Gold nanoparticle loaded polycrystalline wurtzite zinc oxide photocatalyst, preparation method and application thereof

Abstract

The application discloses gold nanoparticle loaded polycrystal face zinc oxide photocatalyst and a preparation method and application thereof, relates to the fields of catalyst preparation and photocatalysis technology. By means of hydrothermal method and calcination treatment, ZnO nanorods and ZnO nanosheets exposing different crystal faces are prepared by controlling the amount of surfactant; finally, gold nanoparticles are loaded on the ZnO by means of photoreduction method to construct Au-ZnO material. The preparation method disclosed by the application can realize efficient and high-selectivity photocatalytic CH4 oxidation coupling to prepare C2H6 at normal temperature and pressure, meets the requirements of sustainable development energy strategy, and has wide application prospect. By the above method, ZnO nanorods mainly exposing 0110 / 1010 crystal faces and ZnO nanosheets mainly exposing 0001 crystal faces are synthesized, and the performance is optimized by specific crystal face regulation, so that the efficiency of methane oxidation coupling is greatly improved.

Description

Technical Field

[0001] This invention relates to the fields of catalyst preparation and photocatalysis, specifically to a gold nanoparticle-supported polycrystalline zinc oxide photocatalyst, its preparation method, and its application. Background Technology

[0002] CH4 is a major component of natural gas, shale gas, and methane hydrate, and its reserves are abundant. With the increasing depletion of crude oil resources, the resource utilization of CH4, as a potential chemical raw material, not only has economic value but also environmental significance, reducing the chemical industry's dependence on crude oil. Directly converting CH4 into high-value-added multi-carbon (C4) compounds... 2+ ) compounds, such as ethane and ethylene, are a promising method for synthesizing fuels and chemicals, which can improve the utilization efficiency and economic value of CH4.

[0003] However, the CH4 molecule possesses high symmetry and a high CH bond energy (435-439 kJ / mol), making it chemically very stable. This makes its activation and transformation thermodynamically unfavorable, often requiring a large additional energy input. Photocatalysis, utilizing solar energy as a driving force, provides a pathway for CH4 transformation under mild conditions. It breaks the theoretical limitations of steady-state thermodynamic equilibrium, avoiding the high energy consumption and harsh reaction conditions of traditional thermocatalytic methods.

[0004] Research has shown that nano-zinc oxide can efficiently photocatalyze the oxidative coupling of CH4, outperforming most known photocatalysts. Besides being non-toxic, inexpensive, and possessing diverse surface chemistry, zinc oxide's application in gas-phase photocatalysis can also suppress ongoing photocorrosion. These advantages make zinc oxide a highly promising candidate material for achieving cost-effective and efficient photocatalytic CH4 oxidative coupling. Since the photocatalytic activity of a catalyst can be highly dependent on the growth direction of specific crystal faces, studying the performance differences of gold nanoparticle-supported polycrystalline zinc oxide photocatalysts in photocatalytic CH4 oxidative coupling is crucial. Summary of the Invention

[0005] The purpose of this invention is to provide a gold nanoparticle-supported polycrystalline zinc oxide photocatalyst, its preparation method, and its application, thereby solving the above-mentioned problems. By selecting zinc oxide morphologies (nanorrods or nanosheets) that expose specific crystal faces, the photogenerated charge separation capability of the catalyst can be directionally controlled, providing a direct basis for the design of efficient methane photocatalytic systems.

[0006] This invention discloses a gold nanoparticle-supported polycrystalline zinc oxide photocatalyst, comprising zinc oxide and gold nanoparticles supported on zinc oxide by photoreduction, wherein the gold nanoparticles constitute gold particle active sites.

[0007] Preferably, the zinc oxide is either zinc oxide nanorods with the 0110 / 1010 nonpolar crystal planes exposed or zinc oxide nanosheets with the 0001 polar crystal planes exposed.

[0008] Preferably, the specific surface area of ​​the zinc oxide nanorods is 15-20 m². 2 / g; the specific surface area of ​​the zinc oxide nanosheets is 5-10m². 2 / g.

[0009] Preferably, the gold nanoparticle-supported polycrystalline zinc oxide photocatalyst exhibits a surface plasmon resonance effect.

[0010] This invention also provides a method for preparing the above-mentioned gold nanoparticle-supported polycrystalline zinc oxide photocatalyst, comprising the following steps:

[0011] Step (1): Prepare zinc oxide;

[0012] Step (2): Disperse the prepared zinc oxide in anhydrous ethanol containing gold salt and stir. Use photoreduction method to place the solution under a xenon lamp and stir while irradiating. After stirring, centrifuge and dry to obtain gold nanoparticle-supported polycrystalline zinc oxide photocatalyst.

[0013] Preferably, the preparation of zinc oxide nanosheets in step (1) includes the following steps: dissolving zinc acetate, sodium hydroxide and hexadecyltrimethylammonium bromide in deionized water and carrying out a hydrothermal reaction, collecting the precursor powder, and calcining it at high temperature to obtain zinc oxide nanosheets;

[0014] The concentrations of zinc acetate, sodium hydroxide, and hexadecyltrimethylammonium bromide are 3-4 mg / mL, 5-7 mg / mL, and 18-20 mg / mL, respectively; the hydrothermal reaction temperature is 130-180℃, and the reaction time is 14-18 hours; the high-temperature calcination temperature is 300-400℃, and the time is 3-5 hours.

[0015] Preferably, the preparation of zinc oxide nanorods in step (1) includes the following steps: dissolving zinc acetate and sodium hydroxide in anhydrous ethanol and carrying out a solvothermal reaction, collecting the precursor powder, and calcining it at high temperature to obtain zinc oxide nanorods;

[0016] The concentrations of zinc acetate and sodium hydroxide are 9-10 mg / mL and 17-18 mg / mL, respectively; the temperature of the solvothermal reaction is 130-180℃, and the reaction time is 22-26 hours; the high-temperature calcination temperature is 250-350℃, and the time is 1-2 hours.

[0017] Preferably, in step (2), the concentration of zinc oxide in ethanol is 1-3 mg / mL; the mass percentage of gold and zinc oxide is 0.5%-3%; the light source is a 300W xenon lamp with a light intensity of 200-400 mW / cm². 2 The wavelength range is 200-1100nm, and the illumination time is 1-2 hours.

[0018] The gold nanoparticle-supported polycrystalline zinc oxide photocatalyst provided by this invention is applied to photocatalytic CH4 oxidative coupling.

[0019] Therefore, the present invention, employing the above-mentioned gold nanoparticle-supported polycrystalline zinc oxide photocatalyst, its preparation method, and its application, possesses the following beneficial effects:

[0020] (1) This invention provides a catalyst for photocatalytic CH4 oxidative coupling, composed of zinc oxide nanorods / nanosheets loaded with gold nanoparticles. Performance optimization is achieved through specific crystal facet modulation. The catalyst utilizes zinc oxide nanorods (ZnO NRs) with (0110) or (1010) nonpolar crystal faces and zinc oxide nanosheets (ZnONSs) with (0001) polar crystal faces as supports. Due to the significant difference in electron-hole separation capabilities between the two surfaces, the loaded gold nanoparticles (Au NPs) directly form photocatalytic systems with distinctly different performances. Simultaneously, it significantly improves the methane oxidative coupling efficiency. The crystal facet-dependent carrier separation characteristics enable Au-ZnO NRs (nonpolar crystal facet dominant) to achieve four times the photocatalytic methane oxidative coupling performance of Au-ZnONSs (polar crystal facet dominant), significantly improving the formation efficiency of the target product.

[0021] (2) The gold nanoparticle-supported polycrystalline zinc oxide photocatalyst prepared in this invention can achieve highly efficient and selective photocatalytic oxidation-coupling of CH4 to C2H6 at room temperature and pressure, which meets the requirements of the sustainable development energy strategy and has broad application prospects. Furthermore, the catalyst has a simple and easy synthesis process, low-cost and abundant raw materials, excellent stability, and recyclability. These characteristics make it an ideal choice to replace rare and precious metal catalysts, improve CH4 utilization efficiency and economic value, and have significant application value in the field of energy conversion.

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0023] Figure 1 The images shown are scanning electron microscope (SEM) images of the synthesized samples from Examples 1-2 of this invention, where a is an SEM image of the ZnO nanorods prepared in Example 1, and b is an SEM image of the ZnO nanosheets prepared in Example 2.

[0024] Figure 2 The images shown are transmission electron microscope (TEM) images of the synthesized samples in Example 3 of the present invention, wherein a is a TEM image of 1% Au-ZnO NRs prepared in Example 3, and b is a TEM image of 1% Au-ZnO NSs prepared in Example 3.

[0025] Figure 3 The UV-Vis-NIR diffuse reflectance spectra of the synthesized samples in Examples 1-3 of this invention are shown below.

[0026] Figure 4 The X-ray diffraction patterns are of the synthesized samples in Examples 1-2 of this invention;

[0027] Figure 5 The graphs show the photocatalytic CH4 oxidative coupling performance of the synthesized samples in Examples 1-6 of Application Example 1 of this invention to produce C2H6 and C3H8.

[0028] Figure 6 This is a graph showing the performance of a four-cycle photocatalytic CH4 oxidation coupling experiment of the 1% Au-ZnO NRs sample synthesized in Example 3 in Application Example 2 of the present invention. Detailed Implementation

[0029] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0030] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered within the scope of protection of this invention.

[0031] This invention provides a method for preparing zinc oxide nanorods, comprising dissolving zinc acetate and sodium hydroxide in anhydrous ethanol and carrying out a solvothermal reaction, collecting the precursor powder, and calcining it at high temperature to obtain ZnO nanorods with a specific surface area of ​​approximately 15-20 m². 2 / g.

[0032] In the above-mentioned method for preparing zinc oxide nanorods, the concentrations of zinc acetate and sodium hydroxide are 9-10 mg / mL and 17-18 mg / mL, respectively; the temperature of the solvothermal reaction is 130-180℃, and the reaction time is 22-26 hours; the temperature of high-temperature calcination is 250-350℃, and the calcination time is 1-2 hours.

[0033] This invention provides a method for preparing zinc oxide nanosheets. The preparation of ZnO nanosheets includes dissolving zinc acetate, sodium hydroxide, and hexadecyltrimethylammonium bromide in deionized water and carrying out a hydrothermal reaction, collecting the precursor powder, and calcining it at high temperature to obtain ZnO nanosheets with a specific surface area of ​​approximately 5-10 m². 2 / g.

[0034] In the above-mentioned method for preparing zinc oxide nanosheets, the concentrations of zinc acetate, sodium hydroxide, and hexadecyltrimethylammonium bromide are 3-4 mg / mL, 5-7 mg / mL, and 18-20 mg / mL, respectively; the hydrothermal reaction temperature is 130-180℃, and the reaction time is 14-18 hours; the high-temperature calcination temperature is 300-400℃, and the calcination time is 3-5 hours.

[0035] This invention also provides a method for preparing a gold nanoparticle-supported polycrystalline zinc oxide photocatalyst. The prepared ZnO nanorods / nanosheets are dispersed in anhydrous ethanol containing gold salt and stirred. The solution is placed under a xenon lamp for stirring and illumination using a photoreduction method. After stirring, the solution is centrifuged and dried to obtain gold nanoparticle-supported zinc oxide.

[0036] In the above-mentioned method for preparing a gold nanoparticle-supported polycrystalline zinc oxide photocatalyst, the concentration of ZnO nanorods / nanosheets in ethanol is 1-3 mg / mL; the mass percentage of gold and ZnO nanorods / nanosheets in the added gold salt is 0.5%-3%; the light source is a 300W xenon lamp with a light intensity of 200-400 mW / cm². 2 The wavelength range is 200–1100 nm, and the illumination time is 1–2 hours.

[0037] A gold nanoparticle-supported polycrystalline zinc oxide photocatalyst was obtained by the above preparation method. Elemental gold was supported on the surface of ZnO nanorods / nanosheets in the form of nanoparticle dispersion, and the resulting zinc oxide-supported gold nanoparticles exhibited a surface plasmon resonance effect.

[0038] When this gold nanoparticle-supported polycrystalline zinc oxide photocatalyst is applied to the photocatalytic CH4 oxidative coupling, there is a four-fold difference in photocatalytic CH4 oxidative coupling performance between Au-ZnONRs and Au-ZnONSs.

[0039] The specific method for the photocatalytic CH4 oxidative coupling experiment is as follows: the catalyst is ultrasonically dispersed in water to obtain a uniform dispersion, the obtained catalyst dispersion is coated on a glass slide and dried, the glass slide covered with the catalyst is placed in a reactor and sealed, and the photocatalytic CH4 oxidative coupling experiment is carried out using a xenon lamp as simulated sunlight in an atmosphere containing high-purity CH4 and a fixed amount of oxygen.

[0040] In the above-mentioned application of a gold nanoparticle-supported polycrystalline zinc oxide photocatalyst in the photocatalytic oxidative coupling of CH4, the amount of photocatalyst used is 4-6 mg, and the area of ​​the glass slide is 8-12 cm². 2 The volume of oxygen is 0.1-0.3 mL.

[0041] The light source is a 300W xenon lamp with a wavelength range of 200-1100nm and a light intensity of 200-400mW / cm². 2 .

[0042] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0044] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered within the scope of protection of this invention.

[0045] Example 1

[0046] This embodiment provides a method for preparing zinc oxide nanorods, specifically including the following steps:

[0047] 650 mg of zinc acetate powder was thoroughly dispersed in 20 mL of anhydrous ethanol under vigorous stirring (800 rpm). Separately, 1.2 g of sodium hydroxide powder was ultrasonically dispersed in 50 mL of anhydrous ethanol. The sodium hydroxide solution was then slowly added dropwise to the zinc acetate solution to form a precursor solution. The precursor solution was then transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and subjected to a solvothermal reaction at 160 °C for 24 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate obtained by centrifugation was washed repeatedly with anhydrous ethanol and then dried in a vacuum drying oven at 60 °C for 3 hours to obtain ZnO nanorods.

[0048] Example 2

[0049] This embodiment provides a method for preparing zinc oxide nanosheets, comprising the following steps: 210 mg zinc acetate, 300 mg sodium hydroxide, and 1.2 g hexadecyltrimethylammonium bromide are thoroughly dispersed in 60 mL of ultrapure water under vigorous stirring (800 rpm). After stirring for 2 hours, the solution is transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave, and hydrothermally reacted at 160 °C for 15 hours. After the reaction is completed and cooled to room temperature, the precipitate obtained by centrifugation is washed repeatedly with anhydrous ethanol and dried in a vacuum drying oven at 60 °C for 3 hours to obtain ZnO nanosheets.

[0050] Example 3

[0051] This embodiment provides a method for preparing a polycrystalline zinc oxide photocatalyst supported on gold nanoparticles, including the following steps:

[0052] 20 mg of zinc oxide powder was ultrasonically dispersed in 15 mL of anhydrous ethanol. Then, 14 μL of 0.092 M chloroauric acid solution was added dropwise to the zinc oxide dispersion. The mixture was then heated under a xenon lamp with an intensity of 300 mW / cm². 2 Under these conditions, the mixture was stirred and illuminated for 2 hours. The precipitate was collected by repeated centrifugation and washing, and then dried at 60°C for 3 hours to obtain the zinc oxide-supported gold nanoparticle photocatalyst. Based on the mass ratio of gold nanoparticles to zinc oxide, it was named 1% Au-ZnO.

[0053] In this embodiment, the zinc oxide nanorods prepared in Example 1 and the zinc oxide nanosheets prepared in Example 2 were used to prepare the catalyst, and were named 1% Au-ZnO NRs and 1% Au-ZnO NSs respectively according to the different types of zinc oxide.

[0054] Example 4

[0055] This embodiment provides a method for preparing a polycrystalline zinc oxide photocatalyst supported on gold nanoparticles. The steps are the same as in Example 3, except that the mass ratio of gold nanoparticles to zinc oxide in this embodiment is 0.5%, i.e., 0.5% Au-ZnO. In this embodiment, the zinc oxide nanorods prepared in Example 1 and the zinc oxide nanosheets prepared in Example 2 were used to prepare the catalyst, and they were named 0.5% Au-ZnO NRs and 0.5% Au-ZnO NSs, respectively, according to the different types of zinc oxide.

[0056] Example 5

[0057] This embodiment provides a method for preparing a polycrystalline zinc oxide photocatalyst supported on gold nanoparticles. The steps are the same as in Example 3, except that the mass ratio of gold nanoparticles to zinc oxide is 2%, i.e., 2% Au-ZnO. In this embodiment, the zinc oxide nanorods prepared in Example 1 and the zinc oxide nanosheets prepared in Example 2 were used to prepare the catalyst, and were named 2% Au-ZnO NRs and 2% Au-ZnO NSs, respectively, according to the different types of zinc oxide.

[0058] Example 6

[0059] This embodiment provides a method for preparing a polycrystalline zinc oxide photocatalyst supported on gold nanoparticles. The steps are the same as in Example 3, except that the mass ratio of gold nanoparticles to zinc oxide is 3%, i.e., 3% Au-ZnO. In this embodiment, the zinc oxide nanorods prepared in Example 1 and the zinc oxide nanosheets prepared in Example 2 were used to prepare the catalyst, and were named 3% Au-ZnO NRs and 3% Au-ZnO NSs respectively, depending on the type of zinc oxide they contain.

[0060] The ZnO nanorods and ZnO nanosheets synthesized in Examples 1-2 were characterized by scanning electron microscopy. Figure 1 As shown in figure a, the morphology of the ZnO nanorods consists of nanorods with a length of 1-3 μm and a diameter of approximately 20-50 nm. Figure 1 As shown in b, the morphology of ZnO nanosheets consists of randomly stacked nanosheets with a size of approximately 0.2-2 μm.

[0061] Furthermore, the 1% Au-ZnO NRs and 1% Au-ZnO NSs synthesized in Example 3 were characterized by transmission electron microscopy, and the results are as follows: Figure 2 a and Figure 2 As shown in b. (As shown in...) Figure 2 As shown in figure a, gold nanoparticles with a diameter of 10-40 nm are loaded on the surface of ZnO nanorods. Figure 2 As shown in b, gold nanoparticles with a diameter of 10-40 nm are loaded on the surface of ZnO nanosheets.

[0062] The ZnO nanorods, ZnO nanosheets, 1% Au-ZnO NRs, and 1% Au-ZnO NSs synthesized in Examples 1-3 were analyzed by UV-Vis-NIR diffuse reflectance spectroscopy. The results are as follows: Figure 3 As shown, the absorption band edge of ZnO nanorods and ZnO nanosheets is around 400 nm; 1% Au-ZnO NRs and 1% Au-ZnO NSs both exhibit the absorption characteristics of both ZnO and Au, showing SPR absorption at 500-600 nm.

[0063] X-ray diffraction analysis was performed on the ZnO nanorods and ZnO nanosheets synthesized in Examples 1-2. Figure 4 As shown, both the synthesized ZnO nanorods and ZnO nanosheets exhibit good crystallinity. Their diffraction peaks correspond one-to-one with the standard diffraction pattern JCPDS:89-1397 (ZnO), indicating successful material preparation. In the XRD patterns, the zinc oxide nanorods show distinct characteristic peaks at the 0110 and 1010 crystal planes, while the zinc oxide nanosheets show obvious diffraction peaks near the 0001 crystal plane.

[0064] Application Example 1

[0065] This application example provides a method for using a gold nanoparticle-supported polycrystalline zinc oxide photocatalyst in the photocatalytic oxidative coupling of CH4, specifically including the following steps:

[0066] 5 mg of ZnO nanorods, ZnO nanosheets, and Au-ZnO photocatalysts with different gold nanoparticle loadings prepared in Examples 1-6 were ultrasonically dispersed in 0.4 mL of deionized water and uniformly coated onto a substrate with an area of ​​9.61 cm². 2 The photocatalyst-coated glass slide was dried and then placed into a 200 mL reactor. The reactor was then sealed with a thick quartz lid and subjected to vacuum treatment for 15 minutes to remove oxygen. Before the reaction, 159 mL of methane and 3 mL of oxygen were added to the reactor. The reaction was conducted using a 300 W xenon lamp as a simulated sunlight source (wavelength 200-1100 nm, light intensity 300 mW / cm²). 2 The photocatalytic CH4 oxidative coupling experiment was conducted by top irradiation for 180 minutes. During this period, the gaseous reaction products were collected every 30 minutes and monitored and analyzed by gas chromatography.

[0067] The measured yields of photocatalytic CH4 oxidative coupling to C2H6 and C3H8 are as follows: Figure 5 As shown, neither ZnO nanorods nor ZnO nanosheets produced any products; product formation only occurred after gold nanoparticles were loaded onto the zinc oxide surface. With increasing loading of gold nanoparticles onto zinc oxide, the C2H6 yield of Au-ZnO exhibited a trend of first increasing and then decreasing, with the highest C2H6 yield observed at 1% Au-ZnO. Furthermore, there was a four-fold difference in photocatalytic CH4 oxidative coupling performance between 1% Au-ZnO NRs and 1% Au-ZnO NSs.

[0068] Application Example 2

[0069] This application example provides a cyclic experiment on the photocatalytic oxidative coupling of CH4 using gold nanoparticle-supported polycrystalline zinc oxide photocatalysts. Following the experimental protocol in Application Example 1, the 1% Au-ZnO NRs prepared in Example 3 were first subjected to a single photocatalytic CH4 oxidative coupling experiment. After 180 minutes of reaction, the reactor was purged with high-purity N2 gas for 15 minutes and then subjected to vacuum treatment for 15 minutes to remove the reduction products generated in the first round of reaction. The experimental protocol in Example 1 was repeated, resulting in a total of four photocatalytic CH4 oxidative coupling experiments.

[0070] The curves showing the change in C2H6 production over time during the four cycles are as follows: Figure 6 As shown in the figure, this catalyst exhibits good photocatalytic CH4 oxidation coupling stability and can be repeatedly recycled.

[0071] In summary, this invention provides a gold nanoparticle-supported polycrystalline zinc oxide photocatalyst, its preparation method, and its applications. The photocatalyst is constructed by loading gold nanoparticles onto the surface of zinc oxide with different crystal planes via photoreduction. ZnO nanorods are predominantly composed of the 0110 / 1010 crystal plane, while ZnO nanosheets are predominantly composed of the 0001 crystal plane. The different electron-hole separation capabilities of zinc oxide with different crystal planes result in a four-fold difference in photocatalytic CH4 oxidative coupling performance between Au-ZnO NRs and Au-ZnO NSs. Therefore, this catalyst has significant application value in the fields of CH4 oxidative coupling and solar energy utilization.

[0072] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and does not limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A gold nanoparticle-supported polycrystalline zinc oxide photocatalyst, characterized in that, The invention includes zinc oxide and gold nanoparticles loaded on zinc oxide by photoreduction, wherein the gold nanoparticles constitute the active sites of the gold particles. The zinc oxide is zinc oxide nanorods with the 0110 / 1010 nonpolar crystal planes exposed as the main feature; The preparation of the zinc oxide nanorods includes the following steps: dissolving zinc acetate and sodium hydroxide in anhydrous ethanol and carrying out a solvothermal reaction, collecting the precursor powder, and calcining it at high temperature to obtain zinc oxide nanorods; The concentrations of zinc acetate and sodium hydroxide are 9-10 mg / mL and 17-18 mg / mL, respectively; the temperature of the solvothermal reaction is 130-180℃ and the reaction time is 22-26 hours; the high-temperature calcination temperature is 250-350℃ and the time is 1-2 hours.

2. The gold nanoparticle-supported polycrystalline zinc oxide photocatalyst according to claim 1, characterized in that, The zinc oxide nanorods have a specific surface area of ​​15-20 m². 2 / g.

3. The gold nanoparticle-supported polycrystalline zinc oxide photocatalyst according to claim 1, characterized in that, The gold nanoparticle-supported polycrystalline zinc oxide photocatalyst exhibits a surface plasmon resonance effect.

4. A method for preparing a gold nanoparticle-supported polycrystalline zinc oxide photocatalyst as described in any one of claims 1-3, characterized in that, Includes the following steps: Step (1): Prepare zinc oxide; Step (2): Disperse the prepared zinc oxide in anhydrous ethanol containing gold salt and stir. Use photoreduction method to place the solution under a xenon lamp and stir while irradiating. After stirring, centrifuge and dry to obtain gold nanoparticle-supported polycrystalline zinc oxide photocatalyst.

5. The method for preparing the gold nanoparticle-supported polycrystalline zinc oxide photocatalyst according to claim 4, characterized in that, In step (2), the concentration of zinc oxide in ethanol is 1-3 mg / mL; the mass percentage of gold and zinc oxide is 0.5%-3%; the light source is a 300W xenon lamp with a light intensity of 200-400 mW / cm². 2 The wavelength range is 200-1100 nm, and the illumination time is 1-2 hours.

6. An application of the gold nanoparticle-supported polycrystalline zinc oxide photocatalyst as described in any one of claims 1-3, characterized in that, Gold nanoparticles supported on polycrystalline zinc oxide photocatalysts are used in photocatalytic CH4 oxidative coupling.

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