Titanium dioxide photocatalytic material as well as preparation method and application thereof

Abstract

The invention discloses a titanium dioxide photocatalytic material as well as a preparation method and application thereof, and belongs to the technical field of nitrogen reduction photocatalytic materials. The preparation method specifically comprises the following steps: (1) mixing ethanol and glycerol, and uniformly stirring to obtain a mixed solvent; (2) adding tetrabutyl titanate into the mixed solvent, and stirring until the tetrabutyl titanate is completely dissolved to obtain a mixed solution; and (3) carrying out hydrothermal reaction on the mixed solution, cooling, cleaning, drying and roasting to obtain the catalyst. The titanium dioxide photocatalytic material capable of absorbing visible light shows excellent photocatalytic activity and photocatalytic cycle stability on nitrogen, and can be applied to photocatalytic nitrogen reduction.

Description

Technical Field

[0001] The present invention relates to the technical field of nitrogen reduction photocatalytic materials, and more particularly to a titanium dioxide photocatalytic material and a preparation method and application thereof. Background Art

[0002] As one of the essential elements for amino acids and nucleotides (DNA / RNA) in organisms, nitrogen plays a vital role in biological processes. However, the traditional Haber-Bosch process has long been the main method for ammonia synthesis, but it consumes more than 1% of the world's energy and releases more than 300 million tons of carbon dioxide each year. Therefore, it is very important to develop photocatalytic nitrogen fixation catalysts with abundant nitrogen active sites, high stability, and broad visible light response characteristics.

[0003] TiO2 is a typical semiconductor with a suitable conduction band (CB) to drive the reduction of N2 to NH3. However, most photocatalysts used to fix N2 have the following disadvantages: (1) high adsorption energy of N2 on the catalyst surface; (2) poor activity under visible light; and (3) insufficient charge carriers on the catalyst surface, resulting in rapid recombination. Current research is mainly limited to anion vacancies, and there is little research on the relationship between cation vacancies and NRR photocatalytic activity and structure. The main reason is that the formation energy of cation vacancies in transition metal oxides is high. Due to the presence of positively charged cation vacancies, nitrogen molecules can be activated for nitrogen fixation.

[0004] Therefore, transition metal oxides containing such cation vacancies may become a potentially viable and efficient photocatalytic nitrogen fixation catalyst. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a titanium dioxide photocatalytic material and a preparation method and application thereof, so as to solve the deficiencies in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a titanium dioxide photocatalytic material comprises the following steps:

[0008] (1) mixing ethanol and glycerol, stirring and mixing to obtain a mixed solvent;

[0009] (2) adding tetrabutyl titanate to a mixed solvent and stirring until completely dissolved to obtain a mixed solution;

[0010] (3) subjecting the mixed solution to a hydrothermal reaction, cooling, washing, drying, and calcining to obtain a titanium dioxide photocatalytic material.

[0011] The preparation principle of the titanium dioxide photocatalytic material of the present invention is as follows: tetrabutyl titanate is subjected to solvent thermal treatment in the presence of glycerol to generate titanium glycerate crystals, in which the glycerol groups block each Ti-O-Ti skeleton layer (assembled TiO4 tetrahedral polymer); at the same time, the remaining Ti-O-Ti layers are interconnected along the c-axis to form a TiO2 phase; the removal of the interlayer organic groups leads to an O-rich structure, which, when recrystallized into TiO2, produces distortion and defects (Ti vacancies and enlarged c-axis).

[0012] Furthermore, in the above step (1), the volume ratio of ethanol to glycerol is (1-3):1.

[0013] A further beneficial effect of the above method is that if the volume of ethanol added is too large, it will result in the inability to form a photocatalytic material rich in titanium vacancies that absorbs visible light.

[0014] Furthermore, in the above step (1), the stirring time is 0.5-1 h, preferably 0.5 h.

[0015] Furthermore, in the above step (2), the usage ratio of tetrabutyl titanate and the mixed solvent is 1 g:30 mL.

[0016] Furthermore, in the above step (2), the stirring time is 0.5-2h, preferably 0.5h.

[0017] Furthermore, in the above step (3), the hydrothermal reaction equipment is a closed polytetrafluoroethylene-lined hydrothermal kettle with a volume of 50-150 mL, preferably 80-150 mL, and more preferably 80-100 mL; the hydrothermal reaction temperature is 180° C. and the time is 24 h.

[0018] Furthermore, in the above step (3), the cleaning reagents are anhydrous ethanol and deionized water, and the number of times is 3-7 times, preferably 3-5 times, and more preferably 5 times.

[0019] Furthermore, in the above step (3), the drying equipment is a vacuum drying oven, and the temperature is 60-100°C, preferably 60-80°C, and more preferably 60°C.

[0020] Furthermore, in the above step (3), the calcination temperature is 400-500°C, preferably 470°C; the heating rate is 3-5°C / min, preferably 5°C / min; and the holding time is 1-2h, preferably 1h.

[0021] The present invention also claims protection for a titanium dioxide photocatalytic material prepared by the above preparation method.

[0022] The present invention also seeks to protect the use of the titanium dioxide photocatalytic material prepared by the above preparation method in photocatalytic nitrogen reduction.

[0023] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The present invention's visible light-absorbing titanium dioxide photocatalytic material is prepared by a hydrothermal method involving heat treatment. The enhanced photocatalytic performance and effective carrier separation are primarily due to the presence of titanium vacancies and their absorption of visible light. The presence of cation vacancies activates localized charge defects in nitrogen, effectively trapping electrons and enhancing carrier separation and transport. Furthermore, cation vacancies can alter the structural characteristics of semiconductors, providing a viable strategy for improving the efficiency of photocatalytic nitrogen fixation processes and presenting new opportunities and challenges for the design and preparation of titanium dioxide-based materials.

[0025] 2. The titanium dioxide photocatalytic material that absorbs visible light of the present invention exhibits excellent photocatalytic activity and photocatalytic cycle stability towards nitrogen and can be applied to photocatalytic nitrogen reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The XRD patterns of the titanium dioxide photocatalytic materials of Example 2 and Comparative Example 1 are shown;

[0027] Figure 2 The UV-visible absorption spectra of the titanium dioxide photocatalytic materials of Examples 1-3 and Comparative Example 1;

[0028] Figure 3 This is a comparison chart of the photocatalytic nitrogen reduction performance of the titanium dioxide photocatalytic material of Examples 1-3 and Comparative Example 1;

[0029] Figure 4 The cyclic stability of the photocatalytic nitrogen reduction of the titanium dioxide photocatalytic material in Example 2;

[0030] Figure 5 This is the EPR spectrum of the titanium dioxide photocatalytic material before and after the photocatalytic reaction of Example 2. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] Unless otherwise specified, the experimental methods used in the examples of the present invention are all conventional methods.

[0033] Unless otherwise specified, the materials, reagents, etc. used in the examples of the present invention can be obtained from commercial sources.

[0034] Example 1

[0035] The preparation method of titanium dioxide photocatalytic material specifically comprises the following steps:

[0036] (1) Mix 30 mL of ethanol and 30 mL of glycerol and stir for 0.5 h to obtain a mixed solvent;

[0037] (2) Add 2 g of tetrabutyl titanate to the mixed solvent and stir for 0.5 h until completely dissolved to obtain a mixed solution;

[0038] (3) The mixed solution was transferred to a sealed 80 mL polytetrafluoroethylene-lined hydrothermal reactor and subjected to hydrothermal reaction at 180 °C for 24 h. After the reaction was completed, it was naturally cooled to room temperature, washed with anhydrous ethanol and deionized water 5 times, and then dried in a vacuum drying oven at 60 °C overnight. The obtained titanium dioxide precursor was calcined at 470 °C at a heating rate of 5 °C / min in an oxygen-argon mixed atmosphere (O2:Ar=30:70) for 1 h to obtain a titanium dioxide photocatalytic material (p-TiO2(I)) that absorbs visible light.

[0039] Example 2

[0040] The preparation method of titanium dioxide photocatalytic material specifically comprises the following steps:

[0041] (1) Mix 40 mL of ethanol and 20 mL of glycerol and stir for 0.5 h to obtain a mixed solvent;

[0042] (2) Add 2 g of tetrabutyl titanate to the mixed solvent and stir for 0.5 h until completely dissolved to obtain a mixed solution;

[0043] (3) The mixed solution was transferred to a sealed 80 mL polytetrafluoroethylene-lined hydrothermal reactor and subjected to hydrothermal reaction at 180 °C for 24 h. After the reaction was completed, it was naturally cooled to room temperature, washed with anhydrous ethanol and deionized water 5 times, and then dried in a vacuum drying oven at 60 °C overnight. The obtained titanium dioxide precursor was calcined at 470 °C at a heating rate of 5 °C / min in an oxygen-argon mixed atmosphere (O2:Ar=30:70) for 1 h to obtain a titanium dioxide photocatalytic material (p-TiO2(Ⅱ)) that absorbs visible light.

[0044] Example 3

[0045] The preparation method of titanium dioxide photocatalytic material specifically comprises the following steps:

[0046] (1) Mix 45 mL of ethanol and 15 mL of glycerol and stir for 0.5 h to obtain a mixed solvent;

[0047] (2) Add 2 g of tetrabutyl titanate to the mixed solvent and stir for 0.5 h until completely dissolved to obtain a mixed solution;

[0048] (3) The mixed solution was transferred to a sealed 80 mL polytetrafluoroethylene-lined hydrothermal reactor and subjected to hydrothermal reaction at 180 °C for 24 h. After the reaction was completed, it was naturally cooled to room temperature, washed with anhydrous ethanol and deionized water 5 times, and then dried in a vacuum drying oven at 60 °C overnight. The obtained titanium dioxide precursor was calcined at 470 °C at a heating rate of 5 °C / min in an oxygen-argon mixed atmosphere (O2:Ar=30:70) for 1 h to obtain a titanium dioxide photocatalytic material (p-TiO2(Ⅲ)) that absorbs visible light.

[0049] Comparative Example 1

[0050] The preparation method of titanium dioxide photocatalytic material specifically comprises the following steps:

[0051] (1) Add 2 g of tetrabutyl titanate to 60 mL of ethanol solvent and stir for 0.5 h until completely dissolved to obtain a mixed solution;

[0052] (2) The mixed solution was transferred to a sealed 80 mL polytetrafluoroethylene-lined hydrothermal reactor and subjected to hydrothermal reaction at 180 °C for 24 h. After the reaction was completed, it was naturally cooled to room temperature, washed with anhydrous ethanol and deionized water 5 times, and then dried in a vacuum drying oven at 60 °C overnight. The obtained titanium dioxide precursor was calcined at 470 °C at a heating rate of 5 °C / min in an oxygen-argon mixed atmosphere (O2:Ar=30:70) for 1 h to obtain a titanium dioxide photocatalytic material (n-TiO2) that absorbs visible light.

[0053] Performance Testing

[0054] 1. Figure 1 2 are X-ray diffraction (XRD) patterns of the titanium dioxide photocatalytic materials of Example 2 and Comparative Example 1.

[0055] Depend on Figure 1 It can be seen that after the TiO2 precursor was calcined at 470℃ for 1h, its diffraction pattern showed characteristic diffraction peaks at 25.2°, 37.8°, 48°, 55° and 62.6°, corresponding to the (101), (004), (200), (211) and (204) crystal planes of anatase TiO2, respectively (JCPDS No. 21-1272). It is worth noting that the finally prepared p-TiO2(Ⅱ) and n-TiO2 samples both maintained a pure anatase phase structure, and their diffraction peak positions were completely consistent with the standard card, and no other crystal phases or impurity peaks were detected.

[0056] 2. Figure 2 It is the ultraviolet-visible absorption spectrum of the titanium dioxide photocatalytic material of Examples 1-3 and Comparative Example 1.

[0057] Depend on Figure 2It can be seen that pure TiO2 photocatalytic materials only respond to ultraviolet light, which is consistent with the test results of n-TiO2 photocatalytic materials. The p-TiO2 photocatalytic material synthesized by the present invention contains abundant Ti vacancies, which makes it responsive to visible light. This is because defect energy levels can store jumping electrons and increase the absorption of visible light. Macroscopic images support this view. In contrast, the visible light response of p-TiO2(I) photocatalytic material is weaker because its vacancy concentration is higher. This is mainly because too many vacancies will become recombination centers for electrons and holes, resulting in a decrease in stored electrons, thereby reducing the response to visible light.

[0058] 3. Figure 3 This is a comparison chart of the photocatalytic nitrogen reduction performance of the titanium dioxide photocatalytic material of Examples 1-3 and Comparative Example 1.

[0059] Depend on Figure 3 It can be seen that there is a significant correlation between the photocatalytic performance and the vacancy concentration, which shows a trend of first increasing and then decreasing. Specifically, the photocatalytic nitrogen fixation activity of n-TiO2 (6.92 μmol·g -1 ·h -1 ) was significantly lower than the activity of p-TiO2(II) (47.13 μmol·g -1 ·h -1 ). Analysis shows that the catalytic activity of n-TiO2 mainly comes from Ti 3+ However, due to its low defect concentration and the fact that it can only absorb photons in the ultraviolet region, its overall performance is limited. It is worth noting that the concentration of titanium vacancies has an important influence on the catalytic activity. Experimental data show that p-TiO2(I) with too high a titanium vacancy concentration (29.556 μmol·g -1 ·h -1 Both high and low concentrations of p-TiO2(III) (26.389 μmol·g⁻¹·h⁻¹) exhibited significant performance degradation. This phenomenon can be explained by the fact that excessively high titanium vacancy concentrations form electron-hole recombination centers, inhibiting the ammonia synthesis reaction; while low vacancy concentrations fail to provide sufficient active sites to promote nitrogen fixation. Therefore, optimal nitrogen fixation catalysis is only achieved at moderate titanium vacancy concentrations.

[0060] 4. Figure 4 This is the cyclic stability of the photocatalytic nitrogen reduction of the titanium dioxide photocatalytic material in Example 2.

[0061] Depend on Figure 4Stability test results indicate that after five cycles, the catalyst's photocatalytic nitrogen fixation performance remained remarkably stable, with only minor fluctuations (slight decreases or increases). These fluctuations were primarily due to physical factors during the experiment (such as catalyst loss), rather than structural changes in the material itself. More importantly, these minor performance fluctuations further confirm the stable presence of titanium vacancies in the material, ensuring the catalyst's structural stability for long-term use.

[0062] 5. Figure 5 This is the electron paramagnetic resonance (EPR) spectrum of the titanium dioxide photocatalytic material in Example 2 before and after the photocatalytic reaction.

[0063] Depend on Figure 5 Electron spin resonance (ESR) testing revealed that after a complete photocatalytic performance test, the intensity of the titanium vacancy characteristic signal of the p-TiO2(II) catalyst remained consistent with its initial state, with no significant attenuation. This key data directly confirms the excellent stability of titanium vacancies during photocatalysis, maintaining their structural integrity over long periods under reaction conditions.

[0064] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a titanium dioxide photocatalytic material, characterized in that: The specific steps include: (1) mixing ethanol and glycerol, stirring and mixing to obtain a mixed solvent; (2) adding tetrabutyl titanate to a mixed solvent and stirring until completely dissolved to obtain a mixed solution; (3) subjecting the mixed solution to a hydrothermal reaction, cooling, washing, drying, and calcining to obtain the titanium dioxide photocatalytic material.

2. The method for preparing a titanium dioxide photocatalytic material according to claim 1, characterized in that: In step (1), the volume ratio of ethanol to glycerol is (1-3):

1.

3. The method for preparing a titanium dioxide photocatalytic material according to claim 1, characterized in that: In step (1), the stirring time is 0.5-1h.

4. The method for preparing a titanium dioxide photocatalytic material according to claim 1, characterized in that: In step (2), the amount ratio of tetrabutyl titanate and mixed solvent is 1g:30mL; and the stirring time is 0.5-2h.

5. The method for preparing a titanium dioxide photocatalytic material according to claim 1, characterized in that: In step (3), the hydrothermal reaction equipment is a closed polytetrafluoroethylene-lined hydrothermal kettle with a volume of 50-150 mL, a temperature of 180° C., and a time of 24 h.

6. The method for preparing a titanium dioxide photocatalytic material according to claim 1, characterized in that: In step (3), the cleaning reagents are anhydrous ethanol and deionized water, and the number of times is 3-7 times.

7. The method for preparing a titanium dioxide photocatalytic material according to claim 1, characterized in that: In step (3), the drying equipment is a vacuum drying oven at a temperature of 60-100°C.

8. The method for preparing a titanium dioxide photocatalytic material according to claim 1, characterized in that: In step (3), the calcination temperature is 400-500°C, the heating rate is 3-5°C / min, and the holding time is 1-2h.

9. A titanium dioxide photocatalytic material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the titanium dioxide photocatalytic material prepared by the preparation method according to any one of claims 1 to 8 in photocatalytic nitrogen reduction.

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