Composite separator for alkaline water electrolysis and method for producing the same

Abstract

This invention discloses a composite membrane for alkaline water electrolysis and its preparation method, relating to the field of alkaline water electrolysis for hydrogen production. The preparation method includes: roughening a polyphenylene sulfide (PPS) support network substrate using an adhesive-peel method; modifying the roughened PPS support network surface with polydopamine; dissolving a thermoplastic resin in an organic solvent and adding hydrophilic inorganic nanoparticles for uniform mixing to obtain a casting solution; coating the casting solution onto at least one surface of the modified PPS support network to form a liquid film; and placing the PPS support network coated with the liquid film in a non-solvent for phase inversion treatment to remove the organic solvent, thus obtaining the composite membrane. This composite membrane has controllable thickness, high airtightness, and low surface resistivity. Its support network, after hydrophilic modification, exhibits excellent alkali resistance and stability, significantly extending the electrolyzer's operating life, effectively isolating hydrogen and oxygen gases, and reducing electrolysis energy consumption, meeting the technical requirements for large-scale clean energy hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of alkaline water electrolysis hydrogen production technology, specifically relating to a composite membrane for alkaline water electrolysis and its preparation method. Background Technology

[0002] Hydrogen energy, as a clean and efficient secondary energy source, is a key vehicle for achieving "dual carbon" goals and transforming the energy structure. Among numerous hydrogen production technologies, alkaline water electrolysis has become the mainstream route for large-scale "green hydrogen" production due to its mature technology, simple process, low cost, and ease of coupling with renewable energy. The membrane, as the core component of the alkaline electrolyzer, directly determines the energy consumption, hydrogen purity, and operational safety of the electrolysis process. An ideal membrane needs excellent airtightness to prevent hydrogen-oxygen mixing, low sheet resistance to reduce ohmic losses, good resistance to alkali corrosion to ensure long-term stability, and sufficient mechanical strength to adapt to industrial production and applications.

[0003] Currently, commercially available alkaline water electrolysis membranes have mainly gone through two development stages. The first generation was asbestos membranes, which, although possessing good hydrophilicity and ion conductivity, have been gradually phased out due to the carcinogenicity of asbestos and its swelling issues in alkaline solutions. The second generation is polyphenylene sulfide (PPS) woven fabric membranes, which have excellent alkali resistance and thermal stability. However, due to their poor hydrophilicity, large and uneven pore size distribution, they exhibit high sheet resistivity and insufficient gas barrier properties, often requiring operation at high current densities, thus increasing system energy consumption.

[0004] To overcome the aforementioned shortcomings, organic-inorganic composite membranes have become a current research hotspot. These membranes typically use a porous polymer woven mesh (such as PPS) as a supporting substrate to impart mechanical strength. A functional barrier layer containing hydrophilic inorganic nanoparticles (such as ZrO2 or TiO2) is then coated onto this substrate using a solvent-inducible phase inversion method, forming a composite membrane with a finely porous structure. This structure allows the membrane to maintain high airtightness while significantly reducing membrane thickness and sheet resistivity, thereby lowering electrolysis voltage and energy consumption.

[0005] However, existing composite membrane technology still faces a core bottleneck: the contradiction between the overall thickness of the membrane and its mechanical stability. To achieve lower energy consumption, the membrane thickness needs to be reduced as much as possible. However, the membrane thickness is mainly limited by the mechanical strength and structural characteristics of the supporting mesh substrate. When using high-mesh (i.e., thinner, denser pores) PPS woven mesh to reduce the substrate thickness, the contact area between the coating and the supporting mesh is significantly reduced. Furthermore, the low surface energy and strong chemical inertness of PPS material result in a much weaker adhesion between the polymer barrier layer and the substrate than the cohesive force of the coating material itself. This easily leads to peeling and detachment of the coatings on both sides during preparation or use, severely compromising the long-term operational stability and safety of the membrane. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a composite membrane for alkaline water electrolysis and its preparation method, so as to solve the technical problems of easy detachment of the functional layer of the composite membrane and poor stability caused by the reduction of the thickness of the support mesh in the prior art.

[0007] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a method for preparing a composite membrane for alkaline water electrolysis, comprising the following steps: S1, The polyphenylene sulfide support mesh substrate is roughened by adhesive-peel method; S2, the roughened polyphenylene sulfide support network is modified with polydopamine surface; S3, dissolve thermoplastic resin in an organic solvent and add hydrophilic inorganic nanoparticles and mix evenly to obtain casting solution; S4, the casting liquid is applied to at least one surface of the polyphenylene sulfide support mesh treated in S2 to form a liquid film; S5, the polyphenylene sulfide support network coated with liquid film is placed in a non-solvent for phase inversion treatment to remove the organic solvent, thus obtaining the composite membrane.

[0008] A further improvement of the present invention is that the specific process of the adhesive-peel roughening treatment in step S1 is as follows: a mixture of polyurethane adhesive and dichloromethane is uniformly coated on the adhesive plate, the polyphenylene sulfide support mesh is pasted on the adhesive plate, and after standing for 20 to 60 seconds, it is peeled off, so that the adhesive adheres to and peels off part of the material on the surface of the support mesh, forming a roughened surface.

[0009] A further improvement of the present invention is that the polydopamine surface modification in step S2 includes: placing the roughened polyphenylene sulfide support mesh in a 2-3 wt% hydrochloric acid dopamine solution, adjusting the pH value to 8.5-9, and reacting at 60-70°C for 20-24 hours to form a polydopamine coating on its surface.

[0010] A further improvement of the present invention is that, after forming the polydopamine coating, step S2 further includes a step of functionalizing the polydopamine-modified polyphenylene sulfide support network to introduce active groups on its surface; the active groups include one or more of amino, hydroxyl, sulfonic acid, and carboxyl groups.

[0011] A further improvement of the present invention is that the thermoplastic resin in step S3 is one or more of polysulfone, polyethersulfone, polyphenylene sulfide, polypropylene, polyetheretherketone, polyimide, and polyetherimide; and the organic solvent is one or more of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetonitrile.

[0012] A further improvement of the present invention is that the hydrophilic inorganic nanoparticles in step S3 are one or more of zirconium dioxide, cerium dioxide, and titanium dioxide, and their particle size is 10~100nm.

[0013] A further improvement of the present invention is that the coating in step S4 is a double-sided coating, specifically: the polyphenylene sulfide support mesh treated in S2 is tightened and fixed, and the casting liquid is evenly coated on both sides from bottom to top with a scraper.

[0014] A further improvement of the present invention is that the non-solvent mentioned in step S5 is one or more of deionized water, n-propanol, isopropanol, and ethanol.

[0015] Secondly, the present invention also provides a composite diaphragm for alkaline water electrolysis, which is prepared by the above-described preparation method.

[0016] A further improvement of this invention is that the composite membrane has a contact angle of less than 30° and a sheet resistivity of less than 0.30 Ω·cm in an 80°C, 30wt% KOH solution. 2 .

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing a composite diaphragm for alkaline water electrolysis. A polyphenylene sulfide (PPS) support mesh is roughened using an adhesive-peel method, which precisely increases the surface roughness of the support mesh without relying on complex equipment or harsh conditions. This significantly improves the contact area and mechanical interlocking force between the subsequent coating and the substrate, effectively solving the problem of easy coating detachment. Combined with polydopamine surface modification, utilizing its excellent adhesion and hydrophilic properties, a uniform and stable active coating is formed on the support mesh surface. This not only further enhances the bonding strength between the support mesh and the barrier layer but also endows the support mesh with good alkali corrosion resistance, enabling long-term stable operation in an alkaline electrolyzer. Subsequently, a casting solution prepared by mixing thermoplastic resin and hydrophilic inorganic nanoparticles is coated onto the modified support mesh. A non-solvent-induced phase transformation forms a porous functional barrier layer. This barrier layer has a fine interconnected pore structure, ensuring high airtightness while reducing ion transport resistance. Simultaneously, the introduction of hydrophilic inorganic nanoparticles further optimizes the hydrophilicity and pore structure of the diaphragm, promoting the rapid transport of hydroxide ions in the electrolyte. The entire preparation method is simple, safe to operate, and cost-controllable. The resulting composite membrane has low surface resistivity, high air tightness, and excellent interfacial stability, providing key technical support for the efficient and energy-saving operation of alkaline water electrolysis hydrogen production systems.

[0018] This invention also provides a composite membrane for alkaline water electrolysis. Through synergistic treatment of adhesive-peel roughening and polydopamine surface modification, the interfacial bonding strength between the support network and the functional barrier layer is significantly enhanced. Compared with commercially available polyphenylene sulfide-based composite membranes, the contact angle is reduced from 50° to below 30° and the sheet resistivity is reduced from 0.40 Ω·cm. 2 Reduced to 0.30 Ω·cm 2 The following key performance indicators have achieved significant breakthroughs, meeting the industrial application requirements of alkaline electrolyzers for low energy consumption, high airtightness, and long-term operational stability. Detailed Implementation

[0019] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0021] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0022] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0023] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0024] This invention provides a method for preparing a composite membrane for alkaline water electrolysis, comprising the following steps: S1, The polyphenylene sulfide support mesh substrate is roughened by adhesive-peel method; S2, the roughened polyphenylene sulfide support network is modified with polydopamine surface; S3, dissolve thermoplastic resin in an organic solvent and add hydrophilic inorganic nanoparticles and mix evenly to obtain casting solution; S4, the casting liquid is applied to at least one surface of the polyphenylene sulfide support mesh treated in S2 to form a liquid film; S5, the polyphenylene sulfide support network coated with liquid film is placed in a non-solvent for phase inversion treatment to remove the organic solvent, thereby obtaining the composite membrane; wherein the non-solvent is one or more of deionized water, n-propanol, isopropanol, and ethanol.

[0025] In this embodiment, the specific process of the adhesive-peel roughening treatment in step S1 is as follows: a mixture of polyurethane adhesive and dichloromethane is uniformly coated on a glass adhesive sheet. A polyphenylene sulfide (PPS) support mesh is then adhered to the adhesive sheet, with the adhered length slightly longer than the adhesive sheet to form an extended gripper. After standing for 20-60 seconds, the support mesh is peeled off using the gripper. During the peeling process, the polyurethane adhesive adheres to and peels off part of the material on the surface of the support mesh, forming a roughened surface. The other side of the PPS support mesh is then roughened in the same way. This method is simple to operate and highly universal, significantly improving the contact area and bonding strength between the coating and the support mesh by increasing surface roughness.

[0026] In this embodiment, the polydopamine surface modification in step S2 includes: placing the roughened polyphenylene sulfide support mesh in a 2-3 wt% hydrochloric acid dopamine solution, adjusting the pH value to 8.5-9, and reacting at 60-70°C for 20-24 hours to form a polydopamine coating on its surface; due to the unique surface adhesion of polydopamine, the adhesion performance of the modified polyphenylene sulfide support mesh surface is greatly improved.

[0027] In this embodiment, after forming the polydopamine coating, step S2 further includes a step of functionalizing the polydopamine-modified polyphenylene sulfide support network to introduce active groups onto its surface; the active groups include one or more of amino, hydroxyl, sulfonic acid, and carboxyl groups. Introducing active groups can improve the hydrophilicity and alkali corrosion resistance of the polyphenylene sulfide support network, enhance the bonding strength between the barrier layer and the support network, and extend the service life of the support network.

[0028] In this embodiment, the thermoplastic resin in step S3 is one or more of polysulfone, polyethersulfone, polyphenylene sulfide, polypropylene, polyetheretherketone, polyimide, and polyetherimide. The thermoplastic resin has a wide processing temperature range, good melt flow, and can be repeatedly processed, resulting in a film material with high mechanical strength and good dimensional stability. The organic solvent is one or more of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetonitrile.

[0029] In this embodiment, the hydrophilic inorganic nanoparticles mentioned in step S3 are one or more of zirconium dioxide, cerium dioxide, and titanium dioxide, with a particle size of 10-100 nm. These hydrophilic nanoparticles can enhance the mechanical strength of the membrane and optimize its pore structure, thereby improving water flux and gas separation efficiency.

[0030] In this embodiment, the coating in step S4 is a double-sided coating, specifically: the polyphenylene sulfide support mesh treated in S2 is tightened and fixed, and the casting liquid is evenly coated on both sides from bottom to top with a scraper.

[0031] The method for preparing the composite membrane for alkaline water electrolysis provided by this invention is simple to operate and cost-controllable, significantly improves the efficiency of alkaline water electrolysis, ensures long-term stable operation of the system in an alkaline environment, and meets the technical requirements of industrial-grade alkaline water electrolysis hydrogen production devices for membrane materials.

[0032] This invention also provides a composite membrane for alkaline water electrolysis, prepared using the above-described method. The composite membrane exhibits a contact angle of less than 30° and a sheet resistivity of less than 0.30 Ω·cm in a 30 wt% KOH solution at 80°C. 2 .

[0033] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0034] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents parts by weight, and "ratio" represents weight proportion.

[0035] Example 1 This embodiment provides a method for preparing a composite membrane for alkaline water electrolysis, including the following steps: Step 1: Evenly coat a mixture of polyurethane adhesive and dichloromethane onto a glass adhesive sheet, wherein the mass ratio of polyurethane adhesive to dichloromethane is 1:10; attach the polyphenylene sulfide support mesh substrate to the adhesive sheet, let it stand for 60 seconds, and then peel off the support mesh to form a roughened surface; repeat the same operation to roughen the other side of the support mesh.

[0036] Step 2: Add dopamine hydrochloride to a tris(hydroxymethyl)aminomethane solution to prepare a 3wt% dopamine hydrochloride solution; wash the roughened polyphenylene sulfide support mesh alternately with ethanol and deionized water, dry it, immerse it in the dopamine hydrochloride solution, add sodium hydroxide to adjust the pH to 8.5, heat to 60℃ and react for 24 hours to obtain the polydopamine-modified polyphenylene sulfide support mesh.

[0037] Step 3: Immerse the above polyphenylene sulfide support mesh in a mixture of 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3:1, and react at 60°C for 2 hours to introduce sulfonic acid groups (-SO3H) and hydroxyl groups (-OH) onto the surface of the support mesh.

[0038] Step 4: At room temperature, add 15g of polysulfone to 85g of N-methyl-2-pyrrolidone (NMP) and stir mechanically until completely dissolved; then add 85g of zirconia particles with a particle size of 40nm in batches, stir and disperse at 2000rpm for 6 hours, and after standing to defoam, obtain the casting solution.

[0039] Step 5: Fix the clean and dry polyphenylene sulfide support mesh after step 3 between two scrapers with a spacing of 25μm, and evenly apply the casting liquid from bottom to top.

[0040] Step 6: Immerse the coated support mesh in deionized water at room temperature for phase inversion, changing the water every half hour until the NMP concentration in the deionized water no longer changes; after removing it, rinse the composite membrane with deionized water, cut it to the required size, and store it in deionized water.

[0041] Example 2 This embodiment provides a method for preparing a composite membrane for alkaline water electrolysis, including the following steps: Step 1: Evenly coat a mixture of polyurethane adhesive and dichloromethane onto a glass adhesive sheet, wherein the mass ratio of polyurethane adhesive to dichloromethane is 1:10; attach the polyphenylene sulfide support mesh substrate to the adhesive sheet, let it stand for 60 seconds, and then peel off the support mesh to form a roughened surface; repeat the same operation to roughen the other side of the support mesh.

[0042] Step 2: Add dopamine hydrochloride to a tris(hydroxymethyl)aminomethane solution to prepare a 2wt% dopamine hydrochloride solution; wash the roughened polyphenylene sulfide support mesh alternately with ethanol and deionized water, dry it, immerse it in the dopamine hydrochloride solution, add sodium hydroxide to adjust the pH to 9, heat to 70℃ and react for 20 hours to obtain the polydopamine-modified polyphenylene sulfide support mesh.

[0043] Step 3: The above-mentioned polyphenylene sulfide support mesh is treated with oxygen plasma at a power of 100W for 5 minutes to activate its surface; then it is immersed in an ethanol solution of 1wt% γ-aminopropyltriethoxysilane (KH550) and reacted at 60°C for 3 hours. After removal, it is washed with ethanol and then cured at 120°C for 1 hour, thereby introducing amino groups (-NH2) onto the surface of the support mesh.

[0044] Step 4: At room temperature, add 20g of polypropylene to 100g of N,N-dimethylformamide (DMF) and stir mechanically until completely dissolved; then add 80g of cerium dioxide particles with a particle size of 30nm in batches, stir and disperse at 2000rpm for 6 hours, and after standing to defoam, obtain the casting solution.

[0045] Step 5: Fix the clean and dry polyphenylene sulfide support mesh after step 3 between two scrapers with a spacing of 25μm, and evenly apply the casting liquid from bottom to top.

[0046] Step 6: Immerse the coated support mesh in deionized water at room temperature for phase inversion, changing the water every half hour until the concentration of DMF in the deionized water no longer changes; after removing it, rinse the composite membrane with deionized water, cut it to the required size, and store it in deionized water.

[0047] Example 3 This embodiment provides a method for preparing a composite membrane for alkaline water electrolysis, including the following steps: Step 1: Evenly coat a mixture of polyurethane adhesive and dichloromethane onto a glass adhesive sheet, wherein the mass ratio of polyurethane adhesive to dichloromethane is 1:10; attach the polyphenylene sulfide support mesh substrate to the adhesive sheet, let it stand for 60 seconds, and then peel off the support mesh to form a roughened surface; repeat the same operation to roughen the other side of the support mesh.

[0048] Step 2: Add dopamine hydrochloride to a tris(hydroxymethyl)aminomethane solution to prepare a 2.5 wt% dopamine hydrochloride solution; wash the roughened polyphenylene sulfide support mesh alternately with ethanol and deionized water, dry it, immerse it in the dopamine hydrochloride solution, add sodium hydroxide to adjust the pH to 8.5, heat to 65℃ and react for 22 hours to obtain the polydopamine-modified polyphenylene sulfide support mesh.

[0049] Step 3: Immerse the above polyphenylene sulfide support network into a mixture of 5% Tween-80 and 10% H2O2 in a volume ratio of 1:1, and react at 70°C for 5 hours; the polyoxyethylene chains of Tween-80 guide the H2O2 to penetrate and oxidize, thereby introducing hydroxyl groups (-OH) on the surface of the support network.

[0050] Step 4: At room temperature, add 25g of polyimide to 100g of acetonitrile and stir mechanically until completely dissolved; then add 80g of titanium dioxide particles with a particle size of 50nm in batches, stir and disperse at 2000rpm for 6 hours, and after standing to defoam, obtain the casting solution.

[0051] Step 5: Fix the clean and dry polyphenylene sulfide support mesh after step 3 between two scrapers with a spacing of 25μm, and evenly apply the casting liquid from bottom to top.

[0052] Step 6: Immerse the coated support mesh in deionized water at room temperature for phase inversion, changing the water every half hour until the solvent concentration in the deionized water no longer changes; after removing it, rinse the composite membrane with deionized water, cut it to the required size, and store it in deionized water.

[0053] Comparative Example 1 This comparative example provides a commercially available polyphenylene sulfide-based composite membrane, specifically structured as follows: a polyphenylene sulfide woven mesh serves as the supporting substrate, with a composite coating composed of zirconium oxide particles and polyvinylidene fluoride on the surface. This membrane is prepared using conventional dip-coating or blade-coating processes, without surface roughening or hydrophilic modification of the supporting mesh; the bonding between the coating and the substrate primarily relies on physical anchoring.

[0054] The hydrophilicity and ion conductivity of the composite membranes prepared in Examples 1-3 and the commercially available composite membrane of Comparative Example 1 were tested. Hydrophilicity was evaluated by measuring the static contact angle between the membrane surface and the alkaline solution, and ion conductivity was characterized by the membrane surface resistance. The test conditions were: 80℃, 30wt% KOH solution. The test results are shown in Table 1.

[0055] Table 1. Performance test results of composite membrane

[0056] As shown in Table 1, the contact angles of the composite membranes prepared in Examples 1-3 of this invention are all less than 30° in alkaline solution, while the contact angle of the commercially available composite membrane in Comparative Example 1 is 50°, indicating that the composite membrane of this invention has superior hydrophilicity. This is due to the surface modification of polydopamine and the introduction of active groups, which significantly improves the surface wetting properties of the support mesh. Regarding sheet resistivity, the sheet resistivity of Examples 1-3 is all below 0.30 Ω·cm. 2 In Examples 1 and 3, the Ω·cm was as low as 0.26 Ω·cm. 2 The surface resistivity of Comparative Example 1 is 0.40 Ω·cm. 2 Lower sheet resistance means lower ion transport resistance, which helps reduce electrolysis energy consumption. In summary, the composite membrane prepared by this invention significantly outperforms commercially available similar products in both hydrophilicity and ion conductivity.

[0057] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a composite diaphragm for alkaline water electrolysis, characterized in that, Includes the following steps: S1, The polyphenylene sulfide support mesh substrate is roughened by adhesive-peel method; S2, the roughened polyphenylene sulfide support network is modified with polydopamine surface; S3, dissolve thermoplastic resin in an organic solvent and add hydrophilic inorganic nanoparticles and mix evenly to obtain casting solution; S4, the casting liquid is applied to at least one surface of the polyphenylene sulfide support mesh treated in S2 to form a liquid film; S5, the polyphenylene sulfide support network coated with liquid film is placed in a non-solvent for phase inversion treatment to remove the organic solvent, thus obtaining the composite membrane.

2. The method for preparing a composite diaphragm for alkaline water electrolysis according to claim 1, characterized in that, The specific process of the adhesive-peel roughening treatment in step S1 is as follows: a mixture of polyurethane adhesive and dichloromethane is evenly coated on the adhesive board, the polyphenylene sulfide support mesh is pasted on the adhesive board, and after standing for 20 to 60 seconds, it is peeled off, so that the adhesive adheres to and peels off part of the material on the surface of the support mesh, forming a roughened surface.

3. The method for preparing a composite diaphragm for alkaline water electrolysis according to claim 1, characterized in that, The polydopamine surface modification in step S2 includes: placing the roughened polyphenylene sulfide support mesh in a 2-3 wt% hydrochloric acid dopamine solution, adjusting the pH value to 8.5-9, and reacting at 60-70°C for 20-24 hours to form a polydopamine coating on its surface.

4. The method for preparing a composite diaphragm for alkaline water electrolysis according to claim 1, characterized in that, Step S2, after forming the polydopamine coating, further includes a step of functionalizing the polydopamine-modified polyphenylene sulfide support network to introduce active groups on its surface; the active groups include one or more of amino, hydroxyl, sulfonic acid, and carboxyl groups.

5. The method for preparing a composite diaphragm for alkaline water electrolysis according to claim 1, characterized in that, The thermoplastic resin in step S3 is one or more of polysulfone, polyethersulfone, polyphenylene sulfide, polypropylene, polyetheretherketone, polyimide, and polyetherimide; the organic solvent is one or more of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetonitrile.

6. The method for preparing a composite diaphragm for alkaline water electrolysis according to claim 1, characterized in that, The hydrophilic inorganic nanoparticles mentioned in step S3 are one or more of zirconium dioxide, cerium dioxide, and titanium dioxide, and their particle size is 10~100nm.

7. The method for preparing a composite diaphragm for alkaline water electrolysis according to claim 1, characterized in that, The coating described in step S4 is a double-sided coating, specifically: the polyphenylene sulfide support mesh treated in S2 is stretched and fixed, and the casting liquid is evenly coated on both sides from bottom to top using a scraper.

8. The method for preparing a composite diaphragm for alkaline water electrolysis according to claim 1, characterized in that, The non-solvent mentioned in step S5 is one or more of deionized water, n-propanol, isopropanol, and ethanol.

9. A composite diaphragm for alkaline water electrolysis, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 8.

10. A composite diaphragm for alkaline water electrolysis according to claim 9, characterized in that, The composite diaphragm exhibits a contact angle of less than 30° and a sheet resistivity of less than 0.30 Ω·cm in a 30 wt% KOH solution at 80°C. 2 .

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