A method for preparing a fuel cell membrane electrode catalyst slurry by ultrasonic spraying

Abstract

The application discloses a kind of fuel cell membrane electrode catalyst slurry preparation methods prepared by ultrasonic spraying method, comprising the following steps: step S1: a certain mass of isopropyl alcohol solution is added to perfluorosulfonic acid resin solution, ultrasonic dispersion is obtained perfluorosulfonic acid resin dispersion liquid;Step S2: platinum carbon catalyst is weighed in reagent bottle, and N2 is purged to replace air;Step S3: under ice water bath, perfluorosulfonic acid resin solution is added dropwise to catalyst, and mixture 1 is obtained by ultrasonic oscillation, glass rod stirring, the application relates to the technical field of catalyst slurry preparation, the beneficial effect of the application is, the perfluorosulfonic acid resin solution is pre-dispersed, isopropyl alcohol can promote perfluorosulfonic acid resin uniform dispersion, so that it is more evenly attached to the surface of catalyst, and the agglomeration degree of catalyst particles in slurry is reduced, and then more active sites can be formed.

Description

Technical Field

[0001] This invention relates to the field of catalyst slurry preparation, and in particular to a method for preparing fuel cell membrane electrode catalyst slurry by ultrasonic spraying. Background Technology

[0002] Energy is an indispensable resource for economic and social development. With ever-increasing energy demand and a shortage of fossil fuels, my country advocates a green and low-carbon lifestyle and vigorously develops renewable energy. Hydrogen energy is currently considered the most promising renewable energy source, possessing advantages such as high calorific value, no pollution, abundant resources, and high energy conversion efficiency. In the utilization of hydrogen energy, the proton exchange membrane fuel cell (PEMFC) is the most critical energy conversion device. The catalyst layer (CL) is considered the most critical and complex part of the PEMFC because electrochemical reactions, proton transfer, charge transfer, reactant gas diffusion, and liquid water transport all occur simultaneously within the catalyst layer. The catalyst layer mainly consists of a catalyst, solvent, and binder. The catalyst accelerates the electrochemical reaction, the solvent uniformly disperses the catalyst, and the binder enhances the contact area between the catalyst layer and the proton exchange membrane. Currently, the most mature and commonly used catalyst is platinum-carbon (Pt / C) catalyst, the most commonly used binder is ionomer perfluorosulfonic acid resin, and the most commonly used solvents are isopropanol (IPA) / H2O and n-propanol (NPA) / H2O mixtures. The content of precious metals, the type of organic solvent, the water content in the solvent, the solid content in the slurry, and the dispersion method all affect the activity and durability of CL. Furthermore, during the spraying process, solvent evaporation causes Pt / C particles to agglomerate, making the catalyst layer prone to cracking. Therefore, how to prepare catalyst slurries with excellent electrochemical performance is a technical problem that needs to be solved by those skilled in the art.

[0003] This invention regulates the solid content and dispersion effect of the catalyst slurry by optimizing its composition, the order of addition, the introduction of high-boiling-point organic alcohols, and the dispersion process. The resulting catalyst slurry exhibits uniform dispersion, a smooth catalyst layer free of cracks, and improved mass transfer efficiency. This catalyst slurry is suitable for preparing membrane electrodes using ultrasonic spraying, yielding membrane electrodes with good performance and saving preparation time.

[0004] Patent application number 202111364434.6 discloses a method for preparing a catalyst slurry for transfer printing technology. The slurry consists of a catalyst, water, a perfluorosulfonic acid resin solution, and an organic alcohol. The slurry preparation steps include: dispersing the catalyst and ion exchange resin A1 in solvent A2 to prepare a mixture A; dispersing ion exchange resin B1 in solvent B2 to prepare a mixture B; and adding mixture B to mixture A to form the catalyst slurry. This slurry reduces water flooding of the catalyst layer and facilitates gas transport. However, the patent directly disperses the catalyst and perfluorosulfonic acid resin solution in the organic alcohol solution. This order of addition can lead to a violent reaction where the solvent in the perfluorosulfonic acid resin solution directly contacts the catalyst powder, potentially causing combustion. Furthermore, the slurry does not employ a dispersion method, resulting in uneven dispersion and a tendency to agglomerate. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems by designing a method for preparing fuel cell membrane electrode catalyst slurry using ultrasonic spraying.

[0006] The technical solution of the present invention to achieve the above objectives is a method for preparing fuel cell membrane electrode catalyst slurry by ultrasonic spraying, comprising the following steps:

[0007] Step S1: Add a certain mass of isopropanol solution to the perfluorosulfonic acid resin solution, and disperse by ultrasonication to obtain a perfluorosulfonic acid resin dispersion.

[0008] Step S2: Weigh the platinum-carbon catalyst into a reagent bottle and purge it with N2 to displace the air;

[0009] Step S3: Under ice-water bath, add perfluorosulfonic acid resin solution dropwise to the catalyst, and then stir with an ultrasonic oscillation and a glass rod to obtain mixture 1;

[0010] Step S4: Add a certain mass of double-distilled water, and disperse by ultrasonication to obtain mixture 2;

[0011] Step S5: Add a certain mass of isopropanol, disperse by ultrasonication, and obtain mixture 3;

[0012] Step S6: Add a certain mass of propylene glycol, and disperse by ultrasonication to obtain mixture 4;

[0013] Step S7: Stir the mixture using a high-speed homogenizer at a certain rotation speed to obtain a catalyst slurry;

[0014] Step S8: Solid content detection of slurry. Use a micropipette to accurately measure 2 mL of slurry into a water evaporator, read the initial and final mass of the slurry, and calculate the solid content.

[0015] Step S9: Spray the catalyst slurry onto both sides of the proton exchange membrane and prepare a single cell to test its performance.

[0016] The perfluorosulfonic acid resin mentioned in step S1 is one or more of Nafion, Aquivion, and Fumion.

[0017] The platinum content in the platinum-carbon catalyst in step S2 is 20-70%.

[0018] In step S6, the mass of propylene glycol accounts for 1 to 10 wt% of the total solvent mass.

[0019] In step S7, the high-speed homogenization dispersion speed is 10000–15000 r / min, the temperature is 0–15℃, and the time is 10–60 min.

[0020] The solid content of the catalyst slurry in step S8 is 1-5 wt%.

[0021] The mass ratio of the organic alcohol solvent to water is (0.5-5):1.

[0022] The ultrasonic cleaner has a total output power of 500 W, an ultrasonic power range of 40%–100%, an ultrasonic time of 1–60 min, and an ultrasonic water bath temperature of 0–15℃.

[0023] The solvent is one or more of water, n-propanol, isopropanol, ethanol, ethylene glycol, propylene glycol, and glycerol.

[0024] This invention discloses a method for preparing fuel cell membrane electrode catalyst slurry using ultrasonic spraying. The invention pre-disperses the perfluorosulfonic acid resin solution. Isopropanol promotes uniform dispersion of the perfluorosulfonic acid resin, allowing it to adhere more evenly to the catalyst surface and reducing catalyst particle agglomeration in the slurry, thereby forming more active sites. The invention adjusts the order of adding the catalyst slurry components: first, the catalyst is purged with inert gas to remove air; then, a Nafion solution diluted with isopropanol is added dropwise; followed by the addition of double-distilled water and an organic solvent. This addition method further avoids the combustion of solvents in the ionomer under air conditions, ensuring high safety. It also effectively reduces catalyst slurry agglomeration, resulting in a more uniform catalyst layer. The organic alcohol solvent can uniformly disperse the catalyst slurry, and the water content in the solvent can affect the solvent evaporation rate. By adjusting the ratio of alcohol to water, this invention can reduce catalyst particle agglomeration during spraying, thereby improving Pt utilization. Furthermore, the addition of the high-boiling-point solvent propylene glycol can effectively improve the smoothness of the catalyst layer and reduce defects such as cracks and mottles. Strong ultrasonic dispersion and excessively long ultrasonic dispersion times can lead to the ablation and dissolution of platinum nanoparticles and the degradation of perfluorosulfonic acid resin solution, thereby reducing the electrochemically active surface area and catalytic performance. This invention reduces ultrasonic power and time, and uses a high-speed homogenizer to disperse the slurry, achieving more uniform dispersion without damaging the catalyst structure. In addition, it saves catalyst slurry preparation time. Excessive solid content will create significant resistance to the uniform dispersion of the catalyst slurry during ultrasonic spraying and clog the nozzle. This invention optimizes the solid content of the slurry, thereby controlling the degree of dispersion of the catalyst slurry, allowing it to be uniformly sprayed onto both sides of the proton exchange membrane. By controlling the water bath temperature during homogenization, solvent evaporation is reduced, solid content is controlled, and slurry loss is minimized. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of a method for preparing fuel cell membrane electrode catalyst slurry by ultrasonic spraying, as described in this invention.

[0026] Figure 2 This is the MEA performance curve of Example 5 of the method for preparing fuel cell membrane electrode catalyst slurry by ultrasonic spraying according to the present invention. Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings, such as... Figure 1-2 As shown, a method for preparing fuel cell membrane electrode catalyst slurry using ultrasonic spraying is disclosed. Example

[0028] 1. Weigh 5 g of platinum-carbon catalyst (70 wt%, Johnson Matthey) into a reagent bottle and purge with N2 for 10 min;

[0029] 2. Under ice-water bath conditions, add 21 g of Nafion solution (5 wt%, D520) dropwise, stir with a glass rod, and sonicate for 10 min to obtain mixture 2;

[0030] 3. Add 26 g of double-distilled water, ultrasonically vibrate at room temperature for 10 min with an ultrasonic power of 500 W to obtain mixture 2;

[0031] 4. Add 41.5 g of isopropanol, ultrasonically vibrate at 500 W for 10 min at room temperature to obtain mixture 3;

[0032] 5. The catalyst slurry was obtained by ultrasonic treatment at room temperature for 10 min and magnetic stirring for 30 min.

[0033] 6. Solid content detection of slurry: Use a micropipette to accurately measure 2 mL of slurry into a water evaporator, read the initial and final mass of the slurry, and calculate the solid content;

[0034] 7. Spray the catalyst slurry onto both sides of the proton exchange membrane and prepare a single cell to test its performance. Example

[0035] 1. Weigh 21 g of Nafion solution (5 wt%, D520), add 15.5 g of isopropanol solution to it, and ultrasonically disperse for 5 min to obtain a perfluorosulfonic acid resin dispersion.

[0036] 2. Weigh 5 g of platinum-carbon catalyst (70 wt%, Johnson Matthey) into a reagent bottle and purge with N2 for 10 min;

[0037] 3. Under ice-water bath, add Nafion dispersion dropwise, stir with a glass rod until gel-like, sonicate at 500 W for 10 min to obtain mixture 1;

[0038] 4. Add 26 g of double-distilled water, ultrasonically vibrate at room temperature for 10 min with an ultrasonic power of 500 W to obtain mixture 2;

[0039] 5. Add 26 g of isopropanol, ultrasonically vibrate at 500 W for 10 min at room temperature to obtain mixture 3;

[0040] 6. The catalyst slurry was obtained by ultrasonic treatment at room temperature for 10 min and magnetic stirring for 30 min.

[0041] 7. Solid content detection of slurry: Use a micropipette to accurately measure 2 mL of slurry into a water evaporator, read the initial and final mass of the slurry, and calculate the solid content;

[0042] 8. The catalyst slurry was sprayed onto both sides of the proton exchange membrane and a single cell was made to test its performance. Example

[0043] 1. Weigh 21 g of Nafion solution (5 wt%, D520), add 15.5 g of isopropanol solution to it, and ultrasonically disperse for 5 min to obtain a perfluorosulfonic acid resin dispersion.

[0044] 2. Weigh 5 g of platinum-carbon catalyst (70 wt%, Johnson Matthey) into a reagent bottle and purge with N2 for 10 min;

[0045] 3. Under ice-water bath, add Nafion dispersion dropwise, stir with a glass rod until gel-like, sonicate at 500 W for 10 min to obtain mixture 1;

[0046] 4. Add 31.5 g of double-distilled water, ultrasonically vibrate at room temperature for 10 min with an ultrasonic power of 500 W to obtain mixture 2;

[0047] 5. Add 46 g of isopropanol, ultrasonically vibrate at room temperature for 10 min with an ultrasonic power of 500 W to obtain mixture 3;

[0048] 5. Add 4.65 g of propylene glycol, ultrasonically vibrate at room temperature for 10 min with an ultrasonic power of 500 W to obtain mixture 4;

[0049] 6. The catalyst slurry was obtained by ultrasonic treatment at room temperature for 10 min and magnetic stirring for 30 min.

[0050] 7. Solid content detection of slurry: Use a micropipette to accurately measure 2 mL of slurry into a water evaporator, read the initial and final mass of the slurry, and calculate the solid content;

[0051] 8. The catalyst slurry was sprayed onto both sides of the proton exchange membrane and a single cell was made to test its performance. Example

[0052] 1. Weigh 21 g of Nafion solution (5 wt%, D520), add 15.5 g of isopropanol solution to it, and ultrasonically disperse for 5 min to obtain a perfluorosulfonic acid resin dispersion.

[0053] 2. Weigh 5 g of platinum-carbon catalyst (70 wt%, Johnson Matthey) into a reagent bottle and purge with N2 for 10 min;

[0054] 3. Under ice-water bath, add Nafion dispersion dropwise, stir with a glass rod until gel-like, sonicate at 300 W for 5 min to obtain mixture 1;

[0055] 4. Add 31.5 g of double-distilled water, ultrasonically vibrate at room temperature for 5 min with an ultrasonic power of 300 W to obtain mixture 2;

[0056] 5. Add 46 g of isopropanol, ultrasonically vibrate at room temperature for 5 min with an ultrasonic power of 300 W to obtain mixture 3;

[0057] 6. Add 4.65 g of propylene glycol, ultrasonically vibrate at room temperature for 5 min with an ultrasonic power of 300 W to obtain mixture 4;

[0058] 7. Stir the mixture at room temperature using a high-speed homogenizer at a speed of 15,000 rpm for 30 minutes to obtain the catalyst slurry.

[0059] 8. Solid content detection of slurry: Use a micropipette to accurately measure 2 mL of slurry into a water evaporator, read the initial and final mass of the slurry, and calculate the solid content;

[0060] 9. The catalyst slurry was sprayed onto both sides of the proton exchange membrane and a single cell was made to test its performance. Example

[0061] 1. Weigh 18 g of Nafion solution (5 wt%, D520), add 15.5 g of isopropanol solution to it, and ultrasonically disperse for 5 min to obtain a perfluorosulfonic acid resin dispersion.

[0062] 2. Weigh 5 g of platinum-carbon catalyst (70 wt%, Johnson Matthey) into a reagent bottle and purge with N2 for 10 min;

[0063] 3. Under ice-water bath, add Nafion dispersion dropwise, stir with a glass rod until gel-like, sonicate at 300 W for 5 min to obtain mixture 1;

[0064] 4. Add 31.5 g of double-distilled water, ultrasonic power 300 W, ultrasonic oscillation for 5 min, ultrasonic water bath temperature 0~15℃, to obtain mixture 2;

[0065] 5. Add 46 g of isopropanol, ultrasonic power 300 W, ultrasonic oscillation for 5 min, ultrasonic water bath temperature 0-15℃, to obtain mixture 3;

[0066] 6. Add 4.65 g of propylene glycol, ultrasonic power 300 W, ultrasonic oscillation for 5 min, ultrasonic water bath temperature 0-15℃, to obtain mixture 4;

[0067] 7. Stir using a high-speed homogenizer at a speed of 15,000 rpm for 30 min, with a water bath temperature of 0–15°C to obtain the catalyst slurry.

[0068] 8. Solid content detection of slurry: Use a micropipette to accurately measure 2 mL of slurry into a water evaporator, read the initial and final mass of the slurry, and calculate the solid content;

[0069] 9. The catalyst slurry was sprayed onto both sides of the proton exchange membrane and a single cell was made to test its performance.

[0070] As shown in Example 5, the membrane electrode assembly prepared in the embodiments of the present invention achieves a performance of 200 mA / cm². 2 The voltage can reach 0.812V at 800 mA / cm². 2 The voltage can reach 0.726 V at 1600 mA / cm². 2 The voltage can reach 0.593 V. Therefore, the catalyst slurry described in this invention is suitable for preparing membrane electrodes using ultrasonic spraying, and the resulting membrane electrodes exhibit excellent performance.

[0071] In this implementation plan:

[0072] 1. In this invention, the perfluorosulfonic acid resin solution is pre-dispersed. Isopropanol can promote the uniform dispersion of the perfluorosulfonic acid resin, making it adhere more evenly to the catalyst surface and reducing the agglomeration of catalyst particles in the slurry, thereby forming more active sites.

[0073] 2. This invention, by adding the high-boiling-point solvent propylene glycol, can effectively improve the smoothness of the catalyst layer and reduce defects such as cracks and mottles. Furthermore, by adjusting the ratio of alcohol to water, catalyst particle agglomeration can be reduced during spraying, thereby improving the utilization rate of Pt. The prepared catalyst layer has high smoothness and is free of defects such as cracks and mottles.

[0074] 3. This invention reduces ultrasonic power and time, and uses a high-speed homogenizing disperser to disperse the slurry, resulting in more uniform slurry dispersion without damaging the catalyst structure. Furthermore, it saves time in catalyst slurry preparation.

[0075] 4. This invention optimizes the solid content of the slurry, thereby controlling the dispersion of the catalyst slurry and enabling it to be uniformly sprayed onto both sides of the proton exchange membrane. Furthermore, by controlling the water bath temperature during the homogenization process, solvent evaporation is reduced, solid content is controlled, and slurry loss is minimized.

[0076] The above technical solutions only embody the preferred technical solutions of the present invention. Any modifications that may be made by those skilled in the art to certain parts thereof embody the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing fuel cell membrane electrode catalyst slurry by ultrasonic spraying, characterized in that, Includes the following steps: Step S1: Add a certain mass of isopropanol solution to the perfluorosulfonic acid resin solution, and disperse by ultrasonication to obtain a perfluorosulfonic acid resin dispersion. Step S2: Weigh the platinum-carbon catalyst into a reagent bottle and purge it with N2 to displace the air; Step S3: Under ice-water bath, add perfluorosulfonic acid resin dispersion dropwise to the catalyst, and then stir with an ultrasonic oscillation and a glass rod to obtain mixture 1; Step S4: Add a certain mass of double-distilled water, and disperse by ultrasonication to obtain mixture 2; Step S5: Add a certain mass of isopropanol, disperse by ultrasonication, and obtain mixture 3; Step S6: Add a certain mass of propylene glycol, and disperse by ultrasonication to obtain mixture 4; Step S7: Stir the mixture using a high-speed homogenizer at a certain rotation speed to obtain a catalyst slurry; Step S8: Solid content detection of slurry. Use a micropipette to accurately measure 2 mL of slurry into a water evaporator, read the initial and final mass of the slurry, and calculate the solid content. Step S9: Spray the catalyst slurry onto both sides of the proton exchange membrane and prepare a single cell to test its performance; In step S6, the mass of propylene glycol accounts for 1 to 10 wt% of the total solvent mass. In step S7, the high-speed homogeneous dispersion speed is 10000-15000 r / min, the temperature is 0-15℃, and the time is 10-60 min. The solid content of the catalyst slurry in step S8 is 1-5 wt%; The mass ratio of isopropanol and propylene glycol to water is (0.5-5):1; The ultrasonic cleaner has a total output power of 500 W, an ultrasonic power range of 40% to 100%, an ultrasonic time of 1 to 60 minutes, and an ultrasonic water bath temperature of 0 to 15℃.

2. The method for preparing fuel cell membrane electrode catalyst slurry by ultrasonic spraying according to claim 1, characterized in that, The perfluorosulfonic acid resin mentioned in step S1 is one or more of Nafion, Aquivion, and Fumion.

3. The method for preparing fuel cell membrane electrode catalyst slurry by ultrasonic spraying according to claim 1, characterized in that, The platinum content in the platinum-carbon catalyst in step S2 is 20-70%.

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