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1.
Nanoplate-like bismuth molybdates (γ-Bi2MoO6) is prepared for the first time by urea assisted solution combustion synthesis (SCS) and studied the structural and electrochemical properties to explore the possibility of using as negative electrodes in pseudocapacitors. The formation of single phase γ-Bi2MoO6 and plate-like morphology is revealed from XRD Rietveld refinement and FESEM, respectively. The pseudocapacitive behaviour of γ-Bi2MoO6 is analyzed by cyclic voltammetry and galvanostatic charge–discharge techniques. The effect of Na based aqueous electrolytes on capacitance of the Aurvillius type structured Bi2MoO6 is investigated. As prepared γ-Bi2MoO6 nanoplates provide the high specific capacitance (519 F g−1) compared with the high-temperature monoclinic phase γ(H) Bi2MoO6 in 1 M NaOH electrolyte. The obtained high specific capacitance of as prepared Bi2MoO6 could be attributed to the decrease in particle size, increase in active sites, and nanoplate-like structure of as prepared γ-Bi2MoO6.  相似文献   

2.
The polymorphism of Bi2MoO6 has been studied by differential thermal analysis, differential dilatometry, and differential scanning calorimetry with γ form specimens having the koechlinite structure prepared by sintering the oxides Bi2O3 and MoO3. Two stable γ and γ′ forms and one metastable γ″ form were observed. The relative thermal stability of the γ form compared with the γ′ form has been examined by isothermal heating of a mixture of the two forms under hydrothermal conditions. Thus the low-temperature stable γ form transformed reversibly to the γ″ form at 604 ± 3°C, and on subsequent heating, the γ″ form transformed irreversibly to the high-temperature stable γ′ form in the range 640 to 670°C, depending on heating rates; however, an isothermal treatment at a temperature above 604 ± 3°C brought the gradual transition of the γ″ form into the γ′ form.  相似文献   

3.
The equilibrium phase diagram between 0 and slightly above 50 mole% Bi2O3 in the Bi2O3MoO3 system has been studied by differential thermogravimetric analysis (DTA) and X-ray diffraction measurements on fused mixtures and single crystals. The results confirm the existence of the four compounds α (Bi2O3·3MoO3), β (Bi2O3·2MoO3), γ (Bi2O3·MoO)3 and ? (~1.3Bi2O3·MoO3) in the system. However, the phase diagram as well as the nature of melting of the α and γ were found disagreed with previous results. The γ compound melts incongruently at 947°C, whereas the α compound melts congruently at 662°C. The crystal class and lattice parameters of the compounds were determined based on the single crystal as well as powder pattern techniques. The results show that all four compounds have the monoclinic structure. The unit cell parameter of the β, γ, and ? compounds were found to be quite different from previously reported data. The lattice parameters obtained from X-ray analysis were also verified by density measurements of the single crystals. The polymorphism of the compounds was also investigated with single crystal samples. No polymorphic transformations for the α, β, and γ phases were detected in the work.  相似文献   

4.
表面Cu2O纳米颗粒修饰高效促进γ-Bi2MoO6的可见光催化活性   总被引:1,自引:0,他引:1  
采用水热法在γ-Bi2MoO6光催化剂表面修饰了纳米级Cu2O, 得到了具有高效可见光响应的复合光催化材料, 并利用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、选区电子衍射(SAED)、X射线光电子能谱(XPS)和紫外-可见漫反射光谱(UV-Vis-DRS)等技术对其相结构、微观形貌和光吸收性能进行了表征. 在可见光条件下(λ>400 nm)考察了Cu2O表面修饰对γ-Bi2MoO6光催化降解亚甲基蓝(MB)性能的促进作用. 结果表明, 纳米级Cu2O(~10 nm)颗粒均匀地修饰于γ-Bi2MoO6的表面, 使γ-Bi2MoO6的可见光吸收带发生明显红移, 且吸收强度大幅提高, 增强了复合材料光生电子-空穴对的分离效率, 从而使复合材料表现出较高的光催化活性. 当Cu2O的表面修饰量为1.5%(w)时, 复合光催化剂降解MB的活性与纯γ-Bi2MoO6相比提高了6.4倍.  相似文献   

5.
Several outstanding aspects of phase behaviour in the systems (Bi,Ln)2WO6 and (Bi,Ln)2MoO6 (Ln=lanthanide) have been clarified. Detailed crystal structures, from Rietveld refinement of powder neutron diffraction data, are provided for Bi1.8La0.2WO6 (L-Bi2WO6 type) and BiLaWO6, BiNdWO6, Bi0.7Yb1.3WO6 and Bi0.7Yb1.3WO6 (all H-Bi2WO6 type). Phase evolution within the solid solution Bi2−xLaxMoO6 has been re-examined, and a crossover from γ(H)-Bi2MoO6 type to γ-R2MoO6 type is observed at x∼1.2. A preliminary X-ray Rietveld refinement of the line phase BiNdMoO6 has confirmed the α-R2MoO6 type structure, with a possible partial ordering of Bi/Nd over the three crystallographically distinct R sites.  相似文献   

6.
Among the different polymorphic phases of the Bi2MoO6 system, the intermediate γ″ compound has been characterized within a metastable state by high temperature X-ray diffraction and Raman spectroscopy. The transition γ ? γ″ is found to be partially displacive and partially reconstructive. In the context of the ferroelectricity of γ, the nature of the paraelectric phase is discussed with the help of space group considerations and Buerger's theory of phase transitions.  相似文献   

7.
The vapor phase catalytic aerial oxidation of toluene to benzaldehyde (BzH) was carried out over La2MoO6 containing the same kind of layered structure as Bi2MoO6. The overall kinetic analysis indicated the oxidation of toluene to BzH to be first order with a frequency factor of log 0.63 and activation energy (Ea) of 26.3 kJ mol–1 and 34.0 kJ mol–1, respectively, for Bi2MoO6 and La2MoO6 catalysts. A relation between the activity and activation energy of conduction (E) is shown.  相似文献   

8.
采用一步水热法制备Bi2MoO6/BiVO4复合光催化剂. 利用X 射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、高分辨透射电子显微镜(HRTEM)等手段对其晶体结构和微观结构进行了表征. 结果表明, Bi2MoO6纳米粒子沉积在BiVO4纳米片表面从而形成异质结结构. 紫外-可见漫反射光谱(UV-Vis DRS)表明所制备的Bi2MoO6/BiVO4异质结较纯相Bi2MoO6和BiVO4对可见光吸收更强. 由于形成异质结结构及其光吸收性能使Bi2MoO6/BiVO4 光催化活性有较大提高. 可见光下(λ>420 nm)光催化降解罗丹明B (RhB)实验结果表明,Bi2MoO6/BiVO4光催化活性较纯相Bi2MoO6和BiVO4高. Bi2MoO6/BiVO4样品光催化性能提高的原因是Bi2MoO6和BiVO4形成异质结, 从而有效抑制光生电子-空穴对的复合, 增大了可见光吸收范围及比表面积.  相似文献   

9.
采用水热、化学沉积和原位光还原的方法成功制备了新型Ag/Ag2MoO4/Bi2MoO6三元复合光催化剂。通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和紫外可见漫反射光谱(UV-Vis DRS)等技术对材料的组成、形貌、光吸收特性和光电化学性能等进行系统分析。以四环素为目标污染物,研究Ag/Ag2MoO4/Bi2MoO6在可见光下的光催化性能。研究结果表明,相比于纯Ag2MoO4和Bi2MoO6,Ag的表面等离子体共振(SPR)效应显著拓宽了催化体系对可见光的吸收能力及响应范围。当Ag2MoO4理论负载量(质量分数)为24.6%时,Ag/Ag2MoO4/Bi2MoO6复合材料在20 min内可将四环素完全降解,且5次循环使用后仍保持较高的催化活性,表现出良好的循环稳定性。  相似文献   

10.
采用水热、化学沉积和原位光还原的方法成功制备了新型Ag/Ag2MoO4/Bi2MoO6三元复合光催化剂。通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和紫外可见漫反射光谱(UV-Vis DRS)等技术对材料的组成、形貌、光吸收特性和光电化学性能等进行系统分析。以四环素为目标污染物,研究Ag/Ag2MoO4/Bi2MoO6在可见光下的光催化性能。研究结果表明,相比于纯Ag2MoO4和Bi2MoO6,Ag的表面等离子体共振(SPR)效应显著拓宽了催化体系对可见光的吸收能力及响应范围。当Ag2MoO4理论负载量(质量分数)为24.6%时,Ag/Ag2MoO4/Bi2MoO6复合材料在20 min内可将四环素完全降解,且5次循环使用后仍保持较高的催化活性,表现出良好的循环稳定性。  相似文献   

11.
以五水硝酸铋为铋源,采用简易的一步水热法合成出Bi_2MoO_6/CoMoO_4绣花球结构。通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶红外光谱(FT-IR)、紫外-可见漫反射光谱(UV-Vis DRS)、荧光光谱(PL)和电化学测试等表征对所制备催化剂的物相组成、微观形貌、光学性质以及光生电荷复合效率进行了分析。研究结果表明,引入Bi_2MoO_6之后,Bi_2MoO_6/CoMoO_4复合异质结的光吸收范围明显被拓宽,其光生电荷的分离率也得到了提升。以亚甲基蓝和头孢曲松钠为污染物来模拟废水,在可见光的条件下评估催化剂样品的光催化降解活性。在可见光下光照60 min后,Bi_2MoO_6负载量为30%(w/w)的复合物具有最佳的光催化性能,其降解速率常数约为纯CoMoO_4的2倍。基于实验的所有表征,进一步地研究了Bi_2MoO_6/CoMoO_4体系相应的光催化机理。  相似文献   

12.
以钼酸钠以及五水合硝酸铋为原料,采用醇热法及高温退火制备了镂空Bi2MoO6微球光催化剂。采用X射线衍射(XRD)、红外光谱(FTIR)、场发射扫描电子显微镜(FESEM)、高分辨透射电镜(HRTEM)、物理吸附分析仪、紫外-可见漫反射(UV-Vis DRS)、荧光光谱分析(PL)以及电化学测试等分析方法分别对制备材料的晶体结构、微观形貌、比表面积和光学特性进行表征。以氧氟沙星(OFX)水溶液作为目标降解物,在可见光照射的条件下,探究了Bi2MoO6对OFX的光催化降解性能。实验结果表明:醇热法合成的球状钼酸铋的平均直径为500 nm,镂空结构使得球状Bi2MoO6的比表面积提高到片状Bi2MoO6的5倍。更大的比表面积为光催化提供了大量的吸附位点,在120 min的可见光辐射下,投放量为1 g·L^-1的Bi2MoO6对p H=7、浓度为10 mg·L^-1OFX水溶液的降解效率可达64%,而片状Bi2MoO6仅为31%。镂空球状的Bi2MoO6在强碱性环境具有优异的光催化效果,对OFX的降解率达到79%,在强碱性环境中,具有更优的光催化降解性能。  相似文献   

13.
《Thermochimica Acta》1987,112(2):245-257
The phase diagram of the system Gd2(MoO4)3-Bi(MoO4)3 has been studied by differential thermal analysis (DTA). Sealed platinum tubes were used as sample holders, in order to prevent the loss of Bi2O3 and MoO3 through volatilization at high temperature. Various solid solutions and new phases are reported: α-Gd2-x-Bix(MoO4)3, β -Gd2-x-Bix(MoO4)3, α-Bi2-xGdx(MoO4)3, 3Gd2(MoO4)3·2Bi2(MoO4)3, etc.  相似文献   

14.
The microstructures of commercially important bismuth molybdate catalysts in relation to olefin oxidation reactions are examined by electron microscopy (EM) techniques. The microstructural characterization has been carried out using dynamic (in situ) EM, high resolution EM, and microanalysis. The coprecipitated catalyst system Bi2MoO6 or γ, together with the γ phase, contains small amounts of tetragonal Bi2MoO6 phase, Bi2Mo3O12 (α phase), Bi2O3, and MoO3. In reduction with propylene, at catalyst operating temperatures of 400–500°C, in the dynamic experiments conducted on α- and γ-phase crystallites under reaction conditions no evidence for extended defects such as crystallographic shear planes has been obtained, instead an ordered intermediate phase similar to (101) Bi2Mo2O9 (β phase) is observed which is found to be unstable. Observations by electron microscopy have been confirmed with parallel measurements made in a reactor connected to a gas chromatograph and mass spectrometer system. The possible influence of the microstructural changes on the catalytic behavior of the system is examined.  相似文献   

15.
Phase equilibrium in the pseudo-quaternary system K2O–MoO3–P2O5–Bi2O3 was studied as three-component solvent K2MoO4–KPO3–MoO3 containing 15 mol% Bi2O3 during slow cooling and spontaneous crystallization. The results of the investigation were shown on a composition diagram, which indicates the crystallization fields of K2Bi(PO4)(MoO4), K5Bi(MoO4)4, BiPO4 and K3Bi5(PO4)6. New phosphate K3Bi5(PO4)6 was characterized by single-crystal X-ray diffraction (space group C2/c, a=17.680(4), b=6.9370(14), c=18.700(4) Å, β=113.79(3)°) and FTIR spectroscopy. The possibility of lone electron pair stereoactivity of bismuth was suggested using the calculations of characteristics of the Voronoi–Dirichlet polyhedra for K3Bi5(PO4)6 and K2Bi(PO4)(MoO4).  相似文献   

16.
The phase diagram of the ternary CoO-V2O5-MoO3 system and in particular its T-CoV2O6-MoO3 slice have been determined with DTA and X-ray phase analysis. CoV2O6 crystallizes in two modifications: a low-temperature γ-form of unknown structure and a high-temperature α-form of brannerite-type structure. The transition temperature is 660-665°C. The γ ? α transformations are very slow and the α-polymorph may be easily frozen. On doping with MoO3, a solid solution is formed that is described by the formula Co1?x?xV2?2xMo2xO6. Above x = 0.02 the α-type structure is stabilized. The xmax equals 0.22 at the eutectic temperature of 620°C and 0.20 at room temperature. Other features of the phase diagram, including its division into the natural subdiagrams and three ternary eutectics, are described in detail. X-Ray data are listed for α-CoV2O6 and for the solid solution having x = 0.20. On doping with MoO3 the monoclinic lattice dilates primarily in the direction of the b-axis.  相似文献   

17.
通过对铁电光催化剂Bi_2MoO_6和聚甲基丙烯酸甲酯(PMMA)构建的有机-无机复合膜材料施加电场极化,来探究铁电极化对Bi_2MoO_6光催化剂活性提升的影响。未极化的Bi_2MoO_6在光照40 min时降解罗丹明B(RhB)的效率为57.6%,在光照150min时对双酚A(BPA)的降解效率为33.4%。在15 V电压下极化1.5 h的Bi_2MoO_6材料在相同条件下降解罗丹明B和双酚A的效率分别达到98.1%和79.2%,光催化活性得到了较大的提升。光催化活性提升的原因归因于内部电场的增强。未极化的Bi_2MoO_6的内电场的铁电畴是无序、分布不均匀的,光生载流子非常容易发生体内复合。当外加电场极化Bi_2MoO_6时,Bi_2MoO_6的铁电畴趋于有序,极化方向趋于同一方向,表面一侧(C+区)产生正电荷,在另一侧(C-区)产生负电荷,从C-区指向C+区的极化电场推动光生电子和空穴分别迁移到C+和C-区域。这一过程促使光生电荷载流子快速从体内迁移至表面,提高和延长了光生载流子的分离效率和寿命,导致光催化活性的提升。  相似文献   

18.
通过水热法制备出一系列Z型异质结Cu2O/Bi2MoO6新型光催化剂。采用扫描电子显微镜、粉末X射线衍射、红外光谱、紫外可见吸收光谱等表征手段研究了催化剂的形貌、结构性质和光电化学性质,并以四环素(TC)为降解目标污染物,进一步探究了其催化效率。实验结果表明,Cu2O的加入提高了复合催化剂的光催化性能,其中20% Cu2O/Bi2MoO6复合催化剂(Cu2O和Bi2MoO6的质量比为20%)降解效果最好,100 min内可降解95%的TC。Cu2O与Bi2MoO6之间的协同作用使其可以吸收更多的可见光,所构建的Z型异质结改变了电子转移途径,提高了电子与空穴的分离效率,光催化活性显著提高。通过自由基捕获实验和能带结构,分析了Z型异质结Cu2O/Bi2MoO6复合催化剂光催化降解TC可能的机理。  相似文献   

19.
Novel Bi2MoO6/TiO2 heterojunction was fabricated by growing Bi2MoO6 nanosheets arrays on the vertically aligned TiO2 nanorods arrays via a two-step solvothermal method. The obtained Bi2MoO6/TiO2 hierarchical heterojunction showed excellent visible light photoelectrochemical performance. Compared with the pure TiO2 and Bi2MoO6, the photocurrent density of the heterojunction was increased 57 and 29 times, respectively. Furthermore, the hydrogen generation rate of the Bi2MoO6/TiO2 for photoelectrocatalytic water-splitting was about 6 times higher than that of the pure Bi2MoO6. The improved performance can be attributed to the synergistic effects of enhanced absorption of visible light, increase of migration rate and separation efficiency of photo-induced carriers.  相似文献   

20.
采用简单的两步水热法制备出了锆基金属有机骨架和钼酸铋的复合材料MOF-808/Bi2MoO6。通过X射线粉末衍射、傅里叶红外光谱、扫描电子显微镜、透射电子显微镜、X射线光电子能谱、紫外可见漫反射光谱、N2吸附-脱附测试和电化学测试对所制备材料的组成、微观结构、光学性质以及光生载流子的复合效率进行了分析。与纯Bi2MoO6和MOF-808相比,0.5%-MOF-808/Bi2MoO6复合材料展示出了较高的光催化活性,在可见光照射120 min时对抗生素环丙沙星(CIP)的降解率达89.7%。通过自由基捕获实验,证明了·O2-是主要活性物种,基于此我们提出了可能的光催化降解机理。  相似文献   

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