Preparation method of cluster-based 2D mesoporous titanium dioxide nanosheet

Abstract

The invention belongs to the technical field of nano materials, and particularly relates to a preparation method of a cluster-based 2D mesoporous titanium dioxide nanosheet. According to the titanium dioxide nanosheet provided by the invention, the minimum thickness is 2.7 nm, and the aperture can be regulated from 8.0 nm to 18.0 nm. The nanosheet is prepared by adopting a titanium-oxygen cluster mediated single micelle growth method, taking PS-b-PAA as a structure-directing agent, taking a titanium-oxygen cluster as a construction unit, and taking a sodium chloride crystal as a substrate. The titanium dioxide nanosheet has excellent optical properties and efficient photocatalytic carbon dioxide reduction capability.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterials, and in particular relates to a method for preparing cluster-based 2D mesoporous titanium dioxide nanosheets. Background Art

[0002] Mesoporous materials are constructed from molecular precursors, but using sub-nanometer or even nanoscale nanoclusters as building blocks presents certain challenges. Constructing two-dimensional mesoporous materials from cluster units presents even greater challenges.

[0003] Nanoclusters have precise structures and sizes, unique properties such as quantum effects, and have excellent application prospects.

[0004] Therefore, providing a simple growth method to construct cluster-based 2D mesoporous titanium dioxide nanosheets has important scientific research and application value. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing cluster-based 2D mesoporous titanium dioxide nanosheets with excellent performance and simple preparation.

[0006] The present invention provides a method for preparing cluster-based 2D mesoporous titanium dioxide nanosheets, which adopts the titanyl cluster-mediated single micelle growth technology, uses the diblock copolymer PS-b-PAA as a structure-directing agent, titanyl clusters as building blocks, and sodium chloride crystals as a substrate to grow cluster-based 2D mesoporous titanium dioxide nanosheets; the specific steps are:

[0007] (1) dissolving the titanium oxide clusters in dichloromethane to obtain a colorless and transparent titanium oxide cluster solution;

[0008] (2) dissolving the diblock copolymer PS-b-PAA in tetrahydrofuran to obtain a PS-b-PAA solution;

[0009] (3) Add the PS-b-PAA solution dropwise to the titanium oxide cluster solution and stir continuously with a magnetic stirrer for 1-5 hours to obtain a mixed solution (light blue);

[0010] (4) adding the obtained mixed solution to a condensation column filled with sodium chloride, vacuum filtering, and sucking out excess liquid to obtain a mixture;

[0011] (5) Pour the mixture into a glass Petri dish and volatilize at room temperature for 12-24 hours. Transfer the Petri dish to an oven and volatilize at 40-45°C for 12-24 hours. Then set the temperature to 80-100°C and cure for 12-24 hours.

[0012] (6) Place it in a tube furnace under a nitrogen atmosphere, heat it to 350-450°C at a rate of 1-5°C / min, and calcine it for 2-4 hours; then transfer it to a muffle furnace, heat it to 350-550°C at a rate of 4-5°C / min in air, and calcine it for 1-3 hours for subsequent testing;

[0013] (7) After the reaction is completed, washing is performed to obtain cluster-based 2D mesoporous titanium dioxide nanosheets.

[0014] Further:

[0015] In step (1), the concentration of the titanium oxide cluster solution is controlled to be 10-40 mg / mL;

[0016] In step (2), the concentration of the PS-b-PAA solution is controlled to be 10-40 mg / mL;

[0017] In step (2), the molecular weight of PS-b-PAA is controlled, wherein the molecular weight of PS is 12000-15000 and the molecular weight of PAA is 1100-4800, for example: 12000 -b-PAA 1100 , P.S. 13000 -b-PAA 1200 、PS 15000 -b-PAA 4800 .

[0018] In step (3), the mass ratio of titanium oxide clusters to PS-b-PAA is 1:2-2:1;

[0019] The titanium dioxide nanosheets prepared by the present invention have adjustable surface morphology parameters. Specifically, the thickness can be as low as 2.7 nm, and the pore size can be adjusted from 8.0 nm to 18.0 nm.

[0020] The titanium dioxide nanosheets prepared by the present invention have excellent optical properties and efficient photocatalytic carbon dioxide reduction ability, and can be used for photocatalytic carbon dioxide reduction reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the preparation process of cluster-based 2D mesoporous titanium dioxide nanosheets.

[0022] Figure 2 This is a scanning electron microscope image of the cluster-based 2D mesoporous titanium dioxide nanosheets prepared in the present invention.

[0023] Figure 3 This is a high-resolution scanning electron microscope image of the cluster-based 2D mesoporous titanium dioxide nanosheets prepared in the present invention.

[0024] Figure 4This is a transmission electron microscope image of the cluster-based 2D mesoporous titanium dioxide nanosheets prepared in the present invention.

[0025] Figure 5 This is a high-resolution transmission electron microscope image of the cluster-based 2D mesoporous titanium dioxide nanosheets prepared in the present invention.

[0026] Figure 6 This is the X-ray diffraction image of the cluster-based 2D mesoporous titanium dioxide nanosheets prepared in the present invention.

[0027] Figure 7 This is a Raman spectrum image of the cluster-based 2D mesoporous titanium dioxide nanosheets prepared in the present invention.

[0028] Figure 8 This is the nitrogen adsorption-desorption curve image of the cluster-based 2D mesoporous titanium dioxide nanosheets prepared in the present invention.

[0029] Figure 9 This is the pore size distribution image of the cluster-based 2D mesoporous titanium dioxide nanosheets prepared in the present invention.

[0030] Figure 10 This is the X-ray diffraction image of the cluster-based 2D mesoporous titanium dioxide nanosheet precursor titanium oxide cluster prepared in the present invention.

[0031] Figure 11 Nitrogen adsorption-desorption curve and pore size distribution image of the cluster-based 2D mesoporous titanium dioxide nanosheet precursor titanium oxide cluster prepared in the present invention.

[0032] Figure 12 Scanning electron microscope, transmission electron microscope and pore size distribution images of cluster-based 2D mesoporous titanium dioxide nanosheets with a pore size of 8 nanometers prepared in the present invention.

[0033] Figure 13 Scanning electron microscope, transmission electron microscope and pore size distribution images of cluster-based 2D mesoporous titanium dioxide nanosheets with a pore size of 13 nanometers prepared by the present invention.

[0034] Figure 14 Scanning electron microscope, transmission electron microscope and pore size distribution images of cluster-based 2D mesoporous titanium dioxide nanosheets with a pore size of 18 nanometers prepared by the present invention.

[0035] Figure 15 This is an image showing the photocatalytic carbon dioxide reduction performance of the cluster-based 2D mesoporous titanium dioxide nanosheets prepared in the present invention. DETAILED DESCRIPTION

[0036] The present invention is further described below through embodiments in conjunction with the accompanying drawings.

[0037] Example 1: Preparation of a cluster-based 2D mesoporous titanium dioxide nanosheet, the process is as follows Figure 1 As shown, the specific steps are:

[0038] (1) Take a small vial and weigh the titanium oxide clusters and dissolve them in dichloromethane to obtain a colorless and transparent solution.

[0039] (2) Take another vial and weigh the diblock copolymer PS-b-PAA (either block can be used) and dissolve it in tetrahydrofuran.

[0040] (3) The PS-b-PAA solution was added dropwise to the titanium oxide cluster solution and stirred continuously with a magnetic stirrer for 2 h.

[0041] (4) Add the obtained light blue solution to a condensation column filled with sodium chloride and vacuum filter to remove excess liquid.

[0042] (5) The obtained mixture of sodium chloride and the composite sample was poured into a 150 mm glass Petri dish and evaporated at room temperature for 24 hours. The Petri dish was transferred to an oven and evaporated at 40°C for 24 hours, and then the temperature was set to 80°C for curing for 24 hours.

[0043] (6) It was placed in a tubular furnace under a nitrogen atmosphere and calcined at 350 °C for 3 h at a heating rate of 1 °C / min, and then transferred to a muffle furnace and calcined at 400 °C for 3 h in air at a heating rate of 5 °C / min for subsequent testing.

[0044] (7) After the reaction is completed, washing is performed to obtain cluster-based 2D mesoporous titanium dioxide nanosheets.

[0045] Scanning electron microscopy images show that it is a large-area two-dimensional sheet structure ( Figure 2 ). High-resolution scanning electron microscope images show uniform mesopores inside the two-dimensional flakes ( Figure 3 ). Transmission electron microscopy images show that its mesoporous structure presents a typical hexagonal stacking structure ( Figure 4 ). High-resolution transmission electron microscopy images show that the mesopore diameter corresponding to the molecular weight is 11.7 nanometers ( Figure 5 ). X-ray diffraction patterns show that the cluster-based 2D mesoporous titanium dioxide nanosheets are highly crystalline anatase structures ( Figure 6 ). Raman spectrum images show that 145, 515 and 635 cm -1 The three peaks correspond to B 1g ,E g and A 1g The characteristic peak of rutile phase is E g and A 1g, The peak is extremely low, and is mainly the characteristic peak B corresponding to the anatase phase 1g , further proving that the obtained titanium dioxide is mainly anatase phase ( Figure 7 ). The nitrogen adsorption-desorption curve image shows a typical type IV nitrogen adsorption-desorption isotherm and an H3 hysteresis loop, indicating that the material has a mesoporous structure. In addition, the results of the adsorption curve show that capillary condensation occurs in the relative pressure range of 0.60-0.90 (P / P0), indicating that the two-dimensional mesoporous titanium dioxide monolayer nanosheets have a narrow pore size distribution and a larger mesoporous structure. At the same time, the results of its desorption curve show that capillary evaporation occurs at a relative pressure (P / P0) of around 0.46. In summary, the synthesized two-dimensional mesoporous titanium dioxide monolayer nanosheets have an interconnected pore structure with a large space between the pores. According to BET, the specific surface area of ​​the sample can be obtained to be 135.69m 2 / g, pore volume 0.36cm 3 / g. According to BJH, its pore size is 11.7nm, with a narrow pore size distribution range ( Figure 8 、 Figure 9 ). X-ray diffraction images show that the arrangement of the precursor-titanium oxide clusters is different from that of 2D mesoporous titanium dioxide nanosheets ( Figure 10 The nitrogen adsorption-desorption curve and pore size distribution image of the titanium oxide cluster show that it has a microporous structure ( Figure 10 、 Figure 11 The scanning electron microscopy, transmission electron microscopy and pore size distribution images of the cluster-based 2D mesoporous titanium dioxide nanosheets with pore sizes of 8, 13 and 18 nm prepared by the present invention show that their macrostructure is consistent with the above-mentioned 2D mesoporous titanium dioxide nanosheets, but the pore sizes are different ( Figure 12 、 Figure 13 、 Figure 14 ). Ultra-high photocatalytic carbon dioxide reduction ability. The reduction product is methane, with a yield of up to 495.33 μmol g -1 h -1 , selectivity up to 99.6% ( Figure 15 ).

[0046] Example 2: The photocatalyst prepared above is used for photocatalytic carbon dioxide reduction, and the specific steps are as follows:

[0047] (1) A certain amount of photocatalyst is uniformly dispersed in deionized water by ultrasonic dispersion technology to form a suspension.

[0048] (2) Using vacuum filtration technology, 10 mg of photocatalyst was evenly loaded onto the surface of a microporous filter membrane with a radius of 2.0 cm. The filter membrane loaded with photocatalyst was placed on the tray of the photocatalytic reactor.

[0049] (3) After the reactor is sealed, open the glass valve and evacuate the reactor to completely remove the air inside.

[0050] (4) Introducing high-purity carbon dioxide gas (purity 99.99%),

[0051] (5) This process was repeated three times to ensure the purity of the gas in the reactor. Afterwards, 0.15 mL of deionized water was injected into the reactor and the valve was closed. To maintain the reactor's tightness, the pressure inside the reactor was adjusted to 90 kPa, slightly below atmospheric pressure.

[0052] (6) The entire system is illuminated by a 300W xenon lamp. During the illumination process, the generated gases are collected and analyzed every hour.

[0053] The titanium dioxide nanosheets prepared by the present invention have excellent optical properties and high efficiency in photocatalytic carbon dioxide reduction ( Figure 15 ), which can be used for photocatalytic carbon dioxide reduction reaction.

Claims

1. A method for preparing cluster-based 2D mesoporous titanium dioxide nanosheets, characterized in that: Cluster-based 2D mesoporous titanium dioxide nanosheets were grown using the titanyl cluster-mediated single micelle growth technique, with the diblock copolymer PS-b-PAA as the structure-directing agent, titanyl clusters as the building blocks, and sodium chloride crystals as the substrate. The specific steps are as follows: (1) dissolving the titanium oxide clusters in dichloromethane to obtain a colorless and transparent titanium oxide cluster solution; (2) dissolving the diblock copolymer PS-b-PAA in tetrahydrofuran to obtain a PS-b-PAA solution; (3) adding the PS-b-PAA solution dropwise to the titanium oxide cluster solution and stirring continuously with a magnetic stirrer for 1-5 hours to obtain a mixed solution; (4) adding the obtained mixed solution to a condensation column filled with sodium chloride, vacuum filtering, and sucking out excess liquid to obtain a mixture; (5) Pour the mixture into a glass Petri dish and volatilize at room temperature for 12-24 hours. Transfer the Petri dish to an oven and volatilize at 40-45°C for 12-24 hours. Then set the temperature to 80-100°C and cure for 12-24 hours. (6) Place it in a tube furnace under a nitrogen atmosphere, heat it to 350-450°C at a rate of 1-5°C / min, and calcine it for 2-4 hours; then transfer it to a muffle furnace, heat it to 350-550°C at a rate of 4-5°C / min in air, and calcine it for 1-3 hours for subsequent testing; (7) After the reaction is completed, washing is performed to obtain cluster-based 2D mesoporous titanium dioxide nanosheets.

2. The preparation method according to claim 1, characterized in that In step (1), the concentration of the titanium oxide cluster solution is controlled to be 10-40 mg / mL.

3. The preparation method according to claim 1, characterized in that In step (2), the concentration of the PS-b-PAA solution is controlled to be 10-40 mg / mL.

4. The preparation method according to claim 3, characterized in that In step (2), the molecular weight of PS-b-PAA is controlled, wherein the molecular weight of PS is 12,000-15,000 and the molecular weight of PAA is 1,100-4,800.

5. The preparation method according to claim 3, characterized in that In step (3), the mass ratio of titanium oxide clusters to PS-b-PAA is 1:2-2:

1.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The surface morphology parameters of titanium dioxide nanosheets are as follows: minimum thickness of 2.7 nm, pore size of 8.0 nm to 18.0 nm.

7. A cluster-based 2D mesoporous titanium dioxide nanosheet obtained by the preparation method according to any one of claims 1 to 6.

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