SEPARATOR PLATE, ELECTROCHEMICAL CELL AND ELECTROLYZER

Abstract

The present disclosure relates to a separator plate for an electrolyzer having a first layer with at least one through-opening for a fluid and an active region with a set of flow channels for the fluid. A first elastomeric molding with at least one sealing lip is arranged on a first side of the first layer at least partially surrounding the through-opening. The sealing lip extends at least partially along a peripheral edge of the through-opening. A second elastomeric molding surrounding the through-opening is arranged on a second side of the first layer, with a set of ribs which form grooves between them as flow channels for the fluid. For each flow channel, one longitudinal end is open to the through-opening and the other is open to the active region. The first layer has a cranked region at a distance from the through-opening and at least partially around the through-opening.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to German Utility Model Application No. 20 2023 102 425.4, entitled “SEPARATOR PLATE, ELECTROCHEMICAL CELL AND ELECTROLYZER”, filed May 4, 2023. The entire contents of the above-identified application is hereby incorporated by reference for all purposes.

TECHNICAL FIELD

The present disclosure relates to a separator plate for an electrolyzer, an electrochemical cell of an electrolyzer and an electrolyzer with such separator plates or electrochemical cells.

BACKGROUND AND SUMMARY

Electrolyzers usually comprise a large number of separator plates arranged in a stack so that each two adjacent separator plates enclose an electrochemically active region and thus form an electrochemical cell. For the electrochemical cells located at the two ends of the stack, the electrochemical cell is formed by such a separator plate and a suitably designed end plate.

An electrochemical cell for an electrolyzer usually comprises an ion-permeable membrane provided with catalyst layers on both sides, a gas diffusion layer, typically made of carbon fleece, arranged between the membrane and one of the separator plates, and a porous transport layer, typically made of sintered titanium, arranged between the membrane and the other separator plate. The active region is typically located in the center with respect to the surface of the separator plates. The membrane essentially extends over this active region. The active region is typically enclosed by a cell frame which, among other things, serves to fix the membrane on the outside and electrically insulate the adjacent separator plates from each other, thus preventing a short circuit.

Single-layer bipolar plates are typically used for electrolyzers, e.g., the bipolar plate has one metallic separator layer. However, it is also possible to use bipolar plates with several separator plates, wherein these separator plates each have a similar shape to the separator plate of a single-layer bipolar plate. In the following, separator plates means separator plates which can be used in single-layer bipolar plates or in double-layer bipolar plates.

The separator plates usually have at least one through-opening, wherein in a stack of an electrochemical system the through-openings of adjacent separator plates form an overall aligned or at least in sections overlapping through-opening through all separator plates as media channels for media supply or for media discharge. These media can, for example, be reactants (e.g. water) or reaction products (e.g. oxygen or hydrogen). Corresponding aligned through-openings may also be formed in the cell frame of an electrochemical cell.

To seal the through-openings or the media channels formed by the through-openings of the separator plates or the cell frames in the media guide area, bead arrangements are usually introduced into the separator plates or the cell frames, which run around one or more of the through-openings in a separator plate or a cell frame and form a closed loop.

The individual separator plates can also have channel structures for supplying the active region of the separator plate with one or more media or for discharging media.

As a result, a sealing bead may be arranged on one side of the separator plate around a through-opening and channel structures extending away from the passage opening may be arranged on the other side of the separator plate in the same area of the separator plate. These can take the form of perforations in a circumferential bead, as described in DE 102 48 531 A1, for example. Two such different structures in the same area of the separator plate are very difficult to form using forming processes, especially with a single-layer separator plate.

Instead of using embossed structures on one side of the separator plate, an elastomeric layer is often injection-molded onto or on the separator plate in the region of the through-openings over the entire surface and/or as edge molding with sealing lips in order to create a seal between the separator plate and adjacent components. Since embossed media guiding structures are present in this area in the prior art, the injection of such an elastomeric sealing compound onto the already embossed sheet metal requires a complex tool contour, which must ensure that overmolding is avoided. In addition, the actual deviations of the embossed contour from the nominal contour (caused by material springback) must be compensated for by the injection mold.

The object of the present disclosure is therefore to provide a separator plate, an electrochemical cell for an electrolyzer and an electrolyzer which can be manufactured simply and inexpensively with a reduced number of manufacturing steps.

This object is solved by the separator plate according to claim 1, the electrochemical cell according to claim 13 and the electrolyzer according to claim 27. Advantageous further embodiments of the separator plate according to the present disclosure and of the electrochemical cell according to the present disclosure are given in the respective dependent claims.

The separator plate for an electrolyzer according to the present disclosure has, as is usual in the prior art, at least one first metallic layer. This first layer in turn has at least one through-opening for a fluid. However, several through-openings for fluids are also possible, wherein the surroundings of these through-openings can be designed partially or completely as described below for the at least one through-opening. In particular, the electrolyzer can have several through-openings for the supply of reactants as well as several through-openings for the discharge of products of the electrochemical reaction.

Adjacent to the through-openings, the metallic layer has an active region in which the electrochemical reaction takes place. As is common in the state of the art, this active region has a set of flow channels to guide the fluid over the separator plate. If the flow channels are embossed into the first metallic layer, for example, the embossings form flow channels on both sides of the separator plate so that fluids can be guided to both sides of the separator plate.

In contrast to the prior art, the separator plate has at least one first elastomeric molding with a sealing lip surrounding the through-opening at least partially, which scaling lip extends at least partially along the peripheral edge of the through-opening. This sealing lip advantageously surrounds the through-opening completely and forms a closed loop and completely seals the through-opening to the active region on its side of the first metallic layer, hereinafter referred to as the “first side”. It is also possible to guide several such sealing lips adjacent to each other along the edge of the through-opening or around the through-opening.

On the second side of the first metallic layer opposite this first side, the through-opening is also surrounded by an elastomeric molding, hereinafter referred to as a second elastomeric molding. This second elastomeric molding now has a set of ribs as a media guiding structure, which form in pairs grooves between them. The ribs run from the through-opening in the direction of the active region. In the same way, the grooves run from the through-opening in the direction of the active region, wherein for each of the flow channels one longitudinal end is open towards the through-opening and the other longitudinal end towards the active region. The grooves form flow channels so that the fluid guided in the through-opening can be guided through the grooves as flow channels in the direction of the active region and up to the active region. In this way, the second elastomeric molding also at least partially surrounds the through-opening on the second side of the first metallic layer, wherein the ribs form the grooves for guiding the fluid and the grooves between these ribs ensure that the fluid is guided from the through-opening to the active region.

The ribs and grooves of the second elastomeric molding can advantageously extend away from the through-opening in the direction of the active region, at least in a section, but can also have any other shape of longitudinal extension.

According to the present disclosure, the first metallic layer of the separator plate according to the present disclosure, but not necessarily of the electrochemical cell or of the electrolyzer, has a cranked region at a distance from the through-opening and at least partially around the through-opening.

Since the sealing of the through-opening and the formation of the media guiding structure in the separator layer according to the present disclosure is achieved entirely by elastomeric molding, it is not necessary to form embossed media guiding structures in this region. In this region, the first metallic layer is substantially smooth at the time of molding of the elastomer, so that molding can be carried out easily on both sides. Above all, simpler mold geometries in the injection mold allow the affected area to be better sealed during the injection molding process, resulting in less elastomer overmolding on the bare separator plate. This form of integral formation of sealing lips and media guiding structures of the separator plate according to the present disclosure eliminates the need for an embossing and/or stamping process in the immediate vicinity of the through-opening, so that one work step can be omitted and the separator plate can be manufactured more cost-effectively. In particular, because an injection molding process is in any case usually required to produce the sealing lips and the media guiding structures can be formed in the same process step.

The arrangement of a cranked region according to the present disclosure, whose offset from the layer plane of the first metallic layer can extend from the through-opening both in the direction of the first side and in the direction of the second side, makes it possible, at least on one side of the separator plate, to continue the surface of the separator layer in an even manner from the elastomeric molding in the direction of the active region and thus to reduce or avoid a height difference on this side at the end of the elastomeric molding.

In a similar way to the sealing lips on the first side of the first metallic layer, the cranked region can extend at a distance from the through-opening around the through-opening, at least partially or also as a closed loop. In particular, it can extend parallel to these sealing lips. If the cranked region is formed in the direction of the first side as seen from the through-opening, the first molding can extend to the cranked region on the first side so that the first molding merges at the same height into the surface of the metallic layer after the cranked region.

In the same way, the cranked region can of course also be designed in such a way that the second elastomeric molding on the second side merges essentially or completely at the same height into the second surface of the first metallic layer in the unpressed state or in the pressed state of the separator layer in an electrolyzer.

The first and second molding can be designed as separate moldings in one or more production steps. However, it is particularly advantageous if the first and second moldings are produced together as an integral molding, with the first molding merging into the second molding, e.g. by the molding surrounding the peripheral edge of the through-opening and merging into the adjacent first or second molding on both sides of the first metallic layer. This type of molding around the edge of the through-opening provides a particularly good seal between the through-opening and adjacent components. It is also possible to design the molding of both sides from one side by means of further openings in the first metallic layer that are different from the through-opening, wherein the elastomer can also be distributed on the opposite side of the first metallic layer during the molding process through this opening.

The second molding can advantageously be designed in such a way that the flow channels formed by it are aligned with the flow channels of the active region in the direction of flow.

A region in which the fluid conducted through the flow channels of the second elastomeric molding can spread and then pass into the flow channels of the active region can be arranged between the flow channels of the second elastomeric molding and the flow channels of the active region. The flow channels of the second elastomeric molding and the flow channels of the active region are therefore spaced apart from each other and form this distribution region between them.

The flow resistance in the flow channels can be influenced by the design of the free cross-section of the flow channels of both the second elastomeric molding and the active region. It is therefore particularly advantageous if the cross-section of the flow channels in the second elastomeric molding is suitably varied in the longitudinal direction of the respective flow channel, for example if it is reduced or enlarged starting from the through-opening in the direction of the active region.

The present disclosure also relates to an electrochemical cell with a first and a second cell frame and a separator plate arranged between these cell frames. The separator plate can be designed completely as described above. However, the cranked region of the separator plate is merely an optional feature for the electrochemical cell according to the present disclosure and is not absolutely necessary.

The present disclosure further provides an electrolyzer comprising a plurality of the previously described separator plates or the previously described electrochemical cells.

An example of an electrolyzer, electrochemical cells according to the present disclosure and separator plates according to the present disclosure is given below. The same and similar reference numbers denote the same and similar elements, so that their description is not always repeated. In the following example, a large number of features are shown in context, which can, however, also be realized individually in addition to the mandatory features of the present disclosure. It is also possible to use such optional features in any combination to improve the present disclosure.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a schematic cross-section of an electrolyzer with electrochemical cells and separator plates.

FIG. 2 shows a second schematic structure of an electrolyzer with electrochemical cells and separator plates in cross-section.

FIG. 3 shows a separator plate in oblique view in cross-section and in detail.

FIG. 4 shows a sectional view of the separator plate in FIG. 3 in detail.

FIG. 5 shows a sectional view of the separator plate in FIG. 3 in detail.

FIG. 6 shows a top view of the first side of the separator plate in FIG. 3 in detail.

FIG. 7 shows a top view of the second side of the separator plate in FIG. 3 in detail.

FIG. 8A shows a separator plate in oblique.

FIG. 8B shows a separator plate in detail.

DETAILED DESCRIPTION

FIG. 1 shows a schematic structure of an electrolyzer 1. This electrolyzer 1 has a plurality of electrochemical cells 2a, 2b, 2c, 2d, which are clamped between two pressure plates 3a and 3b in the form of a stack. The stack is tensioned using threaded rods 4a and 4b, which pass through the pressure plates 3a and 3b.

Furthermore, the electrolyzer has a voltage source 5 with which a voltage can be applied to end plates 11a and 11b via electrical lines 6a and 6b, with which the electrochemical reaction is carried out in the electrochemical cells 2a to 2d.

For example, the electrochemical cell 2b has two cell frames 7b and 7b′, two bipolar plates 12a and 12b with first metallic layers 13a and 13b made of stainless steel or titanium, which enclose between them a sequence of a carbon fleece 19b, a membrane 17b coated on both sides with a catalyst layer 18b or 18b′ and a porous transport layer, PTL, 20b. Flow channels 16aa, 16aa′ and 16ab, 16ab′, etc. are provided in the surfaces of the two bipolar plates 12a and 12b facing each other in an active region 15a and 15b respectively, via which a fluid medium can be fed into or discharged from the space between the bipolar plates 12a and 12b. In the example in FIG. 1, the channels are milled into the bipolar plates. For the transport of the fluid media, through-openings 14a, 14b and 14a′, 14b′ are arranged in the bipolar plates to the side of the flow channels 16aa, 16aa′ and 16ab, 16ab′, which are aligned across several electrochemical cells 2a, 2b, 2c and 2d and enable fluid supply or fluid removal into or out of the spaces between the bipolar plates.

The electrochemical cell 2c is designed in the same way as the electrochemical cell 2b.

The two edge electrochemical cells 2a and 2d do not have a bipolar plate on their sides facing the plates 3a and 3b, but an end plate 11a and 11b, which can be designed and considered as a “half” bipolar plate. The flow channels in the end plates 11a, 11b or the bipolar plates 12a, 12b, 12c form an active region, e.g. active regions 15a, 15b and 15c in the bipolar plates 12a, 12b and 12c, in which the electrochemical reaction takes place at least partially.

The porous transport layers 20a, 20b, 20c and 20d, PTL,—also known as the proton transport layer—are made of sintered titanium, as is common in the prior art. However, other materials may also be used. The present disclosure does not relate to a specific material of the PTL.

FIG. 2 shows a schematic structure of an electrolyzer 1 with embossed bipolar plates 12a to 12d etc., In principle, the design of this electrolyzer 1 is similar to that in FIG. 1. As a representative example, only the electrochemical cell 2a and its components are described in more detail here. In contrast to the structure in FIG. 1, the bipolar plates in FIG. 2 are single-layered and embossed and form the flow channels 16aa, 16aa′, 16ab, 16ab′, 16ac, 16ac′, 16ad, 16ad′, 16ac, 16ac′ etc. due to their embossing. The electrolyzer in FIG. 2 shows essentially the same components as the electrolyzer in FIG. 1. However, the edge electrochemical cells 2a and 2d are not terminated here with a separately designed end plate, but also with a bipolar plate 12a or 12e, which is identical in construction to the other bipolar plates 12b, 12c and 12d.

In the following, a bipolar plate according to the present disclosure is described, which can be used as bipolar plate 12a, 12b or 12c in the electrolyzer of FIG. 2. More general reference signs are therefore sometimes given as reference signs, e.g. the reference sign 12 instead of the reference signs 12a, 12b, 12c etc.

FIG. 3 shows a bipolar plate, which can be used as a bipolar plate 12a, 12b or 12c in the electrolyzer of FIG. 1, in a section which represents an edge 25 of a through-opening 14. At a distance from the edge 25, a set of flow channels 16 is embossed into the bipolar plate 12 in a flow region 15 in such a way that the embossments protrude on a second side of the bipolar plate and channels 16a to 16e are formed between these embossments on the second side 24 of the first metallic layer 13 of the bipolar plate 12.

According to the present disclosure, the bipolar plate 12 has a cranked region 21 which, starting from the through-opening 14 in the present example, extends in the direction of the first side 23 of the bipolar plate 12. This cranked region extends circumferentially along the peripheral edge 25 of the through-opening 14 and, where appropriate, as a closed loop around the through-opening 14. However, it is also possible to provide only a section parallel to the peripheral edge 25 with such a cranked region.

An elastomeric molding 30 is provided for the peripheral edge 25 of the through-opening 14 or the peripheral edge 22 of the bipolar plate 12 along the through-opening 14. The elastomeric molding 30 extends over a part of the first surface 23 and a part of the second surface 24 of the bipolar plate 12 and, in the present example, also surrounds the edge 22 of the bipolar plate 12, so that the peripheral edge 25 of the through opening 14 is formed by the elastomeric molding 30. On the first side 23 of the bipolar plate 12, the elastomeric molding 31 extends from the peripheral edge 25 to the cranked region 21. At least in the area of the cranked region 21, its thickness is designed so that its surface is flush or flat with the surface of the bipolar plate 12 in the active region 15. This molding 31 on the first side 23 of the metallic layer 13 has two scaling lips 32a and 32b, which rise above the first molding 31 adjacent to the sealing lips 32a and 32b. The sealing lips 32a and 32b run around the through opening 14, in particular substantially along the peripheral edge 25 or the edge 22 and advantageously as a closed loop. When the bipolar plate 12 is pressed in a stack, as shown in FIG. 1, the sealing lips 32a and 32b consequently seal the through-opening 14 on the first side 23 of the bipolar plate 12 with respect to the active region 15.

On the second side 24 of the first metallic layer 13 of the bipolar plate 12, the elastomeric molding is designed as elastomeric molding 35, which has ribs 36a to 36f that rise above the otherwise closed molding 35 running along the peripheral edge 25 adjacent to the ribs 36a to 36f. In the present example, these ribs 36a to 36f extend radially from the through-opening 14 towards the peripheral edge 25 of the through-opening 14 in the direction of the active region 15. The molding 35 overlaps the cranked region 21 with the ribs 36a to 36f and only ends behind the cranked region 21, but before the active region 15, as seen from the through-opening 14. The grooves 37a to 37e between the ribs 36a to 36f are each formed in alignment with an embossed channel 16a to 16e and also form passage channels via which a fluid can flow from the through opening 14 in the direction of the active region 15.

Between the channels 37a to 37e, which are designed as grooves, and the elevations of the channels 16 of the active region 15, a transition area 41 is provided as a distribution region, in which the fluid flowing through the grooves 37a to 37e can also flow perpendicular to the direction of the grooves 37a to 37e and the channels 16a to 16e in the active region 15 and mix in the process.

By means of the elastomeric molding 35 on the second side 24 of the metallic layer 12, flow channels are created for a fluid from the through opening 14 to the active region 15 and at the same time the width and height (and thus also the cross-section) of these channels 37a to 37e are defined and ensured by the corresponding projections 36a to 36f. The molding 35 forms a fluid control with the ribs 36a to 36f.

Since the first molding 31 and the second molding 35 can be carried out in a single molding process by means of an edge molding 40, which surrounds the edge 22 of the metallic layer 12, the manufacturing process for the sealing by means of the molding 31 and 35 and the edge molding 40 of the first layer 13 and thus of the bipolar plate 12 is simplified considerably.

FIG. 4 shows a perspective view of the same bipolar plate 12 with the first layer 13, but now in a section through the active region 15 and the channels 16a to 16f of the active region. The embossed ribs forming the channels 16a to 16f in the active region 15 of the first metallic layer 13 also form channels 16a′ to 16f on the first side 23, which can serve to guide fluid in the adjacent electrochemical cell.

FIG. 5 shows a cross-section of the first layer 13 of the bipolar plate 12 corresponding to the left-hand cut edge in FIG. 3.

In this view, too, the cranked region 21 is covered by the molding 35 on the second side 24 of the layer 13, while the molding 31 on the first side 23 of the layer 13 merges at the same height into the surface of the first layer 13 in the area of the active region 15.

FIG. 6 shows a top view of the first side 23 of the first layer 13 of the bipolar plate 12 in a section adjacent to the edge 25 of the through-opening 14. The scaling lips 32a and 32b run parallel to the edge 25 of the through-opening 14 and thus seal the through-opening 14 against the structures of the flow region and active region 15.

FIG. 7 shows the corresponding top view of the second side 24 of the first layer 13 of the bipolar plate 12 with the elastomeric molding 35. The flow channels of the grooves 37a to 37e, which extend radially away from the through-opening 14 with its circumferential edge 25 through the elastomeric molding 35, are each arranged in alignment with the channels 16a to 16e of the active region 15. Between the channels 37a to 37e and the channels 16a to 16e there is a distribution region 41, in which the fluid can also move perpendicular to the extension of said channels and thus also mix.

FIG. 8A shows a further separator plate 12 according to the present disclosure in oblique view, similar to that shown in FIG. 4. In the separator plate 12 of FIG. 8A, the moldings 31 and 32 on both sides were injection-molded from only one of the two sides 23, 24 of the layer 13 of the separator plate 12 through an opening 10, here in the form of a through-opening, e.g., a hole, in the first metallic layer 13, through which the elastomer can also be distributed on the opposite side of the first metallic layer 13 during the injection process through this opening 10. In principle, molding is possible from either side 23, 24 of the metallic layer 13.

Claims

1. A separator plate for an electrolyzer having a first layer, the first layer having a through-opening or a fluid and, adjacent to the through-opening, an active region with a set of flow channels for the fluid, wherein a first elastomeric molding with at least one sealing lip is arranged on a first side of the first layer at least partially surrounding the through-opening, which sealing lip extends at least partially along a peripheral edge of the through-opening, anda second elastomeric molding is arranged on a second side of the first layer opposite the first side, surrounding the through-opening, with a set of ribs which in pairs form grooves between them as flow channels for the fluid, wherein for each flow channel a first longitudinal end is open to the through-opening and a second longitudinal end is open to the active region,wherein the first layer has a cranked region at a distance from the through-opening and at least partially around the through-opening.

2. The separator plate according to claim 1, wherein the cranked region extends at least partially along the peripheral edge of the through-opening and parallel to the peripheral edge of the through-opening, and/or at least partially transversely to the peripheral edge and perpendicular to the ribs of the second elastomeric molding, and/or at least partially along and parallel to the sealing lips of the first elastomeric molding.

3. The separator plate according to claim 1, wherein the second elastomeric molding covers the cranked region on the second side at least partially.

4. The separator plate according to claim 1, wherein the ribs of the second elastomeric molding extend at least partially and/or at least in a section in the direction of the active region up to the end of the second elastomeric molding.

5. The separator plate according to claim 1, wherein the first elastomeric molding extends up to and into the cranked region and the first elastomeric molding merges evenly into a surface of the first side on the side of the cranked region facing away from the first elastomeric molding.

6. The separator plate according to claim 1, wherein the first elastomeric molding and the second elastomeric molding are formed contiguously and are integrally injection-molded over the peripheral edge of the through-opening or through an opening in the separator plate.

7. The separator plate according to claim 6, wherein the peripheral edge of the through-opening is completely coated and integrally injection-molded with the first elastomeric molding and the second elastomeric molding.

8. The separator plate according to claim 1, wherein the first layer extends evenly in a region between the ribs of the second elastomeric molding and the active region.

9. The separator plate according to claim 8, wherein an edge of the second elastomeric molding facing away from the through-opening is arranged at least partially in the region between the ribs of the second elastomeric molding and the active region.

10. The separator plate according to claim 1, wherein for one, several or all of the ribs of the second elastomeric molding, an area of a cross-section of a rib of the set of ribs increases or decreases with increasing distance from the through-opening.

11. An electrochemical cell for an electrolyzer having a first and a second cell frame and a separator plate which is arranged between the first and the second cell frame and has a first layer, wherein the first layer has a through-opening for a fluid and, adjacent to the through-opening, an active region with a set of flow channels for the fluid,wherein a first elastomeric molding with at least one sealing lip is arranged on a first side of the first layer at least partially surrounding the through-opening, which sealing lip extends at least partially along a peripheral edge of the through-opening,a second elastomeric molding is arranged on a second side of the first layer opposite the first side, surrounding the through-opening, with a set of ribs which in pairs form grooves between them as flow channels for the fluid, andfor each flow channel a first longitudinal end is open to the through-opening and a second longitudinal end is open to the active region.

12. The electrochemical cell according to claim 11, wherein the first layer has an cranked region at a distance from the through-opening and at least partially around the through-opening.

13. The electrochemical cell according to claim 12, wherein the cranked region extends at least partially along the peripheral edge of the through-opening and parallel to the peripheral edge of the through-opening, and/or at least partially transversely to the peripheral edge and perpendicular to the ribs of the second elastomeric molding, and/or at least partially along and parallel to the sealing lips of the first elastomeric molding.

14. The electrochemical cell according to claim 12, wherein the second elastomeric molding covers the cranked region on the second side at least partially.

15. The electrochemical cell according to claim 11, wherein the first elastomeric molding merges evenly into a surface of the first side on a side of the cranked region facing away from the first elastomeric molding.

16. The electrochemical cell according to claim 11, wherein the peripheral edge of the through-opening is completely coated and integrally injection-molded with the first elastomeric molding and the second elastomeric molding.

17. The electrochemical cell according to claim 11, wherein an edge of the second elastomeric molding facing away from the through-opening is arranged at least partially in a region between the ribs of the second elastomeric molding and the active region.

18. The electrochemical cell according to claim 11, wherein for one, several or all of the ribs of the second elastomeric molding, an area of a cross-section of a rib of the set of ribs increases or decreases with increasing distance from the through-opening.

19. The electrolyzer comprising a plurality of separator plates according to claim 1.

20. The electrolyzer comprising a plurality of electrochemical cells according to claim 11.