Gas diffusion electrodes and their use

Abstract

This invention relates to gas diffusion electrodes and their use, as well as to methods for manufacturing them.

Description

[Technical Field]

[0001] The present invention relates to the technical field of electrolysis, particularly the electrochemical reduction of carbon dioxide. In particular, the present invention relates to gas diffusion electrodes for the electrochemical reduction of carbon dioxide, and to the use thereof. Furthermore, the present invention relates to a method for manufacturing the aforementioned gas diffusion electrode, and also to an electrolytic cell for the electrochemical reduction of carbon dioxide. [Background technology]

[0002] Through electrochemical reduction in an aqueous environment, valuable chemical raw materials such as carbon monoxide, alcohols, aldehydes, ketones, and carboxylic acids can be obtained from carbon dioxide. In addition to obtaining a valuable raw material, the electrochemical reduction of carbon dioxide also has the advantage that the greenhouse gas CO2 can be removed from the environment or, for example, collected after combustion or industrial processes and further processed, and therefore not even released into the environment. With the expansion of renewable energy and associated carbon-neutral energy production, the electrolysis of carbon dioxide is expected to become more important, particularly for the chemical industry, as it enables both the acquisition of a valuable raw material and the conservation of fossil fuels. Currently, single-layer polymer-containing catalyst layers (CL), single-layer ionomer-containing catalyst layers (CL), and single-layer polymer and ionomer-containing catalyst layers (CL) are used in electrolytic cells for CO2 reduction and CO reduction. In electrodes containing polymer-containing CL, the catalyst composition is bonded to a porous gas diffusion layer (GDL) or porous transport layer (PTL) using the polymer. For this purpose, the mixture of catalyst and polymer binder is typically applied to the porous GDL or porous PTL by a wet manufacturing method, such as spraying. Further manufacturing methods used include, among others, hot pressing or the use of a doctor blade for applying a dry powder mixture. Often, fluoropolymers, such as polytetrafluoroethylene (PTFE), are used in catalyst layers because their hydrophobic properties can reduce pore flooding in electrodes and the associated problems of excess water and CO2 mass transfer. This is particularly relevant in processes involving gaseous raw materials. Examples of the use of such fluoropolymer-based catalyst layers include CO2 electrolysis and CO electrolysis, as well as fuel cell technology and chlorine-alkali electrolysis.

[0003] In the field of CO2 electrolysis, single-layer polymer-containing catalyst layers (CLs) have been primarily used in gas-liquid electrolytic cells because they can thus slow down the undesirable penetration of liquid electrolytes into the gas diffusion electrode (GDE), thereby mitigating the limitations related to CO2 mass transfer. Suitable hydrophobicity in the catalyst layer was found to be key to selective CO2 reduction. By applying a non-catalyst ionomer-containing cover layer, the ionic conductivity and surface wettability of the catalyst layer in the gas-liquid electrolytic cell can be increased, and therefore the product selectivity of CO2 reduction can be improved under industrial current densities (Junge Puring K, Siegmund D, Timm J, et al. Electrochemical CO2Reduction: Tailoring Catalyst Layers in Gas Diffusion Electrodes. Adv. Sustainable Syst. 2021; 5(1): 2000088). Furthermore, it has been shown that the catalyst layer is the primary protective layer against electrode flooding, and that the long-term stability of the electrode can be decisively improved by the appropriate hydrophobicity of the binder (Nwabara UO, Hernandez AD, Henckel DA, et al. Binder-Focused Approaches to Improve the Stability of Cathodes for CO2Electroreduction. ACS Appl. Energy Mater. 2021; 4(5): 5175-86). However, the limited electrolyte conductivity necessitates high energy requirements for the electrochemical process, making the use of such electrodes in gas-liquid electrolytic cells less economical. Similarly, their use in typical, highly alkaline electrolytes, which are preferable for CO2 reduction, is undesirable because neutralization and carbonate formation occur as a result of the reaction between hydroxide and gaseous CO2. In particular, carbonate formation leads to a certain degree of hydrophilization of the gas diffusion electrode, thus resulting in electrowetting and flooding of the electrode. Therefore, for industrial current densities ≥ 300 mA cm⁻¹, these electrodes are not suitable. -2 Therefore, achieving an electrolysis time of ≥ 10 hours is rarely possible.

[0004] Even in zero-gap electrolytic cells, i.e., electrolytic cells in which the catalyst layer is in direct contact with a solid polymer electrolyte composed of an ion-conducting polymer, excess water accumulation in the pores of the cathode-side gas diffusion electrode can occur despite the absence of a liquid electrolyte at the cathode. Therefore, the use of a hydrophobic polymer-containing catalyst layer can also contribute to minimizing the flooding process. Until now, hydrophobic polymer-containing catalyst layers have been used very rarely for CO2 reduction in zero-gap electrolytic cells. Flooding behavior decreased as the PTFE content in the polymer-containing catalyst layer increased, and it was found that the use of thin films thinner than 40 μm was generally advantageous. However, a partial current density of 100 mA cm² was achieved at a cell voltage of 3 V. -2 For electrolysis times less than 25 minutes, 300mA cm² is used for electrolysis times ≥ 10 hours. -2 The results obtained with the above partial current densities fall far short of industrially viable outcomes (Reyes A, Jansonius RP, Mowbray BAW, et al. Managing Hydration at the Cathode Enables Efficient CO2 Electrolysis at Commercially Relevant Current Densities. ACS Energy Lett. 2020; 5(5): 1612-8).

[0005] A drawback of using hydrophobic polymer-containing catalyst layers in CO2 reduction in gas-liquid electrolytic cells and zero-gap electrolytic cells lies in the lack of ionic conductivity in the catalyst. A possible means to improve these systems is an ionomer cover layer. However, the application of low-viscosity ionomers can lead to pore closure or heterogeneity within the polymer-containing catalyst layer, which limits mass transfer. Furthermore, the ionomer cover layer itself does not contain any catalysts and is therefore neither catalytically active nor electrically conductive, which is why inactive regions can occur in hydrophobic polymer-containing CLs. Currently used single-layer hydrophobic polymer-containing catalyst layers, including a single-layer hydrophobic polymer-containing catalyst layer and an ionomer cover layer, achieve an industrially reasonable current density of ≥300 mA cm² at a cell voltage ≤3V. -2 Furthermore, it is not suitable for achieving an electrolysis time of ≥ 10 hours. Regarding ion-conducting monolayer ionomer-containing catalyst layers, in contrast to monolayer polymer-containing catalyst layers, significantly lower cell voltages can be achieved with higher partial current densities and longer electrolysis times. They represent a technological level for CO2 reduction in zero-gap electrolytic cells. For the manufacture of ionomer-containing gas diffusion electrodes, catalyst inks are typically applied to porous electrically conductive gas diffusion layers (GDLs) by wet manufacturing methods such as spraying. Furthermore, manufacturing methods used include, for example, the doctor blade method. The ionomer in the catalyst layer enables good ionic contact between the catalyst layer and the liquid electrolyte in a gas-liquid electrolytic cell or the solid polymer electrolyte membrane (SPE membrane) in a zero-gap electrolytic cell.

[0006] In the field of CO2 reduction, significantly lower cell voltages and longer electrolysis times can now be achieved in zero-gap electrolytic cells at industrial current densities compared to using the polymer-containing catalyst layer described above. Therefore, in zero-gap electrolytic cells using an anion-conducting monolayer ionomer-containing catalyst layer combined with an anion exchange membrane (AEM), industrially viable current densities of ≥300 mA cm² have already been achieved. -2 Under these conditions, it was possible to achieve an electrolysis time of ≥200 hours with a cell voltage of ≤3V. By using an ionomer (Piperion) having a poly(arylpiperidinium) group and a catalyst layer in a solid electrolyte membrane (SPE membrane), for example, for the target product carbon monoxide, in a zero-gap electrolyzer, a partial current density of up to 420 mA cm was achieved at 3.2 V over 200 hours. -2 (Endrodi B, Samu A, Kecsenovity E, Halmagyi T, Sebok D, Janaky C. Operando cathode activation with alkali metal cations for high current density operation of water-fed zero-gap carbon dioxide electrolyzers. Nat. Energy 2021; 6(4): 439-48).

[0007] Regarding a solid electrolyte membrane (SPE membrane) and a catalyst layer (CL) containing an ionomer (Sustainion) based on an imidazolium group, over an electrolysis time of ≧70 hours, a cell voltage (U セル ) of approximately 3.2 V and a current density of 400 mA cm -2 could be achieved (Liu Z, Yang H, Kutz R, Masel RI. CO2Electrolysis to CO and O2at High Selectivity, Stability and Efficiency Using Sustainion Membranes. J. Electrochem. Soc. 2018; 165(15): J3371-J3377). In addition to these results, further studies were carried out using an ionomer-containing catalyst layer at industrial current densities in zero-gap electrolyzers. However, these had a current density of ≧300 mA cm -2Furthermore, electrolysis times exceeding 70 hours could not be achieved at cell voltages ≤ 3.2V. In particular, it was shown that promising results can be achieved when an anion-conducting ionomer is used in the cathode catalyst layer, in addition to the use of AEM and PEM, thus obtaining a bipolar interface layer. This configuration allows for significantly lower cell voltages, and is advantageous for the use of bipolar films because the transfer of CO2 in the form of carbon salt ions from the anode to the cathode becomes more difficult (Patru A, Schmidt TJ, Binninger T, Pribyl B, inventors. Co-Electrolysis Cell Design for Efficient CO2Reduction from Gas Phase at Low Temperature. 2017 Jul 24).

[0008] In addition to its use in zero-gap electrolytic cells, ionomer-containing catalyst layers are also used in gas-liquid electrolytic cells. However, these systems are limited in terms of their electrolysis time due to the strong flooding described above. In one literature, in contrast to the majority of literature, porous polymer foil was used as the gas diffusion layer (GDL) instead of porous hydrophobic carbon fiber fabric. The catalyst was applied to the porous polymer foil using the PVD method for later bonding of the catalyst by spraying the ionomer. Thus, FE C2H4 Using ≥50%, the current density is 1A cm². -2 This made it possible to achieve an electrolysis time of ≥60 hours (Garcia de Arquer FP, Dinh CT, Ozden A, et al. CO2 electrolysis to multicarbon products at activities greater than 1 A cm). -2 .Science 2020; 367(6478): 661-6).

[0009] Therefore, ionomer-containing catalyst layers have been used in the field of CO2 reduction to achieve industrial current densities of ≥300 mA cm⁻¹. -2Under these conditions, the electrolysis time is limited to 60 hours in a gas-liquid electrolytic cell and 2000 hours in a zero-gap electrolytic cell, and generally, a mutually proportional relationship can be observed between electrolysis time and current density. This lack of long-term stability of the catalyst layer is due to the insufficient hydrophobicity of the catalyst layer. In polymer-containing catalyst layers, hydrophobicity can be achieved by selecting the proportion and type of polymer used, as well as by adjusting pore formation by the sintering method, which is not possible with conventionally used ionomer-containing CLs. Due to the fact that ionomer-containing catalyst layers do not have sufficient hydrophobicity to slow the flooding of the gas diffusion electrode, they rely on a strongly hydrophobic gas diffusion layer (GDL). In addition to the use of single-layer polymer-containing catalyst layers and single-layer ionomer-containing catalyst layers, single-layer polymer and ionomer-containing catalyst layers have also been used to combine the binder properties of both types in the catalyst layer. However, in studies of various single-layer catalyst layers containing both hydrophobic polymer and hydrophilic ionomer proportions in zero-gap electrolytic cells, bulk hydrophobicity is reduced by the proportion of ionomer, and ionic conductivity to the SPE film is reduced by the proportion of polymer. Therefore, it has not been possible to establish any improvement in flooding behavior or feasible electrolysis time compared to hydrophobic, pure polymer-containing catalyst layers or pure ionomer-containing catalyst layers.

[0010] In fuel cell technology, electrodes containing multiple different catalyst layers are used to improve water management at the corresponding electrodes. In some cases, multilayer ionomer-containing catalyst layers (CLs) are used to obtain gradients with respect to ionic conductivity or porosity. Furthermore, multilayer structures having hydrophobic and hydrophilic catalyst layers have already been used. For example, such structures are used to improve catalyst utilization in methanol fuel cells disclosed in DE60133879T2 and in PEM fuel cells, for example, as shown in Chinese Patent No. 100521313. Generally, the water content in the catalyst should be set to ensure sufficient mass transfer of gas species, which can result in higher power density and higher long-term stability. However, the hydrophobic catalyst layer according to Chinese Patent No. 100521313 always contains a certain percentage of ionomer, which results in good ionic conductivity but ultimately leads to electrode flooding. The same applies to the multilayer structure according to DE60133879T2.

[0011] As with fuel cell technology, water management in the cathode is also extremely important in the field of electrochemical CO2 reduction. Multilayer catalyst layers developed in the field of fuel cell technology cannot be directly used for CO2 reduction because CO2 reduction is far more complex. The objective of PEM fuel cells is to achieve mass transfer of gaseous raw materials with sufficient ionic conductivity introduced by water, but numerous influences must be considered in CO2 reduction. In CO2 reduction, two raw materials, CO2 and water, must be supplied to the catalyst layer (CL) in the cathode, parasitic hydrogen evolution reactions (HER) must be suppressed, and the desired product must be obtained. This is directly dependent on the catalytic environment. In addition to adjusting the water content by the hydrophobicity of the layer, local pH values, porosity, and catalytic availability can also be adjusted for each CO2 reduction process. Corresponding multilayer catalyst layers have not been developed to date and have not been optimized for CO2 reduction. Since the formation of carbon salts in the catalyst layer (CL) and gas diffusion layer (GDL) is not involved in the field of fuel cell technology, in addition to CO xThere is a need to develop a catalyst layer suitable for suppressing carbon salt formation for electrolysis. Therefore, although the goals of water management in fuel cells and CO2 reduction in zero-gap electrolytic cells are similar, the multilayer catalyst layers conventionally used in the field of fuel cells are not suitable for the requirements of electrolytic cells for CO2 reduction. [Overview of the project]

[0012] One objective of the present invention is to avoid, or at least mitigate, the above-mentioned drawbacks and the drawbacks related to the prior art. In particular, one objective of the present invention is to provide an electrode, especially a gas diffusion electrode, that can be operated continuously with industrial current intensity and high current yield, and is particularly suitable for the reduction of CO2. Therefore, the subject matter of the present invention according to a first aspect of the present invention is the electrode described in claim 1, and a more advantageous embodiment of this aspect of the present invention is the subject matter of the corresponding dependent claim. A further subject matter of the present invention according to a second aspect of the present invention is the use of the electrode according to the present invention as described in claim 12. A further subject matter of the present invention according to a third aspect of the present invention is again the use of the electrode according to the present invention as described in claim 13. A further subject matter of the present invention according to a fourth aspect of the present invention is a method for manufacturing an electrode according to the present invention as described in claim 14, and a further advantageous embodiment of this aspect of the present invention is the subject matter of the corresponding dependent claim. Finally, a further subject matter of the present invention according to a fifth aspect of the present invention is an electrolytic cell for the electrochemical reduction of carbon dioxide as described in claim 17.

[0013] For the purpose of avoiding unnecessary repetition, special features, elements, embodiments, and examples, as well as advantages, etc., described below in relation to one aspect of the present invention do not require explicit mention and will, of course, apply accordingly to other aspects of the present invention. In addition, it is applicable that all the details of the values ​​or parameters below are, in principle, established or obtainable by normalized, standardized, or clearly specified determination methods, or determination methods that are well known to those skilled in the art. Furthermore, it goes without saying that all percentage details related to mass or quantity are to be interpreted by those skilled in the art as totaling 100%. Therefore, the present invention is described in more detail below. This invention First In some aspects of the present invention, the subject matter is a gas diffusion electrode for the electrochemical reduction of CO2, wherein the electrode comprises at least one hydrophobic catalyst layer and at least one hydrophilic catalyst layer. This is because the applicant has unexpectedly discovered that the main problems with gas diffusion electrodes used to date can be avoided by using gas diffusion electrodes containing hydrophobic and hydrophilic catalyst layers. In particular, the drawbacks of hydrophilic ionomer-containing catalyst layers, namely stepwise flooding of the cathode, thus reducing mass transfer and ultimately interrupting electrolysis, can be avoided. At the same time, the drawbacks of pure hydrophobic polymer-containing catalyst layers, namely simply low mass conversion and low useful current density, can also be avoided.

[0014] In the context of the present invention, typically, a hydrophobic catalyst layer (CL) is first applied to a commercially available gas diffusion layer (GDL) or porous carrier material (PTL), followed by the application of a hydrophilic catalyst layer (CL). Effective reduction of the substrate, particularly carbon dioxide, can be achieved at the interface between the electrode and the substrate, especially at the interface between the hydrophobic catalyst layer and the hydrophilic catalyst layer. In particular, effective reduction of the substrate is achieved thanks to the fact that there is no three-phase interface between the electrode, electrolyte, and substrate, and rather the substrate, i.e., carbon dioxide, does not pass through the aqueous phase at the interface between the hydrophilic catalyst layer and the hydrophobic catalyst layer, but rather simply exists in a wet state. The electrode does not undergo flooding by liquid water due to the use of hydrophobic and hydrophilic catalyst layers, but rather is simply very wet, and electrochemical reduction of carbon dioxide can occur. Rapid transport of the formed ions is also possible by the use of the hydrophilic catalyst layer. As an alternative to the above-described method of manufacturing electrodes, a hydrophilic catalyst layer may also be applied first to an ion-conducting film, followed by a hydrophobic catalyst layer. This structure is then applied to a gas diffusion layer via the hydrophobic catalyst layer. The multilayer structure of a gas diffusion electrode described in the present invention, comprising a multiple catalyst layer including at least one hydrophobic, particularly polymer-containing, catalyst layer and at least one hydrophilic, particularly ionomer-containing catalyst layer, makes it possible to adapt the physical properties of the electrode to CO2 reduction and the respective process conditions. In addition to the transport of gases, ions, and electrons, it is also possible to set wetting and ion transport at the electrode-substrate interface, on the one hand, and wetting and ion transport at the electrode-electrolyte interface, on the other hand, on the other hand, on the other hand.

[0015] Simultaneously, hydrophobic, particularly polymer-containing CLs, allow for improved binding to GDL, pore distribution, and bulk hydrophobicity, as well as reduced CL costs. Hydrophilic, particularly ionomer-containing CLs, allow for a decrease in cell voltage due to improved ionic conductivity, and allow the local pH value of the catalyst to be set to suit CO2 reduction. Further advantages are obtained from multilayer structures having at least two catalyst layers. Since the active range of a gas diffusion electrode is a three-dimensional range with a specific depth perpendicular to the plane, rather than a two-dimensional plane, the region of the catalyst layer containing the active catalyst composition can be expanded by catalyst supply and continuous electrical conductivity on both sides of the interface. Furthermore, the use of hydrophilic and hydrophobic catalyst layers allows for a synergistic combination of the properties of different catalyst layers. The hydrophobic catalyst layer prevents flooding of the electrode by water, while the hydrophilic layer allows for rapid transport of formed ions into the membrane. The combination of these two characteristics enables a significantly more effective electrochemical reduction of carbon dioxide, resulting in higher current density, higher yield, and extended usage time.

[0016] In the context of the present invention, the hydrophobic catalyst layer should be understood as a catalyst layer whose material has a contact angle with water of at least 90°, preferably at least 120°, more preferably at least 140°, and particularly preferably at least 160°. In contrast, in the context of the present invention, a hydrophilic catalyst layer should be understood as a catalyst layer whose material has a contact angle with water of less than 90°, preferably less than 50°, more preferably less than 40°, and particularly preferably less than 30°. The contact angle can be determined, for example, by static contact angle measurement using an optical method. In the context of this invention, ionomer should be understood as a copolymer of electrically neutral repeating units and repeating units having ionic functional groups. Typically, the proportion of ionic repeating units is 15 mol% or less based on the polymer. The ionic groups are often carboxylic acid functional groups or carboxylates, or sulfonic acid groups or sulfonates. Ionomers generally have high ionic conductivity but no electrical conductivity and are often used as solid electrolytes in electrolytic cells or as ion-conducting membranes, particularly proton-conducting membranes.

[0017] In the context of the present invention, it is particularly important that both the hydrophilic catalyst layer and the hydrophobic catalyst layer each contain a specific proportion of catalyst for electrochemical reactions, especially reduction. Only in such cases can the remarkably improved properties of the electrode according to the present invention be achieved. The use of a catalyst-free hydrophobic layer and a hydrophilic catalyst layer applied thereto, or the use of a hydrophobic catalyst layer and a catalyst-free hydrophilic layer applied thereto, does not result in improved properties. Mixed layers of hydrophilic and hydrophobic regions, some of which are used in the prior art, are also not equivalent in performance to the system of the present invention. Only electrodes containing both a hydrophobic catalyst layer and a hydrophilic catalyst layer result in an expansion of the region containing the active catalyst composition without the risk of electrode flooding. Furthermore, the electrode according to the present invention differs from electrodes used in the field of fuel cell technology, which include a hydrophobic catalyst layer and a hydrophilic catalyst layer, in that, in the context of the present invention, the binder used in the hydrophobic layer does not contain an ionomer. The multilayer structure according to the present invention, comprising a catalyst layer containing at least one hydrophobic, particularly polymer-containing, and a catalyst layer containing at least one hydrophilic, particularly ionomer-containing, enables higher current yield, lower cell voltage, higher energy efficiency, and at least 10-fold improved long-term stability compared to conventional single-layer polymer-containing catalyst layers (CL), single-layer ionomer-containing catalyst layers (CL), and single-layer polymer and ionomer-containing catalyst layers (CL). Therefore, in the case of CO2 reduction using the system of the present invention, the current yield is higher, and the cell voltage (U セル At approximately 100mV, the stability can increase by up to 16%, potentially resulting in at least a tenfold improvement in long-term stability. In addition, the amount of ionomer used can be significantly reduced, preferably by approximately 20%, thus enabling a corresponding reduction in material costs.

[0018] For use in the fields of CO2 reduction, CO reduction, or other electrochemical processes, the multilayer structure according to the present invention, comprising at least one hydrophobic catalyst layer and at least one hydrophilic catalyst layer, is preferably applied to commercially available GDL or PTL. The coating composition can be applied by dry or wet coating methods, such as spraying, using a doctor blade, drop application, printing, or a combination thereof. In this case, the catalyst layer can be applied to a porous carrier layer (catalyst coating substrate) or to an ion-conducting film (catalyst coating film), while a combination of the two methods is also possible. The catalyst is usually bound to the corresponding structure by a suitable binder, such as a hydrophobic polymer or ionomer. The properties of the structure comprising multiple catalyst layers can be further adjusted by changing the type of catalyst used, the type of binder, the content of the binder and catalyst, and the amount of catalyst packed in each layer. Hydrophilic polymers, particularly ionomers and resins, and hydrophobic polymers, with or without ion-exchange end groups, were found to be particularly suitable binders in the sense described above.

[0019] The gas diffusion electrode according to the present invention is particularly well suited for use in the electrochemical processes described above. For the applications described, the electrode typically functions as a cathode for the reduction of CO2, CO, N2, or O2, or for the electrolytic reduction of organic molecules (e.g., hydrogenation). Depending on the application, it can also be used as an anode for oxidation reactions (oxidation of H2, N2, or CO2, oxidation of organic compounds). In addition, the electrolytic cell is composed of further electrodes from which a suitable oxidation or reduction process may occur. The most important advantage of the present invention described herein is the application of a catalyst layer containing at least one hydrophobic, particularly polymer-containing, material and a catalyst layer containing at least one hydrophilic, particularly ionomer-containing, material. As a result, the hydrophobicity and porosity of the hydrophobic, particularly polymer-containing, material facing the GDL can be adjusted independently of the ionic conductivity and chemical environment, such as the cocatalytic effect of the ionomer, allowing for control of the local pH value in the catalyst layer of the hydrophilic, particularly ionomer-containing, material facing the electrolyte, for example. Thus, ideal conditions for CO2 reduction can be set by forming a three-phase boundary layer, resulting in higher current density, improved current yield for the target product, lower cell voltage, and improved electrolysis time.

[0020] In the context of the present invention, the hydrophobic catalyst layer and the hydrophilic catalyst layer are typically porous. This allows for sufficient mass transfer through the electrodes, while also providing a large surface area for carrying out electrochemical reactions. In the context of the present invention, the hydrophobic catalyst layer and the hydrophilic catalyst layer are in direct or indirect contact with each other. In this case, direct contact is understood to mean that the hydrophilic catalyst layer is applied to the hydrophobic catalyst layer, and vice versa. Preferably, the hydrophilic catalyst layer and the hydrophobic catalyst layer are in direct contact with each other. Similarly, in the context of the present invention, the hydrophobic catalyst layer and the hydrophilic catalyst layer are arranged in sequence, either indirectly or directly. Preferably, the hydrophobic catalyst layer and the hydrophilic catalyst layer are arranged in sequence, directly. In the context of the present invention, multiple hydrophobic or hydrophilic catalyst layers may also be provided to be used to selectively or gradually set hydrophobic and hydrophilic properties in particular regions. Preferably, the electrode according to the present invention comprises a hydrophobic catalyst layer and a hydrophilic catalyst layer.

[0021] According to one preferred embodiment of the present invention, the hydrophobic catalyst layer and the hydrophilic catalyst layer are arranged on a porous layer, particularly a porous carrier layer, preferably a gas diffusion layer. Preferably, the porous layer has a porosity, i.e., a volume fraction of pores, in the range of 50-90%, particularly 50-80%, preferably 55-75%, and more preferably 55-70%, based on the volume of the porous layer. The porous layer is macroporous or microporous. In the context of the present invention, porosity is understood to mean the ratio of the pore volume, also called the void volume, of an object to the total volume of the object in question. The porosity of a porous layer, in percent, can be determined particularly by mercury porosimetry, by calculations according to the BET model, or as an oil absorption value. Similarly, porosity can also be determined by computed tomography (CT), particularly by micro-CT or nano-CT. Preferably, the porous layer is microporous or comprises at least one microporous layer. In the context of the present invention, it has been found that a conventional gas diffusion layer or gas diffusion material is particularly advantageous when used as a porous layer, especially as a carrier material. A hydrophobic catalyst layer and a hydrophilic catalyst layer are then applied on top of it, thus obtaining a porous catalyst layer or a microporous catalyst layer.

[0022] Particularly favorable results are obtained when the porous layer has a pore size in the range of 0.001 to 200 μm, especially 0.001 to 150 μm, preferably 0.01 to 100 μm, and more preferably 0.01 to 100 μm. The pore size can be determined in particular by mercury porosimetry or by calculation according to the BET model. If the porous layer is macroporous, the porous layer may have pore sizes in the range of 0.05 to 200 μm, particularly 0.5 to 150 μm, preferably 0.5 to 100 μm, and more preferably 1 to 100 μm. Preferably, the porous layer is microporous or includes a microporous sublayer. In this case, the porous layer or the microporous sublayer of the layer has pore sizes in the range of 0.001 to 5 μm, particularly 0.001 to 0.5 μm, preferably 0.01 to 0.5 μm, and more preferably 0.01 to 0.2 μm. Due to the porous structure or microporous structure of the porous layer, a porous or microporous structure of the catalyst layer can also usually be obtained. According to the present invention, typically, the hydrophobic catalyst layer is arranged on a porous layer, and the hydrophilic catalyst layer is arranged on the hydrophobic catalyst layer. Alternatively, the hydrophilic catalyst layer may be arranged on a porous layer, and the hydrophobic catalyst layer may be arranged on the hydrophilic catalyst layer, but preferably, the hydrophobic catalyst layer is arranged on a porous layer, and the hydrophilic catalyst layer is arranged on the hydrophobic catalyst layer.

[0023] According to the present invention, therefore preferably, the hydrophobic catalyst layer is applied to the porous layer, and then the hydrophilic catalyst layer is applied to the hydrophobic catalyst layer. In this way, polar electrolytes, especially water, are prevented from penetrating the electrode, while sufficient absorption of water and sufficient ion transport are possible in the hydrophilic region, resulting in particularly effective electrochemical reduction of carbon dioxide. As already described above, according to the present invention, it is preferable that the porous layer, in particular the porous carrier layer, is a conventional gas diffusion layer (GDL). Particularly good results are obtained when the porous carrier layer is selected from the group consisting of carbon fiber fabrics, carbon fiber paper, graphite fabrics, metal felt, metal mesh, sintered metal particles, and mixtures thereof. According to the present invention, if the carrier layer contains or is composed of a metal, it has been found to be advantageous when the metal is selected from the group consisting of silver, copper, platinum, titanium, nickel, zinc, iron, aluminum, and stainless steel, as well as mixtures and alloys thereof. Particularly good results are obtained, in the context of the present invention, when the metal is selected from the group consisting of copper, silver, platinum, and mixtures and alloys thereof.

[0024] According to the present invention, it has been further found that it is advantageous when the porous layer, particularly the porous carrier layer, is selected from a carbon-containing material. In particular, the material of the porous layer is preferably selected from the group consisting of carbon fiber fabrics, carbon fiber paper, and mixtures thereof. Particularly preferably, the porous layer, particularly the porous carrier layer, is a carbon fiber fabric. In particular, in the selection of the porous carrier layer, it is important that the material is conductive and does not have undesirable catalytic properties. As far as the thickness of the porous layer, and especially the porous carrier layer, is concerned, it can actually vary over a wide range. However, particularly good results are obtained according to the present invention when the porous carrier layer has a thickness in the range of 50 to 1000 μm, especially 50 μm to 800 μm, preferably 100 μm to 600 μm, and more preferably 150 μm to 500 μm. As already shown above, according to the present invention, the hydrophobic catalyst layer and the hydrophilic catalyst layer each contain at least one catalyst. Furthermore, according to the present invention, the hydrophobic catalyst layer and the hydrophilic catalyst layer may contain the same catalyst or different catalysts. Particularly good results are obtained according to the present invention when the hydrophobic catalyst layer and the hydrophilic catalyst layer contain the same catalyst.

[0025] As far as catalyst selection is concerned, it can, in principle, be selected from all catalysts suitable for electrolysis, particularly catalysts suitable for the electrochemical reduction of carbon dioxide. Catalysts are typically selected from the group consisting of metal particles, especially metal nanoparticles, monatomic catalysts, metal carbides, metal oxides, metal chalcogenides, molecular catalysts, and mixtures thereof. Particularly favorable results are obtained in the context of the present invention when the catalyst is selected from metal particles, especially metal nanoparticles. In the context of the present invention, it has been found to be advantageous when the catalyst is selected from the group consisting of metal particles, especially metal nanoparticles, metal carbides, metal oxides, metal chalcogenides, molecular catalysts, and mixtures thereof, selected from metal particles of Au, Ag, Zn, Pd, Ga, Cd, In, Hg, Tl, Pb, Bi, Cu, and mixtures and alloys thereof. Particularly favorable results are obtained when the catalyst is selected from the group consisting of metal particles, especially metal nanoparticles, of Au, Ag, Zn, Pd, Ga, Cd, In, Hg, Tl, Pb, Bi, Cu, and mixtures and alloys thereof. Particularly favorable results are obtained in the context of the present invention when the catalyst is selected from the group of metal particles, especially metal nanoparticles, of Au, Ag, Cu, and mixtures and alloys thereof.

[0026] As far as the amount of catalyst in the catalyst layer is concerned, this can also vary widely. However, hydrophobic and hydrophilic catalyst layers have been found to be overwhelmingly advantageous when the catalyst content is high. Particularly favorable results are obtained in the context of the present invention when the hydrophobic catalyst layer and the hydrophilic catalyst layer contain the catalyst in an amount of 10% to 99.9% by mass, particularly 25% to 99.9% by mass, preferably 40% to 99.9% by mass, and more preferably 50% to 99.8% by mass, based on the hydrophobic catalyst layer and the hydrophilic catalyst layer. In particular, the hydrophilic catalyst layer may contain a catalyst in an amount of 50% to 99.9% by mass, particularly 55% to 99.9% by mass, preferably 60% to 99.9% by mass, and more preferably 70% to 99.8% by mass, based on the hydrophilic catalyst layer. When an anion exchange membrane (AEM) is used to separate the anode and cathode portions according to the present invention, the hydrophilic catalyst layer may contain the catalyst in an amount of 50% to 99.9% by mass, particularly 55% to 99.9% by mass, preferably 60% to 99.9% by mass, and more preferably 90% to 99.8% by mass, based on the hydrophilic catalyst layer. When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions according to the present invention, the hydrophilic catalyst layer may contain the catalyst in an amount of 50% to 99.8% by mass, particularly 55% to 99% by mass, preferably 60% to 97% by mass, and more preferably 70% to 95% by mass, based on the hydrophilic catalyst layer.

[0027] Similarly, the hydrophobic catalyst layer may contain a catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 99% by mass, preferably 40% to 97% by mass, and more preferably 50% to 95% by mass, based on the hydrophobic catalyst layer. When an anion exchange membrane (AEM) is used to separate the anode and cathode portions according to the present invention, the hydrophobic catalyst layer may contain the catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 99% by mass, preferably 40% to 97% by mass, and more preferably 50% to 95% by mass, based on the hydrophobic catalyst layer. When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions according to the present invention, the hydrophobic catalyst layer may contain the catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 99% by mass, preferably 40% to 97% by mass, and more preferably 50% to 95% by mass, based on the hydrophobic catalyst layer. Similarly, the hydrophobic catalyst layer and the hydrophilic catalyst layer may contain the catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 99.8% by mass, preferably 40% to 99.8% by mass, and more preferably 50% to 99.5% by mass, based on the solid content of the coating composition from which the hydrophobic catalyst layer and the hydrophilic catalyst layer are obtained.

[0028] In this case, the solid component of the coating composition, particularly the catalyst ink, is understood to mean the portion of the coating composition that remains after the removal of the solvent and other volatile components. In the context of the present invention, the hydrophilic catalyst layer may contain a catalyst in an amount of 50% to 99.8% by mass, particularly 55% to 99.8% by mass, preferably 60% to 99.8% by mass, and more preferably 66% to 99.5% by mass, based on the solid content of the coating composition from which the hydrophilic catalyst layer is obtained. When an anion exchange membrane (AEM) is used to separate the anode and cathode portions according to the present invention, the hydrophilic catalyst layer may contain the catalyst in an amount of 50% to 99.8% by mass, particularly 80% to 99.8% by mass, preferably 89% to 99.8% by mass, and more preferably 89% to 99.5% by mass, based on the solid content of the coating composition from which the hydrophilic catalyst layer is obtained. When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions according to the present invention, the hydrophilic catalyst layer may contain the catalyst in an amount of 50% to 99.8% by mass, particularly 55% to 95% by mass, preferably 60% to 92% by mass, and more preferably 66% to 86% by mass, based on the solid content of the coating composition from which the hydrophilic catalyst layer is obtained.

[0029] Similarly, the hydrophobic catalyst layer may contain the catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 96% by mass, preferably 40% to 96% by mass, and more preferably 50% to 96% by mass, based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained. When an anion exchange membrane (AEM) is used to separate the anode and cathode portions according to the present invention, the hydrophobic catalyst layer may contain the catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 96% by mass, preferably 40% to 96% by mass, and more preferably 50% to 96% by mass, based on the solid content of the coating composition from which the hydrophilic catalyst layer is obtained. When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions according to the present invention, the hydrophobic catalyst layer may contain the catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 96% by mass, preferably 40% to 96% by mass, and more preferably 50% to 96% by mass, based on the solid content of the coating composition from which the hydrophilic catalyst layer is obtained. Typically, hydrophobic and hydrophilic catalyst layers are configured to contain 0.001 to 100 mg / cm³ of catalyst based on the surface area of ​​the hydrophobic or hydrophilic catalyst layer. -2 , especially 0.05-50 mg / cm³ -2 Preferably 0.1 to 10 mg / cm³ -2 More preferably 0.5 to 3 mg / cm³ -2 It contains in that amount.

[0030] According to the present invention, the hydrophilic catalyst layer typically further comprises at least one hydrophilic polymer, particularly at least one ionomer. The polymer acts as a binder for the catalyst, ensuring that the catalyst adheres to a carrier layer, such as a gas diffusion layer or an ion-conducting membrane. Preferably, the hydrophilic catalyst layer contains a hydrophilic polymer, or a mixture of hydrophilic polymers, particularly one or more ionomers, as a single polymer, i.e., as a single binder. According to the present invention, in particular, the hydrophilic catalyst layer is not provided to include a hydrophilic polymer and a hydrophobic polymer. It has been found that hydrophilic polymers are advantageous when selected from the group consisting of polyelectrolytes, ionic polymers, ionomers, and mixtures thereof. Preferably, the hydrophilic polymer is selected from the group consisting of polyacrylic acid, acrylic acid copolymer, acrylamide copolymer, polyethyleneimine, alginate, pectin, lignin, lignin sulfonate, cellulose, cellulose ether, polyvinylpyrrolidone, polyvinylamine, polyvinylpyridine, polymers having sulfonic acid groups, polymers having perfluorosulfonic acid groups, polymers having quaternary ammonium groups, polymers having quaternary nitrogen heterocycles, polymers having phosphonium groups, polymers having sulfonium groups, polymers having organometallic complexes as cationic functionalization, and mixtures thereof.

[0031] Preferably, the hydrophilic polymer is an ionomer. Particularly favorable results are obtained according to the present invention when the hydrophilic polymer, especially the ionomer, is selected from the group consisting of polymers having sulfonic acid groups, polymers having perfluorosulfonic acid groups, polymers having quaternary ammonium groups, polymers having quaternary nitrogen heterocycles, polymers having phosphonium groups, polymers having sulfonium groups, polymers having organometallic complexes as cationic functionalization, and mixtures thereof. According to the present invention, hydrophilic polymers having ionic groups or groups that readily form ions are preferably used in general. Particularly favorable results are obtained in the context of the present invention when the hydrophilic polymer, in particular ionomer, is selected from the group consisting of polymers having a quaternary ammonium group, polymers having a quaternary nitrogen heterocycle, polymers having a phosphonium group, polymers having a sulfonium group, polymers having an organometallic complex as a cationic functionalization, and mixtures thereof. Particularly favorable results are obtained when the hydrophilic polymer, in particular ionomer, is selected from the group consisting of polymers having a quaternary ammonium group, polymers having a quaternary nitrogen heterocycle, and mixtures thereof.

[0032] The best results have so far been obtained when the hydrophilic polymer, particularly the ionomer, is selected from the group consisting of ionomers containing piperidinium groups, ionomers containing imidazolium groups, ionomers containing benzimidazolium groups, and mixtures thereof. Suitable ionomers include, for example, polymers and copolymers containing sulfonic acid groups, particularly polymers and copolymers based on perfluorosulfonic acid, and hydrocarbon-based polymers and copolymers having sulfonic acid groups, such as aromatic hydrocarbons, for example, commercially available Nafion® from DuPont. In addition, polymers and copolymers containing ammonium groups, or polymers having quaternary nitrogen heterocycles, commercially available examples such as Sustainion® from Dioxide Materials, PiperION® from Versogen, or Fumasep-FAA3 from Fumatec are also suitable as ionomers.

[0033] As far as the amount of hydrophilic polymer contained in the hydrophilic catalyst layer is concerned, this can vary widely. Typically, the hydrophilic catalyst layer contains hydrophilic polymer, particularly ionomers, in a smaller amount than the catalyst. Particularly good results can be achieved when the hydrophilic catalyst layer contains hydrophilic polymer, particularly ionomers, in an amount of 0.01% to 50% by mass, especially 0.01% to 40% by mass, preferably 0.01% to 30% by mass, and more preferably 0.1% to 18% by mass, based on the hydrophilic catalyst layer. In the present invention, according to a preferred embodiment, therefore the hydrophilic catalyst layer is based on the hydrophilic catalyst layer in each case. (a) a catalyst in an amount of 50% to 99.9% by mass, particularly 55% to 99.9% by mass, preferably 60% to 99.9% by mass, more preferably 70% to 99.8% by mass, and (b) A hydrophilic polymer, particularly an ionomer, in an amount of 0.01% to 50% by mass, especially 0.01% to 40% by mass, preferably 0.1% to 30% by mass, and more preferably 0.1% to 18% by mass. This shall include: All of the details, advantages, and characteristics described above apply to this embodiment as appropriate.

[0034] When an anion exchange membrane (AEM) is used to separate the anode and cathode portions according to the present invention, the hydrophilic catalyst layer may contain a hydrophilic polymer, particularly an ionomer, in an amount of 0.01% to 50% by mass, particularly 0.01% to 10% by mass, preferably 0.01% to 5% by mass, and more preferably 0.1% to 5% by mass, based on the hydrophilic catalyst layer. When an anion exchange membrane (AEM) is used to separate the anode and cathode, according to one preferred embodiment, the hydrophilic catalyst layer is based on the hydrophilic catalyst layer in each case. (a) a catalyst in an amount of 50% to 99.9% by mass, particularly 55% to 99.9% by mass, preferably 60% to 99.9% by mass, and more preferably 90% to 99.8% by mass, and (b) A hydrophilic polymer, particularly an ionomer, in an amount of 0.01% to 50% by mass, especially 0.01% to 10% by mass, preferably 0.01% to 5% by mass, and more preferably 0.1% to 5% by mass. It shall contain.

[0035] All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions according to the present invention, the hydrophilic catalyst layer may contain a hydrophilic polymer, particularly an ionomer, in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 8% to 18% by mass, based on the hydrophilic catalyst layer. When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions, according to one preferred embodiment, the hydrophilic catalyst layer is based on the hydrophilic catalyst layer in each case. (a) a catalyst in an amount of 50% to 99.8% by mass, particularly 55% to 99% by mass, preferably 60% to 97% by mass, more preferably 70% to 95% by mass, and (b) A hydrophilic polymer, particularly an ionomer, in an amount of 0.01% to 50% by mass, especially 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 8% to 18% by mass. It shall contain. All of the details, advantages, and characteristics described above apply to this embodiment as appropriate.

[0036] Similarly, the hydrophilic catalyst layer may contain a hydrophilic polymer, particularly an ionomer, in an amount of 0.01% to 50% by mass, especially 0.01% to 40% by mass, preferably 0.01% to 30% by mass, and more preferably 0.05% to 33% by mass, based on the solid content of the coating composition from which the hydrophilic catalyst layer is obtained. According to one preferred embodiment, the hydrophilic catalyst layer is thus determined based on the solid content of the coating composition from which the hydrophilic catalyst layer is obtained in each case. (a) a catalyst in an amount of 50% to 99.8% by mass, particularly 55% to 99.8% by mass, preferably 60% to 99.8% by mass, and more preferably 66% to 99.5% by mass, and (b) A hydrophilic polymer, particularly an ionomer, in an amount of 0.01% to 50% by mass, especially 0.01% to 40% by mass, preferably 0.01% to 30% by mass, and more preferably 0.05% to 33% by mass. It shall contain. All of the details, advantages, and characteristics described above apply to this embodiment as appropriate.

[0037] When an anion exchange membrane (AEM) is used to separate the anode and cathode portions according to the present invention, the hydrophilic catalyst layer may contain a hydrophilic polymer, particularly an ionomer, in an amount of 0.01% to 50% by mass, particularly 0.01% to 40% by mass, preferably 0.01% to 10% by mass, and more preferably 0.05% to 10% by mass, based on the solid content of the coating composition from which the hydrophilic catalyst layer is obtained. When an anion exchange membrane (AEM) is used to separate the anode and cathode, according to one preferred embodiment, the hydrophilic catalyst layer is determined based on the solid content of the coating composition from which the hydrophilic catalyst layer is obtained in each case. (a) a catalyst in an amount of 50% to 99.8% by mass, particularly 80% to 99.8% by mass, preferably 89% to 99.8% by mass, and more preferably 89% to 99.5% by mass, and (b) A hydrophilic polymer, particularly an ionomer, in an amount of 0.01% to 50% by mass, especially 0.01% to 40% by mass, preferably 0.01% to 10% by mass, and more preferably 0.05% to 10% by mass. It shall contain.

[0038] All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions according to the present invention, the hydrophilic catalyst layer may contain a hydrophilic polymer, particularly an ionomer, in an amount of 0.01% to 50% by mass, more particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 13% to 33% by mass, based on the solid content of the coating composition from which the hydrophilic catalyst layer is obtained. When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions, according to one preferred embodiment, the hydrophilic catalyst layer is based on the solid content of the coating composition from which the hydrophilic catalyst layer is obtained in each case. (a) a catalyst in an amount of 50% to 99.8% by mass, particularly 55% to 95% by mass, preferably 60% to 92% by mass, more preferably 66% to 86% by mass, and (b) A hydrophilic polymer, particularly an ionomer, in an amount of 0.01% to 50% by mass, especially 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 13% to 33% by mass. It shall contain. All of the details, advantages, and characteristics described above apply to this embodiment as appropriate.

[0039] According to the present invention, the hydrophilic catalyst layer may have a thickness in the range of 0.05 μm to 100 μm, particularly 0.5 μm to 100 μm, preferably 0.5 μm to 50 μm, more preferably 0.5 to 20 μm, especially preferably 0.5 to 10 μm, very especially preferably 0.5 to 5 μm, particularly preferably 0.5 to 3 μm, and especially particularly preferably 0.5 to 1 μm. Particularly favorable results are obtained when the hydrophilic catalyst layer has a pore size in the range of 0.001 to 1 μm, especially 0.001 to 0.8 μm, and preferably 0.01 to 0.5 μm. Furthermore, the hydrophilic catalyst layer contains 10 mg / cm³ 2 Less than 7 mg / cm³, especially 7 mg / cm³ 2 Less than 5 mg / cm³, preferably 5 mg / cm³ 2 Less than 3 mg / cm³, more preferably 3 mg / cm³ 2 It was found to be advantageous when the mass per unit area is less than [a certain value]. Furthermore, the hydrophilic catalyst layer contains 0.2-10 mg / cm³ 2 , especially 0.3-7 mg / cm³ 2 Preferably 0.4-5 mg / cm³ 2 More preferably 0.5 to 1 mg / cm³ 2 It may have a mass per unit area within the range of [specify range].

[0040] As far as the hydrophobic catalyst layer is concerned, it typically contains at least one hydrophobic polymer. Preferably, the hydrophobic catalyst layer exclusively contains one or more hydrophobic polymers as polymers, i.e., binders. According to the present invention, it has been found that it is advantageous when the hydrophobic polymer is selected from the group consisting of polyolefins, polyfluoroolefins, silicones, fluorinated polymers, polyaromatic polymers and polyaromatic copolymers, and mixtures thereof. Particularly favorable results are obtained in the context of the present invention when the hydrophobic polymer is selected from the group consisting of polyolefins, polyfluoroolefins, fluorinated polymers, polyaromatic polymers and polyaromatic copolymers, and mixtures thereof. Preferably, the hydrophobic polymer is selected from the group consisting of polyethylene, polypropylene, cycloolefin copolymer (COC), polystyrene (PS), polyphenylene ether (PPE), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluoroethylene-propylene (FEP), polychlorotrifluoroethylene (PCTFE), perfluoroalkoxy polymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), and copolymers and mixtures thereof, and is particularly selected from the group consisting of polyethylene, polypropylene, polyvinylidene fluoride (PVDF), fluoroethylene-propylene (FEP), and polytetrafluoroethylene (PTFE).

[0041] Using the aforementioned hydrophobic polymer, the penetration of water into the electrode, particularly into the cathode, can be effectively prevented. As far as the amount of hydrophobic polymer in the hydrophobic catalyst layer is concerned, it can vary widely, as can the case with hydrophilic polymers. However, with respect to the hydrophobic catalyst layer, it has been found that the hydrophobic catalyst layer is more advantageous than the hydrophobic polymer when it contains a larger amount of catalyst. Typically, the hydrophobic catalyst layer contains a hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass, based on the hydrophobic catalyst layer. According to one preferred embodiment, therefore the hydrophobic catalyst layer is based on the hydrophobic catalyst layer in each case, (a) a catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 99% by mass, preferably 40% to 97% by mass, more preferably 50% to 95% by mass, and (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass. It shall contain.

[0042] All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. When an anion exchange membrane (AEM) is used to separate the anode and cathode portions according to the present invention, the hydrophobic catalyst layer may contain a hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass, based on the hydrophobic catalyst layer. When an anion exchange membrane (AEM) is used to separate the anode and cathode, according to one preferred embodiment, the hydrophobic catalyst layer is based on the hydrophobic catalyst layer in each case. (a) a catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 99% by mass, preferably 40% to 97% by mass, more preferably 50% to 95% by mass, and (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass. It shall contain. All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. When a bipolar film (BPM) is used to separate the anode and cathode portions according to the present invention, the hydrophobic catalyst layer may contain a hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass, based on the hydrophobic catalyst layer.

[0043] When a bipolar exchange membrane (BPM) is used to separate the anode and cathode, according to one preferred embodiment, the hydrophobic catalyst layer is based on the hydrophobic catalyst layer in each case. (a) a catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 99% by mass, preferably 40% to 97% by mass, more preferably 50% to 95% by mass, and (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass. It shall contain. All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. Similarly, the hydrophobic catalyst layer may contain a hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.05% to 40% by mass, preferably 0.08% to 30% by mass, and more preferably 0.08% to 16% by mass, based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained.

[0044] According to one preferred embodiment, the hydrophobic catalyst layer is thus determined based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained in each case. (a) a catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 96% by mass, preferably 40% to 96% by mass, and more preferably 50% to 96% by mass, (b) A hydrophobic polymer, particularly an ionomer, in an amount of 0.01% to 50% by mass, especially 0.05% to 40% by mass, preferably 0.08% to 30% by mass, and more preferably 0.08% to 16% by mass. It shall contain. All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. When an anion exchange membrane (AEM) is used to separate the anode and cathode portions according to the present invention, the hydrophobic catalyst layer may contain a hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.05% to 40% by mass, preferably 0.08% to 30% by mass, and more preferably 0.08% to 16% by mass, based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained.

[0045] When an anion exchange membrane (AEM) is used to separate the anode and cathode, according to one preferred embodiment, the hydrophobic catalyst layer is determined based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained in each case. (a) a catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 96% by mass, preferably 40% to 96% by mass, and more preferably 50% to 96% by mass, (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.05% to 40% by mass, preferably 0.08% to 30% by mass, and more preferably 0.08% to 16% by mass. It shall contain. All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions according to the present invention, the hydrophobic catalyst layer may contain a hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.08% to 40% by mass, preferably 0.08% to 30% by mass, and more preferably 0.08% to 16% by mass, based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained.

[0046] When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions, according to one preferred embodiment, the hydrophobic catalyst layer is determined based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained in each case. (a) a catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 96% by mass, preferably 40% to 96% by mass, and more preferably 50% to 96% by mass, (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.08% to 40% by mass, preferably 0.08% to 30% by mass, and more preferably 0.08% to 16% by mass. It shall contain. All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. Furthermore, according to the present invention, the hydrophobic catalyst layer may contain a conductivity enhancer, i.e., an enhancer for electrical conductivity. Particularly good results are obtained in the context of the present invention when the conductivity enhancer is selected from carbon black, graphite, carbon nanotubes, and mixtures thereof. Conductivity enhancers can be added to the hydrophobic coating composition to improve the performance of the electrodes, in particular to ensure that the hydrophobic catalyst layer does not act as an electrical insulator. Furthermore, the porosity of the hydrophobic catalyst layer can be increased by adding a conductivity enhancer.

[0047] When the hydrophobic catalyst layer contains a conductivity enhancer, the hydrophobic catalyst layer typically contains the conductivity enhancer in an amount of 0.05% to 90% by mass, particularly 0.5% to 75% by mass, preferably 5% to 60% by mass, and more preferably 6% to 45% by mass, based on the hydrophobic catalyst layer. Similarly, the hydrophobic catalyst layer may contain a conductivity enhancer in an amount of 0.05% to 90% by mass, particularly 0.5% to 75% by mass, preferably 1% to 60% by mass, and more preferably 4% to 45% by mass, based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained. When the hydrophobic catalyst layer contains an conductivity enhancer, preferably the hydrophobic catalyst layer contains the catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 99% by mass, preferably 40% to 97% by mass, and more preferably 50% to 95% by mass, based on the hydrophobic catalyst layer. When the hydrophobic catalyst layer contains an conductivity enhancer, preferably the hydrophobic catalyst layer contains the catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 95% by mass, preferably 40% to 90% by mass, and more preferably 50% to 80% by mass, based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained. Furthermore, according to this embodiment, the hydrophobic catalyst layer may contain a hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass, based on the hydrophobic catalyst layer.

[0048] Similarly, according to this embodiment, the hydrophobic catalyst layer may contain a hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass, based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained. According to one preferred embodiment, therefore the hydrophobic catalyst layer is based on the hydrophobic catalyst layer in each case, (a) A catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 99% by mass, preferably 40% to 97% by mass, more preferably 50% to 95% by mass, (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, more preferably 1% to 10% by mass, and (c) Conductivity enhancer in an amount of 0.05% to 90% by mass, particularly 0.5% to 75% by mass, preferably 5% to 60% by mass, and more preferably 6% to 45% by mass. It shall contain.

[0049] All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. In a more preferred embodiment, the hydrophobic catalyst layer is determined based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained in each case. (a) A catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 95% by mass, preferably 40% to 90% by mass, more preferably 50% to 80% by mass, (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, more preferably 1% to 10% by mass, and (c) Conductivity enhancer in an amount of 0.05% to 90% by mass, particularly 0.5% to 75% by mass, preferably 1% to 60% by mass, and more preferably 4% to 45% by mass. It shall contain. All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. When the hydrophobic catalyst layer contains a conductivity enhancer and the anion exchange membrane (AEM) is used to separate the anode and cathode portions according to the present invention, according to this embodiment, the hydrophobic catalyst layer may contain the catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 99% by mass, preferably 40% to 97% by mass, and more preferably 50% to 95% by mass, based on the hydrophobic catalyst layer.

[0050] When the hydrophobic catalyst layer contains a conductivity enhancer and an anion exchange membrane (AEM) is used to separate the anode and cathode portions according to the present invention, the hydrophobic catalyst layer may contain the catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 95% by mass, preferably 40% to 90% by mass, and more preferably 50% to 80% by mass, based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained. When the hydrophobic catalyst layer contains a conductivity enhancer and the anion exchange membrane (AEM) is used to separate the anode and cathode portions according to the present invention, the hydrophobic catalyst layer may contain a hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass, based on the hydrophobic catalyst layer. When the hydrophobic catalyst layer contains a conductivity enhancer and an anion exchange membrane (AEM) is used to separate the anode and cathode portions according to the present invention, the hydrophobic catalyst layer may contain a hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass, based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained.

[0051] When an anion exchange membrane (AEM) is used to separate the anode and cathode, according to one preferred embodiment, the hydrophobic catalyst layer is based on the hydrophobic catalyst layer in each case. (a) A catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 99% by mass, preferably 40% to 97% by mass, more preferably 50% to 95% by mass, (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, more preferably 1% to 10% by mass, and (c) Conductivity enhancer in an amount of 0.05% to 90% by mass, particularly 0.5% to 75% by mass, preferably 5% to 60% by mass, and more preferably 6% to 45% by mass. It shall contain. All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. When an anion exchange membrane (AEM) is used to separate the anode and cathode, according to one preferred embodiment, the hydrophobic catalyst layer is determined based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained in each case. (a) A catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 95% by mass, preferably 40% to 90% by mass, more preferably 50% to 80% by mass, (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, more preferably 1% to 10% by mass, and (c) Conductivity enhancer in an amount of 0.05% to 90% by mass, particularly 0.5% to 75% by mass, preferably 1% to 60% by mass, and more preferably 4% to 45% by mass. It may also be offered that it contains [something].

[0052] All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. In contrast, when the hydrophobic catalyst layer contains a conductivity enhancer and the bipolar exchange membrane (BPM) is used to separate the anode and cathode portions according to the present invention, the hydrophobic catalyst layer may contain the catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 95% by mass, preferably 40% to 92% by mass, and more preferably 50% to 90% by mass, based on the hydrophobic catalyst layer. When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions according to the present invention, the hydrophobic catalyst layer may contain the catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 95% by mass, preferably 40% to 92% by mass, and more preferably 50% to 80% by mass, based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained. When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions according to this embodiment of the present invention, the hydrophobic catalyst layer may contain a hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass, based on the hydrophobic catalyst layer.

[0053] When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions according to this embodiment of the present invention, the hydrophobic catalyst layer may contain a hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass, based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained. When a bipolar exchange membrane (BPM) is used to separate the anode and cathode, according to one preferred embodiment, the hydrophobic catalyst layer is based on the hydrophobic catalyst layer in each case. (a) A catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 95% by mass, preferably 40% to 92% by mass, more preferably 50% to 90% by mass, (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, more preferably 1% to 10% by mass, and (c) Conductivity enhancer in an amount of 0.05% to 90% by mass, particularly 0.5% to 75% by mass, preferably 5% to 60% by mass, and more preferably 6% to 45% by mass. It shall contain.

[0054] All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. When a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions, according to one preferred embodiment, the hydrophobic catalyst layer is determined based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained in each case. (a) A catalyst in an amount of 10% to 99.8% by mass, particularly 25% to 95% by mass, preferably 40% to 92% by mass, more preferably 50% to 80% by mass, (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, more preferably 1% to 10% by mass, and (c) Conductivity enhancer in an amount of 0.05% to 90% by mass, particularly 0.5% to 75% by mass, preferably 1% to 60% by mass, and more preferably 4% to 45% by mass. It may also be offered that it contains [something]. All of the details, advantages, and characteristics described above apply to this embodiment as appropriate.

[0055] When the hydrophobic catalyst layer does not contain a conductivity enhancer and an anion exchange membrane (AEM) is used to separate the anode and cathode portions, according to one preferred embodiment, the hydrophobic catalyst layer is based on the hydrophobic catalyst layer in each case. (a) a catalyst in an amount of 50% to 99.8% by mass, particularly 55% to 99% by mass, preferably 60% to 97% by mass, more preferably 70% to 95% by mass, and (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass. It shall contain. All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. When the hydrophobic catalyst layer does not contain a conductivity enhancer and an anion exchange membrane (AEM) is used to separate the anode and cathode portions, according to one preferred embodiment, the hydrophobic catalyst layer is determined based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained in each case. (a) a catalyst in an amount of 50% to 99.8% by mass, particularly 55% to 96% by mass, preferably 60% to 96% by mass, more preferably 70% to 96% by mass, and (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.05% to 40% by mass, preferably 0.08% to 30% by mass, and more preferably 0.08% to 16% by mass. It may also be offered that it contains [something].

[0056] All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. When the hydrophobic catalyst layer does not contain a conductivity enhancer and a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions, according to one preferred embodiment, the hydrophobic catalyst layer is based on the hydrophobic catalyst layer in each case. (a) a catalyst in an amount of 50% to 99.8% by mass, particularly 55% to 99% by mass, preferably 60% to 97% by mass, more preferably 70% to 95% by mass, and (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass. It shall contain. All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. When the hydrophobic catalyst layer does not contain a conductivity enhancer and a bipolar exchange membrane (BPM) is used to separate the anode and cathode portions, according to one preferred embodiment, the hydrophobic catalyst layer is determined based on the solid content of the coating composition from which the hydrophobic catalyst layer is obtained in each case. (a) a catalyst in an amount of 50% to 99.8% by mass, particularly 55% to 96% by mass, preferably 60% to 96% by mass, more preferably 70% to 96% by mass, and (b) A hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.08% to 40% by mass, preferably 0.08% to 30% by mass, and more preferably 0.08% to 16% by mass. It may also be offered that it contains [something].

[0057] All of the details, advantages, and characteristics described above apply to this embodiment as appropriate. Furthermore, according to the present invention, the hydrophobic catalyst layer typically has a thickness in the range of 0.05 μm to 100 μm, particularly 0.5 μm to 100 μm, preferably 0.5 μm to 50 μm, more preferably 0.5 to 20 μm, especially preferably 0.5 to 10 μm, very especially preferably 0.5 to 5 μm, particularly preferably 0.5 to 4 μm, and especially especially preferably 0.5 to 3 μm. Particularly favorable results are obtained when the hydrophobic catalyst layer has a pore size of up to 5 μm, especially up to 3 μm, and preferably up to 2 μm.

[0058] Similarly, it was found that the hydrophobic catalyst layer is advantageous when it has a pore size in the range of 0.001 to 5 μm, particularly 0.001 to 3 μm, and preferably 0.01 to 2 μm. Furthermore, the hydrophobic catalyst layer contains 10 mg / cm³ 2 Less than 7 mg / cm³, especially 7 mg / cm³ 2 Less than 5 mg / cm³, preferably 5 mg / cm³ 2 Less than 3 mg / cm³, more preferably 3 mg / cm³ 2 It was found to be advantageous when the mass per unit area is less than [a certain value]. Furthermore, the hydrophobic catalyst layer contains 0.5-10 mg / cm³ 2 , especially 0.8-7 mg / cm³ 2 Preferably 1-5 mg / cm³ 2 More preferably 1-3 mg / cm³ 2 It may have a mass per unit area within the range of [specify range]. Furthermore, according to the present invention, the hydrophilic catalyst layer and the hydrophobic catalyst layer typically have an overall thickness in the range of 0.1 μm to 100 μm, particularly 0.1 μm to 100 μm, preferably 0.5 μm to 50 μm, more preferably 0.5 to 20 μm, especially preferably 0.5 to 10 μm, very especially preferably 1 to 5 μm, particularly preferably 1 to 4 μm, and especially particularly preferably 1 to 3 μm.

[0059] Furthermore, preferably, the electrodes have a range of 0.5 to 50000 cm⁻¹. 2 , especially 1-10000cm 2 Preferably 10-5000 cm 2 more preferably 100-2500cm 2 It has an area within the range of [this range]. Particularly good results are obtained when the electrode has an overall thickness in the range of 2 μm to 200 μm, especially 2 μm to 100 μm, preferably 2 μm to 50 μm, more preferably 3 to 30 μm, especially preferably 4 to 20 μm, and most especially preferably 5 to 15 μm. [Brief explanation of the drawing]

[0060] [Figure 1] This diagram shows a schematic representation of the electrode according to the present invention. [Figure 2] This figure shows an electrolytic cell containing electrodes according to the present invention. [Figure 3] This figure shows the cell voltage and current yield of constant current electrolysis as a function of the PTFE content in the catalyst ink of the cathode. [Figure 4] This figure shows the cell voltage and current yield of constant current electrolysis as a function of the ionomer content in the catalyst ink of the cathode. [Figure 5] This figure shows the cell voltage and current yield of constant current electrolysis as a function of the catalyst load in the hydrophobic catalyst layer and the hydrophilic catalyst layer. [Figure 6] This figure shows the cell voltage and current yield of constant current electrolysis for a simple hydrophobic catalyst layer, for a hydrophobic catalyst layer and a hydrophilic catalyst layer, and for a pure hydrophilic catalyst layer. [Figure 7] This figure shows the current yield of constant current electrolysis as a function of time for electrodes including a hydrophobic catalyst layer, a hydrophilic catalyst layer, and an anion exchange membrane. [Figure 8] This figure shows the cell voltage of constant current electrolysis as a function of time for electrodes including a hydrophobic catalyst layer, a hydrophilic catalyst layer, and an anion exchange membrane. [Figure 9] This figure shows the current yield of constant current electrolysis as a function of time for electrodes including a hydrophobic catalyst layer, a hydrophilic catalyst layer, and a bipolar exchange membrane. [Figure 10] This figure shows the cell voltage of constant current electrolysis as a function of time for electrodes including a hydrophobic catalyst layer, a hydrophilic catalyst layer, and a bipolar exchange membrane. [Figure 11] This figure shows the current yield of constant current electrolysis as a function of time for electrodes including a hydrophobic catalyst layer, a hydrophilic catalyst layer, and a bipolar exchange membrane. [Figure 12] This figure shows the cell voltage of constant current electrolysis as a function of time for electrodes including a hydrophobic catalyst layer, a hydrophilic catalyst layer, and a bipolar exchange membrane. [Modes for carrying out the invention]

[0061] A further subject of the present invention, according to a second aspect of the present invention, is the use of the aforementioned electrodes in electrolysis. The gas diffusion electrode according to the present invention is used, in particular, as a cathode and / or anode in electrolysis, preferably as a cathode. Regarding the application described, the electrodes are typically, in particular, hydrogenated, CO2, CO, N 2、 It functions as a cathode for the reduction of O2 and organic molecules. However, for oxidation reactions, particularly for the oxidation of H2, N2, CO2, and organic compounds, it is also possible to use a gas diffusion electrode as an anode. For further details relating to this embodiment of the present invention, one can refer to the above description relating to the electrode according to the present invention, which may be applied as appropriate with respect to the use of the electrode according to the present invention. A further subject of the present invention, according to a third aspect of the present invention, is again the use of the aforementioned electrode as a cathode in the electrochemical reduction of carbon dioxide. The electrode according to the present invention is particularly well-suited for the electrochemical reduction of carbon dioxide, thereby yielding valuable chemical raw materials, in particular carbon monoxide, alcohols, aldehydes, ketones, and carboxylic acids.

[0062] For further details relating to this aspect of the present invention, one can refer to the above-described description of the present invention, which may be applicable as appropriate to the use of the present invention. A further subject of the present invention, according to a fourth aspect of the present invention, is a method for manufacturing the above-mentioned electrode, (i) In the first method step, a first coating composition for producing a first hydrophilic or hydrophobic, preferably hydrophobic, catalyst layer is applied to a porous carrier material or an ion-conducting film. (ii) In a second method step following the first method step (i), a second coating composition different from the first coating composition is applied to the first catalyst layer, for producing a second hydrophilic or hydrophobic, preferably hydrophilic, catalyst layer. This is a method for manufacturing the electrodes described above. According to the present invention, the coating composition is preferably applied to a porous carrier material, thus obtaining a coated substrate (catalyst-coated substrate). However, the coating composition can also be applied to the ion-conducting membrane of an electrolytic cell, particularly anion exchange membrane (AEM), proton exchange membrane (PEM), or bipolar exchange membrane (BPM) (catalyst-coated membrane), and this structure, including the catalyst layer, can also be applied to a porous carrier material. A combination of the two methods is also possible.

[0063] The porous carrier material corresponds to the porous layer described above. According to the present invention, in particular, when a hydrophilic catalyst layer is first applied to a porous carrier material, the hydrophobic coating is applied in a second step, or when a hydrophobic coating composition is applied to a porous carrier material in a first method step, the hydrophilic coating composition is applied in a second method step. The coating composition is preferably dried or cured in order to obtain the respective catalyst layers. The coating composition may be applied by dry or wet coating methods, such as spraying, using a doctor blade, drop application, or printing, or by a combination of these methods. Hydrophilic coating compositions typically contain hydrophilic polymers, particularly the aforementioned hydrophilic polymers. Hydrophobic coating compositions typically contain hydrophobic polymers, particularly the aforementioned hydrophobic polymers. Hydrophilic coating compositions and hydrophobic coating compositions can contain hydrophilic polymers or hydrophobic polymers in various forms, and typically, hydrophilic coating compositions and hydrophobic coating compositions contain hydrophilic polymers or hydrophobic polymers in the form of solid particles, for example as a dispersion, or also as a thin film, preferably in the form of solid particles.

[0064] Typically, in the context of the present invention, the hydrophilic and / or hydrophobic first and / or second coating compositions exist in the form of a dispersion. Preferably, both the hydrophilic and / or hydrophobic first and / or second coating compositions exist in the form of a dispersion. If the first or second coating composition exists in the form of a dispersion, the dispersion medium is usually removed during or after the application of the first coating composition. Removal of the dispersion medium is particularly preferably performed before carrying out step ii of the second method. In the context of the present invention, therefore preferably, first the first catalyst layer is obtained from the first coating composition, and then the second coating composition is applied to produce the second catalyst layer. Similarly, in the context of the present invention, the dispersion medium is typically removed during or after the application of the second coating composition. Therefore, the second coating composition is preferably dried or cured. According to a preferred embodiment of the present invention, the carrier material is heated during or after the application of the first or second coating composition. In this way, the dispersion medium can be rapidly removed, and any possible crosslinking reactions may occur immediately. Polymer particles can also be directly applied and adhere to the heated carrier material. In the context of the present invention, it is particularly preferred that the carrier material is heated during the application of the first coating composition and during the application of the second coating composition. As a result of heating during the application of the coating composition, the dispersion medium rapidly volatilizes, and the thickness of the catalyst layer can be selectively set by repeated applications as needed.

[0065] As far as the temperature at which the carrier material is heated is concerned, it was found that the carrier material is preferable when heated to a temperature in the range of 25-140°C, particularly 40-120°C, especially 60-120°C, and preferably 70-100°C. According to the present invention, after the application of the first or second coating composition, particularly after the application of the hydrophobic coating composition, the electrode may be subjected to a thermal post-treatment step or a mechanical post-treatment step. In particular, the electrode may be subjected to a sintering step and / or a compression step. In the context of the present invention, after applying the first or second coating composition and, if necessary, removing the dispersion medium, the electrode may be subjected to a sintering step. Preferably, after applying the hydrophobic coating composition and removing the dispersion medium, the electrode is subjected to a sintering step. In the sintering step, the adhesion of the coating composition to the carrier layer or further catalyst layer is improved, and the homogeneity of the catalyst layer is promoted. When the sintering step is performed, the carrier material is typically heated to a temperature in the range of 150-400°C, particularly 150-350°C, preferably 150-300°C, and preferably 200-300°C.

[0066] The time required for the sintering step can vary widely. However, typically, sintering is carried out over a period of 1 to 100 minutes, particularly 5 to 30 minutes, preferably 5 to 15 minutes, and more preferably 10 to 15 minutes. As previously mentioned, hydrophobic coating compositions typically contain hydrophobic polymers. Particularly good results are obtained in the context of the present invention when the hydrophobic coating composition contains a hydrophobic polymer in an amount of 0.05% to 5% by mass, particularly 0.1% to 3% by mass, preferably 0.2% to 1% by mass, and more preferably 0.3% to 0.5% by mass, based on the hydrophobic coating composition. Similarly, in the context of the present invention, the hydrophobic coating composition may contain a catalyst in an amount of 0.1% to 10% by mass, particularly 0.5% to 5% by mass, preferably 1% to 3% by mass, and more preferably 1% to 2% by mass, based on the hydrophobic coating composition. As already mentioned above, the hydrophobic coating composition includes a dispersion medium. Typically, the hydrophobic coating composition contains the dispersion medium in an amount of 85% to 99.9% by mass, particularly 92% to 99.4% by mass, preferably 96% to 98.8% by mass, and more preferably 97% to 98.7% by mass, based on the hydrophobic coating composition.

[0067] Particularly favorable results are obtained in the context of the present invention when the dispersion medium is selected from water, alcohol, N,N-dimethylformamide, acetone, ethyl acetate, acetonitrile, and mixtures thereof. Preferably, the dispersion medium is selected from water, alcohol, and mixtures thereof, and more preferably from mixtures thereof. If the dispersion medium is selected from water, alcohol, and mixtures thereof, it has been found that it is advantageous if the dispersion medium is selected from water, methanol, ethanol, isopropanol, and mixtures thereof, preferably from mixtures thereof. Particularly good results are obtained in the context of the present invention when the dispersion medium is selected from water, isopropanol, and mixtures thereof, preferably from mixtures thereof. Furthermore, the hydrophobic coating composition may contain additives. When the hydrophobic coating composition contains additives, the additives are usually selected from the group consisting of pore-forming agents, stabilizers, rheological additives, surfactants, or mixtures thereof. When the hydrophobic coating composition contains additives, the coating composition typically contains the additives in an amount of 0.01% to 2% by mass, particularly 0.05% to 1% by mass, preferably 0.1% to 0.5% by mass, and more preferably 0.1% to 0.3% by mass, based on the hydrophobic coating composition.

[0068] According to one preferred embodiment of the present invention, the hydrophobic coating composition includes a conductivity enhancer. As already mentioned above in relation to electrodes according to the present invention, it has been found to be advantageous when the conductivity enhancer is selected from the group consisting of carbon black, graphite, carbon nanotubes, and mixtures thereof. When a hydrophobic coating composition contains a conductivity enhancer, generally, the hydrophobic coating composition contains the conductivity enhancer in an amount of 0.01% to 2% by mass, particularly 0.05% to 1% by mass, preferably 0.1% to 0.5% by mass, and more preferably 0.1% to 0.3% by mass, based on the hydrophobic coating composition. As far as hydrophilic coating compositions are concerned, they typically contain hydrophilic polymers. In the context of the present invention, particularly good results are obtained when the hydrophilic coating composition contains a hydrophilic polymer in an amount of 0.01% to 2% by mass, particularly 0.05% to 1.5% by mass, preferably 0.1% to 1% by mass, and more preferably 0.3% to 0.5% by mass, based on the hydrophilic coating composition.

[0069] Similarly, in the context of the present invention, the hydrophilic coating composition may contain a catalyst in an amount of 0.1% to 10% by mass, particularly 0.5% to 5% by mass, preferably 1% to 3% by mass, and more preferably 1% to 2% by mass, based on the coating composition. Similarly, as already mentioned above, hydrophilic coating compositions typically contain a dispersion medium. If a hydrophilic coating composition contains a dispersion medium, it has been found that the hydrophilic coating composition is advantageous when it contains the dispersion medium in an amount of 85% to 99.9% by mass, particularly 92% to 99.4% by mass, preferably 96% to 98.8% by mass, and more preferably 97% to 98.7% by mass, based on the coating composition. Similarly, good results are obtained when the dispersion medium is selected from water, alcohol, N,N-dimethylformamide, acetone, ethyl acetate, acetonitrile, and mixtures thereof, preferably from mixtures thereof. Particularly good results are obtained in the context of the present invention when the dispersion medium is selected from water, alcohol, and mixtures thereof, preferably from mixtures thereof.

[0070] If the dispersion medium is selected from water, alcohol, and mixtures thereof, it has been found that it is preferable if the dispersion medium is selected from water, methanol, ethanol, isopropanol, and mixtures thereof, preferably from mixtures thereof. The best results are obtained when the dispersion medium is selected from water, isopropanol, and mixtures thereof, preferably from mixtures thereof. With respect to hydrophilic coating compositions, the coating composition may also contain additives. If the hydrophilic coating composition contains additives, the additives may be selected from pore-forming agents, stabilizers, rheological additives, surfactants, or mixtures thereof. Similarly, in the context of the present invention, a hydrophilic coating composition may contain an additive in an amount of 0.01% to 2% by mass, particularly 0.05% to 1% by mass, preferably 0.1% to 0.5% by mass, and more preferably 0.1% to 0.3% by mass, based on the hydrophilic coating composition. For further details relating to this aspect of the present invention, one can refer to the above-described description of the present invention, which may be applied as appropriate to methods according to the present invention. Again, according to a fifth aspect of the present invention, a further subject of the present invention is an electrolytic cell, particularly for the electrochemical reduction of carbon dioxide, comprising at least one of the above-described electrodes.

[0071] Generally, the electrolytic cell according to the present invention includes at least two types of chambers, namely an anode section and a cathode section. The electrode according to the present invention, particularly the gas diffusion electrode, typically forms an interface between a liquid and / or gaseous substrate and a liquid or solid electrolyte. In this case, the diffusion layer, which consists of a porous carrier layer and a catalyst layer, is preferably at least partially permeated with the liquid substrate. Thus, the three-phase boundary where the electrochemical process occurs is formed by the substrate, electrolyte, and catalyst. In this case, the gas diffusion electrode according to the present invention can form the cathode and / or anode, preferably the cathode, of the electrolytic cell. In the context of the present invention, preferably, the electrode according to the present invention forms the cathode in the electrolytic cell according to the present invention. The electrode according to the present invention is used, for example, as a cathode for the reduction of CO2, CO, N2, O2, and organic molecules in a hydrogenation scenario. However, it can also be used as an anode for oxidation reactions, such as the oxidation of H2, N2, and organic compounds. In addition to the electrodes according to the present invention, the electrolytic cell also includes at least one or more electrodes, particularly an anode. A preferred oxidation or reduction process can occur at an additional electrode, which may also be an electrode according to the present invention. In the case of electrochemical reduction of CO2, water is oxidized to oxygen, particularly at the anode.

[0072] The second electrode, particularly the anode, can also be made of any suitable material, in particular porous material such as metal felt, sintered metal particles, metal mesh, and mixtures thereof. Furthermore, the second electrode is usually also coated with a catalyst. The catalyst is often a metal or metal oxide, such as iridium oxide. Between the anode and cathode of the electrolyte cell according to the present invention, there is typically a diaphragm or semipermeable membrane, particularly an anion exchange membrane (AEM), a proton exchange membrane (PEM), or a bipolar exchange membrane (BPM). The bipolar exchange membrane typically consists of sequentially stacked PEM and AEM membranes and can be incorporated as "forward bias" or "reverse bias." To increase conversion efficiency, in addition to scaling the electrode area, multiple separate cells can be stacked to form a bipolar stack due to their conductivity perpendicular to the electrode plate. According to one preferred embodiment of the present invention, the electrolytic cell is a so-called zero-gap electrolytic cell. For further details regarding the electrolytic cell according to the present invention, one can refer to the above description relating to other embodiments of the present invention, which may be applied as appropriate to the electrolytic cell according to the present invention.

[0073] The subject matter of the present invention is described below by non-limiting examples with respect to the description in the drawings and exemplary embodiments. Figure 1 shows an electrode 1 according to the present invention, which includes a hydrophobic catalyst layer (CL) 2 and a hydrophilic catalyst layer (CL) 3. Catalyst layer 2 and catalyst layer 3 are both porous and have pore sizes in the range of 0.001 to 5 μm, particularly 0.001 to 3 μm, and preferably 0.01 to 2 μm. The hydrophobic catalyst layer 2 preferably contains at least one hydrophobic polymer in an amount of 0.01% to 50% by mass, particularly 0.1% to 40% by mass, preferably 1% to 30% by mass, and more preferably 1% to 10% by mass, based on the hydrophobic catalyst layer. The hydrophobic polymer is preferably selected from the group consisting of polyethylene, polypropylene, cycloolefin copolymer (COC), polystyrene (PS), polyphenylene ether (PPE), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluoroethylene-propylene (FEP), polychlorotrifluoroethylene (PCTFE), perfluoroalkoxy polymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), and their copolymers and mixtures thereof, and is particularly selected from the group consisting of polyethylene, polypropylene, polyvinylidene fluoride (PVDF), fluoroethylene-propylene (FEP), and polytetrafluoroethylene (PTFE).

[0074] Furthermore, the hydrophobic catalyst layer 2 may contain a conductivity enhancer selected from carbon black, graphite, carbon nanotubes, and mixtures thereof. The hydrophilic catalyst layer 3 preferably comprises at least one hydrophilic polymer, particularly an ionomer. According to the present invention, it is particularly preferable that the hydrophilic polymer is selected from cation exchange polymers and anion exchange polymers, and particularly preferable that it is selected from anion exchange polymers. Particularly good results are obtained in the context of the present invention when the hydrophilic polymer is selected from the group consisting of polymers having a quaternary ammonium group, polymers having a quaternary nitrogen heterocycle, polymers having a phosphonium group, polymers having a sulfonium group, polymers having an organometallic complex as a cationic functionalization, and mixtures thereof. Polymers having a quaternary ammonium group, polymers having a quaternary nitrogen heterocycle, and mixtures thereof are particularly preferred. In the context of the present invention, it is particularly preferable that the hydrophilic polymer, particularly an ionomer, is selected from the group consisting of ionomers containing a piperidinium group, ionomers containing an imidazolium group, ionomers containing a benzimidazolium group, and mixtures thereof. Typically, the hydrophilic catalyst layer 3 contains a hydrophilic polymer in an amount of 0.01% to 50% by mass, particularly 0.01% to 40% by mass, preferably 0.01% to 30% by mass, and more preferably 0.1% to 18% by mass, based on the hydrophilic catalyst layer.

[0075] The hydrophilic catalyst layer 3 and the hydrophobic catalyst layer 2 typically have a thickness in the range of 0.05 μm to 100 μm, particularly 0.5 μm to 100 μm, preferably 0.5 μm to 50 μm, and more preferably 0.5 to 20 μm. Furthermore, according to the present invention, both the hydrophobic catalyst layer 2 and the hydrophilic catalyst layer 3 contain at least one catalyst. The catalysts in the hydrophobic catalyst layer 2 and the hydrophilic catalyst layer 3 may be the same or different. However, typically the same catalyst is used in both the hydrophobic catalyst layer 2 and the hydrophilic catalyst layer 3. The catalyst is distributed as uniformly as possible within each layer. The catalyst is typically selected from the group consisting of metal particles, especially metal nanoparticles, monatomic catalysts (single-atom catalysts), metal carbides, metal oxides, metal chalcogenides, molecular catalysts, and mixtures thereof.

[0076] Particularly favorable results are obtained when the catalyst is selected from the group consisting of metal particles, particularly metal nanoparticles, of silver, gold, zinc, palladium, gallium, cadmium, indium, mercury, thallium, lead, bismuth, copper, and mixtures and alloys thereof. In the context of the present invention, it is particularly preferred when the catalyst is selected from the group consisting of metal particles, particularly metal nanoparticles, of silver, gold, copper, and mixtures and alloys thereof. Typically, the hydrophobic catalyst layer 2 and the hydrophilic catalyst layer 3 contain a catalyst in an amount of 50% to 99.9% by mass, particularly 55% to 99.9% by mass, preferably 60% to 99.8% by mass, and more preferably 70% to 99.8% by mass, based on the hydrophobic catalyst layer 2 or the hydrophilic catalyst layer 3. More preferably, the hydrophobic catalyst layer 2 and the hydrophilic catalyst layer 3 are applied to a porous layer, particularly the gas diffusion layer 4. The porous layer, particularly the gas diffusion layer 4, is in particular a conventional gas diffusion layer (GDL). The material of the porous layer, particularly the gas diffusion layer 4, is generally selected from the group consisting of carbon fiber fabrics, carbon fiber paper, graphite fabrics, metal felt, metal mesh, sintered metal, and mixtures thereof. Particularly good results are obtained when the material of the porous layer, particularly the gas diffusion layer 4, is selected from the group consisting of carbon fiber fabrics, carbon fiber paper, and mixtures thereof. Particularly preferably, the porous layer, particularly the gas diffusion layer 4, is a carbon fiber fabric. Preferably, the porous layer, particularly the gas diffusion layer 4, has a thickness in the range of 50 to 1000 μm, particularly 50 μm to 800 μm, preferably 100 μm to 600 μm, and more preferably 150 μm to 500 μm.

[0077] According to one preferred embodiment, the electrode according to the present invention has the following structure: a hydrophobic catalyst layer 2 is applied to a gas diffusion layer 4, and a hydrophilic catalyst layer 3 is applied to the hydrophobic catalyst layer 2. The electrode 1 according to the present invention is particularly suitable for use as a cathode in an electrolytic cell, especially in a zero-gap electrolytic cell, for the reduction of carbon dioxide. Figure 2 shows an electrolytic cell 5 according to the present invention, in particular an electrolytic cell in the form of a zero-gap electrolytic cell. The electrode structure is composed of an electrode 1 according to the present invention, which includes a gas diffusion layer 4, a hydrophobic catalyst layer 2, and a hydrophilic catalyst layer 3. In this case, the electrode 1 according to the present invention preferably forms a cathode. The anode 6 of the electrolytic cell 5 is preferably composed of titanium felt and an iridium oxide catalyst applied thereto. The electrodes are separated by a semipermeable membrane 7, particularly an anion exchange membrane, a proton exchange membrane, or a bipolar exchange membrane, preferably a proton exchange membrane. On the cathode side, carbon dioxide is introduced, particularly with an inert carrier gas such as nitrogen or argon, moistened with vapor, and diffuses through the porous carrier layer to catalyst layer 2 and catalyst layer 3. On the anode side, water passes through the anode and reaches membrane 7 through the porous anode 6. At electrode 1, which functions as a cathode, CO2 is preferably reduced to organic substances, particularly carbon monoxide, alcohols, aldehydes, ketones, and carboxylic acids. The corresponding reaction products are again flushed out of the cathode section along with the carrier gas flow. On the anode side, water is oxidized to oxygen, while protons move through the semipermeable membrane 7 and react with the reduced CO2 to form organic residues. The subject matter of the present invention is described below non-limitingly with respect to exemplary embodiments.

[0078] Exemplary Embodiments 1. Reference Example A: GDE containing hydrophobic polymer-containing CL A GDE containing a single layer of hydrophobic polymer-containing catalyst (CL) was prepared as a reference example. For this purpose, a carbon fiber fabric (W1S1010, fuelcellstore) containing a microporous layer was coated with a polymer-containing catalyst ink. 1.1 Manufacturing of catalytic ink: The catalyst (AgNPs, Alfa Aesar) is dispersed in a 3:1 isopropanol / water mixture, and therefore the catalyst concentration in the ink is 16.67 mg / ml. -1 This corresponds to [the above]. In addition, Triton X-100 is added as an ink stabilizer and pore-forming agent. Before adding the PTFE dispersion, the ink is homogenized at 13400 rpm for 90 seconds (Ultra-Turrax T18D, IKA). Finally, the catalyst ink is treated with ultrasound for 15 minutes for further homogenization.

[0079] [Table 1] 1.2. Manufacturing of GDE: The manufactured catalyst ink was processed using an airbrush gun (Eclipse, Anest Iwata) with AgNPs 2.5 mg per cm². -2 The catalyst was sprayed onto the carbon fiber fabric until the required amount was reached. To ensure rapid evaporation of the solvent, the carbon fiber fabric was heated to 90°C during the spraying operation. The GDE was then sintered in air at 300°C for 15 minutes. Based on the amount of catalyst measured, GDE with PTFE content in the catalyst ink of 1% by mass, 3.75% by mass, 7.5% by mass, 15% by mass, and 30% by mass was produced.

[0080] 1.3 CO2 electrolysis: CO2 electrolysis requires an active cell area of ​​2 cm². 2 This was performed in a zero-gap electrolytic cell having the following properties: IrO2 (Alfa Aesar) 1 mg cm -2 A porous titanium felt (2-GDL40, Bekaert) with a catalyst packing amount was used as the anode. The anode portion contained 16.6 ml of 0.1 M KHCO3. -1 It was administered continuously. AgNPs (Alfa Aesar) 2.5 mg cm -2GDE produced using [method / technology] was used in the cathode. Five different GDEs containing hydrophobic polymers, including CL, were investigated. The PTFE content in each catalyst ink was 1% by mass, 3.75% by mass, 7.5% by mass, 15% by mass, and 30% by mass. During electrolysis, the cathode contained 50 ml of CO2. -1 and Ar5ml -1 The flow was then adjusted. Argon served as the internal standard. Before entering the cathode, the gas supply flow was brought to a relative humidity of 79% (dew point: 55°C) using a saturated steam humidifier. Immediately before the start of electrolysis, the 40 μm thick Piperion film to be used was activated in 1 M KOH for 30 minutes, and then washed with ultrapure water (18.2 MΩ cm, MilliQ). All electrocatalytic studies performed were conducted at 300 mA cm. -2 The electrolysis was performed at a constant current for 3 hours. The sample of the gaseous product stream obtained at the cathode was analyzed every 20 minutes by GC-MS.

[0081] Current yield (FE) for the target product CO CO ) and the measured cell voltage (U セル Figure 3 shows the polymer-containing CL (PTFE 1% by mass, 3.75% by mass, 7.5% by mass, 15% by mass, and 30% by mass) for all manufactured GDEs. Figure 3 shows the PTFE content in the cathode catalyst ink as a function of 300 mA cm⁻¹. -2 In constant current electrolysis, U セル (A) and FE CO (B) is shown. The experimental time (2 hours to 3 hours) after reaching a stable state is shown for each case. Industrially reasonable current density: 300mA cm² -2 Regarding the hydrophobic polymer-containing CL investigated by U セル FE at 3.5~5.5V CO It was possible to achieve 28-44%. The cell voltage can be seen to increase with the proportion of PTFE in CL. The highest FE... COThis was achieved in CL, and in its catalyst ink, a PTFE content of 7.5% by mass was used based on the amount of catalyst employed. With a PTFE content of 30% by mass, the SPE film dried reproducibly, resulting in cracking.

[0082] 2. Reference Example B: GDE containing hydrophilic ionomer-containing CL A GDE containing a hydrophilic ionomer-containing CL was prepared as a second reference example. For this purpose, a carbon fiber fabric (W1S1010, fuelcellstore) containing a microporous layer was coated with an ionomer-containing catalyst ink. 2.1 Manufacturing of catalytic ink: The catalyst (AgNPs, Alfa Aesar) is dispersed in a 3:1 isopropanol / water mixture, and therefore the catalyst concentration in the ink is 16.67 mg / ml. -1 This corresponds to the catalyst ink being homogenized at 13400 rpm for 90 seconds (Ultra-Turrax T18D, IKA). Finally, the catalyst ink is treated with ultrasound for 15 minutes for further homogenization. [Table 2]

[0083] 2.2 Manufacturing of GDE: The catalyst ink was applied using an airbrush gun (Eclipse, Anest Iwata) with AgNPs 2.5 mg cm². -2 The catalyst was sprayed onto the carbon fiber fabric until the required amount of catalyst was reached. To ensure rapid evaporation of the solvent, the carbon fiber fabric was heated to 90°C during the spraying operation. Based on the amount of catalyst measured, GDEs with piperion content in the catalyst ink of 1% by mass, 3.75% by mass, 7.5% by mass, 15% by mass, and 30% by mass were produced.

[0084] 2.3 CO2 electrolysis: CO2 electrolysis requires an active cell area of ​​2 cm². 2 This was performed in a zero-gap electrolytic cell having the following properties: IrO2 (Alfa Aesar) 1 mg cm -2A porous titanium felt (2-GDL40, Bekaert) with a catalyst packing amount was used as the anode. The anode portion contained 16.6 ml of 0.1 M KHCO3. -1 It was continuously administered. AgNPs (Alfa Aesar) filling amount: 2.5 mg cm -2 GDE containing [specific component] was used as the cathode. Five different GDEs, including ionomer-containing CL, were investigated. The Piperion content in each catalyst ink was 1% by mass, 3.75% by mass, 7.5% by mass, 15% by mass, and 30% by mass. During electrolysis, the cathode contained 50 ml of CO2. -1 and Ar5ml -1 The gas was flowed through. Argon served as the internal standard. Before entering the cathode, the gas supply flow was brought to a relative humidity of 79% (dew point: 55°C) using a saturated steam humidifier. Immediately before the start of electrolysis, both the 40 μm thick Piperion film and GDE were activated in 1 M KOH for 30 minutes, and then washed with ultrapure water (18.2 MΩ cm). All electrocatalyst studies performed were conducted at 300 mA cm. -2 The electrolysis was performed at a constant current for 3 hours. The sample of the gaseous product stream obtained at the cathode was analyzed every 20 minutes by GC-MS.

[0085] Target product CO(FE CO Current yield and measured cell voltage (U) for ) セル Figure 4 shows the results for all manufactured GDEs containing polymer-containing CL (Piperion 1-30% by mass). Figure 4 shows the function of piperion content in the cathode catalyst ink at 300 mA cm⁻¹. -2 The cell voltage (A) and current yield (B) for the product CO during constant current electrolysis are shown. The experimental time (2 to 3 hours) after reaching a stable state is shown for each case. Industrially reasonable current density: 300mA cm² -2 Regarding the hydrophilic ionomer-containing CL investigated by U セル FE at 3.2~3.4V CO It was possible to achieve FE between 12% and 49%.CO The decrease and U セル It can be seen that the increase occurs as the Piperion content increases. The highest FE CO 49% and the lowest U セル However, this can be achieved with 1% by mass of Piperion.

[0086] 3. Exemplary Embodiment 1 of the present invention: (Multiple catalyst layers) As an exemplary embodiment of the invention described herein relating to a multiple catalyst layer (CL) for CO2 reduction, a commercially available carbon fiber fabric (W1S1010, fuelcellstore) containing a microporous layer is coated in a first step with a hydrophobic polymer-containing catalyst layer and in a second step with a hydrophilic ionomer-containing catalyst layer. 3.1 Manufacturing of polymer-containing catalyst inks: The catalyst (AgNPs, Alfa Aesar) is dispersed in a 3:1 isopropanol / water mixture, and therefore the catalyst concentration in the ink is 16.67 mg / ml. -1 This corresponds to [the above]. In addition, Triton X-100 is added as an ink stabilizer and pore-forming agent. Before adding the PTFE dispersion, the ink is homogenized at 13400 rpm for 90 seconds (Ultra-Turrax T18D, IKA). Finally, the catalyst ink is treated with an ultrasonic bath for 15 minutes for further homogenization. Based on the amount of catalyst weighed, the PTFE content in the catalyst ink was 7.5% by mass. 3.2 Manufacturing of ionomer-containing catalyst inks: The catalyst (AgNPs, Alfa Aesar) is dispersed in a 3:1 isopropanol / water mixture, and therefore the catalyst concentration in the ink is 16.67 mg / ml. -1 This corresponds to the following. The catalyst ink is homogenized at 13400 rpm for 90 seconds (Ultra-Turrax T18D, IKA). Finally, the catalyst ink is treated with ultrasound for 15 minutes for further homogenization. Based on the metered catalyst, the Piperion content in the catalyst ink was 1% by mass.

[0087] 3.3 Manufacturing of GDE: To manufacture the catalyst layer, in the first step, polymer-containing catalyst ink is sprayed onto a commercially available carbon fiber fabric using an airbrush gun (Eclipse, Anest Iwata) until the desired catalyst load is reached. Five types of GDE with varying catalyst loads of polymer-containing CL or ionomer-containing CL are used to achieve a total AgNP load of 2.5 mg cm² in the catalyst layer. -2 It was manufactured at [location / factory name]. The corresponding compositions of CL are shown in Table 5. The PTFE content in the polymer-containing catalyst ink was 7.5% by mass based on the amount of catalyst weighed, and the Piperion content in the ionomer-containing catalyst ink was 1% by mass based on the amount of catalyst weighed. The polymer-containing CL is applied directly to GDL, and the ionomer-containing CL is applied to polymer-containing CL. [Table 3]

[0088] 3.4 Manufacturing of GDE To ensure rapid evaporation of the solvent, the carbon fiber fabric was heated to 90°C during the spraying operation. The resulting polymer-containing catalyst ink was then sprayed onto the microporous side of the carbon fiber fabric using an airbrush gun (Eclipse, Anest Iwata) until the desired catalyst load was reached (see Table 3). The resulting GDE was then sintered in air at 300°C for 15 minutes. In the second step, the resulting ionomer-containing catalyst ink was used to achieve the target catalyst load of 2.5 mg cm³ for the entire multilayer CL. -2 It is sprayed onto PTFE-CL, which has been pre-applied to GDL heated to 90°C and contains polymer-containing CL, until it reaches a certain point. 3.5 CO2 electrolysis CO2 electrolysis requires an active cell area of ​​2 cm². 2 This was performed in a zero-gap electrolytic cell having the following properties: IrO2 (Alfa Aesar) 1 mg cm -2 A porous titanium felt (2-GDL40, Bekaert) with a catalyst packing amount was used as the anode. The anode portion contained 16.6 ml of 0.1 M KHCO3. -1and flowed continuously. The AgNPs (Alfa Aesar) filling amount was 2.5 mg cm -2 The GDEs fabricated using -2 were used at the cathode. Five different GDEs containing multilayer CLs were investigated.

[0089] During electrolysis, the cathode section was flowed with 500 ml min of CO2 -1 and 5 ml min of Ar -1 The argon functioned as an internal standard. Before entering the cathode section, the gas feed stream was brought to a relative humidity of 79% (dew point: 55 °C) using a saturated vapor humidifier. Immediately before the start of electrolysis, both the 40-μm thick Piperion membrane and the GDE were activated in 1 M KOH for 30 min and then rinsed with ultrapure water (18.2 MΩ cm). All the electrode catalyst studies conducted were carried out at a constant current of 300 mA cm -2 over an electrolysis time of 3 h. Samples of the resulting gaseous product stream from the cathode were analyzed every 20 min by GC-MS. The current yield (FE CO ) for the target product CO and the measured cell voltage (U セル ) are shown in Fig. 5 for all the fabricated GDEs containing multilayer CLs.

[0090] Fig. 5 shows the cell voltage (A) and the current yield for the product CO (B) for constant current electrolysis at 300 mA cm -2 as a function of the catalyst filling amount in the Piperion-based CL and the PTFE-based CL that result in the multilayer structure of the present invention. The PTFE content in the polymer-based catalyst ink used to fabricate the polymer-based CL was 7.5 wt% based on the weighed catalyst. The Piperion content in the ionomer-based catalyst ink used to fabricate the ionomer-based CL was 1 wt% based on the weighed catalyst. The experimental time (2 h to 3 h) after reaching the steady state is shown in each case. In FIG. 5, for all manufactured multilayer structures of the present invention (Examples 1-A to 1-E, middle column), higher current efficiency FE CO and lower cell voltage U セル are achieved compared to those for the best polymer-containing CL (Reference Example A-3, left column) and the best ionomer-containing CL (Reference Example B-1, right column).

[0091] FIG. 6 shows the cell voltage (A) and current efficiency (B) for the product CO in constant-current electrolysis at 300 mA cm -2 for the polymer-containing CL (Reference A), the ionomer-containing CL (Reference B), and the multilayer structure of the present invention (Example 1-1). The polymer-containing CL (Reference A) has a catalyst loading of 2.5 mg cm -2 and is produced by spraying a catalyst ink containing 7.5 mass% PTFE based on the catalyst AgNPs. The ionomer-containing CL (Reference B) has a catalyst loading of 2.5 mg cm -2 and is produced by spraying a catalyst ink containing 1 mass% Piperion based on the catalyst AgNPs. The structure according to the present invention (Example 1-1) is composed of a first polymer-containing CL (7.5 mass% PTFE) having an AgNPs loading of 2.0 mg cm -2 and a second ionomer-containing CL (Piperion) having an AgNPs loading of 0.5 mg cm -2 , so that the total AgNPs loading corresponds to 2.5 mg cm -2 . The experimental time (2 hours to 3 hours) after reaching the steady state is shown for each case.

[0092] 4. Exemplary Embodiment 2 according to the present invention (Multilayer structure containing carbon in hydrophobic polymer-containing CL) As an exemplary embodiment of the invention described herein relating to a catalyst layer structure containing carbon in a hydrophobic polymer-containing CL for CO2 reduction, a commercially available carbon fiber fabric (W1S1010, fuelcellstore) containing a microporous layer is coated in a polymer-containing and carbon black-containing CL in a first step, and then coated in an ionomer-containing CL in a second step. 4.1 Manufacturing of polymer-containing catalyst inks: The catalyst (AgNPs, Alfa Aesar) is dispersed in a 3:1 isopropanol / water mixture, and therefore the catalyst concentration in the ink is 16.67 mg / ml. -1 This corresponds to [the specified amount]. Subsequently, based on the measured amount of catalyst, 20% by mass of carbon (Ensaco 250G) was added to the catalyst ink and Triton X-100, which is an ink stabilizer and pore-forming agent. Before adding the PTFE dispersion, the ink was homogenized at 13400 rpm for 90 seconds (Ultra-Turrax T18D, IKA). Finally, the catalyst ink was treated with ultrasound for 15 minutes for further homogenization. Based on the catalyst, the PTFE content in the catalyst ink was 7.5% by mass.

[0093] [Table 4]

[0094] 4.2 Manufacturing of ionomer-containing catalyst inks: The catalyst (AgNPs, Alfa Aesar) is dispersed in a 3:1 isopropanol / water mixture, and therefore the catalyst concentration in the ink is 16.67 mg / ml. -1 This corresponds to the following. The catalyst ink was homogenized at 13400 rpm for 90 seconds (Ultra-Turrax T18D, IKA). Finally, the catalyst ink was treated with ultrasound for 15 minutes for further homogenization. Based on the catalyst, the Piperion content in the catalyst ink was 1% by mass. 4.3 Manufacturing of GDE: To ensure rapid evaporation of the solvent, the carbon fiber fabric was heated to 90°C during the spraying operation. The resulting polymer-containing catalyst ink was then sprayed onto the microporous side of the carbon fiber fabric using an airbrush gun (Eclipse, Anest Iwata) until the desired catalyst load was reached (see Table 1). The resulting GDE was then sintered in air at 300°C for 15 minutes. In the second step, the ionomer-containing catalyst ink was filled to a target load of 2.5 mg cm³. -2 It was sprayed onto PTFE-CL pre-applied to GDL heated to 90°C, containing polymer-containing CL, until it reached the desired state.

[0095] 4.4 CO2 electrolysis CO2 electrolysis requires an active cell area of ​​2 cm². 2 This was performed using an internally developed zero-gap electrolytic cell. IrO2 (Alfa Aesar) 1 mg cm -2 A porous titanium felt (2-GDL40, Bekaert) with the specified catalyst packing amount was used as the anode. The anode portion contained 16.67 ml of 0.1 M KHCO3. -1 It was continuously administered. AgNPs (Alfa Aesar) filling amount: 2.5 mg cm -2 GDE manufactured using [this method] was used as the cathode. During electrolysis, the cathode contains 50 ml of CO2. -1 and Ar5ml -1 The gas was then passed through. Argon served as the internal standard. Before entering the cathode, the gas supply stream was brought to a relative humidity of 79% (dew point: 55°C) using a saturated steam humidifier. Immediately before the start of electrolysis, both the 40 μm thick Piperion film and the GDE containing multilayer CL were activated in 1 M KOH for 30 minutes, and then washed with ultrapure water (18.2 MΩ cm). All electrode catalyst studies were conducted at 300 mA cm. -2 The electrolysis was performed at a constant current for 3 hours. The sample of the gaseous product stream obtained at the cathode was analyzed every 20 minutes by GC-MS. Current yield (FE) for the target product CO CO ) and the measured cell voltage (Uセル ) is shown in Figures 7 and 8 as Example 2-1 of a manufactured GDE containing carbon in a multilayer structure and hydrophobic polymer-containing layer according to the present invention.

[0096] Figure 7 shows the current yield (FE) for the target product CO. CO Figure 8 shows the corresponding measurement of 300 mA cm⁻¹. -2 Cell voltage (U) of constant current electrolysis over 180 minutes セル ) shows the averaged FE CO (Gray) and FE H2 (White) is shown as a percentage on the left Y-axis, with the average U セル (Bolts) can be found on the right Y-axis. Both are the electrolysis time (t) on the X-axis. 電気分解 The time is shown over a period of (minutes). The stable region after the final hour of adjustment during electrolysis is highlighted in gray. The additional carbon-containing multilayer CL was manufactured by introducing 20% ​​by mass of carbon, based on the metered catalyst, into a polymer-containing catalyst ink containing 15% by mass of PTFE, based on the metered catalyst (Example 2-1). The catalyst ink for the ionomer-containing CL contained 1% by mass of Piperion, based on the metered catalyst (see Table 4). As shown in Figures 7 and 8, by using this multilayer structure containing carbon in the polymer-containing layer, compared to Examples 1-1 to 1-5, the applied current density was 300 mA cm² at a cell voltage of 3 V. -2 So, FE CO We were able to increase it to 75%.

[0097] 5. Exemplary Embodiment 3 of the present invention (Multilayer CL containing carbon in polymer-containing CL when using a bipolar solid electrolyte membrane) As an exemplary embodiment of a multilayer CL containing carbon in a polymer-containing CL when using a bipolar solid electrolyte membrane for CO2R, as described herein, a commercially available carbon fiber fabric (W1S1010, fuelcellstore) containing a microporous layer is coated in a polymer-containing and carbon black-containing CL in a first step, and then coated in an ionomer-containing CL in a second step. 5.1 Manufacturing of polymer-containing catalyst inks: The catalyst (AgNPs, Alfa Aesar) is dispersed in a 3:1 isopropanol / water mixture, and therefore the catalyst concentration in the ink is 16.67 mg / ml. -1 This corresponds to [the specified amount]. Subsequently, based on the measured amount of catalyst, 20% by mass of carbon (Ensaco 250G) was added to the catalyst ink and Triton X-100, which is an ink stabilizer and pore-forming agent. Before adding the PTFE dispersion, the ink was homogenized at 13400 rpm for 90 seconds (Ultra-Turrax T18D, IKA). Finally, the catalyst ink was treated with ultrasound for 15 minutes for further homogenization. Based on the catalyst, the PTFE content in the catalyst ink was 7.5% by mass.

[0098] [Table 5] 5.2 Manufacturing of ionomer-containing catalyst inks: The catalyst (AgNPs, Alfa Aesar) is dispersed in a 3:1 isopropanol / water mixture, and therefore the catalyst concentration in the ink is 16.67 mg / ml. -1 This corresponds to the following. The catalyst ink was homogenized at 13400 rpm for 90 seconds (Ultra-Turrax T18D, IKA). Finally, the catalyst ink was treated with ultrasound for 15 minutes for further homogenization. Based on the catalyst, the Piperion content in the catalyst ink was 1% by mass.

[0099] 5.3 Manufacturing of GDE: To ensure rapid evaporation of the solvent, the carbon fiber fabric was heated to 90°C during the spraying operation. The resulting polymer-containing catalyst ink was then sprayed onto the microporous side of the carbon fiber fabric using an airbrush gun (Eclipse, Anest Iwata) until the desired catalyst load was reached (see Table 1). The resulting GDE was then sintered in air at 300°C for 15 minutes. In the second step, the ionomer-containing catalyst ink was filled to a target load of 2.5 mg cm³. -2 It was sprayed onto PTFE-CL pre-applied to GDL heated to 90°C, containing polymer-containing CL, until it reached the desired state. 5.4 Manufacturing of Bipolar Films The bipolar film was manufactured by laminating a 40 μm thick piperion film and a 50 μm thick Nafion 212 film in a hot press at 50°C and a pressure of 10 bar for a compression time of 90 seconds.

[0100] 5.5 CO2 electrolysis CO2 electrolysis is performed using an active cell area of ​​12.57 cm². 2 This was performed using an internally developed zero-gap electrolytic cell. IrO2 (Alfa Aesar) 1 mg cm -2 A porous titanium felt (2-GDL40, Bekaert) with a catalyst packing amount was used as the anode. The anode section contained 66.67 ml of ultrapure water (18.2 MΩ cm). -1 It was continuously administered. AgNPs (Alfa Aesar) filling amount: 2.5 mg cm -2 GDE manufactured using [this method] was used as the cathode. During electrolysis, the cathode contains 50 ml of CO2. -1 and Ar 5.5 ml -1 The mixture was then flowed. Argon served as the internal standard. Immediately before the start of electrolysis, both the bipolar film and the multilayer CL-containing GDEs, fabricated by lamination, were activated in 1 M KOH for 30 minutes, and then washed with ultrapure water (18.2 MΩ cm). All electrocatalyst studies were conducted at 300 mA cm. -2The electrolysis was performed at a constant current for 3 hours. The sample of the gaseous product stream obtained at the cathode was analyzed every 20 minutes by GC-MS.

[0101] Figure 9 shows the current yield (FE) for the target product CO. CO Figure 10 shows the cell voltage (U) measured for a fabricated GDE containing a multilayer CL with carbon in the polymer-containing cell when using a bipolar film. セル ) indicates 300mA cm -2 Then, constant current electrolysis was performed for 180 minutes. The averaged FE CO (Gray) and FE H2 (White) is shown as a percentage on the left Y-axis, with the average U セル (Bolts) can be found on the right Y-axis. Both are the electrolysis time (t) on the X-axis. 電気分解 It is shown over a period of (minutes). The additional carbon-containing multilayer CL was prepared by introducing 20% ​​by mass of carbon into a polymer-containing catalyst ink containing 7.5% by mass of PTFE, based on the metered catalyst (Example 2-1). The catalyst ink for the ionomer-containing CL contained 1% by mass of Piperion, based on the metered catalyst (see Table 4). When using a multilayer bipolar film consisting of a 40 μm thick Piperion film and a 50 μm thick Nafion 212 film, the applied current density was 300 mA cm² at a cell voltage of 3.3-3.4 V. -2 And FE up to 50% CO It was possible to achieve this. 6. Exemplary Embodiment 4 of the present invention (Multilayer CL containing carbon in polymer-containing CL when using a bipolar solid electrolyte membrane) As an exemplary embodiment of a multilayer CL containing carbon in a polymer-containing CL when using a bipolar solid electrolyte membrane for CO2R, as described herein, a commercially available carbon fiber fabric (W1S1010, fuelcellstore) containing a microporous layer is coated in a polymer-containing and carbon black-containing CL in a first step, and then coated in an ionomer-containing CL in a second step.

[0102] 6.1 Manufacturing of polymer-containing catalyst inks: The catalyst (AgNPs, Alfa Aesar) is dispersed in a 3:1 isopropanol / water mixture, and therefore the catalyst concentration in the ink is 16.67 mg / ml. -1 This corresponds to [the specified amount]. Subsequently, based on the measured amount of catalyst, 20% by mass of carbon (Ensaco 250G) was added to the catalyst ink and Triton X-100, which is an ink stabilizer and pore-forming agent. Before adding the PTFE dispersion, the ink was homogenized at 13400 rpm for 90 seconds (Ultra-Turrax T18D, IKA). Finally, the catalyst ink was treated with ultrasound for 15 minutes for further homogenization. Based on the catalyst, the PTFE content in the catalyst ink was 7.5% by mass. [Table 6]

[0103] 6.2 Manufacturing of ionomer-containing catalyst inks: The catalyst (AgNPs, Alfa Aesar) is dispersed in a 3:1 isopropanol / water mixture, and therefore the catalyst concentration in the ink is 16.67 mg / ml. -1 This corresponds to the following. The catalyst ink was homogenized at 13400 rpm for 90 seconds (Ultra-Turrax T18D, IKA). Finally, the catalyst ink was treated with ultrasound for 15 minutes for further homogenization. Based on the catalyst, the Piperion content in the catalyst ink was 1% by mass. 6.3 Manufacturing of GDE: To ensure rapid evaporation of the solvent, the carbon fiber fabric was heated to 90°C during the spraying operation. The resulting polymer-containing catalyst ink was then sprayed onto the microporous side of the carbon fiber fabric using an airbrush gun (Eclipse, Anest Iwata) until the desired catalyst load was reached (see Table 1). The resulting GDE was then sintered in air at 300°C for 15 minutes. In the second step, the ionomer-containing catalyst ink was filled to a target load of 2.5 mg cm³. -2It was sprayed onto PTFE-CL pre-applied to GDL heated to 90°C, containing polymer-containing CL, until it reached the desired state.

[0104] 6.4 Manufacturing of Bipolar Films The bipolar film was manufactured by spraying a piperion solution (1% by mass in ethanol) onto a 50 μm thick Nafion 212 film, followed by hot pressing at 50°C and a pressure of 10 bar for a compression time of 90 seconds. 6.5 CO2 electrolysis CO2 electrolysis is performed using an active cell area of ​​12.57 cm². 2 This was performed using an internally developed zero-gap electrolytic cell. IrO2 (Alfa Aesar) 1 mg cm -2 A porous titanium felt (2-GDL40, Bekaert) with a catalyst packing amount was used as the anode. The anode section contained 66.67 ml of ultrapure water (18.2 MΩ cm). -1 It was continuously administered. AgNPs (Alfa Aesar) filling amount: 2.5 mg cm -2 GDE manufactured using [this method] was used as the cathode. During electrolysis, the cathode contains 50 ml of CO2. -1 and Ar 5.5 ml -1 The mixture was then flowed. Argon served as the internal standard. Immediately before the start of electrolysis, both the bipolar film and the multilayer CL-containing GDEs, fabricated by lamination, were activated in 1 M KOH for 30 minutes, and then washed with ultrapure water (18.2 MΩ cm). All electrocatalyst studies were conducted at 300 mA cm. -2 The electrolysis was performed at a constant current for 3 hours. The sample of the gaseous product stream obtained at the cathode was analyzed every 20 minutes by GC-MS.

[0105] Figure 11 shows the current yield (FE) for the target product CO. CO Figure 12 shows the cell voltage (U) measured for a fabricated GDE containing a multilayer CL with carbon in the polymer-containing layer when using a bipolar film. セル ) indicates 300mA cm -2Then, constant current electrolysis was performed for 180 minutes. The averaged FE CO (Gray) and FE H2 (White) is shown as a percentage on the left Y-axis, with the average U セル (Bolts) can be found on the right Y-axis. Both are the electrolysis time (t) on the X-axis. 電気分解 It is shown over a period of (minutes). Additional carbon-containing multilayer CL was prepared by introducing 20% ​​by mass of carbon into a polymer-containing catalyst ink containing 7.5% by mass of PTFE, based on the metered catalyst (Example 2-1). The catalyst ink for ionomer-containing CL contained 1% by mass of Piperion, based on the metered catalyst (see Table 4). When using a bipolar film prepared by spraying a Piperion solution (1% by mass in ethanol) onto a 50 μm thick Nafion 212 film, the applied current density was 300 mA cm² at a cell voltage of 3.3-3.6 V. -2 And up to 43% FE CO It was possible to achieve this.

[0106] List of reference symbols 1 electrode 2. Hydrophobic catalyst layer 3 Hydrophilic catalyst layer 4. Gas diffusion layer 5 Electrolytic Cells 6 Anodes 7 membrane

Claims

1. Especially CO 2 A gas diffusion electrode for electrochemical reduction, A gas diffusion electrode characterized in that the electrode comprises at least one hydrophobic catalyst layer and at least one hydrophilic catalyst layer.

2. The electrode according to claim 1, characterized in that the hydrophobic catalyst layer and the hydrophilic catalyst layer are porous.

3. The electrode according to claim 1 or 2, characterized in that a hydrophobic catalyst layer and a hydrophilic catalyst layer are arranged in order, indirectly or directly, preferably directly.

4. The electrode according to any one of claims 1 to 3, characterized in that a hydrophobic catalyst layer and a hydrophilic catalyst layer are arranged on a porous carrier layer, particularly a gas diffusion layer.

5. The electrode according to claim 4, characterized in that the porous carrier layer is selected from the group consisting of carbon fiber fabric, carbon fiber paper, graphite fabric, metal felt, metal mesh, sintered metal, and mixtures thereof, and is particularly selected from the group consisting of carbon fiber fabric, carbon fiber paper, and mixtures thereof, and is preferably carbon fiber fabric.

6. The electrode according to any one of claims 1 to 5, characterized in that the hydrophobic catalyst layer and the hydrophilic catalyst layer each contain at least one catalyst.

7. The electrode according to any one of claims 1 to 6, characterized in that the catalyst is selected from the group consisting of metal particles, particularly metal nanoparticles, monatomic catalysts (single-atom catalysts), metal carbides, metal oxides, metal chalcogenides, molecular catalysts, and mixtures thereof.

8. The electrode according to any one of claims 1 to 7, characterized in that the hydrophilic catalyst layer comprises at least one hydrophilic polymer, particularly an ionomer.

9. The electrode according to claim 8, characterized in that the hydrophilic polymer is selected from the group consisting of cation exchange polymers, anion exchange polymers, and mixtures thereof.

10. The electrode according to any one of claims 1 to 9, characterized in that the hydrophobic catalyst layer contains at least one hydrophobic polymer.

11. The electrode according to claim 10, characterized in that the hydrophobic polymer is selected from the group consisting of polyolefins, polyfluoroolefins, silicones, fluorinated polymers, polycyclic aromatic polymers and polycyclic aromatic copolymers, and mixtures thereof.

12. Use of an electrode according to any one of claims 1 to 11 in electrolysis.

13. Use of the electrode according to any one of claims 1 to 11 as a cathode in the electrochemical reduction of carbon dioxide.

14. (i) In the first method step, a first coating composition for producing a first hydrophilic or hydrophobic, preferably hydrophobic, catalyst layer is applied to a porous carrier material or an ion-conducting film. (ii) In a second method step following the first method step (I), a second coating composition different from the first coating composition is applied to the first catalyst layer, which is hydrophobic or hydrophilic, preferably hydrophobic, for producing a second hydrophilic or hydrophobic, preferably hydrophilic, catalyst layer. A method for manufacturing an electrode according to any one of claims 1 to 13, characterized in that

15. The method according to claim 14, characterized in that a hydrophilic and / or hydrophobic first and / or second coating composition exists in the form of a dispersion, particularly preferably a first and second hydrophilic and / or hydrophobic coating composition exists in the form of a dispersion.

16. The method according to claim 14 or 15, characterized in that the hydrophobic coating composition comprises a conductivity enhancer, the conductivity enhancer being selected from carbon black, graphite, carbon nanotubes, and mixtures thereof.

17. An electrolytic cell, particularly for the electrochemical reduction of carbon dioxide, comprising at least one electrode as described in any one of claims 1 to 11.

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