Preparation method of fuel cell catalyst slurry, slurry and application thereof

Abstract

The invention relates to the field of fuel cells, and provides a preparation method of fuel cell catalyst slurry, the slurry and application of the slurry, the proportion of the pore volume corresponding to pores smaller than or equal to 5 nm in a catalyst in the total pore volume is greater than 30%, and the preparation method comprises the following steps: S1, acidizing the catalyst in an oxidizing acid solution to obtain a hydrophilic catalyst; s2, mixing the perfluorinated sulfonic acid resin dispersion liquid, water and alcohol to prepare a resin diluent; s3, dispersing the hydrophilic catalyst obtained in the step S1 into water, adding the resin diluent obtained in the step S2, and dispersing to obtain a mixed solution; s4, carrying out vacuum rotary evaporation treatment on the mixed solution obtained in the step S3, grinding and crushing to obtain catalyst powder; and S5, preparing catalyst slurry from water, a perfluorinated sulfonic acid resin dispersion liquid, an organic solvent and the catalyst powder obtained in the step S4. The method has the advantages that the distribution of the perfluorinated sulfonic acid resin around the active metal catalyst is optimized, the poisoning of sulfonate radicals to the catalyst is reduced, and the performance of the membrane electrode is improved.

Description

Technical Field

[0001] The present invention relates to the field of fuel cells, and more specifically, to a method for preparing fuel cell catalyst slurry, the slurry and applications thereof. Background Art

[0002] Membrane electrode is a key component of proton exchange membrane fuel cell, which is made of catalyst, proton exchange membrane, carbon paper, etc. In membrane electrode, catalyst coated membrane (CCM) is its core part; CCM has a three-layer structure, with proton exchange membrane in the middle and catalyst layers on both sides. The catalyst layer is the place where the fuel cell reaction occurs, which is composed of catalyst and proton conductive perfluorosulfonic acid resin; the utilization efficiency of the catalyst in the catalyst layer determines the performance of the membrane electrode, which is affected by the interface, dispersion state and interaction of the catalyst-ionomer.

[0003] The three-phase interface is the interface where the reactant gas meets the electrons in the solid phase and the protons in the electrolyte phase. Improving the three-phase interface can effectively improve the performance of the fuel cell. Platinum is made into nanoparticles and loaded on carbon black to increase the mass specific surface area of ​​platinum and provide a large pore channel for the reactant oxygen to reach the platinum particles. Solid electrolytes such as perfluorosulfonic acid resins are mixed with catalysts to bring protons to the surface of platinum particles.

[0004] The pore distribution of traditional Pt / C catalysts is dispersed and there are many large-diameter (≥10nm) pores, and platinum nanoparticles are distributed inside and outside these pores; in the preparation of catalyst slurry, perfluorosulfonic acid resin can also enter these large-diameter pores and interact with the platinum particles, so that the platinum particles inside and outside the pores are coated with perfluorosulfonic acid resin, causing the platinum particles to be poisoned by sulfonate groups, thereby increasing the catalyst activity loss and the mass transfer resistance.

[0005] If the pore size of the pores on the catalyst is less than 5nm, since the aggregate size of the perfluorosulfonic acid resin is larger than the pore size of the catalyst, it is difficult for the perfluorosulfonic acid resin to enter the catalyst pores of this size, which effectively avoids the catalyst being poisoned by sulfonate groups due to direct contact between the catalyst and the perfluorosulfonic acid resin, and can improve the problem of membrane electrode catalyst being poisoned by sulfonate groups. However, compared with traditional Pt / C catalysts, although the Pt particles that are not coated by ionomers in the pores avoid sulfonate poisoning and have good activity, when the pore depth is deep, the Pt particles are far away from the perfluorosulfonic acid resin, or when the pores are small, the perfluorosulfonic acid resin is difficult to approach the Pt particles, and the transmission of protons participating in the reaction is limited under dry conditions (such as Figure 1 ), which causes the performance of the membrane electrode to decline. Therefore, designing the micro-interface between the catalyst and the perfluorosulfonic acid resin is of great significance for improving the performance of fuel cells. Summary of the invention

[0006] The present invention aims to overcome at least one defect (shortcoming) of the above-mentioned prior art, provide a method for preparing a fuel cell catalyst slurry, a slurry and its application, optimize the distribution of perfluorosulfonic acid resin around the active metal catalyst, reduce the poisoning effect of sulfonate groups on the catalyst and improve the performance of the membrane electrode.

[0007] The technical solution adopted by the present invention is to provide a method for preparing a fuel cell catalyst slurry, wherein the catalyst is formed by a catalyst carrier carrying an active metal, and is characterized in that the pore volume corresponding to the pores ≤5 nm on the catalyst accounts for more than 30% of the total pore volume, and the preparation method comprises the following steps:

[0008] S1, acidifying the catalyst in an oxidizing acid solution to obtain a hydrophilic catalyst;

[0009] S2, mixing the perfluorosulfonic acid resin dispersion, water and alcohol to prepare a resin diluent;

[0010] S3, dispersing the hydrophilic catalyst obtained in step S1 in water, and adding the resin diluent obtained in step S2, dispersing to obtain a mixed solution;

[0011] S4, subjecting the mixed solution obtained in step S3 to vacuum rotary evaporation, grinding and crushing to obtain catalyst powder;

[0012] S5. Prepare a catalyst slurry by mixing water, a perfluorosulfonic acid resin dispersion, an organic solvent and the catalyst powder obtained in step S4.

[0013] The pores ≤5 nm on the catalyst are preferably pores with a pore size of 1.5 nm to 5 nm, and the pore volume thereof preferably accounts for 30% to 60% of the total pore volume, and the content of active metal in the catalyst is 20 to 70 wt%. In one or more embodiments of the present invention, the catalyst carrier is a carbon carrier, and the active metal is usually an active metal particle, such as platinum or a platinum alloy. Compared with traditional catalysts, the catalyst of the present technical solution has more pores with a pore size of less than 5 nm, which reduces the probability of perfluorosulfonic acid resin entering the pores to wrap the active metal, thereby effectively reducing the probability of direct contact between the perfluorosulfonic acid resin and the catalyst, and improving the problem of catalyst poisoning by sulfonic acid groups.

[0014] For step S1, the purpose of acid treatment of the catalyst is to wash away the unstable substances in the catalyst itself, clean the pores, and modify the hydrophilic functional groups in the pores, so as to induce the perfluorosulfonic acid side chains that tend to conduct protons to face inward when the perfluorosulfonic acid resin molecular chains are adsorbed on the catalyst, which is more conducive to "extending" to the inside of the pore. The oxidizing acid solution is an acid or a mixture of acids with certain oxidizing properties such as sulfuric acid, nitric acid, chloric acid, perchloric acid, nitrous acid, acetic acid, etc.

[0015] For step S2, as the solid content in the perfluorosulfonic acid resin dispersion decreases, the size of the perfluorosulfonic acid resin aggregates will decrease significantly, which means that the number of perfluorosulfonic acid resin molecules in a single aggregate decreases, the flexibility increases, and it is easier to deform. Therefore, by adjusting the alcohol-water ratio and solid content in the perfluorosulfonic acid resin solution solvent, the size of the perfluorosulfonic acid resin aggregates in the dispersion is reduced, and the probability of partial intrusion of the resin aggregates into the pores is increased, which facilitates proton transfer. Preferably, the perfluorosulfonic acid resin ion exchange equivalent Ew is 700 to 1100 g / mol.

[0016] For step S4, during the volatilization of the solvent in the pores by vacuum rotary evaporation, since the perfluorosulfonic acid resin is attached to the pore mouth, there is a certain vacuum negative pressure inside and outside the pores, which makes the perfluorosulfonic acid resin molecular chain at the pore mouth bend into the pore or invade the pore, so as to further shorten the distance for protons and reaction gases to be transmitted to the active metal surface, thereby improving the performance of the membrane electrode under high current density.

[0017] For step S5, the organic solvent is a low-polarity alcohol, specifically one or more of methanol, ethanol, propanol, and butanol.

[0018] Furthermore, the most probable pore size of the catalyst carrier is 1.5-5 nm.

[0019] Furthermore, the solid content of the resin diluent is ≤2wt%. Preferably, the solid content of the resin diluent is 0.5wt% to 2wt%.

[0020] Furthermore, in step S3, the weight ratio of the dry weight of the perfluorosulfonic acid resin to the catalyst carrier is 0.01 to 0.2.

[0021] Furthermore, in step S1, in the acidification treatment, the acid concentration is 0.1-1 mol / L, the treatment temperature is 40-100° C., and the treatment time is 60-300 min.

[0022] Furthermore, in step S1, during the acidification treatment, the concentration of the catalyst in the oxidizing acid solution is 10 to 60 g / L.

[0023] Furthermore, in step S2, the weight ratio of alcohol to water in the resin dilution liquid is (2-4): (1-3).

[0024] Furthermore, in step S4, the treatment temperature of the vacuum rotary evaporation treatment is 40-100° C. Preferably, the vacuum degree is 0.1 Pa.

[0025] Another object of the present invention is to provide a catalyst slurry prepared by any of the above-mentioned methods for preparing fuel cell catalyst slurry.

[0026] Another object of the present invention is to provide an application of the above catalyst slurry in preparing a fuel cell catalyst layer.

[0027] The above technical solution involves pore diameter and pore volume obtained by performing nitrogen isothermal adsorption and desorption tests on samples and calculating nitrogen desorption data according to the BJH model.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention improves the problem of sulfonate poisoning the catalyst by limiting the pore size and pore volume of the catalyst. At the same time, by combining acid treatment and the preparation of resin diluent, the distance between the perfluorosulfonic acid resin at the catalyst pore and the catalyst in the pore is shortened, so that the perfluorosulfonic acid resin at the pore becomes a medium for mass transfer, and then the slurry is prepared, so that normal mass transfer can be maintained when the catalyst pore size is small, so that protons and reaction gases can be normally transmitted while avoiding the catalyst from being poisoned by sulfonate, thereby improving the performance of the fuel cell membrane electrode, especially the performance under high current density. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The schematic diagram of the structure of the catalyst with perfluorosulfonic acid resin attached is shown in FIG.

[0031] Figure 2 The schematic diagram of the catalyst structure with perfluorosulfonic acid resin attached thereto according to the present invention.

[0032] Figure 3 The particle size distribution diagram of resin solutions with different dilute concentrations (3M M800, alcohol-water ratio 5:5).

[0033] Figure 4 The polarization curves of the membrane electrodes prepared in Example 1 and Comparative Example 1 are shown.

[0034] Reference numerals: catalyst carrier 1 , active metal 2 , perfluorosulfonic acid resin 3 . DETAILED DESCRIPTION

[0035] The drawings of the present invention are only for illustrative purposes and should not be construed as limiting the present invention. In order to better illustrate the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted.

[0036] An object of the present invention is to provide a method for preparing a fuel cell catalyst slurry, wherein the catalyst is formed by a catalyst carrier carrying an active metal, and is characterized in that the pore volume corresponding to the pores ≤5 nm on the catalyst accounts for more than 30% of the total pore volume, and the preparation method comprises the following steps:

[0037] S1, acidifying the catalyst in an oxidizing acid solution to obtain a hydrophilic catalyst;

[0038] S2, mixing the perfluorosulfonic acid resin dispersion, water and alcohol to prepare a resin diluent;

[0039] S3, dispersing the hydrophilic catalyst obtained in step S1 in water, and adding the resin diluent obtained in step S2, dispersing to obtain a mixed solution;

[0040] S4, subjecting the mixed solution obtained in step S3 to vacuum rotary evaporation, grinding and crushing to obtain catalyst powder;

[0041] S5. Prepare a catalyst slurry by mixing water, a perfluorosulfonic acid resin dispersion, an organic solvent and the catalyst powder obtained in step S4.

[0042] The pores ≤5nm on the catalyst are preferably pores with a pore size of 1.5nm to 5nm, and the pore volume accounts for 30% to 60% of the total pore volume, and the content of active metal in the catalyst is 20 to 70wt%. In one or more embodiments of the present invention, the catalyst carrier is a carbon carrier, and the active metal is platinum. Compared with traditional catalysts, there are more pores with a pore size lower than 5nm in the catalyst of the present technical solution, which reduces the probability of perfluorosulfonic acid resin entering the pores to encapsulate the active metal, effectively reduces the probability of direct contact between perfluorosulfonic acid resin and the catalyst, and improves the problem of catalyst poisoning by sulfonate. In addition, in one or more embodiments of the present invention, in the actual preparation of the catalyst, most of the active metal particles can preferentially enter the micropores of the carbon carrier by controlling the preparation conditions (such as selecting a suitable dispersing solvent), further reducing the poisoning effect of sulfonate on the active metal.

[0043] For step S1, the purpose of acid treatment of the catalyst is to wash away the unstable substances in the catalyst itself, clean the pores, and modify the hydrophilic functional groups in the pores, so as to induce the perfluorosulfonic acid side chains that tend to conduct protons to face inward when the perfluorosulfonic acid resin molecular chains are adsorbed on the catalyst, which is more conducive to its "extending" into the pores.

[0044] For step S2, as the solid content in the perfluorosulfonic acid resin dispersion decreases, the size of the perfluorosulfonic acid resin aggregates will decrease significantly, which means that the number of perfluorosulfonic acid resin molecules in a single aggregate decreases, the flexibility increases, and it is easier to deform. Therefore, by adjusting the alcohol-water ratio and solid content in the perfluorosulfonic acid resin solution solvent, the size of the perfluorosulfonic acid resin aggregates in the dispersion is reduced, and the probability of the resin aggregates partially invading the small holes is increased, which facilitates proton conduction.

[0045] In step S4, during the evaporation of the solvent in the pores by vacuum rotary evaporation, due to the perfluorosulfonic acid resin attached to the pore mouth, there is a certain vacuum negative pressure inside and outside the pores, which makes the perfluorosulfonic acid resin molecular chain at the pore mouth bend into the pores or invade into the pores (such as Figure 2 As shown in the figure), the distance for protons and reaction gases to be transported to the active metal surface can be further shortened, thereby improving the performance of the membrane electrode at high current density.

[0046] Furthermore, the most probable pore size of the catalyst carrier is 1.5-5 nm.

[0047] Furthermore, the solid content of the resin diluent is ≤2wt%.

[0048] Furthermore, in step S3, the weight ratio of the dry weight of the perfluorosulfonic acid resin to the catalyst carrier is 0.01 to 0.2.

[0049] Furthermore, in step S1, in the acidification treatment, the acid concentration is 0.1-1 mol / L, the treatment temperature is 40-100° C., and the treatment time is 60-300 min.

[0050] Furthermore, in step S1, during the acidification treatment, the concentration of the catalyst in the oxidizing acid solution is 10 to 60 g / L.

[0051] Furthermore, in step S2, the weight ratio of alcohol to water in the resin dilution liquid is (2-4): (1-3).

[0052] Furthermore, in step S4, the treatment temperature of the vacuum rotary evaporation treatment is 40-100°C.

[0053] Another object of the present invention is to provide a catalyst slurry prepared by any of the above-mentioned methods for preparing fuel cell catalyst slurry.

[0054] Another object of the present invention is to provide an application of the above catalyst slurry in preparing a fuel cell catalyst layer.

[0055] Example 1

[0056] This embodiment provides a method for preparing a fuel cell catalyst slurry, comprising the following steps:

[0057] S1. Add 10 g of catalyst (the most probable pore size distribution of the catalyst is 3.0 nm, and the BJH pore volume less than 5 nm accounts for 39%) into 250 mL of 0.5 M sulfuric acid solution, the content of the catalyst in the sulfuric acid solution is 40 g / L, stir and heat to 60 ° C, reflux for 150 min, and cool to room temperature; use deionized water to wash and filter repeatedly until the conductivity of the filtrate is <1.0 μS / cm, and dry to obtain a hydrophilic catalyst;

[0058] S2. Add ethanol and deionized water to a dispersion of 3M M800 resin (Ew is ~800 g / mol), stir and disperse for 60 minutes to prepare a resin dilution, wherein the weight ratio of ethanol to water in the resin dilution is 3:2, and the solid content of the resin dilution is 0.5wt%;

[0059] S3, re-dispersing the hydrophilic catalyst obtained in step S1 into water, adding the resin diluent in step S2, the weight ratio (I / C) of the dry weight of the perfluorosulfonic acid resin to the catalyst carrier is 0.1; after ultrasonic dispersion in an ice bath for 30 minutes, transfer to a vacuum rotary evaporator with a vacuum degree of 0.1 Pa, and perform rotary evaporation at 80° C. until the solvent is completely evaporated, and the solid remaining after evaporation is ground and crushed to obtain a catalyst powder attached with the perfluorosulfonic acid resin;

[0060] S4, adding the catalyst powder to water, and adding D2020 resin stock solution and ethanol to form an initial catalyst slurry, the solid content in the slurry is 10wt%, the ratio of ionomer to carbon (I / C) is 0.7, and the weight ratio of ethanol and water in the slurry is 1:1. The catalyst slurry is dispersed by a ball mill to obtain a catalyst slurry after dispersion for 4 hours.

[0061] Example 2

[0062] This embodiment provides a method for preparing a fuel cell catalyst slurry, comprising the following steps:

[0063] S1. Add 10 g of catalyst (the most probable pore size distribution of the catalyst is 3.0 nm, and the BJH pore volume less than 5 nm accounts for 39%) into 1000 mL of 0.1 M sulfuric acid solution, stir and heat to 100 ° C for reaction reflux for 60 min, and cool to room temperature, wherein the content of the catalyst in the sulfuric acid solution is 10 g / L; wash and filter repeatedly with deionized water until the conductivity of the filtrate is <1.0 μS / cm, and dry to obtain the catalyst;

[0064] S2. Add ethanol and water to the Chemours D2021 resin (Ew is ~1100 g / mol) dispersion, stir and disperse for 60 minutes to prepare a resin dilution, wherein the weight ratio of ethanol to water in the resin dilution is 4:1, and the solid content of the resin dispersion is 0.5wt%;

[0065] Steps S3 and S4 are the same as those in Example 1.

[0066] Example 3

[0067] This embodiment provides a method for preparing a fuel cell catalyst slurry, comprising the following steps:

[0068] S1. Add 10 g of catalyst (the most probable pore distribution of the catalyst is 3.0 nm, and the BJH pore volume less than 5 nm accounts for 39%) into 167 mL of 1.0 M sulfuric acid solution, stir and heat to 40 ° C for reaction reflux for 300 min, and cool to room temperature, wherein the content of the catalyst in the sulfuric acid solution is 60 g / L; use deionized water to wash and filter repeatedly until the conductivity of the filtrate is <1.0 μS / cm, and dry to obtain the catalyst;

[0069] S2. Add ethanol and water to a dispersion of Solvay D72 resin (Ew is ~720 g / mol), stir and disperse for 60 minutes to prepare a resin dilution. In the resin dilution, the weight ratio of ethanol to water is 3:1, and the solid content of the resin dispersion is 1.0 wt%.

[0070] Example 4

[0071] This embodiment provides a method for preparing a fuel cell catalyst slurry, which differs from Embodiment 1 in that: in step S3, the weight ratio (I / C) of the dry weight of the perfluorosulfonic acid resin to the catalyst carrier is 0.2.

[0072] Example 5

[0073] This embodiment provides a method for preparing a fuel cell catalyst slurry, which differs from Embodiment 1 in that: in step S3, the ratio of the dry weight of the perfluorosulfonic acid resin to the catalyst carrier (I / C) is 0.01.

[0074] Example 6

[0075] This embodiment provides a method for preparing a fuel cell catalyst slurry, which differs from Embodiment 1 in that: in step S1, the oxidizing acid solution used is a 0.5M nitric acid solution.

[0076] Example 7

[0077] This embodiment provides a method for preparing a fuel cell catalyst slurry, which differs from Embodiment 1 in that: in step S1, the most probable pore distribution of the catalyst is 4.7 nm, and the BJH pore volume smaller than 5 nm accounts for 30%.

[0078] Example 8

[0079] This embodiment provides a method for preparing a fuel cell catalyst slurry, which differs from Embodiment 1 in that: in step S1, the most probable pore size distribution of the catalyst is 1.8 nm, and the BJH pore volume smaller than 5 nm accounts for 52%.

[0080] Comparative Example 1

[0081] This comparative example provides a method for preparing a fuel cell catalyst slurry, which is a traditional slurry preparation method and comprises the following steps:

[0082] 10g of catalyst powder (the most probable pore distribution of the catalyst is 3.0nm, and the BJH pore volume less than 5nm accounts for 39%) is added to 57g of water, and D2020 resin stock solution and ethanol are added to form an initial catalyst slurry. The solid content of the initial slurry is 10wt%, the overall I / C ratio is 0.7, and the weight ratio of ethanol and water in the slurry is 1:1. The catalyst slurry is dispersed by a ball mill and the catalyst slurry is obtained after 4h of dispersion.

[0083] Comparative Example 2

[0084] This comparative example provides a method for preparing a fuel cell catalyst slurry. Compared with Example 1, the preparation step of the resin diluent is omitted. Specifically, the preparation method comprises the following steps:

[0085] S1. Add 10 g of catalyst (the most probable pore distribution of the catalyst is 3.0 nm, and the BJH pore volume less than 5 nm accounts for 39%) into 250 mL of 0.5 M sulfuric acid solution, stir and heat to 60 ° C, reflux for 150 min, and cool to room temperature, wherein the content of the catalyst in the sulfuric acid solution is 40 g / L; use deionized water to wash and filter repeatedly until the conductivity of the filtrate is <1.0 μS / cm, and dry to obtain a hydrophilic catalyst;

[0086] S2. Add the hydrophilic catalyst to water, and add D2020 resin stock solution and ethanol to form an initial catalyst slurry, wherein the solid content in the slurry is 10wt%, the overall I / C ratio is 0.7, and the weight ratio of ethanol and water in the slurry is 1:1. The catalyst slurry is dispersed by a ball mill to obtain a catalyst slurry after dispersion for 4 hours.

[0087] Comparative Example 3

[0088] This comparative example provides a method for preparing a fuel cell catalyst slurry, which is different from Example 1 in that: in step S2, the solid content of the resin diluent is 3 wt%.

[0089] Comparative Example 4

[0090] This comparative example provides a method for preparing a fuel cell catalyst slurry. Compared with Example 1, the step of acid-treating the catalyst is omitted. Specifically, the preparation method comprises the following steps:

[0091] S1. Add ethanol and deionized water to a dispersion of 3M M800 resin (Ew is ~800 g / mol), stir and disperse for 60 minutes to prepare a resin dilution, wherein the weight ratio of ethanol to water in the resin dilution is 1:4, and the solid content of the resin dilution is 0.5wt%;

[0092] S2, dispersing the catalyst (the most probable pore distribution of the catalyst is 3.0 nm, and the BJH pore volume less than 5 nm accounts for 39%) in water, adding the resin diluent in step 1, and the weight ratio of the resin dry weight to the catalyst carrier (I / C) is 0.1; after ultrasonic dispersion in an ice bath for 30 minutes, transfer to a rotary evaporator, the vacuum degree is 0.1 Pa, and rotary evaporation is performed at 80° C. until the solvent is completely evaporated, and the solid remaining after evaporation is ground and crushed to obtain a catalyst powder attached with perfluorosulfonic acid resin;

[0093] S3, adding the catalyst powder to water, and adding D2020 resin stock solution to form an initial catalyst slurry, the solid content in the slurry is 10wt%, the overall I / C ratio is 0.7, and the weight ratio of ethanol and water in the slurry is 1:1. The catalyst slurry is dispersed by a ball mill to obtain a catalyst slurry after dispersion for 4 hours.

[0094] Comparative Example 5

[0095] This comparative example provides a method for preparing a fuel cell catalyst slurry, which is different from Example 1 in that: in step S3, the weight ratio (I / C) of the dry weight of the perfluorosulfonic acid resin to the catalyst carrier is 0.3.

[0096] Comparative Example 6

[0097] This comparative example provides a method for preparing a fuel cell catalyst slurry, which is different from Example 1 in that: in step S3, the weight ratio (I / C) of the dry weight of the perfluorosulfonic acid resin to the catalyst carrier is 0.005.

[0098] Comparative Example 7

[0099] This comparative example provides a method for preparing a fuel cell catalyst slurry, which differs from Example 1 in that: in step S1, the most probable pore distribution of the catalyst is >10nm (10nm-super detection range), and the BJH pore volume less than 5nm accounts for 5%.

[0100] The catalysts used in the above embodiments and comparative examples can be prepared by a conventional platinum particle deposition method. The following is an example of the method: the carbon carrier is added to a mixed solvent of isopropanol and water (the ratio of isopropanol to water is 1:1), ultrasonically dispersed for 15 minutes, an appropriate amount of chloroplatinic acid solution (concentration is 0.01 g / mL) is added and ultrasonically dispersed for 30 minutes, and a 1 mol / L sodium carbonate solution is added to adjust the pH to 8-9; an excess amount of reducing agent (methanol solution) is added and stirred for 2 hours; and a catalyst filter cake is obtained through precipitation, washing, and filtering processes, and the filter cake is transferred to an oven and dried at 80°C for 6 hours to obtain a catalyst.

[0101] The catalyst slurries prepared by the preparation methods provided in Examples 1 to 8 and Comparative Examples 1 to 7 were respectively prepared into cathode catalyst layers, and further assembled into membrane electrodes, specifically as follows: the catalyst slurry was coated on one side of the proton exchange membrane and dried to obtain a cathode catalyst layer, and the platinum loading was 0.25 mg / cm 2 ; Further, an anode catalyst is coated on the other side of the proton exchange membrane and dried to obtain a CCM; and further, a frame and a gas diffusion layer are assembled to obtain a membrane electrode.

[0102] Test experiment 1: Dynamic light scattering (DLS) was used to measure the aggregate size of resin solutions with different dilute concentrations. The results are as follows: Figure 3 shown.

[0103] Test experiment 2: The membrane electrodes prepared in Examples 1 to 8 and Comparative Examples 1 to 7 were subjected to electrical performance tests. The polarization performance curve of the membrane electrode single cell was tested using an 850e fuel cell test system. The test conditions were 60° C. and 67% RH. The test results are shown in Table 1.

[0104] Table 1

[0105]

[0106]

[0107] Figure 3 The particle size distribution diagram of different concentrations of dilute resin solution (3M M800, alcohol-water ratio 3:2) shows that as the solid content of the perfluorosulfonic acid resin dispersion decreases, the size of the aggregates in the dispersion gradually decreases. When the solid content is 2% or less, the size of the main aggregates in the dispersion is no more than 10nm and remains basically unchanged. The reduction of the aggregate size from thousands of nm to <10nm can effectively increase the degree of "invasion" of the pores by the adsorbed resin molecules on the surface of the catalyst particles, thereby effectively shortening the effective distance between the protons and the Pt particles deep in the pores.

[0108] Figure 4Table 1 shows the voltage of the membrane electrode corresponding to Examples 1 to 8 and Comparative Examples 1 to 7 at different current densities. Compared with Comparative Examples 1 to 7, the high current density voltage performance of Examples 1 to 8 is improved, especially at 2.4 A / cm 2 The performance is significantly improved. This shows that after the catalyst carbon carrier pore hydrophilic functional groups are modified by dilute concentration oxidizing acid treatment in the present invention, the small particle size of the low concentration perfluorosulfonic acid resin dispersion and the vacuum rotary evaporation process are used to make the perfluorosulfonic acid ionomer dispersion partially bend into the pore or "invade" the pore, shortening the proton transmission distance of the Pt particles in the pore, and improving the performance degradation caused by the limited proton conduction in the pore under medium and high current density.

[0109] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the claims of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing a fuel cell catalyst slurry, wherein the catalyst is formed by a catalyst carrier carrying an active metal, characterized in that: The pore volume corresponding to the pores of ≤5 nm on the catalyst accounts for more than 30% of the total pore volume, and the preparation method comprises the following steps: S1, acidifying the catalyst in an oxidizing acid solution to obtain a hydrophilic catalyst; S2, mixing the perfluorosulfonic acid resin dispersion, water and alcohol to prepare a resin diluent; S3, dispersing the hydrophilic catalyst obtained in step S1 in water, and adding the resin diluent obtained in step S2, dispersing to obtain a mixed solution; S4, subjecting the mixed solution obtained in step S3 to vacuum rotary evaporation, grinding and crushing to obtain catalyst powder; S5. Prepare a catalyst slurry by mixing water, a perfluorosulfonic acid resin dispersion, an organic solvent and the catalyst powder obtained in step S4.

2. The method for preparing a fuel cell catalyst slurry according to claim 1, characterized in that: The most probable pore size of the catalyst carrier is 1.5-5 nm.

3. The method for preparing a fuel cell catalyst slurry according to claim 1, characterized in that: The solid content of the resin diluent is ≤2wt%.

4. The method for preparing a fuel cell catalyst slurry according to claim 1, characterized in that: In step S3, the weight ratio of the dry weight of the perfluorosulfonic acid resin to the catalyst carrier is 0.01 to 0.

2.

5. The method for preparing a fuel cell catalyst slurry according to claim 1, characterized in that: In step S1, in the acidification treatment, the acid concentration is 0.1-1 mol / L, the treatment temperature is 40-100°C, and the treatment time is 60-300 min.

6. The method for preparing a fuel cell catalyst slurry according to claim 1, characterized in that: In step S1, during the acidification treatment, the concentration of the catalyst in the oxidizing acid solution is 10 to 60 g / L.

7. The method for preparing a fuel cell catalyst slurry according to claim 1, characterized in that: In step S2, the weight ratio of alcohol to water in the resin diluent is (2-4):(1-3).

8. The method for preparing a fuel cell catalyst slurry according to claim 1, characterized in that: In step S4, the treatment temperature of the vacuum rotary evaporation treatment is 40-100°C.

9. A catalyst slurry prepared by the method for preparing a fuel cell catalyst slurry according to any one of claims 1 to 8.

10. Use of the catalyst slurry according to claim 9 in preparing a catalyst layer of a fuel cell.

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