Membrane electrode assembly and preparation method and application thereof

Abstract

The invention provides a membrane electrode assembly and a preparation method and application thereof, and belongs to the technical field of electrolytic tanks. The membrane electrode assembly comprises a diaphragm, an electron conduction layer and a catalyst layer, the electron conduction layer is located on the surface of the diaphragm, the electron conduction layer is of a porous structure containing a plurality of through pore channels, and a direct contact interface is formed between the electron conduction layer and the diaphragm; the catalytic layer is located on at least part of the surface of the diaphragm and / or the electron conducting layer except the contact interface.

Description

Technical Field

[0001] This application relates to the field of electrolytic cell technology, specifically to a membrane electrode assembly, its preparation method, and its application. Background Technology

[0002] Electrolyzers for hydrogen production via water electrolysis mainly consist of water splitting electrodes and a membrane. Taking an alkaline electrolyzer as an example, the electrode material surface is loaded with a high specific surface area catalyst layer. During electrocatalysis, the cathode, membrane, and anode are tightly bonded together to reduce the ion transport distance, thereby reducing ohmic losses in ion transfer.

[0003] In traditional methods, the catalyst is partially covered by the electrode or electron conductor in close contact with the membrane. Due to mass transfer issues, this portion of the catalyst is difficult to fully utilize, resulting in low reaction efficiency. Furthermore, the gas generated on the surface of this portion of the catalyst can easily pass through the membrane to the other side, reducing the purity of the gas. Summary of the Invention

[0004] In view of the above, in order to at least partially solve at least one of the aforementioned technical problems, this application provides a membrane electrode assembly, its preparation method, and its application.

[0005] To achieve the above objectives, the technical solution of this application is as follows:

[0006] According to one embodiment of this application, a membrane electrode assembly is provided, comprising: a membrane, an electron conduction layer, and a catalyst layer; the electron conduction layer is located on the surface of the membrane, the electron conduction layer has a porous structure containing multiple through channels, and has a contact interface in direct contact with the membrane; the catalyst layer is located on at least a portion of the surface of the membrane and / or the electron conduction layer, excluding the contact interface.

[0007] According to another embodiment of this application, a method for preparing a membrane electrode assembly is provided, comprising: providing an electron conduction layer having a porous structure containing multiple through channels; fixing the electron conduction layer onto the surface of a membrane to obtain a composite membrane; and loading a catalyst onto the surface of the composite membrane to obtain a membrane electrode assembly.

[0008] According to another embodiment of this application, an application of the membrane electrode assembly as described above in electrolytic hydrogen production is provided.

[0009] According to an embodiment of this application, an electron conduction layer is first bonded to the surface of a membrane to form a composite membrane, so that there is a direct contact interface between the electron conduction layer and the membrane, so that there is no catalyst at the contact interface, reducing the supersaturation of generated gas at the contact interface, thereby reducing the adverse effect of the large presence of catalyst in the contact interface area on gas purity, and reducing the waste of catalyst resources. Attached Figure Description

[0010] The above and other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0011] Figure 1 This is a schematic diagram of the structure of the membrane electrode assembly according to an embodiment of this application, wherein a is a schematic diagram of the structure of the catalytic layer located in the electron conduction layer excluding the contact interface, b is a schematic diagram of the structure of the catalytic layer located in the membrane excluding the contact interface, and c is a schematic diagram of the structure of the catalytic layer located in the electron conduction layer and the membrane excluding the contact interface.

[0012] Figure 2 The diagram shows the structure of a membrane electrode assembly of a related technology, where a is a structural diagram in which a catalyst layer is formed on the surface of the membrane and is in direct contact with the electron conduction layer, and b is a structural diagram in which a catalyst layer is formed on the surface of the electron conduction layer and is in direct contact with the membrane.

[0013] Figure 3 This is a schematic flowchart illustrating a method for fabricating a membrane electrode assembly according to another embodiment of this application;

[0014] Figure 4 This is a scanning electron microscope image of a cross section of the cathode-film assembly 1 prepared in Example 1 of this application;

[0015] Figure 5 This is a top-view scanning electron microscope image of the cathode-film assembly 1 prepared in Example 1 of this application;

[0016] Figure 6 for Figure 5 A magnified view of a portion of the image;

[0017] Figure 7 Here are scanning electron microscope (SEM) images of the membrane electrode assembly 4 prepared in Example 4 of this application, where a is an SEM image at a 2 μm scale and b is an SEM image at a 1 μm scale; and

[0018] Figure 8 This is a top-view scanning electron microscope image of the cathode-film assembly 5 prepared in Example 5 of this application.

[0019] [Explanation of Labels in the Attached Image]

[0020] 1-Septum;

[0021] 2-Electron conduction layer;

[0022] 3-Catalyst layer. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0024] In the following detailed description, numerous specific details are set forth for ease of explanation to provide a thorough understanding of the embodiments of this application. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0026] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). When using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0027] In this application, the relative position between two components (e.g., a membrane or region), as referred to by terms such as "above," "on," or "above," can mean that the two components are in direct contact or that they are not in direct contact. Similarly, the relative position between two components, as referred to by terms such as "below," "under," or "below," can mean that the two components are in direct contact or that they are not in direct contact. For example, when one component (e.g., a membrane or region) is referred to as "on another component," it can be directly on the other component, or there may be other components between them. On the other hand, when a component is referred to as "directly on another component," there are no components between them. Furthermore, when one component is referred to as "on another component," the two components have a vertical relationship in the planar view, and this component can be above or below the other component, thus this vertical relationship depends on the orientation of the device.

[0028] Hydrogen production through water electrolysis typically involves the separate evolution of hydrogen and oxygen from the cathode and anode with relatively low energy consumption, while preventing the two gases from mixing to ensure gas purity and the safety of the electrolyzer. The water splitting electrode, usually composed of an electron conductor and a catalyst, not only transports electrons but also, due to its catalyst-coated surface, serves as the reaction site for hydrogen production in the electrolyzer. It requires high activity, the largest possible active contact area per unit projected area, and good degassing properties. The diaphragm plays a crucial role in preventing hydrogen and oxygen mixing while retaining ion transport capabilities, thus creating a current loop in the electrolysis process.

[0029] Traditionally, the interface between the electrode or electron conductor and the membrane is covered with a catalyst. Taking an alkaline electrolyzer as an example, the cathode or anode consists of an electron conductor and a catalyst, respectively, with the catalyst covering the surface of the electron conductor. During assembly, the cathode and membrane, or the membrane and anode, are tightly bonded to reduce the ion transfer distance. The applicant has found that the portion of the electron conductor bonded to the membrane is covered with a significant amount of catalyst. Due to mass transfer limitations, this portion of the catalyst is difficult to fully utilize. Furthermore, the gas generated on the excessive catalyst surface in this bonded portion exhibits a supersaturated state due to the high mass transfer resistance. This not only negatively impacts catalytic efficiency but also makes it easier for the supersaturated gas to penetrate the membrane and be released at the opposite electrode, thereby compromising the purity of the gas on the opposite side.

[0030] In realizing the concept of this application, it was discovered that by forming a direct contact interface between the electron conduction layer and the membrane, that is, by having virtually no catalytic material on the direct contact interface, the supersaturation of gas on the contact interface is reduced, thereby reducing the adverse effect of the large presence of catalyst in the contact interface region on gas purity.

[0031] Specifically, according to one embodiment of this application, a membrane electrode assembly is provided. Figure 1 This is a schematic diagram of the membrane electrode assembly according to an embodiment of this application, wherein, a is a schematic diagram of the catalytic layer located in the electron conduction layer excluding the contact interface, b is a schematic diagram of the catalytic layer located in the membrane excluding the contact interface, and c is a schematic diagram of the catalytic layer located in both the electron conduction layer and the membrane excluding the contact interface. Figure 1 As shown in a~c, the membrane electrode assembly provided in this application includes: a membrane 1, an electron conduction layer 2, and a catalyst layer 3. The electron conduction layer 2 is located on the surface of the membrane 1, and has a porous structure containing multiple through channels 21, and has a contact interface that directly contacts the membrane 1. The catalyst layer 3 is located on at least a portion of the surface of the membrane 1 and / or the electron conduction layer 2, excluding the contact interface.

[0032] Based on the embodiments of this application, please continue to refer to... Figure 1In diagrams a-c, the "contact interface" is formed by first fixing the electron conduction layer 2 onto the membrane 1, creating a direct contact between the membrane 1 and the electron conduction layer 2. At this interface, the electron conduction layer 2 and the membrane 1 are in surface contact, and no catalyst is present. It can be understood that the "contact interface" does not include the surface of the membrane exposed to the through-holes 21. Since there is no catalyst at the direct contact interface between the membrane 1 and the electron conduction layer 2, the electrochemical catalytic activity is mainly achieved by a catalyst located elsewhere on the interface. This not only improves catalyst utilization and reduces catalyst waste but also avoids the adverse effects of the catalyst within the contact interface on the electrochemical reaction, thus improving electrocatalytic efficiency.

[0033] More specifically, such as Figure 1 As shown in Figure a, the catalyst layer 3 may be located on at least a portion of the surface of the electron conduction layer 2, excluding the contact interface, and extend to the boundary of the contact interface; as Figure 1 As shown in Figure b, the catalyst layer 3 may be located on at least a portion of the surface of the membrane 1, excluding the contact interface, and extend to the boundary of the contact interface; as Figure 1 As shown in Figure c, the catalyst layer 3 can be located on at least a portion of the surface of the membrane 1 and the electron conduction layer 2, excluding the contact interface, and extends to the boundary of the contact interface. It should be noted that in the actual preparation process, as... Figure 1 The contact interface shown may contain areas of indirect contact. This is because the catalyst will inevitably diffuse partially between the electron conduction layer 2 and the membrane 1, causing the part of the interface that was originally in direct contact between the electron conduction layer 2 and the membrane 1 to be loaded by the catalyst and transformed into an indirect contact interface.

[0034] Figure 2 The diagram shows the structure of a membrane electrode assembly of a related technology. In the diagram, a is a schematic diagram of a catalytic layer formed on the surface of the membrane and in direct contact with the electron conduction layer, and b is a schematic diagram of a catalytic layer formed on the surface of the electron conduction layer and in direct contact with the membrane. Figure 2 Figures a and b show two combinations of membrane electrode assemblies in related technologies. In both combinations, there is no direct contact interface between the membrane 1 and the electron conduction layer 2. Instead, the catalyst is present in the area where the membrane 1 and the electron conduction layer 2 are bonded together.

[0035] With Figure 1A comparison of figures a-c shows that, since there is essentially no catalyst at the interface between the membrane and the electron conduction layer in this application, the possibility of gas generation at the interface is reduced, thereby reducing the supersaturation of gas at the interface. This helps to improve the efficiency of the electrochemical reaction and also reduces the permeation and release of gas from the interface to the opposite electrode, thus reducing the impact on the gas purity at the opposite electrode and improving the utilization rate of the catalyst. Furthermore, the electron conduction layer 2 is located on the surface of the membrane 1, and the porous structure of multiple through-holes 21 helps to provide a transport path for the desorbed product gas, thereby suppressing the supersaturation state of gas on the surface of the membrane 1.

[0036] According to embodiments of this application, the area of ​​the contact interface occupies less than 50% of the surface area of ​​the membrane 1, for example, it can be 10%, 20%, 30%, 40%, 45%, or 50%. When the area of ​​the contact interface is too large, it means that the inefficient active area is larger, which is not conducive to improving the current density per unit area and reducing the gas yield per unit area. Setting the area of ​​the contact interface within the above range can ensure the effective transport of ions and electrons, which is conducive to giving full play to the electrocatalytic effect of the catalyst layer 3 and ensuring a high hydrogen production per unit area for the membrane electrode assembly as a whole.

[0037] According to embodiments of this application, the membrane 1 and the electron-conducting layer 2 are fixedly connected, preferably a non-removable fixed connection. This fixed connection reduces catalyst deposition at the contact interface and facilitates the formation of a direct contact interface between the membrane 1 and the electron-conducting layer 2. The non-removable fixed connection can be, for example, adhesive bonding or welding. Further optionally, welding can be performed, for example, by using hot pressing.

[0038] According to embodiments of this application, the pore size of the porous structure of the electron conduction layer 2 is 30~500μm, for example, it can be 30μm, 50μm, 70μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm or 500μm, preferably 100~400μm. When the pore size of the porous structure is within the above range, it helps to promote the desorption and transport of product gases, and also helps to facilitate effective physical contact between the electron conduction layer 2 and the membrane 1, thereby improving the efficiency of the electrochemical reaction.

[0039] Alternatively, the average pore size of the end of the through-channel 21 near the membrane 1 is less than or equal to the average pore size of the other end. This configuration facilitates the deposition of the catalyst through the through-channel 21 onto the surface of the membrane 1 during the deposition or coating of the catalyst layer. It also allows the catalyst to extend to the boundary of the contact interface, thereby forming a phase-separated interface that enables better transfer of electrons, ions, and gases, thus contributing to improved catalytic activity.

[0040] According to embodiments of this application, the porosity of the electron conducting layer 2 is 60-90%, for example, it can be 60%, 70%, 80% or 90%, preferably 70%-80%, which helps to provide sufficient channels and maintain good electron conductivity. Furthermore, the volume of the closed pores accounts for less than 5% of the volume of the electron conducting layer, for example, it can be 1%, 2%, 3%, 4% or 5%, to ensure the efficiency of gas and electron transport.

[0041] Specifically, the surface openings of the porous structure can be selected according to requirements, and the surface pore openings may vary for different porous materials. Some uniform porous materials, such as foamed metals, can have their single-sided surface openings enlarged through post-processing methods such as strong curling, thereby increasing the average pore diameter on one end of the surface to be larger than that on the other end.

[0042] According to embodiments of this application, the electron conduction layer 2 can be an electrode substrate layer or a gas diffusion layer, including at least one of nickel, stainless steel, nickel-based alloys, titanium, platinum, and gold. It can be a structure of metal mesh or foamed metal, or include at least one of carbon fiber, carbon cloth, and carbon felt. When the electron conduction layer 2 uses the above-mentioned materials, it exhibits both good electrical conductivity and good chemical stability.

[0043] According to embodiments of this application, the thickness of the electron conducting layer 2 is 80~500μm, for example, it can be 80μm, 100μm, 200μm, 300μm, 400μm or 500μm, preferably 120~360μm. When the thickness of the electron conducting layer 2 is within the above range, it can ensure that the electron conducting layer 2 has good flexibility while also having good support, so that the membrane electrode assembly has good mechanical properties and chemical stability.

[0044] According to embodiments of this application, the separator 1 comprises at least one membrane material selected from polymer microporous membranes, organic-inorganic composite microporous membranes, or ceramic membranes. Separator 1 preferably comprises at least one of polypropylene (PP), polysulfone (PSU), polyphenylene sulfide (PPS), polyethylene (PE), polysulfone-zirconia (PSU-ZrO2) composite microporous membranes, polysulfone-titanium oxide (PSU-TiO2) composite microporous membranes, polysulfone-cerium oxide (PSU-CeO2) composite microporous membranes, polysulfone-nickel oxide (PSU-NiO) composite microporous membranes, zirconium oxide (ZrO2), alumina (Al2O3), titanium oxide (TiO2), and nickel oxide (NiO). The aforementioned separator 1 has a swelling degree close to 0, making it resistant to swelling upon contact with water. This facilitates a direct contact interface between the electron conduction layer 2 and the separator 1, and promotes the formation of a phase-separated interface for electron, ion, and gas transport, thereby enhancing the catalytic activity of the membrane electrode assembly.

[0045] Specifically, the appropriate membrane material can be selected according to the application. For example, polymer microporous membranes or organic-inorganic composite microporous membranes can be used in alkaline water electrolysis for hydrogen production, or ceramic membranes can be used in solid oxide electrolysis for hydrogen production.

[0046] According to embodiments of this application, the diaphragm 1 possesses certain acid and alkali resistance, which helps improve the stability and service life of the membrane electrode assembly. The thickness of the diaphragm 1 is 50~700μm, for example, it can be 50μm, 100μm, 200μm, 300μm, 400μm, 500μm, 600μm or 700μm, preferably 200~500μm. When the thickness of the diaphragm 1 is within the above range, it can have both suitable mass transfer effect and good mechanical strength, resulting in good stability and service life of the membrane electrode assembly.

[0047] According to embodiments of this application, the membrane electrode assembly of this application is suitable for use in electrochemical reactions of gas generation, including but not limited to reactions such as water electrolysis for hydrogen and oxygen production, electrocatalytic reduction of carbon dioxide, or ammonia synthesis. Therefore, for different electrochemical reactions, the catalyst layer 3 includes a hydrogen evolution catalyst, an oxygen evolution catalyst, or a carbon dioxide reduction catalyst. The hydrogen evolution catalyst is selected from at least one metal or an alloy composed of at least two metals selected from Pt, Ru, Rh, Ni, Mo, Co, or Fe; the oxygen evolution catalyst is selected from at least one selected from IrO2, RhO2, RuO2, NiO, NiOOH, FeOOH, NiFeOOH, and NiFe-LDH; and the carbon dioxide reduction catalyst is selected from at least one copper-based catalyst. The catalyst in the catalyst layer 3 can be selected according to the needs of the actual reaction, as long as it can serve as an electrocatalytically active component.

[0048] Further optionally, the catalyst layer 3 may contain only the aforementioned catalyst as the active material, or a conductive support containing a carbon-based material may be used as needed. When a conductive support is included, the active material may be loaded onto the surface of the conductive support to form a core-shell structure, or it may be uniformly doped within the conductive support. Further optionally, the catalyst morphology within the catalyst layer 3 is micro / nano particles, such as spherical, rod-shaped, needle-shaped, or layered structures.

[0049] According to embodiments of this application, the catalyst used in the catalyst layer 3 has a content of 100~200 g / m³ in the membrane electrode assembly. 2 For example, it could be 100 g / m 2 150 g / m 2 Or 200 g / m 2 An appropriate catalyst content helps to form sufficient active sites. Compared with traditional membrane electrode assemblies, the catalyst in the membrane electrode assembly of this application still has good electrocatalytic effect even with a smaller amount.

[0050] According to embodiments of this application, the membrane electrode assembly may further include another electron-conducting layer and another catalytic layer, located on another surface of the membrane, employing methods such as... Figure 1 The structure shown in a~c achieves the effect of reducing catalyst usage and improving catalytic efficiency on both sides of the membrane.

[0051] According to another embodiment of this application, a method for fabricating a membrane electrode assembly is provided. Figure 3 This is a schematic flowchart illustrating a method for fabricating a membrane electrode assembly according to another embodiment of this application, as shown below. Figure 1 and Figure 3 As shown, this includes operations S301 to S303.

[0052] In operation S301, an electron conduction layer 2 with a porous structure containing multiple through channels 21 is provided.

[0053] According to embodiments of this application, a porous structure having multiple through-holes 21 is beneficial for the transport of product gases and for forming channels for electron transport.

[0054] In operation S302, the electron conduction layer 2 is fixed on the surface of the diaphragm 1 to obtain a composite membrane.

[0055] According to an embodiment of this application, by first fixing the electron conduction layer 2 and the membrane 1 together to form a contact interface in which the two are in direct contact, there is no catalyst at the contact interface.

[0056] In operation S303, the catalyst is loaded onto the surface of the composite membrane to obtain the membrane electrode assembly.

[0057] According to the embodiments of this application, the catalyst is loaded on the surface of the membrane 1 and / or the electron conduction layer 2, excluding the contact interface, forming a structure in which the catalyst layer 3 is in contact with the boundary of the contact interface, which helps to improve the transfer efficiency of electrons, ions and gases and improve catalytic activity.

[0058] According to the embodiments of this application, based on the above-described preparation method of first preparing a composite membrane and then supporting the catalyst layer 3, while reducing the amount of catalyst used, the area of ​​the formed catalyst layer 3 is moderate, and under the same potential conditions, the current density is greater, the product gas distribution is more uniform, and the purity is higher.

[0059] According to an embodiment of this application, in operation S302, the electron-conducting layer can be fixed to the surface of the diaphragm by hot pressing or casting. For example, when bonding the electron-conducting layer 2 to the surface of the diaphragm 1 by hot pressing, the electron-conducting layer 2 and the diaphragm 1 can be placed in a hot pressing device, such as a heated roller, and bonded under a pressure of, for example, 100°C to 300°C and 10 to 20 MPa. Similarly, when bonding the electron-conducting layer 2 to the surface of the diaphragm 1 by casting, the film material of the diaphragm 1 can be cast in situ onto the electron-conducting layer. Since the fixing methods are not critical to this application, they will not be listed individually here.

[0060] According to an embodiment of this application, in operation S303, the catalyst can be loaded onto the surface of the composite membrane by electrodeposition, chemical deposition, or coating.

[0061] For example, loading a catalyst onto the surface of a composite membrane by coating includes: applying a catalyst slurry comprising a binder, a catalytically active component, and an organic solvent onto the surface of the composite membrane by drop-coating or spray-coating, followed by drying; repeating the coating and drying operations yields a product with the following properties: Figure 1 The membrane electrode assembly with the structure shown in Figure b.

[0062] Drop-coating or spray-coating methods help form a uniform catalytic layer 3 on the surface of the composite membrane, which helps improve catalytic efficiency. Uniform coating of the catalyst slurry facilitates more efficient three-phase mass transfer of ions, electrons, and gas, thereby improving catalytic activity. Furthermore, the membrane electrode assembly prepared by this coating method has the advantages of low catalyst dosage, moderate catalytic reaction area, and superior gas purity in the corresponding electrolyzer.

[0063] According to embodiments of this application, the adhesive may further include, but is not limited to, Nafion ionomer, Sustainion ionomer, polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polytetrafluoroethylene (PTEE), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylic acid-polyacrylonitrile amphiphilic block copolymer (PAA / PAN), fluorinated ethylene propylene (FEP), etc., and the organic solvent may include, but is not limited to, ethanol, isopropanol, etc.

[0064] For example, loading a catalyst onto the surface of a composite membrane via electrodeposition can specifically include: using the composite membrane as the working electrode, performing electrodeposition in an electrolyte containing a catalyst precursor to obtain a membrane electrode assembly. During electrodeposition, the catalyst precursor is converted into a catalyst. For instance, when the catalyst is a metal, the catalyst precursor can be a compound containing metal ions, which are electroreduced to metal during electrodeposition; when the catalyst is a metal oxide, the catalyst precursor can be a metal compound containing metal ions, which are oxidized to metal oxide during electrodeposition. Using electrodeposition allows for more precise adjustment of the thickness and composition of the catalyst layer 3, resulting in a more uniform and continuous catalyst layer 3, which can yield a product with... Figure 1 The membrane electrode assembly with the structure shown in Figure a.

[0065] Electrodeposition helps to control the morphology of the catalyst into micro- and nano-particle shapes, thereby improving catalytic activity. The membrane electrode assembly prepared by this electrodeposition method has the advantages of low catalyst consumption, moderate catalytic reaction area, and superior performance in terms of gas purity in the corresponding electrolyzer.

[0066] According to embodiments of this application, the catalyst layer 3 can be further formed by a combination of drop-coating or spray-coating and electrodeposition. For example, the catalyst layer 3 can be formed by first drop-coating and then electrodeposition, or first electrodeposition and then drop-coating, thereby obtaining a catalyst layer with the following properties: Figure 1 The membrane electrode assembly with the structure shown in Figure c.

[0067] Of course, it is not limited to this. For example, the catalyst layer 3 can also be formed in one step by chemical deposition, thereby obtaining a product with properties such as... Figure 1 The membrane electrode assembly with the structure shown in Figure c is an example of a chemical deposition method, specifically a chemical plating method. This method involves loading the catalyst onto the surface of the composite membrane by chemical deposition, which includes: applying a chemical plating solution comprising a catalyst precursor and a reducing agent to the surface of the composite membrane by drop-coating or spraying, followed by a reduction reaction to obtain the membrane electrode assembly. The catalyst precursor is converted into a catalyst during the chemical plating process. For example, when the catalyst is a metal, the catalyst precursor can be a metal compound containing metal ions, which are reduced to metal by the reducing agent during chemical plating. Alternatively, the chemical deposition method can also be a chemical precipitation reaction. When loading the catalyst onto the surface of the composite membrane, a chemical deposition solution comprising a catalyst precursor and a precipitant can be applied to the surface of the composite membrane by drop-coating or spraying, followed by a precipitation reaction to obtain the membrane electrode assembly.

[0068] Chemical plating allows for the control of catalyst uniform distribution, facilitating the formation of a uniform catalyst layer and improving catalytic efficiency. Uniform coating of the catalyst slurry promotes more efficient ion, electron, and gas phase mass transfer, thereby enhancing catalytic activity. The membrane electrode assembly prepared by this electrodeposition method features low catalyst usage, moderate catalytic reaction area, and superior gas purity in the corresponding electrolytic cell.

[0069] Alternatively, the catalyst layer 3 can be formed stepwise by methods such as drop-coating followed by chemical deposition, or chemical deposition followed by electrodeposition, thereby obtaining a product with properties such as... Figure 1 The membrane electrode assembly shown in Figure c has the following characteristics: The membrane electrode assembly prepared by this chemical deposition method or combined preparation method has the advantages of using a larger amount of catalyst, a larger catalytic reaction area, the highest current density at the same potential, and superior gas purity in the corresponding electrolyzer.

[0070] According to the embodiments of this application, the reducing agent can be further selected according to actual needs, such as formaldehyde, hypophosphite and its salts, phosphorous acid and its salts, borohydride, hydrazine hydrate, etc., as long as it can reduce the catalytically active component to obtain the catalyst.

[0071] It is understandable that the aforementioned catalytically active components or catalyst precursors can be selected according to actual needs, such as catalyst loading methods and catalyst types, to obtain the catalyst. For example, for coating methods, catalyst powders such as metal powders can be selected as catalytically active components, while for electrodeposition or electroless plating methods, catalyst precursors such as soluble metal salts can be selected as catalytically active components.

[0072] According to another embodiment of this application, an application of the membrane electrode assembly as described above or the membrane electrode assembly prepared by the preparation method described above in electrolytic hydrogen production is provided.

[0073] According to the embodiments of this application, in the process of electrolytic hydrogen production, the above-mentioned membrane electrode assembly has a good hydrogen production effect, and can save the amount of catalyst while having high catalytic efficiency and low hydrogen content in oxygen.

[0074] According to embodiments of this application, hydrogen production via electrolysis can be achieved through alkaline water electrolysis, cation exchange membrane electrolysis, or solid oxide electrolysis. It is understood that the materials of each layer in the membrane electrode assembly can be selected based on whether alkaline water electrolysis, cation exchange membrane electrolysis, or solid oxide electrolysis is used.

[0075] According to the embodiments of this application, the above-mentioned membrane electrode assembly is not limited to the field of electrolytic hydrogen production technology. It can be applied to any electrochemical reaction process that requires the use of a membrane electrode structure and involves the generation of product gas. For example, it can also be applied to electrocatalytic fields such as fuel cells, electrocatalytic reduction of CO2 or ammonia synthesis.

[0076] The present application is further illustrated below through embodiments, accompanying drawings, and related test experiments and results. In the following detailed description, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present application. However, it is apparent that one or more embodiments may be implemented without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict.

[0077] It should be noted that the specific embodiments described below are merely illustrative examples, and the scope of protection of this application is not limited thereto. The chemicals and raw materials used in the following embodiments are all commercially available or prepared using recognized processing methods.

[0078] Example 1:

[0079] The diaphragm was made of Agfa Zirfon UTP 500 (composed of open-mesh polyphenylene sulfide fabric, uniformly coated with a mixture of polymer and zirconium oxide). The diaphragm was bonded to a 46-mesh, 250μm diameter twill nickel wire mesh via hot pressing to prepare a membrane-nickel mesh assembly. A nickel slurry with a concentration of approximately 1 g / L was prepared by mixing Nafion membrane solution, 25-30μm nickel powder, and a certain amount of ethanol solution. The membrane-nickel mesh assembly was placed with the nickel mesh side facing up on a 100°C heating plate, and the nickel slurry was dripped onto the surface. After drying, it was dripped again, and this process was repeated 7 times. The final membrane electrode assembly, i.e., cathode-membrane assembly 1, had a nickel content of approximately 126 g / m². 2 . Figure 4 This is a scanning electron microscope image of a cross section of the cathode-film assembly 1 prepared in Example 1 of this application; Figure 5 This is a top-view scanning electron microscope image of the cathode-film assembly 1 prepared in Example 1 of this application. Figure 6 for Figure 5 A partially enlarged view. A detailed partial cross-sectional view of the cathode-film assembly 1 is shown below. Figure 4 As shown, a partial top view is as follows: Figure 5 As shown, when the nickel mesh is forcibly removed from the diaphragm, as... Figure 6 As shown, there are some areas on the diaphragm that contain almost no catalyst. Measurements show that the areas where the nickel mesh is in direct contact with the diaphragm contain no catalyst.

[0080] A nickel wire mesh (46 mesh, 250 μm wire diameter) without catalytic coating was used as the anode and mounted together with the cathode-film assembly 1 in an effective area of ​​100 cm².2 In a single-chamber electrolysis unit, the electrolyte is 30 wt% KOH, the operating temperature is controlled at 85℃, and the voltage is 2 V. After 64 hours of operation, the current density stabilizes at 4250 A / m. 2 This translates to a catalyst mass current density of 33.7 A / g. When using 1000 A / m... 2 At the current density, the percentage of hydrogen in oxygen is 0.21%.

[0081] Example 2:

[0082] The preparation process of Example 2 is similar to that of Example 1, except that Raney nickel with a Ni to Al mass ratio of 4:1 is used as the catalyst, prepared into a 1 g / L slurry, repeatedly drop-coated 10 times, dried, and then aluminum is removed by alkaline washing. The final membrane electrode assembly, i.e., the cathode-membrane assembly 2, has a nickel content of approximately 119 g / m³. 2 Under identical conditions, the test results showed that after 64 hours of operation at 85℃ and 2V, the current density remained stable at 4110 A / m. 2 This translates to a current density of 34.5 A / g per unit mass of catalyst material. When using 1000 A / m... 2 At the current density, the percentage of hydrogen in oxygen is 0.23%.

[0083] Comparative Example 1:

[0084] The diaphragm was an Agfa Zirfon UTP 500 composite membrane. The cathode catalyst layer was made of Raney nickel with a Ni to Al mass ratio of 4:1. Raney nickel was plasma-sprayed onto one side of a 46-mesh, 250μm diameter twill nickel wire mesh. Al was then removed from this layer by alkaline washing. The final cathode surface layer had a nickel content of approximately 208 g / m². 2 The cathode with the catalytic layer is assembled into the electrolytic cell chamber with the diaphragm facing it, while the other side of the diaphragm is a nickel wire mesh (46 mesh, 250 μm wire diameter) without a catalytic coating, which serves as the anode.

[0085] The membrane and electrode combination structure has an effective area of ​​100 cm². 2 In the atmospheric pressure chamber, the electrolyte was 30 wt% KOH, the operating temperature was controlled at 85℃, and the voltage was 2 V. After 64 hours of operation, the current density stabilized at 3960 A / m. 2 This translates to a catalyst mass current density of 19.0 A / g. When using 1000 A / m... 2 At the current density, the percentage of hydrogen in oxygen is 0.38%.

[0086] Comparative Example 2:

[0087] The preparation process of Comparative Example 2 is similar to that of Comparative Example 1, with the main difference being that Raney nickel is not sprayed onto the surface of the nickel wire mesh, but rather mixed with a certain amount of Nafion membrane solution (the mass ratio of Raney nickel to Nafion is 42:1) and applied to the surface of the Agfa Zirfon UTP 500 composite membrane facing the cathode chamber. After drying, the Al content is removed by alkali washing to obtain a porous nickel catalyst layer with a nickel content of 296 g / m³. 2 .

[0088] Then, two nickel wire meshes of the same specifications as in Comparative Example 1 were pressed tightly against the membrane coated with the catalyst layer, and assembled with the electrode plate with flow channels to form an electrolysis chamber. The effective area of ​​the chamber was 100 cm². 2 The electrolyte is 30wt% KOH, and the operating temperature is controlled at 85℃. After operating at 2V for 64 hours, the current density stabilizes at 5300 A / m. 2 This translates to a catalyst mass current density of 17.9 A / g. When using 1000 A / m... 2 At the current density, the percentage of hydrogen in oxygen is 0.39%.

[0089] Example 3:

[0090] The preparation process of Example 3 is similar to that of Example 1, with the main difference being that: the catalyst used is nickel-molybdenum alloy particles with a nickel-molybdenum ratio of 9:1, and the catalyst loading is close to that of Example 1. The final membrane electrode assembly has a nickel-molybdenum content of 122 g / m³ in the cathode-membrane assembly 3. 2 The resulting membrane electrode assembly, when operated for 64 hours in 30% KOH at 2 V and 85 °C, maintained a stable current density of 4350 A / m. 2 Approximately, this translates to a catalyst mass current density of 35.65 A / g. When using 1000 A / m... 2 At the current density, the percentage of hydrogen in oxygen is 0.24%.

[0091] Example 4:

[0092] The diaphragm is a 500μm carbon-based composite membrane (Zirmbrane® 500), and the cathode substrate is a 50-mesh, 220μm diameter straight-weave nickel wire mesh. The nickel wire mesh and diaphragm are composited by hot pressing. The nickel mesh-diaphragm composite is used as the working electrode. Nickel reduction deposition is performed in an electrodeposition solution containing nickel sulfate and nickel chloride. The counter electrode is a nickel block. The electrodeing process is carried out at 1000 A / m. 2 At a current density, electrodeposition was performed for a certain time, and the final membrane electrode assembly, cathode-membrane assembly 4, had a nickel loading of 125 g / m³. 2 . Figure 7The images shown are scanning electron microscope (SEM) images of the membrane electrode assembly 4 prepared in Example 4 of this application, where a is an SEM image at a 2 μm scale and b is an SEM image at a 1 μm scale. Figure 7 As shown in a~b, the deposited nickel particles are mainly distributed on the nickel mesh and nickel wire, and there is no obvious particle deposition in the area where the nickel mesh is in close contact with the diaphragm.

[0093] A 50-mesh, 220μm diameter straight-lined nickel wire mesh is used directly as the anode, and together with the aforementioned cathode-film assembly 4, it is mounted in an effective area of ​​100cm². 2 In a single-chamber electrolysis unit, the electrolyte is 30 wt% KOH, the operating temperature is controlled at 85℃, and the voltage is 2 V. After 64 hours of operation, the current density stabilizes at 4310 A / m. 2 This translates to a catalyst mass current density of 34.5 A / g. When using 1000 A / m... 2 At the current density, the percentage of hydrogen in oxygen is 0.22%.

[0094] Comparative Example 3:

[0095] The preparation process of Comparative Example 3 is similar to that of Example 4, with the main difference being that a separate nickel mesh is used as the working electrode, and electrodeposition is performed for the same time under the same electrolyte and current density conditions. The nickel mesh surface is loaded with nickel particles, and the nickel loading is approximately 128 g / m², similar to the previous example. 2 However, the nickel particles are deposited relatively uniformly on the surface of the nickel mesh. Using this electrode as the cathode and a 50-mesh, 220μm diameter straight-textured nickel wire mesh as the anode, a 500μm carbon composite film was mounted on an effective area of ​​100cm². 2 The electrolysis chamber is a single compartment. The electrolyte is 30wt% KOH, the operating temperature is controlled at 85℃, and the voltage is 2V for 64 hours, during which the current density stabilizes at 4300 A / m. 2 This translates to a catalyst mass current density of 23.6 A / g. When using 1000 A / m... 2 At the current density, the percentage of hydrogen in oxygen is 0.36%.

[0096] Example 5:

[0097] The preparation process of Example 5 is similar to that of Example 1, except that instead of using nickel wire mesh, a 60ppi, 1mm thick nickel foam is used as the nickel substrate. The final membrane electrode assembly, namely the cathode-membrane assembly 5, has a nickel loading of 137g / m³. 2 .

[0098] Figure 8 This is a top-view scanning electron microscope image of the cathode-film assembly 5 prepared in Example 5 of this application. After the surface nickel foam is forcibly removed, the cathode-film assembly 5... Figure 8 As shown, the catalyst content in the contact area between the nickel foam and the diaphragm is negligible. The anode is made of pre-calcined nickel foam, and the two components are assembled to form an effective area of ​​100 cm². 2 The electrolysis chamber was operated for 64 hours in a 30wt% KOH electrolyte at 85℃ and 2V, with the current density stabilizing at 4710 A / m³. 2 This translates to a catalyst mass current density of 34.4 A / g. When using 1000 A / m... 2 At the current density, the percentage of hydrogen in oxygen is 0.26%.

[0099] Comparative Example 4:

[0100] The preparation process of Comparative Example 4 is similar to that of Example 5, except that: the membrane surface is first coated with 137g / m 2 A layer of nickel particles was then combined with nickel foam to form a small chamber. Testing showed that this assembly operated for 64 hours in a 30wt% KOH electrolyte at 85℃ and 2V, maintaining a stable current density of 4230 A / m². 2 This translates to a catalyst mass current density of 20.8 A / g. When using 1000 A / m... 2 At the current density, the percentage of hydrogen in oxygen is 0.38%.

[0101] Example 6:

[0102] The diaphragm is an Agfa 220μm Zirfon microporous membrane with a size of 5×5 cm. 2 A 50-mesh, 200μm diameter straight-weave nickel wire mesh is washed with hydrochloric acid, ethanol, water, and acetone to remove surface oxides and possible oil stains. Then, it is hot-pressed to a 6.5×6.5cm diameter. 2 Diaphragm composite. Using a nickel mesh-diaphragm composite as a substrate, with the nickel mesh side facing upwards, a 0.2 g / L PdCl2 ethanol solution was dropped onto the surface for activation. After activation for 30 seconds, it was washed with ethanol and allowed to air dry. Then, a chemical plating solution containing 1 kg / L nickel sulfate and 1 kg / L sodium hypophosphite was dropped onto the surface of the nickel mesh-diaphragm composite. The substrate was covered and placed in an oven at 40°C for 6 hours. After removal, it was washed with ethanol and dried to obtain electrode-membrane composite 5. The electrode can be used as either a cathode or anode. The weight difference was weighed, and the calculated nickel deposition amount was 120 g / m². 2 Electroless nickel plating grows on both nickel mesh and non-nickel mesh contact membrane surfaces, forming stacked nanoparticles.

[0103] When the electrode of this electrode-film assembly 5 is used as the cathode, a 50-mesh, 200μm wire is thermally sprayed with a content of approximately 146g / m². 2A straight-lined nickel wire mesh of Raney nickel material is used as the anode, mounted on an effective area of ​​25 cm². 2 In a single-chamber electrolysis unit, the electrolyte is 30 wt% KOH. The operating temperature is controlled at 85℃, and the voltage is 2 V. After 64 hours of operation, the current density stabilizes at 5100 A / m. 2 The cathode current density, converted to a unit catalyst mass current density, is 42.5 A / g. When using 1000 A / m... 2 At the current density, the percentage of hydrogen in oxygen is 0.25%.

[0104] When the electrode of the electrode-film assembly 5 is used as the anode, a 50-mesh, 200μm wire is thermally sprayed with a content of approximately 146g / m². 2 A straight-lined nickel wire mesh of Raney nickel material was used as the cathode, mounted on an effective area of ​​25 cm². 2 In a single-chamber electrolysis unit, the electrolyte is 30 wt% KOH, the operating temperature is controlled at 85℃, and the voltage is 2 V. After 64 hours of operation, the current density stabilizes at 4900 A / m. 2 The anode current density, converted to a unit catalyst mass current density, is 40.8 A / g.

[0105] Comparative Example 5:

[0106] The preparation process of Comparative Example 5 is similar to that of Example 6, with the main difference being that both the cathode and anode are 50 mesh, the wire diameter is 200 μm, and the thermal spray coating contains approximately 146 g / m. 2 The straight-weave nickel wire mesh made of Raney nickel material is directly assembled with Agfa 220μm Zirfon film on a 25cm substrate without hot pressing. 2 In a small indoor space, operating at 2V for 64 hours, the current density remained stable at 4980 A / m². 2 The current density per unit catalyst mass for both the anode and cathode is 34.1 A / g.

[0107] Example 7:

[0108] Two 5×5 cm diameter hydrophilic PSU-CeO2 composite microporous membranes were bonded together using a hot-pressing method. 2 1mm thick, 50ppi nickel foam was attached to a 6.5×6.5 cm substrate. 2 The composite membrane is positioned at the center of both sides. One side is coated with an iridium oxide particle dispersion as the anode side, and the other side is coated with a 20% Pt / C dispersion as the cathode side, covering an effective area of ​​25 cm². 2 Performance was tested in an electrolysis chamber using 1M KOH as the electrolyte, at a temperature controlled at 60℃, and at 2V for 48 hours, with a current density of approximately 6700 A / m. 2 .

[0109] Comparative Example 6:

[0110] The preparation process of Comparative Example 6 is similar to that of Example 7, with the main difference being that: nickel foam of the same size pre-loaded with an equal amount of iridium oxide is used as the anode, and nickel foam of the same size pre-loaded with an equal amount of Pt / C is used as the cathode. Both are mounted in the same electrolytic chamber fixture as the aforementioned composite microporous membrane. Under the same conditions, when operating at 2V for 48 hours, the operating current density is approximately 6300 A / m². 2 .

[0111] A comparison of Example 7 and Comparative Example 6 shows that, under the same mass of material loading, the membrane and electrode combination scheme of this application can achieve higher energy utilization efficiency and lower energy consumption per unit of hydrogen production. Based on the above examples and comparative examples, as in Examples 1-3, different types of metal powders can be used in the preparation of the membrane electrode assembly of this application; as in Examples 1, 4-6, different catalyst loading methods can be used to prepare... Figure 1 The membrane electrode assemblies shown in Figures a-c, as in Example 7, can be fabricated using different types of membranes and catalysts. These membrane electrode assemblies all have relatively low catalyst loadings, with catalyst content ranging from 100 to 200 g / m³. 2 When applied to the electrolytic hydrogen production process, it exhibits a stable and high current density, as well as high hydrogen purity, demonstrating superior electrocatalytic performance.

[0112] As can be seen from the comparisons between Example 2 and Comparative Examples 1-2, Example 4 and Comparative Example 3, Example 5 and Comparative Example 4, and Example 6 and Comparative Example 5, the main difference lies in the following: the above examples first fix the membrane and electron conduction layer together, and then electrodeposit, electrolessly plate, or coat the catalyst, while the above comparative examples first load the catalyst onto the membrane or electron conduction layer and then assemble it into a membrane module. Compared with the above comparative examples, the above examples can save at least one-third of the catalyst usage, and the catalyst utilization rate is higher. They can achieve the same or even better electrocatalytic effect as the comparative examples with more catalyst, and can achieve higher power utilization efficiency and lower energy consumption per unit of hydrogen production. Furthermore, on the cathode side, since there is almost no hydrogen evolution catalyst at the interface where the membrane and electron conduction layer directly contact, the supersaturation of gas at the contact interface can be reduced, thereby reducing the hydrogen content in oxygen, improving gas purity and the safety of hydrogen production.

[0113] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A membrane electrode assembly, comprising: a separator, an electron-conducting layer, and a catalytic layer; the electron-conducting layer is located on a surface of the separator, the electron-conducting layer has a porous structure comprising a plurality of through pores, and has a contact interface in direct contact with the separator; the catalytic layer is located on at least part of the surface of the separator and / or the electron-conducting layer other than the contact interface.

2. The membrane electrode assembly of claim 1, wherein, The area of the contact interface accounts for less than 50% of the surface area of the separator.

3. The membrane electrode assembly of claim 1, wherein, The separator and the electron-conducting layer are fixedly connected, preferably in a non-detachable manner. 4.The membrane electrode assembly according to claim 1 or 3, wherein: the electron-conducting layer comprises at least one of nickel, stainless steel, nickel-based alloy, titanium, platinum, gold, or at least one of carbon fiber, carbon cloth, and carbon felt; and / or the thickness of the electron-conducting layer is 80-500 μm, preferably 120-360 μm. 5.The membrane electrode assembly according to claim 1, wherein: the separator comprises at least one of polymeric microporous membrane, organic-inorganic composite microporous membrane, or ceramic membrane, preferably at least one of polypropylene, polysulfone, polyphenylene sulfide, polyethylene, polysulfone-zirconium oxide composite microporous membrane, polysulfone-titanium oxide composite microporous membrane, polysulfone-cerium oxide composite microporous membrane, polysulfone-nickel oxide composite microporous membrane, zirconium oxide, aluminum oxide, titanium oxide, and nickel oxide; and / or the thickness of the separator is 50-700 μm, preferably 200-500 μm. 6.The membrane electrode assembly according to claim 1, wherein: the catalytic layer comprises a hydrogen evolution catalyst, an oxygen evolution catalyst, or a carbon dioxide reduction catalyst. 7.The membrane electrode assembly according to claim 6, wherein: the hydrogen evolution catalyst is selected from at least one metal or an alloy of at least two or more metals selected from Pt, Ru, Rh, Ni, Mo, Co, and Fe, the oxygen evolution catalyst is selected from at least one of IrO 2, RhO 2, RuO 2, NiO, NiOOH, FeOOH, NiFeOOH, and NiFe-LDH, and the carbon dioxide reduction catalyst is selected from at least one of copper-based catalysts; and / or The catalyst is contained in the membrane electrode assembly in an amount of 100 to 200 g / m 2 . 8.A method for preparing a membrane electrode assembly, comprising: providing an electron-conducting layer having a porous structure comprising a plurality of through pores; fixing the electron-conducting layer on a surface of a separator to obtain a composite membrane; loading a catalyst on a surface of the composite membrane to obtain the membrane electrode assembly.

9. The production method according to claim 8, wherein The electron-conducting layer is fixed on the surface of the separator by hot pressing or flow casting.

10. The production method according to claim 8, wherein The catalyst is loaded on the surface of the composite membrane by electrodeposition, chemical deposition, or coating.

11. The production method according to claim 10, wherein The catalyst is loaded on the surface of the composite membrane by coating, comprising: coating a catalyst slurry comprising a binder, a catalytically active ingredient, and an organic solvent on the surface of the composite membrane by drop coating or spray coating, and then drying; repeating the coating and drying to obtain the membrane electrode assembly.

12. The method of making according to claim 10, wherein, The catalyst is loaded on the surface of the composite membrane by electrodeposition, comprising: The composite film is used as a working electrode, and electrodeposition is performed in an electrolyte containing a catalyst precursor to obtain the membrane electrode assembly.

13. The method of making according to claim 10, wherein, The catalyst is loaded on the surface of the composite film by chemical deposition, including: A chemical plating solution containing a catalyst precursor and a reducing agent is applied to the surface of the composite film by drop coating or spray coating, and a reduction reaction is performed to obtain the membrane electrode assembly.

14. Use of the membrane electrode assembly according to any one of claims 1 to 7 or prepared by the preparation method according to any one of claims 8 to 13 in electrolytic hydrogen production.

15. Use according to claim 14, wherein, The electrolytic hydrogen production is alkaline water electrolysis, cation proton exchange membrane electrolysis, or solid oxide electrolysis.

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