The morphology-dependent photocatalysis for rhodamine B degradation over Bi2WO6 hierarchical nanostructure

In this paper, the nanostructured Bi2WO6 with different hierarchical morphologies was synthesized via a warmly hydrothermal route. The structure and morphology of the as-prepared Bi2WO6 products were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), UV-vis absorption spectroscopy (UV-Vis) and N2-sorption analysis. The photocatalytic efficiency of Bi2WO6 was investigated by photodegradation of rhodamine B (RhB) under visible-light irradiation. The present work demonstrated that Bi2WO6 with four different hierarchical structures was effective visible-light-driven photocatalytic functional material for environmental purification. Moreover, the nest-like Bi2WO6 exhibited superior photocatalytic effects on rhodamine B degradation compared with other three Bi2WO6 morphologies. The excellent catalytic effect of the nest-like Bi2WO6 was attributed to its unique structural property and large surface area. The relationship between morphology and photocatalytic performance was discussed in detail. The photocatalytic mechanism for the degradation of RhB was also investigated, which revealed the important role of morphology in improving the photocatalyitc activities of Bi2WO6.     

Novel nanoparticle-assembled tetrakaidekahedron Bi25FeO40 as efficient photo-Fenton catalysts for Rhodamine B degradation

In this study, nanoparticle-assembled Bi₂₅FeO₄₀ materials were synthesized by a novel and simple process, and their microstructure was regulated by different methods of adding Bi³⁺ and Fe³⁺. The novel nanoparticle-assembled tetrakaidekahedron Bi₂₅FeO₄₀ materials exhibited more oxygen vacancy and larger specific surface area than irregular or cubic-like Bi₂₅FeO₄₀ microcrystals and revealed better photo-Fenton catalytic oxidation activity toward degrading Rhodamine B (RhB) pollutants. These novel materials activated H₂O₂ in visible light to produce non-free radicals ¹O₂ and hole (h⁺) active oxidative species that dominated the catalytic degradation of RhB. Complete degradation of RhB was achieved after 1 h. The possible reaction mechanisms of the photo-Fenton catalytic system are discussed in detail by radical scavenging tests, X-ray phosphorescence analysis, and electron paramagnetic resonance spectroscopy. The results provided a way to rationally explore and construct photo-Fenton catalysts for wastewater treatment.     

Novel CuO/Bi2WO6 heterojunction with enhanced visible light photoactivity

Novel CuO/Bi₂WO₆ composites with different CuO to Bi₂WO₆ weight ratios were synthesized via a facile two-step approach. The as-prepared CuO/Bi₂WO₆ composite photocatalyst was characterized by XRD, SEM, TEM, XPS, BET, UV–vis diffused reflectance, fluorescence spectrum and photocurrent measurements to investigate their physical, optical and photochemical properties. The photocatalytic activity of CuO/Bi₂WO₆ composites was evaluated by the photocatalytic degradation of RhB under simulated sunlight. The optimum photocatalytic activity of the CuO/Bi₂WO₆ composites for the degradation of RhB is almost 2 times higher than those of bare Bi₂WO₆ and CuO. The enhanced photocatalytic performance could be mainly attributed to the improved light response and effective separation of the photogenerated electrons and holes at the heterojunction interface of p-CuO and n-Bi₂WO₆.     

Yb,N共掺杂TiO_2光催化剂的制备及可见光下降解亚甲基蓝的研究

采用微波辅助溶胶-凝胶法制备了Yb,N共掺杂的纳米(Yb,N)-TiO2光催化剂,通过XRD、XPS、UV-Vis-DRS、PL等对(Yb,N)-TiO2样品进行了表征和分析,并以亚甲基蓝(MB)作为目标降解物,考察了不同Yb掺杂浓度的(Yb,N)-TiO2对MB的光催化降解效果。结果表明,Yb和N的掺入减小了TiO2的禁带宽度,降低了光生电子-空穴对的复合,使其吸收光谱的阈值波长红移至可见光区,提高了TiO2的光催化活性。当p H值=1.5、m(H2NCONH2)=10 g、热处理温度为650℃、n(Yb)∶n(Ti)=0.005时,(Yb,N)-TiO2粉体在普通日光灯下对亚甲基蓝在5 h内的光催化降解效率达93.55%,明显高于同等条件下P25的降解率45.72%。     

Highly transparent Bi2MoO6- and Bi2WO6-polymer nanocomposites

A combined method of precipitation, phase transfer into organic solvent, solvothermal treatment and subsequent in situ polymerization was used to integrate nanocrystalline Bi2MoO6- and Bi2WO6-particles into a polymer matrix of poly-laurylacrylate. The presented method offers a new and gentle way to produce highly transparent bulk nanocomposites containing evenly distributed Bi2MoO6- and Bi2WO6-nanoparticles. Characterization results of DLS-, XRD-, REM- and TEM-measurements are presented as well as solid state UV/VIS-measurements of the particles. The transparent nanocomposites were characterized using UV/VIS-spectroscopy and ellipsometry. All composites show a good transmission in the range from 800-400 nm. The particle content of the nanocomposites was measured with TG-measurements.     

Bi2WO6/NH2-MIL-88B(Fe) heterostructure: An efficient sunlight driven photocatalyst for the degradation of antibiotic tetracycline in aqueous medium

The development of highly efficient sunlight assisted photocatalysts has been acknowledged as a promising strategy for the enhanced degradation of antibiotics. In this work, effectual fabrication of a novel Bi₂WO₆/NH₂-MIL-88B(Fe) heterostructure was carried through solvothermal route. The structural, morphological and compositional analysis was done by employing number of analytical techniques, namely XRD, FTIR, HRTEM, FESEM, XPS, PL and BET surface area. The prepared Bi₂WO₆/NH₂-MIL-88B(Fe) heterostructure was utilized as an efficient photocatalyst towards decomposition of a typical antibiotic tetracycline (TC) in aqueous medium. It was found that Bi₂WO₆/NH₂-MIL-88B(Fe) heterostructure exhibited improved degradation efficiency of about 89.4% within 130 min of solar illumination than pristine NH₂-MIL-88B(Fe) under optimized parameters i.e. initial drug solution of 10 mg/L concentration at pH 4 with 0.35 g/L dose of catalyst. Moreover, adsorption studies, kinetics and isotherms of adsorption on TC were also investigated. Results revealed that adsorption kinetics followed pseudo 2nd order model and isotherm data fitted well with Freundlich model (R² = 0.99803) as compared to Temkin and Langmuir. The ameliorating photocatalytic capability could be primarily accredited to the heterojunction created among Bi₂WO₆ and NH₂-MIL-88B(Fe) which facilitated the charge transfer and thus determines high catalytic efficiency. The enhanced photocatalyic effect was further verified by electrochemical impedance and photocurrent studies. The prepared composite also exhibited longer carrier lifetime (140.72 ns) compared to pure MOF (132.05 ns) and Bi₂WO₆ (136.39 ns). Further, based on the radical trapping investigations, role of superoxide radicals was dominant and detailed mechanism was proposed for the photocatalytic degradation process. The major intermediates formed during the course of reaction were also examined using LCMS analysis. The photodegradation was also carried over simulated hospital wastewater by the prepared heterostructure and 60.5% TOC was obtained under solar light in 390 min. Moreover, the synthesized heterostructure showed good recyclability up to three cycles depicting good stability.     

Novel Mo/Bi2MoO6/Bi3ClO4 heterojunction photocatalyst for ultra-deep desulfurization of thiophene under simulated sunlight irradiation

In the present work, a visible-light-driven Mo/Bi₂MoO₆/Bi₃ClO₄ heterojunction photocatalyst was fabricated via the Pechini sol–gel process. The type and amount of gelling agent, chelating agent and mole ratio of chelating agent to total metals were balanced to generate ultrafine nanoparticles. The Mo/Bi₂MoO₆/Bi₃ClO₄ nanocomposite as a novel photocatalyst not only exhibited an excellent visible-light photocatalytic desulfurization performance of thiophene (~97%), but also had better photodesulfurization efficiency than Mo/Bi₂MoO₆ and Bi₃ClO₄ nanostructures. The ultra-deep photocatalytic desulfurization performance of the Mo/Bi₂MoO₆/Bi₃ClO₄ nanocomposite can be attributed to the strong visible-light absorption, unique nanostructures, high separation and low recombination of electron–hole pairs due to the as-formed heterojunctions. Furthermore, a photocatalytic desulfurization mechanism was elucidated via radical trapping experiments, which revealed that the ^?O₂^? and ^?OH radicals play a key role in the photocatalytic desulfurization process.     

Novel flower-like (Bi(Bi2S3)9I3)2/3 nanostructure as efficient photocatalyst for photocatalytic desulfurization of benzothiophene under visible light irradiation

Here, we report the preparation of hierarchical flower-like (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures that acts as a strong photocatalyst in the desulfurization of benzothiophene. We optimized the reaction time, type of capping agent and reflux temperature to tune the shape of porous flower-like (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures to achieve the highest desulfurization performance. We investigated the characteristic shape, size, purity, and optical response of the flower-shape nanostructures using XRD, EDS, FESEM, UV–Vis-DRS analysis. The flower-like (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures showed a significant photocatalytic property in desulfurization of benzothiophene as a model fuel. The hierarchical flower-like (Bi(Bi₂S₃)₉I₃)_2/3 photocatalyst with an energy gap of 1.15 eV, exhibits a 92% photocatalytic desulfurization performance after 2 h of visible light irradiation. The (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures show a high photocatalytic reproducibility after 4 rounds of exposure. We proposed a photo-oxidation mechanism based on the active species scavenging, which revealed the role of photo-produced h⁺ and O₂^? species as essential in the photocatalytic desulfurization process. These findings provide a new prospect and design strategy for the development of efficient photocatalysts in desulfurization process.     

Enhanced field-emission from SnO2:WO(2.72) nanowire heterostructures

The field-emission properties of SnO(2):WO(2.72) hierarchical nanowire heterostructure have been investigated. Nanoheterostructure consisting of SnO(2) nanowires as stem and WO(2.72) nanothorns as branches are synthesized in two steps by physical vapor deposition technique. Their field emission properties were recorded. A low turn-on field of ~0.82 V/μm (to draw an emission current density ~10 μA/cm(2)) is achieved along with stable emission for 4 h duration. The emission characteristic shows the SnO(2):WO(2.72) nanoheterostructures are extremely suitable for field-emission applications.     

A novel Z-scheme Bi4O5I2/NiFe2O4 heterojunction photocatalyst with reliable recyclability for Rhodamine B degradation

Construction of heterojunction with reusability is one of the effective ways to avoid secondary pollution and strengthen photocatalysis. Herein, a magnetically recyclable Z-scheme Bi₄O₅I₂/NiFe₂O₄ heterojunction photocatalyst was successfully fabricated by a two-step hydrothermal method. Through adjusting the theoretical molar proportion of NiFe₂O₄ to Bi₄O₅I₂, it was verified that the optimal composite could decompose 98.5% Rhodamine B (RhB, 10 mg/L) within 60 min under simulative sunlight and 98.1% RhB within 80 min under visible light. According to the characterizations, the superior performance was mainly associated with the small band gap energy (2.44 eV) and efficient separation of photo-generated electrons and holes caused by the formation of heterojunction. Meanwhile, the enlarged specific area (27.6 m²/g) provided many adsorptive sites and active sites to improve the reaction further. Moreover, the trapping experiment indicated that the photodegradation involved O₂^–, OH and h⁺. After confirming the reliable activity, reusability and stability of the photocatalyst, an inferred mechanism was shown. In summary, the design of this magnetically recyclable Z-scheme Bi₄O₅I₂/NiFe₂O₄ heterojunction photocatalyst can become a new choice to purify wastewater.     

一步法制备石墨烯复合花状钨酸铋光催化剂

采用一步水热法合成石墨烯复合花状钨酸铋高效可见光光催化剂。降解甲基橙的性能实验结果表明, 与单纯的Bi₂WO₆相比, 所有Bi₂WO₆-rGO复合光催化剂表现出更高的光催化性能。其中, Bi₂WO₆-rGO (0.5wt%)具有最高的光催化活性, 其速率常数达到5.0×10^-2 /min, 是纯Bi₂WO₆的1.7倍。增强光催化性能的原因归结为以下两方面的协同作用: 还原石墨烯在复合光催化剂中起到了电子快速传输作用; 石墨烯提供了有利于吸附有机污染物的大比表面积。本研究可以为设计与合成高性能石墨烯基光催化剂提供新的思路。     

Photocatalytic activities of Mo-doped Bi2WO6 three-dimensional hierarchical microspheres

The Mo-doped Bi₂WO₆ three-dimensional (3D) hierarchical microspheres from nanoplates have been synthesized by a hydrothermal route. The products were characterized in detail by multiform techniques: X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDS), scanning electron microscopy (SEM), and UV-vis absorption spectrum. The results of the photocatalytic degradation of Rhodamine-B (RhB) in aqueous solution showed that molybdenum ions doping greatly improved the photocatalytic efficiency of Bi₂WO₆ 3D hierarchical microspheres. The Mo-doped Bi₂WO₆ microspheres with atomic ratio of Mo-W of 0.05 had the best activity in photodegradation of RhB in aqueous solution under 500 W Xe lamp light irradiation.     

超声协同微球型Bi2O2CO3降解罗丹明B的研究

Bi_2O_2CO_3是一种Bi类半导体催化剂,文章研究了它的超声催化性能。首先,采用水热法制备了微球型的Bi_2O_2CO_3,利用X射线衍射(X-ray Diffraction, XRD)、扫描电子显微镜(Scanning Electron Microscope, SEM)、紫外-可见漫反射光谱对样品的晶体结构、微观形貌、光学特性进行了表征。然后,以罗丹明B(Rh B)作为模型污染物,通过研究超声催化降解罗丹明B来评测Bi_2O_2CO_3的超声催化性能。研究了催化剂的浓度(Ccatalytic)、初始罗丹明B染料的浓度(CRhB)和超声功率(P)等实验因素对超声催化降解效率的影响。得出在Ccatalytic=3 g·L-1,CRhB=10 mg·L-1和P=400 W条件下降解罗丹明B的效率最高,其最高降解效率可以达到91.7%。     

绣球状钨酸铋纳米晶体生长机理的研究

以Bi(NO3)3.5H2O、Na2WO4.2H2O为原料,NaOH为矿化剂,采用水热法合成Bi2WO6纳米晶体,并使用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)对其进行表征,分析了反应时间和温度对晶体生长的影响。利用Johnson-Mehl-Avrami(JMA)方程对不同温度下Bi2WO6的水热晶化过程进行动力学模拟分析。结果表明,120～200℃范围内的Avrami指数n随水热反应温度的升高而增长,n介于0.5～1之间。Bi2WO6纳米晶体的水热晶化过程表现为较低温度下的扩散控制生长以及较高温度(T>160℃)下的相界控制生长。同时,Bi2WO6纳米晶体的生长经历了一个成核、积聚和熟化的过程。     

Synergetic piezo-photocatalytic effect in ultrathin Bi2WO6 nanosheets for decomposing organic dye

In this work, ultrathin Bi₂WO₆ nanosheets (BWO NS) was synthesized by two-step hydrothermal process, which exhibited a lamellar structure with a thickness of about 10 nm and a transverse length of 100–400 nm. The piezoelectric properties and photocatalytic properties of BWO NS were coupled successfully, and the piezo-photocatalytic activity was studied through the decomposition of 10 mg L^??1 Rhodamine B (Rh B). The results showed that the degradation ratio of BWO NS for Rh B was about 98.39% within 70 min, which was higher than that of sole piezocatalysis (48.98%) and photocatalysis (61.84%). There was no significant degradation of the catalytic performance observed after being recycled four times. Moreover, piezo-photocatalysis of BWO NS efficiently produced active radicals that the major reactive oxidative species (ROS) such as superoxide radicals (·O₂^?) and hydroxyl radicals (·OH) were confirmed by radical capture experiment. The excellent piezo-photocatalysis of BWO NS endows it the potential application for decomposing organic dye via making full advantage of the vibration and solar energy present in natural environments.

     

可见光下Bi2WO6纳米片高效光降解四环素的机理研究

作为一种窄带隙半导体材料, Bi₂WO₆在光催化降解有机污染物上具有很大的应用潜力。研究采用水热法合成了Bi₂WO₆纳米片, 并在可见光照射下研究其对四环素的光催化降解。利用XRD、FESEM、TEM、吸收光谱等对材料进行结构和形貌的表征。实验发现, 在pH=8的四环素溶液中加入50 mg Bi₂WO₆纳米片, 可见光照射130 min 后, 85%的四环素（50 mL, 50 mg/L）被降解。实验还研究了Bi₂WO₆纳米片光电化学性质, 通过加入不同的自由基捕获剂研究了光催化降解四环素的反应机理。结果表明, Bi₂WO₆纳米片具有较高的电子密度和电子空穴分离效率是其具有良好光催化性能的原因。