Gas diffusion electrode based on porous hydrophobic substrates with a current collector, and production thereof

Abstract

The invention relates to a gas diffusion electrode comprising a substrate, a catalyst layer and a current collector. The substrate is electrically non-conductive, hydrophobic and has a pore structure. The catalyst layer is applied to the substrate. The current collector has a first side and a second side, the first side having a polymer layer portion and an electrical potential application region. The polymer layer portion is coated with a polymer layer, while the electrical potential application region does not have a polymer layer. Further, the second side has an electrical contact-making portion. The electrical contact-making portion faces the catalyst layer so that electrical contacting with it is possible. The catalyst layer enables an electrical current to flow through the electrical contact-making portion and the electrical potential application region. The invention further relates to a system comprising an electrolytic cell which has the gas diffusion electrode according to the invention and to a method for producing the gas diffusion electrode according to the invention.

Description

[0001] Gas diffusion electrode based on porous hydrophobic substrates with a current collector and its production

[0002] DESCRIPTION

[0003] The invention relates to a gas diffusion electrode comprising a substrate, a catalyst layer, and a current collector. The substrate is electrically non-conductive, hydrophobic, and has a pore structure. The catalyst layer is applied to the substrate. The current collector has a first side and a second side, wherein the first side has a polymer layer section and an electrical potential application region. The polymer layer section is coated with a polymer layer, while the electrical potential application region does not have a polymer layer. Furthermore, the second side has an electrical contacting section. The electrical contacting section faces the catalyst layer, thus enabling electrical contact with it. The catalyst layer can enable an electrical current flow through the electrical contacting section and the electrical potential application region.

[0004] Furthermore, the invention relates to a system comprising an electrolysis cell having the gas diffusion electrode according to the invention and a method for producing the gas diffusion electrode according to the invention.

[0005] Background and state of the art

[0006] Gas diffusion electrodes as such are generally known in the art. A characteristic of a gas diffusion electrode is that three states of matter are brought into contact with each other for an electrochemical reaction. The catalyst, as a component of the gas diffusion electrode, which has a solid state of matter, can catalyze the electrochemical reaction between a gaseous and a liquid substance. For this purpose, the gas diffusion electrode is designed to have a porous structure to enable contact between the gaseous and liquid substances.

[0007] Gas diffusion electrodes have gained interest in research in recent years as a way to advance climate- and environmentally-friendly energy generation. In particular, gas diffusion electrodes can enable the efficient electrochemical conversion of carbon dioxide (CO2) into valuable carbon-based fuels and raw materials. Gas diffusion electrodes can gain significant relevance, especially with regard to CO2 reduction reactions.

[0008] Electrochemical CO2 reduction is often carried out in H-cells or two-compartment cells, in which an electrode is immersed in an electrolyte and the CO2 is continuously flushed through. However, with this type of CO2 supply, only low CO2 concentrations are achieved in the electrolyte, so the associated current densities are also low (e.g., approx. 20 mA / cm 2(milliamperes per square centimeter). However, in order to use electrochemical CO2 reduction on an industrial scale, current densities of over 100 mA / cm 2 required. To achieve this, gas diffusion electrodes are used, which can minimize the CO2 diffusion path from approximately 50 pm to 50 nm, enabling the high currents required for industrial applications. The state of the art includes numerous proposals for electrolysis cells that can be used, in particular, to carry out CO2 reduction in addition to other reactions.

[0009] For example, CN 114395773 A relates to an electrolysis cell for the reduction of carbon dioxide. The electrolysis cell comprises a first and a second plate, with a cathode arranged between the first and second plates. The cathode is formed by a gas diffusion layer and a catalyst layer. Adjacent to the cathode is a flow plate that defines a flow field for the electrolyte. The cathode is positioned between the first and the flow plate. A diaphragm and an anode are arranged between the flow plate and the second plate.

[0010] CN 110453236 A also discloses an electrolysis cell for the reduction of carbon dioxide. The electrolysis cell disclosed therein has an anode end plate, adjacent to which an anode current collector and an anode are connected. Furthermore, the electrolysis cell comprises a cathode with a cathode current collector, which are attached to a cathode end plate. A plate with the function of a flow field is positioned between the anode and the cathode.

[0011] A particularly significant problem in the industrial use of electrochemical CO2 reduction has so far been the stability of gas diffusion electrodes. Many factors can lead to a loss of performance of the gas diffusion electrode. In addition to catalyst or substrate degradation, flooding of the gas diffusion electrode can also occur. The flooding problem specifically refers to the ingress of excess electrolyte into the pore system of the gas diffusion electrode. This leads to a reduced supply of CO2 to the active catalyst species. This can limit the stability of the gas diffusion electrode to a few minutes or a few hours, making its use on a large-scale industrial scale unsuitable.

[0012] In addition to the most commonly used carbon-based gas diffusion electrode types, which usually comprise two or three layers, single-layer gas diffusion electrodes are also known in the prior art, but their functionality also suffers from the described flooding problem. This is due, among other things, to the fact that these types of gas diffusion electrodes, especially their substrates, are based on materials that conduct electrical current and are therefore electrocatalytically active at the high cathodic potentials used in the electrochemical reduction of CO2, thus catalyzing unwanted reactions, such as hydrogen evolution. Other known reasons for the flooding problems are phenomena such as salt formation in the pores and / or electrowetting.

[0013] There are several proposals for the design of gas diffusion electrodes in the prior art. Dinh et al. (2018) describes a polymer-based gas diffusion electrode. The gas diffusion electrode disclosed therein has a PTFE substrate. A copper layer is applied to the PTFE substrate, to which carbon particles and graphite are deposited. The carbon particles and graphite, which represent various forms of carbon, serve as current collectors. The gas diffusion electrode described in Dinh et al. (2018) is also the subject of patent application US 2021 / 0218036 A1.

[0014] Although the gas diffusion electrode disclosed in Dinh et al. (2018) and US2021 / 0218036 A1 exhibits some advantageous effects, such as an operating life of 150 hours, there is still a need for optimization. To tap current from the gas diffusion electrode, especially from the carbon system of the current collector, lateral electrical contact is necessary. This leads to an inhomogeneous current distribution, which in turn is detrimental to the current yield and thus also to the quantity of products that can be produced.

[0015] Another application for constructing a gas diffusion electrode is disclosed in Tiwari et al. (2018). A Gortex substrate is used, onto which a catalyst material and a nickel mesh are applied. The catalyst layer can contain platinum particles, a carbon support, and PTFE as a binder, and can be approximately 200 μm thick. The nickel mesh on the catalyst serves as a current collector. The gas diffusion electrode disclosed in Tiwari et al. (2018) is particularly suitable for oxygen reduction reactions.

[0016] EP 3831982 A1 discloses a gas diffusion electrode as a cathode in an electrochemical cell for the reduction of CO2. CO2 is supplied to the cathode in gaseous form. The electrolyte comprises an aprotic solvent. The gas diffusion electrode used comprises a catalyst layer formed by metallic or metal oxide nanoparticles and a hydrophobic agglomerate. A current collector in the form of a metallic mesh is integrated into the catalyst layer.

[0017] US 4354917 A describes an electrode with a catalyst layer (or active layer) comprising carbon particles bonded to a current collector by carbon black-fibrillated polytetrafluoroethylene (PTFE). The current collector comprises an asymmetrical wire mesh. In the context of US 4354917 A, this means, in particular, that more conductive wire strands are arranged essentially perpendicular to the current flow than wire strands arranged parallel to the current flow. The electrode can be used, in particular, for the electrolysis of oxygen.

[0018] Although approaches to improved gas diffusion electrodes exist in the state of the art, there is still a need to provide gas diffusion electrodes that are more efficient in terms of both their structural design and their functionality.

[0019] Object of the invention

[0020] The object of the invention is to provide a gas diffusion electrode that eliminates the disadvantages of the prior art. In particular, a gas diffusion electrode should be provided with which optimal electrochemical catalysis can be carried out. Furthermore, the gas diffusion electrode should have high functional stability. Furthermore, a process should be developed with which such a gas diffusion electrode can be produced. Summary of the Invention

[0021] The object of the invention is achieved by the independent claims. Advantageous embodiments of the invention are disclosed in the dependent claims.

[0022] In a first aspect, the invention relates to a gas diffusion electrode for electrolysis comprising a substrate, a catalyst layer, and a current collector, wherein the substrate has a pore structure and comprises an electrically non-conductive and hydrophobic material, wherein the current collector has a first side and a second side, and the substrate acts as a support for the catalyst layer and the current collector, wherein the catalyst layer is arranged on the substrate, characterized in that the first side of the current collector has a polymer layer section and an electrical potential application region, wherein a polymer layer is present on the polymer layer section and the electrical potential application region is electrically contactable, and the second side comprises an electrical contacting section, wherein the electrical contacting section faces the catalyst layer,so that an electric current can flow through the gas diffusion electrode during electrolysis.

[0023] The combination of the inventive features leads to a surprising synergistic effect, which results in the advantageous properties and effects and the associated overall success of the invention, with the individual features interacting with each other. The preferred gas diffusion electrode has proven surprisingly advantageous in a variety of aspects.

[0024] A surprisingly significant advantage of the gas diffusion electrode according to the invention is its excellent scalability. Scalability preferably means designing the preferred gas diffusion electrode in such a way that, among other things, it can be used in different dimensions (in particular, length, width, and / or height). Consequently, the preferred gas diffusion electrode can be used not only on a laboratory scale but also in large-scale industrial applications.

[0025] Furthermore, it is surprisingly advantageous that higher partial current densities result using the gas diffusion electrode according to the invention. The average person skilled in the art will appreciate that a partial current density refers to the current density that flows into the formation of the products. In particular, the partial current density refers to a current density that flows at an electrode (anode or cathode) during a reaction. Furthermore, the average person skilled in the art knows that the partial current density results from the product of the applied current density (cathodic or anodic) and the Faradaic efficiency. Advantageously, the higher achievable current density is also accompanied by a higher product rate, since the product rate is essentially proportional to the partial current density. The product rate preferably refers to the amount of product that can be produced per unit electrode area.This allows advantageous current densities of over 300 mA / cm. 2 (milliamperes per square centimeter) and correspondingly significantly higher product rates, which is also relevant for industrial applicability. In particular, higher Faradaic efficiencies were advantageously achieved using the preferred gas diffusion electrode. In the context of the invention, Faradaic efficiency refers to a measure used to characterize the efficiency of the electric current in the corresponding chemical reaction. The advantageously higher current density achievable when using the preferred gas diffusion electrode is associated with a higher Faradaic efficiency.

[0026] Furthermore, a surprisingly significant advantage is that the flooding problem known in the prior art essentially does not occur with the gas diffusion electrode according to the invention. As described above, the flooding problem in the context of gas diffusion electrodes means that the electrolyte can penetrate into the pores of the substrate, thus hindering CO2 transport into the catalyst layer. This reduces the performance of a gas diffusion electrode and its service life. Advantageously, adverse effects due to flooding problems do not occur with the preferred gas diffusion electrode because flooding of the electrolyte into the gas diffusion electrode is prevented. This is achieved in particular by the hydrophobicity of the preferred substrate. Consequently, the preferred gas diffusion electrode advantageously exhibits high long-term stability, in particular the catalyst layer of the preferred gas diffusion electrode.In particular, the combination of the preferred components of the gas diffusion electrode and their arrangement led to a surprisingly high long-term stability of the catalyst layer, enabling excellent catalysis for chemical reactions. The preferred gas diffusion electrode is particularly advantageous in the reduction of CO2. The preferred gas diffusion electrode is also advantageous for other reactions and / or products.

[0027] For example, surprisingly high local pH values ​​can be achieved using the gas diffusion electrode according to the invention, enabling higher product rates of, for example, ethylene, ethanol, propanol, etc. The term "local pH value" refers to the pH value in the vicinity of the catalyst layer and is clear to the person skilled in the art, since the expression "local pH value" is familiar in the prior art. The local pH value corresponds to the concentration of protons in the vicinity of the catalyst layer, so that a higher local pH value is associated with a lower concentration of protons and, accordingly, with a high concentration of hydroxide ions. The local pH value and thus the higher concentration of hydroxide ions can certainly advantageously influence parameters such as the partial current density, without being limited to the exemplary parameter mentioned.

[0028] Another particular advantage of the gas diffusion electrode according to the invention is its ease of manufacture. In particular, the preferred gas diffusion electrode can be produced using processes proven in the prior art, so that it can advantageously be made available in a short time and without significant effort.

[0029] The term "gas diffusion electrode" is familiar to those skilled in the art and refers to an electrode that has a solid, liquid, and gaseous interface. A catalyst supports the electrochemical reaction between the liquid and gaseous phases during electrolysis.

[0030] Electrolysis is a process in which one or more chemical reactions occur, resulting in a change in the oxidation and / or reduction state. Electrolysis is also a chemical process in which one or more chemical reactions are forced by the application of a direct electric current. In particular, ionic conduction occurs between the anode and cathode through the electrolyte, enabling ionic conduction. Electrolysis produces reaction products at the electrodes from the substances contained in the electrolyte.

[0031] The gas diffusion electrode according to the invention comprises a substrate, a catalyst layer, and a current collector. In particular, the gas diffusion electrode comprises all of the aforementioned components.

[0032] In the context of the invention, the substrate can also be referred to as a gas diffusion layer. Furthermore, the substrate is specifically dedicated to gas transport. In other words, the pore structure of the substrate allows a gas to be transported through the pores of the substrate to the catalyst layer. Furthermore, the substrate functions, in particular, as a support for the catalyst layer and the current collector.

[0033] The substrate can preferably be round or square and / or formed as a membrane. The substrate preferably has a length and / or a width that is many times greater than the thickness of the substrate. The multiple of the thickness, which preferably comprises the length and / or width of the substrate, can correspond to a factor of approximately 1.5, 2.5, 100, 1,000, 10,000, 100,000, or more. Furthermore, it can be preferred for the substrate to have a thickness in the submillimeter range up to the millimeter range, preferably between approximately 50 μm and 2 mm.

[0034] Terms such as substantially, approximately, etc. preferably describe a tolerance range of less than ± 40%, preferably less than ± 20%, particularly preferably less than ± 10%, even more preferably less than ± 5%, and especially less than ± 1%, and particularly include the exact value. Partially preferably describes a tolerance of at least ± 5%, particularly preferably at least ± 10%, and especially at least ± 20%, in some cases at least ± 40%.

[0035] The substrate is electrically non-conductive and hydrophobic. The electrically non-conductive nature of the substrate material is important to suppress any chemical side reactions and thus avoid flooding effects or flooding problems. Consequently, the electrical non-conductivity of the substrate ensures reliable operation during electrolysis.

[0036] The hydrophobicity (or hydrophobicity) of the substrate advantageously ensures that the liquid portion, especially the water portion, of an electrolyte is repelled by the substrate. This advantageously prevents electrolyte or undesirable amounts of electrolyte from penetrating the pore structure of the substrate. This has the advantageous effect of avoiding flooding problems, which are known from the prior art and can lead to degradation of the catalyst layer.

[0037] The hydrophobicity of the substrate is preferably characterized by a contact angle of or above approximately 90° when liquid, for example water, is brought into contact with the substrate. Therefore, in a further preferred embodiment, the invention relates to a gas diffusion electrode for electrolysis comprising a substrate, a catalyst layer, and a current collector, wherein the substrate has a pore structure and comprises an electrically non-conductive and hydrophobic material, wherein hydrophobic means that a contact angle of or above 90° is present when water is brought into contact with the substrate, wherein the current collector has a first side and a second side, and the substrate functions as a support for the catalyst layer and the current collector, wherein the catalyst layer is arranged on the substrate, characterized in thatthat the first side of the current collector has a polymer layer section and an electrical potential application region, wherein a polymer layer is present on the polymer layer section and the electrical potential application region is electrically contactable, and the second side comprises an electrical contacting section, wherein the electrical contacting section faces the catalyst layer so that an electrical current can flow through the gas diffusion electrode during electrolysis.

[0038] The substrate has a porous structure. The porous structure of the substrate specifically means that the substrate has pores. The pores are characterized by openings introduced into the substrate. The pores or pore structure allow gas molecules to penetrate the catalyst layer of the gas diffusion electrode, where they can then be catalyzed by the catalyst layer.

[0039] The catalyst layer is present on the substrate. The catalyst layer comprises a material capable of catalyzing a chemical reaction. In particular, the catalyst layer comprises a catalyst material. The catalyst material can also be referred to as a catalytically active material. The catalyst material refers to a material that plays a significant role in the catalysis of a reaction. For example, the catalyst layer can comprise metals and / or metal compounds, which can occur particularly as active material during the reduction of CO2. Preferably, the catalyst layer comprises metal particles. The catalyst layer is located between the substrate and the current collector.

[0040] In the context of the invention, the current collector refers to a Meta II structure that has one or more openings and enables electrical connection to the catalyst layer. Since it is preferred that the current collector comprises a metal, electrical contact with the catalyst layer can be achieved by direct placement on the catalyst layer. It may also be preferred to apply an electrically conductive intermediate layer between the current collector and the catalyst layer to ensure electrical contact. For example, the current collector can be configured as a metal grid or a monopolar plate.

[0041] The current collector preferably comprises a first side and a second side. The terms "first side" and "second side" of the current collector refer to sections of the current collector that can simplify the specification of the positions of individual components of the preferred gas diffusion electrode. Preferably, the terms "first side" and "second side" of the current collector refer to surface portions of the current collector that are opposite one another. The first side and second side can preferably also correspond to the front and rear sides of the current collector. Furthermore, it is preferred that the first side of the current collector faces away from the catalyst layer, while the second side of the current collector faces the catalyst layer.

[0042] The first side of the current collector comprises a polymer layer section and an electrical potential application region. The polymer layer section preferably refers to a section of the first side of the current collector to which a polymer layer is applied. The electrical potential application region preferably refers to a section of the first side of the current collector that does not have a polymer layer. The polymer layer present on the polymer layer section of the first side of the current collector advantageously provides electrical insulation from an electrolyte. This is particularly relevant when the preferred gas diffusion electrode is used during electrolysis in an electrolyte. In particular, the polymer layer on the current collector is particularly relevant for the reduction as such, for example for CO2 reduction. This is because side reactions, such asthe hydrogen evolution that can occur on the surface of the current collector is suppressed by the polymer layer.

[0043] Preferably, the polymer layer is located on the current collector, with only the contacting section and the electrical potential application area not coated with the polymer layer to ensure reliable electrical current transport. In a three-dimensional view, for example, the side walls of the current collector, particularly in the case of a monopolar plate or a grid or grid structure, are also coated with the polymer layer. In other words, a polymer layer is present on the polymer layer section. On other sections of the current collector, there is no polymer layer.

[0044] The electrical potential application region of the current collector offers an electrical contacting option so that a current flow via the electrical potential application region can be tapped. The electrical potential application region is preferably located on the first side of the current collector, for example in the case of a grid plate as the current collector. Furthermore, it may be preferred for the electrical potential application region to be attached to the first and second sides of the current collector. The latter variant can be the case, for example, if the current collector is a monopolar plate and the electrical potential application region has a structure that can be contacted on two sides, e.g. with a terminal, for an electrical connection. Therefore, in the context of the invention, it is legitimate to describe the electrical potential application region as being at least partially located on the first side of the current collector.

[0045] The second side of the current collector comprises an electrical contacting section that does not have a polymer layer. The second side, and accordingly also the electrical contacting section, face the catalyst layer. The electrical contacting section preferably refers to the section that enables electrical contact between the current collector and the catalyst layer. Thus, the electrical contacting section preferably represents a region of the current collector that can be electrically contacted with the catalyst layer. This enables an electrical current to flow through the gas diffusion electrode during electrolysis. In particular, the electrical current can flow through the electrical potential application region of the current collector to the electrical contacting section and then to the catalyst layer.

[0046] In a further preferred embodiment, the gas diffusion electrode is characterized in that the electrolysis comprises a reduction of gaseous carbon dioxide, carbon monoxide, oxygen, nitrogen, nitrogen oxide and / or nitrogen dioxide.

[0047] Advantageously, the preferred gas diffusion electrode can be used in a variety of electrolysis reactions. In particular, the use of the preferred gas diffusion electrode is not limited to a specific electrolysis reaction.

[0048] The preferred gas diffusion electrode is particularly useful in the context of carbon dioxide reduction during electrolysis. This advantageously allows the reduction of CO2 to yield many products and / or precursors that are of great importance to the chemical, pharmaceutical, and / or food industries, such as ethylene, formic acid, ethanol, propanol, etc., which can also be relevant for downstream products of electrochemical CO2 reduction, such as polyethylene, ethylene oxide, synthetic fuels, etc. The average person skilled in the art knows that, in addition to the reducing gas, the product also depends on the catalyst layer used. The diverse application possibilities of the preferred gas diffusion electrode for electrolysis reactions provide a beneficial contribution to the state of the art.

[0049] In a further aspect, the invention relates to a use of the gas diffusion electrode according to the invention and / or of preferred embodiments of the gas diffusion electrode in an electrolysis for a reduction of gaseous carbon dioxide, carbon monoxide, oxygen, nitrogen, nitrogen oxide and / or nitrogen dioxide.

[0050] The average person skilled in the art will recognize that technical features, definitions, advantages of the gas diffusion electrode and of and preferred embodiments for the preferred gas diffusion electrode equally apply to use in electrolysis, and vice versa.

[0051] In a further preferred embodiment, the gas diffusion electrode is characterized in that the current collector is in the form of a monopolar plate or a grid structure, preferably a monopolar plate. In a further preferred embodiment, the current collector is in the form of an expanded metal.

[0052] The above-mentioned preferred embodiments for providing the current collector by a grid structure or a monopolar plate or an expanded metal have proven to be particularly advantageous.

[0053] A grid structure is particularly advantageous on a laboratory scale, as it enables cost-effective and simple implementation. A grid structure preferably refers to a grid-shaped metal plate, with a grid shape being formed by webs of the metal plate. The terms grid structure and grid plate can be used synonymously in the context of the invention. A monopolar plate preferably refers to a metal plate that has one electrical pole such that electrical current can flow across it. The prefix "mono" is intended to suggest that the monopolar plate is a "single-pole plate." The monopolar plate preferably has an essentially disc-shaped configuration. In particular, the length and / or width of the monopolar plate is many times greater than its thickness.Furthermore, the monopolar plate preferably comprises openings, for example, to insert holders for connecting to other components, for example, for constructing an electrolysis cell. The openings are preferably also used for the passage of the electrolyte. Furthermore, the monopolar plate preferably has webs. The webs are particularly preferably located in a central section of the monopolar plate. Furthermore, it is preferred that the webs of a monopolar plate be incorporated into a recess.

[0054] Advantageously, the monopolar plate can be easily scaled and machined. This ease of machining can refer in particular to the easily implemented design options for the preferred webs. The webs advantageously provide a flow field for the electrolyte, i.e., in particular, a directional specification for the flow of the electrolyte. In other words, the webs of the monopolar plate provide a path for the electrolyte, allowing the electrolyte to flow along the catalyst layer.

[0055] The grid structure does have webs. However, unlike a monopolar plate, the grid shape of the grid structure means that no flow field is present, so that an additional flow field would have to be provided if a grid structure were used. When a monopolar plate is used, the flow field for the electrolyte is also advantageously provided by the webs formed within it. One of the advantages of using a monopolar plate is that, among other things, the provision of the flow field means that no additional space is required for a component that would provide one if no flow field were present. Thus, the use of a preferred monopolar plate also reduces the distance between the gas diffusion electrode as the cathode and an anode. The use of a monopolar plate therefore advantageously improves the energy efficiency of the electrolysis process, as the shorter distance results in lower ohmic losses (power loss).

[0056] In a further preferred embodiment, the gas diffusion electrode is characterized in that the current collector is present as a monopolar plate and the electrical potential application region on the first side of the current collector is present as a section uncoated with the polymer layer.

[0057] In a further preferred embodiment, the gas diffusion electrode is characterized in that the current collector is present as a grid structure and the electrical potential application region on the first side of the current collector is present as a section uncoated with the polymer layer.

[0058] In preferred embodiments, a metal tape is applied to the electrical potential application area, particularly preferably in the case of a grid structure as a current collector. The preferred metal tape can advantageously enable reliable electrical contact. The metal tape can be a copper tape, for example, without being limited to this example.

[0059] In a further preferred embodiment, the gas diffusion electrode is characterized in that the current collector comprises webs, wherein the webs are arranged in parallel, serpentine or grid-like manner, wherein a parallel arrangement of the webs is preferred.

[0060] The aforementioned arrangements for the preferred webs of the current collector have proven advantageous in that they enable suitable electrolyte flow across the catalyst layer (except for the grid shape, which does not provide a flow field). Thus, the preferred arrangements for the webs provide reliable current transport across the catalyst layer through the current collector.

[0061] In a further preferred embodiment, the gas diffusion electrode is characterized in that the current collector comprises a material selected from a group comprising nickel, titanium, aluminum, copper, gold, silver, stainless steel and / or combinations of the aforementioned materials.

[0062] The preferred materials for the current collector can function individually to provide the current collector, so it may be preferred that the current collector essentially comprises one material. In further preferred embodiments, the current collector may comprise two or more materials. Furthermore, it may be preferred that a combination of several materials be present.

[0063] In the context of the invention, a combination of several materials is understood to mean, in particular, a chemical compound. The chemical compound can, for example, comprise an ionic bond, a covalent bond, a metallic bond, and / or a weak bond. For example, the current collector may comprise an alloy as its material.

[0064] Advantageously, the use of the preferred materials for the current collector allows for optimal current transport, thus keeping ohmic losses as low as possible. Furthermore, the aforementioned materials are advantageous in that sufficiently stable adhesion of the polymer layer to the current collector can be achieved. Advantageously, the preferred gas diffusion electrode can be incorporated into a variety of electrolytes without experiencing losses of the polymer layer. This advantageously improves the reliability and long-term stability of the preferred gas diffusion electrode.

[0065] In a further preferred embodiment, the gas diffusion electrode is characterized in that the current collector has a thickness between approximately 0.1 - 20 mm, preferably between approximately 0.5 - 10 mm, particularly preferably between approximately 0.5 - 5 mm.

[0066] The aforementioned preferred thicknesses of the current collector are surprisingly advantageous in that, by providing a flow field, an electrolyte can flow particularly easily along the preferred gas diffusion electrode during electrolysis. Furthermore, the aforementioned thicknesses are advantageous in that the smallest possible distance can be achieved between the preferred gas diffusion electrode as the cathode and an anode in an electrolysis cell. Furthermore, the aforementioned preferred thicknesses advantageously ensure efficient current transport, which would not be possible with electrically conductive structures that are too thin (e.g., in the nanometer range). Thus, the aforementioned thicknesses achieve several advantages that result in a surprising synergistic effect for the preferred gas diffusion electrode.

[0067] In a further preferred embodiment, the gas diffusion electrode is characterized in that the polymer layer comprises a material selected from a group comprising polytetrafluoroethylene (PTFE) and / or polyvinylidene fluoride (PVDF).

[0068] In a further preferred embodiment, the polymer layer comprises a polymer from the group of perfluorinated polymers (such as PTFE and / or PFA (perfluoroalkoxy polymers)). In a further preferred embodiment, the polymer layer comprises a polymer from the group of non-perfluorinated polymers (such as polyetheretherketone (PEEK), polypropylene (PP) and / or an epoxy polymer from the group of epoxides). In a further preferred embodiment, the polymer layer comprises a polymer from the group of perfluorinated polymers and a polymer from the group of non-perfluorinated polymers.

[0069] The preferred materials for the polymer layer have proven advantageous in that they can achieve a sufficiently stable bond with the current collector and thus exhibit surprisingly high durability. Furthermore, the preferred materials advantageously provide sufficient electrical insulation of the polymer layer section of the current collector. On the one hand, particularly precise electrical current can be tapped at the electrical potential application area. On the other hand, this is also advantageous due to safety aspects, which highlights the improved applicability of the preferred gas diffusion electrode.

[0070] In a further preferred embodiment, the gas diffusion electrode is characterized in that the pore structure of the substrate comprises pores with a diameter between approximately 100 nm - 50 pm (nanometers to micrometers), preferably approximately 100 nm - 20 pm, particularly preferably between approximately 100 nm - 10 pm.

[0071] The preferred pore diameters are advantageously suited to reliably permit the passage of a gas (e.g., CO2), which can be reduced, for example. Furthermore, the preferred pore diameters are advantageous in that they can also influence the ingress of liquid or liquid components of the electrolyte. This can advantageously prevent flooding and thus a loss of selectivity of the catalyst layer.

[0072] The selectivity of the catalyst layer specifically means that a specific chemical reaction is preferentially catalyzed, although in principle several chemical reactions can occur on the catalyst layer. Either this specific reaction occurs preferentially, or this reaction is the only one that occurs. A loss of selectivity thus refers to a reduction in selectivity.

[0073] In a further preferred embodiment, the gas diffusion electrode is characterized in that the substrate comprises a material selected from a group comprising polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylenepropylene (FEP), polyvinylidene fluoride (PVDF), polyethylene (PE), polypropylene (PP) and / or polychlorotrifluoroethylene (PCTFE).

[0074] In a further preferred embodiment, the substrate comprises a material from the group of perfluorinated polymers (such as PTFE, PVDF, etc.). In a further preferred embodiment, the substrate comprises a material from the group of non-perfluorinated polymers (such as PE, PP, etc.). In a further preferred embodiment, the substrate comprises a material from the group of perfluorinated polymers and a material from the group of non-perfluorinated polymers.

[0075] The preferred materials mentioned for the substrate are particularly advantageous due to their hydrophobicity, so that water can be repelled and thus, in particular, the entry of liquid components from the electrolyte during electrolysis can be prevented.

[0076] In a further preferred embodiment, the gas diffusion electrode is characterized in that the substrate has a thickness between 0.1 - 2 mm, preferably between 0.1 - 1 mm, particularly preferably between 0.1 - 0.5 mm.

[0077] The aforementioned preferred substrate thicknesses advantageously allow for the effects of water repellency and the reliable introduction of gas through the substrate pores to be considered. For the same porosity, a thicker substrate is less permeable to water. However, to allow gas to pass through the pores, the preferred substrate must not be too thick. The aforementioned substrate thicknesses advantageously achieve a compromise between these two factors, which are relevant for the preferred gas diffusion electrode.

[0078] In a further preferred embodiment, the gas diffusion electrode is characterized in that the catalyst layer comprises metal particles.

[0079] The catalyst layer preferably comprises a material selected from a group comprising copper, copper oxide, silver, gold, tin, tin oxide, zinc, indium, bismuth, antimony, palladium, platinum, ruthenium, rhodium, iridium, rhenium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zirconium, niobium, molybdenum, technetium, scandium, yttrium, aluminum, carbon, nitrogen, boron, oxygen, fluorine, chlorine, bromine, iodine, silicon, phosphorus, sulfur, gallium, germanium, arsenic, selenium, tellurium, lead, hafnium, tantalum, tungsten, osmium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium and / or a combination of the aforementioned materials.

[0080] In a further preferred embodiment, the gas diffusion electrode is characterized in that the catalyst layer comprises a material selected from a group comprising copper, silver, gold, tin, zinc, indium, bismuth, antimony, palladium, platinum, ruthenium, rhodium, iridium, rhenium, titanium, vanadium, chromium, manganese, iron, tungsten, cobalt, nickel, zirconium, niobium, molybdenum, technetium, scandium, yttrium, aluminum and / or their oxides.

[0081] The catalyst layer preferably comprises metal particles, wherein the metal particles preferably comprise a material selected from a group comprising copper, silver, gold, tin, zinc, indium, bismuth, antimony, palladium, platinum, ruthenium, rhodium, iridium, rhenium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zirconium, niobium, molybdenum, technetium, scandium, yttrium, aluminum and / or their oxides.

[0082] Materials such as copper, silver, gold, zinc, indium, tin, bismuth, palladium and / or combinations of these materials have proven particularly advantageous for CO2 reduction.

[0083] Furthermore, it may be preferable to use oxidized species of one or more of the materials mentioned, ie, oxides of one or more of the materials mentioned, e.g., metal oxides of preferred metals mentioned. It may also be preferable to use nitrides of one or more of the materials mentioned for the catalyst layer.

[0084] Advantageously, a variety of materials can be used for the catalyst layer, so that there is no restriction to a specific material class.

[0085] The preferred embodiment in which the catalyst layer comprises metal particles is particularly advantageous because it can be provided particularly easily using proven process technologies and has proven particularly efficient for potential catalytic reactions. Furthermore, metal particles can advantageously be distributed over a large area on the substrate, thus enabling large-area catalysis.

[0086] In a further preferred embodiment, the gas diffusion electrode is characterized in that the catalyst layer comprises a binder, wherein the binder preferably comprises a material selected from a group comprising Naphtha, Sustainion, polytetrafluoroethylene (PTFE) and / or polyvinylidene fluoride (PVDF).

[0087] Nation includes, in particular, perfluorinated copolymers. Those skilled in the art will know that perfluorinated copolymers can be substituted for the term "nation."

[0088] Sustainion includes, in particular, alkali ionomers. Those skilled in the art will know that alkali ionomers can be replaced with the term "sustainion."

[0089] In a further preferred embodiment, the catalyst layer comprises a material from the group of ionomers (such as NaCl and / or Sustainion) as a binder. In a further preferred embodiment, the binder is a purely polymeric binder (such as PTFE and / or PVDF). In a further preferred embodiment, the binder can comprise a material from the group of ionomers and a material from the group of polymers.

[0090] In a further preferred embodiment, the gas diffusion electrode is characterized in that the catalyst layer comprises a binder, wherein the binder preferably comprises a material selected from a group comprising ionomeric and / or polymeric binders.

[0091] The binder preferably serves to enable a long-lasting, stable bond between a material of the catalyst layer and the substrate. Thus, the preferred binder, in particular, can achieve a reliable bond between preferred metal particles and the substrate. The aforementioned preferred binders have proven particularly advantageous with regard to the firm bonding of metal particles to the substrate.

[0092] In a further preferred embodiment, the gas diffusion electrode is characterized in that the binder has a weight proportion of approximately 1-20%, preferably between approximately 1-10%, most preferably between approximately 1-5%, to the metal particles.

[0093] It was surprisingly advantageous that the stated weight proportions of the binder to the preferred metal particles allowed for a sufficiently stable bond. These preferred weight proportions have proven surprisingly advantageous in that they achieve a compromise between sufficient electrical conductivity and stability with regard to the bond. If the weight proportion of the binder were too high, this would result in limitations in electrical conductivity. If the weight proportion of the binder were too low, this would result in a loss of stability. The stated preferred values ​​for the weight proportion of the binder represent a surprisingly advantageous balance between both aspects. Furthermore, the type and nature of the metal particles used for the catalyst layer is also relevant for the weight proportion of the binder.

[0094] In a further preferred embodiment, the gas diffusion electrode is characterized in that the catalyst layer comprises an additive, wherein the additive is selected from a group comprising an additional catalyst material, a support material, a protective material and / or a conductivity additive.

[0095] In the context of the invention, the additive refers to a further additive in the catalyst layer in order to achieve further effects.

[0096] An additional catalyst material can advantageously achieve synergistic effects alongside the existing catalyst material, such as the metal particles. For example, the partial current density for a product, in particular the selectivity in the case of CO2 reduction, can be unexpectedly greatly increased. The additional catalyst material is preferably present in addition to an existing catalyst material in the catalyst layer. For example, it may be preferable to use another catalytically active material in the catalyst layer in addition to the preferred metal particles of the catalyst layer.

[0097] A support material preferably serves to advantageously distribute the metal particles of the catalyst layer. In particular, the support material can increase the active surface area of ​​the metal particles used. Furthermore, the support material can promote stability and charge transport. The support material can, for example, support preferred metal particles of the catalyst layer.

[0098] A protective material (also known as a protective layer) preferably refers to an additionally applied layer with a protective effect for the catalyst layer. The application of a protective layer can advantageously increase the longevity of the material to be catalyzed and the local pH value, favoring higher current densities. A protective layer can, for example, comprise ionomers such as NaCl, Sustainion, etc., and / or carbon-containing materials such as graphitic carbon (graphite), carbon nanotubes, and / or graphene.

[0099] A conductivity additive serves primarily to increase electrical conductivity. This can be particularly helpful when a material is used as the catalyst that does not have sufficiently high electrical conductivity. A well-known example of a material for a conductivity additive is carbon. A conductivity additive can also be provided, for example, by doping. The average person skilled in the art is able to select a suitable conductivity additive and incorporate it into the catalyst layer depending on the application.

[0100] The binder content can preferably depend on parameters of the catalyst layer. For example, the binder content can depend on the particle size of the catalyst material used and / or the specific surface area.

[0101] In a further preferred embodiment, the gas diffusion electrode is characterized in that the catalyst layer has a thickness between approximately 0.1 - 100 pm, preferably between approximately 0.1 - 50 pm, particularly preferably between approximately 1 pm - 25 pm, most particularly preferably between approximately 1 - 10 pm.

[0102] Advantageously, the thicknesses mentioned can provide a compact gas diffusion electrode and can be reproducibly applied to the substrate using known methods of the state of the art.

[0103] In a further aspect, the invention relates to a system, preferably for carbon dioxide reduction, comprising an electrolysis cell, wherein the electrolysis cell is configured to receive a liquid electrolyte, preferably also a gas, for example gaseous carbon dioxide, wherein the electrolysis cell comprises an anode and a cathode, wherein the cathode is a preferred gas diffusion electrode.

[0104] One of ordinary skill in the art will recognize that technical features, definitions, advantages of the gas diffusion electrode and preferred embodiments for the gas diffusion electrode apply equally to the preferred system, and vice versa.

[0105] The basic structure of an electrolysis cell is known to the average expert, so it will not be explained in more detail here.

[0106] The preferred system may also comprise additional components. For example, it may be preferred that the system has end plates so that the anode and cathode can be mechanically stabilized and incorporated therein. Furthermore, seals are preferably present to prevent unwanted leakage of liquids and / or gases and to maintain separation between the electrolyte and gas compartments. Thus, a seal can be considered a separating element. Furthermore, it may be preferred that a membrane be mounted between the anode and cathode, for example, a semipermeable membrane, a cation exchange membrane (e.g., comprising Nafion), an anion exchange membrane (e.g., comprising Sustainion), a bipolar membrane (e.g., comprising Fumasep), or a diaphragm (e.g., Zirfon).In a further preferred embodiment, the system may comprise a plurality of electrolysis cells comprising an anode and cathode as the preferred gas diffusion electrode, for example, to obtain a series or parallel connection of a plurality of electrolysis cells. In particular, it may be preferable to provide a cell stack, which typically involves a series connection and is relevant for operation on an industrial scale.

[0107] In a further aspect, the invention preferably relates to a method for producing a preferred gas diffusion electrode comprising the following steps: a) providing a substrate which has a pore structure and comprises an electrically non-conductive and hydrophobic material, b) providing a current collector comprising a first side and a second side, wherein the first side of the current collector has a polymer layer section and an electrical potential application region and the second side has an electrical contacting section, c) coating the substrate with a catalyst layer, d) coating the polymer layer section of the current collector with a polymer layer, e) contacting the electrical contacting section of the current collector with the catalyst layer.

[0108] One of ordinary skill in the art will recognize that technical features, definitions, advantages, and preferred embodiments for the preferred gas diffusion electrode apply equally to the preferred method of manufacturing the preferred gas diffusion electrode, and vice versa.

[0109] The preferred method is advantageously particularly well-suited for producing a preferred gas diffusion electrode. Advantageously, the preferred gas diffusion electrode can be provided using proven state-of-the-art processes, allowing its production to be expanded to include mass production. This advantageously achieves particularly high economic efficiency. Furthermore, the preferred gas diffusion electrode can advantageously also be produced quickly. Furthermore, it is advantageous that the preferred manufacturing method is particularly safe for the user, so there are no concerns regarding safety. Thus, the preferred method is advantageously particularly user-friendly.

[0110] To produce the preferred gas diffusion electrode, a substrate is preferably provided, wherein the substrate has a pore structure and comprises an electrically non-conductive and hydrophobic material. Furthermore, a current collector comprising a first side and a second side is preferably provided. The first side has a polymer layer portion and an electrical potential application region. It may also be preferred that the electrical potential application region be provided. The second side faces the catalyst layer.

[0111] Preferably, the polymer layer section is coated with a polymer layer. It may also be preferable to coat the second side of the current collector substantially completely with the polymer layer and subsequently remove a portion of the polymer layer to provide the electrical potential application region. Furthermore, it is preferable for the current collector to be substantially completely coated with the polymer layer and then the polymer layer to be removed from the electrical potential application region and the electrical contacting section.

[0112] In order for the preferred gas diffusion electrode to have a catalyst layer, it is preferred to coat the substrate with a catalyst layer.

[0113] In addition, the electrical contacting section is preferably contacted with the catalyst layer so that an electrical contact is established between the current collector and the catalyst layer.

[0114] If the preferred gas diffusion electrode were viewed from below according to the preferred production, the following sequence of components and / or layers would be recognizable: substrate, catalyst layer, electrical contacting section of the current collector, since the electrical contacting section faces the catalyst layer, polymer layer on the polymer layer section of the first side of the current collector.

[0115] In a further preferred embodiment, the method is characterized in that the coating of the catalyst layer onto the substrate is carried out by a chemical wet process, wherein the chemical wet process is preferably selected from a group comprising spray coating, dip coating, spin coating, inkjet printing and / or doctor blade coating.

[0116] For the purposes of the invention, a chemical wet process refers to a coating process in which the material to be coated is applied using a material that is in the liquid phase. For example, it may be preferred that the preferred metal particles are dispersed in a liquid and then coated onto the substrate to provide the catalyst layer.

[0117] The preferred wet chemical processes, including spray coating, dip coating, spin coating, inkjet printing, and / or doctor blade coating, have proven particularly useful for this purpose. Furthermore, other wet chemical processes can also be used to coat the catalyst layer onto the substrate, without being limited to the preferred wet chemical processes mentioned.

[0118] In further preferred embodiments, other methods can also be used to apply the catalyst layer to the substrate. For example, gas deposition methods, such as physical vapor deposition methods (such as sputtering), can be used for this purpose.

[0119] In a further preferred embodiment, the method is characterized in that the polymer layer section is coated with a polymer layer using a powder coating method. Other coating methods can also be used for coating the polymer layer onto the current collector. A powder coating method (also called powder coating) refers to a coating method by which the current collector is coated using a powder coating. It may be preferred that the first side of the current collector be coated substantially completely. The electrical potential application region and the polymer layer section can then preferably be provided by removing the coated polymer at the locations relevant to the electrical potential application region.

[0120] It may also be preferable to coat the entire current collector, in particular the first and second sides, substantially completely with the polymer layer. The polymer layer can then preferably be removed in sections, so that the polymer layer remains on the polymer layer section and the electrical potential application region is provided. Furthermore, after the polymer layer has been substantially completely coated on the first and second sides of the current collector, the polymer layer on the second side is preferably also removed to provide the electrical contacting section.

[0121] The removal of the coated polymer to provide the electrical potential application area and the polymer layer on the polymer layer section can be achieved, for example, mechanically (e.g., by milling or scratching), by the action of heat, and / or a laser. The aforementioned exemplary methods, without being limited thereto, can also be used to remove the polymer layer if it has been coated on the first and second sides of the current collector.

[0122] It may also be preferable to carry out the coating only in the polymer layer section, so that both the polymer layer on the polymer layer section and the electrical potential application region are provided in one step.

[0123] Powder coating processes can be advantageously carried out particularly efficiently even in large-scale industrial applications and are particularly useful for preferred materials, such as PTFE and / or PEEK, for the polymer layer.

[0124] Preferably, the provision of the current collector includes the provision of a blank socket for the current collector. The blank socket here refers to a metallic structure without a coating, so that the blank socket enables the geometric design of the current collector. In other words, the blank socket refers to the current collector itself, which has no coating whatsoever. In particular, the blank socket also includes webs, so that the arrangement of the webs can also be specified by the blank socket.

[0125] The raw frame can preferably be provided by etching, milling, punching, and / or lasering a metallic material. The preferred methods and / or components comprising etching, milling, punching, and / or lasering have proven particularly well-suited for providing the raw frame. In particular, the arrangement of the webs can be advantageously accomplished particularly precisely and quickly.

[0126] The aspects of the invention will be explained in more detail below with reference to figures, without being limited to these figures. FIGURES

[0127] Short description of the characters

[0128] Fig. 1 Schematic representation of a preferred embodiment of a current collector

[0129] Fig. 2 Schematic representation of another preferred embodiment of the current collector

[0130] Fig. 3 Schematic representation of a preferred embodiment of a gas diffusion electrode

[0131] Fig. 4 Schematic representation of another preferred embodiment of the gas diffusion electrode

[0132] Fig. 5 Schematic representation of a preferred embodiment of a system

[0133] Fig. 6 Measurement results for the electrochemical performance of a grid structure as a current collector

[0134] Fig. 7 Measurement results for the electrochemical performance of a monopolar plate as a current collector

[0135] Fig. 8 Photos of an installation of a preferred gas diffusion electrode

[0136] Fig. 9 Photos of a monopolar plate as a current collector

[0137] Detailed description of the characters

[0138] Fig. 1 schematically illustrates a preferred embodiment of a current collector 7. Fig. 1a shows the first side of the current collector 7, while Fig. 1b depicts the second side of the current collector 7. The current collector 7 in Fig. 1 is designed as a monopolar plate.

[0139] Advantageously, the monopolar plate can be easily scaled and processed. This ease of processing is particularly evident in the easily implemented design options for webs 15. The webs 15 advantageously provide a flow field for the electrolyte, i.e., in particular, they enable a directional specification for the flow of the electrolyte. Thus, the webs 15 of the monopolar plate define a path for the electrolyte, through which the electrolyte can flow along the catalyst layer. The webs 15 of the monopolar plate are located in a central section of the monopolar plate, in particular within a recess of the monopolar plate.

[0140] An electrical contacting section 13 is located on the second side of the current collector 7 and faces a catalyst layer when installed in the preferred gas diffusion electrode, since the electrical contacting section 13 is used for electrically contacting the current collector 7 with the catalyst layer.

[0141] Furthermore, an electrical potential application region 9 is shown, which is present in particular on the first side of the current collector 7. In the embodiment shown in Fig. 1, the electrical potential application region 9 is present on the first side and on the second side of the current collector 7. The electrical potential application region 9 is structured in such a way that it can be contacted on both sides, for example with an electrical terminal for a contact. The electrical potential application region 9 is not coated with the polymer layer and can therefore be electrically contacted. Thus, an electrical current can advantageously be tapped at the electrical potential application region 9 during electrolysis.

[0142] Fig. 2 schematically illustrates another preferred embodiment of the current collector 7. Fig. 2a shows the first side of the current collector 7, while Fig. 2b depicts the second side of the current collector 7. The current collector 7 in Fig. 2 is designed as a grid structure (synonymously also referred to as a grid plate).

[0143] A grid structure is particularly advantageous on a laboratory scale because it can be provided or acquired inexpensively. Those skilled in the art will recognize that the grid structure also has ridges as a current collector (namely, through the structures to maintain the grid shape), but the ridges of the grid structure do not create a flux field. Therefore, an additional flux field is required when using a grid structure as a current collector. When using a monopolar plate as a current collector 7, a flux field for the electrolyte is already present due to the ridges present therein.

[0144] The electrical potential application region 9 is a section uncoated with the polymer layer. Furthermore, the electrical potential application region 9 can be provided with a metal tape to enable electrical contact with the current collector 7. In other words, the electrical potential application region 9, which belongs to the current collector 7, is electrically contacted with the metal tape.

[0145] The electrical contacting section 13 is located on the second side of the current collector 7 and also serves for electrical contact with the catalyst layer of a preferred gas diffusion electrode.

[0146] Fig. 3 shows a schematic representation of a preferred embodiment of a gas diffusion electrode 1. Fig. 3a is a side view, while Fig. 3b shows a front view of the gas diffusion electrode 1. In the embodiment according to Fig. 3, the current collector 7 is in the form of a grid structure.

[0147] The gas diffusion electrode comprises a substrate 3, a catalyst layer 5, and the current collector 7. The substrate 3 comprises an electrically non-conductive and hydrophobic material and has a pore structure. The substrate 3 serves as a support for the catalyst layer 5 and the current collector 7. The catalyst layer 5 is arranged on the substrate 3. The first side of the current collector 7 has a polymer layer section. Furthermore, an electrical potential application region 9 is present at least on the first side of the current collector 7. The second side of the current collector 7 has the electrical contacting section, which faces the catalyst layer 5. The structure of the gas diffusion electrode 1 enables an electrical current to flow through the gas diffusion electrode 1.

[0148] Since the current collector 7 is designed as a grid structure, the electrical potential application area 9 is located at the edge of the current collector 7, yet still allows for secure electrical contact. The electrical potential application area 9 can also be applied with a metal tape, such as a copper tape, to establish electrical contact.

[0149] The gas diffusion electrode 1 achieves a multitude of surprisingly advantageous effects, which were by no means expected and synergistic in their entirety. The basic design of the gas diffusion electrode 1 can be easily scaled to larger dimensions, enabling its transfer to large-scale plants. Furthermore, higher electrical current densities and thus higher product rates can be advantageously generated, allowing higher Faradaic efficiencies to be achieved. In particular, the flooding problem described in the prior art, which would lead to a loss of selectivity, advantageously does not occur. Thus, the catalyst layer 5 advantageously exhibits long-term stability, enabling high functional stability to be achieved by the gas diffusion electrode 1. Furthermore, the gas diffusion electrode 1 is advantageous in that it provides an efficient electrical current particularly reliably.

[0150] Fig. 4 also shows a preferred embodiment of the gas diffusion electrode 1, wherein the current collector 7 is designed as a monopolar plate and not as a grid structure as in Fig. 3. However, the basic structure shown in Fig. 4 corresponds to that of Fig. 3. Fig. 4a shows a side view and Fig. 4b a front view of the gas diffusion electrode 1.

[0151] A monopolar plate as a current collector 7 is particularly well suited for the gas diffusion electrode 1. This allows for better scalability of the current collector 7 and the gas diffusion electrode 1. Furthermore, the monopolar plate is easy to process to provide a flow field for the electrolyte. In particular, by providing the flow field, the monopolar plate, due to the arrangement of the webs, enables a close spacing of an anode to the gas diffusion electrode as the cathode, thus also advantageously increasing efficiency.

[0152] Fig. 5 shows a preferred embodiment of a system comprising an electrolysis cell 17. The gas diffusion electrode 1 represents a component of the electrolysis cell 17.

[0153] The gas diffusion electrode 1 comprises a monopolar plate as a current collector 7 and a substrate 3, which is attached to the electrical contact section of the current collector 7. The substrate 3 is coated with the catalyst layer 5, which is not visible in Fig. 5. Seals 23 are also provided to prevent unwanted electrolyte flow into other components of the electrolysis cell 17. Furthermore, the electrolysis cell 17 comprises a membrane 25, which is attached between the gas diffusion electrode 1 and an anode 19. Furthermore, end plates 21 hold the gas diffusion electrode together and ensure the stability of the electrolysis cell 17.

[0154] Fig. 6 shows measurement results for the electrochemical conversion of CO2 with a grid structure as current collector.

[0155] In Fig. 6a (a1-a2), the reaction was carried out using a grid structure as a current collector without a polymer layer. The Faradaic efficiency (FE) for hydrogen, ethylene, carbon monoxide, and methane is plotted against the applied cathodic current density j. It is evident that hydrogen is the main product.

[0156] Fig. 6b (b1-b2) shows the results for the electrochemical conversion of CO2 using a grid coated with a polymer layer as a current collector. The Faradaic efficiency (FE) is plotted against the applied cathodic current density j. In contrast to the uncoated grid structure, the polymer coating suppresses hydrogen production, which advantageously leads to a higher Faradaic efficiency to ethylene, among other things.

[0157] Above the measurement results of Fig. 6a and 6b, photos of the grating structure are shown, which is uncoated in Fig. 6a and coated with a polymer layer in Fig. 6b.

[0158] In Fig. 6c, the ratio of the Faradaic efficiency of ethylene to hydrogen (FE Ethylene / Hydrogen) is plotted against the cathodic current density j. The square symbols (“Coated copper grid”) represent the values ​​for the coated grid current collector, and the round symbols (“Uncoated copper grid”) represent the values ​​for the uncoated grid current collector.

[0159] Fig. 7 shows the measurement results for the electrochemical performance of a monopolar plate as a current collector for the reduction of CO2.

[0160] In Fig. 7a (a1-a2), the Faradaic efficiency (FE) is plotted on the y-axis against the cathodic current density j. It can be seen that the selectivity for hydrogen formation remains low, while the formation of, for example, ethylene remains high.

[0161] In Fig. 7b the cell potential (“Cell Potential”) is plotted on the Y-axis against time (“time”) on the X-axis. The dark line (“TUB monopolar plate design”) represents a measurement with the monopolar plate as the current collector, and the lighter line (“TUB cell side contacting”) represents a measurement without a current collector. This clearly shows the behavior when a current is applied. In the presence of the current collector the potential is established immediately, whereas without a current collector the potential initially drops to a very negative value and then slowly approaches a constant value. The better response of the potential when the current is applied clearly demonstrates the better electrical contact provided by the current collector.

[0162] In Fig. 7c (c1-c2), a photo of the monopolar plate as a current collector is shown on the right. On the left, a photo of a preferred embodiment of the gas diffusion electrode after a measurement is shown. The gas diffusion electrode shows the imprints of the uncoated ridges that provide electrical contact. A photo of the monopolar plate is shown on the right.

[0163] Fig. 8 shows photos of end plates into which the gas diffusion electrode can be installed.

[0164] Fig. 8a shows a photograph of an end plate 21 with a built-in grid structure serving as a current collector 7. A metal tape 27, in this case a copper tape (copper adhesive tape), connects the electrical potential application area 9 of the current collector 7 to the end plate 21. Fig. 8b shows the end plate 21 without the gas diffusion electrode. The milled cavity for inserting the gas diffusion electrode is visible.

[0165] Fig. 9 shows photos of a monopolar plate acting as current collector 7.

[0166] Fig. 9a shows the first side of the monopolar plate with a parallel flux field. Fig. 9b shows the second side of the monopolar plate with the parallel flux field, which is achieved by the arrangement of the webs 15. Fig. 9c shows the first side of the current collector 7, while Fig. 9d shows the second side. The flux field of the monopolar plate according to Figs. 9c and 9d is serpentine-shaped, which can also be achieved by the corresponding arrangement of the webs 15.

[0167] LIST OF REFERENCE SYMBOLS

[0168] 1 gas diffusion electrode

[0169] 3 Substrat

[0170] 5 Catalyst layer

[0171] 7 current collectors

[0172] 9 Electrical potential application area

[0173] 11 Polymer layer

[0174] 13 Electrical contact section

[0175] 15 Steg

[0176] 17 Elektrolysezelle

[0177] 19 Anode

[0178] 21 Endplatte

[0179] 23 Dichtung

[0180] 25 Membran

[0181] 27 Metalltape

[0182] LITERATURVERZEICHNIS

[0183] Dinh, Cao-Thang, et al. "CO2 electroreduction to ethylene via hydroxide-mediated copper catalysis at an abrupt interface." Science 360.6390 (2018): 783-787.

[0184] Tiwari, Prerna, et al. "Gortex-based gas diffusion electrodes with unprecedented resistance to flooding and leaking." ACS applied materials & interfaces 10.33 (2018): 28176-28186.

Claims

PATENT CLAIMS 1. A gas diffusion electrode (1) for electrolysis comprising a substrate (3), a catalyst layer (5), and a current collector (7), wherein the substrate (3) has a pore structure and comprises an electrically non-conductive and hydrophobic material, wherein the current collector (7) has a first side and a second side, and the substrate (3) functions as a support for the catalyst layer (5) and the current collector (7), wherein the catalyst layer (5) is arranged on the substrate (3), characterized in that the first side of the current collector (7) has a polymer layer section and an electrical potential application region (9), wherein a polymer layer (11) is present on the polymer layer section and the electrical potential application region (9) is electrically contactable, and the second side comprises an electrical contacting section (13), wherein the electrical contacting section (13) faces the catalyst layer (5),so that an electric current can flow through the gas diffusion electrode (1) during electrolysis., 2. Gas diffusion electrode (1) according to the preceding claim, characterized in that the electrolysis comprises a reduction of gaseous carbon dioxide, carbon monoxide, oxygen, nitrogen, nitrogen oxide and / or nitrogen dioxide.

3. Gas diffusion electrode (1) according to one or more of the preceding claims, characterized in that the current collector (7) is present as a monopolar plate or a grid structure, preferably as a monopolar plate.

4. Gas diffusion electrode (1) according to one or more of the preceding claims, characterized in that the current collector (7) comprises webs (15), wherein the webs (15) are arranged in parallel, serpentine or grid-like manner, wherein a parallel arrangement of the webs (15) is preferred.

5. Gas diffusion electrode (1) according to one or more of the preceding claims, characterized in that the current collector (7) comprises a material selected from a group comprising nickel, titanium, aluminum, copper, gold, silver, stainless steel and / or combinations of the aforementioned materials.

6. Gas diffusion electrode (1) according to one or more of the preceding claims, characterized in that the current collector (7) has a thickness between 0.1 - 20 mm, preferably between 0.5 - 10 mm, particularly preferably between 0.5 - 5 mm. Gas diffusion electrode (1) according to one or more of the preceding claims, characterized in that the polymer layer (11) comprises a material selected from a group comprising an epoxy, polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), and / or polyvinylidene fluoride (PVDF). Gas diffusion electrode (1) according to one or more of the preceding claims, characterized in that the pore structure of the substrate (3) comprises pores with a diameter between 100 nm and 50 pm, preferably 100 nm and 20 pm, particularly preferably between 100 nm and 10 pm. Gas diffusion electrode (1) according to one or more of the preceding claims, characterized in that the substrate (3) comprises a material selected from a group comprising polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylenepropylene (FEP), polyvinylidene fluoride (PVDF), and / or polychlorotrifluoroethylene (PCTFE).Gas diffusion electrode (1) according to one or more of the preceding claims, characterized in that the catalyst layer (5) comprises metal particles, wherein the catalyst layer preferably comprises a material selected from a group comprising copper, copper oxide, silver, gold, tin, tin oxide, zinc, indium, bismuth, antimony, palladium, platinum, ruthenium, rhodium, iridium, rhenium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zirconium, niobium, molybdenum, technetium, scandium, yttrium, aluminum, carbon, nitrogen, boron, oxygen, fluorine, chlorine, bromine, iodine, silicon, phosphorus, sulfur, gallium, germanium, arsenic, selenium, tellurium, lead, hafnium, tantalum, tungsten, osmium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, Ytterbium, lutetium and / or a combination of the above materials.Gas diffusion electrode (1) according to one or more of the preceding claims, characterized in that the catalyst layer (5) comprises a binder, wherein the binder preferably comprises a material selected from a group comprising NaCl, Sustainion, polytetrafluoroethylene (PTFE) and / or polyvinylidene fluoride (PVDF), wherein the binder preferably has a weight fraction of 1-20%, preferably between 1-10%, very particularly preferably between 1-5%, of metal particles. Gas diffusion electrode (1) according to one or more of the preceding claims, characterized in that. the catalyst layer (5) comprises an additive, wherein the additive is selected from a group comprising an additional catalyst material, a support material, a protective material, and / or a conductivity additive. Gas diffusion electrode (1) according to one or more of the preceding claims, characterized in that the catalyst layer (5) has a thickness between 0.1 and 100 pm, preferably between 0.1 and 50 pm, particularly preferably between 1 and 25 pm, most particularly preferably between 1 and 10 pm. A system for carbon dioxide reduction comprising an electrolysis cell (17), wherein the electrolysis cell (17) is configured to hold a liquid electrolyte, wherein the electrolysis cell comprises an anode (19) and a cathode, wherein the cathode is a gas diffusion electrode (1) according to one or more of claims 1-13.Method for producing a gas diffusion electrode according to one or more of claims 1-13, comprising the following steps: a) providing a substrate (3) which has a pore structure and comprises an electrically non-conductive and hydrophobic material, b) providing a current collector comprising a first side and a second side, wherein the first side has a polymer layer section and an electrical potential application region or the electrical potential application region is provided and the second side comprises an electrical contacting section, c) coating the substrate with a catalyst layer, d) coating the polymer layer section with a polymer layer, e) contacting the electrical contacting section with the catalyst layer.

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