Bi2WO6 Hollow Research Articles

Construction of carbon dots modified Cl-doped Bi2WO6 hollow microspheres for boosting photocatalytic degradation of tetracycline under visible light irradiation

The composition of composite photocatalysts with both broad spectral response and efficacious separation of photoinduced carriers were essential. The CDs were installed on the surface of the three-dimensional hollow microsphere nanophotocatalyst Bi2WO6 by the hydrothermal approach. Crystal structure, morphology and composition revealed the synthesis of the composite catalyst. The higher photocatalytic capability of 0.5% CDs/Cl–Bi2WO6 (0.0317 min−1) was observed in the degradation procedure, explained that the doping of Cl and the presence of CDs remarkably strengthened the visible light capture and depressed the rate of electron-hole pair complexation. Notably, scavenger-quenching assays results verified that activities of h+, •OH and •O2‾ were the primary actors in the degradation procedure. Ultimately, the degradation mechanism of a feasible TCH was submitted. This study presented a novel concept for the exploitation of composite nanophotocatalysts for the effective degradation of organic pollutants.

Bi2WO6 hollow microspheres with high specific surface area and oxygen vacancies for efficient photocatalysis N2 fixation

In this work, Bi2WO6 hollow microspheres containing oxygen vacancies (OVs-BWO) was synthesized by a solvothermal template-free method. Raman, EPR and XPS spectra provide sufficient evidence for the existence of OVs in the material. Its activity toward photocatalytic nitrogen fixation was evaluated. Experimental results showed that the OVs-BWO with a BET surface area of 80.5 m2·g−1 exhibited the ammonia yield of 106.4 μmol·gcat−1 under simulated sunlight for 2 h, which is ca. 18 times higher than that of equal-area nest-like Bi2WO6 without oxygen vacancies. The enhanced activity is mainly attributed to the metastable electrons within the sub-band (i.e., defect energy level) induced by oxygen vacancies to π anti-bonding orbitals of N2 with a manner of the non-radiative transfer, leading to the activation of nitrogen molecules. The activation and hydrogeneration processes of nitrogen at active site of OVs-BWO were studied by DFT calculation and the possible mechanisms were proposed. The sub-band extends the light absorption region of OVs-BWO to 700 nm. Transient photocurrent response showed that the sub-band electron excitation accelerates the transfer of charges and hinders the electron-hole recombination. It can be perfectly reused five times when air and nitrogen are used as nitrogen sources, thus the OVs-BWO hollow microspheres offer a promising alternative for efficient N2 fixation under ambient conditions.

Fabrication of HRP/Bi2WO6 photoenzyme-coupled artificial catalytic system for efficiently degrading bisphenol A

A novel photoenzyme-coupled artificial catalytic system is fabricated by immobilizing horseradish peroxidase (HRP) on the Bi2WO6 hollow nanospheres via a facile electrostatic self-assembly process. The obtained Bi2WO6/HRP sample not only improves the visible light harvest ability but also promotes the high-efficiency separation of charge carriers. More importantly, the photogenerated electrons and produced H2O2 on Bi2WO6 directly take part in redox cycle reactions of HRP to induce photoenzyme synergic catalytic effect. In consequence, the degradation activity of Bi2WO6/HRP is significantly improved relative to Bi2WO6 and HRP for removing bisphenol A (BPA) under the visible light irradiation. This work launches a feasible design strategy for exploiting photoenzyme-coupled artificial catalytic system with special structure to degrade organic pollutants in water efficiently.

Pristine Bi2WO6 and hybrid Au-Bi2WO6 hollow microspheres with excellent photocatalytic activities

Pristine Bi2WO6 hollow microspheres have been fabricated in ethylene glycol-water system with CTAB as crystal growth director for the first time, hybrid Au- Bi2WO6 hollow microspheres was also obtained by in situ decoration of Au nanoparticles, the formation mechanisms were explored. Their photocatalytic activities on photo-reduction of Cr(VI) and photo-degradation of phenol in aqueous solution were investigated under visible light irradiation. Hybrid Au- Bi2WO6 hollow microspheres displayed the highest photocatalytic activity, exhibiting a nearly complete reduction of Cr(VI) to Cr(III) within only 20 min. The excellent photocatalytic activities of heterogeneous Au-Bi2WO6 hollow microspheres can be induced by the increased light harvesting efficiency (due to light multi-scattering effect of hollow architecture), high separation of photogenerated electron-hole pairs caused by electron trapping effect and surface plasmon resonance (SPR) effect of Au nanoparticles.

Construction of multi-shelled Bi2WO6 hollow microspheres with enhanced visible light photo-catalytic performance

As a promising structure in enhancing the photo-catalytic performance of the materials, hollow-shell structure still faces the great challenge of constructing an effective architecture for catalytic application. Herein, multi-shelled hollow microspheres of the visible-light photo-catalyst Bi2WO6 with shells up to the triple (BWO-MSH), have been synthesized by using a facile and effective carbonaceous template route. Intriguingly, the photo-catalytic reaction rate constant of BWO-MSH sample is nearly 16 times higher than the Bi2WO6 prepared through solid-state reaction (BWO-SSR). The single-, double-shelled Bi2WO6 microspheres (Broken) could only be synthesized with lower quality (synthesized with many broken species), and their photo-catalytic performance was nearly the same poor as the BWO-SSR sample. Furthermore, multi-shelled hollow microsphere of Bi2O3/Bi2WO6 (BO/BWO-MSH) composite was also synthesized. The present work not only extends the scope of high-performance complex mixed metal oxides with multi-shelled microstructures, but also brings a good reference to engineer other impressive photo-catalyst.

In-situ room-temperature synthesis of amorphous/crystalline contact Bi2S3/Bi2WO6 heterostructures for improved photocatalytic ability

Abstract We developed a facile in-situ growth method to construct amorphous-based Bi2S3/Bi2WO6 heterostructures at room temperature. As demonstrated by HRTEM, XPS and EDX-mapping, amorphous state Bi2S3 dispersed uniformly on the surface of crystalline Bi2WO6 hollow spheres. The photocatalytic activities of prepared Bi2S3/Bi2WO6 heterostructures were evaluated by the photodegradation of RhB and TC under visible light irradiation, indicating that the introduction of appropriate amorphous Bi2S3 significantly improved the photocatalytic activity of Bi2WO6. The amorphous/crystalline contact in Bi2S3/Bi2WO6 heterostructures played a crucial role in the enhancement of photocatalytic efficiency. Based on DRS, photoluminescence spectra, photocurrent intensity, electrochemical impedance spectroscopy and OCVD measurements, it was proposed that the enhanced performance could be ascribed to increased visible light utilization, promoted separation efficiency and prolonged life time of photogenerated electron-hole pairs by the introduction of amorphous Bi2S3. This work may provide new insights into the construction of amorphous-based composited heterostructures for improving photocatalytic activity.

Salt-assisted Synthesis of Hollow Bi2WO6 Microspheres with Superior Photocatalytic Activity for NO Removal

Hollow Bi2WO6 microspheres are successfully synthesized by a facile ultrasonic spray pyrolysis (USP) method using NaCl as a salt template. The as-prepared hollow microspheres assembled as nanoplates with dimensions of approximately 41–148 nm and are dispersed with non-uniform pores on the template surface. By swapping the salt template with KCl or Na2SO4, different morphologies of Bi2WO6 are obtained. The experimental results demonstrate that NaCl plays a key role on the formation of Bi2WO6 with hollow structures. The specific growth mechanism of hollow microspheres was studied in detail. The Bi2WO6 hollow microspheres exhibit an excellent photocatalytic efficiency for NO removal under solar light irradiation, which is 1.73 times higher than for the Bi2WO6 obtained in the absence of any salt template. This enhancement can be ascribed to the simultaneous improvement on the surface area and visible light-harvesting ability from the hollow structures. Electron spin resonance (ESR) results suggest that both radicals of •OH and •O2− are involved in the photocatalytic process over the BWO-NaCl sample. The production of •O2− radicals offers better durability for NO removal.

Synthesis of hierarchical flower-like Bi2MoO6microspheres as efficient photocatalyst for photoreduction of CO2into solar fuels under visible light

Hierarchical flower-like Bi2MoO6 microspheres were successfully synthesized via a facile hydrothermal approach, employing PVP as the crystal growth modifier. The building units of the hierarchical flower-like Bi2MoO6 were constructed by two-dimensional thin flakes, which intercrossed with each other and aggregated together to form the three-dimensional flower-like structure. The PVP amount and hydrothermal duration played crucial roles in the formation of the Bi2MoO6 architectures with evolving morphologies. The Bi2MoO6 samples were first evaluated for the photocatalytic reduction of CO2 into methanol and ethanol as solar fuels under visible-light irradiation. It has been found that the hierarchical flower-like Bi2MoO6 exhibits highly efficient photocatalytic activity. After 4 hours of irradiation, the yields of methanol and ethanol were 24.8 and 18.8 μmol gcat−1 respectively, higher than those obtained over previously-reported Bi2WO6 hollow microspheres. This demonstrates that the hierarchical flower-like Bi2MoO6 is a simple, efficient and promising visible-light-driven photocatalyst for the photoreduction of CO2 into solar fuels.

Magnetically separable ternary hybrid of ZnFe2O4–Fe2O3–Bi2WO6 hollow nanospheres with enhanced visible photocatalytic property

Magnetically separable ternary hybrid ZnFe2O4–Fe2O3–Bi2WO6 hollow nanospheres were designed and synthesized by an effective three-step approach. Specifically, using phenolic formaldehyde microspheres (PFS) as template direct the sequential coating of α-Fe2O3/ZnFe2O4 layer and subsequent Bi2WO6 layer via impregnating-calcination process. The photocatalytic activity under visible light irradiation is in the order of ZnFe2O4–Fe2O3–Bi2WO6>ZnFe2O4–Bi2WO6>Bi2WO6>ZnFe2O4–Fe2O3>ZnFe2O4. The enhanced activity could be attributed to the cascade electron transfer from ZnFe2O4 to α-Fe2O3 then to Bi2WO6 through the interfacial potential gradient in the ternary hybrid conduction bands, which facilitate the charge separation and retard the charge pair recombination. Furthermore, the ternary hybrid ZnFe2O4–Fe2O3–Bi2WO6 hollow nanospheres could be conveniently separated by using an external magnetic field, and be chemically and optically stable after several repetitive tests. The study also provides a general and effective method in the composite hollow nanomaterials with sound heterojunctions that may show a variety of applications.

Solvothermal Synthesis of Bi2WO6 Hollow Microspheres Via Ostwald Ripening with Their Enhanced Photocatalytic Activity

Bi2WO6 hollow microspheres were successfully synthesized by solvothermal process in the presence of urea at proper ethylene glycol (EG)/absolute ethanol (AE) volume ratio (1:1). The samples consisted of microspheres with an average diameter of 1 μm, and the shell consisted of numerous nanoplates. The effect of solvent, the ratio of EG/AE solvents and urea amount on the morphology of the samples was studied systematically, indicating that a certain ratio of EG/AE and urea amount played an important role in the formation of hollow microspheres. Based on the detailed investigation, the formation mechanism of the hollow interior by EG-induced Ostwald ripening process was proposed. By contrast, the Bi2WO6 hollow microspheres exhibited higher catalytic activity for degradation of Rhodamine B under xenon lamp irradiation, and nearly 100 % Rhodamine B is degraded within 120 min.

Facile hydrothermal synthesis of TiO2–Bi2WO6hollow superstructures with excellent photocatalysis and recycle properties

One-dimensional mesoporous TiO2-Bi2WO6 hollow superstructures are prepared using a hydrothermal method and their photocatalysis and recycle properties are investigated. Experimental results indicate that anatase TiO2 nanoparticles are coupled with hierarchical Bi2WO6 hollow tubes on their surfaces. The TiO2-Bi2WO6 structure has a mesoporous wall and the pores in the wall are on average 21 nm. The hierarchical TiO2-Bi2WO6 heterostructures exhibit the highest photocatalytic activity in comparison with P25, pure Bi2WO6 hollow tube and mechanical mixture of Bi2WO6 tube and TiO2 nanoparticle in the degradation of rhodamine B (RhB) under simulated sunlight irradiation. The as-prepared TiO2-Bi2WO6 heterostructures can be easily recycled through sedimentation and they retains their high photocatalytic activity during the cycling use in the simulated sunlight-driving photodegradation process of RhB. The prepared mesoporous TiO2-Bi2WO6 with hollow superstructure is therefore a promising candidate material for water decontamination use.

A Templated Method to Bi2WO6 Hollow Microspheres and Their Conversion to Double-Shell Bi2O3/Bi2WO6 Hollow Microspheres with Improved Photocatalytic Performance

Bi(2)WO(6) hollow microspheres with dimension of ca. 1.5 μm were synthesized via a hydrothermal method using polystyrene particles as the template. The as-prepared Bi(2)WO(6) hollow microspheres can be further transformed to double-shell Bi(2)O(3)/Bi(2)WO(6) hollow microspheres. The samples were fully characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, N(2)-sorption Brunauer-Emmett-Teller surface area, UV-vis diffuse-reflectance spectroscopy, and X-ray photoelectron spectroscopy. The as-formed double-shell Bi(2)O(3)/Bi(2)WO(6) hollow microspheres exhibit enhanced photocatalytic activity due to the hollow nature and formation of the p-n junction between p-type Bi(2)O(3) and n-type Bi(2)WO(6). The study provides a general and effective method in the fabrication of composition and dimension-tunable composite hollow microspheres with sound heterojunctions that may show a variety of applications.

Facile preparation of three-dimensionally ordered macroporous Bi2WO6 with high photocatalytic activity

Three-dimensionally ordered macroporous Bi2WO6 (3DOM Bi2WO6) with mesoporous walls was firstly realized by a hard template synthesis method. The commercially available bismuth nitrate and phosphotungstic acid were used as the precursors to prepare the 3DOM Bi2WO6 sample without introducing other complex agents. The as-prepared 3DOM Bi2WO6 was composed of periodically arranged Bi2WO6 hollow spheres with a diameter of about 90 nm. Because of its particular ordered macroporous and mesoporous structure, the 3DOM Bi2WO6 exhibited excellent photocatalytic activity on the degradation of phenol and aqueous ammonia under irradiation from simulated sunlight. Its photocatalytic activity is much higher than that of the Bi2WO6 samples prepared by hydrothermal synthesis (HR) and solid-state reaction (SSR) methods. This work provides a simple way to prepare bismuth-based 3DOM multiple metal oxides with excellent performance.

An anion exchange approach to Bi2WO6 hollow microspheres with efficient visible light photocatalytic reduction of CO2 to methanol

An anion exchange strategy is explored to synthesize Bi(2)WO(6) hollow microspheres based on the microscale Kirkendall effect. The as-prepared Bi(2)WO(6) hollow microspheres display high CO(2) adsorption capacity and visible light photocatalytic conversion efficiency of CO(2) into methanol without the aid of any co-catalyst.