通过X射线衍射(XRD), 扫描电子显微镜(SEM), X-射线光电子能谱(XPS), 和紫外-可见漫反射光谱(DRS)技术对其进行了表征。XRD数据显示了正交相Bi 2WO 6的特征衍射峰。DRS结果证实了引入FACs后Bi 2WO 6对可见光的吸收增强。在可见光的照射下, 以亚甲基蓝溶液的光催化降解评价了Bi 2WO 6/FACs复合材料的光催化性能。结果表明:Bi 2WO 6/FACs的光催化性能优于纯Bi 2WO 6的, 其一级反应速率常数( k)为后者的2.4倍。尤其是由于漂珠质轻中空的特性, Bi 2WO 6/FACS复合光催化剂可长时间漂浮于水面, 既能充分吸收光能, 又有利于催化剂的回收和重复利用。 相似文献
15.
以工业固体废弃物粉煤灰漂珠(fly ash cenospheres,FACs)为载体,采用水热法制备了新颖的漂珠负载Bi2WO6复合材料(Bi2WO6/FACs),通过X射线衍射(XRD),扫描电子显微镜(SEM),X-射线光电子能谱(XPS),和紫外-可见漫反射光谱(DRS)技术对其进行了表征。XRD数据显示了正交相Bi2WO6的特征衍射峰。DRS结果证实了引入FACs后Bi2WO6对可见光的吸收增强。在可见光的照射下,以亚甲基蓝溶液的光催化降解评价了Bi2WO6/FACs复合材料的光催化性能。结果表明:Bi2WO6/FACs的光催化性能优于纯Bi2WO6的,其一级反应速率常数(k)为后者的2.4倍。尤其是由于漂珠质轻中空的特性,Bi2WO6/FACS复合光催化剂可长时间漂浮于水面,既能充分吸收光能,又有利于催化剂的回收和重复利用。 相似文献
16.
Bi 2WO 6/TiO 2 heterojunction photocatalysts with two different microstructures were controllably fabricated via a facile two-step synthetic route. XRD, XPS, SEM, TEM, BET-surface, DRS, PL spectra, photoelectrochemical measurement (Mott-Schottky), and zeta-potential analyzer were employed to clarify structural and morphological characteristics of the obtained products. The results showed that Bi 2WO 6 nanoparticles/nanosheets grew on the primary TiO 2 nanorods. The TiO 2 nanorods used as a synthetic template inhibit the growth of Bi 2WO 6 crystals along the c-axis, resulting in Bi 2WO 6/TiO 2 heterostructure with one-dimensional (1D) morphology. The photocatalytic properties of Bi 2WO 6/TiO 2 heterojunction photocatalysts were strongly dependent on their shapes and structures. Compared with bare Bi 2WO 6 and TiO 2, Bi 2WO 6/TiO 2 composite have stronger adsorption ability and better visible light photocatalytic activities towards organic dyes. The Bi 2WO 6/TiO 2 composite prepared in EG solvent with optimal Bi:Ti ratio of 2:12 (S-TB2) showed the highest photocatalytic activity, which could totally decompose Rhodamine B within 10 min upon irradiation with visible light (λ > 422 nm), and retained the high photocatalytic performance after five recycles, confirming its stability and practical usability. The results of PL indicated that Bi 2WO 6 and TiO 2 could combine well to form a heterojunction structure which facilitated electron–hole separation, and lead to the increasing photocatalytic activity. 相似文献
17.
In this study, we introduced tungstate into solid oxide fuel cells (SOFCs) for the first time by using a La/Pr-doped CeO 2 (LCP)/K 2WO 4 composite as the electrolyte, which exhibited remarkably enhanced grain boundary conduction compared to that of single-phase LCP. The composition dependence of the electrical conductivity was investigated. As a result, the composite with 10 wt% K 2WO 4 was proven to be the optimum ratio, revealing a significantly higher ionic conductivity than LCP, along with a negligible electronic conductivity. The fuel cell using the LCP/K 2WO 4 electrolyte displayed an encouraging performance of 500 mW cm − 2 at 550 °C. These findings indicate that the LCP/K 2WO 4 composite is a promising electrolyte for low-temperature SOFCs. 相似文献
18.
钨酸铋在水相体系中能光催化降解有机污染物,而对于钨酸铋光催化活性影响因素的研究非常少.本文研究了煅烧温度对花朵状钨酸铋光催化活性的影响.以钨酸钠和硝酸铋为原料,在160°C下水热反应20 h,合成催化剂,并经不同温度煅烧3 h.用X射线衍射(XRD)、拉曼(Raman)光谱、紫外-可见漫反射吸收光谱(UVVis DRS)和荧光(PL)光谱表征样品.结果表明,这些样品具有十分相似的相组成和电子结构.然而,对于水中苯酚的降解,钨酸铋的光催化活性显示出了很大的差异.钨酸铋的光催化活性随着煅烧温度的升高,先上升后下降,最优煅烧温度为350°C,并且不受样品比表面积大小的影响.这些样品的活性差异主要归结于钨酸铋的结晶度、吸光性和表面缺陷对其光生载流子分离效率的综合影响. 相似文献
19.
Cu 3[W(CN) 8] 2(pyrimidine) 2(3-cyanopyridine) 2 · 4H 2O, a cyanide-bridged copper(II) octacyanotungstate(V) with two types of organic ligands (pyrimidine and 3-cyanopyridine), is prepared. In this compound, the coordination geometry of W is an 8-coordinated bicapped trigonal prism where five CN groups of [W(CN) 8] are bridged to five Cu ions, and the remaining three CN groups are free. The coordination geometries of the three types of Cu ions (Cu1, Cu2, and Cu3) are 6-coordinated pseudo-octahedron. The cyano-bridged-Cu2–W–Cu3-layer is linked by a Cu1 pillar unit, and a cavity along the a axis, which is occupied by 3-cyanopyridine molecules and zeolitic water molecules, exists. The present compound shows ferrimagnetism with a Currie temperature of 7 K, a saturation magnetization of 2.9 μB, and a coercive field of 7 Oe at 2 K. 相似文献
20.
A simple route has been employed to prepare nanosized Bi 2O 3 deposited on highly ordered mesoporous carbon. The electrochemical measurements reveal that, by loading only 10% Bi 2O 3 on the mesoporous carbon, the specific capacitance of the composite is improved by 62%, with the maximum value reaching 232 F g ?1 at a sweep rate of 5 mV s ?1. The specific capacitance of Bi 2O 3 is calculated and reaches 1305 F g ?1 at 1 mV s ?1. It is found that the mass transfer in the framework of the crystalline oxide is still difficult in spite of its nanosize, as evidenced by the decline of the specific capacitance of the Bi 2O 3 with the increase of the sweep rate. The cyclic life of composite materials is also measured and the capacitance only declines 21% after 1000 cycles. 相似文献
|