Electrolytic cell having optimized contacting of a catalyst layer

Abstract

The invention relates to an electrolytic cell (01) for the electrolysis of CO2, comprising a cathode side (02) and an anode side (03). The electrolytic cell (01) comprises a cathode plate (04), a gas chamber (06), a gas-diffusion layer (08), a catalyst layer (09), a water chamber (07) and an anode plate (05). The contacting of the catalyst layer (09) is optimized by using a plurality of current bridges (10). To this end, these current bridges (10) are electrically conductively connected to the cathode plate (04) and to the catalyst layer (09) while penetrating the gas-diffusion layer (08).

Description

Description TITLE Electrolysis cell with optimized contacting of a catalyst layer TECHNICAL FIELD

[0001] The invention relates to an electrolysis cell for the electrolysis of CO2. This cell comprises a gas chamber containing CO2 and a water chamber containing an electrolyte, which are separated from each other by a gas diffusion layer and a catalyst layer. Contacting of the catalyst layer is required. BACKGROUND D

[0002] Renewable electricity, such as solar and wind power, can be provided in some locations in quantities that exceed local demand. The effective use of available electricity is problematic in this case. One possibility is the electrolysis of water to produce hydrogen and oxygen. However, the storage and transport of hydrogen are problematic. Furthermore, it is known that available renewable electricity can be utilized through the electrochemical conversion of CO2, thereby capturing the greenhouse gas CO2 as a product. The electrochemical reduction reaction of carbon dioxide (CO2) to hydrocarbons through CO2 electrolysis represents a promising alternative to other energy storage strategies.

[0003] For the reduction of CO2, electrolysis cells are used, which have an anode side and a cathode side. On the anode side, there is an anode, which is in contact with a liquid electrolyte. On the cathode side, there is the cathode, which is in contact with the CO2 to be reduced. In the electrolysis cell used regularly, there is a cavity on the cathode side for the CO2 and on the On the anode side, a cavity is arranged to hold the electrolyte, which is separated from each other by a gas diffusion electrode.

[0004] The general functioning of an electrolysis cell for the electrolysis of CO2 is well known to those skilled in the art. It is described, for example, in WO 2023 217624 A1 or WO 2019 096985 A1. It has proven advantageous if the gas diffusion electrode is formed by a non-conductive gas diffusion layer and a conductive catalyst layer. This requires contact with the catalyst layer from the cathode side. Contact with the catalyst layer is usually made along the peripheral edge of the catalyst layer, for example, by applying copper strips. Provided the electrolysis cell is small, a sufficiently uniform voltage distribution across the surface of the catalyst layer can be achieved.

[0007] The problem is the limited conductivity of the catalyst layer and the thin layer thickness typically used for the catalyst layer. Combined with the need to provide a sufficient surface area for practical application, a sufficient and, in particular, uniform voltage between the catalyst layer and the anode cannot be easily guaranteed. To solve the problem, known designs propose arranging a conductive grid, for example made of copper, on the catalyst layer opposite the gas diffusion layer, i.e. on the anode side in the electrolyte.

[0009] However, this arrangement has several disadvantages. On the one hand, the Arrangement of the conductive grid in the electrolyte can have a detrimental effect on the electrochemical process. Another disadvantage is the lower Distance from the anode to the conductive grid relative to the distance from the anode to the catalyst layer. Furthermore, the effective area of ​​the catalyst layer is reduced by the grid. SUMMARY OF THE INVENTION

[0010] The object of the present invention is to provide the most uniform voltage possible across the surface of the catalyst layer. The effective available area of ​​the catalyst layer should be as large as possible.

[0011] The object is achieved by an embodiment of the invention according to the teaching of claim 1. Advantageous embodiments are the subject of the subclaims.

[0012] The generic electrolysis cell is intended for the electrolysis of CO2. It has a cathode side and an opposite anode side. Starting from the cathode side, in direct or indirect succession, the electrolysis cell comprises - a cathode plate, - a gas chamber, - a gas diffusion layer, - a catalyst layer, - a water chamber, and - an anode plate.

[0013] The cathode plate, together with the anode plate, forms the end of the electrolysis cell on both sides.

[0014] The gas chamber is a cavity in the electrolysis cell to which CO2 is normally supplied during operation. The water chamber is another cavity that contains an electrolyte during operation. The gas diffusion layer, together with the catalyst layer, forms a gas diffusion electrode. This separates the gas chamber from the water chamber. For functional reasons, the gas diffusion layer must be permeable to CO2 but prevent the passage of liquid.

[0016] The gas diffusion layer is particularly advantageously electrically non-conductive. To this end, it consists of an electrically non-conductive material or at least has an electrically non-conductive coating. In contrast, the catalyst layer is particularly advantageously electrically conductive. To this end, it consists of an electrically conductive material or at least has an electrically conductive coating.

[0018] Accordingly, an advantageous gas diffusion electrode in this case is formed by a non-conductive gas diffusion layer and a conductive catalyst layer.

[0019] Furthermore, it is possible to construct the catalyst layer or the gas diffusion layer in multiple layers. Reference is made to the known prior art for possible and advantageous layer structures. [G02Cj It is obvious that the gas chamber, the gas diffusion layer, the catalyst layer, and the water chamber must advantageously be sealed circumferentially in order to realize the gas chamber and the water chamber as cavities. It is obvious that appropriate connections are necessary for the introduction and discharge of fluids into and from the gas chamber and water chamber, respectively.

[0021] In a simple and advantageous manner, the gas chamber is directly adjacent to the cathode plate.

[0022] It is particularly advantageous if the gas diffusion layer is adjacent to the gas chamber.

[0023] Effective CO2 electrolysis can be achieved if the catalyst layer is directly adjacent to the gas diffusion layer.

[0024] It is particularly advantageous if the water chamber is adjacent to the catalyst layer.

[0025] In a simple and advantageous way, the water chamber is adjacent to the anode plate.

[0026] Preferably, the anode plate also serves as the anode of the electrolysis cell. For functional reasons, it is necessary that a voltage can be applied to the electrolysis cell. It is particularly advantageous if the power connection to the electrolysis cell is made at the anode plate on the anode side and at the cathode plate on the cathode side. In order to achieve the most uniform voltage distribution possible on the catalyst layer and to reduce the disadvantages caused by a conductive grid on the anode side, it is further provided that several current bridges penetrate the gas diffusion layer and thereby establish an electrically conductive connection from the catalyst layer directly or indirectly to the cathode plate.

[0029] This design distributes the current flow to the catalyst layer across multiple current bridges, eliminating the need for a corresponding feed from the outer edge of the catalyst layer into the surface of the catalyst layer. This eliminates the need to arrange a conductive grid extending from the edge of the catalyst layer into the water chamber and thus into the electrolyte. This allows for flexible dimensioning of the electrolysis cell and eliminates the limitation to small sizes. [G030] Obviously and advantageously, the peripheral edge of the catalyst layer can be electrically contacted so that the edge region of the catalyst layer is supplied with voltage.

[0031] Contacting the catalyst layer by means of the current bridges can be optimized if the respective current bridge penetrates the catalyst layer. Accordingly, it is further envisaged that at least the majority of the current bridges penetrate the catalyst layer.

[0032] The design in which at least the majority of the current bridges penetrate the catalyst layer particularly advantageously opens up the possibility of arranging an electrically conductive element on the anode side of the catalyst layer, covering the current bridges in sections. Thus, the additional element can further improve contact with the catalyst layer.

[0033] However, the reduction of the effective area due to the additional element must be taken into account and accordingly this should only be chosen to be large enough to ensure reliable contact of the catalyst layer at the respective current bridge.

[0034] According to the invention, optimized contacting is achieved by using cross connections which each electrically connect at least two current bridges to one another and at the same time, with a system on the anode side of the catalyst layer, bring about additional contacting of the catalyst layer.

[0035] Preferably, a cross-connection connects two current bridges, with multiple cross-connections being present. It can also be provided that a cross-connection connects, for example, three or four current bridges. Furthermore, it can be provided that a cross-connection is connected to a plurality of current bridges. It is essential for the invention that connections are present between the current bridges on the anode side, which in this case are in contact with the catalyst layer, but keep the covered area of ​​the catalyst layer as small as possible.

[0036] To ensure a defined distance between the cathode plate and the gas diffusion layer, especially to secure the position of the gas diffusion layer and the width of the gas chamber, it is particularly advantageous to use contact sockets as spacers. On the one hand, it is necessary that the contact sockets are connected to the cathode plate. Opposite, the contact sockets are provided on the gas diffusion layer. It is obvious that the contact sockets are located in the gas chamber or penetrate it.

[0037] The contact sockets can be implemented in various ways. For example, they can be inserted into a respective receptacle in the cathode plate using a plug connection. However, it is advantageous if the contact bases are firmly connected to the cathode plate, thus simplifying handling during the manufacturing process. Fixation is possible, for example, using a screw connection. However, it is particularly advantageous if the cathode plate and the contact bases are manufactured as a single piece or integrally. This can be achieved, for example, using a casting process or an additive manufacturing process. The contact sockets particularly advantageously enable an electrically conductive connection between the cathode plate and the current bridges. Obviously, this requires an electrically conductive connection between the cathode plate and the contact sockets. Accordingly, it is particularly advantageous if the current bridges are electrically connected to the contact sockets. Since the current bridges penetrate the gas diffusion layer and the contact sockets are in contact with the gas diffusion layer, this reduces the required size of the current bridges. The electrically conductive connection of the current bridges with the cathode plate in the presence of contact sockets can be realized in different ways.

[0041] In a particularly advantageous embodiment, it is provided that the current bridges are releasably inserted into receptacles in the contact sockets. This allows greater design freedom for contacting the catalyst layer through the current bridges.

[0042] In an alternative variant, the current bridges are permanently connected to the contact sockets. Similar to the connection of the contact sockets to the cathode plate, this can be achieved, for example, by a screw connection. A one-piece or integral construction of the contact sockets with the current bridges is also possible.

[0043] It is not absolutely necessary for each current bridge to be connected to a cross connection. Rather, it can advantageously be provided that a bridgehead is arranged on each of the current bridges that are not provided with a cross connection. This bridgehead, in the form of a disk, is electrically connected to the respective current bridge and to the catalyst layer surrounding the current bridge. In this respect, some of the current bridges are electrically connected to a cross connection, while others have a bridgehead.

[0044] In order to connect the bridgeheads and / or the cross-connections to the current bridges, it can be provided, on the one hand, that the electrically conductive connection is established by placing the bridgeheads and / or the cross-connections on the current bridges. The aforementioned connection of the bridgeheads and / or the at least one cross connection with contact with the current bridges is particularly advantageous in the case when, in combination, the current bridges are firmly connected to the contact sockets. Alternatively, it is particularly advantageous if the bridgeheads and / or the cross connections are firmly and / or integrally connected to the current bridges.

[0047] The fixed connection of the bridge heads and / or the cross connections with the current bridges is particularly advantageous if the current bridges are releasably inserted into the contact sockets.

[0048] In any case, it is particularly advantageous if there is no conductive connection in the water chamber from the current bridges and cross-connections, and if present, the bridgeheads, to the electrolyte. For this purpose, an electrically non-conductive coating can be provided, for example.

[0049] If an electrically non-conductive coating is specified, an electrically non-conductive cover or sheath can always be provided as an alternative. However, a small size for electrical insulation is advantageously achieved with an electrically non-conductive coating.

[0050] Furthermore, depending on the dimensions of the electrolysis cell and the stiffness of the gas diffusion layer and the catalyst layer, it may be advantageous to place at least one spacer in the water chamber. This requires that the spacer be positioned at a defined position between the anode plate and the catalyst layer.

[0051] The spacer is intended to ensure that the distance between the anode plate and the catalyst layer does not change due to deformation of the catalyst layer.

[0052] In conjunction with the contact bases, the spacer can be used to reliably define the position of the catalyst layer and the gas diffusion layer. This ensures that the catalyst layer adheres evenly to the gas diffusion layer. In a first option, several spacers can be arranged in the water chamber. The spacers are to be firmly connected to the anode plate so that its position is fixed.

[0054] A second option may involve inserting a one-piece spacer between the anode plate and the catalyst layer in the water chamber. To ensure the most unobstructed flow possible in the water chamber, the spacer should be designed in a grid-like manner. The overlapping area of ​​the anode plate and the catalyst layer should be as small as possible, and the grid-like spacer should otherwise be spaced apart from the anode plate and, in particular, the catalyst layer.

[0055] In both cases, it is particularly advantageous if the spacer rests on the catalyst layer side against the respective current bridges and partially surrounds the current bridges on the catalyst layer. The spacer is advantageously placed on the bridgeheads or on the cross connections, at least at the position of the current bridges.

[0056] Particularly advantageously, the contact between the bridgeheads and / or the cross-connections on the catalyst layer can be improved by placing one or more spacers on the bridgeheads and / or the cross-connections. It is advantageously possible to arrange the bridgeheads and / or the cross-connections firmly on the grid-shaped spacer or the multiple spacers connected to the anode plate. This simplifies handling during the assembly process. For example, the bridgeheads and / or the cross-connections can be attached using an adhesive bond.

[0058] Especially when a grid-shaped spacer is used, it is particularly advantageous if the bridgeheads and / or the cross-connections are firmly connected. Depending on the manufacturing process, these can be cast into the cathode side. Alternatively, the spacer can be made of a conductive material that forms the bridgeheads and / or the at least one cross-connection on the cathode side and is insulated from the anode plate.

[0059] If a spacer is used and its core is made of a conductive material, it is particularly advantageous to ensure that there is no conductive connection from the spacer to the electrolyte in the water chamber. To this end, the spacer should preferably be provided with a non-electrically conductive coating (or other electrical insulation) on the side facing the water chamber.

[0060] Likewise, if present, there must be no conductive connection from the current bridges to the anode plate via the spacer. To this end, if the core of the spacer is made of a conductive material, the surface facing the anode plate and / or the catalyst layer must also be provided with an electrically non-conductive coating (or other electrical insulation).

[0061] As an alternative to electrically connecting the current bridges to the cathode plate via contact bases, it is possible to provide at least one current distributor. The current distributor is attached to the cathode plate to determine its position and for electrical connection. Furthermore, at least two current bridges are electrically connected to a current distributor. Preferably, one current distributor is provided for each of four contacted current bridges. It is irrelevant whether contact bases are present to support the gas diffusion layer.

[0062] In the simple version, the current distributor is essentially located in the gas chamber, similar to the version with the contact sockets.

[0063] The use of a current distributor preferably allows for an elastic design, allowing elastic deformation of the current distributor between the current bridges and the cathode plate. This prevents excessive compressive stress due to different dimensions and / or thermal expansion in the electrolysis cell—particularly when the spacing is determined by an external housing.

[0064] In this case, the gas diffusion layer can also be supported by the elastic current distributor. This also allows its position and contact with the catalyst layer to be more effectively secured without the need for additional contact bases. For the electrically conductive connection of the current bridges to the current distributor, it can be provided that the current bridges rest loosely on the current distributor. This is particularly advantageous if the current bridges are provided with firmly connected bridgeheads and / or cross connections. This enables easier installation of the current bridges through the catalyst layer and the gas diffusion layer, starting from the anode side opposite the current distributor on the cathode side. Alternatively, the current bridges can be permanently connected to the current distributor. This requires the current distributor and the current bridges to be mounted from the cathode side through the gas diffusion layer. The number of current bridges per surface area of ​​the catalyst layer can be varied. The larger the number, the more even the voltage distribution across the surface of the catalyst layer will be. However, the problem arises that with an increasing number of current bridges, the effective area of ​​the catalyst layer decreases. Furthermore, a high number of current bridges increases the complexity of manufacturing the electrolysis cell. [0068J It has therefore proven advantageous to provide at least one current bridge per 10 cm2, based on the area of ​​the catalyst layer. In contrast, the number of current bridges should not be greater than one current bridge per 1 cm2. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] FIG 1 shows a schematic cross-sectional view of a first exemplary embodiment of the structure of an electrolytic cell according to the invention. The connection from the current bridges to the cathode plate is established via contact bases.

[0070] FIG. 2 shows a schematic cross-sectional view of a third exemplary embodiment of the structure of an electrolytic cell according to the invention. Based on the example in FIG. 2, a spacer is additionally arranged in the water chamber.

[0071] FIG 3 shows a schematic cross-sectional view of a fourth exemplary embodiment of the structure of an electrolytic cell according to the invention. Alternatively, several spacers are used here, and current distributors are provided in the gas chamber instead of contact sockets. DESCRIPTION OF THE EMBODIMENT

[0072] Figure 1 schematically outlines the structure of a first exemplary embodiment of an electrolysis cell 11 according to the invention. The simplified sketch shows the structure of the electrolysis cell 11 in the sequence from the cathode side 02 to the anode side 03.

[0073] On the cathode side 02 is the cathode plate 14 with the adjacent gas chamber 06. Furthermore, contact bases 16 are integrally attached to the cathode plate 14. These 16 are present at the positions where the current bridges 20 are located.

[0074] It is provided that the contact bases 16 rest against the gas diffusion layer 08 and thus the position of the gas diffusion layer 08 on the cathode side 02 is fixed.

[0075] The current bridges 20 on the anode side 03 of the catalyst layer 09 are either provided with bridgeheads 18 or connected according to the invention with a cross connection 19.

[0076] The bridgeheads 18 are electrically conductively connected to the catalyst layer 09 in a ring-shaped manner around the current bridges 20. The cross connection 19 is also provided with an electrically conductive connection in the area between two current bridges 20 on the catalyst layer 09, either pointwise or linearly.

[0077] This embodiment significantly improves the contacting of the catalyst layer 09. The coverage of the effective area of ​​the catalyst layer 09 must be taken into account, so that the bridgeheads 18 and the cross connection 19 are selected to be only large enough to ensure reliable contacting of the catalyst layer 09 starting from the current bridges 20.

[0078] The arrangement of the contact bases 16 in conjunction with the design of the current bridges 20 with integral bridge head 18 or cross connection 19 enables the continuous contacting of the current bridges 20 with the contact bases 16 by using a plug connection.

[0079] If the position of the current bridges 20 is reliably determined by the plug connection after assembly, this solution can also secure the position of the catalyst layer 09 and the gas diffusion layer 08 in the electrolysis cell 11. Figure 2 schematically outlines another embodiment of an electrolysis cell 21 according to the invention based on the previous example. Therefore, only the differences from the previous embodiment in Figure 2 will be discussed.

[0081] In this embodiment, it is provided that a grid-shaped spacer 17 is located in the water chamber 07. Use of a grid-like shape for the spacer 17 to avoid, if possible, obstruction of the free flow in the water chamber 07.

[0082] At least it is provided that the spacer 17 has a defined position in the water chamber 07. It is furthermore necessary that on the anode side 03 there is a contact with the anode plate 05 and opposite on the cathode side 02 there is a contact at the position of a current bridge 20. In this embodiment, the spacer 17 is provided to cover the respective bridgeheads 18 and cross connection 19. For this purpose, it can also be provided that the current bridges 20 are previously attached to the bridgeheads 18 and cross connection, respectively, on the spacer 17, for example by gluing. Furthermore, it can be seen that the spacer encloses the bridgeheads 18 and the cross connection 19, pointing toward the water chamber 07. When an electrically non-conductive material is used for the spacer 17, an electrically conductive connection from the bridgeheads 18 to the electrolyte in the water chamber 07 is thus prevented.

[0085] Figure 3 outlines another exemplary embodiment of an electrolysis cell 31 based on experience. In contrast to the two previous exemplary embodiments, the use of contact bases is omitted in this case. To realize the electrically conductive connection from the current bridges 20 to the cathode plate 04, this exemplary embodiment provides for the use of current distributors 26. These 26 are attached to the cathode plate 04 and are otherwise located in the gas chamber 06, similar to the contact sockets. This exemplary embodiment now provides for four current bridges 20 to each be electrically conductively connected to a current distributor 26.

[0087] Furthermore, it is provided that the current distributors 26 are designed to be elastically deformable, so that inaccuracies in the position of the current bridges 20 adjacent to the current distributors 26, for example due to tolerances or thermal bonds, can be compensated for. Furthermore, in this exemplary embodiment, instead of a grid-shaped spacer, a plurality of spacers 27 are now used, each of which is integrally attached to the anode plate 25. [00891 To prevent an electrically conductive connection between the spacers 27 and the electrolyte in the water chamber 07, it is further provided that the spacers 27 have an electrically non-conductive coating 28 on the side facing the water chamber 07 and on the side facing the cathode side 02. [00901 Furthermore, in order to simplify assembly, it can also be provided that the respective current bridges 20 are fastened to the bridge heads 18 or cross connection 19, for example by an adhesive connection, to the respective spacers 27.

Claims

Claims 1. Electrolysis cell (01, 1, 21, 31) for the electrolysis of CO2 with a cathode side (02) and an anode side (03) comprising in direct or indirect sequence - a cathode plate (04, 14), - a gas chamber (06), - a gas diffusion layer (08), - a catalyst layer (09), - a water chamber (07), and - an anode plate (05, 25); further comprising a plurality of current bridges (10, 20) which (10, 20) are electrically conductively connected to the cathode plate (04, 14) and the catalyst layer (09) and penetrate the gas diffusion layer (08) and the catalyst layer (09), characterized by cross connections (19) which (18, 19) are each electrically conductively connected to at least two current bridges (20) on the anode side (03) of the catalyst layer (09) and are in conductive contact with the catalyst layer (09).

2. Electrolysis cell (11, 21, 31) according to claim 1, wherein the cross connections (19) are firmly and / or integrally connected to the associated current bridges (20).

3. Electrolysis cell (11, 21, 31) according to claim 2, characterized by contact bases (16) which are connected to the cathode plate (14) and bear against the gas diffusion layer (08); wherein in particular the contact bases (16) are firmly and / or integrally connected to the cathode plate (14).

4. Electrolysis cell (11, 21) according to claim 3, wherein the current bridges (20) are releasably inserted into the contact sockets (16) and are electrically conductively connected.

5. Electrolysis cell (11, 21, 31) according to one of claims 1 to 3, characterized by bridge heads (18), which (18, 19) on the anode side (03) of the catalyst layer (09) are each electrically conductively connected to one of the current bridges (20) and are in conductive contact with the catalyst layer (09).

6. Electrolysis cell (11, 21, 31) according to claim 5, wherein the bridge heads (18) are firmly and / or integrally connected to the current bridges (20).

7. Electrolysis cell (11, 21, 31) according to one of claims 1 to 6, wherein the current bridges (10) and / or the bridge heads (18) and / or the cross connection (19) facing the water chamber (07) have a non-conductive coating.

8. Electrolysis cell (21, 31) according to one of claims 1 to 7, characterized by at least one spacer (17) which is fixed between the anode plate (05) and the catalyst layer (09) in the water chamber (07).

9. Electrolysis cell (21, 31) according to claim 8, wherein a plurality of spacers (27) are fixedly connected to the anode plate (25).

10. Electrolysis cell (21, 31) according to claim 8, wherein the spacer (17) is designed in the shape of a grid.

11. Electrolysis cell (21, 31) according to one of claims 8 to 10, wherein the spacer (17, 27) comprises the bridgeheads (18) and / or the cross connection (19).

12. Electrolysis cell (11, 21, 31) according to one of claims 8 to 10, wherein the spacer (17, 27) consists of an electrically non-conductive material or has a non-conductive coating (28) at least facing the water chamber (07).

13. Electrolysis cell (31) according to one of claims 1 to 12, characterized by a current distributor (26) which is attached to the cathode plate (04) and which is electrically connected to a plurality of current bridges (20).

14. Electrolysis cell (31) according to claim 13, wherein the current distributor (26) enables elastic deformation between the cathode plate (04) and the current bridges (20).

15. Electrolysis cell (01, 11, 21, 31) according to one of claims 1 to 14, wherein, based on the area of ​​the catalyst layer (09), there is at least one current bridge (10, 20) per 10 cm2 and a maximum of one current bridge (10, 20) per 1 cm2.

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