网状钼酸铋的可见光催化活性

采用无助剂、无模板的水热法成功合成网状Bi2MoO6. pH值对这一形貌的形成起重要作用. 所制备的网状Bi2MoO6样品表现出优异的可见光催化活性,其光催化活性比固相法合成的块状Bi2MoO6样品高得多.     

Fe (III)‐grafted Bi2MoO6 nanoplates for enhanced photocatalytic activities on tetracycline degradation and HMF oxidation

Fe (III)‐grafted Bi₂MoO₆ nanoplates (Fe (III)/BMO) with varying small quantity of Fe (III) clusters modification were fabricated through a simple hydrothermal and impregnation process. The characterization results indicate that the modification of Fe (III) clusters on the surface of Bi₂MoO₆ nanoplates with intimate interfacial contact is beneficial to the expansion of visible light absorption range and the separation of photoinduced carriers during the interface charge transfer process. The photocatalytic properties of the samples were studied by degradation of tetracycline (TC) and selective aerobic oxidation of biomass‐derived chemical 5‐hydroxymethylfuraldehyde (HMF) under visible light. The 1.5 wt% Fe (III) clusters‐grafted Bi₂MoO₆ nanoplates exhibited optimum photocatalytic activity, which is the TC degradation kinetic rate constant is 5.3 times higher than that of bare BMO, and the highest HMF conversion of 32.62% can be obtained with a selectivity of 95.30%. Furthermore, a possible visible light photocatalysis mechanism over Fe (III)/BMO sample has been proposed. This study may supply some insight for the development of visible‐light‐driven Bi₂MoO₆‐based photocatalysts applicable to both environmental remediation and biomass‐derived chemical transformation.     

探究超薄Bi2MoO6纳米片高效光催化CO2还原活性

铋系层状半导体材料凭借其独特的表面特性在光催化领域得到广泛的研究及应用,然而在光催化反应过程中光生电荷迁移及其表界面动态变化却鲜见报道。本文中,我们利用准原位X射线光电子能谱仪（QIS-XPS）系统研究超薄Bi2MoO6纳米片光催化CO2还原过程中光生电荷迁移及其表界面演变过程。研究结果表明：在暗态条件下CO2分子吸附于（010）暴露面Bi活性位,由于CO2分子强的拉电子能力,导致内层出现高价态Mo(6 x) 。当光照射至样品表面上时,*CO2峰显著降低,*CO峰明显升高,表明CO2分子在Bi活性位发生活化断键,并与光生电子反应形成*CO,使得高价态Mo(6 x) 含量增大。活性测试表明超薄Bi2MoO6纳米片的CO产量活性为41.8 ?mol g-1 h-1,其比块体Bi2MoO6活性高4.2倍,并且展现出优异的光催化稳定性。该工作为二维层状材料高效光催化CO2还原机理研究提供了一种全新的研究思路。     

Synthesis and Enhanced Photocatalytic Activity of Visible-Light-Driven Co-Doped Bi2MoO6 Photocatalyst with Flower-Like Nanostructures

Russian Journal of Physical Chemistry A - Co-doped Bi2MoO6 photocatalyst has been synthesized by a simple and facile solvothermal method. It exhibits the flower-like microspheres composed of...     

Construction of NH2-MIL-125(Ti) nanoplates modified Bi2WO6 microspheres with boosted visible-light photocatalytic activity

Photoactive metal–organic frameworks (MOFs) have proven to be a promising porous material in the field of catalysis. Controllable integration of these MOFs with inorganic semiconductor materials may endow new multifunctional hybrid materials with preferable photocatalytic properties. In this research, NH₂-MIL-125(Ti) nanoplates modified Bi₂WO₆ microspheres was prepared via a simple solvothermal method. The photocatalytic behaviors of the acquired catalysts was evaluated via the degradation of tetracycline hydrochloride (TC) under visible light. The experimental results showed that NH₂-MIL-125(Ti)/Bi₂WO₆ composites display higher photocatalytic activity than that of single Bi₂WO₆, and the ideal incorporation amount of NH₂-MIL-125(Ti) was around 5 wt%. The steady state fluorescence spectrum, transient photocurrents and electrochemical impedance spectroscopy verified that the introduction of NH₂-MIL-125(Ti) could accelerate the separation and transfer of photogenerated carriers and thus improve the photocatalytic activity of Bi₂WO₆. The photocatalytic mechanism was explored in detail. This work extends the knowledge of integrating MOFs with traditional photocatalysts to form new composite materials in the area of environmental purification.

     

Growth mechanism and photocatalytic properties of flower-like Bi2WO6 powders synthesized by a microwave hydrothermal method

Pure orthorhombic phase Bi₂WO₆ powders were synthesized by a microwave hydrothermal method in the absence of surfactants and templates, using Bi(NO₃)₃·5H₂O and Na₂WO₄·2H₂O as raw materials. Photocatalytic properties of the samples prepared at different reaction temperatures were also studied with Rhodamine B (RhB) solution as the target catabolite under visible light. The results indicate that flower-like Bi₂WO₆ powders can be obtained by controlling the microwave reaction temperatures in the absence of any additives. The growth of flower-like Bi₂WO₆ powders is a multistage layer assembly process, in which the flower-like Bi₂WO₆ self-assembling with the uniform size about 2 μm is synthesized at 180 °C. At the same time, the photocatalytic reaction rate constant (k) gets up to 0.04167/min and the degradation rate of RhB solution is more than 96 % after being irradiated under visible light for 70 min.     

Selective Production of Secondary Amine by the Photocatalytic Cascade Reaction Between Nitrobenzene and Benzyl Alcohol over Nanostructured Bi2MoO6 and Pd Nanoparticles Decorated with Bi2MoO6

The synthesis of secondary amine by the photoalkylation of nitrobenzene with benzyl alcohol using a simple light source and sunlight is a challenging task. Herein, a one-pot cascade protocol is employed to synthesize secondary amine by the reaction between nitrobenzene and benzyl alcohol. The one-pot cascade protocol involves four reactions: (a) photocatalytic reduction of nitrobenzene to aniline, (b) photocatalytic oxidation of benzyl alcohol to benzaldehyde, (c) reaction between aniline and benzaldehyde to form imine, and (d) photocatalytic reduction of imine to a secondary amine. The cascade protocol to synthesize secondary amine is accomplished using Bi₂MoO₆ and Pd nanoparticles decorated Bi₂MoO₆ catalysts. The surface characteristics, oxidation states, and elemental compositions of the materials are characterized by several physicochemical characterization techniques. Optoelectronic and photoelectrochemical measurements are carried out to determine the bandgap, band edge potentials, photocurrents, charge carrier's separation, etc. An excellent yield of secondary amine is achieved with simple household white LED bulbs. The catalyst also exhibits similar or even better activity in sunlight. The structure-activity relationship is established using catalytic activity data, control reactions, physicochemical, optoelectronic characteristics, and scavenging studies. Bi₂MoO₆ and Pd nanoparticles decorated Bi₂MoO₆ exhibit excellent photostability and recyclability. The simple catalyst design with a sustainable and economical light source for the synthesis of useful secondary amine from the nitrobenzene and benzyl alcohol would attract the researchers to develop similar catalytic protocols for other industrially important chemicals.     

Enhanced photocatalytic activity of ZnO nanoparticles by surface modification with KF using thermal shock method

ZnO nanoparticles were modified with KF using thermal shock method at various temperatures in order to improve the photocatalytic activity of ZnO under both UVA and visible light irradiation. The influences of KF-modification on the crystal structure, morphology, UV–visible absorption, specific surface area as well as surface structure of ZnO were respectively characterized by XRD, FE-SEM, UV–Visible diffuse reflectance, N₂ adsorption and XPS spectroscopy. The photocatalytic activity was evaluated via the degradation of methylene blue under UVA irradiation. According to the results, the thermal shock process with KF did not modify the structure, the particle size and the optical properties of ZnO nanoparticles but successfully increase their UVA and visible light induced photocatalytic activity. This enhancement of activity may be attributed to the increase of surface hydroxyl groups and zinc vacancies of modified ZnO samples.     

Bi2MoO6纳米薄膜的制备及其光电性能

采用非晶态配合物法在ITO导电玻璃上制备了Bi2MoO6薄膜. 采用扫描电子显微镜(SEM)、X射线衍射(XRD)、激光拉曼光谱(LRS)、紫外-可见漫反射谱(DRS)、光电流响应谱、光电转换量子效率(IPCE)等技术研究了Bi2MoO6薄膜的制备工艺、形貌、结构与薄膜光电性能的关系. 结果表明, 500 ℃、1 h焙烧后的Bi2MoO6薄膜为γ-Bi2MoO6晶相, 沿(131)晶面方向生长, 薄膜厚度约为69 nm. 随着焙烧温度的升高和焙烧时间的延长, Bi2MoO6薄膜的平均颗粒度增大, 并且在525 ℃焙烧出现β-Bi2MoO6和γ’-Bi2MoO6晶相. Bi2MoO6薄膜具有可见光响应活性, 在可见光照射下可以产生光电流, 优化条件下的Bi2MoO6薄膜在400 nm的光电转换量子效率可以达到2.14%. 薄膜的光电响应和光电转换量子效率受薄膜形貌及结晶状态影响, 可以通过控制薄膜的制备条件来提高薄膜的光电转换量子效率.     

Synthesis of gold nanoparticles by microemulsion assisted photoreduction method

A new, clean, cost-effective and rapid method for the synthesis of stable spherical gold nanoparticles (AuNPs) is developed. This novel technique combines microemulsion as one of soft-nanotechnology techniques of wet chemistry, with photo-physics of UV-radiation in a unique versatile method to design and obtain controlled nanostructures for multifunctional materials. Based on a phase diagram in ternary water/Brij 30/n-heptane system pristine, and thiol functionalized, gold nanoparticles were obtained by a microemulsion assisted photoreduction technique, allowing increased flexibility during the synthesis and selection of materials. The spherical nanoparticles obtained by this route show a homogeneous size distribution, with an average diameter of 11 nm, for pristine gold nanoparticles and of 12 nm, for functionalized species. The evolution of the system at the nanoscale has been studied using, in tandem, UV-VIS and DLS measurements. The structure, size and shape of the final nanoparticles obtained have been evaluated by adequate instrumental techniques: FTIR, XRD and TEM image analysis. Kinetic studies have also been performed in order to follow the evolution of nanospecies during irradiation procedure.     

新型间接Z字结型g-C3N4/Bi2MoO6/Bi空心微球等离子共振增强光吸收和光催化性能（英文）

半导体光催化技术是目前最有前景的绿色化学技术,可通过利用太阳光降解污染物或制氢.作为有潜力的半导体催化剂,钼酸铋具有合适的带隙(2.58 eV).但是,由于低的量子产量,钼酸铋的光催化性能并不理想.为了提高钼酸铋的光催化性能,研究者多考虑采取构造异质结的方式.石墨相氮化碳(g-C3N4)能带位置合适,与多种光催化半导体能带匹配,是构造异质结的常用选择.因此,本文选用g-C3N4与钼酸铋复合,构造异质结结构.为了进一步提高光催化性能,多采用负载贵金属(Pt,Au和Pd)作为助催化剂,利用贵金属特有的等离子共振效应,增加光吸收,促进载流子分离,但贵金属价格昂贵.Bi金属单质价格便宜,具备等效的等离子共振效应,是理想的贵金属替代物.钼酸铋可以采取原位还原的方式还原出Bi单质,构造更紧密的界面结构,更有利于载流子传输.Bi的等离子共振效应可以有效提高材料的光吸收能力和光生载流子分离率.本文采用溶剂热和原位还原方法成功合成了一种新型三元异质结结构g-C3N4/Bi2MoO6/Bi(CN/BMO/Bi)空心微球.结果显示,三元异质结结构的最佳配比为0.4CN/BMO/9Bi,该样品表现出最好的光催化降解罗丹明B效率,是纯钼酸铋的9倍.通过计算DRS和XPS的价带数据,0.4CN/BMO/9Bi是一种Z字型异质结.牺牲试剂实验也提供了Z字型异质结的有力证据,测试显示超氧自由基·O^2-(在-0.33 eV)是光催化降解的主要基团.但是,钼酸铋的导带位置低于-0.33 eV,g-C3N4的导带高于-0.33 eV,因此g-C3N4的导带是唯一的反应位点,从而证明了光生载流子的转移是通过Z字型异质结结构实现的.TEM图显示金属Bi分散在钼酸铋表面.DRS和PL图分析表明金属Bi增加了材料的光吸收能力,同时扮演了中间介质的角色,促进钼酸铋导带的电子和g-C3N4价带的空穴快速复合.因此,g-C3N4/Bi2MoO6/Bi的优异光催化性能主要归功于Z字型异质结和Bi金属的等离子共振吸收效应,提高了材料的光吸收能力和光生载流子分离率.     

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.     

MOF derived Bi2MoO6/TiO2 nanohybrids: enhanced photocatalytic activity for Rhodamine B degradation under sunlike irradiation

Research on Chemical Intermediates - Bi2MoO6/TiO2 nanohybrids were fabricated via a metal–organic frameworks(MOFs) templated method. The samples were characterized by XRD, SEM, TEM,...     

Synthesis and photocatalytic properties of Cu2S-Pd4S hybrid nanoplates

Hex appeal! Cu(2)S-Pd(4)S hybrid nanocrystals with a novel hexagonal nanoplate structure were prepared in high yield by a simple one-pot synthetic method (see figure). Successful synthesis of this unique structure was achieved through a consecutive thermolysis process. The Cu(2)S-Pd(4)S hybrid nanoplates exhibited substantially higher photocatalytic activities than pure Cu(2)S nanoplates.     

ZnCuAl-LDH/Bi2MoO6纳米复合材料的构建及其可见光催化降解性能

In this study, pure Bi₂MoO₆ was synthesized via a solvothermal method. A ZnCuAl-layered double hydroxide (LDH)/Bi₂MoO₆ (denoted as LDH/Bi₂MoO₆) nanocomposite was synthesized via a steady-state co-precipitation route using Bi₂MoO₆ as the matric material. LDH was deposited on the surface of Bi₂MoO₆ with a close contact interface. The specific surface area of the resulting LDH/Bi₂MoO₆ composite increased up to 19.1 m²∙g⁻¹ owing to the stacking arrangement between LDH and the Bi₂MoO₆ nanosheets, resulting in the generation of a large number of reactive sites. In addition, the light absorption region of the LDH/Bi₂MoO₆ composite was larger than those of pure LDH and Bi₂MoO₆ because of the formation of a heterojunction structure and the possible quantum size effect. The photocatalytic performance of the as-prepared samples was evaluated by carrying out the degradation of rhodamine B (RhB) using them under visible light irradiation. Compared to pure LDH and Bi₂MoO₆, the LDH/Bi₂MoO₆ nanocomposite exhibited enhanced photocatalytic activity for the degradation of RhB. With an increase in the LDH content, the photocatalytic activity of the LDH/Bi₂MoO₆ composite first increased and then decreased. Although the addition of an optimum amount of LDH was beneficial for the generation of electron-hole pairs, excessive LDH on the surface of Bi₂MoO₆ decreased the visible light absorption ability of both the components, thus reducing photocatalytic activity of the composite. This indicates that an appropriate LDH:Bi₂MoO₆ molar ratio is necessary for obtaining LDH/Bi₂MoO₆ composites with excellent photocatalytic activity. Furthermore, the LDH/Bi₂MoO₆ composite showed high photocatalytic stability and reusability. The structure of the LDH/Bi₂MoO₆ composite remained almost unchanged even after four photodegradation cycles. The enhanced photocatalytic performance of the composite can be attributed to the combined effect of its heterojunction structure and high specific surface area, which are beneficial for effective separation of photogenerated charge carriers and the availability of a large number of active sites for photocatalysis. It was found that •OH and O₂^•− were the main reactive species, while e⁻ and h⁺ contributed little to the photodegradation process. The generation, transfer, and separation of photoinduced electrons and holes in the composites were investigated by transient photocurrent responses, electrochemical impedance spectroscopy Nyquist plots, and photoluminescence measurements. The results showed that the heterojunction structure of the composites played a key role in enhancing their photocatalytic activity. A possible photodegradation mechanism was proposed for the composite. This study will provide a facile approach for the preparation of LDH- and/or Bi₂MoO₆-based nanocomposites. The LDH/Bi₂MoO₆ nanocomposite prepared in this study showed huge potential to be used as a visible-light photocatalyst for degrading environmental pollutants.     

Bi3+/Ce3+ doped ZnO nanoparticles with enhanced photocatalytic and dielectric properties

In this study, varying % Bi-doped on 1% Ce-doped ZnO (1CZ) nanoparticles (X% B-1CZ) were synthesized via a facile, simple, low-cost, sol–gel process. Various characterization techniques were employed to characterize the synthesized compound, while the dielectric properties i.e. dielectric constant, dielectric loss and AC conductivity against frequency were studied with the help of a precision impedance analyzer. It was observed that by increasing bismuth content in the nanoparticles, the dielectric constant also increased in the range (1.47 × 10⁶ – 4.02 × 10⁶) at 20 Hz, and vice versa for dielectric loss decreased from 1.05 × 10⁶ to 0.39 × 10⁶. The role of prepared compounds as photocatalysts was also investigated against methylene blue under ultraviolet irradiation. The degradation efficiency, as well as the dielectric properties of 7% Bi-doped on 1% Ce-doped ZnO (7%B-1CZ), were found to be the best. Overall, it was found that the synthesized compounds proved promising candidates with enhanced photocatalytic & dielectric properties and hence could safely be employed for environmental remediation purposes and energy storage devices.     

溶剂热合成可调控氧空位的Bi2MoO6纳米晶及其光催化氧化制喹啉和抗生素降解

近年来,半导体光催化在环境净化和有机合成领域的研究引起了广泛的重视.其中,在有机合成领域中,光催化技术已经应用在醇类、环己烷以及芳香族化合物的选择性氧化研究.而另一类具有特殊结构的有机物——N-杂环芳烃,在药物化学和材料科学中具有重要意义.而传统用于合成N-杂化芳烃的脱氢催化氧化反应通常需要高温高压的苛刻环境,传统方法通常还需要使用贵金属催化剂,这也增加了N-杂化芳烃的合成成本;另外,如果合成是均相催化过程,则催化剂难以实现回收利用.因此,开发室温常压条件下的非贵金属多相光催化技术具有巨大的应用前景.本文以能够被可见光驱动的钼酸铋半导体为催化剂,利用氧缺陷策略来提升钼酸铋的光催化氧化性能.不同于传统氧缺陷制备方法(氢气还原热处理、离子掺杂等),本文采用一种低成本的乙二醛辅助溶剂热的方法合成具有可调控的含氧空位Bi₂MoO₆催化剂(OVBMO).通过X射线粉末衍射(XRD)、扫描电镜、透射电镜、紫外可见漫反射吸收光谱、氮气物理吸附脱附、X射线光电子能谱(XPS)、电子自旋共振光谱、光致发光光谱及电化学测试等技术对制备的OVBMO材料进行了物理化学性质及能带研究.XPS,XRD,Raman和FT-IR结果表明,氧空位存在于[Bi₂O₂]²⁺和MoO₆八面体的层间.紫外可见漫反射结果表明,随着氧空位的引入,Bi₂MoO₆的光吸收范围扩大,带隙变窄.结合莫特肖特基和VBXPS分析获得OVBMO的能带位置,发现氧空位的存在不仅会导致禁带中出现缺陷带能级,还会导致价带顶位置上移,促进光生空穴的迁移.PL和电化学结果表明,氧空位的存在使得载流子浓度、载流子的分离能力与界面电荷迁移能力都有较大提升,这是因为氧空位引入的缺陷能级可以浅势捕获电子,抑制光催化剂中的电子与空穴的复合,改变化学反应的速率.同时,氧空位有助于捕获分子氧,分子氧与捕获的光生电子发生反应,产生更多的超氧自由基(·O₂)和空穴(h⁺),从而极大地提升光催化剂的氧化性能.因此,OVBMO在1,2,3,4-四氢喹啉脱氢氧化产生喹啉及系列抗生素(环丙沙星、四环素、盐酸土霉素)的降解反应中,表现出较好的光催化氧化性能.结合多种表征分析,本文还进一步阐明了OVBMO催化剂将1,2,3,4-四氢喹啉脱氢氧化为喹啉的自由基参与的多相催化反应机理.     

Elucidating the structure-dependent photocatalytic properties of Bi2WO6: a synthesis guided investigation

Polycrystalline microspheres and single-crystalline microplates of Bi(2)WO(6) have been synthesized by ultrasonic spray pyrolysis. Herein, these materials are evaluated as photocatalysts for the visible light mediated degradation of rhodamine B, a model pollutant, and the results compared to those obtained with Bi(2)WO(6) prepared by traditional methods. The microplates, which displayed the best crystallinity and highest surface area, were anticipated to facilitate the greatest rate of dye photodegradation. However, the polycrystalline microspheres outperformed both the Bi(2)WO(6) microplates and traditional samples. To understand the origin of this result, the local and macroscale structures of the Bi(2)WO(6) samples were comprehensively characterized by spectroscopy techniques (diffuse reflectance, fluorescence, Raman, and X-ray photoelectron spectroscopy) as well as electron microscopy and diffraction. This analysis found that the enhanced performance of the Bi(2)WO(6) microspheres results from the expression of a hydrophilic surface, a low concentration of point defects, and a moderate surface area. This finding highlights the significant role synthesis plays in imparting structure and functionality to solid materials.     

The photocatalytic properties of amorphous TiO2 composite films deposited by magnetron sputtering

The preparation of amorphous TiO₂ film coupled with various metal-oxide semiconductors and their photocatalytic activities evaluated by photo-degradation of methylene blue and rhodamine B aqueous solution are briefly reviewed. The proposed photoreaction mechanism of the amorphous composite semiconductor and the differences between amorphous TiO₂-based films and crystalline TiO₂ photocatalytic materials in terms of preparation and usage are addressed. The inactive intrinsic amorphous TiO₂ film coupled with various metal oxides were found to gain high photocatalytic activity. These dopants induce forming new energy levels in the band gap of TiO₂ to enhance the charge separation of the photoinduced electrons and holes and extend the light absorption of TiO₂-based photocatalytic films into the visible region. In addition, two different effects of coupling metal oxides have been proved: the introduction of oxides of W, Cr, V, Ag, and Mo can significantly increase the photo-reactivity of amorphous TiO₂ film, while the combination of oxides of Zr, Sn, Sb, Cu, Ta, Fe, and Ni cannot affect the inactivity of pure amorphous TiO₂ film.