Reinforced composite membrane, membrane-electrode assembly, and water electrolysis cell

Abstract

The present disclosure relates to a reinforced composite membrane, a membrane-electrode assembly, and a water electrolysis cell and, more particularly, comprises a dual porous support formed by laminating a first nanoweb and a second nanoweb having different average pore sizes and thus can have an improved water swelling ratio and an improved concentration gradient in the thickness direction, maintain ion conductivity by ensuring a unidirectional channel for ion transport, and have improved mechanical properties and durability.

Description

Reinforced composite membrane, membrane-electrode assembly, and water electrolysis cell

[0001] The present disclosure relates to a reinforced composite membrane, a membrane-electrode assembly, and a water electrolysis cell, and more specifically, by including a dual porous support having a first nanoweb and a second nanoweb with different average pore sizes stacked thereon, the degree of water swelling and the concentration gradient in the thickness direction are improved, ion conductivity is maintained through securing a unidirectional channel for ion transport, and mechanical properties and durability performance can be improved.

[0002] With the increasing demand for alternative energy to replace fossil fuels, interest in highly efficient, inexpensive, and environmentally friendly energy conversion and storage systems is growing. Amidst this, fuel production through water electrolysis is receiving significant attention as an important alternative with high commercialization potential that addresses environmental and energy issues. Water electrolysis is a technology that produces hydrogen and oxygen by electrochemically decomposing water.

[0003] The types of water electrolysis mentioned above are typically classified according to the electrolyte membrane into polymer electrolyte membrane water electrolysis (PEMWE), alkaline water electrolysis (AWE), anion exchange membrane water electrolysis (AEMWE), and solid oxide water electrolysis (SOECs).

[0004] Among them, in a Polymer Electrolyte Membrane Water Electrolysis cell (PEMWE), the Membrane Electrode Assembly (MEA) that actually generates hydrogen has a structure in which an oxygen evolution electrode, where the oxygen evolution reaction takes place, and a hydrogen evolution electrode, where the hydrogen evolution reaction takes place, are located with a polymer electrolyte membrane containing a hydrogen ion-conducting polymer in between.

[0005] For the polymer electrolyte membrane of such water electrolysis cells, a reinforced composite membrane was used in which a porous support was introduced and an ion conductor was impregnated into the porous support to prevent the degradation of mechanical properties caused by the input of high-pressure gas and water as fuel and to block the gas and water from each other.

[0006] A porous support is known that has a uniform pore size in the thickness direction and is positioned in the center of the cross-section of a reinforced composite membrane. In this case, when water is supplied during the operation of a water electrolysis cell, the porous support located in the center adjacent to the oxygen generation electrode, which is in direct contact with the water, may expand asymmetrically compared to the porous support adjacent to the hydrogen generation electrode in a non-humidified environment. In this case, it adversely affects the mechanical properties of the reinforced composite membrane, which may lead to performance degradation, such as an increase in the resistance of the membrane-electrode assembly.

[0007] According to one embodiment, by including a dual porous support having a first nanoweb and a second nanoweb with different average pore sizes, the degree of water swelling and the concentration gradient in the thickness direction are improved, ion conductivity is maintained through securing a unidirectional channel for ion transport, and mechanical properties and durability performance are improved, thereby providing a reinforced composite membrane, a membrane-electrode assembly, and a water electrolysis cell.

[0008] One embodiment provides a reinforced composite membrane comprising a dual porous support having: a first nanoweb having first pores formed by first nanofibers being integrated in a nonwoven form; a second nanoweb having second pores formed by second nanofibers being integrated in a nonwoven form and located on one surface of the first nanoweb; and a third ion conductor filling the first pores and the second pores, wherein the average diameter of the first pores is smaller than the average diameter of the second pores.

[0009] Another embodiment provides a membrane-electrode assembly comprising: a first surface adjacent to the first nanoweb and a second surface facing the first surface and adjacent to the second nanoweb, the aforementioned reinforced composite membrane; a hydrogen generating electrode located on the first surface; and an oxygen generating electrode located on the second surface.

[0010] Another embodiment provides a water electrolysis cell comprising the aforementioned membrane-electrode assembly.

[0011] A reinforced composite membrane according to one embodiment includes a dual porous support having a first nanoweb and a second nanoweb with different average pore sizes, thereby improving water swelling and thickness direction concentration gradient, maintaining ion conductivity by securing a unidirectional channel for ion transport, and improving mechanical properties and durability performance.

[0012] FIG. 1 is a cross-sectional view schematically illustrating a reinforced composite membrane according to one embodiment.

[0013] FIG. 2 is a cross-sectional view schematically illustrating a membrane-electrode assembly according to one embodiment.

[0014] 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.

[0015] In this specification, "combination thereof" means a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, a reaction product, etc.

[0016] 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.

[0017]

[0018] Reinforced composite membrane

[0019] In one embodiment, a reinforcing composite membrane is provided comprising a dual porous support having: a first nanoweb having first pores formed by first nanofibers being integrated in a nonwoven form; a second nanoweb having second pores formed by second nanofibers being integrated in a nonwoven form and located on one surface of the first nanoweb; and a third ion conductor filling the first pores and the second pores, wherein the average diameter of the first pores is smaller than the average diameter of the second pores.

[0020] A reinforced composite membrane according to one embodiment includes a dual porous support having a first nanoweb and a second nanoweb with different average pore sizes, thereby improving water swelling and thickness direction concentration gradient, maintaining ion conductivity by securing a unidirectional channel for ion transport, and improving mechanical properties and durability performance.

[0021] The average diameter of the first pores within the first nanoweb may be 0.1 μm to 2 μm, for example, 0.4 μm to 1.8 μm, 0.7 μm to 1.6 μm, or 1 μm to 1.4 μm. The average diameter of the first pores may be measured using a Capillary Flow Porometer from Porous Materials. The diameter of the first pores within the first nanoweb may be measured according to the above method, and the average may be obtained by dividing the sum of the diameters of the first pores by the number of the first pores. If the average diameter of the first pores in the first nanoweb is less than 0.1㎛, it is difficult to impregnate the ion conductor, so the first pores in the first nanoweb may remain empty when manufacturing the reinforced composite membrane, which may reduce the durability of the membrane-electrode assembly. If the average diameter of the first pores in the first nanoweb is greater than 2㎛, the physical properties of the reinforced composite membrane weaken after manufacturing, making it difficult to perform its role as a support, and the water swelling or hydrogen gas permeability increases excessively, posing a risk of explosion.

[0022] As described above, the average diameter of the first pores of the first nanoweb is smaller than the average diameter of the second pores of the second nanoweb. For example, the ratio of the average diameter of the first pores to the average diameter of the second pores may be 1:3 to 1:10, 1:3 to 1:9, 1:3 to 1:8, 1:3 to 1:7, or 1:4 to 1:6. The average diameter of the first pores and the average diameter of the second pores can be measured according to the method described above. When the ratio of the average diameter of the first pores to the average diameter of the second pores satisfies the above range, the water swelling degree of the reinforced composite membrane can be controlled, hydrogen gas permeability can be maintained while reducing the thickness, and mechanical durability can be improved in the long term by increasing the performance and efficiency of the reinforced composite membrane. If the average diameter of the second pores of the second nanoweb is smaller than the average diameter of the first pores of the first nanoweb, the amount of ion conductor impregnated into the second pores inside the second nanoweb may decrease, and to compensate for this, the thickness of the second ion conductor layer adjacent to the second nanoweb increases, causing an asymmetric expansion phenomenon, which degrades the mechanical properties of the reinforced composite membrane and simultaneously degrades its performance and long-term durability.

[0023] The first nanoweb is a nanoweb in which first nanofibers are integrated in a nonwoven form, and the second nanoweb is a nanoweb in which second nanofibers are integrated in a nonwoven form.

[0024] The first nanofiber comprises a first polymer, and the second nanofiber comprises a second polymer. As for the first polymer and the second polymer, a polymer that independently exhibits excellent chemical resistance and has hydrophobicity, thereby eliminating concerns about shape deformation caused by moisture in a high-humidity environment, can be used.

[0025] For example, the first polymer and the second polymer may each independently include a hydrocarbon-based polymer. More specifically, the first polymer and the second polymer may each independently include nylon, polyamide, polyaramid, polyetherimide, polyacrylonitrile, polyaniline, polyethylene oxide, polyethylene naphthalate, polybutylene terephthalate, styrene butadiene rubber, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyvinylidene fluoride, polyvinyl butylene, polyurethane, polybenzoxazole, polybenzimidazole, polyamideimide, polyethylene terephthalate, polyethylene, polypropylene, copolymers thereof, or mixtures thereof.

[0026] As a polymer electrolyte membrane applied to a water electrolysis cell, when a hydrocarbon-based polymer is used as the polymer forming the double porous support as described above, it is possible to secure cost competitiveness compared to using a fluorine-based polymer, and there are various advantages such as excellent thermal stability enabling operation at higher temperatures, increased efficiency, and reduced use of precious metal catalysts. When the first polymer and the second polymer forming the first nanoweb and the second nanoweb forming the porous support are both hydrocarbon-based polymers as described above, it can be stable during operation. More specifically, in the case of a water electrolysis cell, since the oxygen generating electrode must be operated in an environment where water is 100%, polymers with identical physical properties, such as hydrocarbon-based polymers, must be used so that delamination does not occur, dimensional stability is excellent, and mechanical properties and durability can be improved. On the other hand, when a combination of a support made of a fluorine-based polymer and a support made of a hydrocarbon-based polymer, known as a reinforced composite membrane for a fuel cell, is applied to a water electrolysis cell, delamination may occur during operation because the physical properties of the fluorine-based polymer and the hydrocarbon-based polymer themselves are different. For example, the first polymer and the second polymer may be the same.

[0027] The above-mentioned first nanoweb has a basic weight of 2 g / m² 2 Up to 30 g / m² 2 It may be, and the second nanoweb has a basis weight (basic weight) of 2 g / m² 2 Up to 30 g / m² 2 It may be. The basis weight of the first nanoweb and the second nanoweb is 2 g / m² 2　 If it is less than 30 g / m², even if pores are formed, their thickness is very thin, making it difficult to perform the role of a support, and 30 g / m² 2 If it exceeds [value], the porosity is very low, making it difficult to impregnate the ion conductor, and consequently, the ion conductivity performance may be significantly reduced.

[0028] The thickness of the above-mentioned double porous support may be 20% to 80% with respect to 100% of the total thickness of the reinforced composite membrane, for example, 20% to 60%, or 30% to 50%. When the thickness of the above-mentioned double porous support satisfies the above range with respect to 100% of the total thickness of the reinforced composite membrane, the physical properties of the reinforced composite membrane may be improved, and the performance may be maintained or improved. For example, if the thickness of the above-mentioned double porous support is less than 20% with respect to 100% of the total thickness of the reinforced composite membrane, the physical properties of the reinforced composite membrane may be degraded, and if it exceeds 80%, the impregnation amount of the ion conductor may be insufficient, and the performance of the reinforced composite membrane may be degraded.

[0029] The ratio of the thickness of the first nanoweb to the thickness of the second nanoweb may vary depending on the physical properties of the first polymer and the second polymer forming the first nanoweb and the second nanoweb. For example, it may be 1:9 to 9:1. If the physical properties of the first polymer and the second polymer forming the first nanoweb and the second nanoweb are flexible and have high elongation, the ratio of the thickness of the first nanoweb to the thickness of the second nanoweb may be 5:5 to 9:1; and if the physical properties of the first polymer and the second polymer forming the first nanoweb and the second nanoweb are rigid and have low elongation, the ratio of the thickness of the first nanoweb to the thickness of the second nanoweb may be 1:9 to 5:5. If the ratio of the thickness of the first nanoweb to the thickness of the second nanoweb within the double porous support satisfies the above range, the degree of water swelling can be easily controlled during ion conductor impregnation.

[0030] The porosity of the above-mentioned dual-porous support may be 45% or more, for example, 50% or more, 55% or more, or 60% or more, and 95% or less, 93% or less, or 90% or less. If the porosity of the above-mentioned dual-porous support is less than 45%, the impregnation amount of the ion conductor is low, which may degrade the ion conductivity and the performance of the membrane-electrode assembly; if the porosity of the above-mentioned dual-porous support exceeds 90%, the water swelling and mechanical properties of the reinforced composite membrane may become excessively high, and hydrogen gas permeability may decrease, making it difficult to perform the role of the reinforced composite membrane. The above-mentioned porosity can be calculated by the ratio of the air volume to the total volume of the above-mentioned heterogeneous composite porous support according to the following Equation 1. At this time, the total volume is calculated by manufacturing a rectangular sample and measuring its width, length, and thickness, and the air volume can be obtained by measuring the mass of the sample and subtracting the polymer volume, which is inversely calculated from the density, from the total volume.

[0031] [Mathematical Formula 1]

[0032] Porosity (%) = (Volume of air in heterogeneous porous support / Total volume of heterogeneous porous support) × 100

[0033] The above-described dual porous support can have improved water swelling and thickness direction concentration gradients by stacking a first nanoweb and a second nanoweb having different average pore sizes, maintain ion conductivity by securing unidirectional channels for ion transport, and enhance mechanical properties and durability performance.

[0034] The above-mentioned reinforced composite membrane includes a third ion conductor that fills the first pores and the second pores.

[0035] The third ion conductor may include a fluorine-based ion conductor, a hydrocarbon-based ion conductor, or a combination thereof.

[0036] The above fluorine-based ion conductor is (i) a fluorine-based polymer containing fluorine in the main chain having a cation exchange group or an anion exchange group, or (ii) a partially fluorinated polymer such as a polystyrene-graft-ethylene tetrafluoroethylene copolymer, a polystyrene-graft-polytetrafluoroethylene copolymer, etc.

[0037] The above cation exchange group is a functional group capable of transferring cations such as protons, and may be an acidic group such as, for example, a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphate group, an imide group, a sulfonimide group, a sulfonamide group, etc.

[0038] The above anion exchange group is a functional group capable of transferring anions such as hydroxy ions, carbonate ions, or bicarbonate ions.

[0039] Examples of the above-mentioned fluorine-based ion conductors include, but are not limited to, (i) poly(perfluorosulfonic acid), (ii) poly(perfluorocarboxylic acid), (iii) copolymers of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid groups, and (iv) defluorinated sulfated polyetherketones.

[0040] The above hydrocarbon-based ion conductor is a hydrocarbon polymer having a cation exchange group or an anion exchange group (e.g., imidazole, benzimidazole, polyamide, polyamideimide, polyimide, polyacetal, polyethylene, polypropylene, acrylic resin, polyester, polysulfone, polyether, polyetherimide, polyester, polyethersulfone, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyetheretherketone, polyetherketone, polyarylethersulfone, polyphosphazene, polyphenylquinoxaline, or a combination thereof, included in the main chain).

[0041] The above hydrocarbon-based ion conductor is sulfonated polyimide (S-PI), sulfonated polyarylethersulfone (S-PAES), sulfonated polyetheretherketone (SPEEK), sulfonated polybenzimidazole (SPBI), sulfonated polysulfone (S-PSU), sulfonated polystyrene (S-PS), sulfonated polyphosphazene, sulfonated polyquinoxaline, sulfonated polyketone, sulfonated polyphenylene oxide, sulfonated polyether sulfone, sulfonated polyether ketone, sulfonated sulfonated polyphenylene sulfone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether nitrile,and sulfonated polyarylene ether sulfone ketones, but are not limited to these.

[0042] For example, the double porous support may have a first surface adjacent to the first nanoweb and a second surface facing the first surface and adjacent to the second nanoweb. In this case, the reinforced composite membrane may further include a first ion conductor layer located on the first surface and comprising a first ion conductor; and a second ion conductor layer located on the second surface and comprising a second ion conductor.

[0043] FIG. 1 is a cross-sectional view schematically illustrating a reinforced composite membrane according to one embodiment.

[0044] Referring to FIG. 1, the reinforced composite membrane (100) comprises a double porous support (10) including the first nanoweb (11) and the second nanoweb (12) located on one side of the first nanoweb.

[0045] In the above double porous support (10), the first ion conductor layer (21) is located on the first surface adjacent to the first nanoweb, and the second ion conductor layer (31) is located on the second surface adjacent to the second nanoweb (12) in the above double porous support (10).

[0046] Here, FIG. 1 is illustrated merely for the purpose of understanding the structure of a reinforced composite membrane according to one embodiment, and is not limited to the thickness range of each component illustrated in FIG. 1.

[0047] The first ion conductor layer may be thicker than the second ion conductor layer. For example, the ratio of the thickness of the first ion conductor layer to the thickness of the second ion conductor layer may be 1.5:1 to 5:1, 1.7:1 to 4:1, 1.9:1 to 3:1, or 2:1 to 2.5:1. When the ratio of the thickness of the first ion conductor layer to the thickness of the second ion conductor layer satisfies the above range, it is possible to maintain performance and ensure long-term durability while reducing the thickness direction concentration gradient within the reinforced composite membrane.

[0048] The types of the first ion conductor and the second ion conductor are as described above in the third ion conductor.

[0049] For example, the first ion conductor layer and the second ion conductor layer may be formed as the third ion conductor fills the first pores and the second pores, and the remaining ion conductor forms a thin film on the surface of the double porous support. In this case, the first ion conductor, the second ion conductor, and the third ion conductor may be identical to each other.

[0050] The above-described reinforced composite membrane may be manufactured by electrospinning a first nanoweb and a second nanoweb. Specifically, it may be manufactured by dissolving a first polymer precursor in an organic solvent to prepare a first electrospinning solution, supplying the prepared first electrospinning solution to a first spinning chamber to spin and produce a first nanoweb, dissolving a second polymer precursor in an organic solvent to prepare a second electrospinning solution, and supplying the prepared second electrospinning solution to a second spinning chamber to spin and produce a second nanoweb. When preparing the electrospinning solution, a first polymer precursor and a second polymer precursor capable of forming a first polymer and a second polymer, respectively, may be dissolved in an organic solvent and used. In this case, the first polymer and the second polymer may be formed by a heat treatment process described later.

[0051] The supply amount of solution supplied to the first spinning chamber and the second spinning chamber can be adjusted so that the first nanoweb and the second nanoweb may have different average pore sizes. For example, the supply amount of solution supplied to the first spinning chamber may be 0.1 ml / min to 5 ml / min, 0.1 ml / min to 4 ml / min, 0.1 ml / min to 3 ml / min, or 0.1 ml / min to 2 ml / min, and the supply amount of solution supplied to the second spinning chamber may be 1 ml / min to 10 ml / min, 1 ml / min to 8 ml / min, 1 ml / min to 6 ml / min, 1 ml / min to 4 ml / min, or 1.5 ml / min to 3.5 ml / min. The less the supply solution, the more nanowebs with pores having a smaller average diameter can be produced.

[0052] The first nanoweb and the second nanoweb are prepared with different average pore sizes by adjusting only the supply amount of the solution differently, while all other factors can be performed under the same conditions. For example, the first polymer and the second polymer may be identical to each other, and the first electrospinning solution and the second electrospinning solution may be identical.

[0053] As the method for manufacturing a nanoweb by electrospinning is publicly known, the publicly known details will be omitted.

[0054] Membrane-electrode assembly and water electrolysis cell

[0055] In another embodiment, a membrane-electrode assembly is provided, comprising: a first surface adjacent to the first nanoweb and a second surface facing the first surface and adjacent to the second nanoweb; the aforementioned reinforced composite membrane; a hydrogen generating electrode located on the first surface; and an oxygen generating electrode located on the second surface.

[0056] A hydrogen generating electrode is located on a first surface adjacent to the first nanoweb, and an oxygen generating electrode is located on a second surface adjacent to the second nanoweb, thereby improving the water swelling degree and the concentration gradient in the thickness direction, maintaining ion conductivity through securing a unidirectional channel for ion transfer, and improving mechanical properties and durability performance. When an oxygen generating electrode is located on a first surface adjacent to the first nanoweb and a hydrogen generating electrode is located on a second surface adjacent to the second nanoweb, compared to a membrane-electrode assembly according to one embodiment, one surface of the reinforced composite membrane expands asymmetrically, which may degrade the mechanical properties of the reinforced composite membrane during operation and degrade the performance and durability of the membrane-electrode assembly.

[0057] FIG. 2 is a cross-sectional view schematically illustrating a membrane-electrode assembly according to one embodiment.

[0058] Referring to FIG. 2, the membrane-electrode assembly (200) comprises a reinforced composite membrane (100) comprising a double porous support (10) including the first nanoweb (11) and the second nanoweb (12) located on one side of the first nanoweb.

[0059] The hydrogen generating electrode (40) is located on the first surface adjacent to the first nanoweb (11) in the reinforced composite membrane (100), and the oxygen generating electrode (50) is located on the second surface adjacent to the second nanoweb (12) in the reinforced composite membrane (100).

[0060] Here, FIG. 2 is illustrated for the purpose of understanding the structure of a membrane-electrode assembly according to one embodiment, and is not limited to the thickness range of each component shown in FIG. 2.

[0061] The above hydrogen generation electrode is an electrode where the hydrogen evolution reaction (HER) takes place.

[0062] The above hydrogen generation electrode includes a catalyst layer for a hydrogen generation reaction comprising a catalyst for a hydrogen generation reaction, and the catalyst for a hydrogen generation reaction may include active particles.

[0063] The above active particles may include a precious metal, and the precious metal may be a platinum-based precious metal.

[0064] The platinum-based precious metal mentioned above may be platinum (Pt), a Pt-M alloy, or a combination thereof. 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), rhodium (Rh), or a combination thereof.

[0065] 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.

[0066] The above catalyst for the hydrogen generation reaction may further include a carrier that supports the active particles.

[0067] The above-mentioned carrier may be different from the carrier applied to the oxygen evolution reaction catalyst described later.

[0068] For example, the above carrier may be a carbon-based carrier.

[0069] 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.

[0070] The above oxygen evolution electrode is an electrode where the Oxygen Evolution Reaction (OER) takes place.

[0071] The oxygen generation electrode comprises a catalyst layer for an oxygen generation reaction that includes a catalyst for an oxygen generation reaction, and the catalyst for the oxygen generation reaction may include a precious metal oxide.

[0072] The above precious metal oxide may be iridium oxide, an oxide of an iridium alloy, or a combination thereof.

[0073] 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.

[0074] In addition, the catalyst for the oxygen evolution reaction may further include a support that supports a precious metal oxide.

[0075] 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).

[0076] The catalyst layer for the oxygen generation reaction may further include a fourth ion conductor to improve the adhesion of the catalyst layer and to transfer hydrogen ions.

[0077] The above-mentioned fourth ion conductor is of the same type as the first, second, and third ion conductors described above.

[0078] The fourth ion conductor included in the catalyst layer for the oxygen generation reaction and the first, second, and third ion conductors included in the reinforced composite membrane may all be different or identical.

[0079] The above oxygen generation electrode and hydrogen generation electrode may include only the catalyst layer for the oxygen generation reaction and the catalyst layer for the hydrogen generation reaction, but may each independently include an electrode substrate together with the catalyst layer for the oxygen generation reaction and the catalyst layer for the hydrogen generation reaction.

[0080] 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.

[0081] The electrode substrate may include a microporous layer, a porous diffusion layer, or a combination thereof.

[0082] 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.

[0083] 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).

[0084] The microporous layer and the porous diffusion layer may include known types in addition to those exemplified above.

[0085] 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.

[0086] 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.

[0087] A water electrolysis cell according to another embodiment includes the membrane-electrode assembly.

[0088] If the above-described water electrolysis cell includes the aforementioned membrane-electrode assembly, it may further include other known elements. Details regarding these other elements are known and are therefore omitted below.

[0089] 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.

[0090]

[0091] Example 1

[0092] As a first polymer precursor, polyamic acid was dissolved in a dimethylformamide organic solvent to prepare 5 L of a first electrospinning solution with a solid content of 13 wt% and 480 poise. After transferring the prepared first electrospinning solution to a solution tank, it was supplied through a metering gear pump to a first spinning chamber, which is composed of 20 nozzles and has a high voltage of 46 kV applied, at a supply rate of 0.9 ml / min to produce a first nanoweb having first pores with an average diameter of 1.2 μm, in which first nanofibers were accumulated in a nonwoven form.

[0093] A second electrospinning solution was prepared on the first nanoweb in the same manner as the first electrospinning solution, and the second electrospinning solution was supplied to the second spinning chamber at a rate of 2.5 ml / min and spun to produce a second nanoweb having second pores with an average diameter of 6 μm, in which the second nanofibers were accumulated in the form of a nonwoven fabric.

[0094] A double porous support made of polyamide was manufactured by heat curing the first nanoweb and the second nanoweb located on the first nanoweb at 420°C for 10 minutes, thereby sequentially stacking the first nanoweb and the second nanoweb.

[0095] An ion conductor dispersion containing 25 wt% of Aquivion as a fluorine-based ion conductor was prepared, the ion conductor dispersion was applied onto a polyimide film using a Meyer bar, a double porous support was laminated thereon, and the process was waited until the double porous support was sufficiently soaked in the ion conductor dispersion. Subsequently, the ion conductor dispersion was applied onto the double porous support using a Meyer bar, dried in an 80°C oven for 12 hours, and heat-treated at 200°C for 10 minutes to produce a reinforced composite film with a thickness of 50 μm.

[0096] For the above-mentioned reinforced composite membrane with a thickness of 100%, the thickness of the double porous support was 40%, the thickness of the first ion conductor layer located on the first surface of the first nanoweb was 22.5㎛, and the thickness of the second ion conductor layer located on the second surface of the first nanoweb was 7.5㎛.

[0097]

[0098] Comparative Example 1

[0099] A first nanoweb was prepared to a thickness of 20 μm using the first electrospinning solution of Example 1, and a reinforced composite membrane was prepared in the same manner as in Example 1, except that the first nanoweb and the second nanoweb were not laminated and only a support of the first nanoweb monolayer was used. In the reinforced composite membrane of Comparative Example 1, the thickness of the first ion conductor layer located on the first surface of the first nanoweb was 22.5 μm, and the thickness of the second ion conductor layer located on the second surface of the first nanoweb was 7.5 μm, just like in Example 1.

[0100]

[0101] Comparative Example 2

[0102] A reinforced composite film was prepared in the same manner as Comparative Example 1, except that ion conductor layers of the same thickness were formed on both sides of the first nanoweb of Comparative Example 1. In the reinforced composite film of Comparative Example 2, the thickness of the first ion conductor layer located on the first surface of the first nanoweb was 15 μm, and the thickness of the second ion conductor layer located on the second surface of the first nanoweb was 15 μm.

[0103]

[0104] Evaluation Example: Tensile Strength and Elongation Measurement

[0105] The tensile strength and elongation of the reinforced composite membranes prepared according to Example 1 and Comparative Examples 1 and 2 above were measured as follows.

[0106] For the above tensile strength and elongation, a dumbbell-shaped reinforced composite membrane specimen was prepared in accordance with ISO527-3 with a width of 6 mm in the center, a grip spacing of 80 mm, and a length of 120 mm. The specimen was then evaluated at least 5 times in the longitudinal (MD) and transverse (TD) directions using an Instron 5966 instrument with a crosshead speed of 500 mm / min and a 1 kN load cell to measure the tensile strength and elongation. The results of the tensile strength and elongation in the MD direction are shown in Table 1 below.

[0107] Average pore size of the first pores of the first nanoweb (㎛) / Average pore size of the second pores of the second nanoweb (㎛) Thickness of the first ion conductor layer (㎛) / Thickness of the second ion conductor layer (㎛) Tensile strength of the reinforced composite membrane (MD, MPa) Tensile elongation of the reinforced composite membrane (MD, %) Example 1 1.2 / 6 2 2.5 / 7.5 40 17 Comparative Example 1 1.2 / 1.2 2 2.5 / 7.5 44 14 Comparative Example 2 1.2 / 1.2 15 / 15 47 15

[0108] result

[0109] Comparative Example 2 is a known reinforced composite membrane in which a porous support is located in the center of the reinforced composite membrane in a symmetrical form, and the porous support significantly affects the physical properties of the reinforced composite membrane, resulting in high tensile strength. However, under water electrolysis operating conditions (100% humidification for the oxygen generating electrode and no humidification for the hydrogen generating electrode), the hydrophilic ion conductor absorbs water only at the oxygen generating electrode, causing the ion conductor of the second ion conductor layer to swell. Consequently, in the water electrolysis operating environment, the second ion conductor layer located on the side of the oxygen generating electrode expands excessively compared to the first ion conductor layer located on the side of the hydrogen generating electrode, causing their thicknesses to differ and resulting in an asymmetry phenomenon. This leads to delamination between the ion conductor of the ion conductor layer and the porous support, which degrades physical properties and performance, and is predicted to result in inferior long-term durability performance.

[0110] Comparative Example 1 uses the same known porous support as Comparative Example 2, that is, one in which the pore sizes are identical in the thickness direction, but unlike Comparative Example 1, a reinforced composite membrane is applied that is positioned close to the oxygen generating electrode. Under water electrolysis operating conditions, when the ion conductor of the second ion conductor layer of the oxygen generating electrode absorbs water and expands, the second ion conductor layer located on the side of the oxygen generating electrode expands by the thickness of the first ion conductor layer located on the side of the hydrogen generating electrode. Consequently, the porous support is positioned in the center of the total thickness of the reinforced composite membrane under water electrolysis operating conditions, achieving balance and minimizing the ion concentration gradient phenomenon, thereby improving performance. However, since the pore sizes are identical in the thickness direction of the porous support, it is predicted that delamination will occur when the ion conductor of the second ion conductor layer expands, and long-term durability performance will be inferior.

[0111] Meanwhile, in the case of Example 1, a reinforced composite membrane in which a porous support is positioned close to the oxygen generating electrode is applied to have the advantages of Comparative Example 1 (minimization of the ion concentration gradient phenomenon and consequent performance improvement), and unlike Comparative Examples 1 and 2, a dual porous support having different pore sizes in the thickness direction is used, that is, the pore size of the porous support adjacent to the oxygen generating electrode is larger than the pore size of the porous support adjacent to the hydrogen generating electrode, so that even when the ion conductor of the second ion conductor layer expands, the hydrogen ion concentration gradient phenomenon can be further minimized and delamination can be suppressed, and long-term durability performance is expected to be improved.

[0112] In addition, referring to Table 1, it can be confirmed that the reinforced composite membrane of Example 1 can exhibit the physical properties of the known reinforced composite membranes of Comparative Examples 1 and 2.

[0113] That is, in the case of a reinforced composite membrane in which a porous support is placed close to the side of the oxygen generating electrode as in Example 1, and a dual porous support with different pore sizes in the thickness direction, more specifically, a porous support adjacent to the oxygen generating electrode with a larger pore size, is applied, the material properties are secured that are almost similar to those of a conventional reinforced composite membrane, while at the same time, the water swelling degree and the concentration gradient in the thickness direction are improved, ion conductivity is maintained through securing a unidirectional channel for ion transfer, delamination is suppressed, and long-term durability performance can be improved.

[0114] 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.

[0115] [Explanation of the symbol]

[0116] 10: Dual porous support 11: First nanoweb

[0117] 12: Second nanoweb 21: First ion conductor layer

[0118] 31: Second ion conductor layer 100: Reinforced composite membrane

[0119] 40: Hydrogen generation electrode 50: Oxygen generation electrode

[0120] 200: Membrane-electrode assembly

Claims

1. A first nanoweb having first pores formed by integrating first nanofibers in the form of a nonwoven fabric; A second nanoweb located on one surface of the first nanoweb, having second nanofibers integrated in a nonwoven form to form second pores; and A reinforced composite membrane comprising a double porous support including a third ion conductor filling the first pores and the second pores, The average diameter of the first pores is smaller than the average diameter of the second pores. Reinforced composite membrane.

2. In Paragraph 1, The average diameter of the first pores is 0.1㎛ to 2㎛, Reinforced composite membrane.

3. In Paragraph 1, The ratio of the average diameter of the first pores to the average diameter of the second pores is 1:3 to 1:10, Reinforced composite membrane.

4. In Paragraph 1, The first nanofiber above comprises a first polymer, and The second nanofiber above includes a second polymer, and The first polymer and the second polymer each independently comprise a hydrocarbon-based polymer, Reinforced composite membrane.

5. In Paragraph 4, The first polymer and the second polymer each independently comprise nylon, polyamide, polyaramid, polyetherimide, polyacrylonitrile, polyaniline, polyethylene oxide, polyethylene naphthalate, polybutylene terephthalate, styrene butadiene rubber, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyvinylidene fluoride, polyvinyl butylene, polyurethane, polybenzoxazole, polybenzimidazole, polyamideimide, polyethylene terephthalate, polyethylene, polypropylene, copolymers thereof, or mixtures thereof. Reinforced composite membrane.

6. In Paragraph 1, The first polymer and the second polymer are identical to each other. Reinforced composite membrane.

7. In Paragraph 1, The thickness of the above-mentioned double porous support is 20% to 80% of the total thickness of the reinforced composite membrane, 100% of the total thickness. Reinforced composite membrane.

8. In Paragraph 1, The above double porous support is, Having a first surface adjacent to the first nanoweb and a second surface facing the first surface and adjacent to the second nanoweb, The above-mentioned reinforced composite membrane is, A first ion conductor layer located on the first surface and comprising a first ion conductor; and A second ion conductor layer located on the second surface and comprising a second ion conductor; further comprising Reinforced composite membrane.

9. In Paragraph 8, The ratio of the thickness of the first ion conductor layer to the thickness of the second ion conductor layer is 1.5:1 to 5:1, Reinforced composite membrane.

10. In Paragraph 8, The first ion conductor, the second ion conductor, and the third ion conductor each independently comprise a fluorine-based ion conductor, a hydrocarbon-based ion conductor, or a combination thereof. Reinforced composite membrane.

11. In Paragraph 10, The first ion conductor, the second ion conductor, and the third ion conductor are all the same. Reinforced composite membrane.

12. Having a first surface adjacent to the first nanoweb and a second surface facing the first surface and adjacent to the second nanoweb, A reinforced composite membrane according to any one of paragraphs 1 to 11; A hydrogen generating electrode located on the first surface above; and Oxygen generating electrode located on the second surface; comprising Membrane-electrode assembly.

13. In Paragraph 12, The above hydrogen generation electrode includes a catalyst layer for a hydrogen generation reaction comprising a catalyst for a hydrogen generation reaction, and The above active particles include precious metals, Membrane-electrode assembly.

14. In Paragraph 12, The above oxygen generation electrode includes a catalyst layer for an oxygen generation reaction comprising a catalyst for an oxygen generation reaction, and The above catalyst for the oxygen evolution reaction comprises a precious metal oxide, Membrane-electrode assembly.

15. A water electrolysis cell comprising a membrane-electrode assembly according to paragraph 12.

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