Gas diffusion layer and membrane electrode arrangement for an electrochemical system

Abstract

The present invention relates to a gas diffusion layer for an electrochemical system, which may be, for example, a fuel cell system. The gas diffusion layer has at least one recess on an outer contour and / or at least one opening.

Description

[0001] The present invention relates to a gas diffusion layer for an electrochemical system, which may be, for example, a fuel cell system, and to a membrane electrode arrangement for an electrochemical system, which may be, for example, a fuel cell system. The invention also relates to a method for manufacturing the membrane electrode arrangement.

[0002] Fuel cell systems are electrochemical systems used to generate electrical energy. They typically comprise a large number of individual fuel cells stacked together to form a unit called a stack, which is then operated as such.

[0003] Fuel cells convert a fuel into electrical energy and can be differentiated, for example, by the type of electrolyte they use. The most common categories include alkaline fuel cells, which use a concentrated aqueous solution as the electrolyte; solid oxide fuel cells, which use an oxygen-ion-conducting ceramic material as the electrolyte; phosphoric acid fuel cells, which use phosphoric acid as the electrolyte; and polymer electrolyte membrane (PEM) fuel cells, which use a proton-conducting membrane as the electrolyte. The latter are of particular interest to the automotive industry because PEM fuel cells exhibit high power density even at relatively low operating temperatures, typically 60°C to 120°C (LT-PEMFC, low temperature) or 120°C to 200°C for high-temperature PEM fuel cells (HT-PEMFC), while also being characterized by a compact design.

[0004] A central component of a PEM fuel cell is a membrane electrode assembly (MEA). The MEA typically comprises an ion-conducting membrane (proton exchange membrane, PEM) that separates the cathode from the anode compartment and has catalyst layers on its opposite surfaces. The membrane containing the catalyst layers is also referred to as a catalyst-coated membrane (CCM, 3L-MEA). A fuel-containing anode reactant stream is supplied to the anode side of the fuel cell, and an oxygen-containing cathode reactant stream is supplied to the cathode side. The cathode reaction (reduction of oxygen) and / or the anode reaction (oxidation of the fuel) is usually catalyzed by at least one catalyst.

[0005] To improve the performance of the electrochemical system, the use of so-called gas diffusion layers (GDLs), also known as gas diffusion sheets, has proven effective. These ensure, among other things, optimal distribution of operating fluids such as reactant gases across the catalyst layers, as well as the removal of reaction products and heat of reaction. Furthermore, the GDL facilitates electron transport from the catalyst layer to the bipolar plate.

[0006] For sealing and stabilization, a MEA typically includes at least one sealing layer, which can also be, for example, a subgasket. A seven-layer membrane electrode assembly (7L-MEA) is particularly common in fuel cell systems, featuring the layer sequence GDL-sealing layer-CCM-sealing layer-GDL.

[0007] To ensure the best possible arrangement of the individual layers relative to each other, the layers of the MEA are glued and / or clamped to adjacent layers during assembly.

[0008] In the prior art, heat-activated, pressure-sensitive (PSA), or radiation-curing adhesives are typically used to bond the GDL to at least one sealing layer. Heat-activated adhesives have the disadvantage that at least two elements of the MEA (MEA elements) are subjected to a corresponding thermal stress. Pressure-sensitive adhesives have the disadvantage that the MEA elements are subjected to a corresponding mechanical stress.

[0009] Such stresses can be avoided by using radiation-curing adhesives. The use of a radiation-curing, in particular UV-curing, adhesive is described in document WO 2008 / 040682 A1.

[0010] However, the use of radiation-curing adhesives requires that the adhesive can be irradiated when the components to be bonded are pressed together. This is particularly problematic in a 7L-MEA, where all adjacent elements of the membrane electrode assembly (MEA elements), and especially the two gas diffusion layers, are to be bonded to their respective adjacent sealing layers, as irradiation, particularly with UV light, is not possible through the gas diffusion layers, and therefore the adhesive cannot cure.

[0011] The invention is therefore based on the objective of providing a gas diffusion layer and / or a membrane electrode arrangement which is characterized by a simple structure and at the same time enables the bonding of adjacent MEA elements with at least one radiation-curing adhesive.

[0012] The term "in particular" is used in this description and the attached claims preferably to describe optional features.

[0013] The problem is solved by a gas diffusion layer according to the relevant independent claim.

[0014] The gas diffusion layer can be a gas diffusion layer for an electrochemical system. The electrochemical system is preferably a fuel cell system, in particular a fuel cell system comprising at least one PEM fuel cell. The fuel cell system can also comprise at least one fuel cell stack.

[0015] According to the invention, the gas diffusion layer has at least one recess on an outer contour and / or at least one opening. This has the advantage that, in an installed state, the gas diffusion layer cannot completely conceal and / or cover at least one further layer. Furthermore, less material can be consumed during manufacturing.

[0016] The gas diffusion layer is preferably a flat material. A flat material is preferably a planar material which, in two dimensions (for example, its length and width), can have a significantly larger extent than in another dimension (in particular, its thickness). A plane in which the gas diffusion layer extends with its length and width defines a principal plane of extension of the gas diffusion layer.

[0017] In the context of the present invention, "thickness" preferably refers to a material thickness, in particular an average material thickness, of the respective element, such as the gas diffusion layer (any recesses and / or openings are disregarded).

[0018] The thickness of the gas diffusion layer can be < 320 µm, preferably < 280 µm, particularly preferably between 15 and 195 µm.

[0019] The gas diffusion layer can be structured in two layers. The two layers can be a substrate (support layer) and a microporous layer (MPL).

[0020] The substrate can be paper- or fabric-based and / or have a thickness of < 220 µm, particularly preferably 15 to 100 µm.

[0021] The microporous layer can be applied to this substrate, its composition typically comprising carbon-containing, particularly sintered, particles based on carbon black and / or graphite and at least one hydrophobic binder such as polytetrafluoroethylene, fluorinated ethylene propylene, or polyvinylidene fluoride. In principle, all materials known from the prior art for gas diffusion layers can be used.

[0022] The microporous layer can have a thickness of < 100 µm, preferably 20 to 80 µm.

[0023] For the purposes of the present invention, an opening is understood to be a release that extends through the entire thickness of the gas diffusion layer and is completely encompassed by the gas diffusion layer. The opening can therefore be located, in particular, in the main plane of extension.

[0024] At least one opening can be located at any point in the gas diffusion layer.

[0025] In a preferred embodiment, the gas diffusion layer has at least a peripheral region. In particular, the at least peripheral region can at least partially surround and / or delimit a central region.

[0026] Preferably, the at least one peripheral area extends from an end of the gas diffusion layer, in particular a section of the outer contour such as an edge of the gas diffusion layer, over up to 30%, preferably up to 20%, particularly preferably up to 10%, of the length and / or width of the gas diffusion layer, whereby any recesses in the outer contour can be disregarded.

[0027] In a preferred embodiment, the central region can be a central region along the length and / or width of the gas diffusion layer, which is arranged between two peripheral regions.

[0028] In a further embodiment, the at least one peripheral region has at least partially, preferably completely, a frame-like and / or ring-like structure and / or surrounds the central region on at least two, preferably three, and particularly preferably four sides. In particular, the at least one peripheral region can completely surround the central region.

[0029] It can be advantageous if at least one opening is located in at least one peripheral region of the gas diffusion layer. In this way, the central region is fully available for the essential functions of the gas diffusion layer in an electrical system, namely electrical and thermal contacting and current conduction, as well as the transport of reactants to the catalyst layer and the removal of product water.

[0030] The at least one opening can have a round shape, in particular a circular and / or oval shape, or a polygonal shape, at least partially, preferably completely. The polygon can have 3 to 10, preferably 3 to 8, and in particular 4 to 6, sides. The polygon can, in particular, be a regular polygon. A circular, square, or rectangular shape is especially preferred. This can facilitate the simpler fabrication of the gas diffusion layer.

[0031] The gas diffusion layer can have a basic shape in its main plane of extension. The basic shape of the gas diffusion layer can be, for example, a circle, an oval, or a polygon, preferably a regular one, in particular a rectangle or a square. Any deviation from the corresponding round, rectangular, or square outer contour, such as a notch, constitutes a recess within the meaning of the present invention.

[0032] At least one recess can be located at any point on the outer contour of the gas diffusion layer.

[0033] The at least one recess can have a round shape, in particular a circular and / or oval shape, or a polygonal shape, at least partially. The polygon can have 3 to 8, preferably 3 to 6, and in particular 3 or 4, sides. The polygon can, in particular, be a regular polygon. A circular, triangular, square, or rectangular shape is especially preferred. Since a recess is located on the outer contour of the gas diffusion layer, these recesses are open on one side and can, for example, have the shape of a rectangle open on one side or an open arc of a circle. This can facilitate the simpler manufacture of the gas diffusion layer.

[0034] If the gas diffusion layer comprises at least one opening and at least one recess, the at least one opening and the at least one recess may be located in the same peripheral area and / or in different peripheral areas of the gas diffusion layer. If the at least one opening and the at least one recess are located in the same peripheral area, the end of the gas diffusion layer, in particular the section of the outer contour from which the peripheral area extends, has the at least one recess.

[0035] The length, width, and / or diameter of the at least one recess and / or opening can, in principle, be chosen arbitrarily depending on the dimensions of the MEA. For example, the length, width, and / or diameter can be between 0.5 mm and 5 cm, preferably between 1 mm and 1 cm, and particularly preferably between 2 mm and 5 mm.

[0036] In a preferred embodiment, the gas diffusion layer has two or more recesses and / or two or more openings.

[0037] Depending on the size of the recesses and / or openings as well as the size of the gas diffusion layer, the gas diffusion layer can have between 2 and 100, preferably between 4 and 60, particularly preferably between 8 and 40, recesses and / or openings.

[0038] Preferably, adjacent recesses have a regular distance between them.

[0039] In one embodiment, the distance between two adjacent recesses can be zero. If the distance is zero, the gas diffusion layer can have a wave and / or zigzag contour, at least in sections.

[0040] If the gas diffusion layer includes two or more recesses, the recesses may have the same shape and / or size or different shapes and / or sizes.

[0041] Additionally or alternatively, adjacent openings can have a regular distance between them.

[0042] If the gas diffusion layer includes two or more openings, the openings can have the same shape and / or size or different shapes and / or sizes.

[0043] Gas diffusion layers with two or more openings and / or with two or more recesses of the same shape and / or size can offer the advantage of particularly simple manufacturing, as, for example, only one tool is required for the openings and / or recesses. Different openings and / or recesses, on the other hand, allow for specific adaptation to the structural characteristics of the gas diffusion layer and / or the electrochemical system in which the gas diffusion layer is used.

[0044] The gas diffusion layer can be a cathode or an anode gas diffusion layer.

[0045] The problem according to the invention is further solved by a membrane electrode arrangement according to the relevant independent claim.

[0046] The membrane electrode arrangement can, in particular, be a membrane electrode arrangement for an electrochemical system. The electrochemical system is preferably a fuel cell system, more specifically a fuel cell system comprising at least one PEM fuel cell. The fuel cell system can also comprise at least one fuel cell stack.

[0047] The membrane electrode assembly includes at least the following MEA elements: - a catalyst-coated membrane; - at least one sealing layer; - a first gas diffusion layer; and - a second gas diffusion layer, wherein the catalyst-coated membrane and the at least one sealing layer are arranged at least partially, preferably completely, between the first and the second gas diffusion layer.

[0048] The membrane electrode arrangement can in particular be a 6L-MEA or, if the membrane electrodes comprise two sealing layers, a 7L-MEA.

[0049] In particular, at least two adjacent MEA elements are connected to each other in at least one connection area via a radiation-cured adhesive.

[0050] The catalyst-coated membrane can comprise a proton exchange membrane, preferably a solid polymer electrolyte membrane, which is particularly suitable for protons (H₂). + The membrane is permeable. Preferred base materials for the membrane are so-called ionomers, which belong to the thermoplastic polymers. Copolymers of perfluorosulfonic acid are preferably used to create the ionic conductivity of the membrane, and polytetrafluoroethylene is used as a reinforcing material. Such ionomers are available, for example, under trade names such as Nafion. TM , Flemion TM or Aquivion TM available.

[0051] In a preferred embodiment, the membrane of the catalyst-coated membrane has a thickness of 5 to 50 µm, preferably 10 to 30 µm.

[0052] The catalyst layers of the catalyst-coated membrane preferably have a thickness of 1 to 50 µm, more preferably of 5 to 30 µm. Platinum or platinum compounds on an electrically conductive porous support material such as carbon black are particularly suitable as catalysts. The ionomers described above can also be components of the catalyst layers.

[0053] Methods for producing CCMs are known in the prior art. The application of the catalyst layers can be carried out directly onto the membrane, particularly in the form of a catalytic ink.

[0054] The at least one sealing layer can consist of at least one material, in particular at least one plastic or plastic mixture, which is permeable to radiation, especially UV radiation. This allows radiation curing through the at least one sealing layer.

[0055] Preferably, the at least one sealing layer comprises at least one plastic selected from the group consisting of polyolefins, in particular polyethylene (PE), polypropylene (PP) or cycloolefin copolymers (COC), polyphenyls, in particular polyphenyl sulfide (PPS) or polyphenyl sulfone (PPSU), polyesters, in particular polyethylene terephthalate (PET), polybutylene terephthalate (PBT) or polyethylene naphthalate (PEN), polyimide (PI), polyamide (PA), polyamide-imide (PAI), derivatives of the aforementioned plastics or mixtures thereof.

[0056] The at least one sealing layer can have a thickness of 10 to 200 µm, preferably 20 to 60 µm.

[0057] The adhesive can be radiation-cured, thermo-cured, and / or physically dried. Preferably, the adhesive is radiation-cured, radiation- and thermo-cured, or radiation-cured and physically dried.

[0058] The radiation-cured adhesive is available in particular as a radiation-curable, especially UV-curable, adhesive composition. Irradiation can initiate radical and / or cationic polymerization.

[0059] The adhesive may in particular be at least a polymer and / or at least a copolymer based on a material selected from the group consisting of polyvinyl alcohol, polyvinyl acetate, polyacetal, polyalkylene oxides, polyureas, polyurethanes, poly(meth)acrylates, polyvinylpyrrolidone, or resins based on epoxy, polyisobutylene and / or silicone.

[0060] In a further embodiment, the radiation-cured adhesive can be water-soluble and / or water-soluble. This can have the advantage that only a temporary bond is formed between at least two MEA elements, since the adhesive can be removed from the membrane electrode arrangement during subsequent operation of the electrochemical system.

[0061] The adhesive composition may, in particular, comprise at least one photoinitiator. This photoinitiator may, in particular, be tailored to the curable (crosslinkable) adhesive composition. For vinyl-based crosslinkable monomers, for example, azobisisobutyronitrile may be used. For acrylate-based crosslinkable monomers, an acrylate-based photoinitiator, which in particular comprises at least one acetophenone or benzophenone group, may be used. A preferred example of such a photoinitiator is 4-acryloyloxybenzophenone (ABP).

[0062] The at least one photoinitiator can have a weight fraction of 0.1 to 10.0 wt%, preferably 0.5 to 2.0 wt%, relative to the curable adhesive composition. The remainder can, in particular, consist of at least one crosslinkable monomer and optionally common adhesive components such as stabilizers.

[0063] The adhesive composition may further be heat-cured and / or physically dried. Preferably, the adhesive is a radiation-cured, a radiation- and heat-cured, or a radiation-cured and physically dried adhesive.

[0064] In this way, regular and / or complete curing can be achieved, since, for example, the cross-linking reaction of the curable adhesive composition can be generated not only by irradiation but also by heat.

[0065] Physical drying can in particular include the evaporation and / or vaporization of a component of the adhesive composition, especially a solvent.

[0066] Preferably, the adhesive composition is heated to a temperature between 0 and 200 °C, preferably 20 and 150 °C, particularly preferably between 50 and 100 °C, for heat curing and / or physical drying.

[0067] According to the invention, the first gas diffusion layer and the second gas diffusion layer do not overlap or only partially overlap in the at least one connection area. Partially overlapping means, in particular, not completely overlapping. Preferably, an area in which the first gas diffusion layer and the second gas diffusion layer do not overlap and / or do not overlap each other has a size that allows sufficient irradiation of the adhesive composition to be cured.

[0068] This can have the advantage that a surface section to which the adhesive composition is applied can be irradiated at least partially or completely, directly or preferably indirectly, so that at least one bonding area is formed. "Indirect" can mean that the irradiation occurs through at least one MEA element, in particular through the at least one sealing layer. This can especially enable the exclusive use of radiation-curable or radiation- and heat-curable and / or physically dryable adhesive compositions in the membrane electrode assembly.

[0069] The first gas diffusion layer can be a cathode gas diffusion layer and the second gas diffusion layer an anode gas diffusion layer. Alternatively, the first gas diffusion layer can be an anode gas diffusion layer and the second gas diffusion layer a cathode gas diffusion layer.

[0070] In particular, the first gas diffusion layer and the second gas diffusion layer can be arranged relative to each other in such a way that the first gas diffusion layer and the second gas diffusion layer only partially or not at all overlap in at least one connection area.

[0071] In one embodiment, the first and second gas diffusion layers can have the same shape and size and be arranged offset and / or rotated relative to each other, such that the first and second gas diffusion layers only partially overlap or do not overlap at all in at least one connection area. The shape of the gas diffusion layers includes both external and internal contours, for example, those resulting from an opening.

[0072] Alternatively, the first and second gas diffusion layers can differ in shape and / or size. The size difference can result from at least one difference in dimension between the first and second gas diffusion layers. This difference can be either length and / or width. Therefore, there can be a difference in length and / or width.

[0073] In a preferred embodiment, the first and second gas diffusion layers have the same width but different lengths. It can be advantageous to arrange the shorter gas diffusion layer centered relative to the longer gas diffusion layer, so that two spaced-apart peripheral areas are formed in which the first and second gas diffusion layers do not overlap, or to arrange them flush at a first end, so that a peripheral area is formed at a second end opposite the first end in which the first and second gas diffusion layers do not overlap.

[0074] The first gas diffusion layer and / or the second gas diffusion layer can, in particular, be a gas diffusion layer as described herein, which has at least one recess on an outer contour and / or at least one opening. This can have the advantage that sealing layers bonded on only one side can also be used.

[0075] If only the first gas diffusion layer is a gas diffusion layer as described herein, then, in particular, sequential bonding (formation of a connection area) of the MEA elements can be carried out. In this embodiment, the second gas diffusion layer may, in particular, not have a recess on the outer contour or an opening. Preferably, in the sequential bonding process, the second gas diffusion layer is the last MEA element to be bonded.

[0076] In a preferred embodiment, the first and second gas diffusion layers have at least one recess on an outer contour and / or at least one opening. It can be advantageous if the at least one recess and / or at least one opening of the first gas diffusion layer is at least partially, preferably completely, opposite a surface of the second gas diffusion layer, and / or if the at least one recess and / or at least one opening of the second gas diffusion layer is at least partially, preferably completely, opposite a surface of the first gas diffusion layer. This has the particular advantage that the irradiation for curing the at least one adhesive can be carried out from both sides, and in particular simultaneously from two sides of the membrane electrode arrangement.

[0077] The first and second gas diffusion layers can differ, in particular, by at least one position of the at least one recess and / or the at least one opening, such that the first and second gas diffusion layers do not overlap, or only partially overlap, at the at least one differing position. In this way, the gas diffusion layers can be essentially congruent and thus arranged in a particularly space-saving manner. Essentially congruent can mean that the first and second gas diffusion layers completely overlap, except for the at least one differing position of the at least one recess and / or the at least one opening.

[0078] If the first and / or the second gas diffusion layer has two or more recesses and / or two or more openings, it is advantageous if the two or more recesses and / or two or more openings of the first and second gas diffusion layers are in different positions. It can be particularly advantageous if the two or more recesses and / or two or more openings of the first and second gas diffusion layers are arranged alternately in at least one peripheral region in a top view of a principal extension plane of the membrane electrode assembly. Alternating can mean that an opening and / or recess of the second gas diffusion layer is in a position that, in a top view of the principal extension plane of the membrane electrode assembly, lies between two spaced-apart openings and / or recesses of the first gas diffusion layer.

[0079] The membrane electrode arrangement can in particular comprise two or more connection areas, preferably 2 to 12 connection areas, particularly preferably 3 to 6 connection areas.

[0080] The two or more bonding areas can be formed by the same radiation-cured, heat-cured and / or physically dried adhesive or by two or more different radiation-cured, heat-cured and / or physically dried adhesives.

[0081] It can be advantageous if, in at least one connection area, the first gas diffusion layer is connected to the at least one sealing layer or the catalyst-coated membrane, and in a second connection area, the second gas diffusion layer is connected to the at least one sealing layer, a second sealing layer, or the catalyst-coated membrane. Preferably, the second gas diffusion layer is connected to the second sealing layer, resulting in a 7L-MEA.

[0082] The at least one sealing layer can itself have recesses and / or openings in its peripheral area. The recesses and / or openings of the at least one sealing layer can be at least partially, preferably completely, overlapping with the recesses and / or openings of the first or second gas diffusion layer. In particular, the first sealing layer can have one or more openings and / or recesses in the same area as the second gas diffusion layer, so that a connection area is formed between the first gas diffusion layer adjacent to the first sealing layer and the second gas diffusion layer, and / or vice versa.

[0083] The invention further relates to a method for manufacturing a membrane electrode arrangement.

[0084] The membrane electrode arrangement can, in particular, be a membrane electrode arrangement for an electrochemical system. The electrochemical system is preferably a fuel cell system, in particular a fuel cell system comprising at least one PEM fuel cell. The fuel cell system can also comprise at least one fuel cell stack comprising at least two PEM fuel cells.

[0085] The membrane arrangement can in particular be a membrane electrode arrangement as described herein. Preferably, the membrane electrode arrangement comprises a catalyst-coated membrane, at least one sealing layer, a first gas diffusion layer and a second gas diffusion layer as MEA elements.

[0086] The procedure includes, in particular, the following steps: i. Application of at least one adhesive composition to at least one surface section of at least one of the MEA elements; ii. Arrangement of the catalyst-coated membrane and the at least one sealing layer between the first gas diffusion layer and the second gas diffusion layer, wherein the first gas diffusion layer and the second gas diffusion layer do not overlap or only partially overlap in a region of at least one surface section; and iii. radiation hardening, heat hardening and / or physical drying of the at least one adhesive composition, such that at least one bonding area is formed in the at least one surface section in which the at least one MEA element is bonded to an adjacent MEA element, wherein the radiation hardening preferably takes place by irradiating the adhesive composition at least in at least one area of ​​the at least one surface section.

[0087] The application of the adhesive composition, particularly to the first and / or second gas diffusion layer, can be carried out by a doctor blade, spray, pouring, printing or extrusion process or a combination of the aforementioned processes.

[0088] The at least one surface section can be, in particular, a peripheral region of the MEA element, especially a peripheral region of the first and / or second gas diffusion layer, and / or extend at least partially into the peripheral region. The surface section can therefore be smaller or larger than the peripheral region and / or have a different shape.

[0089] The MEA element, in particular the at least one sealing layer and / or the catalyst-coated membrane, can also be provided with the adhesive composition on a first surface and on a second surface facing away from the first, i.e., on both sides. The adhesive composition on the first surface can be the same or different from the adhesive composition on the second surface.

[0090] The arrangement is carried out in such a way that at least the surface section of the at least one MEA element containing the adhesive composition touches and / or is pressed against an opposing surface of the adjacent MEA element.

[0091] In particular, the MEA elements are arranged so that they have a relative positioning and / or a relative orientation to each other, which corresponds to a relative positioning and / or relative orientation in the finished membrane electrode arrangement.

[0092] Radiation curing can be achieved, in particular, by irradiating the adhesive composition with UV light. The irradiation preferably lasts between 0.2 and 120 seconds, more preferably between 0.5 and 60 seconds. During this process, the adhesive composition polymerizes and cures.

[0093] Heat curing and / or physical drying can be carried out as described herein. The duration of heat curing may depend on the adhesive composition used and / or may last between 0.2 and 120 s, preferably between 0.5 and 60 s. The duration of physical drying may depend on the adhesive composition used and / or a selected drying temperature.

[0094] By curing the adhesive composition to form a radiation-cured adhesive, the bonding area can be created, which represents an adhesive bond, in particular a bonded bond, between adjacent MEA elements.

[0095] Step iii. can take place, in particular, during and / or after step ii. The method can comprise at least one further irradiation step. The irradiation steps can be carried out at least partially, preferably completely, simultaneously or sequentially. The irradiation of the membrane electrode elements can be carried out from different, in particular opposite, directions. Preferably, irradiation takes place from a direction perpendicular to the principal plane of extension of the gas diffusion layer.

[0096] The irradiation, in particular the UV irradiation, of the at least one adhesive composition in step iii. and / or of a further adhesive composition in the at least one further irradiation step can in particular be carried out indirectly through at least one MEA element, in particular through the at least one sealing layer.

[0097] The method according to the invention has the particular advantage that rapid and complete curing of the adhesive composition is possible, since the first gas diffusion layer and the second gas diffusion layer do not only or partially overlap, at least in a region of the at least one surface section on which the adhesive composition is applied. This region can extend over the entire surface section or a part thereof.

[0098] In particular, the first gas diffusion layer and the second gas diffusion layer may not overlap or may only partially overlap in two or more areas of at least one surface section.

[0099] Preferably, at least one area is designed as an opening and / or a recess from the first and / or second gas diffusion layer.

[0100] Consequently, at least one surface section and thus at least one adhesive composition is at least partially accessible to irradiation, which would not be the case, in particular, with complete coverage of the first and second gas diffusion layers.

[0101] In a preferred embodiment, the first gas diffusion layer and / or the second gas diffusion layer is a gas diffusion layer as described herein, which has at least one recess on an outer contour and / or at least one opening.

[0102] Preferably, the at least one recess on an outer contour of the gas diffusion layer and / or the at least one opening in the gas diffusion layer is produced by punching and / or cutting. The production of the at least one recess and / or the at least one opening can, in particular, take place during and / or simultaneously with the fabrication of the gas diffusion layer itself. In this way, a gas diffusion layer with a size suitable for the membrane arrangement and having the at least one recess and / or the at least one opening can be obtained in a single process and / or process step.

[0103] Preferably, before step i. or step ii., the catalyst-coated membrane and the at least one sealing layer can be joined together via an adhesive, preferably an adhesive described herein.

[0104] It can be advantageous if the method produces a 7L-MEA comprising a first and a second sealing layer. In a preferred embodiment, the 7L-MEA has the MEA elements in the sequence first GDL, first sealing layer, CCM, second sealing layer, and second GDL.

[0105] In a preferred embodiment, in step i. the at least one adhesive composition is applied to at least one of the following combinations of surface sections: - on at least one surface section of the first gas diffusion layer and at least one surface section of the second gas diffusion layer, wherein at least one surface section of the second gas diffusion layer faces the first gas diffusion layer; - on at least one surface section of the first gas diffusion layer and at least one surface section of the at least one sealing layer, wherein at least one sealing layer is preferably the second sealing layer, wherein at least one surface section of the at least one sealing layer is facing away from the first gas diffusion layer; - on at least one surface section of the first gas diffusion layer and at least one surface section of the CCM, wherein at least one surface section of the CCM is turned away from the first gas diffusion layer; - on at least one surface section of the second gas diffusion layer and at least one surface section of the at least one sealing layer, wherein the at least one sealing layer is preferably the first sealing layer, wherein the at least one surface section of the at least one sealing layer is facing away from the second gas diffusion layer; - on at least one surface section of the second gas diffusion layer and at least one surface section of the CCM, wherein at least one surface section of the CCM is turned away from the second gas diffusion layer; - on at least one surface section of the CCM and at least one surface section of the at least one sealing layer, wherein at least one surface section of the at least one sealing layer faces away from the CCM; and / or - on at least one surface section of the first sealing layer (and at least one surface section of the second sealing layer), wherein at least one surface section of the second sealing layer is turned away from and / or towards the first gas diffusion layer.

[0106] In this way, two or more connection areas can be formed. The irradiation of the surface sections can be carried out at least partially, preferably completely, simultaneously or sequentially. Sequential, as used in the present invention, means that the formation of the at least one second connection area preferably takes place before the formation of the at least one first connection area, particularly during step ii.

[0107] In simultaneous irradiation, the irradiation occurs from at least two directions. In particular, the irradiation occurs through at least one sealing layer in each case.

[0108] In sequential irradiation, the irradiation preferably occurs from one direction. In particular, the irradiation is carried out through at least one sealing layer in each instance.

[0109] In a preferred embodiment, at least one first connection area is formed between the first gas diffusion layer and a first sealing layer, and at least one second connection area is formed between the second gas diffusion layer and a second sealing layer, wherein the formation of the at least one first connection area and the second connection area takes place in step iii., or the formation of the at least one first connection area in step iii. and the formation of the at least one second connection area takes place before the formation of the at least one first connection area, in particular during step ii., or the formation of the at least one second connection area in step iii. and the formation of the at least one first connection area takes place before the formation of the at least one second connection area, in particular during step ii.

[0110] In simultaneous irradiation, irradiation occurs from at least two directions. Preferably, the second joint area is irradiated from the direction of the first gas diffusion layer, with the irradiation preferably passing through both the first and second sealing layers. The same can apply conversely to the first joint area. Particularly preferred for processes with simultaneous irradiation are gas diffusion layers that include the at least one recess and / or the at least one opening described herein.

[0111] In sequential irradiation, it can be advantageous if only one of the two gas diffusion layers comprises the at least one recess and / or the at least one opening described herein. Preferably, the connecting area to the gas diffusion layer, comprising the at least one recess and / or the at least one opening described herein, is formed upstream of the connecting area to the gas diffusion layer that does not have the at least one recess and / or the at least one opening described herein.

[0112] The first gas diffusion layer can be a cathode gas diffusion layer and the second gas diffusion layer an anode gas diffusion layer. Alternatively, the first gas diffusion layer can be the anode gas diffusion layer and the second gas diffusion layer the cathode gas diffusion layer.

[0113] In a preferred embodiment, the at least one adhesive composition is radiation- and heat-cured or radiation-cured and physically dried. This can have the advantage that the at least one adhesive composition cures quickly and regularly even in areas of the at least one surface section that are not accessible to radiation.

[0114] Further preferred features and / or advantages of the invention are the subject of the following description and the graphic representation of exemplary embodiments.

[0115] The drawings show: Fig. 1: a schematic partial view of a cross-section of a membrane electrode arrangement; Fig. 2: a schematic top view of a membrane electrode arrangement comprising a first and a second gas diffusion layer according to a first embodiment of the invention; Fig. 3: a schematic top view of a membrane electrode arrangement comprising a first and a second gas diffusion layer according to a second embodiment of the invention; Fig. 4: a schematic top view of a membrane electrode arrangement comprising a first and a second gas diffusion layer according to a third embodiment of the invention; Fig. 5: a schematic top view of a membrane electrode arrangement comprising a first and a second gas diffusion layer according to a fourth embodiment of the invention; Fig. 6: a section of the membrane electrode arrangement Fig. 2 along line AA; Fig. 7: a section of the membrane electrode arrangement Fig. 4 along line CC; Fig. 8: a section of the membrane electrode arrangement Fig. 2 along line BB; Fig. 9: a section of the membrane electrode arrangement Fig. 4 along line DD; Fig. 10: a section through a membrane electrode arrangement comprising a first and a second gas diffusion layer according to a fifth embodiment of the invention; Fig. 11: a section through a membrane electrode arrangement comprising a first and a second gas diffusion layer according to a sixth embodiment of the invention; and Fig. 12: another sectional view of the membrane electrode arrangement from Fig. 11.

[0116] Identical or functionally equivalent elements are provided with the same reference symbols in all figures.

[0117] Fig. Figure 1 shows a schematic partial view of a cross-section of a membrane electrode arrangement 2. The membrane electrode arrangement 2 is suitable for an electrochemical system, in particular for a fuel cell system 1. Fig. Figure 1 shows in particular a membrane arrangement 2 according to the state of the art.

[0118] The membrane electrode assembly 2 comprises several MEA elements 10. In particular, the membrane electrode assembly 2 comprises a first GDL 20a, a first sealing layer 12a, a CCM 11, a second sealing layer 12b and a second GDL 20b.

[0119] In the operation of the fuel cell system 1, the polymer electrolyte membrane of the CCM 11 in particular prevents a mixing of the reactant currents, but is suitable for certain ions such as protons (H₂). + ) or oxide ions (O 2- ) permeable. The CCM 11 can therefore separate an anode compartment from a cathode compartment.

[0120] In the present case, the first GDL 20a and the first sealing layer 12a can be anode-side MEA elements 10 and the second GDL 20b and the second sealing layer 12b can be cathode-side MEA elements 10.

[0121] When hydrogen (H2) is used as fuel, the oxidation of hydrogen takes place at the catalyst layer on the anode side (not shown) according to the following reaction equation: 2 H2⇌4 H++4 e−

[0122] At the catalyst layer on the cathode side (not shown), the catalytic reaction of elemental oxygen (O2) to water (H2O) takes place according to the following reaction equation: O2+4 H++4 e−⇌2 H2O

[0123] The overall reaction is therefore 2 H2+O2⇌2 H2O, the protons migrate from the anode side through the CCM 11 to the cathode side, while the electrons travel as an electric current from the anode side via an external circuit (not shown) to the cathode side.

[0124] All of the aforementioned MEA elements 10 can each be designed in any way described herein.

[0125] As shown, the CCM 11 can be arranged between the first sealing layer 12a and the second sealing layer 12b. The first and second sealing layers 12a and 12b can, in particular, have a frame-like structure that surrounds the CCM 11 in a peripheral area. A central area of ​​the CCM 11 is thus available for the fuel cell reactions.

[0126] Preferably, the CCM 11, the first and second sealing layers 12a and 12b are connected to each other via a connection area 14. The connection area 14 is preferably formed in one piece.

[0127] In an alternative embodiment, CCM 11, the first and second sealing layers 12a and 12b can also be connected to each other via several connection areas 14, in particular two or three connection areas 14.

[0128] The connection area 14 is formed by a first, preferably radiation-cured or radiation- and heat-cured, adhesive, which creates an adhesive bond, in particular a bonded connection, between the respective MEA elements.

[0129] To form the connection area 14, the adhesive composition can be applied to a first surface of the first sealing layer 12a and / or a first surface of the second sealing layer 12b and / or to at least one surface, preferably two opposing surfaces, of the CCM 11.

[0130] The first sealing layer 12a is connected to the first GDL 20a via a connection area 13a. The connection area 13a is formed between a second surface 28c facing away from the first surface of the first sealing layer 12a and a surface 28a of the first GDL 20a facing surface 28c. The connection area 13a covers, in particular, a surface section 30a of the surface 28a of the first GDL 20a.

[0131] Accordingly, the second sealing layer 12b can be connected to the second GDL 20b via a connection area 13b. The connection area 13b is formed between a second surface 28d facing away from the first surface of the second sealing layer 12b and a surface 28b of the second GDL 20b facing surface 28d. The connection area 13b covers, in particular, a surface section 30b of surface 28b of the second GDL 20b.

[0132] The connection areas 13a, 13b, and 14 can be located in a peripheral area 23 of the first GDL 20a and / or the second GDL 20b. The peripheral area 23 can at least partially surround and / or delimit a central area of ​​the first GDL 20a and / or the second GDL 20b. In the central area 24, in particular, the supply of reactant flows and / or the removal of reaction products can take place, since it is not blocked by at least one connection area 13a, 13b, and / or 14.

[0133] The connection areas 13a, 13b, and 14 can be formed by the same or different adhesives. The adhesive or adhesives can be obtained from an adhesive composition described herein. In a preferred embodiment, the connection areas 13a and 13b are formed by a first, in particular water-soluble, adhesive, and the connection area 14 by a second, in particular water-insoluble, adhesive.

[0134] The membrane electrode arrangement 2 can in particular include further connection areas 13, 14, especially on one side of the membrane electrode arrangement 2 opposite the partial view shown (not shown).

[0135] The first GDL 20a is in particular structured as a two-layer system. Preferably, the first GDL 20a comprises a substrate 21a as a base, on which a microporous layer 22a is arranged. The microporous layer 22a is in particular oriented towards the CCM 11.

[0136] The second GDL 20b is in particular structured as a two-layer system. Preferably, the second GDL 20b comprises a substrate 21b as a base, on which a microporous layer 22b is arranged. The microporous layer 22b is in particular oriented towards the CCM 11.

[0137] The connection area 13a and / or 13b is preferably arranged offset outwards relative to the CCM 11. In particular, the connection area 13a and / or 13b can be arranged near an outer contour 27a of the first GDL 20a and / or an outer contour 27b of the second GDL 20b. In particular, the connection area 13a and / or 13b can be flush with the contour 27a and / or 27b. This can, in principle, allow the use of at least one radiation-curable, in particular UV-curable, adhesive composition, since irradiation through the CCM 11 is not usually possible.

[0138] A disadvantage of the depicted membrane electrode arrangement 2 is that the first GDL 20a and the second GDL 20b completely overlap, particularly in the area of ​​the connection regions 13a, 13b and 14. In contrast to the first sealing layer 12a and the second sealing layer 12b, irradiation of the at least one radiation-curable adhesive composition by the first GDL 20a and / or second GDL 20b is not possible due to the GDL materials.

[0139] Irradiation from one end face of the membrane electrode arrangement 2 is not practical due to the thickness of the connection areas 13a, 13b and / or 14. Therefore, at least one pressure- and / or temperature-sensitive adhesive composition is usually used to form at least one connection area 13a and / or 13b.

[0140] In Fig. Figure 2 shows a schematic top view of a membrane electrode arrangement 2. The membrane electrode arrangement 2 comprises a first GDL 20a and a second gas diffusion layer 20b according to a first embodiment of the invention.

[0141] The basic structure of the membrane electrode arrangement 2 and the relative arrangement of the MEA elements 10 correspond to that in Fig. The structure shown in Figure 1 is identical. This also applies to all other embodiments.

[0142] It is clearly evident that the first GDL 20a has a multitude of openings 26a in two opposing peripheral areas 23.

[0143] The openings 26a are circular in this case, but can be configured in any other way described herein. The diameter of the openings 26a can be selected depending on the dimensions of the membrane electrode arrangement 2 and / or the first GDL 20a.

[0144] The openings 26a extend through the entire thickness of the first GDL 20a, in particular through the substrate 21a and the microporous layer 22a (not shown).

[0145] The opposing peripheral areas 23 define a central area 24, which is available in the operation of the fuel cell system 1 in particular for supplying the reactant flows and / or removing reaction products.

[0146] In the illustrated embodiment, the second GDL 20b (not shown) also has a plurality of openings 26b, the positions of which are indicated by dashed lines. The openings 26b are preferably designed identically to the openings 26a, but are arranged offset from them, resulting in the illustrated alternating arrangement of openings 26a and 26b.

[0147] Preferably, the first GDL 20a and the second GDL 20b have the same shape, which is defined in this case by the outer contours 27a and 27b (not visible), and size.

[0148] In particular, the first GDL 20a and the second GDL 20b completely overlap, except in areas defined by openings 26a and 26b.

[0149] The surface 28c of the first sealing layer 12a is visible through the openings 26a. In a corresponding view from below, the surface 28d of the second sealing layer 12b would be visible through the openings 26b.

[0150] The connecting areas 13a and 13b extend at least partially, preferably completely, into the peripheral areas 23 indicated schematically by dashed lines. Due to the openings 26a and 26b, the first GDL 20a and the second GDL 20b only partially overlap in the connecting areas 13a and 13b.

[0151] The use of the depicted first and second GDL 20a and 20b allows irradiation of the radiation-curable adhesive compositions through the openings 26a and / or 26b. The formation of the second connection area 13b is achieved through the openings 26a, the first sealing layer 12a, the connection area 14 and the second sealing layer 12b, wherein the first and the second sealing layers 12a and 12b are at least partially radiation-permeable, in particular UV-permeable.

[0152] The training of the first liaison area 13a takes place from in Fig. 2. The underside is not visible through the openings 26b, the second sealing layer 12b, the connection area 14 and the first sealing layer 12a.

[0153] Furthermore, irradiation of the adhesive composition forming the connection area 114 can also be carried out.

[0154] This allows both a sequential manufacturing process described herein and simultaneous irradiation of the membrane electrode arrangement 2 from two opposite directions.

[0155] Fig. Figure 3 shows a schematic top view of a membrane electrode arrangement 2, which comprises a first and a second gas diffusion layer 20a and 20b. The illustrated embodiment is a modification of the one described in Fig. 2 shown embodiment.

[0156] The peripheral region 23 of the first GDL 20a has a frame-like structure that completely surrounds the central region 24. The peripheral region 23 of the first GDL 20a has a multitude of openings 26a.

[0157] Accordingly, the second GDL 20b (not shown), opposite the first GDL 20a, also has a frame-like peripheral area 23. Alternatively, the second GDL 20b can also be the one in Fig. 2 shown peripheral areas 23.

[0158] As shown, the openings 26b in the second GDL 20b and the openings 26a are arranged at least sectionally alternating, so that the adhesive composition located between the respective MEA elements 10 can be irradiated as regularly as possible.

[0159] In Fig. Figure 4 shows a further schematic top view of an embodiment of a membrane electrode arrangement 2 according to the invention, comprising a first and a second gas diffusion layer 20a and 20b (not visible).

[0160] Unlike in Fig. In the embodiment shown in Figure 2, the first GDL 20a has recesses 25a in the outer contour 27a in the peripheral areas 23.

[0161] The recesses 25a shown have a round shape, at least in sections, and are regularly spaced apart from each other, with the recesses 25a forming a wave contour in this case. Alternatively, a zigzag contour comprising regularly spaced, one-sided open recesses 26a in a triangular shape can also be formed.

[0162] The contour 27b of the second GDL 20b on the underside of the membrane electrode arrangement 2 is indicated by a dashed line. The second GDL 20b also exhibits the wave contour in the peripheral areas 23 previously described for the first GDL 20a.

[0163] It is evident that the recesses 26a and 26b are offset from each other, so that a crest of the first GDL 20a always falls on a trough of the second GDL 20b and vice versa. In this way, there is no complete overlap of the two GDL 20a and 20b in at least one surface section 30 where the adhesive composition is applied, thus allowing for irradiation.

[0164] The recesses 25a and 25b thus fulfill the same function as the openings 26a and 26b in the Fig. 2 and Fig. 3. Irradiation of the radiation-curable or radiation- and heat-curable adhesive compositions can thus take place in the area of ​​the recesses 25a and / or 25b. The second connection area 13b is formed by the first sealing layer 12a, the connection area 14 and the second sealing layer 12b.

[0165] The training of the first liaison area 13a is carried out by in the Fig. 4 the underside of the membrane electrode arrangement 2, which is not visible, is sealed by the second sealing layer 12b, the connection area 14 and the first sealing layer 12a.

[0166] In Fig. 5 is one for Fig. 3 analogous modifications of the embodiment from Fig. 4 shown.

[0167] In this embodiment, the central region 24 is completely surrounded by a frame-like peripheral region 23. The first GDL 20a has a wave contour along its entire outer contour 27a. The second GDL 20b also has a wave contour along its entire outer contour 27a.

[0168] It is evident that the recesses 26a and 26b are offset from each other, so that a crest of the first GDL 20a always falls on a trough of the second GDL 20b and vice versa. In this way, there is no complete overlap of the two GDL 20a and 20b in at least one surface section 30 where the adhesive composition is applied, thus allowing irradiation of the adhesive composition.

[0169] The embodiment shown allows in particular maximum sealing of the membrane electrode arrangement 2, since full formation of the connection areas 13a, 13b and / or 14 is possible.

[0170] It can be advantageous to consider the following: Fig. 2, Fig. 3, Fig. 4 to Fig. The 5 illustrated designs can be combined. In particular, a combination of the openings 26a and 26b with the recesses 25a and 25b can enable particularly fast and regular curing of the adhesive composition.

[0171] Fig. Figure 6 shows a schematic section of the membrane electrode arrangement 2. Fig. 2 along line AA. The essential difference to in Fig. In the membrane electrode arrangement 2 shown in Figure 1, the opening 26a extends through the substrate 21a and the microporous layer 22a of the first GDL 20a.

[0172] As previously explained and indicated by the wavy arrow, the opening 26a allows irradiation of the curable adhesive composition applied to surface section 30b of surface 28b of the second GDL 20b. Irradiation is possible, in particular, in the area 31 defined by the opening 26a.

[0173] A cross-sectional view through an opening 26b results in a correspondingly mirrored view.

[0174] The sectional view shown also exists in an alternative embodiment in which only the first GDL 20a has openings 26a. The membrane electrode arrangement 2 can be manufactured sequentially, in particular, using radiation-curable or radiation- and heat-curable adhesive compositions.

[0175] Preferably, the connection area 14 is formed first, so that the CCM 11 and the sealing layers 12a and 12b are connected to each other. In a next step, the adhesive composition can be applied to the surface 28a of the first GDL 20a and / or the surface 28c of the first sealing layer 12a. Curing of the adhesive composition to form the connection area 13a can be achieved by irradiation through the second sealing layer 12b, the connection area 14, and the first sealing layer 12a, since the second GDL 20b is not yet, as in Fig. Figure 6 shows the second sealing layer 12b being arranged on its surface 28d. In a further step, the adhesive composition can be applied to the surface 28b of the second sealing layer 20b and / or the surface 28d of the second sealing layer 12b, and after the second sealing layer 20b is arranged on the second sealing layer 12b, it can be irradiated and cured with preferably UV light via the at least one opening 26a in the first sealing layer, so that the connection area 13b is formed.

[0176] Fig. Figure 7 shows a schematic section of the membrane electrode arrangement 2. Fig. 4 along line CC. The main difference to the one in Fig. In the membrane electrode arrangement 2 shown in Figure 1, the recess 25a is in the outer contour 27a.

[0177] As previously explained and indicated by the wavy arrow, the recess 25a allows irradiation of the curable adhesive composition applied to surface section 30b of surface 28b of the second GDL 20b. Irradiation is particularly possible in the area 31 defined by the recess 25a.

[0178] A cross-sectional view through a recess 25b of the second GDL 20b results in a correspondingly mirrored view.

[0179] The sectional view shown also exists in an alternative embodiment in which only the first GDL 20a has recesses 26a. The fabrication of the membrane electrode arrangement 2 using radiation-curable and / or radiation- and heat-curable adhesive compositions can be based on the methods described in connection with Fig. The 6 described sequential steps will be carried out.

[0180] The sectional view shown also exists in a second alternative embodiment in which the first GDL 20a and the second GDL 20b differ in at least one dimension, in particular their length, and / or are arranged offset from each other.

[0181] In the illustration shown, the first GDL 20a has a shorter length than the second GDL 20b and / or is offset relative to the second GDL 20b in the direction of the CCM 11. As a result, the first and second GDL 20a and 20b do not overlap in region 31. This also enables the sequential fabrication of a membrane electrode arrangement 2 described herein using radiation-curable and / or radiation- and heat-curable adhesive compositions.

[0182] Fig. Figure 8 shows a schematic section of the membrane electrode arrangement 2. Fig. 2 along line BB. It is clearly evident that the openings 26a have a regular distance between them.

[0183] The openings 26b preferably also have the same regular spacing between them as the openings 26a. This particularly enables the alternating arrangement of openings 26a and 26b shown.

[0184] Due to the large number of openings 26a and 26b, there is a corresponding large number of areas 31a and 31b through which the surface sections 30a and 30b, which have the curable adhesive composition, can be irradiated.

[0185] A membrane electrode arrangement 2, in which the first and second GDL 20a and 20b each have at least one opening 26a and 26b, enables, in particular, irradiation from two sides, as indicated by the wavy arrows, even when all MEA elements 10 are already arranged. The two-sided irradiation can, in particular, be carried out simultaneously, so that the connection areas 13a and 13b are formed at the same time.

[0186] Furthermore, the connection area 14 can also be formed during irradiation.

[0187] Fig. Figure 9 shows a schematic section of the membrane electrode arrangement 2. Fig. 4 along line DD. It is clearly visible that the recesses 26a and 26b are offset from each other. This illustrates the in Fig. 4 shown alternating arrangement of recesses 26a and 26b.

[0188] The wave contour of the first and second GDL 20a and 20b has the effect that, at least in sections, the area 31a and / or 31b, in which the first GDL 20a and the second GDL 20b do not overlap and consequently the irradiation of the curable adhesive composition indicated by the wavy arrows to form the connection areas 13a, 13b and / or 14 is possible, has the same dimensions as the surface section 30a and / or 30b, in which the curable adhesive composition is applied to the surfaces 28a, 28b, 28c and / or 28d.

[0189] Bilateral, and especially simultaneous, irradiation as described above is also possible.

[0190] Fig. Figure 10 shows a section through a membrane electrode arrangement 2 comprising a first and a second GDL 20a and 20b according to a further embodiment of the invention.

[0191] Unlike the one in Fig. The embodiment shown in 9 features the Fig. The membrane electron arrangement 2 shown in Figure 10 does not have separate connection areas 13a, via which a first sealing layer 12a is connected to the first gas diffusion layer 20a, and 13b, via which a second sealing layer 12b is connected to the second gas diffusion layer 20b, but rather a continuous connection area 13. Such a connection area 13 can be formed if the first sealing layer 12a and / or the second sealing layer 12b themselves have recesses, in particular in a peripheral area 23, and are arranged relative to each other in such a way that a surface 28c of the first sealing layer 12a is sectionally opposite a surface 28b of the second gas diffusion layer 20b, in particular a microporous layer 22b of the second gas diffusion layer 20b.

[0192] The same applies to the second sealing layer 12b and the first GDL 20a.

[0193] The curing of an adhesive composition leads accordingly to the connection area 13 shown, whereby a connection is formed section by section between the first sealing layer 12a and the second GDL 20b as well as between the second sealing layer 12b and the first GDL 20a.

[0194] In areas where the surface 28c of the first sealing layer 12a and a surface 28d of the second sealing layer 12b are opposite each other, a connection is also formed between the sealing layers 12a and 12b.

[0195] Accordingly, a surface section 30b, which is accessible to irradiation, is formed partly by a surface 28b of the second GDL 20b and partly by the surface 28d.

[0196] Conversely, opposite recesses 25b, a surface section 30a which is accessible to irradiation can be formed partly by a surface 28a of the first GDL 20a and partly by the surface 28c.

[0197] Irradiation of the adhesive composition can be particularly useful as in connection with Fig. 7 and Fig. 9 in the area of ​​exemptions 25a and 25b. In contrast to the one in Fig. In the embodiment shown in Figure 9, the adhesive composition is irradiated, as indicated by the wavy arrows, depending on the direction of irradiation, only through the first sealing layer 12a or the second sealing layer 12b. This is advantageous insofar as the radiation is only attenuated to a small extent.

[0198] With the exception of the different design of the sealing layers 12, the statements regarding Fig. 9 accordingly.

[0199] In Fig. Figure 11 shows a section through a membrane electrode arrangement 2 comprising a first GDL 20a and a second GDL 20b according to a further embodiment of the invention. In contrast to the one shown in Fig. In the embodiment shown in Figure 8, a first sealing layer 12a and a second sealing layer 12b also have openings.

[0200] The openings of the first sealing layer 12a are arranged such that they are opposite the openings 26b of the second sealing layer 20b. The openings of the second sealing layer 12b are arranged such that they are opposite the openings 26a of the first sealing layer 20a.

[0201] According to the to in Fig. In the embodiment shown in Figure 10, a continuous connection area 13 can be formed in this way, and the need for separate connection areas 13a and 13b and optionally 14 can be eliminated, so that an adhesive composition can be applied in one step.

[0202] In areas where the first sealing layer 12a and the second sealing layer 12b have no openings, the sealing layers 12 face each other with their surfaces 28c and 28d, so that a connection is formed between the sealing layers 12 in these areas.

[0203] It is conceivable that only one of the sealing layers has 12 recesses and / or openings (not shown). Furthermore, it is conceivable that the sealing layers have 12 recesses, but the GDL 20 has openings, and vice versa (not shown).

[0204] With the exception of the different design of the sealing layers 12, the statements regarding Fig. 8 accordingly.

[0205] In Fig. Figure 12 is another sectional view of the membrane electrode arrangement 2. Fig. Figure 11 shows that only a single connection area 13 is formed. In contrast to the one in Fig. In the embodiment shown in Figure 6, no separate connection areas 13a, 13b and 14 are necessary.

[0206] By irradiating an adhesive composition, both a CCM 11 with the connecting layers 12a and 12b, and the sealing layers 12a and 12b with the respective opposing GDL 20b and 20a are connected.

[0207] It can be advantageous if, in areas where the first sealing layer 12a borders the first GDL 20a, a connection area 13a is formed by an adhesive (not shown). Additionally or alternatively, it can be advantageous if, in areas where the second sealing layer 12b borders the second GDL 20b, a connection area 13b is formed by an adhesive (not shown).

[0208] Especially in the Fig. 10, Fig. 11 to Fig.In the embodiments shown in Figure 12, it can be advantageous if the curing of the adhesive composition for forming the bonding area 13, and optionally the adhesive compositions for forming the bonding areas 13a and / or 13b, is additionally carried out by heat curing and / or physical drying. In this way, the curing of the bonding composition(s) can also be ensured with all MEA elements 10 fully assembled in areas that are not accessible to irradiation. Reference symbol list 1 electrochemical system 2 membrane electrode arrangement 10 MEA elements 11 catalyst-coated membrane (CCM) 12, 12a-b sealing layer 13, 13a-b Connection area 14 Connection area 20, 20a-b GDL 21, 21a-b Substrat 22. 22a-b microporous layer 23 peripheral area 24 central area 25, 25a-b Exclusion 26, 26a-b Opening 27, 27a-b outer contour 28, 28a-d surface 30, 30a-b Surface section 31, 31a-b area QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2008 / 040682 A1

[0009]

Claims

Gas diffusion layer (20) for an electrochemical system, which may be, for example, a fuel cell system (1), wherein the gas diffusion layer (20) has at least one recess (25) on an outer contour (27) and / or at least one opening (26). Gas diffusion layer (20) according to claim 1, characterized in that the gas diffusion layer (20) has at least one peripheral area (23), wherein the at least one peripheral area (23) at least partially surrounds and / or limits a central area (24) and the at least one recess (25) and / or at least one opening (26) is arranged in the at least one peripheral area (23). Gas diffusion layer (20) according to claim 1 or 2, characterized in that the at least one opening (26) has at least partially a round shape or a shape of a, preferably regular, polygon. Gas diffusion layer (20) according to one of claims 1 to 3, characterized in that the at least one recess (25) has at least sectionally a round shape or a shape of a, preferably regular, polygon. Gas diffusion layer (20) according to one of the preceding claims, characterized in that the gas diffusion layer (20) has two or more recesses (25) and / or two or more openings (26), wherein recesses (25) and / or openings (26) adjacent to each other preferably have a regular distance from each other. Membrane electrode arrangement (2) for an electrochemical system, which may be, for example, a fuel cell system (1), wherein the membrane electrode arrangement (2) comprises at least the following MEA elements (10): - a catalyst-coated membrane (11); - at least one sealing layer (12); - a first gas diffusion layer (20a);and a second gas diffusion layer (20b), wherein the catalyst-coated membrane (11) and the at least one sealing layer (12) are arranged at least partially between the first and the second gas diffusion layer (20a, 20b), wherein at least two adjacent MEA elements (10) are connected to each other in at least one connection area (13, 14) via a radiation-cured, heat-cured and / or physically dried adhesive, in particular a radiation-cured, a radiation- and heat-cured or a radiation-cured and physically dried adhesive, characterized in that the first gas diffusion layer (20a) and the second gas diffusion layer (20a) do not overlap or only partially overlap in the at least one connection area (13). Membrane electrode arrangement (2) according to claim 6, characterized in that the first gas diffusion layer (20a) and the second gas diffusion layer (20b) differ in shape and / or size or are identical. Membrane electrode arrangement (2) according to claim 6 or 7, characterized in that the first gas diffusion layer (20a) and / or the second gas diffusion layer (20b) is a gas diffusion layer (20) according to one of claims 1 to 5. Membrane electrode arrangement (2) according to one of claims 6 to 8, characterized in that the first gas diffusion layer (20a) and the second gas diffusion layer (20b) are a gas diffusion layer (20) according to one of claims 1 to 5, wherein at least one recess (25a) and / or at least one opening (26a) of the first gas diffusion layer (20a) is at least partially, preferably completely, opposite a surface (28b) of the second gas diffusion layer (20b) and / or wherein at least one recess (25b) and / or at least one opening (26b) of the second gas diffusion layer (20b) is at least partially, preferably completely, opposite a surface (28a) of the first gas diffusion layer (20a). Membrane electrode arrangement (2) according to claims 6 to 9, characterized in that in the at least one connection area (13, 13a) the first gas diffusion layer (20a) is connected to the at least one sealing layer (12, 12a) or the catalyst-coated membrane (11) and in a second connection area (13, 13b) the second gas diffusion layer (20b) is connected to the at least one sealing layer (12, 12a), a second sealing layer (12b) or the catalyst-coated membrane (11). Method for producing a membrane electrode arrangement (2), in particular a membrane electrode arrangement (2) according to any one of claims 6 to 10, wherein the membrane electrode arrangement (2) comprises a catalyst-coated membrane (11), at least one sealing layer (12), a first gas diffusion layer (20a) and a second gas diffusion layer (20b) as MEA elements (10), wherein the method comprises the steps: i. Applying at least one adhesive composition to at least one surface section (30) of at least one of the MEA elements (10); ii. Arranging the catalyst-coated membrane (11) and the at least one sealing layer (12) between the first gas diffusion layer (20a) and the second gas diffusion layer (20b), wherein the first gas diffusion layer (20a) and the second gas diffusion layer (20b) do not overlap or only partially overlap in at least one region (31) of the at least one surface section (30); andiii.a radiation hardening, a heat hardening and / or physical drying of the at least one adhesive composition, such that at least one connection area (13, 14) is formed in the at least one surface section (30) in which the at least one MEA element (10) is connected to an adjacent MEA element (10), wherein the radiation hardening is preferably carried out by irradiating the adhesive composition at least in the at least one area (31) of the at least one surface section (30). Method according to claim 11, characterized in that the first gas diffusion layer (20a) and / or the second gas diffusion layer (20b) is a gas diffusion layer (20) according to one of claims 1 to 5, wherein at least one recess (25a, 25b) on an outer contour (27a, 27b) of the first and / or second gas diffusion layer (20a, 20b) and / or at least one opening (26a, 26b) in the first and / or gas diffusion layer (20a, 20b) is produced, preferably by punching and / or cutting. Method according to claim 11 or 12, characterized in that the at least one adhesive composition is applied to at least one surface section (30) of the first gas diffusion layer (20a) and at least one surface section (30) of the second gas diffusion layer (20b), wherein the at least one surface section (30) of the second gas diffusion layer (20b) faces the first gas diffusion layer (20a); and to the at least one surface section (30) of the first gas diffusion layer (20a) and at least one surface section (30) of the at least one sealing layer (12), wherein the at least one sealing layer (12) is preferably the second sealing layer (12b), wherein the at least one surface section (30) of the at least one sealing layer (12) faces away from the first gas diffusion layer (20a).- on at least one surface section (30) of the first gas diffusion layer (20a) and at least one surface section (30) of the CCM (11), wherein the at least one surface section (30) of the CCM (11) faces away from the first gas diffusion layer (20a); - on at least one surface section (30) of the second gas diffusion layer (20b) and the at least one surface section (30) of the at least one sealing layer (12), wherein the at least one sealing layer (12) is preferably the first sealing layer (12a), wherein the at least one surface section (30) of the at least one sealing layer (12) faces away from the second gas diffusion layer (20b); - on at least one surface section (30) of the second gas diffusion layer (20b) and the at least one surface section (30) of the CCM (11), wherein the at least one surface section (30) of the CCM (11) faces away from the second gas diffusion position (20b) is turned away;- applied to at least one surface section (30) of the CCM (11) and at least one surface section (30) of the at least one sealing layer (12), wherein at least one surface section (30) of the at least one sealing layer (12) faces away from the CCM (11); and / or - applied to at least one surface section (30) of the first sealing layer (12a) and at least one surface section (30) of the second sealing layer (12b), wherein at least one surface section (30) of the second sealing layer (12b) faces away from and / or towards the first gas diffusion layer (12a), so that two or more connection areas (13a, 13b, 14) can be formed by irradiation.; A method according to any one of claims 11 to 13, characterized in that at least one first connection area (13a) is formed between the first gas diffusion layer (20a) and a first sealing layer (12a), and at least one second connection area (13b) is formed between the second gas diffusion layer (20b) and a second sealing layer (12b), wherein the formation of the at least one first connection area (13a) and the second connection area (13b) takes place in step iii., or the formation of the at least one first connection area (13a) takes place in step iii. and the formation of the at least one second connection area (13b) takes place before the formation of the at least one first connection area (13a), in particular during step ii., or the formation of the at least one second connection area (12b) takes place in step iii.and the formation of at least one first connection area (13a) takes place before the formation of at least one second connection area (13b), in particular during step ii. Method according to one of claims 11 to 14, characterized in that the at least one adhesive composition is radiation-cured, radiation- and heat-cured, or radiation-cured and physically dried.

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