Composite proton exchange membrane as well as preparation method and application thereof

Abstract

The invention provides a composite proton exchange membrane as well as a preparation method and application thereof. The composite proton exchange membrane comprises a polymer porous supporting layer and perfluorinated sulfonic acid resin layers arranged on the surfaces of the two sides of the polymer porous supporting layer. The perfluorosulfonic acid resin layer contains a functional additive, the functional additive comprises a metal oxide-loaded three-dimensional self-supporting material, and the three-dimensional self-supporting material is composed of sulfonated graphene and carbon nanotubes. The functional additive is introduced into the perfluorinated sulfonic acid resin layer, sulfonated graphene with good conductivity and water solubility enables the composite proton exchange membrane to show extremely high functional density in the use process of a battery, and the mechanical strength of the composite proton exchange membrane is improved by introducing the carbon nanotubes with good conductivity and water solubility; and the introduction of the metal oxide prolongs the service life of the composite proton exchange membrane. Therefore, by introducing the functional additive, the electrical property and the service life of the composite proton exchange membrane are remarkably improved, and the composite proton exchange membrane has a good development prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cell proton exchange membrane preparation, and specifically relates to a composite proton exchange membrane and a preparation method and application thereof. Background Art

[0002] Proton exchange membrane fuel cells (PEMFC) have important advantages such as high energy conversion efficiency, zero emissions, and fast startup speed. In the current preparation of proton exchange membranes, the commonly used perfluorosulfonic acid resin material (PFSR) has low mechanical strength, and the thin pure PFSR membrane is difficult to be used in the working environment of fuel cells. Therefore, porous substrate materials such as expanded polytetrafluoroethylene (ePTFE) and polyvinylidene fluoride (PVDF) are often introduced to improve the mechanical properties of membrane proton exchange membranes.

[0003] Expanded polytetrafluoroethylene (ePTFE) reinforced proton exchange membrane has the advantages of small thickness, high mechanical strength, and good shape stability. However, since ePTFE itself is a non-proton conductor, introducing it into the proton exchange membrane will reduce the proton conductivity of the composite proton exchange membrane to a certain extent, and there is a problem of poor compatibility between the hydrophilic perfluorosulfonic acid resin and the hydrophobic ePTFE. Therefore, during the use of the proton exchange membrane, the resin will expand / contract, while the size of ePTFE is relatively stable. This difference can easily lead to cracks, delamination, and even peeling at the interface, and the mechanical properties will decrease. In addition, the performance of the ePTFE-reinforced proton exchange membrane is sensitive to environmental humidity. It is easy to cause the performance of the fuel cell to deteriorate and the working life to drop sharply.

[0004] Therefore, how to improve the mechanical strength and electrical properties of the proton exchange membrane and increase the service life of the proton exchange membrane is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a composite proton exchange membrane and its preparation method and application. The present invention introduces functional additives into the perfluorosulfonic acid resin layer, wherein the sulfonated graphene with good electrical conductivity and water solubility enables the composite proton exchange membrane to exhibit extremely high functional density during battery use, the introduction of carbon nanotubes with good electrical conductivity and water solubility improves the mechanical strength of the composite proton exchange membrane, and the introduction of metal oxides prolongs the service life of the composite proton exchange membrane. Therefore, the introduction of the functional additive greatly improves the electrical properties and service life of the composite proton exchange membrane, and has good development prospects.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a composite proton exchange membrane, comprising a polymer porous support layer and a perfluorosulfonic acid resin layer disposed on both side surfaces of the polymer porous support layer.

[0008] The perfluorosulfonic acid resin layer contains functional additives, which include three-dimensional self-supporting materials loaded with metal oxides, and the three-dimensional self-supporting materials are composed of sulfonated graphene and carbon nanotubes.

[0009] The present invention introduces functional additives into the perfluorosulfonic acid resin layer, wherein the sulfonated graphene with good electrical conductivity and water solubility enables the composite proton exchange membrane to exhibit extremely high functional density during battery use, the introduction of carbon nanotubes with good electrical conductivity and water solubility improves the mechanical strength of the composite proton exchange membrane, and the introduction of metal oxides prolongs the service life of the composite proton exchange membrane. Therefore, the introduction of the functional additives greatly improves the electrical properties and service life of the composite proton exchange membrane, and has good development prospects.

[0010] In the present invention, sulfonated graphene is the product of converting the surface functional groups of graphene (such as hydroxyl or carboxyl) into sulfonic acid groups. Through this functionalization, graphene obtains more special properties and application functions, such as high hydrophilicity, high conductivity, abundant active sites and large specific surface area.

[0011] In the present invention, sulfonated graphene and carbon nanotubes are used in coordination to construct a support matrix of metal oxide, which can provide good mechanical support for the metal oxide, effectively improve the electronic transmission performance of the metal oxide, form a continuous conductive network, and reduce the resistance of the composite material; secondly, the two-dimensional sheet structure of the sulfonated graphene and the one-dimensional tubular structure of the carbon nanotube are combined, and the presence of the sulfonated groups in the composite structure increases the proton transmission capacity of the membrane and improves the electrical conductivity of the membrane; thirdly, a three-dimensional self-supporting material loaded with metal oxide is introduced into the membrane, and on the basis of improving the mechanical strength of the composite membrane, the introduction of the metal oxide eliminates the unstable groups in the membrane, thereby greatly improving the service life of the membrane.

[0012] In the present invention, in terms of electrochemical performance, due to the introduction of the special structure of sulfonated graphene, the composite membrane exhibits extremely high functional density during the use of batteries or battery stacks; the introduction of multi-walled carbon nanotubes provides the composite membrane with better mechanical strength; the introduction of metal oxides in the composite membrane makes the composite membrane have a longer service life.

[0013] Preferably, the polymer porous support layer comprises an expanded polytetrafluoroethylene layer.

[0014] Preferably, the porosity of the polymer porous support layer is 50-95%, for example, 50%, 60%, 70%, 80%, 90% or 95%, etc., preferably 60-92%, and more preferably 70-90%.

[0015] Preferably, the thickness of the composite proton exchange membrane is 15-30 μm, for example, it can be 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm or 30 μm, etc., preferably 15-25 μm, and more preferably 15-20 μm.

[0016] Preferably, the single-sided thickness of the perfluorosulfonic acid resin layer is 2-8 μm, for example, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm or 8 μm.

[0017] Preferably, in the perfluorosulfonic acid resin layer, the exchange capacity of the perfluorosulfonic acid resin is 0.9-1.25 mmol / g, for example, 0.9 mmol / g, 1 mmol / g, 1.1 mmol / g, 1.15 mmol / g, 1.2 mmol / g or 1.25 mmol / g, etc., preferably 1-1.2 mmol / g, and more preferably 1.05-1.2 mmol / g.

[0018] In the present invention, the selection of perfluorosulfonic acid resin with a suitable exchange capacity is helpful to improve the proton transfer efficiency, optimize the chemical stability of the membrane, improve the mechanical properties of the membrane, and enhance the compatibility with the polymer porous support layer.

[0019] Preferably, the functional additive is a three-dimensional porous structure.

[0020] In the present invention, the functional additives with a three-dimensional porous structure can, on the one hand, provide more conduction channels and provide additional paths for the conduction of protons, thereby effectively improving the proton conductivity; on the other hand, they can enhance the toughness and deformation resistance of the perfluorosulfonic acid resin layer; on the other hand, they can significantly increase the contact area between the perfluorosulfonic acid resin layer and the reactants, so that the chemical reaction can proceed more fully, which is beneficial to improving the reaction rate and efficiency.

[0021] Preferably, the metal oxide comprises manganese dioxide.

[0022] Preferably, based on the mass of the composite proton exchange membrane, the mass fraction of the metal oxide is 0.5-5wt%, for example, it can be 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt% or 4wt%, etc., preferably 1-4wt%, and more preferably 2-3wt%.

[0023] In the present invention, a suitable amount of metal oxide is introduced into the composite proton exchange membrane, which can effectively prolong the service life of the proton exchange membrane.

[0024] Preferably, the carbon nanotubes include multi-walled carbon nanotubes.

[0025] In the present invention, multi-walled carbon nanotubes (MWCNTs) are carbon nanomaterials formed by multiple layers of graphene sheets arranged in concentric cylindrical shapes. Multi-walled carbon nanotubes have excellent mechanical properties, electrical conductivity and thermal conductivity.

[0026] Preferably, the mass ratio of the sulfonated graphene to the carbon nanotubes is (20-50):(50-80), wherein the selection range of the sulfonated graphene "20-50" can be, for example, 20, 25, 30, 35, 40, 45 or 50, etc., and the selection range of the carbon nanotubes "50-80" can be, for example, 50, 60, 70 or 80, etc.

[0027] In a second aspect, the present invention provides a method for preparing the composite proton exchange membrane as described in the first aspect, the preparation method comprising the following steps:

[0028] Preparation of three-dimensional self-supporting materials composed of sulfonated graphene and carbon nanotubes.

[0029] The three-dimensional self-supporting material and a metal oxide source are mixed and subjected to a hydrothermal reaction to obtain a functional additive.

[0030] The functional additive is mixed with a perfluorosulfonic acid resin solution to prepare a perfluorosulfonic acid resin layer casting solution.

[0031] The perfluorosulfonic acid resin layer casting liquid is coated on both side surfaces of the polymer porous support membrane, and the composite proton exchange membrane is obtained after drying.

[0032] Preferably, the method for preparing the three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes comprises the following steps:

[0033] The sulfonated graphene, carbon nanotubes and a solvent are mixed and then vacuum freeze-dried to obtain the three-dimensional self-supporting material.

[0034] In the present invention, the effects of vacuum freeze-drying are: 1) this drying method can maintain the three-dimensional network structure of the material to the greatest extent, preventing the structure from being destroyed due to shrinkage or collapse when the solvent is removed, thereby ensuring that the material has good self-supporting performance and specific physical and chemical properties; 2) by controlling the process parameters of vacuum freeze-drying, the desired three-dimensional structure is obtained.

[0035] Exemplarily, the solvent may be, for example, deionized water.

[0036] Preferably, the vacuum degree of the vacuum freeze-drying is 1-10Pa, for example, it can be 1Pa, 3Pa, 5Pa, 7Pa, 9Pa or 10Pa.

[0037] Preferably, the vacuum freeze-drying temperature is -50°C to 80°C, for example, it can be -50°C, -40°C, -20°C, 0°C, 20°C, 40°C, 60°C or 80°C.

[0038] Preferably, the vacuum freeze-drying time is 48-72 h, for example, it can be 48 h, 54 h, 60 h, 66 h or 72 h.

[0039] Preferably, the metal oxide source comprises potassium permanganate.

[0040] Preferably, the temperature of the hydrothermal reaction is 130-180°C, for example, 130°C, 140°C, 150°C, 160°C, 170°C or 180°C.

[0041] Preferably, the hydrothermal reaction time is 6-24 h, for example, 6 h, 12 h, 18 h or 24 h.

[0042] Preferably, the method for preparing the perfluorosulfonic acid resin solution comprises:

[0043] The perfluorosulfonic acid resin mother liquid is dried, and then the dried perfluorosulfonic acid resin is dissolved in an organic solvent to obtain the perfluorosulfonic acid resin solution.

[0044] It should be noted that the perfluorosulfonic acid resin mother liquor can be purchased from outside or produced by itself, and the alcohol solvent can be any one of ethanol, propanol, isopropanol and ethylene glycol or a mixture of two of them.

[0045] In the present invention, the purposes of adopting the above method are: 1) removing impurities and moisture; 2) the perfluorosulfonic acid resin obtained after drying can be combined with a high boiling point solvent or a required solvent to obtain a perfluorosulfonic acid resin solution with uniform performance; 3) the concentration of the perfluorosulfonic acid resin solution can be effectively adjusted; 4) it is helpful to improve the stability and uniformity of the solution, providing a better basis for subsequent processing and application.

[0046] In the present invention, the purpose of drying is to remove the solvent, such as water, in the perfluorosulfonic acid resin mother liquor.

[0047] Preferably, the resin content in the perfluorosulfonic acid resin mother solution is 5-20wt%, for example, 5wt%, 10wt%, 15wt% or 20wt%.

[0048] Preferably, the organic solvent includes any one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC) solvent or dimethyl sulfoxide (DMSO) or a combination of at least two thereof.

[0049] Preferably, the functional additive and the perfluorosulfonic acid resin solution are mixed with ultrasound, and the ultrasound duration is 2-4 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0050] Preferably, the coating method comprises a dipping method.

[0051] Preferably, the drying temperature is 70-100°C, for example, 70°C, 80°C, 90°C or 100°C.

[0052] Preferably, the drying time is 18-24 hours, for example, it can be 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours.

[0053] Preferably, the drying is vacuum drying.

[0054] Preferably, the preparation method comprises the following steps:

[0055] (1) adding sulfonated graphene to deionized water, and ultrasonically treating it for 2-6 hours (for example, 2 hours, 3 hours, 4 hours, 5 hours or 6 hours, etc.) to obtain a sulfonated graphene dispersion, adding multi-walled carbon nanotubes to the sulfonated graphene dispersion, and ultrasonically treating it for 1-4 hours (for example, 1 hour, 2 hours, 3 hours or 4 hours, etc.) to obtain a mixed solution of sulfonated graphene and multi-walled carbon nanotubes; wherein the mass volume ratio of sulfonated graphene, multi-walled carbon nanotubes and deionized water is (20-100) mg:(10-40 )mg:(20-100)mL (wherein, the selection range of sulfonated graphene "(20-100)mg" can be, for example, 20mg, 40mg, 60mg, 80mg or 100mg, etc., the selection range of multi-walled carbon nanotubes "(10-40)mg" can be, for example, 10mg, 20mg, 30mg or 40mg, etc., and the selection range of deionized water "(20-100)mL" can be, for example, 20mL, 40mL, 60mL, 80mL or 100mL, etc.).

[0056] The mixed solution is ultra-low temperature stored at -70°C to -90°C (for example, -70°C, -75°C, -80°C, -85°C or -90°C, etc.) for 36-48h (for example, 36h, 42h or 48h, etc.), and then vacuum freeze-dried for 48-72h to obtain a three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes; wherein the vacuum degree of vacuum freeze-drying is 1-10Pa, and the temperature of vacuum freeze-drying is -50°C to 80°C.

[0057] (2) adding a metal oxide source into deionized water, and then adding the three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes, and stirring for 0.5-2h (for example, 0.5h, 1h, 1.5h or 2h, etc.) to obtain a mixed solution; wherein the mass volume ratio of the metal oxide source to the deionized water is (50-100)mg:(20-100)mL (wherein, the selection range of the metal oxide source "(50-100)mg" can be, for example, 50mg, 60mg, 70mg, 80mg, 90mg or 100mg, etc., and the selection range of the deionized water "(20-100)mL" can be, for example, 20mL, 40mL, 60mL, 80mL or 100mL, etc.).

[0058] The mixed solution is subjected to a hydrothermal reaction at 130-180°C for 6-24h, and then cooled (for example, by natural cooling), filtered (for example, by vacuum filtration) and washed (the detergent includes deionized water and / or anhydrous ethanol), and dried at 50-70°C (for example, 50°C, 60°C or 70°C, etc.) for 24-48h (for example, 24h, 30h, 36h, 42h or 48h, etc.) to obtain a functional additive.

[0059] (3) evaporating the solvent from a perfluorosulfonic acid resin mother liquor having a perfluorosulfonic acid resin content of 5-20% at 50-100° C. (for example, 50° C., 60° C., 70° C., 80° C., 90° C. or 100° C.), and then redissolving the perfluorosulfonic acid resin obtained after evaporation in an organic solvent to obtain a perfluorosulfonic acid resin solution; wherein the volume ratio of the perfluorosulfonic acid resin mother liquor to the organic solvent is (15-25):(100-200) (wherein the selection range of the perfluorosulfonic acid resin mother liquor "15-25" can be, for example, 15, 20 or 25, and the selection range of the organic solvent "100-200" can be, for example, 100, 120, 140, 160, 180 or 200, etc.).

[0060] The functional additive is added to the perfluorosulfonic acid resin solution, and ultrasonic treatment is performed for 2-4 hours to obtain a perfluorosulfonic acid resin layer casting liquid; wherein the mass volume ratio of the functional additive to the perfluorosulfonic acid resin solution is (5-30) mg:(100-200) mL (wherein, the selection range of the functional additive "(0.5-30) mg" can be, for example, 5 mg, 10 mg, 15 mg, 20 mg, 25 mg or 30 mg, etc., and the selection range of the perfluorosulfonic acid resin solution "(100-200) mL" can be, for example, 100 mL, 120 mL, 140 mL, 160 mL, 180 mL or 200 mL, etc.).

[0061] (4) Preheating the perfluorosulfonic acid resin layer casting liquid and the mold to 30-50°C (for example, 30°C, 40°C or 50°C, etc.), respectively, and then placing the polymer porous support membrane in the mold, dripping the preheated perfluorosulfonic acid resin layer casting liquid into the mold and immersing the polymer porous support membrane, and then vacuum drying at a temperature of 70-100°C (for example, 70°C, 80°C, 90°C or 100°C, etc.) for 18-24h (for example, 18h, 19h, 20h, 21h, 22h, 23h or 24h, etc.) to obtain the composite proton exchange membrane.

[0062] In a third aspect, the present invention provides a use of the composite proton exchange membrane as described in the first aspect in a fuel cell.

[0063] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] The present invention introduces functional additives into the perfluorosulfonic acid resin layer, wherein the sulfonated graphene with good electrical conductivity and water solubility enables the composite proton exchange membrane to exhibit extremely high functional density during battery use, the introduction of carbon nanotubes with good electrical conductivity and water solubility improves the mechanical strength of the composite proton exchange membrane, and the introduction of metal oxides prolongs the service life of the composite proton exchange membrane. Therefore, the introduction of the functional additives greatly improves the electrical properties and service life of the composite proton exchange membrane, and has good development prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 This is a schematic diagram of the structure of the composite proton exchange membrane provided by the present invention.

[0067] Wherein: 1- expanded polytetrafluoroethylene support layer; 2- perfluorosulfonic acid resin layer. DETAILED DESCRIPTION

[0068] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only used to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0069] Example 1

[0070] This embodiment provides a composite proton exchange membrane, and its structural schematic diagram is as follows Figure 1 As shown, it includes an expanded polytetrafluoroethylene support layer 1 and perfluorosulfonic acid resin layers 2 arranged on both side surfaces of the expanded polytetrafluoroethylene support layer 1.

[0071] The perfluorosulfonic acid resin layer 2 contains a functional additive with a three-dimensional porous structure. The functional additive includes a three-dimensional self-supporting material loaded with manganese dioxide. The three-dimensional self-supporting material consists of sulfonated graphene and multi-walled carbon nanotubes.

[0072] The porosity of the expanded polytetrafluoroethylene support layer 1 is 87-90%, and the thickness is 4-10 μm; the single-side thickness of the perfluorosulfonic acid resin layer 2 is 5-7 μm; and the thickness of the composite proton exchange membrane is 18-20 μm.

[0073] In the perfluorosulfonic acid resin layer 2, the exchange capacity of the perfluorosulfonic acid resin is 1.1 mmol / g; based on the mass of the composite proton exchange membrane, the mass fraction of manganese dioxide is 2 wt%; and the mass ratio of sulfonated graphene to multi-walled carbon nanotubes is 50:50.

[0074] This embodiment also provides a method for preparing the composite proton exchange membrane, comprising the following steps:

[0075] (1) 60 mg of sulfonated graphene was added to 60 mL of deionized water, and ultrasonic treatment was performed for 4 h to obtain a sulfonated graphene dispersion, 25 mg of multi-walled carbon nanotubes was added to the sulfonated graphene dispersion, and ultrasonic treatment was performed for 2.5 h to obtain a mixed solution of sulfonated graphene and multi-walled carbon nanotubes; wherein the mass volume ratio of sulfonated graphene, multi-walled carbon nanotubes and deionized water was 60 mg:25 mg:60 mL.

[0076] The mixed liquid was ultra-low temperature stored at -80°C for 42 hours, and then vacuum freeze-dried for 60 hours to obtain a three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes; wherein the vacuum degree of vacuum freeze-drying was 1Pa, and the temperature of vacuum freeze-drying was -50°C.

[0077] (2) 75 mg of potassium permanganate was added to 60 mL of deionized water, and then the three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes was added, and stirred for 1 hour to obtain a mixed solution; wherein the mass volume ratio of potassium permanganate to deionized water was 75 mg:60 mL.

[0078] The mixed solution was added into a hydrothermal reactor, and the mixed solution was subjected to a hydrothermal reaction at 150°C for 15 hours. After the reaction, the mixed solution was naturally cooled to room temperature (25°C), and then vacuum filtered. Subsequently, the mixed solution was washed with deionized water and anhydrous ethanol respectively, and then dried at 60°C for 36 hours to obtain a functional additive.

[0079] (3) 20 mL of a perfluorosulfonic acid resin mother liquor having a perfluorosulfonic acid resin content of 15% is evaporated to dryness with the solvent ethanol at 75° C., and then the perfluorosulfonic acid resin obtained after evaporation is redissolved in 150 mL of a DMF solvent to obtain a perfluorosulfonic acid resin solution; wherein the volume ratio of the perfluorosulfonic acid resin mother liquor to the DMF solvent is 20:150.

[0080] 15 mg of the functional additive was added to the perfluorosulfonic acid resin solution, and ultrasonic treatment was performed for 3 hours to obtain a perfluorosulfonic acid resin layer casting solution; wherein the mass volume ratio of the functional additive to the perfluorosulfonic acid resin solution was 15 mg:150 mL.

[0081] (4) Preheat the perfluorosulfonic acid resin layer casting liquid and the mold to 40°C respectively. After the mold is evenly heated, place the expanded polytetrafluoroethylene membrane in the mold. Drop the preheated perfluorosulfonic acid resin layer casting liquid into the mold and immerse the expanded polytetrafluoroethylene membrane. Then, place the mold in a vacuum drying oven and vacuum dry it at 85°C for 21 hours to completely evaporate the solvent, thereby obtaining a composite proton exchange membrane.

[0082] Example 2

[0083] This embodiment provides a composite proton exchange membrane, including an expanded polytetrafluoroethylene support layer, and perfluorosulfonic acid resin layers arranged on both side surfaces of the expanded polytetrafluoroethylene support layer.

[0084] The perfluorosulfonic acid resin layer contains a functional additive with a three-dimensional porous structure. The functional additive includes a three-dimensional self-supporting material loaded with manganese dioxide. The three-dimensional self-supporting material consists of sulfonated graphene and multi-walled carbon nanotubes.

[0085] The porosity of the expanded polytetrafluoroethylene support layer is 85-88%, and the thickness is 5-14 μm; the single-side thickness of the perfluorosulfonic acid resin layer is 3-5 μm; and the thickness of the composite proton exchange membrane is 15-20 μm.

[0086] In the perfluorosulfonic acid resin layer, the exchange capacity of the perfluorosulfonic acid resin is 1.05 mmol / g; based on the mass of the composite proton exchange membrane, the mass fraction of manganese dioxide is 1wt%; and the mass ratio of sulfonated graphene to multi-walled carbon nanotubes is 20:80.

[0087] This embodiment also provides a method for preparing the composite proton exchange membrane, comprising the following steps:

[0088] (1) 20 mg of sulfonated graphene was added to 60 mL of deionized water, and ultrasonic treatment was performed for 2 h to obtain a sulfonated graphene dispersion, 40 mg of multi-walled carbon nanotubes was added to the sulfonated graphene dispersion, and ultrasonic treatment was performed for 1 h to obtain a mixed solution of sulfonated graphene and multi-walled carbon nanotubes; wherein the mass volume ratio of sulfonated graphene, multi-walled carbon nanotubes and deionized water was 20 mg:40 mg:60 mL.

[0089] The mixed liquid was ultra-low temperature stored at -70°C for 36 hours, and then vacuum freeze-dried for 48 hours to obtain a three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes; wherein the vacuum degree of vacuum freeze-drying was 10Pa, and the temperature of vacuum freeze-drying was -20°C.

[0090] (2) 50 mg of potassium permanganate was added to 100 mL of deionized water, and then a three-dimensional self-supporting material consisting of sulfonated graphene and carbon nanotubes was added, and stirred for 1.5 hours to obtain a mixed solution; wherein the mass volume ratio of potassium permanganate to deionized water was 50 mg:100 mL.

[0091] The mixed solution was added into a hydrothermal reactor, and the mixed solution was subjected to a hydrothermal reaction at 130°C for 24 hours. After the reaction, the mixed solution was naturally cooled to room temperature (25°C), and then vacuum filtered. Subsequently, the mixed solution was washed with deionized water and anhydrous ethanol respectively, and then dried at 50°C for 48 hours to obtain a functional additive.

[0092] (3) 15 mL of a perfluorosulfonic acid resin mother liquor having a perfluorosulfonic acid resin content of 20% is evaporated to dryness at 50° C., and then the perfluorosulfonic acid resin obtained after evaporation is redissolved in 100 mL of a DMF solvent to obtain a perfluorosulfonic acid resin solution; wherein the volume ratio of the perfluorosulfonic acid resin mother liquor to the DMF solvent is 15:100.

[0093] 5 mg of the functional additive was added to the perfluorosulfonic acid resin solution, and ultrasonic treatment was performed for 2 hours to obtain a perfluorosulfonic acid resin layer casting solution; wherein the mass volume ratio of the functional additive to the perfluorosulfonic acid resin solution was 5 mg:100 mL.

[0094] (4) Preheat the perfluorosulfonic acid resin layer casting liquid and the mold to 30°C respectively. After the mold is evenly heated, place the expanded polytetrafluoroethylene membrane in the mold. Drop the preheated perfluorosulfonic acid resin layer casting liquid into the mold and immerse the expanded polytetrafluoroethylene membrane. Then, place the mold in a vacuum drying oven and vacuum dry it at 70°C for 24 hours to completely evaporate the solvent, thereby obtaining a composite proton exchange membrane.

[0095] Example 3

[0096] This embodiment provides a composite proton exchange membrane, including an expanded polytetrafluoroethylene support layer, and perfluorosulfonic acid resin layers arranged on both side surfaces of the expanded polytetrafluoroethylene support layer.

[0097] The perfluorosulfonic acid resin layer contains a functional additive with a three-dimensional porous structure. The functional additive includes a three-dimensional self-supporting material loaded with manganese dioxide. The three-dimensional self-supporting material consists of sulfonated graphene and multi-walled carbon nanotubes.

[0098] The porosity of the expanded polytetrafluoroethylene support layer is 70-73%, and the thickness is 4-10 μm; the single-side thickness of the perfluorosulfonic acid resin layer is 10-12 μm; and the thickness of the composite proton exchange membrane is 28-30 μm.

[0099] In the perfluorosulfonic acid resin layer, the exchange capacity of the perfluorosulfonic acid resin is 1.2 mmol / g; based on the mass of the composite proton exchange membrane, the mass fraction of manganese dioxide is 4wt%; and the mass ratio of sulfonated graphene to multi-walled carbon nanotubes is 100:10.

[0100] This embodiment also provides a method for preparing the composite proton exchange membrane, comprising the following steps:

[0101] (1) 100 mg of sulfonated graphene was added to 60 mL of deionized water, and ultrasonic treatment was performed for 6 h to obtain a sulfonated graphene dispersion, 10 mg of multi-walled carbon nanotubes was added to the sulfonated graphene dispersion, and ultrasonic treatment was performed for 4 h to obtain a mixed solution of sulfonated graphene and multi-walled carbon nanotubes; wherein the mass volume ratio of sulfonated graphene, multi-walled carbon nanotubes and deionized water was 100 mg:10 mg:60 mL.

[0102] The mixed liquid was ultra-low temperature stored at -90°C for 48 hours, and then vacuum freeze-dried for 72 hours to obtain a three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes; wherein the vacuum degree of vacuum freeze-drying was 10Pa, and the temperature of vacuum freeze-drying was -80°C.

[0103] (2) 100 mg of potassium permanganate was added to 20 mL of deionized water, and then a three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes was added, and stirred for 2 hours to obtain a mixed solution; wherein the mass volume ratio of potassium permanganate to deionized water was 100 mg:20 mL.

[0104] The mixed solution was added into a hydrothermal reactor, and the mixed solution was subjected to a hydrothermal reaction at 180°C for 6 hours. After the reaction, the mixed solution was naturally cooled to room temperature (25°C), and then vacuum filtered. Subsequently, the mixed solution was washed with deionized water and anhydrous ethanol respectively, and then dried at 70°C for 24 hours to obtain a functional additive.

[0105] (3) 25 mL of a perfluorosulfonic acid resin mother liquor having a perfluorosulfonic acid resin content of 5% is evaporated to dryness at 100° C., and then the perfluorosulfonic acid resin obtained after evaporation is redissolved in 200 mL of a DMF solvent to obtain a perfluorosulfonic acid resin solution; wherein the volume ratio of the perfluorosulfonic acid resin mother liquor to the DMF solvent is 25:200.

[0106] 30 mg of the functional additive was added to the perfluorosulfonic acid resin solution, and ultrasonic treatment was performed for 4 hours to obtain a perfluorosulfonic acid resin layer casting solution; wherein the mass volume ratio of the functional additive to the perfluorosulfonic acid resin solution was 30 mg:200 mL.

[0107] (4) Preheat the perfluorosulfonic acid resin layer casting liquid and the mold to 50°C respectively. After the mold is evenly heated, place the expanded polytetrafluoroethylene membrane in the mold. Drop the preheated perfluorosulfonic acid resin layer casting liquid into the mold and immerse the expanded polytetrafluoroethylene membrane. Then, place it in a vacuum drying oven and vacuum dry it at 100°C for 18 hours to completely evaporate the solvent to obtain a composite proton exchange membrane.

[0108] Example 4

[0109] The difference between this embodiment and embodiment 1 is that the mass volume ratio of the functional additive and the perfluorosulfonic acid resin solution in step (3) is 0.1 mg:200 mL.

[0110] The rest of the preparation methods and parameters were the same as those in Example 1.

[0111] Example 5

[0112] The difference between this embodiment and embodiment 1 is that the mass volume ratio of the functional additive and the perfluorosulfonic acid resin solution in step (3) is 35 mg:100 mL.

[0113] The rest of the preparation methods and parameters were the same as those in Example 1.

[0114] Example 6

[0115] The difference between this embodiment and embodiment 1 is that the amount of potassium permanganate added in step (2) is adjusted so that the mass fraction of manganese dioxide (based on the mass of the composite proton exchange membrane) is 0.1 wt %.

[0116] The rest of the preparation methods and parameters were the same as those in Example 1.

[0117] Example 7

[0118] The difference between this embodiment and embodiment 1 is that the amount of potassium permanganate added in step (2) is adjusted so that the mass fraction of manganese dioxide (based on the mass of the composite proton exchange membrane) is 6 wt %.

[0119] The rest of the preparation methods and parameters were the same as those in Example 1.

[0120] Example 8

[0121] The difference between this embodiment and embodiment 1 is that the amount of sulfonated graphene in step (1) is adjusted so that the mass ratio of sulfonated graphene to multi-walled carbon nanotubes in the perfluorosulfonic acid resin layer is 20:90.

[0122] The rest of the preparation methods and parameters were the same as those in Example 1.

[0123] Example 9

[0124] The difference between this embodiment and embodiment 1 is that the amount of sulfonated graphene in step (1) is adjusted so that the mass ratio of sulfonated graphene to multi-walled carbon nanotubes in the perfluorosulfonic acid resin layer is 120:10.

[0125] The rest of the preparation methods and parameters were the same as those in Example 1.

[0126] Comparative Example 1

[0127] The difference between this comparative example and Example 1 is that the functional additive does not contain manganese dioxide.

[0128] The rest of the preparation methods and parameters were the same as those in Example 1.

[0129] Comparative Example 2

[0130] The difference between this comparative example and Example 1 is that the functional additive does not contain sulfonated graphene.

[0131] The rest of the preparation methods and parameters were the same as those in Example 1.

[0132] Comparative Example 3

[0133] The difference between this comparative example and Example 1 is that the functional additive does not contain multi-walled carbon nanotubes.

[0134] The rest of the preparation methods and parameters were the same as those in Example 1.

[0135] Comparative Example 4

[0136] The difference between this comparative example and Example 1 is that no functional additive is contained.

[0137] The rest of the preparation methods and parameters were the same as those in Example 1.

[0138] Performance Testing

[0139] The composite proton exchange membranes provided in the above embodiments and comparative examples were tested for tensile strength, functional density and service life.

[0140] The test method for tensile strength includes: cutting a sample (long strip, 10 mm wide and 100 mm long) from the composite proton exchange membrane; installing the sample on the fixture of the tensile testing machine to ensure that the fixture clamps the sample evenly and does not damage the sample; stretching the sample at a stretching speed of 5 mm / min, recording the tension and elongation of the sample during the stretching process, and calculating the tensile strength of the composite proton exchange membrane (maximum tension divided by the initial cross-sectional area of ​​the sample).

[0141] The test method for functional density includes: determining the proton conductivity by the AC impedance method, that is, assembling the composite proton exchange membrane into a test cell, and introducing hydrogen and nitrogen into the test cell under the conditions of 80°C and 90% relative humidity; applying an AC signal (frequency range of 1Hz to 1MHz) through an electrochemical workstation, measuring the AC impedance of the membrane, and calculating the proton conductivity according to the formula. The higher the proton conductivity, the stronger the ability of the membrane to transfer protons, and the higher the functional density.

[0142] The service life test method includes: conducting a long-term continuous operation test on the composite proton exchange membrane in the fuel cell under the conditions of 90°C, relative humidity above 95% and a potential of 0.9V. When the proton conductivity of the membrane drops to 80% of the initial value, the elapsed time is recorded to evaluate the service life of the membrane.

[0143] The test results are shown in Table 1.

[0144] Table 1

[0145]

[0146]

[0147] analyze:

[0148] As can be seen from the above table, the present invention introduces functional additives into the perfluorosulfonic acid resin layer, wherein the sulfonated graphene with good electrical conductivity and water solubility enables the composite proton exchange membrane to exhibit extremely high functional density during battery use, the introduction of carbon nanotubes with good electrical conductivity and water solubility improves the mechanical strength of the composite proton exchange membrane, and the introduction of metal oxides prolongs the service life of the composite proton exchange membrane. Therefore, the introduction of the functional additive greatly improves the electrical properties and service life of the composite proton exchange membrane, and has good development prospects.

[0149] By comparing Example 1 with Examples 4-5, it can be seen that if the amount of functional additives added to the fluorosulfonic acid resin layer is too small, it will be detrimental to improving the electrical properties and service life of the composite proton exchange membrane; if the amount of functional additives added to the fluorosulfonic acid resin layer is too large, it will lead to a decrease in the electrical properties and service life of the composite proton exchange membrane.

[0150] By comparing Example 1 with Examples 6-7, it can be seen that if the mass fraction of manganese dioxide (based on the mass of the composite proton exchange membrane) is too small, it is not conducive to improving the electrical properties and service life of the composite proton exchange membrane; if the mass fraction of manganese dioxide (based on the mass of the composite proton exchange membrane) is too large, it will increase the resistance to proton transmission, thereby reducing the proton conductivity, and ultimately reducing the service life of the proton exchange membrane.

[0151] By comparing Example 1 with Examples 8-9, it can be seen that if the mass ratio of sulfonated graphene to multi-walled carbon nanotubes is too small, the insufficient number of sulfonic acid groups will lead to a decrease in the conduction efficiency of protons in the membrane, a decrease in proton conductivity, and a shortened service life of the proton exchange membrane; if the mass ratio of sulfonated graphene to multi-walled carbon nanotubes is too large, dispersion problems may occur, excessive sulfonated graphene is prone to agglomeration, which may easily lead to a decrease in the tensile strength of the membrane, and excessive sulfonated graphene may occupy too much space, interfering with the formation of the proton conduction network, thereby reducing the proton conductivity, and ultimately reducing the service life of the proton exchange membrane.

[0152] By comparing Example 1 with Comparative Examples 1-4, it can be seen that if the functional additive does not contain manganese dioxide, it is not conducive to significantly improving the service life of the proton exchange membrane; if the functional additive does not contain sulfonated graphene, it is not conducive to significantly improving the proton conductivity of the proton exchange membrane; if the functional additive does not contain multi-walled carbon nanotubes, it is not conducive to the tensile strength of the proton exchange membrane; if the functional additive does not contain functional additives, the performance of the proton exchange membrane is poor.

[0153] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A composite proton exchange membrane, characterized in that: The composite proton exchange membrane comprises a polymer porous support layer and a perfluorosulfonic acid resin layer arranged on both sides of the polymer porous support layer; The perfluorosulfonic acid resin layer contains functional additives, which include three-dimensional self-supporting materials loaded with metal oxides, and the three-dimensional self-supporting materials are composed of sulfonated graphene and carbon nanotubes.

2. The composite proton exchange membrane according to claim 1, characterized in that: The thickness of the composite proton exchange membrane is 15-30 μm, preferably 15-25 μm, and more preferably 15-20 μm; Preferably, the single-sided thickness of the perfluorosulfonic acid resin layer is 2-8 μm; Preferably, in the perfluorosulfonic acid resin layer, the exchange capacity of the perfluorosulfonic acid resin is 0.9-1.25 mmol / g, preferably 1-1.2 mmol / g, and more preferably 1.05-1.2 mmol / g.

3. The composite proton exchange membrane according to claim 1 or 2, characterized in that: The functional additive is a three-dimensional porous structure; Preferably, the metal oxide comprises manganese dioxide; Preferably, based on the mass of the composite proton exchange membrane, the mass fraction of the metal oxide is 0.5-5wt%, preferably 1-4wt%, and more preferably 2-3wt%; Preferably, the carbon nanotubes include multi-walled carbon nanotubes; Preferably, the mass ratio of the sulfonated graphene to the carbon nanotubes is (20-50):(50-80).

4. A method for preparing a composite proton exchange membrane according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: Preparation of three-dimensional self-supporting materials composed of sulfonated graphene and carbon nanotubes; The three-dimensional self-supporting material and a metal oxide source are mixed and subjected to a hydrothermal reaction to obtain a functional additive; The functional additive is mixed with a perfluorosulfonic acid resin solution to prepare a perfluorosulfonic acid resin layer casting solution; The perfluorosulfonic acid resin layer casting liquid is coated on both side surfaces of the polymer porous support membrane, and the composite proton exchange membrane is obtained after drying.

5. The preparation method according to claim 4, characterized in that: The method for preparing the three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes comprises the following steps: Mixing sulfonated graphene, carbon nanotubes and a solvent, and then performing vacuum freeze drying to obtain the three-dimensional self-supporting material; Preferably, the vacuum degree of the vacuum freeze drying is 1-10Pa; Preferably, the vacuum freeze drying temperature is -50°C to 80°C; Preferably, the vacuum freeze-drying time is 48-72 hours.

6. The preparation method according to claim 4 or 5, characterized in that: The temperature of the hydrothermal reaction is 130-180°C; Preferably, the hydrothermal reaction time is 6-24 hours.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The preparation method of the perfluorosulfonic acid resin solution comprises: Drying the perfluorosulfonic acid resin mother liquid, and then dissolving the dried perfluorosulfonic acid resin with an organic solvent to obtain the perfluorosulfonic acid resin solution; Preferably, the resin content in the perfluorosulfonic acid resin mother solution is 5-20wt%; Preferably, the functional additive and the perfluorosulfonic acid resin solution are mixed with ultrasound, and the ultrasound duration is 2-4 hours.

8. The preparation method according to any one of claims 4 to 7, characterized in that: The coating method includes an impregnation method; Preferably, the drying temperature is 70-100°C; Preferably, the drying time is 18-24 hours.

9. The preparation method according to any one of claims 4 to 8, characterized in that: The preparation method comprises the following steps: (1) adding sulfonated graphene to deionized water, ultrasonically treating for 2-6 hours to obtain a sulfonated graphene dispersion, adding multi-walled carbon nanotubes to the sulfonated graphene dispersion, and ultrasonically treating for 1-4 hours to obtain a mixed solution of sulfonated graphene and multi-walled carbon nanotubes; wherein the mass volume ratio of sulfonated graphene, multi-walled carbon nanotubes and deionized water is (20-100) mg:(10-40) mg:(20-100) mL; The mixed solution is ultra-low temperature stored at -70°C to -90°C for 36-48 hours, and then vacuum freeze-dried for 48-72 hours to obtain a three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes; wherein the vacuum degree of vacuum freeze-drying is 1-10Pa, and the temperature of vacuum freeze-drying is -50 to 80°C; (2) adding a metal oxide source to deionized water, and then adding the three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes, and stirring for 0.5-2h to obtain a mixed solution; wherein the mass volume ratio of the metal oxide source to the deionized water is (50-100) mg: (20-100) mL; The mixed solution is subjected to a hydrothermal reaction at 130-180° C. for 6-24 hours, and then cooled, filtered, washed, and dried at 50-70° C. for 24-48 hours to obtain a functional additive; (3) evaporating the solvent from a perfluorosulfonic acid resin mother liquor having a perfluorosulfonic acid resin content of 5-20% at 50-100° C., and then re-dissolving the perfluorosulfonic acid resin obtained after evaporation in an organic solvent to obtain a perfluorosulfonic acid resin solution; wherein the volume ratio of the perfluorosulfonic acid resin mother liquor to the organic solvent is (15-25):(100-200); Adding the functional additive to the perfluorosulfonic acid resin solution and subjecting it to ultrasonic treatment for 2-4 hours to obtain a perfluorosulfonic acid resin layer casting liquid; wherein the mass volume ratio of the functional additive to the perfluorosulfonic acid resin solution is (5-30) mg: (100-200) mL; (4) Preheating the perfluorosulfonic acid resin layer casting liquid and the mold to 30-50° C. respectively, and then placing the polymer porous support membrane in the mold, dripping the preheated perfluorosulfonic acid resin layer casting liquid into the mold and immersing the polymer porous support membrane, and then vacuum drying at a temperature of 70-100° C. for 18-24 hours to obtain the composite proton exchange membrane.

10. Use of the composite proton exchange membrane according to any one of claims 1 to 3 in a fuel cell.

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