Microporous layer and preparation method thereof, gas diffusion layer and fuel cell
By introducing thiooxime esters and surfactants into the microporous layer of fuel cells, a gradient pore structure was constructed, which solved the problem of liquid water removal under high current density and improved the drainage capacity and stability of fuel cells.
Patent Information
- Application Number
- CN202511655429.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-12
- Publication Date
- 2026-02-13
AI Technical Summary
Existing technologies struggle to effectively remove liquid water from fuel cells at high current densities, leading to flooding and impacting battery performance and stability.
Thiooxime esters were used as photosensitive pore-forming agents. By controlling the slurry viscosity and light conditions, a gradient pore structure was formed, and directional drainage was achieved by combining capillary pressure difference to construct a microporous layer.
It significantly improves the fuel cell's drainage capacity and reactant gas mass transfer efficiency under high current density, enhancing the cell's stability and performance.
Smart Images
Figure CN121528944A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of batteries, in particular to a microporous layer, a preparation method thereof, a gas diffusion layer and a fuel cell. BACKGROUND
[0002] Fuel cells have become a research and development hotspot in recent years as a high-efficiency and environmentally friendly power generation device. The core component of the fuel cell, the membrane electrode, is prepared by hot pressing process from a gas diffusion layer, a catalyst layer and a proton exchange membrane. The gas diffusion layer (GDL) is a key component in the proton exchange membrane fuel cell, which is usually arranged between the flow field plate and the catalyst layer (CL) on both sides of the anode and the cathode. It is usually composed of two parts: one is the carbon fiber substrate (GDB) for supporting, such as porous carbon paper or carbon cloth; the other is the microporous layer (MPL) coated on the substrate.
[0003] When the fuel cell operates at high current density, the water generation rate of the cathode catalyst layer increases rapidly, and excessive liquid water is easily accumulated. If the water cannot be discharged in time, it will block the gas diffusion channel and hinder the transmission of reaction gas to the catalyst layer, resulting in "waterlogging" phenomenon, which causes the performance of the fuel cell to deteriorate rapidly or even fail. Therefore, the GDL must have excellent water vapor management capability, i.e. balance the discharge of water and the supply of reaction gas, which is crucial to improve the high current density performance and operating stability of the fuel cell.
[0004] The microporous layer (MPL) as the core functional part of the GDL, its pore structure characteristics (such as pore size distribution, porosity, hydrophobicity, etc.) have a decisive influence on the water vapor transmission behavior. Studies have shown that by reasonably designing the pore size gradient distribution of the MPL, a directional drainage path can be constructed by using capillary pressure difference, thereby significantly enhancing the liquid water removal capacity and improving the performance of the fuel cell at high current density.
[0005] At present, the construction of the gradient pore structure of the MPL mainly depends on the addition of pore-forming agents (such as ammonium bicarbonate, ammonium oxalate, lithium carbonate, ammonium sulfate, etc.) in the slurry or the use of special processes such as electrospinning. However, the traditional pore-forming agent method has obvious defects: the pore size generated in the pore-forming process is difficult to control accurately, and the uniformity is poor; and after high-temperature decomposition, by-products are often left which are difficult to completely remove, which may contaminate the catalyst layer or the proton exchange membrane, affecting the service life and reliability of the fuel cell. On the other hand, although processes such as electrospinning can realize the regulation of pore structure, the equipment is complex, the process conditions are harsh, and the production cost is high, which is difficult to meet the needs of large-scale industrial application.
[0006] Therefore, it is urgent to develop a new type of microporous layer to solve the water drainage problem of the membrane electrode at high current density, thereby improving the performance of the fuel cell. SUMMARY
[0007] The application provides a microporous layer, a preparation method thereof, a gas diffusion layer and a fuel cell to solve the water drainage problem of a membrane electrode under high current density, thereby improving the stability of the fuel cell.
[0008] In a first aspect, the application provides a microporous layer, wherein raw material components of the microporous layer include conductive carbon black, a hydrophobic agent, a surfactant, a thiohydroxamic acid ester and a solvent.
[0009] The application can generate gas under specific conditions by introducing the thiohydroxamic acid ester as a photosensitive pore-forming agent, and can adjust the viscosity by the surfactant, thereby changing the liquid surface tension, ultimately affecting the bubble radius, according to the Laplace pressure equation: ΔP = 2σ / R, wherein ΔP is the pressure difference between the inside and outside of the bubble, σ is the surface tension of the liquid, and R is the radius of the bubble. By controlling the viscosity of the microporous layer slurry, the intermolecular force in the slurry can be affected, thereby changing the liquid surface tension and realizing the control of the size of the generated bubbles, so as to form a pore size gradient distribution in situ in the microporous layer; the structure effectively optimizes the water-gas transmission balance inside the gas diffusion layer, significantly improves the water drainage capacity and reaction gas mass transfer efficiency under high current density, and finally enhances the performance and stability of the fuel cell.
[0010] In some embodiments, the molecular structure of the thiohydroxamic acid ester includes:
[0011] wherein R is selected from one of structure formula 1, structure formula 2 and structure formula 3: .
[0012] The thiohydroxamic acid ester with the above structure generates alkyl radicals by uniform cleavage of the N-O bond under light conditions, and finally combines with a hydrogen donor to realize hydrogenation while releasing CO2 gas, and the specific reaction process is as follows: .
[0013] In some embodiments, the mass ratio of the thiohydroxamic acid ester to the conductive carbon black is 1: (1-3). The inventors have found that if the content of the thiohydroxamic acid ester is too small, it will not be able to generate enough ideal pore diameters; if the content of the thiohydroxamic acid ester is too large, the pore-forming agent will eventually be removed by toluene, resulting in an unstable microporous layer structure.
[0014] In some embodiments, the surfactant includes Triton. By selecting the surfactant as described above, the viscosity can be controlled by the addition ratio of the surfactant.
[0015] In some embodiments, the hydrophobic agent includes polytetrafluoroethylene (PTFE).
[0016] In some embodiments, the solvent comprises ethanol. The use of the solvent described above can well dissolve the thiohydroxamic acid ester and disperse more uniformly, thereby forming a more uniform pore size distribution.
[0017] In some embodiments, the microporous layer comprises a first layer and a second layer stacked in sequence, and the pore size of the first layer is smaller than that of the second layer. By constructing a double-layer structure with a pore size gradient (small pore size of the first layer and large pore size of the second layer), a directional drainage driving force from inside to outside is formed based on the capillary pressure difference: the smaller pore size of the first layer close to the catalytic layer generates a higher capillary pressure, which can effectively extract the reaction-generated water; the larger pore size of the second layer on the outside provides a lower resistance water transmission channel to accelerate the discharge of liquid water to the gas flow channel. Thus, the water-gas management efficiency is optimized, the cathode waterlogging under high current density is avoided, the efficient transmission of reaction gas is ensured, and thus the stability of the fuel cell is improved. As a result, liquid water is drained between the small pore size channel and the large pore size channel, and the pressure on the small pore size channel side is high, and the drainage is achieved by the capillary pressure difference.
[0018] In some embodiments, the pore size of the first layer is 5-20 μm. The inventors have found that if the pore size of the first layer is too small, it cannot guarantee that water can easily enter the pore channel; if the pore size of the first layer is too large, it cannot form an effective gradient pore.
[0019] In some embodiments, the pore size of the second layer is 20-50 μm. If the pore size of the second layer is too large, it will cause structural collapse and large cracks.
[0020] In a second aspect, the application provides a preparation method of the microporous layer of the first aspect, comprising: S1, mixing conductive carbon black, a hydrophobic agent, a first surfactant and a solvent to obtain a first slurry; S2, performing first light curing on the first slurry to obtain a first layer; S3, mixing conductive carbon black, a hydrophobic agent, a second surfactant and a solvent to obtain a second slurry; S4, coating the second slurry on at least part of the surface of the first layer, and sintering after second light curing to obtain a microporous layer.
[0021] In the method steps, the construction of the gradient pore size structure of the microporous layer is realized by the process of layered coating and step-by-step photocuring. First, the two-time coating and curing allows the composition (such as viscosity) of the first layer and the second layer slurry to be independently adjusted, thereby forming an asymmetric structure with a gradually changing pore size from the bottom layer to the surface layer in the vertical direction, which can enhance the water management capability and reaction gas mass transfer efficiency of the gas diffusion layer; second, the porous framework of each layer is preliminarily shaped by photocuring, and then a high-temperature sintering treatment is performed, which can ensure firm combination between the two layers and avoid delamination between the layers, and also form a solid and conductive overall carbon framework, thereby simultaneously realizing excellent drainage and gas diffusion.
[0022] In some embodiments, in step S2, the wavelength of the first photocuring is 380-1000 nm. The wavelength of the light within the above range can effectively excite the homolysis of the N-O bond in the thiohydroxamic acid ester molecule, allowing it to generate alkyl radicals and release CO2 gas, thereby forming uniform and dense bubble nuclei in the microporous layer slurry.
[0023] In some embodiments, in step S2, the temperature of the first photocuring is 60-75°C. The temperature of the first photocuring within the above range is beneficial for slow evaporation of the solvent to form the microporous layer.
[0024] In some embodiments, in step S3, the viscosity of the second slurry is 250-1000 mPa·s@25s -1 According to the Prandtl equation, the second slurry within the above viscosity range can control the generated bubble pore size.
[0025] In some embodiments, in step S1, the mass ratio of the first surfactant to the conductive carbon black is 8-12%. Limiting the mass ratio of the first surfactant to the conductive carbon black within the above range can effectively adjust the viscosity of the system, allowing it to remain at a relatively low level in subsequent step S3, which is helpful for forming smaller and more uniform bubble nuclei during foaming.
[0026] In some embodiments, in step S3, the mass ratio of the second surfactant to the conductive carbon black is 5-8%. Limiting the mass ratio of the second surfactant to the conductive carbon black within the above range can control the final viscosity within the range of 250-1000 mPa·s@25s -1
[0027] In some embodiments, in step S4, the thickness of the coating is 30-70 μm. The inventors have found that when the coating is too thin, the solvent volatilizes too quickly, causing the slurry to solidify too early, and failing to provide sufficient space for the bubbles generated by the light reaction to form pores, resulting in insufficient pore formation; if the coating is too thick, it will hinder the effective penetration of light to the deep layer, causing incomplete solidification reaction and uneven pore structure in the bottom layer. Therefore, by controlling the thickness of the coating within the above range, both the light can fully induce the pore-forming reaction in the entire coating layer, and the solvent volatilization rate can be coordinated with the bubble generation and stabilization process, thereby enabling the preparation of a microporous layer with uniform and controllable pore structure.
[0028] In some embodiments, in step S4, the wavelength of the light for the second light curing is 380-1000 nm.
[0029] In some embodiments, in step S4, the temperature for the second light curing is 60-75 °C.
[0030] In a third aspect, the application provides a gas diffusion layer, which comprises the microporous layer of the first aspect or the microporous layer obtained by the preparation method of the second aspect.
[0031] In a fourth aspect, the application provides a fuel cell comprising the gas diffusion layer of the third aspect. BRIEF DESCRIPTION OF DRAWINGS
[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the description of the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.
[0033] Figure 1 The electrochemical performance test comparison curves of the membrane electrode obtained by using the gas diffusion layer of Example 1 and the membrane electrode obtained by using the gas diffusion layer of Comparative Example 1 are shown. DETAILED DESCRIPTION
[0034] In order to enable those skilled in the art to better understand the technical solutions of the present application, the technical solutions in the embodiments of the present application are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.
[0035] As a key component between the flow field plate and the catalyst layer (CL) on the anode and cathode side of a fuel cell, the gas diffusion layer (GDL) is usually composed of a microporous layer (MPL) and a substrate layer (GDB) made of porous carbon paper or carbon cloth. Its main functions include: promoting the transport and distribution of reactant gas and product water, providing mechanical support to protect the membrane electrode, and conducting electrons and heat. Especially at high current densities, a large amount of water is produced in the cathode CL, which needs to be discharged to the cathode flow channel through the pore structure of the GDL in a timely manner to avoid blockage and prevent the supply of reaction gas to the CL. Therefore, the GDL needs to achieve a balance between water and gas management in the structure design and material preparation.
[0036] The structure and properties of the MPL have a significant impact on the output performance of the fuel cell. Studies have shown that the MPL can improve the performance of the fuel cell at high current densities. By reasonably designing the pore size gradient distribution of the MPL, the drainage capacity can be enhanced according to the capillary pressure mechanism, thereby improving the overall performance of the fuel cell. Traditional pore-forming methods often use salts such as ammonium bicarbonate, ammonium oxalate, and ammonium sulfate as pore-forming agents, or use processes such as electrospinning to achieve a gradient pore structure. However, such methods often have problems such as difficulty in controlling pore size, complex process, and difficulty in completely removing by-products.
[0037] In view of this, the present application provides a microporous layer and a preparation method thereof, a gas diffusion layer, and a fuel cell to solve the problem of water drainage of the membrane electrode at high current densities, thereby improving the stability of the fuel cell.
[0038] In a first aspect, the present application provides a microporous layer, the raw material components of the microporous layer comprising conductive carbon black, a hydrophobic agent, a surfactant, a thiohydroxamic acid ester, and a solvent.
[0039] The present application introduces a thiohydroxamic acid ester into the raw material components of the microporous layer, which can undergo N-O bond homolysis under light conditions to produce alkyl radicals, ultimately combine with a hydrogen donor to achieve a hydrogenation reaction, and release CO2 gas (the specific reaction process is shown below), thereby forming pores inside the material.
[0040]
[0041] In addition, according to the Laplace equation (ΔP = 2σ / R, where ΔP is the pressure difference inside and outside the bubble, σ is the surface tension of the liquid, and R is the bubble radius), the viscosity of the raw material component slurry can be adjusted by the amount of surfactant added, thereby affecting the intermolecular forces, so the surface tension can be adjusted to control the size of the generated bubbles, and ultimately a microporous layer with a gradient pore structure can be obtained. The microporous layer with a gradient pore structure can optimize the water-gas transport balance inside the gas diffusion layer, thereby improving the drainage capacity and reaction gas transmission at high current densities.
[0042] In some embodiments of the first aspect, the molecular structure of the thiohydroxamic acid ester comprises:
[0043] wherein R is selected from one of the following structures: .
[0044] The thiohydroxamic acid ester of the above structure, the thiohydroxamic acid ester is split by N-O bond under light conditions to produce alkyl radicals, which ultimately combine with hydrogen donors to achieve hydrogenation, while releasing CO2 gas. The specific reaction process is shown below: .
[0045] In some embodiments of the first aspect, the mass ratio of the thiohydroxamic acid ester to the conductive carbon black is 1:(1-3). The inventors have found that if the content of the thiohydroxamic acid ester is too low, it will not be possible to generate enough ideal pore diameters; if the content of the thiohydroxamic acid ester is too high, the pore former will eventually be removed by toluene, resulting in an unstable microporous layer structure.
[0046] For example, the mass ratio of the thiohydroxamic acid ester to the conductive carbon black can be 1:1, 1:2, 1:3, etc.
[0047] In some embodiments of the first aspect, the surfactant comprises Triton. By selecting the above surfactant, the viscosity can be controlled by the addition ratio of the surfactant.
[0048] In some embodiments of the first aspect, the hydrophobic agent comprises polytetrafluoroethylene (PTFE).
[0049] In some embodiments of the first aspect, the solvent comprises ethanol. By selecting the above solvent, the thiohydroxamic acid ester can be well dissolved, and the dispersion is more uniform, thereby forming a more uniform pore size distribution.
[0050] In some embodiments of the first aspect, the microporous layer comprises a first layer and a second layer stacked in sequence, and the pore size of the first layer is smaller than that of the second layer. By constructing a double-layer structure with a pore size gradient (small pore size of the first layer and large pore size of the second layer), a directional drainage driving force from inside to outside is formed based on the capillary pressure difference: the smaller pore size of the first layer close to the catalyst layer generates a higher capillary pressure, which can effectively extract the reaction water; the larger pore size of the second layer on the outside provides a lower resistance water transport channel to accelerate the discharge of liquid water to the gas flow channel. Thus, the water-gas management efficiency is optimized, the cathode flooding under high current density is avoided, the efficient transmission of reaction gas is ensured, and the stability of the fuel cell is improved. Thus, the liquid is drained between the small pore size channel and the large pore size channel, and the pressure on the small pore size channel side is high, and the drainage is achieved by the capillary pressure difference.
[0051] In some embodiments of the first aspect, the pore size of the first layer is 5-20 μm. The inventors have found that if the pore size of the first layer is too small, it cannot ensure that water can easily enter the pore channel; if the pore size of the first layer is too large, it cannot form an effective gradient pore.
[0052] For example, the pore size of the first layer can be 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, etc.
[0053] In some embodiments of the first aspect, the pore size of the second layer is 20-50 μm. If the pore size of the second layer is too large, it can cause structural collapse and large cracks.
[0054] For example, the pore size of the second layer can be 20 μm, 30 μm, 40 μm, 50 μm, etc.
[0055] In a second aspect, the application provides a preparation method of the microporous layer of the first aspect, comprising: S1, mixing conductive carbon black, a hydrophobic agent, a first surfactant and a solvent to obtain a first slurry; In this step, the conductive carbon black, the hydrophobic agent, the first surfactant and the solvent are mixed to obtain the first slurry.
[0056] In some embodiments of the second aspect, in step S1, the mass ratio of the first surfactant to the conductive carbon black is 8-12%. Limiting the mass ratio of the first surfactant to the conductive carbon black to the above range can effectively adjust the viscosity of the system, so that it remains at a relatively low level in the subsequent step S3, which helps to form smaller and more uniform bubble nuclei during foaming.
[0057] S2, performing first light curing on the first slurry to obtain a first layer; In this step, the first slurry is subjected to the first light curing, and the thiohydroxamic acid ester decomposes under light to release CO2 gas and generate uniformly distributed micro-bubbles in situ in the slurry; at the same time, the solvent in the system is volatilized by heat, which promotes the curing and shaping of the slurry, thereby forming a first layer structure with a specific pore size and pore structure.
[0058] It should be noted that, before the slurry is subjected to light curing, the obtained slurry can be coated on a substrate and then subjected to light curing. The material of the substrate is not particularly limited in the present application. For example, when preparing a gas diffusion layer, the slurry can be blade-coated on a bare carbon paper of the gas diffusion layer, and then subjected to the first light curing.
[0059] The thickness of the blade coating is not particularly limited and can be selected as needed by those skilled in the art. According to a specific embodiment of the present application, the thickness of the blade coating is 30-70 μm. The inventors have found that when the coating is too thin, the solvent will volatilize too quickly, causing the slurry to cure too early and failing to provide sufficient space for the bubbles generated by the light reaction to form pores, resulting in insufficient pore formation. If the coating is too thick, it will hinder the effective penetration of light to the deep layer, causing incomplete curing reaction of the bottom layer and uneven pore structure. Therefore, by controlling the thickness of the coating within the above range, both the light can fully initiate the pore-forming reaction in the entire coating layer and the solvent volatilization rate can be coordinated with the bubble generation and stabilization process, thereby enabling the preparation of a microporous layer with a uniform and controllable pore structure.
[0060] For example, the thickness of the blade coating can be 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, etc. In combination with the second aspect, in some embodiments provided by the present application, the wavelength of the light in the first light curing in step S2 is 380-1000 nm. The wavelength of light within the above range can effectively initiate the homolysis of the N-O bond in the thiohydroxamic acid ester molecule, allowing it to generate alkyl radicals and release CO2 gas, thereby forming uniform and dense bubble nuclei in the microporous layer slurry.
[0061] For example, the wavelength of the light can be 380 nm, 400 nm, 600 nm, 800 nm, 1000 nm, etc.
[0062] In combination with the second aspect, in some embodiments provided by the present application, the temperature of the first light curing in step S2 is 60-75°C. The temperature of the first light curing within the above range is conducive to the slow evaporation of the solvent, thereby forming a microporous layer.
[0063] For example, the temperature of the first light curing can be 60°C, 65°C, 70°C, 75°C, etc.
[0064] S3, mixing the conductive carbon black, the hydrophobic agent, the second surfactant and the solvent to obtain a second slurry; In this step, the conductive carbon black, the hydrophobic agent, the second surfactant and the solvent are mixed to obtain a second slurry.
[0065] In combination with the second aspect, in some embodiments provided in the present application, in step S3, the viscosity of the second slurry is 250-1000 mPa·s@25s -1 According to the Prandtl equation, the second slurry with the above viscosity range can control the pore size of the generated bubbles.
[0066] For example, the viscosity of the second slurry can be 250 mPa·s@25s -1 , 600 mPa·s@25s -1 , 800 mPa·s@25s -1 , 1000 mPa·s@25s -1 , etc.
[0067] In combination with the second aspect, in some embodiments provided in the present application, the mass ratio of the second surfactant to the conductive carbon black is 5-8%. Limiting the mass ratio of the second surfactant to the conductive carbon black in the above range can control the final viscosity in the range of 250-1000 mPa·s@25s -1 .
[0068] S4, coating the second slurry on at least part of the surface of the first layer, and sintering after the second light curing to obtain a microporous layer.
[0069] In this step, the second slurry with the regulated viscosity is coated on the solidified first layer and subjected to the second light irradiation. On the one hand, the second light irradiation initiates a new pore-forming reaction in the second slurry. Since the viscosity of the second slurry is different from that of the first layer, the size and distribution of the generated bubbles also change, thereby constructing a gradient structure with gradually changing pore size in the direction perpendicular to the GDB. On the other hand, the second light irradiation not only solidifies the second slurry itself, but also enables the released CO2 gas and the solidification process to form a firm physical combination with the lower layer. The subsequent sintering process completely removes the organic components, making the porous carbon skeleton firm, and finally obtaining a microporous layer with a stable structure and a precisely designed pore size gradient, which is conducive to improving the water vapor management capability of the gas diffusion layer.
[0070] In some embodiments of the second aspect, the thickness of the coating in step S4 is 30-70 μm. The inventors have found that when the coating is too thin, the solvent volatilizes too quickly, causing the slurry to solidify too early and not providing enough space for the bubbles generated by the light reaction to form pores, resulting in insufficient pore formation. If the coating is too thick, it will hinder the effective penetration of light to the deep layer, causing incomplete solidification reaction and uneven pore structure in the bottom layer. Therefore, by controlling the thickness of the coating within the above range, the light can fully induce the pore-forming reaction in the entire coating layer, and the solvent volatilization rate can be coordinated with the bubble generation and stabilization process, thereby preparing a microporous layer with uniform and controllable pore structure.
[0071] For example, the thickness of the coating can be 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, etc.
[0072] In some embodiments of the second aspect, the wavelength of the second light curing in step S4 is 380-1000 nm. Within the above wavelength range, the thiohydroxamic acid ester compound can be effectively excited to undergo photolysis, causing the N-O bond to break efficiently and generate alkyl radicals, which in turn induce the subsequent pore-forming process of releasing CO2 gas.
[0073] For example, the wavelength of the second light curing can be 380 nm, 400 nm, 600 nm, 800 nm, 1000 nm, etc.
[0074] In some embodiments of the second aspect, the temperature of the second light curing in step S4 is 60-75 °C.
[0075] For example, the temperature of the second light curing can be 60 °C, 65 °C, 70 °C, 75 °C, etc.
[0076] In some embodiments of the second aspect, before the sintering step, the product after the second light curing is further subjected to organic solvent immersion treatment. The immersion treatment with organic solvent can remove the organic matter generated after the thiohydroxamic acid ester reaction.
[0077] In some embodiments of the second aspect, the organic solvent includes toluene.
[0078] In a fourth aspect, the present application provides a gas diffusion layer, which includes the microporous layer of the first aspect or the microporous layer obtained by the preparation method of the second aspect.
[0079] The gas diffusion layer includes a substrate layer and a microporous layer on one side surface of the substrate layer, and the microporous layer is the microporous layer of the first aspect.
[0080] In some embodiments provided in the application in combination with the third aspect, the substrate layer is a carbon fiber paper layer.
[0081] The application further provides a preparation method of the gas diffusion layer, comprising: coating the first slurry on the surface of the carbon fiber paper layer to form a first layer; coating the second slurry on the surface of the second layer to form a second layer; and impregnating the carbon fiber paper carrying the first layer and the second layer with an organic solvent and then sintering at high temperature to obtain the gas diffusion layer.
[0082] In this step, the gradient pore size structure of the microporous layer is constructed by the process of layered coating and stepwise photocuring. First, the two-time coating and curing allows the composition (such as viscosity) of the first layer and the second layer slurry to be independently adjusted, thereby forming an asymmetric structure with a gradually changing pore size from the bottom layer to the surface layer in the vertical direction, which can enhance the water management capability and the reaction gas mass transfer efficiency of the gas diffusion layer. Second, the porous framework of each layer is initially shaped by photocuring, and then uniformly impregnated with an organic solvent and sintered at high temperature, which can ensure firm combination between the two layers and avoid delamination between the layers, and also form a solid and conductive carbon framework, thereby simultaneously achieving excellent drainage, gas diffusion, mechanical strength and electrical conductivity.
[0083] In a sixth aspect, the application provides a fuel cell comprising the gas diffusion layer of the third aspect.
[0084] The technical solutions provided in the application will be described in detail below with reference to the embodiments.
[0085] Embodiment 1 The gas diffusion layer provided in Embodiment 1 of the application comprises a substrate layer and a microporous layer on one side of the substrate layer, and the raw material components of the microporous layer include conductive carbon black, a hydrophobic agent, a thiohydroxamic acid ester and a solvent.
[0086] The gas diffusion layer of Embodiment 1 can be prepared by the following method: 1) 5 g of Vulcan XC-72 conductive carbon black, 3 g of a hydrophobic agent PTFE emulsion (60%), 0.5 g of a surfactant Triton X100 and 5 g of a thiohydroxamic acid ester were added to 80 mL of anhydrous ethanol, and stirred on a magnetic stirrer for 20 minutes, and then ultrasonically dispersed for 30 minutes to obtain a first slurry; 2) The first slurry was coated on the surface of a bare carbon paper by silk screen printing with a coating thickness of 60 μm, and the carbon paper was placed on a 70°C heating table under the illumination of a 60W white LED lamp (wavelength 400 nm) for 3 hours to obtain a first layer containing pores with a pore size of 5-20 μm; 3) Adjust the formulation of step 1, the amount of surfactant Triton X100 is 0.3g, stir on a magnetic stirrer for 20 minutes, then ultrasonic dispersion for 30 minutes, to get the second slurry with viscosity of 600 mPa·s@25s -1 ; 4) The second slurry is coated on the surface of the first layer by silk screen printing, the coating thickness is 60μm, the carbon paper is placed on the heating table at 70℃ under the irradiation of 60W white LED lamp (wavelength is 400nm) for reaction for 5 hours, to get the second layer containing micropores with a pore size of 20-50μm; 5) The carbon paper loaded with the first layer and the second layer is immersed in toluene for 24h, and finally is put into a tube furnace for sintering, to get the gradient microporous layer with hydrophobicity and conductivity.
[0087] The microporous layer in the gas diffusion layer of Example 2-3 is similar to Example 1 except that some experimental parameters are different from Example 1.
[0088] The parameters of the microporous layer of Examples 1-3 are shown in Table 1: Table 1
[0089] Comparative Example 1 The present application provides a gas diffusion layer prepared by the following method: 1) 5g Vulcan XC-72 conductive carbon black, 3g hydrophobic agent PTFE emulsion (60%), and 0.5g surfactant Triton X100 are added into 80mL anhydrous ethanol, and stirred on a magnetic stirrer for 20 minutes, then ultrasonic dispersion for 30 minutes, to get a mixed slurry; 2) The mixed slurry is coated on the bare carbon paper by silk screen printing, the coating thickness is 120μm, and is put into a tube furnace for sintering to get a common microporous layer.
[0090] Comparative Example 2 The present application provides a gas diffusion layer, which is similar to Example 1, except that the raw material components of the microporous layer in the gas diffusion layer do not contain sulfonoxime ester.
[0091] Comparative Example 3 The present application provides a gas diffusion layer, which is similar to Example 1, except that the viscosity is not adjusted, and the coating thickness is directly 120μm.
[0092] Performance test (1) The pore size distribution of the gas diffusion layers of Examples 1-3 and Comparative Examples 1-3 is tested, and the specific test results are shown in Table 2: Table 2
[0093] The content of the pore size of the GDL in different pore size intervals is shown in Table 2. The GDL of Example 1 has a gradient pore size of 5-20 μm and 20-50 μm. According to the principle of capillary pressure, the gradient pore size distribution is more conducive to the drainage of water from the high current density of the cathode GDL to prevent water blockage. Comparative Example 1 has large pores mainly concentrated in the range of 50-100, and the distribution is wide without obvious gradient and small pores. Therefore, the membrane electrode of Examples 1-3 forms a gradient pore structure due to the use of the microporous layer provided in the present application.
[0094] Comparative Example 2 cannot form a gradient pore because the raw material component of the microporous layer in the gas diffusion layer does not contain a thiohydroxamic acid ester, and there is no pore former, so there are no small pores.
[0095] Comparative Example 3 does not form a gradient pore structure because the viscosity is not adjusted during the preparation of the gas diffusion layer, and the thickness of the blade coating is 120 μm, which is relatively thick, and the pore former in the deep layer does not work well.
[0096] (2) The gas diffusion layers of Example 1 and Comparative Example 1 are applied to 25 cm 2 membrane electrodes, respectively, and the electrochemical performance of the obtained membrane electrodes is tested, wherein the working temperature of the proton exchange membrane fuel cell is 80℃, the cathode air inlet pressure is 150 kpa, the stoichiometric ratio is 4.0, the relative humidity is 100%, the anode air inlet pressure is 150 kpa, the stoichiometric ratio is 1.5, the relative humidity is 100%, and the working area of the cell is 25 cm 2 . The test results are shown in Figure 1 . Figure 1 The electrochemical performance test comparison curves of the membrane electrode using the gas diffusion layer of Example 1 and the membrane electrode using the gas diffusion layer of Comparative Example 1 are shown. As can be seen from the figure, in the high current density region (> 1600 mA / cm 2 ), the test performance of Example 1 is significantly higher than that of Comparative Example 1, and at the same time, the internal resistance of Comparative Example 1 in the high current density region fluctuates obviously, which is because water cannot be drained in time under high current density, causing local water blockage. The microporous layer of Example 1 is more conducive to water drainage due to the gradient pore size distribution, so the internal resistance is stable and the electrochemical performance is better in the high current density region.
[0097] In summary, by introducing thiohydroxamic acid ester as a photosensitive pore-forming agent, gas can be generated under certain conditions. The viscosity is adjusted by the surfactant, and then the liquid surface tension is changed, which ultimately affects the bubble radius. According to the Laplace pressure equation: ΔP = 2σ / R, where ΔP is the pressure difference between the inside and outside of the bubble, σ is the surface tension of the liquid, and R is the radius of the bubble. By controlling the viscosity of the microporous layer slurry, the intermolecular force in the slurry can be affected, and the liquid surface tension can be changed to control the size of the generated bubbles, thereby forming a pore size gradient distribution in situ in the microporous layer. This structure effectively optimizes the water-gas transport balance inside the gas diffusion layer, significantly improves the water removal capacity and reaction gas mass transfer efficiency under high current density, and ultimately enhances the performance and stability of the fuel cell.
[0098] In the description of the present specification, the description of the terms "one embodiment / way", "some embodiments / ways", "example", "specific example" or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment / way or example are included in at least one embodiment / way or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment / way or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments / ways or examples. In addition, different embodiments / ways or examples described in the present specification and the features of different embodiments / ways or examples can be combined and combined by those skilled in the art without contradiction.
[0099] It should be noted that in the present application, the relationship terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method, article or device including the element. In the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified.
[0100] The foregoing detailed description of the application has been presented for purposes of illustration and description. Various modifications and changes can be made to these embodiments without departing from the spirit and scope of the application. It is intended that the scope of the application should not be limited by the particular representative embodiments described above.
Claims
1. A microporous layer, characterized in that, The raw material components of the microporous layer include conductive carbon black, hydrophobic agent, surfactant, thiooxime ester and solvent.
2. The microporous layer as described in claim 1, characterized in that, The molecular structural formula of the thiooxime ester includes: Wherein, R is selected from one of structural formulas 1, 2, and 3: 。 3. The microporous layer as described in claim 1, characterized in that, The mass ratio of the thiooxime ester to the conductive carbon black is 1:(1-3); and / or, The surfactant includes Triton; and / or, The hydrophobic agent includes polytetrafluoroethylene; and / or, The solvent includes ethanol.
4. The microporous layer according to any one of claims 1-3, characterized in that, The microporous layer comprises a first layer and a second layer stacked sequentially, wherein the pore size of the first layer is smaller than the pore size of the second layer; and / or, The pore size of the first layer is 5-20 μm; and / or, The pore size of the second layer is 20-50 μm.
5. A method for preparing a microporous layer as described in any one of claims 1-4, characterized in that, include: S1. The conductive carbon black, hydrophobic agent, first surfactant and solvent are mixed to obtain the first slurry; S2. The first slurry is cured by light for the first time to obtain the first layer; S3. Mix conductive carbon black, hydrophobic agent, second surfactant and solvent to obtain second slurry; S4. The second slurry is coated on at least a portion of the surface of the first layer, and after a second photocuring, it is sintered to obtain a microporous layer.
6. The preparation method according to claim 5, characterized in that, In step S2, the wavelength of the light used for the first photocuring is 380-1000 nm; and / or, In step S2, the temperature for the first photocuring is 60-75℃.
7. The preparation method according to claim 5, characterized in that, In step S1, the mass ratio of the first surfactant to the conductive carbon black is 8-12%; and / or, In step S3, the viscosity of the second slurry is 250-1000 mPa·s@25s. -1 ; and / or, In step S3, the mass ratio of the second surfactant to the conductive carbon black is 5-8%.
8. The preparation method according to claim 5, characterized in that, In step S4, the coating thickness is 30-70 μm; and / or, In step S4, the wavelength of the second photocuring is 380-1000 nm; and / or, In step S4, the temperature for the second photocuring is 60-75℃.
9. A gas diffusion layer, characterized in that, The gas diffusion layer comprises a microporous layer as described in any one of claims 1-4 or a microporous layer obtained by the preparation method of the microporous layer as described in any one of claims 5-8.
10. A fuel cell, characterized in that, The fuel cell includes the gas diffusion layer as described in claim 9.