Copper-tungsten oxide / zinc oxide heterojunction photocatalysts, their preparation methods and applications

Abstract

This invention discloses a copper-tungsten oxide / zinc oxide heterojunction photocatalyst, its preparation method, and its application, belonging to the field of nanomaterials and photocatalysis technology. Firstly, a single-atom copper-modified plasma W-type photocatalyst is synthesized using a solution-thermal method combined with an impregnation-thermal reduction process. 18 O 49 Nanowires were first prepared; then porous ZnO nanosheets were prepared via a hydrothermal method combined with calcination; finally, single-atom copper-modified plasma W was constructed via electrostatic self-assembly. 18 O 49 Nanowire / porous ZnO nanosheet heterojunction composite material. This invention utilizes the above-described preparation method to prepare Cu-W nanowires with matched band structures. 18 O 49 / ZnO heterojunction can realize the photogenerated electrons of ZnO into the plasma Cu-W 18 O 49 Nanowire implantation stabilizes and increases the surface oxygen vacancy concentration and free electron density, thereby enhancing the surface plasmon resonance effect and promoting the continuous generation of high-energy hot electrons. Single-atom copper active sites and W 18 O 49 The synergistic effect of nanowires enables the enriched hot carriers to efficiently and selectively photocatalytically reduce CO2 to CH4.

Description

Technical Field

[0001] This invention relates to the fields of nanomaterials and photocatalysis, and particularly to copper-tungsten oxide / zinc oxide heterojunction photocatalysts, their preparation methods, and applications. Background Technology

[0002] The excessive consumption of fossil fuels has not only triggered a severe energy crisis but also resulted in massive emissions of greenhouse gases such as CO2, exacerbating global climate change. Converting CO2 into high-value-added chemicals or fuels is crucial for achieving carbon neutrality and sustainable development. Among numerous CO2 conversion technologies, photocatalysis, capable of converting CO2 and H2O into valuable fuels, possesses significant advantages such as being clean and mild, and is considered one of the most promising solutions.

[0003] However, due to the inherent chemical inertness of CO2 molecules and the complex electron coupling and proton transfer processes in photocatalysis, the photocatalytic reduction of CO2 still faces challenges such as low catalytic efficiency and poor product selectivity. An ideal CO2 reduction photocatalyst needs to possess characteristics such as broad-spectrum absorption, efficient charge separation, and specific active sites. Non-metallic plasma tungsten oxide (W... 18 O 49 Due to its unique full-spectrum response, abundant oxygen vacancies, and surface plasmon resonance (SPR) effect, it exhibits excellent photocatalytic CO2 reduction potential. However, W 18 O 49 In practical applications, three key problems still exist: (1) the instability of surface oxygen vacancies leads to a decrease in free electron concentration and SPR light absorption; (2) the plasma hot carrier separation efficiency is low; and (3) there is a lack of design for active sites that can precisely control product selectivity. Therefore, stable W 18 O 49 Surface oxygen vacancy concentration, promoting the separation of plasma hot carriers, and constructing suitable reactive sites are key to achieving efficient and highly selective photocatalytic CO2 reduction. Summary of the Invention

[0004] This invention discloses a copper-tungsten oxide / zinc oxide heterojunction photocatalyst, its preparation method, and its application, solving the aforementioned problems and enriching photothermal electrons in plasma with specific active sites. 18 O 49 On the surface, efficient and highly selective photocatalytic CO2 reduction to produce hydrocarbon fuels is achieved.

[0005] This invention discloses a copper-tungsten oxide / zinc oxide heterojunction photocatalyst, comprising plasma W 18 O 49 Nanowires and ZnO nanosheets, plasma W 18 O 49The nanowires are modified with elemental copper; among them, plasma W 18 O 49 Nanowires and ZnO nanosheets form a heterojunction structure through electrostatic self-assembly, and photogenerated electrons from the ZnO nanosheets can be injected into the plasma W. 18 O 49 Inside the nanowire.

[0006] Preferably, the elemental copper is supported on W in an atomically dispersed form. 18 O 49 On the surface of nanowires, W modified with single-atom copper 18 O 49 Nanowires possess abundant oxygen vacancies and localized surface plasmon resonance effects, exhibiting strong light absorption capabilities in the ultraviolet-visible-near-infrared region.

[0007] Preferably, the ZnO nanosheets have a porous structure and a specific surface area of ​​20-50 m². 2 / g.

[0008] This invention also provides a method for preparing the above-mentioned copper-tungsten oxide / zinc oxide heterojunction photocatalyst, comprising the following steps:

[0009] S1. Preparation of single-atom copper-modified plasma-modified tungsten oxide nanowires;

[0010] S2. Preparation of porous zinc oxide nanosheets;

[0011] S3. The prepared single-atom copper-modified plasma-modified tungsten oxide nanowires and porous zinc oxide nanosheets were ultrasonically dispersed in anhydrous ethanol. Using an electrostatic self-assembly method, the ethanol solution containing single-atom copper-modified plasma-modified tungsten oxide was dropwise added to the ethanol solution containing porous zinc oxide nanosheets. After stirring, the mixture was centrifuged and dried to obtain single-atom copper-modified plasma-modified tungsten oxide nanowires. 18 O 49 / Porous ZnO nanosheet heterojunction photocatalyst.

[0012] Preferably, in step S1, the preparation of plasma-modified copper-modified tungsten oxide includes the following steps:

[0013] S1-1, Dissolve tungsten hexacarbonyl in anhydrous ethanol and carry out a solubility reaction to obtain plasma W. 18 O 49 Nanowires;

[0014] S1-2, Plasma W 18 O 49 Nanowire powder was dispersed in anhydrous ethanol containing copper salt and stirred. After centrifugation and drying, the sample was thermally reduced in a 10% H2 / Ar mixed gas to obtain single-atom copper-modified W. 18 O 49Nanowires.

[0015] Preferably, in step S1-1, the temperature of the heat of dissolution reaction is 150-180℃, and the time is 12-20 hours; the concentration of the hexacarbonyl tungsten in anhydrous ethanol is 5-8 mg / mL; in step S1-2, copper from the copper salt is added and reacted with plasma W 18 O 49 The nanowires have a mass percentage of 0.15%-1.0%, and the thermal reduction temperature is 100-150℃ for 1-3 hours.

[0016] Preferably, in step S2, the preparation of porous zinc oxide nanosheets includes a hydrothermal reaction of zinc nitrate, polyvinylpyrrolidone and urea, collection of precursor powder, and calcination to obtain porous ZnO nanosheets.

[0017] The concentrations of zinc nitrate, polyvinylpyrrolidone, and urea are 5-7 mg / mL, 9-12 mg / mL, and 2-4 mg / mL, respectively; the hydrothermal reaction temperature is 100-150℃, and the reaction time is 8-16 hours; the high-temperature calcination temperature is 300-400℃, and the time is 2-4 hours.

[0018] Preferably, in step S3, the concentration of porous zinc oxide nanosheets in ethanol is 1-3 mg / mL; the mass ratio of single-atom copper-modified plasma-modified tungsten oxide nanowires to porous zinc oxide nanosheets is 5%-25%, and the stirring time is 4-6 hours.

[0019] The present invention also provides the application of the above-mentioned copper-tungsten oxide / zinc oxide heterojunction photocatalyst, wherein the copper-tungsten oxide / zinc oxide heterojunction photocatalyst is applied to photocatalytic CO2 reduction, and the photocatalytic reduction of CO2 to CH4 has a selectivity of ≥80%.

[0020] Therefore, this invention provides a copper-tungsten oxide / zinc oxide heterojunction photocatalyst, its preparation method, and its application, which have the following beneficial effects:

[0021] (1) This invention provides a heterojunction catalyst for photocatalytic CO2 reduction, comprising a single-atom copper-modified plasma W 18 O 49 Nanowires and porous ZnO nanosheets are constructed via electrostatic self-assembly. In this band-matched heterojunction system, photogenerated electrons from ZnO can be injected into a single-atom copper-modified plasma W. 18 O 49 On nanowires, the surface oxygen vacancies were stabilized and the surface free electron concentration was increased, enhancing the single-atom copper-modified W 18 O 49 The surface plasmon resonance effect of nanowires promotes the continuous generation of high-energy hot electrons. With the help of single-atom copper active sites, these electrons are enriched in W...18 O 49 Photogenerated thermal carriers in nanowires can achieve efficient and highly selective photocatalytic reduction of CO2 to CH4.

[0022] (2) The single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst prepared in this invention can achieve highly efficient and selective CO2 reduction to CH4 at room temperature and pressure, meeting the requirements of the sustainable energy strategy and possessing broad application prospects. Furthermore, the catalyst's synthesis process is simple and easy, the raw materials are inexpensive and abundant, it exhibits high stability, and it is recyclable. These characteristics make it an ideal choice to replace traditional precious metal catalysts and achieve large-scale CO2 resource utilization, holding significant application value in the field of renewable energy.

[0023] 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

[0024] Figure 1 These are characterization diagrams of the synthesized samples in Examples 1-7 of this invention, where a represents ZnO and Cu-W. 18 O 49 and different Cu-W 18 O 49 X-ray diffraction patterns of the loaded copper-tungsten oxide / zinc oxide heterojunction photocatalyst, b represents the Cu foil, CuO, Cu2O reference sample and Cu-W 18 O 49 Fourier transform extended X-ray absorption fine structure;

[0025] Figure 2 These are scanning electron microscope images of the synthesized samples from Examples 1-2 of this invention, where a is the Cu-W prepared in Example 1. 18 O 49 Scanning electron microscope (SEM) images of nanowires, b is a scanning electron microscope image of ZnO prepared in Example 2;

[0026] Figure 3 15% Cu-W prepared in Example 3 of this invention 18 O 49 Microstructure of the ZnO heterojunction, where a is 15% Cu-W 18 O 49 / Transmission electron microscope image of ZnO heterojunction, b is 15% Cu-W 18 O 49 High-resolution transmission electron microscope image of a ZnO heterojunction;

[0027] Figure 4The UV-Vis-NIR diffuse reflectance spectra of the synthesized samples in Examples 1-7 of this invention are shown below.

[0028] Figure 5 The graphs show the photocatalytic CO2 reduction to CH4 and CO performance and CH4 selectivity of the synthesized samples in Examples 1-7 of Application Example 1 of this invention.

[0029] Figure 6 In Application Example 2 of this invention, the 15% Cu-W synthesized in Example 3 is used. 18 O 49 / Performance diagram of four photocatalytic CO2 reduction cycles of the ZnO heterojunction sample. Detailed Implementation

[0030] The present invention will be further described below through specific embodiments. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any way, that is, not intended to limit the scope of protection of the present invention.

[0031] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0032] This invention provides a method for preparing single-atom copper-modified plasma-modified tungsten oxide, which involves dissolving hexacarbonyl tungsten in anhydrous ethanol and undergoing a solubility heat reaction to obtain plasma W. 18 O 49 W 18 O 49 The powder was dispersed in anhydrous ethanol containing copper chloride and stirred. After centrifugation and drying, the sample was thermally reduced in a 10% H2 / Ar mixed gas to obtain W modified with single-atom copper. 18 O 49 .

[0033] In the above-mentioned method for preparing single-atom copper-modified plasma-derived tungsten oxide, the concentration of hexacarbonyl tungsten in ethanol is approximately 5-8 mg / mL; copper from the copper source is added and reacts with W... 18 O 49 The mass percentage is 0.15%-1.0%.

[0034] In the above-mentioned method for preparing plasma-modified tungsten oxide with single-atom copper, the temperature of the heat of dissolution reaction is 150-180℃ and the reaction time is 12-20 hours; the temperature of the thermal reduction reaction in a 10% H2 / Ar mixed gas is 100-150℃ and the reaction time is 1-3 hours.

[0035] This invention also provides a method for preparing a single-atom copper-modified plasma-modified tungsten oxide / zinc oxide heterojunction photocatalyst, wherein the photocatalyst comprises plasma W 18 O 49 Nanowires and ZnO nanosheets, plasma W 18 O 49 The nanowires are modified with elemental copper; among them, plasma W 18 O 49 Nanowires and ZnO nanosheets form a heterojunction structure through electrostatic self-assembly, and photogenerated electrons from the ZnO nanosheets can be injected into the plasma W. 18 O 49 Inside the nanowire.

[0036] A precursor aqueous solution containing zinc nitrate, polyvinylpyrrolidone, and urea was subjected to a hydrothermal reaction. The precursor powder was collected and calcined to obtain porous ZnO nanosheets with a specific surface area of ​​approximately 20-50 m². 2 / g. The prepared single-atom copper-modified W 18 O 49 W nanosheets containing single-atom copper were ultrasonically dispersed in anhydrous ethanol and then electrostatically self-assembled. 18 O 49 An ethanol solution was added dropwise to an ethanol solution containing porous ZnO nanosheets. After stirring, the heterojunction composite material was centrifuged and dried.

[0037] In the above-mentioned method for preparing a single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst, the concentrations of zinc nitrate, polyvinylpyrrolidone, and urea are 5-7 mg / mL, 9-12 mg / mL, and 2-4 mg / mL, respectively; the hydrothermal reaction temperature is 100-150℃, and the reaction time is 8-16 hours; the high-temperature calcination temperature is 300-400℃, and the time is 2-4 hours.

[0038] In the above-mentioned method for preparing a single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst, the concentration of porous ZnO nanosheets in ethanol is 1-3 mg / mL; the single-atom copper-modified plasma W 18 O 49 The mass ratio of the mixed solution to porous ZnO nanosheets is 5%-25%; the stirring time of the mixed solution is 4-6 hours.

[0039] A single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst was obtained using the above preparation method, wherein elemental copper was supported on W in an atomically dispersed form. 18 O 49 On the surface of nanowires, W modified with single-atom copper 18 O 49Nanowires possess abundant oxygen vacancies and localized surface plasmon resonance effects, exhibiting strong light absorption in the ultraviolet-visible-near-infrared region. Furthermore, photogenerated electrons from ZnO nanosheets can be injected into the plasma. 18 O 49 Inside the nanowire.

[0040] The single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst was applied in the photocatalytic reduction of CO2, achieving a selectivity of ≥80% for the photocatalytic reduction of CO2 to CH4.

[0041] The specific method for the photocatalytic CO2 reduction experiment is as follows: the catalyst is ultrasonically dispersed in water to obtain a uniform suspension, the obtained catalyst dispersion is dropped onto a glass slide and dried, the glass slide covered with the catalyst is placed in a reactor, and the photocatalytic CO2 reduction experiment is carried out using a xenon lamp as a simulated sunlight in an atmosphere containing high-purity CO2 and water vapor.

[0042] In the application of the aforementioned single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst in photocatalytic CO2 reduction, the amount of photocatalyst used is 4-6 mg, and the area of ​​the glass slide is 8-12 cm². 2 Add 0.1-0.3 mL of deionized water as water vapor.

[0043] The light source is a 300W xenon lamp with a wavelength range of 200–1100nm and a light intensity of 200–400mW / cm². 2 .

[0044] To provide a clearer and more detailed description of the single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst, its preparation method, and its applications, specific embodiments will be described below.

[0045] Example 1

[0046] This embodiment provides a method for preparing single-atom copper-modified plasma-modified tungsten oxide, specifically including the following steps:

[0047] 170 mg of tungsten hexacarbonyl powder was thoroughly dissolved in 30 mL of anhydrous ethanol under vigorous stirring (800 rpm). The precursor solution was then transferred to a 50 mL PTFE-lined stainless steel autoclave and solvothermal reacted at 180 °C for 16 hours. After the reaction, the mixture was allowed to cool 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 5 hours to obtain plasma W. 18 O 49 Nanowires. 60 mg of plasma was prepared using W... 18 O 49Nanowires were ultrasonically dispersed in 30 mL of anhydrous ethanol containing 0.783 mg of copper dichloride. The suspension was stirred for 4 hours, and the product was centrifuged and dried. The resulting powder sample was placed in a tube furnace and heated to 140 °C in a 10% H2 / Ar mixed gas atmosphere, held at that temperature for 1.5 hours, and then cooled to room temperature to obtain single-atom copper-modified plasma-modified tungsten oxide, i.e., Cu-W. 18 O 49 .

[0048] Example 2

[0049] This embodiment provides a method for preparing porous zinc oxide nanosheets, comprising the following steps: dissolving 0.6 g of zinc nitrate hexahydrate, 0.24 g of urea, and 1 g of polyvinylpyrrolidone in 80 mL of ultrapure water; after stirring for 1 hour, transferring the solution to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave; and hydrothermally reacting at 130 °C for 12 hours. After the reaction is complete, cooling to room temperature, centrifuging, washing, and drying yields a ZnO precursor. Finally, calcining the obtained ZnO precursor at 350 °C for 3 hours yields porous ZnO nanosheets with a specific surface area of ​​approximately 20-50 m² / g. 2 / g.

[0050] Example 3

[0051] This embodiment provides a method for preparing a single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst, including the following steps:

[0052] 30 mg of porous zinc oxide nanosheet powder was ultrasonically dispersed in 15 mL of anhydrous ethanol, and then 4.5 mg of W modified with single-atom copper was added. 18 O 49 The mixture was ultrasonically dispersed in 5 mL of anhydrous ethanol. The single-atom copper-modified W... 18 O 49 The suspension was added dropwise to the ZnO suspension, and the mixture was stirred for 5 hours. The precipitate was collected by centrifugation and dried at 60°C for 5 hours to obtain single-atom copper-modified W. 18 O 49 The / ZnO composite material, namely the plasma-modified tungsten oxide / zinc oxide heterojunction photocatalyst with single-atom copper, is named 15%Cu-W based on the mass ratio of single-atom copper-modified plasma-modified tungsten oxide nanowires to zinc oxide nanosheets. 18 O 49 / ZnO.

[0053] Example 4

[0054] This embodiment provides a method for preparing a single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst. The steps are the same as in Example 3, except that the mass ratio of the single-atom copper-modified plasma tungsten oxide nanowires to zinc oxide nanosheets in this embodiment is 5%, i.e., 5%-Cu-W. 18 O 49 / ZnO.

[0055] Example 5

[0056] This embodiment provides a method for preparing a single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst. The steps are the same as in Example 3, except that in this embodiment, the mass ratio of the single-atom copper-modified plasma tungsten oxide nanowires to zinc oxide nanosheets is 10%, i.e., 10%-Cu-W. 18 O 49 / ZnO.

[0057] Example 6

[0058] This embodiment provides a method for preparing a single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst. The steps are the same as in Example 3, except that the mass ratio of the single-atom copper-modified plasma tungsten oxide nanowires to zinc oxide nanosheets in this embodiment is 20%, i.e., 20%-Cu-W. 18 O 49 / ZnO.

[0059] Example 7

[0060] This embodiment provides a method for preparing a single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst. The steps are the same as in Example 3, except that the mass ratio of the single-atom copper-modified plasma tungsten oxide nanowires to zinc oxide nanosheets in this embodiment is 25%, i.e., 25%-Cu-W. 18 O 49 / ZnO.

[0061] ZnO and Cu-W synthesized in Examples 1-7 18 O 49 and different Cu-W 18 O 49 Cu-W loading 18 O 49 X-ray diffraction analysis was performed on the ZnO heterostructure. Figure 1 As shown in a, the synthesized Cu-W 18 O 49 Both ZnO and ZnO exhibit good crystallinity. Their diffraction peaks and standard diffraction patterns (JCPDS:71-2450) are consistent. 18 O 49() and JCPDS:36-1451(ZnO) correspond one-to-one. With Cu-W 18 O 49 With the increase of load, Cu-W 18 O 49 The (010) crystal plane diffraction peaks gradually appeared, preliminarily verifying Cu-W 18 O 49 Successful preparation of / ZnO heterojunction. Figure 1 b shows the Cu foil, CuO, Cu2O reference sample, and Cu-W. 18 O 49 Fourier transform extended X-ray absorption fine structure analysis revealed that the synthesized Cu-W 18 O 49 The presence of only Cu-O bonds and the absence of typical Cu-Cu bonds proves that Cu exists in plasma W in monatomic form. 18 O 49 Surface. For the prepared Cu-W 18 O 49 ZnO was characterized using scanning electron microscopy, such as... Figure 2 As shown, Cu-W 18 O 49 The morphology of ZnO consists of nanowires with a length of 200-700 nm and a diameter of about 10 nm; the morphology of ZnO consists of randomly porous nanosheets with a size of about 0.5-5 μm stacked together.

[0062] Furthermore, regarding the synthesis of 15% Cu-W 18 O 49 The ZnO heterojunction was characterized by transmission electron microscopy, such as... Figure 3 As shown in a, Cu-W 18 O 49 Nanowires are tightly adhered to the surface of porous ZnO nanosheets. For example... Figure 3 As shown in b, 15% Cu-W 18 O 49 The high-resolution transmission electron microscopy image of the ZnO heterostructure shows two lattice spacings of 0.261 nm and 0.377 nm, corresponding to the (002) crystal plane of ZnO and the Cu-W crystal plane, respectively. 18 O 49 The (010) crystal plane further proves the successful preparation of the heterojunction.

[0063] For the synthesized ZnO, Cu-W 18 O 49 and different Cu-W 18 O 49 Cu-W loading 18 O 49 / ZnO heterojunction was subjected to UV-Vis-NIR diffuse reflectance spectroscopy analysis. For example... Figure 4 As shown, the absorption band edge of porous ZnO nanosheets is around 400 nm, while the enhanced light absorption between 400-1400 nm is due to the presence of oxygen vacancies in ZnO; Cu-W 18 O 49 Two absorption characteristics were observed: intrinsic band absorption and SPR absorption; all different Cu-W 18 O 49 Cu-W loading 18 O 49 The ZnO heterostructure exhibits both ZnO and Cu-W 18 O 49 The absorption characteristics of both increase Cu-W 18 O 49 The loading can improve the visible-near infrared light absorption of the heterojunction.

[0064] Application Example 1

[0065] This application example provides a method for using a single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction in photocatalytic CO2 reduction, specifically including the following steps:

[0066] 5 mg of Cu-W prepared in Examples 1-7 18 O 49 ZnO and different Cu-W 18 O 49 Cu-W loading 18 O 49 The ZnO photocatalyst was ultrasonically dispersed in 0.35 mL of ultrapure water and then uniformly coated on a surface with an area of ​​9.61 cm². 2 The photocatalyst-coated glass slide was dried and then placed into a 160 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, the reactor was purged with high-purity CO2 gas for 15 minutes, and 0.2 mL of water was added to the bottom of the reactor. A 300 W xenon lamp was used as a simulated sunlight source (wavelength 200-1100 nm, light intensity 200 mW / cm²). 2 The photocatalytic CO2 reduction 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 rates of photocatalytic CO2 reduction to CH4 and CO are as follows: Figure 5 As shown, the CH4 and CO yields of porous ZnO nanosheets were 5.85 and 5.36 μmol / g / h, respectively. -1 h-1 Its CH4 production selectivity is only 52.19%; Cu-W 18 O 49 The yields of CH4 and CO from the nanowires were 6.83 and 1.70 μmol g, respectively. -1 h -1 Its CH4 selectivity is as high as 80.06%; with Cu-W 18 O 49 The increased loading of nanowires on porous ZnO nanosheets, Cu-W 18 O 49 The CH4 yield of the / ZnO heterojunction showed a trend of first increasing and then decreasing, among which 15% Cu-W 18 O 49 The ZnO heterojunction exhibited the highest CH4 yield and selectivity, at 32.68 μmol g, respectively. -1 h -1 The yields of CH4 were 87.62% and 87.62%, respectively, for Cu-W. 18 O 49 The nanowires and porous ZnO nanosheets showed a 4.8-fold and 5.6-fold increase in efficiency, respectively. This result validates the advantages of a single-atom copper-modified plasma-modified tungsten oxide / zinc oxide heterojunction in photocatalytic CO2 reduction.

[0068] Application Example 2

[0069] This application example provides a cyclic experiment of a single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction in photocatalytic CO2 reduction. Following the experimental protocol in Application Example 1, the 15% Cu-W2O3 prepared in Example 3 was used... 18 O 49 The ZnO heterojunction was first subjected to a photocatalytic CO2 reduction experiment. After 180 minutes of reaction, the reactor was purged with high-purity CO2 gas for 30 minutes to remove the reduction products generated in the first round of reaction. The experimental scheme in Example 1 was repeated, and a total of four photocatalytic CO2 reduction experiments were conducted.

[0070] The curves showing the changes in CH4 and CO production over time during the four cycles are as follows: Figure 6 As shown in the figure, this catalyst exhibits good stability in photocatalytic CO2 reduction and can be repeatedly recycled.

[0071] In summary, this invention provides a single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst, its preparation method, and its application. The heterojunction photocatalyst is a single-atom copper-modified plasma W... 18 O 49Nanowires and porous ZnO nanosheets are constructed via electrostatic self-assembly. In this band-matched heterojunction system, photogenerated electrons from the porous ZnO nanosheets can be injected into a single-atom copper-modified plasma W. 18 O 49 On nanowires, the surface oxygen vacancies were stabilized and the surface free electron concentration was increased, enhancing the single-atom copper-modified W 18 O 49 The surface plasmon resonance effect of the nanowires promotes the continuous generation of high-energy hot electrons. Furthermore, with the help of single-atom copper active sites, W... 18 O 49 Photogenerated thermal carriers in nanowires can achieve highly efficient and selective photocatalytic reduction of CO2 to CH4. Therefore, this catalyst has significant application value in CO2 conversion 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 copper-tungsten oxide / zinc oxide heterojunction photocatalyst, characterized in that, Including plasma W 18 O 49 Nanowires and ZnO nanosheets, plasma W 18 O 49 The nanowires are modified with elemental copper; among them, plasma W 18 O 49 Nanowires and ZnO nanosheets form a heterojunction structure through electrostatic self-assembly, and photogenerated electrons from the ZnO nanosheets can be injected into the plasma W. 18 O 49 Inside the nanowire; The elemental copper is loaded onto plasma W in an atomically dispersed form. 18 O 49 Nanowire surface; The ZnO nanosheets have a porous structure and a specific surface area of ​​20-50 m². 2 / g.

2. The copper-tungsten oxide / zinc oxide heterojunction photocatalyst according to claim 1, characterized in that, Single-atom copper-modified plasma W 18 O 49 Nanowires possess abundant oxygen vacancies and localized surface plasmon resonance effects, exhibiting strong light absorption capabilities in the ultraviolet-visible-near-infrared region.

3. A method for preparing a copper-tungsten oxide / zinc oxide heterojunction photocatalyst as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. Preparation of single-atom copper-modified plasma W 18 O 49 Nanowires; S2. Preparation of porous ZnO nanosheets; S3. The prepared single-atom copper-modified plasma-modified tungsten oxide nanowires and porous zinc oxide nanosheets were ultrasonically dispersed in anhydrous ethanol. Using an electrostatic self-assembly method, the ethanol solution containing single-atom copper-modified plasma-modified tungsten oxide was dropwise added to the ethanol solution containing porous zinc oxide nanosheets. After stirring, the mixture was centrifuged and dried to obtain single-atom copper-modified plasma-modified tungsten oxide nanowires. 18 O 49 / Porous ZnO nanosheet heterojunction photocatalyst, namely copper-tungsten oxide / zinc oxide heterojunction photocatalyst.

4. The preparation method of the copper-tungsten oxide / zinc oxide heterojunction photocatalyst according to claim 3, characterized in that, In step S1, the plasma W modified with single-atom copper 18 O 49 The preparation includes the following steps: S1-1, Dissolve tungsten hexacarbonyl in anhydrous ethanol and carry out a solubility reaction to obtain plasma W. 18 O 49 Nanowires; S1-2, Plasma W 18 O 49 Nanowire powder was dispersed in anhydrous ethanol containing copper salt and stirred. After centrifugation and drying, the sample was thermally reduced in a 10% H2 / Ar mixed gas to obtain a single-atom copper-modified plasma W. 18 O 49 Nanowires.

5. The preparation method of the copper-tungsten oxide / zinc oxide heterojunction photocatalyst according to claim 4, characterized in that, In step S1-1, the temperature of the heat of dissolution reaction is 150-180℃, and the time is 12-20 hours; the concentration of the hexacarbonyl tungsten in anhydrous ethanol is 5-8 mg / mL; in step S1-2, copper from the copper salt is added and reacted with plasma W 18 O 49 The nanowires have a mass percentage of 0.15%-1.0%, and the thermal reduction temperature is 100-150℃ for 1-3 hours.

6. The method for preparing the copper-tungsten oxide / zinc oxide heterojunction photocatalyst according to claim 3, characterized in that, In step S2, the preparation of porous ZnO nanosheets includes a hydrothermal reaction of zinc nitrate, polyvinylpyrrolidone and urea, collection of precursor powder, and high-temperature calcination to obtain porous ZnO nanosheets. The concentrations of zinc nitrate, polyvinylpyrrolidone, and urea are 5-7 mg / mL, 9-12 mg / mL, and 2-4 mg / mL, respectively; the hydrothermal reaction temperature is 100-150℃, and the reaction time is 8-16 hours; the high-temperature calcination temperature is 300-400℃, and the time is 2-4 hours.

7. The method for preparing the copper-tungsten oxide / zinc oxide heterojunction photocatalyst according to claim 3, characterized in that, In step S3, the concentration of porous ZnO nanosheets in ethanol is 1-3 mg / mL; the mass ratio of single-atom copper-modified plasma-modified tungsten oxide nanowires to porous zinc oxide nanosheets is 5%-25%, and the stirring time is 4-6 hours.

8. The application of a copper-tungsten oxide / zinc oxide heterojunction photocatalyst as described in any one of claims 1-2, characterized in that, The copper-tungsten oxide / zinc oxide heterojunction photocatalyst is used in photocatalytic CO2 reduction, and the selectivity of photocatalytic reduction of CO2 to CH4 is ≥80%.

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