Membrane electrode assembly for water electrolysis and method for manufacturing the same.

Abstract

The objective is to provide a membrane electrode assembly for water electrolysis that can improve the barrier performance against hydrogen gas permeation through a solid electrolyte membrane. [Solution] 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, wherein 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 functional layer side surface of the solid electrolyte membrane, the cathode catalyst layer is formed on the opposite side of the functional layer side of the solid electrolyte membrane, and the functional layer includes a resin and catalyst metal particles dispersed in the resin.

Description

Technical Field

[0001] The present invention relates to a membrane electrode assembly for water electrolysis used in a water electrolysis device and a method for manufacturing the same.

Background Art

[0002] In recent years, as a water electrolysis device, a water electrolysis cell using a solid electrolyte membrane and arranged in a predetermined array has been adopted. Such a water electrolysis cell has a membrane electrode assembly including a solid electrolyte membrane, an anode catalyst layer and a cathode catalyst layer sandwiching the solid electrolyte membrane. As a membrane electrode assembly for water electrolysis, for example, a catalyst layer is formed using a catalyst layer forming material mainly composed of catalyst particles and an electrolyte component, and the electrolyte component in the catalyst layer does not unevenly distribute near the surface of the catalyst layer. There is known a membrane electrode assembly for water electrolysis in which the distribution state of the catalyst particles and the electrolyte component forming the catalyst layer is inclined (Patent Document 1). Further, as a method for manufacturing a membrane electrode assembly for water electrolysis, for example, a support film for holding the electrolyte membrane in an extended state is adhered to the first surface of a long electrolyte membrane, and either an anode or a cathode is formed on the second surface opposite to the first surface. A first forming step of forming one catalyst layer, a first adhering step of peeling a holding member from the first surface of the electrolyte membrane and adhering a diffusion member constituting a diffusion layer for diffusing a fluid constituting a fuel or an oxidant necessary for the electrochemical reaction of the fuel cell to the second surface, a second forming step of forming the other catalyst layer on the first surface, and a second adhering step of adhering a diffusion member to the first surface are provided, and a method performed by roll-to-roll is disclosed (Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional membrane electrode assemblies for water electrolysis and their manufacturing methods have improved the composition and formation method of the catalyst layer to enhance the water electrolysis performance of water electrolysis cells. On the other hand, to ensure the safety of water electrolysis cells, it is necessary to suppress the generation of explosive oxyhydrogen gas 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 performance of blocking the permeation of hydrogen gas through the solid electrolyte membrane.

[0005] The present invention has been made in view of these points, and its object is to provide a membrane electrode assembly for water electrolysis and a method for manufacturing the same that can improve the performance of blocking the permeation of hydrogen gas through a solid electrolyte membrane. [Means for solving the problem]

[0006] To solve the above problems, the present invention provides 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, wherein the solid electrolyte membrane includes 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 functional layer side of the solid electrolyte membrane, the cathode catalyst layer is formed on the opposite side of the functional layer of the solid electrolyte membrane, and the functional layer includes a resin and catalyst metal particles dispersed in the resin.

[0007] Furthermore, the present invention relates to a method for manufacturing a membrane electrode assembly for water electrolysis, comprising a preparation step of preparing an electrolyte membrane sheet having an existing backsheet (sometimes abbreviated as "BS") and a solid electrolyte membrane attached to the existing backsheet, wherein the solid electrolyte membrane includes a solid electrolyte layer and a functional layer formed on the side of the solid electrolyte layer opposite to the existing backsheet side, and a laminate formed by stacking the electrolyte membrane sheet and the new backsheet so that the new backsheet is in contact with the side of the solid electrolyte membrane on the functional layer side, and pressing the laminate from both sides in the stacking direction. The invention is characterized by comprising: a bonding step of attaching a new backsheet to the functional layer side of the solid electrolyte membrane by heat and pressure bonding while heating; an existing backsheet peeling step of peeling the existing backsheet from the solid electrolyte membrane; a cathode catalyst layer formation step of forming a cathode catalyst layer on the side of the solid electrolyte membrane opposite to the functional layer side after the existing backsheet peeling step; a new backsheet peeling step of peeling the new backsheet from the solid electrolyte membrane after the cathode catalyst layer formation step; and an anode catalyst layer formation step of forming an anode catalyst layer on the functional layer side of the solid electrolyte membrane after the new backsheet peeling step. [Effects of the Invention]

[0008] According to the present invention, the ability to block the permeation of hydrogen gas through a solid electrolyte membrane can be improved. [Brief explanation of the drawing]

[0009] [Figure 1] (a) is a schematic cross-sectional view showing a membrane electrode assembly for WE (water electrolysis) according to one embodiment, and (b) is a schematic exploded cross-sectional view showing a water electrolysis apparatus according to one embodiment. [Figure 2] (a) is a schematic cross-sectional view showing a membrane electrode assembly for WE according to the prior art, and (b) is a schematic exploded cross-sectional view showing a water electrolysis device according to the prior art. [Figure 3] This is a schematic flowchart illustrating a mixed-flow production method for manufacturing a film electrode assembly for WE according to one embodiment. [Figure 4]This is a schematic cross-sectional view showing a manufacturing line for a film electrode assembly for WE according to one embodiment. The equipment of the manufacturing line MF shown in Figure 4 operates based on the control of the control device CR. [Figure 5] (a) is a graph showing the amount of hydrogen in the gas generated on the anode side in water electrolysis experiments using water electrolysis cells prepared from the membrane electrode assemblies of the Examples and Comparative Examples 1 and 2, with the amount of hydrogen in the gas generated on the anode side in the water electrolysis experiment of Comparative Example 2 set as the reference value of 1. (b) is a graph showing the hydrogen permeability of the solid electrolyte membranes prepared for the membrane electrode assemblies of the Examples and Comparative Example 1 and the solid electrolyte membranes prepared for the membrane electrode assemblies of Comparative Example 2, at different relative humidity levels. [Figure 6] (a) is a graph showing the peel strength [N / m] of the new BS for Reference Examples 1 to 10. In addition, (a) also shows the peel strength [N / m] of the existing BS obtained by performing a 90-degree peel test to peel the existing BS from the solid electrolyte membrane of the electrolyte membrane S prepared in Reference Examples 1 to 10. (b) is a figure showing photographs of the existing BS peeled samples S from Reference Examples 5 to 8, taken from the new BS side 20 minutes after the mixed solvent was dropped, and a photograph of the existing BS peeled sample S from Reference Example 1, taken from the new BS side 15 minutes after the mixed solvent was dropped. For reference, the left end of (b) also shows a photograph of the electrolyte membrane S sample taken from the existing BS side 20 minutes after the mixed solvent was dropped. [Modes for carrying out the invention]

[0010] The following describes embodiments of the membrane electrode assembly for water electrolysis and its manufacturing method according to the present invention. Hereinafter, water electrolysis may be abbreviated as "WE," which stands for Water Electrolysis.

[0011] A. Embodiments relating to a membrane electrode assembly for WE of the present invention An embodiment of the present invention relating to a film electrode assembly for WE will be described first by illustrating one embodiment.

[0012] As shown in Figure 1(a), a membrane electrode assembly 10 for WE according to one embodiment comprises a solid electrolyte membrane 2, 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 layer-side surface 2ps (the surface opposite the functional layer side) of the solid electrolyte membrane 2. The functional layer 2f includes a resin 2fp, a carrier 2fc dispersed in the resin 2fp, and catalyst metal particles 2fm supported on the carrier 2fc. The resin layer 2p includes a resin 2pp.

[0013] As shown in Figure 1(b), the water electrolysis apparatus 100 according to one embodiment is composed of multiple sets of WE cells 50 stacked together. The WE cell 50 is a solid polymer type WE cell comprising a membrane electrode gas diffusion layer assembly 20 for WE, and an anode-side separator 12 and a cathode-side separator 14 that sandwich the membrane electrode gas diffusion layer assembly 20. The membrane electrode gas diffusion layer assembly 20 has a membrane electrode assembly 10 for WE according to one embodiment, and an anode-side gas diffusion layer (sometimes abbreviated as "anode-side GDL") 6a and a cathode-side gas diffusion layer (sometimes abbreviated as "cathode-side GDL") 6c that sandwich the membrane electrode assembly 10. In the membrane electrode gas diffusion layer assembly 20, the anode-side GDL 6a is laminated on the surface 4aa opposite to the solid electrolyte membrane side of the anode catalyst layer 4a, and the cathode-side GDL 6c is laminated on the surface 4cc opposite to the solid electrolyte membrane side of the cathode catalyst layer 4c. In the WE cell 50, the anode-side separator 12 is laminated on the surface 6aa opposite to the membrane electrode assembly side of the anode-side GDL 6a, and the cathode-side separator 14 is laminated on the surface 6cc opposite to the membrane electrode assembly side of the cathode-side GDL 6c.

[0014] On the other hand, as shown in Figure 2(a), the conventional membrane electrode assembly 110 for WE is the same as the membrane electrode assembly 10 according to 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 the 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-side surface 2ps (the surface opposite the functional layer side) and the functional layer-side surface 2fs of the solid electrolyte membrane 2, respectively. As shown in Figure 2(b), the conventional water electrolysis apparatus 200 (WE cell 150) is the same as the water electrolysis apparatus 100 according to one embodiment, except that the membrane electrode gas diffusion layer assembly 120 has the conventional membrane electrode assembly 110 instead of the membrane electrode assembly 10 according to one embodiment.

[0015] The effects of the membrane electrode assembly 10 for WE according to one embodiment will be explained in comparison with the prior art. When producing hydrogen gas by electrolyzing raw water using a water electrolysis device using the membrane electrode assembly, first, raw water is supplied from the water inlet 12f of the anode-side separator 12 to the fluid passage 12p, and at the same time, electricity is transmitted to the anode catalyst layer 4a and the cathode catalyst layer 4c by the anode-side separator 12 and the cathode-side separator 14, respectively. As a result, the raw water is electrolyzed in the anode catalyst layer 4a, producing hydrogen ions (H +) Electrons and oxygen gas (O2) are generated. Most of the raw water and the oxygen gas are discharged from the drain port 12d. Next, hydrogen ions move from the anode catalyst layer 4a side to the cathode catalyst layer 4c side by passing through the solid electrolyte membrane 2 due to the potential difference. Next, at the cathode catalyst layer 4c, hydrogen gas (H2) is generated when hydrogen ions receive electrons. The generated hydrogen gas is taken out from the hydrogen outlet 14d via the fluid passage 14p of the cathode-side separator 14, but it becomes high-pressure. Therefore, in the water electrolysis device 200 using the membrane electrode assembly 110 according to the prior art, the hydrogen gas may reverse flow through the solid electrolyte membrane 2 due to the pressure difference to the fluid passage 12p of the anode-side separator 12. Then, when the reverse-flowing hydrogen gas mixes with the oxygen gas, explosive oxyhydrogen gas is generated, and there is a risk of a safety problem. In contrast, in the water electrolysis device 100 using the membrane electrode assembly 10 according to one embodiment, since the anode catalyst layer 4a is adjacent to the functional layer 2f of the solid electrolyte membrane 2, it is considered that the interaction between the catalyst in the anode catalyst layer 4a and the functional layer 2f is manifested. Therefore, when the hydrogen gas attempts to reverse flow through the solid electrolyte membrane 2 to the fluid passage 12p of the anode-side separator 12, at the interface between the solid electrolyte membrane and the solid electrolyte membrane २ and the anode catalyst layer 4a, due to this interaction, the hydrogen gas can be converted into hydrogen ions and moved back to the cathode side through the solid electrolyte membrane 2 again, or the hydrogen gas can be converted into water and discharged from the drain port 12d. Thereby, the blocking performance of the permeation of the hydrogen gas through the solid electrolyte membrane 2 can be improved, and the generation of explosive oxyhydrogen gas can be suppressed.

[0016] Hereinafter, embodiments of the membrane electrode assembly for WE according to the present invention will be further described. The solid electrolyte layer of the solid electrolyte membrane is not particularly limited as long as it contains a proton-conductive solid polymer material (electrolyte). For example, an ion exchange layer containing a solid polymer material can be mentioned. Examples of the solid polymer material contained in the ion exchange layer include fluorine-based resins (e.g., perfluorinated electrolytes), hydrocarbon-based resins, and the like. The functional layer of the solid electrolyte membrane is not particularly limited. For example, those containing a resin, a carrier dispersed in the resin, and catalytic metal particles supported on the carrier can be mentioned. The resin is not particularly limited. For example, those containing a proton-conductive solid polymer material can be mentioned. Examples of the solid polymer material include fluorine-based resins (e.g., perfluorinated electrolytes), hydrocarbon-based resins, and the like. Examples of the catalytic metal contained in the catalytic metal particles include one or more selected from the group consisting of Pt (platinum), Au (gold), Pd (palladium), Rh (rhodium), and Ir (iridium). Examples of the carrier include carbon carriers such as carbon black.

[0017] The solid electrolyte membrane is not particularly limited. For example, it may further include a resin layer formed on the cathode-side surface of the solid electrolyte layer. The resin layer of the solid electrolyte membrane is not particularly limited as long as it contains a resin containing a proton-conductive solid polymer material. Examples of the solid polymer material contained in the resin layer include fluorine-based resins (e.g., perfluorinated electrolytes), hydrocarbon-based resins, and the like.

[0018] The anode catalyst layer is for the reaction in the anode catalyst layer (2H2O → O2 + 4H + + 4e -The catalyst layer is not particularly limited as long as it contains a catalyst component that exhibits catalytic activity, but for example, it may be a layer containing a support and a catalyst component supported on the support. Examples of the catalyst component include one or more selected from the group consisting of noble metals (e.g., Pt, Ru, and Ir, etc.) and oxides of said noble metals, and specifically, for example, Pt, iridium oxide, ruthenium oxide, iridium-ruthenium oxide, and mixtures thereof. Examples of iridium oxides include iridium oxide (e.g., IrO2, IrO3, etc.), iridium-tin oxide, and iridium-zirconium oxide. Examples of ruthenium oxides include ruthenium oxide (e.g., RuO2, Ru2O3, etc.), 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 the support include titanium oxide, manganese oxide, and cobalt oxide. The anode catalyst layer preferably contains an ionomer in addition to the catalyst, and the catalyst is coated with the ionomer. This is because, in addition to improving coating properties, the hydrophilicity of the ionomer allows for smooth permeation of the raw material water. Examples of ionsomers include ionsomers containing perfluoroelectrolytes used in solid electrolyte layers.

[0019] The cathode catalyst layer reacts (4H) in the cathode catalyst layer. + +4e -The cathode catalyst layer is not particularly limited as long as it contains a catalyst component that exhibits catalytic activity in →2H2, and any known catalyst layer can be used, but for example, a layer containing a catalyst that contains a support and a catalyst component supported on the support may also be used. Examples of such catalysts include Pt, Pt-coated titanium, Pt-supported carbon, Pd-supported carbon, Co(cobalt)glyoxime, Ni(nickel)glyoxime, etc. As the cathode catalyst layer, a layer containing an ionomer in addition to the catalyst, in which the catalyst is coated with the ionomer, is preferred. This is because, in addition to improving coating properties, the hydrophilicity of the ionomer allows for smoother permeation of raw material water. Examples of ionomers include ionomers containing perfluoroelectrolytes used in solid electrolyte layers.

[0020] The membrane electrode assembly is not particularly limited as long as the functional layer and anode catalyst layer of the solid electrolyte membrane are adjacent to each other. The anode catalyst layer may be coated on the functional layer side of the solid electrolyte membrane, or an anode catalyst layer formed on a separate component beforehand may be attached to the functional layer side of the solid electrolyte membrane.

[0021] A membrane electrode gas diffusion layer assembly using a membrane electrode assembly has an anode-side GDL and a cathode-side GDL that sandwich the membrane electrode assembly. The anode-side GDL is not particularly limited and known materials can be used, but examples include gas-permeable and conductive materials, specifically porous conductive materials made of sintered bodies of metal fibers (e.g., titanium fibers) or metal particles (e.g., titanium particles). The cathode-side GDL is not particularly limited and known materials can be used, but examples include gas-permeable and conductive materials, specifically porous conductive materials such as carbon cloth and carbon paper. The water electrolysis cell of a water electrolysis apparatus using the membrane electrode gas diffusion layer assembly is equipped with an anode-side separator and a cathode-side separator that sandwich the membrane electrode gas diffusion layer assembly. The anode-side separator and cathode-side separator are not particularly limited and known materials can be used.

[0022] B. Embodiments relating to a method for manufacturing a membrane electrode assembly for WE of the present invention The embodiments of the present invention relating to the method for manufacturing a membrane electrode assembly for WE will first be described by illustrating one embodiment. The method for manufacturing a membrane electrode assembly for WE according to one embodiment is a method for manufacturing a membrane electrode assembly for WE and a membrane electrode assembly for fuel cells (sometimes abbreviated as "FC") in a roll-to-roll manner on a common production line.

[0023] In a mixed-model production method for manufacturing a membrane electrode assembly according to one embodiment, as shown in Figure 3, first, an electrolyte membrane sheet (sometimes abbreviated as "electrolyte membrane S") used in common for membrane electrode assemblies for WE and membrane electrode assemblies for FC is prepared (S1). Specifically, an electrolyte membrane S roll R1 (Figure 4) is prepared in which the electrolyte membrane S is wound into a roll shape. The electrolyte membrane S (Figure 4) has an existing back sheet (sometimes abbreviated as "existing BS") 3 and a solid electrolyte membrane 2 attached to the existing BS 3, and the solid electrolyte membrane 2 includes a solid electrolyte layer 2h and a functional layer 2f and a resin layer 2p formed on one side and the other side of the solid electrolyte layer 2h, respectively. Subsequently, the operator selects either a membrane electrode assembly for WE or a membrane electrode assembly for FC as the membrane electrode assembly to be produced (S2).

[0024] Next, when selecting a membrane electrode assembly for WE as the membrane electrode assembly to be produced, first, using the membrane electrode assembly 10 for WE according to one embodiment as the production target on the common production line described above, it is determined whether or not it is necessary to replace the BS (backsheet) when forming the anode catalyst layer 4a on the functional layer side surface 2fs of the solid electrolyte membrane 2 (S3). Specifically, in the electrolyte membrane S, it is determined whether or not the functional layer 2f of the solid electrolyte membrane 2 is formed on the surface 2hr opposite to the existing BS side of the solid electrolyte layer 2h. If the determination is positive, it is determined that the BS needs to be replaced; if the determination is negative, it is determined that the BS does not need to be replaced.

[0025] Next, if it is determined that the BS needs to be replaced, a new backsheet (sometimes abbreviated as "new BS") 5 is attached (S4). Specifically, as shown in Figure 4, first, in addition to the electrolyte membrane S roll R1, a new BS roll R2 is prepared, on which the new BS 5 is wound in a roll shape. The new BS 5 is a new product containing a PET sheet 5p and a release layer 5r formed on the surface of the PET sheet 5p. Next, the electrolyte membrane S roll R1 and the new BS roll R2 are set in the manufacturing line MF by arranging them above and below each other, respectively, at the upstream position of the manufacturing line MF. Next, the electrolyte membrane S and the new BS 5 are fed downstream from the electrolyte membrane S roll R1 and the new BS roll R2, respectively, so that the functional layer side 2fs of the solid electrolyte membrane 2 of the electrolyte membrane S and the release layer side of the new BS 5 face each other. Next, a heating and pressing roller R3, which includes a pair of rolls equipped with a pressing mechanism and a heating mechanism, is used to stack the electrolyte membrane S and the new BS5 between the pair of rolls so that the release layer side of the new BS5 contacts the functional layer side 2fs of the solid electrolyte membrane S, thereby forming a laminate and holding the laminate between the rolls. In this state, the pair of rolls are rotated in opposite directions to transport the laminate, and the laminate is heated and pressurized from both sides in the stacking direction by the pair of rolls, thereby heat-pressing the new BS5 (release layer side) onto the functional layer side 2fs of the solid electrolyte membrane S, and the sheet with the new BS attached (sometimes abbreviated as "new BS attached S") is transported downstream. The transport speed of the laminate and the new BS attached S at this time is preferably, for example, 3 m / min or less.

[0026] Next, the existing BS3 is peeled off (S5). Specifically, as shown in Figure 4, the existing BS peeling roller R4 peels off the existing BS3 from the solid electrolyte membrane 2 in the new BS application S, and the sheet after the existing BS has been peeled off (sometimes abbreviated as "existing BS peeled off S") is transported downstream.

[0027] Next, the cathode catalyst layer 4c for WE is formed (S6). Specifically, as shown in Figure 4, the cathode catalyst ink is applied to the resin layer side 2ps (the side opposite the functional layer side) of the solid electrolyte membrane 2 of the existing BS peeled off S using the cathode catalyst coating apparatus C1. Then, the cathode catalyst ink is dried using the cathode catalyst drying oven C2 to form the cathode catalyst layer 4c, and the sheet after the cathode catalyst layer has been formed (sometimes abbreviated as "cathode catalyst layer formed S") is transported downstream.

[0028] Next, the cathode-side GDL6c for WE is attached (S7). Specifically, as shown in Figure 4, first, in conjunction with the transport of the cathode catalyst layer formation S, the cathode-side GDL6c is fed from the cathode-side GDL roll R5 to the downstream cathode-side GDL transfer roller. Next, the cathode-side GDL transfer roller R6 is used to heat-press the cathode-side GDL6c onto the cathode catalyst layer side surface 4cc of the cathode catalyst layer formation S, and the sheet with the cathode-side GDL attached (sometimes abbreviated as "cathode-side GDL attached S") is transported downstream.

[0029] Next, the new BS5 is peeled off (S8). Specifically, as shown in Figure 4, the new BS peeling roller R7 peels the new BS5 from the solid electrolyte membrane 2 of the cathode-side GDL attached S, and the sheet after the new BS has been peeled off (sometimes abbreviated as "new BS peeled S") is transported downstream. Subsequently, as shown in Figure 4, the new BS peeled S is wound up by the intermediate product winding roller R8.

[0030] Next, the anode catalyst layer 4a for WE is formed (S9). Specifically, as shown in Figure 4, first, the new BS peel S is fed downstream from the intermediate product winding roller R8 after winding is complete, with the functional layer side 2fs of the solid electrolyte membrane 2 facing upwards, and is transported downstream. Next, using the anode catalyst coating apparatus C3, the anode catalyst ink is applied to the functional layer side 2fs of the solid electrolyte membrane 2 of the new BS peel S, and then the anode catalyst layer 4a is formed by drying the anode catalyst ink using the anode catalyst drying oven C4, and the sheet after the anode catalyst layer formation (sometimes abbreviated as "anode catalyst layer formed S") is transported downstream.

[0031] Next, the anode-side GDL6a for WE is attached (S10). Specifically, as shown in Figure 4, first, in conjunction with the transport of the anode catalyst layer formation S, the anode-side GDL6a is fed from the anode-side GDL roll R9 to the downstream anode-side GDL transfer roller. Next, using the anode-side GDL transfer roller R10, the anode-side GDL6a is attached to the anode catalyst layer side surface 4aa of the anode catalyst layer formation S by thermocompression, and the sheet with the attached anode-side GDL (sometimes abbreviated as "anode-side GDL attached S") is transported downstream. Subsequently, as shown in Figure 4, the anode-side GDL attached S, which is the membrane electrode gas diffusion layer assembly, is wound up by the product winding roller R11. In this way, by carrying out the manufacturing method (S1 to S10) according to one embodiment in a mixed-flow production method, the membrane electrode assembly 10 according to one embodiment is manufactured as part of the membrane electrode gas diffusion layer assembly for WE.

[0032] In the above mixed-model production method, in determining whether or not BS replacement is necessary (S3), it is determined whether or not 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 in the electrolyte membrane S. If the determination is positive, the manufacturing method for a membrane electrode assembly for WE according to one embodiment (S1 to S10) is carried out to replace the BS (S4 and S5), and then the cathode catalyst layer 4c, cathode-side GDL 6c, anode catalyst layer 4a, and anode-side GDL 6a for WE are formed in this order to manufacture the membrane electrode assembly 10 according to one embodiment. If a negative determination is made, the membrane electrode assembly 10 according to one embodiment can be manufactured by performing the manufacturing method for other membrane electrode assemblies for WE (S1-S3 and S11-S15) on a common manufacturing line, as shown in Figure 3, without replacing the BS (S4 and S5), by forming the cathode catalyst layer 4c for WE on the resin layer side surface 2ps of the solid electrolyte membrane 2 of the electrolyte membrane S in step (S11), and then forming the cathode-side GDL 6c, anode catalyst layer 4a, and anode-side GDL 6a for WE in this order. Furthermore, if the FC type is selected in the selection of a membrane electrode assembly for WE or FC (S2), the FC type membrane electrode assembly can be manufactured by performing the manufacturing method for a membrane electrode assembly for FC (S1, S2, and S21-S25) on a common manufacturing line, as shown in Figure 3, by forming the anode catalyst layer, anode-side GDL, cathode catalyst layer, and cathode-side GDL for FC in this order. On the other hand, in a common production line where such mixed-flow production methods are used, at least the cathode catalyst layer (anode catalyst layer for FCs) forming apparatus C1, C2, the cathode-side GDL (anode-side GDL for FCs) attachment apparatus R5, R6, and the anode-side GDL (cathode-side GDL for FCs) attachment apparatus R9, R10 can be standardized in the manufacturing method for film electrode assemblies for WEs and the manufacturing method for film electrode assemblies for FCs, and the order of use of the standardized apparatus can be standardized. In the manufacturing method according to one embodiment and in other manufacturing methods for film electrode assemblies for WEs, in addition to these apparatuses, the anode catalyst layer forming apparatus C3, C4 can be further standardized, and the order of use of the standardized apparatus can be standardized.

[0033] Therefore, in the mixed-flow production method, both membrane electrode assemblies for WE and FC can be produced in a mixed flow on a common production line with most of the equipment shared. Furthermore, even if the functional layer 2f of the solid electrolyte membrane 2 is formed on the surface 2hr opposite to the existing BS side of the solid electrolyte layer 2h in the electrolyte membrane S, by implementing the manufacturing method for the membrane electrode assemblies for WE according to one embodiment (S1 to S10), a membrane electrode assemblies 10 according to one embodiment, in which the anode catalyst layer 4a is formed on the functional layer side surface 2fs of the solid electrolyte membrane 2, can be manufactured on a production line common to the manufacturing method for other membrane electrode assemblies for WE. Thus, a membrane electrode assemblies 10 that can improve the performance of blocking the permeation of hydrogen gas through the solid electrolyte membrane 2 and suppress the generation of oxyhydrogen gas can be manufactured efficiently and inexpensively.

[0034] The following describes further embodiments of the method for manufacturing a film electrode assembly for WE according to the present invention. The preparation process is not particularly limited as long as it is a process for preparing the electrolyte membrane S. The existing BS that the electrolyte membrane S has is not particularly limited as long as it includes a base sheet (for example, a PET (polyethylene terephthalate) sheet), but examples include those that further include a release layer formed on the surface of the base sheet.

[0035] The bonding process is not particularly limited, but it is preferable to heat the laminate while applying pressure from both sides in the lamination direction to a heating temperature of 120°C or higher and below the thermal decomposition temperature, and among these, it is preferable to heat the laminate to a temperature of 120°C or higher and below 130°C. The "heating temperature" refers to the temperature of a heating element that heats the laminate, such as a pair of rolls equipped with a heating mechanism. The "thermal decomposition temperature" refers to the heating temperature at which the material of the solid electrolyte membrane decomposes. In the bonding process, the surface of the new BS to be bonded to the solid electrolyte membrane may be either the surface on the PET sheet side or the surface on the release layer side. For example, the bonding process may be the process (S4) according to one embodiment. As for the new BS, it is preferable that the width of the new BS (width perpendicular to the feeding direction of the new BS roll) is equal to or greater than the width of the solid electrolyte membrane of the electrolyte membrane S (width perpendicular to the feeding direction of the electrolyte membrane S roll). This is because it prevents the solid electrolyte membrane from sticking to the roller that transports the solid electrolyte membrane. For new balance sheets (BS), they can be similar to existing ones, but they can be either new (newly purchased BS) or reused (repurposed BS after delamination).

[0036] The existing backsheet peeling process is not particularly limited, but it may be a process in which the existing backsheet is peeled off from the solid electrolyte membrane while the new backsheet is attached to the functional layer side of the solid electrolyte membrane during the attachment process, or it may be a process in which the existing backsheet is peeled off from the solid electrolyte membrane after the attachment process. [Examples]

[0037] The following provides a more detailed description of the film electrode assembly for WE and the method for manufacturing the film electrode assembly for WE according to the embodiment, with reference to examples, comparative examples, and reference examples.

[0038] 1.Membrane electrode assembly [Examples] An example of a membrane electrode assembly for WE according to the above embodiment was prepared according to the following procedure. During this process, the hydrogen permeability of the solid electrolyte membrane used in the membrane electrode assembly was measured individually. Then, a water electrolysis cell was prepared from the membrane electrode assembly, and water electrolysis experiments were conducted using the water electrolysis cell.

[0039] <Procedure for fabricating a membrane electrode assembly> First, the anode catalyst layer was formed. To do this, 48.0 g of anode catalyst (iridium oxide catalyst (Umicore)), 9.6 g of proton-conducting ionomer (AGC), 36.0 g of deionized water, and 54.7 g of alcohol (21.5 g of 1-propanol and 33.2 g of ethanol) were mixed in a beaker and dispersed using an ultrasonic homogenizer to obtain a catalyst ink. Next, the catalyst ink was applied to the surface of a substrate sheet (Teflon® sheet, thickness: 1.0 mm) using an applicator. Then, the catalyst ink was dried at 85°C for 5 minutes to form the anode catalyst layer (thickness: approximately 2 μm).

[0040] Next, the cathode catalyst layer was formed. First, 6.1 g of cathode catalyst (Pt-supported carbon (Pt load 18%, manufactured by Cataler)), 6.0 g of proton-conductive ionomer (manufactured by AGC), 88.4 g of deionized water, and 45.2 g of alcohol (ethanol) were mixed in a beaker and dispersed using an ultrasonic homogenizer to obtain a catalyst ink. Next, the catalyst ink was applied to the surface of a substrate sheet (Teflon® sheet, thickness: 1.0 mm) using an applicator. Then, the catalyst ink was dried at 85°C for 5 minutes to form a cathode catalyst layer (thickness: approximately 6 μm).

[0041] Next, a solid electrolyte membrane (Membrane (M775.15) manufactured by Gore Japan, thickness: approximately 15 μm) attached to an existing BS was prepared. The solid electrolyte membrane includes a solid electrolyte layer (thickness: approximately 3 μm) and a functional layer (thickness: approximately 6 μm) and a resin layer (thickness: approximately 6 μm) formed on one and the other side of the solid electrolyte layer, respectively. The solid electrolyte layer is expanded polytetrafluoroethylene (ePTFE). The functional layer includes a resin (perfluorosulfonic acid polymer), a carrier (carbon carrier) dispersed in the resin, and catalyst metal particles (platinum group metals) supported on the carrier. The resin layer contains a resin (perfluorosulfonic acid polymer). Next, after peeling off the existing BS from the solid electrolyte membrane, as shown in Figure 1, the anode catalyst layer was placed on the functional layer side of the solid electrolyte membrane, and the cathode catalyst layer was placed on the resin layer side of the solid electrolyte membrane, so that the anode catalyst layer and cathode catalyst layer were adjacent to the functional layer and resin layer of the solid electrolyte membrane, respectively. After that, the substrate sheets were peeled off from these catalyst layers, and the assembly was hot-pressed at 130°C and 130kPa for more than 4 minutes. This produced a membrane electrode assembly.

[0042] <Procedure for measuring the hydrogen permeability of a solid electrolyte membrane on its own> For each prepared solid electrolyte membrane, using a gas permeability measuring device (manufactured by GTR Tech Co., Ltd.), the hydrogen permeability [cc / m³] was measured at a temperature of 55°C using the isobaric method at various relative humidity levels [%RH]. 2 The following measurements were taken: [24hr·atm].

[0043] <Procedure for making a water electrolysis cell> In the membrane electrode assembly, anode-side GDL (Pt-deposited titanium fiber) and anode-side separator were laminated in this order on the side of the anode catalyst layer opposite the solid electrolyte membrane side, and cathode-side GDL (carbon fiber) and cathode-side separator were laminated in this order on the side of the cathode catalyst layer opposite the solid electrolyte membrane side. A water electrolysis cell was fabricated by pressing the laminate obtained in this way.

[0044] <Experimental procedure for water electrolysis> In a water electrolysis cell, a sufficient amount of pure water (raw water) is supplied from the water inlet of the anode-side separator, and at the same time, the temperature of the water electrolysis cell is raised to 60°C, and the electrolysis current density is 2.5 A / cm². 2 A voltage was applied between the anode and cathode separators to achieve the desired configuration, and water electrolysis was performed for 5 hours. The gas generated from the anode during water electrolysis was collected using a sampling bag, and the amount of hydrogen in the gas generated from the anode was measured by analyzing its components using mass spectrometry.

[0045] [Comparative Example 1] During hot pressing, the existing BS was peeled off from the solid electrolyte membrane. Then, as shown in Figure 2, the cathode catalyst layer was placed on the functional layer side of the solid electrolyte membrane, and the anode catalyst layer was placed on the resin layer side of the solid electrolyte membrane, so that the cathode catalyst layer and anode catalyst layer were adjacent to the functional layer and resin layer of the solid electrolyte membrane, respectively. After that, the substrate sheets were peeled off from these catalyst layers, and a membrane electrode assembly was fabricated using the same procedure as in the example, except that hot pressing was performed. A water electrolysis cell was then fabricated from the membrane electrode assembly using the same procedure as in the example, and a water electrolysis experiment using this cell was performed using the same procedure as in the example.

[0046] [Comparative Example 2] When preparing the solid electrolyte membrane, a solid electrolyte membrane was prepared that included a solid electrolyte layer and resin layers formed on one side and the other side of the solid electrolyte layer, respectively. These solid electrolyte layer and resin layers were the same as those in the solid electrolyte membrane of the example. Furthermore, during hot pressing, the existing BS was peeled off from the solid electrolyte membrane, and then the anode catalyst layer and cathode catalyst layer were placed on one side and the other side of the solid electrolyte membrane, respectively, so that the anode catalyst layer and cathode catalyst layer were adjacent to the resin layers on both sides of the solid electrolyte membrane, respectively. After that, the substrate sheet was peeled off from these catalyst layers, and then hot pressing was performed. Except for these points, a membrane electrode assembly was fabricated using the same procedure as in the example. At this time, the hydrogen permeability of the prepared solid electrolyte membrane was measured using the same procedure as in the example. Then, a water electrolysis cell was fabricated from the membrane electrode assembly using the same procedure as in the example, and a water electrolysis experiment using this cell was performed using the same procedure as in the example.

[0047] [evaluation] As shown in Figure 5(b), the solid electrolyte membranes prepared for the membrane electrode assemblies of the Examples and Comparative Example 1 exhibit higher hydrogen permeability at each relative humidity level compared to the solid electrolyte membrane prepared for the membrane electrode assemblies of Comparative Example 2, making them more permeable to hydrogen gas. Nevertheless, as shown in Figure 5(a), in water electrolysis experiments using the water electrolysis cell made from the membrane electrode assemblies of the Examples, the amount of hydrogen in the generated gas on the anode side decreased specifically, resulting in favorable results, not only compared to water electrolysis experiments using the water electrolysis cell made from the membrane electrode assemblies of Comparative Example 1, but also compared to water electrolysis experiments using the water electrolysis cell made from the membrane electrode assemblies of Comparative Example 2. The favorable results showing specific hydrogen barrier properties in the membrane electrode assemblies of the Examples are due to the interaction between the catalyst and the functional layer in the anode catalyst layer, which occurs when hydrogen gas attempts to flow back from the cathode side through the solid electrolyte membrane to the anode side. As a result of this interaction, the hydrogen gas is converted into hydrogen ions (H) + This is thought to be because it converts hydrogen into water (H2O) and blocks the permeation of hydrogen itself.

[0048] 2. Method for manufacturing a membrane electrode assembly [Reference example 1] The following procedure was followed to carry out the essential steps of an example of a method for manufacturing a film electrode assembly for WE according to the above embodiment, and an existing BS peel S (sheet after existing BS peeling) was prepared.

[0049] First, an electrolyte membrane S roll is prepared, in which an electrolyte membrane S (electrolyte membrane sheet) is wound into a roll shape. The electrolyte membrane S has an existing backsheet (BS) and a solid electrolyte membrane attached to the existing backsheet. The solid electrolyte membrane includes a solid electrolyte layer and a functional layer and a resin layer formed on one side and the other side of the solid electrolyte layer, respectively, with the resin layer and functional layer located on the existing backsheet side and the opposite side of the existing backsheet side, respectively. Furthermore, a new backsheet roll is prepared, in which a new backsheet (BS) is wound into a roll shape. The new backsheet is new, consisting of a PET sheet and a release layer containing a cycloolefin copolymer formed on the surface of the PET sheet.

[0050] Next, the electrolyte membrane S roll and the new BS roll were positioned above and below each other, facing each other. Then, the electrolyte membrane S and the new BS were fed downstream from the electrolyte membrane S roll and the new BS roll, respectively, so that the functional layer side of the solid electrolyte membrane of the electrolyte membrane S and the PET sheet side of the new BS faced each other. Next, a heating and pressing roller, including a pair of rolls equipped with a pressing mechanism and a heating mechanism, was used to stack the electrolyte membrane S and the new BS between the pair of rolls so that the PET sheet side of the new BS was in contact with the functional layer side of the solid electrolyte membrane of the electrolyte membrane S, thereby forming a laminate, and the laminate was held between the rolls. In this state, the pair of rolls were rotated in opposite directions to transport the laminate, and the laminate was heated and pressurized from both sides in the stacking direction by the pair of rolls, thereby attaching the new BS (PET sheet side) to the functional layer side of the solid electrolyte membrane of the electrolyte membrane S by thermocompression to form a new BS attachment S, and the new BS attachment S was transported downstream. Next, the existing BS was peeled off from the solid electrolyte membrane of the electrolyte membrane S in the new BS application S using an existing BS peeling roller, and the peeled existing BS S was transported downstream. Then, the peeled existing BS S was wound up using a winding roller. This produced the peeled existing BS S. In this case, the heating temperature [°C], applied pressure [MPa], and transport speed [m / min] during thermocompression bonding were set as shown in Table 1 below.

[0051] [Reference examples 2~10] In Reference Examples 2-10, the existing BS release strip S was prepared in the same manner as in Reference Example 1, with the exception of some conditions. Specifically, in Reference Examples 2-10, as shown in Table 1 below, either new or reused BS strips were used as the new BS strips, as in Reference Example 1. Also, as shown in Table 1 below, the new BS roll was changed so that the side of the new BS strip attached to the solid electrolyte membrane was either the side facing the PET sheet or the side facing the release layer. Furthermore, as shown in Table 1 below, the heating temperature [°C], applied pressure [MPa], and transport speed [m / min] during thermocompression bonding were set. Except for these conditions, the existing BS release strip S was prepared in the same manner as in Reference Example 1.

[0052] [Table 1]

[0053] [Peel test of new BS] For the existing BS peels S of Reference Examples 1 to 10, peel tests were conducted to determine the peel strength of the new BS. First, a sample of a predetermined size was cut from the existing BS peels S of each example. Next, using an autograph, a 90-degree peel test was performed on each sample to peel the new BS from the solid electrolyte membrane, and the peel strength of the new BS was determined. As shown in Figure 6(a), while the peel strength of the existing BS was 4 N / m, the peel strength of the new BS in Reference Examples 1 to 10 ranged from 1.2 N / m to 5.1 N / m.

[0054] [Confirmation test for membrane detachment of new BS] For the existing BS peel S of Reference Example 1, where the peel strength of the new BS was 2.8 N / m, and for the existing BS peel S of Reference Examples 5-8, where the peel strength of the new BS was 3.1 N / m to 5.1 N / m, a confirmation test of film delamination of the new BS was conducted to evaluate the effect of the solvent on the new BS when applying catalyst ink to form a catalyst layer on the surface of the solid electrolyte membrane. In this test, first, a sample of a predetermined size was cut from the existing BS peel S of each example. Next, a mixed solvent was prepared by mixing ion-exchanged water and ethanol in a 1:1 mass ratio. Next, one drop of the mixed solvent, taken with a dropper, was dropped onto the side of the solid electrolyte membrane of each sample that was opposite to the new BS. Next, each sample was observed over time to confirm film delamination of the new BS.

[0055] As shown in Figure 6(b), in the samples of Reference Examples 5-8, where the peel strength of the new BS was 3.1 N / m to 5.1 N / m, the new BS remained attached to the solid electrolyte membrane even 20 minutes after the mixed solvent was dropped. It is thought that the new BS did not peel off because the adhesion between the solid electrolyte membrane and the new BS was strong, even though the mixed solvent penetrated into the solid electrolyte membrane and accumulated at the interface between the solid electrolyte membrane and the new BS. In other words, it is thought that sufficient adhesion between the solid electrolyte membrane and the new BS was achieved in the existing BS peeling samples of Reference Examples 5-8. In contrast, in the sample of Reference Example 1, where the peel strength of the new BS was 2.8 N / m, film lifting of the new BS was observed 15 minutes after the mixed solvent was dropped. It is thought that the new BS peeled off because the adhesion between the solid electrolyte membrane and the new BS was low, causing the mixed solvent to penetrate into the solid electrolyte membrane and accumulate at the interface between the solid electrolyte membrane and the new BS. Furthermore, as shown on the far left of Figure 6(b), in the electrolyte membrane S sample, the existing BS remained attached to the existing BS on the solid electrolyte membrane even 20 minutes after the mixed solvent was dropped.

[0056] [evaluation] Based on the results of the above tests, if the peel strength of the new BS is 3 N / m or higher, as in the existing BS peel S in Reference Examples 5-8, it is considered that film delamination of the new BS will not occur due to the influence of the solvent when applying the catalyst ink, and that mass production of the film electrode assembly is possible. On the other hand, if the peel strength of the new BS is less than 3 N / m, as in the existing BS peel S in Reference Example 1, it is considered that film delamination of the new BS may occur due to the influence of the solvent when applying the catalyst ink, and that mass production of the film electrode assembly is difficult. Furthermore, if the heating temperature during thermocompression bonding is 120°C or higher and below the thermal decomposition temperature, it is considered that the peel strength of the new BS will be 3 N / m or higher, regardless of whether the new BS is new or not, and regardless of whether the side of the new BS attached to the solid electrolyte membrane is the side facing the PET sheet or the side facing the release layer. Therefore, if the heating temperature during thermocompression bonding is 120°C or higher and below the thermal decomposition temperature, it is considered that sufficient adhesion can be achieved when attaching the new BS to the solid electrolyte membrane.

[0057] Although embodiments of the membrane electrode assembly and the method for manufacturing the membrane electrode assembly according to the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various design modifications can be made without departing from the spirit of the invention as described in the claims. [Explanation of symbols]

[0058] 10: Membrane electrode assembly, 2: Solid electrolyte membrane, 2h: Solid electrolyte layer, 2f: Functional layer, 2fp: Resin, 2fc: Carrier, 2fm: Catalyst metal particles, 2p: Resin layer, 4a: Anode catalyst layer, 4c: Cathode catalyst layer

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 solid electrolyte membrane includes 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 functional layer side of the solid electrolyte membrane. The cathode catalyst layer is formed on the side of the solid electrolyte membrane opposite to the functional layer side. The film electrode assembly is characterized in that the functional layer comprises a resin and catalyst metal particles dispersed in the resin.

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

3. A method for manufacturing a membrane electrode assembly for water electrolysis, A preparation step for preparing an electrolyte membrane sheet having an existing backsheet and a solid electrolyte membrane attached to the existing backsheet, wherein the solid electrolyte membrane includes a solid electrolyte layer and a functional layer formed on the side of the solid electrolyte layer opposite to the existing backsheet side, A lamination step is to form a laminate by stacking an electrolyte membrane sheet and a new back sheet so that the new back sheet is in contact with the functional layer side of the solid electrolyte membrane, and to attach the new back sheet to the functional layer side of the solid electrolyte membrane by heat and pressure by heating the laminate while applying pressure from both sides in the stacking direction, thereby attaching the new back sheet to the functional layer side of the solid electrolyte membrane by heat and pressure. An existing BS peeling step for peeling the existing backsheet from the solid electrolyte membrane, After the existing BS peeling step, a cathode catalyst layer formation step is performed to form a cathode catalyst layer on the side of the solid electrolyte membrane opposite to the functional layer side. After the cathode catalyst layer formation step, a new BS peeling step is performed to peel the new backsheet from the solid electrolyte membrane, A method for manufacturing a membrane electrode assembly, comprising an anode catalyst layer formation step, which involves forming an anode catalyst layer on the functional layer side of the solid electrolyte membrane after the novel BS peeling step.

4. The method for manufacturing a film electrode assembly according to claim 3, characterized in that, in the bonding step, the heating temperature when heating the laminate while applying pressure from both sides in the lamination direction is set to 120°C or higher and below the thermal decomposition temperature.

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