Preparation method of Au nanoparticle modified photocatalyst and application thereof

Abstract

The application belongs to the technical field of photocatalysts, and particularly relates to a preparation method of a photocatalyst for Au nanoparticle modification and application thereof. The ZnO / TiO2 heterojunction can be controllably prepared by a hydrothermal method, a heterojunction interface in close contact is formed, and chemical reduction deposition is carried out under the condition of an ice water bath. The obtained Au nanoparticles are uniformly dispersed on the surface of the carrier, which is conducive to fully exerting the local surface plasmon resonance effect. TiN is loaded on the quartz wool, the three-dimensional porous structure of the quartz wool is used to realize rapid transport of gas and water vapor, TiN has strong absorption and light-heat conversion capacity in the near-infrared region, can locally heat up to accelerate ethanol desorption and inhibit peroxidation. The Au / ZnO / TiO2 dispersion liquid is uniformly coated on the surface of the TiN / quartz wool by using an ultrasonic spraying method. The quartz wool has good mechanical strength and chemical inertness as a flexible skeleton, TiN is combined with the Au nanoparticles firmly, and the combination is suitable for photocatalytic reaction.

Description

Technical Field

[0001] This invention belongs to the field of photocatalyst technology, specifically relating to a method for preparing photocatalysts modified with Au nanoparticles and their applications. Background Technology

[0002] Methane, a potent greenhouse gas, is also an abundant carbon resource found in natural gas, biogas, and coal mine emissions, but its utilization rate remains very low (HD Gesser, NR Hunter, CB Prakash, The direct conversion of methane to methanol by controlled oxidation. Chemical Reviews 85, 235-244 (1985). NF Dummer et al., Methane Oxidation to Methanol. Chemical Reviews 123, 6359-6411 (2023).). Directly converting it into liquid fuels such as ethanol offers a sustainable, land-saving alternative to biomass-based routes. However, this conversion process faces two fundamental challenges: the high activation energy of the CH bond and the difficulty in forming C / C bonds (especially through asymmetric coupling). Furthermore, the wide variation in methane concentration (from nearly 100% in natural gas to as low as 0.5% in diluted gas sources, as seen in C. Ö.Karacan, FA Ruiz, M. Cotè, S. Phipps, Coal mine methane: A review of capture and utilization practices with benefits to mining safety and to greenhouse gas reduction. International Journal of Coal Geology 86, 121-156 (2011). H. Hosseiniamoli et al., Understanding Structure–Function Relationships in Zeolite-Supported Pd Catalysts for Oxidation of Ventilation Air Methane. ACS Catalysis 8, 5852-5863 (2018)) further complicates its selective and efficient conversion.

[0003] The direct conversion of methane to ethanol is primarily limited by two fundamental barriers: the activation of its strong CH bonds and the formation of C-C bonds (especially through asymmetric coupling). Symmetric radical coupling strategies, such as methyl-methyl (·CH3-·CH3) coupling facilitated by conjugated organic frameworks (e.g., phenyl or triazine polymers reported by Tang et al., J. Xie et al., Methane oxidation to ethanol by amolecular junction photocatalyst. Nature 639, 368-374 (2025).), typically produce ethane as an intermediate, which is subsequently oxidized to ethanol. However, this pathway often suffers from the drawbacks of over-oxidation and the formation of undesirable high-carbon products. Another approach is the asymmetric coupling between ·CH3 and highly reactive species (such as ·CH2OH), which provides a more selective pathway (S. Hao et al., Photocatalytic CH4-to-Ethanol Conversion on Asymmetric Multishelled Interfaces. Journal of the American Chemical Society 146, 25870-25877 (2024)). However, ·CH2OH is usually formed through indirect conversion of relatively stable oxygen-containing intermediates (such as CH3OH, CO, or ·CH3OOH) (J. Mao et al., Directconversion of methane with O2 at room temperature over edge-rich MoS2. NatureCatalysis 6, 1052-1061 (2023). S. Hao et al., Switching PhotocatalyticMethane Oxidation Toward Ethanol by Tuning Spin States. Angewandte Chemie International Edition 64, e202510241 (2025)), which reduces the overall CC coupling rate. Therefore, achieving rapid in-situ generation and spatial confinement of ·CH2OH, and promoting its direct coupling with ·CH3 under mild conditions, remains a key challenge for the selective production of ethanol from methane.

[0004] To address the challenges in methane-to-ethanol conversion, catalytic strategies capable of precisely controlling and converting short-lived radical intermediates are needed. In this context, localized surface plasmon resonance (LSPR), generated by the collective oscillation of conduction electrons in noble metal nanostructures, has emerged as a powerful tool for modulating interfacial reactivity under photoexcitation. LSPR not only enhances light absorption and hot carrier generation but also selectively activates and stabilizes key intermediates (such as ·CH3 and ·CH2OH) and modulates surface adsorption behavior, thereby facilitating previously difficult-to-achieve reaction pathways. These effects collectively provide a multifunctional platform for driving asymmetric CC coupling reactions under mild and energy-efficient conditions. However, effectively guiding such plasmonic processes to achieve selective product generation, especially for reactions involving multiple transient intermediates and competing pathways, remains a core challenge. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments.

[0006] As one aspect of the present invention, the present invention provides a method for preparing a photocatalyst modified with Au nanoparticles, comprising the following steps: (1) ZnO / TiO2 heterostructure composite material was prepared by hydrothermal method, wherein the molar ratio of ZnO to TiO2 was 3-4:1; (2) The obtained ZnO / TiO2 heterostructure composite material was dispersed in a solvent, and chloroauric acid solution was added and stirred. Gold nanoparticles were deposited on the ZnO / TiO2 heterostructure composite material using a chemical reduction method with NaBH4 as the reducing agent to obtain an Au / ZnO / TiO2 photocatalyst. The amount of chloroauric acid added was controlled at 0.05-1 wt.% based on the theoretical gold loading. (3) TiN powder is dispersed in a solvent to form a suspension, and silica wool is immersed in the suspension. After drying, a TiN / silica wool composite material is obtained; wherein the silica wool thickness is 0.5-2 mm, the silica wool fiber diameter is 10-30 µm, and the TiN loading is 37.8-75.6 g / m² based on the surface area of ​​the silica wool. 2 ; (4) The Au / ZnO / TiO2 photocatalyst obtained in step (2) is dispersed in water to obtain a dispersion. The dispersion is then sprayed onto the surface of the TiN / quartz wool composite material obtained in step (3) using an ultrasonic spraying method. After heating and drying, the Au / ZnO / TiO2 / TiN / quartz wool composite catalyst is obtained.

[0007] As a preferred embodiment of the method for preparing photocatalysts modified with Au nanoparticles according to the present invention, in step (1), the hydrothermal reaction temperature is 95-100℃, the reaction time is 36-48 hours, and calcination is carried out at 450-500℃ for 2-2.5 hours.

[0008] As a preferred embodiment of the method for preparing photocatalysts modified with Au nanoparticles according to the present invention, in step (2), the amount of chloroauric acid added is controlled at 0.05-0.25 wt. based on the theoretical gold loading.

[0009] As a preferred embodiment of the method for preparing photocatalysts modified with Au nanoparticles according to the present invention, in step (2), the reaction is carried out under ice-water bath conditions.

[0010] In a preferred embodiment of the method for preparing photocatalysts modified with Au nanoparticles according to the present invention, in step (3), the loading of TiN is 37.8-56.7 g / m³. 2 .

[0011] As a preferred embodiment of the method for preparing photocatalysts modified with Au nanoparticles according to the present invention, in step (4), the mass ratio of Au / ZnO / TiO2 photocatalyst to water is 1:4-5.

[0012] The present invention also provides the application of the Au / ZnO / TiO2 / TiN / quartz wool composite catalyst prepared by the method described above for preparing photocatalysts modified with Au nanoparticles in the photocatalytic methane oxidation reaction.

[0013] Preferably, in the photocatalytic methane oxidation reaction, a three-wavelength combination of light is used for irradiation, wherein the three-wavelength combination of light is: ultraviolet light with a wavelength of 360 nm, visible light with a wavelength of 540 nm, and infrared light with a wavelength of 850 nm.

[0014] Preferably, the power density of the 360 ​​nm ultraviolet light is 10 mW / cm². 2 The power density of the 540 nm visible light is 8 mW / cm². 2 The power density of the 850 nm infrared light is 89 mW / cm². 2 .

[0015] Preferably, in the photocatalytic methane oxidation reaction, the volume ratio of methane to oxygen is 3:1-17, and the total gas flow rate is 40 mL / min. -1 .

[0016] The beneficial effects of this invention are as follows: This invention enables the controlled preparation of ZnO / TiO2 heterojunctions via a hydrothermal method, forming a tightly contacted heterojunction interface. Chemical reduction deposition is then performed under ice-water bath conditions, resulting in Au nanoparticles uniformly dispersed on the carrier surface. This facilitates the full utilization of localized surface plasmon resonance effects. Furthermore, TiN is loaded onto quartz wool, utilizing its three-dimensional porous structure to achieve rapid gas and water vapor transport. Simultaneously, TiN exhibits strong absorption and photothermal conversion capabilities in the near-infrared region, allowing for localized heating to accelerate ethanol desorption and inhibit peroxidation. Ultrasonic spraying is used to uniformly coat the Au / ZnO / TiO2 dispersion onto the TiN / quartz wool surface. This method is simple, requires no high-temperature or high-pressure equipment, and is easy to scale up. Quartz wool, as a flexible framework, possesses good mechanical strength and chemical inertness, and the TiN and Au nanoparticles are firmly bonded, making it suitable for photocatalytic reactions.

[0017] This invention also provides the application of Au / ZnO / TiO2 / TiN / quartz wool composite catalyst in the photocatalytic oxidation of methane. By combining three wavelength light sources—360 nm (UV), 540 nm (Visible), and 850 nm (Infrared)—it achieves highly efficient and selective conversion of methane to ethanol. Under mild conditions, the ethanol yield reaches 966 μmol g. cat -1 h -1 The selectivity is as high as 96.8%. Ultraviolet light excites CH bond breaking, visible light drives plasma gold to promote C / C asymmetric coupling, and infrared light induces local heating to accelerate product desorption and inhibit excessive oxidation. This invention overcomes the dual challenges of methane activation and C / C bond formation, providing a new approach for the resource utilization of low-concentration methane. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, wherein: Figure 1 This is a schematic diagram of a photocatalytic flow reaction device.

[0019] Figure 2 It is a UV-Vis absorption spectrum.

[0020] Figure 3 Optimization of photocatalytic methane oxidation reaction conditions.

[0021] Figure 4 The photocatalytic methane oxidation efficiency of Au / ZnO / TiO2 is 0.05 wt. %

[0022] Figure 5 High-angle annular dark-field scanning electron microscope image of 0.05 wt.% Au / ZnO / TiO2.

[0023] Figure 6 The effect of illumination conditions on the methane oxidation reaction on the surface of 0.05 wt. % Au / ZnO / TiO2.

[0024] Figure 7 The effect of quartz fiber diameter on catalytic activity.

[0025] Figure 8 The effect of quartz wool thickness on catalytic activity.

[0026] Figure 9 The effect of different light intensities on catalytic activity.

[0027] Figure 10 The effect of different light sources on catalytic activity.

[0028] Figure 11 The image shows the proton NMR spectrum of the product. Detailed Implementation

[0029] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0030] Materials and reagents: All chemical reagents used were commercially available and required no further purification before use. Zinc nitrate hexahydrate (Zn(NO3)2·6H2O, purity ≥99.7%) was purchased from Sinopharm Chemical Reagent Co., Ltd.; anhydrous titanium tetrachloride (TiCl4, purity ≥99.9%) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; urea (purity ≥99.7%) was purchased from TCI Chemicals (Tokyo Chemical Industry Co., Ltd.); chloroauric acid tetrahydrate (HAuCl4·4H2O, purity ≥99.7%) was purchased from Shanghai Tengzhun Biotechnology Co., Ltd.; sodium borohydride (NaBH4, purity ≥99.7%) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; titanium nitride (TiN, particle size 20nm, purity ≥99.7%) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; quartz wool (specifications 100 mm × 100 mm × 1 mm) was purchased from Shanghai Xinhu Experimental Equipment Co., Ltd.; and polyurethane foam was purchased from Kunshan Lvchuang Electronic Technology Co., Ltd. 5,5-Dimethyl-1-pyrrololine-N-oxide (DMPO, purity ≥99.99%, Tongren Chemical), methane (CH4, purity ≥99.999%) and oxygen (O2, purity ≥99.999%) were purchased from Qingdao Kerundong New Energy Co., Ltd.

[0031] Example 1: Preparation of Au / ZnO / TiO2 / TiN / quartz wool composite photocatalyst (1) Preparation of ZnO / TiO2 heterostructure composite materials: Urea (3.00 g, 50.0 mmol) and zinc nitrate hexahydrate (1.427 g, 4.80 mmol) were dissolved in 100 mL of deionized water and stirred for 30 min. Titanium tetrachloride (132 µL, 1.20 mmol) was added dropwise with stirring, and stirring continued for 10 min. The mixture was transferred to a 100 mL PTFE-lined autoclave and reacted at 100 °C for 48 h. After natural cooling, the mixture was centrifuged at 8000 rpm for 10 min and washed 4–5 times with deionized water. It was then vacuum dried at 70 °C for 12 h, ground, and calcined in a muffle furnace at 500 °C for 2 h to obtain a ZnO / TiO2 heterojunction material with a ZnO to TiO2 molar ratio of 4:1.

[0032] (2) Preparation of Au / ZnO / TiO2 photocatalyst: Disperse 100 mg of the above ZnO / TiO2 material in 30 mL of deionized water, sonicate for 5 min, and stir for 2 h. Add 10 mg / mL of HAuCl4 aqueous solution. -1 10 μL of NaBH4 was stirred for 12 h. Separately, 0.06 g (1.58 mmol) of NaBH4 was dissolved in 20 mL of deionized water. The NaBH4 solution was then injected at 0.167 mL / min using a syringe pump under ice-water bath conditions. -1 The injection rate was within 30 min. After centrifugation, the sample was washed 8–10 times with deionized water and dried under vacuum at 80 °C for 12 h to obtain 0.05 wt.% Au / ZnO / TiO2 photocatalyst.

[0033] (3) Preparation of TiN / quartz wool composite material: 20 mg of TiN powder (particle size 20 nm) was dispersed in 3 mL of deionized water and sonicated at 100 W for 5 min. Quartz wool (23 × 23 mm, thickness 1 mm, fiber diameter 10 μm) was immersed in the suspension for 10 min, and this process was repeated several times. The mixture was then removed and vacuum dried at 90 °C for 12 h to obtain a TiN / quartz wool composite material (TiN loading approximately 37.8 g / m³). 2 ).

[0034] (4) Preparation of Au / ZnO / TiO2 / TiN / quartz wool composite catalyst Weigh 5 mg of the Au / ZnO / TiO2 catalyst obtained in step (2) and disperse it in 20 mL of deionized water. Transfer the dispersion to a syringe and spray it onto the surface of the TiN / quartz wool obtained in step (3) using an ultrasonic sprayer with the heating stage set to 80 °C. After spraying, continue heating for 20 min to obtain the Au / ZnO / TiO2 / TiN / quartz wool composite catalyst.

[0035] Example 2: The Au / ZnO / TiO2 / TiN / quartz wool composite catalyst prepared in Example 1 was used for photocatalytic methane oxidation reaction: The composite catalyst was placed in a flow reactor, which was a quartz reactor equipped with three passages, having an outer diameter of 9 cm, an inner diameter of 4 cm, a height of 3 cm, and M6 fixing screws. A CH4:O2 mixture of 3:1 was introduced at a total flow rate of 40 mL / min. -1 Irradiation was performed using a combination of three wavelengths: 360 nm (UV), power density 10 mW / cm² 2 540 nm (visible), power density 8 mW / cm² 2 850 nm (infrared), power density 89 mW / cm² 2 Under these conditions, the ethanol yield reached 966 μmol gcat. -1 h -1 The selectivity rate was 96.8%.

[0036] Study Example 1: (1) Preparation of ZnO / TiO2 heterostructure composite materials: Urea (3.00 g, 50.0 mmol) and zinc nitrate hexahydrate were dissolved in 100 mL of deionized water and stirred for 30 min. Titanium tetrachloride (132 µL, 1.20 mmol) was added dropwise with stirring, and stirring continued for 10 min. The mixture was transferred to a 100 mL PTFE-lined autoclave and reacted at 100 ℃ for 48 h. After natural cooling, the mixture was centrifuged at 8000 rpm for 10 min and washed 4–5 times with deionized water. It was then vacuum dried at 70 ℃ for 12 h, ground, and calcined in a muffle furnace at 500 ℃ for 2 h to obtain a ZnO / TiO2 heterojunction material. The molar ratios of ZnO to TiO2 were adjusted to 1:0, 8:1, 4:1, 2:1, 1:1, 1:2, 1:4, and 0:1, respectively.

[0037] (2) Preparation of TiN / quartz wool composite material: 30 mg of TiN powder (particle size 20 nm) was dispersed in 3 mL of deionized water and sonicated at 100 W for 5 min. Quartz wool (23×23 mm, thickness 1 mm, fiber diameter 10 μm) was immersed in the suspension for 10 min. After repeated immersion several times, the mixture was removed and vacuum dried at 90 °C for 12 h to obtain the TiN / quartz wool composite material.

[0038] (3) Preparation of ZnO / TiO2 / TiN / quartz wool composite catalyst: Weigh 5 mg of the ZnO / TiO2 heterostructure composite material obtained in step (1) and disperse it in 20 mL of deionized water. Transfer the dispersion to a syringe and spray it onto the surface of the TiN / quartz wool obtained in step (2) using an ultrasonic sprayer with the heating stage set to 80 °C. After spraying, continue heating for 20 min to obtain the composite catalyst.

[0039] The photocatalytic methane oxidation reaction was carried out according to the method in Example 2. Experimental results are shown below. Figure 3 The optimal molar ratio of A, ZnO / TiO2 is 4:1.

[0040] Study Example 2: The ultraviolet-visible absorption spectra of each photocatalyst were studied.

[0041] The Au loadings were investigated at 0.01%, 0.05%, 0.25%, 0.5%, and 1%, respectively, which means the photocatalysts in step (2) were 0.01 wt.% Au / ZnO / TiO2 photocatalyst, 0.05 wt.% Au / ZnO / TiO2 photocatalyst, 0.25 wt.% Au / ZnO / TiO2 photocatalyst, 0.5 wt.% Au / ZnO / TiO2 photocatalyst, and 1 wt.% Au / ZnO / TiO2 photocatalyst.

[0042] Examine step (1) the ultraviolet-visible absorption spectrum of ZnO / TiO2 heterostructure composite material.

[0043] Meanwhile, the ultraviolet-visible absorption spectra of 0.05 wt.% Au / ZnO photocatalyst (compared to Example 1, titanium tetrachloride was not added in step (1), and 0.05 wt.% Au / ZnO photocatalyst was prepared according to steps (1) and (2) of Example 1) respectively; and 0.05 wt.% Au / TiO2 photocatalyst (compared to Example 1, zinc nitrate hexahydrate was not added in step (1), and 0.05 wt.% Au / TiO2 photocatalyst was prepared according to steps (1) and (2) of Example 1) were investigated respectively.

[0044] Furthermore, compared with Example 1, in step (1) without adding titanium tetrachloride, the ZnO photocatalyst was prepared according to step (1) of Example 1; and compared with Example 1, in step (1) without adding zinc nitrate hexahydrate, the photocatalyst was prepared according to step (1) of Example 1, and the UV-Vis absorption spectrum was examined.

[0045] See Figure 2 . Figure 2The UV-Vis absorption spectrum shows that the ZnO / TiO2 heterojunction exhibits a characteristic absorption edge at 360 nm, while the Au nanoparticles show a significant LSPR peak at 540 nm, indicating enhanced visible light harvesting ability. Figure 2 A represents the UV-Vis absorption spectrum of all samples. Figure 2 B represents the UV-Vis absorption spectrum of TiN. When gold (Au) is loaded, the catalyst exhibits enhanced absorption in the visible light region (e.g., 540 nm), thereby improving the methane conversion efficiency to some extent. Meanwhile, the prototype photothermal material titanium nitride (TiN) effectively absorbs infrared light (e.g., 850 nm). Figure 2 This allows for localized heating and water evaporation, which is crucial for the desorption of polar products such as ethanol.

[0046] Study Example 3: The effect of TiN loading on the photocatalytic methane oxidation reaction in Example 1 was investigated. Referring to Example 1, the amount of TiN powder added in step (3) of Example 1 was 5 mg, 10 mg, 20 mg, 30 mg, and 40 mg, respectively. All other steps were the same as in Example 1. The photocatalytic methane oxidation reaction was carried out according to the method of Example 2. The experimental results are shown in […]. Figure 3 The optimal loading of TiN for B is 20 mg.

[0047] The effect of Au loading on the photocatalytic methane oxidation reaction in Example 1 was investigated. Referring to Example 1, the Au loading in step (2) of Example 1 was 0.01 wt.%, 0.05 wt.%, 0.25 wt.%, 0.5 wt.%, and 1 wt.%, respectively, to obtain Au / ZnO / TiO2 photocatalysts with different loadings. All other steps were the same as in Example 1. The photocatalytic methane oxidation reaction was carried out according to the method of Example 2. The experimental results are shown in […]. Figure 3 The optimal loading of C and Au is 0.05 wt.%.

[0048] The ZnO / TiO2 / TiN / quartz wool composite catalyst was prepared according to the method in Example 1. The effect of the volume ratio of CH4 to O2 on the yield in the photocatalytic methane oxidation reaction of Example 2 was investigated. (See...) Figure 3 D, from Figure 3 As can be seen from D, the optimal ratio of CH4 to O2 is 3:1.

[0049] The ZnO / TiO2 / TiN / quartz wool composite catalyst was prepared according to the method in Example 1. The effect of the volume ratio of CH4 to O2 on the yield in the photocatalytic methane oxidation reaction of Example 2 was investigated. (See...) Figure 3 D, from Figure 3 As can be seen from D, the effect of gas flow rate on yield is shown in [reference]. Figure 3E, total gas flow rate 40 mL / min -1 Optimal.

[0050] Study Example 4: The ZnO / TiO2 / TiN / quartz wool composite catalyst was prepared according to the method in Example 1. The effects of light wavelength and intensity on the yield were investigated in the photocatalytic methane oxidation reaction of Example 2. Figure 4 and Figure 9 .

[0051] Figure 4 The A wavelength was irradiated with light at wavelengths of 350-420 nm, 540 nm and 850 nm. The other reaction conditions were the same as in Example 2. The highest yield was obtained after irradiation with a combination of three wavelengths of light: 360 nm, 540 nm and 850 nm.

[0052] Figure 4 The B light was irradiated with light of wavelengths of 360 nm, 510-550 nm and 850 nm. All other reaction conditions were the same as in Example 2. Among them, the highest yield was obtained after irradiation with a combination of three wavelengths of light: 360 nm, 540 nm and 850 nm.

[0053] Figure 9 A represents the change in light intensity at 540 nm compared to Example 2, while all other reaction conditions remain the same as in Example 2. Figure 9 In Example B, compared to Example 2, the light intensity at 360 nm was changed, while all other reaction conditions remained the same as in Example 2. Figure 9 As can be seen, the power density at 360 nm (ultraviolet) is 10 mW / cm². 2 540 nm (visible) power density 8 mW / cm² 2 It has the highest yield.

[0054] This invention discovered that under a three-wavelength combination of light at 360 nm, 540 nm, and 850 nm, the formation rate and selectivity of ethanol are significantly improved, reaching 966 μmol g, respectively. cat -1 h -1 And 96.8%.

[0055] Figure 10 Under full-spectrum xenon lamp irradiation, following the method of Example 2, only the light source was changed to a xenon lamp, while other conditions remained the same as in Example 2. It can be seen that methanol remains the main product, with an ethanol selectivity of only 23.7%. Figure 10 ).

[0056] Study Example 5: In Example 1, the effects of fiber fineness and thickness of quartz wool on yield were investigated in step (2). Figure 7The effect of different fiber diameters on catalytic performance was investigated. The highest catalytic performance was achieved under the condition of the optimal fiber diameter (10 μm), indicating that the appropriate fiber diameter has a significant impact on improving catalytic performance. Figure 8 The study demonstrated the effect of different quartz wool thicknesses on catalytic performance. A suitable quartz wool thickness not only facilitates light transmission but also promotes the transport of water vapor. Figure 11 The reliability of the product distribution was proven.

[0057] In addition, to elucidate the structure-performance relationship of the catalyst, we performed aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) analysis. Figure 5 The results showed that gold nanoparticles with an average diameter of 2-3 nm were uniformly dispersed on the ZnO / TiO2 support without compromising the integrity of the support structure. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) provided further mechanistic insights into the plasma-mediated activation pathway. Figure 6 ). Figure 6 To illustrate the effect of illumination conditions on the methane oxidation reaction on the surface of 0.05 wt. % Au / ZnO / TiO2, time-resolved in-situ Fourier transform infrared spectra (30 min) of the methane oxidation reaction of the 0.05 wt. % Au / ZnO / TiO2 catalyst were obtained under illumination systems of (A) 360 nm, (B) 360 + 850 nm, and (C) 540 + 850 nm.

[0058] The methane oxidative coupling reaction is carried out in a flow reactor. Figure 1 ),in, Figure 1 A represents the contrast between the dark state and the illuminated state. Figure 1 B is a schematic diagram of the experimental setup. Figure 1 C represents the top and front views of the reactor. Its catalytic structure consists of three parts: (i) a photocatalyst layer capable of selectively activating and converting methane; (ii) a photothermal evaporation layer that promotes water evaporation to facilitate product desorption and inhibit over-oxidation; and (iii) a floating foam layer that maintains the catalyst at the gas-water interface. The photocatalyst is uniformly deposited on the TiN / quartz wool composite material (photothermal layer) using a spraying method to obtain an integrated catalytic assembly.

[0059] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. The application of a photocatalyst modified with Au nanoparticles in the photocatalytic oxidation of methane to ethanol, characterized in that, The preparation method of the photocatalyst for Au nanoparticle modification includes the following steps: (1) ZnO / TiO2 heterostructure composite material was prepared by hydrothermal method, wherein the molar ratio of ZnO to TiO2 was 3-4:1; (2) The obtained ZnO / TiO2 heterostructure composite material was dispersed in a solvent, and chloroauric acid solution was added and stirred. Gold nanoparticles were deposited on the ZnO / TiO2 heterostructure composite material using a chemical reduction method with NaBH4 as the reducing agent to obtain an Au / ZnO / TiO2 photocatalyst. The amount of chloroauric acid added was controlled at 0.05-1 wt.% based on the theoretical gold loading. (3) TiN powder is dispersed in a solvent to form a suspension, and silica wool is immersed in the suspension. After drying, a TiN / silica wool composite material is obtained; wherein the silica wool thickness is 0.5-2 mm, the silica wool fiber diameter is 10-30 µm, and the TiN loading is 37.8-56.7 g / m² based on the surface area of ​​the silica wool. 2 ; (4) The Au / ZnO / TiO2 photocatalyst obtained in step (2) is dispersed in water to obtain a dispersion. The dispersion is sprayed onto the surface of the TiN / quartz wool composite material obtained in step (3) by ultrasonic spraying. After heating and drying, the Au / ZnO / TiO2 / TiN / quartz wool composite catalyst is obtained. In the photocatalytic oxidation of methane to produce ethanol, irradiation is performed using a three-wavelength combination of light: ultraviolet light at 360 nm, visible light at 540 nm, and infrared light at 850 nm; the power density of the 360 ​​nm ultraviolet light is 10 mW / cm². 2 The power density of the 540 nm visible light is 8 mW / cm². 2 The power density of the 850nm infrared light is 89 mW / cm². 2 The volume ratio of methane to oxygen is 3:1-17, and the total gas flow rate is 40 mL / min. -1 .

2. The application according to claim 1, characterized in that, In step (1), the hydrothermal reaction temperature is 95-100℃, the reaction time is 36-48 hours, and calcination is carried out at 450-500℃ for 2-2.5 hours.

3. The application according to claim 1 or 2, characterized in that, In step (2), the amount of chloroauric acid added is controlled at 0.05-0.25 wt. based on the theoretical gold loading.

4. In the application according to claim 1 or 2, in step (2), the reaction is carried out under ice-water bath conditions.

5. In the application according to claim 1 or 2, in step (4), the mass ratio of Au / ZnO / TiO2 photocatalyst to water is 1:4-5.

Images