Preparation method for catalyst layer slurry, catalyst layer, membrane electrode, and fuel cell

Abstract

A preparation method for a catalyst layer slurry, a catalyst layer, a membrane electrode, and a fuel cell. The preparation method for the catalyst layer slurry comprises: wetting solid catalyst particles, and then mixing the solid catalyst particles with a solvent, to obtain a first mixed solution; adding a perfluorosulfonic acid resin solution into the first mixed solution, to obtain a second mixed solution; adding a dispersing agent into the second mixed solution, and dispersing, to obtain a catalyst layer slurry, the dispersing agent being a dispersing agent having steric hindrance, and able to form a Van der Waals force with the perfluorosulfonic acid resin. Adding a dispersant having steric hindrance during a catalyst layer slurry preparation process can prevent entanglement of Nafion, causing the catalyst particles to be uniformly wrapped by Nafion, thereby obtaining catalyst particles having a good dispersion effect and high dispersion efficiency, and effectively solving the problems of uneven catalyst particle size, reduced active sites, an unreasonable catalyst layer structure, decreased electrochemical performance of a membrane electrode, and low slurry dispersion process efficiency due to catalyst particle agglomeration.

Description

Method for preparing catalytic layer slurry, catalytic layer, membrane electrode, and fuel cell Technical Field

[0001] The present application relates to the technical field of fuel cell catalyst layers, and in particular to a method for preparing a catalyst layer slurry, a catalyst layer, a membrane electrode, and a fuel cell. Background Art

[0002] The membrane electrode is the core component of the proton exchange membrane fuel cell, directly affecting the battery's performance, lifespan, and price. The catalyst layer is the primary site of reactions within the membrane electrode. During battery operation, hydrogen and oxygen undergo hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) in the catalyst layers at the anode and cathode of the membrane electrode, respectively. However, due to the slow kinetics of the oxygen reduction reaction, the cathode catalyst layer becomes a key factor affecting the performance of the membrane electrode.

[0003] The catalytic layer is primarily prepared from a catalytic layer slurry through spraying, direct coating, transfer printing, and other methods. However, the catalyst particles in the catalytic layer slurry are easily agglomerated in the slurry due to van der Waals forces, resulting in active site coating and an irrational pore size distribution in the catalytic layer. Since the dispersion of the catalyst particles in the slurry directly affects the performance of the catalytic layer, agglomerated catalyst particles will ultimately lead to a decline in membrane electrode performance. Currently, high-power, long-duration dispersion processes (ultrasound, shearing, ball milling, etc.) or changes to the slurry solvent system are often used to achieve high dispersion of catalyst particles, but these often produce poor results and are inefficient.

[0004] Summary of the Invention

[0005] The present application provides a method for preparing a catalytic layer slurry, a catalytic layer, a membrane electrode, and a fuel cell to solve the technical problems of poor dispersion and low efficiency of catalyst particles in the catalytic layer slurry in the prior art.

[0006] In a first aspect, the present application provides a method for preparing a catalytic layer slurry, the preparation method comprising:

[0007] Wetting the solid catalyst particles and then mixing them with a solvent to obtain a first mixed solution;

[0008] adding a perfluorosulfonic acid resin solution to the first mixed solution to obtain a second mixed solution;

[0009] adding a dispersant to the second mixed liquid and dispersing the mixture to obtain a catalytic layer slurry;

[0010] The dispersant is a dispersant with steric hindrance and can form van der Waals force with the perfluorosulfonic acid resin.

[0011] Optionally, the dispersant includes a steric hindering group and an organic carbon skeleton, and the steric hindering group includes at least one of the following:

[0012] Benzene ring, five-membered ring and ester group.

[0013] Optionally, the dispersion time is ≥15 min.

[0014] Optionally, the catalyst particles include at least one of the following:

[0015] Pt / C catalyst particles, Pt alloy catalyst particles, non-Pt-based precious metal catalyst particles and non-precious metal catalyst particles.

[0016] Optionally, when the catalyst particles are Pt / C catalyst particles, the mass ratio of the dispersant to the carbon carrier in the Pt / C catalyst particles is 0.5% to 5%.

[0017] Optionally, the solvent includes ethanol and / or isopropanol.

[0018] In a second aspect, the present application provides a catalytic layer, which is prepared from the catalytic layer slurry obtained by the preparation method described in the first aspect.

[0019] In a third aspect, the present application provides a method for preparing the catalytic layer according to the second aspect, the method comprising:

[0020] The catalyst layer slurry obtained by the preparation method described in the first aspect is printed on a proton exchange membrane substrate to obtain a catalyst layer.

[0021] In a fourth aspect, the present application provides a membrane electrode, which includes the catalytic layer described in the second aspect.

[0022] In a fifth aspect, the present application provides a fuel cell comprising the membrane electrode described in the fourth aspect.

[0023] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0024] An embodiment of the present application provides a method for preparing a catalytic layer slurry. During the preparation of the catalytic layer slurry, a dispersant having a steric hindrance group and an organic carbon skeleton is added. The dispersant can utilize its organic carbon skeleton to react with an entangled perfluorosulfonic acid resin solution (Nafion) to form van der Waals forces. At the same time, the large steric hindrance groups contained therein can avoid entanglement between long-chain molecular structures in Nafion, thereby allowing Nafion to evenly wrap the catalyst particles. This allows the catalyst particles to be evenly dispersed, thereby obtaining catalyst particles with good dispersion effect and high dispersion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0027] FIG1 is a schematic flow chart of a method for preparing a catalytic layer slurry provided in an embodiment of the present application;

[0028] FIG2 is a schematic flow chart of a method for preparing a catalytic layer provided in an embodiment of the present application;

[0029] FIG3 is a schematic diagram of the structure of a styrene-maleic anhydride copolymer provided in an embodiment of the present application;

[0030] FIG4 is a schematic diagram of the structure of polyacrylate provided in an embodiment of the present application;

[0031] FIG5 is a schematic diagram of the structure of long-chain alkanols provided in an embodiment of the present application;

[0032] FIG6 is a schematic diagram of the electrochemical performance of the catalytic layers obtained in Examples and Comparative Examples of the present application;

[0033] FIG7 is a schematic diagram of the mechanism of dispersing Nafion with a dispersant provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0035] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0036] The creative thinking of this application is:

[0037] The catalyst particles in the catalytic layer slurry are easily agglomerated in the slurry due to the influence of van der Waals force, resulting in active site coating and unreasonable pore size distribution of the catalytic layer. Since the dispersion state of the catalyst particles in the slurry will directly affect the performance of the catalytic layer, the agglomerated catalyst particles will eventually lead to a decline in the performance of the membrane electrode.

[0038] Nafion is a type of long-chain polymer with sulfonic acid groups (-SO3H) on the side chain. In the catalytic layer slurry, Nafion is wrapped around the surface of the catalyst particles. 2- The charge repulsion of the ) groups prevents catalyst particles from agglomerating, aiding their dispersion and exposing more active sites. However, Nafion's long-chain molecular structure is prone to entanglement, preventing it from evenly coating the catalyst particle surface, ultimately failing to prevent some catalyst particles from agglomerating.

[0039] Therefore, people currently often use high-power, long-term dispersion processes (ultrasound, shearing, ball milling, etc.) or change the slurry solvent system to cooperate with Nafion to achieve high dispersion of catalyst particles, but the effect is often poor and the efficiency is low.

[0040] As shown in FIG1 , an embodiment of the present application provides a method for preparing a catalytic layer slurry, the preparation method comprising:

[0041] S1. Wetting the solid catalyst particles and then mixing with a solvent to obtain a first mixed solution;

[0042] S2. To the first mixed solution was added a perfluorosulfonic acid resin solution to obtain a second mixed solution;

[0043] S3. adding a dispersant to the second mixed solution and dispersing the mixture to obtain a catalytic layer slurry;

[0044] The dispersant is a dispersant that has steric hindrance and can form van der Waals force with the perfluorosulfonic acid resin.

[0045] It should be noted that the equipment used for the dispersion can be a mechanical stirrer, a homogenizer, or a water bath ultrasound.

[0046] In some optional embodiments, the dispersant includes a steric hindering group, and the steric hindering group includes at least one of the following:

[0047] Benzene ring, five-membered ring and ester group.

[0048] In the embodiments of the present application, by limiting the specific types of steric hindering groups in the dispersant, since these groups are all groups with high steric hindrance, they can effectively react with the entangled Nafion in the dispersant, and the entanglement of Nafion can be avoided by utilizing the large steric hindered groups contained therein, so that Nafion can evenly wrap the catalyst particles, so that the catalyst particles can be evenly dispersed.

[0049] In some optional embodiments, the dispersion time is ≥15 min.

[0050] In the embodiments of the present application, the specific time for dispersion is limited so that the dispersant has enough time to react with the entangled Nafion, thereby allowing the Nafion to evenly wrap the catalyst particles, thereby allowing the catalyst particles to be evenly dispersed.

[0051] In some optional embodiments, the catalyst particles include at least one of the following:

[0052] Pt / C catalyst particles, Pt alloy catalyst particles, non-Pt-based precious metal catalyst particles and non-precious metal catalyst particles.

[0053] In the embodiments of the present application, the specific types of catalyst particles are refined to cover most catalysts used in fuel cells, thereby increasing the application scope of the preparation method.

[0054] In some optional embodiments, when the catalyst particles are Pt / C catalyst particles, the mass ratio of the dispersant to the carbon support in the Pt / C catalyst particles is 0.5% to 5%.

[0055] In the embodiments of the present application, on the basis of limiting the specific type of catalyst particles, by limiting the specific amount of dispersant added, the entangled Nafion can be effectively dispersed by the dispersant, so that the Nafion uniformly wraps the catalyst particles, and the catalyst particles can be evenly dispersed, thereby obtaining catalyst particles with good dispersion effect and high dispersion efficiency.

[0056] The mass ratio of the dispersant to the carbon carrier in the Pt / C catalyst particles can be 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, or 5.0%.

[0057] In some optional embodiments, the solvent includes ethanol and / or isopropanol.

[0058] In the embodiments of the present application, the specific type of solvent is limited so that the solid catalyst particles can be wetted to form a uniform mixed solution, which facilitates the subsequent uniform wrapping of the catalyst particles by Nafion, thereby allowing the catalyst particles to be evenly dispersed.

[0059] Based on a general inventive concept, an embodiment of the present application provides a catalytic layer, which is prepared from the catalytic layer slurry obtained by the preparation method.

[0060] The catalytic layer is realized based on the above-mentioned preparation method. The specific steps of the preparation method can refer to the above-mentioned embodiments. Since the catalytic layer adopts part or all of the technical solutions of the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0061] As shown in FIG2 , based on a general inventive concept, an embodiment of the present application provides a method for preparing the catalytic layer, the method comprising:

[0062] S1. Printing the catalytic layer slurry obtained by the preparation method onto a proton exchange membrane substrate to obtain a catalytic layer.

[0063] This method is a method for preparing the above-mentioned catalytic layer. The specific composition of the catalytic layer can refer to the above-mentioned embodiments. Since this method adopts part or all of the technical solutions of the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0064] It should be noted that the printing process can be a spraying process, a direct coating process, or a transfer process.

[0065] Based on a general inventive concept, an embodiment of the present application provides a membrane electrode, which includes the catalytic layer.

[0066] The membrane electrode is realized based on the above-mentioned catalytic layer. The specific composition of the catalytic layer can refer to the above-mentioned embodiment. Since the membrane electrode adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be described one by one here.

[0067] Based on a general inventive concept, an embodiment of the present application provides a fuel cell, which includes the membrane electrode.

[0068] The fuel cell is realized based on the above-mentioned membrane electrode. The specific composition of the membrane electrode can refer to the above-mentioned embodiments. Since the fuel cell adopts part or all of the technical solutions of the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0069] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0070] Example 1

[0071] The preparation process of the catalytic layer is as follows:

[0072] 1. Weigh 0.679 g of Pt / C catalyst particles with a TKK of 47%, add 4.518 g of water to wet the catalyst particles, and then add 20.45 g of isopropanol and mechanically stir to obtain a first mixed solution;

[0073] 2. Add 4.10 g of Nafion solution to the first mixed solution obtained in step 1 and mix with mechanical stirring to obtain a second mixed solution;

[0074] 3. Add 3.9 mg of dispersant (using styrene-maleic anhydride copolymer as shown in Figure 3) to the second mixed solution obtained in step 2, and then use a homogenizer to disperse at 10,000 rpm for 20 minutes to obtain a catalyst layer slurry;

[0075] 4. Add the catalytic layer slurry prepared in step 3 into the spray paint barrel, take a 72×72 mm proton exchange membrane, and spray it on a heating table at 80°C using a spraying method to form a catalytic layer.

[0076] Example 2

[0077] The preparation process of the catalytic layer is as follows:

[0078] 1. Weigh 0.679 g of Pt / C catalyst particles with a TKK of 47%, add 4.518 g of water to wet the catalyst particles, and then add 20.45 g of isopropanol and mechanically stir to obtain a first mixed solution;

[0079] 2. Add 4.10 g of Nafion solution to the first mixed solution obtained in step 1 and mix with mechanical stirring to obtain a second mixed solution;

[0080] 3. Add 9.75 mg of dispersant (using polyacrylate as shown in Figure 4) to the second mixed solution obtained in step 2, and then use a homogenizer to disperse at 10,000 rpm for 20 minutes to obtain a catalyst layer slurry;

[0081] 4. Add the catalytic layer slurry prepared in step 3 into the spray paint barrel, take a 72×72 mm proton exchange membrane, and spray it on a heating table at 80°C using a spraying method to form a catalytic layer.

[0082] Example 3

[0083] The preparation process of the catalytic layer is as follows:

[0084] 1. Weigh 0.679 g of Pt / C catalyst particles with a TKK of 47%, add 4.518 g of water to wet the catalyst particles, and then add 20.45 g of isopropanol and mechanically stir to obtain a first mixed solution;

[0085] 2. Add 4.10 g of Nafion solution to the first mixed solution obtained in step 1 and mix with mechanical stirring to obtain a second mixed solution;

[0086] 3. Add 15.6 mg of dispersant (using styrene-maleic anhydride copolymer as shown in Figure 3) to the second mixed solution obtained in step 2, and then use a homogenizer to disperse at 10,000 rpm for 20 minutes to obtain a catalyst layer slurry;

[0087] 4. Add the catalytic layer slurry prepared in step 3 into the spray paint barrel, take a 72×72 mm proton exchange membrane, and spray it on a heating table at 80°C using a spraying method to form a catalytic layer.

[0088] Comparative Example 1

[0089] Comparing Comparative Example 1 with Example 1, the difference between Comparative Example 1 and Example 1 is:

[0090] Without adding dispersant, the specific preparation process is as follows:

[0091] 1. Weigh 0.679 g of Pt / C catalyst particles with a TKK of 47%, add 4.518 g of water to wet the catalyst particles, and then add 20.45 g of isopropanol and mechanically stir to obtain a mixed solution;

[0092] 2. Add 4.10 g of Nafion solution to the mixed solution obtained in step 1 and mix with mechanical stirring. Use a homogenizer to disperse at 10,000 r / min for 20 min to obtain a catalyst layer slurry;

[0093] 3. Add the catalytic layer slurry prepared in step 2 into the spray paint barrel, take a 72×72 mm proton exchange membrane, and spray it on a heating table at 80°C using a spraying method to form a catalytic layer.

[0094] Comparative Example 2

[0095] Comparing Comparative Example 2 with Example 2, the difference between Comparative Example 2 and Example 2 is:

[0096] Without adding a dispersant with steric hindrance, the specific preparation process is as follows:

[0097] 1. Weigh 0.679 g of Pt / C catalyst particles with a TKK of 47%, add 4.518 g of water to wet the catalyst particles, and then add 20.45 g of isopropanol and mechanically stir to obtain a first mixed solution;

[0098] 2. Add 4.10 g of Nafion solution to the first mixed solution obtained in step 1 and mix with mechanical stirring to obtain a second mixed solution;

[0099] 3. Add 3.9 mg of a dispersant (using a long-chain alkanol structure as shown in FIG5 ) to the second mixed solution obtained in step 2, and then disperse the mixture using a homogenizer at 10,000 rpm for 20 minutes to obtain a catalyst layer slurry;

[0100] 4. Add the catalytic layer slurry prepared in step 3 into the spray paint barrel, take a 72×72 mm proton exchange membrane, and spray it on a heating table at 80°C using a spraying method to form a catalytic layer.

[0101] Related experiments and effect data:

[0102] The catalytic layer slurries prepared in the examples and comparative examples were subjected to nano-particle size analysis to test their particle size distribution. The results are shown in Table 1.

[0103] Table 1 Particle size analysis of the catalytic layer slurry obtained in each embodiment and comparative example

[0104] As shown in Table 1, the addition of dispersants having sterically hindered styrene maleic anhydride copolymer structure and polyacrylate structure in Examples 1-3 can achieve good dispersion of the catalyst particles, and the average particle size and polydispersity index of the catalyst particles are significantly reduced.

[0105] The proton exchange membrane fuel cell catalyst layers prepared in Example 1-2 and Comparative Example 1-2 were made into corresponding 25 cm 2 The membrane electrode was prepared and its electrochemical performance was measured by polarization curve, and the results are shown in Figure 6. As can be seen from Figure 6, Example 1, which has the largest steric hindrance, has the best electrochemical performance due to the more complete dispersion of catalyst particles. Compared with Comparative Example 1 without dispersant, its electrochemical performance at 2000 mA / cm 2 Increased from 0.611V to 0.629V.

[0106] In summary, the embodiment of the present application provides a method for preparing a catalytic layer slurry. In the process of preparing the catalytic layer slurry, a dispersant with steric hindrance is added, as shown in Figure 7, to avoid the entanglement of Nafion, so that the Nafion evenly wraps the catalyst particles, thereby obtaining catalyst particles with good dispersion effect and high dispersion efficiency, and effectively solving the problems of uneven catalyst particle size, reduced active sites, unreasonable catalytic layer structure, decreased electrochemical performance of membrane electrode, and low efficiency of slurry dispersion process caused by catalyst particle agglomeration.

[0107] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0108] In this application, unless otherwise specified, the directional words used, such as "upper" and "lower", refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple.

[0109] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for preparing a catalytic layer slurry, characterized in that: The preparation method comprises: Wetting the solid catalyst particles and then mixing them with a solvent to obtain a first mixed solution; adding a perfluorosulfonic acid resin solution to the first mixed solution to obtain a second mixed solution; adding a dispersant to the second mixed liquid and dispersing the mixture to obtain a catalytic layer slurry; The dispersant is a dispersant with steric hindrance and can form van der Waals force with the perfluorosulfonic acid resin.

2. The preparation method according to claim 1, characterized in that The dispersant includes a steric hindering group and an organic carbon skeleton, and the steric hindering group includes at least one of the following: Benzene ring, five-membered ring and ester group.

3. The preparation method according to claim 1, characterized in that The dispersion time is ≥15 min.

4. The preparation method according to claim 1, characterized in that The catalyst particles include at least one of the following: Pt / C catalyst particles, Pt alloy catalyst particles, non-Pt-based precious metal catalyst particles and non-precious metal catalyst particles.

5. The preparation method according to claim 4, characterized in that When the catalyst particles are Pt / C catalyst particles, the mass ratio of the dispersant to the carbon carrier in the Pt / C catalyst particles is 0.5% to 5%.

6. The preparation method according to claim 1, characterized in that The solvent includes ethanol and / or isopropanol.

7. A catalytic layer, characterized in that: The catalytic layer is prepared by the catalytic layer slurry obtained by the preparation method according to any one of claims 1 to 6.

8. A method for preparing the catalytic layer according to claim 7, characterized in that: The method comprises: The catalyst layer slurry obtained by the preparation method according to any one of claims 1 to 6 is printed on a proton exchange membrane substrate to obtain a catalyst layer.

9. A membrane electrode, characterized in that The membrane electrode comprises the catalytic layer according to claim 7.

10. A fuel cell, characterized in that: The fuel cell comprises the membrane electrode according to claim 9.

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