Gas diffusion layer, membrane electrode assembly, fuel cell and power device

Abstract

The present invention relates to the technical field of fuel cell materials, and in particular to a gas diffusion layer, a membrane electrode assembly, a fuel cell, and an electrical device. The gas diffusion layer comprises a base layer and a microporous layer disposed on the base layer, wherein the components of the microporous layer include carbon powder, a binder, and a metal oxide. The gas diffusion layer employs a metal oxide doping method to add metal oxide to the microporous layer. The gas diffusion layer is applied to a high-temperature fuel cell using a phosphoric acid-doped polymer membrane as a proton exchange membrane. As the fuel cell operates at high temperatures, phosphoric acid in the proton exchange membrane vaporizes and migrates into the gas diffusion layer, reacting with the metal oxide in the microporous layer to form phosphates. This reduces the corrosion of the carbon powder in the microporous layer by phosphoric acid, improves the gas diffusion layer's resistance to phosphoric acid corrosion and electrochemical corrosion, and increases the service life of the high-temperature fuel cell.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell materials, in particular to a gas diffusion layer, a membrane electrode assembly, a fuel cell and an electrical device. Background Art

[0002] A fuel cell is a high-efficiency, pollution-free power generation battery. Currently, the most widely used type of fuel cell is the proton exchange membrane fuel cell. Depending on the operating temperature, proton exchange membrane fuel cells can be divided into high-temperature proton exchange membrane fuel cells (HT-PEMFC) and low-temperature proton exchange fuel cells (LT-PEMFC). The operating temperature of HT-PEMFC is 160-220°C, while the operating temperature of LT-PEMFC is usually 60-95°C. The higher operating temperature can not only increase the electrochemical reaction rate, but also improve the resistance of the precious metal Pt / C catalyst to CO poisoning. Therefore, HT-PEMFC has relatively low requirements for the purity of hydrogen on the anode side and has more application scenarios than LT-PEMFC.

[0003] The main functional structure of a fuel cell is the membrane electrode, specifically including a proton exchange membrane, a catalyst layer, and a gas diffusion layer. The proton exchange membrane is an insulator that separates the anode and cathode, preventing the fuel and air from directly mixing and reacting chemically. The catalyst layers on either side are where the fuel and oxidant undergo electrochemical reactions. The outermost gas diffusion layer serves as a diffusion medium for fuel gas, oxygen, reaction products, and electrons, and has high electrical conductivity, high thermal conductivity, corrosion resistance, and hydrophobicity. The mechanisms that shorten the service life and degrade the performance of fuel cells mainly include: the migration and dissolution of catalyst atoms, corrosion of the catalyst support carbon; chemical, thermal, and mechanical attenuation of the proton exchange membrane; and corrosion of the carbon in the gas diffusion layer, which changes the microporous structure, hindering the transport of reaction raw materials and products, and increasing resistivity. Therefore, preparing a gas diffusion layer with good corrosion resistance and electrical conductivity is important for improving the life of fuel cells. Summary of the Invention

[0004] Based on this, the present invention provides a gas diffusion layer, which is applied to a fuel cell and can increase the service life of the fuel cell.

[0005] A first object of the present invention is to provide a gas diffusion layer, comprising a base layer and a microporous layer disposed on the base layer, wherein components of the microporous layer include carbon powder, a binder, and a metal oxide.

[0006] In some specific embodiments, the components of the microporous layer include, by weight, 60 to 85 parts of carbon powder, 10 to 30 parts of a binder, and 1 to 10 parts of a metal oxide.

[0007] In some specific embodiments, the components of the microporous layer include, by mass percentage, 60% to 85% of carbon powder, 10% to 30% of binder, and 1% to 10% of metal oxide.

[0008] In some specific embodiments, the components of the microporous layer include, by mass percentage, 70% to 80% carbon powder, 15% to 25% binder, and 3% to 8% metal oxide.

[0009] In some specific embodiments, the metal oxide can react with phosphoric acid at a temperature of 160-220° C. to generate phosphate.

[0010] In some specific embodiments, the metal oxide is selected from one or more of Fe2O3, Al2O3, MnO2 and MgO.

[0011] In some specific embodiments, the particle size of the metal oxide is 40 nm to 100 nm.

[0012] In some specific embodiments, the carbon powder is one or more of XC-72, XC-72R, Ketjen black, carbon nanotubes, graphene and graphite.

[0013] In some specific embodiments, the particle size of the carbon powder is 30 nm to 500 nm.

[0014] In some specific embodiments, the binder is one or more of polytetrafluoroethylene, perfluoroethylene propylene copolymer, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer and polysilazane resin.

[0015] In some specific embodiments, the thickness of the base layer is 150 μm to 200 μm.

[0016] In some specific embodiments, the thickness of the microporous layer is 20 μm to 50 μm.

[0017] A second object of the present invention is to provide a method for preparing the gas diffusion layer, comprising:

[0018] S1: mixing carbon powder with alcohol and water to obtain a carbon powder treatment solution;

[0019] S2: mixing the carbon powder treatment solution with a binder and a metal oxide to obtain a microporous layer slurry;

[0020] S3: coating the microporous layer slurry on the surface of the base layer, and performing drying and sintering treatment to form the microporous layer to obtain a gas diffusion layer.

[0021] In some specific embodiments, the volume ratio of the alcohol to the water is 1:0.1-1; the alcohol is one or more of methanol, n-propanol, isopropanol, ethylene glycol and n-butanol.

[0022] In some specific embodiments, the binder is added in the form of a binder emulsion. The components of the binder emulsion include: a binder, a surfactant and water. The binder accounts for 10% to 20% of the mass of the binder emulsion.

[0023] In some specific embodiments, the solid content of the microporous layer slurry is 8% to 30%.

[0024] In some specific embodiments, the sintering process is performed in an inert atmosphere, the sintering temperature is 200-380° C., and the sintering time is 0.5-2 h.

[0025] The third object of the present invention is to provide use of the above-mentioned gas diffusion layer in a high-temperature fuel cell.

[0026] The fourth object of the present invention provides a membrane electrode assembly, comprising a first gas diffusion layer, a first catalytic layer, a proton exchange membrane, a second catalytic layer and a second gas diffusion layer stacked in sequence, wherein the first gas diffusion layer and / or the second gas diffusion layer is the above-mentioned gas diffusion layer.

[0027] In some specific embodiments, the proton exchange membrane is a polymer membrane doped with phosphoric acid.

[0028] A fifth object of the present invention is to provide a fuel cell comprising the above-mentioned membrane electrode assembly and bipolar plates arranged on both sides of the membrane electrode assembly.

[0029] The sixth object of the present invention is to provide an electrical device comprising the above-mentioned fuel cell.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The gas diffusion layer of the present invention employs a metal oxide doping method to add metal oxides to the microporous layer. Therefore, the gas diffusion layer is applicable to high-temperature fuel cells using a phosphoric acid-doped polymer membrane as a proton exchange membrane. As the fuel cell operates at high temperatures, phosphoric acid in the proton exchange membrane vaporizes and migrates into the gas diffusion layer, where it reacts with the metal oxides in the microporous layer to form phosphates. This reduces the corrosion of carbon powder in the microporous layer by phosphoric acid, improves the gas diffusion layer's resistance to phosphoric acid corrosion and electrochemical corrosion, and thereby extends the service life of the high-temperature fuel cell.

[0032] The method for preparing the gas diffusion layer of the present invention has a wide range of raw material sources, a simple preparation process, mild conditions, and is suitable for industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Polarization curves of the gas diffusion layer provided in Example 1 of the present invention before and after aging experiments on a fuel cell;

[0034] Figure 2 Polarization curves of the gas diffusion layer provided in Example 2 of the present invention before and after aging experiments on a fuel cell;

[0035] Figure 3 Polarization curves of the gas diffusion layer provided in Comparative Example 1 of the present invention before and after aging experiments in a fuel cell. DETAILED DESCRIPTION

[0036] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the relevant embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0037] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the description of the present invention, the meaning of "several" is at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0038] The terms "preferably," "more preferably," and the like, used herein refer to embodiments of the present invention that may provide certain benefits under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the present invention.

[0039] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0040] Unless otherwise indicated, all percentages, fractions, and ratios are calculated based on the total weight of the compositions of the present invention. Unless otherwise indicated, all masses relating to listed ingredients are given as active ingredients and therefore do not include solvents or byproducts that may be present in commercially available materials. The term "mass percentage content" may be expressed herein with the symbol "%." All molecular weights herein are weight-average molecular weights expressed in Daltons, unless otherwise indicated. All formulations and testing herein took place at 25°C, unless otherwise indicated. The terms "comprise," "include," "contain," "have," "have," and other variations herein are intended to encompass non-exclusive inclusions, and do not distinguish between these terms. The term "comprising" means that additional steps and ingredients that do not affect the end result may be added. The compositions and methods / processes of the present invention comprise, consist of, and consist essentially of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. The terms "efficacy," "performance," "effect," and "efficacy" are not used herein to distinguish between.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0042] The study found that in the HT-PEMFC using a phosphoric acid-doped polymer membrane as the proton exchange membrane, during high-temperature operation, the phosphoric acid in the polymer membrane vaporizes, passes through the catalytic layer, and penetrates into the gas diffusion layer. On the one hand, the phosphoric acid causes chemical corrosion to the carbon powder in the microporous layer. On the other hand, when the phosphoric acid electrolyte is present, the carbon powder undergoes high-potential electrochemical corrosion under the reverse polarity of the battery, which increases the resistance of the gas diffusion layer and reduces the current density, thereby shortening the service life of the HT-PEMFC.

[0043] Based on this, one embodiment of the present invention provides a gas diffusion layer, which includes a base layer and a microporous layer disposed on the base layer, wherein the microporous layer comprises carbon powder, a binder, and a metal oxide.

[0044] In some embodiments, the metal oxide can react with phosphoric acid to form phosphate at 160-220° C. Specifically, the metal oxide can be one or more of Fe2O3, Al2O3, MnO2, and MgO. Preferably, the metal oxide is Al2O3.

[0045] Furthermore, the metal oxide may be a nano-scale metal oxide powder. As an example, the particle size thereof may be 40 nm to 100 nm.

[0046] The above metal oxides can react chemically with phosphoric acid at a temperature of about 200°C to generate corresponding phosphates and water. Taking Fe2O3 and Al2O3 as an example, the reaction equation is as follows:

[0047] Fe2O3+3H3PO4→Fe3(PO4)2+3H2O

[0048] Al2O3+6H3PO4→2Al(H2PO4)3+3H2O

[0049] The above reaction conditions are close to the operating temperature of HT-PEMFC. When the fuel cell operates at around 200°C, the phosphoric acid that migrates to the gas diffusion layer through the proton exchange membrane reacts with the above metal oxides at this operating temperature, thereby slowing the corrosion of phosphoric acid on carbon powder and extending the service life of the gas diffusion layer.

[0050] In some embodiments, the components of the microporous layer include, by weight, 60 to 85 parts of carbon powder, 10 to 30 parts of a binder, and 1 to 10 parts of a metal oxide.

[0051] It can be understood that, in parts by weight, carbon powder includes but is not limited to 60 parts, 62 parts, 64 parts, 65 parts, 68 parts, 70 parts, 72 parts, 75 parts, 78 parts, 80 parts, 82 parts, and 85 parts; binders include but are not limited to 10 parts, 12 parts, 14 parts, 15 parts, 16 parts, 18 parts, 20 parts, 22 parts, 25 parts, 28 parts, and 30 parts; and metal oxides include but are not limited to 1 part, 2 parts, 4 parts, 5 parts, 6 parts, 8 parts, and 10 parts.

[0052] In some examples, the value may be within a range formed by any two of these point values ​​as end values, and the same applies below.

[0053] In some embodiments, the components of the microporous layer include, by mass percentage, 60% to 85% carbon powder, 10% to 30% binder, and 1% to 10% metal oxide.

[0054] It can be understood that, in terms of weight percentage, carbon powder includes but is not limited to 60%, 62%, 64%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%; binder includes but is not limited to 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, 25%, 28%, 30%; metal oxide includes but is not limited to 1%, 2%, 4%, 5%, 6%, 8%, 10%.

[0055] In some examples, the value may be within a range formed by any two of these point values ​​as end values, and the same applies below.

[0056] Furthermore, the components of the microporous layer include, by mass percentage, 70% to 80% of carbon powder, 15% to 25% of binder, and 3% to 8% of metal oxide.

[0057] When the metal oxide content is too low, the effect of absorbing phosphoric acid is weak, and when the metal oxide content is too high, the resistance of the gas diffusion layer will increase.

[0058] In some embodiments, the carbon powder may be one or more of XC-72, XC-72R, Ketjen Black, carbon nanotubes, graphene, or a combination of graphite. Further, the carbon powder may be nano-scale carbon powder with a particle size of 30 nm to 500 nm.

[0059] In some embodiments, the binder is one or more of polytetrafluoroethylene (PTFE), perfluoroethylene propylene copolymer (FEP), tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA), and polysilazane resin, preferably polytetrafluoroethylene (PTFE).

[0060] In some embodiments, the base layer of the gas diffusion layer is a carbon fiber layer. The carbon fiber layer is formed by stacking carbon fibers. Furthermore, the base layer has a thickness of 150 μm to 200 μm and a pore radius of 10 to 30 μm.

[0061] In some embodiments, the thickness of the microporous layer is 20 μm to 50 μm, and the pore radius is less than 100 nm.

[0062] The present invention dopes metal oxides into the microporous layer. Such metal oxides can react with phosphoric acid entering the gas diffusion layer during operation of the high-temperature fuel cell, thereby reducing the corrosion of carbon powder in the microporous layer by phosphoric acid, improving the gas diffusion layer's resistance to phosphoric acid corrosion and electrochemical corrosion, and extending the service life of the high-temperature fuel cell.

[0063] The present invention further controls the proportion of metal oxides in the microporous layer, thereby ensuring the conductivity of the gas diffusion layer and minimizing the corrosion of carbon powder in the microporous layer by phosphoric acid. This stabilizes the microporous layer structure, ensures the air permeability of the gas diffusion layer, and slows down the attenuation of the gas diffusion layer, thereby extending the service life of the high-temperature fuel cell.

[0064] Another embodiment of the present invention provides a method for preparing the gas diffusion layer, comprising the following steps S1 to S3.

[0065] S1: Mixing carbon powder with alcohol and water to obtain carbon powder treatment solution.

[0066] In this step, the volume ratio of alcohol to water is 1:0.1-1, and the alcohol can be selected from one or more of methanol, n-propanol, isopropanol, ethylene glycol, and n-butanol. Preferably, the alcohol is isopropanol or ethylene glycol. The mixing process in this step can be ground using a sand mill at 2000-2500 rpm for 1-2 hours.

[0067] S2: mixing the carbon powder treatment solution with a binder and a metal oxide to obtain a microporous layer slurry.

[0068] In this step, the binder is added in the form of a binder emulsion. The components of the binder emulsion include: a binder, a surfactant and water. The binder accounts for 10% to 20% of the mass of the binder emulsion. It can be prepared by yourself or by purchasing a high-concentration binder emulsion containing the corresponding binder and diluting it before use. The main function of the surfactant is to uniformly disperse the binder in water and be removed in the subsequent sintering process. In the mixing process of this step, sand milling can be used. In a specific embodiment, the mixing process is carried out by two sand millings and ultrasonic treatment. The first grinding is carried out at 2000 to 2500 rpm for 1 to 3 hours, and the second grinding is carried out at 1000 to 1500 rpm for 1 to 2 hours, and finally ultrasonic dispersion is performed. The solid content of the microporous layer slurry obtained in this process is 8% to 30%.

[0069] S3: coating the microporous layer slurry on the surface of the base layer, and performing drying and sintering treatment to form a microporous layer to obtain a gas diffusion layer.

[0070] Among them, coating includes spraying, brushing, scraping, screen coating and other methods. The coating rate is 40-60 mm / min, preferably 50 mm / min; the coating thickness is 40 μm-80 μm, preferably 50 μm. Among them, the temperature of the drying process is 50-90 ° C, and the time is 1-2 hours. The sintering treatment is carried out in an inert atmosphere, the sintering temperature is 200-380 ° C, and the sintering time is 0.5-2 hours. It should be understood that the specific temperature and time of the sintering process can be adjusted according to the material of the surfactant in the binder emulsion.

[0071] The raw materials used in the gas diffusion layer preparation method of the present invention are cheap and easily available, the process is simple, and the conditions in each process are mild, environmentally friendly, and suitable for industrial production and application.

[0072] Another embodiment of the present invention provides use of the gas diffusion layer in preparing a fuel cell.

[0073] Another embodiment of the present invention provides a membrane electrode assembly comprising a first gas diffusion layer, a first catalytic layer, a proton exchange membrane, a second catalytic layer, and a second gas diffusion layer stacked in sequence. The first gas diffusion layer and / or the second gas diffusion layer is the aforementioned gas diffusion layer. The microporous layer in the gas diffusion layer is bonded to the catalytic layer.

[0074] In a specific example, the proton exchange membrane is a polymer membrane doped with phosphoric acid, including but not limited to phosphoric acid-doped polybenzimidazole membrane (PBI membrane), phosphoric acid-doped polyvinylpyrrolidone membrane (PVP membrane), etc. The catalysts in the first and second catalytic layers include but are not limited to Pt / C, Ir / C, Ag / C, and Ru / C.

[0075] Another embodiment of the present invention provides a fuel cell, comprising the above-mentioned membrane electrode assembly and bipolar plates provided on both sides of the membrane electrode assembly.

[0076] Another embodiment of the present invention provides an electrical device comprising the aforementioned fuel cell. Such electrical devices include, but are not limited to, devices in the fields of stationary generators, transportation equipment, and portable power supplies. Transportation equipment includes, but is not limited to, passenger cars, commercial vehicles, bicycles, motorcycles, aircraft, and ships.

[0077] The present invention is described in detail below with reference to specific embodiments. These embodiments are for understanding rather than for limiting the present invention.

[0078] Example 1

[0079] Preparation of gas diffusion layer with added metal oxide Al2O3:

[0080] S1: Add 400 mL of isopropyl alcohol, 45 mL of ultrapure water, and 50 g of XC-72 carbon black to a sand mill. After the addition is completed, turn on the sand mill and grind at 2200 rpm for 2 h to obtain a carbon powder treatment solution.

[0081] S2: 125 g of PTFE emulsion with a binder content of 10 wt% and 3 g of Al2O3 powder were added to the sand mill containing the carbon powder treatment solution. The sand mill was turned on again and ground at 2500 rpm for 2 h. The speed of the sand mill was then reduced to 1200 rpm and ground for another 1.5 h. The mixed solution after sand milling was taken out and ultrasonically dispersed in an ice bath for 1 h to obtain a microporous layer slurry.

[0082] S3: The microporous layer slurry was applied to the carbon fiber substrate using a slot coating method at a coating speed of 50 mm / min, a height of 50 μm, and a table temperature of 60°C. After coating, the sample was dried on the table for 1 hour. The dried sample was then sintered in a tubular furnace at 360°C for 1.5 hours under a nitrogen atmosphere to obtain a gas diffusion layer.

[0083] Example 2

[0084] Preparation of gas diffusion layer with added metal oxide Fe2O3:

[0085] S1: Add 400 mL of ethylene glycol, 45 mL of ultrapure water, and then add 50 g of XC-72 carbon black into a sand mill. After the addition is completed, turn on the sand mill and grind at 2000 rpm for 1 hour to obtain a carbon powder treatment solution.

[0086] S2: 125 g of EEP emulsion with a binder content of 10 wt% and 3 g of Fe2O3 powder were added to the sand mill containing the carbon powder treatment solution. The sand mill was turned on again and ground at 2000 rpm for 1 h. The speed of the sand mill was then reduced to 1500 rpm and ground for another 2 h. The mixed solution after sand milling was taken out and ultrasonically dispersed in an ice bath for 2 h to obtain a microporous layer slurry.

[0087] S3: The microporous layer slurry was applied to the carbon fiber substrate using a slot coating method at a coating speed of 50 mm / min, a height of 50 μm, and a table temperature of 80°C. After coating, the sample was dried on the table for 1 hour. The dried sample was then sintered in a tubular furnace at 300°C for 1.5 hours under a nitrogen atmosphere to obtain a gas diffusion layer.

[0088] Example 3

[0089] Preparation of gas diffusion layer with added metal oxide MnO2:

[0090] S1: Add 400 mL of methanol, 45 mL of ultrapure water, and 50 g of XC-72 carbon black to a sand mill. After the addition is completed, start the sand mill and grind at 2200 rpm for 1.5 hours to obtain a carbon powder treatment solution.

[0091] S2: 125 g of PFA emulsion with a binder content of 10 wt% and 3 g of MnO2 powder were added to the sand mill containing the carbon powder treatment liquid. The sand mill was turned on again and ground at 2000 rpm for 3 h. Then, the sand mill speed was reduced to 1000 rpm and ground for another 1 h. The mixed solution after sand milling was taken out and ultrasonically dispersed in an ice bath for 1 h to obtain a microporous layer slurry.

[0092] S3: The microporous layer slurry was applied to the carbon fiber substrate using a slot coating method at a coating speed of 50 mm / min, a height of 50 μm, and a table temperature of 50°C. After coating, the sample was dried on the table for 1 hour. The dried sample was then sintered in a tubular furnace at 340°C for 0.5 hours under a nitrogen atmosphere to obtain a gas diffusion layer.

[0093] Example 4

[0094] Preparation of gas diffusion layer with added metal oxide MgO:

[0095] S1: Add 400 mL of ethanol, 45 mL of ultrapure water, and 50 g of XC-72 carbon black to a sand mill. After the addition is completed, turn on the sand mill and grind at 2300 rpm for 1.5 hours to obtain a carbon powder treatment solution.

[0096] S2: 125 g of PFA emulsion with a binder content of 10 wt% and 3 g of MgO powder were added to the sand mill containing the carbon powder treatment liquid. The sand mill was turned on again and ground at 2100 rpm for 3 h. The speed of the sand mill was then reduced to 1200 rpm and ground for another 1 h. The mixed solution after sand milling was taken out and ultrasonically dispersed in an ice bath for 1.5 h to obtain a microporous layer slurry.

[0097] S3: The microporous layer slurry was applied to the carbon fiber substrate using a slot coating method at a coating speed of 50 mm / min, a height of 50 μm, and a table temperature of 50°C. After coating, the sample was dried on the table for 1 hour. The dried sample was then sintered in a tubular furnace at 340°C for 1.5 hours under a nitrogen atmosphere to obtain a gas diffusion layer.

[0098] Example 5

[0099] Preparation of gas diffusion layer with added metal oxide Al2O3:

[0100] S1: Add 400 mL of isopropyl alcohol, 100 mL of ultrapure water, and then add 50 g of XC-72 carbon black into a sand mill. After the addition is completed, turn on the sand mill and grind at 2200 rpm for 2 h to obtain a carbon powder treatment solution.

[0101] S2: 150 g of PTFE emulsion with a binder content of 10 wt% and 3 g of Al2O3 powder were added to the sand mill containing the carbon powder treatment solution. The sand mill was turned on again and ground at 2500 rpm for 2 h. The speed of the sand mill was then reduced to 1200 rpm and ground for another 1.5 h. The mixed solution after sand milling was taken out and ultrasonically dispersed in an ice bath for 1 h to obtain a microporous layer slurry.

[0102] S3: The microporous layer slurry was applied to the carbon fiber substrate using a slot coating method at a coating speed of 50 mm / min, a height of 50 μm, and a table temperature of 60°C. After coating, the sample was dried on the table for 1 hour. The dried sample was then sintered in a tubular furnace at 360°C for 1.5 hours under a nitrogen atmosphere to obtain a gas diffusion layer.

[0103] Example 6

[0104] Preparation of gas diffusion layer with added metal oxide Al2O3:

[0105] S1: Add 400 mL of isopropyl alcohol, 150 mL of ultrapure water, and then add 50 g of XC-72 carbon black into a sand mill. After the addition is completed, turn on the sand mill and grind at 2200 rpm for 2 h to obtain a carbon powder treatment solution.

[0106] S2: 80 g of PTFE emulsion with a binder content of 10 wt% and 3 g of Al2O3 powder were added to the sand mill containing the carbon powder treatment solution. The sand mill was turned on again and ground at 2500 rpm for 2 h. The speed of the sand mill was then reduced to 1200 rpm and ground for another 1.5 h. The mixed solution after sand milling was taken out and ultrasonically dispersed in an ice bath for 1 h to obtain a microporous layer slurry.

[0107] S3: The microporous layer slurry was applied to the carbon fiber substrate using a slot coating method at a coating speed of 50 mm / min, a height of 50 μm, and a table temperature of 60°C. After coating, the sample was dried on the table for 1 hour. The dried sample was then sintered in a tubular furnace at 360°C for 1.5 hours under a nitrogen atmosphere to obtain a gas diffusion layer.

[0108] Example 7

[0109] Preparation of gas diffusion layer with added metal oxide Al2O3:

[0110] S1: Add 400 mL of isopropyl alcohol, 45 mL of ultrapure water, and 50 g of XC-72 carbon black to a sand mill. After the addition is completed, turn on the sand mill and grind at 2200 rpm for 2 h to obtain a carbon powder treatment solution.

[0111] S2: 125 g of PTFE emulsion with a binder content of 10 wt% and 2 g of Al2O3 powder were added to the sand mill containing the carbon powder treatment solution. The sand mill was turned on again and ground at 2500 rpm for 2 h. The speed of the sand mill was then reduced to 1200 rpm and ground for another 1.5 h. The mixed solution after sand milling was taken out and ultrasonically dispersed in an ice bath for 1 h to obtain a microporous layer slurry.

[0112] S3: The microporous layer slurry was applied to the carbon fiber substrate using a slot coating method at a coating speed of 50 mm / min, a height of 50 μm, and a table temperature of 60°C. After coating, the sample was dried on the table for 1 hour. The dried sample was then sintered in a tubular furnace at 360°C for 1.5 hours under a nitrogen atmosphere to obtain a gas diffusion layer.

[0113] Example 8

[0114] Preparation of gas diffusion layer with added metal oxide Al2O3:

[0115] S1: Add 400 mL of isopropyl alcohol, 45 mL of ultrapure water, and 50 g of XC-72 carbon black to a sand mill. After the addition is completed, turn on the sand mill and grind at 2200 rpm for 2 h to obtain a carbon powder treatment solution.

[0116] S2: 125 g of PTFE emulsion with a binder content of 10 wt% and 2.5 g of Al2O3 powder were added to the sand mill containing the carbon powder treatment liquid. The sand mill was turned on again and ground at 2500 rpm for 2 h. The speed of the sand mill was then reduced to 1200 rpm and ground for another 1.5 h. The mixed solution after sand milling was taken out and ultrasonically dispersed in an ice bath for 1 h to obtain a microporous layer slurry.

[0117] S3: The microporous layer slurry was applied to the carbon fiber substrate using a slot coating method at a coating speed of 50 mm / min, a height of 50 μm, and a table temperature of 60°C. After coating, the sample was dried on the table for 1 hour. The dried sample was then sintered in a tubular furnace at 360°C for 1.5 hours under a nitrogen atmosphere to obtain a gas diffusion layer.

[0118] Example 9

[0119] Preparation of gas diffusion layer with added metal oxide Al2O3:

[0120] S1: Add 400 mL of isopropyl alcohol, 45 mL of ultrapure water, and 50 g of XC-72 carbon black to a sand mill. After the addition is completed, turn on the sand mill and grind at 2200 rpm for 2 h to obtain a carbon powder treatment solution.

[0121] S2: Add 125 g of PTFE emulsion with a binder content of 10 wt% and 4 g of Al2O3 powder to the sand mill containing the carbon powder treatment liquid, turn on the sand mill again and grind at 2500 rpm for 2 h, then reduce the sand mill speed to 1200 rpm and grind for another 1.5 h. Take out the sand-milled mixed solution and perform ice bath ultrasonic dispersion for 1 h to obtain a microporous layer slurry.

[0122] S3: The microporous layer slurry was applied to the carbon fiber substrate using a slot coating method at a coating speed of 50 mm / min, a height of 50 μm, and a table temperature of 60°C. After coating, the sample was dried on the table for 1 hour. The dried sample was then sintered in a tubular furnace at 360°C for 1.5 hours under a nitrogen atmosphere to obtain a gas diffusion layer.

[0123] Example 10

[0124] Preparation of gas diffusion layer with added metal oxide Al2O3:

[0125] S1: Add 400 mL of isopropyl alcohol, 45 mL of ultrapure water, and 50 g of XC-72 carbon black to a sand mill. After the addition is completed, turn on the sand mill and grind at 2200 rpm for 2 h to obtain a carbon powder treatment solution.

[0126] S2: 125 g of PTFE emulsion with a binder content of 10 wt% and 5 g of Al2O3 powder were added to the sand mill containing the carbon powder treatment solution. The sand mill was turned on again and ground at 2500 rpm for 2 h. The speed of the sand mill was then reduced to 1200 rpm and ground for another 1.5 h. The mixed solution after sand milling was taken out and ultrasonically dispersed in an ice bath for 1 h to obtain a microporous layer slurry.

[0127] S3: The microporous layer slurry was applied to the carbon fiber substrate using a slot coating method at a coating speed of 50 mm / min, a height of 50 μm, and a table temperature of 60°C. After coating, the sample was dried on the table for 1 hour. The dried sample was then sintered in a tubular furnace at 360°C for 1.5 hours under a nitrogen atmosphere to obtain a gas diffusion layer.

[0128] Example 11

[0129] Preparation of gas diffusion layer with added metal oxide Al2O3

[0130] S1: Add 400 ml of isopropyl alcohol, 45 ml of ultrapure water, and 50 g of XC-72 carbon black to a sand mill. After the addition is completed, turn on the sand mill and grind at 2200 rpm for 2 hours to obtain a carbon powder treatment solution.

[0131] S2: 125 g of PTFE emulsion with a binder content of 10 wt% and 8 g of Al2O3 powder were added to the sand mill containing the carbon powder treatment solution. The sand mill was turned on again and ground at 2500 rpm for 2 h. The speed of the sand mill was then reduced to 1200 rpm and ground for another 1.5 h. The mixed solution after sand milling was taken out and ultrasonically dispersed in an ice bath for 1 h to obtain a microporous layer slurry.

[0132] S3: The microporous layer slurry was applied to the carbon fiber substrate using a slot coating method at a coating speed of 50 mm / min, a height of 50 μm, and a table temperature of 60°C. After coating, the sample was dried on the table for 1 hour. The dried sample was then sintered in a tubular furnace at 360°C for 1.5 hours under a nitrogen atmosphere to obtain a gas diffusion layer.

[0133] Example 12

[0134] Preparation of gas diffusion layer with added metal oxide Al2O3:

[0135] S1: Add 400 ml of isopropyl alcohol, 45 ml of ultrapure water, and 50 g of XC-72 carbon black to a sand mill. After the addition is completed, start the sand mill and grind at 2200 rpm for 2 hours to obtain a carbon powder treatment solution.

[0136] S2: Add 250 g of PTFE emulsion with a binder content of 10 wt% and 3 g of Al2O3 powder to the sand mill containing the carbon powder treatment liquid, turn on the sand mill again and grind at 2500 rpm for 2 h, then reduce the sand mill speed to 1200 rpm and grind for another 1.5 h. Take out the sand-milled mixed solution and perform ice bath ultrasonic dispersion for 1 h to obtain a microporous layer slurry.

[0137] S3: The microporous layer slurry was applied to the carbon fiber substrate using a slot coating method at a coating speed of 50 mm / min, a height of 50 μm, and a table temperature of 60°C. After coating, the sample was dried on the table for 1 hour. The dried sample was then sintered in a tubular furnace at 360°C for 1.5 hours under a nitrogen atmosphere to obtain a gas diffusion layer.

[0138] Comparative Example 1

[0139] Preparation of gas diffusion layer without adding metal oxides:

[0140] S1: Add 400 ml of isopropyl alcohol, 45 ml of ultrapure water, and 50 g of XC-72 carbon black to a sand mill. After the addition is completed, start the sand mill and grind at 2200 rpm for 2 hours to obtain a carbon powder treatment solution.

[0141] S2: Continue to add 125g of PTFE emulsion with a binder content of 10wt% into the above-mentioned sand mill containing the carbon powder treatment liquid, turn on the sand mill again and grind at 2500rpm for 2h, then reduce the sand mill speed to 1200rpm and grind for another 1.5h, take out the mixed liquid after sand milling and perform ice bath ultrasonic dispersion for 1h to obtain a microporous layer slurry.

[0142] S3: The microporous layer slurry was applied to the carbon fiber substrate using a slot coating method at a coating speed of 50 mm / min, a height of 50 μm, and a table temperature of 60°C. After coating, the sample was dried on the table for 1 hour. The dried sample was then sintered in a tubular furnace at 360°C for 1.5 hours under a nitrogen atmosphere to obtain a gas diffusion layer.

[0143] Comparative Example 2

[0144] This comparative example is substantially the same as Example 1, except that the metal oxide is changed to CaO.

[0145] The raw materials and proportions of Examples 1 to 12 and Comparative Examples 1 to 2 are specifically shown in Table 1.

[0146] Table 1 Raw materials and proportions of each embodiment and comparative example

[0147]

[0148]

[0149] GDL samples obtained from Examples 1-12 and Comparative Examples 1-2 were subjected to phosphoric acid corrosion experiments. The phosphoric acid concentration used in these experiments was 50%, the immersion time was 100 hours, and the temperature was 20°C. Before and after the phosphoric acid corrosion experiments, the thickness, air permeability, electrical resistance, and tensile strength of each GDL sample were measured. The results are shown in Table 2.

[0150] Table 2 Phosphoric acid corrosion test results of each gas diffusion layer in the embodiment and comparative example

[0151]

[0152]

[0153] According to the performance parameter comparison of each embodiment and comparative example before and after immersion in phosphoric acid in Table 2, it can be concluded that the gas diffusion layer doped with metal oxide has a smaller increase in resistance before and after immersion, while the gas diffusion layer without metal oxide has a larger increase in resistance. The increase in resistance of the gas diffusion layer in Example 1 after immersion is only 0.02 mΩ @ 1 MPa, while the corresponding increase in resistance of the gas diffusion layer in Comparative Example 1 is 0.2 mΩ @ 1 MPa, a difference of one order of magnitude. At the same time, the change in tensile strength of the gas diffusion layer doped with metal oxide after immersion in phosphoric acid is much smaller than that of the gas diffusion layer without metal oxide. The tensile strength of the gas diffusion layer in Example 1 after immersion in phosphoric acid decreases by about 2 N / cm, while the tensile strength of the gas diffusion layer in Comparative Example 1 decreases by about 20 N / cm. In a fuel cell, the increase in resistance of the gas diffusion layer leads to a decrease in its conductivity, and its weakened tensile strength can easily cause mechanical damage, thereby shortening the service life of the fuel cell. In addition, when the metal oxide is doped with an appropriate proportion (comparing Examples 1 and 11), according to the various performance parameters before and after immersion, it can not only ensure the permeability and conductivity of the gas diffusion layer, but also minimize phosphoric acid corrosion. The metal oxide in Comparative Example 2 is CaO. After being soaked in phosphoric acid, the gas diffusion layer with added CaO still shows a significant increase in resistance. This indicates that not all metal oxides can provide good resistance to phosphoric acid corrosion. The reason for this phenomenon may be related to the slow reaction between CaO and phosphoric acid at the operating temperature of the fuel cell.

[0154] The gas diffusion layer samples obtained in Examples 1 to 12 and Comparative Examples 1 to 2 were used as cathode and anode gas diffusion layers of HT-PEMFC for fuel cell testing. The membrane electrode effective area was 5×5 cm 2 The platinum loading of the cathode and anode catalyst layers is 1 mg / cm 2 The high-temperature proton exchange membrane is a PBI membrane doped with phosphoric acid. The battery operating temperature is 200°C and there is no back pressure. In order to accelerate the aging of the membrane electrode, a triangle wave of 0.6-1.0V is used for 1000 cycles with a sweep rate of 100mV / s. The performance curves of the membrane electrode before and after accelerated aging are recorded. The current density at 0.6V before and after the aging test is shown in Table 3. The polarization curves before and after aging of Examples 1, 2 and Comparative Example 1 are shown in Table 3. Figure 1-Figure 3 shown.

[0155] Table 3 Peak power density (mW / cm2) of each gas diffusion layer before and after aging in the examples and comparative examples 2 )

[0156]

[0157] The current density at 0.6V before and after aging tests for each of the Examples and Comparative Examples in Table 3 shows that, compared to the decrease in current density before and after aging for fuel cells corresponding to gas diffusion layers doped with specific metal oxides, the decrease in current density for the undoped metal oxides is more pronounced. This indicates that fuel cells corresponding to gas diffusion layers doped with metal oxides can mitigate performance degradation and extend their service life. Furthermore, according to Examples 11 and 12, excessive amounts of metal oxide or binder doping increase their resistance, resulting in poor initial electrical performance for the corresponding fuel cells, which fail to meet the basic requirements of fuel cells.

[0158] according to Figures 1 to 3 Comparative Example 1 shows significant performance degradation after aging testing, which is related to the corrosion of phosphoric acid in the membrane electrode. After the addition of metal oxides, the performance degradation of the fuel cell corresponding to the gas diffusion layer doped with metal oxide Al2O3 is less than that of the cell without the gas diffusion layer. Combined with the relevant test results in Table 2, it can be concluded that metal oxide doping can effectively alleviate phosphoric acid corrosion of the gas diffusion layer, slowing cell performance degradation and extending the service life of the fuel cell.

[0159] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0160] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A membrane electrode assembly, characterized in that: The invention comprises a first gas diffusion layer, a first catalytic layer, a proton exchange membrane, a second catalytic layer and a second gas diffusion layer stacked in sequence, wherein the proton exchange membrane is a polymer membrane doped with phosphoric acid, and at least one of the first gas diffusion layer and the second gas diffusion layer comprises a base layer and a microporous layer provided on the base layer, wherein the components of the microporous layer include carbon powder, a binder and a metal oxide, wherein the metal oxide can react with phosphoric acid at a temperature of 160°C to 220°C to generate phosphate.

2. The membrane electrode assembly according to claim 1, wherein: The components of the microporous layer include, by weight, 60 to 85 parts of carbon powder, 10 to 30 parts of binder, and 1 to 10 parts of metal oxide.

3. The membrane electrode assembly according to claim 1, wherein: The components of the microporous layer include, by mass percentage, 60% to 85% of carbon powder, 10% to 30% of binder and 1% to 10% of metal oxide.

4. The membrane electrode assembly according to claim 3, characterized in that The components of the microporous layer include, by mass percentage, 70% to 80% of carbon powder, 15% to 25% of binder and 3% to 8% of metal oxide.

5. The membrane electrode assembly according to any one of claims 1 to 4, characterized in that: The metal oxide includes at least one of the following characteristics (1) to (2): (1) The metal oxide is selected from one or more of Fe2O3, Al2O3, MnO2 and MgO; (2) The particle size of the metal oxide is 40 nm to 100 nm.

6. The membrane electrode assembly according to any one of claims 1 to 4, characterized in that: The membrane electrode assembly includes at least one of the following features (3) to (7): (3) The carbon powder is one or more of XC-72, XC-72R, Ketjen Black, carbon nanotubes, graphene and graphite; (4) The particle size of the carbon powder is 30 nm to 500 nm; (5) The binder is one or more of polytetrafluoroethylene, perfluoroethylene propylene copolymer, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer and polysilazane resin; (6) The thickness of the base layer is 150 μm to 200 μm; (7) The thickness of the microporous layer is 20 μm to 50 μm.

7. The membrane electrode assembly according to any one of claims 1 to 4, characterized in that: The proton exchange membrane includes one of a phosphoric acid-doped polybenzimidazole membrane and a phosphoric acid-doped polyvinylpyrrolidone membrane.

8. A fuel cell, characterized in that: The invention comprises a membrane electrode assembly according to any one of claims 1 to 7 and bipolar plates arranged on both sides of the membrane electrode assembly.

9. An electrical device, characterized in that: The electrical device comprises the fuel cell according to claim 8.

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