A high-temperature fuel cell gas diffusion layer structure and its preparation method

Abstract

This invention belongs to the field of battery gas diffusion layer preparation, and in particular, a high-temperature fuel cell gas diffusion layer structure and its preparation method. Addressing the problem that in existing high-temperature proton exchange membrane fuel cells, the operating environment easily leads to oxidation and acid corrosion of the gas diffusion layer, causing damage and failure, reduced durability, and consequently, a sharp decline in battery performance, the invention includes the following steps: S1: Preparation of high-temperature graphitized carbon black: Weigh ordinary carbon black and pretreat it at 300–500°C for 10–30 minutes to remove surface impurities. This invention performs high-temperature graphitization treatment on the carbon black used in the microporous layer and prepares a microporous layer slurry with good coating quality. Then, using a hydrophobic agent with superior performance compared to traditional PTFE, its oxidation and acid corrosion resistance are greatly improved, and its durability is enhanced. This makes it suitable for application in high-temperature proton exchange membrane fuel cells, enabling long-term, undiminished battery performance.

Description

Technical Field

[0001] This invention relates to the field of battery gas diffusion layer preparation technology, and in particular to a high-temperature fuel cell gas diffusion layer structure and its preparation method. Background Technology

[0002] High-temperature proton exchange membrane fuel cells (HT-PEMFCs) typically operate at temperatures between 100°C and 200°C, unlike traditional low-temperature fuel cells (~80°C). HT-PEMFCs offer several significant advantages in applications. Firstly, they improve the PEMFC's tolerance to carbon monoxide (CO). Platinum catalysts are extremely sensitive to CO in fuel gas; even trace amounts of CO can poison the catalyst and drastically reduce its performance. HT-PEMFCs, due to their improved CO tolerance, can even use reformed gas as fuel, greatly reducing their dependence on hydrogen source purity. Secondly, they operate at high temperatures. Under certain conditions, the electrochemical reaction rate on the electrodes is significantly accelerated, improving the intrinsic performance of the battery. Furthermore, the high-temperature operation results in a larger temperature difference between the stack and the coolant, making heat dissipation easier and simplifying the thermal management system, which is highly beneficial for high-power stacks. Then, HT-PEMFC can simplify the water management system. It uses high-temperature membranes such as phosphoric acid-doped PBI membranes, whose proton conduction does not depend on liquid water. Therefore, the system does not require humidification, completely avoiding the problems of "flooding" and "drying out". The system structure is greatly simplified and the reliability is improved. In addition, the generated high-temperature waste heat can be used to realize combined heat and power, improving the overall energy utilization efficiency.

[0003] Therefore, developing HT-PEMFC is a strategically significant differentiated technology. By "trading temperature for purity," it provides a realistic and feasible path to solving the challenges of hydrogen fuel production, storage, and transportation, and is particularly suitable for playing an irreplaceable role in specific fields such as stationary power generation and heavy transportation. However, its further development has also encountered many bottlenecks and technical challenges, especially the higher requirements placed on the core component materials of proton exchange membrane fuel cells. Traditional gas diffusion layers (GDLs) are more prone to oxidation corrosion, acid corrosion, compression creep, and structural collapse during HT-PEMFC operation, leading to a sharp decline in the mechanical properties, durability, and battery performance of the materials. Therefore, developing a gas diffusion layer suitable for HT-PEMFC is crucial.

[0004] Existing technical solutions

[0005] The published patent CN115064708A, "A Gas Diffusion Layer and Its Preparation Method and Application", describes a lateral gradient setting of the microporous layer in the gas diffusion layer. This effectively optimizes the uniform distribution of gas within the gas diffusion layer, ensures the uniformity of gas in each reaction region, and improves the stability and durability of the battery. It also solves the problem of uniform gas transport in high-temperature fuel cells with no flow channels on the plates.

[0006] In the published patent CN116387536B, "Gas Diffusion Layer, Membrane Electrode Assembly, Fuel Cell and Electrical Device", a metal oxide doping method is used to add metal oxides to the microporous layer. This method is applied to a high-temperature fuel cell that uses a phosphoric acid-doped polymer membrane as the proton exchange membrane. As the fuel cell operates at high temperatures, the phosphoric acid in the proton exchange membrane vaporizes and migrates to the gas diffusion layer, where it reacts with the metal oxides in the microporous layer to form phosphates. This reduces the corrosion of carbon powder in the microporous layer by phosphoric acid, improves the resistance of the gas diffusion layer to phosphoric acid corrosion and electrochemical corrosion, and extends the service life of the high-temperature fuel cell.

[0007] In the existing technology, to set the microporous layer in the gas diffusion layer in a lateral gradient, it is necessary to prepare a variety of different microporous layers and to partially cover the substrate to coat the microporous layer in different areas. This process is very complicated and difficult to mass-produce.

[0008] By adding metal oxides to the microporous layer to react with acidic substances in a high-acid environment to produce salts, the corrosion of the toner by the acidic substances is reduced, thereby improving the lifespan of the gas diffusion layer. However, this technology does not solve the problem of high-temperature oxidation and corrosion of the toner itself under high-temperature conditions. Over time, the gas diffusion layer will still age rapidly and fail under high-temperature conditions. This technology does not fundamentally solve the durability problem of the gas diffusion layer.

[0009] Therefore, a high-temperature fuel cell gas diffusion layer structure and its preparation method are needed to solve the problems mentioned above. Summary of the Invention

[0010] This invention proposes a high-temperature fuel cell gas diffusion layer structure and its preparation method, solving the problem that in existing high-temperature proton exchange membrane fuel cells, the operating environment easily leads to oxidation and acid corrosion of the gas diffusion layer, damaging the structure of the gas diffusion layer itself and causing failure, reduced durability, and consequently, a sharp decline in battery performance, significantly reducing battery life. This invention, through high-temperature graphitization of the carbon black used in the microporous layer and the preparation of a microporous layer slurry with good coating quality, and by utilizing a hydrophobic agent with superior performance compared to traditional PTFE, significantly improves the gas diffusion layer's resistance to oxidation and acid corrosion, enhancing its durability. This makes it suitable for application in high-temperature proton exchange membrane fuel cells, enabling long-term, undiminished battery performance.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] A high-temperature fuel cell gas diffusion layer structure and its preparation method, comprising the following steps:

[0013] S1: Preparation of high-temperature graphitized carbon black: Weigh ordinary carbon black and pretreat it at 300-500℃ for 10-30 minutes to remove surface impurities; tightly pack the pretreated carbon black into a high-purity graphite crucible and perform programmed temperature graphitization treatment under an inert atmosphere, specifically: the first stage is to heat from room temperature to 1000℃ at a heating rate of 10-20℃ / min; the second stage is to heat from 1000℃ to 2800℃ at a heating rate of 5-10℃ / min; the third stage is to hold at 2800℃ for 30-60 minutes; then naturally cool to room temperature, and after grinding and sieving, obtain high-temperature graphitized carbon black;

[0014] S2: Preparation of microporous layer slurry: Using a planetary stirring and dispersing device, the following components are mixed in sequence: pure water, dispersant accounting for 5-15% of the mass of the mixed solution, hydrophobic agent, the high-temperature graphitized carbon black, and ordinary carbon black; wherein, the mass ratio of the hydrophobic agent to the total carbon black is 0.3-0.7:1, the high-temperature graphitized carbon black accounts for 30-60% of the total carbon black mass, and the ordinary carbon black accounts for 40-70% of the total carbon black mass; the mixing process includes dispersing the hydrophobic agent at a speed of 500-800 rpm for 15-45 minutes, dispersing the high-temperature graphitized carbon black and ordinary carbon black at a speed of 1500-2000 rpm for 30-60 minutes each, and finally dispersing at a speed of 6000-8000 rpm while maintaining a vacuum state for 6-8 hours to obtain the microporous layer slurry;

[0015] S3: Hydrophobic treatment of carbon paper substrate: Immerse the carbon paper in a 5-30% hydrophobic agent solution for 3-10 minutes, then remove and dry at 50-80℃;

[0016] S4: Forming of the gas diffusion layer: The microporous layer slurry obtained in step S2 is coated onto the carbon paper after hydrophobic treatment in step S3, and then heat-treated at 330–380°C to obtain a microporous layer with a thickness of 20–50 μm and a loading of 1.5–2.5 mg / cm³. 2 The gas diffusion layer.

[0017] Preferably, in step S1, the ordinary carbon black is selected from one or more of acetylene black, Ketjen black, Vulcan XC72, and BP2000.

[0018] Preferably, in step S2, the hydrophobic agent is selected from one of perfluoroalkoxy resin, soluble polytetrafluoroethylene, polyimide, and polyetheretherketone; the dispersant is selected from one of Triton X-100, Tween 20, polyethylene glycol, and N-methylpyrrolidone.

[0019] Preferably, in step S2, the hydrophobic agent is the same material as the hydrophobic agent used for the hydrophobic treatment of carbon paper in step S3.

[0020] Preferably, in step S4, the coating method is screen printing, scraping, or slot coating.

[0021] A high-temperature fuel cell gas diffusion layer structure includes a diffusion layer body (1), wherein the diffusion layer body (1) includes a carbon paper substrate treated with a hydrophobic agent and a microporous layer coated on the carbon paper substrate.

[0022] Preferably, the microporous layer comprises high-temperature graphitized carbon black, ordinary carbon black, and a water-repellent agent; wherein the high-temperature graphitized carbon black is obtained by graphitizing ordinary carbon black at 2800℃, and its mass percentage in the total carbon black of the microporous layer is 30-60%; the water-repellent agent is a material with superior performance to traditional PTFE, and its mass ratio to the total carbon black is 0.3-0.7:1; the thickness of the microporous layer is 20-50 μm, and the loading is 1.5-2.5 mg / cm³. 2 .

[0023] Preferably, the raw material for the high-temperature graphitized carbon black is selected from one or more of acetylene black, Ketjen black, Vulcan XC72, and BP2000.

[0024] Preferably, the hydrophobic agent is selected from one of perfluoroalkoxy resin, soluble polytetrafluoroethylene, polyimide, and polyetheretherketone.

[0025] Preferably, the hydrophobic agent used in the hydrophobic treatment of the carbon paper substrate is the same material as the hydrophobic agent in the microporous layer.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. Highly graphitized carbon black is obtained by heat-treating ordinary carbon black at high temperature. As part of the microporous layer, it improves the durability of carbon black materials in high temperature and high acid environment.

[0028] 2. By using hydrophobic materials with superior performance compared to traditional hydrophobic agents such as PTFE as hydrophobic agents for the substrate and microporous layer, the loss caused by high-temperature environments is reduced, the changes in the hydrophilicity and hydrophobicity of the diffusion layer and the damage to the structure are slowed down, thereby alleviating the mass transfer problem of the battery.

[0029] 3. In the accelerated aging test under simulated harsh conditions (150°C high-pressure water boiling), the gas diffusion layer of the present invention exhibits an extremely low mass loss rate (<1.5%), extremely high hydrophobicity (contact angle) retention rate, and intact microstructure, far exceeding the comparative ratio composed of traditional PTFE and ordinary carbon black.

[0030] High-level graphitization of carbon black: Treatment at an ultra-high temperature of 2800℃ transforms carbon black from a disordered, easily oxidized amorphous carbon structure into a highly ordered crystalline structure with extremely inert chemical properties—a "graphite-like" structure. This fundamentally inhibits the electrochemical corrosion and oxidation reactions of carbon materials under high temperature, acidity, and high potential conditions.

[0031] High-performance hydrophobic agents are used: traditional PTFE is replaced with materials such as perfluoroalkoxy resin (PFA) and polyether ether ketone (PEEK). These materials have higher glass transition temperatures, melting points, and thermal decomposition temperatures. Under long-term high-temperature operation of fuel cells, their molecular chains are more stable and less prone to thermal aging and degradation, thus maintaining hydrophobicity and bonding strength for a long time.

[0032] A unique stepwise, high-speed, vacuum dispersion slurry preparation process ensures uniform mixing and tight coating between graphitized carbon black, ordinary carbon black, and water-repellent agents, forming a firmly bonded, stable composite microporous layer. This structure is not prone to pulverization, peeling, or collapse during long-term operation.

[0033] Overall hydrophobic synergy: The carbon paper substrate and the microporous layer are treated with the same high-performance hydrophobic agent, achieving "integration" and "synergy" of hydrophobic properties, avoiding performance shortcomings or early failures caused by mismatched interface materials. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the main structure of the diffusion layer of a high-temperature fuel cell gas diffusion layer proposed in this invention;

[0035] Figure 2 This is a schematic diagram of the internal cross-sectional structure of the diffusion layer body of a high-temperature fuel cell gas diffusion layer structure proposed in this invention.

[0036] In the figure: 1, diffusion layer main body; 101, microporous layer; 102, carbon paper substrate. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0038] A high-temperature fuel cell gas diffusion layer structure includes a diffusion layer body 1, wherein the diffusion layer body 1 includes a carbon paper substrate treated with a hydrophobic agent and a microporous layer coated on the carbon paper substrate.

[0039] In this embodiment, the microporous layer comprises high-temperature graphitized carbon black, ordinary carbon black, and a water-repellent agent. The high-temperature graphitized carbon black is obtained by graphitizing ordinary carbon black at 2800°C, and its mass percentage in the total carbon black of the microporous layer 101 is 30-60%. The water-repellent agent is a material with superior performance to traditional PTFE, and its mass ratio to the total carbon black is 0.3-0.7:1. The thickness of the microporous layer 101 is 20-50 μm, and its loading is 1.5-2.5 mg / cm³. 2 .

[0040] In this embodiment, the raw material for high-temperature graphitized carbon black is selected from one or more of acetylene black, Ketjen black, Vulcan XC72, and BP2000.

[0041] In this embodiment, the hydrophobic agent is selected from one of perfluoroalkoxy resin, soluble polytetrafluoroethylene, polyimide, and polyetheretherketone.

[0042] In this embodiment, the hydrophobic agent used for the hydrophobic treatment of the carbon paper substrate 102 is the same material as the hydrophobic agent in the microporous layer 101.

[0043] Example 1

[0044] A method for preparing a gas diffusion layer for a high-temperature fuel cell includes the following steps:

[0045] S1: Preparation of High-Temperature Graphitized Carbon Black

[0046] Weigh 50g of Vulcan XC-72 carbon black and spread it evenly in a ceramic crucible. Place the crucible in a muffle furnace and heat-treat at 400℃ for 20 minutes in air to remove adsorbed volatiles and some amorphous carbon. After cooling, tightly pack the pretreated carbon black into a high-purity graphite crucible. Place the graphite crucible in a high-temperature graphitization furnace, close the furnace door, evacuate to below 10Pa, and then purge with high-purity argon to a slightly positive pressure (approximately 0.05MPa). Set the heating program: First stage, increase from room temperature to 1000℃ at a rate of 15℃ / min; second stage, increase from 1000℃ to 2800℃ at a rate of 8℃ / min; third stage, maintain a constant temperature of 2800℃ for 45 minutes. After the program is completed, stop heating and allow the furnace to cool naturally to room temperature (approximately 24 hours). The graphite crucible was removed, and the lumpy product was poured into a mortar and gently ground. It was then passed through a 400-mesh sieve to obtain a black, metallic-lustered high-temperature graphitized carbon black powder. X-ray diffraction analysis showed that its graphitization degree was significantly higher than that of the raw material.

[0047] S2: Preparation of microporous layer slurry

[0048] A planetary mixer with both revolution and rotation was used. First, 200g of deionized water was added to the mixing tank, followed by 20g of polyethylene glycol (PEG-400) as a dispersant (approximately 9% of the initial solution mass). The mixture was stirred at 700 rpm for 30 minutes to ensure the dispersant was fully dissolved.

[0049] Subsequently, 45g of soluble polytetrafluoroethylene (DuPont, 602A dispersion, solid content approximately 60%, equivalent to 27g of solids) was added as a water-repellent agent. The mixture was stirred at 700rpm for 30 minutes to allow for initial and uniform dispersion.

[0050] Next, weigh 18g of the high-temperature graphitized carbon black prepared in step S1 above, and slowly add it to the slurry while stirring. Increase the stirring speed to 1800 rpm and continue to disperse for 45 minutes to ensure that the graphitized carbon black is fully wetted and initially dispersed.

[0051] Then, weigh 12g of untreated Vulcan XC-72 ordinary carbon black (i.e., the total carbon black mass is 30g, of which graphitized carbon black accounts for 60%), add it slowly at 1800rpm, and disperse for 45 minutes. At this time, the mass ratio of water-repellent solids to total carbon black is 27:30 = 0.9:1.

[0052] Finally, the mixing tank was sealed, and the vacuum pump was turned on to maintain the pressure inside the tank at approximately -0.095 MPa. The stirring speed was then significantly increased to 7000 rpm for high-speed shear dispersion. This process lasted for 7 hours, during which the slurry temperature was controlled below 40°C using cooling water from the jacket. After dispersion, a uniform, fine, and highly fluid black slurry was obtained, which showed no sedimentation after standing for 24 hours.

[0053] S3: Hydrophobic treatment of carbon paper substrate

[0054] Prepare a 15wt% soluble polytetrafluoroethylene (PTFE) aqueous solution. Cut Toray TGP-H-060 carbon paper to the required size, immerse it in the solution, ensuring complete saturation, for 5 minutes. After removal, gently squeeze out excess solution with a roller, then place it in an 80°C forced-air drying oven for 30 minutes.

[0055] S4: Formation of the gas diffusion layer

[0056] The hydrophobic carbon paper prepared in step S3 was fixed on a flatbed coating machine. Using a doctor blade coating method, the microporous layer slurry prepared in step S2 was uniformly coated onto one side of the carbon paper. The wet film thickness was made uniform by controlling the doctor blade gap and coating speed. After coating, the sample was pre-dried at 100℃ for 10 minutes, then transferred to a hot air circulating oven and heat-treated at 360℃ for 30 minutes to melt and sinter the hydrophobic agent and firmly bond it with the carbon black particles. The final gas diffusion layer was obtained. Measurements showed that the microporous layer thickness was approximately 35±3 μm, and the carbon black loading was approximately 2.0±0.1 mg / cm³. 2 .

[0057] Example 2

[0058] The main difference between this embodiment and Example 1 lies in the type of carbon black, the ratio, and the type of water-repellent agent.

[0059] S1: Acetylene black is used as raw material, and the pretreatment conditions are 350℃ / 15min, with the same graphitization procedure.

[0060] S2: In slurry preparation, 250g of deionized water and 12.5g of Triton X-100 (approximately 5% of the solution mass) are used as dispersant. The hydrophobic agent is perfluoroalkoxy resin (PFA) powder, which needs to be dissolved in a small amount of N-methylpyrrolidone (NMP) to form a pre-solution. The total carbon black mass is 40g, of which high-temperature graphitized acetylene black accounts for 40% (16g) and ordinary acetylene black accounts for 60% (24g). The amount of PFA solids added is 20g, with a mass ratio of 0.5:1 to the total carbon black. The feeding sequence is: water + Triton X-100 (600rpm / 20min) → PFA / NMP solution (600rpm / 20min) → graphitized carbon black (1600rpm / 50min) → ordinary carbon black (1600rpm / 50min) → high-speed dispersion at 7500rpm under vacuum for 6.5 hours.

[0061] S3: Impregnate the carbon paper with a 10wt% PFA / NMP solution for 8 minutes and dry at 70°C.

[0062] S4: Coated using screen printing, with a heat treatment temperature of 350℃ for 40 minutes. The resulting gas diffusion layer microporous layer has a thickness of approximately 28 μm and a loading of approximately 1.7 mg / cm³. 2 .

[0063] Example 3

[0064] This embodiment focuses on verifying the effect of different graphitized carbon black ratios.

[0065] S1: Same as in Example 1.

[0066] S2: The total carbon black mass is 50g. The proportion of graphitized carbon black (Vulcan XC-72 source) is adjusted to 30% (15g), and the proportion of ordinary carbon black (Ketjen Black EC-300J) is adjusted to 70% (35g). The water-repellent agent is polyetheretherketone (PEEK) ultrafine powder, with an addition amount of 17.5g (0.35:1 mass ratio to total carbon black). The dispersant is 15g Tween 20. The process parameters for slurry preparation are adapted and finely adjusted according to Example 1, with a high-speed dispersion time of 8 hours.

[0067] S3: Treat carbon paper with an 8wt% PEEK / concentrated sulfuric acid sulfonated aqueous solution (subsequent neutralization and washing are required), and dry at 60°C.

[0068] S4: Slit coating was used, with a heat treatment temperature of 380℃ for 25 minutes. The resulting product has a microporous layer thickness of approximately 45μm and a loading of approximately 2.3mg / cm³. 2 .

[0069] A sort of

[0070] Comparative Example

[0071] To verify the effectiveness of the present invention, two comparative examples were set up.

[0072] Comparative Example 1 (Conventional PTFE binder): Except for replacing the soluble polytetrafluoroethylene in Example 1 with a conventional PTFE emulsion of equal solid content (DuPont, 30-J, 60% solid content), the other steps, formulations, and process parameters were exactly the same as in Example 1.

[0073] Comparative Example 2 (without graphitized carbon black): Except for replacing all the high-temperature graphitized carbon black in Example 1 with an equal mass of ordinary Vulcan XC-72 carbon black (i.e., all carbon black is ordinary carbon black), the other steps, formulations, and process parameters are exactly the same as in Example 1.

[0074] Performance Testing and Effect Analysis

[0075] To evaluate the durability of the gas diffusion layer, the samples prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to accelerated aging tests simulating harsh environments—high-pressure water boiling tests.

[0076] Test Method: Each sample was cut into 3cm × 3cm pieces, weighed (W0), and the initial water contact angle (θ0) was measured. Then, each sample was placed in the lining of a high-pressure reactor containing 50mL of deionized water, sealed, and placed in an oven. The oven temperature was raised to 150℃ (corresponding to an internal pressure of approximately 0.4MPa), and the samples were boiled continuously for 48 hours under these conditions. After the experiment, the samples were removed, rinsed with deionized water, and thoroughly dried at 80℃ to constant weight. They were weighed again (W1), and the water contact angle (θ1) was measured. The mass loss rate was calculated as: [(W0-W1) / W0] × 100%. Simultaneously, the surface morphology of the microporous layer of the samples before and after boiling was observed using a scanning electron microscope.

[0077] The test results are shown in the table below:

[0078]

[0079]

[0080] Results analysis:

[0081] Contact angle retention: Examples 1-3, using novel hydrophobic agents and graphitized carbon black, showed only a small decrease in contact angle after boiling (2-6°), maintaining excellent hydrophobicity. Comparative Example 1, using conventional PTFE, showed a 23° decrease in contact angle, indicating significant degradation or surface reconstruction of PTFE under high temperature and high pressure hydrothermal conditions, resulting in a severe decline in hydrophobic properties. Comparative Example 2, without graphitized carbon black, showed the largest decrease in contact angle (38°), indicating that ordinary carbon black is easily oxidized and corroded under harsh environments, destroying the overall structure of the microporous layer and causing the hydrophobic agent coating to fail.

[0082] Mass loss rate: The mass loss of the sample in the examples was less than 1.5%, indicating that the material structure was stable and the loss of components was minimal. The mass loss of Comparative Example 1 reached 3.5%, and that of Comparative Example 2 was as high as 8.2%, which directly proves the excellent antioxidant and corrosion resistance of graphitized carbon black and the stronger bonding and stabilizing effect of the novel hydrophobic agent.

[0083] Microstructure: SEM images clearly show that the microstructure of the example sample remained intact after boiling in water, while the comparative sample showed varying degrees of damage. This is consistent with the data on mass loss and contact angle changes.

[0084] Furthermore, the gas diffusion layers from Example 1 and Comparative Examples 1 and 2 were assembled into a high-temperature proton exchange membrane fuel cell single cell, and subjected to long-term constant current (0.6 A / cm²) testing at 160°C, atmospheric pressure, and humidification. 2 Operational testing. After 500 hours of operation, the battery voltage decay rate using the gas diffusion layer of Example 1 was less than 5%, while the battery voltage decay rates of Comparative Example 1 and Comparative Example 2 exceeded 15% and 30%, respectively. This fully demonstrates that the gas diffusion layer prepared in this invention can significantly improve the long-term operational stability of high-temperature fuel cells.

[0085] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a gas diffusion layer for a high-temperature fuel cell, characterized in that, Includes the following steps: S1: Preparation of high-temperature graphitized carbon black: Weigh ordinary carbon black and pretreat it at 300-500℃ for 10-30 minutes to remove surface impurities; tightly pack the pretreated carbon black into a high-purity graphite crucible and perform programmed temperature graphitization treatment under an inert atmosphere, specifically: the first stage is to heat from room temperature to 1000℃ at a heating rate of 10-20℃ / min; the second stage is to heat from 1000℃ to 2800℃ at a heating rate of 5-10℃ / min; the third stage is to hold at 2800℃ for 30-60 minutes; then naturally cool to room temperature, and after grinding and sieving, obtain high-temperature graphitized carbon black; S2: Preparation of microporous layer slurry: Using a planetary stirring and dispersing device, the following components are mixed in sequence: pure water, dispersant accounting for 5-15% of the mass of the mixed solution, hydrophobic agent, the high-temperature graphitized carbon black, and ordinary carbon black; wherein, the mass ratio of the hydrophobic agent to the total carbon black is 0.3-0.7:1, the high-temperature graphitized carbon black accounts for 30-60% of the total carbon black mass, and the ordinary carbon black accounts for 40-70% of the total carbon black mass; the mixing process includes dispersing the hydrophobic agent at a speed of 500-800 rpm for 15-45 minutes, dispersing the high-temperature graphitized carbon black and ordinary carbon black at a speed of 1500-2000 rpm for 30-60 minutes each, and finally dispersing at a speed of 6000-8000 rpm while maintaining a vacuum state for 6-8 hours to obtain the microporous layer slurry; S3: Hydrophobic treatment of carbon paper substrate: Immerse the carbon paper in a 5-30% hydrophobic agent solution for 3-10 minutes, then remove and dry at 50-80℃; S4: Forming of the gas diffusion layer: The microporous layer slurry obtained in step S2 is coated onto the carbon paper after hydrophobic treatment in step S3, and then heat-treated at 330–380°C to obtain a microporous layer with a thickness of 20–50 μm and a loading of 1.5–2.5 mg / cm³. 2 The gas diffusion layer.

2. The method for preparing a high-temperature fuel cell gas diffusion layer according to claim 1, characterized in that, In step S1, the ordinary carbon black is selected from one or more of acetylene black, Ketjen black, Vulcan XC72, and BP2000.

3. The method for preparing a high-temperature fuel cell gas diffusion layer according to claim 1, characterized in that, In step S2, the hydrophobic agent is selected from one of perfluoroalkoxy resin, soluble polytetrafluoroethylene, polyimide, and polyetheretherketone; the dispersant is selected from one of Triton X-100, Tween 20, polyethylene glycol, and N-methylpyrrolidone.

4. The method for preparing a high-temperature fuel cell gas diffusion layer according to claim 1, characterized in that, In step S2, the hydrophobic agent is the same material as the hydrophobic agent used for the hydrophobic treatment of carbon paper in step S3.

5. The high-temperature fuel cell gas diffusion layer structure and its preparation method according to claim 1, characterized in that, In step S4, the coating method is screen printing, scraping, or slot coating.

6. A high-temperature fuel cell gas diffusion layer prepared by the preparation method according to any one of claims 1 to 5, characterized in that, It includes a diffusion layer body (1), which includes a carbon paper substrate (102) treated with a hydrophobic agent and a microporous layer (101) coated on the carbon paper substrate.

7. The high-temperature fuel cell gas diffusion layer structure according to claim 6, characterized in that, The microporous layer (101) comprises high-temperature graphitized carbon black, ordinary carbon black, and a water-repellent agent; wherein the high-temperature graphitized carbon black is obtained by graphitizing ordinary carbon black at a high temperature of 2800℃, and its mass percentage in the total carbon black of the microporous layer is 30-60%; the water-repellent agent is a material with superior performance to traditional PTFE, and its mass ratio to the total carbon black is 0.3-0.7:1; the thickness of the microporous layer is 20-50 μm, and the loading is 1.5-2.5 mg / cm³. 2 .

8. The high-temperature fuel cell gas diffusion layer structure according to claim 1, characterized in that, The raw materials for the high-temperature graphitized carbon black are selected from one or more of acetylene black, Ketjen black, Vulcan XC72, and BP2000.

9. The high-temperature fuel cell gas diffusion layer structure according to claim 1, characterized in that, The water-repellent agent is selected from one of perfluoroalkoxy resin, soluble polytetrafluoroethylene, polyimide, and polyetheretherketone.

10. The high-temperature fuel cell gas diffusion layer structure according to claim 1, characterized in that, The hydrophobic agent used in the hydrophobic treatment of the carbon paper substrate (102) is the same material as the hydrophobic agent in the microporous layer.

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