A photocatalytic composite material, a preparation method and application thereof

Abstract

The application relates to the technical field of photocatalysts, and discloses a photocatalytic composite material as well as a preparation method and application thereof. The photocatalytic composite material comprises a base material and metal elemental silver loaded on the base material, wherein the base material is titanium dioxide nanospheres doped with nitrogen elements and potassium ions. In addition, the preparation method of the photocatalytic composite material comprises the following steps: (1) mixing titanium potassium oxalate, water, ethylene glycol, N,N-dimethylformamide and silver nitrate to obtain a mixed solution; (2) performing hydrothermal reaction on the mixed solution, and performing centrifugation, washing and drying to obtain the photocatalytic composite material. The prepared photocatalytic composite material is used for photocatalytic reduction of CO2 to prepare methane. The method is simple and effective, the prepared photocatalytic composite material has high stability and activity, and the methane preparation efficiency is as high as 110 mu mol / g / h.

Description

Technical Field

[0001] This invention relates to the field of photocatalyst technology, specifically to a photocatalytic composite material, its preparation method, and its application. Background Technology

[0002] The shortage and depletion of non-renewable fossil fuels has always been a global concern. From the perspective of green environmental protection and sustainable development, solar-driven photocatalytic reactions hold promise as an alternative to traditional thermally driven chemical synthesis. Photocatalysis utilizes the holes and electrons generated by light-excited semiconductors to undergo oxidation and reduction reactions, effectively utilizing CO2 to reduce it into CO, C2H4, or liquid products such as common ethanol, acetic acid, and formic acid. This not only realizes the carbon cycle in nature but also addresses current problems such as the greenhouse effect and acid rain, and alleviates current energy pressures.

[0003] Among numerous photocatalysts, titanium dioxide (TiO2) is widely recognized as one of the most promising environmentally friendly catalysts due to its advantages such as safety, non-toxicity, high activity, resistance to chemical and photocorrosion, and low cost. However, due to limited charge separation efficiency and a lack of effective reactive sites, the performance of titanium dioxide photocatalysts in converting CO2 to methane is unsatisfactory. Therefore, there is an urgent need to provide a photocatalyst that can improve the performance of photocatalytic reduction of CO2 to methane. Summary of the Invention

[0004] The purpose of this invention is to overcome the poor performance of photocatalytic reduction of CO2 to methane in the prior art, and to provide a photocatalytic composite material and its preparation method. At the same time, a method for photocatalytic reduction of CO2 to methane is also provided. This photocatalytic composite material can effectively improve the performance of photocatalytic reduction of CO2 to methane and has great application potential.

[0005] To achieve the above objectives, the first aspect of the present invention provides a photocatalytic composite material comprising a matrix material and elemental silver loaded on the matrix material, wherein the matrix material is TiO2 nanospheres doped with nitrogen and potassium ions.

[0006] Preferably, the content of elemental silver is 2-12% by weight, based on the total weight of the composite material.

[0007] More preferably, the content of elemental silver is 5.5 to 8.5% by weight, based on the total weight of the composite material.

[0008] Preferably, based on the total weight of the photocatalytic composite material, the nitrogen content is 0.3-0.9% by weight, and the potassium ion content is 0.4-3% by weight.

[0009] More preferably, based on the total weight of the photocatalytic composite material, the nitrogen content is 0.45–0.76% by weight, and the potassium ion content is 0.4–2.6% by weight.

[0010] Preferably, the TiO2 nanospheres have a particle size of 200–1400 nm.

[0011] A second aspect of the present invention provides a method for preparing the photocatalytic composite material described in the first aspect, the method comprising the following steps:

[0012] (1) Mix potassium titanium oxalate, water, ethylene glycol, N,N-dimethylformamide and silver nitrate to obtain a mixed solution;

[0013] (2) The mixed solution was subjected to a hydrothermal reaction, centrifuged, washed and dried to obtain a photocatalytic composite material.

[0014] Preferably, in step (1), the ratio of potassium titanium oxalate to water is 1g: 5-60mL.

[0015] Preferably, in step (1), the ratio of potassium titanium oxalate to ethylene glycol is 1g:10-50mL.

[0016] Preferably, in step (1), the ratio of potassium titanium oxalate to N,N-dimethylformamide is 1g:2.5-30mL.

[0017] Preferably, in step (1), the weight ratio of potassium titanium oxalate to silver nitrate is 1g: 20-130mg.

[0018] Preferably, the method includes the following steps:

[0019] S1. Disperse potassium titanium oxalate in water, then add ethylene glycol and sonicate, then add N,N-dimethylformamide and sonicate again to obtain solution A;

[0020] S2. Mix solution A with silver nitrate solution to obtain solution B;

[0021] S3. Solution B is subjected to a hydrothermal reaction. After the reaction is completed, the solution is cooled, centrifuged, washed, and dried to obtain the photocatalytic composite material.

[0022] Preferably, in step (2), the conditions for the hydrothermal reaction include: a temperature of 150–220°C and a time of 8–24 h.

[0023] A third aspect of the present invention provides a photocatalytic composite material prepared by the method described in the second aspect above.

[0024] The fourth aspect of the present invention provides a method for photocatalytic reduction of CO2 to prepare methane, the method comprising: passing CO2 into a photoreactor containing a catalyst and a reaction solution to carry out a photocatalytic reduction reaction; wherein the catalyst is the photocatalytic composite material described in the first aspect above or the photocatalytic composite material described in the third aspect above.

[0025] Preferably, the conditions for the photocatalytic reduction reaction include: a light source power of 150-300W, a reaction solution to catalyst ratio of 1mL:10-30mg, and a pressure of 75-85KPa.

[0026] The main advantages of the present invention through the above technical solution are as follows:

[0027] (1) The present invention prepares a photocatalytic composite material by mixing specific raw materials, potassium titanium oxalate, water, ethylene glycol, N,N-dimethylformamide and silver nitrate, wherein ethylene glycol adjusts the morphology of the product titanium dioxide. This material has high product selectivity when used in the photocatalytic reduction of CO2 reaction.

[0028] (2) The photocatalytic composite material synthesized in this invention can extend the light absorption range to the visible light region, improve the photocatalytic performance, and can effectively convert CO2 molecules into methane.

[0029] (3) This method is simple and effective, and the prepared photocatalytic composite material has high stability and activity. Attached Figure Description

[0030] Figure 1 These are X-ray diffraction (XRD) patterns of the materials prepared in Example 1 and Comparative Examples 1 and 2.

[0031] Figure 2 These are X-ray photoelectron spectroscopy (XPS) spectra of the materials prepared in Example 1 and Comparative Examples 1 and 2.

[0032] Figure 3 These are scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS-mapping) images of the material prepared in Example 1.

[0033] Figure 4 These are the ultraviolet-visible diffuse reflectance spectra of the materials prepared in Example 1 and Comparative Examples 1 and 2. Detailed Implementation

[0034] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] The present invention provides a photocatalytic composite material comprising a matrix material and elemental silver loaded on the matrix material, wherein the matrix material is TiO2 nanospheres doped with nitrogen and potassium ions.

[0037] The inventors discovered that a photocatalytic composite material obtained by loading elemental silver onto a matrix material in which nitrogen and potassium ions are simultaneously doped into TiO2 nanospheres can effectively improve the efficiency of photocatalytic reduction of CO2 to methane, and the efficiency of methane production can reach up to 110 μmol / g / h.

[0038] In this invention, the content of elemental silver, nitrogen, and potassium ions in the photocatalytic composite material has a significant impact on improving the efficiency of photocatalytic reduction of CO2 to methane. To further improve the efficiency of photocatalytic reduction of CO2 to methane, the content of elemental silver, nitrogen, and potassium ions needs to be controlled within appropriate ranges.

[0039] In a preferred embodiment, based on the total weight of the photocatalytic composite material, the content of the elemental silver can be 2 to 12% by weight, more preferably 5.5 to 8.5% by weight, for example 5.58% by weight, 6.48% by weight, 7.17% by weight, 7.9% by weight, 8.15% by weight, or 8.48% by weight, and any value within the range formed by any two of these values.

[0040] In a preferred embodiment, based on the total weight of the photocatalytic composite material, the nitrogen content can be 0.3–0.9 wt%, more preferably 0.45–0.76 wt%, for example 0.45 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, or 0.76 wt%; the potassium ion content is 0.4–3 wt%, more preferably 0.4–2.6 wt%, for example 0.42 wt%, 0.45 wt%, 0.46 wt%, 1.5 wt%, 2.11 wt%, or 2.59 wt%.

[0041] In the photocatalytic composite material described in this invention, by controlling the particle size of the TiO2 nanospheres, the specific surface area of ​​the microspheres can be increased, thereby increasing the absorption of visible light and promoting the photocatalytic reduction of carbon dioxide. In a specific embodiment, the particle size of the TiO2 nanospheres can be 200–1400 nm.

[0042] In a preferred embodiment, a photocatalytic composite material having the aforementioned specific morphological and size characteristics, and with the content of each element controlled within the range described above, can effectively improve the reactive sites, thereby effectively improving the performance of photocatalytic reduction of CO2 to methane.

[0043] A second aspect of the present invention provides a method for preparing the photocatalytic composite material described in the first aspect, the method comprising the following steps:

[0044] (1) Mix potassium titanium oxalate, water, ethylene glycol, N,N-dimethylformamide and silver nitrate to obtain a mixed solution;

[0045] (2) The mixed solution was subjected to a hydrothermal reaction, centrifuged, washed and dried to obtain a photocatalytic composite material.

[0046] There is no specific restriction on the order of adding materials in the method described in this invention, as long as the raw materials can be mixed and reacted.

[0047] In a specific embodiment, the method for preparing photocatalytic composite materials includes:

[0048] S1. Disperse potassium titanium oxalate in distilled water, then add ethylene glycol and sonicate, followed by adding dimethylformamide and sonicating until uniform dispersion is achieved, to obtain solution A;

[0049] S2. Mix solution A with silver nitrate solution to obtain solution B;

[0050] S3. Solution B is subjected to a hydrothermal reaction. After the reaction is completed, the solution is cooled, centrifuged, washed, and dried to obtain the photocatalytic composite material.

[0051] In the method described in this invention, potassium titanium oxalate in step (1) is used to provide titanium and potassium sources, ethylene glycol can be used to adjust the morphology, and N,N-dimethylformamide is used to provide nitrogen source.

[0052] According to the present invention, in order to obtain a photocatalytic composite material with appropriate amounts of metallic silver, nitrogen, and potassium ions, and to improve the efficiency of photocatalytic reduction of CO2 to methane, it is necessary to limit the ratio of potassium titanium oxalate to ethylene glycol, potassium titanium oxalate to N,N-dimethylformamide, and potassium titanium oxalate to silver nitrate to an appropriate range.

[0053] In a specific embodiment, the ratio of potassium titanium oxalate to water can be 1g:5 to 60mL, for example, 1g:5mL, 1g:10mL, 1g:15mL, 1g:18mL, 1g:20mL, 1g:25mL, 1g:30mL, 1g:50mL, 1g:55mL or 1g:60mL.

[0054] In the method described in this invention, under preferred conditions, the ratio of potassium titanium oxalate to ethylene glycol in step (1) can be 1g:10-50mL, for example 1g:10mL, 1g:15mL, 1g:20mL, 1g:25mL, 1g:30mL, 1g:32mL, 1g:35mL, 1g:40mL, 1g:45mL or 1g:50mL.

[0055] In the method described in this invention, under preferred conditions, the ratio of potassium titanium oxalate to N,N-dimethylformamide in step (1) can be 1g:2.5-30mL, for example 1g:2.5mL, 1g:5mL, 1g:7.5mL, 1g:10mL, 1g:12.5mL, 1g:15mL, 1g:17.5mL, 1g:20mL, 1g:25mL, 1g:27.5mL or 1g:30mL.

[0056] In the method described in this invention, under preferred conditions, the weight ratio of potassium titanium oxalate to silver nitrate in step (1) can be 1g:20-130mg, for example 1g:20mg, 1g:24mg, 1g:30mg, 1g:50mg, 1g:60mg, 1g:75mg, 1g:86mg, 1g:97mg, 1g:114mg, 1g:127mg or 1g:130mg.

[0057] In the method described in this invention, in step (2), in order to make the reaction effective and obtain a high-performance photocatalytic composite material, it is necessary to carry out the reaction under specific conditions.

[0058] In a specific embodiment, the reaction temperature can be 150–220°C, for example, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 205°C, 210°C, or 220°C, preferably 160–200°C; the reaction time can be 8–24 hours, for example, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, or 24 hours, preferably 10–15 hours.

[0059] In the method described in this invention, step (2) further includes: after the hydrothermal reaction is completed, the hydrothermal reactor is cooled to room temperature, the precipitate is collected by centrifugation, washed with anhydrous ethanol and deionized water, and then dried in a vacuum drying oven to obtain the photocatalytic composite material.

[0060] In a more specific embodiment, the method for preparing the photocatalytic composite material includes:

[0061] S1. Disperse potassium titanium oxalate in distilled water, then add ethylene glycol and sonicate, followed by N,N-dimethylformamide and sonicate to disperse evenly, to obtain solution A;

[0062] S2. Mix solution A with silver nitrate solution to obtain solution B;

[0063] S3. Place solution B in a reaction vessel and carry out a hydrothermal reaction at 150-220℃ for 8-24 hours. After the reaction is completed, cool, centrifuge, wash, and dry to obtain the photocatalytic composite material.

[0064] A third aspect of the present invention provides a catalytic composite material prepared by the method described in the second aspect above. This catalytic composite material can effectively improve the performance of photocatalytic reduction of CO2 to methane.

[0065] The fourth aspect of the present invention provides a method for photocatalytic reduction of CO2 to prepare methane, the method comprising: passing CO2 into a photoreactor containing a catalyst and a reaction solution to carry out a photocatalytic reduction reaction; wherein the catalyst is the photocatalytic composite material described in the first aspect above or the photocatalytic composite material described in the third aspect above.

[0066] In a specific implementation, the light source can be a xenon lamp, and the power of the light source can be 150 to 300W, such as 150W, 160W, 170W, 180W, 190W, 220W, 240W, 260W, 280W or 300W.

[0067] In the method described in this invention, the reaction solution is deionized water, which provides electrons in the photocatalytic reduction of CO2. The ratio of reaction solution to catalyst can be 1 mL: 10 to 30 mg, for example, 1 mL: 10 mg, 1 mL: 12 mg, 1 mL: 14 mg, 1 mL: 16 mg, 1 mL: 18 mg, 1 mL: 20 mg, 1 mL: 22 mg, 1 mL: 24 mg, 1 mL: 25 mg, or 1 mL: 30 mg.

[0068] In the method described in this invention, CO2 is blown into the photoreactor through a gas bag to maintain the pressure inside the reactor at 75-85 kPa, for example, 75 kPa, 76 kPa, 76 kPa, 77 kPa, 78 kPa, 79 kPa, 80 kPa, 82 kPa, 83 kPa or 85 kPa.

[0069] The present invention will be described in detail below through examples. Unless otherwise specified, all methods are conventional in the art. Unless otherwise specified, the experimental materials used in the following examples can be purchased from biochemical reagent stores.

[0070] Example 1

[0071] (1) Disperse 1.4g of potassium titanium oxalate in 25mL of distilled water, then add 30mL of ethylene glycol and sonicate, then add 15mL of N,N-dimethylformamide and sonicate to disperse evenly to obtain solution A;

[0072] (2) Mix 84.9 mg of silver nitrate with 500 μL of water to obtain a silver nitrate solution;

[0073] (3) Add the silver nitrate solution to the solution A to obtain solution B;

[0074] (4) Pour the solution B into the reaction vessel and hydrothermally react at 180°C for 12 hours. After the reaction is completed, wait for the hydrothermal vessel to cool to room temperature, centrifuge the reaction product, and then wash the obtained solid part with anhydrous ethanol and deionized water, and dry it in a vacuum drying oven to obtain N / K-TiO2-Ag photocatalytic composite material.

[0075] Example 2

[0076] (1) Disperse 1.4g of potassium titanium oxalate in 25mL of distilled water, then add 30mL of ethylene glycol and sonicate, then add 15mL of N,N-dimethylformamide and sonicate to disperse evenly to obtain solution A;

[0077] (2) Mix 33.9 mg of silver nitrate with 200 μL of water to obtain a silver nitrate solution;

[0078] (3) Add the silver nitrate solution to the solution A to obtain solution B;

[0079] (4) Pour the solution B into the reaction vessel and hydrothermally react at 220°C for 8 hours. After the reaction is completed, wait for the hydrothermal vessel to cool to room temperature, centrifuge the reaction product, and then wash the obtained solid part with anhydrous ethanol and deionized water, and dry it in a vacuum drying oven to obtain the photocatalytic composite material.

[0080] Example 3

[0081] (1) Disperse 1.4g of potassium titanium oxalate in 25mL of distilled water, then add 30mL of ethylene glycol and sonicate, then add 15mL of N,N-dimethylformamide and sonicate to disperse evenly to obtain solution A;

[0082] (2) Mix 135.9 mg of silver nitrate with 800 μL of water to obtain a silver nitrate solution;

[0083] (3) Add the silver nitrate solution to the solution A to obtain solution B;

[0084] (4) Pour the solution B into the reaction vessel and hydrothermally react at 150°C for 24 hours. After the reaction is completed, wait for the hydrothermal vessel to cool to room temperature, centrifuge the reaction product, and then wash the obtained solid part with anhydrous ethanol and deionized water, and dry it in a vacuum drying oven to obtain the photocatalytic composite material.

[0085] Comparative Example 1

[0086] (1) Disperse 1.4g of potassium titanium oxalate in 70mL of distilled water to obtain solution A;

[0087] (2) Pour solution A into the reaction vessel and hydrothermally react at 180°C for 12 hours. After the reaction is completed, wait for the hydrothermal vessel to cool to room temperature, take out the precipitate from the hydrothermal vessel, wash it with anhydrous ethanol and deionized water, and then put it into a vacuum drying oven to dry it to obtain K-TiO2 catalyst.

[0088] Comparative Example 2

[0089] The method described in Example 1 was followed, except that silver nitrate solution was not added in step (1). The specific process is as follows:

[0090] (1) Add 1.4g of potassium titanium oxalate, 25mL of distilled water and 30mL of ethylene glycol to 15mL of N,N-dimethylformamide and mix them evenly by ultrasonication to obtain solution A;

[0091] (2) Pour solution A into the reaction vessel and hydrothermally react at 180°C for 12 hours. After the reaction is completed, wait for the hydrothermal vessel to cool to room temperature, take out the precipitate from the hydrothermal vessel, wash it with anhydrous ethanol and deionized water, and then put it into a vacuum drying oven to dry it to obtain N / K-TiO2 catalyst.

[0092] Test case

[0093] (1) The contents of elemental silver, nitrogen, and potassium ions in the materials prepared in Examples 1-3 and Comparative Examples 1-2 were detected using X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha). The test results are shown in Table 1. The test results for the materials prepared in Examples 1-3 and Comparative Examples 1-2 are as follows: Figure 2 As shown, from Figure 2 As can be seen, the binding energies of 367.93 and 373.94 eV correspond to the 3d phase of elemental silver in N / K-TiO2-Ag. 5 / 2 and 3D 3 / 2The characteristic peaks at 292.86 and 295.68 eV indicate the presence of potassium ions in the sample, while the peaks at 400.08 and 400.14 eV are attributed to nitrogen elements (NO-Ti bonds) bound to oxygen sites.

[0094] Table 1

[0095] Example 1 5.58 0.76 0.73 Example 2 2.36 0.8 1.58 Example 3 11.61 0.64 0.41 Comparative Example 1 0 0 2.59 Comparative Example 2 0 0.45 0.63

[0096] (2) The particle size of TiO2 nanospheres in the materials prepared in Examples 1-3 and Comparative Examples 1-2 was detected by scanning electron microscopy (SEM), and the results are shown in Table 2. The test results for the material prepared in Example 1 are as follows: Figure 3 As shown, from Figure 3 As can be seen, the N / K-TiO2-Ag prepared in Example 1 exhibits an aggregated, spherical structure, and obvious silver particles can be observed on the surface of the spheres. EDS-mapping results further indicate that the prepared material contains nitrogen, potassium ions, and elemental silver, and is uniformly dispersed.

[0097] Table 2

[0098]

[0099]

[0100] (3) The efficiency of photocatalytic reduction of CO2 to methane was tested. The experimental conditions were: a 300W xenon lamp as the light source, 20mg of catalyst, 80KPa pressure, and 1mL of deionized water as the reaction solution. The test results are shown in Table 3.

[0101] Table 3

[0102] <![CDATA[CH4 efficiency (μmol / g / h)]]> 110 88 67 0 3

[0103] As can be seen from the results in Table 3, the photocatalytic composite material prepared by the present invention can effectively improve the efficiency of photocatalytic reduction of CO2 to CH4.

[0104] (4) Examples 1-3 and Comparative Examples 1-2 were tested respectively, and the test results are as follows:

[0105] Figure 1 The images show the XRD patterns of the materials prepared in Example 1 and Comparative Examples 1 and 2. Figure 1 It can be seen that the diffraction peaks of the sample correspond to the standard card of anatase TiO2 (JCPDS NO.4–477), indicating that the added ethylene glycol, N,N-dimethylformamide and silver nitrate do not affect the crystal structure of TiO2 nanoparticles.

[0106] Figure 4The images show the UV-Vis diffuse reflectance spectra of the materials prepared in Example 1 and Comparative Examples 1-2. The light absorption of all samples is closely related to the electronic transitions from the valence band to the conduction band. Figure 4 It can be seen that, compared with Comparative Examples 1-2, the N / K-TiO2-Ag prepared in Example 1 has an extended light absorption range in the visible light region (400-800nm) and strong absorption.

[0107] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for photocatalytic reduction of CO2 to produce methane, characterized in that, The method includes: passing CO2 into a photoreactor containing a catalyst and a reaction solution to carry out a photocatalytic reduction reaction; The catalyst comprises a matrix material and elemental silver supported on the matrix material, wherein the matrix material is titanium dioxide nanospheres doped with nitrogen and potassium ions. Specifically, based on the total weight of the catalyst, the content of elemental silver is 2-12% by weight, the content of nitrogen is 0.3-0.9% by weight, and the content of potassium ions is 0.4-3% by weight. The titanium dioxide nanospheres have a particle size of 200~1400 nm. The method for preparing the catalyst includes the following steps: (1) Mix potassium titanium oxalate, water, ethylene glycol, N,N-dimethylformamide and silver nitrate to obtain a mixed solution; (2) The mixed solution was subjected to hydrothermal reaction, centrifuged, washed and dried to obtain photocatalytic composite material.

2. The method according to claim 1, characterized in that, Based on the total weight of the catalyst, the content of elemental silver is 5.5 to 8.5% by weight.

3. The method according to claim 1 or 2, characterized in that, Based on the total weight of the catalyst, the nitrogen content is 0.45~0.76% by weight, and the potassium ion content is 0.4~2.6% by weight.

4. The method according to claim 1, characterized in that, In step (1), the ratio of potassium titanium oxalate to water is 1g: 5~60mL.

5. The method according to claim 1 or 4, characterized in that, In step (1), the ratio of potassium titanium oxalate to ethylene glycol is 1g:10~50mL.

6. The method according to claim 1 or 4, characterized in that, In step (1), the ratio of potassium titanium oxalate to N,N-dimethylformamide is 1g:2.5~30mL.

7. The method according to claim 1 or 4, characterized in that, In step (1), the weight ratio of potassium titanium oxalate to silver nitrate is 1g:20~130mg.

8. The method according to claim 1, characterized in that, The method for preparing the catalyst includes the following steps: S1. Disperse potassium titanium oxalate in water, then add ethylene glycol and sonicate, then add N,N-dimethylformamide and sonicate again to obtain solution A; S2. Mix solution A with silver nitrate solution to obtain solution B; S3. Solution B is subjected to a hydrothermal reaction. After the reaction is completed, the solution is cooled, centrifuged, washed, and dried to obtain the catalyst.

9. The method according to claim 1, characterized in that, In step (2), the conditions for the hydrothermal reaction include: a temperature of 150~220℃ and a time of 8~24h.

10. The method according to claim 1, characterized in that, The conditions for the photocatalytic reduction reaction include: a light source power of 150~300W, a reaction solution to catalyst ratio of 1mL:10~30mg, and a pressure of 75~85KPa.

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