A multi-level pore titanium dioxide super particle, and a preparation method and application thereof

Abstract

The application discloses a kind of multi-level hole titanium dioxide super particles and its preparation method and application, belong to porous material technical field, the super particle is composed of big hollow ball in center and small hollow ball distributed on its surface, big hollow ball pore size is 100-500nm, small hollow ball pore size is 50-200nm, small hollow ball shell layer is distributed with the spherical mesoporous of pore size 15-50nm, titanium dioxide shell layer thickness is 5-50nm, specific surface area reaches 100-300m 2 / g.Preparation method includes: preparing amino modification and sulfonation modification different size SiO2 Nanosphere template respectively, form multi-level hole template by electrostatic super assembly, then combine pore forming agent and titanium source coating, calcination and template removal etc., prepare the titanium dioxide super particle with hierarchical pore structure and uniform morphology.The material has high specific surface area and good mass transfer performance, suitable for photocatalysis, energy storage and photoelectrochemistry field, especially in photocatalytic carbon dioxide reduction and shows superior activity.

Description

Technical Field

[0001] This invention belongs to the field of porous materials technology, specifically relating to a hierarchical porous titanium dioxide superparticle, its preparation method, and its application. Background Technology

[0002] Titanium dioxide (TiO2) is an important inorganic functional material with characteristics such as low cost, low toxicity, high thermal stability, stable chemical properties, strong resistance to photocorrosion, and excellent semiconductor properties. It is widely used in energy storage, photoelectrochemistry, photocatalysis and other fields.

[0003] Mesoporous superstructure materials, through precise control of the size, morphology, and arrangement of mesoporous units, simultaneously possess characteristics such as high specific surface area, adjustable pore volume, and uniform pore structure. Secondary superassembly of mesoporous superstructure materials to form superassembled multi-level pore templates optimizes the pore structure, thereby providing the material with more active sites and reducing mass transfer resistance, offering a new path to overcome the performance limitations of traditional mesoporous superstructure materials.

[0004] Currently, common methods for preparing titanium dioxide materials include soft and hard template methods and template-free methods. Among them, the template-free method is simple to prepare mesoporous crystalline frameworks, but the structural parameters are uncontrollable; the soft template method can achieve precise structural control, and the synthesis process is also simple, with high product quality and good reproducibility, but structural collapse is prone to occur during annealing, resulting in unsatisfactory crystallinity; the hard template method can prepare ordered and replicated mesoporous structures with high product crystallinity, but the preparation process is cumbersome, the yield is low, the flexibility is limited, and defects are easily generated during template removal.

[0005] Therefore, developing a multi-level porous titanium dioxide superparticle with mild synthesis conditions, stable structure, and tunable structure is of great research value. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a multi-level porous titanium dioxide superparticle with uniform morphology, stable structure, and controllable preparation process, as well as its preparation method and application. This method utilizes a template-assisted super-assembly strategy to achieve the construction of multi-level pores in titanium dioxide materials, significantly improving their specific surface area.

[0007] This invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing hierarchical porous titanium dioxide ultraparticles, comprising the following steps:

[0009] Step 1: Preparation of aminated superstructured SiO2 nanosphere templates:

[0010] The template agent was dissolved in an inorganic acid solution with a concentration of 1-10 mol / L to form a homogeneous solution with a concentration of 1-8 wt%. A pore-expanding agent and an organosilicon source were added, and the mixture was stirred for 1-5 h to form a stable nanoemulsion. Subsequently, a pre-synthesized SiO2 nanosphere aqueous solution was added, and the mixture was stirred at room temperature for 1-10 h. Then, an organosilicon end-capping agent was added, and the mixture was stirred for another 10-48 h. After centrifugation and washing, the mixture was dispersed in deionized water to obtain an aminated superstructured SiO2 nanosphere template.

[0011] Step 2: Preparation of sulfonated modified SiO2 nanosphere templates:

[0012] Take the pre-synthesized SiO2 nanosphere aqueous solution, add silane coupling agent, and stir the reaction at 25-50℃ for 10-24h; then add hydrogen peroxide aqueous solution and continue stirring the reaction for 10-24h; centrifuge, wash, and disperse in deionized water to obtain sulfonated modified SiO2 nanosphere template.

[0013] Step 3: Preparation of super-assembled hierarchical porous titanium dioxide hollow spheres:

[0014] The solutions obtained in step one and step two are mixed in a volume ratio of 1:1; the pH is adjusted to 4-6 with an inorganic acid, and the mixture is stirred at 50°C for 10-48 hours. After centrifugation, washing, and drying, a white powder is obtained. The powder is dispersed in anhydrous ethanol, and the pH is adjusted to 9-11 with ammonia. A pore-forming agent is added and stirred. A titanium source is added dropwise, and the mixture is stirred and reacted. After centrifugation, washing, and drying, a pale yellow powder is obtained. Finally, the powder is calcined in air at 300-600°C for 2-10 hours to remove the pore-forming agent, and then placed in an aqueous sodium hydroxide solution for 4-18 hours to remove the SiO2 nanosphere template, thus obtaining the hierarchical porous titanium dioxide ultraparticles.

[0015] Further, in step one, the mass ratio of the SiO2 nanosphere aqueous solution to the template agent, the pore-expanding agent, and the organosilicon source is 1:5-10:5-10:5-10, and the mass ratio of the SiO2 nanospheres to the organosilicon end-capping agent is 1:2-5.

[0016] Further, in step one, the template agent is selected from F127 (EO) 106 -PO 70 -EO 106 ), P123 (EO) 20 -PO 70 -EO 20 F108 (EO) 132 -PO 50 -EO 132 ), F98 (EO) 132 -PO 45 -EO 132 ), F87 (EO) 106 -PO40 -EO 106 ), F68 (EO) 132 -PO 30 -EO 132 ) or P65 (EO 20 -PO 30 -EO 20 One or more of the following;

[0017] The inorganic acid solution is selected from one or more of hydrochloric acid, nitric acid, and sulfuric acid solutions;

[0018] The pore-expanding agent is selected from one or more of benzene, toluene, ethylbenzene, xylene, trimethylbenzene, chlorobenzene, and bromobenzene;

[0019] The organosilicon source is selected from one or more of tetraethyl orthosilicate, methyl orthosilicate, propyl orthosilicate, dimethyldimethoxysilane, and 1,2-bis(triethoxysilyl)ethane;

[0020] The organosilane end-capping agent is selected from one or more of vinyltrimethoxysilane, trimethylethoxysilane, 3-aminopropyltriethoxysilane, dimethyldimethoxysilane, and dimethyldiethoxysilane.

[0021] Furthermore, in step two, the volume ratio of the SiO2 nanosphere aqueous solution to the silane coupling agent is 20-5:1, and the volume ratio of the SiO2 nanosphere aqueous solution to the hydrogen peroxide aqueous solution is 5-10:1.

[0022] Further, in step two, the silane coupling agent is selected from one or more of mercaptopropyltrimethoxysilane, KH590 (γ-mercaptopropyltriethoxysilane), KH560 (γ-glycidyl etheroxypropyltrimethoxysilane), or KH550 (γ-aminopropyltriethoxysilane).

[0023] Furthermore, in step three, the pore-forming agent is one or more of decylamine, tetradecylamine, hexadecylamine, dodecylamine, and octadecylamine;

[0024] The titanium source is selected from one or more of isopropyl titanate, tetrabutyl titanate, tetraethyl titanate, titanium tetrachloride, titanium trichloride, and titanium acetylacetonate.

[0025] Furthermore, the centrifugation speed is 3000-12000 r / min, and the centrifugation time is 3-15 min.

[0026] Furthermore, the washing conditions are one or more of deionized water, 95wt% ethanol solution, and anhydrous ethanol, and the number of washing cycles is 2-6.

[0027] Secondly, the present invention also provides hierarchical porous titanium dioxide superparticles, prepared by the method described in the first aspect. The hierarchical porous titanium dioxide superparticles comprise a large hollow sphere at the center and small hollow spheres distributed on its surface. The pore size of the large hollow sphere is 100-500 nm, and the pore size of the small hollow spheres on the surface is 50-200 nm. Spherical mesopores with a pore size of 15-50 nm are distributed on the shell of the small hollow spheres. The thickness of the titanium dioxide shell is 5-50 nm, and the radial mesopore size is 3-10 nm. The specific surface area of ​​the hierarchical porous titanium dioxide superparticles is 100-300 m². 2 / g.

[0028] Thirdly, the present invention also provides an application of hierarchical porous titanium dioxide superparticles in photocatalysis, energy storage or photoelectrochemistry.

[0029] Compared with the prior art, the advantages of the present invention are as follows:

[0030] 1. The multi-level porous titanium dioxide superparticles prepared in this invention have a central large hollow sphere and a peripheral superstructure small hollow sphere that are closely connected. The pore size of the large hollow sphere is 100-500 nm, and the pore size of the small hollow spheres on the surface is 50-200 nm. The shell of the small hollow spheres has spherical mesopores with a pore size of 15-50 nm distributed on it. The thickness of the titanium dioxide shell is 5-50 nm and the radial mesopore size is 3-10 nm. The specific surface area of ​​the multi-level porous titanium dioxide superparticles is 100-300 m² / g. The hollow spheres composed of two different sizes of titanium dioxide hollow spheres have tightly connected channels at all levels, which increases the specific surface area of ​​the material and enables reactants to be transported and transferred more quickly.

[0031] 2. In the preparation process of the hierarchical porous titanium dioxide superparticles of the present invention, SiO2 nanospheres of different sizes are modified with different surface groups and superstructured SiO2 nanospheres, and then superassembled to form a hierarchical porous SiO2 nanosphere template. While the titanium source coats the hierarchical porous template, a pore-forming agent is added to form mesopores in the titanium dioxide layer. This realizes the secondary assembly of the superstructured material and improves the performance of the mesoporous hollow titanium dioxide sphere material in photocatalysis, energy storage, photoelectrochemistry and other fields. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0033] Figure 1Transmission electron microscopy image of the hierarchical porous titanium dioxide ultraparticles prepared in Example 1 of this invention;

[0034] Figure 2 This is a partial transmission electron microscope (TEM) magnification image of the hierarchical porous titanium dioxide superparticles prepared in Example 1 of the present invention.

[0035] Figure 3 Transmission electron microscopy image of the hierarchical porous titanium dioxide ultraparticles prepared in Example 2 of this invention;

[0036] Figure 4 This is a transmission electron microscope image of the hierarchical porous titanium dioxide ultraparticles prepared in Example 3 of the present invention;

[0037] Figure 5 Transmission electron microscope image of the hierarchical porous titanium dioxide ultraparticles prepared in Comparative Example 1 of this invention;

[0038] Figure 6 This is a transmission electron microscope image of the hierarchical porous titanium dioxide superparticles prepared in Comparative Example 2 of this invention.

[0039] Figure 7 This is a comparison chart of the photocatalytic performance tests of Example 1, Comparative Example 1, and Comparative Example 2 of the present invention;

[0040] Figure 8 Nitrogen adsorption-desorption curves and pore size distribution curves of the hierarchical porous titanium dioxide superparticles prepared in Example 1 of this invention;

[0041] Figure 9 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the hierarchical porous titanium dioxide superparticles prepared in Example 1 of this invention.

[0042] Among them, a is the XPS plot of the titanium 2p orbital, b is the XPS plot of the oxygen 1s orbital, c is the XPS plot of the nitrogen 1s orbital, and d is the XPS plot of the sulfur 2p orbital.

[0043] Figure 10 Wide-angle X-ray diffraction (XRD) image of the hierarchical porous titanium dioxide superparticles prepared in Example 1 of this invention;

[0044] Figure 11 This is a schematic diagram illustrating the formation of hierarchical porous titanium dioxide superparticles according to the present invention. Detailed Implementation

[0045] To clearly and completely describe the technical solution and its specific working process of the present invention, the specific embodiments of the present invention are as follows, in conjunction with the accompanying drawings:

[0046] Example 1

[0047] like Figure 5As shown, this embodiment provides a method for preparing hierarchical porous titanium dioxide ultraparticles, specifically including the following steps:

[0048] (1) 100 nm SiO2 nanospheres were prepared using the Stöber method as templates. Specifically, 60 mL of anhydrous ethanol, 1 mL of deionized water, and 3 mL of ammonia were uniformly mixed in a double-necked flask, and then 2.3 mL of TEOS was added dropwise. The mixture was stirred at 35 °C for 5 h, centrifuged, and washed 3 times to obtain 100 nm SiO2 nanospheres. The obtained 100 nm SiO2 nanospheres were uniformly dispersed in 10 mL of deionized water. At room temperature, 0.25 g of F108 was dissolved in 15 mL of water. In a 2 mol / L HCl solution, 300 μL of tricresylbenzene and 280 μL of TEOS were added, and the mixture was stirred vigorously. After 1 h, 1 mL of the above 100 nm SiO2 nanosphere solution was added, and after 3 h, 130 μL of 3-aminopropyltriethoxysilane was added dropwise. After reacting for 24 h, the mixture was centrifuged and washed three times to obtain 100 nm amino-modified superstructured SiO2 nanospheres. The obtained 100 nm amino-modified superstructured SiO2 nanospheres were uniformly dispersed in 10 mL of deionized water.

[0049] (2) 300 nm SiO2 nanospheres were prepared using the Stöber method as a template. Specifically, 16.25 mL of ethanol, 24.75 mL of deionized water, and 9.0 mL of ammonia were uniformly mixed in a flask as solution A. Then, 45.5 mL of anhydrous ethanol and 4.5 mL of TEOS were uniformly mixed in the flask as solution B. Solution B was quickly added to solution A, and the mixture was stirred at 25 °C for 2 h. After centrifugation and washing three times, 300 nm SiO2 nanospheres were obtained. 300 nm SiO2 nanospheres were uniformly dispersed in 10 mL of deionized water. Then, 300 μL of γ-mercaptopropyltriethoxysilane was added, and the mixture was stirred at 50 °C for 24 h. After that, 1 mL of 30 wt% hydrogen peroxide solution was added, and the mixture was stirred at 50 °C for another 24 h. The mixture was then centrifuged and washed three times to obtain 300 nm sulfonated modified superstructured SiO2 nanospheres. The obtained 300 nm sulfonated modified SiO2 nanospheres were then uniformly dispersed in 10 mL of deionized water.

[0050] (3) Preparation of hierarchical porous SiO2 nanosphere template: Specifically, 10 mL of the above-obtained 100 nm aminated modified superstructured SiO2 nanospheres and 10 mL of 300 nm sulfonated modified SiO2 nanospheres were mixed evenly, and 20 μL of 2 mol / L HCl solution was added to adjust the pH of the solution to 4. The mixture was stirred vigorously at 50 °C for 48 h. The solution was centrifuged, washed, and dried to obtain a white powder. 0.08 g of the white powder obtained above was dissolved in 10 mL of anhydrous ethanol, and 100 μL of ammonia was added to adjust the pH of the solution to 9. 0.08 g of hexadecylamine was added, and the mixture was stirred at room temperature for 10 min. 100 μL of isopropyl titanate was slowly added dropwise to the above solution, and the solution gradually turned pale yellow. The mixture was stirred for 10 min. The solution was centrifuged, washed, and dried to obtain a pale yellow powder. The obtained sample was calcined in air at 400℃ for 4 hours to remove the pore-forming agent, and then placed in a 2M NaOH solution and stirred at 35℃ for 2 hours to remove the hierarchical porous SiO2 nanosphere template, thus obtaining hierarchical porous titanium dioxide superparticles.

[0051] The microstructure of the hierarchical porous titanium dioxide superparticles prepared in Example 1 was observed using transmission electron microscopy, and the results are as follows: Figure 1 and Figure 2 As shown, from Figure 1 and Figure 2 As can be seen, the multi-level porous titanium dioxide superparticles prepared in Example 1 have a 300nm large hollow titanium dioxide sphere as the center, on which 100nm superstructured small hollow titanium dioxide spheres are uniformly grown. The surface of the small hollow spheres is distributed with 15-20nm spherical mesopores, the titanium dioxide layer thickness is 15-25nm, and the radial mesopore size is 3-5nm. Figure 8 The nitrogen adsorption-desorption curves and pore size distribution diagrams obtained from nitrogen adsorption-desorption tests on the samples shown demonstrate that the radial mesopore size on the surface of the titanium dioxide superparticles is 3.4 nm, and that spherical mesopores with a pore size of 18.6 nm are distributed on the shell of the small hollow spheres. Figure 9 X-ray photoelectron spectroscopy (XPS) of hierarchical porous titanium dioxide ultraparticles shows that the material contains nitrogen and sulfur elements, proving that the material was successfully sulfonated and amination during synthesis. Figure 10 Wide-angle X-ray diffraction (XRD) images of multi-level porous titanium dioxide superparticles were obtained to obtain information on the crystalline phase of the material, proving that the material is titanium dioxide.

[0052] Example 2

[0053] This embodiment provides a method for preparing hierarchical porous titanium dioxide ultraparticles, specifically including the following steps:

[0054] (1) Prepare 100 nm aminated modified superstructure SiO2 nanosphere templates. The specific operation scheme is the same as in Example 1.

[0055] (2) Preparation of 300nm sulfonated modified SiO2 nanosphere templates: The specific operation procedure is the same as in Example 1. The difference is that: the obtained 300nm SiO2 nanospheres are uniformly dispersed in 10mL of deionized water, then 100μL of γ-mercaptopropyltriethoxysilane is added, and the mixture is stirred at 50℃ for 24h. Then, 500μL of 30wt% hydrogen peroxide solution is added, and the mixture is stirred at 50℃ for another 24h. After centrifugation and washing three times, 300nm sulfonated modified superstructured SiO2 nanospheres are obtained. The obtained 300nm sulfonated modified SiO2 nanospheres are uniformly dispersed in 10mL of deionized water.

[0056] (3) Prepare a multi-level porous SiO2 nanosphere template and obtain multi-level porous titanium dioxide superparticles. The specific operation scheme is the same as in Example 1.

[0057] The microstructure of the hierarchical porous titanium dioxide superparticles prepared in Example 2 was observed using transmission electron microscopy, and the results are as follows: Figure 3 As shown, the hierarchical porous titanium dioxide superparticles prepared in Example 2, after reducing the sulfonation degree of the central sphere, can adsorb fewer 100nm aminated modified superstructured SiO2 nanospheres through electrostatic interaction, compared with Example 1 which grew fewer 100nm superstructured hollow titanium dioxide spheres.

[0058] Example 3

[0059] This embodiment provides a method for preparing hierarchical porous titanium dioxide ultraparticles, specifically including the following steps:

[0060] (1) Prepare 100 nm aminated modified superstructure SiO2 nanosphere templates. The specific operation scheme is the same as in Example 1.

[0061] (2) Preparation of 300nm sulfonated modified SiO2 nanosphere templates: The specific operation procedure is the same as in Example 1. The difference is that: the obtained 300nm SiO2 nanospheres are uniformly dispersed in 10mL of deionized water, then 600μL of γ-mercaptopropyltriethoxysilane is added, and the reaction is stirred at 50℃ for 24h. Then, 2mL of 30wt% hydrogen peroxide solution is added, and the reaction is continued at 50℃ for 24h. After centrifugation and washing three times, 300nm sulfonated modified superstructured SiO2 nanospheres are obtained. The obtained 300nm sulfonated modified SiO2 nanospheres are uniformly dispersed in 10mL of deionized water.

[0062] (3) Prepare a multi-level porous SiO2 nanosphere template and obtain multi-level porous titanium dioxide superparticles. The specific operation scheme is the same as in Example 1.

[0063] The microstructure of the hierarchical porous titanium dioxide superparticles prepared in Example 3 was observed using transmission electron microscopy, and the results are as follows: Figure 4 As shown, the hierarchical porous titanium dioxide superparticles prepared in Example 3, after increasing the sulfonation degree of the central sphere, can adsorb more 100nm aminated modified superstructured SiO2 nanospheres through electrostatic interaction, compared with Example 1 which grew more 100nm superstructured hollow titanium dioxide spheres.

[0064] Comparative Example 1

[0065] This comparative example provides a method for preparing titanium dioxide ultraparticles, specifically including the following steps:

[0066] (1) 100 nm SiO2 nanospheres were prepared using the Stöber method as templates. Specifically, 60 mL of anhydrous ethanol, 1 mL of deionized water, and 3 mL of ammonia were uniformly mixed in a double-necked flask, and then 2.3 mL of TEOS was added dropwise. The mixture was stirred at 35 °C for 5 h, centrifuged, and washed 3 times to obtain 100 nm SiO2 nanospheres. The obtained 100 nm SiO2 nanospheres were uniformly dispersed in 10 mL of deionized water. At room temperature, 1.3 mL of 3-aminopropyltriethoxysilane was added dropwise, and the mixture was reacted for 24 h. After centrifugation and washing 3 times, the obtained 100 nm amino-modified SiO2 nanospheres were uniformly dispersed in 10 mL of deionized water.

[0067] (2) 300 nm SiO2 nanospheres were prepared using the Stöber method as a template. Specifically, 16.25 mL of ethanol, 24.75 mL of deionized water, and 9.0 mL of ammonia were uniformly mixed in a flask as solution A. Then, 45.5 mL of anhydrous ethanol and 4.5 mL of TEOS were uniformly mixed in the flask as solution B. Solution B was quickly added to solution A, and the mixture was stirred at 25 °C for 2 h. After centrifugation, the mixture was washed three times. The obtained 300 nm SiO2 nanospheres were uniformly dispersed in 10 mL of deionized water. Then, 300 μL of γ-mercaptopropyltriethoxysilane was added, and the mixture was stirred at 50 °C for 24 h. After stirring, 1 mL of 30 wt% hydrogen peroxide solution was added, and the mixture was stirred at 50 °C for another 24 h. After centrifugation, the mixture was washed three times. The obtained 300 nm sulfonated modified SiO2 nanospheres were uniformly dispersed in 10 mL of deionized water.

[0068] (3) Preparation of SiO2 super-assembled template: Specifically, 10 mL of 100 nm aminated SiO2 nanospheres and 10 mL of 300 nm sulfonated SiO2 nanospheres were mixed evenly, and 20 μL of 2 mol / L HCl solution was added to adjust the pH of the solution to 4. The mixture was stirred vigorously at 50 °C for 48 h. The solution was then centrifuged, washed, and dried to obtain a white powder. 0.08 g of the obtained white powder was dissolved in 10 mL of anhydrous ethanol, and 200 μL of ammonia was added to adjust the pH of the solution to 10. 0.08 g of hexadecylamine was added, and the mixture was stirred at room temperature for 10 min. 150 μL of isopropyl titanate was slowly added dropwise to the above solution, and the solution gradually turned pale yellow. The mixture was stirred for 10 min. The solution was then centrifuged, washed, and dried to obtain a pale yellow powder. The obtained sample was calcined in air at 400℃ for 4 hours to remove the pore-forming agent, and then placed in a 2M NaOH solution and stirred at 35℃ for 2 hours to remove the SiO2 super-assembly template, thus obtaining titanium dioxide superparticles.

[0069] The microstructure of the titanium dioxide superparticles prepared in Comparative Example 1 was observed using transmission electron microscopy, and the results are as follows: Figure 5 As shown, from Figure 5 As can be seen from the above, the spherical mesopores on the small hollow titanium dioxide spheres of the titanium dioxide ultraparticles prepared in this embodiment disappear, the size of the radial mesopores in the titanium dioxide layer is 3-5 nm, and the thickness of the titanium dioxide layer is 30-40 nm.

[0070] Comparative Example 2

[0071] This comparative example provides a method for preparing titanium dioxide ultraparticles, specifically including the following steps:

[0072] (1) 100 nm SiO2 nanospheres were prepared using the Stöber method as templates. Specifically, 60 mL of anhydrous ethanol, 1 mL of deionized water, and 3 mL of ammonia were uniformly mixed in a double-necked flask, and then 2.3 mL of TEOS was added dropwise. The mixture was stirred at 35 °C for 5 h, centrifuged, and washed three times. The obtained 100 nm SiO2 nanospheres were uniformly dispersed in 10 mL of deionized water. At room temperature, 1.3 mL of 3-aminopropyltriethoxysilane was added dropwise, and the mixture was reacted for 24 h. After centrifugation, the mixture was washed three times. The obtained 100 nm amino-modified SiO2 nanospheres were uniformly dispersed in 10 mL of deionized water.

[0073] (2) 300 nm SiO2 nanospheres were prepared using the Stöber method as a template. Specifically, 16.25 mL of ethanol, 24.75 mL of deionized water, and 9.0 mL of ammonia were uniformly mixed in a flask as solution A. Then, 45.5 mL of anhydrous ethanol and 4.5 mL of TEOS were uniformly mixed in the flask as solution B. Solution B was quickly added to solution A, and the mixture was stirred at 25 °C for 2 h. After centrifugation, the mixture was washed three times. The obtained 300 nm SiO2 nanospheres were uniformly dispersed in 10 mL of deionized water. Then, 300 μL of γ-mercaptopropyltriethoxysilane was added, and the mixture was stirred at 50 °C for 24 h. After stirring, 1 mL of 30% hydrogen peroxide solution was added, and the mixture was stirred at 50 °C for another 24 h. After centrifugation, the mixture was washed three times. The obtained 300 nm sulfonated modified SiO2 nanospheres were uniformly dispersed in 10 mL of deionized water.

[0074] (3) Preparation of SiO2 superstructure template: 10 mL of 100 nm aminated SiO2 nanospheres and 10 mL of 300 nm sulfonated SiO2 nanospheres were mixed evenly. 20 μL of 2 mol / L HCl solution was added, and the pH of the solution was adjusted to 4. Then, the pH of the solution was adjusted to 11, and the mixture was stirred vigorously at 50 °C for 48 h. The solution was centrifuged, washed, and dried to obtain a white powder. 0.08 g of the obtained white powder was dissolved in 10 mL of anhydrous ethanol, 400 μL of ammonia water was added, and 0.08 g of hexadecylamine was added. The mixture was stirred at room temperature for 10 min. 200 μL of isopropyl titanate was slowly added dropwise to the above solution, and the solution gradually turned pale yellow. The mixture was stirred for 10 min. The solution was centrifuged, washed, and dried to obtain a pale yellow powder. The obtained sample was calcined in air at 400℃ for 4 hours to remove the pore-forming agent, and then placed in a 2M NaOH solution and stirred at 35℃ for 2 hours to remove the SiO2 super-assembly template, thus obtaining titanium dioxide superparticles.

[0075] The microstructure of the titanium dioxide superparticles prepared in Comparative Example 1 was observed using transmission electron microscopy, and the results are as follows: Figure 6 As shown, from Figure 6 As can be seen, the spherical mesopores on the 100nm superstructure titanium dioxide hollow spheres disappear, the size of the radial mesopores in the titanium dioxide layer is 3-5nm, and the thickness of the titanium dioxide layer is 40-50nm.

[0076] The photocatalytic performance of the samples prepared in Example 1, Comparative Example 1, and Comparative Example 2 was tested, specifically including the following steps:

[0077] (1) The titanium dioxide ultraparticles prepared in Example 1, Comparative Example 1 and Comparative Example 2 were dispersed in 20 mL of deionized water to obtain photocatalyst solutions for further testing.

[0078] (2) The photocatalytic carbon dioxide reduction activity of the photocatalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2 was tested respectively, and the results are as follows: Figure 7 As shown, by Figure 7 It can be seen that the photocatalyst prepared in Example 1 exhibits superior photocatalytic performance in reducing carbon dioxide to carbon monoxide, which is far superior to the photocatalysts prepared in Comparative Examples 1 and 2. This demonstrates the importance of the thickness of the titanium dioxide layer and the presence or absence of spherical mesopores to its photocatalytic performance. It also proves that the titanium dioxide superparticles prepared in this invention have high photocatalytic performance in reducing carbon dioxide.

[0079] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0080] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0081] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing hierarchical porous titanium dioxide ultraparticles, characterized in that, Includes the following steps: Step 1: Preparation of aminated superstructured SiO2 nanosphere templates: The template agent was dissolved in an inorganic acid solution with a concentration of 1-10 mol / L to form a homogeneous solution with a concentration of 1-8 wt%. A pore-expanding agent and an organosilicon source were added, and the mixture was stirred for 1-5 h to form a stable nanoemulsion. Subsequently, a pre-synthesized SiO2 nanosphere aqueous solution was added, and the mixture was stirred at room temperature for 1-10 h. Then, an organosilicon end-capping agent was added, and the mixture was stirred for another 10-48 h. After centrifugation and washing, the mixture was dispersed in deionized water to obtain an aminated superstructured SiO2 nanosphere template. Step 2: Preparation of sulfonated modified SiO2 nanosphere templates: Take the pre-synthesized SiO2 nanosphere aqueous solution, add silane coupling agent, and stir the reaction at 25-50℃ for 10-24h; then add hydrogen peroxide aqueous solution and continue stirring the reaction for 10-24h; centrifuge, wash, and disperse in deionized water to obtain sulfonated modified SiO2 nanosphere template. Step 3: Preparation of super-assembled hierarchical porous titanium dioxide hollow spheres: The solutions obtained in step one and step two are mixed in a volume ratio of 1:1; the pH is adjusted to 4-6 with an inorganic acid, and the mixture is stirred at 50°C for 10-48 hours. After centrifugation, washing, and drying, a white powder is obtained. The powder is dispersed in anhydrous ethanol, and the pH is adjusted to 9-11 with ammonia. A pore-forming agent is added and stirred. A titanium source is added dropwise, and the mixture is stirred and reacted. After centrifugation, washing, and drying, a pale yellow powder is obtained. Finally, the powder is calcined in air at 300-600°C for 2-10 hours to remove the pore-forming agent, and then placed in an aqueous sodium hydroxide solution for 4-18 hours to remove the SiO2 nanosphere template, thus obtaining the hierarchical porous titanium dioxide ultraparticles.

2. The method for preparing multi-level porous titanium dioxide ultraparticles as described in claim 1, characterized in that, In step one, the mass ratio of the SiO2 nanosphere aqueous solution to the template agent, the pore-expanding agent, and the organosilicon source is 1:5-10:5-10:5-10, and the mass ratio of the SiO2 nanospheres to the organosilicon end-capping agent is 1:2-5.

3. The method for preparing multi-level porous titanium dioxide ultraparticles as described in claim 1, characterized in that, In step one, the template agent is selected from F127 (EO) 106 -PO 70 -EO 106 ), P123 (EO) 20 -PO 70 -EO 20 F108 (EO) 132 -PO 50 -EO 132 ), F98 (EO) 132 -PO 45 -EO 132 ), F87 (EO) 106 -PO 40 -EO 106 ), F68 (EO) 132 -PO 30 -EO 132 ) or P65 (EO 20 -PO 30 -EO 20 One or more of the following; The inorganic acid solution is selected from one or more of hydrochloric acid, nitric acid, and sulfuric acid solutions; The pore-expanding agent is selected from one or more of benzene, toluene, ethylbenzene, xylene, trimethylbenzene, chlorobenzene, and bromobenzene; The organosilicon source is selected from one or more of tetraethyl orthosilicate, methyl orthosilicate, propyl orthosilicate, dimethyldimethoxysilane, and 1,2-bis(triethoxysilyl)ethane; The organosilane end-capping agent is selected from one or more of vinyltrimethoxysilane, trimethylethoxysilane, 3-aminopropyltriethoxysilane, dimethyldimethoxysilane, and dimethyldiethoxysilane.

4. The method for preparing multi-level porous titanium dioxide ultraparticles as described in claim 1, characterized in that, In step two, the volume ratio of SiO2 nanosphere aqueous solution to silane coupling agent is 20-5:1, and the volume ratio of SiO2 nanosphere aqueous solution to hydrogen peroxide aqueous solution is 5-10:

1.

5. The method for preparing multi-level porous titanium dioxide ultraparticles as described in claim 1, characterized in that, In step two, the silane coupling agent is selected from one or more of mercaptopropyltrimethoxysilane, KH590 (γ-mercaptopropyltriethoxysilane), KH560 (γ-glycidyl etheroxypropyltrimethoxysilane), or KH550 (γ-aminopropyltriethoxysilane).

6. The method for preparing multi-level porous titanium dioxide ultraparticles as described in claim 1, characterized in that, In step three, the pore-forming agent is one or more of decylamine, tetradecylamine, hexadecylamine, dodecylamine, and octadecylamine; The titanium source is selected from one or more of isopropyl titanate, tetrabutyl titanate, tetraethyl titanate, titanium tetrachloride, titanium trichloride, and titanium acetylacetonate.

7. The method for preparing multi-level porous titanium dioxide ultraparticles as described in claim 1, characterized in that, The centrifugation speed is 3000-12000 r / min, and the centrifugation time is 3-15 min.

8. The method for preparing multi-level porous titanium dioxide ultraparticles as described in claim 1, characterized in that, The washing conditions are one or more of deionized water, 95wt% ethanol solution, and anhydrous ethanol, and the number of washing cycles is 2-6.

9. A multi-level porous titanium dioxide superparticle, characterized in that, The multi-level porous titanium dioxide superparticles are prepared by the method according to any one of claims 1-8, comprising a large hollow sphere at the center and small hollow spheres distributed on its surface. The pore size of the large hollow sphere is 100-500 nm, and the pore size of the small hollow spheres on the surface is 50-200 nm. Spherical mesopores with a pore size of 15-50 nm are distributed on the shell of the small hollow spheres. The thickness of the titanium dioxide shell is 5-50 nm, and the radial mesopore size is 3-10 nm. The specific surface area of ​​the multi-level porous titanium dioxide superparticles is 100-300 m². 2 / g.

10. The application of the hierarchical porous titanium dioxide superparticles as described in claim 9 in photocatalysis, energy storage, or photoelectrochemistry.

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