CN115084541B - Modified substrate layer, preparation method, gas diffusion layer, membrane electrode and fuel cell - Google Patents

Modified substrate layer, preparation method, gas diffusion layer, membrane electrode and fuel cell Download PDF

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CN115084541B
CN115084541B CN202210701740.2A CN202210701740A CN115084541B CN 115084541 B CN115084541 B CN 115084541B CN 202210701740 A CN202210701740 A CN 202210701740A CN 115084541 B CN115084541 B CN 115084541B
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substrate layer
layer
gas diffusion
alginate
modified substrate
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CN115084541A (en
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赵航
韩凯凯
高佳武
唐雪君
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Dongfeng Motor Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8605—Porous electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H01M4/8803—Supports for the deposition of the catalytic active composition
    • H01M4/8807—Gas diffusion layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/1004—Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

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  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
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  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
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Abstract

The invention discloses a modified substrate layer, a preparation method, a gas diffusion layer, a membrane electrode and a fuel cell, which are used for solving the problems that the gas diffusion layer is low in porosity and poor in permeability, so that the overall performance of the fuel cell is reduced. After a cyclic compression experiment, the gas diffusion layer prepared from the modifier bottom layer provided by the invention has the advantages of transverse tensile strength of 13.2-16.1MPa, longitudinal tensile strength of 8.1-9.8MPa, high strength, porosity of 61.25-70.22%, porosity reduction rate of 6.91-10.58%, high retention rate, voltage of 0.386-0.412V, reduction rate of 22.8-25.0%, low reduction amplitude, high power density of the fuel cell and good performance.

Description

Modified substrate layer, preparation method, gas diffusion layer, membrane electrode and fuel cell
Technical Field
The invention belongs to the technical field of preparation of gas diffusion layers, and particularly relates to a modified substrate layer, a preparation method, a gas diffusion layer, a membrane electrode and a fuel cell.
Background
The gas diffusion layer is a main component of the membrane electrode, and is used in a fuel cell together with the catalyst layer, and the fuel cell can directly convert chemical energy possessed by fuel into electric energy. The gas diffusion layer comprises a basal layer and a microporous layer, wherein the basal layer can be directly contacted with the catalytic layer, so that the gas diffusion layer has the functions of supporting the microporous layer and the catalytic layer, and simultaneously has the functions of collecting current, conducting gas, discharging water and the like.
At present, the gas diffusion layer has low porosity and poor permeability, so that the overall performance of the fuel cell is reduced.
Disclosure of Invention
In order to solve the technical problems, the invention provides a modified substrate layer, a preparation method, a gas diffusion layer, a membrane electrode and a fuel cell, which have high porosity and good permeability and improve the power density of the fuel cell. The technical scheme of the invention is as follows:
in one aspect, the present invention provides a modified substrate layer comprising a carbon substrate layer and a composite gel layer supported on the carbon substrate layer, the composite gel layer having a network backbone and a polymer filled within the network backbone.
In some embodiments, the loading of the composite gel layer is 0.01-1 μg/cm 2 。
In some embodiments, the loading of the composite gel layer is 0.1-0.5 μg/cm 2 。
In some embodiments, the composite gel layer comprises polyacrylamide-alginate.
In some embodiments, the polyacrylamide-alginate comprises at least one of polyacrylamide-sodium alginate, polyacrylamide-potassium alginate, and polyacrylamide-calcium alginate.
In some embodiments, the carbon substrate layer has a hydrophobic coating.
In a second aspect, the present invention also provides a method for preparing a modified substrate layer as described above, the method comprising the steps of:
immersing the carbon substrate layer in the composite hydrogel for 20-40min at 20-60 ℃ and then curing to obtain a modified substrate layer; the composite hydrogel has a network skeleton and a polymer filled in the network skeleton.
In some embodiments, the temperature of the dipping treatment is 35-60 ℃ and the time of the dipping treatment is 25-35min.
In some embodiments, the composite hydrogel comprises a polyacrylamide-alginate hydrogel.
In some embodiments, the preparation steps of the polyacrylamide-alginate hydrogel include:
mixing alginate, acrylamide, a first crosslinking agent and an initiator, then dripping an accelerator, stirring and curing for 2.5-3.5 hours to prepare crosslinked gel;
and (3) placing the crosslinked gel into a second crosslinking agent, soaking for 18-22min, and carrying out hybridization to obtain the polyacrylamide-alginate hydrogel.
In some embodiments, the alginate comprises at least one of sodium alginate, potassium alginate, and calcium alginate.
In some embodiments, prior to the impregnation treatment of the carbon substrate layer with the composite hydrogel, the method further comprises the steps of:
soaking the carbon substrate layer in a hydrophobizing agent for 25-35min, and drying at 50-70deg.C for 50-70min.
In a third aspect, the present invention also provides a gas diffusion layer comprising:
the modified substrate layer described above or the modified substrate layer produced by the production method described above;
and the microporous layer is covered on the modified basal layer.
In a fourth aspect, the present invention also provides a membrane electrode comprising the modified substrate layer described above, or the modified substrate layer produced by the production method described above, or the gas diffusion layer described above.
In a fifth aspect, the present invention also provides a fuel cell comprising the modified substrate layer described above, or the modified substrate layer produced by the production method described above, or the gas diffusion layer described above, or the membrane electrode described above.
The beneficial effects of the invention at least comprise:
the modified substrate layer provided by the invention comprises a carbon substrate layer and a composite gel layer loaded on the carbon substrate layer, wherein the composite gel layer is provided with a net-shaped framework and a polymer filled in the net-shaped framework. The carbon substrate layer can be carbon paper and carbon fiber, and is used as a substrate layer for supporting the microporous layer; the net-shaped framework of the composite gel layer is high in hardness and brittle, the polymer filled in the net-shaped framework has good toughness, the composite gel layer is adhered to the carbon substrate, and in the stacking process, if the loading pressure is smaller, the hardness of the net-shaped framework is higher than the loading pressure, so that the structure of the substrate layer can be prevented from being damaged, and the microporous layer adhered to the modified substrate layer is prevented from being damaged, namely, the structures of the vent holes and the liquid through holes of the microporous layer are protected, and the porosity of the gas diffusion layer is ensured; if the loading pressure is large, the gas diffusion layer prepared from the modified carbon substrate shows good elasticity due to the tough polymer inside the reticular framework, and under the large loading pressure, the gas diffusion layer generates tiny deformation, only a very small number of reticular frameworks are crushed and attached to the tough polymer inside, the high-strength reticular frameworks continue to provide support, the microstructure of the ventilation holes and the liquid through holes of the microporous layer is prevented from being damaged, the porosity of the gas diffusion layer is ensured, meanwhile, the internal network structure is gradually compact due to the very small number of damaged reticular frameworks, the strength is further increased, and further support is provided for the microporous layer. The gas diffusion layer prepared by modifying the substrate layer has good strength and toughness under the action of loading pressure repeatedly loaded on the macro scale, ensures the porosity of the gas diffusion layer, ensures that the gas diffusion layer has good ventilation and drainage capacity, ensures that the chemical reaction of the fuel cell is smoothly carried out, and shows higher voltage under the same current density, thereby improving the power density of a galvanic pile and ensuring that the fuel cell has good performance. After a cyclic compression experiment, the gas diffusion layer prepared from the modifier bottom layer provided by the invention has the advantages of transverse tensile strength of 13.2-16.1MPa, longitudinal tensile strength of 8.1-9.8MPa, high strength, porosity of 61.25-70.22%, porosity reduction rate of 6.91-10.58%, high retention rate, voltage of 0.386-0.412V, reduction rate of 22.8-25.0%, low reduction amplitude, high power density of the fuel cell and good performance.
Drawings
FIG. 1 is a diagram showing the steps of the preparation process of a polyacrylamide-alginate hydrogel.
Fig. 2 shows polarization curves of the gas diffusion layers of example 1, comparative example 1 and comparative example 2 of the present application before the cyclic compression experiment.
Fig. 3 shows polarization curves of the gas diffusion layers of example 1, comparative example 1 and comparative example 2 of the present application after cyclic compression experiments.
Detailed Description
In order to make the technical solution more clearly understood by those skilled in the art, the following detailed description is made with reference to the accompanying drawings.
In the process of stacking the fuel cells, in order to ensure the tightness of the fuel cells, the fuel cells must be fastened and assembled under a relatively high loading pressure, the mechanical strength of the gas diffusion layer is low, the gas diffusion layer is compressed by the loading pressure, the structure of the compressed gas diffusion layer is destroyed, the porosity of the gas diffusion layer is reduced, the permeability is reduced, and the overall performance of the fuel cells is reduced.
Based on the shortcomings in the prior art, the application provides a modified substrate layer, a preparation method thereof, a gas diffusion layer, a membrane electrode and a fuel cell.
In a first aspect, the embodiment of the application provides a modified substrate layer, which can be used for manufacturing a gas diffusion layer, a membrane electrode or a fuel cell, wherein a composite gel layer with a reticular framework and a polymer structure filled in the reticular framework is loaded on a carbon substrate layer, and the carbon substrate layer has good strength due to the reticular framework of the composite gel layer, and the polymer filled in the reticular framework has elasticity, so that the carbon substrate layer has good toughness, thereby having good mechanical strength and compression performance under repeated press-fitting force in a pile, the porosity of the gas diffusion layer can be ensured after the pile is assembled, the gas diffusion layer has good permeability, ventilation and drainage can be smooth, and the performance of the fuel cell is improved.
The modified substrate layer provided by the embodiment of the application comprises a carbon substrate layer and a composite gel layer loaded on the carbon substrate layer, wherein the composite gel layer is provided with a net-shaped framework and a polymer filled in the net-shaped framework. The carbon substrate layer can be carbon paper and carbon fiber, and is used as a substrate layer for supporting the microporous layer; the net-shaped framework of the composite gel layer is high in hardness and brittle, the polymer filled in the net-shaped framework has good toughness, the composite gel layer is adhered to the carbon substrate, and in the stacking process, if the loading pressure is smaller, the hardness of the net-shaped framework is higher than the loading pressure, so that the structure of the substrate layer can be prevented from being damaged, and the microporous layer adhered to the modified substrate layer is prevented from being damaged, namely, the structures of the vent holes and the liquid through holes of the microporous layer are protected, and the porosity of the gas diffusion layer is ensured; if the loading pressure is large, the gas diffusion layer prepared from the modified carbon substrate shows good elasticity due to the tough polymer inside the reticular framework, and under the large loading pressure, the gas diffusion layer generates tiny deformation, only a very small number of reticular frameworks are crushed and attached to the tough polymer inside, the high-strength reticular frameworks continue to provide support, the microstructure of the ventilation holes and the liquid through holes of the microporous layer is prevented from being damaged, the porosity of the gas diffusion layer is ensured, meanwhile, the internal network structure is gradually compact due to the very small number of damaged reticular frameworks, the strength is further increased, and further support is provided for the microporous layer. The gas diffusion layer prepared by modifying the substrate layer has good strength and toughness under the action of loading pressure repeatedly loaded on the macro scale, ensures the porosity of the gas diffusion layer, ensures that the gas diffusion layer has good ventilation and drainage capacity, ensures that the chemical reaction of the fuel cell is smoothly carried out, and shows higher voltage under the same current density, thereby improving the power density of a galvanic pile and ensuring that the fuel cell has good performance.
In some embodiments, the loading of the composite gel layer is 0.01-1 μg/cm 2 . The excessive loading of the composite gel layer can cause the blockage of the holes of the basal layer, namely the carbon paper, so as to reduce the number of vent holes and liquid through holes in the microporous layer; too low a loading of the composite gel layer can reduce the improvement effect of the porosity. Preferably, the loading of the composite gel layer may be from 0.1 to 0.5 μg/cm 2 More preferably, the loading of the composite gel layer is 0.3 μg/cm 2 。
In particular, the composite gel layer comprises polyacrylamide-alginate. The polyacrylamide-alginate has a reticular framework and a tough polymer structure filled in the reticular framework, and the structure ensures that the modified basal layer has good strength and toughness, ensures good porosity of gas diffusion in repeated loading and pressing of fuel cell stacks, and improves the performance of the fuel cell.
In some embodiments, the polyacrylamide-alginate comprises at least one of polyacrylamide-sodium alginate, potassium polyacrylamide-alginate, and calcium polyacrylamide-alginate, that is, the polyacrylamide-alginate may be polyacrylamide-sodium alginate, may be polyacrylamide-potassium alginate, may be polyacrylamide-calcium alginate, and may of course be any two of the three, and in other embodiments, the polyacrylamide-alginate may be a mixture of the three.
In some embodiments, the carbon substrate layer has a hydrophobic coating, such that the modified substrate layer has hydrophobicity, and the formed liquid passing holes have good drainage capacity, improving the service performance of the fuel cell.
In a second aspect, based on the same inventive concept as the first aspect, the embodiment of the application further provides a preparation method of the modified substrate layer, so that the prepared modified substrate layer has good strength and toughness, and the gas diffusion layer prepared by the modified substrate layer can ensure that the fuel cell has good porosity under repeated loading pressure of loading, has good ventilation and liquid ventilation effects, and ensures the service performance of the fuel cell.
The preparation method of the modified substrate layer provided by the embodiment of the application comprises the following steps:
immersing the carbon substrate layer in the composite hydrogel for 20-40min at 20-60 ℃ and then curing to obtain a modified substrate layer; the composite hydrogel has a network skeleton and a polymer filled in the network skeleton.
The carbon substrate layer may be immersed in the composite hydrogel or the composite hydrogel may be coated on a hydrophobic carbon substrate, such as screen printing. The time and temperature of the dipping treatment are controlled, so that the composite hydrogel can be firmly combined on the carbon substrate layer, the pores of the carbon substrate are not blocked, and the strength and toughness of the composite hydrogel are improved. The contact time of the hydrophobic carbon substrate and the composite hydrogel is too long, and the composite hydrogel combined on the hydrophobic carbon substrate is too much, so that the pores on the carbon substrate layer can be blocked; the contact time of the carbon substrate layer and the composite hydrogel is too short, the composite hydrogel combined on the carbon substrate layer is too small, the modification effect cannot be achieved, and the porosity of the gas diffusion layer cannot be ensured. The impregnation treatment temperature of the carbon substrate layer and the composite hydrogel is too high, the combination rate of the water carbon substrate layer and the composite hydrogel is too high, the uniformity of attachments on the carbon substrate layer is poor, the pore blocking phenomenon of carbon paper can occur at some positions, and the modification effect can be poor at some positions; the dipping treatment temperature of the carbon substrate layer and the composite hydrogel is too low, and the molecular movement rate is slow, so that the time for modifying the carbon substrate layer by the composite hydrogel can be prolonged, and the production efficiency is reduced. The curing method may be ultraviolet curing (UV curing), and hot air circulation curing, which is not limited herein.
Preferably, the temperature of the dipping treatment is 35-60 ℃, and the time of the dipping treatment is 25-35min.
In some embodiments, the composite hydrogel may comprise a polyacrylamide-alginate hydrogel having a network skeleton and a tough polymer structure filled in the network skeleton at a microscopic level, which results in a modified substrate layer having good strength and toughness, ensuring good porosity for gas diffusion during repeated loading and compression of fuel cell stacks, and improving the performance of the fuel cell.
In some embodiments, in conjunction with fig. 1, the preparation steps of the polyacrylamide-alginate hydrogel include:
s1, mixing alginate, acrylamide, a first crosslinking agent and an initiator, then dripping an accelerator, stirring and curing for 2.5-3.5 hours to prepare the crosslinked gel.
The first crosslinking agent may be Methylene Bisacrylamide (MBAA), the initiator may be Ammonium Persulfate (APS), the accelerator may be tetramethyl ethylenediamine (TEMED), and the accelerator may have the same mass as the acrylamide. The curing treatment may be a light treatment.
S2, soaking the crosslinked gel in a second crosslinking agent for 18-22min, and carrying out hybridization to obtain the polyacrylamide-alginate hydrogel.
The second crosslinking agent may be a calcium chloride solution, and calcium ions in the calcium chloride solution may promote polymerization of the alginate monomer. Specifically, the concentration of the calcium chloride solution may be 0.03M.
Specifically, the preparation of polyacrylamide-alginate can be obtained by the following method: mixing alginate, acrylamide, methylene Bisacrylamide (MBAA) and Ammonium Persulfate (APS) solution, dropwise adding tetramethyl ethylenediamine (TEMED) with the weight of the methylene bisacrylamide, fully stirring, carrying out ultraviolet irradiation treatment on the solution for 3h, taking out gel, and soaking in calcium chloride solution for 20min to obtain the polyacrylamide-alginate hydrogel.
In some embodiments, the alginate comprises at least one of sodium alginate, potassium alginate, and calcium alginate.
In some embodiments, prior to the impregnation treatment of the carbon substrate layer with the composite hydrogel, the method further comprises the steps of:
soaking the carbon substrate layer in a hydrophobizing agent for 25-35min, and drying at 50-70deg.C for 50-70min.
The carbon substrate layer can form a hydrophobic coating on the surface of the carbon substrate after being immersed in the hydrophobic agent, and the polyacrylamide-alginate is attached to the carbon substrate layer with the hydrophobic coating, so that the hydrophobic performance is prevented from being damaged in the press-fitting process. The hydrophobic agent is Polytetrafluoroethylene (PTFE), the hydrophobic performance of the liquid through hole can be improved after hydrophobic treatment, the good drainage capability is achieved, and the normal operation of the fuel cell is ensured.
In a third aspect, embodiments of the present application further provide a gas diffusion layer having good strength and toughness, so as to maintain good porosity under repeated press-fitting forces of the stack, and improve the power density of the fuel cell.
The gas diffusion layer provided in the embodiment of the application comprises a microporous layer and the modified substrate layer, or the gas diffusion layer comprises a microporous layer and the modified substrate layer manufactured by the manufacturing method, and the microporous layer is covered on the modified substrate layer.
The preparation method of the gas diffusion layer provided by the embodiment of the application comprises the following steps:
1. the preparation method of the microporous layer slurry comprises the following steps: mixing a pore-forming agent, a conductive agent, a water repellent and a dispersing agent to prepare microporous layer slurry;
2. the preparation step of the gas diffusion layer comprises the following steps: coating the microporous layer slurry on the modified substrate layer, and performing first roasting; and coating the microporous layer slurry on the modified substrate layer after the first roasting, and carrying out second roasting to obtain the gas diffusion layer.
In some embodiments, the conductive agent may include at least one of acetylene black, vulcan XC-72, carbon nanotubes. Acetylene black is acetylene with purity of more than 99% obtained by decomposing and refining by-product gas during pyrolysis of calcium carbide method or naphtha (crude gasoline), and is obtained by continuous pyrolysis; vulcan XC-72 is a carbon black model produced by Kabot, U.S.A.; the carbon nanotube, also called bucky tube, is a one-dimensional quantum material with a special structure (the radial dimension is in the order of nanometers, the axial dimension is in the order of micrometers, and both ends of the tube are basically sealed).
Roasting can be performed in a drying box or a resistance heating box; the first firing time may be 1 to 3 hours and the first firing temperature may be 250 to 350 ℃. The first roasting process is controlled to enable the pore-forming agent to form a plurality of vent holes and liquid through holes in the holes formed after the pore-forming agent is coated with the polyacrylamide-alginate, and the binding force between the microporous layer and the modified substrate layer is improved. The first roasting time is too long, so that the production efficiency can be influenced; the first roasting time is too short, the structures of the vent holes and the liquid passing holes of the microporous layer are not firm enough, and collapse is easy to occur; the first roasting temperature is too high, so that energy waste is caused; too low a first firing temperature may prolong the firing time, affecting the production efficiency. And after the first roasting is finished, coating the microporous layer slurry again and carrying out secondary roasting, namely second roasting, so that the number of vent holes and liquid through holes in the microporous layer can be increased, and the power density of the fuel cell can be improved. In some embodiments, the second firing time is 2-5 hours and the second firing temperature is 250-350 ℃. Controlling the second firing time to be longer than the first firing time can make the structure of all the vent holes and the liquid through holes firm.
In some embodiments, the mass ratio of pore-forming agent, conductive agent, water repellent and dispersant is (12-200): (3-10): (0.8-1.2): (10-30).
In a fourth aspect, embodiments of the present application also provide a membrane electrode with good strength and compression resistance, and good porosity after stacking, so that the fuel cell has a higher power density.
The membrane electrode provided in the embodiment of the present application includes the modified substrate layer of the first aspect, or the modified substrate layer manufactured by the manufacturing method provided in the second aspect, or the gas diffusion layer provided in the third aspect.
In a fifth aspect, embodiments of the present application also provide a fuel cell with good porosity such that the fuel cell has a higher power density.
The fuel cell provided in the embodiments of the present application includes the modified substrate layer provided in the first aspect, or the modified substrate layer manufactured by the manufacturing method provided in the second aspect, or the gas diffusion layer provided in the third aspect, or the membrane electrode provided in the fourth aspect.
The modified substrate layer and the gas diffusion layer of the embodiments of the present application will be further described below with reference to specific examples.
Example 1
Example 1 provides a modified substrate layer and a preparation method thereof, carbon paper is put into a hydrophobic agent PTFE to be subjected to hydrophobic treatment for 10min, then is put into polyacrylamide-sodium alginate hydrogel with the temperature of 60 ℃ for 30min, and finally is cured by ultraviolet to obtain the modified substrate layer.
And mixing pore-forming agent ethylene glycol, acetylene black, water repellent PTFE and dispersant isopropanol according to a ratio of 12:5:1:12 to prepare microporous layer slurry, coating the microporous layer slurry on a modified substrate layer, roasting for 3 hours, then coating the microporous layer slurry once, and roasting for 3 hours again to obtain the gas diffusion layer.
Example 2
Example 2 with reference to example 1, example 2 differs from example 1 in that: the contact temperature of the carbon paper and the polyacrylamide-sodium alginate is 35 ℃, and the contact time is 35min; the other steps in example 2 are the same as in example 1.
Example 3
Example 3 with reference to example 1, example 3 differs from example 1 in that: the contact temperature of the carbon paper and the polyacrylamide-sodium alginate is 40 ℃, and the contact time is 20min; the other steps in example 3 are the same as those in example 1.
Example 4
Example 4 provides a modified substrate layer and a method for preparing the same, carbon is arranged in a hydrophobic agent PTFE for hydrophobic treatment for 5min, then the carbon is put into polyacrylamide-potassium alginate hydrogel with the temperature of 60 ℃ for 30min, and finally the modified substrate layer is obtained through ultraviolet curing.
Mixing pore-forming agent ammonium bicarbonate, carbon nano tubes, hydrophobic PTFE and dispersing agent oxidized polyethylene wax according to a ratio of 50:8:1:18 to prepare microporous layer slurry, coating the microporous layer slurry on a modified substrate layer, roasting for 2.5 hours, then coating the microporous layer slurry once, and roasting for 3.5 hours for the second time to obtain the gas diffusion layer.
Example 5
Example 5 provides a modified substrate layer and a method for preparing the same, wherein carbon is arranged in a hydrophobing agent for hydrophobing treatment for 5min, then the carbon is put into polyacrylamide-calcium alginate hydrogel with the temperature of 40 ℃ for 25min, and finally the modified substrate layer is obtained through ultraviolet curing.
Mixing pore-forming agent lithium carbonate, carbon nanotube CS1001, water repellent PTFE and dispersant polyethylene glycol according to the ratio of 80:5:1:25 to prepare microporous layer slurry, coating the microporous layer slurry on a modified substrate layer, roasting for 2 hours, then coating the microporous layer slurry once, and roasting for 4 hours again to obtain the gas diffusion layer.
Comparative example 1
Comparative example 1 provides a method of preparing a gas diffusion layer comprising the steps of:
1. placing the carbon paper into a hydrophobing agent for hydrophobing treatment;
2. preparing microporous layer slurry: mixing isopropanol serving as a pore-forming agent with Vulcan XC-72 carbon powder in a mass ratio of 3:1, then magnetically stirring to obtain slurry A, adding ethylene glycol serving as the pore-forming agent and PTFE emulsion with a solid content of 60% into the slurry A dispersed to a certain extent, continuously magnetically stirring, and ball-milling to obtain uniformly dispersed microporous layer slurry;
3. preparing a gas diffusion layer: and (3) carrying out screen printing on the microporous layer slurry obtained in the step (2) twice, firstly fixing a substrate layer in a magnetic attraction mode, taking out the substrate layer after the first printing is finished, placing the substrate layer in a baking oven to dry for 1h at 60 ℃, then placing the substrate layer in a box-type resistance furnace to heat up to 300 ℃ to bake for 3h, carrying out screen printing for the second time, placing the substrate layer in the baking oven to dry for 1h at 60 ℃ after the second screen printing is finished, and placing the substrate layer in the box-type resistance furnace to heat up to 300 ℃ to bake for 3h, thus obtaining the final gas diffusion layer.
Comparative example 2
Comparative example 2 provides a method of preparing a gas diffusion layer comprising the steps of:
1. preparation of polyacrylamide-ammonium alginate: first, 5g of nano aluminum hydroxide was added to 100mL of deionized water at room temperature, and stirred for 15min. Subsequently, 5g of ammonium alginate was slowly added and continuously stirred to obtain a uniform sol. Pouring the sol into a mould, quickly freezing with liquid nitrogen, freeze-drying the frozen sample in a freeze dryer at-85 to-95 ℃ for about 72 hours. And finally, transferring the aerogel into a vacuum oven for drying for 3 hours to obtain aerogel, putting the aerogel into a calcium chloride/ethanol solution for soaking for 3 hours at room temperature to ensure complete crosslinking, and drying the crosslinked sample in the vacuum oven for 24 hours to remove ethanol to obtain the crosslinked ammonium alginate hydrogel.
2. Pretreatment of the substrate layer: firstly, immersing carbon paper in a PTFE (polytetrafluoroethylene) solution with the mass fraction of 15%, putting the carbon paper into an oven after immersing for 30 minutes, drying for 1h at 60 ℃, repeating the steps to enable the PETF content in the pretreated carbon paper to be 5.5%, immersing a substrate layer in an alginate-based nanocomposite aerogel for 30 minutes, combining the alginate-based nanocomposite aerogel with the substrate layer in a UV curing mode, and finally obtaining a modified substrate layer, wherein the loading amount of the alginate-based nanocomposite aerogel on the substrate layer is 0.1 microgram per square centimeter.
3. Preparing microporous layer slurry: mixing isopropanol serving as a pore-forming agent with Vulcan XC-72 carbon powder in a mass ratio of 3:1, then magnetically stirring to obtain slurry A, adding ethylene glycol serving as the pore-forming agent and PTFE emulsion with a solid content of 60% into the slurry A dispersed to a certain extent, continuously magnetically stirring, and ball-milling to obtain uniformly dispersed microporous layer slurry;
4. preparing a gas diffusion layer: and (3) carrying out screen printing on the microporous layer slurry obtained in the step (3) twice, firstly fixing the pretreated substrate layer in the step (2) in a magnetic attraction mode, taking out the pretreated substrate layer after the first printing is finished, placing the pretreated substrate layer in an oven to dry for 1h at 60 ℃, placing the pretreated substrate layer in the oven to bake for 3h at 300 ℃ after heating to a box-type resistance furnace, carrying out screen printing for the second time, placing the pretreated substrate layer in the oven to dry for 1h at 60 ℃ after finishing, and placing the pretreated substrate layer in the oven to bake for 3h at 300 ℃ after heating to the box-type resistance furnace, thus obtaining the final gas diffusion layer.
Comparative example 3
Comparative example 3 provides a method for producing a gas diffusion layer, comparative example 3 is referred to in example 1, and comparative example 3 differs from example 3 in that: the contact temperature of the carbon paper and the polyacrylamide-sodium alginate is 10 ℃, and the contact time is 10min; the other steps in comparative example 3 are the same as in example 1.
Comparative example 4
Comparative example 4 provides a method for preparing a gas diffusion layer, comparative example 4 is referred to in example 1, and comparative example 4 differs from example 3 in that: the contact temperature of the carbon paper and the polyacrylamide-sodium alginate is 80 ℃ and the contact time is 50min; the other steps in comparative example 4 are the same as in example 1.
The gas diffusion layers of examples 1 to 5 and comparative examples 1 to 4 were subjected to 10 cyclic compression testsThe pressure is 1MPa, and the pressure is maintained for 30s; simultaneously, respectively carrying out polarization curve test on the gas diffusion layers before and after the cyclic compression test, wherein the current of the polarization curve is 2000mA/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the The gas diffusion layers before and after the cyclic compression test were subjected to transverse (MD), longitudinal (TD) tensile strength test and tested for porosity, as shown in tables 1 and 2.
TABLE 1
TABLE 2
Numbering device Rate of voltage drop/% Porosity reduction rate/%
Example 1 25.0 6.91
Example 2 22.8 6.96
Example 3 23.4 9.88
Example 4 23.3 10.58
Example 5 24.5 8.05
Comparative example 1 30.2 10.7
Comparative example 2 30.1 15.61
Comparative example 3 28.7 13.58
Comparative example 4 30.8 13.03
As can be seen from the data in Table 1, the loading of polyacrylamide-alginate in the modified substrate layer provided by the application is 0.06-0.15 mug/cm < 2 >, the transverse tensile strength of the gas diffusion layer prepared by the modified substrate layer is 17.1-19.2MPa, the longitudinal tensile strength is 11.9-13.7MPa, the porosity is 67.18-75.43%, and the voltage is 0.511-0.549V; after the cyclic compression experiment, the transverse tensile strength is 13.2-16.1MPa, the longitudinal tensile strength is 8.1-9.8MPa, the porosity is 61.25-70.22%, the porosity reduction rate is 6.91-10.58%, the retention rate is high, the voltage is 0.386-0.412V, the reduction rate is 22.8-25.0%, and the reduction amplitude is low.
The gas diffusion layers prepared from the modified substrate layers provided in comparative examples 1 to 4 had a transverse tensile strength of 15.2 to 16.9MPa, a longitudinal tensile strength of 8.5 to 10.3MPa, a porosity of 56.08 to 63.24%, and a voltage of 0.467 to 0.509V before the cyclic compression test, which is lower than examples 1 to 5 of the present application; after cyclic compression experiments, the transverse tensile strength is 9.2-11.6MPa, the longitudinal tensile strength is 3.3-5.7MPa, the porosity is 48.77-53.37 percent, and the porosity is lower than that of examples 1-5 of the application; the porosity reduction rate is 13.03-15.61%, the retention rate is lower than the application examples 1-5, the voltage is 0.326-0.356V, the voltage is lower than the application examples 1-5, the voltage reduction rate is 28.0-30.8%, the reduction amplitude is higher than the application examples 1-5, and the power density is lower than the application examples.
As can be seen from fig. 2 and 3, the voltage of example 1 before and after the cyclic compression test is higher than that of comparative examples 1 and 2, which is consistent with the data in table 1.
The modified substrate layer provided by the invention comprises a carbon substrate layer and a composite hydrogel layer loaded on the carbon substrate layer, wherein the composite gel layer is provided with a reticular framework and a polymer filled in the reticular framework. The carbon substrate layer can be carbon paper and carbon fiber, and is used as a substrate layer for supporting the microporous layer; the net-shaped framework of the composite gel layer is high in hardness and brittle, the polymer filled in the net-shaped framework has good toughness, the composite gel layer is adhered to the carbon substrate, and in the stacking process, if the loading pressure is smaller, the hardness of the net-shaped framework is higher than the loading pressure, so that the structure of the substrate layer can be prevented from being damaged, and the microporous layer adhered to the modified substrate layer is prevented from being damaged, namely, the structures of the vent holes and the liquid through holes of the microporous layer are protected, and the porosity of the gas diffusion layer is ensured; if the loading pressure is large, the gas diffusion layer prepared from the modified carbon substrate shows good elasticity due to the tough polymer inside the reticular framework, and under the large loading pressure, the gas diffusion layer generates tiny deformation, only a very small number of reticular frameworks are crushed and attached to the tough polymer inside, the high-strength reticular frameworks continue to provide support, the microstructure of the ventilation holes and the liquid through holes of the microporous layer is prevented from being damaged, the porosity of the gas diffusion layer is ensured, meanwhile, the internal network structure is gradually compact due to the very small number of damaged reticular frameworks, the strength is further increased, and further support is provided for the microporous layer. The gas diffusion layer prepared by modifying the substrate layer has good strength and toughness under the action of loading pressure repeatedly loaded on the macro scale, ensures the porosity of the gas diffusion layer, ensures that the gas diffusion layer has good ventilation and drainage capacity, ensures that the chemical reaction of the fuel cell is smoothly carried out, and shows higher voltage under the same current density, thereby improving the power density of a galvanic pile and ensuring that the fuel cell has good performance.
After a cyclic compression experiment, the gas diffusion layer provided by the invention has the advantages of transverse tensile strength of 13.2-16.1MPa, longitudinal tensile strength of 8.1-9.8MPa, high strength, porosity of 61.25-70.22%, porosity reduction rate of 6.91-10.58%, high retention rate, voltage of 0.386-0.412V, reduction rate of 22.8-25.0%, low reduction amplitude, high power density of the fuel cell and good performance.
While the preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the spirit or scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims and the equivalents thereof, the present application is intended to cover such modifications and variations.

Claims (11)

1. A modified substrate layer, characterized in that the modified substrate layer comprises a carbon substrate layer and a composite gel layer supported on the carbon substrate layer, the composite gel layer having a network skeleton and a polymer filled in the network skeleton;
the preparation method of the modified substrate layer comprises the following steps:
step 1, preparing polyacrylamide-alginate hydrogel:
mixing alginate, acrylamide, a first crosslinking agent and an initiator, then dripping an accelerator, stirring and curing for 2.5-3.5 hours to prepare crosslinked gel;
soaking the crosslinked gel in a second crosslinking agent for 18-22min, and carrying out hybridization to obtain polyacrylamide-alginate hydrogel;
and 2, immersing the carbon substrate layer in polyacrylamide-alginate hydrogel for 20-40min at 20-60 ℃ and then curing to obtain the modified substrate layer.
2. The modified substrate layer of claim 1, wherein the loading of the composite gel layer is 0.01-1 μg/cm 2 。
3. The modified substrate layer of claim 2, wherein the loading of the composite gel layer is 0.1-0.5 μg/cm 2 。
4. The modified substrate layer of claim 1, wherein the polyacrylamide-alginate comprises at least one of polyacrylamide-sodium alginate, polyacrylamide-potassium alginate, and polyacrylamide-calcium alginate.
5. The modified substrate layer of claim 1, wherein the carbon substrate layer has a hydrophobic coating.
6. The modified substrate layer according to any one of claims 1 to 5, wherein the temperature of the impregnation treatment is 35 to 60 ℃, and the time of the impregnation treatment is 25 to 35min.
7. The modified substrate layer of any one of claims 1-5, wherein the alginate comprises at least one of sodium alginate, potassium alginate, and calcium alginate.
8. The modified substrate layer according to any one of claims 1 to 5, further comprising the steps of, prior to the carbon substrate layer being impregnated with the polyacrylamide-alginate hydrogel:
soaking the carbon substrate layer in a hydrophobizing agent for 25-35min, and drying at 50-70deg.C for 50-70min.
9. A gas diffusion layer, the gas diffusion layer comprising:
the modified substrate layer of any one of claims 1-8;
and the microporous layer is covered on the modified basal layer.
10. A membrane electrode comprising the modified substrate layer of any one of claims 1-8, or the gas diffusion layer of claim 9.
11. A fuel cell comprising the modified substrate layer of any one of claims 1-8, or the gas diffusion layer of claim 9, or the membrane electrode of claim 10.
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