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

Abstract

Provided is an electrode for a water electrolysis cell, the electrode comprising: a microporous layer; and a porous pattern layer positioned on one surface of the microporous layer. The porous pattern layer comprises: first patterns that extend in a first direction parallel to the one surface of the microporous layer and are arranged spaced apart in a second direction parallel to the one surface of the microporous layer and different from the first direction; and second patterns that extend in the second direction, are arranged spaced apart in the first direction, and intersect the first patterns, wherein the first patterns and the second patterns each include a plurality of stacked nanowires, and the nanowires include a metal oxide doped with fluorine.

Description

Electrode for electrolytic cell and method for manufacturing same, and membrane-electrode assembly for electrolytic cell and electrolytic cell including same

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

[0002] This research was supported by the Ministry of Trade, Industry and Energy (MOTIE) and the Korea Institute of Energy Technology Evaluation and Planning (KETEP). (Project ID: 20223030040220)

[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 categorized as gray, blue, and green hydrogen depending on its production method. Gray and blue hydrogen use fossil fuels, which generate carbon dioxide during production and pose the problem of not being able to completely eliminate it. Green hydrogen is produced through water electrolysis. Because it produces no carbon dioxide, it is attracting attention as the ultimate eco-friendly energy source. Water electrolysis technology is required to produce green hydrogen.

[0005] 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.

[0006] Conventional electrolysis cell electrodes suffer from problems such as mass transfer resistance and Schottky contact, which affect electrolysis performance depending on the electrode surface condition. To address these issues, a separate membrane is required; however, research into membranes with electrochemical corrosion resistance and conductivity is still needed.

[0007] Provides an electrode for a water electrolysis cell that can exhibit high electrochemical durability and conductivity even in a high-voltage and low-pH water electrolysis operating environment.

[0008] In one embodiment, an electrode for a water electrolysis cell is provided, comprising: a microporous layer; and a porous pattern layer positioned on one surface of the microporous layer; wherein the porous pattern layer includes first patterns extending in a first direction parallel to the one surface of the microporous layer and spaced apart from the one surface of the microporous layer in a second direction different from the first direction, and second patterns extending in the second direction and spaced apart from the first direction and intersecting the first patterns, wherein the first pattern and the second pattern each include a plurality of stacked nanowires, and the nanowires include a fluorine-doped metal oxide.

[0009] In another embodiment, a method for manufacturing an electrode for a water electrolysis cell is provided, comprising: (i) manufacturing a nanowire including a metal oxide; (ii) forming a porous pattern layer including a plurality of first patterns extending in a first direction and spaced apart from a second direction different from the first direction by radiating a solution in which the nanowires are dispersed onto a microporous layer and a plurality of second patterns extending in the second direction and spaced apart from the first direction and intersecting with the plurality of first patterns; (iii) forming a nanostructure by bonding the porous pattern layer to a microporous layer; and (iv) mixing the nanostructure and a fluorine precursor and then performing a heat treatment.

[0010] In another embodiment, a membrane-electrode assembly for a water electrolysis cell is provided, comprising: a polymer electrolyte membrane; an oxygen generation electrode positioned on one side of the polymer electrolyte membrane and including an electrode for the water electrolysis cell; and a hydrogen generation electrode positioned on the other side of the polymer electrolyte membrane.

[0011] In another embodiment, a water electrolysis cell comprising a membrane-electrode assembly for the water electrolysis cell is provided.

[0012] An electrode for a water electrolysis cell according to an embodiment of the present invention can exhibit high electrochemical durability and conductivity even in a high-voltage and low-pH water electrolysis operating environment.

[0013] Figure 1 is an exploded perspective view showing an electrode for a water electrolysis cell according to one embodiment.

[0014] Figures 2 and 3 are drawings showing a method for manufacturing an electrode for a water electrolysis cell according to one embodiment.

[0015] Figure 4 is a diagram showing the corresponding equivalent circuit used for fitting the EIS obtained at 1.5 V and 1.9 V.

[0016] Figure 5 is a diagram showing the electrolysis performance of a membrane-electrode assembly according to one embodiment.

[0017] Below, specific implementation examples are described in detail to facilitate their implementation by those skilled in the art. However, the present invention may be implemented in various different forms and is not limited to the implementation examples described herein.

[0018] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0019] “Combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0020] It should be understood that terms such as "include," "comprise," or "have" 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.

[0021] To clearly illustrate various layers and regions in the drawings, their thicknesses are enlarged, and similar parts are designated by the same drawing reference numerals throughout the specification. When an element such as a layer, film, region, or plate is said to be "over" or "on" another element, this includes not only the case where it is "directly over" the other element, but also the case where there are other elements in between. Conversely, when an element is said to be "directly over" another element, it means that there are no other elements in between.

[0022] “Layer” includes not only shapes formed on the entire surface when observed in a plan view, but also shapes formed on some surfaces.

[0023] The average particle size can be measured by methods well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with transmission electron microscope images or scanning electron microscope images. Alternatively, the average particle size can be obtained by measuring using dynamic light scattering, performing data analysis, counting the number of particles for each particle size range, and calculating from the counted number. Unless otherwise defined, the average particle size is the diameter (D) of the particles in the particle size distribution that have a cumulative volume of 50% by volume. 50 ) can mean. In addition, unless otherwise defined, the average particle size is obtained by measuring the size (diameter or length of major axis) of about 20 particles randomly in a scanning electron microscope image to obtain a particle size distribution, and the diameter (D) of the particle having a cumulative volume of 50% by volume in the particle size distribution 50 ) may be taken as the average particle diameter.

[0024] “Or” is not interpreted as exclusive, for example, “A or B” is interpreted as including A, B, A+B, etc.

[0025] “Metal” is interpreted as a concept that includes common metals, transition metals, and metalloids (semi-metals).

[0026] Electrode for electrolysis cell

[0027] Fig. 1 is an exploded perspective view showing an electrode (200) for a water electrolysis cell according to one embodiment. Hereinafter, the electrode for a water electrolysis cell will be described with reference to Fig. 1.

[0028] Microporous layer (230)

[0029] An electrode for a water electrolysis cell according to one embodiment includes a microporous layer, and the microporous layer may be formed by integrating a plurality of fibers in the form of a nonwoven fabric including a plurality of pores.

[0030] A microporous layer, also commonly known as a porous transport layer (PTL), is applied to a water electrolysis cell to bring reactant water to a polymer electrolyte membrane (PEM) while guiding the products back away from the PEM, and to collect and transport electrons generated by the electrochemical reaction. To maximize the function of this microporous layer, various physical properties such as corrosion resistance, electrical conductivity, diffusivity, and mechanical strength are required, and the microporous layer may include Ti, Ni, Zr, Hf, or a combination thereof.

[0031] The length of the fiber can be adjusted without limitation within the range of the active area of ​​the electrode for the electrolysis cell. In addition, the diameter of the fiber can be 10 μm to 70 μm, for example, 12 μm to 65 μm, 13 μm to 60 μm, or 14 μm to 50 μm. When the fiber has a length and diameter within the above range, it can efficiently collect and transfer substances or electrons that react in the electrolysis cell.

[0032] The thickness of the microporous layer included in the electrode for the electrolysis cell according to one embodiment may be 100 ㎛ to 2,000 ㎛, for example, 150 ㎛ to 500 ㎛, 170 ㎛ to 290 ㎛, or 200 ㎛ to 250 ㎛. Here, the thickness of the coating layer may be measured, for example, through FIB, SEM, TEM, TOF-SIMS, XPS, or EDS analysis. When the thickness of the microporous layer is within the above range, it can play a role in efficiently collecting and transmitting substances or electrons that react in the electrolysis cell.

[0033] The porosity of the microporous layer included in the electrode for the electrolysis cell according to one embodiment may be 30% to 90%, for example, 35% to 85%, 45% to 80%, or 50% to 80%. When the porosity of the microporous layer is within the above range, it can play a role in efficiently collecting and transferring substances or electrons that react in the electrolysis cell.

[0034] Porous pattern layer (220)

[0035] An electrode for a water electrolysis cell according to one embodiment includes a microporous layer; and a porous pattern layer positioned on one surface of the microporous layer; wherein the porous pattern layer includes first patterns extending in a first direction parallel to the one surface of the microporous layer and spaced apart from the one surface of the microporous layer in a second direction different from the first direction, and second patterns extending in the second direction and spaced apart from the first direction and intersecting with the first patterns. In this case, each of the first patterns and the second patterns may be included in multiple numbers.

[0036] In one embodiment, the first direction may be parallel to the longitudinal direction of one side of the microporous layer, and the longitudinal direction of one side of the microporous layer may mean a surface direction that is perpendicular to the thickness direction of one side of the microporous layer. The second direction may be parallel to the longitudinal direction of one side of the catalyst layer, and the longitudinal direction of one side of the catalyst layer may mean a surface direction that is perpendicular to the thickness direction of one side of the catalyst layer. In this case, the second direction is a different direction from the first direction, and as an example of the second direction, the second direction and the first direction may be perpendicular to each other.

[0037] The extension length of the first pattern in the first direction can be adjusted without limitation within the range of the active area of ​​the electrode for the electrolysis cell. In addition, the width of the first pattern in the second direction can be 0.2 μm to 5 μm, for example, 0.3 μm to 3 μm, 0.4 μm to 2 μm, or 0.5 μm to 2 μm. In addition, the separation distance of the first pattern in the second direction can be 0.5 μm to 20 μm, for example, 1 μm to 15 μm, or 1.5 μm to 8 μm. In addition, the thickness in the third direction perpendicular to one surface of the microporous layer of the first pattern may be 0.5 ㎛ to 10 ㎛, for example, 0.5 ㎛ to 7.5 ㎛, 0.5 ㎛ to 5 ㎛, or 0.5 ㎛ to 2.5 ㎛. When the first pattern has the extended length, width, separation distance, and thickness in the above ranges, the desorption and discharge of oxygen generated during the electrolysis reaction can be facilitated, thereby lowering the mass transfer resistance, and thus, there is an advantage of reducing performance degradation at high voltage.

[0038] The extension length of the second pattern in the second direction can be adjusted without limitation within the range of the active area of ​​the electrode for the electrolysis cell. In addition, the width of the second pattern in the first direction can be 0.2 μm to 5 μm, for example, 0.3 μm to 3 μm, 0.4 μm to 2 μm, or 0.5 μm to 2 μm. In addition, the separation distance of the second pattern in the first direction can be 0.5 μm to 20 μm, for example, 1 μm to 15 μm, or 1.5 μm to 10 μm. In addition, the thickness in the third direction perpendicular to one surface of the microporous layer of the second pattern may be 0.5 ㎛ to 10 ㎛, for example, 0.5 ㎛ to 7.5 ㎛, 0.5 ㎛ to 5 ㎛, or 0.5 ㎛ to 2.5 ㎛. When the second pattern has the extended length, width, separation distance, and thickness in the above ranges, the desorption and discharge of oxygen generated during the electrolysis reaction can be facilitated, thereby lowering the mass transfer resistance, and thus, there is an advantage of reducing performance degradation at high voltage.

[0039] One end of the first pattern may be connected to one end of another first pattern that is spaced apart from one side in the second direction, and the other end of the first pattern may be connected to one end of another first pattern that is spaced apart from the other side in the second direction. In addition, one end of the second pattern may be connected to one end of another second pattern that is spaced apart from one side in the first direction, and the other end of the second pattern may be connected to one end of another second pattern that is spaced apart from the other side in the first direction. That is, the first pattern may have a continuously cross-aligned shape. In addition, the second pattern may have a continuously cross-aligned shape. Consequently, the porous pattern layer may have a mesh shape in which the plurality of first patterns and the plurality of second patterns intersect.

[0040] According to one embodiment, the first pattern and the second pattern included in the porous pattern layer included in the electrode for the electrolysis cell each include a plurality of stacked nanowires, and the nanowires include a metal oxide doped with fluorine.

[0041] The metal may include, for example, tungsten (W), titanium (Ti), nickel (Ni), ruthenium (Ru), tantalum (Ta), tin (Sn), cobalt (Co), or a combination thereof. Accordingly, the metal oxide may include tungsten oxide, titanium oxide, nickel oxide, ruthenium oxide, tantalum oxide, tin oxide, cobalt oxide, or a combination thereof, and more specifically, may include tin oxide. In addition, the metal oxide is characterized by being doped with fluorine, and since the fluorine-doped metal oxide is included in the nanowire, the bonding force with the metal oxide is improved and the aspect ratio of the metal oxide is increased, so that the metal of the doped material or the metal oxide is prevented from being eluted in the electrolysis operating environment, thereby deteriorating the membrane electrode performance, and there is an advantage of increasing durability.

[0042] In one embodiment, the fluorine content relative to 100 at% of the total components measured by X-ray photoelectron spectroscopy (XPS) in the entire fluorine-doped metal oxide may be 1 at% to 10 at%, for example, 5 at% to 10 at%, or 8 at% to 10 at%. When the fluorine content in the entire fluorine-doped metal oxide satisfies the above range, uniform fluorine doping becomes possible, thereby reducing the sheet resistance of the electrode and improving the performance of the electrolysis cell.

[0043] The length of the nanowire may be 1 μm to 500 μm, for example, 3 μm to 400 μm, 5 μm to 300 μm, or 10 μm to 100 μm. In addition, the diameter of the nanowire may be 0.1 μm to 1 μm, for example, 0.1 μm to 0.9 μm, or 0.2 μm to 0.8 μm. When the nanowire has a length and diameter in the above range, the electrical conductivity is improved due to the networking of the metal oxide particles, which has the advantage of reducing the contact resistance.

[0044] The thickness of the porous pattern layer included in the electrode for the electrolysis cell according to one embodiment may be 0.5 ㎛ to 10 ㎛, for example, 1 ㎛ to 8 ㎛, 1 ㎛ to 6 ㎛, or 1 ㎛ to 4 ㎛. Here, the thickness of the porous pattern layer may be measured, for example, through FIB, SEM, TEM, TOF-SIMS, XPS, or EDS analysis. When the thickness of the porous pattern layer is within the above range, the desorption and release of oxygen generated during the electrolysis reaction can be facilitated, thereby lowering the mass transfer resistance, and thus, there is an advantage of reducing performance degradation at high voltage.

[0045] The porosity of the porous pattern layer included in the electrode for the electrolysis cell according to one embodiment may be 30% to 95%, for example, 35% to 90%, or 45% to 85%. When the porosity of the porous pattern layer is within the above range, the desorption and discharge of oxygen generated during the electrolysis reaction can be facilitated, thereby reducing the mass transfer resistance, and thus, there is an advantage of reducing performance degradation at high voltage.

[0046] catalyst layer (210)

[0047] An electrode for a water electrolysis cell according to one embodiment may further include a catalyst layer including active particles including a precious metal oxide and an ion conductor, located on one surface of the porous pattern layer.

[0048] The above precious metal may be a non-platinum based precious metal, and for example, the non-platinum based precious metal may include palladium (Pd), ruthenium (Ru), iridium (Ir), an alloy thereof, or a combination thereof. The precious metal oxide according to one embodiment is IrO x (x is an integer from 1 to 3), RuO x (x is an integer from 1 to 3), PdO x (x is an integer from 1 to 3), IrMO x (M includes Ru, Sn, Ti, Te, Nb, or a combination thereof, and x is an integer from 1 to 3), or a combination thereof, and more specifically, IrO x (x is an integer from 1 to 3). When the noble metal oxide is included in the catalyst layer, there is an advantage of exhibiting high catalytic activity.

[0049] The electrode for the above-mentioned electrolysis cell may further include an ion conductor to improve the adhesion of the catalyst and to transfer hydrogen ions, and the ion conductor may include a cation exchanger to secure ion conductivity.

[0050] 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.

[0051] The above ion conductor may be a fluorine-based ion conductor, a hydrocarbon-based ion conductor, or a mixture thereof. 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, such as poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), etc. 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,It may be sulfonated polyarylene ether, sulfonated polyarylene ether nitrile, sulfonated polyarylene ether ether nitrile, sulfonated polyarylene ether sulfone ketone, etc.

[0052] The ion conductor according to one embodiment may have hydrogen ion conductivity. The ion conductor having the hydrogen ion conductivity may also have H substituted with Na, K, Li, Cs or tetrabutylammonium in the cation exchanger at the end of the side chain. When H is substituted 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 H is substituted with tetrabutylammonium, tetrabutylammonium hydroxide is used. K, Li or Cs may also be substituted using an appropriate compound. Since this substitution method is widely known in the art, a detailed description thereof will be omitted.

[0053] The above ion conductor can be used as a single substance or in the form of a mixture, and can also be optionally used together with a non-conductive compound for the purpose of further improving adhesion to a polymer electrolyte membrane. The content of the non-conductive compound can be appropriately adjusted depending on the intended use. As the 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.

[0054] In one embodiment, with respect to 100 wt% of the total active particles and ion conductors including the noble metal oxide, the active particles including the noble metal oxide may be included in an amount of 90 wt% to 99.5 wt%, for example, 91 wt% to 99 wt%, or 92 wt% to 98 wt%. In addition, with respect to 100 wt% of the total active particles and ion conductors including the noble metal oxide, the ion conductor may be included in an amount of 0.5 wt% to 10 wt%, for example, 1 wt% to 9 wt%, or 2 wt% to 8 wt%. When the content of the active particles and ion conductors including the noble metal oxide is within the above range, the catalyst including them may form a conductive network to reduce the sheet resistance of an electrode and improve the performance of a water electrolysis cell.

[0055] Method for manufacturing electrodes for electrolysis cells

[0056] A method for manufacturing an electrode for a water electrolysis cell according to one embodiment includes: (i) a step of manufacturing a nanowire including a metal oxide; (ii) a step of forming a porous pattern layer including a plurality of first patterns extending in a first direction and spaced apart from a second direction different from the first direction by radiating a solution in which the nanowire is dispersed onto a microporous layer and a plurality of second patterns extending in the second direction, spaced apart from the first direction, and intersecting with the plurality of first patterns; (iii) a step of forming a nanostructure by bonding the porous pattern layer to a microporous layer; and (iv) a step of mixing the nanostructure and a fluorine precursor and then performing a heat treatment.

[0057] In one embodiment, the step (i) may be performed according to a manufacturing method such as a hydrothermal synthesis method, an electrospinning synthesis method, an electroplating method, etc., and more specifically, may be performed according to an electrospinning synthesis method. More specifically, a metal oxide precursor may be mixed with a predetermined solvent to prepare a spinning solution, and the spinning solution may be electrospun onto a collector plate and then heat-treated to produce a nanowire including a metal oxide.

[0058] The above metal oxide precursor refers to a material that is a previous step of a metal oxide. The type of the metal oxide may be tungsten oxide, titanium oxide, nickel oxide, ruthenium oxide, tantalum oxide, tin oxide, cobalt oxide, or a combination thereof, and preferably tin oxide (SnO2). Accordingly, the type of the metal oxide precursor is not limited as long as it can produce the final product, SnO2. For example, the metal oxide precursor may be tin ethoxide, tin butoxide, tin isopropoxide, SnCl2, SnCl2·2H2O, SnCl2·5H2O, Sn(OH)4, or Sn(SO4)2, and more specifically, SnCl2 may be used.

[0059] The solvent is not limited in type as long as it can dissolve the metal oxide precursor. For example, the solvent may include water, alcohol, dimethylformamide (DMF), or a combination thereof, and the alcohol may include methanol, ethanol, butanol, or isopropanol.

[0060] The solution in which the metal oxide precursor is mixed with a solvent may further include a dispersant, and the dispersant may include polyvinylpyrrolidone (PVP).

[0061] FIG. 2 and FIG. 3 are drawings showing a method for manufacturing an electrode for a water electrolysis cell according to one embodiment. As in FIG. 2, the solution in which the nanowires of step (ii) are dispersed is sprayed onto a microporous layer to form one layer of a first pattern extending in the first direction and spaced apart in the second direction, and then, as in FIG. 3, the collector plate is rotated by 90° and one layer of a second pattern is formed extending in the second direction and spaced apart in the first direction, and then the process as in FIG. 2 and FIG. 3 is repeated to sequentially stack the first pattern and the second pattern to manufacture a porous pattern layer.

[0062] In one embodiment, in the step of radiating the solution in which the nanowires are dispersed in step (ii) onto the microporous layer, the extension length of the first pattern in the first direction can be adjusted without limitation as long as it is within the range of the active area of ​​the electrode for the electrolysis cell. In addition, the width of the first pattern in the second direction may be 0.2 μm to 5 μm, for example, 0.3 μm to 3 μm, 0.4 μm to 2 μm, or 0.5 μm to 2 μm. In addition, the separation distance of the first pattern in the second direction may be 0.5 μm to 20 μm, for example, 1 μm to 15 μm, or 1.5 μm to 10 μm. Additionally, the thickness in the third direction perpendicular to one side of the microporous layer of the first pattern may be 0.5 µm to 10 µm, for example, 0.5 µm to 7.5 µm, 0.5 µm to 5 µm, or 0.5 µm to 2.5 µm.

[0063] The extension length of the second pattern in the second direction can be adjusted without limitation within the range of the active area of ​​the electrode for the electrolysis cell. In addition, the width of the second pattern in the first direction can be 0.2 μm to 5 μm, for example, 0.3 μm to 3 μm, 0.4 μm to 2 μm, or 0.5 μm to 2 μm. In addition, the separation distance of the second pattern in the first direction can be 0.5 μm to 20 μm, for example, 1 μm to 15 μm, or 1.5 μm to 10 μm. Additionally, the thickness in the third direction perpendicular to one side of the microporous layer of the second pattern may be 0.5 µm to 10 µm, for example, 0.5 µm to 7.5 µm, 0.5 µm to 5 µm, or 0.5 µm to 2.5 µm.

[0064] In one embodiment, in step (iii), a first heat treatment process may be performed to bond the porous pattern layer to the microporous layer. The first heat treatment may be performed in an air atmosphere, and the first heat treatment temperature may be 400°C to 600°C, 410°C to 590°C, 420°C to 580°C, 430°C to 570°C, 440°C to 560°C, or 450°C to 550°C, and the first heat treatment time may be 4 hours to 8 hours, or 5 hours to 7 hours.

[0065] In one embodiment, in the step (iv), the type of the fluorine precursor may include at least one material selected from the group consisting of NH4F and NH4HF2, and preferably NH4F. At this time, the molar ratio of the nanostructure and the fluorine precursor may be included as 1:0.1 to 1:20, for example, 1:0.5 to 1:20, 1:1 to 1:20, 1:3 to 1:20, 1:8 to 1:20, 1:13 to 1:20, or 1:18 to 1:20. When the molar ratio of the nanostructure and the fluorine precursor is included in the above range, the amount of fluorine to be doped can be easily controlled, making it possible to uniformly dope with fluorine, thereby reducing the sheet resistance of the electrode and improving the performance of the electrolysis cell.

[0066] After the mixing process of the above nanostructure and fluorine precursor is performed, a second heat treatment process may be performed. The second heat treatment may be performed in an inert gas atmosphere, the second heat treatment temperature may be 80°C to 450°C, 100°C to 430°C, or 120°C to 400°C, and the second heat treatment time may be 4 hours to 8 hours, 4.5 hours to 7.5 hours, or 5 hours to 7 hours.

[0067] The above fluorine precursor may be in a solid state, and the solid fluorine precursor may be vaporized through a second heat treatment to dope the nanowire containing the one-dimensional metal oxide. With a typical solution-based synthesis method, there is a problem in that it is difficult to control the amount of fluorine doping. However, when a solid fluorine precursor is used, the amount of fluorine doping can be easily controlled, and agglomeration can be suppressed during the process of doping fluorine into the nanowire containing the metal oxide, thereby synthesizing uniform particles.

[0068] Membrane-electrode assembly for electrolysis cell

[0069] A membrane-electrode assembly for a water electrolysis cell according to one embodiment comprises a polymer electrolyte membrane, an oxygen generation electrode positioned on one side of the polymer electrolyte membrane and including an electrode for the water electrolysis cell, and a hydrogen generation electrode positioned on the other side of the polymer electrolyte membrane.

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

[0071] oxygen generation electrode

[0072] The oxygen evolution electrode refers to an electrode where an oxygen evolution reaction (OER) occurs, and the oxygen evolution electrode includes the electrode for the water electrolysis cell described above. Since the electrode for the water electrolysis cell has been described above, a detailed description thereof will be omitted.

[0073] hydrogen generation electrode

[0074] A hydrogen evolution electrode refers to an electrode where a hydrogen evolution reaction (HER) occurs, and 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 carrier, and the active particles may include a precious metal, and the precious metal may be a platinum-based precious metal.

[0075] 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).

[0076] 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.

[0077] The above-mentioned carrier may be a carbon-based carrier. 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.

[0078] The above oxygen generation electrode and the hydrogen generation electrode may each include only a catalyst layer including an oxygen generation reaction catalyst and a hydrogen generation reaction catalyst, but may also include an electrode substrate together with the catalyst layer. At this time, the electrode substrate may serve to support the electrode and diffuse the fuel and oxidant to the catalyst layer. The electrode substrate is not specifically limited and any known electrode substrate may be used, 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 on which a metal film is formed on the surface) that can be used as a conductive substrate may be used. The electrode substrate may be one that has been water-repellent treated with a fluorine-based resin, in which case, the reactant diffusion efficiency may be prevented from being reduced by water generated during operation of the water electrolysis cell. 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.

[0079] polymer electrolyte membrane

[0080] A polymer electrolyte membrane has an ion exchange function that transfers hydrogen ions generated at an oxygen generation electrode to a hydrogen generation reaction catalyst. According to one embodiment, a polymer electrolyte membrane may include a porous support including a plurality of pores, and an ion conductor filling the pores of the porous support.

[0081] The porous support may be a fluorinated support or a nanoweb support. The fluorinated 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.

[0082] The fluorinated support may include a perfluorinated polymer. The porous support may correspond to a more porous and stronger porous support obtained by extruding dispersion polymerized PTFE into a tape in the presence of a lubricant and stretching the material obtained thereby. In addition, the amorphous content of the PTFE may be increased by heat treating the e-PTFE at a temperature exceeding the melting point of the PTFE (about 342°C). The e-PTFE film manufactured by the method may have micropores with various diameters and a porosity. The e-PTFE film manufactured by the method may have at least 35% pores, and the diameter of the micropores may be about 0.01 to 1 μm (micrometer).

[0083] The above nano web support may be a non-woven fibrous web composed of a plurality of randomly oriented fibers. The non-woven fibrous web refers to a sheet having a structure of individual fibers or filaments that are interlaid, but not in the same manner as a woven fabric. The non-woven fibrous web may be manufactured by carding, garnetting, air-laying, wet-laying, melt blowing, spun bonding, or stitch bonding.

[0084] The fibers may comprise one or more polymeric materials, and any material that is generally used as a fiber-forming polymeric material may be used, and specifically, a hydrocarbon-based fiber-forming polymeric material may be used. For example, the fiber-forming polymeric material may comprise a polyolefin such as polybutylene, polypropylene, and polyethylene, a polyester such as polyethylene terephthalate and polybutylene terephthalate, a polyamide (nylon-6 and nylon-6,6), a polyurethane polybutene, polylactic acid, polyvinyl alcohol, polyphenylene sulfide, polysulfone, a fluid crystalline polymer, polyethylene-co-vinylacetate, polyacrylonitrile, a cyclic polyolefin, polyoxymethylene, a polyolefin-based thermoplastic elastomer, or a combination thereof.

[0085] 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.

[0086] The above nanofibers exhibit excellent chemical resistance and have hydrophobicity, so hydrocarbon polymers that are free from moisture-induced deformation in high-humidity environments can be preferably used. Specifically, the hydrocarbon polymers may include nylon, polyimide, polyaramid, polyetherimide, polyacrylonitrile, polyaniline, polyethylene oxide, polyethylene naphthalate, polybutylene terephthalate, styrene butadiene rubber, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyvinylidene fluoride, polyvinyl butylene, polyurethane, polybenzoxazole, polybenzimidazole, polyamideimide, polyethylene terephthalate, polyphenylene sulfide, polyethylene, polypropylene, copolymers thereof, or mixtures thereof.

[0087] The above nanoweb support is an aggregate of nanofibers manufactured by electrospinning and randomly arranged. At this time, the nanofibers may have an average diameter of 40 nm to 5000 nm when the average diameter of 50 fibers is measured using a scanning electron microscope (JSM6700F, JEOL) and calculated from the average, taking into account the porosity and thickness of the nanoweb. When the average diameter of the nanofibers is within the above range, the mechanical strength is excellent and an appropriate porosity can be secured.

[0088] The thickness of the nonwoven fibrous web may be 10 ㎛ to 50 ㎛ or 15 ㎛ to 43 ㎛. When the thickness of the nonwoven fibrous web is within the above range, the mechanical strength, weight reduction, and integration may be excellent. The nonwoven fibrous web may have a basic weight of 5 to 30 mg / cm. 2 It can be. If the basis weight of the nonwoven fibrous web is less than the above numerical range, visible pores may be formed, making it difficult to function as a porous support, and if it exceeds the above numerical range, it may be manufactured in the form of paper or fabric in which pores are hardly formed. The porosity can be calculated by the ratio of the air volume in the porous support to the total volume of the porous support according to the following mathematical formula 1. At this time, the total volume is calculated by manufacturing a rectangular sample and measuring the width, length, and thickness, and the air volume can be obtained by measuring the mass of the sample and then subtracting the polymer volume calculated inversely from the density from the total volume.

[0089] [Mathematical Formula 1]

[0090] Porosity (%) = (air volume in porous support / total volume of porous support) X 100

[0091] For example, the porosity of the porous support may be 30 to 90%. When the porosity of the porous support is within the above range, problems such as a decrease in the impregnation property of the ion conductor or a problem of post-processing not proceeding smoothly due to a decrease in stability may not occur.

[0092] The above ion conductor is as described above. 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.

[0093] Susan Haesel

[0094] In one embodiment, the electrolysis cell comprises a membrane-electrode assembly for the electrolysis cell.

[0095] 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.

[0096] Hereinafter, examples and comparative examples of the present invention are described. The following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples.

[0097] Example 1

[0098] 1. Manufacturing of microporous layer

[0099] The microporous layer uses a titanium microporous layer (PTL (Porous Transfer Layer)) from BEKART, with a thickness of 250 ㎛ and a weight of 450 g / m. 2 , a porous pattern layer was manufactured on a 2GDL09N product having a porosity of 60%.

[0100] 2. Manufacturing of porous pattern layers

[0101] A spinning solution was prepared by adding 0.5 g of SnCl2 to 4 g of a solution containing dimethylformamide (DMF) and ethanol in a weight ratio of 1:1, mixing them evenly for 30 minutes, and then adding 0.5 g of polyvinylpyrrolidone (PVP). The spinning solution was injected into a syringe, and then spun onto a microporous layer (230) at a flow rate of 1.2 ml / hr and a voltage of 12 kV using a syringe pump to produce a nonwoven film. As shown in Fig. 2, a first pattern was formed on the microporous layer (230) on a moving bed moving at a constant speed. The first pattern had a width of 1 μm in the second direction, a separation distance of 10 μm between the first patterns in the second direction, and a porous pattern layer having a thickness of 1 μm was produced. After the first pattern was irradiated, as shown in Fig. 3, the moving bed was rotated 90° and then moved at a constant speed to form a second pattern. The second pattern had a width of 1 μm in the second direction, a separation distance of 10 μm from the first pattern in the second direction, and a thickness of 1 μm. The microporous layer (230) and the porous pattern layer formed on the microporous layer were heat-treated at 500°C for 6 hours in an air atmosphere.

[0102] A porous pattern layer including the manufactured SnO2 nanowires was mixed with NH4F as a fluorine precursor, and then heat-treated at a temperature of 400°C for 6 hours in an inert gas atmosphere, washed with ethanol and distilled water, and dried at a temperature of 60°C for 12 hours to manufacture a porous pattern layer including fluorine-doped SnO2 nanowires.

[0103] 3. Preparation of catalyst layer

[0104] IrO xA catalyst composition for oxygen generation reaction was prepared by mixing and dispersing a catalyst and ionomer solution so that the ionomer / catalyst ratio was 0.3, followed by stirring for 24 hours. The catalyst composition for oxygen generation reaction is referred to as the first catalyst composition. The first catalyst composition was thinly applied to a transfer substrate by spraying, decaling, or ultrasonic spray coating to prepare a catalyst layer, and the catalyst layer is referred to as the first electrode layer.

[0105] 4. Manufacturing of membrane-electrode assemblies for water electrolysis

[0106] A second catalyst composition was prepared by mixing a catalyst containing 46 wt% of platinum particles on a graphitized carrier and an ionomer solution such that the ionomer / carbon ratio was 1.0. The second catalyst composition was applied to a transfer substrate to prepare a second electrode layer, and then a first electrode layer including the porous pattern layer was attached to one side of a polymer electrolyte membrane, and the second electrode layer was attached to the opposite side to bond them together, thereby preparing a membrane-electrode assembly.

[0107] Example 2

[0108] In the manufacture of the porous pattern layer, a membrane-electrode assembly for a water electrolysis cell was manufactured in substantially the same manner as in Example 1, except that the thickness of the porous pattern layer was designed to be 10 μm.

[0109] Example 3

[0110] In the manufacture of the porous pattern layer, a membrane-electrode assembly for a water electrolysis cell was manufactured in substantially the same manner as in Example 1, except that the spacing between the porous pattern layers was designed to be 5 μm.

[0111] Comparative Example 1

[0112] A membrane-electrode assembly for a water electrolysis cell was manufactured in substantially the same manner as in Example 1, except that the porous pattern layer was not manufactured in Example 1.

[0113] Comparative Example 2

[0114] In the manufacture of nanowires, a membrane-electrode assembly for a water electrolysis cell was manufactured in substantially the same manner as in Example 1, except that fluorine doping was not performed on the SnO2 nanowires.

[0115]

[0116] Evaluation Example 1: Impedance Analysis

[0117] Impedance analysis was performed by EIS fitting with the equivalent circuit of Fig. 4 at an applied voltage of 1.5 V and 1.9 V over a frequency range of 50 kHz to 50 mHz at a flow rate of 5 ml / min at 80°C. The resistance component in the high-frequency region (High Frequency Resistance (HFR)) was measured and evaluated, and the results are shown in Table 1. The resistance component in the high-frequency region is a factor representing the contact resistance, and a larger value means that the interface between components is broken and the contact becomes poor.

[0118] Additionally, impedance analysis was performed by EIS fitting with the equivalent circuit of Fig. 2 over the frequency range of 50 kHz to 50 mHz at 1.9 V, and the results are shown in Table 1. At this time, R ct means the charge transfer resistance due to electrolytic reaction, and R mt This refers to the mass transfer resistance of the oxygen gas product generated by the electrolytic reaction. The larger these values ​​are, the more they act as resistance and affect the electrolytic performance, causing a decrease in performance.

[0119] HFR (mΩ·cm 2 )R ct (mΩ·cm 2 )R mt (mΩ·cm 2 )Example 170.114.212.5Example 2131.818.115.1Example 3125.315.116.8Comparative Example 1142.519.817.9Comparative Example 2257.545.624.3

[0120] Referring to Table 1, it can be confirmed that when an electrode according to one embodiment is used, the HFR is reduced, effectively reducing the contact resistance of the electrode interface, compared to Comparative Example 1 using a general electrode or Comparative Example 2 which is composed only of tin oxide (SnO2) not doped with fluorine and thus has no electrical conductivity and thus has a significantly increased HFR.

[0121] Additionally, compared to Example 2 in which the thickness of the porous pattern layer was increased, Example 1 in which the thickness of the porous pattern layer was optimized showed a minimum HFR, confirming that the contact resistance of the electrode interface was effectively reduced.

[0122] Also, R of Example 1 mt The value was found to be the smallest, facilitating the movement of oxygen gas generated through R mt It can be confirmed that the reduction effect has appeared. If the product generated in the electrolysis is oxygen gas, the larger the amount generated, the larger the bubbles become, which can interfere with the electrolysis reaction and cause a decrease in performance. Oxygen gas must be discharged quickly so that the reaction can continue and maintain good performance. The mass transfer of oxygen gas can be indirectly confirmed through resistance analysis of impedance, and R mt It can be confirmed that oxygen discharge becomes easier as the amount of oxygen decreases.

[0123] Evaluation Example 2: Performance Evaluation

[0124] The performance was evaluated by measuring current and resistance at specific voltages from 1.4 V to 2 V while applying a flow rate of 5 ml / min at 80°C, and the results are shown in Fig. 5.

[0125] Referring to FIG. 5, compared to Comparative Example 1 using a general electrode or Comparative Example 2 in which the electrolysis performance is reduced due to lack of electrical conductivity caused by being composed only of tin oxide (SnO2) that is not doped with fluorine, it can be confirmed that when an electrode according to one embodiment is used, the contact resistance at the interface between the electrode and the microporous layer is lowered to lower the ohmic resistance, and the tortuosity of the oxygen transport path in the pattern layer is reduced to alleviate the performance degradation, thereby improving the electrolysis performance. In addition, it can be confirmed through Examples 2 and 3 that the performance decreases depending on the thickness and separation distance of the porous pattern layer, and that the performance decreases when the separation distance is narrow.

[0126] Although the preferred embodiments have been described in detail above, the scope of the present invention 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 present invention.

Claims

1. Microporous layer; and A porous pattern layer positioned on one side of the above microporous layer; The porous pattern layer includes first patterns extending in a first direction parallel to one side of the microporous layer and arranged in a second direction that is parallel to one side of the microporous layer and spaced apart from the first direction, and second patterns extending in the second direction and spaced apart from the first direction and intersecting with the first patterns. The first pattern and the second pattern each include a plurality of stacked nanowires, The above nanowire is an electrode for a water electrolysis cell containing a fluorine-doped metal oxide.

2. In paragraph 1, An electrode for a water electrolysis cell, wherein each of the first pattern and the second pattern is included in multiples.

3. In paragraph 1, The width of the first pattern in the second direction is 0.2 ㎛ to 5 ㎛, The separation distance of the first pattern in the second direction is 0.5 ㎛ to 20 ㎛, An electrode for a water electrolysis cell, wherein the thickness in a third direction perpendicular to one surface of the microporous layer of the first pattern is 0.5 ㎛ to 10 ㎛.

4. In paragraph 1, The width of the second pattern in the first direction is 0.2 ㎛ to 5 ㎛, The separation distance of the second pattern in the first direction is 0.5 ㎛ to 20 ㎛, An electrode for a water electrolysis cell, wherein the thickness in a third direction perpendicular to one surface of the microporous layer of the second pattern is 0.5 ㎛ to 10 ㎛.

5. In paragraph 1, One end of the first pattern is connected to one end of another first pattern spaced apart from one another in the second direction, An electrode for a hydroelectric cell, wherein the other end of the first pattern is connected to one end of another first pattern spaced apart from the other end in the second direction.

6. In paragraph 2, An electrode for a hydrolysis cell, wherein the porous pattern layer has a mesh shape in which the plurality of first patterns and the plurality of second patterns intersect.

7. In paragraph 1, An electrode for a water electrolysis cell, wherein the fluorine content is 1 at% to 10 at% based on 100 at% of the total components measured by X-ray photoelectron spectroscopy (XPS) in the entire fluorine-doped metal oxide.

8. In paragraph 1, The length of the above nanowire is 1 ㎛ to 500 ㎛, An electrode for a water electrolysis cell, wherein the diameter of the nanowire is 0.1 ㎛ to 1 ㎛.

9. In paragraph 1, An electrode for a water electrolysis cell, wherein the thickness of the porous pattern layer is 0.5 ㎛ to 10 ㎛.

10. In paragraph 1, An electrode for a water electrolysis cell, wherein the porosity of the porous pattern layer is 50% to 80%.

11. In paragraph 1, An electrode for a water electrolysis cell further comprising a catalyst layer comprising active particles including a precious metal oxide and an ion conductor, the catalyst layer being located on one surface of the porous pattern layer. 12.(i) A step of manufacturing a nanowire including a metal oxide; (ⅱ) a step of forming a porous pattern layer including a plurality of first patterns extending in a first direction and spaced apart in a second direction different from the first direction by radiating a solution in which the nanowires are dispersed onto a microporous layer, and a plurality of second patterns extending in the second direction, spaced apart in the first direction, and intersecting with the plurality of first patterns; (ⅲ) a step of forming a nano structure by bonding the porous pattern layer with a microporous layer; and (ⅳ) A method for manufacturing an electrode for a water electrolysis cell, comprising the step of mixing the nanostructure and the fluorine precursor and then performing a heat treatment.

13. Polymer electrolyte membrane; An oxygen generation electrode positioned on one side of the polymer electrolyte membrane and including an electrode for a water electrolysis cell according to claim 1; and A membrane-electrode assembly for a water electrolysis cell, comprising a hydrogen generation electrode positioned on the other side of the polymer electrolyte membrane.

14. A water electrolysis cell comprising a membrane electrode assembly according to Article 13.

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