A composite proton exchange membrane, its preparation method and application

Abstract

This invention provides a composite proton exchange membrane, its preparation method, and its applications. The composite proton exchange membrane includes a porous polymer support layer and perfluorosulfonic acid resin layers disposed on both sides of the porous polymer support layer. The perfluorosulfonic acid resin layers contain functional additives, including a three-dimensional self-supporting material loaded with metal oxides, which is composed of sulfonated graphene and carbon nanotubes. This invention introduces functional additives into the perfluorosulfonic acid resin layer. The sulfonated graphene, with its good 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 their good conductivity and water solubility, improves the mechanical strength of the composite proton exchange membrane, while the introduction of metal oxides extends its service life. Therefore, the introduction of these functional additives significantly improves the electrical performance and service life of the composite proton exchange membrane, showing promising development prospects.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell proton exchange membrane preparation technology, specifically relating to a composite proton exchange membrane, its preparation method, and its application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) have important advantages such as high energy conversion efficiency, zero emissions, and fast start-up speed. Currently, in the preparation of proton exchange membranes, the commonly used perfluorosulfonic acid resin (PFSR) material has low mechanical strength, and pure PFSR membranes with small thicknesses are difficult to apply to 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 the proton exchange membrane.

[0003] Expanded polytetrafluoroethylene (ePTFE) reinforced proton exchange membranes (PEMs) offer advantages such as thinness, high mechanical strength, and good shape stability. However, because ePTFE itself is a non-proton conductor, its introduction into PEMs can reduce the proton conductivity of the composite PEM to some extent. Furthermore, there is poor compatibility between hydrophilic perfluorosulfonic acid resins and hydrophobic ePTFE. During PEM use, the resin expands / contracts, while ePTFE remains relatively dimensionally stable. This difference can easily lead to cracks, delamination, or even peeling at the interface, resulting in decreased mechanical properties. In addition, the performance of ePTFE-reinforced PEMs is highly sensitive to environmental humidity, which can easily cause performance degradation in fuel cells and a sharp decrease in their service life.

[0004] Therefore, improving the mechanical strength and electrical properties of proton exchange membranes and extending their service life are urgent technical problems that need to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a composite proton exchange membrane, its preparation method, and its applications. This invention introduces functional additives into a perfluorosulfonic acid resin layer. Sulfonated graphene, with its excellent conductivity and water solubility, enables the composite proton exchange membrane to exhibit extremely high functional density during battery use. The introduction of carbon nanotubes, also with excellent conductivity and water solubility, improves the mechanical strength of the composite proton exchange membrane, while the introduction of metal oxides extends its service life. Therefore, the introduction of these functional additives significantly improves the electrical performance and service life of the composite proton exchange membrane, demonstrating promising development prospects.

[0006] To achieve this objective, the present invention adopts the following technical solution:

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

[0008] The perfluorosulfonic acid resin layer contains functional additives, including a three-dimensional self-supporting material loaded with metal oxides, which is composed of sulfonated graphene and carbon nanotubes.

[0009] This invention introduces functional additives into a perfluorosulfonic acid resin layer. The sulfonated graphene, with its excellent conductivity and water solubility, enables the composite proton exchange membrane to exhibit extremely high functional density during battery use. The introduction of carbon nanotubes, also with good conductivity and water solubility, improves the mechanical strength of the composite proton exchange membrane, while the introduction of metal oxides extends its service life. Therefore, the introduction of these functional additives significantly improves the electrical performance and service life of the composite proton exchange membrane, demonstrating promising development prospects.

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

[0011] In this invention, sulfonated graphene and carbon nanotubes are used in synergy to construct a supporting matrix for metal oxides, which can provide good mechanical support for the metal oxides and effectively improve their electron transport performance, forming a continuous conductive network and reducing the resistance of the composite material. Secondly, the combination of the two-dimensional sheet structure of sulfonated graphene and the one-dimensional tubular structure of carbon nanotubes, and the presence of sulfonated groups in the composite structure, increases the proton transport capacity of the membrane and improves its conductivity. Furthermore, the introduction of a three-dimensional self-supporting material loaded with metal oxides into the membrane not only improves the mechanical strength of the composite membrane, but also eliminates unstable groups in the membrane, greatly improving its service life.

[0012] In this 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 battery or stack use; the introduction of multi-walled carbon nanotubes provides the composite membrane with better mechanical strength; and the introduction of metal oxides into the composite membrane results in 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, it can be 50%, 60%, 70%, 80%, 90% or 95%, more 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 thickness of the perfluorosulfonic acid resin layer on one side is 2-8 μm, for example, it can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm or 8 μm.

[0017] Preferably, the perfluorosulfonic acid resin in the perfluorosulfonic acid resin layer has an exchange capacity of 0.9-1.25 mmol / g, for example, it can be 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 this invention, the selection of a perfluorosulfonic acid resin with a suitable exchange capacity helps to improve proton transfer efficiency, optimize the chemical stability of the membrane and improve the mechanical properties of the membrane, and enhance compatibility with the polymer porous support layer.

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

[0020] In this invention, the functional additive with a three-dimensional porous structure can provide more conduction channels, providing additional pathways for proton conduction and thus effectively improving proton conductivity. On the other hand, it can enhance the toughness and deformation resistance of the perfluorosulfonic acid resin layer. Furthermore, it can significantly increase the contact area between the perfluorosulfonic acid resin layer and the reactants, allowing the chemical reaction to proceed more fully and thus improving the reaction rate and efficiency.

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

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

[0023] In this invention, the introduction of a suitable amount of metal oxide into the composite proton exchange membrane can effectively extend the service life of the proton exchange membrane.

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

[0025] In this invention, multi-walled carbon nanotubes (MWCNTs) are carbon nanomaterials composed of multiple layers of graphene sheets arranged in a concentric cylindrical shape. MWCNTs possess excellent mechanical properties, electrical conductivity, and thermal conductivity.

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

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

[0028] A three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes was prepared.

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

[0030] The functional additive and the perfluorosulfonic acid resin solution are mixed to prepare a perfluorosulfonic acid resin layer casting solution.

[0031] The perfluorosulfonic acid resin layer is cast onto both sides of the polymer porous support membrane and dried to obtain the composite proton exchange membrane.

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

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

[0034] In this invention, the role of vacuum freeze-drying is: 1) This drying method can maintain the three-dimensional network structure of the material to the greatest extent and prevent the structure from being destroyed by shrinkage or collapse during solvent removal, thereby ensuring that the material has good self-supporting properties and specific physicochemical properties; 2) By controlling the process parameters of vacuum freeze-drying, the desired three-dimensional structure can be obtained.

[0035] For example, the solvent may be deionized water or the like.

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

[0037] Preferably, the temperature of the vacuum freeze drying 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 hours, for example, 48 hours, 54 hours, 60 hours, 66 hours, or 72 hours.

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

[0040] Preferably, the temperature of the hydrothermal reaction is 130-180℃, for example, it can be 130℃, 140℃, 150℃, 160℃, 170℃ or 180℃.

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

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

[0043] The perfluorosulfonic acid resin mother liquor 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 or produced in-house using alcohol-based perfluorosulfonic acid resin mother liquor. The alcohol solvent can be any one of alcohols such as ethanol, propanol, isopropanol, and ethylene glycol, or a mixture of two of them.

[0045] The purpose of using the above method in this invention is to: 1) remove impurities and moisture; 2) allow the dried perfluorosulfonic acid resin to be combined with a high-boiling-point solvent or the desired solvent to obtain a perfluorosulfonic acid resin solution with uniform performance; 3) effectively adjust the concentration of the perfluorosulfonic acid resin solution; and 4) help improve the stability and uniformity of the solution, providing a better foundation for subsequent processing and application.

[0046] In this invention, the purpose of drying is to remove solvents, such as water, from the perfluorosulfonic acid resin mother liquor.

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

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

[0049] Preferably, the mixing process of the functional additive and the perfluorosulfonic acid resin solution is accompanied by ultrasound, and the ultrasound time is 2-4 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0050] Preferably, the coating method includes an impregnation method.

[0051] Preferably, the drying temperature is 70-100℃, for example, it can be 70℃, 80℃, 90℃ or 100℃.

[0052] Preferably, the drying time is 18-24 hours, for example, 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 includes the following steps:

[0055] (1) Sulfonated graphene is added to deionized water and ultrasonically treated for 2-6 hours (e.g., 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours) to obtain a sulfonated graphene dispersion. Multi-walled carbon nanotubes are added to the sulfonated graphene dispersion and ultrasonically treated for 1-4 hours (e.g., 1 hour, 2 hours, 3 hours, or 4 hours) to obtain a mixture of sulfonated graphene and multi-walled carbon nanotubes. The mass-to-volume ratio of sulfonated graphene, multi-walled carbon nanotubes, and deionized water is (20-100) mg:(10-40) mg. )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 mixture is cryogenically stored at -70°C to -90°C (e.g., -70°C, -75°C, -80°C, -85°C, or -90°C) for 36-48 hours (e.g., 36 hours, 42 hours, or 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 1-10 Pa, and the vacuum freeze-drying temperature is -50°C to 80°C.

[0057] (2) Add the metal oxide source to deionized water, then add the three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes, and stir for 0.5-2h (e.g., 0.5h, 1h, 1.5h or 2h, etc.) to obtain a mixed solution; wherein, the mass-volume ratio of the metal oxide source and 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 6-24 hours. After the reaction, it is cooled (e.g., by natural cooling), filtered (e.g., by vacuum filtration), and washed (the washing agent includes deionized water and / or anhydrous ethanol). It is then dried at 50-70°C (e.g., 50°C, 60°C, or 70°C, etc.) for 24-48 hours (e.g., 24 hours, 30 hours, 36 hours, 42 hours, or 48 hours, etc.) to obtain the functional additive.

[0059] (3) Evaporate the solvent in a perfluorosulfonic acid resin mother liquor with a perfluorosulfonic acid resin content of 5-20% at 50-100℃ (e.g., 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃, etc.), and then redissolve the perfluorosulfonic acid resin obtained after evaporation with 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, etc., 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 subjected to ultrasonic treatment for 2-4 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 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) The perfluorosulfonic acid resin layer casting liquid and the mold are preheated to 30-50℃ (e.g., 30℃, 40℃ or 50℃, etc.). Then, the polymer porous support membrane is placed in the mold. The preheated perfluorosulfonic acid resin layer casting liquid is dripped into the mold and immersed in the polymer porous support membrane. Then, it is vacuum dried at 70-100℃ (e.g., 70℃, 80℃, 90℃ or 100℃, etc.) for 18-24h (e.g., 18h, 19h, 20h, 21h, 22h, 23h or 24h, etc.) to obtain the composite proton exchange membrane.

[0062] Thirdly, the present invention provides an application of the composite proton exchange membrane as described in the first aspect in a fuel cell.

[0063] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

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

[0065] This invention introduces functional additives into a perfluorosulfonic acid resin layer. The sulfonated graphene, with its excellent conductivity and water solubility, enables the composite proton exchange membrane to exhibit extremely high functional density during battery use. The introduction of carbon nanotubes, also with good conductivity and water solubility, improves the mechanical strength of the composite proton exchange membrane, while the introduction of metal oxides extends its service life. Therefore, the introduction of these functional additives significantly improves the electrical performance and service life of the composite proton exchange membrane, demonstrating promising development prospects. Attached Figure Description

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

[0067] Among them, 1-expanded polytetrafluoroethylene support layer; 2-perfluorosulfonic acid resin layer. Detailed Implementation

[0068] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0069] Example 1

[0070] This embodiment provides a composite proton exchange membrane, the structural schematic of which is shown below. Figure 1 As shown, it includes an expanded polytetrafluoroethylene support layer 1 and perfluorosulfonic acid resin layers 2 disposed on both sides of the expanded polytetrafluoroethylene support layer 1.

[0071] The perfluorosulfonic acid resin layer 2 contains functional additives with a three-dimensional porous structure, including a three-dimensional self-supporting material loaded with manganese dioxide, which is composed of sulfonated graphene and multi-walled carbon nanotubes.

[0072] The expanded polytetrafluoroethylene support layer 1 has a porosity of 87-90% and a thickness of 4-10 μm; the perfluorosulfonic acid resin layer 2 has a single-sided thickness of 5-7 μm; and the composite proton exchange membrane has a thickness of 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 above-mentioned composite proton exchange membrane, including the following steps:

[0075] (1) 60 mg of sulfonated graphene was added to 60 mL of deionized water and sonicated for 4 h to obtain a sulfonated graphene dispersion. 25 mg of multi-walled carbon nanotubes were added to the sulfonated graphene dispersion and sonicated for 2.5 h to obtain a mixture of sulfonated graphene and multi-walled carbon nanotubes. The mass-volume ratio of sulfonated graphene, multi-walled carbon nanotubes and deionized water was 60 mg: 25 mg: 60 mL.

[0076] The mixture was cryogenically stored at -80℃ 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. The vacuum degree of the vacuum freeze-drying was 1 Pa, and the vacuum freeze-drying temperature was -50℃.

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

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

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

[0080] 15 mg of functional additive was added to a perfluorosulfonic acid resin solution and subjected to ultrasonic treatment for 3 hours to obtain a perfluorosulfonic acid resin layer casting solution; wherein the mass-volume ratio of functional additive to 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 heated evenly, place the expanded polytetrafluoroethylene membrane in the mold. The preheated perfluorosulfonic acid resin layer casting liquid is dripped into the mold and immersed in the expanded polytetrafluoroethylene membrane. Then, place it in a vacuum drying oven and vacuum dry at 85°C for 21 hours to allow the solvent to evaporate completely, thus 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 disposed on both sides of the expanded polytetrafluoroethylene support layer.

[0084] The perfluorosulfonic acid resin layer contains functional additives with a three-dimensional porous structure, including a three-dimensional self-supporting material loaded with manganese dioxide, which is composed of sulfonated graphene and multi-walled carbon nanotubes.

[0085] The expanded polytetrafluoroethylene support layer has a porosity of 85-88% and a thickness of 5-14 μm; the perfluorosulfonic acid resin layer has a single-sided thickness of 3-5 μm; and the composite proton exchange membrane has a thickness of 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 1 wt%; 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 above-mentioned composite proton exchange membrane, including the following steps:

[0088] (1) Add 20 mg of sulfonated graphene to 60 mL of deionized water and sonicate for 2 h to obtain a sulfonated graphene dispersion. Add 40 mg of multi-walled carbon nanotubes to the sulfonated graphene dispersion and sonicate for 1 h to obtain a mixture of sulfonated graphene and multi-walled carbon nanotubes. The mass-volume ratio of sulfonated graphene, multi-walled carbon nanotubes and deionized water is 20 mg: 40 mg: 60 mL.

[0089] The mixture was cryogenically stored at -70℃ 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. The vacuum degree of the vacuum freeze-drying was 10 Pa, and the vacuum freeze-drying temperature was -20℃.

[0090] (2) Add 50 mg of potassium permanganate to 100 mL of deionized water, then add a three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes, and stir for 1.5 h to obtain a mixed solution; wherein the mass-volume ratio of potassium permanganate to deionized water is 50 mg: 100 mL.

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

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

[0093] 5 mg of functional additive was added to a perfluorosulfonic acid resin solution and subjected to ultrasonic treatment for 2 hours to obtain a perfluorosulfonic acid resin layer casting solution; wherein the mass-volume ratio of functional additive to 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 heated evenly, place the expanded polytetrafluoroethylene membrane in the mold. The preheated perfluorosulfonic acid resin layer casting liquid is dripped into the mold and immersed in the expanded polytetrafluoroethylene membrane. Then, place it in a vacuum drying oven and vacuum dry at 70°C for 24 hours to allow the solvent to evaporate completely, thus 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 disposed on both sides of the expanded polytetrafluoroethylene support layer.

[0097] The perfluorosulfonic acid resin layer contains functional additives with a three-dimensional porous structure, including a three-dimensional self-supporting material loaded with manganese dioxide, which is composed of sulfonated graphene and multi-walled carbon nanotubes.

[0098] The expanded polytetrafluoroethylene support layer has a porosity of 70-73% and a thickness of 4-10 μm; the perfluorosulfonic acid resin layer has a single-sided thickness of 10-12 μm; and the composite proton exchange membrane has a thickness of 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 4 wt%; 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 above-mentioned composite proton exchange membrane, including the following steps:

[0101] (1) Add 100 mg of sulfonated graphene to 60 mL of deionized water and sonicate for 6 h to obtain a sulfonated graphene dispersion. Add 10 mg of multi-walled carbon nanotubes to the sulfonated graphene dispersion and sonicate for 4 h to obtain a mixture of sulfonated graphene and multi-walled carbon nanotubes. The mass-volume ratio of sulfonated graphene, multi-walled carbon nanotubes and deionized water is 100 mg: 10 mg: 60 mL.

[0102] The mixture was cryogenically stored at -90℃ 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. The vacuum degree of the vacuum freeze-drying was 10 Pa, and the vacuum freeze-drying temperature was -80℃.

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

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

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

[0106] 30 mg of functional additive was added to a perfluorosulfonic acid resin solution and subjected to ultrasonic treatment for 4 hours to obtain a perfluorosulfonic acid resin layer casting solution; wherein the mass-volume ratio of functional additive to 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 heated evenly, place the expanded polytetrafluoroethylene membrane in the mold. The preheated perfluorosulfonic acid resin layer casting liquid is dripped into the mold and immersed in the expanded polytetrafluoroethylene membrane. Then, place it in a vacuum drying oven and vacuum dry at 100°C for 18 hours to allow the solvent to evaporate completely, thus obtaining a composite proton exchange membrane.

[0108] Example 4

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

[0110] The remaining preparation methods and parameters are consistent with those in Example 1.

[0111] Example 5

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

[0113] The remaining preparation methods and parameters are consistent with 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 remaining preparation methods and parameters are consistent with 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 remaining preparation methods and parameters are consistent with 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 remaining preparation methods and parameters are consistent with 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 remaining preparation methods and parameters are consistent with 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 remaining preparation methods and parameters are consistent with 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 remaining preparation methods and parameters are consistent with 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 remaining preparation methods and parameters are consistent with those in Example 1.

[0135] Comparative Example 4

[0136] The difference between this comparative example and Example 1 is that it does not contain functional additives.

[0137] The remaining preparation methods and parameters are consistent with those in Example 1.

[0138] Performance testing

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

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

[0141] The functional density testing method includes: determining the proton conductivity using the AC impedance method, which involves assembling the composite proton exchange membrane into a test cell, introducing hydrogen and nitrogen gas into the test cell at 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 membrane's ability to transfer protons, and the higher the functional density.

[0142] The lifespan test method includes: conducting a long-term continuous operation test on the composite proton exchange membrane in the fuel cell under conditions of 90°C, relative humidity above 95% and 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 membrane's lifespan.

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

[0144] Table 1

[0145]

[0146]

[0147] analyze:

[0148] As shown in the table above, this invention introduces functional additives into the perfluorosulfonic acid resin layer. The sulfonated graphene, with its excellent conductivity and water solubility, enables the composite proton exchange membrane to exhibit extremely high functional density during battery use. The introduction of carbon nanotubes, also with good conductivity and water solubility, improves the mechanical strength of the composite proton exchange membrane, while the introduction of metal oxides extends its service life. Therefore, the introduction of these functional additives significantly improves the electrical performance and service life of the composite proton exchange membrane, demonstrating promising development prospects.

[0149] As can be seen from the comparison between Example 1 and Examples 4-5, if the amount of functional additives added to the fluorosulfonic acid resin layer is too small, it will not be conducive to improving the electrical performance 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 performance and service life of the composite proton exchange membrane.

[0150] As can be seen from the comparison between Example 1 and Examples 6-7, if the mass fraction of manganese dioxide (based on the mass of the composite proton exchange membrane) is too small, it will not be conducive to improving the electrical performance 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 transport, thereby reducing the proton conductivity and ultimately reducing the service life of the proton exchange membrane.

[0151] As can be seen from the comparison between Examples 1 and Examples 8-9, 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 proton conduction efficiency within the membrane, a decrease in proton conductivity, and a shortening of the proton exchange membrane's lifespan. 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 can easily lead to a decrease in the tensile strength of the membrane. Furthermore, 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 lifespan of the proton exchange membrane.

[0152] As can be seen from the comparison between Example 1 and Comparative Examples 1-4, 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 is not present, the performance of the proton exchange membrane is poor.

[0153] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in 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 includes a polymer porous support layer and perfluorosulfonic acid resin layers disposed on both sides of the polymer porous support layer. The perfluorosulfonic acid resin layer contains functional additives, including a three-dimensional self-supporting material loaded with manganese dioxide, which is composed of sulfonated graphene and carbon nanotubes. The raw material for preparing the composite proton exchange membrane includes a perfluorosulfonic acid resin solution; The mass-to-volume ratio of the functional additive to the perfluorosulfonic acid resin solution is (5-30) mg:(100-200) mL. Based on the mass of the composite proton exchange membrane, the mass fraction of manganese dioxide is 0.5-5 wt%. The mass ratio of the sulfonated graphene to carbon nanotubes is (20-50):(50-80).

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.

3. The composite proton exchange membrane according to claim 2, characterized in that, The thickness of the composite proton exchange membrane is 15-25 μm.

4. The composite proton exchange membrane according to claim 3, characterized in that, The thickness of the composite proton exchange membrane is 15-20 μm.

5. The composite proton exchange membrane according to claim 1, characterized in that, The thickness of the perfluorosulfonic acid resin layer on one side is 2-8 μm.

6. The composite proton exchange membrane according to claim 1, characterized in that, The perfluorosulfonic acid resin layer has an exchange capacity of 0.9-1.25 mmol / g.

7. The composite proton exchange membrane according to claim 6, characterized in that, The perfluorosulfonic acid resin layer has an exchange capacity of 1-1.2 mmol / g.

8. The composite proton exchange membrane according to claim 7, characterized in that, The perfluorosulfonic acid resin layer has an exchange capacity of 1.05-1.2 mmol / g.

9. The composite proton exchange membrane according to claim 1, characterized in that, The functional additive has a three-dimensional porous structure.

10. The composite proton exchange membrane according to claim 1, characterized in that, Based on the mass of the composite proton exchange membrane, the mass fraction of manganese dioxide is 1-4 wt%.

11. The composite proton exchange membrane according to claim 10, characterized in that, Based on the mass of the composite proton exchange membrane, the mass fraction of manganese dioxide is 2-3 wt%.

12. The composite proton exchange membrane according to claim 1, characterized in that, The carbon nanotubes include multi-walled carbon nanotubes.

13. A method for preparing a composite proton exchange membrane as described in any one of claims 1-12, characterized in that, The preparation method includes the following steps: Preparation of a three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes; The three-dimensional self-supporting material and the metal oxide source are mixed and subjected to a hydrothermal reaction to obtain a functional additive; The functional additive and the perfluorosulfonic acid resin solution are mixed to prepare a perfluorosulfonic acid resin layer casting solution. The perfluorosulfonic acid resin layer is cast onto both sides of the polymer porous support membrane and dried to obtain the composite proton exchange membrane.

14. The preparation method according to claim 13, characterized in that, The preparation method of the three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes includes the following steps: Sulfonated graphene, carbon nanotubes, and a solvent were mixed and then freeze-dried under vacuum to obtain the three-dimensional self-supporting material.

15. The preparation method according to claim 14, characterized in that, The vacuum degree of the vacuum freeze-drying is 1-10 Pa.

16. The preparation method according to claim 14, characterized in that, The temperature for vacuum freeze drying is -50℃ to 80℃.

17. The preparation method according to claim 14, characterized in that, The vacuum freeze-drying time is 48-72 hours.

18. The preparation method according to claim 13, characterized in that, The temperature of the hydrothermal reaction is 130-180℃.

19. The preparation method according to claim 13, characterized in that, The hydrothermal reaction takes 6-24 hours.

20. The preparation method according to claim 13, characterized in that, The preparation method of the perfluorosulfonic acid resin solution includes: The perfluorosulfonic acid resin mother liquor is dried, and then the dried perfluorosulfonic acid resin is dissolved in an organic solvent to obtain the perfluorosulfonic acid resin solution.

21. The preparation method according to claim 20, characterized in that, The resin content in the perfluorosulfonic acid resin mother liquor is 5-20 wt%.

22. The preparation method according to claim 13, characterized in that, The functional additive and perfluorosulfonic acid resin solution are mixed with ultrasound for 2-4 hours.

23. The preparation method according to claim 13, characterized in that, The coating method includes impregnation.

24. The preparation method according to claim 13, characterized in that, The drying temperature is 70-100℃.

25. The preparation method according to claim 13, characterized in that, The drying time is 18-24 hours.

26. The preparation method according to claim 13, characterized in that, The preparation method includes the following steps: (1) Sulfonated graphene is added to deionized water and ultrasonically treated for 2-6 hours to obtain a sulfonated graphene dispersion. Multi-walled carbon nanotubes are added to the sulfonated graphene dispersion and ultrasonically treated for 1-4 hours to obtain a mixture of sulfonated graphene and multi-walled carbon nanotubes. 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 mixture was cryogenically 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 was 1-10 Pa, and the vacuum freeze-drying temperature was -50~80°C. (2) Add the metal oxide source to deionized water, then add the three-dimensional self-supporting material composed of sulfonated graphene and carbon nanotubes, and stir for 0.5-2h to obtain a mixed solution; wherein the mass-volume ratio of the metal oxide source and deionized water is (50-100)mg:(20-100)mL. The mixed solution is subjected to a hydrothermal reaction at 130-180℃ for 6-24 hours. After the reaction, it is cooled, filtered and washed, and then dried at 50-70℃ for 24-48 hours to obtain the functional additive. (3) Evaporate the solvent in the perfluorosulfonic acid resin mother liquor with a perfluorosulfonic acid resin content of 5-20% at 50-100℃, and then redissolve the perfluorosulfonic acid resin obtained after evaporation with an organic solvent to obtain a perfluorosulfonic acid resin solution; wherein the volume ratio of perfluorosulfonic acid resin mother liquor to organic solvent is (15-25):(100-200). The functional additive is added to the perfluorosulfonic acid resin solution and subjected to ultrasonic treatment for 2-4 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 is (5-30) mg:(100-200) mL. (4) The perfluorosulfonic acid resin layer casting liquid and the mold are preheated to 30-50°C respectively. Then the polymer porous support membrane is placed in the mold. The preheated perfluorosulfonic acid resin layer casting liquid is dripped into the mold and immersed in the polymer porous support membrane. Then the membrane is vacuum dried at 70-100°C for 18-24 hours to obtain the composite proton exchange membrane.

27. The application of a composite proton exchange membrane as described in any one of claims 1-12 in a fuel cell.

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