Low-particle-size catalyst slurry for fuel cell and preparation method of low-particle-size catalyst slurry

Abstract

The invention relates to the technical field of fuel cells, in particular to low-granularity catalyst slurry for a fuel cell and a preparation method of the low-granularity catalyst slurry. The slurry comprises the following components: a catalyst, water, an ionomer and a solvent, wherein the weight ratio of the catalyst to the water to the ionomer to the solvent is 1: (4-10): (1-4): (2-6). Through a specific ball milling dispersion method, catalyst particles can be better combined with the perfluorinated sulfonic acid resin, and the particle size of the obtained catalyst slurry is smaller.

Description

Technical Field

[0001] This invention relates to the technical field of fuel cells, and more specifically, to a low-particle-weight fuel cell catalyst slurry and its preparation method. Background Technology

[0002] The membrane electrode assembly (MEA), as a core component of a proton exchange membrane fuel cell, consists of a proton exchange membrane, anode and cathode catalyst layers, and anode and cathode gas diffusion layers. The design of the catalyst layer directly affects the electrochemical catalytic performance of the MEA. The catalyst layer is formulated with carbon-supported platinum catalyst, polymer binder, additives, and solvents. Different component formulations and preparation processes have a significant impact on the performance of the catalyst layer. Currently, to ensure thorough 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. Next, perfluorosulfonic acid resin is mixed with the solvent, stirred, and added to the catalyst dispersion to prepare the catalyst slurry. Finally, it is transferred to a homogenizer for high-energy dispersion treatment to prepare the catalyst slurry. The resulting slurry has a relatively large particle size, which affects the reaction activity.

[0003] Chinese invention patent application CN114039059A discloses a method for preparing a fuel cell membrane electrode catalyst slurry. The method involves mixing a catalyst, a dispersing solvent, a polymer ionomer, a thickener, and a surfactant in a specific mass ratio to obtain a slurry mixture. The slurry mixture is then subjected to repeated operations in an ultrasonic disperser and a high-shear emulsifier for pre-dispersion, resulting in a pre-dispersion. Finally, the pre-dispersion is dispersed in a high-pressure homogenizer to obtain the catalyst slurry. This invention's homogenization process significantly impacts particle size and polarization. Summary of the Invention

[0004] The first aspect of the present invention provides a low-particle-size catalyst slurry for fuel cells, comprising: catalyst, water, ionomer and solvent, wherein the weight ratio of the catalyst, water, ionomer and solvent is 1:(4-10):(1-4):(2-6).

[0005] Preferably, the weight ratio of the catalyst, water, ionomer and solvent is 1:(4-8):(1-3):(2-5).

[0006] More preferably, the weight ratio of the catalyst, water, ionomer and solvent is 1:(4-8):(1-3):(2-5).

[0007] More preferably, the weight ratio of the catalyst, water, ionomer and solvent is 1:6:2:3.5.

[0008] The average particle size of the catalyst slurry is no higher than 5 micrometers.

[0009] Preferably, the average particle size of the catalyst slurry is 0.2-5 micrometers.

[0010] The catalyst includes Pt / C catalysts and / or PtM / C catalysts.

[0011] Preferably, the catalyst comprises a Pt / C catalyst.

[0012] Preferably, the solid content of the catalyst slurry is 10-40 wt%.

[0013] The ionomer is selected from at least one of perfluorosulfonic acid resin, partially fluorinated sulfonic acid resin, and non-fluorinated sulfonic acid resin.

[0014] Further preferably, the ionomer is selected as a perfluorosulfonic acid resin.

[0015] The solvent includes alcohol solvents.

[0016] Preferably, the solvent includes at least one selected from methanol, ethanol, n-propanol, isopropanol, butanol, pentanol, or hexanol.

[0017] More preferably, the solvent includes n-propanol.

[0018] This study found that the ionomer is selected from at least one of perfluorosulfonic acid resin, partially fluorinated sulfonic acid resin, and non-fluorinated sulfonic acid resin. In particular, selecting perfluorosulfonic acid resin can further improve the catalytic effect, possibly by enhancing the wetting effect of the catalyst. However, excessive ionomer content can also lead to intensified interactions, causing drastic changes in the microstructure of the perfluorosulfonic acid resin. The interacting resins easily combine to form large aggregates, resulting in increased slurry particle size. Some active sites cannot bind well to the perfluorosulfonic acid resin, reducing the number of exposed active sites and affecting the catalytic activity of the reaction process.

[0019] A second aspect of the present invention provides a method for preparing a low-particle-size catalyst slurry for fuel cells, comprising the following steps: S1, the catalyst is mixed with water to obtain a catalyst dispersion; S2, mix the ionomer and solvent evenly to obtain a mixture; S3, add the mixture to the catalyst dispersion and mix evenly to obtain a pre-dispersed catalyst slurry; S4. Mix the pre-dispersed catalyst slurry with grinding balls and ball mill it to obtain the final product.

[0020] The ball mill rotates at a speed of 400-2000 r / min.

[0021] Preferably, the rotational speed of the ball mill is 1000-1500 r / min.

[0022] More preferably, the ball mill rotates at a speed of 1200 r / min.

[0023] The ball milling time is 50-150 minutes.

[0024] Preferably, the ball milling time is 80-120 minutes.

[0025] More preferably, the ball milling time is 90 minutes.

[0026] The grinding balls include grinding balls with a particle size of 0.1-1.5 mm and grinding balls with a particle size of 2-5 mm.

[0027] Preferably, the grinding balls include grinding balls with a particle size of 0.2-1.5 mm and grinding balls with a particle size of 2.5-5 mm.

[0028] More preferably, the grinding balls include grinding balls with a particle size of 0.2-1 mm and grinding balls with a particle size of 2.5-4 mm.

[0029] More preferably, the grinding balls include grinding balls with a particle size of 0.5 mm and grinding balls with a particle size of 3 mm.

[0030] Preferably, the weight ratio of the grinding balls with a particle size of 0.1-1.5 mm to the grinding balls with a particle size of 2-5 mm is 1:(0.5-2).

[0031] More preferably, the weight ratio of the grinding balls with a particle size of 0.1-1.5 mm to the grinding balls with a particle size of 2-5 mm is 1:(0.5-1).

[0032] More preferably, the weight ratio of the grinding balls with a particle size of 0.1-1.5 mm to the grinding balls with a particle size of 2-5 mm is 1:1.

[0033] The mass ratio of the grinding balls to the pre-dispersed catalyst slurry is 2:(0.5-2).

[0034] Preferably, the mass ratio of the grinding balls to the pre-dispersed catalyst slurry is 2:(1-2).

[0035] More preferably, the mass ratio of the grinding balls to the pre-dispersed catalyst slurry is 2:1.

[0036] Further research in this application revealed that using a specific ball milling process can improve the utilization rate of Pt in the catalyst. The heat generated during the ball milling process is conducive to the diffusion of perfluorosulfonic acid resin in the microporous layer inside the catalyst particles, which can promote the bonding between the perfluorosulfonic acid resin and the internal catalyst particles, so that the Pt active sites inside the microporous layer of the carbon support can be fully utilized, thereby improving the utilization rate of Pt.

[0037] Further research revealed that a mass ratio of grinding balls to pre-dispersed catalyst slurry of 2:(0.5-2) can reduce the average particle size of polymer microclusters to 5 micrometers, which is beneficial for forming more three-phase interface points and improving catalytic activity.

[0038] Beneficial effects 1. The catalytic effect can be improved by adjusting the weight ratio of catalyst, water, ionomer and solvent in the catalyst slurry to 1:(4-10):(1-4):(2-6).

[0039] 2. Using a specific ball milling process can improve the utilization rate of Pt in the catalyst while reducing the risk of ionomer agglomeration.

[0040] 3. The mass ratio of grinding balls to pre-dispersed catalyst slurry is 2:(0.5-2), which can reduce the average particle size of polymer microclusters to 5 micrometers.

[0041] 4. Using grinding balls with a particle size of 0.1-1.5mm and a particle size of 2-5mm at a weight ratio of 1:(0.5-2) can improve grinding efficiency and shorten grinding time while reducing the amount of grinding balls used.

[0042] 5. The catalyst slurry preparation method proposed in this invention can achieve kilogram-level catalyst slurry preparation and can be directly applied to mass production. Attached Figure Description

[0043] Figure 1 The polarization curves are for Examples 2, 3, 6 and Comparative Example 1.

[0044] Figure 2 The particle size distributions of Examples 1-6 and Comparative Example 1 are shown.

[0045] Figure 3 The coating effect of the catalyst slurry prepared for Comparative Example 1 was studied.

[0046] Figure 4 The coating effect of the catalyst slurry prepared in Example 3 is shown. Detailed Implementation

[0047] Example 1 A low-particle-size fuel cell catalyst slurry comprises a catalyst, water, an ionomer, and a solvent, wherein the weight ratio of the catalyst, water, ionomer, and solvent is 1:6:2:3.5.

[0048] The catalyst is selected as a Pt / C catalyst; the ionomer is selected as a perfluorosulfonic acid resin; the solvent is selected as n-propanol; and the water is selected as ultrapure water.

[0049] A method for preparing a low-particle-weight catalyst slurry for fuel cells comprises the following steps: S1, the catalyst is mixed with water to obtain a catalyst dispersion; S2, mix the ionomer and solvent evenly to obtain a mixture; S3, add the mixture to the catalyst dispersion and mix for 40 min to obtain the pre-dispersed catalyst slurry; S4. Mix the pre-dispersed catalyst slurry with grinding balls and ball mill it to obtain the final product.

[0050] The ball mill operates at a speed of 1200 r / min and a milling time of 90 min. The grinding balls include grinding balls with a particle size of 0.5 mm and grinding balls with a particle size of 3 mm, and the weight ratio of the grinding balls with a particle size of 0.5 mm to the grinding balls with a particle size of 3 mm is 1:1. The mass ratio of the grinding balls to the pre-dispersed catalyst slurry is 2:1.

[0051] Example 2 A low-particle-size fuel cell catalyst slurry comprises a catalyst, water, an ionomer, and a solvent, wherein the weight ratio of the catalyst, water, ionomer, and solvent is 1:6:2:3.5.

[0052] The catalyst is selected as a Pt / C catalyst; the ionomer is selected as a perfluorosulfonic acid resin; the solvent is selected as n-propanol; and the water is selected as ultrapure water.

[0053] A method for preparing a low-particle-weight catalyst slurry for fuel cells comprises the following steps: S1, the catalyst is mixed with water to obtain a catalyst dispersion; S2, mix the ionomer and solvent evenly to obtain a mixture; S3, add the mixture to the catalyst dispersion and mix for 40 min to obtain the pre-dispersed catalyst slurry; S4. Mix the pre-dispersed catalyst slurry with grinding balls and ball mill it to obtain the final product.

[0054] The ball mill operates at a speed of 1200 r / min and a milling time of 60 min. The grinding balls include grinding balls with a particle size of 0.5 mm and grinding balls with a particle size of 3 mm, and the weight ratio of the grinding balls with a particle size of 0.5 mm to the grinding balls with a particle size of 3 mm is 1:1. The mass ratio of the grinding balls to the pre-dispersed catalyst slurry is 2:1.

[0055] Example 3 A low-particle-size fuel cell catalyst slurry comprises a catalyst, water, an ionomer, and a solvent, wherein the weight ratio of the catalyst, water, ionomer, and solvent is 1:6:2:3.5.

[0056] The catalyst is selected as a Pt / C catalyst; the ionomer is selected as a perfluorosulfonic acid resin; the solvent is selected as n-propanol; and the water is selected as ultrapure water.

[0057] A method for preparing a low-particle-weight catalyst slurry for fuel cells comprises the following steps: S1, the catalyst is mixed with water to obtain a catalyst dispersion; S2, mix the ionomer and solvent evenly to obtain a mixture; S3, add the mixture to the catalyst dispersion and mix for 40 min to obtain the pre-dispersed catalyst slurry; S4. Mix the pre-dispersed catalyst slurry with grinding balls and ball mill it to obtain the final product.

[0058] The ball mill operates at a speed of 800 r / min and a milling time of 90 min. The grinding balls include grinding balls with a particle size of 0.5 mm and grinding balls with a particle size of 3 mm, and the weight ratio of the grinding balls with a particle size of 0.5 mm to the grinding balls with a particle size of 3 mm is 1:1. The mass ratio of the grinding balls to the pre-dispersed catalyst slurry is 2:1.

[0059] Example 4 A low-particle-size fuel cell catalyst slurry comprises a catalyst, water, an ionomer, and a solvent, wherein the weight ratio of the catalyst, water, ionomer, and solvent is 1:6:2:3.5.

[0060] The catalyst is selected as a Pt / C catalyst; the ionomer is selected as a perfluorosulfonic acid resin; the solvent is selected as n-propanol; and the water is selected as ultrapure water.

[0061] A method for preparing a low-particle-weight catalyst slurry for fuel cells comprises the following steps: S1, the catalyst is mixed with water to obtain a catalyst dispersion; S2, mix the ionomer and solvent evenly to obtain a mixture; S3, add the mixture to the catalyst dispersion and mix for 40 min to obtain the pre-dispersed catalyst slurry; S4. Mix the pre-dispersed catalyst slurry with grinding balls and ball mill it to obtain the final product.

[0062] The ball mill operates at a speed of 800 r / min and a milling time of 60 min. The grinding balls include grinding balls with a particle size of 0.5 mm and grinding balls with a particle size of 3 mm, and the weight ratio of the grinding balls with a particle size of 0.5 mm to the grinding balls with a particle size of 3 mm is 1:1. The mass ratio of the grinding balls to the pre-dispersed catalyst slurry is 2:1.

[0063] Example 5 A low-particle-size fuel cell catalyst slurry comprises a catalyst, water, an ionomer, and a solvent, wherein the weight ratio of the catalyst, water, ionomer, and solvent is 1:6:2:3.5.

[0064] The catalyst is selected as a Pt / C catalyst; the ionomer is selected as a perfluorosulfonic acid resin; the solvent is selected as n-propanol; and the water is selected as ultrapure water.

[0065] A method for preparing a low-particle-weight catalyst slurry for fuel cells comprises the following steps: S1, the catalyst is mixed with water to obtain a catalyst dispersion; S2, mix the ionomer and solvent evenly to obtain a mixture; S3, add the mixture to the catalyst dispersion and mix for 40 min to obtain the pre-dispersed catalyst slurry; S4. Mix the pre-dispersed catalyst slurry with grinding balls and ball mill it to obtain the final product.

[0066] The ball mill operates at a speed of 600 r / min and a milling time of 120 min. The grinding balls include grinding balls with a particle size of 0.5 mm and grinding balls with a particle size of 3 mm, and the weight ratio of the grinding balls with a particle size of 0.5 mm to the grinding balls with a particle size of 3 mm is 1:1. The mass ratio of the grinding balls to the pre-dispersed catalyst slurry is 2:1.

[0067] Example 6 A low-particle-size fuel cell catalyst slurry comprises a catalyst, water, an ionomer, and a solvent, wherein the weight ratio of the catalyst, water, ionomer, and solvent is 1:6:2:3.5.

[0068] The catalyst is selected as a Pt / C catalyst; the ionomer is selected as a perfluorosulfonic acid resin; the solvent is selected as n-propanol; and the water is selected as ultrapure water.

[0069] A method for preparing a low-particle-weight catalyst slurry for fuel cells comprises the following steps: S1, the catalyst is mixed with water to obtain a catalyst dispersion; S2, mix the ionomer and solvent evenly to obtain a mixture; S3, add the mixture to the catalyst dispersion and mix for 40 min to obtain the pre-dispersed catalyst slurry; S4. Mix the pre-dispersed catalyst slurry with grinding balls and ball mill it to obtain the final product.

[0070] The ball mill operates at a speed of 400 r / min and a milling time of 180 min. The grinding balls include grinding balls with a particle size of 0.5 mm and grinding balls with a particle size of 3 mm, with a weight ratio of 1:1 between the grinding balls with a particle size of 0.5 mm and the grinding balls with a particle size of 3 mm. The mass ratio of the grinding balls to the pre-dispersed catalyst slurry is 2:1.

[0071] Comparative Example 1 A catalyst slurry for fuel cells comprises a catalyst, water, an ionomer, and a solvent, wherein the weight ratio of the catalyst, water, ionomer, and solvent is 1:6:2:3.5.

[0072] The catalyst is selected as a Pt / C catalyst; the ionomer is selected as a perfluorosulfonic acid resin; the solvent is selected as n-propanol; and the water is selected as ultrapure water.

[0073] A method for preparing a catalyst slurry for fuel cells includes the following steps: mixing the catalyst, water, ionomer and solvent evenly.

[0074] S1, the catalyst is mixed with water to obtain a catalyst dispersion; S2, mix the ionomer and solvent evenly to obtain a mixture; S3, add the mixture to the catalyst dispersion and mix for 40 min to obtain the pre-dispersed catalyst slurry; S4. Mix the pre-dispersed catalyst slurry with grinding balls and homogenize to obtain the final product.

[0075] The linear velocity for homogenization is 40 m / s; the homogenization time is 10 min; and the temperature inside the tank is controlled by the chiller to not exceed 10℃ during homogenization.

[0076] Performance testing methods and data The slurries from Example 1 and Comparative Example 1 were applied to fuel cells for polarization testing, and the polarization curves are shown below. Figure 1 As shown, the electrochemical performance of the catalyst slurry is improved after ball milling.

[0077] The particle size distribution of the slurry in Test Examples 1-7 and Comparative Example 1 was as follows: Figure 2 As shown, the particle size of the catalyst slurry after ball milling is even lower. The D(v, 0.9) particle size is read from the figure and listed in Table 1, indicating that slurries with a D(v, 0.9) particle size of less than 5 micrometers can be prepared in Examples 1-7.

[0078] like Figure 2 As shown, within a certain range, reducing the slurry particle size is beneficial to improving initial activity, meaning that smaller particle size slurries can provide more catalyst active sites. When the slurry particle size is sufficiently small, although the initial activity is improved, mass transfer at high current densities deteriorates, lowering the overall performance. In summary, the slurry particle size can be selected within a suitable range according to the membrane electrode application scenario to find a balance between initial activity and mass transfer characteristics, achieving the maximum overall catalytic activity.

[0079] like Figure 4 As shown, the catalyst slurry prepared by the ball milling process in this application exhibits excellent dispersion performance, such as... Figure 3 As shown, the catalyst slurry prepared using the traditional homogenization process (Primix) has poor dispersion and uneven particle size distribution, resulting in unevenly distributed agglomerates in the coated catalyst layer, which affects the durability of the membrane electrode.

[0080] Table 1

Claims

1. A low-particle-size catalyst slurry for fuel cells, characterized in that, The components are: catalyst, water, ionomer and solvent, wherein the weight ratio of the catalyst, water, ionomer and solvent is 1:(4-10):(1-4):(2-6); The method for preparing the low-particle-size fuel cell catalyst slurry is characterized by comprising the following steps: S1, mixing the catalyst with water to obtain a catalyst dispersion; S2, mixing the ionomer and solvent evenly to obtain a mixture; S3, adding the mixture to the catalyst dispersion and mixing evenly to obtain a pre-dispersed catalyst slurry; S4, mixing the pre-dispersed catalyst slurry with grinding balls and ball milling to obtain the final product; the ball milling speed is 400-2000 r / min; the ball milling time is 20-300 min; the grinding balls include grinding balls with a particle size of 0.1-1.5 mm and grinding balls with a particle size of 2-5 mm.

2. The low-particle-size fuel cell catalyst slurry according to claim 1, wherein the average particle size of the catalyst slurry is not higher than 5 micrometers.

3. The low-particle-size fuel cell catalyst slurry according to claim 1, wherein the mass ratio of the grinding balls to the pre-dispersed catalyst slurry is 1:(4-8):(1-3):(2-5).

4. The low-particle-size fuel cell catalyst slurry according to claim 1, wherein the catalyst comprises a Pt / C catalyst and / or a PtM / C catalyst.

5. The low-particle-size fuel cell catalyst slurry according to claim 1, wherein the solid content of the catalyst slurry is 10-40 wt%.

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