High-current-density-resistant PEM (Proton Exchange Membrane) for electrolysis and preparation method thereof

Abstract

The invention discloses a high-current-density-resistant proton exchange membrane for PEM electrolysis. A proton exchange membrane body sequentially comprises an acid-corrosion-resistant conductive substrate layer, a high-current-density-resistant conductive substrate layer and a high-current-density-resistant conductive substrate layer from an anode side to a cathode side, according to the invention, the conductive substrate layer is used for effective current-sharing heat dissipation, the gradient proton conduction layer is used for guaranteeing efficient proton transfer in a wide humidity range, and the gas diffusion layer is used for realizing rapid directional discharge of gas, so that the membrane can stably operate for more than 1000 hours under the current density of more than or equal to 3 A / cm through the cooperation of the three layers, and excellent high-current-density adaptability is achieved; the gradient design enables the membrane to maintain high proton conductivity in both low-humidity and high-humidity environments; the hydrogen permeability is reduced to 2.0 * 10 <-6 > cm / (cm.s) or below through the super-hydrophobic microstructure gas diffusion layer; the composite structure endows the film with high mechanical strength, the tensile strength is greater than or equal to 40 MPa, and excellent comprehensive performance is achieved; and the material system is corrosion-resistant, the layers are firmly combined through physical and chemical effects, and the interface stability is high.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis technology, specifically to a proton exchange membrane for PEM electrolysis that can withstand high current density and its preparation method. Background Technology

[0002] Proton exchange membrane water electrolysis technology is considered an important way to produce green hydrogen due to its advantages such as high efficiency, fast response and high hydrogen purity. With the decline in the cost of renewable energy electricity and the growth in demand for large-scale hydrogen production, PEM electrolyzers are developing towards higher current density and higher power density in order to improve the hydrogen production rate per unit area and reduce equipment size and cost.

[0003] However, when PEM electrolyzers operate under high voltage and high current density, more stringent requirements are placed on the core component, the proton exchange membrane. Existing commercial proton exchange membranes (such as the DuPont Nafion® series) and their improved versions, such as the five-layer composite membrane disclosed in publication number CN120888977A, perform well under normal operating conditions (such as <2 A / cm²), but reveal the following key problems under high current density: Under high current density, the electrochemical reaction is intense, and the heat generated per unit area increases dramatically, which can easily lead to excessively high local temperature of the membrane, causing thermal degradation of the perfluorosulfonic acid resin skeleton, shedding of sulfonic acid groups, and damage to the proton conduction network.

[0004] The consumption rate of water on the anode side and the generation rate of water on the cathode side are both significantly increased. If the water transport capacity within the membrane is insufficient, a localized dry zone is easily formed near the anode catalyst layer, and the proton conduction resistance increases sharply. At the same time, the cathode side may be "flooded" due to excessively rapid water generation, hindering gas discharge.

[0005] The generation rate and partial pressure of hydrogen and oxygen are significantly increased; if the gas barrier performance of the membrane is insufficient, the cross-permeation of hydrogen and oxygen will intensify, which will not only reduce the purity of hydrogen, but also bring serious safety hazards; the existing membrane anti-permeation structure has limited effectiveness under high gas flux.

[0006] Under the combined stress of high temperature, high humidity, strong acidity, and high gas erosion, membrane materials are prone to swelling and creep. The interlayer interface may peel off during long-term operation, and the microcrack propagation is accelerated, leading to premature membrane failure.

[0007] Therefore, developing a novel proton exchange membrane specifically designed for high current density operating environments, capable of simultaneously addressing challenges related to heat, water, gas management, and mechanical stability, has become a key technological bottleneck driving PEM water electrolysis technology towards higher efficiency and longer lifespan. Summary of the Invention

[0008] The purpose of this invention is to provide a proton exchange membrane for PEM electrolysis that can withstand high current densities and its preparation method. This membrane is particularly suitable for long-term stable operation at high current densities of ≥3 A / cm², and has excellent proton conductivity, extremely low gas permeability, good water balance capability and high mechanical strength, so as to solve the problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a proton exchange membrane for PEM electrolysis with high current density resistance, wherein the proton exchange membrane body comprises, from the anode side to the cathode side, the following components in sequence: The acid-resistant conductive substrate is composed of graphene nanosheets, sulfonated carbon nanotubes, and polytetrafluoroethylene. A gradient proton conduction layer is formed by gradient deposition of at least two perfluorosulfonic acid resin materials with different degrees of sulfonation on the surface of the substrate layer, and the degree of sulfonation decreases from the side closer to the substrate layer to the side farther away. A high-speed gas diffusion layer has an array of oriented conical microchannels on its surface, and the outer surface of the diffusion layer is modified with fluorosilane to be superhydrophobic.

[0010] For example, in the conductive substrate layer, the mass ratio of graphene nanosheets, sulfonated carbon nanotubes and polytetrafluoroethylene is (1-5):(1-4):(85-95); the number of graphene nanosheets is 1-5 layers, and the lateral dimension is 1-10 μm; the degree of sulfonation of the sulfonated carbon nanotubes is 0.8-1.5 mmol / g, the diameter is 5-20 nm, and the length is 5-30 μm.

[0011] For example, the gradient proton conduction layer comprises 2-4 layers of perfluorosulfonic acid resin sublayers with different degrees of sulfonation, and the adjacent sublayers are in a continuous transition structure; the degree of sulfonation of each sublayer ranges from 0.6 to 1.4 meq / g, and the total thickness is 15-30 μm.

[0012] For example, in the conical microchannel array on the surface of the high-speed gas diffusion layer, the bottom diameter of a single conical structure is 8-20 μm, the height is 5-15 μm, and the center-to-center distance between adjacent conical structures is 15-30 μm; the axial angle between the conical structure and the normal to the membrane plane is 0-30°.

[0013] For example, the high-speed gas diffusion layer includes a hydrophobically modified proton-conducting resin layer located on the surface of the conical array structure. The resin layer contains perfluorosulfonic acid resin and a hydrophobic modifier and has a thickness of 0.5-2.0 μm.

[0014] A preparation method, applied to the above-mentioned high current density resistant PEM proton exchange membrane for electrolysis, includes the following steps: S1. Preparation of acid-resistant conductive substrate layer: Graphene nanosheets and sulfonated carbon nanotubes are dispersed in a solvent, polytetrafluoroethylene emulsion is added, and a uniform slurry is formed by high-speed shearing and ultrasonic treatment. The slurry is cast onto the surface of a substrate and then subjected to drying, high-temperature sintering and plasma activation treatment in sequence to obtain a porous conductive substrate layer. S2. Preparation of the gradient proton conduction layer: An electrostatic spray deposition method is used to spray at least two perfluorosulfonic acid resin solutions with different degrees of sulfonation onto the surface of the substrate layer in descending order of sulfonation degree. Each layer is cured at low temperature after spraying to form a continuous gradient proton conduction layer. S3. Preparation of high-speed gas diffusion layer: An array of oriented conical microchannels is constructed on the surface of the gradient proton conduction layer using laser etching technology; A coating liquid containing perfluorosulfonic acid resin and hydrophobic modifier is prepared and coated onto a surface with a conical array. After curing, a preliminary diffusion layer is obtained. The preliminary diffusion layer is modified by fluorosilane vapor deposition to obtain a superhydrophobic high-speed gas diffusion layer. S4. The composite membrane obtained in step S3 is subjected to hot pressing integration treatment, and the substrate is peeled off to obtain the proton exchange membrane body.

[0015] 7. The preparation method according to claim 6, characterized in that: in step S1, the conditions for high-temperature sintering are: heating to 320-380℃ at a rate of 2-5℃ / min under nitrogen or argon atmosphere, and holding at that temperature for 30-90min; the conditions for plasma activation treatment are: using a mixed gas of argon and oxygen, with a gas flow ratio of (3-5):1, plasma power of 80-150W, and treatment time of 3-10min.

[0016] 8. A preparation method according to claim 6, characterized in that: in step S2, the conditions for electrostatic spray deposition are: working voltage of 10-20kV, distance between nozzle and substrate of 10-20cm, solution propulsion rate of 0.2-1.0mL / h, and substrate temperature of 40-60℃; the conditions for low-temperature curing are: treatment at 60-90℃ for 10-30min.

[0017] 9. A preparation method according to claim 6, characterized in that: in step S3, the laser etching conditions are: using an ultraviolet or green pulsed laser, with a laser power of 5-15W, a scanning speed of 100-500mm / s, and 1-5 scans; the fluorosilane vapor deposition conditions are: at 80-120℃, perfluorooctyltrichlorosilane or perfluorodecyltrichlorosilane vapor is introduced, and the processing time is 30-90min.

[0018] 10. The preparation method according to claim 6, characterized in that: in step S4, the conditions for the hot pressing integration treatment are: temperature of 120-160℃, pressure of 1.0-3.0MPa, and time of 5-15min.

[0019] Compared with the prior art, the beneficial effects of the present invention are: This invention utilizes a conductive substrate layer for effective heat dissipation and uniform current distribution, a gradient proton conduction layer to ensure efficient proton transfer across a wide humidity range, and a gas diffusion layer to enable rapid and directional gas expulsion. These three elements work synergistically to allow the membrane to operate stably for over 1000 hours at current densities ≥3 A / cm², achieving excellent high current density adaptability. The gradient design ensures the membrane maintains high proton conductivity in both low and high humidity environments. The superhydrophobic microstructure gas diffusion layer reduces hydrogen permeability to 2.0 × 10⁻⁶. -6 The composite structure imparts high mechanical strength to the membrane, with a tensile strength ≥40 MPa, achieving excellent comprehensive performance. The material system is corrosion resistant, and the interlayer is firmly bonded through physicochemical action, resulting in high interface stability and effective resistance to various attenuation mechanisms under high current density, thus exhibiting good long-term operational stability.

[0020] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the proton exchange membrane body composite layer of the present invention.

[0022] In the figure: 1. Proton exchange membrane body; 11. Acid-resistant conductive substrate layer; 12. Gradient proton conduction layer; 13. High-speed gas diffusion layer. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a proton exchange membrane for PEM electrolysis that can withstand high current densities. The proton exchange membrane body 1 comprises, from the anode side to the cathode side, the following components: The acid-resistant conductive substrate 11 is composed of graphene nanosheets, sulfonated carbon nanotubes and polytetrafluoroethylene. The gradient proton conduction layer 12 is formed by gradient deposition of at least two perfluorosulfonic acid resin materials with different degrees of sulfonation on the surface of the substrate layer, and the degree of sulfonation decreases from the side closer to the substrate layer to the side farther away. The high-speed gas diffusion layer 13 has an array of oriented conical microchannels on its surface, and the outer surface of the diffusion layer is modified with fluorosilane to be superhydrophobic.

[0025] Preferably, in the conductive substrate layer, the mass ratio of graphene nanosheets, sulfonated carbon nanotubes, and polytetrafluoroethylene is (1-5):(1-4):(85-95); the number of graphene nanosheets is 1-5 layers, and the lateral dimension is 1-10 μm; the degree of sulfonation of the sulfonated carbon nanotubes is 0.8-1.5 mmol / g, the diameter is 5-20 nm, and the length is 5-30 μm.

[0026] Furthermore, the gradient proton conduction layer 12 comprises 2-4 layers of perfluorosulfonic acid resin sublayers with different degrees of sulfonation, and the adjacent sublayers have a continuous transition structure; the degree of sulfonation of each sublayer ranges from 0.6 to 1.4 meq / g, and the total thickness is 15-30 μm.

[0027] Furthermore, in the conical microchannel array on the surface of the high-speed gas diffusion layer 13, the bottom diameter of a single conical structure is 8-20 μm, the height is 5-15 μm, and the center-to-center distance between adjacent conical structures is 15-30 μm; the axial angle between the conical structure and the normal to the membrane plane is 0-30°.

[0028] Furthermore, the high-speed gas diffusion layer 13 includes a hydrophobically modified proton-conducting resin layer located on the surface of the conical array structure. The resin layer contains perfluorosulfonic acid resin and a hydrophobic modifier, and has a thickness of 0.5-2.0 μm.

[0029] Graphene nanosheets: 1-3 layers, 3-5 μm in diameter.

[0030] Sulfonated carbon nanotubes: diameter 10-15nm, length 10-20μm, degree of sulfonation 1.2mmol / g.

[0031] PTFE emulsion: solid content 60wt%.

[0032] Perfluorosulfonic acid resin solutions (different degrees of sulfonation): The solvent is a mixture of ethanol and water, with a solid content of 10 wt%. The degrees of sulfonation are 1.3 meq / g (high), 1.0 meq / g (medium), and 0.7 meq / g (low).

[0033] Perfluorooctyltrichlorosilane (PFOTS).

[0034] Release PET film: 100μm thick.

[0035] A preparation method, applied to the above-mentioned high current density resistant PEM proton exchange membrane for electrolysis, includes the following steps: S1. Preparation of acid-resistant conductive substrate layer 11: Graphene nanosheets and sulfonated carbon nanotubes are dispersed in a solvent, polytetrafluoroethylene emulsion is added, and a uniform slurry is formed by high-speed shearing and ultrasonic treatment. The slurry is cast onto the surface of the substrate and then subjected to drying, high-temperature sintering and plasma activation treatment in sequence to obtain a porous conductive substrate layer. S2, Preparation of gradient proton conduction layer 12: An electrostatic spray deposition method was used to spray at least two perfluorosulfonic acid resin solutions with different degrees of sulfonation onto the surface of the substrate layer in order of decreasing sulfonation degree. Each layer was cured at low temperature after spraying to form a continuous gradient proton conduction layer 12. S3, Preparation of high-speed gas diffusion layer 13: An array of oriented conical microchannels was constructed on the surface of the gradient proton conduction layer 12 using laser etching technology; A coating liquid containing perfluorosulfonic acid resin and hydrophobic modifier is prepared and coated onto a surface with a conical array. After curing, a preliminary diffusion layer is obtained. The initial diffusion layer was modified by fluorosilane vapor deposition to obtain a superhydrophobic high-speed gas diffusion layer 13. S4. The composite membrane obtained in step S3 is subjected to hot pressing integration treatment, and the substrate is peeled off to obtain the proton exchange membrane body 1.

[0036] In step S1, the conditions for high-temperature sintering are: heating to 320-380℃ at a rate of 2-5℃ / min under a nitrogen or argon atmosphere, and holding at that temperature for 30-90min; the conditions for plasma activation treatment are: using a mixture of argon and oxygen gas with a gas flow ratio of (3-5):1, plasma power of 80-150W, and treatment time of 3-10min.

[0037] In step S2, the conditions for electrostatic spray deposition are: working voltage of 10-20kV, distance between nozzle and substrate of 10-20cm, solution propulsion rate of 0.2-1.0mL / h, and substrate temperature of 40-60℃; the conditions for low-temperature curing are: treatment at 60-90℃ for 10-30min.

[0038] In step S3, the laser etching conditions are as follows: using an ultraviolet or green pulsed laser, with a laser power of 5-15W, a scanning speed of 100-500mm / s, and 1-5 scans; the fluorosilane vapor deposition conditions are as follows: at 80-120℃, perfluorooctyltrichlorosilane or perfluorodecyltrichlorosilane vapor is introduced, and the processing time is 30-90min.

[0039] In step S4, the conditions for hot pressing integration are: temperature 120-160℃, pressure 1.0-3.0MPa, and time 5-15min.

[0040] Example 1: Preparation of acid-resistant conductive substrate layer 11: 1.5g of graphene nanosheets and 1.0g of sulfonated carbon nanotubes were added to 100g of N-methylpyrrolidone (NMP) and ultrasonically dispersed for 2 hours.

[0041] Add 90g of PTFE emulsion (60% solids content) and emulsify at high speed for 30 minutes to obtain a uniform slurry.

[0042] The slurry was cast onto a release PET film to a thickness of 300 μm. It was then dried in an oven at 80°C for 2 hours to remove most of the solvent.

[0043] The dried membrane was transferred to a tube furnace and sintered under a nitrogen atmosphere at a rate of 3°C / min to 360°C, and held for 60 minutes.

[0044] The sintered membrane was subjected to argon-oxygen plasma treatment (Ar:O2=4:1, flow rate 40sccm, power 120W, time 5min) to obtain a conductive porous substrate layer with a thickness of approximately 8μm.

[0045] Preparation of gradient proton conduction layer 12: The acid-resistant conductive substrate 11 is fixed on the receiving plate of the electrostatic spraying device, and the temperature is set to 50°C.

[0046] Spraying was performed sequentially using perfluorosulfonic acid resin solutions with sulfonation degrees of 1.3, 1.0, and 0.7 meq / g. Process parameters: voltage 15kV, receiving distance 15cm, and propulsion rate 0.5mL / h.

[0047] First, spray a high sulfonation resin solution, with a spraying amount of about 8 μm based on the dry film thickness, and then cure at 70°C for 15 min.

[0048] Next, spray a medium-sulfonated resin solution with a target dry film thickness of 7 μm and cure at 70°C for 15 min.

[0049] Finally, spray a low-sulfonation resin solution, aiming for a dry film thickness of 5 μm, and cure at 70°C for 15 min.

[0050] The total gradient layer thickness is approximately 20 μm.

[0051] Preparation of high-speed gas diffusion layer 13: Laser etching: A conical array was scanned and etched on the surface of the gradient proton conduction layer 12 using an ultraviolet laser; parameters: power 8W, scanning speed 300mm / s, 2 scans; forming an array with a cone base diameter of about 12μm, a height of about 8μm, and a center-to-center spacing of about 20μm.

[0052] Solution coating: Prepare coating solution: 10g of perfluorosulfonic acid resin solution (10wt%) with sulfonation degree of 0.7meq / g, add 0.1g of polytetrafluoroethylene micro powder (hydrophobic agent), mix evenly; spin-coat it onto the etched surface, dry at 70℃ to form a coating with a thickness of about 1.0μm.

[0053] Vapor deposition modification: The membrane is placed in a reaction chamber, heated to 100°C, and PFOTS vapor is introduced for 60 minutes; after natural cooling, the surface exhibits superhydrophobicity.

[0054] Hot-press integration: The composite film was treated in a hot press at 140°C and 2.0 MPa pressure for 10 minutes.

[0055] After cooling, the membrane was carefully peeled off from the release PET film to obtain the final proton exchange membrane 1; the total thickness was approximately 29 μm.

[0056] Example 2: It is basically the same as Example 1, except that: In the acid-resistant conductive substrate layer 11, the dry material mass ratio of graphene: sulfonated carbon nanotubes: PTFE is 2:2:90.

[0057] The gradient proton conduction layer 12 uses two types of sulfonated resins with high (1.3) and low (0.7) degrees of sulfonation, each sprayed to form a sublayer with a thickness of about 10 μm, for a total thickness of 20 μm.

[0058] High-speed gas diffusion layer 13 cone array parameters: cone base diameter 15μm, height 10μm, spacing 25μm.

[0059] Hot pressing conditions: 150℃, 2.5MPa, 8min.

[0060] The total thickness of the resulting membrane is approximately 30 μm.

[0061] Example 3: It is basically the same as Example 1, except that: The acid-resistant conductive substrate 11 was sintered at 350℃ and held for 75 minutes.

[0062] The gradient proton conduction layer 12 uses four types of sulfonated resins with high (1.3), medium (1.0), medium-low (0.85), and low (0.7) degrees of sulfonation, with a total thickness of 25 μm.

[0063] The hydrophobic agent content in the coating liquid of the high-speed gas diffusion layer 13 is increased to 0.15g, and the coating thickness is about 1.2μm.

[0064] The vapor deposition temperature was 110℃ and the time was 45 min.

[0065] The total thickness of the resulting membrane is approximately 35 μm.

[0066] Comparative Example 1: Based on Example 1, the gradient design of the gradient proton conduction layer 12 was removed and replaced with a single sulfonation degree (1.0 meq / g) perfluorosulfonic acid resin layer, with a total thickness of 20 μm. The other steps were exactly the same as in Example 1.

[0067] Comparative Example 2: Based on Example 1, when preparing the high-speed gas diffusion layer 13, laser etching was not performed. Instead, the same hydrophobic coating was directly coated on the surface of the gradient proton conduction layer 12 and vapor deposition was performed to form a smooth surface. The other steps were exactly the same as in Example 1.

[0068] Comparative Example 3: Based on Example 1, the graphene and sulfonated carbon nanotubes in the acid-resistant conductive substrate 11 were replaced with an equal mass of ordinary conductive carbon black (Vulcan XC-72); the other steps were exactly the same as in Example 1.

[0069] Performance testing and results analysis: The following performance tests were performed on the membranes prepared in Examples 1-3 and Comparative Examples 1-3: High current density long-term operation test: The membrane is assembled into a single cell with an effective area of ​​5 cm² and operated under constant voltage of 2.0 V, 80 °C and normal pressure until the current density decays to 90% of the initial value. The time (h) is recorded. The initial current density reflects the membrane's conductivity under high overpotential.

[0070] Sheet resistance test: The sheet resistance (mΩ·cm²) of the film was measured using the four-probe method at 80℃ and 100%RH.

[0071] Proton conductivity: Electrochemical impedance spectroscopy was used to test the conductivity at 80°C and under conditions of 50% RH and 100% RH, respectively.

[0072] Hydrogen permeability: Tested using gas chromatography at 80°C, 100% RH, with nitrogen flowing through the cathode side and hydrogen flowing through the anode side.

[0073] Contact angle: The water contact angle on the surface of the high-speed gas diffusion layer 13 on the cathode side was measured using a contact angle meter.

[0074] Tensile strength: Tested at room temperature in accordance with GB / T1040.3 standard.

[0075] The test results are shown in the table below:

[0076] As can be seen from the data in the table above, the proton exchange membranes prepared in Examples 1-3 of this invention exhibit excellent and balanced performance in all test items, especially showing significant advantages in high current density operating life, low humidity proton conductivity and low hydrogen permeability.

[0077] Compared to Comparative Example 1 (without gradient), the Example showed significantly higher proton conductivity at 50% RH and a longer operating life, demonstrating the key role of the gradient proton conduction layer in maintaining stable performance over a wide humidity range, especially under low humidity conditions.

[0078] Compared to Comparative Example 2 (without microstructure), the hydrogen permeability of the embodiment was significantly reduced, the contact angle was higher, and the operating life was better, demonstrating the necessity of synergy between directional conical microchannel arrays and superhydrophobic surfaces for efficient exhaust and water blocking.

[0079] Compared to Comparative Example 3 (ordinary carbon substrate), the embodiments exhibited lower sheet resistance, higher initial current density, and significantly longer operating life, demonstrating the important role of the high thermal and electrical conductivity network composed of graphene and sulfonated carbon nanotubes in uniform heat dissipation, improving the overall electrochemical performance and thermal stability of the membrane.

[0080] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A proton exchange membrane for PEM electrolysis that can withstand high current densities, characterized in that, The proton exchange membrane body (1) comprises, from the anode side to the cathode side, the following components: Acid-resistant conductive substrate (11) is composed of graphene nanosheets, sulfonated carbon nanotubes and polytetrafluoroethylene. A gradient proton conduction layer (12) is formed by gradient deposition of at least two perfluorosulfonic acid resin materials with different degrees of sulfonation on the surface of the substrate layer, and the degree of sulfonation decreases from the side closer to the substrate layer to the side farther away. The high-speed gas diffusion layer (13) has an array of oriented conical microchannels on its surface, and the outer surface of the diffusion layer is modified with fluorosilane to be superhydrophobic.

2. The high current density resistant proton exchange membrane for PEM electrolysis according to claim 1, characterized in that: In the conductive substrate layer, the mass ratio of graphene nanosheets, sulfonated carbon nanotubes, and polytetrafluoroethylene is (1-5):(1-4):(85-95); the number of graphene nanosheets is 1-5 layers, and the lateral dimension is 1-10 μm; the degree of sulfonation of the sulfonated carbon nanotubes is 0.8-1.5 mmol / g, the diameter is 5-20 nm, and the length is 5-30 μm.

3. The high current density resistant proton exchange membrane for PEM electrolysis according to claim 1, characterized in that: The gradient proton conduction layer (12) comprises 2-4 layers of perfluorosulfonic acid resin sublayers with different degrees of sulfonation, and the adjacent sublayers are in a continuous transition structure; the degree of sulfonation of each sublayer ranges from 0.6 to 1.4 meq / g, and the total thickness is 15-30 μm.

4. The high current density resistant proton exchange membrane for PEM electrolysis according to claim 1, characterized in that: In the conical microchannel array on the surface of the high-speed gas diffusion layer (13), the bottom diameter of a single conical structure is 8-20 μm, the height is 5-15 μm, and the center-to-center distance between adjacent conical structures is 15-30 μm; the axial angle between the conical structure and the normal to the membrane plane is 0-30°.

5. The high current density resistant proton exchange membrane for PEM electrolysis according to claim 1, characterized in that: The high-speed gas diffusion layer (13) includes a hydrophobic modified proton-conducting resin layer located on the surface of the conical array structure. The resin layer contains perfluorosulfonic acid resin and a hydrophobic modifier and has a thickness of 0.5-2.0 μm.

6. A preparation method, applied to the high current density-resistant PEM proton exchange membrane for electrolysis as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Preparation of acid-resistant conductive substrate layer (11): Graphene nanosheets and sulfonated carbon nanotubes are dispersed in a solvent, polytetrafluoroethylene emulsion is added, and a uniform slurry is formed by high-speed shearing and ultrasonic treatment. The slurry is cast onto the surface of a substrate and then subjected to drying, high-temperature sintering and plasma activation treatment in sequence to obtain a porous conductive substrate layer. S2, Preparation of gradient proton conduction layer (12): At least two perfluorosulfonic acid resin solutions with different degrees of sulfonation were sprayed onto the surface of the substrate layer in order of decreasing sulfonation degree using an electrostatic spray deposition method. Each layer was cured at low temperature after spraying to form a continuous gradient proton conduction layer (12). S3. Preparation of high-speed gas diffusion layer (13): An array of oriented conical microchannels is constructed on the surface of the gradient proton conduction layer (12) using laser etching technology; A coating liquid containing perfluorosulfonic acid resin and hydrophobic modifier is prepared and coated onto a surface with a conical array. After curing, a preliminary diffusion layer is obtained. The preliminary diffusion layer was modified by fluorosilane vapor deposition to obtain a superhydrophobic high-speed gas diffusion layer (13). S4. The composite membrane obtained in step S3 is subjected to hot pressing integration treatment, and the substrate is peeled off to obtain the proton exchange membrane body (1).

7. The preparation method according to claim 6, characterized in that: In step S1, the conditions for high-temperature sintering are: heating to 320-380℃ at a rate of 2-5℃ / min under a nitrogen or argon atmosphere, and holding at that temperature for 30-90min; the conditions for plasma activation treatment are: using a mixed gas of argon and oxygen with a gas flow ratio of (3-5):1, plasma power of 80-150W, and treatment time of 3-10min.

8. The preparation method according to claim 6, characterized in that: In step S2, the conditions for electrostatic spray deposition are: working voltage of 10-20kV, distance between nozzle and substrate of 10-20cm, solution propulsion rate of 0.2-1.0mL / h, and substrate temperature of 40-60℃; the conditions for low-temperature curing are: treatment at 60-90℃ for 10-30min.

9. The preparation method according to claim 6, characterized in that: In step S3, the laser etching conditions are as follows: using an ultraviolet or green pulsed laser, with a laser power of 5-15W, a scanning speed of 100-500mm / s, and 1-5 scans; the fluorosilane vapor deposition conditions are as follows: at 80-120℃, perfluorooctyltrichlorosilane or perfluorodecyltrichlorosilane vapor is introduced, and the processing time is 30-90min.

10. The preparation method according to claim 6, characterized in that: In step S4, the conditions for the hot-pressing integration process are: temperature 120-160℃, pressure 1.0-3.0MPa, and time 5-15min.

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