Electrochemical reactor with circumferential seal

Abstract

Described and illustrated is an electrochemical reactor (1), in particular a redox flow battery, fuel cell, electrolyzer or electrosynthesis cell, with a cell stack (Z) consisting of a plurality of cells (2) stacked in a stacking direction (R), wherein each cell (2) has at least one cell frame (12), wherein a seal (13) is provided around a cell interior (14) between at least two adjacent cell frames (12) and wherein the seal (13) is provided at least partially in adjacent grooves (20, 21) of the adjacent cell frames (12).In order to obtain an improved seal, it is provided that the cross-section of at least one groove (21) has an inner area (24) with a lower area of ​​the groove base (27) and an outer area (25) with a higher area of ​​the groove base (27), that the inner area (24) of the groove (21) and the outer area (25) of the groove (21) are connected to each other, in particular directly, via a step (26) of the groove base (27), and that the seal (13) rests against the at least one step (26).

Description

[0001] The invention relates to an electrochemical reactor, in particular a redox flow battery, fuel cell, electrolyzer or electrosynthesis cell, having a cell stack comprising a plurality of cells stacked in a stacking direction, each cell having at least one cell frame, a seal being provided circumferentially around a cell interior between at least two adjacent cell frames, and the seal being provided at least partially in adjacent grooves of the adjacent cell frames.

[0002] Electrochemical reactors are known in various designs. Redox reactions take place in electrochemical reactors, whereby these reactions can be driven by an externally applied voltage difference, as is the case, for example, when charging a redox flow battery or when operating an electrolyzer or an electrosynthesis cell. In an electrolyzer, a chemical reaction in the form of electrolysis is carried out with the help of an electric current to produce a product, such as hydrogen. In an electrosynthesis cell, electrochemical synthesis processes take place when the cell is subjected to a voltage. For example, hydrogen peroxide can be synthesized from oxygen and water, and basic organic chemicals from carbon dioxide and water.Alternatively, the redox reactions taking place in the electrochemical reactor can also be used to generate an electrical voltage. This is the case, for example, when discharging a redox flow battery or operating a fuel cell.

[0003] Electrochemical reactors of this type are typically constructed from a plurality of electrochemical cells, each of which carries out a corresponding redox reaction. The individual cells of an electrochemical reactor, such as a storage battery, are often arranged in a row or stacked on top of one another. In this context, they are therefore also referred to as a cell stack. Depending on the application, cell stacks allow for the simple provision of a higher voltage or a larger product flow of the product being manufactured. Such cell stacks and their uses have been known for a long time and in a wide variety of applications, which is why they will not be discussed in detail here.

[0004] The individual electrochemical cells are composed of half-cells comprising electrodes separated from one another by a separator. The electrodes and the separator of a cell are integrated in an interior space, which can be provided by at least one cell frame. If required, a cell can also have multiple cell frames, for example one cell frame per half-cell of the electrochemical cell. The electrodes, the at least one cell frame, and the separator are arranged at least substantially parallel to one another. This results in a layering that extends in a so-called stacking direction. The individual cells of a cell stack can be separated from one another by so-called bipolar plates. In this case, an anode and a cathode of adjacent cells are usually located on opposite sides of the bipolar plates.In addition, the anode and the cathode are typically each in direct, electrically conductive contact with the at least one bipolar plate arranged therebetween.

[0005] The cell frames and bipolar plates are typically made of different materials, although for cost and manufacturing reasons, cell frames and bipolar plates comprising at least one thermoplastic material are sometimes considered. To ensure sufficient electrical conductivity of the bipolar plates, the bipolar plates often contain an electrically conductive filler in addition to the thermoplastic material, for example, in the form of fine particles such as graphite or carbon black.

[0006] The separator can contain an electrolyte required for the operation of the electrochemical reactor. The separator can have an open-pore, porous structure in which a liquid electrolyte can be accommodated. However, it can also be provided that the electrodes are in contact with the electrolyte, with the electrolytes and the electrodes of a cell being separated by the separator, for example in the form of a membrane. Separators that contain an electrolyte can be used in fuel cells, such as polymer electrolyte fuel cells (PEM) or solid oxide fuel cells (SOFC), while electrolytes separated by the separator, for example in the form of a membrane, can be used in redox flow batteries. In the case of redox flow batteries, the electrolytes can flow at least partially through the electrodes.

[0007] In some cases, the separator itself can provide the electrolyte, as is the case with a polymer electrolyte fuel cell or a solid oxide fuel cell. In such fuel cells, the separator is divided into two parts, with a hydrogen-containing gas flowing through one part of the separator and an oxygen-containing gas flowing through the other part. The transfer of gases from one part of the separator to the other is prevented by a membrane, which, however, allows the transfer of charge carriers. Here, too, the entirety of the two parts of the separator and the membrane can be understood as the separator between the electrodes. The exact structure of the separator is of only limited importance in the context of the invention.In the case of a polymer electrolyte fuel cell, the membrane consists of a solid polymer, while in a solid oxide fuel cell, an oxide-ceramic electrolyte is used. However, other fuel cells can also use different membranes or even dispense with them altogether.

[0008] But even electrochemical reactors in the form of fuel cells require a fluid. These are working fluids in the form of hydrogen- or oxygen-containing gases flowing through the separator in the anode chamber and the separator in the cathode chamber. Consequently, care must be taken with electrochemical reactors to ensure that no unwanted fluid escapes, such as leaks, occur during operation. It is initially irrelevant whether the fluid is an electrolyte or a working fluid.

[0009] Against this background, the tightness of a corresponding electrochemical reactor must be ensured during its manufacture. This can be achieved by clamping the cell stack between two end plates. The cells and / or individual cell components, particularly their cell frames, are pressed against each other. Seals can be provided between the cells and / or individual cell components, particularly the cell frames. To ensure sufficient tightness, sufficient surface pressure must be applied to the seals when clamping the cell stack.

[0010] The seals are designed to prevent the exchange of solid, liquid, and / or gaseous media between two adjacent spaces. The additional seals arranged between the primary sealing surfaces to be sealed are referred to as secondary sealing elements, which provide secondary sealing surfaces. Absolute tightness cannot be achieved regardless of the seals and contact pressures, as diffusion processes cannot be ruled out.

[0011] Typically, removable seals in the form of flat gaskets, molded seals such as O-rings, FIP (Formed-In-Place) seals, or CIP (Cured-In-Place) seals are used, allowing significantly lower contact pressures than if secondary seals were omitted. At the same time, secondary seals take up space, so the cell stacks have larger dimensions in the stacking direction due to the seals. Furthermore, the preload forces required to provide the required contact pressures can be reduced if smaller sealing surfaces are required.

[0012] Round ring seals, also known as O-ring seals, are often used and are housed in grooves, especially rectangular grooves. With FIP and CIP (cured-in-place) seals, a sealant is applied between the two primary sealing surfaces and, after joining, cured under UV light or heat. Therefore, these seals are also referred to as integrated elastomer seals.

[0013] O-ring seals offer the advantage over flat seals for use in electrochemical reactors in that they are at least partially accommodated in at least one groove, which reduces the dimensions in the stacking direction. Furthermore, the forces required for sealing are lower. O-ring seals are usually accommodated in grooves with a rectangular cross-section, with the groove depth of at least one groove being smaller than the diameter of the O-ring seal, at least if the latter has a round cross-section. Compression can typically be 15% to 30% of the diameter.

[0014] Despite the known sealing technologies, the sealing of electrochemical reactors is not yet completely satisfactory.

[0015] Therefore, the object of the present invention is to design and further develop electrochemical reactors of the type mentioned at the outset and described in more detail above in such a way that an improved seal can be obtained.

[0016] This object is achieved in an electrochemical reactor according to the preamble of claim 1 in that the cross section of at least one groove has an inner region with a lower region of the groove base and an outer region with a higher region of the groove base, that the inner region of the groove and the outer region of the groove are connected to one another, in particular directly, via a step of the groove base and that the seal rests against the at least one step.

[0017] According to the invention, the seal is not accommodated in two grooves with a purely rectangular, square, round or oval cross-section. Rather, the cross-section of at least one groove of a cell frame, in which the seal is at least partially accommodated, has at least two regions of different depths that are separated from one another by a step. In an inner region, the groove base of the corresponding groove is arranged deeper than in an adjacent outer region. The outer region is provided closer to an edge of the corresponding groove than the inner region of the corresponding groove. In this case, inside does not necessarily mean inside in the direction of the cell interior. The inner region can also be arranged on the side of the groove facing away from the cell interior and vice versa.

[0018] The inner region and the outer region are separated from one another by at least one step in the groove base against which the seal rests. The seal is preferably deformed by the step, in particular deformed precisely at the step in order to provide increased tightness. In principle, a particularly tight seal can be achieved if the seal rests against the groove base on both sides of the step, thus against the inner region and the outer region of the corresponding groove. For reasons of tightness, it is further preferred if the step has an at least substantially rectangular shape. The seal is then deformed particularly strongly locally by the step in order to provide high tightness.

[0019] If the at least one step has a sufficient shape, position in the groove, and size, a single step may be sufficient to provide a very good seal. Then, virtually no liquid and / or gas can bypass the seal and pass over the step. It is also desirable for the seal to fit tightly against the opposing cell frame in its opposite groove. Then, the area between the two cell frames is protected from excessive liquid and / or gas passing over the seal, and the corresponding area is thus well sealed.

[0020] In a first particularly preferred embodiment of the electrochemical reactor, in order to increase the tightness, the cross-section of the at least one groove has an inner region with a low-lying region of the groove base and two outer regions, each with a higher-lying region of the groove base. In this case, an outer region can be arranged on one of the two sides of the inner region. The outer regions are then assigned in particular to the two edges of the groove, while the inner region is assigned to a central region of the groove. Furthermore, for reasons of space, it is preferred if the inner region of the groove and the outer regions of the groove are each connected to one another, in particular directly, via a step of the groove base. The seal can then lie very tightly against the steps and thus ensure a high level of tightness.

[0021] To ensure a highly leak-tight connection between the two adjacent cell frames, the seal should also fit tightly against the other, opposite groove. This can be achieved by arranging the edges of the opening of the groove having the at least one step further outwards in relation to the inner region than the edges of the opening of the adjacent groove. In this case, the seal can be clamped between at least one outer region of one groove and an area outside the opposite groove. The clamping area creates a highly leak-tight connection. This is particularly true if the step is arranged further inwards in relation to the inner region than the corresponding edge of the opening of the adjacent groove. From a central point of the at least one groove, the at least one step is therefore arranged further inwards than the outer edge of the opposite groove.If two steps are arranged on opposite sides of the inner region of a groove, both outer edges of the other groove can be arranged further outwards than the steps.

[0022] Alternatively or additionally, the groove having at least one step can form sections of a sealing channel further outward relative to the inner region, on the one hand, and the adjacent cell frame further outward relative to the opening of the groove of this cell frame, on the other hand. The sealing channel is formed between the adjacent cell frames and the groove having at least one step, so that the seal can rest against the two adjacent cell frames in the sealing channel. The seal's contact with the opposing sealing surfaces of the sealing channel can lead to increased tightness.

[0023] The seal is particularly useful when it has a round, oval, or rectangular cross-section. The seal then fits well into the grooves of the opposing cell frames. Alternatively, the electrochemical reactor can be a redox flow battery, a fuel cell, an electrolyzer, or an electrosynthesizer with a plurality of stacked electrochemical cells. Irrespective of this, the cell frames can each be the sole cell frame of two adjacent half-cells forming an electrochemical cell. It is also conceivable, however, that the electrochemical cell comprises more than two stacked cell frames and / or that a half-cell has more than one cell frame.

[0024] In a particularly preferred electrochemical reactor, in which the invention is particularly useful, a separator in the form of a, particularly semipermeable, membrane for separating two cell interiors and / or a bipolar plate is provided between the adjacent grooves. This allows not only the cell frames to be sealed, but also the separator and / or the bipolar plate. It is understood that the separator and / or the bipolar plate are preferably provided only in sections between the adjacent grooves and otherwise delimit two adjacent cell interiors from each other.

[0025] For reasons of tightness, it may be advisable for the separator or bipolar plate to rest against at least one step. Furthermore, this can be done so that the separator or bipolar plate rests on one side against the step and, at least in part, against the inner region of the associated groove. This can increase the effective sealing surface. Furthermore, it can be beneficial for tightness if the other side rests against the seal in the region of at least one step and / or in the inner region of the groove instead of the cell frame. The separator or bipolar plate is thus clamped between one cell frame and the adjacent seal.

[0026] It may be expedient for sealing and space requirements if a groove, in particular one opposite the at least one step, has a groove width to groove depth ratio of between 0.5 and 5, preferably between 1 and 3, in particular between 1.5 and 2.5. Alternatively or additionally, for the same reasons, the groove having the at least one step may have a groove width to groove depth ratio of between 12 and 2, preferably between 9 and 4, in particular between 8 and 5.

[0027] For sealing and space requirements, it may be appropriate, regardless of this, for the width of the inner region to the width of the groove having the at least one step to have a ratio of between 0.1 and 1.2, preferably between 0.3 and 1, in particular between 0.5 and 0.7. However, it may also be expedient for the height of the at least one step to the depth of the groove having the at least one step to have a ratio of between 0.2 and 0.8, preferably between 0.3 and 0.7, in particular between 0.4 and 0.6.

[0028] It may also be expedient for tightness and space requirements if the height of the at least one step to the height of the sealing channel has a ratio of between 0.3 and 2, preferably between 0.6 and 1.5, in particular between 0.8 and 1.2. However, it may also expediently have a ratio of 0.6 and 1, preferably between 0.7 and 0.95, in particular between 0.8 and 0.9, between the width of one groove, in particular the groove opposite the at least one step, to the width of the groove having the at least one step.

[0029] For the sake of tightness and space requirements, it may be advantageous, regardless of this, for the width of one groove, in particular the groove opposite the at least one step, to have a ratio of between 1 and 2, preferably between 1.05 and 1.6, in particular between 1.1 and 1.3, to the width of the inner region of the groove having at least one step. However, it may also expediently have a ratio of between 1 and 5, preferably between 1.5 and 4, in particular between 2 and 3, between the groove depth of the one groove, in particular the groove opposite the at least one step, to the groove depth of the groove having the at least one step.

[0030] The invention is explained in more detail below with reference to a drawing which merely represents an exemplary embodiment. Fig. 1 an electrochemical reactor according to the invention in a schematic sectional view transverse to the stacking direction of the cells of one cell stack, Fig. 2 a cell frame of the electrochemical reactor Fig. 1 in a plan view, Fig. 3 a detail of the electrochemical reactor from Fig. 1 in the area of ​​the sealing of two cell frames against each other in a sectional view and Fig. 4 another detail of the electrochemical reactor from Fig. 1 in the area of ​​two cell frames against each other in a sectional view.

[0031] In the Fig. 1 shows an electrochemical reactor 1 in the form of a redox flow battery with a bipolar structure in a sectional side view. The electrochemical reactor 1 comprises a stack (cell stack Z) of individual cells 2 arranged next to one another in a stacking direction R. Between the individual cells 2, bipolar plates 3 are provided, each of which borders on half-cells 4 and which, on one side, rests against a negative electrode 5 of a cell 2 and, on the opposite side, against a positive electrode 6 of an adjacent cell 2. At the two opposite ends of the electrochemical reactor 1, an end plate 7 with internal, electrically conductive discharge plates 8 is provided, via which voltage can be tapped off and applied to the electrochemical reactor 1. This is not shown in detail.

[0032] Each cell 2 comprises two electrodes 5, 6 which are separated from one another by a separator 9 arranged between the electrodes 5, 6, which can preferably be designed as a semipermeable membrane. In the electrochemical reactor 1 shown, the two electrodes 5, 6 are each in contact with an electrolyte 10, 11. The electrodes 5, 6 are each accommodated in a cell frame 12 and are in direct contact with the adjacent bipolar plates 3. The cell frames 12 are clamped together by an external clamping device and sealed against one another by a seal 13. A separator 9, in particular in the form of a semipermeable membrane, or a bipolar plate 3 is provided between each of the adjacent cell frames 12.

[0033] In the Fig. 2 is an exemplary cell frame 12 of the electrochemical reactor 1 of the Fig. 1. The cell frame 12 encloses a cell interior 14, in which an electrode 5, 6 is located, around which an electrolyte 10, 11 flows. The electrolyte 10, 11 is supplied via an inlet opening 15 in the cell frame 12 and conveyed to the cell interior 14 via inlet channels 16. After flowing through the cell interior 14, the electrolyte 10, 11 is collected via outlet channels 17 and discharged via an outlet opening 18. The further openings 19 serve to transport another electrolyte 11, 10 to the cell channel spaces 14 of other cell frames 12. In the edge area, a circumferential groove 20 is provided in the cell frame 12 for receiving the seal 13 in the form of an O-ring seal.

[0034] In the Fig. Figure 3 shows a detail of two adjacent cell frames 12, which are sealed against each other by a seal 13 in the form of a circumferential O-ring seal. The two adjacent cell frames 12 have grooves 20, 21 with openings 22, 23, each of which points in the direction of the other groove 20, 21 and overlaps each other. The grooves 20, 21 of the illustrated and, in this respect, preferred cell frames 12 are of different widths and depths. While the groove 20 shown above has a rectangular or square cross-section, the shape of the groove 21 of the cell frame 12 shown below is somewhat more complex. This groove 21 has an inner, deeper region 24 and two outer, shallower regions 25. Thus, the groove depth in the inner region 24 is greater than the groove depth in the outer regions 25.In the illustrated and thus preferred groove 21, the outer regions 25 directly adjoin the inner region 24, wherein the inner region 24 is separated from the outer regions 25 by a step 26 in the groove base 27. In the illustrated and thus preferred groove 21, the steps 26 are formed at least substantially at right angles, with one leg oriented parallel to the depth of the groove 21 and one leg parallel to the width of the groove 21.

[0035] The inner region 24 in the illustrated and in this respect preferred groove 21 is more than twice as wide as the two outer regions 25 combined. In addition, the groove 21 having the steps 26 is less than half as deep as the adjacent groove 20. The groove 21 having the steps 26 is further wider than the adjacent groove 20, with the groove 21 having the steps 26 protruding outwards on both sides relative to the adjacent groove 20. Thus, a sealing channel 28 is formed between the groove 21 having the steps 26 in the region of the outer regions 25 and the adjacent cell frame 12 in the region adjacent to its groove 20, in which the seal 13 is partially received and squeezed by both cell frames 12 with high forces. In addition, the seal 13 is squeezed with high forces against the steps 26, whereby the seal 13 rests against the steps 26 as well as against the inner region 24 and the outer regions 25 of the corresponding groove 21.The seal 13 is large enough in cross-section for the seal 13 to rest firmly against the groove base 29 of the groove 20 opposite the steps 26. For the sake of clarity, the regions 30 of increased deformation of the seal 13 and / or increased compression of the seal 13 are schematically identified by hatching. In the illustrated and thus preferred grooves 20, 21, the inner region 24 is narrower than the opposite groove 20 is wide. Also, the groove base 27 of the inner region 24 is approximately twice as deep as the groove 21 in the outer regions 25. The outer regions 25 are of approximately the same depth in the illustrated and thus preferred groove 21. Furthermore, the illustrated and thus preferred groove 20, which does not have a step 26, is at least one and a half times as wide as it is deep, whereas the groove 21 having the steps 26 is at least three times as wide as it is deep.

[0036] In the Fig. 4 is a detail of two adjacent cell frames 12 analogous to Fig.3. In contrast, however, a separator 9 in the form of a membrane is provided between the seal 13 and the groove base 27 of the groove 21 having the steps 26. The separator 9 extends from the cell interior 14 into the inner region 24 of the groove 21 having the steps 26, in particular at least substantially as far as the step 26 facing away from the cell interior 14, and there it rests against the groove base 27 and the seal 13 received in the associated groove 21. The separator 9 therefore extends beyond the step 26 assigned to the cell interior 14 and rests against the corresponding outer region 25 and the inner region 24 of the groove 21. The seal 13 does not rest directly against the step 26 assigned to the cell interior 14, but rather against the separator 9, i.e. indirectly. However, the seal 13 lies directly against the opposite step 26 of the groove 21 having the steps 26. Reference symbol 1 electrochemical reactor 2 cells 3 bipolar plate 4 half-cell 5 Electrode 6 Electrode 7 End plate 8 arrester plate 9 Separator 10 Electrolyte 11 Electrolyte 12 cell frames 13 Seal 14 Cell interior 15 Inlet opening 16 Inlet channel 17 Drain channel 18 Drain opening 19 Opening cell frame 20 grooves 21 grooves 22 Opening groove 23 Opening groove 24 inner area 25 outer area 26th level 27 Groove base 28 Sealing channel 29 Groove base 30 Area of ​​increased deformation R Stacking direction Z cell stack

Claims

[1] Electrochemical reactor (1), in particular redox flow battery, fuel cell, electrolyzer or electrosynthesis cell, with a cell stack (Z) comprising a plurality of cells (2) stacked in a stacking direction (R), wherein each cell (2) has at least one cell frame (12), wherein between at least two adjacent cell frames (12) a seal (13) is provided circumferentially around a cell interior (14), and wherein the seal (13) is provided at least partially in adjacent grooves (20, 21) of the adjacent cell frames (12), characterized bythat the cross section of at least one groove (21) has an inner region (24) with a lower region of the groove base (27) and an outer region (25) with a higher region of the groove base (27), that the inner region (24) of the groove (21) and the outer region (25) of the groove (21) are connected to one another, in particular directly, via a step (26) of the groove base (27), and that the seal (13) bears against the at least one step (26). [2] Electrochemical reactor according to claim 1, characterized bythat the cross section of at least one groove (21) has an inner region (24) with a lower region of the groove base (27) and two outer regions (25) arranged on both sides of the inner region (24), each with a higher region of the groove base (27), that the inner region (24) of the groove (21) and the outer regions (25) of the groove (21) are each connected to one another, in particular directly, via a step (26) of the groove base (27), and that the seal (13) rests against the two steps (26). [3] Electrochemical reactor according to claim 1 or 2, characterized by that the edges of the opening (23) of the groove (21) having at least one step (26) are arranged further outwards with respect to the inner region (24) than the edges of the opening (22) of the adjacent groove (20) and that, preferably, the step (26) is arranged further inwards with respect to the inner region (24) than the associated edge of the opening (22) of the adjacent groove (20). [4] Electrochemical reactor according to one of claims 1 to 3, characterized by that the groove (21) having at least one step (26) further out with respect to the inner region (24) and the adjacent cell frame (12) further out with respect to the opening of the groove (20) of the adjacent cell frame (12) form at least in sections a sealing channel (28) between the adjacent cell frames (12) and the groove (21) having at least one step (26) and that the seal (13) rests against the two adjacent cell frames (12) in the sealing channel (28). [5] Electrochemical reactor according to one of claims 1 to 4, characterized by that the seal (13) has a round, oval or rectangular cross-section and / or that the electrochemical reactor (1) is a redox flow battery and / or that the cell frame (12) is the only cell frame (12) of a half-cell (4). [6] Electrochemical reactor according to one of claims 1 to 5, characterized by that a separator (9) in the form of a, in particular semi-permeable, membrane for separating two cell interiors (14) and / or a bipolar plate (3), in particular in sections, is provided between the adjacent grooves (20, 21). [7] Electrochemical reactor according to claim 6, characterized by that the separator (9) or the bipolar plate (3) rests against the at least one step (26) and that, preferably, the separator (9) or the bipolar plate (3) rests on one side against the step (26) and at least in sections against the inner region (24) of the associated groove (21) and that, further preferably, the other side rests against the seal (13) in the region of the at least one step (26) and / or in the inner region (24) of the groove (21). [8] Electrochemical reactor according to one of claims 1 to 7, characterized bythat the one groove (20), in particular the one opposite the at least one step (26), has a ratio of groove width to groove depth between 0.5 and 5, preferably between 1 and 3, in particular between 1.5 and 2.5, and / or that the groove having the at least one step (26) has a ratio of groove width to groove depth between 12 and 2, preferably between 9 and 4, in particular between 8 and 5. [9] Electrochemical reactor according to one of claims 1 to 8, characterized by that the width of the inner region (24) to the width of the groove (21) having the at least one step (26) has a ratio of between 0.1 and 1.2, preferably between 0.3 and 1, in particular between 0.5 and 0.

7. [10] Electrochemical reactor according to one of claims 1 to 9, characterized bythat the height of the at least one step (26) to the depth of the groove (21) having the at least one step (26) has a ratio between 0.2 and 0.8, preferably between 0.3 and 0.7, in particular between 0.4 and 0.

6. [11] Electrochemical reactor according to one of claims 1 to 10, characterized by that the height of the at least one step (26) to the height of the sealing channel (28) has a ratio between 0.3 and 2, preferably between 0.6 and 1.5, in particular between 0.8 and 1.

2. [12] Electrochemical reactor according to one of claims 1 to 11, characterized by that the width of the one groove (20), in particular the one opposite the at least one step (26), has a ratio of between 0.6 and 1, preferably between 0.7 and 0.95, in particular between 0.8 and 0.9, to the width of the groove (21) having the at least one step (26). [13] Electrochemical reactor according to one of claims 1 to 12, characterized bythat the width of the one groove (20), in particular the one opposite the at least one step (26), to the width of the inner region (24) of the groove (21) having at least one step (26) has a ratio of between 1 and 2, preferably between 1.05 and 1.6, in particular between 1.1 and 1.

3. [14] Electrochemical reactor according to one of claims 1 to 13, characterized by that the groove depth of the one groove (20), in particular the groove opposite the at least one step (16), has a ratio of between 1 and 5, preferably between 1.5 and 4, in particular between 2 and 3, to the groove depth of the groove (21) having the at least one step (26).

Images