Water electrolysis electrode, membrane electrode assembly comprising same, and electrolysis cell comprising membrane electrode assembly

Abstract

The present invention relates to a water electrolysis electrode, a membrane electrode assembly comprising same, and an electrolysis cell comprising the membrane electrode assembly. Provided are a water electrolysis electrode, a membrane electrode assembly comprising same, and an electrolysis cell, the water electrolysis electrode comprising: a substrate; and a catalyst layer positioned on the substrate and comprising an iridium oxide and an iridium oxide-ionomer aggregate.

Description

A water electrolysis electrode, a membrane electrode assembly including the same, and an electrolysis cell including the membrane electrode assembly.

[0001] [Cross-reference with related applications]

[0002] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0131048 dated September 26, 2024 and Korean Patent Application No. 10-2024-0133180 dated September 30, 2024, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of the specification.

[0003] [Technology Field]

[0004] The present invention relates to a water electrolysis electrode, a membrane electrode assembly including the same, and an electrolysis cell including the membrane electrode assembly.

[0005]

[0006] Hydrogen has the advantages of being suitable for storage and transportation and being eco-friendly, leading to various recent attempts to utilize it as an energy source. While various methods for producing hydrogen are known, the method of producing hydrogen through water electrolysis has the advantage of being environmentally friendly as it does not generate harmful byproducts.

[0007] Water electrolysis is a method of producing hydrogen and oxygen using electrons generated during the redox reaction of water.

[0008] Representative methods of water electrolysis include Alkaline Electrolysis (AEC) and Polymer Electrolyte Membrane Electrolysis (PEM). Among these, Alkaline Electrolysis is a method that electrolyzes water using an alkaline electrolyte and is the most commercialized technology among various electrolysis methods. Alkaline Electrolysis has the advantages of relatively low process operating costs, a simple production structure making it suitable for large-scale hydrogen production, and excellent durability. However, Alkaline Electrolysis has limitations, such as the need to continuously replenish the electrolyte consumed during the electrolysis process, corrosion problems caused by alkaline components, and low current density efficiency.

[0009] Meanwhile, Polymer Electrolyte Membrane (PEM) water electrolysis is a method that utilizes a polymer electrolyte membrane as the electrolyte. It features a structure in which an anode and a cathode are coated on either side of the polymer electrolyte membrane, and this is referred to as a Membrane Electrode Assembly. The principle of PEM water electrolysis is that water (H2O) is supplied to the anode and decomposed into oxygen gas, electrons, and hydrogen ions, while at the cathode, hydrogen ions that have passed through the polymer electrolyte membrane combine with electrons to be released as pure hydrogen gas.

[0010] The electrochemical performance of polymer electrolyte membrane water electrolysis is significantly influenced by key materials such as the polymer electrolyte membrane, catalyst, and electrode binder composed of an ionomer. It has the advantage of high energy efficiency because operation at high current densities is possible using precious metal catalysts, and the purity of the produced hydrogen is very high because it does not require an electrolyte component. In such polymer electrolyte membrane water electrolysis, since the oxygen evolution reaction is much slower than the hydrogen evolution reaction and requires a large overpotential, increasing the electrode activity of the anode is the most important consideration for improving overall cell performance. In particular, to maximize catalytic activity, it is important to increase the contact area of ​​the precious metal components constituting the catalyst layer of the anode and to have an appropriate distribution.

[0011] Meanwhile, the distribution of precious metal components within the catalyst layer is significantly influenced by the catalyst ink composition, catalyst content, distribution state, and coating process during the formation of the catalyst layer. Since there are limitations to controlling the appropriate distribution with conventionally known structures, methods to increase the amount of precious metal used are adopted to enhance catalytic activity. However, this increase in the amount of precious metal used raises the price of the precious metal catalyst, ultimately reducing the economic efficiency of the overall water electrolysis process. Therefore, there is a need to develop water electrolysis electrodes and membrane electrode assemblies that can secure high cell performance of polymer electrolyte membrane (PEM) while reducing the amount of precious metal catalyst used.

[0012] [Prior Art Literature]

[0013] [Patent Literature]

[0014] (Patent Document 1) KR 10-2023-0128481 A

[0015]

[0016] The problem to be solved by the present invention is to provide a water electrolysis electrode capable of reducing the loading amount of iridium oxide (IrO2) by inducing high dispersion of iridium oxide on the surface of the catalyst layer and providing high electrolysis cell performance.

[0017] Another problem to be solved by the present invention is to provide a membrane electrode assembly having a high current density by including the above-mentioned water electrolysis electrode as an anode.

[0018] Another problem to be solved by the present invention is to provide an electrolysis cell having a high level of electrolysis efficiency.

[0019]

[0020] The present invention provides an electrolysis cell comprising a water electrolysis electrode, a membrane electrode assembly, and a membrane electrode assembly.

[0021] (1) The present invention comprises a substrate; and a catalyst layer positioned on the substrate and comprising iridium oxide and an iridium oxide-ionomer aggregate, wherein the iridium loading amount of the catalyst layer is 0.1 mg / cm² 2 ≥ 1.0 mg / cm² 2 The present invention provides a water electrolysis electrode having an average particle size of iridium oxide of 1 nm or more and less than 10 nm, which is less than or equal to the above.

[0022] (2) The present invention provides a water electrolysis electrode according to (1), wherein the iridium (Ir) elemental ratio of the catalyst layer surface portion measured by X-ray photoelectron spectroscopy (XPS) analysis is 7 at% to 20 at%.

[0023] (3) The present invention provides a water electrolysis electrode in which the iridium (Ir) elemental ratio of the catalyst layer surface portion measured by X-ray photoelectron spectroscopy (XPS) analysis is 7 at% to 14 at% in (1) or (2).

[0024] (4) The present invention provides a water electrolysis electrode in which, in any one of (1) to (3), the iridium oxide-ionomer aggregate has an average particle size of 10 nm or more and 10 μm or less.

[0025] (5) The present invention provides a water electrolysis electrode in which, in any one of (1) to (4), the iridium oxide-ionomer aggregate has one or more structures of plate-like and elliptical shapes and has a size of 0.5 μm or more and less than 10.0 μm based on the major axis.

[0026] (6) In any one of (1) to (5) above, the present invention is such that the iridium oxide density in the catalyst layer is 1.5 g / cm³ 3 The above provides a water electrolysis electrode.

[0027] (7) The present invention provides a water electrolysis electrode in any one of (1) to (6), wherein the catalyst layer comprises a high-density catalyst layer and a low-density catalyst layer, and the low-density catalyst layer is located close to the substrate.

[0028] (8) The present invention provides a water electrolysis electrode according to (7), wherein the high-density catalyst layer has an iridium (Ir) elemental ratio of 7 at% to 20 at% as analyzed by X-ray photoelectron spectroscopy (XPS), and the low-density catalyst layer has an iridium (Ir) elemental ratio of 3 at% or more and less than 7 at% as analyzed by X-ray photoelectron spectroscopy (XPS).

[0029] (9) The present invention provides a water electrolysis electrode in which, in any one of (1) to (8), the ionomer is one or more selected from the group consisting of perfluorinated ionomers, partially fluorinated ionomers, and hydrocarbon ionomers.

[0030] (10) The present invention provides a water electrolysis electrode in which, in any one of (1) to (9), the substrate is one or more selected from the group consisting of polyether sulfone, cellulose acetate, polyvinylidene fluoride, polytetrafluoroethylene, ethylene tetrafluoroethylene, polyamide, polyimide, nylon and polyolefin.

[0031] (11) The present invention comprises an ion exchange membrane; a cathode located on one side of the ion exchange membrane; and an anode located on the other side of the ion exchange membrane, wherein the anode comprises a substrate and a catalyst layer located on the substrate and comprising iridium oxide, and the iridium loading amount of the catalyst layer is 0.1 mg / cm² 2 ≥ 1.0 mg / cm² 2 The present invention provides a membrane electrode assembly for water electrolysis having an average particle size of iridium oxide of 1 nm or more and less than 10 nm, wherein the average particle size of the iridium oxide is 1 nm or more and less than 10 nm.

[0032] (12) The present invention provides a membrane electrode assembly for water electrolysis in which the iridium (Ir) elemental ratio of the catalyst layer surface portion measured by X-ray photoelectron spectroscopy (XPS) analysis is 7 at% to 20 at%.

[0033] (13) The present invention provides a membrane electrode assembly for water electrolysis in which, in (11) or (12), the ion exchange membrane is one or more selected from the group consisting of perfluorosulfonic acid, polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP).

[0034] (14) The present invention provides an electrolytic cell comprising a membrane electrode assembly for water electrolysis according to any one of (11) to (13).

[0035]

[0036] The water electrolysis electrode according to the present invention includes a catalyst layer in which iridium oxide nanoparticles are highly dispersed, and despite containing a low loading amount of iridium, it has the effect of having a high level of current density in membrane electrode assemblies and electrolysis cells to which it is applied.

[0037] In addition, the water electrolysis electrode according to the present invention includes a high-density catalyst layer having a surface iridium element ratio of 7 to 20 at%, and despite containing a low loading amount of iridium, it has the effect of having a high level of current density in membrane electrode assemblies and electrolysis cells to which it is applied.

[0038]

[0039] The following drawings attached to this specification illustrate specific embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the aforementioned description; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0040] Figure 1 is an image of the TEM analysis result of the water electrolysis electrode catalyst layer prepared in Example 1.

[0041] Figure 2 is an image of the TEM analysis result of the water electrolysis electrode catalyst layer prepared in Example 2.

[0042] Figure 3 is an image of the TEM analysis result of the water electrolysis electrode catalyst layer prepared in Comparative Example 1.

[0043] Figure 4 is an image of the surface of the water electrolysis electrode catalyst layer prepared in Example 1, with (a) a magnification 5K image and (b) a magnification 20K image.

[0044] Figure 5 is an image of the surface SEM (5K) analysis result of the water electrolysis electrode catalyst layer prepared in Example 2.

[0045] Figure 6 is an image of the surface SEM (10K) analysis result of the water electrolysis electrode catalyst layer prepared in Comparative Example 1.

[0046] Figure 7 is an image of the surface SEM (5K) analysis result of the water electrolysis electrode catalyst layer prepared in Comparative Example 2.

[0047] Figure 8 is an image of the SEM analysis result of the cross-section of the water electrolysis electrode prepared in Example 1.

[0048] Figure 9 is an image of the SEM analysis result of the cross-section of the water electrolysis electrode prepared in Comparative Example 1.

[0049]

[0050] Hereinafter, the present invention will be described in more detail to aid in understanding the invention. In this case, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0051] The terms used in this specification are used merely to describe exemplary embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0052]

[0053] terminology

[0054] In this specification, 'iridium oxide-ionomer aggregate' may refer to a mass formed by an ionomer attached to the surface of an iridium oxide particle.

[0055] In this specification, 'catalyst layer surface portion' refers to the outermost surface of the catalyst layer.

[0056] In this specification, terms such as 'comprising,' 'having,' or 'having' are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0057]

[0058] Measurement conditions

[0059] In this specification, the average particle size of iridium oxide was calculated by preparing an electrode cross-sectional specimen using a low-temperature Ultramicrotome, collecting the particle size from the specimen through cross-sectional image analysis in TEM mode using a transmission electron microscope (TEM, JEM-ARM200F, NEOARM), and calculating the average value.

[0060] In this specification, the iridium oxide density was calculated by determining the mass of Ir per unit area within the electrode by gravimetric method, calculating the electrode thickness through analysis of the electrode cross-sectional image using SEM, and then calculating [mass of Ir per unit area within the electrode / electrode thickness].

[0061] In this specification, the iridium loading amount in the catalyst layer can be measured using an energy-dispersive fluorescence X-ray analyzer (XRF, Rigaku NEx-CG), and specifically, the absolute amount of the component in the catalyst layer measured by the energy-dispersive fluorescence X-ray analyzer was quantified to calculate the relative ratio.

[0062] In this specification, the aggregate particle size can be calculated as the average value of particle sizes confirmed through surface and cross-sectional image analysis using a field emission scanning electron microscope (FE-SEM, JEOL, JSM7610F), or as the average value of aggregate particle sizes collected through cross-sectional image analysis in STEM mode using a transmission electron microscope (TEM, JEM-ARM200F, NEOARM).

[0063] In this specification, the elemental ratio of iridium on the surface of the catalyst layer was measured using an X-ray photoelectron spectrometer (K-Alpha+, Thermo Fisher Scientific Inc). Specifically, an electrode specimen was cut to an appropriate size, fixed to carbon tape, and loaded into the photoelectron spectrometer. Qualitative analysis was performed after a survey scan according to the following conditions, and based on the results of each qualitative analysis, a narrow scan for each element was obtained at three points and measured through quantitative analysis and binding state analysis.

[0064] X-ray source: monochromatic Al Kα (1486.6 eV)

[0065] Operation mode: CAE (Constant Analyzer Energy) mode

[0066] Software: Avantage software (version 5.980)

[0067] X-ray spot size: 400 µm

[0068] Survey scan: Scan range 0–1360 eV, step size 1 eV

[0069] Narrow scan: Scan range 13–29 eV, step size 0.1 eV

[0070] In this specification, the thickness of the catalyst layer can be measured using a field emission scanning electron microscope (FE-SEM, JEOL, JSM7610F) and calculated as the average value of the thickness confirmed through surface and cross-sectional image analysis.

[0071]

[0072] water electrolysis electrode

[0073] The present invention provides a water electrolysis electrode in which iridium oxide is highly dispersed in a nanoscale within a catalyst layer to form a high-density surface catalyst layer, thereby enabling the membrane electrode assembly to maintain high electrolysis performance even though it contains a low loading amount of iridium, by being applied as an anode constituting a membrane electrode assembly.

[0074] According to one embodiment of the present invention, the water electrolysis electrode comprises a substrate; and a catalyst layer positioned on the substrate and comprising iridium oxide and an iridium oxide-ionomer aggregate, wherein the iridium loading amount of the catalyst layer is 0.1 mg / cm² 2 ≥ 1.0 mg / cm² 2 The average particle size of the iridium oxide may be 1 nm or more and less than 10 nm.

[0075] In addition, the water electrolysis electrode according to one embodiment of the present invention may have an iridium (Ir) elemental ratio on the surface of the catalyst layer measured by X-ray photoelectron spectroscopy (XPS) analysis of 7 at% to 20 at%.

[0076] The electrochemical performance of polymer electrolyte membrane water electrolysis is significantly influenced by key materials such as the polymer electrolyte membrane, catalyst, and electrode binder composed of an ionomer. It has the advantage of high energy efficiency because operation at high current densities is possible using precious metal catalysts, and the purity of the produced hydrogen is very high because it does not require an electrolyte component. In such polymer electrolyte membrane water electrolysis, since the oxygen evolution reaction is much slower than the hydrogen evolution reaction and requires a large overpotential, increasing the electrode activity of the anode is the most important consideration for improving overall cell performance. In particular, to maximize catalytic activity, it is important to increase the contact area of ​​the precious metal components constituting the catalyst layer of the anode and to have an appropriate distribution.

[0077] Meanwhile, the distribution of precious metal components within the catalyst layer is significantly influenced by the catalyst ink composition, catalyst content, distribution state, and coating process during the formation of the catalyst layer. Since there are limitations to controlling the appropriate distribution with conventionally known structures, methods to increase the amount of precious metal used are adopted to enhance catalytic activity; however, the relatively high cost of precious metal catalysts poses a problem that reduces the economic efficiency of the overall water electrolysis process.

[0078] However, a water electrolysis electrode according to one embodiment of the present invention comprises a catalyst layer containing iridium oxide, wherein the iridium oxide within the catalyst layer is highly dispersed at a nanoparticle size, thereby controlling the distribution of iridium to increase the amount of iridium element on the surface of the catalyst layer to 1.0 mg / cm² 2 A membrane electrode assembly and an electrolysis cell capable of having high cell performance of a polymer electrolyte membrane (PEM) even with a reduced iridium loading amount can be provided.

[0079]

[0080] The above material may be one or more selected from the group consisting of polyether sulfone, cellulose acetate, polyvinylidene fluoride, polytetrafluoroethylene, ethylene tetrafluoroethylene (ETFE), polyamide, polyimide, nylon, and polyolefin, and more specifically, the above material may be polytetrafluoroethylene.

[0081] The catalyst layer is located on the substrate and may include iridium oxide, and the iridium loading amount of the catalyst layer is 0.1 mg / cm² 2 ≥ 1.0 mg / cm² 2 The average particle size of the iridium oxide may be 1 nm or more and less than 10 nm. Additionally, the iridium (Ir) elemental ratio on the surface of the catalyst layer, as measured by X-ray photoelectron spectroscopy (XPS) analysis, may be 7 at% to 20 at%.

[0082] Reducing the amount of iridium, a precious metal, is one of the major challenges to be solved in the technical field to which this invention belongs. Furthermore, it is not enough to simply reduce the iridium loading amount; high electrolysis efficiency must be maintained while reducing the loading amount.

[0083] The present invention enables the simultaneous reduction of iridium loading and the maintenance of high electrolysis efficiency by implementing a catalyst layer in which iridium oxide is highly dispersed at the nano-particle size.

[0084] Specifically, in the present invention, the iridium loading amount of the catalyst layer is 1.0 mg / cm² 2 Below, 0.9 mg / cm² 2 Below, 0.8 mg / cm² 2 Below, 0.7 mg / cm² 2 Less than or equal to 0.6 mg / cm² 2 It may be less than, and also 0.1 mg / cm² 2 Above, 0.2 mg / cm² 2 Above, 0.3 mg / cm² 2 ≥ or 0.4 mg / cm²2 It could be more than that.

[0085] If the iridium loading amount within the above range is not satisfied, the excessive use of iridium is undesirable in terms of cost and economics, and this may act as a significant impediment to the commercialization of the PEM water electrolysis implemented in the present invention.

[0086] In addition, the average particle size of the iridium oxide in the catalyst layer may be 1 nm or more and less than 10 nm, or 1 nm or more and less than 5 nm. Conventional water electrolysis electrodes have a low batch density in which the iridium oxide particle size in the catalyst layer is 10 nm or more, so in order to obtain a highly active electrode, the absolute iridium loading amount had to be increased. However, the water electrolysis electrode according to one embodiment of the present invention is manufactured and applied by using a catalyst ink for forming the catalyst layer during the manufacturing process, in which the catalyst particles are reduced to nano-sized particles through a high-energy dispersion process and have uniform dispersibility and appropriate viscosity, thereby having a low loading amount of iridium while having excellent electrical connectivity between catalysts and sufficient current density.

[0087] Specifically, in the present invention, the average particle size of the iridium oxide may be less than 10 nm, 9 nm or less, 8 nm or less, 7 nm or less, 6 nm or less, 5 nm or less, 4.8 nm or less, 4.6 nm or less, 4.4 nm or less, 4.2 nm or less, 4.0 nm or less, 3.8 nm or less, 3.6 nm or less, 3.4 nm or less, or 3.2 nm or less, 1.0 nm or more, 1.2 nm or more, 1.4 nm or more, 1.6 nm or more, 1.8 nm or more, or 2.0 nm or more.

[0088] In addition, the iridium oxide density in the catalyst layer is 1.5 g / cm³ 3 It may be above. Specifically, the iridium oxide density in the catalyst layer is 1.5 g / cm³ 3 Above 2.5 g / cm³ 3 It may be less than.

[0089] Meanwhile, the iridium oxide particle size and density within the catalyst layer may be influenced by the type of catalyst metal used in the process of forming the catalyst layer, the type and amount of ionomer and binder, the composition of the catalyst ink, the coating method, and the drying process. If the amount of catalyst metal included in the catalyst layer is excessively large, it is undesirable in terms of catalyst cost; conversely, if the amount of catalyst metal is excessively small, the electrical connectivity between catalysts is broken, leading to increased resistance and making it impossible to obtain a sufficient current density.

[0090] In the present invention, the fact that the average particle size of the iridium oxide in the catalyst layer is less than 10 nm may mean that the catalyst particles are more uniformly distributed within the catalyst layer, and when the average particle size of the iridium oxide in the catalyst layer satisfies the aforementioned range, an electrolysis cell having a sufficient current density with a small amount of iridium loading can be realized as described above.

[0091] In addition, the iridium (Ir) elemental ratio on the surface of the catalyst layer, as measured by X-ray photoelectron spectroscopy (XPS) analysis, may be 7 at% to 20 at%. Specifically, the iridium elemental ratio on the surface of the catalyst layer may be 7 at% to 16 at% or 7 at% to 14 at%.

[0092] Meanwhile, the iridium elemental ratio on the surface of the catalyst layer may be influenced by the type of catalyst metal used in the process of forming the catalyst layer, the type and amount of ionomer and binder, the composition of the catalyst ink, the coating method, and the drying process. If the amount of catalyst metal included in the catalyst layer is excessively large, it is undesirable in terms of catalyst cost; conversely, if the amount of catalyst metal is excessively small, the electrical connectivity between catalysts is broken, increasing resistance and making it impossible to obtain a sufficient current density.

[0093] In the present invention, the iridium elemental ratio on the surface of the catalyst layer may indicate a high density of catalyst components within the catalyst layer, and when the iridium elemental ratio on the surface of the catalyst layer satisfies the aforementioned range, an electrolysis cell having a sufficient current density even with a small iridium loading amount can be realized as described above.

[0094] In addition, according to one embodiment of the present invention, the catalyst layer may include a high-density catalyst layer and a low-density catalyst layer, and the low-density catalyst layer may be located in close proximity to a substrate. In other words, a water-retaining electrode according to one embodiment of the present invention may have a structure comprising a substrate; a low-density catalyst layer located on the substrate; and a high-density catalyst layer located on the low-density catalyst layer.

[0095] The high-density catalyst layer may have an iridium (Ir) elemental ratio of 7 at% or more, and the low-density catalyst layer may have an iridium (Ir) elemental ratio of less than 7 at%. Specifically, the high-density catalyst layer may have an iridium (Ir) elemental ratio of 7 at% to 20 at% as determined by X-ray photoelectron spectroscopy (XPS) analysis, and the low-density catalyst layer may have an iridium (Ir) elemental ratio of 3 at% or more and less than 7 at% as determined by X-ray photoelectron spectroscopy (XPS) analysis.

[0096] Meanwhile, the high-density catalyst layer can be measured using X-ray photoelectromagnetism in the same way as the method for measuring the elemental ratio of iridium on the surface of the catalyst layer described above, and the low-density catalyst layer can be measured using X-ray photoelectromagnetism after peeling off the electrode surface with Scotch tape to expose the lower part.

[0097] If the catalyst layer has a structure including a low-density catalyst layer and a high-density catalyst layer, an electrolysis cell having a sufficient current density can be realized even with a small amount of iridium loading.

[0098]

[0099] In addition, the iridium oxide-ionomer aggregate may have an average particle size of 10 nm or more and 10 μm or less. Specifically, the average particle size of the iridium oxide-ionomer aggregate may be 10 nm or more, 50 nm or more, 100 nm or more, 150 nm or more, 200 nm or more, 250 nm or more, 300 nm or more, 350 nm or more, 400 nm, 500 nm or more, 800 nm or more, or 1000 nm or more, or 10 μm or less, 9 μm or less, 8 μm or less, 7 μm or less, 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, or 2 μm or less.

[0100]

[0101] In addition, the iridium oxide-ionomer aggregate may have a structure of either plate-like or elliptical. In addition, the iridium oxide-ionomer aggregate may have one or more structures of plate-like and elliptical, and may have a size of 0.5 μm or more and less than 10.0 μm based on the major axis, 0.5 μm or more and less than 5.0 μm, or 0.5 μm or more and less than 2.0 μm.

[0102] As another example, the iridium oxide-ionomer aggregate may have a size of 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, or 0.8 μm or more based on the long axis, and may have a size of 5.0 μm or less, 4.0 μm or less, 3.0 μm or less, 2.5 μm or less, or 2.0 μm or less.

[0103] As another example, the iridium oxide-ionomer aggregate may have a size of 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, or 0.8 μm or more based on the long axis, and may have a size of less than 5.0 μm, 4.0 μm or less, 3.5 μm or less, 3.0 μm or less, 2.5 μm or less, or 2.0 μm or less.

[0104] If the above aggregate has a plate-like and / or elliptical structure as described above, it may be advantageous to secure excellent in-plane conductivity with a small amount of iridium loading in a water electrolysis electrode containing it.

[0105] The above-mentioned ionomer acts as a binder and can be included together with the catalyst metal during the preparation of the catalyst ink for forming the catalyst layer. It can be attached to the surface of the catalyst metal particles to prevent aggregation between the catalyst particles and to ensure that the catalyst particles are evenly distributed within the catalyst layer. However, catalytic activity can be significantly affected by the ratio between the ionomer content and the catalyst content, and to maintain excellent catalytic activity, it is important to ensure an appropriate distribution of catalyst particles and ionomer within the catalyst layer. The water electrolysis electrode according to the present invention can achieve excellent electrolysis efficiency without the influence of the ionomer by uniformly dispersing a low loading amount of iridium while maintaining the uniform dispersion of the catalyst ink for forming the catalyst layer through a high-energy dispersion process during its manufacturing process.

[0106] The above ionomer may be used without special limitation as long as it is commonly used in the industry, but, for example, it may be one or more selected from the group consisting of perfluorinated ionomers, partially fluorinated ionomers, and hydrocarbon ionomers.

[0107] For example, the perfluorinated ionomer may be a copolymer of poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), or fluorovinyl ether such as tetrafluoroethylene containing a sulfonic acid group, and a mixture thereof, and commercially available products may include Nafion, Flemion, Asiplex, 3M ionomer, Dow ionomer, Solvay ionomer, Sumitomo ionomer, and mixtures thereof.

[0108] In addition, the above-mentioned partial fluorinated ionomers may include, for example, sulfonated poly(arylene ethersulfone-co-vinylidene fluoride), sulfonated trifluorostyrene-graft-poly(tetrafluoroethylene) (PTFE-g-TES), styrene-graft-sulfonated polyvinylidene fluoride (PVDF-g-PSSA), copolymers containing dicarboxybiphenyl as a monomer, copolymers containing hexafluorobenzene as a monomer, and mixtures thereof.

[0109] In addition, the above hydrocarbon-based ionomer may include, for example, sulfonized imide, sulfonated aryl ether sulfone, sulfonated ether ether ketone, sulfonated benzimidazole, sulfonated sulfone, sulfonated styrene, sulfonated phosphazene, sulfonated ether ether sulfone, sulfonated ether sulfone, sulfonated ether ketone ketone, aryl ether benzimidazole, and mixtures thereof.

[0110] Meanwhile, the electrochemical performance of polymer electrolyte membrane water electrolysis can be significantly influenced by the catalytic metal and ionomer constituting the catalytic layer of the polymer electrolyte membrane and the anode. In a water electrolysis electrode according to one embodiment of the present invention, the catalytic metal iridium on the surface of the catalytic layer has adsorption rate and area conditions as described above, thereby maintaining an appropriate dispersion of iridium within the catalytic layer and enabling excellent activity even with a low loading amount of iridium.

[0111] In addition, according to one embodiment of the present invention, the thickness of the catalyst layer may be, for example, less than 5.0 μm, 4.9 μm or less, 4.7 μm or less, 4.5 μm or less, 4.3 μm or less, 4.1 μm or less, 4.0 μm or less, 3.9 μm or less, 3.7 μm or less, 3.5 μm or less, 3.3 μm or less, 3.1 μm or less, 3.0 μm or less, 2.9 μm or less, 2.7 μm or less, 2.5 μm or less, 0.1 μm or more, 0.3 μm or more, 0.5 μm or more, 0.7 μm or more, 0.9 μm or more, and 1.0 μm or more. When the thickness of the catalyst layer satisfies the aforementioned range, the problem of increased overpotential can be prevented by ensuring sufficient catalytic activity area and facilitating mass transfer within the catalyst layer, and excellent activity can be achieved without increasing electrical resistance while maintaining a uniform distribution of catalyst metal particles.

[0112] Meanwhile, the water electrolysis electrode according to one embodiment of the present invention can be manufactured by preparing a catalyst ink and coating it onto a substrate.

[0113] The above catalyst ink can be prepared by mixing iridium oxide and a solvent, and an ionomer may be further used.

[0114] The above solvent is not particularly limited as long as it is commonly used in the industry, but, for example, one or more selected from the group consisting of water, alcohol, acetone, ethyl carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, fluoroethylene carbonate, dimethylacetamide, dimethyl sulfoxide, dimethylformamide, and N-methylpyrrolidone may be used, and specifically, a mixed solvent of water and alcohol may be used. When a mixed solvent of water and alcohol is used as the above solvent, water and alcohol may be used in a weight ratio of 1 to 9:9 to 1.

[0115] The above alcohols are, for example, methanol, ethanol, 1-propanol, isopropyl alcohol, butanol, isobutanol, 2-butanol, tert-butanol, n-pentanol, isopenyl alcohol, 2-methyl-1-butanol, neopentyl alcohol, diethyl carbinol, methyl propyl carbinol, methyl isopropyl carbinol, dimethyl ethyl carbinol, 1-hexanol, 2-hexanol, 3-hexanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 4-methyl-1-pentanol, 2-methyl-2-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-3-pentanol, 2,2-dimethyl-1-butanol, 2,3-dimethyl-1-butanol, Examples include 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, and 4-heptanol, and mixtures thereof, but are not particularly limited thereto.

[0116] In addition, when using an ionomer in the preparation of the catalyst ink, any ionomer commonly known in the art may be used without particular limitation, but materials such as those described above may be used as examples. Furthermore, when using the ionomer, the iridium oxide and the ionomer may be used in a weight ratio of 1:0.02 to 0.2, or 1:0.05 to 0.2, or 1:0.05 to 0.2. As another example, the iridium oxide and the ionomer may be used in a weight ratio of 1:0.05, 1:0.1, or 1:0.2. As yet another example, when using the ionomer, the iridium oxide and the ionomer may be used in a weight ratio of 1:0.01 to 0.2, or 1:0.01 to 0.1, or 1:0.01 to 0.05.

[0117] In addition, the mixture for manufacturing the above catalyst ink can be manufactured using a mechano fusion process, that is, a high-energy dispersion method.

[0118] The above mechano fusion process is a method of diffusion immobilization by applying mechanical energy to the surface of a mother particle and adding thermal energy. For example, the above mechano fusion process may include a high energy ball mill device, a planetary mill device, a stirred ball mill device, a vibrating mill device, etc.

[0119] A manufacturing method according to one embodiment of the present invention utilizes a mechano-fusion process (high-energy dispersion method) for the catalyst ink to reduce the average particle size of iridium oxide, which is a catalyst particle in the catalyst composition, to a nanometer particle size of 1 nm or more and less than 10 nm, thereby uniformly dispersing the catalyst particles in the catalyst composition and improving coating properties, so that a catalyst layer of a desired thickness can be formed, and a high level of electrolysis efficiency can be achieved by using a low loading amount of catalyst.

[0120] Meanwhile, in the case of mixing / dispersion using a homogenizer commonly used in the past for manufacturing the above catalyst ink, the iridium oxide particles, which are catalyst particles, have a particle size of 10 nm or more, or 10 nm to 30 nm. It is difficult to reduce the average particle size to a size smaller than the above range, and consequently, it is difficult to achieve uniform dispersion within the catalyst layer and the batch density is low. Therefore, in order to obtain a highly active electrode, the absolute iridium loading amount must be increased, and there is a problem in that it is difficult to realize an electrode with the same performance.

[0121] In addition, the coating can be performed by methods such as bar coating, dip coating, spin coating, and spray coating, and preferably by a bar coating method. For example, the catalyst ink can be coated on one surface of a substrate using methods such as a Meyer bar, doctor blade, slot die, comma bar, and spin coat.

[0122]

[0123] Membrane electrode assembly

[0124] The present invention comprises an ion exchange membrane; a cathode located on one surface of the ion exchange membrane; and an anode located on the other surface of the ion exchange membrane, wherein the anode comprises a substrate and a catalyst layer located on the substrate and comprising iridium oxide, and the iridium loading amount of the catalyst layer is 0.1 mg / cm² 2 ≥ 1.0 mg / cm² 2 The present invention provides a membrane electrode assembly for water electrolysis having an average particle size of iridium oxide of 1 nm or more and less than 10 nm, wherein the average particle size of the iridium oxide is 1 nm or more and less than 10 nm.

[0125] The above membrane electrode assembly can be utilized in all electrochemical conversion devices, and the electrochemical conversion device may include a device capable of producing useful chemical substances through electrochemical conversion such as water electrolysis, carbon dioxide electrolysis, and fuel cells, and a device capable of being utilized for the reduction and conversion of carbon dioxide and NOx.

[0126] Electrochemical conversion, or electrolysis, refers to the decomposition of substances through redox reactions by applying a direct current voltage to a decomposition reaction that does not occur spontaneously. The anode acts as an oxidation electrode, oxidizing water to generate oxygen, thereby producing hydrogen ions. The hydrogen ions generated at the anode are transferred to the cathode through the separator, and the cathode acts as a reduction electrode, reacting with the electrons and hydrogen ions transferred from the anode to produce a product.

[0127] In a membrane electrode assembly, the anode is a portion that receives water (H2O), and when electricity is applied to the electrode catalyst layer, it electrolyzes water to generate oxygen, hydrogen ions, and electrons. It may include a catalyst that is active in the electrolysis of water, and the catalyst layer of the anode may include one or more selected from the group consisting of Pt, Au, Pd, Ir, Ag, Rh, Ru, Ni, Al, Mo, Cr, Cu, Ti, W, alloys thereof, or mixed metal oxides, such as RuO2, IrO2, etc., for the oxygen generation reaction.

[0128] In the membrane electrode assembly according to one embodiment of the present invention, the anode is the aforementioned water electrolysis electrode; that is, the membrane electrode assembly utilizes the aforementioned water electrolysis electrode as the anode. Accordingly, the anode in the membrane electrode assembly includes all the characteristics of the aforementioned water electrolysis electrode.

[0129]

[0130] The above ion exchange membrane is composed of an inert material that does not participate in electrochemical reactions itself, provides a pathway for ions to move between the anode and the cathode, and can serve to prevent physical contact between the anode and the cathode. The above ion exchange membrane may be a polymer electrolyte membrane and enables ion exchange that moves hydrogen ions generated in the catalyst layer of the anode to the catalyst layer of the cathode. The above ion exchange membrane may be one or more selected from the group consisting of perfluorosulfonic acid, polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene, and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). The ion exchange membrane of the present invention may include a fluorine-based polymer, and the fluorine-based polymer has excellent hydrogen ion conductivity, so it can smoothly transport hydrogen ions generated from the anode.

[0131] According to one embodiment of the present invention, the thickness of the separator may be 30 μm or more and 140 μm or less. For example, the thickness of the separator may be 30 μm or more, 40 μm or more, 50 μm or more, 60 μm or more, 70 μm or more, 80 μm or more, 140 μm or less, 135 μm or less, 130 μm or less, 127 μm or less, 125 μm or less, 120 μm or less, 115 μm or less, 110 μm or less, 105 μm or less, and 100 μm or less. More specifically, the thickness of the separator may be 70 μm or more and 127 μm or less. When the thickness range of the separator is satisfied, the electrical resistance is reduced, the overvoltage is reduced, and the transport of hydrogen ions can proceed smoothly, thereby increasing the electrolysis efficiency.

[0132] In addition, the cathode serves as a hydrogen generating component, allowing hydrogen ions transferred from the anode to combine with electrons transferred through an external circuit to produce pure hydrogen. Such a cathode may be one commonly used in the industry and may be composed of, for example, platinum (Pt) or platinum-supported carbon (Pt / C).

[0133] According to one embodiment of the present invention, the membrane electrode assembly of the present invention has a current density of 2.2 A / cm² when the voltage of the reference cell below is 1.9 V at a temperature of 70°C. 2 It could be more than that.

[0134] [Reference Cell]

[0135] Anode catalyst: IrO2 (<0.4 mg / cm²) 2 )

[0136] Cathode catalyst: Pt / C

[0137] Catalyst layer active area: 25 cm 2

[0138] Separator: Nafion 115 (Thickness: 127 µm)

[0139] Porous diffusion layer: Pt-Coated Ti-PTL (Thickness: 250 µm)

[0140] Gas Diffusion Layer: Carbon GDL (Thickness: 285 µm)

[0141]

[0142] The membrane electrode assembly of the present invention can be implemented to have an excellent level of current density value by including an anode comprising a low loading amount of iridium oxide and a high-density catalyst layer with controlled iridium distribution. Specifically, under a temperature condition of 70°C, when the voltage of the reference cell below is 1.9V, the current density is 2.2 A / cm² 2 The above may be the case, and having a current density within the above range means that the electrolysis cell including the membrane electrode assembly can have an excellent level of electrolysis efficiency. Generally, the current density value increases as the catalyst loading amount increases, but the membrane electrode assembly of the present invention can exhibit a high level of current density value despite a low catalyst loading amount. For example, the current density when the cell voltage is 1.9 V is 2.20 A / cm² 2 Above, 2.25 A / cm 2 Above, 2.30 A / cm 2 Above, 2.35 A / cm 2 Above or 2.40 A / cm 2 It may be above. As another example, the current density when the cell voltage is 1.9V is 2.40 A / cm² 2 Above, 2.45 A / cm 2 Above, 2.50 A / cm 2 Above, 2.55 A / cm 2 Above or 2.60 A / cm 2 It could be more than that.

[0143]

[0144] electrolysis cell

[0145] The present invention provides an electrolytic cell comprising the membrane electrode assembly of the present invention described above. The electrolytic cell may include the membrane electrode assembly, a gas diffusion layer, a porous diffusion layer, and a separator.

[0146] Here, the above membrane electrode assembly is as described above.

[0147] The above gas diffusion layer may use a porous body made of carbon material such as carbon fiber cloth, carbon fiber felt, or carbon fiber paper, or a porous metal body made of a thin metal plate with a mesh structure such as expanded metal or metal mesh, and in the electrolysis cell of the present invention, the gas diffusion layer may use carbon fiber cloth.

[0148] The porous diffusion layer may include titanium felt. The porous diffusion layer can absorb processing errors occurring during the fabrication of the electrolysis cell by improving the contact force between the separator plate and the membrane electrode assembly and reducing the gap when the electrolysis cell is assembled. In addition, it acts as a flow path between the separator plate and the catalyst layer, thereby facilitating the smooth transport of fluid materials.

[0149] The above separator plate can serve to provide spatial separation between unit cells and can facilitate the transport and reaction of fluid materials by including a flow path. The above separator plate may include a corrosion-resistant metal material such as titanium or stainless steel.

[0150]

[0151] Examples

[0152] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0153] Example 1

[0154] (1) Catalytic ink manufacturing

[0155] IrO2 catalyst (Thermo-Fisher, Ir content: 84.5%, BET 25~35 m) 2A catalyst ink was prepared by performing a mechanofusion process for 4 days on a solution mixed with 2.625 g of 1-propanol, 1.965 g of Nafion binder (Nafion D-2020, Nafion content: 20 wt%, DuPont), 7.485 g of 1-propanol, and 2.925 g of distilled water.

[0156]

[0157] (2) Manufacturing of water electrolysis electrode (anode)

[0158] The above-mentioned prepared catalyst ink was coated onto a PTFE film using a bar coater at a speed of 10 mm / s under a temperature of 40°C, and dried in an 80°C oven for about 1 hour to manufacture a water electrolysis electrode.

[0159]

[0160] (3) Fabrication of membrane electrode assembly

[0161] A catalyst ink was prepared by performing a mechanofusion process for 3 days in a solution containing 2.0 g of Pt / C catalyst (Tanaka, TEC10V50E), 3.7 g of Nafion binder (Nafion D-2020, Nafion content: 20 wt%, DuPont), 13.84 g of 1-propanol, and 0.46 g of distilled water, and the cathode was prepared by coating the solution onto a PTFE film at a speed of 10 mm / s at a temperature of 40°C and drying it in an oven at 80°C for about 1 hour.

[0162] The above-mentioned water electrolysis electrode (anode) and cathode each have a cell active area (2 × 2 cm²) 2 The anode and cathode catalyst electrodes were placed against each other with a separator (Nafion N115, thickness: 127 μm) in between. The electrodes and the separator were placed between iron plates, and a membrane electrode assembly was manufactured by hot pressing (pressure: 0.5 ton) for about 5 minutes at a temperature of 140°C.

[0163]

[0164] Example 2

[0165] A water electrolysis electrode (anode) and a membrane electrode assembly were prepared in the same manner as in Example 1, except that 0.66 g of Nafion binder (Nafion D-2020, Nafion content: 20 wt%, DuPont), 8.25 g of 1-propanol, and 3.465 g of distilled water were mixed when preparing the catalyst ink in Example 1.

[0166]

[0167] Example 3

[0168] A water electrolysis electrode (anode) and a membrane electrode assembly were prepared in the same manner as in Example 1, except that 0.68 g of Nafion binder (Nafion D-2020, Nafion content: 20 wt%, DuPont), 2.75 g of 1-propanol, and 1.155 g of distilled water were mixed when preparing the catalyst ink in Example 1.

[0169]

[0170] Comparative Example 1

[0171] In Example 1, the catalyst ink was an IrO2 catalyst (Thermo-Fisher, Ir content: 84.5%, BET 25~35 m 2 A water electrolysis electrode (anode) and a membrane electrode assembly were prepared in the same manner as in Example 1, except that the solution was mixed and dispersed at 10,000 rpm for 1 hour using a homogenizer, in a solution of 0.75 g (1-g), 0.56 g of Nafion binder (Nafion D-2020, Nafion content: 20 wt%, DuPont), 0.89 g of 1-propanol, and 0.3 g of distilled water.

[0172]

[0173] Comparative Example 2

[0174] A water electrolysis electrode (anode) and a membrane electrode assembly were prepared in the same manner as in Example 1, except that the catalyst ink was prepared by mixing and dispersing the solution with a homogenizer at 10,000 rpm for 1 hour instead of the mechano fusion process.

[0175]

[0176] Experimental Example 1

[0177] Surface and cross-sectional analyses were performed on each water electrolysis electrode (anode) prepared in the examples and comparative examples, and the results are shown in Table 1 and Figures 1 to 9 below.

[0178] (1) Iridium oxide average particle size (nm)

[0179] Electrode cross-sectional specimens were prepared using a low-temperature Ultramicrotome, and particle sizes were collected and average values ​​were calculated by analyzing cross-sectional images in TEM mode using a transmission electron microscope (TEM, JEM-ARM200F, NEOARM) from the specimens.

[0180]

[0181] (2) Iridium oxide density

[0182] The mass of Ir per unit area within the electrode was calculated using the gravimetric method, and the electrode thickness was calculated through the analysis of the electrode cross-sectional image using SEM; the result was calculated as [mass of Ir per unit area within the electrode / electrode thickness].

[0183]

[0184] (3) Iridium loading amount (mg / cm²) 2 )

[0185] It can be measured using an energy-dispersive fluorescence X-ray analyzer (XRF, Rigaku NEx-GC), and specifically, the absolute amount of the components within the catalyst layer measured by the X-ray analyzer was quantified to calculate the relative ratio.

[0186]

[0187] (4) Iridium element ratio (at%)

[0188] The iridium elemental ratios of the catalyst layer surface (upper) and lower portions were measured by X-ray photoelectron spectroscopy (XPS) analysis. The catalyst layer surface was analyzed, and the lower portions were measured by peeling off the catalyst layer surface of the electrode using Scotch tape to expose the lower portions.

[0189] Specifically, electrode specimens were cut to an appropriate size, fixed to carbon tape, and loaded into a photoelectron spectrometer (K-Alpha+, Thermo Fisher Scientific Inc.). Qualitative analysis was performed after a survey scan according to the following conditions, and based on the results of each qualitative analysis, narrow scans were obtained for each element at three points for quantitative analysis and binding state analysis.

[0190] X-ray source: monochromatic Al Kα (1486.6 eV)

[0191] Operation mode: CAE (Constant Analyzer Energy) mode

[0192] Software: Avantage software (version 5.980)

[0193] X-ray spot size: 400 µm

[0194] Survey scan: Scan range 0–1360 eV, step size 1 eV

[0195] Narrow scan: Scan range 13–29 eV, step size 0.1 eV

[0196]

[0197] (5) Electrode formation quality

[0198] The relative standard deviation (RSD, %) of the iridium distribution within the catalyst layer was confirmed using an energy-dispersive fluorescence X-ray analyzer (XRF, Rigaku NEx-CG).

[0199]

[0200] (6) Analysis of the catalyst layer structure

[0201] It was confirmed through the analysis of catalyst layer surface and cross-sectional images using a field emission scanning electron microscope (FE-SEM).

[0202] In addition, scanning electron microscopy-elemental analysis (SEM-EDS) was performed to measure the Ir content (wt%) on the surface of the catalyst layer.

[0203]

[0204] (7) Catalyst layer thickness (㎛)

[0205] The thickness was calculated as an average value based on the analysis of surface and cross-sectional images of the catalyst layer using a field emission scanning electron microscope (FE-SEM).

[0206]

[0207] As shown in Table 1 above, Examples 1 to 3 have a catalyst layer Ir loading amount of 0.4 mg / cm² 2 and 1.0 mg / cm² 2 With a reduced Ir loading amount, the average particle size of the iridium oxide is less than 5 nm, and the iridium oxide density in the catalyst layer is 1.5 g / cm³ 3 As shown above, it can be confirmed that the average particle size of Ir has decreased and the density of Ir oxide has increased compared to Comparative Examples 1 and 2. In addition, it can be confirmed that Examples 1 to 3 have an Ir elemental ratio on the surface of the catalyst layer of 7 at% or higher, which is significantly higher than Comparative Example 1, even though the Ir loading amount is lower. Furthermore, it can be seen that Examples 1 to 3 have a significantly smaller relative standard deviation of iridium distribution (electrode formation quality) within the catalyst layer compared to Comparative Example 2, which has the same or lower Ir loading amount, and through this, it can be confirmed that iridium is uniformly highly dispersed within the catalyst layer of Examples 1 to 3.

[0208]

[0209] Experimental Example 2

[0210] A water electrolysis cell was fabricated using the membrane electrode assembly prepared in the above examples and comparative examples, and the current density and high current range mass activity were measured. The results are shown in Table 2 below.

[0211] (1) Electrolytic cell

[0212] The water electrolysis cell was manufactured by stacking an end plate / current collector / separator (bipolar plate, senpentine flow channel structure, Pt coating) / porous transport layer (Pt-coated PTL) / membrane electrode assembly / gas diffusion layer (36BB, SGL) / separator (bipolar plate) / current collector / end plate.

[0213]

[0214] (2) Current density (A / cm²) 2 )

[0215] Starting from a set initial potential (0V), the current-potential curve was measured while varying the voltage at a constant scan rate of 10 mV / s up to a specific potential (2V or 3V), and the current value corresponding to 1.9V was read and set as the current density. At this time, the flow rate of water injected into the cell was 10 mL / min, and the temperature of the cell was 70℃.

[0216]

[0217] (3) Mass activity (A / mg) Ir )

[0218] The current density value measured in (2) was calculated by dividing it by the Ir loading amount.

[0219]

[0220] Through Table 2 above, it was confirmed that Examples 1 to 3 exhibited excellent mass activity, with current densities at an equivalent level or increased by approximately 60% or more, even with Ir loading amounts significantly reduced to 20% and 50% of Comparative Example 1. Additionally, Examples 1 to 3 showed a significantly increased current density of approximately 30% to 135% compared to Comparative Example 2, and Examples 1 and 2, which had the same Ir loading amount as Comparative Example 2, showed a mass activity improvement of approximately 30% to 40% compared to Comparative Example 2.

[0221] Through this, it can be seen that the water electrolysis electrode presented in the present invention has the effect of having a high level of current density in membrane electrode assemblies and electrolysis cells to which it is applied, even though it contains a low loading amount of iridium, by including a high-density catalyst layer in which iridium oxide nanoparticles are highly dispersed and the surface iridium elemental ratio is 7 to 20 at%.

Claims

1. Recording; and A catalyst layer located on the above substrate and comprising iridium oxide and iridium oxide-ionomer aggregates, and The iridium loading amount of the catalyst layer is 0.1 mg / cm² 2 ≥ 1.0 mg / cm² 2 Below, A water electrolysis electrode having an average particle size of iridium oxide of 1 nm or more and less than 10 nm.

2. In Paragraph 1, A water electrolysis electrode having an iridium (Ir) elemental ratio on the surface of the catalyst layer measured by X-ray photoelectron spectroscopy (XPS) analysis of 7 at% to 20 at%.

3. In Paragraph 1, A water electrolysis electrode having an iridium (Ir) elemental ratio on the surface of the catalyst layer measured by X-ray photoelectron spectroscopy (XPS) analysis of 7 at% to 14 at%.

4. In Paragraph 1, The above iridium oxide-ionomer aggregate is a water electrolysis electrode having an average particle size of 10 nm or more and 10 µm or less.

5. In Paragraph 1, A water electrolysis electrode having one or more structures selected from plate-shaped and elliptical shapes, and having a size of 0.5 μm or more and less than 10.0 μm based on the major axis.

6. In Paragraph 1, The density of iridium oxide in the catalyst layer is 1.5 g / cm³ 3 Electrolysis electrode that is the above.

7. In Paragraph 1, The catalyst layer comprises a high-density catalyst layer and a low-density catalyst layer, The above low-density catalyst layer is a water electrolysis electrode located in close proximity to the substrate.

8. In Paragraph 7 A water electrolysis electrode in which the high-density catalyst layer has an iridium (Ir) elemental ratio of 7 at% to 20 at% as determined by X-ray photoelectron spectroscopy (XPS) analysis, and the low-density catalyst layer has an iridium (Ir) elemental ratio of 3 at% or more and less than 7 at% as determined by X-ray photoelectron spectroscopy (XPS) analysis.

9. In Paragraph 1, A water electrolysis electrode in which the above ionomer is one or more selected from the group consisting of perfluorinated ionomers, partially fluorinated ionomers, and hydrocarbon ionomers.

10. In Paragraph 1, The above description is a water electrolysis electrode comprising one or more selected from the group consisting of polyether sulfone, cellulose acetate, polyvinylidene fluoride, polytetrafluoroethylene, ethylene tetrafluoroethylene, polyamide, polyimide, nylon, and polyolefin.

11. Ion exchange membrane; A cathode located on one side of the above ion exchange membrane; and It includes an anode located on the other side of the above-mentioned ion exchange membrane, and The above anode comprises a substrate and a catalyst layer located on the substrate and comprising iridium oxide, and The iridium loading amount of the catalyst layer is 0.1 mg / cm² 2 ≥ 1.0 mg / cm² 2 Below, A membrane electrode assembly for water electrolysis in which the average particle size of the iridium oxide is 1 nm or more and less than 10 nm.

12. In Paragraph 11, A membrane electrode assembly for water electrolysis having an iridium (Ir) elemental ratio on the surface of the catalyst layer measured by X-ray photoelectron spectroscopy (XPS) analysis of 7 at% to 20 at%.

13. In Paragraph 11, The above ion exchange membrane is a membrane electrode assembly for water electrolysis, wherein the above ion exchange membrane is one or more selected from the group consisting of perfluorosulfonic acid, polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene, and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP).

14. An electrolytic cell comprising a membrane electrode assembly for water electrolysis according to paragraph 11.

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