Preparation method of high-stability and high-conductivity composite anion exchange membrane

Abstract

The invention belongs to the field of functional polymer membrane materials, and discloses a preparation method of a high-stability and high-conductivity composite anion exchange membrane. The composite porous anion exchange membrane is formed by compounding an anion exchange layer and a porous phase inversion layer, the graft modified nano inorganic filler is added into a membrane casting solution to be uniformly mixed, the membrane casting solution is coated on the non-porous anion exchange layer in a blade coating mode, a wet membrane is cured through phase inversion, and the composite porous anion exchange membrane is obtained. Grafting groups can form a continuous hydrogen bond network and a hydration layer, an efficient ion transmission channel is constructed, ion migration activation energy is reduced, the conductivity is remarkably improved, the chemical stability of the film at high temperature is enhanced through the gradient barrier effect, and efficient unification of high conductivity and high chemical stability is achieved. The composite anion exchange membrane with the pore-free / porous structure is high in tensile strength, the conductivity is remarkably improved, the attenuation rate is obviously reduced, the chemical stability is remarkably improved, and the comprehensive performance is excellent.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer membrane materials, specifically relating to a method for preparing a composite anion exchange membrane with high stability and high conductivity. Background Technology

[0002] Anion exchange membranes (AEMs), as a class of functional polymer membrane materials capable of selectively transporting anions, have a core structure composed of a polymer backbone and cationic functional groups. The backbone provides mechanical support and thermal stability, while the functional groups endow ion conduction capabilities, playing a crucial role in energy conversion, water treatment, and chemical separation. Current mainstream technologies are based on polymer backbones such as polyarylethers, polysulfones, and polybenzimidazoles, which introduce cationic groups (such as quaternary ammonium salts and piperidinium salts) through modifications such as quaternization and imidazole ondenylation, forming nanoscale channels capable of conducting anions such as OH⁻ and Cl⁻.

[0003] Despite the significant market demand and potential for quaternary ammonium salts (AEMs), their technological development still faces numerous challenging problems. For example, currently available AEMs generally suffer from the core issue of balancing ion exchange efficiency and chemical stability. While traditional quaternary ammonium salt groups are easy to synthesize and have high ion exchange capacities (1.5-3.5 meq / g), they are prone to degradation reactions such as Hoffmann elimination and nucleophilic substitution in high-temperature alkaline environments, leading to a rapid decline in conductivity. Even with novel cyclic ammonium groups such as piperidinium salts, their stability is significantly affected by the main chain structure. Increased main chain rigidity can raise the cation degradation rate from 3% to 13%, and the loss rate can even reach as high as 40% in a 5M strongly alkaline environment.

[0004] To address the stability issue, researchers have discovered that adding alkali-resistant metal oxides and alkali-resistant metal hydroxides to anion exchange membranes can improve their stability and has become a common practice. From a theoretical perspective, utilizing the alkali-resistant chemical structure and stability of nano-inorganic fillers can effectively enhance the heat resistance of membrane materials under high-temperature environments, thereby reducing degradation reactions such as "Hoffmann elimination" and "nucleophilic substitution," and ultimately improving their chemical stability.

[0005] While traditional processes involving the addition of alkali-resistant nano-inorganic fillers can reduce degradation reactions and improve chemical stability, they often suffer from van der Waals forces between inorganic powders. These forces lead to uneven dispersion, poor compatibility, and easy agglomeration, resulting in blocked ion channels, longer ion conduction paths, and reduced continuity. Consequently, the ion conduction rate decreases significantly, making it difficult to simultaneously achieve both high ion conduction efficiency and chemical stability. Summary of the Invention

[0006] The purpose of this invention is to overcome at least one deficiency of the prior art and provide a method for preparing a composite anion exchange membrane with high stability and high conductivity.

[0007] The technical solution adopted in this invention is: The first aspect of the present invention provides: A method for preparing a composite porous anion exchange membrane, wherein the composite porous anion exchange membrane is composed of a non-porous anion exchange layer and a porous phase-inversion layer, comprising the following steps: The surface of the nano-inorganic filler was modified by grafting an agent containing quaternary ammonium groups to obtain grafted nano-inorganic fillers. An organic polymer is dissolved in an organic solvent, and the mixture is heated and stirred until it is completely dissolved to obtain a reverse casting film solution; The grafted nano-inorganic filler was added to the reverse casting film solution and mixed thoroughly to obtain a mixed reverse casting film solution; The mixed phase-conversion casting solution is coated onto the surface of a non-porous anion exchange layer to form a phase-conversion wet film. Then, the phase-conversion wet film is cured using a phase-inversion method to obtain a composite porous anion exchange membrane.

[0008] In some instances, the nano-inorganic filler is selected from at least one of nano-zirconia, nano-silica, nano-layered bimetallic hydroxide, nano-cerium oxide, nano-alumina, nano-magnesium oxide, and nano-titanium oxide.

[0009] In some instances, the organic polymer in the reverse casting solution is selected from at least one of polysulfones, polyethersulfones, polyetheretherketones, polyvinyl chlorides, polyaryletherketones, poly(biphenylalkyl) compounds, poly(aryl-piperidine) compounds, and styrene compounds.

[0010] In some instances, the organic solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, and N-methyl-2-pyrrolidone.

[0011] In some instances, the organic polymer in the reverse casting solution is selected from at least one of polysulfones, polyethersulfones, polyetheretherketones, polyvinyl chlorides, polyaryletherketones, poly(biphenylalkyl) compounds, poly(aryl-piperidine) compounds, and styrene compounds, and the organic solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, and N-methyl-2-pyrrolidone.

[0012] In some instances, the quaternary ammonium-containing grafting agent is selected from at least one of N-(3-trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride, 3-triethoxysilylpropyldimethyloctadecylammonium chloride, bisquaternary ammonium silane, and 3-chloro-2-hydroxypropyltrimethylammonium chloride-modified silane.

[0013] In some instances, the grafting modification method includes: The nano-inorganic filler is pretreated and dried to obtain activated nano-inorganic filler; Dissolve the grafting agent in ethanol, add deionized water dropwise, adjust the pH to 5-6, and disperse thoroughly to obtain the grafting agent solution; The activated nano-inorganic filler is added to the grafting agent solution and mixed thoroughly to react. Preferably, the grafting agent is added in excess. After the reaction is complete, the unreacted grafting agent is removed by washing, and the grafted nano-inorganic filler is obtained by drying.

[0014] In some instances, the mass ratio of grafted nano-inorganic filler to organic polymer in the mixed reverse casting solution is (1-6):(1-30); or The content of organic polymer in the mixed reverse casting solution is 5-30 wt.%, and the content of grafted nano-inorganic filler is 1-30 wt.%.

[0015] In some examples, the thickness of the non-porous anion exchange layer is 30–200 μm, the thickness of the porous phase-inversion layer is 5–50 μm, and the thickness of the composite anion exchange membrane is 35–250 μm.

[0016] In some instances, the method for preparing the non-porous anion exchange layer includes: Dissolve the organic polymer in an organic solvent, heat and stir until completely dissolved to obtain a casting solution; Anion exchange layer was prepared by coating the casting solution using a blade coating method.

[0017] In some instances, the organic polymer in the casting solution is selected from at least one of poly(aryl-piperidine), poly(aryl-alkylene), poly(biphenylalkyl), styrene, and polytetrafluoroethylene.

[0018] In some examples, the organic polymer in the casting solution is selected from at least one of poly(aryl-piperidine), poly(aryl-alkylene), poly(biphenylalkyl), styrene, and polytetrafluoroethylene, and the organic solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, and N-methyl-2-pyrrolidone.

[0019] These features can be combined arbitrarily as long as they do not conflict with each other.

[0020] A second aspect of the present invention provides: A composite anion exchange membrane is prepared according to the preparation method described in the first aspect of the present invention.

[0021] The beneficial effects of this invention are: The preparation methods of some examples of this invention employ a phase inversion process to construct the protective layer of the anion exchange membrane, combined with chemical modification of the surface of the nano-inorganic filler by grafting quaternary ammonium groups. This achieves a highly efficient balance between high conductivity and high chemical stability in the anion exchange membrane. Phase inversion is a method that can efficiently form a microporous structure. The phase inversion layer can be formed by liquid-induced phase inversion, resulting in a dense and porous structure that can improve OH- ion exchange membrane performance. - Transmission efficiency; its three-dimensional porous network can also form a physical barrier, providing a certain degree of mechanical support; the nano-inorganic oxides it uses can effectively block external OH... - Cl - The direct erosion of the base film by corrosive anions reduces the degradation of ion exchange groups (such as quaternary ammonium groups) in the base film at high temperatures, thereby achieving high chemical stability of the film. Quaternary ammonium groups, as OH groups... - The number of transport groups affects the OH groups of ion-exchange polymers. - Transport efficiency. Therefore, quaternary ammonium groups are chemically modified onto the surface of the inorganic nanofiller. Leveraging the high specific surface area of ​​the inorganic nanofiller and anchoring these groups via chemical bonds, the density of effective ion exchange sites within the membrane is significantly increased, enhancing the adsorption and transport capacity of anions and forming a high-density three-dimensional ion transport network, providing a dedicated transport pathway for OH⁻ migration. Simultaneously, due to the anchoring effect of the chemical bonds between the inorganic nanofiller and the quaternary ammonium groups, the loss of ion groups is greatly reduced, extending the effective service life of the ion channel.

[0022] In some examples of the preparation methods of this invention, the grafted quaternary ammonium groups can form a continuous hydrogen bond network and hydration layer, constructing a highly efficient ion transport channel, reducing the ion migration activation energy, and achieving a significant improvement in conductivity. Simultaneously, because inorganic powder materials form a solid-liquid two-phase structure in the polymer solution, the different interfacial tensions and intermolecular forces can lead to uneven dispersion of inorganic particles in the polymer solution, making them prone to aggregation during film formation. Therefore, grafting quaternary ammonium groups can improve their nucleophilicity to the solution, inhibit excessive aggregation of the nano-inorganic filler, improve the interfacial compatibility between the nano-inorganic filler and the polymer matrix, and avoid the "physical blockage" of ion channels caused by the formation of nano-inorganic filler agglomerates, thereby ensuring the continuity and integrity of the channels and ultimately achieving high membrane conductivity.

[0023] The composite anion exchange membranes of some examples of the present invention employ a phase inversion process to construct a protective layer and combine it with nano-inorganic fillers grafted with quaternary ammonium groups. This can enhance its chemical stability at high temperatures through the gradient barrier effect. At the same time, by increasing ion conduction sites and improving compatibility, a highly efficient balance between high conductivity and high chemical stability is achieved. Attached Figure Description

[0024] Figure 1 The following is a schematic diagram of the structure of the high-performance phase-inversion composite anion exchange membrane of the present invention: 1-Porous phase-inversion layer doped with grafted inorganic filler; 2-Anion exchange layer.

[0025] Figure 2 The surface SEM image of the high-performance phase-inversion composite anion exchange membrane prepared in Example 4 is shown.

[0026] Figure 3 The surface SEM image of the phase-inverting composite anion exchange membrane prepared for Comparative Example 4 is shown.

[0027] Depend on Figure 2 and Figure 3 The comparison shows that the quaternized nano-inorganic filler is uniformly dispersed in the polymer, with no obvious agglomeration, and its compatibility and hydrophilicity with the polymer are significantly improved.

[0028] Figure 4 The results are from the performance test of the voltage decay rate of the electrolytic cell. Detailed Implementation

[0029] A method for preparing a composite porous anion exchange membrane, wherein the composite porous anion exchange membrane is composed of a non-porous anion exchange layer and a porous phase-inversion layer, comprising the following steps: The surface of the nano-inorganic filler was modified by grafting an agent containing quaternary ammonium groups to obtain grafted nano-inorganic fillers. An organic polymer is dissolved in an organic solvent, and the mixture is heated and stirred until it is completely dissolved to obtain a reverse casting film solution; The grafted nano-inorganic filler was added to the reverse casting film solution and mixed thoroughly to obtain a mixed reverse casting film solution; The mixed phase-conversion casting solution is coated onto the surface of a non-porous anion exchange layer to form a phase-conversion wet film. Then, the phase-conversion wet film is cured using a phase-inversion method to obtain a composite porous anion exchange membrane.

[0030] There are no special requirements for the nano-inorganic filler; it only needs to be alkali-resistant and not affect the reaction of other components in the AEM. In some examples, the nano-inorganic filler is selected from at least one of nano-zirconia, nano-silica, nano-layered bimetallic hydroxide (LDH, hydrotalcite), nano-cerium oxide, nano-alumina, nano-magnesium oxide, and nano-titanium oxide.

[0031] In some instances, the organic polymer in the reverse casting solution is selected from at least one of polysulfones, polyethersulfones, polyetheretherketones, polyvinyl chlorides, polyaryletherketones, poly(biphenylalkyl) compounds, poly(aryl-piperidine) compounds, and styrene compounds.

[0032] In some instances, the organic solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, and N-methyl-2-pyrrolidone.

[0033] There are no special requirements for the organic polymer in the reverse casting solution, as long as it meets the requirements for AEM applications. In some examples, the organic polymer in the reverse casting solution is selected from at least one of polysulfones, polyethersulfones, polyetheretherketones, polyvinyl chlorides, polyaryletherketones, poly(biphenylalkyl) compounds, poly(aryl-piperidine) compounds, and styrene compounds, and the organic solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, and N-methyl-2-pyrrolidone.

[0034] In some instances, the organic solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, and N-methyl-2-pyrrolidone.

[0035] In some instances, the quaternary ammonium-containing grafting agent is selected from at least one of N-(3-trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride, 3-triethoxysilylpropyldimethyloctadecylammonium chloride, bisquaternary ammonium silane, and 3-chloro-2-hydroxypropyltrimethylammonium chloride-modified silane.

[0036] In some instances, the grafting modification method includes: The nano-inorganic filler is pretreated and dried to obtain activated nano-inorganic filler; Dissolve the grafting agent in ethanol, add deionized water dropwise, adjust the pH to 5-6, and disperse thoroughly to obtain the grafting agent solution; The activated nano-inorganic filler was added to the grafting agent solution and mixed thoroughly to react. After the reaction is complete, the unreacted grafting agent is removed by washing, and the grafted nano-inorganic filler is obtained by drying.

[0037] In some cases, the grafting agent is added in excess during grafting modification. This allows for more thorough modification of the nano-inorganic filler. Excess grafting agent can be easily removed by washing.

[0038] When cleaning nano-inorganic fillers, acid washing or salt washing can be used depending on the type of inorganic filler used to hydroxylate the surface of the inorganic filler, thereby activating the nano-inorganic filler and facilitating subsequent grafting reactions.

[0039] In some instances, the mass ratio of grafted nano-inorganic filler to organic polymer in the mixed reverse casting solution is (1-6):(1-30); or The content of organic polymer in the mixed reverse casting solution is 5-30 wt.%, and the content of grafted nano-inorganic filler is 1-30 wt.%.

[0040] In some examples, the thickness of the non-porous anion exchange layer is 30–200 μm, the thickness of the porous phase-inversion layer is 5–50 μm, and the thickness of the composite anion exchange membrane is 35–250 μm.

[0041] In some instances, the method for preparing the non-porous anion exchange layer includes: Dissolve the organic polymer in an organic solvent, heat and stir until completely dissolved to obtain a casting solution; Anion exchange layer was prepared by coating the casting solution using a blade coating method.

[0042] There are no special requirements for the organic polymer used in the preparation of the anion exchange layer. It can be a common organic polymer used in AEM. In some examples, the organic polymer in the casting solution is selected from at least one of poly(aryl-piperidine), poly(aryl-alkylene), poly(biphenylalkyl), styrene, and polytetrafluoroethylene.

[0043] In some examples, the organic polymer in the casting solution is selected from at least one of poly(aryl-piperidine), poly(aryl-alkylene), poly(biphenylalkyl), styrene, and polytetrafluoroethylene, and the organic solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, and N-methyl-2-pyrrolidone.

[0044] These features can be combined arbitrarily as long as they do not conflict with each other.

[0045] The technical solution of the present invention will be further illustrated below with examples. Example 1

[0046] 1) Add 3g of nano-zirconia to a 5% hydrochloric acid solution and stir continuously for 1 hour. Then wash with deionized water until neutral, centrifuge and vacuum dry to obtain pretreated nano-zirconia. 2) Dissolve 1.5g of N-(3-trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride in 200mL of ethanol, slowly add 20mL of deionized water, stir for 10min, adjust the pH of the solution to 5-6 with a small amount of acetic acid, and continue stirring for 30min. 3) Add the pretreated nano-zirconia powder to the above-mentioned N-(3-trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride solution, ultrasonically disperse for 10-15 minutes, stir at 80°C for 4-6 hours, centrifuge and wash with ethanol more than 3 times to remove unreacted grafting agent; vacuum dry at 60°C for at least 12 hours to obtain grafted nano-zirconia; 4) Dissolve poly(aryl-piperidine) polymer in N,N-dimethylformamide, heat and stir until completely dissolved to obtain a casting solution with 20wt% solid content; add 3wt% grafted nano-zirconia, heat and stir for 4-8 hours, then coat a 650μm anion exchange wet membrane on a clean glass plate and dry it to obtain a non-porous anion exchange membrane with high conductivity. Example 2

[0047] 1) Add 3g of nano-layered bimetallic hydroxide (LDH) to a 12% NaNO3 solution and stir continuously for 1h. Then wash with deionized water until neutral, centrifuge and vacuum dry to obtain pretreated nano-layered bimetallic hydroxide. 2) Dissolve 1.5g of N-(3-trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride in 200mL of ethanol, slowly add 20mL of deionized water, stir for 10min, and then adjust the pH of the solution to 5-6 with a small amount of acetic acid. 3) The pretreated nano-layered bimetallic hydroxide powder was added to the above-mentioned N-(3-trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride solution, ultrasonically dispersed for 10-15 minutes, stirred at 80°C for 4-6 hours, centrifuged and washed with ethanol more than 3 times to remove unreacted grafting agent; vacuum dried at 60°C for at least 12 hours to obtain grafted nano-layered bimetallic hydroxide; 4) Dissolve poly(aryl-piperidine) polymer in N,N-dimethylformamide, heat and stir until completely dissolved to obtain a casting solution with 20wt% solid content; add 3wt% grafted nanolayered bimetallic hydroxide, heat and stir for 4-8 hours, then coat a 650μm anion exchange wet membrane on a clean glass plate and dry it to obtain a non-porous anion exchange membrane with high conductivity. Example 3

[0048] 1) Add 3g of nano-layered bimetallic hydroxide to a 12% NaNO3 solution and stir continuously for 1 hour. Then wash with deionized water until neutral, centrifuge and vacuum dry to obtain the pretreated nano-layered bimetallic hydroxide. 2) Dissolve 1.5g of N-(3-trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride in 200mL of ethanol, slowly add 20mL of deionized water, stir for 10min, and then adjust the pH of the solution to 5-6 with a small amount of acetic acid. 3) The pretreated nano-layered bimetallic hydroxide powder was added to the above-mentioned N-(3-trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride solution, ultrasonically dispersed for 10-15 minutes, stirred at 80°C for 4-6 hours, centrifuged and washed with ethanol more than 3 times to remove unreacted grafting agent; vacuum dried at 60°C for at least 12 hours to obtain grafted nano-layered bimetallic hydroxide; 4) Dissolve poly(aryl-piperidine) polymer in N,N-dimethylformamide, heat and stir until completely dissolved to obtain a casting solution with a solid content of 20wt%; coat a 200μm anion exchange wet membrane on a clean glass plate and dry it to obtain a common anion exchange membrane; 5) Dissolve polysulfone polymer in N-methyl-2-pyrrolidone, heat and stir until completely dissolved to obtain a 10wt% solid phase inversion casting solution; add 20wt% grafted nanolayered bimetallic hydroxide, heat and stir for 4-8h, then coat an 80μm phase inversion wet membrane onto the above anion exchange membrane and convert it into a membrane by immersion in sodium hydroxide solution to obtain a high-performance phase inversion composite anion exchange membrane. Example 4

[0049] 1) Add 3g of nano-zirconia to a 5% hydrochloric acid solution and stir continuously for 1 hour. Then wash with deionized water until neutral, centrifuge and vacuum dry to obtain pretreated nano-zirconia. 2) Dissolve 1.5g of N-(3-trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride in 200mL of ethanol, slowly add 20mL of deionized water, stir for 10min, and then adjust the pH of the solution to 5-6 with a small amount of acetic acid. 3) Add the pretreated nano-zirconia powder to the above-mentioned N-(3-trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride solution, ultrasonically disperse for 10-15 minutes, stir at 80°C for 4-6 hours, centrifuge and wash with ethanol more than 3 times to remove unreacted grafting agent; vacuum dry at 60°C for at least 12 hours to obtain grafted nano-zirconia; 4) Dissolve poly(aryl-piperidine) polymer in N,N-dimethylformamide, heat and stir until completely dissolved to obtain a casting solution with a solid content of 20wt%; coat a 200μm anion exchange wet membrane on a clean glass plate and dry it to obtain a common non-porous anion exchange membrane; 5) Dissolve polysulfone polymer in N-methyl-2-pyrrolidone, heat and stir until completely dissolved to obtain a 10wt% solid phase inversion casting solution; add 20wt% grafted nano-zirconia, heat and stir for 4-8h, then coat an 80μm phase inversion wet membrane onto the above anion exchange membrane and immerse it in sodium hydroxide solution to convert it into a membrane, thus obtaining a high-performance phase inversion composite anion exchange membrane. Comparative Example 1

[0050] 1) Dissolve poly(aryl-piperidine) polymer in N,N-dimethylformamide, heat and stir until completely dissolved to obtain a casting solution with a solid content of 20wt%. Add nano-zirconia at 3wt%, heat and stir for 4-8 hours, then coat a 650μm anion exchange wet membrane onto a clean glass plate and dry it to obtain a non-porous anion exchange membrane. Comparative Example 2

[0051] 1) Dissolve poly(aryl-piperidine) polymer in N,N-dimethylformamide, heat and stir until completely dissolved to obtain a casting solution with a solid content of 20wt%. Add 3wt% nanolayered bimetallic hydroxide, heat and stir for 4-8 hours, then coat a 650μm anion exchange wet membrane onto a clean glass plate and dry it to obtain a non-porous anion exchange membrane. Comparative Example 3

[0052] 1) Dissolve poly(aryl-piperidine) polymer in N,N-dimethylformamide, heat and stir until completely dissolved to obtain a casting solution with a solid content of 20 wt%. Coat a 200 μm anion exchange wet membrane onto a clean glass plate and dry to obtain a common non-porous anion exchange membrane; 2) Dissolve polysulfone polymer in N-methyl-2-pyrrolidone, heat and stir until completely dissolved to obtain a phase inversion casting solution with a solid content of 10 wt%. Add 20 wt% nanolayered bimetallic hydroxide, heat and stir for 4-8 h, then coat an 80 μm phase inversion wet membrane onto the above anion exchange membrane and immerse it in sodium hydroxide solution to convert it into a membrane, thus obtaining a phase inversion composite anion exchange membrane. Comparative Example 4

[0053] 1) Dissolve poly(aryl-piperidine) polymer in N,N-dimethylformamide, heat and stir until completely dissolved to obtain a casting solution with a solid content of 20 wt%. Coat a 200 μm anion exchange wet membrane onto a clean glass plate and dry to obtain a conventional anion exchange membrane; 2) Dissolve polysulfone polymer in N-methyl-2-pyrrolidone, heat and stir until completely dissolved to obtain a phase inversion casting solution with 10wt% solid content; add nano-zirconia at 20wt%, heat and stir for 4-8 hours, then coat an 80μm phase inversion wet membrane onto the above anion exchange membrane and immerse it in sodium hydroxide solution to convert it into a membrane, thus obtaining a phase inversion composite anion exchange membrane. Performance testing

[0054] Figure 1 The following is a schematic diagram of the composite anion exchange membrane based on the high-performance phase-inversion non-porous / porous structure of the present invention: 1-Porous phase-inversion layer doped with grafted inorganic filler; 2-Anion exchange layer.

[0055] Figure 2 The surface SEM image of the high-performance phase-inversion composite anion exchange membrane prepared in Example 4 is shown. Figure 3 The surface SEM image of the phase-inversion composite anion exchange membrane prepared for Comparative Example 4 is shown. Figure 2 and Figure 3 The comparison shows that the quaternized nano-inorganic filler is uniformly dispersed in the polymer, with no obvious agglomeration, and its compatibility and hydrophilicity with the polymer are significantly improved.

[0056] The anion exchange membranes prepared in each embodiment and comparative example were tested for permeability conductivity, tensile strength, and operating electrolyzer voltage decay rate. The test methods and results are as follows: (1) Through conductivity and tensile strength test: Tested according to (T / CRES 0028—2025). The test results are shown in Table 1.

[0057] Table 1. Permeability and tensile strength of anion exchange membranes in different examples Test Project Through conductivity / mS / cm Tensile strength / MPa Example 1 5.25 43.36 Example 2 5.68 40.88 Example 3 4.41 37.96 Example 4 4.74 38.95 Comparative Example 1 3.08 38.67 Comparative Example 2 3.27 37.91 Comparative Example 3 2.24 34.12 Comparative Example 4 2.57 29.3 (2) Testing the voltage decay rate of the operating electrolytic cell: Anode catalyst layer preparation: 0.67 g of polyaryl resin was dissolved in 15.2 g of methanol and stirred at room temperature until the solid dissolved. Then, 45.6 g of n-propanol and 15.2 g of deionized water were added sequentially, and stirring was continued for one hour. After filtration of the ionomer solution, 3.3 g of nickel ferrite (NiFe2O4) particles were added, stirred, and sonicated for one hour to obtain the catalyst slurry. Nickel ferrite was sprayed onto the anion exchange membrane phase inversion layer using a flatbed spraying device, with the loading controlled at 1 mg / cm³. 2 After being kept at 60℃ on a hot plate for 20 minutes, it was transferred to an oven and dried at 50℃ for 3 hours to obtain a single-sided CCM containing an anode catalyst layer.

[0058] Cathode catalyst layer preparation: The steps are the same as those for the anode catalyst layer preparation. Platinum-carbon is selected as the cathode catalyst to prepare the cathode catalyst slurry, which is then sprayed onto the other side of the anion exchange membrane with an effective loading of 0.5 mg / cm³. 2 This forms the final CCM structure.

[0059] The membranes prepared in the above examples and comparative examples were selected as the core material. A single-anode electrolyte feeding method was adopted, and nickel sintered felt was used as the anode and cathode gas diffusion layer. The effective area of ​​the MEA was 25 cm². 2 1 mol / L KOH was used as the electrolyte, the alkaline solution temperature was 40-80 °C, and the flow rate was 125 mL / min. The stability of the relevant membrane electrodes was tested using a self-developed AEM testing platform. The stability test involved applying a constant current density (1 A / cm²) to the membrane electrodes. 2 ), observe the overall voltage change trend of the membrane electrode over 1000 hours, and use η=(V BOT -V EOT ) / 1000×10 6 The test results obtained by calculating using the formula are shown in Table 2 and Figure 4 As shown. In the formula: η——1A / cm 2 The rate of voltage decay per hour at current density, expressed in microvolts per hour (μV / h). V BOT —At the beginning of the stability test, 1A / cm 2 Voltage at current density, measured in volts (V). V EOT —At the end of the 1000h stability test, 1A / cm 2 Voltage at current density, measured in volts (V).

[0060] Table 2. Voltage decay rate of operating electrolyzers in different examples Test Project Example 3 Example 4 Comparative Example 1 Comparative Example 2 1000h decay rate μV / h 24 28 98 89 As shown in Table 1, Examples 1-2 and Comparative Examples 1-2, as well as Examples 3-4 and Comparative Examples 3-4, demonstrate that the electrical conductivity of nano-inorganic fillers with grafted quaternary amine groups is significantly improved without reducing their tensile strength and chemical stability.

[0061] As can be seen from Examples 3-4 and Comparative Examples 1-2 in Table 2, after constructing the phase inversion protective layer, the decay rate is significantly reduced and the chemical stability is significantly improved.

[0062] As can be seen from Tables 1 and 2, in Example 4 and Comparative Example 1, after the nano-inorganic filler with a protective layer and grafted quaternary amine groups is incorporated, its electrical conductivity is significantly improved, its decay rate is significantly reduced, its chemical stability is significantly improved, and its overall performance is effectively enhanced without reducing its tensile strength.

[0063] The above is a further detailed description of the present invention and should not be considered as a limitation on the specific implementation of the present invention. For those skilled in the art, simple deductions or substitutions without departing from the concept of the present invention are all within the protection scope of the present invention.

Claims

1. A method for preparing a composite porous anion exchange membrane, characterized in that, The composite porous anion exchange membrane is composed of a non-porous anion exchange layer and a porous phase inversion layer, and includes the following steps: The surface of the nano-inorganic filler was modified by grafting an agent containing quaternary ammonium groups to obtain grafted nano-inorganic fillers. An organic polymer is dissolved in an organic solvent, and the mixture is heated and stirred until it is completely dissolved to obtain a reverse casting film solution; The grafted nano-inorganic filler was added to the reverse casting film solution and mixed thoroughly to obtain a mixed reverse casting film solution; The mixed phase-conversion casting solution is coated onto the surface of a non-porous anion exchange layer to form a phase-conversion wet film. Then, the phase-conversion wet film is cured using a phase-inversion method to obtain a composite porous anion exchange membrane.

2. The preparation method according to claim 1, characterized in that, The nano-inorganic filler is selected from at least one of nano-zirconia, nano-silica, nano-layered bimetallic hydroxide, nano-cerium oxide, nano-alumina, nano-magnesium oxide, and nano-titanium oxide.

3. The preparation method according to claim 1, characterized in that, The organic polymer in the reverse casting solution is selected from at least one of polysulfone, polyethersulfone, polyetheretherketone, polyvinyl chloride, polyaryletherketone, poly(biphenylalkyl), poly(aryl-piperidine), and styrene.

4. The preparation method according to claim 1, characterized in that, The organic solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, and N-methyl-2-pyrrolidone.

5. The preparation method according to claim 1, characterized in that, The grafting agent containing the quaternary ammonium group is selected from at least one of N-(3-trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride, 3-triethoxysilylpropyldimethyloctadecylammonium chloride, bisquaternary ammonium silane, and 3-chloro-2-hydroxypropyltrimethylammonium chloride modified silane.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The grafting modification method includes: The nano-inorganic filler is pretreated and dried to obtain activated nano-inorganic filler; Dissolve the grafting agent in ethanol, add deionized water dropwise, adjust the pH to 5-6, and disperse thoroughly to obtain the grafting agent solution; The activated nano-inorganic filler is added to the grafting agent solution and mixed thoroughly to react. Preferably, the grafting agent is added in excess. After the reaction is complete, the unreacted grafting agent is removed by washing, and the grafted nano-inorganic filler is obtained by drying.

7. The preparation method according to any one of claims 1 to 5, characterized in that, In the mixed reverse casting solution, the mass ratio of grafted nano-inorganic filler to organic polymer is (1-6):(1-30); or The content of organic polymer in the mixed reverse casting solution is 5-30 wt.%, and the content of grafted nano-inorganic filler is 1-30 wt.%.

8. The preparation method according to any one of claims 1 to 5, characterized in that, The thickness of the non-porous anion exchange layer is 30–200 μm, the thickness of the porous phase inversion layer is 5–50 μm, and the thickness of the composite anion exchange membrane is 35–250 μm.

9. The preparation method according to claim 1, characterized in that, The method for preparing the non-porous anion exchange layer includes: Dissolve the organic polymer in an organic solvent, heat and stir until completely dissolved to obtain a casting solution; A non-porous anion exchange layer was prepared by using a blade coating method to prepare the casting solution.

10. A composite anion exchange membrane, characterized in that, It is prepared according to the preparation method according to any one of claims 1 to 9.

Images