Catalyst slurry and preparation method thereof

Abstract

The invention relates to catalyst slurry and a preparation method, and belongs to the technical field of fuel cells. The preparation method comprises the following steps: weighing catalyst particles, ultrapure water, perfluorinated sulfonic acid resin and solvent organic alcohol; completely infiltrating the catalyst particles with ultrapure water to obtain a catalyst dispersion liquid; the preparation method comprises the following steps: mixing perfluorinated sulfonic acid resin with normal propyl alcohol to obtain an ionomer-alcohol mixed solution; adding the ionomer-alcohol mixed liquid into the catalyst dispersion liquid to obtain primary dispersion slurry; and transferring the preliminarily dispersed slurry into a ball mill, adding grinding balls, and carrying out ball milling treatment to obtain the catalyst slurry after ball milling is completed. According to the preparation method, the catalyst particles can be better combined with the perfluorinated sulfonic acid resin, the particle size of the obtained catalyst slurry is smaller, when the catalyst slurry forms the catalyst layer, the exposed number of active sites in the catalyst layer can be effectively increased, and then the catalytic activity of the catalyst layer is greatly improved. And a large amount of catalyst slurry can be prepared at one time.

Description

Technical Field

[0001] This invention relates to a catalyst slurry and its preparation method, belonging to the field of fuel cell technology. Background Technology

[0002] In a proton exchange membrane fuel cell (PEMFC), the membrane electrode assembly (MEA) is the core component, serving as the site of electrochemical reactions and determining the overall reaction activity and lifespan. The MEA consists of a proton exchange membrane, anode and cathode catalyst layers, and a gas diffusion layer. The catalyst layer is the direct site of electrochemical reactions, and its performance plays a decisive role in the overall MEA performance. Electrochemical reactions must occur at the interface of protons, electrons, and reactant gases. The number of these three-phase points directly corresponds to the number of active reaction sites; more sites result in higher reaction efficiency. However, the stability of the three-phase interface affects the MEA lifespan.

[0003] The catalyst layer is prepared by coating a catalyst slurry containing Pt / C particles, proton-conducting polymers, and other components. The mixing and dispersion effect of the slurry determines the quality of the three-phase interface. The key influencing factor is the size of the slurry aggregates, which directly affects the degree of exposure of Pt active sites.

[0004] In existing technologies, to ensure uniform mixing of the catalyst slurry, catalyst particles, solvent, and surfactant are typically mixed first, and then stirred to uniformly disperse the catalyst in the solvent to form a catalyst dispersion. Perfluorosulfonic acid resin is then mixed with the solvent, stirred, and added to this catalyst dispersion to prepare the catalyst slurry. Finally, the mixture is transferred to a homogenizer for high-energy dispersion treatment to prepare the catalyst slurry. However, under the dispersion effect of high-energy shear, the interaction between perfluorosulfonic acid resins intensifies, causing drastic changes in the microstructure of the perfluorosulfonic acid resins (such as increased entanglement). The interacting resins easily combine to form large agglomerates with increased particle size. Some catalyst particles cannot bind well with the perfluorosulfonic acid resin, reducing the number of exposed active sites and affecting the catalytic activity of the reaction process. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a catalyst slurry and its preparation method. The catalyst particles can better bond with perfluorosulfonic acid resin, resulting in a smaller particle size in the catalyst slurry. When the catalyst slurry prepared using this dispersion method forms a catalytic layer, it effectively increases the number of exposed active sites in the catalytic layer, thereby significantly improving the catalytic activity of the catalytic layer. Furthermore, this process allows for the one-time preparation of large quantities of catalyst slurry. The technical solution of this invention is as follows: A method for preparing a catalyst slurry, wherein the catalyst slurry has a solid content (including catalyst and solid ionomer) of 10-20%, a Pt content of 20-60%, an I:C (ionomer: carbon support) mass ratio of 0.7-1.4:1, and a water:organic alcohol ratio of 0.8-2:1; wherein the organic alcohol is any one of n-propanol, isopropanol, or ethanol; preferably, the catalyst slurry has a solid content of 15%, a Pt content of 33%, an I:C mass ratio of 1:1, and a water:n-propanol ratio of 1.2:1; The preparation method involves the following steps: (1) Weigh the catalyst particles, ultrapure water, perfluorosulfonic acid resin and solvent n-propanol; (2) The catalyst particles were completely soaked in ultrapure water and stirred evenly to obtain a catalyst dispersion. (3) The perfluorosulfonic acid resin is mixed with n-propanol and stirred until homogeneous to obtain an ionomer-alcohol mixture; (4) Add the ionomer-alcohol mixture obtained in step (3) to the catalyst dispersion obtained in step (2), and stir on a magnetic stirrer for 40 minutes to obtain a preliminary dispersion slurry; (5) Transfer the preliminary dispersion slurry obtained in step (4) to a ball mill, add grinding balls and perform ball milling to obtain catalyst slurry after ball milling; The ball mill operates at a speed of 600-1800 r / min and a running time of 100-180 min. The grinding balls include grinding balls A, B, and C, with a mass ratio of 1:1:1. The particle size of grinding balls A and B is 1-10 mm. The mass ratio of the grinding balls to the initially dispersed slurry is 0.5-2:1.

[0006] Furthermore, the ball mill operates at a speed of 800 r / min for 180 min. Preferably, the particle sizes of grinding balls A, B, and C are 1 mm, 3 mm and 5 mm, 1 mm, 3 mm and 8 mm, or 1 mm, 5 mm and 8 mm, respectively. Preferably, the mass ratio of the grinding balls to the initially dispersed slurry is 2:1.

[0007] The advantages of this invention compared to the prior art are as follows: The heat generated during ball milling in this invention facilitates the diffusion of perfluorosulfonic acid resin within the microporous layer of the catalyst particles, promoting the bonding between the perfluorosulfonic acid resin and the internal catalyst particles. This allows for the full utilization of the Pt active sites within the microporous layer of the carbon support, thereby improving Pt utilization. The ball milling process allows for the control of the average particle size reduction of polymer microclusters, which is beneficial for forming more three-phase interface points and enhancing catalytic activity. This invention enables the preparation of kilogram-scale catalyst slurries, which can be directly applied to mass production. Attached Figure Description

[0008] Figure 1 The surface morphology images are of the catalyst slurry obtained using the present invention and the catalyst slurry obtained in prior art document 1 after coating. Detailed Implementation

[0009] The technical solution of the present invention will be described in detail below through specific embodiments. It should be understood that the following specific embodiments are merely exemplary, and any modifications or changes that do not depart from the technical solution design of the present invention should be within the scope of protection of the claims of the present invention. The present invention will be described in detail below with reference to embodiments.

[0010] Example 1: A catalyst slurry and its preparation method The catalyst slurry contains 15% solids (including catalyst and solid ionomer), 33% Pt, an I:C (ionomer: carbon support) ratio of 1:1, and a water:n-propanol ratio of 1.2:1. The preparation method involves the following steps: (1) Weigh the catalyst particles, ultrapure water, perfluorosulfonic acid resin and solvent n-propanol; (2) The catalyst particles were completely soaked in ultrapure water and stirred evenly to obtain a catalyst dispersion. (3) The perfluorosulfonic acid resin is mixed with n-propanol and stirred until homogeneous to obtain an ionomer-alcohol mixture; (4) Add the ionomer-alcohol mixture obtained in step (3) to the catalyst dispersion obtained in step (2), and stir on a magnetic stirrer for 40 minutes to obtain a preliminary dispersion slurry; (5) Transfer the preliminary dispersion slurry obtained in step (4) to a ball mill, add grinding balls and perform ball milling to obtain catalyst slurry after ball milling; set the ball mill speed to 800 r / min and the running time to 180 min, select grinding balls with particle sizes of 1 mm, 3 mm and 5 mm, the mass ratio of the three particle sizes of grinding balls is 1:1:1, and the mass ratio of grinding balls to catalyst slurry is 2:1.

[0011] Example 2: A catalyst slurry and its preparation method The catalyst slurry contains 11% solids (including catalyst and solid ionomer), 20% Pt, an I:C (ionomer: carbon support) ratio of 0.8:1, and a water:ethanol ratio of 0.8:1. The preparation method involves the following steps: Steps (1)-(4) are the same as in Example 1; (5) Transfer the preliminary dispersion slurry obtained in step (4) to a ball mill, add grinding balls and perform ball milling to obtain catalyst slurry after ball milling; set the ball mill speed to 800 r / min and the running time to 180 min, select grinding balls with particle sizes of 1 mm, 3 mm and 8 mm, the mass ratio of the three particle sizes of grinding balls is 1:1:1, and the mass ratio of grinding balls to catalyst slurry is 2:1.

[0012] Example 3: A catalyst slurry and its preparation method The catalyst slurry contains 20% solids (including catalyst and solid ionomer), 55% Pt, an I:C (ionomer: carbon support) ratio of 1.4:1, and a water:isopropanol ratio of 2:1. The preparation method involves the following steps: Steps (1)-(4) are the same as in Example 1; (5) Transfer the preliminary dispersion slurry obtained in step (4) to a ball mill, add grinding balls and perform ball milling. After ball milling, the catalyst slurry is obtained. Set the ball mill speed to 800 r / min and the running time to 180 min. Select grinding balls with particle sizes of 1 mm, 5 mm and 8 mm. The mass ratio of the three particle sizes of grinding balls is 1:1:1. The mass ratio of grinding balls to catalyst slurry is 2:1.

[0013] Comparative Example 1: The catalyst slurry contained 15% solids (including catalyst and solid ionomer), 33.3% Pt, 1:1 I:C (ionomer: carbon support) mass ratio, and 1.2:1 water:n-propanol. The preparation method involves the following steps: (1) Weigh the catalyst particles, ultrapure water, perfluorosulfonic acid resin and solvent n-propanol; (2) The catalyst particles were completely soaked in ultrapure water and stirred evenly to obtain a catalyst dispersion. (3) The perfluorosulfonic acid resin is mixed with n-propanol and stirred until homogeneous to obtain an ionomer-alcohol mixture; (4) Add the ionomer-alcohol mixture obtained in step (3) to the catalyst dispersion obtained in step (2), and stir on a magnetic stirrer for 40 minutes to obtain a preliminary dispersion slurry; (5) Transfer the preliminary dispersed slurry obtained in step (4) to the Primix homogenizer and perform high-speed shearing treatment. After high-speed shearing, the catalyst slurry is obtained. The Primix homogenizer speed is set to 18000 r / min, the running time is 10 min, and the chiller control the operating temperature to 5℃. Depending on the size of the equipment used, the slurry that can be processed at one time is 30 ml and 400 ml respectively.

[0014] Experiment 1: Particle size measurement The particle size of the catalyst slurry obtained in Examples 1-3 of the present invention and the catalyst slurry obtained in Comparative Document 1 were measured respectively. The results are as follows: the particle size of Example 1 is 0.3 μm, the particle size of Example 2 is 1.6 μm, the particle size of Example 3 is 4 μm, and the particle size of the comparative example is 6 μm.

[0015] Experimental Example 2: Surface Morphology Observation The catalyst slurry obtained using this invention and the catalyst slurry obtained in prior art 1 were coated, and after complete drying, the surface morphology was observed using an electron microscope, such as... Figure 1 As shown. The catalyst slurry prepared in Comparative Example 1 had a large particle size and uneven particle size distribution. During the drying process, the stress released by the large particles caused cracks in the coating. In contrast, the catalyst slurry obtained by this invention had a more uniform particle size and no cracks appeared after coating.

Claims

1. A method for preparing a catalyst slurry, characterized in that, The catalyst slurry has a solid content of 10-20%, a Pt content of 20-60%, an I:C (ionomer:carbon support) mass ratio of 0.7-1.4:1, and a water:organic alcohol ratio of 0.8-2:1; wherein the solid content refers to the weight of the catalyst and the solid ionomer; the organic alcohol is any one of n-propanol, isopropanol, or ethanol; The preparation method involves the following steps: (1) Weigh the catalyst particles, ultrapure water, perfluorosulfonic acid resin and solvent n-propanol; (2) The catalyst particles were completely soaked in ultrapure water and stirred evenly to obtain a catalyst dispersion. (3) The perfluorosulfonic acid resin is mixed with n-propanol and stirred until homogeneous to obtain an ionomer-alcohol mixture; (4) Add the ionomer-alcohol mixture obtained in step (3) to the catalyst dispersion obtained in step (2), and stir on a magnetic stirrer for 40 minutes to obtain a preliminary dispersion slurry; (5) Transfer the preliminary dispersion slurry obtained in step (4) to a ball mill, add grinding balls and perform ball milling to obtain catalyst slurry after ball milling.

2. The preparation method according to claim 1, characterized in that, The catalyst slurry has a solid content of 15%, a Pt content of 33%, an I:C mass ratio of 1:1, and a water:n-propanol ratio of 1.2:

1.

3. The preparation method according to claim 1, characterized in that, The ball mill operates at a speed of 600-1800 r / min and a running time of 100-180 min.

4. The preparation method according to claim 1, characterized in that, The grinding balls include grinding ball A, grinding ball B, and grinding ball C, with a mass ratio of 1:1:1; the particle size of grinding ball A, grinding ball B, and grinding ball C is 1-10 mm.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the grinding balls to the initially dispersed slurry is 0.5-2:

1.

6. The preparation method according to claim 1, characterized in that, The ball mill has a rotational speed of 800 r / min and a running time of 180 min.

7. The preparation method according to claim 3, characterized in that, The particle sizes of grinding balls A, B, and C are 1mm and 3mm and 5mm, 1mm and 3mm and 8mm, or 1mm and 5mm and 8mm, respectively.

8. The preparation method according to claim 5, characterized in that, The mass ratio of the grinding balls to the initially dispersed slurry is 2:

1.

9. The catalyst slurry obtained by the preparation method according to any one of claims 1-8.

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