A titanate nanofiber material, its preparation method and application

Abstract

The present invention belongs to the technical field of functional semiconductor materials, and particularly relates to a titanate nanofiber material, a preparation method thereof and an application. The preparation method of the titanate nanofiber material of the present invention comprises the following steps: (1) uniformly mixing a block copolymer, a titanium source and a solvent to obtain a precursor spinning solution; (2) electrospinning the precursor spinning solution to obtain precursor nanofibers, and calcining the precursor nanofibers to obtain porous titanium oxide nanofibers; (3) adding the porous titanium oxide nanofibers into an alkali metal hydroxide solution, and heating under ultrasonic conditions to obtain the titanate nanofiber material. The titanate nanofiber material of the present invention presents a multi-level structural morphology feature, and has advantages such as a large specific surface area, a high porosity and a large number of active sites.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional semiconductor materials, and particularly relates to a titanate nanofiber material, a preparation method thereof, and an application thereof. Background Art

[0002] Titanates are an important class of functional semiconductor ceramic materials, with excellent physical and chemical properties (such as dielectric, piezoelectric, ferroelectric, photocatalytic, photochromic, wave-absorbing and other characteristics), and are widely used in the fields of energy, environment, sensing, electronic devices, etc. Traditional titanates are mainly prepared by solid-phase sintering method. However, the titanates synthesized by this method are mostly powder particles, often having disadvantages such as large particle size, easy agglomeration, many impurities, and small specific surface area, and it is difficult to meet the development needs of modern functional ceramic technology.

[0003] One-dimensional titanate nanomaterials have shown unique advantages in improving physical and chemical properties and expanding applications due to their large aspect ratio and excellent optoelectronic transport properties, and have become the forefront and hot spot in the research field of titanate materials. In the prior art, there are reports of obtaining titanate products by hydrothermal method, and then obtaining the final titanate nanotubes through vacuum activation treatment and chemical vapor deposition treatment. However, this method has a cumbersome preparation process, long time consumption, harsh conditions (high temperature, high pressure, vacuum, etc.), and high energy consumption, and is not suitable for large-scale preparation. There are also literature reports of directly preparing titanate nanofibers by electrospinning technology. Although the synthesis method is simple, the obtained fibers are relatively dense, have a small specific surface area, single morphology, and poor structural tunability, which severely restricts the application performance of titanate fiber materials.

[0004] Therefore, it is necessary to provide an improved technical solution for the deficiencies of the above-mentioned prior art. Summary of the Invention

[0005] The purpose of the present invention is to provide a titanate nanofiber material, a preparation method thereof, and an application thereof, so as to solve or improve the problems of complex preparation process of titanate nanofibers or poor application performance of titanate nanofibers in the prior art.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A preparation method of a titanate nanofiber material, comprising the following steps: (1) mixing a block copolymer, a titanium source, and a solvent evenly to obtain a precursor spinning solution; (2) performing electrospinning on the precursor spinning solution to obtain precursor nanofibers, and calcining the precursor nanofibers to obtain porous titanium oxide nanofibers; (3) adding the porous titanium oxide nanofibers into an alkali metal hydroxide solution, and heating under ultrasonic conditions to obtain the titanate nanofiber material.

[0007] Preferably, in step (3), the alkali metal hydroxide is at least one of lithium hydroxide, barium hydroxide, and strontium hydroxide.

[0008] Preferably, in step (3), the power of the ultrasound is 0.3 - 1 kW, and the ultrasound frequency is 10 - 30 kHz; the temperature of the heating is 80 - 150 °C, and the heating time is 1 - 3 h.

[0009] Preferably, in step (3), the concentration of the alkali metal hydroxide in the alkali metal hydroxide solution is 2 - 10 mol / L; the mass ratio of the porous titanium oxide nanofibers to the alkali metal hydroxide solution is 1:(20 - 200).

[0010] Preferably, in step (1), the titanium source is isopropyl titanate and / or tetrabutyl titanate; the block copolymer is at least one of polyvinylpyrrolidone - b - polystyrene, polymethyl methacrylate - b - polystyrene, and polyethylene glycol - b - polystyrene; the solvent is at least one of ethanol, acetic acid, chloroform, tetrahydrofuran, and N,N - dimethylformamide; the mass ratio of the block copolymer, the titanium source, and the solvent is 1:(2 - 10):(10 - 20).

[0011] Preferably, in step (2), the parameters of the electrospinning are: spinning voltage 8 - 30 kV, perfusion speed 0.5 - 6 mL / h, and fiber receiving distance 8 - 30 cm.

[0012] Preferably, in step (2), the calcination is carried out in an air atmosphere; the heating rate during the calcination is 1 - 5 °C / min, the calcination temperature is 350 - 500 °C, and the holding time is 30 - 240 min.

[0013] The present invention also provides a titanate nanofiber material, which adopts the following technical solution: a titanate nanofiber material, which is prepared by the method described above.

[0014] Preferably, the titanate nanofiber material includes a nanofiber axis and nano - needles, and the nano - needles are distributed on the surface of the nanofiber axis; the average diameter of the nanofiber axis is 120 - 900 nm; the average diameter of the nano - needles is 10 - 50 nm; the specific surface area of the titanate nanofiber material is 100 - 350 m 2 / g.

[0015] The present invention also provides the application of the titanate nanofiber material described above, which adopts the following technical solution: the application of the titanate nanofiber material described above in photocatalytic organic pollutants, piezoelectric catalytic organic pollutants, or battery anode materials.

[0016] Beneficial effects:

[0017] The present invention realizes the preparation of titanate nanofiber materials (which can have a pine needle-like structure) by combining electrospinning and an ultrasonic-assisted thermal alkali reaction (reacting with an alkali metal hydroxide solution under heating conditions). Compared with existing methods such as hydrothermal / vacuum activation - chemical vapor deposition method and single electrospinning method, the prepared one-dimensional titanate materials have the advantages of high specific surface area, rich morphology and structure, and strong tunability.

[0018] The preparation method of the titanate nanofiber materials of the present invention has mild reaction conditions, short time consumption, simple steps, and easy operation. The multi-level structure and morphology of the materials can be effectively regulated simply by controlling the solution concentration, reaction time, and ultrasonic heating conditions.

[0019] The titanate nanofiber materials of the present invention exhibit multi-level structure and morphology characteristics, have the advantages of large specific surface area, high porosity, and many active sites, and at the same time have the unique optoelectronic transmission characteristics of one-dimensional semiconductor nanomaterials. Compared with the traditional single-structure titanate nanofiber materials, the titanate nanofiber materials (which can have a pine needle-like structure) have significantly improved physical and chemical properties such as light, electricity, and catalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The schematic diagrams in the specification, which form a part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments and descriptions thereof are used to explain the present invention and do not unduly limit the present invention. Among them:

[0021] Figure 1 is the microscopic morphology diagram of the titanate (strontium titanate) nanofiber materials provided in Example 3 of the present invention;

[0022] Figure 2 is the microscopic morphology diagram of the product obtained in Comparative Example 1;

[0023] Figure 3 is the microscopic morphology diagram of the product obtained in Comparative Example 2;

[0024] Figure 4 Among them, (a) is the microscopic morphology diagram of the product obtained in Comparative Example 3, and (b) is the XRD diagram of the product obtained in Comparative Example 3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art shall fall within the protection scope of the present invention.

[0026] The present invention will be described in detail below in conjunction with embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0027] Aiming at the problems of complex preparation process of titanate nanofibers or poor application performance of titanate nanofibers (relatively dense, small specific surface area, single morphology or poor structural tunability) existing currently, the present invention provides a preparation method of a titanate nanofiber material. The preparation method of the titanate nanofiber material in the embodiments of the present invention includes the following steps: (1) mixing a block copolymer, a titanium source and a solvent evenly to obtain a precursor spinning solution; (2) performing electrospinning on the precursor spinning solution to obtain precursor nanofibers, and calcining the precursor nanofibers to obtain porous titanium oxide nanofibers; (3) adding the porous titanium oxide nanofibers into an alkali metal hydroxide solution, and heating under ultrasonic conditions to obtain the titanate nanofiber material.

[0028] The preparation method of the titanate nanofiber material of the present invention first prepares porous titanium oxide nanofibers by electrospinning, and then realizes the transformation of titanium oxide nanofibers into titanate nanofibers through an ultrasonic-assisted hot alkali reaction (reacting with an alkali metal hydroxide solution under heating conditions). This method is simple and easy to operate, has low cost, and the obtained titanate nanofibers have multi-level structural characteristics, similar to a pine needle-like morphology, with an easily controllable microstructure, a large specific surface area, and broad application prospects.

[0029] Among them: The preparation principle of the porous titanium oxide nanofibers in step (2) of the present invention is as follows: adding a block copolymer (preferably an amphiphilic block copolymer) to the precursor spinning solution can, on the one hand, increase the solution viscosity to improve spinnability; on the other hand, during the flight of the spinning jet, due to the rapid evaporation of the solvent, the block copolymer in the precursor nanofibers will undergo microphase separation, and finally the polymer template is removed by calcination to obtain porous titanium oxide nanofibers.

[0030] The principle of preparing the titanate nanofiber material (showing a pine needle-like structure) by ultrasonic-assisted hot alkali reaction in step (3) of the present invention is as follows: adding the porous titanium oxide nanofibers into an alkali metal hydroxide solution, and then heating the solution under ultrasonic action. Since the porous titanium oxide nanofibers have abundant active sites, ultrasonic treatment will promote the full contact and collision between the hot alkali solution and the active sites on the surface of the titanium oxide fibers, thereby reducing the activation energy of the reaction and accelerating the reaction rate, enabling the titanium oxide nanofibers to be rapidly transformed into titanate nanofibers, and at the same time, titanate nanosheets with an unstable structure are generated on the fiber surface; further under the ultrasonic shear force, these ultra-thin two-dimensional titanate nanosheets will gradually curl into one-dimensional titanate nanoneedles, and finally a titanate nanofiber material with a nanostructure of uniformly distributed nanoneedles on the surface of the nanofibers, that is, a pine needle-like structure, is formed.

[0031] In a preferred embodiment of the present invention, in step (3), the alkali metal hydroxide is at least one of lithium hydroxide, barium hydroxide and strontium hydroxide.

[0032] In a preferred embodiment of the present invention, in step (3), the power of the ultrasonic wave is 0.3 - 1 kW (for example, 0.3 kW, 0.5 kW, 0.7 kW, 0.9 kW or 1 kW), and the ultrasonic frequency is 10 - 30 kHz (for example, 10 kHz, 15 kHz, 20 kHz, 25 kHz or 30 kHz); the heating temperature is 80 - 150 °C (for example, 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C or 150 °C), and the heating time is 1 - 3 h (for example, 1 h, 1.5 h, 2 h, 2.5 h or 3 h). Among them, the ultrasonic treatment mainly promotes the occurrence of the hot alkali reaction, reduces the reaction temperature, increases the conversion rate, and promotes the formation of the final nano-needle structure; therefore, the power and frequency of the ultrasonic wave cannot be too low, otherwise the content of the titanate produced and the nano-needle structure are both less. The heating temperature determines whether titanium oxide can be converted into titanate, so the temperature cannot be too low, and the heating time will affect the conversion degree of the titanate and the length of the nano-needles.

[0033] In a preferred embodiment of the present invention, in step (3), the concentration of the alkali metal hydroxide in the alkali metal hydroxide solution is 2 - 10 mol / L (for example, 2 mol / L, 4 mol / L, 6 mol / L, 8 mol / L or 10 mol / L); the mass ratio of the porous titanium oxide nanofibers to the alkali metal hydroxide solution is 1:(20 - 200) (for example, 1:20, 1:50, 1:100, 1:150 or 1:200). Among them, the concentration of the alkali metal cannot be too low, otherwise it will lead to a reduction in the yield of the titanate and the inability to form a nano-needle structure.

[0034] In a preferred embodiment of the present invention, in step (1), the titanium source is isopropyl titanate and / or tetrabutyl titanate; the block copolymer is at least one of polyvinylpyrrolidone-b-polystyrene, polymethyl methacrylate-b-polystyrene, and polyethylene glycol-b-polystyrene; the solvent is at least one of ethanol, acetic acid, chloroform, tetrahydrofuran, and N,N-dimethylformamide; the mass ratio of the block copolymer, titanium source, and solvent is 1:(2-10):(10-20) (for example, 1:2:10, 1:2:20, 1:6:10, 1:6:20, 1:10:10, 1:10:15, or 1:10:20). The block copolymer in the precursor spinning solution undergoes microphase separation during the electrospinning process, and a polymer-rich phase and an inorganic-rich phase will be formed inside the precursor nanofibers; during the subsequent calcination process, the polymer-rich phase will undergo thermal decomposition to form tiny voids, while the inorganic phase will crystallize and transform into titanium oxide. Therefore, the finally produced titanium oxide nanofibers have a porous structure.

[0035] In a preferred embodiment of the present invention, in step (2), the parameters of electrospinning are: the spinning voltage is 8-30 kV (for example, 8 kV, 13 kV, 18 kV, 23 kV, 28 kV, or 30 kV), the perfusion rate is 0.5-6 mL / h (0.5 mL / h, 1 mL / h, 2 mL / h, 3 mL / h, 4 mL / h, 5 mL / h, or 6 mL / h), and the fiber receiving distance is 8-30 cm (for example, 8 cm, 12 cm, 16 cm, 20 cm, 24 cm, 27 cm, or 30 cm). The parameters of electrospinning will affect the diameter of the nanofiber axis in the prepared titanate nanofiber material.

[0036] In a preferred embodiment of the present invention, in step (2), the calcination is carried out in an air atmosphere; the heating rate during calcination is 1-5 °C / min (for example, 1 °C / min, 2 °C / min, 3 °C / min, 4 °C / min, or 5 °C / min), the calcination temperature is 350-500 °C (for example, 350 °C, 400 °C, 450 °C, or 500 °C), and the holding time is 30-240 min (for example, 30 min, 90 min, 130 min, 160 min, 200 min, or 240 min).

[0037] The present invention also proposes a titanate nanofiber material, and the titanate nanofiber material of the embodiment of the present invention is prepared by the method described above.

[0038] In a preferred embodiment of the titanate nanofiber material of the present invention, the titanate nanofiber material includes a nanofiber axis and nanoacicular projections, and the nanoacicular projections are distributed on the surface of the nanofiber axis; the average diameter of the nanofiber axis is 120 - 900 nm (for example, 120 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm or 900 nm); the average diameter of the nanoacicular projections is 10 - 50 nm; the specific surface area of the titanate nanofiber material is 100 - 350 m 2 / g (for example, 100 m 2 / g, 150 m 2 / g, 200 m 2 / g, 250 m 2 / g, 300 m 2 / g or 350 m 2 / g).

[0039] The present invention also provides an application of the titanate nanofiber material. In the embodiments of the present invention, the titanate nanofiber material is used in photocatalytic organic pollutants, piezocatalytic organic pollutants or battery anode materials. Preferably, when the alkali metal hydroxide used is strontium hydroxide, the product obtained in step (3) is strontium titanate nanofibers, which can be used for photocatalytic degradation of tetracycline; when the alkali metal hydroxide used is barium hydroxide, the product obtained in step (3) is barium titanate nanofibers, which can be used for piezocatalytic degradation of methylene blue; when the alkali metal hydroxide used is lithium hydroxide, the product obtained in step (3) is lithium titanate nanofibers, which can be used as a battery anode material.

[0040] The following specifically describes the titanate nanofiber material of the present invention, its preparation method and application through specific examples.

[0041] The block copolymer used in the following examples was purchased from Delta Reagents; the solvents, titanium sources and alkaline hydroxides were purchased from Aladdin Reagents.

[0042] Example 1

[0043] The preparation method of the titanate nanofiber material in this example includes the following steps:

[0044] (1) Polyvinylpyrrolidone-b-polystyrene and titanium isopropoxide were added to N,N-dimethylformamide and mixed and stirred evenly at a mass ratio of 1:2:10 to obtain a precursor spinning solution;

[0045] (2) Electrospinning was performed on the precursor spinning solution (spinning voltage 8 kV, perfusion rate 0.5 mL / h, fiber receiving distance 8 cm) to obtain precursor nanofibers. The precursor nanofibers were calcined at a heating rate of 5 °C / min to 500 °C (holding time 30 min, calcination carried out in an air atmosphere) to obtain porous titanium oxide nanofibers;

[0046] (3) The porous titanium oxide nanofibers were added to a strontium hydroxide solution (concentration of strontium hydroxide 2 mol / L, mass ratio of porous titanium oxide nanofibers to strontium hydroxide solution 1:20), and heated at 80 °C for 1 h under ultrasonic conditions (ultrasonic power 0.3 kW, ultrasonic frequency 10 kHz) to obtain the titanate nanofiber material (strontium titanate nanofibers) of this example.

[0047] The titanate nanofiber material of this example was prepared by the method described above. The titanate nanofiber material of this example is strontium titanate nanofibers, including a nanofiber axis and nano needles. The average diameter of the nanofiber axis is 120 nm, and the average diameter of the nano needles is 10 nm. The specific surface area of the strontium titanate nanofibers of this example is 220 m 2 / g.

[0048] Example 2

[0049] The preparation method of the titanate nanofiber material of this example includes the following steps:

[0050] (1) Polymethyl methacrylate-b-polystyrene and tetrabutyl titanate were added to tetrahydrofuran and mixed and stirred evenly in a mass ratio of 1:10:20 to obtain a precursor spinning solution;

[0051] (2) Electrospinning was performed on the precursor spinning solution (spinning voltage 30 kV, perfusion rate 6 mL / h, fiber receiving distance 30 cm) to obtain precursor nanofibers. The precursor nanofibers were calcined at a heating rate of 1 °C / min to 350 °C (holding time 240 min, calcination carried out in an air atmosphere) to obtain porous titanium oxide nanofibers;

[0052] (3) The porous titanium oxide nanofibers were added to a strontium hydroxide solution (concentration of strontium hydroxide 10 mol / L, mass ratio of porous titanium oxide nanofibers to strontium hydroxide solution 1:200), and heated at 150 °C for 3 h under ultrasonic conditions (ultrasonic power 1 kW, ultrasonic frequency 30 kHz) to obtain the titanate nanofiber material (strontium titanate nanofibers) of this example.

[0053] The titanate nanofiber material of this embodiment is prepared by the method described above. The titanate nanofiber material of this embodiment is strontium titanate nanofiber, which includes a nanofiber axis and nano needles. The average diameter of the nanofiber axis is 900 nm, and the average diameter of the nano needles is 50 nm. The specific surface area of the strontium titanate nanofiber of this embodiment is 100 m 2 / g.

[0054] Example 3

[0055] The preparation method of the titanate nanofiber material of this embodiment includes the following steps:

[0056] (1) Add polyethylene glycol-b-polystyrene and titanium isopropoxide to chloroform, mix and stir evenly according to a mass ratio of 1:5:15 to obtain a precursor spinning solution;

[0057] (2) Perform electrospinning on the precursor spinning solution (spinning voltage 15 kV, perfusion speed 2 mL / h, fiber receiving distance 15 cm) to obtain precursor nanofibers, and heat the precursor nanofibers to 450 °C at a heating rate of 2 °C / min (holding time is 180 min, and the calcination is carried out in an air atmosphere) to obtain porous titanium oxide nanofibers;

[0058] (3) Add the porous titanium oxide nanofibers to a strontium hydroxide solution (the concentration of strontium hydroxide is 5 mol / L, and the mass ratio of the porous titanium oxide nanofibers to the strontium hydroxide solution is 1:100), and heat at 120 °C for 2 h under ultrasonic conditions (ultrasonic power 0.5 kW, ultrasonic frequency 20 kHz) to obtain the titanate nanofiber material (strontium titanate nanofiber) of this embodiment.

[0059] The titanate nanofiber material of this embodiment is prepared by the method described above. The titanate nanofiber material of this embodiment is strontium titanate nanofiber, which includes a nanofiber axis and nano needles. The average diameter of the nanofiber axis is 275 nm, and the average diameter of the nano needles is 28 nm. The specific surface area of the strontium titanate nanofiber of this embodiment is 350 m 2 / g.

[0060] Example 4

[0061] The preparation method of the titanate nanofiber material of this embodiment includes the following steps:

[0062] (1) Add polyethylene glycol-b-polystyrene and titanium isopropoxide to chloroform, mix and stir evenly according to a mass ratio of 1:6:15 to obtain a precursor spinning solution;

[0063] (2) Electrospin the precursor spinning solution (spinning voltage 18 kV, perfusion rate 3 mL / h, fiber receiving distance 16 cm) to obtain precursor nanofibers, and calcine the precursor nanofibers at a heating rate of 2 °C / min to 500 °C (holding time is 120 min, calcination is carried out in an air atmosphere) to obtain porous titanium oxide nanofibers;

[0064] (3) Add the porous titanium oxide nanofibers to a barium hydroxide solution (concentration of barium hydroxide is 5 mol / L, mass ratio of porous titanium oxide nanofibers to barium hydroxide solution is 1:120), and heat at 120 °C for 3 h under ultrasonic conditions (ultrasonic power 0.5 kW, ultrasonic frequency 15 kHz) to obtain the titanate nanofiber material (barium titanate nanofibers) of this example.

[0065] The titanate nanofiber material of this example is prepared by the method described above. The titanate nanofiber material of this example is barium titanate nanofibers, including a nanofiber axis and nanoneedles. The average diameter of the nanofiber axis is 410 nm, and the average diameter of the nanoneedles is 33 nm. The specific surface area of the barium titanate nanofibers of this example is 295 m 2 / g.

[0066] Example 5

[0067] The preparation method of the titanate nanofiber material of this example includes the following steps:

[0068] (1) Add polyethylene glycol-b-polystyrene and titanium isopropoxide to chloroform, mix and stir evenly according to a mass ratio of 1:5:17 to obtain a precursor spinning solution;

[0069] (2) Electrospin the precursor spinning solution (spinning voltage 15 kV, perfusion rate 1.5 mL / h, fiber receiving distance 15 cm) to obtain precursor nanofibers, and calcine the precursor nanofibers at a heating rate of 2 °C / min to 480 °C (holding time is 150 min, calcination is carried out in an air atmosphere) to obtain porous titanium oxide nanofibers;

[0070] (3) Add the porous titanium oxide nanofibers to a lithium hydroxide solution (concentration of lithium hydroxide is 5 mol / L, mass ratio of porous titanium oxide nanofibers to lithium hydroxide solution is 1:80), and heat at 100 °C for 3 h under ultrasonic conditions (ultrasonic power 0.5 kW, ultrasonic frequency 20 kHz) to obtain the titanate nanofiber material (lithium titanate nanofibers) of this example.

[0071] The titanate nanofiber material of this embodiment is prepared by the method described above. The titanate nanofiber material of this embodiment is lithium titanate nanofiber, including a nanofiber axis and nano needles. The average diameter of the nanofiber axis is 350 nm, and the average diameter of the nano needles is 30 nm. The specific surface area of the lithium titanate nanofiber of this embodiment is 330 m 2 / g.

[0072] Comparative Example 1

[0073] The difference between this comparative example and Example 3 is only that an equal amount of polyvinylpyrrolidone is selected to replace polyethylene glycol-b-polystyrene; the rest are the same as those in Example 3. Compared with Example 3, the dense non-porous titanium oxide nanofibers are obtained after the treatment in step (2) in Comparative Example 1; the conversion rate of the titanate nanofibers (the product obtained after the treatment in step (3)) finally obtained in Comparative Example 1 is low, and there are only a small number of nano needle structures on the fiber surface (the microscopic morphology is as Figure 2 shown).

[0074] The average diameter of the nanofiber axis of the titanate nanofibers prepared in this comparative example is 385 nm, the average diameter of the nano needles is 32 nm, and the specific surface area is 39 m 2 / g.

[0075] This is mainly because the non-porous titanium oxide nanofibers have few active sites, and the hot alkali solution can only react with the fiber surface. However, due to the lack of a pore structure connected to the outside in the fiber interior, it is difficult to react with the hot alkali solution, resulting in a small amount of titanate nanofibers generated, low conversion rate, and sparse distribution of nano needles.

[0076] Comparative Example 2

[0077] The difference between this comparative example and Example 3 is only that ultrasonic assistance is not used during the hot alkali reaction (step (3)), and the rest are the same as those in Example 3.

[0078] Compared with Example 3, the conversion rate of the titanate nanofibers finally obtained in Comparative Example 2 is low, and there are no nano needle structures on the fiber surface (the microscopic morphology diagram is as Figure 3 shown).

[0079] The average diameter of the nanofiber axis of the titanate nanofibers prepared in this comparative example is 285 nm, and the specific surface area is 78 m 2 / g.

[0080] This is mainly because the lack of ultrasonic treatment reduces the contact and collision opportunities between the hot alkali solution and the porous titanium oxide fibers, making it difficult for the titanium oxide nanofibers to be fully converted into titanate nanofibers; in addition, the lack of ultrasonic shear force also causes the non-steady nano sheets generated on the fiber surface not to curl into nano needle structures.

[0081] Comparative Example 3

[0082] The difference between this comparative example and Example 3 is only that the heating temperature of the hot alkali reaction is 70 °C, and the rest are the same as those in Example 3.

[0083] Compared with Example 3, no titanate nanofibers were finally obtained in Comparative Example 3, and it was still titanium oxide nanofibers (the microscopic morphology is as shown in (a) in Figure 4 and the XRD pattern is as shown in (b) in Figure 4 ). This is mainly because the heating temperature of the hot alkali reaction is too low, and even with the assistance of ultrasonic waves, the critical conditions required for the formation of titanate nanofibers are not reached.

[0084] Comparative Example 4

[0085] The difference between this comparative example and Example 4 is only that ultrasonic wave-assisted treatment was not used during the hot alkali reaction (step (3)), and the rest are the same as those in Example 4. Compared with Example 4, the conversion rate of the titanate nanofibers finally obtained in Comparative Example 4 is low, and the fiber surface does not contain nano-needle structures.

[0086] Comparative Example 5

[0087] The difference between this comparative example and Example 5 is only that ultrasonic wave-assisted treatment was not used during the hot alkali reaction (step (3)), and the rest are the same as those in Example 5. Compared with Example 5, the conversion rate of the titanate nanofibers finally obtained in Comparative Example 5 is low, and the fiber surface does not contain nano-needle structures.

[0088] Experimental Example

[0089] 1. The strontium titanate nanofibers of Examples 1-3 and the products obtained in Comparative Examples 1-3 were used for photocatalytic degradation of tetracycline:

[0090] Reaction conditions: A UV lamp with a power of 40 W and a wavelength of 365 nm was selected as the light source, the reaction time was 30 min, the catalyst dosage was 10 mg, and the pollutant concentration was 10 mg / L.

[0091] The photocatalytic performances of the strontium titanate nanofibers of Examples 1-3, the nanofibers of Comparative Examples 1-3, and electrospun ordinary strontium titanate nanofibers (without a pine needle-like structure) were measured.

[0092] Among them, the specific steps for preparing ordinary strontium titanate nanofibers are as follows: Polyvinylpyrrolidone, tetrabutyl titanate, and strontium acetate are added to a mixed solvent of ethanol, acetic acid, and water, and mixed and stirred evenly according to a mass ratio of 1:11:7:10:6:2 to obtain a precursor spinning solution. Subsequently, electrospinning is carried out on it (spinning voltage 15 kV, perfusion rate 2 mL / h, fiber receiving distance 15 cm) to obtain precursor nanofibers, and then the precursor nanofibers are calcined at a heating rate of 2 °C / min to 500 °C (holding time is 150 min, and the calcination is carried out in an air atmosphere), and finally ordinary strontium titanate nanofibers are obtained (without a nano-needle structure, small specific surface area, and few high-activity sites).

[0093] The experimental results are shown in Table 1 below:

[0094] Table 1

[0095]

[0096] 2. Use the barium titanate nanofibers of Example 4 and the product obtained in Comparative Example 4 for piezoelectric catalytic degradation of methylene blue:

[0097] Reaction conditions: Ultrasonic waves with a power of 240 W and a frequency of 40 kHz are selected to drive the piezoelectric effect for catalytic performance testing. The reaction time is 30 min, the catalyst dosage is 10 mg, and the pollutant concentration is 10 mg / L.

[0098] Determine the piezoelectric catalytic performance of the barium titanate nanofibers of Example 4 and electrospun ordinary barium titanate nanofibers (without a pine needle-like structure).

[0099] Among them, the specific steps for preparing ordinary barium titanate nanofibers are as follows: Polyvinylpyrrolidone, tetrabutyl titanate, and barium acetate are added to a mixed solvent of ethanol, acetic acid, and water, and mixed and stirred evenly according to a mass ratio of 1:11:8.5:10:6:2 to obtain a precursor spinning solution. Subsequently, electrospinning is carried out on it (spinning voltage 15 kV, perfusion rate 2 mL / h, fiber receiving distance 15 cm) to obtain precursor nanofibers, and then the precursor nanofibers are calcined at a heating rate of 2 °C / min to 500 °C (holding time is 150 min, and the calcination is carried out in an air atmosphere), and finally ordinary barium titanate nanofibers are obtained (without a nano-needle structure, small specific surface area, and few high-activity sites).

[0100] The experimental results are shown in Table 2 below:

[0101] Table 2

[0102] Sample Example 4 Comparative Example 4 Ordinary barium titanate nanofibers Organic matter degradation rate 88％ 57％ 53％

[0103] 3. The lithium titanate nanofibers of Example 5 and the product obtained in Comparative Example 5 were used as the anode material for charge and discharge tests.

[0104] Charge and discharge conditions: Cycle 1000 times at a current density of 5C. The charge and discharge performance of the lithium titanate nanofibers of Example 5 and the electrospun ordinary lithium titanate nanofibers (without the pine needle-like structure) was measured.

[0105] The specific steps for preparing the ordinary lithium titanate nanofibers are as follows: Polyvinylpyrrolidone, tetrabutyl titanate, and lithium acetate were added to a mixed solvent of ethanol, acetic acid, and water, and mixed and stirred evenly according to a mass ratio of 1:11:4:10:6:2 to obtain a precursor spinning solution. Subsequently, electrospinning was carried out on it (spinning voltage 15 kV, perfusion rate 2 mL / h, fiber receiving distance 15 cm) to obtain precursor nanofibers, and then the precursor nanofibers were calcined at a heating rate of 2 °C / min to 500 °C (holding time 150 min, calcination carried out in an air atmosphere), and finally ordinary lithium titanate nanofibers were obtained (without a nano-needle structure, small specific surface area, and few high-activity sites).

[0106] The experimental results are shown in Table 3 below:

[0107] Table 3

[0108] Sample Example 5 Comparative Example 5 Ordinary lithium titanate nanofibers Initial specific capacity 148.6 mAh / g 117.6 mAh / g 113.8 mAh / g Specific capacity after 1000 cycles 147.4 mAh / g 110.3 mAh / g 105.4 mAh / g

[0109] To sum up:

[0110] (1) The present invention realizes the preparation of titanate nanofiber materials (which can have a pine needle-like structure) by combining electrospinning and ultrasonic-assisted hot alkali reaction (reacting with an alkali metal hydroxide solution under heating conditions). The prepared titanate materials have the advantages of high conversion rate, large specific surface area, rich and adjustable morphology and structure levels.

[0111] (2) The preparation method of the titanate nanofiber materials of the present invention has mild reaction conditions, short time consumption, simple steps, strong universality, and easy operation. The multi-level structure morphology of the materials can be effectively regulated simply by controlling the solution concentration, reaction time, and ultrasonic heating conditions, and the controllable preparation of various titanate nanomaterials can be realized, such as strontium titanate, barium titanate, lithium titanate, etc.

[0112] (3) The titanate nanofiber materials of the present invention exhibit multi-level structure morphology characteristics, have the advantages of large specific surface area, high porosity, and many active sites, and at the same time have the unique optoelectronic transmission characteristics of one-dimensional semiconductor nanomaterials. Compared with ordinary electrospun titanate nanofiber materials, the titanate nanofiber materials of the present invention (with a pine needle-like structure) have been significantly improved in terms of physical and chemical properties such as light, electricity, and catalysis.

[0113] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a titanate nanofiber material, characterized in that, It includes the following steps: (1) Mix the block copolymer, titanium source and solvent evenly to obtain a precursor spinning solution; (2) Perform electrospinning on the precursor spinning solution to obtain precursor nanofibers, and calcine the precursor nanofibers to obtain porous titanium oxide nanofibers; (3) Add the porous titanium oxide nanofibers into an alkali metal hydroxide solution, and heat under ultrasonic conditions to obtain the titanate nanofiber material; In step (1), the block copolymer is an amphiphilic block copolymer; In step (2), the calcination is carried out in an air atmosphere, and the calcination temperature is 350 - 500 °C; In step (3), the heating temperature is 80 - 150 °C, and the heating time is 1 - 3 h.

2. The preparation method of the titanate nanofiber material according to claim 1, characterized in that In step (3), the alkali metal hydroxide is at least one of lithium hydroxide, barium hydroxide and strontium hydroxide; 3. The preparation method of the titanate nanofiber material according to claim 1, characterized in that, In step (3), the power of the ultrasonic wave is 0.3 - 1 kW, and the ultrasonic frequency is 10 - 30 kHz; 4. The preparation method of the titanate nanofiber material according to claim 1, characterized in that, In step (3), the concentration of the alkali metal hydroxide in the alkali metal hydroxide solution is 2 - 10 mol / L; The mass ratio of the porous titanium oxide nanofibers to the alkali metal hydroxide solution is 1:(20 - 200).

5. The preparation method of the titanate nanofiber material according to claim 1, characterized in that, In step (1), the titanium source is isopropyl titanate and / or tetrabutyl titanate; The block copolymer is at least one of polyvinylpyrrolidone-b-polystyrene, polymethyl methacrylate-b-polystyrene and polyethylene glycol-b-polystyrene; The solvent is at least one of ethanol, acetic acid, chloroform, tetrahydrofuran and N,N-dimethylformamide; The mass ratio of the block copolymer, titanium source and solvent is 1:(2 - 10):(10 - 20).

6. The preparation method of the titanate nanofiber material according to claim 1, characterized in that, In step (2), the parameters of the electrospinning are: spinning voltage 8 - 30 kV, perfusion speed 0.5 - 6 mL / h, and fiber receiving distance 8 - 30 cm.

7. The preparation method of the titanate nanofiber material according to claim 1, characterized in that, In step (2), The heating rate during the calcination is 1 - 5 °C / min, and the heat preservation time is 30 - 240 min.

8. A titanate nanofiber material, characterized in that, The titanate nanofiber material is prepared by the method described in any one of claims 1 - 7.

9. The titanate nanofiber material according to claim 8, wherein The titanate nanofiber material includes a nanofiber shaft and nano needles, and the nano needles are distributed on the surface of the nanofiber shaft; The average diameter of the nanofiber shaft is 120 - 900 nm; The average diameter of the nano needles is 10 - 50 nm; The specific surface area of the titanate nanofiber material is 100 - 350 m 2 / g.

10. Application of the titanate nanofiber material according to claim 8 or 9 in photocatalytic organic pollutants, piezoelectric catalytic organic pollutants or battery anode materials.

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