Composite proton exchange membrane and preparation method and application thereof

Abstract

The application relates to the field of proton exchange membrane preparation, and discloses a composite proton exchange membrane as well as a preparation method and application thereof. The composite proton exchange membrane comprises a first proton exchange resin layer and at least one proton exchange membrane unit stacked with each other, the proton exchange membrane unit is composed of a porous reinforcing layer and a second proton exchange resin layer, the porous reinforcing layer comprises a porous reinforcing material and a proton exchange resin embedded in the porous reinforcing material; the first proton exchange resin layer and the adjacent porous reinforcing layer are integrally formed; wherein in any 5cm*5cm composite proton exchange membrane, the number of defects between the proton exchange resin and the porous reinforcing material is 0 after being tested by adopting a hydrogen peroxide bubbling method. The composite proton exchange membrane has the advantages that the PEM resin and the porous reinforcing material are combined compactly, no defects are generated, the surface resistance increasing rate and the performance attenuation rate are lower.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of proton exchange membrane preparation, in particular to a composite proton exchange membrane and its preparation method and application. BACKGROUND

[0002] Proton exchange membranes can be widely used in fuel cells or hydrogen production due to their excellent proton conduction performance. When used in fuel cells, the proton exchange membrane transports protons formed at the hydrogen electrode to the oxygen electrode; when used in electrolytic hydrogen production, its main function is to conduct protons and block gas.

[0003] The development of proton exchange membranes requires lower energy consumption and longer service life, which requires proton exchange membranes to have lower surface resistance and higher mechanical strength. The usual method is to reduce the thickness of the proton exchange membrane to reduce the surface resistance, and to composite a porous reinforcing layer to improve the mechanical strength. The proton exchange membrane with a porous reinforcing layer is called a composite proton exchange membrane.

[0004] The problem of composite proton exchange membranes is that the resin layer and the porous reinforcing layer are not tightly bonded, leaving gaps at the interface, which can be regarded as defects inside the composite proton exchange membrane. Defects are usually not visible to the naked eye, but they will gradually increase after long-term use of the composite proton exchange membrane, causing the proton exchange resin and the porous reinforcing material to partially peel off and form obvious "bubbles". The bubbles will cause the surface resistance of the composite proton exchange membrane to increase, the energy consumption to rise, and the operating life of the entire system to be affected.

[0005] In the prior art, CN112514150A discloses a monolithic composite membrane with a continuous ionomer phase, which is composed of a microporous polymer structure and an ion exchange material partially embedded in the microporous polymer structure and at least partially occluding the microporous polymer structure, and there is no internal interface between the ion exchange material layers, i.e. there are no defects between the ion exchange material layers, but it does not solve the problem that when it is applied to water electrolysis for hydrogen production, the micro-defects between the ion exchange material and the microporous polymer gradually expand under the action of gas, causing material failure, limiting its application scenarios. SUMMARY

[0006] The purpose of the present application is to overcome the problems existing in the prior art and provide a composite proton exchange membrane and its preparation method and application. The composite proton exchange membrane of the present application has a tight bond between the proton exchange resin and the porous reinforcing material, no defects are generated, and has a lower surface resistance increase rate and a performance decay rate.

[0007] To achieve the above objectives, a first aspect of the present invention provides a composite proton exchange membrane, comprising a first proton exchange resin layer and at least one proton exchange membrane unit stacked on top of each other, wherein the proton exchange membrane unit is composed of a porous reinforcement layer and a second proton exchange resin layer, the porous reinforcement layer comprising a porous reinforcement material and a proton exchange resin embedded in the porous reinforcement material; the first proton exchange resin layer and the adjacent porous reinforcement layer are integrally formed.

[0008] In any 5cm×5cm composite proton exchange membrane, after testing with the hydrogen peroxide bubbling method, the number of defects between the proton exchange resin and the porous reinforcing material is 0.

[0009] A second aspect of the present invention provides a method for preparing a composite proton exchange membrane, the method comprising:

[0010] S1. A first proton exchange resin dispersion comprising a proton exchange resin and a dispersant is coated onto a substrate to obtain a first proton exchange resin dispersion layer.

[0011] S2. Apply a predetermined tensile tension to the porous reinforcing material, causing its pore volume change rate to be between 1.5% and 10%, and keep it in a stretched state. Cover the stretched porous reinforcing material onto the first proton exchange resin dispersion layer, so that the first proton exchange resin dispersion fills the pores of the porous reinforcing material. Then, optionally perform a first drying to form a porous reinforcing layer.

[0012] S3. A second proton exchange resin dispersion is coated onto the porous reinforcing layer, wherein the second proton exchange resin dispersion comprises a proton exchange resin and a dispersant;

[0013] S4. According to the predetermined number of proton exchange unit layers, optionally repeat steps S2-S3, and then perform a second drying to obtain a composite proton exchange membrane;

[0014] The drying temperatures of the first drying and the second drying are each independently within the range of 60°C below the boiling point of the dispersant to 20°C above the boiling point.

[0015] The first drying and the second drying are each carried out independently in three stages, with the temperature in the latter stage being higher than that in the former.

[0016] The third aspect of this invention provides the application of the composite proton exchange membrane described in the first aspect or the composite proton exchange membrane prepared by the preparation method described in the second aspect in fuel cells or water electrolysis for hydrogen production.

[0017] The beneficial effects of the present invention through the above technical solution include:

[0018] The composite proton exchange membrane provided by this invention has a tight bond between the proton exchange resin and the porous reinforcing material, with no defects, and has a lower surface resistivity increase rate and performance degradation rate, thereby improving the service life of the composite proton exchange membrane.

[0019] The method for preparing the composite proton exchange membrane of the present invention, by strictly controlling the tensile tension of the porous reinforcing material and by performing segmented drying and controlling the drying temperature, can effectively eliminate the generation of internal defects. Attached Figure Description

[0020] Figure 1 This is a physical image of the composite proton exchange membrane prepared in Example 1 of the present invention after defect testing;

[0021] Figure 2 These are SEM images of the composite proton exchange membrane prepared in Example 2 of this invention before and after defect testing;

[0022] Figure 3 This is a physical image of the composite proton exchange membrane prepared in Comparative Example 1 of this invention after defect testing.

[0023] Figure 4 These are SEM images of the composite proton exchange membrane prepared in Comparative Example 1 of this invention before and after defect testing.

[0024] Figure 5 This is a photograph of the porous reinforcing material of Comparative Example 4 of the present invention immersed in PEM dispersion;

[0025] Figure 6 This is a roll-to-roll (R2R) device provided in a preferred embodiment of the present invention.

[0026] Figure description markings

[0027] exist Figure 6 middle,

[0028] 1. Substrate unwinding device; 2. Slit coating head; 3. Coating back roller;

[0029] 4. Porous material unwinding device; 5. Composite roller; 6. Drying oven;

[0030] 7. Winding device; 8. Transition roller. Detailed Implementation

[0031] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] The first aspect of the present invention provides a composite proton exchange membrane (PEM) comprising a first proton exchange resin layer and at least one proton exchange membrane unit stacked on top of each other. The proton exchange membrane unit is composed of a porous reinforcement layer and a second proton exchange resin layer. The porous reinforcement layer comprises a porous reinforcement material and a proton exchange resin embedded in the porous reinforcement material. The first proton exchange resin layer and the adjacent porous reinforcement layer are integrally formed.

[0033] In any 5cm×5cm composite proton exchange membrane, after testing with the hydrogen peroxide bubbling method, the number of defects between the proton exchange resin and the porous reinforcing material is 0.

[0034] It is understood that in any 5cm×5cm composite proton exchange membrane, the number of defects between the proton exchange resin and the porous reinforcing material is 0. In composite proton exchange membranes with smaller areas, the same condition of zero defects between the proton exchange resin and the porous reinforcing material is also met, and this is also within the scope of protection of this invention.

[0035] In this invention, preferably, the hydrogen peroxide bubbling method test includes: cutting a 5cm×5cm composite proton exchange membrane, placing it in an aqueous hydrogen peroxide solution (2wt%-5wt%), heating it to 90℃-105℃, preferably 95℃-105℃, maintaining it for 25min-30min, then removing the composite proton exchange membrane, observing the surface morphology, and recording the number of defects.

[0036] When performing the hydrogen peroxide bubbling test on a composite proton exchange membrane (PEM), if pores exist between the proton exchange resin and the porous reinforcing material, H2O2 will be largely absorbed by the PEM at high temperatures and enter the pores. It then rapidly decomposes, generating a large amount of gas, causing significant pressure within the pores. This leads to continuous tearing of the interface between the proton exchange resin and the porous reinforcing material, gradually expanding into bubbles with a diameter ≥0.5 mm visible to the naked eye. When PEM is used in fuel cells or for hydrogen production via water electrolysis, the presence of these pores will cause the resin layer and porous reinforcing layer to peel off after long-term operation, resulting in a significant reduction in the service life of the fuel cell or electrolyzer, failing to meet requirements. The hydrogen peroxide bubbling test process of this invention approximates the process of pore enlargement in hydrogen production via water electrolysis and fuel cells. This method can quickly detect the number of defects and is used to assess its suitability for hydrogen production via water electrolysis or fuel cells.

[0037] In this invention, the defect is: after the foaming test, visible bubbles with a diameter of ≥0.5mm appear on the composite proton exchange membrane (macro level), and when the cross-section is observed by SEM, the proton exchange resin layer and the porous reinforcement layer are delaminated (micro level).

[0038] In this invention, the number of proton exchange membrane units can be set according to application needs, preferably 2-6.

[0039] Preferably, in the composite proton exchange membrane, the thickness of the first proton exchange resin layer and the second proton exchange resin layer are each independently in the range of 2-40 micrometers, more preferably in the range of 5-35 micrometers, and even more preferably in the range of 8-30 micrometers.

[0040] Preferably, in the composite proton exchange membrane, the thickness of the porous reinforcement layer is in the range of 1-20 micrometers, more preferably in the range of 5-15 micrometers.

[0041] The thicknesses of the porous reinforcing layer and the proton exchange resin layer described in this invention were measured by SEM.

[0042] In this invention, various porous reinforcing materials well known to those skilled in the art can be used as the porous reinforcing material. The porous reinforcing material is preferably selected from at least one of expanded polytetrafluoroethylene (ePTFE), polyetheretherketone (PEEK), polypropylene (PP), polyethylene (PE), and polyphenylene sulfide (PPS).

[0043] According to the present invention, preferably, the porosity of the porous reinforcing material is 55-95%, more preferably 60-90%, and even more preferably 65-85%.

[0044] In this invention, the proton exchange resin can be any proton exchange resin known to those skilled in the art, preferably a perfluorosulfonic acid type proton exchange resin.

[0045] A second aspect of the present invention provides a method for preparing a composite proton exchange membrane, comprising:

[0046] S1. A first proton exchange resin dispersion comprising a proton exchange resin and a dispersant is coated onto a substrate to obtain a first proton exchange resin dispersion layer.

[0047] S2. Apply a predetermined tensile tension to the porous reinforcing material, causing its pore volume change rate to be between 1.5% and 10%, and keep it in a stretched state. Cover the stretched porous reinforcing material onto the first proton exchange resin dispersion layer, so that the first proton exchange resin dispersion fills the pores of the porous reinforcing material. Then, optionally perform a first drying to form a porous reinforcing layer.

[0048] S3. A second proton exchange resin dispersion is coated onto the porous reinforcing layer, wherein the second proton exchange resin dispersion comprises a proton exchange resin and a dispersant;

[0049] S4. According to the predetermined number of proton exchange unit layers, optionally repeat steps S2-S3, and then perform a second drying to obtain a composite proton exchange membrane;

[0050] The drying temperatures of the first drying and the second drying are each independently within the range of 60°C below the boiling point of the dispersant to 20°C above the boiling point.

[0051] The first drying and the second drying are each carried out independently in three stages, with the temperature in the latter stage being higher than that in the former.

[0052] First, in step S1, a first proton exchange resin dispersion comprising a proton exchange resin and a dispersant is coated onto a substrate to obtain a first proton exchange resin dispersion layer.

[0053] In this invention, the substrate serves as the support material; however, there are no particular limitations, and any conventional choice in the art can be used. The substrate is preferably a polyethylene terephthalate (PET) film.

[0054] Preferably, the thickness of the substrate is 20-100 μm.

[0055] In this invention, the proton exchange resin can be any conventional choice in the art. Preferably, a perfluorosulfonic acid type proton exchange resin is used.

[0056] In this invention, various porous reinforcing materials well known to those skilled in the art can be used as the porous reinforcing material. The porous reinforcing material is preferably selected from at least one of expanded polytetrafluoroethylene (ePTFE), polyetheretherketone (PEEK), polypropylene (PP), polyethylene (PE), and polyphenylene sulfide (PPS).

[0057] According to the present invention, preferably, the porosity of the porous reinforcing material is 55-95%, more preferably 60-90%, and even more preferably 65-85%.

[0058] The present invention does not impose any particular limitation on the type of dispersant, and any conventional choice in the art can be made. Preferably, the dispersant is selected from at least one of water, n-propanol, isopropanol, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0059] In this invention, preferably, the content of proton exchange resin in the first proton exchange resin dispersion and the second proton exchange resin dispersion is independently 3-30 wt%, specifically 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, and a range of any two of these values.

[0060] Next, after coating the first proton exchange resin dispersion onto the substrate to form the first proton exchange resin dispersion layer, step S2 is performed. A predetermined tensile tension is applied to the porous reinforcing material to make its pore volume change rate between 1.5% and 10%, and the material is kept in a stretched state. During stretching, the predetermined tensile tension is applied to the porous reinforcing material by controlling the rotation speed of the front and rear rollers of the roll-to-roll (R2R) device. The stretched porous reinforcing material is then placed on the first proton exchange resin dispersion layer, so that the first proton exchange resin dispersion layer fully fills the pores of the porous reinforcing material.

[0061] Through research, the inventors discovered that in the prior art, when porous reinforcing materials are coated onto a dispersion, the porous reinforcing material is generally stretched on a roll-to-roll (R2R) device to flatten it and prevent wrinkles. However, even when it is only flattened, wrinkles still exist in micro-local areas, causing the proton exchange resin to not fully fill the porous material, thus creating defects. If excessive tensile tension is applied to the porous reinforcing material, although the surface morphology does not change, the micropore structure is actually destroyed (e.g., pore volume decreases, pore size decreases, or pores close), thus preventing the porous reinforcing material from being fully wetted by the proton exchange resin. As a result, after the porous reinforcing layer is formed, defects are easily formed between the proton exchange resin and the porous reinforcing material.

[0062] Through further experimental exploration, the inventors discovered that applying a predetermined tensile tension to the porous reinforcing material, causing its pore volume change rate to be 1.5-10% and maintaining it in a stretched state, preferably with a total pore volume change rate of 2-8%, and more preferably 2-5%, can not only allow the porous reinforcing material to fully expand and solve the problem of micro-wrinkles, but also prevent permanent damage and deformation of the micropore volume. This allows the proton exchange resin to fully wet the porous reinforcing material, thereby effectively solving the problem of defects between the proton exchange resin and the porous reinforcing material.

[0063] In this invention, after the porous reinforcing material is kept in a stretched state and fully impregnated with the first proton exchange resin dispersion layer, a first drying process can be performed, or the first drying process can be skipped and the process can proceed directly to step S3.

[0064] According to the present invention, preferably, the first drying includes three stages of drying with progressively increasing temperatures. The temperature of the first stage of drying is 20-60°C below the boiling point of the dispersant, preferably 35-60°C below the boiling point of the dispersant; the temperature of the second stage of drying is 20°C below the boiling point of the dispersant to the boiling point of the dispersant, preferably 20°C below the boiling point of the dispersant to 5°C below the boiling point of the dispersant; and the temperature of the third stage of drying is from the boiling point of the dispersant to 20°C above the boiling point of the dispersant, preferably from the boiling point of the dispersant to 15°C above the boiling point of the dispersant.

[0065] According to the present invention, preferably, in the first drying process, the drying time of the first stage is 5-50 min, specifically 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, and any two of these values ​​forming a range, more preferably 10-40 min, and even more preferably 15-35 min.

[0066] According to the present invention, preferably, in the first drying, the drying time of the second stage is 5-50 min, specifically 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, and any two of these values ​​forming a range, more preferably 10-40 min, and even more preferably 15-35 min.

[0067] According to the present invention, preferably, in the first drying, the drying time of the third stage is 5-50 min, specifically 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, and any two of these values ​​forming a range, more preferably 10-40 min, and even more preferably 15-35 min.

[0068] Step S3: Prepare a second proton exchange resin dispersion. The second proton exchange resin dispersion may have the same composition as the first proton exchange resin dispersion. Coat the second proton exchange resin dispersion onto the porous reinforcing layer.

[0069] Step S4: Selectively repeat steps S2-S3 according to a predetermined number of proton exchange unit layers, and then perform a second drying to obtain a composite proton exchange membrane.

[0070] According to the present invention, preferably, the second drying comprises three stages of drying with progressively increasing temperatures: the temperature of the first stage of drying is 20-60°C below the boiling point of the dispersant, preferably 35-60°C below the boiling point of the dispersant; the temperature of the second stage of drying is 20°C below the boiling point of the dispersant to the boiling point of the dispersant, preferably 20°C below the boiling point of the dispersant to 5°C below the boiling point of the dispersant; and the temperature of the third stage of drying is from the boiling point of the dispersant to 20°C above the boiling point of the dispersant, preferably from the boiling point of the dispersant to 15°C above the boiling point of the dispersant.

[0071] According to the present invention, preferably, in the second drying process, the drying time of the first stage is 5-50 min, specifically 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, and any range of any two of these values.

[0072] According to the present invention, preferably, in the second drying process, the drying time of the second stage is 5-50 min, specifically 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, and any range of any two of these values.

[0073] According to the present invention, preferably, in the second drying process, the drying time of the third stage is 5-50 min, specifically 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, and any range of any two of these values.

[0074] In this invention, the pore volume of the porous reinforcing material is calculated by the following formula: total pore volume = porous reinforcing material volume × porosity, where porosity = 1 - porous reinforcing material density / material density without pores.

[0075] Total pore volume change rate = (pore volume before stretching V1 - pore volume after stretching V2) / pore volume before stretching V1 × 100%.

[0076] It should be noted that, in this invention, the method for testing the density after stretching includes: stretching the roll along the winding and unwinding direction using a tensile testing machine, maintaining the stretched state, and measuring the density using a density meter.

[0077] In this invention, the tensile tension of the porous reinforcing material is determined according to the following formula: T = S × σ

[0078] Where T is the tensile tension of the material, in N; σ is the yield stress of the material, in N; S is the tension coefficient, the value of S is not greater than 30%, specifically it can be 2%, 5%, 10%, 15%, 20%, 25%, 30%, and the range of any two of these values, preferably 5-20%.

[0079] In this invention, the yield stress of the material is measured using a universal tensile testing machine. Specifically, the following steps are taken: A dumbbell-shaped IB specimen conforming to GB / T1040.3-2018 is cut, and parallel lines with a spacing of 50 mm are marked. The thickness of the specimen is measured at three points—the middle and both ends—using a thickness gauge, and the arithmetic mean is taken as the specimen thickness. The clamping distance of the tensile testing machine is adjusted to approximately 115 mm, and the specimen is clamped on the machine, ensuring that the centerline of the specimen's length is aligned with the center of the machine clamps. The specimen is stretched at a tensile speed of 5 mm / min until fracture, yielding the yield stress. Five specimens are tested, and the average value is taken.

[0080] When testing the mechanical properties of porous reinforced materials, the specimen is of type IB with a mark distance of 50 mm and a width of 10 mm at the narrowest point (the effective cross-sectional area width for calculating yield stress). The yield strength is obtained by dividing the yield stress by the effective cross-sectional area of ​​the specimen.

[0081] When the porous reinforced material is tested in the following examples and comparative examples, the width is 160 mm (the effective cross-sectional area width for calculating the yield stress). The actual yield stress is obtained by multiplying the yield strength calculated above by the effective cross-sectional area of ​​the specimen.

[0082] Preferably, the method further includes: in step S4, steps S2-S3 are optionally repeated according to a predetermined number of proton exchange unit layers, followed by a second drying and optional annealing to remove the substrate and obtain a composite proton exchange membrane.

[0083] It should be noted that, in this invention, the annealing step is performed when the second drying temperature is not greater than 120°C.

[0084] The annealing described in this invention can be performed using conventional methods in the art. Preferably, the annealing conditions include: a temperature of 120-180°C and a time of 1-60 minutes.

[0085] The method for removing the substrate described in this invention can employ various methods conventionally used in the art.

[0086] According to a specific embodiment of the present invention, the process of preparing the composite proton exchange membrane uses, for example... Figure 6 The roll-to-roll (R2R) apparatus shown includes a substrate unwinding device 1, a slot coating head 2, a coating back roller 3, a porous material unwinding device 4, a composite roller 5, an oven 6, a winding device 7, and a transition roller 8. The specific process includes:

[0087] (1) The substrate is spread out using the substrate unwinding device 1 and linked with the winding device 7 to move the substrate from the unwinding device to the winding device. At the same time, the first proton exchange resin dispersion is coated on the substrate at the coating back roller 3 using the coating head 2.

[0088] (2) The porous material unwinding device 4 and the winding device 7 are linked. By controlling the relative rotation speed of the winding device 7, tensile tension is applied to the porous reinforcing material. Then, the porous reinforcing material is immersed in PEM dispersion on the composite roller 5 and then sent to the oven 6 for first drying to form a porous reinforcing layer. When the material is being wound, the transition roller 8 plays a supporting role.

[0089] (3) Continue to unwind the substrate by the unwinding device 1, and apply the second proton exchange resin dispersion to the porous reinforcement layer by the coating head 2;

[0090] (4) Optionally repeat steps (2)-(3), and then send it into oven 6 for a second drying and optional annealing; remove the substrate to obtain a composite proton exchange membrane.

[0091] The third aspect of this invention provides the application of the composite proton exchange membrane described in the first aspect or the composite proton exchange membrane prepared by the preparation method described in the second aspect in water electrolysis for hydrogen production or in fuel cells.

[0092] The composite proton exchange membrane described in this invention is suitable for hydrogen production by water electrolysis or for fuel cells. The method for hydrogen production by water electrolysis or the fuel cell can refer to conventional solutions in the field.

[0093] The present invention will be described in detail below through embodiments.

[0094] The PET was purchased from Beijing Tianshui Science and Trade Co., Ltd., model CX-101;

[0095] PEM dispersion was purchased from Shanghai Hancheng Industrial Co., Ltd., model HCD-1820;

[0096] The ePTFE was purchased from Shanghai Hancheng Industrial Co., Ltd., model HA-06, with a thickness of 20μm and a porosity of 85%.

[0097] Under the aforementioned mechanical property test conditions, the total pore volume change rate of ePTFE under different tensile tension conditions was tested, so as to select a suitable tension coefficient. The specific results are listed in Table 1.

[0098] Table 1

[0099]

[0100] Example 1

[0101] (1) The substrate is a 50 μm thick polyethylene terephthalate (PET) film, using, for example Figure 6 The apparatus shown has a substrate unwinding device 1 that lays out the substrate and a coating head 2 that coats the PET with a PEM dispersion. The mass fractions of the PEM dispersion are: 20% PEM resin and 80% N,N-dimethylacetamide (boiling point 165℃). The gap between the coating head 2 and the substrate is 120 μm, and the coating width is 160 mm.

[0102] (2) By controlling the relative rotation speed of the winding device 7, a tensile tension is applied to the porous reinforcing material, σ=5N×16=80N, S is taken as 5%, T=80N×5%=4N, so that the total pore volume change rate before and after stretching is about 2%. Then the porous reinforcing material is immersed in PEM dispersion on the composite roller 5, so that the dispersion fills part of the pores, and then dried in the oven 6;

[0103] The drying process is as follows: 105℃ for 30 min, 145℃ for 30 min, and 165℃ for 5 min.

[0104] (3) Continue to coat the porous reinforcing material with a layer of PEM dispersion to completely fill the pores; the gap between the coating head 2 and the porous reinforcing material is 120 μm and the width is 160 mm.

[0105] (4) Repeat steps (2)-(3) for a total of 3 times, and then dry;

[0106] The drying process is as follows: 105℃ for 30 min, 145℃ for 30 min, and 165℃ for 5 min.

[0107] The substrate was removed to obtain a composite proton exchange membrane, the thickness of each layer of which is shown in Table 2.

[0108] Example 2

[0109] (1) The substrate is a 50 μm thick polyethylene terephthalate (PET) film, using Figure 6 The apparatus shown has a substrate unwinding device 1 that lays out the substrate and a coating head 2 that coats the PET with a PEM dispersion. The mass fractions of the components in the PEM dispersion are: 20% PEM resin and 80% ethanol (boiling point 78.4℃). The gap between the coating head 2 and the substrate is 120 μm, and the width is 160 mm.

[0110] (2) By controlling the relative rotation speed of the winding device 7, tensile tension (T=S×σ=80N×10%=8N) is applied to the porous reinforcing material, so that the total pore volume change rate before and after stretching is about 4%; then the porous reinforcing material is immersed in PEM dispersion on the composite roller 5, so that the dispersion fills part of the pores, and then dried in the oven 6.

[0111] The drying process is as follows: 35℃ for 30 minutes, 60℃ for 30 minutes, and 80℃ for 5 minutes.

[0112] (3) Continue to coat the porous reinforcing material with a layer of PEM dispersion to completely fill the pores; the gap between the coating head 2 and the porous reinforcing material is 120 μm and the width is 160 mm.

[0113] (4) Dry and anneal the product from step (3);

[0114] The drying process is as follows: 35℃ for 30 minutes, 60℃ for 30 minutes, and 80℃ for 5 minutes.

[0115] The annealing process is 160℃ for 5 minutes.

[0116] The substrate was removed to obtain a composite proton exchange membrane, the thickness of each layer of which is shown in Table 2.

[0117] Example 3

[0118] (1) The substrate is a 50 μm thick polyethylene terephthalate (PET) film, using, for example Figure 6 The apparatus shown has a substrate unwinding device 1 that lays out the substrate and a coating head 2 that coats the PET with a PEM dispersion. The mass fractions of the PEM dispersion are: 20% PEM resin and 80% N,N-dimethylacetamide. The gap between the coating head 2 and the substrate is 120 μm, and the width is 160 mm.

[0119] (2) By controlling the relative rotation speed of the winding device 7, tensile tension (T=S×σ=80N×5%=4N) is applied to the porous reinforcing material, so that the total pore volume change rate before and after stretching is about 2%; then the porous reinforcing material is immersed in PEM dispersion on the composite roller 5, so that the dispersion fills part of the pores, and then dried in the oven 6.

[0120] The drying process is as follows: 125℃ for 30 min, 155℃ for 30 min, and 175℃ for 5 min.

[0121] (3) Continue to coat the porous reinforcing material with a layer of PEM dispersion to completely fill the pores; the gap between the coating head 2 and the porous reinforcing material is 120 μm and the width is 160 mm.

[0122] (4) Dry the product from step (3);

[0123] The drying process is as follows: 125℃ for 30 min, 155℃ for 30 min, and 175℃ for 5 min.

[0124] The substrate was removed to obtain a composite proton exchange membrane, the thickness of each layer of which is shown in Table 2.

[0125] Example 4

[0126] The method of Example 2 is followed, except that in step (2), the applied tensile tension (T=S×σ=80N×20%=16N) makes the total pore volume change rate before and after stretching about 5%.

[0127] A composite proton exchange membrane was obtained, and the thickness of each layer is shown in Table 2.

[0128] Comparative Example 1

[0129] The method of Example 2 is followed, except that in step (2), the applied tensile tension (T=S×σ=80N×40%=32N) makes the change rate of the hole volume before and after stretching about 16%.

[0130] A composite proton exchange membrane was obtained, and the thickness of each layer is shown in Table 2.

[0131] Comparative Example 2

[0132] The process was carried out according to the method of Example 1, except that the drying process was 100℃ for 30 min, 120℃ for 30 min, and 150℃ for 5 min.

[0133] A composite proton exchange membrane was obtained, and the thickness of each layer is shown in Table 2.

[0134] Comparative Example 3

[0135] The process was carried out according to the method of Example 1, except that the drying process was 165℃ for 30 min, 170℃ for 30 min, and 175℃ for 5 min.

[0136] A composite proton exchange membrane was obtained, and the thickness of each layer is shown in Table 2.

[0137] Comparative Example 4

[0138] The method of Example 2 is followed, except that in step (2), the applied tensile tension (T=S×σ=80N×2.5%=2N) makes the total pore volume change rate before and after stretching about 1%.

[0139] Because the tension is too low, the porous reinforcing material cannot be flattened, resulting in vertical lines during impregnation and making subsequent operations impossible. Figure 5 As shown.

[0140] Test Example 1

[0141] The composite proton exchange membranes prepared in the examples and comparative examples were cut into 5cm×5cm pieces, placed in a 3wt% hydrogen peroxide aqueous solution, heated to 100°C, and held for 30 minutes. Then, the composite proton exchange membranes were removed, the surface morphology was observed, and the number of defects was recorded. See Table 2 for details.

[0142] Test Example 2

[0143] Test of surface resistivity rise rate

[0144] The rate of increase in sheet resistivity = (resistance after bubbling test - resistance before bubbling test) / resistance before bubbling test × 100%, that is, (sheet resistivity of the composite proton exchange membrane after test example 1 - sheet resistivity of the composite proton exchange membrane before test example 1) / sheet resistivity of the composite proton exchange membrane before test example 1 × 100%.

[0145] Surface resistance test method

[0146] The composite proton exchange membrane was fixed in a four-electrode fixture and immersed in deionized water, with the temperature maintained at 25°C. After stabilization, the sheet resistance (Ro) of the composite proton exchange membrane was measured using an electrochemical workstation via AC impedance spectroscopy. a The specific conditions included: frequency: 10Hz-1MHz, bias voltage: 10mV. The resulting test curve was obtained.

[0147] The sheet resistance (R) of composite proton exchange membranes a It is determined by the following formula:

[0148]

[0149] Where R1 represents the AC impedance of the composite proton exchange membrane, i.e., the intersection of the high-frequency portion (above 500 Hz) of the curve with the horizontal axis, in Ω; S represents the cross-sectional area, in cm². 2 .

[0150] The test results are shown in Table 2.

[0151] Test Example 3

[0152] Performance degradation rate test

[0153] First, catalysts (iridium oxide for the anode and platinum-carbon for the cathode) were coated on both sides of the composite proton exchange membranes prepared in the examples and comparative examples to prepare membrane electrodes with an active area of ​​5 cm × 5 cm. Then, the membrane electrodes were assembled into an electrolytic cell (assembly method referred to reference 10.1016 / j.chempr.2024.09.004). Figure 1 At a water temperature of 60℃, a flow rate of 150mL / min, and a current density of 2A / cm³, 2 Water electrolysis was carried out. After 48 hours of operation, the system stabilized and testing began. The electrolysis voltage at this point was the initial electrolysis voltage.

[0154] Performance degradation rate = (Electrolysis voltage after 1000 hours of testing - Initial electrolysis voltage) / 1000h

[0155] The electrolysis voltage is defined as the current density of 2 A / cm². 2 At that time, the voltage of the electrolytic cell is measured. Current is supplied by a power source, and voltage is measured by a voltmeter.

[0156] The test results are shown in Table 2.

[0157] Table 2

[0158]

[0159] Note: In Table 2, the number of defects refers to the number of defects between the PEM resin and the porous reinforcing material.

[0160] As can be seen from the results in Table 2, the composite proton exchange membrane provided by this invention achieves a defect-free internal structure, a lower rate of increase in sheet resistivity, and a lower performance degradation rate. Its application in hydrogen electrolysis can reduce the power consumption of the hydrogen electrolysis system and extend its lifespan.

[0161] Figure 1 This is a photograph of the composite proton exchange membrane prepared in Example 1 of this invention after defect testing. Figure 2 As can be seen, after the bubble test, the composite proton exchange membrane remained colorless and transparent, with a smooth and flat surface and no bubbles generated.

[0162] Figure 2 These are SEM images of the composite proton exchange membrane prepared in Example 2 of this invention before and after defect testing. Figure 3 It can be seen that no stratification occurred before or after the defect test.

[0163] Figure 3 This is a photograph of the composite proton exchange membrane prepared in Comparative Example 1 of this invention after defect testing. Figure 4 As can be seen, after the bubbling test, the composite proton exchange membrane showed bubbles with a diameter greater than 0.5 mm.

[0164] Figure 4 These are SEM images of the composite proton exchange membrane prepared in Comparative Example 1 of this invention before and after defect testing. (The images are obtained through...) ​ It can be seen that without defect testing, the internal defects of the composite proton exchange membrane are usually not obvious; after defect testing, obvious stratification appears.

[0165] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composite proton exchange membrane, characterized by, The composite proton exchange membrane comprises a first proton exchange resin layer and at least one proton exchange membrane unit stacked with each other, the proton exchange membrane unit is composed of a porous reinforcing layer and a second proton exchange resin layer, the porous reinforcing layer comprises a porous reinforcing material and a proton exchange resin embedded in the porous reinforcing material; the first proton exchange resin layer and the adjacent porous reinforcing layer are integrally formed. In any 5 cm x 5 cm composite proton exchange membrane, the number of defects between the proton exchange resin and the porous reinforcing material is 0 after testing by the hydrogen peroxide bubbling method.

2. The composite proton exchange membrane according to claim 1, wherein the porous reinforcing material is selected from at least one of expanded polytetrafluoroethylene, polyether ether ketone, polypropylene, polyethylene and polyphenylene sulfide.

3. The composite proton exchange membrane according to claim 1 or 2, wherein the thickness of the porous reinforcing layer is in the range of 1-20 microns; and the thickness of each of the first proton exchange resin layer and the second proton exchange resin layer is independently in the range of 2-40 microns.

4. The composite proton exchange membrane according to claim 1 or 2, wherein the porosity of the porous reinforcing material is 55-95%. The preparation method comprises: S1, coating a first proton exchange resin dispersion liquid comprising a proton exchange resin and a dispersant on a substrate to obtain a first proton exchange resin dispersion liquid layer; S2, applying a predetermined tensile stress to the porous reinforcing material to change the pore volume change rate of the porous reinforcing material to 1.5-10% and keeping the tensile state, covering the porous reinforcing material in the tensile state on the first proton exchange resin dispersion liquid layer, filling the pores of the porous reinforcing material with the first proton exchange resin dispersion liquid, and then performing an optional first drying to form a porous reinforcing layer; S3, coating a second proton exchange resin dispersion liquid on the porous reinforcing layer, the second proton exchange resin dispersion liquid comprising a proton exchange resin and a dispersant; S4, repeating the steps of S2-S3 according to a predetermined number of proton exchange unit layers, and then performing a second drying to obtain a composite proton exchange membrane; 5. A method for preparing the composite proton exchange membrane according to any one of claims 1 to 4, characterized in that, wherein the drying temperature of the first drying and the second drying is independently in the range of 60°C below the boiling point of the dispersant to 20°C above the boiling point of the dispersant; wherein the first drying and the second drying are each independently performed in three stages and the temperature of the later stage is higher than that of the earlier stage; the first drying comprises three-stage drying with increasing temperature, the temperature of the first stage is 20-60°C below the boiling point of the dispersant; the temperature of the second stage is 20°C below the boiling point of the dispersant to the boiling point of the dispersant; and the temperature of the third stage is the boiling point of the dispersant to 20°C above the boiling point of the dispersant. ​ ​ ​ ​ ​ The second drying comprises three-stage drying with temperature rising in sequence, the first-stage drying temperature is 20-60℃ below the boiling point of the dispersant, the second-stage drying temperature is 20℃ below the boiling point of the dispersant to the boiling point of the dispersant, and the third-stage drying temperature is the boiling point of the dispersant to 20℃ above the boiling point of the dispersant.

6. The production method according to claim 5, wherein The content of the proton exchange resin in the first and second proton exchange resin dispersions is independently 3-30wt%; The dispersant is at least one selected from water, n-propanol, isopropanol, N,N dimethylformamide, N,N dimethylacetamide and N-methylpyrrolidone.

7. The preparation method according to claim 5, characterized in that, The total pore volume change rate of the porous reinforcing material when it is kept in the stretched state is between 2-8% after the predetermined tensile tension is applied to the porous reinforcing material in step S2.

8. Use of the composite proton exchange membrane according to any one of claims 1-4 in a fuel cell or water electrolysis to produce hydrogen.

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