Visible-light response nano titanium dioxide with mixed-crystal multilevel structure as well as preparation method and application of visible-light response nano titanium dioxide

Abstract

The invention discloses visible-light response nano titanium dioxide with a mixed-crystal multilevel structure as well as a preparation method and application of the visible-light response nano titanium dioxide. The preparation method of the visible-light response nano titanium dioxide comprises the following steps: 1) uniformly mixing peroxy titanic acid sol, a metal doping source and a structure inducer, adjusting the pH value to 0.1-2, and heating to carry out a crystallization reaction; and 2) separating a product of the crystallization reaction to obtain a precipitate, and removing impurities to obtain the visible light response nano titanium dioxide with the mixed crystal multilevel structure.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic nanomaterials. More specifically, it relates to a visible-light-responsive nanometer titanium dioxide with a mixed crystal multi-level structure, a preparation method thereof, and an application thereof. Background Art

[0002] With the urgent demands for environmental pollution control and clean energy development, the development of efficient and stable photocatalytic materials has become a research hotspot in the field of materials science. As a wide-bandgap semiconductor material (Eg = 3.2 eV), titanium dioxide (TiO2) exhibits great application potential in multiple fields such as photocatalytic degradation of organic pollutants, photocatalytic water splitting for hydrogen production, CO2 reduction, and self-cleaning due to its excellent chemical stability, environmental friendliness, and cost advantages. However, inherent defects of titanium dioxide, such as a relatively wide bandgap (3.2 eV), lead to low visible-light utilization efficiency, low quantum efficiency, and easy agglomeration, severely restricting its actual application efficiency.

[0003] Titanium dioxide has three crystal forms: brookite, rutile, and anatase, among which anatase titanium dioxide has relatively high photocatalytic activity. Currently, single anatase TiO2 still has problems such as a high recombination rate of photo-generated carriers and low visible-light utilization efficiency. Research shows that the photocatalytic performance of TiO2 can be effectively improved by constructing an anatase-rutile mixed crystal structure. This dual-crystal form structure can form a Type-II heterojunction at the interface of the two phases, generating a built-in electric field to promote the separation and migration of photo-generated electron-hole pairs. Specifically, the energy level difference (about 0.2 eV) between the anatase phase (Eg = 3.2 eV) and the rutile phase (Eg = 3.0 eV) can form a Schottky barrier at the interface, enabling photo-generated electrons to migrate from the anatase phase to the rutile phase, while holes migrate in the opposite direction, thus realizing the spatial separation of carriers. For example, the commercial titanium dioxide P25 has a ratio of anatase / rutile of approximately 79 / 21. In addition, by introducing defect states such as oxygen vacancies, intermediate energy levels can be formed in the bandgap, further broadening the light response range of the material to the visible light region.

[0004] Currently, the preparation of mixed crystal TiO2 mainly relies on traditional processes such as high-temperature chemical vapor deposition (CVD), hydrothermal method, and sol-gel method. These methods generally have the following limitations: (1) Harsh reaction conditions and high energy consumption; (2) It is difficult to precisely control the product morphology and crystal phase ratio; (3) It is easy to cause particle agglomeration, affecting the dispersibility and specific surface area; (4) The subsequent treatment process is complex and not conducive to large-scale production. Especially for application scenarios where TiO2 thin films need to be prepared on flexible substrates or heat-sensitive substrates, the existing technologies are difficult to meet the requirements of low-temperature preparation. Therefore, developing a new method for controllable preparation of mixed crystal TiO2 under mild conditions is of great significance for promoting the practical application of photocatalytic technology. Summary of the Invention

[0005] Based on this, the object of the present invention is to provide a visible-light-responsive nano-titanium dioxide with a mixed-crystal multi-level structure, its preparation method and application.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides a preparation method of visible-light-responsive nano-titanium dioxide with a mixed-crystal multi-level structure, and the preparation method includes the following steps:

[0008] 1) Mix the peroxotitanic acid sol, the metal doping source and the structure inducer, adjust the pH to 0.1 - 2, and raise the temperature for crystallization reaction;

[0009] 2) Separate the product of the crystallization reaction to obtain a precipitate, remove impurities, and obtain the visible-light-responsive nano-titanium dioxide with a mixed-crystal multi-level structure.

[0010] Further, in step 1), the method of adjusting the pH to 0.1 - 2 includes adding an acidic regulator, and the acidic regulator is selected from one or more of nitric acid, acetic acid and hydrochloric acid.

[0011] Further, in step 1), the pH is preferably 0.5 - 1.

[0012] Further, in step 1), the temperature of the crystallization reaction is 80 - 100 °C, preferably 90 - 100 °C, and the time of the crystallization reaction is 2 - 6 h, preferably 3 - 6 h.

[0013] Further, the metal doping source is selected from one or more soluble salts of vanadium, chromium, manganese, iron, cobalt, nickel, copper, zirconium, barium, tungsten, bismuth, aluminum or tin. Exemplary soluble salts are sulfates, nitrates, chlorides, etc.

[0014] In some specific examples, the metal doping source is selected from one or more of aluminum chloride, cobalt nitrate, copper nitrate, bismuth nitrate, aluminum nitrate.

[0015] Further, the structure inducer is selected from one or more of n-butanol, isopropanol and ethylene glycol.

[0016] Further, the dosage ratio of the peroxotitanic acid sol, the metal doping source and the structure inducer is (0.01 - 0.02) mol : (0.001 - 0.003) mol : (5 - 20) ml.

[0017] Further, in step 1), the preparation of the peroxotitanic acid sol includes the following steps:

[0018] Dissolve the inorganic titanium salt in deionized water, and stir and mix at room temperature to obtain an aqueous solution of the inorganic titanium salt;

[0019] A precipitant is added to the aqueous solution of the inorganic titanium salt to adjust the pH to 9-11, obtaining a white precipitate;

[0020] Sulfate ions in the white precipitate are removed to obtain a metatitanic acid precipitate;

[0021] The metatitanic acid precipitate is dispersed in deionized water, and then hydrogen peroxide is added until the precipitate is completely dissolved, and then aged at room temperature to obtain the yellow transparent peroxotitanic acid sol.

[0022] During the preparation process of the above peroxotitanic acid sol, hydrogen peroxide can react with Ti 4+ to form a stable yellow peroxotitanic acid complex; at the same time, it can also oxidize a small amount of Ti 3+ impurities to Ti 4+ ; In addition, its weak acidity may slightly reduce the pH of the solution.

[0023] Further, during the preparation process of the peroxotitanic acid sol, the stirring time at room temperature is 30-60 min.

[0024] Further, the inorganic titanium salt is selected from one or more of titanium sulfate, titanium tetrachloride, titanium oxysulfate and tetraethyl titanate.

[0025] Further, the precipitant is an inorganic base precipitant, and the inorganic base precipitant is selected from sodium carbonate, sodium hydroxide, potassium hydroxide or ammonia water.

[0026] Further, during the preparation process of the peroxotitanic acid sol, a step of adding a nitrogen doping source is further included before aging. The addition of the nitrogen doping source can further improve the visible light catalytic activity of the nano-titanium dioxide.

[0027] Further, the nitrogen doping source is selected from one or more of urea, methylamine, ethylamine, melamine, ethylenediamine, triethylamine.

[0028] Further, the molar ratio of nitrogen atoms in the nitrogen doping source to titanium atoms in the inorganic titanium salt is 0.2-3.

[0029] Further, in step 2), the method for separating the product of the crystallization reaction is centrifugal separation.

[0030] Further, in the visible light-responsive nano-titanium dioxide with a mixed crystal multi-stage structure prepared by the preparation method, the mass ratio of the anatase phase to the rutile phase is 70:30-85:15.

[0031] The preparation process of the present invention is simple, the preparation process is green, and the cost is low, with higher adaptability for industrial production. By adopting the atmospheric pressure low-temperature liquid-phase synthesis technology, high-temperature calcination, high-pressure reaction or complex post-treatment steps are not required, significantly reducing the equipment requirements and production costs. By selecting specific precursors and additives, the uniform growth and good dispersion of nano-titanium dioxide are achieved at low temperature, avoiding the problem of particle agglomeration. Without adding surfactants or noble metal doping, the obtained product has excellent dispersion and stability, suitable for large-scale industrial production.

[0032] In a second aspect, the present invention provides a visible-light-responsive nano-titanium dioxide with a mixed-crystal multi-level structure prepared by the preparation method described above.

[0033] Furthermore, the shape of the visible-light-responsive nano-titanium dioxide is a mixture of needle-like and rhombic structures.

[0034] Furthermore, the length of the needle-like visible-light-responsive nano-titanium dioxide is 100 - 300 nm, and the particle size is 30 - 80 nm.

[0035] Furthermore, the length of the rhombic visible-light-responsive nano-titanium dioxide is 10 - 20 nm, and the particle size is 5 - 15 nm.

[0036] In yet another aspect, the present invention provides a visible-light-responsive nano-titanium dioxide dispersion liquid, which is obtained by dispersing the visible-light-responsive nano-titanium dioxide with a mixed-crystal multi-level structure prepared by the preparation method provided in the first aspect or the visible-light-responsive nano-titanium dioxide with a crystal multi-level structure provided in the second aspect in deionized water.

[0037] Furthermore, the dispersion liquid is milky white or slightly yellowish.

[0038] Furthermore, in the dispersion liquid, the dosage ratio of the visible-light-responsive nano-titanium dioxide to deionized water is 0.01 mol : (40 - 100) ml.

[0039] The beneficial effects of the present invention are as follows:

[0040] The preparation method provided in the present invention is a low-temperature green preparation process. In the present invention, a one-step low-temperature preparation strategy is innovatively adopted to construct an N / metal-doped source ion / TiO2 double-crystalline-phase multi-doped high-efficiency catalyst system. The reaction temperature is significantly lower than that of traditional high-temperature calcination or hydrothermal synthesis processes (usually >200°C), and high-efficiency crystallization is achieved at 80 - 100°C. Preferably, by precisely controlling the reaction conditions of the reaction system (such as pH value, dopant ratio, crystallization time, etc.), the controllable preparation of the ratio of anatase to rutile phase is realized at low temperature. This process avoids the adverse effects of high temperature on the material structure (such as grain coarsening, uncontrollable crystal phase, etc.), and at the same time significantly reduces energy consumption and production costs, meeting the requirements of green chemistry and sustainable development.

[0041] The visible-light catalytic activity synergistic enhancement mechanism of the visible-light-responsive nano-titanium dioxide prepared by the preparation method in the present invention is as follows: First, the double-doping synergistic effect. The multi-doping of metal ions and nitrogen element can significantly expand the light-responsive range of titanium dioxide. Second, the mixed crystal effect: The Type-II heterojunction interface formed between the anatase and rutile phases generates a built-in electric field, promoting the efficient separation and migration of photo-generated electron-hole pairs. The Fermi level difference (about 0.2 eV) between the two phases further enhances the carrier transport efficiency. Third, the multi-level structure synergistic effect: The multi-level structure (needle-like and rhombic composite morphology) not only increases the specific surface area and the density of active sites, but also further optimizes the separation and transfer path of photo-generated carriers through the synergistic effect between different crystal planes. Brief Description of the Drawings

[0042] The following further elaborates on the specific implementation manners of the present invention in conjunction with the drawings.

[0043] Figure 1 Show the transmission electron microscope photograph of the visible-light-responsive nano-titanium dioxide in Example 1.

[0044] Figure 2 Show the high-magnification transmission electron microscope photograph of the visible-light-responsive nano-titanium dioxide in Example 1.

[0045] Figure 3 Show the ultra-high-magnification transmission electron microscope photograph of the visible-light-responsive nano-titanium dioxide in Example 1.

[0046] Figure 4 Show the X-ray diffraction spectrum of the visible-light-responsive nano-titanium dioxide in Example 1.

[0047] Figure 5 Show the ultraviolet-visible absorption spectrum of the visible-light-responsive nano-titanium dioxide in Example 1.

[0048] Figure 6Shows the X-ray photoelectron spectroscopy of the visible-light-responsive nano-titanium dioxide in Example 4. Detailed implementation manners

[0049] To illustrate the present invention more clearly, the present invention will be further described below in conjunction with preferred embodiments and drawings. Similar components in the drawings are denoted by the same reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0050] Example 1

[0051] A preparation method of a visible-light-responsive nano-titanium dioxide with a mixed crystal multi-stage structure includes the following steps:

[0052] 1) Preparation of nitrogen-doped peroxotitanic acid sol:

[0053] Dissolve 0.01 mol of titanium oxysulfate in 100 ml of deionized water, stir at room temperature (25 °C) for 150 min, and add ammonia water to adjust the pH to 11 to obtain a white precipitate;

[0054] Wash the white precipitate with deionized water until there is no sulfate ion to obtain a metatitanic acid precipitate;

[0055] Redisperse the metatitanic acid precipitate in deionized water to prepare a 0.1 mol / L solution, then slowly add 30 wt% hydrogen peroxide to the solution until the precipitate completely dissolves, and then add 0.01 ml of urea, stir for 30 min to obtain a yellow transparent intermediate product, and let it stand at room temperature for 24 hours for aging to obtain the nitrogen-doped peroxotitanic acid sol;

[0056] 2) Preparation of a twin-crystalline visible-light-responsive nano-titanium dioxide:

[0057] Mix 0.01 mol of the peroxotitanic acid sol, 0.002 mol of aluminum chloride and 5 ml of the structure inducer isopropanol, and add acetic acid to adjust the pH to 1.0;

[0058] Heat to 100 °C and react at this temperature for 3 hours. During this process, the synergistic growth of anatase and rutile phases is induced; after the reaction is completed, the product is centrifuged and washed to obtain the visible-light-responsive nano-titanium dioxide with a mixed crystal multi-stage structure.

[0059] The transmission electron microscope photograph of the visible-light-responsive nano-titanium dioxide is as Figures 1 - 3 shown. It can be seen from the figure that the sample prepared in Example 1 is a mixed crystal nano-TiO2 with a rod-like and rhombic structure. The lattice fringe with a lattice spacing of 0.34 nm corresponds to the (101) crystal plane of anatase, and the lattice fringe with a lattice spacing of 0.30 nm corresponds to the (110) crystal plane of rutile.

[0060] The X-ray diffraction spectrum of the visible light-responsive nano-titanium dioxide is as Figure 4 shown. It can be seen from Figure 4 that the prepared titanium dioxide is a mixed phase of anatase phase and rutile phase.

[0061] The ultraviolet-visible absorption spectrum of the visible light-responsive nano-titanium dioxide is as Figure 5 shown. It can be seen from Figure 5 that the light absorption of nitrogen and aluminum-doped titanium dioxide shifts towards the visible light region.

[0062] 0.01 mol of the visible light-responsive nano-titanium dioxide with the mixed crystal multi-level structure was redispersed in 50 ml of deionized water to obtain a dispersion of copper-doped twin crystal multi-level structure visible light-responsive nano-titanium dioxide composite particles.

[0063] The dispersion was placed at room temperature for 12 h. It can be seen that in this dispersion, the nano-titanium dioxide composite particles were still uniformly dispersed. This dispersion (in the nano-titanium dioxide composite particles, the mass ratio of anatase type to rutile type is 87:13) was used to degrade the organic dye Rhodamine B (5 ppm), with a visible light illumination intensity of 10 W / m 2 , and the photocatalytic degradation efficiency was 90% after 30 min.

[0064] Example 2

[0065] A preparation method of visible light-responsive nano-titanium dioxide with a mixed crystal multi-level structure, comprising the following steps:

[0066] 1) Preparation of peroxotitanic acid sol:

[0067] 0.02 mol of titanium oxysulfate was dissolved in 100 ml of deionized water, stirred at room temperature for 180 min, and the precipitant sodium hydroxide was added dropwise to adjust the pH to 11 to obtain a white precipitate;

[0068] The white precipitate was washed with deionized water until there was no sulfate ion to obtain a metatitanic acid precipitate;

[0069] The metatitanic acid precipitate was redispersed in deionized water to prepare a 0.1 mol / L solution, and then 30 wt% hydrogen peroxide was slowly added dropwise to this solution until the precipitate was completely dissolved, stirred for 40 min to obtain a yellow transparent intermediate product, and aged at room temperature for 24 hours to obtain the peroxotitanic acid sol;

[0070] 2) Preparation of twin crystal type visible light-responsive nano-titanium dioxide:

[0071] Mix 0.02 mol of the titanyl peroxide sol, 0.001 mol of cobalt nitrate, and 20 ml of the structure inducer ethylene glycol evenly, add nitric acid dropwise, and adjust the pH to 0.5;

[0072] Heat to 100 °C and react at this temperature for 3 hours. During this process, the synergistic growth of anatase and rutile phases is induced; after the reaction, centrifuge and wash the product to obtain the visible-light-responsive nano-titanium dioxide with a mixed crystal multi-level structure.

[0073] Redisperse 0.02 mol of the visible-light-responsive nano-titanium dioxide with a mixed crystal multi-level structure into 100 ml of deionized water to obtain the dispersion liquid of visible-light-responsive nano-titanium dioxide composite particles with a twin crystal multi-level structure.

[0074] Let the dispersion liquid stand at room temperature for 12 h. It can be seen that in this dispersion liquid, the nano-titanium dioxide composite particles are still evenly dispersed. Use this dispersion liquid (in the nano-titanium dioxide composite particles, the mass ratio of anatase type to rutile type is 85:15) to degrade the organic fuel rhodamine B (5 ppm), with a visible light illumination intensity of 10 W / m 2 , and the photocatalytic degradation efficiency is 88% after 30 min of visible light irradiation.

[0075] Example 3

[0076] A preparation method of visible-light-responsive nano-titanium dioxide with a mixed crystal multi-level structure, comprising the following steps:

[0077] 1) Preparation of titanyl peroxide sol:

[0078] Dissolve 0.01 mol of titanium oxysulfate in 100 ml of deionized water, stir at room temperature for 150 min, and add ammonia water dropwise to adjust the pH to 11 to obtain a white precipitate;

[0079] Wash the white precipitate with deionized water until there is no sulfate ion to obtain a metatitanic acid precipitate;

[0080] Redisperse the metatitanic acid precipitate in deionized water to prepare a 0.1 mol / L solution, and then slowly add 30 wt% hydrogen peroxide to this solution until the precipitate completely dissolves, stir for 35 min to obtain a yellow transparent intermediate product, and let it age at room temperature for 24 hours, which is the titanyl peroxide sol;

[0081] 2) Preparation of twin-crystalline visible-light-responsive nano-titanium dioxide:

[0082] Mix 0.01 mol of the titanyl peroxide sol, 0.003 mol of copper nitrate, and 10 ml of the structure inducer n-butanol evenly, add the acidic catalyst nitric acid dropwise, and adjust the pH to 1.0;

[0083] Heat to 90 °C and react at this temperature for 6 hours. During this process, the co-growth of anatase and rutile phases is induced; after the reaction, the product is centrifuged and washed to obtain the visible-light-responsive nano-titanium dioxide with a mixed crystal multi-level structure.

[0084] Redisperse 0.01 mol of the visible-light-responsive nano-titanium dioxide with a mixed crystal multi-level structure into 50 ml of deionized water to obtain a dual-crystalline visible-light-active composite titanium dioxide dispersion.

[0085] Leave this dispersion at room temperature for 24 h. It can be seen that in this dispersion, the nano-titanium dioxide composite particles are still evenly dispersed. Use this dispersion (in the nano-titanium dioxide composite particles, the mass ratio of anatase type to rutile type is 82:18) to degrade the organic dye Rhodamine B (5 ppm), with a visible light illumination intensity of 10 W / m 2 , and the photocatalytic degradation efficiency after 30 min of visible light irradiation is 85%.

[0086] Example 4

[0087] A preparation method of visible-light-responsive nano-titanium dioxide with a mixed crystal multi-level structure, comprising the following steps:

[0088] 1) Preparation of nitrogen-doped peroxotitanic acid sol:

[0089] Dissolve 0.01 mol of titanium oxysulfate in 100 ml of deionized water, stir at room temperature for 150 min, and add ammonia water to adjust the pH to 11 to obtain a white precipitate;

[0090] Wash the white precipitate with deionized water until there is no sulfate ion to obtain a metatitanic acid precipitate;

[0091] Redisperse the metatitanic acid precipitate in deionized water to prepare a 0.1 mol / L solution, then slowly add 30 wt% hydrogen peroxide to this solution until the precipitate completely dissolves, and then add 0.008 mol of urea, stir for 30 min to obtain a yellow transparent intermediate product, and leave it at room temperature for 24 hours for aging to prepare the yellow transparent nitrogen-doped peroxotitanic acid sol;

[0092] 2) Preparation of dual-crystalline visible-light-responsive nano-titanium dioxide:

[0093] Mix 0.01 mol of the above-mentioned nitrogen-doped peroxotitanic acid sol, 0.001 mol of bismuth nitrate, 0.001 mol of aluminum nitrate and 15 ml of the structure inducer isopropanol, and add acetic acid to adjust the pH to 1.0;

[0094] Heat to 90 °C and react for 6 hours at this temperature; the synergistic growth of anatase and rutile phases is induced during this process; after the reaction, the product is centrifuged and washed to obtain the visible-light-responsive nano-titanium dioxide with a mixed-crystalline multi-level structure.

[0095] The X-ray photoelectron spectroscopy pattern of the visible-light-responsive nano-titanium dioxide is as Figure 6 shown. It can be seen from Figure 6 that there are O, Ti, N, Bi, and Al elements in the prepared sample.

[0096] Redisperse 0.01 mol of the visible-light-responsive nano-titanium dioxide with a mixed-crystalline multi-level structure into 50 ml of deionized water to obtain a dispersion of double-crystalline visible-light-responsive nano-titanium dioxide composite particles. This dispersion (in the nano-titanium dioxide composite particles, the mass ratio of anatase type to rutile type is 88:12) is used to degrade the organic fuel Rhodamine B (5 ppm), with a visible-light illumination intensity of 10 W / m 2 , and the photocatalytic degradation efficiency is 92% after 30 min.

[0097] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation manners here. Any obvious changes or modifications derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for preparing a mixed crystal multi-level structure visible light responsive nano titanium dioxide, characterized in that: The steps include: 1) mixing the peroxotitanic acid sol, the metal doping source and the structure inducing agent, adjusting the pH to 0.1-2, and heating to perform a crystallization reaction; 2) separating the product of the crystallization reaction to obtain a precipitate, removing impurities, and obtaining the mixed crystal multi-level structure visible light responsive nano titanium dioxide.

2. The preparation method according to claim 1, characterized in that: In step 1), the preparation of the peroxotitanate sol comprises the following steps: Dissolving an inorganic titanium salt in deionized water, stirring and mixing at room temperature to obtain an aqueous solution of the inorganic titanium salt; Adding a precipitant to the aqueous solution of the inorganic titanium salt to adjust the pH to 9-11 to obtain a white precipitate; removing sulfate ions from the white precipitate to obtain orthotitanic acid precipitate; The orthotitanic acid precipitate is dispersed in deionized water, and hydrogen peroxide is added until the precipitate is completely dissolved, and then aged at room temperature to obtain the yellow transparent peroxytitanic acid sol.

3. The preparation method according to claim 2, characterized in that: During the preparation of the peroxotitanic acid sol, the stirring time at room temperature is 30-60 minutes.

4. The preparation method according to claim 2, characterized in that: The inorganic titanium salt is selected from one or more of titanium sulfate, titanium tetrachloride, titanyl sulfate and ethyl titanate; and / or The precipitant is an inorganic base precipitant, and the inorganic base precipitant is selected from sodium carbonate, sodium hydroxide, potassium hydroxide or ammonia water.

5. The preparation method according to claim 2, characterized in that: The preparation process of the peroxotitanic acid sol also includes the step of adding a nitrogen doping source before aging; Preferably, the nitrogen doping source is selected from one or more of urea, methylamine, ethylamine, melamine, ethylenediamine, and triethylamine; Preferably, the molar ratio of nitrogen atoms in the nitrogen doping source to titanium atoms in the inorganic titanium salt is 0.2-3.

6. The preparation method according to claim 1, characterized in that: In step 1), the crystallization reaction temperature is 80-100°C and the time is 2-6h; and / or The metal doping source is selected from soluble salts of one or more of vanadium, chromium, manganese, iron, cobalt, nickel, copper, zirconium, barium, tungsten, bismuth, aluminum or tin; and / or The structural inducing agent is selected from one or more of n-butanol, isopropanol and ethylene glycol; and / or The method for adjusting the pH to 0.1-2 comprises adding an acidic regulator, wherein the acidic regulator is selected from one or more of nitric acid, acetic acid and hydrochloric acid; and / or The dosage ratio of the peroxotitanic acid sol, the metal doping source and the structure inducing agent is (0.01-0.02) mol: (0.001-0.003) mol: (5-20) ml.

7. Visible light responsive nano titanium dioxide with mixed crystal multi-level structure prepared by the preparation method according to any one of claims 1 to 6.

8. The visible light responsive nano titanium dioxide according to claim 7, characterized in that: The shape of the visible light responsive nano titanium dioxide is a mixture of needle-shaped and diamond-shaped structures.

9. The visible light responsive nano titanium dioxide according to claim 8, characterized in that: The needle-shaped visible light responsive nano titanium dioxide has a length of 100-300 nm and a particle size of 30-80 nm; or The length of the rhombus-shaped visible light responsive nano titanium dioxide is 10-20 nm, and the particle size is 5-15 nm.

10. A visible light responsive nano titanium dioxide dispersion, characterized in that: The mixed crystal multi-level structure visible light responsive nano titanium dioxide prepared by the preparation method according to any one of claims 1 to 6 or the mixed crystal multi-level structure visible light responsive nano titanium dioxide according to any one of claims 7 to 9 is dispersed in deionized water to obtain the dispersion.

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