Hierarchically ordered macroporous-mesoporous titanium dioxide and its preparation method and application

Abstract

The present invention is applicable to the technical field of porous materials, and is a multi-level ordered macroporous-mesoporous titanium dioxide and its preparation method and application, comprising the following steps: (1) preparing a superstructured photonic crystal solid; (2) forming a light yellow solution with a concentration of 0.2-0.5 mol / L; (3) adding the superstructured photonic crystal solid in step (1) to the light yellow solution in step (2) to prepare the multi-level ordered macroporous-mesoporous titanium dioxide. Beneficial effect: In the preparation method of the multi-level ordered macroporous-mesoporous titanium dioxide disclosed in the present invention, the stability of the mesoporous superstructure unit can be ensured, and the precise and perfect replication of the pore structure can be achieved; the separation efficiency of the photogenerated charges and photogenerated holes of the titanium dioxide disclosed in the present invention in the photocatalytic water decomposition is greatly improved, and due to the multi-level ordered macroporous-mesoporous structure, the multiple scattering of the incident light in the porous framework can be ensured, thereby improving the efficiency of hydrogen production by photocatalytic water decomposition.

Description

Technical Field

[0001] The invention relates to the technical field of porous materials, and more specifically to a multi-level ordered macroporous-mesoporous titanium dioxide and a preparation method and application thereof. Background Art

[0002] The rapid development of society has brought about increasingly serious resource and ecological environmental problems. How to make good use of solar energy, a clean and renewable energy, is a major challenge faced by researchers. Three-dimensional ordered macroporous materials have suitable photonic band gaps, large specific surface areas, interconnected and orderly cavity structures, as well as the slow light effect, multiple scattering effect and enhanced light absorption of photonic crystals. TiO2 is one of the most widely and deeply studied materials in the field of photocatalysis and has great potential for photocatalytic applications. However, due to a series of problems such as high recombination rate of photogenerated carriers and narrow light absorption range, its further application is limited. Constructing traditional TiO2 nanomaterials into porous inverse opal structures can not only increase the specific surface area of ​​the material, but also give the material a slow light effect, enhance TiO2's absorption of light, and improve the quantum efficiency of photocatalysts.

[0003] Currently, there are many methods for synthesizing TiO2-based porous three-dimensional ordered macroporous materials, mainly template-free method, liquid crystal template method, soft template method, etc. The inverse opal structure obtained by the traditional template-free method is usually irregular; the inverse opal structure synthesized by the liquid crystal template method only contains abundant macropores, a certain amount of micropores, and very few mesopores; and in the synthesis method of the soft template method, the building unit is often uncontrollable, so the number, size and thickness of the obtained mesoporous structure are uneven, and the mesoporous structure is prone to collapse. The existing process cannot produce porous materials with uniform size and thickness, macropores, and abundant spherical mesopores. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a multi-level ordered macroporous-mesoporous titanium dioxide and a preparation method and application thereof, which prepares a high specific surface area, an interconnected pore structure and abundant spherical mesopores, greatly improving the separation efficiency of photogenerated charges and holes in the photocatalytic water splitting of the titanium dioxide disclosed in the present invention. Due to the multi-level ordered macroporous-mesoporous structure, the incident light energy is multiply scattered in the porous framework structure, thereby improving the absorption of light energy and the efficiency of hydrogen production by photocatalytic water splitting.

[0005] To achieve the above object, the present invention provides the following technical solution on one hand: a method for preparing multi-level ordered macroporous-mesoporous titanium dioxide, comprising the following steps:

[0006] (1) Dissolving the template in an inorganic acid solution with a concentration of 1-8 mol / L, stirring evenly to form a template solution with a concentration of 1.5-5%; then adding a pore expander to the template solution and stirring for 2-24 h to form a nanoemulsion; then adding an organic silicon source to the nanoemulsion, stirring and reacting at room temperature for 0.5-10 h, then adding SiO2 nanospheres with a particle size of 200-500 nm, continuing to stir and react for 1-10 h, then adding an organic silane capping agent, stirring and reacting for another 1-36 h to obtain a mixed solution, and sequentially centrifuging, washing, and drying the mixed solution to obtain a superstructured photonic crystal solid;

[0007] (2) adding an inorganic acid with a concentration of 10-20 mol / L to anhydrous ethanol and stirring thoroughly to form a clear transparent solution, and then adding an organic titanium source to the clear solution to form a light yellow solution with a concentration of 0.2-0.5 mol / L;

[0008] (3) Adding the superstructured photonic crystal solid in step (1) to the light yellow solution in step (2), and placing it in an oven at 20-50°C for volatilization for 2-48 hours, then heating it to 60-120°C and continuing to volatilize it for 2-32 hours; calcining the sample obtained after volatilization in an air atmosphere at a temperature of 300-800°C for 2-10 hours to remove the template; and then placing it in a NaOH solution with a concentration of 1-5 mol / L for 2-18 hours to remove the SiO2 nanospheres, thereby obtaining a hierarchically ordered macroporous-mesoporous titanium dioxide.

[0009] Furthermore, in step (1), the mass ratio of the template, the pore expanding agent, the organosilicon source, the SiO2 nanospheres and the organosilane capping agent is 5-7:5-7:5-7:1-2:2-3; and the stirring speed is 500-15000 r / min.

[0010] Furthermore, in step (1), the template is F127 (EO 106 -PO 70 -EO 106 )、F68(EO 132 -PO 30 -EO 132 )、F98(EO 132 -PO 45 -EO 132 )、P85(EO 26 -PO 39 -EO 20 )、P123(EO 20 -PO 70 -EO 20 )、F108(EO132 -PO 50 -EO 132 )、F88(EO 132 -PO 40 -EO 132 )、F87(EO 106 -PO 40 -EO 106 ) one or more of the following;

[0011] The pore-enlarging agent is one or more of benzene, toluene and trimethylbenzene;

[0012] The organic silicon source is one or more of tetraethyl orthosilicate, 1,2-bis(triethoxysilyl)ethane, and dimethyldimethoxysilane;

[0013] The organosilane end-capping agent is one or more of dimethyldimethoxysilane and dimethyldiethoxysilane;

[0014] Furthermore, the inorganic acid in step (1) and step (2) is one or more of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, hydroiodic acid, hydrobromic acid, and hydrofluoric acid.

[0015] Furthermore, in step (1), the centrifugation speed is 1000-10000 rpm, and the centrifugation time is 5-15 min.

[0016] Furthermore, in step (1), the washing conditions are: first using distilled water for 1-5 times, and then using anhydrous ethanol for 1-5 times.

[0017] Furthermore, in step (1), the drying process is to disperse and dissolve the washed substance in anhydrous ethanol to obtain an alcohol solution with a concentration of 0.1-0.5 mol / L, and then place it in a drying oven at 20-60°C to volatilize for 2-48 hours.

[0018] Furthermore, in step (2), the organic titanium source is one or more of tetrabutyl titanate, isopropyl titanate, and tetraethyl titanate.

[0019] Furthermore, in step (3), the mass ratio of the superstructure photonic crystal solid to the light yellow solution is 1:50-300.

[0020] Furthermore, the macroporous-mesoporous titanium dioxide has spherical macropores, a single layer of spherical mesopores is evenly distributed on the inner wall of the spherical macropores, the pore size of the spherical macropores is 200-500 nm, the pore size of the spherical mesopores is 10-50 nm, and the specific surface area of ​​the macroporous-mesoporous titanium dioxide is 50-200 m 2 / g.

[0021] Another aspect of the present invention provides the following technical solution: application of hierarchically ordered macroporous-mesoporous titanium dioxide in photocatalytic water decomposition.

[0022] The advantages of the present invention are:

[0023] 1. In the preparation method of the multi-level ordered macroporous-mesoporous titanium dioxide disclosed in the present invention, a template agent, a pore expander and an organic silicon source are used to form a composite single micelle for constructing mesopores; the composite single micelle is assembled with SiO2 nanospheres to obtain a SiO2@single micelle superstructure, forming an assembly unit of a three-dimensional ordered structure for manufacturing a uniform and controllable pore structure; the organic titanium source is used as a skeleton of the three-dimensional ordered structure and filled into the gaps of the photonic crystal, and finally the template agent and the SiO2 nanospheres are removed by high-temperature calcination and etching to obtain a multi-level ordered macroporous-mesoporous titanium dioxide; the stability of the mesoporous superstructure unit can be guaranteed, and accurate and perfect replication can be achieved.

[0024] 2. The multi-level ordered macroporous-mesoporous titanium dioxide disclosed in the present invention has interconnected spherical macropores, a single layer of spherical mesopores is evenly distributed on the inner wall of the spherical macropores, the pore size of the spherical macropores is 200-500 nm, the pore size of the spherical mesopores is 10-50 nm, and the specific surface area of ​​the material is 50-220 m 2 / g; A large number of ordered spherical mesopores are distributed on the surface of the inner wall of the macropore, which is difficult to achieve with existing three-dimensional ordered macroporous materials.

[0025] 3. The multi-level ordered macroporous-mesoporous titanium dioxide disclosed in the present invention is used in photocatalytic water decomposition. Since the multi-level ordered macroporous-mesoporous titanium dioxide disclosed in the present invention has a high specific surface area, an interconnected pore structure and abundant spherical mesopores, the separation efficiency of the photogenerated charges and photogenerated holes of the titanium dioxide disclosed in the present invention in photocatalytic water decomposition is greatly improved. Due to the multi-level ordered macroporous-mesoporous structure, the incident light is multiply scattered, thereby improving the reaction efficiency of photocatalytic water decomposition to produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the formation of the hierarchically ordered macroporous-mesoporous titanium dioxide of the present invention.

[0027] Figure 2 This is a 500 nm scanning electron microscope (SEM) image of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 1 of the present invention.

[0028] Figure 3 This is a 50 nm scanning electron microscope (SEM) image of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 1 of the present invention.

[0029] Figure 4This is a scanning electron microscope (SEM) image of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 2 of the present invention.

[0030] Figure 5 This is a scanning electron microscope (SEM) image of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 3 of the present invention.

[0031] Figure 6 This is a scanning electron microscope (SEM) image of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 4 of the present invention.

[0032] Figure 7 This is a scanning electron microscope (SEM) image of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 5 of the present invention.

[0033] Figure 8 This is a diagram of the hydrogen production rate of the photocatalytic hydrolysis of carbon dioxide and titanium dioxide P25 prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0034] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0035] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0036] In the present invention, unless otherwise specified, the directions used, such as "up" and "down", usually refer to the directions shown in the drawings, or to the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "left" and "right" usually refer to the left and right shown in the drawings; "inside" and "outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directions are not used to limit the present invention.

[0037] Example 1: A method for preparing hierarchically ordered macroporous-mesoporous titanium dioxide, comprising the following steps: Figure 1 As shown,

[0038] (1) At room temperature, 0.25 g of F108 (EO 132 -PO 50 -EO 132) was dissolved in 15 mL of 2 mol / L hydrochloric acid, and stirred to form a template solution with a concentration of 3.5%; then 100 μL of trimethylbenzene was added to the template solution and stirred for 12 h to form a nanoemulsion; then 200 μL of tetraethyl orthosilicate was added dropwise to the nanoemulsion, and stirred for reaction at room temperature for 3 h, then 2 mL of 1 mol / L SiO2 nanosphere alcohol solution was added, and the stirring reaction continued for 2 h, then 30 μL of dimethyldimethoxysilane was added dropwise, and the stirring reaction was continued for 36 h to obtain a mixed solution, and the mixed solution was centrifuged in sequence, wherein the centrifugal speed was 8000 rpm and the centrifugal time was 10 min; then it was washed 3 times with distilled water first, and then washed 3 times with anhydrous ethanol; then the washed material was dispersed and dissolved in 5 mL of anhydrous ethanol to obtain an alcohol solution with a concentration of 0.2 mol / L, and then placed in a drying oven at 40 °C for 48 h, and finally a superstructured photonic crystal solid is obtained.

[0039] The preparation method of SiO2 nanosphere alcohol solution is as follows: colloidal silica nanospheres (350 nm) are prepared as core templates by the Stöber method, that is, 24.75 mL of deionized water, 16.25 mL of ethanol and 9.0 mL of concentrated ammonia solution are vigorously stirred and mixed in a 100 mL round-bottom flask as solution A for use; 4.50 mL of TEOS is uniformly dispersed in 45.5 mL of anhydrous ethanol as solution B for use; the above-obtained solution B is quickly poured into the above-obtained solution A and vigorously stirred, reacted at 25°C for 2 h, centrifuged, and washed three times; the obtained SiO2 nanospheres with a particle size of 200-500 nm are dispersed in ethanol to form a homogeneous alcohol solution with a concentration of 1.0 mg / mL, and the SiO2 nanospheres are used as hard templates for constructing superstructures.

[0040] (2) Add 2.4 mL of 12.1 mol / L concentrated hydrochloric acid and 2.4 mL of 17.5 mol / L acetic acid to 30 mL of anhydrous ethanol in sequence and stir thoroughly to form a clear transparent solution. Then, add 3.4 g of tetrabutyl titanate dropwise to the clear solution to form a light yellow solution with a concentration of 0.43 mol / L.

[0041] (3) Adding the superstructured photonic crystal solid in step (1) to the light yellow solution in step (2), and placing it in a 40°C oven for volatilization for 24 hours, then heating it to 80°C and continuing to volatilize it for 12 hours; calcining the sample obtained after volatilization in an air atmosphere at a temperature of 400°C for 3 hours to remove the template; and then placing it in a 2 mol / L NaOH solution for 12 hours to remove the SiO2 nanospheres, thereby obtaining a hierarchically ordered macroporous-mesoporous titanium dioxide.

[0042] The microstructure of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 1 was observed by scanning electron microscopy (SEM). Figure 2 and Figure 3 As shown, from Figure 2 and Figure 3 It can be seen that the multi-level ordered macroporous-mesoporous titanium dioxide prepared in Example 1 has interconnected spherical macropores, a single layer of spherical mesopores is evenly distributed on the inner wall of the spherical macropores, the pore size of the spherical macropores is 300-350 nm, and the pore size of the spherical mesopores is 13-15 nm. The specific surface area of ​​the macroporous-mesoporous titanium dioxide in Example 1 is measured by a fully automatic gas adsorption instrument, and the specific surface area of ​​the macroporous-mesoporous titanium dioxide is 130 m 2 / g.

[0043] Example 2: The overall method is the same as that of Example 1, except that in step (1), the amount of tetraethyl orthosilicate added is 280 μL, the reaction is stirred at room temperature for 3 h, and then 1 mL of 1 mol / L SiO2 nanosphere alcohol solution is added, and the stirring reaction is continued for 2 h.

[0044] The microstructure of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 2 was observed by scanning electron microscopy (SEM). Figure 4 ,from Figure 4 It can be seen that the pore size of the spherical macropores of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 2 is 300-350 nm, and the pore size of the spherical mesopores is 15-18 nm. The specific surface area of ​​the macroporous-mesoporous titanium dioxide in Example 2 is measured by a fully automatic gas adsorption instrument, and the specific surface area of ​​the macroporous-mesoporous titanium dioxide is 120 m 2 / g.

[0045] Example 3: The overall method is the same as that of Example 1, except that in step (1), the amount of tetraethyl orthosilicate added is 350 μL, the reaction is stirred at room temperature for 3 h, and then 1 mL of 1 mol / L SiO2 nanosphere alcohol solution is added, and the stirring reaction is continued for 2 h.

[0046] The microstructure of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 3 was observed by scanning electron microscopy (SEM). Figure 5 ,from Figure 5It can be seen that the pore size of the spherical macropores of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 3 is 300-350 nm, and the pore size of the spherical mesopores is 20-25 nm. The specific surface area of ​​the macroporous-mesoporous titanium dioxide in Example 3 is measured by a fully automatic gas adsorption instrument, and the specific surface area of ​​the macroporous-mesoporous titanium dioxide is 110 m 2 / g.

[0047] Example 4: A method for preparing hierarchically ordered macroporous-mesoporous titanium dioxide, comprising the following steps: Figure 1 As shown,

[0048] (1) At room temperature, 0.2 g of F127 (EO 106 -PO 70 -EO 106 ) was dissolved in 20 mL of 1 mol / L hydrochloric acid, and stirred to form a template solution with a concentration of 1.5%; then 80 μL of toluene was added to the template solution and stirred for 2 h to form a nanoemulsion; then 100 μL of 1,2-bis(triethoxysilyl)ethane was added dropwise to the nanoemulsion, and the reaction was stirred at room temperature for 0.5 h, and then 1 mL of 1 mol / L SiO2 nanosphere alcohol solution was added, and the reaction was continued to be stirred for 1 h, and then 20 μL of dimethyldiethoxysilane was added dropwise, and the reaction was stirred for another 1 h to obtain a mixed solution, and the mixed solution was centrifuged in sequence, wherein the centrifugal speed was 1000 rpm and the centrifugal time was 5 min; then the washed material was first washed once with distilled water and then washed once with anhydrous ethanol; then the washed material was dispersed and dissolved in 10 mL of anhydrous ethanol to obtain an alcohol solution with a concentration of 0.1 mol / L, and then placed in a drying oven at 20 °C for 2 h, and finally a superstructured photonic crystal solid is obtained.

[0049] The preparation method of SiO2 nanosphere alcohol solution is as follows: colloidal silica nanospheres (350 nm) are prepared as core templates by the Stöber method, that is, 24.75 mL of deionized water, 16.25 mL of ethanol and 9.0 mL of concentrated ammonia solution are vigorously stirred and mixed in a 100 mL round-bottom flask as solution A for use; 4.50 mL of TEOS is uniformly dispersed in 45.5 mL of anhydrous ethanol as solution B for use; the above-obtained solution B is quickly poured into the above-obtained solution A and vigorously stirred, reacted at 25°C for 2 h, centrifuged, and washed three times; the obtained SiO2 nanospheres with a particle size of 200-500 nm are dispersed in ethanol to form a homogeneous alcohol solution with a concentration of 1.0 mg / mL, and the SiO2 nanospheres are used as hard templates for constructing superstructures.

[0050] (2) Add 1 mL of 10 mol / L concentrated hydrochloric acid and 1 mL of 10 mol / L acetic acid to 40 mL of anhydrous ethanol in sequence and stir thoroughly to form a clear transparent solution. Then, add 0.1 g of tetrabutyl titanate dropwise to the clear solution to form a light yellow solution with a concentration of 0.2 mol / L.

[0051] (3) Adding the superstructured photonic crystal solid in step (1) to the light yellow solution in step (2), and placing it in a 20°C oven for volatilization for 2 h, then heating it to 60°C and continuing to volatilize it for 2 h; calcining the sample obtained after volatilization in an air atmosphere at a temperature of 300°C for 2 h to remove the template; and then placing it in a 1 mol / L NaOH solution for 2 h to remove the SiO2 nanospheres, thereby obtaining a hierarchically ordered macroporous-mesoporous titanium dioxide.

[0052] The microstructure of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 4 was observed by scanning electron microscopy (SEM). Figure 6 ,from Figure 6 It can be seen that the pore size of the spherical macropores of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 4 is 300-350 nm, and the pore size of the spherical mesopores is 15-20 nm. The specific surface area of ​​the macroporous-mesoporous titanium dioxide in Example 4 was measured by a fully automatic gas adsorption instrument, and the specific surface area of ​​the macroporous-mesoporous titanium dioxide was 105 m 2 / g.

[0053] Example 5: A method for preparing hierarchically ordered macroporous-mesoporous titanium dioxide, comprising the following steps: Figure 1 As shown,

[0054] (1) At room temperature, 0.3 g of P85 (EO 26 -PO 39 -EO 20) was dissolved in 10 mL of 8 mol / L acetic acid, and stirred to form a 5% template solution; then 200 μL of benzene was added to the template solution and stirred for 24 h to form a nanoemulsion; then μL of dimethyldimethoxysilane was added dropwise to the nanoemulsion, and stirred for reaction at room temperature for 10 h, then 3 mL of 1 mol / L SiO2 nanosphere alcohol solution was added, and the stirring reaction continued for 10 h, then 100 μL of dimethyldimethoxysilane was added dropwise, and the stirring reaction was continued for 18 h to obtain a mixed solution, and the mixed solution was centrifuged in sequence, wherein the centrifugal speed was 10000 rpm and the centrifugal time was 15 min; then it was washed 5 times with distilled water first, and then washed 5 times with anhydrous ethanol; then the washed material was dispersed and dissolved in 2 mL of anhydrous ethanol to obtain an alcohol solution with a concentration of 0.5 mol / L, and then placed in a drying oven at 60 °C for 25 h, and finally a superstructured photonic crystal solid is obtained.

[0055] The preparation method of SiO2 nanosphere alcohol solution is as follows: colloidal silica nanospheres (350 nm) are prepared as core templates by the Stöber method, that is, 24.75 mL of deionized water, 16.25 mL of ethanol and 9.0 mL of concentrated ammonia solution are vigorously stirred and mixed in a 100 mL round-bottom flask as solution A for use; 4.50 mL of TEOS is uniformly dispersed in 45.5 mL of anhydrous ethanol as solution B for use; the above-obtained solution B is quickly poured into the above-obtained solution A and vigorously stirred, reacted at 25°C for 2 h, centrifuged, and washed three times; the obtained SiO2 nanospheres with a particle size of 200-500 nm are dispersed in ethanol to form a homogeneous alcohol solution with a concentration of 1.0 mg / mL, and the SiO2 nanospheres are used as hard templates for constructing superstructures.

[0056] (2) Add 3 mL of 20 mol / L concentrated hydrochloric acid and 3 mL of 20 mol / L acetic acid to 20 mL of anhydrous ethanol in sequence and stir thoroughly to form a clear transparent solution. Then, add 0.5 g of tetrabutyl titanate dropwise to the clear solution to form a light yellow solution with a concentration of 0.5 mol / L.

[0057] (3) Adding the superstructured photonic crystal solid in step (1) to the light yellow solution in step (2), and placing it in a 50°C oven for volatilization for 48 hours, then heating it to 120°C and continuing to volatilize it for 32 hours; calcining the sample obtained after volatilization in an air atmosphere at a temperature of 800°C for 10 hours to remove the template; and then placing it in a 5 mol / L NaOH solution for 18 hours to remove the SiO2 nanospheres, thereby obtaining a hierarchically ordered macroporous-mesoporous titanium dioxide.

[0058] The microstructure of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 5 was observed by scanning electron microscopy (SEM). Figure 7 ,from Figure 7 It can be seen that the pore size of the spherical macropores of the hierarchically ordered macroporous-mesoporous titanium dioxide prepared in Example 5 is 300-350 nm, and the pore size of the spherical mesopores is 15-25 nm. The specific surface area of ​​the macroporous-mesoporous titanium dioxide in Example 5 is measured by a fully automatic gas adsorption instrument, and the specific surface area of ​​the macroporous-mesoporous titanium dioxide is 100 m 2 / g.

[0059] Hierarchical ordered macroporous-mesoporous titanium dioxide with spherical macropores having a pore size of 300-350 nm was prepared by the preparation methods of Examples 1-5. The hierarchical ordered macroporous-mesoporous titanium dioxide prepared in Example 1 had smaller spherical mesopores and larger specific surface area than the hierarchical ordered macroporous-mesoporous titanium dioxide prepared in other examples.

[0060] Experiment: Titanium dioxide prepared in Examples 1-5 and purchased titanium dioxide P25 were uniformly dispersed in 15 mL of deionized water, 5 mL of methanol (as a sacrificial agent) and 0.1 mg of potassium chloroplatinate were added as a co-catalyst. A 300-watt xenon lamp was used as a simulated solar light source to carry out photocatalytic hydrolysis in a closed cycle gas system. The generated hydrogen content was analyzed by an online trace gas chromatograph. Figure 8 As shown, the hydrogen production of Example 1 is 9.9 mmol g -1 h -1 The hydrogen production of Example 2 is 8.4 mmol g -1 h -1 The hydrogen production of Example 3 is 7.9 mmol g -1 h -1 The hydrogen production of Example 4 is 7.2 mmol g -1 h -1 The hydrogen production of Example 5 is 6.4 mmol g -1 h -1 , which is much higher than the hydrogen production of commercial P25 catalyst (3.3 mmol g -1 h -1 ), among which Example 1 has the largest hydrogen production amount because it has the largest accessible specific surface area and can therefore provide the most active sites for hydrogen production.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0062] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing multi-level ordered macroporous-mesoporous titanium dioxide, characterized in that: The following steps are involved: (1) Preparation of superstructured photonic crystal solid: dissolve the template in an acid solution with a concentration of 1-8 mol / L, and stir to form a template solution with a concentration of 1.5-5%; then add a pore expander to the template solution and stir for 2-24 h to form a nanoemulsion; then add an organic silicon source to the nanoemulsion, stir and react at room temperature for 0.5-10 h, then add SiO2 nanospheres with a particle size of 200-500 nm, continue to stir and react for 1-10 h, then add an organic silane capping agent, and stir and react for 1-36 h to obtain a mixed solution, and centrifuge, wash, and dry the mixed solution in sequence to finally obtain a superstructured photonic crystal solid; (2) preparing a titanium source solution: adding an acid with a concentration of 10-20 mol / L into anhydrous ethanol and stirring thoroughly to form a clear transparent solution, and then adding an organic titanium source into the clear solution to form a light yellow solution with a concentration of 0.2-0.5 mol / L; (3) Preparing hierarchically ordered macroporous-mesoporous titanium dioxide: adding the superstructured photonic crystal solid in step (1) to the light yellow solution in step (2), and placing it in an oven at 20-50°C for volatilization for 2-48 hours, then heating it to 60-120°C and continuing to volatilize it for 2-32 hours; calcining the sample obtained after volatilization in an air atmosphere at a temperature of 300-800°C for 2-10 hours to remove the template; then placing it in a NaOH solution with a concentration of 1-5 mol / L for 2-18 hours to remove the SiO2 nanospheres, thereby obtaining hierarchically ordered macroporous-mesoporous titanium dioxide; The acid in step (1) and step (2) is one or more of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, hydroiodic acid, hydrobromic acid, and hydrofluoric acid.

2. The method for preparing hierarchically ordered macroporous-mesoporous titanium dioxide according to claim 1, characterized in that: In step (1), the mass ratio of the template, the pore expanding agent, the organosilicon source, the SiO2 nanospheres and the organosilane capping agent is 5-7:5-7:5-7:1-2:2-3; and the stirring speed is 500-15000 r / min.

3. The method for preparing hierarchically ordered macroporous-mesoporous titanium dioxide according to claim 2, characterized in that: In step (1), the template is F127 (EO 106 -PO 70 -EO 106 )、F68(EO 132 -PO 30 -EO 132 )、F98(EO 132 -PO 45 -EO 132 )、P85(EO 26 -PO 39 -EO 20 )、P123(EO 20 -PO 70 -EO 20 )、F108(EO 132 -PO 50 -EO 132 )、F88(EO 132 -PO 40 -EO 132 )、F87(EO 106 -PO 40 -EO 106 ) one or more of the following; The pore-enlarging agent is one or more of benzene, toluene and trimethylbenzene; The organic silicon source is one or more of tetraethyl orthosilicate, 1,2-bis(triethoxysilyl)ethane, and dimethyldimethoxysilane; The organosilane end-capping agent is one or more of dimethyldimethoxysilane and dimethyldiethoxysilane.

4. The method for preparing hierarchically ordered macroporous-mesoporous titanium dioxide according to claim 1, characterized in that: In step (1), the centrifugal speed is 1000-10000 rpm, and the centrifugal time is 5-15 min.

5. The method for preparing hierarchically ordered macroporous-mesoporous titanium dioxide according to claim 1, characterized in that: In step (1), the washing conditions are: first use distilled water for 1-5 times, and then use anhydrous ethanol for 1-5 times.

6. The method for preparing hierarchically ordered macroporous-mesoporous titanium dioxide according to claim 1, characterized in that: In step (1), the drying process is to disperse and dissolve the washed material in anhydrous ethanol to obtain an alcohol solution with a concentration of 0.1-0.5 mol / L, and then place it in a drying oven at 20-60°C to volatilize for 8-48 hours.

7. The method for preparing hierarchically ordered macroporous-mesoporous titanium dioxide according to claim 1, characterized in that: In step (2), the organic titanium source is one or more of tetrabutyl titanate, isopropyl titanate, and tetraethyl titanate.

8. The method for preparing hierarchically ordered macroporous-mesoporous titanium dioxide according to claim 1, characterized in that: In step (3), the mass ratio of the superstructure photonic crystal solid to the light yellow solution is 1:50-300.

9. The hierarchically ordered macroporous-mesoporous titanium dioxide prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The macroporous-mesoporous titanium dioxide has spherical macropores, and a single layer of spherical mesopores is evenly distributed on the pore walls of the spherical macropores. The pore size of the spherical macropores is 100-500 nm, the pore size of the spherical mesopores is 10-50 nm, and the specific surface area of ​​the macroporous-mesoporous titanium dioxide is 50-200 m 2 / g.

10. Use of the hierarchically ordered macroporous-mesoporous titanium dioxide according to claim 9 in photocatalytic water decomposition.

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