Catalyst ink composition and catalyst coating film for electrolysis

Abstract

A catalyst ink formulation for preparing a CCM is described. The catalyst ink formulation includes a catalyst, an ionomer, a solvent, and a porogen soluble in the solvent. The catalyst ink formulation may also include additives such as an electronically conductive polymer. The anode catalyst coating layer, or both the anode and cathode catalyst coating layers, prepared from the catalyst ink formulation contain uniformly distributed nanopores that allow for easy gas removal and uniform water supply distribution, thereby avoiding or reducing direct energy loss in the electrolytic cell. A catalyst-coated membrane and a method for making the catalyst-coated membrane are also described.

Description

[Technical Field]

[0001] (Statement of priority) This application claims priority to U.S. Patent Application No. 18 / 064,023, filed December 9, 2022, which is incorporated herein by reference in its entirety. [Background technology]

[0002] Hydrogen as an energy vector for grid balancing or power-to-gas and power-to-liquid processes plays an important role on the path toward a green, low-carbon energy structure. Water electrolysis produces high-quality hydrogen by electrochemically splitting water into hydrogen and oxygen, and the reaction occurs according to Equation 1 below. The water electrolysis process is endothermic, and electricity is the energy source. If the process is powered by renewable power sources such as wind, solar, or geothermal energy, the carbon footprint of water electrolysis is zero. The main water electrolysis technologies include alkaline electrolysis, proton exchange membrane (PEM) water electrolysis (PEMWE shown in Figure 1), anion exchange membrane (AEM) water electrolysis (AEMWE shown in Figure 2), and solid oxide water electrolysis.

[0003] As shown in Figure 1, in a PEMWE system 100, an anode 105 and a cathode 110 are separated by a solid PEM electrolyte 115, such as a sulfonated tetrafluoroethylene-based co-fluoropolymer sold by Chemours under the trade name Nafion®. 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 gas 125, electrons (e -), and protons are produced, and the reaction proceeds according to Equation 2 below. The 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 in which electrons from the cathode 110 are donated to the protons to form hydrogen gas 130, and the reaction proceeds according to Equation 3 below. The PEM 115 not only conducts the protons from the anode 105 to the cathode 110, but also separates the H gas 130 and O gas 125 produced in the water electrolysis reaction. PEM water electrolysis is one of the preferred methods for converting renewable energy into high-purity hydrogen, and has the advantages of high differential pressure, high current density, high efficiency, fast response, small footprint, low-temperature (20-90°C) operation, and a compact system design with high-purity oxygen by-product. However, one of the major challenges of PEM water electrolysis is the high capital cost of the cell stack, which includes expensive acid-resistant stack hardware such as Pt-coated Ti bipolar plates, expensive precious metal catalysts required for the electrodes, and expensive PEMs. Water electrolysis reaction: 2H2O → 2H2 + O2 (1) Anode oxidation reaction in PEMWE: 2H2O → O2 + 4H + +4e - (2) Reduction reaction at the cathode in the case of PEMWE: 2H + +2e - →H2(3)

[0004] AEMWE is an emerging technology. As shown in FIG. 2, in an AEMWE system 200, an anode 205 and a cathode 210 are separated by a solid AEM electrolyte 215. A water feed 220, typically containing an additive electrolyte such as dilute KOH or K2CO3 or deionized water, is supplied to the cathode side. The anode and cathode catalysts typically contain platinum-free Ni-based or Ni-alloy catalysts. At the negatively charged cathode 210, water is reduced by the addition of four electrons to form hydrogen 225 and hydroxyl ions. The reaction occurs according to Equation 4 below. The hydroxyl ions diffuse from the cathode 210 to the anode 205 through the hydroxyl ion-conducting AEM 215. At the positively charged anode 205, the hydroxyl ions recombine as water and oxygen 230, according to Equation 5 below. The AEM 215 not only conducts hydroxyl ions from the cathode 210 to the anode 205, but also separates the H 2225 and O 2230 produced in the water electrolysis reaction. The AEM 215 allows for the production of very high purity hydrogen 225, at least 99.9%, under high pressures of up to 35 bar. The cathode reduction reaction in the case of AEMWE is: 4H2O + 4e - →2H2+4OH - (4) The oxidation reaction at the anode in the case of AEMWE: 4OH → 2H2O + O2 + 4e - (5)

[0005] AEMWEs have advantages over PEMWEs because they allow the use of less expensive platinum-free catalysts, such as Ni and Ni alloy catalysts. Furthermore, the gas diffusion layer (GDL) for AEMWEs can use much cheaper stainless steel bipolar plates instead of the expensive Pt-coated Ti bipolar plates currently used in PEMWEs. However, the biggest obstacles to the development of AEM systems are the hydroxyl ion conductivity and stability of the membranes and the unknowns of how to incorporate catalysts into AEM systems. Research on AEMWEs in the literature has focused on electrocatalysts, AEM development, and understanding the operating mechanisms, with the general goal of achieving highly efficient, low-cost, and stable AEMWE technology.

[0006] PEM-WE and AEM-WE systems integrate several components to generate green H2, including a three-layer membrane electrode assembly (MEA) consisting of a current collector plate, a bipolar plate (BP), two porous transport layers (PTL), a membrane, an anode layer, and a cathode layer. In some cases, a five-layer MEA, consisting of a membrane, an anode layer, a cathode layer, and two PTL layers, is used in PEM-WE and AEM-WE systems, if one surface of the PTL is coated with a catalyst. Among the major components, the MEA is the most important because the electrochemical water electrolysis reaction occurs in the MEA. There are two main methods for fabricating MEAs, including catalyst-coated substrates (CCS) and catalyst-coated membranes (CCM). Different MEA fabrication techniques and different catalyst loadings on the anode and / or cathode coating layers often result in different performance.

[0007] The membrane is one of the key components in the MEA and is a key driver for safety and performance. Some important properties of membranes for membrane 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 cost, low area resistance to minimize efficiency losses resulting from ohmic polarization, high resistance to oxidizing and reducing conditions, chemical inertness over a wide pH range, high thermal stability along with high proton conductivity, and high mechanical strength (thickness, low swelling).

[0008] In an MEA for an electrochemical cell, the anode is an electrode where the dominant reaction is oxidation (e.g., a water oxidation / oxygen evolution electrode in the case of a water electrolyzer) while the cathode is an electrode where the dominant reaction is reduction (e.g., a proton reduction / hydrogen evolution electrode in the case of a water electrolyzer). Both the anode and the cathode are important components in an MEA. Typically, in PEM-WEs, an unsupported or supported iridium (Ir)-based rare platinum-group electrocatalyst is used for the oxygen evolution reaction (OER) on the anode, and a carbon-supported platinum electrocatalyst (Pt / C) is used for the hydrogen evolution reaction (HER) on the cathode. With the increase in gigawatt-scale PEM-WE installation projects, a significant reduction in the platinum-group catalyst loading on the catalyst coating layer will be required. Methods to reduce the loading of platinum group catalysts include supporting platinum group metals or metal oxides such as IrO2 on high surface area support materials, designing catalysts with unique structures such as nanostructured thin films, nanowires, or core-shell structures, using advanced catalyst layer coating techniques, and reducing the thickness of the catalyst coating layer.

[0009] However, reducing the loading of Ir-based catalysts in the anode coating layer usually results in a kinetic disadvantage for the oxygen evolution reaction (OER) in PEM-WEs. Research on CCM fabrication methods has focused on the influence of catalyst inks on the fabrication and performance of CCMs in water electrolysis. The catalyst inks used to form the anode and cathode coating layers on the membrane surface or PTL are important for providing the MEA with high catalytic activity, high proton or hydroxide conductivity, and high electrical conductivity in the catalyst layer.

[0010] Eliminating or mitigating the direct and indirect energy losses resulting from bubble formation in the catalyst coating layer within the electrolytic cell can result in significant energy savings for water electrolysis. Bubble formation on the electrode can involve four steps, including bubble nucleation, bubble growth, bubble separation, and mass transfer of bubbles away from the electrode.

[0011] Significant advances are needed in cost-effective, high-performance, and stable catalysts, catalyst ink formulations, membrane materials, and other cell stack components for water electrolysis, which has widespread applications in renewable energy systems. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram of an embodiment of a PEMWE cell. [Figure 2] FIG. 1 is a diagram of an embodiment of an AEMWE cell. [Figure 3] 1 is a graph showing polarization curves for water electrolysis cells fabricated using MEAs fabricated both with and without the use of porogen. DETAILED DESCRIPTION OF THE INVENTION

[0013] We have developed a novel catalyst ink formulation for preparing CCMs. The anode catalyst coating layer, or both the anode and cathode catalyst coating layers, on the CCM prepared from this catalyst ink formulation contain uniformly distributed nanopores that allow for easy gas removal and uniform water supply distribution, thereby avoiding or reducing direct energy loss in the electrolytic cell. The catalyst ink formulation for preparing CCMs may contain a catalyst, an ionomer, a solvent, and a solvent-soluble porogen. The catalyst ink formulation may also contain additives such as electronically conductive polymers. The use of this catalyst ink formulation containing a solvent-soluble porogen to create a nanoporous morphology on the anode or both the anode and cathode accelerates gas release from the electrode and uniform water supply distribution within the anode catalyst coating layer.

[0014] The porogen can be incorporated into the anode ink formulation, the cathode ink formulation, or both the anode and cathode ink formulations. The porogen can be removed from the final CCM to generate nanopores by immersing the CCM in a solvent, an acidic solution for PEM-based CCMs, or a basic solution for AEM-based CCMs, prior to use in an electrolytic bath. The porogen can also be removed from the final CCM to generate nanopores by washing the CCM with a solvent, an acidic solution for PEM-based CCMs, or a basic solution for AEM-based CCMs, prior to use in an electrolytic bath. The nanopores have a pore size of less than 200 nm, or less than 175 nm, or less than 150 nm, or less than 125 nm, or less than 100 nm.

[0015] Suitable porogens include, but are not limited to, glycerol, glycine, ethylene glycol, poly(ethylene glycol), poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), co-block-poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO), tri-block-poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO), sorbitol, polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), diethylene glycol, sulfosuccinic acid, tetradecyltrimethylammonium bromide, tetramethylammonium bromide, tetradecyltrimethylammonium acetate, tetramethylammonium acetate, or combinations thereof.

[0016] Prior to use in an electrolytic cell, the porogens can be removed from the final CCM to generate nanopores by immersion in a solvent, an acidic solution for PEM-based CCMs, or a basic solution for AEM-based CCMs for 10 minutes to 48 hours, or 30 minutes to 24 hours, or 2 hours to 12 hours, at temperatures ranging from 20° C. to 120° C., or 20° C. to 80° C., or 20° C. to 40° C. Alternatively, prior to use in an electrolytic cell, the porogens can be removed from the final CCM to generate nanopores by washing with a solvent, an acidic solution for PEM-based CCMs, or a basic solution for AEM-based CCMs for 10 minutes to 4 hours, or 30 minutes to 2 hours, at temperatures ranging from 20° C. to 80° C., or 20° C. to 40° C.

[0017] Suitable solvents for removing the porogen include, but are not limited to, water, alcohol, acetone, methyl ethyl ketone, ethers such as diethyl ether or di-n-propyl ether, tetrahydrofuran, 1,3-dioxolane, methyl acetate, ethyl acetate, or combinations thereof. Suitable acidic solutions for removing the porogen include, but are not limited to, HCl or H2SO4 solutions. Suitable basic solutions for removing the porogen include, but are not limited to, KOH, KHCO3, K2CO3, Na2CO3, NaHCO3, or NaOH solutions.

[0018] The catalyst can be any catalyst suitable for electrolysis. Suitable cathode catalysts include, but are not limited to, platinum, ruthenium, osmium, rhodium, palladium, tin, tungsten, vanadium, cobalt, silver, gold, nickel, molybdenum, iron, copper, chromium, alloys thereof, oxides thereof, carbides thereof, phosphides thereof, or combinations thereof.

[0019] Suitable anode catalysts include, but are not limited to, iridium, platinum, ruthenium, osmium, rhodium, palladium, tin, tungsten, vanadium, cobalt, silver, gold, copper, nickel, molybdenum, iron, chromium, alloys thereof, oxides thereof, carbides thereof, phosphides thereof, or combinations thereof.

[0020] The cathode catalyst and / or the anode catalyst may be supported or unsupported.

[0021] Suitable high surface area support materials for preparing supported catalysts include titanium oxide, aluminum oxide, silicon dioxide, zirconium dioxide, yttrium oxide, cerium oxide, cerium dioxide, lanthanum oxide, tin oxide, tungsten oxide, molybdenum oxide, niobium oxide, tantalum oxide, tin oxide, and anion- and cation-doped versions of these oxides, including, but not limited to, fluorine-doped tin oxide, indium-doped and antimony-doped tin oxide, and mixtures thereof.

[0022] The polymer ionomer, acting as a binder for the catalyst particles, provides a barrier between the membrane and the reaction sites in the electrocatalyst coating layer, providing protons (H + ) or hydroxide (OH - ) transport pathways. The polymer ionomer improves the utilization of the electrocatalyst particles while reducing the internal resistance. The polymer ionomer is preferably insoluble in water and has a high H + or OH -The polymer ionomer has high conductivity, high chemical, oxidative, and thermal stability, and high solubility or dispersibility in solvents. The polymer ionomer may be a fluorinated ionomer such as Nafion®, a non-fluorinated ionomer, or a hydroxide-conductive polymer ionomer, or a combination thereof. In some embodiments, the chemical structure of the polymer ionomer is similar to that of the membrane in the MEA, which allows for low interfacial resistance and similar swelling when in contact with water to avoid delamination, but higher O2 and H2 permeability than the membrane.

[0023] Suitable proton-conducting fluorinated polymer ionomers include, but are not limited to, perfluorosulfonic acid (PFSA) polymers such as Nafion®, Flemion®, Aquivion®, Aciplex®, NEOSEPTA®-F, and Fumapem®, sulfonated trifluorostyrene-trifluorostyrene copolymers, sulfonated polystyrene-poly(vinylidene fluoride) copolymers, or combinations thereof. Suitable proton-conducting non-fluorinated polymer ionomers include, but are not limited to, sulfonated polysulfone, crosslinked sulfonated polysulfone, sulfonated poly(phenylene sulfone), sulfonated phenylated poly(phenylene), sulfonated polystyrene, sulfonated polyethersulfone, crosslinked sulfonated polyethersulfone, sulfonated polyetheretherketone, crosslinked sulfonated polyetheretherketone, or combinations thereof. Suitable hydroxide-conducting polymer ionomers include, but are not limited to, alkylammonium polyfluorene ionomers, poly(arylpiperidinium) ionomers, benzyltrimethylammonium-functionalized high density polyethylene, N-heterocyclic and alkylammonium-based polyphenylenes, benzyltrimethylammonium-functionalized poly(ethylene-co-tetrafluoroethylene), or combinations thereof.

[0024] A solvent can be used to disperse the catalyst particles, polymeric ionomer, and porogen to form a uniform catalyst ink. The solvent should have a low boiling point so that it can be easily removed during or after the ink coating process. Suitable solvents include, but are not limited to, water, alcohol, 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 are not limited to, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, or tert-butanol, or combinations thereof.

[0025] The membrane may be an ion-conducting membrane.

[0026] The ion-conducting membrane can be a proton exchange membrane (PEM) or an anion exchange membrane (AEM). The ion-conducting membrane can be a PEM or a polyelectrolyte multilayer-coated PEM comprising a PEM and a polyelectrolyte multilayer coating on the surface of the PEM, the polyelectrolyte multilayer coating comprising alternating layers of polycationic polymers and polyanionic polymers, the polycationic polymer layer being in contact with the PEM. The ion-conducting membrane can also be an AEM or a polyelectrolyte multilayer-coated AEM comprising an AEM and a polyelectrolyte multilayer coating on the surface of the AEM, the polyelectrolyte multilayer coating comprising alternating layers of polycationic polymers and polyanionic polymers, the polycationic polymer layer being in contact with the AEM.

[0027] The polyelectrolyte multilayer-coated PEM comprises a polycationic polymer layer deposited on and in contact with the PEM. One, two, three, four, five, or more sets of alternating polycationic and polyanionic polymer layers may be present on one or both sides of the PEM. The polyelectrolyte multilayer-coated AEM comprises a polyanionic polymer layer deposited on and in contact with the AEM. One, two, three, four, five, or more sets of alternating polycationic and polyanionic polymer layers may be present on one or both sides of the AEM. The top layer of the polyelectrolyte multilayer coating may be either a polycationic polymer layer or a polyanionic polymer layer. See U.S. Patent Application No. 17 / 451,227, filed October 18, 2021, entitled "Polyelectrolyte Multilayer Coated Proton Exchange Membrane for Electrolysis and Fuel Cell Applications," which is incorporated herein in its entirety.

[0028] Polyelectrolyte multilayer coatings can be formed using a layer-by-layer self-assembly method. Layer-by-layer self-assembly can be achieved, for example, by adsorption, electrostatic interactions, covalent bonds, hydrogen bonds, van der Waals forces, hydrophobic interactions, or a combination thereof. The layer-by-layer self-assembly method can be selected from, but is not limited to, dip coating, spray deposition, centrifugal deposition, electrodeposition, meniscus / slot die coating, brushing, roller coating, metering rod / Meyer bar coating, knife casting, etc.

[0029] The choice of fabrication method depends on the polycations and polyanions to be organized, the time required for layer-by-layer deposition, and the shape of the cation exchange membrane onto which the polyelectrolyte multilayer coating is deposited. A first polyelectrolyte layer is formed (for example) by adsorbing a polycation or polyanion onto one or both surfaces of a PEM or AEM having an opposite charge. A second layer of polyelectrolyte having an opposite charge to the first layer of polyelectrolyte is then deposited on the first layer of polyelectrolyte to form a set of alternating layers on the PEM or AEM. From the nanostructured polyelectrolyte multilayer coating having n sets of alternating layers on one or both surfaces of the PEM, a PEM (or AEM) / (polycation-polyanion) multilayer is formed, respectively. n or (polyanion-polycation)n / PEM (or AEM) / (polycation-polyanion) n A new proton exchange membrane of this order is obtained. The increase in thickness of the polyelectrolyte multilayer depends on the number of layers deposited and can be either linear or nonlinear. Several parameters, such as ionic strength, pH, temperature, polyelectrolyte structure, concentration, and charge density, can be adjusted during the layer-by-layer deposition process. Oppositely altered polyelectrolyte layers are deposited on the surface of the PEM or AEM. The polyelectrolyte multilayer is insoluble and thermally and chemically stable.

[0030] The polyanionic polymer in the polyelectrolyte multilayer coating may be different from the ion exchange polymer in the PEM or AEM.

[0031] The PEM comprises a cation exchange polymer or a mixture of a cation exchange polymer and an inorganic filler containing covalently bound acidic functional groups. The PEM in the polyelectrolyte multilayer coating PEM has a negative ionic charge -SO3 - , -COO - , -PO3 2- , or -PO3H -The PEM contains a cation exchange functional group. The cation exchange polymer in the PEM may be selected from, but is not limited to, perfluorosulfonic acid (PFSA) polymers such as Nafion®, Flemion®, Fumion®, Aciplex®, Aquivion®, Fumapem® FS, BAM®, or NEOSEPTA®-F; 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 PEM has high mechanical strength, good chemical and thermal stability, and good proton conductivity. The polyelectrolyte multilayer-coated PEM has low membrane area specific resistance, reduced swelling, significantly reduced H2 and O2 crossover, and enhanced proton conductivity compared to PEMs without the polyelectrolyte multilayer coating.

[0032] The PEM for preparing the polyelectrolyte multilayer coated PEM may be a composite proton conducting membrane as described in U.S. Patent Application No. 17 / 162,421, filed January 29, 2021, entitled "Composite Proton Conductive Membranes," which is incorporated herein by reference in its entirety. That application includes a polyelectrolyte multilayer coated PEM having a covalently bonded acidic functional group and at least 150 m 2 A new type of composite proton-conducting membrane has been disclosed, which comprises an inorganic filler with a high surface area of ​​0.1µm / g and a water-insoluble ion-conducting polymer. Depositing a polyelectrolyte multilayer coating on the composite proton-conducting membrane reduced membrane swelling, significantly reduced H2 and O2 crossover, and enhanced proton conductivity compared to a composite proton-conducting membrane without the polyelectrolyte multilayer coating.

[0033] The inorganic filler containing covalently bonded acidic functional groups in the cation exchange membrane may be selected from, but is not limited to, silica gel, precipitated silica, fumed silica, colloidal silica, alumina, silica-alumina, zirconium oxide, molecular sieves, metal organic frameworks, zeolitic imidazolate frameworks, covalent organic frameworks, or combinations thereof, wherein the filler contains covalently bonded acidic functional groups and 150m 2 / g or more, or 300m 2 / g or more, or 400m 2Molecular sieves can include both high surface areas of 0.1 to 1.0 keV / g or more. Molecular sieves have a framework structure that can be characterized by a unique wide-angle X-ray diffraction pattern. Zeolites are a subclass of molecular sieves based on aluminosilicate compositions. Non-zeolitic molecular sieves are based on other compositions such as aluminophosphates, silicoaluminophosphates, and silica. Molecular sieves can have a variety of chemical compositions and framework structures. Molecular sieves can be microporous or mesoporous and must be stable in aqueous solutions at a pH below 6. The acidic functional group covalently bonded to the inorganic filler may be selected from, but is not limited to, -H2PO3, -R-H2PO3, -SO3H, -R-SO3H, -COOH, -R-COOH, -CH5OH, -R-CH5OH, or a combination thereof, where R represents a linear alkyl group, a branched 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 1 to 20, more preferably 1 to 10. The inorganic filler may be in the form of, but is not limited to, particles, fine beads, thin plates, rods, or fibers. The size of the inorganic filler is in the range of 2 nm to 200 μm, or 10 nm to 100 μm, or 50 nm to 80 μm. In some embodiments, the inorganic filler is an aminopropyl-N,N-bis(methylphosphonic acid) functionalized silica gel such as SilicaMetS® AMPA, aminopropyl-N,N-bis(methylphosphonic acid) functionalized fumed silica, n-propylphosphonic acid functionalized silica gel, n-propylphosphonic acid functionalized fumed silica, p-toluenesulfonic acid functionalized silica gel, p-toluenesulfonic acid functionalized fumed silica, 4-ethylbenzenesulfonic acid functionalized silica gel such as SilicaBond® tosylate, 4-ethylbenzenesulfonic acid functionalized fumed silica, n-propylsulfonic acid functionalized silica gel, n-propylsulfonic acid functionalized fumed silica, or a combination thereof.

[0034] Suitable cation exchange polymers for preparing PEMs include, but are not limited to, perfluorinated sulfonic acid polymers, perfluorinated carboxylic acid polymers, sulfonated aromatic hydrocarbon polymers, crosslinked sulfonated aromatic hydrocarbon polymers, or combinations thereof. Suitable cation exchange polymers include 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, ...3,6-dioxa-4-methyl-7-octene-sulfonic acid, copolymers of tetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid, copolymers of tetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid, copolymers of tetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl- Copolymer of perfluoro-5-oxa-6-heptene-sulfonic acid and perfluoro(2,2-dimethyl-1,3-dioxole), copolymer of perfluoro-4-oxa-5-hexene-sulfonic acid and perfluoro(2,2-dimethyl-1,3-dioxole), copolymer of perfluoro-3-oxa-4-pentene-sulfonic acid and perfluoro 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), ,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-dioxole, copolymers of perfluoro-5-oxa-6-heptene-sulfonic acid and 2,2,4-trifluoro-5-trifluoromethoxy-1,copolymers of perfluoro-4-oxa-5-hexene-sulfonic acid and 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, copolymers of perfluoro-3-oxa-4-pentene-sulfonic acid and 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, copolymers of perfluoro-4-oxa-5-hexene-sulfonic acid and 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, and sulfonated poly(ether ether ketone). ketone), SPEEK), sulfonated polyethersulfone, sulfonated polyphenylsulfone, sulfonated poly(2,6-dimethyl-1,4-phenylene oxide), sulfonated poly(4-phenoxybenzoyl-1,4-phenylene), sulfonated polyphenylene oxide, sulfonated poly(phenylene), sulfonated poly(phthalazinone), crosslinked SPEEK, crosslinked sulfonated polyethersulfone, crosslinked sulfonated polyphenylsulfone, crosslinked poly(phenylene sulfide sulfonitrile), sulfonated polystyrene, sulfonated poly(vinyl toluene), crosslinked sulfonated polystyrene, crosslinked sulfonated poly(vinyl toluene), or combinations thereof.

[0035] The first layer deposited on one or both surfaces of the negatively ion-charged PEM must be a polycationic polymer layer with a positive ionic charge opposite that of the cation exchange membrane, thereby forming a stable coating as the first portion of the first polyelectrolyte bilayer through electrostatic interactions between the cation exchange polymer of the PEM and the polycation deposited on the surface of the PEM. A polyanionic polymer with an opposite charge is then deposited on the surface of the first polycationic polymer coating layer through electrostatic interactions to form the second portion of the first polyelectrolyte bilayer. PEM / (polycation-polyanion) n or polyanion-polycation) n / PEM / (polycation-polyanion) nEither polyelectrolyte multilayer can be formed according to the same layer-by-layer deposition process. The thickness of each polyanion or polycation layer is less than 50 nm, or less than 20 nm, or less than 10 nm, or less than 5 nm. The polyanion polymer in the polyelectrolyte multilayer has a negative charge and can be the same or different from the cation exchange polymer in the PEM, but the polyanion polymer cannot be the first polyelectrolyte layer deposited on the surface of the negatively charged PEM. Polyanion polymers suitable for preparing polyelectrolyte multilayer-coated PEMs have proton conductivity comparable to or higher than that of the PEM and H2 and O2 permeabilities comparable to or lower than that of the PEM. However, polyanion and polycation polymers can be soluble in aqueous solutions, making membranes prepared from either polyanion or polyanion polymers unsuitable for water electrolysis or fuel cell applications. The polyelectrolyte multilayers deposited on one or both surfaces of the PEM via layer-by-layer deposition are not only insoluble and thermally and chemically stable, but also exhibit significantly reduced swelling of the cation exchange membrane and H and O crossover, and enhanced proton conductivity compared to PEMs for water electrolysis or fuel cell applications.

[0036] Suitable polycationic polymers for the preparation of polyelectrolyte multilayer coated PEMs or AEMs include, but are not limited to: protonated chitosan;Polybiguanide, quaternary ammonium polyethyleneimine, quaternary ammonium polypropyleneimine, quaternary ammonium polyamidoamine (PAMAM), poly(vinylamine hydrochloride) (PVH), poly(allylamine hydrochloride) (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, poly an amine-based linear, hyperbranched, or dendrimeric polycationic polymer selected from the group consisting of realginine, 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 a combination thereof;

[0037] Suitable polyanionic polymers for preparing polyelectrolyte multilayer-coated PEMs or AEMs 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 oxide, 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 curdlan, sodium carboxymethyl curdlan, potassium carboxymethyl curdlan, calcium carboxymethyl curdlan, ammonium carboxymethyl curdlan, carboxymethyl cellulose, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, calcium carboxymethyl cellulose, ammonium carboxymethyl cellulose, or combinations thereof.

[0038] Another aspect is a catalyst coated membrane. In one embodiment, the catalyst coated membrane includes a membrane; a catalyst layer on one surface of the membrane, the catalyst layer including a catalyst, an ionomer, and optionally an additive, and formed from a catalyst ink including the catalyst; an ionomer; a solvent; a porogen soluble in the solvent; and optionally an additive.

[0039] There may be a layer of catalyst on the opposite side of the membrane, and the catalyst layers on the two sides may be the same or different.

[0040] The catalyst, ionomer, solvent, porogen, and additives are as described above.

[0041] Another aspect of the present invention is a method for preparing a catalyst-coated membrane. In one embodiment, the method includes coating a layer of catalyst ink on a first surface of a membrane to form a coated membrane, drying the layer of catalyst ink to form a catalyst layer on the first surface of the membrane, and removing porogen from the catalyst layer to form nanopores in the catalyst layer. The catalyst ink includes a catalyst, an ionomer, a porogen, a solvent, and optional additives. Suitable coating application methods include, but are not limited to, spray coating, comma roll coating, meniscus / slot die coating, gravure coating, brushing, roller coating, metering rod / Meyer rod coating, knife casting, and the like.

[0042] In some embodiments, removing the porogen from the catalyst layer comprises immersing the coating film in a solvent, an acidic solution for a PEM-based CCM, or a basic solution for an AEM-based CCM at a temperature ranging from 20°C to 120°C, or from 20°C to 80°C, or from 20°C to 40°C for 10 minutes to 48 hours, or from 30 minutes to 24 hours, or from 2 hours to 12 hours, to generate nanopores, prior to using the CCM in an electrolytic cell. Alternatively, the porogen can be removed from the catalyst layer and generate nanopores by washing the coating film with a solvent, an acidic solution for a PEM-based CCM, or a basic solution for an AEM-based CCM at a temperature ranging from 20°C to 80°C, or from 20°C to 40°C, for 10 minutes to 4 hours, or from 30 minutes to 2 hours. Suitable solvents, acidic solutions, and basic solutions for removing the porogen are described above.

[0043] In some embodiments, the method further comprises coating a layer of catalyst on the second surface of the membrane.

[0044] Yet another aspect of the present invention is a membrane electrode assembly. In one embodiment, the membrane electrode assembly comprises an ion-conducting membrane, a first porous transport layer adjacent to a first side of the ion-conducting membrane, and a second porous transport layer adjacent to a second side of the ion-conducting membrane. An anode is present between the first side of the ion-conducting membrane and the first porous transport layer, and the anode comprises an anode catalyst coating layer on the first side of the ion-conducting membrane adjacent to the first porous transport layer, or on the first side of the first porous transport layer adjacent to the first side of the ion-conducting membrane, or both. A cathode is present between the second side of the ion-conducting membrane and the second porous transport layer, and the cathode comprises a cathode catalyst coating layer on the second side of the ion-conducting membrane adjacent to the second porous transport layer, or on the first side of the second porous transport layer adjacent to the second side of the ion-conducting membrane, or both. The anode catalyst coating layer, the cathode catalyst coating layer, or both include a catalyst, an ionomer, and optional additives. The anode catalyst coating layer, the cathode catalyst coating layer, or both are formed from a catalyst ink containing a catalyst, an ionomer, a solvent, a porogen soluble in the solvent, and optional additives. The porogen can be removed from the catalyst layer as described above to form pores in the catalyst layer. "Adjacent" means that the layers are next to each other, but not necessarily directly next to each other. For example, a first porous transport layer is adjacent to one side of the ion-conducting membrane, with a catalyst coating layer between them, which is on the membrane, the porous transport layer, or both.

[0045] The catalyst, porogen, polymeric ionomer, additive, and ion-conducting membrane are described above.

[0046] In some embodiments, the membrane electrode assembly further includes a pair of bipolar plates, one plate adjacent to the outside of the first porous transport layer and one plate adjacent to the outside of the second porous transport layer.

[0047] Another aspect is an electrolysis system. In one embodiment, the electrolysis system includes at least one cell forming a cell stack, the at least one cell including a membrane electrode assembly including an ion-conducting membrane, a first side of a first porous transport layer adjacent to the first side of the ion-conducting membrane, a first side of a second porous transport layer adjacent to the second side of the ion-conducting membrane, and an anode between the first side of the ion-conducting membrane and the first side of the first porous transport layer, the anode including a first porous transport layer on the first side of the ion-conducting membrane adjacent to the first porous transport layer or adjacent to the first side of the ion-conducting membrane. an anode comprising an anode catalyst coating layer on a first side of the porous transport layer, or both; and a cathode between the second side of the ion-conducting membrane and the first side of the second porous transport layer, the cathode comprising a cathode catalyst coating layer on the second side of the ion-conducting membrane adjacent to the second porous transport layer, or on the first side of the second porous transport layer adjacent to the second side of the ion-conducting membrane, or both, wherein the anode catalyst coating layer, the cathode catalyst coating layer, or both, comprises a catalyst, an ionomer, and optionally an additive. The anode catalyst coating layer, the cathode catalyst coating layer, or both, are formed from an anode catalyst ink, or a cathode catalyst ink, or both, respectively. The electrolysis system may also include a pair of bipolar plates, a first bipolar plate adjacent to the second side of the first porous transport layer and a second bipolar plate adjacent to the second side of the second porous transport layer, and a pair of current collectors, a first current collector adjacent to the first end of the cell stack and a second current collector adjacent to the second end of the cell stack. The anode catalyst ink, the cathode catalyst ink, or both include a catalyst, an ionomer, a solvent, a porogen soluble in the solvent, and optional additives. The porogen can be removed from the catalyst layer as described above to form pores in the catalyst layer.

[0048] The bipolar plate may be any bipolar plate known to those skilled in the art. Suitable bipolar plates include, but are not limited to, Pt-coated Ti bipolar plates, stainless steel bipolar plates, Ti-coated stainless steel bipolar plates, Ti and C-coated stainless steel bipolar plates, stainless steel bipolar plates, graphite bipolar plates, or combinations thereof. The bipolar plate must have high resistance to prevent outward diffusion of harmful ions from the bipolar plate and to prevent embrittlement due to hydrogen adsorption. The bipolar plate must also have low and stable electrical contact resistance over the life of the stack.

[0049] In some embodiments, there is a pair of gaskets, a first gasket between the first porous transport layer and the first bipolar plate, and a second gasket between the second porous transport layer and the second bipolar plate.

[0050] An electrolysis system typically includes more than one cell. For example, the number of cells may range from 2 cells to several thousand cells, or from 2 cells to 3000 cells, or from 2 cells to 2000 cells, or from 2 cells to 1500 cells, or from 2 cells to 1000 cells, or from 2 cells to 750 cells, or from 2 cells to 500 cells, or from 10 cells to 3000 cells, or from 10 cells to 2000 cells, or from 10 cells to 150 The cell size may range from 0 cells, or from 10 cells to 1000 cells, or from 10 cells to 750 cells, or from 10 cells to 500 cells, or from 20 cells to 3000 cells, or from 20 cells to 2000 cells, or from 20 cells to 1500 cells, or from 20 cells to 1000 cells, or from 20 cells to 750 cells, or from 20 cells to 500 cells. Multiple cells are stacked together to form a cell stack. Current collectors are placed at each end of the cell stack, and end plates are outside the current collectors at each end.

[0051] The current collector may be any current collector known to those skilled in the art. Suitable current collectors may be made from materials including, but not limited to, nickel, steel, aluminum, copper, titanium, platinum, and gold.

[0052] The end plates may be any end plate known to those skilled in the art. Suitable end plate materials include, but are not limited to, aluminum alloy, stainless steel, Ti, and Pt-coated Ti. [Example]

[0053] Example 1: Preparation of a three-layer MEA (abbreviated as 3-L MEA-glycerol) comprising a PEM, an anode catalyst coating layer formed from an anode catalyst ink containing glycerol porogen, and a cathode catalyst coating layer A three-layer MEA (abbreviated as 3-L MEA-glycerol) comprising an anode catalyst coating layer formed from an anode catalyst ink comprising Fumasep® FS-990-PK PEM, IrO catalyst, Nafion® ionomer, poly(3,4-ethylenedioxythiophene) (PEDOT) electronically conductive polymer, and glycerol porogen in a mixture of water and ethanol solvent, and a cathode catalyst coating layer formed from a cathode catalyst ink comprising 40% Pt / C catalyst and Nafion® ionomer in a mixture of water and ethanol solvent was prepared as follows: The anode catalyst ink was prepared by mixing IrO catalyst, glycerol porogen, a blend solution of PEDOT and poly(styrenesulfonate) (PSS), and Nafion® ionomer in H2O and ethanol. The weight ratio of glycerol to IrO catalyst was 1 / 10. The anode catalyst ink was coated onto the first surface of a Fumasep® FS-990-PK PEM using the Mayer rod coating method and dried at 80 °C to form a two-layer MEA with glycerol porogen in the IrO2 anode catalyst coating layer. The IrO2 loading was 1.0 mg / cm2.2 It was.

[0054] The cathode catalyst ink was prepared by mixing 40% Pt / C catalyst and Nafion® ionomer in HO and ethanol. The mixture was finely dispersed using an ultrasonic bath. The cathode catalyst ink was coated onto the second surface of a Fumasep® FS-990-PK PEM using the Mayer rod coating method and dried at 80°C to form a three-layer MEA. The Pt loading was 0.1 mg / cm. 2 It was.

[0055] The three-layer MEA was immersed in 0.1 M H2SO4 acidic aqueous solution for 24 h, washed three times with ultrapure water, and then air-dried for 12 h to form 3-L MEA-glycerol.

[0056] Comparative Example 1. Preparation of a three-layer MEA (abbreviated as 3-L MEA-non-G) including a PEM, an anode catalyst coating layer formed from an anode catalyst ink containing no glycerol porogen, and a cathode catalyst coating layer A three-layer MEA (abbreviated as 3-L MEA-non-G) comprising Fumasep® FS-990-PK PEM, an anode catalyst coating layer formed from an anode catalyst ink comprising an IrO catalyst, a Nafion® ionomer, and a PEDOT electronically conductive polymer in a mixture of water and ethanol solvent, and a cathode catalyst coating layer formed from a cathode catalyst ink comprising a 40% Pt / C catalyst and a Nafion® ionomer in a mixture of water and ethanol solvent was prepared using the procedure of Example 1, except that the anode catalyst ink did not contain glycerol porogen.

[0057] Example 2. Evaluation of water electrolysis performance of 3-L MEA-non-G and 3-L MEA-glycerol A proton exchange membrane (PEM) water electrolysis test station (Scribner 600 electrolyzer test system) was used to measure the 5 cm 2The water electrolysis performance of a 3-L MEA-non-G (a) MEA and a 3-L MEA-glycerol (b) MEA in a single-cell cell with an active membrane area of ​​1000 sq m was evaluated. The test station included an integrated power supply, a potentiostat, an impedance analyzer for electrochemical impedance spectroscopy (EIS) and high-frequency resistance (HFR), and real-time sensors for product flow and crossover monitoring. The MEA was sandwiched between two Pt-coated Ti felt porous transport layers (PTLs). Tests were conducted at 80 °C and atmospheric pressure. Ultrapure water was supplied to the anode of the MEA at a flow rate of 100 mL / min. Polarization curves were collected at 80 °C, and the results are shown in Figure 3.

[0058] The 3-L MEA-non-G MEA (a), fabricated from an anode catalyst ink containing no glycerol porogen, exhibited a current density of 2 A / cm. 2 It can be observed from the polarization curves in Figure 3 that the anode catalyst ink exhibited significant mass transfer resistance at current densities above 2 A / cm. Without wishing to be bound by theory, this is most likely due to the dense anode catalyst coating layer, which made it difficult to remove the large amount of gas generated at high current densities. On the other hand, the 3-L MEA-glycerol MEA prepared from the anode catalyst ink containing glycerol porogen exhibited significant mass transfer resistance at current densities above 2 A / cm, as shown in curve (b). 2 Furthermore, the 3-L MEA-glycerol MEA exhibited no mass transfer resistance at current densities above 1 A / cm. 2 At these current densities, the 3-L MEA-non-G MEA fabricated from an anode catalyst ink containing no glycerol porogen, as shown in curve (b), exhibited a much lower cell voltage than the 3-L MEA-non-G MEA fabricated from an anode catalyst ink containing no glycerol porogen, as shown in curve (a). These results indicate that the 3-L MEA-glycerol MEA, which has a more porous anode catalyst coating layer, enabled rapid removal of evolved gases at high current densities, and no mass transfer resistance was observed.

[0059] Specific Embodiments While the following will be described in conjunction with specific embodiments, it will be understood that this description is illustrative, but not intended to limit the scope of the preceding description and appended claims.

[0060] A first embodiment of the present invention is a catalyst ink comprising a catalyst, an ionomer, a solvent, a porogen soluble in the solvent, and optionally an additive. An embodiment of the present invention is one, any, or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, wherein the porogen comprises glycerol, glycine, ethylene glycol, poly(ethylene glycol), poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), co-block-poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO), tri-block-poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO), sorbitol, polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), diethylene glycol, sulfosuccinic acid, tetradecyltrimethylammonium bromide, tetramethylammonium bromide, tetradecyltrimethylammonium acetate, tetramethylammonium acetate, or a combination thereof. An embodiment of the invention is one, any, or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, wherein the porogen comprises glycerol, glycine, ethylene glycol, diethylene glycol, sulfosuccinic acid, or a combination thereof.An embodiment of the invention is one, any, or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, wherein the catalyst comprises iridium, platinum, ruthenium, osmium, rhodium, palladium, tin, tungsten, vanadium, cobalt, silver, gold, copper, nickel, molybdenum, iron, chromium, an alloy thereof, an oxide thereof, a carbide thereof, a phosphide thereof, or a combination thereof. An embodiment of the invention is one, any, or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, wherein the catalyst comprises platinum, ruthenium, osnium, rhodium, palladium, tin, tungsten, vanadium, cobalt, silver, gold, nickel, molybdenum, iron, copper, chromium, alloys thereof, oxides thereof, carbides thereof, phosphides thereof, or combinations thereof.An embodiment of the invention is one, any, or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, wherein the solvent comprises water, alcohol, acetone, methyl ethyl ketone, ether, tetrahydrofuran, 1,3-dioxolane, methyl acetate, ethyl acetate, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, or a combination thereof. An embodiment of the invention is one, any, or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, wherein the ionomer comprises a proton-conducting fluorinated or non-fluorinated polymer ionomer, or a hydroxide-conducting polymer ionomer, or a combination thereof. An embodiment of the invention is one, any, or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, wherein the additive comprises an electronically conductive polymer.

[0061] A second embodiment of the present invention is a catalyst-coated membrane comprising: a membrane; a layer of catalyst on a first surface of the membrane, the layer comprising a catalyst, an ionomer, and optionally an additive, the catalyst layer being formed from a catalyst ink comprising the catalyst; an ionomer; a solvent; a solvent-soluble porogen; and optionally an additive. An embodiment of the present invention is one, any, or all of the preceding embodiments in this paragraph through the second embodiment of this paragraph, further comprising a layer of catalyst on a second surface of the membrane. An embodiment of the present invention is one, any, or all of the preceding embodiments in this paragraph through the second embodiment of this paragraph, wherein the catalyst layer on the second surface comprises a catalyst; an ionomer; and optionally an additive, the catalyst layer being formed from a catalyst ink comprising the catalyst; the ionomer; a solvent; a solvent-soluble porogen; and optionally an additive. An embodiment of the invention is one, any, or all of the preceding embodiments of this paragraph through the second embodiment of this paragraph, wherein the porogen comprises glycerol, glycine, ethylene glycol, poly(ethylene glycol), poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), co-block-poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO), tri-block-poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO), sorbitol, polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), diethylene glycol, sulfosuccinic acid, tetradecyltrimethylammonium bromide, tetramethylammonium bromide, tetradecyltrimethylammonium acetate, tetramethylammonium acetate, or a combination thereof. An embodiment of the invention is one, any, or all of the preceding embodiments of this paragraph through the second embodiment of this paragraph, wherein the catalyst comprises iridium, platinum, ruthenium, osnium, rhodium, palladium, tin, tungsten, vanadium, cobalt, silver, gold, copper, nickel, molybdenum, iron, chromium, alloys thereof, oxides thereof, carbides thereof, phosphides thereof, or combinations thereof.An embodiment of the present invention is any one, any, or all of the preceding embodiments of this paragraph through the second embodiment of this paragraph, wherein the catalyst comprises platinum, ruthenium, osnium, rhodium, palladium, tin, tungsten, vanadium, cobalt, silver, gold, nickel, molybdenum, iron, copper, chromium, an alloy thereof, an oxide thereof, a carbide thereof, a phosphide thereof, or a combination thereof. An embodiment of the present invention is any one, any, or all of the preceding embodiments of this paragraph through the second embodiment of this paragraph, wherein the solvent comprises water, an alcohol, acetone, methyl ethyl ketone, ether, tetrahydrofuran, 1,3-dioxolane, methyl acetate, ethyl acetate, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, or a combination thereof. An embodiment of the present invention is any one, any, or all of the preceding embodiments of this paragraph through the second embodiment of this paragraph, wherein the additive comprises an electronically conductive polymer. An embodiment of the invention is one, any, or all of the preceding embodiments of this paragraph through the second embodiment of this paragraph, wherein the ionomer comprises a proton-conducting fluorinated or non-fluorinated polymer ionomer, or a hydroxide-conducting polymer ionomer, or a combination thereof.An embodiment of the invention is one, any, or all of the preceding embodiments of this paragraph through the second embodiment of this paragraph, wherein the membrane comprises a proton exchange membrane or an anion exchange membrane.

[0062] A third embodiment of the present invention is a method of making a catalyst-coated membrane, the method comprising: coating a layer of catalyst ink on a first surface of a membrane to form a coating membrane, the catalyst ink comprising a catalyst, an ionomer, a porogen, a solvent, and optionally an additive; drying the layer of catalyst ink to form a catalyst layer on the first surface of the membrane; and removing the porogen from the catalyst layer to create pores in the catalyst layer. An embodiment of the present invention is one, any, or all of the preceding embodiments in this paragraph through the third embodiment of this paragraph, wherein removing the porogen from the catalyst layer comprises immersing the coating membrane in a solvent, an acidic solution, or a basic solution, or washing the coating membrane with a solvent, an acidic solution, or a basic solution.

[0063] Without further elaboration, it is believed that, using the preceding description, one skilled in the art can utilize the present invention to its fullest extent and easily ascertain the essential characteristics of the present invention, and can make various changes and modifications to the present invention to adapt it to various uses and conditions, without departing from the spirit and scope of the present invention. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way, and are intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0064] Above, all temperatures are set forth in degrees Celsius and all parts and percentages are by weight unless otherwise indicated.

Claims

1. 1. A catalyst ink comprising: A catalyst; Ionomer and a solvent; a porogen that is soluble in the solvent; Optionally, an additive.

2. 2. The catalyst ink of claim 1, wherein the porogen comprises glycerol, glycine, ethylene glycol, poly(ethylene glycol), poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), co-block-poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO), tri-block-poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO), sorbitol, polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), diethylene glycol, sulfosuccinic acid, tetradecyltrimethylammonium bromide, tetramethylammonium bromide, tetradecyltrimethylammonium acetate, tetramethylammonium acetate, or a combination thereof.

3. 10. The catalytic ink of claim 1, wherein the catalyst comprises iridium, platinum, ruthenium, osnium, rhodium, palladium, tin, tungsten, vanadium, cobalt, silver, gold, copper, nickel, molybdenum, iron, chromium, alloys thereof, oxides thereof, carbides thereof, phosphides thereof, or combinations thereof.

4. 10. The catalyst ink of claim 1, wherein the solvent comprises water, alcohol, acetone, methyl ethyl ketone, ether, tetrahydrofuran, 1,3-dioxolane, methyl acetate, ethyl acetate, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, or a combination thereof.

5. 10. The catalyst ink of claim 1, wherein the ionomer comprises a proton-conducting fluorinated or non-fluorinated polymer ionomer, or a hydroxide-conducting polymer ionomer, or a combination thereof.

6. The catalyst ink of claim 1 , wherein the additive comprises an electronically conductive polymer.

7. 1. A method for making a catalyst coated membrane, comprising: coating a layer of a catalyst ink on a first surface of the membrane to form a coating membrane, the catalyst ink comprising: A catalyst; Ionomer and A porogen, A solvent; and optionally an additive; drying the layer of catalyst ink to form a catalyst layer on the first surface of the membrane; removing the porogen from the catalyst layer to form pores in the catalyst layer; A method comprising:

8. 8. The method of claim 7, wherein removing the porogen from the catalyst layer comprises immersing the coating film in a solvent, an acidic solution, or a basic solution, or washing the coating film with a solvent, an acidic solution, or a basic solution.

9. 8. The method of claim 7, wherein the porogen comprises glycerol, glycine, ethylene glycol, poly(ethylene glycol), poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), co-block-poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO), tri-block-poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO), sorbitol, polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), diethylene glycol, sulfosuccinic acid, tetradecyltrimethylammonium bromide, tetramethylammonium bromide, tetradecyltrimethylammonium acetate, tetramethylammonium acetate, or a combination thereof.

10. 8. The method of claim 7, wherein the catalyst comprises iridium, platinum, ruthenium, osnium, rhodium, palladium, tin, tungsten, vanadium, cobalt, silver, gold, copper, nickel, molybdenum, iron, chromium, alloys thereof, oxides thereof, carbides thereof, phosphides thereof, or combinations thereof.

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