Proton exchange membrane, preparation method thereof and fuel cell

Abstract

The invention provides a proton exchange membrane, a preparation method thereof and a fuel cell, and relates to the technical field of fuel cells. The proton exchange membrane comprises a base material with a porous structure, pores of the base material contain active components, and the active components comprise a heteropolyacid modified MOF material and sulfonated polyfluorene biphenyl indole; the weight ratio of the heteropoly acid to the MOF material is 1: (1-3). The proton exchange membrane provided by the invention has the characteristics of excellent mechanical durability, high proton conductivity and ultra-thinness, and can improve the mechanical strength, ductility and chemical stability of the membrane while reducing the expansion of the membrane.

Description

Technical Field

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

[0002] The proton exchange membrane used in traditional proton exchange membrane fuel cells is composed of perfluorosulfonic acid resin. The hydrophilic and hydrophobic domains in the perfluorosulfonic acid resin structure have a distinct phase separation structure, which makes it chemically stable and has high proton conductivity. However, the proton exchange membrane prepared by perfluorosulfonic acid resin (such as nafion, Aquivion) ​​has the disadvantages of easy swelling, easy permeability, and poor durability during use. The high price of perfluorosulfonic acid resin and the potential harm of fluoride to the environment further restrict its use. Summary of the invention

[0003] The present application provides a proton exchange membrane and a preparation method thereof, and a fuel cell to solve the following technical problem: how to improve the performance of the proton exchange membrane.

[0004] In a first aspect, the present application provides a proton exchange membrane, the proton exchange membrane comprising a substrate having a porous structure, the pores of the substrate containing active components, the active components comprising: a MOF material modified by a heteropolyacid;

[0005] The weight ratio of the heteropoly acid to the MOF material is 1:(1-3).

[0006] Optionally, the heteropolyacid includes at least one of the following: phosphotungstic heteropolyacid and phosphomolybdic heteropolyacid.

[0007] Optionally, the MOF material includes ZIF-67.

[0008] Optionally, the active component further comprises: an enhancer, wherein the enhancer contains a sulfonic acid group and an aromatic skeleton structure.

[0009] Optionally, the enhancer comprises sulfonated polyfluorene biphenyl indole.

[0010] Optionally, the weight ratio of the heteropolyacid-modified MOF material to the enhancer is (1-2):1.

[0011] In a second aspect, the present application provides a method for preparing a proton exchange membrane according to any one of the first aspects, the method comprising:

[0012] Obtaining a heteropolyacid-modified MOF material;

[0013] The heteropolyacid-modified MOF material, the enhancer and the first solvent are first mixed, and then the mixture obtained by the first mixing is infiltrated into the pores of the substrate with a porous structure to obtain a proton exchange membrane semi-finished product;

[0014] The proton exchange membrane semi-finished product is hot-pressed to obtain a proton exchange membrane.

[0015] Optionally, the heteropolyacid-modified MOF material comprises:

[0016] The heteropoly acid, the MOF material and the second solvent are mixed for a second time to obtain a heteropoly acid-modified MOF material.

[0017] Optionally, the process parameters of the second mixing include: temperature of 20°C to 30°C, time of ≥60 min, stirring speed of 600 r / min to 1000 r / min; and / or,

[0018] The process parameters of the hot pressing include: pressure of 0.8 MPa to 1.2 MPa, temperature of 110° C. to 130° C., and time of 60 s to 90 s.

[0019] In a third aspect, the present application provides a fuel cell, comprising the proton exchange membrane as described in any one of the first aspects.

[0020] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0021] The proton exchange membrane provided in the embodiment of the present application comprises a substrate with a porous structure, the pores of the substrate contain active components, and the active components include: a MOF material modified with a heteropoly acid; the weight ratio of the heteropoly acid to the MOF material is 1:(1-3). The substrate with a porous structure provides a support structure for the proton exchange membrane; the pores of the substrate contain active components, the heteropoly acid is a cluster hydrate with a Keggin structure, which can form a hydrated crystal structure with water, can improve the proton conductivity of the proton exchange membrane and exhibit a certain water retention, thereby improving the anti-swelling performance of the proton exchange membrane; the MOF material has an organic-inorganic hollow skeleton structure, and its structure can fix the heteropoly acid and provide a channel for proton conduction, thereby improving the proton conductivity and the stability of the heteropoly acid in a strong acidic environment. The MOF material has a high specific The surface area and organic ligands can significantly enhance the proton conduction ability, and can easily complex with heteropoly acids to form a complex (heteropoly acid-modified MOF material); the heteropoly acid-modified MOF material can enhance the working environment of the heteropoly acid, stabilize the anti-swelling properties of the proton exchange membrane, and can grade the protons for transmission, thereby further enhancing the proton conductivity of the proton exchange membrane; the weight ratio of heteropoly acids to MOF materials can be 1: (1 to 3), which can enable the proton exchange membrane to have both excellent anti-swelling properties and high proton conductivity, thereby improving the performance of the proton exchange membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 A schematic flow chart of a method for preparing a proton exchange membrane provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0026] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0027] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "include", "comprise", etc. refer to "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "at least one" refers to one or more, and "multiple" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, wherein a, b, c can be single or multiple, respectively.

[0028] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0029] In a first aspect, the present application provides a proton exchange membrane, the proton exchange membrane comprising a substrate having a porous structure, the pores of the substrate containing active components, the active components comprising: a MOF material modified by a heteropolyacid;

[0030] The weight ratio of the heteropoly acid to the MOF material is 1:(1-3).

[0031] In the embodiment of the present application, a substrate with a porous structure provides a support structure for the proton exchange membrane; the pores of the substrate contain active components, and the heteropoly acid is a cluster hydrate with a Keggin structure, which can form a hydrated crystal structure with water, can improve the proton conductivity of the proton exchange membrane and show a certain water retention, thereby improving the anti-swelling performance of the proton exchange membrane; the MOF material has an organic-inorganic hollow skeleton structure, and its structure can fix the heteropoly acid and provide a channel for proton conduction, thereby improving the proton conductivity and the stability of the heteropoly acid in a strong acidic environment. The high specific surface area and organic ligand can significantly enhance the proton conductivity, and can be easily complexed with heteropolyacid to form a complex (heteropolyacid-modified MOF material); the heteropolyacid-modified MOF material can strengthen the working environment of the heteropolyacid, stabilize the anti-swelling performance of the proton exchange membrane, and can grade the protons for transmission, thereby further enhancing the proton conductivity of the proton exchange membrane; the weight ratio of the heteropolyacid to the MOF material can be 1: (1-3), which can make the proton exchange membrane have both excellent anti-swelling performance and high proton conductivity, thereby improving the performance of the proton exchange membrane. If the weight ratio of the heteropolyacid to the MOF material is higher than 1: 1, to a certain extent, the excess heteropolyacid will cover the MOF material, blocking the hollow pores on the MOF material, making it difficult to improve the proton conductivity of the proton exchange membrane; if the weight ratio of the heteropolyacid to the MOF material is lower than 1: 3, to a certain extent, the heteropolyacid will cover less on the MOF material, making it difficult to improve the anti-swelling performance of the proton exchange membrane. Illustratively, the weight ratio of the heteropoly acid to the MOF material can be 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2.0, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, etc.

[0032] In some embodiments, the heteropoly acid includes at least one of the following: phosphotungstic heteropoly acid and phosphomolybdic heteropoly acid.

[0033] In the embodiment of the present application, the heteropoly acid may be phosphotungstic heteropoly acid (H3PW 12 O 40 ), phosphorus molybdenum heteropoly acid (H3PMo 12 O 40 ) or a combination of one or more thereof.

[0034] In some embodiments, the MOF material includes ZIF-67.

[0035] In the embodiment of the present application, the MOF material may include ZIF-67. The MOF material is composed of metal ions or metal clusters and organic ligands. As one of the MOF materials, ZIF-67 is generally composed of cobalt ions (Co 2+) and imidazole and its derivative organic ligands are self-assembled through coordination bonds to form a crystalline material with a zeolite imidazole ester framework structure. The structure of ZIF-67 has a high porosity and a regular pore structure, so that ZIF-67 can fix heteropolyacids and provide channels for proton conduction, improve proton conductivity, and will not affect other properties of the proton exchange membrane. Exemplarily, the ZIF-67 can be prepared by using cobalt nitrate hexahydrate and 2-methylimidazole as raw materials, and the molecular formula of the obtained ZIF-67 is C8H 12 N4·Co, molecular weight is 223.14, the coordination metal is Co, and the organic ligand is 2-methylimidazole (CAS: 693-98-1).

[0036] In some embodiments, the active component further comprises: an enhancer, wherein the enhancer contains a sulfonic acid group and an aromatic skeleton structure.

[0037] In the embodiment of the present application, the active component also includes: an enhancer, which contains a sulfonic acid group and an aromatic skeleton structure. The sulfonic acid group can provide more proton binding sites and transmission paths, making the conduction of protons in the membrane smoother, thereby improving the proton conductivity of the proton exchange membrane; the aromatic skeleton structure can improve the mechanical properties of the proton exchange membrane.

[0038] In some embodiments, the enhancer comprises sulfonated polyfluorene biphenyl indole.

[0039] In the embodiment of the present application, the enhancer may include sulfonated polyfluorene biphenyl indole, which is a polymer with an aromatic skeleton structure, has excellent amphiphilicity, and can penetrate into the pores of the substrate skeleton gap. The substrate may be polytetrafluoroethylene (PTFE), which has excellent chemical stability and mechanical stability. The above active components have excellent hydrophilicity and alcohol affinity, and have good compatibility with PTFE, which is conducive to processing to form a proton exchange membrane.

[0040] In some embodiments, the weight ratio of the heteropolyacid-modified MOF material to the reinforcing agent is (1-2):1.

[0041] In the embodiment of the present application, the weight ratio of the MOF material modified by the heteropoly acid to the reinforcing agent can be (1-2): 1, so that the proton exchange membrane has good mechanical properties and can also have excellent anti-swelling properties and high proton conductivity. If the weight ratio of the MOF material modified by the heteropoly acid to the reinforcing agent is higher than 2: 1, the anti-swelling properties and proton conductivity of the proton exchange membrane will deteriorate to a certain extent. If the weight ratio of the MOF material modified by the heteropoly acid to the reinforcing agent is lower than 1: 1, it is difficult to improve the proton exchange membrane to a certain extent. Exemplarily, the weight ratio of the MOF material modified by the heteropoly acid to the reinforcing agent can be 1: 1, 1.1: 1, 1.2: 1, 1.3: 1, 1.4: 1, 1.4: 1, 1.5: 1, 1.6: 1, 1.7: 1, 1.8: 1, 1.9: 1, 2.0: 1, etc.

[0042] In a second aspect, the present application provides a method for preparing a proton exchange membrane according to any one of the first aspects, Figure 1 A schematic diagram of a process for preparing a proton exchange membrane provided in an embodiment of the present application; see Figure 1 , the method comprising:

[0043] S1, obtaining a MOF material modified by a heteropoly acid;

[0044] In some embodiments, the heteropolyacid-modified MOF material is obtained, comprising:

[0045] The heteropoly acid, the MOF material and the second solvent are mixed for a second time to obtain a heteropoly acid-modified MOF material.

[0046] In some embodiments, the process parameters of the second mixing include: temperature of 20°C to 30°C, time of ≥60 min, stirring speed of 600 r / min to 1000 r / min;

[0047] In the embodiment of the present application, the MOF material modified by the heteropoly acid can be obtained by mixing the heteropoly acid, the MOF material and the second solvent for the second time, and the process parameters of the mixing and stirring can be: temperature of 20°C to 30°C, time of ≥60min, stirring speed of 600r / min to 1000r / min, so as to fully realize the compounding of the heteropoly acid and the MOF material, and the heteropoly acid and the MOF material can be combined together through hydrogen bonds and van der Waals forces, and the second solvent can be water. Exemplarily, the temperature can be 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, etc.; the time can be 60min, 70min, 80min, 90min, 100min, etc.; the stirring speed can be 600r / min, 650r / min, 700r / min, 750r / min, 800r / min, 850r / min, 900r / min, 950r / min, 1000r / min, etc.

[0048] The MOF material modified by heteropoly acid can be ZIF-67 modified by heteropoly acid. The preparation method of ZIF-67 comprises: taking 1g of cobalt nitrate hexahydrate and 1.2g of 2-methylimidazole and adding them into a beaker, then adding 400mL of methanol into the beaker and stirring them fully, stirring them at room temperature for 6h and centrifuging them, and washing them with methanol to obtain ZIF-67. The ZIF-67 is added into a beaker, and then heteropoly acid and deionized water (second solvent) are added for magnetic stirring, and finally centrifuged and dried to obtain ZIF-67 modified by heteropoly acid.

[0049] S2, performing a first mixing of the heteropolyacid-modified MOF material, the enhancer and the first solvent, and then infiltrating the mixture obtained by the first mixing into the pores of the substrate having a porous structure to obtain a proton exchange membrane semi-finished product;

[0050] S3, hot pressing the proton exchange membrane semi-finished product to obtain a proton exchange membrane. The hot pressing process parameters include: pressure of 0.8MPa to 1.2MPa, temperature of 110°C to 130°C, and time of 60s to 90s.

[0051] In the embodiment of the present application, the enhancer can be selected from sulfonated polyfluorene biphenyl indole. The preparation method of sulfonated polyfluorene biphenyl indole includes: pouring biphenyl and fluorene into a three-necked flask, then adding 10g of dichloromethane to completely dissolve the monomers, then slowly dripping trifluoroacetic acid and trifluoromethylbissulfonyl imide into the flask and reacting in an ice bath at 0°C, reacting for 12 hours, and precipitating in methanol to obtain polyfluorene biphenyl indole. Tetrabutylammonium bromide and polyfluorene biphenyl indole are added to a three-necked flask and dissolved in dimethyl sulfoxide, then the three-necked flask is filled with nitrogen atmosphere, and then potassium hydroxide and 1,3-propane sulfonone are added thereto for reaction, reacting at 80°C for 4 hours, and finally the solution is poured into methanol to precipitate the reaction product to obtain sulfonated polyfluorene biphenyl indole.

[0052] In the embodiment of the present application, step S3 includes: taking a substrate and placing it in a culture dish. Take sulfonated polyfluorene biphenyl indole and heteropoly acid modified ZIF-67 and add it to a water / alcohol mixture (first solvent), stir evenly and slowly drip the mixed solution into the culture dish, so that the solution slowly penetrates into the gap of the substrate, and finally tear off the film on the substrate and perform hot pressing to integrate the proton exchange membrane. The process parameters of hot pressing can be: pressure of 0.8MPa~1.2MPa, temperature of 110℃~130℃, time of 60s~90s, hot pressing makes the active components better combined with the substrate, and the proton exchange membrane becomes thinner, thereby improving the performance of the proton exchange membrane. Therefore, the proton exchange membrane has excellent mechanical durability, high proton conductivity, and ultra-thin characteristics, and can improve mechanical strength, ductility and chemical stability while reducing membrane expansion, thereby solving the problem that the proton exchange membrane is easy to absorb water and swell and the proton membrane is easy to rupture under long-term operation conditions. For example, the pressure can be 0.8 MPa, 0.9 MPa, 1.0 MPa, 1.1 MPa, 1.2 MPa, etc., the temperature can be 110°C, 115°C, 120°C, 125°C, 130°C, etc., and the time can be 60s, 65s, 70s, 75s, 80s, 85s, 90s, etc.

[0053] The preparation method of the proton exchange membrane is implemented based on the above-mentioned proton exchange membrane. The specific structure of the proton exchange membrane can refer to the above-mentioned embodiment. Since the preparation method of the proton exchange membrane adopts part or all of the technical solutions of the above-mentioned embodiment, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be repeated here one by one.

[0054] In a third aspect, the present application provides a fuel cell, comprising the proton exchange membrane as described in any one of the first aspects.

[0055] The fuel cell is realized based on the above-mentioned proton exchange membrane. The specific structure of the proton exchange membrane can refer to the above-mentioned embodiment. Since the fuel cell adopts part or all of the technical solutions of the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0056] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0057] Example 1

[0058] A proton exchange membrane, the proton exchange membrane comprises PTFE, the pores of the PTFE contain active components, the active components include: heteropoly acid (H3PW 12 O 40 ) modified ZIF-67 and sulfonated polyfluorene biphenyl indole; the heteropoly acid (H3PW 12 O 40 ) and the ZIF-67 in a weight ratio of 1:1, and the heteropoly acid (H3PW 12 O 40 )The weight ratio of modified ZIF-67 to sulfonated polyfluorene biphenyl indole is 1:1.

[0059] A method for preparing a proton exchange membrane, specifically comprising:

[0060] (1) Heteropolyacid-modified ZIF-67

[0061] Take 1g of cobalt nitrate hexahydrate and 1.2g of 2-methylimidazole and add them to a beaker. Then add 400mL of methanol to the beaker and stir thoroughly. Stir at room temperature for 6h and then centrifuge. Wash with methanol to obtain ZIF-67. Add 1g of ZIF-67 to the beaker and add 1g of H3PW 12 O 40 and deionized water for mixing and stirring, and the stirring process parameters include: temperature of 25° C., rotation speed of 800 r / min, time of 2 h, and finally centrifugation and drying to obtain a heteropoly acid-modified ZIF-67 complex.

[0062] (2) Preparation of sulfonated polyfluorene biphenyl indole

[0063] Pour biphenyl and fluorene into a three-necked flask, then add 10g of dichloromethane to completely dissolve the monomers, then slowly drop trifluoroacetic acid and trifluoromethylbissulfonyl imide into the flask and react in an ice bath at 0°C. After reacting for 12 hours, precipitate in methanol to obtain polyfluorene biphenyl indole. Add tetrabutylammonium bromide and polyfluorene biphenyl indole to a three-necked flask and dissolve them in dimethyl sulfoxide. Then fill the three-necked flask with nitrogen atmosphere, then add potassium hydroxide and 1,3-propane sulfonone to react, react at 80°C for 4 hours, and finally pour the solution into methanol to precipitate the reaction product to obtain sulfonated polyfluorene biphenyl indole.

[0064] (3) Proton exchange membrane preparation

[0065] Take a piece of commercial PTFE and place it in a culture dish. Take 1g of sulfonated polyfluorene biphenyl indole and 1g of heteropoly acid modified ZIF-67 and add them to the water / alcohol mixture. After stirring evenly, slowly drip the mixed solution into the culture dish to allow the solution to slowly penetrate into the gaps of PTFE. Finally, tear off the film on the PTFE and perform hot pressing. The process parameters of hot pressing include: hot pressing pressure of 1MPa, hot pressing temperature of 120℃, hot pressing time of 60s, and integrate to obtain a proton exchange membrane.

[0066] Example 2

[0067] A proton exchange membrane, the proton exchange membrane comprises PTFE, the pores of the PTFE contain active components, the active components include: heteropoly acid (H3PMo 12 O 40 ) modified ZIF-67 and sulfonated polyfluorene biphenyl indole; the heteropoly acid (H3PMo 12 O 40 ) and the ZIF-67 in a weight ratio of 1:2, and the heteropoly acid (H3PMo 12 O 40 )The weight ratio of modified ZIF-67 to sulfonated polyfluorene biphenyl indole is 2:1.

[0068] A method for preparing a proton exchange membrane, specifically comprising:

[0069] (1) Heteropolyacid-modified ZIF-67

[0070] Take 1g of cobalt nitrate hexahydrate and 1.2g of 2-methylimidazole and add them to a beaker. Then add 400mL of methanol to the beaker and stir thoroughly. Stir at room temperature for 6h and then centrifuge. Wash with methanol to obtain ZIF-67. Add 2g of ZIF-67 to the beaker and add 1g of H3PMo 12 O 40and deionized water for mixing and stirring, and the stirring process parameters include: temperature of 25° C., rotation speed of 800 r / min, time of 2 h, and finally centrifugation and drying to obtain a heteropoly acid-modified ZIF-67 complex.

[0071] (2) Preparation of sulfonated polyfluorene biphenyl indole

[0072] Pour biphenyl and fluorene into a three-necked flask, then add 10g of dichloromethane to completely dissolve the monomers, then slowly drop trifluoroacetic acid and trifluoromethylbissulfonyl imide into the flask and react in an ice bath at 0°C. After reacting for 12 hours, precipitate in methanol to obtain polyfluorene biphenyl indole. Add tetrabutylammonium bromide and polyfluorene biphenyl indole to a three-necked flask and dissolve them in dimethyl sulfoxide. Then fill the three-necked flask with nitrogen atmosphere, then add potassium hydroxide and 1,3-propane sulfonone to react, react at 80°C for 4 hours, and finally pour the solution into methanol to precipitate the reaction product to obtain sulfonated polyfluorene biphenyl indole.

[0073] (3) Proton exchange membrane preparation

[0074] Take a piece of commercial PTFE and place it in a culture dish. Take 1g of sulfonated polyfluorene biphenyl indole and 2g of heteropoly acid modified ZIF-67 and add them to the water / alcohol mixture. After stirring evenly, slowly drip the mixed solution into the culture dish to allow the solution to slowly penetrate into the gaps of PTFE. Finally, tear off the film on the PTFE and perform hot pressing. The process parameters of hot pressing include: hot pressing pressure of 1MPa, hot pressing temperature of 120℃, hot pressing time of 60s, and integrate to obtain a proton exchange membrane.

[0075] Example 3

[0076] A proton exchange membrane, the proton exchange membrane comprises PTFE, the pores of the PTFE contain active components, the active components include: heteropoly acid (H3PW 12 O 40 ) modified ZIF-67 and sulfonated polyfluorene biphenyl indole; the heteropoly acid (H3PW 12 O 40 ) and the ZIF-67 in a weight ratio of 1:3, and the heteropoly acid (H3PW 12 O 40 )The weight ratio of modified ZIF-67 to sulfonated polyfluorene biphenyl indole is 1.5:1.

[0077] A method for preparing a proton exchange membrane, specifically comprising:

[0078] (1) Heteropolyacid-modified ZIF-67

[0079] Take 1g of cobalt nitrate hexahydrate and 1.2g of 2-methylimidazole and add them to a beaker. Then add 400mL of methanol to the beaker and stir thoroughly. Stir at room temperature for 6h and then centrifuge. Wash with methanol to obtain ZIF-67. Add 3g of ZIF-67 to the beaker and add 1g of H3PMo 12 O 40 and deionized water for mixing and stirring, and the stirring process parameters include: temperature of 25° C., rotation speed of 800 r / min, time of 2 h, and finally centrifugation and drying to obtain a heteropoly acid-modified ZIF-67 complex.

[0080] (2) Preparation of sulfonated polyfluorene biphenyl indole

[0081] Pour biphenyl and fluorene into a three-necked flask, then add 20g of dichloromethane to completely dissolve the monomers, then slowly drop trifluoroacetic acid and trifluoromethylbissulfonyl imide into the flask and react in an ice bath at 0°C. After reacting for 12 hours, precipitate in methanol to obtain polyfluorene biphenyl indole. Add tetrabutylammonium bromide and polyfluorene biphenyl indole to a three-necked flask and dissolve them in dimethyl sulfoxide. Then fill the three-necked flask with nitrogen atmosphere, then add potassium hydroxide and 1,3-propane sulfonone to react, react at 80°C for 4 hours, and finally pour the solution into methanol to precipitate the reaction product to obtain sulfonated polyfluorene biphenyl indole.

[0082] (3) Proton exchange membrane preparation

[0083] Take a piece of commercial PTFE and place it in a culture dish. Take 1g of sulfonated polyfluorene biphenyl indole and 1.5g of heteropoly acid modified ZIF-67 and add them to the water / alcohol mixture. After stirring evenly, slowly drip the mixed solution into the culture dish to allow the solution to slowly penetrate into the gaps of PTFE. Finally, tear off the film on the PTFE and perform hot pressing. The process parameters of hot pressing include: hot pressing pressure of 1MPa, hot pressing temperature of 120℃, hot pressing time of 60s, and integrate to obtain a proton exchange membrane.

[0084] Comparative Example 1

[0085] Nafion212 proton exchange membrane.

[0086] Comparative Example 2

[0087] A proton exchange membrane, the proton exchange membrane comprises PTFE, the pores of the PTFE contain active components, the active components include: heteropoly acid (H3PW 12 O 40 ) modified ZIF-67 and sulfonated polyfluorene biphenyl indole; the heteropoly acid (H3PW 12 O 40 ) and the ZIF-67 in a weight ratio of 1:4, and the heteropoly acid (H3PW 12 O 40)The weight ratio of modified ZIF-67 to sulfonated polyfluorene biphenyl indole is 1:1.

[0088] A method for preparing a proton exchange membrane, specifically comprising:

[0089] (1) Heteropolyacid-modified ZIF-67

[0090] Take 1g of cobalt nitrate hexahydrate and 1.2g of 2-methylimidazole and add them to a beaker. Then add 400mL of methanol to the beaker and stir thoroughly. Stir at room temperature for 6h and then centrifuge. Wash with methanol to obtain ZIF-67. Add 4g of ZIF-67 to the beaker and add 1g of H3PMo 12 O 40 and deionized water for mixing and stirring, and the stirring process parameters include: temperature of 25° C., rotation speed of 800 r / min, time of 2 h, and finally centrifugation and drying to obtain a heteropoly acid-modified ZIF-67 complex.

[0091] (2) Preparation of sulfonated polyfluorene biphenyl indole

[0092] Pour biphenyl and fluorene into a three-necked flask, then add 20g of dichloromethane to completely dissolve the monomers, then slowly drop trifluoroacetic acid and trifluoromethylbissulfonyl imide into the flask and react in an ice bath at 0°C. After reacting for 12 hours, precipitate in methanol to obtain polyfluorene biphenyl indole. Add tetrabutylammonium bromide and polyfluorene biphenyl indole to a three-necked flask and dissolve them in dimethyl sulfoxide. Then fill the three-necked flask with nitrogen atmosphere, then add potassium hydroxide and 1,3-propane sulfonone to react, react at 80°C for 4 hours, and finally pour the solution into methanol to precipitate the reaction product to obtain sulfonated polyfluorene biphenyl indole.

[0093] (3) Proton exchange membrane preparation

[0094] Take a piece of commercial PTFE and place it in a culture dish. Take 1g of sulfonated polyfluorene biphenyl indole and 1g of heteropoly acid modified ZIF-67 and add them to the water / alcohol mixture. After stirring evenly, slowly drip the mixed solution into the culture dish to allow the solution to slowly penetrate into the gaps of PTFE. Finally, tear off the film on the PTFE and perform hot pressing. The process parameters of hot pressing include: hot pressing pressure of 1MPa, hot pressing temperature of 120℃, hot pressing time of 60s, and integrate to obtain a proton exchange membrane.

[0095] The performance tests were conducted on the proton exchange membranes of Examples 1 to 3 and Comparative Examples 1 to 2. Please refer to Table 1 for the results.

[0096] Table 1 Performance of proton exchange membrane

[0097] Serial number Proton conductivity Water absorption size change rate Tensile modulus Example 1 3.9S / cm 0.25％ 88Mpa Example 2 3.7S / cm 0.3％ 82Mpa Example 3 3.9S / cm 0.27％ 86Mpa Comparative Example 1 1.9S / cm 3.2％ 50MPa Comparative Example 2 1.7S / cm 3.5％ 60Mpa

[0098] The proton exchange membranes of Examples 1 to 3 and Comparative Examples 1 to 2 were used for open circuit testing. After running for 500 hours, the open circuit voltage decay was shown in Table 2.

[0099] Table 2 Open circuit voltage decay

[0100] Serial number Open circuit voltage decay Example 1 21mV Example 2 24mV Example 3 23mV Comparative Example 1 49mV Comparative Example 2 51mV

[0101] It can be seen from Table 1 that the proton exchange membrane provided in the present application has high proton conductivity, excellent mechanical properties and low swelling. Experimental tests show that its proton conductivity, tensile modulus and swelling are all improved. It can be seen from Table 2 that the proton exchange membrane still maintains good performance after running for 500 hours in the actual open circuit test.

[0102] One or more technical solutions in the embodiments of the present application also have at least the following technical effects or advantages:

[0103] (1) The active component based on sulfonated polyfluorene biphenyl indole and heteropoly acid modified ZIF-67 provided in the present application has excellent hydrophilicity and alcohol affinity, and has good compatibility with PTFE, which is conducive to processing to form a proton exchange membrane;

[0104] (2) Heteropolyacid is a cluster hydrate with a Keggin structure, which can form a hydrated crystal structure with water, provide high proton conductivity and manage water. However, it cannot exist stably in a strong acidic environment. The functionalized MOF structure can fix heteropolyacids and enable them to exert their effects in a strong acidic environment. MOF materials have a high specific surface area and organic ligands (amino groups, sulfonic acid groups) that can significantly enhance proton conductivity and can easily complex with heteropolyacids to form complexes;

[0105] (3) Polyfluorene biphenyl indole is a polymer with an aromatic skeleton structure. It has excellent amphiphilicity and can penetrate into the pores of the PTFE skeleton. Polyfluorene biphenyl indole is sulfonated to further improve the proton conductivity of the proton exchange membrane.

[0106] (4) The proton exchange membrane provided in the present application has excellent mechanical durability, high proton conductivity, and ultra-thin characteristics, and can reduce membrane expansion while improving mechanical strength, ductility, and chemical stability.

[0107] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A proton exchange membrane, characterized in that: The proton exchange membrane comprises a substrate having a porous structure, wherein the pores of the substrate contain active components, and the active components include: a MOF material modified by a heteropoly acid; The weight ratio of the heteropoly acid to the MOF material is 1:(1-3).

2. The proton exchange membrane according to claim 1, characterized in that The heteropoly acid includes at least one of the following: phosphotungstic heteropoly acid and phosphomolybdic heteropoly acid.

3. The proton exchange membrane according to claim 1, characterized in that The MOF material includes ZIF-67.

4. The proton exchange membrane according to claim 1, characterized in that The active component also includes: an enhancer, which contains a sulfonic acid group and an aromatic skeleton structure.

5. The proton exchange membrane according to claim 4, characterized in that: The enhancer includes sulfonated polyfluorene biphenyl indole.

6. The proton exchange membrane according to claim 4 or 5, characterized in that: The weight ratio of the heteropolyacid-modified MOF material to the reinforcing agent is (1-2):

1.

7. A method for preparing a proton exchange membrane according to any one of claims 1 to 6, characterized in that: The method comprises: Obtaining a heteropolyacid-modified MOF material; The heteropolyacid-modified MOF material, the enhancer and the first solvent are first mixed, and then the mixture obtained by the first mixing is infiltrated into the pores of the substrate with a porous structure to obtain a proton exchange membrane semi-finished product; The proton exchange membrane semi-finished product is hot-pressed to obtain a proton exchange membrane.

8. The method according to claim 7, characterized in that The heteropolyacid-modified MOF material comprises: The heteropoly acid, the MOF material and the second solvent are mixed for a second time to obtain a heteropoly acid-modified MOF material.

9. The method according to claim 8, characterized in that The process parameters of the second mixing include: temperature of 20°C to 30°C, time of ≥60min, stirring speed of 600r / min to 1000r / min; and / or, The process parameters of the hot pressing include: pressure of 0.8 MPa to 1.2 MPa, temperature of 110° C. to 130° C., and time of 60 s to 90 s.

10. A fuel cell, characterized in that: The fuel cell comprises the proton exchange membrane according to any one of claims 1 to 6.

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