Bi2WO6 Nanoparticles Research Articles

Constructing two-dimension MoS2/Bi2WO6 core-shell heterostructure as carriers transfer channel for enhancing photocatalytic activity

A MoS2/Bi2WO6 core-hell heterostructure constructed by two-dimension MoS2 and BiWO6 nanoparticles was obtained though a simple hydrothermal reaction and the photocatalytic activity was compared. The HRTEM images show that the two-dimension MoS2 grown on the surface of Bi2WO6 nanoparticles to construct a core-shell heterostructure. In the photocatalytic degradation of dye, MoS2/Bi2WO6 composite with optimal Mo:Bi ratio demonstrated an obvious enhancement of photocatalytic activity as much as 82% than that of pristine Bi2WO6 nanoparticles. The result confirms this MoS2/Bi2WO6 core-hell heterostructure is an ideal transfer channel for photo-induced carriers. In this way, photo-induced electrons produced in MoS2 will flow to Bi2WO6; thus, photo-induced holes produced in Bi2WO6 will transfer to MoS2. This carriers' transfer will improve the separation efficiency and enhance the photocatalytic activity of composites. This two-dimension MoS2 composite is finally confirmed an effective approach to improve the photocatalytic activity of semiconductors.

Congo red removal by PANi/Bi2WO6 nanocomposites: Kinetic, equilibrium and thermodynamic studies

Polyaniline/Bismuth tungstate (PANi/Bi2WO6) nanocomposites were synthesized by a facile chemical method. The prepared samples were characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-Ray Energy dispersive Spectroscopy (EDS) and Scanning electron microscopy (SEM). Bismuth tungstate co-modified by PANi was used as an eco-friedly adsorbent to remove anionic dye Congo red (CR) from aqueous solution. The obtained experimental results showed that the CR dye removal efficiency is significantly dependent on different physico-chemical conditions including initial pH, contact time, PANi weight content in PANi/Bi2WO6 nanocomposite, adsorbent dose, CR initial concentration and temperature. It was found that The CR adsorption efficiency increased from 13.74 to 92.03% for when the PANi content coated on Bi2WO6 nanoparticles was increased from 0 to 10wt.%, respectively. This was explained by improvement in the amino groups of PANi, the creation of porous nanostructures and the increases in the specific surface area and decreases mean particle sizes. In addition, the experimental kinetic results were fitted by the pseudo-second-order model. Also, the equilibrium data were best represented by Redlich-Peterson and Langmuir isotherm models. The thermodynamic parameters indicate that the adsorption process was spontaneous and endothermic in nature. Furthermore, the adsorption capacity PANi/Bi2WO6 for CR dye was not significantly affected during four regeneration cycles.

Facile Fabrication of Bi2WO6/Ag2S Heterostructure with Enhanced Visible-Light-Driven Photocatalytic Performances.

In this report, a novel photocatalyst based on Bi2WO6/Ag2S heterostructures was prepared by a 3-mercaptopropionic acid (MPA)-assisted route at room temperature. Compared to bare Bi2WO6 and Ag2S nanoparticles, the as-formed Bi2WO6/Ag2S heterostructures exhibit enhanced photocatalytic activity for the degradation of rhodamine B (Rh B) under visible-light irradiation. This kind of enhancement in the photocatalytic activity is considered to be the synergistic effects of both the effective electron-hole separation and expansion of the light-absorption range. The pH of the solution is of vital importance to the photocatalytic activity of the as-formed Bi2WO6/Ag2S heterostructures. Under low pH value, the photosensitization process is suppressed, while under higher pH value, the photosensitization process is favored. The mechanism of the photocatalytic process was proposed by the active-species-trapping experiments, indicating that the photogenerated holes (h+) play a crucial role in the degradation of Rh B under visible light. The enhanced photocatalytic performance of this heterostructure makes it a promising material for the treatment of dye-containing wastewater.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1319-7) contains supplementary material, which is available to authorized users.

A C3N4/Bi2WO6 organic–inorganic hybrid photocatalyst with a high visible-light-driven photocatalytic activity

Abstract

Highly photocatalytic active thiomolybdate [Mo3S13]2− clusters/Bi2WO6 nanocomposites

The Mo3S132−/Bi2WO6 nanocomposites were facilely fabricated by depositing [Mo3S13]2− clusters onto the hydrothermally prepared Bi2WO6 nanoparticles. This novel Mo3S132−/Bi2WO6 nanocomposite exhibited unprecedented visible light photocatalytic activities. The deposited [Mo3S13]2− clusters enhanced the photocatalytic activity of Bi2WO6 by promoting the migration of photoinduced charges, which restrained the recombination of photogenerated hole–electron (h+/e−) pairs on the surface of Bi2WO6. Furthermore, the high photocatalytic stability and recyclability of Mo3S132−/Bi2WO6 nanocomposite enable it to be a promising candidate for the environmental remediation especially in wastewater treatment. In all, [Mo3S13]2− clusters with advantages of low cost and earth-abundance are great potential as co-catalyst for photocatalysts.

Optimized Design of Pt‐Doped Bi2WO6 Nanoparticle Synthesis for Enhanced Photocatalytic Properties

AbstractThe preparation of photocatalytic heterostructures of platinum on Bi2WO6 nanoparticles by a wet reduction method is described in this report and compared with other preparation methods. The as‐obtained photocatalysts were characterized by XPS and TEM, the results of which confirmed the presence of solely zero‐valent metal nanoparticles on the surface of Bi2WO6. The photocatalytic activity of these heterostructures was evaluated by the degradation of Rhodamine B under blue light (λmax = 445 nm). The deposited noble metal nanoparticles were shown to significantly improve the photocatalytic performance of the bismuth‐based material under visible light. Both the preparation mode and the metal loading may impact on the efficiency. The observed photocatalytic enhancement has been attributed to an electron transfer from the semiconductor to the metal, which prevents fast electron/hole recombination. The electrons trapped in the metals may then participate in the multi‐electron reduction of O2.

Enhanced photocatalytic performance in Bi2WO6/SnS heterostructures: Facile synthesis, influencing factors and mechanism of the photocatalytic process

Highly-efficient photocatalyst based on Bi2WO6/SnS heterostructure was prepared via a surface functionalization method using 3-mercaptopropionic (MPA) as the surface functionalizing agent. Compared to bare Bi2WO6 and SnS nanoparticles, the as-formed Bi2WO6/SnS heterostructure exhibits enhanced photocatalytic activity for the degradation of Rhodamine B (Rh B). Photoluminescence and photocurrent measurements demonstrate that the enhanced photocatalytic activity during the photocatalytic process is closely related to the enhanced electron–hole separation efficiency. The photocatalytic activity of the as-formed Bi2WO6/SnS heterostructure can be perfectly remained even after being used for five times, showing excellent durability during the photocatalytic process. The influence of pH and inorganic ions are systematically investigated. And the optimum pH for the photocatalytic process is determined to be 6. The addition of chloride ion will exert negative effect on the photodegradation process of Rh B. The mechanism of photodegradation process was investigated by exploring the quenching effects of different scavengers and the results suggest that the reactive holes play the major role in the photodegradation process of Rh B.

Nano-Bi2WO6 functionalized flexible SiO2 fibrous film for water purification

Electrospinning-derived nanofibrous films functionalized by photocatalysts have been extensively studied in the applications of environmental remediation. In this investigation, we propose a simple strategy for preparation of flexible and chemically stable nanofibrous films with high photocatalytic efficiency. Specifically, SiO2 nanofibrous film modified with Bi2WO6 nanoparticles was studied as a representative. Flexible SiO2 nanofibers were derived through sol–gel and electrospinning techniques. By simple soaking in precursor solution of Bi2WO6 and calcination, the SiO2 nanofibrous film was functionalized by Bi2WO6 nanoparticles, forming hierarchically porous composite film. Micro morphology, mechanical property and photocatalytic performance were tuned via changing the concentration of the soaking solution. Photocatalytic removal of organic pollutant from water was performed using RhB (Rhodamine B) as a model. The strategy proposed here is also widely applicable for preparation of composite films modified with other kinds of photocatalysts. SiO2–Bi2MoO6, SiO2–TiO2 and SiO2–CuO composite films were prepared in a similar way to demonstrate the versatility of the proposed preparation strategy.

Photocatalytic Chemoselective Aerobic Oxidation of Thiols to Disulfides Catalyzed by Combustion Synthesized Bismuth Tungstate Nanoparticles in Aqueous Media

Bismuth tungstate (Bi2WO6) nanoparticles were synthesized by solution combustion synthesis method using different N-containing organic compounds as fuels (urea, glycine, hexamethylenetetramine (HMTA), malonic acid dihydrazide (MDH)). The Bi2WO6 nanoparticles have been characterized using XRD, UV–Vis–DRS, photoluminescence, FESEM, HRTEM and sorptometric techniques. Glycine as fuel was effective for synthesis of phase pure Bi2WO6 nanoparticles. Employing HMTA and MDH as fuel lead to mixed phase complex oxide system with Bi14W2O27 as minor (impurity) phase. The nature of the fuel significantly influences the particle size and morphology. Formation of spherical, flake like and elongated polyhedral particles were observed in FESEM study depending upon the nature of the fuel. TEM study of Bi2WO6 prepared using glycine fuel depicted the presence of spherical particles with size in the range of 5–8 nm. The Bi2WO6 nanoparticles were used as an efficient photocatalyst for the visible light driven chemoselective oxidation of substituted thiophenols to disulfide using air as oxidant. The effect of various reaction parameters such as catalyst amount, reaction media, time, along with catalyst recyclability were studied in detail. Structurally diverse diphenyl disulfide moieties were obtained in high yield and excellent selectivity within a time span of 6 h of visible light irradiation.

Study of photocatalytic activities of Bi2WO6 nanoparticles synthesized by fast microwave-assisted method

We present a study of photocatalytic activities of Bi2WO6 nanoparticles synthesized by fast microwave-assisted method. The photocatalytic activities of the nanoparticles were evaluated by the decolorization of methylene-blue under visible-light-irradiation. Our results show that the surface area of Bi2WO6 nanoparticles plays a major role for improving photocatalytic activity, while visible-light absorption has only a weak effect on photocatalytic activity. This suggests efficient transportation of photo-generated electrons and holes to the oxidation active sites on the surface of nanoparticles, indicating Bi2WO6 nanoparticles synthesized by fast microwave-assisted method are promising for achieving high photocatalytic activity under visible-light-irradiation.

Effect of carbon coating on the electrochemical properties of Bi2WO6 nanoparticles by PVP-assisted sonochemical method

Polyvinylpyrrolidone (PVP)-assisted Bi2WO6 nanoparticles were successfully synthesized by sonochemical method. Three different concentrations of PVP (0.05, 0.1, and 0.2 g) were used, and their effects over the structural, morphological, compositional, and electrochemical analysis were studied. The structural investigation revealed the formation of 100 % pure Bi2WO6 phase. The presence of carbon in the PVP-assisted materials was evidenced from differential scanning calorimetry, Fourier transform infra red (FT-IR) spectroscopy and Raman analysis. There was a reduction in the particle size of Bi2WO6 (30–35 nm) upon using PVP. The highly crystalline nature and the presence of carbon coating over Bi2WO6 were evidenced from the high-resolution transmission electron microscopic image. Besides, the calculated d-spacing of 0.19 nm attributed to (2 0 6) lattice plane of Bi2WO6 nanoparticles. Subsequently, a shift in binding energy toward larger values while using PVP was identified through X-ray photoelectron spectroscopic analysis. The electrochemical analysis showed a subsequent enhancement in specific capacitance of PVP-assisted Bi2WO6 (462 F g−1) compared with pristine Bi2WO6 (304 F g−1) at 3 mA cm−2.

Enhanced photocatalytic activity of cadmium-doped Bi2WO6 nanoparticles under simulated solar light

Novel cadmium-doped Bi2WO6 nanoparticles with different Cd contents have been synthesized by a one-step route using ethylene glycol and water as solvents at 180 °C for 12 h. The as-synthesized samples were characterized in detailed by SEM, XRD, EDS, HRTEM, UV–Vis DRS, BET techniques, and so on. The results shown that with the increase of the Cd2+ addition, the crystal structure, lattice space, and absorption edge were not significantly changed and the calculated band gap value was 2.58 eV. However, the flower-like Bi2WO6 sphere was gradually destroyed. Simultaneously, the surface area and photocurrent responses of the catalysts were greatly increased. Photocatalytic activity of the Cd-doped Bi2WO6 samples was determined by monitoring the change of RhB concentration under simulated solar light. The results revealed that cadmium doping greatly improved the photocatalytic efficiency of Bi2WO6. The Bi2WO6 sample with R Cd = 0.05 displayed the highest photocatalytic activity, and the degradation rate is about two times greater than pure Bi2WO6. Moreover, the Cd–Bi2WO6 photocatalyst remained stable even after five consecutive cycles. A possible mechanism of photocatalytic activity enhancement on basis of the experimental results was proposed.

Enhanced performance of nano-Bi2WO6-graphene as pseudocapacitor electrodes by charge transfer channel.

The nano-Bi2WO6/reduced graphene oxide composite obtained by a simple hydrothermal reaction demonstrates a larger specific capacitance of 922 F/g at a charge and discharge currents of 3 A/g with longer cycle life. The As comparison, pristine Bi2WO6 nanoparticles have poor specific capacitance of 574 F/g at a charge and discharge currents of 2 A/g with weak cycle life. Though analyzing the Cyclic voltammetry curves, it is found that there are two oxidation reaction occurring in the materials: oxidation of Bi (III) to Bi (IV) and Bi (III) to Bi (V). The oxidation of Bi (III) to Bi (IV) is reversible while Bi (III) to Bi (V) will cause nonreversible destroy on structure. In this nano-Bi2WO6/reduced graphene oxide composite, graphene with well conductivity will enhance the electrically conducting as charge transfer channel, so that electrons will be transfer much faster in oxidation and most Bi (III) is oxidized to be Bi (IV) which ensure larger specific capacitance and long cycle life. This nano-Bi2WO6/reduced graphene oxide composite has application prospect in high-performance pseudo-capacitors.

Synthesis of Spherical Bi2WO6 Nanoparticles by a Hydrothermal Route and Their Photocatalytic Properties

Spherical Bi2WO6 nanoparticles were synthesized by a hydrothermal route. SEM observation shows that the size of the particles ranges from 60 to 120 nm and the average particle size is ~85 nm. TEM investigation shows that the particles are made up of subgrains with size of 5–10 nm. The bandgap energy of the particles is measured to be 2.93 eV by ultraviolet‐visible diffuse reflectance spectroscopy. RhB was chosen as the target pollutant to evaluate the photocatalytic activity of the particles under irradiation of simulated sunlight, revealing that they exhibit an obvious photocatalytic activity. The effects of ethanol, KI, and BQ on the photocatalytic efficiency of Bi2WO6 particles towards the RhB degradation were investigated. It is observed that ethanol has no effect on the photocatalytic degradation of RhB, whereas KI and BQ exhibit a substantial suppression of RhB degradation. No hydroxyl (•OH) is found, by the photoluminescence technique using terephthalic acid as a probe molecule, to be produced over the irradiated Bi2WO6 particles. Based on the experimental results, photoexcited hole (h+) and superoxide (•) are suggested to be the two main active species responsible for the dye degradation, while •OH plays a negligible role in the photocatalysis.

Synthesis of functionalized 1,2,3-triazoles using Bi2WO6 nanoparticles as efficient and reusable heterogeneous catalyst in aqueous medium

The regioselective synthesis of functionalized triazoles is achieved using a combination of Bi2WO6 nanoparticles (10 mol%) and click conditions from β-nitrostyrenes, phenylacetylene and chalcones with azides.

Nano Ag@AgBr surface-sensitized Bi2WO6 photocatalyst: oil-in-water synthesis and enhanced photocatalytic degradation

Nano Ag@AgBr decorated on the surface of flower-like Bi2WO6 (hereafter designated Ag@AgBr/Bi2WO6) were prepared via a facile oil-in-water self-assembly method. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy (DRS), etc. The characterization results indicated that nano Ag@AgBr was observed to be evenly dispersed on the surface of Bi2WO6, and was approximately 20nm in size. Ag@AgBr/Bi2WO6 composites exhibited excellent UV–vis absorption, due to quantum dimension effect of Ag@AgBr, the surface plasmonic resonance (SPR) of Ag nanoparticles and the special flower-like structure of Bi2WO6. The photoelectrochemical measurement verified that the suitable band potential of Ag@AgBr and Bi2WO6 and the existence of metal Ag resulted in the high efficiency in charge separation of the composite. The photocatalytic activities of the Ag@AgBr/Bi2WO6 samples were examined under visible-light irradiation for the degradation of methylene blue (MB). The composite presented excellent photocatalytic activity due to the synergetic effect of Bi2WO6, AgBr, and Ag nanoparticles. The Ag@AgBr(20wt.%)/Bi2WO6 sample exhibited the best photocatalytic activity, degrading 95.03% MB after irradiation for 2h, which was respectively 1.29 times and 1.28 times higher than that of Ag@AgBr and Bi2WO6 photocatalyst. Meanwhile, phenol and salicylic acid were degraded to further prove the degradation ability of Ag@AgBr/Bi2WO6. Additionally, studies performed using radical scavengers indicated that O2−•, •OH and Br0 acted as the main reactive species. Based on above, a photocatalytic mechanism for organics degradation over Ag@AgBr/Bi2WO6 was proposed.

Oil-in-water self-assembled Ag@AgCl QDs sensitized Bi2WO6: Enhanced photocatalytic degradation under visible light irradiation

Quantum dots (QDs) Ag@AgCl decorated on the surface of flower-like Bi2WO6 (hereafter designated Ag@AgCl/Bi2WO6) were prepared via a facile oil-in-water self-assembly method. The photocatalysts were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy (DRS) and X-ray fluorescence spectrometer (XRF) etc. The characterization results indicated that QDs Ag@AgCl was observed to be evenly dispersed on the surface of Bi2WO6, and was approximately 10–20nm in size. Ag@AgCl/Bi2WO6 composites exhibited excellent UV–vis absorption, due to quantum dimension effect of Ag@AgCl QDs, the surface plasmonic resonance (SPR) of Ag nanoparticles and the special flower-like structure of Bi2WO6. The photo-electrochemical measurement verified that the suitable band potential of Ag@AgCl and Bi2WO6 and the existence of metal Ag resulted in the high efficiency in charge separation of the composite. The photocatalytic activities of the Ag@AgCl/Bi2WO6 samples were examined under visible light irradiation for the degradation of Rhodamine B (RhB). The composite presented excellent photocatalytic activity due to the synergetic effect of Bi2WO6, AgCl, and Ag nanoparticles. The Ag@AgCl(20wt.%)/Bi2WO6 sample exhibited the best photocatalytic activity, degrading 97.61% RhB after irradiation for 2h, which was, respectively, 1.33 times and 1.32 times higher than that of Ag@AgCl and Bi2WO6 photocatalyst. Meanwhile, phenol was degraded to further prove the degradation ability of Ag@AgCl/Bi2WO6. Additionally, studies performed using radical scavengers indicated that O2−·, h+ and Cl0 acted as the main reactive species. Based on above, a photocatalytic mechanism for organics degradation over Ag@AgCl/Bi2WO6 was proposed.

Bi<sub>2</sub>WO<sub>6</sub> Nanoparticles Prepared by Combustion Synthesis with Different Fuels and their Photocatalytic Activity

The influence of glycine, glycerine, ethylene glycol and citric acid fuel and their ratio to NO3- on formation and dispersity of Bi2WO6 nanoparticles prepared by combustion synthesis has been studied. The pure crystalline Bi2WO6 with specific surface area 24,8 m2/g and crystallite size of 28 nm was obtained by using glycerine as fuel at its ratio to NO3- of 0,67. The photocatalytic activity of the prepared Bi2WO6 in degradation of methylene blue depended on its specific surface area of samples and solution pH.

A high-performance Bi2WO6–graphene photocatalyst for visible light-induced H2and O2generation

We developed a highly efficient photocatalyst for both H2 and O2 generation under visible-light irradiation by attaching Bi2WO6 (BWO) nanocrystals on graphene nanosheets to produce a graphene-Bi2WO6 composite (Gr-BWO-T). The composite was prepared by a sonochemical method where graphene oxide (GO) served as the support on which BWO formed in situ. Bi2WO6 nanoparticles with the size of 30-40 nm were homogeneously dispersed on the surface of graphene sheets, due to their bonding with graphene. When used as a photocatalyst under visible-light irradiation, O2 production rate reached a value up to 20.60 μmol h(-1), 4.18 times higher than that of bare BWO, resulting from the strong covalent bonding between graphene and BWO nanoparticles. The chemical bonding facilitated the electron collection and transportation and inhibited the recombination of photo-generated charge carriers, even in this system with a large amount of graphene inside (40 wt%). More interestingly, H2-production by Gr-BWO-T was also observed to be as high as 159.20 μmol h(-1). This could be ascribed to the existence of the graphene that led to decrease in conduction band potential and resulted in a more negative reduction potential than H(+)/H2. This facile sonochemical approach provides a new strategy for engineering ternary compound nanoparticles on graphene sheets, with great potential application in energy conversion.

Recyclable Bi2WO6-nanoparticle mediated one-pot multicomponent reactions in aqueous medium at room temperature

Room temperature multicomponent reactions (MCRs) are reported using Bi2O3, BiVO4, and Bi2WO6 (nanoparticle) as heterogeneous catalysts. Among these, Bi2WO6 (5 mol%) nanoparticles showed excellent reactivity for the synthesis of functionalized dihydropyridine, polyhydroquinoline, 4H-chromene and 2-amino-4H-benzo[b]pyran derivatives in aqueous medium.