A separator cloth for electrolytic hydrogen production

Abstract

The application relates to the field of diaphragms and discloses a diaphragm cloth for electrolytic hydrogen production, which comprises a polymer woven diaphragm and a functional coating coated on the surface of the diaphragm, and the functional coating comprises the following components: a high-molecular polymer, a composite additive, modified chitosan and an organic solvent; the composite additive is prepared by reacting 2-chloroethyl isocyanate grafted onto the surface of a composite filler with sodium p-hydroxybenzenesulfonate; the composite filler is prepared by taking zirconium oxychloride octahydrate as a precursor, evaporating Zr 4+ The modified halloysite nanotube surface fixed with the polydopamine-based layer on the surface is then reacted with Zr 4+ to form nano zirconium phosphate on the surface of the modified halloysite nanotube; and the modified chitosan is prepared by using succinic anhydride carboxylated polyvinyl alcohol microspheres and a condensing agent for modification; by adding the composite additive and the modified chitosan, the diaphragm cloth has good hydrophilicity and air tightness, excellent performance in alkaline water electrolysis and high mechanical strength.

Description

Technical Field

[0001] This invention belongs to the field of diaphragm technology, and specifically relates to a diaphragm cloth for electrolytic hydrogen production. Background Technology

[0002] To address the global warming and fossil fuel shortage crisis, accelerating the development of clean and renewable energy has become a general consensus in the international community. Hydrogen energy, with its high energy density and diverse sources, has attracted widespread attention. Alkaline water electrolysis for hydrogen production is one of the most mature hydrogen production technologies currently available, offering advantages such as ease of operation, low investment costs, and long service life. The diaphragm, as a core component of the alkaline electrolyzer, primarily functions to prevent the mixing of hydrogen and oxygen at the anode and cathode, and to facilitate the migration of electrolyte ions. Therefore, its quality determines the electrolysis energy consumption, hydrogen purity, and safety of the electrolyzer under the same catalytic electrode conditions. This necessitates that the diaphragm possess high gas barrier properties, low resistivity, and high mechanical strength.

[0003] Existing commercial alkaline water electrolysis membranes, such as Zirfon membranes and polyphenylene sulfide (PPS) membranes, exhibit excellent stability but suffer from poor hydrophilicity and gas barrier properties. The average pore size of most commercial Zirfon membranes is distributed around 0.15 μm. These large pores result in high gas permeability, largely originating from gaps created by interconnected zirconium oxide. While the large pores in zircon promote electrolyte transfer through the membrane to improve OH- conductivity, they also lead to poor membrane gas tightness. Poor gas tightness reduces hydrogen purity, and gases in the liquid electrolyte affect ion transport rates, thereby increasing the ohmic resistance of the electrolyzer and reducing performance. Furthermore, excessively high pressures can easily cause gas cross-contamination, posing extremely adverse consequences for operational safety. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a diaphragm cloth for electrolytic hydrogen production. By adding composite additives and modified chitosan, the diaphragm cloth is endowed with good hydrophilicity and airtightness, exhibits excellent performance in alkaline water electrolysis, and has high mechanical strength.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A diaphragm fabric for electrolytic hydrogen production includes a polymer fabric diaphragm and a functional coating applied to the surface of the polymer fabric diaphragm. The functional coating comprises the following components in parts by weight: 40-70 parts of polymer, 10-20 parts of composite additive, 2-7 parts of modified chitosan, and 60-85 parts of organic solvent.

[0007] The composite additive is prepared by grafting 2-chloroethyl isocyanate onto the surface of the composite filler, followed by a nucleophilic substitution reaction with sodium p-hydroxybenzenesulfonate; the composite filler is prepared by using zirconium oxychloride octahydrate as a precursor, and by evaporating Zr... 4+ Modified halloysite nanotubes were fixed onto the surface to form a polydopamine base layer, and then phosphoric acid and Zr were used. 4+ The modified chitosan was formed on the surface of the modified halloysite nanotubes after the reaction, and was made by modifying the chitosan with carboxylated polyvinyl alcohol microspheres and condensing agents.

[0008] Preferably, the polymer fabric diaphragm is a polyphenylene sulfide fabric diaphragm.

[0009] Preferably, the polymer is one or a combination of polysulfone, polyethersulfone, and polytetrafluoroethylene.

[0010] Preferably, the organic solvent is one or a combination of N-methylpyrrolidone, dimethyl sulfoxide, dimethylacetamide, and N,N-dimethylformamide.

[0011] Preferably, the preparation method of the composite additive includes the following steps:

[0012] A. Halloysite nanotubes, copper sulfate pentahydrate, and dopamine were added sequentially to a Tris-HCl buffer solution with a pH of 8.5. Then, hydrogen peroxide solution was added and the mixture was stirred in a dark environment for 40–60 min. After the reaction was completed, the mixture was filtered, washed, and dried to prepare modified halloysite nanotubes.

[0013] B. Take zirconium oxychloride octahydrate into a reactor, add a mixed solution of ethanol and deionized water and stir evenly. Then add modified halloysite nanotubes and place in a water bath at 55-65℃ and stir continuously until the solution in the reactor evaporates to dryness. Then wash with deionized water and filter. Add the obtained solid product into phosphoric acid solution and stir continuously for 10-12 hours. After the reaction is completed, filter, wash and dry to prepare the composite filler.

[0014] C. Disperse the composite filler in N,N-dimethylformamide, heat it to 60-70℃ under a nitrogen atmosphere, add 2-chloroethyl isocyanate and stir to mix, then add dibutyltin dilaurate and stir to react for 3-5 hours. After the reaction is completed, filter, wash and dry to prepare the modified composite filler.

[0015] D. Disperse the modified composite filler in N,N-dimethylformamide, purge the reaction with nitrogen, add sodium carbonate acid binder and sodium p-hydroxybenzenesulfonate, heat to 60-70℃, then add potassium iodide catalyst, stir and react for 10-12 hours, filter and dry after the reaction is complete to prepare the composite additive.

[0016] Preferably, the volume fraction of the phosphoric acid solution in step B is 20-30%.

[0017] Preferably, the method for preparing the modified chitosan includes the following steps:

[0018] (1) Take n-heptane and Span 60 in a reactor, mix and stir, then heat to 55-70℃, slowly add polyvinyl alcohol and hydrochloric acid, stir for 0.5-1h, then add glutaraldehyde, and react at a constant temperature for 2-3h. After the reaction is complete, wash with ethanol and deionized water and then dry to prepare polyvinyl alcohol microspheres.

[0019] (2) Take polyvinyl alcohol microspheres in a reactor, add ethyl acetate, succinic anhydride and 4-dimethylaminopyridine, stir at 70-85℃ for 3-4 hours, wash with ethanol and deionized water and dry to prepare carboxylated polyvinyl alcohol microspheres.

[0020] (3) Take chitosan and acetic acid aqueous solution and stir to obtain chitosan solution. Take carboxylated polyvinyl alcohol microspheres and disperse them in deionized water, then add them to chitosan solution. At the same time, add N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. Stir at 35-40℃ for 8-12h to prepare modified chitosan.

[0021] Preferably, in step (3), the mass ratio of chitosan, carboxylated polyvinyl alcohol microspheres, N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is 1:0.05-0.15:0.025-0.075:0.05-0.15.

[0022] A method for preparing a diaphragm cloth for electrolytic hydrogen production includes the following steps:

[0023] S1. Weigh each component according to the weight parts, dissolve the polymer in an organic solvent, then add the modified chitosan, stir for 4-6 hours, then add the composite additive, continue stirring for 20-24 hours, and after stirring evenly, perform degassing treatment to prepare the functional coating.

[0024] S2. The functional coating is evenly applied to the surface of the polymer fabric membrane. The formed liquid membrane is pre-evaporated at room temperature for 1-2 minutes, then immersed in deionized water for 15-30 minutes to carry out non-solvent-induced phase transformation. Then, it is repeatedly soaked in deionized water until the exchanged wastewater is no longer turbid, thus preparing the membrane cloth for electrolytic hydrogen production.

[0025] The beneficial effects of this invention are:

[0026] This invention utilizes halloysite nanotubes as a carrier. Halloysite nanotubes are naturally occurring nanotube particles with high modulus and large aspect ratio, possessing advantages such as high usability, rich functionality, good biocompatibility, and high mechanical strength. A polydopamine base layer is formed on their surface to prepare modified halloysite nanotubes. Then, using zirconium oxychloride octahydrate as a precursor, Zr is evaporated to dryness... 4+ Immobilized on the surface of a polydopamine base layer with modified halloysite nanotubes, followed by Zr 4+ A composite filler was prepared by directly reacting phosphoric acid with a polydopamine substrate, allowing the resulting nano-zirconium phosphate to be uniformly loaded onto the modified halloysite nanotubes. The polydopamine substrate was uniformly coated on the halloysite nanotube surface, with a dense coating covering the layered structure and a relatively smooth surface. The functional groups on the polydopamine substrate surface provided abundant binding sites for the nano-zirconium phosphate, effectively solving the aggregation problem. Then, 2-chloroethyl isocyanate was grafted onto the surface of the composite filler to prepare a modified composite filler. The modified composite filler was then subjected to a nucleophilic substitution reaction with sodium p-hydroxybenzenesulfonate, where SO3 on the benzene ring of the sodium p-hydroxybenzenesulfonate was... - As an electron-withdrawing group, it increases the stability and nucleophilicity of oxygen anions. Due to the electron-withdrawing effect of the amide bond in the composite filler, the carbon atom becomes positively charged. In the presence of potassium iodide, the hydroxyl group in sodium p-hydroxybenzenesulfonate is rapidly converted into an oxygen anion. The oxygen anion attacks the carbocation, removes the small molecule of hydrochloric acid, and prepares a composite additive. Thus, a strongly hydrophilic sodium sulfonate group is introduced into the surface of the modified composite filler, which is beneficial to enhance the hydrophilicity of the material, increase the ion transport rate of the material, reduce the resistance, and improve the gas barrier properties. At the same time, it can also improve the mechanical strength of the material.

[0027] This invention utilizes succinic anhydride to modify the surface of polyvinyl alcohol (PVA) microspheres with carboxylation. Then, carboxylated PVA microspheres and a condensing agent are added to a chitosan solution. The addition of carboxylated PVA microspheres improves the hydrophilicity and mechanical strength of the material. The condensing agent readily inserts into the chitosan polymer chains, causing a reaction between the carboxylated PVA microspheres and chitosan, or interaction with hydroxyl and amino groups to form hydrogen bonds. This creates a partial network structure, increasing the distance between chitosan molecular chains, effectively disrupting the hydrogen bonds formed between and within the chitosan molecular chains, weakening the interactions between chitosan molecules, softening the rigid structure of the chitosan membrane, and improving the material's mechanical strength and water absorption / moisture retention properties. The hydroxyl and sodium sulfonate groups in the composite additive prepared by this invention, along with the hydroxyl and amino groups in the modified chitosan, enhance the material's hydrophilicity. When the solvent and hydrophilic particles are uniformly mixed, non-solvent water rapidly penetrates into the functional coating during phase inversion, the solvent is quickly exchanged, reducing the material's pore size, minimizing gas cross-contamination, and improving the material's airtightness. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1: A method for preparing a composite additive includes the following steps:

[0030] A. Take 2g halloysite nanotubes, 0.27g copper sulfate pentahydrate and 0.4g dopamine and add them to 200mL of Tris-HCl buffer solution with pH 8.5 and 50mM. Then add 0.5mL of 30% hydrogen peroxide solution and stir the mixture in the dark for 60min. After the reaction is completed, filter, wash and dry to prepare modified halloysite nanotubes.

[0031] B. Take 8g of zirconium oxychloride octahydrate into a reactor, add 20mL of ethanol and 180mL of deionized water and stir until homogeneous. Then add 2g of modified halloysite nanotubes and place in a water bath at 60℃. Continue stirring until the solution in the reactor evaporates to dryness. Then wash with deionized water and filter. Add the obtained solid product to 100mL of 20% phosphoric acid solution and stir continuously for 12h. After the reaction is completed, filter, wash and dry to prepare the composite filler.

[0032] C. Take 3g of composite filler and disperse it in 100mL of N,N-dimethylformamide. Heat it to 65℃ under a nitrogen atmosphere, add 6mL of 2-chloroethyl isocyanate and stir to mix. Then add 0.005g of dibutyltin dilaurate and stir to react for 4h. After the reaction is completed, filter, wash and dry to prepare the modified composite filler.

[0033] D. Take 3g of modified composite filler and disperse it in 100mL of N,N-dimethylformamide. Purge the reaction with nitrogen gas, add 2.7g of sodium carbonate acid binder and 3.1g of sodium p-hydroxybenzenesulfonate, heat to 65℃, then add 2.1g of potassium iodide catalyst, stir and react for 12h. After the reaction is completed, filter and dry to prepare the composite additive.

[0034] Example 2: A method for preparing modified chitosan includes the following steps:

[0035] (1) Take 40 mL of n-heptane and 0.5 g of Span 60 in a reactor, mix and stir, then heat to 65 °C, slowly add 20 mL of 5% polyvinyl alcohol and 2 mL of hydrochloric acid, stir for 1 h, then add 5 mL of glutaraldehyde, and react at a constant temperature for 2 h. After the reaction is complete, wash with ethanol and deionized water and dry to prepare polyvinyl alcohol microspheres.

[0036] (2) Take 5g of polyvinyl alcohol microspheres into a reactor, add 75mL of ethyl acetate, 1g of succinic anhydride and 0.1g of 4-dimethylaminopyridine, stir at 80℃ for 3h, and after the reaction is completed, wash with ethanol and deionized water and dry to prepare carboxylated polyvinyl alcohol microspheres.

[0037] (3) Take 5g of chitosan and mix it with 60mL of 2% acetic acid aqueous solution to obtain chitosan solution. Take 0.6g of carboxylated polyvinyl alcohol microspheres and disperse them in 10mL of deionized water, then add them to the chitosan solution. At the same time, add 0.15g of N-hydroxysuccinimide and 0.6g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. Stir at 40℃ for 12h to prepare modified chitosan.

[0038] Example 3: A functional coating comprises the following components in parts by weight: 45 parts polysulfone, 12 parts of the composite additive prepared in Example 1, 3 parts of the modified chitosan prepared in Example 2, and 67 parts of the organic solvent N-methylpyrrolidone.

[0039] A method for preparing a diaphragm cloth for electrolytic hydrogen production includes the following steps:

[0040] S1. Weigh each component according to the weight parts, dissolve polysulfone in N-methylpyrrolidone, then add modified chitosan, stir for 4 hours, then add composite additive, continue stirring for 24 hours, and after stirring evenly, perform degassing treatment to prepare functional coating.

[0041] S2. Apply the functional coating evenly to the surface of the polyphenylene sulfide fabric diaphragm (the fabric is plain weave and the unit area mass is 450g / m²). 2 The liquid membrane (with a warp density of 170 threads / 10cm and a weft density of 90 threads / 10cm) was pre-evaporated at room temperature for 1 minute and then immersed in deionized water for 30 minutes to carry out a non-solvent-induced phase transformation. The membrane was then repeatedly soaked in deionized water until the exchanged wastewater was no longer turbid, thus preparing a diaphragm cloth for electrolytic hydrogen production.

[0042] Example 4: A functional coating comprises the following components in parts by weight: 51 parts polysulfone, 15 parts of the composite additive prepared in Example 1, 5 parts of the modified chitosan prepared in Example 2, and 78 parts of the organic solvent N-methylpyrrolidone.

[0043] The preparation method of a diaphragm cloth for electrolytic hydrogen production is the same as in Example 3.

[0044] Example 5: A functional coating comprises the following components in parts by weight: 66 parts polysulfone, 18 parts of the composite additive prepared in Example 1, 6.5 parts of the modified chitosan prepared in Example 2, and 84 parts of the organic solvent N-methylpyrrolidone.

[0045] The preparation method of a diaphragm cloth for electrolytic hydrogen production is the same as in Example 3.

[0046] Comparative Example 1: A functional coating comprises the following components in parts by weight: 66 parts polysulfone, 18 parts of the composite filler prepared in Example 1, 6.5 parts of the modified chitosan prepared in Example 2, and 84 parts of the organic solvent N-methylpyrrolidone.

[0047] The preparation method of a diaphragm cloth for electrolytic hydrogen production is the same as in Example 3.

[0048] Comparative Example 2: A functional coating comprises the following components in parts by weight: 66 parts polysulfone, 18 parts zirconium dioxide, 6.5 parts modified chitosan prepared in Example 2, and 84 parts organic solvent N-methylpyrrolidone.

[0049] The preparation method of a diaphragm cloth for electrolytic hydrogen production is the same as in Example 3.

[0050] Comparative Example 3: A functional coating comprises the following components in parts by weight: 66 parts polysulfone, 18 parts of the composite additive prepared in Example 1, 6.5 parts chitosan, and 84 parts of the organic solvent N-methylpyrrolidone.

[0051] The preparation method of a diaphragm cloth for electrolytic hydrogen production is the same as in Example 3.

[0052] Performance testing

[0053] The membrane fabrics prepared in Examples 3-5 and Comparative Examples 1-3 for electrolytic hydrogen production were subjected to performance testing:

[0054] (1) Hydrophilicity test: The water contact angle was measured using a fully automatic water contact angle measuring instrument, and the data results are shown in Table 1.

[0055] (2) Alkali Absorption Test: First, cut out 1cm × 1cm diaphragm fabric, dry it completely in an 80℃ oven, and measure the dry weight of the diaphragm fabric. Then, soak the prepared diaphragm fabric in anhydrous ethanol for 2 hours, and then soak it in alkali solution for 24 hours. Finally, weigh it after soaking in alkali solution and calculate the alkali absorption. The formula for calculating alkali absorption is: M(%) = (M wet -M dry ) / Mdry×100%, M wet M represents the weight of the sample after absorbing the alkali solution. dryThe original dry weight of the sample is given, and the data results are shown in Table 1.

[0056] (3) Bubble point pressure test: The bubble pressure method filter membrane pore size analyzer was used for testing. The bubble point pressure value represents the minimum pressure required for gas to pass through the pores of the diaphragm cloth. The air tightness of the diaphragm cloth can also be understood through the bubble point pressure test. The data results are shown in Table 1.

[0057] (4) Average pore size detection: The average pore size of the diaphragm cloth was measured using a bubble compression membrane pore size analyzer, which can reflect the air tightness of the diaphragm cloth to a certain extent. The data results are shown in Table 1.

[0058] (5) Electrochemical performance testing: During the alkaline water electrolysis hydrogen production process, OH... - During the migration process through the diaphragm, charge transfer resistance and ohmic resistance are generated. The ohmic resistance and charge transfer resistance of the diaphragm cloth are tested by electrochemical impedance spectroscopy. The diaphragm cloth is inserted into the electrolytic cell, and a 30wt% KOH solution is circulated inside the electrolytic cell by a peristaltic pump. The test results are recorded in the frequency range of 10kHz-1Hz. The areal resistivity is calculated by current-voltage during the alkaline water electrolysis process. No precious metal catalysts are used in the test. Low-cost nickel foam is used as the catalyst. The data results are shown in Table 1.

[0059] (6) Mechanical performance test: The tensile strength and elongation at break of the sample were tested using an electronic tensile testing machine. The data results are shown in Table 1.

[0060] Table 1 Sample performance test results

[0061]

[0062] As can be seen from the data in Table 1, the diaphragm fabrics prepared in Examples 3-5 of this invention have good hydrophilicity and airtightness, high mechanical strength, and excellent performance in alkaline water electrolysis. In Comparative Example 1, the composite additive was replaced with an equal amount of composite filler; in Comparative Example 2, the composite additive was replaced with an equal amount of zirconium dioxide; and in Comparative Example 3, no modification treatment was performed on chitosan. The hydrophilicity, airtightness, and performance in alkaline water electrolysis of Comparative Examples 1-3 were all lower than those of Examples 3-5, indicating that the addition of composite additives and modified chitosan can improve the hydrophilicity and airtightness of the diaphragm fabric and result in excellent performance in alkaline water electrolysis. Furthermore, the tensile strength and elongation at break of Comparative Examples 2-3 were lower than those of Examples 3-5. This is because the introduction of nanofillers in the composite additives and the grafting of polyvinyl alcohol microspheres into the chitosan improved the mechanical properties of the samples to a certain extent.

[0063] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0064] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A diaphragm cloth for electrolytic hydrogen production, characterized in that, The invention includes a polymer fabric diaphragm and a functional coating applied to the surface of the polymer fabric diaphragm. The functional coating comprises the following components by weight: 40-70 parts of polymer, 10-20 parts of composite additive, 2-7 parts of modified chitosan, and 60-85 parts of organic solvent. The composite additive is prepared by grafting 2-chloroethyl isocyanate onto the surface of the composite filler, followed by a nucleophilic substitution reaction with sodium p-hydroxybenzenesulfonate; the composite filler is prepared by using zirconium oxychloride octahydrate as a precursor, and by evaporating Zr... 4+ Modified halloysite nanotubes were fixed onto the surface to form a polydopamine base layer, and then phosphoric acid and Zr were used. 4+ The modified chitosan was formed on the surface of the modified halloysite nanotubes after the reaction, and was made by modifying the modified chitosan with polyvinyl alcohol microspheres carboxylated with succinic anhydride and a condensing agent, wherein the condensing agent is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide.

2. The diaphragm cloth for electrolytic hydrogen production according to claim 1, characterized in that, The polymer fabric diaphragm is a polyphenylene sulfide fabric diaphragm.

3. The diaphragm cloth for electrolytic hydrogen production according to claim 1, characterized in that, The polymer is one or a combination of polysulfone, polyethersulfone, and polytetrafluoroethylene.

4. The diaphragm cloth for electrolytic hydrogen production according to claim 1, characterized in that, The organic solvent is one or a combination of N-methylpyrrolidone, dimethyl sulfoxide, dimethylacetamide, and N,N-dimethylformamide.

5. The diaphragm cloth for electrolytic hydrogen production according to claim 1, characterized in that, The preparation method of the composite additive includes the following steps: A. Halloysite nanotubes, copper sulfate pentahydrate, and dopamine were added sequentially to a Tris-HCl buffer solution with a pH of 8.

5. Then, hydrogen peroxide solution was added and the mixture was stirred in a dark environment for 40-60 minutes. After the reaction was completed, the mixture was filtered, washed, and dried to prepare modified halloysite nanotubes. B. Take zirconium oxychloride octahydrate into a reactor, add a mixed solution of ethanol and deionized water and stir evenly. Then add modified halloysite nanotubes and place in a water bath at 55~65℃ and stir continuously until the solution in the reactor evaporates to dryness. Then wash with deionized water and filter. Add the obtained solid product to phosphoric acid solution and stir continuously for 10~12h. After the reaction is completed, filter, wash and dry to prepare the composite filler. C. Disperse the composite filler in N,N-dimethylformamide, heat it to 60~70℃ under a nitrogen atmosphere, add 2-chloroethyl isocyanate and stir to mix, then add dibutyltin dilaurate and stir to react for 3~5h. After the reaction is completed, filter, wash and dry to prepare the modified composite filler. D. Disperse the modified composite filler in N,N-dimethylformamide, purge the reaction with nitrogen, add sodium carbonate acid binder and sodium p-hydroxybenzenesulfonate, heat to 60~70℃, then add potassium iodide catalyst, stir and react for 10~12h, after the reaction is completed, filter and dry to prepare the composite additive.

6. The diaphragm cloth for electrolytic hydrogen production according to claim 5, characterized in that, The volume fraction of the phosphoric acid solution in step B is 20-30%.

7. The diaphragm cloth for electrolytic hydrogen production according to claim 1, characterized in that, The preparation method of the modified chitosan includes the following steps: (1) Take n-heptane and Span 60 in a reactor, mix and stir, then heat to 55~70℃, slowly add polyvinyl alcohol and hydrochloric acid, stir for 0.5~1h, then add glutaraldehyde, and react at a constant temperature for 2~3h. After the reaction is completed, wash with ethanol and deionized water and dry to prepare polyvinyl alcohol microspheres. (2) Take polyvinyl alcohol microspheres in a reactor, add ethyl acetate, succinic anhydride and 4-dimethylaminopyridine, stir at 70~85℃ for 3~4h, wash with ethanol and deionized water and dry to prepare carboxylated polyvinyl alcohol microspheres. (3) Take chitosan and acetic acid aqueous solution and stir to obtain chitosan solution. Take carboxylated polyvinyl alcohol microspheres and disperse them in deionized water, then add them to chitosan solution. At the same time, add N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. Stir at 35~40℃ for 8~12h to prepare modified chitosan.

8. The diaphragm cloth for electrolytic hydrogen production according to claim 7, characterized in that, In step (3), the mass ratio of chitosan, carboxylated polyvinyl alcohol microspheres, N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is 1:0.05~0.15:0.025~0.075:0.05~0.

15.

9. A method for preparing a diaphragm cloth for electrolytic hydrogen production according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Weigh each component according to the weight parts, dissolve the polymer in an organic solvent, then add the modified chitosan, stir for 4-6 hours, then add the composite additive, continue stirring for 20-24 hours, and after stirring evenly, perform degassing treatment to prepare the functional coating. S2. The functional coating is evenly applied to the surface of the polymer fabric membrane. The formed liquid membrane is pre-evaporated at room temperature for 1-2 minutes and then immersed in deionized water for 15-30 minutes to carry out non-solvent-induced phase transformation. Then, it is repeatedly soaked in deionized water until the exchanged wastewater is no longer turbid, thus preparing the membrane cloth for electrolytic hydrogen production.

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