Bi2Ti2O7 nanofiber photocatalyst and its preparation method and application

Abstract

The present invention belongs to the technical field of preparation and application of photocatalysts, and specifically relates to Bi2Ti2O7 nanofiber photocatalysts, preparation methods and applications thereof. The preparation method of the Bi2Ti2O7 nanofiber photocatalyst described in the present invention comprises the following steps: adding bismuth acetate to a mixed solution of glacial acetic acid and methanol to obtain solution A; adding tetrabutyl titanate to acetylacetone and methanol to obtain solution B; adding solution B dropwise to solution A to obtain solution C; adding polyvinyl pyrrolidone to solution C to obtain a precursor solution; loading the precursor solution into a syringe, performing electrostatic spinning, and simultaneously irradiating with infrared light to obtain precursor nanofibers; calcining the precursor nanofibers to obtain a Bi2Ti2O7 nanofiber photocatalyst. The Bi2Ti2O7 nanofiber photocatalyst prepared by the present invention has a single-phase structure, a large specific surface area, and good dispersibility. The present invention also provides applications of the catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation and application of photocatalysts, and specifically relates to a Bi2Ti2O7 nanofiber photocatalyst and a preparation method and application thereof. Background Art

[0002] Among the many advanced oxidation technologies, photocatalysis can use sunlight to excite photocatalysts to produce highly active free radicals, which can effectively degrade organic molecules and has broad application prospects in wastewater treatment. One-dimensional nanofibers can support a greater degree of mechanical deformation, have good dispersion uniformity, a large specific surface area, and high activity, giving them greater performance advantages in applications. Electrospinning has unique advantages in the preparation of one-dimensional nanomaterials: 1) low cost, no need for expensive experimental equipment; 2) high yield, and can be prepared on a large scale industrially; 3) easy control, which can achieve uniform doping at the molecular level. Therefore, electrospinning technology is expected to become the mainstream preparation technology for the industrial production of one-dimensional nanomaterials.

[0003] Although the traditional photocatalytic material TiO2 has advantages such as low cost and low toxicity, its wide band gap, which can only be excited by ultraviolet light, limits its application. Therefore, the development of photocatalytic materials that can utilize visible light is of great significance. Bi2Ti2O7 has a pyrochlore phase structure, a narrow band gap, high visible light absorption rate, and good stability, and has great application potential in visible light catalysis. However, because bismuth titanate materials have multiple phases and the crystallization temperatures of different phases are very close, the products after the electrospinning sintering process are often prone to forming multi-phase systems. In addition, the electrospinning precursor solution is often prepared using solvents such as N,N-dimethylformamide and ethylene glycol dimethyl ether, which have high boiling points. Since the solvent cannot evaporate quickly and effectively, the spun precursor nanofibers are prone to cross-linking between the fibers on the collector, resulting in poor dispersion uniformity of the prepared nanofiber photocatalyst, reducing its photocatalytic activity.

[0004] For example, CN106345451A discloses a multiphase bismuth titanate nanofiber, wherein a spinning solution is prepared using N,N-dimethylformamide and anhydrous ethanol as solvents, polyvinyl pyrrolidone K90 as a template, citric acid as a crosslinking agent, bismuth nitrate hydrate and tetrabutyl titanate as raw materials; a precursor fiber is prepared by electrospinning; and a precursor fiber is calcined to obtain Bi 12 TiO 20 / Bi4Ti3O 12 Multiphase nanofibers lose the advantages brought by single-phase structure. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing a Bi2Ti2O7 nanofiber photocatalyst. The prepared catalyst has a single-phase structure and good dispersibility. The present invention also provides the application of the catalyst.

[0006] The method for preparing the Bi2Ti2O7 nanofiber photocatalyst of the present invention comprises the following steps:

[0007] (1) adding a bismuth source to a mixed solution of glacial acetic acid and methanol and stirring until dissolved to obtain solution A; adding a titanium source to acetylacetone and methanol and stirring until dissolved to obtain solution B;

[0008] (2) adding solution B dropwise to solution A to obtain solution C;

[0009] (3) adding polyvinyl pyrrolidone to solution C and stirring to obtain a precursor solution;

[0010] (4) The precursor solution is loaded into a syringe with a metal needle and electrospun while being irradiated with infrared light to obtain precursor nanofibers on aluminum foil;

[0011] (5) The precursor nanofibers were heated to 450-550°C at a heating rate of 5-6°C / min, kept warm for 2-2.5 hours in an air atmosphere, and naturally cooled to room temperature to obtain Bi2Ti2O7 nanofiber photocatalysts.

[0012] In step (1), the bismuth source is bismuth acetate, and the titanium source is tetrabutyl titanate.

[0013] The volume ratio of glacial acetic acid to methanol in step (1) is (1:1)-(1:2); the concentration of bismuth source in solution A is 0.05-0.1 mol / L.

[0014] In step (1), the molar ratio of tetrabutyl titanate to acetylacetone is (1:2)-(1:2.5), and the concentration of tetrabutyl titanate in solution B is 0.5-1 mol / L.

[0015] The stirring temperature of step (1) is 45-55° C., and the stirring speed is 450-550 rpm.

[0016] In step (2), the molar ratio of Bi in solution A to Ti in solution B is (1:1)-(1:1.5).

[0017] The mass concentration of polyvinyl pyrrolidone in the precursor solution of step (3) is 4.5-5.5%.

[0018] In step (3), the stirring temperature is 45-55° C., the stirring speed is 450-550 rpm, and the stirring time is 12-24 h.

[0019] During the spinning process in step (4), the voltage is 15-20 kV, the feed rate is 0.5-1 mL / h, the distance between the tip of the metal needle and the aluminum foil is 10-15 cm; the power of the infrared light irradiation is 200-300 W, and the spinning machine chamber is maintained at 70-80° C.

[0020] The Bi2Ti2O7 nanofiber photocatalyst is obtained by the preparation method of the Bi2Ti2O7 nanofiber photocatalyst.

[0021] The Bi2Ti2O7 nanofiber photocatalyst is used for photocatalytic degradation of dyes. The specific steps are: manually grind the Bi2Ti2O7 nanofiber photocatalyst for 5 minutes, place it in a rhodamine B solution (1g / L Bi2Ti2O7 nanofiber photocatalyst and 5mg / L rhodamine B solution), and stir at 450-550 rpm for 30-40 minutes in the dark. The solution is then placed in a 25°C constant temperature water bath and illuminated with a xenon lamp (200-300W with a 420nm filter). Every 10 minutes, the solution is centrifuged and the absorbance of the supernatant is measured to calculate the degradation efficiency.

[0022] Specifically, the preparation method of the Bi2Ti2O7 nanofiber photocatalyst comprises the following steps:

[0023] (1) adding bismuth acetate to a mixed solution of glacial acetic acid and methanol, wherein the concentration of bismuth acetate is 0.05-0.1 mol / L, the volume ratio of glacial acetic acid to methanol is (1:1)-(1:2), and stirring at 45-55°C and 450-550 rpm until dissolved to obtain solution A; adding tetrabutyl titanate to acetylacetone and methanol, wherein the molar ratio of tetrabutyl titanate to acetylacetone is (1:2)-(1:2.5), the concentration of tetrabutyl titanate is 0.5-1 mol / L, and stirring at 45-55°C and 450-550 rpm until dissolved to obtain solution B;

[0024] (2) slowly adding solution B dropwise to solution A at 45-55°C and 450-550 rpm, wherein the molar ratio of Bi in solution A to Ti in solution B is (1:1)-(1:1.5), to obtain solution C;

[0025] (3) adding polyvinyl pyrrolidone to solution C at a concentration of 4.5-5.5%, stirring at 450-550 rpm for 12-24 hours at 45-55° C. to obtain a uniform, transparent precursor solution;

[0026] (4) The precursor solution was loaded into a syringe with a metal needle (the inner diameter of the metal needle was 0.34 mm and the exposed length was 13 mm) for electrospinning. During the spinning process, the voltage was 15-20 kV, the feed rate was 0.5-1 mL / h, and the distance between the tip of the metal needle and the aluminum foil was 10-15 cm. At the same time, infrared light irradiation was performed with a power of 200-300 W. The spinning chamber was maintained at 70-80° C. to obtain precursor nanofibers on the aluminum foil.

[0027] (5) The precursor nanofibers prepared in step (3) are placed in a corundum crucible, and then the crucible is placed in a muffle furnace, and the temperature is raised to 450-550°C at a heating rate of 5-6°C / min, kept at this temperature for 2-2.5 hours in an air atmosphere, and naturally cooled to room temperature to obtain a Bi2Ti2O7 nanofiber photocatalyst.

[0028] The present invention uses bismuth acetate and tetrabutyl titanate as bismuth and titanium sources, low-boiling-point methanol as solvent, and glacial acetic acid as solvent and stabilizer, and adopts three steps to prepare a uniform and transparent precursor solution. The solution is then rapidly evaporated by infrared irradiation during the electrospinning process. This "low-boiling-point solvent + infrared irradiation heating" method can effectively solve the cross-linking problem between precursor fibers during the spinning process. After a post-sintering process and controlled sintering temperature, highly dispersed, porous, single-phase Bi2Ti2O7 nanofibers can be obtained. The nanofiber photocatalyst has very excellent catalytic activity in dye degradation. Compared with the existing technology, the present invention has the following beneficial effects:

[0029] (1) The Bi2Ti2O7 nanofiber photocatalyst prepared by the method of the present invention has excellent dispersibility.

[0030] (2) The nanofiber photocatalyst prepared by the method of the present invention is made of pure single-phase Bi2Ti2O7 material.

[0031] (3) The Bi2Ti2O7 nanofiber photocatalyst prepared by the method of the present invention still retains a good nanofiber morphology after grinding.

[0032] (4) The Bi2Ti2O7 nanofibers prepared in the present invention have excellent photocatalytic degradation activity for Rhodamine B.

[0033] (5) The preparation method of the Bi2Ti2O7 nanofiber photocatalyst of the present invention is safe and reliable, with simple process and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the X-ray diffraction pattern of the Bi2Ti2O7 nanofiber photocatalyst prepared in Example 1.

[0035] Figure 2 This is a scanning electron microscope image of the Bi2Ti2O7 nanofiber photocatalyst prepared in Example 1.

[0036] Figure 3 This is a transmission electron microscope image of the Bi2Ti2O7 nanofiber photocatalyst prepared in Example 1.

[0037] Figure 4 This is a performance diagram of the Bi2Ti2O7 nanofiber photocatalyst prepared in Example 1 and applied to the degradation of Rhodamine B.

[0038] Figure 5 This is the X-ray diffraction pattern of the material prepared in Comparative Example 1.

[0039] Figure 6 This is the X-ray diffraction pattern of the material prepared in Comparative Example 2.

[0040] Figure 7 The Tauc relationship diagram of the samples prepared in Example 1 and Comparative Example 2 is shown.

[0041] Figure 8 The absorption spectra of the samples prepared in Example 1 and Comparative Example 2 are shown.

[0042] Figure 9 This is a scanning electron microscope image of the material prepared in Comparative Example 3.

[0043] Figure 10 This is a scanning electron microscope image of the material prepared in Comparative Example 5. DETAILED DESCRIPTION

[0044] The present invention will be further described below with reference to specific embodiments.

[0045] Example 1

[0046] The preparation method of the Bi2Ti2O7 nanofiber photocatalyst comprises the following steps:

[0047] (1) adding bismuth acetate to a mixed solution of glacial acetic acid and methanol, wherein the concentration of bismuth acetate is 0.1 mol / L and the volume ratio of glacial acetic acid to methanol is 1:1, and stirring at 50°C and 500 rpm until dissolved, to obtain solution A; adding tetrabutyl titanate to acetylacetone and methanol, wherein the molar ratio of tetrabutyl titanate to acetylacetone is 1:2 and the concentration of tetrabutyl titanate is 0.5 mol / L, and stirring at 50°C and 500 rpm until dissolved, to obtain solution B;

[0048] (2) Solution B was slowly added dropwise to solution A at 50°C and 500 rpm, wherein the molar ratio of Bi in solution A to Ti in solution B was 1:1, to obtain solution C;

[0049] (3) Add polyvinyl pyrrolidone to solution C at a concentration of 5%, and stir at 50°C and 500 rpm for 24 h to obtain a uniform, transparent precursor solution;

[0050] (4) The precursor solution was loaded into a syringe with a metal needle (the inner diameter of the metal needle was 0.34 mm and the exposed length was 13 mm) for electrospinning. During the spinning process, the voltage was 20 kV, the feed rate was 1 mL / h, and the distance between the tip of the metal needle and the aluminum foil was 15 cm. At the same time, infrared light irradiation was performed with a power of 300 W. The spinning chamber was maintained at 70°C to obtain precursor nanofibers on the aluminum foil.

[0051] (5) The precursor nanofibers were placed in a corundum crucible, and then the crucible was placed in a muffle furnace, and the temperature was raised to 500°C at a rate of 6°C / min. The temperature was kept at this temperature for 2 h in an air atmosphere, and the crucible was naturally cooled to room temperature to obtain a Bi2Ti2O7 nanofiber photocatalyst.

[0052] Example 2

[0053] The preparation method of the Bi2Ti2O7 nanofiber photocatalyst comprises the following steps:

[0054] (1) adding bismuth acetate to a mixed solution of glacial acetic acid and methanol, wherein the concentration of bismuth acetate is 0.05 mol / L and the volume ratio of glacial acetic acid to methanol is 1:1, and stirring at 50°C and 500 rpm until dissolved, to obtain solution A; adding tetrabutyl titanate to acetylacetone and methanol, wherein the molar ratio of tetrabutyl titanate to acetylacetone is 1:2.5 and the concentration of tetrabutyl titanate is 0.5 mol / L, and stirring at 50°C and 500 rpm until dissolved, to obtain solution B;

[0055] (2) Solution B was slowly added dropwise to solution A at 50°C and 5000 rpm, wherein the molar ratio of Bi in solution A to Ti in solution B was 1:1, to obtain solution C;

[0056] (3) Add polyvinyl pyrrolidone to solution C at a concentration of 5%, and stir at 50°C and 500 rpm for 12 h to obtain a uniform, transparent precursor solution;

[0057] (4) The precursor solution was loaded into a syringe with a metal needle (the inner diameter of the metal needle was 0.34 mm and the exposed length was 13 mm) for electrospinning. During the spinning process, the voltage was 15 kV, the feed rate was 0.5 mL / h, and the distance between the tip of the metal needle and the aluminum foil was 10 cm. At the same time, infrared light irradiation was performed with a power of 200 W. The spinning chamber was maintained at 70°C to obtain precursor nanofibers on the aluminum foil.

[0058] (5) The precursor nanofibers were placed in a corundum crucible, and then the crucible was placed in a muffle furnace, and the temperature was raised to 450°C at a heating rate of 5°C / min. The temperature was kept at this temperature for 2 h in an air atmosphere, and the crucible was naturally cooled to room temperature to obtain a Bi2Ti2O7 nanofiber photocatalyst.

[0059] Example 3

[0060] The preparation method of the Bi2Ti2O7 nanofiber photocatalyst comprises the following steps:

[0061] (1) adding bismuth acetate to a mixed solution of glacial acetic acid and methanol, wherein the concentration of bismuth acetate is 0.05 mol / L and the volume ratio of glacial acetic acid to methanol is 1:1, and stirring at 50°C and 500 rpm until dissolved, to obtain solution A; adding tetrabutyl titanate to acetylacetone and methanol, wherein the molar ratio of tetrabutyl titanate to acetylacetone is 1:2.5 and the concentration of tetrabutyl titanate is 0.5 mol / L, and stirring at 50°C and 500 rpm until dissolved, to obtain solution B;

[0062] (2) Solution B was slowly added dropwise to solution A at 50°C and 5000 rpm, wherein the molar ratio of Bi in solution A to Ti in solution B was 1:1, to obtain solution C;

[0063] (3) Add polyvinyl pyrrolidone to solution C at a concentration of 5%, and stir at 50°C and 500 rpm for 24 h to obtain a uniform, transparent precursor solution;

[0064] (4) The precursor solution was loaded into a syringe with a metal needle (the inner diameter of the metal needle was 0.34 mm and the exposed length was 13 mm) for electrospinning. During the spinning process, the voltage was 15 kV, the feed rate was 0.5 mL / h, and the distance between the tip of the metal needle and the aluminum foil was 10 cm. At the same time, infrared light irradiation was performed with a power of 300 W. The spinning chamber was maintained at 70°C to obtain precursor nanofibers on the aluminum foil.

[0065] (5) The precursor nanofibers were placed in a corundum crucible, and then the crucible was placed in a muffle furnace, and the temperature was raised to 550°C at a rate of 5°C / min. The temperature was kept at this temperature for 2 h in an air atmosphere, and the crucible was naturally cooled to room temperature to obtain a Bi2Ti2O7 nanofiber photocatalyst.

[0066] Example 4

[0067] The preparation method of the Bi2Ti2O7 nanofiber photocatalyst comprises the following steps:

[0068] (1) adding bismuth acetate to a mixed solution of glacial acetic acid and methanol, wherein the concentration of bismuth acetate is 0.1 mol / L and the volume ratio of glacial acetic acid to methanol is 1:2, and stirring at 55°C and 450-550 rpm until dissolved, to obtain solution A; adding tetrabutyl titanate to acetylacetone and methanol, wherein the molar ratio of tetrabutyl titanate to acetylacetone is 1:2 and the concentration of tetrabutyl titanate is 1 mol / L, and stirring at 45°C and 450 rpm until dissolved, to obtain solution B;

[0069] (2) Solution B was slowly added dropwise to solution A at 45°C and 550 rpm, wherein the molar ratio of Bi in solution A to Ti in solution B was 1:1.2, to obtain solution C;

[0070] (3) Add polyvinyl pyrrolidone to solution C at a concentration of 4.5%, and stir at 55°C and 550 rpm for 12 h to obtain a uniform, transparent precursor solution;

[0071] (4) The precursor solution was loaded into a syringe with a metal needle (the inner diameter of the metal needle was 0.34 mm and the exposed length was 13 mm) for electrospinning. During the spinning process, the voltage was 15 kV, the feed rate was 0.5 / h, and the distance between the tip of the metal needle and the aluminum foil was 10 cm. At the same time, infrared light irradiation was performed with a power of 200 W. The spinning chamber was maintained at 80°C to obtain precursor nanofibers on the aluminum foil.

[0072] (5) The precursor nanofibers were placed in a corundum crucible, and then the crucible was placed in a muffle furnace, and the temperature was raised to 500°C at a rate of 5°C / min. The temperature was kept for 2.5 hours in an air atmosphere, and the crucible was naturally cooled to room temperature to obtain a Bi2Ti2O7 nanofiber photocatalyst.

[0073] Example 5

[0074] The preparation method of the Bi2Ti2O7 nanofiber photocatalyst comprises the following steps:

[0075] (1) adding bismuth acetate to a mixed solution of glacial acetic acid and methanol, wherein the concentration of bismuth acetate is 0.1 mol / L and the volume ratio of glacial acetic acid to methanol is 1:2, and stirring is carried out at 55°C and 550 rpm until dissolved, thereby obtaining solution A; adding tetrabutyl titanate to acetylacetone and methanol, wherein the molar ratio of tetrabutyl titanate to acetylacetone is 1:2 and the concentration of tetrabutyl titanate is 1 mol / L, and stirring is carried out at 45°C and 550 rpm until dissolved, thereby obtaining solution B;

[0076] (2) Solution B was slowly added dropwise to solution A at 55°C and 450 rpm, wherein the molar ratio of Bi in solution A to Ti in solution B was 1:1.5, to obtain solution C;

[0077] (3) Add polyvinyl pyrrolidone to solution C at a concentration of 4.5%, and stir at 55°C and 550 rpm for 24 h to obtain a uniform, transparent precursor solution;

[0078] (4) The precursor solution was loaded into a syringe with a metal needle (the inner diameter of the metal needle was 0.34 mm and the exposed length was 13 mm) for electrospinning. During the spinning process, the voltage was 18 kV, the feed rate was 0.8 mL / h, and the distance between the tip of the metal needle and the aluminum foil was 13 cm. At the same time, infrared light irradiation was performed with a power of 250 W. The spinning chamber was maintained at 75°C to obtain precursor nanofibers on the aluminum foil.

[0079] (5) The precursor nanofibers were placed in a corundum crucible, and then the crucible was placed in a muffle furnace and heated to 500°C at a rate of 5.5°C / min. The temperature was kept at this temperature for 2.5 hours in an air atmosphere and the crucible was naturally cooled to room temperature to obtain a Bi2Ti2O7 nanofiber photocatalyst.

[0080] Comparative Example 1

[0081] A method for preparing a nanofiber photocatalyst comprises the following steps:

[0082] (1) adding bismuth acetate to a mixed solution of glacial acetic acid and methanol, wherein the concentration of bismuth acetate is 0.1 mol / L and the volume ratio of glacial acetic acid to methanol is 1:1, and stirring at 50°C and 500 rpm until dissolved, to obtain solution A; adding tetrabutyl titanate to acetylacetone and methanol, wherein the molar ratio of tetrabutyl titanate to acetylacetone is 1:2 and the concentration of tetrabutyl titanate is 0.5 mol / L, and stirring at 50°C and 500 rpm until dissolved, to obtain solution B;

[0083] (2) Solution B was slowly added dropwise to solution A at 50°C and 500 rpm, wherein the molar ratio of Bi in solution A to Ti in solution B was 1:1, to obtain solution C;

[0084] (3) Add polyvinyl pyrrolidone to solution C at a concentration of 5%, and stir at 50°C and 500 rpm for 24 h to obtain a uniform, transparent precursor solution;

[0085] (4) The precursor solution was loaded into a syringe with a metal needle (the inner diameter of the metal needle was 0.34 mm and the exposed length was 13 mm) for electrospinning. During the spinning process, the voltage was 20 kV, the feed rate was 1 mL / h, and the distance between the tip of the metal needle and the aluminum foil was 15 cm. At the same time, infrared light irradiation was performed with a power of 300 W. The spinning chamber was maintained at 70°C to obtain precursor nanofibers on the aluminum foil.

[0086] (5) The precursor nanofibers were placed in a corundum crucible, and then the crucible was placed in a muffle furnace, and the temperature was raised to 400°C at a rate of 6°C / min, kept at this temperature for 2 hours in an air atmosphere, and naturally cooled to room temperature to obtain a nanofiber photocatalyst.

[0087] Comparative Example 2

[0088] A method for preparing a nanofiber photocatalyst comprises the following steps:

[0089] (1) adding bismuth acetate to a mixed solution of glacial acetic acid and methanol, wherein the concentration of bismuth acetate is 0.1 mol / L and the volume ratio of glacial acetic acid to methanol is 1:1, and stirring at 50°C and 500 rpm until dissolved, to obtain solution A; adding tetrabutyl titanate to acetylacetone and methanol, wherein the molar ratio of tetrabutyl titanate to acetylacetone is 1:2 and the concentration of tetrabutyl titanate is 0.5 mol / L, and stirring at 50°C and 500 rpm until dissolved, to obtain solution B;

[0090] (2) Solution B was slowly added dropwise to solution A at 50°C and 500 rpm, wherein the molar ratio of Bi in solution A to Ti in solution B was 1:1, to obtain solution C;

[0091] (3) Add polyvinyl pyrrolidone to solution C at a concentration of 5%, and stir at 50°C and 500 rpm for 24 h to obtain a uniform, transparent precursor solution;

[0092] (4) The precursor solution was loaded into a syringe with a metal needle (the inner diameter of the metal needle was 0.34 mm and the exposed length was 13 mm) for electrospinning. During the spinning process, the voltage was 20 kV, the feed rate was 1 mL / h, and the distance between the tip of the metal needle and the aluminum foil was 15 cm. At the same time, infrared light irradiation was performed with a power of 300 W. The spinning chamber was maintained at 70°C to obtain precursor nanofibers on the aluminum foil.

[0093] (5) The precursor nanofibers were placed in a corundum crucible, and then the crucible was placed in a muffle furnace, and the temperature was raised to 600°C at a heating rate of 6°C / min, kept at this temperature for 2 hours in an air atmosphere, and naturally cooled to room temperature to obtain a nanofiber photocatalyst.

[0094] Comparative Example 3

[0095] A method for preparing a nanofiber photocatalyst comprises the following steps:

[0096] (1) adding bismuth acetate to a mixed solution of glacial acetic acid and methanol, wherein the concentration of bismuth acetate is 0.1 mol / L and the volume ratio of glacial acetic acid to methanol is 1:1, and stirring at 50°C and 500 rpm until dissolved, to obtain solution A; adding tetrabutyl titanate to acetylacetone and methanol, wherein the molar ratio of tetrabutyl titanate to acetylacetone is 1:2 and the concentration of tetrabutyl titanate is 0.5 mol / L, and stirring at 50°C and 500 rpm until dissolved, to obtain solution B;

[0097] (2) Solution B was slowly added dropwise to solution A at 50°C and 500 rpm, wherein the molar ratio of Bi in solution A to Ti in solution B was 1:1, to obtain solution C;

[0098] (3) Add polyvinyl pyrrolidone to solution C at a concentration of 5%, and stir at 50°C and 500 rpm for 24 h to obtain a uniform, transparent precursor solution;

[0099] (4) The precursor solution was loaded into a syringe with a metal needle (the inner diameter of the metal needle was 0.34 mm and the exposed length was 13 mm) for electrospinning. During the spinning process, the voltage was 20 kV, the feed rate was 1 mL / h, and the distance between the tip of the metal needle and the aluminum foil was 15 cm. Electrospinning was performed at room temperature to obtain precursor nanofibers on the aluminum foil.

[0100] (5) The precursor nanofibers were placed in a corundum crucible, and then the crucible was placed in a muffle furnace, and the temperature was raised to 500°C at a heating rate of 6°C / min, kept warm for 2 hours in an air atmosphere, and naturally cooled to room temperature to obtain a nanofiber photocatalyst.

[0101] Comparative Example 4

[0102] A method for preparing a nanofiber photocatalyst comprises the following steps:

[0103] (1) adding bismuth acetate to a mixed solution of glacial acetic acid and methanol, wherein the concentration of bismuth acetate is 0.1 mol / L and the volume ratio of glacial acetic acid to methanol is 2:1, and stirring at 50°C and 500 rpm until dissolved, to obtain solution A; adding tetrabutyl titanate to acetylacetone and methanol, wherein the molar ratio of tetrabutyl titanate to acetylacetone is 1:2 and the concentration of tetrabutyl titanate is 0.5 mol / L, and stirring at 50°C and 500 rpm until dissolved, to obtain solution B;

[0104] (2) Solution B was slowly added dropwise to solution A at 50°C and 500 rpm, wherein the molar ratio of Bi in solution A to Ti in solution B was 1:1, to obtain solution C;

[0105] (3) Add polyvinyl pyrrolidone to solution C at a concentration of 5%, and stir at 50°C and 500 rpm for 24 h to obtain a uniform, transparent precursor solution;

[0106] (4) The precursor solution was loaded into a syringe with a metal needle (the inner diameter of the metal needle was 0.34 mm and the exposed length was 13 mm) for electrospinning. During the spinning process, the voltage was 20 kV, the feed rate was 1 mL / h, and the distance between the tip of the metal needle and the aluminum foil was 15 cm. At the same time, infrared light irradiation was performed with a power of 300 W. The spinning chamber was maintained at 70°C to obtain precursor nanofibers on the aluminum foil.

[0107] (5) The precursor nanofibers were placed in a corundum crucible, and then the crucible was placed in a muffle furnace, and the temperature was raised to 500°C at a heating rate of 6°C / min, kept warm for 2 hours in an air atmosphere, and naturally cooled to room temperature to obtain a nanofiber photocatalyst.

[0108] Comparative Example 5

[0109] A method for preparing a photocatalyst comprises the following steps:

[0110] (1) adding bismuth acetate to a mixed solution of glacial acetic acid and methanol, wherein the concentration of bismuth acetate is 0.1 mol / L and the volume ratio of glacial acetic acid to methanol is 2:1, and stirring at 50°C and 500 rpm until dissolved, to obtain solution A; adding tetrabutyl titanate to acetylacetone and methanol, wherein the molar ratio of tetrabutyl titanate to acetylacetone is 1:2 and the concentration of tetrabutyl titanate is 0.5 mol / L, and stirring at 50°C and 500 rpm until dissolved, to obtain solution B;

[0111] (2) Solution B was slowly added dropwise to solution A at 50°C and 500 rpm, wherein the molar ratio of Bi in solution A to Ti in solution B was 1:1, to obtain solution C;

[0112] (3) Add polyvinyl pyrrolidone to solution C at a concentration of 5%, and stir at 50°C and 500 rpm for 24 h to obtain a uniform, transparent precursor solution;

[0113] (4) The precursor solution was poured into a corundum crucible, and then the crucible was placed in a muffle furnace, and the temperature was raised to 500°C at a heating rate of 6°C / min, kept warm for 2 hours in an air atmosphere, and naturally cooled to room temperature to obtain a nanoparticle photocatalyst.

[0114] The photocatalysts prepared in the above examples and comparative examples were subjected to the following steps: manual grinding for 5 minutes, placing the ground sample in a beaker containing a 1 g / L Rhodamine B solution (5 mg / L). Stirring was performed at 500 rpm in the dark for 30 minutes to achieve adsorption equilibrium. The beaker was then placed in a 25°C water bath and illuminated with a 350 W xenon lamp fitted with a 420 nm filter. Every 10 minutes, 2 mL of the sample was collected and centrifuged at 10,000 rpm. The absorbance of the supernatant was measured at the maximum absorption wavelength of 552 nm using a visible light spectrophotometer, and the degradation efficiency was calculated.

[0115] The results are shown in Table 1.

[0116]

[0117] Table 1 Test results

[0118]

[0119] like Figure 1 As shown, the diffraction peaks of the material prepared in Example 1 are consistent with the standard card of Bi2Ti2O7, and there are no other diffraction peaks, indicating that the prepared sample is pure phase. Figure 2 and Figure 3 It can be seen that the Bi2Ti2O7 material prepared in Example 1 presents a porous fiber morphology with a length of 1-5 μm. In addition, Examples 2-5 also present the above-mentioned spectrum, which will not be repeated here.

[0120] pass Figure 4 It can be seen that the prepared Bi2Ti2O7 nanofibers have excellent activity in the photocatalytic degradation of Rhodamine B, and the degradation efficiency can reach 90% after 1 hour of illumination.

[0121] By comparing the data of Example 1, the nanofibers prepared at a sintering temperature of 400°C did not form an obvious Bi2Ti2O7 phase ( Figure 5 ), so its photocatalytic degradation performance is poor.

[0122] By comparing the data of Example 2, when the sintering temperature is increased to 600℃, the prepared nanofibers are multiphase (Bi2Ti2O7 and Bi3Ti4O 12 )( Figure 6 ), due to Bi3Ti4O 12 Has a larger band gap than Bi2Ti2O7 ( Figure 7 ), and has a low absorption rate for visible light ( Figure 8 ), so the photocatalytic degradation efficiency is lower than that of Example 1.

[0123] By comparing the data of Example 3, the nanofibers prepared by electrospinning at room temperature are easily cross-linked during the spinning process because the solvent cannot evaporate quickly during the spinning process ( Figure 9 ), poor dispersibility, resulting in decreased photocatalytic degradation performance.

[0124] It can be seen from Comparative Example 4 that when there is more glacial acetic acid in the solvent, due to its high boiling point, it cannot evaporate faster during the spinning process, resulting in cross-linking between the nanofibers, which in turn makes the dispersion between the nanofibers poor, which is not conducive to the improvement of the photocatalytic degradation performance.

[0125] From Comparative Example 5, it can be seen that the nanomaterials prepared by direct sintering of the precursor solution without the spinning process mostly present large particle aggregation ( Figure 10 ), poor dispersibility and poor photocatalytic degradation performance.

[0126] Of course, the above contents are only preferred embodiments of the present invention and should not be considered as limiting the scope of the embodiments of the present invention. The present invention is not limited to the above examples. Equivalent changes and improvements made by ordinary technicians in this technical field within the essential scope of the present invention should all fall within the scope of the patent of the present invention.

Claims

1. A method for preparing Bi2Ti2O7 nanofiber photocatalyst, characterized by: The following steps are involved: (1) Adding a bismuth source to a mixed solution of glacial acetic acid and methanol and stirring until dissolved to obtain solution A; Add the titanium source to acetylacetone and methanol and stir until dissolved to obtain solution B; the volume ratio of glacial acetic acid to methanol is (1:1)-(1:2); (2) Add solution B dropwise to solution A to obtain solution C; (3) Add polyvinyl pyrrolidone to solution C and stir to obtain a precursor solution; (4) The precursor solution is loaded into a syringe with a metal needle and electrospun while being irradiated with infrared light to obtain precursor nanofibers on aluminum foil; (5) The precursor nanofibers were heated to 450-550°C at a heating rate of 5-6°C / min, kept warm in an air atmosphere, and then naturally cooled to room temperature to obtain Bi2Ti2O7 nanofiber photocatalysts.

2. The method for preparing the Bi2Ti2O7 nanofiber photocatalyst according to claim 1, characterized in that: In step (1), the bismuth source is bismuth acetate, and the titanium source is tetrabutyl titanate.

3. The method for preparing the Bi2Ti2O7 nanofiber photocatalyst according to claim 1, characterized in that: The concentration of bismuth source in solution A is 0.05-0.1 mol / L.

4. The method for preparing the Bi2Ti2O7 nanofiber photocatalyst according to claim 1, characterized in that: The molar ratio of the titanium source to acetylacetone in step (1) is (1:2)-(1:2.5), and the concentration of the titanium source in solution B is 0.5-1 mol / L.

5. The method for preparing the Bi2Ti2O7 nanofiber photocatalyst according to claim 1, characterized in that: In step (2), the molar ratio of Bi in solution A to Ti in solution B is (1:1)-(1:1.5).

6. The method for preparing the Bi2Ti2O7 nanofiber photocatalyst according to claim 1, characterized in that: The mass concentration of polyvinylpyrrolidone in the precursor solution of step (3) is 4.5-5.5%.

7. The method for preparing Bi2Ti2O7 nanofiber photocatalyst according to claim 1, characterized in that: In step (4), during the spinning process, the voltage is 15-20 kV, the feed rate is 0.5-1 mL / h, the distance between the tip of the metal needle and the aluminum foil is 10-15 cm, the power of the infrared light irradiation is 200-300 W, and the spinning machine chamber is maintained at 70-80° C.

8. The method for preparing Bi2Ti2O7 nanofiber photocatalyst according to claim 1, characterized in that: In step (5), the holding time in air atmosphere is 2-2.5 hours.

9. A Bi2Ti2O7 nanofiber photocatalyst, characterized by: The photocatalyst is obtained by the preparation method of the Bi2Ti2O7 nanofiber according to any one of claims 1 to 8.

10. An application of the Bi2Ti2O7 nanofiber photocatalyst according to claim 9, characterized in that: Bi2Ti2O7 nanofiber photocatalyst was applied to photocatalytic degradation of dyes.

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