Electrode for an electrochemical converter and electrochemical converter

Abstract

The present invention relates to an electrode (1) for an electrochemical converter, and to an electrochemical converter having said electrode. The electrode has a substantially cylindrical shape and has, in its interior, a plurality of first channels for supplying a first process medium and a plurality of second channels for discharging a second process medium. The first channels and the second channels are separated from one another, and thus the first process medium can be supplied in the interior of the electrode separately from the second process medium. On a lateral face (12) of the electrode, orifices (7, 9) are provided via which the process media can exit and / or enter their channels.

Description

[0001] Electrode for an electrochemical converter and electrochemical converter

[0002] Broadly speaking, the present invention relates to electrochemical converters, for example, electrolyzers for splitting water into hydrogen and oxygen and fuel cells for generating water through an electrochemical reaction of hydrogen and oxygen. More specifically, the invention relates to an electrode for use in an electrochemical converter. This electrode has a substantially cylindrical shape. The preamble of patent claim 1 and the subordinate patent claim 19 respectively define the technical field.

[0003] Technical area

[0004] Electrochemical converters play a major role in the so-called "energy transition," both in the form of fuel cells, in which an electrochemical reaction between the components hydrogen and oxygen produces water and generates energy, and in the form of electrolyzers, in which exactly the opposite reaction takes place and hydrogen and oxygen are produced using water. The reaction in the fuel cell serves to generate energy. The reaction in the electrolyzer is used, for example, to store energy in the form of hydrogen gas, such as that provided by photovoltaic systems. When generating electricity from wind turbines or photovoltaic systems, the question of energy storage is crucial, since energy and surplus energy are generated discontinuously and in uneven quantities.As a result, at times when energy consumption is low, there is more energy available than needed, and at times when no energy is being generated, consumers demand a lot of it. Fuel cells, on the other hand, are considered a "clean energy source" because no climate-damaging CO2 is produced during energy production.

[0005] State of the art

[0006] There are several basic design principles for fuel cells and electrolyzers. This article will discuss so-called PEM systems as examples. In such systems, a solid polymer membrane, such as a polyamide membrane, is used as the electrolyte. PEM is an abbreviation for polymer electrolyte or proton exchange membrane. Systems based on polymer membranes, so-called PEM systems, are used in both electrolysis and fuel cells.

[0007] As an alternative to a PEM membrane, an anion exchange membrane (AEM) can be used. Similar to a PEM, it is semipermeable. It is permeable to anions but impermeable to gases such as oxygen and hydrogen. A well-known example is the hydroxide anion exchange membrane, which is used in a direct methanol fuel cell or a direct ethanol fuel cell.

[0008] Electrochemical cells each have an anode and a cathode separated by a membrane. The reduction reaction takes place at one of the two electrodes, and the oxidation reaction at the other. Depending on the application, whether as a fuel cell or as an electrolyzer, the reactions at the electrodes therefore vary.

[0009] Both electrodes share a basic structure consisting of a so-called gas diffusion layer and a bipolar plate, which also acts as a current distributor. In addition, a catalyst layer is required, which can also be applied to the membrane.

[0010] Typically, electrochemical converters are constructed in a plate-like manner from individual layers, called stacks. In this way, a more or less "endless" system can be constructed from a multitude of consecutive stacks of anode, membrane, and cathode.

[0011] A tubular electrode for use in a fuel cell is described in EP 2 744 028 A1 (applicant: Technical University of Darmstadt; disclosure date: June 18, 2014). In the patent application, the geometric shape is referred to as tubular. The tubular electrode in EP 2 744 028 A1 is manufactured using an additive manufacturing process, with tantalum, titanium, platinum, palladium, gold, and their alloys and / or steels, particularly high-alloy stainless steels with high chromium and molybdenum contents, being used as the material for an electrically conductive layer. Furthermore, in a preferred embodiment, the electrode has so-called surface modifications, which are intended to increase the power density by enlarging the electrode surface. Surface modifications include, for example, triangular, hemispherical, or star-shaped geometries.

[0012] The article "Additive manufacturing of liquid / gas diffusion layers for low-cost and high-efficiency hydrogen production" by Mo et al., International Journal of Hydrogen Energy 41 (2016) 3128-3135, deals with the microstructural design of gas diffusion layers in electrodes of a PEM electrolyzer. Using an additive manufacturing process known as EBM (electron beam melting), a controllable pore morphology and structure for the electrodes are described. Titanium is the material of choice. A lattice-like structure is described, which is used as the gas diffusion layer of the anode.It is found that, thanks to the described additive manufacturing process, the mesh surfaces are smooth and flat with a uniform thickness—in contrast to woven meshes used as a comparison. This increases the contact area and thus reduces the contact resistance between the gas diffusion layer and the catalyst layer. The catalyst was present as a coating on a membrane. The performance of such electrolyzers, or electrolyzers with such anodes, was found to be improved. A 12% efficiency improvement was observed when comparing the EBM-printed gas diffusion layers with similarly large and porous titanium meshes.

[0013] An overview of the state of the art and the problems of PEM water electrolyzers can be found in Boris Bensmann's dissertation (2017), System Analysis of Pressurized Water Electrolysis in the Context of Power-to-Gas Applications, Otto von Guericke University Magdeburg, from page 18. Electrolyzer designs and electrode design options can also be found in DE 102018 105 115 A1 (applicant: German Aerospace Center; disclosure date: September 12, 2019).

[0014] Furthermore, reference should be made to DE 2629 506 A1, which focuses on electrolysis cells designed to convert a salt solution in an anode chamber into a halogen gas at the anode and to produce alkali metal hydroxides at the cathode. Such an electrolysis cell is said to have a hollow, tubular anode member and a hollow, tubular cathode member, each of which is preferably made of an expanded metal grid. Thus, due to the expanded metal grid used, each electrode has an open area of ​​30% to 70%. A membrane with a typical thickness of 25 pm to 250 pm is arranged between the electrodes. The reactants, such as reactants and products, are thus conducted to and from the membrane via the holes. The expanded metal grids serve to conduct the electrolysis current, but not for the targeted conduction of reactants and products.The efficiency of the electrolysis cells described in DE 2629 506 A1 is likely to be correspondingly poor.

[0015] Task

[0016] Despite some promising approaches and the fundamental robustness of electrochemical converters, such as PEM-based electrochemical converters, PEM electrolyzers, for example, are used only to a very limited extent for global industrial hydrogen production due to their comparatively high costs and relatively low efficiency. The object of the present invention is therefore to provide electrochemical converters with increased efficiency, ideally with an improved cost factor, i.e., a better price-performance ratio. The starting point here should primarily be the electrode used in an electrochemical converter. In other words, the object of the present invention is to improve electrodes for use in electrochemical converters, in particular to improve anodes for use in electrolyzers.

[0017] Description of the invention

[0018] The present object is achieved by an electrode according to patent claim 1 and an electrochemical converter according to patent claim 20. Advantageous embodiments are the subject of the subclaims.

[0019] The present invention is based on an electrode with a substantially cylindrical shape, as the inventors have recognized that cylindrical electrodes have a particularly good surface-to-reaction area ratio and are also suitable for use in smaller systems. For example, electrolyzers could be provided for domestic use, for storing electrical energy generated by solar systems in residential buildings, small residential complexes, public buildings such as hospitals or administrative buildings, or industrial buildings.

[0020] For the purposes of this invention, the electrode is considered "cylindrical" even if it deviates from a strictly circular cylindrical shape. This is the case, for example, in the end regions of the electrode to accommodate the process media connections. Furthermore, the term "cylindrical" refers to all geometric, three-dimensional figures that can be considered cylinders in the mathematical sense, i.e., in addition to circular cylinders, also elliptical cylinders and prisms, for example. A cylinder based on a polygon, particularly an equilateral one, i.e., a prism-shaped cylinder, has a number n of corners, where n is equal to 3 to infinity (oo): n = 3 - oo.

[0021] According to the invention, the electrode has a plurality of channels within it. These channels serve to conduct the process and / or reaction media, in particular their supply and discharge. Each channel has at least one opening on the outer surface of the cylindrical electrode body, so that each channel opens on or above the outer surface. The process medium conveyed in a single channel exits the electrode through this opening to be fed to the membrane, or the medium enters the electrode through this opening to be discharged by the membrane – depending on the medium and the application of the electrode.

[0022] First and second channels are provided, wherein a first process medium is to be conducted in the first channels and a second process medium in the second channels, wherein the first and second process media are different from one another. According to the invention, the first and second channels are separated from one another inside the electrode so that the process medium to be supplied to the electrode can be supplied separately from the second process medium. A reactant of the electrochemical process in which the electrode is used is supplied under pressure according to the invention. For example, water is supplied under pressure in an electrolyzer. The electrode according to the invention has channels by means of which the reactant can be conducted from an inlet side to an outlet side. The inlet side is located at one end of the electrode and the outlet side is located on a lateral surface of the electrode.

[0023] Both the first and second channels each end on the outer surface of the electrode in at least one opening each, through which the process medium to be supplied leaves the associated channels and into which the process media to be discharged enters them. Each channel therefore has at least one opening on the outer surface of the electrode. Particularly preferably, each channel has a plurality, even more preferably a multiplicity, of openings on the outer surface of the electrode. The openings preferably have different dimensions, depending on the process medium to be passed through and whether the process medium is being supplied or discharged. Furthermore, the edges of the openings form the support for a membrane or a membrane support grid.

[0024] The above principle is explained using an anode for an electrolyzer as an example. Here, water channels are provided for conducting water as one process medium and oxygen channels for conducting oxygen as the second process medium. A plurality of water channels and oxygen channels are present in each electrode. Water is supplied via the water channels to a membrane, in particular a PEM membrane or an AEM membrane, which surrounds the anode and rests on the membrane support grid or directly on the edges of the orifices, for example, wrapped around them, in order to moisten the membrane. The reaction medium, water, is split into oxygen, hydrogen, and electrons at the membrane or at the electrodes (in the case of the electrolysis process: the electrolysis takes place at the electrodes).The oxygen remains on the anode side and is transported away from the membrane via the oxygen conduction channels. Hydrogen protons migrate through the membrane, where they react with electrons on the cathode side to form hydrogen gas. The resulting hydrogen, H2, is removed on the cathode side.

[0025] Preferably, the oxygen discharge ports are relatively large so that the oxygen (O2) can be discharged particularly quickly without disrupting the electrolysis reaction. Particularly preferably, a large oxygen discharge port is provided for each supply port—water (H2O) in electrolysis—so that each process chamber can operate efficiently without disruptive oxygen.

[0026] In a fuel cell, the situation is essentially the opposite of that in an electrolyzer. Here, the electrode according to the invention serves as the cathode. Hydrogen is supplied on the anode side. Oxygen or air, in particular humidified air, is supplied through the cathode, and water is discharged through the cathode. Consequently, several water supply channels and several oxygen supply channels are present. The hydrogen gas is supplied under pressure to the individual channels inside the electrode, for example via an air collection supply line from above. The water is discharged without pressure, for example via the channels and a subsequent water collection discharge line downwards. Here, too, physical properties are exploited. The water follows gravity and flows downwards, i.e. it will not penetrate the pressurized air supply lines.

[0027] In existing systems, the gas diffusion layer has a porous structure in which water and oxygen are distributed in a mixed manner. However, oxygen that is not carried away by the membrane blocks the membrane and thus leads to a reduction in the membrane's performance, so-called fouling. Pores clogged with oxygen gas mean that water cannot be transported to the membrane sufficiently, so that the membrane is not sufficiently humidified and insufficient reaction medium is available. With the present invention, water is specifically transported to the membrane in an electrolyzer through many orifices so that the membrane is always optimally humidified overall and there is an excess of reaction medium available. Furthermore, oxygen is specifically removed from the membrane at the point where the oxygen is produced through separate oxygen orifices that open into oxygen channels.An increase in the performance of electrolyzers equipped with such anodes of approximately 10% was observed, which represents a significant performance improvement.

[0028] Ideally, an electrolyzer would convert exactly as many water molecules into oxygen and hydrogen as the amount of water supplied to the system. However, it is assumed that an excess of water must be supplied. This water must therefore also be removed again. Typically, however, water is supplied to the electrolyzer under pressure, so that pressure is exerted in the water supply channels, but not in the oxygen supply channels. The oxygen supply channels are therefore preferentially used to remove this excess water from the system. Since the recirculated water, unlike in the prior art, is not channeled through pores but through channels – i.e., through structures that are significantly larger than pores – it does not interfere with the oxygen removal. Any water vapor that may be released with the oxygen is also unproblematic. The oxygen can simply be dried after being removed from the system.It turned out that the reaction at the membrane was far more efficient than with known anodes in conventional electrolyzers. Furthermore, the preferred arrangement is such that the gaseous oxygen escapes upwards through the oxygen channels and the excess water flows downwards.

[0029] For the purposes of this invention, the terms "process media" and "reaction media" are used interchangeably. These are liquid or gaseous media involved in the reaction in the electrochemical cell, regardless of whether they are reactants or products.

[0030] In a particularly preferred embodiment, support structures are formed on the shell surface, also referred to as beyond the shell surface. In the version of the electrochemical cell with a membrane support grid, these structures support the grid, and in the gridless version, the membrane directly. In one embodiment, the edges of the outlet openings are used as support structures. In a preferred embodiment, additional three-dimensional structures, also referred to as support structures, webs, or dams, are formed. These structures separate individual process zones from one another, which in the context of this invention are also referred to as reaction cells. The spaces created by the edges of the outlet openings together with the adjoining webs contain reaction volumes.The electrochemical converter according to the invention has at least a first electrode and at least one second electrode, and has a membrane arranged between the first and second electrodes, in particular a polymer electrolyte membrane (PEM) or an anion exchange membrane (AEM). The first electrode is as previously described according to the invention. The second electrode at least partially surrounds the first electrode. In other words: the second electrode encloses the first electrode, with the membrane being arranged between the two electrodes. Viewed from the inside to the outside, the first electrode with the compartmentalized channel structure is therefore in the innermost position, followed and surrounded by the membrane, which is in turn followed by the second electrode, which encloses the membrane.

[0031] In the preferred embodiment, the membrane rests directly on support structures formed on the lateral surface of the first electrode, also referred to as webs or ridges.

[0032] This preferably results in a cylindrical body, i.e. the electrochemical converter is also cylindrical, the definition of the cylinder being mathematical here too, and encompassing both cylinders based on circles or ellipses and prisms based on polygons with a number n of corners, where n = 3 - oo. The cylindrical first electrode is enclosed by a membrane layer and that by a tubular second electrode. However, it is also conceivable for the outer shape of the second electrode to have a shape different from a cylindrical one - similar to the first electrode - and to be, for example, cuboidal or hexa- or octahedral, i.e. not circular in cross-section, but in the shape of a polygon, for example a square, hexagon or octagon.

[0033] The electrochemical converter is particularly preferably manufactured using a selective laser melting process, wherein a first cylindrical electrode is surrounded by a second electrode in the form of two half-shells that together form the surrounding second electrode. These two half-shells are preferably conical on the outer circumference. A sleeve, which is conical on the inner circumference, is pushed over the electrode structure. This allows the two halves of the second cathode to be pressed together and thus sealed; the membrane is pressed against the anode, establishing good electrical contact.

[0034] Membranes available on the market vary in thickness. It has proven advantageous, also in terms of sealing, if the first electrode, i.e. the inner electrode, is manufactured to a specific size using the selected additive manufacturing process and ground along the outer circumference to adapt to the membrane to be used.

[0035] As mentioned above, first and second channels in the electrode according to the invention are guided separately inside the electrode and open separately. According to a preferred embodiment, the channels have the shape of circular sectors when viewed in cross-section. In other words, they can also be referred to as pie slices. This means that the electrode, which is circular in cross-section, is divided into circular segments, and each circular segment is an individual first or second channel. The tip of each "pie slice" can be shortened, since a clamping bolt can be guided in a separate through-opening running along the longitudinal axis in the center of the electrode and thus in the center of an electrochemical converter containing the same.

[0036] In an alternative embodiment, threads can be provided instead of the clamping bolt.

[0037] Clamping bolts or threads preferably also provide the contact option.

[0038] In order to wet the outer surface of the electrode as effectively as possible with, for example, water as the first reaction medium, and to remove the second process medium, for example, oxygen, particularly quickly and as completely as possible from the outer surface or the membrane surrounding the anode or the electrode, a plurality of outlet openings of the first and second channels are arranged distributed over the outer surface. Accordingly, a plurality of channels is also present; particularly preferably, 10-100 channels are formed per electrode (depending on the size of the electrode). As already mentioned, reaction cells, also referred to as reaction spaces or process volumes, are preferably formed in which the reaction takes place.

[0039] First and second channels are particularly preferably arranged alternately, ie viewed from a circumference of the cylindrical electrode, a first channel is followed by a second channel, followed again by a first channel, followed again by a second channel, etc., which serves to improve the media supply and discharge.

[0040] It is preferably provided that each channel extends continuously from one end of the electrode to the other end of the electrode. Preferably, at least one of the first and second channels has one end of the channel closed, while the opposite end is open. Consequently, the process media can only enter the channel at one end or exit it via one end.

[0041] The above is explained using the electrolyzer as an example. The water supply channels are closed at one end, whereas the oxygen discharge channels are open at both ends. Gaseous oxygen escapes from the oxygen channel through the upper end; excess reaction water drains out the opposite, lower end of the oxygen channel.

[0042] If the electrode is an anode, water can be fed in at the lower end of the anode, for example, i.e. the channels which carry water as the reaction medium are open at the lower end of the electrode and closed at the opposite upper end of the electrode, so that pressurised water can be fed into the electrode from below. Oxygen as the product to be removed is therefore carried in the second channels of the anode. In this particularly preferred embodiment, the second channels are open both at the bottom and at the top. The oxygen leaves the electrode via the second channels which are open at the top. Since oxygen is gaseous, it will rise and can therefore be removed particularly easily by the membrane by utilising the physical properties of gaseous oxygen. Any water entering the channel flows down and is fed back into the water cycle there.

[0043] All channels of the electrode are preferably combined into collecting channels, with all first channels being combined into a first collecting channel and all second channels being combined into a second collecting channel, particularly preferably at opposite ends of the electrode, as briefly explained above. The media are supplied and removed via these collecting lines and are introduced into the respective channels or discharged from them in a collected manner.

[0044] The outlet openings of the channels on the lateral surface can, in principle, simply end by an opening or hole formed on the lateral surface. The hole can, for example, have the shape of a circle, a triangle, a square, or a polygon, or even have an irregular, so to speak, free form. The shapes and / or sizes of the outlet openings of the first channels are preferably different from the outlet openings of the second channels. It has proven advantageous if the outlet openings and / or the channels of the product – oxygen in the case of the electrode being used as an anode in an electrolyzer and water in the case of the electrode being used as a cathode in a fuel cell – are larger than the channels and / or outlet openings of the reactant to be supplied – water in the case of the electrolyzer and oxygen or air in the case of the fuel cell.

[0045] In a particularly preferred embodiment, the jacket openings are not simply holes in the jacket or in the jacket surface of the electrode, but are designed three-dimensionally, for example in the form of bulges or projections in which the outlet openings are located. Consequently, projections, elevations, bulges, or webs protrude from the jacket surface of the electrode. The outlet opening can be located on the tip of these three-dimensional structures; however, the outlet openings are preferably not located on the tip or top of these structures, but rather, for example, inside these structures or underneath. This directs the inflow and / or outflow of the medium. The outlet openings can also be arranged on the three-dimensional structures in such a way that they lie in a plane that deviates from a plane arranged parallel to the jacket surface, i.e.the orifice plane intersects the lateral surface plane of the electrode. In other words, the orifices are arranged obliquely to the lateral surface plane, for example, on the sides of the structures. This creates a type of nozzle effect. The process media are fed to and removed from the membrane in a directed manner. The orifices or bulges or other structures particularly preferably point in different directions depending on the channel type, i.e. the orifices and thus the bulges of the first channels point in a different, preferably opposite direction than the orifices and thus bulges or structures of the second channels. As briefly explained at the beginning, certain mixing effects cannot be completely ruled out in the channel that removes the medium, for example oxygen mixing with water in the case of the electrolyzer.It was shown that directing the outlet openings and thus the inflow and / or outflow in opposite directions can reduce this mixing effect.

[0046] As already mentioned, it is particularly preferred to have a plurality of orifices distributed over the outer surface of the electrode. Each channel has at least one orifice. According to a particularly preferred and advantageous embodiment of the invention, each channel has a plurality of orifices, wherein the plurality of orifices is distributed over the length of the channel, and above all is evenly distributed. Thus, several orifices of each individual channel are arranged in a row one behind the other, one above the other, or next to each other, depending on the direction from which the electrode is viewed. The medium conveyed in a channel can thus enter or leave the channel at several points. In the preferred embodiment, orifices arranged next to one another form self-contained process stages, also referred to as process series.If, in addition to horizontally running webs, essentially vertically running webs are added to form the tiered reaction cells, the result is individual cells, also known as microcells.

[0047] The channels are arranged inside the electrode and thus form a so-called channel structure body, on whose lateral surface the orifices end.

[0048] According to a preferred embodiment, the electrode additionally has a grid formed around the channel structure body. A type of outer grid thus surrounds the channel structure body. Preferably, the grid is firmly connected to the channel structure body; more preferably, the channel structure body and grid are integrally formed. However, the outer grid can also be manufactured as a separate component and placed around the channel structure body. The grid structure serves as a support surface for the membrane. With an appropriate geometric design, it can also have a supporting function in guiding the process media into and out of the electrode. Particularly preferably, the openings in the grid are smaller, even more preferably much smaller, than the mouth openings of the channels in order to support the membrane evenly.

[0049] In an alternative design, the membrane, e.g., the PEM or AEM, rests directly on the electrode. Raised support structures, the ridges, are designed for this purpose. In addition to eliminating the need for a grid, this has the advantage of creating individual process cells. The process space is compartmentalized so that the electrochemical reaction can proceed in each individual reaction cell under excellent conditions, since the reactants are added and removed locally, directly at the reaction site. Particularly preferably, the support structures form the cell walls and simultaneously serve as flow guides.

[0050] It should be noted that no sharp distinction is made here between the outer surface of the electrode and the outer surface of the channel structure body. If an outer grid is present, the outlet openings of the process media-carrying channels end on the outer surface of the channel structure body, i.e., that part of the electrode in which the channels are located. The outer grid is therefore considered part of the electrode, since according to the preferred embodiment it is integral with the channel structure body. If an outer grid is missing, the outlet openings end on the outer surface of the electrode. Consequently, "outer surface" here is to be equated with the surface of the electrode according to the invention on or above which the channels open.

[0051] According to an even more preferred embodiment, a catalyst required for the reaction, for example platinum or another noble metal from the platinum group, is applied, in particular sputtered, to the outer grid. Due to the grid structure, the catalyst also penetrates somewhat into the grid openings or the side walls of the grid openings. In the preferred embodiment without a grid, in which the membrane rests on support structures on the inner electrode, the catalyst can be applied to the outer surface of the membrane and in the orifice area to increase the reaction rate.

[0052] It is known in the art to also apply the catalyst to the membrane. A membrane is a two-dimensional structure on which the catalyst is present only as a two-dimensional layer. However, if the catalyst can be applied to the lattice structure or to the support structures, i.e., to a three-dimensional structure, the catalyst can also wet the side walls of the lattice structure or the surface structures present in the reaction cell. In this way, a larger catalyst surface is provided compared to catalyst applied to the membrane, which, moreover, is particularly well-permeated by the process medium.

[0053] The electrode is preferably made of a metal such as titanium. This allows voltage to be applied directly to the electrode without the need for a separate or additional power distributor.

[0054] According to a particularly preferred embodiment, the electrode is manufactured by an additive manufacturing process, for example, by selective laser melting using metal powder, in particular titanium powder. It should be noted that there is currently no other reasonable technology for manufacturing such parts.

[0055] According to an even more preferred embodiment, the catalyst, for example platinum, has already been added to the metal powder, for example titanium, used to produce the electrode through additive manufacturing, or the metal and catalyst have been mixed together. In this way, the entire electrode contains the catalyst and is not just applied two-dimensionally to the surface. This also results in increased efficiency.

[0056] Alternatively, for example, only the part of the metal powder used to produce the outer grid can be mixed with the catalyst that promotes or enables the reaction. In such a case, the electrode could be produced in two parts or in two steps using an additive manufacturing process, because metal powder mixed with catalyst would be applied where the metal powder is fused to form the grid. Whereas inside the electrode, in the channel structure body where the channels are formed, simple metal powder, catalyst-free metal powder is used to create the first structure. The first structure can be manufactured in a first step, and in a further manufacturing step the material mixed with catalyst can then be used to produce an attached grid. The two structures or parts could initially be built separately.For example, the outer grid can be made from a metal powder mixed with platinum, which is then printed as a separate component. This structure can then be combined with the anode in the system, ultimately creating a single (complete) component. This allows the amount of particularly valuable catalysts in the electrode to be reduced.

[0057] The electrochemical converter in which the electrode can be used could be an electrolyzer, for example, in which case the electrode serves as the anode. If a fuel cell is used as the electrochemical converter, the electrode serves as the cathode. These are the current main applications of the electrode. Other uses are conceivable.

[0058] The electrochemical converter is preferably designed modularly, similar to state-of-the-art fuel cell stacks, for example. A plurality or even a multitude of individual systems consisting of anode, membrane, and cathode can be combined to form a larger system. The cylindrical shape, both in the form of a circular cylinder and in the form of a prism, e.g., based on a hexagon or octagon, is particularly well suited for achieving high packing densities.

[0059] As previously mentioned, in the electrochemical converter according to the invention, the second electrode preferably has a tubular shape and surrounds the first electrode. Particularly preferably, the second electrode is not a single piece, but rather a multi-piece configuration. For example, it is divided into two parts, i.e., it has the shape of two half-shells. This is advantageous because the second electrode must tightly enclose the first electrode and the membrane arranged above it. The multi-piece second electrode can thus be assembled around the first electrode and membrane construct.

[0060] According to a particularly preferred embodiment, two grid half-shells are provided, each conically shaped toward the outside. When assembling the electrodes, the membrane is first pressed against the inner electrode by the two grid half-shells. Then, a metal cylinder, which is correspondingly conically shaped on the inside, is pushed over the assembly, pressing the two half-shells against the membrane, which is thereby pressed firmly against the inner electrode.

[0061] Preferably, the second electrode is also made of a metal, so that the gas diffusion layer and current collector are combined in a single part. Electrical voltage can thus be applied directly to the electrode without the need for an additional bipolar plate or bipolar layer.

[0062] The second electrode is preferably constructed in multiple layers, consisting of an outer shell that is closed so that no process medium penetrates the shell, a structural body, and an inner grid, referred to as the inner grid. The structural body serves as a gas diffusion layer and has corresponding pores and / or channels. The process medium(s) move or are moved within these channels. If the second electrode is a cathode, as in the case of an electrolyzer, gaseous hydrogen moves within the electrode and is discharged from the electrode. The inner grid serves as a support for the membrane. A catalyst can also be applied, in particular sputtered, to the inner grid, similar to the outer grid of the first electrode. Furthermore, the membrane can also be coated on both sides with catalyst material.

[0063] The electrochemical converter preferably has a housing which houses the arrangement of first and second electrodes, separated from one another by the membrane. In a preferred embodiment, the gas-tight casing of the second electrode can be used as a housing wall. However, the construct of electrodes and PEM can also be introduced into a separate container, i.e. there can be an additional outer wall, for example in the form of a tube. The bottom and the lid of the container and thus of the housing are formed by a base plate and a top plate, i.e. plate-like structures. The housing is clamped via the plates, for example via an internal bolt or via clamps or tensioning bolts guided externally. Such a housing design should be familiar to those skilled in the art. In an alternative embodiment, a screw connection is made via an internal thread.

[0064] The clamping bolt or screw can also serve as the electrical pole for the first electrode. The housing wall, for example, the gas-tight casing of the counter electrode, can serve as the second pole. To seal the housing, annular seals can be provided, for example, which also separate the individual channels, or more precisely the collecting channels, i.e., the supply and discharge channels. Accordingly, it is particularly preferred to provide recesses, e.g., in the form of grooves, in the base plate and top plate into which the ends of the two electrodes and the membrane can be inserted. Seals, e.g., O-ring seals, are provided in the recesses for sealing.

[0065] The base plate, also called the floor, and the top plate, also called the lid, are preferably made of a non-conductive material, such as plastic. If they are made of an electrical conductor, they must be electrically separated from each other.

[0066] The manifold channels, i.e., the combined first and second channels, are particularly preferably located in the base plate and / or the top plate. Consequently, the process media are supplied and removed via the base plate and top plate.

[0067] If the electrode is used in an electrolyzer, the water supply is preferably via the base plate. A water connection is provided there, through which water can be introduced under pressure into the collection channel and from there distributed into the individual water supply channels of the electrode structure body. The oxygen removal and hydrogen removal take place in the top plate. The oxygen channels leading out of the anode are combined into a collection oxygen channel in the top plate, which is then led out of the top plate. The oxygen can be fed into an oxygen collection container, if necessary after undergoing a drying step. If excess water enters the oxygen channels, it will flow downwards into them and can then be fed back in as process water via the water supply channels.The hydrogen conducted in the cathode is fed to a hydrogen collection channel and a hydrogen connection, where the hydrogen leaves the top plate and thus the electrolyzer and can be fed to a hydrogen collection container.

[0068] In a fuel cell, the situation described above is essentially similar. The base plate contains water collection channels into which the water conduction channels of the electrode structure flow and are combined to remove the resulting water. The top plate contains gas connections for supplying the hydrogen and the oxygen or air. The oxygen / air channels are divided so that oxygen or air can be supplied to each oxygen conduction channel in the electrode. From the above, it is clear that the electrode according to the invention has the great advantage that the medium to be removed can be removed directly via a channel at the point of origin—for example, the oxygen at the membrane surface in the case of electrolysis. The oxygen therefore remains in the membrane region for as short a time as possible. Unlike with conventional electrolyzers, blockages caused by oxygen in the membrane region occur much less frequently.Likewise, the reaction medium to be supplied, for example, water in an electrolyzer, is fed directly to the membrane. For this purpose, the channels extend radially out of the electrode.

[0069] Unlike the prior art, the process media can be directed through the electrode according to the invention. The prior art uses porous gas diffusion layers in which water and oxygen reside and move together. This results in problems such as membrane clogging, which prevents the resulting hydrogen or protons from being removed. Hydrogen passes through the membrane, but the oxygen formed displaces the process water, which leads to a reduction in efficiency. Furthermore, unlike in known gas-liquid diffusion layers, the pores are not "clogged" by individual molecules. The present invention specifically counteracts these problems.Due to the segmentation of the channel structure body, on the one hand the channels inside are large enough to conduct the media unhindered and on the other hand the large number of channels and outlet openings per channel serves to ensure good distribution and drainage of the media.

[0070] It has been shown that the size and shape of the orifices also influence the supply and discharge of the process media. Therefore, embodiments are included in which the orifices of the first channels, i.e., the channels for conveying a first process medium, have a different size and / or shape than the orifices of the second channels, i.e., the channels for conveying a second process medium.

[0071] In the figures, the diameters of the channels are always shown as approximately the same. However, it is also intended that the channels for the first process medium have a larger cross-section than the channels for the second process medium. Oxygen molecules, for example, are relatively large. Furthermore, it is very important in the electrolyzer to remove any oxygen produced from the reaction site as quickly as possible. Consequently, one embodiment provides for the orifices for oxygen to be larger than those for water. Likewise, but not shown in the drawing, it is intended that the oxygen supply channels have a larger diameter than the water supply channels. Water is supplied under pressure; this also works, or particularly well, in a channel with a small diameter. Oxygen, however, is discharged without pressure. Furthermore, any excess process water must be drained off through the oxygen channel.As a result, oxygen supply channels are equipped with a larger diameter than water supply channels.

[0072] Advantageous embodiments and further developments are set out below, which, viewed individually or in combination, may also reveal inventive aspects.

[0073] Short character description

[0074] The present invention can be understood even better if reference is made to the accompanying figures, which illustrate particularly advantageous embodiments by way of example, without limiting the present invention to these, wherein

[0075] Figure 1 shows a first embodiment of an electrode according to the invention in perspective view;

[0076] Figure 2 shows a cross section through a further embodiment of an electrode in perspective view (A) and in plan view (B);

[0077] Figure 3 is a schematic sectional view of an electrolyzer with a cylindrical electrode;

[0078] Figure 4 shows an external view of an embodiment of an electrochemical converter in perspective;

[0079] Figure 5 shows a first section (A), a first side view (B), a second section (C) and a second side view of an embodiment of an electrolyzer;

[0080] Figure 6 shows schematic representations of various sections through another embodiment of an electrolyzer;

[0081] Figure 7 shows Figures 6B and 6D in an enlarged view and in more detail;

[0082] Figure 8 shows two schematic sections through an embodiment of a fuel cell;

[0083] Figure 9 shows a second embodiment of an electrode according to the invention in a perspective view;

[0084] Figure 10 shows a schematic representation of a section of views of two different embodiments of electrodes;

[0085] Figure 11 shows a third embodiment of an electrode according to the invention; and

[0086] Figures 12A and 12B each show plan views of sections of a developed version of further electrodes according to the invention. Description of the Figures

[0087] Figure 1 shows an embodiment of an electrode 1 according to the invention in a perspective view. The electrode described in Figure 1 is designed as an anode for use in an electrolyzer, but can also be designed with a similar construction as a cathode for use in a fuel cell. To simplify the description, the electrode in Figure 1 is described below in its function as an anode.

[0088] The anode 1 comprises a channel structure body 3 and an outer grid 5. However, the outer grid 5, which in the present embodiment is machined integrally with the channel structure body 3 of the anode 1, is only shown around half its circumference in order to also show underlying structures. The membrane 20 is located around the anode 1 and on the grid 5—shown in detail in Figure 1.

[0089] The anode 1 was manufactured in its entirety by a selective laser melting process, in particular from a metal such as titanium. Numerous channels are incorporated into the channel structure body 3; examples of such channels are shown in Figure 2.

[0090] The water H2O is supplied to the anode 1 at a first end of the electrode 16. A water inlet 15 is provided there for this purpose. Via this inlet, pressurized water is supplied to the internal water supply channels 6. Any excess water flowing back is collected and returned via the downwardly open ends of the second channels 8, i.e., the oxygen supply channels, in the water outlet 17. The water, which is supplied to the channel structure body 3 via the water inlet 15 and distributed within it via the water supply channels 6, reaches the outer surface or outer surface 12 of the channel structure body 3 via outlet openings 7 and thus to the membrane 20 resting on the outer grid 5, e.g., a polymer electrolyte membrane (PEM) or an anion exchange membrane (AEM), which surrounds the anode 1.Excess water enters the oxygen outlet openings 9 and flows downwards in the oxygen line channels 8 via the water outlet 17, where the excess water is again available for supply via the water inlet 15.

[0091] In addition to outlet openings for water 7, outlet openings for oxygen 9 are also provided, through which oxygen O2 produced during the electrolysis process is discharged via the channel structure body 3. The outlet openings 9 are in turn openings on the outer surface 12 into the oxygen conduction channels 8 - see reference numeral 108 in Figure 2. All oxygen conduction channels 8 of the channel structure body 3 are open at both their ends, i.e., open to both the first end 16 and the second end 18 of the electrode. Since oxygen rises as a gaseous substance and water follows gravity, the oxygen O2 leaves the anode 1 via a corresponding oxygen outlet (not shown in Figure 1), and excess water leaves the oxygen conduction channels at the opposite, lower end. The individual oxygen conduction channels are bundled into a corresponding oxygen collection channel (not shown) at end 18 to discharge the oxygen.

[0092] Unlike the oxygen supply channels 8, the water supply channels 6 are closed at the second end 18 and open exclusively towards the first end 16.

[0093] In the illustration in Figure 1, two different types of outlet openings can be distinguished not only by their purpose, but also by their size and shape. The outlet opening for water 7 is triangular and is essentially a corresponding hole in the outer surface 12 of the channel structure body 3 of the anode 1. The outlet openings for oxygen 9, in contrast, are three-dimensional structures, with the opening itself being larger than the outlet opening for water 7. In the embodiment shown in Figure 1, the outlet opening 9 itself is located on the front side of this three-dimensional structure, which could be described as igloo-like. This igloo-like bulge is designated 10 in Figure 1.

[0094] The orifices protruding from the lateral surface preferably have a flow-guiding function and serve as a support for the outer grille 5 or, in another preferred embodiment (not shown in Figure 1; however, see Figure 12), as part of the support structures for the membrane 20.

[0095] It can also be seen that there is a whole number of both superimposed mouth openings 7 and correspondingly superimposed mouth openings 9.

[0096] All outlet openings 9 are provided with or equipped with the bulge 10. Figure 1 also shows that two outlet openings 9, 9' are located opposite each other, with an outlet opening for water 7 located in the middle. The outlet openings 9 are arranged such that the outlet openings 9 face each other, whereas the corresponding bulges 10, 10' are arranged behind them, so to speak. By arranging the outlet opening 9 for oxygen at an angle to the outer surface 12, i.e. not parallel to it, but obliquely to it, for example at an angle of 60 degrees, oxygen can be drawn off from the membrane (not shown in Figure 1) particularly efficiently and quickly. Water, on the other hand, is supplied to the membrane via the outlet openings 7 over as large an area as possible.

[0097] A major advantage of the inventive electrode lies in the targeted supply of the substrate, for example, water, and the targeted removal of the product from the reaction site. In addition to the separate channels formed inside the electrode for supplying the substrate and removing the product, the numerous outlet openings for both process media, and possibly their different sizes, shapes, and / or arrangements, it has been shown that flow guide elements, also referred to as profiles, present in the area of ​​the outlet openings, positively influence this supply and removal. One exemplary embodiment of flow guide elements is the bulges 10.

[0098] As already briefly mentioned at the beginning, the outer grid 5 is only shown in half. It can therefore be clearly seen that the outer grid 5 closely encloses the channel structure body 3 of the anode 1. The outer grid 5 is equipped with a plurality of grid openings 11. The grid openings 11 can have a uniform shape, i.e. one grid opening can look like the other. The grid openings 11 can, for example, have the shape of a grid. However, the grid openings can also have several different shapes. For example, the outer grid 5 can be designed like a perforated plate, i.e. have holes, in this case holes with an irregular shape. In the present case, moreover, two different types of grid openings 11 or grid structures are present. The grid can also contain flow guidance geometries.

[0099] It can also be seen that the grid openings 11 are smaller, in other words, significantly smaller, than the outlet openings 7 and 9 of the underlying channel structure body 3. The membrane 20 rests on the grid 5. One function is thus to support the membrane. Furthermore, the numerous grid openings 11 are intended to quickly conduct oxygen into the interior of the anode 1, i.e., to the channel structure body 3. It is important that the oxygen can quickly pass through the grid openings 11. Furthermore, water supplied via the outlet openings 7 is to be evenly distributed to the membrane 20.

[0100] As already mentioned, the outer grille 5 rests on the channel structure body 3, more precisely on the raised support structures present there, the bulges 10 of the outlet openings. The height of these three-dimensional structures thus indicates the distance from the lateral surface or from the outlet openings 7, 9 present there, which the outer grille 5 and thus the membrane 20 resting on it occupy. If no outer grille 5 is present (cf.

[0101] Figures 12), the membrane rests directly on these supporting structures.

[0102] Figure 1 also shows the layout of the individual water supply channels 6 and oxygen supply channels 8 arranged inside the channel structure body 3. As can be seen, a plurality of outlet openings 9 are arranged one above the other. This represents the totality of outlet openings 9 that belong to a single oxygen supply channel. Consequently, oxygen is supplied to the same oxygen supply channel via the outlet openings 9, which are arranged one above the other. A water supply channel is adjacent to each oxygen supply channel, and accordingly, a plurality of outlet openings for water 7 are arranged one above the other. This is followed in turn by another oxygen supply channel. Accordingly, outlet openings 9 are again arranged one above the other.Consequently, within the channel structure body 3, a water conduction channel always follows an oxygen conduction channel, which is then followed by another water conduction channel and then another oxygen conduction channel, etc. Oxygen conduction channels and hydrogen conduction channels alternate. Outlet openings 7 and 9 located in a row each belong to a single channel. Consequently, all channels run from the first end 16 to the second end 18, along a longitudinal axis L of the electrode 1.

[0103] The longitudinal axis L runs through the electrical pole 13. Pole 13 is also used for the assembly and clamping of an assembled electrolyzer. An internal thread 19 is provided for this purpose.

[0104] The end faces of the outer grille 5, the pipe 13, and the partition between the water inlet 15 and the water outlet 17 serve as sealing surfaces (see Figure 9). These end faces engage in corresponding grooves of the closing components, such as the cover and base, and can be sealed with ring seals.

[0105] Figure 2 shows a section through an electrode such as that shown in Figure 1. However, the illustration is somewhat simplified. It shows a section through an electrode 101, which in turn consists of a channel structure body 103 with a centrally formed electrical pole 113 and an outer grid 105. Here, too, the outer grid is only shown over approximately half the circumference. The channel structure body 103 in the interior 104 of the electrode 101 is not exactly circular in cross-section, as can be seen in Figure 2B. It can roughly be described as octagonal. This body, which has the shape of an eight-sided prism, is surrounded by a shell in the shape of the outer grid 105, so that overall a circular cylindrical body is present.

[0106] As already explained in relation to Figure 1, a whole number of outlet openings terminate on the lateral surface 112 of the channel structure body 103, namely outlet openings of a first channel 107, for example outlet openings for water, and of a second channel 109, for example outlet openings for oxygen 109.

[0107] It is clear that the channel structure body 103 is subdivided into multiple circular sectors; one could also refer to the circular sectors as pie slices. Each circular sector represents a single channel for conveying process media. A distinction is made between a first channel 106, for example, a water line channel, and a second channel 108, for example, an oxygen line channel. The first and second channels alternate.

[0108] If the first channel 106 is a water conduit, water 45 is conducted inside it. If the second channel 108 is an oxygen conduit, oxygen 40 is conducted inside it.

[0109] Figure 2B also shows that the outer grille 105 itself does not have to be a flat, purely two-dimensional structure, but can also be designed three-dimensionally. In the present case, the grille openings 111 are not always located on the same circular line, i.e., at the same distance from a center of the channel structure body 103, but rather on two circular lines with different radii. In other words, there are grille openings 111 1 , which are located on an outer circular line and thus farther away from a longitudinal axis L (see Figure 1) than the grid openings 111, which are located on a further inner circular line. The grid openings 111 are designed here as flow-guiding geometries.

[0110] It should be clarified that Figure 2 is not to be understood as a design drawing, but merely as a schematic representation. Dimensions, including relative dimensions of two components to each other, etc., are not shown; only the functional principle is shown.

[0111] Figure 3 is also a schematic representation. It shows a longitudinal section through an electrolyzer 200 as an example of an electrochemical cell. An anode 201, similar in type to the anode 1 shown in Figure 1, is inserted into the electrolyzer 200 as a first electrode 98. Furthermore, a second electrode 99, the cathode, is present in the electrolyzer 200. As previously described, the anode 201 has, in its interior 204, a channel structure body 203 in which oxygen 40 and water 45 are conducted. As previously explained, oxygen and water are guided separately from one another in the channel structure body 203 of the anode 201, each in separate water conduction channels and oxygen conduction channels (neither shown here). The channel structure body 203 is surrounded by an outer grid 205. Also shown are the membrane 220, in particular a PEM or an AEM, as well as the cathode 230 which is connected to the outside.

[0112] The cathode 230 has a grid-shaped cathode body 231, which connects to the membrane 220. Further outwardly is an electrode jacket 232, which is gas-tight. In an alternative embodiment, the cathode 230 has a porous cathode body, which is gas-tight to the outside and can therefore also be used as a housing. However, here the entire structure consisting of the cathode, anode, and membrane is enclosed in a separate housing.

[0113] Water 45 is supplied to the anode via a corresponding water inlet 215 and distributed through the channel structure body 203 and its orifices on the outer surface (see respective description of Figure 1) and the membrane 220 arranged at a distance from the orifices. Water 45 is circulated, i.e., it leaves the anode again via the oxygen conduit channels, at the opposite end to the oxygen outlet, which open into a corresponding water outlet 217, from where the water re-enters the circuit and is supplied to the anode. Oxygen formed at the membrane 220 is collected via oxygen conduit channels in the channel structure body and discharged via an oxygen outlet 221. Hydrogen produced is discharged via hydrogen outlets 222 on the cathode side.

[0114] Figure 4 shows an external view of an electrochemical converter 300. The electrochemical converter 300 can be an electrolyzer, for example, a fuel cell, or another type of electrochemical converter. The electrochemical converter 300 has a housing 360 composed of a top plate 361, a container wall 363, and a base plate 362. The top plate 361 and base plate 362 seal the electrochemical converter at the top and bottom, respectively.

[0115] In the embodiment of Figure 4, the device is clamped via a clamping bolt 364, which can be guided in a central pipe or bore, for example (see Figure 1, reference numeral 13). Base plate 362, container wall 363 and top plate 361 are threaded onto the clamping bolt 364 and clamped together via the nut 367. The electrodes and the membrane, i.e. the electrochemical cell, are arranged inside, as explained in relation to Figure 3. The clamping bolt 364 can be used as the first electrical pole 365 and the container wall 363 as the second electrical pole 366. The inlets and outlets for the process media are incorporated in the top plate 361 and base plate 362. A single inlet and outlet 368 are shown as an example.

[0116] Figure 5 shows various views of an electrolyzer 400 as a further example of an electrochemical converter in which the electrode according to the invention comprising a channel structure and an outer grid can be used. The electrolyzer 400, in turn, is assembled from a top plate 461, a housing wall 463, and a base plate 462. A hydrogen connection 469 and an oxygen connection 470 are formed in the top plate 461 to discharge hydrogen and oxygen, respectively. A water inlet valve 471 and a water outlet valve 472 are provided in the base plate 462, with the water outlet valve also serving as a return line, since the water is circulated, as described here with reference to Figure 3. Furthermore, grooves for seals are provided in the top and base plates to seal the electrolyzer. The electrolyzer 400 is also clamped together using a clamping bolt 464 and a corresponding nut 467.The positive pole is applied to the clamping bolt as the first electrical pole 465 and electrical voltage is also applied to the housing wall 463 so that it can be used as the second electrical pole 466, here the negative pole.

[0117] Figure 6 shows an electrolyzer 500 schematically, but in more detail. Various sectional views are shown, although some of the details are only partially shown, for example, the channels in Figures 6B and 6D. The electrolyzer 500 is constructed from a top plate 561 and a base plate 562, which are clamped together by means of a nut 567 and a clamping bolt 564.

[0118] A separate housing wall, such as in Figures 4 and 5, is not provided; instead, the gas-tight wall 532 of the cathode 530 is used as the housing wall. At the same time, the wall 532 serves as the negative pole, the second electrical pole 566, for supplying the cathode 530.

[0119] The cathode 530 also has a porous cathode grid body, reference numeral 531. The hydrogen 50 is collected in the porous, grid-shaped cathode body 531 and discharged via the hydrogen connection 569. In the present exemplary embodiment, the cathode 530 functions as the second electrode within the meaning of the invention. It should be clarified that, due to the additive manufacturing process also preferably used for the production of the cathode, the cathode body 531 has a precisely defined three-dimensional grid structure.

[0120] The anode 501 is the first electrode in the sense of the invention; its construction has been described by way of example in Figure 1. A channel structure 503 is surrounded by an outer grid 505. The membrane 520, for example, a polymer electrolyte membrane or an anion exchange membrane, is arranged between the anode and cathode. The clamping bolt 564 is used as the positive pole for the anode, the first electrical pole 565, and also serves to brace the housing. Water is supplied to and removed from the structure via the base plate 562; a water inlet valve 571 and a water outlet valve 572 are provided accordingly. As already explained above, water 45 is circulated. Oxygen 40, in turn, is withdrawn via the top plate, into which a corresponding oxygen connection (not shown) is incorporated.

[0121] In the longitudinal sections of Figures 6A and 6C, a single channel is shown to the right and left of the clamping bolt 564. In Figure 6A, the section is held such that two oxygen supply channels 508, 508 1 can be seen. The oxygen 40 is discharged via the upper, first end 516 of the electrode. In the embodiment of Figure 6A, a return opening is provided in the lower region of the oxygen conduit channel. Should water flow through the orifice into the oxygen conduit channel 508, 508 1 penetrate, it can flow downwards to the second end 518 and be fed into the water cycle.

[0122] In Figure 6C, however, two water pipes 506, 506 1 shown. Towards the top, at the first end of the electrode 516, transverse walls 502 are provided, which form the water supply channel 506, 506 1each at the top. This means that no water can escape from the electrode or towards the top plate 561 and thus also not into the collecting channels 508, 508 1 for oxygen. Water 45 is supplied via water connection 571 and thus reaches membrane 520 through water orifices 507.

[0123] Figures 6B and 6D show the design of the first and second channels in more detail, although to simplify the illustration, only four channels are shown in the channel structure body 503. Two water supply channels 506, 506 are shown for each cross-section. 1 as first channels and two oxygen supply channels 508, 508 1as second channels. The position and shape of the oxygen orifices 509 and the water orifices 507 can also be seen. Figure 7 again shows an electrolyzer 600. This is comparable in structure to the electrolyzer in Figure 6. To avoid repetition, reference is made to what was said there. In short, a first electrode, the anode 601, consisting of a channel structure body 603 and an outer grid 605, is surrounded by a second electrode, the cathode 630, consisting of a grid-shaped electrode body 631 and a gas-tight casing 632, wherein the two electrodes are separated from one another by a membrane 620, e.g., a polymer electrolyte membrane.

[0124] The design of Figure 7 differs, however, in the second electrode, since the cathode 630 is a two-part cathode with a first cathode half 634 and a second cathode half 635, which are joined together to form the tubular cathode 630. The cathode body 631 is accordingly a two-part cathode grid body 631a and 631b. The cathode 630 is tubular in the design of Figure 7 and consists of two longitudinal halves. These shell-like cathode halves 634 and 635 are placed over the membrane 620, which in turn is placed over the first electrode, the anode 601, and connected to one another to form the cathode 630. In the present design, a connecting flange 637 with an O-ring seal is provided to make the system gas-tight despite the two-part nature of the second electrode.By designing the second electrode as an electrode consisting of shell-shaped halves, the assembly of an electrochemical cell is significantly simplified. The two cathode halves 634, 635 are connected to each other at the junction 636 and, if necessary, also electrically connected to each other via this connection.

[0125] In a particularly preferred embodiment (not shown), the two cathode grid bodies 631a, 631b are preferably conical on the outer circumference. Instead of the connecting flanges 637, the cathode grid body halves are connected to the anode and the membrane to form the electrolyzer using a sleeve—the gas-tight casing 632—which is pushed over the cathode grid halves. The sleeve is conical on the inner circumference, whereby the cathode grid halves are pressed together and onto the anode above the anode and the membrane resting thereon (possibly an additional grid). It has been found that assembling the electrolyzer in this way is particularly easy, and the electrolyzer produced in this way is very well sealed. In the present case, an electrolyzer is referred to as an exemplary embodiment. Of course, this basic structure can also be used for the production of a fuel cell.

[0126] In the embodiment shown in Figure 7, the channels are designed in different sizes. Similar to the oxygen outlet openings 609 being larger than the water outlet openings 607, the water supply channels 606 are smaller than the oxygen supply channels 608. As already described, this has the advantage that the oxygen 40 can be quickly removed from the electrolyzer 600. Likewise, excess water, which is also removed through the oxygen supply channels 608, does not interfere with the oxygen removal.

[0127] Figure 8 shows a fuel cell 700 as a further embodiment of an electrochemical converter. The first electrode, and thus the electrode according to the invention, is used in this case as the cathode 730. The electrode 730 has a channel structure body 703, surrounded by an outer grid 705, on which the membrane 720, in particular a PEM, rests. In a fuel cell, the cathode is surrounded by an anode, here the anode 701, which is fundamentally similar in structure to the cathode 630, as described above for the electrolyzer in Figure 6. The anode 701 consists of a porous electrode body 731; however, a gas-tight casing is missing. This electrode is also two-part, thus having two half-shells of the electrode body 731. The anode halves 734 and 735 in the form of half-shells are arranged around the membrane 720.

[0128] Unlike the embodiment of Figure 6, however, the fuel cell 700 of Figure 8 is surrounded by a housing tube 738, which provides gas tightness to the outside. The anode 701 in the present embodiment is tubular, similar to the cathode 630 of Figure 6, and accordingly, the first anode half 734 and second anode half 735 are connected to each other via the connection point 736.

[0129] Since in a fuel cell, hydrogen is supplied via the anode, oxygen 40 or oxygen as a component of air under pressure is supplied via the cathode, and water 45 is discharged via the cathode, the conduits present in the channel structure body 703 of the cathode 630 are dedicated to the aforementioned media. The first channel is an oxygen conduit 708 with outlet openings 709, and the second channel is a water conduit 706 with outlet openings 707. Voltage is applied via terminals 765 and 766.

[0130] Figure 9 shows an electrode 80 with a corresponding channel structure body 83 and an outer grid 85 resting thereon. Similar to Figure 1, the outer grid 85 is again only shown in half in order to also obtain a view of the outer surface 96 of the channel structure body 83. In the present exemplary embodiment, the outer grid 85 is grid-shaped in the sense of a net grid. The electrode 80 has channels 86 for a first process medium and channels 88 for a second process medium. As can be seen, these channels alternate with one another, so that a channel 86 is followed by a channel 88, which is followed again by a channel 86, and so on. Each channel 86, 88 ends with a plurality of outlet openings 87 for a first process medium and 89 for a second process medium. The channel 86 for a first process medium is thus provided with a number of outlet openings 87 for a first process medium.The channel 88 for a second process medium is equipped with a plurality of orifices 89 for a second process medium.

[0131] Again, the outlet openings 89 and 87 differ in shape and size. Thus, the outlet openings for a first process medium 87 are smaller than the outlet openings 89. They could be described as slot-like holes in the jacket surface 96. The outlet openings 89, on the other hand, are relatively large openings. The outlet openings 89 also run parallel to the plane of the jacket surface 96, but are each partially surrounded by support structures, which can also serve as flow guide elements, in this case a so-called wall or web 97. The support structures serve to space the membrane from the outlet openings and as a support surface for the outer grid 85 or - see Figure 12 - directly, without an intermediate grid, as a support surface for the membrane.The web 97 rises from the lateral surface 96 toward the outer grid 85 and, in addition to its function as a spacer, enables a directed supply or introduction of process media into the outlet opening 89 or a directed discharge or expulsion of the process medium out of the outlet opening 89. The outlet openings for a second process medium 89 can thus assume a nozzle-like function in the case of supply openings. The web 97 also prevents, for example, a gaseous process medium, such as oxygen generated in the electrolyzer, from migrating along the electrode. Instead, the web 97 captures the oxygen and guides it to a corresponding oxygen conduit channel, here channel 88.

[0132] Due to the row-like, adjacent arrangement of the outlet openings 87 and 89, the course of each individual channel 86 and 88 is clearly visible. The outlet openings 87 in a row are each assigned to a single channel 86. Likewise, all outlet openings 89 in a row belong to a single channel 88. Each channel 86, 88 has a plurality of outlet openings 87, 89, which are distributed over the lateral surface of the channel structure body 83, corresponding to the course of the associated channel inside the electrode. It is also clearly visible in Figure 9 that all channels 88 for a second process medium are brought together at the first end of the electrode 94 and combine in a collective supply and / or discharge channel 90 for the first process medium P1.In the case of the electrode as an anode for an electrolyzer, the first process medium is water and the water return is guided via the channels for the second process medium 88, which are combined at the first end of the electrode 94 to form a collecting channel.

[0133] The channels 86 for supplying the first process medium P1, e.g., water in the case of an anode for an electrolyzer, are open in the inner region of the electrode. The process medium P1 is supplied via a collective supply channel 91 and distributed among the individual channels 86.

[0134] Several sealing surfaces are designed to make the assembled electrolyzer both liquid-tight and gas-tight to the outside. A first sealing surface 82 is provided on the outer grid 85. The two collecting supply and / or discharge channels for a first and a second process medium 91, 90 have a second sealing surface 92. Finally, the pipe 93 also has a sealing surface, the third sealing surface 96.

[0135] The electrode has a central tube 93 through which the voltage can be applied and in which a clamping bolt can be guided if necessary.

[0136] Figures 10A and 10B depict further geometric shapes and arrangements of orifices. Each shows a section of a lateral surface 196 or 296 of an electrode not otherwise shown in detail.

[0137] Figure 10A shows a section of a lateral surface 196. Shown are three outlet openings, each of which is a channel. The channels are indicated by dashed lines. The outlet openings 187 are triangular, whereas the outlet openings 189 are quadrangular in shape, similar to a kite. The tips of the outlet openings 189 are arranged exactly the opposite way round to the tips of the outlet openings 187. As already explained several times, different process media are conveyed in the channels 186 than in the channels 188.

[0138] Figure 10B shows a further exemplary embodiment, again in the form of a section of the lateral surface 296. Here, too, the channels 286, 288 are indicated by dashed lines. The orifices 289 are semicircular, whereas the orifices 287 of the channels 286 are obliquely slit-like. Finally, Figure 11 shows a further exemplary embodiment of an electrode 380. The outer grid 385 is again only shown in sections to allow a view of the lateral surface 396. A number of orifices 387, 389 are incorporated into the lateral surface 396 of the channel structure body 383. It can be clearly seen that the orifices 387 and 389 are surrounded by a zigzag, wall-like structure—referred to as a wall or web 397. This bridge 397 is present on one side only - here referred to as “back”.Water that might, for example, escape from the orifice 387 is thus directed to the membrane and does not interfere with the oxygen entering the orifice 389. The web 397 serves as a nozzle and, at the same time, as a spacing and protective function.

[0139] Figures 12A and 12B each show a section of an electrode; more precisely, they show, at a greatly enlarged and schematic level, a top view of an unwound electrode—here realized as an anode. Internally, the electrode is constructed as explained in the preceding figures—the individual process media are routed separately. Particularly preferably, each channel terminates in different reaction cells via its plurality of openings.

[0140] The channel structure body of these electrodes, in Figure 12A the channel structure body 883 and in Figure 12B the channel structure body 983, or the surface of the respective channel structure body is designed in such a way that individual, separate reaction spaces or process zones are created, here called reaction cells and provided with the reference numerals 881 and 981, respectively.

[0141] Each reaction cell 881, 981 has access to at least one channel each for supplying a first process medium and for discharging a second process medium. Accordingly, each reaction cell 881, 981 has at least one outlet opening for a first process medium 887 or 987 and at least one outlet opening for a second process medium 889 or 989.

[0142] The individual reaction chambers are separated from one another by means of web-like structures, also referred to as webs, designated with the reference numerals 897 and 997a / b, respectively. These are raised structures that extend outward from a central longitudinal axis of the cylindrical or prismatic electrode, from the cylindrical shell, or beyond the cylindrical shell. The geometries 897 and 997a / b are equally protruding and form the cell height.

[0143] The reaction chambers are sealed off from the outside by the overlying membrane (not shown in Figures 12A / 12B - see, for example, reference numeral 220 in Figure 3 or 520 in Figure 6), e.g., a PEM membrane or an AEM membrane. It rests directly on the webs 897, 997a / b.

[0144] In Figure 12A, the reaction cells 881 are arranged in tiers, also referred to as rows or slices. For better understanding, individual reaction cells are shown separately as reaction cells 881, 881', 881" and 881 IH . Each reaction cell 881 , 881 ', 881" and 881 Hl comprises a whole number of outlet openings for a first process medium 887 and outlet openings for a second process medium 889. Again, to illustrate what has been said, individual outlet openings are marked separately, see, for example, reference numerals 889, 889 1 , 889" and 889 1 ".

[0145] In Figure 12B, the individual reaction cells are reduced in size to such an extent that each reaction cell 981 has only a single outlet opening for a first process medium 987 and a single outlet opening for a second process medium 989. This is explained using reaction cell 981 as an example. It has only one outlet opening 987, e.g., for supplying water, and only one outlet opening 989, e.g., for removing oxygen and any excess process water.

[0146] Each of Figures 12 shows an anode. The orifices for oxygen removal—reference numerals 889 and 989—are preferably particularly large so that the gaseous oxygen produced during the reaction can be removed particularly quickly without interfering with or inhibiting the reaction.

[0147] Particularly preferably, the number of orifices 887, 987 is at least as large as the number of orifices 889, 989. In other words, for each relatively small supply orifice 887, 987—in the case of electrolysis, water H2O—there is at least one large discharge orifice 889, 989—oxygen O2. This ensures that each individual reaction cell 881, 981 can operate efficiently.

[0148] Each individual reaction cell 981 - for example, the reaction cells 981 , 981 ', 981", 981 Hl and 981 lv - is bounded by web-like structures, the webs 997a and 997b. Unlike in Figure 12A, in addition to the tier-by-tier separating webs 997a, transverse separating webs 997b are also provided. This is illustrated by the example of reaction cell 981, which is defined by two webs 997a, 997a. 1 and two bridges 997b, 997b 1 from the neighboring reaction cells 981 1 and 981v are separated. Reference is again made to Figure 11, which shows similar structures to the electrode in Figure 12A. The electrode 380 in Figure 11 has separating structures, the webs 397, so that, similar to Figure 12A, individual reaction cells can be formed that are arranged in rows, i.e., have a short cylindrical shape. To form the reaction spaces, the membrane does not rest on the grid 385, but is placed directly on the webs 397.

[0149] As can also be seen from Figure 11, in an alternative embodiment, instead of a membrane, an external grid (cf. reference numeral 385 in Figure 11) can be placed on the channel structure body 883 or 983, or the cylindrical membrane thus produced can be covered with it.

[0150] The design options shown in the individual figures can also be combined with each other in any way.

[0151] List of reference symbols

Claims

Patent claims:

1. Electrode (1, 80, 101, 201, 380, 501, 601, 701) for an electrochemical converter (200, 300, 400, 500, 600, 700), in particular for an electrolyzer (200, 400, 500, 600) for splitting water (45) into hydrogen (50) and oxygen (40) or for a fuel cell (700) for generating water by an electrochemical reaction of hydrogen and oxygen, wherein the electrode has a substantially cylindrical shape, characterized in that the electrode has in its interior (104, 204) a plurality of first channels (106) for supplying a first process medium, in particular water line channels (506, 606, 706) for supplying water as the first process medium, and a plurality of second Channels (108) for discharging a second process medium, in particular oxygen line channels (508, 608, 708) for discharging oxygen as the second process medium, wherein the first channels and the second channels are separated from each other,so that the first process medium can be supplied inside the electrode separately from the second process medium, and that each first channel as well as each second channel on a lateral surface (12, 96, 112, 196, 296, 396) of the electrode opens into at least one orifice (7, 9, 107, 109, 507, 509, 607, 609, 707, 709), in particular into a plurality of orifices, via which the process media can leave and / or enter their channels.

2. Electrode according to claim 1, characterized in that the first and the second channels are circular sectors in a cross-section, so that the interior of the electrode is divided into a kind of pie slices, each circular sector being either a first or a second channel.

3. Electrode according to claim 2, characterized in that first and second channels are arranged alternately, so that, viewed in a cross-section of the electrode, each first channel is followed by a second channel, followed by a further first channel.

4. Electrode according to one of the preceding claims, characterized in that the channels extend from a first end (16, 94, 516) to an opposite second end (18, 95, 518) of the electrode viewed in a longitudinal direction of the electrode, wherein all Channels are open at at least one end for introducing and / or discharging the process media into the corresponding channel and wherein at least one of the first and second channels ends blindly at the end of the electrode opposite the open end.

5. Electrode according to claim 4, characterized in that all first channels of the electrode are combined at the end of the electrode at which they are open, so that the first process medium to be guided in the first channels can be collectively discharged or supplied, and that all second channels of the electrode are combined at the end of the electrode at which they are open, so that the second process medium to be guided in the second channels can be collectively discharged or supplied.

6. Electrode according to one of the preceding claims, characterized in that the first mouth openings (7, 87, 107, 187, 287, 387, 507, 607, 707, 887, 987) of the first channels opening onto the lateral surface have a different shape than the second mouth openings (9, 89, 109, 189, 289, 389, 509, 609, 709, 889, 989) of the second channels opening onto the lateral surface and wherein in particular the first mouth openings are larger than the second mouth openings.

7. Electrode according to one of the preceding claims, characterized in that each mouth opening is arranged in a bulge (10) of the lateral surface, wherein the bulge results in the mouth openings lying in a plane which is arranged deviating from a plane imaginary parallel to the lateral surface.

8. Electrode according to claim 7, characterized in that the bulges of the first orifices point in a different direction than the bulges of the second orifices.

9. Electrode according to one of claims 6 - 8, characterized in that the orifices are triangular, in particular wherein all tips of the first orifices are oriented in an opposite direction to all tips of the second orifices.

10. Electrode according to one of the preceding claims, characterized in that, viewed along a longitudinal axis of the electrode, each channel opens into a plurality of orifices, in particular three to fifteen orifices per channel, on the lateral surface and that all orifices of an individual channel are arranged in a row arranged one behind the other.

11. Electrode according to one of the preceding claims, characterized in that the electrode has a channel structure body (3, 83, 103, 203, 503, 603, 703) in which the first and the second channels are formed, and in that the electrode has an outer grid (5, 85, 105, 205, 505, 605, 705) which surrounds the channel structure body, wherein the electrode is preferably in one piece.

12. Electrode according to claim 11, characterized in that the outer grid has a grid structure whose grid openings (11, 111) are smaller than the mouth openings (7, 9, 87, 89, 107, 109, 187, 189, 287, 289, 387, 389, 507, 509, 607, 609, 707, 709, 887, 889, 987, 989) of the channels (106, 86, 108, 186, 286, 506, 508, 606, 508, 706, 708).

13. Electrode according to claim 11 or 12, characterized in that at least one catalyst, in particular a catalyst made of a noble metal which is a platinum group metal, preferably platinum, is applied, in particular sputtered, to the outer grid or, in the absence of the outer grid, to the outer surface.

14. Electrode according to one of the preceding claims, characterized in that the electrode is an anode (1, 201, 501, 601) for an electrolyzer (200, 400, 500, 600).

15. Electrode according to one of claims 1 - 13, characterized in that the electrode is a cathode (701) for a fuel cell (700).

16. Electrode according to one of the preceding claims, characterized in that the electrode has been produced by a selective laser melting process.

17. Electrode according to one of the preceding claims, characterized in that the electrode consists of a metal, in particular titanium.

18. Electrode according to claim 16 or 17, characterized in that the electrode has been produced by the selective laser melting process from the metal, in particular titanium, to which a catalyst, in particular a catalyst made of a noble metal which is a platinum group metal, preferably platinum, has been added.

19. Electrode according to one of the preceding claims, characterized in that the Electrode has a circular cylindrical shape or a shape of a prism with a number of corners n, where n = 3 - oo.

20. Electrochemical converter (200, 300, 400, 500, 600, 700), in particular an electrolyzer (200, 400, 500, 600) for splitting water (45) into hydrogen (50) and oxygen (40), or a fuel cell (700) for generating water by an electrochemical reaction of hydrogen and oxygen, with at least one first electrode (98) and with at least one second electrode (99) and with a membrane (20, 220, 520, 620, 720) arranged between the first electrode and the second electrode, in particular a polymer electrolyte membrane or an anion exchange membrane, wherein the second electrode at least partially surrounds the first electrode, characterized in that the first electrode is an electrode (1, 80, 101, 201, 380, 501, 601, 701) according to any one of claims 1-19.

21. Electrochemical converter according to claim 20, characterized in that a catalyst is applied, in particular sputtered, to the outer surface of the first electrode, in particular to an outer grid (5, 85, 105, 205, 505, 605, 705) which is present above the outer surface (12, 96, 112, 196, 296, 396) of the first electrode and which is a part of the first electrode.

22. Electrochemical converter according to claim 20 or 21, characterized in that the second electrode is a tubular electrode (230, 530, 630, 730), in particular comprising two half-shells (634, 635, 734, 735), which is arranged around the first electrode.

23. Electrochemical converter according to one of claims 20 - 22, characterized in that the second electrode is made of a metal, in particular titanium, and preferably has a multi-layer structure.

24. Electrochemical converter according to claim 23, characterized in that the second electrode has an outer jacket, and a structural body, in particular a porous and / or grid-shaped electrode body, wherein the casing is closed in a gas-tight manner and wherein pores and / or channels and / or grid structures are present in the structural body, which serve to transport at least one process medium, and wherein the membrane adjoins the electrode body inwards.

25. Electrochemical converter according to claim 24, characterized in that a catalyst is applied, in particular sputtered, to the grid-shaped electrode body.

26. Electrochemical converter according to one of claims 20 - 25, characterized in that a plurality of reaction cells (881, 981) are formed by forming raised structures, in particular webs (397, 897, 997a, 997b), on which the membrane is arranged and wherein in each reaction cell at least one single outlet opening for a first process medium (487, 587) and at least one single outlet opening for a second process medium (489, 589) is present for the supply and discharge of the first and second process medium.

27. Electrochemical converter according to one of claims 20 - 26, characterized in that the electrodes and the membrane are arranged in a housing (360), wherein in particular the housing comprises a base plate (362, 462, 562) and a top plate (361, 461, 561) which are combined with the electrodes and the membrane to form the housing and are clamped together via at least one clamping element such as a clamping bolt (364, 464, 564, 664) or one, in particular several clamps, or which are screwed together.

28. Electrochemical converter according to claim 27, characterized in that a gas-tight, outer jacket (532, 632, 732) of the second electrode serves as the container wall (363, 463), wherein the second electrode is clamped together with the base plate and the top plate to form the housing.

29. Electrochemical converter according to claim 27 or 28, characterized in that in the base plate and in the top plate there is in each case at least one collecting line (90) for a supply or discharge of reaction educts and reaction products from the electrochemical converter, which can be supplied to the respective collecting line via first (106) and second channels (108) which are formed in an interior (104, 204) of at least the first electrode.

30. Electrochemical converter according to one of claims 20-29, characterized in that the first and second electrodes are manufactured by a selective laser melting process.

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