Low-concentration alkaline electrolytic water composite diaphragm, and preparation method and application thereof

Abstract

The application discloses a low-concentration alkaline electrolytic water composite diaphragm and a preparation method and application thereof, and belongs to the technical field of hydrogen production by electrolytic water and new energy materials. The application is based on the core idea of "interface reinforcement and ion transmission synergistic regulation", and a catechol functional unit is introduced by grafting an interface modifier (such as 3,4-dihydroxybenzaldehyde) to a polymer matrix main chain, in-situ anchoring inorganic hydrophilic fillers by using the strong coordination effect, and a continuous and anti-shedding efficient hydrated ion network is constructed; meanwhile, sulfonated modification is carried out on a polyphenylene sulfide (PPS) support net to improve the surface polarity, and then a multi-scale interface coupling structure with synergistic hydrogen bonds and coordination bonds is formed between a skin layer and a skeleton, and between a polymer and fillers. On this basis, the application adopts a non-solvent induced phase separation method to construct a composite membrane with a gradient pore structure, and perfect balance between ion transmission efficiency and gas barrier performance is realized.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen production by water electrolysis and the preparation technology of new energy materials, specifically relating to a low-concentration alkaline water electrolysis composite membrane, its preparation method and application. Background Technology

[0002] Hydrogen production through water electrolysis is a core technology for the large-scale and low-carbon development of hydrogen energy, and it is of great significance to energy transition and carbon neutrality. Alkaline water electrolysis (AWE) technology has the dual advantages of low cost and mature technology, making it one of the most economically feasible paths for industrial hydrogen production. The diaphragm, as a core component of the AWE system, plays a crucial role in transporting ions and separating the cathode and anode to prevent gas cross-mixing. However, existing diaphragms have insufficient ion transport performance, forcing the system to rely on high-concentration alkaline electrolytes (such as 20%-30% KOH) to maintain efficiency. This increases the technical requirements for equipment corrosion resistance and sealing, accelerates diaphragm aging and degradation, and also promotes electrolyte deterioration. Simultaneously, traditional diaphragms have high area resistivity and poor interfacial compatibility, resulting in low system electrolysis efficiency and insufficient safety, severely restricting the industrial upgrading of AWE technology. Therefore, developing new diaphragms with high ion transport performance, high safety, and industrial applicability is crucial for improving the overall performance of electrolyzers.

[0003] Currently, porous polyphenylene sulfide (PPS) woven membranes widely used in industry possess excellent chemical stability and mechanical strength. However, their inherent strong hydrophobicity, large thickness, and uneven pore size distribution lead to high sheet resistivity and limited gas barrier performance. To improve their performance, constructing composite membranes with PPS as the support layer and introducing functional skin layers on its surface has become a research hotspot. The commercial Zirfon membrane uses polysulfone (PSU) and ZrO2 particles to construct the functional layer, which reduces sheet resistivity and improves gas barrier capability to a certain extent. However, traditional aromatic polymer binders are highly hydrophobic, and the interfacial compatibility between polymer-filler and skin-support layer is limited. Under long-term alkaline conditions, interlayer delamination and inorganic filler shedding are prone to occur, which restricts the ion transport efficiency and structural stability of composite membranes under low-concentration electrolyte conditions. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a low-concentration alkaline water electrolysis composite membrane, its preparation method and application, so as to solve the technical problems of easy peeling at the interface and unstable operation over a long period of time in traditional composite membranes.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a method for preparing a low-concentration alkaline water electrolysis composite membrane, comprising the following steps: S1. Immerse polyphenylene sulfide (PPS) in sulfuric acid solution and sulfonate it at 70-90℃ for 7-9 hours. Rinse to obtain SPPS base film grafted with polar sulfonic acid groups. S2. The composite membrane is prepared using the non-solvent-induced phase separation (NIPS) method. The polymer matrix is ​​dissolved in solvent A, followed by the addition of an interface modifier and an acidic catalyst under a nitrogen atmosphere at 70-90℃. After mixing, the reaction proceeds for 10-14 hours. Finally, a crosslinking agent and an inorganic hydrophilic filler are added, and the mixture is stirred to obtain the casting slurry. The mass ratio of polymer matrix, interface modifier, acidic catalyst, crosslinking agent, and inorganic hydrophilic filler is 0.8-1.2:0.05-0.4:0.03-0.08:0.01-0.5:0.1-0.8. The inorganic hydrophilic filler is one or more of the following: alkali-resistant metal oxides, alkali-resistant metal hydroxides, alkali-resistant inorganic salts, and layered bimetallic hydroxides (LDHs). S3. Apply the casting slurry to the substrate surface, then lay the SPPS base film evenly, then apply another layer of casting slurry, and then immerse the whole thing in solvent B and cure at 5-25℃ for 10-14h. Through non-solvent-induced phase separation curing, a low-concentration alkaline electrolytic water composite membrane with an asymmetric sponge-like gradient pore structure is formed.

[0006] The composite membrane prepared by this invention has a "sandwich" structure, comprising an SPPS base membrane as a supporting framework layer and a functional skin layer, i.e., a casting slurry, coated on both sides or covering the surface of the supporting framework layer. The supporting framework layer is a porous support network with optimized surface polarity, specifically a sulfonated polyphenylene sulfide (SPPS) mesh with sulfonic acid groups (-SO3H) grafted onto its surface. The functional skin layer is a cross-linked polymer network incorporating interface strengthening units and hydrophilic inorganic fillers. The aldehyde groups in the interface modifier undergo a condensation reaction with some hydroxyl groups on the polymer matrix backbone to form a stable six-membered acetal ring structure, thereby introducing catechol groups with strong hydrogen bond donors and metal-philic coordination capabilities into the polymer network. Pre-crosslinking with a crosslinking agent constructs a three-dimensional acetal crosslinked network in the polymer matrix to restrict chain segment movement and improve the matrix's anti-swelling ability and structural stability. The inorganic hydrophilic filler is uniformly dispersed in the polymer matrix, and the metal ions in the filler form chelate coordination bonds with the catechol groups on the interface modifier.

[0007] Based on the above technical solution, the present invention can be further improved as follows: Furthermore, the mass fraction of the sulfuric acid solution is 95.0%-98.0%.

[0008] The polymer matrix is ​​a hydrophilic polymer rich in hydroxyl or amino groups.

[0009] Furthermore, the polymer matrix is ​​one or more of polyvinyl alcohol (PVA), ethylene-vinyl alcohol copolymer (EVOH), polyhydroxyethyl methacrylate (PHEMA), chitosan, and hydroxyethyl cellulose.

[0010] The interface modifier is a bifunctional or multifunctional compound containing at least one reactive group for grafting onto a polymer matrix and at least one multicoordinating / multipolar group for interface anchoring. The reactive group is one of an aldehyde group, a carboxyl group, an isocyanate group, or an epoxy group; the multicoordinating / multipolar group for interface anchoring is an ortho-dihydroxyl group (catechol group), a trihydroxyl group (gallic group), a phosphonic acid group, or a silaneoxy group.

[0011] Furthermore, the interface modifier is one or more of 3,4-dihydroxybenzaldehyde (DBA), 2,3-dihydroxybenzaldehyde, 3,4,5-trihydroxybenzaldehyde, 3,4-dihydroxybenzoic acid, gallic acid, and tannic acid.

[0012] Acidic catalysts are used to catalyze the condensation and crosslinking reactions between the polymer matrix and the interface modifier and crosslinking agent.

[0013] Furthermore, the acidic catalyst is one or more of organic protic acids, inorganic protic acids, solid acids, and Lewis acids.

[0014] Furthermore, the acidic catalyst is one or more of p-toluenesulfonic acid or its hydrate, benzenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, sulfuric acid, hydrochloric acid, phosphoric acid, strong acidic cation exchange resin, heteropoly acid, zinc chloride, and ferric chloride.

[0015] The crosslinking agent is a compound containing two or more functional groups that can undergo crosslinking reactions with the active groups of the polymer matrix, wherein the functional groups are selected from one or more of aldehyde, epoxy, carboxyl and isocyanate groups.

[0016] Furthermore, the crosslinking agent is a dialdehyde or polyaldehyde crosslinking agent, or a crosslinking agent containing multiple epoxy groups or a polycarboxylic acid crosslinking agent.

[0017] Furthermore, the crosslinking agent is one or more of terephthalaldehyde (TPA), glutaraldehyde (GA), glyoxal, succinaldehyde, ethylene glycol diglycidyl ether (EGDE), polyethylene glycol diglycidyl ether (PEGDE), citric acid, and tetraethyl orthosilicate (TEOS).

[0018] Inorganic hydrophilic fillers are inorganic particles that are chemically stable in alkaline electrolytes. Their surfaces contain metal sites or hydroxyl groups that can chemically coordinate or strongly hydrogen bond with polar groups (such as catechol groups) in interface modifiers.

[0019] Furthermore, the inorganic hydrophilic filler is one or more of zirconium dioxide (ZrO2), titanium dioxide (TiO2), cerium dioxide (CeO2), hafnium dioxide (HfO2), magnesium hydroxide (Mg(OH)2), barium titanate (BaTiO3), barium sulfate (BaSO4), and layered bimetallic hydroxides (LDHs).

[0020] Furthermore, solvent A is one or more of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), propylene carbonate (PC), sulfolane, water, alcohols, and ketones; solvent B is one or more of water, n-propanol, n-butanol, ethanol, and isopropanol.

[0021] The present invention also discloses a low-concentration alkaline water electrolysis composite membrane prepared by the above preparation method.

[0022] The present invention also discloses the application of the above-mentioned low-concentration alkaline water electrolysis composite membrane in the preparation of materials for electrolytic hydrogen production batteries.

[0023] The beneficial effects of this invention are as follows: 1. Completely solves the problems of "powder shedding" and interlayer peeling of inorganic fillers, and significantly improves interface stability.

[0024] Traditional composite membranes (such as commercial Zirfon membranes) are prone to peeling and detachment under long-term alkaline erosion due to the strong hydrophobicity of the polymer matrix and the weak physical entanglement between the polymer matrix and the inorganic particles and support layer. This invention, through biomimetic interface engineering, constructs a multi-scale chemical coupling network between the polymer skin layer and the inorganic filler and support layer. At the skin-support layer interface, the introduced catechol groups (ortho-dihydroxyl groups) specifically interact with the resonantly stable sulfonic acid groups on the sulfonated PPS (SPPS) surface, forming a microscopic "bitetooth-locked" strong hydrogen bond network. Combined with the "mechanical interlocking" effect generated by the roughening of the fiber surface due to sulfonation etching, the interface possesses extremely high peel resistance. Tape peeling tests confirmed that the functional layer of the composite membrane showed no significant peeling.

[0025] At the polymer-filler interface: Catechol groups utilize their "metalophilic" properties to interact with ZrO2 on the Zr surface. 4+ Stable chelate coordination bonds were formed at the center. This chemical anchoring effect has a higher bond energy than traditional hydrogen bonds, effectively overcoming the migration and aggregation of particles under strong alkali and ultrasonic disturbance. Ultrasonic testing confirmed no significant cortex separation or ZrO2 shedding.

[0026] 2. It overcomes the bottleneck of high internal resistance under low-concentration alkaline solution conditions and has excellent ion transport efficiency.

[0027] Traditional membranes cannot establish continuous hydration channels in low-concentration alkaline solutions (such as 1M KOH), leading to a surge in ohmic impedance and low electrolysis efficiency. This invention achieves synergistic regulation of a multi-scale hydrophilic network. The polymer backbone, phenolic hydroxyl groups grafted with interface modifiers, hydroxyl groups on the surface of inorganic hydrophilic fillers, and sulfonic acid groups of SPPS work together to significantly enhance the surface energy and pore wetting rate of the membrane. This highly polar interface causes the composite membrane to exhibit extremely high solution uptake in low-concentration (1M KOH) electrolytes (e.g., a 720.39% increase in mass for the Z25PD membrane). Sufficient pore filling provides OH... - The rapid migration via the Grotthuss mechanism provides a continuous liquid-phase channel, enabling a 0.47 Ω cm⁻¹ solution to be achieved even at low concentrations of 1 M KOH. 2 Extremely low surface resistance.

[0028] 3. It balances high gas barrier properties with long-term structural stability, significantly extending the service life of the equipment.

[0029] Hydrophilic polymers such as PVA are prone to severe swelling or even dissolution under high-temperature and strong alkaline conditions, leading to pore structure collapse and gas cross-contamination. This invention introduces a crosslinking agent (such as terephthalaldehyde, TPA) before film formation to construct a three-dimensional acetal crosslinking network, effectively restricting the thermal motion of polymer chain segments and significantly improving the matrix's resistance to swelling and thermodynamic stability. Simultaneously, this invention combines non-solvent-induced phase separation (NIPS) with a secondary coating process to prepare an asymmetric gradient sponge-like structure with large pores at the top and dense small pores at the bottom. This structure ensures rapid electrolyte wetting while maintaining a high bubble point pressure exceeding 16 bar, exhibiting excellent gas barrier capabilities. Ultimately, this allows the electrolyzer to operate stably for 1500 hours under 1M KOH low-concentration alkaline solution and 60°C conditions without significant voltage decay. Attached Figure Description

[0030] Figure 1 SEM image of the cross-section of the composite membrane Z25PD; Figure 2 Comparative photographs of tape peeling tests on commercial UTP220 membrane and composite separator Z25PD; Figure 3 Comparative images of ultrasonic vibration experiments on commercial UTP220 membrane and composite separator Z25PD; Figure 4 Polarization curves for composite membranes Z0PD, Z25PD, Z50PD, and Z75PD; Figure 5 This is the long-term in-situ stability test data for the composite diaphragm Z25PD. Detailed Implementation

[0031] The specific embodiments of the present invention are described below to facilitate understanding of the invention by those skilled in the art. Unless otherwise specified, specific conditions are applied according to conventional conditions or the manufacturer's recommendations. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various modifications are obvious as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims. All inventions utilizing the concept of this invention are protected.

[0032] Example 1 A method for preparing a low-concentration alkaline water electrolysis composite membrane includes the following steps: S1. Cut polyphenylene sulfide (PPS) mesh into small pieces, immerse them in concentrated sulfuric acid with a mass fraction of 96.0%, sulfonate them at 80°C for 8 hours, rinse them with deionized water until neutral, and obtain an SPPS base film grafted with polar sulfonic acid groups. S2. Dissolve 12g of polyvinyl alcohol (PVA) in 130.3g of dimethyl sulfoxide (DMSO), then add 3.8g of 3,4-dihydroxybenzaldehyde (DBA) and 0.9g of p-toluenesulfonic acid monohydrate (TsOH·H2O) under a nitrogen atmosphere at 80℃. After mixing, react for 12h. Finally, add 2.4g of terephthalaldehyde and 4g of zirconium dioxide (ZrO2) with a particle size of 50nm. The amount of ZrO2 added is 25% of the total mass of the polymer (PVA+DBA). After mixing, the casting slurry is obtained. S3. Using an adjustable coating tool, the casting slurry is scraped onto a clean glass plate surface, then the SPPS base film is laid flat, followed by another layer of casting slurry. The whole thing is then immersed in deionized water at 15°C and cured at 15°C for 12 hours to obtain a low-concentration alkaline electrolyzed water composite membrane, named Z25PD.

[0033] Example 2 The difference between this embodiment and Example 1 is that the amount of ZrO2 added is adjusted to 50% of the total mass of the polymer (PVA+DBA), while the other implementation conditions are the same as in Example 1, resulting in a low-concentration alkaline water electrolysis composite membrane, named Z50PD.

[0034] Example 3 The difference between this embodiment and Example 1 is that the amount of ZrO2 added is adjusted to 75% of the total mass of the polymer (PVA+DBA), while the other implementation conditions are the same as in Example 1, resulting in a low-concentration alkaline water electrolysis composite membrane, named Z75PD.

[0035] Example 4 A method for preparing a low-concentration alkaline water electrolysis composite membrane includes the following steps: S1. Cut polyphenylene sulfide (PPS) mesh into small pieces, immerse them in concentrated sulfuric acid with a mass fraction of 95.0%, sulfonate them at 90°C for 9 hours, rinse them with deionized water until neutral, and obtain an SPPS base film grafted with polar sulfonic acid groups. S2. Dissolve 12g of poly(hydroxyethyl methacrylate) (PHEMA) in 130.3g of N,N-dimethylformamide (DMF), then add 3.8g of 2,3-dihydroxybenzaldehyde and 0.9g of benzenesulfonic acid under a nitrogen atmosphere at 70°C. After mixing, react for 14h. Finally, add 5g of ethylene glycol diglycidyl ether, 2g of barium titanate (BaTiO3) and 2g of barium sulfate (BaSO4), mix well to obtain the casting slurry. S3. Using an adjustable coating applicator, the casting slurry is scraped onto a clean glass plate surface, then the SPPS base film is laid flat, followed by another layer of casting slurry. The entire assembly is then immersed in n-propanol at 15°C and cured at 25°C for 10 hours to obtain a low-concentration alkaline water electrolysis composite membrane.

[0036] Example 5 A method for preparing a low-concentration alkaline water electrolysis composite membrane includes the following steps: S1. Cut polyphenylene sulfide (PPS) mesh into small pieces, immerse them in concentrated sulfuric acid with a mass fraction of 98.0%, sulfonate them at 70°C for 7 hours, rinse them with deionized water until neutral, and obtain an SPPS base film grafted with polar sulfonic acid groups. S2. Dissolve 6g of chitosan and 6g of hydroxyethyl cellulose in 130.3g of N-methylpyrrolidone (NMP). Then, under a nitrogen atmosphere at 90°C, add 2g of 3,4,5-trihydroxybenzaldehyde, 2g of 3,4-dihydroxybenzoic acid and 0.9g of zinc chloride. After mixing, react for 10h. Finally, add 1g of glyoxal, 1g of succinaldehyde and 4g of titanium dioxide (TiO2), mix well and obtain the casting slurry. S3. Using an adjustable coating applicator, the casting slurry is scraped onto a clean glass plate surface, then the SPPS base film is laid flat, followed by another layer of casting slurry. The entire assembly is then immersed in isopropanol at 15°C and cured at 5°C for 14 hours to obtain a low-concentration alkaline water electrolysis composite membrane.

[0037] Comparative Example The difference between this comparative example and Example 1 is that ZrO2 is omitted, while the other implementation conditions are the same as in Example 1, resulting in a composite membrane named Z0PD.

[0038] The samples used in the following experiments are composite membranes prepared in Examples 1-3 and comparative examples.

[0039] Experimental Example 1: Microscopic Characterization Figure 1 The image shows a magnified SEM image of the Z25PD composite membrane cross-section. The SEM of the composite membrane cross-section reveals almost no gaps between the PPS mesh support layer and the skin layer interface, indicating good interfacial adhesion and tight bonding. This is due to the multi-scale coupling structure formed by hydrogen-bonded skin / support layer coupling, coordination-reinforced polymer / filler anchoring, and cross-linked network and physical encapsulation structural support in this invention. This coupling structure can maintain the integration of the skin-support layer under strong alkaline conditions, temperature fluctuations, and fluid scouring, inhibiting inorganic filler detachment and interlayer delamination, thus providing a structural basis for subsequent low electrochemical surface resistance and long-term stability in water electrolysis.

[0040] Experiment Example 2 Performance Testing 1. Sheet resistance test: The sheet resistance of the composite separator is tested using an electrochemical workstation in accordance with the provisions of standard SJ / T-10171-2016 "General Test Method for Basic Performance of Alkaline Battery Separator".

[0041] 2. Tensile strength test: The test shall be conducted in accordance with the provisions of the national standard GB1039-79 "Plastics Tensile Test Method" and using a tensile testing machine.

[0042] 3. Water contact angle test: According to the standard GB / T-30693-2014 "Measurement of contact angle between plastic film and water", the test is conducted using a contact angle measuring instrument.

[0043] 4. Bubble point pressure test: The test is conducted using a membrane pore size analyzer in accordance with the standard GB / T-32361-2015 "Test Methods for Pore Size of Separation Membranes - Bubble Point and Average Flow Rate Method".

[0044] 5. Electrolyte absorption rate test: The electrolyte absorption rate of the membrane sample in deionized water (H2O) and 1 mol L⁻¹ was determined by gravimetric method. -1 The absorption rate in KOH (1M KOH) solution. The test procedure is as follows: After washing the membrane with deionized water, freeze-dry it and weigh the dry membrane (G1). Then, immerse it completely in the corresponding electrolyte for 4 hours, remove it, and let it stand for 30 seconds to remove excess liquid from the surface. Weigh the wet membrane again (G2) and calculate the alkali absorption rate of the composite membrane: ; Where a is the alkali absorption rate of the composite membrane (%), G1 is the mass of the composite membrane when dry (g), and G2 is the mass of the composite membrane after soaking (g).

[0045] 6. Tape peel test: Wrap both sides of the commercial UTP220 membrane and the composite separator Z25PD with tape, and fully compress them with the same external force and time to make both sides of the membrane completely bonded to the tape. Then peel off the composite membrane skin by tearing the tape.

[0046] 7. Ultrasonic test: Immerse the composite membrane sample and the UTP220 membrane in a 6M KOH solution at 60℃ and sonicate continuously for 30 min.

[0047] The experimental results are shown in Table 1.

[0048] Table 1 Performance data of composite membranes prepared in Examples 1-3 and comparative examples

[0049] As shown in Table 1, the composite membrane exhibits high wettability, high bubble point pressure, low sheet resistance, and good mechanical properties. This is because the hydrophilic polymer and alkali-resistant hydrophilic inorganic nanomaterials in this invention serve as the hydrophilic components, endowing the membrane with extremely high wettability, reducing the contact angle (contact angle < 65°), significantly improving the wetting rate, and accelerating the penetration and diffusion of the electrolyte within the membrane, thus providing kinetic support for ion transport. This invention employs a combination of secondary coating and phase inversion to create a certain degree of structural asymmetry in the thickness direction of the composite membrane, ultimately producing a composite membrane with a small sponge-like pore structure, good pore interconnectivity, and no obvious through-holes. This structure ensures sufficient electrolyte penetration and maintains low ion transport resistance while providing high gas barrier capability, effectively increasing the bubble point pressure (bubble point pressure > 16 bar). The abundant hydrogen bond network in the composite membrane prepared by this invention facilitates rapid ion transport and reduces sheet resistance (Z25PD has a sheet resistance as low as 0.47 Ω cm in 1 M KOH). 2 The composite membrane has a high alkali absorption rate, which helps to reduce ion transport resistance and improve electrolysis efficiency. Since the SPPS base membrane provides a continuous fiber-reinforced framework as a support layer, the composite membrane also has good mechanical properties and can fully meet the actual operation requirements.

[0050] like Figure 2 As shown, the tape peel test revealed severe peeling of the functional layer of the commercial UTP220 membrane, exposing the PPS substrate; in contrast, the Z25PD membrane maintained its structural integrity with only very slight surface detachment. This confirms that the Z25PD membrane has superior interfacial adhesion between its functional layer and the substrate, resulting in significantly improved interfacial compatibility.

[0051] like Figure 3 As shown, the ultrasonic vibration experiment confirmed that the inorganic filler in the composite membrane is stably bonded. The coordination effect of catechol-ZrO2 not only improves the dispersion stability of the filler in the polymer matrix, but also inhibits the filler shedding and pore structure instability during operation, thereby improving the overall structural integrity and durability of the composite membrane.

[0052] 8. Referring to the testing standard GB / T 45092—2024 "Performance Testing and Evaluation of Electrodes for Hydrogen Production by Electrolysis of Water", under the conditions of 80℃ and 1M KOH, the electrolyzer of Example 1 (Z25PD) can achieve 1059 mA cm⁻¹ at 2.0V. -2 Its high current density results in extremely low high-frequency impedance (ohmic loss), only about 0.0534Ω. Figure 4 In 60℃ and 1M KOH, the composite membrane was first tested at 500 mA cm⁻¹. -2 It operated stably for 1000 hours at current density (with extremely low voltage decay, only 20µV h). -1 ), then at 1000mAcm -2 It continued to run stably for another 500 hours, for a total of 1500 hours, with no significant performance degradation. Figure 5 ).

Claims

1. A method for preparing a low-concentration alkaline water electrolysis composite membrane, characterized in that, Includes the following steps: S1. Immerse polyphenylene sulfide in sulfuric acid solution and sulfonate at 70-90℃ for 7-9 hours, then rinse to obtain SPPS base film; S2. The polymer matrix is ​​dissolved in solvent A, and then an interface modifier and an acidic catalyst are added under a nitrogen atmosphere at 70-90℃. After mixing, the mixture is reacted for 10-14 hours. Finally, a crosslinking agent and an inorganic hydrophilic filler are added, and after mixing, a casting slurry is obtained. The mass ratio of the polymer matrix, interface modifier, acidic catalyst, crosslinking agent, and inorganic hydrophilic filler is 0.8-1.2:0.05-0.4:0.03-0.08:0.01-0.5:0.1-0.

8. The inorganic hydrophilic filler is one or more of alkali-resistant metal oxides, alkali-resistant metal hydroxides, alkali-resistant inorganic salts, and layered bimetallic hydroxides. S3. Apply the casting slurry to the substrate surface, then lay the SPPS base film smoothly, then apply another layer of casting slurry, and then immerse the whole thing in solvent B and cure it at 5-25℃ for 10-14h to obtain a low-concentration alkaline electrolytic water composite membrane.

2. The method for preparing the low-concentration alkaline water electrolysis composite membrane according to claim 1, characterized in that, The sulfuric acid solution has a mass fraction of 95.0%-98.0%.

3. The method for preparing the low-concentration alkaline water electrolysis composite membrane according to claim 1, characterized in that, The polymer matrix is ​​one or more of polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyhydroxyethyl methacrylate, chitosan and hydroxyethyl cellulose.

4. The method for preparing the low-concentration alkaline water electrolysis composite membrane according to claim 1, characterized in that, The interface modifier is one or more of 3,4-dihydroxybenzaldehyde, 2,3-dihydroxybenzaldehyde, 3,4,5-trihydroxybenzaldehyde, 3,4-dihydroxybenzoic acid, gallic acid, and tannic acid.

5. The method for preparing the low-concentration alkaline water electrolysis composite membrane according to claim 1, characterized in that, The acidic catalyst is one or more of p-toluenesulfonic acid or its hydrate, benzenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, sulfuric acid, hydrochloric acid, phosphoric acid, strong acidic cation exchange resin, heteropoly acid, zinc chloride, and ferric chloride.

6. The method for preparing the low-concentration alkaline water electrolysis composite membrane according to claim 1, characterized in that, The crosslinking agent is one or more of the following: terephthalaldehyde, glutaraldehyde, glyoxal, succinaldehyde, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, citric acid, and tetraethyl orthosilicate.

7. The method for preparing the low-concentration alkaline water electrolysis composite membrane according to claim 1, characterized in that, The inorganic hydrophilic filler is one or more of zirconium dioxide, titanium dioxide, cerium dioxide, hafnium dioxide, magnesium hydroxide, barium titanate, barium sulfate, and layered bimetallic hydroxides.

8. The method for preparing the low-concentration alkaline water electrolysis composite membrane according to claim 1, characterized in that, Solvent A is one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, propylene carbonate, sulfolane, water, alcohols, and ketones; solvent B is one or more of water, n-propanol, n-butanol, ethanol, and isopropanol.

9. A low-concentration alkaline water electrolysis composite membrane, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of the low-concentration alkaline water electrolysis composite membrane according to claim 9 in the preparation of materials for electrolytic hydrogen production batteries.

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