Cathode gas diffusion layer and preparation method thereof, membrane electrode and anion exchange membrane electrolytic cell

Abstract

The embodiment of the invention discloses a cathode gas diffusion layer and a preparation method thereof, a membrane electrode and an anion exchange membrane electrolyzer, the cathode gas diffusion layer comprises a matrix layer, a transition layer and a hydrophilic layer which are sequentially stacked, and the transition layer comprises at least two layers of hydrophobic layers which are stacked; the contact angle between the hydrophobic layer close to the hydrophilic layer and water is smaller than that between the hydrophobic layer away from the hydrophilic layer and water, the contact angle between the hydrophilic layer and water is smaller than or equal to 90 degrees, and the contact angle between the hydrophobic layer and water is larger than 90 degrees. According to the cathode gas diffusion layer provided by the invention, under anode liquid inlet circulation, the hydrophilic layer can ensure the wetting of the cathode side anion exchange membrane, so that the transmission efficiency of OH <-> and the total gas production amount of hydrogen are improved, the problem of rapid loss of the anion exchange membrane caused by water shortage and concentration difference of the cathode side anion exchange membrane is relieved, and the service life of the cathode side anion exchange membrane is prolonged. The gradient hydrophobic transition layer can regulate and control the moisture permeation amount of the cathode side, so that the risk of water logging is reduced, and the hydrogen discharge efficiency and the hydrogen purity are improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of anion exchange membrane electrolysis of water to produce hydrogen, and particularly relates to a cathode gas diffusion layer and a preparation method thereof, a membrane electrode and an anion exchange membrane electrolyzer. BACKGROUND

[0002] In recent years, anion exchange membrane (AEM) electrolysis of water to produce hydrogen has become the most promising hydrogen production technology, which combines the advantages of alkaline (ALK) and proton exchange membrane (PEM), and has the advantages of low cost and high dynamic response. In addition, AEM electrolysis of water to produce hydrogen can use pure water or low-concentration alkaline solution instead of concentrated KOH solution as electrolyte, effectively avoiding the strong corrosion of the electrode assembly, and reducing the leakage risk and processing difficulty of the entire water electrolysis device.

[0003] The AEM water electrolyzer is mainly composed of an anion exchange membrane, a catalyst layer, a gas diffusion layer and a bipolar plate, and its working principle is similar to that of other water electrolysis hydrogen production principles. It also involves two half-reactions: oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). As the core component of the AEM water electrolysis system, the membrane electrode (MEA) dominates the key process of hydrogen production, and its performance directly affects the electrolysis efficiency and the overall performance of the system. The MEA is usually composed of an anion exchange membrane, a catalyst layer and a diffusion layer.

[0004] AEM electrolysis of water to produce hydrogen usually adopts a liquid electrolyte flowing through two electrode compartments, namely the so-called double-side circulation mode, which leads to slow gas transmission efficiency and high hydrogen dew point on the cathode side. The mode can solve the above problems by circulating the liquid electrolyte only through the anode side, but the water management on the cathode side still needs to be solved to ensure the film wetting and hydrogen transmission efficiency. SUMMARY

[0005] The application provides a cathode gas diffusion layer and a preparation method thereof, a membrane electrode and an anion exchange membrane electrolyzer, aiming to solve the problems of limited cathode gas transmission and water management of film wetting under anode circulation.

[0006] The application provides a cathode gas diffusion layer, which comprises a substrate layer, a transition layer and a hydrophilic layer which are sequentially stacked, the transition layer comprises at least two layers of hydrophobic layers which are stacked, the contact angle of the hydrophobic layer close to the hydrophilic layer with water is smaller than that of the hydrophobic layer away from the hydrophilic layer, the contact angle of the hydrophilic layer with water is less than or equal to 90°, and the contact angle of the hydrophobic layer with water is greater than 90°.

[0007] Optionally, in some embodiments of the present application, the hydrophilic layer comprises a hydrophilic material, the hydrophilic material comprises one or more of a metal element, a metal oxide, a metal hydroxide, a metal layered double hydroxide, and a hydrophilic carbon material, the metal element in the metal element, the metal oxide, the metal hydroxide, and the metal layered double hydroxide independently comprises one of Ni, Co, Fe, Pt, Ru, Mo, Ir, and Ti; and / or The hydrophilic layer comprises an anion exchange resin.

[0008] Optionally, in some embodiments of the present application, the hydrophilic layer comprises a hydrophilic material and an anion exchange resin, the mass percentage of the hydrophilic material and the anion exchange resin in the hydrophilic layer is (50%-90%):(10%-50%); and / or The contact angle of the hydrophilic layer with water is 0°-30°.

[0009] Optionally, in some embodiments of the present application, the hydrophobic layer comprises a hydrophobic material, the hydrophobic material comprises one or more of a perfluoroalkoxy resin, a polyperfluoroethylene propylene, and a polytetrafluoroethylene; and / or The hydrophobic layer comprises a carbon material, the carbon material comprises one or more of carbon black, carbon nanotubes, graphene, reduced graphene oxide, and carbon fibers.

[0010] Optionally, in some embodiments of the present application, the hydrophobic layer comprises a hydrophobic material and a carbon material, in the hydrophobic layer, the ratio of the mass content of the hydrophobic material to the mass content of the carbon material is (5%-50%):(50%-95%); and / or The kinds of the hydrophobic material in the at least two layers of the hydrophobic layer are the same, the mass content of the hydrophobic material in the hydrophobic layer close to the hydrophilic layer is less than the mass content of the hydrophobic material in the hydrophobic layer away from the hydrophilic layer.

[0011] Optionally, in some embodiments of the present application, along the direction away from the hydrophilic layer, the contact angle of the hydrophobic layer with water increases in turn; and / or The contact angle of the at least two layers of the hydrophobic layer with water is 100°-160°.

[0012] Optionally, in some embodiments of the present application, the transition layer comprises a first hydrophobic layer and a second hydrophobic layer stacked along the direction close to the hydrophilic layer, the contact angle of the first hydrophobic layer with water is 140°-160°, and the contact angle of the second hydrophobic layer with water is 100°-140°; and / or The transition layer comprises a first hydrophobic layer and a second hydrophobic layer stacked in a direction close to the hydrophilic layer, the mass content of the hydrophobic material in the first hydrophobic layer is 20%-50%, and the mass content of the hydrophobic material in the second hydrophobic layer is 5%-20%.

[0013] Optionally, in some embodiments of the present application, the thickness of the hydrophilic layer is 10 μm-50 μm; and / or The thickness of the transition layer is 10 μm-50 μm; and / or The thickness of a single layer of the hydrophobic layer is 5 μm-10 μm.

[0014] Optionally, in some embodiments of the present application, the substrate layer comprises one or more of carbon fiber paper and carbon cloth; and / or The porosity of the substrate layer is 50%-95%.

[0015] Correspondingly, the present application also provides a preparation method of a cathode gas diffusion layer, comprising: forming a transition layer on one side surface of a substrate layer, and then forming a hydrophilic layer on the side of the transition layer away from the substrate layer to obtain a cathode gas diffusion layer; The transition layer comprises at least two layers of hydrophobic layers stacked together, the contact angle of the hydrophobic layer close to the hydrophilic layer with water is less than the contact angle of the hydrophobic layer away from the hydrophilic layer with water, the contact angle of the hydrophilic layer with water is less than or equal to 90°, and the contact angle of the hydrophobic layer with water is greater than 90°.

[0016] Optionally, in some embodiments of the present application, the forming of the transition layer on one side surface of the substrate layer comprises: setting a first hydrophobic slurry on one side surface of the substrate layer, and then performing first sintering and first plasma treatment to form a first hydrophobic layer; setting a second hydrophobic slurry on the side surface of the first hydrophobic layer away from the substrate layer, and then performing second sintering and second plasma treatment to form a second hydrophobic layer; The first hydrophobic slurry and the second hydrophobic slurry each comprise a hydrophobic material.

[0017] Optionally, in some embodiments of the present application, the temperature of the first sintering is 300°C-500°C, and the time of the first sintering is 20 min-30 min; and / or The first sintering is performed in a vacuum or an inert atmosphere; and / or The plasma used in the first plasma treatment is a mixed gas of Ar and O2, wherein the volume percentage of Ar and O2 is (70%-90%):(30%-10%); and / or The surface energy of the first hydrophobic layer after the first plasma treatment is 20 mN / m-60 mN / m on the side surface away from the base layer; and / or The temperature of the second sintering is 300℃-500℃, and the time of the second sintering is 20 min-30 min; and / or The second sintering is performed in vacuum or inert atmosphere; and / or The plasma used in the second plasma treatment is a mixed gas of Ar and O2, wherein the volume percentage of Ar and O2 is (70%-90%):(30%-10%); and / or The surface energy of the second hydrophobic layer after the second plasma treatment is 20 mN / m-60 mN / m on the side surface away from the first hydrophobic layer.

[0018] Optionally, in some embodiments of the present application, the hydrophilic layer is formed on the side of the transition layer away from the base layer, comprising: The hydrophilic slurry is arranged on the side of the transition layer away from the base layer, and then dried and shaped to form the hydrophilic layer.

[0019] Optionally, in some embodiments of the present application, the drying comprises drying at 50℃-65℃ for 20 min-25 min, and then drying at 80℃-85℃ for 50 min-60 min; and / or The shaping comprises shaping in an inert gas atmosphere at 100℃-105℃ for 10 min-15 min.

[0020] Correspondingly, the present application also provides a membrane electrode, comprising a cathode catalyst layer and the above-mentioned cathode gas diffusion layer or the cathode gas diffusion layer prepared by the above-mentioned preparation method of cathode gas diffusion layer, and the cathode catalyst layer is arranged on the side of the hydrophilic layer away from the transition layer.

[0021] In addition, the present application also provides an anion exchange membrane electrolyzer comprising the above-mentioned membrane electrode.

[0022] The cathode gas diffusion layer provided by the present application can ensure the wetting of the cathode side anion exchange membrane under the circulation of anode liquid, thereby improving the transmission efficiency of OH - and the total amount of hydrogen production, alleviating the problem of rapid consumption of anion exchange membrane caused by water shortage and concentration difference of the cathode side anion exchange membrane, and the transition layer with gradient hydrophobicity can regulate the water permeation amount of the cathode side, thereby reducing the risk of waterlogging and improving the hydrogen discharge efficiency and hydrogen purity. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.

[0024] Figure 1 is a structural schematic diagram of a cathode gas diffusion layer provided by the embodiments of the present application; Figure 2 is a structural schematic diagram of a membrane electrode provided by the embodiments of the present application.

[0025] Legend: base layer-1; transition layer-2; first hydrophobic layer-21; second hydrophobic layer-22; hydrophilic layer-3; cathode catalytic layer-4. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments only constitute some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0027] The embodiments of the present application provide a cathode gas diffusion layer and a preparation method thereof, a membrane electrode and an anion exchange membrane electrolytic cell. The following will be described in detail respectively. It should be noted that the description order of the following embodiments is not regarded as a limitation on the preferred order of the embodiments. In addition, in the description of the present application, the term "comprises" means "comprises but is not limited to". The terms first, second, third, etc. are only used as labels and do not impose numerical requirements or establish sequences. Various embodiments of the present application can exist in a range form; it should be understood that the description in a range form is only for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the described range has been specifically disclosed all possible sub-ranges and single values in the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers in the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated in this text, it means that any cited number (fraction or integer) in the indicated range is included.

[0028] Please refer to Figure 1The embodiment of the present application provides a cathode gas diffusion layer, which comprises a substrate layer 1, a transition layer 2 and a hydrophilic layer 3 which are sequentially stacked, the transition layer 2 comprises at least two layers of hydrophobic layers which are stacked, the contact angle of the hydrophobic layer close to the hydrophilic layer 3 with water is smaller than the contact angle of the hydrophobic layer far from the hydrophilic layer 3 with water, the contact angle of the hydrophilic layer 3 with water is less than or equal to 90 degrees, and the contact angle of the hydrophobic layer with water is greater than 90 degrees.

[0029] In the present application, the hydrophilic layer 3 can ensure the wetting of the cathode side anion exchange membrane, thereby improving the transmission efficiency of OH - and the total amount of hydrogen production, relieving the problem of rapid loss of the anion exchange membrane caused by water shortage and concentration difference of the cathode side anion exchange membrane, and the transition layer 2 with gradient hydrophobicity can regulate the water permeation amount of the cathode side, thereby reducing the risk of waterlogging and improving the hydrogen discharge efficiency and hydrogen purity.

[0030] It can be understood that the hydrophobic layer of the cathode gas diffusion layer (GDL) can establish a reverse osmosis "air pressure barrier", optimize the water-gas two-phase flow, preferentially discharge gas, thereby manage and maintain the water-gas balance inside the cathode side, and effectively regulate the water permeation amount of the cathode side.

[0031] Optionally, in some embodiments of the present application, the contact angle of the hydrophobic layer with water increases in sequence along the direction away from the hydrophilic layer 3.

[0032] Optionally, in some embodiments of the present application, the contact angle of the at least two layers of hydrophobic layers with water is 100-160 degrees, for example, can be 100 degrees, 110 degrees, 120 degrees, 130 degrees, 140 degrees, 150 degrees, 160 degrees or the like.

[0033] Optionally, in some embodiments of the present application, the thickness of the hydrophilic layer 3 is 10-50 microns, for example, can be 10 microns, 15 microns, 20 microns, 25 microns, 30 microns, 35 microns, 40 microns, 45 microns, 50 microns or the like. In this way, a stable and sufficient water supply can be formed, a sufficient hydration environment can be provided to maintain high ionic conductivity, and the thickness is moderate, so that the ion transmission path is short, thereby keeping the ohmic loss at a low level, realizing efficient gas transmission, ensuring good mechanical support and interface contact, and further realizing efficient co-transmission of water, ions and gas.

[0034] It can be understood that if the hydrophilic layer 3 is too thick, the cathode side anion exchange membrane will be waterlogged, thereby causing the bubble mass transfer resistance to increase, the cell pressure to rise, and the long-term stable operation of the electrolytic cell to be adversely affected; if the hydrophilic layer 3 is too thin, the water content will be insufficient, the water supply of the cathode side anion exchange membrane will be insufficient, and the ionic conductivity will decrease; and if the hydrophilic layer 3 is too thick, the transmission path will be too long, and the resistance will also increase.

[0035] Optionally, in some embodiments of the present application, the hydrophilic layer 3 comprises a hydrophilic material, the hydrophilic material comprises one or more of a metal element, a metal oxide, a metal hydroxide, a metal layered double hydroxide and a hydrophilic carbon material, the metal element in the metal element, the metal oxide, the metal hydroxide and the metal layered double hydroxide independently comprises one of Ni, Co, Fe, Pt, Ru, Mo, Ir and Ti.

[0036] As an example, the hydrophilic material comprises NiO, Co3O4, Fe2O3, Ni(OH)2, Ni, nickel-iron layered double hydroxide (NiFe-LDH). It can be understood that NiFe-LDH and Ni(OH)2 have catalytic activity, and the carbon material can improve the electronic conductivity.

[0037] It can be understood that the hydrophilic carbon material refers to a carbon material with a hydrophilic surface, which can form a strong interaction with water molecules, thereby showing good hydrophilicity.

[0038] Optionally, in some embodiments of the present application, the hydrophilic layer 3 further comprises an anion exchange resin.

[0039] In the present application, the addition of an anion exchange resin in the hydrophilic layer 3 can construct efficient ion conduction channels in the porous matrix of the hydrophilic layer 3 and optimize the reaction interface.

[0040] Optionally, in some embodiments of the present application, the mass percentage of the hydrophilic material and the anion exchange resin in the hydrophilic layer 3 is (50%-90%):(10%-50%), for example, it can be 50%:50%, 60%:40%, 70%:30%, 80%:20%, 90%:10% and the like. In this way, the hydrophilic layer 3 can have sufficient pores to ensure the effective transmission of gas / liquid, while forming a continuous ion conduction network and an electronic conduction network to ensure the effective transmission of ions and electrons.

[0041] It can be understood that the hydrophilic material is the main body of the mechanical skeleton and the porous structure of the hydrophilic layer 3, and when its proportion is too low (<50%), the ionomer is too much, which will block these pores, leading to the densification of the layered structure, which will hinder the supply of water and the discharge of oxygen, causing the "waterlogging" of the cathode side and causing the mass transfer loss; the anion exchange resin as the "binder" and "ion conductor" is filled in the pores and surface of the hydrophilic material skeleton, and when its proportion is too low (<10%), it cannot form a continuous ion conduction network, which will cause a sharp decrease in ion conductivity and increase the ohmic polarization.

[0042] Optionally, in some embodiments of this application, the contact angle between the hydrophilic layer 3 and water is 0°-30°, for example, it can be 0°, 2°, 5°, 8°, 10°, 12°, 15°, 17°, 20°, 22°, 25°, 27°, 30°, etc. In this way, the hydrophilic layer 3 can ensure the wetting of the anion exchange membrane on the cathode side, thereby improving OH... - This improves transmission efficiency and total hydrogen production, alleviating the problem of rapid anion exchange membrane wear caused by water shortage and concentration difference on the cathode side.

[0043] Optionally, in some embodiments of this application, the hydrophobic layer comprises a hydrophobic material and a carbon material, wherein the hydrophobic material comprises one or more of perfluoroalkoxy resin (PFA), perfluoroethylene propylene (FEP), and polytetrafluoroethylene (PTFE).

[0044] In this application, carbon materials can provide porous channels for gas-liquid transport and serve as a substrate for the hydrophobic agent. After hydrophobic treatment, the micropores formed by the carbon materials generate capillary pressure, which can improve gas transport efficiency; simultaneously, the carbon materials can form a continuous, highly conductive network within the hydrophobic layer, which can improve the electron transport efficiency of the hydrogen evolution reaction; the carbon materials can also increase mechanical stress, forming a good interfacial contact with the catalyst layer / hydrophilic layer 3. PFA, FEP, and PTFE have good chemical stability and durability, can provide low surface energy, form stable gas evolution channels, and have good thermal processability and adhesion, facilitating the formation of the hydrophobic layer.

[0045] It is understandable that the types of hydrophobic materials used in different hydrophobic layers can be the same or different.

[0046] Optionally, in some embodiments of this application, the carbon material includes one or more of carbon black, carbon nanotubes, graphene, reduced graphene oxide (rGO), and carbon fiber.

[0047] As an example, carbon fiber can be carbon nanofiber.

[0048] Optionally, in some embodiments of this application, the hydrophobic materials in the at least two hydrophobic layers are of the same type, and the mass content of the hydrophobic material in the hydrophobic layer closer to the hydrophilic layer 3 is less than the mass content of the hydrophobic material in the hydrophobic layer farther from the hydrophilic layer 3.

[0049] Optionally, in some embodiments of this application, the mass content of the hydrophobic material and the mass content of the carbon material in the hydrophobic layer are (5%-50%):(50%-95%), for example, 5%:95%, 10%:90%, 20%:80%, 30%:70%, 40%:60%, 50%:50%, etc.

[0050] It is understandable that as the content of hydrophobic material increases, the hydrophobicity and mechanical strength of the hydrophobic layer will first rise rapidly and then tend to stabilize, while the conductivity and porosity will continue to decrease. By controlling the mass content of hydrophobic material, the conductivity / permeability and water resistance / mechanical properties of the hydrophobic layer can be balanced, so that the hydrophobic layer has good hydrophobicity, pore structure, conductivity and mechanical strength.

[0051] Optionally, in some embodiments of this application, the transition layer 2 includes a first hydrophobic layer 21 and a second hydrophobic layer 22 stacked along the direction close to the hydrophilic layer 3. The contact angle between the first hydrophobic layer 21 and water is 140°-160°, for example, 140°, 142°, 145°, 147°, 150°, 152°, 155°, 157°, 160°, etc. The contact angle between the second hydrophobic layer 22 and water is 100°-140°, for example, 100°, 105°, 110°, 115°, 120°, 125°, 130°, 140°, etc. In this way, the first hydrophobic layer 21 and the second hydrophobic layer 22 can effectively control the amount of water permeation on the cathode side, thereby reducing the risk of flooding and improving hydrogen discharge efficiency and hydrogen purity.

[0052] Optionally, in some embodiments of this application, the mass content of the hydrophobic material in the first hydrophobic layer 21 is 20%-50%, for example, it can be 20%, 30%, 45%, 50%, etc.

[0053] Optionally, in some embodiments of this application, the mass content of the hydrophobic material in the second hydrophobic layer 22 is 5%-20%, for example, it can be 5%, 10%, 15%, 20%, etc.

[0054] Optionally, in some embodiments of this application, the thickness of the transition layer 2 is 10μm-50μm, for example, it can be 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, etc. This allows for control of the mass transfer resistance of the cathode gas diffusion layer, while reducing ohmic losses, maintaining mechanical stability and interfacial contact, lowering costs, and increasing volumetric power density.

[0055] Optionally, in some embodiments of this application, the thickness of the single-layer hydrophobic layer is 5μm-10μm, for example, it can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc. In this way, the hydrophobic layer can effectively play the role of regulating the amount of water permeation on the cathode side and reduce its obstruction to mass transport and electron conduction.

[0056] Optionally, in some embodiments of this application, the porosity of the substrate layer 1 is 50%-95%, for example, it can be 50%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc. This optimizes the transport channels for reactants and products while ensuring the structural stability and conductivity of the substrate layer 1.

[0057] Optionally, in some embodiments of this application, the thickness of the substrate layer 1 is 0.28μm-0.30μm, for example, it can be 0.28μm, 0.29μm, 0.30μm, etc.

[0058] Optionally, in some embodiments of this application, the substrate layer 1 includes one or more of carbon fiber paper and carbon cloth.

[0059] Optionally, in some embodiments of this application, the fiber diameter of the carbon fiber paper is 10μm-30μm, for example, it can be 10μm, 12μm, 15μm, 17μm, 20μm, 22μm, 25μm, 27μm, 30μm, etc.

[0060] Understandably, the fiber diameter of carbon fiber paper determines its pore structure and pore size distribution. While excessively fine fibers can create a higher specific surface area at the same volume fraction, they may increase the tortuosity of gas and water transport, thus increasing mass transfer resistance. Excessively coarse fibers can form larger pores, which is beneficial for the expulsion of reactive gases under high current density and reduces the probability of water flooding. However, excessively large pores are not conducive to the subsequent coating of a hydrophobic layer (MPL) and will reduce mechanical strength. Fiber diameters that are too fine or too coarse will affect the mechanical strength and flexibility of the matrix layer 1, and will also affect electronic conductivity.

[0061] This application also provides a method for preparing a cathode gas diffusion layer, including: A transition layer 2 is formed on one side of the substrate layer 1, and a hydrophilic layer 3 is formed on the side of the transition layer 2 away from the substrate layer 1 to obtain a cathode gas diffusion layer. The transition layer 2 includes at least two stacked hydrophobic layers. The contact angle between the hydrophobic layer closer to the hydrophilic layer 3 and water is smaller than the contact angle between the hydrophobic layer farther from the hydrophilic layer 3 and water. The contact angle between the hydrophilic layer 3 and water is less than or equal to 90°, and the contact angle between the hydrophobic layer and water is greater than 90°.

[0062] As an example, the transition layer 2 can be applied to one side surface of the substrate layer 1 by coating or impregnation.

[0063] Optionally, in some embodiments of this application, before forming the transition layer 2 on one side surface of the substrate layer 1, the method further includes: The substrate layer 1 is cleaned and subjected to plasma treatment.

[0064] It is understandable that cleaning the substrate layer 1 can remove residual organic matter on its surface, and plasma treatment can increase the surface energy of the substrate layer 1, making it more hydrophilic. When applying hydrophobic slurry, it can improve the wettability and coating uniformity of the slurry and enhance the adhesion to the hydrophobic layer.

[0065] As an example, the substrate layer 1 was ultrasonically cleaned with ethanol for 30 minutes to remove residual organic matter from its surface. The surface of the substrate layer 1 was then subjected to plasma treatment with an Ar / O2 mixed gas to increase its surface energy.

[0066] Optionally, in some embodiments of this application, forming a transition layer 2 on one side surface of the substrate layer 1 includes: A first hydrophobic layer 21 is formed on one side surface of the substrate layer 1; A second hydrophobic layer 22 is formed on the surface of the first hydrophobic layer 21 that is away from the substrate layer 1.

[0067] Optionally, in some embodiments of this application, forming a first hydrophobic layer 21 on one side surface of the substrate layer 1 includes: A first hydrophobic slurry is applied to one side surface of the substrate layer 1, and then a first sintering is performed to form a first hydrophobic layer 21. The first hydrophobic slurry includes hydrophobic materials.

[0068] It is understandable that sintering can melt and flow hydrophobic materials, thereby achieving the transformation from "physical mixing" to "chemical functionalization", and thus enabling the first hydrophobic slurry to form a stable and reliable porous hydrophobic structure.

[0069] Optionally, in some embodiments of this application, the temperature of the first sintering is 300℃-500℃, for example, it can be 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 500℃, etc., and the time of the first sintering is 20min-30min, for example, it can be 20min, 20min, 21min, 22min, 23min, 24min, 25min, 26min, 27min, 28min, 29min, 30min, etc.

[0070] Optionally, in some embodiments of this application, the first sintering is performed in a vacuum or inert atmosphere.

[0071] Optionally, in some embodiments of this application, after the first sintering, the process further includes performing a first plasma treatment. This can increase the surface energy of the side of the first hydrophobic layer 21 facing away from the substrate layer 1, improving the wettability and coating uniformity of the second hydrophobic slurry during coating, enhancing the adhesion of the first hydrophobic layer 21, and thus improving the adhesion between the first hydrophobic layer 21 and the second hydrophobic layer 22.

[0072] Optionally, in some embodiments of this application, the plasma used for the first plasma treatment is a mixture of Ar and O2, wherein the volume percentage of Ar and O2 is (70%-90%):(30%-10%), for example, it can be 70%:30%, 75%:25%, 80%:20%, 85%:15%, 90%:10%, etc.

[0073] Optionally, in some embodiments of this application, the surface energy of the side of the first hydrophobic layer 21 after the first plasma treatment that is away from the substrate layer 1 is 20mN / m-60mN / m, for example, it can be 20mN / m, 25mN / m, 30mN / m, 35mN / m, 40mN / m, 45mN / m, 50mN / m, 55mN / m, 60mN / m, etc.

[0074] Optionally, in some embodiments of this application, the first hydrophobic slurry further includes carbon materials.

[0075] Optionally, in some embodiments of this application, forming a second hydrophobic layer 22 on the surface of the first hydrophobic layer 21 facing away from the substrate layer 1 includes: A second hydrophobic slurry is applied to the surface of the first hydrophobic layer 21 away from the substrate layer 1, and then a second sintering is performed to form a second hydrophobic layer 22. The second hydrophobic slurry includes hydrophobic materials.

[0076] Optionally, in some embodiments of this application, the second sintering temperature is 300℃-500℃, for example, it can be 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 500℃, etc., and the second sintering time is 20min-30min, for example, it can be 20min, 20min, 21min, 22min, 23min, 24min, 25min, 26min, 27min, 28min, 29min, 30min, etc.

[0077] Optionally, in some embodiments of this application, the second sintering is performed in a vacuum or inert atmosphere.

[0078] Optionally, in some embodiments of this application, after the second sintering, a second plasma treatment is further performed. This can increase the surface energy of the side of the second hydrophobic layer 22 facing away from the first hydrophobic layer 21, improving the wettability and coating uniformity of the hydrophilic slurry during coating, enhancing the adhesion of the second hydrophobic layer 22, and thus improving the adhesion between the second hydrophobic layer 22 and the hydrophilic layer 3.

[0079] Optionally, in some embodiments of this application, the plasma used for the second plasma treatment is a mixture of Ar and O2, wherein the volume percentage of Ar and O2 is (70%-90%):(30%-10%), for example, it can be 70%:30%, 75%:25%, 80%:20%, 85%:15%, 90%:10%, etc.

[0080] Optionally, in some embodiments of this application, the surface energy of the side of the second hydrophobic layer 22 away from the first hydrophobic layer 21 after the second plasma treatment is 20mN / m-60mN / m, for example, it can be 20mN / m, 25mN / m, 30mN / m, 35mN / m, 40mN / m, 45mN / m, 50mN / m, 55mN / m, 60mN / m, etc.

[0081] Optionally, in some embodiments of this application, the second hydrophobic slurry further includes carbon materials.

[0082] Optionally, in some embodiments of this application, forming a hydrophilic layer 3 on the side of the transition layer 2 opposite to the substrate layer 1 includes: The hydrophilic slurry is placed on the side of the transition layer 2 away from the substrate layer 1, and then dried and shaped to form the hydrophilic layer 3.

[0083] Optionally, in some embodiments of this application, the drying includes drying at 50℃-65℃ (e.g., 50℃, 52℃, 53℃, 60℃, 62℃, 65℃, etc.) for 20min-25min (e.g., 20min, 21min, 22min, 23min, 24min, 25min, etc.), and then drying at 80℃-85℃ (e.g., 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, etc.) for 50min-60min (e.g., 50min, 52min, 54min, 56min, 58min, 60min, etc.).

[0084] Optionally, in some embodiments of this application, the shaping includes shaping in an inert gas atmosphere at 100℃-105℃ (e.g., 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, etc.) for 10min-15min (e.g., 10min, 11min, 12min, 13min, 14min, 15min, etc.).

[0085] Please see Figure 2 This application also provides a membrane electrode, including a cathode catalytic layer 4 and the above-mentioned cathode gas diffusion layer, wherein the cathode catalytic layer 4 is stacked on the side of the hydrophilic layer 3 away from the transition layer 2.

[0086] Optionally, in some embodiments of this application, the cathode catalytic layer 4 includes a cathode catalyst and an ionomer.

[0087] It is understandable that ionomers are the functional form of anion exchange resins.

[0088] Optionally, in some embodiments of this application, the mass ratio of the cathode catalyst to the ionomer is (8-2):(6-1), for example, it can be 8:1, 8:3, 8:4, 8:6, 6:1, 6:3, 6:4, 6:6, 4:1, 4:3, 4:4, 4:6, 2:1, 2:3, 2:4, 2:6, etc.

[0089] Optionally, in some embodiments of this application, the loading of the cathode catalyst is 1 g / cm³. 2 -10g / cm 2 For example, it can be 1g / cm 2 2g / cm 2 3g / cm 2 4g / cm 2 5g / cm 2 6g / cm 2 7g / cm 2 8g / cm 2 9g / cm 2 10g / cm 2 wait.

[0090] Optionally, in some embodiments of this application, the cathode catalyst includes one or more of platinum-carbon catalyst, platinum-nickel-carbon, and nickel-molybdenum alloy.

[0091] This application also provides an anion exchange membrane electrolyzer, including the membrane electrode described above.

[0092] Optionally, in some embodiments of this application, the anion exchange membrane electrolyzer includes a cathode chamber, an anode chamber, and a liquid electrolyte, wherein the liquid electrolyte circulates only in the anode chamber.

[0093] Example 1 A cathode gas diffusion layer and its preparation method, comprising: Carbon black was mixed with PTFE emulsion (PTFE content was 60% by mass) to obtain the first hydrophobic slurry (PTFE to carbon black mass ratio was 40:60). Carbon black was mixed with PTFE emulsion (PTFE content was 20%) to obtain a second hydrophobic slurry (PTFE to carbon black mass ratio was 20:80). Carbon fiber paper (porosity 75%, thickness 0.3μm) was ultrasonically treated with ethanol for 30 min, then the first hydrophobic slurry was coated on one side of the carbon fiber paper, and then sintered at 350℃ for 25 min in N2 environment. Then, Ar / O2 mixed gas was introduced for plasma treatment to form the first hydrophobic layer 21 (thickness 10μm). The second hydrophobic slurry is coated on the side of the first hydrophobic layer 21 away from the carbon fiber paper, and then sintered at 350°C for 25 minutes in a N2 environment. Then, Ar / O2 mixed gas is introduced for plasma treatment to form the second hydrophobic layer 22 (thickness of 10 μm). Nickel hydroxide (Ni(OH)2) was mixed with an anion exchange resin solution to form a suspension (solid content 25wt%, mass ratio of nickel hydroxide to anion exchange resin 50:50). The suspension is coated onto the surface of the second hydrophobic layer 22 away from the first hydrophobic layer 21, then pre-dried at 65°C for 25 min, then dried at 85°C for 50 min, and finally set at 105°C for 15 min in a N2 atmosphere to form a hydrophilic layer 3 (20 μm thick), thus obtaining the cathode gas diffusion layer.

[0094] A method for preparing a cathode electrode includes: Platinum-carbon catalyst, water, Alkymer anion exchange resin and ethanol were mixed sequentially in a mass ratio of 8:10:6:10, and then placed in a high-speed shearing machine for 25 minutes to mix evenly, thus obtaining the cathode catalyst slurry. The cathode catalyst slurry is coated onto the surface of the hydrophilic layer of the cathode gas diffusion layer on the side facing away from the second hydrophobic layer, and then vacuum dried in an 80℃ drying oven for 45 minutes to form the cathode catalyst layer and obtain the cathode electrode.

[0095] Example 2 This embodiment is basically the same as Embodiment 1, except that the hydrophobic material PTFE is replaced with polytetrafluoroethylene propylene (FEP) in this embodiment.

[0096] Example 3 This embodiment is basically the same as Embodiment 1, except that the hydrophilic material Ni(OH)2 is replaced with NiO in this embodiment.

[0097] Example 4 This embodiment is basically the same as Embodiment 1, except that the carbon material carbon black is replaced with graphene in this embodiment.

[0098] Example 5 This embodiment is basically the same as Embodiment 1, except that the mass ratio of PTFE and carbon black in the first hydrophobic slurry is changed to 50:50.

[0099] Example 6 This embodiment is basically the same as Embodiment 1, except that the mass ratio of PTFE and carbon black in the second hydrophobic slurry is changed to 10:90.

[0100] Example 7 This embodiment is basically the same as Embodiment 1, except that the thickness of the first hydrophobic layer in this embodiment is 5 μm.

[0101] Example 8 This embodiment is basically the same as Embodiment 1, except that the thickness of the first hydrophobic layer in this embodiment is 2μm.

[0102] Example 9 This embodiment is basically the same as Embodiment 1, except that in this embodiment, a 5μm thick hydrophobic layer is provided between the second hydrophobic layer and the hydrophilic layer (the mass ratio of PTFE and carbon black in the hydrophobic layer is 10:90, and the rest is the same as the second hydrophobic layer), and the thickness of the second hydrophobic layer is changed to 5μm.

[0103] Example 10 This embodiment is basically the same as Embodiment 1, except that a 5μm thick hydrophobic layer is added between the first hydrophobic layer and the substrate layer (the mass ratio of PTFE and carbon black in this hydrophobic layer is 50:50, and the rest is the same as the first hydrophobic layer), and the thickness of the first hydrophobic layer is changed to 5μm.

[0104] Comparative Example 1 This comparative example is basically the same as Example 1, except that the material of the first hydrophobic layer in this comparative example is replaced with the same material as the material of the second hydrophobic layer.

[0105] Comparative Example 2 This comparative example is basically the same as Example 1, except that the second hydrophobic layer material is replaced with the same material as the first hydrophobic layer material in this comparative example.

[0106] Test examples: The surface energy, contact angle between the first hydrophobic layer and water and its surface energy after plasma treatment, the contact angle between the second hydrophobic layer and water and its surface energy after plasma treatment, and the contact angle between the hydrophilic layer and water of the plasma-treated carbon fiber paper in the examples and comparative examples were tested. The test results are shown in Table 1. The cathode electrodes obtained in the examples and comparative examples were applied to anion exchange membrane electrolyzers for polarization curve testing and hydrogen purity testing. The test results are shown in Table 1.

[0107] Surface energy testing: The surface energy is obtained by measuring the contact angle of a liquid with known surface tension on a solid surface and then calculating it using a certain mathematical model.

[0108] Contact angle test: Using the image analysis method of the contact angle measuring instrument, a droplet is dropped onto the surface of a solid sample. The shape image of the droplet is obtained through a microscope and camera. Then, digital image processing and some algorithms (such as tangent method, circle fitting method, ellipse fitting method, Young-Laplace equation fitting method, etc.) are used to calculate the contact angle of the droplet in the image.

[0109] Polarization curve test: constant current method—starting from the open circuit voltage, the current is increased stepwise, and the record is made after the voltage stabilizes.

[0110] Hydrogen purity: The hydrogen composition at the cathode outlet is continuously monitored using online gas chromatography (GC). The content of oxygen (from cross-contamination) and other impurity gases is measured directly. Higher purity (e.g., >99.99%) indicates higher hydrogen removal efficiency and less cathode blockage by liquid water.

[0111] Table 1 Test Results

[0112] As can be seen from Table 1: Compared with Example 5, the cell voltage of the electrolytic cell in Example 1 is lower. It can be seen that the content of hydrophobic material in the first hydrophobic layer affects the performance of the cathode gas diffusion layer, and thus affects the performance of the electrolytic cell.

[0113] Compared with Example 6, the cell voltage of the electrolytic cell in Example 1 is lower. It can be seen that the content of hydrophobic material in the second hydrophobic layer affects the performance of the cathode gas diffusion layer, and thus affects the performance of the electrolytic cell.

[0114] Compared to Examples 7 and 8, Example 1 exhibits a lower cell voltage, indicating that the thickness of the first hydrophobic layer affects the performance of the cathode gas diffusion layer, thereby influencing the performance of the electrolyzer. Example 8 shows a higher cell voltage, suggesting that a thinner hydrophobic layer may reduce the breakthrough pressure of liquid water, slightly decreasing flood resistance, drastically reducing the electron conduction path in the electrolyzer, and significantly increasing resistance. If the thickness is too thin (e.g., 2 μm), it may lead to coating discontinuities and defects, making the coating locally susceptible to water penetration and increasing the risk of flooding.

[0115] Compared with Examples 9 and 10, Example 1 shows that the cell pressure and hydrogen purity of the electrolyzer are similar. It can be seen that by setting two hydrophobic layers with gradient hydrophobicity, this application can improve the hydrogen purity of the electrolyzer and make the electrolyzer have good resistance to flooding.

[0116] Compared with Comparative Examples 1 and 2, Examples 1-10 show that the electrolyzers of Examples 1-10 have lower cell pressure and higher hydrogen purity. It can be seen that by setting a gradient hydrophobic layer between the hydrophilic layer and the substrate layer, this application can improve the hydrogen purity and reduce the cell pressure of the electrolyzer, thereby improving the performance of the electrolyzer.

[0117] The foregoing has provided a detailed description of a cathode gas diffusion layer and its preparation method, membrane electrode, and anion exchange membrane electrolyzer provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A cathode gas diffusion layer, characterized in that, It includes a matrix layer (1), a transition layer (2) and a hydrophilic layer (3) stacked in sequence. The transition layer (2) includes at least two hydrophobic layers stacked in sequence. The contact angle between the hydrophobic layer near the hydrophilic layer (3) and water is smaller than the contact angle between the hydrophobic layer away from the hydrophilic layer (3) and water. The contact angle between the hydrophilic layer (3) and water is less than or equal to 90°, and the contact angle between the hydrophobic layer and water is greater than 90°.

2. The cathode gas diffusion layer according to claim 1, characterized in that, The hydrophilic layer (3) comprises a hydrophilic material, which includes one or more of the following: elemental metal, metal oxide, metal hydroxide, layered metal double hydroxide, and hydrophilic carbon material. The elemental metal, the metal oxide, the metal hydroxide, and the layered metal double hydroxide each independently include one of the following: Ni, Co, Fe, Pt, Ru, Mo, Ir, and Ti; and / or The hydrophilic layer (3) includes anion exchange resin.

3. The cathode gas diffusion layer according to claim 1, characterized in that, The hydrophilic layer (3) comprises a hydrophilic material and anion exchange resin, wherein the mass percentage of the hydrophilic material and the anion exchange resin in the hydrophilic layer (3) is (50%-90%): (10%-50%). The contact angle between the hydrophilic layer (3) and water is 0°-30°.

4. The cathode gas diffusion layer according to claim 1, characterized in that, The hydrophobic layer comprises a hydrophobic material, which includes one or more of perfluoroalkoxy resins, perfluoroethylene propylene, and polytetrafluoroethylene; and / or The hydrophobic layer comprises carbon materials, including one or more of carbon black, carbon nanotubes, graphene, reduced graphene oxide, and carbon fibers.

5. The cathode gas diffusion layer according to claim 1, characterized in that, The hydrophobic layer comprises a hydrophobic material and a carbon material, wherein the mass content of the hydrophobic material to the mass content of the carbon material in the hydrophobic layer is (5%-50%) : (50%-95%); and / or The hydrophobic materials in the at least two hydrophobic layers are of the same type, and the mass content of the hydrophobic material in the hydrophobic layer closer to the hydrophilic layer (3) is less than the mass content of the hydrophobic material in the hydrophobic layer farther from the hydrophilic layer (3).

6. The cathode gas diffusion layer according to claim 1, characterized in that, Along the direction away from the hydrophilic layer (3), the contact angle between the hydrophobic layer and water increases sequentially; and / or The contact angle between at least two of the hydrophobic layers and water is 100°-160°.

7. The cathode gas diffusion layer according to claim 4, characterized in that, The transition layer (2) includes a first hydrophobic layer (21) and a second hydrophobic layer (22) stacked along the direction close to the hydrophilic layer (3), wherein the contact angle between the first hydrophobic layer (21) and water is 140°-160°, and the contact angle between the second hydrophobic layer (22) and water is 100°-140°; and / or The transition layer (2) includes a first hydrophobic layer (21) and a second hydrophobic layer (22) stacked along the direction close to the hydrophilic layer (3). The mass content of the hydrophobic material in the first hydrophobic layer (21) is 20%-50%, and the mass content of the hydrophobic material in the second hydrophobic layer (22) is 5%-20%.

8. The cathode gas diffusion layer according to claim 1, characterized in that, The thickness of the hydrophilic layer (3) is 10 μm-50 μm; and / or The thickness of the transition layer (2) is 10 μm-50 μm; and / or The thickness of the single-layer hydrophobic layer is 5μm-10μm.

9. The cathode gas diffusion layer according to claim 1, characterized in that, The substrate layer (1) includes one or more of carbon fiber paper and carbon cloth; and / or The porosity of the matrix layer (1) is 50%-95%.

10. A method for preparing a cathode gas diffusion layer, characterized in that, include: A transition layer (2) is formed on one side surface of the substrate layer (1), and a hydrophilic layer (3) is formed on the side of the transition layer (2) away from the substrate layer (1) to obtain a cathode gas diffusion layer. The transition layer (2) includes at least two stacked hydrophobic layers. The contact angle between the hydrophobic layer near the hydrophilic layer (3) and water is smaller than the contact angle between the hydrophobic layer away from the hydrophilic layer (3) and water. The contact angle between the hydrophilic layer (3) and water is less than or equal to 90°, and the contact angle between the hydrophobic layer and water is greater than 90°.

11. The method for preparing the cathode gas diffusion layer according to claim 10, characterized in that, The formation of a transition layer (2) on one side surface of the substrate layer (1) includes: The first hydrophobic slurry is placed on one side surface of the substrate layer (1), and then the first sintering and first plasma treatment are performed to form the first hydrophobic layer (21). The second hydrophobic slurry is placed on the side surface of the first hydrophobic layer (21) away from the substrate layer (1), and then a second sintering and a second plasma treatment are performed to form the second hydrophobic layer (22). The first hydrophobic slurry and the second hydrophobic slurry each contain hydrophobic materials.

12. The method for preparing the cathode gas diffusion layer according to claim 11, characterized in that, The first sintering temperature is 300℃-500℃, and the first sintering time is 20min-30min; and / or The first sintering is carried out in a vacuum or inert atmosphere; and / or The plasma used in the first plasma treatment is a mixture of Ar and O2, wherein the volume percentages of Ar and O2 are (70%-90%):(30%-10%); and / or The surface energy of the side of the first hydrophobic layer (21) after the first plasma treatment that faces away from the substrate layer (1) is 20 mN / m-60 mN / m; and / or The second sintering temperature is 300℃-500℃, and the second sintering time is 20min-30min; and / or The second sintering is carried out in a vacuum or inert atmosphere; and / or The plasma used in the second plasma treatment is a mixture of Ar and O2, wherein the volume percentages of Ar and O2 are (70%-90%):(30%-10%); and / or The surface energy of the side of the second hydrophobic layer (22) after the second plasma treatment is 20mN / m-60mN / m away from the first hydrophobic layer (21).

13. The method for preparing the cathode gas diffusion layer according to claim 10, characterized in that, The formation of a hydrophilic layer (3) on the side of the transition layer (2) opposite to the matrix layer (1) includes: The hydrophilic slurry is placed on the side of the transition layer (2) away from the matrix layer (1), and then dried and shaped to form the hydrophilic layer (3).

14. The method for preparing the cathode gas diffusion layer according to claim 13, characterized in that, The drying process includes drying at 50℃-65℃ for 20-25 minutes, followed by drying at 80℃-85℃ for 50-60 minutes; and / or The setting process includes setting in an inert gas atmosphere at 100℃-105℃ for 10-15 minutes.

15. A membrane electrode, characterized in that, The cathode gas diffusion layer includes a cathode catalyst layer (4) and a cathode gas diffusion layer as described in any one of claims 1-9 or as described in any one of claims 10-14, wherein the cathode catalyst layer (4) is stacked on the side of the hydrophilic layer (3) away from the transition layer (2).

16. An anion exchange membrane electrolyzer, characterized in that, Includes the membrane electrode as described in claim 15.

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