Titanium dioxide-graphene oxide composite material as well as preparation method and application thereof

Abstract

The invention discloses a titanium dioxide-graphene oxide composite material and a preparation method and application thereof, and belongs to the technical field of composite materials, the titanium dioxide-graphene oxide composite material comprises a graphene oxide matrix and titanium dioxide particles loaded on the graphene oxide matrix; in the composite material, the mass percentage of the graphene oxide is 1-25 wt%. According to the invention, electron-hole pair compounding is effectively inhibited, and the photocatalytic performance of the composite material is improved.

Description

Technical Field

[0001] The present application relates to a titanium dioxide-graphene oxide composite material, a preparation method and application thereof, and belongs to the technical field of composite materials. Background Art

[0002] A large amount of water is used in the coal production process, and the wastewater contains organic pollutants that are difficult to remove. In the laboratory, the technology of wastewater treatment has achieved a lot of research results, but in actual industrial production, most companies still use traditional adsorption processes. It is urgent to develop an economical, efficient catalyst that can be applied to existing production processes. Although traditional chemical, biological and photochemical degradation methods have certain effects on organic pollutants, persistent organic pollutants still exist in most industrial wastewater.

[0003] Photocatalytic technology is a promising advanced oxidation method. It is often used to degrade organic pollutants due to its high efficiency, simplicity, good reproducibility and easy operation. This technology can degrade pollutants in water by converting solar energy into chemical energy through photocatalysts and driving redox reactions. It has the advantages of energy saving, green, safe and low cost, and is considered to be an ideal environmental governance method. Photocatalytic technology is based on the reaction of organic pollutants with strong redox agents on the surface of photocatalysts.

[0004] Titanium dioxide (TiO2) is a good photocatalyst with high reaction stability and suitable bandgap width. It can catalyze the degradation reaction of most pollutants, so it is widely used. However, there are some problems with using TiO2 alone, including ① the electron-hole recombination is too fast. The degradation rate of pollutants is greatly reduced. ② The utilization rate of light energy is too low, and the degradation effect is poor. ③ Most photocatalysts are powdered, which are difficult to recycle after photocatalytic degradation, increasing the cost of wastewater treatment. Therefore, laboratories usually use a uniform mixing method, using metal or non-metallic substances to uniformly mix to improve the chemical catalytic performance of TiO2; doping will significantly improve the ability to treat wastewater. Therefore, other substances can be doped to improve the chemical catalytic performance of titanium dioxide. Summary of the invention

[0005] According to one aspect of the present application, a titanium dioxide-graphene oxide composite material is provided, which effectively suppresses electron-hole recombination and improves the photocatalytic performance of the composite material.

[0006] A titanium dioxide-graphene oxide composite material, characterized by comprising:

[0007] A graphene oxide matrix and titanium dioxide particles supported on the graphene oxide matrix;

[0008] In the composite material, the mass percentage of graphene oxide is 1 to 25 wt%.

[0009] Furthermore, the particle size of the titanium dioxide particles is 3-5 nm.

[0010] According to another aspect of the present application, a method for preparing a titanium dioxide-graphene oxide composite material is also provided, characterized in that it comprises:

[0011] obtaining a graphene oxide dispersion;

[0012] Adding titanium dioxide to the graphene oxide dispersion to carry out a hydrothermal reaction;

[0013] The hydrothermal reaction product is dried to obtain the titanium dioxide-graphene oxide composite material.

[0014] Furthermore, in the graphene oxide dispersion, the mass volume ratio of graphene oxide to dispersant is 0.03-0.08:50-95 g / ml;

[0015] The dispersant is at least one of water, DMF and ethylene glycol.

[0016] Further, the conditions of the hydrothermal reaction are:

[0017] First, heat the reaction at 25-45°C for 0.8-1.5h;

[0018] The reaction was then continued to stir.

[0019] Furthermore, the heating method is ultrasonic heating;

[0020] The stirring reaction conditions are: controlling the stirring speed to 520-650 r / min and stirring for 0.3-0.6 h.

[0021] Further, the drying conditions are:

[0022] The hydrothermal reaction product is wrapped with a plastic film, and the hydrothermal product is dried at 65-110° C. for 14-24 hours.

[0023] According to another aspect of the present application, a photocatalyst is also provided.

[0024] The photocatalyst absorbs visible light with a wavelength of 500-570 nm.

[0025] Furthermore, the application of photocatalysts in environmental purification.

[0026] Furthermore, the environmental purification treatment includes sewage treatment, air purification and degradation of organophosphorus pesticides;

[0027] Preferably, in sewage treatment, the photocatalyst is used to catalytically degrade dyes in sewage;

[0028] The dye includes at least one of rhodamine B, methyl orange and methylene blue.

[0029] The beneficial effects of this application include:

[0030] A titanium dioxide graphene oxide photocatalyst provided by the present application includes a graphene oxide matrix and titanium dioxide particles loaded on the graphene oxide matrix, wherein the proportion of graphene oxide is 1 to 25wt%, the rest is titanium dioxide, and the titanium dioxide is evenly dispersed on the surface of graphene oxide. Due to the introduction of graphene oxide, the photocatalytic performance of the material is significantly improved. Specifically, under visible light and ultraviolet light illumination conditions, the photocatalytic degradation efficiency of the composite material exceeds 80%, which is much higher than that of traditional titanium dioxide photocatalysts. By optimizing the proportion of graphene and the structure of the composite material, the recombination rate of electron-hole pairs is effectively reduced, thereby improving the photocatalytic efficiency. Through a specific preparation method and structural design, the stability of the material is improved, so that it can still maintain good photocatalytic performance after long-term use. At the same time, the photocatalyst can be effectively applied in the fields of sewage treatment, air purification and degradation of organophosphorus pesticides. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 X-ray diffraction comparison diagram of the titanium dioxide-graphene oxide composite material prepared in Example 1 of the present application, graphene oxide, and titanium dioxide;

[0032] Figure 2 This is a scanning electron microscope comparison diagram of the titanium dioxide-graphene oxide composite material prepared in Example 1 of the present application, graphene oxide, and titanium dioxide;

[0033] Figure 3 This is a flow chart of a method for preparing a titanium dioxide graphene oxide photocatalyst in one embodiment of the present application;

[0034] Figure 4 This is a diagram showing the effect of a light adsorption test of a titanium dioxide graphene oxide photocatalyst in one embodiment of the present application. DETAILED DESCRIPTION

[0035] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0036] TiO2 is a common and effective photocatalytic semiconductor material, which is better than other materials in degrading pollutants. However, TiO2 has a wide band gap, which limits its photocatalytic reaction under visible light. In order to enhance the photocatalytic reaction of TiO2 under visible light, people began to introduce graphene into it. Graphene oxide (GO) is a two-dimensional honeycomb structure material composed of carbon atoms, which has the advantages of huge specific surface area, good thermal conductivity and high mechanical strength. Graphene oxide can also be transported ballistically without scattering, which makes it have achieved excellent achievements in the fields of photocatalysis and adsorption. Incorporating GO into TiO2 can enhance the photocatalytic reaction under visible light. The graphene oxide-titanium dioxide composite not only enhances the adsorption of reactants in the visible light range, but also makes charge migration and separation easier.

[0037] The titanium dioxide-graphene oxide composite material provided in the present application comprises:

[0038] A graphene oxide matrix and titanium dioxide particles supported on the graphene oxide matrix;

[0039] In the composite material, the mass percentage of graphene oxide is 1 to 25wt%;

[0040] The particle size of the titanium dioxide particles is 3-5 nm.

[0041] The composite material of the present application is a nanocomposite material of TiO2 microspheres and graphene oxide, wherein the proportion of graphene oxide is 1 to 25wt%, and the rest is titanium dioxide, and the titanium dioxide is evenly dispersed on the surface of graphene. Due to the introduction of graphene oxide, the photocatalytic performance of the material is significantly improved. Specifically, under the conditions of visible light and ultraviolet light illumination, the photocatalytic efficiency of the composite material exceeds 80%, which is much higher than that of traditional titanium dioxide photocatalysts. By optimizing the proportion of graphene and the structure of the composite material, the recombination rate of electron-hole pairs is effectively reduced, thereby improving the photocatalytic efficiency. Through a specific preparation method and structural design, the stability of the material is improved, so that it can still maintain good photocatalytic performance after long-term use.

[0042] The preparation method of the titanium dioxide-graphene oxide composite material provided in the present application is:

[0043] obtaining a graphene oxide dispersion;

[0044] Specifically, during the preparation process, graphene oxide was introduced as a carrier, which significantly improved the conductivity and specific surface area of ​​the composite material. Compared with the traditional method, this improvement makes the TiO2@GO composite material have better performance in the fields of photocatalysis and energy storage.

[0045] Adding titanium dioxide to the graphene oxide dispersion to carry out a hydrothermal reaction;

[0046] The hydrothermal reaction product is dried to obtain the titanium dioxide-graphene oxide composite material.

[0047] In the graphene oxide dispersion, the mass volume ratio of graphene oxide to dispersant is 0.03-0.08:50-95 g / ml;

[0048] The dispersant is at least one of water, DMF and ethylene glycol.

[0049] The conditions of the hydrothermal reaction are:

[0050] First, heat the reaction at 25-45°C for 0.8-1.5h;

[0051] The reaction was then continued to stir.

[0052] Specifically, during the hydrothermal reaction stage, the reaction temperature, time and other parameters were precisely controlled to ensure that the TiO2 nanoparticles could be evenly attached to the GO surface to form a stable composite structure. The optimization of these conditions is the key to achieving high-performance composite materials.

[0053] The heating method is ultrasonic heating;

[0054] The stirring reaction conditions are: controlling the stirring speed to 520-650 r / min and stirring for 0.3-0.6 h.

[0055] Specifically, ultrasonic treatment and stirring effectively promoted the uniform mixing of TiO2 nanoparticles and GO, avoiding the occurrence of agglomeration. This step is crucial to improving the stability and dispersibility of the composite material.

[0056] The drying conditions are:

[0057] The hydrothermal reaction product is wrapped with a plastic film, and the hydrothermal product is dried at a temperature of 65-110° C. for 14-24 hours.

[0058] Specifically, after the hydrothermal reaction, the excess water and impurities were removed by filtration and drying to obtain a pure TiO2@GO composite material. This step is of great significance for improving the purity and performance of the composite material.

[0059] It is worth noting that the Ti-OC bond in the titanium dioxide-graphene oxide composite material promotes the transfer of electrons from TiO2 to GO, effectively inhibits electron-hole recombination, and improves the photocatalytic performance of the composite material. Under light, there is a synergistic effect between TiO2 microspheres and GO nanosheets. The nano-TiO2 microspheres in the TiO2@GO composite material promote the transfer of electrons (e - ) and holes (h + ) is formed. The study found that in terms of removing pollutants in water, the introduction of GO greatly increased the adsorption of organic pollutants in water by TiO2 nanoparticles; and the presence of TiO2 nanoparticles between GO sheets can effectively inhibit the agglomeration of GO, thereby ensuring that the adsorption performance of the composite gradually increases with the increase of GO content. The present invention has made innovative improvements to the TiO2@GO preparation method.

[0060] Embodiment 1:

[0061] The preparation method of the titanium dioxide-graphene oxide composite material provided in the present application is:

[0062] obtaining a graphene oxide dispersion;

[0063] Adding titanium dioxide to the graphene oxide dispersion to carry out a hydrothermal reaction;

[0064] The hydrothermal reaction product is dried to obtain the titanium dioxide-graphene oxide composite material.

[0065] In the graphene oxide dispersion, the mass volume ratio of graphene oxide to dispersant is 0.05:80 g / ml;

[0066] The dispersant is at least one of water, DMF and ethylene glycol.

[0067] The conditions of the hydrothermal reaction are:

[0068] First, the reaction was heated at 40 °C for 1 h;

[0069] The reaction was then continued to stir.

[0070] The heating method is ultrasonic heating;

[0071] The stirring reaction conditions are: controlling the stirring speed to 570 r / min and stirring for 0.5 h.

[0072] The drying conditions are:

[0073] The hydrothermal reaction product was wrapped with a plastic film and dried at 65° C. for 18 h.

[0074] Embodiment 2:

[0075] The preparation method of the titanium dioxide-graphene oxide composite material provided in the present application is:

[0076] obtaining a graphene oxide dispersion;

[0077] Adding titanium dioxide to the graphene oxide dispersion to carry out a hydrothermal reaction;

[0078] The hydrothermal reaction product is dried to obtain the titanium dioxide-graphene oxide composite material.

[0079] In the graphene oxide dispersion, the mass volume ratio of graphene oxide to dispersant is 0.03:50 g / ml;

[0080] The dispersant is at least one of water, DMF and ethylene glycol.

[0081] The conditions of the hydrothermal reaction are:

[0082] First, the reaction was heated at 25 °C for 0.8 h;

[0083] The reaction was then continued to stir.

[0084] The heating method is ultrasonic heating;

[0085] The stirring reaction conditions are: controlling the stirring speed to 520 r / min and stirring for 0.3 h.

[0086] The drying conditions are:

[0087] The hydrothermal reaction product was wrapped with a plastic film and dried at 65° C. for 14 h.

[0088] Embodiment 3:

[0089] The preparation method of the titanium dioxide-graphene oxide composite material provided in the present application is:

[0090] obtaining a graphene oxide dispersion;

[0091] Adding titanium dioxide to the graphene oxide dispersion to carry out a hydrothermal reaction;

[0092] The hydrothermal reaction product is dried to obtain the titanium dioxide-graphene oxide composite material.

[0093] In the graphene oxide dispersion, the mass volume ratio of graphene oxide to dispersant is 0.08:95 g / ml;

[0094] The dispersant is at least one of water, DMF and ethylene glycol.

[0095] The conditions of the hydrothermal reaction are:

[0096] First, the reaction was heated at 45 °C for 1.5 h;

[0097] The reaction was then continued to stir.

[0098] The heating method is ultrasonic heating;

[0099] The stirring reaction conditions are: controlling the stirring speed to 650 r / min and stirring for 0.6 h.

[0100] The drying conditions are:

[0101] The hydrothermal reaction product was wrapped with a plastic film and dried at a temperature of 110° C. for 24 hours.

[0102] The present application has carried out microstructure analysis on the composite material prepared in the examples by using X-ray diffractometer (XRD) and scanning electron microscope (SEM). Typically, taking the product obtained in Example 1 as an example, the results are as follows: Figure 1 , 2 As shown:

[0103] in, Figure 1 It is a comparison diagram of X-ray diffraction spectra (XRD) of graphene oxide GO, titanium dioxide TiO2 and the carbon dioxide-graphene oxide composite material TiO2@GO prepared in Example 1; Figure 2 (a) and (b) are scanning electron microscope images of pure graphene oxide with a diameter of about 10 μm; Figure 2 (c) is a scanning electron microscope image of a carbon dioxide oxide graphene photocatalyst with a diameter of about 10 μm in one embodiment of the present application; Figure 2 (d) is a scanning electron micrograph of titanium dioxide with a particle size of about 3-5 nm.

[0104] from Figure 1 It can be seen that the peak of TiO2@GO has both partial peaks of TiO2 and peaks of GO, which shows that TiO2@GO is successfully composited without changing the crystal structure of TiO2 itself. Figure 2 For SEM images, Figure 2 (ab) are scanning images of pure GO. It can be seen from the figure that GO has a layered structure. It is a flaky graphene oxide with a relatively smooth surface, but it has many wrinkles and many irregular bends. Figure 2 (c) is the SEM image of TiO2@GO. It can be seen from the figure that titanium dioxide is dispersed on the surface of GO. Figure 2 (d) shows TiO2. The dispersion of TiO2 nanoparticles varies. In some places, the dispersion is poor and agglomeration occurs. The reason is related to the different structures on the nano surface.

[0105] The present application also discloses a photocatalyst, wherein the photocatalyst comprises at least the titanium dioxide-graphene oxide composite material according to claim 1 or 2, or a method for preparing the titanium dioxide-graphene oxide composite material according to any one of claims 3 to 7;

[0106] The photocatalyst absorbs visible light with a wavelength of 500-570 nm.

[0107] The application of the photocatalyst in environmental purification treatment.

[0108] The environmental purification treatment includes sewage treatment, air purification and degradation of organophosphorus pesticides.

[0109] Specifically, the photocatalyst combines the high adsorption performance of graphene oxide and the photocatalytic activity of titanium dioxide, further improving the sewage treatment effect. This composite material can effectively adsorb and photodegrade organic pollutants in water. The composite material can be reused after calcination at 400°C, showing good economy and sustainability. The graphene oxide and titanium dioxide composite material combines the advantages of both, not only improving the efficiency and effect of sewage treatment, but also reducing costs and reducing the impact on the environment. It is a sewage treatment material with broad application prospects.

[0110] In addition, the photocatalyst can be used to effectively reduce nitrogen oxides in the atmosphere, thereby improving urban air quality. The obtained nano-titanium dioxide / graphene oxide composite photocatalyst is used to degrade organophosphorus pesticides. This composite photocatalyst has the performance of efficiently adsorbing and degrading organophosphorus pesticides under visible light.

[0111] In summary, titanium dioxide graphene oxide photocatalysts have significant application value in the fields of environmental protection and energy conversion. With the deepening of research, it is expected that these materials will play a greater role in the future and promote the development of green technology.

[0112] Preferably, in sewage treatment, the photocatalyst is used to catalytically degrade dyes in sewage;

[0113] The dye comprises at least one of rhodamine B, methyl orange and methylene blue;

[0114] Among them, methylene blue was completely degraded within half an hour.

[0115] Specifically, the photocatalyst can effectively degrade dyes in sewage under visible light excitation. Under ultraviolet light and visible light, the adsorption capacity and photocatalytic ability of TiO2@GO are improved. The specific surface area of ​​TiO2@GO is increased compared with pure TiO2 or GO, π-π bonds are formed between the dye molecules and the aromatic rings, and methylene blue (MB) forms covalent bonds with oxygen-containing groups on the surface of GO. In terms of optical properties, the addition of graphene oxide allows the formation of Ti-O-C bonds, reduces the energy band gap of TiO2, and also enhances the photodegradation effect of organic dyes. Wastewater treatment technology can effectively remove pollutants, improve water quality, reduce water pollution, protect water quality, and promote the healthy development of ecology and society. When treating sewage, graphene oxide and TiO2 composites can enrich heavy metal ions in water through electrochemical adsorption, electrostatic action, complex reaction and internal diffusion mechanism. The hydroxyl radicals and superoxides generated by the composite under light can oxidize and decompose organic pollutants, and finally convert them into non-toxic and harmless substances.

[0116] In order to ensure the adsorption performance of the photocatalyst provided in this application, the following experiments were performed on the photocatalyst:

[0117] 1. Adsorption kinetics experiment:

[0118] The present application conducts an adsorption experiment with a methylene blue reagent and the photocatalyst, records the amount of methylene blue used during adsorption, observes its adsorption effect on the photocatalyst, measures the concentration of the methylene blue reagent before and after using a spectrophotometer, and finally obtains the specific surface area; the calculation formula is as follows:

[0119] S S =(C0-C)V×2.45 / 1000W S

[0120] Where: S S is the specific surface area of ​​the material m 2 / g;

[0121] C0 is the initial concentration of the dye reagent, mg / L;

[0122] C is the concentration after reaching the monolayer saturation state, mg / L;

[0123] V is the volume of dye consumed, mL;

[0124] W S To weigh the mass of TiO2@GO, g.

[0125] Take 20 mg of TiO2@rGO composite and 100 ml of methylene blue solution and mix them evenly in a 250 ml conical flask. After mixing evenly, place it in a 25 ° C water bath and shake it rapidly. Take 4 mL of the mixed sample at the same interval, filter the solution with a filter, and measure the concentration. Methyl orange (MO) and rhodium B (RH B) were used instead of methylene blue (MB) for the adsorption experiment again.

[0126] The experimental results are as follows Figure 4 As shown in the figure, specifically: the adsorption amount and adsorption rate of the three dyes increase very quickly at the beginning of adsorption, because there is a concentration difference between the dye body and the material body, and the dye diffuses into the material body. During the diffusion process, the dye occupies the active adsorbable sites of the composite material. The more active adsorbable sites, the faster the rate. After a period of time, the curve becomes flat and the adsorption rate slows down significantly, because there are a certain number of active adsorbable sites in a certain amount of composite material. Starting from 30 minutes, the adsorption rate slows down significantly, and the adsorption amount does not change after 60 minutes. Until the end, there is no concentration difference between the two bodies, indicating that adsorption equilibrium is reached.

[0127] In order to explain the diffusion mode followed in the adsorption kinetics process, the adsorption kinetics of TiO2@rGO to MB, MO and RHB are studied, and a suitable model is selected. Two kinetic models will be used to verify the internal diffusion method. After processing the experimental data and fitting it, the adsorption method is verified.

[0128] 2. Kinetic model experiment:

[0129] Pseudo-first-order kinetic adsorption model: Assuming that the adsorption amount of the composite material to the dye changes exponentially with time, the adsorption process is consistent with the pseudo-first-order kinetic adsorption theory in adsorption kinetics, which is mainly affected by the diffusion step. The calculation formula is as follows

[0130] Q t =Q e (1-exp(-k1t / 2.303))

[0131] Here, Q t It is expressed in mg·g at a certain time. -1 Indicates the adsorption amount;

[0132] K1 is the pseudo-first-order reaction kinetic constant;

[0133] When the absorption reaches equilibrium, the -1 Q e .

[0134] Quasi-second-order kinetic adsorption: It is a model affected by multiple chemical controls. In chemical adsorption, multiple diffusion modes occur, such as external diffusion, pore diffusion, reaction at the proton center, and electron transfer. The calculation formula is as follows:

[0135]

[0136] Where: Q t is the amount of substance absorbed at a specific moment, in milligrams / grams -1 ;

[0137] k2 is the pseudo-second-order dynamic adsorption rate constant;

[0138] When the equilibrium state is reached, mg·g -1 To describe Q e .

[0139] The pseudo-first-order kinetics and pseudo-second-order kinetics model parameters of the photocatalyst for dyes are shown in Table 1.

[0140]

[0141] Table 1

[0142] Table 1 shows the comparison of the kinetic adsorption model parameters of the photocatalyst for different dyes. The fitting coefficients R for the first-order kinetic model of MB, MO and RHB are 2 The value of the adsorption coefficient of MB, MO and RHB is between 0.70 and 0.80, indicating that the adsorption process is not affected by the diffusion step. For the quasi-second-order kinetic model, the correlation coefficients of the three fittings are all around 0.99, indicating that the adsorption process of MB, MO and RHB by TiO2@GO is controlled by the chemical step. It can be shown that the chemical adsorption process is the rate-limiting reaction. In the adsorption process, the external diffusion process of the dye body to the material body and the internal diffusion and pore diffusion in the material body also occur.

[0143] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A titanium dioxide-graphene oxide composite material, characterized in that: include: A graphene oxide matrix and titanium dioxide particles supported on the graphene oxide matrix; In the composite material, the mass percentage of graphene oxide is 1 to 25 wt%.

2. A titanium dioxide-graphene oxide composite material according to claim 1, characterized in that: The particle size of the titanium dioxide particles is 3-5 nm.

3. A method for preparing a titanium dioxide-graphene oxide composite material, characterized in that: include: obtaining a graphene oxide dispersion; Adding titanium dioxide to the graphene oxide dispersion to carry out a hydrothermal reaction; The hydrothermal reaction product is dried to obtain the titanium dioxide-graphene oxide composite material.

4. The method for preparing the titanium dioxide graphene oxide photocatalyst according to claim 3, characterized in that: In the graphene oxide dispersion, the mass volume ratio of graphene oxide to dispersant is 0.03-0.08:50-95 g / ml; The dispersant is at least one of water, DMF and ethylene glycol.

5. The method for preparing the titanium dioxide graphene oxide photocatalyst according to claim 3, characterized in that: The conditions of the hydrothermal reaction are: First, heat the reaction at 25-45°C for 0.8-1.5h; The reaction was then continued to stir.

6. The method for preparing the titanium dioxide graphene oxide photocatalyst according to claim 5, characterized in that: The heating method is ultrasonic heating; The stirring reaction conditions are: controlling the stirring speed to 520-650 r / min and stirring for 0.3-0.6 h.

7. The method for preparing the titanium dioxide graphene oxide photocatalyst according to claim 3, characterized in that: The drying conditions are: The hydrothermal reaction product is wrapped with a plastic film, and the hydrothermal product is dried at 65-110° C. for 14-24 hours.

8. A photocatalyst, characterized in that The photocatalyst comprises at least the titanium dioxide-graphene oxide composite material according to claim 1 or 2, or the preparation method of the titanium dioxide-graphene oxide composite material according to any one of claims 3 to 7; The photocatalyst absorbs visible light with a wavelength of 500-570 nm.

9. Use of the photocatalyst according to claim 8 in environmental purification.

10. The use of the photocatalyst in sewage treatment according to claim 8, characterized in that: The environmental purification treatment includes sewage treatment, air purification and degradation of organophosphorus pesticides; Preferably, in sewage treatment, the photocatalyst is used to catalytically degrade dyes in sewage; The dye includes at least one of rhodamine B, methyl orange and methylene blue.

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