A proton exchange membrane and its preparation method

Abstract

This application provides a proton exchange membrane and a method for preparing the same. The proton exchange membrane comprises the following raw materials, in parts by weight: 100 parts sulfonated polyetheretherketone (SPEEK) and 1 to 10 parts modified MOFs (metal-organic frameworks) material; the modified MOFs material comprises a MOFs material grafted with a block polymer, the block polymer comprising a polyvinyl imidazole (PEI) segment and a hydrophobic segment, with the PIEI segment positioned on the side proximal to the MOFs material. The proton exchange membrane, using SPEEK as the primary material and optimized using the modified MOFs material, exhibits high proton conductivity and low swelling ratio, and can be used to improve the overall performance of fuel cells.

Description

Technical Field

[0001] The present application relates to the field of fuel cell technology, and in particular to a proton exchange membrane and a preparation method thereof. Background Art

[0002] With the development of clean energy technologies such as fuel cells, hydrogen energy, and hydrogen production from water electrolysis, the performance of proton exchange membranes (PEMs), core fuel cell components, directly determines their overall efficiency and service life. Currently, the most widely used PEMs on the market are primarily perfluorosulfonic acid resins (such as Nafion), which offer high proton conductivity and excellent chemical stability. However, the high cost of perfluorosulfonic acid resins, due to their complex synthesis process and expensive raw materials, has been a major obstacle to the commercialization of fuel cells.

[0003] To reduce costs, non-fluorinated polymers, such as sulfonated polyetheretherketone (SPEEK), have attracted widespread attention in recent years due to their low-cost raw materials and simple synthesis process. As a low-cost proton exchange membrane material, SPEEK achieves high proton conductivity in a hydrated state, but it also presents some challenges. For example, the relatively random distribution of sulfonic acid groups in SPEEK makes it difficult to form continuous, optimized proton conduction channels similar to perfluorosulfonic acid resins. The resulting microphase separation structure is also discontinuous, resulting in decreased conductivity under low humidity or high temperature conditions. Furthermore, while increasing the degree of sulfonation can improve proton conductivity, it can also cause the membrane to absorb excessive water, resulting in excessive swelling, which can lead to decreased mechanical properties and dimensional instability.

[0004] In order to overcome the above problems and improve the comprehensive performance of SPEEK proton exchange membrane while maintaining the low-cost advantage, researchers have tried to adopt strategies such as functionalized nanofillers in recent years to improve the proton conduction performance and control the swelling rate by optimizing the microphase separation structure of the membrane.

[0005] For example, Patent 119447391A discloses a proton exchange membrane. The preparation method of the proton exchange membrane includes the following steps: dissolving sulfonated polyetheretherketone in dimethyl sulfoxide to prepare a sulfonated polyetheretherketone solution, adding amino acid-modified cellulose nanocrystalline powder to obtain a uniform and stable solution, and filtering to obtain a casting solution; thoroughly mixing the modified cellulose nanocrystalline powder and sulfonated polyetheretherketone at a mass ratio of 0.03 to 0.12:1, and obtaining a sulfonated polyetheretherketone / modified cellulose composite proton exchange membrane by a casting method. The patent discloses that the proton exchange membrane has high proton transfer efficiency and overcomes the shortcomings of sulfonated non-fluorocarbon polymers with high sulfonation rates, such as high swelling rates and poor stability.

[0006] However, the problem with the above patent is that the amino acid-modified cellulose nanocrystals are highly hydrophilic and are mainly distributed in the hydrophilic phase of SPEEK. They have limited effect in increasing the proton conduction rate and improving the proton conductivity under the original proton conduction channel. In addition, the amino acid-modified cellulose nanocrystals do not contain a hydrophobic phase, and their effect on reducing swelling is also limited.

[0007] Therefore, it is necessary to provide a proton exchange membrane with high proton conductivity and low swelling rate. Summary of the Invention

[0008] The present application provides a proton exchange membrane and a preparation method thereof. The proton exchange membrane uses SPEEK as the main material and is optimized using modified MOFs material. It has high proton conductivity and low swelling rate, and can be used to improve the overall performance of fuel cells.

[0009] In the first aspect, the present application provides a proton exchange membrane comprising the following raw materials in parts by mass: 100 parts of sulfonated polyetheretherketone and 1 to 10 parts of modified MOFs material; the modified MOFs material comprises a MOFs material grafted with a block polymer, the block polymer comprises a polyvinyl imidazole segment and a hydrophobic segment, and the polyvinyl imidazole segment is arranged on one side close to the MOFs material.

[0010] According to the present application, the proton exchange membrane uses sulfonated polyetheretherketone as the main material. By adding MOFs materials grafted with block polymers, an ordered microphase separation structure can be induced at the interface to promote the formation of continuous proton conduction channels. At the same time, the polyvinyl imidazole segment can form hydrogen bonds and ion pairs with the sulfonic acid groups on SPEEK, which helps to build a stable hydration network. The MOFs material at one end of the polyvinyl imidazole segment can efficiently conduct protons in the membrane through the Grotthuss mechanism, so that the proton exchange membrane has a higher proton conductivity. At the same time, in addition to reducing the swelling rate of SPEEK by inducing the formation of an ordered phase separation structure, the modified MOFs material can also provide additional mechanical support for the membrane with the rigid skeleton and hydrophobic segments on the surface. The interaction between the polyvinyl imidazole segment and the sulfonic acid group can reduce the swelling of the hydrophilic volume, thereby obtaining a proton exchange membrane with a lower swelling rate.

[0011] Specifically, a block polymer is grafted onto the modified MOFs material in the proton exchange membrane. The block polymer includes a polyvinyl imidazole segment and a hydrophobic segment close to the side of the MOFs material. Due to the thermodynamic incompatibility between the hydrophilic and hydrophobic components, the modified MOFs material can serve as a template to induce SPEEK to form an ordered microphase separation structure at the interface, thereby improving the problem of reduced proton conductivity caused by the insufficient continuity of the microphase separation structure of pure SPEEK. At the same time, from the structure of the modified MOFs material, it can be seen that the MOFs material will be dispersed in the proton channel formed by microphase separation, and cooperate with the polyvinyl imidazole segment and the sulfonic acid group on SPEEK to form a stable hydration network, which can effectively increase the conduction path of protons on the proton channel, so that protons are efficiently conducted in the membrane through the Grotthuss mechanism, so that the proton exchange membrane has a higher proton conductivity.

[0012] On the other hand, the modified MOFs material can also effectively reduce the swelling rate of SPEEK. The reason may be that the modified MOFs material induces the formation of an ordered microphase separation structure in SPEEK, which has a lower swelling rate than the disordered microphase structure. The MOF material itself has high rigidity and a stable crystal structure. Embedding in the SPEEK matrix can effectively restrict the free movement of polymer chains, thereby reducing the chain segment expansion caused by water absorption. At the same time, in the surface-grafted block polymer, the hydrophobic segment is located on the outside and cooperates with the hydrophobic region of SPEEK to form a protective barrier, forming a complementary interface with the polyvinyl imidazole segment and the hydrophilic region of SPEEK, which not only helps to form a continuous proton channel, but also forms a physical support at the interface to inhibit excessive water penetration. The polyvinyl imidazole segment and the sulfonic acid group on SPEEK can form cross-linking points in the polymer network by forming hydrogen bonds and ion pairs, further restricting the free movement of the polymer chain. Therefore, the modified MOFs material can effectively reduce the swelling rate of the proton exchange membrane through the above-mentioned effects.

[0013] It is worth noting that the proton exchange membrane provided in this application uses SPEEK as a cheap matrix material. By doping and modifying the MOFs material at a low ratio, the proton exchange membrane has good proton conductivity and low swelling rate, which can effectively reduce the production cost of the proton exchange membrane.

[0014] In some embodiments, the modified MOFs material is further loaded with heteropoly acid.

[0015] In some of the above embodiments, the proton conductivity and swelling rate of the proton exchange membrane can be further improved by loading heteropolyacids on the modified MOFs material. The reason may be that: since the modified MOFs material has a large specific surface area, and the polyvinyl imidazole segment in the block polymer can be combined with the heteropolyacid through hydrogen bonding, coordination, and π bond and anion interaction, the modified MOFs material can stably and evenly load the heteropolyacid. The heteropolyacid bound to the MOF material and the polyvinyl imidazole segment can further stabilize the proton conduction channel, thereby further improving the proton conductivity; in addition, the interaction between the heteropolyacid and the polyvinyl imidazole segment can further stabilize the stability of the hydrophilic phase structure in the proton exchange membrane, reduce the swelling of the hydrophilic phase, and thus further reduce the swelling rate of the proton exchange membrane.

[0016] It is also understandable that although the fixation effect of MOFs materials on heteropolyacids in the modified MOFs materials is relatively weak, the externally grafted polyvinyl imidazole chain segments can effectively reduce the loss of heteropolyacids in the MOFs materials, thereby making the proton exchange membrane have a more stable proton conductivity.

[0017] In some embodiments, the hydrophobic segment includes at least one of a polystyrene segment and a polyfluorinated styrene segment.

[0018] In some of the above embodiments, the hydrophobic segments use polystyrene segments and / or polyfluorinated styrene. These hydrophobic segments have high mechanical strength, provide stronger physical support at the interface between the hydrophilic and hydrophobic phases, and have good hydrophobicity. They can form a stable hydrophobic barrier with the hydrophobic region of SPEEK, further reducing excessive water infiltration, thereby further reducing the swelling rate of the proton exchange membrane. Polystyrene segments and / or polyfluorinated styrene have freer side chain benzene ring structures, which cooperate with the benzene ring structure of the SPEEK backbone to form a more effective hydrophobic barrier, more effectively restricting the free movement of the polymer chains. Therefore, the selection of the above hydrophobic segments achieves a better swelling reduction effect in the SPEEK system.

[0019] In some embodiments, the method for preparing the modified MOFs material comprises the following steps:

[0020] S1: MOFs-NH2 material was prepared by solvent thermal method using zirconium salt and aminoterephthalic acid;

[0021] S2: using 2-bromoisobutyryl bromide to react with the MOFs-NH2 material to graft ATRP initiation sites on the material to obtain a MOFs-Br material;

[0022] S3: using N-vinylimidazole as a monomer to graft polyvinylimidazole segments onto the MOF-Br material to obtain MOFs-g-PNVI-Br material;

[0023] S4: Grafting a hydrophobic segment onto the MOFs-g-PNVI-Br material using a hydrophobic monomer to obtain a MOFs-g-PNVI-b-HB material as a modified MOFs material.

[0024] In some of the above embodiments, a preparation method of a modified MOFs material is specifically described, specifically using zirconium salt and amino terephthalic acid to prepare a MOFs material grafted with amino groups by a solvent thermal method, and then using 2-bromoisobutyryl bromide to react with the amino groups on the surface of the MOFs material to graft ATRP initiation sites, so that the functional monomer is polymerized and grafted on the surface of the MOFs material, first using N-vinyl imidazole to graft polyvinyl imidazole segments on the surface of the MOFs material, and then using a hydrophobic monomer to further graft hydrophobic segments at the ATRP initiation site at one end of the polyvinyl imidazole segment, thereby obtaining a MOFs material grafted with a block polymer. The modified MOFs material prepared by the above method can effectively improve the proton conductivity and swelling rate of the proton exchange membrane.

[0025] In some embodiments, the hydrophobic monomer includes at least one of styrene and fluorinated styrene.

[0026] In some embodiments, the method for preparing the modified MOFs material further comprises the following steps:

[0027] S5: Soaking the MOFs-g-PNVI-b-HB material in a heteropoly acid solution, so that the material loads the heteropoly acid to obtain HPAs-MOFs-g-PNVI-b-HB as a modified MOFs material.

[0028] In some of the above embodiments, since the MOFs-g-PNVI-b-HB material has a good loading effect on heteropolyacids, by directly immersing the material in a heteropolyacid solution, the heteropolyacid can be fully and stably loaded on the MOFs material and the surface-grafted PNVI chain segment through hydrogen bonding, coordination, and π bond interaction with anions. The modified MOFs material obtained at this time can further improve the proton conductivity and swelling rate of the proton exchange membrane.

[0029] In some embodiments, in S1, the aminoterephthalic acid includes 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid, and the mass ratio of the 2-aminoterephthalic acid to the 2,5-diaminoterephthalic acid is 1:0.1~0.5; more preferably, 1:0.2~0.4; further preferably, 1:0.3.

[0030] In some of the above embodiments, the inventors found that the MOFs-NH2 materials prepared using different aminoterephthalic acids have a certain influence on the proton conductivity and swelling rate of the proton exchange membrane. When the MOFs-NH2 material is prepared using 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid with a mass ratio of 1:0.1~0.3, the proton conductivity and swelling rate of the obtained proton exchange membrane are better. The reason may be that, in general, the greater the grafting density of the block polymer on the surface of the modified MOFs material, the more stable the hydration network formed by the polyvinyl imidazole chain segment and the sulfonic acid group in SPEEK, and the higher and more stable the content of the heteropolyacid that can be loaded, the better the proton conductivity and swelling property of the obtained proton exchange membrane. The grafting density of the block polymer on the surface of the modified MOFs material prepared by the above method mainly depends on the content of active amino groups on the surface of the MOFs-NH2 material prepared by the solvent thermal method and the influence of steric hindrance during the grafting process. Therefore, the use of a certain amount of 2,5-diaminoterephthalic acid can improve the proton conductivity and swelling rate of the proton exchange membrane by increasing the content of active amino groups on the surface of the material; however, the use of different types of amino terephthalic acid can improve the proton conductivity and swelling rate of the proton exchange membrane. Dicarboxylic acid also has a certain impact on the structural stability of MOFs materials. When too much 2,5-diaminoterephthalic acid is used, it may affect the crystallinity and pore structure of the MOFs material, and have an adverse effect on the proton conductivity and swelling rate of the proton exchange membrane. The inventors found that when using 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid in the above-mentioned mass ratio to prepare MOFs-NH2 material, it is possible to adjust the amino density on the surface of the MOF-NH2 material without destroying the crystallinity and pore structure of the MOFs material, optimize the interfacial compatibility of the modified MOFs material in SPEEK and induce the formation of an ordered microphase separation structure. At the same time, it is easier to cooperate with heteropoly acids to make the proton exchange membrane have better proton conductivity and swelling rate.

[0031] In some embodiments, the heteropoly acid comprises at least one of phosphotungstic acid and phosphomolybdic acid. Based on the above embodiment, the use of the above heteropoly acid loaded on the modified MOFs material can further improve the proton conductivity and swelling rate of the proton exchange membrane.

[0032] In some embodiments, the method for preparing the modified MOFs material comprises the following steps:

[0033] S1: Dissolve 10 parts of zirconium chloride, 15-25 parts of aminoterephthalic acid, and 50-100 parts of acetic acid in 500-1000 parts of N,N-dimethylformamide, and react in an autoclave at 115-130° C. for 16-32 hours to obtain MOFs-NH2 material;

[0034] S2: Disperse 10 parts of the MOFs-NH2 material, 5-8 parts of 2-bromoisobutyryl bromide and 5-8 parts of triethylamine in 300-500 parts of dichloromethane, and react at 20-30° C. for 8-16 hours to obtain a MOFs-Br material;

[0035] S3: Dispersing 10 parts of the MOFs-Br material, 50-60 parts of N-vinylimidazole, 0.1-0.3 parts of cuprous bromide, and 0.3-0.9 parts of 2,2'-bipyridine in 200-400 parts of dimethyl sulfoxide, reacting at 65-75°C for 5-7 hours under an inert atmosphere to obtain a MOFs-g-PNVI-Br material;

[0036] S4: Dispersing 10 parts of the MOFs-g-PNVI-Br material, 40-50 parts of a hydrophobic monomer, 0.1-0.3 parts of cuprous bromide, and 0.3-0.9 parts of 2,2'-bipyridine in 200-400 parts of N,N-dimethylformamide, reacting at 55-65° C. under an inert atmosphere for 5-7 hours to obtain a MOFs-g-PNVI-b-HB material;

[0037] S5: Soaking the MOFs-g-PNVI-b-HB material in a 5 wt% to 20 wt% heteropolyacid solution for 16 to 32 hours to obtain HPAs-MOFs-g-PNVI-b-HB as a modified MOFs material.

[0038] In some of the above methods, the reaction conditions and dosage ratios of each step in the preparation process of the modified MOFs material are specifically described. Under these conditions, a modified MOFs material grafted with polyvinyl imidazole chain segments and hydrophobic segments of appropriate length can be obtained, which can enable the proton exchange membrane to better balance proton conductivity and swelling rate.

[0039] In some embodiments, the sulfonated polyetheretherketone has a weight average molecular weight of 20,000 to 100,000 and a degree of sulfonation of 50% to 70%.

[0040] In some of the above embodiments, it is understood that the degree of sulfonation of the sulfonated polyetheretherketone is proportional to the proton conductivity and swelling rate of the proton exchange membrane. When using the sulfonated polyetheretherketone with the above weight-average molecular weight and degree of sulfonation, combined with the above-mentioned modified MOFs material, the resulting proton exchange membrane can better balance proton conductivity and swelling rate. As an example, in one embodiment of the present application, a sulfonated polyetheretherketone with a weight-average molecular weight of 80,000 and a degree of sulfonation of 60% was used, purchased from Dongguan Tianzhihong Plastics Co., Ltd.

[0041] In some embodiments, the proton exchange membrane has a thickness of 20-100 μm.

[0042] In a second aspect, the present application provides a method for preparing a proton exchange membrane, comprising:

[0043] Providing a raw material for the proton exchange membrane according to any embodiment of the first aspect;

[0044] dispersing the raw materials in a solvent to obtain a slurry;

[0045] The slurry is cast and dried to obtain a proton exchange membrane.

[0046] According to the present application, the method can prepare the proton exchange membrane of the first aspect, thus having the beneficial effects of the first aspect, and the obtained proton exchange membrane has good proton conductivity and swelling rate.

[0047] In some embodiments, the solvent comprises N-methylpyrrolidone.

[0048] In some embodiments, the solid content of the slurry is 5 wt % to 10 wt %.

[0049] In some embodiments, the drying conditions include: pre-drying at 70-80°C for 3-6 hours, drying at 110-130°C for 1-2 hours, and then drying at 170-190°C for 2-4 hours. Based on the above embodiment, the above drying conditions are more conducive to the formation of an ordered microphase separation structure, resulting in a proton exchange membrane with better proton conductivity and swelling rate.

[0050] In some embodiments, the method further includes immersing the dried proton exchange membrane in a 0.5-2 mol / L sulfuric acid aqueous solution for 8-16 hours for activation, then washing the proton exchange membrane with water until the washing solution is neutral, and vacuum drying at 50-70° C. to obtain the proton exchange membrane.

[0051] In a third aspect, the present application provides a fuel cell comprising a proton exchange membrane according to any embodiment of the first aspect or a proton exchange membrane prepared by the method according to any embodiment of the second aspect.

[0052] According to the present application, since the proton exchange membrane has good proton conductivity and swelling rate, the fuel cell can have lower energy loss and higher output power. The low swelling rate can also make the fuel cell have a longer service life.

[0053] Compared with the prior art, the present invention has the following advantages:

[0054] SPEEK is used as the main material of the proton exchange membrane and is modified with a MOFs material grafted with polyimidazole segments and hydrophobic segments. By optimizing the microphase structure and forming a hydration network to coordinate the MOFs material structure, the proton exchange membrane has a high proton conductivity. The rigid skeleton of the MOFs material and the hydrophobic segments on the surface can provide additional mechanical support for the membrane. The interaction between the polyimidazole segments and the sulfonic acid groups can reduce the swelling of the hydrophilic volume, making the proton exchange membrane have a low swelling rate. In addition, the special structure of the modified MOFs material can stably load heteropolyacids, further improving the proton conductivity and swelling rate of the proton exchange membrane.

[0055] The proton exchange membrane provided in this application uses SPEEK as a cheap matrix material. By modifying the MOFs material with a low proportion of doping, the proton exchange membrane has good proton conductivity and low swelling rate, which can effectively reduce the production cost of the proton exchange membrane. DETAILED DESCRIPTION

[0056] The various embodiments or implementation schemes in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments.

[0057] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with an embodiment or example is included in at least one embodiment or example of the present application. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0058] Furthermore, 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 the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0059] In the description of this specification, unless otherwise specified, "parts" refer to "parts by mass".

[0060] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0061] Preparation Example 1

[0062] Preparation of modified MOFs materials:

[0063] 10 parts of zirconium chloride, 18 parts of aminoterephthalic acid and 60 parts of acetic acid were dissolved in 800 parts of N,N-dimethylformamide, mixed evenly, and the mixture was transferred to a high-pressure reactor, heated to 120°C for reaction for 24 hours, cooled to room temperature, and the product was collected by centrifugation, washed with ethanol, and dried at 60°C to obtain MOFs-NH2 material; wherein the aminoterephthalic acid is a mixture of 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid in a mass ratio of 1:0.1;

[0064] Take 10 parts of the above MOFs-NH2 material and ultrasonically disperse it in 400 parts of dichloromethane. Add 6 parts of 2-bromoisobutyryl bromide and 6 parts of triethylamine dropwise in an ice bath. After the addition is complete, heat to 25°C and react for 12 hours. After the reaction is complete, the product is collected by centrifugation, washed with ethanol, and vacuum dried to obtain MOFs-Br material.

[0065] 10 parts of the above MOFs-Br material were ultrasonically dispersed in 300 parts of dimethyl sulfoxide, and then 55 parts of N-vinylimidazole, 0.2 parts of cuprous bromide and 0.6 parts of 2,2'-bipyridine were added. The mixture was reacted at 70 ° C for 6 hours under a nitrogen atmosphere. After cooling to room temperature, the product was collected by centrifugation, washed with ethanol, and vacuum dried to obtain MOFs-g-PNVI-Br material;

[0066] 10 parts of the above MOFs-g-PNVI-Br material were ultrasonically dispersed in 300 parts of N,N-dimethylformamide, and then 45 parts of styrene, 0.2 parts of cuprous bromide and 0.6 parts of 2,2'-bipyridine were added. The mixture was reacted at 60°C for 7 hours under a nitrogen atmosphere. After cooling to room temperature, the product was collected by centrifugation, washed with ethanol, and dried in vacuo to obtain MOFs-g-PNVI-b-PS material.

[0067] The MOFs-g-PNVI-b-PS material was immersed in a 10 wt% phosphotungstic acid solution (the solvent was an ethanol aqueous solution with a V / V ratio of 50 / 50) for 24 h, and then filtered and dried to obtain the HPAs-MOFs-g-PNVI-b-PS material as a modified MOFs material.

[0068] Preparation Example 2

[0069] Preparation of modified MOFs materials:

[0070] The method is substantially the same as Example 1, except that the MOFs-g-PNVI-b-PS material is not further loaded with phosphotungstic acid, and the MOFs-g-PNVI-b-PS material is used as a modified MOFs material.

[0071] Preparation Example 3

[0072] Preparation of modified MOFs materials:

[0073] The method is substantially the same as Example 1, except that the aminoterephthalic acid is a mixture of 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid in a mass ratio of 1:0.3.

[0074] Preparation Example 4

[0075] Preparation of modified MOFs materials:

[0076] The process is substantially the same as Example 1, except that aminoterephthalic acid is 2-aminoterephthalic acid.

[0077] Preparation Example 5

[0078] Preparation of modified MOFs materials:

[0079] The method is substantially the same as Example 1, except that the aminoterephthalic acid is a mixture of 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid in a mass ratio of 1:0.5.

[0080] Preparation Example 6

[0081] Preparation of modified MOFs materials:

[0082] 10 parts of zirconium chloride, 18 parts of aminoterephthalic acid and 60 parts of acetic acid were dissolved in 800 parts of N,N-dimethylformamide, mixed evenly, and the mixture was transferred to a high-pressure reactor, heated to 120°C for reaction for 24 hours, cooled to room temperature, and the product was collected by centrifugation, washed with ethanol, and dried at 60°C to obtain MOFs-NH2 material; wherein the aminoterephthalic acid is a mixture of 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid in a mass ratio of 1:0.1;

[0083] Take 10 parts of the above MOFs-NH2 material and ultrasonically disperse it in 400 parts of dichloromethane. Add 6 parts of 2-bromoisobutyryl bromide and 6 parts of triethylamine dropwise in an ice bath. After the addition is complete, heat to 25°C and react for 12 hours. After the reaction is complete, the product is collected by centrifugation, washed with ethanol, and vacuum dried to obtain MOFs-Br material.

[0084] 10 parts of the above MOFs-Br material were ultrasonically dispersed in 300 parts of dimethyl sulfoxide, and then 55 parts of N-vinylimidazole, 0.2 parts of cuprous bromide and 0.6 parts of 2,2'-bipyridine were added. The mixture was reacted at 70°C for 6 hours under a nitrogen atmosphere. After cooling to room temperature, the product was collected by centrifugation, washed with ethanol, and vacuum dried to obtain MOFs-g-PNVI-Br material.

[0085] 10 parts of the above MOFs-g-PNVI-Br material were ultrasonically dispersed in 300 parts of N,N-dimethylformamide, and then 45 parts of methyl methacrylate, 0.2 parts of cuprous bromide and 0.6 parts of 2,2'-bipyridine were added. The mixture was reacted at 70°C for 7 hours under a nitrogen atmosphere. After cooling to room temperature, the product was collected by centrifugation, washed with ethanol, and dried in vacuo to obtain MOFs-g-PNVI-b-PMMA material.

[0086] The MOFs-g-PNVI-b-PMMA material was immersed in a 10 wt% phosphotungstic acid solution (the solvent was an ethanol aqueous solution with a V / V ratio of 50 / 50) for 24 h, and then filtered and dried to obtain the HPAs-MOFs-g-PNVI-b-PMMA material as a modified MOFs material.

[0087] Comparative Preparation Example 1

[0088] Preparation of modified MOFs materials:

[0089] 10 parts of zirconium chloride, 18 parts of aminoterephthalic acid and 60 parts of acetic acid were dissolved in 800 parts of N,N-dimethylformamide, mixed evenly, and the mixture was transferred to a high-pressure reactor, heated to 120°C for reaction for 24 hours, cooled to room temperature, and the product was collected by centrifugation, washed with ethanol, and dried at 60°C to obtain MOFs-NH2 material; wherein the aminoterephthalic acid is a mixture of 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid in a mass ratio of 1:0.1;

[0090] The MOFs-NH2 material was immersed in a 10 wt% phosphotungstic acid solution (the solvent was an ethanol aqueous solution with a V / V ratio of 50 / 50) for 24 hours, and then filtered and dried to obtain the HPAs-MOFs material as a modified MOFs material.

[0091] Preparation of block polymers:

[0092] 0.5 parts of ethyl α-bromoisobutyrate, 55 parts of N-vinylimidazole, 0.2 parts of cuprous bromide and 0.6 parts of 2,2'-bipyridine were dissolved in 300 parts of dimethyl sulfoxide, reacted at 70°C for 6 hours under a nitrogen atmosphere, cooled to room temperature, and then cold ethanol was added to precipitate the product. The precipitate was washed with ethanol and dried in vacuo to obtain PNVI-Br;

[0093] The above-mentioned PNVI-Br material was ultrasonically dispersed in 300 parts of N,N-dimethylformamide, and then 45 parts of styrene, 0.2 parts of cuprous bromide and 0.6 parts of 2,2'-bipyridine were added. The mixture was reacted at 60°C for 7 hours under a nitrogen atmosphere. After cooling to room temperature, cold ethanol was added to precipitate the product. The precipitate was washed with ethanol and dried in vacuum to obtain PNVI-b-PS.

[0094] Comparative Preparation Example 2

[0095] Preparation of modified MOFs materials:

[0096] 10 parts of zirconium chloride, 18 parts of aminoterephthalic acid and 60 parts of acetic acid were dissolved in 800 parts of N,N-dimethylformamide, mixed evenly, and the mixture was transferred to a high-pressure reactor, heated to 120°C for reaction for 24 hours, cooled to room temperature, and the product was collected by centrifugation, washed with ethanol, and dried at 60°C to obtain MOFs-NH2 material; wherein the aminoterephthalic acid is a mixture of 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid in a mass ratio of 1:0.1;

[0097] Take 10 parts of the above MOFs-NH2 material and ultrasonically disperse it in 400 parts of dichloromethane. Add 6 parts of 2-bromoisobutyryl bromide and 6 parts of triethylamine dropwise in an ice bath. After the addition is complete, heat to 25°C and react for 12 hours. After the reaction is complete, the product is collected by centrifugation, washed with ethanol, and vacuum dried to obtain MOFs-Br material.

[0098] 10 parts of the above MOFs-Br material were ultrasonically dispersed in 300 parts of water, and then 55 parts of sodium p-styrenesulfonate, 0.2 parts of cuprous bromide and 0.6 parts of 2,2'-bipyridine were added. The mixture was reacted at 70°C for 6 hours under a nitrogen atmosphere. After cooling to room temperature, the product was collected by centrifugation, washed with ethanol, and vacuum dried to obtain MOFs-g-PSS-Br material.

[0099] 10 parts of the above MOFs-g-PSS-Br material were ultrasonically dispersed in 300 parts of N,N-dimethylformamide, and then 45 parts of styrene, 0.2 parts of cuprous bromide and 0.6 parts of 2,2'-bipyridine were added. The mixture was reacted at 60°C for 7 hours under a nitrogen atmosphere. After cooling to room temperature, the product was collected by centrifugation, washed with ethanol, and dried in vacuo to obtain MOFs-g-PSS-b-PS material.

[0100] The MOFs-g-PSS-b-PS material was immersed in a 10 wt% phosphotungstic acid solution (the solvent was an ethanol aqueous solution with a V / V ratio of 50 / 50) for 24 h, and then filtered and dried to obtain the HPAs-MOFs-g-PSS-b-PS material as a modified MOFs material.

[0101] Comparative Preparation Example 3

[0102] Preparation of modified MOFs materials:

[0103] 10 parts of zirconium chloride, 18 parts of aminoterephthalic acid and 60 parts of acetic acid were dissolved in 800 parts of N,N-dimethylformamide, mixed evenly, and the mixture was transferred to a high-pressure reactor, heated to 120°C for reaction for 24 hours, cooled to room temperature, and the product was collected by centrifugation, washed with ethanol, and dried at 60°C to obtain MOFs-NH2 material; wherein the aminoterephthalic acid is a mixture of 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid in a mass ratio of 1:0.1;

[0104] Take 10 parts of the above MOFs-NH2 material and ultrasonically disperse it in 400 parts of dichloromethane. Add 6 parts of 2-bromoisobutyryl bromide and 6 parts of triethylamine dropwise in an ice bath. After the addition is complete, heat to 25°C and react for 12 hours. After the reaction is complete, the product is collected by centrifugation, washed with ethanol, and vacuum dried to obtain MOFs-Br material.

[0105] 10 parts of the above MOFs-Br material were ultrasonically dispersed in 300 parts of N,N-dimethylformamide, and then 45 parts of styrene, 0.2 parts of cuprous bromide and 0.6 parts of 2,2'-bipyridine were added. The mixture was reacted at 60°C for 7 hours under a nitrogen atmosphere. After cooling to room temperature, the product was collected by centrifugation, washed with ethanol, and vacuum dried to obtain MOFs-g-PS-Br material.

[0106] 10 parts of the above MOFs-g-PS-Br material were ultrasonically dispersed in 300 parts of dimethyl sulfoxide, and then 55 parts of N-vinylimidazole, 0.2 parts of cuprous bromide and 0.6 parts of 2,2'-bipyridine were added. The mixture was reacted at 70 ° C for 6 hours under a nitrogen atmosphere. After cooling to room temperature, the product was collected by centrifugation, washed with ethanol, and vacuum dried to obtain MOFs-g-PS-b-PNVI material;

[0107] The MOFs-g-PS-b-PNVI material was immersed in a 10 wt% phosphotungstic acid solution (the solvent was an ethanol aqueous solution with a V / V ratio of 50 / 50) for 24 hours, and then filtered and dried to obtain the HPAs-MOFs-g-PS-b-PNVI material as a modified MOFs material.

[0108] Example 1

[0109] Preparation of proton exchange membrane:

[0110] 100 parts of SPEEK with a weight average molecular weight of 80,000 and a sulfonation degree of 60% were dissolved in N-methylpyrrolidone, and 5 parts of the modified MOFs material obtained in Preparation Example 1 were added. N-methylpyrrolidone was added to make the solid content of the slurry 10 wt %. The mixture was ultrasonically treated for 30 min and mixed for 6 h to obtain a slurry.

[0111] The slurry was cast into a glass mold with a target film thickness of approximately 50 μm. It was pre-dried at 80°C for 5 hours to remove part of the solvent, then dried at 120°C for 1 hour, and then dried at 180°C for 3 hours. The slurry was taken out and immersed in a 1 mol / L aqueous sulfuric acid solution for 12 hours. The slurry was taken out and washed with water until the washing liquid was neutral. Finally, the membrane was vacuum dried at 60°C to constant weight to obtain a proton exchange membrane.

[0112] Example 2

[0113] Preparation of proton exchange membrane:

[0114] It is substantially the same as Example 1, except that the modified MOFs material obtained in Preparation Example 2 is used.

[0115] Example 3

[0116] Preparation of proton exchange membrane:

[0117] It is substantially the same as Example 1, except that the modified MOFs material obtained in Preparation Example 3 is used.

[0118] Example 4

[0119] Preparation of proton exchange membrane:

[0120] It is substantially the same as Example 1, except that the modified MOFs material obtained in Preparation Example 4 is used.

[0121] Example 5

[0122] Preparation of proton exchange membrane:

[0123] It is substantially the same as Example 1, except that the modified MOFs material obtained in Preparation Example 5 is used.

[0124] Example 6

[0125] Preparation of proton exchange membrane:

[0126] It is substantially the same as Example 1, except that the modified MOFs material obtained in Preparation Example 6 is used.

[0127] Comparative Example 1

[0128] Preparation of proton exchange membrane:

[0129] It is substantially the same as Example 1, except that 4 parts of the modified MOFs material obtained in Comparative Preparation Example 1 and 1 part of the block polymer prepared in Comparative Preparation Example 1 are used instead of 5 parts of the modified MOFs material obtained in Preparation Example 1.

[0130] Comparative Example 2

[0131] Preparation of proton exchange membrane:

[0132] It is substantially the same as Example 1, except that the modified MOFs material obtained in Comparative Preparation Example 2 is used.

[0133] Comparative Example 3

[0134] Preparation of proton exchange membrane:

[0135] It is substantially the same as Example 1, except that the modified MOFs material obtained in Comparative Preparation Example 3 is used.

[0136] Comparative Example 4

[0137] Preparation of proton exchange membrane:

[0138] The method is similar to Example 1 except that no modified MOFs material is used. 105 parts of SPEEK with a weight average molecular weight of 80,000 and a sulfonation degree of 60% are dissolved in N-methylpyrrolidone to make the solid content of the slurry 10 wt%.

[0139] Test section

[0140] The proton conductivity σ0 of the proton exchange membranes prepared in each embodiment and comparative example was tested at 25° C. and a relative humidity of 95% with reference to GB / T 20042.3-2022 “Proton Exchange Membrane Fuel Cells Part 3: Proton Exchange Membrane Test Methods”. The results are shown in Table 1.

[0141] In addition, the proton exchange membranes prepared in each embodiment and comparative example were immersed in water for 30 days, and the water was changed every 1 day. After 30 days, the proton conductivity σ1 of the proton exchange membrane was measured at 80°C and a relative humidity of 95%. The results are shown in Table 1.

[0142] The proton exchange membranes prepared in the examples and comparative examples were cut into pieces of 10 cm × 10 cm, placed in a water bath at 80°C for 2 h, and then taken out to dry the surface moisture. The area after swelling was measured as S1 cm 2 The swelling ratio was calculated by the following formula: δ = (S1-100) / 100×100%. The results are shown in Table 1.

[0143] Table 1

[0144] <![CDATA[σ0(mS / cm)]]> <![CDATA[σ1(mS / cm)]]> δ (%) Example 1 178 178 5.7 Example 2 134 134 7.2 Example 3 182 182 5.5 Example 4 155 155 6.2 Example 5 162 161 5.9 Example 6 167 166 6.5 Comparative Example 1 107 93 18.6 Comparative Example 2 116 114 11.3 Comparative Example 3 121 105 18.2 Comparative Example 4 71 71 34.7

[0145] According to Table 1, the proton conductivity of the proton exchange membrane obtained in each embodiment is higher than that of each comparative example, and the swelling rate is lower than that of each comparative example, indicating that the proton exchange membrane provided by the present application has better proton conductivity and swelling rate, and good stability of proton conductivity. The possible reasons are as follows: in Comparative Example 1, MOFs materials loaded with heteropolyacids and block polymers having hydrophobic segments and polyvinyl imidazole segments were added to SPEEK respectively, and the proton conductivity and swelling rate of the SPEEK membrane were better than those of the pure SPEEK membrane in Comparative Example 3. Although the block polymer can induce SPEEK to form a more ordered microphase separation structure to a certain extent, the MOFs material that has not been grafted has poor dispersibility in the system, and the heteropolyacid loading amount is small, and the improvement of proton conductivity is limited. It is also difficult for the poorly dispersed MOFs material to further reduce the swelling rate of the proton exchange membrane. In addition, since the MOFs material that has not been grafted has poor loading stability for heteropolyacids, its proton conductivity is easily reduced during use; in Comparative Example 2, poly(p-styrene sulfonic acid) is used as the hydrophilic segment, and the segment has poor loading performance for heteropolyacids compared to the polyvinyl imidazole segment, and Due to steric hindrance and electrostatic effects, the loading capacity of the modified MOFs material for heteropolyacid is low, resulting in limited effect on improving proton conductivity. In addition, its effect of inducing SPEEK to form an ordered microphase separation structure is worse than that of the polyvinyl imidazole segment. The electrostatic repulsion between the sulfonic acid groups on the modified MOFs material and the sulfonic acid groups on SPEEK also causes its swelling rate to be higher than that of the embodiments. In Comparative Example 3, the polyvinyl imidazole segment is set on the outside of the MOFs material, which will cause the hydration network formed by the polyvinyl imidazole segment and the sulfonic acid groups on SPEEK to be unable to cooperate with the MOFs material. At the same time, due to the hydrophobicity of the polystyrene segment, the heteropolyacid is not easy to load inside the MOFs material, and is mainly loaded on the polyvinyl imidazole segment on the outside, which is easy to lose, resulting in low proton conductivity and easy to decrease during use. In addition, the hydrophobic segment on the inside cannot effectively reduce the swelling rate of the membrane.

[0146] Comparison of Examples 1 and 2 shows that by further loading heteropoly acid, the proton conductivity of the proton exchange membrane can be made higher and the swelling rate can be made lower.

[0147] By comparing Examples 1 and 3 to 5, it can be seen that the MOFs-NH2 materials prepared using different aminoterephthalic acids have a certain influence on the proton conductivity and swelling rate of the proton exchange membrane. When 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid with a mass ratio of 1:0.3 are used to prepare the MOFs-NH2 material, a balanced grafting density and pore structure are obtained, and the proton conductivity and swelling rate of the obtained proton exchange membrane are better.

[0148] From comparative examples 1 and 6, it can be seen that the MOFs-NH2 materials prepared using different hydrophobic segments have a certain influence on the proton conductivity and swelling rate of the proton exchange membrane. When polystyrene segments are used as hydrophobic segments, the proton conductivity and swelling rate of the obtained proton exchange membrane are better.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A proton exchange membrane, characterized in that Including the following raw materials by weight: 100 parts of sulfonated polyetheretherketone, 1-10 parts of modified MOFs material; The modified MOFs material includes a MOFs material grafted with a block polymer, wherein the block polymer includes a polyvinyl imidazole segment and a hydrophobic segment, and the polyvinyl imidazole segment is arranged on a side close to the MOFs material; The modified MOFs material is also loaded with heteropoly acid; The hydrophobic segment includes at least one of a polystyrene segment and a polyfluorinated styrene segment.

2. The proton exchange membrane according to claim 1, characterized in that The preparation method of the modified MOFs material comprises the following steps: S1: MOFs-NH2 material was prepared by solvent thermal method using zirconium salt and aminoterephthalic acid; S2: using 2-bromoisobutyryl bromide to react with the MOFs-NH2 material to graft ATRP initiation sites on the material to obtain a MOFs-Br material; S3: using N-vinylimidazole as a monomer to graft polyvinylimidazole segments onto the MOF-Br material to obtain MOFs-g-PNVI-Br material; S4: Grafting a hydrophobic segment onto the MOFs-g-PNVI-Br material using a hydrophobic monomer to obtain a MOFs-g-PNVI-b-HB material as a modified MOFs material.

3. The proton exchange membrane according to claim 2, characterized in that The preparation method of the modified MOFs material further comprises the following steps: S5: Soaking the MOFs-g-PNVI-b-HB material in a heteropoly acid solution, so that the material loads the heteropoly acid to obtain a HPAs-MOFs-g-PNVI-b-HB material as a modified MOFs material.

4. The proton exchange membrane according to claim 2 or 3, characterized in that In S1, the aminoterephthalic acid includes 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid, and the mass ratio of the 2-aminoterephthalic acid to the 2,5-diaminoterephthalic acid is 1:0.2-0.

4.

5. The proton exchange membrane according to claim 1 or 3, characterized in that The heteropoly acid includes at least one of phosphotungstic acid and phosphomolybdic acid.

6. The proton exchange membrane according to claim 3, characterized in that The preparation method of the modified MOFs material comprises the following steps: S1: Dissolve 10 parts of zirconium chloride, 15-25 parts of aminoterephthalic acid, and 50-100 parts of acetic acid in 500-1000 parts of N,N-dimethylformamide, and react in an autoclave at 115-130° C. for 16-32 hours to obtain MOFs-NH2 material; S2: Disperse 10 parts of the MOFs-NH2 material, 5-8 parts of 2-bromoisobutyryl bromide and 5-8 parts of triethylamine in 300-500 parts of dichloromethane, and react at 20-30° C. for 8-16 hours to obtain a MOFs-Br material; S3: Dispersing 10 parts of the MOFs-Br material, 50-60 parts of N-vinylimidazole, 0.1-0.3 parts of cuprous bromide, and 0.3-0.9 parts of 2,2'-bipyridine in 200-400 parts of dimethyl sulfoxide, reacting at 65-75°C for 5-7 hours under an inert atmosphere to obtain a MOFs-g-PNVI-Br material; S4: Dispersing 10 parts of the MOFs-g-PNVI-Br material, 40-50 parts of a hydrophobic monomer, 0.1-0.3 parts of cuprous bromide, and 0.3-0.9 parts of 2,2'-bipyridine in 200-400 parts of N,N-dimethylformamide, reacting at 55-65° C. under an inert atmosphere for 5-7 hours to obtain a MOFs-g-PNVI-b-HB material; S5: Soaking the MOFs-g-PNVI-b-HB material in a 5 wt% to 20 wt% heteropolyacid solution for 16 to 32 hours to obtain HPAs-MOFs-g-PNVI-b-HB as a modified MOFs material.

7. The proton exchange membrane according to claim 1, characterized in that At least one of the following conditions is met: 1) The weight average molecular weight of the sulfonated polyetheretherketone is 20,000 to 100,000, and the degree of sulfonation is 50% to 70%; 2) The thickness of the proton exchange membrane is 20-100 μm.

8. A method for preparing a proton exchange membrane, characterized in that: include: Providing a raw material for the proton exchange membrane according to any one of claims 1 to 7; dispersing the raw materials in a solvent to obtain a slurry; The slurry is cast and dried to obtain a proton exchange membrane.