Membrane electrode assembly for water electrolysis and method for producing same

Abstract

The invention provides a membrane electrode assembly for water electrolysis and a method for manufacturing the same. This membrane electrode assembly for water electrolysis is provided with a solid electrolyte membrane, and an anode catalyst layer and a cathode catalyst layer that sandwich the solid electrolyte membrane, and is characterized in that: the solid electrolyte membrane includes a solid electrolyte layer and a functional layer formed on the anode-side surface of the solid electrolyte layer; the anode catalyst layer is formed on the surface of the solid electrolyte membrane on the functional layer side, the cathode catalyst layer is formed on the surface of the solid electrolyte membrane on the opposite side to the functional layer side, and the functional layer contains a resin and catalyst metal particles dispersed in the resin.

Description

Technical Field

[0001] This invention relates to a membrane electrode assembly for water electrolysis in a water electrolysis apparatus and a method for manufacturing the same. Background Technology

[0002] In recent years, water electrolysis devices have employed apparatuses that arrange water electrolysis chambers using solid electrolyte membranes in a predetermined group. Such water electrolysis chambers have a membrane electrode assembly comprising a solid electrolyte membrane, an anode catalyst layer, and a cathode catalyst layer that holds the solid electrolyte membrane. For example, a known membrane electrode assembly for water electrolysis uses a catalyst layer forming material primarily composed of catalyst particles and electrolyte components to form the catalyst layer, and tilts the distribution of the catalyst particles and electrolyte components in the catalyst layer to prevent the electrolyte components from agglomerating near the surface of the catalyst layer (Japanese Patent Application Laid-Open No. 2001-303285). In addition, as a method for manufacturing membrane electrode assemblies for water electrolysis, a method implemented by roll-to-roll is disclosed, which includes: a first forming step in which a catalyst layer, either an anode or a cathode, is formed on a second side opposite to the first side while a support film for holding the electrolyte membrane in an unfolded state is attached to a first side of a strip electrolyte membrane; a first attaching step in which a holding member is peeled off from the first side of the electrolyte membrane and a diffusion member constituting a diffusion layer is attached to the second side, the diffusion layer allowing the diffusion of fluids of fuel or oxidant required for the electrochemical reaction constituting the fuel cell; a second forming step in which another catalyst layer is formed on the first side; and a second attaching step in which the diffusion member is attached to the first side (Japanese Patent Application Laid-Open No. 2015-35256).

[0003] In conventional membrane electrode assemblies and their manufacturing methods for water electrolysis, improvements have been made to the composition and formation methods of the catalyst layer to enhance the water electrolysis performance of the water electrolysis chamber. On the other hand, to ensure the safety of the water electrolysis chamber, it is necessary to suppress the generation of explosive hydrogen and oxygen gases by blocking the permeation of hydrogen gas generated on the cathode side through the solid electrolyte membrane. Therefore, there is a need to improve the blocking performance against hydrogen permeation through the solid electrolyte membrane. Summary of the Invention

[0004] The present invention was made in view of this, and its object is to provide a membrane electrode assembly for water electrolysis that can improve the blocking performance against hydrogen permeation through a solid electrolyte membrane, and a method for manufacturing the same.

[0005] To address the aforementioned issues, the membrane electrode assembly of the present invention is a membrane electrode assembly for water electrolysis comprising a solid electrolyte membrane and an anode catalyst layer and a cathode catalyst layer sandwiching the solid electrolyte membrane. The solid electrolyte membrane comprises a solid electrolyte layer and a functional layer formed on the anode-side surface of the solid electrolyte layer. The anode catalyst layer is formed on the functional layer-side surface of the solid electrolyte membrane, and the cathode catalyst layer is formed on the opposite side of the functional layer-side surface of the solid electrolyte membrane. The functional layer comprises a resin and catalyst metal particles dispersed in the resin.

[0006] Furthermore, the manufacturing method of the membrane electrode assembly of the present invention is a manufacturing method of a membrane electrode assembly for water electrolysis. The manufacturing method of the membrane electrode assembly is characterized by comprising the following steps: a preparation step, preparing an electrolyte membrane sheet having a conventional back sheet (sometimes simply referred to as "BS") and a solid electrolyte membrane adhered to the conventional back sheet, the solid electrolyte membrane comprising a solid electrolyte layer and a functional layer formed on the side opposite to the conventional back sheet side of the solid electrolyte layer; and an adhesion step, stacking the electrolyte membrane sheet and the new back sheet in such a manner that a new back sheet contacts the functional layer side of the solid electrolyte membrane, thereby forming a laminate, and then... The laminate is pressed and heated on both sides, thereby bonding a new back sheet to the functional layer side of the solid electrolyte membrane by heat pressing; a conventional BS peeling process peels the conventional back sheet from the solid electrolyte membrane; a cathode catalyst layer forming process forms a cathode catalyst layer on the opposite side of the functional layer side of the solid electrolyte membrane after the conventional BS peeling process; a new BS peeling process peels the new back sheet from the solid electrolyte membrane after the cathode catalyst layer forming process; and an anode catalyst layer forming process forms an anode catalyst layer on the functional layer side of the solid electrolyte membrane after the new BS peeling process.

[0007] According to the present invention, the blocking performance against hydrogen permeation through the solid electrolyte membrane can be improved. Attached Figure Description

[0008] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, wherein the same symbols denote the same elements, wherein:

[0009] Figure 1A This is a schematic cross-sectional view of a membrane electrode assembly for WE (water electrolysis) according to one embodiment.

[0010] Figure 1B This is a schematic anatomical view of a water electrolysis apparatus according to one embodiment.

[0011] Figure 2AThis is a schematic cross-sectional view of a membrane electrode assembly used in the prior art for WE.

[0012] Figure 2B This is a schematic diagram showing the dissected structure of a prior art water electrolysis device.

[0013] Figure 3 This is a schematic flowchart illustrating a mixed-flow production method for manufacturing a membrane electrode assembly for a WE according to one embodiment.

[0014] Figure 4 This is a cross-sectional view of a production line schematically illustrating a method for manufacturing a membrane electrode assembly for a WE according to one embodiment. Additionally, Figure 4 The device in the production line MF shown operates based on the control of the control device CR.

[0015] Figure 5A The graph represents the amount of hydrogen in the generated gas on the anode side of the water electrolysis experiment using the membrane electrode assembly of the water electrolysis chamber made in Examples 1 and 2, with the amount of hydrogen in the generated gas on the anode side set as the standard value of reference value 1.

[0016] Figure 5B This is a graph showing the hydrogen permeability of the solid electrolyte membrane prepared for the membrane electrode assembly of Example 1 and Comparative Example 2 at each relative humidity.

[0017] Figure 6A This is a graph showing the peel strength [N / m] of the novel BS in Reference Examples 1 to 10; additionally, Figure 6A The term "includes the peel strength [N / m] of the existing BS obtained by performing a 90-degree peel test on the solid electrolyte membrane of the electrolyte membrane prepared in Reference Examples 1 to 10.

[0018] Figure 6B These are images showing photographs taken from the new BS side 20 minutes after the mixed solvent was applied to samples of existing BS peeling sheets from Reference Examples 5 to 8, and photographs taken from the new BS side 15 minutes after the mixed solvent was applied to samples of existing BS peeling sheets from Reference Example 1. Additionally, in... Figure 6B The left end, for reference, also shows a photograph taken from the existing BS side 20 minutes after the sample of the electrolyte membrane was dropped from the same mixed solvent. Detailed Implementation

[0019] The following describes embodiments of the membrane electrode assembly for water electrolysis and its manufacturing method according to the present invention. Hereinafter, water electrolysis will sometimes be referred to simply as the abbreviation for Water Electrolysis, i.e., "WE".

[0020] A. Embodiment of the membrane electrode assembly for WE according to the present invention

[0021] Regarding embodiments of the membrane electrode assembly for WE of the present invention, one embodiment will be described first.

[0022] like Figure 1A As shown, a membrane electrode assembly 10 for a WE according to one embodiment includes a solid electrolyte membrane 2, and an anode catalyst layer 4a and a cathode catalyst layer 4c sandwiching the solid electrolyte membrane 2. The solid electrolyte membrane 2 includes a solid electrolyte layer 2h, and a functional layer 2f and a resin layer 2p formed on the anode-side surface 2ha and the cathode-side surface 2hc of the solid electrolyte layer 2h, respectively. The anode catalyst layer 4a is formed on the functional layer-side surface 2fs of the solid electrolyte membrane 2, and the cathode catalyst layer 4c is formed on the resin-side surface 2ps of the solid electrolyte membrane 2 (the surface opposite to the functional layer side). The functional layer 2f includes resin 2fp, a support 2fc dispersed in the resin 2fp, and catalyst metal particles 2fm supported on the support 2fc. The resin layer 2p includes resin 2pp.

[0023] like Figure 1B As shown, a water electrolysis apparatus 100 according to one embodiment is constructed by stacking multiple sets of WE (electrolyte) chambers 50. Each WE chamber 50 is a solid polymer-type WE chamber comprising a membrane electrode gas diffusion layer (MED) junction 20 for WE and an anode-side diaphragm 12 and a cathode-side diaphragm 14 that hold the MED junction 20. The MED junction 20 comprises a MED junction 10 for WE according to one embodiment, and an anode-side gas diffusion layer (sometimes simply referred to as "anode-side GDL") 6a and a cathode-side gas diffusion layer (sometimes simply referred to as "cathode-side GDL") 6c that hold the MED junction 10. In the MED junction 20, the anode-side GDL 6a is stacked on the surface 4aa opposite to the solid electrolyte membrane side of the anode catalyst layer 4a, and the cathode-side GDL 6c is stacked on the surface 4cc opposite to the solid electrolyte membrane side of the cathode catalyst layer 4c. In the WE chamber 50, the anode-side diaphragm 12 is laminated on the opposite side 6aa of the membrane electrode assembly side of the anode side GDL6a, and the cathode-side diaphragm 14 is laminated on the opposite side 6cc of the membrane electrode assembly side of the cathode side GDL6c.

[0024] On the other hand, such as Figure 2AAs shown, the membrane electrode assembly 110 used in the prior art WE is the same as the membrane electrode assembly 10 of one embodiment, except that the functional layer 2f and resin layer 2p of the solid electrolyte membrane 2 are formed on the cathode side surface 2hc and anode side surface 2ha of the solid electrolyte layer 2h, respectively, and the anode catalyst layer 4a and cathode catalyst layer 4c are formed on the resin layer side surface 2ps (the opposite side of the functional layer side) and functional layer side surface 2fs of the solid electrolyte membrane 2, respectively. Figure 2B As shown, the prior art water electrolysis device 200 (WE chamber 150) is the same as the water electrolysis device 100 of one embodiment, except that the membrane electrode gas diffusion layer junction 120 has the prior art membrane electrode junction 110 instead of the membrane electrode junction 10 of one embodiment.

[0025] The effect of the membrane electrode assembly 10 for WE according to one embodiment will be explained by comparison with the prior art. When producing hydrogen by electrolyzing feed water using a water electrolysis device employing the membrane electrode assembly, feed water is first supplied from the water supply port 12f of the anode-side diaphragm 12 to the fluid passage 12p, while simultaneously conducting electricity through the anode-side diaphragm 12 and the cathode-side diaphragm 14 to the anode catalyst layer 4a and the cathode catalyst layer 4c, respectively. As a result, the feed water undergoes electrolysis in the anode catalyst layer 4a, thereby generating hydrogen ions (H+). +Hydrogen ions, along with electrons and oxygen (O2), are discharged from the drain outlet 12d along with most of the raw water. Then, hydrogen ions, due to the potential difference, permeate through the solid electrolyte membrane 2, moving from the anode catalyst layer 4a side to the cathode catalyst layer 4c side. Next, the hydrogen ions accept electrons in the cathode catalyst layer 4c, thereby generating hydrogen gas (H2). The generated hydrogen gas is extracted from the hydrogen outlet 14d through the fluid passage 14p of the cathode-side diaphragm 14, but at high pressure. Therefore, in the water electrolysis device 200 using the prior art membrane electrode assembly 110, hydrogen gas sometimes flows backward through the solid electrolyte membrane 2 to the fluid passage 12p of the anode-side diaphragm 12 due to the pressure difference. Moreover, the backflowing hydrogen gas mixes with oxygen, thereby generating explosive hydrogen-oxygen gas, potentially causing safety problems. In contrast, in the water electrolysis apparatus 100 using the membrane electrode assembly 10 of one embodiment, it is believed that since the anode catalyst layer 4a is adjacent to the functional layer 2f of the solid electrolyte membrane 2, an interaction occurs between the catalyst in the anode catalyst layer 4a and the functional layer 2f. Therefore, it is believed that when hydrogen gas permeates through the solid electrolyte membrane 2 and flows back to the fluid passage 12p of the anode-side diaphragm 12, this interaction allows the hydrogen gas to be converted into hydrogen ions and move again to the cathode side via the solid electrolyte membrane 2, or the hydrogen gas to be converted into water and discharged from the drain outlet 12d. This improves the blocking performance against hydrogen gas permeation through the solid electrolyte membrane 2, thereby suppressing the generation of explosive hydrogen and oxygen gases.

[0026] The following describes further embodiments of the membrane electrode assembly for WE according to the present invention.

[0027] The solid electrolyte layer of the solid electrolyte membrane is not particularly limited as long as it contains a solid polymer material (electrolyte) with proton conductivity; examples include ion exchange layers containing solid polymer materials. Examples of solid polymer materials contained in the ion exchange layer include fluorinated resins (e.g., perfluorinated electrolytes) and hydrocarbon resins. The functional layer of the solid electrolyte membrane is not particularly limited; examples include functional layers containing a resin, a support dispersed in the resin, and catalyst metal particles supported on the support. The resin is not particularly limited; examples include resins containing solid polymer materials with proton conductivity. Examples of solid polymer materials include fluorinated resins (e.g., perfluorinated electrolytes) and hydrocarbon resins. The catalyst metal contained in the catalyst metal particles can be one or more selected from the group consisting of Pt (platinum), Au (gold), Pd (palladium), Rh (rhodium), and Ir (iridium). Examples of supports include carbon supports such as carbon black.

[0028] There are no particular limitations on the solid electrolyte membrane; for example, it may further include a resin layer formed on the cathode side of the solid electrolyte layer. The resin layer of the solid electrolyte membrane is not particularly limited, for example, as long as it contains a resin of a solid polymer material with proton conductivity. Examples of solid polymer materials contained in the resin layer include fluorinated resins (e.g., perfluorinated electrolytes) and hydrocarbon resins.

[0029] The anode catalyst layer is simply a reaction contained within the anode catalyst layer (2H2O→O2+4H). + +4e - The layer of catalyst components exhibiting catalytic activity is not particularly limited, and can, for example, be a layer of catalyst containing a support and catalyst components supported on the support. Examples of such catalyst components include noble metals (e.g., Pt, Ru, and Ir) and one or more selected from the group consisting of oxides of such noble metals; specifically, examples include Pt, iridium oxide, ruthenium oxide, iridium-ruthenium oxide, and mixtures thereof. Examples of iridium oxides include iridium oxide (e.g., IrO2, IrO3), iridium-tin oxide, and iridium-zirconium oxide. Examples of ruthenium oxides include ruthenium oxide (e.g., RuO2, Ru2O3), ruthenium-tantalum oxide, ruthenium-zirconium oxide, ruthenium-titanium oxide, and ruthenium-titanium-cerium oxide. Examples of iridium-ruthenium oxides include iridium-ruthenium-cobalt oxide, iridium-ruthenium-tin oxide, iridium-ruthenium-iron oxide, and iridium-ruthenium-nickel oxide. Examples of carriers include titanium oxide, manganese oxide, and cobalt oxide. The anode catalyst layer includes an ionomer in addition to the catalyst, preferably a layer where the catalyst is covered by the ionomer. This is because, in addition to improved coatability, the hydrophilicity of the ionomer facilitates the permeation of feed water. Examples of ionomers include those containing perfluorinated electrolytes used in the solid electrolyte layer.

[0030] The cathode catalyst layer is any reaction (4H) contained in the cathode catalyst layer. + +4e - The layer containing the catalyst component exhibiting catalytic activity in →2H2) is not particularly limited, and a layer containing a known catalyst can be used, such as a layer containing a catalyst component with a support and a catalyst component supported on the support. Examples of such catalysts include Pt, Pt-coated titanium, Pt-supported carbon, Pd-supported carbon, Co (cobalt) oxime, Ni (nickel) oxime, etc. As the cathode catalyst layer, in addition to the catalyst, it also contains an ionomer, preferably a layer in which the catalyst is covered by an ionomer. This is because, in addition to improved coating properties, the hydrophilicity of the ionomer can facilitate the permeation of feed water. Examples of ionomers include ionomers containing perfluorinated electrolytes used in solid electrolyte layers.

[0031] As a membrane electrode assembly, there are no particular limitations as long as the functional layer of the solid electrolyte membrane and the anode catalyst layer are adjacent. The anode catalyst layer can be coated on the side of the functional layer of the solid electrolyte membrane, or the anode catalyst layer pre-formed on other components can be pasted on the side of the functional layer of the solid electrolyte membrane.

[0032] The membrane electrode gas diffusion layer (GDL) of the membrane electrode assembly includes an anode-side GDL and a cathode-side GDL that hold the membrane electrode assembly. The anode-side GDL is not particularly limited; any known anode-side GDL can be used, such as a component with permeability and conductivity. Specifically, a porous conductive component formed from a sintered body of metal fibers (e.g., titanium fibers) or metal particles (e.g., titanium particles) can be used. The cathode-side GDL is also not particularly limited; any known cathode-side GDL can be used, such as a component with permeability and conductivity. Specifically, a porous conductive component such as carbon cloth or carbon paper can be used. The water electrolysis chamber of the water electrolysis apparatus using this membrane electrode gas diffusion layer assembly includes an anode-side diaphragm and a cathode-side diaphragm that hold the membrane electrode gas diffusion layer assembly. There are no particular limitations on the anode-side and cathode-side diaphragms; any known diaphragm can be used.

[0033] B. Embodiment of the method for manufacturing the membrane electrode assembly for WE according to the present invention

[0034] Regarding an embodiment of the method for manufacturing a membrane electrode assembly for a fuel cell (WE) according to the present invention, an embodiment will be described first. The method for manufacturing a WE membrane electrode assembly according to one embodiment is a method for manufacturing a WE membrane electrode assembly and a fuel cell (sometimes simply referred to as "FC") membrane electrode assembly in a roll-to-roll manner on a shared production line.

[0035] In the mixed-flow production method of the manufacturing method of the membrane electrode assembly according to one embodiment, such as Figure 3 As shown, firstly, an electrolyte membrane sheet (S1) shared by the membrane electrode assembly for WE and the membrane electrode assembly for FC is prepared. Specifically, an electrolyte membrane sheet roll R1 is prepared by winding the electrolyte membrane sheet into a roll. Figure 4 Electrolyte membrane ( Figure 4 The device has an existing backsheet (sometimes simply referred to as "existing BS") 3 and a solid electrolyte membrane 2 adhered to the existing BS 3. The solid electrolyte membrane 2 includes a solid electrolyte layer 2h, and functional layers 2f and resin layers 2p formed on one and the other side of the solid electrolyte layer 2h, respectively. Next, the operator selects a membrane electrode assembly for WE or FC as the membrane electrode assembly (S2) to be produced.

[0036] Next, when selecting a membrane electrode assembly for WE as the membrane electrode assembly to be produced, firstly, on the aforementioned common production line, after forming an anode catalyst layer 4a on the functional layer side surface 2fs of the solid electrolyte membrane 2 using the membrane electrode assembly 10 of one embodiment as the production target, it is determined whether the BS (backsheet) needs to be replaced (S3). Specifically, in the electrolyte membrane sheet, based on determining whether the functional layer 2f of the solid electrolyte membrane 2 is formed on the side 2hr opposite to the existing BS side of the solid electrolyte layer 2h, if an affirmative determination is made, it is determined that the BS needs to be replaced; if a negative determination is made, it is determined that the BS does not need to be replaced.

[0037] Next, if it is determined that the BS needs to be replaced, the new backing film (sometimes simply referred to as "new BS") 5 is pasted on (S4). Specifically, as follows... Figure 4 As shown, firstly, in addition to the electrolyte membrane roll R1, a new BS roll R2 is prepared to be wound into a roll shape. The new BS5 is a new product including a PET sheet 5p and a release layer 5r formed on the surface of the PET sheet 5p. Next, the electrolyte membrane roll R1 and the new BS roll R2 are positioned opposite each other at the uppermost position of the production line MF, respectively, thereby setting them on the production line MF. Next, the electrolyte membrane and the new BS5 are fed downstream from the electrolyte membrane roll R1 and the new BS roll R2, respectively, with the functional layer side 2fs of the solid electrolyte membrane 2 of the electrolyte membrane facing the release layer side of the new BS5. Next, using a pair of heated and pressurized rollers R3 including a pressurizing mechanism and a heating mechanism, the electrolyte membrane and the new BS5 are stacked between the pair of rollers in such a way that the release layer side of the new BS5 is in contact with the functional layer side 2fs of the solid electrolyte membrane 2 of the electrolyte membrane, thereby forming a laminated body, thereby clamping the laminated body. In this state, by rotating a pair of rollers in opposite directions, the laminate is conveyed while being pressurized and heated from both sides of the lamination direction using the rollers. This heat-pressing bonding attaches the new BS5 (the release layer side) to the functional layer side 2fs of the solid electrolyte membrane 2 of the electrolyte membrane sheet, and the sheet with the new BS attached (sometimes simply referred to as the "new BS attached sheet") is then conveyed downstream. Furthermore, the conveying speed of the laminate and the new BS attached sheet is preferably, for example, 3 m / min or less.

[0038] Next, the existing BS3 is stripped (S5). Specifically, as follows: Figure 4 As shown, the existing BS 3 is peeled off from the solid electrolyte membrane 2 in the new BS adhesive sheet using the existing BS peeling roller R4, and the sheet after peeling off the existing BS (sometimes simply referred to as the "existing BS peel sheet") is conveyed downstream.

[0039] Next, the cathode catalyst layer 4c for WE is formed (S6). Specifically, as follows... Figure 4 As shown, using a cathode catalyst coating apparatus C1, cathode catalyst ink is coated on the resin layer side surface 2ps (the opposite side of the functional layer side) of the solid electrolyte membrane 2 of the existing BS stripper sheet. Then, the cathode catalyst ink is dried using a cathode catalyst drying oven C2, thereby forming a cathode catalyst layer 4c. The sheet after the cathode catalyst layer is formed (sometimes simply referred to as the "cathode catalyst layer forming sheet") is transported downstream.

[0040] Next, the GDL6c cathode side for WE is attached (S7). Specifically, as follows: Figure 4 As shown, firstly, in conjunction with the conveying of the cathode catalyst layer forming sheet, the cathode-side GDL6c is fed from the cathode-side GDL roller R5 to the downstream cathode-side GDL transfer roller. Next, using the cathode-side GDL transfer roller R6, the cathode-side GDL6c is bonded to the cathode catalyst layer side 4cc of the cathode catalyst layer forming sheet via hot pressing, and the bonded sheet (sometimes simply referred to as the "cathode-side GDL bonded sheet") is conveyed downstream.

[0041] Next, the new BS5 is stripped (S8). Specifically, as follows: Figure 4 As shown, the new BS5 is peeled off from the solid electrolyte membrane 2 of the GDL bonded sheet on the cathode side using the new BS peeling roller R7, and the peeled sheet (sometimes simply referred to as the "new BS peel sheet") is conveyed downstream. Then, as... Figure 4 As shown, the new BS stripping sheet is wound using intermediate product winding roller R8.

[0042] Next, the anode catalyst layer 4a for WE is formed (S9). Specifically, as follows... Figure 4 As shown, firstly, the new BS release sheet is fed downstream from the intermediate product take-up roller R8 with the functional layer side 2fs of the solid electrolyte membrane 2 facing upwards. Next, using the anode catalyst coating apparatus C3, anode catalyst ink is coated onto the functional layer side 2fs of the solid electrolyte membrane 2 of the new BS release sheet. Then, using the anode catalyst drying oven C4, the anode catalyst ink is dried, thereby forming the anode catalyst layer 4a. The sheet with the formed anode catalyst layer (sometimes simply referred to as the "anode catalyst layer formed sheet") is then conveyed downstream.

[0043] Next, the anode-side GDL6a for WE is attached (S10). Specifically, as follows: Figure 4As shown, firstly, in conjunction with the conveying of the anode catalyst layer forming sheet, the anode-side GDL6a is fed from the anode-side GDL roller R9 to the downstream anode-side GDL transfer roller. Next, using the anode-side GDL transfer roller R10, the anode-side GDL6a is heat-pressed onto the anode catalyst layer side surface 4aa of the anode catalyst layer forming sheet, and the sheet with the anode-side GDL bonded (sometimes simply referred to as the "anode-side GDL bonded sheet") is conveyed downstream. Then, as... Figure 4 As shown, the anode-side GDL adhesive sheet, which serves as the membrane electrode gas diffusion layer bonding body, is wound using a product winding roller R11. As described above, in the mixed-flow production method, a membrane electrode bonding body 10 of one embodiment is manufactured by implementing a manufacturing method (S1 to S10) of one embodiment and used as part of the membrane electrode gas diffusion layer bonding body for WE.

[0044] In the above mixed-flow production method, in determining whether the BS needs to be replaced (S3), it is determined whether the functional layer 2f of the solid electrolyte membrane 2 in the electrolyte membrane sheet is formed on the side 2hr of the solid electrolyte layer 2h opposite to the existing BS side. If the determination is affirmative, the membrane electrode assembly 10 of one embodiment can be manufactured by implementing the manufacturing method of the WE membrane electrode assembly of one embodiment (S1 to S10), based on the replacement of the BS (S4 and S5), and sequentially forming the cathode catalyst layer 4c, the cathode-side GDL6c, the anode catalyst layer 4a, and the anode-side GDL6a for the WE, thereby manufacturing the membrane electrode assembly 10 of one embodiment. If the determination is negative, on a common production line, such as Figure 3 As shown, by implementing other methods for manufacturing membrane electrode assemblies for WE (S1 to S3 and S11 to S15), without replacing the BS (S4 and S5), in step (S11), after forming the cathode catalyst layer 4c for WE on the resin layer side surface 2ps of the solid electrolyte membrane 2 of the electrolyte sheet, the cathode side GDL6c, the anode catalyst layer 4a, and the anode side GDL6a for WE are formed sequentially, thereby manufacturing the membrane electrode assembly 10 of one embodiment. Furthermore, when selecting the FC-use membrane electrode assembly (S2) from either WE-use or FC-use, on a common production line, such as Figure 3As shown, by implementing the manufacturing method of the membrane electrode assembly for FC (S1, S2, and S21 to S25), an anode catalyst layer, an anode-side GDL, a cathode catalyst layer, and a cathode-side GDL for FC are formed sequentially, thereby enabling the manufacture of the membrane electrode assembly for FC. On the other hand, in a shared production line performing such a mixed-flow production method, in both the manufacturing method for the membrane electrode assembly for WE and the manufacturing method for the membrane electrode assembly for FC, at least the cathode catalyst layer (anode catalyst layer for FC) forming apparatuses C1 and C2, the cathode-side GDL (anode-side GDL for FC) bonding apparatuses R5 and R6, and the anode-side GDL (cathode-side GDL for FC) bonding apparatuses R9 and R10 can be shared, allowing for the shared use sequence of these shared apparatuses. In the manufacturing method of one embodiment and other manufacturing methods for the membrane electrode assembly for WE, in addition to these apparatuses, the anode catalyst layer forming apparatuses C3 and C4 can also be shared, allowing for the shared use sequence of these shared apparatuses.

[0045] Therefore, in the mixed-flow production method, both membrane electrode assemblies for WE and FC can be produced in a shared production line that shares most of the equipment. Furthermore, even if the functional layer 2f of the solid electrolyte membrane 2 is formed on the surface 2hr opposite to the conventional BS side of the solid electrolyte layer 2h, by implementing the manufacturing method (S1 to S10) for the membrane electrode assembly for WE of one embodiment, a membrane electrode assembly 10 of one embodiment in which the anode catalyst layer 4a is formed on the surface 2fs of the functional layer side of the solid electrolyte membrane 2 can be manufactured using a production line common to other manufacturing methods for membrane electrode assemblies for WE. Therefore, the blocking performance against hydrogen permeation of the solid electrolyte membrane 2 can be improved, and a membrane electrode assembly 10 capable of suppressing the generation of hydrogen and oxygen gases can be manufactured efficiently and inexpensively.

[0046] The following describes an embodiment of the method for manufacturing the membrane electrode assembly for WE according to the present invention.

[0047] The preparation process is simply the process of preparing the electrolyte membrane sheet, and there are no particular limitations. As for the existing BS (Base Layer) of the electrolyte membrane sheet, it is acceptable as long as it includes a substrate sheet (e.g., PET (polyethylene terephthalate) sheet), and there are no particular limitations. For example, a BS that further includes a release layer formed on the surface of the substrate sheet can be cited.

[0048] The bonding process is not particularly limited, but it is preferable to set the heating temperature to 120°C or higher and below the thermal decomposition temperature while applying pressure to the laminate from both sides in the lamination direction. Preferably, the heating temperature is 120°C or higher and below 130°C. It should be noted that "heating temperature" refers to the temperature of a heating component that heats the laminate, such as a pair of rollers equipped with a heating mechanism. "Thermal decomposition temperature" refers to the heating temperature at which the solid electrolyte membrane material decomposes. As the bonding process, the surface of the new BS bonded to the solid electrolyte membrane can be either the PET sheet side or the release layer side. For example, the bonding process can be step (S4) of one embodiment. As the new BS, it is preferable that the width of the new BS (the width perpendicular to the feed direction of the new BS roller) is greater than or equal to the width of the solid electrolyte membrane of the electrolyte membrane sheet (the width perpendicular to the feed direction of the electrolyte membrane sheet roller). This is because it prevents the solid electrolyte membrane from adhering to the roller that transports the solid electrolyte membrane. As a new BS, it can be the same BS as an existing BS, but it can also be a new product (a new product of a purchased BS) or a recycled product (a reused product of a stripped BS).

[0049] There are no particular limitations on the existing BS peeling process. It can be a process in which a new backsheet is pasted onto the functional layer side of the solid electrolyte membrane while the existing backsheet is peeled off from the solid electrolyte membrane during the pasting process, or it can be a process in which the existing backsheet is peeled off from the solid electrolyte membrane after the pasting process.

[0050] Hereinafter, examples, comparative examples, and reference examples are provided to give a more detailed description of the membrane electrode assembly for WE and the method for manufacturing the membrane electrode assembly for WE according to the embodiments.

[0051] 1. Membrane electrode assembly

[0052] An example of a membrane electrode assembly for WE according to the above embodiment is prepared according to the following steps. At this time, the hydrogen permeability of the monomer of the solid electrolyte membrane used in the membrane electrode assembly is measured. Then, a water electrolysis chamber is prepared from the membrane electrode assembly, and an experiment on water electrolysis using the water electrolysis chamber is conducted.

[0053] Fabrication steps of membrane electrode assembly

[0054] First, the anode catalyst layer is formed. Here, 48.0 g of the anode catalyst (iridium oxide catalyst (Umicore)), 9.6 g of a proton-conducting ionomer (AGC), 36.0 g of ion-exchanged water, and 54.7 g of alcohol (21.5 g of 1-propanol and 33.2 g of ethanol) are mixed in a beaker and dispersed using an ultrasonic homogenizer to obtain catalyst ink. Next, the catalyst ink is coated onto the surface of a substrate sheet (Teflon sheet, thickness: 1.0 mm) using a coating tool. Then, the catalyst ink is dried at 85°C for 5 minutes, thereby forming the anode catalyst layer (thickness: approximately 2 μm).

[0055] Next, the cathode catalyst layer was formed. First, 6.1 g of cathode catalyst (Pt-supported carbon (18% Pt loading, Cataler-made)), 6.0 g of proton-conductive ionomer (AGC-made), 88.4 g of ion-exchanged water, and 45.2 g of alcohol (ethanol) were mixed in a beaker and dispersed using an ultrasonic homogenizer to obtain catalyst ink. Then, the catalyst ink was coated onto the surface of a substrate sheet (Teflon sheet, thickness: 1.0 mm) using a coating tool. Next, the catalyst ink was dried at 85°C for 5 minutes, thereby forming the cathode catalyst layer (thickness: approximately 6 μm).

[0056] Next, a solid electrolyte membrane (M775.15, manufactured by Gore Corporation, Japan, thickness: approximately 15 μm) is prepared for adhesion to the existing BS. The solid electrolyte membrane comprises a solid electrolyte layer (thickness: approximately 3 μm), and functional layers (thickness: approximately 6 μm) and a resin layer (thickness: approximately 6 μm) formed on one and the other sides of the solid electrolyte layer, respectively. The solid electrolyte layer is expanded polytetrafluoroethylene (ePTFE). The functional layer comprises a resin (perfluorosulfonic acid polymer), a support (carbon support) dispersed in the resin, and catalyst metal particles (platinum group metals) supported on the support. The resin layer comprises a resin (perfluorosulfonic acid polymer). Then, after peeling the existing BS from the solid electrolyte membrane, as follows... Figure 1A , Figure 1B As shown, the anode catalyst layer and cathode catalyst layer are respectively adjacent to the functional layer and resin layer of the solid electrolyte membrane. The anode catalyst layer is disposed on the functional layer side of the solid electrolyte membrane, and the cathode catalyst layer is disposed on the resin layer side of the solid electrolyte membrane. Then, the substrate sheet is peeled off from these catalyst layers, and then hot-pressed at 130°C and 130 kPa for more than 4 minutes. Thus, a membrane electrode assembly is fabricated.

[0057] Procedure for determining the hydrogen permeability of monomers in solid electrolyte membranes

[0058] For the prepared solid electrolyte membrane monomer, a gas permeability measuring device (manufactured by GTR TECH) was used to measure the hydrogen permeability [cc / m²·24hr·atm] at various relative humidities [%RH] by using the isobaric method with the measurement temperature set at 55°C.

[0059] Construction steps of a water electrolysis chamber

[0060] In the membrane electrode assembly, an anode-side GDL (Pt vapor-deposited titanium fiber) and an anode-side separator are sequentially stacked on the opposite side of the solid electrolyte membrane side of the anode catalyst layer, and a cathode-side GDL (carbon fiber) and a cathode-side separator are sequentially stacked on the opposite side of the solid electrolyte membrane side of the cathode catalyst layer. The resulting laminate is then pressed to fabricate a water electrolysis chamber.

[0061] Experimental steps of water electrolysis

[0062] In the water electrolysis chamber, while a sufficient amount of pure water (raw water) is supplied from the water inlet of the anode-side diaphragm, the temperature of the water electrolysis chamber is raised to 60°C, and then the electrolysis current density is 2.5 A / cm². 2 A voltage was applied between the diaphragm on the anode side and the diaphragm on the cathode side to perform water electrolysis for 5 hours. Then, during water electrolysis, the gas generated from the anode side was collected using a sampling bag, and the gas composition was analyzed using mass analysis to determine the amount of hydrogen in the gas generated on the anode side.

[0063] Comparative Example 1

[0064] During hot pressing, based on the peeling of the existing BS from the solid electrolyte membrane, such as Figure 2A , Figure 2B As shown, the cathode catalyst layer and the anode catalyst layer are respectively adjacent to the functional layer and resin layer of the solid electrolyte membrane. The cathode catalyst layer is disposed on the functional layer side of the solid electrolyte membrane, and the anode catalyst layer is disposed on the resin layer side of the solid electrolyte membrane. Then, substrate sheets are peeled off from these catalyst layers, and hot-pressed on them. Otherwise, the membrane electrode assembly is fabricated according to the same steps as in the embodiment. Then, a water electrolysis chamber is fabricated from the membrane electrode assembly according to the same steps as in the embodiment, and water electrolysis experiments using the water electrolysis chamber are conducted according to the same steps as in the embodiment.

[0065] Comparative Example 2

[0066] In preparing the solid electrolyte membrane, a solid electrolyte membrane comprising a solid electrolyte layer and resin layers formed on one and the other sides of the solid electrolyte layer is prepared. These solid electrolyte layers and resin layers are identical to those in the solid electrolyte membrane of the embodiment. Furthermore, during hot pressing, after peeling off the existing substrate from the solid electrolyte membrane, the anode catalyst layer and cathode catalyst layer are respectively disposed on one and the other sides of the solid electrolyte membrane, with the anode catalyst layer and cathode catalyst layer adjacent to the resin layers on both sides of the solid electrolyte membrane. Then, the substrate sheet is peeled off from these catalyst layers, and hot pressing is performed. Except for these aspects, the membrane electrode assembly is fabricated according to the same steps as in the embodiment. At this time, the hydrogen permeability of the monomer of the prepared solid electrolyte membrane is measured according to the same steps as in the embodiment. Then, a water electrolysis chamber is fabricated from the membrane electrode assembly according to the same steps as in the embodiment, and an experiment on water electrolysis using the water electrolysis chamber is conducted according to the same steps as in the embodiment.

[0067] evaluate

[0068] like Figure 5B As shown, in the solid electrolyte membranes prepared for the membrane electrode assembly used in Examples and Comparative Example 1, compared with the solid electrolyte membrane prepared for the membrane electrode assembly used in Comparative Example 2, the hydrogen permeability of the monomer at various relative humidity levels is higher, making it easier for hydrogen gas to permeate. Nevertheless, as... Figure 5A As shown, in the water electrolysis experiment using the water electrolysis chamber made with the membrane electrode assembly of the embodiment, the amount of hydrogen in the generated gas on the anode side was significantly reduced, not only compared to the water electrolysis experiment using the water electrolysis chamber made with the membrane electrode assembly of Comparative Example 1, but also compared to the water electrolysis experiment using the water electrolysis chamber made with the membrane electrode assembly of Comparative Example 2, resulting in good results. The good results exhibiting specific hydrogen blocking properties in the membrane electrode assembly of the embodiment are believed to be due to the adjacency of the anode catalyst layer and the functional layer of the solid electrolyte membrane. This interaction between the catalyst and the functional layer in the anode catalyst layer allows hydrogen gas to be converted into hydrogen ions (H+) through this interaction when it flows countercurrently from the cathode side through the solid electrolyte membrane to the anode side. + ( ) or water (H2O), thus blocking the permeation of hydrogen itself.

[0069] 2. Manufacturing method of membrane electrode assembly

[0070] Reference Example 1

[0071] The following steps are performed to carry out the main part of the manufacturing method of the WE membrane electrode assembly of the above-described embodiment to produce an existing BS release sheet (a sheet after existing BS release).

[0072] First, an electrolyte membrane sheet is prepared to be wound into a roll. The electrolyte membrane sheet has an existing backsheet (BS) and a solid electrolyte membrane adhered to the existing BS. The solid electrolyte membrane includes a solid electrolyte layer, and functional layers and resin layers formed on one and the other side of the solid electrolyte layer, respectively. In the solid electrolyte membrane, the resin layer and the functional layers are respectively disposed on the existing BS side and the opposite side of the existing BS side. Next, a new BS (new backsheet) is prepared to be wound into a roll. The new BS is a new product, comprising a PET sheet and a release layer formed on the surface of the PET sheet containing a cyclic olefin copolymer.

[0073] Next, the electrolyte membrane roll and the new BS roll are positioned above and below each other, facing each other. Then, the electrolyte membrane and the new BS are fed downstream from the electrolyte membrane roll and the new BS roll, respectively, with the functional layer side of the solid electrolyte membrane of the electrolyte membrane facing each other and the PET sheet side of the new BS facing each other. Next, using a pair of heated pressure rollers equipped with a pressure mechanism and a heating mechanism, the electrolyte membrane and the new BS are stacked between the pair of rollers with the PET sheet side of the new BS in contact with the functional layer side of the solid electrolyte membrane of the electrolyte membrane, thus forming a laminate, which is then held in a clamped state. In this state, by rotating the pair of rollers in opposite directions, the laminate is conveyed while being pressurized and heated from both sides of the stacking direction using the pair of rollers, thereby heat-pressing the new BS (PET sheet side) onto the functional layer side of the solid electrolyte membrane of the electrolyte membrane, forming a new BS bonded sheet, which is then conveyed downstream. Next, using an existing BS peeling roller, the solid electrolyte membrane of the electrolyte membrane sheet in the new BS adhesive sheet is peeled off from the existing BS, and the existing BS peeling sheet is conveyed downstream. Then, the existing BS peeling sheet is wound around a winding roller. Thus, the existing BS peeling sheet is produced. In this case, the heating temperature [°C], the pressure [MPa], and the conveying speed [m / min] during hot pressing are set as shown in Table 1 below.

[0074] Refer to Examples 2 to 10

[0075] In Reference Examples 2 to 10, existing BS release sheets were manufactured in the same manner as in Reference Example 1, except for a few conditions. Specifically, in Reference Examples 2 to 10, as shown in Table 1 below, either new or recycled materials were used as the new BS, just as in Reference Example 1. Furthermore, as shown in Table 1 below, by changing the new BS roll, the side of the new BS adhered to the solid electrolyte membrane was set to either the PET sheet side or the release layer side. Furthermore, as shown in Table 1 below, the heating temperature [°C], pressure [MPa], and conveying speed [m / min] during heat pressing were set. Except for these conditions, existing BS release sheets were manufactured in the same manner as in Reference Example 1.

[0076] (Table 1)

[0077] New BS types The new BS surface adhered to the solid electrolyte membrane Heating temperature [°C] Apply pressure [MPa] Conveying speed [m / min] Reference Example 1 New product PET sheet side 90 0.5 0.5 Reference Example 2 New product Surface of the mold layer 90 0.5 0.5 See Example 3 New product PET sheet side 110 0.5 0.5 Reference Example 4 New product PET sheet side 120 0.5 0.5 See Example 5 New product PET sheet side 130 0.5 0.5 See Example 6 Recycled products Surface of the mold layer 130 0.5 0.5 See Example 7 Recycled products PET sheet side 130 0.5 0.5 See Example 8 New product PET sheet side 130 0.5 3.0 See Example 9 Recycled products Surface of the mold layer 130 0.5 3.0 See Example 10 Recycled products PET sheet side 130 0.5 3.0

[0078] New BS peel test

[0079] For the existing BS peel sheets of Reference Examples 1 to 10, peel tests were performed to determine the peel strength of the new BS. First, samples of a specified size were cut from the existing BS peel sheets of each example. Then, using a tensile testing machine, a 90-degree peel test was performed on the samples of each example to peel the new BS from the solid electrolyte membrane, and the peel strength of the new BS was determined. Figure 6A As shown, the peel strength of existing BS is 4 N / m, while the peel strength of new BS in Reference Examples 1 to 10 is 1.2 N / m to 5.1 N / m.

[0080] Confirmation test of membrane buoyancy of the new BS

[0081] For existing BS release sheets of Reference Example 1 (with a release strength of 2.8 N / m) and Reference Examples 5 to 8 (with release strengths of 3.1 N / m to 5.1 N / m), a confirmation test of the membrane buoyancy of the new BS was conducted to evaluate the effect of the solvent used to coat the catalyst ink used to form a catalyst layer on the surface of the solid electrolyte membrane. First, samples of a specified size were cut from the existing BS release sheets of each example. Next, a mixed solvent was prepared by mixing ion-exchanged water and ethanol at a 1:1 mass ratio. Then, one drop of the mixed solvent, collected using a dropper, was added to the side of the solid electrolyte membrane opposite to the new BS of each sample. Next, the membrane buoyancy of the new BS was confirmed by observing the changes in the samples over time.

[0082] like Figure 6B As shown, in the samples of existing BS release sheets in Reference Examples 5 to 8, where the peel strength of the new BS was 3.1 N / m to 5.1 N / m, the new BS remained adhered to the solid electrolyte membrane 20 minutes after the addition of the mixed solvent. It is believed that although the mixed solvent penetrated into the solid electrolyte membrane and accumulated at the interface between the solid electrolyte membrane and the new BS, the new BS did not peel off due to the strong adhesion between the solid electrolyte membrane and the new BS. That is, it is believed that sufficient adhesion between the solid electrolyte membrane and the new BS can be achieved in the existing BS release sheets of Reference Examples 5 to 8. In contrast, in the sample of existing BS release sheet in Reference Example 1, where the peel strength of the new BS was 2.8 N / m, it was confirmed that the new BS membrane floated after 15 minutes after the addition of the mixed solvent. It is believed that due to the low adhesion between the solid electrolyte membrane and the new BS, the mixed solvent penetrated into the solid electrolyte membrane and accumulated at the interface between the solid electrolyte membrane and the new BS, thereby causing the new BS to peel off. Furthermore, as... Figure 6BAs shown on the left, in the sample of electrolyte membrane, the existing BS still adhered to the solid electrolyte membrane 20 minutes after being dropped from the mixed solvent.

[0083] evaluate

[0084] Based on the results of the above tests, as with the existing BS release sheets in Examples 5 to 8, if the peel strength of the new BS is 3 N / m or higher, it is considered that the new BS film will not float due to the influence of the solvent during the coating of the catalyst ink, and the mass production process of the membrane electrode assembly can be carried out. On the other hand, as with the existing BS release sheet in Example 1, if the peel strength of the new BS is less than 3 N / m, it is considered that the new BS film may float due to the influence of the solvent during the coating of the catalyst ink, and the mass production process of the membrane electrode assembly is considered difficult. In addition, when the heating temperature during hot pressing is 120°C or higher and below the thermal decomposition temperature, regardless of whether the new BS is virgin or not, and regardless of whether the side of the new BS adhered to the solid electrolyte membrane is the PET sheet side or the release layer side, the peel strength of the new BS is considered to be 3 N / m or higher. Therefore, when the heating temperature during hot pressing is 120°C or higher and below the thermal decomposition temperature, it is considered that sufficient adhesion can be achieved when the new BS is adhered to the solid electrolyte membrane.

[0085] The embodiments of the membrane electrode assembly and the method for manufacturing the membrane electrode assembly of the present invention have been described in detail above. However, the present invention is not limited to the embodiments described above, and various design changes can be made without departing from the spirit of the present invention as set forth in the claims.

Claims

1. A membrane electrode assembly for water electrolysis, comprising a solid electrolyte membrane, an anode catalyst layer and a cathode catalyst layer sandwiching the solid electrolyte membrane. The membrane electrode assembly is characterized in that... The solid electrolyte membrane comprises a solid electrolyte layer and a functional layer formed on the anode side of the solid electrolyte layer. The anode catalyst layer is formed on the side of the functional layer of the solid electrolyte membrane. The cathode catalyst layer is formed on the side opposite to the functional layer side of the solid electrolyte membrane. The functional layer comprises a resin and catalyst metal particles dispersed in the resin.

2. The membrane electrode assembly according to claim 1, characterized in that, The catalyst metal particles mentioned above contain one or more catalyst metal particles selected from the group consisting of Pt, Au, Pd, Rh and Ir.

3. A method for manufacturing a membrane electrode assembly, specifically a method for manufacturing a membrane electrode assembly for water electrolysis. The method for manufacturing the membrane electrode assembly is characterized by comprising the following steps: The preparation process includes preparing an electrolyte membrane sheet, which has an existing back sheet and a solid electrolyte membrane adhered to the existing back sheet. The solid electrolyte membrane includes a solid electrolyte layer and a functional layer formed on the side opposite to the existing back sheet side of the solid electrolyte layer. In the bonding process, the electrolyte membrane sheet and the new back sheet are stacked in such a way that the new back sheet is in contact with the functional layer side of the solid electrolyte membrane to form a laminate. The laminate is then pressed and heated from both sides of the stacking direction, thereby bonding the new back sheet to the functional layer side of the solid electrolyte membrane by heat pressing. The existing backsheet peeling process peels the existing backsheet from the solid electrolyte membrane; The cathode catalyst layer forming process involves forming a cathode catalyst layer on the surface opposite to the functional layer side of the solid electrolyte membrane after the existing backsheet peeling process. The new backsheet stripping process involves stripping the new backsheet from the solid electrolyte membrane after the cathode catalyst layer formation process; and The anode catalyst layer formation process involves forming an anode catalyst layer on the surface of the solid electrolyte membrane on the side of the functional layer after the new backsheet peeling process.

4. The method for manufacturing the membrane electrode assembly according to claim 3, characterized in that, In the bonding process, the heating temperature when applying pressure and heating the laminate from both sides in the lamination direction is set to above 120°C and below the thermal decomposition temperature.

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