Method for producing a catalytically coated membrane as well as a membrane electrode assembly and fuel cell stack with such a

Abstract

A method for producing a catalytically coated membrane (19) for a fuel cell (10), wherein the catalytically coated membrane (19) comprises a membrane (11) and a catalyst layer (12, 13) of a catalytic material arranged on at least one of its flat sides, and a non-rectangular active region (20) bounded in one direction by two opposing outer sides (30), wherein the method comprises a continuous application of the catalytic material to a membrane material (33) generating a constant coating width (B) such that a region (35) coated with the catalytic material corresponds at least to the active region (20), characterized in that the membrane material (33) is coated with the catalytic material such that a coating direction (D) has an angle to the opposing outer sides (30) of the active region (20) other than 90° and other than 0°.

Description

[0001] The invention relates to a method for producing a catalytically coated membrane, comprising a membrane and a catalyst layer of a catalytic material arranged on at least one of its flat sides. The invention further relates to a membrane electrode assembly comprising such a catalytically coated membrane, and to a fuel cell comprising a plurality of such membrane electrode assemblies stacked alternately with bipolar plates.

[0002] Fuel cells utilize the chemical reaction of a fuel with oxygen to produce water, thereby generating electrical energy. As a core component, fuel cells contain the membrane electrode assembly (MEA), which consists of an ion-conducting (usually proton-conducting) membrane and an electrode (anode and cathode) positioned on either side of the membrane. Gas diffusion layers (GDLs) can also be located on either side of the MEA, on the electrodes facing away from the membrane. Typically, a fuel cell is formed by a stack of multiple MEAs, whose electrical outputs are additive. Bipolar plates (also called flux plates) are usually positioned between the individual MEAs. These plates ensure the supply of the operating fluids, i.e., the reactants, to the individual cells and also typically serve for cooling.In addition, the bipolar plates ensure an electrically conductive contact with the membrane electrode units.

[0003] In the operation of the fuel cell, the fuel, in particular hydrogen H2 or a hydrogen-containing gas mixture, is supplied to the anode via an anode-side open flux field of the bipolar plate, where an electrochemical oxidation of H2 to H occurs. + This process involves the release of electrons. The transport of protons (H₂) occurs via the electrolyte or the membrane, which provides gas-tight and electrical insulation to the reaction chambers. + from the anode compartment to the cathode compartment. The electrons supplied at the anode are directed to the cathode via an electrical conductor. Oxygen or an oxygen-containing gas mixture (for example, air) is supplied to the cathode via an open flux field on the cathode side of the bipolar plate, so that a reduction of O₂ to O₂ occurs. 2-This occurs with the uptake of electrons. Simultaneously, in the cathode compartment, the oxygen anions react with the protons transported across the membrane to form water.

[0004] The electrodes of a fuel cell are typically present as a catalytic coating on the gas diffusion layers, which are then referred to as gas diffusion electrodes, or as a catalytic coating on the membrane. In the latter case, they are also called catalytically coated membranes or CCMs (for catalytic coated membranes). Various techniques are known for coating a membrane material with a catalytic material to create the catalyst layers in order to produce a CCM. These include printing processes, spraying processes, deposition processes, coating processes, etc. For mass production, cost-effective processes with high production rates are desirable.

[0005] The area of ​​a mechanical energy assembly (MEA) within the fuel cell stack that is exposed to both reactant gases for the anode and cathode, and where the fuel cell reaction takes place to generate electricity, is called the active area. However, the active area only occupies a portion of the total MEA surface. The remaining areas, which can have variable shapes, serve to supply and distribute the operating media to the active area, as well as to seal and mechanically stabilize the MEA. These areas are referred to as non-active or inactive areas. In conventional fuel cells, the active area is usually rectangular. In an effort to achieve high surface area utilization for the active area, arrangements with non-rectangular active areas have recently been developed, for example, with a regular or irregular hexagonal contour, as shown in [reference to diagram]. Fig. Figure 2 shows that, for cost reasons, it is generally desirable to coat only the active area with the catalytic layer. Selective coating of only the active area is possible using printing processes such as offset or screen printing. However, these processes are comparatively slow in the case of screen printing or require expensive machinery (offset printing). Continuous coating processes, in which the membrane material is continuously coated with the catalytic material and the catalytically coated membrane is later cut out in a finishing step, are faster and less expensive. A disadvantage of this method is that, in the case of non-rectangular active areas, coating inactive areas of the membrane or membrane offcuts is unavoidable.If inactive areas are unintentionally coated with catalytic material, these areas must subsequently be blocked, for example by applying diffusion barrier layers. In any case, the excess coating results in a loss of catalytic material.

[0006] DE 11 2012 000 558 T5 describes a catalytically coated membrane (CCM) of a membrane electrode assembly for a fuel cell with a rectangular active area that borders meandering flow fields of the anode and cathode fluids within the fuel cell. To achieve more effective catalyst utilization, the amount of catalyst per unit area is greater in the central region of the active area than in the surrounding peripheral region. Furthermore, the amount of catalyst decreases towards the main flow of reactant gases. The different amounts of catalyst are achieved by varying the layer thickness. The membrane is manufactured by spraying a catalyst ink onto it, with the peripheral areas not to be coated being masked off.

[0007] According to EP 1 296 399 A1, a catalytic layer is produced on a polymer electrolyte membrane by continuously spraying on a catalyst ink. The coating direction extends orthogonally to the subsequent main flow direction of the reactant gases. To achieve variation in the catalyst properties, particularly the catalyst concentration in the main flow direction, a spray tool is used for production. The longitudinal opening of this tool is divided into two or more compartments, allowing different catalyst inks to be applied simultaneously, overlapping each other with graduated layer thicknesses.

[0008] The invention is based on the objective of defining a method with which catalytically coated membranes (CCM) for fuel cells can be produced cost-effectively and at a high production rate.

[0009] This problem is solved by a method, a membrane electrode assembly, and a fuel cell stack with the features of the independent claims. The method according to the invention thus relates to the production of a catalytically coated membrane (CCM) for a fuel cell, wherein the catalytically coated membrane comprises a membrane and a catalyst layer (anode and / or cathode) of a catalytic material arranged on at least one of its flat sides. The catalytically coated membrane to be produced by the method further comprises a non-rectangular active region, which is bounded in one direction by two opposing outer surfaces.In particular, these outer surfaces of the active region correspond to a main flow direction of the reactant gases (anode and cathode consumables) in the fuel cell stack and preferably run parallel to each other and parallel to two corresponding outer edges of the CCM. The method comprises a continuous application of the catalytic material to a membrane material, generating a constant coating width such that an area coated with the catalytic material corresponds at least to the active region, i.e., covers the active region. According to the invention, the membrane measuring material is coated with the catalytic material such that one coating direction has an angle to the opposing outer surfaces of the active region that is neither 90° nor 0°.In other words, the coating process is neither orthogonal nor parallel to the two opposing outer surfaces of the active area of ​​the catalytically coated membrane. By pivoting the coating direction according to the invention, compared to conventional methods, areas that are undesirably coated with the catalytic material are reduced. This reduces the required amount of catalytic material. At the same time, the process is a continuous coating process that produces a continuous coating surface of constant width and rectangular shape, and is particularly suitable for a roll-to-roll process using a membrane material in the form of an endless strip.

[0010] In a preferred embodiment of the invention, the active region has a contour with at least four corners, bounded by the two said opposing outer sides (corresponding to the main flow direction of the operating means) and at least one first pair of opposing short sides. In particular, the active region has a contour with at least six corners, bounded by the two outer sides and at least two further opposing pairs of short sides. Preferably, the coating direction has an angle to the first pair of short sides of at most 10°, in particular at most 5°, and preferably as close to 0° as possible. Since the inactive regions of the catalytically coated membrane are mainly adjacent to these short sides, coating of the inactive regions can thus be largely restricted or prevented.Preferably, the coated area terminates laterally at the first pair of short sides of the active area of ​​the catalytically coated membrane. In a particularly preferred embodiment, the active area has a hexagonal contour bounded by two opposing outer sides and by exactly two pairs of opposing short sides. Furthermore, preferably, the short sides of a pair and / or the opposing outer sides are arranged parallel to each other. All of these aforementioned embodiments lead to a further reduction of excess coated areas of the membrane material and thus to a saving of catalytic material.

[0011] According to a preferred embodiment of the process, a plurality of catalytically coated membranes are produced by continuously coating the membrane material, wherein the outer surfaces of the active areas of adjacent catalytically coated membranes are arranged parallel to each other on the membrane material, preferably with the smallest possible distance between them. In this way, on the one hand, the amount of membrane material wasted is reduced, and on the other hand, the area of ​​membrane material unintentionally coated with the catalytic material is also reduced.

[0012] A particular advantage of the membrane material is its ribbon-like shape with two parallel longitudinal sides, and it is especially designed as an endless ribbon that can be stored and transported, for example, on rolls. In this case, the coating direction preferably runs parallel to the longitudinal sides of the ribbon-like membrane material. This design allows for the application of a continuous coating area along the length of the membrane material, thus enabling a high production rate.

[0013] In a preferred embodiment, the majority of catalytically coated membranes are arranged on the membrane material such that the first short sides of the active areas are aligned parallel to the long sides of the ribbon-shaped membrane material. In this way, the rolling direction of the membrane material is aligned with the coating direction, and the width of the coating area can be aligned with the first short sides of the active areas.

[0014] Preferably, after the application of the catalytic material, a processing step is carried out in which the membrane material is cut according to the desired shape of the catalytically coated membrane to be produced. In other words, the catalytically coated membrane is cut out of the membrane material. In this way, the catalytically coated membrane is brought to the required dimensions.

[0015] Furthermore, it is advantageous to remove catalytic material applied to the membrane material in areas outside the catalytically coated membrane being produced, preferably after fabrication, and to reuse (recycle) it. This prevents the expensive catalytic material from being wasted.

[0016] In principle, any known method can be used to apply the catalytic material to the membrane material. However, the invention eliminates the need for selective, but expensive and slow, printing processes. Preferably, the catalytic material is applied by spraying, brushing, or rolling. These techniques are characterized by their ease of implementation and high production rates, and their ability to be integrated into continuous roll processes. The catalytic material is used, for example, in an aqueous or non-aqueous solvent as a more or less viscous paste, or as a liquid suspension or solution. The solvent is removed after application and before or after processing by active or inactive drying processes.

[0017] Another aspect of the present invention relates to a membrane electrode assembly (MEA) comprising a catalytically coated membrane produced or producible according to the inventive method. In addition to the catalytically coated membrane, the MEA comprises various service ports (through-openings) for supplying and removing fuel cell service media, which are arranged outside the non-rectangular active area. Preferably, it further comprises a support layer arranged on one or both sides, which surrounds the MEA and, in particular, the service ports in a frame-like manner and serves for mechanical stabilization. Optionally, seals can be arranged on the MEA. The coating direction used in the manufacturing process is usually detectable, for example, by microscopic examination of the MEA.Furthermore, the coating direction can be determined from the edge areas of the coating area.

[0018] Furthermore, the invention relates to a fuel cell stack comprising a plurality of membrane electrode assemblies stacked alternately with bipolar plates according to the invention. The fuel cell stack can be used, in particular, in a vehicle equipped with an electric motor drive, wherein the fuel cell stack serves to supply electricity to the electric motor and / or a traction battery.

[0019] Further preferred embodiments of the invention result from the other features mentioned in the dependent claims.

[0020] Unless otherwise stated in individual cases, the various embodiments of the invention mentioned in this application can be advantageously combined with one another.

[0021] The invention is explained below using exemplary embodiments with reference to the accompanying drawings. These show: Fig. 1 a schematic sectional view of a fuel cell stack; Fig. 2 Top view of a membrane electrode assembly with a non-rectangular active area; Fig. 3 Top view of a catalytically coated membrane of the membrane electrode assembly according to Fig. 2; Fig. 4. Production of a catalytically coated membrane according to Fig. 3 using a state-of-the-art method; Fig. 5. Production of a catalytically coated membrane according to Fig. 3 with a method according to a first embodiment of the invention; Fig. 6. Continuous production of a large number of catalytically coated membranes according to Fig. 3 with a method according to a second embodiment of the invention and Fig. 7. Continuous production of a variety of catalytically coated membranes according to Fig. 3 with a method according to a third embodiment of the invention.

[0022] Fig. Figure 1 shows a section of a fuel cell stack designated as 100 in total, of which only two individual fuel cells 10 are shown here.

[0023] Each fuel cell 10 has a polymer electrolyte membrane 11, which consists of an electrolytically conductive polymer material, in particular a proton-conducting one. Typically, the polymer material requires a certain level of moisture to maintain its electrolytic conductivity. A catalyst layer borders each of the two flat sides of the membrane 11: an anodic catalyst layer 12 and a cathodic catalyst layer 13. The catalyst layers 12 and 13 comprise a catalytic material, which is typically a noble metal, especially platinum. The catalyst layers 12 and 13 also usually comprise a porous, electrically conductive support material on which the catalytic material is finely dispersed, for example, a carbon-based material. The catalyst layers 12 and 13 may include other components, such as polymeric binder materials and the like.

[0024] Each catalyst layer 12, 13 is connected to a gas diffusion layer (GDL) 14. The GDL comprises a fluid-permeable material that is also electrically conductive. For example, the GDL 14 comprises a carbon-based foam or paper material. The structure consisting of the membrane 11, the catalyst layers 12, 13, and the gas diffusion layers 14 is also referred to as the membrane electrode assembly 15, although the assignment of the gas diffusion layers 14 to the membrane electrode assembly 15 is inconsistent in the literature.

[0025] A bipolar plate 16, also known as a flow field plate or flux field plate, is arranged between each pair of membrane electrode assemblies 15. The bipolar plate 16 has anode flow channels 17 on its anode side, through which an anode medium (fuel), in particular hydrogen, is supplied to the anodic catalyst layer 12. Furthermore, the bipolar plate 16 has cathode flow channels 18 on its cathode side, through which a cathode operating gas, usually an oxygen-containing gas, most often air, is supplied to the cathodic catalyst layer 13. The bipolar plate 16 also typically has internal coolant channels (not shown here) through which a coolant can be passed to cool the fuel cell stack 100.The bipolar plate 16 is made of an electrically conductive material, for example, a metal, a metal alloy, graphite, or an electrically conductive polymer or polymer composite material. The bipolar plate 16 thus combines the functions of supplying the operating medium, cooling, and electrically connecting the catalytic electrodes 12, 13 to an external circuit.

[0026] Typically, a large number of such individual cells 10 are arranged in a fuel cell stack 100, the electrical power outputs of which are additive. For electromobility applications, fuel cell stacks 100 typically comprise several hundred individual cells 10.

[0027] The catalyst layers 12 and 13 can be present as a coating on the membrane 11. In this case, it is also referred to as a catalytically coated membrane or CCM (for catalytic coated membrane), which is Fig. The entire assembly is designated as 19. Alternatively, the catalyst layers 12 and 13 can be arranged as a coating of the gas diffusion layers 14, in which case these are referred to as gas diffusion electrodes. The present invention relates primarily to the case of a catalytically coated membrane 19 and a method for its production.

[0028] Fig. Figure 2 shows a membrane electrode assembly 15 in a top view of one of its flat sides. The membrane electrode assembly 15 has the catalytically coated membrane 19, which is also available in isolated form in Fig. Figure 3 shows the following. In the illustrated example, the catalytically coated membrane 19 has a hexagonal contour. Within this hexagonal contour, an active region 20 is arranged, which is indicated by a dashed line. Outside the active region 20, the catalytically coated membrane 19 has inactive regions 21. The active region 20 is characterized by the fact that, when the membrane electrode assembly 15 is installed in a fuel cell stack 100, the fuel cell reactions take place at the anode and cathode in this region, thus generating electricity. The inactive regions 21, on the other hand, serve other functions, such as supplying the operating media to the active region 20. Ideally, the polymer electrolyte membrane 11 is coated with the catalytic coatings 12 and 13 only in the active region 20, as shown in Figure 3. Fig. 3 is shown.

[0029] The membrane electrode assembly 15 comprises various through-ports 22 to 27, which serve for the supply and discharge of the various operating media. A first anode port 22 serves to supply the anode operating gas to the cathodes 12 of the fuel cell stack 100, and a second anode gas port 23 opposite it serves to discharge the anode operating gas. Similarly, a first cathode port 24 serves to supply a cathode operating gas to the cathodes 13 of the fuel cell stack 100, and a second cathode port 25 opposite it serves to discharge the cathode operating gas. Finally, a first coolant port 26 serves to supply a coolant to the internal coolant channels of the bipolar plates 16, and a second coolant port 27 opposite it serves to discharge the coolant.The bipolar plates 16, not shown in detail, have essentially the same shape as the illustrated membrane electrode assemblies 15, in particular corresponding ports. In this way, when the membrane electrode assemblies 15 and bipolar plates 16 are stacked, main service channels are formed which support the fuel cell stack 100 in its stacking direction S (see figure 1). Fig. 1) enforce. (These main operational media channels are in Fig. (Figure 1 not shown, which only shows a section through the active region 20 of the fuel cell stack.) The anode and cathode ports 22 to 25 are fluid-carrying connected via open distribution channels of the bipolar plates 16 adjacent in the stack 100 to the corresponding anode and cathode channels 17, 18 of the bipolar plates 16. The coolant ports 26, 27 are connected to the internal coolant channels of the bipolar plates 16. The distribution channel structures connecting ports 22-27 and the anode and cathode channels 17, 18 of the active region 20 run in the inactive regions 21.

[0030] For mechanical support, the membrane 11 is typically framed on both sides by a support layer 28, which surrounds the membrane 11 at its edges. Optionally, the membrane 11 can also extend over the entire surface of the membrane-electrode unit 15 and be laminated with support layers 28 at its edges. Furthermore, in Fig. Two seals 29 are visible, which surround the service medium passage openings 22 to 27 and the catalytically coated membrane 19 to seal them to the outside. Optionally, the seals 29 can be arranged on the bipolar plates 16 or on both, instead of on the membrane electrode assembly 15.

[0031] As previously explained, the fuel cell reaction takes place only in the active region 20. Therefore, the aim is to apply the catalyst layers 12 and 13 only in this region, as the catalytic material is by far the most expensive single component of the fuel cell stack. On the other hand, the goal is to make the active region 20 as large as possible and the inactive regions 21 as small as possible in order to achieve the highest possible energy yield and to minimize the required installation space and weight of the fuel cell. Accordingly, the contours of the active region 20 may deviate from the conventional rectangular shape and exhibit an irregular contour. For example, as in Fig. 2 and Fig. Figure 3 shows a hexagonal contour of the active region 20. This region is bounded in a direction parallel to the main flow direction of the operating equipment by two opposing, parallel outer sides 30. The irregularly hexagonal contour of the depicted active region 20 further comprises a first pair of opposing short sides 31 and a second pair of opposing short sides 32. The short sides 31 are longer than the short sides 32.

[0032] The cost-effective and time-saving mass production of catalytically coated membranes 19 with a non-rectangular active area has so far only been unsatisfactorily resolved. For example, production can be carried out by selective coating processes in which the catalytic material is applied exclusively to the active area 20 of a membrane material, for example by selective printing processes such as screen printing or offset printing. However, these processes are characterized by slow production speeds (screen printing) or by expensive machinery (offset printing). Continuous coating processes, in which the catalytic material is applied to the membrane material while producing a constant coating width, are faster and more cost-efficient. This is illustrated by the example of Fig. Figure 4 illustrates such a continuous coating process according to the state of the art.

[0033] In Fig. 4 is designated by 33 as the membrane material onto which the catalytic material is applied along a continuous strip of width B bounded by the longitudinal sides 34. Also in Fig. 4. The catalytically coated membrane 19, to be cut out in a later processing step of the process, and the desired active area 20. According to the prior art, the application direction D runs in a direction that is orthogonal, i.e., oriented at 90° to the two opposing outer surfaces 30 of the active area 20. This results in a coated area 35 with a rectangular contour. However, according to the prior art, the coated area 35 covers not only the active area 20, but also parts of the inactive areas 21 of the catalytically coated membrane 19, as well as protruding offcut areas that are cut off during the subsequent processing. Only the simply hatched areas 36 of the catalytically coated membrane 19 remain uncoated.The cross-hatched areas 37, however, are coated with catalytic material according to the conventional procedure, even though this is not required at this location. This leads, on the one hand, to unnecessarily high costs for the catalytic material and, on the other hand, to the necessity of blocking these unintentionally coated areas 37, for example by applying gas barrier layers, in order to prevent the fuel cell reaction in these areas.

[0034] According to the invention, the known continuous process is therefore modified by coating the membrane material with the catalytic material in such a way that the coating direction D has an angle to the opposite outer sides 30 of the active area 20, which, unlike in Fig. 4 is not equal to 90°. This principle is in Fig. Figure 5 shows that the catalytic material is applied to the membrane material 33 in a continuous process, producing a coated surface 35 with a constant coating width B. However, the coating direction D is not orthogonal to the outer surface 30 of the active area 20 as in Figure 5. Fig. 4 (and also not parallel to the outer surfaces 30, as is known from other methods). Rather, the coating direction D runs in a direction that is as close as possible to the

[0035] The orientation of one of the two short side pairs 31, 32 of the active area 21 corresponds, preferably to the longer short sides 31

[0036] As can be seen from the simply hatched areas 36, which mark the uncoated area of ​​the membrane 19 to be cut out, the inactive areas 21 of the catalytically coated membrane 19 are completely uncoated in the illustrated example. After cutting out the catalytically coated membrane 19 from the membrane material 33, only the cross-hatched areas 37 remain as excess coated areas. The comparison of the (excess) coated areas 37 of the method according to the invention according to Fig. 5 with whom to Fig. Figure 4 shows that the invention significantly reduces this excess coating. The excess coated areas 37 produced in the inventive method have a 6 to 10% smaller area than those produced by conventional methods, in which the coating direction D is orthogonal to the outer sides 30 of the active area 20. Furthermore, in the inventive coating method, the excess coated areas 37 (cross-hatching) are practically completely removed by cutting them out of the membrane material 33 during the subsequent fabrication of the catalytically coated membrane 19. This allows the catalytic coating to be separated and the catalytic material to be recycled, so that it is essentially not wasted in the process. The need to block unwanted catalytic material with barrier layers is eliminated or at least reduced.

[0037] Fig. Figure 6 shows a further embodiment for the continuous production of a plurality of catalytically coated membranes 19 according to Fig. 3 made of a membrane material 33 having a ribbon-shaped blank with parallel longitudinal sides 38, in particular an endless ribbon stored on a roll (not shown). Here, the catalytically coated membranes 19 to be produced are arranged on the membrane material 33 such that the two opposing outer sides 30 of the active areas 20 of the adjacent catalytically coated membranes 19 are each aligned parallel to each other. At the same time, the short sides 31 of the active areas 20 are aligned parallel to the longitudinal sides 38 of the membrane material 33. As a result, the coating direction D runs parallel to the longitudinal sides 38 of the ribbon-shaped membrane material 33.As an example of a single catalytically coated membrane 19 to be produced, the uncoated area 36 to the right and left of the longitudinal sides 34 of the coating area is marked with simple hatching, while the continuously coated area 35 is highlighted with cross-hatching. After cutting out the catalytically coated membranes 19, only the excess coated areas 37, shown here as triangular sections, remain. These areas 37 are preferably recycled after cutting to reuse the catalytic material. In this way, the process can be carried out in a continuous roll-to-roll process, whereby the catalytic material is continuously applied to a moving membrane material 33 with a constant width B.

[0038] A further advantageous embodiment of the method according to the invention is in Fig. Figure 7 shows the catalytically coated membranes 19 to be produced, arranged in two parallel rows on the membrane material 33. Their orientation with respect to their outer sides 30 and short sides 31 of the catalytic areas 20 corresponds to that shown in Figure 7. Fig. 6. The hexagonal membranes 19 are arranged in such a nested manner that their pointed ends interlock. This arrangement reduces the amount of membrane material 33 that is wasted. In the example shown, approximately 7% of membrane material 33 can be saved relative to the total area. In this example, two parallel, surface-coated areas 35, each with a coating width B, are continuously produced. It is obvious that more than two parallel rows of catalytically coated membranes 19 can also be produced in this way. Reference symbol list 100 fuel cell stacks 10 Fuel cell (single cell) 11 Polymer electrolyte membrane 12 anodic catalyst layer / anode 13 cathodic catalyst layer / cathode 14 Gas diffusion layer 15 Membrane Electrode Unit 16 Bipolar plate 17 anode flow channels 18 cathode flow channels 19 catalytically coated membranes 20 active area 21 inactive areas 22 first anode port 23 second anode port 24 first cathode port 25 second cathode port 26 first coolant port 27 second coolant port 28 Support layer 29 Seal 30 Outside of the active area 31 Short side of the active area 32 Short side of the active area 33 Membrane material 34 long sides of the coated area 35 coated area 36 uncoated area 37 excess coated area 38 longitudinal sides of the membrane material B Coating width D Coating direction S Stacking direction

Claims

[1] Method for producing a catalytically coated membrane (19) for a fuel cell (10), wherein the catalytically coated membrane (19) comprises a membrane (11) and a catalyst layer (12, 13) of a catalytic material arranged on at least one of its flat sides, and a non-rectangular active area (20) bounded in one direction by two opposing outer sides (30), wherein the method comprises continuously applying the catalytic material to a membrane material (33) to produce a constant coating width (B), such that an area (35) coated with the catalytic material corresponds at least to the active area (20), characterized by , that the membrane material (33) is coated with the catalytic material such that a coating direction (D) has an angle to the opposite outer sides (30) of the active area (20) other than 90° and other than 0°. [2] Method according to claim 1, characterized by , that the active area (20) has a contour with at least four corners, in particular with at least six corners, which is bounded by the two opposite outer sides (30) and at least a first pair of opposite short sides (31), wherein the coating direction (D) has an angle to the first pair of short sides (31) of at most 10°, in particular at most 5°, preferably 0°. [3] Method according to claim 2, characterized by , that the coated area (35) terminates laterally with the first pair of short sides (31) of the active area (20). [4] Method according to any one of the preceding claims, characterized by, that a plurality of catalytically coated membranes (19) are produced by continuously coating the membrane material (33), wherein the outer surfaces (30) of the active areas (20) of adjacent catalytically coated membranes (19) are aligned parallel to each other on the membrane material (33). [5] Method according to any one of the preceding claims, characterized by , that the membrane material (33) is a ribbon-shaped blank with parallel longitudinal sides (38), in particular an endless ribbon, and the coating direction (D) is parallel to the longitudinal sides (38) of the ribbon-shaped membrane material (33). [6] Method according to claim 4 or 5, characterized by , that the majority of catalytically coated membranes (19) are arranged on the membrane material (33) such that the first short sides (31) of the active areas (20) are aligned parallel to the long sides (38) of the ribbon-shaped membrane material (33). [7] Method according to any one of the preceding claims, characterized by , that after the application of the catalytic material the membrane material (33) is prepared according to a desired shape of the catalytically coated membrane (19). [8] Method according to any one of the preceding claims, characterized by , that catalytic material applied to the membrane material (33) in areas outside the catalytically coated membrane (19) is removed from the membrane material and recycled. [9] Membrane electrode assembly (15) comprising a catalytically coated membrane (19) produced by a method according to any one of claims 1 to 8, and operating medium ports (22-27) arranged outside the active area (20) of the catalytically coated membrane (19) for supplying and removing operating medium of the fuel cell (10). [10] Fuel cell stack (100) comprising a plurality of membrane electrode assemblies (15) stacked alternately with bipolar plates (16) according to claim 9.

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