Composite anion exchange membrane, method for preparing the same, and use thereof

Abstract

The application relates to the technical field of hydrogen production by water electrolysis, in particular to a composite anion exchange membrane and a preparation method and application thereof. The preparation method of the composite anion exchange membrane comprises the following steps: mixing a polymer, an organic solvent and an aldehyde compound to form a casting solution; forming the casting solution to prepare an aldehyde compound-combined anion exchange membrane; immersing the aldehyde compound-combined anion exchange membrane into an acid solution containing an amino compound to perform an aldehyde amine condensation reaction, and forming the composite anion exchange membrane; and the polymer and the amino compound contain quaternary ammonium groups. The application can simply and quickly synthesize a large-area composite anion exchange membrane doped with a covalent organic framework, and the composite anion exchange membrane has good structural stability and excellent ion conduction performance, and can meet the application requirements of hydrogen production by water electrolysis.

Description

Technical Field

[0001] This application relates to the field of hydrogen production technology through water electrolysis, and in particular to composite anion exchange membranes, their preparation methods, and applications. Background Technology

[0002] Hydrogen energy is a crucial carrier for achieving deep decarbonization and energy interconnection. Producing hydrogen through fossil fuel reforming or gasification is easy to scale up and relatively inexpensive, making it the primary method of hydrogen production. However, this method uses non-renewable resources such as coal and natural gas as raw materials, and the production process involves significant carbon release, exacerbating the greenhouse effect and harming the environment. Electrolysis of water to produce hydrogen, which uses electricity to decompose water into hydrogen and oxygen, is considered an ideal path for green hydrogen production.

[0003] However, the large-scale development of hydrogen production through water electrolysis depends on the performance of the membrane. An ideal membrane needs to meet two requirements: efficient conduction of hydroxide ions (OH-). - This reduces ohmic losses and increases current density; on the other hand, it effectively blocks the cross-penetration of hydrogen and oxygen to prevent the risk of explosion and ensure gas purity.

[0004] Covalent organic frameworks (COFs), as porous sheet materials, exhibit unique advantages in ion conduction and gas barrier properties due to their regular pore structure and excellent chemical stability. Their ordered pores provide low-resistance directional transport paths for ions, while the tightly stacked sheet structure effectively inhibits gas permeation across the membrane, mechanistically meeting the dual requirements of high-efficiency conduction and reliable barrier properties for water electrolysis hydrogen production membranes.

[0005] However, standalone COF materials still face key bottlenecks in practical applications. Firstly, their poor film-forming properties make it difficult to form continuous, dense, large-area films using conventional processes. Secondly, the difficulty in exfoliating them into stable nanosheets limits their adaptability in membrane electrode assembly. These problems result in insufficient processing performance. More critically, under long-term high-potential electrolysis conditions, COF materials are prone to structural collapse and performance degradation, limiting their application in water electrolysis for hydrogen production. Summary of the Invention

[0006] Based on this, the main objective of this application is to provide a method for preparing a composite anion exchange membrane. This method can easily and quickly synthesize a large-area covalent organic framework-doped composite anion exchange membrane, and the prepared composite anion exchange membrane has good stability and ion conductivity, which can meet the application requirements of water electrolysis for hydrogen production.

[0007] In a first aspect, this application provides a method for preparing a composite anion exchange membrane, comprising the following steps:

[0008] A casting solution is formed by mixing polymers, organic solvents, and aldehyde compounds.

[0009] The casting solution is molded to prepare an aldehyde-based compound composite anion exchange membrane;

[0010] The anion exchange membrane composed of the aldehyde compound is immersed in an acid solution containing an amino compound to carry out an aldehyde-amine condensation reaction, thereby forming the composite anion exchange membrane.

[0011] The polymer and the amino compound contain quaternary ammonium groups.

[0012] In some embodiments, the method for preparing the composite anion exchange membrane satisfies one or more of the following characteristics:

[0013] (1) The polymer comprises at least one of the following: ether-free polyaromatic hydrocarbons having piperidine cationic groups, quaternized polysulfones, quaternized polyether ether ketones, quaternized polyphenylene ethers, and quaternized polybenzimidazoles;

[0014] (2) The aldehyde compound includes a polyaldehyde monomer;

[0015] (3) The organic solvent includes at least one of dimethyl sulfoxide, N-methylpyrrolidone and tetrahydrofuran;

[0016] (4) The amino compound includes 3,8-diamino-5-ethyl-6-phenylphenanthridine bromide.

[0017] In some embodiments, the ether-free polyaromatic hydrocarbon having a piperidine cationic group comprises -Ar-, and structural units shown in Formula I and Formula II:

[0018] Formula I; Formula II;

[0019] Wherein, -Ar- is an aryl group with 6 to 30 cyclic atoms; with the molar percentage of the structural unit shown in Formula I and the structural unit shown in Formula II being 100%, the molar percentage of the structural unit shown in Formula I is 50% to 90%.

[0020] In some embodiments, the polyaldehyde monomer includes at least one selected from trialdehyde phloroglucinol, 1,3,5-tricarboxyphenyl, tri(4-formylphenyl)amine, 2,4,6-tricarboxymethyltrimethylbenzene, and terephthalaldehyde.

[0021] In some embodiments, the method for preparing the composite anion exchange membrane satisfies one or more of the following characteristics:

[0022] (1) The mass ratio of the polymer to the aldehyde compound is 1:(0.01~0.2);

[0023] (2) The molar ratio of the aldehyde compound to the amino compound is (0.3~1):1.

[0024] In some embodiments, the method for preparing the composite anion exchange membrane satisfies one or more of the following characteristics:

[0025] (1) In the casting solution, the mass concentration of the polymer is 0.01wt%~30wt%;

[0026] (2) In the acid solution containing the amino compound, the mass-volume concentration of the amino compound is 0.01 mg / mL to 10 mg / mL;

[0027] (3) The mass-to-volume ratio of the anion exchange membrane composed of the aldehyde compound to the acid solution containing the amino compound is 1 g: (30~800) mL;

[0028] (4) The acid in the amino-containing acid solution includes acetic acid;

[0029] (5) In the acid solution containing the amino compound, the concentration of the acid is 1M~12M;

[0030] (6) The conditions for the aldehyde-amine condensation reaction include: reaction temperature of 20℃~55℃; reaction time of 24h~168h.

[0031] Secondly, this application provides a composite anion exchange membrane prepared by the method described in the first aspect.

[0032] Thirdly, this application provides the application of the composite anion exchange membrane described in the second aspect in hydrogen production by water electrolysis.

[0033] Fourthly, this application provides a method for producing hydrogen by electrolysis of water, comprising the following steps:

[0034] A composite anion exchange membrane is placed between the cathode catalyst layer and the anode catalyst layer to form an anion exchange membrane water electrolyzer.

[0035] Using an aqueous solution as the anode electrolyte, a direct current is applied to carry out the hydrogen production reaction by electrolysis of water.

[0036] The composite anion exchange membrane includes the composite anion exchange membrane described in the second aspect.

[0037] In some embodiments, the water electrolysis method for producing hydrogen satisfies one or more of the following characteristics:

[0038] (1) The aqueous solution includes at least one of pure water, seawater, potassium hydroxide aqueous solution and sodium hydroxide aqueous solution;

[0039] (2) The rate at which the aqueous solution is introduced is 0.5 mL / min to 10 mL / min.

[0040] The beneficial effects of this application are as follows:

[0041] This application involves mixing a polymer, an organic solvent, and an aldehyde compound to form a casting solution, which is then molded to prepare an aldehyde compound composite anion exchange membrane. This process uniformly disperses and fixes the aldehyde compound within the anion exchange membrane. The membrane is then immersed in an acidic solution containing an amino compound. The amino compound reacts with the aldehyde compound in the anion exchange membrane via an aldehyde-amine condensation reaction, resulting in a simple and rapid in-situ formation of a large-area covalently doped organic framework composite anion exchange membrane. Because the covalent organic framework is bound by imine groups, it exhibits good alkaline stability and good tolerance to alkaline electrolysis environments, thus improving the structural stability of the composite anion exchange membrane and expanding its application range. Furthermore, since both the polymer and the amino compound contain quaternary ammonium groups, the prepared composite anion exchange membrane contains abundant quaternary ammonium sites, which can effectively reduce the anion transport energy barrier, providing a suitable environment for OH- ions. - Ion transport provides a pathway, exhibiting excellent anionic conductivity. In summary, this application enables the simple and rapid synthesis of large-area covalently organic framework-doped composite anion exchange membranes, which possess both good structural stability and excellent ion conductivity, meeting the application requirements for hydrogen production via water electrolysis. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings are only for illustrating preferred embodiments and are not intended to limit this application. Throughout the drawings, the same reference numerals denote the same parts. In the drawings:

[0043] Figure 1 This is an external view of the composite anion exchange membrane of Example 1;

[0044] Figure 2 The image shows the appearance of the reaction solution and the composite anion exchange membrane after the reaction in step 3) of Example 1 is completed, where A is the reaction solution and B is the composite anion exchange membrane.

[0045] Figure 3 The image shows the appearance of the reaction solution and the composite anion exchange membrane after the reaction in step 3) of Comparative Example 3 is completed. In this image, A is the reaction solution and B is the composite anion exchange membrane.

[0046] Figure 4 The graph shows the changes in swelling rate and water absorption rate of Example 1 and Comparative Example 1 as a function of temperature;

[0047] Figure 5 OH for Example 1 and Comparative Examples 1 to 3 - Graph showing the change in electrical conductivity with temperature;

[0048] Figure 6 The apparent activation energies of Example 1 and Comparative Example 1 at different temperatures;

[0049] Figure 7 The polarization curves are for Examples 1 to 3 and Comparative Examples 1 to 3;

[0050] Figure 8 The polarization curves for Example 1 at different temperatures are shown. Detailed Implementation

[0051] The present application will be further described in detail below with reference to specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application and in its specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0053] In this application, "one or more" means any one, two or more of the listed items.

[0054] In this application, terms such as "first aspect" and "second aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, terms such as "first" and "second" serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0055] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0056] In this application, numerical ranges are involved. Unless otherwise specified, the numerical ranges mentioned above are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed in this application should be understood to include any and all subranges to which they are included.

[0057] Unless otherwise specified, the percentage content mentioned in this application refers to mass percentage for solid-liquid mixtures and liquid-liquid mixtures, and volume (molar) percentage for gas-gas mixtures.

[0058] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0059] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows for temperature fluctuations within the precision range controlled by the instrument.

[0060] Research has found that covalent organic frameworks (COFs), as porous sheet materials, exhibit unique advantages in ion conduction and gas barrier properties due to their regular pore structure and excellent chemical stability, mechanistically meeting the dual requirements of efficient conduction and reliable barrier properties for water electrolysis hydrogen production membranes. However, standalone COF materials still face key bottlenecks in practical applications. First, their poor film-forming properties make it difficult to form continuous, dense, large-area films using conventional processes. Second, the difficulty in exfoliating them into stable nanosheets limits their processing adaptability in membrane electrode assembly. These problems result in insufficient processing performance. More critically, under long-term high-potential electrolysis environments, COF materials are prone to structural collapse and performance degradation, limiting their application in water electrolysis hydrogen production.

[0061] In view of this, this application provides a composite anion exchange membrane, its preparation method and application. The preparation method can simply and quickly synthesize a large-area covalent organic framework-doped composite anion exchange membrane, and the prepared composite anion exchange membrane has good stability and ion conduction performance, which can meet the application requirements of water electrolysis for hydrogen production.

[0062] In a first aspect, this application provides a method for preparing a composite anion exchange membrane, comprising the following steps:

[0063] A casting solution is formed by mixing polymers, organic solvents, and aldehyde compounds.

[0064] The casting solution is molded to prepare an aldehyde-based compound composite anion exchange membrane;

[0065] The anion exchange membrane composed of the aldehyde compound is immersed in an acid solution containing an amino compound to carry out an aldehyde-amine condensation reaction, thereby forming the composite anion exchange membrane.

[0066] The polymer and the amino compound contain quaternary ammonium groups.

[0067] This application involves mixing a polymer, an organic solvent, and an aldehyde compound to form a casting solution, which is then molded to prepare an aldehyde compound composite anion exchange membrane. This process uniformly disperses and fixes the aldehyde compound within the anion exchange membrane. The membrane is then immersed in an acidic solution containing an amino compound. The amino compound reacts with the aldehyde compound in the anion exchange membrane via an aldehyde-amine condensation reaction, resulting in a simple and rapid in-situ formation of a large-area covalently doped organic framework composite anion exchange membrane. Because the covalent organic framework is bound by imine groups, it exhibits good alkaline stability and good tolerance to alkaline electrolysis environments, thus improving the structural stability of the composite anion exchange membrane and expanding its application range. Furthermore, since both the polymer and the amino compound contain quaternary ammonium groups, the prepared composite anion exchange membrane contains abundant quaternary ammonium sites, which can effectively reduce the anion transport energy barrier, providing a suitable environment for OH- ions. - Ion transport provides a pathway, exhibiting excellent anionic conductivity. In summary, this application enables the simple and rapid synthesis of large-area covalently organic framework-doped composite anion exchange membranes, which possess both good structural stability and excellent ion conductivity, meeting the application requirements for hydrogen production via water electrolysis.

[0068] In some embodiments, the polymer comprises at least one of the following: ether-free polyaromatic hydrocarbons having piperidine cationic groups, quaternized polysulfones, quaternized polyether ether ketones, quaternized polyphenylene ethers, and quaternized polybenzimidazoles.

[0069] Understandably, aldehyde compounds can be either small molecule aldehyde compounds or large molecule aldehyde compounds, and this application does not limit them. Furthermore, aldehyde compounds can be either monoaldehyde compounds or polyaldehyde compounds, wherein polyaldehyde compounds are beneficial for forming cross-linked networks and improving the mechanical strength of the composite anion exchange membrane.

[0070] Understandably, the amino compound can be either a small molecule amino compound or a large molecule amino compound, and there is no limitation in this application. Furthermore, the amino compound can be either a monoamino compound or a polyamino compound, wherein polyamino compounds are beneficial for forming a cross-linking network and increasing the quaternary ammonium sites of the composite anion exchange membrane, thereby further improving the mechanical strength and anion conductivity of the composite anion exchange membrane.

[0071] In some embodiments, the aldehyde compound comprises a polyaldehyde monomer. It is understood that a polyaldehyde monomer refers to an aldehyde monomer containing at least two aldehyde groups.

[0072] In some embodiments, the organic solvent includes at least one of dimethyl sulfoxide, N-methylpyrrolidone, and tetrahydrofuran.

[0073] In some embodiments, the amino compound includes 3,8-diamino-5-ethyl-6-phenylphenanthridine bromide.

[0074] In some embodiments, the polyaldehyde monomer includes at least one selected from trialdehyde phloroglucinol, 1,3,5-tricarboxyphenyl, tri(4-formylphenyl)amine, 2,4,6-tricarboxymethyltrimethylbenzene, and terephthalaldehyde.

[0075] In some embodiments, the ether-free polyaromatic hydrocarbon having a piperidine cationic group comprises -Ar-, and structural units shown in Formula I and Formula II:

[0076] Formula I; Formula II;

[0077] Wherein, -Ar- is an aryl group with 6 to 30 cyclic atoms; with the molar percentage of the structural unit shown in Formula I and the structural unit shown in Formula II being 100%, the molar percentage of the structural unit shown in Formula I is 50% to 90%.

[0078] In some embodiments, the molar percentage of the structural unit shown in Formula I can be 50%, 60%, 70%, 80%, 90%, etc.

[0079] Understandably, in this application, the "*" in each structural formula refers to a linking site, that is, the position may contain substituents, but does not limit the specific structure of the linked substituents.

[0080] Understandably, in this application, substituents of compounds are disclosed by groups or ranges. It is expressly contemplated that such a description includes each individual sub-combination of members of these groups and ranges. For example, the number of cyclic atoms in the range of 6 to 30 is disclosed individually for each integer between 6 and 30, as well as ranges of cyclic atoms formed by different integers between 6 and 30, such as 6, 10, 12, 14, 18, 22, 24, 26, 28, or 30, or 6 to 14, 6 to 18, 6 to 30, 14 to 30, etc.

[0081] In this application, the term "aryl" refers to an aromatic hydrocarbon group derived from an aromatic ring compound by removing one hydrogen atom. It can be a monocyclic aryl, a fused-ring aryl, or a polycyclic aryl, and for polycyclic rings, at least one is an aromatic ring system. For example, "aryl with 6 to 18 ring atoms" can independently refer to aryl groups with 6, 10, 12, 14, or 18 ring atoms. Understandably, aryl is an abbreviation for aromatic groups and can include monocyclic aryl (phenyl), fused-ring aryl (such as naphthyl or anthracene), or polycyclic aryl (such as biphenyl).

[0082] In this application, the term "arylene" refers to an aromatic hydrocarbon group derived from an aromatic ring compound by removing two hydrogen atoms. This group can be a monocyclic aryl, a fused-ring aryl, or a polycyclic aryl; for polycyclic rings, at least one is an aromatic ring system. The phrase "arylene with 6 to 30 ring atoms" can independently refer to arylenes with 6, 10, 12, 14, 18, 20, 24, 26, 28, or 30 ring atoms, such as phenylene, naphthylene, anthracene, biphenylene, terphenylene, and triphenylene. Here, phenylene is... Biphenyl is Triphenylene is... .

[0083] In some embodiments, with the molar percentage of the structural units shown in Formula I and Formula II being 100%, the molar percentage of -Ar- is 90% to 110%, optionally 100%. It is understood that the molar percentage of -Ar- may vary depending on the end group, potentially being greater than 100% or less than 100%. For example, when the group corresponding to the structural unit shown in Formula I and / or the structural unit shown in Formula II is at the end position, the molar percentage of -Ar- is less than or equal to 100%; when the group corresponding to -Ar- is at the end position, the molar percentage of -Ar- is greater than or equal to 100%.

[0084] In some embodiments, the preparation process of the ether-free polyaromatic hydrocarbon with piperidine cationic groups is not particularly limited, and can be carried out, for example, according to the method described in the journal article "Poly(aryl piperidinium) membranes and ionomers for hydroxide exchange membrane fuel cells". Exemplarily, the preparation of the ether-free polyaromatic hydrocarbon with piperidine cationic groups includes the following steps:

[0085] A prepolymer was prepared by reacting N,N-methyl-4-piperidinone, 2,2,2-trifluoroacetophenone and aromatic hydrocarbons in the presence of trifluoroacetic acid and trifluoromethanesulfonic acid.

[0086] The prepolymer was reacted with iodomethane to prepare ether-free polyaromatic hydrocarbons with piperidine cationic groups.

[0087] With N,N-methyl-4-piperidinone and 2,2,2-trifluoroacetophenone as 100% molar proportions, the molar proportion of N,N-methyl-4-piperidinone is 50% to 90%, such as 50%, 60%, 70%, 80%, 90%, etc.

[0088] In some embodiments, the mass ratio of the polymer to the aldehyde compound is 1:(0.01~0.2), optionally 1:(0.01~0.03), such as 1:0.01, 1:0.02, 1:0.03, 1:0.05, 1:0.1, 1:0.15, 1:0.2, etc.

[0089] In some embodiments, the molar ratio of the aldehyde compound to the amino compound is (0.3~1):1, for example 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.

[0090] In some embodiments, the mass concentration of the polymer in the casting solution is 0.01wt% to 30wt%, optionally 2wt% to 30wt%, such as 0.01wt%, 0.1wt%, 1wt%, 2wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, etc.

[0091] Understandably, the process of mixing polymers, organic solvents, and aldehyde compounds to form a casting solution can be carried out in one step or in stages. For example, the polymer and organic solvent can be mixed first to form a mixture, and then the mixture can be mixed with the aldehyde compound to form a casting solution.

[0092] Understandably, the steps for forming the casting solution specifically include: coating the casting solution onto a substrate to form a wet film; and drying the wet film to form an aldehyde-based compound composite anion exchange membrane. The substrate includes at least one of a glass substrate, a metal substrate, a ceramic substrate, and a polymer substrate; the drying conditions include a drying temperature of 30°C to 80°C.

[0093] In some embodiments, the mass-volume concentration of the amino compound in the acidic solution containing the amino compound is 0.01 mg / mL to 10 mg / mL, and may be selected as 0.1 mg / mL to 1 mg / mL, such as 0.01 mg / mL, 0.05 mg / mL, 0.1 mg / mL, 0.5 mg / mL, 1 mg / mL, 5 mg / mL, 10 mg / mL, etc.

[0094] In some embodiments, the mass-to-volume ratio of the aldehyde compound-composite anion exchange membrane to the amino compound-containing acid solution is 1g:(30~800)mL, for example, 1g:50mL, 1g:60mL, 1g:80mL, 1g:100mL, 1g:200mL, 1g:400mL, 1g:600mL, 1g:800mL, etc.

[0095] In some embodiments, the acid in the amino compound-containing acid solution includes acetic acid.

[0096] In some embodiments, the concentration of the acid in the amino compound-containing acid solution is 1M to 12M, such as 1M, 2M, 4M, 6M, 8M, 12M, etc.

[0097] In some embodiments, the solvent in the acid solution containing the amino compound includes water.

[0098] In some embodiments, the conditions for the aldehyde-amine condensation reaction include: a reaction temperature of 20°C to 55°C, optionally 20°C to 40°C, such as 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, etc.; and a reaction time of 24h to 168h, such as 24h, 36h, 48h, 60h, 72h, 84h, 96h, 120h, 144h, 168h, etc.

[0099] Secondly, this application provides a composite anion exchange membrane prepared by the method described in the first aspect.

[0100] Thirdly, this application provides the application of the composite anion exchange membrane described in the second aspect in hydrogen production by water electrolysis.

[0101] Fourthly, this application provides a method for producing hydrogen by electrolysis of water, comprising the following steps:

[0102] A composite anion exchange membrane is placed between the cathode catalyst layer and the anode catalyst layer to form an anion exchange membrane water electrolyzer.

[0103] Using an aqueous solution as the anode electrolyte, a direct current is applied to carry out the hydrogen production reaction by electrolysis of water.

[0104] The composite anion exchange membrane includes the composite anion exchange membrane described in the second aspect.

[0105] In some embodiments, the aqueous solution includes at least one of pure water, seawater, potassium hydroxide aqueous solution, and sodium hydroxide aqueous solution.

[0106] In some embodiments, the influent rate of the aqueous solution is 0.5 mL / min to 10 mL / min, for example, 0.5 mL / min, 1 mL / min, 2 mL / min, 4 mL / min, 6 mL / min, 8 mL / min, 10 mL / min, etc.

[0107] In some embodiments, the conditions for the water electrolysis hydrogen production reaction include: torque of 2 N·m to 6 N·m, such as 2 N·m, 3 N·m, 4 N·m, 5 N·m, 6 N·m, etc.; and DC voltage of 1.2 V to 2 V, such as 1.2 V, 1.4 V, 1.6 V, 1.8 V, 2 V, etc.

[0108] For experimental parameters not specified in the following specific embodiments, please refer to the guidelines given in this application document first, or refer to experimental manuals or other experimental methods known in the art, or refer to the experimental conditions recommended by the manufacturer.

[0109] Preparation Example 1

[0110] Preparation of ether-free polyaromatic hydrocarbons with piperidine cationic groups (polymer 1): Polymer 1 is PAP-TP-85 from the literature "Poly(aryl piperidinium) membranes and ionomers for hydroxide exchange membrane fuel cells". The specific preparation process is as follows:

[0111] N,N-methyl-4-piperidinone (8.6239 g, 76.21 mmol), 2,2,2-trifluoroacetophenone (2.3419 g, 13.45 mmol), p-terphenyl (20.6487 g, 89.66 mmol), and dichloromethane (75 mL) were added to a 250 mL three-necked flask. Trifluoroacetic acid (6 mL) and trifluoromethanesulfonic acid (75 mL) were then slowly added dropwise at 0 °C, and the reaction was continued at this temperature for 24 h. The resulting reaction product was slowly poured into an aqueous ethanol solution. After the solid precipitated, it was filtered, washed with water, soaked in a 1 M K₂CO₃ aqueous solution for 12 h, filtered and washed again, and dried at 60 °C to obtain the prepolymer.

[0112] The prepolymer (1.0 g) was suspended in dimethyl sulfoxide (20 mL), and iodomethane (1 mL) was quickly added. The mixture was stirred at room temperature for more than 12 h. The reaction product was added dropwise to diethyl ether. After the solid precipitated, it was filtered, washed with water, and dried at 60 °C to obtain polymer 1.

[0113] Example 1

[0114] Preparation of composite anion exchange membranes:

[0115] 1) Preparation of casting solution: Dissolve 2g of polymer 1 in 8g of dimethyl sulfoxide and stir magnetically for 4h to form a mixed solution. Then add 0.02g of trialdehyde phloroglucinol (about 95.2μmol) to the mixed solution and stir thoroughly to form a casting solution.

[0116] 2) Preparation of anion exchange membrane composed of aldehyde compounds: The casting solution was drop-coated onto a glass plate and dried at 40°C for 36 hours on a heating stage to obtain an anion exchange membrane composed of aldehyde compounds (5cm long × 5cm wide × 40μm thick).

[0117] 3) Preparation of the composite anion exchange membrane: The anion exchange membrane composed of aldehyde compounds was soaked in deionized water for 24 hours, and then immersed in 80 mL of an aqueous solution of acetic acid containing an amino compound (the amino compound was 3,8-diamino-5-ethyl-6-phenylphenanthridine bromide, the acetic acid concentration was 3M, the mass-volume concentration of the amino compound was 0.625 mg / mL, and the total amount of the amino compound was 0.05 g, approximately 126.8 μmol). The membrane was soaked at room temperature (25°C) for 72 hours to carry out the aldehyde-amine condensation reaction. After the reaction was completed, the membrane was removed and rinsed three times each with deionized water and ethanol to obtain the composite anion exchange membrane. See the reaction solution after step 3) of Example 1. Figure 2 In Figure A, the appearance of the composite anion exchange membrane prepared in Example 1 is shown in Figure 1. Figure 1 and Figure 2 As shown in B, the reaction solution is uniform, and the prepared composite anion exchange membrane is uniform and intact without obvious defects. This demonstrates that the present application can prepare a complete and uniform composite anion exchange membrane by immersion at room temperature.

[0118] Example 2

[0119] Preparation of composite anion exchange membranes:

[0120] 1) Preparation of casting solution: Dissolve 1g of polymer 1 in 30g of dimethyl sulfoxide and stir magnetically for 2h to form a mixed solution. Then add 0.02g of trialdehyde phloroglucinol (about 95.2μmol) to the mixed solution and stir thoroughly to form a casting solution.

[0121] 2) Preparation of anion exchange membrane composed of aldehyde compounds: The casting solution was drop-coated onto a glass plate and dried at 40°C for 24 hours on a heating stage to obtain an anion exchange membrane composed of aldehyde compounds (5cm long × 5cm wide × 40μm thick).

[0122] 3) Preparation of the composite anion exchange membrane: The anion exchange membrane composed of aldehyde compounds was soaked in deionized water for 12 hours, and then immersed in 80 mL of an aqueous solution of acetic acid containing an amino compound (the amino compound was 3,8-diamino-5-ethyl-6-phenylphenanthridine bromide, the acetic acid concentration was 6 M, the mass-volume concentration of the amino compound was 0.5625 mg / mL, and the total amount of the amino compound was 0.045 g, approximately 114.1 μmol). The membrane was soaked at room temperature (25°C) for 120 hours to carry out the aldehyde-amine condensation reaction. After the reaction was completed, the membrane was removed and rinsed three times each with deionized water and ethanol to obtain the composite anion exchange membrane. The composite anion exchange membrane prepared in Example 2 was uniform and intact, and its appearance was similar to that of Example 1, and will not be shown in detail again.

[0123] Example 3

[0124] Preparation of composite anion exchange membranes:

[0125] 1) Preparation of casting solution: Dissolve 0.1g of polymer 1 in 3.3g of dimethyl sulfoxide and stir magnetically for 1h to form a mixed solution. Then add 0.003g of trialdehyde phloroglucinol (about 14.28μmol) to the mixed solution and stir thoroughly to form a casting solution.

[0126] 2) Preparation of anion exchange membrane composed of aldehyde compounds: The casting solution was drop-coated onto a glass plate and dried at 40°C for 24 hours on a heating stage to obtain an anion exchange membrane composed of aldehyde compounds (5cm long × 5cm wide × 40μm thick).

[0127] 3) Preparation of the composite anion exchange membrane: The anion exchange membrane composed of aldehyde compounds was soaked in deionized water for 12 hours, and then immersed in 80 mL of an aqueous solution of acetic acid containing an amino compound (the amino compound was 3,8-diamino-5-ethyl-6-phenylphenanthridine bromide, the acetic acid concentration was 6 M, the mass-volume concentration of the amino compound was 0.1 mg / mL, and the total amount of the amino compound was 0.008 g, approximately 20.29 μmol). The membrane was soaked at room temperature (25°C) for 168 hours to carry out the aldehyde-amine condensation reaction. After the reaction was completed, the membrane was removed and rinsed three times each with deionized water and ethanol to obtain the composite anion exchange membrane. The composite anion exchange membrane prepared in Example 3 was uniform and intact, and its appearance was similar to that of Example 1, and will not be shown in detail again.

[0128] Comparative Example 1

[0129] Preparation of anion exchange membranes:

[0130] 0.1 g of polymer 1 containing quaternary ammonium groups was dissolved in 3.3 g of dimethyl sulfoxide and stirred thoroughly to form a casting solution. The casting solution was drop-coated onto a glass plate and dried at 40 °C for 24 h on a heating table to obtain an anion exchange membrane (5 cm long × 5 cm wide × 40 μm thick).

[0131] Comparative Example 2

[0132] Preparation of composite anion exchange membranes:

[0133] 1) Preparation of casting solution: 2g of polymer 1 containing quaternary ammonium groups was dissolved in 8g of dimethyl sulfoxide and magnetically stirred for 4h to form a mixed solution. Then, 0.05g of 3,8-diamino-5-ethyl-6-phenylphenanthridine bromide was added to the mixed solution and stirred thoroughly to form a casting solution.

[0134] 2) Preparation of amino compound composite anion exchange membrane: The casting solution was drop-coated onto a glass plate and dried at 40°C for 36 hours on a heating stage to obtain an amino compound composite anion exchange membrane (5cm long × 5cm wide × 40μm thick).

[0135] 3) Preparation of composite anion exchange membrane: The amino compound composite anion exchange membrane was soaked in deionized water for 24 h, and then mixed with 0.02 g of trialdehyde phloroglucinol and 80 mL of 3M acetic acid aqueous solution. The mixture was soaked at room temperature (25℃) for 72 h to carry out aldehyde-amine condensation reaction. After the reaction was completed, the membrane was taken out and rinsed three times each with deionized water and ethanol to obtain the composite anion exchange membrane.

[0136] Comparative Example 3

[0137] Preparation of composite anion exchange membranes:

[0138] 1) Preparation of casting solution: Dissolve 2g of polymer 1 in 8g of dimethyl sulfoxide and stir magnetically for 4h to form casting solution;

[0139] 2) Preparation of anion exchange membrane: The casting solution was drop-coated onto a glass plate and dried at 40°C for 36 hours on a heating stage to obtain an anion exchange membrane (5cm long × 5cm wide × 40μm thick).

[0140] 3) Preparation of the composite anion exchange membrane: The anion exchange membrane was soaked in deionized water for 24 hours, and then immersed in a mixed solution consisting of 80 mL of 3M acetic acid aqueous solution, 0.05 g of amino compound (3,8-diamino-5-ethyl-6-phenylphenanthridine bromide), and 0.02 g of trialdehyde resorcinol. The aldehyde-amine condensation reaction was carried out at room temperature (25℃) for 72 hours. After the reaction was completed, the membrane was removed and rinsed three times each with deionized water and ethanol to obtain the composite anion exchange membrane. See the reaction solution after step 3) of Comparative Example 3. Figure 3 The appearance of the composite anion exchange membrane prepared in Comparative Example 3 (A) is shown in Figure 3. Figure 3 As shown in B, the covalent organic framework prepared through the one-step reaction aggregates in large quantities and settles at the bottom of the reaction solution. At the same time, the surface uniformity of the prepared composite anion exchange membrane is poor.

[0141] Test case

[0142] The membranes prepared in the examples and comparative examples were subjected to performance tests, as detailed below:

[0143] 1. Swelling rate: Prepare 2cm×2cm samples (8 samples per group, and take the average swelling rate). Before testing, vacuum dry the samples at 60℃ for 24h and record the volume V. 浸泡前 The samples were then immersed in pure water at different temperatures and allowed to stand for 24 hours before their volume (V) was measured. 浸泡后 The swelling ratio is calculated using the following formula:

[0144] .

[0145] 2. Water absorption rate: Prepare 2cm×2cm samples (8 samples per group, and take the average water absorption rate). Before testing, vacuum dry the samples at 60℃ for 24h and record the mass m. 浸泡前 The samples were then immersed in pure water at different temperatures and allowed to stand for 24 hours before their mass (m) was measured. 浸泡后 The water absorption rate can be calculated using the following formula:

[0146] .

[0147] 3. OH - Conductivity and Apparent Activation Energy: A 2cm × 2cm sample was prepared and immersed in 100mL of 1M KOH solution at 60℃ for 10 hours for ion exchange. The solution was changed every 2 hours. After rinsing with deionized water, the sample was immersed in 500mL of pure water for 24 hours. Subsequently, the ionic conductivity of the two-electrode thin film was measured. The specific steps are as follows: The sample was clamped between two parallel platinum wires (distance L = 1cm), and the clamp was immersed in pure water. Impedance testing was performed using an electrochemical workstation at an amplitude of 10mV and a frequency of 1Hz-1MHz. The OH group was calculated using the following formula. - Electrical conductivity:

[0148] Where σ is the OH content of the sample. - Electrical conductivity, measured in mS·cm -1 S represents the cross-sectional area parallel to the platinum wire (i.e., the cross-sectional area of ​​the membrane), in cm². 2 The spacing between the parallel platinum wires; R is the resistance of the sample, in kΩ.

[0149] Furthermore, based on the Arrhenius equation, a linear fit is performed on the relationship between 1 / T and ln(σ) to obtain the apparent activation energy at different temperatures. Here, ln(σ) is the natural logarithm of σ, and T is the test temperature in K.

[0150] The swelling ratio and water absorption rate of Example 1 and Comparative Example 1 as a function of temperature are shown in the graphs. Figure 4 As can be seen, Example 1 has a lower water absorption rate and swelling rate compared to Comparative Example 1. The OH groups of Examples 1-3 and Comparative Examples 1-3... - The graph showing the change in conductivity with temperature is shown below. Figure 5 As shown in Table 1, Examples 1-3 exhibit better OH content compared to Comparative Examples 1-3. - Electrical conductivity. The apparent activation energies of Example 1 and Comparative Example 1 at different temperatures are shown in [reference needed]. Figure 6 As can be seen, Example 1 has a higher apparent activation energy than Comparative Example 1.

[0151] Table 1 OH of Examples and Comparative Examples- electrical conductivity

[0152]

[0153] Application examples

[0154] The composite anion exchange membranes prepared in Examples 1-3, Comparative Examples 2-3, and the anion exchange membrane prepared in Comparative Example 1 were used as membrane modules in anion exchange membrane water electrolyzers to produce hydrogen through water electrolysis. The method for producing hydrogen through water electrolysis is as follows:

[0155] A composite anion exchange membrane (or anion exchange membrane) is placed between the cathode catalyst layer and the anode catalyst layer to form an anion exchange membrane water electrolyzer; the torque is set to 4 N·m.

[0156] A 1M potassium hydroxide aqueous solution was pumped into the anode chamber as the anolyte, with the flow rate controlled at 1.5 mL / min. -1 Air is introduced into the cathode chamber; direct current (1.2V~2V) is applied to electrolyze water to produce hydrogen. The polarization curves of Examples 1~3 and Comparative Examples 1~3 are shown below. Figure 7 The polarization curves at different temperatures in Example 1 are shown below. Figure 8 It can be seen that at 80℃ and with the same current density, the voltage of Examples 1 to 3 is significantly lower than that of Comparative Examples 1 to 3. That is, the hydrogen production efficiency of water electrolysis in Examples 1 to 3 is significantly better than that in Comparative Examples 1 to 3. Furthermore, the voltage change is small with increasing temperature, and it has good hydrogen production efficiency over a wide temperature range. Therefore, the composite anion exchange membrane prepared in this application has good structural stability and a wide range of applications.

[0157] In summary, this application demonstrates a simple and rapid method for synthesizing large-area covalently organic framework-doped composite anion exchange membranes. These membranes exhibit both good structural stability and excellent ion conductivity, meeting the requirements for hydrogen production via water electrolysis. Furthermore, comparing Example 1 with Comparative Examples 2-3 shows that a specific reaction sequence is necessary to prepare the target composite anion exchange membrane, achieving both good ion conductivity and efficient hydrogen production via water electrolysis.

[0158] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0159] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of this application.

Claims

1. A method for preparing a composite anion exchange membrane, characterized in that, Includes the following steps: A casting solution is formed by mixing polymers, organic solvents, and aldehyde compounds. The casting solution is molded to prepare an aldehyde-based compound composite anion exchange membrane; The anion exchange membrane composed of the aldehyde compound is immersed in an acid solution containing an amino compound to carry out an aldehyde-amine condensation reaction, thereby forming the composite anion exchange membrane. The polymer and the amino compound contain quaternary ammonium groups.

2. The method for preparing the composite anion exchange membrane as described in claim 1, characterized in that, The method for preparing the composite anion exchange membrane satisfies one or more of the following characteristics: (1) The polymer comprises at least one of the following: ether-free polyaromatic hydrocarbons having piperidine cationic groups, quaternized polysulfones, quaternized polyether ether ketones, quaternized polyphenylene ethers, and quaternized polybenzimidazoles; (2) The aldehyde compound includes a polyaldehyde monomer; (3) The organic solvent includes at least one of dimethyl sulfoxide, N-methylpyrrolidone and tetrahydrofuran; (4) The amino compound includes 3,8-diamino-5-ethyl-6-phenylphenanthridine bromide.

3. The method for preparing the composite anion exchange membrane as described in claim 2, characterized in that, The ether-free polyaromatic hydrocarbon having piperidine cationic groups includes -Ar-, and structural units shown in Formula I and Formula II: Formula I; Formula II; Wherein, -Ar- is an aryl group with 6 to 30 cyclic atoms; with the molar percentage of the structural unit shown in Formula I and the structural unit shown in Formula II being 100%, the molar percentage of the structural unit shown in Formula I is 50% to 90%.

4. The method for preparing the composite anion exchange membrane as described in claim 2, characterized in that, The polyaldehyde monomers include at least one of trialdehyde phloroglucinol, 1,3,5-tricarboxyphenyl, tri(4-carboxyphenyl)amine, 2,4,6-tricarboxymethyltrimethylbenzene, and terephthalaldehyde.

5. The method for preparing the composite anion exchange membrane according to any one of claims 1 to 4, characterized in that, The method for preparing the composite anion exchange membrane satisfies one or more of the following characteristics: (1) The mass ratio of the polymer to the aldehyde compound is 1:(0.01~0.2); (2) The molar ratio of the aldehyde compound to the amino compound is (0.3~1):

1.

6. The method for preparing the composite anion exchange membrane according to any one of claims 1 to 4, characterized in that, The method for preparing the composite anion exchange membrane satisfies one or more of the following characteristics: (1) In the casting solution, the mass concentration of the polymer is 0.01wt%~30wt%; (2) In the acid solution containing the amino compound, the mass-volume concentration of the amino compound is 0.01 mg / mL to 10 mg / mL; (3) The mass-to-volume ratio of the anion exchange membrane composed of the aldehyde compound to the acid solution containing the amino compound is 1 g: (30~800) mL; (4) The acid in the amino-containing acid solution includes acetic acid; (5) In the acid solution containing the amino compound, the concentration of the acid is 1M~12M; (6) The conditions for the aldehyde-amine condensation reaction include: reaction temperature of 20℃~55℃; reaction time of 24h~168h.

7. The composite anion exchange membrane prepared by the method according to any one of claims 1 to 6.

8. The application of the composite anion exchange membrane as described in claim 7 in hydrogen production by water electrolysis.

9. A method for producing hydrogen by electrolysis of water, characterized in that, Includes the following steps: A composite anion exchange membrane is placed between the cathode catalyst layer and the anode catalyst layer to form an anion exchange membrane water electrolyzer. Using an aqueous solution as the anode electrolyte, a direct current is applied to carry out the hydrogen production reaction by electrolysis of water. The composite anion exchange membrane includes the composite anion exchange membrane according to claim 7.

10. The method for producing hydrogen by water electrolysis as described in claim 9, characterized in that, The method for producing hydrogen by water electrolysis satisfies one or more of the following characteristics: (1) The aqueous solution includes at least one of pure water, seawater, potassium hydroxide aqueous solution and sodium hydroxide aqueous solution; (2) The rate at which the aqueous solution is introduced is 0.5 mL / min to 10 mL / min.

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