Preparation method of reinforced titanium dioxide photocatalytic material based on nonlinear optical crystal

Abstract

The invention discloses a preparation method of an enhanced titanium dioxide photocatalytic material based on nonlinear optical crystals, which comprises the following steps: (1) adding Ba (NH2SO3) 2 crystals into a mixed solution, stirring to uniformly disperse the Ba (NH2SO3) 2 crystals, and then dropwise adding an ammonia water solution; under the stirring condition, continuously dropwise adding tetraethyl orthosilicate, continuously stirring for 5-7 hours after dropwise adding is completed, and centrifuging, washing and drying precipitates to obtain Ba (NH2SO3) 2 (at) SiO2; and (2) ultrasonically dispersing TiO2 in an ethanol solution, adding Ba (NH2SO3) 2-coated SiO2, performing ultrasonic treatment again to uniformly disperse TiO2, completely evaporating the solvent, and performing heat treatment on a sample obtained after evaporation to dryness at 150-200 DEG C for 1.5-2.5 hours to obtain the composite photocatalytic material. The method is simple, and the light energy utilization efficiency of the composite material is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic material preparation, and in particular relates to a preparation method of a titanium dioxide photocatalytic material based on nonlinear optical crystal enhancement. Background Art

[0002] With the accelerated pace of industrialization, environmental pollution and energy shortages have become major challenges hindering sustainable social development. Against this backdrop, photocatalytic technology has attracted considerable attention due to its unique advantages in environmental remediation (such as pollutant degradation) and clean energy production (such as water splitting to produce hydrogen and carbon dioxide reduction). Among numerous photocatalysts, titanium dioxide (TiO2) offers advantages such as stable physicochemical properties and low cost and availability. However, its wide bandgap (~3.2 eV) limits its ability to effectively absorb only ultraviolet light, which accounts for less than 5% of the solar spectrum. This significantly limits its utilization of sunlight, severely restricting its efficiency in utilizing sunlight. To overcome these limitations, exploiting the frequency-doubled (FSH) effect of nonlinear optical crystals (NLOs) has become an effective strategy for broadening light utilization. The FSH effect stems from the material's second-order nonlinear polarization response to the optical electric field, converting incident fundamental frequency light into FSH light at a doubled frequency. Introducing NLOs with FSH into photocatalytic systems could theoretically convert low-energy, long-wavelength photons into high-energy, short-wavelength photons, significantly improving the catalytic material's efficiency in utilizing sunlight. Barium sulfamate (Ba(NH2SO3)2), a second-order nonlinear optical crystal with excellent performance and a significant frequency-doubling effect, is an ideal candidate for improving light-harvesting efficiency. However, its practical application suffers from problems such as insufficient chemical stability and poor mechanical strength, which seriously restrict its application in the field of photocatalysis. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation method of titanium dioxide photocatalytic material based on nonlinear optical crystal enhancement, so as to solve the problems of insufficient stability of Ba(NH2SO3)2 and poor visible light utilization of TiO2 in the prior art.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for preparing a titanium dioxide photocatalytic material based on nonlinear optical crystal enhancement comprises the following steps:

[0006] (1) Ba(NH2SO3)2 crystals are added to a mixed solution and stirred and dispersed uniformly by ultrasonic stirring. Ammonia solution is added dropwise under stirring, and stirring is continued for 25-35 minutes after the addition is completed. Tetraethyl orthosilicate is added dropwise under stirring, and stirring is continued for 5-7 hours after the addition is completed. The solution is filtered to obtain a precipitate, which is centrifuged, washed, and dried to obtain Ba(NH2SO3)2@SiO2. The ultrasonic frequency and ultrasonic time are sufficient to ensure that the Ba(NH2SO3)2 crystals are completely and uniformly dispersed in the mixed solution.

[0007] (2) TiO2 is dispersed in anhydrous ethanol to form a stable suspension, Ba(NH2SO3)2@SiO2 is added to the suspension, and Ba(NH2SO3)2@SiO2 is completely dispersed in the solution; then, the mixture is stirred in a water bath at 50-70°C until the solvent is completely evaporated to obtain a sample after evaporation, and the sample after evaporation is heat-treated at 150-200°C for 1.5-2.5h to obtain the photocatalytic material TiO2 / Ba(NH2SO3)2@SiO2.

[0008] Preferably, in step (1), the mass ratio of Ba(NH2SO3)2 to tetraethyl orthosilicate is 1:(1-2).

[0009] Preferably, in step (1), the mass ratio of Ba(NH2SO3)2 and tetraethyl orthosilicate is 1:1.5; the dropping speed of tetraethyl orthosilicate is 10 drops / minute; Ba(NH2SO3)2 crystals are ultrasonically dispersed in the mixed solution at 60KHz and stirred for 30 minutes; stirring is continued for 30 minutes after the addition of ammonia water is completed; stirring is continued for 6 hours after the addition of tetraethyl orthosilicate is completed.

[0010] Preferably, in step (1), the mixed solution consists of ethanol and water, and the volume ratio of ethanol to water is 4:1.

[0011] Preferably, to achieve better results, in step (1), the mass concentration of the ammonia water is 28%, the volume of the concentrated ammonia water added is an excess volume, and the dropping speed is 20 drops / minute.

[0012] Preferably, in step (2), the mass ratio of TiO2 to Ba(NH2SO3)2@SiO2 is (20-30):1, and TiO2 is ultrasonically dispersed in anhydrous ethanol at 60KHz.

[0013] Preferably, the mass ratio of TiO2 to Ba(NH2SO3)2@SiO2 is 25:1; the water bath temperature is 60°C, the heat treatment temperature is 150°C, and the time is 2h.

[0014] The method of the present invention uses ammonia water to catalyze the hydrolysis of tetraethyl orthosilicate in an alcohol-water mixed system, and coats a SiO2 layer on the surface of Ba(NH2SO3)2 to form Ba(NH2SO3)2@SiO2 with a core-shell structure, effectively improving the stability of the core optical crystal while not affecting the light absorption behavior of the material; then, Ba(NH2SO3)2@SiO2 and TiO2 are uniformly dispersed in ethanol; and heat treatment is used to strengthen the interface bonding to obtain TiO2 / Ba(NH2SO3)2@SiO2; at the same time, the nonlinear optical frequency doubling effect of Ba(NH2SO3)2 can convert incident light (especially visible light) into ultraviolet / near-ultraviolet light that is more easily absorbed by TiO2, thereby significantly improving the utilization efficiency of the composite material for light energy, and further promoting the improvement of its catalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The XRD patterns of Ba(NH2SO3)2 and Ba(NH2SO3)2@SiO2 in Example 1 of the present invention are shown; (a) is the XRD pattern of Ba(NH2SO3)2, and (b) is the XRD pattern of Ba(NH2SO3)2@SiO2;

[0016] Figure 2 This is the UV-visible absorption spectrum of TiO2 / Ba(NH2SO3)2@SiO2 in Example 2 of the present invention;

[0017] Figure 3 This is the performance diagram of the photocatalytic degradation of Rhodamine B by TiO2 / Ba(NH2SO3)2@SiO2 in Example 3 of the present invention. DETAILED DESCRIPTION

[0018] The above contents of the present invention are further described in detail below through examples, but this should not be understood as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above contents of the present invention fall within the scope of the present invention.

[0019] Example 1

[0020] A method for preparing a titanium dioxide photocatalytic material based on nonlinear optical crystal enhancement comprises the following steps:

[0021] (1) 0.02 g of Ba(NH2SO3)2 crystals were dispersed in 100 mL of mixed solution (V) under 60 KHz ultrasonication. 乙醇 :V 水=4:1) and stirred for 30 minutes to ensure uniform dispersion. Subsequently, 1.0 mL of 28% ammonia solution was added dropwise to the suspension at a rate of 20 drops / minute and stirring continued for 30 minutes. Next, 0.03 g of tetraethyl orthosilicate solution was added dropwise to the mixed solution at a rate of 10 drops / minute while stirring. After the addition was complete, stirring was continued for 6 hours, and the mixture was filtered to obtain a precipitate. Finally, the precipitate was centrifuged, washed, and dried to obtain Ba(NH2SO3)2@SiO2.

[0022] (2) 0.25 g of TiO2 was ultrasonically dispersed in 5 mL of anhydrous ethanol at 60 kHz to form a stable suspension. 0.01 g of Ba(NH2SO3)2@SiO2 was added to the suspension and ultrasonicated again at 60 kHz for 30 min to ensure that the Ba(NH2SO3)2@SiO2 was uniformly dispersed in the solution. The mixture was then stirred in a 60°C water bath until the solvent evaporated. Finally, the sample obtained after evaporation was heat-treated at 150°C for 2 h to obtain a solid product, namely TiO2 / Ba(NH2SO3)2@SiO2.

[0023] Example 2

[0024] A method for preparing a titanium dioxide photocatalytic material based on nonlinear optical crystal enhancement comprises the following steps:

[0025] (1) 0.05 g Ba(NH2SO3)2 crystals were dispersed in 100 mL of mixed solution (V) under 60 KHz ultrasonication. 乙醇 :V 水 =4:1) and stirred for 30 minutes to ensure uniform dispersion. Subsequently, 1.0 mL of 28% ammonia solution was added dropwise to the suspension at a rate of 20 drops / minute and stirring continued for 30 minutes. Next, 0.075 g of tetraethyl orthosilicate solution was added dropwise to the mixed solution at a rate of 10 drops / minute while stirring. After the addition was complete, stirring was continued for 6 hours and filtered to obtain a precipitate. Finally, the precipitate was centrifuged, washed, and dried to obtain Ba(NH2SO3)2@SiO2.

[0026] (2) 0.5 g of TiO2 was ultrasonically dispersed in 5 mL of anhydrous ethanol at 60 kHz to form a stable suspension system. 0.2 g of Ba(NH2SO3)2@SiO2 was added to the suspension and ultrasonicated again at 60 kHz for 30 min to ensure that Ba(NH2SO3)2@SiO2 was uniformly dispersed in the solution. Subsequently, the above mixture was stirred in a 60°C water bath until the solvent was completely evaporated. Finally, the sample obtained after evaporation was heat-treated at 150°C for 2 h, and the resulting solid product was TiO2 / Ba(NH2SO3)2@SiO2.

[0027] Example 3

[0028] A method for preparing a titanium dioxide photocatalytic material based on nonlinear optical crystal enhancement comprises the following steps:

[0029] (1) 0.02 g of Ba(NH2SO3)2 crystals were dispersed in 100 mL of mixed solution (V) under 60 KHz ultrasonication. 乙醇 :V 水 =4:1) and stirred for 30 minutes to ensure uniform dispersion. Subsequently, 1.0 mL of 28% ammonia solution was added dropwise to the suspension at a rate of 20 drops / minute and stirring continued for 30 minutes. Next, 0.03 g of tetraethyl orthosilicate solution was added dropwise to the mixed solution at a rate of 10 drops / minute while stirring. After the addition was complete, stirring was continued for 6 hours, and the mixture was filtered to obtain a precipitate. Finally, the precipitate was centrifuged, washed, and dried to obtain Ba(NH2SO3)2@SiO2.

[0030] (2) 2.5 g of TiO2 was ultrasonically dispersed in 5 mL of anhydrous ethanol solution at 60 kHz to form a stable suspension system. 0.1 g of Ba(NH2SO3)2@SiO2 prepared in step S1 was added to the suspension, and the suspension was ultrasonically treated again at 60 kHz for 30 min to ensure that Ba(NH2SO3)2@SiO2 was completely and evenly dispersed in the solution. Subsequently, the above mixture was stirred in a 60°C water bath until the solvent was completely evaporated. Finally, the sample obtained after evaporation was heat-treated at 180°C for 1.5 h. The resulting solid product was TiO2 / Ba(NH2SO3)2@SiO2.

[0031] Example 4

[0032] A method for preparing a titanium dioxide photocatalytic material based on nonlinear optical crystal enhancement comprises the following steps:

[0033] (1) 0.02 g of Ba(NH2SO3)2 crystals were dispersed in 100 mL of mixed solution (V) under 60 KHz ultrasonication. 乙醇 :V水 =4:1) and stirred for 25 minutes to ensure uniform dispersion. Subsequently, 1.0 mL of 28% ammonia solution was added dropwise to the suspension at a rate of 20 drops / minute and stirring continued for 25 minutes. Next, 0.02 g of tetraethyl orthosilicate solution was added dropwise to the mixed solution at a rate of 10 drops / minute while stirring. After the addition was complete, stirring was continued for 5 hours, and the mixture was filtered to obtain a precipitate. Finally, the precipitate was centrifuged, washed, and dried to obtain Ba(NH2SO3)2@SiO2.

[0034] (2) 2.0 g of TiO2 was ultrasonically dispersed in 5 mL of anhydrous ethanol solution at 60 kHz to form a stable suspension system. 0.1 g of Ba(NH2SO3)2@SiO2 prepared in step S1 was added to the suspension, and the suspension was ultrasonically treated again at 60 kHz for 30 min to ensure that Ba(NH2SO3)2@SiO2 was uniformly dispersed in the solution. Subsequently, the above mixture was stirred in a 50°C water bath until the solvent was completely evaporated. Finally, the sample obtained after evaporation was heat-treated at 200°C for 1.5 h. The resulting solid product was TiO2 / Ba(NH2SO3)2@SiO2.

[0035] Example 5

[0036] A method for preparing a titanium dioxide photocatalytic material based on nonlinear optical crystal enhancement comprises the following steps:

[0037] (1) 0.02 g of Ba(NH2SO3)2 crystals were dispersed in 100 mL of mixed solution (V) under 60 KHz ultrasonication. 乙醇 :V 水 =4:1) and stirred for 35 minutes to ensure uniform dispersion. Subsequently, 1.0 mL of 28% ammonia solution was added dropwise to the suspension at a rate of 20 drops / minute and stirring continued for 35 minutes. Next, 0.04 g of tetraethyl orthosilicate solution was added dropwise to the mixed solution at a rate of 10 drops / minute while stirring. After the addition was complete, stirring was continued for 7 hours, and the mixture was filtered to obtain a precipitate. Finally, the precipitate was centrifuged, washed, and dried to obtain Ba(NH2SO3)2@SiO2.

[0038] (2) 3.0 g of TiO2 was ultrasonically dispersed in 5 mL of anhydrous ethanol solution at 60 kHz to form a stable suspension system. 0.1 g of Ba(NH2SO3)2@SiO2 prepared in step S1 was added to the suspension, and the suspension was ultrasonically treated again at 60 kHz for 30 min to ensure that Ba(NH2SO3)2@SiO2 was uniformly dispersed in the solution. Subsequently, the above mixture was stirred in a 70°C water bath until the solvent was completely evaporated. Finally, the sample obtained after evaporation was heat-treated at 170°C for 1.5 h. The resulting solid product was TiO2 / Ba(NH2SO3)2@SiO2.

[0039] The stability of Ba(NH2SO3)2@SiO2 and Ba(NH2SO3)2 prepared in Example 1 was verified. Ba(NH2SO3)2@SiO2 and Ba(NH2SO3)2 prepared in Example 1 were placed in water for soaking, and XRD test analysis was performed on the samples without soaking, soaking for 30 minutes, and soaking for 3 hours. The results are as follows Figure 1 As shown by Figure 1 a It can be seen that after Ba(NH2SO3)2 is immersed in water for 3 hours, the diffraction peak of Ba(NH2SO3)2 crystal basically disappears, indicating that the crystal structure has been destroyed. Figure 1 In b, the diffraction peak position and intensity of Ba(NH2SO3)2@SiO2 in XRD remained unchanged after being immersed in water for 3 h, indicating that the SiO2 shell effectively increased the stability of Ba(NH2SO3)2 in water.

[0040] The light absorption characteristics of TiO2 / Ba(NH2SO3)2@SiO2, TiO2 and Ba(NH2SO3)2 in Example 2 were tested and the results were as follows: Figure 2 The UV-visible absorption spectrum shown is Figure 2 It can be seen that Ba(NH2SO3)2 optical crystals exhibit strong absorption across the entire spectrum, while TiO2 exhibits strong light absorption only in the ultraviolet region. Compared to pure TiO2, the absorption band edge of the TiO2 / Ba(NH2SO3)2@SiO2 catalyst exhibits a significant red shift and increased absorption in the visible region, indicating that the addition of Ba(NH2SO3)2 effectively broadens the catalyst's light absorption range and enhances its spectral response.

[0041] TiO2, Ba(NH2SO3)2, and the TiO2 / Ba(NH2SO3)2@SiO2 catalyst in Example 3 were used to perform a rhodamine degradation experiment. First, 20 mg of the prepared sample was evenly dispersed in 50 mL of 20 mg / L rhodamine solution. The resulting mixed solution was transferred to a quartz tube and stirred for 30 minutes under dark conditions to establish an adsorption-desorption equilibrium between the catalyst and the rhodamine molecules. Then, the photocatalytic reaction experiment was started in a rotatable photocatalytic multifunctional reactor. The process used a 500W xenon lamp light source and was equipped with a λ>420nm ultraviolet cutoff filter). During the reaction, 1.5 mL of the reaction solution was taken out every 10 minutes and filtered with a 0.22μm microporous water filter membrane. Finally, the pollutant concentration was detected at 554nm using a UV-visible spectrophotometer. The evaluation results are as follows. Figure 3 As shown in the figure, it can be seen that the Ba(NH2SO3)2 crystal material itself has no catalytic activity. The degradation efficiency of Rhodamine B under 60 minutes of illumination is almost zero, indicating that the crystal lacks effective catalytic active sites. Pure TiO has a weak response to visible light and an extremely low yield of photogenerated carriers, so it shows very poor photocatalytic activity. It is worth noting that after the two are combined, the resulting material shows significantly enhanced catalytic activity and the degradation efficiency of Rhodamine B is greatly improved. This is because (1) Ba(NH2SO3)2 crystals convert part of visible light into ultraviolet light through nonlinear optical effects, significantly improving the utilization efficiency of TiO2 for incident light; (2) this upconversion effect not only greatly increases the concentration of photogenerated carriers, but also promotes the generation and separation of photogenerated electron pairs; (3) the outer SiO2 shell not only improves the structural stability of TiO2 / Ba(NH2SO3)2 in aqueous phase, but also may further optimize the carrier transport process through surface modification. For the above reasons, TiO2 / Ba(NH2SO3)2@SiO2 exhibits significantly better photocatalytic activity than a single component.

[0042] The above embodiments describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a titanium dioxide photocatalytic material based on nonlinear optical crystal enhancement, characterized in that: The following steps are involved: (1) Ba(NH2SO3)2 crystals are added to the mixed solution and stirred to disperse evenly. Ammonia solution is added dropwise under stirring and stirring is continued for 25-35 minutes after the addition is complete. Tetraethyl orthosilicate is added dropwise under stirring and stirring is continued for 5-7 hours after the addition is complete. The solution is filtered to obtain a precipitate, which is then centrifuged, washed, and dried to obtain Ba(NH2SO3)2@SiO2. (2) TiO2 is dispersed in anhydrous ethanol to form a stable suspension, Ba(NH2SO3)2@SiO2 is added to the suspension, and Ba(NH2SO3)2@SiO2 is completely dispersed in the solution; then, the mixture is stirred in a water bath at 50-70°C until the solvent is completely evaporated to obtain a sample after evaporation, and the sample after evaporation is heat-treated at 150-200°C for 1.5-2.5h to obtain the photocatalytic material TiO2 / Ba(NH2SO3)2@SiO2.

2. The method for preparing a nonlinear optical crystal-enhanced titanium dioxide photocatalytic material according to claim 1, characterized in that: In step (1), the mass ratio of Ba(NH2SO3)2 to tetraethyl orthosilicate is 1:(1-2).

3. The method for preparing a nonlinear optical crystal-enhanced titanium dioxide photocatalytic material according to claim 2, characterized in that: In step (1), the mass ratio of Ba(NH2SO3)2 and tetraethyl orthosilicate is 1:1.5; the dropping speed of tetraethyl orthosilicate is 10 drops / minute; Ba(NH2SO3)2 crystals are dispersed in the mixed solution and stirred for 30 minutes; after the addition of ammonia water is completed, stirring is continued for 30 minutes; after the addition of tetraethyl orthosilicate is completed, stirring is continued for 6 hours.

4. The method for preparing a nonlinear optical crystal-enhanced titanium dioxide photocatalytic material according to claim 1, characterized in that: In step (1), the mixed solution consists of ethanol and water, and the volume ratio of ethanol to water is 4:

1.

5. The method for preparing a nonlinear optical crystal-enhanced titanium dioxide photocatalytic material according to claim 1, characterized in that: In step (1), the mass concentration of the ammonia water is 28%, and the dropping speed is 20 drops / minute.

6. The method for preparing a nonlinear optical crystal-enhanced titanium dioxide photocatalytic material according to claim 1, characterized in that: The mass ratio of TiO2 to Ba(NH2SO3)2@SiO2 in step (2) is (20-30):

1.

7. The method for preparing a nonlinear optical crystal-enhanced titanium dioxide photocatalytic material according to claim 6, characterized in that: The mass ratio of TiO2 to Ba(NH2SO3)2@SiO2 is 25:1; the water bath temperature is 60℃, the heat treatment temperature is 150℃, and the time is 2h.

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