Gas diffusion layer and preparation method and application thereof

Abstract

The invention relates to the technical field of fuel cells, and provides a gas diffusion layer and a preparation method and application thereof. The gas diffusion layer comprises a substrate layer and a microporous layer attached to the surface of one side of the substrate layer, the substrate layer is provided with stacked carbon fibers, substrate layer pores are formed among the carbon fibers, the microporous layer comprises stacked conductive particles, at least part of the conductive particles permeate into the substrate layer, and the microporous layer comprises first pores and second pores; wherein the aperture of the first pores is R1, R1 is larger than or equal to 5 microns and smaller than or equal to 10 microns, the aperture of the second pores is R2, R2 is larger than or equal to 1 microns and smaller than 5 microns, and the pore area rate of the first pores is 25%-35%. According to the gas diffusion layer, through the synergistic effect of the multi-stage distribution pores of the pore size, the air permeability is effectively improved while the performance is improved, so that the gas diffusion layer has good drainage performance and air permeability.

Description

Technical Field

[0001] This application belongs to the field of fuel cell technology, and in particular relates to a gas diffusion layer, its preparation method and application. Background Technology

[0002] A proton exchange membrane fuel cell (PEMFC) is a device that converts the energy released from the reaction of clean energy hydrogen and oxygen to produce water into electrical energy. Its core unit structure consists of a proton exchange membrane (PEM) and symmetrically arranged catalyst layer (CL), gas diffusion layer (GDL), and bipolar plate (BP). The gas diffusion layer, as a key mass transfer component, is responsible for gas transport and liquid water management. Its porous structure allows the reactant gases (hydrogen and oxygen) to flow from the bipolar plate channels to the catalyst layer reaction interface, while simultaneously discharging the water produced by the electrochemical reaction to the bipolar plate.

[0003] Specifically, in the operation of a proton exchange membrane fuel cell, oxygen (or air) passes through the gas diffusion layer to the cathode catalyst layer, where it forms oxygen ions under the action of the cathode catalyst; hydrogen passes through the gas diffusion layer to the anode catalyst layer, where it loses electrons and becomes protons (H+) under the action of the anode catalyst. + Electrons flow through the external circuit to the cathode, generating an electric current, while protons (H)... + The oxygen ions are specifically transferred to the cathode on the proton exchange membrane and react with oxygen ions to generate water molecules, which are then discharged through the gas diffusion layer.

[0004] To improve the performance of the proton exchange membrane, the gas diffusion layer needs to have good permeability to ensure that enough hydrogen and oxygen can enter the catalyst layer for reaction. At the same time, the gas diffusion layer also needs to have good drainage performance so that the generated water can be discharged in time to prevent flooding that would reduce the performance of the proton exchange membrane fuel cell.

[0005] A gas diffusion layer typically consists of a macroporous substrate (MPS) and a microporous layer (MPL), with the microporous layer in direct contact with the catalyst layer. Gas enters the catalyst layer from the microporous layer, while water generated in the catalyst layer first enters the microporous layer. Therefore, the drainage and permeability of the gas diffusion layer mainly depend on the microporous layer. However, in existing technologies, while the microporous layer exhibits good drainage performance, its permeability is difficult to guarantee; conversely, improving the permeability of the microporous layer can decrease its drainage performance. For example, in existing technologies, drainage of the microporous layer mainly relies on the hydrophobic gradient within the microporous layer and between the microporous layer and the substrate. This method is cumbersome to prepare, difficult to control precisely, and excessive hydrophobic agents can easily clog the pores in the microporous layer, thus affecting its permeability. To ensure good permeability and uniformly deliver gas to all areas of the microporous layer, tiny pores need to be arranged within it. Drainage of the microporous layer relies on capillary action to drive liquid water into the pores of the microporous layer. Under the combined action of capillary force and hydrophobic gradient, the water is transported to the substrate and discharged. When the pores in the microporous layer are too small, the surface tension of the liquid water will hinder its entry into the pores, resulting in poor drainage performance. This means that existing gas diffusion layers cannot simultaneously achieve good drainage and permeability, thus affecting the performance of proton exchange membrane fuel cells. Summary of the Invention

[0006] The purpose of this application is to provide a gas diffusion layer and its preparation method, as well as a proton exchange membrane fuel cell, to solve the technical problem that the gas diffusion layer in the proton exchange membrane fuel cell cannot simultaneously achieve both drainage performance and air permeability performance.

[0007] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0008] In a first aspect, embodiments of this application provide a gas diffusion layer. The gas diffusion layer of this application includes a substrate layer and a microporous layer attached to one surface of the substrate layer. The substrate layer has stacked carbon fibers, with pores formed between the carbon fibers. The microporous layer includes stacked conductive particles, at least some of which permeate into the substrate layer. The microporous layer includes first pores and second pores.

[0009] Wherein, the pore size of the first pore is R1, wherein 5μm≤R1≤10μm, the pore size of the second pore is R2, wherein 1μm≤R2<5μm, and the pore area ratio of the first pore is 25%~35%.

[0010] The pore area ratio of the first pore is the percentage of the area of ​​the first pore opening on the surface of the microporous layer facing away from the substrate.

[0011] The microporous layer of the gas diffusion layer in this embodiment includes stacked conductive particles, a first pore, and a second pore. The conductive particles are rigid objects, thus creating tiny pores between them. This microporous layer forms a pore structure with a graded distribution of pore sizes through the tiny pores between the stacked conductive particles and the first and second pores. Through the synergistic effect of these graded pores, the gas diffusion layer simultaneously possesses good air permeability and drainage. By controlling the pore sizes of the first and second pores in the gas diffusion layer within a specific range, liquid water can easily enter the larger first pores. Simultaneously, the tiny pores formed by the conductive particles stacked on the sidewalls of the first pores increase the roughness of the sidewalls, further reducing the resistance to liquid water entering the pores and improving the drainage effect of the microporous layer. Furthermore, the first pores can also form mainstream gas channels, effectively shortening the gas transport path and promoting faster gas transport within the gas diffusion layer. The smaller pore size of the second pore forms a gas diffusion channel. The second pore and the tiny pores between the conductive particles work together to form a gas diffusion region, promoting the diffusion of gas between the substrate layer and the microporous layer. This allows the gas to be uniformly delivered to all areas of the gas microporous layer, thereby effectively improving the permeability of the microporous layer.

[0012] Furthermore, by controlling the pore area ratio of the first pore within a specific range, while effectively promoting the entry of liquid water into the microporous layer and ensuring drainage performance, the surface of the microporous layer also has sufficient gas diffusion area, thereby effectively improving the uniformity of gas diffusion in and on the surface of the microporous layer. Simultaneously, the pore area ratio of the first pore in the microporous layer affects its mechanical strength and conductivity. Controlling the pore area ratio within this range also ensures good mechanical structural stability and conductivity of the microporous layer, preventing structural loosening or interruption of conductive pathways due to excessive pores. Moreover, allowing at least some conductive particles to penetrate into the pores of the substrate layer further enhances the interfacial bonding force between the microporous layer and the substrate layer, improving the overall structural stability and effectively reducing the interfacial contact resistance between the substrate layer and the microporous layer, thus improving electron transport efficiency.

[0013] In this embodiment, the gas diffusion layer effectively promotes the entry of liquid and gas into the first pores, thereby forming the main gas and drainage channels in the first pores and effectively shortening the transport path of gas and liquid. The second pores form a gas diffusion region, promoting gas diffusion between the substrate layer and the microporous layer, reducing the mass transfer resistance of liquid and gas, and improving the water and air permeability of the gas diffusion layer.

[0014] In some embodiments, the pore area ratio of the second pore is 5% to 15%, and in exemplary cases, it can be a typical but not limiting size such as 5%, 8%, 10%, or 15%. The pore area ratio of the second pore is the percentage of the area of ​​the second pore openings on the surface of the microporous layer facing away from the substrate layer. Increasing the pore area ratio of the second pore can effectively reduce mass transfer resistance and improve gas diffusion efficiency, but an excessively high pore area ratio will weaken the mechanical stability of the microporous layer and affect the continuity of the conductive pathway. Controlling the pore area ratio of the second pore within this range effectively improves the gas permeability of the gas diffusion layer, while ensuring that the microporous layer has sufficient structural density to maintain mechanical strength and conductivity.

[0015] In some embodiments, the microporous layer further includes a third pore, the diameter of which is smaller than that of the second pore, and the average pore size of the microporous layer is 0.1–1.5 μm. The third pore includes tiny pores formed by the accumulation of conductive particles. In an exemplary embodiment, the entire gas diffusion layer can be tested using a PMI pore size analyzer, and the measured average PMI pore size is the average pore size of the microporous layer. The size of the average pore size in the microporous layer affects the synergistic regulation of liquid water drainage and gas transport by the pore structure of the microporous layer. While reducing the average pore size can refine the distribution channels in the microporous layer, further promoting uniform gas transport to various regions of the microporous layer and improving permeability, when the pores in the microporous layer are too small, the surface tension of liquid water will hinder liquid water from entering the pores of the microporous layer, resulting in poor drainage performance. Increasing the average pore size of the microporous layer can promote the infiltration of liquid water and reduce the mass transfer resistance. However, an excessively large average pore size can weaken the uniformity of gas diffusion, leading to localized gas flow short-circuiting. This causes reactant gases (such as oxygen or hydrogen) to leak directly through localized large pores or cracks, failing to diffuse effectively to the catalyst layer, reducing the contact area between the gas and the catalyst, and affecting the stability of the reaction interface. By controlling the average pore size of the microporous layer within this range, and combining the pore size and pore area ratio of the first and second pores, the pore distribution of the microporous layer can be further optimized. This achieves further synergistic optimization of gas transport and liquid water discharge within the microporous layer, improving the stability and efficiency of the fuel cell at high current densities.

[0016] In some embodiments, the carbon fibers in the substrate layer extend at least partially into the microporous layer. This partial extension of the carbon fibers into the microporous layer effectively enhances the interfacial bonding strength between the substrate layer and the microporous layer, reduces interfacial contact resistance, and provides a continuous channel for electron transport, thereby improving overall conductivity. The extension of the carbon fibers also inhibits cracking and peeling of the microporous layer during drying or wetting cycles, enhancing the structural stability of the gas diffusion layer.

[0017] In a further embodiment, the carbon fiber density gradually decreases from the interface between the substrate layer and the microporous layer to the surface of the microporous layer (the side facing away from the substrate layer), forming a gradient conductive network. The decreasing carbon fiber density gradient along the direction from the substrate layer to the surface of the microporous layer effectively improves the structural stability of the microporous layer, enhances the interfacial bonding between the microporous layer and the substrate layer, and further improves the mass transfer and conductivity of the microporous layer. This gradient distribution concentrates electron conduction paths near the interface, reducing electron transport impedance, while simultaneously forming a relatively loose porous structure on the surface of the microporous layer, thereby further promoting gas diffusion and liquid water drainage. This gradient structure optimizes the pore connectivity and transport path distribution within the microporous layer while ensuring electron conduction efficiency. The lower carbon fiber density on the surface facilitates the formation of continuous gas-liquid transport channels, improves the uniformity of reactant gas diffusion, and reduces resistance to liquid water drainage.

[0018] In some embodiments, the microporous layer includes through pores that penetrate the microporous layer and communicate with the pores of the substrate layer. By having through pores penetrate the microporous layer and communicate with the pores of the substrate layer, a continuous mass transfer channel from the substrate layer to the microporous layer is effectively constructed, reducing gas transport resistance, improving the connectivity of the drainage channel, and enhancing the diffusion efficiency of reactant gases toward the catalyst layer and the discharge efficiency of liquid water.

[0019] In a further embodiment, the sidewalls of the through-pores include the carbon fibers extending into the microporous layer. By extending the carbon fibers into the microporous layer to form part of the sidewalls of the through-pores, the carbon fibers act as a supporting framework, effectively improving the conductivity and mechanical strength of the microporous layer. Simultaneously, this enhances the structural stability of the through-pores, strengthens their resistance to deformation, and reduces the occurrence of collapse or blockage of the through-pores due to the contraction or expansion of the microporous layer. This further maintains the geometry and connectivity of the through-pores, promoting the efficient transport of gas and liquid water along the pore channels.

[0020] In some embodiments, the through-pores are non-uniform pores with different pore sizes in different locations. The maximum pore size in a single through-pore is D1, and the minimum pore size is D2. Therefore, the average maximum pore size in the microporous layer is d1, and the average minimum pore size is d2. The ratio between d1 and d2 can be 1 to 2. The pore size distribution of the through-pores affects the resistance to gas and liquid passage. Non-uniform through-pores tend to increase the resistance to liquid water and gas passage. Controlling the ratio between d1 and d2 within this range makes the through-pore structure more regular, reducing the resistance to liquid water and gas passage and further improving the drainage and permeability of the gas diffusion layer. It is understood that d1 and d2 can be determined by sampling and testing the size of the through-pores in a cross-section perpendicular to the surface of the microporous layer.

[0021] In a further embodiment, A represents the roughness of the substrate layer. A is positively correlated with d1, and the relationship between A and d1 / d2 is A:(d1 / d2) = 10~20 μm. When the surface roughness of the substrate layer is large, the number of carbon fibers extending into the microporous layer in the substrate layer increases, and the penetration depth of the carbon fibers increases. This is beneficial to further improve the conductivity and mechanical properties of the microporous layer, and can increase the pore size of the through pores, thereby further improving the drainage and air permeability of the microporous layer. Conversely, when the surface roughness of the substrate layer is low, the number of carbon fibers extending into the microporous layer in the substrate layer decreases, and the penetration depth of the carbon fibers decreases. In this case, it is necessary to reduce the pore size of the through pores in the microporous layer so that the microporous layer has good conductivity and mechanical properties. Within this range, the relationship between A and d1, and between A and d1 / d2, allows for a higher pore size when the substrate roughness is high and the carbon fibers penetrate the microporous layer to a greater depth. This increases the pore size of the through-pores, thereby further increasing the pore size of the through-pores while maintaining the microporous layer's low resistivity and good mechanical strength. This reduces the resistance of liquid water and gas passing through the microporous layer and improves the drainage and permeability of the gas diffusion layer.

[0022] In some embodiments, the surface roughness of the substrate layer is 10–20 μm. In exemplary cases, the surface roughness of the substrate layer can be typical but not limiting sizes such as 10 μm, 12 μm, 15 μm, 18 μm, and 20 μm. When the surface roughness of the substrate layer is low, the interlayer bonding force between the substrate layer and the microporous layer is insufficient, and the microporous layer is prone to peeling. When the surface roughness of the substrate layer is too high, the substrate layer surface is too uneven, which can easily lead to uneven coating, localized excessive thickness or thinness when coating the microporous layer slurry. This is detrimental to the precise control of the microporous layer thickness and the uniformity of the microstructure, and may even cause stress concentration between layers, affecting the overall structural stability of the gas diffusion layer. Controlling the substrate layer roughness within this range effectively improves the interlayer bonding force between the substrate layer and the microporous layer, effectively reduces the peeling problem of the microporous layer during use, and promotes the uniform spreading of the microporous layer slurry on the substrate layer surface, reducing coating defects caused by excessive surface unevenness, such as localized excessive thickness or thinness.

[0023] In some embodiments, the compressibility of the gas diffusion layer in this application embodiment at 1 MPa can be 25% to 50%. In exemplary examples, the compressibility of the gas diffusion layer at 1 MPa in this application embodiment can be typical but not limiting values ​​such as 25%, 30%, 35%, 40%, 45%, and 50%. Controlling the compressibility of the gas diffusion layer at 1 MPa is related to the pore size and porosity, thereby affecting the conductivity, drainage performance, and permeability of the gas diffusion layer. Controlling the compressibility of the gas diffusion layer at 1 MPa within the range of 25% to 50% ensures that the gas diffusion layer has sufficient pore space and good conductivity, reducing the probability of complete blockage of the gas-liquid water transport channels, improving drainage and permeability efficiency, and reducing water flooding. The good conductivity of the gas diffusion layer can effectively improve the electrochemical reaction efficiency of the proton exchange membrane fuel cell, reduce power loss, and thus improve the overall output performance of the battery. Furthermore, the compressibility of the gas diffusion layer within this range gives it good structural stability and mechanical strength, which further improves the long-term performance stability of the fuel cell when subjected to repeated compressive stress during operation.

[0024] In some examples, the thickness of the gas diffusion layer in this application embodiment can be 150–350 μm, and the thickness of the microporous layer can be 10–100 μm. In exemplary examples, the thickness of the gas diffusion layer can be typical but not limiting thicknesses such as 150 μm, 180 μm, 200 μm, 230 μm, 250 μm, 300 μm, and 350 μm; the thickness of the microporous layer can be typical but not limiting thicknesses such as 10 μm, 50 μm, 80 μm, and 100 μm. Gas diffusion layers and microporous layers within this thickness range exhibit good mass transfer, electrical conductivity, and mechanical support properties. While improving structural stability and enhancing the assembly tolerance and stability of the battery, they effectively shorten the gas and electron transport paths, improve gas transport efficiency, reduce the internal resistance of the fuel cell, and increase the battery's output efficiency.

[0025] In some examples, the thickness of the gas diffusion layer in this application embodiment can be 150–350 μm, and the thickness of the microporous layer can be 10–100 μm. In exemplary examples, the thickness of the gas diffusion layer can be typical but not limiting, such as 150 μm, 180 μm, 200 μm, 230 μm, 250 μm, 300 μm, and 350 μm; the thickness of the microporous layer can be typical but not limiting, such as 10 μm, 50 μm, 80 μm, and 100 μm. When the thickness of the gas diffusion layer and the microporous layer is relatively thin, the mass transfer resistance of the gas diffusion layer is low, which is beneficial for the rapid permeation of the reactant gas to the catalyst layer, while reducing the length of the liquid water discharge path and improving drainage efficiency. However, an excessively thin diffusion layer may lead to insufficient mechanical strength, increasing the risk of damage to the membrane electrode assembly during assembly and operation. By controlling the thickness of the gas diffusion layer in this application embodiment within this range, the structural stability and mechanical strength of the gas diffusion layer and the microporous layer are ensured, while further optimizing the mass transfer efficiency and improving drainage permeability.

[0026] In some embodiments, the resistivity of the gas diffusion layer in this application is 400–500 mΩ·cm. In exemplary examples, the resistivity of the gas diffusion layer can be typical but not limited to 400 mΩ·cm, 420 mΩ·cm, 450 mΩ·cm, 480 mΩ·cm, 500 mΩ·cm, etc. The resistivity of the gas diffusion layer directly affects the ohmic loss, current distribution, and thermal management of the fuel cell. A lower resistivity helps reduce energy loss during electron transport and improves the overall conductivity of the battery.

[0027] In some embodiments, the tensile strength of the gas diffusion layer in this application is higher than 10-15 MPa. In exemplary cases, the tensile strength of the gas diffusion layer can be typical but not limiting tensile strengths such as 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, and 15 MPa. The tensile strength of the gas diffusion layer has a significant impact on the mechanical stability, fabrication feasibility, and long-term performance of the proton exchange membrane fuel cell. When the tensile strength of the gas diffusion layer is insufficient, it is prone to breakage or deformation during the assembly or operation of the proton exchange membrane fuel cell, leading to fiber shedding, pore structure damage, increased contact resistance, or uneven local reactions, affecting the uniformity of the electrochemical reaction and the overall performance of the battery. High tensile strength can effectively resist compressive stress during assembly and expansion and contraction caused by humidity and temperature cycling during operation, maintaining structural integrity.

[0028] Secondly, embodiments of this application provide a method for preparing a gas diffusion layer. The method for preparing a gas diffusion layer according to embodiments of this application includes the following steps:

[0029] Step S01: The microporous layer slurry is deposited on one side surface of the substrate to obtain the gas diffusion layer precursor;

[0030] Step S02: The gas diffusion layer precursor is sintered to obtain the gas diffusion layer.

[0031] The substrate layer has stacked carbon fibers, and the carbon fibers form substrate layer pores;

[0032] The microporous layer slurry includes conductive particles, a hydrophobic agent, and a pore-forming agent. The pore-forming agent includes ammonium salt and carbonate, and the mass ratio of the ammonium salt to the carbonate is (0.1~1):1.

[0033] The sintering process includes a first sintering process and a second sintering process, wherein the temperature of the first sintering process is 250-320℃ and the temperature of the second sintering process is 350-400℃.

[0034] The preparation method of this application involves placing a microporous layer slurry on one side of the substrate layer, allowing the slurry to penetrate into the pores of the substrate layer surface, and then performing a subsequent sintering process. This results in a structure in which some of the conductive particles of the microporous layer in the gas diffusion layer have penetrated into the pores of the substrate layer, creating a transitional structure where the microporous layer and the substrate layer interweave. This transitional structure strengthens the interlayer bonding between the microporous layer and the substrate layer, effectively inhibiting microporous layer peeling. Simultaneously, its gradient structure alleviates abrupt changes in porosity and pore size between the substrate layer and the microporous layer, significantly reducing gas transport resistance at the interface, improving gas transport smoothness, and increasing gas diffusion efficiency. Furthermore, its interwoven gradient structure enhances the continuity of capillary forces in the gas diffusion layer, guiding liquid water more smoothly from the catalyst layer through the microporous layer towards the substrate layer, effectively inhibiting the accumulation and blockage of liquid water at the interface.

[0035] Meanwhile, the preparation method of this application uses ammonium salt and carbonate with significant differences in decomposition temperature as composite pore-forming agents, and combines them with a stepwise sintering process to achieve precise control of the multi-level pore size structure of the microporous layer. In the first sintering stage (250-320℃), the ammonium salt decomposes first in this temperature range, releasing gases such as ammonia. At this time, the slurry system is not yet fully solidified, and the escaped gases easily form pores with relatively large pore sizes. Subsequently, in the second sintering stage (350-400℃), the slurry skeleton has been initially strengthened, while the carbonate (such as sodium bicarbonate) begins to decompose at this temperature, producing carbon dioxide and water vapor. These gases are released in a matrix with higher viscosity and stronger rigidity, and their diffusion is restricted, thus forming finer and denser micropores. By controlling the mass ratio of the ammonium salt and carbonate within the range of (0.1-1):1, combined with the sintering temperature, the timing, proportion, and total amount of the two gases are effectively controlled, ultimately constructing a pore structure with a multi-level distribution of pore sizes in the microporous layer, thereby effectively improving the air permeability and drainage performance of the gas diffusion layer.

[0036] In a further embodiment, the mass ratio of ammonium salt to carbonate in the microporous layer slurry can also be (0.2-1):1 or (0.3-0.8):1. In exemplary examples, the mass ratio of ammonium salt to carbonate in the microporous layer slurry can be typical but not limiting mass ratios such as 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, and 1:1. By adjusting the ratio of the two pore-forming agents in the microporous layer slurry within this range, and by synergizing the differences in their decomposition temperature and gas release characteristics, combined with the sintering temperature, a first and second pore with a hierarchical pore size distribution are constructed in the microporous layer, optimizing the pore network, thereby improving gas diffusion efficiency while enhancing water management capabilities. In exemplary examples, the ammonium salt can include ammonium chloride, and the carbonate includes at least one of sodium carbonate and potassium carbonate.

[0037] In some embodiments, the content of the porogen in the microporous layer slurry can be 3% to 6%. In exemplary examples, the content of the porogen can be 3%, 4%, 5%, 6%, etc., which are typical but not limited contents. The level of the porogen content directly affects the pore structure, conductivity, and mechanical strength of the microporous layer. When the porogen content is low, a strong and dense conductive framework can be formed, resulting in good mechanical strength and conductivity of the microporous layer. However, if the porogen content is too low, less gas is generated, making it difficult to form a well-connected hierarchical pore structure, thus affecting gas diffusion and liquid water drainage. When the porogen content is high, sufficient gas promotes the formation of a hierarchical pore structure, effectively improving gas permeability and drainage performance. However, excessively high porogen content can easily lead to coarsening of the pores and thinning of the pore walls in the microporous layer, resulting in a fragile structure and damage to the conductive network of the microporous layer, significantly increasing resistance. By controlling the content of the pore-forming agent within this range, a sufficient, interconnected, and appropriately gradient pore network is formed in the microporous layer, ensuring efficient mass transfer and drainage and avoiding performance degradation; at the same time, it can maintain a continuous and stable conductive framework, reduce resistance, and improve mechanical reliability.

[0038] In some embodiments, the content of conductive particles in the microporous layer slurry can be 10% to 20%. In exemplary examples, the content of conductive particles can be typical but not limiting, such as 10%, 12%, 15%, 18%, and 20%. A lower content of conductive particles is beneficial for forming a microporous layer structure with high porosity; however, too low a content can affect the continuity of the conductive network, increase electron transport resistance, and negatively impact the mechanical strength of the microporous layer. While a higher content of conductive particles can give the microporous layer excellent conductivity and mechanical strength, excessively high levels can compress pore spaces, affecting the connectivity of gas and water transport channels. Furthermore, a high content of conductive particles results in high viscosity of the microporous layer slurry, making coating difficult. By controlling the content of conductive particles in the microporous layer slurry within this range, the conductive particles in the microporous layer can construct continuous, low-resistance electronic conduction paths, providing basic conductivity and structural support for the microporous layer. Simultaneously, it allows sufficient space for the decomposition of the pore-forming agent, promoting the formation of a rich, interconnected gradient pore structure, further improving gas diffusion and liquid water drainage performance. Furthermore, the microporous layer slurry with conductive particle content within this range exhibits suitable rheological properties, facilitating uniform coating and stable molding, thereby further improving the structural uniformity of the microporous layer. In the example, the conductive particles include carbon particles.

[0039] In some embodiments, the particle size Dv50 of the conductive particles can be 30–100 nm. In exemplary examples, the particle size of the conductive particles can be typical but not limiting, such as 30 nm, 50 nm, 80 nm, or 100 nm. Reducing the particle size is beneficial for improving the surface smoothness of the microporous layer and reducing the contact resistance between the microporous layer and the catalyst layer. However, excessively small particle sizes can easily cause agglomeration of the conductive particles, reducing the stability of the microporous layer slurry, and the pores between the conductive particles are too small, thus hindering mass transfer. Increasing the particle size of the conductive particles can effectively increase the gap between the conductive particles and improve gas diffusion performance. However, excessively large particle sizes can easily lead to a rough surface of the microporous layer, which reduces the effective contact area between the microporous layer and the catalyst layer, resulting in increased contact resistance. Controlling the particle size of conductive particles within this range can effectively improve the smoothness of the microporous layer surface, increase the effective contact area between the microporous layer and the catalyst layer, reduce the contact resistance, and reduce the agglomeration of conductive particles in the microporous layer slurry, thereby improving the stability of the microporous layer slurry and further enhancing the uniformity of the microporous layer structure. At the same time, conductive particles within this particle size range can also increase the gap between conductive particles and improve gas diffusion performance.

[0040] In some embodiments, the mass ratio of conductive particles to porogen in the microporous layer slurry is (10-20):(3-6), optionally (10-20):4, (10-20):5, or 15:(3-6). In exemplary examples, the mass ratio of conductive particles to porogen can be typical but not limiting mass ratios such as 10:6, 10:5, 15:4, 15:5, 20:3, or 20:5. Increasing the mass ratio of conductive particles to porogen can effectively improve the conductivity and mechanical strength of the microporous layer; however, an excessively high mass ratio can lead to insufficient pore structure in the microporous layer, affecting gas diffusion and drainage performance. Decreasing the mass ratio of conductive particles to porogen can form a well-developed porous structure in the microporous layer; however, an excessively low mass ratio can lead to a fragile microporous layer structure, reduced continuity of the conductive network, and increased resistance. By controlling the mass ratio of conductive particles to pore-forming agent in the microporous slurry within this range, the conductive particles can construct a continuous and stable conductive framework, giving the microporous layer excellent electronic conductivity and mechanical support. At the same time, an appropriate amount of pore-forming agent can form a rich and interconnected pore network in the conductive framework, providing channels for efficient gas diffusion and smooth drainage of liquid water, thereby improving gas-liquid transport performance while achieving high conductivity and high strength.

[0041] In some embodiments, the content of the hydrophobic agent in the conductive paste can be 5% to 10%. In exemplary embodiments, the content of the hydrophobic agent can be typical but not limiting, such as 5%, 6%, 7%, 8%, 9%, and 10%. Increasing the content of the hydrophobic agent can enhance the hydrophobic properties of the microporous layer, effectively reduce the accumulation of liquid water in the microporous layer, and improve the battery's flood resistance. However, if the hydrophobic agent content is too high, some pores in the microporous layer may be filled by the hydrophobic agent, affecting gas transport efficiency. Reducing the content of the hydrophobic agent can give the microporous layer a higher porosity to promote gas-liquid transport, but insufficient hydrophobicity will make the microporous layer easily wetted by water, and liquid water will easily remain. Controlling the hydrophobic agent content within this range imparts good hydrophobic properties to the microporous layer, effectively draining the water generated in the reaction, while also effectively reducing the clogging of pores by the hydrophobic agent, thereby giving the microporous layer a suitable pore structure and further improving the drainage and air permeability of the microporous layer. In exemplary embodiments, the hydrophobic agent may include at least one of polytetrafluoroethylene (PTFE) and polydifluoroethylene (PDFE).

[0042] In some embodiments, the microporous layer slurry may further include a dispersant. In further embodiments, the content of the dispersant may be 1% to 6%. In exemplary examples, the content of the dispersant may be typical but not limiting, such as 1%, 2%, 3%, 4%, 5%, and 6%. Adding a dispersant to the microporous layer slurry and controlling the content of the dispersant within this range can effectively improve the dispersion uniformity of the components in the microporous layer slurry, reduce the probability of agglomeration of solid particles such as conductive particles and hydrophobic agents due to surface tension or van der Waals forces, and make the particles uniformly dispersed in the solvent. This results in a more regular microporous layer structure, reduces uneven pore distribution or breakage of conductive pathways caused by local agglomeration, and further improves the conductivity and drainage and air permeability of the microporous layer. In exemplary examples, the dispersant may include at least one of cellulose ether, polyethylene glycol octylphenyl ether (Triton X-100), polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS).

[0043] In some embodiments, the microporous slurry may further include a thickener. In a further embodiment, the content of the thickener may be 1% to 2%. In an exemplary embodiment, the thickener may include at least one of carboxymethyl cellulose (CMC), hydroxypropyl methyl cellulose (HPMC), and hydroxyethyl cellulose (HEC). Adding a thickener to the microporous slurry and controlling the content of the thickener within the range of 1% to 2% can effectively adjust the viscosity of the microporous slurry, improve problems such as sagging and uneven thickness during the coating process caused by the microporous slurry being too thin, and reduce the impact of excessively high viscosity of the microporous slurry on the smoothness and uniformity of the coating, further promoting the formation of a continuous and smooth coating on the substrate surface.

[0044] In some embodiments, the microporous layer slurry may further include a leveling agent. In a further embodiment, the leveling agent content may be 1% to 2%. In an exemplary example, the leveling agent may include at least one of polyethylene glycol (PEG) and acrylate polymers. Adding a leveling agent to the microporous layer slurry and controlling the leveling agent content within this range can effectively reduce the surface tension of the microporous layer slurry, promote the wetting and spreading of the microporous layer slurry on the substrate surface, and reduce defects such as pinholes, craters, and orange peel caused by differences in surface tension during the coating process. At the same time, the leveling agent can improve the rheological properties of the microporous layer slurry, promote the uniform distribution of solid particles in the microporous layer slurry, and reduce local accumulation or agglomeration during coating and drying, thereby further improving the surface smoothness and microstructure uniformity of the microporous layer coating.

[0045] In some embodiments, the microporous layer slurry further includes a defoaming agent. In a further embodiment, the content of the defoaming agent can be 1% to 3%. In an exemplary example, the defoaming agent may include at least one of silicone-based and fluorocarbon-based defoaming agents. Adding a defoaming agent to the microporous layer slurry and controlling the content of the defoaming agent in the microporous layer slurry within this range can effectively suppress and eliminate air bubbles in the microporous layer slurry, reducing defects such as pinholes and bubbles in the microporous layer after coating due to residual air bubbles. At the same time, controlling the content of the defoaming agent within the range of 1% to 3% improves the defoaming effect and reduces the adverse effects of the defoaming agent on the stability of the microporous layer slurry and the bonding force between the microporous layer and the substrate layer, further improving the integrity and mechanical properties of the microporous layer structure.

[0046] In some embodiments, when the temperature of the first sintering treatment is 250–320°C, the time of the first sintering treatment can be 1–5 min. In exemplary examples, the temperature of the first sintering treatment can be typical but not limiting temperatures such as 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, and 320°C; the time of the first sintering treatment can be typical but not limiting times such as 1 min, 2 min, 3 min, 4 min, and 5 min. Controlling the temperature of the first sintering treatment at 250–320°C, combined with a treatment time of 1–5 min, promotes the complete decomposition of ammonium salts to construct pores with relatively large pore sizes, while moderately softening the hydrophobic agent to initially stabilize the structure, and reserving reaction space and structural basis for the subsequent decomposition of carbonates at higher temperatures to form small pores. The first sintering treatment, combined with the subsequent second sintering treatment, jointly constructs a microporous layer with a multi-level pore size structure.

[0047] In some embodiments, when the temperature of the second sintering treatment is 350–400°C, the time of the second sintering treatment can be 10–30 min. In exemplary examples, the temperature of the second sintering treatment can be typical but not limiting temperatures such as 350°C, 360°C, 370°C, 380°C, 390°C, and 400°C; the time of the second sintering treatment can be typical but not limiting times such as 10 min, 15 min, 20 min, 25 min, and 30 min. Controlling the temperature of the second sintering treatment at 350–400°C, combined with a treatment time of 10–30 min, promotes the complete melting of the hydrophobic agent and its encapsulation of the conductive particles, forming a hydrophobic three-dimensional network, thereby significantly enhancing the mechanical strength of the microporous layer and its adhesion to the substrate layer. This temperature and time also promote the complete decomposition of the carbonate porogen, generating abundant relatively small pore structures within the preliminarily stabilized framework, thereby obtaining a microporous layer with a multi-level pore structure, and further improving the drainage and permeability of the gas diffusion layer.

[0048] In some embodiments, the heating rate of the sintering process can be 3–9 °C / min. In exemplary cases, typical but not limiting heating rates such as 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, and 9 °C / min can be used. Controlling the heating rate within this range reduces internal stress concentration caused by excessively rapid heating, thus decreasing the probability of defects such as cracking and deformation in the microporous layer during sintering and improving the integrity of the material structure. Simultaneously, a suitable heating rate facilitates uniform reaction and diffusion of the components during heating, allowing additives such as hydrophobic agents and pore-forming agents to interact more fully with conductive particles, promoting the uniform construction of the hydrophobic network and the orderly decomposition of the pore-forming agent, thereby further optimizing the microstructure of the microporous layer and further improving the drainage and permeability of the gas diffusion layer.

[0049] Thirdly, this application provides a proton exchange membrane fuel cell. The proton exchange membrane fuel cell of this application includes the gas diffusion layer described above.

[0050] The gas diffusion layer described above possesses excellent drainage and permeability, effectively optimizing the water-gas balance within the proton exchange membrane fuel cell of this embodiment. This results in higher energy conversion efficiency and a longer service life for the proton exchange membrane fuel cell. Specifically, the excellent permeability of the gas diffusion layer ensures that the reactant gases (hydrogen and oxygen) can diffuse rapidly and uniformly to the catalyst layer, significantly reducing concentration polarization. This allows the proton exchange membrane fuel cell of this embodiment to maintain high output voltage and power density even at high current densities. The efficient drainage capacity of the gas diffusion layer promptly removes water generated by the electrochemical reaction from both the catalyst layer and the gas diffusion layer, effectively preventing reduced gas diffusion capacity and flooding due to liquid water accumulation. This ensures continuous unobstructed gas flow and improves gas utilization efficiency. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0052] Figure 1 This is an electron microscope image of the surface of the microporous layer in the gas diffusion layer of Example 1, wherein... Figure 1 The magnification is 2000 times;

[0053] Figure 2 This is a cross-sectional electron microscope image of the gas diffusion layer along its thickness direction in Example 1, wherein... Figure 2The magnification is 200x; Detailed Implementation

[0054] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0055] 1. Gas diffusion layer and its preparation method

[0056] Example 1

[0057] This embodiment provides a gas diffusion layer, which includes a substrate layer and a microporous layer attached to one surface of the substrate layer. The substrate layer is carbon paper with stacked carbon fibers forming pores between them. The microporous layer includes stacked conductive particles, some of which permeate into the substrate layer. The microporous layer includes first pores and second pores. The gas diffusion layer preparation method of this embodiment includes the following steps:

[0058] Step S01: Prepare the microporous layer slurry. Conductive particles (carbon powder), pore-forming agent, hydrophobic agent, dispersant, thickener, leveling agent, defoamer, and water are mixed evenly according to the proportions shown in Table 1 to obtain the microporous layer slurry. The conductive particles are carbon particles with a particle size of 50 nm; the pore-forming agents are sodium carbonate and sodium chloride; the hydrophobic agent is tetrafluoroethylene; and the dispersant, thickener, leveling agent, and defoamer are Triton X-100, HPMC, PEG-1000, and a silane defoamer, respectively. The content of Triton X-100 is 3%, HPMC is 1%, PEG-1000 is 1%, the silane defoamer is 1%, tetrafluoroethylene is 5%, and the balance is water.

[0059] Step S02: Microporous layer slurry coating. The microporous layer slurry from step S01 is coated onto the surface of carbon paper to form a conductive slurry layer, thus obtaining the gas diffusion layer precursor. The surface roughness of the carbon paper is shown in Table 1.

[0060] Step S03: Sintering treatment. The gas diffusion layer precursor obtained in step S02 is subjected to sintering treatment. The heating rate of the sintering treatment is 5℃ / min. After holding at 300℃ for 2 minutes, the temperature is further increased to 380℃ and held for another 15 minutes. After cooling, the gas diffusion layer of this embodiment is obtained. The thickness of the gas diffusion layer in this embodiment is shown in Table 2.

[0061] Examples 2 to 9

[0062] Examples 2 to 9 each provide a gas diffusion layer. The preparation methods of the gas diffusion layers in Examples 2 to 9 are basically the same as those in Example 1, except that the microporous layer slurry formulations are shown in Table 1, the sintering temperature and substrate surface roughness are shown in Table 2, and the thickness of the gas diffusion layer is shown in Table 2.

[0063] Comparative Examples 1 to 3

[0064] Comparative Examples 1 to 3 each provide a gas diffusion layer. The preparation methods of the gas diffusion layers in Comparative Examples 1 to 3 are basically the same as those in Example 1. The difference is that the proportion of the microporous layer slurry is shown in Table 1, the sintering temperature is shown in Table 2, and the thickness of the gas diffusion layer is shown in Table 2.

[0065] Table 1

[0066]

[0067] Table 2

[0068]

[0069]

[0070] 2. Structural Characteristics Analysis of the Gas Diffusion Layer

[0071] The gas diffusion layers from Examples 1 to 9 and Comparative Examples 1 to 3 were examined under an electron microscope. The thickness of the gas diffusion layer and the thickness of the microporous layer were also examined. The pore area ratio of the first pore with a diameter of 5-10 μm and the pore area ratio of the second pore with a diameter of 1-5 μm were also examined. Simultaneously, the cross-section of the microporous layer along the thickness direction was observed under an electron microscope to confirm the maximum and minimum average pore diameters of the microporous layer penetrating the pores.

[0072] The testing methods for parameters such as pore area ratio, pore size, and diameter are as follows: After characterizing the morphology of the microporous layer structure using a scanning electron microscope, measurements are performed using computer software or manually, and corresponding calculations are made. In actual measurement, such as measuring pore size, the surface (or cross-section) of the microporous layer can be characterized using an electron microscope to obtain the corresponding SEM image. A certain area is selected, such as 10μm×10μm or 20μm×20μm, the specific area size depending on the actual situation. Then, all pore sizes on this area are measured using appropriate computer software or manually (the number counted should not be less than 10), and then the average pore size of the area is calculated.

[0073] The results are shown in Table 3.

[0074] Table 3

[0075]

[0076] As shown in Table 2, the thickness of the gas diffusion layer in Example 1 is approximately 245 μm, of which the thickness of the microporous layer is approximately 45 μm. The thicknesses of the gas diffusion layers and the microporous layers in Examples 2 to 9, Comparative Examples 1 and 2 are similar to those in Example 1.

[0077] As shown in Table 3, in Comparative Example 3, the temperature was raised to 380℃ during the sintering process. Due to the rapid decomposition of the pore-forming agent, a large amount of gas was suddenly released, resulting in more cracks on the surface of the microporous layer.

[0078] 2. Performance evaluation of the gas diffusion layer

[0079] The gas diffusion layers of Examples 1 to 9 and Comparative Examples 1 to 3 were used to determine the tensile strength, resistivity, compressibility, air permeability and drainage of the gas diffusion layers of each example and comparative example using the following methods. The results are shown in Table 4.

[0080] (1) Tensile strength test method:

[0081] The specimen is cut into strips of a certain size, and the tensile strength is tested using a universal testing machine. The tensile strength of the specimen is calculated using the following formula:

[0082]

[0083] In the formula:

[0084] Ts: Tensile strength of the sample, in megapascals (MPa);

[0085] Fb: The load recorded when the sample is disconnected, in Newtons (N);

[0086] Wcp: Width of the sample, in millimeters (mm);

[0087] d: The average thickness of the sample under a certain pressure, in millimeters (mm).

[0088] (2) Resistivity testing method:

[0089] Cut the sample into a regular size and place it between two measuring electrodes in the resistivity meter. The measuring electrodes are gold electrodes or gold-plated copper electrodes. Wait 100 seconds after the pressure reaches 1 MPa, and calculate the resistivity using the following formula:

[0090] ρt= [(Rm*S) -2Rc] / d Formula (2)

[0091] In the formula:

[0092] d: Average thickness of the sample at 1 MPa;

[0093] ρt: Sample resistivity, in milliohm-cm (mΩ·cm);

[0094] Rm: The instrument's measured value, which is the sum of the sample's vertical resistance, the copper electrode's body resistance, and the contact resistance between the two samples and the electrode, in milliohms (mΩ).

[0095] S: The contact area between the sample and the two electrodes, in square centimeters (cm2);

[0096] Rc: The sum of the bulk resistance of the two copper electrodes and the contact resistance between the sample and the two electrodes, in milliohm square centimeters (mΩ·cm2);

[0097] (3) Compression ratio test method:

[0098] Cut the sample into regular 1cm*1cm specimens and test them using a compression ratio meter. Calculate the compression ratio of the sample using the following formula:

[0099]

[0100] In the formula:

[0101] γ: Compression ratio under a certain pressure, expressed as a percentage (%);

[0102] dpi: Thickness under a certain pressure, in millimeters (mm);

[0103] d0: Initial thickness of the sample, in millimeters (mm).

[0104] (4) Air permeability test method:

[0105] The air permeability was tested using a Gurley air permeability tester, with the gas volume set to 300 mL.

[0106] (5) Drainage performance evaluation

[0107] A 5.0 cm diameter GDL sample was inserted into a stainless steel test cell for water permeability measurement. The test cell was 12 cm high and had two 1 / 2-inch diameter Teflon tubes attached to the top. 200 mL of water was pumped into the test cell until the water permeated the GDL sample. The permeability was then calculated (in g / s / m³). 2 ).

[0108] Table 4

[0109]

[0110]

[0111] As shown in Table 4, the tensile strength of the gas diffusion layer in Examples 1 to 9 is in the range of 20 to 23 MPa, and the resistivity is in the range of 400 to 470 mΩ·cm. The gas diffusion layer in the present application has good tensile strength and electronic conductivity.

[0112] As shown in Table 4, the drainage and air permeability of the gas diffusion layers in Examples 1 to 9 are significantly better than those in Comparative Examples 1 and 2. This indicates that the embodiments of this application effectively improve the drainage and air permeability of the gas diffusion layer by setting first and second pores with a pore size gradient distribution on the microporous layer and controlling the pore area ratio of the first pores within a specific range. In Comparative Examples 1-2, the pore area ratio of the first pores is outside the defined range, therefore the drainage and air permeability are poor.

[0113] Furthermore, the drainage and air permeability of the gas diffusion layers in Examples 1 to 3 are better than those in Examples 4 to 9. Specifically, in this application, parameters such as the pore area ratio of the second pores in the gas diffusion layer (Examples 5-7), the ratio of the maximum to minimum diameter in the through pores (Example 8), and the roughness to the ratio of the maximum to minimum diameter in the through pores (Example 9) are controlled outside a specific range, which further affects the drainage and air permeability of the gas diffusion layer.

[0114] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A gas diffusion layer comprising a substrate layer and a microporous layer attached to one surface of the substrate layer, the substrate layer having stacked carbon fibers, wherein the carbon fibers form pores in the substrate layer, characterized in that, The microporous layer includes stacked conductive particles, at least a portion of which penetrate into the substrate layer, and the microporous layer includes a first pore and a second pore. Wherein, the pore size of the first pore is R1, wherein 5μm≤R1≤10μm, the pore size of the second pore is R2, wherein 1μm≤R2<5μm, and the pore area ratio of the first pore is 25%~35%.

2. The gas diffusion layer as described in claim 1, characterized in that, The pore area ratio of the second pore is 5% to 15%; and / or The microporous layer further includes a third pore, the diameter of which is smaller than that of the second pore, and the average pore diameter of the microporous layer is 0.1 to 1.5 μm.

3. The gas diffusion layer as described in claim 1, characterized in that, The microporous layer includes through pores, wherein the through pores penetrate the microporous layer and communicate with the pores of the substrate layer; and / or At least a portion of the carbon fibers extend into the microporous layer.

4. The gas diffusion layer as described in claim 3, characterized in that, The sidewalls of the through-pores include the carbon fibers extending into the microporous layer.

5. The gas diffusion layer according to any one of claims 1-4, characterized in that, The maximum pore diameter in the through-hole is d1, the minimum pore diameter is d2, and the ratio of d1 to d2 is 1 to 2; and / or The roughness of the substrate layer is A, and A satisfies at least one of the following (1) to (3); (1) The A and d1 are positively correlated; (2) The relationship between A and d1 / d2 is A: (d1 / d2) = 10~20μm; (3) The A is 10-20 μm.

6. The gas diffusion layer according to any one of claims 1-4, characterized in that, The gas diffusion layer satisfies at least one of the following (1) to (4): (1) The compressibility of the gas diffusion layer at 1 MPa is 10% to 30%; (2) The thickness of the gas diffusion layer is 150-350 μm; (3) The resistivity of the gas diffusion layer is 400-500 mΩ·cm; (4) The tensile strength of the gas diffusion layer is 10-15 MPa.

7. The method for preparing the gas diffusion layer according to any one of claims 1-6, characterized in that, Includes the following steps: A microporous layer slurry is deposited on one side surface of the substrate to obtain a gas diffusion layer precursor. The gas diffusion layer precursor is sintered to obtain the gas diffusion layer; The substrate layer has stacked carbon fibers, and the carbon fibers form substrate layer pores; The microporous layer slurry includes conductive particles, a hydrophobic agent, and a pore-forming agent. The pore-forming agent includes ammonium salt and carbonate, and the mass ratio of the ammonium salt to the carbonate is (0.1~1):

1. The sintering process includes a first sintering process and a second sintering process, wherein the temperature of the first sintering process is 250-320℃ and the temperature of the second sintering process is 350-400℃.

8. The preparation method according to claim 7, characterized in that, The microporous layer slurry satisfies at least one of the following (1) to (5): (1) The mass ratio of the conductive particles to the pore-forming agent is (10-20):(3-6); (2) The content of the conductive particles is 10% to 20%; (3) The particle size of the conductive particles is 30-100 nm; (4) The conductive particles include carbon particles; (5) The content of the pore-forming agent is 3% to 6%.

9. The preparation method according to claim 7 or 8, characterized in that, The hydrophobic agent content is 5% to 10%; and / or The hydrophobic agent includes at least one of polytetrafluoroethylene and polydifluoroethylene.

10. The preparation method according to claim 7 or 8, characterized in that, The microporous layer slurry further includes a dispersant, and the dispersant satisfies at least one of the following (1) to (2): (1) The content of the dispersant is 1% to 6%; (2) The dispersant includes at least one of cellulose ether, Triton X-100, PVP, and SDS.

11. The preparation method according to claim 7 or 8, characterized in that, The microporous slurry further includes at least one of a thickener, a leveling agent, and a defoamer, and the contents of the thickener, leveling agent, and defoamer are respectively: Thickener 1%–2%; Leveling agent 1%–3%; Defoamer 1%–3%.

12. The preparation method according to claim 7 or 8, characterized in that, The first sintering treatment time is 1 to 5 minutes; and / or The second sintering treatment takes 10–30 min; and / or The heating rate of the sintering process is 3 to 9 °C / min.

13. A proton exchange membrane fuel cell, characterized in that, It includes the gas diffusion layer as described in any one of claims 1-6, or the gas diffusion layer prepared by the preparation method as described in any one of claims 8-12.

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