阅读说明：本技术 一种MoO3自组装空心球结构的制备方法 (MoO (MoO)3Preparation method of self-assembled hollow sphere structure ) 是由 郭嘉 黄立峰 李世伟 孟庆乐 张鹏 高峰 马谦 于 2020-06-05 设计创作，主要内容包括：本发明公开了一种MoO<Sub>3</Sub>自组装空心球结构的制备方法,步骤包括：将可溶性钼盐加入到水、乙醇、1,3,5-三甲苯和乙醇胺的混合溶剂中,搅拌均匀；然后,加入适量的氢氧化钾、丙烯酰胺、聚甲基丙烯酸甲酯,搅拌得到均匀溶液,经水热反应,将产物离心、洗涤干燥后得到前驱体；将前驱体进行煅烧,得到正交相的MoO<Sub>3</Sub>材料。本发明通过设计一种新颖的水热反应体系和调节煅烧机制,得到了尺寸均一、形貌可控的MoO<Sub>3</Sub>自组装空心球结构。本发明的优点在于所用的原料来源丰富,易于储存,合成工艺简单,产品的形貌特殊可控且尺寸均匀,可大量合成,在合成催化剂、电池电极、传感器等领域具有潜在的应用价值。(The invention discloses a MoO 3 The preparation method of the self-assembled hollow sphere structure comprises the following steps: adding soluble molybdenum salt into a mixed solvent of water, ethanol, 1,3, 5-trimethylbenzene and ethanolamine, and uniformly stirring; then, adding a proper amount of potassium hydroxide, acrylamide and polymethyl methacrylate, stirring to obtain a uniform solution, performing hydrothermal reaction, centrifuging a product, washing and drying to obtain a precursor; calcining the precursor to obtain orthorhombic MoO 3 A material. The invention designs a novel hydrothermal reaction system and adjusts a calcination mechanism to obtain MoO with uniform size and controllable morphology 3 Self-assembled hollow ball structure. The invention has the advantages of rich raw material sources, easy storage, simple synthesis process, special and controllable product appearance, uniform size, capability of large-scale synthesis and potential application value in the fields of synthesis catalysts, battery electrodes, sensors and the like.)

1. MoO (MoO)₃The preparation method of the self-assembly hollow sphere structure is characterized by comprising the following steps of:

(1) mixing water, ethanol, 1,3, 5-trimethylbenzene and ethanolamine to obtain a uniform mixed solution, adding soluble molybdenum salt, potassium hydroxide, acrylamide and polymethyl methacrylate into the obtained mixed solution, uniformly stirring, pouring into a reaction kettle, and reacting at a certain temperature for a period of time to obtain a precursor;

(2) calcining the precursor to obtain the orthorhombic MoO with adjustable size₃Self-assembled hollow ball structure.

2. The method of claim 1, wherein: in the step (1), the mol ratio of the soluble molybdenum salt, the potassium hydroxide, the acrylamide and the polymethyl methacrylate (PMMA) is 1: 0.6-1.8: 0.02-0.08: 0.03 to 0.075, wherein the molar amount of PMMA is based on the molar amount of the polymerized monomers thereof.

3. The method according to claim 1 or 2, characterized in that: in the step (1), the volume ratio of water, ethanol, 1,3, 5-trimethylbenzene and ethanolamine is 1: 0.7-1.5: 0.006-0.015: 0.1-0.2; in the step (1), the concentration of the soluble molybdenum salt in the mixed solution is 0.015-0.04 mol/L.

4. The method of claim 1, 2 or 3, wherein: in the step (1), the soluble molybdenum salt is ammonium salt of molybdenum.

5. The method according to any one of claims 1 to 4, wherein: in the step (1), the reaction time of the oven is 16-24 h, and the temperature is 160-200 ℃.

6. The method according to any one of claims 1 to 5, wherein: in the step (2), the calcining process is as follows: the precursor is insulated for 1-4 h at 480-600 ℃.

7. The method according to claim 1 or 6, wherein: in the step (2), the calcination is carried out in an air atmosphere; preferably, the temperature is raised from room temperature to 480-600 ℃ at a temperature raising rate of 1-3 ℃/min during the calcination.

8. The method according to any one of claims 1 to 4, wherein: the diameter of the hollow sphere is 0.4-3.6 μm, the structural unit is a plate-shaped structure with adjustable size, the side length of the plate-shaped structure is 0.1-1.8 μm, and the thickness is 50-400 nm.

Technical Field

The invention belongs to the field of preparation of environmental materials, and particularly relates to an orthogonal phase MoO with adjustable size₃A hydrothermal synthesis method of a self-assembled hollow sphere structure.

Background

Nowadays, environmental problems are more and more serious in China, and toxic, harmful, flammable and explosive hazardous gases discharged from the air can seriously threaten the safety of life, environment and property of people. The gas sensor can convert the information measured by the detected gas into an electric signal which can be measured through the gas sensor when the gas sensor works. Due to MoO₃Special layered structures, metal-semiconductor MoO₃Is becoming one of the most potential n-type semiconductor materials for detecting harmful gases, and has been reported to detect NO₂Ethanol, H₂S and H₂And the like.

MoO₃As a wide band gap n-type semiconductor oxide, there are mainly three crystal structures of orthorhombic phase (α -MoO)₃) Hexagonal phase (h-MoO)₃) And monoclinic phase (β -MoO)₃). Due to [ MoO ]₆]Octahedron [001 ]]More Mo-O-Mo bonds can be formed in the direction, and the arrangement mode can release more energy, so that MoO₃Preferred growth along the c-axis is more favored, so one-dimensional MoO₃The material is easier to prepare. As for the gas-sensitive property of the material, it is closely related to the crystal structure, the micro-morphology, the particle size, etc. of the material, and thus efforts are made to improve the gas-sensitive property of the material by changing and developing a new microstructure. At present, people prepare various two-dimensional and three-dimensional structures including nano arrays, nano sheets, nano spheres, nano tubes and the like by methods such as chemical vapor deposition, a sol-gel method, a hydrothermal method, an electrostatic spinning method and the like, and research the gas sensitivity of the structuresCan be used. For example, "Ling Zhu, Wen Zeng, Yanqiong Li and Jingdong Yang, Physica E, 106(2019) 170-₃The micro-cage structure is found to be similar to solid MoO₃Compared with a hollow structure, the polyhedron provides more surface active sites, and the gas sensitivity to ethanol gas is improved. "self-assembled MoO prepared by Electron Beam vapor deposition, LeiZhang, Zhongli Liu, Long Jin, Binbin Zhang, Haitao Zhang, Minhao Zhu and Weiqing Yang, Sens. initiators B Chem, 237 (2016) 350-₃The nanobelt obtains high-sensitivity H with excellent selectivity and stability₂And an S sensor having a detection limit of 1 ppm.

The hydrothermal method is a chemical reaction carried out in a closed pressure vessel under the conditions of high temperature and high pressure by using water as a solvent, and is used for preparing MoO₃The powder material prepared by a hydrothermal method has the advantages of high yield and purity, uniform appearance and size, good dispersibility and the like. To date, researchers have focused on one-dimensional and two-dimensional MoO₃The continuous research of nano materials aims at three-dimensional MoO at home and abroad₃The research on the nano material is less, and the orthorhombic phase MoO is not found yet₃The report on the self-assembly of hollow sphere structure. However, the traditional method for preparing the hollow sphere structure usually adopts a template method, has the problems of complicated preparation and poor repeatability, and can realize the preparation of the MoO with adjustable size by utilizing a one-step hydrothermal method and a subsequent calcination process by selecting a proper hydrothermal solvent system₃The hollow ball structure is formed by self-assembly. The characteristics of large specific surface area and many reaction active sites of the plate hollow sphere structure are favorable for researching MoO₃The forming mechanism and the gas-sensitive property of the hollow sphere structure.

Disclosure of Invention

Aiming at the problem that no orthorhombic phase MoO is prepared by hydrothermal method in the prior art₃The invention provides a self-assembled hollow sphere structure material, and provides a method for synthesizing orthorhombic MoO by a hydrothermal method and a subsequent calcination process₃The method for self-assembling the hollow sphere structure material can simply adjust the solvent system, the hydrothermal time and the hydrothermal temperatureThe addition amount of the surfactant and the calcining process are controlled, so that the micro morphology and the size of the product are controlled, and the obtained product is good in uniformity, good in repeatability and excellent in gas-sensitive performance.

The traditional method for preparing the hollow sphere structure usually adopts a template method, the template preparation and template removal steps are omitted by the template-free method, and the orthorhombic phase MoO is synthesized by utilizing a hydrothermal method and a subsequent calcination process₃Self-assembled hollow ball structure material. The specific scheme of the invention is as follows:

quadrature phase MoO₃The preparation method of the self-assembled hollow sphere structure material comprises the following steps:

(1) adding soluble molybdenum salt into a mixed solvent of water, ethanol and 1,3, 5-trimethylbenzene, and uniformly stirring;

(2) adding KOH, acrylamide and PMMA, stirring uniformly, adding ethanolamine, and stirring uniformly to obtain a mixed solution;

(3) carrying out hydrothermal reaction on the obtained uniform mixed solution to obtain a precursor;

(4) calcining the obtained precursor to obtain the orthorhombic phase MoO with adjustable size₃A hollow ball structure formed by self-assembly;

according to the method, water, ethanol, 1,3, 5-trimethylbenzene and ethanolamine are used as a mixed solvent, ammonium molybdate tetrahydrate is used as a molybdenum source, KOH, acrylamide and PMMA are introduced into a system, the reaction rate and the size and assembly of a microstructure are controlled, and finally the MoO with adjustable size is synthesized₃The hollow ball structure is formed by self-assembly. According to the invention, different surfactants are added, so that the growth process and the nucleation rate of the crystal are directly influenced, and different crystal faces are exposed. In the subsequent calcining process, the surface energy is reduced as a driving force, so that the surface ligand is removed, the surface active sites are exposed outside, and the MoO with adjustable size is obtained₃Self-assembled hollow ball structure.

Preferably, in the steps (1) and (2), the molar ratio of the soluble molybdenum salt, the potassium hydroxide, the acrylamide and the PMMA is 1: 0.6-1.8: 0.02-0.08: 0.03 to 0.075, wherein the molar amount of PMMA is based on the molar amount of the polymerized monomers thereof.

Further, in the step (1), the volume ratio of the water, the ethanol, the 1,3, 5-trimethylbenzene and the ethanolamine is 1: 0.7-1.5: 0.006-0.015: 0.1-0.2; in the step (1), the concentration of the soluble molybdenum salt in the mixed solution is 0.015-0.04 mol/L.

Further, in the step (1), the soluble molybdenum salt is an ammonium salt of molybdenum.

Further, in the step (3), the solvothermal reaction temperature is 160-200 ℃ and the time is 16-24 h.

Further, in the step (4), the treatment is performed in an air atmosphere; preferably, the temperature is raised from room temperature to 480-600 ℃ at a temperature raising rate of 1-3 ℃/min during the calcination.

According to the method, the obtained product is orthorhombic MoO₃The hollow sphere has the diameter of 0.4-3.6 microns, and the structural unit of the hollow sphere is a plate-shaped structure with adjustable size, the side length of the plate-shaped structure is 0.1-1.8 microns, and the thickness of the plate-shaped structure is 50-400 nm.

In the hydrothermal reaction, potassium hydroxide and ethanolamine are added to adjust the pH of the solution together, so that an alkaline environment required by the reaction is provided. The addition of ethanol and 1,3, 5-trimethylbenzene can make the molybdenum salt reach a certain critical saturation in the system, inhibit the preferred orientation in the crystal growth process, relatively increase the growth speed in the thickness direction of the crystal, and regulate the process of hydrothermal reaction. The solvent system consisting of water, ethanol, ethanolamine and 1,3, 5-trimethylbenzene enables the surfactant to be better deprotonated, and the reaction is easy to carry out. Acrylamide and PMMA are added to jointly play roles of a structure directing agent and a surfactant, on one hand, the acrylamide and the PMMA can interact with the surface of a crystal and selectively adsorb on different crystal faces, so that the appearance of a product is controlled, on the other hand, the viscosity of the solution can be improved, the moving rate of molybdenum ions under a high-temperature condition is adjusted, and a structure with good dispersity and uniform size is obtained. In the calcining process, long carbon chain ligands on the surface of the material disappear, the specific surface area is increased, the surface of the particle is exposed, and active sites are exposedIn addition, charge transmission and catalytic activity among particles are improved, crystallinity is improved, and more reactive sites are provided for target gas. Finally, the orthorhombic phase MoO with uniform and controllable size is obtained₃Self-assembled hollow ball structure. Therefore, the method is used for synthesizing MoO with hydrothermal method reported in other documents on the aspects of synthesis mechanism and micro-morphology regulation₃The materials have great difference and better technical innovation.

The invention designs a novel solution system, and prepares MoO with uniform size and stable appearance by regulating the proportion of each component of each surfactant and solvent and utilizing hydrothermal reaction and calcination process₃The hollow ball structure is formed by self-assembly. According to the invention, the precursor is prepared by a hydrothermal method, and then is calcined in the atmosphere of air, so that the method is simple and controllable, and is beneficial to large-scale production; meanwhile, reagents used for synthesis are common reagents in the market and have wide sources; the product has special appearance and has potential application value in the gas-sensitive field.

Drawings

FIG. 1 is a MoO synthesized in example 1 of the present invention₃X-ray diffraction (XRD) pattern of (a).

FIG. 2 shows the MoO synthesized in example 1 of the present invention₃Scanning Electron Microscope (SEM) images of (a).

FIG. 3 shows the MoO synthesized in example 1 of the present invention₃SEM pictures of (d).

Detailed Description

The present invention is further illustrated by the following examples, which are provided for the purpose of illustration only and are not intended to limit the scope of the invention.

In the examples which follow, the molar mass of PMMA, calculated as monomer, is 100.