Quasi-two-dimensional amorphous TiO2-Au photocatalyst and its application in degradation of organic pollutants

Abstract

The present invention discloses a quasi-two-dimensional amorphous TiO2-Au photocatalyst and its application in degrading organic pollutants. The preparation method of the composite photocatalyst is to add a diisopropyl di(acetylacetonate)titanate solution dropwise to an alkaline mixed solution of isopropyl alcohol and deionized water, stir the reaction, centrifuge to obtain a precipitate, and wash it with isopropyl alcohol to obtain a quasi-two-dimensional amorphous TiO2, and then load Au nanoparticles on its surface to obtain a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst. The quasi-two-dimensional amorphous TiO2-Au composite photocatalyst proposed in the present invention can be prepared at room temperature and pressure, and the preparation process is energy-saving and low-cost. The prepared TiO2-Au photocatalyst not only has a large specific surface area and shows high adsorption capacity for volatile organic pollutants, but also has excellent surface reactivity and charge transfer performance, and can effectively degrade adsorbed organic matter. The efficient adsorption and degradation capabilities complement each other, promoting the environmental governance ability and recyclability of the TiO2-Au photocatalyst.

Description

Technical Field

[0001] The invention relates to a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst and application thereof in degrading organic pollutants, belonging to the technical field of catalytic materials. Background Art

[0002] In recent years, large quantities of organic water pollutants such as dyes, antibiotics, and pesticides, as well as volatile organic pollutants such as aldehydes, hydrocarbons, alcohols, and benzene series, have been released into the environment, causing serious environmental pollution and threatening human health. Therefore, the control of these organic pollutants is essential. Adsorption is the most widely used method for organic pollutant control. This method is highly mature and simple to operate, but it also presents complex process steps, such as desorption and oxidation, after adsorption saturation. Photocatalytic oxidation, a solar-powered method for degrading pollutants into CO2 and H2O, has attracted widespread attention due to its low cost, non-toxicity, mild reaction conditions, and high efficiency and energy conservation. Integrating adsorption with photocatalytic oxidation effectively addresses the adsorption saturation issue inherent in adsorption, enabling the recyclability of adsorbents. Furthermore, the large-scale adsorption and accumulation of pollutants on the catalyst surface further enhances photocatalytic degradation efficiency. Common semiconductor photocatalysts such as TiO2 and ZnO have wide band gaps and are only photocatalytically active under ultraviolet light. This results in low sunlight utilization and the easy recombination of photogenerated electrons and holes, resulting in suboptimal photocatalytic performance. Therefore, there is an urgent need to develop a visible light-responsive, efficient and stable photocatalyst.

[0003] In addition, currently common photocatalysts are all crystalline materials, which usually require a high temperature or high pressure preparation process to crystallize them, and the crystallization process often causes rearrangement inside the material, a decrease in specific surface area, and a weak adsorption capacity. Amorphous materials can be prepared at room temperature and pressure, and most of them have the advantages of large specific surface area and strong adsorption capacity, but due to the presence of a large number of defects inside them, the carrier recombination efficiency is high and the photocatalytic performance is very weak, which limits their application. Therefore, it is crucial to optimize the performance of amorphous catalysts. However, the atomic isotropic nature of amorphous materials makes their preparation and growth process irregular and uncontrollable, and the resulting morphology is usually large particles or thin films with irregular aggregation, which makes it difficult to achieve morphology and performance regulation.

[0004] Based on the above two points, the present invention proposes a preparation method and application of a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst. The prepared composite photocatalyst has an ultra-thin, corrugated paper-like morphology, which gives it a large specific surface area, high surface reaction activity and efficient charge transfer performance. It exhibits excellent adsorption and degradation properties for organic pollutants, thereby achieving efficient treatment of pollutants. Summary of the Invention

[0005] Technical problem: In order to solve the problems of irregular and uncontrollable morphology and performance of amorphous photocatalysts, low carrier recombination efficiency and low sunlight utilization, the present invention provides a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst and its application in the degradation of VOCs.

[0006] Technical solution: The present invention provides a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst, the preparation method of which includes the following steps:

[0007] (1) adding an alkaline solution to a mixed solution of isopropyl alcohol and deionized water to adjust the pH to obtain solution I;

[0008] (2) Then, diisopropyl di(acetylacetonato)titanate solution was added dropwise to solution I, stirred evenly, and then centrifuged;

[0009] (3) washing the precipitate obtained after centrifugation in step (2) with isopropanol to obtain quasi-two-dimensional amorphous TiO2;

[0010] (4) Loading Au nanoparticles on the surface of the quasi-two-dimensional amorphous TiO2 obtained in step (3) to prepare the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst.

[0011] in:

[0012] The volume ratio of the isopropyl alcohol, deionized water and diisopropyl di(acetylacetonate) titanate is 60:20:1 to 20:10:1.

[0013] The alkaline solution is ammonia water, sodium hydroxide or potassium hydroxide solution, which makes the pH of solution I be 8-11 after being added.

[0014] The dropping speed of the diisopropyl di(acetylacetonate)titanate solution is 10 to 500 uL / min.

[0015] The method for loading Au nanoparticles onto the surface of quasi-two-dimensional amorphous TiO2 involves adding a chloroauric acid solution to the quasi-two-dimensional amorphous TiO2 and in-situ growing the Au nanoparticles under ultraviolet light. Alternatively, the Au nanoparticle solution and the quasi-two-dimensional amorphous TiO2 solution are mixed and stirred to form a composite. The Au nanoparticles have a particle size of 5 to 50 nm.

[0016] The present invention also provides an application of a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst in degrading organic pollutants.

[0017] in:

[0018] The organic pollutants include organic pollutants in water bodies and volatile organic pollutants in the air.

[0019] The specific method for degrading organic pollutants in water is as follows: adding a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst to an aqueous solution containing organic pollutants, stirring and adsorbing for 60 minutes in the dark, and then irradiating with a visible light source to react.

[0020] The specific method for degrading volatile organic pollutants in gas is as follows: a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst is placed in a sealed container containing volatile organic pollutants, placed in the dark for adsorption for 60 minutes, and then irradiated with a visible light source for reaction.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0022] 1. In the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst proposed in the present invention, since the quasi-two-dimensional TiO2 is an amorphous material, it avoids the high-temperature and high-pressure crystallization step required in the preparation of common crystalline photocatalyst materials. Therefore, the preparation process of the catalyst is simple, energy-saving and low-cost as a whole.

[0023] 2. In the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst proposed in the present invention, the morphology of amorphous TiO2 is ultra-thin, corrugated paper-like. This special morphology shortens the transmission distance of carriers and improves the utilization rate of carriers in photocatalysis.

[0024] 3. The composite of Au nanoparticles in the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst prepared by the present invention effectively improves the photocatalytic efficiency under visible light. On the one hand, Au nanoparticles absorb visible light and generate thermal electrons through the surface plasmon resonance effect, thereby increasing the utilization of visible light; on the other hand, the Schottky barrier constructed between Au nanoparticles and TiO2 improves the separation efficiency of photogenerated electrons and holes, thereby improving the photocatalytic efficiency.

[0025] 4. The quasi-two-dimensional amorphous TiO2 in the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst prepared by the present invention has a large specific surface area, which provides a large number of loading sites for Au nanoparticles and also provides sufficient adsorption sites for pollutant molecules.

[0026] 5. The quasi-two-dimensional amorphous TiO2 in the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst prepared by the present invention has an ultra-thin quasi-two-dimensional structure, which enables it to have a large number of surface defects that can serve as active sites, while there are fewer body defects that serve as carrier recombination centers, thereby improving the surface reaction activity of the photocatalyst and the carrier transport and separation efficiency, which is beneficial to the degradation of organic pollutants adsorbed on the surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1This is a transmission electron microscope image of the quasi-two-dimensional amorphous TiO2 prepared in Example 1;

[0028] Figure 2 This is a transmission electron microscope image of the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst prepared in Example 1;

[0029] Figure 3 The high-resolution Ti 2p spectrum of the quasi-two-dimensional amorphous TiO2 prepared in Example 1 is obtained by X-ray photoelectron spectroscopy (XPS);

[0030] Figure 4 This is the high-resolution O 1s spectrum of the quasi-two-dimensional amorphous TiO2 prepared in Example 1 in the X-ray photoelectron spectroscopy (XPS).

[0031] Figure 5 This is a diagram showing the adsorption and photocatalytic degradation of the organic pollutant Bismarck brown in water by the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst prepared in Example 1.

[0032] Figure 6 This is a diagram showing the adsorption and photocatalytic degradation of formaldehyde, a volatile organic pollutant in the air, by the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst prepared in Example 1. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are only used to further illustrate the present invention and are not intended to limit the present invention.

[0034] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0035] Example 1:

[0036] A method for preparing a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst comprises the following steps:

[0037] 1) Mix 300 mL of isopropyl alcohol and 100 mL of deionized water, add ammonia water to adjust the pH to 9, and stir at room temperature;

[0038] 2) Then, 10 mL of diisopropyl di(acetylacetonato)titanate (TDAA) solution was added dropwise to the above solution at a rate of 200 uL / min. At this time, the volume ratio of isopropyl alcohol, deionized water, and TDAA in the solution was 30:10:1. The mixture was stirred and centrifuged.

[0039] 3) washing the precipitate obtained after centrifugation in step 2) with isopropyl alcohol to obtain quasi-two-dimensional amorphous TiO2;

[0040] 4) Mixing and stirring the 20 nm Au nanoparticle solution with the quasi-two-dimensional amorphous TiO2 obtained in step 3) to prepare the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst.

[0041] Example 2:

[0042] A method for preparing a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst comprises the following steps:

[0043] 1) Mix 60 mL of isopropyl alcohol and 15 mL of deionized water, add sodium hydroxide solution to adjust the pH to 10, and stir at room temperature;

[0044] 2) Then, 1 mL of diisopropyl di(acetylacetonate) titanate (TDAA) solution was added dropwise to the above solution at a rate of 10 uL / min. At this time, the volume ratio of isopropyl alcohol, deionized water, and TDAA in the solution was 60:15:1. The mixture was stirred and centrifuged.

[0045] 3) washing the precipitate obtained after centrifugation in step 2) with isopropyl alcohol to obtain quasi-two-dimensional amorphous TiO2;

[0046] 4) Mixing and stirring the 50 nm Au nanoparticle solution with the quasi-two-dimensional amorphous TiO2 obtained in step 3) to prepare the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst.

[0047] Example 3:

[0048] A method for preparing a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst comprises the following steps:

[0049] 1) Mix 60 mL of isopropyl alcohol and 30 mL of deionized water, add sodium hydroxide solution to adjust the pH to 11, and stir at room temperature;

[0050] 2) Then, 3 mL of diisopropyl di(acetylacetonate) titanate (TDAA) solution was added dropwise to the above solution at a rate of 500 uL / min. At this time, the volume ratio of isopropyl alcohol, deionized water, and TDAA in the solution was 20:10:1. The mixture was stirred and centrifuged.

[0051] 3) washing the precipitate obtained after centrifugation in step 2) with isopropyl alcohol to obtain quasi-two-dimensional amorphous TiO2;

[0052] 4) Mixing and stirring the 10 nm Au nanoparticle solution with the quasi-two-dimensional amorphous TiO2 obtained in step 3) to prepare the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst.

[0053] Example 4:

[0054] A method for preparing a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst comprises the following steps:

[0055] 1) Mix 600 mL of isopropyl alcohol and 200 mL of deionized water, add potassium hydroxide solution to adjust the pH to 9, and stir at room temperature;

[0056] 2) Then, 10 mL of diisopropyl di(acetylacetonato)titanate (TDAA) solution was added dropwise to the above solution at a rate of 300 uL / min. At this time, the volume ratio of isopropyl alcohol, deionized water, and TDAA in the solution was 30:10:1. The mixture was stirred and centrifuged.

[0057] 3) washing the precipitate obtained after centrifugation in step 2) with isopropyl alcohol to obtain quasi-two-dimensional amorphous TiO2;

[0058] 4) Adding chloroauric acid solution to the quasi-two-dimensional amorphous TiO2 obtained in step 3) and irradiating the mixture under ultraviolet light for one hour to obtain the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst.

[0059] Test methods and results:

[0060] 1) Transmission electron microscopy images of quasi-two-dimensional amorphous TiO2 and quasi-two-dimensional amorphous TiO2-Au composite photocatalysts

[0061] The transmission electron microscope image of the quasi-two-dimensional amorphous TiO2 prepared in Example 1 is as follows: Figure 1 The transmission electron microscope image of the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst prepared in Example 1 is shown in FIG. Figure 2 As shown, 20 nm Au nanoparticles are loaded on the ultra-thin quasi-two-dimensional structured TiO2 surface.

[0062] 2) Specific surface area test of quasi-two-dimensional amorphous TiO2;

[0063] The specific surface area of ​​the quasi-two-dimensional amorphous TiO2 prepared in Example 1 was tested by nitrogen adsorption and desorption method, and the specific surface area of ​​the quasi-two-dimensional amorphous TiO2 was found to be 436.660 m 2 / g, which provides a large number of binding sites for the composite of Au nanoparticles and sufficient active sites for the adsorption of gaseous pollutants, which is beneficial to the adsorption and capture of gaseous pollutants.

[0064] 3) X-ray photoelectron spectroscopy (XPS) of quasi-two-dimensional amorphous TiO2;

[0065] Figure 3 Shown is the high-resolution XPS Ti 2p spectrum of the quasi-two-dimensional amorphous TiO2 prepared in Example 1. Figure 4Shown is a comparison of high-resolution XPS O 1s spectra of the quasi-two-dimensional amorphous TiO2 prepared in Example 1. Figure 3 The two peaks at 458.2eV and 463.2eV correspond to Ti 3+ defect, Figure 4 The peak at 531.0 eV corresponds to oxygen vacancy defects, indicating that the quasi-two-dimensional amorphous TiO2 has a large number of surface defects, which is beneficial to improving its surface catalytic oxidation activity.

[0066] 4) Determination of the efficiency of quasi-two-dimensional amorphous TiO2-Au composite photocatalyst for degradation of Bismarck brown organic pollutants in water;

[0067] Bismarck brown degradation performance was tested in a beaker by adding 10 mg of the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst powder prepared in Example 1 to 50 mL of a 50 mg / L Bismarck brown solution. The mixture was stirred in the dark for 60 minutes to establish adsorption-desorption equilibrium. The composite photocatalyst was then irradiated with visible light above 400 nm. 3 mL of the solution was sampled every 10 minutes, filtered to remove the catalyst, and the Bismarck brown concentration in the solution was measured. Figure 5 Figures show the adsorption and photocatalytic degradation of Bismarck brown by a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst. The figure shows that after 60 minutes of light-shielded adsorption, 36.55% of the Bismarck brown in the container remained. After 90 minutes of degradation under visible light, only 8.77% remained. This demonstrates the excellent adsorption and degradation performance of this composite photocatalyst for the organic pollutant Bismarck brown in water.

[0068] 5) Determination of the efficiency of quasi-two-dimensional amorphous TiO2-Au composite photocatalyst in degrading formaldehyde, a volatile organic pollutant in the air;

[0069] Formaldehyde degradation performance was tested in a 500ml sealed container. 10mg of the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst prepared in Example 1 was fixed to glass and placed in the center of the sealed container. A certain amount of formaldehyde gas was then injected. The initial formaldehyde concentration was 40ppm. The container was kept in the dark for 60 minutes to establish adsorption-desorption equilibrium. The composite photocatalyst was then irradiated with visible light above 400nm, and 5mL gas samples were taken every 20 minutes to measure the formaldehyde concentration. Figure 6 Figures show the adsorption and photocatalytic degradation of formaldehyde by a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst. The figure shows that after 60 minutes of light-blocking adsorption of formaldehyde by the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst, 43.24% of the formaldehyde remained in the container. After 100 minutes of visible light irradiation, the formaldehyde remained at 5%. This demonstrates that the composite photocatalyst exhibits excellent adsorption and degradation performance for formaldehyde, a volatile organic pollutant in air.

Claims

1. A quasi-two-dimensional amorphous TiO2-Au composite photocatalyst, characterized by: The preparation method comprises the following steps: (1) adding an alkaline solution to a mixed solution of isopropyl alcohol and deionized water to adjust the pH to obtain solution I; (2) Then, diisopropyl di(acetylacetonate) titanate solution was added dropwise to solution I, stirred evenly, and then centrifuged; (3) washing the precipitate obtained after centrifugation in step (2) with isopropanol to obtain quasi-two-dimensional amorphous TiO2; (4) loading Au nanoparticles on the surface of the quasi-two-dimensional amorphous TiO2 obtained in step (3) to prepare the quasi-two-dimensional amorphous TiO2-Au composite photocatalyst; In the preparation method, the volume ratio of isopropyl alcohol, deionized water and diisopropyl di(acetylacetonate) titanate is 60:20:1 to 20:10:1; In the preparation method, the dropwise addition rate of the diisopropyl di(acetylacetonate)titanate solution is 10 to 500 uL / min; In the preparation method, the method of loading Au nanoparticles on the surface of quasi-two-dimensional amorphous TiO2 is to add chloroauric acid solution to the quasi-two-dimensional amorphous TiO2 and in-situ grow Au nanoparticles under ultraviolet light.

2. The quasi-two-dimensional amorphous TiO2-Au composite photocatalyst according to claim 1, characterized in that: In the preparation method, the alkaline solution is aqueous ammonia, sodium hydroxide or potassium hydroxide solution, which is added to make the pH of solution I be 8-11.

3. The quasi-two-dimensional amorphous TiO2-Au composite photocatalyst according to claim 1, characterized in that: In the preparation method, the particle size of the Au nanoparticles is 5-50 nm.

4. Use of a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst according to any one of claims 1 to 3 in the degradation of organic pollutants, characterized in that: The organic pollutants include organic pollutants in water bodies and volatile organic pollutants in the air.

5. The use of a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst in the degradation of organic pollutants as claimed in claim 4, characterized in that: The specific method for degrading organic pollutants in water bodies is as follows: a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst is added to an aqueous solution containing organic pollutants, stirred and adsorbed in the dark for 60 minutes, and then irradiated with a visible light source for reaction.

6. The use of a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst in the degradation of organic pollutants according to claim 4, characterized in that: The specific method for degrading volatile organic pollutants in the air is as follows: a quasi-two-dimensional amorphous TiO2-Au composite photocatalyst is placed in a sealed container containing volatile organic pollutants, placed in the dark for adsorption for 60 minutes, and then irradiated with a visible light source for reaction.

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