Composite separator, preparation method thereof, electrolytic cell and hydrogen production system

Abstract

The application discloses a composite diaphragm and a preparation method thereof, an electrolytic cell and a hydrogen production system. The composite diaphragm comprises a base film and a modified film layer on the surface of the base film. The base film comprises an alkaline electrolytic water diaphragm. The modified film layer comprises an additive, and the additive comprises an organic small molecule substance. The organic small molecule substance has an aromatic ring structure and contains an N-H group. The surface of the diaphragm is modified, so that the surface resistance of the composite diaphragm is reduced, and the hydrophilic performance is improved.

Description

Technical Field

[0001] This application relates to the field of hydrogen production technology, specifically to composite membranes and their preparation methods, electrolyzers, and hydrogen production systems. Background Technology

[0002] Alkaline water electrolysis for hydrogen production is currently a more reliable and mature application in the industrial electrolysis of water. Key materials in pressure filter electrolyzers include bipolar plates, electrodes, diaphragms, and gaskets. Among these, the diaphragm, as the intermediate component of the electrolysis chamber, plays a crucial role in isolating hydrogen and oxygen generated during the electrolysis process.

[0003] However, as industrial applications demand increasingly higher energy consumption and safety performance, traditional diaphragms (such as PPS diaphragms) can no longer meet the needs of the production process. Therefore, it is necessary to develop diaphragms with lower resistance and stronger hydrophilicity. Summary of the Invention

[0004] This application aims to at least partially address one of the technical problems in the related art. To this end, one objective of this application is to propose a composite membrane and its preparation method, an electrolyzer, and a hydrogen production system, wherein surface modification of the membrane facilitates a reduction in sheet resistivity and an improvement in hydrophilicity.

[0005] The first aspect of this application proposes a composite membrane, comprising a base membrane and a modified membrane layer located on the surface of the base membrane;

[0006] The base membrane includes an alkaline water electrolysis membrane;

[0007] The modified film layer includes additives, which include small organic molecules with aromatic ring structures and containing NH groups.

[0008] This application employs additives to modify the surface of the base membrane. These small-molecule organic additives have an NH structure, enabling them to adsorb OH- ions from the electrolyte via hydrogen bonds and other forces such as van der Waals forces. Subsequently, under the influence of an electric field, the ions migrate towards the anode through the membrane's porous structure, thereby improving ionic conductivity and reducing the resistance of the composite membrane. Furthermore, the NH structure of these small-molecule organic additives also allows them to adsorb water molecules from the electrolyte via hydrogen bonds and other forces such as van der Waals forces, enhancing hydrophilicity.

[0009] Furthermore, the additives used for membrane surface modification in this application are small organic molecules with aromatic ring structures, which facilitate the formation of a stable modified membrane layer on the base membrane, reduce the problem of weak adsorption and shedding of the modified membrane layer during use, maintain high stability during the electrolysis of water to produce hydrogen, ensure the continuous operation of the water electrolysis process, and promote the additive to better exert its ion-conducting and hydrophilic properties.

[0010] In some embodiments, the additives include one or more of 1,2,3,4-tetrahydro-1,5-naphthidine, 2-naphthium chloride, and 5,6,7,8-tetrahydro-2-naphthylamine; and / or, the alkaline water electrolysis membrane includes one or more of polyphenylene sulfide membrane, sulfonated polyphenylene sulfide membrane, polysulfone membrane, and polyetheretherketone membrane.

[0011] In some embodiments, the modified film layer also includes a dispersant.

[0012] In some embodiments, the dispersant includes one or more of polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and polyvinyl alcohol.

[0013] The second aspect of this application discloses a method for preparing a composite membrane, comprising:

[0014] A pre-formed film layer is formed on the surface of a base film using a dispersion liquid; the dispersion liquid includes additives, which include small organic molecules with aromatic ring structures and containing NH groups;

[0015] A pre-fabricated membrane layer is heat-set to form a modified membrane layer on the surface of the base membrane, resulting in a composite membrane.

[0016] In some embodiments, the dispersion further includes a solvent, which includes one or more of ethanol, isopropanol, acetone, ethyl acetate, methanol, and butanone.

[0017] And / or, the dispersion also includes a dispersant, which includes one or more of polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and polyvinyl alcohol.

[0018] In some embodiments, the volume ratio of dispersant to solvent is 1:(2-3).

[0019] In some embodiments, the temperature during the heat setting process is 150°C-200°C and the pressure is 2MPa-10MPa.

[0020] The third aspect of this application provides an electrolytic cell comprising the composite membrane described in the first aspect above, or a composite membrane prepared by the method described in the second aspect above.

[0021] The fourth aspect of this application proposes a hydrogen production system, including the electrolyzer proposed in the third aspect above.

[0022] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Detailed Implementation

[0023] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0024] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more.

[0025] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this application.

[0026] In this application, the terms "comprising" or "including" are open-ended expressions, meaning they include the content specified in this application but do not exclude other aspects.

[0027] In an alkaline electrolyzer, the middle section of the electrolysis chamber forms an electrolytic diaphragm, which plays a crucial role in isolating hydrogen and oxygen generated during the electrolysis process. However, while preventing gas cross-contamination, it is also necessary to ensure the flow of the electrolyte and maintain a high OH content during electrolysis. - For optimal membrane performance, a high migration rate is desirable, and good resistance, along with good hydrophilicity and gas-repellency, is essential. Currently, sulfonated polyphenylene sulfide (PPS) membranes are the most mature and widely used type. However, with increasingly stringent requirements for energy consumption and safety in industrial applications, traditional membranes (such as PPS membranes) can no longer meet the needs of the production process. Therefore, it is necessary to develop membranes with lower resistance and stronger hydrophilicity.

[0028] Taking sulfonated PPS membranes as an example, sulfonated PPS membranes are commonly used in alkaline water electrolysis. However, in practice, it has been found that simply increasing the hydrophilicity of the PPS membrane through sulfonation does not significantly improve its application performance. Although sulfonation introduces more hydrophilic sulfonic acid groups, increasing the OH groups is necessary to enhance the hydrophilicity of the membrane during alkaline water electrolysis. - The throughput is increased, that is, the conductivity is increased and the resistance is reduced, thereby improving the electrolysis efficiency.

[0029] Therefore, the first aspect of the embodiments of this application proposes a composite membrane, a base membrane and a modified membrane layer located on the surface of the base membrane;

[0030] The base membrane includes an alkaline water electrolysis membrane;

[0031] The modified film layer includes additives, which include small organic molecules with aromatic ring structures and containing NH groups.

[0032] In this embodiment, additives are used to modify the surface of the base membrane. These small-molecule organic additives have an NH structure, which can adsorb OH- ions from the electrolyte through hydrogen bonds and other forces such as van der Waals forces. Subsequently, under the influence of an electric field, the ions move towards the anode through the pore structure of the membrane, thereby improving ionic conductivity and reducing the resistance of the composite membrane. Furthermore, the NH structure of these small-molecule organic additives also allows them to adsorb water molecules from the electrolyte through hydrogen bonds and other forces such as van der Waals forces, thus improving hydrophilicity.

[0033] Furthermore, when modifying the diaphragm, it is necessary to consider, on the one hand, the impact of the additives used for modification on the ion transport function and hydrophilicity of the water electrolysis process; and on the other hand, it is necessary to possess good physical properties, that is, the modified membrane layer should remain intact during water electrolysis. If the modified membrane layer is unstable in adsorption on the base membrane surface, it is prone to detachment during water electrolysis, which would reduce the improvement effect of the modified membrane layer on the base membrane. In the embodiments of this application, the additives used for modifying the diaphragm surface are small organic molecules with aromatic ring structures, which facilitate the formation of a stable modified membrane layer on the base membrane, reduce the problem of weak adsorption and detachment of the modified membrane layer during use, maintain high stability during the water electrolysis hydrogen production process, ensure the continuous operation of the water electrolysis process, and promote the additive to better exert its ion-conducting and hydrophilic properties. This is because, at the interface between the base membrane and the modified membrane layer, the connection between the additive and the base membrane includes physical entanglement. Small organic molecules with aromatic structures can bind to organic molecules in the base membrane through physical cross-linking or physical entanglement. The two form a physically interlocked structure through the spatial entanglement and interpenetration of molecular chains, thereby enhancing the mechanical stability of the additive on the membrane surface.

[0034] As an example, the aromatic ring structures of small organic molecules include bicyclic structures containing benzene rings. These bicyclic structures can consist of two benzene rings, or they can be combinations of benzene rings with cycloalkanes, combinations of benzene rings with other benzene rings (such as fused-ring aromatics), or combinations of benzene rings with heterocycles, etc.

[0035] In some embodiments of this application, the additives include one or more of 1,2,3,4-tetrahydro-1,5-naphthidine, 2-naphthium chloride, and 5,6,7,8-tetrahydro-2-naphthylamine; and / or, the alkaline water electrolysis membrane includes one or more of polyphenylene sulfide membrane, sulfonated polyphenylene sulfide membrane, polysulfone membrane, and polyetheretherketone membrane.

[0036] In the embodiments of this application, one or more of 1,2,3,4-tetrahydro-1,5-naphthidine, 2-naphthium chloride, and 5,6,7,8-tetrahydro-2-naphthylamine can be used as additives to modify the surface of the base membrane, which can further improve the ionic conductivity of the composite membrane, reduce the resistance of the composite membrane, improve the hydrophilicity of the composite membrane, and effectively improve the electrolysis efficiency.

[0037] In addition, the bonding mechanisms between additives and the base film also include interfacial forces and diffusion. These additives can form connections with the base film through intermolecular forces (such as van der Waals forces, hydrogen bonds, π-π stacking, etc.), thereby enhancing the stability of the interface.

[0038] 1,2,3,4-Tetrahydro-1,5-naphthidine, 2-naphthium chloride, and 5,6,7,8-tetrahydro-2-naphthylamine are bicyclic structures containing benzene rings. They are compatible with the formation of the base film and promote interfacial diffusion. In addition, they can provide intermolecular forces, promote the binding of additives and base film components through intermolecular forces, improve interfacial stability, and better promote the modification effect of additives on the base film.

[0039] The CAS number for 1,2,3,4-tetrahydro-1,5-naphthidine is 13993-61-8; the CAS number for 2-naphthium chloride is 91-58-7; and the CAS number for 5,6,7,8-tetrahydro-2-naphthylamine is 2217-43-8.

[0040] In the embodiments of this application, the surface of commonly used membranes in the art can be modified. For example, alkaline water electrolysis membranes may include, but are not limited to, one or more of polyphenylene sulfide membranes, sulfonated polyphenylene sulfide membranes, polysulfone membranes, and polyetheretherketone membranes.

[0041] As an example, sulfonated PPS membranes are a highly competitive membrane material in the field of alkaline water electrolysis for hydrogen production. In this application embodiment, sulfonated PPS membranes can be used as the base membrane.

[0042] In some embodiments of this application, the modified film layer also includes a dispersant.

[0043] In this embodiment, a dispersant can be added to the modified film as an excipient to improve the performance of the modified film. Introducing a dispersant during the preparation process helps to improve the dispersion stability of the additives and form a uniform and stable modified film on the surface of the base film.

[0044] In some embodiments of this application, the dispersant includes one or more of polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and polyvinyl alcohol.

[0045] In the embodiments of this application, the dispersant may be a dispersant known in the art, including but not limited to one or more of polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and polyvinyl alcohol.

[0046] Furthermore, polyethylene glycol can be used as the dispersant.

[0047] In this embodiment, polyethylene glycol and ethanol are used as dispersants to form a modified film layer, which helps to improve the bonding stability between the additive and the base film and enhance the adsorption strength of the additive on the base film surface, thereby allowing the additive to fully exert its improving effect on the base film. This is because polyethylene glycol is a substance with a relatively large molecular weight, and its own molecular network structure can encapsulate and constrain small organic molecules, improving the overall stability of the additive on the base film surface.

[0048] A second aspect of this application provides a method for preparing a composite membrane, comprising:

[0049] A pre-formed film layer is formed on the surface of a base film using a dispersion liquid; the dispersion liquid includes additives, which include small organic molecules with aromatic ring structures and containing NH groups;

[0050] A pre-fabricated membrane layer is heat-set to form a modified membrane layer on the surface of the base membrane, resulting in a composite membrane.

[0051] In this embodiment, a dispersion containing additives can be provided first. The method of forming a pre-film layer on the surface of the base film using the dispersion includes wetting, coating, etc. Finally, heat setting treatment is performed to enhance the stability of the additives on the surface of the base film.

[0052] In this embodiment, additives are used to modify the surface of the base membrane. These small-molecule organic additives have an NH structure, which can adsorb OH- ions from the electrolyte through hydrogen bonds and other forces such as van der Waals forces. Subsequently, under the influence of an electric field, the ions move towards the anode through the pore structure of the membrane, thereby improving ionic conductivity and reducing the resistance of the composite membrane. Furthermore, the NH structure of these small-molecule organic additives also allows them to adsorb water molecules from the electrolyte through hydrogen bonds and other forces such as van der Waals forces, thus improving hydrophilicity.

[0053] Furthermore, when modifying the diaphragm, it is necessary to consider, on the one hand, the impact of the additives used for modification on the ion transport function and hydrophilicity of the water electrolysis process; and on the other hand, it is necessary to possess good physical properties, that is, the modified membrane layer should remain intact during water electrolysis. If the modified membrane layer is unstable in adsorption on the base membrane surface, it is prone to detachment during water electrolysis, which would reduce the improvement effect of the modified membrane layer on the base membrane. In the embodiments of this application, the additives used for modifying the diaphragm surface are small organic molecules with aromatic ring structures, which facilitate the formation of a stable modified membrane layer on the base membrane, reduce the problem of weak adsorption and detachment of the modified membrane layer during use, maintain high stability during the water electrolysis hydrogen production process, ensure the continuous operation of the water electrolysis process, and promote the additive to better exert its ion-conducting and hydrophilic properties. This is because, at the interface between the base membrane and the modified membrane layer, the connection between the additive and the base membrane includes physical entanglement. Small organic molecules with aromatic structures can bind to organic molecules in the base membrane through physical cross-linking or physical entanglement. The two form a physically interlocked structure through the spatial entanglement and interpenetration of molecular chains, thereby enhancing the mechanical stability of the additive on the membrane surface.

[0054] In some embodiments of this application, the dispersion further includes a solvent, which includes one or more of ethanol, isopropanol, acetone, ethyl acetate, methanol, and butanone; and / or, the dispersion further includes a dispersant, which includes one or more of polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and polyvinyl alcohol.

[0055] In the embodiments of this application, the solvent is primarily used as a continuous phase dispersion additive. The solvent may be any solvent known in the art. Furthermore, the boiling point of the solvent is lower than the heat setting temperature. As examples, the solvent includes, but is not limited to, one or more of ethanol, isopropanol, acetone, ethyl acetate, methanol, and butanone.

[0056] These solvents have low boiling points and are easily volatile. During solvent removal processes such as drying or baking the dispersion on the base film surface, solvent evaporation can increase the proportion of additives in the dispersion, increase the solid content, improve the content or purity of additives in the modified film layer, reduce the influence of non-additive components such as solvents, and ensure that the additives can fully play their role in improving the base film.

[0057] Furthermore, solvents include ethanol. Ethanol has a low boiling point, is inexpensive, and is environmentally friendly.

[0058] In this embodiment, a dispersant can be added to the modified film layer to improve its performance. Introducing a dispersant during the preparation process helps improve the dispersion stability of the additives, resulting in a uniform and stable modified film layer on the base film surface.

[0059] In this embodiment, the dispersant may be a dispersant known in the art, including but not limited to one or more of polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and polyvinyl alcohol. These additives help improve the dispersion stability of the additives and form a uniform and stable modified film layer on the surface of the base film. In addition, these additives have relatively low molecular weights and can be well dispersed in solvents.

[0060] Furthermore, polyethylene glycol can be used as the dispersant.

[0061] In this embodiment, polyethylene glycol and ethanol are used as dispersants to form a modified film layer, which helps to improve the bonding stability between the additive and the base film and enhance the adsorption strength of the additive on the base film surface, thereby allowing the additive to fully exert its improving effect on the base film. This is because polyethylene glycol is a substance with a relatively large molecular weight, and its own molecular network structure can encapsulate and constrain small organic molecules, improving the overall stability of the additive on the base film surface.

[0062] In some embodiments of this application, the volume ratio of dispersant to solvent is 1:(2-3).

[0063] Because dispersants have relatively large molecular weights, they are prone to agglomeration during the preparation process, affecting the quality of the modified film. Taking polyethylene glycol (PEG) as the dispersant and ethanol as the solvent as an example, dissolving PEG in ethanol provides good dispersion and dilution for PEG, facilitating its uniform dispersion in the solvent, mitigating agglomeration, fully utilizing its dispersing effect on the additives, and ultimately ensuring uniform dispersion in the modified film, thereby strengthening the bond between the additives and the base film.

[0064] In this embodiment, the volume ratio of dispersant to solvent is further defined as 1:(2-3), which helps to further improve the solvent and dispersibility of the dispersant in the solvent, promote the dissolution of the dispersant in the solvent, reduce the occurrence of agglomeration, further exert the dispersing effect on the additive, and finally uniformly disperse in the modified film layer, thereby strengthening the connection between the additive and the base film.

[0065] As examples, the volume ratio of dispersant to solvent is 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, etc.

[0066] In some embodiments of this application, the temperature in the heat setting process is 150°C-200°C and the pressure is 2MPa-10MPa.

[0067] The heat setting conditions can be determined based on the actual application environment of the diaphragm. The temperature and pressure of the heat setting treatment can be higher than the actual application temperature and pressure of the diaphragm in order to improve the stability of the modified membrane layer on the base membrane surface and reduce the temperature at which the modified membrane layer falls off.

[0068] For example, the temperatures are 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, etc., and the pressures are 2MPa, 3MPa, 4MPa, 5MPa, 6MPa, 7MPa, 8MPa, 9MPa, 10MPa, etc.

[0069] In some embodiments of this application, the method of forming a pre-film layer on the surface of a base film using a dispersion includes:

[0070] The base film is wetted with a dispersion and then subjected to solvent removal treatment.

[0071] The base membrane is immersed in a dispersion, and the dispersion is adsorbed onto the surface of the base membrane through physical diffusion, capillary action, etc. Then, through desolventizing treatment, the additives are retained on the surface of the base membrane, or the additives and dispersants are retained to form a pre-formed film layer.

[0072] Furthermore, the solvent removal method includes drying.

[0073] Furthermore, the soaking and solvent removal steps can be repeated.

[0074] As an example, the base membrane (such as sulfonated PPS membrane) was immersed in the dispersion for 24 hours and then taken out and placed in an oven for 12 hours to dry. The overall immersion and drying were carried out in multiple times, that is, immersion for the first time, drying and then taking out, immersion and drying again, and this was repeated 3 times.

[0075] Furthermore, the concentration of the dispersion can be adjusted to improve preparation efficiency and film quality. The concentration of the dispersion can be determined by considering the properties of the solvent and dispersant, as well as the solvent removal method and conditions.

[0076] As an example, the dispersion concentration is 0.1 mol / L-0.5 mol / L.

[0077] A third aspect of this application provides an electrolytic cell that includes the composite membrane described in the first aspect, or a composite membrane prepared by the method described in the second aspect.

[0078] The electrolytic cell proposed in this application has the beneficial effects of the composite diaphragm mentioned above, which will not be repeated here.

[0079] The fourth aspect of this application provides a hydrogen production system, including the electrolyzer described in the third aspect above.

[0080] The hydrogen production system proposed in this application has the beneficial effects of the composite membrane mentioned above, which will not be repeated here.

[0081] The following will explain the solution of this application with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0082] [Preparation of the diaphragm]

[0083] Example 1

[0084] 1) Immerse the PPS membrane cloth in concentrated sulfuric acid for sulfonation reaction for 30 minutes at a temperature of 55°C. After the reaction is complete, rinse with deionized water for 10 minutes and then dry to obtain the sulfonated PPS membrane.

[0085] 2) Cut the sulfonated PPS membrane to obtain a 50mm×50mm×1mm membrane, which will be used as the base membrane;

[0086] 3) Mix polyethylene glycol (PEG200-400) with anhydrous ethanol as a continuous phase, so that polyethylene glycol is dissolved in ethanol. The volume ratio of polyethylene glycol to anhydrous ethanol is 1:2.

[0087] 4) Dissolve additive 1,2,3,4-tetrahydro-1,5-naphthidine in the continuous phase, stir mechanically for 5 min, and then place it in an ultrasonic generator for ultrasonic dispersion for 10 min to obtain a dispersion. The concentration of the additive is 0.2 mol / L.

[0088] 5) After immersing the base membrane in the dispersion for 24 hours, remove it and place it in an oven for 12 hours to dry. The overall immersion and drying process is carried out in multiple stages, that is, after the first immersion and drying, remove it, then immerse it a second time and dry it again, repeating this process 3 times. The finally dried membrane is used as an intermediate sample for later use.

[0089] 6) The membrane after impregnation and drying is heat-set at a temperature of 200℃ and a pressure of 10 MPa to obtain a composite membrane.

[0090] Example 2

[0091] 1) Immerse the PPS membrane cloth in concentrated sulfuric acid for sulfonation reaction for 30 minutes at a temperature of 55°C. After the reaction is complete, rinse with deionized water for 10 minutes and then dry to obtain the sulfonated PPS membrane.

[0092] 2) Cut the sulfonated PPS membrane to obtain a 50mm×50mm×1mm membrane, which will be used as the base membrane;

[0093] 3) Mix polyethylene glycol (PEG200-400) with anhydrous ethanol as a continuous phase, so that polyethylene glycol is dissolved in ethanol. The volume ratio of polyethylene glycol to anhydrous ethanol is 1:2.

[0094] 4) Dissolve the additive 2-naphthylamine chloride in the continuous phase, stir mechanically for 5 min, and then place it in an ultrasonic generator for ultrasonic dispersion for 10 min to obtain a dispersion. The concentration of the additive is 0.2 mol / L.

[0095] 5) After immersing the base membrane in the dispersion for 24 hours, remove it and place it in an oven for 12 hours to dry. The overall immersion and drying process is carried out in multiple stages, that is, after the first immersion and drying, remove it, then immerse it a second time and dry it again, repeating this process 3 times. The finally dried membrane is used as an intermediate sample for later use.

[0096] 6) The membrane after impregnation and drying is heat-set at a temperature of 200℃ and a pressure of 10 MPa to obtain a composite membrane.

[0097] Example 3

[0098] 1) Immerse the PPS membrane cloth in concentrated sulfuric acid for sulfonation reaction for 30 minutes at a temperature of 55°C. After the reaction is complete, rinse with deionized water for 10 minutes and then dry to obtain the sulfonated PPS membrane.

[0099] 2) Cut the sulfonated PPS membrane to obtain a 50mm×50mm×1mm membrane, which will be used as the base membrane;

[0100] 3) Mix polyethylene glycol (PEG200-400) with anhydrous ethanol as a continuous phase, so that polyethylene glycol is dissolved in ethanol. The volume ratio of polyethylene glycol to anhydrous ethanol is 1:2.

[0101] 4) Dissolve the additive 5,6,7,8-tetrahydro-2-naphthylamine in the continuous phase, stir mechanically for 5 min, and then place it in an ultrasonic generator for ultrasonic dispersion for 10 min to obtain a dispersion. The concentration of the additive is 0.2 mol / L.

[0102] 5) After immersing the base membrane in the dispersion for 24 hours, remove it and place it in an oven for 12 hours to dry. The overall immersion and drying process is carried out in multiple stages, that is, after the first immersion and drying, remove it, then immerse it a second time and dry it again, repeating this process 3 times. The finally dried membrane is used as an intermediate sample for later use.

[0103] 6) The membrane after impregnation and drying is heat-set at a temperature of 200℃ and a pressure of 10 MPa to obtain a composite membrane.

[0104] Example 4

[0105] The method of Example 2 is used, except that in step 3), the volume ratio of polyethylene glycol to ethanol is 1:3.

[0106] 1) Immerse the PPS membrane cloth in concentrated sulfuric acid for sulfonation reaction for 30 minutes at a temperature of 55°C. After the reaction is complete, rinse with deionized water for 10 minutes and then dry to obtain the sulfonated PPS membrane.

[0107] 2) Cut the sulfonated PPS membrane to obtain a 50mm×50mm×1mm membrane, which will be used as the base membrane;

[0108] 3) Mix polyethylene glycol (PEG200-400) with anhydrous ethanol as a continuous phase, so that polyethylene glycol is dissolved in ethanol. The volume ratio of polyethylene glycol to anhydrous ethanol is 1:3.

[0109] 4) Dissolve the additive 2-naphthylamine chloride in the continuous phase, stir mechanically for 5 min, and then place it in an ultrasonic generator for ultrasonic dispersion for 10 min to obtain a dispersion. The concentration of the additive is 0.2 mol / L.

[0110] 5) After immersing the base membrane in the dispersion for 24 hours, remove it and place it in an oven for 12 hours to dry. The overall immersion and drying process is carried out in multiple stages, that is, after the first immersion and drying, remove it, then immerse it a second time and dry it again, repeating this process 3 times. The finally dried membrane is used as an intermediate sample for later use.

[0111] 6) The membrane after impregnation and drying is heat-set at a temperature of 200℃ and a pressure of 10 MPa to obtain a composite membrane.

[0112] Example 5

[0113] The method of Example 2 is used, except that in step 3), ethanol is used as the continuous phase and polyethylene glycol is not added.

[0114] 1) Immerse the PPS membrane cloth in concentrated sulfuric acid for sulfonation reaction for 30 minutes at a temperature of 55°C. After the reaction is complete, rinse with deionized water for 10 minutes and then dry to obtain the sulfonated PPS membrane.

[0115] 2) Cut the sulfonated PPS membrane to obtain a 50mm×50mm×1mm membrane, which will be used as the base membrane;

[0116] 3) Take an appropriate amount of anhydrous ethanol as the dispersed phase;

[0117] 4) Dissolve the additive 2-naphthylamine chloride in the continuous phase, stir mechanically for 5 min, and then place it in an ultrasonic generator for ultrasonic dispersion for 10 min to obtain a dispersion. The concentration of the additive is 0.2 mol / L.

[0118] 5) After immersing the base membrane in the dispersion for 24 hours, remove it and place it in an oven for 12 hours to dry. The overall immersion and drying process is carried out in multiple stages, that is, after the first immersion and drying, remove it, then immerse it a second time and dry it again, repeating this process 3 times. The finally dried membrane is used as an intermediate sample for later use.

[0119] 6) The membrane after impregnation and drying is heat-set at a temperature of 200℃ and a pressure of 10 MPa to obtain a composite membrane.

[0120] Example 6

[0121] The method of Example 2 is used, except that in step 6), the temperature is 150°C and the pressure is 2 MPa.

[0122] 1) Immerse the PPS membrane cloth in concentrated sulfuric acid for sulfonation reaction for 30 minutes at a temperature of 55°C. After the reaction is complete, rinse with deionized water for 10 minutes and then dry to obtain the sulfonated PPS membrane.

[0123] 2) Cut the sulfonated PPS membrane to obtain a 50mm×50mm×1mm membrane, which will be used as the base membrane;

[0124] 3) Mix polyethylene glycol (PEG200-400) with anhydrous ethanol as a continuous phase, so that polyethylene glycol is dissolved in ethanol. The volume ratio of polyethylene glycol to anhydrous ethanol is 1:2.

[0125] 4) Dissolve the additive 2-naphthylamine chloride in the continuous phase, stir mechanically for 5 min, and then place it in an ultrasonic generator for ultrasonic dispersion for 10 min to obtain a dispersion. The concentration of the additive is 0.2 mol / L.

[0126] 5) After immersing the base membrane in the dispersion for 24 hours, remove it and place it in an oven for 12 hours to dry. The overall immersion and drying process is carried out in multiple stages, that is, after the first immersion and drying, remove it, then immerse it a second time and dry it again, repeating this process 3 times. The finally dried membrane is used as an intermediate sample for later use.

[0127] 6) The membrane after impregnation and drying is heat-set at a temperature of 150℃ and a pressure of 2 MPa to obtain a composite membrane.

[0128] Comparative Example 1

[0129] The sulfonated PPS membrane provided in step 1) of Example 1 is used.

[0130] Comparative Example 2

[0131] The method of Example 1 is used, except that in step 4), ethylenediamine is used as the additive.

[0132] 1) Immerse the PPS diaphragm cloth in concentrated sulfuric acid for sulfonation reaction for 30 minutes at a temperature of 55°C. After the reaction is complete, rinse with deionized water for 10 minutes and then dry to obtain the sulfonated PPS diaphragm.

[0133] 2) Cut the sulfonated PPS membrane to obtain a 50mm×50mm×1mm membrane, which will be used as the base membrane;

[0134] 3) Mix polyethylene glycol (PEG200-400) with anhydrous ethanol as a continuous phase, so that polyethylene glycol is dissolved in ethanol. The volume ratio of polyethylene glycol to anhydrous ethanol is 1:2.

[0135] 4) Dissolve the additive ethylenediamine in the continuous phase, stir mechanically for 5 min, and then place it in an ultrasonic generator for ultrasonic dispersion for 10 min to obtain a dispersion. The concentration of the additive is 0.2 mol / L.

[0136] 5) After immersing the base membrane in the dispersion for 24 hours, remove it and place it in an oven for 12 hours to dry. The overall immersion and drying process is carried out in multiple stages, that is, after the first immersion and drying, remove it, then immerse it a second time and dry it again, repeating this process 3 times. The finally dried membrane is used as an intermediate sample for later use.

[0137] 6) The membrane after impregnation and drying is heat-set at a temperature of 200℃ and a pressure of 10 MPa to obtain a composite membrane.

[0138] [Performance Testing]

[0139] I. Performance Testing Methods

[0140] 1. Contact angle test:

[0141] Wetting tests were conducted using a contact angle meter. A 1cm x 1cm square block was cut out, and pure water was used as the solvent. The contact angle of water on the diaphragm surface was observed and recorded.

[0142] 2. Surface resistance test:

[0143] Sheet resistance testing can measure the conductivity of a diaphragm in an alkaline solution. A two-electrode electrochemical workstation was used. A 2.5cm × 2.5cm square diaphragm piece was cut and placed in the workstation for sheet resistance testing. A 30% KOH solution was selected for the test, and the solution temperature was controlled at 80℃. The sheet resistance measurement results were observed and recorded.

[0144] 3. Alkali absorption rate test:

[0145] The alkali absorption rate can be used to test the compatibility between the diaphragm and the alkali solution. A square block of 2.5cm × 2.5cm is cut and soaked in a 30% KOH solution for 24 hours. The solution temperature is controlled at 80℃. After soaking, the diaphragm is placed in a 100℃ oven to dry its surface for 5 hours and then weighed. The mass of the diaphragm before and after the soaking test is weighed, and the alkali absorption rate is calculated by the mass difference.

[0146] 4. Electrolysis performance test:

[0147] The electrolytic performance of the diaphragm was tested in a single-chamber electrolytic cell. A diaphragm measuring 20cm x 20cm was used as the test diaphragm. Common nickel-based electrodes were used. The electrolyte was controlled at 30% KOH and the temperature was 80℃. The electrolysis voltage of water under the same hydrogen production conditions was measured.

[0148] II. Performance Test Results

[0149] The performance of the diaphragm samples provided in each embodiment and comparative example was tested, and the test results are shown in Table 1.

[0150] Table 1

[0151] Serial Number Contact angle (°) <![CDATA[Surface resistance (Ω·cm 2 )]]> Alkali absorption rate (%) Voltage (V) Example 1 56.0 0.26 189 1.71 Example 2 52.9 0.21 201 1.66 Example 3 56.2 0.28 188 1.72 Example 4 52 0.21 191 1.67 Example 5 59.3 0.42 185 1.76 Example 6 52.4 0.33 184 1.72 Comparative Example 1 62.3 0.50 158 1.88 Comparative Example 2 59.4 0.45 181 1.79

[0152] In this embodiment, the base membrane is modified with additives (any one of 1,2,3,4-tetrahydro-1,5-naphthidine, 2-naphthium chloride, and 5,6,7,8-tetrahydro-2-naphthylamine). By introducing the polar NH group structure, the resistance of the traditional membrane during electrolysis is reduced, the electrolysis energy consumption is decreased, and the hydrophilicity of the composite membrane is enhanced. Furthermore, these additives can form a stable interface with the base membrane surface. Combined with polyethylene glycol dispersant, this enhances the physical connection between the additives and the molecules on the base membrane surface, thereby improving the membrane's stability. The additives are not easily detached during water electrolysis, allowing them to fully exert their modifying effect. This results in a composite membrane exhibiting lower sheet resistance, higher alkali absorption rate, and a lower contact angle, which is beneficial for improving electrolysis performance.

[0153] Comparative Example 1, without modification, exhibits high electrical resistance, weak hydrophilicity, and poor electrolytic performance. Comparative Example 2 uses organic additives to modify the base film, but the effect is not as good as that of this application.

[0154] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A composite diaphragm, characterized in that, Includes a base film and a modified film layer located on the surface of the base film; The base membrane includes an alkaline water electrolysis membrane; The modified film layer includes additives, which include small organic molecules having an aromatic ring structure and containing NH groups.

2. The composite diaphragm according to claim 1, characterized in that, The additives include one or more of 1,2,3,4-tetrahydro-1,5-naphthidine, 2-naphthium chloride, and 5,6,7,8-tetrahydro-2-naphthylamine; and / or, the alkaline water electrolysis membrane includes one or more of polyphenylene sulfide membrane, sulfonated polyphenylene sulfide membrane, polysulfone membrane, and polyetheretherketone membrane.

3. The composite diaphragm according to claim 1 or 2, characterized in that, The modified film also includes a dispersant.

4. The composite diaphragm according to claim 3, characterized in that, The dispersant includes one or more of polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and polyvinyl alcohol.

5. A method for preparing a composite diaphragm, characterized in that, include: A pre-formed film layer is formed on the surface of a base film using a dispersion liquid; the dispersion liquid includes an additive, which includes a small organic molecule having an aromatic ring structure and containing an NH group; The pre-fabricated membrane layer is heat-set to form a modified membrane layer on the surface of the base membrane, thereby obtaining a composite membrane.

6. The method according to claim 5, characterized in that, The dispersion further includes a solvent, which includes one or more of ethanol, isopropanol, acetone, ethyl acetate, methanol, and butanone. And / or, the dispersion further includes a dispersant, the dispersant comprising one or more of polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and polyvinyl alcohol.

7. The method according to claim 6, characterized in that, The volume ratio of the dispersant to the solvent is 1:(2-3).

8. The method according to claim 6, characterized in that, In the heat setting process, the temperature is 150℃-200℃ and the pressure is 2MPa-10MPa.

9. An electrolytic cell, characterized in that, It includes the composite membrane according to any one of claims 1 to 4, or the composite membrane prepared by the method according to any one of claims 5 to 8.

10. A hydrogen production system, characterized in that, Includes the electrolytic cell as described in claim 9.