Method for improving content of surface hydroxyl group of nano-titanium dioxide material and application thereof
By preparing nano-titanium dioxide materials with rich surface hydroxyl structures, the problem of balancing high crystallinity and high hydroxyl content was solved, and the photocatalytic performance of the material was significantly improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHAN UNIV OF TECH
- Filing Date
- 2026-02-11
- Publication Date
- 2026-06-02
AI Technical Summary
Existing technologies struggle to significantly increase the surface hydroxyl content of titanium dioxide while maintaining its high crystallinity, and traditional methods are complex and costly.
Amorphous titanium dioxide precursors were prepared using a titanium source and an ammonia solution with a specific pH value. These precursors were then subjected to hydrothermal treatment with ionic liquid and acetic acid, followed by high-temperature calcination to form nano-titanium dioxide materials with a surface hydroxyl-rich structure.
While maintaining high crystallinity, the surface hydroxyl content of nano-titanium dioxide materials was significantly increased, enhancing photocatalytic activity, especially showing a significant activity improvement in the photocatalytic hydrogen production reaction of seawater.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of nano-titanium dioxide material preparation and surface modification, specifically relating to a method and application for increasing the hydroxyl content on the surface of nano-titanium dioxide materials. Background Technology
[0002] Titanium dioxide materials have wide applications in energy, environmental, and chemical catalysis fields due to their advantages such as low cost, ease of large-scale preparation, and high chemical and thermal stability. Highly crystalline titanium dioxide materials typically possess a more ordered crystal structure and fewer bulk defects, which helps suppress bulk recombination of photogenerated carriers, thus exhibiting higher reactivity and stability in catalytic reactions. Therefore, a large amount of research has focused on the design and synthesis of highly crystalline titanium dioxide materials.
[0003] Surface hydroxyl groups, as key hydrophilic groups in titanium dioxide, can significantly improve the wettability of titanium dioxide materials and also serve as trapping sites for photogenerated holes, promoting the effective separation of photogenerated carriers. They also play a crucial role in catalysis. Therefore, constructing titanium dioxide materials with both high crystallinity and a hydroxyl-rich structure is an effective way to improve titanium dioxide performance. However, highly crystalline titanium dioxide usually requires high-temperature calcination, while the thermal stability of surface hydroxyl groups is poor, and their content decreases significantly during high-temperature calcination (>400 °C), making it difficult to achieve both high crystallinity and a hydroxyl-rich structure in titanium dioxide materials. Although post-treatment of highly crystalline titanium dioxide materials with alkaline solutions or polyhydroxyl organic compounds can introduce surface hydroxyl groups, these methods are often complex and costly. Therefore, developing a controllable synthesis strategy for titanium dioxide with both high crystallinity and a hydroxyl-rich structure is of great significance for promoting the design and practical application of high-performance titanium dioxide materials. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a method for controlling the hydroxyl content on the surface of nano-titanium dioxide materials in order to overcome the shortcomings of the prior art, thereby significantly increasing the hydroxyl content on the surface of titanium dioxide while maintaining its high crystallinity.
[0005] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows: A method for increasing the hydroxyl content on the surface of nano-titanium dioxide materials includes the following steps: 1) Add the titanium source to an ammonia solution and stir at room temperature to obtain a solid precipitate. After washing and drying, an amorphous titanium dioxide precursor is obtained. 2) The amorphous titanium dioxide precursor is mixed evenly with acetic acid, water and ionic liquid, and a hydrothermal reaction is carried out in a reactor to achieve the combination of amorphous titanium dioxide precursor and ionic liquid. After washing and drying, the reaction product is used to obtain fluorine-containing titanium dioxide powder. 3) The fluorine-containing titanium dioxide powder is calcined at high temperature to obtain nano-titanium dioxide material with a rich surface hydroxyl structure, thereby improving the surface hydroxyl content of the nano-titanium dioxide material.
[0006] According to the above scheme, in step 1), the titanium source is an organic titanium source.
[0007] Furthermore, the titanium source is preferably a titanate ester. In some specific embodiments, the titanate ester may be one or more of tetrabutyl titanate, isopropyl titanate, etc.
[0008] According to the above scheme, in step 1), the pH of the ammonia solution is 10-12, and the volume percentage of the titanium source in the ammonia solution is 2%-5%.
[0009] According to the above scheme, in step 1), the reaction is stirred at room temperature for 10-20 min, and then centrifuged to obtain a solid precipitate.
[0010] According to the above scheme, the ionic liquid is an imidazole-based fluorine-containing ionic liquid.
[0011] Furthermore, in some specific embodiments, the imidazole-based fluorinated ionic liquid may specifically be one or more of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-octyl-3-methylimidazolium tetrafluoroborate, tri-n-butylphosphine fluoroborate, etc.
[0012] According to the above scheme, in step 2), the mass ratio of acetic acid, water, ionic liquid, and amorphous titanium dioxide precursor is 1:(0.5-2):(0.02-0.08):(0.01-0.03). Further, glacial acetic acid is specifically used.
[0013] According to the above scheme, in step 2), the temperature of the hydrothermal reaction is 160-200 °C and the time is 18-36 h.
[0014] Furthermore, in some specific embodiments, the temperature of the hydrothermal reaction is preferably in the range of 170 to 190 ℃, and specific temperature values such as 170 ℃, 175 ℃, 180 ℃, 185 ℃, and 190 ℃ can be used.
[0015] Furthermore, in some specific embodiments, the hydrothermal reaction is preferably carried out for 20 to 30 hours, and specific reaction times such as 20 hours, 22 hours, 24 hours, 26 hours, and 28 hours can be used.
[0016] According to the above scheme, in step 3), the high-temperature calcination temperature is 300-650 ℃ and the time is 3-8 h.
[0017] Furthermore, in some specific embodiments, the calcination temperature is preferably in the range of 500 to 650 ℃, and specific temperature values such as 500 ℃, 550 ℃, 600 ℃, and 650 ℃ can be used.
[0018] Furthermore, in some specific embodiments, the calcination time is preferably in the range of 3 to 5 hours, and specific calcination times such as 3 hours, 4 hours, and 5 hours can be used.
[0019] The nano-titanium dioxide material with a surface hydroxyl-rich structure prepared by the above method has anatase crystal phase and a surface hydroxyl concentration greater than 10 mmol / g.
[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: This invention uses titanium source and ammonia solution with a specific pH value as raw materials. First, an amorphous titanium dioxide precursor is prepared via hydrolysis. This precursor has small particle size and an amorphous structure, facilitating effective bonding with ionic liquids. Then, the amorphous precursor, ionic liquid, and acetic acid are mixed in a solvent of water and subjected to hydrothermal treatment, allowing the ionic liquid to stably bind to the precursor surface. Finally, high-temperature calcination removes the ionic liquid, simultaneously inducing the formation of surface-rich hydroxyl structures. This invention uses amorphous titanium dioxide as a precursor, achieving surface-confined bonding with ionic liquids under hydrothermal conditions, replacing the traditional approach of directly using organic titanium sources. This improves product purity and ionic liquid utilization. The weakly acidic hydrothermal reaction environment provided by acetic acid regulates the surface charge of titanium dioxide, inhibiting excessive crystallization during the hydrothermal stage and promoting uniform and stable loading of the ionic liquid on the surface, thus controlling the hydroxyl content. Finally, high-temperature calcination removes fluorine bound to the titanium dioxide surface, significantly enhancing crystallinity and exposing active sites, thereby inducing the formation of surface-rich hydroxyl structures. Attached Figure Description
[0021] Figure 1 The images show the powder XRD patterns of the surface-rich hydroxyl nano-titanium dioxide materials prepared in the three embodiments of the present invention and the ordinary titanium dioxide materials prepared in the three comparative examples.
[0022] Figure 2 SEM images of the surface-rich hydroxyl nano-titanium dioxide materials prepared in the three embodiments of the present invention and the ordinary titanium dioxide materials prepared in the three comparative examples.
[0023] Figure 3Fourier transform infrared spectra of the surface-rich hydroxyl nano-titanium dioxide materials prepared in the three embodiments of the present invention and the ordinary titanium dioxide materials prepared in the three comparative examples.
[0024] Figure 4 The graph shows the surface hydroxyl content of the nano-titanium dioxide materials rich in surface hydroxyl content prepared in the three embodiments of the present invention and the ordinary titanium dioxide materials prepared in the three comparative examples.
[0025] Figure 5 The images show the surface-rich hydroxyl nano-titanium dioxide material prepared in Example 1 of this invention and the photocatalytic hydrogen production performance curves of Comparative Example 1. Detailed Implementation
[0026] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the present invention is not limited to the following embodiments.
[0027] Example 1 A method for increasing the hydroxyl content on the surface of nano-titanium dioxide materials, comprising the following specific steps: 1) Add 3 mL of commercially available ammonia water (concentration of 25%-28%) to 100 mL of water, stir well to prepare an ammonia solution with a pH of about 11, add 3 mL of tetrabutyl titanate, stir at room temperature for 10 min, centrifuge to obtain a solid precipitate; wash the obtained solid precipitate with water and ethanol and dry it to obtain an amorphous titanium dioxide precursor; wherein, the mass ratio of ammonia solution to tetrabutyl titanate is 1:0.03.
[0028] 2) Mix 25 mL of glacial acetic acid, 25 mL of water, and 1 mL of 1-butyl-3-methylimidazolium tetrafluoroborate evenly. Add 0.5 g of amorphous titanium dioxide precursor and disperse evenly. Transfer the mixture to a PTFE-lined tempered reactor and hydrothermally react at 180 ℃ for 24 h. The reaction product, after washing and drying, is the fluorinated titanium dioxide material. The mass ratio of glacial acetic acid, water, 1-butyl-3-methylimidazolium tetrafluoroborate, and amorphous titanium dioxide precursor is 1:1:0.04:0.02.
[0029] 3) After washing and drying the above-mentioned fluorine-containing titanium dioxide material with water and ethanol, it was calcined at 600 °C for 4 h to obtain nano-titanium dioxide material with a surface-rich hydroxyl structure.
[0030] Example 2 A method for increasing the hydroxyl content on the surface of nano-titanium dioxide materials, comprising the following specific steps: 1) Add 3 mL of commercially available ammonia water (concentration of 25%-28%) to 100 mL of water, stir well to prepare an ammonia solution with a pH of about 11, add 3 mL of tetrabutyl titanate, stir at room temperature for 10 min, centrifuge to obtain a solid precipitate; wash the obtained solid precipitate with water and ethanol and dry it to obtain an amorphous titanium dioxide precursor; wherein, the mass ratio of ammonia solution to tetrabutyl titanate is 1:0.03.
[0031] 2) Mix 25 mL of glacial acetic acid, 25 mL of water, and 0.5 mL of 1-butyl-3-methylimidazolium tetrafluoroborate evenly. Add 0.5 g of amorphous titanium dioxide precursor and disperse evenly. Transfer the mixture to a PTFE-lined tempered reactor and hydrothermally react at 180 ℃ for 24 h. The reaction product, after washing and drying, is the fluorinated titanium dioxide material. The mass ratio of glacial acetic acid, water, 1-butyl-3-methylimidazolium tetrafluoroborate, and amorphous titanium dioxide precursor is 1:1:0.02:0.02.
[0032] 3) After washing and drying the above-mentioned fluorine-containing titanium dioxide material with water and ethanol, it was calcined at 600 °C for 4 h to obtain nano-titanium dioxide material with a surface-rich hydroxyl structure.
[0033] Example 3 A method for increasing the hydroxyl content on the surface of nano-titanium dioxide materials, comprising the following specific steps: 1) Add 3 mL of commercially available ammonia water (concentration of 25%-28%) to 100 mL of water, stir well to prepare an ammonia solution with a pH of about 11, add 3 mL of tetrabutyl titanate, stir at room temperature for 10 min, centrifuge to obtain a solid precipitate; wash the obtained solid precipitate with water and ethanol and dry it to obtain an amorphous titanium dioxide precursor; wherein, the mass ratio of ammonia solution to tetrabutyl titanate is 1:0.03.
[0034] 2) Mix 25 mL of glacial acetic acid, 25 mL of water, and 2 mL of 1-butyl-3-methylimidazolium tetrafluoroborate evenly. Add 0.5 g of amorphous titanium dioxide precursor and disperse evenly. Transfer the mixture to a PTFE-lined tempered reactor and react hydrothermally at 180 ℃ for 24 h. The reaction product, after washing and drying, is the fluorinated titanium dioxide material. The mass ratio of glacial acetic acid, water, 1-butyl-3-methylimidazolium tetrafluoroborate, and amorphous titanium dioxide precursor is 1:1:0.08:0.02.
[0035] 3) After washing and drying the above-mentioned fluorine-containing titanium dioxide material with water and ethanol, it was calcined at 600 °C for 4 h to obtain nano-titanium dioxide material with a surface-rich hydroxyl structure.
[0036] Comparative Example 1 1) Add 3 mL of commercially available ammonia water (concentration of 25%-28%) to 100 mL of water, stir well to prepare an ammonia solution with a pH of about 11, add 3 mL of tetrabutyl titanate, stir at room temperature for 10 min, centrifuge to obtain a solid precipitate; wash the obtained solid precipitate with water and ethanol and dry it to obtain an amorphous titanium dioxide precursor; wherein, the mass ratio of ammonia solution to tetrabutyl titanate is 1:0.03.
[0037] 2) Disperse 0.5 g of amorphous titanium dioxide precursor in a mixture of 25 mL glacial acetic acid and 25 mL water, and transfer it to a PTFE-lined tempered reactor for hydrothermal treatment at 180 °C for 24 h.
[0038] 3) After washing and drying the hydrothermal reaction product, it was calcined at 600 ℃ for 4 h to obtain a highly crystalline ordinary titanium dioxide material.
[0039] Comparative Example 2 1 mL of tetrabutyl titanate, 25 mL of glacial acetic acid, 25 mL of water, and 1 mL of 1-butyl-3-methylimidazolium tetrafluoroborate were mixed thoroughly and transferred to a PTFE-lined tempered reactor for hydrothermal reaction at 180 °C for 24 h. The hydrothermal reaction product was washed, dried, and then calcined at 600 °C for 4 h to obtain the product of Comparative Example 2.
[0040] Comparative Example 3 1) Add 3 mL of commercially available ammonia water (concentration of 25%-28%) to 100 mL of water, stir well to prepare an ammonia solution with a pH of about 11, add 3 mL of tetrabutyl titanate, stir at room temperature for 10 min, centrifuge to obtain a solid precipitate; wash the obtained solid precipitate with water and ethanol and dry it to obtain an amorphous titanium dioxide precursor; wherein, the mass ratio of ammonia solution to tetrabutyl titanate is 1:0.03.
[0041] 2) Disperse 0.5 g of amorphous titanium dioxide precursor evenly in 50 mL of water, add 1 mL of 1-butyl-3-methylimidazolium tetrafluoroborate, transfer to a PTFE-lined tempered reactor, and hydrothermally react at 180 ℃ for 24 h. The reaction product, after washing and drying, is the titanium dioxide material. The mass ratio of water, 1-butyl-3-methylimidazolium tetrafluoroborate, and amorphous titanium dioxide precursor is 1:0.02:0.01.
[0042] 3) The above titanium dioxide material was washed with water and ethanol and dried, and then calcined at 600 °C for 4 h to obtain the product of Comparative Example 3.
[0043] like Figure 1As shown, the surface-rich hydroxyl-structured nano-titanium dioxide materials prepared in Examples 1-3 and the titanium dioxide materials prepared in Comparative Examples 1-3 are both anatase phases, and have high diffraction peak intensities and good crystallinity.
[0044] like Figure 2 As shown, the particle size of the surface-rich hydroxyl-structured nano-titanium dioxide materials prepared in Examples 1-3 is approximately 20-40 nm. The particle size of the nano-titanium dioxide materials prepared in Comparative Examples 1 and 3 is slightly larger than that in the examples, and there is more agglomeration and adhesion. The particle size of the nano-titanium dioxide material prepared in Comparative Example 2 is approximately 100 nm.
[0045] like Figure 3 As shown, the surface-rich hydroxyl-structured nano-titanium dioxide materials prepared in Examples 1-3 were subjected to a temperature of 3400 cm⁻¹. - ¹ and 1630 cm - The peaks at position ¹ show obvious characteristic peaks of hydroxyl stretching and bending vibrations, and the peak intensity is significantly higher than that of the titanium dioxide materials prepared in comparative examples 1-3, indicating that the hydroxyl content on the material surface is significantly increased.
[0046] The surface hydroxyl content of the nano-titanium dioxide materials prepared in the examples and comparative examples was determined using the fluoride ion substitution method. Specifically, 80 mg of nano-titanium dioxide material was dispersed in 20 mL of 0.1 mol / L sodium fluoride solution, the pH was adjusted to 3 with nitric acid, and the mixture was stirred for 18 h to allow fluoride ions to substitute for the surface hydroxyl groups. The sample was then washed with a nitric acid solution at pH 3 to prevent fluoride loss, yielding a fluorinated sample. 60 mg of the fluorinated sample was dispersed in 10 mL of 1 mol / L sodium hydroxide solution to redissolve the surface-bound fluoride. After filtration, 5 mL of the filtrate was diluted to 25 mL, and the fluoride content was determined by ion chromatography. The surface hydroxyl content was then calculated based on this determination. Figure 4 As shown.
[0047] Depend on Figure 4 It can be seen that the hydroxyl content of the nano-titanium dioxide materials prepared in Examples 1-3 is about 2-4 times that of Comparative Examples 1-3, indicating that ionic liquid and glacial acetic acid play an important role in significantly increasing the hydroxyl content of the materials.
[0048] Application examples The photocatalytic hydrogen production rate of the nano-titanium dioxide materials prepared in Example 1 and Comparative Example 1 was tested using the Pofil 6A hydrogen production system. The specific procedure is as follows: 80 mL of a reaction solution with a seawater-methanol volume ratio of 1:1 was prepared using methanol as a sacrificial agent. The pH was measured to be approximately 8. Then, 20 mg of nano-titanium dioxide and 0.4 mg of chloroplatinic acid were added. Using a xenon lamp as the light source, the photocatalytic hydrogen production rate of the samples was calculated by recording the hydrogen production at different times. Figure 5 As shown.
[0049] Depend on Figure 5 It can be seen that the photocatalytic hydrogen production rate of seawater by the nano-titanium dioxide material with rich surface hydroxyl structure prepared in Example 1 is about 4 times that of Comparative Example 1, indicating that the rich surface hydroxyl structure can significantly enhance the photocatalytic hydrogen production activity of seawater per unit mass of titanium dioxide.
[0050] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.
Claims
1. A method for increasing the hydroxyl content on the surface of nano-titanium dioxide materials, characterized in that, Includes the following steps: 1) Add the titanium source to ammonia water and stir at room temperature to obtain a solid precipitate. After washing and drying, an amorphous titanium dioxide precursor is obtained. 2) The amorphous titanium dioxide precursor is mixed evenly with acetic acid, water and ionic liquid, and a hydrothermal reaction is carried out in a reactor to achieve the combination of amorphous titanium dioxide precursor and ionic liquid. The hydrothermal reaction product is washed and dried to obtain fluorine-containing titanium dioxide powder. 3) The fluorine-containing titanium dioxide powder is calcined at high temperature to obtain nano-titanium dioxide material with a rich surface hydroxyl structure, thereby improving the surface hydroxyl content of the nano-titanium dioxide material.
2. The method for increasing the hydroxyl content on the surface of nano-titanium dioxide materials according to claim 1, characterized in that, In step 1), the pH of the ammonia solution is 10-12, and the volume percentage of the titanium source in the ammonia solution is 2%-5%.
3. The method for increasing the hydroxyl content on the surface of nano-titanium dioxide materials according to claim 1, characterized in that, The titanium source is an organic titanium source titanate; the ionic liquid is an imidazole-based fluorine-containing ionic liquid.
4. The method for increasing the hydroxyl content on the surface of nano-titanium dioxide materials according to claim 3, characterized in that, Titanate esters are one or both of tetrabutyl titanate and isopropyl titanate; imidazole-based fluorinated ionic liquids include one or more of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-octyl-3-methylimidazolium tetrafluoroborate, and tri-n-butylphosphine fluoroborate.
5. The method for increasing the hydroxyl content on the surface of nano-titanium dioxide materials according to claim 1, characterized in that, In step 2), the mass ratio of acetic acid, water, ionic liquid and amorphous titanium dioxide precursor is 1:(0.5-2):(0.02-0.08):(0.01-0.03).
6. The method for increasing the hydroxyl content on the surface of nano-titanium dioxide materials according to claim 1, characterized in that, In step 2), the hydrothermal reaction temperature is 160–200 °C and the time is 18–36 h; in step 3), the high-temperature calcination temperature is 300–650 °C and the time is 3–8 h.
7. The method for increasing the hydroxyl content on the surface of nano-titanium dioxide materials according to claim 6, characterized in that, The hydrothermal reaction temperature ranges from 170 to 190 °C, and the time ranges from 20 to 30 h.
8. The method for increasing the hydroxyl content on the surface of nano-titanium dioxide materials according to claim 6, characterized in that, The calcination temperature is in the range of 500 to 650 ℃, and the calcination time is in the range of 3 to 5 h.
9. The surface-rich hydroxyl-structured nano-titanium dioxide material prepared by any one of claims 1 to 8, characterized in that, The crystal phase is anatase, and the surface hydroxyl content is greater than 10 mmol / g.
10. The application of the surface-rich hydroxyl-structured nano-titanium dioxide material of claim 9 in photocatalytic hydrogen production from seawater.