Diaphragm and preparation method thereof

Abstract

The invention discloses a diaphragm and a preparation method thereof, and the diaphragm is used for producing hydrogen by electrolyzing water and comprises: a base layer having a pore structure; the covering layer is porous and covers at least one side surface of the base layer, and the combination between the base layer and the covering layer comprises physical combination and chemical bond combination. According to the diaphragm provided by the invention, the base layer with the pore structure and the covering layer are tightly combined in a physical combination and chemical bond combination manner, so that the combination strength between the covering layer and the base layer is improved, the stability and durability of the diaphragm are improved, the mechanical strength and chemical stability are enhanced, and the ion transmission performance is optimized; and the diaphragm has environmental adaptability and long-term stability, so that the service life of the diaphragm is prolonged, and the safety in the use process is enhanced.

Description

Technical Field

[0001] The present application relates to the fields of materials and electrochemistry, and in particular to a diaphragm for producing hydrogen by electrolysis of water and a preparation method thereof. Background Art

[0002] The diaphragm is a key component of the electrolytic cell in the electrolysis of water to produce hydrogen. It plays a core role in the electrolysis of water to produce hydrogen. It can effectively separate hydrogen and oxygen to prevent gas mixing, while allowing ions to pass through to maintain the electrical neutrality of the electrolyte, prevent short circuits, and improve the purity of hydrogen. It must also have chemical resistance and sufficient mechanical strength to ensure efficient and safe operation of the system.

[0003] In the process of producing hydrogen by electrolysis of water, alkaline electrolytes are widely used due to their high conductivity, low electrode corrosion rate, wide operating range, and higher safety and stability. Alkaline electrolytes have high requirements for diaphragm materials, requiring the diaphragm to have good chemical stability, ionic conductivity, and mechanical strength. At present, the third-generation composite diaphragm prepared by polyphenylene sulfide mesh and organic-inorganic material coating has high hydrophilicity and small pore structure. However, the covering layer of this composite diaphragm is attached to the surface of the polyphenylene sulfide mesh by physical bonding, and cannot withstand the continuous circulation impact of high-concentration alkaline solution, which easily causes the covering layer to fall off, affects the performance of the diaphragm, increases the risk of hydrogen and oxygen combining in the electrolyzer, and easily causes the explosion of the electrolyzer.

[0004] Therefore, how to provide a diaphragm material that can improve the bonding force between the covering layer and the base layer is a technical problem that needs to be solved urgently in the field of electrochemical materials. Summary of the invention

[0005] In view of this, the present application proposes a diaphragm and a method for preparing the same.

[0006] According to the first aspect of the present application, a diaphragm is proposed, which is used for electrolyzing water to produce hydrogen and comprises: a base layer having a pore structure; and a covering layer, which is porous and covers at least one side of the base layer, wherein: the bonding between the base layer and the covering layer comprises physical bonding and chemical bond bonding.

[0007] Specifically, the base layer is one of hydroxylated polyphenylene sulfide non-woven fabric, polyphenylene sulfide mesh, polyetheretherketone fabric, polypropylene film, polyamide, nylon, polytetrafluoroethylene mesh, polyvinylidene fluoride mesh and polyimide fiber.

[0008] Specifically, the covering layer is made of a hydrophilic material, which includes an aromatic hydrocarbon polymer and hydrophilic inorganic particles. The aromatic hydrocarbon polymer includes one or more of hydroxylated polysulfone, polyarylsulfone, polyethersulfone, polybenzimidazole, and polyphenylene ether. The hydrophilic inorganic particles include one or more of zirconium oxide, titanium oxide, silicon oxide, and zinc oxide.

[0009] Specifically, the chemical bond is an asymmetric chemical bond; preferably, the chemical bond is alkali-resistant; preferably, the chemical bond is a covalent bond; preferably, the chemical bond is an ether bond.

[0010] According to a second aspect of the present application, a method for preparing a diaphragm is provided, the method comprising the following steps:

[0011] (1) preparing a base layer and a covering layer;

[0012] (2) applying the cover layer to the base layer to form a first diaphragm;

[0013] (3) The first separator is cross-linked and cured.

[0014] Specifically, in step (1), the base layer is one of hydroxylated polyphenylene sulfide non-woven fabric, polyphenylene sulfide mesh, polyetheretherketone fabric, polypropylene film, polyamide, nylon, polytetrafluoroethylene mesh, polyvinylidene fluoride mesh and polyimide fiber; the covering layer includes aromatic hydrocarbon polymers and hydrophilic inorganic particles, the aromatic hydrocarbon polymer includes one or more of hydroxylated polysulfone, polyaryl sulfone, polyether sulfone, polybenzimidazole, polyphenylene ether, and the hydrophilic inorganic particles include one or more of zirconium oxide, titanium oxide, silicon oxide and zinc oxide.

[0015] Specifically, the hydroxylation method is: directly preparing the unhydroxylated base layer and the unhydroxylated aromatic polymer through a hydroxylation reaction; or preparing the halogen-methylated base layer and the halogen-methylated aromatic polymer through a halogen-methylation reaction of the unhydroxylated base layer and the unhydroxylated aromatic polymer, and then reacting the halogen-methylated base layer and the halogen-methylated aromatic polymer with a hydroxylation agent to prepare the base layer and the aromatic polymer.

[0016] Specifically, the halogen methylation reaction is one of chloromethylation, bromomethylation, iodomethylation or fluoromethylation, preferably bromomethylation.

[0017] Specifically, the bromomethylation is to treat the unhydroxylated base layer and the unhydroxylated aromatic hydrocarbon polymer with a bromomethylation solution.

[0018] Specifically, the bromomethylation solution for treating the unhydroxylated base layer and the unhydroxylated aromatic polymer includes at least one of brominated alkanes, metal bromides, and brominated hydrocarbons.

[0019] Specifically, the brominated alkane includes one of 1-bromomethoxy-4-chlorobutane, di(bromomethyl)methyl ether, monobromomethyl methyl ether, 1,4-di(bromomethyl)butane and 1-bromomethyloxy-4-bromobutane, preferably 1-bromomethoxy-4-chlorobutane; the metal halide includes one of zinc dibromide, tin dibromide and aluminum bromide, preferably zinc dibromide; the brominated hydrocarbon includes one of monobromomethane, dibromomethane and tribromomethane, preferably dibromomethane.

[0020] Specifically, in the bromomethylation solution for treating the unhydroxylated base layer, the mass percentage of the brominated alkane is 23.3%-28.76%, the mass percentage of the metal bromide is 0.04%-0.05%, and the mass percentage of the brominated hydrocarbon is 71.19%-76.66%.

[0021] Specifically, in the bromomethylation solution for treating the unhydroxylated aromatic polymer, the mass percentage of the brominated alkane is 12.99%-51.79%, the mass percentage of the metal bromide is 0.08%-0.09%, and the mass percentage of the brominated hydrocarbon is 48.12%-86.92%.

[0022] Specifically, the covering layer further includes a pore-forming agent, and the mass percentage of the pore-forming agent in the covering layer is 0.98%.

[0023] Specifically, the mass percentage of the hydroxylated aromatic hydrocarbon polymer in the covering layer is 9.8%, and the mass percentage of the hydrophilic inorganic particles is 39.22%.

[0024] Specifically, the covering layer further includes an organic solvent, the organic solvent is N-methylpyrrolidone, and the mass percentage of the organic solvent is 50%.

[0025] Specifically, the cross-linking and curing is to cross-link and cure the cover layer and the base layer by a cross-linking agent.

[0026] Specifically, the cross-linking agent is one of formaldehyde, 1,4-piperazine dicarboxaldehyde, glutaraldehyde, citric acid, and 4-pyridylbenzaldehyde.

[0027] The diaphragm proposed in the present application uses physical bonding and chemical bonding to tightly bond the base layer and the covering layer with a porous structure, thereby improving the bonding strength between the covering layer and the base layer, improving the stability and durability of the diaphragm, enhancing the mechanical strength and chemical stability, optimizing the ion transmission performance, and having environmental adaptability and long-term stability, thereby extending the service life of the diaphragm and enhancing safety during use.

[0028] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings constituting a part of the present application are used to provide a further understanding of the present application, and the schematic implementation modes and descriptions of the present application are used to explain the present application. In the accompanying drawings:

[0030] Figure 1 is the surface resistance of the diaphragm according to the examples and comparative examples of the present application.

[0031] Figure 2 is the tensile strength of the diaphragms according to the examples and comparative examples of the present application.

[0032] Figure 3 is the bubble point pressure of the diaphragm according to the examples and comparative examples of the present application.

[0033] Figure 4 is the stabilization time of the diaphragms according to the examples and comparative examples of the present application. DETAILED DESCRIPTION

[0034] The technical solution of the present application will be described in detail below with reference to the accompanying drawings and in combination with the implementation modes.

[0035] In the production of hydrogen by alkaline hydrolysis, the diaphragm is used to separate the cathode and the anode to prevent the mixing of the gas products at the two electrodes, and has high ionic conductivity to facilitate the transfer of hydroxide ions from the cathode to the anode. At present, the commonly used third-generation composite diaphragms have the advantages of high hydrophilicity, high porosity, high gas purity, and low ionic resistance. However, the third-generation composite diaphragms have the problem of poor bonding between the covering layer and the base layer. During long-term use, the covering layer may easily fall off, which ultimately leads to a decrease in the ionic conductivity and gas purity of the diaphragm.

[0036] According to the first aspect of the present application, a diaphragm is proposed, which is used for electrolyzing water to produce hydrogen and comprises: a base layer having a pore structure; and a covering layer, which is porous and covers at least one side of the base layer, wherein: the bonding between the base layer and the covering layer comprises physical bonding and chemical bond bonding.

[0037] The above-mentioned base layer is the basis of the diaphragm, and has high mechanical strength, good chemical and thermal stability, electrochemical inertness, high porosity, hydrophilicity, and excellent dimensional stability and processing performance, which can provide physical strength and long-term chemical stability to the diaphragm. The pore structure of the above-mentioned base layer is designed to provide an ion conduction channel, achieve gas separation, and reduce resistance, while maintaining appropriate mechanical strength to ensure the stability and electrolysis efficiency of the diaphragm. The above-mentioned covering layer, as a key functional layer of the diaphragm, has high ionic conductivity, good gas barrier properties, high hydrophilicity, excellent chemical stability, durability, and a thin and uniform texture. The pores of the above-mentioned covering layer are small, which is used to optimize ion transmission, maintain gas separation effects, improve hydrophilicity, reduce diffusion resistance, and prevent the covering layer from falling off, thereby improving electrolysis performance and hydrogen purity. The characteristics of the base layer and the covering layer jointly guarantee the efficient ion transmission and gas separation performance of the diaphragm in the process of water electrolysis to produce hydrogen.

[0038] The above-mentioned physical bonding method between the base layer and the covering layer refers to a bonding method between the covering layer and the base layer that does not involve chemical bonds, which can be hydrogen bonds, van der Waals forces, mechanical interlocking, etc. Hydrogen bonds are a relatively strong intermolecular force that helps to improve the bonding between the covering layer and the base layer; a weaker physical force will be formed between polymer materials; after the covering layer and the base layer come into contact, the covering layer will penetrate into the base layer to form a mechanical interlocking, thereby enhancing the bonding between the two.

[0039] The diaphragm proposed in the present application uses physical bonding and chemical bonding to tightly bond the base layer and the covering layer with a porous structure, thereby improving the bonding strength between the covering layer and the base layer, improving the stability and durability of the diaphragm, enhancing the mechanical strength and chemical stability, optimizing the ion transmission performance, and having environmental adaptability and long-term stability, thereby extending the service life of the diaphragm and enhancing safety during use.

[0040] In order to provide mechanical strength and stability to the diaphragm, a uniform and stable base layer is provided for the covering layer. Specifically, the base layer can be one of hydroxylated polyphenylene sulfide non-woven fabric, polyphenylene sulfide mesh, polyetheretherketone fabric, polypropylene film, polyamide, nylon, polytetrafluoroethylene mesh, polyvinylidene fluoride mesh and polyimide fiber. Preferably, the base layer is a hydroxylated polyphenylene sulfide mesh. In the electrolysis of water to produce hydrogen, the polyphenylene sulfide mesh can withstand a strong alkaline environment and has good chemical stability, which can ensure the stability of the diaphragm in long-term operation. In addition, the polyphenylene sulfide mesh also has excellent thermal stability and can maintain performance under high temperature conditions. At the same time, it has high mechanical strength, can withstand physical pressure and mechanical stress during the electrolysis process, and can maintain the mechanical integrity of the diaphragm. The mesh structure provides good porosity, which helps ion transport and gas separation, while reducing resistance and improving electrolysis efficiency. The hydroxylated polyphenylene sulfide mesh has good hydrophilicity and can improve the ion conductivity of the diaphragm. The price of polyphenylene sulfide mesh is relatively low, which helps to reduce the production cost in the hydrogen production process.

[0041] In order to promote ion conduction in the process of electrolysis of water to produce hydrogen and improve the electrolysis efficiency, specifically, the covering layer can be made of a hydrophilic material, which can include an aromatic hydrocarbon polymer and a hydrophilic inorganic particle. The aromatic hydrocarbon polymer and the hydrophilic inorganic particle can quickly wet the electrolyte, have a high ion conductivity, and can improve the electrolysis efficiency. The chemical stability of the two materials is also good, and they can remain stable in a strong alkaline environment; the hydrophilic inorganic particles have good mechanical strength, which can increase the durability of the covering layer, and the aromatic hydrocarbon polymer provides flexibility for the covering layer, can provide good adhesion, and is conducive to the combination of the covering layer and the base layer. The above-mentioned aromatic hydrocarbon polymer can include one or more of hydroxylated polysulfone, polyaryl sulfone, polyether sulfone, polybenzimidazole, and polyphenylene ether. Preferably, the above-mentioned aromatic hydrocarbon polymer is a hydroxylated polysulfone, and the polysulfone has excellent chemical stability, can remain stable in a strong alkaline environment, and does not react with the electrolyte. Secondly, polysulfone has high heat resistance, can maintain performance under high temperature conditions, and adapt to temperature changes during electrolysis. In addition, polysulfone has good mechanical properties, including flexibility and rigidity, which contributes to good bonding between the covering layer and the base layer, thereby improving the overall performance of the diaphragm. Hydroxylated polysulfone has good hydrophilicity, which can improve the ionic conductivity of the diaphragm; polysulfone has relatively low cost, is easy to prepare and process, is suitable for large-scale production, and helps to reduce the overall cost of hydrogen production. The above-mentioned hydrophilic inorganic particles may include one or more of zirconium oxide, titanium oxide, silicon oxide, and zinc oxide, preferably zirconium oxide, which also has excellent chemical stability and heat resistance. In addition, zirconium oxide has high mechanical strength and rigidity, and the cost of zirconium oxide is relatively low.

[0042] In order to enhance the bonding force between the base layer and the covering layer, specifically, the chemical bond can be an asymmetric chemical bond. Asymmetric chemical bonds can provide a stronger bonding force than physical bonding forces, reduce the risk of the covering layer falling off during use, and the chemical bonds can be alkali-resistant, so that the diaphragm can be suitable for alkaline environments, maintain the performance of the diaphragm, and is not affected by the electrolyte; the chemical bonds can be covalent bonds, which have high chemical stability and can adapt to high temperature environments. The chemical bonds can be ether bonds, which not only enhance the structural stability of the diaphragm, prevent physical stratification and rupture during electrolysis, but also improve the chemical corrosion resistance of the diaphragm in alkaline environments. At the same time, the presence of ether bonds ensures the close bonding between the base layer and the covering layer, does not affect the ionic conductivity, and thus ensures the electrolysis efficiency. In addition, the ether bonds also promote the interface compatibility between different materials, avoid the problems caused by material mismatch, and thus improve the overall performance and durability of the diaphragm.

[0043] According to the second aspect of the present application, a method for preparing a diaphragm is proposed, which may include the following steps: (1) preparing a base layer and a covering layer; (2) coating the covering layer on the base layer to form a first diaphragm; and (3) cross-linking and curing the first diaphragm.

[0044] The above-mentioned covering layer can be coated on the base layer in an appropriate form, for example, it can be horizontal coating or vertical coating, horizontal coating includes spraying, scraping and rolling, and vertical coating includes dip coating, spraying, scraping and rolling. In this application, scraping in vertical coating is taken as an example.

[0045] Specifically, in step (1), the base layer is one of hydroxylated polyphenylene sulfide non-woven fabric, polyphenylene sulfide mesh, polyetheretherketone fabric, polypropylene film, polyamide, nylon, polytetrafluoroethylene mesh, polyvinylidene fluoride mesh and polyimide fiber; the covering layer includes aromatic hydrocarbon polymers and hydrophilic inorganic particles, the aromatic hydrocarbon polymer includes one or more of hydroxylated polysulfone, polyaryl sulfone, polyether sulfone, polybenzimidazole, polyphenylene ether, and the hydrophilic inorganic particles include one or more of zirconium oxide, titanium oxide, silicon oxide and zinc oxide.

[0046] In order to obtain the base layer and the covering layer, specifically, the hydroxylation method can be: directly preparing the unhydroxylated base layer and the unhydroxylated aromatic polymer by hydroxylation reaction; or preparing the halogenated base layer and the halogenated aromatic polymer by halogen methylation reaction, and then reacting the halogenated base layer and the halogenated aromatic polymer with a hydroxylation agent to prepare the base layer and the aromatic polymer. In the present application, the base layer and the aromatic polymer are indirectly prepared by halogen methylation reaction. The indirect preparation can better control the reaction, so that the hydroxyl group can be accurately introduced into the specific position of the aromatic ring, avoiding the complex products caused by multiple substitutions, thereby improving the purity of the product. In addition, it is usually carried out under mild reaction conditions, which reduces the damage to the main chain of the polymer, ensures the safety of the reaction and the simplicity of operation. The high reactivity of the halogenated intermediate helps to improve the yield of the subsequent hydroxylation step. At the same time, the method can also reduce the generation of by-products and reduce the difficulty of separation and purification.

[0047] In order to carry out halogen methylation treatment to the base layer of unhydroxylated and unhydroxylated aromatic polymer, specifically, the halogen methylation reaction can be one of chloromethylation, bromomethylation, iodomethylation or fluoromethylation, preferably bromomethylation. The reactivity of bromomethylation is moderate, stronger and easier to control than chloromethylation, weaker than iodomethylation but more controllable, reduces the occurrence of side reactions, and improves the purity of product. Compared with chloromethylation, bromomethylation provides better selectivity, especially in the processing of aromatic compounds, avoids multiple substitution or overreaction. In addition, bromomethylation reaction conditions are mild, easy to operate, does not need extreme temperature or pressure, and is suitable for laboratory and industrial-scale applications. Bromomethylation products are also more superior in stability, easy to handle and preserve, with fewer by-products and higher operational safety.

[0048] In order to achieve bromomethylation treatment, specifically, the bromomethylation can be to treat the unhydroxylated base layer and the unhydroxylated aromatic polymer by a bromomethylation solution. The bromomethylation solution for treating the unhydroxylated base layer and the unhydroxylated aromatic polymer includes at least one of bromoalkanes, metal bromides and brominated hydrocarbons. The bromoalkanes include one of 1-bromomethoxy-4-chlorobutane, di(bromomethyl)methyl ether, monobromomethylmethyl ether, 1,4-di(bromomethyl)butane and 1-bromomethyloxy-4-bromobutane, preferably 1-bromomethoxy-4-chlorobutane; the metal halide includes one of zinc dibromide, tin dibromide and aluminum bromide, preferably zinc dibromide; the brominated hydrocarbon includes one of monobromomethane, dibromomethane and tribromomethane, preferably dibromomethane. Dibromomethane can efficiently introduce bromomethyl groups, and 1-bromomethoxy-4-chlorobutane can simultaneously introduce specific bromomethyl groups and other functional groups, so that the unhydroxylated base layer and unhydroxylated aromatic polymers have the potential for further reactions while being bromomethylated. Zinc dibromide can be used as a catalyst to enhance the reaction activity and improve the selectivity and yield.

[0049] Specifically, in the bromomethylation solution for treating the unhydroxylated base layer, the mass percentage of the brominated alkane is 23.3%-28.76%, the mass percentage of the metal bromide is 0.04%-0.05%, and the mass percentage of the brominated hydrocarbon is 71.19%-76.66%.

[0050] Specifically, in the bromomethylation solution for treating the unhydroxylated aromatic polymer, the mass percentage of the brominated alkane is 12.99%-51.79%, the mass percentage of the metal bromide is 0.08%-0.09%, and the mass percentage of the brominated hydrocarbon is 48.12%-86.92%.

[0051] In order to adjust the microporous structure of the diaphragm and improve the ionic conductivity of the diaphragm, specifically, the covering layer may further include a pore former, and the mass percentage of the pore former in the covering layer is 0.98%.

[0052] In order to make the separator have better mechanical strength, ionic conductivity and hydrophilicity, specifically, the mass percentage of the aromatic hydrocarbon polymer in the covering layer can be 9.8%, and the mass percentage of the hydrophilic inorganic particles can be 39.22%.

[0053] In order to prepare the covering layer, specifically, the covering layer also includes an organic solvent, and the organic solvent is N-methylpyrrolidone, and the mass percentage of the organic solvent is 50%. N-methylpyrrolidone is a kind of solvent with high polarity and good solubility, which can dissolve aromatic hydrocarbon polymers, and can also provide high solubility or dispersibility for hydrophilic inorganic particles and pore-forming agents, so that the hydrophilic inorganic particles and pore-forming agents are evenly distributed in the covering layer. Secondly, N-methylpyrrolidone has good chemical stability and low viscosity, and can form a uniform solution, which can ultimately maintain the performance and consistency of the diaphragm.

[0054] In order to bond the base layer and the covering layer by chemical bonds, specifically, the cross-linking and curing can be cross-linking and curing the covering layer and the base layer by a cross-linking agent. The cross-linking agent is one of formaldehyde, 1,4-piperazine dicarboxaldehyde, glutaraldehyde, citric acid, and 4-pyridylbenzaldehyde, preferably glutaraldehyde, which has excellent cross-linking ability and moderate reactivity, can form a stable cross-linked network, and enhance the bonding strength of the covering layer and the base layer. At the same time, glutaraldehyde shows good stability during the cross-linking process, avoids the occurrence of side reactions, and has a high cost performance and good performance effect. Therefore, it is selected as a cross-linking agent to ensure the high quality and stability of the film.

[0055] The above is a detailed description of the technical solution of the diaphragm and the preparation method thereof provided by the present application. The following is a further exemplary description of the diaphragm and the preparation method thereof provided by the present application in conjunction with embodiments.

[0056] 1. Example of the preparation method of the diaphragm

[0057] Example 1

[0058] This embodiment provides a method for preparing a diaphragm, comprising the following steps:

[0059] A1. 13 g of polysulfone was treated with a bromomethylation solution, wherein the bromomethylation solution included 25.9% by mass of 1-bromomethoxy-4-chlorobutane and 0.08% by mass of zinc dibromide added to a 74.02% by mass solution of dibromomethane, stirred for 10 min, and heated to 60° C. for reaction for 3 h to obtain an organic solution containing bromomethylated polysulfone, which was filtered, dried at 80° C., and washed with ethanol to obtain powder particles of bromomethylated polysulfone.

[0060] 15 g of bromomethylated polysulfone particles were dissolved in 45 g of dimethylformamide (DMF), 2 g of KOH was added and stirred, and after 1 hour, the particles were transferred to methanol for recrystallization to obtain hydroxylated polysulfone powder particles.

[0061] A2. The polyphenylene sulfide PPS mesh was immersed in a bromomethylation solution, wherein the bromomethylation solution included 23.31% by mass of 1-bromomethoxy-4-chlorobutane and 0.04% by mass of zinc dibromide added to a 76.65% by mass of dibromomethane solution, heated to 60° C. for reaction for 3 hours, and the excess solution on the surface was washed off with ethanol several times to obtain a bromomethylated PPS mesh;

[0062] The bromomethylated PPS mesh was immersed in 1000 ml of dimethylformamide (DMF), 40 g of KOH was added and stirred for 1 h, and then the PPS mesh was immersed in methanol for 20 min to obtain a hydroxylated PPS mesh;

[0063] A3. 9.8% by mass of hydroxylated polysulfone, 0.98% by mass of polyvinyl pyrrolidone, and 39.22% by mass of zirconium oxide were dispersed in 50% by mass of N-methylpyrrolidone NEP, mixed and stirred for 6 hours, and centrifuged at 1000r for 10 minutes to degas, and a casting solution was obtained;

[0064] A4. The casting solution is evenly coated on the base layer by vertical double-sided coating, and pre-evaporated in air for 30 seconds to obtain a first diaphragm containing a covering layer;

[0065] A5. Transfer the treated first diaphragm to a 20% glutaraldehyde ethanol solution for cross-linking reaction, immerse vertically for 1 hour, and transfer to pure water for 30 minutes to obtain a diaphragm.

[0066] Example 2

[0067] The preparation method of the diaphragm of Example 1 is adopted, wherein:

[0068] A1. The bromomethylation solution includes 12.99% by mass of 1-bromomethoxy-4-chlorobutane and 0.09% by mass of zinc dibromide added to 86.92% by mass of dibromomethane solution.

[0069] A2. The bromomethylation solution includes 23.3% by mass of 1-bromomethoxy-4-chlorobutane and 0.04% by mass of zinc dibromide added to 76.66% by mass of dibromomethane solution.

[0070] Example 3

[0071] The preparation method of the diaphragm of Example 1 is adopted, wherein:

[0072] A1. The bromomethylation solution includes 51.79% by mass of 1-bromomethoxy-4-chlorobutane and 0.09% by mass of zinc dibromide added to 48.12% by mass of dibromomethane solution.

[0073] A2. The bromomethylation solution includes 28.76% by mass of 1-bromomethoxy-4-chlorobutane and 0.05% by mass of zinc dibromide added to 71.19% by mass of dibromomethane solution.

[0074] Example 4

[0075] The preparation method of the diaphragm of Example 1 is adopted, wherein:

[0076] A1. The aromatic hydrocarbon polymer is polyphenylene ether.

[0077] A2. The base layer is a polyetheretherketone mesh.

[0078] Comparative Example 1

[0079] The preparation method of the diaphragm of Example 1 is adopted, wherein A1 and A2 are not included.

[0080] Comparative Example 2

[0081] The preparation method of the diaphragm of Example 1 is adopted, which does not include A2.

[0082] Comparative Example 3

[0083] The preparation method of the diaphragm of Example 1 was adopted, but A1 was not included.

[0084] 2. Test methods

[0085] 2.1 Surface resistance test of diaphragm

[0086] Surface resistance is the resistance per unit area of ​​the conductor surface when current passes through it.

[0087] In this application form, the diaphragm is cut into a size of 1.2 cm x 1.2 cm and immersed in a 30% KOH solution for 24 hours. The impedance of the diaphragm is tested using a fixture with an effective area of ​​a circle with a radius of 1 cm and an electrochemical workstation (interface 5000E, Gamry), and its surface resistance is calculated.

[0088] 2.2 Tensile strength test of diaphragm

[0089] Tensile strength is the maximum stress value that a material can withstand in a tensile test. It represents the maximum force that a material can withstand before being stretched to fracture, and is expressed in units of stress (usually MPa or psi).

[0090] The diaphragm was cut into a size of 1 cm x 7 cm and dried for 30 min before testing. An electronic universal testing machine (AGS-X, Shimadzu Corporation) was used to perform a tensile test on the diaphragm sample.

[0091] 2.3 Bubble point pressure test of diaphragm

[0092] Bubble point pressure refers to the minimum pressure required for a bubble to pass through a porous material or membrane for the first time. It is an important parameter for evaluating the pore size and integrity of filtration membranes, microporous materials or similar structures.

[0093] The diaphragm was cut into a size of 1 cm x 1 cm and a bubble point pressure test was performed using a gas permeation pore size analyzer (CFP-1500AEX, PMI, USA).

[0094] 2.4 Diaphragm stability test

[0095] Stability testing is the process of evaluating the performance and quality of a diaphragm over time under environmental conditions.

[0096] The polarization stability of the diaphragm was tested using a zero-gap electrolyzer with an effective catalytic area of ​​2cmx2cm. The electrolyte was 30% KOH at 80°C and the current density was 300mA / cm 2 Under the conditions of , the nickel mesh is used as cathode and anode, and the time taken for the cell voltage to decay by 10% is tested.

[0097] 3. Test results

[0098] 3.1 Analysis of the surface resistance of the diaphragm

[0099] The surface resistance analysis of the diaphragm in this application is as follows Figure 1 As shown by Figure 1 It can be seen that the surface resistance of Example 1, Example 3 and Example 4 is greater than that of Comparative Example 1 (the base layer and the covering layer of the diaphragm have not been hydroxylated), Comparative Example 2 and Comparative Example 3, and the surface resistance of Example 2 is greater than that of Comparative Example 2 and Comparative Example 3. It can be seen that after the base layer and the covering layer of the diaphragm in the embodiment of the present application are hydroxylated, ether bonds are formed in the diaphragm, resulting in a reduction in the gap and pores between the base layer and the covering layer, resulting in a slightly larger surface resistance.

[0100] 3.2 Analysis of tensile strength of diaphragm

[0101] The tensile strength analysis of the diaphragm of this application is as follows Figure 2 As shown by Figure 2 It can be seen that the tensile strength of Examples 1-4 (the base layer and the cover layer of the diaphragm are hydroxylated) is significantly greater than the tensile strength of Comparative Examples 1-4. It can be seen that an ether bond is formed between the cover layer and the base layer of the diaphragm in the embodiment of the present application, which increases the bonding force between the cover layer and the base layer, thereby improving the tensile strength of the diaphragm.

[0102] 3.3 Analysis of bubble point pressure of diaphragm

[0103] The bubble point pressure analysis of the diaphragm in this application is as follows Figure 3 As shown by Figure 3 It can be seen that the bubble point pressure of Examples 1 to 4 is much greater than the bubble point pressure of the diaphragm in Comparative Examples 1 to 3. The size of the bubble point pressure is related to the size and number of pores. Therefore, after the ether bond is formed between the base layer and the cover layer after hydroxylation treatment, the structural stability and uniformity of the diaphragm are good, and defects or uneven pores are not easy to appear during use.

[0104] 3.4 Diaphragm stability analysis

[0105] The stability analysis of the diaphragm in this application is as follows Figure 4 As shown by Figure 4 It can be seen that the stability of the diaphragm of Example 1-4 is higher than that of Comparative Example 1-3, indicating that the stability of the diaphragm is significantly improved after the base layer and the covering layer of the diaphragm are bonded through ether bonds after hydroxylation treatment.

[0106] The diaphragm proposed in the present application uses physical bonding and chemical bonding to tightly bond the base layer and the covering layer with a porous structure, thereby improving the bonding strength between the covering layer and the base layer, improving the stability and durability of the diaphragm, enhancing the mechanical strength and chemical stability, optimizing the ion transmission performance, and having environmental adaptability and long-term stability, thereby extending the service life of the diaphragm and enhancing safety during use.

[0107] The preferred embodiments of the present application are described in detail above; however, the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, a variety of simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the protection scope of the present application.

[0108] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

[0109] In addition, the various implementation modes of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A diaphragm for producing hydrogen by electrolysis of water and comprising: a base layer having a porous structure; and A covering layer, which is porous and covers at least one side of the base layer, wherein: The bonding between the base layer and the cover layer includes physical bonding and chemical bonding.

2. The diaphragm according to claim 1, wherein The base layer is one of hydroxylated polyphenylene sulfide non-woven fabric, polyphenylene sulfide mesh, polyetheretherketone fabric, polypropylene film, polyamide, nylon, polytetrafluoroethylene mesh, polyvinylidene fluoride mesh and polyimide fiber.

3. The diaphragm according to claim 1, wherein The covering layer is made of a hydrophilic material, which includes an aromatic hydrocarbon polymer and hydrophilic inorganic particles. The aromatic hydrocarbon polymer includes one or more of hydroxylated polysulfone, polyarylsulfone, polyethersulfone, polybenzimidazole, and polyphenylene ether. The hydrophilic inorganic particles include one or more of zirconium oxide, titanium oxide, silicon oxide, and zinc oxide.

4. The diaphragm according to claim 1, characterized in that The chemical bond is an asymmetric chemical bond; Preferably, the chemical bond is alkali-resistant; Preferably, the chemical bond is a covalent bond; Preferably, the chemical bond is an ether bond.

5. A method for preparing a diaphragm, characterized in that: The preparation method comprises the following steps: (1) preparing a base layer and a covering layer; (2) applying the cover layer to the base layer to form a first diaphragm; (3) The first separator is cross-linked and cured.

6. The preparation method according to claim 5, characterized in that: In step (1), the base layer is one of hydroxylated polyphenylene sulfide nonwoven fabric, polyphenylene sulfide mesh, polyetheretherketone fabric, polypropylene film, polyamide, nylon, polytetrafluoroethylene mesh, polyvinylidene fluoride mesh and polyimide fiber; The covering layer includes an aromatic polymer and hydrophilic inorganic particles, wherein the aromatic polymer includes one or more of hydroxylated polysulfone, polyarylsulfone, polyethersulfone, polybenzimidazole, and polyphenylene ether, and the hydrophilic inorganic particles include one or more of zirconium oxide, titanium oxide, silicon oxide, and zinc oxide.

7. The preparation method according to claim 6, characterized in that: The hydroxylation method is: Directly preparing the unhydroxylated base layer and the unhydroxylated aromatic polymer through a hydroxylation reaction; or The unhydroxylated base layer and the unhydroxylated aromatic polymer are subjected to a halogen methylation reaction to prepare a halogen methylated base layer and a halogen methylated aromatic polymer, and then the halogen methylated base layer and the halogen methylated aromatic polymer are reacted with a hydroxylation agent to prepare a base layer and an aromatic polymer.

8. The preparation method according to claim 7, characterized in that: The halogen methylation reaction is one of chloromethylation, bromomethylation, iodomethylation or fluoromethylation, preferably bromomethylation.

9. The preparation method according to claim 8, characterized in that: The bromomethylation is to treat the unhydroxylated base layer and the unhydroxylated aromatic polymer with a bromomethylation solution.

10. The preparation method according to claim 9, characterized in that: The bromomethylation solution for treating the unhydroxylated base layer and the unhydroxylated aromatic polymer comprises at least one of a brominated alkane, a metal bromide and a brominated hydrocarbon.

11. The preparation method according to claim 10, characterized in that: The brominated alkane includes one of 1-bromomethoxy-4-chlorobutane, di(bromomethyl)methyl ether, monobromomethyl methyl ether, 1,4-di(bromomethyl)butane and 1-bromomethyloxy-4-bromobutane, preferably 1-bromomethoxy-4-chlorobutane; The metal halide includes one of zinc dibromide, tin dibromide and aluminum bromide, preferably zinc dibromide; The brominated hydrocarbon includes one of monobromomethane, dibromomethane and tribromomethane, preferably dibromomethane.

12. The preparation method according to claim 10, characterized in that: In the bromomethylation solution for treating the unhydroxylated base layer, the mass percentage of the brominated alkane is 23.3%-28.76%, the mass percentage of the metal bromide is 0.04%-0.05%, and the mass percentage of the brominated hydrocarbon is 71.19%-76.66%.

13. The preparation method according to claim 10, characterized in that: In the bromomethylation solution for treating the unhydroxylated aromatic hydrocarbon polymer, the mass percentage of the brominated alkane is 12.99%-51.79%, the mass percentage of the metal bromide is 0.08%-0.09%, and the mass percentage of the brominated hydrocarbon is 48.12%-86.92%.

14. The preparation method according to claim 6, characterized in that: The covering layer also includes a pore-forming agent, and the mass percentage of the pore-forming agent in the covering layer is 0.98%.

15. The preparation method according to claim 6, characterized in that: The mass percentage of the hydroxylated aromatic hydrocarbon polymer in the covering layer is 9.8%, and the mass percentage of the hydrophilic inorganic particles is 39.22%.

16. The preparation method according to claim 6, characterized in that: The covering layer also includes an organic solvent, which is N-methylpyrrolidone, and the mass percentage of the organic solvent is 50%.

17. The preparation method according to claim 5, characterized in that: The cross-linking and curing is to cross-link and cure the cover layer and the base layer by using a cross-linking agent.

18. The preparation method according to claim 17, characterized in that: The cross-linking agent is one of formaldehyde, 1,4-piperazine dicarboxaldehyde, glutaraldehyde, citric acid and 4-pyridylbenzaldehyde.

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