Method for preparing rapid hydrochromic mesoporous tungsten oxide film based on plasma etching technology

Abstract

The invention relates to a method for preparing a rapid hydrochromic mesoporous tungsten oxide film based on a plasma etching technology. The preparation method comprises the following steps: mixing an amphoteric block copolymer template agent with a tungsten source precursor, and coating the surface of a substrate with obtained sol to construct an organic-inorganic hybrid film; then introducing oxygen-containing plasma to etch the hybrid film; and finally loading a catalyst layer on the surface of the film. By utilizing the synergistic effect of high-energy active particles and active oxygen species in the plasma, through coupling of physical bombardment and chemical oxidation / volatilization reaction, the rapid removal of the organic template is realized under a low-temperature condition, meanwhile, the structural integrity of a mesoporous skeleton is kept, and the pore collapse and the specific surface area loss caused by traditional high-temperature calcination are avoided. The obtained mesoporous WO3 thin film has a high specific surface area and abundant surface active sites, and hydrogen diffusion and interface reaction kinetics can be effectively improved, so that the coloring / fading response is remarkably accelerated, and the hydrogen-induced discoloration performance is improved.

Description

Technical Field

[0001] This invention belongs to the field of functional thin film material preparation technology, specifically relating to a method for preparing rapid hydrogen-chromatic mesoporous tungsten oxide (WO3) thin films based on plasma etching technology, and more particularly a method for preparing mesoporous tungsten oxide (WO3) hydrogen-chromatic thin films with excellent response speed by removing organic template agents using plasma etching process. Background Technology

[0002] Tungsten trioxide (WO3) is an n-type semiconductor with hydrogen-sensitive gas-induced color change properties. When supported with platinum or palladium catalysts, WO3 exhibits strong absorption of visible and near-infrared light even when exposed to low concentrations of hydrogen at room temperature, changing its color from transparent / pale yellow (bleached state) to deep blue (colored state). This process is reversible upon exposure to air or oxygen, returning it to transparent / pale yellow.

[0003] This unique hydrogen-induced color-changing property makes WO3 a promising candidate for applications in smart dimming glass and optical hydrogen sensors. To meet the requirements of practical applications for sensor response speed and sensitivity, researchers typically use amphoteric block copolymers (such as PEO-b-PS, Pluronic F127, and PEO-b-P4VP) as soft templates, and prepare mesoporous WO3 films with high specific surface area and abundant pore structures using a sol-gel method combined with evaporation-induced self-assembly (EISA) technology. This porous structure can significantly shorten the diffusion path of hydrogen molecules and protons, thereby improving the color-changing performance.

[0004] However, in existing mesoporous WO3 film preparation processes, the removal of the organic polymer template mainly relies on high-temperature calcination heat treatment, typically requiring calcination for several hours in an air atmosphere at 350℃-500℃. This traditional method has the following significant drawbacks:

[0005] (1) Skeleton shrinkage and collapse: Long-term high-temperature treatment will cause the inorganic skeleton to undergo severe thermal shrinkage, which can easily cause deformation, collapse or even closure of mesoporous channels, resulting in a significant reduction in specific surface area and hindering the rapid diffusion of hydrogen.

[0006] (2) Excessive grain growth: High temperature can easily lead to excessive growth and coarsening of WO3 grains, reducing the number of grain boundaries and hindering the rapid transport of ions.

[0007] (3) Substrate limitations: High-temperature processes limit the use of flexible polymer substrates (such as PET, PEN, etc.) or temperature-sensitive conductive glass (such as some ITO / FTO), thus narrowing the application range.

[0008] (4) High energy consumption and long process cycle: In order to prevent the organic template from decomposing violently in a short time and generating a large amount of gas that breaks through the skeleton, and in order to reduce the thermal stress caused by the difference in thermal expansion coefficients between the film and the substrate (to avoid cracking), the heat treatment process must strictly control the heating and cooling rates (usually as low as 1~2℃ / min). This makes the entire template removal process often last for several hours or even tens of hours, which not only leads to extremely low production efficiency, but also causes huge energy consumption due to long-term high-temperature operation, increases the preparation cost, and is not conducive to large-scale industrial production.

[0009] To overcome the limitations of high-temperature heat treatment, researchers have explored surface cleaning and activation techniques such as solvent extraction, ultraviolet-ozone (UVO) cleaning, and plasma etching. Solvent extraction utilizes the dissolving effect of organic solvents to remove organic templates. While the conditions are mild, it often fails to completely remove organic matter embedded deep within the inorganic framework, potentially damaging the original micro / nano structures. It is also time-consuming, and the use of large amounts of organic solvents is not only hazardous but also environmentally unfriendly. UVO cleaning uses high-energy ultraviolet light to break the chemical bonds of organic molecules, combined with the strong oxidizing properties of ozone, to oxidize and decompose them. Its advantages include that the entire process is carried out at room temperature or low temperature, effectively avoiding framework shrinkage caused by thermal effects and better preserving the integrity of the mesoporous structure. However, UVO technology has limited penetration depth, lower efficiency for thicker films, and a relatively slow removal rate. Plasma etching utilizes the dual effects of physical bombardment and chemical reaction between high-energy active particles (electrons, ions, free radicals, etc.) generated by gas discharge and the organic template. Its characteristics and advantages lie in high efficiency and energy saving, low temperature and environmental protection, and surface modification, making it a commonly used surface pretreatment technology in fields such as physical vapor deposition (PVD), semiconductor lithography, and polymer bonding technology. However, there are no reports on applying different types (microwave, radio frequency, low frequency) oxygen-containing plasma systems to the preparation of mesoporous WO3 hydrogen-chromic films, and on deeply controlling their influence on the pore structure and surface defect state of WO3 films. Summary of the Invention

[0010] The purpose of this invention is to overcome the problems of long processing time, easy collapse of pore structure and slow fading response in existing high-temperature calcination heat treatment processes for removing organic templates, and to provide a method for preparing rapid hydrogen-induced color-changing mesoporous tungsten oxide (WO3) thin films based on plasma etching technology.

[0011] This invention utilizes oxygen-containing plasma etching to achieve efficient and rapid removal of organic templates, thereby preparing high-performance, rapidly hydrogen-chromic mesoporous tungsten oxide (WO3) films. The method includes: mixing an amphoteric block copolymer template with a tungsten source precursor sol and coating it onto a substrate surface to construct an organic-inorganic hybrid film; subsequently, introducing oxygen-containing plasma to etch the hybrid film to achieve rapid removal of the template and induce in-situ crystallization or partial crystallization of the WO3 framework during the etching process; finally, loading a catalyst layer on the film surface to enhance hydrogen molecule dissociation and transport. This invention utilizes the synergistic effect of high-energy active particles and reactive oxygen species in plasma, coupling physical bombardment with chemical oxidation / volatilization reactions to achieve rapid removal of the organic template at low temperatures while maintaining the integrity of the mesoporous framework structure, avoiding pore collapse and specific surface area loss caused by traditional high-temperature calcination. The resulting mesoporous WO3 film has a high specific surface area and abundant surface active sites, which can effectively improve hydrogen diffusion and interfacial reaction kinetics, thereby significantly accelerating the coloring / fading response and improving hydrogen-chromic performance.

[0012] The objective of this invention can be achieved through the following methods: This invention provides a method for preparing rapid hydrogen-induced color-changing mesoporous tungsten oxide (WO3) thin films based on plasma etching technology, comprising the following steps: S1. Preparation of precursor sol: Tungsten source and amphoteric block copolymer are dissolved in solvent to obtain tungsten source solution and copolymer solution, respectively. The two are then mixed to obtain precursor sol. S2. Preparation of hybrid membrane: Precursor sol was deposited on a substrate and aged at low temperature to obtain an organic-inorganic hybrid film. S3, Plasma Etching: The organic-inorganic hybrid thin film was subjected to plasma etching in an oxygen-containing atmosphere. The organic template was removed by oxygen-containing plasma to obtain the etched porous tungsten oxide film. S4, Catalyst Support: A nanocatalyst layer was prepared on the surface of the etched porous WO3 film to obtain the hydrogen-chromic mesoporous tungsten oxide (WO3) film.

[0013] As one embodiment of the present invention, in step S1, the tungsten source includes one or more of tungsten hexachloride (WCl6), tungsten ethoxide (W(OC2H5)6), tungsten tetrachloride (WOCl4), polytungstic acid peroxy (PTA), ammonium tungstate, and scheelic acid.

[0014] In one embodiment of the present invention, in step S1, the amphoteric block copolymer includes one or more of the following: polyethylene oxide-polystyrene (PEO-b-PS), polyethylene oxide-polymethyl methacrylate (PEO-b-PMMA), polyethylene oxide-poly2-vinylpyridine (PEO-b-P2VP), polyethylene oxide-poly4-vinylpyridine (PEO-b-P4VP), and polyethylene oxide-polypropylene-polyethylene oxide (PEO-PPO-PEO, Pluronics series). The amphoteric block copolymer (amphiphilic BCP) facilitates the microscopic self-assembly of WO3 colloids, contributing to the formation of well-ordered micro / nano structures with high porosity.

[0015] As one embodiment of the present invention, in step S1, the solvent for the tungsten source includes one or more of methanol, ethanol, n-propanol, and isopropanol.

[0016] As one embodiment of the present invention, in step S1, the solvent of the amphoteric block copolymer includes one or more of tetrahydrofuran (THF), chloroform, 1,4-dioxane, N,N-dimethylformamide (DMF), toluene, xylene, and benzene.

[0017] The solvents used for the tungsten source and the amphoteric block copolymer are different, with the goal of promoting mesoscopic co-assembly. The solvents for the tungsten source and the amphoteric block copolymer are completely miscible, such as the ethanol / tetrahydrofuran (THF) combination. Ethanol is a good solvent for PEO but not for PS, while THF is a good solvent for both PEO and PS, and its volatility is significantly higher than that of ethanol. During solution deposition, THF will preferentially evaporate, causing the ethanol in the solvent to concentrate. Thus, the poor solubility of PS segments drives self-assembly.

[0018] As one embodiment of the present invention, in step S1, the mass ratio of tungsten atoms in the tungsten source to the amphoteric block copolymer is 1:(0.2-5), preferably 1:(0.3-0.6).

[0019] As one embodiment of the present invention, in step S1, the ratio of tungsten atoms in the tungsten source to solvent is 1g:2~15 ml, preferably 1g:3~6 ml.

[0020] In one embodiment of the present invention, in step S1, the ratio of the amphoteric block copolymer to the solvent is 1 g: 5~100 ml, preferably 1 g: 15~25 ml.

[0021] In one embodiment of the present invention, step S1 further includes a chelating agent in the precursor sol. The chelating agent is acetylacetone. After the tungsten source is dissolved in the solvent, the chelating agent is added to obtain a tungsten source solution. The mass ratio of tungsten atoms in the tungsten source to the chelating agent is 1:1.5~2.0. The addition of the chelating agent can extend the service life of the self-assembly solution and reduce the environmental humidity requirements for film deposition. For self-assembly solutions without chelating agents, deposition in an environment with >30% relative humidity will result in the tungsten source undergoing excessively rapid hydrolysis and condensation, which will destroy the ordered mesoscopic structure of the self-assembly. However, with the addition of the chelating agent, good self-assembly results can still be obtained even when the humidity reaches nearly 70%.

[0022] In one embodiment of the present invention, in step S2, the substrate includes one of PET, PEN, ITO, and FTO.

[0023] As one embodiment of the present invention, in step S2, the method of depositing the precursor sol on the substrate includes one of spin coating, dip coating, and spray coating.

[0024] Preferably, the method for depositing the precursor sol on the substrate is spin coating, with a rotation speed of 1500-2000 rpm and a time of 0.5-2 min.

[0025] In one embodiment of the present invention, in step S2, the low-temperature aging temperature is 80-120°C and the time is 10-15 hours.

[0026] As one embodiment of the present invention, in step S2, the thickness of the obtained organic-inorganic hybrid film is 400-1000 nm, preferably 600-700 nm.

[0027] As one embodiment of the present invention, in step S3, the excitation source used in the plasma etching process includes one of microwave plasma, radio frequency plasma (RF), and low frequency plasma (LF).

[0028] As one embodiment of the present invention, in step S3, the microwave power of plasma etching is 450W to 1000W, the time is 3min to 120min, and the working gas pressure is 20Pa to 200Pa.

[0029] The preferred microwave power for plasma etching is 500W to 600W, the preferred time is 10min to 20min, and the preferred working pressure is 80Pa to 120Pa.

[0030] If the microwave power is too low or the time is too short, the block copolymer template may not be etched across the entire film thickness, and the amphoteric block copolymer template in the hybrid film may not be completely removed.

[0031] In one embodiment of the present invention, in step S3, during the plasma etching process, an etching gas is introduced, which is oxygen or an oxygen-containing gas. The oxygen flow rate in the etching gas accounts for 80-100%, and the oxygen flow rate is 10-500 sccm, preferably 200-250 sccm.

[0032] In one embodiment of the present invention, in step S4, the nanocatalyst layer is prepared by vapor deposition or chemical reduction deposition. Vapor deposition methods include atomic layer deposition and sputtering deposition, while chemical reduction deposition methods include one of polyol deposition and impregnation-reduction deposition.

[0033] In one embodiment of the present invention, in step S4, the catalyst is one of Pt, Pd, Pt-Pd alloy, and Pd-Au alloy, with a thickness of 1 nm to 10 nm.

[0034] The present invention also provides a rapidly hydrogen-induced color-changing mesoporous tungsten oxide thin film prepared by the method described above.

[0035] Compared with the prior art, the present invention has the following beneficial effects: (1) High efficiency and energy saving: No slow heating and cooling process is required. The template can be removed in a few minutes to tens of minutes, which significantly shortens the process cycle and reduces energy consumption; (2) Low temperature and good structure preservation: It can quickly remove organic components at a lower temperature, avoiding pore collapse, pore closure and grain coarsening caused by high temperature sintering, and preserving the highly ordered mesoporous structure to the greatest extent. (3) Surface modification: The physical bombardment of plasma helps to open the closed pores on the surface of WO3 film, further increasing the effective specific surface area; (4) Introduction of active sites: The action of high-energy particles can easily induce the generation of oxygen vacancies and low-valence tungsten ions on the WO3 surface. 5+ These surface defects, as highly active sites, can significantly promote the dissociation of hydrogen and the transport of protons, thereby greatly improving the response speed of WO3 gas color change. (5) Ultrafast response: The measured coloring time (tc,90) of WO3 thin film prepared by plasma etching is only about 18s, and the fading time (tb,90) can be shortened to less than 5 seconds, which is significantly better than that of heat-treated samples; (6) Wide process compatibility: It is suitable for various plasma equipment such as microwave, radio frequency (RF) and has strong adaptability to the types of tungsten source precursors. Attached Figure Description

[0036] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 Process flow diagram for preparing rapid hydrogen-induced color-changing mesoporous WO3 thin films; Figure 2 This diagram illustrates the key process steps and membrane structure; where 1-oxygen-containing plasma; 2-a mixture of tungsten oxide and hydrophilic segments of block copolymer; 3-a spherical core in the "core-shell" structure obtained after the ordered self-assembly of the block copolymer; 4-substrate; 5-catalyst layer; 6-porous WO3 membrane layer after template removal; Figure 3 The images show the morphology and performance test results of the nanoporous WO3 hydrogen-induced color-changing film prepared in Example 1, where a) is a surface microstructure image; b) is a curve showing the change in transmittance with wavelength before and after contact with hydrogen; c) is a curve showing the change in monochromatic light transmittance at a wavelength of 1000 nm with time after the sample is contacted with 4% H2 + 96% Ar; and d) is a curve showing the change in monochromatic light transmittance at a wavelength of 1000 nm with time after the sample is contacted with air. Figure 4 The images show the morphology and performance of the nanoporous WO3 hydrogen-induced color-changing film prepared in Example 2, where a) is a surface microstructure image; b) is a curve showing the change in transmittance with wavelength before and after contact with hydrogen; c) is a curve showing the change in transmittance of monochromatic light at a wavelength of 1000 nm with time after the sample is contacted with 4% H2 + 96% Ar; and d) is a curve showing the change in transmittance of monochromatic light at a wavelength of 1000 nm with time after the sample is contacted with air. Figure 5 The images show the morphology and performance of the nanoporous WO3 hydrogen-induced color-changing film prepared in Comparative Example 1. a) shows the surface microstructure; b) shows the transmittance as a function of wavelength before and after contact with hydrogen; c) shows the transmittance of monochromatic light at 1000 nm as a function of time after the sample is contacted with 4% H2 + 96% Ar; and d) shows the transmittance of monochromatic light at 1000 nm as a function of time after the sample is contacted with air. Figure 6 The images show the morphology and performance of the nanoporous WO3 hydrogen-induced color-changing film prepared in Comparative Example 2. In the images, a) is the surface microstructure; b) is the curve of transmittance versus wavelength before and after contact with hydrogen; c) is the curve of transmittance of monochromatic light at a wavelength of 1000 nm versus time after the sample is contacted with 4% H2 + 96% Ar; and d) is the curve of transmittance of monochromatic light at a wavelength of 1000 nm versus time after the sample is contacted with air. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0038] This invention provides a method for rapidly preparing hydrogen-chromatic mesoporous tungsten oxide (WO3) thin films based on plasma etching technology. Key process steps and film structure are as follows: Figure 2 As shown, a precursor sol is deposited on substrate 4 to obtain an organic-inorganic hybrid film, which includes a mixture 2 of tungsten oxide and hydrophilic segments of block copolymers and a spherical core 3 in a "core-shell" structure obtained by the ordered self-assembly of block copolymers. The spherical core is etched and a catalyst is deposited using oxygen-containing plasma 1 to obtain a porous WO3 film 6 containing a catalyst layer 5 after template removal.

[0039] The preparation method includes the following steps: (1) Preparation of precursor sol: Dissolve tungsten source reagents (such as WCl6, ethoxylate, WOCl4, scheelic acid, etc.) in a solvent, and add amphoteric block copolymers (such as PEO-b-PS, Pluronics series (F127, P123), PEO-b-P2VP, PEO-b-P4VP, etc.) as pore-forming agents (templating agents). These polymers (block copolymers containing hydrophilic groups) can assemble with tungsten species in a specific solvent through hydrogen bonds or coordination bonds to form an ordered mesoscopic structure. Stir evenly to obtain a mixed sol.

[0040] (2) Preparation of hybrid film: Organic-inorganic hybrid films are deposited on the substrate by spin coating, dip coating or spray coating and aged at low temperature.

[0041] (3) Plasma etching (key step): The hybrid thin film is placed in a plasma generator device, and oxygen-containing plasma is used to remove the organic template. Its function is as follows: ① The oxygen free radicals react with the organic template to generate CO2 and H2O, which are then discharged from the template. At the same time, the physical bombardment of plasma is used to open the surface pores.

[0042] ② This process is a low-temperature process (usually the substrate temperature is <150 ℃), which effectively preserves the integrity of the mesoporous skeleton.

[0043] ③ Plasma treatment also introduces abundant oxygen vacancies and hydrophilic groups on the WO3 surface, which greatly promotes ion transport during the hydrogen-induced color change process.

[0044] ④ The plasma process parameters (power, time) can be optimized and adjusted according to the substrate's tolerance. For substrates with poor heat resistance or that are susceptible to ion bombardment damage (such as some ITO conductive glasses), a flexible etching mode with lower power and longer time can be selected, or intermittent etching can be used to reduce the substrate's thermal load.

[0045] (4) Catalyst loading: A nano-catalyst layer is deposited on the surface of the etched porous WO3 film.

[0046] The following embodiments provide a method for preparing a rapidly discoloring and fading nanoporous WO3 hydrogen-induced color-changing film on the surface of quartz glass. The method mainly includes the steps of sequentially preparing an organic-inorganic hybrid nanocomposite layer on the quartz glass, removing the polymer template agent and the supported catalyst by oxygen plasma etching.

[0047] Example 1 On a quartz glass substrate (diameter of...) Methods for preparing rapidly discoloring and fading nanoporous WO3 hydrogen-induced color-changing films on a 37mm surface include: Figure 1 As shown, the main steps include: (1) Preparation of mixed sol solution: Dissolve 0.1 g of polyoxyethylene-b-polystyrene (PEO-b-PS) template agent in 2 ml of tetrahydrofuran (THF); separately dissolve 0.4 g of tungsten hexachloride (WCl6, 0.232 g tungsten atoms) in 1 ml of ethanol, and add 0.4 g of acetylacetone as a chelating agent. Mix the two solutions and stir for 2 hours to form a homogeneous sol.

[0048] (2) Deposition preparation of organic-inorganic hybrid material film: On a quartz glass substrate, a mixed solution was spin-coated for 1 minute at a speed of 2,000 rpm to obtain an organic-inorganic hybrid material film. The film was then dried in an oven at 100°C for 12 hours to fully cure the obtained hybrid film (thickness of 664 nm).

[0049] (3) Plasma etching to remove polymer template: Place the sample in a microwave plasma stripper (such as PVATeppla 300 or other similar equipment). Introduce oxygen at a flow rate of 200 sccm. Set the microwave power to 550W, the working pressure to 100 Pa, and the processing time to 10 min. After etching, the film can be observed to change from a slightly yellowish color to transparent, indicating that the template has been completely removed.

[0050] (4) Supported catalyst: A Pt layer of about 5 nm was deposited on the surface of mesoporous WO3 by magnetron sputtering.

[0051] This example demonstrates the ability to obtain a rapidly discoloring and fading nanoporous WO3 hydrogen-chromic film. Testing showed that, under a 4% hydrogen / argon mixed atmosphere, the transmittance change of this film at a wavelength of 1000 nm was ΔT = 40.9%, and the coloring response time was t. 90 = 18.3 s, recovery time of fading in air t 90 = 4.3 s. The surface microstructure photographs of the obtained WO3 hydrogen-chromatic thin film, the transmittance curves of the sample before and after contact with hydrogen gas as a function of wavelength, and the transmittance curves of monochromatic light at a wavelength of 1000 nm after contact with 4% H2 + 96% Ar and air are attached. Figure 3 As shown.

[0052] Example 2 On a quartz glass substrate (diameter of...) Methods for preparing rapidly discoloring and fading nanoporous WO3 hydrogen-induced color-changing films on a 37mm surface include: Figure 1 As shown, the main steps include: (1) Preparation of mixed sol solution: Dissolve 0.1g of polyoxyethylene-b-polystyrene (PEO-b-PS) template agent in 2ml of tetrahydrofuran (THF); dissolve 0.4g of tungsten hexachloride (WCl6) in 1ml of ethanol, and add 0.4g of acetylacetone as a chelating agent. Mix the two solutions and stir for 2 hours to form a homogeneous sol.

[0053] (2) Deposition preparation of organic-inorganic hybrid material film: On a quartz glass substrate, a mixed solution was spin-coated for 1 minute at a speed of 2,000 rpm to obtain an organic-inorganic hybrid material film, which was then dried in an oven at 100°C for 12 hours to fully cure the obtained hybrid film.

[0054] (3) Plasma etching to remove polymer template: The sample was placed in a microwave plasma stripper (such as a PVATeppla 300 or other similar equipment). Oxygen was introduced at a flow rate of 250 sccm. The microwave power was set to 550 W, the working pressure to 100 Pa, and the processing time to 5 min. After etching, the slightly yellow color of the film only became lighter.

[0055] (4) Supported catalyst: A Pt layer of about 5 nm was deposited on the surface of mesoporous WO3 by magnetron sputtering.

[0056] This example demonstrates the ability to obtain a rapidly discoloring and fading nanoporous WO3 hydrogen-induced color-changing film. Testing showed that the transmittance change of this film at 1000 nm wavelength in a 4% hydrogen / argon mixed atmosphere was ΔT = 25.2%, and the coloring response time was t. 90 =17.2 s, recovery time of fading in air t 90=11.2 s. The surface microstructure photographs of the obtained WO3 hydrogen-chromatic thin film, the transmittance curves of the sample before and after contact with hydrogen gas as a function of wavelength, and the transmittance curves of monochromatic light at a wavelength of 1000 nm after contact with 4% H2 + 96% Ar and air are attached. Figure 4 As shown.

[0057] Example 3 On a quartz glass substrate (diameter of...) Methods for preparing rapidly discoloring and fading nanoporous WO3 hydrogen-induced color-changing films on a 37mm surface include: Figure 1 As shown, the main steps include: (1) Preparation of mixed sol solution: Dissolve 0.1g of polyoxyethylene-b-polystyrene (PEO-b-PS) template agent in 2ml of tetrahydrofuran (THF); dissolve 0.4g of tungsten hexachloride (WCl6) in 1ml of ethanol, and add 0.4g of acetylacetone as a chelating agent. Mix the two solutions and stir for 2 hours to form a homogeneous sol.

[0058] (2) Deposition preparation of organic-inorganic hybrid material film: On a quartz glass substrate, a mixed solution was spin-coated for 1 minute at a speed of 2,000 rpm to obtain an organic-inorganic hybrid material film, which was then dried in an oven at 100°C for 12 hours to fully cure the obtained hybrid film.

[0059] (3) Plasma etching to remove polymer template: Place the sample in a microwave plasma stripper (such as a PVATeppla 300 or other similar equipment). Introduce an oxygen / argon mixture at a flow rate of 200 / 30 sccm. Set the microwave power to 550W, the working pressure to 100 Pa, and the processing time to 15 min. After etching, the film changes from slightly yellow to transparent, indicating that the template has been completely removed.

[0060] (4) Supported catalyst: A Pt layer of about 5 nm was deposited on the surface of mesoporous WO3 by magnetron sputtering.

[0061] This example demonstrates the ability to obtain a fast-responding and recovering nanoporous WO3 hydrogen-chromic film. Testing showed that the transmittance change of this film at a wavelength of 1000 nm in a 4% hydrogen / argon mixed atmosphere was ΔT = 42.6%, and the coloring response time was t. 90 = 18.2 s, recovery time of fading in air t 90 = 4.6 s.

[0062] Comparative Example 1 The difference between this comparative example and Example 1 is that step (3) uses a heat treatment method to remove the PEO-b-PS polymer template agent. The specific heat treatment method is as follows: First, the dried organic-inorganic hybrid film is placed in a tube furnace for calcination heat treatment. First, it is heated to 350°C in an argon atmosphere at a heating rate of 2°C / min and held for 1 hour. Then, it is heated to 500°C at a heating rate of 5°C / min and held for 1 hour. After cooling to room temperature, the resulting film is placed in an air atmosphere and heated to 400°C at a heating rate of 5°C / min and held for 3 hours to obtain a nanoporous WO3 layer containing mesopores with a pore size of 25 nm.

[0063] This example demonstrates the production of a nanoporous WO3 hydrochromic film with a relatively slow color change and fading rate. Testing showed that the transmittance change of this film at 1000 nm wavelength in a 4% hydrogen / argon mixed atmosphere was ΔT = 46.5%, and the coloring response time was t. 90 = 32.4 s, recovery time of fading in air t 90 = 26.9 s. The surface microstructure of the WO3 hydrogen-chromatic thin film obtained by this method, the transmittance curves of the sample before and after contact with hydrogen gas as a function of wavelength, and the transmittance curves of monochromatic light at a wavelength of 1000 nm after contact with 4% H2 + 96% Ar and air are attached. Figure 5 As shown, compared to the oxygen plasma removal of the template agent in Example 1, the color change response speed and fading recovery speed to hydrogen are both slower.

[0064] Comparative Example 2 The difference between this comparative example and Example 1 is that the power used in step (3) is 400W and the duration is 5min, while the other operating conditions are the same as those in Example 1.

[0065] The nanoporous WO3 hydrogen-induced coloring film obtained in this example exhibits poor coloring and fading properties. Testing showed that the transmittance change of this film at a wavelength of 1000 nm in a 4% hydrogen / argon mixed atmosphere was ΔT = 6.2%, and the coloring response time was t. 90 = 133.3 s, recovery time of fading in air t 90 = 201.5 s. The surface microstructure of the WO3 hydrogen-chromatic thin film obtained under this process, the transmittance curves of the sample before and after contact with hydrogen gas as a function of wavelength, and the transmittance curves of monochromatic light at a wavelength of 1000 nm after contact with 4% H2 + 96% Ar and air are attached. Figure 6As shown in the figure, this comparative example demonstrates that if the process parameters are inappropriate, the oxygen plasma etching is very insufficient, resulting in a high proportion of polymer template agent and low porosity in the hydrogen-induced color-changing Pt / WO3 film. Therefore, under otherwise identical conditions, the color-changing response speed and fading recovery speed to hydrogen are both slower than in Example 1.

[0066] Comparative Example 3 The difference between this comparative example and Example 1 is that, after plasma etching to remove the block copolymer template in step (3), no catalyst loading was performed, and the remaining operating conditions were the same as those in Example 1.

[0067] The nanoporous WO3 film obtained in this example cannot change its color when exposed to hydrogen gas.

[0068] Comparative Example 4 The difference between this comparative example and Example 1 is that the power used in step (3) is 300W and the duration is 10min, while the other operating conditions are the same as those in Example 1.

[0069] The nanoporous WO3 hydrogen-induced coloring film obtained in this example exhibits poor coloring and fading properties. Testing showed that the transmittance change of this film at a wavelength of 1000 nm under a 4% hydrogen / argon mixed atmosphere was ΔT = 2.6%, and the coloring response time was t. 90 = 316.8 s, recovery time of fading in air t 90 = 215.7 s. This comparative example shows that if the power used is low, even with a long oxygen plasma etching time, sufficient etching cannot be achieved. Consequently, the hydrogen-chromic Pt / WO3 film still contains a high proportion of polymer template agent and has low porosity. Therefore, under otherwise identical conditions, the discoloration response speed and fading recovery speed to hydrogen are both slower than in Example 1.

[0070] Test method: 1) Coloring process: A flow rate of 200 sccm of 4% H2 / Ar (in from one side and out from the other) is introduced into a specially designed sealed aluminum alloy chamber, while the transmittance of the Pt / WO3 film at a wavelength of 1000 nm is monitored over time. The coloring response time is defined as the time interval from when the transmittance begins to change until the decrease reaches 90% of the total change.

[0071] 2) Transmittance change value: When the film is saturated with color, the transmittance decreases to the lowest value and no longer changes with time even if hydrogen is continued to be introduced. The difference between the initial and final transmittance at this time is the transmittance change value at 1000nm.

[0072] 3) Fading process: After the film is saturated with color, the hydrogen gas flow is stopped, and 20% O2 / N2 (synthetic air) at a flow rate of 300 sccm is introduced. Simultaneously, the transmittance of the Pt / WO3 film at a wavelength of 1000 nm is monitored over time. The fading recovery time is defined as the time interval from the start of the transmittance increase until the increase reaches 90% of the total change.

[0073] If we define the change in transmittance of WO3 in its colored and faded states ( T) is the modulation interval. The average rate of change of the transmittance of the sample during the coloring / fading process from the beginning to the point where the change reaches 90% of the modulation interval is the coloring / fading rate. The performance of the samples in Examples 1, 2, 3 and Comparative Examples 1, 2 are shown in Table 1.

[0074] Table 1. Performance comparison of Samples from Examples 1-3 and Comparative Examples 1-2 (test wavelength 1000nm)

[0075] The specific embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing rapid hydrogen-chromatic mesoporous tungsten oxide thin films based on plasma etching technology, characterized in that, Includes the following steps: S1. Preparation of precursor sol: Tungsten source and amphoteric block copolymer are dissolved in solvent to obtain tungsten source solution and copolymer solution, respectively. The two are then mixed to obtain precursor sol. S2. Preparation of hybrid membrane: Precursor sol was deposited on a substrate and aged at low temperature to obtain an organic-inorganic hybrid film. S3, Plasma Etching: The organic-inorganic hybrid thin film was subjected to plasma etching in an oxygen-containing atmosphere. The organic template was removed by oxygen-containing plasma to obtain the etched porous tungsten oxide film. S4, Catalyst Support: A nanocatalyst layer is prepared on the surface of the etched porous tungsten oxide film to obtain the hydrogen-chromic mesoporous tungsten oxide film.

2. The preparation method according to claim 1, characterized in that, In step S1, the tungsten source includes one or more of tungsten hexachloride, tungsten ethoxide, tungsten tetrachloride, polytungstic acid peroxide, ammonium tungstate, and scheelic acid; And / or, in step S1, the amphoteric block copolymer includes one or more of the following: polyoxyethylene-polystyrene, polyoxyethylene-polymethyl methacrylate, polyoxyethylene-poly2-vinylpyridine, polyoxyethylene-poly4-vinylpyridine, and polyoxyethylene-polyoxypropylene-polyoxyethylene. And / or, in step S1, the solvent for the tungsten source includes one or more of methanol, ethanol, n-propanol, and isopropanol; And / or, in step S1, the solvent for the amphoteric block copolymer includes one or more of tetrahydrofuran, chloroform, 1,4-dioxane, N,N-dimethylformamide, toluene, xylene, and benzene.

3. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of tungsten atoms in the tungsten source to the amphoteric block copolymer is 1:(0.2-5); And / or, in step S1, the ratio of tungsten atoms in the tungsten source to solvent is 1g: 2~15ml; And / or, in step S1, the ratio of the amphoteric block copolymer to the solvent is 1g: 5~100ml.

4. The preparation method according to claim 1, characterized in that, In step S1, the precursor sol also includes a chelating agent; the chelating agent includes acetylacetone.

5. The preparation method according to claim 1, characterized in that, In step S2, the method for depositing the precursor sol on the substrate includes one of spin coating, dip coating, or spray coating.

6. The preparation method according to claim 1, characterized in that, In step S2, the low-temperature aging temperature is 80–120°C, and the time is 10–15 hours; And / or, in step S2, the thickness of the resulting organic-inorganic hybrid film is 400-1000 nm.

7. The preparation method according to claim 1, characterized in that, In step S3, the excitation source used in the plasma etching process includes one of microwave plasma, radio frequency plasma, and low frequency plasma. And / or, in step S3, the microwave power of plasma etching is 450W to 1000W, the time is 3min to 120min, and the working gas pressure is 20Pa to 200Pa.

8. The preparation method according to claim 1, characterized in that, In step S3, during plasma etching, an etching gas is introduced, which is oxygen or a gas containing oxygen. The oxygen flow rate in the etching gas is 80-100%, and the oxygen flow rate is 10-500 sccm.

9. The preparation method according to claim 1, characterized in that, In step S4, the nanocatalyst layer is prepared by vapor deposition or chemical reduction deposition; And / or, in step S4, the catalyst in the nanocatalyst layer is one of Pt, Pd, Pt-Pd alloy, and Pd-Au alloy; And / or, in step S4, the thickness of the nanocatalyst layer is 1 nm to 10 nm.

10. A rapidly hydrogen-chromic mesoporous tungsten oxide thin film prepared by the method of any one of claims 1-9.

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