3-chamber cell

Abstract

The present invention relates to a three-compartment cell that allows the formation of a three-compartment cell stack in which three-compartment cells are connected in series, the three-compartment cell comprising a gas diffusion electrode (1), a flow plate (2), a flow frame (3), at least one conductive seal (4, 5), an anode (6), and a membrane (7), the conductive seals (4, 5) being present on both sides of the gas diffusion electrode (1), the two sides of the seals (4, 5) being in conductive contact with each other, and the seals (4, 5) being placed against one side of the flow plate (2), and on the opposite side of the flow plate (2) there is an abutment point for the anode (6) of a subsequent three-compartment cell, the abutment point being in conductive contact with the seals (4, 5) via the flow plate (2).

Description

[Technical Field]

[0001] The present invention relates to a three-compartment cell for the electrocatalytic reduction of gases, suitable for forming a cell stack.

[0002] The cell design thus allows for the construction of an electrochemical three-compartment cell stack.

[0003] In particular, the three-compartment cell stack can be used as a reactor for electrocatalytic reactions.

[0004] A cell stack should be understood as a plurality of cells arranged in series to form a block, and thus a three-compartment cell stack is a block comprising a plurality of individual three-compartment cells.

[0005] According to the prior art, there are both "zero gap" cells and "zero gap" cell stacks (only for gaseous products), as well as individual electrochemical cells with a "three-compartment" cell design (also called "three-chamber cells" for liquid and gaseous products).

[0006] The present invention particularly relates to a three-compartment cell for the electrocatalytic reaction / reduction of CO2 and N2 to form liquid and gaseous products.

[0007] The three-compartment cell designs known from the prior art are briefly described below.

[0008] The essential part of a three-compartment cell is a gas diffusion electrode located between the catholyte and gas compartments of the three-compartment cell. The third compartment of the three-compartment cell is the anolyte compartment.

[0009] The gas chamber is located behind the gas diffusion electrode. Therefore, according to the prior art, the gas chamber is typically made of an insulating material and is therefore not electrically conductive. Prior art three-compartment cells additionally include a seal, which is also made of an insulating material and is therefore not electrically conductive.

[0010] Opposite the gas diffusion electrode is the first liquid or electrolyte compartment, called the catholyte compartment due to the placement of the cathode (gas diffusion electrode). Catholyte is a combination of the words cathode and electrolyte.

[0011] The anode contains a second liquid or electrolyte compartment, called the anolyte compartment due to its location at the anode. Anolyte is a combination of the words anode and electrolyte.

[0012] The anolyte and catholyte compartments are separated by a membrane.

[0013] The gas diffusion electrode is in contact with the gas on one side and the liquid electrolyte (catholyte) on the other side, which normally requires high quality non-conductive sealing materials.

[0014] For this reason, the series connection required in a cell stack between the gas diffusion electrode of the first cell in the stack and the anode of the connecting second cell in the stack is not easily realized.

[0015] In known cell stacks, each component is typically in the form of a flat disk or flat ring, extending to the periphery of the stack, where they are pressed against each other and therefore exert the same force on each seal of the stack, in particular the seals of the gas diffusion electrodes.

[0016] The underlying object of the present invention is to provide a three-compartment cell design that allows the formation of a three-compartment cell stack in which the cells are connected in series.

[0017] To this end, it is proposed to form the gas chamber by means of an electrically conductive structural flow plate which is placed against the gas diffusion electrode via an electrically conductive seal.

[0018] In particular, a three-compartment cell as claimed in claim 1 is proposed to achieve this object.

[0019] One embodiment of the present invention is a three-compartment cell that allows the formation of a three-compartment cell stack in which cells are connected in series, the three-compartment cell comprising a gas diffusion electrode, a flow plate, a flow frame, at least one conductive seal, an anode, and a membrane, the conductive seals being present on both sides of the gas diffusion electrode, with both sides of the seal being in conductive contact with each other, the seal being placed against the flow plate, and on the opposite side of the flow plate there is an abutment for the anode of the subsequent three-compartment cell, with the abutment being in conductive contact with the seal via the flow plate.

[0020] The flow plate is preferably constructed entirely from an electrically conductive material.

[0021] On the side of the flow plate that faces the gas diffusion electrode there is preferably a recess in which the gas diffusion electrode is housed together with its seal, and at the bottom of the recess there is a gas guiding structure.

[0022] The gas guiding structure is preferably connected to the flow plate in a fixed manner, in particular monolithically, and can for example be milled out of the material of the flow plate.

[0023] On the other side of the flow plate, a liquid guiding structure is present as an anolyte guiding structure, which is preferably connected to the flow plate in a fixed manner, in particular monolithically, and can be milled, for example, from the material of the flow plate.

[0024] The side of the flow plate facing the anode preferably has a recess in which the anode is housed, and a liquid guiding structure is present on the bottom surface of the recess.

[0025] Preferably, the conductive seal consists of two seals extending around the gas diffusion electrode, protruding circumferentially beyond the gas diffusion electrode and connected to each other in an area outside the gas diffusion electrode, the outer edge area of ​​the gas diffusion electrode being enclosed between the two seals.

[0026] A flow frame rests against the seal on the opposite side of the flow plate, and the flow frame preferably has a raised area that projects into a recess in the flow plate where the gas diffusion electrode resides with the seal.

[0027] The side of the flow plate facing the gas diffusion electrode preferably has at least three flat surfaces, the first flat surface being the bottom surface formed by the bottom surface of the gas guiding structure, the second flat surface in the middle having the contact surface for the gas diffusion electrode and its seal, which contact surface extends around the periphery of the gas guiding structure, and the third flat surface at the top including the outer surface of the protrusion extending around the periphery of the contact surface.

[0028] Preferably, the protrusion is surrounded by the recess.

[0029] Preferably, the upper surface of the web of the gas guiding structure lies in the central second plane.

[0030] The flow plate preferably has two passage openings for the gas, starting from each of which at least one horizontal gas guiding channel leads into the gas guiding structure.

[0031] Preferably, each of the two gas passages has a receiving space for an insert, each horizontal gas guide channel leads from the receiving space to the gas guide structure, and the insert includes a connection from the vertical passage to the horizontal gas guide channel.

[0032] Two types of inserts can be used, the first type being closed at the top, so that the passage to the next cell is closed, and the second type preferably including at least one opening at the top, so that the passage to the next cell is open.

[0033] The flow plate and flow frame have passages for the anolyte, catholyte and gases, which are preferably located horizontally outside the area of ​​the flow plate where the gas diffusion electrodes are located.

[0034] The membrane is between two seals, which have ports for the anolyte, catholyte and gas, which ports are preferably located horizontally outside the area of ​​the flow plate where the gas diffusion electrodes are located.

[0035] The passages for the anolyte, catholyte, and gases are preferably present in the following components of the replicated unit: flow plate, flow frame, membrane seal. The passages are present so that they coincide with each other, so that they form vertical channels that penetrate all the cells of the cell stack. The anode and gas diffusion electrode and their seals, and preferably also the membrane, do not contain any passages. The anode and gas diffusion electrode and their seals, and preferably also the membrane, are located in the planar areas that are located between the passages when viewed horizontally.

[0036] Each of the gas guide structures includes one connection for each of the two gas passage ports, the anolyte guide structure includes one connection for each of the two anolyte passage ports, and the catholyte guide structure includes one connection for each of the two catholyte passage ports.

[0037] Thereby, a flow of the respective medium occurs from the first passage opening to the second passage opening via the respective guide structure.

[0038] The connections can be made through channels that open outward in the surface of the flow plate or flow frame, or through channels or bores that extend surrounded by the material of the flow plate or flow frame.

[0039] In one embodiment, the present invention relates to a three-compartment cell stack, said stack being assembled from a plurality of three-compartment cells according to the present invention.

[0040] It is preferred that the flow plate of the first of the two outermost three-compartment cells in the cell stack be replaced with a cathode end plate, and that the flow plate of the second of the two outermost three-compartment cells in the cell stack be replaced with an anode end plate.

[0041] In one embodiment, the present invention relates to the use of a three-compartment cell stack according to the present invention as a reactor for electrocatalytic reactions.

[0042] The structure of the flow plate creates at least one flow path for the gas from the inlet to the outlet on the flow plate, and this structure or flow path serves to distribute the gas emerging from the inlet in as uniform a manner as possible over the entire area of ​​the gas diffusion electrode.

[0043] The flow plate has a solid body separating a gas chamber present on a first side of the flow plate from an anolyte chamber present on a back side of the flow plate. A structure is also preferably present on the back side of the flow plate. The structure forms at least one flow path for the liquid anolyte from an inlet to an outlet on the flow plate. The anolyte and gas flows each occur parallel to the surface of the gas diffusion electrode.

[0044] On the other side of the gas diffusion electrode, as is common in the prior art, there is a liquid chamber in the form of a catholyte chamber, which is formed by a flow frame. The flow frame is placed against one of the conductive seals of the gas diffusion electrode from the other side. In contrast to a flow plate, the flow frame is open, i.e., has an opening extending through the base body of the flow frame. As a result, a catholyte chamber is created between the gas diffusion electrode and the membrane present on the other side of the flow frame and separating it from the anode. The flow frame has an inlet and an outlet for the catholyte. The catholyte flow occurs parallel to the two opposing faces of the flow frame. The opening in the flow frame allows the flow of current or ions through the catholyte from the anode to the cathode (gas diffusion electrode).

[0045] The flow frame can be made from an electrically insulating material, preferably a plastic such as polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), or polymethyl methacrylate (PMMA).

[0046] The flow plate comprises or is entirely formed from a conductive material, allowing current flow between a first planar side of the flow plate and a second planar side of the flow plate. A cathode in the form of a gas diffusion electrode (of the first cell) is placed against the first planar side of the flow plate via a conductive seal, and an anode (of the second cell) is placed against the other planar side of the flow plate, thereby achieving series connection of the cell stack. The material of the flow plate can be selected from conductive plastic, metal, or graphite. Specific, non-limiting examples are gold-coated metal, particularly gold-coated bronze, stainless steel, or titanium. The flow plate can be entirely constructed from a conductive material, or can be constructed from a combination of conductive and non-conductive materials. For example, the conductive material extending through the flow plate between the anode and the conductive seal can be inserted or molded into a non-conductive material, such as plastic.

[0047] The seal preferably extends beyond and surrounds the gas diffusion electrode. Thus, the two opposing faces of the gas diffusion electrode are electrically connected via the seal. This allows current to flow between the flow plate and the side of the gas diffusion electrode facing away from the flow plate. This is particularly important because some gas diffusion electrodes have only one of their two opposing faces made of an electrically conductive material.

[0048] The flow frame and flow plate are placed against the membrane from different sides in the cell stack via non-conductive seals. The anode is located between the membrane and the flow plate, and resides in a recess in the flow plate and is surrounded by the flow plate. The anode is preferably in conductive contact with the structure of the flow plate facing the anode.

[0049] Whether or not conductive contact between the gas diffusion electrode and the structure of the flow plate facing the gas diffusion electrode is possible depends on the characteristics of the gas diffusion electrode used. However, no current flow is required at this location, since said current flow is achieved via the conductive seal. There may also be a gap between the structure of the flow plate and the gas diffusion electrode.

[0050] The conductive seal is made from an elastically deformable conductive material. Conductive elastomers are known in the art. For example, the seal can be made from a mixture of conductive carbon, PTFE powder, and a binder, particularly by hot pressing. Graphite seals can also be used.

[0051] Compared to the prior art, the present invention is advantageous in that it enables the construction of a novel electrochemical three-compartment cell stack for highly efficient production of liquid and gaseous products on the cathode side during electrocatalytic CO reduction.

[0052] Thus, there is a single cell of the following design: conductive structural flow plate-conductive seal-gas diffusion electrode-conductive seal-flow frame-membrane-anode.

[0053] In the case of two consecutive cells, the anode of one cell is conductively connected to the gas diffusion electrode of the second cell, i.e., via the conductive structural flow plate and conductive seal located therebetween.

[0054] The cells are present in a bipolar connection, i.e., in a series electrical connection, so that the same stack current flows through all the cells and the stack voltage is the sum of the cell voltages.

[0055] The invention will now be explained using schematic diagrams. [Brief explanation of the drawings]

[0056] [Figure 1] 1 shows a schematic representation of a cathode subunit of a three-compartment cell according to the invention.

[0057] [Figure 2] 1 shows a schematic representation of a gas diffusion electrode and its seal in a three-compartment cell according to the invention.

[0058] [Figure 3] 10 shows a schematic representation of the assembly of the electrode subunit and the anode subunit.

[0059] [Figure 4] 1 shows a schematic representation of a cell stack made of three-compartment cells according to the invention.

[0060] [Figure 5] 1 shows a detailed schematic view of a three-compartment cell according to the invention;

[0061] [Figure 6] 1 shows an exploded view of a particularly preferred variant of a three-compartment cell seen from a first direction.

[0062] [Figure 7] 1 shows an exploded view of a particularly preferred variant of the three-compartment cell as seen from a second direction.

[0063] [Figure 8] 1 shows an exploded view of a particularly preferred variant of a three-compartment cell stack as seen from a first direction.

[0064] [Figure 9] 10 shows an exploded view of a particularly preferred variant of a three-compartment cell stack as seen from a second direction.

[0065] [Figure 10] 1 shows a particularly preferred variant of the first side of the flow plate.

[0066] [Figure 11] 1 shows a particularly preferred variant of the second side of the flow plate.

[0067] [Figure 12]1 shows a particularly preferred variant of the first side of the flow frame.

[0068] [Figure 13] 1 shows a particularly preferred variant of the second side of the flow frame. DETAILED DESCRIPTION OF THE INVENTION

[0069] The directional designation "vertical" or "vertical" in this specification refers to the direction perpendicular to the plane of the gas diffusion electrode 1, which corresponds to the longitudinal direction of the cell stack. The horizontal direction is used to designate the direction parallel to the plane of the gas diffusion electrode 1.

[0070] FIG. 1 shows schematically how a gas diffusion electrode 1, a flow plate 2, and a flow frame 3 can be assembled to form a cathode subunit.

[0071] The gas diffusion electrode 1 can be realized by conventional techniques. According to the present invention, said electrode is provided with conductive seals 4, 5. As depicted, the seals can be assembled from a first conductive seal 4 and a second conductive seal 5.

[0072] The flow plate 2 has a recess in which the gas diffusion electrode 1 is housed together with its seals 4, 5, and a second conductive seal 5 rests against the bottom surface of the recess. The bottom surface of the recess can include at least one raised web that presses against the seal 5 when the components are pressed together. The web can be located in the area where the gas diffusion electrode 1 is located between the seals 4, 5.

[0073] The gas diffusion electrode 1 is exposed in the area between the peripheral seals 4, 5. In said area, raised structures acting as gas guiding structures 32 are arranged on the bottom surface of the recesses in the flow plate 2.

[0074] On the other side of the gas diffusion electrode 1, facing the flow plate 2, there is a flow frame 3. The flow frame 3 preferably comprises a peripheral frame whose legs are connected by material bridges. Between the material bridges, the flow frame 3 comprises openings that extend from one area of ​​the flow frame 3 to the opposite area.

[0075] Preferably, the flow frame 3 has raised elements that correspond to the recesses in the flow plate 2. When pressed together, the raised elements of the flow frame 3 preferably protrude into the recesses in the flow plate 2. The raised elements rest against the first seal 4. The surface of the raised element can include at least one raised web that presses against the seal 4 when the components are pressed together. In the example of Figure 1, there are two parallel webs on the raised element. The inner web can be located in the area where the gas diffusion electrode 1 is located between the seals 4 and 5. The outer web can be located in the area where the seals 4 and 5 are directly against each other.

[0076] FIG. 1 shows by way of example structures which may be present on the flow plate 2 as gas guiding structures 32 and / or liquid guiding structures.

[0077] FIG. 2 shows a possible manufacturing method for the gas diffusion electrode 1 and its seals 4, 5. The seals 4, 5 are thereby each present as a flat material in the shape of a frame. Each frame is embodied so that its outer edge is placed outside the periphery of the gas diffusion electrode 1 and its inner edge is placed inside the periphery of the gas diffusion electrode 1. In the example of FIG. 2, the gas diffusion electrode 1 and the seals 4, 5 are embodied in a square shape as can be seen from the top view. However, other shapes are not excluded: for example, the gas diffusion electrode 1 can be rectangular, circular, oval or polygonal.

[0078] The outer shape of the flow plate 2 and flow frame 3 can correspond to or differ from the shape of the gas diffusion electrode 1. For example, a circular gas diffusion electrode 1 can be inserted into a circular recess in an angular flow plate 2.

[0079] FIG. 3 shows how a previously assembled cathode subunit is assembled with an anode subunit to form a replicated unit for the formation of a cell stack.

[0080] The anode subunit includes an anode 6 that resides on a membrane 7. The anode 6 can be connected to the membrane 7 in a fixed manner, e.g., compressed. The membrane 7 protrudes beyond the anode 6 and includes a seal 8 in the area that protrudes beyond the anode 6. As depicted, there can be one seal 8 on each of two opposite sides of the membrane 7. The membrane 7 can protrude laterally from or between the seals 8. The seal 8 is formed from an electrically insulating material. Less preferably, the membrane 7 can reside directly between the flow plate 2 and the flow frame 3 if the material allows for a seal, or if a seal resides directly between the flow plate 2 and the flow frame 3 in the outer area of ​​the membrane 7.

[0081] In the example of Figure 3, the anode subunit is positioned on the exposed side of the flow frame 3. However, it is also conceivable to position the anode subunit on the exposed side of the flow plate 2, since the only fundamental importance for a replicated unit of a stack is that said replicated unit contains all components for forming a three-compartment cell.

[0082] The side of the flow frame 3 facing the membrane 7 is preferably embodied to be flat (without protrusions or recesses). In the area of ​​the seal 8 there is preferably at least a raised web which is pressed against the seal 8 when the components are pressed together.

[0083] The completed replica unit contains the following components: anode 6; membrane 7; seal 8; flow frame 3; seals 4, 5; gas diffusion electrode 1; and flow plate 2.

[0084] To make a replica unit into a three-compartment cell, the bottom side of said replica unit needs to be closed in that a further replica unit is positioned there or the flow plate 2 is replaced by a cathode end plate 9.

[0085] The bottom side of the flow plate 2 is closed by a membrane 7. Preferably, the flow plate 2 has an internal recess on the side facing the membrane 7, with a raised structure on its bottom surface that serves as a liquid guide structure for the anolyte. The anode 6 rests against this structure. When the components are pressed together, the anode 6 sits in the internal recess of the flow plate 2. Outside the periphery of the internal recess, a raised area follows the internal recess and rests against the seal 8. The surface of the raised area can include at least one raised web that presses against the seal 8 when the components are pressed together. In the example of Figure 3, the raised area has two parallel webs.

[0086] Generally, it is preferred that there be one web on one side of each of seals 4, 5 and 8, and two webs on the other side of each of seals 4, 5 and 8.

[0087] There can be a peripheral recess around the raised area surrounding the internal recess, and a second raised area around the peripheral recess on the outside. The second raised area can protrude further from the flow plate than the previously described raised area against which the seal 8 is applied. The second raised area can be symmetrical to the protrusion on the other side of the flow plate 2 that surrounds the recess into which the gas diffusion electrode 1 is inserted.

[0088] An exemplary cell stack is shown in Figure 4. The cell stack can be assembled from any desired number of replicate units or three-compartment cells.

[0089] As depicted, one end of the stack is bounded by a cathode end plate 9, and the other end of the stack is bounded by an anode end plate 10. On one side, the cathode end plate 9 is embodied such that it corresponds to the side of the flow plate 2 where the gas diffusion electrode 1 is present. On the other side, it is embodied, for example, as a planar or flat plate. On one side, the anode end plate 10 is embodied such that it corresponds to the side of the flow plate 2 where the anode 6 is present. On the other side, it is embodied, for example, as a planar or flat plate.

[0090] A cathode current collector 11 may be present on the cathode end plate 9 .

[0091] On the anode end plate 10 may be an anode current collector 12 .

[0092] Applying a voltage between the end plates 9, 10 or their current collectors 11, 12 causes current to flow through the cell stack.

[0093] Figure 5 shows a detailed view of a three-compartment cell of the cell stack, with the current flow indicated by arrows.

[0094] As depicted, the three-compartment cell comprises a catholyte compartment 13 located between the membrane 7 and the gas diffusion electrode 1 and bounded laterally by a flow frame 3. The catholyte compartment 13 is laterally sealed by seals 8 and 4.

[0095] The three-compartment cell comprises an anolyte compartment 14 located between the anode 6 and the flow plate 2, which also forms the lateral boundary of the anolyte compartment 14. The anolyte compartment 14 is laterally sealed by a seal 8.

[0096] The three-compartment cell comprises a gas chamber 15 present between a gas diffusion electrode 1 and a flow plate 2, which also forms the lateral boundary of the gas chamber 15. The gas chamber 15 is laterally sealed by a seal 5.

[0097] In Figure 5, the arrows indicate the flow of current through the three-compartment cell. The flow through the membrane 6, i.e., the flow between the anolyte and the catholyte, occurs due to ion transport. Preferably, the side of the gas diffusion electrode 1 facing the catholyte is conductive, while the other side is insulating or low-conductivity. Therefore, the current flows through the conductive layer of the gas diffusion electrode 1 toward the seal 4, from seal 4 to seal 5. The seal 5 guides the current to the flow plate 2, which is in contact with the anode 6 of the next three-compartment cell. The current flow between the flow plate 2 and the anode 6 preferably occurs via the liquid-guiding structure of the flow plate 2.

[0098] While Figures 1-5 show only the core area of ​​the three-compartment cell, Figures 6-13 also show the gas, anolyte, and catholyte passages, which extend vertically through the cell and stack. Figures 6-9 also show an additional set of seals 16, 17, and 18 for sealing the passages. The flow plate 2 and flow frame 3 from Figures 6-9 are depicted in enlarged form in Figures 10-13.

[0099] Figures 6, 8 and 11 provide views of the anolyte guiding structure of the flow plate 2. Figures 7, 9 and 10 provide views of the gas guiding structure of the flow plate 2.

[0100] 6, 8 and 13 provide a side view of the flow frame 3 facing the gas diffusion electrode 1. FIGS. 7, 9 and 12 provide a side view of the flow frame 3 facing the membrane 7.

[0101] In the depicted example from Figures 6-9, the flow plate 2, flow frame 3, and seal 8 each have two passages extending vertically through the stack for the gas and each liquid, so that the flows of the gas and the two liquids occur in parallel through the stack. If one of the passages extending vertically through the stack for the gas and the liquid is closed or absent in one of the specified elements, it is also possible that one or more flows selected from the flow of the gas and the flows of the two liquids occur sequentially through the stack.

[0102] The choice between parallel and serial flow can be made via an insert 19, which in one embodiment is provided with a passage hole and in a second embodiment is not provided with a passage hole. This type of insert 19 is particularly preferred when it is used for a gas channel, as shown. The depicted insert 19 additionally includes the function of creating a connection between the passage hole in the flow plate 2 and the gas guide structure 32 of the flow plate 2. For this purpose, the insert 19 has an opening or cutout facing the gas guide structure 32. At least one gas guide bore 20 (or another opening not created by drilling) extends from the inner wall of the receiving space 31 for the insert 19 to the wall of the gas guide structure 32. Thus, by providing this gas guide bore 20 in the material of the flow plate 2, a horizontal gas channel is formed between the passage hole and the gas guide structure 32.

[0103] The insert 19 may include recesses for the sealing elements of the seal set 17. Alternatively, the sealing elements of the seal set 17 may be present around the insert 19 in the recesses of the flow plate 2.

[0104] All depicted inserts 19 include passage holes. Inserts 19 without passage holes are closed at the top (there are no three bores, and with this type of insert, no recess in the insert for an O-ring is required).

[0105] The insert 19 is preferred as it facilitates the manufacture of the flow plate 2. However, instead of an insert, it is also possible to provide only one passage opening for the gas on the flow plate 2, from which a horizontal gas channel extends to the gas guiding structure 32.

[0106] The outlets of the horizontal gas channels are between the bottom surface of the gas guiding structure 32 and the gas diffusion electrode 1 .

[0107] The flow plate 2 has a recess that receives the gas diffusion electrode 1 together with its seals 4, 5. Said seals 4, 5 therefore do not protrude to the periphery of the cell or stack. The receiving recess is bounded by a peripheral protrusion 28 of the flow plate 2.

[0108] The upper surface of the web of the gas guide structure 32 and the contact surface of the gas diffusion electrode 1 present around the gas guide structure 32 and its seals 4, 5 form the bottom of the receiving recess. The upper surface of the web and the contact surface can thereby lie in a common second plane. The bottom surface of the gas guide structure 32 lies in a first plane below the second plane. In the illustrated example, a single web 24 is present at the contact surface to enhance the sealing effect. A peripheral protrusion 28 of the flow plate 2 is present around the contact surface, with the upper surface of the protrusion 28 lying in a third plane above the second plane. The protrusion 28 is preferably surrounded by the recess 26, and its bottom surface can lie in the second plane or another plane.

[0109] The seal elements (particularly rectangular seal rings) of the seal set 17 preferably extend around the protrusions 28. Additionally, the seal sets 17 preferably each include one seal element (particularly an O-ring) around the respective feedthrough. Preferably, the flow plate 2 has a recess for a respective seal element around each passage opening. As depicted, the recesses 26 extending around the protrusions 28 can also extend around the protrusions of the respective passage openings, although this is optional. Instead of the rectangular seal elements of the seal set 17 shown, it is also possible to have seal elements corresponding to the overall shape of the recesses 26 shown, so that the seal elements surround the protrusions 28 and each passage opening individually. In this case, it is possible to omit the individual seal elements (particularly O-rings) of the seal set 17.

[0110] Outside the periphery of the aforementioned recess 26 there is a frame-shaped contact area for the flow frame 3 .

[0111] In this contact area, there are a plurality of passage openings, in particular six passage openings, for fasteners, in particular threaded bolts or screws. Outside the periphery of these passage openings, there may be a peripheral groove in the contact area. The surface of the contact area preferably lies in a third plane.

[0112] The insert 19, shown enlarged in Figures 6 to 9, can be present in such a way that it is made of a sealing material and is larger than the receiving space 31 for the insert, so that said insert 19 can be pressed in a sealing manner into the receiving space 31. Alternatively, the insert 19 can be glued to the receiving space 31 using an airtight glue or a hardening epoxy. Another possibility is a sealing element present in a ring space that forms a recess 26 around the periphery of the insert 19 on the flow plate 2, for example around the protrusion in which the receiving space 31 is located.

[0113] In this example, the gas guiding structure 32 is embodied as a closed structure, so that the flow of gas must occur across the web of the structure, i.e. between the surface of the web and the gas diffusion electrode 1. Alternatively, the structure could form one or more continuous connections between two opposing gas guiding bores 20.

[0114] Preferably, each gas passage port is located between passage ports for liquid, and the passage ports are located along two opposite edges of the square or rectangular flow plate 2, preferably on the shorter edges of the rectangular flow plate 2.

[0115] FIG. 13 depicts the side of the flow frame 3 facing the flow plate 2. This side includes a contact area and a first area that rests against the protrusion 28 of the flow plate 2. The seal elements of the seal set 17 are thereby pressed into the recesses provided for them. A second area, raised relative to the first area, exists within the inner area of ​​the first area, thus forming a raised area 29. The raised area 29 is received in a receiving recess of the flow plate 2 and presses the seals 4, 5 against the contact surface of the flow plate 2. The raised area 29 includes a frame-shaped outer area surrounding the catholyte guiding structure of the flow frame 3. This outer area preferably has a peripheral web, in particular a peripheral double web 25, to enhance the sealing effect. The catholyte guiding structure is formed by one or more channels, at least one of which is embodied as or provided with a passage opening through the flow frame 2. In Figure 13, the channels are visible which extend completely through the flow frame 2. In Figure 12, additional channels are visible which include groove bases.

[0116] The flow frame 3 preferably has the same circumference or dimensions as the flow plate 2. Corresponding to the flow plate 2, the flow frame 3 has a number of passage openings, in particular six passage openings, for fasteners, in particular threaded bolts or screws. The fasteners are made of a non-conductive material or are present in sleeves made of a non-conductive material.

[0117] The sides of the flow frame 3 (FIG. 12) and the flow plate 2 (FIG. 11) facing the anode 6 can be embodied to be substantially identical to each other, with the difference that the catholyte guiding structure of the flow frame 3 includes passage openings and the anolyte guiding structure of the flow plate 2 includes a closed bottom surface. However, the two sides can also be embodied differently from each other.

[0118] The catholyte guiding structure of the flow frame 3 comprises connections to passage ports for the catholyte on both sides, either symmetrically (not shown, but optionally possible) or diagonally (as shown).

[0119] The anolyte guiding structure of the flow plate 2 includes connections to anolyte passage ports on either side, either symmetrically (not shown, but optionally possible) or diagonally (as shown).

[0120] The grooves shown are optional, although they do exist between each opening and each structure, crossing horizontal channels (three of each as shown).

[0121] Each guide structure and the two passage openings connected to it are surrounded by a recess 27 into which a correspondingly shaped sealing element of seal set 18 or seal set 16 is inserted. To indicate the path of recess 27, it is shown by a dotted line.

[0122] Surrounding the four unnecessary passage openings are other seal elements of seal set 18 or seal set 16. Alternatively, the individual seal elements may include three or five of the illustrated seal elements (e.g., in that each opening surrounded by a seal element is punched or cut out of a planar seal element).

[0123] Providing separate sealing elements for each liquid and / or gas has the advantage that the material of the seal can be purposefully adapted to the media.

[0124] The seals of seal sets 16 and 18 may be embodied to be identical to one another.

[0125] Around each of the two unnecessary passage openings for the other liquid, there can be a receiving space 30 for a closure element, as shown. When a closure element of this type is positioned in one of the two receiving spaces, a serial flow of liquid through the cell is achieved.

[0126] There may be a peripheral groove outside the perimeter of the fastener passage opening.

[0127] The sides of the flow plate 2 and flow frame 3 depicted in Figures 11 and 12 face each other in the assembled stack, between which reside the membrane 7, its seal 8, and the anode 6. The anode 6, typically made of a porous material, rests against the anolyte guiding structure of the flow plate 2. Depending on the thickness of the anode 6, the plane of the upper surface of the webs of the anolyte guiding structure may lie against the outer frame-shaped areas of the flow plate 2 such that they are notched.

[0128] The seals 8 preferably project to the outer periphery of the cell and each seal 8 includes a passage opening for a fastener and two passage openings for each medium (anolyte, catholyte, gas).

[0129] Finally, Figures 8 and 9 also illustrate the components that bound both ends of the stack. For clarity, the depicted stack comprises only one three-compartment cell, which can be expanded by adding replica units.

[0130] At one end of the stack is located a cathode end plate 9, the side of which facing the gas diffusion electrode 1 is embodied as depicted in and described in connection with Figure 10.

[0131] At the other end of the stack is an anode end plate 10, the side of which facing the anode 6 is embodied as depicted in and described in connection with FIG.

[0132] The other side of each of the cathode end plate 9 and the anode end plate 10 can be embodied flat, with recesses for end seals 23 around the passage openings. Preferably, the end seals 23 are separate O-rings for each passage opening. On the side of the end plates 9, 10 facing away from the cell, there is a planar current collector 11, 12, respectively, made of a conductive material, such as copper or aluminum. Each current collector 11, 12 preferably includes a connection tab that protrudes laterally from the stack. The current collectors 11, 12 include openings for the passage openings and their seals.

[0133] Outside the current collectors 11, 12 is a cover plate 21, preferably made of a non-conductive material. The cover plate 21 may include protrusions that penetrate the current collectors 11, 12 and press against end seals 23. On the outside, the cover plate 21 includes openings for inserting connectors and closures 22. The connectors and closures 22 can be pressed, glued, or screwed onto the cover plate 21. Tubes or pipes can be connected to the connectors. The closures serve to seal the end-side passages. Three connectors and three closures are positioned on each side of the stack so that the respective media can pass from an inlet on one side of the stack to an outlet on the second side of the stack. The media can flow in the same direction or in opposite directions through the stack.

[0134] The use of a cover plate 21 with two passages for each medium has the advantage that the connectors and closures 22 can be positioned according to the intended flow pattern (parallel or series) within the stack.

[0135] Less preferably, specific cover plates 21 and / or end plates 9, 10 each having only one passage opening for each medium can also be used and thus replaced by freely positionable closures.

[0136] The end plates 9, 10 and current collectors 11, 12 and cover plate 21 include passage openings for fasteners.

[0137] The fasteners are not shown. Each of the fasteners extends through the entire stack. The fasteners may include threads on both sides or may have a head and threads. The fasteners may be part of one of the cover plates 21 or may be threaded into one of the cover plates 21 and protrude through a second cover plate at the other end.

[0138] This form of fastening or pressing the stack together is preferred. However, other forms are not intended to be excluded. For example, it would be possible to omit the passage openings and use external tensioning means to press the stack together. The external tensioning means could extend from one cover plate 21 to the other cover plate 21, i.e., outside the perimeter of the three-compartment cell, in which case the cover plates 21 would have to project horizontally beyond the three-compartment cell.

Claims

1. A three-compartment cell that allows the formation of a three-compartment cell stack in which three-compartment cells are connected in series, the three-compartment cell comprising a gas diffusion electrode, a flow plate, a flow frame, at least one conductive seal, an anode, and a membrane, the conductive seals being present on both sides of the gas diffusion electrode, the two sides of the conductive seal being in conductive contact with each other, and the conductive seal being placed against one side of the flow plate, and on the opposite side of the flow plate, an abutment point for the anode of a subsequent three-compartment cell being present, the abutment point being in conductive contact with the conductive seal via the flow plate.

2. 2. The three-compartment cell of claim 1, wherein the flow plate is constructed entirely of an electrically conductive material.

3. 3. The three-compartment cell according to claim 1, wherein a recess is present on the side of the flow plate facing the gas diffusion electrode in which the gas diffusion electrode is housed together with its conductive seal, and a gas guide structure is present on the bottom surface of the recess.

4. 3. The three-compartment cell according to claim 1, wherein a recess in which the anode is accommodated is present on the side of the flow plate facing the anode, and a liquid guide structure is present on the bottom surface of the recess.

5. 3. The three-compartment cell according to claim 1, wherein the conductive seal is composed of two seals extending around the gas diffusion electrode, the seals protruding circumferentially beyond the gas diffusion electrode and connected to each other in an area outside the gas diffusion electrode, and the outer edge area of ​​the gas diffusion electrode is surrounded between the two seals.

6. 3. The three-compartment cell of claim 1, wherein the flow frame is positioned against the conductive seal on the opposite side of the flow plate, and the flow frame has a raised area that protrudes into a recess in the flow plate, and the gas diffusion electrode resides in the recess together with the conductive seal.

7. 3. The three-compartment cell of claim 1, wherein the side of the flow plate facing the gas diffusion electrode has at least three flat surfaces, the lowermost first flat surface being formed by the bottom surface of the gas guide structure; the middle second flat surface having a contact surface for the gas diffusion electrode and its conductive seal, the contact surface extending around the periphery of the gas guide structure; and the third upper flat surface including the outer surface of a protrusion extending around the periphery of the contact surface.

8. The three-compartment cell according to claim 7 , wherein the protrusion is surrounded by a recess.

9. 8. The three-compartment cell according to claim 7, wherein the upper surface of the web of the gas guiding structure is in a central second plane.

10. 8. The three-compartment cell according to claim 7, wherein the flow plate has two passage openings for gas, each opening leading to at least one horizontal gas guiding channel in the gas guiding structure.

11. 11. The three-compartment cell according to claim 10, wherein each of the two gas passages has a receiving space for an insert, each of the horizontal gas guide channels leading from the receiving space to the gas guide structure, and the insert includes a connection from the vertical passage to the horizontal gas guide channel.

12. 12. The three-compartment cell of claim 11, wherein two types of inserts are available, the first type being closed at the top so that the passage to the next cell is closed, and the second type including at least one opening at the top so that the passage to the next cell is open.

13. 3. The three-compartment cell according to claim 1, wherein the flow plate and the flow frame have passages for the anolyte, the catholyte, and the gas, the passages being located, in a horizontal direction, outside the area of ​​the flow plate where the gas diffusion electrodes are located.

14. 14. The three-compartment cell of claim 13, wherein the membrane is between two seals, the seals having passages for the anolyte, the catholyte, and the gas, the passages being located horizontally outside the area of ​​the flow plate where the gas diffusion electrodes are located.

15. A three-compartment cell stack, the three-compartment cell stack being assembled from a plurality of three-compartment cells according to claim 1 or 2.

16. 16. The three-compartment cell stack of claim 15, wherein the flow plate of a first cell of the two outermost three-compartment cells is replaced with a cathode end plate, and the flow plate of a second cell of the two outermost three-compartment cells is replaced with an anode end plate.

17. 16. Use of a three-compartment cell stack according to claim 15 as a reactor for electrocatalytic reactions.

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