A gas diffusion layer for a fuel cell cathode and a method for manufacturing the same

Abstract

The application discloses a kind of gas diffusion layer for fuel cell cathode and its preparation method, belong to fuel cell technical field.Aiming at the technical problem that proton exchange membrane fuel cell is insufficient in low humidity proton exchange membrane wetting, difficult in high humidity drainage, the application adopts single-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube (MWCNT) with good conductivity to construct hierarchical pore network structure as water-retention function layer, and inserts it into the middle of base layer and hydrophobic microporous layer to prepare self-humidifying GDL.In the process of fuel cell operation, the middle layer acts as a self-humidifier under low humidity conditions, keeping the proton membrane (PEM) in a wet state under dry conditions;Under high humidity conditions, it acts as a drainage facilitator to prevent flooding.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, specifically relating to a gas diffusion layer for a fuel cell cathode and its preparation method. Background Technology

[0002] Hydrogen energy is an ideal clean energy source. Hydrogen fuel cell vehicles have advantages such as fast refueling, good low-temperature performance, and long driving range, making them an important direction for the electrification and decarbonization of future automobiles. They have profound significance for improving the future energy structure and developing low-carbon transportation. Among them, proton exchange membrane fuel cells (PEMFCs) are widely researched and applied due to their advantages such as high power density and fast start-up speed. The gas diffusion layer is a key material in PEMFCs, playing roles such as supporting the catalyst, collecting current, gas transport, and drainage. During the reaction, the proton exchange membrane needs to be fully wetted because the protons generated in the anode catalyst layer are hydrated protons (H3O). + The protons are transported to the cathode in the form of [missing information]. In the absence of water, the proton conductivity drops sharply, leading to a decline in the performance of the membrane electrode and the battery.

[0003] To address the issue of insufficient proton exchange membrane (PEM) wetting in fuel cells under low humidity conditions, researchers have proposed various methods for obtaining self-humidifying electrodes, primarily including self-humidifying composite membranes, self-humidifying catalyst layers, and self-humidifying gas diffusion layers (GDLs). However, self-humidifying membranes and catalysts, besides being complex and costly to manufacture, inevitably reduce the membrane's proton conductivity or the catalyst's catalytic efficiency. The GDL, located adjacent to the catalyst layer, is the main channel for drainage and gas supply; therefore, the structural design of the GDL, which aims to avoid affecting the performance of the catalyst and PEM, is a key research focus. US Patent 6821661 discloses a hydrophilic anode gas diffusion layer by adding carbon fibers with a water contact angle of less than 140° to the anode gas diffusion layer side, while the cathode is more hydrophobic than the anode, achieving a hydrophilic anode through synergistic effects. This patent primarily targets carbon paper, which is some distance from the PEM, leaving room for improvement in wetting performance. Most researchers have implemented specific structural designs for the MPL: CN1309109 utilizes a gradient pore structure created by adding a pore-forming agent to the microlayer to facilitate the rapid drainage of liquid water; US6605381 improves the uniform distribution of reactant gases in the flow field plate and catalyst layer by constructing a gradient with gradually increasing permeability in a local region of the gas diffusion layer; some researchers have also considered adding water-retaining components, such as SiO2 and TiO2, to the GDL to increase the water retention of the electrode, but these additives can affect conductivity and are detrimental to the performance of the fuel cell. CN101662031A discloses a gas diffusion layer structure with low gas diffusivity, which optimizes the pore distribution of the MPL by adding anisotropic particles such as conductive flakes (e.g., graphite flakes) to the microlayer, ensuring conductivity while giving the GDL good water retention capacity. However, simple water retention is insufficient to meet the application requirements of gas diffusion layers, especially on the cathode side of fuel cells. Protons react with oxygen to produce water. Excessive water production that cannot be drained promptly can cause catalyst flooding and failure. It also blocks oxygen from reaching the catalyst layer, reducing battery performance. Therefore, higher requirements are placed on the gas diffusion layer on the cathode side of fuel cells: good water retention under low humidity to ensure wetting of the proton exchange membrane; and good drainage under high humidity to prevent catalyst flooding and block gas flow. Summary of the Invention

[0004] To address the technical challenges of insufficient wetting of the proton exchange membrane in low humidity and difficulty in drainage in high humidity in current proton exchange membrane fuel cells, this invention provides a gas diffusion layer for the cathode of a fuel cell and its preparation method.

[0005] To achieve the above objectives, the present invention employs the following technical solutions:

[0006] A gas diffusion layer for a fuel cell cathode includes a base layer, an intermediate layer, and a microporous layer MPL; the intermediate layer is located between the base carbon paper and the microporous layer; the intermediate layer is composed of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) in a mass ratio of 25:75 to 90:10.

[0007] Furthermore, the single-walled carbon nanotubes (SWCNTs) have a length of 5–60 μm, a diameter of 1–4 nm, and a zeta potential of -60–60 mV; the multi-walled carbon nanotubes (MWCNTs) have a length of 1–30 μm, a diameter of 8–30 nm, and a zeta potential of -60–60 mV; the intermediate layer has a thickness of 0.5–10 μm; and the microporous layer has a thickness of 10–60 μm.

[0008] Furthermore, the porosity of the gas diffusion layer is 58%–70%, the pore size distribution is 50 nm–1 μm, the resistivity is 4–20 mΩ·cm, and the contact resistance is 5–15 mΩ·cm. 2 The contact angle is 130° to 150°.

[0009] A method for preparing a gas diffusion layer for a fuel cell cathode as described above includes the following steps:

[0010] Step 1, hydrophobic treatment of the substrate: Immerse the substrate in an aqueous solution of hydrophobic agent for 3-5 minutes, remove and dry it, and then heat it in an atmosphere furnace to melt and homogenize the hydrophobic agent. Then calculate the weight gain of the substrate after hydrophobic treatment.

[0011] Step 2, fixation of the intermediate layer: First, prepare a carbon nanotube dispersion: SWCNT and MWCNT are added to the solvent in proportion, and a dispersant is added at the same time. After ball milling and ultrasonic treatment, a uniform carbon nanotube dispersion is obtained. Then, the carbon nanotube dispersion is deposited and fixed on the surface of the hydrophobic substrate by electrophoretic deposition or simple filtration.

[0012] Step 3, Preparation of the gas diffusion layer: First, prepare the microporous layer MPL slurry: Add the surfactant to deionized water and stir magnetically to obtain a mixed solution; then add toner and stir continuously until homogeneous, and sonicate for 2-8 minutes to obtain a toner dispersion; add binder and hydrophobic agent to the toner dispersion, and use a sand mill to mix to obtain a uniformly mixed microporous layer slurry; coat the microporous layer slurry onto the surface of the intermediate layer by means of a wire rod or doctor blade, and then obtain the gas diffusion layer by vacuum drying and high temperature homogenization treatment.

[0013] Furthermore, the weight gain of the substrate after hydrophobic treatment in step 1 is 5% to 40%. If the weight gain of the substrate is less than 5%, the hydrophobic treatment is insufficient, and product water will accumulate in the substrate during fuel cell operation; if the weight gain of the substrate is greater than 40%, the hydrophobicity is too strong, which is not conducive to water entering the substrate layer and being discharged into the flow channel, and water is prone to accumulate at the microporous layer and substrate interface, causing flooding.

[0014] Furthermore, the hydrophobic agent in step 1 and / or step 3 is one or a mixture of two or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and fluorinated ethylene propylene copolymer (FEP); the concentration of the hydrophobic agent is 1% to 20%. Since the pore size of the substrate layer mentioned in this patent is usually at the micron or submicron level, if the concentration of the hydrophobic agent is too high, the hydrophobic agent will not be able to enter the submicron level pores, resulting in a blind spot in hydrophobic treatment, which is not conducive to mass transfer during fuel cell operation; if the concentration of the hydrophobic agent is too low, the treatment efficiency will be greatly reduced.

[0015] In step 1, the substrate layer is carbon paper, carbon cloth, or a metal mesh; in step 2, the solvent is water or an alcohol solvent; and in step 2, the dispersant is a surfactant. Specifically, it is a commonly used surfactant such as sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), nonylphenol polyoxyethylene ether (NP-10), or Triton.

[0016] Furthermore, in step 1, the homogenization process involves heating to 350–380°C at a rate of 3–8°C / min and then holding for 10–40 min. If the heating rate is too fast (above 8°C / min), residual thermal stress will occur in the hydrophobic agent film, leading to stress orientation in micro-regions, which is detrimental to the stability of the gas diffusion layer structure, and the hydrophobic agent will not be sufficiently homogenized. Similarly, if the holding time is less than 10 min, the same problem will occur, while a holding time longer than 40 min will increase the processing time and energy consumption, and the excessive time will damage the stability of the hydrophobic agent and destroy the hydrophobicity of the substrate layer.

[0017] Furthermore, in step 2, the single-walled carbon nanotubes (SWCNTs) have a length of 5–60 μm, a diameter of 1–4 nm, and a zeta potential of -60–60 mV; the multi-walled carbon nanotubes (MWCNTs) have a length of 1–30 μm, a diameter of 8–30 nm, and a zeta potential of -60–60 mV. If the carbon nanotubes are too short, the overlapping network structure is unstable; if they are too long, the dispersibility deteriorates, which is not conducive to forming a uniform and stable dispersion. If the zeta potential is too small, it cannot provide sufficient deposition driving force during electrophoretic deposition; if the zeta potential is too large, it indicates that the carbon nanotube structure has introduced a lot of functional groups and unstable six-membered rings, increasing structural defects and decreasing conductivity. If the diameter of SWCNTs is too large, it is not conducive to forming a "film" with good water retention; if the diameter is too small, the pore size formed is small, which is not conducive to mass transfer. If the diameter of MWCNTs is too large, the capillary force of the pores formed is reduced, and it cannot provide a good transport driving force; if the diameter is too small, the intermediate layer formed is limited.

[0018] Furthermore, the thickness of the intermediate layer in step 2 is 0.5–10 μm. If the intermediate layer is too thin, the capillary force provided is insufficient; if the intermediate layer is too thick, the moisturizing effect is lost.

[0019] Furthermore, in step 2, the electrophoretic deposition potential is 0.5V to 10V, and the electrophoretic deposition time is 2 to 20 minutes. If the electrophoretic deposition potential is too low, it may result in weak carbon nanotube deposition and an overly loose morphology, which is not conducive to subsequent microporous layer coating; if the deposition potential is too high, free radicals will be generated, leading to the destruction of the stability of the base layer structure. If the deposition time is too short, the density of the intermediate layer formed will be insufficient; if the electrophoretic deposition time is too long, both the carbon nanotubes and the base layer will deteriorate, and the pore size will be too small, which is not conducive to the efficient mass transfer of the gas diffusion layer.

[0020] Furthermore, in step 2, the concentration of the carbon nanotube dispersion is 0.2% to 5%. Too low a concentration of the carbon nanotube dispersion will result in an uneven and sparse intermediate layer, failing to achieve good water retention and drainage effects; too high a concentration will easily lead to clumping and reduced dispersibility.

[0021] Furthermore, in step 3, the high-temperature homogenization treatment specifically involves heating to 250–280°C at a rate of 3–8°C / min under a nitrogen atmosphere and holding for 10–40 minutes to remove water and surfactants from the gas diffusion layer. Then, the temperature is increased to 350–380°C at a rate of 3–8°C / min and held for 10–40 minutes. If the heating rate is too rapid, residual thermal stress will occur in the hydrophobic agent film, leading to stress orientation in micro-regions, which is detrimental to the structural stability of the gas diffusion layer and results in insufficient homogenization of the hydrophobic agent. Similarly, if the holding time is too short or the treatment temperature is too low, the hydrophobic agent cannot be sufficiently homogenized and flowed. If the temperature is too high, the hydrophobic agent will have excessive fluidity, resulting in uneven distribution between the upper and lower layers, and may even decompose and deteriorate.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. This invention employs MWCNTs and SWCNTs with good electrical conductivity to construct a hierarchical porous network structure as a water-retaining functional layer, which is inserted between the substrate layer and the hydrophobic microporous layer to prepare a self-humidifying GDL. This structure achieves excellent water management performance: on the one hand, the SWCNT layer with appropriate wettability can retain product moisture to maintain membrane hydration; simultaneously, it acts as a water storage layer, locking in moisture, and humidifying dry gas as it passes through, which also helps reduce membrane resistance. On the other hand, the MWCNTs and SWCNTs layers provide greater capillary forces and have good water absorption, accelerating the diffusion of liquid water from the catalyst layer to the carbon paper substrate and promptly removing excess moisture. Compared to traditional gas diffusion layers, the gas diffusion layer of this invention introduces an intermediate layer that acts as a self-humidifier under low humidity conditions, keeping the PEM moist under dry conditions; and acts as a drainage promoter under high humidity conditions, preventing flooding.

[0024] 2. The gas diffusion layer protected by this invention allows liquid and gas transport to proceed in separate paths, resulting in better mass transfer performance. The MWCNTs and SWCNTs construct a hierarchical pore network structure with micropores (0.01-0.017μm) and mesopores (0.1-0.5μm). Water adsorbed in the micropores is difficult to move into the flow field channels, thus playing a water retention role, while the larger pores provide more gas transport channels.

[0025] 3. The intermediate layer introduced by the gas diffusion layer protected in this invention can reduce MPL slurry leakage. The excellent conductivity and flexibility of the intermediate layer can reduce the ohmic resistance of the gas diffusion layer. At the same time, as a buffer layer, it can offset the influence of the surface flatness of the carbon paper on the roughness of the microporous layer, reduce contact resistance, and achieve more efficient electron transfer. Attached Figure Description

[0026] Figure 1 Schematic diagram of gas diffusion layer

[0027] Figure 2 Cross-sectional image of the gas diffusion layer taken by scanning electron microscope (SEM) a; Comparative Example 1 (conventional gas diffusion layer): obvious leakage of microporous layer slurry; b Example 1 gas diffusion layer: almost no leakage of microporous layer slurry; c Example 2 gas diffusion layer: almost no leakage of microporous layer slurry. Detailed Implementation

[0028] Example 1

[0029] Method for preparing gas diffusion layer for fuel cell cathode

[0030] Hydrophobic treatment of the substrate layer. Prepare a 10% PTFE aqueous solution. Immerse the carbon paper substrate layer in the hydrophobic agent solution for 5 minutes, then remove and dry in a vacuum oven at 60°C. Further heat treatment is performed in an atmosphere furnace, with a heating rate of 5°C / min to 380°C, and held at that temperature for half an hour to ensure the PTFE melts and homogenizes. The carbon paper is weighed before and after the hydrophobic treatment, and the weight gain of the substrate after hydrophobic treatment is calculated to be 10%.

[0031] Preparation of carbon nanotube dispersion: Take 18g of SWCNT (length 5-10μm, diameter 1-4nm, ζ potential -60mV) and 2g of MWCNT (length 1-5μm, diameter 8-15nm, ζ potential -60mV) and add them to water to prepare a dispersion with a concentration of 5%. Add 0.2g of sodium dodecylbenzenesulfonate as a dispersant. After ball milling for 1 hour and ultrasonic treatment for 50 minutes, a uniform dispersion of carbon nanotubes is obtained.

[0032] Intermediate layer preparation: Using carbon paper as the anode and graphite plate as the cathode, carbon nanotubes were deposited on the surface of carbon paper to form a hybrid carbon nanotube intermediate layer by electrophoretic deposition. The electrophoretic deposition voltage was 0.5V and the deposition time was 20min.

[0033] First, prepare the microporous layer coating slurry: ① Add the surfactant to deionized water and stir magnetically for 3 minutes; ② Add the toner to the above mixed solution, stir continuously for 10 minutes, and sonicate for 3 minutes using a high-power ultrasonic device; ③ Add PTFE to the above mixed toner dispersion, and use a sand mill to mix and obtain a uniformly mixed MPL slurry.

[0034] Further microporous layer (MPL) coating: The prepared slurry is coated onto one side of the substrate by wire rod coating, and the thickness of the microporous layer is controlled to be 50 μm. After vacuum drying at 60 °C, the temperature is raised to 250 °C at a rate of 5 °C / min under a nitrogen atmosphere and held for half an hour. Then, the temperature is raised to 380 °C at a rate of 5 °C / min and held for half an hour to ensure that the PTFE melts and homogenizes, thus obtaining the gas diffusion layer.

[0035] The parameters of the gas diffusion layer obtained by the above method are detailed in Table 2.

[0036] Examples 2-7

[0037] The preparation method is basically the same as in Example 1, except for: the type and concentration of the hydrophobic agent in step 1, the weight gain of the substrate after hydrophobic treatment; the length, diameter, and zeta potential of the single-walled carbon nanotubes and multi-walled carbon nanotubes selected in step 2, their ratio, and the concentration of the dispersion. The conditions for electrophoretic deposition (or filtration) (if the carbon nanotube potential is negative, carbon paper acts as the anode; if the carbon nanotube potential is positive, carbon paper acts as the cathode), control of the intermediate layer thickness, and the materials and process conditions are detailed in Table 1.

[0038] Comparative Example 1

[0039] The preparation of the carbon nanotube-free dispersion and the intermediate layer were the same as in Example 1.

[0040] Comparative Example 2

[0041] The nano-carbon material in the intermediate layer slurry was entirely SWCNT, with no MWCNT added; otherwise, it was the same as in Example 1.

[0042] Comparative Example 3

[0043] The nano-carbon material in the intermediate layer slurry was entirely MWCNT, with no SWCNT added; otherwise, it was the same as in Example 1.

[0044] Table 1 Comparison of Materials and Process Conditions

[0045]

[0046]

[0047] Table 2 Gas Diffusion Layer Parameters

[0048]

[0049] Comparative analysis revealed that the gas diffusion layers obtained in Examples 1-7 exhibited significantly reduced roughness, which is more conducive to adhesion to the catalyst layer. The in-plane resistivity and contact resistance were also reduced compared to the comparative examples, demonstrating that the intermediate layer, as a flexible buffer layer, can improve the conductivity of the gas diffusion layer.

[0050] The gas diffusion layers obtained from Examples 1-7 were used as cathode GDLs, and the comparative example GDL was used as anode GDLs. The fuel cell performance was evaluated, and the evaluation results are listed in Table 3. The gas diffusion layers used in the comparative example anodes and cathodes were both comparative example GDLs.

[0051] Table 3 Fuel Cell Performance

[0052]

[0053]

[0054] Note: The fuel cell temperature for performance testing is 80℃, and the back pressure is 50kPa. (See table J). d The limiting current density is expressed in A / cm². 2 ;P m Maximum power density, in W / cm³ 2 .

[0055] By comparing the fuel cell performance, it can be found that the maximum power density and limiting current density of Examples 1-7 are significantly improved compared with the comparative example, especially in high and low humidity conditions, where the improvement is particularly noticeable. Adding a cathode GDL with an intermediate layer can prevent water flooding and maintain high mass transfer efficiency.

[0056] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A gas diffusion layer for a fuel cell cathode, characterized in that: It includes a base layer, an intermediate layer, and a microporous layer; the base layer is carbon paper; the intermediate layer is located between the base carbon paper and the microporous layer; the intermediate layer is composed of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) in a mass ratio of 25:75 to 90:

10. The thickness of the intermediate layer is 0.5~10 μm; the thickness of the microporous layer is 10~60 μm; The method for preparing the gas diffusion layer includes the following steps: Step 1, hydrophobic treatment of the substrate: Immerse the substrate in an aqueous solution of hydrophobic agent for 3-5 minutes, remove and dry it, and then heat it in an atmosphere furnace to melt and homogenize the hydrophobic agent. Then determine that the weight gain of the substrate after hydrophobic treatment is controlled within the range of 5% to 40%. Step 2, fixation of the intermediate layer: First, prepare a carbon nanotube dispersion: SWCNT and MWCNT are added to the solvent in proportion, and a dispersant is added at the same time. After ball milling and ultrasonic treatment, a uniform carbon nanotube dispersion is obtained; then, the carbon nanotube dispersion is deposited and fixed on the surface of the hydrophobic substrate by electrophoretic deposition. Step 3, Preparation of the gas diffusion layer: First, prepare the microporous layer slurry: Add the surfactant to deionized water and stir magnetically to obtain a mixed solution; then add carbon powder and stir continuously until homogeneous, followed by ultrasonication for 2-8 minutes to obtain a carbon powder dispersion; add a binder and a hydrophobic agent to the carbon powder dispersion, and then use a sand mill to mix them to obtain a uniformly mixed microporous layer slurry; coat the microporous layer slurry onto the surface of the intermediate layer, and then perform vacuum drying and high-temperature homogenization treatment to obtain the gas diffusion layer; In step 3, the high-temperature homogenization process specifically involves heating the gas at a rate of 3-8°C / min to 250-280°C and holding it for 10-40 min under a nitrogen atmosphere to remove water and surfactants from the gas diffusion layer, and then heating the gas at a rate of 3-8°C / min to 350-380°C and holding it for 10-40 min.

2. The gas diffusion layer for a fuel cell cathode according to claim 1, characterized in that: The single-walled carbon nanotubes have a length of 5~60μm, a diameter of 1~4nm, and a zeta potential of -60~60mV; the multi-walled carbon nanotubes have a length of 1~30μm, a diameter of 8~30 nm, and a zeta potential of -60~60mV.

3. The gas diffusion layer for a fuel cell cathode according to claim 1, characterized in that: The gas diffusion layer has a porosity of 58%–70%, a pore size distribution of 50 nm–1 μm, a resistivity of 4–20 mΩ·cm, and a contact resistance of 5–15 mΩ·cm. 2 The contact angle is 130°~150°.

4. A method for preparing a gas diffusion layer for a fuel cell cathode as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1, hydrophobic treatment of the substrate: Immerse the substrate in an aqueous solution of hydrophobic agent for 3-5 minutes, remove and dry it, and then heat it in an atmosphere furnace to melt and homogenize the hydrophobic agent. Then determine that the weight gain of the substrate after hydrophobic treatment is controlled within the range of 5% to 40%. Step 2, fixation of the intermediate layer: First, prepare a carbon nanotube dispersion: SWCNT and MWCNT are added to the solvent in proportion, and a dispersant is added at the same time. After ball milling and ultrasonic treatment, a uniform carbon nanotube dispersion is obtained; then, the carbon nanotube dispersion is deposited and fixed on the surface of the hydrophobic substrate by electrophoretic deposition. Step 3, Preparation of gas diffusion layer: First, prepare microporous layer slurry: Add surfactant to deionized water and stir magnetically to obtain a mixed solution; then add toner and stir continuously until homogeneous, and sonicate for 2-8 minutes to obtain toner dispersion; add binder and hydrophobic agent to toner dispersion, and use a sand mill to mix to obtain uniformly mixed microporous layer slurry; The microporous layer slurry is coated onto the surface of the intermediate layer, and then subjected to vacuum drying and high-temperature homogenization to obtain the gas diffusion layer. In step 2, the electrophoretic deposition potential is 0.5V~10V, and the electrophoretic deposition time is 2~20min; In step 3, the high-temperature homogenization process specifically involves heating the gas at a rate of 3-8°C / min to 250-280°C and holding it for 10-40 min under a nitrogen atmosphere to remove water and surfactants from the gas diffusion layer, and then heating the gas at a rate of 3-8°C / min to 350-380°C and holding it for 10-40 min.

5. The method for preparing a gas diffusion layer for a fuel cell cathode according to claim 4, characterized in that: The hydrophobic agent in step 1 and / or step 3 is one or a mixture of two or more of polytetrafluoroethylene, polyvinylidene fluoride, and fluorinated ethylene propylene copolymer; the concentration of the hydrophobic agent is 1% to 20%; the solvent in step 2 is water or an alcohol solvent; and the dispersant in step 2 is a surfactant.

6. The method for preparing a gas diffusion layer for a fuel cell cathode according to claim 4, characterized in that: In step 1, the homogenization process involves heating the temperature to 350-380°C at a rate of 3-8°C / min, and then holding it for 10-40 min.

7. The method for preparing a gas diffusion layer for a fuel cell cathode according to claim 4, characterized in that: The concentration of the carbon nanotube dispersion in step 2 is 0.2% to 5%.

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