Electrode for water electrolysis cell, manufacturing method therefor, and membrane-electrode assembly and water electrolysis cell for water electrolysis cell including same

Abstract

Provided is an electrode for water electrolysis cells, which comprises: a catalyst layer including noble metal oxide-containing active particles and an ion conductor; and a porous pattern layer located on one surface of the catalyst layer, wherein the porous pattern layer extends in a first direction parallel to one surface of the catalyst and includes first patterns parallel to the one surface of the catalyst layer and spaced apart in a second direction different from the first direction, the first patterns including a stack of multiple nanowires, the nanowires including 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 layer is needed; however, research into layers 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 catalyst layer including active particles and an ion conductor including a noble metal oxide; and a porous pattern layer positioned on one surface of the catalyst layer; wherein the porous pattern layer includes first patterns extending in a first direction parallel to the one surface of the catalyst layer and spaced apart in a second direction parallel to the one surface of the catalyst layer and different from the first direction; wherein the first pattern includes a plurality of stacked nanowires, and wherein 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 comprising a metal oxide; (ii) mixing the nanowire and a fluorine precursor, and then performing a heat treatment to manufacture a nanowire comprising a fluorine-doped metal oxide; (iii) disposing a first patterning mask comprising a plurality of slits extending in a first direction and spaced apart in a second direction different from the first direction on a catalyst layer comprising active particles and an ion conductor comprising a noble metal oxide; and (iv) spraying a slurry in which nanowires comprising the fluorine-doped metal oxide are dispersed on the first patterning mask to form a plurality of first patterns on the catalyst layer.

[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 a drawing showing a method for manufacturing an electrode for a water electrolysis cell according to one embodiment.

[0014] Figure 2 is a diagram showing the corresponding equivalent circuit used for fitting the EIS obtained at 1.5 V and 1.9 V.

[0015] Figure 3 is a drawing showing the electrolysis performance of a membrane-electrode assembly according to one embodiment.

[0016] 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.

[0017] 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.

[0018] “Combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0019] 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.

[0020] 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.

[0021] “Layer” includes not only shapes formed on the entire surface when observed in a plan view, but also shapes formed on some surfaces.

[0022] 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.

[0023] “Or” is not interpreted as exclusive, for example, “A or B” is interpreted as including A, B, A+B, etc.

[0024] “Metal” is interpreted as a concept that includes common metals, transition metals, and metalloids (semi-metals).

[0025] Electrode for electrolysis cell

[0026] catalyst layer

[0027] An electrode for a water electrolysis cell according to one embodiment includes a catalyst layer including active particles including a precious metal oxide and an ion conductor.

[0028] 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.

[0029] The electrode for the above-mentioned electrolysis cell may further include an ion conductor to improve the adhesion of active particles and to transfer hydrogen ions, and the ion conductor may include a cation exchanger to secure ion conductivity.

[0030] 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.

[0031] 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 ion conductor is a hydrocarbon 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 can be sulfonated polyarylene ether, sulfonated polyarylene ether nitrile, sulfonated polyarylene ether ether nitrile, sulfonated polyarylene ether sulfone ketone, etc.

[0032] The ion conductor according to one embodiment may have hydrogen ion conductivity. The ion conductor having hydrogen ion conductivity may substitute H 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.

[0033] 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 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.

[0034] 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.

[0035] porous pattern layer

[0036] An electrode for a water electrolysis cell according to one embodiment comprises: a catalyst layer comprising active particles including a noble metal oxide and an ion conductor; and a porous pattern layer positioned on one surface of the catalyst layer; wherein the porous pattern layer includes first patterns extending in a first direction parallel to the one surface of the catalyst layer and spaced apart in a second direction parallel to the one surface of the catalyst layer and different from the first direction. In this case, the first patterns may be included in plurality.

[0037] In one embodiment, the first 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 plane direction perpendicular to the thickness direction of one side of the catalyst layer. At this time, an example of the first direction may mean a coating progress direction when the catalyst layer is coated by a method such as spray coating, or a plane direction of a pattern of a pattern mask used when a porous pattern layer is coated on the catalyst 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 plane direction perpendicular to the thickness direction of one side of the catalyst layer. At this time, the second direction is a direction different from the first direction, and an example of the second direction may be that the second direction and the first direction are perpendicular to each other, and may mean a plane direction perpendicular to the coating progress direction when the catalyst layer is coated by a method such as spray coating, or a width direction of a pattern of a pattern mask used when a porous pattern layer is coated on the catalyst layer.

[0038] 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 20 ㎛ to 800 ㎛, for example, 20 ㎛ to 400 ㎛, 20 ㎛ to 250 ㎛, 80 ㎛ to 200 ㎛, or 100 ㎛ to 150 ㎛. In addition, the separation distance of the first pattern in the second direction can be 20 ㎛ to 800 ㎛, for example, 20 ㎛ to 400 ㎛, 20 ㎛ to 250 ㎛, 80 ㎛ to 200 ㎛, or 100 ㎛ to 150 ㎛. In addition, the thickness of the first pattern in a third direction perpendicular to one surface of the catalyst layer may be 0.01 ㎛ to 500 ㎛, for example, 0.03 ㎛ to 400 ㎛, 0.05 ㎛ to 300 ㎛, 0.05 ㎛ to 150 ㎛, or 0.05 ㎛ to 100 ㎛. 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.

[0039] A porous pattern layer included in an electrode for a water electrolysis cell according to one embodiment may further include second patterns positioned on one side of the first patterns, extending in the second direction, and spaced apart from each other in the first direction. In this case, the second patterns may be included in multiple numbers.

[0040] 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 20 ㎛ to 800 ㎛, for example, 20 ㎛ to 400 ㎛, 20 ㎛ to 250 ㎛, 80 ㎛ to 200 ㎛, or 100 ㎛ to 150 ㎛. In addition, the separation distance of the second pattern in the first direction can be 20 ㎛ to 800 ㎛, for example, 20 ㎛ to 400 ㎛, 20 ㎛ to 250 ㎛, 80 ㎛ to 200 ㎛, or 100 ㎛ to 150 ㎛. In addition, the thickness of the second pattern in a third direction perpendicular to one surface of the catalyst layer may be 0.01 ㎛ to 500 ㎛, for example, 0.03 ㎛ to 400 ㎛, 0.05 ㎛ to 300 ㎛, 0.05 ㎛ to 150 ㎛, or 0.05 ㎛ to 100 ㎛. 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.

[0041] 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.

[0042] 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, since the fluorine-doped metal oxide is included in the nanowire, the bonding force between the metal oxides is improved and the aspect ratio of the metal oxide is increased, so that the metal of the doped material or 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.

[0043] 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.

[0044] The length of the nanowire may be 1 μm to 200 μm, for example, 3 μm to 180 μm, 5 μm to 165 μm, or 10 μm to 150 μm. In addition, the diameter of the nanowire may be 0.1 μm to 1.0 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, electrical conductivity is improved due to networking of metal oxide particles, which has the advantage of reducing contact resistance.

[0045] The thickness of the porous pattern layer included in the electrode for the electrolysis cell according to one embodiment may be 0.01 ㎛ to 500 ㎛, for example, 0.02 ㎛ to 400 ㎛, 0.03 ㎛ to 300 ㎛, 0.04 ㎛ to 150 ㎛, or 0.05 ㎛ to 100 ㎛. 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 the performance degradation at high voltage.

[0046] 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%, 45% to 85%, or 50% to 80%. When the porosity 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 reducing the mass transfer resistance, and thus, there is an advantage of reducing performance degradation at high voltage.

[0047] microporous layer

[0048] An electrode for a water electrolysis cell according to one embodiment may further include a microporous layer located on one surface of the porous pattern 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.

[0049] A microporous layer, commonly known as a porous transport layer (PTL), is applied to a water electrolysis cell to transport reactant water toward a polymer electrolyte membrane (PEM), while simultaneously directing the products away from the PEM. It also collects and transports electrons generated by the electrochemical reaction. To maximize the functionality of this microporous layer, various properties are required, including corrosion resistance, electrical conductivity, diffusivity, and mechanical strength.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] Method for manufacturing electrodes for electrolysis cells

[0054] A method for manufacturing an electrode for a water electrolysis cell according to one embodiment includes: (i) manufacturing a nanowire including a metal oxide; (ii) mixing the nanowire and a fluorine precursor, and then performing a heat treatment to manufacture a nanowire including a fluorine-doped metal oxide; (iii) disposing a first patterning mask including a plurality of slits extending in a first direction and spaced apart in a second direction different from the first direction on a catalyst layer including active particles including a noble metal oxide and an ion conductor; and (iv) spraying a slurry in which nanowires including the fluorine-doped metal oxide are dispersed on the first patterning mask to form a plurality of first patterns on the catalyst layer.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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).

[0059] After electrospinning the above-described spinning solution onto a current collector, a first heat treatment process may be performed. 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.

[0060] The above nanowires can be adjusted to various sizes and shapes depending on pH, temperature, time, etc., and the length of the nanowires can be 1 μm to 200 μm, for example, 3 μm to 180 μm, 5 μm to 165 μm, or 10 μm to 150 μm. In addition, the diameter of the nanowires can be 0.1 μm to 1 μm, for example, 0.1 μm to 1 μm, 0.2 μm to 0.9 μm, or 0.2 μm to 0.8 μm. When the nanowires have the length and diameter in the above ranges, electrical conductivity is improved due to networking of metal oxide particles, which has the advantage of reducing contact resistance.

[0061] In one embodiment, the type of the fluorine precursor in the step (ii) 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 nanowire 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 nanowire 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.

[0062] After mixing the nanowires and the fluorine precursor, 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.

[0063] 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.

[0064] In one embodiment, in steps (iii) and (iv), a first patterning mask including a plurality of slits extending in a first direction and spaced apart in a second direction different from the first direction is disposed on a catalyst layer including active particles and an ion conductor including a noble metal oxide, and then a slurry in which nanowires including a fluorine-doped metal oxide are dispersed is sprayed on the first patterning mask to form a plurality of first patterns on the catalyst layer.

[0065] Fig. 1 is a drawing showing a method for manufacturing an electrode for a water electrolysis cell according to an embodiment. As shown in Fig. 1, a slurry in which nanowires including a fluorine-doped metal oxide manufactured in step (ii) are dispersed is sprayed onto a current collector to form one layer of a first pattern extending in a first direction and spaced apart in a second direction, thereby manufacturing a porous pattern layer.

[0066] The extension length of the slit included in the first patterning mask 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 slit included in the first patterning mask in the second direction can be 20 ㎛ to 800 ㎛, for example, 20 ㎛ to 400 ㎛, 20 ㎛ to 250 ㎛, 80 ㎛ to 200 ㎛, or 100 ㎛ to 150 ㎛. In addition, the separation distance of the slit included in the first patterning mask in the second direction can be 20 ㎛ to 800 ㎛, for example, 20 ㎛ to 400 ㎛, 20 ㎛ to 250 ㎛, 80 ㎛ to 200 ㎛, or 100 ㎛ to 150 ㎛.

[0067] The above slurry may be a slurry mixing nanowires containing a fluorine-doped metal oxide and an ionomer, and the ionomer may be a cation conductor having a cation exchange group capable of exchanging cations, or an anion conductor having an anion exchange group capable of exchanging anions such as hydroxyl ions, carbonates, or bicarbonates.

[0068] The above cation exchange group may be any one selected from the group consisting of a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphoric acid group, an imide group, a sulfonimide group, a sulfonamide group, and combinations thereof, and may generally be a sulfonic acid group or a carboxyl group.

[0069] The above cation conductor may include the above cation exchange group, and may include a fluorine-based polymer containing fluorine in the main chain; a hydrocarbon-based polymer such as benzimidazole, polyamide, polyamideimide, polyimide, polyacetal, polyethylene, polypropylene, acrylic resin, polyester, polysulfone, polyether, polyetherimide, polyester, polyethersulfone, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyetheretherketone, polyetherketone, polyarylethersulfone, polyphosphazene or polyphenylquinoxaline; a partially fluorinated polymer such as a polystyrene-graft-ethylenetetrafluoroethylene copolymer or a polystyrene-graft-polytetrafluoroethylene copolymer; and a sulfone imide.

[0070] In addition, the cation conductor may substitute H in the cation exchange group at the end of the side chain with Na, K, Li, Cs or tetrabutylammonium. When replacing H in the cation exchange group at the end of the side chain with Na, NaOH is used during the preparation of the carbon structure composition, and when replacing H with tetrabutylammonium, tetrabutylammonium hydroxide is used. K, Li or Cs may also be substituted using an appropriate compound.

[0071] As the above anion conductor, a polymer doped with a metal hydroxide can generally be used, and specifically, a metal hydroxide doped poly(ethersulfone), polystyrene, a vinyl polymer, poly(vinyl chloride), poly(vinylidene fluoride), poly(tetrafluoroethylene), poly(benzimidazole), or poly(ethylene glycol) can be used.

[0072] The weight ratio of the nanowires containing the fluorine-doped metal oxide and the ionomer in the slurry may be from 0.1:1 to 1:1, for example, from 0.1:1 to 1:1, from 0.1:1 to 1:1, or from 0.1:1 to 1:1. When the content of the ionomer is within the above range, the performance of the electrolysis cell is improved, and at the same time, there is an advantage in that aggregation between ionomers due to an excess of ionomer can be suppressed.

[0073] Membrane-electrode assembly for electrolysis cell

[0074] 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.

[0075] Below, the oxygen generation electrode, hydrogen generation electrode, and polymer electrolyte membrane are described in detail.

[0076] oxygen generation electrode

[0077] 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.

[0078] hydrogen generation electrode

[0079] 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.

[0080] 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).

[0081] 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.

[0082] 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.

[0083] 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.

[0084] polymer electrolyte membrane

[0085] 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.

[0086] 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.

[0087] 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).

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] [Mathematical Formula 1]

[0095] Porosity (%) = (air volume in porous support / total volume of porous support) X 100

[0096] 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.

[0097] 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.

[0098] Susan Haesel

[0099] In one embodiment, the electrolysis cell comprises a membrane-electrode assembly for the electrolysis cell.

[0100] 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.

[0101] 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.

[0102] Example 1

[0103] 1. Preparation of catalyst layer

[0104] IrO x A catalyst composition for oxygen generation reaction was prepared by mixing and dispersing a catalyst and ionomer solution at an ionomer / catalyst ratio of 0.3 and 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.

[0105] 2. Manufacturing of nanowires

[0106] A spinning solution was prepared by adding 0.5 g of SnCl2 to 4 g of a solution of dimethylformamide (DMF) and ethanol in a 1:1 weight ratio, mixing uniformly for 30 minutes, and then adding 0.5 g of polyvinylpyrrolidone (PVP). The spinning solution was injected at a flow rate of 0.3 ml / hr, applied at a voltage of 18 kV, and spun onto a conductive collector to produce a non-woven film, followed by heat treatment at 500°C for 6 hours in an air atmosphere to produce SnO2 nanowires with a diameter of 500 nm and a length of 150 μm.

[0107] After mixing the manufactured SnO2 nanowires with NH4F as a fluorine precursor, the particle size of the powders is uniformized to ensure homogeneous mixing. Here, the amount of fluorine doped can be controlled by adjusting the amount of the fluorine precursor and the manufactured SnO2 powder. The mixture with the controlled molar ratio was heat-treated at a temperature of 400°C for 6 hours in an inert gas atmosphere, and the heat-treated powder was washed and filtered using ethanol and distilled water, and then dried at a temperature of 60°C for 12 hours to produce fluorine-doped SnO2 nanowires.

[0108] 3. Manufacturing of porous pattern layers

[0109] The manufactured fluorine-doped SnO2 nanowires were dispersed in isopropyl alcohol with a Nafion ionomer resin solution (5 wt%) at a weight ratio of 4.1: 1 to prepare a slurry. A pattern mask having a pattern length of 5 cm, a pattern width of 125 ㎛, and a pattern spacing of 125 ㎛ was aligned on the catalyst layer, and the manufactured slurry was sprayed to coat the catalyst layer with a coating thickness of 0.5 ㎛. Next, the pattern mask was rotated to perform a second coating, and the coating was performed at a rotation angle of the pattern mask in a vertical direction, and the coating was performed with a thickness of 0.5 ㎛ to manufacture a first electrode layer formed with a catalyst layer and a porous pattern layer on a transfer substrate.

[0110] 4. Manufacturing of membrane-electrode assemblies for electrolysis cells

[0111] 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 the first electrode layer was transferred to one side of a polymer electrolyte membrane and the second electrode layer was transferred to the opposite side and bonded to produce a membrane-electrode assembly.

[0112] Example 2

[0113] 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 coating was performed using a pattern mask having a pattern length of 5 cm, a pattern width of 30 μm, and a pattern spacing of 30 μm.

[0114] Example 3

[0115] 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 coating was performed using a pattern mask having a pattern length of 5 cm, a pattern width of 300 μm, and a pattern spacing of 300 μm.

[0116] Comparative Example 1

[0117] A membrane-electrode assembly for a water electrolysis cell was manufactured in substantially the same manner as in Example 1, except that the nanowires and porous pattern layer were not manufactured in Example 1.

[0118] Comparative Example 2

[0119] 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.

[0120]

[0121] Evaluation Example 1: Impedance Analysis

[0122] Impedance analysis was performed by EIS fitting with the equivalent circuit of Fig. 2 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 unstable and the contact is poor.

[0123] 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 gaseous product produced by the electrolysis reaction, and the larger this value is, the more it acts as a resistance and affects the electrolysis performance, causing a decrease in performance.

[0124] HFR (mΩ·cm 2 )R ct (mΩ·cm 2 )R mt (mΩ·cm 2 ) Example 149.918.712.6 Example 276.520.414.5 Example 3131.823.213.0 Comparative Example 1142.521.125.2 Comparative Example 2257.555.533.1

[0125] Referring to Table 1, it can be confirmed that when using an electrode according to one embodiment, 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.

[0126] Additionally, in comparison with Example 2, where the pattern width is smaller than a certain level and thus greatly affects the electrical characteristics of the interface, causing interference, or Example 3, where the pattern width is larger than a certain number and thus reduces the contact area, thereby reducing the effect of the pattern electrode layer, it can be confirmed that Example 1, where the pattern width is optimized, shows a minimum HFR, effectively reducing the contact resistance of the electrode interface.

[0127] Evaluation Example 2: Performance Evaluation

[0128] The performance was evaluated by measuring voltage and resistance at specific currents from 1 mA to 2 A while applying a flow rate of 5 ml / min at 80°C, and the results are shown in Fig. 3.

[0129] Referring to FIG. 3, it can be confirmed that when the porous pattern layer according to Example 1 is included, the contact resistance at the interface between the electrode and the microporous layer can be lowered, thereby lowering the ohmic resistance in the electrolysis performance, and thereby improving the performance.

[0130] In addition, compared to Examples 2 and 3, the improvement in performance of Example 1 can be confirmed in terms of electrolysis performance by showing that the spacing of the porous pattern layer affects the mass transfer resistance, and in the case of Comparative Example 2 having a non-conductive porous pattern layer, the ohmic resistance increases rapidly, showing the lowest electrolysis performance.

[0131] 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. A catalyst layer comprising active particles including a precious metal oxide and an ion conductor; and A porous pattern layer positioned on one side of the catalyst layer; The above porous pattern layer includes first patterns extending in a first direction parallel to one side of the catalyst layer and arranged spaced apart in a second direction parallel to one side of the catalyst layer and different from the first direction, The above first pattern comprises 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 hydrolysis cell, wherein the first pattern is included in multiple numbers.

3. In paragraph 1, The width of the first pattern in the second direction is 20 ㎛ to 800 ㎛, The separation distance of the first pattern in the second direction is 20 ㎛ to 800 ㎛, An electrode for a water electrolysis cell, wherein the thickness in a third direction perpendicular to one surface of the catalyst layer of the first pattern is 0.01 ㎛ to 500 ㎛.

4. In paragraph 1, The above porous pattern layer is located on one side of the first patterns, Further comprising second patterns extending in the second direction and spaced apart from each other in the first direction, The second pattern comprises a plurality of stacked nanowires, The above nanowire is an electrode for a water electrolysis cell containing a fluorine-doped metal oxide.

5. In paragraph 4, The second pattern is an electrode for a water electrolysis cell, which is included in multiple numbers.

6. In paragraph 4, The width of the second pattern in the first direction is 20 ㎛ to 800 ㎛, The separation distance of the second pattern in the first direction is 20 ㎛ to 800 ㎛, An electrode for a water electrolysis cell, wherein the thickness in a third direction perpendicular to one surface of the catalyst layer of the second pattern is 0.01 ㎛ to 500 ㎛.

7. In paragraph 1, The above metal oxide is an electrode for a water electrolysis cell, which is tin oxide.

8. 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.

9. In paragraph 1, The length of the above nanowire is 1 ㎛ to 200 ㎛, An electrode for a water electrolysis cell, wherein the diameter of the above nanowire is 0.1 ㎛ to 1.0 ㎛.

10. In paragraph 1, An electrode for a water electrolysis cell, wherein the thickness of the porous pattern layer is 0.01 ㎛ to 500 ㎛.

11. In paragraph 1, An electrode for a water electrolysis cell, wherein the porosity of the porous pattern layer is 30% to 95%.

12. In paragraph 1, An electrode for a water electrolysis cell further comprising a microporous layer positioned on one side of the porous pattern layer. 13.(i) A step of manufacturing a nanowire including a metal oxide; (ⅱ) a step of mixing the nanowire and the fluorine precursor and then performing a heat treatment to produce a nanowire including a metal oxide doped with fluorine; (iii) a step of arranging a first patterning mask including a plurality of slits extending in a first direction and spaced apart in a second direction different from the first direction on a catalyst layer including active particles including a precious metal oxide and an ion conductor; and (iv) A method for manufacturing an electrode for a water electrolysis cell, comprising the step of spraying a slurry in which nanowires containing the fluorine-doped metal oxide are dispersed onto the first patterning mask to form a plurality of first patterns on the catalyst layer.

14. In paragraph 13, The width of the slit included in the first patterning mask in the second direction is 20 ㎛ to 800 ㎛, A method for manufacturing an electrode for a water electrolysis cell, wherein the distance between slits included in the first patterning mask in the second direction is 20 ㎛ to 800 ㎛.

15. 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.

16. A water electrolysis cell comprising a membrane electrode assembly according to Article 15.

Images