Copper-tungsten oxide / zinc oxide heterojunction photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a copper-tungsten oxide / zinc oxide heterojunction photocatalyst as well as a preparation method and application thereof, and belongs to the technical field of nano materials and photocatalysis. The preparation method comprises the following steps: firstly, synthesizing a monatomic copper modified plasma W18O49 nanowire by adopting a dissolution heat method in combination with an impregnation-thermal reduction process; secondly, preparing a porous ZnO nanosheet by combining a hydrothermal method with calcination treatment; and finally, constructing the plasma W18O49 nanowire / porous ZnO nanosheet heterojunction composite material modified by monatomic copper through electrostatic self-assembly. By the adoption of the preparation method, the Cu-W18O49 / ZnO heterojunction with the matched energy band structure is prepared, photo-induced electrons of ZnO can be injected into plasma Cu-W18O49 nanowires, the surface oxygen vacancy concentration and the free electron density of the plasma Cu-W18O49 nanowires are stabilized and improved, and therefore the surface plasma resonance effect is enhanced, and continuous generation of high-energy hot electrons is promoted. Under the synergistic effect of a monatomic copper active site and the W18O49 nanowire, the enriched hot carriers can efficiently and highly selectively reduce CO2 into CH4 in a photocatalytic manner.

Description

Technical Field

[0001] The present invention relates to the field of nanomaterials and photocatalysis technology, and in particular to a copper-tungsten oxide / zinc oxide heterojunction photocatalyst and a preparation method and application thereof. Background Art

[0002] 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, offers significant advantages such as cleanliness and gentleness, making it considered one of the most promising solutions.

[0003] However, due to the inherent chemical inertness of CO2 molecules and the complex electron-coupled proton transfer process in the photocatalytic process, the current photocatalytic reduction of CO2 still faces challenges such as low catalytic efficiency and poor product selectivity. The ideal CO2 reduction photocatalyst needs to have the characteristics of broad spectrum absorption, efficient charge separation and specific active sites. 18 O 49 ) shows good photocatalytic CO2 reduction potential due to its unique full-spectrum response, abundant oxygen vacancies and surface plasmon resonance (SPR) effect. 18 O 49 There are still three key problems in practical applications: (1) unstable surface oxygen vacancies lead to reduced free electron concentration and SPR light absorption; (2) low efficiency of plasma hot carrier separation; (3) lack of active site design to precisely control product selectivity. 18 O 49 Surface oxygen vacancy concentration, promoting the separation of plasma hot carriers and constructing suitable reaction active sites are the keys to achieving efficient and highly selective photocatalytic CO2 reduction. Summary of the Invention

[0004] The present invention discloses a copper-tungsten oxide / zinc oxide heterojunction photocatalyst and its preparation method and application, which solves the above problems and enriches the photothermal electrons in the plasma W with specific active sites. 18 O 49 surface, achieving efficient and highly selective photocatalytic CO2 reduction to produce hydrocarbon fuels.

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

[0006] Preferably, the element copper is loaded on W in an atomically dispersed form. 18 O 49 Nanowire surface, single-atom copper modified W 18 O 49 The nanowires have abundant oxygen vacancies and localized surface plasmon resonance effects, and have strong light absorption capabilities in the ultraviolet-visible-near-infrared region.

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

[0008] The present 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 plasmonic tungsten oxide nanowires;

[0010] S2, preparing porous zinc oxide nanosheets;

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

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

[0013] S1-1, dissolving tungsten hexacarbonyl in anhydrous ethanol and performing a dissolution thermal reaction to obtain plasma W 18 O 49 nanowires;

[0014] S1-2, the plasma W 18 O 49 The nanowire powder was dispersed in anhydrous ethanol containing copper salt and stirred. The sample was centrifuged and dried and then 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 dissolution heat reaction is 150-180°C 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, the copper in the copper salt is added to the plasma W 18 O 49 The mass percentage of the nanowires is 0.15%-1.0%, the temperature of the thermal reduction is 100-150° C., and the time is 1-3 hours.

[0016] Preferably, in step S2, the preparation of the porous zinc oxide nanosheets comprises subjecting zinc nitrate, polyvinyl pyrrolidone and urea to a hydrothermal reaction, collecting the precursor powder, and calcining the precursor powder to obtain the porous ZnO nanosheets;

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

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

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

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

[0021] (1) The present invention provides a heterojunction catalyst for photocatalytic CO2 reduction, which is composed of plasma W modified by single-atom copper. 18 O 49 Nanowires and porous ZnO nanosheets are constructed by electrostatic self-assembly. In a band-matched heterojunction system, the photogenerated electrons of ZnO can be injected into the plasma W modified by single-atom copper. 18 O 49 On the nanowires, the surface oxygen vacancies were stabilized and the surface free electron concentration was increased, which enhanced the W modified by single-atom copper. 18 O 49 The surface plasmon resonance effect of the nanowires promotes the continuous generation of high-energy hot electrons. With the help of single-atom copper active sites, the W18 O 49 Photogenerated hot carriers in the nanowires can achieve efficient and highly selective photocatalytic CO2 reduction to CH4.

[0022] (2) The single-atom copper-modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst prepared by the present invention can achieve efficient and highly selective CO2 reduction to CH4 at room temperature and pressure, meeting the requirements of sustainable energy strategies and having broad application prospects. In addition, the catalyst synthesis process is simple and easy, the raw materials are inexpensive and abundant in storage, it has high stability, and it has the characteristics of repeated recycling. These characteristics make it an ideal choice to replace traditional precious metal catalysts and realize large-scale CO2 resource utilization, and it has important application value in the field of renewable energy.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Characterization diagram of the samples synthesized in Examples 1-7 of the present invention, wherein a is ZnO, Cu-W 18 O 49 and different Cu-W 18 O 49 X-ray diffraction patterns of loaded copper-tungsten oxide / zinc oxide heterojunction photocatalysts, b is Cu foil, CuO, Cu2O reference sample and Cu-W 18 O 49 Fourier transform extended X-ray absorption fine structure;

[0025] Figure 2 The scanning electron microscope images of the samples synthesized in Example 1-2 of the present invention, wherein a is the Cu-W prepared in Example 1 18 O 49 a is a scanning electron microscopy image of the nanowires, b is a scanning electron microscopy image of the ZnO prepared in Example 2;

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

[0027] Figure 4The UV-visible-near-infrared diffuse reflectance spectra of the synthetic samples of Examples 1-7 of the present invention are shown;

[0028] Figure 5 The performance diagram of photocatalytic CO2 reduction to CH4 and CO and the CH4 selectivity diagram of the synthetic samples of Examples 1-7 in Application Example 1 of the present invention are shown;

[0029] Figure 6 The 15%-Cu-W synthesized in Example 3 in Application Example 2 of the present invention is 18 O 49 Performance diagram of four photocatalytic CO2 reduction cycles of the ZnO heterojunction sample. DETAILED DESCRIPTION

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

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] The present invention provides a method for preparing plasma tungsten oxide modified with single-atom copper, wherein tungsten hexacarbonyl is dissolved in anhydrous ethanol and subjected to a dissolution thermal reaction to obtain plasma W 18 O 49 , W 18 O 49 The powder was dispersed in anhydrous ethanol containing copper chloride and stirred. The sample was centrifuged and dried and then thermally reduced in a 10% H2 / Ar mixed gas to obtain single-atom copper-modified W 18 O 49 .

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

[0034] In the above-mentioned method for preparing plasma tungsten oxide modified with single-atom copper, the temperature of the dissolution thermal reaction is 150-180°C, 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°C, and the reaction time is 1-3 hours.

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

[0036] The precursor aqueous solution containing zinc nitrate, polyvinyl pyrrolidone and urea is subjected to hydrothermal reaction, the precursor powder is collected and calcined to obtain porous ZnO nanosheets with a specific surface area of about 20-50m 2 / g. The prepared single-atom copper modified W 18 O 49 and porous ZnO nanosheets were ultrasonically dispersed in anhydrous ethanol, and the W nanosheets containing single-atom copper were assembled by electrostatic self-assembly. 18 O 49 The ethanol solution is added dropwise to the ethanol solution containing the porous ZnO nanosheets, and after continued stirring, the heterojunction composite material is 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, polyvinyl pyrrolidone, and urea are 5-7 mg / mL, 9-12 mg / mL, and 2-4 mg / mL, respectively; the hydrothermal reaction temperature is 100-150°C, and the reaction time is 8-16 hours; and the high-temperature calcination temperature is 300-400°C, and the reaction time is 2-4 hours.

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

[0039] The above preparation method is used to obtain a single-atom copper modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst, in which the element copper is loaded on the W in an atomically dispersed form. 18 O 49 Nanowire surface, single-atom copper modified W 18 O 49Nanowires have abundant oxygen vacancies and localized surface plasmon resonance effects, and have strong light absorption capabilities in the ultraviolet-visible-near infrared region. The photogenerated electrons of ZnO nanosheets can be injected into the plasma W 18 O 49 Inside the nanowire.

[0040] The single-atom copper modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst is used in photocatalytic CO2 reduction, and the selectivity of photocatalytic reduction of CO2 to CH4 is ≥80%.

[0041] The specific method of the photocatalytic CO2 reduction experiment is as follows: ultrasonically disperse the catalyst in water to obtain a uniform suspension, attach the obtained catalyst dispersion droplets to a glass sheet and dry it, place the glass sheet covered with the catalyst in a reactor, and perform the photocatalytic CO2 reduction experiment using a xenon lamp as simulated sunlight in an atmosphere containing high-purity CO2 and water vapor.

[0042] In the application of the above-mentioned 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 sheet is 8-12 cm 2 , deionized water was added as water vapor in a volume of 0.1-0.3 mL.

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

[0044] In order to more clearly and in detail introduce the single-atom copper modified plasma tungsten oxide / zinc oxide heterojunction photocatalyst and its preparation method and application provided by the present invention, it will be described in conjunction with specific examples below.

[0045] Example 1

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

[0047] 170 mg of tungsten hexacarbonyl powder was fully dissolved in 30 mL of anhydrous ethanol under vigorous stirring (800 rpm). The precursor solution was then transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave and subjected to a solvent thermal reaction at 180 ° C for 16 hours. After the reaction, it was naturally cooled to room temperature, and the precipitate obtained by centrifugation was washed several times with anhydrous ethanol and dried in a vacuum drying oven at 60 ° C for 5 hours to obtain plasma W. 18 O 49 Nanowires. 60 mg of prepared plasma W 18 O 49The nanowires were ultrasonically dispersed in 30 mL of anhydrous ethanol dissolved with 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, heated to 140°C in a 10% H2 / Ar mixture, and kept warm for 1.5 hours. After cooling to room temperature, single-atom copper-modified plasma tungsten oxide, namely Cu-W, was obtained. 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 polyvinyl pyrrolidone in 80 mL of ultrapure water, 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 completed, the mixture is cooled to room temperature, centrifuged, washed and dried to obtain a ZnO precursor. Finally, the obtained ZnO precursor is calcined at 350°C for 3 hours to obtain porous ZnO nanosheets with a specific surface area of approximately 20-50 m 2 / g.

[0050] Example 3

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

[0052] 30 mg of porous ZnO nanosheet powder was ultrasonically dispersed in 15 mL of anhydrous ethanol, and 4.5 mg of single-atom copper-modified W 18 O 49 Ultrasonic dispersion in 5 mL of anhydrous ethanol. 18 O 49 The suspension was added dropwise to the ZnO suspension, and the mixed solution 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 15% Cu-W / ZnO composite material is a single-atom copper-modified plasmonic tungsten oxide / zinc oxide heterojunction photocatalyst. It is named 15% Cu-W based on the mass ratio of single-atom copper-modified plasmonic 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 those in Example 3, except that the mass ratio of the single-atom copper modified plasma tungsten oxide nanowires to the 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 those in Example 3, except that the mass ratio of the single-atom copper modified plasma tungsten oxide nanowires to the zinc oxide nanosheets in this embodiment 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 those in Example 3, except that the mass ratio of the single-atom copper modified plasma tungsten oxide nanowires to the 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 those in Example 3, except that the mass ratio of the single-atom copper modified plasma tungsten oxide nanowires to the zinc oxide nanosheets in this embodiment is 25%, i.e., 25%-Cu-W 18 O 49 / ZnO.

[0061] The ZnO, Cu-W synthesized in Examples 1-7 18 O 49 and different Cu-W 18 O 49 Cu-W loading 18 O 49 / ZnO heterojunction was analyzed by X-ray diffraction. Figure 1 As shown in a, the synthesized Cu-W 18 O 49 Both ZnO and ZnO have good crystallinity, and the diffraction peaks of both are consistent with the standard diffraction pattern JCPDS: 71-2450 (W 18 O 49) and JCPDS:36-1451(ZnO) correspond one to one. 18 O 49 With the increase of Cu-W 18 O 49 The (010) crystal plane diffraction peak gradually appeared, which preliminarily verified that Cu-W 18 O 49 / ZnO heterojunction was successfully prepared. Figure 1 Cu foil, CuO, Cu2O reference samples and Cu-W shown in b 18 O 49 The Fourier transform extended X-ray absorption fine structure shows that the synthesized Cu-W 18 O 49 There are only Cu-O bonds, and no typical Cu-Cu bonds, which proves that Cu exists in the plasma W in the form of single atoms. 18 O 49 Surface. 18 O 49 and ZnO were characterized by scanning electron microscopy, as Figure 2 As shown, Cu-W 18 O 49 The morphology of ZnO is composed of nanowires with a length of 200-700 nm and a diameter of about 10 nm; the morphology of ZnO is composed of irregular porous nanosheets with a size of about 0.5-5 μm stacked together.

[0062] In addition, the synthesized 15%-Cu-W 18 O 49 / ZnO heterojunctions were characterized by transmission electron microscopy, such as Figure 3 As shown in a, Cu-W 18 O 49 The nanowires are tightly attached to the surface of the porous ZnO nanosheets. Figure 3 b, 15%-Cu-W 18 O 49 The high-resolution transmission electron microscopy image of the Cu-W / ZnO heterojunction shows two lattice spacings of 0.261 nm and 0.377 nm, corresponding to the (002) crystal plane of ZnO and the Cu-W 18 O 49 This result further proves the successful preparation of the heterojunction.

[0063] The synthesized ZnO, Cu-W 18 O 49 and different Cu-W 18 O 49 Cu-W loading 18 O 49UV-visible-near-infrared diffuse reflectance spectroscopy was performed on the ZnO / ZnO heterojunction. Figure 4 As shown in Figure 2, the absorption band edge of porous ZnO nanosheets is around 400nm, and the enhanced light absorption between 400-1400nm is due to the presence of oxygen vacancies in ZnO; Cu-W 18 O 49 It shows two absorption characteristics, namely intrinsic band absorption and SPR absorption; all different Cu-W 18 O 49 Cu-W loading 18 O 49 / ZnO heterojunctions show the ZnO and Cu-W 18 O 49 The absorption characteristics of both, increase Cu-W 18 O 49 The loading of can enhance the visible-near-infrared light absorption of the heterojunction.

[0064] Application Example 1

[0065] This application example provides an application of 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 Example 1-7 was added 18 O 49 , ZnO and different Cu-W 18 O 49 Cu-W loading 18 O 49 The ZnO photocatalysts were ultrasonically dispersed in 0.35 mL of ultrapure water and uniformly coated on an area of 9.61 cm 2 After drying, the glass sheet coated with the photocatalyst was placed in a 160 mL reactor, which was then sealed with a thick quartz cover and treated under vacuum 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. The reaction was carried out using a 300 W xenon lamp as a simulated sunlight light source (wavelength 200-1100 nm, light intensity 200 mW / cm 2 ), a photocatalytic CO2 reduction experiment was carried out by top irradiation. The reaction time was 180 minutes, during which the gas 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 in Figure 2, the CH4 and CO production rates of porous ZnO nanosheets were 5.85 and 5.36 μmol g / h, respectively. -1 h-1 ), the selectivity of CH4 production is only 52.19%; Cu-W 18 O 49 The CH4 and CO yields of the nanowires were 6.83 and 1.70 μmol g, respectively. -1 h -1 , its CH4 selectivity is as high as 80.06%; with the Cu-W 18 O 49 The increase of nanowire loading on porous ZnO nanosheets, Cu-W 18 O 49 The CH4 yield of the 15% Cu-W / ZnO heterojunction showed a trend of first increasing and then decreasing. 18 O 49 The / ZnO heterojunction exhibited the highest CH4 yield and selectivity of 32.68 μmol g -1 h -1 and 87.62%, respectively, the CH4 yields of Cu-W 18 O 49 The results show that the prepared single-atom copper-modified plasmonic tungsten oxide / zinc oxide heterojunction has the advantages of 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. According to the experimental scheme in application example 1, the 15% Cu-W prepared in example 3 was 18 O 49 The ZnO / 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 produced in the first round of reaction. The experimental protocol described in Example 1 was repeated for a total of four photocatalytic CO2 reduction experiments.

[0070] The curves of CH4 and CO production over time under the four cycles collected are as follows: Figure 6 As shown in the figure, it can be seen that the catalyst has good photocatalytic CO2 reduction stability and can be repeatedly recycled.

[0071] In summary, the present invention provides a plasma tungsten oxide / zinc oxide heterojunction photocatalyst modified by a single atom of copper and its preparation method and application. The heterojunction photocatalyst is a plasma tungsten oxide / zinc oxide heterojunction photocatalyst modified by a single atom of copper. 18 O 49Nanowires and porous ZnO nanosheets are constructed by electrostatic self-assembly. In a band-matched heterojunction system, photogenerated electrons from the porous ZnO nanosheets can be injected into the single-atom copper-modified plasma W 18 O 49 On the nanowires, the surface oxygen vacancies were stabilized and the surface free electron concentration was increased, which enhanced the W modified by single-atom copper. 18 O 49 The surface plasmon resonance effect of the nanowires promotes the continuous generation of high-energy hot electrons. In addition, with the help of single-atom copper active sites, the W 18 O 49 The photogenerated hot carriers in the nanowires enable efficient and highly selective photocatalytic reduction of CO₂ to CH₄. Therefore, this catalyst has important application value in the fields of CO₂ conversion and solar energy utilization.

[0072] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific implementation method of the present invention and does not limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. 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 decorated with elemental copper; the plasma W 18 O 49 Nanowires and ZnO nanosheets form a heterojunction structure through electrostatic self-assembly, and the photogenerated electrons of ZnO nanosheets can be injected into the plasma W 18 O 49 Inside the nanowire.

2. The copper-tungsten oxide / zinc oxide heterojunction photocatalyst according to claim 1, characterized in that: The elemental copper is loaded into the plasma W in an atomically dispersed form. 18 O 49 Nanowire surface, single-atom copper modified plasma W 18 O 49 The nanowires have abundant oxygen vacancies and localized surface plasmon resonance effects, and have strong light absorption capabilities in the ultraviolet-visible-near-infrared region.

3. The copper-tungsten oxide / zinc oxide heterojunction photocatalyst according to claim 1, characterized in that: The ZnO nanosheets are porous and have a specific surface area of 20-50 m 2 / g.

4. A method for preparing the copper-tungsten oxide / zinc oxide heterojunction photocatalyst according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Preparation of single-atom copper-modified plasma W 18 O 49 nanowires; S2, preparing porous ZnO nanosheets; S3, the prepared single-atom copper modified plasma tungsten oxide nanowires and porous zinc oxide nanosheets were ultrasonically dispersed in anhydrous ethanol respectively, and the ethanol solution containing the single-atom copper modified plasma tungsten oxide was added dropwise to the ethanol solution containing the porous zinc oxide nanosheets by the electrostatic self-assembly method, and after stirring, centrifuged and dried to obtain the single-atom copper modified plasma tungsten oxide nanowires. 18 O 49 / porous ZnO nanosheet heterojunction photocatalyst, namely copper-tungsten oxide / zinc oxide heterojunction photocatalyst.

5. The method for preparing the copper-tungsten oxide / zinc oxide heterojunction photocatalyst according to claim 4, characterized in that: In step S1, the plasma W modified by single-atom copper 18 O 49 The preparation comprises the following steps: S1-1, dissolving tungsten hexacarbonyl in anhydrous ethanol and performing a dissolution thermal reaction to obtain plasma W 18 O 49 nanowires; S1-2, the plasma W 18 O 49 The nanowire powder was dispersed in anhydrous ethanol containing copper salt and stirred. The sample was centrifuged and dried and then thermally reduced in a 10% H2 / Ar mixed gas to obtain single-atom copper modified plasma W. 18 O 49 Nanowires.

6. The method for preparing the copper-tungsten oxide / zinc oxide heterojunction photocatalyst according to claim 5, characterized in that: In step S1-1, the temperature of the dissolution heat reaction is 150-180°C 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, the copper in the copper salt is added to the plasma W 18 O 49 The mass percentage of the nanowires is 0.15%-1.0%, the temperature of the thermal reduction is 100-150° C., and the time is 1-3 hours.

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

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

9. Use of the copper-tungsten oxide / zinc oxide heterojunction photocatalyst according to any one of claims 1 to 3, characterized in that: The copper-tungsten oxide / zinc oxide heterojunction photocatalyst is applied to photocatalytic CO2 reduction, and the selectivity of photocatalytic reduction of CO2 to CH4 is ≥80%.

Images