Titanium dioxide film with three-dimensional reticular macroporous structure and preparation method of titanium dioxide film

Abstract

The invention belongs to the technical field of thin film materials, and particularly relates to a titanium dioxide thin film with a three-dimensional reticular macroporous structure and a preparation method of the titanium dioxide thin film. The preparation method comprises the following steps: by adopting a base catalysis sol-gel method, taking water as a solvent, adding an active agent PVP (Polyvinyl Pyrrolidone) into alkaline sol, inducing TiO2 primary particles to form loose clusters by utilizing a synergistic template effect and a phase separation mechanism of the active agent PVP, and constructing a continuous network containing macropores by the clusters in a self-assembly manner during dip-coating; pVP decomposition (residual space is converted into pores) and TiO2 crystallization strengthening are realized through high-temperature annealing, a three-dimensional reticular macroporous structure is finally formed, and PVP plays a key role through a synergistic template effect and a phase separation mechanism. The thin film has high activity, high mass transfer efficiency and strong light capture capability, and the light absorption performance is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of nanomaterials, and particularly relates to a three-dimensional reticular macroporous structure titanium dioxide film and a preparation method thereof. BACKGROUND

[0002] TiO2 material has a wide application in the fields of catalysis, superhydrophilic, gas sensing, etc. due to its strong oxidation ability, good stability and environmental friendliness. The performance of TiO2 depends largely on the specific surface area and microstructure of the material. A high specific surface area provides more active sites, and a suitable pore structure is conducive to the transmission and diffusion of reactants. Therefore, porous TiO2 film has been a research hotspot in the field of nanomaterials.

[0003] At present, the commonly used methods for preparing porous TiO2 film include template method, anodic oxidation method, hydrothermal method, sol-gel method, etc. However, these methods have some limitations: the mainstream hard template method has a complex preparation process and high cost, and the template removal process is easy to cause the collapse of the pore structure; and most of the processes need high-temperature (500-700℃) sintering to realize TiO2 crystallization, and the temperature in some scenes even exceeds 600℃. High temperature not only aggravates the excessive aggregation of particles, but also may block the pores, finally reducing the specific surface area of the material. The anodic oxidation method is limited to titanium metal substrate, and has high cost; the hydrothermal method has high requirements for equipment, and has certain safety risks, and it is challenging to prepare large-area uniformity; the sol-gel method has simple process, low cost and easy operation, and is suitable for large-area and complex-shaped substrates.

[0004] At present, the sol-gel method for preparing porous titanium dioxide film usually adopts adding surfactants or pre-segment copolymer templates such as CTAB, PEG, P123, etc. to obtain a porous structure with a mesopore size (2-50nm). Although this mesoporous film has a high active site, it has a large mass transfer resistance to macromolecules, is easy to block, and has a low mass transfer efficiency. At the same time, due to the mesopore size being much smaller than the light wavelength, the scattering effect is weak, resulting in weak light trapping ability. SUMMARY

[0005] One of the purposes of the present application is to provide a preparation method of a three-dimensional reticular macroporous structure titanium dioxide film, and the obtained three-dimensional macroporous titanium dioxide film has the advantages of high active site, high mass transfer efficiency and strong light trapping ability: small grains provide high active sites, three-dimensional network macropores are conducive to the rapid diffusion of macromolecules, ions and gases without obstacles, and the macroporous structure will cause strong light scattering, which will "trap" light in the film for a longer time, and improve light absorption.

[0006] To achieve the above purpose, the present application adopts the following technical scheme: a preparation method of a three-dimensional reticular macroporous structure titanium dioxide film, comprising the following steps: S1, take 95 parts by mass of basic TiO2sol, add 5 parts by mass of polyvinylpyrrolidone PVP, mix, stir and dissolve to obtain TiO2-PVP composite sol; S2, clean and dry the glass substrate, dip-coat in the above TiO2-PVP composite sol, then dry the coated glass substrate, repeat the process of dip-coating and drying 2-3 times to obtain TiO2-PVP composite film; S3, after annealing the TiO2-PVP composite film at 500℃ for 2 hours and cooling to room temperature, a three-dimensional network macroporous structure titanium dioxide film is prepared.

[0007] Further improvement of the preparation method of the three-dimensional network macroporous structure titanium dioxide film: Preferably, in step S2, the glass substrate is repeatedly scrubbed in the washing liquid, rinsed with tap water, then ultrasonically treated in NaOH solution and deionized water for 10-20 minutes, rinsed with tap water, soaked in deionized water and carefully wiped with a dust-free cloth, and dried to obtain the cleaned and dried glass substrate.

[0008] Preferably, the TiO2-PVP composite sol in step S2 is ultrasonically treated for 5-10 minutes before dip-coating.

[0009] Preferably, the specific process parameters for dip-coating in step S2 are as follows: the lowering speed is 1500-1800 um / s, the immersion time is 10-30 s, the rising speed is 1500-1800 um / s, and the residence time is 90-120 s.

[0010] Preferably, the specific process parameters for dip-coating in step S2 are as follows: the lowering speed is 1670 um / s, the immersion time is 30 s, the rising speed is 1670 um / s, and the residence time is 90 s.

[0011] Preferably, in step S2, the coated glass substrate is placed in an oven at 60-80℃ for 30-40 minutes to dry.

[0012] Preferably, in step S3, the TiO2-PVP composite film is placed in a muffle furnace and heated to 500℃ at a rate of 5-10℃ / min in air atmosphere.

[0013] Preferably, the preparation method of the basic TiO2sol in step S1 is as follows: S11, mix and stir deionized water, tetrabutyl titanate, isopropyl alcohol and diethanolamine according to a volume ratio of 15:5:5:2 to obtain 27 parts by volume of solution A; mix isopropyl alcohol and deionized water according to a volume ratio of 5:50 to obtain 55 parts by volume of solution B; S12. Slowly add solution A to solution B, place in a water bath at 28~30℃ and stir for 4~6 hours at a speed of 750~800 r / min to obtain a transparent and uniform alkaline TiO2 sol.

[0014] Preferably, solution A in step S11 is obtained by stirring at 750-800 rpm for 1 hour at room temperature.

[0015] The second objective of this invention is to provide a titanium dioxide thin film with a three-dimensional network macroporous structure prepared by any of the above-mentioned methods.

[0016] The advantages of this invention compared to the prior art are as follows: (1) This application provides a method for preparing a three-dimensional network macroporous titanium dioxide thin film, the specific process of which is as follows: Alkaline TiO2 sol was prepared using the sol-gel method with tetrabutyl titanate as the titanium source. The alkaline TiO2 sol was mixed and stirred with PVP (polyvinylpyrrolidone) to obtain TiO2-PVP composite sol. After cleaning and drying the glass substrate, a film was deposited in the TiO2-PVP composite sol, dried, and then annealed at 500℃ to obtain a three-dimensional network macroporous titanium dioxide film.

[0017] This invention employs an alkaline-catalyzed sol-gel method, using water as a solvent, to prepare titanium dioxide films with a three-dimensional network macroporous structure by adding the surfactant PVP to an alkaline sol. In the formation of the three-dimensional network macroporous structure, PVP plays a crucial role through a synergistic template effect and a phase separation mechanism: in alkaline Ti... In the sol, PVP induces Ti through molecular bridging. The original particles form loose clusters, which self-assemble during dip coating to build a continuous network with large pores. Annealing at 500℃ decomposes the PVP (residual space is transformed into pores) and reacts with Ti. Crystallization strengthens the structure, ultimately forming a three-dimensional macroporous network. Furthermore, PVP serves as a process adaptant; its thermal decomposition temperature range is 400-500℃, and it can completely decompose under conditions of holding at 500℃ for 2 hours without requiring an increase in annealing temperature. The three-dimensional macroporous titanium dioxide film obtained by this invention possesses the advantages of high active sites, high mass transfer efficiency, and strong light-trapping ability: small grains provide high active sites, the three-dimensional network of macropores facilitates the unimpeded and rapid diffusion of macromolecules, ions, and gases, while the macroporous structure induces strong light scattering, "trapping" light within the film for a longer period, thus enhancing light absorption.

[0018] (2) The preparation process of this invention uses deionized water as the main solvent, and the resulting Ti - PVP composite sol poses no flammability hazard, and its flash point meets standard safety standards for transportation and storage, making it highly convenient to handle. Using inexpensive and environmentally friendly PVP as a template agent, it forms a cross-linked network of oligomers through a unique interaction mechanism between PVP and alkaline colloidal structures. Simultaneously, the presence of PVP lowers the energy barrier for phase separation, providing a strong guarantee for the final formation of a three-dimensional macroporous network structure. Furthermore, PVP can be completely removed in a single calcination step, avoiding complex and time-consuming template removal procedures.

[0019] Through a reasonable design, this invention achieves both effective retention of high porosity and successful avoidance of the technical problems of severe particle agglomeration and pore structure collapse after a heat treatment process at 500℃, ultimately enabling the film to have both good mechanical strength and long-term structural durability.

[0020] The unique three-dimensional network structure of this invention is constructed from 20-100 nm TiO2 nanoparticles, forming macroscopic open channels with pore sizes ranging from hundreds of nanometers to micrometers. This structure not only provides a huge specific surface area and exposes a large number of active sites, but also facilitates the rapid diffusion and transport of reactants and products, significantly improving mass transport efficiency. Simultaneously, the macroporous structure induces strong light scattering, enhancing light-harvesting capabilities. The entire process of this invention requires no complex equipment (such as high-pressure reactors or precision template preparation devices), and can be completed using only a conventional magnetic stirrer, a Czochralski coating machine, and a muffle furnace.

[0021] (3) Compared with existing technologies that use alcohol / alcohol-water mixed solvents, acid catalysis, or base catalysis that only plays a stabilizing role, or a single pore-forming agent (such as P123, PEG) to prepare mesoporous films or powders, this application uses water as the main solvent, diethanolamine as a base catalyst (to promote the chemical bonding of particles), and PVP to construct a three-dimensional network continuous macroporous film of hundreds of nanometers to micrometers through a dual mechanism. It does not require long-term aging and can obtain a structure with high mass transfer and strong light absorption without collapse at 500°C in one step of annealing. This structure has the advantages of high active sites, high mass transfer efficiency and strong light-harvesting ability. The three-dimensional network macroporous titanium dioxide film prepared by this invention combines high specific surface area, open channels and good chemical and mechanical stability, which makes it show great potential in multiple fields such as photocatalysis, gas sensing and photoelectrochemical cells. Attached Figure Description

[0022] Figure 1 These are SEM images of the three-dimensional mesh-like macroporous titanium dioxide thin film prepared in Example 1 of the present invention, wherein (a) is at low magnification and (b) is at high magnification.

[0023] Figure 2 This is a SEM image of the titanium dioxide thin film prepared in the comparative example of this invention.

[0024] Figure 3This is a mechanical stability test of the titanium dioxide thin film prepared in Example 1 of the present invention.

[0025] Figure 4 These are the light absorption performance test curves of the titanium dioxide film with added PVP in Example 1 of the present invention and the titanium dioxide film without added PVP in the comparative example.

[0026] Figure 5 The light absorption performance test curves are those of the titanium dioxide film with added PVP in Example 1 and the titanium dioxide film without added PVP in the comparative example. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] Preparation Example 1 This preparation example provides a method for preparing alkaline TiO2 sol, the specific steps of which are as follows: In a 100ml beaker, add 15ml of deionized water, 5ml of tetrabutyl titanate, 5ml of isopropanol, and 2ml of diethanolamine in sequence. Stir at 800rpm for 1 hour at room temperature. This solution is labeled A. In a 100ml Erlenmeyer flask, add 5ml of isopropanol and 50ml of deionized water. This solution is labeled B.

[0029] Solution A was slowly added dropwise to solution B, and the mixture was placed in a water bath at 29°C and stirred for 4.5 hours at a speed of 800 r / min to obtain a transparent and homogeneous alkaline TiO2 sol.

[0030] Preparation Example 2 This preparation example provides a method for preparing an alkaline TiO2 sol. The specific steps are the same as in Preparation Example 1, except that solution A is slowly added dropwise to solution B, and the mixture is placed in a water bath at 28°C and stirred for 6 hours at a speed of 750 r / min to obtain a transparent and uniform alkaline TiO2 sol.

[0031] Preparation Example 3 This preparation example provides a method for preparing an alkaline TiO2 sol. The specific steps are the same as in Preparation Example 1, except that solution A is slowly added dropwise to solution B, and the mixture is placed in a water bath at 30°C and stirred for 4 hours at a speed of 800 r / min to obtain a transparent and uniform alkaline TiO2 sol.

[0032] Example 1 This embodiment provides a method for preparing a three-dimensional mesh-like macroporous titanium dioxide thin film, specifically including the following steps: S1. Take 95 parts by mass of the alkaline TiO2 sol prepared in Example 1, add 5 parts by mass of polyvinylpyrrolidone (PVP), and stir at 800 rpm at room temperature until dissolved to obtain TiO2-PVP composite sol.

[0033] S2. Place the glass substrate in the washing solution and scrub it repeatedly. After rinsing it with tap water, sonicate it with NaOH solution and deionized water for 15 minutes in sequence. After that, rinse it with tap water, soak it in deionized water, wipe it carefully with a lint-free cloth, and dry it to obtain a clean and dry glass substrate for later use. TiO2-PVP composite sol was placed in a centrifuge tube and sonicated for 10 minutes to prepare a coating solution. Titanium dioxide thin films were prepared using the dip-coating method. The clean glass slides were used for coating, and the parameters were set as follows: descent speed of 1670 μm / s, immersion time of 30 s, ascent speed of 1670 μm / s, and dwell time of 90 s. The coated glass was then placed in a 60°C oven for 30 minutes to allow the solvent to evaporate slowly. The dip-coating-drying process was repeated three times to obtain a smooth, white TiO2-PVP composite thin film.

[0034] S3. The TiO2-PVP composite film was placed in a muffle furnace and heated to 500°C at a rate of 5°C / min in air atmosphere, held for 2 hours, and then cooled to room temperature with the furnace to obtain a three-dimensional network macroporous titanium dioxide film 1.

[0035] Figure 1 These are SEM images of the three-dimensional network macroporous titanium dioxide thin film prepared in Example 1 of this invention, where (a) is at low magnification and (b) is at high magnification. It can be clearly seen that the unique three-dimensional network structure of this invention is constructed from 20-100 nm TiO2 nanoparticles, forming macroscopic open channels with pore sizes ranging from hundreds of nanometers to micrometers, demonstrating that the thin film has a high specific surface area and open channels.

[0036] Example 2 This embodiment provides a method for preparing a three-dimensional network macroporous titanium dioxide thin film. The specific steps are the same as in Example 1, except that in step S1, 95 parts by mass are used to prepare the alkaline TiO2 sol obtained in Example 2.

[0037] Finally, a three-dimensional network macroporous titanium dioxide thin film 2 was prepared.

[0038] Example 3 This embodiment provides a method for preparing a three-dimensional network macroporous titanium dioxide thin film. The specific steps are the same as in Example 1, except that in step S1, 95 parts by mass are used to prepare the alkaline TiO2 sol obtained in Example 3.

[0039] Finally, a three-dimensional network macroporous titanium dioxide thin film was obtained.

[0040] Example 4 This embodiment provides a method for preparing a three-dimensional mesh-like macroporous titanium dioxide thin film. The specific steps are the same as in Embodiment 1, except that the parameters during coating are set as follows: descent speed is 1670 μm / s, immersion time is 30 s, ascent speed is 1670 μm / s, and residence time is 120 s.

[0041] Finally, a three-dimensional network macroporous titanium dioxide thin film was obtained.

[0042] Comparative Example This comparative example provides a method for preparing a titanium dioxide thin film. The specific steps are the same as in Example 1, except that in step S1, 100 parts by mass are taken to prepare the alkaline TiO2 sol obtained in Example 1, and polyvinylpyrrolidone (PVP) is not added.

[0043] Figure 2 This is a SEM image of the titanium dioxide thin film prepared in the comparative example of this invention. (From...) Figure 2 It can be seen that the final titanium dioxide film is dense and has no open pores.

[0044] Performance testing: 1. Mechanical Stability: A substrate with a titanium dioxide film prepared in Example 1 was selected and tightly adhered to the film surface with a transparent tape of moderate adhesion, ensuring complete contact between the tape and the film without any air bubbles. After standing for 1-2 minutes, the tape was pinched at the edge and quickly and steadily torn off, avoiding pulling or shaking the substrate throughout the process. After tearing, the film surface was carefully observed. There were no signs of peeling, flaking, scratches, or color fading. The film maintained its original smooth texture and intact shape, fully demonstrating the strong adhesion between the film and the substrate, as well as the film's mechanical stability (see Appendix). Figure 3 Under the same conditions, the mechanical stability of the titanium dioxide films prepared in Examples 2-4 was tested, and the results showed that they also exhibited mechanical stability.

[0045] 2. Light Harvesting Capacity: The light absorption performance of the titanium dioxide film with added PVP prepared in Example 1 and the comparative titanium dioxide film without added PVP were tested using an ultraviolet spectrophotometer. The test wavelength range was set to 250–1100 nm. The test absorption spectrum curves are shown below. Figure 4As shown in the figure, comparing the absorption spectrum curves of the two films reveals that the intensity of the curve for the titanium dioxide film with added PVP is consistently higher than that for the titanium dioxide film without added PVP. This test result directly proves that the titanium dioxide film with added PVP has a stronger ability to capture incident light in the 250–1100 nm wavelength range. Under the same conditions, the light-capturing ability of the titanium dioxide films prepared in Examples 2-4 was also tested, and the results showed that they also have a strong ability to capture incident light in the 250–1100 nm wavelength range.

[0046] 3. Environmental stability: The light absorption performance of the titanium dioxide film with added PVP prepared in Example 1 and the titanium dioxide film without added PVP prepared in the comparative example were tested after being placed for different periods of time. The test curves are shown in Figure 1. Figure 5 As shown. By Figure 5 The test results show that the absorption spectrum curves of the samples at each time point basically overlap, and there are no significant differences in the absorption intensity and absorption range within the test band, indicating that the titanium dioxide thin film prepared in this application has good stability in light absorption performance. Under the same conditions, environmental stability tests were conducted on the titanium dioxide thin films prepared in Examples 2-4, and the results also showed strong stability.

[0047] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional network macroporous titanium dioxide thin film, characterized in that, Includes the following steps: S1. Take 95 parts by weight of alkaline TiO2 sol, add 5 parts by weight of polyvinylpyrrolidone (PVP), mix and stir to dissolve, and obtain TiO2-PVP composite sol. S2. Clean and dry the glass substrate, then perform a lift-coating process in the above TiO2-PVP composite sol, and then dry the coated glass substrate. Repeat the lift-coating-drying process 2-3 times to obtain the TiO2-PVP composite film. S3. After annealing the TiO2-PVP composite film at 500℃ for 2 hours, the film was cooled to room temperature to obtain a three-dimensional network macroporous titanium dioxide film.

2. The method for preparing a three-dimensional network macroporous titanium dioxide thin film according to claim 1, characterized in that, In step S2, the glass substrate is repeatedly scrubbed in the washing solution, rinsed with tap water, and then ultrasonicated with NaOH solution and deionized water for 10-20 minutes in sequence. After that, it is rinsed with tap water, soaked in deionized water, and carefully wiped and dried with a lint-free cloth to obtain a clean and dried glass substrate for use.

3. The method for preparing a three-dimensional network macroporous titanium dioxide thin film according to claim 1, characterized in that, The TiO2-PVP composite sol in step S2 is ultrasonically treated for 5-10 minutes before dip-coating.

4. The method for preparing a three-dimensional network macroporous titanium dioxide thin film according to claim 1, characterized in that, The specific process parameters for the dip coating in step S2 are as follows: descent speed is 1500-1800 um / s, immersion time is 10~30s, ascent speed is 1500-1800 um / s, and dwell time is 90~120s.

5. The method for preparing a three-dimensional network macroporous titanium dioxide thin film according to claim 1 or 4, characterized in that, The specific process parameters for the dip coating in step S2 are as follows: descent speed is 1670 um / s, immersion time is 30 s, ascent speed is 1670 um / s, and dwell time is 90 s.

6. The method for preparing a three-dimensional network macroporous titanium dioxide thin film according to claim 1, characterized in that, In step S2, the coated glass substrate is dried in an oven at 60-80℃ for 30-40 minutes.

7. The method for preparing a three-dimensional network macroporous titanium dioxide thin film according to claim 1, characterized in that, In step S3, the TiO2-PVP composite film is placed in a muffle furnace and heated to 500°C at a rate of 5-10°C / min under an air atmosphere.

8. The method for preparing a three-dimensional network macroporous titanium dioxide thin film according to claim 1, characterized in that, The preparation method of alkaline TiO2 sol in step S1 is as follows: S11. Mix deionized water, tetrabutyl titanate, isopropanol and diethanolamine in a volume ratio of 15:5:5:2 and stir to obtain 27 volume parts of solution A; mix isopropanol and deionized water in a volume ratio of 5:50 to obtain 55 volume parts of solution B. S12. Slowly add solution A to solution B, place in a water bath at 28~30℃ and stir for 4~6 hours at a speed of 750~800 r / min to obtain a transparent and uniform alkaline TiO2 sol.

9. The method for preparing a three-dimensional network macroporous titanium dioxide thin film according to claim 8, characterized in that, Solution A was obtained by stirring at 750-800 rpm for 1 hour at room temperature.

10. A titanium dioxide thin film with a three-dimensional network macroporous structure prepared by a method for preparing a titanium dioxide thin film with a three-dimensional network macroporous structure according to any one of claims 1-9.

Images