Membrane sealing arrangement

Abstract

Reinforced membrane sealing arrangement, wherein the reinforced membrane sealing arrangement comprises an inner region and a perimeter region, and wherein the inner region comprises an ion-conducting component and the perimeter region comprises a sealing component, wherein the first and second planar reinforcing components each extend over the inner region into the perimeter region, and wherein the pores of each of the first and second planar reinforcing components in the inner region are impregnated with ion-conducting component, and the pores of each of the first and second planar reinforcing components in the perimeter region are impregnated with sealing component.

Description

Field of the InventionThe present invention relates to a reinforced membrane-seal assembly and, more particularly, to a reinforced membrane-seal assembly having a plurality of reinforcing layers. The reinforced membrane-seal assembly of the invention is suitable for use in a fuel cell or an electrolyser.BACKGROUND OF THE INVENTIONA fuel cell is an electrochemical cell that includes two electrodes separated by an electrolyte. A fuel such as hydrogen or an alcohol such as methanol or ethanol is supplied to the anode, and an oxidizing agent such as oxygen or air is supplied to the cathode. Electrochemical reactions occur at the electrodes and the chemical energy of the fuel and oxidant is converted to electrical energy and heat. Electrocatalysts are used to promote electrochemical oxidation of the fuel at the anode and electrochemical reduction of oxygen at the cathode.In hydrogen fuel-powered or alcohol fuel-powered proton exchange membrane fuel cells (PEMFC), the electrolyte is a solid polymer membrane that is electronically insulating and proton conductive. Protons produced at the anode are transported through the membrane to the cathode where they combine with oxygen to form water. The most commonly used alcohol fuel is methanol and this variant of PEMFC is often referred to as a direct methanol fuel cell (DMFC).The main component of the PEMFC is known as a membrane electrode assembly (MEA) and consists essentially of five layers. The central layer is the polymeric ion conducting membrane. On each side of the ion conducting membrane is an electrocatalyst layer containing an electrocatalyst configured for the particular electrocatalytic reaction. Finally, adjacent each electrocatalyst layer is a gas diffusion layer. The gas diffusion layer must allow the reactants to reach the electrocatalyst layer and must conduct the electrical current generated by the electrochemical reactions. Consequently, the gas diffusion layer must be porous and electrically conductive.Conventionally, the MEA can be manufactured by a series of methods described below:(i) The electrocatalyst layer may be applied to the gas diffusion layer to form a gas diffusion electrode. Two gas diffusion electrodes may be placed on each side of an ion conductive membrane and laminated together to form a five layer MEA.(ii) The electrocatalyst layer may be applied to both surfaces of the ion conductive membrane to form a catalyst coated ion conductive membrane. Subsequently, gas diffusion layers are applied to both surfaces of the catalyst-coated ion conducting membrane.(iii) An MEA may be formed from an ion conducting membrane coated with an electrocatalyst layer on one side, a gas diffusion layer adjacent to the electrocatalyst layer, and a gas diffusion electrode on the other side of the ion conducting membrane.Conventionally, the MEA is constructed so that the central polymeric ion-conducting membrane extends to the edge of the MEA, with the gas diffusion layers and electrocatalyst layers being smaller area than the membrane in such a manner that an area remains around the periphery of the MEA, which comprises only ion-conducting membrane. The area where there is no electrocatalyst is a non-electrochemically active region. Film layers, typically formed from non-ion conducting polymers, are generally positioned around the edge region of the MEA on the exposed surfaces of the ion conducting membrane where there is no electrocatalyst to seal and / or reinforce the edge of the MEA. An adhesive layer may be present on one or both surfaces of the film layer.The layers comprising the components in the MEA are typically bonded by a lamination process. Typically, a large portion of the polymeric ion-conducting material used in the membrane extends beyond the electrochemically active region into a non-electrochemically active region, often up to several centimeters. For MEAs with a small geometric area, this non-electrochemically active area can make up up to 50% of the total geometric area of the MEA. The membrane extending beyond the electrochemically active region does not contribute activity and performance. The polymeric ion conducting membrane is one of the most expensive components in the fuel cell and it is therefore desirable to minimize its use. Furthermore, the seal film layers positioned around the edge portion of the MEA are typically formed by using a roll of the film and cutting out a center portion to form a window frame which is then positioned around the edge of the MEA. Thus, a significant portion of the sealing film material is also wasted. It is common practice that the polymeric ion-conducting membrane also comprises a reinforcing material, such as a planar porous material embedded in the thickness of the membrane, to provide better mechanical strength of the membrane and thus increased durability of the MEA and life of the fuel cell.SUMMARY OF THE INVENTIONIn order to achieve a faster speed in fuel cell commercialization and higher market penetration, it is necessary to achieve further improvements in the performance and durability of the MEA and further reduce material consumption and thus cost, and also significantly reduce manufacturing cost and increase the manufacturing output rate of the MEA. Consequently, continuous high volume manufacturing methods in which a continuous roll of MEA is produced at high speed are introduced as alternatives to manufacturing methods in which individual MEAs are assembled from the separated MEA components. Therefore, MEA designs are required that simultaneously (i) improve the performance characteristics of the MEA, (ii) maximize the utilization of the cost intensive materials and components, and (iii) can be further manufactured by manufacturing processes that have low cost, high speed, and high throughput.The present invention provides an embodiment for a reinforced membrane-seal assembly that provides increased strength, mechanical stability and thus durability, high utilization of the ion-conducting membrane and seal film material, and that is amenable to a continuous, high-speed manufacturing process.The present invention provides a reinforced membrane-seal assembly, wherein the reinforced membrane-seal assembly comprises an inner portion and a rim portion, and wherein the inner portion comprises an ion conductive component and the rim portion comprises a sealing component; wherein the first and second planar reinforcing components each extend into the rim portion via the inner portion, and wherein the pores of each of the first and second planar reinforcing components in the inner portion are impregnated with ion conductive component, and wherein the pores of each of the first and second planar reinforcing components in the rim portion are impregnated / impregnated with sealing component.Further provided is a method of making the reinforced membrane-seal assembly.The invention further provides a catalyst coated reinforced membrane seal assembly and a reinforced membrane seal electrode assembly.Brief Description of the FiguresFigure 1 shows the inner and edge regions of a reinforced membrane-seal assembly of the invention.Figures 2 to 4 show cross-sectional views of reinforced membrane seal assemblies according to the invention.DETAILED DESCRIPTION OF THE INVENTIONThe present invention provides a reinforced membrane-seal assembly, wherein the reinforced membrane-seal assembly comprises an inner portion and a rim portion, and wherein the inner portion comprises an ion conductive component and the rim portion comprises a sealing component; wherein the first and second planar reinforcing components each extend into the rim portion via the inner portion, and wherein the pores of each of the first and second planar reinforcing components in the inner portion are impregnated with ion conductive component, and wherein the pores of each of the first and second planar reinforcing components in the rim portion are impregnated / impregnated with sealing component.One or more additional planar reinforcing components may extend across the inner region into the edge region of the reinforced membrane-seal assembly.Inner region and edge regionThe inner region refers to a planar surface in the x / y direction (in-plane direction) and extends through the thickness of the reinforced membrane-seal assembly in a direction through the plane (z direction).The edge portion refers to a planar surface in the in-plane direction and extends through the thickness of the reinforced membrane-seal assembly in a direction through the plane (z-direction), the edge portion extending around the periphery (outer edge) of the inner portion.A better understanding of the terms "inner region" and "edge region" is obtained from Figure 1, which shows a reinforced membrane-seal assembly (1) having an inner region (2) and an edge region (3).Conventionally, the inner portion has a quadrilateral geometry such as a rectangle or a square, and the edge portion forms a frame around the inner portion. However, it is understood that the inner region can have any geometric shape; the inner edge of the edge region then has the same geometric shape as the inner region. The outer edge of the rim portion need not necessarily have a geometric shape corresponding to the shape of the inner edge; for example, the inner edge may be round and the outer edge may be square.The total planar area (i.e., the combined planar (x / y) area of the inner portion and the rim portion) of the reinforced membrane-seal assembly depends upon the end use of the reinforced membrane-seal assembly; selection of an appropriate total planar area is within the skill of those skilled in the art.The dimensions of the inner and edge regions in each layer are determined by the total planar area and also depend on the end use of the reinforced membrane-seal assembly; the selection of suitable dimensions is within the skill of those skilled in the art.ion-conducting componentDepending on the method of making the reinforced membrane-seal assembly of the invention, one or more different ion conducting components may be present in the reinforced membrane-seal assembly.The ion conducting component(s) are either selected from the group of proton conducting polymers or are selected from the group of anion conducting polymers such as a hydroxyl anion conducting polymer. Examples of suitable proton conducting polymers include perfluorosulfonic acid ionomers (e.g., Nafion ®( E.I. duPont de Nemours and Company), Aciplex ®( Asahi Kasei), Aquivion™ (Solvay Specialty Polymers), Flemion ®( Asahi Glass Company), or sulfonated hydrocarbon ionomers such as those available from FuMA-Tech GmbH as the fumapem ® of the P, E, or K product series, from JSR Corporation, Toyobo Corporation, among others. Examples of suitable anion conducting polymers include A901 manufactured by Tokuyama Corporation and Fumasep FAA manufactured by FuMA-Tech GmbH.The ion conducting components can independently comprise one or more components that aid in the chemical resistance of the membrane, for example, a hydrogen peroxide decomposition catalyst, a radical scavenger, etc. Examples of such components are known to those skilled in the art.Sealing componentDepending on the method of making the reinforced membrane-seal assembly, more than one type of seal component may be present.The sealing component is required to be compatible with the ion conducting component and the planar reinforcing component. The sealing component should not be ion conductive and must have the necessary mechanical, thermal and chemical properties in the final product for operation in a fuel cell stack. The sealing component must be capable of withstanding any deformation when the substrate is removed at the completion of the processing.Examples of suitable materials that can be used for the sealant component include fluorosilicones, polyurethanes, co-polyamides, epoxy compounds, and fluoroacrylates. Specific examples of suitable sealing components include polyvinylidene fluoride (PVDF), polyetherimide (PEI), polyimide (PI), polyethersulfone (PES), fluorinated ethylene propylene (FEP), polyethylene naphthalate (PEN), ethylene tetrafluoroethylene (ET-FE), Viton ®, polyethylene oxide (PEO), polyphenylene ether (PPE), polyethylene terephthalate (PET), polyacrylonitrile (PAN), poly(p-phenylene sulfide) (PPS), polyolefins, and silicones.Planar reinforcing componentThe first, second, and any additional planar reinforcing components are present to provide strength and reinforcement to the reinforced membrane-seal assembly.The first, second and any additional planar reinforcing components are formed from a porous material. The first, second and any additional planar reinforcing components may be formed from the same porous material or from different porous materials. The porous material should have at least one of the following properties: compatible with the ion conducting and sealing component(s) so that these components can be easily impregnated into the porous material while maintaining a porous structure; provide improved mechanical strength and dimensional stability under changing humidity conditions of the final MEA; be non-conductive; and be chemically and thermally stable at the temperatures at which the fuel cell is operated.Suitable planar reinforcing components include, but are not limited to, those formed from nanofibre structures (e.g. formed by electro-spinning or pressure-spinning), those formed from expanded polymer nets and those formed by processing a planar nonporous structure. Examples of materials suitable for use are typically polymers and include polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), polyetheretherketone (PEEK), polyimide (PI), polyetherimide, polyethersulfone (PES), and polypropylene (PP).The porosity of the porous material forming the first, second and any further planar reinforcing components is suitably greater than 30%, preferably greater than 50% and most preferably greater than 70%. Suitably the porosity is less than 95%. The porosity (n) is calculated according to the formula n = V v / V t x 100, where n is the porosity, V v is the void volume and V t is the total volume of the porous material. The void volume and total volume of the porous material can be determined by methods known to those skilled in the art.The porous material forming the first, second and any other planar reinforcing components may be isotropic or anisotropic. If anisotropic, the direction of isotropy in adjacent planar reinforcing components may be the same or may be at an angle, such as 90°, to provide additional stability in all directions in the reinforced membrane-seal assembly.The first, second and any further planar reinforcing component may extend towards the outer edge of the edge portion in all directions, i.e. the planar reinforcing component is co-planar with the outer edge of the edge portion.Alternatively, the first, second and any other planar reinforcing component may be larger in planar area than the planar area of the inner region but smaller in area than the entire planar area of the reinforced membrane-seal assembly.Alternatively, at least one of the first, second and any further planar reinforcing component extends to the outer edge of the edge portion and at least one other of the first, second and any further planar reinforcing component is larger in planar area than the planar area of the inner portion but smaller in area than the entire planar area of the reinforced membrane-seal assembly.Alternatively, one or more of the first, second, and any other planar reinforcing component is co-planar with the outer edge of the edge region in a planar direction (e.g., the x-direction), but ceases at a point between an inner edge and an outer edge of the edge region in the second planar direction (e.g., the y-direction).Although the invention is described as having an ion conducting component present in the inner region and the sealing component present in the edge region, there may be a mixed region of up to 5 mm in the planar (x and / or y) direction at the interface of the ion conducting component(s) and the sealing component(s); this mixed region therefore comprises both ion conducting component and sealing component.In the mixed region, when the sealing component and the ion conducting component are miscible, there may be complete intermixing of the two components such that the distribution of the components throughout the mixed region is uniform.Alternatively, if the sealing component and the ion-conducting component are immiscible, one or more "islands" of sealing components surrounded by ion-conducting component may be present in the mixed region.Alternatively, one or more "islands" of the ion conducting component surrounded by the sealing component may be present in the mixed region.Alternatively, the mixed region may comprise a mixture of two or more of the above-described embodiments.Alternatively, the interface of the ion conducting component and the sealing component may not be perfectly linear, but may be irregular, providing for example a "wavy" line.Alternatively, there may be a mixture of an irregular interface and a mixed region.Although the mixed region and the irregular interface are described with reference to the x and / or y directions, the mixed region and the irregular interface may also apply to the direction through the plane (x direction).Alternatively, one component may overlap another component by up to 5 mm in the planar direction at the interface of the two components.In one embodiment, the ion-conducting component and / or sealing component does not extend beyond the planar reinforcing component in an in-plane direction (z-direction), such that there is no ion-conducting component and / or sealing component that is not impregnated into one or other of the first and / or second planar reinforcing component(s).Alternatively, the ion-conducting component and / or the sealing component extends beyond the planar reinforcing component in the thickness direction so that there is a layer of the ion-conducting component and / or sealing component that is not impregnated into either the first or second planar reinforcing component. This unreinforced layer of the ion-conducting component and / or the sealing component can be applied in an additional step or the unreinforced layer of the ion-conducting component and / or the sealing component can be produced by shrinking the planar reinforcing component on drying. When this unreinforced layer is applied as an additional step, the interface between the unreinforced layer of the sealing component and the unreinforced layer of the ion-conducting component may be offset from the interface between the sealing component and the ion-conducting component in the layer containing the planar reinforcing component and / or from the interface in any unreinforced layer on the other side of the planar reinforcing component.Any non-reinforced layer of the sealing component may overlap the ion-conducting component (wherein the ion-conducting component is either impregnated into the pores of the planar reinforcing component or the ion-conducting component extends across the planar reinforcing component in a direction through the plane (z-direction)). Each overlap may be greater than or equal to 1 mm. Each overlap may be less than or equal to 10 mm. Alternatively, instead of an overlap, a mixed region, as described hereinabove, comprising both the ion-conducting component and the sealing component may be present.The thickness of the reinforced membrane-seal assembly in the through-plane direction (z-direction) in the inner region depends on its end use. Generally, however, the thickness is ≤50 μm, such as ≤35 μm, e.g. ≤25 μm. Suitably, the thickness is ≥ 5 μm. In one embodiment, the reinforced membrane-seal assembly has a thickness in the direction through the plane (z-direction) in the inner range of 8-25 μm.The invention will now be described in more detail with reference to the drawings, which are given by way of illustration and not by way of limitation.Figure 2 shows a cross-sectional view of a reinforced membrane-seal assembly (1) of the invention (having) an inner portion (2) and a rim portion (3). The inner portion of each layer comprises the ion conducting component (4) and the peripheral portion of each component (or layer) comprises a sealing component (5). A first planar reinforcing component (6) and a second planar reinforcing component (7) (indicated by the cross-hatching) extend across the inner region (2) and into the edge region (3) of the reinforced membrane-seal assembly (1). The first and second reinforcing components (6 and 7) are embedded in the ion-conducting component (4) and the sealing component (5) so that all pores of the first and second reinforcing components (6 and 7) are substantially filled with ion-conducting component (4) or sealing component (5). By the term "substantially filled" is meant that at least 90%, suitably at least 95%, and preferably at least 99% of the pore volume of the reinforcing component is filled.Although FIG. 2 shows the two planar reinforcing components separated by an unreinforced strip of ion-conductive component and sealing component, it will be appreciated by those skilled in the art that this separation can be reduced during the fabrication and / or further processing of the reinforced membrane-seal assembly and can be reduced to such an extent that the two planar reinforcing components are substantially adjacent to each other and in contact with each other.Figure 3 shows a cross-sectional view of a reinforced membrane-seal assembly (1) of the invention similar to that shown in Figure 2; all component numbering remains the same. However, it can be seen in FIG. 3 that the first and second reinforcing components ( 6 and 7) do not extend to the edge of the edge portion, but stop at a location between the inner edge and the outer edge of the edge portion. The first and second reinforcing components (6 and 7) may cease at a location between the inner and outer edges of the skirt portion in both planar directions or in only one planar direction, such as the cross-web direction in the case of a continuously manufactured reinforced membrane-seal assembly.Figure 4 shows an expanded cross-sectional view of a reinforced membrane-seal assembly (1) of the invention similar to Figure 1, but wherein the ion-conducting component (4) and the sealing component (5) extend beyond the first and second planar reinforcing components (6 and 7) in an in-plane direction (z-direction) to form non-reinforced layers (8 and 9). It will be understood by those skilled in the art that the interface between the sealing component and the ion conducting component in one or both of the non-reinforced layer(s) (8 and 9) may be offset from each other and / or offset from one or both of the interfaces of the sealing component and ion conducting component embedded in the planar reinforcing components.Although the figures show interior regions and edge regions of the same dimensions throughout the reinforced membrane-seal assembly, it will be understood by those skilled in the art that the dimensions of the interior and edge regions may vary across the reinforced membrane-seal assembly in an in-plane direction depending upon the requirements of the final design and fabrication methods.The reinforced membrane-seal assembly of the invention can be made by a number of different methods. In one method, the reinforced membrane-seal assembly is constructed in layers, for example, on a substrate, by depositing the ion-conducting component on the substrate (to form the inner region) and the seal component around the ion-conducting component (to form the edge region). Alternatively, the sealant component may be deposited first followed by the ion conducting component. The layer is then dried. When the layer comprises a planar reinforcing component, it is applied to the wet seal component / ion conducting component prior to drying to allow the planar reinforcing component to be embedded in the ion conducting component / seal component such that all pores of the planar reinforcing component are substantially filled with either ion conducting component or seal component. Further layers are then added as required. The support material is then removed from the reinforced membrane seal assembly at a suitable time.The ion conducting component and the sealing component are individually dried after deposition of each, or may be dried in a single step once both have been deposited. Drying essential for removal of the solvent(s) from the coating dispersions of the ion conducting component or sealant component can be carried out by any suitable heating technique known in the art, for example, air impingement, infrared irradiation, etc. Suitably, the drying is typically carried out at a temperature of 70-120°C, but it depends on the nature of the solvent and may be carried out at temperatures up to or above 200°C.The sealing component may also be cured depending on the ion conductive component in addition to drying to provide mechanical and chemical strength to the component. Curing is a chemical reaction to effect a change, such as cross-linking, and may be thermally (e.g., by heat or IR radiation) activated or UV activated.Furthermore, the ion conducting component can be annealed in addition to drying (and optionally curing) to alter and strengthen the crystalline structure of the ionomer. Any annealing step would use elevated temperatures as compared to the drying step, for example up to 200°C.The curing and / or tempering steps may be performed after each drying step or at the end of the deposition process prior to removal of the support material. Depending on the materials used for the sealing component and the ion conducting component, the curing and annealing can be performed in a single process.The carrier material is not part of the final reinforced membrane-seal assembly, but is to be removed in a subsequent step. This step can be performed immediately after the reinforced membrane seal assemblies are formed, or it can be performed at some point downstream in the manufacturing process when the reinforced membrane seal assembly is combined with other components to produce a catalyst coated reinforced membrane seal assembly or a reinforced membrane seal electrode assembly. The support material provides support for the reinforced membrane-seal assembly during manufacture and, if not immediately removed, may provide support and strength during any subsequent storage and / or transport. The material from which the backing material is made should provide the necessary support, be compatible with the planar reinforcing component, the ion-conducting component and the sealing component, be impervious to the ion-conducting component and the sealing component, be capable of withstanding the process conditions used in making the reinforced membrane-seal assembly, and be capable of being easily removed without damage to the reinforced membrane-seal assembly. Examples of materials suitable for use include a fluoropolymer such as polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), perfluoroalkoxy polymer (PFA), fluorinated ethylene propylene (FEP - a copolymer of hexafluoropropylene and tetrafluoroethylene), and polyolefins such as biaxially oriented polypropylene (BOPP). Further examples include laminates, multilayer extrusions, and coated films / sheets capable of maintaining their mechanical strength / integrity at elevated temperatures, for example temperatures up to 200°C. Examples include laminates of: poly(ethylene-co-tetrafluoroethylene) (ETFE) and polyethylene naphthalate (PEN); polymethylpentene (PMP) and PEN; polyperfluoroalkoxy (PFA) and polyethylene terephthalate (PET) and polyimide (PI). The laminates may have two or more layers, for example, ETFE-PEN-ETFE, PMP-PEN-PMP, PFA-PET-PFA, PEN-PFA, FEP-PI-FEP, PFA-PI-PFA and PTFE-PI-PTFE. The layers may be bonded using an adhesive such as acrylic or polyurethane.The reinforced membrane-seal assembly of the invention can be used in any electrochemical device requiring an ion-conducting membrane. Accordingly, another aspect of the invention provides an electrochemical device comprising a reinforced membrane-seal assembly as described above. Alternatively, the use of a reinforced membrane-seal assembly as described above in an electrochemical device is provided. An example of an electrochemical device in which the reinforced membrane-seal assembly of the invention is particularly useful is a fuel cell, such as a PEMFC.The invention further provides a catalyst coated reinforced membrane seal assembly comprising a reinforced membrane seal assembly as described above and a catalyst layer present on at least one side of the reinforced membrane seal assembly. The catalyst layer may be present on both sides of the reinforced membrane-seal assembly.The catalyst layer comprises one or more electrocatalysts, which may be a particulate unsupported metal powder, or may be a supported catalyst with small metal nanoparticles dispersed on electrically conductive particulate carbon supports. The electrocatalyst metal is suitably selected from(i) the platinum group metals (platinum, palladium, rhodium, ruthenium, iridium and osmium),(ii) gold or silver,(iii) a base metal,or an alloy or a mixture comprising one or more of these metals or oxides thereof. The preferred electrocatalyst metal is platinum, which may be alloyed with other noble metals or base metals. When the electrocatalyst is a supported catalyst, the loading of the metal particles on the carbon support material is suitably in a range of 10-90 wt%, preferably 15-75 wt%, based on the weight of the resultant electrocatalyst.The catalyst layer is suitably applied to one side of the reinforced membrane-seal assembly as a printing ink, either organic or aqueous (but preferably aqueous). The ink may suitably comprise further components, such as an ion conducting polymer as described in EP 0 731 520 A1, which are included to improve the ionic conductivity in the layer. Alternatively, the catalyst is applied to one side of the reinforced membrane-seal assembly by decal transfer (decal transfer) of a previously prepared catalyst layer.The catalyst layer may further comprise further components. Such other components include, but are not limited to, a catalyst that facilitates oxygen evolution and is thus useful in cell reversal and on / off situations, or a hydrogen peroxide decomposition catalyst. Examples of such catalysts and any other additives suitable for incorporation into the catalyst layer are known to those skilled in the art.The invention further provides a reinforced membrane-sealing electrode assembly comprising a reinforced membrane-sealing assembly as described above and a gas diffusion electrode provided on at least one side of the reinforced membrane-sealing assembly. A gas diffusion electrode may be provided on both sides of the reinforced membrane-seal assembly.The reinforced membrane-seal electrode assembly can be constructed in a number of ways, without being limited thereto:(i) a reinforced membrane-seal assembly of the invention may be positioned between two gas diffusion electrodes (an anode and a cathode);(ii) a catalyst coated reinforced membrane-seal assembly of the invention coated with a catalyst layer only on one side may be positioned between a gas diffusion layer and a gas diffusion electrode, the gas diffusion layer contacting the catalyst coated reinforced membrane-seal assembly side coated with the catalyst layer, or(iii) A catalyst coated reinforced membrane seal assembly of the invention coated on both sides with a catalyst layer may be positioned between two gas diffusion layers.To aid in the bonding of the components and to form an integrated membrane-seal assembly, an adhesive layer may be applied to at least a portion of the exposed edge portion(s) of the reinforced membrane-seal assembly.The anode and cathode gas diffusion layers are suitably based on conventional gas diffusion substrates. Typical substrates include non-woven papers or fabrics comprising a network of carbon fibers and a thermosetting resin binder (e.g., the TGP-H series of carbon fiber paper available from Toray Industries, Inc., Japan, or the H2315 series available from Freudenberg, FCCT KG, Germany, or the Sigacet ®- series available from SGL Technologies, GmbH, Germany, or the AvCarb ®- series of Ballard Power Systems, Inc.), or woven carbon sheets. The carbon paper, fabric or cloth may be provided with a further treatment before it is incorporated into an MEA, either to make it more wettable (hydrophilic) or more wet strength (hydrophobic). The type of any treatment will depend on the type of fuel cell and the operating conditions used. The substrate may be made more wettable by incorporating materials such as amorphous carbon blacks by impregnation from liquid suspensions, or may be made more hydrophobic by impregnating the pore structure of the substrate with a colloidal suspension of a polymer such as PTFE or polyfluoroethylene propylene (FEP), followed by drying and heating above the melting point of the polymer. For applications such as the PEMFC, a microporous layer may be applied to the gas diffusion substrate on the surface that contacts the electrocatalyst layer. The microporous layer typically comprises a mixture of a carbon black and a polymer such as polytetrafluoroethylene (PTFE).The reinforced membrane seal assembly, catalyst coated reinforced membrane seal assembly, or reinforced membrane seal electrode assembly may further comprise an additive. The additive may be present internally in any of the individual component layers of the reinforced membrane-seal assembly, the catalyst coated reinforced membrane-seal assembly or the reinforced membrane-seal electrode assembly, or in the case of a catalyst coated reinforced membrane-seal assembly or a reinforced membrane-seal electrode assembly, may be present on one or more of the interfaces between the various layers and / or in one or more of the layers.The additive may be one or more selected from the group consisting of hydrogen peroxide decomposition catalysts, radical scavengers, a free radical decomposing catalyst, a self-regenerating antioxidant, a primary hydrogen donor (H-donor) antioxidant, a secondary free radical scavenging antioxidant and oxygen absorbers (oxygen scavengers). Examples of these different additives can be found in WO 2009 / 040571 A and WO 2009 / 109780 A. A preferred additive is ceria (ceria).Another aspect of the present invention provides a catalyst coated reinforced membrane seal assembly with a lower seal comprising a catalyst coated reinforced membrane seal assembly of the invention and a lower seal applied to the seal component on one or both surfaces of the catalyst coated reinforced membrane seal assembly. The lower seal is configured to provide further strength and robustness at the edges of the catalyst coated membrane seal assembly. The lower gasket is usually a polymeric material and may be selected from the same materials as the sealing component materials or may be a different type of polymer specifically selected for its use as the lower gasket. The bottom seal may be applied to the sealing components of the catalyst coated membrane-seal assembly using methods similar to those described for applying the sealing components or may be applied as a preformed picture frame film over the sealing components. The lower seal may be applied to one or both surfaces of the catalyst coated membrane seal assembly, but if applied to both surfaces, this may be accomplished only after removal of the support material.A layer comprising an adhesive may be used to aid in the adhesion of the lower gasket to the catalyst coated reinforced membrane seal assembly. The adhesive layer may be an integral part of the lower gasket, for example, in a manner such that the lower gasket and the adhesive layer are applied in a single stage, or the adhesive layer may be first applied to the catalyst coated reinforced membrane-gasket assembly and then the lower gasket is applied to the adhesive layer.Another aspect of the invention provides a bottom gasketed reinforced membrane seal electrode assembly comprising a catalyst coated reinforced membrane seal assembly, a gas diffusion layer on one or both sides of the catalyst coated reinforced membrane seal assembly, and a bottom gasket on one or both sides of the catalyst coated reinforced membrane seal assembly.The present invention further provides a fuel cell comprising a reinforced membrane sealing assembly, a catalyst coated reinforced membrane sealing assembly or a reinforced membrane sealing electrode assembly as described above. In one embodiment, the fuel cell is a PEMFC.The embodiments of the invention have been described so far with respect to individual reinforced membrane seal assemblies, catalyst coated reinforced membrane seal assemblies, or reinforced membrane seal electrode assemblies. However, the teachings of the invention can also be applied to a continuous roll of multiple reinforced membrane seal assemblies, catalyst coated reinforced membrane seal assemblies, and reinforced membrane seal electrode assemblies. Such products can be made using a process similar to that described in the co-pending UK patent application.All the embodiments described above are equally applicable to use in proton exchange membrane (PEM)-based electrolyzers. In these PEM electrolysers, the voltage is applied across the membrane electrode assemblies such that the water fed to the device is split into hydrogen and oxygen at the cathode and anode, respectively. The MEAs may require different catalyst components to a PEM fuel cell, such as Ir and Ru based materials at the anode, but on the other hand are very similar in design to the MEAs for fuel cells.

Claims

A reinforced membrane-seal assembly, wherein the reinforced membrane-seal assembly comprises an inner portion and a rim portion, and wherein the inner portion comprises an ion-conductive component and the rim portion comprises a seal component, wherein the first and second planar reinforcing components each extend across the inner portion into the rim portion, and wherein the pores of each of the first and second planar reinforcing components in the inner portion are impregnated with ion-conductive component and the pores of each of the first and second planar reinforcing components in the rim portion are impregnated with seal component.The reinforced membrane-seal assembly of claim 1, wherein one or more additional porous planar reinforcing components extend across the interior region into the edge region of the reinforced membrane-seal assembly.The reinforced membrane-seal assembly of claim 1 or claim 2, wherein the ion-conducting component and / or sealing component does not extend beyond the first or second planar reinforcing component in a direction through the plane.The reinforced membrane-seal assembly of claim 1 or claim 2, wherein the ion-conducting component and / or sealing component extends beyond first or second planar reinforcing component such that there is a layer of ion-conducting component and / or sealing component that is not impregnated into either the first or second planar reinforcing component.A catalyst coated reinforced membrane seal assembly comprising a membrane seal assembly according to any one of claims 1 to 4 and a catalyst layer present on at least one surface of the membrane seal assembly.The catalyst coated reinforced membrane seal assembly of claim 5, wherein the catalyst layer is present on both surfaces of the membrane seal assembly.A reinforced membrane-sealing electrode assembly comprising a reinforced membrane-sealing assembly according to any one of claims 1 to 4 and an electrode provided on at least one surface of the membrane-sealing assembly.The reinforced membrane-sealing electrode assembly of claim 7, wherein a catalyst layer is present on both surfaces of the reinforced membrane-sealing assembly.An electrochemical device comprising a reinforced membrane-seal assembly according to any one of claims 1 to 4.The electrochemical device of claim 9, wherein the electrochemical device is a fuel cell.

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