A composite photocatalyst SnO2 / W 18 O 49 Preparation method and in-situ testing method of electron transport mechanism

Abstract

This invention discloses a composite photocatalyst SnO2 / W 18 O 49 Preparation method and in-situ testing method of electron transport mechanism for SnO2 / W 18 O 49 Composite photocatalyst, then the composite photocatalyst SnO2 / W 18 O 49 As a sample, the sample stage was placed in the instrument's transition chamber for pre-vacuuming. After the vacuum reached the testing requirements, the sample stage was sent into the test chamber for testing. In-situ irradiation XPS technology was used to study electron migration paths at different wavelengths. A light source with a light-guiding fiber was added to the original state, and light was irradiated onto the sample in the test chamber through the instrument's observation window. This invention uses electrospinning to prepare SnO2 nanofibers, followed by the growth of non-noble metal plasma W on them using a solvothermal method. 18 O 49 Nanowires were prepared to obtain LSPR-modified SnO2 / W nanowires with a three-dimensional hierarchical morphology. 18 O 49 A composite photocatalyst. Compared with SnO2, this catalyst exhibits significantly improved photocatalytic activity, with a hydrogen yield 2.79 times that of SnO2. This demonstrates the excellent catalytic performance of the composite photocatalyst prepared in this invention.

Description

Technical Field

[0001] This invention relates to the field of energy materials technology, specifically to a localized surface plasmon resonance (LSPR) modified composite photocatalyst SnO2 / W 18 O 49 Preparation methods and the application of in-situ irradiation XPS in mechanism research. Background Technology

[0002] The global energy shortage and environmental pollution problems are intensifying, attracting widespread social attention. To meet the ever-growing energy demands, seeking sustainable, clean, and efficient new energy production methods is crucial. Solar-driven semiconductor photocatalysis, which splits water and reduces carbon dioxide to produce hydrogen and carbon-based chemical fuels, is known as "artificial photosynthesis" and is an effective way to address the energy crisis and environmental pollution. However, due to inherent drawbacks such as severe recombination of photogenerated carriers and underutilization of the solar spectrum, the photocatalytic efficiency of single semiconductors remains relatively low. To improve the activity of semiconductor photocatalysts, researchers have proposed many modification techniques, such as morphology design, heterostructure construction, co-catalyst loading, introduction of vacancies and doping, and plasma-induced hot electron injection. Single modification methods have limited impact on improving the performance of semiconductor photocatalysts, while multiple modifications can combine the advantages of different methods to jointly enhance the activity of photocatalysts, representing the future direction of photocatalyst design.

[0003] In recent years, the design and construction of highly efficient photocatalysts to produce solar fuels through water splitting and carbon dioxide reduction, directly converting inexhaustible solar energy into chemical energy, has been regarded as an effective solution to the energy crisis and environmental pollution. Morphology design, heterostructure construction, co-catalyst loading, and defect engineering can all effectively improve the efficiency of semiconductor photocatalysts, but this improvement remains relatively limited due to the narrow range of usable solar wavelengths. Of the sunlight reaching the Earth's surface, ultraviolet, visible, and infrared light account for approximately 5%, 45%, and 50%, respectively. How to effectively utilize sunlight in the visible and infrared regions should become a new focus in the design of highly efficient photocatalysts. The localized plasmon surface resonance (LSPR) effect can significantly enhance the light absorption capacity of materials in the visible and infrared regions. Currently, the plasmas used in photocatalyst design are mainly precious metals such as gold and silver, which are expensive and difficult to obtain, making large-scale application impractical. Therefore, how to develop and utilize non-precious metal plasmas to enhance light absorption has become a key focus in current photocatalyst design. Meanwhile, since the excitation behavior of plasma differs from that of conventional semiconductors at different wavelengths, the mechanism by which plasma enhances photocatalyst activity remains unclear. Therefore, exploring reliable and effective methods to study the mechanism of plasma-modified photocatalysts is currently a challenge in the design of plasma photocatalysts. (Non-stoichiometric blue tungsten oxide W) 18 O49 It is a common non-noble metal plasma with a large number of oxygen vacancies on its surface, which can serve as active sites for reactions, and is therefore often used in the design of photocatalysts. Summary of the Invention

[0004] This invention provides a reliable and convenient in-situ testing method for electron transport paths, used to study LSPR-modified composite photocatalysts SnO2 / W. 18 O 49 The transport path of electrons in the plasma. Due to the W plasma 18 O 49 The addition of W significantly enhances the light absorption capacity of the system in the visible and infrared regions, while W 18 O 49 Thermionic electrons excited by the LSPR effect can be injected into the conduction band of SnO2 to participate in the catalytic reaction and enhance the activity of the system. Due to the complex composition and abundant internal interfaces of this multi-component photocatalyst, and the additional photoelectron injection brought about by LSPR, traditional mechanistic research methods cannot accurately describe the electron transport paths under normal conditions and under LSPR excitation, posing significant challenges to mechanistic studies. Therefore, this invention proposes to use in-situ irradiation XPS to study the transfer direction of photogenerated electrons at different wavelengths. The material was irradiated with 300 nm ultraviolet light and 700 nm near-infrared light to investigate the electron transport direction under these two conditions.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A composite photocatalyst SnO2 / W 18 O 49 The preparation method involves dispersing SnO2 nanofibers prepared by electrospinning in anhydrous ethanol, adding tungsten hexachloride and stirring magnetically until a yellow, transparent solution is formed. The solution is then transferred to a hydrothermal reactor for a solvothermal reaction. After cooling to room temperature, the solution is centrifuged three times with deionized water and twice with anhydrous ethanol, and finally vacuum dried to obtain SnO2 / W. 18 O 49 Composite photocatalyst.

[0007] Nanofibers were prepared by electrospinning. The polymer solution flow rate was 0.5–2.0 mL / h, the roller speed was 80–200 rpm, the voltage was 12–25 kV, and the receiving distance between the syringe and the receiving roller was 8–20 cm. Environmental parameters were adjusted as follows: ambient temperature 20–28℃, ambient humidity 40–60%. The precursor solution was injected into a syringe with a needle, and a 20 kV high-voltage electrostatic charge was applied to the needle. Simultaneously, a grounded rotating roller was used to receive the fibers. The obtained nanofibers were dried in a 60℃ electric heating oven for 12 h, and then placed in a muffle furnace at 2℃·min⁻¹. -1 SnO2 nanofibers were obtained by heating the temperature to 600℃ and holding it for 100 min.

[0008] The prepared SnO2 nanofibers were dispersed in a 1:10 mixture of anhydrous ethanol and tungsten hexachloride and magnetically stirred for 7–12 h until a yellow, transparent solution was formed. The solution was then transferred to a 100 mL Teflon-lined stainless steel autoclave and heated to 150–200 °C in an electric forced-air drying oven at a rate of 1–3 °C / min, and held at this temperature for 10–15 h. After cooling to room temperature, the solution was centrifuged three times with deionized water and twice with anhydrous ethanol, and then placed in a vacuum drying oven at 55–60 °C for 8–12 h to obtain SnO2 / W. 18 O 49 Composite photocatalyst.

[0009] The composite photocatalyst SnO2 / W obtained by the preparation method is described above. 18 O 49 In-situ testing method for electron transport mechanism: First, prepare the sample to be tested on the sample stage. After preparation, place the sample stage in the instrument's transition chamber for pre-vacuuming. Once the vacuum meets the testing requirements, send the sample stage into the test chamber for testing. In-situ irradiation XPS technology is used to study electron migration paths at different wavelengths. A light source with a light guide fiber is added to the original state, and light is irradiated onto the sample in the test chamber through the instrument's observation window.

[0010] The irradiation wavelengths of the light source are 300nm ultraviolet light and 700nm near-infrared light, respectively, to study the migration direction of photogenerated electrons under different environments.

[0011] During the pre-vacuuming process, all light sources in the transition chamber and test chamber are turned off, so that the sample is in a completely dark environment. After the pre-vacuuming is completed, the test is conducted under the same completely dark conditions. The test results are the data under the dark conditions. Then, 300nm ultraviolet light and 700nm near-infrared light are added. The test results are the data under the illumination conditions.

[0012] Three-dimensional hierarchical morphology and plasma W 18 O 49The loading greatly improves the system's light absorption capacity in the visible and near-infrared regions, and under sunlight W 18 O 49 Free electrons near the Fermi level are excited into hot electrons via the LSPR effect and injected into the SnO2 conduction band to decompose water and produce hydrogen. Simultaneously, photogenerated electrons excited to the SnO2 conduction band by ultraviolet light flow towards W under the drive of the built-in electric field of the type II heterojunction. 18 O 49 The electrons are transferred to the conduction band and then back to the vicinity of the Fermi level to replenish free electrons. This self-consistent electron transfer mechanism greatly enhances the photocatalytic activity of the system.

[0013] Based on the electron shielding effect, the change in outer electron density caused by the transfer of electrons between components is ultimately reflected in the binding energy of the tested element. An increase in binding energy indicates the outflow of electrons, and vice versa.

[0014] The beneficial effects of this invention are as follows:

[0015] This invention provides an LSPR-modified composite photocatalyst SnO2 / W 18 O 49 This invention employs an in-situ mechanism research method, utilizing in-situ XPS irradiation technology, to investigate the migration direction of photogenerated electrons under 300nm ultraviolet and 700nm near-infrared light, focusing on the characteristics of two materials. Therefore, this invention proposes the preparation of SnO2 nanofibers using in-situ electrospinning technology, followed by the solvothermal growth of W nanofibers on them. 18 O 49 Nanowires were prepared to obtain SnO2 / W 18 O 49 Composite photocatalyst. Due to plasma W 18 O 49 The addition of W significantly enhances the light absorption capacity of the system in the visible and infrared regions, while W 18 O 49 The hot electrons excited by the LSPR effect can be injected into the conduction band of SnO2 to participate in the catalytic reaction and enhance the activity of the system. The reason for the activity enhancement was revealed by in-situ irradiation XPS.

[0016] This invention investigates the LSPR-modified composite photocatalyst SnO2 / W 18 O 49 An in-situ testing method for electron transport mechanisms was employed, using in-situ irradiated XPS to investigate the migration direction of photogenerated electrons under 300 nm ultraviolet and 700 nm near-infrared light irradiation, revealing the reason for the enhanced activity of the composite photocatalyst. This three-dimensional hierarchical morphology and plasma W 18 O 49 The loading greatly improves the system's light absorption capacity in the visible and near-infrared regions, and under sunlight W18 O 49 Free electrons near the Fermi level are excited into hot electrons via the LSPR effect and injected into the SnO2 conduction band to decompose water and produce hydrogen. Simultaneously, photogenerated electrons excited to the SnO2 conduction band by ultraviolet light flow towards W under the drive of the built-in electric field of the type II heterojunction. 18 O 49 The electrons are transferred to the conduction band and then back to the vicinity of the Fermi level to replenish free electrons. This self-consistent electron transfer mechanism greatly enhances the photocatalytic activity of the system.

[0017] The in-situ mechanism research method provided by this invention has the following characteristics: (1) Compared with the ordinary XPS test method, the experimental method with added light can better simulate the scenario of photocatalyst in actual use. (2) Traditional mechanism research methods cannot accurately describe the electron transport path under normal conditions and LSPR excitation, which brings great difficulties to mechanism research, while the XPS test method can reflect the direction of electron transport based on the change of binding energy.

[0018] SnO2 nanofibers will be prepared by electrospinning, followed by the growth of non-noble metal plasma W on them via a solvothermal method. 18 O 49 Nanowires were prepared to obtain LSPR-modified SnO2 / W nanowires with a three-dimensional hierarchical morphology. 18 O 49 A composite photocatalyst. Compared with SnO2, this catalyst exhibits significantly improved photocatalytic activity, with a hydrogen yield 2.79 times that of SnO2. This demonstrates the excellent catalytic performance of the composite photocatalyst prepared in this invention. Attached Figure Description

[0019] Figure 1 To prepare LSPR-modified SnO2 / W 18 O 49 The composite photocatalyst and the XRD and UV-vis DRS spectra of different samples;

[0020] Figure 2 To prepare the LSPR-modified composite photocatalyst SnO2 / W 18 O 49 Topographical diagram;

[0021] Figure 3 The LSPR-modified composite photocatalyst SnO2 / W prepared in Example 1 18 O 49 The results of the activity test;

[0022] Figure 4 Schematic diagram of an in-situ XPS irradiation device;

[0023] Figure 5The figure shows the SnO2 / W prepared in Example 2. 18 O 49 In-situ irradiation XPS spectra of composite photocatalyst samples (a) SnO2 / W 18 O 49 (a) High-resolution W4f in-situ irradiation XPS spectra of the composite photocatalyst under monochromatic light at 300 nm and 700 nm, and (b) Sn3d in-situ irradiation XPS spectra. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention discloses an LSPR-modified composite photocatalyst SnO2 / W 18 O 49 A composite photocatalyst was prepared by electrospinning and subsequent calcination to obtain SnO2 nanofibers formed by stacked nanoparticles. The fibers have a diameter of approximately 400 nm and possess numerous pores and cracks, providing a large number of active sites. The prepared SnO2 / W 18 O 49 The composite photocatalyst grew a large amount of W on the outside of SnO2 nanofibers. 18 O 49 Nanowires, with fibers having a diameter increased to approximately 450 nm.

[0026] The LSPR-modified composite photocatalyst SnO2 / W disclosed in this invention 18 O 49 The preparation method was applied to high-efficiency photocatalysts, and the improvement of semiconductor photocatalyst performance by LSPR modification was verified. The steps are as follows:

[0027] (1) Preparation of SnO2 nanofibers: SnO2 nanofibers were prepared by electrospinning. First, polyvinylpyrrolidone (PVP), tin dichloride, anhydrous ethanol, and N,N-dimethylformamide (DMF) were added to a sample vial and stirred with a magnetic stirrer until a transparent and homogeneous precursor solution was formed. A suitable needle type was selected, and appropriate environmental factors such as temperature and humidity were adjusted using a temperature and humidity control system. Suitable parameters such as rotation speed, injection speed, and step rate were set. The spinning solution was injected into the syringe, and nanofibers were obtained by electrospinning using an electrospinning machine. Finally, SnO2 nanofibers were obtained through drying and high-temperature treatment.

[0028] (2)SnO2 / W 18 O 49 Preparation of composite photocatalyst: The SnO2 nanofibers prepared in step (1) were dispersed in anhydrous ethanol, and then tungsten hexachloride was added and magnetically stirred until a yellow transparent solution was formed. The solution was then transferred to a hydrothermal reactor and subjected to a solvothermal reaction in an electric forced-air drying oven. After the solution cooled to room temperature, it was centrifuged three times with deionized water and twice with anhydrous ethanol, and then vacuum dried to obtain SnO2 / W 18 O 49 Composite photocatalyst;

[0029] (3)SnO2 / W 18 O 49 Mechanism study of composite photocatalysts: In-situ irradiation XPS technology was used to study electron migration pathways at different wavelengths.

[0030] In step (1), the stirring time is 7-12 hours, the drying temperature is 60°C, and the drying time is 12 hours. After mixing 1g of tin dichloride with 2-3g of polyvinylpyrrolidone (PVP), a certain amount of anhydrous ethanol and N,N-dimethylformamide are added and stirred evenly. Next, in step (2), W... 18 O 49 SnO2 nanofibers were prepared using the same method, but without the addition of SnO2 nanofibers during the solvothermal process.

[0031] In step (2), the prepared SnO2 nanofibers were dispersed in a 1:10 mixture of anhydrous ethanol and tungsten hexachloride and magnetically stirred until a yellow, transparent solution was formed. The solution was then transferred to a 100 mL Teflon-lined stainless steel autoclave and heated to 150–200 °C in an electric drying oven at a rate of 1–3 °C / min, and held at this temperature for 10–15 h. After cooling to room temperature, the solution was centrifuged three times with deionized water and twice with anhydrous ethanol, and then dried overnight in a 60 °C vacuum drying oven to obtain SnO2 / W. 18 O 49 Composite photocatalyst.

[0032] In step (3), the prepared SnO2 / W 18 O 49 A composite photocatalyst was adhered to the surface of a conductive adhesive and subjected to in-situ irradiation testing using an XPS instrument. The irradiation sources were selected as ultraviolet light with a wavelength of 300 nm and near-infrared light with a wavelength of 750 nm, respectively, to investigate the differences in electron migration under normal conditions and when the LSPR phenomenon occurs.

[0033] The technical solution of the present invention will be further described below with reference to specific embodiments:

[0034] Example 1

[0035] SnO2, W 18 O 49 LSPR-modified composite photocatalyst SnO2 / W in a ratio of 1:4 18 O 49 The preparation and mechanism study of [the substance] were carried out in the following steps:

[0036] (1) Preparation of SnO2 nanofibers: SnO2 nanofibers were prepared by electrospinning. First, 1.2 g of polyvinylpyrrolidone (PVP), 0.45 g of tin dichloride, 5.6 mL of anhydrous ethanol and 4.6 mL of N,N-dimethylformamide (DMF) were added to a sample vial and stirred overnight with a magnetic stirrer until a transparent and homogeneous precursor solution was formed. The precursor solution was injected into a syringe with a needle, and nanofibers were obtained by electrospinning using an electrospinning machine. The temperature and humidity control parameters were set as follows: temperature 30℃, humidity 20%, etc. The electrospinning parameters were set as follows: a No. 21 needle was selected, the needle injection speed was 0.6 mL / h, the roller speed was 100 rpm, the voltage was 20 kV, and the receiving distance between the syringe and the receiving roller was 12 cm. The precursor solution was injected into the syringe with a needle, and a high voltage of 20 kV was applied to the needle. At the same time, a grounded rotating roller was used to receive the fibers. The obtained nanofibers were dried in an electrically heated drying oven at 60°C for 12 hours, and then placed in a muffle furnace at 2°C·min. -1 SnO2 nanofibers were obtained by heating the temperature to 600℃ and holding it for 100 min.

[0037] (2)SnO2 / W 18 O 49 Preparation of composite photocatalyst: 50 mg of SnO2 nanofibers prepared in step (1) above were dispersed in 30 mL of anhydrous ethanol. Then, 200 mg of tungsten hexachloride was added and the mixture was magnetically stirred until a yellow, transparent solution was formed. The solution was then transferred to a 100 mL Teflon-lined stainless steel high-pressure hydrothermal reactor and heated to 180 °C in an electric forced-air drying oven for 12 h. After cooling to room temperature, the solution was centrifuged three times with deionized water and twice with anhydrous ethanol, and then dried overnight in a 60 °C vacuum drying oven to obtain SnO2 / W 18 O 49 Composite photocatalyst. W 18 O 49 SnO2 nanofibers were prepared using the same method, but without adding them during the solvothermal process.

[0038] (3)SnO2 / W 18 O 49 Mechanism study of composite photocatalysts: SnO2 / W prepared in step (2) above 18 O 49The composite photocatalyst was adhered to the surface of conductive adhesive and then sent to an XPS instrument for in-situ irradiation testing. The X-ray source target of the testing instrument was an aluminum target with a power of 150W and a radiation energy of 1496eV. The irradiation source was a wavelength-tunable high-intensity light source, model PLS EM-150, which was introduced into the chamber through an irradiation device mounted on the side of the equipment to irradiate the sample.

[0039] After preparation, the sample stage is placed in the instrument's transition chamber for pre-vacuuming. Once the vacuum meets the testing requirements, the sample stage is transferred to the test chamber for testing. In-situ irradiation XPS technology is used to study electron migration paths at different wavelengths. A light source with a fiber optic guide is added to the original state, and light is projected onto the sample in the test chamber through the instrument's observation window. During the pre-vacuuming process, all light sources in the transition chamber and test chamber are turned off, placing the sample in complete darkness. After pre-vacuuming, the test is conducted under complete darkness; the results are obtained under these dark conditions. Then, 300nm ultraviolet light and 700nm near-infrared light are added; the results are obtained under illumination conditions.

[0040] Figure 1 The LSPR-modified SnO2 / W prepared in this embodiment 18 O 49 (a) Phase structure diagram of the composite photocatalyst, (b) UV-Vis diffuse reflectance spectrum. From... Figure 1 As can be seen from (a), the prepared W 18 O 49 Nanowires and monoclinic phase W 18 O 49 The prepared SnO2 nanofibers are consistent with the standard card (JCPDS:05-0392), and are consistent with the standard card of tetragonal SnO2 (JCPDS:077-0449). The prepared SnO2 / W 18 O 49 Composite photocatalysts simultaneously possess monoclinic W 18 O 49 The characteristic peaks of tetragonal SnO2 confirm the successful synthesis of the composite material. From... Figure 1 (b) shows that W 18 O 49 The intrinsic absorption cutoff edge is approximately 410 nm, indicating its semiconductor characteristics. In addition, W... 18 O 49 It also has a very broad absorption band from 450 nm to the near-infrared region, reaching an absorption peak at around 1300 nm, which is W 18 O 49 This is caused by a collective resonance of a large number of electrons on the surface, resulting in a SPR effect similar to that of noble metals. Compared with pure SnO2, the composite photocatalyst SnO2 / W...18 O 49 The absorption curve showed a significant upward tilt after 450 nm, proving that the plasma W 18 O 49 Successful loading of nanowires significantly enhances the light absorption capacity of SnO2 in the visible light region.

[0041] Figure 2 The LSPR-modified composite photocatalyst SnO2 / W prepared in Example 1 18 O 49 SEM images; by Figure 2 (a) It can be seen that SnO2 nanofibers formed by stacked nanoparticles can be obtained through electrospinning and subsequent calcination. The fibers have a diameter of approximately 400 nm and possess numerous pores and cracks, providing a large number of active sites. SnO2 nanofibers can also be prepared using a solvothermal method. Figure 2 (b) W 18 O 49 Nanowires, without the addition of any template, will spontaneously cluster into a chrysanthemum-like shape, exposing their active sites. Figure 2 As can be seen in (c), a large number of W atoms grew on the outside of SnO2 nanofibers. 18 O 49 Nanowires, with fibers having a diameter increased to approximately 450 nm.

[0042] Figure 3 The results (a) and (b) obtained in Example 1 are W 18 O 49 SnO2 and SnO2 / W 18 O 49 Hydrogen production and average hydrogen yield as a function of illumination time. Because the conduction band position cannot satisfy the potential required for the hydrogen evolution reaction, W... 18 O 49 It does not possess photocatalytic hydrogen production activity.

[90] Furthermore, SnO2 itself has low photocatalytic hydrogen production activity. This is partly because SnO2 has a wide band gap, preventing it from utilizing light in the visible and near-infrared regions, and partly because of severe recombination of photogenerated carriers within SnO2. 18 O 49 The addition of SnO2 significantly enhances its light absorption capacity in the visible and near-infrared regions, increasing the SnO2 / W ratio. 18 O 49 The hydrogen yield of the composite photocatalyst was significantly improved, reaching 2.79 times that of SnO2.

[0043] Figure 4 This is a schematic diagram of an in-situ XPS irradiation device, SnO2 / W 18 O49 The composite photocatalyst is fixed to the sample stage surface using conductive adhesive. X-ray irradiation of the sample excites photoelectrons to escape from the material surface. These photoelectrons then enter the hemispherical analyzer through an upper lens group, and the corresponding image is automatically plotted on the software based on their kinetic energy. 300nm ultraviolet light and 750nm near-infrared light are introduced through an irradiation source.

[0044] Figure 5 The images are in-situ irradiation XPS spectra, (ab) represent SnO2 / W 18 O 49 The ISI-XPS peak spectra of W 4f and Sn 3d of the composite photocatalyst under 700 nm monochromatic light (top), without external light source (middle), and under 300 nm monochromatic light (bottom). Compared with the case without light, the SnO2 / W 4f peaks under 300 nm monochromatic light are significantly higher. 18 O 49 The W 4f peak shifts towards the direction with lower binding energy, while the Sn 3d peak shifts towards the direction with higher binding energy, indicating that under an external excitation source of 300 nm, photogenerated electrons transfer from SnO2 to W. 18 O 49 A 300nm wavelength light source is used in SnO2 and W 18 O 49 In the intrinsically excited band, at this wavelength, electrons in the valence band of SnO2 are excited to jump to its conduction band, and then flow towards W under the drive of the built-in electric field. 18 O 49 The conduction band, the formation of type II heterojunction, and the presence of the built-in electric field can effectively achieve spatial separation of photogenerated carriers, but due to W 18 O 49 The conduction band potential is insufficient for the hydrogen evolution reaction to occur, and no hydrogen gas is produced in the system. Compared to the state without illumination, under 700 nm monochromatic light, SnO2 / W 18 O 49 The W 4f peak shifts towards the direction with higher binding energy, while the Sn 3d peak shifts towards the direction with lower binding energy, indicating that photogenerated electrons move from W... 18 O 49 It flows to SnO2. The 700nm wavelength light source is located at W. 18 O 49 In the SPR band, at this wavelength, electrons in the conduction band of SnO2 cannot be excited. Due to the LSPR effect, W 18 O 49 Electrons near the Fermi level are excited to produce hot electrons, which are then injected into the conduction band of SnO2, causing a hydrogen evolution reaction. The results of the above wavelength-dependent in-situ irradiation XPS measurements strongly confirm the SnO2 / W... 18 O 49Composite photocatalysts enhance photocatalytic activity through hot electron injection.

[0045] Example 2

[0046] Preparation of SnO2, W 18 O 49 A 1:6 ratio of three-dimensional hierarchical composite photocatalyst SnO2 / W 18 O 49 The steps for creating a composite photocatalyst are as follows:

[0047] (1) Preparation of SnO2 nanofibers: SnO2 nanofibers were prepared by electrospinning. First, 1.2 g of polyvinylpyrrolidone (PVP), 0.45 g of tin dichloride, 5.6 mL of anhydrous ethanol and 4.6 mL of N,N-dimethylformamide (DMF) were added to a sample vial and stirred overnight with a magnetic stirrer until a transparent and homogeneous precursor solution was formed. The precursor solution was injected into a syringe with a needle, and nanofibers were obtained by electrospinning using an electrospinning machine. The temperature and humidity control parameters were set as follows: temperature 30℃, humidity 20%, etc. The electrospinning parameters were set as follows: a No. 21 needle was selected, the needle injection speed was 0.6 mL / h, the roller speed was 100 rpm, the voltage was 20 kV, and the receiving distance between the syringe and the receiving roller was 12 cm. The precursor solution was injected into the syringe with a needle, and a high voltage of 20 kV was applied to the needle. At the same time, a grounded rotating roller was used to receive the fibers. The obtained nanofibers were dried in an electrically heated drying oven at 60°C for 12 hours, and then placed in a muffle furnace at 2°C·min. -1 SnO2 nanofibers were obtained by heating the temperature to 600℃ and holding it for 100 min.

[0048] (2)SnO2 / W 18 O 49 Preparation of composite photocatalyst: 50 mg of the SnO2 nanofibers prepared in step (1) above were dispersed in 30 mL of anhydrous ethanol. Then, 300 mg of tungsten hexachloride was added and the mixture was magnetically stirred until a yellow, transparent solution was formed. The solution was then transferred to a 100 mL Teflon-lined stainless steel high-pressure hydrothermal reactor and heated to 180 °C in an electric forced-air drying oven for 12 h. After cooling to room temperature, the solution was centrifuged three times with deionized water and twice with anhydrous ethanol, and then dried overnight in a 60 °C vacuum drying oven to obtain SnO2 / W 18 O 49 Composite photocatalyst. W 18 O 49 SnO2 nanofibers were prepared using the same method, but without the addition of SnO2 nanofibers during the solvothermal process.

[0049] Example 3

[0050] Preparation of SnO2, W 18 O 49 A 1:8 ratio of three-dimensional hierarchical composite photocatalyst SnO2 / W 18 O 49 The steps for creating a composite photocatalyst are as follows:

[0051] (1) Preparation of SnO2 nanofibers: SnO2 nanofibers were prepared by electrospinning. First, 1.2 g of polyvinylpyrrolidone (PVP), 0.45 g of tin dichloride, 5.6 mL of anhydrous ethanol and 4.6 mL of N,N-dimethylformamide (DMF) were added to a sample vial and stirred overnight with a magnetic stirrer until a transparent and homogeneous precursor solution was formed. The precursor solution was injected into a syringe with a needle, and nanofibers were obtained by electrospinning using an electrospinning machine. The temperature and humidity control parameters were set as follows: temperature 30℃, humidity 20%, etc. The electrospinning parameters were set as follows: a No. 21 needle was selected, the needle injection speed was 0.6 mL / h, the roller speed was 100 rpm, the voltage was 20 kV, and the receiving distance between the syringe and the receiving roller was 12 cm. The precursor solution was injected into the syringe with a needle, and a high voltage of 20 kV was applied to the needle. At the same time, a grounded rotating roller was used to receive the fibers. The obtained nanofibers were dried in an electrically heated drying oven at 60°C for 12 hours, and then placed in a muffle furnace at 2°C·min. -1 SnO2 nanofibers were obtained by heating the temperature to 600℃ and holding it for 100 min.

[0052] (2)SnO2 / W 18 O 49 Preparation of composite photocatalyst: 50 mg of the SnO2 nanofibers prepared in step (1) above were dispersed in 30 mL of anhydrous ethanol. Then, 400 mg of tungsten hexachloride was added and the mixture was magnetically stirred until a yellow, transparent solution was formed. The solution was then transferred to a 100 mL Teflon-lined stainless steel high-pressure hydrothermal reactor and heated to 180 °C in an electric forced-air drying oven for 12 h. After cooling to room temperature, the solution was centrifuged three times with deionized water and twice with anhydrous ethanol, and then dried overnight in a 60 °C vacuum drying oven to obtain SnO2 / W 18 O 49 Composite photocatalyst. W 18 O 49 SnO2 nanofibers were prepared using the same method, but without the addition of SnO2 nanofibers during the solvothermal process.

[0053] The above describes the LSPR-modified SnO2 / W provided by this invention. 18 O 49The composite photocatalyst and its preparation method are described in detail. Specific examples are used to illustrate the principles and implementation methods of the invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the invention. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of the invention.

Claims

1. A composite photocatalyst SnO2 / W 18 O 49 The preparation method is characterized by: SnO2 nanofibers prepared by electrospinning were dispersed in anhydrous ethanol, and tungsten hexachloride was added and magnetically stirred until a yellow transparent solution was formed. The solution was then transferred to a hydrothermal reactor for a solvothermal reaction. After the solution was cooled to room temperature, it was centrifuged three times with deionized water and twice with anhydrous ethanol, and then vacuum dried to obtain SnO2 / W. 18 O 49 Composite photocatalyst.

2. The composite photocatalyst SnO2 / W according to claim 1 18 O 49 The preparation method is characterized by: Nanofibers were prepared by electrospinning. The polymer solution flow rate was 0.5–2.0 mL / h, the roller speed was 80–200 rpm, the voltage was 12–25 kV, and the receiving distance between the syringe and the receiving roller was 8–20 cm. Environmental parameters were adjusted as follows: ambient temperature 20–28 ℃, ambient humidity 40–60%. The precursor solution was injected into a syringe with a needle, and a 20 kV high-voltage electrostatic charge was applied to the needle. Simultaneously, a grounded rotating roller was used to receive the fibers. The obtained nanofibers were dried in a 60 ℃ electric heating oven for 12 h, and then placed in a muffle furnace at 2 ℃·min. -1 SnO2 nanofibers were obtained by heating the temperature to 600 °C and holding it for 100 min.

3. The composite photocatalyst SnO2 / W according to claim 1 18 O 49 The preparation method is characterized by: The prepared SnO2 nanofibers were dispersed in a 1:10 mixture of anhydrous ethanol and tungsten hexachloride and magnetically stirred for 7–12 h until a yellow, transparent solution was formed. The solution was then transferred to a 100 mL Teflon-lined stainless steel autoclave and heated to 150–200 °C in an electric forced-air drying oven at a rate of 1–3 °C / min, and held at this temperature for 10–15 h. After cooling to room temperature, the solution was centrifuged three times with deionized water and twice with anhydrous ethanol, and then placed in a vacuum drying oven at 55–60 °C for 8–12 h to obtain SnO2 / W. 18 O 49 Composite photocatalyst.

4. The composite photocatalyst SnO2 / W obtained by the preparation method of claim 1 18 O 49 An in-situ testing method for electron transport mechanisms, characterized by: First, prepare the SnO2 / W to be tested on the sample stage. 18 O 49 After the composite photocatalyst sample is prepared, the sample stage is placed in the instrument's transition chamber for pre-vacuuming. Once the vacuum meets the testing requirements, the sample stage is sent into the test chamber for testing. In-situ irradiation XPS technology is used to study the electron migration path at different wavelengths. The original state is equipped with an irradiation light source with a light guide fiber, and the light is irradiated onto the sample in the test chamber through the equipment's observation window.

5. The composite photocatalyst SnO2 / W according to claim 4 18 O 49 An in-situ testing method for electron transport mechanisms, characterized by: The irradiation wavelengths of the light source are 300 nm ultraviolet light and 700 nm near-infrared light.

6. The composite photocatalyst SnO2 / W according to claim 4 18 O 49 An in-situ testing method for electron transport mechanisms, characterized by: During the pre-vacuuming process, all light sources in the transition chamber and test chamber are turned off, so that the sample is in a completely dark environment. After the pre-vacuuming is completed, the test is conducted under the same completely dark conditions. The test results are the data under the dark conditions. Then, 300 nm ultraviolet light and 700 nm near-infrared light are added. The test results are the data under the illumination conditions.

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