A method for preparing tungsten oxide nanomaterials assisted by metal ions in acidic and alkaline environments

Abstract

The present invention relates to a method for preparing tungsten oxide nano-micro materials assisted by metal ions and in acidic and alkaline environments. Tungstate is used as a reactant, mixed with a certain amount of sodium chloride and a metal salt auxiliary agent and dissolved in water, the pH value of the aqueous solution system is adjusted to 3.5-4.5, reacted at 160-220°C in a hydrothermal reactor for 2-48 hours, and then calcined at 300-900°C for 1-3 hours to obtain a spherical tungsten oxide nano-micro material with a particle size of 200-3000nm. Different from conventional synthesis methods, the advantage of the method of the present invention is that it realizes the high-yield synthesis of tungsten oxide nano-micro materials in an acidic environment; in particular, it can produce tungsten oxide materials that cannot be obtained without the assistance of metal ions under alkaline conditions, avoid the use of acid, and the preparation process is safe and simple. The synthesis under alkaline conditions provides practical guidance for solving the difficult problem of alkali recovery in tungsten metallurgical processes; the synthesized tungsten oxide has good crystallinity, high yield, uniform particles, stable crystal structure, and strong electron transmission ability. The present invention can provide tungsten oxide nanomaterials with adjustable structure, composition and uniform particle size, which is helpful to expand the practical application of the materials in the fields of photo / electrochromic devices, lithium ion batteries, gas sensors, photocatalysis, anti-fouling and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of nano-micro material preparation, and relates to a method for preparing tungsten oxide nano-micro material. Background Art

[0002] Tungsten oxide is an eco-friendly, cheap, abundant and readily available material. It has attracted much attention due to its special properties and wide range of modification methods. Tungsten oxide is an n-type semiconductor material with a suitable band gap. It can absorb visible light in a wide range and become one of the most promising photocatalysts. The adsorption of tungsten oxide on a variety of gases gives it excellent gas-sensitive properties. Tungsten oxide has the ability to embed lithium ions, which makes it both an energy storage material and an electrochromic material. In addition, tungsten oxide also has advantages such as chemical stability, photocorrosion resistance, biocompatibility, adjustable band gap, excellent hole mobility, etc. Therefore, tungsten oxide has important application value in the fields of photo / electrochromic devices, lithium-ion batteries, gas sensors, photocatalysis, and anti-fouling.

[0003] From the perspective of crystal structure, tungsten oxide is a highly complex material. Different synthesis routes and post-treatments will affect the morphology, crystal phase and defect structure of the obtained tungsten oxide, thereby affecting the intrinsic properties of the material and its application. The synthesis method of tungsten oxide is usually liquid phase synthesis, which is simple and easy to adjust, including hydrothermal method and solvothermal method. Among them, the hydrothermal method is the most widely used, mainly using tungstate as a tungsten source, controlling the pH range between 1 and 2, and hydrothermally decomposing to form tungsten oxide. For example, Sun et al. used sodium tungstate as the tungsten source and sodium oleate as the structure directing agent, and prepared tungsten trioxide nanotubes by hydrothermal treatment at 180°C under pH 1 (S. Sun, et al., Journal of the American Chemical Society, 2018, 140 (20), 6474-6482); Zhang et al. added hexadecyltrimethylammonium bromide (CTAB) surfactant to assist hydrothermal synthesis at a pH of 1-1.5 to achieve an orthorhombic phase tungsten trioxide hierarchical structure (Y. Zhang, et al., Materials Letters, 2019, 235, 49-52); Liu et al. prepared tungsten trioxide nano-micro hollow microspheres by dissolving sodium tungstate and oxalic acid in a mixed solution of isopropanol and hydrochloric acid (Y. Liu, et al., Crystal Engineering Communication, 2014, 16, 7493-7501). Most of the reported hydrothermal synthesis methods are carried out in an environment with a pH value less than 2, which requires a large amount of strong acid for adjustment. In addition, tungsten oxide cannot be formed under alkaline conditions using the original reported methods. There are no reports on the synthesis of tungsten oxide induced by metal ions under weakly acidic or alkaline conditions with high pH, ​​which is still a blank.

[0004] The present invention proposes a method for synthesizing tungsten oxide nanomaterials in an acidic or alkaline environment with the assistance of metal ions. The process is simple and controllable. The tungsten oxide material synthesized by the method has the characteristics of high purity, good dispersibility, high crystallinity, uniform size, etc., and shows good photocatalytic activity and gas-sensitive properties, and has a wide range of application prospects. At present, there is a problem of difficulty in alkali recovery in tungsten metallurgical processes. In order to achieve alkali recovery in industry, multiple unit operations such as solution conversion, solvent extraction, ion exchange, evaporation crystallization, etc. are required in the process operation. The method proposed in the present invention will have substantial guiding significance for the process of directly precipitating tungsten trioxide or its hydrate to recover alkali. Summary of the invention

[0005] The invention provides a method for preparing a tungsten oxide nano-micro material, which is simple and easy to implement and can be controlled to synthesize a series of tungsten oxide nano-micro materials with different crystal structures, different morphologies, different sizes and different compositions.

[0006] The preparation method provided by the present invention adopts the following technical scheme:

[0007] A method for preparing tungsten oxide nanomaterials in an acidic or alkaline environment with the assistance of metal ions, characterized in that it comprises the following steps:

[0008] Dissolve tungstate and sodium chloride in water, add a certain amount of metal salt, adjust the pH value with a small amount of acid to make the solution acidic or alkaline, mix well and transfer to a high-pressure reactor, react at 160-220℃ for 2-48 hours, wash, dry and grind the formed solid product into fine powder, calcine at 300-900℃ for 1-3 hours to obtain solid powder, which is tungsten oxide nano-micro material. The preparation method has the following main features:

[0009] The introduction of metal ion additives is the key condition for the formation of tungsten oxide nanomaterials in an alkaline environment.

[0010] In an acidic environment, the interaction between metal ion additives and tungstate intermediates can regulate the formation and structure of tungsten oxide nanomaterials.

[0011] The adjusted acidic and alkaline system means that the pH value of the reaction solution before hydrothermal treatment is in the range of 0.5-9.0.

[0012] The metal ion additive is derived from one or more of the nitrates, acetates or chlorides of chromium, manganese, nickel, iron, cobalt, nickel, copper or zinc metals, such as chromium nitrate, nickel nitrate, chromium chloride and the like.

[0013] The amount of the added metal ion additive accounts for 0.5%-15% of the mole percentage of the added tungsten element.

[0014] The particle size of the prepared tungsten oxide nano-micro material is 200-3000nm.

[0015] The prepared tungsten oxide is a material having a cubic phase, a monoclinic phase, a hexagonal phase and a mixed phase crystal structure.

[0016] The obtained solid powder product is a tungsten oxide nano-micro material containing a trace amount of doped metal, or a tungsten oxide nano-micro material without doped metal and having metal vacancies obtained after acid treatment.

[0017] Different from other preparation methods, the method provided by the present invention is to form tungsten oxide by regulating the interaction between metal ions and tungstate intermediates, and to achieve the formation of tungsten oxide in an alkaline environment, and to improve the uniformity of tungsten oxide particles under acidic conditions. The tungsten oxide material prepared by this method has good photocatalytic and gas-sensitive properties, and its composition, structure, and performance are easy to modulate, and has a wide range of market application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a SEM image of a tungsten oxide material obtained in an example of the present invention;

[0019] Figure 2 The gas-sensitivity performance of the tungsten oxide material prepared in the example of the present invention to acetone is compared. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with examples, but the present invention is not limited to the following examples.

[0021] Example 1

[0022] Dissolve 6.6000g of sodium tungstate in 30ml of water, add 5.8500g of sodium chloride, and after the solution becomes clear and transparent, adjust the solution to neutrality with hydrochloric acid, add 0.4637g of chromium nitrate, adjust the pH to 3.5, stir for 1 hour, transfer to a polytetrafluoroethylene-lined high-pressure reactor, keep the temperature at 180℃ for 24 hours, centrifuge the product, wash, dry at 60℃, grind, and calcine at 300℃ in a muffle furnace for 2 hours to obtain tungsten oxide material.

[0023] Example 2

[0024] Dissolve 6.6000g of sodium tungstate in 30ml of water, add 5.8500g of sodium chloride, and after the solution becomes clear and transparent, adjust the solution to neutrality with hydrochloric acid, add 0.2319g of chromium nitrate, adjust the pH to 4.5, stir for 2 hours, transfer to a polytetrafluoroethylene-lined high-pressure reactor, keep the temperature at 180℃ for 18 hours, centrifuge the product, wash, dry at 60℃, grind, and calcine at 300℃ in a muffle furnace for 2 hours to obtain tungsten oxide material.

[0025] Example 3

[0026] Dissolve 6.6000g of sodium tungstate in 30ml of water, add 5.8500g of sodium chloride, and after the solution becomes clear and transparent, adjust the solution to neutrality with hydrochloric acid, add 0.4637g of chromium nitrate, stir for 1 hour, transfer to a polytetrafluoroethylene-lined high-pressure reactor, keep the temperature at 180℃ for 24 hours, centrifuge, wash, dry at 60℃, grind, and calcine at 300℃ in a muffle furnace for 1 hour to obtain tungsten oxide material.

Claims

1. A method for preparing tungsten oxide nanomaterials in a metal ion-assisted and acidic environment, characterized in that: The following steps are involved: Dissolve tungstate and sodium chloride in water, add a certain amount of metal salt, adjust the pH value to 3.5-4.5 with a small amount of acid, transfer to a high-pressure reactor, react at 160-220°C for 2-48 hours, wash, dry, grind into fine powder, calcine at 300°C for 1-3 hours, and obtain solid powder, which is tungsten oxide nano-micro material; In an acidic environment, the interaction between metal ions and tungstate intermediates promotes the formation of uniform tungsten oxide nanostructures. The amount of added metal ions accounts for 4.33%-8.67% of the mole percentage of tungsten element; The metal salt is chromium nitrate.

2. The method for preparing tungsten oxide nanomaterials in a metal ion-assisted and acidic environment according to claim 1, characterized in that: The tungsten oxide nanomaterial prepared by this method has a particle size of 200-3000nm.

3. The method for preparing tungsten oxide nanomaterials in a metal ion-assisted and acidic environment according to claim 1, characterized in that: The tungsten oxide prepared by the method includes cubic phase, monoclinic phase, hexagonal phase and mixed phase crystal structure materials.

4. The method for preparing tungsten oxide nanomaterials in a metal ion-assisted and acidic environment according to claim 1, characterized in that: After acid treatment, a tungsten oxide nanomaterial without metal doping and with metal vacancies is obtained.

Images