Membrane-electrode assembly for water electrolysis cell, and water electrolysis cell comprising same

Abstract

The present disclosure relates to a membrane-electrode assembly for a water electrolysis cell and a water electrolysis cell comprising same, wherein the membrane-electrode assembly for a water electrolysis cell further comprises a coating layer positioned on one surface of a catalyst layer to prevent an ion conductor exposed on the surface of the catalyst layer from contacting a microporous layer, and a polymer electrolyte membrane exposed through an opening in which the catalyst layer does not exist due to low loading from contacting the microporous layer, thereby reducing a band bending phenomenon, so that a pinch-off effect can be reduced and performance can be improved. In addition, furthermore, the coating layer serves to connect catalyst layers, which are not in contact with the microporous layer, to each other, thereby enabling smooth electron movement.

Description

Membrane-electrode assembly for electrolysis cell and electrolysis cell including same

[0001] The present disclosure relates to a membrane-electrode assembly for a water electrolysis cell and a water electrolysis cell including the same, and more particularly, to a membrane-electrode assembly for a water electrolysis cell and a water electrolysis cell including the same, which further includes a coating layer located on one side of a catalyst layer, thereby blocking contact between a polymer electrolyte membrane and a microporous layer at an interface between the catalyst layer and the microporous layer, thereby reducing a band bending phenomenon, thereby reducing a pinch-off effect and improving performance accordingly.

[0002] This disclosure relates to the results of a project (Project ID: 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] Among them, in the polymer electrolyte membrane water electrolysis cell (PEMWE) system, 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 located with a polymer electrolyte membrane in between.

[0008] In addition, a porous transport layer (PTL) and a gasket are sequentially laminated on the outer part of the electrode, that is, the outer part where the oxygen generation electrode and the hydrogen generation electrode are located, and a separator having a flow field formed therein to supply water and discharge hydrogen generated by the reaction is located on the outermost part of the microporous layer, and an end plate is coupled to support or fix each of the above components.

[0009] Non-patent document 0001 discloses that a pinch-off effect occurs in which a band bending phenomenon occurs at the interface between the electrode and the microporous layer.

[0010] This pinch-off effect refers to a phenomenon in which the semiconductor in mixed contact with the catalyst particles of the electrode at the nanometer scale is dominated by band bending due to contact with the polymer electrolyte membrane, and it can be confirmed that the more the microporous layer comes into contact with the ion conductor, the greater the band bending occurs in the microporous layer.

[0011] In particular, when the ion conductor exposed on the surface of the catalyst layer comes into contact with the microporous layer, and / or when the polymer electrolyte membrane exposed through an opening where the catalyst layer is not present due to low loading comes into contact with the microporous layer, a pinch-off effect occurs, which causes a problem of deterioration in the performance of the membrane-electrode assembly.

[0012] [Prior Art Literature]

[0013] (Non-patent Document 0001) Doo, Gisu, et al. “Contact Problems of IrO x Anodes in Polymer Electrolyte Membrane Water Electrolysis.” ACS Energy Letters 8.5 (2023): 2214-2220.

[0014] According to one embodiment, by further including a coating layer located on one side of a catalyst layer, the membrane-electrode assembly for a water electrolysis cell is provided, which blocks contact between an ion conductor exposed on the surface of the catalyst layer and the microporous layer, and between a polymer electrolyte membrane exposed through an opening where the catalyst layer is not present due to low loading of the catalyst layer and the microporous layer, thereby reducing the band bending phenomenon, thereby reducing the pinch-off effect and improving performance, and furthermore, the coating layer serves to connect the microporous layer and the catalyst layer not in contact with each other, thereby facilitating electron transfer.

[0015] According to another embodiment, a water electrolysis cell is provided comprising the membrane-electrode assembly for the water electrolysis cell.

[0016] According to one embodiment, a membrane-electrode assembly for a water electrolysis cell comprises: a polymer electrolyte membrane; an oxygen generation electrode positioned on one side of the polymer electrolyte membrane; and a hydrogen generation electrode positioned on the other side of the polymer electrolyte membrane; wherein the oxygen generation electrode comprises: a catalyst layer comprising an oxygen generation reaction catalyst including active particles including a noble metal oxide, and an ion conductor; and a coating layer positioned on one side of the catalyst layer, the coating layer comprising a metal or a metal oxide.

[0017] A hydrolysis cell according to another embodiment comprises the membrane-electrode assembly.

[0018] According to one embodiment, a membrane-electrode assembly for a water electrolysis cell further includes a coating layer positioned on one side of a catalyst layer, thereby preventing contact between an ion conductor exposed on the surface of the catalyst layer and the microporous layer, and between a polymer electrolyte membrane exposed through an opening where the catalyst layer is not present due to low loading of the catalyst layer and the microporous layer, thereby reducing band bending phenomenon, thereby reducing the pinch-off effect and improving performance accordingly. Furthermore, the coating layer can serve to connect the microporous layer and the catalyst layer that are not in contact with each other, thereby facilitating electron transfer.

[0019] FIG. 1 is a schematic drawing of a membrane-electrode assembly (MEA) for a water electrolysis cell according to one embodiment.

[0020] Figure 2 is a photograph of the upper surface of the catalyst layer in the case of normal loading and low loading in Patent Document 1, taken using an atomic force microscope (AFM).

[0021] FIG. 3 is a schematic diagram showing how the ion conductor of the catalyst layer is prevented from contacting the microporous layer by a coating layer formed on a general loaded catalyst layer according to Example 1.

[0022] FIG. 4 is a schematic diagram showing that the ion conductor of the polymer electrolyte membrane and the catalyst layer is prevented from contacting the microporous layer by a coating layer formed on the low-loaded catalyst layer according to Example 2.

[0023] Figure 5 is a schematic diagram showing that the ion conductor of a general loaded catalyst layer according to Comparative Example 1 is exposed to and in contact with a microporous layer.

[0024] Figure 6 is a schematic diagram showing the ion conductor of the low-loaded catalyst layer according to Comparative Example 2 and the polymer electrolyte membrane exposed thereby coming into contact with the microporous layer.

[0025] Figure 7 is a graph showing the results of evaluating the IV characteristics of the membrane-electrode assemblies manufactured in Examples 1 and 2 and Comparative Examples 1 and 2.

[0026] 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.

[0027] As used herein, “combination thereof” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0028] 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.

[0029] In this specification, terms are used solely to distinguish one component from another. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0030] In this specification, the terms “first side” and “second side” are used only to identify different sides, and do not indicate the priority between the sides.

[0031]

[0032] Membrane-electrode assembly for electrolysis cell

[0033] FIG. 1 is a schematic drawing of a membrane-electrode assembly for a water electrolysis cell according to one embodiment. Referring to FIG. 1, the membrane-electrode assembly (200) is described below.

[0034] The above membrane-electrode assembly (200) includes a polymer electrolyte membrane (30), an oxygen generation electrode (10) positioned on one side of the polymer electrolyte membrane (30), and a hydrogen generation electrode (20) positioned on the other side of the polymer electrolyte membrane (30). The oxygen generation electrode may include a catalyst layer and a coating layer positioned on one side of the catalyst layer.

[0035] The catalyst layer has a first surface in contact with the polymer electrolyte membrane and a second surface facing the first surface, and the coating layer can be disposed on the second surface of the catalyst layer.

[0036] The catalyst layer includes a catalyst for oxygen evolution reaction and an ion conductor, as described below. The ion conductor may be randomly arranged and positioned on the surface of the catalyst particles and may be exposed on the surface of the catalyst layer. In this case, when the microporous layer described below is positioned on the second surface of the catalyst layer, the microporous layer may come into contact with the ion conductor exposed at the interface between the microporous layer and the catalyst layer, and a pinch-off effect due to a band bending phenomenon may occur. The band bending phenomenon due to the ion conductor exposed to the catalyst layer may occur regardless of the loading amount of the catalyst layer.

[0037] A membrane-electrode assembly according to one embodiment includes an oxygen generation electrode having a coating layer positioned on a second surface facing a first surface in contact with a polymer electrolyte membrane of a catalyst layer, thereby preventing contact between an ion conductor exposed on the surface of the catalyst layer and a microporous layer.

[0038] Fig. 2 is a photograph (a) taken using an AFM of the upper surface of the catalyst layer in the case of normal loading in Patent Document 1, and a photograph (b) taken using an AFM of the upper surface of the catalyst layer in the case of low loading. Referring to Fig. 2, it can be confirmed that in the case of normal loading, there is no region where the polymer electrolyte membrane is exposed, and in the case of low loading, there is a region where the polymer electrolyte membrane is exposed (membrane exposed) (the part indicated by ↓ in Fig. 2). As described above, the coating layer according to one embodiment can prevent contact with the ion conductor exposed on the surface of the catalyst layer regardless of the loading amount, as well as prevent contact with the polymer electrolyte membrane exposed through the opening in the case of low loading, as shown in Fig. 2(b). Here, in the case of low loading, the loading amount is 0.2 mg / cm 2 This means the following cases, and in the case of normal loading, 0.2 mg / cm2 Exceeding 1 mg / cm 2 It can mean less than.

[0039] Here, the catalyst layer refers to a region in the plane direction and thickness direction where the oxygen evolution reaction catalyst exists. The catalyst layer may exist in a continuous form on one side of the polymer electrolyte membrane, or may exist in a discontinuous form, depending on the loading amount. For example, in the case of normal loading, there is no region in the plane direction and thickness direction where the oxygen evolution reaction catalyst does not exist on one side of the polymer electrolyte membrane, and the catalyst layer may exist in a continuous form. On the other hand, in the case of low loading, there is a region in the plane direction and thickness direction where the oxygen evolution reaction catalyst does not exist on one side of the polymer electrolyte membrane, in which case the catalyst layer may exist in a discontinuous form.

[0040] The catalyst layer may further have an opening exposing the polymer electrolyte membrane to the second surface. In other words, as described above, in the case of low loading, the catalyst layer may exist in a discontinuous form, and may have an area on one surface of the polymer electrolyte membrane where the catalyst layer does not exist, 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 forming the catalyst layer, and may be formed, for example, in the case of low loading. In this case, the loading amount of the catalyst layer may satisfy the range of the loading amount in the case of low loading described above. The polymer electrolyte membrane may be exposed to the second surface of the catalyst layer through the opening.

[0041] The coating layer may also be disposed on the second side and opening of the catalyst layer to cover the exposed polymer electrolyte membrane. By disposing the coating layer on the second side and opening of the catalyst layer, when the microporous layer described below exists on the other side of the catalyst layer, contact between the microporous layer and the polymer electrolyte membrane can be blocked. Furthermore, since the composition for forming the catalyst layer is loaded low, parts where the catalyst layer and the microporous layer are not in contact due to the opening can be connected to each other by the coating layer to secure an electron transfer path.

[0042] The area of ​​the opening of the catalyst layer may be within a predetermined range relative to the total area of ​​the catalyst layer and the opening. For example, the lower limit of the area of ​​the opening of the catalyst layer may be approximately 0%, 5%, 10%, 15%, 20%, 25%, or 30% of the total area of ​​the catalyst layer, and the upper limit may be approximately 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, or 30%.

[0043] The area of ​​the opening of the catalyst layer may be greater than or equal to any one of the lower limits described above; 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. The area of ​​the opening may vary depending on the loading amount of the composition for forming the catalyst layer, and when the loading amount is small, the area of ​​the opening may increase, and when the loading amount is the general loading amount when forming the catalyst layer or greater, the area of ​​the opening may decrease or may be 0%.

[0044] Most of the area of ​​the catalyst layer may be covered with a coating layer. The area of ​​the catalyst layer refers to the area where the catalyst layer-forming composition is applied to form the catalyst layer. For example, the area of ​​the coating layer positioned on the catalyst layer may be within the range of 90% to 100% of the total area of ​​the catalyst layer.

[0045] Additionally, when the catalyst layer is low-loaded and the polymer electrolyte membrane has an opening where the catalyst layer is absent and exposed, most of the area of ​​the opening may also be covered with the coating layer. For example, the area of ​​the coating layer located at the opening of the catalyst layer may be within the range of 90% to 100% of the total area of ​​the opening of the catalyst layer.

[0046] That is, by positioning the coating layer with the above-described area on the catalyst layer and the opening, contact between the microporous layer described below and the ion conductor exposed on the surface of the catalyst layer, and the polymer electrolyte membrane exposed through the microporous layer and the opening can be blocked, thereby reducing the band bending phenomenon, thereby reducing the pinch-off effect, and improving the performance of the membrane-electrode assembly.

[0047] The above oxygen generation electrode (10) may have a first surface in contact with the polymer electrolyte membrane (30) and a second surface facing the first surface.

[0048] The membrane-electrode assembly for the above-mentioned electrolysis cell may further include a microporous layer (40), which may be positioned on the second surface of the oxygen generation electrode (10). The microporous layer (40) serves to enhance the reactant diffusion effect.

[0049] When the membrane-electrode assembly for the above-mentioned electrolytic cell further includes the microporous layer (40), the coating layer is positioned between the catalyst layer and the microporous layer (40), and when the catalyst layer further has an opening, the coating layer may be positioned between the polymer electrolyte membrane (30) and the microporous layer (40) at the opening of the catalyst layer.

[0050] The above-mentioned microporous layer (40) may be made of any material known in the art without limitation. For example, the above-mentioned microporous layer (40) may include a plurality of fibers. The plurality of fibers may be integrated into a nonwoven fabric form containing a large number of pores.

[0051] The above-mentioned plurality of fibers may include an inorganic material including carbon, silica, etc., which has excellent electrochemical properties and excellent heat resistance, a polymer such as polyimide, nylon, polypropylene, etc., a metal oxide, or a metal.

[0052] For example, the plurality of fibers may include a metal oxide or a metal.

[0053] For example, the plurality of fibers may include a metal including gold (Au), silver (Ag), iron (Fe), aluminum (Al), copper (Cu), stainless steel (SUS), titanium (Ti), tantalum (Ta), or a combination thereof; a metal oxide including titanium dioxide (TiO2), tungsten oxide (WO3), silicon oxide (SnO2), ruthenium oxide (RuO2), antimony tin oxide (ATO), indium tin oxide (ITO), manganese dioxide (MnO2), molybdenum trioxide (MoO3), or a combination thereof; or a combination thereof. The plurality of fibers may include, without limitation, known ones in addition to the listed metals or metal oxides.

[0054] The diameter and length of the plurality of fibers may be within a predetermined range. The diameter and length of the plurality of fibers can be measured by photographing the microporous layer using a scanning electron microscope (SEM).

[0055] For example, the diameter may be in the range of 5 μm to 100 μm. Additionally, the length may be in the range of 10 μm to 2 mm.

[0056] The above microporous layer (40) can have its thickness and porosity appropriately adjusted to ensure an appropriate diffusion effect of the reactant.

[0057] For example, the thickness of the microporous layer (40) may be within a predetermined range. The thickness of the microporous layer (40) may be measured according to a method for measuring the diameter and length of the plurality of fibers.

[0058] The thickness of the above microporous layer (40) may be in the range of 30 ㎛ to 500 ㎛.

[0059] Additionally, the porosity of the microporous layer (40) may be within a range of 30% to 80%. The porosity of the microporous layer (40) may be measured using a mercury intrusion porosimetry method.

[0060] The coating layer may include a metal or metal oxide that blocks contact between the microporous layer (40) and the ion conductor exposed on the surface of the catalyst layer, and the polymer electrolyte membrane (30) exposed through the microporous layer (40) and the opening of the catalyst layer, while not deteriorating the function of the polymer electrolyte membrane (30) and the catalyst layer. As the metal, a metal having high electrical conductivity and high corrosion resistance may be used. For example, the metal may include Ir, Au, Pt, Ru, Al, Mo, W, Ta, Rh, Re, Cu, or a combination thereof. The metal oxide may include indium tin oxide (ITO).

[0061] The coating layer may be continuous or discontinuous, and the coating layer may have an uneven shape following the shape of the catalyst particles on the surface of the catalyst layer.

[0062] The above coating layer may be formed relatively thinly, and the thickness of the coating layer may be significantly thinner than the thickness of the catalyst layer.

[0063] For example, the lower limit of the thickness of the catalyst layer may be about 3 ㎛, 3.5 ㎛, 4 ㎛, 4.5 ㎛, or 5 ㎛, and the upper limit may be about 25 ㎛, 20 ㎛, 15 ㎛, 10 ㎛, 9 ㎛, 8 ㎛, 7 ㎛, 6 ㎛, or 5 ㎛. The catalyst layer may have a range that is more than or exceeds any one of the lower limits described above; less than or equal to any one of the upper limits described above; or more than or exceeds any one of the lower limits described above and less than or equal to any one of the upper limits described above.

[0064] In addition, the lower limit of the thickness of the coating layer may be about 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, or 20 nm, and the upper limit may be about 1000 nm, 900 nm, 800 nm, 700 nm, 600 nm, 500 nm, 400 nm, 300 nm, 200 nm, 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, or 50 nm. The coating layer is more than or exceeds any one of the lower limits described above; or is less than or equal to any one of the upper limits described above; Or it may have a range that is 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.

[0065] By having the above catalyst layer and coating layer having a thickness within the above range, contact between the microporous layer (40) and the ion conductor exposed on the surface of the catalyst layer, and the microporous layer (40) and the polymer electrolyte membrane (30) exposed through the opening can be blocked, and accordingly, band bending can be reduced, thereby reducing the pinch-off effect, thereby improving the performance of the membrane-electrode assembly.

[0066] The coating layer may be formed to be thin and dense at the same time. Here, the meaning of the coating layer being dense may mean that there are almost no pores or no pores within the coating layer, and may be expressed as the porosity of the coating layer. For example, the porosity of the coating layer may be less than 10%, and for example, may be 5% or less, 2.5% or less, 1% or less, or 0%. The porosity of the coating layer may be measured using a mercury intrusion method.

[0067] In addition, the density of the coating layer is 1 g / cm2 30 g / cm 2 It can be 1.5 g / cm 2 28 g / cm 2 , 2 g / cm 2 26 g / cm 2 , or 2.5 g / cm 2 24 g / cm 2 The coating layer may have little or no pores therein, and the density of the coating layer may be the same as the theoretical density of the metal or metal oxide included in the coating layer.

[0068] When the porosity and density of the above coating layer satisfy the above range, the electrical conductivity can be excellent and electron movement can be facilitated.

[0069] The above coating layer can be manufactured according to a known method, and for example, can be formed by a sputtering method or a spraying method. When manufactured according to a sputtering method or a spraying method, a relatively thin, yet dense coating layer can be formed.

[0070] Below, the oxygen generation electrode, hydrogen generation electrode, and polymer electrolyte membrane are described.

[0071] 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 noble metal oxide.

[0072] The catalyst layer included in the oxygen generation electrode may include pores formed by a catalyst for oxygen generation reaction, and the ion conductor may be randomly present on the surface of the catalyst for oxygen generation reaction and within the catalyst layer. That is, the catalyst layer included in the oxygen generation 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 within the catalyst layer may be measured according to a mercury intrusion porosimetry method. When the porosity within the catalyst layer satisfies the above range, it can improve the polymer electrolyte membrane electrolysis performance by helping the transfer of reactants (H2O) and the removal of products (O2), and it is possible to secure optimal electrical conductivity. As described above, the coating layer according to one embodiment can be positioned on the surface of the catalyst layer without significantly affecting the porosity of the catalyst layer, thereby preventing contact between the microporous layer and the ion conductor exposed to the surface of the catalyst layer, and between the microporous layer and the polymer electrolyte membrane, thereby improving the performance of the membrane-electrode assembly.

[0073] 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.

[0074] 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, Sn, Ti, Te, Ta, Nb, Sb, Se, W, or a combination thereof, and x is an integer from 1 to 3), or may include a combination thereof.

[0075] 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.

[0076] 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.

[0077] For example, the carrier may be a metal oxide, and the carrier may be titanium dioxide (TiO2).

[0078] The above ion conductor is included to improve the adhesion of the catalyst layer and to transfer hydrogen ions.

[0079] The above ion conductor may include a cation exchanger to ensure ion conductivity.

[0080] 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.

[0081] The above ion conductor may be a fluorine-based ion conductor, a hydrocarbon-based ion conductor, or a mixture thereof.

[0082] 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.

[0083] 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.

[0084] According to one embodiment, the ion conductor may have hydrogen ion conductivity.

[0085] 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.

[0086] The content of the above ion conductor can be appropriately adjusted as needed.

[0087] For example, the lower limit of the content of the ion conductor relative to 100 parts by weight of the oxygen generation reaction catalyst may be about 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 may be about 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.

[0088] The ion conductor may have a range of at least or exceeding any one of the lower limits described above, relative to 100 parts by weight of the oxygen evolution reaction catalyst; or at most or exceeding any one of the upper limits described above, or at most or exceeding any one of the lower limits described above, and at most or less than any one of the upper limits described above. When the ion conductor is within the above range, the performance and durability are excellent.

[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 for the purpose of further improving 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 above hydrogen generation electrode may include a catalyst for hydrogen generation reaction. The above hydrogen generation reaction catalyst may include active particles and a carrier.

[0092] The above active particles may include a precious metal.

[0093] For example, the precious metal may be a platinum-based precious metal.

[0094] 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).

[0095] 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.

[0096] The above carrier may be a carbon-based carrier.

[0097] 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.

[0098] The above oxygen generation electrode and the above hydrogen generation electrode may each include only a catalyst layer including an oxygen generation reaction catalyst and a hydrogen generation reaction catalyst, but may include an electrode substrate together with the catalyst layer.

[0099] At this time, the electrode substrate can play a role in supporting the electrode and diffusing the fuel and oxidant to the catalyst layer.

[0100] 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.

[0101] 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 due to water generated during operation of the electrolysis cell.

[0102] 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.

[0103] The above polymer electrolyte membrane has an ion exchange function that moves hydrogen ions generated at an oxygen generation electrode to a catalyst for hydrogen generation reaction.

[0104] A polymer electrolyte membrane according to one embodiment may include a porous support including a plurality of pores, and an ion conductor filling the pores of the porous support.

[0105] The above porous support may be a fluorine-based support or a nano web support.

[0106] 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.

[0107] 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.

[0108] The above ion conductor is as described above.

[0109] The ion conductor included in the polymer electrolyte membrane may be the same as or different from the ion conductor included in the oxygen generation electrode. For example, the ion conductor included in the polymer electrolyte membrane may be the same as the ion conductor included in the oxygen generation electrode.

[0110]

[0111] Susan Haesel

[0112] A hydrolysis cell according to one embodiment may include the membrane-electrode assembly.

[0113] 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.

[0114] 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.

[0115]

[0116] Example 1

[0117] In normal propyl alcohol (nPA) as a solvent, commercial IrO x Black powder (Merck Sigma-Aldrich, Iridium(IV) oxide 206237) and Nafion as an ion conductor in a weight ratio of 1:0.2 (IrO x :Nafion) was mixed to form a catalyst layer for an oxygen generation electrode, and a solvent was added to make the solid content 5 wt% to prepare a composition for forming a catalyst layer for an oxygen generation electrode.

[0118] 2cm wide, 2cm long, active area 4cm 2 , and the loading amount is 0.5 mg / cm on the coating substrate film (PI advanced material, PI film) with a thickness of about 200 ㎛. 2To this end, the catalyst layer was formed by spray coating the composition for forming a catalyst layer for the oxygen generation electrode. At this time, the catalyst layer had a thickness of approximately 5 μm and a porosity of 35%. At this time, the catalyst layer did not have an opening through which the polymer electrolyte membrane was exposed.

[0119] A composition for forming a catalyst layer for a hydrogen generation electrode was prepared by mixing carbon of Pt / C with 50 wt% Pt loading and Nafion as an ion conductor in a weight ratio of 1:1.2, and adding the solvent so that the solid content was 5 wt%. The loading amount was 0.5 mg / cm on a coating substrate film (PI Advanced Materials, PI film) with a width of 2 cm, a length of 2 cm, and a thickness of about 200 ㎛. 2 To this end, the composition for forming a catalyst layer for the hydrogen generation electrode was spray-coated to form a hydrogen generation electrode having a thickness of approximately 30 μm.

[0120] The above oxygen generation electrode, the commercial NR212 polymer electrolyte membrane of Chemours with a thickness of about 50.8 ㎛, and the hydrogen generation electrode were sequentially overlapped and hot-pressed at 150°C for 5 minutes with 5N, and then the coating substrate film was removed to manufacture a membrane-electrode assembly.

[0121] A coating layer was formed on the catalyst layer of the oxygen generation electrode using a radio frequency (RF) magnetron sputtering machine VPA 21 of Aurion Anlagentechnik. Specifically, initially, 5.0×10 -3After exhausting to a pressure of 10 Pa to prevent contamination by the remaining gas, a borosilicate glass cover slip D263 from Duran Group with a width of 50 mm, a length of 50 mm, and a thickness of approximately 0.145 mm was used as a substrate. The membrane-electrode assembly was fixed on the substrate, and a circular flat iridium target with a purity of 99.9% was used. The target was positioned so that the distance between the substrates was 120 mm and the inclination angle was 40°. During deposition, the gas was argon gas with a flow rate of 50 sccm, the gas pressure was maintained at 0.25 Pa, and the RF power was 6 W at 300 in, and the deposition was performed for about 2.8 minutes at a deposition rate of 7 nm / min to a thickness of 20 nm, and the substrate was rotated at 8 rpm to form a dense coating layer with a thickness of 20 nm and a porosity of 0% on the catalyst layer of the oxygen evolution electrode.

[0122] A final membrane-electrode assembly was manufactured by laminating a microporous layer of Currento® PTL Ti-68 / 350 product from Bekaert on the oxygen generation electrode having the above-mentioned coating layer formed thereon. The microporous layer has a nonwoven fabric form in which multiple fibers made of titanium are integrated, and the porosity of the microporous layer was approximately 68% and its thickness was 350 μm.

[0123]

[0124] Example 2

[0125] When manufacturing the oxygen generation electrode of Example 1, the loading amount of the catalyst layer was 0.1 mg / cm 2 A membrane-electrode assembly was manufactured in substantially the same manner as in Example 1, except that the catalyst layer was formed to achieve this.

[0126] At this time, the thickness of the catalyst layer of the oxygen generation electrode was approximately 1.5 ㎛, the area of ​​the opening of the oxygen generation electrode was approximately 30% of the total area of ​​the catalyst layer and opening (same as the active area), and the porosity of the catalyst layer of the oxygen generation electrode was 47%.

[0127]

[0128] Comparative Example 1

[0129] A membrane-electrode assembly was manufactured in substantially the same manner as in Example 1, except that a coating layer was not formed during the manufacture of the oxygen generation electrode of Example 1.

[0130] At this time, the oxygen generation electrode contained only a catalyst layer with a thickness of about 5 ㎛ on one side of a polymer electrolyte membrane (Chemours, NR212) with a thickness of about 50.8 ㎛, and the porosity of the catalyst layer of the oxygen generation electrode was 35%.

[0131]

[0132] Comparative Example 2

[0133] When manufacturing the oxygen generation electrode of Comparative Example 1, the loading amount of the catalyst layer was 0.1 mg / cm 2 A membrane-electrode assembly was manufactured in substantially the same manner as in Comparative Example 1, except that a catalyst layer was formed.

[0134] At this time, the thickness of the catalyst layer of the oxygen generation electrode was approximately 1.5 ㎛, the area of ​​the opening of the oxygen generation electrode was approximately 30% of the total area of ​​the catalyst layer and opening (same as the active area), and the porosity of the catalyst layer of the oxygen generation electrode was 47%.

[0135]

[0136] Evaluation Example 1. IV Characteristics

[0137] The membrane-electrode assembly for a water electrolysis cell according to Examples 1 to 2 and Comparative Examples 1 to 2 was applied inside a unit cell designed and manufactured for a water electrolysis cell, and the voltage and resistance were measured at a specific current from 1 mA to 200 A under conditions of a cell temperature of 80°C, a water temperature of 80°C, and a flow rate of 5 ml / min, using a protocol for measuring the voltage and resistance, and the measurement was stopped at 2 V.

[0138] The result at this time is as shown in Fig. 7.

[0139]

[0140] conclusion

[0141] FIGS. 3 to 6 are schematic drawings of a polymer electrolyte membrane (1) - a catalyst layer (2) - a microporous layer (3) in a membrane-electrode assembly according to Examples 1 and 2 and Comparative Examples 1 and 2. Referring to FIGS. 3 to 6, the catalyst layer (2) of Example 1 and Comparative Example 1, in which the catalyst layer was formed with a general loading amount, does not have a portion where the polymer electrolyte membrane is exposed, i.e., an opening (A), unlike the catalyst layer (2) of Example 2 and Comparative Example 2, in which the catalyst layer was formed by loading a relatively small amount. In the case of Example 1 and Comparative Example 1, the possibility of the polymer electrolyte membrane (1) and the microporous layer (3) coming into contact is low. On the other hand, since an ion conductor (5) exposed on the surface of the catalyst layer exists regardless of the loading amount of the catalyst layer, in Examples 1 and 2 and Comparative Examples 1 and 2, the ion conductor (5) exposed on the surface of the catalyst layer (2) and the microporous layer (3) come into contact. In Example 1, unlike Comparative Example 1, a coating layer (4) is formed on the catalyst layer to suppress contact between the ion conductor (5) exposed on the surface of the catalyst layer and the microporous layer (3). In Example 2, unlike Comparative Example 2, a coating layer (5) is formed on the catalyst layer and the opening to suppress contact between the ion conductor (5) exposed on the surface of the catalyst layer and the microporous layer (3), as well as contact between the polymer electrolyte membrane (1) exposed through the opening and the microporous layer (3). Furthermore, the coating layer (4) serves to connect the catalyst layer that is not in contact with the microporous layer (3) to each other, thereby facilitating electron transfer. Here, the microporous layer is formed of a nonwoven fabric, and when enlarged, it should be understood as greatly enlarging one fiber forming the nonwoven fabric. In addition, the coating layer (4) is formed relatively thinly and densely as shown in FIGS. 3 and 4, and can be formed unevenly depending on the shape of the oxygen generation reaction catalyst (6) particles located on the surface of the catalyst layer.

[0142] This is explained in more detail with reference to Fig. 7. Referring to Fig. 7, the loading amount is 0.5 mg / cm 2Based on this, it can be confirmed that the membrane-electrode assembly of Example 1, which includes an oxygen generation electrode having a coating layer formed on a catalyst layer, exhibits improved performance by showing a higher current density at the same voltage compared to the membrane-electrode assembly of Comparative Example 1, which includes an oxygen generation electrode not including the coating layer.

[0143] Meanwhile, the loading amount was 0.1 mg / cm 2 Based on this, it can be confirmed that the membrane-electrode assembly of Example 2, which includes an oxygen generation electrode having a coating layer formed on a catalyst layer, exhibits improved performance by showing a higher current density at the same voltage compared to the membrane-electrode assembly of Comparative Example 2, which includes an oxygen generation electrode not including the coating layer.

[0144] This is because a relatively thin and dense coating layer is formed on the catalyst layer, preventing contact between the ion conductor and the microporous layer exposed on the surface of the catalyst layer, and the polymer electrolyte membrane and the microporous layer exposed through the opening when the catalyst layer has an opening, thereby exhibiting a high current density at the same voltage, which appears to improve performance.

[0145] In addition, the coating layer according to one embodiment is relatively thin and dense, so that when formed on the catalyst layer, it is formed in an uneven manner along the catalyst particles located on the surface of the catalyst layer and does not affect the pores inside the catalyst layer, so that it can contribute to improving performance without increasing the material transfer resistance of the catalyst layer.

[0146]

[0147] 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.

[0148] [Explanation of symbols]

[0149] 200: Membrane-electrode assembly for water electrolysis cell 10: Oxygen evolution electrode

[0150] 20: Hydrogen generation electrode 30: Polymer electrolyte membrane

[0151] 40: Microporous layer 1: Polymer electrolyte membrane

[0152] 2: Catalyst layer 3: Microporous layer

[0153] 4: Coating layer 5: Ionic conductor

[0154] 6: Catalyst for oxygen generation reaction A: Opening

Claims

1. Polymer electrolyte membrane; An oxygen generation electrode positioned on one side of the polymer electrolyte membrane; and A hydrogen generation electrode positioned on the other side of the polymer electrolyte membrane; The above oxygen generation electrode comprises a catalyst for oxygen generation reaction including active particles including a precious metal oxide, and a catalyst layer including an ion conductor; and A coating layer comprising a metal or metal oxide, located on one side of the catalyst layer; Membrane-electrode assembly for a water electrolysis cell.

2. In paragraph 1, The above catalyst layer has a first surface in contact with the polymer electrolyte membrane and a second surface facing the first surface, The above coating layer is disposed on the second surface of the catalyst layer, Membrane-electrode assembly for a water electrolysis cell.

3. In paragraph 2, The catalyst layer further has an opening exposing the polymer electrolyte membrane to the second surface, The above coating layer is also arranged in the above opening to cover the exposed polymer electrolyte membrane. Membrane-electrode assembly for a water electrolysis cell.

4. In paragraph 3, The area of ​​the coating layer positioned on the catalyst layer is within the range of 90% to 100% of the total area of ​​the catalyst layer, The area of ​​the coating layer located at the opening of the catalyst layer is within the range of 90% to 100% of the total area of ​​the opening of the catalyst layer. Membrane-electrode assembly for a water electrolysis cell.

5. In paragraph 3, The above oxygen generation electrode has a first surface in contact with the polymer electrolyte membrane and a second surface facing the first surface, The membrane electrode assembly for the above-mentioned water electrolysis cell further includes a microporous layer located on the second surface of the above-mentioned oxygen generation electrode. Membrane-electrode assembly for a water electrolysis cell.

6. In paragraph 5, The above coating layer is located between the catalyst layer and the microporous layer, In the opening of the above catalyst layer, the coating layer is located between the polymer electrolyte membrane and the microporous layer. Membrane-electrode assembly for a water electrolysis cell.

7. In paragraph 5, The above microporous layer is formed by integrating multiple fibers into a nonwoven fabric form containing a large number of pores. The above plurality of fibers include a metal including gold (Au), silver (Ag), iron (Fe), aluminum (Al), copper (Cu), stainless steel (SUS), titanium (Ti), tantalum (Ta), or a combination thereof; a metal oxide including titanium dioxide (TiO2), tungsten oxide (WO3), silicon oxide (SnO2), ruthenium oxide (RuO2), antimony tin oxide (ATO), indium tin oxide (ITO), manganese dioxide (MnO2), molybdenum trioxide (MoO3), or a combination thereof; or a combination thereof; Membrane-electrode assembly for a hydroelectric cell.

8. In paragraph 5, The diameter of the above plurality of fibers is in the range of 5 ㎛ to 100 ㎛, and the length is in the range of 10 ㎛ to 2 mm. Membrane-electrode assembly for a hydroelectric cell.

9. In paragraph 5, The thickness of the above microporous layer is in the range of 30 ㎛ to 500 ㎛, Membrane-electrode assembly for a hydroelectric cell.

10. In paragraph 5, The porosity of the above microporous layer is in the range of 30% to 80%. Membrane-electrode assembly for a hydroelectric cell.

11. In paragraph 1, The above metal includes Ir, Au, Pt, Ru, Al, Mo, W, Ta, Rh, Re, Cu, or a combination thereof, The above metal oxide includes indium tin oxide (ITO). Membrane-electrode assembly for a hydroelectric cell.

12. In paragraph 1, The above coating layer may be in a continuous form or in a discontinuous form. Membrane-electrode assembly for a hydroelectric cell.

13. In paragraph 1, The porosity of the above coating layer is less than 10%, The density of the above coating layer is 1 g / cm 2 Within 30 g / cm 2 person, Membrane-electrode assembly for a hydroelectric cell.

14. In paragraph 1, The thickness of the above catalyst layer is in the range of 3 ㎛ to 25 ㎛, The thickness of the above coating layer is in the range of 3 nm to 1000 nm. Membrane-electrode assembly for a hydroelectric cell.

15. In paragraph 1, The above precious 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 comprises Ru, Sn, Ti, Te, Ta, Nb, Sb, Se, W, or a combination thereof, and x is an integer from 1 to 3), or a combination thereof, Membrane-electrode assembly for a hydroelectric cell.

16. In paragraph 1, 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 hydroelectric cell.

17. In paragraph 1, The above ion conductor is included in the catalyst layer in an amount of 5 wt% or more, Membrane-electrode assembly for a hydroelectric cell.

18. In paragraph 1, The above hydrogen generation electrode Comprising a carbon-based carrier, and active particles supported on the carbon-based carrier and including a precious metal, Membrane-electrode assembly for a hydroelectric cell.

19. In paragraph 1, The polymer electrolyte membrane comprises a porous support including a plurality of pores, and an ion conductor filling the pores of the porous support. Membrane-electrode assembly for a hydroelectric cell.

20. A water electrolysis cell comprising a membrane electrode assembly according to paragraph 1.

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