Membrane electrode assembly for water electrolysis cell and water electrolysis cell comprising the same

Abstract

The present disclosure relates to a membrane-electrode assembly for a water electrolyzer, which is capable of blocking the contact between an ion conductor exposed to the surface of a catalyst layer and a micro-porous layer, and the contact between a polymer electrolyte membrane exposed from an opening portion of the catalyst layer due to a low catalyst layer loading amount and the micro-porous layer, to reduce a band bending phenomenon, thereby reducing a pinch-off effect, thus improving performance, by further including a coating layer on one side surface of the catalyst layer. In addition, further, the coating layer is capable of functioning to connect the catalyst layers not in contact with the micro-porous layer to each other, thereby smoothly moving electrons.

Description

Technical Field

[0001] This disclosure relates to a membrane electrode assembly for a water electrolyzer and a water electrolyzer including the assembly. Specifically, it relates to a membrane electrode assembly for a water electrolyzer with improved performance, which further includes a coating on one side surface of the catalyst layer to block the contact between the polymer electrolyte membrane and the microporous layer at the interface between the catalyst layer and the microporous layer, thereby reducing band bending and pinch-off effect.

[0002] This disclosure relates to the results of a project (project number: 20022451) funded by the Ministry of Trade, Industry and Energy of Korea and the Korea Institute for Evaluation and Management of Industrial Technology (KEIT). Background Technology

[0003] Recent energy demands and environmental requirements necessitate sustainable supply, environmental friendliness, and high efficiency, with hydrogen gaining significant attention as a renewable energy source.

[0004] Hydrogen energy is classified into gray hydrogen, blue hydrogen, and green hydrogen based on its production method. Gray hydrogen and blue hydrogen use fossil fuels, so there are problems such as the generation of carbon dioxide during the production process or the inability to completely remove it.

[0005] Green hydrogen refers to hydrogen produced by electrolyzing an unlimited supply of water, without generating carbon dioxide in the process. Therefore, it has attracted much attention as a potential environmentally friendly energy source. Water electrolysis technology is required to produce green hydrogen.

[0006] Water electrolysis technology refers to the electrolysis of water and the use of a membrane to move ions to generate hydrogen and oxygen. Water electrolysis can be divided into two types of half-cell reactions: one is the hydrogen evolution reaction (HER) that occurs at the reduction electrode, and the other is the oxygen evolution reaction (OER) that occurs at the oxidation electrode.

[0007] In the polymer electrolyte membrane water electrolysis cell (PEMWE) system, the membrane electrode assembly (MEA) that actually performs hydrogen evolution has a structure in which the oxygen evolution electrode and the hydrogen evolution electrode that perform hydrogen evolution are separated by a polymer electrolyte membrane.

[0008] In addition, outside the electrodes, i.e. outside the oxygen evolution electrode and the hydrogen evolution electrode, a microporous transport layer (PTL) and a gasket are stacked in sequence. A baffle with a flow field is disposed outside the microporous layer to supply water and discharge hydrogen produced by the reaction. An end plate for supporting and fixing the above-mentioned components is attached to the outermost side.

[0009] Non-patent document 0001 discloses a pinch-off effect that occurs at the interface between the electrode and the microporous layer, resulting in bandbending.

[0010] This pinch-off effect refers to the phenomenon where, at the nanoscale, a semiconductor in which the catalyst particles mixed with the electrode are in contact with the polymer electrolyte membrane is dominated by band bending. It can be confirmed that the more the microporous layer is in contact with the ionic conductor, the greater the band bending is generated in the microporous layer.

[0011] In particular, a pinch-off effect occurs when ionic conductors exposed on the surface of the catalyst layer come into contact with the microporous layer, and / or when polymer electrolyte membranes exposed from openings with no catalyst layer due to low catalyst loading come into contact with the microporous layer, resulting in a degraded performance of the membrane electrode assembly.

[0012] Prior art literature

[0013] Non-patent literature 0001: Doo, Gisu, et al. “Contact Problems of IrO x Anodes inPolymer Electrolyte Membrane Water Electrolysis." ACS Energy Letters 8.5(2023): 2214-2220. Summary of the Invention

[0014] Technical issues

[0015] According to one embodiment, a membrane electrode assembly for a water electrolyzer is provided. This assembly further includes a coating on one side surface of the catalyst layer, which can block the contact between the ion conductors exposed on the surface of the catalyst layer and the microporous layer, as well as the contact between the polymer electrolyte membrane exposed from the opening where there is no catalyst layer due to low catalyst layer loading and the microporous layer. This reduces band bending and thus reduces the pinch-off effect, thereby improving performance. Furthermore, the coating can connect the catalyst layers that are not in contact with the microporous layer to each other, thereby allowing electrons to move smoothly.

[0016] According to another embodiment, a water electrolysis cell including the membrane electrode assembly for the water electrolysis cell is provided.

[0017] Technical solution

[0018] One embodiment of a membrane electrode assembly for a water electrolyzer includes: a polymer electrolyte membrane; an oxygen evolution electrode located on one side surface of the polymer electrolyte membrane; and a hydrogen evolution electrode located on the other side surface of the polymer electrolyte membrane. The oxygen evolution electrode includes: a catalyst layer containing an oxygen evolution reaction catalyst and an ion conductor, the oxygen evolution reaction catalyst containing active particles containing noble metal oxides; and a coating layer located on one side surface of the catalyst layer and containing a metal or metal oxide.

[0019] Another embodiment of the water electrolysis cell includes the membrane electrode assembly.

[0020] Beneficial effects

[0021] One embodiment of the membrane electrode assembly for a water electrolyzer further includes a coating on one side surface of the catalyst layer. This coating blocks the contact between the ion conductors exposed on the surface of the catalyst layer and the microporous layer, as well as the contact between the polymer electrolyte membrane exposed from openings where there is no catalyst layer due to low catalyst loading and the microporous layer. This reduces band bending and thus reduces pinch-off effects, thereby improving performance. Furthermore, the coating also serves to connect the catalyst layers that are not in contact with the microporous layer, allowing for smooth electron movement. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating a membrane-electrode assembly (MEA) for a water electrolyzer according to one embodiment.

[0023] Figure 2 These are photographs of the upper surface of the catalyst layer under conventional and low loading conditions, taken using scanning probe microscopy (AFM) as described in Patent Document 1.

[0024] Figure 3 This is a schematic diagram illustrating how a coating formed on a conventionally supported catalyst layer in Example 1 prevents the ionic conductors of the catalyst layer from contacting the microporous layer.

[0025] Figure 4 This is a schematic diagram illustrating how the coating formed on a low-load catalyst layer in Example 2 prevents the polymer electrolyte membrane and the ion conductors of the catalyst layer from contacting the microporous layer.

[0026] Figure 5 This is a schematic diagram showing the ion conductors of the conventionally supported catalyst layer of Comparative Example 1 exposed and in contact with the microporous layer.

[0027] Figure 6 This is a schematic diagram showing the ion conductor of the low-loaded catalyst layer of Comparative Example 2 and the thus exposed polymer electrolyte membrane in contact with the microporous layer.

[0028] Figure 7 The graphs show the IV characteristic evaluation results of the membrane electrode assemblies manufactured in Examples 1 to 2 and Comparative Examples 1 to 2. Detailed Implementation

[0029] The embodiments of this disclosure will now be described in detail to enable those skilled in the art to implement them. However, this disclosure can be implemented in different forms and is not limited to the embodiments described herein.

[0030] In this specification, "combinations thereof" refers to mixtures, laminates, composites, copolymers, alloys, blends, reaction products, etc. of the components.

[0031] In this specification, terms such as “comprising,” “possessing,” or “having” should be understood to indicate the presence of the implemented features, figures, steps, constituent elements, or combinations thereof, rather than precluding the possibility of the presence or addition of one or more other features, figures, steps, constituent elements, or combinations thereof.

[0032] In this specification, multiple terms are used only to distinguish one constituent element from another. Unless otherwise defined, the singular expression includes the plural expression.

[0033] In this specification, the terms "first surface" and "second surface" are used to distinguish them from each other, and do not indicate any order of priority among the aforementioned surfaces.

[0034] Membrane electrode assembly for water electrolysis cells

[0035] Figure 1This is a schematic diagram illustrating a membrane electrode assembly for a water electrolysis cell according to one embodiment. (Refer to...) Figure 1 The membrane electrode assembly 200 is described below.

[0036] The membrane electrode assembly 200 includes a polymer electrolyte membrane 30, an oxygen evolution electrode 10 located on one side surface of the polymer electrolyte membrane 30, and a hydrogen evolution electrode 20 located on the other side surface of the polymer electrolyte membrane 30. The oxygen evolution electrode may include a catalyst layer and a coating on one side surface of the catalyst layer.

[0037] The catalyst layer has a first surface that abuts against the polymer electrolyte membrane and a second surface that opposes the first surface, and the coating may be disposed on the second surface of the catalyst layer.

[0038] As described below, the catalyst layer comprises a catalyst for the oxygen evolution reaction and an ionic conductor. This ionic conductor is randomly arranged on the surface of the catalyst particles and exposed to the surface of the catalyst layer. When the microporous layer (described later) is located on the second surface of the catalyst layer, the microporous layer contacts the ionic conductor exposed to the catalyst layer, resulting in a pinch-off effect due to band bending. The band bending phenomenon caused by the ionic conductor exposed to the catalyst layer is independent of the catalyst layer loading.

[0039] One embodiment of the membrane electrode assembly includes an oxygen evolution electrode with a coating located on a second surface of a catalyst layer, the second surface being opposite to a first surface of the catalyst layer that abuts against the polymer electrolyte membrane, thereby preventing ion conductors exposed on the surface of the catalyst layer from contacting the microporous layer.

[0040] Figure 2 These are photographs (a) of the catalyst layer surface under conventional loading conditions and (b) of the catalyst layer surface under low loading conditions, taken using scanning probe microscopy (AFM) in Patent Document 1. Reference Figure 2 It can be confirmed that under normal load conditions, there are no areas of polymer electrolyte membrane exposure, while under low load conditions, there are areas of polymer electrolyte membrane exposure (in...). Figure 2 (The portion marked with ↓ in the text). As described above, regardless of the loading amount, the coating of one embodiment not only prevents contact with ionic conductors exposed on the surface of the catalyst layer, but also... Figure 2 As shown in (b), contact with the polymer electrolyte membrane exposed from the opening under low load conditions can be prevented. Low load conditions can be defined as a loading of 0.2 mg / cm³. 2In the following cases, a normal loading condition can be represented as greater than 0.2 mg / cm³. 2 And less than 1 mg / cm 2 The situation.

[0041] Here, the catalyst layer refers to the region in the planar and thickness directions where the catalyst for the oxygen evolution reaction (OER) is located. Depending on the loading, the catalyst layer can exist in a continuous or discontinuous form on one side of the polymer electrolyte membrane. For example, under conventional loading, there is no region in the planar and thickness directions of the OER catalyst on one side of the polymer electrolyte membrane; instead, it exists in a continuous form. On the other hand, under low loading, there is a region in the planar and thickness directions of the OER catalyst on one side of the polymer electrolyte membrane; in this case, the catalyst layer exists in a discontinuous form.

[0042] The catalyst layer may further have an opening on the second surface to expose the polymer electrolyte membrane. In other words, as described above, under low load, the catalyst layer exists in a discontinuous form and has a region without the catalyst layer on one side surface of the polymer electrolyte membrane, i.e., an opening exposing the polymer electrolyte membrane. The opening may be formed according to the loading amount of the catalyst layer forming composition used to form the catalyst layer; for example, it may be formed under low load. In this case, the loading amount of the catalyst layer can satisfy the loading amount range of the low load condition described above. The polymer electrolyte membrane can be exposed to the second surface of the catalyst layer through the opening.

[0043] The coating can also be disposed on the second surface and openings of the catalyst layer to cover the exposed polymer electrolyte membrane. By disposing the coating on the second surface and openings of the catalyst layer, when the microporous layer (described later) is located on the other side of the catalyst layer, the contact between the microporous layer and the polymer electrolyte membrane can be blocked. Furthermore, when the loading of the catalyst layer forming composition is low, the coating can also connect the portions of the catalyst layer and the microporous layer that are not in contact with each other due to the openings, thereby ensuring the electron movement path.

[0044] The area of ​​the opening in the catalyst layer can be within a predetermined range relative to the total area of ​​the catalyst layer and the opening. As an example, the lower limit of the area of ​​the opening in the catalyst layer relative to the total area of ​​the catalyst layer can be approximately 0%, 5%, 10%, 15%, 20%, 25%, or 30%, and the upper limit can be approximately 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, or 30%.

[0045] The area of ​​the opening in the catalyst layer can be above or greater than any of the aforementioned lower limits, or below or less than any of the aforementioned upper limits, or above or greater than any of the aforementioned lower limits and below or less than any of the aforementioned upper limits. The area of ​​the opening can vary depending on the loading amount of the catalyst layer forming composition; when the loading amount is low, the opening area increases; when the loading amount is the conventional loading amount for forming the catalyst layer or higher, the opening area decreases or becomes 0%.

[0046] A majority of the area of ​​the catalyst layer can be covered by a coating. The area of ​​the catalyst layer refers to the area of ​​the catalyst layer formed by coating the catalyst layer forming composition. As an example, the area of ​​the coating on the catalyst layer can be in the range of 90% to 100% of the total area of ​​the catalyst layer.

[0047] Furthermore, when the catalyst layer loading is low, and there is an opening exposing the polymer electrolyte membrane without a catalyst layer, most of the area of ​​the opening can also be covered by the coating. For example, the area of ​​the coating located at the opening of the catalyst layer can account for 90% to 100% of the total area of ​​the opening of the catalyst layer.

[0048] That is, by placing the coating on the catalyst layer and the opening according to the above-mentioned area, it is possible to block the contact between the microporous layer (described later) and the ion conductor exposed on the surface of the catalyst layer, as well as the contact between the microporous layer and the polymer electrolyte membrane exposed from the opening, thereby reducing band bending, thus reducing the pinch-off effect and improving the performance of the membrane electrode assembly.

[0049] The oxygen evolution electrode 10 may have a first surface that abuts against the polymer electrolyte membrane 30 and a second surface that is opposite to the first surface.

[0050] The membrane electrode assembly for the water electrolysis cell may further include a microporous layer 40, which may be located on the second surface of the oxygen evolution electrode 10. The microporous layer 40 serves to enhance the diffusion of reactants.

[0051] When the membrane electrode assembly for the water electrolysis cell further includes the microporous layer 40, the coating is located between the catalyst layer and the microporous layer 40. When the catalyst layer is further provided with an opening, the coating is located between the polymer electrolyte membrane 30 and the microporous layer 40 at the opening of the catalyst layer.

[0052] The microporous layer 40 can be made of materials known in the art without limitation. As an example, the microporous layer 40 may include multiple fibers. The multiple fibers may be integrated into a nonwoven fabric containing multiple pores.

[0053] The fibers may contain inorganic materials such as carbon and silicon dioxide, polymers such as polyimide, nylon, and polypropylene, metal oxides, or metals that have excellent electrochemical properties and heat resistance.

[0054] As an example, the plurality of fibers may contain metal oxides or metals.

[0055] For example, the plurality of fibers may comprise metals including gold (Au), silver (Ag), iron (Fe), aluminum (Al), copper (Cu), stainless steel (SUS), titanium (Ti), tantalum (Ta), or combinations thereof; metal oxides including titanium dioxide (TiO2), tungsten trioxide (WO3), silicon dioxide (SnO2), ruthenium dioxide (RuO2), antimony tin oxide (ATO), indium tin oxide (ITO), manganese dioxide (MnO2), molybdenum trioxide (MoO3), or combinations thereof; or combinations thereof. In addition to the metals or metal oxides listed, the plurality of fibers may also use known metals without limitation.

[0056] The diameter and length of the plurality of fibers can be within a predetermined range. The diameter and length of the plurality of fibers can be measured by imaging the microporous layer using a scanning electron microscope (SEM).

[0057] For example, the diameter can be in the range of 5 μm to 100 μm. Additionally, the length can be in the range of 10 μm to 2 mm.

[0058] The thickness and porosity of the microporous layer 40 can be adjusted appropriately to ensure proper reactant diffusion.

[0059] For example, the thickness of the microporous layer 40 can be within a predetermined range. The thickness of the microporous layer 40 can be measured by methods for measuring the diameter and length of the plurality of fibers.

[0060] The thickness of the microporous layer 40 can be in the range of 30μm to 500μm.

[0061] Furthermore, the porosity of the microporous layer 40 can be in the range of 30% to 80%. The porosity of the microporous layer 40 can be measured by mercury porosimetry.

[0062] The coating may comprise a metal or metal oxide capable of blocking contact between the microporous layer 40 and ionic conductors exposed on the surface of the catalyst layer, and between the microporous layer 40 and the polymer electrolyte membrane 30 exposed through openings in the catalyst layer, without degrading the functionality of the polymer electrolyte membrane 30 and the catalyst layer. The metal may be a metal with high conductivity and high corrosion resistance. For example, the metal may include Ir, Au, Pt, Ru, Al, Mo, W, Ta, Rh, Re, Cu, or combinations thereof. The metal oxide may include indium tin oxide (ITO).

[0063] The coating can be continuous or discontinuous, and the coating can have an uneven shape depending on the shape of the catalyst particles on the surface of the catalyst layer.

[0064] The coating can be formed to be relatively thin, and the thickness of the coating can be significantly thinner than the thickness of the catalyst layer.

[0065] For example, the lower limit of the thickness of the catalyst layer can be approximately 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm, and the upper limit can be approximately 25 μm, 20 μm, 15 μm, 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, or 5 μm. The catalyst layer can be above or greater than any of the aforementioned lower limits, or below or less than any of the aforementioned upper limits, or above or greater than any of the aforementioned lower limits and below or less than any of the aforementioned upper limits.

[0066] Furthermore, the lower limit of the coating thickness can be approximately 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, or 20nm, and the upper limit can be approximately 1000nm, 900nm, 800nm, 700nm, 600nm, 500nm, 400nm, 300nm, 200nm, 100nm, 90nm, 80nm, 70nm, 60nm, or 50nm. The coating thickness can be above or greater than any of the aforementioned lower limits, or below or less than any of the aforementioned upper limits, or above or greater than any of the aforementioned lower limits and below or less than any of the aforementioned upper limits.

[0067] By giving the catalyst layer and coating a thickness within the aforementioned range, it is possible to block the contact between the microporous layer 40 and the ion conductor exposed on the surface of the catalyst layer, as well as the contact between the microporous layer 40 and the polymer electrolyte membrane 30 exposed from the opening. This reduces band bending, thereby reducing the pinch-off effect and improving the performance of the membrane electrode assembly.

[0068] The coating can be formed to be thin and dense. Dense coating means that the coating contains almost no or no pores, which can be expressed by the coating's porosity. For example, the porosity of the coating can be less than 10%, for example, less than 5%, less than 2.5%, less than 1%, or 0%. The porosity of the coating can be measured by mercury porosimetry.

[0069] In addition, the density of the coating can be 1 g / cm³. 2 ~30g / cm 2 It can be 1.5g / cm³. 2 ~28g / cm 2 2g / cm 2 ~26g / cm 2 Or 2.5g / cm 2 ~24g / cm 2 The coating contains almost no or no pores; therefore, the density of the coating can be the same as the theoretical density of the metal or metal oxide contained in the coating.

[0070] When the porosity and density of the coating meet the above-mentioned range, it exhibits excellent conductivity and enables electrons to move smoothly.

[0071] The coating can be manufactured by known methods, for example, by sputtering or spraying. When manufactured by sputtering or spraying, a thin and dense coating can be formed.

[0072] The oxygen evolution electrode, hydrogen evolution electrode, and polymer electrolyte membrane are described below.

[0073] The catalyst layer in the oxygen evolution electrode includes a catalyst for the oxygen evolution reaction and an ion conductor. The catalyst for the oxygen evolution reaction includes active particles containing noble metal oxides.

[0074] The catalyst layer in the oxygen evolution electrode may contain pores formed by the catalyst for the oxygen evolution reaction, and the ionic conductor may exist disorderedly on the surface of the catalyst and in the catalyst layer. That is, the catalyst layer of the oxygen evolution electrode may have a porous structure, and the porosity of the catalyst layer may be 30% to 60%, for example, 32% to 55%, 32% to 50%, 32% to 47%, or 35% to 47%. The porosity in the catalyst layer can be measured by mercury porosimetry. When the porosity in the catalyst layer meets the above range, it helps to transfer reactants (H2O) and remove products (O2), thereby improving the water electrolysis performance of the polymer electrolyte membrane and ensuring optimal conductivity. As described above, the coating of one embodiment hardly affects the porosity of the catalyst layer and is located on the surface of the catalyst layer, which can prevent the microporous layer from contacting the ionic conductor exposed on the surface of the catalyst layer, and from contacting the microporous layer with the polymer electrolyte membrane, thereby improving the performance of the membrane electrode assembly.

[0075] The type of noble metal oxide is not limited as long as it can be used as a catalyst for the oxygen evolution reaction in a conventional water electrolyzer.

[0076] For example, the noble metal oxide may include IrO. x (where x is an integer from 1 to 3), RuO x (where x is an integer from 1 to 3), IrMO x (The M includes Ru, Sn, Ti, Te, Ta, Nb, Sb, Se, W or combinations thereof, and the x is an integer from 1 to 3) or combinations thereof.

[0077] The catalyst for the oxygen evolution reaction can use the active particles alone, or it can further include a support for loading the active particles.

[0078] The type of carrier is not limited as long as it can also be used as a catalyst for the oxygen evolution reaction in a conventional water electrolyzer.

[0079] For example, the support can be a metal oxide, such as titanium dioxide (TiO2).

[0080] The ion conductor is used to improve the adhesion of the catalyst layer and to transfer hydrogen ions.

[0081] The ionic conductor may contain cation substituents to ensure ionic conductivity.

[0082] The cationic substituent can be sulfonic acid group, carboxyl group, boric acid group, phosphoric acid group, phosphonic acid group, imide group, sulfonamide group, sulfonamide group or sulfonyl fluoride group.

[0083] The ionic conductor may be a fluorine-based ionic conductor, a hydrocarbon-based ionic conductor, or a mixture thereof.

[0084] The fluorine-based ionic conductor can be a fluorine polymer having the cation substituents in the side chain and containing fluorine in the main chain, such as poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), etc.

[0085] The hydrocarbon ionic conductor can be a hydrocarbon polymer containing the cationic substituent in its side chain, such as 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 polyethersulfone, sulfonated polyetherketone, and 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, sulfonated polyarylene ether ether nitrile, sulfonated polyarylene ether sulfone ketone, etc.

[0086] One embodiment of the ion conductor may have hydrogen ion conductivity.

[0087] The ionic conductor with hydrogen ion conductivity can also have the H in the cation substituent at the end of the side chain replaced with Na, K, Li, Cs, or tetrabutylammonium. When the H in the ionic substituent at the end of the side chain is replaced with Na, NaOH can be used in the preparation of the catalyst composition; when replaced with tetrabutylammonium, tetrabutylammonium hydroxide can be used; K, Li, or Cs can also be replaced with suitable compounds. This substitution method is well known in the art and therefore will not be described in detail in this specification.

[0088] The content of the ionic conductor can be adjusted appropriately as needed.

[0089] As an example, relative to 100 parts by weight of the catalyst for the oxygen evolution reaction, the lower limit of the content of the ionic conductor can be approximately 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, or 20 parts by weight, and the upper limit can be approximately 100 parts by weight, 90 parts by weight, 80 parts by weight, 70 parts by weight, 60 parts by weight, 50 parts by weight, 40 parts by weight, 30 parts by weight, or 20 parts by weight.

[0090] Relative to 100 parts by weight of the catalyst for the oxygen evolution reaction, the ionic conductor can be above or greater than any of the aforementioned lower limits, or below or less than any of the aforementioned upper limits, or above or greater than any of the aforementioned lower limits and below or less than any of the aforementioned upper limits. When the content of the ionic conductor is within the aforementioned range, the performance and durability are excellent.

[0091] The ionic conductor can be used in elemental or mixed form. Alternatively, it can be used in conjunction with a non-conductive compound to further enhance adhesion to the polymer electrolyte membrane. The content of the non-conductive compound can be adjusted appropriately according to the intended use.

[0092] The non-conductive compound may be selected from at least one of polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene (ETFE), ethylene-trifluorochloroethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), dodecylbenzenesulfonic acid, and sorbitol.

[0093] The hydrogen evolution electrode may include a catalyst for the hydrogen evolution reaction. The catalyst for the hydrogen evolution reaction may include active particles and a support.

[0094] The active particles may contain precious metals.

[0095] For example, the precious metal may be a platinum-based precious metal.

[0096] The platinum-based precious metal may be platinum (Pt) and / or Pt-M alloys. 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).

[0097] Specifically, the Pt-M alloy may use 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 mixtures thereof.

[0098] The carrier can be a carbon-based carrier.

[0099] The carbon-based carrier may be graphite, superconducting carbon black (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 combinations thereof.

[0100] The oxygen evolution electrode and the hydrogen evolution electrode may each include only a catalyst layer containing a catalyst for the oxygen evolution reaction and a catalyst for the hydrogen evolution reaction, or they may include both the catalyst layer and the electrode substrate.

[0101] At this point, the electrode substrate can both support the electrode and facilitate the diffusion of fuel and oxidant into the catalyst layer.

[0102] There are no specific limitations on the electrode substrate, and known electrode substrates can be used, including carbon paper, carbon cloth, carbon felt, or metal cloth (a porous membrane composed of fibrous metal cloth or a metal film formed on the surface of a cloth formed of polymer fibers) used as conductive substrates.

[0103] The electrode substrate can be treated with fluoropolymer hydrophobicity, which can prevent the diffusion efficiency of reactants from being reduced by water generated during the operation of the water electrolysis cell.

[0104] The fluororesin may be polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkylvinyl ether, polyperfluorosulfonyl fluoride, alkoxyvinyl ether, fluorinated ethylenepropylene, polychlorotrifluoroethylene, or copolymers thereof.

[0105] The polymer electrolyte membrane has an ion exchange function that allows hydrogen ions generated at the oxygen evolution electrode to move toward the catalyst used in the hydrogen evolution reaction.

[0106] One embodiment of the polymer electrolyte membrane may include: a porous support comprising a plurality of pores; and an ion conductor filling the pores of the porous support.

[0107] The porous support can be a fluorine-based carrier or a nano-mesh support.

[0108] The fluorinated support can be, for example, expanded polytetrafluoroethylene (e-PTFE) with a polymer fibrillary microstructure or a microstructure in which nodes are connected by fibrils. Alternatively, the porous support can be a thin film with a polymer fibrillary microstructure without nodes.

[0109] The nanofiber support can be a carrier in the form of a nonwoven fabric containing multiple pores, which is composed of multiple nanofibers.

[0110] The ionic conductor is as described above.

[0111] The ion conductor in the polymer electrolyte membrane may be the same as or different from the ion conductor in the oxygen evolution electrode. For example, the ion conductor in the polymer electrolyte membrane may be the same as the ion conductor in the oxygen evolution electrode.

[0112] Water electrolysis cell

[0113] One embodiment of the water electrolysis cell may include the membrane electrode assembly.

[0114] Apart from the membrane electrode assembly included in this application, the water electrolysis cell is the same as known technology, and therefore will not be described in detail.

[0115] Example

[0116] The embodiments are described in detail below to enable those skilled in the art to implement them. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0117] Example 1

[0118] In n-propanol (nPA) as a solvent, commercial IrO will be used. x Black powder (Merck Sigma-Aldrich, Iridium(IV) oxide 206237) and Nafion, as an ionic conductor, were mixed in a weight ratio of 1:0.2 (IrO x The components are mixed with Nafion and a solvent is added to bring the solid content to 5% by weight, thereby preparing a composition for forming a catalyst layer for an oxygen evolution electrode.

[0119] The horizontal dimension is 2cm and the vertical dimension is 2cm (the active area is 4cm). 2 A coating substrate film (PI tip material, PI film) with a thickness of approximately 200 μm was applied with a concentration of 0.5 mg / cm². 2 The catalyst layer is formed by spraying the catalyst layer forming composition for the oxygen evolution electrode with a loading amount of [amount missing]. At this time, the thickness of the catalyst layer is approximately 5 μm, and the porosity of the catalyst layer is 35%. At this time, the catalyst layer does not have openings that expose the polymer electrolyte membrane.

[0120] Carbon in a Pt / C mixture with a Pt loading of 50 wt% was mixed with Nafion, an ion conductor, at a weight ratio of 1:1.2, and the solvent was added to bring the solid content to 5 wt%, thereby preparing a composition for forming a catalyst layer for a hydrogen evolution electrode. A coating substrate film (PI tip material, PI film) with a transverse dimension of 2 cm, a longitudinal dimension of 2 cm, and a thickness of approximately 200 μm was applied at a concentration of 0.5 mg / cm². 2 The catalyst layer forming composition for the hydrogen evolution electrode is sprayed with a loading amount to form a hydrogen evolution electrode with a thickness of about 30 μm.

[0121] The oxygen evolution electrode, a Chemours commercial NR212 polymer electrolyte membrane with a thickness of approximately 50.8 μm, and the hydrogen evolution electrode are sequentially stacked and hot-pressed at 150°C with 5N for 5 minutes. Afterward, the coated substrate membrane is removed to fabricate a membrane electrode assembly.

[0122] A coating was formed on the catalyst layer of the oxygen evolution electrode using an Aurion Anlagentechnik VPA 21 radio frequency (RF) magnetron sputtering system. Specifically, the gas was first evacuated to 5.0 × 10⁻⁶ ppm. -3 To prevent contamination from residual gas, a pressure of Pa was applied. A borosilicate glass cover glass D263 from Duran Group, measuring 50 mm laterally and 50 mm longitudinally with a thickness of approximately 0.145 mm, was then used as the substrate. The membrane electrode assembly was fixed to the substrate using a circular planar iridium target with a purity of 99.9%, positioned 120 mm from the substrate at a 40° angle. During deposition, the gas pressure was maintained at 0.25 Pa using argon at a flow rate of 50 sccm, RF power was applied at 6 W at 300 inches, and deposition was performed at a deposition rate of 7 nm / min for approximately 2.8 minutes to achieve a thickness of 20 nm. The substrate was then rotated at 8 rpm to form a dense coating with a thickness of 20 nm and 0% porosity on the catalyst layer of the oxygen evolution electrode.

[0123] A microporous layer of Bekaert's Currento® PTLTi-68 / 350 product is stacked on an oxygen evolution electrode with the aforementioned coating to produce a finished membrane electrode assembly. The microporous layer is in the form of a nonwoven fabric composed of multiple titanium fibers, with a porosity of approximately 68% and a thickness of 350 μm.

[0124] Example 2

[0125] Except for the oxygen evolution electrode manufactured in Example 1 at 0.1 mg / cm³ 2 In addition to forming a catalyst layer, the membrane electrode assembly is fabricated using a method substantially the same as that in Example 1.

[0126] At this time, the thickness of the catalyst layer of the oxygen evolution electrode is about 1.5 μm, the area of ​​the opening of the oxygen evolution electrode accounts for about 30% of the total area of ​​the catalyst layer and the opening (which is the same as the active area), and the porosity of the catalyst layer of the oxygen evolution electrode is 47%.

[0127] Comparative Example 1

[0128] Except that no coating was formed during the fabrication of the oxygen evolution electrode in Example 1, the membrane electrode assembly was fabricated using a method substantially the same as that in Example 1.

[0129] At this point, the oxygen evolution electrode has only a catalyst layer with a thickness of about 5 μm on one side of the polymer electrolyte membrane (Chemours, NR212) with a thickness of about 50.8 μm, and the porosity of the catalyst layer of the oxygen evolution electrode is 35%.

[0130] Comparative Example 2

[0131] Except in Comparative Example 1, when manufacturing the oxygen evolution electrode, 0.1 mg / cm³ was used. 2 Apart from forming a catalyst layer with a loading amount, a membrane electrode assembly was fabricated by a method substantially the same as that of Comparative Example 1.

[0132] At this time, the thickness of the catalyst layer of the oxygen evolution electrode is about 1.5 μm, the area of ​​the opening of the oxygen evolution electrode accounts for about 30% of the total area of ​​the catalyst layer and the opening (which is the same as the active area), and the porosity of the catalyst layer of the oxygen evolution electrode is 47%.

[0133] Evaluation Example 1. IV Characteristics

[0134] The membrane electrode assembly for water electrolysis cells described in Examples 1 to 2 and Comparative Examples 1 to 2 was applied inside a unit cell designed and manufactured specifically for water electrolysis cells. Under the conditions of a cell temperature of 80°C, a water temperature of 80°C, and a flow rate of 5 mL / min, the voltage and resistance were measured using a test protocol that measures voltage and resistance at a specific current from 1 mA to 200 A, and the measurement was stopped at 2 V.

[0135] The result at this time is as follows Figure 7 As shown.

[0136] in conclusion

[0137] Figures 3 to 6 This is a schematic diagram illustrating the polymer electrolyte membrane 1-catalyst layer 2-microporous layer 3 in the membrane electrode assemblies of Examples 1 to 2 and Comparative Examples 1 to 2. (See reference) Figures 3 to 6The catalyst layer 2 of Examples 1 and Comparative Example 1, which forms the catalyst layer with a conventional loading, differs from the catalyst layer 2 of Examples 2 and Comparative Example 2, which forms the catalyst layer with a smaller loading, in that it lacks a portion where the polymer electrolyte membrane is exposed, i.e., the opening A. In Examples 1 and Comparative Example 1, the probability of the polymer electrolyte membrane 1 contacting the microporous layer 3 is low. On the other hand, regardless of the loading of the catalyst layer, there are ion conductors 5 exposed on the surface of the catalyst layer. Therefore, in Examples 1 to 2 and Comparative Examples 1 to 2, the ion conductors 5 exposed on the surface of the catalyst layer 2 contact the microporous layer 3. Example 1 differs from Comparative Example 1 in that it forms a coating 4 on the catalyst layer, which can suppress the contact between the ion conductor 5 exposed on the surface of the catalyst layer and the microporous layer 3. Example 2 differs from Comparative Example 2 in that it forms a coating on the catalyst layer and the opening, which can not only suppress the contact between the ion conductor 5 exposed on the surface of the catalyst layer and the microporous layer 3, but also suppress the contact between the polymer electrolyte membrane 1 exposed from the opening and the microporous layer 3. Furthermore, the coating 4 can connect the catalyst layers that are not in contact with the microporous layer 3 to each other, thereby allowing electrons to move smoothly. The microporous layer is formed of nonwoven fabric; therefore, when magnified, it should be understood as magnifying a single fiber constituting the nonwoven fabric. Additionally, as... Figure 3 and Figure 4 As shown, the coating 4 is formed thin and dense, thus it can be formed unevenly along the morphology of the oxygen evolution reaction catalyst 6 particles located on the surface of the catalyst layer.

[0138] refer to Figure 7 This will be explained in more detail. (See reference) Figure 7 At 0.5 mg / cm 2 Based on the loading amount, the membrane electrode assembly of Example 1, which includes an oxygen evolution electrode with a coating formed on the catalyst layer, exhibited a higher current density at the same voltage compared to the membrane electrode assembly of Comparative Example 1, which includes an oxygen evolution electrode without the coating, thereby confirming that the performance was improved.

[0139] On the other hand, at 0.1 mg / cm 2 Based on the loading amount, the membrane electrode assembly of Example 2, which includes an oxygen evolution electrode with a coating formed on the catalyst layer, exhibited a higher current density at the same voltage compared to the membrane electrode assembly of Comparative Example 2, which includes an oxygen evolution electrode without the coating, thereby confirming that the performance was improved.

[0140] This is because by forming a thinner and denser coating on the catalyst layer, it is possible to prevent the contact between the ionic conductors exposed on the surface of the catalyst layer and the microporous layer. Furthermore, when the catalyst layer has openings, it is possible to prevent the contact between the polymer electrolyte membrane exposed from the openings and the microporous layer. Therefore, at the same voltage, a higher current density is exhibited, which indicates that the performance has been improved.

[0141] In addition, the coating in one embodiment is thin and dense. Therefore, when it is formed on the catalyst layer, it is formed unevenly along the catalyst particles located on the surface of the catalyst layer without affecting the pores in the catalyst layer. Thus, the performance can be improved without increasing the mass transfer resistance of the catalyst layer.

[0142] The preferred embodiments have been described in detail above. However, the scope of the claims is not limited thereto. Various modifications and improvements made by those skilled in the art using the basic concepts defined in the appended claims also fall within the scope of the claims.

[0143] Figure label: 200: Membrane electrode assembly for water electrolysis cell; 10: Oxygen evolution electrode. 20: Hydrogen evolution electrode; 30: Polymer electrolyte membrane 40: Microporous layer 1: Polymer electrolyte membrane 2: Catalyst layer; 3: Microporous layer 4: Coating 5: Ion conductor 6: Catalyst A for oxygen evolution reaction: Opening section

Claims

1. A membrane electrode assembly for a water electrolysis cell, comprising: Polymer electrolyte membrane; An oxygen evolution electrode is located on one side surface of the polymer electrolyte membrane; as well as The hydrogen evolution electrode is located on the other side surface of the polymer electrolyte membrane. The oxygen evolution electrode includes: The catalyst layer includes an oxygen evolution reaction catalyst and an ion conductor, wherein the oxygen evolution reaction catalyst comprises active particles containing noble metal oxides. as well as The coating is located on one side surface of the catalyst layer and contains a metal or metal oxide.

2. The membrane electrode assembly for a water electrolysis cell according to claim 1, wherein, The catalyst layer has a first surface that abuts against the polymer electrolyte membrane and a second surface that opposes the first surface. The coating is disposed on the second surface of the catalyst layer.

3. The membrane electrode assembly for a water electrolysis cell according to claim 2, wherein, The catalyst layer further has an opening on the second surface that exposes the polymer electrolyte membrane. The coating is further disposed on the opening to cover the exposed polymer electrolyte membrane.

4. The membrane electrode assembly for a water electrolysis cell according to claim 3, wherein, The area of ​​the coating on the catalyst layer accounts for 90% to 100% of the total area of ​​the catalyst layer. The area of ​​the coating located at the opening of the catalyst layer accounts for 90% to 100% of the total area of ​​the opening of the catalyst layer.

5. The membrane electrode assembly for a water electrolysis cell according to claim 3, wherein, The oxygen evolution electrode has a first surface that abuts against the polymer electrolyte membrane and a second surface that opposes the first surface. The membrane electrode assembly for the water electrolyzer further includes a microporous layer located on the second surface of the oxygen evolution electrode.

6. The membrane electrode assembly for a water electrolysis cell according to claim 5, wherein, The coating is located between the catalyst layer and the microporous layer. At the opening of the catalyst layer, the coating is located between the polymer electrolyte membrane and the microporous layer.

7. The membrane electrode assembly for a water electrolysis cell according to claim 5, wherein, The microporous layer is composed of multiple fibers integrated in the form of a nonwoven fabric containing multiple pores. The plurality of fibers comprise metals, metal oxides, or combinations thereof, wherein the metals include gold, silver, iron, aluminum, copper, stainless steel, titanium, tantalum, or combinations thereof, and the metal oxides include titanium dioxide, tungsten trioxide, silicon dioxide, ruthenium dioxide, antimony-tin oxide, indium-tin oxide, manganese dioxide, molybdenum trioxide, or combinations thereof.

8. The membrane electrode assembly for a water electrolysis cell according to claim 5, wherein, The diameter of the plurality of fibers is in the range of 5μm to 100μm, and the length is in the range of 10μm to 2mm.

9. The membrane electrode assembly for a water electrolysis cell according to claim 5, wherein, The thickness of the microporous layer is in the range of 30 μm to 500 μm.

10. The membrane electrode assembly for a water electrolysis cell according to claim 5, wherein, The porosity of the microporous layer is in the range of 30% to 80%.

11. The membrane electrode assembly for a water electrolysis cell according to claim 1, wherein, The metal includes Ir, Au, Pt, Ru, Al, Mo, W, Ta, Rh, Re, Cu, or combinations thereof. The metal oxide includes indium tin oxide.

12. The membrane electrode assembly for a water electrolysis cell according to claim 1, wherein, The coating can be continuous or discontinuous.

13. The membrane electrode assembly for a water electrolysis cell according to claim 1, wherein, The porosity of the coating is less than 10%. The density of the coating is 1 g / cm³. 2 ~30g / cm 2 .

14. The membrane electrode assembly for a water electrolysis cell according to claim 1, wherein, The thickness of the catalyst layer is in the range of 3 μm to 25 μm. The thickness of the coating is in the range of 3nm to 1000nm.

15. The membrane electrode assembly for a water electrolysis cell according to claim 1, wherein, The noble metal oxide includes IrO. x RuO x IrMO x Or combinations thereof, where IrO x In this context, x is an integer from 1 to 3, RuO x In IrMO, x is an integer from 1 to 3. x M is Ru, Sn, Ti, Te, Ta, Nb, Sb, Se, W or a combination thereof, and x is an integer from 1 to 3.

16. The membrane electrode assembly for a water electrolysis cell according to claim 1, wherein, The catalyst for the oxygen evolution reaction further comprises a support for loading the active particles. The carrier is titanium dioxide.

17. The membrane electrode assembly for a water electrolysis cell according to claim 1, wherein, The ionic conductor in the catalyst layer is more than 5% by weight.

18. The membrane electrode assembly for a water electrolysis cell according to claim 1, wherein, The hydrogen evolution electrode includes: Carbon-based supports; and Active particles, loaded on the carbon-based support and containing noble metals.

19. The membrane electrode assembly for a water electrolysis cell according to claim 1, wherein, The polymer electrolyte membrane comprises: A porous support containing multiple pores; and An ion conductor fills the pores of the porous support.

20. A water electrolysis cell, comprising: The membrane electrode assembly as described in claim 1.

Images