Multilayer ion exchange membranes for electrolytic applications

Abstract

A novel multilayer ion exchange membrane has been developed for electrolytic applications, the novel multilayer ion exchange membrane includes an ion exchange membrane layer, a catalyst layer coated on a first surface of the ion exchange membrane, a first polyelectrolyte multilayer coated on the catalyst layer, and optionally a second polyelectrolyte multilayer coated on a second surface of the ion exchange membrane.

Description

[0001] Priority Claim

[0002] This application claims the priority of U.S. Provisional Patent Application Serial No. 63 / 476,983, filed on December 23, 2022, the entire content of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to ion exchange membranes and, more particularly, to such membranes for electrochemical reactions. Background Art

[0004] Hydrogen plays an important role on the path towards an environmentally friendly low-carbon energy structure as an energy carrier for grid balancing or power-to-gas and power-to-liquid processes. Water electrolysis produces high-quality hydrogen by electrochemically decomposing water into hydrogen and oxygen; this reaction is given by Equation 1 below. The water electrolysis process is endothermic and electricity is the energy source. When this method is powered by renewable energy such as wind, solar or geothermal energy, water electrolysis has a zero carbon footprint. The main water electrolysis technologies include alkaline electrolysis, proton exchange membrane (PEM) water electrolysis (such as Figure 1 PEMWE as shown), anion exchange membrane (AEM) water electrolysis (such as Figure 2 AEMWE as shown) and solid oxide water electrolysis.

[0005] As Figure 1 shown, in the PEMWE system 100, the anode 105 and the cathode 110 are separated by a solid PEM electrolyte 115, such as a sulfonated tetrafluoroethylene-based fluoropolymer sold under the trade mark by the Chemours company. The anode and cathode catalysts typically comprise IrO2 and Pt, respectively. At the positively charged anode 105, pure water 120 is oxidized to produce oxygen 125, electrons (e -) and protons; this reaction is given by Equation 2. Protons are transported from the anode 105 to the cathode 110 through the proton-conducting PEM 115. At the negatively charged cathode 110, a reduction reaction occurs where electrons from the cathode 110 are given to protons to form hydrogen gas 130; this reaction is given by Equation 3. The PEM 115 not only conducts protons from the anode 105 to the cathode 110 but also separates the H2 gas 130 and O2 gas 125 produced in the water electrolysis reaction. PEM water electrolysis is one of the advantageous methods for converting renewable energy into high-purity hydrogen, with the advantages of a compact system design under high pressure difference, high current density, high efficiency, fast response, small footprint, low-temperature (20 °C - 90 °C) operation, and high-purity oxygen by-products. However, one of the main challenges of PEM water electrolysis is the high capital cost of the cell stack, including expensive acid-resistant stack hardware (such as Pt-coated Ti bipolar plates), expensive noble metal catalysts required for the electrodes, and expensive PEMs.

[0006] Water electrolysis reaction: 2H2O → 2H2 + O2 (1)

[0007] Anodic oxidation reaction of PEMWE: 2 H2O → O2 + 4 H + + 4 e - (2)

[0008] Cathodic reduction reaction of PEMWE: 2 H + + 2 e- → H2 (3)

[0009] AEMWE is a developing technology. As Figure 2 shown, in the AEMWE system 200, the anode 205 and the cathode 210 are separated by a solid AEM electrolyte 215. Generally, a water feed 220 with an added electrolyte (such as diluted KOH or K2CO3 or deionized water) is fed to the cathode side. For some cases, a water feed 220 with an added electrolyte (such as diluted KOH or K2CO3 or deionized water) is fed to the anode side or both the cathode side and the anode side. Anode and cathode catalysts typically include Ni-based or Ni-alloy catalysts without platinum group metals. At the negatively charged cathode 210, water is reduced by adding four electrons to form hydrogen gas 225 and hydroxide ions; this reaction is given by Equation 4. The hydroxide ions diffuse from the cathode 210 to the anode 205 through the hydroxide-ion-conducting AEM 215. At the positively charged anode 205, the hydroxide ions recombine to form water and oxygen gas 230; this reaction is given by Equation 5. The AEM 215 not only conducts hydroxide ions from the cathode 210 to the anode 205 but also separates the H2 225 and O2 230 produced in the water electrolysis reaction. The AEM 215 allows the preparation of very high-purity hydrogen gas 225 with at least 99.9% purity at pressures up to 35 bar.

[0010] Cathodic reduction reaction of AEMWE: 4 H2O + 4 e - → 2 H2 + 4 OH - (4)

[0011] Anodic oxidation reaction of AEMWE: 4 OH - → 2 H2O + O2 + 4 e - (5)

[0012] AEMWE has advantages over PEMWE as it allows the use of cheaper catalysts without platinum group metals, such as Ni and Ni alloy catalysts. In addition, much cheaper stainless steel bipolar plates can be used in the gas diffusion layer (GDL) of AEMWE instead of the expensive Pt-coated Ti bipolar plates currently used in PEMWE. However, the biggest obstacles in developing AEM systems are membrane hydroxyl ion conductivity and stability, as well as the lack of understanding of how to integrate catalysts into AEM systems. Research on AEMWE in the literature has focused on developing electrocatalysts, AEMs, and understanding the operating mechanism, with the general aim of obtaining an efficient, low-cost, and stable AEMWE technology.

[0013] The anode in an electrochemical cell is the electrode where the main reaction is oxidation (e.g., the water oxidation / oxygen evolution reaction electrode for a water electrolyzer). The cathode in an electrochemical cell is the electrode where the main reaction is reduction (e.g., the proton reduction / hydrogen evolution reaction electrode for a water electrolyzer). The membrane is one of the key materials constituting the electrolyzer and is an important driver for safety and performance. Some important properties of the membrane for electrolysis include high conductivity, high ion permeability, high ion exchange capacity (for ion exchange membranes), high ion / H2 and O2 selectivity (low H2 and O2 permeability / crossover), low price, low area resistance that minimizes efficiency losses due to ohmic polarization, high tolerance to oxidation and reduction conditions, chemical inertness over a wide pH range, high thermal stability, and high proton conductivity and high mechanical strength (thickness, low swelling).

[0014] Recently, newer cost-effective high-performance membrane materials for use with battery stack components for water electrolysis that have wide applications in renewable energy systems have been invented. Although presumed to be effective for their intended purposes, it is known that hydrogen can migrate through thin films and affect the effectiveness and efficiency of the battery. If the concentration of H2 in O2 reaches 2%, the H2 crossover from the cathode to the anode flow also causes safety problems.

[0015] Therefore, there is a desire to provide a membrane that reduces or eliminates the amount of hydrogen gas flowing through the membrane. Summary of the Invention

[0016] The present invention provides an ion exchange membrane, which includes a catalyst layer on one side of the membrane. A polyelectrolyte multilayer coating is provided on the catalyst layer. The catalyst layer forms water from the permeated hydrogen and oxygen, which results in higher gas purity and solves the safety problem of gas migration through the membrane. A radical scavenger may be included to improve the chemical / electrochemical stability of the membrane.

[0017] Thus, in a first aspect, the present invention is generally characterized by providing a multilayer ion exchange membrane having: an ion exchange membrane layer; a catalyst layer coated on a first surface of the ion exchange membrane layer; and a first polyelectrolyte multilayer coating coated on the catalyst layer.

[0018] The first polyelectrolyte multilayer coating may be thinner than the ion exchange membrane layer and may include alternating polycationic polymer layers and polyanionic polymer layers.

[0019] The multilayer ion exchange membrane may further include a second polyelectrolyte multilayer coating coated on a second surface of the ion exchange membrane layer. The first polyelectrolyte multilayer coating and the second polyelectrolyte multilayer coating may be thinner than the ion exchange membrane layer. One or both of the first polyelectrolyte multilayer coating and the second polyelectrolyte multilayer coating may include alternating polycationic polymer layers and polyanionic polymer layers.

[0020] The catalyst layer may contain a catalyst and an ionomer. The catalyst may include Pt, PtCo, Pd, PdCo, or a mixture thereof. The ionomer may be a proton-conducting fluorinated or non-fluorinated polymer ionomer, or a hydroxide-conducting polymer ionomer.

[0021] The catalyst layer may further contain an additive. The additive may be CeO2, Ce(OH)4, CeO2 / ZrO2, Ce(OH)4 / ZrO2, or a mixture thereof.

[0022] The catalyst layer may be thinner than the ion exchange membrane layer and thicker than the first polyelectrolyte multilayer coating.

[0023] In a second aspect, the present invention can be generally characterized as providing a membrane electrode assembly having: an ion exchange membrane layer; a catalyst layer coated on a first surface on a first side of the ion exchange membrane layer; a first polyelectrolyte multilayer coating coated on the catalyst layer; an anode electrode disposed on a surface of the first polyelectrolyte multilayer coating; and a cathode electrode disposed on a second side of the ion exchange membrane layer.

[0024] The first polyelectrolyte multilayer coating may be thinner than the ion exchange membrane layer and may include alternating polycationic polymer layers and polyanionic polymer layers.

[0025] The membrane electrode assembly may include a second polyelectrolyte multilayer coating between the ion exchange membrane layer and the cathode electrode. The second polyelectrolyte multilayer coating may be coated on a second surface on a second side of the ion exchange membrane layer. The first polyelectrolyte multilayer coating and the second polyelectrolyte multilayer coating may be thinner than the ion exchange membrane layer. One or both of the first polyelectrolyte multilayer coating and the second polyelectrolyte multilayer coating may include alternating polycationic polymer layers and polyanionic polymer layers.

[0026] The catalyst layer may comprise a catalyst and an ionomer. The catalyst may be Pt, PtCo, Pd, PdCo, or a mixture thereof. The ionomer may be a proton-conducting fluorinated or non-fluorinated polymer ionomer, or a hydroxide-conducting polymer ionomer.

[0027] The catalyst layer further comprises an additive. The additive may be CeO2, Ce(OH)4, CeO2 / ZrO2, Ce(OH)4 / ZrO2, or a mixture thereof.

[0028] The catalyst layer may be thinner than the ion exchange membrane layer and thicker than the first polyelectrolyte multilayer coating.

[0029] In a third aspect, the invention may be broadly characterized as providing a method for preparing a multilayer ion exchange membrane, the method comprising the steps of: coating a catalyst layer on a first surface on a first side of the ion exchange membrane; and coating a first polyelectrolyte multilayer on the catalyst layer.

[0030] The method may further comprise coating a second polyelectrolyte multilayer on a second surface on a second side of the ion exchange membrane. The coating of the second polyelectrolyte multilayer may be carried out during or after the coating of the first polyelectrolyte multilayer.

[0031] The method may further comprise applying a cathode electrode on a second surface on a second side of the ion exchange membrane.

[0032] The method may further comprise applying an anode electrode on the first polyelectrolyte multilayer.

[0033] Additional aspects, embodiments, and details of the invention (all of which may be combined in any way) are set forth in the following detailed description of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a diagram of an embodiment of a PEMWE cell.

[0035] Figure 2 is a diagram of an embodiment of an AEMWE cell.

[0036] Figure 3 is a diagram of an embodiment of the multilayer ion exchange membrane of the invention for PEMWE applications.

[0037] Figure 4 It is a diagram of an embodiment of the multi-layer ion exchange membrane of the present invention for AEMWE applications.

[0038] Figure 5 It is a graph of the polarization curves of a water electrolyzer at 80 °C and atmospheric pressure, respectively including the following substances: (a) PEL-PEM-MEA; (b) PEL-H2R-PEM-MEA; and (c) PEL-H2RCe-PEM-MEA. Detailed Description

[0039] A new multi-layer ion exchange membrane for electrolysis applications has been developed. The multi-layer ion exchange membrane includes an ion exchange membrane layer, a catalyst layer coated on the first surface of the ion exchange membrane, a first polyelectrolyte multi-layer coated on the catalyst layer, and optionally a second polyelectrolyte multi-layer coated on the second surface of the ion exchange membrane.

[0040] The new multi-layer ion exchange membrane reduces H2 in the O2 content at the anode flow of the water electrolyzer by incorporating an H2 recombination catalyst layer into the ion exchange membrane. The catalyst layer is coated to form a thin layer of the H2 recombination catalyst layer on one surface of the substrate ion exchange membrane. The H2 recombination catalyst layer effectively reduces H2 crossover from the cathode flow to the anode flow and prevents the formation of an explosive H2 / O2 mixture in the anode flow. The H2 recombination reaction of H2 and O2 results in the formation of water, thus reducing the H2 concentration in O2 in the anode flow. A polyelectrolyte multi-layer coating is applied on the catalyst layer. These layers can be applied by dip coating, spray deposition, centrifugal deposition, electrodeposition, meniscus / slot die coating, brush coating, roll coating, metering rod / Meyer rod coating, doctor blade casting, etc. When developing a membrane electrode assembly including a multi-layer ion exchange membrane, an anode, and a cathode, the polyelectrolyte multi-layer coating on the H2 recombination catalyst layer is used to prevent direct contact between the H2 recombination catalyst and the anode catalyst. The polyelectrolyte multi-layer coating on the H2 recombination catalyst layer also reduces gas crossover without degrading the electrolysis performance. The new multi-layer ion exchange membrane may also contain a radical scavenger, such as CeO2 or Ce(OH)4.

[0041] The permeated H2 and O2 form H2O at the H2 recombination catalyst layer, resulting in higher gas purity and solving safety problems. Additionally, the radical scavenger improves the chemical / electrochemical stability of the membrane.

[0042] Figure 3 It is a diagram of a multi-layer ion exchange membrane 300 for PEMWE, which has a substrate ion exchange membrane 302 having a first side 304 with a first surface 306 and a second side 308 with a second surface 310.

[0043] The ion exchange membrane 302 comprises a cation exchange polymer or a mixture of a cation exchange polymer and an inorganic filler, the inorganic filler comprising covalently bonded acidic functional groups. The ion exchange membrane 302 in the novel multilayer improved ion exchange membrane 300 comprises negatively charged -SO3 - , -COO - , –PO3 2- or -PO3H - cation exchange functional groups. The cation exchange polymer in the ion exchange membrane 302 can be selected from, but is not limited to, perfluorinated ionomers such as or crosslinked perfluorinated cation exchange polymers, partially fluorinated polymers, crosslinked partially fluorinated cation exchange polymers, non-fluorinated hydrocarbon polymers, crosslinked non-fluorinated hydrocarbon cation exchange polymers, or combinations thereof. The ion exchange membrane 302 has high mechanical strength, good chemical and thermal stability, and good proton conductivity. However, when thinner membranes with lower cost and lower area specific resistance are used in electrolysis applications, the ion exchange membrane 302 typically has high H2 and O2 crossover. Compared with the ion exchange membrane 302 without a catalyst layer and a polyelectrolyte multilayer coating, the novel multilayer ion exchange membrane 300 has a low membrane area specific resistance, low swelling, significantly reduced H2 and O2 crossover, and enhanced proton conductivity.

[0044] The ion exchange membrane 302 used to prepare the multilayer ion exchange membrane 300 can be the composite proton conductive membrane described in U.S. Patent Application No. 17 / 162,421, filed on January 29, 2021, entitled Composite Proton Conductive Membranes, the entire text of which is incorporated herein by reference. This application discloses a novel composite proton conductive membrane that comprises an inorganic filler having covalently bonded acidic functional groups and a high surface area of at least 150 m 2 / g, and a water-insoluble ion conductive polymer.

[0045] The inorganic filler comprising covalently bonded acidic functional groups in the ion exchange membrane 302 can be selected from, but is not limited to, silica gel, precipitated silica, pyrogenic silica, colloidal silica, alumina, silica-alumina, zirconia, molecular sieves, metal-organic frameworks, zeolitic imidazolate frameworks, covalent organic frameworks, or combinations thereof, and wherein the filler can have covalently bonded acidic functional groups and 150 m 2 / g or higher, or 300 m 2 / g or higher, or 400 m 2both having a high surface area of / g or higher. The molecular sieve has a framework structure, which may be characterized by a unique wide-angle X-ray diffraction pattern. Zeolites are a subclass of molecular sieves based on aluminosilicate compositions. Non-zeolite molecular sieves are based on other compositions, such as aluminophosphates, silicoaluminophosphates, and silica. Molecular sieves can have different chemical compositions and different framework structures. Molecular sieves can be microporous or mesoporous molecular sieves and need to be stable in an aqueous solution with a pH less than 6. Acidic functional groups covalently bonded to the inorganic filler can be selected from, but are not limited to, -H2PO3, -R-H2PO3, -SO3H, -R-SO3H, -COOH, -R-COOH, -C6H5OH, -R-C6H5OH, or combinations thereof, where R represents a straight-chain alkyl group, a branched-chain alkyl group, a cycloalkyl group, an organic amino group, an acid group-substituted organic amino group, or an aryl group, and the number of carbon atoms in these groups is preferably from 1 to 20, more preferably from 1 to 10. The inorganic filler can be in the form of, but is not limited to, particles, beads, sheets, rods, or fibers. The size of the inorganic filler is in the range of 2 nm to 200 μm, or in the range of 10 nm to 100 μm, or in the range of 50 nm to 80 μm. In some embodiments, the inorganic filler is aminopropyl-N,N-bis(methylphosphonic acid)-functionalized silica such as AMPA, aminopropyl-N,N-bis(methylphosphonic acid)-functionalized fumed silica, n-propylphosphonic acid-functionalized silica, n-propylphosphonic acid-functionalized fumed silica, p-toluenesulfonic acid-functionalized silica, p-toluenesulfonic acid-functionalized fumed silica, 4-ethylbenzenesulfonic acid-functionalized silica such as methylbenzenesulfonic acid, 4-ethylbenzenesulfonic acid-functionalized fumed silica, n-propylsulfonic acid-functionalized silica, n-propylsulfonic acid-functionalized fumed silica, or combinations thereof.

[0046] Suitable cation exchange polymers include, but are not limited to, perfluorinated sulfonic acid polymers, perfluorinated carboxylic acid polymers, sulfonated aromatic polymers, crosslinked sulfonated aromatic polymers, or combinations thereof. Suitable cation exchange polymers include, but are not limited to, copolymers of tetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid, copolymers of tetrafluoroethylene and perfluoro-5-oxa-6-heptene-sulfonic acid, copolymers of tetrafluoroethylene and perfluoro-4-oxa-5-hexene-sulfonic acid, copolymers of tetrafluoroethylene and perfluoro-3-oxa-4-pentene-sulfonic acid, copolymers of perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid and perfluoro(2,2-dimethyl-1,3-dioxolane), copolymers of perfluoro-5-oxa-6-heptene-sulfonic acid and perfluoro(2,2-dimethyl-1,3-dioxolane), copolymers of perfluoro-4-oxa-5-hexene-sulfonic acid and perfluoro(2,2-dimethyl-1,3-dioxolane), copolymers of perfluoro-3-oxa-4-pentene-sulfonic acid and perfluoro(2,2-dimethyl-1,3-dioxolane), copolymers of perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid and perfluoro(2-methylene-4-methyl-1,3-dioxolane), copolymers of perfluoro-5-oxa-6-heptene-sulfonic acid and perfluoro(2-methylene-4-methyl-1,3-dioxolane), copolymers of perfluoro-4-oxa-5-hexene-sulfonic acid and perfluoro(2-methylene-4-methyl-1,3-dioxolane), copolymers of perfluoro-3-oxa-4-pentene-sulfonic acid and perfluoro(2-methylene-4-methyl-1,3-dioxolane), copolymers of perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid and 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxolane, copolymers of perfluoro-5-oxa-6-heptene-sulfonic acid and 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxolane, copolymers of perfluoro-4-oxa-5-hexene-sulfonic acid and 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxolane, copolymers of perfluoro-3-oxa-4-pentene-sulfonic acid and 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxolane, sulfonated poly(ether ether ketone) (SPEEK), sulfonated polyethersulfone, sulfonated polyphenylsulfone, sulfonated poly(2,6-dimethyl-1,4-phenylene oxide), sulfonated poly(4-phenoxybenzoyl-1,4-phenylene), sulfonated polyphenylene ether, sulfonated poly(phenylene), sulfonated poly(phthalazinone), crosslinked SPEEK, crosslinked sulfonated polyethersulfone, crosslinked sulfonated polyphenylsulfone, crosslinked (polyphenylene sulfide sulfone nitrile), sulfonated polystyrene, sulfonated poly(vinyl toluene), crosslinked sulfonated polystyrene, crosslinked sulfonated poly(vinyl toluene), or combinations thereof.

[0047] The novel multilayer ion exchange membrane 300 includes a catalyst layer 312 applied to the first surface 306 of the ion exchange membrane 302. The catalyst layer 312 may include a catalyst and an ionomer. The catalyst is used for hydrogen recombination reaction and may be Pt, Pt / Co, Pd, Pd / Co, and mixtures thereof. The ionomer may be a proton conducting fluorinated or non-fluorinated polymer ionomer.

[0048] The catalyst layer 312 may further include additives such as CeO2, Ce(OH)4, CeO2 / ZrO2, Ce(OH)4 / ZrO2, or mixtures thereof. These additives, such as CeO2, Ce(OH)4, CeO2 / ZrO2, Ce(OH)4 / ZrO2, or mixtures thereof, are free radical scavengers having an active redox pair of Ce(IV) / Ce(III). The H2 recombination catalyst layer 312 catalyzes the H2 recombination reaction and the Figure 1 The catalytic reaction in the cathode 110 shown in the presence of O2 also produces hydrogen peroxide and free radical intermediates such as peroxyhydroxyl radical (HOO π ) and hydroxyl (HO π ) free radicals. These reactive oxygen species lead to membrane and ionomer degradation. Incorporation of free radical scavengers into the H2 recombination catalyst layer provides improved durability of the multilayer ion exchange membrane.

[0049] On catalyst layer 312, there is a polyelectrolyte multilayer coating 314, which may include alternating polycationic polymer layers 316 and polyanionic polymer layers 318. On second surface 310 of ion exchange membrane 302, there may be a second polyelectrolyte multilayer coating 320, which may include alternating polycationic polymer layers 322 and polyanionic polymer layers 324.

[0050] The first layer of polyelectrolyte layer 314 deposited on catalyst layer 312 should be a layer of polycationic polymer with a positive ionic charge opposite to the ionic charge on the ionomer in catalyst layer 312. This results in the formation of a stable polyelectrolyte coating via electrostatic interactions between catalyst layer 312 and polyelectrolyte coating 316.

[0051] A polyanionic polymer with an opposite charge is then deposited on the surface of the first polycationic polymer coating via electrostatic interaction to form a second portion of the first polyelectrolyte bilayer. The polyelectrolyte multilayer can be formed following the same alternating deposition process.

[0052] The first layer of polyelectrolyte layer 322 optionally deposited on the second surface of ion exchange membrane 302 should be a polycationic polymer layer with a positive ionic charge opposite to the ionic charge on ion exchange membrane layer 302. This results in the formation of a stable polyelectrolyte coating via electrostatic interactions between ion exchange membrane layer 302 and polyelectrolyte coating 322.

[0053] Then, a polyanionic polymer with an opposite charge is deposited on the surface of the first polycationic polymer coating 322 via electrostatic interaction to form the second part of the first polyelectrolyte bilayer. The polyelectrolyte multilayers can be formed according to the same alternating deposition process.

[0054] The thickness of each layer 318, 316, 322, 324 of the polyanion or polycation can be less than 50 nm, or less than 20 nm, or less than 10 nm, or less than 5 nm.

[0055] The first polyelectrolyte multilayer coating 314 can be thinner than the ion exchange membrane 302. Additionally, the first polyelectrolyte multilayer coating 314 and the second polyelectrolyte multilayer coating 320 can be thinner than the ion exchange membrane 302. The catalyst layer 312 can be thinner than the ion exchange membrane layer 302 and thicker than the first polyelectrolyte multilayer 314.

[0056] The polyanionic polymer in the polyelectrolyte multilayers 314, 320 has a negative charge and can be the same as or different from the cation exchange polymer in the ion exchange membrane 302, provided that the polyanionic polymer cannot be the first polyelectrolyte layer deposited on the surface of a negatively charged cation exchange membrane. The polyanionic polymers suitable for preparing the multilayer ion exchange membrane have a proton conductivity similar to or higher than that of the cation exchange membrane and an inherent H2 and O2 permeability similar to or lower than that of the cation exchange membrane. However, the polyanionic polymer and the polycationic polymer are soluble in aqueous solutions, which renders the membranes prepared from the polyanionic polymer or the polyanionic polymer unsuitable for water electrolysis or fuel cell applications. Compared with the cation exchange membrane used for water electrolysis applications, the polyelectrolyte layers 314, 320 deposited on the catalyst layer 312 and the ion exchange membrane 302 via layer-by-layer self-assembly are not only insoluble and thermally and chemically stable, but also have a significantly reduced swelling of the cation exchange membrane and H2 and O2 crossover, as well as enhanced proton conductivity.

[0057] The polycationic polymers suitable for preparing the multilayer ion exchange membrane 300 include, but are not limited to, protonated chitosan; amine-based linear, highly branched or dendritic polycationic polymers selected from the group consisting of: polybiguanide, quaternary ammonium polyethyleneimine, quaternary ammonium polypropyleneimine, quaternary ammonium polyamidoamine (PAMAM), poly(vinylamine hydrochloride) (PVH), poly(allylamine hydrochloride) (PAH), poly(amidoamine hydrochloride), poly(N-isopropylallylamine hydrochloride), poly(N-tert-butylallylamine hydrochloride), poly(N-1,2-dimethylpropylallylamine hydrochloride), poly(N-methylallylamine hydrochloride), poly(N,N-dimethylallylamine hydrochloride), poly(2-vinylpiperidine hydrochloride), poly(4-vinylpiperidine hydrochloride), poly(diallyldimethylammonium chloride), poly(acrylamide-co-diallyldimethylammonium chloride), poly(diallylmethylamine hydrochloride), a copolymer of 2-propen-1-amine hydrochloride and N-2-propenyl-2-propen-1-amine hydrochloride, poly(N-alkyl-4-vinylpyridinium) salts, polylysine, polyornithine, polyarginine, poly(ethylene oxide)-block-poly(vinylbenzyltrimethylammonium chloride), poly(ethylene oxide)-block-poly(l-lysine), poly(2-methacryloyloxyethyl phosphorylcholine methacrylate)-block-poly(vinylbenzyltrimethylammonium chloride), poly[2-(dimethylamino)-ethyl methacrylate], poly[3-(dimethylamino)-propyl methacrylate], poly[2-(dimethylamino)-ethyl methacrylamide], poly[3-(dimethylamino)propyl methacrylamide], poly[2-(trimethylamino)ethyl methacrylate chloride], poly[2-(diethylamino)ethyl methacrylate], poly[2-(dimethylamino)ethyl acrylate]; or combinations thereof.

[0058] Polymeric anions suitable for preparing the multilayer ion exchange membrane 300 include, but are not limited to, sulfonated hydrocarbon polymers, poly(acrylic acid), poly(sodium phosphate), or negatively charged polysaccharide polymeric anions, or combinations thereof. Suitable sulfonated hydrocarbon polymers include, but are not limited to, sulfonated poly(ether ether ketone), sulfonated polyethersulfone, sulfonated polyphenylsulfone, sulfonated poly(2,6-dimethyl-1,4-phenylene oxide), sulfonated poly(4-phenoxybenzoyl-1,4-phenylene), sulfonated polyphenylene ether, sulfonated poly(phenylene), sulfonated poly(phthalazinone), sulfonated polystyrene, sulfonated poly(vinyltoluene), poly(acrylic acid), poly(sodium vinylsulfonate), poly(sodium phosphate), or combinations thereof. Suitable negatively charged polysaccharide polymeric anions include, but are not limited to, sodium alginate, potassium alginate, calcium alginate, ammonium alginate, alginic acid, sodium hyaluronate, potassium hyaluronate, calcium hyaluronate, ammonium hyaluronate, hyaluronic acid, κ-carrageenan, λ-carrageenan, ι-carrageenan, carboxymethyl gellan gum, sodium carboxymethyl gellan gum, potassium carboxymethyl gellan gum, calcium carboxymethyl gellan gum, ammonium carboxymethyl gellan gum, carboxymethyl cellulose, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, calcium carboxymethyl cellulose, ammonium carboxymethyl cellulose, or combinations thereof.

[0059] Figure 4 is a diagram of a multilayer ion exchange membrane 400 for AEMWE, which has a base ion exchange membrane 402 with a first side 404 having a first surface 406 and a second side 408 having a second surface 410. The ion exchange membrane 402 is an anion exchange membrane comprising an anion exchange polymer. The ion exchange membrane 402 in the novel multilayer improved ion exchange membrane 400 comprises anion exchange functional groups with positive ionic charges, such as piperidinium, quaternized carbazole derivatives, quaternized phenothiazine derivatives, or piperidinium salts. The anion exchange polymer in the ion exchange membrane 402 not only has a stable hydrophobic polymer backbone comprising linear aromatic units (such as biphenyl and terphenyl) and / or polycyclic aromatic units (such as naphthalene and phenanthrene), but also has cationic groups covalently bonded to the polymer, such as piperidinium, quaternized carbazole derivatives, quaternized phenothiazine derivatives, or piperidinium salts. The ion exchange membrane 402 has high mechanical strength, good chemical and thermal stability, high OH - conductivity and low swelling in an electrolytic cell. Compared with the ion exchange membrane 402 without a catalyst layer and polyelectrolyte multilayer coatings, the novel multilayer ion exchange membrane 400 has a low membrane area specific resistance, low swelling, significantly reduced H2 and O2 crossover, and enhanced OH - conductivity.

[0060] The ion exchange membrane 402 for preparing the multi-layer ion exchange membrane 400 may be the anion exchange membrane described in U.S. Patent Application No. 17 / 474,198, entitled Anion Exchange Polymers and Membranes for Electrolysis, filed on September 14, 2021, the entire text of which is incorporated herein by reference. The ion exchange membrane 402 for preparing the multi-layer ion exchange membrane 400 may be the anion exchange membrane described in U.S. Patent Application No. 17 / 662,676, entitled Anion Exchange Polymers and Membranes for Electrolysis, filed on May 10, 2022, the entire text of which is incorporated herein by reference. The ion exchange membrane 402 for preparing the multi-layer ion exchange membrane 400 may be the anion exchange membrane described in U.S. Patent Application No. 17 / 823,975, entitled Anion Exchange Polymers and Membranes for Electrolysis, filed on September 1, 2022, the entire text of which is incorporated herein by reference.

[0061] The novel multi-layer ion exchange membrane 400 includes a catalyst layer 412 applied on the first surface 406 of the ion exchange membrane 402. The catalyst layer 412 may comprise a catalyst and an ionomer. The catalyst is used for the hydrogen recombination reaction and may be Pt, Pt / Co, Pd, Pd / Co, and mixtures thereof. The ionomer may be a hydroxide-conducting polymer ionomer.

[0062] The catalyst layer 412 may further comprise additives such as CeO2, Ce(OH)4, CeO2 / ZrO2, Ce(OH)4 / ZrO2, or mixtures thereof. These additives, such as CeO2, Ce(OH)4, CeO2 / ZrO2, Ce(OH)4 / ZrO2, or mixtures thereof, are radical scavengers with an active redox pair of Ce(IV) / Ce(III). The catalytic H2 recombination reaction in the H2 recombination catalyst layer 412 and the catalytic reaction in the cathode 210 as Figure 2 shown also generate hydrogen peroxide and radical intermediates such as hydroperoxyl (HOO π ) and hydroxyl (HO π ) radicals in the presence of O2. These reactive oxygen species cause membrane and ionomer degradation. Incorporating radical scavengers into the H2 recombination catalyst layer provides improved durability of the multi-layer ion exchange membrane.

[0063] On the catalyst layer 412, there is a polyelectrolyte multilayer coating 414, which may include alternating polyanion polymer layers 416 and polycation polymer layers 418. A second polyelectrolyte multilayer coating 420 may be present on the second surface 410 of the ion exchange membrane 402, which includes alternating polyanion polymer layers 422 and polycation polymer layers 424.

[0064] The first layer of the polyelectrolyte layer 414 deposited on the catalyst layer 412 should be a polyanion polymer layer with a negative ionic charge opposite to the ionic charge on the ionomer in the catalyst layer 412. This results in the formation of a stable polyelectrolyte coating via electrostatic interaction between the catalyst layer 412 and the polyelectrolyte coating 416.

[0065] Then, a polycation polymer with an opposite charge is deposited on the surface of the first polyanion polymer coating via electrostatic interaction to form the second part of the first polyelectrolyte bilayer. The polyelectrolyte multilayer can be formed according to the same alternating deposition process.

[0066] Optionally, the first layer of the polyelectrolyte layer 422 deposited on the second surface of the ion exchange membrane 402 should be a polyanion polymer layer with a negative ionic charge opposite to the ionic charge on the ion exchange membrane layer 402. This results in the formation of a stable polyelectrolyte coating via electrostatic interaction between the ion exchange membrane layer 402 and the polyelectrolyte coating 422.

[0067] Then, a polycation polymer with an opposite charge is deposited on the surface of the first polyanion polymer coating 422 via electrostatic interaction to form the second part of the first polyelectrolyte bilayer. The polyelectrolyte multilayer can be formed according to the same alternating deposition process.

[0068] The thickness of each layer 418, 416, 422, 424 of the polycation or polyanion can be less than 50 nm, or less than 20 nm, or less than 10 nm, or less than 5 nm.

[0069] The first polyelectrolyte multilayer coating 414 can be thinner than the ion exchange membrane 402. Additionally, the first polyelectrolyte multilayer coating 414 and the second polyelectrolyte multilayer coating 420 can be thinner than the ion exchange membrane 402. The catalyst layer 412 can be thinner than the ion exchange membrane layer 402 and thicker than the first polyelectrolyte multilayer 414.

[0070] The polycationic polymers in the polyelectrolyte multilayers 414, 420 have a positive charge and can be the same as or different from the anion-exchange polymer in the ion-exchange membrane 402, provided that the polycationic polymer cannot be the first polyelectrolyte layer deposited on the surface of an anion-exchange membrane having a positive charge. The polycationic polymers suitable for preparing the multilayer ion-exchange membrane 400 have a hydroxide conductivity similar to or higher than that of the anion-exchange membrane 402 and an inherent H2 and O2 permeability similar to or lower than that of the anion-exchange membrane 402. However, the polyanionic polymer and the polycationic polymer are soluble in aqueous solution, which makes the membranes prepared from the polyanionic polymer or the polyanionic polymer unsuitable for water electrolysis or fuel cell applications. Compared with the anion-exchange membrane 402 for water electrolysis applications, the polyelectrolyte layers 414, 420 deposited on the catalyst layer 412 and the ion-exchange membrane 402 via layer-by-layer self-assembly are not only insoluble and thermally and chemically stable, but also have a significantly reduced swelling of the anion-exchange membrane 402 and H2 and O2 crossover, as well as enhanced hydroxide conductivity.

[0071] The polycationic polymers suitable for preparing the multilayer ion exchange membrane 400 include, but are not limited to, protonated chitosan; amine-based linear, highly branched or dendritic polycationic polymers selected from the group consisting of: polybiguanide, quaternary ammonium polyethyleneimine, quaternary ammonium polypropyleneimine, quaternary ammonium polyamidoamine (PAMAM), poly(vinylamine hydrochloride) (PVH), poly(allylamine hydrochloride) (PAH), poly(amidoamine hydrochloride), poly(N-isopropylallylamine hydrochloride), poly(N-tert-butylallylamine hydrochloride), poly(N-1,2-dimethylpropylallylamine hydrochloride), poly(N-methylallylamine hydrochloride), poly(N,N-dimethylallylamine hydrochloride), poly(2-vinylpiperidine hydrochloride), poly(4-vinylpiperidine hydrochloride), poly(diallyldimethylammonium chloride), poly(acrylamide-co-diallyldimethylammonium chloride), poly(diallylmethylamine hydrochloride), copolymer of 2-propen-1-amine hydrochloride and N-2-propenyl-2-propen-1-amine hydrochloride, poly(N-alkyl-4-vinylpyridinium) salts, polylysine, polyornithine, polyarginine, poly(ethylene oxide)-block-poly(vinylbenzyltrimethylammonium chloride), poly(ethylene oxide)-block-poly(l-lysine), poly(2-methacryloyloxyethyl phosphorylcholine methacrylate)-block-poly(vinylbenzyltrimethylammonium chloride), poly[2-(dimethylamino)-ethyl methacrylate], poly[3-(dimethylamino)-propyl methacrylate], poly[2-(dimethylamino)-ethyl methacrylamide], poly[3-(dimethylamino)propyl methacrylamide], poly[2-(trimethylamino)ethyl methacrylate chloride], poly[2-(diethylamino)ethyl methacrylate], poly[2-(dimethylamino)ethyl acrylate]; or combinations thereof.

[0072] The polyanionic polymers suitable for preparing the multilayer ion exchange membrane 400 include, but are not limited to, sulfonated hydrocarbon polymers, poly(acrylic acid), poly(sodium phosphate), or negatively charged polysaccharide polyanionic polymers, or combinations thereof. Suitable sulfonated hydrocarbon polymers include, but are not limited to, sulfonated poly(ether ether ketone), sulfonated polyethersulfone, sulfonated polyphenylsulfone, sulfonated poly(2,6-dimethyl-1,4-phenylene oxide), sulfonated poly(4-phenoxybenzoyl-1,4-phenylene), sulfonated polyphenylene ether, sulfonated poly(phenylene), sulfonated poly(phthalazinone), sulfonated polystyrene, sulfonated poly(vinyltoluene), poly(acrylic acid), poly(sodium vinyl sulfonate), poly(sodium phosphate), or combinations thereof. Suitable negatively charged polysaccharide polyanionic polymers include, but are not limited to, sodium alginate, potassium alginate, calcium alginate, ammonium alginate, alginic acid, sodium hyaluronate, potassium hyaluronate, calcium hyaluronate, ammonium hyaluronate, hyaluronic acid, κ-carrageenan, λ-carrageenan, ι-carrageenan, carboxymethyl gellan, sodium carboxymethyl gellan, potassium carboxymethyl gellan, calcium carboxymethyl gellan, ammonium carboxymethyl gellan, carboxymethyl cellulose, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, calcium carboxymethyl cellulose, ammonium carboxymethyl cellulose, or combinations thereof.

[0073] Another aspect of the present invention is a membrane electrode assembly. In one embodiment, the membrane electrode assembly includes: an ion exchange membrane layer, a catalyst layer coated on the first surface on the first side of the ion exchange membrane, a first polyelectrolyte multilayer coated on the catalyst layer, an anode electrode disposed on the surface of the first polyelectrolyte multilayer, and a cathode electrode disposed on the second side of the ion exchange membrane.

[0074] In some embodiments, the catalyst layer of the membrane electrode assembly comprises a catalyst and an ionomer. The catalyst may include Pt, PtCo, Pd, PdCo, or mixtures thereof. The ionomer may include a proton-conducting fluorinated or non-fluorinated polymer ionomer, or a hydroxide-conducting polymer ionomer.

[0075] In some embodiments, the catalyst layer of the membrane electrode assembly further comprises an additive. The additive may include CeO2, Ce(OH)4, CeO2 / ZrO2, Ce(OH)4 / ZrO2, or mixtures thereof.

[0076] In some embodiments, the catalyst layer of the membrane electrode assembly is thinner than the ion exchange membrane layer and thicker than the first polyelectrolyte multilayer.

[0077] In some embodiments, the membrane electrode assembly further includes: a second polyelectrolyte multilayer, which is located between the ion exchange membrane and the cathode electrode and coated on the second surface on the second side of the ion exchange membrane.

[0078] In some embodiments, the first polyelectrolyte multilayer coating of the membrane electrode assembly is thinner than the ion exchange membrane and comprises alternating polycationic polymer layers and polyanionic polymer layers.

[0079] In some embodiments, the first polyelectrolyte multilayer coating and the second polyelectrolyte multilayer coating are thinner than the ion exchange membrane.

[0080] In some embodiments, both the first polyelectrolyte multilayer coating and the second polyelectrolyte multilayer coating comprise alternating polycationic polymer layers and polyanionic polymer layers.

[0081] In some embodiments, the membrane electrode assembly further comprises: an anodic porous transport layer adjacent to the anode; and a cathodic porous transport layer adjacent to the cathode. In some embodiments, the anode and cathode catalysts are platinum group metal (PGM) electrocatalysts or PGM-free electrocatalysts. The anode and cathode catalysts are respectively used for the oxygen evolution reaction and the hydrogen evolution reaction. The anode and cathode catalysts should have good electrical conductivity, good electrocatalytic activity and stability. Suitable PGM cathode catalysts may be selected from but not limited to platinum, ruthenium, osmium, rhodium, palladium, tin, tungsten, vanadium, cobalt, silver, gold, nickel, molybdenum, iron, copper, chromium, their alloys, their oxides, their carbides, their phosphides, or combinations thereof. Suitable PGM anode catalysts may be selected from but not limited to iridium, platinum, ruthenium, osmium, rhodium, palladium, tin, tungsten, vanadium, cobalt, silver, gold, copper, nickel, molybdenum, iron, chromium, their alloys, their oxides, their carbides, their phosphides, or combinations thereof. Suitable PGM-free cathode catalysts may be selected from but not limited to Ni-based alloys (such as Ni-Mo, Ni-Al, Ni-Cr, Ni-Sn, Ni-Co, Ni-W and Ni-Al-Mo), metal carbides (such as Mo2C), metal phosphides (such as CoP), metal dichalcogenides (such as MoSe2), and mixtures thereof. Suitable PGM-free anode catalysts may be selected from but not limited to Ni-Fe alloys, Ni-Mo alloys, spinel Cu x Co 3x O3, Ni-Fe layered double hydroxide nanoplates on carbon nanotubes, immobilized metal catalysts on conductive supports, and mixtures thereof.

[0082] The anodic porous transport layer and the cathodic porous transport layer simultaneously transport electrons, heat, and products with minimal voltage, current, heat, interface, and fluid losses. The cathodic porous transport layer can be made of but not limited to stainless steel, titanium mesh, titanium felt, titanium foam, or carbon-based materials (such as non-woven carbon paper, non-woven carbon cloth, or woven carbon cloth). The anodic porous transport layer can be made of but not limited to stainless steel, titanium mesh, titanium felt, or titanium foam.

[0083] Another embodiment of the present invention is a method for preparing a multilayer ion exchange membrane, the method comprising coating a catalyst layer on a first surface of a first side of the ion exchange membrane, and coating a first polyelectrolyte multilayer on the catalyst layer.

[0084] In some embodiments, the method for preparing a multilayer ion exchange membrane further comprises coating a second polyelectrolyte multilayer on a second surface of a second side of the ion exchange membrane, wherein the coating of the second polyelectrolyte multilayer is during or after the coating of the first polyelectrolyte multilayer.

[0085] In some embodiments, the catalyst layer is formed by the steps of: coating a catalyst ink on a first surface of a first side of the ion exchange membrane via meniscus coating, dip coating, slot die coating, brush coating, knife coating, spray coating, painting, metering rod / Meyer rod coating, or other known conventional ink coating techniques, and then drying the coated membrane.

[0086] In some embodiments, the first polyelectrolyte multilayer on the catalyst layer is formed by the steps of: applying a polyelectrolyte multilayer coating to the catalyst layer, and the polyelectrolyte multilayer coating comprises alternating polycationic polymer layers and polyanionic polymer layers; and optionally treating the coated membrane in an acidic solution. There are at least two sets of alternating polycationic polymer layers and polyanionic polymer layers present on the surface of the catalyst layer. The first polyelectrolyte multilayer can be formed by the steps of: coating alternating polycationic polymer layers and polyanionic polymer layers via layer-by-layer deposition, meniscus coating, dip coating, centrifugal deposition, slot die coating, brush coating, knife coating, spray coating, painting, metering rod / Meyer rod coating, or other known conventional coating techniques, and then drying the coated membrane. The second polyelectrolyte multilayer on a second surface of a second side of the ion exchange membrane can be formed by the steps of: coating alternating polycationic polymer layers and polyanionic polymer layers via layer-by-layer deposition, meniscus coating, dip coating, centrifugal deposition, slot die coating, brush coating, knife coating, spray coating, painting, metering rod / Meyer rod coating, or other known conventional coating techniques, and then drying the coated membrane.

[0087] Another embodiment of the present invention is a method for preparing a membrane electrode assembly, the membrane electrode assembly comprising a multilayer ion exchange membrane having an ion exchange membrane layer, a catalyst layer coated on a first surface of a first side of the ion exchange membrane, a first polyelectrolyte multilayer coated on the catalyst layer, an anode electrode disposed on a surface of the first polyelectrolyte multilayer, and a cathode electrode disposed on a second side of the ion exchange membrane.

[0088] In some embodiments, the anode electrode is formed by coating an anode catalyst ink on the surface of the first polyelectrolyte multilayer via meniscus coating, dip coating, slot die coating, brush coating, knife coating, spray coating, painting, metering rod / Meyer rod coating, or other known conventional ink coating techniques, and then drying the coated film at a temperature in the range of 40°C to 80°C.

[0089] In some embodiments, the cathode electrode is formed by coating a cathode catalyst ink on the second side of the ion exchange membrane via meniscus coating, dip coating, slot die coating, brush coating, knife coating, spray coating, painting, metering rod / Meyer rod coating, or other known conventional ink coating techniques, and then drying the coated film at a temperature in the range of 40°C to 80°C.

[0090] In some embodiments, after drying the membrane electrode assembly, the membrane electrode assembly can be annealed at a temperature in the range of 90°C to 150°C.

[0091] In some embodiments, the anode catalyst ink comprises an anode catalyst, an ionomer, and a solvent. In some embodiments, the cathode catalyst ink comprises a cathode catalyst, an ionomer, and a solvent. The ionomer creates proton or hydroxide transport channels between the reaction sites within the membrane and the electrodes, thus greatly improving the utilization of electrocatalyst particles while reducing the internal resistance. The solvent can be selected from but not limited to water, alcohols, acetone, methyl ethyl ketone, ethers (such as diethyl ether or di-n-propyl ether), tetrahydrofuran, 1,3-dioxolane, methyl acetate, ethyl acetate, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, or combinations thereof. Suitable alcohols include but not limited to methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, or tert-butanol, or combinations thereof.

[0092] Another embodiment of the present invention is the use of a multilayer ion exchange membrane for electrolysis applications (such as water electrolysis, CO2 electrolysis, and co-electrolysis of water and CO2), the multilayer ion exchange membrane comprising an ion exchange membrane, a catalyst layer on the first surface of the first side of the ion exchange membrane, and a first polyelectrolyte multilayer on the catalyst layer.

[0093] Example

[0094] The following examples are provided to illustrate one or more preferred embodiments of the present invention, but are not limited to its embodiments. Many variations can be made to the following examples that fall within the scope of the present invention.

[0095] Comparison Example 1. Preparation of a polyelectrolyte multilayer-coated cation exchange membrane without an H2 recombination catalyst layer (abbreviated as PEL-PEM)

[0096] Preparation of poly(allylamine hydrochloride) (PAH) and sulfonated poly(ether ether ketone) (SPEEK) polyelectrolyte multilayers coated on a 212 membrane (abbreviated as PEL-PEM): A PAH polycationic solution containing NaCl and PAH was prepared by dissolving NaCl and PAH in deionized (DI) H2O and adjusting the pH to 2.3 using an aqueous HCl solution. A SPEEK polyanionic aqueous solution containing NaCl and SPEEK was prepared by dissolving NaCl and SPEEK in DI H2O at 80 °C. After cooling to room temperature, the solution was filtered and the pH was adjusted to 5.8. A piece of 212 membrane was immersed in the PAH polycationic solution for 5 minutes and the membrane was rinsed 3 times with deionized (DI) H2O. Then the membrane was immersed in the SPEEK polyanionic solution for 5 minutes. The membrane was rinsed 3 times with DI H2O, and one PAH / SPEEK polyelectrolyte bilayer was deposited on the surface of the 212 membrane. This process was repeated to deposit 3 sets of PAH / SPEEK polyelectrolyte bilayers on the surface of the 212 membrane to form the PEL-PEM membrane.

[0097] Comparative Example 2. Preparation of a membrane electrode assembly including a PEL-PEM membrane (abbreviated as PEL-PEM-MEA)

[0098] An anode catalyst ink was prepared by mixing an additive solution of IrO2, poly(3,4-ethylenedioxythiophene) (PEDOT), and poly(styrene sulfonic acid) (PSS), ionomer D2021 solution, H2O, and ethanol. The mixture was finely dispersed using an ultrasonic bath and an ultrasonic probe. The anode catalyst ink was coated onto the first surface of the PEL-PEM membrane using the Mayer rod coating method. The anode IrO2 loading was 1.0 mg / cm 2 .

[0099] A cathode catalyst ink was prepared by mixing a 40% Pt / C catalyst, ionomer in H2O and ethanol. The mixture was finely dispersed using an ultrasonic bath and an ultrasonic probe. The cathode catalyst ink was coated onto the second surface of the PEL-PEM membrane using the Mayer rod coating method to form a three-layer membrane electrode assembly (abbreviated as PEL-PEM-MEA). The cathode Pt loading was 0.2 mg / cm 2 .

[0100] Example 1. Including Polyelectrolyte Multilayer and multilayer cation exchange membrane with an H2 recombination catalyst layer (abbreviated as PEL- H2R-PEM)

[0101] Prepare a membrane coated with PAH and SPEEK polyelectrolyte multilayers and an H2R catalyst layer (abbreviated as PEL-H2R-PEM) as follows: Prepare an H2 recombination (H2R) catalyst ink by mixing Pt black catalyst, D2021 ionomer solution, H2O, and ethanol. Use an ultrasonic bath and an ultrasonic probe to finely disperse the mixture. Use the Mayer rod coating method to coat the H2R catalyst ink onto the first surface of a 212 membrane to form an H2R layer-coated 212 membrane. The Pt loading in the H2R catalyst layer is 0.05 mg / cm 2 .

[0102] Prepare a PAH polycation solution containing NaCl and PAH by dissolving NaCl and PAH in deionized (DI) H2O and adjusting the pH to 2.3 using an aqueous HCl solution. Prepare an aqueous SPEEK polyanion solution containing NaCl and SPEEK by dissolving NaCl and SPEEK in DI H2O at 80 °C. After cooling to room temperature, filter the solution and adjust the pH to 5.8. Immerse the H2R layer on the 212 membrane with the other surface of the membrane covered in the PAH polycation solution for 5 minutes and rinse the membrane 3 times with DI H2O. Then immerse the membrane in the SPEEK polyanion solution for 5 minutes. Rinse the membrane 3 times with DI H2O and deposit one PAH / SPEEK polyelectrolyte bilayer on the surface of the H2R layer on the 212 membrane coated with the H2R layer. Repeat the process to deposit 3 sets of PAH / SPEEK polyelectrolyte bilayers on the surface of the H2R layer on the 212 membrane coated with the H2R layer to form a PEL-H2R-PEM membrane.

[0103] Example 2. Preparation of a membrane electrode assembly including a PEL-H2R-PEM membrane (abbreviated as PEL-H2R-PEM-MEA)

[0104] Prepare an anode catalyst ink by mixing an additive solution of IrO2, poly(3,4-ethylenedioxythiophene) (PEDOT), and poly(styrenesulfonic acid) (PSS), ionomer D2021 solution, H2O, and ethanol. Use an ultrasonic bath and an ultrasonic probe to finely disperse the mixture. Use the Mayer rod coating method to coat the anode catalyst ink onto the surface of the PAH / SPEEK polyelectrolyte bilayer of the PEL-H2R-PEM membrane. The anode IrO2 loading is 1.0 mg / cm 2 .

[0105] Prepare by mixing 40% Pt / C catalyst, An ionomer D2021 solution, H2O, and ethanol were used to prepare the cathode catalyst ink. An ultrasonic bath and an ultrasonic probe were used to finely disperse the mixture. The cathode catalyst ink was coated onto the second surface of the PEL-H2R-PEM membrane using a Meyer rod coating method to form a three-layer membrane electrode assembly (abbreviated as PEL-H2R-PEM-MEA). The cathode Pt loading was 0.2 mg / cm 2 .

[0106] Example 3. Preparation of a multilayer cation exchange membrane including a polyelectrolyte multilayer, an H2 recombination catalyst layer, and CeO2 in the H2 recombination catalyst layer (abbreviated as PEL-H2RCe-PEM)

[0107] The following was used to prepare a PAH and SPEEK polyelectrolyte multilayer and a membrane coated with an H2R catalyst layer containing Pt and CeO2 (abbreviated as PEL-H2RCe-PEM): An H2 recombination (H2R) catalyst ink containing Pt and CeO2 was prepared by mixing Pt black catalyst, CeO2, D2021 ionomer solution, H2O, and ethanol. An ultrasonic bath and an ultrasonic probe were used to finely disperse the mixture. The H2R catalyst ink containing Pt and CeO2 was coated onto the first surface of the 212 membrane to form a Pt- and CeO2-coated 212 membrane. The Pt loading in the H2R catalyst layer was 0.05 mg / cm 2 . The weight ratio of Pt to CeO2 was 15:1.

[0108] A PAH polycation solution containing NaCl and PAH was prepared by dissolving NaCl and PAH in deionized (DI) H2O and adjusting the pH to 2.3 using an aqueous HCl solution. An aqueous SPEEK polyanion solution containing NaCl and SPEEK was prepared by dissolving NaCl and SPEEK in DI H2O at 80 °C. After cooling to room temperature, the solution was filtered and the pH was adjusted to 5.8. The coated 212 membrane with the other surface covered was immersed in the PAH polycation solution for 5 minutes and the membrane was rinsed 3 times with DI H2O. Then the membrane was immersed in the SPEEK polyanion solution for 5 minutes. The membrane was rinsed 3 times with DI H2O, and one PAH / SPEEK polyelectrolyte bilayer was deposited on the surface of the H2R layer on the coated 212 membrane. This process was repeated to deposit 3 sets of PAH / SPEEK polyelectrolyte bilayers on the surface of the H2R layer on the coated 212 membrane to form the PEL-H2RCe-PEM membrane. 212 membrane to form the PEL-H2RCe-PEM membrane.

[0109] Example 4. Preparation of a membrane electrode assembly including a PEL-H2RCe-PEM membrane (abbreviated as PEL-H2RCe-PEM-MEA)

[0110] An anode catalyst ink is prepared by mixing an additive solution of IrO2, poly(3,4-ethylenedioxythiophene) (PEDOT), and poly(styrenesulfonic acid) (PSS), an ionomer D2021 solution, H2O, and ethanol. An ultrasonic bath and an ultrasonic probe are used to finely disperse the mixture. The anode catalyst ink is coated onto the surface of the PAH / SPEEK polyelectrolyte bilayer of the PEL-H2RCe-PEM membrane using a Mayer rod coating method. The anode IrO2 loading is 1.0 mg / cm 2 .

[0111] A cathode catalyst ink is prepared by mixing a 40% Pt / C catalyst, an ionomer D2021 solution, H2O, and ethanol. An ultrasonic bath and an ultrasonic probe are used to finely disperse the mixture. The cathode catalyst ink is coated onto the second surface of the PEL-H2RCe-PEM membrane to form a three-layer membrane electrode assembly (abbreviated as PEL-H2RCe-PEM-MEA) using a Mayer rod coating method. The cathode Pt loading is 0.2 mg / cm 2 .

[0112] Example 5. Evaluation of the water electrolysis performance of a) PEL-PEM MEA; (b) PEL-H2R-PEM MEA; and (c) PEL-H2RCe-PEM MEA at 80 °C and atmospheric pressure

[0113] A proton exchange membrane (PEM) water electrolysis test station (Scribner 600 electrolyzer test system) is used to evaluate the water electrolysis performance of a) PEL-PEM-MEA; (b) PEL-H2R-PEM-MEA; and (c) PEL-H2RCe-PEM-MEA, respectively, in a single electrolyzer with an active membrane area of 5 cm 2 . The test station includes an integrated power supply, a voltage regulator, an impedance analyzer for electrochemical impedance spectroscopy (EIS) and high-frequency resistance (HFR), and real-time sensors for product flow rate and permeation monitoring. The MEA is sandwiched between carbon paper (as the cathode PTL) and Pt-Ti felt (as the anode PTL). The tests are conducted at 80 °C and atmospheric pressure. Ultra-pure water is supplied to the anode of the MEA at a flow rate of 100 mL / min. Polarization curves are collected at 80 °C, and the results are shown in Figure 5 . The H2 concentration in O2 in the anode gas stream is measured by gas chromatography (GC).

[0114] From Figure 5From the polarization curves, it can be observed that both the PEL-H2R-PEM-MEA (b) and the PEL-H2RCe-PEM-MEA (c) with the H2R layer show performance comparable to that of the PEL-PEM-MEA (a) without the H2R layer. In addition, the PEL-H2R-PEM-MEA and the PEL-H2RCe-PEM-MEA show an ultra-low H2 concentration in O2 of less than 0.1% at a current density of 2 A / cm 2 in the anode gas stream. The PEL-PEM-MEA without the H2R layer shows a higher H2 concentration in O2 of 1.0% at a current density of 2 A / cm 2 in the anode gas stream.

[0115] Specific embodiments

[0116] Although the following is described in connection with specific embodiments, it should be understood that the description is intended to illustrate rather than limit the scope of the foregoing description and the appended claims.

[0117] A first embodiment of the present invention is a multilayer ion exchange membrane, which comprises an ion exchange membrane layer; a catalyst layer coated on a first surface of the ion exchange membrane layer; and a first polyelectrolyte multilayer coating coated on the catalyst layer. An embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the first polyelectrolyte multilayer coating is thinner than the ion exchange membrane layer and comprises alternating polycationic polymer layers and polyanionic polymer layers. An embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, and further comprises a second polyelectrolyte multilayer coating coated on a second surface of the ion exchange membrane layer. An embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the first polyelectrolyte multilayer coating and the second polyelectrolyte multilayer coating are thinner than the ion exchange membrane layer. An embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein both the first polyelectrolyte multilayer coating and the second polyelectrolyte multilayer coating comprise alternating polycationic polymer layers and polyanionic polymer layers. An embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the catalyst layer contains a catalyst and an ionomer. An embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the catalyst comprises Pt, PtCo, Pd, PdCo or a combination thereof. An embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the ionomer comprises a proton-conducting fluorinated or non-fluorinated polymer ionomer, or a hydroxide-conducting polymer ionomer. An embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the catalyst layer further contains an additive. An embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the additive comprises CeO2, Ce(OH)4, CeO2 / ZrO2, Ce(OH)4 / ZrO2 or a mixture thereof. An embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the first embodiment in this paragraph, wherein the catalyst layer is thinner than the ion exchange membrane layer and thicker than the first polyelectrolyte multilayer coating.

[0118] A second embodiment of the present invention is a membrane electrode assembly, which includes an ion exchange membrane layer; a catalyst layer coated on the first surface of the first side of the ion exchange membrane layer; a first polyelectrolyte multilayer coating coated on the catalyst layer; an anode electrode disposed on the surface of the first polyelectrolyte multilayer coating; and a cathode electrode disposed on the second side of the ion exchange membrane layer. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, wherein the first polyelectrolyte multilayer coating is thinner than the ion exchange membrane layer and includes alternating polycationic polymer layers and polyanionic polymer layers. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, further including a second polyelectrolyte multilayer coating between the ion exchange membrane layer and the cathode electrode, and a second polyelectrolyte multilayer coating coated on the second surface of the second side of the ion exchange membrane layer. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, wherein the first polyelectrolyte multilayer coating and the second polyelectrolyte multilayer coating are thinner than the ion exchange membrane layer. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, wherein both the first polyelectrolyte multilayer coating and the second polyelectrolyte multilayer coating include alternating polycationic polymer layers and polyanionic polymer layers. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, wherein the catalyst layer contains a catalyst and an ionomer. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, wherein the catalyst includes Pt, PtCo, Pd, PdCo or a combination thereof. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, wherein the ionomer contains a proton-conducting fluorinated or non-fluorinated polymer ionomer, or a hydroxide-conducting polymer ionomer. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, wherein the catalyst layer further contains an additive. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, wherein the additive includes CeO2, Ce(OH)4, CeO2 / ZrO2, Ce(OH)4 / ZrO2 or a mixture thereof. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, wherein the catalyst layer is thinner than the ion exchange membrane layer and thicker than the first polyelectrolyte multilayer coating.

[0119] A third embodiment of the present invention is a method for preparing a multilayer ion exchange membrane, the method comprising coating a catalyst layer on a first surface on a first side of the ion exchange membrane; and coating a first polyelectrolyte multilayer on the catalyst layer. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the third embodiment in this paragraph, and further comprises coating a second polyelectrolyte multilayer on a second surface on a second side of the ion exchange membrane, wherein the coating of the second polyelectrolyte multilayer is carried out during or after the coating of the first polyelectrolyte multilayer. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the third embodiment in this paragraph, and further comprises applying a cathode electrode on a second surface on a second side of the ion exchange membrane. One embodiment of the present invention is one, any, or all of the previous embodiments in this paragraph to the third embodiment in this paragraph, and further comprises applying an anode electrode on the first polyelectrolyte multilayer film.

[0120] Although no further detailed description is provided, it is believed that those skilled in the art can make the most of the present invention by using the foregoing description and can easily determine the basic features of the present invention without departing from the essence and scope of the present invention to make various changes and modifications thereto and adapt it to various uses and conditions. Therefore, the foregoing preferred specific embodiments should be construed as merely illustrative and not in any way limiting the remainder of the disclosure, and are intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0121] In the foregoing, all temperatures are shown in degrees Celsius, and all parts and percentages are by weight unless otherwise indicated.

Claims

1. A multilayer ion exchange membrane (300, 400), comprising: Ion exchange membrane layers (302, 402); Catalyst layers (312, 412) coated on the first surfaces (306, 406) of the ion exchange membrane layers (302, 402); and, First polyelectrolyte multilayer coatings (316, 416) coated on the catalyst layers (312, 412).

2. The multilayer ion exchange membrane (300, 400) according to claim 1, wherein the first polyelectrolyte multilayer coatings (316, 416) are thinner than the ion exchange membrane layers (302, 402) and comprise alternating polycationic polymer layers (322, 424) and polyanionic polymer layers (324, 422).

3. The multilayer ion exchange membrane (300, 400) according to claim 1, further comprising: Second polyelectrolyte multilayer coatings (320, 420) coated on the second surfaces (310, 410) of the ion exchange membrane layers (302, 402).

4. The multilayer ion exchange membrane (300, 400) according to claim 3, wherein the first polyelectrolyte multilayer coatings (316, 416) and the second polyelectrolyte multilayer coatings (320, 420) are thinner than the ion exchange membrane layers (302, 402).

5. The multilayer ion exchange membrane according to claim 4, wherein both the first polyelectrolyte multilayer coatings (316, 416) and the second polyelectrolyte multilayer coatings (320, 420) comprise alternating polycationic polymer layers (322, 424) and polyanionic polymer layers (324, 422).

6. The multilayer ion exchange membrane (300, 400) according to any one of claims 1 to 5, wherein the catalyst layers (312, 412) contain a catalyst and an ionomer.

7. The multilayer ion exchange membrane (300, 400) according to claim 6, wherein the catalyst comprises Pt, PtCo, Pd, PdCo or a mixture thereof.

8. The multilayer ion exchange membrane (300, 400) according to claim 6, wherein the ionomer comprises a proton-conducting fluorinated or non-fluorinated polymer ionomer, or a hydroxide-conducting polymer ionomer.

9. The multilayer ion exchange membrane (300, 400) according to any one of claims 1 to 5, wherein the catalyst layers (312, 412) further contain an additive, preferably comprising CeO2, Ce(OH)4, CeO2 / ZrO2, Ce(OH)4 / ZrO2 or a mixture thereof.

10. The multilayer ion exchange membrane (300, 400) according to any one of claims 1 to 5, wherein the catalyst layers (312, 412) are thinner than the ion exchange membrane layers (302, 402) and thicker than the first polyelectrolyte multilayer coatings (316, 416).

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