Facile one-pot synthesis of a BiOBr/Bi2WO6 heterojunction with enhanced visible-light photocatalytic activity for tetracycline degradation

Photocatalytic removal of tetracycline (TC) from the wastewater is of great value in the chemical and environmental engineering field. Here, we introduced a facile one-step method for the synthesis of BiOBr/Bi₂WO₆ heterojunctions by using cheap CTAB as the Br source. We showed the possibility of our method to fine-tune the content of BiOBr in the produced BiOBr/Bi₂WO₆ by simply changing the dosage of cetyltrimethylammonium bromide (CTAB), providing a platform for the delicate tuning of the visible-light absorbance ability of the composites. With a suitable heterojunction structure of BiOBr/Bi₂WO₆-0.2, it exhibited an ultrarapid photocatalytic activity towards TC (20 mg·L^-1), with a competitive removal efficiency of 88.1% within 60 min and an ultrahigh removal rate of 0.0349 min^-1. It could also be robustly recycled for at least 5 cycles with slight removal efficiency loss. We demonstrated that this exciting photocatalytic performance was due to the highly decreased recombination of photoinduced electrons and holes on our composites by constructing this heterojunction structure, and the resulting OH and contributed to the effective degradation of TC to CO₂.     

Rational manipulation of lattice strain to tailor the electronic and optical properties of nanostructures

Optoelectronic devices with different energy ranges requires materials with different band gaps, sometimes even within the same device. Structural distortions within the nanostructures produce lattice strains, which can change physical properties. However, the detailed knowledge of lattice strains in nanostructures remains confusing. Here, we rationally design and employ a simple and effective scheme to fabricate strained BiVO₄/ZnS nanostructures. Lattice strain originates from lattice distortion caused by the intentional incorporation of metal ions into the inner layer of nanostructures. Experimental findings show that the maximum and minimum band gap energies of BiVO₄/ZnS nanostructures are 2.87 and 2.79 eV under the tensile strain, which are increased by 4.4% and 1.4%, respectively, compared with that of the reference sample (2.75 eV). Impressively, BiVO₄/ZnS nanostructures exhibit tunable dual emission behavior, and lattice strain significantly changes the electron band structure of the nanostructures. In addition, we identify the composite structure of BiVO₄/ZnS nanomaterials and elucidate the mechanistic origin of regulation of the optical and electronic properties by lattice strain in combination with experimental and density functional theory calculations. These results provide a deep understanding of the relationship between lattice strain and optical properties and indicate that strain engineering can be potentially used in the design of nanostructures.     

Novel Lu-doped Bi2WO6 nanosheets: Synthesis,growth mechanisms and enhanced photocatalytic activity under UV-light irradiation

Polycrystalline systems of lutetium doped bismuth tungstates Bi₂WO₆: Lu (Lu at% 0, 2, 5 and 8) were synthesized using the coprecipitation method, followed by thermal treatment at 500 °C. The Bi₂WO₆:Lu samples were characterized by X-Ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-Ray analysis (EDS) and UV–vis diffuse reflectance spectra (DRS). The XRD and SEM analyses showed that the as-prepared samples crystallized in the same orthorhombic structure and consist of agglomerated nanosheets. To characterize the photocatalytic activities, UV–visible spectrometry was used to analyze the evolution of Rhodamine B photodegradation in presence of the Bi₂WO₆: Lu photocatalysts. The characteristic absorption band of Rhodamine B at 554 nm shifted to lower wavelengths under UV irradiation. The pure Bi₂WO₆ and the 5% Lu doped Bi₂WO₆ photocatalysts presented the lowest and highest efficiencies, respectively. An interpretation of improved photocatalytic efficiencies was proposed.     

A facile hydrothermal synthesis of visible-light responsive BiFeWO6/MoS2 composite as superior photocatalyst for degradation of organic pollutants

In the present study, we have fabricated a new Z-scheme BiFeWO₆/MoS₂ composite for photocatalytic elimination of organic contaminants from the waste-water. A series of BiFeWO₆/MoS₂ composites were obtained by changing the amounts of BiFeWO₆ from 1 to 10 mg through a facile hydrothermal method. The phase structures and morphologies of these BiFeWO₆/MoS₂ composites were analyzed by SEM, HR-TEM, XRD, UV–vis DRS, element mapping and XPS techniques. Afterward, the dye-degradation experiments were conducted for the removal of Rhodamine B (RhB) using as-obtained BiFeWO₆/MoS₂ composite samples under visible-light illumination to evaluate their photocatalytic activity. It is found that the BiFeWO₆/MoS₂ composites exhibited great photocatalytic behavior than the pure BiFeWO₆ and MoS₂ samples. In particular, the BiFeWO₆/MoS₂ composite with 5 mg of BiFeWO₆ showed a quickly complete photocatalyst degradation ability of RhB in 75 min with high photo-stability and reusability behavior. This superior catalytic response of BiFeWO₆/MoS₂ composite may be contributed by its high light harvesting capacity as well as fast separation and movement of photo-generated electron-hole pairs. This proposed BiFeWO₆/MoS₂ composite is a very promising photocatalyst for environmental remediation work.     

CoPcS/Bi_2WO_6复合材料的制备及其光催化性能

采用超声复合方法制备了磺化酞菁钴/钨酸铋纳米复合材料,以四环素为降解对象,考察了CoPcS/Bi2WO6复合材料的光催化性能。结果表明,当磺化酞菁钴的掺杂质量为1%时,CoPcS/Bi2WO6对四环素具有较好的光催化活性,反应60 min后,降解率可达80%左右。     

An S-scheme heterojunction of Bi2WO6/AgIO3 nanocomposites that enhances photocatalytic degradation of Rhodamine B and antifouling properties

Bi₂WO₆/AgIO₃ (BWO/AIO) nanosheet composites were constructed by a two-step hydrothermal method. The structure, morphology and photoelectrochemical properties of the composites were characterized by X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (UV-DRS), transmission electron microscopy (TEM), impedance, X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The constructed photocatalyst composites exhibited the best photocatalytic performance at a molar ratio of BWO/AIO-0.8. In addition, there was complete degradation of RhB by the BWO/AIO-0.8 in 180 min under illumination, and the bactericidal rates were 99.10%, 97.32% and 96.3% for P. aeruginosa, S. aureus and E. coli, respectively, in 60 min. Based on the energy band structure of the semiconductor and radical trapping experiments, the S-scheme heterojunction was associated with the enhanced photocatalytic properties.     

Bi2WO6的静电纺丝法制备及其光催化性能

以聚乙烯吡咯烷酮(PVP)、钨酸铵[(NH4)10W12O41]和柠檬酸铋铵(C6H13BiN2O7.H2O)为原料,利用静电纺丝技术成功制备了PVP/C6H13BiN2O7.H2O-(NH4)10W12O41(简写为PVP/BiWO)前躯体,对PVP/BiWO缓慢控温处理制得Bi2WO6。采用差热-热重分析(TG-DTA)、X射线粉末衍射(XRD)、傅里叶红外光谱(FTIR)、X-射线光电子能谱(XPS)、场发射扫描电镜(FE-SEM)、紫外可见漫反射(UV-Vis-NIR/DR)等分析手段研究热处理温度对材料结构的影响,通过罗丹明B(RhB)光降解反应研究其光催化性能。结果表明,可见光照射下,热处理温度600℃时材料的光催化活性最好,并探讨了其光催化机理。     

Thiourea assisted one-pot easy synthesis of CdS/rGO composite by the wet chemical method: Structural,optical, and photocatalytic properties

We report on the synthesis of CdS/reduced graphene oxide (rGO) composite by a wet chemical method. Thiourea was used both as a sulfur source and as a reducing agent to convert graphene oxide to rGO. The structural and morphological confirmation for the reduction of graphene oxide and the formation of the CdS/rGO composite was demonstrated by X-ray diffractometry, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy analyses. Photoluminescence spectra of the composite exhibited a more efficient luminescence quenching in comparison with pure CdS nanoparticles. The composite demonstrated 99% photodegradation of methyl orange under UV irradiation, which is much superior than the photodegradation of methyl orange under similar conditions exhibited by CdS nanoparticles (72%).     

Controllable synthesis, optical and photocatalytic properties of CuS nanomaterials with hierarchical structures

The controlled synthesis of CuS nanomaterials with hierarchical structures has been realized by chemical synthesis between copper nitrate trihydrate and thiourea via a solvothermal route. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to characterize the products. It was shown that CuS nanomaterials with hierarchical structures were composed of numerous nanoplates or nanorods. Experiments demonstrated that the morphologies of CuS nanomaterials were significantly influenced by reaction temperature, growth time and sulfur sources. A growth model was proposed for the selective formation of CuS hierarchical structures. The optical properties of the CuS hierarchical structures were investigated by ultraviolet-visible spectroscopy and photoluminescence spectroscopy. The ultraviolet-visible spectrum had a broad absorption in the visible range and the photoluminescence spectrum showed a strong green emission. Photocatalytic performance of the CuS hierarchical structures was evaluated by measuring the decomposition rate of methylene blue solution under natural light. The CuS hierarchical structures showed good photocatalytic activity.     

Construction of g-C3N4/TiO2/Ag composites with enhanced visible-light photocatalytic activity and antibacterial properties

In this study, the multifunctional carbon nitride based composite graphitic-C₃N₄ (g-C₃N₄)/TiO₂/Ag was prepared through a simple and efficient vacuum freeze-drying route. TiO₂ and Ag nanoparticles were demonstrated to decorate onto the surface of g-C₃N₄ sheet. In the ultraviolet–visible absorption test, a narrower band gap and red-shift of light absorption edge were observed for g-C₃N₄/TiO₂/Ag compared to pristine g-C₃N₄ and single-component modified g-C₃N₄/TiO₂. The photodegradation property of g-C₃N₄/TiO₂/Ag was investigated toward the degradation of methylene blue (abbreviated as MB) under the irradiation of visible light. These results indicated that the degradation performance of organic dyes for g-C₃N₄/TiO₂/Ag was obviously improved compared with g-C₃N₄/TiO₂ and g-C₃N₄. The reaction rate constant of MB degradation for g-C₃N₄/TiO₂/Ag was 4.24 times higher than that of pristine g-C₃N₄. In addition, such rationally constructed nanocomposite presented evidently enhanced antibacterial performance against the Gram-negative Escherichia coli. Concentration dependent antibacterial performance was systematically investigated. And 84% bacterial cell viability loss had been observed at 500 μg/mL g-C₃N₄/TiO₂/Ag within 2 h visible light irradiation.     

微波蚀刻法制备RGO-BiOCl/Bi2WO6异质结型催化剂及其催化性能

采用改进的Hummers法制备氧化石墨烯,以Bi（NO₃）₃·5H₂O、KCl、Na₂WO₄为原料,采用微波蚀刻法在其基础上负载BiOCl/Bi₂WO₆。通过X射线衍射（XRD）、扫描电镜（SEM）、比表面积测定仪（BET）、紫外-可见漫反射（UV-Vis）及透射电镜（TEM）等对所制备的催化剂进行表征。以RhB作为目标降解物,考察其光催化性能。结果表明,当RGO：RGO-BiOCl（质量比）为2%、Bi₂WO₆：RGO-BiOCl/Bi₂WO₆（摩尔比）为50%,降解率可达94.6%,远高于纯BiOCl。     

掺杂型Bi2WO6光催化剂的制备及其光催化性能研究

复合氧化物Bi2WO6可作为一种高效的光催化材料,但Bi2WO6的光生电子空穴对复合率高,分离困难,导致对光的吸收能力下降,光催化效率降低。金属Cu和Ag是良好的光催化剂助剂,能有效降低光催化剂的光生电子空穴对复合率,改善催化剂的光吸收性能。采用水热法制备金属Cu和Ag掺杂的可见光催化剂Bi2WO6,并进行X射线衍射、扫描电子显微镜、紫外-可见光谱和比表面积表征。结果表明,掺杂的金属离子并未进入Bi2WO6晶格内部,只是负载于Bi2WO6表面。掺杂金属后,Bi2WO6的吸收边带变宽,吸光强度变强,比表面积显著增加。以模拟含酚废水为处理对象,考察掺杂型Bi2WO6对苯酚光催化降解效果的影响。实验结果表明,Cu-Bi2WO6光催化剂在光照作用下对苯酚有降解作用,随着光照时间的延长,苯酚的降解程度不断提高,在空气通入量为25 mL·min-1和400 W金卤灯下光照180 min,Cu-Bi2WO6和Ag-Bi2WO6对10 mg·L-1的模拟含酚废水基本降解完成。     

Hydrothermal synthesis of CdS/CoWO4 heterojunctions with enhanced visible light properties toward organic pollutants degradation

Effective solar energy harvesting and charge carrier separation are two key factors of the photocatalysis system. In this work, the heterojunction photocatalyst of CdS/CoWO₄ was fabricated by a facile hydrothermal method. Compared with the pristine CdS and CoWO₄, the CdS/CoWO₄ heterojunction photocatalyst showed enhanced photocatalytic activity for the methylene blue (MB) degradation under visible light irradiation. Particularly, the sample with molar ratio of CdS:CoWO₄ (sample C2) controlled at 3:5 showed the highest MB degradation ratio (83%) in 1 h among all samples, which is about 3 times over the pure CdS and 8 times over pure CoWO₄, respectively. The greatly enhanced photocatalytic activity (3–8 times) of CdS/CoWO₄ is due to the efficient separation of electron-hole pairs by the heterojunction structure and strong visible light absorption of CdS. This work provides a new insight into the application of tungstate-based heterojunction photocatalysts in environmental remediation.     

A novel nano-sized MoS2 decorated Bi2O3 heterojunction with enhanced photocatalytic performance for methylene blue and tetracycline degradation

In this paper, MoS₂ was used as a band-suitable semiconductor to construct the Bi₂O₃/MoS₂ heterostructured photocatalysts for the first time via a deposition-hydrothermal method. The XRD, SEM and HRTEM analysis indicated that the surface of Bi₂O₃ was decorated with MoS₂ nanoparticles and Bi₂O₃/MoS₂ heterojunctions were formed. The performances on photocatalytic degradation of methylene blue (MB) and tetracycline (TC) were evaluated under visible light irradiation. The results demonstrated that the Bi₂O₃/MoS₂ heterojunctions displayed remarkably improved photocatalytic activity for both MB and TC degradation, compared to the base material (Bi₂O₃). Specifically, as the molar ratio of MoS₂ was 23.81%, the obtained Bi₂O₃/MoS₂-23.81 heterojunctions exhibited promising photocatalytic activities, and approximately 100% MB and 97% TC were degraded within 100 min, respectively. The superior photocatalytic activity was mainly attributed to its large surface area, high visible-light harvesting and the efficient separation of photogenerated electrons and holes caused by the unique heterojunction architecture. Notably, the Bi₂O₃/MoS₂ heterojunctions showed remarkable stability in recycling photocatatlytic experiments. The active species trapping and terephthalic acid (TA) fluorescence experiments indicated that the •OH was the major reactive oxidizing species for MB degradation. Furthermore, the intermediates were detected by UPLC-MS spectrometry and the possible degradation pathways for MB and TC were proposed. Finally, a possible reaction mechanism of Bi₂O₃/MoS₂ heterojunctions for the photodegradation MB was also proposed. This interesting interfacial architecture strategy will provide useful insights for designing and fabricating new class of binary heterojunctions with high-efficient photocatalytic activity towards practical application.     

One-pot synthesis of 3D porous Bi7O9I3/N-doped graphene aerogel with enhanced photocatalytic activity for organic dye degradation in wastewater

The compound Bi₇O₉I₃ has been considered as a promising candidate for organic dye degradation in wastewater, but it has relatively low photocatalytic activity and difficulties in the recycling processes. In this work, a novel floating 3D porous Bi₇O₉I₃/N-doped graphene aerogel (Bi₇O₉I₃/NGA) composite was successfully synthesized through a facile hydrothermal route. The Bi₇O₉I₃/NGA composite exhibited highly enhanced photocatalytic performance toward degrading rhodamine B under visible-light irradiation, which increased 6.0 and 2.3 times compared with the Bi₇O₉I₃ and Bi₇O₉I₃/GA, respectively. The enhancement of photocatalytic degradation activity could be ascribed to the extensively promoted charge generation and migration efficiency, visible light utilization ability and reactive oxygen species production. Besides, the special 3D macroscopic block structure of Bi₇O₉I₃/NGA allowed it to float, making it easy to recycle. The photocatalytic degradation efficiency of Bi₇O₉I₃/NGA composite still could reach up to 92.7% after four consecutive cycles and presented satisfactory stability and reusability. Moreover, a possible photocatalytic degradation mechanism was revealed by radical species trapping and semi-quantitative analyses experiments.     

Simple fabrication and photocatalytic activity of S-doped TiO2 under low power LED visible light irradiation

A series of S-doped TiO₂ with visible-light photocatalytic activity were prepared by a simple hydrolysis method using titanium tetrachloride (TiCl₄) and sodium sulfate (Na₂SO₄) as precursors. The photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV–vis diffuse reflectance spectrophotometer (UV–Vis DRS), and X-ray photoelectron spectroscopy (XPS). With the doping of S, photocatalysts with small crystal size, high content of anatase phase were obtained. The result showed that S-doped TiO₂ demonstrate considerably high photoactivity under low power visible LED light irradiation, while undoped TiO₂ and the Degussa P25 have nearly no activity at all. The possible mechanism of S-doped for the visible-light activity was discussed.     

Textural/structural evolution of cube/cauliflower-like MgSn(OH)6 nanophotocatalyst with excellent photocatalytic degradation of toxic dye pollutants

In this research, Mg–Sn hydroxide (MgSn(OH)₆) nano semiconductor was synthesized using three different routes to investigate the texture/structure of MgSn(OH)₆ on the photocatalytic properties of MgSn(OH)₆ in RhB degradation. The nano semiconductors were characterized using XRD, FE-SEM, TEM, EDX, BET-BJH, DRS, PL, and the pHpzc. Morphological analyses for sono-hydrothermal sample showed 3D cubic microstructure. However, 3D cauliflower-like morphology was observed in the other samples. XRD analysis demonstrated the higher crystallinity of the sono-hydrothermal sample. BET-BJH analysis showed that the specific surface area and pore volume of this sample were 138.7 m²/g and 0.111 cm³/g, respectively. DRS analysis showed band-gap energy of about 4.1eV for all samples. Photocatalytic degradation experiments were conducted under UV-C light irradiation. The results demonstrated the advantage of the sono-hydrothermal sample owing to the cubic morphology, higher crystallinity and S_BET, and lower recombination rate of the charge carriers. The photocatalytic degradation performance of the sample was evaluated in degradation of RhB, AO7, MO, and MB, which were 96, 93, 60, and 40%, respectively. The reusability study of sono-hydrothermal and hydrothermal samples was conducted in which the sono-hydrothermal sample showed higher efficiency and stability in four successive runs.     

石墨烯/TiO2复合材料光催化降解有机污染物的研究进展

石墨烯是一种新型的碳纳米材料,具有超大的比表面积和优良的导电性能,将石墨烯与TiO₂复合可显著提高复合材料的光催化性能,在光催化领域具有广泛的应用前景。主要介绍了石墨烯/TiO₂复合纳米材料的制备方法以及在光催化降解有机污染物方面的应用,并分析了石墨烯/TiO₂复合材料促进光催化机理,最后对石墨烯/TiO₂复合光催化剂未来的发展趋势提出了展望。     

Rational design of hyperbranched 3D heteroarrays of SrS/CdS: synthesis, characterization and evaluation of photocatalytic properties for efficient hydrogen generation and organic dye degradation

Hyperbranched 3D SrS/CdS nanostructures were synthesized using a one pot hydrothermal method. Transmission Electron Microscopy (TEM) and Field Emission-Scanning Electron Microscopy (FE-SEM) analysis showed the formation of flower-like structure and the crystalline phase was confirmed by powder X-ray diffraction. The prepared 3D SrS/CdS exhibited improved photocatalytic activity for water splitting leading to H(2) generation (AQY 10%) and nearly complete degradation of methyl orange (MO) dye. The dye degradation followed first order kinetics and the apparent reaction rate constant (k(app)) was 0.136 min(-1). The present 3D SrS/CdS structure promise to be efficient photocatalysts due to (i) the facile intersystem charge transfer resulting from their band alignment (ii) enhanced specific surface area and (iii) crystallinity.