Catalyst slurry and uniformity control method and application thereof

Abstract

The invention provides a catalyst slurry and a uniformity control method and application thereof, the catalyst slurry comprises a catalyst, an ionomer, an ionic liquid, a dispersant, ultrapure water and an alcoholic solution, and the platinum load in the catalyst is 20-70%. According to the invention, the viscosity of the slurry can be accurately regulated and controlled to an optimal coating window of 50-500 mPa.s by accurately regulating and controlling the molar ratio of alcohol to water in the alcohol-water mixed solvent and the dielectric constant of the alcohol-water mixed solvent, adding the ionic liquid and the dispersing agent in the dispersing process and synergistically optimizing the composition and the I / C ratio of the composite ionomer, so that the viscosity of the slurry can be accurately regulated and controlled to be the optimal coating window of 50-500 mPa.s. And the distribution pattern and the coverage rate of the ionomer are balanced, so that the catalytic efficiency and the durability of the membrane electrode are remarkably improved. According to the technical scheme, by regulating and controlling the coating degree of the ionomer on the surface of the catalyst, the dispersion uniformity and stability of the slurry are remarkably improved, meanwhile, a gas transmission channel and a proton conduction network in a catalyst layer are optimized, and a reliable technical guarantee is provided for preparing a high-performance membrane electrode.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, and mainly relates to the preparation of membrane electrode assembly (MEA) for proton exchange membrane fuel cells, and particularly to a catalyst slurry and its preparation, which improves the uniformity and stability of the catalyst slurry. Background Technology

[0002] With the continued growth of global energy demand and the increasingly severe problem of climate change, the development of efficient and clean energy conversion technologies has become an urgent need. Proton exchange membrane fuel cells (PEMFCs), as a highly efficient electrochemical energy conversion device, can directly convert chemical energy into electrical energy, reduce energy losses in traditional heat engine cycles, and have advantages such as zero emissions and high energy density. They are considered an important component of the future sustainable energy system.

[0003] The membrane electrode assembly (MEA) is a core component of a PEMFC, and its performance directly affects the battery's energy conversion efficiency. The cathode catalyst layer undergoes the oxygen reduction reaction (ORR), while the anode catalyst layer is responsible for the hydrogen oxidation reaction (HOR). Studies have shown that the microstructure of the catalyst layer has a decisive influence on reactant transport and product removal, especially the efficiency of oxygen diffusion and water removal, which directly affect the overall performance of the fuel cell.

[0004] The uniformity of catalyst slurry dispersion is a key factor affecting the performance of the catalyst layer. The presence of agglomerates in the slurry leads to uneven catalyst distribution, which in turn affects the formation of the three-phase interface and reduces the utilization rate of reactive active sites. Furthermore, uneven slurry coating can also result in an unreasonable pore structure distribution in the catalyst layer, hindering reactant transport and product discharge, ultimately affecting the battery's power output and durability. Therefore, it is necessary to optimize the catalyst slurry dispersion process to improve its uniformity and stability, while also considering production efficiency, reducing agglomeration, and enhancing the catalytic performance of the membrane electrode assembly (MEA).

[0005] This invention utilizes the synergistic effect of a composite alcohol solvent and an ionic liquid to directionally design the dielectric constant and solvation capability of the dispersion medium, thereby working with the dispersant to optimize the dispersion uniformity and long-term stability of the slurry. Summary of the Invention

[0006] In existing processes for preparing membrane electrode assemblies (MEAs) for hydrogen fuel cells, catalyst slurries often suffer from insufficient dispersion uniformity, particle agglomeration during drying, and coating cracking due to metal particle sedimentation. This not only wastes precious metals but also limits the overall performance of the MEA. Therefore, this invention aims to provide a novel catalyst slurry and a method for controlling the uniformity of the catalyst slurry to improve slurry stability and uniformity, achieve a uniform distribution of platinum loading, and thereby improve catalyst utilization and battery performance.

[0007] To address the aforementioned technical problems, the present invention provides a catalyst slurry comprising a catalyst, an ionomer, an ionic liquid, a dispersant, ultrapure water, and an alcohol solution.

[0008] The catalyst is selected from one or more of platinum-carbon catalysts, platinum-nickel alloy catalysts, platinum-iron alloy catalysts, and ternary alloy catalysts, with the platinum content accounting for 20%-70% of the total mass of the catalyst;

[0009] The ionomer is one or more of the following: perfluorosulfonic acid resin (Nafion) and phosphorylated covalent organic frameworks (P-RCOFs), sulfonated polyether ether ketone (SPEEK), and sulfonated polyimide (SPI);

[0010] The ionic liquid is a salt that is liquid at 25°C and is composed of organic cations and inorganic or organic anions (meaning the ionic liquid is a salt that is liquid at 25°C and is composed of organic cations and inorganic anions; or, the ionic liquid is a salt that is liquid at 25°C and is composed of organic cations and organic anions).

[0011] The dispersant is selected from one or more of the following: alkyl polysaccharide glycoside (APG-0810), ketal alkyl glycoside (APG), polyethylene glycol-polypropylene glycol block copolymer (Pluronic), polyglycerol fatty acid ester, and Triton X-100 (4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol, also known as polyethylene glycol octylphenyl ether).

[0012] The alcohol solvent is selected from at least one of n-propanol, n-butanol, isopropanol, 1,2-butanediol, propylene glycol, glycerol, diethylene glycol, dipropylene glycol, ethylene glycol, ethanol, and methanol.

[0013] Furthermore, the organic cation is selected from one of imidazoles, pyrrolidines, quaternary ammonium salts, or quaternary phosphonium salts;

[0014] The organic anion is selected from either bis(trifluoromethanesulfonyl)imide or trifluoromethanesulfonate; the inorganic anion is selected from either tetrafluoroborate or hexafluorophosphate.

[0015] The dispersant optimizes the ionomer network structure, improves the steric stability of the slurry, and enhances proton conduction and gas diffusion. The alcohol solvent serves as the main liquid phase medium of the slurry.

[0016] The present invention also provides a method for controlling the uniformity of the catalyst slurry, comprising the following steps:

[0017] Step 1, Primary Mixing: The catalyst, ultrapure water, ionic liquid and alcohol solvent are mixed to form a primary mixed solution; wherein: the amount of catalyst is 0.4-0.8 g; the alcohol solvent is composed of a low boiling point drying regulator, a medium boiling point main dispersant and a high boiling point film-forming modifier, in a mass ratio of (1-3):(4-6):(2-5);

[0018] Step 2, low-speed pre-dispersion: The primary mixed solution is mechanically stirred and pre-dispersed at a speed of 300-800 rpm for 10-30 minutes;

[0019] Step 3, Stepwise Ultrasonic Dispersion: Add ionomer to the mixture after Step 2; the ratio of the total dry matter mass of the added ionomer to the dry matter mass of the carbon support in the mixture of Step 2 is controlled at 0.8-1.2; then add the dispersant in multiple batches, the amount of which is 0.1%-0.8% of the total mass of the catalyst slurry, and after each addition, perform ultrasonic treatment, the ultrasonic frequency is 20-60 kHz, and the single treatment time is 5-10 minutes;

[0020] Step 4, Vacuum high-speed homogenization and dispersion: Place the mixture obtained in step 3 in a vacuum homogenizer and perform continuous shear dispersion and vacuum degassing at a speed of 8000-12000 rpm for 10-30 minutes under a vacuum of -0.09 MPa ± 0.01 MPa to obtain a catalyst slurry with uniform solid content and no visible bubbles.

[0021] In step 3, if the addition of an ionomer mixture is chosen, 1g of perfluorosulfonic acid resin solution (based on solids) and 1g of P-RCOFs dispersion (based on solids) need to be weighed to obtain an internal ionomer mixture with a mass ratio of 1:1. The I / C ratio is calculated in reverse based on the carbon support mass known in step 2 to determine the required solid mass of the ionomer. For example, if the carbon support mass is 1g and the target I / C ratio is 1.0, then 1g of an ionomer mixture with a solid content needs to be added.

[0022] The purpose of step 2, low-speed pre-dispersion, is to initially wet and mix the components, avoiding local overheating caused by premature high-speed shearing.

[0023] The main function and purpose of step 3, stepwise ultrasonic dispersion: This stepwise addition and coupled ultrasonic method can effectively break down catalyst agglomerates and allow dispersant molecules to be fully adsorbed on the particle surface, achieving efficient dispersion at the microscale.

[0024] The main function and purpose of step 4, vacuum high-speed homogenization dispersion, is to simultaneously perform high-shear dispersion and vacuum degassing. High shear force further refines the particles, ensuring uniform encapsulation of ionomers; simultaneously, the high vacuum environment instantly removes bubbles generated during the shearing process and inhibits the formation of new bubbles. The rotor-stator gap of the vacuum homogenizer is preferably controlled at 0.1-0.5 mm to produce the best shearing effect. The final result is a catalyst slurry with highly uniform solids content and no visible bubbles.

[0025] Furthermore, in step 1, the low-boiling-point drying regulator is selected from one of ethanol, propylene glycol, and methanol;

[0026] The medium-boiling-point main dispersant is selected from one of isopropanol, n-propanol, and 1,2-butanediol;

[0027] The high-boiling-point film-forming modifier is selected from one of ethylene glycol, diethylene glycol, and n-butanol;

[0028] The ionic liquid includes a fluoroimidazolium ionic liquid with the general chemical formula [Rm-Fmim][X], where Rm is a C4-C8 alkyl chain, Fmim is an imidazolium cation substituted with one or more fluorine atoms, and X is a bis(trifluoromethanesulfonyl)imide group [NTf2]. — Or tetrafluoroborate [BF4] — .

[0029] Preferably, the alcohol solvent in step 1 is composed of 1,2-butanediol, propylene glycol and ethylene glycol in a mass ratio of (1-3):(4-6):(2-5).

[0030] Preferably, the mass ratio of ultrapure water to alcohol solvent in step 1 is 1:4-9.

[0031] Furthermore, in step 3, the ionomer is a phosphorylated covalent organic framework or a mixed solution prepared by mixing perfluorosulfonic acid resin and phosphorylated covalent organic framework in a dry matter mass ratio of (1-3):(1-6).

[0032] The dispersant is Triton X-100.

[0033] Furthermore, the low-speed dispersion process in step 2 should be kept at a constant temperature, between 20-35°C.

[0034] Furthermore, in step 3, the dispersant is added in 3-10 portions, and the amount of dispersant added each time is 10%-30% of the total amount of dispersant to be added.

[0035] Furthermore, in step 4, the gap between the rotor and stator of the vacuum homogenizer is 0.1-0.5 mm.

[0036] Furthermore, the inert atmosphere used in step 4 is nitrogen or argon, and the oxygen content is controlled to be <50ppm.

[0037] Furthermore, the settling rate of the catalyst slurry is ≤0.3 mm / 24 h, and the viscosity fluctuation rate is ≤5%.

[0038] The present invention also provides an application of the catalyst slurry prepared using the aforementioned control method in the preparation of proton exchange membrane fuel cell electrodes.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] Excellent slurry uniformity and stability: A multi-stage synergistic dispersion process, consisting of low-speed pre-dispersion, stepwise ultrasonication, and high-speed vacuum homogenization, achieves highly uniform dispersion of catalyst particles. The prepared slurry exhibits an extremely low settling rate, demonstrating excellent physical stability and ensuring batch consistency during long-term storage and continuous coating.

[0041] Effective elimination of microscopic defects: The unique vacuum homogenization dispersion step simultaneously achieves efficient dispersion and deep degassing, fundamentally solving the problem of residual bubbles in the slurry, resulting in a dense and defect-free catalytic layer formed by coating, effectively increasing the three-phase reaction interface area.

[0042] Optimized electrode structure: Specific dispersants (such as dodecyl mercaptan, Triton X-100, etc.) work synergistically with ionomers to help form more reasonable proton conduction channels and gas diffusion pores within the catalyst layer, improving the mass transfer capacity of the catalyst layer, thereby enhancing the performance and durability of the battery.

[0043] The process is highly controllable and suitable for large-scale production: The parameters of each step in this method are clear, easy to control and scale up, and provide a reliable slurry preparation process for the industrial and standardized production of high-performance membrane electrodes.

[0044] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the membrane electrode preparation process using the catalyst of the present invention;

[0046] Figure 2 This is a comparison diagram of the single-cell polarization curves of the membrane electrodes obtained in Examples 1-2 and Comparative Examples 1-3 of the present invention;

[0047] Figure 3 This is a comparison graph of the polarization curve and power density curve of the single cells prepared in Example 1 and Comparative Example 2 of the present invention.

[0048] Figure 4 This is a comparison of the SEM microstructure of the catalyst layers prepared in Example 1 and Comparative Example 4 of the present invention;

[0049] Figure 5 These are particle size distribution diagrams of the catalyst slurries in the examples and comparative examples after being treated by the uniformity control method described in this invention;

[0050] Figure 6 The viscosity characteristics of the catalyst slurry prepared in Example 1 and Comparative Examples 2-4 of this invention are shown.

[0051] Figure 7 This describes the sedimentation of the slurry in Example 1 and Comparative Example 3 of the present invention after standing for 48 hours. Detailed Implementation

[0052] The following specific embodiments illustrate the detailed implementation of the present invention. Those skilled in the art can easily understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented in other different ways, that is, different modifications and changes can be made without departing from the scope disclosed in the present invention.

[0053] In the accompanying drawings, "implementation examples" are abbreviated as "examples".

[0054] Example 1

[0055] A method for controlling the uniformity of catalyst slurry includes the following steps:

[0056] Step 1: First, weigh 0.5 g of Pt / C catalyst (20 wt% Pt) and mix it with 5.53 g of ultrapure water for pre-wetting and primary dispersion of the catalyst. Then, take 0.5 g of [C4mim][NTf2] ionic liquid and premix it with 1.0 g of 1,2-butanediol (a portion of the total mass of the alcohol solvent) from the following mixed alcohol solvent at room temperature, stirring until a homogeneous and transparent ionic liquid dilution is formed. Next, slowly add the mixed alcohol solvent consisting of 12.14 g of 1,2-butanediol, 14.59 g of ethylene glycol, and 3.21 g of propylene glycol to the catalyst mixture. Then, add the prepared ionic liquid dilution to the system.

[0057] Step 2: Stir at a gentle speed of 600 r / min for 30 minutes to ensure that all components are fully mixed and wetted, thus completing the preparation of the primary mixture;

[0058] Step 3: Next, add Nafion and P-RCOFs (I / C=0.9) in a mass ratio of 1:1 to ensure the ionomers fully cover the surface of the catalyst particles, forming proton conduction channels. Then, add 0.1 wt% Triton X-100 in three portions. After each addition, immediately follow with ultrasonic treatment at 60 kHz for 30 minutes. This utilizes ultrasound to forcefully break down any remaining hard agglomerates and promotes the uniform adsorption of Triton X-100 dispersant on the particle surface, achieving steric stabilization.

[0059] Step 4: Finally, the mixture is transferred to a vacuum homogenizer for homogenization and degassing. Under a vacuum of -0.09 MPa, it is sheared and dispersed at 10,000 r / min for 40 minutes. The high shear force ensures the slurry achieves microscopic uniformity; simultaneously, the vacuum environment effectively removes air bubbles introduced during stirring and ultrasonication, preventing them from forming defects in subsequent coating processes. Ultimately, a catalyst slurry with uniform solids content, no visible air bubbles, and excellent stability is obtained.

[0060] The fabrication process of the membrane electrode using the above catalyst is as follows: The catalyst slurry is coated onto both sides of a proton exchange membrane with an area of ​​150 mm × 80 mm using ultrasonic spraying technology (the sprayed catalyst layer is tested with XRF, and the Pt loading of the anode and cathode is controlled at 0.50 mg / cm²), and then dried. The above CCM (catalyst-coated membrane) is then sealed with a frame, and a gas diffusion layer (carbon paper) is attached to encapsulate it into a membrane electrode.

[0061] The fabricated membrane electrode was assembled into a single cell for testing. The test conditions were: cell temperature 75℃, anode and cathode humidity 100%, and anode and cathode back pressure 150 kPa.

[0062] Example 2

[0063] The difference between this embodiment and Example 1 lies in the process of controlling the uniformity of the catalyst slurry.

[0064] Step 1: First, weigh 0.5 g (20 wt% Pt loading) of Pt / C catalyst and place it in a jacketed beaker, then add 4.8 g of ultrapure water. Take 0.4 g of [C6mim][BF4] ionic liquid and premix it with 1.6 g of ethyl acetate from the following mixed alcohol solvent at room temperature, stirring until a homogeneous and transparent ionic liquid dilution is formed. Subsequently, slowly add the mixed alcohol solvent consisting of 13.4 g of ethyl acetate, 12.00 g of isopropanol, and 6.00 g of diethylene glycol to the catalyst mixture, and mix it with the prepared ionic liquid dilution.

[0065] Step 2: Stir at a gentle speed of 300 r / min for 10 minutes to ensure that all components are fully mixed and wetted, thus completing the preparation of the primary mixture;

[0066] Step 3: Next, add Nafion and P-RCOFs at a mass ratio of 1:3 (I / C = 1.1) to ensure the ionomer fully covers the surface of the catalyst particles. Then, add 0.6 wt% Triton X-100 in 5 portions. After each addition, immediately follow with ultrasonic treatment at 40 kHz for 10 minutes to promote uniform adsorption of Triton X-100 dispersant on the particle surface and achieve steric stabilization.

[0067] Step 4: Finally, transfer the above mixture to a vacuum homogenizer for homogenization and degassing. Under a vacuum of -0.09 MPa, shear dispersion is performed at 5000 r / min for 10 minutes. A homogeneous catalyst slurry is then obtained.

[0068] Subsequently, the membrane electrode was prepared in the same manner as in Example 1 (including spraying, drying, and encapsulation). The platinum loading in the catalyst layer on the proton exchange membrane was controlled to be 0.50 mg / cm2. The prepared single cell was assembled and its performance was tested.

[0069] Comparative Example 1

[0070] A method for preparing a catalyst slurry differs from Example 1 primarily in the dispersion process and formulation system. The specific steps are as follows: 0.5 g (20 wt% Pt loading) of Pt / C catalyst is weighed and placed in a jacketed beaker. 6.34 g of ultrapure water is added to fully wet the catalyst, followed by the addition of 15.0 g of ethanol, 5.0 g of isopropanol, and 1.0 g of ethylene glycol to ensure homogeneity, forming mixed solution one. Subsequently, 1.5 g of D2020 perfluorosulfonic acid resin solution (20 wt% solid content) is added to obtain mixed solution two. After mixing the two solutions, a suspension stirrer is used to stir the mixture, with constant temperature water (25°C) circulated into the jacket during the stirring process. Then, 0.85 wt% Triton X-100 (based on the total mass of the catalyst slurry) is added to the above mixture, and stirring continues for 20 min. After homogeneity, ultrasonic dispersion is used to obtain a uniform catalyst slurry.

[0071] The catalyst slurry was coated onto the proton exchange membrane using the same spraying and encapsulation process as in Example 1. The platinum loading in the catalyst layer on the proton exchange membrane was controlled to be 0.48 mg / cm³. 2 The prepared membrane electrode was assembled into a single cell for testing, and the testing conditions were the same as in Example 1.

[0072] Comparative Example 2

[0073] 0.5 g (20 wt% Pt loading) of Pt / C catalyst was weighed and placed in a jacketed beaker, and 7.59 g of ultrapure water and 5.0 g of ethanol were added to obtain mixed solution one. Then, 3.0 g of ethylene glycol, 18.0 g of isopropanol, and 1.92 g of D2020 perfluorosulfonic acid resin solution (20 wt% solid content) were weighed to obtain mixed solution two. After mixing the two mixed solutions, they were stirred using a suspension stirrer, with constant temperature water at 25°C circulated into the jacket during stirring. Subsequently, 0.08 wt% of Triton X-100 (based on the catalyst mass) was added to the above mixture, and stirring was continued for 20 min. After homogenization, the mixture was forcibly dispersed using a vacuum homogenizer for 30 min at a speed of 9000 r / min.

[0074] The catalyst slurry was coated onto the proton exchange membrane using the same spraying and encapsulation process as in Example 1. The platinum loading in the catalyst layer on the proton exchange membrane was controlled to be 0.55 mg / cm³. 2 The prepared membrane electrode was assembled into a single cell for testing, and the testing conditions were the same as in Example 1.

[0075] Comparative Example 3

[0076] 0.5 g (20 wt% Pt loading) of Pt / C catalyst was weighed and placed in a jacketed beaker, and 5.7 g of ultrapure water and 10.0 g of ethanol were added to obtain mixed solution one. Then, 20.0 g of isopropanol and 3.00 g of D2020 perfluorosulfonic acid resin solution were weighed to obtain mixed solution two. After mixing the two solutions, they were stirred using a suspension stirrer, with constant temperature water at 25°C circulated into the jacket during stirring. After homogenization, the mixture was ultrasonically dispersed for 30 min at a frequency of 100 Hz.

[0077] The catalyst slurry was coated onto the proton exchange membrane using the same transfer and encapsulation process as in Example 1. The platinum loading in the catalyst layer on the proton exchange membrane was controlled to be 0.58 mg / cm³. 2 The prepared membrane electrode was assembled into a single cell for testing, and the testing conditions were the same as in Example 1.

[0078] Comparative Example 4

[0079] 0.5 g (20 wt% Pt loading) of Pt / C catalyst was weighed and placed in a jacketed beaker, and 9.77 g of ultrapure water and 15.0 g of ethanol were added to obtain mixed solution one. Then, 15.0 g of isopropanol and 3.00 g of D2020 perfluorosulfonic acid resin solution (20 wt% solid content) were weighed to obtain mixed solution two. After mixing the two solutions, they were stirred using a suspension stirrer, with constant temperature water at 25°C circulated into the jacket during stirring. Subsequently, the mixture was ultrasonically dispersed for 30 min at a frequency of 100 Hz.

[0080] The catalyst slurry was coated onto the proton exchange membrane using the same spraying and encapsulation process as in Example 1. The platinum loading in the catalyst layer on the proton exchange membrane was controlled to be 0.42 mg / cm³. 2 The prepared membrane electrode was assembled into a single cell for testing, and the testing conditions were the same as in Example 1.

[0081] Figure 1 This is a schematic diagram of the membrane electrode preparation process using the catalyst of the present invention. Figure 2 This is a comparison of the single-cell polarization curves of the membrane electrodes obtained in Examples 1-2 and Comparative Examples 1-3 of the present invention (the vertical axis represents cell voltage, and the horizontal axis represents current density). The test results show that the voltage retention capability of the cells in each embodiment of the present invention is significantly better than that of the comparative examples in the high current density region. Specifically, at a high current density of 2.4 A / cm², the voltage of Example 1 is 0.64 V, and the voltage of Example 2 is 0.62 V, both significantly higher than the 0.57 V of Comparative Example 3. This performance ranking is consistent with the slurry stability and the uniformity of the microstructure of the formed catalyst layer. The solvent ratio used in Example 1 may have shown a better synergistic effect in achieving optimal ionomer distribution and constructing efficient gas transport channels.

[0082] Figure 3 The graphs show a comparison of the single-cell polarization curves and power density curves of the membrane electrodes obtained in Example 1 and Comparative Example 2 (the left ordinate represents cell voltage, the horizontal ordinate represents current density, and the right ordinate represents power density). The test results indicate that precise catalyst slurry uniformity control methods (such as using ionic liquids, optimizing ionomer systems, multi-step dispersion and degassing) can significantly improve the microstructure of the catalyst layer, reduce mass transfer resistance, and thus enhance the performance of the membrane electrode, especially at high current densities.

[0083] Figure 4 The SEM microstructure comparison of the catalyst layers prepared in Example 1 and Comparative Example 4 is shown. Figure 4As shown in (a), the catalyst layer structure of Example 1 is complete, dense, and continuous, with uniform catalyst particle distribution and no signs of cracking or peeling. In stark contrast, the catalyst layer of Comparative Example 4 ( Figure 4 b) shows obvious macroscopic cracks and structural defects. This structural damage can be attributed to the lack of dispersant and the unreasonable high ethanol ratio in its slurry formulation. Both of these factors combined lead to poor slurry stability and stress concentration during drying, ultimately causing the coating to crack.

[0084] Figure 5 The particle size distribution diagrams (vertical axis: volume, horizontal axis: size distribution diagram) of the catalyst slurries of various embodiments and comparative examples after treatment with the uniformity control method described in this invention are shown. The slurry of Example 1 exhibits a narrow, single-peaked particle size distribution, concentrated at the nanoscale, indicating uniform catalyst particle dispersion and effective dissolution of agglomerates. In contrast, the slurry of Comparative Example 4 shows a distinct bimodal particle size distribution, indicating the simultaneous presence of fine particles and larger agglomerates in the system. This confirms a dispersion defect in the formulation or process, potentially leading to uneven catalyst distribution in the catalyst layer, resulting in catalyst detachment from the membrane electrode after testing.

[0085] Figure 6 The viscosity characteristics of different catalyst slurries are shown (viscosity on the ordinate and shear rate on the abscissa). In Example 1, the optimized alcohol-water ratio and the synergistic effect of the ionic liquid and dispersant significantly weakened the network structure between particles, resulting in much smaller Pt / C agglomerates and more uniform dispersion. In contrast, the larger and non-uniform Pt / C agglomerate size in the dispersion in Comparative Example 4 may be the cause of the severe cracks observed in CCL.

[0086] Figure 7 These are comparative photographs showing the sedimentation of the slurries from Example 1 and Comparative Example 3 after standing for 48 hours. Figure 7 As shown, the slurry of Comparative Example 3 showed obvious stratification and a solid sedimentation layer, while the slurry of Example 1 remained in a uniform suspension state.

[0087] This invention, by precisely controlling the molar ratio and dielectric constant of alcohol and water in an alcohol-water mixed solvent, combined with the addition of ionic liquids and dispersants during dispersion, and through synergistic optimization of the composite ionomer composition and I / C ratio, can precisely control the slurry viscosity within the optimal coating window of 50-500 mPa·s and balance the distribution morphology and coverage of the ionomers, thereby significantly improving the catalytic efficiency and durability of the membrane electrode. This technical solution, by controlling the degree of ionomer coating on the catalyst surface, not only significantly improves the dispersion uniformity and stability of the slurry, but also optimizes the gas transport channels and proton conduction network in the catalyst layer, providing a reliable technical guarantee for the preparation of high-performance membrane electrodes.

[0088] The inventiveness of this invention does not lie in the isolated use of conventional components or steps, but in providing a complete technical solution with synergistic effects of "components and processes". Specifically: 1) In terms of components, we innovatively adopted a perfluorosulfonic acid resin / phosphorylated covalent organic framework (P-RCOFs) composite ionomer and introduced ionic liquid and a specific dispersant, Triton X-100. The synergistic effect of these three elements solves the problems of ionomer self-aggregation, slurry rheological control, and particle surface stabilization, respectively; 2) In terms of process, we designed a multi-stage synergistic dispersion sequence of "low-speed pre-dispersion - stepwise ultrasonication - vacuum high-speed homogenization". Its specific timing and parameter coupling enables precise control of the entire process of catalyst agglomerates from macroscopic wetting to microscopic dissociation and then to synchronous bubble removal.

[0089] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structure made using the contents of the present invention specification and drawings, or directly or indirectly applied to other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A catalyst slurry, characterized in that: The catalyst slurry comprises a catalyst, an ionomer, an ionic liquid, a dispersant, ultrapure water, and an alcohol solution; The catalyst is selected from one or more of platinum-carbon catalysts, platinum-nickel alloy catalysts, platinum-iron alloy catalysts, and ternary alloy catalysts, with the platinum content accounting for 20%-70% of the total mass of the catalyst; The ionomer is one or more of the following: perfluorosulfonic acid resin and phosphorylated covalent organic framework, sulfonated polyether ether ketone, and sulfonated polyimide; The ionic liquid is a salt that is liquid at 25°C and is composed of organic cations and inorganic or organic anions; The dispersant is selected from one or more of alkyl polysaccharides, ketal alkyl glycosides, polyethylene glycol-polypropylene glycol block copolymers, polyglycerol fatty acid esters, and Triton X-100; The alcohol solvent is selected from at least one of n-propanol, n-butanol, isopropanol, 1,2-butanediol, propylene glycol, glycerol, diethylene glycol, dipropylene glycol, ethylene glycol, ethanol, and methanol.

2. The catalyst slurry according to claim 1, characterized in that: The organic cation is selected from one of imidazoles, pyrrolidines, quaternary ammonium salts, or quaternary phosphorus salts; The organic anion is either bis(trifluoromethanesulfonyl)imide or trifluoromethanesulfonate; The inorganic anions are selected from tetrafluoroborate or hexafluorophosphate.

3. A method for controlling the uniformity of catalyst slurry according to any one of claims 1-2, characterized in that: Includes the following steps: Step 1, Primary Mixing: The catalyst, ultrapure water, ionic liquid and alcohol solvent are mixed to form a primary mixed solution; wherein: the amount of catalyst is 0.4-0.8 g; the alcohol solvent is composed of a low boiling point drying regulator, a medium boiling point main dispersant and a high boiling point film-forming modifier, in a mass ratio of (1-3):(4-6):(2-5); Step 2, low-speed pre-dispersion: The primary mixed solution is mechanically stirred and pre-dispersed at a speed of 300-800 rpm for 10-30 minutes; Step 3, Stepwise Ultrasonic Dispersion: Add ionomer to the mixture after Step 2; the ratio of the total dry matter mass of the added ionomer to the dry matter mass of the carbon support in the mixture of Step 2 is controlled at 0.8-1.2; then add dispersant in multiple batches, the total amount of dispersant added is 0.1%-0.8% of the total mass of the catalyst slurry; after each addition, perform ultrasonic treatment, the ultrasonic frequency is 20-60 kHz, and the single treatment time is 5-10 minutes; Step 4, Vacuum high-speed homogenization and dispersion: Place the mixture obtained in step 3 in a vacuum homogenizer and perform continuous shear dispersion and vacuum degassing at a speed of 8000-12000 rpm for 10-30 minutes under a vacuum of -0.09 MPa ± 0.01 MPa to obtain a catalyst slurry with uniform solid content and no visible bubbles.

4. The control method according to claim 3, characterized in that: In step 1, the low-boiling-point drying regulator is selected from one of ethanol, propylene glycol, and methanol; The medium-boiling-point main dispersant is selected from one of isopropanol, n-propanol, and 1,2-butanediol; The high-boiling-point film-forming modifier is selected from one of ethylene glycol, diethylene glycol, and n-butanol; The ionic liquid includes a fluoroimidazolium ionic liquid with the general chemical formula [Rm-Fmim][X], where Rm is a C4-C8 alkyl chain, Fmim is an imidazolium cation substituted with one or more fluorine atoms, and X is a bis(trifluoromethanesulfonyl)imide or tetrafluoroborate.

5. The control method according to claim 3, characterized in that: In step 3, the ionomer is a phosphorylated covalent organic framework or a mixed solution prepared by mixing perfluorosulfonic acid resin and phosphorylated covalent organic framework in a dry matter mass ratio of (1-3):(1-6). The dispersant is Triton X-100.

6. The control method according to claim 3, characterized in that, The low-speed dispersion process in step 2 should be kept at a constant temperature of 20-35℃.

7. The control method according to claim 3, characterized in that, In step 3, the dispersant is added in 3-10 portions, and the amount of dispersant added each time is 10%-30% of the total amount of dispersant to be added.

8. The control method according to claim 3, characterized in that, In step 4, the gap between the rotor and stator of the vacuum homogenizer is 0.1-0.5 mm.

9. The control method according to claim 3, characterized in that, The settling rate of the catalyst slurry is ≤0.3mm / 24h, and the viscosity fluctuation rate is ≤5%.

10. The application of a catalyst slurry prepared using the control method described in claims 3-9 in the preparation of proton exchange membrane fuel cell electrodes.

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