Plate arrangement for an electrochemical system and method for manufacturing a plate arrangement

Abstract

A plate arrangement (1) for an electrochemical system, for example a fuel cell or electrolysis system, comprises a bipolar plate (3) through which parallel channels (4) are formed. The plate arrangement (1) further comprises a proton-permeable membrane (13) spaced parallel to the bipolar plate (3), in which grooves (9) are located that are congruent with the aforementioned channels (4) and are filled with a catalytic coating (8).

Description

[0001] The invention relates to a plate arrangement intended for use in an electrochemical system. The invention further relates to a method for manufacturing such a plate arrangement.

[0002] DE 10 2022 110 834 A1 discloses a fuel cell system and a method for manufacturing a plate arrangement for a fuel cell stack. In particular, DE 10 2022 110 834 A1 addresses sealing arrangements within a cell stack.

[0003] German patent DE 10 2005 051 162 A1 relates to an ion-conducting polymer electrolyte membrane intended for use in an electrolysis cell. The polymer electrolyte membrane is composed of several polymer electrolyte membrane materials and has a three-dimensional structure. The polymer electrolyte membrane materials contain an ionomer that has sulfonic acid, carboxylic acid, and / or phosphonic acid groups.

[0004] US 2007 / 0026291 A1 proposes creating ribbed surface structures on membranes using tools with corresponding counter-contours. US 2005 / 0181252 A1 states that the surface area of ​​a membrane for an electrochemical system can be increased using chemical or physical deposition processes. EP 1 171 924 B1 mentions, among other things, roughening a membrane as a possible processing step before applying a catalyst layer.

[0005] Various membranes designed for electrochemical systems, which feature microstructuring, for example in the form of microholes, are described in documents JP 2005-174565 A, WO 2004 / 001876 A2 and US 2023 / 0253595 A1.

[0006] US patent 2018 / 0331380 A1 discloses a device and a method for manufacturing membrane electrode assemblies for fuel cells. In this method, web-shaped material is unwound from a roll and passed through various processing stations.

[0007] WO 2006 / 065618 A2 describes an electrolyte plate with a striped pattern. The electrolyte plate is made of a polycrystalline ceramic. The possible thickness of the electrolyte plate is specified as ranging from 5 micrometers to 100 micrometers.

[0008] The invention is based on the objective of further developing plate arrangements for electrochemical systems compared to the aforementioned prior art, whereby a particularly good utilization of the available installation space for the desired electrochemical reactions as well as economical material use is sought.

[0009] This problem is solved according to the invention by a plate arrangement having the features of claim 1. Likewise, the problem is solved by a method designed according to claim 7 for producing a plate arrangement for an electrochemical system.

[0010] The plate arrangement is designed, for example, for use in a fuel cell system or an electrolysis system and comprises a bipolar plate through which parallel channels are formed. Cooling and / or operating media of the electrochemical system can flow through these channels. Furthermore, the plate arrangement according to the application comprises a proton-permeable membrane spaced parallel to the bipolar plate, in which grooves are located that are congruent with the aforementioned channels and are filled with a catalytic coating.

[0011] The medium flowing in the channels formed by the bipolar plate flows parallel to the strip-shaped, catalytically active areas. Each channel can have a cross-section open towards the catalytic coating of the membrane. Thus, the catalytically coated membrane covers one side of the channel's cross-section, while the remaining channel cross-section is defined by the bipolar plate. Optionally, a permeable material layer is inserted between the channel and the catalytically active surface of the membrane. This material layer can be a gas diffusion layer and / or a porous transport layer. In any case, the strip shape of the catalytic coating, adapted to the channels, ensures efficient use of the coating material. The membrane surface facing the bipolar plate, including the catalytic coating, can be completely flat.

[0012] Optionally, the catalytic coating can also cover the membrane surface areas located between the grooves. The catalytic coating can form a closed, flat surface, meaning that the coating has a certain thickness within the grooves, while the same coating is present in a comparatively thinner layer outside the grooves. This is particularly useful in cases where, as mentioned earlier, a fluid-permeable material layer (i.e., liquids and / or gases) is located between the membrane and the bipolar plate. In such cases, the fluid flowing through the channel can also reach areas of the coating located laterally to the channel via the permeable material layer.In comparison to the catalytically coated area located directly on the side of the permeable material layer opposite the channel, i.e., in the area of ​​the groove, the coating areas located laterally next to the channel are exposed to relatively little fluid. Thus, the thickness of the catalytic coating is adapted to the fluid flow reaching the membrane.

[0013] For example, the maximum thickness of the catalytic coating within the grooves is at least twice and at most five times the minimum thickness of the catalytic coating outside the grooves. Regardless of the presence of a permeable material layer between the membrane and the bipolar plate, both the membrane (considered here without a coating) and the bipolar plate can have a ribbed shape, with ribs formed by strip-shaped protrusions between the grooves or between the channels.

[0014] The height of the channel, measured in the stacking direction of the plate arrangement, i.e. in the normal direction to the mutually parallel planes in which the bipolar plate and the membrane lie, deviates from the sum of the thickness of the permeable material layer and the maximum thickness of the catalytic coating, for example, by no more than 30%.

[0015] The patented method for manufacturing a plate arrangement for an electrochemical system is characterized by the fact that grooves are formed in a membrane and the surface of the membrane, including the grooves, is provided with a catalytic coating such that a flat surface is created. Subsequently, a permeable material layer is applied to this catalytically active surface. Finally, a bipolar plate provided with channels is placed on the permeable material layer such that the channels, which are open towards the permeable material layer, are aligned with the grooves in the membrane.

[0016] The grooves in the membrane can be created, for example, by plasma etching. Plasma etching, also known as plasma-assisted ion etching, involves material removal through the impact of ions on a surface. For further technical background, see, for example, documents EP 1 255 690 B1 and DE 10 2007 018 010 A1.

[0017] It is also possible to introduce grooves into the membrane surface using photochemical methods. Such methods are described, for example, in documents DE 10 2016 219 732 A1 and DE 10 2016 219 733 A1. Grooves can also be created by mechanical processing.

[0018] Regarding the formation of the channels in the bipolar plate, established technologies can be used, including forming processes and additive manufacturing. In this context, reference is made to documents WO 2022 / 268256 A1 and WO 2024 / 041685 A1 as examples.

[0019] An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing shows: Fig. 1. A plate arrangement of an electrochemical system in a sectional view, Fig. 2 an excerpt from the arrangement according Fig. 1, Fig. 3. In a diagram, the spatial dependence of the concentration of different substances within the plate arrangement according to Fig. 1.

[0020] A plate arrangement, designated as a whole by reference numeral 1, is intended for use in an electrochemical system not shown, for example in a fuel cell system or in an electrolyzer for producing hydrogen from water.

[0021] The plate arrangement 1 is used in a stacked arrangement of electrochemical cells 2, referred to as a stack 10, i.e., in a cell stack 10, and comprises a bipolar plate 3 which separates a half-cell of a first electrochemical cell 2 from a half-cell of another identical electrochemical cell 2. The cell stack 10 comprises a plurality of cells 2, although means for clamping the cells 2 are not shown.

[0022] Through bipolar plate 3, as can be seen from the Fig. 1 and Fig. 2, several channels 4 are formed, which in this case have a trapezoidal cross-section. The parallel channels, arranged according to the Fig. 1 and Fig. Two downward-facing channels 4 are permeable to operating and / or cooling media of the electrochemical system to which the plate arrangement 1 belongs. Where geometric terms such as "bottom" or "top" are used in this text, they refer only to the arrangements illustrated in the figures and do not imply any statement about the actual orientation of the components of the plate arrangement 1 in space. For example, plate-shaped components, such as the bipolar plate 3, can be vertically oriented.

[0023] The channels 4 are formed by a structuring 5 of the bipolar plate 3. The structuring 5 can be produced, in particular, by forming processes, whereby the bipolar plate 3 can be constructed in one or more parts. The channel width is specified as B4, and the channel height as H4. The channels 4 are separated from each other by ribs 6 of the bipolar plate 3, which are also formed by the structuring 5. The undersides of the ribs 6 lie in a common plane that is tangent to a surface of a permeable material layer 7. The permeable material layer 7 can be composed of a single material or a mixed material and may include a gas diffusion layer and / or a porous transport layer.

[0024] Between the half-cells of the same electrochemical cell 2 is a proton-permeable membrane 13, which is provided with a catalytic coating 8. The permeable material layer 7, whose thickness is specified as H7, rests on the membrane 13. Grooves 9 are formed in the membrane 13, the width B9 of which, in the exemplary embodiment, corresponds to the width B4 of a channel 4 above it. Each groove 9 runs parallel below a channel 4, so that there is a congruent arrangement of channels 4 and grooves 9.

[0025] The catalytic coating 8 fills both the grooves 9 and the surface areas of the membrane 13 located between the grooves 9 in such a way that the coating 8 has a completely flat surface. The permeable material layer 7 lies completely on the coating 8.

[0026] The ones with H8 maxThe maximum thickness of the coating 8 is given in the groove 9. With H8 min The minimum thickness of the coating 8 to be measured between adjacent grooves 9 is designated. In the exemplary embodiment according to the Fig. The maximum thickness is H8 for 1 to 3. max at least twice and at most five times the minimum thickness H8 min the catalytic coating 8. At the same time, the maximum thickness corresponds to H8 max less than half of the total thickness of the membrane 13, including the coating 8. Areas of the coating 8 that fill the groove 9 are to be understood as areas 12 of high catalyst concentration CC. In contrast, the areas located between each pair of grooves 9, which represent the minimum thickness H8 min The strip-shaped areas of the coating represent areas 11 with low catalyst concentration CC.

[0027] The height H4 of the channel 4, to be measured in the stacking direction of the plate arrangement, in this case in the vertical direction, deviates from the sum of the thickness H7 of the permeable material layer 7 and the maximum thickness H8. max The catalytic coating 8 deviates by no more than 30%. Channel 4, like groove 9, has a trapezoidal cross-section. The flanks of channel 4 are designated 14, and the flanks of groove 9 are designated 15.

[0028] The trapezoidal shape of groove 3 is also reflected in the diagram. Fig. Figure 3 shows, among other things, the spatially dependent profile VC of the catalyst concentration. The x-axis is oriented orthogonally to the groove 9 and the channel 4, lying in the same plane as the membrane 13.

[0029] In addition to the concentration profile VC, which refers to the catalyst contained in coating 8, in Fig. Figure 3 shows an idealized concentration profile VR, which refers to a reactant located in the electrochemical cell 2. In the middle of the section of the plate arrangement 1 according to the Fig. 2 and Fig. 3, that is, in the middle region of channel 4 and the underlying permeable material layer 7, the concentration profile VR exhibits a maximum. Through the permeable material layer 7, and also laterally adjacent to channel 4, reactant is distributed into cell 2, as shown in Fig. 3 is indicated.

[0030] This means that the reactant reaches the entire surface of the coating 8, but not in a uniform distribution. Rather, the concentration of the reactant, generally denoted by CR, decreases from an area located centrally under channel 4 to the areas to the sides of channel 4. This results in a concentration profile, which is expressed as the curved VR curve of the reactant concentration. As shown from Fig. As can be clearly seen in Figure 3, the concentration profile VC of the catalyst approximately reflects the concentration profile VR of the reactant. The catalyst, which enables or accelerates the electrochemical reactions taking place in the cells 2 of the stack 10, is thus distributed in the coating 8 according to requirements. Reference symbol list 1. Plate arrangement 2 electrochemical cells 3 Bipolar plate 4-channel 5. Structuring 6th rib 7 permeable material layer 8 catalytic coating 9 grooves in the membrane 10 cell stacks, Stack 11. Low catalyst concentration range 12 Area of ​​high catalyst concentration 13 Membran 14. Flank of the canal 15 Flank of the groove B4 Channel width B9 Width of the groove CC concentration of a catalyst CR concentration of a reactant H4 Height of the canal H7 Material layer thickness H8 min minimum coating thickness H8 max maximum coating thickness x x-direction, perpendicular to the canal VC concentration profile catalyst VR concentration profile reactant

Claims

[1] Plate arrangement (1) for an electrochemical system comprising a bipolar plate (3) through which parallel channels (4) are formed, and a proton-permeable membrane (13) spaced parallel to the bipolar plate (3), in which grooves (9) corresponding to the said channels (4) are located and which are filled with a catalytic coating (8). [2] Plate arrangement (1) according to claim 1, characterized by , that the catalytic coating (8) also covers the surface areas of the membrane (13) located between the grooves (9). [3] Plate arrangement (1) according to claim 2, characterized by , that the catalytic coating (8) has a flat surface. [4] Plate arrangement (1) according to claim 3, characterized by , that the maximum thickness (H8) given in the grooves (9) max) the catalytic coating (8) at least twice and at most five times the minimum thickness (H8) given outside the grooves (9) min ) of the catalytic coating (8). [5] Plate arrangement (1) according to any one of claims 1 to 4, characterized by a permeable material layer (7) located between the membrane (13) and the bipolar plate (3). [6] Plate arrangement (1) according to any one of claims 1 to 5, characterized by , that the height (H4) of the channel (4) to be measured in the stacking direction of the plate arrangement (1) is the sum of the thickness (H7) of the permeable material layer (7) and the maximum thickness (H8) max ) the catalytic coating (8) does not deviate by more than 30%. [7] Method for producing a plate arrangement (1) for an electrochemical system, wherein grooves (9) are provided in a membrane (13), the surface of the membrane (13) including the grooves (9) is provided with a catalytic coating (8) such that a flat surface is formed, a permeable material layer (7) is applied to this surface, and a bipolar plate (3) provided with channels (4) is placed on the said material layer (7) such that the channels (4) are in an identical arrangement with the grooves (9) in the membrane (13). [8] Method according to claim 7, characterized by , that the grooves (9) are produced by plasma etching. [9] Method according to claim 7, characterized by , that the grooves (9) are produced by photochemical processing. [10] Method according to claim 7, characterized by , that the grooves (9) are produced by mechanical processing.

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