Method for preparing a catalytic layer of a fuel cell, catalytic layer and use

Abstract

The application relates to the field of fuel cells and provides a preparation method of a fuel cell catalytic layer, which comprises the following steps: S1, mixing perfluorosulfonic acid ionomer and low-polarity dispersion solvent A, dispersing to obtain perfluorosulfonic acid dispersion liquid A; S2, mixing perfluorosulfonic acid ionomer and high-polarity dispersion solvent B, dispersing to obtain perfluorosulfonic acid dispersion liquid B; S3, mixing catalyst, deionized water and perfluorosulfonic acid dispersion liquid A, then drying in a vacuum environment, naturally cooling, and uniformly grinding to obtain ionomer-modified catalyst powder; and S4, mixing the catalyst powder obtained in the step S3 and the perfluorosulfonic acid dispersion liquid B, dispersing to obtain catalyst slurry, and coating the catalyst slurry on a proton exchange membrane to obtain a coated catalytic layer. The application has the advantages that the preparation method of the catalytic layer reduces the transmission resistance of reaction gas without introducing other substances and improves the performance of a membrane electrode.

Description

Technical Field

[0001] This invention relates to the field of fuel cells, and more specifically, to a method for preparing a fuel cell catalyst layer, the catalyst layer itself, and its applications. Background Technology

[0002] A proton exchange membrane fuel cell (PEMFC) is a device that converts hydrogen and oxygen into electrical energy through an electrochemical reaction. Compared with other technologies, it has advantages such as environmental friendliness, high energy conversion efficiency, and mild operating conditions. The membrane electrode assembly (MEA) is a key component in the PEMFC where the electrochemical reaction occurs. It consists of a proton exchange membrane, anode and cathode catalyst layers, and gas diffusion layers on both sides. The performance of the MEA largely depends on the microstructure of the catalyst layers, as they control the transport characteristics of electrons, protons, reactants, and products, especially the cathode catalyst layer where the oxygen reduction reaction occurs. The catalyst layer has a microporous structure at the micro- and nano-scale, composed of a carbon-supported catalyst (typically carbon-supported platinum) and ionomers. The ionomers covering the catalyst surface primarily provide diffusion paths and channels for the transport of reactant gases (oxygen / hydrogen) and protons.

[0003] Currently, perfluorosulfonic acid ionomers are widely used in fuel cells, with perfluorosulfonic acid ionomers being a typical example. These ionomers consist of a rigid polytetrafluoroethylene backbone with extremely hydrophobic properties and perfluoroethylene ether side chains with sulfonic acid groups. Typically, the conventional method for preparing catalyst inks involves directly mixing and dispersing the wetted catalyst, ionomer, and solvent. However, when the ionomer is densely distributed around the catalyst, it obstructs the transport of reactant gases (oxygen), increasing the resistance to the transport of reactant gases to the catalyst and reducing the performance of the membrane electrode under high electrical density. Simultaneously, when the dense ionomer is in direct contact with the catalyst, the sulfonic acid groups (-SO3H) at the tail ends of the ionomer side chains can be specifically adsorbed onto the Pt surface through oxygen atoms, causing catalyst poisoning, reducing catalyst utilization, and also leading to a decline in membrane electrode performance.

[0004] To address the aforementioned issues, Chinese patent CN113314722A utilizes the strong interaction between the hydroxyl groups of highly hindered alcohol compounds and the sulfonic acid groups of perfluorosulfonic acid ion polymers to construct a "reversible barrier layer" of highly hindered alcohol compounds around the sulfonic acid groups of the ionomer. This reduces the direct contact between the ionomer and Pt particles on the catalyst surface, thereby mitigating the poisoning effect of sulfonic acid groups on Pt and improving the performance of the fuel cell membrane electrode assembly (MEA). Chinese patent CN114361488A utilizes a mercapto compound to first occupy Pt sites on the catalyst surface, reducing the poisoning effect of the sulfonic acid groups of the Nafion ion polymer on Pt during subsequent catalyst slurry preparation. The mercapto compound is then removed through electrochemical activation, achieving the goal of improving MEA performance. While these methods can alleviate the poisoning of active sites on the catalyst surface to some extent, the additional introduction of these substances may associate with the catalyst, leading to the occupation of catalytic active sites or blockage of micropores in the catalyst layer, reducing the formation of the three-phase interface. Therefore, researching a method to reduce the poisoning effect of ionomers on Pt particles on the catalyst surface by directly controlling the morphology and distribution of ionomers on the catalyst surface, while reducing oxygen transport resistance, is of great significance for improving the performance of membrane electrodes. Summary of the Invention

[0005] The present invention aims to overcome at least one defect (deficiency) of the prior art and provide a method for preparing a fuel cell catalyst layer, which can reduce the poisoning effect of ionomers on the catalyst, reduce gas transport resistance, and improve the performance of membrane electrode.

[0006] One object of the present invention is to provide a method for preparing a fuel cell catalyst layer, comprising the following steps: S1, mixing a perfluorosulfonic acid ionomer and a low-polarity dispersion solvent A, dispersing to obtain a perfluorosulfonic acid dispersion A; S2, mixing a perfluorosulfonic acid ionomer and a high-polarity dispersion solvent B, dispersing to obtain a perfluorosulfonic acid dispersion B; S3, mixing a catalyst and a perfluorosulfonic acid dispersion A, dispersing, and solidifying to prepare an ionomer-modified catalyst powder; mixing the catalyst powder with the perfluorosulfonic acid dispersion B, dispersing to obtain a catalyst slurry; S4, coating the catalyst slurry obtained in step S3 onto a proton exchange membrane to obtain a coated catalyst layer.

[0007] In this technical solution, the perfluorosulfonic acid ionomer is one or more of Nafion, 3M, Aquivion, Dongyue, and AGC, with an ion exchange equivalent of 700-1000 g / mol. Dispersion in step S1 refers to uniformly mixing the perfluorosulfonic acid ionomer in dispersion solvent A. Dispersion in step S2 refers to uniformly mixing the perfluorosulfonic acid ionomer in dispersion solvent B. In step S3, the catalyst, perfluorosulfonic acid dispersion A, and perfluorosulfonic acid dispersion B are uniformly mixed through dispersion. The catalyst powder and perfluorosulfonic acid dispersion B are uniformly mixed through dispersion. The dispersion treatment in step S3 can be one of ultrasonic dispersion, high-speed shear dispersion, or ball milling dispersion, and the dispersion time, power, and rotation speed can be determined according to the particle size of the catalyst slurry. The solidification treatment refers to further fixing the perfluorosulfonic acid ionomer on the catalyst surface to prevent damage during subsequent dispersion. The solid content of the catalyst slurry in step S3 ranges from 5-15 wt%.

[0008] In existing technologies, catalysts and ionomers are usually directly mixed and then dispersed, resulting in uneven distribution of ionomers in the final catalyst layer, and severe poisoning of the active sites of the catalyst at the accumulation of side chain sulfonic acid groups.

[0009] In this technical solution, perfluorosulfonic acid ionomers are mixed in a low-polarity dispersion solvent A to form a gel-like perfluorosulfonic acid dispersion A. The gel-like perfluorosulfonic acid ionomers coat the catalyst. Due to the high main chain mobility of the ionomers in the low-polarity solvent, and the mutual repulsion of the sulfonic acid groups in the side chains, a first layer of perfluorosulfonic acid ionomers with a uniform distribution and loose structure is formed on the catalyst surface. Its loose structure provides sufficient channel space for the reactant gas to reach the catalyst surface through the perfluorosulfonic acid ionomers. At the same time, since the perfluorosulfonic acid ionomers are gel-like, they will not undergo phase changes or stacking as the solvent evaporates.

[0010] The perfluorosulfonic acid ionomer is mixed in a highly polar dispersion solvent B to form a solution-like perfluorosulfonic acid dispersion B. Due to the low main chain mobility of the ionomer in the highly polar solvent, the main chain is entangled, thus forming a second layer of perfluorosulfonic acid ionomer with a network structure on the catalyst surface. This provides the catalyst layer with excellent mechanical properties and a continuous proton-conducting phase. In this application, by constructing a loosely structured first layer of perfluorosulfonic acid ionomer and a network structured second layer of perfluorosulfonic acid ionomer, the uniformity of the distribution of perfluorosulfonic acid ionomer on the catalyst surface is improved, the poisoning effect of sulfonate groups on the catalyst is reduced, and the gas transport resistance is reduced, allowing the reactant gas to easily pass through the perfluorosulfonic acid ionomer to reach the catalyst surface. This also provides sufficient conductivity for the reactants, thereby improving the performance of the membrane electrode.

[0011] Further, step S3 specifically involves: first mixing perfluorosulfonic acid dispersion A and the catalyst, dispersing them under low temperature conditions to obtain a pre-catalyst slurry; vacuum drying, cooling, and grinding the pre-catalyst slurry to obtain ionomer-modified catalyst powder; then sequentially mixing the ionomer-modified catalyst powder, perfluorosulfonic acid dispersion B, and dispersion solvent C, dispersing them under low temperature conditions to obtain the final catalyst slurry.

[0012] In this technical solution, the addition of dispersing solvent C further ensures that the perfluorosulfonic acid ionomers forming a network structure in the perfluorosulfonic acid dispersion B are uniformly distributed on the catalyst surface. Dispersing solvent C is one or more mixed solvents selected from water, ethanol, isopropanol, and n-propanol. When dispersing solvent C is a mixed solvent, the ratio between various mixtures can be adjusted according to actual needs to achieve the best dispersion effect. The modified catalyst powder is catalyst powder modified with perfluorosulfonic acid ionomers, meaning that a first layer of perfluorosulfonic acid ionomers is constructed on the catalyst surface. The purpose of vacuum heating and drying the prepared catalyst slurry is to solidify the colloidal perfluorosulfonic acid ionomer coated on the catalyst surface and remove high-boiling-point low-polarity solvents, ensuring the stability of the loose first layer of perfluorosulfonic acid ionomer formed on the catalyst surface. Based on the first layer of perfluorosulfonic acid ionomer, a second layer of network-structured perfluorosulfonic acid ionomer is constructed. That is, under the loose first layer of perfluorosulfonic acid ionomer framework, the second layer of perfluorosulfonic acid ionomer is dispersed during distribution, preventing it from piling up. Combined with its network structure, this helps to improve the uniformity of its distribution.

[0013] Furthermore, the temperature of the low-temperature environment is no more than 15°C, and the average particle size of the catalyst in the prepared catalyst slurry ranges from 1 to 3 μm; the average particle size of the catalyst in the catalyst slurry ranges from 1 to 3 μm.

[0014] In this technical solution, the range of no more than 15°C is defined in a manner that can be understood by those skilled in the art, and is generally between 5 and 15°C.

[0015] Furthermore, the method for heating and drying the prepared catalyst slurry is vacuum baking, with a heating and drying temperature range of 60–160°C and a heating and drying time of 30–60 min.

[0016] Furthermore, it also includes refrigeration treatment, specifically, after dispersion as described in steps S1 and S2, refrigeration is carried out at 0℃ to 15℃ for two to four days (96 hours).

[0017] In this technical solution, the purpose of cold storage is to increase the viscosity of the perfluorosulfonic acid ionomer, further maintaining the mutual repulsion of the sulfonic acid groups in the side chains, and ensuring the stability of the uniform distribution structure of the first layer of perfluorosulfonic acid ionomer. Preferably, the cold storage time is three days.

[0018] Furthermore, the mass of the perfluorosulfonic acid ionomer in step S1 is 10-40% of the mass of the perfluorosulfonic acid ionomer in the catalyst slurry in step S4.

[0019] In this technical solution, the perfluorosulfonic acid ionomer of the perfluorosulfonic acid dispersion A is in a loose state, which can effectively reduce the oxygen conduction resistance and the poisoning effect of sulfonate on the active sites of the catalyst. However, excessive coating of this gel-like ionomer is not conducive to proton transport.

[0020] Furthermore, in steps S1 and S2, the dispersion specifically involves stirring followed by ultrasonic treatment, with the stirring time being two to four days; the ultrasonic treatment time being 5 to 10 minutes; the solid content of the perfluorosulfonic acid dispersion A being 10 to 30 wt%; and the solid content of the perfluorosulfonic acid dispersion B being 5 to 20 wt%.

[0021] Furthermore, in step S3, the catalyst is Pt / C, and in step S4, the mass ratio of perfluorosulfonic acid ionomer in the catalyst slurry to carbon in the catalyst is 0.3 to 0.9, and the Pt content in the catalyst is 20-60%.

[0022] In this technical solution, by optimizing the mass ratio of carbon in the ionomer and the catalyst, the final slurry is made more suitable for the working conditions of fuel cells.

[0023] Another object of the present invention is to provide a catalyst layer for a fuel cell, which is prepared by any of the preparation methods described above.

[0024] Another object of the present invention is to provide an application of the above-described catalyst layer in a proton exchange membrane fuel cell.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: The catalyst layer preparation method of the present invention, without introducing other substances, reduces the poisoning effect of the side chain sulfonic acid groups in the perfluorosulfonic acid ionomer on the catalyst by controlling the morphology and structure of the perfluorosulfonic acid ionomer on the catalyst surface, provides the catalyst layer with excellent mechanical properties and a continuous proton-conducting phase, reduces the transport resistance of the reaction gas, improves the utilization rate of the reaction gas and the catalyst, improves the performance of the membrane electrode, and saves costs. Attached Figure Description

[0026] Figure 1 The graphs show the polarization curves of the membrane electrodes in Example 1 and Comparative Example 1.

[0027] Figure 2 This is a schematic diagram showing the distribution of perfluorosulfonic acid ionomers on the catalyst surface in the catalyst slurry of Comparative Example 1.

[0028] Figure 3This is a schematic diagram showing the distribution of perfluorosulfonic acid ionomers on the catalyst surface in the catalyst slurry of Example 1.

[0029] Figure 4 The voltages of the membrane electrodes under different current densities in Examples 1-3 and Comparative Examples 1-4;

[0030] Figure 5 Information on the percentage of perfluorosulfonic acid and curing treatment in Examples 1-3 and Comparative Examples 1-4. Detailed Implementation

[0031] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the invention. To better illustrate the following embodiments, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions; it is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0032] Example 1

[0033] This embodiment provides a method for preparing a catalyst layer for a fuel cell, including the following steps:

[0034] S1. Preparation of perfluorosulfonic acid dispersion A: Weigh 2.00g of perfluorosulfonic acid ionomer powder (3M EW800) and add 8.00g of cyclohexanol. Stir magnetically at room temperature for 3 days. After mixing evenly, sonicate for 10 minutes and refrigerate in a refrigerator for 3 days to obtain a gel-like perfluorosulfonic acid dispersion A. The solid content of perfluorosulfonic acid dispersion A is 20wt%.

[0035] S2. Preparation of perfluorosulfonic acid dispersion B: Weigh 2.00g of perfluorosulfonic acid ionomer powder (3M EW800) and add it to a mixed solution of 8.00g of isopropanol and water (mixing ratio of 6:4). Stir magnetically at room temperature for 3 days. After mixing evenly, sonicate for 10 minutes and refrigerate in a refrigerator for 3 days to obtain a solution of perfluorosulfonic acid dispersion B. The solid content of perfluorosulfonic acid dispersion B is 15wt%.

[0036] S3. Preparation of ionomer-modified catalyst powder: Weigh 3.46g of 50% Pt / C catalyst and wet it with a small amount of deionized water. Gradually add it to 1.56g of perfluorosulfonic acid dispersion A, stir, and disperse it in a high-speed shear machine at 10000rpm for 30min to obtain a pre-catalyst slurry. Place the pre-catalyst slurry in a vacuum oven and heat it to 90℃ for 30min. After cooling, grind it to obtain the ionomer-modified catalyst powder.

[0037] S4. Preparation of catalyst slurry: Modified catalyst powder was added to 18.76 g of deionized water, along with 4.85 g of perfluorosulfonic acid dispersion B and 2.60 g of n-propanol. The mixture was dispersed in a high-speed shear press at 10,000 rpm for 30 min to obtain the catalyst slurry. The mass ratio of perfluorosulfonic acid ionomer to carbon in the Pt / C catalyst slurry was 0.6; the solid content of the catalyst slurry was 15 wt%; and the perfluorosulfonic acid ionomer in perfluorosulfonic acid dispersion A accounted for 30% of the total perfluorosulfonic acid ionomer in the catalyst slurry.

[0038] S5. The catalyst slurry prepared in step S4 is coated onto one side of the proton exchange membrane using a slit-coating method to form a cathode catalyst layer. The Pt loading in the catalyst layer is 0.250 mg / cm³. 2 ;

[0039] Furthermore, this embodiment also provides a fuel cell membrane electrode assembly (MEA), prepared by the following steps: First, an anode catalyst slurry is prepared according to the following steps: 3.10g of 50% Pt / C catalyst is added to 14.68g of deionized water, followed by the addition of the above-mentioned 9.31g of perfluorosulfonic acid dispersion B and 2.90g of n-propanol, and dispersed to obtain the anode catalyst slurry. In step S5, the anode catalyst slurry is coated on the other side of the proton exchange membrane to prepare a CCM, wherein the platinum loading of the anode catalyst layer of the CCM is 0.050mg / cm³. 2 The CCM, border, and gas diffusion layer are combined to form a membrane electrode.

[0040] Example 2

[0041] This embodiment provides a method for preparing a catalyst layer for a fuel cell, including the following steps:

[0042] S1. Preparation of perfluorosulfonic acid dispersion A: Weigh 2.00g of perfluorosulfonic acid ionomer powder (3M EW800) and add 8.00g of cyclohexanol. Stir magnetically at room temperature for 3 days. After mixing evenly, sonicate for 10 minutes and refrigerate in a refrigerator for 3 days to obtain a gel-like perfluorosulfonic acid dispersion A. The solid content of perfluorosulfonic acid dispersion A is 20wt%.

[0043] S2. Preparation of perfluorosulfonic acid dispersion B: Weigh 2.00g of perfluorosulfonic acid ionomer powder (3M EW800) and add it to a mixed solution of 8.00g of isopropanol and water (mixing ratio of 6:4). Stir magnetically at room temperature for 3 days. After mixing evenly, sonicate for 10 minutes and refrigerate in a refrigerator for 3 days to obtain a solution of perfluorosulfonic acid dispersion B. The solid content of perfluorosulfonic acid dispersion B is 15wt%.

[0044] S3. Preparation of ionomer-modified catalyst powder: Weigh 3.46g of 50% Pt / C catalyst and wet it with a small amount of deionized water. Gradually add it to 0.52g of perfluorosulfonic acid dispersion A, stir, and disperse it in a high-speed shear machine at 10000rpm for 30min to obtain a pre-catalyst slurry. Place the pre-catalyst slurry in a vacuum oven and heat it to 90℃ for 30min. After cooling, grind it to obtain the ionomer-modified catalyst powder.

[0045] S4. Preparation of catalyst slurry: Modified catalyst powder was added to 18.76 g of deionized water, along with 6.23 g of perfluorosulfonic acid dispersion B and 1.92 g of n-propanol. The mixture was dispersed in a high-speed shear press at 10,000 rpm for 30 min to obtain the catalyst slurry. The mass ratio of perfluorosulfonic acid ionomer to carbon in the Pt / C catalyst slurry was 0.6; the solid content of the catalyst slurry was 15 wt%; and the perfluorosulfonic acid ionomer in perfluorosulfonic acid dispersion A accounted for 10% of the total perfluorosulfonic acid ionomer in the catalyst slurry.

[0046] S5. The catalyst slurry prepared in step S4 is coated onto one side of the proton exchange membrane using a slit-coating method to form a cathode catalyst layer. The Pt loading in the catalyst layer is 0.250 mg / cm³. 2 ;

[0047] Furthermore, this embodiment also provides a fuel cell membrane electrode assembly (MEA), prepared by the following steps: First, an anode catalyst slurry is prepared according to the following steps: 3.10g of 50% Pt / C catalyst is added to 14.68g of deionized water, followed by the addition of the above-mentioned 9.31g of perfluorosulfonic acid dispersion B and 2.90g of n-propanol, and dispersed to obtain the anode catalyst slurry. In step S5, the anode catalyst slurry is coated on the other side of the proton exchange membrane to prepare a CCM, wherein the platinum loading of the anode catalyst layer of the CCM is 0.050mg / cm³. 2 The CCM, border, and gas diffusion layer are combined to form a membrane electrode.

[0048] Example 3

[0049] This embodiment provides a method for preparing a catalyst layer for a fuel cell, including the following steps:

[0050] S1. Preparation of perfluorosulfonic acid dispersion A: Weigh 2.00g of perfluorosulfonic acid ionomer powder (3M EW800) and add 8.00g of cyclohexanol. Stir magnetically at room temperature for 3 days. After mixing evenly, sonicate for 10 minutes and refrigerate in a refrigerator for 3 days to obtain a gel-like perfluorosulfonic acid dispersion A. The solid content of perfluorosulfonic acid dispersion A is 20wt%.

[0051] S2. Preparation of perfluorosulfonic acid dispersion B: Weigh 2.00g of perfluorosulfonic acid ionomer powder (3M EW800) and add it to a mixed solution of 8.00g of isopropanol and water (mixing ratio of 6:4). Stir magnetically at room temperature for 3 days. After mixing evenly, sonicate for 10 minutes and refrigerate in a refrigerator for 3 days to obtain a solution of perfluorosulfonic acid dispersion B. The solid content of perfluorosulfonic acid dispersion B is 15wt%.

[0052] S3. Preparation of ionomer-modified catalyst powder: Weigh 3.46g of 50% Pt / C catalyst and wet it with a small amount of deionized water. Gradually add it to 2.08g of perfluorosulfonic acid dispersion A, stir, and disperse it in a high-speed shear machine at 10000rpm for 30min to obtain a pre-catalyst slurry. Place the pre-catalyst slurry in a vacuum oven and heat it to 90℃ for 30min. After drying, grind it to obtain ionomer-modified catalyst powder.

[0053] S4. Preparation of catalyst slurry: Modified catalyst powder was added to 18.99 g of deionized water, along with 4.15 g of perfluorosulfonic acid dispersion B and 2.98 g of n-propanol. The mixture was dispersed in a high-speed shear press at 10,000 rpm for 30 min to obtain the catalyst slurry. The mass ratio of perfluorosulfonic acid ionomer to carbon in the Pt / C catalyst slurry was 0.6; the solid content of the catalyst slurry was 15 wt%; and the perfluorosulfonic acid ionomer in perfluorosulfonic acid dispersion A accounted for 40% of the total perfluorosulfonic acid ionomer in the catalyst slurry.

[0054] S5. The catalyst slurry prepared in step S4 is coated onto one side of the proton exchange membrane using a slit-coating method to form a cathode catalyst layer. The Pt loading in the catalyst layer is 0.250 mg / cm³. 2 ;

[0055] Furthermore, this embodiment also provides a fuel cell membrane electrode assembly (MEA), prepared by the following steps: First, an anode catalyst slurry is prepared according to the following steps: 3.10g of 50% Pt / C catalyst is added to 14.68g of deionized water, followed by the addition of the above-mentioned 9.31g of perfluorosulfonic acid dispersion B and 2.90g of n-propanol, and dispersed to obtain the anode catalyst slurry. In step S5, the anode catalyst slurry is coated on the other side of the proton exchange membrane to prepare a CCM, wherein the platinum loading of the anode catalyst layer of the CCM is 0.050mg / cm³. 2 The CCM, border, and gas diffusion layer are combined to form a membrane electrode.

[0056] Comparative Example 1

[0057] This comparative example provides a method for preparing a catalyst layer for a fuel cell, including the following steps:

[0058] S1. Preparation of perfluorosulfonic acid dispersion B: Weigh 2.00g of perfluorosulfonic acid ionomer powder (3M EW800) and add it to a mixed solution of 8.00g of isopropanol and water (mixing ratio of 6:4). Stir magnetically at room temperature for 3 days. After mixing evenly, sonicate for 10 minutes and refrigerate in a refrigerator for 3 days to obtain a solution of perfluorosulfonic acid dispersion B. The solid content of perfluorosulfonic acid dispersion B is 15wt%.

[0059] S2. Preparation of catalyst slurry: Weigh 3.46g of 50% Pt / C catalyst and disperse it in 18.05g of deionized water. Add 6.92g of perfluorosulfonic acid ionomer dispersion B and 1.57g of n-propanol sequentially and stir. After initial uniform dispersion, process in a high-speed shear press at 10000rpm for 30min to obtain the catalyst slurry. The mass ratio of perfluorosulfonic acid ionomer to carbon in the Pt / C catalyst slurry is 0.6; the solid content of the catalyst slurry is 15wt%; the perfluorosulfonic acid ionomer in perfluorosulfonic acid dispersion A accounts for 30% of the total perfluorosulfonic acid ionomer in the catalyst slurry.

[0060] S3. The catalyst slurry prepared in step S2 is coated onto one side of the proton exchange membrane using a slit-coating method to form a cathode catalyst layer. The Pt loading in the catalyst layer is 0.250 mg / cm³. 2 ;

[0061] Furthermore, this comparative example also provides a fuel cell membrane electrode, prepared by the following steps: First, an anode catalyst slurry is prepared according to the following steps; 3.10 g of 50% Pt / C catalyst is added to 14.68 g of deionized water, followed by the addition of the above-mentioned 9.31 g of perfluorosulfonic acid dispersion B and 2.90 g of n-propanol, and dispersed to obtain the anode catalyst slurry. In step S5, the anode catalyst slurry is coated on the other side of the proton exchange membrane to prepare a CCM, wherein the platinum loading of the anode catalyst layer of the CCM is 0.050 mg / cm². The CCM, frame, and gas diffusion layer are combined to form the membrane electrode.

[0062] Comparative Example 2

[0063] This comparative example provides a method for preparing a catalyst layer for a fuel cell, including the following steps:

[0064] S1. Preparation of perfluorosulfonic acid dispersion A: Weigh 2.00g of perfluorosulfonic acid ionomer powder (3M EW800) and add it to 8.00g of cyclohexanol. Stir magnetically at room temperature for 3 days. After mixing evenly, sonicate for 10 minutes and refrigerate in a refrigerator for 3 days to obtain a gel-like perfluorosulfonic acid dispersion A. The solid content of perfluorosulfonic acid dispersion A is 20wt%.

[0065] S2. Preparation of catalyst slurry: Weigh 3.46g of 50% Pt / C catalyst and disperse it in 20.40g of deionized water. Add 5.19g of colloidal perfluorosulfonic acid ionomer dispersion A and 0.95g of n-propanol sequentially and stir. After initial uniform dispersion, process in a high-speed shear machine at 10000rpm for 30min to obtain catalyst slurry. The mass ratio of perfluorosulfonic acid ionomer to carbon in the Pt / C catalyst slurry is 0.6. The solid content of the catalyst slurry is 15wt%. The perfluorosulfonic acid ionomer in perfluorosulfonic acid dispersion A accounts for 30% of the total perfluorosulfonic acid ionomer in the catalyst slurry.

[0066] S3. The catalyst slurry prepared in step S2 is coated onto one side of the proton exchange membrane using a slit-coating method to form a cathode catalyst layer. The Pt loading in the catalyst layer is 0.250 mg / cm³. 2 ;

[0067] Furthermore, this comparative example also provides a fuel cell membrane electrode, prepared by the following steps: First, an anode catalyst slurry is prepared according to the following steps: 3.10 g of 50% Pt / C catalyst is added to 14.68 g of deionized water, followed by the addition of the above-mentioned 9.31 g of perfluorosulfonic acid dispersion B and 2.90 g of n-propanol, and dispersed to obtain the anode catalyst slurry. In step S5, the anode catalyst slurry is coated on the other side of the proton exchange membrane to prepare a CCM, wherein the platinum loading of the anode catalyst layer of the CCM is 0.050 mg / cm². The CCM, frame, and gas diffusion layer are combined to form the membrane electrode.

[0068] Comparative Example 3

[0069] This comparative example provides a method for preparing a catalyst layer for a fuel cell, including the following steps:

[0070] S1. Preparation of perfluorosulfonic acid dispersion A: Weigh 2.00g of perfluorosulfonic acid ionomer powder (3M EW800) and add it to 8.00g of cyclohexanol. Stir magnetically at room temperature for 3 days. After mixing evenly, sonicate for 10 minutes and refrigerate in a refrigerator for 3 days to obtain a gel-like perfluorosulfonic acid dispersion A. The solid content of perfluorosulfonic acid dispersion A is 20wt%.

[0071] S2. Preparation of perfluorosulfonic acid dispersion B: Weigh 2.00g of perfluorosulfonic acid ionomer powder (3M EW800) and add it to a mixed solution of 8.00g of isopropanol and water (mixing ratio of 6:4). Stir magnetically at room temperature for 3 days. After mixing evenly, sonicate for 10 minutes and refrigerate in a refrigerator for 3 days to obtain a solution of perfluorosulfonic acid dispersion B. The solid content of perfluorosulfonic acid dispersion B is 15wt%.

[0072] S3. Preparation of ionomer-modified catalyst powder: Weigh 3.46g of 50% Pt / C catalyst and wet it with a small amount of deionized water. Gradually add 2.08g of perfluorosulfonic acid ionomer dispersion B in solution form and stir. After initial uniform dispersion, process it in a high-speed shear machine at 10000rpm for 30min to obtain a pre-catalyst slurry. Heat the pre-catalyst slurry to 90℃ in a vacuum oven and dry it for 30min. Cool and grind to obtain ionomer-modified catalyst powder.

[0073] S4. Preparation of catalyst slurry: The treated catalyst powder is dispersed in 20.40g of deionized water and 3.63g of perfluorosulfonic acid ionomer dispersion A and 2.19g of n-propanol are added sequentially. After initial uniform dispersion, the mixture is processed in a high-speed shear machine at 10000rpm for 30min to obtain the catalyst slurry. The mass ratio of ionomer to catalyst carbon support in the catalyst slurry is 0.6. The perfluorosulfonic acid ionomer in the perfluorosulfonic acid dispersion B accounts for 30% of the total perfluorosulfonic acid ionomer in the catalyst slurry. The solid content of the slurry is controlled at 15wt%.

[0074] S5. The catalyst slurry prepared in step S4 is coated onto one side of the proton exchange membrane using a slit-coating method to form a cathode catalyst layer. The Pt loading in the catalyst layer is 0.250 mg / cm³. 2 ;

[0075] Furthermore, this comparative example also provides a fuel cell membrane electrode assembly (MEA), prepared by the following steps: First, an anode catalyst slurry is prepared according to the following steps: 3.10 g of 50% Pt / C catalyst is added to 14.68 g of deionized water, followed by the addition of the above-mentioned 9.31 g of perfluorosulfonic acid dispersion B and 2.90 g of n-propanol, and dispersed to obtain the anode catalyst slurry. In step S5, the anode catalyst slurry is coated on the other side of the proton exchange membrane to prepare a CCM, wherein the platinum loading of the anode catalyst layer of the CCM is 0.050 mg / cm³. 2 The CCM, border, and gas diffusion layer are combined to form a membrane electrode.

[0076] Comparative Example 4

[0077] This comparative example provides a method for preparing a catalyst layer for a fuel cell, including the following steps:

[0078] S1. Preparation of perfluorosulfonic acid dispersion A: Weigh 2.00g of perfluorosulfonic acid ionomer powder (3M EW800) and add it to 8.00g of cyclohexanol. Stir magnetically at room temperature for 3 days. After mixing evenly, sonicate for 10 minutes and refrigerate in a refrigerator for 3 days to obtain a gel-like perfluorosulfonic acid dispersion A. The solid content of perfluorosulfonic acid dispersion A is 20wt%.

[0079] S2. Preparation of perfluorosulfonic acid dispersion B: Weigh 2.00g of perfluorosulfonic acid ionomer powder (3M EW800) and add it to a mixed solution of 8.00g of isopropanol and water (mixing ratio of 6:4). Stir magnetically at room temperature for 3 days. After mixing evenly, sonicate for 10 minutes and refrigerate in a refrigerator for 3 days to obtain a solution of perfluorosulfonic acid dispersion B. The solid content of perfluorosulfonic acid dispersion B is 15wt%.

[0080] S3. Preparation of catalyst slurry: Weigh 3.46g of 50% Pt / C catalyst and disperse it in 18.75g of deionized water. Then, add 1.56g of colloidal perfluorosulfonic acid ionomer dispersion A, 4.85g of perfluorosulfonic acid ionomer dispersion B, and 1.38g of n-propanol and stir. After initial uniform dispersion, process it in a high-speed shear machine at 10,000 rpm for 30 minutes to obtain the final catalyst slurry.

[0081] S4. The catalyst slurry prepared in step S4 is coated onto one side of the proton exchange membrane using a slit-coating method to form a cathode catalyst layer. The Pt loading in the catalyst layer is 0.250 mg / cm³. 2 ;

[0082] Furthermore, this comparative example also provides a fuel cell membrane electrode assembly (MEA), prepared by the following steps: first, an anode catalyst slurry is prepared according to the following steps; 50% Pt / C catalyst is added to deionized water, followed by the above-mentioned perfluorosulfonic acid dispersion B and n-propanol, and dispersed to obtain the anode catalyst slurry. In step S5, the anode catalyst slurry is coated on the other side of the proton exchange membrane to prepare a CCM, wherein the platinum loading of the anode catalyst layer of the CCM is 0.050 mg / cm³. 2 The CCM, border, and gas diffusion layer are combined to form a membrane electrode.

[0083] The membrane electrodes prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to polarization curve testing, and the results are as follows: Figure 1 and Figure 4 As shown.

[0084] Combination Figures 1-3 It is evident that the membrane electrode performance in Example 1 is superior to that in Comparative Example 1. This demonstrates that the method described in this study first uses a gel-like perfluorosulfonic acid ionomer to form a loose perfluorosulfonic acid ionomer layer on the catalyst surface, which reduces oxygen transport resistance. The solution-like perfluorosulfonic acid provides the catalyst layer with excellent mechanical properties and a continuous proton-conducting phase. Compared to conventional catalyst layer preparation methods, this method improves the membrane electrode performance without introducing other substances.

[0085] Figure 4 The voltages (in V) of the membrane electrodes at different current densities in Examples 1-3 and Comparative Examples 1-4 are shown. Figure 5This includes information on the percentage of perfluorosulfonic acid and the curing treatment in Examples 1-3 and Comparative Examples 1-4. Combined with... Figure 4 and Figure 5 It is evident that the membrane electrode performance of Examples 1 to 3 is superior to that of Comparative Examples 1-4. This demonstrates that in this scheme, both gel-like and solution-like perfluorosulfonic acid ionomer dispersions are used to modify the catalyst, and that constructing the gel-like perfluorosulfonic acid ionomer layer first, followed by the solution-like layer, is necessary to improve membrane electrode performance. Furthermore, the test results of Examples 1 and 4 show that curing the first perfluorosulfonic acid layer to prevent its destruction during subsequent dispersion is beneficial for improving membrane electrode performance.

[0086] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a catalyst layer for a fuel cell, characterized in that, Includes the following steps: S1. Mix the perfluorosulfonic acid ionomer and the low-polarity dispersion solvent A, and disperse to obtain perfluorosulfonic acid dispersion A; S2. Mix the perfluorosulfonic acid ionomer and the highly polar dispersion solvent B, and disperse to obtain perfluorosulfonic acid dispersion B; S3. Mix the catalyst and perfluorosulfonic acid dispersion A, disperse and solidify to prepare ionomer-modified catalyst powder; mix the ionomer-modified catalyst powder with perfluorosulfonic acid dispersion B and disperse to obtain catalyst slurry. S4. Coat the catalyst slurry obtained in step S3 onto a proton exchange membrane to obtain a coated catalyst layer; In step S1, the mass of the perfluorosulfonic acid ionomer is 10-40% of the mass of the perfluorosulfonic acid ionomer in the catalyst slurry in step S3. The dispersing solvent A is one or more selected from glycerol, cyclohexanol, N-methylpyrrolidone, and butyl acetate; the dispersing solvent B is one or more selected from water, ethanol, isopropanol, and n-propanol. The solid content of the perfluorosulfonic acid dispersion A is 10-30 wt%; the solid content of the perfluorosulfonic acid dispersion B is 5-20 wt%.

2. The method for preparing the fuel cell catalyst layer according to claim 1, characterized in that, Step S3 specifically involves: first, mixing perfluorosulfonic acid dispersion A and the catalyst, and dispersing them under low temperature conditions to obtain a pre-catalyst slurry; vacuum drying, cooling, and grinding the pre-catalyst slurry to obtain ionomer-modified catalyst powder; then, sequentially mixing the ionomer-modified catalyst powder, perfluorosulfonic acid dispersion B, and dispersion solvent C, and dispersing them under low temperature conditions to obtain the final catalyst slurry; the temperature of the low-temperature environment is no more than 15°C.

3. The method for preparing the fuel cell catalyst layer according to claim 2, characterized in that, The average particle size of the catalyst in the prepared catalyst slurry ranges from 1 to 3 μm; the average particle size of the catalyst in the catalyst slurry ranges from 1 to 3 μm.

4. The method for preparing the fuel cell catalyst layer according to claim 2, characterized in that, The method for heating and drying the prepared catalyst slurry is vacuum baking, with a heating and drying temperature range of 60~160℃ and a heating and drying time of 30~60min.

5. The method for preparing the fuel cell catalyst layer according to claim 1, characterized in that, It also includes refrigeration treatment, specifically, after dispersion as described in steps S1 and S2, refrigeration is carried out at 0℃~15℃ for two to four days.

6. The method for preparing the catalyst layer of a fuel cell according to claim 1, characterized in that, In steps S1 and S2, the dispersion specifically involves stirring followed by ultrasonic treatment, with the stirring time being two to four days and the ultrasonic treatment time being 5 to 10 minutes.

7. A catalyst layer for a fuel cell, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 6.

8. The application of the catalyst layer as described in claim 7 in a proton exchange membrane fuel cell.

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