Gas diffusion layer, preparation method thereof and membrane electrode

Abstract

The invention relates to a gas diffusion layer and a preparation method thereof, and a membrane electrode, the gas diffusion layer comprises a base material and a microporous layer attached to at least part of the surface of the base material, and the raw material of the microporous layer comprises a phosphorus-containing compound solution; the mass concentration of the phosphorus-containing compound solution is 45%-47%; the mass of the phosphorus-containing compound solution is 2-5% of the total mass of the raw materials of the microporous layer. The phosphorus-containing compound is placed in the gas diffusion layer, and due to the porous structure and good air permeability of the gas diffusion layer, the phosphorus-containing compound can be fully diffused in the gas diffusion layer, and the opportunity of contact with free radicals is increased, so that the attack of the free radicals on the proton exchange membrane is effectively reduced, and the chemical structure of the membrane is further protected; and the reduction speed of the proton conductivity is relieved to a certain extent. Therefore, for the membrane electrode containing the gas diffusion layer, the durability and the electrical performance of the membrane electrode are both considered.

Description

Technical Field

[0001] The present application relates to the field of fuel cell technology, and in particular to a gas diffusion layer and a preparation method thereof, and a membrane electrode. Background Art

[0002] Proton exchange membrane fuel cell (PEMFC) is a device that converts chemical energy into electrical energy. Its main advantages are: high energy conversion efficiency, zero pollution, and low noise. Therefore, it has received widespread attention. The main function of proton exchange membranes (PEMs) is to conduct protons while preventing hydrogen and oxygen from diffusing between the anode and cathode electrodes. However, a small amount of gas passing through the PEM will produce hydrogen peroxide in the catalyst layer. This peroxide will decompose into free radicals under the action of Fenton's reagent, causing damage to the PEM. For example, the main attack sites of the perfluorosulfonic acid (PFSA) membrane that is widely used today include terminal carboxyl groups, ether groups in the side chains, tertiary carbon atoms, and sulfonic acid CS bonds. Inevitably, the attack of free radicals will lead to polymer chain breakage and reduced membrane electrode durability.

[0003] Adding free radical quenchers to membrane electrodes is a generally accepted method, among which cerium ions are widely used. They are usually added to the membrane or catalytic layer where free radicals are directly generated, which can significantly inhibit the free radicals. However, the proton conductivity of the membrane and the electrical properties of the membrane electrode are inevitably lost, and there are problems such as easy agglomeration and migration loss of cerium ions. Summary of the invention

[0004] The present application provides a gas diffusion layer and a preparation method thereof, and a membrane electrode to solve the following technical problem: how to balance the durability and electrical performance of the membrane electrode.

[0005] In a first aspect, the present application provides a gas diffusion layer, the gas diffusion layer comprising a substrate and a microporous layer attached to at least a portion of the surface of the substrate, wherein a raw material of the microporous layer comprises a phosphorus-containing compound solution;

[0006] The mass concentration of the phosphorus-containing compound solution is 45% to 47%;

[0007] The mass of the phosphorus-containing compound solution is 2% to 5% of the total mass of the raw materials of the microporous layer.

[0008] Optionally, the mass of the phosphorus-containing compound solution is 3% of the total mass of the raw materials of the microporous layer.

[0009] Optionally, the phosphorus-containing compound includes at least one of the following: phosphoric acid, phosphate, phosphonate, phosphonic acid.

[0010] Optionally, the raw materials of the microporous layer further include: a conductive agent, a solvent, a hydrophobic agent and an activator.

[0011] Optionally, the conductive agent includes at least one of the following: carbon powder, carbon fiber, carbon nanotube, Ketjen black, acetylene black; and / or,

[0012] The solvent comprises at least one of the following: water, isopropanol, ethanol, n-propanol, ethyl acetate; and / or,

[0013] The hydrophobic agent comprises at least one of the following: polytetrafluoroethylene emulsion, fatty acid metal soap, paraffin, polyolefin, silicone resin, fluorocarbon polymer; and / or,

[0014] The activator comprises at least one of the following: a Triton activator, a fatty acid glyceride, and a polyoxyethylene fatty acid ester.

[0015] Optionally, when the phosphorus-containing compound solution is 2 to 5 parts by mass, the conductive agent is 50 to 55 parts by mass, the solvent is 20 to 35 parts by mass, the hydrophobic agent is 5 to 10 parts by mass, and the activator is 2 to 5 parts by mass.

[0016] In a second aspect, the present application provides a method for preparing a gas diffusion layer according to any one of the first aspects, the method comprising:

[0017] Mixing and stirring the raw materials of the microporous layer to obtain a microporous layer slurry;

[0018] Applying the microporous layer slurry to at least a portion of the surface of the substrate to obtain a first gas diffusion layer;

[0019] The first gas diffusion layer is heat treated to obtain a gas diffusion layer.

[0020] Optionally, the process parameters of the mixing and stirring include: a stirring speed of 1000 r / min to 2000 r / min, and a stirring time of 1 h to 2 h.

[0021] Optionally, the process parameters of the heat treatment include: temperature of 280°C to 400°C and time of 0.5h to 2h.

[0022] In a third aspect, the present application provides a membrane electrode, which comprises the gas diffusion layer described in any one of the first aspects.

[0023] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0024] The gas diffusion layer provided in the embodiment of the present application comprises a substrate and a microporous layer attached to at least part of the surface of the substrate, and the raw material of the microporous layer comprises a phosphorus-containing compound solution. The phosphorus-containing compound has excellent antioxidant properties, has a certain inhibitory quenching effect on free radicals, converts free radicals into relatively stable products, thereby terminating the chain reaction of free radicals; the phosphorus-containing compound is located in the gas diffusion layer, and due to the porous structure and good air permeability of the gas diffusion layer, the phosphorus-containing compound can be fully diffused therein, increasing the chance of contact with free radicals, thereby effectively reducing the attack of free radicals on the proton exchange membrane, thereby protecting the chemical structure of the membrane, and to a certain extent, alleviating the rate of reduction of proton conductivity. Therefore, for the membrane electrode containing the above-mentioned gas diffusion layer, both the durability and electrical properties of the membrane electrode are taken into account. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0027] Figure 1 A schematic flow chart of a method for preparing a gas diffusion layer provided in an embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0029] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0030] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. refer to "including but not limited to". In this article, relational 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 that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A, B can be singular or plural. In this article, "at least one" refers to one or more, and "plural" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.

[0031] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0032] In a first aspect, the present application provides a gas diffusion layer, the gas diffusion layer comprising a substrate and a microporous layer attached to at least a portion of the surface of the substrate, wherein a raw material of the microporous layer comprises a phosphorus-containing compound solution;

[0033] The mass concentration of the phosphorus-containing compound solution is 45% to 47%;

[0034] The mass of the phosphorus-containing compound solution is 2% to 5% of the total mass of the raw materials of the microporous layer.

[0035] In some embodiments, the mass of the phosphorus-containing compound solution is 3% of the total mass of the raw material of the microporous layer.

[0036] In the embodiments of the present application, the phosphorus-containing compound has excellent antioxidant properties and has a certain inhibitory quenching effect on free radicals, so that the free radicals are converted into relatively stable products, thereby terminating the chain reaction of free radicals. The gas diffusion layer (GDL) is an important component of electrochemical devices such as fuel cells and electrolytic cells. The gas diffusion layer has a large number of micropores or pore structures inside, which can allow hydrogen, oxygen and other reaction gases to be evenly transmitted to the electrode reaction area to ensure the smooth progress of the electrochemical reaction; the gas diffusion layer is used as a supporting material for the electrode: it is usually composed of a material with good conductivity, and can be used as a support for the electrode to effectively transmit the current from the electrode to the electrolyte membrane. The gas diffusion layer participates in water management and thermal management. On the one hand, it can discharge the water generated by the electrode reaction to prevent the "flooding" phenomenon from affecting the battery performance; on the other hand, it can conduct the heat generated during the reaction process to maintain the uniformity of the temperature inside the battery. The gas diffusion layer is composed of a substrate and a hydrophobic coating on the surface, while the microporous layer (MPL) is an extremely thin hydrophobic coating coated on the surface of the gas diffusion layer. The gas diffusion layer can cooperate with the microporous layer to better achieve gas transmission, water management and electron conduction.

[0037] The phosphorus-containing compound is located in the gas diffusion layer. Due to the porous structure and good air permeability of the gas diffusion layer, the phosphorus-containing compound can fully diffuse therein, increasing the chance of contact with free radicals, thereby effectively reducing the attack of free radicals on the proton exchange membrane, thereby protecting the chemical structure of the membrane and alleviating the rate of reduction of proton conductivity to a certain extent. Therefore, the phosphorus-containing compound can be used as a free radical scavenger. For example, structures such as phosphorus-oxygen bonds (P=O) or phosphorus-hydrogen bonds (PH) in the phosphorus-containing compound can react with free radicals, such as hydroxyl radicals (OH·), peroxyhydroxyl radicals (OOH·), etc. Therefore, in this way, the phosphorus-containing compound can reduce the damage of free radicals to the gas diffusion layer and other fuel cell components.

[0038] The mass concentration of the phosphorus-containing compound solution can be 45% to 47%, which can make the phosphorus-containing compound have good dispersibility in the phosphorus-containing compound solution, so that the contact area with the free radicals generated by the membrane electrode can be increased later. Exemplarily, the mass concentration of the above-mentioned phosphorus-containing compound solution can be 45%, 45.5%, 46%, 46.5%, 47%, etc. The mass of the phosphorus-containing compound solution can be 2% to 5% of the total mass of the raw materials of the microporous layer, because: the phosphorus-containing compound can achieve a good effect of eliminating free radicals in the membrane electrode without damaging the electrical properties of the membrane electrode, further reducing the negative impact on battery performance. Exemplarily, the mass of the phosphorus-containing compound solution can be 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3.0%, 3.2%, 3.4%, 3.6%, 3.8%, 4.0%, 4.2%, 4.3%, 4.4%, 4.6%, 4.8%, 5.0%, etc. of the total mass of the raw material of the microporous layer. Furthermore, the mass of the phosphorus-containing compound solution can be 3% of the total mass of the raw material of the microporous layer.

[0039] In some embodiments, the phosphorus-containing compound comprises at least one of the following: phosphoric acid, a phosphate, a phosphonate, or a phosphonic acid.

[0040] In the embodiment of the present application, the above-mentioned phosphorus-containing compound can be a combination of one or more of phosphoric acid, phosphate, phosphonate, and phosphonic acid. These phosphorus-containing compounds are applied to the effective free radical scavengers of phosphorus-containing compounds in the membrane electrode, and in order to avoid their influence on the performance, they are added to the part with less influence on the performance, that is, the gas diffusion layer. The phosphorus-containing compound is located in the gas diffusion layer. Due to the porous structure and good air permeability of the gas diffusion layer, the phosphorus-containing compound can be fully diffused therein, increasing the chance of contact with free radicals, thereby effectively reducing the attack of free radicals on the proton exchange membrane, thereby protecting the chemical structure of the membrane, and to a certain extent, alleviating the rate of reduction of proton conductivity.

[0041] In some embodiments, the raw materials of the microporous layer further include: a conductive agent, a solvent, a hydrophobic agent, and an activator.

[0042] In some embodiments, the conductive agent includes at least one of the following: carbon powder, carbon fiber, carbon nanotube, Ketjen black, acetylene black; and / or,

[0043] The solvent comprises at least one of the following: water, isopropanol, ethanol, n-propanol, ethyl acetate; and / or,

[0044] The hydrophobic agent comprises at least one of the following: polytetrafluoroethylene emulsion, fatty acid metal soap, paraffin, polyolefin, silicone resin, fluorocarbon polymer; and / or,

[0045] The activator comprises at least one of the following: a Triton activator, a fatty acid glyceride, and a polyoxyethylene fatty acid ester.

[0046] In the embodiment of the present application, the raw materials of the microporous layer further include a conductive agent, a solvent, a hydrophobic agent and an activator; wherein,

[0047] Conductive agent has good electrical conductivity, can provide good channel for electron transmission, and can increase the pore structure of microporous layer, is conducive to the diffusion of gas, conductive agent can be one or more combinations of carbon powder, carbon fiber, carbon nanotube, Ketjen black, acetylene black, further can select carbon powder. Solvent can dissolve other raw materials of dispersed microporous layer, regulate the viscosity of microporous layer slurry, solvent can be one or more combinations of water, isopropanol, ethanol, n-propanol, ethyl acetate, further can select mixed solvent of water and isopropanol. Hydrophobic agent has excellent hydrophobicity and chemical stability, hydrophobic agent can be one or more combinations of polytetrafluoroethylene emulsion (PTFE), fatty acid metal soap, paraffin, polyolefin, silicone resin, fluorocarbon polymer, such as PTFE can form hydrophobic network structure in microporous layer, prevent liquid water from entering microporous layer, while maintaining good transmission of gas. By adjusting the content of PTFE, the hydrophobicity and porosity of microporous layer can be controlled, thereby optimizing the performance of gas diffusion layer. Activator can effectively reduce the interfacial tension between different substances in microporous layer, so that various granular raw materials can be better dispersed in solvent system. This helps to form a uniform microporous structure, avoid local defects caused by particle agglomeration, and thus improve the performance stability of the microporous layer. It also enhances the wettability of the microporous layer, adjusts the surface properties of the microporous layer, etc. The activator can be a combination of one or more of a Triton activator, a fatty acid glyceride, and a polyoxyethylene fatty acid ester, and a Triton activator can be further selected.

[0048] In some embodiments, when the phosphorus-containing compound solution is 2 to 5 parts by mass, the conductive agent is 50 to 55 parts by mass, the solvent is 20 to 35 parts by mass, the hydrophobic agent is 5 to 10 parts by mass, and the activator is 2 to 5 parts by mass.

[0049] In the embodiments of the present application, further, the mass of the conductive agent, solvent, hydrophobic agent and hydrophobic agent is reasonably designed to achieve the functions of the conductive agent, solvent, hydrophobic agent and hydrophobic agent. Exemplarily, the phosphorus-containing compound solution can be 2 parts by mass, 2.2 parts by mass, 2.4 parts by mass, 2.6 parts by mass, 2.8 parts by mass, 3.0 parts by mass, 3.2 parts by mass, 3.4 parts by mass, 3.6 parts by mass, 3.8 parts by mass, 4.0 parts by mass, 4.2 parts by mass, 4.3 parts by mass, 4.4 parts by mass, 4.6 parts by mass, 4.8 parts by mass, 5.0 parts by mass, etc., and the conductive agent can be 50 parts by mass, 51 parts by mass, etc. The above-mentioned amount of the above-mentioned agent is 2 parts by mass, 5 parts by mass, 52 parts by mass, 53 parts by mass, 54 parts by mass, 55 parts by mass, etc., the above-mentioned solvent is 20 parts by mass, 22 parts by mass, 24 parts by mass, 26 parts by mass, 28 parts by mass, 30 parts by mass, 32 parts by mass, 34 parts by mass, 35 parts by mass, etc., the above-mentioned hydrophobic agent is 5 parts by mass, 6 parts by mass, 7 parts by mass, 8 parts by mass, 9 parts by mass, 10 parts by mass, etc., and the above-mentioned activator is 2 parts by mass, 3 parts by mass, 4 parts by mass, 5 parts by mass, etc.

[0050] In a second aspect, the present application provides a method for preparing a gas diffusion layer according to any one of the first aspects, Figure 1 A schematic diagram of a method for preparing a gas diffusion layer provided in an embodiment of the present application; see Figure 1 , the method comprising:

[0051] S1, mixing and stirring the raw materials of the microporous layer to obtain a microporous layer slurry;

[0052] In some embodiments, the process parameters of the mixing and stirring include: a stirring speed of 1000 r / min to 2000 r / min, and a stirring time of 1 h to 2 h.

[0053] In the embodiment of the present application, the raw materials of the microporous layer are stirred at a stirring speed of 1000 r / min to 2000 r / min and a stirring time of 1 h to 2 h, so that the raw materials of the microporous layer can be evenly dispersed. For example, the stirring speed can be 1000 r / min, 1100 r / min, 1200 r / min, 1300 r / min, 1400 r / min, 1500 r / min, 1600 r / min, 1700 r / min, 1800 r / min, 1900 r / min, 2000 r / min, etc.; the stirring time can be 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2.0 h, etc.

[0054] S2, coating the microporous layer slurry on at least a portion of the surface of the substrate to obtain a first gas diffusion layer;

[0055] S3. Heat-treating the first gas diffusion layer to obtain a gas diffusion layer.

[0056] In some embodiments, the process parameters of the heat treatment include: a temperature of 280° C. to 400° C. and a time of 0.5 h to 2 h.

[0057] In the embodiment of the present application, the first gas diffusion layer is heat treated at a temperature of 280°C to 400°C for 0.5h to 2h, which can make the various components in the microporous layer more stable, improve its tolerance in the electrochemical environment, and improve the dispersibility and connectivity of the microporous layer slurry. The substrate is made of carbon that has been heat treated at high temperature, so the impurity content is extremely low and has excellent corrosion resistance; the conductive agent is more firmly bonded to the carbon, resulting in better conductivity; its high porosity allows the gas to flow smoothly through the carbon paper, has better gas conductivity, and has excellent compression characteristics. Exemplarily, the temperature of the heat treatment is 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, etc.; the time of the heat treatment can be 0.5h, 0.8h, 1.0h, 1.2h, 1.4h, 1.6h, 1.8h, 2.0h, etc.

[0058] The preparation method of the gas diffusion layer is implemented based on the above-mentioned gas diffusion layer. The specific structure of the gas diffusion layer can refer to the above-mentioned embodiment. Since the preparation method of the gas diffusion layer adopts part or all of the technical solutions of the above-mentioned embodiment, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be described one by one here.

[0059] In a third aspect, the present application provides a membrane electrode, which comprises the gas diffusion layer described in any one of the first aspects.

[0060] In the embodiment of the present application, the composition of the membrane electrode includes a proton exchange membrane, a catalyst layer and a gas diffusion layer; the membrane electrode contains the above-mentioned gas diffusion layer, which inhibits the free radicals mainly generated in the membrane electrode through diffusion, and at the same time alleviates the problem of reduced proton conductivity, so that the fuel cell containing the membrane electrode can extend its life without losing its performance, and even achieve an effect better than the original peak power.

[0061] The membrane electrode is realized based on the above-mentioned gas diffusion layer. The specific structure of the gas diffusion layer can refer to the above-mentioned embodiment. Since the membrane electrode adopts part or all of the technical solutions of the above-mentioned embodiment, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be described one by one here.

[0062] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0063] Example 1

[0064] A gas diffusion layer comprises a substrate and a microporous layer attached to the surface of the substrate, wherein raw materials of the microporous layer comprise phosphoric acid solution, carbon powder, water, isopropanol, polytetrafluoroethylene emulsion and Triton activator; the mass concentration of the phosphoric acid solution is 46%; in terms of mass fraction, the phosphoric acid solution is 2%wt, the carbon powder is 55%wt, the solvent is 31%wt (the ratio of the mass of water to the mass of isopropanol is 77:23), the polytetrafluoroethylene emulsion is 8%wt, and the Triton activator is 4%wt.

[0065] A method for preparing a gas diffusion layer comprises: mixing and stirring raw materials of a microporous layer according to the above mass fraction to obtain a microporous layer slurry; coating the microporous layer slurry on the surface of a substrate to obtain a first gas diffusion layer; heat treating the first gas diffusion layer to obtain a gas diffusion layer; wherein the stirring speed is 1000 r / min, and the stirring time is 1.5 h; the heat treatment temperature is 280°C, and the heat treatment time is 0.5 h; the substrate is carbon paper (hydrophobic treatment of carbon paper: cutting bare carbon paper of a certain size, immersing it in a mixed solution of water and PTFE, the immersion time is unlimited, taking it out and hanging it, and putting it in an oven for drying after it stops dripping).

[0066] Example 2

[0067] A gas diffusion layer comprises a substrate and a microporous layer attached to the surface of the substrate, wherein raw materials of the microporous layer comprise phosphoric acid solution, carbon powder, water, isopropanol, polytetrafluoroethylene emulsion and Triton activator; the mass concentration of the phosphoric acid solution is 45%; in terms of mass fraction, the phosphoric acid solution is 3%wt, the carbon powder is 55%wt, the solvent is 30%wt (the ratio of the mass of water to the mass of isopropanol is 77:23), the polytetrafluoroethylene emulsion is 8%wt, and the Triton activator is 4%wt.

[0068] A method for preparing a gas diffusion layer, comprising: mixing and stirring raw materials of a microporous layer according to the above mass fraction to obtain a microporous layer slurry; coating the microporous layer slurry on the surface of a substrate to obtain a first gas diffusion layer; heat treating the first gas diffusion layer to obtain a gas diffusion layer; wherein the stirring speed is 1500r / min, and the stirring time is 1.5h; the heat treatment temperature is 350°C, and the heat treatment time is 0.5h; the substrate is carbon paper (hydrophobic treatment of carbon paper: cut bare carbon paper of a certain size, soak it in a mixed solution of water and PTFE, the soaking time is unlimited, take it out and hang it, and put it in an oven for drying after it stops dripping).

[0069] Example 3

[0070] A gas diffusion layer comprises a substrate and a microporous layer attached to the surface of the substrate, wherein raw materials of the microporous layer comprise phosphoric acid solution, carbon powder, water, isopropanol, polytetrafluoroethylene emulsion and Triton activator; the mass concentration of the phosphoric acid solution is 47%; in terms of mass fraction, the phosphoric acid solution is 5%wt, the carbon powder is 55%wt, the solvent is 28%wt (the ratio of the mass of water to the mass of isopropanol is 77:23), the polytetrafluoroethylene emulsion is 8%wt, and the Triton activator is 4%wt.

[0071] A method for preparing a gas diffusion layer, comprising: mixing and stirring raw materials of a microporous layer according to the above mass fraction to obtain a microporous layer slurry; coating the microporous layer slurry on the surface of a substrate to obtain a first gas diffusion layer; heat treating the first gas diffusion layer to obtain a gas diffusion layer; wherein the stirring speed is 2000r / min, and the stirring time is 1h; the heat treatment temperature is 400°C, and the heat treatment time is 0.7h; the substrate is carbon paper (hydrophobic treatment of carbon paper: cut bare carbon paper of a certain size, immerse it in a mixed solution of water and PTFE, the immersion time is unlimited, take it out and hang it, and put it in an oven for drying after it stops dripping).

[0072] Comparative Example 1

[0073] A gas diffusion layer comprises a substrate and a microporous layer attached to the surface of the substrate, wherein raw materials of the microporous layer comprise carbon powder, water, isopropanol, polytetrafluoroethylene emulsion and Triton activator; in terms of mass fraction, the carbon powder is 55%wt, the solvent is 33%wt (the ratio of the mass of water to the mass of isopropanol is 77:23), the polytetrafluoroethylene emulsion is 8%wt, and the Triton activator is 4%wt.

[0074] A method for preparing a gas diffusion layer comprises: mixing and stirring raw materials of a microporous layer according to the above mass fraction to obtain a microporous layer slurry; coating the microporous layer slurry on the surface of a substrate to obtain a first gas diffusion layer; heat treating the first gas diffusion layer to obtain a gas diffusion layer; wherein the stirring speed is 1500 r / min, the stirring time is 1.5 h; the heat treatment temperature is 350°C, and the heat treatment time is 0.5 h.

[0075] Comparative Example 2

[0076] A gas diffusion layer comprises a substrate and a microporous layer attached to the surface of the substrate, wherein raw materials of the microporous layer comprise cerium oxide, carbon powder, water, isopropanol, polytetrafluoroethylene emulsion and Triton activator; in terms of mass fraction, cerium oxide accounts for 3%wt, carbon powder accounts for 55%wt, solvent accounts for 30%wt (the ratio of the mass of water to the mass of isopropanol is 77:23), polytetrafluoroethylene emulsion accounts for 8%wt, and Triton activator accounts for 4%wt.

[0077] A method for preparing a gas diffusion layer comprises: mixing and stirring raw materials of a microporous layer according to the above mass fraction to obtain a microporous layer slurry; coating the microporous layer slurry on the surface of a substrate to obtain a first gas diffusion layer; heat treating the first gas diffusion layer to obtain a gas diffusion layer; wherein the stirring speed is 1500 r / min, the stirring time is 1.5 h; the heat treatment temperature is 350°C, and the heat treatment time is 0.5 h.

[0078] The gas diffusion layer prepared in Examples 1 to 3 and Comparative Examples 1 to 2 is used to prepare a membrane electrode, and the membrane electrode prepared in Examples 1 to 3 and Comparative Examples 1 to 2 is used to assemble a single electrode, including: assembling a single cell in the order of anode terminal plate, anode flow field plate, membrane electrode, cathode flow field plate, and cathode terminal plate. Single cell test: Before the test, the single cell is activated at a high current density of 0.6V, and the activation time varies from 2 hours to 8 hours, depending on the specific situation of the battery activation. After the activation is completed, the polarization curve and electrochemical performance are tested. Then, a durability test is carried out according to the DOE proton membrane chemical durability test conditions. The test results are shown in Table 1.

[0079] Table 1 Single battery test results

[0080]

[0081] It can be seen from Table 1 that phosphoric acid added to MPL as a free radical quencher has no effect on the battery performance, and has a significant inhibitory effect on free radicals, which is significantly better than the traditional cerium oxide free radical quencher.

[0082] One or more technical solutions in the embodiments of the present application also have at least the following technical effects or advantages:

[0083] (1) Phosphorus-containing compounds are excellent antioxidants and have stability for more than thousands of hours in fuel cells. Phosphonic acid added to the membrane electrode can react with free radicals and remove them, thereby improving the durability of the membrane electrode. Compared with traditional cerium ions, it shows effective free radical scavenging activity;

[0084] (2) Adding phosphorus-containing compounds (free radical quenchers) to the gas diffusion layer (MPL) can inhibit free radicals generated mainly in the membrane electrode through diffusion, and at the same time alleviate the problem of reduced proton conductivity, thereby extending the life of the fuel cell without sacrificing performance, and even achieving an effect that is better than the original peak power;

[0085] (3) Phosphoric acid is a cheap raw material and its preparation method is relatively simple, which is a relatively low-cost method.

[0086] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A gas diffusion layer, characterized in that: The gas diffusion layer comprises a substrate and a microporous layer attached to at least a portion of the surface of the substrate, wherein the raw material of the microporous layer comprises a phosphorus-containing compound solution; The mass concentration of the phosphorus-containing compound solution is 45% to 47%; The mass of the phosphorus-containing compound solution is 2% to 5% of the total mass of the raw materials of the microporous layer.

2. The method according to claim 1, characterized in that The mass of the phosphorus-containing compound solution is 3% of the total mass of the raw materials of the microporous layer.

3. The gas diffusion layer according to claim 1 or 2, characterized in that: The phosphorus-containing compound includes at least one of the following: phosphoric acid, phosphate, phosphonate, and phosphonic acid.

4. The gas diffusion layer according to claim 1, characterized in that: The raw materials of the microporous layer also include: a conductive agent, a solvent, a hydrophobic agent and an activator.

5. The gas diffusion layer according to claim 4, characterized in that The conductive agent comprises at least one of the following: carbon powder, carbon fiber, carbon nanotube, Ketjen black, acetylene black; and / or, The solvent comprises at least one of the following: water, isopropanol, ethanol, n-propanol, ethyl acetate; and / or, The hydrophobic agent comprises at least one of the following: polytetrafluoroethylene emulsion, fatty acid metal soap, paraffin, polyolefin, silicone resin, fluorocarbon polymer; and / or, The activator comprises at least one of the following: a Triton activator, a fatty acid glyceride, and a polyoxyethylene fatty acid ester.

6. The gas diffusion layer according to claim 4 or 5, characterized in that: When the phosphorus-containing compound solution is 2 to 5 parts by mass, the conductive agent is 50 to 55 parts by mass, the solvent is 20 to 35 parts by mass, the hydrophobic agent is 5 to 10 parts by mass, and the activator is 2 to 5 parts by mass.

7. A method for preparing a gas diffusion layer according to any one of claims 1 to 6, characterized in that: The method comprises: Mixing and stirring the raw materials of the microporous layer to obtain a microporous layer slurry; Applying the microporous layer slurry to at least a portion of the surface of the substrate to obtain a first gas diffusion layer; The first gas diffusion layer is heat treated to obtain a gas diffusion layer.

8. The method according to claim 7, characterized in that The process parameters of the mixing and stirring include: a stirring speed of 1000 r / min to 2000 r / min, and a stirring time of 1 h to 2 h.

9. The method according to claim 7, characterized in that: The process parameters of the heat treatment include: temperature of 280° C. to 400° C. and time of 0.5 h to 2 h.

10. A membrane electrode, characterized in that: The membrane electrode comprises the gas diffusion layer according to any one of claims 1 to 6.

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