The effect of the annealing atmosphere on the properties of Sr2Bi4Ti5O18 ferroelectric thin films

The Sr₂Bi₄Ti₅O₁₈ (SBT-5) ferroelectric thin films were prepared on Pt/Ti/SiO₂/Si substrate using the sol-gel method and annealing in oxygen, air, and nitrogen. Their properties were measured. After annealing in oxygen, the films showed good crystallization and a larger average grain size of approximately 34.05 nm. XPS analysis clearly showed that annealing in oxygen inhibited the generation of oxygen vacancies in the films, which contributed to the melioration of the ferroelectric properties. The remanent polarization was 20.09 μC/cm² and the coercive field was 75 kV/cm. When the electric field was 15 kV/cm, the leakage current density was approximately 3.88 × 10⁻⁷A/cm², while the Ohmic conduction was the dominating leakage mechanism. Because the content of the oxygen vacancy in the samples annealed in oxygen atmosphere was lower, the fixing effect on the domain structure was weaker and the volume effect was not obvious, so the aging degree of the samples was low. The larger relative dielectric constant was 742, while the dielectric loss was 0.037 when the test frequency was 2.0 × 10⁵ Hz.     

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

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.     

Enhanced photocatalytic activity of nonstoichiometric crystalline TaO2F and Ta2O5 with carbon coating

Pure and carbon-coated tantalum-based oxides photocatalysts were synthesized via the mesocrystalline precursor transformation method by annealing pure and polydopamine-coated (NH₄)₂Ta₂O₃F₆ mesocrystals in Ar. The oxygen-poor atmosphere thermal annealing process assisted the formation of nonstoichiometric TaO₂F mesocrystals with more F and Ta₂O₅ nanorods with oxygen vacancies and the associated lower valence state Ta ions (Ta⁴⁺). Furthermore, the carbon coating, decomposed from coated polydopamine, helped to control their particle size within 100 nm by isolating the connection of (NH₄)₂Ta₂O₃F₆ subunits. Hence, as-synthesized products, particularly carbon-coated Ta₂O₅ nanosheets, owning large surface area (67.6 m² g^?1), fine particle size (<100 nm), excellent electronic conductivity, decreased bandgap energy, enhanced and extended absorption in the visible range, exhibited preferable photocatalytic activity in the photodegradation of methylene blue, reaching a 76.54 % and 41.71 % removal under ultraviolet and visible light illumination, suggesting a promising candidate for wide-range responsive photocatalytic applications.     

Novel 0D/2D Bi2WO6/MoSSe Z-scheme heterojunction for enhanced photocatalytic degradation and photoelectrochemical activity

The catalytic activity of a single catalyst could be optimized by constructing a Z-scheme heterojunction structure with another adaptive material. 0D Bi₂WO₆ nanoparticles exhibit good oxidation ability, while 2D MoSSe nanoplates with low internal resistance show excellent reduction ability. Herein, novel 0D/2D Bi₂WO₆/MoSSe Z-scheme heterojunction catalysts (BMSS) with different Mo: Bi molar ratios were developed by combining the advantages of pure Bi₂WO₆ and MoSSe. The matched energy bands may provide the possibility to construct heterojunction, and the internal electric fields could facilitate the separation and transmission of internal carriers. Energy band structure analyses and electron spin resonance (ESR) results have further confirmed the existence of the above Z-scheme heterojunction structure and internal electric field. More importantly, as-prepared BMSS catalysts were proved to have excellent oxidation and reduction ability from photocatalytic and photoelectrochemical results. With an optimized MoSSe loading ratio of 3.66%, the BMSS3 catalyst showed 4.13 times of photocurrent density than that of pure Bi₂WO₆ and displayed an excellent degradation rate (0.0377 min^?1). It can be concluded that BMSS catalysts will have promising applications in photoelectrochemistry and photocatalysis.     

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。     

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。     

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.     

Mesoporous yolk-shell structure Bi2MoO6 microspheres with enhanced visible light photocatalytic activity

Mesoporous yolk-shell structure Bi₂MoO₆ (BMO-YS) microspheres were successfully synthesized via a facile solvothermal route in Bi₂MoO₆ precursor solution. The morphology, structure and photocatalytic performance of the BMO-YS in the degradation of Rhodamine B (RhB) were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nitrogen adsorption–desorption, UV–vis absorption spectroscopy and electrochemical impedance spectra, respectively. The as-prepared BMO-YS mainly consists of microspheres with diameters of about 1.5 μm. The photocatalytic studies reveal that the BMO-YS not only exhibits optimum photocatalytic performance, which may be attributed to the excellent charge separation characteristics and the enhanced light absorption offered by its unique yolk-shell structure, but also possesses excellent recyclability for photocatalysis.     

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。     

等离子体改性TiO2/WO3/Bi2WO6纳米 复合材料及其可见光催化活性

以二水合钨酸钠和五水合硝酸铋为原料，通过优化水热法反应温度制备了WO3/Bi2WO6纳米片，将其与锐钛矿型TiO2纳米颗粒复合制备了可见光催化性能优良的TiO2/WO3/Bi2WO6复合光催化剂，并采用一种高密度管状等离子体放电装置对其进行表面改性。利用XRD、SEM、TEM、HRTEM、XPS、UV-Vis DRS、PL对样品进行了表征和分析，考察了其在可见光下降解亚甲基蓝的光催化性能。结果表明，当水热温度为120 ℃时，WO3/Bi2WO6纳米片具有较好的光催化性能；TiO2/WO3/Bi2WO6复合催化剂中掺入TiO2质量分数为10.7%时，所得三元复合材料的光催化性能远优于WO3/Bi2WO6纳米片；经等离子体改性处理后，三元复合材料的吸收边向可见光红移，放电输入功率的增加有助于提高复合材料的光催化活性，当放电电压为1.1 kV时，复合材料的降解速率常数分别是未处理样品和WO3/Bi2WO6的2.2倍和3.9倍。     

Fabrication of TiO2 nanofibers assembled by Bi2WO6 nanosheets with enhanced visible light photocatalytic activity

A series of Bi₂WO₆/TiO₂ nanofibers (BT NF) hierarchical photocatalysts were synthesized by a facile two-step strategy consisting of electrospinning technique and subsequent solvothermal method. The results showed that the secondary two-dimensional Bi₂WO₆ nanosheets were uniformly assembled onto the surface of the TiO₂ NF. It was also verified that the density of Bi₂WO₆ nanosheets could be tailed by controlling the precursor concentration during the solvothermal process. Photocatalytic tests demonstrated that BT NF with a low concentration of precursor (S1) possessed a much higher visible light degradation rate for Rhodamine B than TiO₂ NF, Bi₂WO₆ and their mixture. The enhanced photocatalytic activity of S1 was ascribed to the extension of the light absorption region induced by the introduction of narrow band gap Bi₂WO_6, and the formation of heterojunction accelerating the interfacial charge separation. Moreover, BT NF with a high concentration of precursor (S2) manifested a higher photocatalytic activity than S1 due to the higher loading of Bi₂WO₆ nanosheets. S2 could be reused by sedimentation, and the photocatalytic activities of S2 were retained with a slight decline after four cycles, which confirmed its stability. Therefore, BT NF composites will be ideal candidates for highly efficient and recyclable photocatalysts for the treatment of organic pollutants under visible light.     

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。     

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.     

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.     

Fabrication of direct Z-scheme FeIn2S4/Bi2WO6 hierarchical heterostructures with enhanced photocatalytic activity for tetracycline hydrochloride photodagradation

A series of direct Z-scheme FeIn₂S₄/Bi₂WO₆ hierarchical heterostructures with intimate interface contacts were synthesized by in-situ growth route and characterized by systematical analyses. All as-prepared FeIn₂S₄/Bi₂WO₆ nanocomposites showed significantly enhanced photocatalytic activity towards photodegradation for the removal of tetracycline hydrochloride (TCH) in comparison with individual FeIn₂S₄ and Bi₂WO₆. Meanwhile, the highest photocatalytic degradation activity can be achieved by modulating adding amount of FeIn₂S₄ in FeIn₂S₄/Bi₂WO₆ nanocomposites and the optimized component ratio of FeIn₂S₄ to Bi₂WO₆ is determined to be 10 wt%. The enhanced photocatalytic activity could be ascribed to efficient separation between photogenerated holes and electrons based on the construction of direct Z-scheme system. The high photocatalytic stability of resultant 10 wt% FeIn₂S₄/Bi₂WO₆ nanocomposites was revealed through six successive recycling reactions. The main intermediate generated during TCH photodegradation was explored by HPLC-MS. Besides, the direct Z-scheme photocatalytic mechanism was confirmed by band position analysis, electron spin resonance (ESR) and active species capture experiment.     

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.     

Rational design,fabrication, optical properties and high-efficiency visible-light photocatalytic degradation performance for organic pollutants of Eu:Bi2WO6/CdS nanostructures

Over the past few years, semiconductor materials (especially bismuth tungstate) exhibiting unique environment purification and energy conversion capacities arouse huge attention as impacted by issues of environmental pollution and energy shortage, whereas its application is restricted by the problems of high carrier recombination rate and unsatisfactory degradation efficiency. In this study, Eu:Bi₂WO₆ nanostructures containing Eu ions of different concentrations were synthesized with a chemical solution method, and CdS was generated on the surface of Eu:Bi₂WO₆ nanostructures in situ epitaxial to synthesize the Eu:Bi₂WO₆/CdS composites. The effects of Eu doping concentration on the crystal structure, chemical composition, local structure, optical properties and visible-light photocatalytic properties exhibited by Eu:Bi₂WO₆/CdS nanostructures were studied more specifically, and the Eu doping behavior on the improvement mechanisms for optical and photocatalytic performance exhibited by Eu:Bi₂WO₆/CdS nanostructures was clarified. The robust PL emission peak at about 390 nm and weak emission peak at nearly 450 nm are attributed to the exciton emission and defect state of Bi₂WO₆/CdS nanostructure, respectively. As indicated from the mechanism insights, the reasonable introduction of Eu³⁺ could alter the band gap of the photocatalyst, and the epitaxial CdS could decrease the recombination probability of electron and hole in the Bi₂WO₆/CdS, while improving the photocatalytic activity. This study supplies new occasions for rational excogitation and better comprehending of atomic-scale complicated structures for applications in numerous fields (e.g., energy and environmental protection).