A method for preparing high performance metal porous electrodes

Abstract

This invention relates to a method for preparing a porous electrode, comprising: preparing a slurry comprising a solvent, a polymer binder material comprising, by weight, between 1% and 25% of a polymer binder material, and by weight, between 10% and 80% of particles comprising an electrochemically active material, wherein the polymer binder material is at least partially dissolved in the solvent; applying the slurry onto a porous conductive support; and subjecting the slurry comprising the coated support to a phase transformation, thereby forming a porous electrode comprising a porous conductive support and a porous composite material comprising a porous matrix, comprising the polymer binder material, and particles comprising an electrochemically active material, wherein the particles are dispersed in the porous matrix, wherein the weight ratio of the polymer binder material to the particles in the slurry is between 2:98 and 50:50, and wherein, based on the total weight of the slurry, the total amount of the polymer binder material and the particles in the slurry is between 32% and 80% by weight. The invention further relates to a porous electrode comprising a porous conductive support and a porous composite material, the porous composite material comprising a porous matrix comprising the polymer binder material and particles comprising an electrochemically active material.

Description

Technical Field

[0001] This invention relates to a method for preparing porous electrodes, particularly porous electrodes comprising a porous conductive support and an electrochemically active material. The invention further relates to a porous electrode, particularly one obtained by the method of this invention. Background Technology

[0002] Water electrolysis is an electrochemical process that involves splitting water into its constituent elements (hydrogen and oxygen) using an external electrical energy source. It is a promising technology with a wide range of applications, including hydrogen production for clean fuels, energy storage, and industrial processes. Water electrolysis plays a crucial role in the development of sustainable energy solutions. As a clean and renewable method, it can produce hydrogen, a versatile energy support that can be used in fuel cells and industrial processes, and as a clean transportation fuel. When combined with renewable energy sources such as solar and wind, water electrolysis offers an effective method for energy storage and grid balancing, addressing the intermittency of renewable energy sources.

[0003] Electrolysis takes place in an electrolytic cell. The electrolytic cell consists of a membrane immersed in the electrolyte, an anode, and a cathode. When an electric current is applied through an external power source, a chemical reaction occurs at the electrodes.

[0004] There are two main types of electrolytes: solid electrolytes and liquid electrolyte solutions. Known solid electrolytes include proton exchange membranes, anion exchange membranes, and solid oxide ceramic electrolytes. Known liquid electrolytes include alkaline aqueous solutions and acidic aqueous solutions.

[0005] In proton exchange membrane electrolysis, a proton exchange membrane (PEM) separates the anode and cathode chambers and conducts protons. PEM electrolysis has become important due to its ability to operate at relatively low temperatures and pressures. PEM electrolysis technology offers fast response times, high efficiency, and good controllability. However, its reliance on expensive platinum-based catalysts presents a cost challenge for widespread adoption.

[0006] Solid oxide ceramic electrolytes are used in solid oxide electrolyzers (SOECs) that operate at high temperatures. High-temperature operation allows for efficient thermal integration with other industrial processes. However, SOECs require robust materials capable of withstanding these high temperatures.

[0007] In acidic electrolysis, an aqueous solution containing strong acids such as sulfuric acid and hydrochloric acid is used as the electrolyte. However, managing concentrated acid electrolytes causes corrosion problems, and these techniques are expensive.

[0008] In alkaline electrolysis, an aqueous solution containing a strongly alkaline electrolyte such as potassium hydroxide is used. Alkaline electrolysis is one of the earliest and most mature electrolysis technologies. It typically operates at relatively high temperatures (60-90°C) and pressures up to 30 bar. Currently, commonly used electrodes include nickel-based and iron-based electrodes. This method is characterized by its relatively low capital cost, long-term stability, and scalability, making it suitable for large-scale hydrogen production.

[0009] Commercially available electrodes used in industrial alkaline electrolysis systems for electrolytic cells include nickel-based electrodes deposited on steel, such as nickel-coated steel mesh, and solid nickel, such as stretched nickel metal, nickel wire mesh, and nickel foam. However, these electrodes tend to have limited catalytic activity, i.e., limited conversion rates of water to hydrogen and oxygen at a given power input, and are often rigid and / or brittle.

[0010] "Self-supported micron-scale thin nanomesh electrode for high-throughput electrochemical applications, achieving over 100-fold current density enhancement" Freestanding μm-thin nanomesh electrodes exceeding 100x current density enhancement for high-throughput electrochemical applications "(N. Plankensteiner, R. Rupp et al., Materials Today Energy, vol. 30, 2022, 101172) discloses a method for fabricating a self-supporting metal electrode with a thickness of only a few micrometers for water electrolysis. The electrode is a three-dimensional (3D) porous nanomesh composed of a regular 3D network of interconnected nanowires. This nanomesh has a high surface area and a high porosity between 85% and 97%. A porous support structure is required to ensure the mechanical stability of the nanowire network while maintaining its accessibility from all sides to allow for the transport of water and gas."

[0011] The water splitting performance of nickel electrodes can be improved by optimizing the pore structure using a phase transformation method. Improving the water splitting performance of nickel electrodes by optimizing their pores structure using a phase inversion method Ruigen Ding, Shengsheng Cui et al., Catalyst Science & Technology, issue 14 2017, disclose a method for preparing a porous nickel electrode, including phase inversion and casting processes, followed by heat treatment to remove polymers. The nickel electrode comprises finger-like straight open pores with an average diameter of approximately 100 μm and smaller pores in the wall with an average diameter between 1 μm and 3 μm. This electrode can be used for the oxygen evolution reaction (OER) and for the hydrogen evolution reaction (HER).

[0012] The disadvantages of the aforementioned porous nanomesh electrodes are that they are fragile, which limits their use; and that the pores in the electrodes obtained by the phase inversion method are large, with high internal resistance and therefore low electrochemical activity.

[0013] The problem with today's highly porous (metallic) electrodes is that they have a small electrochemical surface area for electrochemical reactions. Most research aims to coat or grow catalyst layers on top of porous electrodes. However, such catalyst layers are known to have poor adhesion to porous electrodes, thus limiting the long-term stability and durability of these electrodes in electrolyzers, and consequently limiting the lifespan of the electrolyzers. Summary of the Invention

[0014] The present invention aims to overcome one or more of the aforementioned disadvantages. An object of the present invention is to provide a method for obtaining porous electrodes, particularly porous electrodes comprising a porous matrix containing a polymer binder material and particles containing electrochemically active materials, which is relatively uncomplicated. A further object is to provide a method for producing such porous electrodes at a lower cost than existing methods.

[0015] Another object of the present invention is to provide a porous electrode, particularly a porous electrode comprising a porous matrix containing a polymer binder material and particles containing electrochemically active materials, which exhibits superior stability and durability compared to existing porous electrodes. A further object is to provide a porous electrode that exhibits excellent electrochemical performance and efficiency, excellent mass transfer characteristics, ion diffusion, and / or lifetime during use.

[0016] According to a first aspect of the invention, a method for producing a porous electrode as set forth in the appended claims is provided.

[0017] The porous electrode produced by this method comprises a porous conductive support and a porous composite material, or is substantially composed of a porous conductive support and a porous composite material. The porous composite material comprises a porous matrix and particles, or is substantially composed of a porous matrix and particles, wherein the particles comprise or are substantially composed of electrochemically active materials. The porous matrix comprises or is substantially composed of a polymer binder material. Particles comprising or substantially composed of electrochemically active materials are dispersed (i.e., embedded) within the porous matrix. In other words, the porous matrix comprises a polymer binder material and particles comprising or substantially composed of electrochemically active materials, wherein the electrochemically active materials are dispersed within the porous matrix.

[0018] The method includes preparing a slurry, applying the slurry to a porous conductive support, and subjecting the slurry-coated support containing the slurry to a phase transformation to obtain the porous electrode.

[0019] The slurry comprises or is substantially composed of a solvent, a polymer binder material, particles comprising or substantially composed of electrochemically active materials, and optionally a pore-forming agent.

[0020] Pore-forming agents are known in the art as materials added to a system (e.g., a slurry) to create pores within the final product. According to this disclosure, a pore-forming agent is a reagent that functions by being removed during the manufacturing process, thereby leaving voids that form pores in their locations. It will therefore be understood that the optional use of a pore-forming agent in the slurry depends on the composition of the slurry, the structure of the slurry components, and the porosity of the porous electrode to be obtained or achieved.

[0021] According to an embodiment, the slurry is substantially composed of a solvent, a polymer binder material, particles comprising or substantially composed of electrochemically active materials, and optionally a pore-forming agent. Therefore, the porous electrode prepared from this slurry comprises a porous conductive support and a porous composite material, the latter comprising a porous matrix, which is composed of a polymer binder material and particles comprising or substantially composed of electrochemically active materials. The particles comprising or substantially composed of electrochemically active materials are advantageously dispersed in the porous matrix, i.e., dispersed in the polymer binder material.

[0022] Advantageously, the polymeric adhesive material is at least partially, preferably substantially entirely, dissolved in the solvent, for example, at least 50% of the polymeric adhesive material is dissolved in the solvent, such as at least 75%, at least 80%, preferably at least 90%, more preferably at least 95%, at least 98%, most preferably at least 99%, or 100%.

[0023] Based on the total weight of the slurry, the total amount of polymer binder material and particles in the slurry is between 32% and 80% by weight, preferably between 35% and 75% by weight, and more preferably between 35% and 70% by weight.

[0024] The weight ratio of polymer binder material to particles in the slurry is 2:98-50:50, preferably 5:95-50:50, more preferably 10:90-50:50, and even more preferably 20:80-50:50, such as 30:70-50:50 or 40:60-50:50.

[0025] Advantageously, the polymeric adhesive material comprises or is substantially composed of a nonionic conductive polymer. Non-limiting examples of nonionic conductive polymers include polysulfone (PSU), polyethersulfone, polyvinylidene fluoride, poly(acrylonitrile), polyethylene-co-vinyl alcohol, polycarbonate, polyimide, polyamide, polyamide-imide, polyetherimide, polyetheretherketone, cellulose acetate, and copolymers of two or more thereof.

[0026] Advantageously, based on the total weight of the slurry, the slurry contains between 1% and 25% by weight of polymeric binder material, preferably between 1% and 20% by weight.

[0027] Advantageously, based on the total weight of the slurry, the slurry comprises between 10% and 80% by weight particles, which consist of or are substantially composed of an electrochemically active metal, preferably between 15% and 75% by weight, more preferably between 15% and 70% by weight.

[0028] As used herein, the terms "electrochemically active metal" or "electrochemically active material" refer to the ability of a material (including, but not limited to, solid metals, metal oxides, or metal dichalcogenides) to participate in electrochemical reactions in which electrons are exchanged between chemical substances. Therefore, electrochemically active materials directly participate in electrochemical reactions and are thus not inert to them. In other words, in this disclosure, the electrochemically active material differs from known conductive compounds or additives that are inert to electrochemical reactions. Advantageously, the slurry and porous electrode are substantially free of conductive compounds or additives.

[0029] Advantageously, the electrochemically active material comprises or is substantially composed of an electrochemically active metal selected from nickel, silver, tin, copper, iron, manganese, cobalt, zinc, titanium, bismuth, selenium, and noble metals.

[0030] Advantageously, the electrochemically active material (especially the electrochemically active metal) exists in the particles in the form of one or a combination of metal solids, metal oxides or metal dichalcogenides.

[0031] Advantageously, these particles have an average particle size between 1 nm and 250 µm, preferably between 5 nm and 200 µm, and more preferably between 10 nm and 100 µm. The average particle size can be determined using any method known to those skilled in the art, including, for example, laser diffraction or electron microscopy such as scanning electron microscopy (SEM). Laser diffraction is advantageously performed according to standard ASTM B822-20 (2020). Particle size determined by SEM includes calculating the particle size from an SEM image (advantageously via a software application such as ImageJ) and calculating the average particle size therefrom. According to this disclosure, the particle size refers to the size of the particles before they are added to the slurry, i.e., the so-called starting particles.

[0032] Advantageously, particles comprising or substantially composed of electrochemically active materials have a multi-peaked, particularly bi-peaked, particle size distribution. A multi-peaked particle size distribution means that portions of the (average) particle size with different ranges are used to fabricate porous electrodes using methods as disclosed herein.

[0033] For example, in the case of a bimodal particle size distribution, one group of particles has a size within a first size range (e.g., the micrometer range), and the second group of particles has a size within a second size range (e.g., the nanometer range). While these nanoparticles offer a high electrochemically active surface area, they are more expensive. Larger particles in the micrometer range ensure good electrochemical contact and percolation and are less expensive. Therefore, combining nanoparticles with particles in the micrometer range (i.e., particles with a bimodal particle size distribution) allows for the combination of the advantages of both size ranges of particles and allows for cost reduction when using nanoparticles alone.

[0034] Advantageously, the particles comprising or substantially composed of the electrochemically active material have a bimodal particle size distribution. Advantageously, 25% to 75% of the particles have a size between 1 µm and 250 µm, preferably between 5 µm and 200 µm, more preferably between 5 µm and 150 µm, and 75% to 25% of the particles have a size between 1 nm and 750 nm, preferably between 5 nm and 500 nm, more preferably between 10 nm and 250 nm, as measured above. In other words, these particles consist of a mixture of fine and coarse portions, wherein: the fine portion has an average particle size between 5 nm and 500 nm (as measured above) and the coarse portion has an average particle size between 1 µm and 250 µm (as measured above), wherein the fine portion constitutes between 25% and 75% of these particles by weight and the coarse portion constitutes between 25% and 75% by weight.

[0035] Advantageously, at an atmospheric pressure of 1 bar, the solvent has a boiling point of at least 175°C, preferably at least 180°C, such as at least 190°C.

[0036] Advantageously, when the slurry includes a pore-forming agent, it includes between 0.5% and 15% by weight of the pore-forming agent, preferably between 1% and 10% by weight, based on the total weight of the slurry.

[0037] The inventors have discovered that when the slurry contains between 1% and 10% by weight of pore-forming material based on the total weight of the slurry, pore formation is significantly promoted, with a particular increase in the porosity of the porous matrix.

[0038] Advantageously, when the slurry includes a pore-forming agent, the pore-forming agent is at least partially, preferably substantially completely, dissolved in the solvent, for example, at least 50% of the pore-forming agent is dissolved in the solvent, for example, at least 75%, at least 80%, preferably at least 90%, more preferably at least 95%, at least 98%, most preferably at least 99%, or 100%.

[0039] Advantageously, when the slurry includes a pore-forming agent, the pore-forming agent is at least partially, preferably substantially completely, dissolved in the solvent, for example, at least 50% of the pore-forming agent is dissolved in the solvent, for example, at least 75%, at least 80%, preferably at least 90%, more preferably at least 95%, at least 98%, most preferably at least 99%, or 100%.

[0040] Advantageously, the porous conductive support comprises or is substantially composed of one or more of the following: nickel, silver, gold, aluminum, tungsten, zinc, lithium, iron, platinum, tin, titanium, manganese, and stainless steel, with nickel, aluminum, zinc, iron, and stainless steel being preferred. A particularly preferred electrochemically active metal is nickel. Advantageously, the electrochemically active material exists in the particles as one or a combination of a metal solid, a metal oxide, or a metal dichalcogenide (e.g., a selenide or a sulfide). Non-limiting examples include ZnO, BiSe, CuS, CuO, and (Cu,Ag)O. x S y .

[0041] Advantageously, the slurry is applied by applying it to the porous conductive support structure. Alternatively or additionally, it is also advantageous to apply the slurry by impregnating the porous conductive support with the slurry.

[0042] Advantageously, the phase transformation of the slurry comprising a coated support (i.e., a support on which the slurry is applied) involves exposing the slurry to a non-solvent for the polymer binder material, for example, by contacting it with the non-solvent. This causes the slurry to separate into a polymer binder material-enriched phase and a polymer binder material-depleted phase. Upon further separation, the solubility of the polymer binder material in the solvent decreases and the polymer binder material precipitates, thereby forming a solid phase with a specific porous morphology, thus obtaining a porous electrode comprising or substantially consisting of a porous conductive support and a porous matrix, the porous matrix comprising the polymer binder material and particles comprising or substantially consisting of electrochemically active materials.

[0043] Advantageously, the contact between the green body and the non-solvent-free material for the polymer binder lasts for a duration between 5 minutes and 24 hours, preferably between 10 minutes and 4 hours, and more preferably between 30 minutes and 1 hour.

[0044] Advantageously, the solvent includes a polar aprotic solvent and the non-solvent used in the polymeric adhesive material includes a polar protic solvent. These solvents are well known to those skilled in the art, and in this specification, the term "polar solvent" refers to a solvent that favors ion formation (as defined in the Encyclopædia Britannica). More specifically, a polar solvent refers to a liquid (solvent) whose dielectric constant is sufficiently high to dissolve an electrolyte ('Polar Solvents', Fawcett, W. Ronald, Liquids, Solutions, and Interfaces: From Classical Macroscopic Descriptions to Modern Microscopic Details (Abstract of New York, 2004; online edn, Oxford Academic, 12 Nov. 2020).

[0045] According to a second aspect of the invention, a porous electrode as set forth in the appended claims is provided.

[0046] The porous electrode is advantageously manufactured by a method according to the first aspect of the invention, i.e., preparation, production or manufacturing.

[0047] The porous electrode comprises a porous conductive support and a porous composite material, or is substantially composed of a porous conductive support and a porous composite material. The porous composite material comprises a porous matrix and particles, or is substantially composed of a porous matrix and particles, wherein the particles comprise or are substantially composed of electrochemically active materials. The porous matrix comprises or is substantially composed of a polymer binder material. Particles comprising or substantially composed of electrochemically active materials are dispersed (i.e., embedded) within the porous matrix. In other words, the porous matrix comprises a polymer binder material and particles comprising or substantially composed of electrochemically active materials, wherein the electrochemically active materials are dispersed within the porous matrix.

[0048] Advantageously, the porous conductive support, polymer binder material, and particles containing electrochemically active materials are as described above.

[0049] The porous composite material comprises, by weight, between 2% and 50%, preferably between 2% and 45%, and more preferably between 5% and 40% of a polymeric binder, measured by thermogravimetric analysis (TGA), specifically according to test standard ASTM E1131, based on the total weight of the porous composite material.

[0050] The porous composite material further comprises particles, by weight, between 50% and 98%, preferably between 55% and 98%, more preferably between 60% and 95%, based on the total weight of the porous composite material, as measured by thermogravimetric analysis (TGA), particularly according to test standard ASTM E1131.

[0051] The porous electrode has a porosity equal to or greater than 40%, preferably at least 50%, and more preferably at least 60%, wherein the porosity is measured by a mercury porosimetry method. Advantageously, the porous electrode has a porosity between 40% and 85%, preferably between 50% and 80%, and more preferably between 60% and 80%.

[0052] Advantageously, the pores of the porous electrode have an average pore diameter between 0.05 µm and 5 µm, preferably between 0.075 µm and 2.5 µm, and more preferably between 0.1 µm and 1 µm, as determined by capillary flow porosity measurement.

[0053] Advantageously, the porous electrode exhibits non-in-situ gas permeability, particularly wherein the gas used in the testing process is air, i.e., non-in-situ air permeability between 0.50 L / min / cm² / bar and 50 L / min / cm² / bar, preferably between 0.60 L / min / cm² / bar and 30 L / min / cm² / bar, and more preferably between 0.70 L / min / cm² / bar and 30 L / min / cm² / bar. According to this disclosure, the terms "non-in-situ air permeability," "air permeability," "non-in-situ air permeability," and "air permeability" are used interchangeably.

[0054] According to a third aspect of the invention, a water electrolyzer as set forth in the appended claims is provided. The water electrolyzer comprises a porous electrode according to a second aspect of the invention, or a porous electrode obtained by the method according to a first aspect of the invention.

[0055] According to another aspect of the invention, a membrane electrode assembly (MEA) as set forth in the appended claims is provided. The MEA comprises a porous electrode according to a second aspect of the invention, or a porous electrode obtained by a method according to a first aspect of the invention. It should be understood that the MEA also comprises other components known in the art, such as a membrane. The MEA can be manufactured using one or more porous electrodes of the invention by methods known in the art.

[0056] Another aspect of the invention provides the use of a porous electrode according to a second aspect of the invention, or a porous electrode obtained by a method according to a first aspect of the invention, in a water electrolyzer or membrane electrode assembly. Attached Figure Description

[0057] Aspects of the invention will now be described in more detail with reference to the accompanying drawings, wherein like reference numerals indicate like features, and wherein: Figure 1 The method according to the invention is illustrated schematically.

[0058] Figure 2A and Figure 2B SEM images of the top surfaces of two different porous electrodes obtained using the method of the present invention are shown.

[0059] Figure 3 This demonstrates the hydrogen evolution reaction (HER) at 1 M KOH, room temperature, and a scan rate of 2 mV / sec for two reference electrodes and four electrodes obtained using the method of this invention.

[0060] Figure 4 The oxygen evolution reaction (OER) of two reference electrodes and four electrodes obtained by the method of the present invention is shown at 1M KOH, room temperature and 2mV / sec scan rate.

[0061] Figure 5 The OER overpotential for two reference electrodes and four electrodes obtained by the method of the present invention is shown under different conditions at 1M KOH, room temperature and 2 mV / sec scan rate.

[0062] Figure 6 The alkaline water electrolysis performance of two reference electrodes and two porous electrodes of the present invention under ambient conditions is shown.

[0063] Figure 7 The alkaline water electrolysis performance of two reference electrodes and one porous electrode of the present invention under high temperature and pressure is shown.

[0064] Figure 8 The durability of the porous electrode of the present invention in alkaline water electrolysis at 80°C and 10 bar is demonstrated. Detailed Implementation

[0065] Figure 1 The diagram schematically illustrates a method 1 for manufacturing a porous electrode according to the present invention, wherein the porous electrode comprises a porous conductive support and a porous matrix, the porous matrix comprising a polymer binder material and particles comprising an electrochemically active material.

[0066] Method 1 includes steps 2 (preparing a slurry), 3 (applying the slurry to or impregnating the porous conductive support), and 4 (substituting the slurry on the coated support for a phase transformation). Step 4 aims to cure the slurry, thereby forming a porous electrode according to the invention. Method 1 may further optionally include steps 5 (drying the porous electrode) and / or one or more post-processing steps 6.

[0067] Advantageously, the porous conductive support provides mechanical support for the porous electrode. Alternatively or additionally, it is also advantageous that the porous conductive support is a current collector for the porous electrode. The porous conductive support advantageously has at least 10 at 20°C. -5 Conductivity in S / m.

[0068] Advantageously, the porous conductive support comprises or is substantially composed of one or more of nickel, silver, gold, aluminum, tungsten, zinc, lithium, iron, platinum, tin, titanium, manganese, and stainless steel (e.g., alloys). Preferably, the porous conductive support comprises or is substantially composed of nickel, silver, gold, aluminum, iron, stainless steel, and combinations of two or more thereof, more preferably nickel.

[0069] Advantageously, the porous conductive support has a porosity of at least 50%, preferably at least 60%, more preferably at least 75%, and most preferably at least 90%, as measured by mercury porosity determination. Advantageously, the pores in the porous conductive support are macropores.

[0070] The porous conductive support can have any three-dimensional (3D) structure that provides the porosity described above. Non-limiting shapes include foams, particularly open-cell foams, meshes, grids, woven structures, non-woven structures, knitted structures (e.g., knitted nets or springs), crocheted structures, and braided structures.

[0071] The slurry comprises or is substantially composed of a polymeric binder material in a solvent and particles comprising or are substantially composed of electrochemically active materials. Advantageously, the polymeric binder material is substantially completely dissolved in the solvent.

[0072] Advantageously, the slurry is substantially free of non-solvents, such as polymer binder materials. The inventors have discovered that when the slurry is substantially free of (i.e., does not contain) non-solvents, a phase inversion reaction does not initiate before the slurry is applied to the porous conductive support. This allows for better control over the phase inversion and the resulting porosity and structure of the porous electrode obtained by the method of the present invention.

[0073] Advantageously, based on the total weight of the slurry, the slurry contains between 1% and 25% by weight of polymeric binder material, preferably between 1% and 20% by weight.

[0074] Advantageously, the polymeric adhesive material comprises or is substantially composed of a phase inversion polymer (i.e., a polymer suitable for undergoing phase inversion). Examples of suitable polymeric adhesive materials (phase inversion polymers) include polysulfone, polyethersulfone, polyvinylidene fluoride, poly(acrylonitrile), polyethylene-co-vinyl alcohol, polycarbonate, polyimide, polyamide, polyamide-imide, polyetherimide, polyetheretherketone, cellulose acetate, and copolymers of two or more thereof.

[0075] Advantageously, the polymeric adhesive material has an average molecular weight of at least 10,000 g / mol, preferably at least 20,000 g / mol, more preferably at least 25,000 g / mol, and most preferably at least 30,000 g / mol.

[0076] Polymer binder materials may comprise or consist substantially of inert (i.e., non-conductive) phase inversion polymers, conductive phase inversion polymers, or copolymers comprising a combination of both. When a polymer binder material comprises or consists substantially of a conductive phase inversion polymer, it can contribute to the conductivity of the porous electrode. Non-limiting examples of suitable conductive phase inversion polymers include polypyrrole (PPy), polyaniline (PAni), polythiophene (PTh), and poly(3,4-ethylenedioxythiophene) (PEDOT). Advantageously, PEDOT is combined with another polymer, such as polystyrene sulfonate (PSS), as a phase inversion polymer.

[0077] Advantageously, based on the total weight of the slurry, the slurry contains 2% to 98% by weight particles containing electrochemically active material, preferably 10% to 80% by weight, more preferably 15% to 70% by weight, and even more preferably 50% to 98% by weight. The inventors have found that for slurries containing less than 10% by weight of such particles, the metal loading in the resulting porous electrode is insufficient to provide the porous electrode with adequate electrochemical activity and / or sufficient electrical connections between these particles. In other words, slurries containing less than 10% by weight of particles result in porous electrodes with poor properties.

[0078] Advantageously, particles that contain or are substantially composed of electrochemically active materials are selected such that they do not react with the solvent.

[0079] Advantageously, the electrochemically active material substantially comprises an electrochemically active metal selected from nickel, silver, tin, copper, iron, manganese, cobalt, zinc, titanium, bismuth, selenium, and noble metals. A particularly preferred electrochemically active metal is nickel. Advantageously, the electrochemically active material (especially the electrochemically active metal) exists in the particles as one or a combination of a metal solid, a metal oxide, or a metal dichalcogenide (e.g., a selenide or a sulfide). Non-limiting examples include ZnO, BiSe, CuS, CuO, and (Cu,Ag)OxSy.

[0080] Advantageously, the particles comprise two or more electrochemically active materials, for example, in the form of core-shell particles, clusters on particles, stable single atoms on particles, and particles with a layered structure. The particles can have various shapes, such as, but not limited to, spherical or cylindrical (e.g., filaments or rods). The slurry can include particles of various shapes.

[0081] Advantageously, these particles have a bimodal particle size distribution. Advantageously, the bimodal particle size distribution is obtained by mixing fine and coarse particles. These fine particles advantageously have an average size of less than 1 µm, such as less than 750 nm, preferably less than 500 nm (i.e., nanoparticles classified according to IUPAC). These coarse particles advantageously have an average size of at least 1 µm, for example 5 µm or greater.

[0082] Advantageously, the bimodal particle size distribution includes particles between 25% and 75%, preferably between 40% and 60%, such as about 50%, having a size between 1 µm and 250 µm, preferably between 5 µm and 200 µm, more preferably between 5 µm and 150 µm; and particles between 75% and 25%, preferably between 60% and 40%, such as about 50%, having a size between 1 nm and 750 nm, preferably between 5 nm and 500 nm, more preferably between 10 nm and 250 nm. Particle size is measured by laser diffraction or scanning electron microscopy (SEM). For non-spherical particles, when using SEM, the particle size used to calculate the average particle size is advantageously the maximum size of the corresponding particle as seen in the SEM image, or when using laser diffraction, the maximum size of the corresponding particle. According to this disclosure, the particle size refers to the size of the particles before they are added to the slurry, i.e., the so-called starting particles.

[0083] The inventors have unexpectedly discovered that, compared to porous electrodes containing only fine particles or only coarse particles, the use of particles with a bimodal particle size distribution (and particularly those obtained by a mixture of fine and coarse particles) allows for the acquisition of porous electrodes with increased electrochemical active surface area and excellent electrical connectivity.

[0084] Advantageously, based on the total weight of the slurry, the slurry contains a solvent at a weight of between 10% and 68%, preferably between 15% and 60%, more preferably between 20% and 55%, and most preferably between 20% and 50%.

[0085] Advantageously, the solvent comprises or is substantially composed of dialkyl carbonate, alicyclic ether, liquid pyrrolidone, aliphatic ketone, or liquid piperidine, or combinations thereof.

[0086] Dialkyl carbonates can be straight-chain or branched. Non-limiting examples of dialkyl carbonates include ethylene carbonate, propylene carbonate, diethyl carbonate, diallyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, methyl isobutyl carbonate, methyl pentyl carbonate, and methyl hexyl carbonate.

[0087] Non-limiting examples of alicyclic ethers include ethylene oxide, tetrahydrofuran, dioxane, dioxolane, and dioxane-heptane.

[0088] Non-limiting examples of liquid pyrrolidones include N-methylpyrrolidone (NMP), N-ethylpyrrolidone (NEP), and 2-pyrrolidone.

[0089] Non-limiting examples of aliphatic ketones include acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl sec-butyl ketone, and methyl tert-butyl ketone.

[0090] Non-limiting examples of liquid piperidine include formylpiperidine, N-methylpiperidine, N-ethylpiperidine, and N-propylpiperidine.

[0091] Advantageously, the solvent is a non-volatile solvent. A non-volatile solvent is defined as a solvent having a boiling point of at least 150°C, preferably at least 175°C, and more preferably at least 180°C at 1 bar atmospheric pressure. By using a non-volatile solvent, solvent evaporation during the slurry preparation and application steps is avoided. Therefore, pores are formed in a controlled manner during phase inversion, allowing control over the (average) pore size and porosity of the obtained porous electrode. Consequently, the obtained porous electrode has higher porosity compared to using solvents with lower boiling points (e.g., boiling points below 100°C at 1 bar atmospheric pressure) (i.e., volatile solvents). In this case, the solvent has already evaporated during slurry formation and application to the support, and the amount of polymer binder increases uncontrollably, resulting in a matrix with fewer pores.

[0092] Examples of nonvolatile solvents include NMP, NEP, acetamide, dimethyl sulfoxide (DMSO), formylpiperidine, ε-caprolactam, γ-butyrolactone, ethylene carbonate, propylene carbonate, methyl butyl carbonate, methyl isobutyl carbonate, methyl pentyl carbonate, methyl hexyl carbonate, 2-pyrrolidone, N-methylpiperidine, N-ethylpiperidine, N-propylpiperidine, γ-pentylactone, ε-caprolactone, and δ-decylactone.

[0093] The inventors have unexpectedly discovered that, provided the weight ratio of polymer binder material to particles in the slurry is between 2:98 and 50:50, and the slurry contains between 32% and 80% by weight of polymer binder material and particles based on the total weight of the slurry, the porous electrode obtained by the method of this disclosure exhibits improved electrochemical properties, particularly improved electrochemical activity in alkaline water electrolysis. The electrode thus obtained can be used as both an anode and cathode and is suitable for alkaline water electrolysis. The porous electrode of this invention exhibits better electrochemical performance in alkaline water electrolysis, CO2 reduction, fuel cells, and battery packs. It can have a wider range of applications than commercially available reference electrodes.

[0094] The inventors have discovered that when the weight ratio of the polymer binder material to the particles in the slurry is outside the range described above and the slurry comprises less than 32% by weight of the polymer binder material and particles based on the total weight of the slurry, the porous electrode obtained from the slurry does not have sufficient electrochemically active material to serve as a suitable electrode.

[0095] The slurry may contain additional additives, such as a pore-forming agent.

[0096] Advantageously, the slurry includes up to 10% by weight of a pore-forming agent based on the total weight of the slurry, such as 7.5% or 5% by weight. A particularly preferred pore-forming agent is polyvinylpyrrolidone (PVP).

[0097] The slurry can be prepared by methods known in the art.

[0098] According to a first embodiment, a first mixture is prepared by dissolving a polymeric adhesive material in a first portion of a solvent. A second mixture is prepared by adding particles to the remaining solvent. The first solution is then added to the second mixture, or vice versa, to obtain a slurry. If present, a pore-forming agent is advantageously added to the second mixture.

[0099] According to the second embodiment, a polymeric adhesive material and particles, and a pore-forming agent, if present, are added simultaneously or sequentially to a solvent to obtain a slurry.

[0100] Operation 3 involves applying slurry to a porous conductive support using procedures or techniques known in the art. Advantageously, the slurry is applied to one or both sides of the porous conductive support (i.e., two opposite sides).

[0101] Advantageously, the porous conductive support is coated or impregnated with a slurry. Applying or impregnating the porous conductive support with a slurry can be achieved by one or more of the following: pouring the slurry onto the top of the support, immersing the support in the slurry, pulling the support through the slurry, spraying, dipping, casting (e.g., using a casting knife), doctor blade coating, induction, pressing, spin coating, filtration, vacuum deposition, and lamination. It should be understood that the coating or impregnation method is selected depending on whether the slurry is applied to one or both sides of the porous conductive support. It should also be understood that one side of the porous conductive support can be masked before applying the slurry to prevent slurry from being applied to it. For example, a doctor blade is particularly suitable for applying slurry to one side of the porous conductive support, and if necessary, the slurry can be repeatedly applied to the opposite (second) side.

[0102] Advantageously, the slurry is applied to the porous conductive support by impregnating the support with the slurry, because the inventors have found that impregnation produces optimal performance.

[0103] Advantageously, the slurry is applied to a thickness between 1 nm and 5 mm, preferably between 1 µm and 2 mm, for example between 10 µm and 1 mm, preferably between 10 µm and 500 µm, and particularly between 50 µm and 200 µm. The thickness of the applied slurry can be measured using a micrometer. The thickness of the applied slurry can vary from one region of the porous conductive support to another.

[0104] Then, in operation 4, the slurry containing the porous conductive support (e.g., a coated and / or impregnated porous conductive support) is subjected to a phase transformation, thereby converting the dissolved polymer binder material into a porous, cured form. In other words, the phase transformation induces pores in the resulting electrode. The phase transformation can be performed by methods known in the art.

[0105] Preferred phase inversion methods include liquid-induced phase inversion (LIPS), vapor-induced phase inversion (VIPS), or a combination of LIPS and VIPS. The liquid and vapor (which may be the same or different compounds) are non-solvents for the polymer binder material. Therefore, in operation 4, the coated / impregnated porous conductive support is contacted with a non-solvent (which may be a liquid phase and / or a gas phase) for the polymer binder material. This results in the stratification of the applied slurry in a phase rich in polymer binder material and a phase poor in polymer binder material. Upon further separation, the solubility of the solvent further decreases, and the polymer binder material precipitates, thereby obtaining a matrix containing polymer binder material in which particles of electrochemically active material are dispersed.

[0106] Advantageously, the non-solvent comprises or substantially constitutes a polar protic solvent. Non-limiting examples of non-solvents suitable for the polymeric adhesive materials of the present invention include water, alcohols, acids, or combinations thereof. Particularly preferred non-solvents include water and mixtures of NMP and water, for example having a volume ratio of NMP to water between 0:100 (100% water) and 75:25 (e.g., 50:50).

[0107] Advantageously, the phase transformation is induced by immersing the coated / impregnated support in the non-solvent and / or by contacting the electrode green body with the vapor of the non-solvent. Alternatively or additionally, it is also advantageous to atomize the non-solvent onto the coated / impregnated support.

[0108] It should be understood that the conditions of the phase inversion method, as well as the selection of polymer binder materials, solvents, optional additives, and non-solvents, contribute to the porosity and pore size of the obtained porous electrode. In other words, phase inversion allows control over the porosity and pore size of the porous electrode.

[0109] Alternatively, phase transformation operation 4 includes a thermally induced phase transformation. A thermally induced phase transformation involves using a solvent in which the polymer dissolves at an elevated temperature, while the polymer is insoluble in the solvent at a lower temperature. A slurry 2 is prepared and applied at an elevated temperature 3. The coated / impregnated porous conductive support is then cooled to a temperature at which the polymer binder material is insoluble in the solvent, thereby causing the polymer binder material to precipitate and obtain a porous electrode.

[0110] The porous electrode structure obtained after phase inversion can also be dried in optional operation 5. Advantageously, optional drying 5 removes any remaining solvent, and if phase inversion 4 is carried out using a non-solvent for polymer binder materials, removes any remaining non-solvent. Advantageously, the porous electrode structure obtained after phase inversion is dried by exposing it to high temperature (heating) and / or reducing pressure.

[0111] Advantageously, the drying operation 5 includes heating the porous electrode structure to a temperature below the maximum continuous operating temperature of the polymer binder material as defined by the Relative Thermal Index (RTI) of Underwriters Laboratories (UL 746B). The maximum continuous operating temperature of the polymer binder material is the maximum acceptable temperature above which the mechanical or electrical properties of the polymer binder material significantly deteriorate over the reasonable lifespan of the porous electrode. Therefore, by heating to a temperature below the maximum continuous operating temperature of the polymer binder material, damage to the polymer binder material in the porous electrode is avoided.

[0112] Optionally, the porous electrode may also undergo one or more additional post-treatment operations 6. Advantageously, during post-treatment operation 6, the contact between particles comprising or substantially composed of electrochemically active materials is improved, thereby improving the conductivity of the porous electrode. Alternatively or additionally, it is also advantageous that the post-treatment improves the immobilization of particles comprising or substantially composed of electrochemically active materials in the porous matrix of the porous electrode, thereby reducing the risk of leaching of the electrochemically active material from the porous electrode. Alternatively or additionally, it is also advantageous that the post-treatment activates the electrochemically active material, for example by known treatment methods, such as passing current or voltage through the electrochemically active material or by heat treatment.

[0113] Advantageously, optional post-treatment operation 6 is carried out at a temperature below the maximum continuous use temperature of the polymer adhesive material as defined by the Relative Thermal Index (RTI) of Underwriters Laboratories (UL746B).

[0114] Non-limiting examples of post-processing operation 6 include electroplating, impregnation, thermal annealing, and pressing / calendering of the porous electrode, for example, using additional components of the electrode, such as electrode active materials and / or current collectors.

[0115] The porous electrode of the present invention comprises a porous conductive support and a porous composite material, or is substantially composed of a porous conductive support and a porous composite material. The porous composite material comprises or is substantially composed of a porous matrix and particles, wherein the porous matrix comprises or is substantially composed of a polymer binder material, and the particles comprise or are substantially composed of an electrochemically active material. Advantageously, the particles are embedded or dispersed within the matrix, thereby forming the porous composite material. The porous conductive support, polymer binder material, and particles are advantageously as described above.

[0116] Based on the total weight of the porous composite material, the porous composite material comprises between 50% and 98% by weight of particles and between 2% and 50% by weight of polymer binder material.

[0117] The porous electrode has a porosity equal to or greater than 40%, preferably at least 50%, more preferably at least 60%, as measured by mercury porosimetry. Advantageously, the porous electrode has a porosity of up to 90%, preferably up to 80%, as measured by mercury porosimetry. A porosity greater than 90% results in insufficient mechanical strength of the porous electrode and is therefore very susceptible to structural damage. It has been found that a porosity below 30% is insufficient to provide adequate accessibility to the electrochemically active material and insufficient to provide sufficiently high liquid and gas transport, i.e., the liquid and gas transport values ​​required for the corresponding application of the porous electrode, such as in a water electrolyzer or membrane electrode assembly.

[0118] The advantages of porous electrodes with porosity between 30% and 90% include, but are not limited to: - Good accessibility of electrochemically active materials; - The high electrochemical surface area of ​​porous electrodes, especially the high volumetric surface area (electrochemical surface area per unit volume of porous electrode), provides more active sites for electrochemical reactions with electrochemically active materials; - Promotes the transport of ions and electrons in porous electrodes, thereby reducing the risk of ohmic loss and mass transfer loss; -Enhanced transport of liquid electrolytes and gaseous products in this porous electrode; - Improved electrochemical performance and durability (lifetime) of porous electrodes; - Uniform distribution of electrochemically active materials in the obtained porous electrode.

[0119] Advantageously, the average pore size of the porous electrode, as determined by capillary flow porosity measurement, is between 0.01 µm and 10 µm, preferably between 0.02 µm and 5 µm, and more preferably between 0.05 µm and 1 µm.

[0120] Advantageously, the micropore volume of the porous electrode is at least 20%, preferably at least 25%, more preferably at least 30%, such as at least 40% or at least 50%, of the micropore volume comprising or substantially composed of electrochemically active material particles, wherein the micropore volume is determined by the t-curve method using an argon isotherm at 87 K. "Micropore volume" refers to the total volume of micropores in an article (e.g., porous electrodes and particles). Porous electrodes having such a micropore volume allow water and other reactants to diffuse into the electrode material and allow gases to diffuse out of the electrode material. Therefore, porous electrodes are suitable for use in water electrolyzers.

[0121] Advantageously, the porous electrode has a thickness of at least 30 µm, such as at least 50 µm, or at least 100 µm, preferably at least 150 µm, more preferably at least 200 µm, and most preferably at least 250 µm. Advantageously, the thickness of the porous electrode is at most 2000 µm, preferably at most 1500 µm, more preferably at most 1000 µm, and most preferably at most 750 µm, for example at most 500 µm.

[0122] Advantageously, the porous electrode has a porosity of 0.001 to 1000 L / (min) as measured by a capillary flow porosity meter. cm² Between 0.01 and 500 L / (min) cm² Between 0.05 and 250 L / (min) cm² Between 0.1 and 100 L / (min) cm² The ratio is between 0.2 and 50 L / (min), more preferably between 0.2 and 50 L / (min). cm² The optimal value is between 0.5 and 25 L / (min) cm² Non-in-situ gas permeability between (bar)

[0123] Example

[0124] Example 1: Fabrication of porous electrodes

[0125] Three reference porous electrodes and five porous electrodes of the present invention were prepared using three different porous conductive support structures: a nickel foam (NI00-FA-000152, Goodfellow) with a thickness of 1.6 mm and a porosity of 95%, a nickel mesh (400 mesh, Heanjia Super Metal Co., Ltd.) with a thickness of 73 µm and a pore size of 30 µm, and a nickel spring (knitted metal mesh, two strands of 0.16 mm diameter nickel 2.4066 wire, Rhodius GmbH i. Ins).

[0126] The three reference porous electrodes consist of three porous conductive support structures (Ni foam, Ni mesh, and Ni spring), and no further treatment is applied to them.

[0127] For the five porous electrodes of the present invention, Ni foam and Ni mesh are used as porous conductive supports. All five porous electrodes of the present invention are prepared from the same slurry, which is applied to one or both sides of the Ni mesh or Ni foam at different thicknesses.

[0128] The slurry was prepared using polysulfone (PSU) as the polymer binder, nickel microparticles (particularly Ni powder with an average particle size of 50 µm) as particles containing electrochemically active materials, NMP as the solvent, and PVP as the pore-forming agent.

[0129] First, 1 g of PSU and 1 g of PVP were dissolved in 5 mL of NMP by centrifuging the mixture at 2000 rpm for 2 minutes using a Thinky planetary centrifuge mixer (Thinky Corporation, USA). Then, 10 g of nickel particles were added and the mixture was centrifuged at 2000 rpm for another 2 minutes. Next, the remaining 9 g of nickel particles were added and the mixture was centrifuged at 2000 rpm for another 2 minutes. Then, 5 mL of NMP was added and the slurry was mixed (centrifuged) again at 2000 rpm for 2 minutes. The resulting slurry was then degassed at 900 rpm for 1.5 minutes.

[0130] The slurry was then applied to one side of the corresponding Ni support for each of the five porous electrodes of the present invention. The slurry was applied by pouring it onto a spatula and spreading it onto the Ni support using the spatula. For a 200 µm thick slurry, spreading was performed at a speed of 0.25 m / min with 200 µm gaps (porous electrodes IE-1, IE-4, and IE-5 in Table 1). For a 50 µm thick slurry, spreading was performed at a speed of 0.25 m / min with 50 µm gaps (porous electrodes IE-2 and IE-3 in Table 1). The slurry-coated Ni supports were then transferred to a coagulation bath containing a solvent-free mixture of NMP and water (50:50) for 30 minutes at room temperature. In the case of electrodes coated on both sides (porous electrodes IE-3 and IE-5), the Ni supports coated on one side were then gently dried with dry air or thin paper to remove water from the sample. The remaining slurry was coated onto the other side in the same manner as described above (same gap, same speed), and the phase inversion step was repeated (for 30 minutes at room temperature in a coagulation bath containing a solvent-free mixture of NMP and water (50:50)). The resulting porous electrodes were then immersed in reverse osmosis (RO) water overnight, followed by heating in water at 80°C for 1 hour to remove any remaining solvent, PVP, or impurities. These electrodes were then stored in plastic containers containing some water (in a wet state) until further characterization.

[0131] All five porous electrodes of the present invention comprise a porous matrix comprising 95% by weight nickel microparticles and 5% by weight PSU, based on the total weight of the porous matrix (i.e., the weight of the porous electrode minus the weight of the Ni support).

[0132] The fourth reference porous electrode (referred to as CE-1) was prepared solely from a slurry without the use of any porous support (Ni mesh, Ni foam, Ni spring). Table 1 summarizes the composition of the reference and the porous electrodes of this invention. This fourth reference electrode was prepared by pouring a slurry onto a scraper and then casting it onto a clean glass plate with a defined gap of 200 µm at a speed of 0.25 m / min. The glass plate with the cast slurry was then placed in a coagulation bath containing 50 / 50 vol.% NMP / water and held at room temperature for 30 minutes to initiate a phase inversion. The resulting porous electrode was then immersed in RO water overnight, followed by heating in water at 80°C for 1 hour to remove any remaining solvent, PVP, or impurities. This reference porous electrode consisted of a porous matrix containing 95% by weight of nickel microparticles and 5% by weight of PSU based on the total weight of the porous matrix (i.e., the porous electrode).

[0133] Table 1: Overview of Porous Electrodes

[0134] The five porous electrodes obtained according to the method of the present invention (IE-1, IE-2, IE-3, IE-4, and IE-5 in Table 1) were then characterized by density (bulk density and apparent density), porosity, average pore size, total cumulative volume (total CV), and total specific surface area (total SSA). Total cumulative volume is a measure of the total pore volume in the electrode. The results are shown in Table 2.

[0135] Porosity, total cumulative volume, and total specific surface area were determined using the mercury porosimetry method. Electrode density was assessed using the helium specific gravity bottle method. Average pore size was determined using capillary flow porosimetry (CFP) with Porolux™ 1000 as a wetting agent.

[0136] Table 2: Density, porosity, average pore size, total cumulative volume, and total specific surface area of ​​various porous electrodes of the present invention.

[0137] The high total cumulative volume (CV) value confirms the porous nature of the prepared electrode. Such a high CV value is expected to play a positive role in enhancing mass transport during water electrolysis operations. By applying (impregnating) the active material within the porous support, the method of this disclosure allows the use of previously unused regions of Ni mesh or Ni foam for the reaction, while maintaining sufficiently high porosity for gas and liquid transport. High stability of these active species has also been observed, as they are well-integrated (impregnated) into the underlying porous material matrix.

[0138] The microstructure of the electrode, including its surface and cross-section, was analyzed using scanning electron microscopy (SEM).

[0139] Figure 2A A SEM image of a cross-section of the porous electrode IE-5 is shown, illustrating Ni foam 10 as a porous conductive support and a porous matrix containing nickel particles 12 and a PSU polymer binder 11.

[0140] Figure 2B A SEM image of the cross-section of the porous electrode IE-1 is shown, illustrating the Ni mesh 20 as a porous conductive support and the porous matrix containing the PSU polymer binder 21 with nickel particles 22.

[0141] A hydrogen cell was constructed using 1 M KOH solution as both the cathode and anolyte, and a self-made composite membrane (approximately 200 µm thick) as the separator. An Ag / AgCl reference electrode or a resonant hydrogen ionomer (RHE) electrode was inserted close to the working electrode. A metallic Ni filter with an area of ​​approximately 3 cm² was used as the counting electrode. The working electrode was clamped by a stainless steel electrode holder with an area of ​​approximately 1.5 cm² immersed in the electrolyte.

[0142] The overpotential of the hydrogen evolution reaction (HER) was measured at 2 mV / s at 1 M KOH and room temperature. Figure 3 Results are shown for four electrodes of the present invention (IE-1, IE-2, IE-3, and IE-4 in Table 1) and two reference electrodes (Ni mesh and Ni foam in Table 1). From Figure 3 Clearly, all porous electrodes of the present invention exhibit lower overpotentials at any given potential value, indicating higher electrochemical activity.

[0143] The oxygen evolution reaction (OER) overpotential was measured at 2 mV / s in 1 M KOH at room temperature. Figure 4 Results are shown for four electrodes of the present invention (IE-1, IE-2, IE-3, and IE-4 in Table 1) and two reference electrodes (Ni mesh and Ni foam in Table 1). From Figure 4 It is clear that all porous electrodes of the present invention exhibit higher overpotentials at any given potential value, indicating higher electrochemical activity.

[0144] Then at three different current densities ( Figure 5 Under these conditions, the overpotential is calculated for the same four electrodes of this invention and the same two reference electrodes. It is known that higher current density leads to higher overpotential values. The lower the overpotential value, the lower the energy required to produce gases (O2 and H2). Figure 5 Of the electrodes presented, the electrodes of the present invention exhibited lower overpotential values ​​than the reference electrodes at all current densities studied. Furthermore, the porous electrode IE-4 had the lowest overpotential, followed by IE-3, IE-2, and IE-1.

[0145] For the same Ni mesh as the support, different thicknesses of the slurry (and the resulting matrix) (where the slurry is applied on one side) do not appear to significantly affect the results (IE-1 vs. IE-2). When the slurry is applied to both sides of the Ni mesh (IE-3) instead of one side (IE-2), the overpotential is significantly lower, which can contribute to a more uniform presence of the porous matrix in the porous electrode. Due to its higher porosity, using Ni foam (IE-4) instead of the Ni mesh (IE-1) for the same slurry thickness (applied only on one side) allows for a further reduction in the overpotential value.

[0146] Example 2: Alkaline water electrolyzer under environmental conditions

[0147] The performance of two porous electrodes IE-3 and IE-5 of the present invention, and two reference electrodes, Ni foam and Ni mesh, of Example 1 were investigated using a 13 cm² circular water electrolyzer under ambient conditions (25°C and atmospheric pressure). The electrodes were used as the anode and cathode. A self-made composite membrane with a thickness of 200 µm was used as the diaphragm. The electrolyte was 6 M KOH.

[0148] Figure 6 The cell voltage as a function of current density for the four electrodes is shown. It is clear that for all current densities, the two porous electrodes of this invention result in a lower cell voltage than the two reference electrodes, thus exhibiting a reduced overpotential and therefore outperforming the reference electrodes under ambient conditions. For example, the cell voltage of electrode IE-5 at 1000 mA / cm² is only 2.58 V, while it is 3.16 V for the reference (commercial) Ni foam electrode. This represents a 580 mV reduction in overpotential at ambient temperature and pressure.

[0149] Example 3: High-temperature and high-pressure alkaline water electrolyzer

[0150] The performance of the porous electrode IE-5 of this invention, and two reference electrodes (the Ni mesh of Example 1 and CE-1, respectively), were investigated using a 13 cm² circular water electrolyzer at high temperature (70°C) and pressure (10 bar). The electrodes were used as the anode and cathode. A self-made composite membrane with a thickness of 200 µm was used as the diaphragm. The electrolyte was 6.9 M KOH, i.e., 6.9 M KOH was used as both the anode and cathode electrolyte solution.

[0151] exist Figure 7 The results for the electrode IE-5 of the present invention, the reference electrode CE-1, and the Ni mesh are shown, illustrating the change in battery voltage with current density. It clearly demonstrates that the electrode IE-5 of the present invention outperforms the two reference electrodes, highlighting the importance of porous conductive supports as electrical conductors and porous matrices containing polymer binders and electrochemically active particles. Specifically, a current density of 1000 mA / cm² is achieved using the IE-5 electrode. 2 The battery voltage is below 2 V, while the two reference electrodes have a voltage of at least 2.1 V. This is an overpotential reduction of more than 100 mV under high temperature and high pressure.

[0152] Example 4: Electrode Durability Test

[0153] An alkaline water electrolyzer battery (cross-section: 50 cm²) 2The porous electrode IE-5 of this invention was used as both the anode and cathode. A self-made composite membrane with a thickness of 200 µm was used as the separator. 30 wt.% KOH was used as both the anode and cathode electrolyte solutions. The electrolyte was tested at high temperature (80°C), pressure (10 bar), and current density (800 mA / cm²). 2 Water electrolysis experiments were conducted under these conditions.

[0154] Figure 8 The variation of delivered battery voltage over operating time (up to 16 hours) is shown. In addition to a stable voltage output throughout the entire 16-hour test duration, the electrolyzer using the electrode IE-5 of the present invention as both anode and cathode exhibited very low voltage fluctuations over time, demonstrating the excellent mass transfer and superior durability of the electrode of the present invention.

Claims

1. A method (1) for manufacturing a porous electrode, comprising the following steps: - Preparation of (2) a slurry, the slurry comprising a solvent,, based on the total weight of the slurry, between 1% and 25% by weight of a polymeric binder material and between 10% and 80% by weight of particles containing an electrochemically active material, wherein the polymeric binder material is at least partially dissolved in the solvent. - Applying the slurry (3) to the porous conductive support (10, 20) includes applying and impregnating one or a combination of the porous conductive support (10, 20) with the slurry to obtain a coated support containing the slurry, and - The slurry of the coated support undergoes a phase transformation (4) to form the porous electrode, wherein the porous electrode comprises the porous conductive support (10, 20) and a porous composite material, the porous composite material comprising a porous matrix and particles (12, 22) containing the electrochemically active material, wherein the porous matrix comprises the polymer binder material (11, 21), and wherein the particles are dispersed in the porous matrix. The invention is characterized in that the weight ratio of the polymer binder material to the particles in the slurry is between 2:98 and 50:50, and based on the total weight of the slurry, the total amount of the polymer binder material and the particles in the slurry is between 32% and 80% by weight.

2. The method according to claim 1, wherein, The electrochemically active material is an electrochemically active metal selected from the group consisting of nickel, silver, tin, copper, iron, manganese, cobalt, zinc, titanium, bismuth, selenium, and precious metals.

3. The method according to any one of the preceding claims, wherein, The electrochemically active material exists in the particles as one or a combination of a metal solid, a metal oxide, or a metal dichalcogenide.

4. The method according to any one of the preceding claims, wherein the particles have an average particle size between 5 nm and 200 µm, preferably between 10 nm and 100 µm, as measured by scanning electron microscopy (SEM).

5. The method according to any one of the preceding claims, wherein the particles have a bimodal particle size distribution.

6. The method of claim 5, wherein the particles in 25% to 75% have an average particle size between 1 µm and 250 µm as measured by SEM, and the particles in 75% to 25% have an average particle size between 5 nm and 500 nm as measured by SEM.

7. The method according to any one of the preceding claims, wherein the polymer adhesive material comprises a nonionic conductive polymer.

8. The method according to any one of the preceding claims, wherein the slurry further comprises a pore-forming agent at a weight of between 1% and 10% based on the total weight of the slurry.

9. The method according to any one of the preceding claims, wherein, The solvent has a boiling point of at least 180°C at an atmospheric pressure of 1 bar.

10. The method according to any one of the preceding claims, wherein, The slurry is applied to one side of the porous conductive support (10, 20).

11. The method according to any one of claims 1 to 9, wherein the slurry is applied to both sides of the porous conductive support (10, 20).

12. The method according to any one of the preceding claims, wherein the slurry is applied to a thickness between 1 nm and 5 mm, preferably between 1 µm and 2 mm, more preferably between 10 µm and 1 mm.

13. The method according to any one of the preceding claims, wherein the slurry is applied to a thickness between 10 µm and 500 µm, preferably between 50 µm and 200 µm.

14. The method according to any one of the preceding claims, wherein, The phase transformation (4) of the porous conductive support containing the slurry includes contacting the porous conductive support containing the slurry with a non-solvent for the polymer binder material to precipitate the polymer binder material, thereby obtaining the porous electrode.

15. The method of claim 14, wherein the solvent comprises a polar aprotic solvent and the non-solvent used for the polymeric adhesive material comprises a polar protic solvent.

16. The method according to claim 14 or claim 15, wherein the contact between the green compact and the non-solvent material for the polymer binder lasts for a duration between 5 minutes and 24 hours, preferably between 10 minutes and 4 hours, and more preferably between 30 minutes and 1 hour.

17. A porous electrode comprising a porous conductive support (10, 20) and a porous composite material, said porous composite material comprising a porous matrix and particles (12, 22) comprising an electrochemically active material, wherein said porous matrix comprises a polymer binder material (11, 21), wherein, The particles are dispersed in the porous matrix, and the porous composite material comprises particles (12, 22) at a weight of between 50% and 98% based on the total weight of the porous composite material and polymer binder material (11, 21) at a weight of between 2% and 50%, characterized in that the porous electrode has a porosity equal to or greater than 40% as measured by mercury porosimetry.

18. The porous electrode according to claim 17, wherein the pores have an average pore diameter between 0.05 µm and 5 µm, preferably between 0.1 µm and 5 µm, and more preferably between 0.1 µm and 1 µm, as determined by capillary flow porosity measurement.

19. The porous electrode according to claim 17 or 18, wherein the porous electrode has non-in-situ gas permeability measured by capillary flow porosity measurement between 0.50 and 50 L / min / cm² / bar, preferably between 0.60 and 30 L / min / cm² / bar, more preferably between 0.70 and 30 L / min / cm² / bar.

20. A water electrolyzer comprising a porous electrode according to any one of claims 17 to 19, or a porous electrode obtained by the method according to any one of claims 1 to 16.

21. A membrane electrode assembly comprising a porous electrode according to any one of claims 17 to 19, or a porous electrode obtained by the method according to any one of claims 1 to 16.

22. Use of the porous electrode according to any one of claims 17 to 19, or the porous electrode obtained by the method according to any one of claims 1 to 16, in a water electrolyzer or membrane electrode assembly.

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