Membrane electrode assembly and preparation method and application thereof

Abstract

The invention discloses a membrane electrode assembly and a preparation method and application thereof. The membrane electrode assembly comprises a catalyst coating film and a porous transmission layer which are arranged in a stacked mode, the surface of the catalyst coating film is provided with a first area and a second area different from the first area, the second area is provided with a protrusion array, and protrusions in the protrusion array are correspondingly arranged in a mesh structure of the porous transmission layer. The porous transmission layer is tightly attached to the first area of the surface of the catalyst coating film, the porous transmission layer and the catalyst coating film form a mechanical occlusion structure, and the area, making contact with the catalyst coating film, of the porous transmission layer is of a plane structure which is the same as or similar to the surface of the catalyst coating film in shape. According to the invention, the reticular porous transmission layer is intensively enhanced, the radial cross section of the porous transmission layer is extruded from a cylindrical shape to a capsule shape, and the contact of the original porous transmission layer and the catalyst coating film (CCM) is expanded from a point to a surface, so that the pressure of the structure of the catalyst coating film (CCM) on external mechanical pressing is effectively relieved.

Description

TECHNICAL FIELD

[0001] The application particularly relates to a membrane electrode assembly as well as a preparation method and application thereof, and belongs to the field of energy and clean technology. BACKGROUND

[0002] Hydrogen production by water electrolysis is a new technology for obtaining "green hydrogen" using renewable energy power. The membrane electrode assembly (MEA) is the core of the entire water electrolysis cell, and the polarization limitation is a key factor affecting the performance and efficiency of the MEA for water electrolysis, mainly limited by the structural stability of the catalyst coated membrane (CCM) and the planar contact effect of the catalyst layer (CL) and the porous transport layer (PTL). Although the existing membrane electrode assembly structure has good mass transfer rate, the complex structure design and poor interface contact result in high production cost of the membrane electrode assembly and serious electronic / ionic transmission resistance, further limiting their scalability in large-scale commercial applications.

[0003] Researchers have carried out a series of new processes to optimize the membrane electrode assembly, such as using ordered array membranes, self-supporting catalysts, multi-layer composite PTLs and integrated membranes, which have good gas transport management and higher electrolysis activity, and are further improved in performance by adjusting the order degree, element doping, in-situ growth and other methods.

[0004] As disclosed in Chinese patent CN 114628750 A, a membrane electrode assembly and a preparation method and application thereof, the preparation method of the membrane electrode assembly comprises the following steps: providing an ion exchange membrane, at least one side surface of the ion exchange membrane has an array structure, the array structure includes a plurality of protruding parts arranged in an array; at least the catalyst, the electronic conductor are sequentially loaded on the array structure; the transmission channel of the three-phase interface (electronic, proton, mass transfer) inside the catalyst layer can be greatly increased, which is beneficial to reduce the catalyst loading, improve the catalyst utilization rate, and improve the performance and stability. However, the catalyst is easy to fall off on the 3D ordered array, and the array is also easy to agglomerate and collapse, so that the effective area is greatly reduced, and the stability is also rapidly attenuated.

[0005] CN 116575045 B invents a MEA electrochemical energy conversion and storage device applied to water decomposition catalysis and a preparation method thereof, wherein the electrochemical energy conversion and storage device comprises a nickel mesh stack and a MEA device, the nickel mesh stack is placed in the MEA device; the nickel mesh stack has 2 layers, one layer is a 60-mesh nickel mesh, and the other layer is a 300-mesh nickel mesh. This kind of superimposed composite nickel mesh can protect the anion exchange membrane while promoting the water decomposition technical effect. However, the superimposed nickel mesh as the PTL or self-supporting catalyst layer has poor contact effect with the exchange membrane, resulting in large planar contact impedance and difficult electronic transfer, which seriously limits the performance of electrochemical water decomposition.

[0006] CN 219731080U discloses an electrode nickel mesh for electrolytic water hydrogen production, which can be connected with two nickel meshes, increase the contact area of the nickel mesh with water during use, and improve the hydrogen production efficiency. However, this way of connecting the nickel mesh is slightly complex in the application process of electrolytic water, and in the actual operation process, the movement of the warp and weft of the nickel mesh may damage the structure of the catalyst layer, resulting in a decrease in the stability of the membrane electrode in electrolyzing water. SUMMARY

[0007] The main purpose of the present application is to provide a membrane electrode assembly, a preparation method and application thereof, so as to overcome the deficiencies in the prior art.

[0008] To achieve the above-mentioned purposes, the technical scheme adopted by the present application comprises:

[0009] The first aspect of the embodiment of the present application provides a membrane electrode assembly, which comprises: a catalyst coated membrane and a porous transport layer arranged in a stack, the surface layer of the catalyst coated membrane is a catalyst layer, the surface of the catalyst coated membrane has a first area and a second area different from the first area, the second area has an array of protrusions, the protrusions in the array of protrusions are arranged in a mesh structure of the porous transport layer, the porous transport layer is tightly attached to the first area of the surface of the catalyst coated membrane, the porous transport layer and the catalyst coated membrane form a mechanical interlocking structure, and the area where the porous transport layer contacts the catalyst coated membrane is a planar structure identical or similar to the shape of the surface of the catalyst coated membrane.

[0010] The second aspect of the embodiment of the present application provides an electrochemical energy conversion and storage device, which comprises the membrane electrode assembly.

[0011] The third aspect of the embodiment of the present application provides a preparation method of a membrane electrode assembly, which comprises: calendering a metal mesh formed by braiding metal wires with a capsule-shaped radial cross-section in the thickness direction, and controlling the compression deformation amount of the metal wires in the radial direction to be between 50% and 80%.

[0012] Compared with the prior art, the advantages of the present application include:

[0013] The present application focuses on enhancing the mesh-shaped porous transport layer by extruding the radial cross-section of the porous transport layer from a cylindrical shape to a capsule shape, and the contact between the original porous transport layer and the catalyst coated membrane (CCM) is expanded from a point to a plane, effectively relieving the pressure of external mechanical pressing on the structure of the catalyst coated membrane (CCM).

[0014] Different from other composite porous transport layer designs (although also involving extrusion composite or high temperature bonding, the cross-sectional morphology of the reticular porous transport layer also deforms, but the contact problem between the porous transport layer and the catalyst coated membrane (CCM) is not essentially solved), the present application is based on the structure of the occlusal or armoured membrane electrode, and the ordered array structure can complement each other with the enhanced porous transport layer, and the combination is more closely, ensuring the conductivity while enhancing the overall gas-liquid management effect of the membrane electrode. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a compression process schematic diagram of the enhanced nickel mesh in a typical embodiment of the present application;

[0016] Figure 2 is a structure schematic diagram of the nickel mesh before and after calendering enhancement and the contact part of the nickel mesh and the catalyst coated membrane in a typical embodiment of the present application;

[0017] Figure 3a , Figure 3b are electron microscope images of the nickel mesh before and after calendering enhancement, respectively;

[0018] Figure 4 is the electrolytic water performance curve of the water splitting device in Example 1 and Comparative Example 1;

[0019] Figure 5 is a comparison diagram of hydrogen permeation current density of the water splitting device in Example 1 and Comparative Example 1;

[0020] Figure 6 is a comparison diagram of hydrogen permeation flux of the water splitting device in Example 1 and Comparative Example 1;

[0021] Figure 7a and Figure 7b are the resistances of the membrane electrode assemblies of Example 1, Comparative Example 1 and Comparative Example 2, respectively;

[0022] Figure 8a , Figure 8b are SEM images of the CCM after reaction in Comparative Example 1 and Example 1, respectively;

[0023] Figure 9a , Figure 9b is a diagram of the corresponding relationship between the compression amount of the nickel mesh and the performance. DETAILED DESCRIPTION

[0024] In view of the deficiencies in the prior art, the present inventors have long-term research and a large amount of practice, and have proposed the technical solution of the present application. The technical solution, its implementation process and principles will be further explained as follows.

[0025] In order to make the electron, proton and substance in the membrane electrode transmit faster, the CCM (catalyst coated membrane) obtained by the application is in close contact with the PTL (porous transport layer) of the membrane electrode assembly, the inside of the membrane electrode assembly presents an ordered structure, the three-phase interface is greatly increased, and the performance and stability of the water electrolysis device are improved.

[0026] The first aspect of the embodiment of the application provides a membrane electrode assembly, which comprises: a catalyst coated membrane and a porous transport layer which are arranged in a stack, a surface layer of the catalyst coated membrane is a catalyst layer, a surface of the catalyst coated membrane has a first region and a second region which is different from the first region, the second region has a protrusion array, protrusions in the protrusion array are arranged in a mesh structure of the porous transport layer, the porous transport layer is in close contact with the first region of the surface of the catalyst coated membrane, the porous transport layer and the catalyst coated membrane form a mechanical engagement structure, and the region where the porous transport layer is in contact with the catalyst coated membrane is a planar structure which is the same as or similar to the shape of the surface of the catalyst coated membrane.

[0027] Further, the porous transport layer comprises a metal mesh formed by interlacing a plurality of metal wires, the metal wires are located in the gaps between the protrusion array, and the region where the metal wires are in contact with the catalyst coated membrane is a planar structure.

[0028] Further, the metal wire has a flat structure with an approximate rectangular shape in a radial cross section.

[0029] Further, the side surface of the metal wire comprises a first surface, a second surface, a third surface and a fourth surface which are sequentially and smoothly connected, the first surface and the third surface are oppositely arranged, the second surface and the fourth surface are oppositely arranged, the first surface and the third surface are planar surfaces, the second surface and the fourth surface are arc surfaces, and the third surface is in contact with the catalyst layer.

[0030] Further, the width of a single metal wire is equal to the sum of the pore diameter of a single mesh of the metal mesh and the width of a single gap of the protrusion array, the difference between the height of the protrusion array and the diameter of the metal wire is more than 1 / 5 of the thickness of the metal wire and less than the thickness of the metal wire.

[0031] Further, the porosity of the metal mesh is 50 mesh to 400 mesh.

[0032] Further, the metal mesh comprises a nickel mesh, a copper mesh, a titanium mesh or a stainless steel mesh.

[0033] The second aspect of the embodiment of the application provides an electrochemical energy conversion and storage device, which comprises the membrane electrode assembly.

[0034] Further, the electrochemical energy conversion and storage device is specifically an electrochemical energy conversion and storage device including a separator / exchange membrane and a porous transport layer interface contact optimized electrochemical energy conversion and storage device, including water splitting devices, anion exchange membrane water electrolysis devices, proton exchange membrane water electrolysis devices, metal batteries or fuel cells and other devices related to the contact of the separator / exchange membrane and the porous transport layer.

[0035] It should be noted that when the electrochemical energy conversion and storage device is a proton exchange membrane water electrolysis device, the metal mesh in the membrane electrode assembly needs to be replaced with a titanium mesh or a stainless steel mesh, etc.

[0036] The third aspect of the embodiment of the application provides a preparation method of a membrane electrode assembly, which comprises: calendering a metal mesh formed by braiding metal wires with a capsule-shaped radial cross section in the thickness direction, and controlling the compression deformation amount of the metal wires in the radial direction to be between 50%-80%.

[0037] Further, the preparation method of the membrane electrode assembly specifically comprises: placing the metal mesh in the opening of the open hole sealing gasket, the size / shape of the opening is the same as that of the metal mesh, and then calendering the metal mesh, and the size / shape of the metal mesh before and after the calendering treatment remains unchanged.

[0038] The technical solution, its implementation process and principles will be further explained in combination with the drawings and specific implementation cases as follows.

[0039] At present, one of the biggest problems hindering the further commercialization of anion exchange membrane water electrolysis or other fields involving exchange membranes is the defects of the membrane itself, including fast aging rate, large internal pore of the membrane, poor effect of the membrane emulsion as a catalyst binder and other problems. These problems will eventually lead to two major disadvantages that seriously affect the efficiency and service life of the electrolytic tank: first, under large current and long time working conditions, serious hydrogen permeation problems will occur, and once the hydrogen concentration in oxygen reaches a certain concentration, there is a serious safety hazard; second, under the same large current and long time working conditions, the catalyst will be passively shed in the dynamic three-phase environment for a long time, and the working efficiency and service life will be greatly reduced.

[0040] In view of the above problems, there are two most direct improvement methods: first, improve the properties of the membrane solution and synthesize a new type of high molecular emulsion, although this method can essentially solve the above problems, but the actual research and development process is difficult and the cost is extremely high; second, improve the membrane electrode assembly process, reduce hydrogen permeation and protect the catalyst through external physical means to prolong the service life under actual working conditions.

[0041] By designing a more compact membrane electrode assembly, the porous transport layer (PTL) in the assembly is highly attached to the catalyst coated membrane (CCM), which not only protects the catalyst layer on the surface of the catalyst coated membrane from falling off, but also successfully limits the hydrogen from the cathode to penetrate into the anode due to the tight attachment. Moreover, the good structural design further improves the electrolysis performance. Specifically, the nickel mesh and other porous transport layers are compressed and enhanced to perfectly attach to the catalyst coated membrane (CCM), and the process is simple, but the improvement effect is significant and the cost is very low, which is beneficial to subsequent large-scale commercial application.

[0042] In a more typical embodiment, a membrane electrode assembly includes a catalyst coated membrane and a porous transport layer arranged in a stack, the surface of the catalyst coated membrane has a first region and a second region different from the first region, the second region has an array of protrusions, the catalyst layer continuously covers the first region and the second region of the surface of the catalyst coated membrane, the protrusions in the array of protrusions are correspondingly arranged in the mesh structure of the porous transport layer, the porous transport layer is tightly attached to the first region of the surface of the catalyst coated membrane, and the porous transport layer and the catalyst coated membrane form a mechanical engagement structure, wherein the region where the porous transport layer contacts the catalyst coated membrane is a planar structure identical or similar to the shape of the surface of the catalyst coated membrane.

[0043] Specifically, the catalyst coated membrane (CCM) includes an ion exchange membrane and a catalyst layer (CL) loaded on the surface of the ion exchange membrane, the surface of the ion exchange membrane has an array of protrusions, the array of protrusions includes a plurality of protrusions arranged in order, specifically, the plurality of protrusions are arranged in a first direction and a second direction, the first direction and the second direction are arranged in a cross direction, one of the first direction and the second direction is a row direction, and the other is a column direction, the longitudinal section of the protrusion is generally triangular, the width (the size along the first direction or the second direction) is about 16 μm, the height is about 18 μm, and the gap width (the size along the first direction or the second direction) between the protrusions is about 65 μm, and the catalyst layer (CL) is continuously arranged on the surface of the ion exchange membrane, and it can be understood that the catalyst layer (CL) also covers the surface of the protrusion.

[0044] The porous transport layer in the application includes a metal mesh formed by interlacing a plurality of metal wires, and the porous transport layer is arranged on the surface of the catalyst coated membrane (CCM), wherein the metal wires are located in the gap between the array of protrusions and are tightly attached to the catalyst coated membrane. Specifically, the region where the metal wire contacts the catalyst coated membrane is a planar structure, thereby increasing the contact area between the porous transport layer and the catalyst coated membrane, and effectively protecting the catalyst layer on the surface of the catalyst coated membrane.

[0045] It should be noted that the plurality of metal wires are interlaced in the first direction and the second direction.

[0046] Specifically, the metal wire has a flat structure with a cross section in the radial direction in the shape of a rectangle. More specifically, the side surface (specifically, the circumferential side surface) of the metal wire includes a first surface, a second surface, a third surface, and a fourth surface that are sequentially and smoothly connected. The first surface and the third surface are oppositely arranged, and the second surface and the fourth surface are oppositely arranged. The first surface and the third surface are flat surfaces, and the second surface and the fourth surface are arc-shaped surfaces. The third surface is attached to the catalyst layer. It is learned through tests that the contact area between the metal mesh formed by the metal wire with a flat structure in the shape of a rectangle and the catalyst coated membrane (CCM) is about three times larger than the contact area between the metal mesh formed by the metal wire with a circular cross section and the catalyst coated membrane (CCM).

[0047] More specifically, the width of a single metal wire is equal to the sum of the pore diameter of a single mesh of the metal mesh and the width of a single gap of the protrusion array. The difference between the height of the protrusion array and the diameter of the metal wire is more than 1 / 5 of the thickness of the metal wire and less than the thickness of the metal wire, so that each protrusion is arranged in a mesh of the metal mesh. The porosity of the metal mesh is 50-400 mesh. For example, the metal mesh includes a nickel mesh, a copper mesh, a titanium mesh, or a stainless steel mesh.

[0048] In a more typical embodiment, as shown in Figure 1 The porous transport layer in the present application can be prepared in the following way:

[0049] A conventional metal mesh (volume x1*y1*z1, the radial cross section of the metal wire in the conventional metal mesh is in the shape of a capsule) is placed in the opening of the opening sealing gasket (the opening size is x1*y1, and the thickness z2: 0<z2<z1). The sealing gasket serves to fix the metal mesh and make the metal mesh bear force uniformly. Then, the sealing gasket with fixed position and size + metal mesh is placed between two smooth stainless steel plates, which facilitates the extrusion / calendering (including cold pressing or hot pressing) of the metal mesh by a hydraulic press or other compression device. The radial cross section of the metal wire in the metal mesh after calendering and strengthening is in the shape of a flat rectangle.

[0050] It should be noted that the pressure for calendering and strengthening the metal mesh can be adjusted according to the size of the metal mesh and the required compression degree. The calendering deformation amount of the metal mesh is generally controlled between 50%-80%. For example, the compression amount / deformation amount of the metal wire can be 6-20 μm.

[0051] Taking a nickel mesh as the porous transport layer, as shown in Figure 2As shown, the radial cross-section of the nickel wire in the conventional nickel mesh presents a capsule shape, and the diameter of the nickel wire is about 35 pm. After compression enhancement, the radial cross-section of the nickel wire presents a quasi-rectangular shape, and the width of the bottom surface is about 39 pm, and the height or thickness is about 32 pm. The biggest difference between the two is that the original nickel mesh structure is relatively loose and is easy to deform during assembly, which greatly reduces the matching effect with the protrusion array. In addition, the circular nickel wire structure leads to a smaller contact area between the nickel mesh and the CCM (catalyst coated membrane) and an excessive local area pressure. Thanks to the unique structure of the enhanced nickel mesh, the contact area with the CCM is larger, and the catalyst on the CCM can be pressed better. By Figure 3a 、 Figure 3b As can be seen, the nickel mesh before the enhancement treatment is relatively loose, and the nickel wire of the enhanced nickel mesh is more flat and has a larger contact surface area.

[0052] In a typical embodiment, the water splitting device using the membrane electrode assembly in the present application is characterized, and the structural composition of the water splitting device is consistent with that known in the art, which is not specifically limited here.

[0053] The electrolytic water performance of the water splitting device is tested: the hydrogen production performance of electrolytic water is compared by observing the current density change at different potentials through linear sweep voltammetry (LSV) test.

[0054] The membrane electrode assembly used in Comparative Example 1 is: array membrane + conventional 300 mesh nickel mesh / 80 mesh nickel foam, the membrane electrode assembly used in Comparative Example 2 is: array membrane + 80 mesh nickel foam, and the membrane electrode assembly used in Example 1 is: array membrane + 300 mesh enhanced nickel mesh after rolling / 80 mesh nickel foam. The array membrane has a protrusion array side surface sprayed with IrO2 catalyst (COTRUN NEW ENERGY, > 95%), which is the anode side, and the other side is a smooth surface and serves as the cathode side, which is sprayed with pt / C catalyst.

[0055] Electrolyte: 1M KOH; test temperature: 80℃; liquid flow rate: 12 mL / min; test method: LSV, scan rate 5 mV / s, potential 0.8V (vs. reference) ~ 2.0V (vs. reference).

[0056] Hydrogen permeation test: according to the test method of GB / T 30074-2013, the permeation current and permeation flux are measured.

[0057] Specific steps: Permeation current - hydrogen permeation current density is tested at 80℃ and atmospheric pressure. The anode side of the electrolytic cell is supplied with hydrogen gas, and the cathode side is supplied with nitrogen gas. The test method is linear sweep voltammetry, and the scan voltage range is 0.01V ~ 0.9V, and the scan speed is 10 mV / s.

[0058] Permeation flux - Hydrogen permeation flux was tested at 80°C and atmospheric pressure using a constant current density test (including 1A / cm 2 and 2A / cm 2 ) The anode side product gas was collected and the hydrogen content in the oxygen was calibrated using gas chromatography-mass spectrometry (GC-MS).

[0059] The test results are as follows Figure 4 As shown by Figure 4 It can be seen that the water splitting device of Example 1 greatly improves its current density, reaching 10.24 A / cm at 2.0 V. 2 .

[0060] like Figure 5 As shown in the figure, the crossover current (hydrogen permeation current) of Example 1 and Comparative Example 1 at 0.4V is significantly lower than that of Comparative Example 2, indicating that the armor-like structure formed by adding the metal mesh can effectively protect the membrane electrode. In addition, the crossover current of Example 1 is lower than that of Comparative Example 1, indicating that the protection ability of the rolled reinforced nickel mesh is stronger.

[0061] like Figure 6 As shown, at 1 A / cm 2 Under the conditions of 0.003% hydrogen permeation, Example 1 showed a hydrogen permeation rate of less than 0.003%, which was much lower than the 0.019% permeation rate of Comparative Example 1. As the current density increased, the permeation rate of Example 1 barely increased, while the permeation rate of Comparative Example 1 increased to 0.034%, indicating that the rolled reinforced nickel mesh structure in Example 1 has stronger protection and is more capable of stabilizing the membrane electrode structure under high current density conditions.

[0062] Figure 7a and Figure 7b The resistance of the membrane electrode assemblies of Example 1, Comparative Example 1, and Comparative Example 2 are shown. The rolled reinforced nickel mesh in Example 1 is in closer contact with the catalytic layer (inhibiting catalyst shedding and providing better stability), reducing the interface resistance (the charge transfer impedance and ohmic impedance are reduced, which verifies the effect of increasing the current density).

[0063] The SEM images of CCM after reaction in Comparative Example 1 and Example 1 are as follows: Figure 8a 、 Figure 8b As shown by Figure 8a and Figure 8b It can be seen that the mesh-shaped PTL interlocks well with the ordered array, protecting the protrusion array structure. The cylindrical nickel filaments in the nickel mesh in Comparative Example 1 resulted in a relatively small contact area between the nickel mesh and the CCM, and the contact between the two was loose, leading to cracking and delamination of the CCM. In contrast, the rolled reinforced nickel mesh in Example 1 exhibited a more robust interface and extensive coverage. Thanks to the tight and comprehensive protection, the CCM maintained its excellent morphological and structural integrity.

[0064] The relationship between the nickel mesh compression amount and performance is shown in Figure 9a 、 Figure 9b The mesh PTL and the ordered array are well matched and interlocked, and the current density of the comparative example 1 (which is already a high level of data) can be obtained; the PTL is further calendered into a capsule shape or a cuboid shape, the contact effect is greatly improved, and the internal resistance is effectively reduced, and the combination of these positive factors can obtain a current density of 10 A / cm 2 .

[0065] The present application focuses on enhancing the mesh porous transport layer, by extruding the radial cross section of the porous transport layer from a cylindrical shape into a capsule shape, the contact between the original porous transport layer and the catalyst coated membrane (CCM) is expanded from a point to a surface, effectively relieving the pressure of the catalyst coated membrane (CCM) structure on the external mechanical pressing.

[0066] Unlike other composite porous transport layer designs (although it also involves extrusion composite or high temperature bonding, the cross section morphology of the mesh porous transport layer also changes, but the essence does not solve the contact problem between the porous transport layer and the catalyst coated membrane (CCM)), the present application is based on the structure of the occlusal or armor type membrane electrode, the ordered array structure can complement each other with the enhanced porous transport layer, and the combination is more closely, ensuring the conductivity while enhancing the overall gas-liquid management effect of the membrane electrode.

[0067] The service life of the membrane electrode assembly is prolonged, the content of hydrogen in oxygen is actually reduced, and the mesh porous transport layer in the present application is a commercial product, which is stable in nature, low in price and simple in processing process, and can be used in large quantities.

[0068] It should be understood that the above embodiments are only to illustrate the technical concepts and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A membrane electrode assembly, characterized in that: include: A catalyst coated membrane and a porous transport layer are stacked, the surface layer of the catalyst coated membrane is a catalyst layer, the surface of the catalyst coated membrane has a first area and a second area different from the first area, the second area has a protrusion array, the protrusions in the protrusion array are arranged correspondingly in the mesh structure of the porous transport layer, the porous transport layer is tightly fitted with the first area on the surface of the catalyst coated membrane, the porous transport layer and the catalyst coated membrane form a mechanical interlocking structure, wherein the area where the porous transport layer contacts the catalyst coated membrane is a planar structure with the same or similar shape as the surface of the catalyst coated membrane.

2. The membrane electrode assembly according to claim 1, characterized in that: The porous transmission layer includes a metal mesh formed by interlacing and weaving a plurality of metal wires, wherein the metal wires are located in the gaps between the protrusion arrays, and the area where the metal wires contact the catalyst coating membrane is a planar structure.

3. The membrane electrode assembly according to claim 2, characterized in that: The metal wire is a flat structure with a radial cross section that is approximately rectangular.

4. The membrane electrode assembly according to claim 2 or 3, characterized in that: The side surfaces of the metal wire include a first surface, a second surface, a third surface and a fourth surface which are smoothly connected in sequence, the first surface and the third surface are arranged opposite to each other, the second surface and the fourth surface are arranged opposite to each other, the first surface and the third surface are planes, the second surface and the fourth surface are arcuate surfaces, and the third surface is in contact with the catalytic layer.

5. The membrane electrode assembly according to claim 2 or 3, characterized in that: The sum of the width of a single metal wire and the aperture of a single mesh of the metal mesh is equal to the width of a single gap of the protrusion array, and the difference between the height of the protrusion array and the diameter of the metal wire exceeds 1 / 5 of the thickness of the metal wire and is less than the thickness of the metal wire.

6. The membrane electrode assembly according to claim 2 or 3, characterized in that: The porosity of the metal mesh is 50-400 meshes.

7. The membrane electrode assembly according to claim 1 or 2, characterized in that: The metal mesh includes nickel mesh, copper mesh, titanium mesh or stainless steel mesh.

8. An electrochemical energy conversion and storage device, characterized in that: The electrochemical energy conversion and storage device comprises the membrane electrode assembly according to any one of claims 1 to 7.

9. A method for preparing a membrane electrode assembly, characterized in that: include: A metal mesh formed by weaving metal wires with capsule-shaped radial cross sections is subjected to a calendering treatment along a thickness direction, and the compression deformation of the metal wires in the radial direction is controlled to be between 50% and 80%.

10. The method for preparing a membrane electrode assembly according to claim 9, characterized in that: Specifically include: The metal mesh is placed in the opening of the opening sealing gasket, the size / shape of the opening is the same as the size / shape of the metal mesh, and then the metal mesh is calendered, and the size / shape of the metal mesh before and after the calendering treatment remains unchanged.

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