Membrane Seal Assembly

Abstract

The present invention provides a membrane seal assembly comprising a central region, an inner peripheral border region, and an outer peripheral border region, the inner peripheral border region and the outer peripheral border region comprising different sealing materials.

Description

[Technical Field]

[0001] The present invention relates to a membrane seal assembly and its use in electrochemical devices, particularly in proton exchange membrane fuel cells. [Background technology]

[0002] A fuel cell is an electrochemical cell containing two electrodes separated by an electrolyte. A fuel, e.g., hydrogen, an alcohol such as methanol or ethanol, or formic acid, is supplied to the anode, and an oxidant, e.g., oxygen or air, is supplied to the cathode. Electrochemical reactions occur at the electrodes, converting the chemical energy of the fuel and oxidant into electrical energy and heat. Electrocatalysts are used to promote the electrochemical oxidation of the fuel at the anode and the electrochemical reduction of oxygen at the cathode.

[0003] Fuel cells are typically classified according to the nature of the electrolyte used. Often, the electrolyte is a solid polymer membrane that is electronically insulating but ionically conductive. In proton exchange membrane fuel cells, the ion-conducting membrane conducts protons, and protons generated at the anode are transported across the ion-conducting membrane to the cathode, where they combine with oxygen to form water.

[0004] The primary component of a proton exchange membrane fuel cell is a five-layer structure conventionally known as a membrane electrode assembly. The central layer is a polymeric ion-conducting membrane. On either side of the ion-conducting membrane are catalyst layers containing electrocatalysts designed for specific electrolysis reactions. The catalyst layers also generally contain proton-conducting materials, such as proton-conducting polymers, to aid in the transfer of protons from the anode electrocatalyst to the ion-conducting membrane and / or from the ion-conducting membrane to the cathode electrocatalyst. Adjacent to each catalyst layer is a gas diffusion layer. The gas diffusion layers must allow reactants to reach the catalyst layer and must conduct the electrical current generated by the electrochemical reaction. Therefore, the gas diffusion layers must be porous and electrically conductive. This five-layer structure is conventionally known as a membrane electrode assembly.

[0005] Conventionally, membrane electrode assemblies are constructed such that a central polymer ion-conducting membrane extends to the edges of the membrane electrode assembly, and the gas diffusion layers and catalyst layers are smaller in area than the membrane, so that regions containing only the ion-conducting membrane exist around the periphery of the membrane electrode assembly. The regions without the catalyst layer are non-electrochemically active. A separate film layer, e.g., a subgasket, formed from a non-ion-conducting polymer is typically positioned around the edge region of the membrane electrode assembly on the exposed surface of the ion-conducting membrane where the catalyst layer is not present (often overlapping the edge of the catalyst layer). These films provide a seal to prevent leakage of reactant and product gases, reinforce and strengthen the edges of the membrane electrode assembly, and provide a suitable surface for supporting subsequent components, such as a subgasket or elastomeric gasket. An adhesive layer may be present on one or both sides of the sealing film layer. The layers or components within the membrane electrode assembly are typically joined by a lamination process. Alternatively, the sealing material may be deposited in a picture-frame type arrangement around a central ion-conducting membrane, for example as disclosed in WO 2015 / 145127. Summary of the Invention

[0006] Durability issues remain with conventional membrane electrode assembly structures involving the use and bonding of separate sealing films and ion-conducting membranes or catalyst-coated ion-conducting membranes. These issues can result, for example, from mechanical stresses that can build up within the ion-conducting membrane and at the edges of the ion-conducting membrane electrode assembly at the interface where the seal overlaps or frames the ion-conducting membrane. Such mechanical stresses can arise due to dimensional changes that can occur during hydration and dehydration as fuel cell operating conditions change. In particular, these stresses result in weakness of the ion-conducting membrane in the edge region near the interface with the seal, which can lead to tearing of the ion-conducting membrane and eventual failure of the membrane electrode assembly and fuel cell. Therefore, there is a need to improve the durability and lifespan of membrane electrode assemblies.

[0007] Accordingly, the present invention provides in a first aspect a membrane seal assembly comprising a first side and a second side, the membrane seal assembly comprising: (i) a central region having a first surface and a second surface corresponding to the first side and the second side of the membrane seal assembly, respectively, the central region comprising an ion-conducting material; (ii) an inner peripheral boundary region having a first surface and a second surface corresponding to the first side and the second side, respectively, of the membrane seal assembly, the inner peripheral boundary region comprising the first seal material, the inner peripheral boundary region surrounding the central region; (iii) an outer peripheral boundary region having a first surface and a second surface corresponding to the first side and the second side, respectively, of the membrane seal assembly, the outer peripheral boundary region comprising the second seal material, the outer peripheral boundary region surrounding the inner peripheral boundary region; A membrane seal assembly is provided in which the first seal material and the second seal material are different.

[0008] The use of two different sealing materials, which may have different chemical and mechanical properties, in the inner and outer peripheral boundary regions allows for the targeted use of a more chemically robust, potentially more expensive, and more difficult-to-handle material. In particular, a sealing material may be used in the inner peripheral boundary region, thereby avoiding issues related to mechanical stress at the interface with the central region. At the same time, a material that is easier to handle may be used in the outer peripheral boundary region. In certain embodiments, the inventors have found that it may be beneficial to use a first material in the inner peripheral boundary region that has a smaller Young's modulus than the second sealing material in the outer peripheral boundary region. This arrangement has the advantage that the inner peripheral boundary region can absorb mechanical stress from the interface with the ion-conducting central region while maintaining the rigidity needed in the outer peripheral boundary region to support, for example, a subgasket.

[0009] In a second aspect, the present invention provides a subgasketed membrane seal assembly comprising a membrane seal assembly according to the first aspect of the present invention, a first subgasket on a first side of the membrane seal assembly, and a second subgasket on a second side of the membrane seal assembly, wherein the first subgasket contacts a first surface of the outer peripheral boundary region and the second subgasket contacts a second surface of the outer peripheral boundary region.

[0010] In a third aspect, the present invention provides a catalyzed membrane seal assembly comprising the membrane seal assembly according to the first aspect of the present invention and a first catalyst layer on a first surface of the central region, wherein the catalyst layer has a first surface and a second surface, and the second surface of the catalyst layer is in contact with the first surface of the central region.

[0011] In a fourth aspect, the present invention provides a subgasketed catalyzed membrane seal assembly comprising a catalyzed membrane seal assembly according to the third aspect of the present invention, a first subgasket on a first side of the catalyzed membrane seal assembly, and a second subgasket on a second side of the catalyzed membrane seal assembly, wherein the first subgasket contacts a first surface of the outer peripheral boundary region and the second subgasket contacts a second surface of the outer peripheral boundary region.

[0012] In a fifth aspect, the present invention provides a subgasketed membrane seal electrode assembly comprising a subgasketed catalyzed membrane seal assembly according to the fourth aspect of the present invention, a first gas diffusion layer on a first side of the subgasketed catalyzed membrane seal assembly, and a second gas diffusion layer on a second side of the subgasketed catalyzed membrane seal assembly.

[0013] In a sixth aspect, the present invention provides a fuel cell comprising a membrane seal assembly according to the first aspect of the invention, a membrane seal assembly with a subgasket according to the second aspect of the invention, a catalysed membrane seal assembly according to the third aspect of the invention, a catalysed membrane seal assembly with a subgasket according to the fourth aspect of the invention, or a membrane seal electrode assembly with a subgasket according to the fifth aspect of the invention.

[0014] In a seventh aspect, the present invention provides a method of preparing a membrane seal assembly according to the first aspect of the invention, the method comprising: (a) depositing an ionically conductive material to form a central region; (b) depositing a first sealing material to form an inner peripheral boundary region; (c) depositing a second sealing material to form an outer peripheral boundary region.

[0015] In an eighth aspect, the present invention provides a method for preparing a catalyzed membrane seal assembly according to the third aspect of the invention, the method comprising: (d) preparing a membrane seal assembly by the method according to the seventh aspect of the present invention; (e) depositing a catalyst component on the central region to form a first catalyst layer on the central region.

[0016] In a ninth aspect, the present invention provides a method of preparing a catalyzed membrane seal assembly according to the third aspect of the invention, the method comprising: (f) depositing a catalyst component on the support material to form a first catalyst layer; (g) depositing an ion-conducting material on the catalyst layer to form a central region; (i) depositing a first sealing material to form an inner peripheral boundary region; (j) depositing a second seal material to form an outer peripheral boundary region. [Brief explanation of the drawings]

[0017] [Figure 1a] FIG. 2 is a plan view of a membrane seal assembly according to the present invention. [Figure 1b] FIG. 1b is a cross-sectional view of the membrane seal assembly shown in FIG. 1a. [Figure 2a] 1 is a cross-sectional view of a membrane seal assembly with a subgasket according to the present invention. [Figure 2b] 1 is a cross-sectional view of a membrane seal assembly with a subgasket according to the present invention. [Figure 3a] 1 is a cross-sectional view of a catalyzed membrane seal assembly according to the present invention. [Figure 3b] 1 is a cross-sectional view of a catalyzed membrane seal assembly according to the present invention. [Figure 3c] 1 is a cross-sectional view of a catalyzed membrane seal assembly according to the present invention. [Figure 3d] 1 is a cross-sectional view of a catalyzed membrane seal assembly according to the present invention. [Figure 4a] 1 is a cross-sectional view of a catalyzed membrane seal assembly with a subgasket according to the present invention. [Figure 4b]1 is a cross-sectional view of a catalyzed membrane seal assembly with a subgasket according to the present invention. [Figure 5a] 1 is a cross-sectional view of a membrane-sealed electrode assembly with a subgasket according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Preferred and / or optional features of the invention will now be described. Any aspect of the invention may be combined with any other aspect of the invention unless the context requires otherwise. Any preferred or optional feature of any aspect may be combined with any aspect of the invention, singly or in any combination, unless the context requires otherwise.

[0019] The central region is an ion-conducting membrane. The ion-conducting material is preferably a proton-conducting polymer or an anion-conducting polymer, such as a hydroxyl anion-conducting polymer. Preferably, the ion-conducting material is a proton-conducting polymer, preferably a perfluorinated sulfonic acid material. Examples of suitable proton-conducting polymers include perfluorinated sulfonic acid materials such as Nafion™ (Chemours Company), Aquivion® (Solvay Specialty Polymers), Flemion® (Asahi Glass Group), and Aciplex™ (Asahi Kasei Chemicals Corp.), as well as perfluorinated sulfonic acid ionomer materials supplied by 3M®. Alternatively, the ion-conducting material may be based on a sulfonated hydrocarbon membrane, such as those available as fumapem® P, E, or K series products from FuMA-Tech GmbH, or from JSR Corporation, Toyobo Corporation, etc.

[0020] The central region may contain one or more hydrogen peroxide decomposition catalysts. Examples of hydrogen peroxide decomposition catalysts suitable for use are known to those skilled in the art and include metal oxides such as cerium oxide, manganese oxide, titanium oxide, beryllium oxide, bismuth oxide, tantalum oxide, niobium oxide, hafnium oxide, vanadium oxide, and lanthanum oxide, preferably cerium oxide, manganese oxide, or titanium oxide, and preferably cerium dioxide (ceria). The central region may contain a recombination catalyst, particularly a catalyst for the recombination of unreacted hydrogen and oxygen, which can diffuse into the central region from the anode and cathode, respectively, to produce water. Suitable recombination catalysts include metals (e.g., platinum) on high-surface-area oxide support materials (such as silica, titania, or zirconia). Further examples of recombination catalysts are disclosed in EP 0 631 337 and WO 00 / 24074.

[0021] Both the first and second sealing materials should be non-ionically conductive. Thus, the inner peripheral boundary region is a seal, and the outer peripheral boundary region is a seal. Preferably, the inner peripheral boundary region does not include the second sealing material, and the outer peripheral boundary region does not include the first sealing material. The first and second sealing materials are preferably different in the sense that they have different chemical compositions. In other words, they are different chemical substances. Preferably, the first sealing material has a Young's modulus that is smaller than that of the second material. Young's modulus defines the relationship between stress and strain in a material when it is in the elastic regime, and this property can be measured using an instrument such as a tensiometer or dynamic mechanical analyzer. Preferably, Young's modulus is obtained using a Houndsfield tensiometer, using measurements defined in ASTM E111-17. The relationship between the materials should be true over the fuel cell operating temperature range, preferably from -20 to 180°C, and preferably from -20 to 120°C. The first seal material may also preferably have a Young's modulus greater than that of the ion-conductive material in the central region. Preferably, the Young's modulus of the first seal material is 3 GPa or less, typically 2.5 GPa or less, for example, 2 GPa or less. Preferably, the Young's modulus of the first seal material is at least 200 MPa. The first seal material should also be compatible with the fuel cell environment. For example, the first seal material should be able to withstand temperatures in the range of -20 to 180°C, inclusive, preferably -20 to 120°C, and the presence of water, hydrogen, and / or oxygen. The first seal material preferably has a lower gas permeability than the ion-conductive material under fuel cell operating conditions, and is preferably impermeable to gases under fuel cell operating conditions. The first seal material should be compatible with the ion-conductive material and the second seal material. For example, the first seal material should be able to form an airtight seal with the ion-conductive material in the central region and the second seal material in the outer peripheral boundary region. Those skilled in the art are aware of the interactions that must be considered when creating a gas-tight seal, for example, if materials are applied to form a tight fit, a gas-tight seal can be formed due to van der Waals interactions.The edges of the central region, inner peripheral boundary region, and outer peripheral boundary region, which form the interfaces between the regions, can be individually contoured to optimize contact and form an airtight seal. A mixed region may exist in the planar (x and / or y) direction at the interface between the central region and inner peripheral boundary region and / or the interface between the inner peripheral boundary region and outer peripheral boundary region. In the mixed region, if the materials are miscible, there may be thorough mixing of the two materials such that the distribution of the components throughout the mixed region is uniform. Alternatively, if the materials are not miscible, there may be one or more "islands" of one of the materials in the mixed region.

[0022] Suitable first seal materials include silicone rubbers, including polysiloxanes and polydimethylsiloxanes. Suitable first seal materials also include polyvinylidene difluoride (PVDF) homopolymers and copolymers. A preferred PVDF copolymer is poly(vinylidene fluoride-co-hexafluoropropylene), also known as PVDF-HFP. PVDF-HFP copolymers have the formula (-CH2CF2-). x [-CF2CF(CF3-] y where x is suitably in the range 0.2 to 0.8 inclusive, preferably 0.4 to 0.6, and y is suitably in the range 0.8 to 0.2 inclusive, preferably 0.6 to 0.4. Advantageously, the properties of the inner peripheral boundary region can be adjusted by varying the ratio of x to y.

[0023] The second sealing material is preferably a polymer material conventionally used as a sealing material in fuel cell membrane electrode assemblies. Suitable second sealing materials include polyetherimide (PEI), polyimide (PI), polyethersulphone (PES), fluorinated ethylene propylene (FEP), ethylene tetrafluoroethylene (ETFE), Viton®, polyethylene oxide (PEO), polyphenylene ether (PPE), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyacrylonitrile (PAN), poly(p-phenylene sulfide) (PPS), polyolefins, and silicones. UV-curable acrylic and UV-curable cationic materials may also be used.

[0024] The central region is preferably a planar region in the x and y directions of a Cartesian coordinate system, also referred to as the in-plane direction, extending through the thickness of the membrane seal assembly between the first and second faces in the z direction of a Cartesian coordinate system, also referred to as the through-plane direction. The inner peripheral boundary region is preferably a planar region in the x and y directions of a Cartesian coordinate system, extending around the periphery of the central region and extending through the thickness of the membrane seal assembly between the first and second faces in the z direction of a Cartesian coordinate system. The outer peripheral boundary region is preferably a planar region in the x and y directions of a Cartesian coordinate system, extending around the inner peripheral boundary region and extending through the thickness of the membrane seal assembly between the first and second faces in the z direction of a Cartesian coordinate system. The central region, inner peripheral boundary region, and outer peripheral boundary region typically each independently have a substantially uniform thickness, where substantially uniform thickness preferably means that the thickness of each region independently does not vary by more than 0.5 μm, typically 0.25 μm, across the x, y plane. Preferably, the thickness of each region independently is the same at every point within the x, y plane. The thickness of the membrane seal assembly is not particularly limited and will depend on the intended application. For example, the central region of a typical fuel cell membrane seal assembly will have a thickness of at least 5 μm, preferably at least 10 μm. The central region of a typical fuel cell membrane seal assembly will have a thickness of 100 μm or less, preferably 80 μm or less, typically 20 μm or less.

[0025] Preferably, the central region has a quadrilateral geometric shape, such as a rectangle or square, and the inner peripheral boundary region creates a frame around the central region. However, it will be understood that the central region can be any geometric shape, with the inner edge of the inner peripheral boundary region having the same geometric shape as the central region. The outer edge of the inner peripheral boundary region does not necessarily have a geometric shape corresponding to the shape of the inner edge; for example, the inner edge can be circular and the outer edge can be square. It will also be understood that the inner edge of the outer peripheral boundary region will have the same geometric shape as the outer edge of the inner peripheral boundary region. The outer edge of the outer peripheral boundary region does not necessarily have a geometric shape corresponding to the shape of the inner edge; for example, the inner edge can be square and the outer edge can have a more complex shape.

[0026] Figure 1a shows a plan view of a membrane seal assembly of the present invention, and Figure 1b shows a cross-sectional view of the same membrane seal assembly. Membrane seal assembly 1 has a first side 3 and a second side 5. Central region 6 has a first surface 7 and a second surface 9 corresponding to the first and second sides 3 and 5 of the membrane seal assembly, respectively. Inner peripheral boundary region 11 surrounds central region 6 and has a first surface 13 and a second surface 15 corresponding to the first and second sides 3 and 5 of the membrane seal assembly. Outer peripheral boundary region 17 surrounds the inner peripheral boundary region and has a first surface 19 and a second surface 21 corresponding to the first and second sides 4 and 5 of the membrane seal assembly, respectively.

[0027] In the membrane seal assembly shown in Figures 1a and 1b, the central region, inner peripheral boundary region, and outer peripheral boundary region each independently have a uniform thickness. The first and second surfaces 7, 13, and 19 of the central region, inner peripheral boundary region, and outer peripheral boundary region are coplanar. Preferably, the first and second surfaces of each of these regions are in the same xy plane. Alternatively, the first and second surfaces of the central region may not be coplanar with the first and second surfaces of the inner peripheral boundary region. In this case, the thickness of the central region is less than the thickness of the inner peripheral boundary region. In addition, the first and second surfaces of the inner peripheral boundary region may not be coplanar with the first and second surfaces of the outer peripheral boundary region. In this case, the thickness of the inner peripheral boundary region is less than the thickness of the outer peripheral boundary region.

[0028] The following alternative configuration to that shown in Figures 1a and 1b is exemplary, in which the central region, inner peripheral border region, and outer peripheral border region each independently have a uniform thickness.

[0029] The first and second surfaces of the central region are not coplanar with the first and second surfaces of the inner peripheral boundary region, the first and second surfaces of the inner peripheral boundary region are coplanar with the first and second surfaces of the outer peripheral boundary region, and the thickness of the central region is less than the thickness of the inner peripheral boundary region. The first and second surfaces of the inner and outer peripheral regions are in the same x,y plane that is different from the x,y plane of the first and second surfaces of the central region.

[0030] The first and second surfaces of the central region are coplanar with the first and second surfaces of the inner peripheral boundary region, respectively, and the first and second surfaces of the inner peripheral boundary region are not coplanar with the first and second surfaces of the outer peripheral boundary region, and the thicknesses of the central region and the inner peripheral boundary region are the same and less than the thickness of the outer peripheral boundary region. The first and second surfaces of the central region and the inner peripheral boundary region are in the same x,y plane that is different from the x,y plane of the first and second surfaces of the outer peripheral boundary region.

[0031] The first and second surfaces of the central region are non-coplanar with the first and second surfaces of the inner peripheral boundary region, the first and second surfaces of the inner peripheral boundary region are non-coplanar with the first and second surfaces of the outer peripheral boundary region, the thickness of the central region is less than the thickness of the inner peripheral boundary region, and the thickness of the inner peripheral boundary region is less than the thickness of the outer peripheral boundary region, and the first and second surfaces of the central region, inner peripheral boundary region, and outer peripheral boundary region all lie in different x,y planes.

[0032] The total planar area of ​​the membrane seal assembly will depend on the end use of the membrane seal assembly, and selecting a suitable total planar area will be within the ability of one skilled in the art. Furthermore, the dimensions of the central region and the inner and outer peripheral boundary regions will be determined by the total planar area and will depend on the end use of the reinforced membrane seal assembly, and selecting suitable dimensions will be within the ability of one skilled in the art. For example, in the case of a fuel cell, the outer peripheral boundary region will have a width that may depend on the design of the fuel cell stack in which the fuel cell is used and may include porting or manifold holes that allow for fuel cell reactant inlet and product outlet. The inner peripheral boundary region is typically narrower than the outer peripheral boundary region.

[0033] Configurations may exist in which the inner peripheral boundary region does not have a uniform thickness. In such cases, preferably, the first surface, the second surface, or the first and second surfaces of the inner peripheral boundary region have a step. If the first and second surfaces have a step, the step is preferably aligned in the z-direction of a Cartesian coordinate system passing through the surfaces. If the inner peripheral boundary region does not have a uniform thickness, the inner peripheral boundary region is divided into two regions: an inner region adjacent to the central region and an outer region adjacent to the outer peripheral boundary region, and the outer region preferably has a greater thickness than the inner region. Thus, while the first surface, second surface, or first and second surfaces of the central region and outer peripheral boundary region, respectively, are not in the same x, y plane, the first surface, second surface, or first and second surface of the inner peripheral boundary region may be coplanar with the first surface, second surface, or first and second surface, respectively, of the central region and the first surface, second surface, or first and second surface, respectively, of the outer peripheral boundary region.

[0034] A second aspect of the present invention provides a subgasketed membrane seal assembly comprising the membrane seal assembly of the present invention and a subgasket applied to one or both sides of the outer peripheral boundary region or both the inner and outer peripheral boundary regions. Figure 2a shows an example of such a subgasketed membrane seal assembly 31, in which a first subgasket 33 is present on a first side 3 of the membrane seal assembly and a second subgasket 36 is present on a second side 5 of the membrane seal assembly. In this case, the first and second subgaskets contact and adhere to the outer peripheral boundary region 17 and do not overlap the inner peripheral boundary region 11. In Figure 2b, the first and second subgaskets 33 and 36 overlap the inner peripheral boundary region 11 and are adhered to both the inner peripheral region 11 and the outer peripheral region 17. In addition to the configurations shown in Figures 2a and 2b, the subgasketed membrane seal assembly of the present invention can comprise a membrane seal assembly having any configuration within the scope of the present invention.

[0035] The subgasket is designed to provide additional strength and robustness to the edges of the membrane seal assembly. The subgasket can be made of any material compatible with the fuel cell environment. For example, the subgasket must be able to withstand temperatures ranging from -20 to 180°C, inclusive, preferably from -20 to 120°C, and the presence of water, hydrogen, and / or oxygen. Suitable materials include polyester, polyimide, polyethylene naphthalate, and polyethylene terephthalate. The thickness of the subgasket is not particularly limited, but preferably ranges from 10 to 100 μm, inclusive. The subgaskets do not need to have identical properties. For example, subgaskets can have different thicknesses and / or be made from different materials. The subgaskets can also have features to facilitate handling or fuel cell operation. For example, the subgaskets can have openings in their respective peripheral regions. These openings can facilitate gas porting within the fuel cell stack, for example. These openings can also facilitate handling of the subgasketed membrane seal assembly. The shape of the subgasket is not particularly limited. Stated another way, the peripheries of the first and second subgaskets may define any shape, which is typically dictated by the placement of components within a particular fuel cell stack.

[0036] The subgasket may be applied to the boundary region using coating processes known to those skilled in the art as a coating from a solution or dispersion, as a bead from a viscous mixture, or as a preformed picture-frame film over the outer peripheral boundary region or both the inner and outer peripheral boundary regions. An adhesive layer may be used to aid in the adhesion of the subgasket. The adhesive layer may be an integral part of the subgasket so that the subgasket and adhesive layer are applied in a single step, or the adhesive layer may be applied first to the outer peripheral boundary region or both the inner and outer peripheral boundary regions of the membrane seal assembly, and then the subgasket may be applied to the adhesive layer. The subgasket may be adhered using any suitable adhesive, such as a pressure-sensitive adhesive, a heat-sensitive adhesive, a UV-activated adhesive, or the like. For example, the adhesive layer may include an acrylic-based pressure-sensitive adhesive, a rubber-based adhesive, an ethylene maleic anhydride copolymer, an olefin adhesive, a nitrile-based adhesive, an epoxy-based adhesive, or a urethane-based adhesive.

[0037] FIG. 3a shows a cross-section of a catalyzed membrane seal assembly 22 in which first and second catalyst layers 23 and 25 are applied to the central region 6 of the membrane seal assembly as shown in FIGS. 1a and 1b. These first and second catalyst layers 23 and 25 do not overlap the inner peripheral boundary region 11. FIG. 3b shows an alternative configuration in which the first and second catalyst layers 23 and 25 overlap the inner peripheral boundary region 11. The configuration shown in FIG. 3a has the advantage that all of the applied catalyst material will be active because all of the layers are in contact with the electrolyte material. The design of FIG. 3b in which the catalyst layers overlap the inner peripheral boundary region will have lower catalyst utilization, but the step height caused by the termination of the catalyst layer will be moved onto the inner peripheral boundary region, thus reducing the effect of any stress caused by the step height on the interface between the central region and the inner peripheral boundary region. The catalyzed membrane seal assembly shown in Figures 3c and 3d has a different configuration of the central region, inner peripheral boundary region, and outer peripheral boundary region compared to Figures 3a and 3b. In Figure 3c, the first and second surfaces 7 and 9 of the central region 6 are not coplanar with the first and second surfaces 13 and 15 of the inner peripheral boundary region 11, and the thickness of the central region 6 is less than the thickness of the inner peripheral boundary region 11. Furthermore, the first and second surfaces 13 and 15 of the inner peripheral boundary region 11 are coplanar with the first and second surfaces 19 and 21 of the outer peripheral boundary region 17, and the thicknesses of the inner and outer peripheral boundary regions are the same. Therefore, the first and second surfaces of the inner and outer peripheral boundary regions, respectively, lie in the same x- and y-plane. The reduced thickness of the central region 6 compared to the inner peripheral boundary region 11 makes it possible to apply the first and second catalyst layers 23 and 25 to the central region 6 so that the first faces 27 and 29 of the first and second catalyst layers are flush with the first and second faces 13 and 15 of the inner peripheral boundary region 11, respectively.

[0038] In FIG. 3d, the first and second faces 7 and 9 of the central region 6 are coplanar with the first and second faces 13 and 15 of the inner peripheral boundary region 11. Thus, the first and second faces of the central and inner peripheral boundary regions, respectively, lie in the same x-y plane. However, the first and second faces 13 and 15 of the inner peripheral boundary region 11 are not coplanar with the first and second faces 19 and 21 of the outer peripheral boundary region 17, and the thickness of the inner peripheral boundary region 11 is less than that of the outer peripheral boundary region 17. The reduced thickness of the central region 6 and the inner peripheral boundary region 11 relative to the outer peripheral boundary region 17 allows the first and second catalyst layers 23 and 25 to be applied to the central region 6 such that the first faces 27 and 29 of the first and second catalyst layers 23 and 25 are coplanar with the first and second faces 13 and 15 of the outer peripheral boundary region 17. Both the configurations shown in Figures 3c and 3d have the advantage of having no step between the catalyst layer and the seal material. This means that, if a gas diffusion layer is applied, the gas diffusion layer will be supported by the membrane seal assembly across its entire width; i.e., there will be no unsupported gap between the catalyst layer and the membrane seal assembly. This prevents the membrane seal assembly material from deforming and entering the gap. The configuration shown in Figure 3c has the additional advantage of having no catalyst material outside the active area of ​​the assembly, i.e., beyond the perimeter of the central region. In addition to the configurations shown in Figures 3a-3d, the catalyzed membrane seal assembly of the present invention can include a membrane seal assembly having any configuration within the scope of the present invention.

[0039] The catalyst layer in the catalyzed membrane seal assembly of the present invention comprises one or more electrocatalysts. The one or more electrocatalysts may independently be finely divided unsupported metal powders or supported catalysts in which small catalyst nanoparticles are dispersed on a conductive, high-surface-area support, such as particulate carbon black material. The exact electrocatalyst used will depend on the reaction intended to be catalyzed, and its selection is within the ability of one skilled in the art. The electrocatalyst may preferably be a cathode or anode electrocatalyst in a fuel cell or electrolyzer, more preferably a proton exchange membrane fuel cell or electrolyzer. The thickness of the catalyst layer is not particularly limited and will depend on the intended application. In a fuel cell anode, the thickness of the catalyst layer is preferably at least 1 μm, typically at least 5 μm. In a fuel cell anode, the thickness of the catalyst layer is preferably 15 μm or less, typically 10 μm or less. In a fuel cell cathode, the thickness of the catalyst layer is preferably at least 2 μm, typically at least 5 μm. In fuel cell cathodes, the thickness of the catalyst layer is preferably 20 μm or less, typically 15 μm or less.

[0040] The electrocatalyst is preferably (i) platinum group metals (platinum, palladium, rhodium, ruthenium, iridium, and osmium); (ii) gold or silver; (iii) base metals; or an alloy or mixture containing one or more of these metals or their oxides. The base metal is tin or a transition metal that is not a noble metal. The noble metal is a platinum group metal (platinum, palladium, rhodium, ruthenium, iridium, or osmium) or gold. Preferred base metals are copper, cobalt, nickel, zinc, iron, titanium, molybdenum, vanadium, manganese, niobium, tantalum, chromium, and tin. Typically, the electrocatalyst comprises a platinum group metal, or an alloy of a platinum group metal with a base metal, preferably a preferred base metal as defined above. In particular, the electrocatalyst comprises platinum, or an alloy of platinum with a base metal, preferably a preferred base metal as defined above, more preferably nickel or cobalt, most preferably nickel. The atomic ratio of platinum to the alloying metal is typically in the range of 3:1 to 1:3, inclusive. When the electrocatalyst is a supported catalyst, the loading of metal particles on the support material may suitably be in the range of 10 to 90 wt %, preferably 15 to 75 wt %, of the weight of the resulting electrocatalyst.

[0041] The catalyst layer preferably includes an ion-conducting polymer, such as a proton-conducting ionomer, to improve the ionic conductivity of the layer. Thus, the ion-conducting material may include an ionomer such as perfluorosulfonic acid (e.g., perfluorosulfonic acid ionomer materials from Nafion® (Chemours Company), Aciplex® (Asahi Kasei), Aquivion® (Solvay Specialty Polymer), Flemion® (Asahi Glass Co.), and 3M®), or a partially fluorinated or non-fluorinated hydrocarbon-based ionomer that is a sulfonated or phosphonated polymer, such as those available from FuMA-Tech GmbH as products in the fumapem® P, E, or K series, or from JSR, Toyobo, and other companies. Preferably, the ionomer is a perfluorosulfonic acid, especially the Nafion® series available from Chemours, especially Nafion® 1100EW, and the Aquivion® series available from Solvay, especially Solvay® 830EW.

[0042] The catalyst layer may contain additional components, including, but not limited to, an oxygen generation catalyst, a hydrogen peroxide decomposition catalyst, a hydrophobic additive (e.g., a polymer such as polytetrafluoroethylene (PTFE) or an inorganic solid, with or without a surface treatment) or a hydrophilic additive to control reactant and water transport properties. The selection of additional components depends on whether the catalyst layer is used in the anode or cathode, and it is within the ability of one skilled in the art to determine which additional components are appropriate.

[0043] A fourth aspect of the present invention provides a subgasketed catalyzed membrane seal assembly, comprising a catalyzed membrane seal assembly of the present invention, a first subgasket on a first side of the catalyzed membrane seal assembly, and a second subgasket on a second side of the catalyzed membrane seal assembly. Figure 4a shows an example of such a subgasketed catalyzed membrane seal assembly 32, in which a first subgasket 33 is present on a first side 3 of the catalyzed membrane seal assembly and a second subgasket 36 is present on a second side 5 of the membrane seal assembly. In this case, the first and second subgaskets contact and adhere to the outer peripheral boundary region 17 and do not overlap the inner peripheral boundary region 11. In Figure 4b, the first and second subgaskets 33 and 36 overlap the inner peripheral boundary region 11, such that the first subgasket 33 also contacts the first surface 13 of the inner peripheral boundary region and the second subgasket 36 also contacts the second surface 15 of the inner peripheral boundary region. In this case, the first subgasket 33 and the second subgasket 36 are adhered to both the inner peripheral boundary region 11 and the outer peripheral boundary region 17 .

[0044] FIG. 5a shows an example of a subgasketed membrane seal electrode assembly according to a fifth aspect of the present invention. This particular subgasketed membrane seal electrode assembly 32 has first and second gas diffusion layers 38 and 40 on first and second sides of the subgasketed catalyzed membrane seal assembly. It can be seen in FIG. 5a that the absence of steps between the catalyst layers 23 and 25 and the membrane seal assembly, as discussed above in connection with FIGS. 3c and 3d, means that the gas diffusion layers are fully supported by the membrane seal assembly. This particular subgasketed membrane seal electrode assembly 36 also includes a planar reinforcing element 42 that extends to both the inner and outer peripheral boundary regions but does not span the entire thickness of the subgasketed membrane seal electrode assembly.

[0045] The gas diffusion layer comprises a gas diffusion substrate and, preferably, a microporous layer. Typical gas diffusion substrates include nonwoven paper or webs containing a carbon fiber network and a thermosetting resin binder (e.g., the TGP-H series of carbon fiber papers available from Toray Industries Inc., Japan, or the H2315 series available from Freudenberg FCCT KG, Germany, or the Sigracet® series available from SGL Technologies GmbH, Germany, or the AvCarb® series manufactured by Ballard Power Systems Inc.), or carbon fiber cloth. The carbon paper, web, or cloth may be pretreated and incorporated into the membrane-sealed electrode assembly prior to electrode fabrication to make the membrane-sealed electrode assembly either more wettable (hydrophilic) or more moisture-resistant (hydrophobic). The nature of any optional treatments will depend on the type of fuel cell and the operating conditions used. The substrate can be made more wettable by incorporating materials such as amorphous carbon black by impregnation from a liquid suspension, or made more hydrophobic by impregnating the pore structure of the substrate with a colloidal suspension of a polymer such as PTFE or polyfluoroethylenepropylene (FEP), followed by drying and heating above the melting point of the polymer. A typical microporous layer comprises a mixture of carbon black and a polymer such as polytetrafluoroethylene (PTFE).

[0046] In the subgasketed membrane-sealed electrode assembly according to the fifth aspect of the present invention, the first and second gas diffusion layers preferably do not overlap the outer peripheral boundary region. An adhesive can be used to assist adhesion to the inner peripheral boundary region (and, if applicable, the outer peripheral boundary region). The adhesive can be an integral part of the gas diffusion layer, such that the gas diffusion layer and adhesive layer are applied in a single step, or the adhesive layer can be applied first to the inner peripheral boundary region (and, if applicable, the outer peripheral boundary region), followed by application of the gas diffusion layer to the adhesive layer.

[0047] The fuel cell according to the sixth aspect of the present invention is preferably a proton exchange membrane fuel cell. While the present invention will be described primarily with reference to a proton exchange membrane fuel cell, it will be understood that the membrane seal assembly may be used in other electrochemical systems, such as an electrolyzer. In a proton exchange membrane electrolyzer, a voltage is applied across the membrane seal electrode assembly so that water supplied to the device is split into hydrogen and oxygen at the cathode and anode, respectively. The membrane seal electrode assembly may require different catalytic components than a proton exchange membrane fuel cell, such as Ir- and Ru-based materials in the anode, but is otherwise very similar in structure to the proton exchange membrane of a fuel cell.

[0048] In the method according to the seventh aspect of the present invention, the ion-conductive material, the first seal material, and the second seal material are each suitably deposited as a liquid or dispersion by any technique known to those skilled in the art. Such techniques include gravure coating, slot die (slot, extrusion) coating (wherein the coating is squeezed onto the substrate through a slot under pressure), screen printing, rotary screen printing, inkjet printing, spraying, painting, bar coating, pad coating, gap coating techniques, such as knife or doctor blade over roll (wherein the coating is applied to the substrate and then passes through a split between a knife and a support roller), and metering rod application, such as using a Mayer bar. Each of the ion-conductive material, the first seal material, and the second seal material may be deposited in two or more passes. Preferably, the ion-conductive material and the first seal material are deposited by inkjet printing, which may be deposited simultaneously to facilitate alignment of the central region with the inner peripheral boundary region.

[0049] The ion-conducting material and the sealing material may be dried individually after deposition of each material, or after deposition of both the ion-conducting material and the first sealing material, or after deposition of all three of the ion-conducting material, the first sealing material, and the second sealing material. If any material is deposited using two or more passes, there may be a drying step after each pass. Drying to essentially remove the solvent from the ion-conducting or sealing material coating dispersion can be accomplished by any suitable heating technique known to those skilled in the art, such as air impingement, infrared radiation, etc. Preferably, the drying step is performed at a temperature ranging from 70°C to 120°C, inclusive, but will depend on the nature of the solvent and may be up to or exceeding 200°C.

[0050] The first seal material, the second seal material, and the ion-conducting material may be cured in addition to being dried to provide mechanical and chemical strength to the materials. Curing is a chemical reaction that results in changes such as crosslinking and may be thermally activated (e.g., by heat or IR) or UV activated. Furthermore, the ion-conducting material may be annealed in addition to being dried (and optionally cured) to modify and strengthen the crystalline structure of the ion-conducting material. The optional annealing step may use a higher temperature, e.g., up to 200°C, compared to the drying step. The curing and / or annealing steps may be performed after each drying step or at the end of the deposition process. Depending on the materials used for the seal material and the ion-conducting material, curing and annealing may be performed in a single process.

[0051] The ion-conducting material, first seal material, and second seal material may be deposited on a carrier material that does not form part of the final membrane seal assembly but is intended to be removed in a subsequent step, which may be immediately after the membrane seal assembly is formed or at some point downstream in the manufacturing process if the membrane seal assembly is combined with other components, such as a subgasket. The carrier material provides support for the membrane seal assembly during manufacturing and, if not immediately removed, can provide support and strength during any subsequent storage and / or transportation. The material from which the carrier material is made should provide the necessary support, be compatible with and impermeable to the ion-conducting material and seal material, be able to withstand the process conditions involved in manufacturing the membrane seal assembly, and be easily removed without damaging the membrane seal assembly. Examples of materials suitable for use include fluoropolymers such as polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), perfluoroalkoxy polymers (PFA), fluorinated ethylene propylene (FEP—a copolymer of hexafluoropropylene and tetrafluoroethylene), and polyolefins such as biaxially oriented polypropylene (BOPP). Other examples include laminates, multilayer extrusions, and coated films / foils that can retain their mechanical strength / integrity at high temperatures, e.g., up to 200°C. Examples include laminates of poly(ethylene-co-tetrafluoroethylene) (ETFE) with polyethylene naphthalate (PEN), laminates of polymethylpentene (PMP) with PEN, and laminates of polyperfluoroalkoxy (PFA), polyethylene terephthalate (PET), and polyimide (PI).Laminates can have two or more layers, such as ETFE-PEN-ETFE, PMP-PEN-PMP, PFA-PET-PFA, PEN-PFA, FEP-PI-FEP, PFA-PI-PFA, and PTFE-PI-PTFE. The layers can be bonded using adhesives such as acrylic or polyurethane.

[0052] If a planar reinforcing component is present in the membrane seal assembly, the planar reinforcing component may be preferably applied to the ion-conducting material after deposition and before the formation of the central region. Suitable reinforcing component materials include planar porous materials, such as expanded polytetrafluoroethylene (ePTFE), as described in USRE 37307, embedded within the thickness of the membrane seal assembly to provide improved mechanical strength of the membrane seal assembly, such as increased tear resistance, and reduced dimensional change upon hydration and dehydration, thereby further improving the durability of the membrane seal electrode assembly and the lifespan of fuel cells incorporating the membrane seal assembly of the present invention. The reinforcing component material and the first seal material are suitably different in the sense that they have different chemical compositions. In other words, they are suitably different chemicals. For example, the planar reinforcing component is suitably made from a material different from the first seal material. Similarly, the reinforcing component material and the second seal material are suitably different in the sense that they have different chemical compositions. For example, the planar reinforcing component is suitably made from a material different from the second seal material. Any planar reinforcing component present may extend through the entire thickness of the membrane seal assembly or only a portion of the thickness of the membrane seal assembly. The planar reinforcing component may extend within the inner peripheral boundary region and also within the outer peripheral boundary region.

[0053] In the method according to the eighth aspect of the present invention, the catalyst layer is suitably deposited on the central region as either an organic or aqueous (but preferably aqueous) ink. Alternatively, the first catalyst layer may be applied by transfer of a pre-prepared catalyst layer, for example, the catalyst layer is applied onto a decal transfer substrate film (e.g., PTFE), and then the catalyst layer is transferred to the membrane seal assembly of the present invention by pressure and temperature techniques well known to those skilled in the art.

[0054] In optional step (k) of the method according to the ninth aspect of the present invention, the catalyst component is suitably deposited on the central region as either an organic or aqueous (but preferably aqueous) ink. Alternatively, the second layer may be applied by transfer of a pre-prepared catalyst layer, for example, the catalyst layer is applied onto a decal transfer substrate film (e.g., PTFE), and the catalyst layer is then transferred to the membrane seal assembly of the present invention by techniques involving pressure and temperature well known to those skilled in the art.

[0055] The present invention will be further described with reference to the following examples, which are intended to be illustrative and not limiting of the invention.

[0056] The membrane seal assembly of the present invention, as shown in Figures 1a and 1b, is fabricated as follows: A liquid dispersion of perfluorosulfonic acid (PFSA) ion-conducting material is coated as a thin layer onto a release film of a carrier material simultaneously with a solution of PVDF / HFP copolymer. These materials are dispensed using an inkjet system capable of aligning the two liquids with each other, with the PFSA material occupying a central region and the PVDF / HFP copolymer surrounding it to form an inner peripheral boundary region. Once dried, both liquids form a continuous film 3 μm thick. A second layer of each material is coated over the first layer, and while the second layer is still wet, an ePTFE reinforcement component is placed over the second layer, holding the reinforcement component under tension. The reinforcement component is drawn down into the wet PFSA and PVDF / HFP layers so that all of the openings in the reinforcement component are completely filled with PFSA or PVDF / HFP from the second coating once dried. After drying, a final coating of the PFSA dispersion and PVDF / HFP solution is applied to the top surface of the reinforcement component and allowed to dry, ensuring that the central region of the reinforcement component is completely encapsulated by the material in the coating region. Finally, a UV-curable polymer material, poly(4-vinylphenol-co-methyl methacrylate) (PVP-co-PMMA), is dispensed using an inkjet and cured using UV radiation to form an outer peripheral border region around the PVDF / HFP inner peripheral border region. Once cured, the outer peripheral border region will be the same thickness as the central region and the inner peripheral border region.

Claims

1. 1. A membrane seal assembly comprising a first side and a second side, the membrane seal assembly comprising: (i) a central region having a first surface and a second surface corresponding to the first side and the second side, respectively, of the membrane seal assembly, the central region comprising an ionically conductive material; (ii) an inner peripheral boundary region having a first surface and a second surface corresponding to the first side and the second side, respectively, of the membrane seal assembly, the inner peripheral boundary region including a first seal material, the inner peripheral boundary region surrounding the central region in a plan view; (iii) an outer peripheral boundary region having a first surface and a second surface corresponding to the first side and the second side, respectively, of the membrane seal assembly, the outer peripheral boundary region including a second seal material, the outer peripheral boundary region surrounding the inner peripheral boundary region in a plan view; the first seal material and the second seal material are different; 10. A membrane seal assembly, wherein the first seal material has a Young's modulus that is less than the Young's modulus of the second seal material, and the first seal material has a Young's modulus that is greater than the Young's modulus of the ion-conducting material in the central region.

2. The membrane seal assembly of claim 1 , wherein the first and second surfaces of the central region are coplanar with the first and second surfaces of the inner peripheral boundary region, respectively.

3. 2. The membrane seal assembly of claim 1, wherein the first and second surfaces of the central region are not coplanar with the first and second surfaces of the inner peripheral boundary region, respectively, and the thickness of the central region is less than the thickness of the inner peripheral boundary region.

4. The membrane seal assembly of claim 1 , wherein the first and second surfaces of the inner peripheral boundary region are coplanar with the first and second surfaces of the outer peripheral boundary region, respectively.

5. 2. The membrane seal assembly of claim 1, wherein the first and second surfaces of the inner peripheral boundary region are not coplanar with the first and second surfaces of the outer peripheral boundary region, respectively, and the thickness of the inner peripheral boundary region is less than the thickness of the outer peripheral boundary region.

6. The membrane seal assembly of claim 1 , further comprising a planar reinforcing component in the central region.

7. The membrane seal assembly of claim 6 , wherein the planar reinforcing component extends within the inner peripheral boundary region.

8. The membrane seal assembly of claim 7 , wherein the planar reinforcing component extends within the outer peripheral boundary region.

9. 10. A membrane seal assembly with a subgasket, comprising: the membrane seal assembly of claim 1; a first subgasket on the first side of the membrane seal assembly; and a second subgasket on the second side of the membrane seal assembly, wherein the first subgasket contacts the first surface of the outer peripheral boundary region and the second subgasket contacts the second surface of the outer peripheral boundary region.

10. 10. The subgasketed membrane seal assembly of claim 9, wherein the first subgasket and the second subgasket overlap the inner peripheral boundary region, the first subgasket contacting the first surface of the inner peripheral boundary region, and the second subgasket contacting the second surface of the inner peripheral boundary region.

11. 10. A catalyzed membrane seal assembly comprising: the membrane seal assembly of claim 1; and a first catalyst layer on the first surface of the central region, wherein the catalyst layer has a first surface and a second surface, and the second surface of the catalyst layer is in contact with the first surface of the central region.

12. 12. The catalyzed membrane seal assembly of claim 11, wherein the first catalyst layer overlies the inner peripheral boundary region and the second surface of the first catalyst layer contacts the first surface of the inner peripheral boundary region.

13. 12. The catalyzed membrane seal assembly of claim 11, further comprising a second catalyst layer on the second surface of the central region, the second catalyst layer having a first surface and a second surface, the second surface of the second catalyst layer contacting the second surface of the central region.

14. 14. The catalyzed membrane seal assembly of claim 13, wherein the second catalyst layer overlies the inner peripheral boundary region and the second surface of the second catalyst layer contacts the second surface of the inner peripheral boundary region.

15. The catalyzed membrane seal assembly of claim 11 , wherein the first surface of the first catalyst layer is coplanar with the first surface of the inner peripheral boundary region.

16. The catalyzed membrane seal assembly of claim 13 , wherein the first surface of the second catalyst layer is coplanar with the second surface of the inner peripheral boundary region.

17. 12. A catalyzed membrane seal assembly with a subgasket, comprising: the catalyzed membrane seal assembly of claim 11; a first subgasket on the first side of the catalyzed membrane seal assembly; and a second subgasket on the second side of the catalyzed membrane seal assembly, wherein the first subgasket contacts the first surface of the outer peripheral boundary region and the second subgasket contacts the second surface of the outer peripheral boundary region.

18. 18. The subgasketed catalyzed membrane seal assembly of claim 17, wherein the first subgasket and the second subgasket overlap the inner peripheral boundary region, the first subgasket contacting the first surface of the inner peripheral boundary region, and the second subgasket contacting the second surface of the inner peripheral boundary region.

19. 20. A subgasketed membrane seal electrode assembly comprising: the subgasketed catalyzed membrane seal assembly of claim 17; a first gas diffusion layer on the first side of the subgasketed catalyzed membrane seal assembly; and a second gas diffusion layer on the second side of the subgasketed catalyzed membrane seal assembly.

20. 20. The subgasketed membrane-sealed electrode assembly of claim 19, wherein the first gas diffusion layer and the second gas diffusion layer do not overlap the outer peripheral boundary region.

21. 20. The subgasketed membrane-sealed electrode assembly of claim 19, wherein the first gas diffusion layer and the second gas diffusion layer are bonded to the first and second surfaces of the inner peripheral boundary region, respectively.

22. A fuel cell comprising the membrane seal assembly of claim 1.

23. 23. The fuel cell of claim 22, wherein the fuel cell is a proton exchange membrane fuel cell.

24. 10. A method for preparing the membrane seal assembly of claim 1, comprising: (a) depositing an ionically conductive material to form the central region; (b) depositing a first sealing material to form the inner peripheral boundary region; (c) depositing a second seal material to form the outer peripheral boundary region.

25. 12. A method for preparing the catalyzed membrane seal assembly of claim 11, comprising: (d) preparing a membrane seal assembly according to the method of claim 24; (e) depositing a catalyst component on the central region to form the first catalyst layer on the central region.

26. 12. A method for preparing the catalyzed membrane seal assembly of claim 11, comprising: (f) depositing a catalyst component on the support material to form a first catalyst layer; (g) depositing an ion-conducting material on the catalyst layer to form the central region; (i) depositing a first sealing material to form the inner peripheral boundary region; (j) depositing a second seal material to form the outer peripheral boundary region.

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