Composite polymer membrane

Abstract

FIELD: composite polymer membranes.SUBSTANCE: invention can be used in membrane-electrode units and fuel cells based on them. A composite polymer membrane for use in low-temperature hydrogen fuel cells comprises a track-etched membrane made of polyvinylidene fluoride with through pores, onto which a filler is applied, filling the through pores of the track-etched membrane and covering its surface. The membrane is obtained by irradiation with high-energy ions followed by chemical etching in an alkali solution comprising potassium permanganate, the material being destroyed by ionization, with the formation of through cylindrical pores in place of the tracks. A filler formed as a result of graft polymerization of a mixture of styrene with divinylbenzene is grafted into the resulting through pores and onto the membrane surface, followed by sulfonation to create proton-conducting clusters. The filler covers both surfaces of the track membrane, forming a strong frame.EFFECT: increase in proton conductivity, strength and stability of the membrane structure, chemical resistance, and service life with high technological indicators.6 cl, 2 dwg

Description

[0001] FIELD OF TECHNOLOGY

[0002] The invention relates to composite polymer membranes, predominantly proton-conducting, to membrane-electrode units (MEU) and fuel cells based on them - PEMFC - Proton-exchange membrane fuel cell (fuel cells with a proton exchange membrane), as well as to other energy devices (proton pumps, gas analyzers, condensers, tritium filters, etc.).

[0003] PRIOR ART

[0004] The most common commercial membranes are perfluorinated electrolyte membranes such as "Nafion", "Flemion", "Neosepta" and their domestic analogue ("MF-4SK") based on copolymers of tetrafluoroethylene with perfluorinated vinyl ethers, which have satisfactory proton-conducting properties of the order of 10 -1 -10 -2 Cm / cm. An essential feature of these membranes is a polymer matrix containing sulfonic acid groups.

[0005] Along with their undeniable advantages, these membranes also have certain disadvantages (limited operating temperature range, low mechanical strength, extremely high cost, etc.), which currently hinder their large-scale implementation in various sectors of the national economy.

[0006] US Patent 10868322, "Hydrocarbon-Based Cross-Linked Membrane in Which Nanoparticles Are Used, Method for Manufacturing Said Membrane, and Fuel Cell," published December 15, 2020, claims a cross-linked composite membrane for PEMFCs made from sulfonated polyphenylsulfone and sulfonated polyhedral oligomers, silsesquioxane, and cross-linked with sulfonic acid groups. In the cross-linked membrane, the molecules are linked together by cross-links (chemically or physically), which imparts strength, stability, and improved properties to the membrane.

[0007] US Patent 11196072 "Composite proton-conducting membrane", published July 30, 2021, discloses a composite proton-conducting membrane consisting of 70-90% by weight of an inorganic polymer with pores filled with 30-10% by weight of an organic polymer, wherein both polymers are capable of conducting protons up to approximately 220°C without the addition of water or solvent. The inorganic polymer is a ceramic form of the tin pyrophosphate anion (TiP2O7 4 ), doped with trivalent metal ions and H + The organic polymer is "polyphenylene coordinated by a quaternary ammonium bisphosphate ion pair"; the ionic liquid cation can be bound to the polymer via bisphosphate anions (H2PO4), creating a Grotthuss relay in a semicrystalline state.

[0008] The disadvantages of the above-mentioned membranes are their structure, which causes insufficient mechanical strength and stability, a tendency to swelling, destruction (up to complete destruction) at temperatures above 90°C, as well as a decrease in proton-conducting properties during the operation of the fuel cell.

[0009] An analogue of the present invention is a composite polymer membrane disclosed in patent RU 2492916, published on September 20, 2013, for the invention "Composite polymer membrane for nanofiltration and method for producing it." The composite polymer membrane comprises a non-woven substrate, an ultrafiltration layer of polysulfone or polyethersulfone applied to its surface, and an ultra-thin selective layer of polypiperazinamide covering it.

[0010] The composite polymer membrane has a structure that ensures high mechanical strength, stability, and service life, along with excellent technological parameters, including filtration performance and selectivity. However, its application is limited and it cannot be used as a proton-conducting membrane for hydrogen energy technologies.

[0011] The technical objective of the invention is to create membranes, primarily proton-conducting ones, and devices based on them, free from the indicated disadvantages.

[0012] SUMMARY OF THE INVENTION

[0013] The said objective is achieved due to the fact that the composite polymer membrane is made in the form of a track membrane made of a fluoropolymer material with through pores, onto which a filler is applied, filling the through pores of the track membrane and covering the surfaces of the track membrane (Fig. 1), obtained by irradiating it with high-energy ions, followed by chemical etching in a solution of concentrated alkali or an alkali solution containing potassium permanganate of the material destroyed by ionization with the formation of pores in place of the tracks in order to obtain through, cylindrical pores, followed by the stage of grafting the filler into the obtained through pores and onto the surface of the membrane, followed by sulfonation to create proton-conducting clusters.

[0014] In a particular case of the invention, the membrane is proton-conducting.

[0015] In a particular embodiment of the invention, the filler forms a high-strength frame around the track membrane.

[0016] In a particular embodiment of the invention, the filler material is chemically bonded to the track membrane material.

[0017] In a particular case of the invention, the material of the track membrane belongs to a group that includes: polyvinylidene fluoride.

[0018] In embodiments of the invention, at least a portion of the filler is formed by graft polymerization of a monomer onto the track membrane. The monomer belongs to a group consisting of: styrene, acrylic monomers, including methyl methacrylate (MMA), methacrylate monomers, including glycol methacrylate, epoxy monomers, amino and carboxyl monomers, and silicone monomers.

[0019] In a particular case of the invention, at least part of the filler is formed as a result of the polymerization of a copolymer grafted onto a track membrane, wherein the copolymer belongs to a group that includes: polystyrene, a mixture of styrene with divinylbenzene; water-soluble polymers: a copolymer of acrylic acid and N-vinylimidazole, poly-N-vinylamides, polyvinyl alcohol, polyethylene glycol, heparin, grafted into the through, cylindrical pores of the membrane and onto the surface of the membrane itself.

[0020] In a particular case of the invention, the filler is sulfonated or doped with inorganic sulfuric or chloric acid.

[0021] In a particular embodiment of the invention, the track membrane is made from a polymer film by bombarding it with high-energy ions and selectively dissolving the material destroyed by ionization with the formation of pores in place of the tracks.

[0022] In a particular case of the invention, the track membrane is additionally irradiated with gamma radiation.

[0023] In a particular case of the invention, the thickness of the track membrane is in the range from 10 μm to 30 μm.

[0024] In a particular embodiment of the invention, the filler covers both surfaces of the track membrane with a layer having a thickness of 0.1 μm to 5 μm.

[0025] In a particular case of the invention, the membrane is hydrated.

[0026] In a particular case of the invention, the proton conductivity of the membrane is not less than 0.3 mS / cm, and the maximum operating temperature is not less than 90°C and the peak power is not less than 500 mW / cm 2 .

[0027] These advantages make composite track membranes attractive in a range of industrial applications where high efficiency and reliability are required.

[0028] The technical result of the claimed invention is the creation of composite polymer membranes characterized by high proton conductivity, a highly durable structure, high stability, chemical resistance, and an extended service life, while maintaining high technological parameters (the membrane and filler materials are fluoropolymers). The resulting membranes can be used in membrane-electrode assemblies (MEAs) for use in fuel cells, electrolyzers, energy management systems, gas purification and separation systems, and other devices.

[0029] BRIEF DESCRIPTION OF DRAWINGS

[0030] The essence of the invention is explained by drawings, in which:

[0031] Fig. 1 - schematic representation of a composite polymer membrane,

[0032] Fig. 2 - Schematic diagram of the production of a composite polymer membrane.

[0033] In the drawings, the same device elements have the same reference numbers.

[0034] The drawings do not cover and, moreover, do not limit the entire scope of implementation options for this technical solution, but represent only illustrative material of particular cases of its implementation.

[0035] EMBODIMENTS OF THE INVENTION

[0036] Fig. 1 schematically shows a composite polymer membrane 1 containing a track membrane 2 with through pores 3, onto which a filler 4 is applied, filling the through pores of the track membrane and covering the surfaces of the track membrane.

[0037] In accordance with the diagram of Fig. 2, the track membrane 2 is made of a polymer film 5 by bombarding it with high-energy ions using a radiation source 6 and selectively dissolving the ionization-destroyed material in an etching bath 7 to form pores 3 at the site of the tracks, followed by applying a filler 4 using a track membrane coating unit 8. Preferably, polyvinylidene fluoride is used as the material of the track membrane for obtaining proton-conducting membranes. This type of membranes has high chemical resistance and strength compared to existing analogues. The main advantage of proton-conducting membranes based on track membranes is the through cylindrical pores 3 filled with a filler 4, preferably sulfonated styrene grafted onto the radicals present in the track membrane 2, Fig. 1, Fig. 2.In addition, a filler consisting of styrene, polystyrene, acrylic monomers including methyl methacrylate (MMA), methacrylate monomers including glycol methacrylate, epoxy monomers, amino and carboxyl monomers, silicone monomers, a mixture of styrene with divinylbenzene, water-soluble polymers, copolymers of acrylic acid and N-vinylimidazole, poly-N-vinylamides, polyvinyl alcohol, polyethylene glycol, heparin is grafted not only into the pores, but also onto the surface, forming a layer up to 5 μm thick.

[0038] A feature of the proton-conducting composite polymer membrane made in accordance with embodiments of the invention is the use of sulfonated styrene 4 not only to fill the pores 3 and provide proton conductivity and gas impermeability, but also to apply sulfonated styrene 4 to the surface of the membrane to form a high-strength framework, Fig. 1, Fig. 2.

[0039] In embodiments of the invention, the polymer composite membrane material is hydrated, which increases the membrane permeability and improves performance.

[0040] This configuration allows for not only an increase in proton conductivity compared to analogs, but also improved physical and mechanical properties due to the formation of a strong styrene framework, which analogs do not have.

[0041] The advantages of this invention lie in the improved performance properties of the membrane, compared to analogues, which include proton conductivity and physical and mechanical properties.

[0042] This membrane is used in the membrane-electrode assembly (MEA) of low-temperature polymer fuel cells. The MEA is typically used as part of a fuel cell.

[0043] The MEA contains a proton-conducting composite polymer membrane, a gas-diffusion cathode and anode, and cathode and anode active layers, to which hydrogen is separately supplied to the cathode layer and air to the anode layer. The electrochemical reaction of hydrogen with air results in the formation of water and allows the process of hydrogen decomposition into electrons and protons to be used as electrical energy.

[0044] The membrane's role is to transfer protons from the cathode layer, where hydrogen is supplied, to the anode layer, where air is supplied, as well as to prevent oscillations and the direct chemical reaction of the gaseous reactants. The electrons obtained after hydrogen decomposition at the cathode enter the grid to generate electrical energy.

[0045] Proton transfer occurs via the Grotthuss mechanism (the "relay" mechanism), which is a proton transfer mechanism in hydrogen-bonded media. The transfer of a hydrogen ion along a chain of hydrogen-bonded molecules occurs in several stages; in practice, the rate of proton movement in a proton-conducting material is determined by the rate of polarization of its molecules. The anomalously high proton conductivity of the composite polymer membrane 1 is provided by filler 4, preferably in the form of sulfonated styrene grafted onto radicals present in the through pores 3 of the polymer track membrane 2, Fig. 1, Fig. 2.

[0046] The composite proton-conducting membrane based on track technology, made in accordance with the present invention, solves the problem of degradation of proton-conducting membranes for temperatures above 80°C from swelling upon contact with an electrolyte.

[0047] The membrane manufactured in accordance with this invention exhibits virtually no swelling, no more than 5% of its original thickness, resulting in stable proton conductivity and strength characteristics, even with its reduced thickness. This new structure allows operation at temperatures above 90°C, which is unachievable with most similar devices. At these temperatures, proton conduction pathways are not disrupted, and there is no degradation or failure of the membrane, which would lead to the cessation of operation of the membrane-electrode assembly based on it.

[0048] INDUSTRIAL APPLICATION

[0049] The proposed devices are designed for a number of applications in various industrial sectors, including energy, automotive, chemical, medical, electronic, environmental.

Claims

1. A composite polymer membrane for use in low-temperature hydrogen fuel cells, characterized in that it contains a track membrane made of polyvinylidene fluoride with through pores, onto which a filler is applied, filling the through pores of the track membrane and covering the surfaces of the track membrane, obtained by irradiating it with high-energy ions, followed by chemical etching in an alkali solution containing potassium permanganate, the material destroyed by ionization with the formation of pores in place of the tracks with the production of through cylindrical pores, followed by the stage of grafting the filler into the obtained through pores and onto the surface of the membrane, with subsequent sulfonation to create proton-conducting clusters, wherein the filler is formed as a result of graft polymerization of a mixture of styrene with divinylbenzene and covers both surfaces of the track membrane, forming a high-strength framework.

2. The membrane according to claim 1, characterized in that the track membrane is additionally irradiated with gamma radiation.

3. The membrane according to paragraph 1, characterized in that the thickness of the track membrane is in the range from 10 µm to 30 µm.

4. The membrane according to item 1, characterized in that the filler covers both surfaces of the track membrane with a layer having a thickness of 0.1 μm to 5 μm.

5. The membrane according to claim 1, characterized in that it is hydrated.

6. The membrane according to paragraph 1, characterized in that its proton conductivity is at least 0.3 mS / cm, the maximum operating temperature is at least 90°C and the peak power is at least 500 mW / cm. 2 .

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