Composite diaphragm for hydrogen production by alkaline electrolyzed water as well as preparation method and application of composite diaphragm

Abstract

The invention relates to a composite diaphragm for hydrogen production from alkaline electrolyzed water and a preparation method and application thereof.The composite diaphragm comprises a supporting substrate, mixed matrix layers are arranged on the two sides of the supporting substrate, each mixed matrix layer comprises a mixture of functional polymer resin and thermoplastic resin, each mixed matrix layer is of a porous structure, and the mixed matrix layers are arranged on the supporting substrate. And the functional polymer resin is orderly arranged on the outer surfaces of the pore channels of the mixed matrix layer. The preparation method comprises the following steps: preparing a membrane casting solution; coating two sides of the support substrate with the casting solution; phase inversion; and cleaning and storing. Compared with the prior art, the functional polymer resin is distributed on the surfaces of the pore channels of the composite diaphragm by regulating and controlling the phase separation step of the mixed matrix layer, and the composite diaphragm has excellent stability, air tightness and OH <-> conductivity and is relatively low in diaphragm preparation cost.

Description

Technical Field

[0001] The present invention relates to the technical field of diaphragms for hydrogen production by alkaline water electrolysis, and particularly to a composite diaphragm for alkaline water electrolysis hydrogen production, a preparation method thereof, and an application thereof. Background Art

[0002] As an ideal energy carrier, hydrogen has the advantages of high calorific value, large energy density, clean and pollution-free, etc., and is of great significance for realizing the clean transformation of energy, optimizing the energy structure, promoting the deep decarbonization of industry, and promoting the consumption and utilization of renewable energy. As the most promising hydrogen production technology in the 21st century, electrolytic water hydrogen production is considered to be the only source of green hydrogen. Among them, alkaline water electrolysis hydrogen production (AWE) is considered to be the most commercially feasible option for large-scale hydrogen evolution due to its low investment cost and mature technology.

[0003] The diaphragm is one of the core materials of the AWE diaphragm electrolyzer. When the electrolyzer is in operation, OH - moves from the cathode through the diaphragm to the anode, while the hydrogen and oxygen generated by electrolysis are blocked on both sides by the diaphragm. In order to prevent the phenomenon of hydrogen-oxygen intermixing, the thickness of the diaphragm has certain limitations. The mainstream polyphenylene sulfide (PPS) woven fabric is usually above 800 μm, and the thickness of the third-generation alkaline water diaphragm (organic-inorganic composite diaphragm) is about 500 μm, which is ten times that of the anion exchange membrane. The increase in thickness will lead to an increase in the transport resistance of OH - and further manifest as a higher electrolysis voltage. Therefore, improving the OH - conductivity of the diaphragm is the key to reducing the energy consumption of AWE.

[0004] The organic-inorganic composite diaphragm mainly based on the Zirfon Perl series of Agfa company is currently the greatest possibility for alkaline water diaphragms to have both airtightness and electrochemical performance. This organic-inorganic composite diaphragm uses polysulfone as the film-forming material, zirconia provides hydrophilicity, and the PPS network substrate provides mechanical strength, and is prepared by the non-solvent induced phase separation process (NIPS). On this basis, CN118147702A starts from the physical and chemical properties of the inorganic filler itself, and obtains a composite diaphragm with lower surface resistance and higher uniformity by regulating the particle size and mass ratio of the inorganic filler; CN115125582A introduces layered double metal hydroxide (LDH), and uses the hydrophilicity of LDH and good intrinsic OH - conducting ability to reduce the surface resistance of the organic-inorganic composite diaphragm.

[0005] It can be seen that regulating the inorganic filler is to improve the OH -Effective solutions for conductivity. However, the excellent stability of polysulfone results in poor interfacial compatibility between it and inorganic fillers. Coupled with the fact that the content of inorganic fillers (70 - 90 wt%) is much higher than that of polysulfone (10 - 30 wt%), it causes powder shedding problems during the transportation or use of the organic-inorganic composite separator, that is, the separator has poor stability and low lifespan. CN117230484A, CN118581518A, etc. propose to add a hydrophilic coating on the surface of the base film to wrap the inorganic fillers while not affecting the surface resistance, achieving an improvement in the stability of the organic-inorganic composite separator. However, in the production of separators, considering from the perspectives of materials, processes, or equipment, adding an additional coating will increase the production cost of the separator and lose its competitive advantage. Summary of the Invention

[0006] The object of the present invention is to provide a composite separator for alkaline electrolytic water hydrogen production, its preparation method and application. The prepared composite separator has excellent stability, airtightness, and OH - conductivity.

[0007] The object of the present invention can be achieved by the following technical solutions:

[0008] In the first aspect, the present invention provides a composite separator for alkaline electrolytic water hydrogen production, including a support substrate, and mixed matrix layers are arranged on both sides of the support substrate. The mixed matrix layer includes a mixture of a functional polymer resin and a thermoplastic resin.

[0009] Preferably, the mixed matrix layer is a porous structure, with a pore size of 1 - 100 nm and a porosity of 30 - 70%.

[0010] Preferably, the thickness of the mixed matrix layer is 30 - 300 μm, and the thickness of the support substrate is 70 - 300 μm.

[0011] Preferably, in the mixed matrix layer, the functional polymer resin is orderly arranged on the outer surface of the pores of the mixed matrix layer.

[0012] In the present invention, the "orderly arrangement" means that the functional polymer resin can be more concentratedly distributed on the pore surface, rather than being evenly distributed in the mixed matrix layer.

[0013] Preferably, the functionality of the functional polymer resin refers to having hydrophilicity and the ability to conduct hydroxide ions, being able to remain stable in alkaline solutions, having film-forming ability, and being soluble in organic solvents.

[0014] Preferably, the functional polymer resin includes, but is not limited to, one or more of perfluorosulfonic acid resin, quaternized polysulfone, sulfonated polysulfone, quaternized polyphenylene oxide, quaternized polybenzimidazole, polyarylpiperidine, and polyarylquinine.

[0015] Preferably, the thermoplastic resin includes, but is not limited to, one or more of polysulfone, polyethersulfone, polyetheretherketone, polyimide, and polyetherimide.

[0016] Preferably, the support substrate includes any one of a mesh, a porous membrane, a non-woven fabric, and a woven fabric, and its material includes, but is not limited to, one or more of polyphenylene sulfide, polyethylene, polypropylene, polytetrafluoroethylene, polyetheretherketone, and polyimide.

[0017] In a second aspect, the present invention provides a method for preparing the composite diaphragm for alkaline electrolytic water hydrogen production, comprising the following steps:

[0018] S1: Dissolve the thermoplastic resin and the functional polymer resin in an organic solvent and stir to prepare a casting solution;

[0019] S2: Coat the casting solution on both sides of the support substrate;

[0020] S3: Phase inversion;

[0021] S4: Wash and store.

[0022] Preferably, step S1 specifically includes the following steps: At 70-90 °C, dissolve the thermoplastic resin and the functional polymer resin in an organic solvent, stir at a speed of 300-1000 rpm for more than 4 hours to ensure that the polymer chains are fully unfolded, and the uniform solution after complete dissolution of the polymer is the casting solution.

[0023] Preferably, in step S1, the addition amount of the functional polymer resin is 1-50 wt% of the thermoplastic resin, and the content of the thermoplastic resin in the organic solvent is 5-40 wt%.

[0024] More preferably, in step S1, the addition amount of the functional polymer resin is 10 wt% of the thermoplastic resin.

[0025] In step S1 of the present invention, the optimal addition amount of the functional polymer resin needs to comprehensively consider factors such as whether the casting solution is easy to coat and the material cost.

[0026] Preferably, in step S1, the organic solvent includes, but is not limited to, one or more of N-methyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, formamide, and N,N-dimethylacetamide.

[0027] Preferably, step S2 includes the following steps: At 20-27 °C and 50-70% relative humidity, coat the casting solution on the left and right sides of the support substrate with a doctor blade or a coating head.

[0028] Preferably, step S3 includes the following steps: soaking the support substrate coated with the casting solution in non-solvents at low temperature, room temperature, and high temperature in sequence, with each soaking time not less than 30 minutes, and taking it out after the organic solvent is completely replaced.

[0029] Preferably, in step S3, the non-solvent includes, but is not limited to, one or more of deionized water, n-propanol, isopropanol, and ethanol.

[0030] Preferably, in step S3, the low temperature is -15 - 15°C, the room temperature is 15 - 40°C, and the high temperature is 40 - 100°C.

[0031] Further preferably, in step S3, when the non-solvent is deionized water, the lowest temperature of the deionized water is 0°C, and if further cooling is required, other non-solvents such as ethanol can be added.

[0032] Further preferably, in step S3, the non-solvent at high temperature is usually deionized water.

[0033] Further preferably, in step S3, each soaking time is 1 hour.

[0034] Preferably, step S4 includes the following steps: cleaning the composite separator with deionized water, cutting it to a suitable size, and storing it in deionized water.

[0035] Further preferably, in step S4, the deionized water for cleaning and storing is at room temperature.

[0036] In a third aspect, the present invention also provides an application of the composite separator for alkaline electrolytic water hydrogen production in alkaline water electrolysis hydrogen production.

[0037] Further preferably, the preparation method of the composite separator for alkaline electrolytic water hydrogen production includes the following steps:

[0038] S1: At 80°C, batchwise put the thermoplastic resin and the functional polymer resin into an organic solvent, and mechanically stir for more than 4 hours to ensure that the polymer chains are fully unfolded. The uniform solution after the polymer is completely dissolved is the casting solution.

[0039] S2: At 25°C and 60% relative humidity, tighten the dry and clean support substrate with a fixture, and coat the casting solution on both left and right sides of the support substrate by a doctor blade or a coating head.

[0040] S3: Soak the support substrate after coating in non-solvents at low temperature, room temperature, and high temperature in sequence, with each soaking time being 1 hour, and take out the mixed matrix separator after the organic solvent is completely replaced.

[0041] S4: Clean the separator with deionized water, cut it to a suitable size, and store it in deionized water.

[0042] The present invention provides a composite diaphragm for alkaline electrolytic water hydrogen production. By using a functional polymer resin that is alkali-resistant, hydrophilic and has OH - conductivity to replace traditional inorganic fillers, and taking advantage of the different interactions between different types of polymers and solvents and non-solvents, the functional polymer resin is induced to segregate during the NIPS process (i.e., the phase inversion process of the present invention), and is orderly arranged on the surface of the pore channels of the porous composite diaphragm. Through ion exchange, promoting the diffusion of hydrated ions, etc., the functional groups of the functional polymer resin can directly or indirectly interact with OH - in the pore channels, accelerating the OH - conductivity speed in the membrane and realizing the functionalization of the porous structure. In addition, the bonding effect of two polymers with relatively close polarities is much better than that between polymers and inorganic fillers. Therefore, using functional polymer resins fundamentally solves the problem of powder shedding of organic-inorganic composite diaphragms, which is a good way to improve the stability of alkaline water diaphragms.

[0043] The present invention regulates the phase separation step of the mixed matrix layer (i.e., the phase inversion step of the present invention) according to the different solubilities of two types of polymers in solvents and non-solvents, so that the thermoplastic resin first shows a solid-liquid phase separation trend, and the functional polymer resin is affected by the combined action of the solvent and non-solvent and moves to the lean phase region of the thermoplastic resin, and finally forms the outer surface of the porous structure. The functionalized polymer resin used in the present invention has excellent hydrophilicity. When the composite film with a porous structure prepared by the present invention is placed in an electrolyte (30 wt% KOH aqueous solution), the functional polymer resin swells on the surface of the pore channels of the mixed matrix layer, resulting in a decrease in the pore diameter of the mixed matrix layer, thereby improving the airtightness of the porous membrane. And the functional resin has the ability to conduct hydroxide ions, which can minimize the negative impact of the decrease in pore size on hydroxide ion conduction. Therefore, the present invention has good OH - conductivity while also having excellent airtightness.

[0044] In addition, traditional composite diaphragms need to add inorganic fillers to improve hydrophilicity to enhance the conductivity of hydroxide ions. However, during the assembly or operation of the electrolytic cell, due to the poor compatibility between inorganic fillers and polymers, the phenomenon of inorganic filler shedding often occurs, resulting in a decrease in the conductivity of hydroxide ions. At the same time, the dropped inorganic fillers will enlarge the pore channels and reduce the airtightness. The present invention uses a functional polymer resin with hydroxide ion conductivity to replace inorganic fillers, eliminating the possibility of powder shedding while ensuring the conduction of hydroxide ions, and improving the stability.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The present invention prepares a composite diaphragm for alkaline electrolyzed water hydrogen production by arranging mixed matrix layers on both sides of a support substrate. The mixed matrix layer includes a mixture of a functional polymer resin and a thermoplastic resin. The composite diaphragm has excellent stability, airtightness, and OH - conductivity.

[0047] (2) The present invention uses a functional polymer resin with better compatibility to replace the hydrophilic inorganic filler (such as zirconia, etc.) in the traditional organic-inorganic composite diaphragm for alkaline water electrolysis hydrogen production, which can avoid the problem of diaphragm failure caused by the shedding of inorganic fillers, exclude the possibility of powdering while ensuring the conduction of hydroxide ions, and thus improve stability.

[0048] (3) The mixed matrix layer proposed by the present invention is a porous structure. By regulating the phase separation step of the mixed matrix layer, the functional polymer resin is distributed on the surface of the pores of the composite diaphragm. The rich functional groups of the functional polymer resin promote the rapid movement of OH - and its hydrates in the electrolyte, greatly improving the OH - conductivity of the composite diaphragm.

[0049] (4) The functional polymer resin used in the present invention has excellent hydrophilicity and is easily swollen in alkaline solution, achieving the positive effect of pore shrinkage and improved airtightness of the diaphragm under working conditions.

[0050] (5) The preparation method of the present invention improves the utilization rate of the functional polymer resin and reduces the film-making cost of the alkaline water diaphragm.

[0051] (6) The method of the present invention is simple, easy to operate, safe, and easy to industrialize.

[0052] (7) The preparation method of the composite diaphragm for alkaline electrolyzed water hydrogen production proposed by the present invention can realize the specific arrangement of different polymers in the porous membrane, providing new ideas for the structural design of the composite diaphragm with a mixed matrix layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a flow chart of the preparation method of the present invention;

[0054] Figure 2 is a schematic structural diagram of the present invention (in the figure: 1 - thermoplastic resin; 2 - functional polymer resin). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] The present invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and gives detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0056] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0057] A composite diaphragm for alkaline electrolytic water hydrogen production, comprising a support substrate, with mixed matrix layers provided on both sides of the support substrate. The mixed matrix layer comprises a mixture of a functional polymer resin 2 and a thermoplastic resin 1. The mixed matrix layer is a porous structure, with its pore size being 1 - 100 nm and its porosity being 30 - 70%. The functional polymer resin 2 is arranged in an orderly manner on the outer surface of the pores of the mixed matrix layer.

[0058] Its preparation method is as follows:

[0059] S1: Dissolve the thermoplastic resin and the functional polymer resin in an organic solvent and stir to prepare a casting solution;

[0060] S2: Coat the casting solution on both sides of the support substrate;

[0061] S3: Phase inversion;

[0062] S4: Wash and store.

[0063] Example 1

[0064] A composite diaphragm for alkaline electrolytic water hydrogen production, the preparation process is as follows: At 80 °C, put 20 g of polysulfone and 1 g of sulfonated polysulfone into 85 g of N-methyl-2-pyrrolidone and mechanically stir for 4 hours to obtain a casting solution; at 25 °C and 60% relative humidity, use a clamp to tighten a 50-mesh, 280-μm-thick polyphenylene sulfide woven mesh, fix a scraper with a specification of 300 μm on both sides, and after the casting solution fills the gap between the scrapers, push the clamp downward at a speed of 0.2 m / min; soak the whole set of clamps in isopropyl alcohol at 5 °C, deionized water at 25 °C and 90 °C in sequence, with each soaking time being 1 hour; remove the whole set of clamps, take out the composite diaphragm and rinse the surface with deionized water, cut it to a suitable size and store it in deionized water for subsequent testing and use.

[0065] Example 2

[0066] A composite diaphragm for alkaline electrolytic water hydrogen production, the preparation process is as follows: At 80 °C, 20 g of polysulfone and 2 g of sulfonated polysulfone are put into 85 g of N-methyl-2-pyrrolidone and mechanically stirred for 4 hours to obtain a casting solution; at 25 °C and 60% relative humidity, use a fixture to tighten a 50-mesh, 280-μm-thick polyphenylene sulfide woven mesh, and fix scrapers with a specification of 300 μm on both sides. After the casting solution fills the gap between the scrapers, push the fixture downward at a speed of 0.2 m / min; soak the whole set of fixtures in isopropyl alcohol at 5 °C, deionized water at 25 °C, and deionized water at 90 °C in sequence, and the soaking time for each time is 1 hour; remove the whole set of fixtures, take out the composite diaphragm and rinse the surface with deionized water, cut it to a suitable size and store it in deionized water for convenient subsequent testing and use.

[0067] Example 3

[0068] A composite diaphragm for alkaline electrolytic water hydrogen production, the preparation process is as follows: At 80 °C, 20 g of polysulfone and 5 g of sulfonated polysulfone are put into 85 g of N-methyl-2-pyrrolidone and mechanically stirred for 4 hours to obtain a casting solution; at 25 °C and 60% relative humidity, use a fixture to tighten a 50-mesh, 280-μm-thick polyphenylene sulfide woven mesh, and fix scrapers with a specification of 300 μm on both sides. After the casting solution fills the gap between the scrapers, push the fixture downward at a speed of 0.2 m / min; soak the whole set of fixtures in isopropyl alcohol at 5 °C, deionized water at 25 °C, and deionized water at 90 °C in sequence, and the soaking time for each time is 1 hour; remove the whole set of fixtures, take out the composite diaphragm and rinse the surface with deionized water, cut it to a suitable size and store it in deionized water for convenient subsequent testing and use.

[0069] Example 4

[0070] A composite diaphragm for alkaline electrolytic water hydrogen production, the preparation process is as follows: At 80 °C, 20 g of polysulfone and 2 g of quaternized polysulfone are put into 85 g of N-methyl-2-pyrrolidone and mechanically stirred for 6 hours to obtain a casting solution; at 25 °C and 60% relative humidity, use a fixture to tighten a 50-mesh, 280-μm-thick polyphenylene sulfide woven mesh, and fix scrapers with a specification of 300 μm on both sides. After the casting solution fills the gap between the scrapers, push the fixture downward at a speed of 0.2 m / min; soak the whole set of fixtures in deionized water at 5 °C, 25 °C, and 90 °C in sequence, and the soaking time for each time is 1 hour; remove the whole set of fixtures, take out the composite diaphragm and rinse the surface with deionized water, cut it to a suitable size and store it in deionized water for convenient subsequent testing and use.

[0071] Example 5

[0072] A composite diaphragm for alkaline electrolytic water hydrogen production is prepared as follows: At 80 °C, 20 g of polysulfone and 5 g of quaternized polysulfone are placed in 85 g of N-methyl-2-pyrrolidone and mechanically stirred for 6 hours to obtain a casting solution; at 25 °C and 60% relative humidity, a 50-mesh, 280-μm-thick polyphenylene sulfide woven mesh is tightened using a fixture, and scrapers with a specification of 300 μm are fixed on both sides. After the casting solution fills the gap between the scrapers, the fixture is pushed downward at a speed of 0.2 m / min; the entire fixture is successively immersed in deionized water at 5 °C, 25 °C, and 90 °C, with each immersion time being 1 hour; the entire fixture is removed, the composite diaphragm is taken out and its surface is rinsed with deionized water, and it is cut to a suitable size and stored in deionized water for subsequent testing and use.

[0073] Comparative Example 1

[0074] A commercial product of an organic-inorganic composite diaphragm, model Zirfon PERL UTP 500.

[0075] Comparative Example 2

[0076] Pure polysulfone-coated alkaline water diaphragm.

[0077] Test the OH - conductivity and airtightness of Comparative Examples 1-2 and Examples 1-5. Among them, the test conditions for OH - conductivity: two-electrode system, temperature 20 °C, electrolyte 30 wt% KOH solution, electrode 20-mesh 300-μm-thick nickel mesh; test conditions for airtightness: the test method is the bubble pressure method, temperature 20 °C, wetting liquid anhydrous ethanol, nitrogen displacement. The results are shown in Table 1.

[0078] Table 1 OH of Comparative Examples 1-2 and Examples 1-5 - Conductivity and airtightness

[0079]

[0080] Table 1 shows the test data of the OH - conductivity and airtightness of Comparative Examples 1-2 and Examples 1-5. It can be seen that as the addition amount of the functional polymer resin increases, the surface resistance of the diaphragm gradually decreases and the bubble point pressure gradually increases, proving that the electrochemical performance (OH - conductivity) and airtightness of the diaphragm have been significantly improved, and even better than the representative of the commercial product of the alkaline water organic-inorganic composite diaphragm - Zirfon PERL UTP 500 (Comparative Example 1).

[0081] The porosity of Comparative Examples 1-2 and Examples 1-5 was tested by the weighing method, and the infiltration liquids were anhydrous ethanol and deionized water, respectively. The test results are shown in Table 2. Anhydrous ethanol has no swelling effect on polysulfone, sulfonated polysulfone, and quaternized polysulfone. However, when the infiltration liquid was changed to deionized water, the porosity of Examples 1-5 decreased significantly, proving that the functional polymer resin swelled on the pore surface of the mixed matrix layer, resulting in a smaller pore size of the mixed matrix layer, thereby improving the airtightness of the porous composite separator prepared by the present invention.

[0082] Table 2 Porosity of Comparative Examples 1-2 and Examples 1-5

[0083]

[0084] The powder loss rate of Comparative Example 1 and Examples 1-5 was tested by ultrasonic powder loss test. The conditions of the ultrasonic powder loss test were as follows: temperature was 80 °C, ultrasonic frequency was 40 kHz, ultrasonic time was 1 hour, and the soaking solution was 30 wt% KOH solution. There was no residual alkali solution in the dry films tested. The results are shown in Table 3.

[0085] Table 3 Powder loss rate of Comparative Example 1 and Examples 1-5

[0086]

[0087] Table 3 shows the powder loss rate of Comparative Example 1 and Examples 1-5. It can be seen that the composite separator of the present invention did not show powder loss, that is, there was no obvious change in weight after ultrasound, effectively solving the powder loss problem of the organic-inorganic composite separator and improving the stability of the alkaline water separator.

[0088] Table 4 Electrochemical performance of Comparative Examples 1-2 and Examples 1-5 in actual cell tests

[0089]

[0090]

[0091] The electrochemical performance of Comparative Examples 1-2 and Examples 1-5 in actual cell tests was tested. The conditions of the cell test were as follows: the temperature of the electrolytic cell was 90 °C, both the anode and the cathode were ordinary nickel meshes, the electrolyte was 30 wt% KOH solution, the flow rate was 500 ml / min, and the liquid was fed in from both sides. The test results are shown in Table 4. It can be seen that when the airtightness was improved by adding the functional polymer resin to the mixed matrix layer, the electrochemical performance was also improved, and the electrochemical performance of Examples 3 and 5 far exceeded that of the commercial alkaline water organic-inorganic composite separator, matching the data in Table 1.

[0092] In summary, the present invention provides a composite diaphragm for alkaline electrolytic water hydrogen production, its preparation method and application. By providing a porous mixed matrix layer composed of a functional polymer resin and a thermoplastic resin on a support substrate, the OH - conductivity, stability and airtightness are improved.

[0093] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A composite diaphragm for producing hydrogen by alkaline water electrolysis, characterized in that: The invention comprises a supporting substrate. Mixed matrix layers are arranged on both sides of the supporting substrate. The mixed matrix layers comprise a mixture of a functional polymer resin and a thermoplastic resin.

2. A composite diaphragm for producing hydrogen by alkaline water electrolysis according to claim 1, characterized in that: The mixed matrix layer is a porous structure with a pore diameter of 1-100 nm and a porosity of 30-70%.

3. The composite diaphragm for producing hydrogen by alkaline water electrolysis according to claim 1, characterized in that: The functional polymer resin is orderly arranged on the outer surface of the pores of the mixed matrix layer.

4. The composite diaphragm for producing hydrogen by alkaline water electrolysis according to claim 1, characterized in that: The functional polymer resin includes one or more of perfluorosulfonic acid resin, quaternized polysulfone, sulfonated polysulfone, quaternized polyphenylene ether, quaternized polybenzimidazole, polyaryl piperidine, and polyaryl quinine; The thermoplastic resin includes one or more of polysulfone, polyethersulfone, polyetheretherketone, polyimide, and polyetherimide; The support substrate includes any one of a mesh, a porous membrane, a non-woven fabric, and a woven fabric, and its material includes one or more of polyphenylene sulfide, polyethylene, polypropylene, polytetrafluoroethylene, polyetheretherketone, and polyimide.

5. A method for preparing a composite diaphragm for producing hydrogen by alkaline water electrolysis as claimed in any one of claims 1 to 4, characterized in that: The steps include: S1: dissolving a thermoplastic resin and a functional polymer resin in an organic solvent and stirring the mixture to prepare a casting solution; S2: coating the casting solution on both sides of the supporting substrate; S3: phase inversion; S4: Wash and save.

6. The method for preparing a composite diaphragm for producing hydrogen by alkaline water electrolysis according to claim 5, characterized in that: Step S1 specifically includes the following steps: dissolving the thermoplastic resin and the functional polymer resin in an organic solvent at 70-90° C., and stirring at a rotation speed of 300-1000 rpm for more than 4 hours to prepare the casting solution.

7. The method for preparing a composite diaphragm for producing hydrogen by alkaline water electrolysis according to claim 5, characterized in that: In step S1, the added amount of the functional polymer resin is 1-50wt% of the thermoplastic resin, and the content of the thermoplastic resin in the organic solvent is 5-40wt%; the organic solvent includes one or more of N-methyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, formamide, and N,N-dimethylacetamide.

8. The method for preparing a composite diaphragm for producing hydrogen by alkaline water electrolysis according to claim 5, characterized in that: Step S3 includes the following steps: immersing the supporting substrate coated with the casting liquid in low-temperature, room-temperature, and high-temperature non-solvents in turn, with each immersion time being not less than 30 minutes, and taking it out after the organic solvent is completely replaced.

9. The method for preparing a composite diaphragm for producing hydrogen by alkaline water electrolysis according to claim 8, characterized in that: In step S3, the non-solvent includes one or more of deionized water, n-propanol, isopropanol, and ethanol; the low temperature is -15-15°C, the normal temperature is 15-40°C, and the high temperature is 40-100°C.

10. Use of the composite diaphragm for producing hydrogen by alkaline water electrolysis as claimed in any one of claims 1 to 4 in producing hydrogen by alkaline water electrolysis.

Images