Reinforced composite membrane for water electrolysis cell, membrane-electrode assembly for water electrolysis cell comprising same, and water electrolysis cell comprising same

Abstract

The present invention relates to a reinforced composite membrane for a water electrolysis cell, a membrane-electrode assembly for a water electrolysis cell, comprising same, and a water electrolysis cell comprising same, wherein in the reinforced composite membrane for a water electrolysis cell, a porous support is arranged to be biased toward the surface adjacent to an oxygen evolution electrode before operation of the water electrolysis cell, on the basis of a prediction of the area that expands after the operation, the oxygen evolution electrode undergoing relatively greater expansion, thereby evenly distributing the expansion stress applied to the reinforced composite membrane for a water electrolysis cell after operation and improving the performance and durability of the membrane-electrode assembly and water electrolysis cell comprising same.

Description

Reinforced composite membrane for electrolysis cell, membrane-electrode assembly for electrolysis cell including same, and electrolysis cell

[0001] The present disclosure relates to a reinforced composite membrane for a water electrolysis cell, a membrane-electrode assembly for a water electrolysis cell including the same, and a water electrolysis cell, and more particularly, to a reinforced composite membrane for a water electrolysis cell, which predicts an area that expands after operation of the water electrolysis cell and arranges a porous support before operation so that the porous support is relatively more inclined toward a surface adjacent to an oxygen generation electrode that expands a lot, thereby uniformly applying expansion stress to the reinforced composite membrane for a water electrolysis cell after operation, and a membrane-electrode assembly for a water electrolysis cell including the same, and a water electrolysis cell.

[0002] This disclosure relates to the results of a project (project number: 20022451) carried out with the support of the Materials and Components Technology Development Project of the Ministry of Trade, Industry and Energy and the Korea Institute for Advancement of Technology (KEIT).

[0003] Recent energy demands and environmental concerns demand sustainable supply, environmental friendliness, and high efficiency, and among these, hydrogen is attracting attention as a raw material for renewable energy.

[0004] Hydrogen energy is classified into gray, blue, and green hydrogen depending on the production method. Gray and blue hydrogen have the problem that carbon dioxide is generated during the production process or cannot be completely removed because they use fossil fuels.

[0005] Green hydrogen refers to hydrogen produced through the electrolysis of infinite water. Because the hydrogen production process produces no carbon dioxide, it is attracting attention as the ultimate eco-friendly energy source. Water electrolysis technology is necessary to produce green hydrogen.

[0006] Water electrolysis is an electrochemical technology that generates hydrogen and oxygen by electrolyzing water and transporting ions across a membrane. Water electrolysis can be divided into two half-cell reactions: the hydrogen evolution reaction (HER), which occurs at the reduction electrode, and the oxygen evolution reaction (OER), which occurs at the oxidation electrode.

[0007] The types of electrolysis mentioned above are, depending on the electrolyte membrane, representative ones such as polymer electrolyte membrane electrolysis (PEM), alkaline electrolysis (AEC), anion exchange membrane electrolysis (AEM), and solid oxide electrolysis (SOECs).

[0008] Among them, in the system of a polymer electrolyte membrane water electrolysis cell (PEMWE), the membrane electrode assembly (MEA) that actually generates hydrogen has a structure in which an oxygen generation electrode, which is an electrode where an oxygen generation reaction occurs, and a hydrogen generation electrode, where a hydrogen generation reaction occurs, are positioned with a polymer electrolyte membrane containing a hydrogen ion conductive polymer interposed therebetween.

[0009] In this polymer electrolyte membrane electrolysis cell, water is supplied to the oxygen generation electrode and comes into contact with the water, but the hydrogen generation electrode does not come into contact with the water, so that the water content of the polymer electrolyte membrane has a concentration gradient in the thickness direction from the oxygen generation electrode to the hydrogen generation electrode. The expansion coefficient of the polymer electrolyte membrane varies depending on the water content, and generally, as the water content increases, the expansion coefficient also tends to increase. Accordingly, after the electrolysis cell is operated, the degree of expansion in the thickness direction from the oxygen generation electrode to the hydrogen generation electrode in the polymer electrolyte membrane is reduced (Non-patent Document 0001).

[0010] In a polymer electrolyte membrane including a support (hereinafter, “reinforced composite membrane”), when the support is positioned in the center of the polymer electrolyte membrane during the manufacture of the reinforced composite membrane, there is a problem in that the performance of the reinforced composite membrane is deteriorated due to an asymmetrical stress that occurs because the degree of expansion of the reinforced composite membrane adjacent to the oxygen generation electrode is greater than the degree of expansion of the reinforced composite membrane adjacent to the hydrogen generation electrode after the operation of the electrolysis cell including the reinforced composite membrane.

[0011] Accordingly, it is necessary to appropriately adjust the position of the support included in the reinforced composite membrane of the electrolysis cell.

[0012] [Prior Art Literature]

[0013] (Non-patent Document 0001) Hwang, Gi Suk, et al. “Understanding water uptake and transport in nafion using x-ray microtomography.” ACS Macro Letters 2.4 (2013): 288-291.

[0014] According to one embodiment, a reinforced composite membrane for a water electrolysis cell is provided, which evenly distributes the expansion stress received by the reinforced composite membrane for a water electrolysis cell by predicting the area that expands when the water electrolysis cell is driven and disposing the porous support so that it is biased toward the surface adjacent to the oxygen generation electrode that expands relatively more.

[0015] According to another embodiment, a membrane-electrode assembly and electrolysis cell having improved performance and durability are provided, including a reinforced composite membrane for the electrolysis cell.

[0016] One embodiment provides a reinforced composite membrane for a water electrolysis cell, comprising: a porous support including a plurality of pores and having a thickness in a first direction; and an ion conductor filling the pores of the porous support; wherein the reinforced composite membrane for a water electrolysis cell has a first side and a second side which are arranged to face each other in the first direction, and when a distance from the first side to the center of the porous support is referred to as a 1-1 distance and a distance from the second side to the center of the porous support is referred to as a 1-2 distance, the 1-1 distance is greater than the 1-2 distance.

[0017] Another embodiment provides a membrane-electrode assembly for a water electrolysis cell comprising a reinforced composite membrane for the water electrolysis cell, a hydrogen generation electrode positioned on the first surface (S1), and an oxygen generation electrode positioned on the second surface (S2).

[0018] Another embodiment provides a water electrolysis cell comprising the membrane-electrode assembly.

[0019] According to one embodiment, a reinforced composite membrane for a water electrolysis cell can uniformly distribute expansion stress received by the reinforced composite membrane for a water electrolysis cell by predicting an area that expands when the water electrolysis cell is driven and disposing the porous support so that it is biased toward a surface adjacent to an oxygen generation electrode that expands relatively more, and a membrane-electrode assembly and a water electrolysis cell including the same can have improved performance and durability.

[0020] FIG. 1 is a cross-sectional view showing a reinforced composite membrane for a water electrolysis cell according to one embodiment.

[0021] FIG. 2 is a graph showing a function of the expansion coefficient of a reinforced composite membrane for a water electrolysis cell with respect to the thickness of the reinforced composite membrane for a water electrolysis cell according to one embodiment.

[0022] Figure 3 is a graph showing the performance evaluation results of Example 1 and Comparative Examples 1 and 2.

[0023] Hereinafter, embodiments of the present disclosure will be described in detail so that those skilled in the art can easily implement the present disclosure. However, the present disclosure may be implemented in various different forms and is not limited to the embodiments described herein.

[0024] As used herein, “combination thereof” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0025] It should be understood that the terms “include,” “comprising,” or “having” used in this specification are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0026] In this specification, terms are used solely to distinguish one component from another. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0027] In this specification, “first side (S1)” and “second side (S2)” are denoted as “first” and “second” respectively only to identify different sides, and do not indicate the priority between the sides.

[0028] In this specification, “1-1st distance”, “1-2nd distance”, “2-1st distance”, etc. are only expressed as “1-1”, “1-2”, “2-1”, etc. to identify different distances, and do not indicate the priority between the distances.

[0029] Reinforced composite membrane for electrolysis cell

[0030] Fig. 1 is a cross-sectional view showing a reinforced composite membrane for a water electrolysis cell according to one embodiment. Hereinafter, the reinforced composite membrane for a water electrolysis cell will be described with reference to Fig. 1.

[0031] FIG. 1 is a diagram illustrating, for convenience, the first surface (S1), the second surface (S2), the center of the porous support, the D1 axis direction, and the D2 axis direction of the reinforced composite membrane for a water electrolysis cell, and it should be understood that what is illustrated in FIG. 1 does not indicate the thickness of the porous support, the thickness of the oxygen generation electrode, and the thickness of the hydrogen generation electrode, and that the thickness of the porous support, the thickness of the oxygen generation electrode, and the thickness of the hydrogen generation electrode are as described below.

[0032] According to one embodiment, a reinforced composite membrane (100) for a water electrolysis cell includes a porous support (101) including a plurality of pores and having a thickness in a first direction; and an ion conductor (102) filling the pores of the porous support (101). To clearly explain this embodiment, directions are defined, and the D1 axis and D2 axis shown in the drawing represent the thickness direction and the length direction of the porous support (101), respectively. Here, the thickness direction (D1 axis direction) may be a direction perpendicular to a wide surface (main surface) of sheet-shaped components. The length direction (D2 axis direction) may be a direction extending parallel to the wide surface (main surface) of sheet-shaped components and may be a direction approximately perpendicular to the thickness direction (D1 axis direction).

[0033] The above reinforced composite membrane (100) for the electrolytic cell has a first surface (S1) and a second surface (S2) which are arranged to face each other in the first direction (D1). The center (CL) of the porous support (101) is located at the middle (1 / 2) point of the porous support (101) and refers to an imaginary plane parallel to the first surface (S1) and the second surface (S2).

[0034] When the distance from the first surface (S1) to the center (CL) of the porous support is referred to as the 1-1 distance (L1), and the distance from the second surface (S2) to the center of the porous support is referred to as the 1-2 distance (L2), the 1-1 distance (L1) is greater than the 1-2 distance (L2). That is, the porous support is positioned asymmetrically in the reinforced composite membrane.

[0035] In the case of a water electrolysis cell, the part of the reinforced composite membrane for water electrolysis cell adjacent to the oxygen generation electrode into which water is injected is humidified and expands depending on operation, but the part of the reinforced composite membrane for water electrolysis cell adjacent to the hydrogen generation electrode is not humidified and does not expand. That is, a concentration gradient of the water content of the reinforced composite membrane in the thickness direction from the hydrogen generation electrode to the oxygen generation electrode is generated, and as the water content increases, the expansion coefficient also increases, so that the degree of expansion is lower for the hydrogen generation electrode with a low water content than for the oxygen generation electrode with a high water content, and the degree of expansion stress is uneven. The porous support included in the conventional reinforced composite membrane for water electrolysis cell is arranged to be located at the center of the reinforced composite membrane. In this case, as described above, when the water electrolysis cell is operated, the expansion stress received by the reinforced composite membrane occurs asymmetrically, which may result in a problem of reduced effectiveness of the reinforced composite membrane.

[0036] Accordingly, the inventors of the present invention intend to provide a reinforced composite membrane that resolves the unevenness of expansion stress by determining the position of a porous support so that the degree of expansion stress is uniform and arranging the porous support at that position.

[0037] 다공성 지지체의 위치 결정

[0038] The position of the porous support in the reinforced composite membrane for a water electrolysis cell according to one embodiment can be determined according to the following.

[0039] As mentioned above, the water content in the thickness direction can increase from the reinforced composite membrane for water electrolysis cell adjacent to the hydrogen evolution electrode to the reinforced composite membrane for water electrolysis cell adjacent to the oxygen evolution electrode. Although the water content in the thickness direction of the reinforced composite membrane does not increase completely linearly, it shows a pattern similar to a linear increase (see Hwang, Gi Suk, et al. "Understanding water uptake and transport in nafion using x-ray microtomography." ACS Macro Letters 2.4 (2013): 288-291.). In this specification, it is assumed that the water content in the thickness direction of the reinforced composite membrane increases linearly, and that the expansion coefficient also increases linearly as the water content increases. Based on this assumption, the expansion coefficient of the reinforced composite membrane in the thickness direction will also increase linearly, which is represented in the graph.

[0040] Fig. 2 is a graph showing the expansion coefficient at each point from the first side to the second side (hereinafter, the thickness of the reinforced composite membrane for a water electrolysis cell) of the reinforced composite membrane for a water electrolysis cell. The graph shown in Fig. 2 is shown for convenience in explaining that the expansion coefficient of the reinforced composite membrane for a water electrolysis cell can increase linearly, and the slope of the reinforced composite membrane for a water electrolysis cell is not limited to the slope of Fig. 2, and may vary depending on the type of ion conductor forming the reinforced composite membrane, the thickness of the reinforced composite membrane, etc.

[0041] When the first surface (S1), that is, the surface adjacent to the hydrogen generation electrode in the later reinforced composite membrane, is taken as the standard, when the first surface (S1) is x = 0, the expansion coefficient, that is, y = 0, and the second surface (S2), that is, the surface adjacent to the oxygen generation electrode in the later reinforced composite membrane, is taken as x = When , the coefficient of expansion, i.e. y= Assuming this, the graph in Fig. 2 can be derived, and using this, the slope of the expansion coefficient with respect to the thickness of the reinforced composite membrane can be calculated, which is as shown in Equation 1 below.

[0042] [Formula 1]

[0043]

[0044] 상기 식 1에서, is the thickness of the reinforced composite membrane for the electrolysis cell before operation, i.e. before water is injected and humidified or before expansion, is the maximum water content of the reinforced composite membrane for the above-mentioned electrolytic cell ( ) is the coefficient of thickness expansion, and the maximum water content refers to the number of water molecules per ionic conductive group of the ionic conductor, and a is a positive number.

[0045] Through Figure 2, the expansion thickness of the reinforced composite membrane for the electrolysis cell can be derived, and the reinforced composite membrane for the electrolysis cell is the thickness of the reinforced composite membrane before humidification, i.e. before expansion ( ) can be expanded by the area (△S) of the graph shown in Fig. 2. Here, the area (△S) according to Fig. 2 is It can be calculated as

[0046] Accordingly, the total thickness of the reinforced composite membrane for the electrolysis cell after operation can be calculated as shown in Equation 2 below.

[0047] [Formula 2]

[0048]

[0049] In equation 1, is the thickness of the reinforced composite membrane for the electrolytic cell before operation, is the thickness of the reinforced composite membrane for the electrolytic cell after operation, refers to the coefficient of thickness expansion on the second surface adjacent to the oxygen generation electrode.

[0050] Using the function of the expansion coefficient for the thickness of the reinforced composite membrane for the electrolysis cell, the thickness of the reinforced composite membrane for the electrolysis cell after the operation can be predicted, as well as the distance to the first side (S1) and the distance to the second side (S2) based on the center (CL) of the porous support. Specifically, the 2-1 distance, which is the distance from the first side (S1) after humidification to the center (CL) of the porous support, and the 2-2 distance, which is the distance from the second side (S2) to the center (CL) of the porous support, can be derived as the 1-1 distance (L1), which is the distance from the first side (S1) before humidification to the center (CL) of the porous support.

[0051] Using the above equation 2, the 2-1 distance, which is the distance from the first surface (S1) after the humidification to the center (CL) of the porous support, can be expressed as in equation 3 below when the 2-2 distance, which is the distance from the second surface (S2) to the center (CL) of the porous support, is expressed on the left side of the equal sign in equation 3, and the 3-4 distance, which is the distance from the second surface (S2) to the center (CL) of the porous support, is expressed on the right side of the equal sign in equation 3.

[0052] [Formula 3]

[0053]

[0054] In equation 3, is the location of the center (CL) of the initial porous support, is the location of the second side (S2) before humidification, Is is the coefficient of thickness expansion at the point, Is It is the coefficient of thickness expansion at the point.

[0055] The above equation 3 If we organize it into an equation, it is as follows: Equation 4.

[0056] That is, the 1-1 distance (L1), which is the distance from the first surface (S1) to the center (CL) of the porous support, can satisfy Equation 4 below. When the 1-1 distance (L1) satisfies Equation 4 below, the expansion stress applied to the reinforced composite membrane for the electrolysis cell after the electrolysis cell is operated can be uniform.

[0057] [Formula 4]

[0058]

[0059] In Equation 4, the above is the above 1-1 distance (L1), and is the distance from the first surface (S1) to the second surface (S2) (i.e., equal to the thickness of the reinforced composite membrane before driving), and a is the slope of the expansion coefficient function for the thickness of the reinforced composite membrane for the electrolysis cell.

[0060] The position of the above porous support is according to the above formula 4. And it can be positioned so that the ratio of the distance from the first side (S1) to the second side (S2) is within a predetermined range.

[0061] The above ratio is, for example, when the distance from the first surface (S1) to the center (CL) of the porous support is referred to as the 1-1 distance (L1), and the distance from the first surface (S1) to the second surface (S2) is referred to as the 1-3 distance (L3), the K value, which is the ratio of the 1-1 distance (L1) to the 1-3 distance (L3), can be calculated according to Equation 5 below, and the K value can be in the range of more than 50% and less than or equal to 60%.

[0062] [Formula 5]

[0063]

[0064] In the above equation 5,

[0065] Above The maximum water content of the reinforced composite membrane for the above-mentioned electrolytic cell ( ) means the coefficient of thickness expansion, and the maximum water content means the number of water molecules per ionic conductive group of the ionic conductor.

[0066] 상기 식 5는, 상기 식 4의 In the expression expressed as The value of K is derived by dividing by . That is, by substituting Equation 1 into a of Equation 4, and in Equation 4, is the distance from the first side (S1) to the second side (S2) before driving, i.e., the thickness of the reinforced composite membrane of the electrolytic cell before driving ( )와 같으므로, On behalf of The equation summarized by substituting If divided into , it can be expressed as in Equation 5 above.

[0067] In order for the expansion stress applied to the reinforced composite membrane for the above-mentioned electrolysis cell to be uniform, the K value may be within a predetermined range, and the porous support may be positioned so that the K value is within the predetermined range.

[0068] The lower limit of the above K may be about 50.1%, 50.2%, 50.3%, 50.4%, 50.5%, 50.6%, 50.7%, 50.8%, 50.9%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, or 60%, and the upper limit may be about 60%, 59%, 58%, 57%, 56%, 55%, 54%, 53%, 52%, or 51%.

[0069] The above K may have a range that is greater than or equal to any one of the lower limits described above, provided that it is greater than 50%; less than or equal to any one of the upper limits described above; or greater than or equal to any one of the lower limits described above and less than or equal to any one of the upper limits described above.

[0070] If the above K is 50%, the porous support is located at the center of the first and second surfaces, so this is excluded.

[0071] In order to satisfy the above-mentioned K value, the following parameters can be appropriately adjusted.

[0072] The expansion coefficient on the first surface (S1) and the expansion coefficient on the second surface (S2) can be appropriately adjusted.

[0073] For example, the lower limit of the expansion coefficient in the first surface (S1) may be about 0, 0.01, 0.02, 0.03, 0.04, or 0.05, and the upper limit may be about 0.05, 0.04, 0.03, 0.02, 0.01, or 0.

[0074] Additionally, the lower limit of the expansion coefficient in the second surface (S2) may be about 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65 or 0.7, and the upper limit may be about 1, 0.95, 0.9, 0.85, 0.8, 0.75 or 0.7.

[0075] The expansion coefficients on the first surface (S1) and the second surface (S2) may each have a range that is equal to or greater than any one of the lower limits described above; equal to or less than any one of the upper limits described above; or equal to or greater than any one of the lower limits described above and equal to or less than any one of the upper limits described above.

[0076] 제1 및 제2 이온 전도체 층

[0077] According to one embodiment, a reinforced composite membrane for a water electrolysis cell may further include, in addition to an ion conductor filling the pores of a porous support, a first ion conductor layer (102_1) positioned on one surface of the porous support and including the ion conductor, and a second ion conductor layer (102_2) positioned on the other surface of the porous support and including the ion conductor. That is, the porous support (101) may be positioned between the first ion conductor layer (102_1) and the second ion conductor layer (102_2).

[0078] In the above “first ion conductor layer” and the above “second ion conductor layer,” “first” and “second” are only intended to identify that the ion conductor layers are formed as separate layers and are separated, and do not indicate that the ion conductor layers are formed of different materials or have a priority.

[0079] Meanwhile, the first ion conductor layer (102_1) and the second ion conductor layer (102_2) may have different thicknesses since the reinforced composite membrane is manufactured according to the method for determining the position of the porous support described above.

[0080] The thickness of the first ion conductor layer (102_1) may be a value calculated by subtracting 1 / 2 of the thickness of the porous support from the distance from the first side to the center of the porous support, and the thickness of the second ion conductor layer (102_2) may be a value calculated by subtracting 1 / 2 of the thickness of the porous support from the distance from the center of the porous support to the second side from the total thickness of the reinforced composite membrane. The thickness of the first ion conductor layer (102_1) may be thicker than the thickness of the second ion conductor layer (102_2).

[0081] The first ion conductor layer (102_1) having a relatively thick thickness may be positioned adjacent to the hydrogen generation electrode, and the second ion conductor layer (102_2) having a relatively thin thickness may be positioned adjacent to the oxygen generation electrode. In this case, the membrane-electrode assembly includes a reinforced composite membrane having an asymmetrical structure in which a porous support is positioned on ion conductor layers having different thicknesses, and the oxygen generation electrode is positioned on the second ion conductor layer having a relatively thin ion conductor layer, thereby eliminating unevenness in expansion stress and improving performance and durability.

[0082] The above ion conductor may include a cation exchanger to ensure ion conductivity.

[0083] The above cation exchanger may be a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphoric acid group, a phosphonic acid group, an imide group, a sulfonimide group, a sulfonamide group, or a sulfonic acid fluoride.

[0084] The above ion conductor may be a fluorine-based ion conductor, a hydrocarbon-based ion conductor, or a mixture thereof.

[0085] The above fluorine-based ion conductor may be a fluorine-based polymer having the cation exchange group in the side chain and containing fluorine in the main chain, for example, poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), etc.

[0086] The hydrocarbon-based ion conductor is a hydrocarbon-based polymer having the cation exchange group in the side chain [e.g., 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 polyphenylene sulfone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether nitrile, sulfonated polyarylene ether ether nitrile,It may be polyarylene ether sulfone ketone, etc.

[0087] According to one embodiment, the ion conductor may have hydrogen ion conductivity.

[0088] The ion conductor having the above hydrogen ion conductivity can also substitute H with Na, K, Li, Cs or tetrabutylammonium in the cation exchanger at the end of the side chain. When substituting H with Na in the ion exchanger at the end of the side chain, NaOH is used during the preparation of the catalyst composition, and when substituting H with tetrabutylammonium, tetrabutylammonium hydroxide is used. K, Li or Cs can also be substituted using an appropriate compound. Since this substitution method is widely known in the art, a detailed description thereof will be omitted herein.

[0089] The above ion conductor can be used as a single substance or as a mixture, and may also be optionally used together 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 depending on the intended use.

[0090] 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 chlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), dodecylbenzenesulfonic acid, and sorbitol can be used.

[0091] The ion conductors included in the first ion conductor layer and the second ion conductor layer may be the same.

[0092] porous support

[0093] The type of the porous support is not limited as long as it is applied to a water electrolysis cell, but may be, for example, a fluorine-based support or a nano web support.

[0094] The fluorine-based support may correspond to, for example, expanded polytetrafluoroethylene (e-PTFE) having a microstructure of polymer fibrils or a microstructure in which nodes are interconnected by fibrils. In addition, a film having a microstructure of polymer fibrils without nodes may also be used as the porous support.

[0095] The fluorinated support may comprise a perfluorinated polymer. The porous support may be formed by extruding dispersed polymerized PTFE into a tape in the presence of a lubricant, and stretching the resulting material to form a more porous and stronger porous support.

[0096] In addition, the amorphous content of PTFE can be increased by heat-treating the e-PTFE at a temperature exceeding the melting point of PTFE (about 342°C). The e-PTFE film manufactured by the method can have micropores and porosity with various diameters. The e-PTFE film manufactured by the method can have at least 35% of pores, and the diameter of the micropores can be about 0.01 to 1 ㎛ (micrometer).

[0097] The above nano web support may be a non-woven fibrous web composed of a plurality of randomly oriented fibers. The non-woven fibrous web refers to a sheet having a structure of individual fibers or filaments that are interlaid, but not in the same manner as a woven fabric. The non-woven fibrous web may be manufactured by carding, garnetting, air-laying, wet-laying, melt blowing, spun bonding, or stitch bonding.

[0098] The fiber may comprise one or more polymeric materials, and any material generally used as a fiber-forming polymeric material may be used, and specifically, a hydrocarbon-based fiber-forming polymeric material may be used. For example, the fiber-forming polymeric material may comprise a polyolefin such as polybutylene, polypropylene, and polyethylene, a polyester such as polyethylene terephthalate and polybutylene terephthalate, a polyamide (nylon-6 and nylon-6,6), a polyurethane polybutene, polylactic acid, polyvinyl alcohol, polyphenylene sulfide, polysulfone, a fluid crystalline polymer, polyethylene-co-vinylacetate, polyacrylonitrile, a cyclic polyolefin, polyoxymethylene, a polyolefin-based thermoplastic elastomer, or a combination thereof. However, the technical idea of ​​the present invention is not limited thereto.

[0099] The above nano web support may be a support in which nano fibers are integrated in the form of a non-woven fabric containing a large number of pores.

[0100] The above nanofibers exhibit excellent chemical resistance and have hydrophobicity, so hydrocarbon polymers that are free from moisture-induced deformation in high-humidity environments can be preferably used. Specifically, the hydrocarbon polymers may include nylon, polyimide, 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, polyphenylene sulfide, polyethylene, polypropylene, copolymers thereof, or mixtures thereof.

[0101] The above nanoweb support is an aggregate of nanofibers manufactured by electrospinning and randomly arranged. At this time, the nanofibers may have an average diameter of 40 nm to 5000 nm when the average diameter of 50 fibers is measured using a scanning electron microscope (JSM6700F, JEOL) and calculated from the average, taking into account the porosity and thickness of the nanoweb. When the average diameter of the nanofibers is within the above range, the mechanical strength is excellent and an appropriate porosity can be secured.

[0102] The thickness of the above nonwoven fibrous web may be 10 ㎛ to 50 ㎛ or 15 ㎛ to 43 ㎛. When the thickness of the above nonwoven fibrous web is within the above range, the mechanical strength, weight reduction, and integration may be excellent.

[0103] The above nonwoven fibrous web has a basic weight of 5 to 30 mg / cm 2If the basis weight of the nonwoven fibrous web is less than the above numerical range, visible pores may be formed, making it difficult to function as a porous support, and if it exceeds the above numerical range, it may be manufactured in the form of paper or fabric in which pores are hardly formed.

[0104] The above porosity can be calculated by the ratio of the air volume within the porous support to the total volume of the porous support according to the following mathematical formula 1. At this time, the total volume is calculated by manufacturing a rectangular sample and measuring the width, length, and thickness, and the air volume can be obtained by measuring the mass of the sample and then subtracting the polymer volume calculated inversely from the density from the total volume.

[0105] [Mathematical Formula 1]

[0106] Porosity (%) = (air volume in porous support / total volume of porous support) × 100

[0107] For example, the porosity of the porous support may be 30 to 90%. When the porosity of the porous support is within the above range, problems such as a decrease in the impregnation property of the ion conductor or a problem of post-processing not proceeding smoothly due to a decrease in stability may not occur.

[0108] Membrane-electrode assembly for electrolysis cell

[0109] A membrane-electrode assembly for a water electrolysis cell according to one embodiment may include a reinforced composite membrane for a water electrolysis cell according to claim 1 having a first side and a second side facing each other in a first direction, a hydrogen generation electrode positioned on the first side, and an oxygen generation electrode positioned on the second side.

[0110] By applying the above-mentioned reinforced composite membrane for electrolysis cells, the expansion stress applied to the above-mentioned reinforced composite membrane for electrolysis cells can be uniform even after the electrolysis cells are operated, thereby improving performance and durability.

[0111] The above oxygen generation electrode and the above hydrogen generation electrode are described below.

[0112] Oxygen evolution electrode and hydrogen evolution electrode

[0113] The catalyst layer included in the above oxygen generation electrode includes a catalyst for oxygen generation reaction and an ion conductor, and the catalyst for oxygen generation reaction includes active particles including a precious metal oxide.

[0114] The above noble metal oxide is not limited in type as long as it can be applied as a catalyst for the oxygen generation reaction of a typical electrolysis cell.

[0115] For example, the noble metal oxide is IrO x (wherein x is an integer from 1 to 3), RuO x (where x is an integer from 1 to 3), IrMO x (wherein M includes Ru, Pt, Sn, Se, Sb, Ta, Te, Nb, W, Zn, Au or a combination thereof, and x is an integer from 1 to 3), or a combination thereof.

[0116] The above oxygen generation reaction catalyst may be used alone with the active particles, or may further include a carrier that supports the active particles.

[0117] The type of the above carrier is not limited as long as it can be applied to a catalyst for oxygen generation reaction of a typical electrolysis cell.

[0118] For example, the carrier may be a metal oxide, and the carrier may be titanium dioxide (TiO2).

[0119] The above ion conductor is included to improve the adhesion of the catalyst layer and to transfer hydrogen ions.

[0120] The types of the above ion conductors are as described in the first and second ion conductor layers of the reinforced composite membrane for the electrolysis cell.

[0121] The ion conductor included in the above oxygen generation electrode and the ion conductor included in the reinforced composite membrane for the water electrolysis cell may be the same.

[0122] The above hydrogen generation electrode may include a catalyst for hydrogen generation reaction. The hydrogen generation reaction catalyst may include active particles and a carrier for supporting the active particles.

[0123] The above active particles may include a precious metal.

[0124] For example, the precious metal may be a platinum-based precious metal.

[0125] The platinum-based precious metal may be platinum (Pt) and / or a Pt-M alloy. The 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).

[0126] Specifically, the Pt-M alloy includes 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 these Mixtures can be used.

[0127] The above carrier may be a carbon-based carrier.

[0128] 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.

[0129] The above oxygen generation electrode and the above hydrogen generation electrode may each include only a catalyst layer including a catalyst for oxygen generation reaction and a catalyst for hydrogen generation reaction, but may include an electrode substrate together with the catalyst layer.

[0130] At this time, the electrode substrate can play a role in supporting the electrode and diffusing the fuel and oxidant to the catalyst layer.

[0131] As the electrode substrate, a known electrode substrate can be used without specific limitation, but specifically, carbon paper, carbon cloth, carbon felt, or metal cloth (a porous film composed of a fiber-like metal cloth or a cloth formed of polymer fibers in which a metal film is formed on the surface of the cloth) that can be used as a conductive substrate are included.

[0132] The above electrode substrate can be treated with a water-repellent fluorine resin, in which case the diffusion efficiency of reactants can be prevented from being reduced by water generated after the electrolysis cell is operated.

[0133] As the above fluorine-based resin, polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxy vinyl ether, fluorinated ethylene propylene, polychlorotrifluoroethylene or a copolymer thereof can be used.

[0134] Susan Haesel

[0135] A hydrolysis cell according to one embodiment may include the membrane-electrode assembly.

[0136] The above electrolytic cell is the same as the known one except that it includes a membrane-electrode assembly according to the present application, and therefore a detailed description thereof is omitted.

[0137] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0138]

[0139] Example 1

[0140] 1. Determination of position of porous support

[0141] First, assuming that the expansion coefficient of the reinforced composite film increases linearly with the thickness, the slope (a) is calculated according to Equation 1 above.

[0142] As described below, Nafion® D2020 is used as the ion conductor included in the reinforced composite membrane, so the maximum expansion coefficient of Nafion® D2020 was 0.2, and the thickness of the reinforced composite membrane before driving was 50 ㎛, so the slope a of the expansion coefficient with respect to the thickness of the reinforced composite membrane is 0.004.

[0143] In the above equation 4, the distance from the first surface to the second surface, i.e. the thickness of the reinforced composite membrane before driving x b The distance from the first surface to the center of the porous support, i.e., the 1-1 distance, was calculated by substituting the value of a calculated above into 50 ㎛.

[0144] As a result, x according to equation 4 a was 26.78㎛.

[0145] When the K value was calculated by substituting it into the above equation 5, it was 53.57%, which satisfied the range of the K value mentioned above.

[0146] 2. Manufacturing of reinforced composite membranes for electrolysis cells

[0147] Nafion® D2020 (20%, Chemours) was used as an ionic conductor, and an ionic conductor dispersion was prepared by adding it to a mixture of 1-propanol, water, and ethanol in a weight ratio of 44:34:2. In addition, an e-PTFE film from Gore with a thickness of 10 μm, an average pore size of 0.2 μm, and a porosity of 70% was prepared as a porous support.

[0148] First, the ion conductor dispersion was applied on a glass substrate using a blade coating technique at a coating speed of 3 mm / s, and then a flattening process was performed in a natural state for 5 minutes.

[0149] Then, the prepared e-PTFE film was placed on the ion conductor dispersion cast on the glass substrate and left for 10 minutes to allow the ion conductor solution to penetrate the e-PTFE film. The ion conductor dispersion was applied on the e-PTFE film in the same manner as the first time to manufacture a composite structure. At this time, the first coating was applied so that the distance to the center of the porous support after the final drying was 26.78 μm, and the second coating was applied so that the distance to the center of the porous support after the final drying was 23.22 μm.

[0150] The above composite structure was dried at 80°C for 12 hours to remove the solvent, and then heat-treated at 150°C for 30 minutes to produce a reinforced composite membrane.

[0151] The above reinforced composite membrane has an asymmetric structure with different thicknesses based on the center of the porous support, and the thickness of the ion conductor layer that is relatively thick based on the center of the porous support is 21.78 ㎛, and the thickness of the ion conductor layer that is relatively thin is 18.22 ㎛.

[0152] 3. Manufacturing of CCM (Catalyst Coated Membrane)

[0153] Commercial IrO as a catalyst for oxygen evolution electrodes x A composition for forming a catalyst layer for an oxygen generation electrode was prepared by mixing black powder (Merck Sigma-Aldrich, Iridium(IV) oxide 206237) and Nafion as an ion conductor in a weight ratio of 1:0.2 (catalyst:ion conductor), adding ethanol as a solvent, and dispersing the mixture through ultrasonic treatment.

[0154] Meanwhile, a Pt / C catalyst having a Pt loading of 50 wt% as a catalyst for a hydrogen generation electrode and Nafion as an ion conductor were mixed in a weight ratio of 1:1.2 (catalyst:ion conductor), and ethanol was added as a solvent and dispersed through ultrasonic treatment to prepare a composition for forming a catalyst layer for a hydrogen generation electrode.

[0155] The reinforced composite membrane for the electrolysis cell manufactured above was placed on a metal plate heated to 80°C, and the loading amount was 0.4 mg / cm 2 The composition for forming a catalyst layer for the oxygen generation electrode was applied to the ion conductor layer having a thinner thickness based on the center of the porous support of the reinforced composite membrane by spray coating, and the loading amount was 0.15 mg / cm 2 The composition for forming a catalyst layer for the hydrogen generation electrode was applied to the ion conductor layer having a thicker thickness based on the center of the porous support of the reinforced composite membrane by a spray coating method.

[0156] Thereafter, the reinforced composite membrane coated with the catalyst layer was hot pressed at 180°C for 3 minutes under a pressure of 5 kN to manufacture a CCM. The weight ratio of the catalyst and the ion conductor in the catalyst layer for the oxygen generation electrode was 85:15, and the weight ratio of the catalyst and the ion conductor in the catalyst layer for the hydrogen generation electrode was 70:30.

[0157] 4. MEA (Membrane-Electrode Assembly) Manufacturing

[0158] In the CCM manufactured above, a titanium fiber mesh with a porosity of 78%, a fiber diameter of 20 ㎛, and a thickness of 0.3 mm was positioned as a gas diffusion layer on the surface where the catalyst layer for the oxygen generation electrode was formed, and carbon paper was positioned as a gas diffusion layer on the surface where the catalyst layer for the hydrogen generation electrode was formed, thereby manufacturing an MEA. The active area of ​​the final MEA was 9 cm 2 It was.

[0159]

[0160] Comparative Example 1

[0161] In the above Example 1, when manufacturing a reinforced composite membrane, the porous support was not positioned according to the positioning of the porous support, and the ion conductor dispersion was applied so that the distance from the center of the porous support to one side of the reinforced composite membrane and the distance to the other side within a total of 50 ㎛ of the reinforced composite membrane were the same, i.e., the thicknesses of the ion conductor layers positioned on both sides of the porous support were the same, and the reinforced composite membrane, CCM, and MEA were manufactured in the same manner as in Example 1.

[0162]

[0163] Comparative Example 2

[0164] In the above Example 1, when manufacturing a reinforced composite membrane, the porous support was positioned so that the K value according to the positioning of the porous support was 65%, and the ion conductor dispersion was applied so that the distance from the porous support to one side of the reinforced composite membrane was 32.5 μm and the distance to the other side was 17.5 μm out of a total of 50 μm of the reinforced composite membrane, thereby forming an ion conductor layer, and a reinforced composite membrane, CCM, and MEA were manufactured in the same manner as in Example 1. When manufacturing the CCM, the hydrogen generation electrode was manufactured so as to be positioned on an ion conductor layer having a thicker thickness based on the center of the porous support of the reinforced composite membrane.

[0165]

[0166] Evaluation Example 1. Performance Evaluation

[0167] The membrane-electrode assembly for electrolysis cells manufactured in the above Example 1 and Comparative Examples 1 to 2 was applied inside a unit cell designed and manufactured for electrolysis cells, and the voltage and resistance were measured at specific currents from 1 mA to 200 A under conditions of cell temperature 80°C, water temperature 80°C, and flow rate 5 ml / min, using a protocol for measuring voltage and resistance, and 4.5 A / cm 2 Measurement was stopped at .

[0168] 이 때의 결과는 도 3과 같다.

[0169]

[0170] Evaluation example 2. Durability evaluation

[0171] The membrane-electrode assembly for the electrolysis cell manufactured in the above Example 1 and Comparative Examples 1 to 2 was applied inside a unit cell designed and manufactured for the electrolysis cell, and the activated cell was operated at a cell temperature of 80°C and a current density of 2 A / cm. 2 The initial voltage was measured under the conditions of cell temperature 80℃, current density 2A / cm 2 After driving the constant current for 3500 hours, the voltage was measured.

[0172] The above voltage was measured using a potentiostat from BioLogic, and the voltage increase rate was calculated using the measured voltage according to the following mathematical formula 2. The results at this time are as shown in Table 2 below.

[0173] [Equation 2]

[0174] Voltage increase rate (%) = (voltage after driving - initial voltage) / (initial voltage) × 100

[0175] Example 1 Comparative Example 1 Comparative Example 2 Voltage Increase Rate (%) 3.15 3.86 5.44

[0176] conclusion

[0177] Referring to FIG. 3, it can be confirmed that the membrane-electrode assembly of Example 1, which includes a reinforced composite membrane manufactured by positioning the porous support according to the positioning of the porous support, exhibits a higher current density at the same voltage than the membrane-electrode assembly of Comparative Example 1, which includes a reinforced composite membrane manufactured by positioning the porous support in the center of the reinforced composite membrane without positioning the porous support, and the membrane-electrode assembly of Comparative Example 2, which includes a reinforced composite membrane manufactured by positioning the porous support at 65% of the K value that is outside the appropriate range within the specification according to the positioning of the porous support, thereby demonstrating improved performance.

[0178] In addition, referring to Table 2 above, it can be confirmed that the membrane-electrode assembly of Example 1 including a reinforced composite membrane manufactured by positioning the porous support according to the positioning of the porous support has a reduced voltage increase rate and thus increased durability compared to the membrane-electrode assembly of Comparative Example 1 including a reinforced composite membrane manufactured by positioning the porous support in the center of the reinforced composite membrane without depending on the positioning of the porous support, and the membrane-electrode assembly of Comparative Example 2 including a reinforced composite membrane manufactured by positioning the porous support at 65%, which is outside the appropriate range within the specification, of the K value according to the positioning of the porous support.

[0179] Through this, it can be confirmed that in the case of a membrane-electrode assembly including a reinforced composite membrane manufactured by positioning a porous support according to the positioning of the porous support, the expansion stress received by the reinforced composite membrane for a water electrolysis cell becomes uniform, thereby improving performance and durability.

[0180]

[0181] Although the preferred embodiments have been described in detail above, the scope of the rights is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the following claims also fall within the scope of the rights.

[0182] [Explanation of symbols]

[0183] 100: Reinforced composite membrane for electrolysis cell

[0184] 102_1: First ion conductor layer

[0185] 101: Porous support

[0186] 102_2: Second ion conductor layer

[0187] 102: Ionic conductor

[0188] S1: Page 1

[0189] S2: Second side

[0190] CL: Center of the porous support

[0191] L1: 1-1 distance

[0192] L2: 1st-2nd distance

[0193] L3: 1-3rd street

Claims

1. A porous support including a plurality of pores and having a thickness in a first direction; and A reinforced composite membrane for a water electrolysis cell, comprising an ion conductor filling the pores of the porous support; The above reinforced composite membrane for the water electrolysis cell is Having a first side and a second side facing each other in the first direction, When the distance from the first surface to the center of the porous support is called the 1-1 distance, and the distance from the second surface to the center of the porous support is called the 1-2 distance, the 1-1 distance is greater than the 1-2 distance. Reinforced composite membrane for water electrolysis cells.

2. In paragraph 1, The distance from the first surface to the center of the porous support is called the 1-1 distance. When the distance from the first side to the second side is called the 1-3 distance, The K value, which is the ratio of the above 1-1 distance to the above 1-3 distance, is calculated according to Equation 5 below, The above K value is within the range of 50% to 60%, Reinforced composite membrane for water electrolysis cell: [Formula 5] In the above equation 5, Above The maximum water content of the reinforced composite membrane for the above-mentioned water electrolysis cell ( ) means the coefficient of thickness expansion, and the maximum functional content means the number of water molecules per ion conductive group of the ion conductor.

3. In paragraph 1, The above reinforced composite membrane for the water electrolysis cell is, A first ion conductor layer positioned on one surface of the porous support and including the ion conductor, and Further comprising a second ion conductor layer positioned on the other surface of the porous support and including the ion conductor, The porous support is positioned between the first ion conductor layer and the second ion conductor layer. Reinforced composite membrane for water electrolysis cells.

4. In paragraph 3, The thickness of the first ion conductor layer is thicker than the thickness of the second ion conductor layer. Reinforced composite membrane for water electrolysis cells.

5. Reinforced composite membrane for water electrolysis cell according to Article 1; A hydrogen generation electrode located on the first surface, and Including an oxygen generation electrode located on the second surface, Membrane-electrode assembly for a water electrolysis cell.

6. In paragraph 5, The above oxygen generation electrode comprises an oxygen generation reaction catalyst including active particles including a precious metal oxide and an ion conductor. Membrane-electrode assembly for a water electrolysis cell.

7. In paragraph 6, The above oxygen generation reaction catalyst further includes a carrier that supports the active particles, The above carrier is titanium dioxide (TiO2). Membrane-electrode assembly for a water electrolysis cell.

8. In paragraph 5, The above hydrogen generation electrode comprises a carbon-based carrier and active particles supported on the carbon-based carrier and containing a precious metal. Membrane-electrode assembly for a water electrolysis cell.

9. A water electrolysis cell comprising a membrane electrode assembly for a water electrolysis cell according to paragraph 5.

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