Proton exchange membrane with ion exchange equivalent distribution gradient

Abstract

The invention provides a proton exchange membrane with an ion exchange equivalent distribution gradient, the proton exchange membrane is prepared through multiple spraying, coating or transfer printing processes, and the ion exchange equivalent of the proton exchange membrane gradually changes from the inner surface to the inside to the outside to form a gradient distribution structure. The proton exchange membrane has the following beneficial effects that the problem that the proton conduction capability of the proton exchange membrane is rapidly reduced due to chemical degradation of the ionic polymer layer on the outer side of the proton exchange membrane can be effectively avoided.

Description

Technical Field

[0001] The present invention belongs to the field of proton exchange membranes, and particularly relates to a proton exchange membrane having a gradient distribution of ion exchange equivalent. Background Art

[0002] The gradual depletion and long-term consumption of traditional fossil energy have led to energy crises and environmental pollution. Hydrogen, as a carrier of clean energy, is an ideal alternative to fossil energy. Electrolyzing water to produce hydrogen using renewable energy-derived electricity can achieve green hydrogen production throughout the process.

[0003] Currently, there are mainly three technical routes for the electrolytic water hydrogen production process: alkaline electrolyzer (AEL), solid oxide electrolyzer (SOEL), and proton exchange membrane electrolyzer (PEMEL). Among them, PEMEL has a compact structure, high current density, fast response speed, small floor area, and can operate at a relatively low temperature (20 - 80°C) to electrolyze water into ultra-pure hydrogen and by-product oxygen. The highly dynamic PEMEL technology is very suitable for forming a dynamic, efficient, and clean hydrogen production process based on the fluctuating energy generated by renewable energy such as wind energy and solar energy, converting electrical energy into hydrogen energy for efficient storage to achieve global energy decarbonization in the future. PEMEL uses a solid polymer electrolyte membrane (also known as a proton exchange membrane) as an ion conductor, and has the advantages of high efficiency, high gas purity, no alkaline solution, small volume, and the ability to achieve higher gas production pressure. It is one of the electrolytic water hydrogen production technologies with the most potential for practical application in the field of hydrogen production.

[0004] Therefore, it is necessary to develop a new proton exchange membrane to reduce the energy consumption of electrolytic water and improve the durability of the electrolytic water device. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a proton exchange membrane having a gradient distribution of ion exchange equivalent, and to solve the problems raised in the above background art.

[0006] The present invention is achieved through the following technical solutions: A proton exchange membrane having a gradient distribution of ion exchange equivalent, characterized in that the proton exchange membrane is prepared by multiple spraying, coating, or transfer printing processes, and the ion exchange equivalent of the proton exchange membrane gradually changes from the inner surface to the inside to the outside, forming a gradient distribution structure.

[0007] As a preferred embodiment, it is prepared by the following steps:

[0008] Step 1: Prepare a proton exchange material solution or dispersion containing sulfonic acid groups to produce proton exchange materials with different ion exchange equivalents.

[0009] Step 2: Through multiple spraying, coating, or transfer printing processes, layer by layer coat proton exchange materials with different ion exchange equivalents on the substrate membrane. After each coating, through drying or curing treatment, make the ion exchange equivalent of the proton exchange membrane gradually change from the inner surface to the interior and then to the outer surface, forming a stepped distribution structure of small - large - small ion exchange equivalents.

[0010] Step 3: Add reinforcing materials between adjacent coating layers (each time the proton exchange material is layer by layer coated on the substrate membrane, a coating layer is formed). The reinforcing materials are selected from one or more of biaxially stretched polytetrafluoroethylene, PPS, PEEK, PVDF, and PI.

[0011] Step 4: Post - process the formed small - large - small gradient distribution membrane of ion exchange equivalents, including drying, heat treatment, or chemical stabilization treatment to enhance the performance of the proton exchange membrane.

[0012] In Step 2, the ion exchange equivalent concentrations of the proton exchange material solution or dispersion for each coating are different to achieve a small - large - small gradient distribution of ion exchange equivalents.

[0013] The substrate membrane in Step 2 is any one of release polyethylene terephthalate, release polyimide, release polyethylene naphthalate, release polytetrafluoroethylene, or release polypropylene membrane, with a thickness of 30 - 180 μm.

[0014] The reinforcing materials in Step 3 are added between adjacent coating layers in the form of thin films, fiber meshes, or particles.

[0015] In Step 4, the heat treatment is carried out at 80 °C to 200 °C for 0.1 hour to 3 hours.

[0016] As a preferred embodiment, the proton exchange membrane is applied in fuel cells, electrolytic water devices, or other electrochemical energy conversion systems.

[0017] After adopting the above - mentioned technical solution, the beneficial effect of the present invention is: It can effectively avoid the problem of rapid decline in the proton conduction ability of the proton exchange membrane caused by chemical degradation of the outer - side ion polymer layer of the proton exchange membrane. Description of the Drawings

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a multi-layer structure diagram of the proton exchange membrane.

[0020] Figure 2 It is a stability curve diagram of the proton exchange membrane of the embodiment operating in the water electrolysis device for 1000 h. Detailed implementation manners

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0022] The present invention provides a technical solution: a proton exchange membrane with a gradient distribution of ion exchange equivalent, characterized in that the proton exchange membrane is prepared by multiple spraying, coating or transfer printing processes, and the ion exchange equivalent of the proton exchange membrane gradually changes from the inner surface to the inside to the outside, forming a gradient distribution structure.

[0023] It is prepared by the following steps:

[0024] Step 1: Prepare a proton exchange material solution or dispersion containing sulfonic acid groups to make proton exchange materials with different ion exchange equivalents;

[0025] Step 2: Through multiple spraying, coating or transfer printing processes, layer by layer coat proton exchange materials with different ion exchange equivalents on the substrate membrane. After each coating, through drying or curing treatment, the ion exchange equivalent of the proton exchange membrane gradually changes from the inner surface to the inside and then to the outer surface, forming a stepped distribution structure of small-large-small ion exchange equivalent;

[0026] Step 3: Add a reinforcing material between adjacent coating layers (each time the proton exchange material is layer by layer coated on the substrate membrane, a coating layer is formed), and the reinforcing material is selected from one or more of biaxially stretched polytetrafluoroethylene, PPS, PEEK, PVDF, and PI;

[0027] Step 4: Perform post-treatment on the formed small-large-small gradient distribution membrane of ion exchange equivalent, including drying, heat treatment or chemical stabilization treatment to enhance the performance of the proton exchange membrane.

[0028] In the second step, the ion exchange equivalent concentration of the proton exchange material solution or dispersion coated each time is different to achieve a gradient distribution of small - large - small ion exchange equivalents.

[0029] The substrate membrane in the second step is any one of a release polyethylene terephthalate, a release polyimide, a release polyethylene naphthalate, a release polytetrafluoroethylene, or a release polypropylene membrane, with a thickness of 30 - 180 μm.

[0030] The reinforcing material in the third step is added in the form of a thin film, a fiber web, or particles between adjacent coating layers.

[0031] In the fourth step, the heat treatment is carried out at 80°C to 200°C for 0.1 hour to 3 hours.

[0032] Example 1, the proton exchange membrane is applied in a fuel cell, an electrolytic water device, or other electrochemical energy conversion systems.

[0033] Example 2,

[0034] Prepared by the following steps:

[0035] Step 1, prepare the membrane - forming solution: fully mix perfluorosulfonic acid resin with a water - alcohol solution and a high - boiling solvent to obtain a proton exchange material;

[0036] The water - alcohol solution includes one or more of ethanol, ethylene glycol, n - propanol, isopropanol, propylene glycol, n - butanol, cyclohexanol;

[0037] The high - boiling solvent includes one or more of dimethyl sulfone, dimethyl sulfoxide, N,N - dimethylformamide, N,N - dimethylacetamide, N - methylpyrrolidone, dimethoxyethanol;

[0038] In the perfluorosulfonic acid resin solution, the mass fraction of the perfluorosulfonic acid resin is 5 wt% - 35 wt%, and in the perfluorosulfonic acid resin solution, the ion exchange equivalent is between 700 g / mol and 1200 g / mol.

[0039] Step 2, make the proton exchange membrane: coat the proton exchange material on the substrate in sequence according to different ion exchange equivalents, and carry out drying or curing treatment after each coating.

[0040] Step 3, cure and heat - treat the proton exchange membrane: dry and anneal the substrate and the wet membrane thereon layer by layer, finally peel off the formed membrane from the substrate, and carry out layer - by - layer transfer printing according to different ion exchange equivalents to obtain a proton exchange membrane with a gradient change in ion exchange equivalent.

[0041] Example 3:

[0042] The steps include:

[0043] Step 1: Prepare the film-forming solution: First, fully mix perfluorosulfonic acid resin, water-alcohol solution, and high-boiling solvent to obtain the film-forming solution.

[0044] Step 2: Fabricate the proton exchange membrane: Coat the film-forming solution on the substrate successively according to different ion exchange equivalents, and perform drying or curing treatment after each coating.

[0045] Step 3: Cure and heat-treat the proton exchange membrane: Dry and anneal the substrate and the wet film on it layer by layer, and finally peel off the formed film from the substrate to obtain a proton exchange membrane with a gradient change in ion exchange equivalent.

[0046] Dry the perfluorosulfonic acid resin dispersion into solid powder by spray drying or freeze drying.

[0047] Perfluorosulfonic acid resins with different exchange equivalents need to be prepared by blending high-exchange-equivalent resin and low-exchange-equivalent resin in different proportions.

[0048] The EW value of the low ion exchange equivalent resin used is 720 g / mol, and the EW value of the high ion exchange equivalent resin is 1000 g / mol.

[0049] The perfluorosulfonic acid resin dispersion is selected as a water-alcohol system and any one meeting the corresponding EW value is acceptable, with no other special requirements.

[0050] Example 4:

[0051] Step 1:

[0052] Take 10 g of perfluorosulfonic acid resin with an EW value of 720 g / mol and 10 g of perfluorosulfonic acid resin with an EW value of 1000 g / mol and place them in a reaction kettle. Add 5 g of N-methylpyrrolidone, 40 g of ultrapure water, 15 g of isopropanol, and 20 g of absolute ethanol respectively. Stir at 60 °C for 6 h to obtain a resin dispersion with a solid content of 20%, denoted as RD-1.

[0053] Take 6.7 g of perfluorosulfonic acid resin with an EW value of 720 g / mol and 13.3 g of perfluorosulfonic acid resin with an EW value of 1000 g / mol and place them in a reaction kettle. Add 5 g of N-methylpyrrolidone, 40 g of ultrapure water, 15 g of isopropanol, and 20 g of absolute ethanol respectively. Stir at 60 °C for 6 h to obtain a resin dispersion with a solid content of 20%, denoted as RD-2.

[0054] 16 g of perfluorosulfonic acid resin (EW = 720 g / mol) and 4 g of perfluorosulfonic acid resin (EW = 1000 g / mol) were placed in a reaction kettle. 5 g of N-methylpyrrolidone, 40 g of ultrapure water, 15 g of isopropyl alcohol, and 20 g of anhydrous ethanol were added, respectively. Stirring was performed at 60°C for 6 hours to obtain a resin dispersion with a solids content of 20%, designated RD-3.

[0055] Step 2: Dispersions RD-1, RD-2, and RD-3 obtained in Step 1 were sequentially cast onto a polyimide substrate. The coating machine was set to a gap of 150 μm, a speed of 2 m / min, a coating width of 200 mm, and a coating distance of 400 mm to obtain wet films.

[0056] Step 3: The wet film obtained by coating was baked under 80℃ infrared for 3 minutes, and then dried in a 120℃ oven for 8 minutes.

[0057] Step 4: The above dry films were placed in an oven at 180°C for annealing for 30 minutes to obtain dry films with a thickness of 10 μm, which were recorded as DP-1, DP-2 and DP-3.

[0058] Step 5: Transfer in the order of DP-3, DP-2, DP-1, DP-1, DP-2, and DP-3 to obtain a new proton exchange membrane named PEM-1.

[0059] Step 6: Place PEM-1 in an oven at 180°C for 30 minutes and then test.

[0060] Example 5:

[0061] Step 1:

[0062] ① Place 10 g of perfluorosulfonic acid resin with an EW value of 720 g / mol and 10 g of perfluorosulfonic acid resin with an EW value of 1000 g / mol in a reaction kettle. Add 5 g of N-methylpyrrolidone, 40 g of ultrapure water, 15 g of isopropyl alcohol, and 20 g of anhydrous ethanol, respectively. Stir at 60°C for 6 hours to obtain a resin dispersion with a solid content of 20%, designated RD-1.

[0063] ② Place 16 g of 720 g / mol perfluorosulfonic acid resin and 4 g of 1000 g / mol perfluorosulfonic acid resin in a reaction kettle. Add 5 g of N-methylpyrrolidone, 40 g of ultrapure water, 15 g of isopropyl alcohol, and 20 g of anhydrous ethanol, respectively. Stir at 60°C for 6 h to obtain a resin dispersion with a solids content of 20%, designated RD-3.

[0064] Step 2: The dispersion liquids RD-1 and RD-3 obtained in Step 1 are successively applied onto the polyimide substrate by casting. The gap of the coater is set to 150 μm, the running speed is 2 m / min, the coating width is set to 200 mm, and the coating distance is 400 mm, and wet films are respectively obtained by coating.

[0065] Step 3: The wet films obtained by coating are baked under an infrared lamp at 80 °C for 3 min, and then dried in an oven at 120 °C for 8 min respectively.

[0066] Step 4: The above dry films are respectively put into an oven at 180 °C for annealing for 30 min, and dry films with a thickness of 10 μm are respectively obtained, denoted as DP-1 and DP-3.

[0067] Step 5: Transfer printing is successively carried out in the order of DP-3, DP-3, DP-1, DP-1, DP-3, DP-3 to obtain a new proton exchange membrane named PEM-2.

[0068] Step 6: PEM-2 is put into an oven at 180 °C for annealing for 30 min for testing.

[0069] Example 6:

[0070] Step 1:

[0071] Take 6.7 g of perfluorosulfonic acid resin with an EW value of 720 g / mol and 13.3 g of perfluorosulfonic acid resin with an EW value of 1000 g / mol and place them in a reaction kettle. Add 5 g of N-methylpyrrolidone, 40 g of ultrapure water, 15 g of isopropanol, and 20 g of absolute ethanol respectively. Stir at 60 °C for 6 h to obtain a resin dispersion liquid with a solid content of 2 *%, denoted as RD-2.

[0072] Step 2: The dispersion liquid 2 obtained in Step 1 is applied onto the polyimide substrate by casting. The gap of the coater is set to 150 μm, the running speed is 2 m / min, the coating width is set to 200 mm, and the coating distance is 400 mm, and wet films are respectively obtained by coating.

[0073] Step 3: The wet films obtained by coating are baked under an infrared lamp at 80 °C for 3 min, and then dried in an oven at 120 °C for 8 min respectively.

[0074] Step 4: The above dry films are respectively put into an oven at 180 °C for annealing for 30 min, and dry films with a thickness of 10 μm are respectively obtained, denoted as DP-2.

[0075] Step 5: Transfer printing is successively carried out in the order of DP-2, DP-2, DP-2, DP-2, DP-2, DP-2 to obtain a new proton exchange membrane named PEM-3.

[0076] Step 6: Anneal PEM-3 in an oven at 180 °C for 30 min for testing.

[0077] The proton exchange membranes with a gradient of ion exchange equivalent distribution in Examples 4-6 were used for the long-term durability test of electrolytic water. The test contents are as follows:

[0078] Taking PEM-1 as an example, a proton exchange membrane with a size of 5 cm * 5 cm was cut, and the anode and cathode catalysts were transferred to both sides to prepare a membrane electrode. The iridium loading in the anode catalyst layer was 0.6 mg / cm 2 , and the platinum loading in the cathode catalyst layer was 0.2 mg / cm 2 , and the durability test was carried out at 80 °C and a current density of 3 A / cm 2 .

[0079] Figure 1 It is the CCM durability curve of Examples 1-3 under the condition of a current density of 3 A / cm 2 . It can be seen from the figure that under the long-term high current density condition, the proton exchange membrane with 5 ion exchange equivalent distribution gradients in Example 4 has no problem with the electrolyte resistance during the long-term durability test, and the voltage retention is better than that of Examples 5-6. It is not difficult to see that the multi-ion exchange equivalent concentration gradient distribution is beneficial to reducing the attenuation of the proton membrane conduction ability.

[0080] The film of the present invention is prepared by a homogeneous film-forming method. One or more of polytetrafluoroethylene, PPS, PEEK, and PVDF can be added between the resin layers according to actual needs to enhance the mechanical properties of the proton membrane. And all are within the protection scope of the present invention.

[0081] The proton exchange membrane with a gradient of ion exchange equivalent distribution is obtained by the method of coating first and then transferring in the present invention. In actual operation, various different processes such as coating-drying-coating, spraying-drying-spraying, or coating, spraying, and transferring between layers can be combined to prepare the film. And all are within the protection scope of the present invention.

[0082] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A proton exchange membrane with a gradient in ion exchange equivalent distribution, characterized in that, The proton exchange membrane is prepared by multiple spraying, coating or transfer printing processes, and the ion exchange equivalent of the proton exchange membrane gradually changes from the inner surface to the interior to the exterior, forming a gradient distribution structure.

2. The proton exchange membrane with an ion exchange equivalent distribution gradient as described in claim 1, characterized in that: It is prepared by the following steps: Step 1: Prepare a proton exchange material solution or dispersion containing sulfonic acid groups to make proton exchange materials with different ion exchange equivalents; Step 2: Through multiple spraying, coating or transfer printing processes, layer by layer coat the proton exchange materials with different ion exchange equivalents on the substrate membrane. After each coating, through drying or curing treatment, make the ion exchange equivalent of the proton exchange membrane gradually change from the inner surface to the interior and then to the outer surface, forming a stepped distribution structure of small-large-small ion exchange equivalent; Step 3: Add a reinforcing material between adjacent coating layers, and the reinforcing material is selected from one or more of biaxially stretched polytetrafluoroethylene, PPS, PEEK, PVDF, and PI; Step 4: Perform post-treatment on the formed small-large-small gradient distribution membrane of ion exchange equivalent, including drying, heat treatment or chemical stabilization treatment to enhance the performance of the proton exchange membrane.

3. The proton exchange membrane with a gradient in ion exchange equivalent distribution according to claim 2, characterized in that: In Step 2, the ion exchange equivalent concentration of the proton exchange material solution or dispersion for each coating is different to achieve a small-large-small gradient distribution of ion exchange equivalent.

4. A proton exchange membrane having a gradient in ion exchange equivalent distribution as described in claim 3, characterized in that: The substrate membrane in Step 2 is any one of a release polyethylene terephthalate, a release polyimide, a release polyethylene naphthalate, a release polytetrafluoroethylene, or a release polypropylene membrane, with a thickness of 30 - 180 μm.

5. A proton exchange membrane having a gradient in ion exchange equivalent distribution as claimed in claim 4, wherein: The reinforcing material in Step 3 is added between adjacent coating layers in the form of a film, a fiber mesh or particles.

6. A proton exchange membrane having a gradient of ion exchange equivalent distribution as described in claim 5, characterized in that: In Step 4, the heat treatment is carried out at 80°C to 200°C for a time of 0.1 hour to 3 hours.

7. A proton exchange membrane having a gradient in ion exchange equivalent distribution according to any one of claims 1 to 6, characterized in that: The proton exchange membrane is applied in fuel cells, electrolytic water devices or other electrochemical energy conversion systems.

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