A method for preparing a membrane electrode coating slurry for hydrogen fuel cells.

Abstract

This invention belongs to the field of hydrogen fuel cell technology, specifically relating to a method for preparing a hydrogen fuel cell membrane electrode coating slurry. The preparation method includes: mixing water and alcohol to obtain a first water-alcohol solution; mixing a catalyst with water to obtain a catalyst aqueous solution and pre-dispersing it; pouring the first water-alcohol solution into the catalyst aqueous solution to obtain a catalyst pre-dispersed solution and pre-dispersing it; mixing water and alcohol to obtain a second water-alcohol solution and pre-dispersing it; pouring a Nafion solution into the second water-alcohol solution to obtain a Nafion pre-dispersed solution; mixing the catalyst pre-dispersed solution and the Nafion pre-dispersed solution, and homogenizing at high speed to obtain the hydrogen fuel cell membrane electrode coating slurry. Compared with existing methods, this invention can significantly reduce Nafion agglomeration, making it more uniformly dispersed, thereby improving membrane electrode performance.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen fuel cell technology, and specifically relates to a method for preparing a slurry for spraying hydrogen fuel cell membrane electrode assemblies. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Hydrogen fuel cell technology is a technology that directly converts the chemical energy of hydrogen into electrical energy through a catalytic reaction process. It offers many advantages, including safety, high efficiency, environmental friendliness, and quiet operation. This process is achieved through single hydrogen fuel cell cells or stacks, with stacks consisting of numerous cells connected in series. A single hydrogen fuel cell, composed of components such as a membrane electrode assembly (MEA), a gas diffusion layer, and electrode plates, is a crucial energy conversion device in a hydrogen fuel cell. Membrane electrode assembly (MEA) fabrication technology is one of the most important technologies for hydrogen fuel cells.

[0004] Common membrane electrode assembly (MEA) fabrication techniques include blade coating, thermal transfer printing, and spray coating. Different catalyst slurry preparation methods correspond to different MEA fabrication methods. Spray coating requires slurries with lower solids content compared to other methods, meaning that more dispersant is needed. Common dispersants for spray coating are mixtures of water and alcohol in varying proportions, with alcohol typically referring to ethanol, isopropanol, or n-propanol. Common slurry dispersion methods include magnetic stirring, ultrasonic dispersion, high-speed shear dispersion, high-intensity stirring, ball milling, and combinations of these methods. During slurry preparation, it is crucial not only to uniformly disperse the catalyst particles but also to prevent the aggregation of the ionic polymer Nafion. Traditional dispersion methods and slurry formulations often emphasize the universality of slurry ratios and dispersion methods. However, universal methods cannot account for the changes in the state of Nafion during slurry preparation, leading to slurry instability, sedimentation, and aggregation. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing a spray coating slurry for hydrogen fuel cell membrane electrode assemblies (MEAs). The method provided by this invention addresses the characteristics of the slurry required for MEA preparation via spray coating, and, combined with the composition of the Nafion solution, ensures that the state of the ionic polymers in the Nafion solution remains unchanged during slurry preparation. This effectively prevents Nafion agglomeration and standardizes the slurry preparation process, further avoiding the impact of random factors on slurry consistency, thereby reducing the risk of poor MEA consistency from the outset.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a spray slurry for a hydrogen fuel cell membrane electrode assembly, such as... Figure 1 As shown, it includes the following steps:

[0008] S1. Mix water and alcohol to obtain a first aqueous alcohol solution;

[0009] S2. Mix the catalyst with water to obtain an aqueous catalyst solution and pre-disperse it;

[0010] S3. Pour the first aqueous alcohol solution into the catalyst aqueous solution to obtain a catalyst pre-dispersion solution, and perform pre-dispersion.

[0011] S4. Mix water and alcohol to obtain a second aqueous alcohol solution and pre-disperse it;

[0012] S5. Pour the Nafion solution into the second aqueous alcohol solution to obtain the Nafion pre-dispersed solution;

[0013] S6. The catalyst pre-dispersion solution and Nafion pre-dispersion solution are mixed and homogenized at high speed to obtain the hydrogen fuel cell membrane electrode coating slurry.

[0014] Preferably, the Nafion aqueous solution has a solid content of 1-15%, and the solvent is a mixed solution of water and alcohol in a mass ratio of 1:0.8-1.2, wherein the alcohol includes at least one of isopropanol, ethanol and n-propanol.

[0015] More preferably, in steps S1 and S4, the alcohol is the same as the alcohol used in the Nafion solution solvent.

[0016] Preferably, the mass ratio of water to alcohol in the first aqueous alcohol solution is 1:1.9 to 2.1, and the mass ratio of water in the first aqueous alcohol solution to water in the catalyst aqueous solution is 1:0.9 to 1.1.

[0017] Preferably, in steps S2 and S4, the pre-dispersion process is ultrasonic for 50-70 seconds.

[0018] Preferably, the mass ratio of water to alcohol in the second aqueous alcohol solution is 1:0.9 to 1.1.

[0019] Preferably, the mass ratio of Nafion solution to second aqueous alcohol solution is 1 to 10:1.

[0020] Preferably, in step S3, the pre-dispersion process involves ultrasonication for 50–70 seconds, followed by high-speed homogenization.

[0021] Further preferred, the high-speed homogenization is a sealed process, with a time of 5 to 20 minutes, a rotation speed of 9000 to 11000 rpm, and defoaming for 2 to 5 minutes.

[0022] In a second aspect, the present invention provides a hydrogen fuel cell membrane electrode coating slurry, which is obtained by the preparation method described in the first aspect.

[0023] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0024] 1. The catalyst was pre-dispersed by ultrasound in water and water-alcohol solution, and then high-speed homogenization was performed. This process not only improved the dispersion efficiency, but also improved the stability of the slurry dispersion.

[0025] 2. By controlling the water-to-alcohol ratio in each step, Nafion is always kept in a solution environment with the same water-to-alcohol ratio as its own solution. This avoids the aggregation of Nafion under different water-to-alcohol ratios, thereby achieving effective dispersion of the slurry.

[0026] 3. By using a closed-loop high-speed homogenization method, air can be prevented from mixing into the slurry, thus reducing the adverse effects of dissolved air on catalyst performance.

[0027] 4. By ultrasonically degassing the water-alcohol mixture in each step, the influence of dissolved gases on the dispersion process can be avoided, thereby improving the stability and consistency of the dispersion slurry.

[0028] 5. By further refining and constraining the components and operations of each step in the slurry preparation process, the preparation process can be further standardized, effectively ensuring the consistency of the slurry.

[0029] 6. By controlling the water-to-alcohol ratio in each step, the membrane electrode prepared from the slurry exhibits a higher power density. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0031] Figure 1 This is a flowchart of the preparation method of the hydrogen fuel cell membrane electrode spraying slurry of the present invention;

[0032] Figure 2 The voltage of the membrane electrode prepared by spraying the slurry prepared in Example 1 and Comparative Example 1 of the present invention under different current intensities;

[0033] Figure 3The power density of the membrane electrode prepared by spraying the slurry prepared in Example 1 and Comparative Example 1 of the present invention under different current intensities. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0035] Implementation Case 1

[0036] In a dispersion cup, 10 ml of water and 20 ml of isopropanol are mixed and sonicated for 1 min to obtain a water-alcohol solution (I). In another dispersion cup, 10 ml of water is added, followed by 1 g of Pt / C catalyst with a platinum content of 50%. The mixture is sonicated for 1 min to remove any small amount of gas dissolved in the water, thus obtaining an ultrasonically dispersed aqueous solution of the Pt / C catalyst. The water-alcohol solution (I) is added to the Pt / C catalyst ultrasonically dispersed aqueous solution, and sonicated for 1 min. Then, high-speed homogenization is performed for 5 min, followed by degassing for 2 min to obtain a pre-dispersed aqueous solution of the Pt / C catalyst. In a clean dispersion cup, 5 ml of water and 5 ml of isopropanol are mixed and sonicated for 1 min. Then, 10 ml of Nafion solution is added and sonicated for 1 min to obtain a Nafion pre-dispersed solution. The Nafion pre-dispersed solution is added to the Pt / C catalyst pre-dispersed aqueous solution, and sonicated for 1 min. Then, high-speed homogenization is performed for 5 min, followed by degassing for 2 min to obtain a Pt / C catalyst slurry.

[0037] Comparison Case 1

[0038] Add 45ml of water, 5ml of isopropanol, 10ml of Nafion, and 1g of Pt / C catalyst with 50% platinum content to a dispersion cup in sequence. Then, homogenize at high speed for 5 minutes and degas for 2 minutes to obtain Pt / C catalyst slurry.

[0039] The Pt / C catalyst slurry from Implementation Case 1 and the Pt / C catalyst slurry from Comparative Case 1 were prepared into six 50cm plates using an ultrasonic spraying method with identical parameters. 2 Membrane electrode assemblies (MEAs) were used, and graphite bipolar plates were assembled into air-cooled fuel cell stacks. Under identical testing conditions, the performance of the fuel cell stacks and MEAs was tested, thereby evaluating the advantages and disadvantages of the two slurry preparation methods.

[0040] The main parameters for evaluating fuel cell stack performance include the monolayer voltage distribution of the membrane electrode and the membrane electrode power density. Monolayer voltage testing of the fuel cell stack is as follows: Figure 2 As shown, the power density is as follows Figure 3 As shown. From Figure 2As can be seen, under the conditions of current intensity of 15A, 20A, 25A, and 30A in the fuel cell stack, the membrane electrode voltage in Example 1 is always higher than that in Comparative Example 1. This indicates that the membrane electrode prepared by the slurry obtained in Example 1 has better performance than that in Comparative Example 1, suggesting that the slurry preparation method of the present invention is more suitable for preparing membrane electrodes by ultrasonic spraying. Figure 3 It can be seen that when the current intensity is 30A, the average power density of the five film electrodes in Implementation Case 1 is about 2.4% higher than that in Comparative Case 1, and can be increased by more than 5%.

[0041] Implementation Case 2

[0042] In a dispersion cup, mix 10 ml of water and 20 ml of ethanol, and sonicate for 1 min to obtain a water-ethanol solution (I). In another dispersion cup, add 10 ml of water and 1 g of Pt / C catalyst with a platinum content of 40%, and sonicate for 1 min to remove any small amount of gas dissolved in the water, thus obtaining an ultrasonically dispersed aqueous solution of the Pt / C catalyst. Add the water-ethanol solution (I) to the ultrasonically dispersed aqueous solution of the Pt / C catalyst, sonicate for 1 min, then homogenize at high speed for 5 min, and degas for 2 min to obtain a pre-dispersed aqueous solution of the Pt / C catalyst. In a clean dispersion cup, mix 5 ml of water and 5 ml of ethanol, sonicate for 1 min, then add 10 ml of Nafion solution, and sonicate for 1 min to obtain a Nafion pre-dispersed solution. Add the Nafion pre-dispersed solution to the pre-dispersed aqueous solution of the Pt / C catalyst, sonicate for 1 min, then homogenize at high speed for 5 min, and degas for 2 min to obtain a Pt / C catalyst slurry.

[0043] Implementation Case 3

[0044] In a dispersion cup, 10 ml of water and 20 ml of n-propanol are mixed and sonicated for 1 min to obtain an aqueous-alcohol solution (I). In another dispersion cup, 10 ml of water is added, followed by 1 g of 50% platinum Pt / C catalyst. The mixture is sonicated for 1 min to remove any small amount of dissolved gas and obtain an ultrasonically dispersed Pt / C catalyst aqueous solution. The aqueous-alcohol solution (I) is added to the Pt / C catalyst ultrasonically dispersed aqueous solution, and sonicated for 1 min. Then, high-speed homogenization is performed for 5 min, followed by degassing for 2 min to obtain a pre-dispersed Pt / C catalyst aqueous solution. In a clean dispersion cup, 5 ml of water and 5 ml of n-propanol are mixed and sonicated for 1 min. Then, 15 ml of Nafion solution is added and sonicated for 1 min to obtain a Nafion pre-dispersed solution. The Nafion pre-dispersed solution is added to the Pt / C catalyst pre-dispersed aqueous solution, and sonicated for 1 min. Then, high-speed homogenization is performed for 5 min, followed by degassing for 2 min to obtain a Pt / C catalyst slurry.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a spray coating slurry for a hydrogen fuel cell membrane electrode assembly, characterized in that, Includes the following steps: S1. Mix water and alcohol to obtain a first aqueous alcohol solution; S2. Mix the catalyst with water to obtain an aqueous catalyst solution and pre-disperse it; S3. Pour the first aqueous alcohol solution into the catalyst aqueous solution to obtain a catalyst pre-dispersion solution, and perform pre-dispersion. S4. Mix water and alcohol to obtain a second aqueous alcohol solution and pre-disperse it; S5. Pour the Nafion solution into the second aqueous alcohol solution to obtain the Nafion pre-dispersed solution; S6. Mix the catalyst pre-dispersion solution with the Nafion pre-dispersion solution and homogenize at high speed to obtain the hydrogen fuel cell membrane electrode coating slurry. The Nafion solution has a solid content of 1-15%, and the solvent is a mixed solution of water and alcohol in a mass ratio of 1:0.8-1.2, wherein the alcohol includes at least one of isopropanol, ethanol and n-propanol; The mass ratio of water to alcohol in the first aqueous alcohol solution is 1:1.9~2.1, and the mass ratio of water in the first aqueous alcohol solution to water in the catalyst aqueous solution is 1:0.9~1.

1. The mass ratio of water to alcohol in the second aqueous alcohol solution is 1:0.9~1.1; The mass ratio of Nafion solution to second aqueous alcohol solution is 1~10:1; In steps S1 and S4, the alcohol is the same alcohol used in the Nafion solution solvent; In steps S2 and S4, the pre-dispersion process involves ultrasonication for 50-70 seconds. In step S3, the pre-dispersion process involves ultrasonication for 50-70 seconds, followed by high-speed homogenization. The high-speed homogenization is a sealed process.

2. The preparation method according to claim 1, characterized in that, The high-speed homogenization time is 5~20 min, the rotation speed is 9000-11000 rpm, and defoaming is performed for 2~5 min.

3. A slurry for spraying membrane electrode assemblies of hydrogen fuel cells, characterized in that, Obtained by the preparation method as described in any one of claims 1-2.

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