无助剂一步合成巢状钨酸铋微球及其光催化性能的研究

采用微波水热法在200℃时制备了形貌均一的正交晶型的巢状微球状的Bi2WO6光催化剂。利用X射线衍射(XRD)、场发射扫描电镜(FESEM)、透射电镜(TEM)和紫外可见光谱仪(UV-Vis)分别对巢状Bi2WO6微球的结构和形貌进行了表征,同时也考察了Bi2WO6在可见光的照射下对罗丹明B的光催化降解效果。结果表明,在500W氙灯的照射下降解罗丹明B的过程中,巢状Bi2WO6微球表现出良好的光催化活性,这与组成它的纳米片的纳米尺寸效应、微球大的表面积、本身层状堆积结构密切相关,其纳米片堆积起来的巢状结构可以使可见光在层状微球内经过多次散射和反射,延长了可见光传输的光程,增加了可见光的利用率。     

Bi2WO6 nano- and microstructures: shape control and associated visible-light-driven photocatalytic activities

The shape-controlled synthesis of nano- and microstructured materials has opened up new possibilities to improve their physical and chemical properties. In this work, new types of Bi(2)WO(6) with complex morphologies, namely, flowerlike, tyre- and helixlike, and platelike shapes, have been controllably synthesized by a facile hydrothermal process. The benefits of the present work also stem from the first report on the transformation of Bi(2)WO(6) from three-dimensional (3D) flowerlike superstructures to 2D platelike structures, and on the formation of tyre- and helixlike Bi(2)WO(6) superstructures. UV/Vis absorption spectra show that the optical properties of Bi(2)WO(6) samples are relevant to their size and shape. More importantly, the photocatalytic activities of Bi(2)WO(6) nano- and microstructures are strongly dependent on their shape, size, and structure for the degradation of Rhodamine B (RhB) under visible-light irradiation. The reasons for the differences in the photocatalytic activities of these Bi(2)WO(6) nano- and microstructures are further investigated.     

Preparation and modification of hierarchical nanostructured Bi2WO6 with high visible light-induced photocatalytic activity

Hierarchical nanostructured Bi(2)WO(6) micro-clews were synthesized by a solvothermal process with mixed solvents and formaldehyde. The hierarchical Bi(2)WO(6) micro-clews, with an average diameter of ca. 1.0 μm, consisted of nano-sheets assembled in a special fashion and the formation process mainly went through an Ostwald ripening-anisotropic growth and self-assembling process. The Bi(2)WO(6) micro-clews were further modified by Bi(2)O(3) to fabricate heterojunction photocatalysts, where Bi(2)O(3) nanoparticles were uniformly assembled on the surface of Bi(2)WO(6) nano-sheets. Compared with pure Bi(2)WO(6) and Bi(2)O(3), the composite photocatalyst exhibits higher photocatalytic activity for the degradation of rhodamine B under visible light. On the basis of characterization by x-ray diffraction, photoluminescence and UV-vis diffuse reflectance spectroscopies, a mechanism was proposed to account for the enhanced photocatalytic activity of the Bi(2)O(3)/Bi(2)WO(6) heterojunction.     

Hydrangeas-like Bi2WO6: facile synthesis, visible-light driven photocatalysis and theoretical analysis

Hydrangeas-like Bi2WO6 powders were synthesized successfully by salt-ultrasonic assisted hydrothermal process, which were characterized by scanning electron microscopy (SEM), Energy dispersive X-ray (EDS), X-ray diffraction (XRD), and UV-visible diffuse reflectance spectra (UV-Vis DRS), respectively. Bi, W and O elements were contained in the product, which could be tested by EDS. The crystal structure of the catalyst was orthorhombic phase (JCPDS card no.73-1126). And the band gap was estimated to be 2.56 eV from the onset of UV-Vis absorption spectra of the catalyst. In addition, the photocatalytic activities of the products were investigated on the degradation of Rhodamine B (RhB). It demonstrated that photocatalysts exhibited excellent visible-light driven photocatalytic performance. And the target residue was less than 1% in 20 min under Xenon lamp irradiation. First-principles calculations based on density functional theory (DFT) were used to explore the electronic and optical properties of Bi2WO6. And the theoretical calculations could illustrate the photocatalytic performance of Bi2WO6 powders under visible light irradiation.     

Novel Bi(2)WO(6)-TiO(2) heterostructures for Rhodamine B degradation under sunlike irradiation

Highly efficient Bi(2)WO(6)-TiO(2) heterostructure is synthesized by means of a hydrothermal method having highly photoactivity for the degradation of Rhodamine B under sunlike irradiation. From the structural characterization it has been demonstrated that TiO(2) is incorporated on the Aurivillius structure. Interesting synergetic effect between TiO(2) and Bi(2)WO(6) leads to an improved charge carrier separation mechanism, causing the excellent photocatalytic performance under sunlike irradiation. The photocatalytic performance of Bi(2)WO(6) and Bi(2)WO(6)-TiO(2) was compared under different irradiation conditions and using increasing Rhodamine B concentration up to 25 ppm. After the photocatalytic analysis of both systems, the mineralization efficiency of the heterostructure appears significantly higher with respect to Bi(2)WO(6).     

Nest-like structures of Sr doped Bi2WO6: Synthesis and enhanced photocatalytic properties

A series of Sr-doped Bi₂WO₆ with three-dimensional (3D) nest-like structures were synthesized through simple hydrothermal route and characterized by XRD, FESEM, TEM, XPS, UV-vis DRS, etc. Morphology observation revealed that the as-synthesized Bi₂WO₆ were self-assembled three-dimensional (3D) nest-like structures, which were constructed from nanoplates. UV-vis diffuse reflectance spectra indicated that the samples had absorption in both UV and visible light areas. Their photocatalytic activities were evaluated by photodegradation of rhodamine B (RhB) under UV and visible light irradiation (λ > 420 nm). The photocatalytic properties were enhanced after Sr doping. Samples subsequently thermal treated at 500 °C showed higher photocatalytic activities. The reasons for the differences in the photocatalytic activities of these nest-like Bi₂WO₆ microstructures were further investigated.     

Microwave Synthesis of Cuprous Oxide Micro-/Nanocrystals with Different Morphologies and Photocatalytic Activities

Cuprous oxide micro-/nanocrystals were synthesized by using a simple liquid phase reduction process under microwave irradiation.Copper sulfate was used as the starting materials and macromolecule surfactants served as the templates.The morphologies phase and optical properties of them are characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM) and ultraviolet-visible diffuse reflection absorptive spectra (UV-vis/DRS),respectively.The crystals had four different shapes,namely spheres,strips,octahedrons,and dandelions.The photocatalytic behavior of the cuprous oxide particles were investigated by monitoring the degradation of rhodamine B.In spite of the different morphologies,all of the cuprous oxide micro-/nanocrystals exhibited photocatalytic activities under visible light irradiation in the following order:dandelions,strips,spheres,and octahedral crystals.The photocatalytic degradation rates of rhodamine B are 56.37%,55.68%,51.83% and 46.16%,respectively.The morphology affects significantly the photocatalytic performance.     

球状SiO2@ZnO核壳结构的制备及其光催化活性

使用Stober法水热反应制备球状SiO2@ZnO核壳结构,通过样品对罗丹明B水溶液的降解研究其光催化活性,使用X-射线衍射（XRD）、扫描电子显微镜（SEM）、X-射线能量色散谱（EDS）、光致发光谱（PL）及紫外-可见分光光度计（UV—vis）等测试手段对材料物性进行表征,结果表明,SiO2表面包覆的ZnO层结晶良好,且不与SiO2核发生反应,表面致密、厚度均匀,保持了SiO2微球体的形貌特征;球状SiO2@ZnO核壳结构的吸收边和紫外发光峰位置相比于ZnO均发生红移,禁带宽度减小;通过光催化实验分析可知,球状SiO2@ZnO核壳结构光催化剂对罗丹明B水溶液的降解率有所提高,光照3h其降解率高达11％。     

简易合成Bi/Bi2MoO6/TiO2复合纳米纤维及其增强的可见光催化性能

以电纺TiO₂ 纳米纤维为基质, 葡萄糖为还原剂, 采用简单一步溶剂热法制备了等离子体Bi/Bi₂MoO₆/TiO₂复合纳米纤维。利用X射线衍射、场发射扫描电镜、透射电子显微镜、X射线光电子能谱、紫外-可见漫反射光谱和光致发光谱等对样品进行表征。以RhB和4-CP为模拟有机污染物, 评价材料的光催化性能。结果表明: 部分Bi ³⁺被葡萄糖还原成金属Bi纳米粒子, 原位沉积在Bi₂MoO₆纳米片上, 同时构筑在TiO₂纳米纤维表面。金属Bi的等离子体共振效应, 有效提高了样品的光催化活性。可见光照50 min, 样品对RhB的降解率为95.8%, 五次循环后仍保持在92%以上; 可见光照180 min, 样品对4-CP的降解率达68.8%。证实该材料具有良好的可见光催化活性和稳定性。     

M(M= Mg, Ca, Sr, Ba, Ni)Nb2O6的光催化性能的研究

应用固相烧结法制备了半导体光催化材料MgNb2O6,CaNb2O6,SrNb2O6,BaNb2O6,NiNb2O6粉体.利用XRD、UV-Vis漫反射谱、扫描电镜对上述粉体晶体结构、光谱性质和形貌进行了分析.在紫外光下对其降解罗丹明B（RhB）的光催化性能进行了评估.结果表明,碱土金属Sr、Ba对NiNb2O6中Ni的取代能很好地提高铌酸盐的光催化效果,在10h紫外光照射下能分别将RhB的浓度降解到原来的21%和37%.     

Solvent directed fabrication of Bi2WO6 nanostructures with different morphologies: Synthesis and their shape-dependent photocatalytic properties

In this work, Bi₂WO₆ with complex morphologies, namely, flower-like, pancake-like, and tubular shapes have been controllably synthesized by a facile solvothermal process. The as-obtained samples are systematically investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The effects of solvents on the morphologies of Bi₂WO₆ nanostructures are systematically investigated. According to the time-dependent experiments, a two-step growth mode basing on Ostwald ripening process and self-assembly has been proposed for the formation of the flower-like and pancake-like Bi₂WO₆ nanostructures. The photocatalytic properties of Bi₂WO₆ nanostructures are strongly dependent on their shapes, sizes, and structures for the degradation of rhodamine B (RhB) under visible-light irradiation. The deduced reasons for the differences in the photocatalytic activities of these Bi₂WO₆ nanostructures are further discussed.     

改进溶液燃烧法制备Fe3+掺杂Bi24O31Cl10及其光催化性能的研究

采用改进溶液燃烧法,以硝酸铋、柠檬酸、氯化铵和硝酸铁为原材料制备Fe-Bi24O31Cl10光催化物质,并通过在可见光下降解RhB评价Fe^3+掺杂对其光催化性能的影响。采用XRD,XPS,UV-vis,SEM,HTEM,FT-IR等表征手段研究了不同Fe^3+掺杂量对Bi24O31Cl10的物相、元素价态、光吸收性能、微观形貌以及颗粒分布、晶面间距、化学结构组成等的影响。结果表明:掺杂Fe^3+未改变Bi24O31Cl10的物相,片状形貌,但其片状大小明显变小且厚度变薄,光吸收性能增强,光生电子-空穴复合率下降,与纯Bi24O31Cl10相比,Fe^3+掺杂能显著提高Bi24O31Cl10的光催化活性,当Fe^3+掺杂量为0.5%(摩尔分数)时,对Bi24O31Cl10的光催化性能促进最高,在可见光下光照50 min,对RhB的脱色率可达75%,较纯Bi24O31Cl10提高了44%。     

Investigation of photocatalytic activities over Bi₂WO₆/ZnWO₄ composite under UV light and its photoinduced charge transfer properties

Bi(2)WO(6)/ZnWO(4) composite photocatalysts have been successfully synthesized by a facile hydrothermal process. The catalysts were characterized by powder X-ray diffraction (XRD), transmission electron microcopy (TEM), and UV-vis diffuse reflectance spectrum (DRS). The results show that Bi(2)WO(6) nanoparticles grow on the primary ZnWO(4) nanorods. The Bi(2)WO(6)/ZnWO(4) composites have better UV light photocatalytic activities compared to single ZnWO(4) nanorods. Furthermore, the photoinduced charge transfer properties of Bi(2)WO(6)/ZnWO(4) composites were investigated by means of transient photovoltage (TPV) technique in detail. The interconnected interface of Bi(2)WO(6)/ZnWO(4) composites led to the low recombination ratios of photoinduced electron-hole pairs and enhanced photocatalytic activities.     

The Ag-based SPR effect drives effective degradation of organic pollutants by BiOCOOH/AgBr composites

The easy recombination of electron-hole pairs produced by monomeric photocatalysts under light exposure severely limits their application in wastewater treatment. Based on this, BiOCOOH/Ag/AgBr ternary photocatalysts in flower-like microspheres were controllably synthesized by precipitation photoreduction and characterized by various techniques. In addition, the effects of different molar ratio of BiOCOOH and AgBr, catalyst dose, pH and coexisting ions on the photocatalytic degradation of rhodamine B (RhB) and tetracycline (TC) were investigated. The results showed that the BOC/Ag/AgBr-0.5 composite exhibited excellent photocatalytic activity for the degradation of RhB and TC. The excellent photocatalytic activity was mainly attributed to the surface plasmon resonance (SPR) effect of metallic Ag and charge transfer mechanism between composites, thus promoting charge separation. The degradation efficiency of RhB and TC was 92.7% and 72.3% with the degradation rate constant of 0.073 and 0.023 under light irradiation of xenon lamp in 30 and 45 min, respectively, which was 6 and 2 times higher than that of BiOCOOH and AgBr. The stability studies showed that BOC/Ag/AgBr-0.5 maintained a high catalytic activity after four cycles. The results of radical capture experiments showed that h⁺ and ·O₂^– were the main reactive radicals, while ·OH played a secondary role in the photocatalytic system. Subsequently, a potential photocatalytic mechanism was proposed based on the experimental results.     

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。     

CTAB-assisted synthesis of monoclinic BiVO4 photocatalyst and its highly efficient degradation of organic dye under visible-light irradiation

A highly efficient monoclinic BiVO₄ photocatalyst (C-BVO) was synthesized by an aqueous method with the assistance of cetyltrimethylammonium bromide (CTAB). The structure, morphology and photophysical properties of the C-BVO were characterized by XRD, FE-SEM and diffuse reflectance spectroscopy, respectively. The photocatalytic efficiencies were evaluated by the degradation of rhodamine B (RhB) under visible-light irradiation, revealing that the degradation rate over the C-BVO was much higher than that over the reference BiVO₄ prepared by aqueous method and over the one prepared by solid-state reaction. The efficiency of de-ethylation and that of the cleavage of conjugated chromophore structure were investigated, respectively. The chemical oxygen demand (COD) values of the RhB were measured after the photocatalytic degradation over the C-BVO and demonstrated a 53% decrease in COD. The effects of CTAB on the synthesis of C-BVO were investigated, which revealed that CTAB not only changed the reaction process via the formation of BiOBr as an intermediate, but also facilitated the transition from BiOBr to BiVO₄. Comparison experiments were carried out and showed that the existence of impurity level makes significant contribution to the high photocatalytic efficiency of the C-BVO.     

Preparation of a novel Bi2MoO6 flake-like nanophotocatalyst by molten salt method and evaluation for photocatalytic decomposition of rhodamine B

The flake-like nanoscale γ-bismuth molybdate (Bi₂MoO₆) powders as a novel photocatalyst was prepared using Bi(NO₃)₃·5H₂O and Na₂MoO₄·2H₂O as raw materials by a simple low-temperature molten salt method at 350 °C for 1, 4 and 8 h, respectively. The as-prepared samples were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–vis absorption spectra (UV–vis). The photocatalytic activity of Bi₂MoO₆ crystals was evaluated using the photocatalytic oxidation of rhodamine B (RhB) at room temperature under ultraviolet irradiation. It was found that the band gap adsorption edge of Bi₂MoO₆ is estimated to be 477 nm corresponding to the band gap energy to be 2.60 eV. In addition, the Bi₂MoO₆ powders exhibit good photocatalytic properties to photodegrade RhB at room temperature. Finally, the mechanism of photocatalytic property of Bi₂MoO₆ had been also discussed.     

The enhanced visible light photocatalytic activity of nanosheet-like Bi2WO6 obtained by acid treatment for the degradation of rhodamine B

Bi₂WO₆ samples were fabricated by chemical solution decomposition (CSD) method and nanosheet-like Bi₂WO₆ samples could be obtained by concentrated nitric acid treatment at 70 °C for 20 min. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and UV-vis diffuse reflectance spectra. Photocatalytic activities of the samples were evaluated by the degradation of rhodamine B (RhB) under visible light irradiation. The temperature of acid treatment obviously influenced morphology and the visible light photocatalytic activity of the Bi₂WO₆ samples. The nanosheet-like Bi₂WO₆ photocatalysts obtained by acid treatment exhibited the highest photocatalytic activity under visible light irradiation.     

碳纤维负载NaTaO3光催化复合材料的制备及其性能碳纤维负载NaTaO3光催化复合材料的制备及其性能

以聚丙烯腈基碳纤维（CF）为基体,TaCl₅和乙酸钠为原料,十六烷基三甲基溴化铵（CTAB）为表面活性剂,通过溶胶-凝胶法和浸渍提拉法将纳米NaTaO₃薄膜负载于CF上,制备得到高效光催化特性的复合材料。采用SEM、TEM、XRD等表征了NaTaO₃-CF的形貌和结构,以罗丹明B （RhB）溶液为目标降解物,测试了NaTaO₃-CF复合材料的光催化性能。结果表明:所制备的NaTaO₃-CF复合材料具备良好光催化活性和重复使用稳定性,暗中吸附30 min、光照80 min时,对RhB的去除率为99.35%,5次循环使用后,去除率为89.17%,其光催化反应过程符合伪一级反应动力学模型。      

Highly enhanced photocatalytic degradation of dye rhodamine B on the biogenic hierarchical porous TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> with 1D/3D-chain

A hybrid photocatalyst consisting of TiO₂ and nonporous SiO₂ (TiO₂/CS-RH) is prepared by loading TiO₂ sol on one-dimensional/three-dimensional chain (1D/3D-chain) which is synthesized from rice husk. The products are characterized by X-ray diffraction, N₂-adsorption–desorption analysis and scanning electron microscopy. Meanwhile, the corresponding photocatalytic activity is evaluated by measuring the photocatalytic oxidation of rhodamine B (RhB). The results reveal that TiO₂/CS-RH displays a hierarchical porous structure from micrometer to nanometer scale with high BET surface area (574.7–719.4 cm²/g). Meanwhile, the activity of TiO₂/CS-RH for the photocatalytic degradation of RhB in aqueous slurry is significantly higher than that of the unsupported TiO₂. The optimal TiO₂ loaded on the support was two times and then treated at 600 °C for 120 min to complete the conversion of RhB. In contrast, the unsupported TiO₂ photocatalyst could convert only 20% of RhB in the same irradiation time and condition.