Catalytic inks and their applications

Abstract

To provide a catalyst ink that achieves both solubility with an ionomer and suppression of attack on an ion exchange membrane. 【Solution】The catalyst ink disclosed herein includes a catalyst composed of metal-based particles, an ionomer, and a solvent. The volume ratio of the catalyst to the ionomer is 1.0:9.0 or more and 9.0:1.0 or less, and the dispersion term δD 2 , s , i , , 0.5 , i , s , i , 2 , s , 2 , the polar term δP i , the hydrogen bond term δH i in the Hansen solubility parameter of the ionomer, and the dispersion term δD s , the polar term δP s , the hydrogen bond term δH [[ID=I3]] s in the Hansen solubility parameter of the solvent satisfy the following formulas (1) and (2), and the solubility index R of the solvent with respect to the ionomer represented by the following formula (3) is less than 10. δP i ―5.5 < δP s < δP i ···(1) δH i ―7.0 < δH s < δH i ···(2) R = (4×(δD s - δD i ) 2 + (δP s - δP i ) 2 + (δH s - δH i ) 2 ) 0.5 ···(3)

Description

[Technical Field]

[0001] The technology disclosed herein relates to catalytic inks and their applications. [Background technology]

[0002] From the perspective of energy and environmental issues, various technologies have been proposed to convert renewable energy into electricity (such as solar cells and wind power generation). However, storing renewable energy in the form of electricity requires large-scale energy storage facilities, which leads to soaring equipment costs. Therefore, in recent years, water electrolysis devices that use electricity to decompose an aqueous electrolyte (such as an alkaline aqueous solution) into oxygen and hydrogen have been proposed. This allows renewable energy to be converted into useful gases, thereby reducing the equipment costs required for storing renewable energy.

[0003] The catalyst layer constituting a water electrolysis device is typically formed by drying a catalyst ink. For example, Patent Publication 1 discloses a catalyst ink comprising nano-sized precious metal particles and at least one acidic ionomer. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2016-505193 [Overview of the project] [Problems that the invention aims to solve]

[0005] In recent years, from the perspective of improving the catalytic reaction efficiency, the requirements for a membrane-catalyst layer conjugate body that forms (supports) a catalyst layer on an ion exchange membrane have been increasing. Such a catalyst layer can be obtained, for example, by applying (printing) a catalyst ink on an ion exchange membrane and drying it. A solvent capable of dissolving an ionomer is used in such a catalyst ink. On the other hand, when the catalyst ink is printed (applied) onto the ion exchange membrane, there is a risk that the solvent will penetrate into the ion exchange membrane, causing sheet attack such as wrinkles and distortion. Therefore, the catalyst ink is required to have the performance of suppressing sheet attack.

[0006] The technology disclosed herein has been made in view of the above circumstances, and its main object relates to providing a catalyst ink that achieves both solubility with an ionomer and suppression of attack on an ion exchange membrane.

Means for Solving the Problems

[0007] The catalyst ink disclosed herein is a catalyst ink for an electrode of an anion exchange membrane type water electrolysis device containing a catalyst composed of metal-based particles, an ionomer, and a solvent, wherein the volume ratio of the catalyst to the ionomer is 1.0:9.0 or more and 9.0:1.0 or less, and the dispersion term δD in the Hansen solubility parameter of the ionomer i , the polar term δP i , the hydrogen bond term δH i and the dispersion term δD in the Hansen solubility parameter of the solvent s , the polar term δP s , the hydrogen bond term δH s satisfy the following formulas (1) and (2), and the dissolution index R of the solvent with respect to the ionomer represented by the following formula (3) is less than 10. δP i ―\\(5.5 \lt δP \lt\\) s <δP i ···(1) δH i ―\\(7.0 \lt δH \lt\\) s <δH i ···(2) R = (4×(δD s - δD i )² + (δP 2 - δPs -δP i ) 2 +(δH s -δH i ) 2 ) 0.5 ...(3)

[0008] With this configuration, the relationship between the ionomer contained in the catalyst ink and the solvent satisfies the following formulas (1) and (2), and the solvent solubility index R is controlled to be less than 10. The inventors have experimentally confirmed that by satisfying the above requirements in the relationship between the ionomer contained in the catalyst ink and the solvent, a catalyst ink can be obtained that achieves both solubility with the ionomer and suppression of attack on the ion exchange membrane.

[0009] In one preferred embodiment of the catalyst ink disclosed herein, the solvent comprises at least one selected from the group consisting of alcohol-based solvents, ether-based solvents, sulfoxide-based solvents, water, and ester-based solvents.

[0010] In one preferred embodiment of the catalyst ink disclosed herein, the solvent comprises two or more solvents.

[0011] In one preferred embodiment of the catalyst ink disclosed herein, the solvent is a mixed solvent mainly comprising at least one selected from the group consisting of ethanol and methanol, and butyl carbitol, wherein the weight ratio of the butyl carbitol to the total weight of the mixed solvent is 40% or more.

[0012] In one preferred embodiment of the catalyst ink disclosed herein, the solvent comprises 2-methoxyethanol.

[0013] In one preferred embodiment of the catalyst ink disclosed herein, the dispersion term δD of the ionomer is i , polarity term δP i , hydrogen bond term δH i However, these values ​​are 17.1±1, 12±1, and 17.4±1, respectively.

[0014] In one preferred embodiment of the catalyst ink disclosed herein, the solvent is a highly polar solvent.

[0015] In one preferred embodiment of the catalyst ink disclosed herein, the catalyst comprises at least one selected from the group consisting of nickel, iron, cobalt, and molybdenum.

[0016] Another aspect of the technology disclosed herein is a catalyst layer comprising the dried catalyst ink described above.

[0017] Another aspect of the technology disclosed herein is a membrane catalyst layer assembly comprising an ion exchange membrane and a catalyst layer disposed on the ion exchange membrane, wherein the catalyst layer is a dried form of the catalyst ink.

[0018] Another aspect of the technology disclosed herein is provided, which is a catalyst electrode comprising a conductive substrate and a catalyst layer disposed on the conductive substrate, wherein the catalyst layer is a dried form of the catalyst ink.

[0019] Another aspect of the technology disclosed herein is provided, which is a catalyst electrode comprising a conductive substrate and a catalyst layer disposed on the conductive substrate, wherein the catalyst layer is a dried form of the catalyst ink.

[0020] Another aspect of the technology disclosed herein is a membrane electrode assembly comprising an ion exchange membrane, a catalyst layer disposed on the ion exchange membrane, and a conductive substrate disposed on the catalyst layer, wherein the catalyst layer is a dried form of the catalyst ink.

[0021] Another aspect of the technology disclosed herein is provided, an anion exchange membrane type water electrolysis apparatus comprising an ion exchange membrane and a catalyst layer disposed on the ion exchange membrane, wherein the catalyst layer is a dried form of the catalyst ink. [Brief explanation of the drawing]

[0022] [Figure 1]Figure 1 is a schematic cross-sectional view showing a water electrolysis apparatus according to this embodiment. [Figure 2] Figure 2 is an exploded view schematically showing the configuration of the film electrode assembly according to this embodiment. [Figure 3] Figure 3 is a flow chart showing a method for manufacturing a membrane catalyst layer assembly according to one embodiment. [Figure 4] Figure 4 is a schematic cross-sectional view showing a modified water electrolysis apparatus. [Figure 5] Figure 5 is an exploded view schematically showing the configuration of a modified membrane electrode assembly. [Modes for carrying out the invention]

[0023] Preferred embodiments of the technology disclosed herein will be described below. Matters other than those specifically mentioned herein but necessary for implementing the technology disclosed herein can be understood as design matters for those skilled in the art based on the prior art. The technology disclosed herein can be implemented based on the content disclosed herein and common technical knowledge in the art. The following description is not intended to limit the technology disclosed herein to any particular embodiment. In this specification and in the claims, when a predetermined numerical range is written as A to B (where A and B are arbitrary numbers), it means "A or greater and B or less." Therefore, it includes "greater than A and less than B."

[0024] The Hansen solubility parameter (HSP) is a value used to predict the solubility of a substance. Specifically, the HSP is represented by coordinate positions in a three-dimensional space (Hansen space) consisting of a dispersion term δD, a polarity term δP, and a hydrogen bonding term δH. The dispersion term δD represents the energy due to intermolecular dispersion forces. The polarity term δP represents the energy due to intermolecular dipole interactions. The hydrogen bonding term δH represents the energy due to intermolecular hydrogen bonds. The HSP can be calculated, for example, using software such as HSPiP (Hansen Solubility Parameters in Practice).

[0025] <Catalyst ink> The catalyst ink disclosed herein is a composition used in the manufacture of electrodes for water electrolysis apparatus. The catalyst ink disclosed herein contains a catalyst, an ionomer, and a solvent. In this specification, "ink" refers to a mixture in which some or all of the solid components are dispersed in the solvent, and includes so-called "slurry," "paste," etc. Each component will be described in detail below.

[0026] (1) Catalyst The catalyst is a powder material (a collection of fine particles) consisting of metal particles. The catalyst is the main component of the catalyst layer in a water electrolysis apparatus. The catalyst can be any metal particles that are conventionally known and can be used as catalysts in water electrolysis apparatuses. From the viewpoint of having suitable catalytic activity and electrical conductivity, it is preferable that the catalyst contains at least one selected from the group consisting of nickel (Ni), iron (Fe), cobalt (Co), and molybdenum (Mo). Here, "metal-based particles" in this specification means that the metal content of the entire catalyst is approximately 80% by weight or more, for example, 85% by weight or more, preferably 90% by weight or more, and more preferably 95% by weight or more.

[0027] The average particle size of the catalyst particles contained in the catalyst ink is not particularly limited, but is preferably 150 nm or less, more preferably 100 nm or less, and even more preferably 80 nm or less. By using catalyst particles with a small average particle size, the surface activity of the catalyst particles is increased. This makes it possible to obtain high catalytic activity. On the other hand, the lower limit of the average particle size of the catalyst particles is not particularly limited, but from the viewpoint of productivity and handling, it is preferably 10 nm or more, and more preferably 30 nm or more. In this specification, "average particle size" refers to the cumulative 50% particle size (D) based on the number of particles in the particle size distribution of 1000 Ni particles extracted from an image of Ni particles taken using a field emission scanning electron microscope (FE-SEM). 50 ) indicates.

[0028] The coefficient of variation (CV) of the catalyst particles is not particularly limited, but is preferably 0.2 or less, more preferably 0.18 or less, and particularly preferably 0.15 or less. In this specification, "CV value" refers to the ratio of the standard deviation σ to the average particle diameter of the catalyst particles obtained above (standard deviation σ / average particle diameter). In other words, the smaller the CV value, the more uniform the particles are. Therefore, catalyst particles with a small CV value (in other words, uniform particles) can suppress the decrease in catalytic activity caused by coarse particles with large particle diameters or secondary particles formed by the aggregation of multiple fine particles. In addition, adhesion to electrodes and ion exchange membranes is improved, and a smooth catalyst layer can be obtained.

[0029] The shape of the catalyst particles is not particularly limited and may be spherical or non-spherical. Examples of non-spherical catalyst particles include plate-shaped, flaky, or irregularly shaped particles. When spherical catalyst particles are used, the aspect ratio of the catalyst particles is preferably 1.2 or less, more preferably 1.15 or less, and particularly preferably 1.1 or less. This makes it easier to improve the packing density of the catalyst particles when forming the catalyst layer. The lower limit of the aspect ratio of such spherical catalyst particles is 1 or more. On the other hand, when non-spherical catalyst particles are used, the aspect ratio of the catalyst particles is preferably 1.3 or more, more preferably 1.5 or more, even more preferably 1.7 or more, and particularly preferably 2 or more. When catalyst particles with such high aspect ratios are used, the specific surface area of ​​the catalyst particles increases when forming the catalyst layer, thereby increasing the reaction surface. This improves reaction efficiency and allows for better catalytic activity. On the other hand, considering the ease of particle generation, the upper limit of the aspect ratio of non-spherical catalyst particles is preferably 5 or less, more preferably 4 or less, and particularly preferably 3 or less. Furthermore, the catalyst in this embodiment may be a mixed powder obtained by mixing spherical particles and non-spherical particles.

[0030] (2) Ionomer In an ink catalyst, the ionomer disperses the catalyst in the solvent and facilitates ion exchange. In this embodiment, the ionomer can be an anion exchange resin equipped with an anion exchange group (e.g., a quaternary ammonium group, a pyridinium group, etc.) or a proton exchange resin equipped with a proton exchange group (e.g., a sulfonic acid group, etc.), with the anion exchange resin being preferred. Examples of such anion exchange resins include Sustainion® ionomer from Dioxide Materials, Inc. and Piperion® ionomer from Versogen, Inc. Examples of such proton resins include Nafion®, Inc.

[0031] The HSP of ionomers is not particularly limited, but the dispersion term δD i It is preferable that it is in the range of 17.1±1, and more preferably in the range of 17.1±0.5. Also, the polarity term δP i It is preferably in the range of 12±1, and more preferably in the range of 12±0.5. Hydrogen bond term δH i It is preferable that the value is in the range of 17.4 ± 1, and more preferably in the range of 17.4 ± 0.5.

[0032] The HSP of an ionomer can be determined, for example, by the following method. First, a 40 μm thick film of the ionomer to be measured for HSP is deposited and cut into 3 mm x 3 mm pieces to prepare a test specimen. Next, several solvents (e.g., 10 or more) with known HSP values ​​(e.g., the HSP of the solvent is recorded in a database) are prepared and 2 ml each is placed in a glass bottle. Then, the test specimen is placed in the glass bottle containing the solvent and immersed at room temperature (25°C) for 24 hours. After that, the test specimen is removed from the glass bottle, the solvent adhering to the surface is wiped off with a cloth, and the weight of the test specimen is measured. The degree of swelling (%) is then calculated using the following formula. A degree of swelling of 10% or more, or the test specimen being completely dissolved, is considered "good," while a degree of swelling of less than 10% is considered "poor." Swelling degree (%) = (Weight of specimen after immersion - Weight of specimen before immersion) / Weight of specimen before immersion × 100 Then, by inputting the solvent and swelling degree as "good" or "poor" into the HSPiP software, the HSP(dispersion term δD) of the ionomer can be determined. i , polarity term δP i , hydrogen bond term δH i The HSP of the ionomer can be obtained in this way.

[0033] The volume ratio of catalyst to ionomer in the catalyst ink of this disclosure is controlled to be 1.0:9.0 or higher (preferably 3.0:7.0 or higher, more preferably 4.0:6.0 or higher). The higher the volume ratio of catalyst, the higher the conductivity reliability of the dried catalyst ink tends to be. On the other hand, if the volume ratio of catalyst becomes too high (exceeding 9.0:1.0), cracking or peeling may occur when the dried catalyst ink is formed, which may impair conductivity reliability. Therefore, the volume ratio of catalyst to ionomer in the catalyst ink of this disclosure is controlled to be 9.0:1.0 or lower (preferably 8.0:2.0 or lower, more preferably 7.0:3.0 or lower).

[0034] (3) Solvent The solvent is a medium for dispersing the catalyst and ionomer. The solvent evaporates upon heating after printing (coating) the catalyst ink. In the catalyst ink disclosed herein, the dispersion term δD in the HSP of the ionomer i , polarity term δP i , hydrogen bond term δH i And the dispersion term δD in the HSP of solvents s , polarity term δP s , hydrogen bond term δH s The relationship is given by the following equations (1) and (2): Erotica P i -5.5<δP s <δP i ...(1); δH i -7.0<δH s <δH i ...(2); The process is controlled to satisfy the following conditions. This achieves both ionomer solubility and suppression of sheet attack on the ion exchange membrane. A detailed explanation follows.

[0035] In the catalyst ink disclosed herein, the polar term δP of the solvent s and ionomer δP i The relationship is set as appropriate. Specifically, the polarity term δP of the solvent s δP i -δP s <5.5 (preferably δP i -δP s <5.0, more preferably δP i -δP s Set to <4.6). δP s It is too low (δP i If the difference is too large, the ionomer tends to be poorly soluble in the solvent. On the other hand, the polarity term δP of the solvent s The polar term δP of the ionomer i If it is too close (i.e., δP s ≒δP i ), there is a risk of attack on the ion exchange membrane by the solvent. Therefore, the polarity term of the solvent δP s δP i ―δP s >0 (preferably δP i ―δP s >0.5, more preferably δP i ―δP s It will be set to >1.0).

[0036] Furthermore, in the catalyst ink disclosed herein, the hydrogen bonding term δH of the solvent s and the hydrogen bonding term δH of the ionomer i The relationship is set as appropriate. Specifically, the hydrogen bonding term δH of the solvent s δH i ―δH s <5.5 (preferably δH i ―δH s <5.0, more preferably δH i ―δH s Set to <4.5). δH s (δH sIf the difference with [the other one] is too large, the ionomer tends to be poorly soluble in the solvent. On the other hand, when the hydrogen bonding term δH of the solvent s is too close to the hydrogen bonding term δH of the ionomer i (that is, δH s ≈ δH i ), there is a risk of attack on the anion exchange membrane by the solvent. Therefore, the hydrogen bonding term δH of the solvent s is set such that δH i − δH s > 0 (preferably δH i − δH s > 0.5, more preferably δH i − δH s > 1.0).

[0037] The dispersion term δD in the HSP of the solvent s is not particularly limited, but the larger δD s becomes, the larger the solvent molecules become, that is, the larger the van der Waals force becomes. As a result, the boiling point of the solvent becomes higher, and it takes time to dry the solvent. From this point of view, it is preferable to satisfy δD i −​5.0 < δD s < δD i , and it is more preferable to satisfy δD i −​3.0 < δD s < δD <(0000096) .

[0038] In the catalyst ink disclosed herein, the dissolution index R of the solvent with respect to the ionomer is controlled to be less than 10. Thereby, the ionomer can be dissolved in the solvent. The dissolution index R of the solvent with respect to the ionomer can be obtained by the following formula (3). R = (4 × (δD s − δD ) i ) 2 + (δP s [[ID=]] i ) 2 + (δH s − δH i ) 2 ) 0.5 ···(3)

[0039] The solubility index R calculated using equation (3) above is the distance between two substances (in this case, the ionomer and the solvent) in the Hansen space. The smaller this solubility index, the more similar the solubility of the two substances can be considered to be. Therefore, the smaller the solubility index R calculated using equation (3) above, the easier it is to dissolve the ionomer in the solvent. Accordingly, the solubility index R of the solvent for the ionomer is preferably 7 or less, more preferably 6.5 or less, and even more preferably 6 or less. The lower limit of the solubility index R of the solvent for the ionomer is not particularly limited, but from the viewpoint of further suppressing attack on the ion exchange film during catalyst ink coating, for example, it is 3 or more, and preferably 3.5 or more.

[0040] The solvent should satisfy the relationship between the solvent and the ionomer's HSP (Heat Spice Units) given by formulas (1) and (2) above, and have a solubility index R of less than 10. The solvent preferably contains at least one selected from the group consisting of alcohol-based solvents, ether-based solvents, sulfoxide-based solvents, water, and ester-based solvents, and a highly polar solvent is preferred. Suitable solvents include 2-methoxyethanol, butyl carbitol, ethanol, methanol, and dimethyl sulfoxide. Furthermore, the solvent may be a single solvent or a so-called mixed solvent containing two or more solvents. For example, by including two or more solvents, the relationship between the solvent and the ionomer's HSP can be controlled to satisfy formulas (1) and (2) above, and to have a solubility index R of less than 10. Including two or more solvents makes it easier to control the relationship between the solvent and the ionomer's HSP. When including two or more solvents, it is preferable that the solvents are miscible with each other at room temperature (25°C).

[0041] While not limited to this, when a mixed solvent is used as the solvent, a mixed solvent mainly consisting of at least one selected from the group consisting of ethanol and methanol, and butyl carbitol can be preferably used. With such a configuration, the hydrogen bonding term δH of the solvent is preferably s and the hydrogen bonding term δH of the ionomer iThe relationship can be adjusted so that it satisfies (1) and (2) above, and the solubility index R is less than 10. Furthermore, butyl carbitol has the property of exhibiting suitable dispersibility with respect to the catalyst. Ethanol and methanol have the property of exhibiting suitable dispersibility with respect to the ionomer. Moreover, the above solvents have good miscibility with respect to each other. When a mixed solvent mainly consisting of butyl carbitol and at least one selected from the group consisting of ethanol and methanol is used as the solvent, from the viewpoint of printability, the weight ratio of butyl carbitol to the total weight of the mixed solvent is preferably 40% or more, preferably 45% or more, and more preferably 50% or more. On the other hand, if the weight ratio of butyl carbitol is too high (higher than 90%), the ionomer tends to be poorly soluble in the solvent. Therefore, the weight ratio of butyl carbitol to the total weight of the mixed solvent is preferably 85% or less, and more preferably 80% or less. In this specification, "a mixed solvent mainly consisting of ethanol and methanol, and butyl carbitol" means that the total amount of butyl carbitol and ethanol and / or methanol in the catalyst ink is at least 90 wt%, preferably 95 wt%, more preferably 98 wt%, even more preferably 99 wt%, or 100 wt% of the total solvent contained in the catalyst ink.

[0042] From the viewpoint of printability, the proportion of solvent in the catalyst ink is, for example, 30 wt% or more, and preferably 40 wt% or more, when the total amount of catalyst ink is considered to be 100 wt%. On the other hand, from the viewpoint of saving labor in the drying process, the proportion of solvent in the catalyst ink is, for example, 90 wt% or less, and preferably 85 wt% or less, when the total amount of catalyst ink is considered to be 100 wt%.

[0043] The boiling point of the solvent is not limited and can be adjusted as appropriate, but from the viewpoint of saving labor in the drying process, it is preferable that it be, for example, 250°C or lower. Furthermore, from the viewpoint of continuous printability, it is preferable that the boiling point of the solvent be, for example, 60°C or higher.

[0044] (4) Other additives Furthermore, the catalyst inks disclosed herein may use additives as raw materials without particular limitation, as long as they do not significantly impair the effects of the technology disclosed herein. Examples of such additives include dispersants, comb-type nonionic dispersants, and long-chain amine organic compounds. The content of these additives may also be adjusted as appropriate, within a range that does not significantly impair the effects of the technology disclosed herein.

[0045] <Manufacturing method for catalytic ink> Such catalyst inks can be manufactured by weighing the above-mentioned materials in a predetermined proportion (parts by weight) and mixing (dispersing) them homogeneously. The manner in which the above-mentioned materials are mixed is not particularly limited; for example, all components may be mixed at once, or they may be mixed in an appropriately set order. For example, although not limited to this, a catalyst slurry may be prepared by mixing (dispersing) a catalyst and a solvent, and a high-viscosity ionomer may be prepared by mixing (dispersing) an ionomer and a solvent, and the catalyst ink may be manufactured by mixing the catalyst slurry and the high-viscosity ionomer, respectively. Although not limited to this, when two or more solvents are used as solvents, the solvent used when preparing the catalyst slurry and the solvent used when preparing the high-viscosity ionomer may be different. Conventional known stirring and mixing devices can be used for mixing (dispersing) the catalyst ink without particular limitation. Examples of devices used for kneading the catalyst ink in this disclosure include a three-roll mill, a roll mill, a magnetic stirrer, a rotation-and-revolution mixer, a planetary mixer, a disperser, a bead mill, etc.

[0046] The catalyst ink according to this embodiment has been described above. As mentioned above, the catalyst ink according to this embodiment is used in the manufacture of electrodes for a water electrolysis apparatus. In addition, a water electrolysis apparatus is provided as another aspect of the technology disclosed herein. Below, a water electrolysis apparatus will be described as an example of an application of the catalyst ink disclosed herein.

[0047] <Water electrolysis device> Figure 1 is a schematic cross-sectional view of a water electrolysis apparatus according to this embodiment. The following is merely an example of an application of the catalyst ink and is not intended to limit the applications of the technology disclosed herein.

[0048] As shown in Figure 1, the water electrolysis apparatus 100 according to this embodiment comprises an oxygen generation electrode (anode) 110, a hydrogen generation electrode (cathode) 120, and an anion exchange membrane 130. In this embodiment, the water electrolysis apparatus 100 is an anion exchange membrane (AEM) type water electrolysis apparatus, comprising an anion exchange membrane 130 as an ion exchange membrane. In this embodiment, the oxygen generation electrode 110 comprises a first substrate 111 and a first catalyst layer 112. The hydrogen generation electrode 120 comprises a second substrate 121 and a second catalyst layer 122. As will be described in detail later, in this embodiment, the first catalyst layer 112, the second catalyst layer 122, and the anion exchange membrane 130 are configured as a membrane catalyst layer assembly 150. Furthermore, in this embodiment, the first substrate 111, the second substrate 121, and the membrane catalyst layer assembly 150 are configured as a membrane electrode assembly 140.

[0049] Note that, with the exception of the oxygen generation electrode 110, the hydrogen generation electrode 120, and the anion exchange membrane 130, any other components that can be used in this type of water electrolysis apparatus can be used without particular limitation, so a detailed explanation is omitted. Note that the water electrolysis apparatus 100 is an example of a "water electrolysis apparatus comprising an ion exchange membrane and a catalyst layer disposed on the ion exchange membrane" in the technology disclosed herein.

[0050] Here, a water supply channel 162 is attached to the hydrogen generation electrode 120. An aqueous electrolyte is supplied to the hydrogen generation electrode 120 through this water supply channel 162. As such an aqueous electrolyte, an alkaline aqueous solution such as an aqueous NaOH solution or an aqueous KOH solution is preferably used. In addition, an oxygen recovery tube 164 is attached to the oxygen generation electrode 110. This oxygen recovery tube 164 penetrates the first substrate 111 and is connected to the first catalyst layer 112. On the other hand, a hydrogen recovery tube 166 is attached to the hydrogen generation electrode 120. The hydrogen recovery tube 166 penetrates the second substrate 121 and is connected to the second catalyst layer 122.

[0051] Next, the oxygen generation electrode 110 and the hydrogen generation electrode 120 are electrically connected by a conductive line 170. Specifically, the conductive line 170 connects the first substrate 111 of the oxygen generation electrode 110 and the second substrate 121 of the hydrogen generation electrode 120. A power supply 180 is also placed on this conductive line 170. For example, a generator that converts renewable energy into electricity (such as a solar cell or wind turbine) is used as the power supply 180.

[0052] Next, the operation of this water electrolysis device 100 will be explained. First, in this water electrolysis device 100, an aqueous electrolyte is supplied from the water supply passage 162 to the hydrogen generation electrode 120. Also, electrons (e) are supplied to the hydrogen generation electrode 120 from the power supply 180. - At this time, the aqueous electrolyte (H2O) is supplied to the hydrogen generation electrode 120, where hydrogen gas (H2) and hydroxide ions (OH) are mixed. - ) is decomposed into (see equation (A) below). The hydrogen gas produced at the hydrogen generation electrode 120 is then recovered from the hydrogen recovery tube 166. Meanwhile, the hydroxide ions produced at the hydrogen generation electrode 120 move to the oxygen generation electrode 110 through the anion exchange membrane 130. As a result, oxygen gas (O2) and water (H2O) are produced at the oxygen generation electrode 110, as shown in equation (B) below. The oxygen gas is then recovered from the oxygen recovery tube 164. The water is discharged to the outside of the device through a drain pipe (not shown). As described above, this water electrolysis device 100 can convert the electricity generated by the power supply 180 into oxygen gas and hydrogen gas. 4H2O+4e - →2H2+4OH - (A) 4OH - →O2+2H2O+4e - (B)

[0053] Next, the membrane electrode assembly 140 and the membrane catalyst layer assembly 150 according to this embodiment will be described. Figure 2 is a schematic exploded view showing the configuration of the membrane electrode assembly 140 according to this embodiment. As shown in Figure 2, the membrane electrode assembly 140 comprises a membrane catalyst layer assembly 150, a first substrate 111, and a second substrate 121. The membrane catalyst layer assembly 150 comprises an anion exchange membrane 130, a first catalyst layer 112, and a second catalyst layer 122. The first catalyst layer 112 is arranged (supported) on one surface of the anion exchange membrane 130. In other words, in this embodiment, the first catalyst layer 112 is arranged (supported) on the anion exchange membrane 130 by the CCM (Catalyst-Coated Membrane) method, which forms (arranges) a catalyst layer on an ion exchange membrane (anion exchange membrane). On the other hand, the second catalyst layer 122 is arranged (supported) on the other surface of the anion exchange membrane 130. Then, the first substrate 111 is placed on the first catalyst layer 112. Meanwhile, the second substrate 121 is placed on the second catalyst layer 122. In other words, the film electrode assembly 140 is constructed such that the film catalyst layer assembly 150 is sandwiched between the first substrate 111 and the second substrate 121.

[0054] The first substrate 111 is, in this case, a conductive metal member (conductive substrate). The first substrate 111 can be any conventionally known substrate that can be used as an electrode for a water electrolysis device without any particular limitations. Examples of materials for such a first substrate 111 include Ni, Ti, NiCr alloy, and SUS. Among these, a first substrate 111 made of Ni (Ni substrate) is preferably used. In this embodiment, the first substrate 111 is a plate-shaped member. However, the shape of the first substrate 111 is not limited to the technology disclosed herein. The shape of the first substrate 111 can be appropriately changed according to the structure of the water electrolysis device to which it is applied.

[0055] The first substrate 111 is preferably a porous material having multiple pores. This makes it easier for fluids such as water and oxygen gas to pass through the first substrate 111. As a result, this can contribute to improving the operating efficiency of the water electrolysis device 100. For example, the average pore diameter of the first substrate 111 is preferably 0.05 mm or more, more preferably 0.1 mm or more, even more preferably 0.15 mm or more, and particularly preferably 0.2 mm or more. This ensures sufficient fluid permeability of the first substrate 111. On the other hand, the average pore diameter of the first substrate 111 is preferably 5.5 mm or less, more preferably 5.0 mm or less, even more preferably 4.5 mm or less, and particularly preferably 4.0 mm or less. This ensures sufficient strength of the first substrate 111.

[0056] Furthermore, the porosity of the first substrate 111 is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, and particularly preferably 85% or more. This allows for a more favorable improvement of the fluid permeability of the first substrate 111. On the other hand, considering the strength of the first substrate 111, the porosity of the first substrate 111 is preferably 98% or less, more preferably 97% or less, and particularly preferably 96% or less. Note that the "porosity of the conductive substrate" in this specification was measured according to the following procedure. First, the conductive substrate was cut to 1 cm 3 Cut out a sample and measure its weight to calculate the actual specific gravity. Next, calculate the apparent specific gravity based on the specific gravity of the conductive substrate material (Ni, Ti, etc.). Finally, the result of the calculation (apparent specific gravity / actual specific gravity) is defined as the "porosity."

[0057] Furthermore, the thickness of the first substrate 111 is preferably 50 μm or more, more preferably 100 μm or more, and particularly preferably 150 μm or more. This ensures sufficient strength of the first substrate 111. On the other hand, the upper limit of the thickness of the first substrate 111 is preferably 500 μm or less, more preferably 450 μm or less, and particularly preferably 400 μm or less. This ensures sufficient fluid permeability in the first substrate 111.

[0058] The first catalyst layer 112 is a layer containing an oxidation catalyst that generates water and oxygen, as shown in formula (B) above. By providing the dried catalyst ink according to this embodiment as the first catalyst layer 112, a highly conductive oxygen generating electrode 110 is provided.

[0059] The thickness of the first catalyst layer 112 is not particularly limited, but from the viewpoint of obtaining sufficient catalytic activity, it is preferably 10 μm or more, and more preferably 20 μm or more. The upper limit of the thickness of the first catalyst layer 112 is not particularly limited, but it may be, for example, 100 μm or less.

[0060] The second substrate 121 is, in this case, a conductive metal member (conductive substrate). The second substrate 121 can be any conventionally known substrate that can be used as an electrode for a water electrolysis device without any particular restriction. Examples of materials for such a second substrate 121 include Ni, Ti, NiCr alloy, and SUS. Among these, a second substrate 121 made of Ni (Ni substrate) is preferably used. In this embodiment, the second substrate 121 is a plate-shaped member. However, the shape of the second substrate 121 is not limited to the technology disclosed herein. The shape of the second substrate 121 can be appropriately changed according to the structure of the water electrolysis device to which it is applied.

[0061] The second substrate 121 is preferably a porous material having multiple pores. This makes it easier for fluids such as water and oxygen gas to pass through the second substrate 121. As a result, it can contribute to improving the operating efficiency of the water electrolysis device 100. For example, the average pore diameter of the second substrate 121 is preferably 0.05 mm or more, more preferably 0.1 mm or more, even more preferably 0.15 mm or more, and particularly preferably 0.2 mm or more. This ensures sufficient fluid permeability of the second substrate 121. On the other hand, the average pore diameter of the second substrate 121 is preferably 5.5 mm or less, more preferably 5.0 mm or less, even more preferably 4.5 mm or less, and particularly preferably 4.0 mm or less. This ensures sufficient strength of the second substrate 121.

[0062] Furthermore, the porosity of the second substrate 121 is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, and particularly preferably 85% or more. This allows for a more favorable improvement in the fluid permeability of the second substrate 121. On the other hand, considering the strength of the second substrate 121, the porosity of the second substrate 121 is preferably 98% or less, more preferably 97% or less, and particularly preferably 96% or less.

[0063] Furthermore, the thickness of the second substrate 121 is preferably 50 μm or more, more preferably 100 μm or more, and particularly preferably 150 μm or more. This ensures sufficient strength of the second substrate 121. On the other hand, the upper limit of the thickness of the second substrate 121 is preferably 500 μm or less, more preferably 450 μm or less, and particularly preferably 400 μm or less. This ensures sufficient fluid permeability in the second substrate 121.

[0064] The second catalyst layer 122 is a layer containing a reduction catalyst that generates hydrogen, as shown in formula (A) above. The thickness of the second catalyst layer 122 is not particularly limited, but from the viewpoint of obtaining sufficient catalytic activity, it is preferably 10 μm or more, and more preferably 20 μm or more. The upper limit of the thickness of the second catalyst layer 122 is not particularly limited, but for example it may be 100 μm or less.

[0065] The anion exchange membrane 130 is an ion exchange membrane that has ion conductivity. The anion exchange membrane 130 is a hydroxide ion (OH - Conventional ion exchange membranes that can be moved and used in water electrolysis applications can be used without particular limitation. As the anion exchange membrane 130, for example, an anion exchange resin having anion exchange groups such as quaternary ammonium groups and pyridinium groups can be used.

[0066] The thickness of the anion exchange film 130 is not particularly limited, but is preferably 10 μm or more, more preferably 20 μm or more, and especially preferably 30 μm or more. On the other hand, the upper limit of the thickness of the anion exchange film 130 is preferably 100 μm or less, more preferably 90 μm or less, and especially preferably 80 μm or less.

[0067] In some preferred embodiments, it is preferable to directly support the dried catalyst ink of this embodiment (first catalyst layer 112) on the anion exchange film 130 as the first catalyst layer 112. With this configuration, the adhesion between the anion exchange film 130 and the first catalyst layer 112 is improved, and hydroxide ions (OH) - This makes it easier to move them.

[0068] As described above, the catalyst ink of this embodiment takes the form of a so-called membrane catalyst layer assembly, in which the catalyst ink is arranged (supported) on one side of the anion exchange membrane 130 in the form of a dried catalyst ink (first catalyst layer 112). Another aspect of the technology disclosed herein is the provision of a membrane catalyst layer assembly. The "membrane catalyst layer assembly 150 comprising an anion exchange membrane 130 and a first catalyst layer 112 arranged on the anion exchange membrane 130" is an example of the "membrane electrode assembly comprising an ion exchange membrane and a catalyst layer arranged on the ion exchange membrane" in the technology disclosed herein.

[0069] <Method for manufacturing the film catalyst layer assembly 150> Although not limited thereto, the film catalyst layer assembly 150 according to this embodiment can be obtained by, for example, the following manufacturing method. Figure 3 is a flow chart showing a manufacturing method for the film catalyst layer assembly 150 according to one embodiment. The manufacturing method for the film catalyst layer assembly 150 disclosed herein includes a catalyst ink coating step S110 and a catalyst ink drying step S120. Each step will be described below.

[0070] (Catalyst ink coating process S110) In the catalyst ink coating step S110, the catalyst ink according to this embodiment is coated (printed) onto the anion exchange film 130. Conventional methods such as screen printing, inkjet printing, and die-coating can be used for coating.

[0071] (Catalyst ink drying process S120) In the catalyst ink drying step S120, the catalyst ink is dried. This allows the first catalyst layer 112 to be obtained as a dried catalyst ink body. The drying temperature of the catalyst ink can be adjusted as appropriate depending on the type of solvent, etc., and can be carried out at approximately 50 to 80°C. The drying time of the catalyst ink can be adjusted depending on the amount of catalyst ink applied, etc., and can be carried out at approximately 30 to 60 minutes.

[0072] Herein, the catalyst ink of this disclosure has the effect of suppressing attack on the ion exchange membrane. Therefore, when the catalyst ink is printed (coated) onto the anion exchange membrane 130, the attack of the solvent on the anion exchange membrane 130 is suppressed. Furthermore, even after the catalyst ink dries, a dried product with suppressed wrinkles and distortions can be obtained. As a result, a catalyst layer with high conductivity, a film catalyst layer assembly, a film electrode assembly, and a water electrolysis device can be obtained.

[0073] Although not limited thereto, the second catalyst layer 122 may be formed on the other surface of the anion exchange film 130 (the surface on which the first catalyst layer 112 is not formed). Such a formation method can be achieved, for example, by preparing a catalyst ink for forming the second catalyst layer 122, applying it to the other surface of the anion exchange film 130, and drying it. The order in which the first catalyst layer 112 and the second catalyst layer 122 are formed is not particularly limited. In this way, a film catalyst layer assembly 150 can be obtained in which the first catalyst layer 112 is arranged (supported) on one surface of the anion exchange film 130 and the second catalyst layer 122 is arranged (supported) on the other surface.

[0074] Next, the first substrate 111 and the second substrate 121 are prepared as described above. The first substrate 111 and the first catalyst layer 112, and the second substrate 121 and the second catalyst layer 122 are brought into contact with each other, and the membrane catalyst layer assembly 150 obtained by the above method is placed and sandwiched between them. This gives rise to the membrane electrode assembly 140. Then, by attaching the water supply channel 162, oxygen recovery pipe 164, hydrogen recovery pipe 166, conductive line 170, and power supply 180, the water electrolysis apparatus 100 according to this embodiment can be manufactured. Note that the "membrane electrode assembly 140 comprising an anion exchange membrane 130, a first catalyst layer 112 disposed on the anion exchange membrane 130, and a first substrate 111 disposed on the first catalyst layer 112" is an example of the "membrane electrode assembly comprising an ion exchange membrane, a catalyst layer disposed on the ion exchange membrane, and a conductive substrate disposed on the catalyst layer" in the technology disclosed herein.

[0075] <Other Embodiments> The above describes one embodiment of the technology disclosed herein. However, the above embodiment is not intended to limit the technology disclosed herein. That is, the technology disclosed herein may include various modifications to the above embodiment.

[0076] In the above-described embodiment, the first catalyst layer 112 was formed on the anion exchange membrane 130 by the CCM method, which forms (places) a catalyst layer on the ion exchange membrane (anion exchange membrane). However, in some preferred embodiments, which are not limited to this, the CCS (Catalyst-Coated Substrate) method, which forms (places) a catalyst layer on a conductive substrate, can be employed.

[0077] Figure 4 is a schematic cross-sectional view showing a modified water electrolysis apparatus 200. Figure 5 is a schematic exploded view showing the configuration of the membrane electrode assembly 240 according to the modified example. As shown in Figure 4, the modified water electrolysis apparatus 200 includes a membrane electrode assembly 240 instead of a membrane electrode assembly 140. Except for this point, the configuration may be the same as that of the water electrolysis apparatus 100.

[0078] As shown in Figure 5, the membrane electrode assembly 240 comprises an oxygen generation electrode 210, a hydrogen generation electrode 220, and an anion exchange membrane 230. The oxygen generation electrode 210 comprises a first substrate 211 and a first catalyst layer 212. The hydrogen generation electrode 220 comprises a second substrate 221 and a second catalyst layer 222. Here, the first catalyst layer 212 is placed (supported) on one surface of the first substrate 211. On the other hand, the second catalyst layer 222 is placed (supported) on one surface of the second substrate 221. The membrane electrode assembly 240 is configured such that the anion exchange membrane 230 is sandwiched between the oxygen generation electrode 210 and the hydrogen generation electrode 220. At this time, one surface of the anion exchange membrane 230 is in contact with the first catalyst layer 212, and the other surface of the anion exchange membrane 230 is in contact with the second catalyst layer 222. In other words, in some preferred embodiments of the electrode, a dried form of the catalyst ink according to this embodiment may be placed (supported) on the first substrate as a first catalyst layer. In such embodiments as well, the electricity generated by the power source can be converted into oxygen gas and hydrogen gas by a mechanism similar to the process described above. The oxygen generating electrode 210 is an example of a "catalyst-equipped electrode" as described herein. Furthermore, the configuration may be the same as that of the film electrode assembly 140, except that the first catalyst layer 212 is supported on the surface of the first substrate 211 and the second catalyst layer 222 is supported on the surface of the second substrate 221. For this reason, redundant explanations are omitted here.

[0079] Furthermore, the oxygen generating electrode 210 (electrode with catalyst) can be manufactured by applying (printing) the catalyst ink onto the first substrate 211 and drying it, as described in the above embodiment. The application and drying conditions may be the same as those for the catalyst ink application step S110 and the catalyst ink drying step S120.

[0080] Next, the hydrogen generation electrode 220 and the anion exchange membrane 230 are prepared. Then, the oxygen generation electrode 210 and the hydrogen generation electrode 220 are positioned so that the first catalyst layer 112 and the second catalyst layer 222 are in contact with the anion exchange membrane 230, and the anion exchange membrane 230 is sandwiched between them. This gives rise to the membrane electrode assembly 240. Then, the water electrolysis apparatus 200 can be manufactured in the same manner as the water electrolysis apparatus 100 described above.

[0081] In the above, an oxygen-generating electrode having a first catalyst layer as the dried form of the catalyst ink was described as an example of the application of the catalyst ink according to this embodiment. However, the invention is not limited to this, and the dried form of the catalyst ink can be used as the catalyst layer (second catalyst layer 122) of a hydrogen-generating electrode.

[0082] The above describes one embodiment of the technology disclosed herein. However, the above embodiment is not intended to limit the technology disclosed herein. That is, the technology disclosed herein may include various modifications to the above embodiment.

[0083] [Example Test] The following describes examples of tests related to the technology disclosed herein. However, the technology disclosed herein is not limited to the following examples of tests.

[0084] 1. Preparation of catalytic ink (Examples 1-16) In this test example, 16 different catalyst inks (Examples 1 to 16) with varying compositions were prepared. Specifically, first, the weight ratio (wt%) of catalyst to ionomer was determined from their respective densities so that the catalyst-to-ionomer ratio (volume ratio) was as shown in Table 1. Next, the catalyst inks for Examples 1 to 16 were prepared by mixing the catalyst, ionomer, and solvent in the weight ratio (wt%) shown in Table 1. Ni powder (average particle size 60 nm) was used as the catalyst, and PiperION® Anion Exchange Resin was used as the ionomer. Furthermore, in Examples 1 to 16, the type of solvent used and the mixing ratio were changed as shown in Table 1. In Table 1, "BC" represents butyl carbitol, "EtOH" represents ethanol, "MeOH" represents methanol, and "DMF" represents dimethylformamide.

[0085] Furthermore, the HSP (dispersion term δD) of the solvents related to each example is also important. s , polarity term δP s , hydrogen bond term δH sThe HSP(dispersion term δD) of the ionomer was calculated using the HSPiP software based on the values ​​registered in the database. The results are shown in Table 1. i , polarity term δP i , hydrogen bond term δH i The measurement was performed using the HSPiP software, following the HSP measurement method for ionomers described above. As a result, the dispersion term δD of the ionomer was i , polarity term δP i , hydrogen bond term δH i The values ​​were 17.1, 12, and 17.4, respectively.

[0086] Based on the HSP values ​​of the solvent and ionomer obtained above, the solubility index R for each example of solvent in relation to the ionomer was calculated. Specifically, the solubility index R was calculated using the following formula (3)'. The results are shown in Table 1. R=(4×(δD s -17.1) 2 +( δP s -12) 2 +(δH s -17.4) 2 ) 0.5 ...(3)

[0087] 2. Evaluation Test (1) Feasibility of producing catalyst ink After preparing the catalyst ink as described above, the catalyst ink was left to stand at room temperature (25°C) for 60 minutes. After standing, those in which the ionomer dissolved and catalyst ink could be produced were marked with "○", and those in which the ionomer did not dissolve and catalyst ink could not be produced (i.e., ionomer precipitated and cloudiness was observed) were marked with "×". The solubility of the ionomer was judged visually. The results are recorded in the "Ionomer Solubility" column of Table 1.

[0088] (2) Evaluation of attack ability on anion exchange membrane Here, we evaluated the attack properties of the catalyst film (dried catalyst ink) on the anion exchange film. Specifically, for each sample from which catalyst ink was prepared in the above evaluation (1) (i.e., Examples 1-9 and 11-15), we used a metal mask to dry the catalyst layer on a 4cm x 4cm anion exchange film (PiperION®, 60μm thick) and measured the weight of the catalyst layer after drying to 2mg / cm². 2 The printout was prepared as shown. After printing, the catalyst ink was dried at room temperature for 24 hours, and then dried in an oven at 40°C for 8 hours. After the catalyst ink dried, the surface of the anion exchange film coated with the catalyst ink (i.e., the catalyst film) was observed with the naked eye. At this time, if no deformation (wrinkles, distortion, etc.) was observed at the interface between the catalyst film and the anion exchange film, it was marked with "○", and if deformation was observed at the interface between the catalyst film and the anion exchange film, it was marked with "×". Note that in Examples 10 and 16, catalyst ink could not be produced, and therefore catalyst films could not be produced, so they were marked with "―". The results are recorded in the "Attack Performance Evaluation" section of Table 1.

[0089] (3) Continuity evaluation Here, the conductivity of the catalyst films in each example was evaluated using a resistance meter. Specifically, the resistance meter (Loresta GP MCP-T610, manufactured by Mitsubishi Chemical Analytec) was used to measure the conductivity by applying the terminals to the catalyst layer printed on the anion exchange film. When the catalyst layer was not damaged when the terminals were applied, the resistance value was detected, which was marked with "○". When the catalyst layer was damaged and the resistance value could not be detected due to poor conductivity, it was marked with "×". Note that for Examples 10 and 16, it was not possible to produce catalyst ink and therefore not be able to produce catalyst films, so they were marked with "―". The results are shown in the "Conductivity Evaluation" column of Table 1.

[0090] [Table 1]

[0091] As shown in Examples 1-9 of Table 1, the HSP (dispersion term δD) of ionomers i , polarity term δP i , hydrogen bond term δH i ) and the HSP (dispersion term δD) of the solvents , polarity term δP s , hydrogen bond term δH s In catalyst inks where the relationship between ) satisfies the above-mentioned equations (1) and (2), and the solubility index R is less than 10, ionomers can be dissolved, and attack on the anion exchange film can be suppressed. Furthermore, as shown in Examples 2-9, the same effect could be obtained when multiple solvents were mixed. On the other hand, the polarity term δP of the solvent... s , hydrogen bond term δH s The polar term δP of the ionomer i or hydrogen bond term δH i In larger examples 11, 14, and 15, a tendency for sheet attack on the anion exchange membrane was observed. Furthermore, δP i -δP s In Examples 10 and 16, where the value was ≥5.5, the ionomer tended not to dissolve (precipitated), and catalyst inks could not be produced.

[0092] The technologies disclosed herein have been described in detail above, but these are merely illustrative examples and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. In other words, the technologies disclosed herein encompass the forms described in the following sections.

[0093] <Section 1> A catalyst ink for the electrodes of an anion exchange membrane type water electrolysis apparatus, comprising a catalyst consisting mainly of metal particles, an ionomer, and a solvent, wherein the volume ratio of the catalyst to the ionomer is 1.0:9.0 or more and 9.0:1.0 or less, and the dispersion term δD of the Hansen solubility parameter of the ionomer is i , polarity term δP i , hydrogen bond term δH i And the dispersion term δD in the Hansen solubility parameter of the above solvent. s , polarity term δP s , hydrogen bond term δH s A catalyst ink having a relationship with the above ionomer that satisfies the following formulas (1) and (2), and the solubility index R of the above solvent for the above ionomer, represented by the following formula (3), is less than 10. Erotica Pi -5.5<δP s <δP i ...(1) δH i -7.0<δH s <δH i ...(2) R=(4×(δD s -δD i ) 2 +( δP s -δP i ) 2 +(δH s -δH i ) 2 ) 0.5 ...(3)

[0094] <Section 2> The catalyst ink according to item 1, wherein the solvent comprises at least one selected from the group consisting of alcohol-based solvents, ether-based solvents, sulfoxide-based solvents, water, and ester-based solvents.

[0095] <Section 3> The catalyst ink according to item 1 or 2, comprising two or more solvents as the solvent.

[0096] <Section 4> The above solvent is a mixed solvent mainly composed of at least one selected from the group consisting of ethanol and methanol, and butyl carbitol. The catalyst ink according to item 3, wherein the weight ratio of the butyl carbitol to the total weight of the mixed solvent is 40% or more.

[0097] <Section 5> A catalyst ink according to any one of items 1 to 3, wherein the solvent is 2-methoxyethanol.

[0098] <Section 6> The dispersion term δD of the above ionomer i , polarity term δP i , hydrogen bond term δH i However, the catalyst inks described in any one of items 1 to 5 are 17.1±1, 12±1, and 17.4±1, respectively.

[0099] <Section 7> The above solvent is a highly polar solvent, and is a catalyst ink as described in any one of items 1 to 6.

[0100] <Section 8> The catalyst ink according to any one of claims 1 to 7, wherein the catalyst comprises at least one selected from the group consisting of nickel, iron, cobalt, and molybdenum.

[0101] <Section 9> A catalyst layer comprising a dried catalyst ink as described in any one of items 1 to 8.

[0102] <Section 10> A membrane catalyst layer assembly comprising an ion exchange membrane and a catalyst layer disposed on the ion exchange membrane, The catalyst layer described above is a dried catalyst ink according to any one of items 1 to 8. Membrane catalyst layer assembly.

[0103] <Section 11> A catalyst electrode comprising a conductive substrate and a catalyst layer disposed on the conductive substrate, The catalyst layer described above is a dried catalyst ink according to any one of items 1 to 8. electrode.

[0104] <Section 12> A membrane electrode assembly comprising an ion exchange membrane, a catalyst layer disposed on the ion exchange membrane, and a conductive substrate disposed on the catalyst layer, The catalyst layer described above is a dried catalyst ink according to any one of items 1 to 8. Membrane electrode assembly.

[0105] <Section 13> An anion exchange membrane type water electrolysis apparatus comprising an ion exchange membrane and a catalyst layer disposed on the ion exchange membrane, A water electrolysis apparatus in which the catalyst layer is a dried catalyst ink as described in any one of items 1 to 8. [Explanation of symbols]

[0106] 100, 200 water electrolysis equipment 110, 210 Oxygen-evolving electrode (anode) 111, 211 1st base material 112, 212 1st catalyst layer 120, 220 Hydrogen generation electrode (cathode) 121, 221 2nd base material 122, 222 2nd catalyst layer 130, 230 Anion exchange membrane 170 conductive lines 180 Power supply 162 Water supply channel 164 Oxygen recovery tube 166 Hydrogen recovery tube

Claims

1. A catalyst ink for the electrodes of an anion exchange membrane type water electrolysis apparatus, comprising a catalyst consisting mainly of metal particles, an ionomer, and a solvent, The volume ratio of the catalyst to the ionomer is 1.0:9.0 or more and 9.0:1.0 or less. The dispersion term δD in the Hansen solubility parameter of the ionomer. ｉ , polarity term δP ｉ , hydrogen bond term δH ｉ And the dispersion term δD in the Hansen solubility of the aforementioned solvent. ｓ , polarity term δP ｓ , hydrogen bond term δH ｓ The relationship satisfies the following equations (1) and (2), and The solubility index R of the solvent for the ionomer, represented by the following formula (3), is less than 10. Catalytic ink. δP ｉ ―5.5<δP ｓ <δP ｉ ・・・(1) δH ｉ ―5.5<δH ｓ <δH ｉ ・・・(2) R=(4×(δD ｓ -δD ｉ ) ２ +(δP ｓ -δP ｉ ) ２ +(δH ｓ -δH ｉ ) ２ ) ０．５ ・・・(3)

2. The catalyst ink according to claim 1, wherein the solvent comprises at least one selected from the group consisting of alcohol-based solvents, ether-based solvents, sulfoxide-based solvents, water, and ester-based solvents.

3. The catalyst ink according to claim 1, wherein the solvent comprises two or more solvents.

4. The solvent is a mixed solvent mainly composed of at least one selected from the group consisting of ethanol and methanol, and butyl carbitol. The catalyst ink according to claim 3, wherein the weight ratio of the butyl carbitol to the total weight of the mixed solvent is 40% or more.

5. The catalyst ink according to claim 1, wherein the solvent comprises 2-methoxyethanol.

6. The dispersion term δD of the ionomer ｉ , polarity term δP ｉ , hydrogen bond term δH ｉ The catalyst ink according to claim 1, wherein the values ​​are 17.1±1, 12±1, and 17.4±1, respectively.

7. The catalyst ink according to claim 1, wherein the solvent is a highly polar solvent.

8. The catalyst ink according to claim 1, wherein the catalyst comprises at least one selected from the group consisting of nickel, iron, cobalt, and molybdenum.

9. A catalyst layer comprising a dried catalyst ink according to any one of claims 1 to 8.

10. A membrane catalyst layer assembly comprising an ion exchange membrane and a catalyst layer disposed on the ion exchange membrane, The catalyst layer is a dried catalyst ink according to any one of claims 1 to 8. Membrane catalyst layer assembly.

11. A catalyst electrode comprising a conductive substrate and a catalyst layer disposed on the conductive substrate, The catalyst layer is a dried catalyst ink according to any one of claims 1 to 8. electrode.

12. A membrane electrode assembly comprising an ion exchange membrane, a catalyst layer disposed on the ion exchange membrane, and a conductive substrate disposed on the catalyst layer, The catalyst layer is a dried catalyst ink according to any one of claims 1 to 8. Membrane electrode assembly.

13. An anion exchange membrane type water electrolysis apparatus comprising an ion exchange membrane and a catalyst layer disposed on the ion exchange membrane, The catalyst layer is a dried catalyst ink according to any one of claims 1 to 8, in a water electrolysis apparatus.

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