Gas diffusion electrode for electrochemical processes

Abstract

The present invention relates to a gas diffusion electrode for electrochemical processes, comprising: an electrically conductive porous gas diffusion layer; at least one porous catalyst layer arranged adjacent to the gas diffusion layer, wherein the catalyst layer is obtained from a precursor material free of any ionomer; and an ionomer layer arranged adjacent to the at least one porous catalyst layer, the catalyst layer being obtained from a precursor material free of any ionomer. The present invention further relates to an electrochemical cell comprising such a gas diffusion electrode, and to a method of manufacturing such a gas diffusion electrode.

Description

Technical Field

[0001] This invention relates to gas diffusion electrodes for electrochemical processes, particularly for the electrochemical reduction of carbon dioxide (CO2) to valuable carbon-based products such as carbon monoxide (CO) or ethylene (C2H4). The invention also relates to methods for manufacturing such gas diffusion electrodes and electrochemical cells using such gas diffusion electrodes. Background Technology

[0002] Significant advancements in energy conversion and storage technologies have driven the growing demand for highly efficient electrochemical systems. Among these, gas diffusion electrodes (GDEs) have become key components, revolutionizing the field by facilitating enhanced mass transfer and electrode kinetics. With their unique construction and versatile applications, GDEs have garnered considerable attention across various sectors, including fuel cells, electrochemical sensors, and electrolyzers. Also known as three-phase electrodes, GDEs play a crucial role in bridging electrochemical processes and gaseous reactants occurring at the solid electrode-electrolyte interface. Their unique architecture enables efficient transport of reactant gases, electron transfer, and electrolyte management, thereby improving the overall performance of electrochemical devices. The construction of GDEs involves a carefully designed, layered structure combining a porous catalyst layer, a gas diffusion layer, and a hydrophobic binder. The porous catalyst layer acts as the site of electrochemical reactions, where catalytic materials (such as platinum, palladium, or other transition metals) facilitate the conversion of reactant gases. It provides a high surface area for efficient catalysis and promotes efficient electron transfer between the electroactive material and the electrode. The porosity of this layer allows for the entry and exit of reactant gases and facilitates the transport of ions and products. The gas diffusion layer, positioned adjacent to the catalyst layer, acts as a conductive pathway for both gaseous reactants and electrons. Typically composed of carbon-based materials such as carbon cloth or paper, carbon nanotubes, or graphene, the gas diffusion layer must exhibit high gas permeability, electrical conductivity, and mechanical stability. It not only contributes to the uniform distribution of reactant gases within the catalyst layer but also aids in the effective removal of reaction byproducts and water, thus preventing flooding and ensuring sustained electrochemical activity. To enhance the stability and durability of the gas diffusion electrode, hydrophobic binders are introduced, imparting water repellency to the gas diffusion layer. This hydrophobicity prevents flooding and helps maintain the desired gas diffusion characteristics by minimizing the intrusion of liquid water into the electrode structure. Commonly used binders include polytetrafluoroethylene (PTFE) and various perfluorosulfonic acid (PFSA) polymers.

[0003] Gas diffusion electrodes have diverse applications in various electrochemical devices: in fuel cells, they act as catalyst supports for oxygen reduction and fuel oxidation reactions, facilitating the conversion of chemical energy into electrical energy. They also play a crucial role in electrochemical sensors, providing rapid and selective detection of various analytes by utilizing the electrochemical signals generated at the electrode-electrolyte interface. Furthermore, gas diffusion electrodes are an essential component of electrolyzers, such as in chlor-alkali electrolysis.

[0004] In recent years, the use of gas diffusion electrodes for the electrochemical reduction of carbon dioxide has become a rapidly growing research area, especially because burning fossil fuels (which still account for the majority of global energy demand) involves the emission of carbon dioxide into the atmosphere, leading to environmental crises such as climate change and ocean acidification. To mitigate the problems associated with the release of carbon dioxide into the environment, technologies aimed at capturing and reusing carbon dioxide, such as from the atmosphere or directly from carbon dioxide-producing sources, have been investigated in recent years. However, carbon dioxide is a very stable molecule, requiring a significant energy input to convert it into other valuable carbon-based products. Particularly promising technologies for such applications involve electrochemical CO2 reduction reactions, especially when using energy from renewable energy sources. Typical valuable products obtained from electrochemical CO2 reduction are C1-C3 products, such as carbon monoxide (CO) and ethylene (C2H4).

[0005] Initially, the gas diffusion electrode for electrochemical CO2 reduction was based on a gas diffusion electrode originally developed for fuel cells. Typically, a catalyst layer is deposited on a microporous layer by spraying a mixture of catalyst and ionomer onto the microporous layer. The resulting structure exhibits several beneficial features, such as a thin overall structure that enhances carbon dioxide accessibility and ensures good ionic conductivity of the electrolyte in the catalyst region. However, the structural effect of the ionomer can cause problems regarding the structure's conductivity and durability because ionomers are typically electrically insulating. Furthermore, stability issues caused by carbonate precipitation can arise.

[0006] Patent application US 2023 / 0307677 A1 describes electrodes and membrane electrode assemblies (MEAs) for high-temperature proton exchange membrane fuel cells, wherein the MEA includes an anode gas diffusion electrode, a cathode gas diffusion electrode, and a proton-conducting ion-pair membrane. The gas diffusion electrode includes a carbon substrate / support layer, a microporous layer containing carbon and a hydrophobic binder, and a catalyst layer containing an ionomer-type binder. A thin top coating of ionomer and phosphoric acid is also provided to improve interfacial properties with the ion-pair membrane.

[0007] International patent application WO 2021 / 084935 A1 describes a catalyst-supported porous substrate for water electrolysis and an electrode for water electrolysis. A membrane electrode assembly is described, in which a polymer electrolyte membrane (PEM) is sandwiched between the catalyst-supported porous substrate. An ionomer is provided that contacts the catalyst from the surface to the interior of the porous substrate.

[0008] International patent application WO 2019 / 020239 A1 describes an electrolyzer design for the electrochemical reduction of carbon dioxide. The cathode of this electrolyzer is based on a mixture of a powdered electrocatalyst for carbon dioxide reduction and an anion-exchange ionomer.

[0009] The electrodes described in these existing technical documents still contain a mixture of catalyst and ionomer, and therefore still suffer from the aforementioned problems regarding reduced electrical conductivity and durability of the structure.

[0010] Therefore, the object of this invention is to provide a gas diffusion electrode that solves problems related to electrochemical CO2 reduction. Specifically:

[0011] Due to the poor solubility of CO2 in liquid electrolytes and its limited diffusion range, good gas accessibility must be ensured throughout the entire structure to minimize the competitive hydrogen evolution reaction caused by water electrolysis.

[0012] In addition, good electrical conductivity of the overall structure must be ensured to allow electrons to come into contact with the catalyst and assist the reduction reaction.

[0013] In addition, it is essential to ensure the presence of sufficient liquid electrolyte in the catalyst region while avoiding immersion of the entire structure, which would also lead to the takeover of the aforementioned competitive hydrogen evolution reaction.

[0014] Finally, carbonate precipitation must be limited, which can occur when using alkaline hydroxides as electrolytes. This is because CO2 reacts with hydroxyl ions generated during the electrochemical reduction of CO2 or provided by alkaline electrolytes (such as metal hydroxides (MOHs)), which undergo further conversion into metal carbonates in an alkaline environment. The precipitation of solid metal carbonates can disrupt the electrode structure and lead to a reduction in the overall process efficiency. Summary of the Invention

[0015] Various aspects of the invention are set forth in the appended claims.

[0016] In one aspect, the present invention relates to a gas diffusion electrode for electrochemical processes, particularly for the electrochemical reduction of carbon dioxide, comprising: a conductive porous gas diffusion layer; at least one porous catalyst layer disposed adjacent to the gas diffusion layer, the catalyst layer being obtained from a precursor material free of any ionomers; and an ionomer layer disposed adjacent to the at least one porous catalyst layer, the ionomer layer being obtained from a precursor material free of any catalyst. In the sense of the present invention, the catalyst layer and the ionomer layer are structurally separated layers obtained from different precursor materials. Compared to the prior art described above, the precursor material for the catalyst layer is free of any ionomers, and the precursor material for the ionomer layer is free of any catalyst. This results in the presence of two separate layers, which provides a new way to regulate the permeation of electrolyte solution into the structure of the gas diffusion electrode, and thus can be customized according to the electrochemical process of interest.

[0017] Therefore, according to the present invention, the at least one porous catalyst layer disposed to the gas diffusion layer is substantially free of any ionomers, and the ionomer layer disposed adjacent to the at least one porous catalyst layer is substantially free of any catalyst. In the context of the present invention, the terms "substantially free of ionomers" or "catalyst" respectively mean that the catalyst layer precursor material is free of any ionomers and the ionomer layer precursor material is free of any catalyst. However, in some embodiments, depending on the manufacturing process, some penetration of ionomers into the catalyst layer may still occur, such that certain embodiments of the gas diffusion electrode of the present invention can exhibit an interface region comprising a mixture of catalyst and ionomers between the porous catalyst layer and the ionomer layer. However, in the above context, the term "substantially" means that the interface region has a thickness much smaller than the thickness of the corresponding layer itself. For example, the thickness of the interface region may be less than 50% of the thickness of the corresponding catalyst layer or ionomer layer, preferably less than 25% of the thickness of the catalyst layer or ionomer layer, and more preferably even less than 10% of the thickness of the catalyst layer or ionomer layer. Since ionomers are generally hydrophilic substances, the ionomer layer increases the hydrophilicity of the electrode surface without compromising the overall catalyst layer structure.

[0018] In addition to providing the catalyst and ionomer in separate layers, the catalyst layer preferably comprises a mixture of catalyst material (e.g., catalyst powder or catalyst precursor powder) and hydrophobic material (e.g., hydrophobic resin). In the context of this invention, a "hydrophobic" material is one that ensures the resulting porous catalyst layer exhibits hydrophobic properties, i.e., the porous catalyst layer exhibits a water contact angle greater than 90°, preferably greater than 120°. Since ionomers are generally hydrophilic, the hydrophobic porous surface layer ensures that no ionomers permeate into the porous catalyst layer during the fabrication of the gas diffusion electrode of this invention, thereby minimizing or completely avoiding the interfacial region containing the mixture of catalyst and ionomer. Therefore, according to one embodiment, the catalyst layer is ionomer-free. Thus, the pathway of reactants to the catalyst material can be independently optimized by adjusting the properties of the ionomer layer and the porous catalyst layer.

[0019] Furthermore, the construction of the gas diffusion electrode of the present invention allows the ionomer layer to be applied on top of a pre-formed catalyst layer, enabling the catalyst layer and the ionomer layer to be manufactured separately. Separate treatment of the two layers allows for heat treatment on the catalyst layer, ensuring enhanced stability and hydrophobicity to the desired level. Such heat treatment cannot be performed using conventional mixtures of catalyst and ionomer, as most ionomers are unstable at high temperatures. Moreover, the construction of the gas diffusion electrode of the present invention allows for the use of a catalyst precursor material that can be converted into the final catalyst material through in-situ heat treatment prior to the application of the ionomer layer. Therefore, in one embodiment of the invention, the at least one porous catalyst layer is obtained by heat treating the precursor layer applied to the gas diffusion layer.

[0020] In addition to the catalyst material, the catalyst layer may contain components that adjust conductivity, such as carbon powder; components that adjust porosity, such as fibrous materials like cellulose; and components that adjust hydrophobicity, such as fluoropolymers.

[0021] In one embodiment, the at least one porous catalyst layer comprises not only the first catalyst layer described above, but also a second catalyst layer containing a second catalyst material different from the first catalyst material. In certain electrochemical processes, it can be advantageous to deposit two or more different catalysts in separate layers, for example, to achieve a tandem effect, which is beneficial for the production of certain desired products. The weight ratio of the first catalyst layer to the second catalyst layer is preferably selected in the range of 20:1 to 2:1.

[0022] In one aspect of the invention, the gas diffusion electrode is specifically configured to promote the electrochemical reduction of carbon dioxide. Therefore, the catalyst material is preferably selected from transition metal complexes, metal microparticles, metal nanoparticles, metal oxides, metal oxide microparticles, metal oxide nanoparticles, or combinations thereof. Microparticles are particles whose size (e.g., diameter for spherical particles, or effective diameter for non-spherical particles) is in the micrometer range. Nanoparticles have sizes in the nanometer range. Transition metal complexes are preferably selected from porphyrins, phthalocyanines, metalloporphyrins, metal phthalocyanines, or metal-organic frameworks (MOFs), especially nickel-based MOFs. Microparticles and nanoparticles are preferably selected from gold (Au), silver (Ag), copper (Cu), palladium (Pd), platinum (Pt), or alloys thereof. Particularly preferred are silver microparticles with diameters in the range of 1 to 10 μm, and copper particles with diameters in the range of 20 nm to 10 μm. If two catalyst layers are used, it is particularly preferred that the second catalyst layer comprises silver nanoparticles with diameters in the range of 20 nm to 200 nm.

[0023] The catalyst loading in at least one catalyst layer is preferably between 0.3 and 10 mg / cm³. 2 between.

[0024] In some embodiments, the conductive porous gas diffusion layer of the gas diffusion electrode of the present invention comprises a macroporous layer acting as a support and a microporous layer disposed between the macroporous layer and the at least one catalyst layer. According to the present invention, "Macroporous layer" Typically, they are carbon-based fiber structures, such as cloth, paper, or felt, in which the fibers have a diameter of 5-50 μm, and "Microporous layer" It is typically a carbon-based continuous structure that includes pores with an average diameter of 0.5–15 μm.

[0025] Preferably, the macroporous layer is a carbon base layer, such as carbon cloth or carbon paper, and its thickness is preferably selected in the range of 90 μm to 200 μm.

[0026] The microporous layer preferably comprises a mixture of carbon and a hydrophobic material. The thickness of the microporous layer is preferably selected in the range of 45 μm to 140 μm. Similar to the above definition, in the sense of this invention, "hydrophobic material" is a material that ensures the microporous layer exhibits hydrophobic properties (i.e., a water contact angle greater than 90°, preferably greater than 120°).

[0027] The hydrophobic material of the at least one porous catalyst layer and / or the hydrophobic material of the microporous layer is preferably a hydrophobic resin, preferably a fluoropolymer, such as a polytetrafluoroethylene (PTFE) polymer or a perfluorosulfonic acid (PFSA) polymer.

[0028] The ionomer layer arranged adjacent to at least one porous catalyst layer may comprise anion-exchange polymers or cation-exchange polymers. Depending on the electrochemical process of interest, the ionomer layer can be tailored in such a way that unwanted counterions from the electrolyte reach the catalytic reaction site, thereby preventing the diffusion of unwanted side reactions and thus improving the overall efficiency of the electrochemical process. In the case of the electrochemical reduction of carbon dioxide, the ionomer layer is made of anion-exchange polymer, which preferably has ammonium functional groups, such as piperidinium and imidazolium functional groups. The anion-exchange polymer may also include phosphonium and sulfonium structural moieties.

[0029] The present invention also relates to an electrochemical cell comprising an anode chamber, a cathode chamber, and a separator disposed between the anode chamber and the cathode chamber, wherein at least one of the anode chamber and the cathode chamber comprises a gas diffusion electrode as described above. The separator may be a membrane or a diaphragm. Typically, the anode chamber and the cathode chamber comprise current collectors that are in electrical contact with the electrodes in the respective chambers. The current collectors may be part of the gas diffusion electrode of the present invention and may, for example, be bonded to the outer surface of a gas diffusion layer, or, in the case of a real gas diffusion layer, to the outer surface of a microporous layer.

[0030] The present invention also relates to a method for manufacturing a gas diffusion electrode, particularly a gas diffusion electrode as described above, comprising the following steps:

[0031] a) Catalyst ink is prepared by dispersing a catalyst material in a first solvent, wherein the catalyst ink does not contain any ionomers;

[0032] b) An ionomer-based ink is prepared by dispersing the ionomer in a second solvent, wherein the ionomer ink does not contain any catalyst;

[0033] c) Prepare a conductive porous gas diffusion layer;

[0034] d) Coating the conductive porous gas diffusion layer with the catalyst ink to form a catalyst layer;

[0035] e) Drying and / or heat-treating the catalyst layer to allow the catalyst material to migrate over the gas diffusion layer; and

[0036] f) Coating the catalyst layer with the ionomer-based ink.

[0037] The catalyst ink in step a) is typically prepared by dissolving catalyst powder in a first solvent (e.g., in water). The ink may also contain hydrophobic materials, such as the fluoropolymers described above, and optionally surfactants, such as nonionic surfactant polymers having a hydrophilic polyether moiety and a hydrophobic aromatic moiety. The catalyst ink may also include a viscosity modifier, preferably a cellulose derivative. In some embodiments, the catalyst ink may also include carbon, preferably a mixture of hydrophobic and hydrophilic acetylene black.

[0038] The ionomer-based ink in step b) is obtained by dispersing an ionomer (e.g., anion-exchange ionomer and / or cation-exchange ionomer) in a second solvent (which is typically a water-alcohol mixture). The water-alcohol solvent mixture is preferably in a weight ratio of about 1:1.

[0039] The coating in step d) can be accomplished using various deposition techniques, such as brush coating, roll-to-roll gravure printing, slot die coating, or similar techniques. Typically, coating is performed until a concentration of 0.3 to 10 mg / cm³ is obtained. 2 Until the catalyst loading is reached.

[0040] In step e), the applied coating may be dried to form a catalyst layer on the gas diffusion layer. In some embodiments, step e) may include heat treatment at a higher temperature to increase the adhesion of the catalyst layer to the gas diffusion layer and / or to convert the catalyst precursor material into a finer catalyst material. Preferably, the heat treatment in step e) includes baking the porous gas diffusion layer and catalyst layer assembly at a temperature of 170°C to 350°C for 10 minutes to 24 hours.

[0041] In the embodiment, wherein the conductive porous gas diffusion layer comprises a macroporous layer and a microporous layer, step c) preferably includes the following detailed sub-steps c1)-c3) performed prior to step d):

[0042] c1) Provide a macroporous layer, such as carbon cloth or carbon paper.

[0043] c2) A carbon-based ink, such as a mixture of acetylene black and water, may be provided, but mixtures of different carbons may also be used. Hydrophobic carbon materials are preferred for gas diffusion electrodes. The carbon-based ink may also contain a hydrophobic resin, typically a fluoropolymer, preferably with a particle size in the range of 0.005 to 10 μm.

[0044] c3) The carbon-based ink is deposited on the macroporous layer to form a microporous layer. In step c3), a deposition technique similar to that described above can be used, such as brush coating, roll-to-roll gravure printing, slot die coating, or similar methods.

[0045] In some implementations, depending on the deposition technique used in sub-step c3), step c) may include an additional sub-step c4) performed after sub-steps c1)-c3) and before step d):

[0046] c4) Bake the assembly of the macroporous layer and the applied microporous layer in air at a temperature of 170°C to 350°C for 10 minutes to 24 hours.

[0047] Carbon loading is typically 25-100 g / m³ 2Within the range, preferably 58-63 g / m 2 Within the range.

[0048] In step f), various deposition techniques can be used, but preferably, the ionomer-based ink is deposited onto the catalyst layer by spraying. The final ionomer loading is preferably 0.05 to 0.4 mg / cm³. 2 .

[0049] The gas diffusion electrode of this invention can be used in a variety of applications. A preferred application is the electrochemical reduction of carbon dioxide to valuable carbon-based products such as CO and ethylene. Other possible applications include anion exchange membrane (AEM) fuel cells, including regenerative modular fuel cells (URFCs), which can operate in fuel cell mode to combine oxygen and hydrogen to generate electricity and in regenerative electrolyzer mode to electrolyze water. Other possible applications include acting as a cathode in AEM water electrolysis. The gas diffusion electrode of this invention ensures good performance and stability during operation. Attached Figure Description

[0050] The invention will now be described in more detail with reference to certain preferred embodiments and the accompanying drawings.

[0051] In the attached diagram:

[0052] Figure 1 A schematic diagram of a first embodiment of the gas diffusion electrode of the present invention is shown;

[0053] Figure 2 A second embodiment of the gas diffusion electrode of the present invention is shown; and

[0054] Figure 3 A schematic diagram of an electrolytic cell including the gas diffusion electrode of the present invention is shown. Detailed Implementation

[0055] Figure 1 A first embodiment of the gas diffusion electrode 10 according to the present invention is shown, wherein a single catalyst layer is provided. As can be seen from the figure, the gas diffusion electrode 10 is provided with a gas diffusion layer 11, which comprises a macroporous layer 12 and a microporous layer 13. The macroporous layer 12 acts as a support for the microporous layer 13 deposited on the macroporous layer 12. A catalyst layer 14 is applied on top of the microporous layer 13. An ionomer layer 15 is applied on top of the catalyst layer 14. The side of the macroporous layer 12 opposite to the side where the microporous layer 13 is applied contacts a current collector 16.

[0056] Figure 2 A second embodiment of the gas diffusion electrode 20 according to the invention is shown, which substantially corresponds to Figure 1The second embodiment of the gas diffusion electrode 20 further includes a gas diffusion layer 21, which comprises a macroporous layer 22 and a microporous layer 23. A catalyst layer 24 is disposed on top of the microporous layer 23. An ionomer layer 25 is applied on top of the catalyst layer 24. The macroporous layer 22 is also in contact with the current collector 26. Figure 1 Compared to the previous implementation scheme, the catalyst layer 24 is formed by multiple layers 24a and 24b, wherein the multiple layers are different in catalyst composition.

[0057] Figure 3 An electrochemical cell 30 with an anode chamber 31 and a cathode chamber 32 is shown. The anode chamber 31 includes an anode current collector 32 with an anode gas flow channel 33, and the cathode chamber 32 includes a cathode current collector 35 with a cathode gas flow channel 36. The anode chamber 31 and the cathode chamber 34 are separated by a membrane 37. In an embodiment of the invention, the anode chamber includes an anode gas diffusion electrode 38 with an anode catalyst layer 39, such as an iridium-based catalyst. The cathode chamber 34 includes a cathode gas diffusion electrode 40 according to the invention, such as according to... Figure 1 and 2 One embodiment of the cathode gas diffusion electrode is described. The cathode gas diffusion electrode 40 includes a cathode catalyst layer 41, which may be, for example, a silver-based catalyst, a MOF-based catalyst, or a copper-based catalyst as described in more detail below. The cathode chamber 34 also includes a CO2 gas inlet 42 and a reduction product outlet 43. The anode chamber 31 includes an anolyte inlet 45 and a reaction product outlet 44.

[0058] When using, such as Figure 3 In the battery depicted for the electrochemical reduction of carbon dioxide, the reduction takes place in the cathode chamber. The specific reactions and products can vary depending on the catalyst, electrolyte, applied voltage, and product selectivity required for a particular application. In the anode chamber, an oxidation reaction occurs to maintain charge balance within the electrolyzer. The specific reaction depends on the choice of electrolyte, system design, and operating conditions. For example, a primary desired reaction in the cathode chamber is the reduction of carbon dioxide to carbon monoxide. This reaction is often targeted due to the industrial importance of carbon monoxide as a versatile chemical feedstock. This reaction can be represented as follows:

[0059] Cathode: CO2 + 2e - +H₂O→2OH - +CO

[0060] Another common reaction is the reduction of carbon dioxide to formate, which can be used as a precursor for various organic compounds. This reaction can be represented as follows:

[0061] Cathode: CO2 + 2e - +H2O→HCOO - +OH -

[0062] The choice of catalyst on the cathode surface plays a crucial role in determining the selectivity of carbon dioxide reduction and the formation of specific products. Different catalyst materials can promote different reaction pathways, thus affecting the formation of the desired products.

[0063] If an aqueous electrolyte is used in a neutral or alkaline environment, the reaction in the anode chamber can be represented as follows:

[0064] Anode: 2OH - →H₂O + 1 / 2O₂ + 2e -

[0065] In non-aqueous or solid electrolytes, other substances present in the electrolyte can undergo oxidation to maintain charge balance. For example, in non-aqueous electrolytes, the anodic half-cell reaction can involve the oxidation of anions or other substances. The specific reaction will depend on the properties of the electrolyte and the available oxidizable substances.

[0066] Anode: X - →X+e -

[0067] The invention will now be described with reference to certain embodiments.

[0068] Example

[0069] Example 1: Silver-based electrode

[0070] 1.1: Preparation of Catalyst Ink

[0071] Aqueous inks were prepared by mixing silver powder (0.5 μm to 5 μm in size), acetylene black, fluoropolymers (such as PTFE), surfactants (such as Triton X100 surfactant), and thickeners (such as carboxymethyl cellulose) with water. The resulting ink was stirred for 15 minutes under vigorous magnetic stirring.

[0072] 1.2: Preparation of Ionomer-Based Ink

[0073] A diluted solution of anion exchange ionomer ink is prepared by dissolving the anion exchange ionomer (in this embodiment, a functionalized poly(arylpiperidine) resin) in a water-alcoholic solvent to obtain a diluted solution.

[0074] 1.3: Preparation of a conductive porous gas diffusion layer

[0075] A suitable conductive porous gas diffusion layer can be prepared as follows: Acetylene black is mixed with water, a nonionic surfactant, an aqueous dispersant, a fluoropolymer (such as PTFE), and a poly(ethylene oxide) (PEO) polymer. The resulting ink is stirred for 60 to 200 minutes. The ink, acting as a microporous layer, is then deposited onto commercially available carbon cloth (acting as the microporous layer) using a slit die or gravure coating machine, and subsequently baked at 250–320°C for 1 to 14 hours. The final gas diffusion layer has a thickness of 320–370 μm. The water contact angle of the microporous layer is in the range of 130–140°, and the in-plane conductivity measured on the microporous layer side is in the range of 40–60 S / cm. -1 Within the range.

[0076] 1.4: Coat a conductive porous gas diffusion layer with catalyst ink.

[0077] Then, the ink prepared in step 1.1 is coated onto the gas diffusion layer prepared in step 1.3 by multiple (two or more) brushing cycles to achieve 2.8 mg / cm². 2 The final catalyst loading. Between cycles, a drying step is performed, including heat-treating the manufactured article at a temperature of 50 to 100°C for 5 to 30 minutes, preferably at 80°C for 15 minutes.

[0078] 1.5: Fixing the catalyst material

[0079] The resulting components were then baked at 300°C for 2 hours.

[0080] 1.6: Coating with ionomer-based ink

[0081] The ionomer ink prepared in step 1.2 was uniformly sprayed onto the top of the catalyst layer of the component obtained in step 1.5. The resulting layer was dried at room temperature. The final ionomer loading was 0.05-0.4 mg / cm³. 2 .

[0082] Example 2: MOF-based electrode

[0083] 2.1: Preparation of Catalyst Ink

[0084] Aqueous inks are prepared by mixing MOF Ni, acetylene black, fluoropolymers (such as PTFE), surfactants (such as Triton X100), and thickeners (such as carboxymethyl cellulose) with water. The resulting ink is stirred for 15 minutes under vigorous magnetic stirring.

[0085] 2.2: The preparation of ionomer-based ink corresponds to step 1.2 of Example 1.

[0086] 2.3: The preparation of the conductive porous gas diffusion layer corresponds to step 1.3 of Example 1.

[0087] 2.4: Coating a conductive porous gas diffusion layer with catalyst ink corresponds to step 1.4 of Example 1.

[0088] 2.5: Fixing the catalyst material

[0089] The resulting components were then baked at 300°C for 2 hours in an argon inert atmosphere.

[0090] The final samples had a thickness of 385–410 μm. The water contact angle of the catalyst layer ranged from 120° to 130°, and the in-plane conductivity measured on the catalyst layer side ranged from 50 to 60 S / cm. -1 Within the range.

[0091] 2.6: Coating with ionomer-based ink, corresponding to step 1.6 of Example 1.

[0092] MOF-based gas diffusion electrodes exhibit enhanced activity in terms of Faraday efficiency and stability over time. Using this gas diffusion electrode, the Faraday efficiency of the electrochemical reduction of carbon monoxide from CO2 is in the range of 90%–98%, with a decay of 2%–5% during online testing.

[0093] Compared to MOF-based gas diffusion electrodes without ionomers, the stability is improved by approximately 400%.

[0094] Throughout the test, at 1 kA / m 2 At the given current density, the battery voltage is below 2.7 V.

[0095] Example 3: Copper-based electrode

[0096] 3.1: Preparation of Catalyst Ink

[0097] A water-based ink was prepared by mixing metallic copper powder, a fluoropolymer (such as polytetrafluoroethylene (PTFE)), a surfactant (such as Triton X100), and a thickener (such as carboxymethyl cellulose) with water. The resulting ink was stirred for 15 minutes under vigorous magnetic stirring.

[0098] 3.2: The preparation of ionomer-based ink corresponds to step 1.2 of Example 1.

[0099] 3.3: The preparation of the conductive porous gas diffusion layer corresponds to step 1.3 of Example 1.

[0100] 3.4: Coat a conductive porous gas diffusion layer with catalyst ink.

[0101] The catalyst ink is then coated onto the microporous layer of the gas diffusion layer obtained in step 3.3 through multiple (two or more) brushing cycles to achieve a concentration of 1.0 mg / cm³.2 The final catalyst loading. Between cycles, a drying step is performed, including heat-treating the product at 50 to 100°C for 5 to 30 minutes, preferably at 80°C for 15 minutes.

[0102] 3.5: Fixing the catalyst material

[0103] The resulting component was then baked at 300°C for 2 hours in an inert argon atmosphere to produce a copper (Cu) catalyst.

[0104] The final samples had a thickness of 370–400 μm. The water contact angle of the catalyst layer ranged from 130° to 140°, and the in-plane conductivity measured on the catalyst layer side ranged from 45 to 55 S / cm. -1 Within the range.

[0105] 3.6: Coating with ionomer-based ink, corresponding to step 1.6 of Example 1.

[0106] Cu-based gas diffusion electrodes show performance against C 2+ The product exhibits enhanced activity and good stability over time. (Targeting C) 2+ The product's Faraday efficiency is 40%-55%, with a 5%-10% decay during online testing. The online testing lasted 200 hours. Throughout the testing period, at 2 kA / m... 2 At the given current density, the battery voltage remained stable at 2.9 V.

[0107] Example 4: Silver-based second catalyst layer

[0108] 4.1: Preparation of Catalyst Ink

[0109] A water-based ink was prepared by mixing silver nanoparticles, isopropanol, and hydroxypropyl methylcellulose with water. The resulting ink was then sonicated for 15 minutes.

[0110] 4.2: The preparation of ionomer-based ink corresponds to step 1.2 of Example 1.

[0111] 4.3: The preparation of the conductive porous gas diffusion layer corresponds to step 1.3 of Example 1.

[0112] 4.4: Coating a conductive porous gas diffusion layer with catalyst ink, corresponding to step 1.4 of Example 1, except that the final catalyst loading is 0.1 mg / cm³. 2 .

[0113] 4.5: Fix the catalyst material, corresponding to step 2.5 of Example 2.

[0114] 4.6: Coating with ionomer-based ink, corresponding to step 1.6 of Example 1.

[0115] The above description is not intended to limit the invention, which can be used in various embodiments without departing from its purpose, and its scope is defined only by the appended claims.

[0116] In the specification and claims of this application, the terms “comprising,” “including,” and “containing” are not intended to exclude the presence of other additional elements, components, or process steps.

[0117] The discussions of documents, articles, materials, devices, and other materials included in this specification are intended only to provide context for the invention. They do not imply that any or all of these subjects constitute part of the prior art or formed common general knowledge in the relevant field prior to the priority date of each claim of this application.

[0118] The project that gave rise to this application was funded by the EU’s Horizon 2020 research and innovation program under grant agreement number 851441.

Claims

1. A gas diffusion electrode for use in electrochemical processes, comprising: Conductive porous gas diffusion layer; At least one porous catalyst layer is arranged adjacent to the gas diffusion layer, the catalyst layer being obtained from a precursor material free of any ionomers; and An ionomer layer is arranged adjacent to the at least one porous catalyst layer, the ionomer layer being obtained from a precursor material that does not contain any catalyst.

2. The electrode according to claim 1, wherein the porous catalyst layer comprises a mixture of a catalyst material and a hydrophobic material.

3. The electrode according to any one of claims 1 or 2, wherein the at least one porous catalyst layer is obtained by heat-treating a precursor layer applied to the gas diffusion layer.

4. The electrode according to any one of claims 1 to 3, wherein the at least one porous catalyst layer comprises a first catalyst layer and a second catalyst layer, the first catalyst layer comprising a first catalyst material and the second catalyst layer comprising a second catalyst material.

5. The electrode according to claim 4, wherein the weight ratio of the first catalyst layer to the second catalyst layer is selected from the range of 20:1 to 2:

1.

6. The electrode according to any one of claims 1 to 5, wherein the gas diffusion electrode is configured to promote the electrochemical reduction of carbon dioxide, and the catalyst layer comprises a catalyst material selected from transition metal complexes, metal microparticles, metal nanoparticles, metal oxides, metal oxide microparticles, metal oxide nanoparticles, or combinations thereof.

7. The electrode according to claim 6, wherein the conductive porous gas diffusion layer comprises a macroporous layer and a microporous layer, the microporous layer being disposed between the macroporous layer and the at least one catalyst layer.

8. The electrode according to claim 7, wherein the macroporous layer is carbon cloth or carbon paper.

9. The electrode according to any one of claims 7 or 8, wherein the microporous layer comprises a mixture of carbon and a hydrophobic material.

10. The electrode according to any one of claims 2 to 9, wherein the hydrophobic material is a hydrophobic resin selected from polytetrafluoroethylene (PTFE) and perfluorosulfonic acid (PFSA) polymers.

11. An electrochemical cell comprising an anode chamber, a cathode chamber, and a partition disposed between the anode chamber and the cathode chamber, wherein at least one of the anode chamber and the cathode chamber comprises a gas diffusion electrode according to any one of claims 1 to 10.

12. A method for manufacturing a gas diffusion electrode, comprising the following steps: a) Catalyst ink is prepared by dispersing a catalyst material in a first solvent, wherein the catalyst ink does not contain any ionomers; b) Ionomer-based ink is prepared by dispersing the ionomer in a second solvent, wherein the ionomer-based ink does not contain any catalyst; c) Prepare a conductive porous gas diffusion layer; d) Coating the conductive porous gas diffusion layer with the catalyst ink to form a catalyst layer; e) Dry and / or heat-treat the catalyst layer to fix the catalyst material onto the gas diffusion layer; and f) Coating the catalyst layer with the ionomer-based ink.

13. The method of claim 12, wherein step e) comprises baking the assembly of the porous gas diffusion layer and the catalyst layer at a temperature of 170°C to 350°C for 10 minutes to 24 hours.

14. The method according to any one of claims 13 or 12, wherein in step c), the preparation of the conductive porous gas diffusion layer comprises the following sub-steps: c1) providing a macroporous layer, c2) providing carbon-based ink, c3) depositing the carbon-based ink on the macroporous layer to form a microporous layer, and optionally, c4) baking the components of the macroporous layer and the microporous layer in air at a temperature of 170°C to 350°C for 10 minutes to 24 hours.

15. The method according to any one of claims 12 to 14, wherein in step f), the ionomer-based ink is deposited on the catalyst layer by spraying.

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