Electrode, membrane-electrode assembly, manufacturing method therefor, and water electrolysis cell comprising same

Abstract

The present invention provides a water electrolysis cell electrode, a water electrolysis cell membrane-electrode assembly comprising same, a manufacturing method therefor, and a water electrolysis cell. The water electrolysis cell electrode comprises: a catalyst; a polymer including a first repeating unit including one or more hydroxyl groups and a second repeating unit including one or more carboxyl groups; and a metal-based material bonded to the hydroxyl group of the first repeating unit and the carboxyl group of the second repeating unit.

Description

Electrode, membrane-electrode assembly, method of manufacturing the same, water electrolysis cell including the same

[0001] The invention relates to an electrode, a membrane-electrode assembly, a method of manufacturing the same, and a water electrolysis cell comprising the same.

[0002] The present disclosure relates to the results of a project (Project No.: 00418612) carried out with the support of the Ministry of Trade, Industry and Energy (MOTIE) and the Korea Energy Technology Evaluation Institute (KETEP).

[0003] To address the issues of fossil fuel depletion and environmental pollution, efforts are being made to conserve fossil fuels by improving usage efficiency or to apply renewable energy to a wider range of fields. For instance, fuel cells, which directly convert chemical reaction energy—such as the oxidation / reduction reactions of hydrogen and oxygen contained in hydrocarbon fuels like methanol, ethanol, and natural gas—into electrical energy, and water electrolysis cells, which produce hydrogen and oxygen by electrochemically decomposing water, are attracting attention as next-generation clean energy technologies to replace fossil fuels.

[0004] The Membrane Electrode Assembly (MEA), a core component of a Polymer Electrolyte Membrane Water Electrolysis Cell (PEMWE) that uses a dual polymer electrolyte membrane as a separator, has a structure in which an electrode where oxidation occurs and an electrode where reduction occurs are located on opposite sides with the polymer electrolyte membrane in between.

[0005] In this case, in conventional membrane-electrode assemblies, the electrode is mainly a porous structure in which a catalyst and a binder are mixed, and the binder is mainly an ion-conducting polymer electrolyte. However, due to swelling problems caused by water and weak bonding with the catalyst, irreversible changes can occur during system operation, leading to a decrease in performance and durability. Furthermore, the membrane-electrode assembly is mainly operated under high voltage conditions in the presence of an excess amount of water, and there is still a need to improve the low electrical conductivity resulting from the difficulty of using electrically conductive carbon materials.

[0006] According to one embodiment, an electrode composition for a water electrolysis cell is provided that has excellent adhesion, solubility, electrochemical stability, and a low swelling rate under aqueous conditions, and by including the electrode composition for a water electrolysis cell, the electrical conductivity of the existing electrode for water electrolysis is compensated for, thereby providing a water electrolysis cell with improved performance.

[0007] In one embodiment, an electrode for a water electrolysis cell is provided, comprising: a catalyst; a polymer comprising a first repeating unit comprising one or more hydroxyl groups and a second repeating unit comprising one or more carboxyl groups; and a metal-based material coupled to the hydroxyl group of the first repeating unit and the carboxyl group of the second repeating unit.

[0008] In another embodiment, a membrane-electrode assembly for a water electrolysis cell is provided, comprising: a hydrogen generating electrode; an oxygen generating electrode; and a polymer electrolyte membrane located between the hydrogen generating electrode and the oxygen generating electrode, wherein at least one of the hydrogen generating electrode and the oxygen generating electrode is an electrode for the water electrolysis cell.

[0009] In another embodiment, a method for manufacturing a membrane-electrode assembly for a water electrolysis cell is provided, comprising: (i) a step of manufacturing a hydrogen generation electrode; (ii) a step of manufacturing an oxygen generation electrode; and (iii) a step of bonding a polymer electrolyte membrane to the hydrogen generation electrode and the oxygen generation electrode, wherein the polymer electrolyte membrane is located between the hydrogen generation electrode and the oxygen generation electrode, and at least one of the hydrogen generation electrode and the oxygen generation electrode is an electrode for the water electrolysis cell.

[0010] In another embodiment, a water electrolysis cell comprising a membrane-electrode assembly for the water electrolysis cell is provided.

[0011] According to one embodiment, a water electrolysis cell comprising an electrode composition for a water electrolysis cell that exhibits excellent adhesion, solubility, electrochemical stability, and a low swelling rate under aqueous conditions, thereby improving stability and durability, has improved electrical conductivity, mechanical properties, etc.

[0012] FIG. 1 is a schematic diagram showing a polymer and a metal-based material according to one embodiment.

[0013] Figure 2 is a graph showing the underwater tensile adhesive strength of the compositions excluding the oxygen generation reaction catalyst among the oxygen generation electrode compositions of the examples and comparative examples.

[0014] Figure 3 is a diagram showing the bonding force between the electrodes and the polymer electrolyte membrane of the examples and comparative examples.

[0015] Hereinafter, embodiments of the present disclosure are described in detail so that those skilled in the art to which the present disclosure pertains can easily implement them. However, the present disclosure may be embodied in various different forms and is not limited to the embodiments described herein.

[0016] In this specification, "combination thereof" means a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, a reaction product, etc.

[0017] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0018] In this specification, terms are used solely for the purpose of distinguishing one component from another. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0019] Electrode for water electrolysis cell

[0020] One embodiment provides an electrode for a water electrolysis cell comprising: a catalyst; a polymer comprising a first repeating unit comprising one or more hydroxyl groups and a second repeating unit comprising one or more carboxyl groups; and a metal-based material coupled to the hydroxyl group of the first repeating unit and the carboxyl group of the second repeating unit.

[0021] In conventional membrane-electrode assemblies for water electrolysis cells, the electrode is primarily a porous structure composed of a mixture of a catalyst and a binder, and the binder is mainly an ion-conducting polymer electrolyte. However, due to swelling caused by water and weak bonding with the catalyst, irreversible changes can occur during system operation, leading to a decrease in performance and durability. Furthermore, water electrolysis membrane-electrode assemblies are operated primarily under high-voltage conditions in the presence of an excess amount of water. Consequently, unlike fuel cell systems, the need for ion-conducting materials within the electrode is reduced due to the presence of water; conversely, there is a need to improve the low electrical conductivity resulting from the difficulty of using electrically conductive materials containing carbon that decompose at high voltages. Accordingly, the performance and durability of water electrolysis membrane-electrode assemblies can be improved by using an electrode for water electrolysis cells that is usable under aqueous conditions and has excellent electrical conductivity. The above electrode for a water electrolysis cell has excellent adhesion, solubility, electrochemical stability, and a low swelling rate under aqueous conditions, and uses an electrode composition for a water electrolysis cell that enables electrode dispersion without aggregation due to high film-forming ability, and can provide an electrode for a water electrolysis cell with improved adhesion and retention through drying and heat treatment processes and post-curing and crosslinking in a high temperature and high pressure transfer process for forming a membrane-electrode assembly for a water electrolysis cell.

[0022] In one embodiment, the first repeating unit and the second repeating unit may form a cross-linked polymer, for example, by being ester-bonded to each other, and the ester bond may be an ester bond between the hydroxyl group of the first repeating unit and the carboxyl group of the second repeating unit. Due to the ester bond structure, the polymer is not easily broken or destroyed, so it can stably serve as a binder for an electrode for a water electrolysis cell.

[0023] At this time, the molar ratio of the first repeating unit and the second repeating unit may be 0.1:1 to 10:1, for example, 0.1:1 to 0.8:1, 0.1:1 to 0.5:1, 2:1 to 10:1, 3:1 to 7:1, 0.25:1 to 8:1, 0.3:1 to 6:1, or 0.4:1 to 5:1. When the molar ratio of the first repeating unit and the second repeating unit falls within the above range, the effects of the first repeating unit and the second repeating unit are harmoniously realized, so that the polymer is not easily broken or destroyed even in water, and can serve as a binder for an electrode for a water electrolysis cell that has stable and excellent adhesion.

[0024] In one embodiment, the polymer comprises a first repeating unit comprising one or more hydroxyl groups, and the first repeating unit may be derived from polyvinyl alcohol. In this case, the first repeating unit may include a hydroxyl group remaining after the polyvinyl alcohol has been ester-bonded. That is, the first repeating unit and the second repeating unit may be ester-bonded via the metal-based material, and the hydroxyl group of the first repeating unit and the carboxyl group of the second repeating unit may be ester-bonded via the metal-based material, for example, the hydroxyl group of the first repeating unit derived from polyvinyl alcohol and the carboxyl group of the second repeating unit derived from one or more selected from polyacrylic acid, citric acid, and succinic acid may be ester-bonded via the metal-based material, and the hydroxyl group remaining after ester-bonding may be included in the first repeating unit. The above-mentioned first repeating unit contains a large number of hydroxyl groups (-OH) that are highly hydrophilic toward water, so it dissolves well in water, is easy to form a transparent film, has excellent properties such as tensile strength, tear strength, friction resistance, and flexural strength, and can have adhesion to various materials.

[0025] In one embodiment, the polymer comprises a second repeating unit comprising one or more carboxyl groups, and the second repeating unit may be derived from one or more selected from polyacrylic acid, citric acid, and succinic acid. In this case, the second repeating unit may include a carboxyl group remaining after ester bonding with one or more selected from polyacrylic acid, citric acid, and succinic acid. That is, the first repeating unit and the second repeating unit can be ester-bonded via the metal-based material, and the hydroxyl group of the first repeating unit and the carboxyl group of the second repeating unit can be ester-bonded via the metal-based material. For example, the hydroxyl group of the first repeating unit derived from polyvinyl alcohol and the carboxyl group of the second repeating unit derived from one or more selected from polyacrylic acid, citric acid, and succinic acid can be ester-bonded via the metal-based material, and the remaining carboxyl group after ester-bonding can be included in the second repeating unit. The second repeating unit can act as a thickener because it dissolves in water to become a solution with high viscosity due to the carboxyl group, and it can improve water solubility by combining with the hydroxyl group of the first repeating unit and can have adhesion to various materials.

[0026] In one embodiment, the electrode for the water electrolysis cell comprises a metal-based material, and the metal-based material is bonded to the hydroxyl group of the first repeating unit and the carboxyl group of the second repeating unit. At this time, the metal-based material may coordinately bond to the hydroxyl group of the first repeating unit or the carboxyl group of the second repeating unit, and as a result, the first repeating unit and the second repeating unit may be ester-bonded through the metal-based material to form a cross-linked polymer.

[0027] In one embodiment, the metal-based material may mean a metal or a compound containing a metal, and may include, for example, a metal, a metal oxide, a metal nitrate, a metal chloride, a metal sulfate, or a combination thereof. At this time, the metal may be one or more selected from Ag, Cu, Ni, Zn, and Sn, the metal oxide may be one or more selected from AgO, Ag2O, Ag2O3, CuO, Cu2O, NiO, ZnO, and SnO2, the metal nitrate may be one or more selected from AgNO3, Cu(NO3)2, Ni(NO3)2, Zn(NO3)2, and Sn(NO3)2, the metal chloride may be one or more selected from AgCl, AgCl2, CuCl, CuCl2, NiCl2, ZnCl2, and SnCl2, and the metal sulfate may be one or more selected from Ag2SO4, CuSO4, NiSO4, ZnSO4, and SnSO4.

[0028] Additionally, the metal-based material may be in the form of particles or precursors, and the precursor may form a chelate with a hydroxyl group included in the first repeating unit, a carboxyl group included in the second repeating unit, or a combination thereof. If the metal-based material is in the form of particles, it may be spherical, elliptical-spherical, plate-shaped, or a combination thereof. If the metal-based material is in the form of particles, the average particle size (D 50 ) can be 0.1 nm to 1,000 nm, for example, 1 nm to 500 nm, or 2 nm to 100 nm. Here, the average particle size (D 50 ) can be measured by a particle size analyzer (PSA) for positive electrode active materials, and the diameter of the particle with a cumulative volume of 50 volume% in the particle size distribution may be taken as the average particle size.

[0029] In one embodiment, the metal-based material may be included in an amount of 0.1% to 10% by weight relative to 100% by weight of the total polymer, for example, 0.2% to 7% by weight, 0.5% to 5% by weight, or 1% to 3% by weight. When the weight percentage of the metal-based material relative to the polymer satisfies the above range, it can serve as a binder for an electrode for a water electrolysis cell, having improved electrical conductivity and excellent mechanical / chemical stability due to strong interactions between the polymer and the metal-based material. If the weight percentage of the metal-based material relative to the polymer is less than the above range, the electrical conductivity may not be sufficient, and if it exceeds the above range, it may be difficult to serve as a binder due to a decrease in the adhesion of the polymer within the electrode, or there may be problems with dispersion and uniformity due to interactions between the metal-based materials.

[0030] The electrode for the water electrolysis cell may further include an alkylene glycol-based compound as a plasticizer, and due to the alkylene glycol-based compound, the formation of adhesive bonds and polymer film formation is facilitated, and the dispersion level and long-term stability of the electrode composition may be improved. For example, the alkylene glycol-based compound may be one or more selected from dipropylene glycol, glycerol, tetraethelin glycol, and polyethylene glycol.

[0031] In one embodiment, the alkylene glycol-based compound may be included in an amount of 5% to 100% by weight, 10% to 50% by weight, or 20% to 30% by weight, based on 100% by weight of the total polymer. Within this range, the effects of the polymer and the alkylene glycol-based compound are harmoniously realized, thereby improving adhesion, dispersibility, and long-term stability of the electrode composition.

[0032] In one embodiment, the electrode for the water electrolysis cell further includes a catalyst.

[0033] In one embodiment, when the electrode for the water electrolysis cell is a hydrogen generation electrode, the hydrogen generation electrode includes a catalyst layer for a hydrogen generation reaction that includes a catalyst for a hydrogen generation reaction, and the catalyst for a hydrogen generation reaction may include active particles.

[0034] The above active particles may include a precious metal, and the precious metal may be a platinum-based precious metal.

[0035] Platinum (Pt) and / or a Pt-M alloy may be used as the platinum-based precious metal. M may be palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), gallium (Ga), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), gold (Au), zinc (Zn), tin (Sn), molybdenum (Mo), tungsten (W), lanthanum (La), or rhodium (Rh).

[0036] Specifically, as the above Pt-M alloy, Pt-Pd, Pt-Sn, Pt-Mo, Pt-Cr, Pt-W, Pt-Ru, Pt-Ni, Pt-Co, Pt-Y, Pt-Ru-W, Pt-Ru-Ni, Pt-Ru-Mo, Pt-Ru-Rh-Ni, Pt-Ru-Sn-W, Pt-Ru-Ir-Ni, Pt-Co-Mn, Pt-Co-Ni, Pt-Co-Fe, Pt-Co-Ir, Pt-Co-S, Pt-Co-P, Pt-Fe, Pt-Fe-Ir, Pt-Fe-S, Pt-Fe-P, Pt-Au-Co, Pt-Au-Fe, Pt-Au-Ni, Pt-Ni, Pt-Ni-Ir, Pt-Cr, Pt-Cr-Ir, or a mixture thereof may be used. there is.

[0037] The above catalyst for the hydrogen generation reaction may further include a carrier that supports the active particles.

[0038] The above-mentioned carrier may be different from the carrier applied to the oxygen evolution reaction catalyst described later.

[0039] For example, the above carrier may be a carbon-based carrier.

[0040] The carbon-based carrier may be graphite, super P, carbon fiber, carbon sheet, carbon black, Ketjen black, Denka black, acetylene black, carbon nanotube (CNT), carbon sphere, carbon ribbon, fullerene, activated carbon, carbon nanofiber, carbon nanowire, carbon nanoball, carbon nanohorn, carbon nanocage, carbon nanoring, ordered nano- / meso-porous carbon, carbon aerogel, mesoporous carbon, graphene, stabilized carbon, activated carbon, or a combination thereof.

[0041] In one embodiment, when the electrode for the water electrolysis cell is an oxygen generation electrode, the oxygen generation electrode includes a catalyst layer for an oxygen generation reaction that includes a catalyst for an oxygen generation reaction, and the catalyst for an oxygen generation reaction may include a precious metal oxide.

[0042] The above precious metal oxide may be iridium oxide, an oxide of an iridium alloy, or a combination thereof.

[0043] For example, the above precious metal oxide is IrO x (The above x is an integer from 1 to 3), IrMO x (M includes Ru, Pt, Sn, Se, Zn, Au, Te, Nb, or a combination thereof, and x is an integer from 1 to 3) or a combination thereof.

[0044] In addition, the catalyst for the oxygen evolution reaction may further include a support that supports a precious metal oxide.

[0045] The above carrier is typically applied as a carrier that supports precious metal oxides, and its type is not limited; for example, it may be titanium dioxide (TiO2).

[0046] In the above description, the catalyst for the hydrogen generation reaction is described as comprising active particles containing a precious metal, and the catalyst for the oxygen generation reaction is described as comprising a precious metal oxide; however, the present invention is not limited thereto, and the catalyst for the hydrogen generation reaction may also comprise a precious metal oxide, and the catalyst for the oxygen generation reaction may also comprise active particles containing a precious metal.

[0047] The electrode for the above-mentioned water electrolysis cell may be a hydrogen generation electrode or an oxygen generation electrode, the hydrogen generation electrode is an electrode where a hydrogen evolution reaction (HER) occurs, and the oxygen generation electrode may be an electrode where an oxygen evolution reaction (OHER) occurs.

[0048] The above oxygen generation electrode and hydrogen generation electrode may comprise only the catalyst layer for the oxygen generation reaction and the catalyst layer for the hydrogen generation reaction, but may each independently comprise an electrode substrate together with the catalyst layer for the oxygen generation reaction and the catalyst layer for the hydrogen generation reaction. Since the catalyst for the oxygen generation reaction and the catalyst for the oxygen generation reaction have been described above, a detailed explanation is omitted.

[0049] The above electrode substrate can perform the role of supporting the electrode while diffusing fuel and oxidant into the catalyst layer for the oxygen generation reaction and the catalyst layer for the hydrogen generation reaction.

[0050] The electrode substrate may include a microporous layer, a porous diffusion layer, or a combination thereof.

[0051] The above microporous layer serves to enhance the reactant diffusion effect and may generally include a conductive powder with a small particle size, for example, carbon powder, carbon black, acetylene black, activated carbon, metal oxide nanowires, carbon fibers, fullerenes, carbon nanotubes, carbon nanowires, carbon nanohorns, or carbon nanorings.

[0052] The above porous diffusion layer is porous titanium, carbon paper, carbon cloth, carbon felt, or metal cloth (referring to a porous film composed of a metal cloth in a fibrous state or a metal film formed on the surface of a cloth formed of polymer fibers).

[0053] The microporous layer and the porous diffusion layer may include known types in addition to those exemplified above.

[0054] The above electrode substrate may be treated with a fluorine-based resin for water repellency, in which case the reduction in reactant diffusion efficiency caused by water generated during the operation of the water electrolysis cell can be prevented.

[0055] As the above fluorine-based resin, polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxyvinyl ether, fluorinated ethylene propylene, polychlorotrifluoroethylene, or copolymers thereof may be used.

[0056] The electrode for the water electrolysis cell may be composed of: a catalyst; a polymer cross-linked in which a first repeating unit containing one or more hydroxyl groups and a second repeating unit containing one or more carboxyl groups are ester-bonded to each other; and a metal-based material bonded to the hydroxyl group of the first repeating unit and the carboxyl group of the second repeating unit. A binder for a general electrode for a water electrolysis cell includes an ion-conducting polymer, wherein the ion-conducting polymer is included in an amount of 5% to 50% by weight relative to 100% by weight of the total electrode for the water electrolysis cell. In contrast, the electrode for the water electrolysis cell may not include an ion-conducting polymer, for example, and the content of the ion-conducting polymer relative to 100% by weight of the total electrode for the water electrolysis cell may be 5% by weight or less, 1% by weight or less, 0.1% by weight or less, 0.01% by weight or less, or 0% to 0.01% by weight.

[0057] Membrane-electrode assembly for water electrolysis cell

[0058] A membrane-electrode assembly for a water electrolysis cell according to one embodiment comprises: a hydrogen generating electrode; an oxygen generating electrode; and a polymer electrolyte membrane located between the hydrogen generating electrode and the oxygen generating electrode, wherein at least one of the hydrogen generating electrode and the oxygen generating electrode is an electrode for the water electrolysis cell.

[0059] Another embodiment provides a water electrolysis cell comprising the aforementioned membrane-electrode assembly for a water electrolysis cell, wherein the water electrolysis cell can expect improved performance and durability due to the reinforced bonding strength between materials within the electrode, a low swelling rate with respect to moisture, and improved electrical conductivity by including the membrane-electrode assembly for the water electrolysis cell.

[0060] Since the water electrolysis cell is identical to the known one except for including the membrane-electrode assembly for the water electrolysis cell described above, a detailed description is omitted.

[0061] polymer electrolyte membrane

[0062] The polymer electrolyte membrane is located between the hydrogen generation electrode and the oxygen generation electrode. The polymer electrolyte membrane may have an ion exchange function that moves ions between the hydrogen generation electrode and the oxygen generation electrode.

[0063] The above polymer electrolyte membrane may include an ion conductor.

[0064] The above ion conductor can play a role in improving adhesion within the electrode and ion transfer.

[0065] The above ion conductor may include fluorine-based ion conductors, hydrocarbon-based ion conductors, and combinations thereof, and the ion conductor may have a cation exchanger or an anion exchanger.

[0066] The above hydrocarbon-based ion conductor may use at least one selected from, for example, imidazole, benzimidazole, polybenzoxazole, polybenzthiazole, polyamide, polyamideimide, polyimide, polyimidesulfone, polyacetal, polyethylene, polypropylene, acrylic resin, polyester, polysulfone, polyether, polyetherimide, polyarylene ether-based polymer, polyarylene ketone, polyarylenephosphine oxide, polyester, polyethersulfone, polycarbonate, polystyrene, polyphenylene-based polymer, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfidesulfone, polyparaphenylene, polyetheretherketone, polyetherketone, polyetherphosphine oxide, polyarylethersulfone, polyphosphazene, and polyphenylquinoxaline.

[0067] The above ion conductor may be used in the form of a single material or a mixture, and may also be optionally used in combination with a non-conductive compound to further enhance adhesion to the polymer electrolyte membrane. The content of the non-conductive compound can be appropriately adjusted according to the intended use.

[0068] As the above non-conductive compound, at least one selected from polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride, copolymer of polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), dodecylbenzenesulfonic acid, and sorbitol may be used.

[0069] Commercially available examples of the above-mentioned ion conductors include Nafion and Aquivion.

[0070] The polymer electrolyte membrane may be in the form of a reinforced membrane comprising a porous support having a plurality of pores and an ion conductor filling the pores of the porous support.

[0071] The above porous support may be a fluorine-based support, a nanoweb support, or a combination thereof.

[0072] The above-mentioned fluorine-based support may correspond, for example, to expanded polytetrafluoroethylene (e-PTFE) having a microstructure of polymer fibrils or a microstructure in which nodes are interconnected by fibrils.

[0073] The above nanoweb support may be a support in which nanofibers are integrated in the form of a nonwoven fabric containing a number of pores.

[0074] Method for manufacturing a membrane-electrode assembly for a water electrolysis cell

[0075] In one embodiment, a method for manufacturing a membrane-electrode assembly for a water electrolysis cell is provided, comprising: (i) a step of manufacturing a hydrogen generation electrode; (ii) a step of manufacturing an oxygen generation electrode; and (iii) a step of bonding a polymer electrolyte membrane to the hydrogen generation electrode and the oxygen generation electrode, wherein the polymer electrolyte membrane is located between the hydrogen generation electrode and the oxygen generation electrode, and at least one of the hydrogen generation electrode and the oxygen generation electrode is an electrode for the water electrolysis cell.

[0076] The hydrogen generating electrode and the oxygen generating electrode can each be manufactured by independently preparing an electrode composition for a water electrolysis cell comprising a catalyst, a solvent, a binder comprising a first repeating unit containing one or more hydroxyl groups and a second repeating unit containing one or more carboxyl groups that can be crosslinked by ester bonding to each other, and a metal-based material capable of bonding to the hydroxyl group of the first repeating unit and the carboxyl group of the second repeating unit, and then applying the same to a release film. At this time, the first repeating unit, the second repeating unit, and the metal-based material may be in a hydrogen bonded state, and may be crosslinked as ester bonds are formed during subsequent drying and heat treatment processes.

[0077] As the above catalyst, a binder comprising a first repeating unit comprising one or more hydroxyl groups and a second repeating unit comprising one or more carboxyl groups that can be crosslinked by ester bonding to each other, and a metal-based material capable of being bonded to the hydroxyl groups of the first repeating unit and the carboxyl groups of the second repeating unit have been described above, a detailed description is omitted.

[0078] The above solvent may be water, a hydrophilic solvent, an organic solvent, or a mixture of one or more of these.

[0079] The above hydrophilic solvent may have one or more functional groups selected from alcohols, ketones, aldehydes, carbonates, carboxylates, carboxylic acids, ethers, and amides, comprising a straight-chain or branched saturated or unsaturated hydrocarbon having 1 to 12 carbon atoms as a main chain, and these may include an alicyclic or aromatic cyclocompound as at least part of the main chain. Specific examples include alcohols such as methanol, ethanol, isopropyl alcohol, ethoxyethanol, n-propyl alcohol, butyl alcohol, 1,2-propanediol, 1-pentanol, 1.5-pentanediol, 1.9-nonanediol, etc.; ketones such as heptanone, octanone, etc.; aldehydes such as benzaldehyde, tolualdehyde, etc.; and esters such as methylpentanoate, ethyl-2-hydroxypropanoate, etc. Carboxylic acids include pentanoic acid, heptanoic acid, etc.; ethers include methoxybenzene, dimethoxypropane, etc.; and amides include propanamide, butylamide, dimethylacetamide, etc.

[0080] The above organic solvent can be selected from N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, and mixtures thereof.

[0081] The above solvent may be contained in an amount of 30% to 97% by weight relative to 100% by weight of the electrode composition for the water electrolysis cell.

[0082] As a specific example of the step of manufacturing the hydrogen generating electrode or the step of manufacturing the oxygen generating electrode, the electrode composition for the water electrolysis cell can be manufactured by coating the electrode composition onto a release film. Depending on the viscosity of the electrode composition for the water electrolysis cell, it may be continuously transferred via a pump to a coater such as a die, gravure, bar, or comma coater, and then applied onto a decal film using methods such as slot die coating, bar coating, comma coating, screen printing, spray coating, doctor blade coating, or brushing, and dried to volatilize the solvent. The drying may be performed at 25°C to 90°C for 6 hours or more.

[0083] Subsequently, the electrode prepared by coating the electrode composition for the water electrolysis cell onto a release film can be heat-treated to form ester bonds between the first repeating unit, the second repeating unit, and the metal-based material, thereby crosslinking. At this time, the heat treatment can be performed at 120°C to 200°C for 1 hour to 8 hours.

[0084] Next, the hydrogen generation electrode, the oxygen generation electrode, and the polymer electrolyte membrane are bonded.

[0085] As an example, a transfer method can be used to bond the electrode and the polymer electrolyte membrane, and the transfer method can be performed by a metal press alone or by a hot pressing method in which heat and pressure are applied by attaching a soft plate of rubber material, such as silicone rubber material, to a metal press.

[0086] The above transfer method is 5 kgf / cm² at a temperature of 80℃ to 200℃. 2 Up to 200 kgf / cm² 2 This can be performed. When the transfer temperature and pressure satisfy the above range, structural changes in the electrode accompanying the high temperature and high pressure transfer process are minimized, and through post-curing, interactions between polymers within the electrode and between polymers and metal-based materials are strengthened, thereby forming an electrode layer with excellent mechanical / chemical stability even in water. If the above temperature is below 80°C, durability may be reduced due to insufficient curing of the electrode, and the transfer of the electrode layer to the membrane may not be fully completed; if the above temperature is above 200°C, the functional groups of the polymer electrolyte membrane may decompose, leading to a decrease in cell performance.

[0087] In addition, the above pressure is 5 kgf / cm² 2 If it is less than, the transfer to the electrode layer film may not be fully achieved, and the pressure is 200 kgf / cm² 2If exceeded, the electrode layer structure may be destroyed, leading to performance degradation due to increased mass transfer resistance.

[0088] Hereinafter, embodiments are described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0089] Example 1

[0090] IrO as a catalyst for oxygen evolution reaction x An electrode composition for an oxygen evolution reaction was prepared by dispersing a composition comprising 5g of / TiO2 (Alfa Aesar, 43396), 10g of a polymer mixed with polyvinyl alcohol and polyacrylic acid in a molar ratio of 5:1 as a binder, 0.1g of copper nanoparticles as a metallic material, and water and n-propanol mixed in a weight ratio of 4:6 (=water:n-propanol) as a solvent using a homogeneous mixer.

[0091] A composition comprising 5g of Pt / C (Tanaka, TEC10E50E) as a catalyst for hydrogen generation reaction, 10g of Nafion D2021 (Dupont) as an ion conductor, and water and n-propanol as solvents mixed in a weight ratio of 4:6 (=water:n-propanol) was dispersed in a homogeneous mixer to prepare an electrode composition for a hydrogen generation reaction.

[0092] 0.2 mg / cm² of the above oxygen evolution reaction electrode composition on the first surface of a polyimide film of PI Advanced Materials Co., Ltd. having a thickness of 150 μm 2 Apply with a doctor blade so as to be, and apply the above hydrogen generation reaction electrode composition to the second surface facing the first surface at 1.0 mg / cm 2 A hydrogen generating electrode on the first surface and an oxygen generating electrode on the second surface were prepared by applying a doctor blade and drying at 80°C for 8 hours. At this time, the oxygen generating electrode was further heat-treated at 200°C for 1 hour after drying to proceed with crosslinking.

[0093] A 100 μm thick fluorinated polymer electrolyte membrane is interposed between the hydrogen generating electrode and the oxygen generating electrode prepared above, and at 160°C and 20 kgf / cm² 2 A membrane-electrode assembly in which a hydrogen generating electrode and an oxygen generating electrode are bonded to a polymer electrolyte membrane was prepared by applying heat and pressure for 10 minutes under certain conditions and then peeling off the polyimide film.

[0094] Example 2

[0095] In Example 1, an oxygen generating electrode composition and a membrane-electrode assembly were prepared in substantially the same manner as in Example 1, except that 2 g of glycerol was further added as a plasticizer to the oxygen generating electrode composition.

[0096] Example 3

[0097] In Example 2, an oxygen generating electrode composition and a membrane-electrode assembly were prepared in substantially the same manner as in Example 2, except that a polymer of polyvinyl alcohol and polyacrylic acid mixed in a molar ratio of 1:5 was used when preparing the oxygen generating electrode composition.

[0098] Example 4

[0099] In Example 2, an oxygen generating electrode composition and a membrane-electrode assembly were prepared in substantially the same manner as in Example 2, except that a polymer of polyvinyl alcohol and polyacrylic acid mixed in a 1:1 molar ratio was used when preparing the oxygen generating electrode composition.

[0100] Example 5

[0101] In Example 2, an oxygen generating electrode composition and a membrane-electrode assembly were prepared in substantially the same manner as in Example 2, except that citric acid was used instead of polyacrylic acid when preparing the oxygen generating electrode composition.

[0102] Example 6

[0103] In Example 2, an oxygen-generating electrode composition and a membrane-electrode assembly were prepared in substantially the same manner as in Example 2, except that CuSO4 was used instead of copper nanoparticles as a metallic material when preparing the oxygen-generating electrode composition.

[0104] Example 7

[0105] In Example 2, a composition for an oxygen generating electrode and a membrane-electrode assembly were prepared in substantially the same way as in Example 2, except that a hydrocarbon electrolyte membrane of the same thickness was used instead of a fluorine-based electrolyte membrane.

[0106]

[0107] Comparative Example 1

[0108] In Example 1, an oxygen generating electrode composition and a membrane-electrode assembly were prepared in substantially the same manner as in Example 1, except that a conventional fluorine-based compound was used instead of a polymer mixed with polyvinyl alcohol and polyacrylic acid and copper nanoparticles when preparing the oxygen generating electrode composition.

[0109] Comparative Example 2

[0110] In Comparative Example 1, a composition for an oxygen generating electrode and a membrane-electrode assembly were prepared in substantially the same way as in Comparative Example 1, except that a hydrocarbon-based electrolyte membrane of the same thickness was used instead of a fluorine-based electrolyte membrane.

[0111]

[0112] Evaluation example

[0113] 1. Evaluation of underwater tensile adhesive strength

[0114] The composition of the oxygen-generating electrode composition of the example and comparative example, excluding the catalyst for the oxygen generation reaction, was dispersed in a homogeneous mixer, and then treated at 10,000 RPM for 10 minutes using a centrifuge to obtain the adhesive composition that settled at the bottom.

[0115] To measure the underwater adhesive strength of the obtained adhesive composition, a cylindrical specimen with a diameter of 10 mm made of SUS material was fabricated, attached to a water tank, filled with water, and then 40 mg of the adhesive composition was coated onto the cylindrical specimen underwater. Using the cylindrical specimen with a diameter of 10 mm made of SUS material, the adhesive composition was pressed with a force of 5 N for 30 seconds, and then detached at a speed of 1 mm / min to measure the underwater tensile adhesive strength, and the results are shown in Figure 2.

[0116] Referring to Fig. 2, it can be seen that Examples 1 to 6, which use a polymer containing a first repeating unit and a second repeating unit, exhibit high underwater tensile adhesive strength compared to Comparative Example 1, which uses a conventional fluorine-based compound. In the case of Example 4, the molar ratio of the first repeating unit to the second repeating unit is 1:1, and the adhesive strength was relatively lower compared to Example 3 due to excessive cross-linking between the polymers. In the case of Example 5, a relatively lower adhesive strength was confirmed compared to Example 2 due to the low molecular weight of the monomeric citric acid used as the second repeating unit.

[0117] 2. Evaluation of adhesion between electrode and polymer electrolyte membrane

[0118] In the method for manufacturing membrane-electrode assemblies of the examples and comparative examples, the bonding strength between the electrode and the polymer electrolyte membrane of the membrane-electrode assembly manufactured by bonding an oxygen-generating electrode composition to both sides was evaluated as follows using a universal material testing machine (UTM_5966, Instron).

[0119] A specimen was prepared by cutting the electrode portion of the manufactured membrane-electrode assembly to a width of 15 mm and a length of 30 mm, and the shape of the electrode detached upon impact when the specimen was stretched and fractured using a program elongation rate of 500 mm / min was analyzed, and the results are shown in Fig. 3.

[0120] Referring to FIG. 3, compared to Comparative Example 1 using a conventional fluorine-based compound, in the case of Examples 1 to 3 and Example 6, which use a polymer containing a first repeating unit and a second repeating unit, it can be seen that the electrodes remain well bonded even after the polymer electrolyte membrane is broken.

[0121] 3. Evaluation of Performance and Durability of Membrane-Electrode Assembly

[0122] The membrane-electrode assemblies for water electrolysis cells prepared in Examples 1, 2, 7, Comparative Example 1, and Comparative Example 2 were evaluated for cell performance and chemical durability as follows, and the results are shown in Table 1.

[0123] The membrane-electrode assembly for the water electrolysis cell was applied inside a unit cell designed and fabricated for the water electrolysis cell, and measurements were taken by applying a protocol to measure voltage and resistance at specific currents from 1 mA to 20 A under conditions of cell temperature 80℃, water temperature 80℃, and flow rate 5 ml / min. The current density was measured at a voltage of 1.8V, and a higher result value indicates superior output performance.

[0124] The evaluation of chemical durability was performed after the initial performance evaluation of the above membrane-electrode assembly, at a cell temperature of 80°C and a current density of 1 A / cm². 2 The voltage growth rate was measured after driving a constant current for 500 hours. The voltage growth rate was measured using a BioLogic instrument, calculated according to Equation 1 below, and the results are shown in Table 1 below.

[0125] [Equation 1]

[0126] Voltage increase rate (%) = (Voltage after operation - Initial voltage) / (Initial voltage) × 100

[0127] Battery Performance Evaluation (A / cm) 2Voltage Increase Rate (%) Example 1 1.7 3.5.3 Example 2 1.7 6.3.6 Example 7 1.7 5.7 4.5 (360 hours) Comparative Example 1 1.7 5.1 6.2 Comparative Example 2 1.7 6.7 4.6 (100 hours)

[0128] Referring to Table 1, the membrane-electrode assemblies of Examples 1 and 2 exhibited equivalent performance and improved chemical durability compared to the membrane-electrode assembly of Comparative Example 1. In the case of Example 2, the inclusion of an alkylene glycol-based compound as a plasticizer strengthened adhesion and exhibited improved durability. Similarly, compared to the membrane-electrode assembly of Comparative Example 2, the membrane-electrode assembly of Example 7 exhibited equivalent performance and improved chemical durability, confirming that the same effect is observed in membrane-electrode assemblies using hydrocarbon-based electrolyte membranes. Through this, it can be confirmed that the polymer containing the first repeating unit and the second repeating unit and the metal-based material in the water electrolysis cell electrode bind to the catalyst through mutual interaction, ensuring stability in an underwater environment, and that they can replace existing fluorine-based compounds.

[0129] Although preferred embodiments have been described in detail above, the scope of the rights is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concepts defined in the following claims are also included within the scope of the rights.

Claims

1. Catalyst; A polymer comprising a first repeating unit comprising one or more hydroxyl groups and a second repeating unit comprising one or more carboxyl groups; and An electrode for a water electrolysis cell comprising a metal-based material combined with the hydroxyl group of the first repeating unit and the carboxyl group of the second repeating unit.

2. In Paragraph 1, The above polymer is an electrode for a water electrolysis cell, wherein the first repeating unit and the second repeating unit are cross-linked by ester bonding to each other.

3. In Paragraph 2, The above first repeating unit is derived from polyvinyl alcohol, and The above second repeating unit is an electrode for a water electrolysis cell derived from one or more selected from polyacrylic acid, citric acid, and succinic acid.

4. In Paragraph 3, The above first repeating unit includes a hydroxyl group remaining after polyvinyl alcohol has ester-bonded, and The above second repeating unit is an electrode for a water electrolysis cell comprising one or more carboxyl groups selected from polyacrylic acid, citric acid, and succinic acid that have been ester-bonded.

5. In Paragraph 1, An electrode for a water electrolysis cell in which the molar ratio of the first repeating unit and the second repeating unit is 0.1:1 to 10:

1.

6. In Paragraph 1, The above metal-based material coordinates with the hydroxyl group of the first repeating unit or the carboxyl group of the second repeating unit, and The first repeating unit and the second repeating unit are electrodes for a water electrolysis cell that are ester-bonded via the metal-based material.

7. In Paragraph 1, The above metallic material comprises a metal, a metal oxide, a metal nitrate, a metal chloride, a metal sulfate, or a combination thereof, and The above metallic material is in the form of particles or precursors, and Average particle size (D of the above particles) 50 ) is an electrode for a water electrolysis cell having a diameter of 0.1 nm to 1000 nm.

8. In Paragraph 7, The above precursor is an electrode for a water electrolysis cell that forms a chelate with a hydroxyl group included in the first repeating unit, a carboxyl group included in the second repeating unit, or a combination thereof.

9. In Paragraph 1, An electrode for a water electrolysis cell comprising 0.1% to 10% by weight of the metal-based material based on 100% by weight of the total polymer.

10. In Paragraph 1, The above electrode for a water electrolysis cell is an electrode for a water electrolysis cell that further comprises an alkylene glycol-based compound.

11. In Paragraph 10, The above alkylene glycol-based compound is one or more selected from dipropylene glycol, glycerol, tetraethelin glycol, and polyethylene glycol, an electrode for a water electrolysis cell.

12. Hydrogen generating electrode; Oxygen generating electrode; A polymer electrolyte membrane located between the hydrogen generation electrode and the oxygen generation electrode; comprising A membrane-electrode assembly for a water electrolysis cell in which at least one of the above hydrogen generation electrode and the above oxygen generation electrode is an electrode for a water electrolysis cell according to claim 1.

13. (i) Step of manufacturing a hydrogen generating electrode; (ii) A step of manufacturing an oxygen generating electrode; (iii) a step of bonding a hydrogen generation electrode and an oxygen generation electrode with a polymer electrolyte membrane; comprising, The above polymer electrolyte membrane is located between the hydrogen generation electrode and the oxygen generation electrode, and A method for manufacturing a membrane-electrode assembly for a water electrolysis cell, wherein at least one of the above hydrogen generation electrode and the above oxygen generation electrode is an electrode for a water electrolysis cell according to claim 1.

14. In Paragraph 13, The step of manufacturing the hydrogen generation electrode or the step of manufacturing the oxygen generation electrode is, An electrode composition for a water electrolysis cell comprising: a catalyst; a solvent; a binder comprising a first repeating unit comprising one or more hydroxyl groups and a second repeating unit comprising one or more carboxyl groups, which can be crosslinked by ester bonding to each other; and a metal-based material capable of bonding to the hydroxyl groups of the first repeating unit and the carboxyl groups of the second repeating unit; is applied to a release film and then dried at 25°C to 90°C for at least 6 hours, and A method for manufacturing a membrane-electrode assembly for a water electrolysis cell, comprising the step of heat treating at 120℃ to 200℃ for 1 hour to 8 hours.

15. In Paragraph 13, The step of bonding the above hydrogen generation electrode and oxygen generation electrode with the polymer electrolyte membrane is performed at a temperature of 80°C to 200°C at 5 kgf / cm² 2 Up to 200 kgf / cm² 2 A method for manufacturing a membrane-electrode assembly for a water electrolysis cell.

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