Integrated membrane electrode and application thereof

Abstract

The invention relates to the technical field of energy and cleaning, in particular to an integrated membrane electrode and application thereof. The membrane electrode comprises a membrane, a gas diffusion layer and a catalyst layer coated on the membrane, wherein the gas diffusion layer comprises a microporous layer and a porous transmission layer; the microporous layer is of a fiber network structure and contains perfluorinated sulfonic acid resin, and the microporous layer and the catalyst layer are integrated into an integrated structure through hot pressing transfer printing; grooves distributed at intervals are formed in the surface of the side, away from the microporous layer, of the porous transmission layer, and a flow field structure of a flow channel and a ridge is formed. The integrated membrane electrode disclosed by the invention has the advantages of remarkably reducing the contact resistance among the components, preventing the microporous layer from permeating to the porous transmission layer to influence the mass transfer efficiency and improving the reaction gas supply speed, the utilization efficiency and the product water discharge speed, so that the effects of improving the performance and the volume power density of a fuel cell and greatly reducing the cost are achieved.

Description

Technical Field

[0001] This invention relates to the field of energy and clean technology, and more particularly to an integrated membrane electrode and its application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are characterized by zero carbon emissions, low pollution, and high energy conversion efficiency, making them one of the most promising energy conversion devices for the future. The core component of a PEMFC is the membrane electrode assembly (MEA), which is fabricated by stacking a gas diffusion layer, a catalyst layer, and a proton exchange membrane. The catalyst layers on both sides are where the electrochemical reactions take place; the proton exchange membrane in the middle plays multiple roles, isolating gases, conducting protons, and preventing electron transfer; the gas diffusion layer is generally composed of a microporous layer and a carbon paper substrate layer, and its main function is to provide gas transport channels and improve water management. Adding bipolar plates with flow channels to both sides of the membrane electrode assembly constitutes the basic structure of the fuel cell.

[0003] In traditional fuel cells, the gas diffusion layer is made by coating a microporous slurry onto carbon paper. During fabrication, problems inevitably arise, such as microporous layer cracking, uneven surface smoothness, and slurry penetration into the substrate layer leading to blockage. These issues reduce PEMFC performance and durability to varying degrees. Furthermore, traditional flow field bipolar plates suffer from water accumulation under the ridges and significant oxygen concentration differences between the underside of the ridges and the flow channel region during water-gas transport. This not only degrades battery performance but also reduces its durability. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an integrated membrane electrode and its application, which aims to solve the problems of low water vapor transmission efficiency caused by battery structure components and large oxygen concentration difference between the flow channel and the ridge catalyst layer in the existing technology.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: The first aspect of the present invention provides an integrated membrane electrode, the membrane electrode comprising a membrane, a gas diffusion layer, and a catalyst layer coated on the membrane, the gas diffusion layer comprising a microporous layer and a porous transport layer; the microporous layer having a fiber network structure and containing perfluorosulfonic acid resin, the microporous layer being integrated with the catalyst layer into an integrated structure by hot pressing transfer; the surface of the porous transport layer away from the microporous layer having spaced grooves forming a flow field structure of channels and ridges.

[0006] In this invention, the catalyst layer (CCM) coated on the membrane is integrated with the microporous layer, and the porous transport layer is integrated with the flow field. The microporous layer contains perfluorosulfonic acid resin (Nafion), which becomes viscous when heated, and is integrated with the catalyst layer coated on the membrane into a single structure through hot pressing transfer. The surface of the porous transport layer is processed to form spaced grooves, with the grooves serving as the main mass transfer channels and the gaps between adjacent grooves forming ridges of the flow channels, acting as secondary mass transfer channels. The porous structure enables the porous transport layer to function as a flow field, thus integrating the porous transport layer with the flow field. The combination of the CCM and the microporous layer, as well as the porous transport layer and the flow field, forms an integrated membrane electrode.

[0007] Based on the above scheme, preferably, the parameters of the hot pressing transfer are: hot pressing temperature of 120~150℃ and pressure of 0.01~1MPa.

[0008] Based on the above scheme, preferably, the thickness of the microporous layer is 3~30μm, the porosity is 60%~80%, the average pore size is 100~1000nm, and the hydrophobic angle is 120°~160°; the thickness of the porous transport layer is 0.1~0.6mm, the porosity is 60%~85%, the average pore size is 1~50μm, and the hydrophobic angle is 120°~155°; the depth of the grooves in the porous transport layer is 0.1~0.5mm, and the shape of the grooves in the porous transport layer and the porous ridges formed between any two adjacent grooves is not limited, and can be any regular polygon or an irregular curved shape.

[0009] Based on the above scheme, preferably, the porous transport layer includes one of carbon paper, carbon felt, carbon cloth, titanium felt, foamed titanium, foamed nickel, and foamed silver.

[0010] Based on the above scheme, preferably, the microporous layer is formed by randomly arranged nanofibers to form a fiber network structure, wherein the nanofibers are a core-shell structure, wherein the core material is polymer nanofibers, and the shell material includes conductive materials and perfluorosulfonic acid resin; the conductive material includes one or more of XC-72, acetylene black, conductive carbon black Super P, carbon nanofibers, graphene, and carbon nanotubes; the polymer nanofibers are polymers obtained by crosslinking and esterification reaction of polyacrylic acid and polyvinyl alcohol, wherein the mass ratio of polyacrylic acid to polyvinyl alcohol is (1~2):(1~2).

[0011] Based on the above scheme, preferably, the polymer nanofibers have a diameter of 100~1000 nm, a porosity of 50%~80%, and a pore size of 100~1000 nm, and the porosity and pore size show an increasing trend or remain consistent in the distribution from the catalyst layer to the porous transport layer.

[0012] Based on the above scheme, preferably, the method for preparing the microporous layer includes the following steps: (1) Add the polymer to solvent 1 and stir to obtain a spinning aid. Disperse the conductive material and perfluorosulfonic acid resin solution in solvent 2 by ultrasonication, add the spinning aid, mix and stir to obtain a microporous layer spinning slurry. (2) Electrospinning technology is used to spin the microporous layer spinning slurry to obtain the microporous layer precursor; (3) The microporous layer precursor is heat-treated to cause cross-linking and esterification of polyacrylic acid and polyvinyl alcohol, and then pressed at ambient temperature to obtain the microporous layer.

[0013] Based on the above scheme, preferably, in step (1), the mass ratio of the conductive material, perfluorosulfonic acid resin and polymer is (5~8):(1~2):(1~4), and the conductive material accounts for 50%~80% of the total mass of the conductive material, perfluorosulfonic acid resin and polymer. When the mass ratio of the conductive material is less than 50%, a uniform carbon-coated spun polymer nanofiber skeleton structure cannot be formed; when the mass ratio of the conductive material is greater than 80%, the diameter and strength of the polymer nanofiber skeleton are greatly reduced and cannot be applied. The polymer is a mixture of polyacrylic acid and polyvinyl alcohol, wherein the mass ratio of polyacrylic acid to polyvinyl alcohol is (1~2):(1~2). The conductive material includes one or more of XC-72, acetylene black, conductive carbon black Super P, carbon nanofibers, graphene, and carbon nanotubes. Solvent 1 and Solvent 2 are independently one or more of deionized water, isopropanol, n-propanol, propanol, and ethanol; The concentration of the high molecular weight polymer in the spinning aid is 2-10 wt%.

[0014] Based on the above scheme, preferably, in step (2), the environmental parameters for electrospinning are: temperature 20~40℃, relative humidity greater than 50%RH; the spinning parameters are: microporous layer slurry propulsion rate of 0.2~1.0 mL / h, voltage of 6.0~22.0kV, rotation speed of drum receiver of 100~1000 rpm / min, needle diameter of 10~26G, and distance between needle and receiver of 8~18 cm.

[0015] Based on the above scheme, preferably, in step (3), the heat treatment temperature is 120~150℃; the pressing pressure is 0.2~3 MPa.

[0016] Based on the above scheme, preferably, the porous transport layer is processed by forming spaced grooves by one or more of the following methods: mechanical milling, laser etching, ion beam etching, chemical etching, and mold pressing.

[0017] Based on the above scheme, preferably, the porous transport layer processing method is as follows: after the required groove parameters are designed using software, they are imported into a mechanical milling or etching equipment to process the porous transport layer; or after processing the mold with the required groove parameters, the porous transport layer is pressed.

[0018] A second aspect of the present invention provides an application of the above-described integrated membrane electrode in fuel cells and electrolyzers.

[0019] Based on the above scheme, preferably, the integrated membrane electrode and bipolar plate are assembled to obtain a single cell, and then the single cells are stacked to form a stack. The bipolar plate is made of metal or graphite and has a groove for accommodating the porous transport layer. The groove is 0.1 to 1.0 mm deep and its size matches that of the porous transport layer.

[0020] The beneficial effects of this invention are as follows: 1. In the integrated membrane electrode provided by this invention, the catalytic layer and the microporous layer on the CCM are integrated into one unit. On the one hand, the catalytic layer is prepared on the membrane, which enhances the interfacial bonding between the membrane and the catalytic layer, reduces the proton transfer resistance between the membrane and the catalytic layer, and decreases the interfacial resistance. On the other hand, the integration of the microporous layer and the catalytic layer on the CCM further strengthens the interfacial contact between the two, increases the effective electrochemical active area of ​​the catalytic layer, reduces electron transport resistance, thereby reducing the interfacial resistance of the membrane electrode, avoiding localized delamination of the interface due to long-term operation, and improving the performance and stability of the membrane electrode. In addition, this integrated structure can also avoid the effects of water accumulation in the surface cracks and depressions of the traditional microporous layer, thereby reducing the water saturation of the catalytic layer; at the same time, it prevents the microporous layer slurry from penetrating into the substrate layer, ensuring the water vapor transport efficiency of the substrate layer, thereby enhancing the water vapor transport efficiency of the membrane electrode, improving battery performance and volumetric power density; it also broadens the selectivity of the substrate layer and enhances the compatibility of battery component materials.

[0021] 2. In subsequent use, the integrated membrane electrode provided by this invention utilizes the grooves in the porous transport layer as the main transport channel, while its porous structure itself serves as a secondary transport channel, achieving integrated flow channel, porous transport layer, and microporous layer transport channels. This structure significantly shortens the mass transfer path, greatly improves mass transfer efficiency, simplifies the battery structure, and reduces battery volume, thereby effectively enhancing battery performance, increasing battery volumetric power density, and reducing battery cost. Furthermore, the grooves, acting as the main transport channel, avoid the problems of high gas flow resistance and uneven gas distribution that arise from using the porous transport layer's own pore structure as a transport channel. This helps to control the gas flow direction, optimize gas distribution, reduce gas flow resistance and inlet pressure, and reduce air compressor power consumption, thereby enhancing the uniformity of water-gas distribution in the membrane electrode, reducing parasitic power consumption of fuel cell air compressors, and improving the net power output of the fuel cell. The grooves on the porous transport layer can change the gas transport mode from diffusion to convection to the catalyst layer, altering the water-gas transport path. The gaps between the grooves form ridges in the flow channel. These ridges have a porous structure, which helps alleviate the problem of water accumulation under the ridges in traditional battery flow channels, improves the oxygen concentration and uniformity within the catalytic layer, and enhances water management capabilities, thereby significantly improving battery performance. This invention achieves the above effects by separating the microporous layer from the porous transport layer, while avoiding the porosity reduction caused by the microporous layer itself permeating into the porous transport layer. It also prevents adverse effects such as contamination, scratches, or denaturation of the microporous layer caused by the groove processing of the porous transport layer.

[0022] 3. The integrated membrane electrode provided by the present invention contains Nafion in the microporous layer. The integration of the microporous layer and the catalyst layer in the CCM can be completed by simple thermal transfer. This method not only solves the problem of complicated assembly caused by the separation of the microporous layer and the porous transport layer, but also provides convenience for the large-scale preparation of large-area batteries.

[0023] 4. The microporous layer in the integrated membrane electrode provided by this invention is prepared by electrospinning. This microporous layer forms a core-shell structure through the anisotropic distribution of polymer nanofibers and a coating layer composed of conductive materials and Nafion. This structural feature not only increases the gas permeability of the microporous layer but also effectively reduces the tortuosity and water breakthrough pressure of the microporous layer, thereby significantly improving the mass transfer efficiency. At the same time, the core polymer in the core-shell structure further optimizes the mechanical properties of the microporous layer through cross-linking reactions, enhancing not only the mechanical strength and flexibility of the core polymer but also providing a more stable structural basis for subsequent nanofiber stacking. The microporous layer, composed of stacked nanofibers with a core-shell structure, enhances the bonding force between the stacked nanofibers in the microporous layer, strengthens the interlayer bonding force of the microporous layer, and prevents delamination and breakage during use, thereby improving the durability of the membrane electrode. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the integrated membrane electrode of the present invention; In the diagram: 1. Electrode, 2. Porous transport layer, 3. Microporous layer, 4. Catalytic layer, 5. Membrane, 6. Groove, 7. Ridge; Figure 2 This is a SEM image of the microporous layer in Example 1; Figure 3 This is the EDS elemental analysis diagram of the microporous layer in Example 1; Figure 4 The hydrophobic angle test results are for the microporous layer in Example 1; Figure 5 The results are the hydrophobic angle test results of the gas diffusion layer in Example 1; Figure 6 This is a cross-sectional SEM image of the integrated structure of the microporous layer and the catalyst layer in Example 1; Figure 7 This is a cross-sectional SEM image of the commercial gas diffusion layer in Comparative Example 1; Figure 8 SEM image of the microporous layer in the gas diffusion layer of Comparative Example 1; Figure 9 The diagram shows the structure of the electrode plate of Example 1 and the graphite flow field plate of the conventional battery of Comparative Example 1. a is Example 1 and b is Comparative Example 1. Figure 10 This is a comparison diagram of the polarization curves of Example 1 and Comparative Examples 1 and 2; Figure 11 This is a comparison graph of the power density curves of Example 1 and Comparative Examples 1 and 2; Figure 12 This is a comparison graph of the electrochemical impedance spectroscopy between Example 1 and Comparative Example 1; Figure 13 This is a comparison chart of polarization curves for Examples 2, 3, and 4; Figure 14 This is a schematic diagram of water vapor transport in the battery assembly of Example 1; Figure 15 This is a schematic diagram of water vapor transport in the battery assembly for Comparative Example 1. Detailed Implementation

[0025] The following embodiments are further illustrations of the present invention, which also protects obvious variations and equivalent alternatives.

[0026] This invention provides an integrated membrane electrode, the structure of which is as follows: Figure 1As shown, the membrane electrode includes a membrane 5, a gas diffusion layer, and a catalyst layer 4 coated on the membrane 5. The gas diffusion layer includes a porous transport layer 2 and a microporous layer 3. The microporous layer 3 has a fiber network structure and contains perfluorosulfonic acid resin. The microporous layer 3 is integrated with the catalyst layer 4 into an integral structure by hot pressing transfer. The surface of the porous transport layer 2 away from the microporous layer 3 is provided with grooves 6 distributed at intervals to form a flow field structure of flow channels and ridges 7.

[0027] As a preferred embodiment, the parameters for hot pressing transfer are: hot pressing temperature of 120~150℃; and pressure of 0.01~1MPa.

[0028] In a preferred embodiment, the microporous layer 3 has a thickness of 3~30 μm, a porosity of 60%~80%, an average pore size of 100~1000 nm, and a hydrophobic angle of 120°~160°.

[0029] In a preferred embodiment, the porous transport layer 2 has a thickness of 0.1~0.6 mm, a porosity of 60%~85%, an average pore size of 1~50 μm, and a hydrophobic angle of 120°~155°.

[0030] In a preferred embodiment, the depth of the groove 6 in the porous transmission layer 2 is 0.1~0.5mm, and is less than the thickness of the porous transmission layer 2.

[0031] In a preferred embodiment, the porous transport layer 2 includes one of carbon paper, carbon felt, carbon cloth, titanium felt, titanium foam, nickel foam, and silver foam.

[0032] In a preferred embodiment, the microporous layer 3 is formed by randomly arranged nanofibers to form a fiber network structure, a nanofiber core-shell structure, wherein the core material is polymer nanofibers, and the shell material includes conductive materials and perfluorosulfonic acid resin. Conductive materials include one or more of the following: XC-72, acetylene black, conductive carbon black Super P, carbon nanofibers, graphene, and carbon nanotubes. The polymer nanofibers are polymers obtained by cross-linking and esterification of polyacrylic acid and polyvinyl alcohol, wherein the mass ratio of polyacrylic acid to polyvinyl alcohol is (1~2):(1~2).

[0033] In a preferred embodiment, the polymer nanofibers have a diameter of 100~1000 nm, a porosity of 50%~80%, and a pore size of 100~1000 nm. The porosity and pore size distribution in the direction from the catalyst layer 4 to the porous transport layer 2 show an increasing trend or remain consistent.

[0034] As a preferred embodiment, the method for preparing the microporous layer 3 includes the following steps: (1) Add the polymer to solvent 1 and stir to obtain a spinning aid. Disperse the conductive material and perfluorosulfonic acid resin solution in solvent 2 by ultrasonication, add the spinning aid, mix and stir to obtain a microporous layer spinning slurry. (2) Electrospinning technology is used to spin the microporous layer spinning slurry to obtain the microporous layer precursor; (3) The microporous layer precursor is heat-treated to cause cross-linking and esterification of polyacrylic acid and polyvinyl alcohol, and then pressed at ambient temperature to obtain the microporous layer. In step (1), the mass ratio of the conductive material, perfluorosulfonic acid resin, and polymer is (5~8):(1~2):(1~4), and the conductive material accounts for 50%~80% of the total mass of the conductive material, perfluorosulfonic acid resin, and polymer; the polymer is a mixture of polyacrylic acid and polyvinyl alcohol, wherein the mass ratio of polyacrylic acid and polyvinyl alcohol is (1~2):(1~2); the conductive material includes one or more of XC-72, acetylene black, conductive carbon black Super P, carbon nanofibers, graphene, and carbon nanotubes; solvent 1 and solvent 2 are independently one or more of deionized water, isopropanol, n-propanol, propanol, and ethanol; the concentration of the polymer in the spinning aid is 2~10wt%; In step (2), the environmental parameters for electrospinning are: temperature 20~40℃, relative humidity greater than 50%RH; the spinning parameters are: microporous layer slurry feed rate 0.2~1.0 mL / h, voltage 6.0~22.0 kV, drum receiver rotation speed 100~1000 rpm / min, needle diameter 10~26G, and distance between needle and receiver 8~18 cm. In step (3), the heat treatment temperature is 120~150℃; the pressing pressure is 0.2~3 MPa.

[0035] As a preferred embodiment, the porous transport layer 2 is processed by forming spaced grooves 6 by one or more of the following methods: mechanical milling, laser etching, ion beam etching, chemical etching, and die pressing. The shape of the grooves 6 of the porous transport layer 2 and the ridges 7 formed between any two adjacent grooves 6 are not limited and can be any regular polygon or an irregular curve.

[0036] Example 1 Polyvinyl alcohol (PVA) and polyacrylic acid (PAA) in a mass ratio of 1:1 were added to deionized water and stirred to prepare a spinning aid with a polymer concentration of 5 wt%. XC-72 carbon material and a 5 wt% Nafion solution were ultrasonically dispersed in isopropanol, and the spinning aid was added. High-shear homogenization stirring was used to prepare a microporous layer spinning slurry, wherein the mass ratio of XC-72 carbon material, Nafion and polymer was 7:1:3 (XC-72 carbon material accounted for 63.6% of the total mass of XC-72 carbon material, Nafion and polymer). Electrospinning technology was used to spin the microporous layer slurry. The environmental parameters for electrospinning were: temperature 27℃, relative humidity 65%RH; the spinning parameters were: microporous layer slurry feed rate 0.3mL / h, voltage 8.0kV, drum receiver rotation speed 150 rpm / min, needle diameter 20G, and needle-to-receiver distance 15cm, to obtain the microporous layer precursor. The microporous layer precursor was heat-treated at 140℃ for 1 hour, and then pressed at 1.2 MPa at ambient temperature to obtain a microporous layer with a thickness of 7 μm. Figure 4 As shown, the hydrophobic angle is 140°; Using Toray TGP-H-120 carbon paper (22.5 mm long, 22.5 mm wide, 370 μm thick, 75% porosity, average pore size 24.0 μm) as a porous transport layer, grooves with a laser etching depth of 0.2 mm, a width of 1 mm, a length of 22.5 mm, and a spacing of 1 mm were created. These grooves served as the main mass transfer channels, while the gaps between adjacent grooves formed ridges in the flow channels, acting as secondary mass transfer channels. The laser-etched carbon paper was then hydrophobically treated with a PTFE solution. Figure 5 As shown, the hydrophobic angle is 140°; The microporous layer prepared above was thermally transferred onto the catalyst layer coated on the CCM. A commercially available CCM (with a platinum loading of 0.2 mg / cm² in the anode catalyst layer) was used. 2 The platinum loading of the cathode catalyst layer is 0.4 mg / cm³. 2 The proton exchange membrane is a Gore 8 μm proton exchange membrane. The hot pressing temperature is 140℃, the pressure is 0.1MPa, and the hot pressing time is 90s, so that the microporous layer and the catalyst layer are integrated into a single structure. The obtained integrated structure is stacked with the porous transport layer with laser-etched grooves, and the surfaces of the microporous layer and the porous transport layer away from the electrode are attached to obtain an integrated membrane electrode.

[0037] The microporous layer morphology obtained in Example 1 is as follows: Figure 2 As shown, from Figure 2As can be seen, the microporous layer has a three-dimensional disordered arrangement of macroporous fibers with a porosity of 78% and an average pore size of 600 nm. Furthermore, the XC-72 carbon material is uniformly coated on the polymer fibers and exhibits high roughness, thus possessing excellent electrical conductivity and hydrophobicity. Figure 3 The image shows the EDS elemental analysis of the microporous layer. The red dots in the image represent sulfur distributed on the outer layer of the fiber, indicating that perfluorosulfonic acid resin exists on the outer side of the fiber.

[0038] Cross-sectional SEM image of the integrated structure of the microporous layer and the catalyst layer in Example 1, as shown below. Figure 6 As shown, the anisotropically arranged microporous layer of fibers is integrated with the catalyst layer to form an integrated structure. This integrated structure improves the contact between the microporous layer and the catalyst layer, reducing contact resistance.

[0039] The integrated membrane electrode described above was assembled into a single cell for electrochemical performance evaluation. The anode side of the single cell used a commercially available gas diffusion layer (Toray XGL-R-055) and a conventional graphite parallel flow field to prepare the membrane electrode. The cathode side was assembled using the integrated membrane electrode from Example 1 and a flat graphite bipolar plate. The flat graphite bipolar plate had a groove for accommodating the porous transport layer, the groove being 0.2 mm deep and its dimensions matching the porous transport layer.

[0040] The test conditions were: battery temperature 80℃, anode hydrogen flow rate 0.3L / min. -1 53% humidification, cathode flow rate 1.2 L / min -1 53% humidification. From Figure 10 As can be seen from the data, the battery performance obtained by the integrated membrane electrode assembly in Example 1 is significantly enhanced compared with the batteries in Comparative Example 1 and Comparative Example 2, especially the performance of the mass transfer region is greatly improved and the limiting current density is increased.

[0041] from Figure 11 As can be seen from the data, the highest power density in Example 1 is 2.3 W / cm². -2 The maximum power density is increased by 77% compared to the conventional battery structure in Comparative Example 1.

[0042] To investigate the reasons for the significant performance improvement of the integrated membrane electrode, the battery was characterized using electrochemical impedance spectroscopy. For example... Figure 12As shown, the electrochemical impedance and mass transfer impedance of the battery using an integrated membrane electrode are significantly lower than those of the battery using a conventional membrane electrode. This is mainly due to the integration of the ultrathin independent microporous layer and the catalyst layer, which greatly shortens the mass transfer path and enhances the interfacial contact between the microporous layer and the catalyst layer. In addition, the integration of the porous transport layer and the flow field also significantly enhances water vapor transport, reduces mass transfer polarization, improves the uniformity of water vapor distribution within the membrane electrode surface, and solves the problem of water accumulation under the ridges of the flow channels in conventional batteries.

[0043] Example 2 A microporous layer with a fiber network structure was prepared by electrospinning combined with high-temperature carbonization of polymer nanofibers (referencing the literature "Fuel cell stack redesign and component integration radically increase power density"). Polyacrylonitrile with a molecular weight of 150,000 was dissolved in N,N-dimethylformamide and mechanically stirred at 80°C for 4 hours to prepare a 12wt% spinning solution. The solution was then spun using electrospinning technology with the following environmental parameters: spinning voltage 14 kV, feed rate 0.4 mL / h, temperature 26°C, relative humidity 24%RH, drum receiver rotation speed 150 rpm / min, needle diameter 20 G, and needle-to-receiver distance 15 cm, yielding a microporous layer precursor. This precursor was first cured in air at 240°C for 2 hours at a heating rate of 5°C / min, and then carbonized at 1000°C in a nitrogen atmosphere for 1 hour at a heating rate of 5°C / min to obtain a carbon nanofiber network structure microporous layer.

[0044] The microporous layer prepared above was placed on a heating plate at a temperature of 105°C. A 5% wt Nafion solution was added to deionized water and diluted to 1% wt. Nafion was then applied to any surface of the microporous layer using ultrasonic spraying. After drying, the coating load was measured to be 0.02 mg / cm³. -2 .

[0045] The Nafion side of the carbon nanofiber microporous layer prepared in this embodiment was placed on the catalyst layer for thermal transfer to achieve the preparation of an integrated membrane electrode. The hot pressing temperature was 140°C, the hot pressing pressure was 0.1 MPa, and the hot pressing time was 90 s.

[0046] From the battery polarization curve ( Figure 13 As can be seen from the example, the microporous layer with fiber network structure and Nafion characteristics prepared in Example 2, after being integrated with the catalyst layer into an integrated structure by hot pressing transfer, has a significant performance improvement compared with the traditional battery structure.

[0047] Example 3 The difference between this embodiment and Embodiment 1 is that the temperature for hot pressing transfer is 130°C, while the other conditions are the same as in Embodiment 1.

[0048] Figure 13 Example 3 shows that, by changing the hot-pressing transfer temperature while still achieving integrated fabrication, the integrated film electrode prepared exhibits significant advantages in battery performance compared to traditional batteries, with a maximum power density of 2.3 W / cm². -2 Similar to Example 1.

[0049] Example 4 The difference between this embodiment and Example 1 is that the mass ratio of XC-72 carbon material, Nafion and polymer in the microporous layer spinning slurry is 5:1:3 (XC-72 carbon material accounts for 55.6% of the total mass of XC-72 carbon material, Nafion and polymer). The same preparation parameters are used to prepare the microporous layer, and the other conditions are the same as in Example 1.

[0050] The microporous layer was stacked on a carbon paper substrate, and its planar resistance was tested at 1.2 MPa. Compared with 6.8 mOhm cm in Example 1, the microporous layer was significantly reduced. 2 In Example 2, the planar resistance increased to 7.9 mOhm cm. 2 This is because as the amount of carbon material used decreases, the planar resistance of the microporous layer also increases accordingly.

[0051] Figure 13 The battery performance of Example 4 shows a more significant decrease in the ohmic region due to the increased resistance compared to Example 3, which has a higher content of conductive carbon material.

[0052] Comparative Example 1 The difference between this comparative example and Example 1 is that the membrane electrode cathode side directly uses a commercial gas diffusion layer (Toray XGL-R-055) and a traditional graphite parallel flow field for membrane electrode preparation, battery assembly and electrochemical performance evaluation.

[0053] Figure 7 The image shows a cross-sectional SEM image of a commercial gas diffusion layer, clearly demonstrating the penetration of the microporous layer slurry. Furthermore, to reduce mass transfer polarization in the battery, the loading of the microporous layer slurry is typically reduced, thus decreasing the thickness of the microporous layer. However, this results in the microporous layer failing to form a uniform, flat surface.

[0054] like Figure 8 As shown, the infiltration of the microporous layer slurry results in an uneven morphology on the surface of the microporous layer. These depressions not only affect the contact between the microporous layer and the catalyst layer, thereby reducing the electrochemical active area, but also cause water to accumulate between the catalyst layer and the microporous layer, which in turn affects the gas transport to the catalyst layer and leads to severe mass transfer polarization.

[0055] Commercial gas diffusion layers involve coating a microporous slurry onto a carbon paper substrate. This process allows the slurry to penetrate into the carbon paper substrate, affecting its pore structure and restricting mass transfer. Furthermore, traditional graphite parallel flow fields... Figure 9 b) Solid ridges can also lead to uneven water vapor transport and distribution, especially in the area below the ridge, where there is severe water accumulation and insufficient reactive gas.

[0056] Figure 15 This is a schematic diagram of water vapor distribution in a traditional battery. The diagram illustrates the contact poorness and interfacial water accumulation problems caused by the high roughness of the microporous layer, as well as the water accumulation under the ridges and low gas transport efficiency in traditional flow fields. These problems limit the performance of traditional batteries. Compared to traditional batteries, the integrated membrane electrode of this invention, with its integrated microporous layer and catalyst layer structure, avoids water accumulation in the interfacial region, reduces the water saturation of the catalyst layer, and the integrated porous transport layer solves the problem of water accumulation under the ridges of traditional flow field plates. Furthermore, the grooves serve as the main transport channel, and their porous structure as the secondary transport channel, significantly improving gas transport efficiency and the uniformity of oxygen concentration within the plane. Figure 14 ).

[0057] Figure 10 The results showed that the performance of the conventional battery in Comparative Example 1 was significantly lower than that of the battery with the integrated membrane electrode in Example 1, at 3000 mA cm⁻¹. -2 Its voltage is 0.34V.

[0058] Figure 11 It showed a maximum power density of 1.3 W cm⁻¹. -2 The highest power density is 1 W / cm² lower than that of integrated membrane electrode cells. -2 .

[0059] Figure 12 The results show that the electrochemical impedance and mass transfer impedance of the conventional battery in Comparative Example 1 are much greater than those of the integrated battery, which confirms the above analysis of the reasons for the poor performance of the conventional battery.

[0060] Comparative Example 2 In this comparative example, the CCM and porous transport layer are the same as in Example 1. The difference is that a conventional microporous layer slurry is used. The microporous layer slurry is coated on the side of the porous transport layer without grooves to obtain a gas diffusion layer. The gas diffusion layer is then stacked with the CCM to obtain a membrane electrode.

[0061] The traditional method for preparing microporous layer slurry is as follows: XC-72 carbon powder is added to ethanol and ultrasonically dispersed evenly, then 5wt% PTFE emulsion is added, with the mass ratio of PTFE to XC-72 being 1:4. The mixture is stirred evenly to obtain microporous layer slurry. Figure 10The battery in Comparative Example 2 showed a performance degradation at high current density, indicating that the battery underwent mass transfer polarization at high current density. This suggests that the inherent defects of the traditional microporous layer reduce water vapor transport efficiency, further confirming the effect of the integrated membrane electrode of the present invention in significantly enhancing water vapor transport.

[0062] Figure 11 Comparative Example 2 shows that, compared to Example 1, only the microporous layer structure was changed. The original integrated catalyst layer and microporous layer were replaced with a traditional microporous layer coated on a porous transport layer. This resulted in a significant decrease in battery performance, with a maximum power density of 2.14 W / cm². -2 .

[0063] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. An integrated membrane electrode, the membrane electrode comprising a membrane, a gas diffusion layer, and a catalyst layer coated on the membrane, characterized in that, The gas diffusion layer includes a microporous layer and a porous transport layer; The microporous layer has a fiber network structure and contains perfluorosulfonic acid resin. The microporous layer is integrated with the catalyst layer into an integral structure by hot pressing transfer. The porous transport layer has spaced grooves on the side of its surface away from the microporous layer, forming a flow field structure of channels and ridges.

2. The integrated membrane electrode according to claim 1, characterized in that, The parameters for the hot-press transfer are: hot-press temperature of 120~150℃ and pressure of 0.01~1MPa.

3. The integrated membrane electrode according to claim 1, characterized in that, The microporous layer has a thickness of 3~30μm, a porosity of 60%~80%, an average pore size of 100~1000nm, and a hydrophobic angle of 120°~160°. The porous transport layer has a thickness of 0.1~0.6mm, a porosity of 60%~85%, an average pore size of 1~50μm, and a hydrophobic angle of 120°~155°. The depth of the grooves in the porous transmission layer is 0.1~0.5mm.

4. The integrated membrane electrode according to claim 1, characterized in that, The porous transport layer includes one of carbon paper, carbon felt, carbon cloth, titanium felt, titanium foam, nickel foam, and silver foam.

5. The integrated membrane electrode according to claim 1, characterized in that, The microporous layer is formed by a fiber network structure of randomly arranged nanofibers. The nanofibers have a core-shell structure, wherein the core material is polymer nanofibers, and the shell material includes conductive materials and perfluorosulfonic acid resin. The conductive materials include one or more of XC-72, acetylene black, conductive carbon black Super P, carbon nanofibers, graphene, and carbon nanotubes. The polymer nanofibers are polymers obtained by cross-linking and esterification reaction of polyacrylic acid and polyvinyl alcohol, wherein the mass ratio of polyacrylic acid to polyvinyl alcohol is (1~2):(1~2).

6. The integrated membrane electrode according to claim 5, characterized in that, The polymer nanofibers have a diameter of 100~1000 nm, a porosity of 50%~80%, and a pore size of 100~1000 nm. The porosity and pore size show an increasing trend or remain consistent in the distribution from the catalyst layer to the porous transport layer.

7. The integrated membrane electrode according to claim 5, characterized in that, The method for preparing the microporous layer includes the following steps: (1) Add the polymer to solvent 1 and stir to obtain a spinning aid. Disperse the conductive material and perfluorosulfonic acid resin solution in solvent 2 by ultrasonication, add the spinning aid, mix and stir to obtain a microporous layer spinning slurry. (2) Electrospinning technology is used to spin the microporous layer spinning slurry to obtain the microporous layer precursor; (3) The microporous layer precursor is heat-treated and then pressed at ambient temperature to obtain the microporous layer.

8. The integrated membrane electrode according to claim 7, characterized in that, In step (1), the mass ratio of the conductive material, perfluorosulfonic acid resin, and polymer is (5~8):(1~2):(1~4), and the conductive material accounts for 50%~80% of the total mass of the conductive material, perfluorosulfonic acid resin, and polymer. The polymer is a mixture of polyacrylic acid and polyvinyl alcohol, wherein the mass ratio of polyacrylic acid to polyvinyl alcohol is (1~2):(1~2). The conductive material includes one or more of XC-72, acetylene black, conductive carbon black Super P, carbon nanofibers, graphene, and carbon nanotubes. Solvent 1 and Solvent 2 are independently one or more of deionized water, isopropanol, n-propanol, propanol, and ethanol; The concentration of the high molecular weight polymer in the spinning aid is 2-10 wt%. In step (2), the environmental parameters for electrospinning are: temperature 20~40℃, relative humidity greater than 50%RH; the spinning parameters are: microporous layer slurry feed rate 0.2~1.0 mL / h, voltage 6.0~22.0 kV, drum receiver rotation speed 100~1000 rpm / min, needle diameter 10~26G, and distance between needle and receiver 8~18 cm. In step (3), the heat treatment temperature is 120~150℃; the pressing pressure is 0.2~3 MPa.

9. The integrated membrane electrode according to claim 1, characterized in that, The porous transport layer is processed by forming spaced grooves through one or more of the following methods: mechanical milling, laser etching, ion beam etching, chemical etching, and mold pressing.

10. The application of an integrated membrane electrode according to any one of claims 1-9 in a fuel cell or electrolyzer.

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