Recovery and utilization method of fuel cell catalyst slurry

Abstract

The invention relates to a method for recycling fuel cell catalyst slurry. The method comprises the following steps: shearing and dispersing to-be-recycled catalyst slurry, and filtering for the first time to obtain a primary filter cake and primary filtrate; performing low-temperature centrifugal treatment on the primary filtrate, and performing secondary filtration to obtain a secondary filter cake and secondary filtrate; the obtained secondary filtrate is the recycled catalyst slurry. According to the present invention, the new particle aggregation is controlled and reduced while the large aggregated particles are separated so as to ensure that the slurry obtained after the separation of the catalyst-resin aggregate without the large particles can be used for the CCM production. Specifically, the low temperature is controlled, catalyst particle aggregation in the centrifugal process is relieved (namely, the dispersed state of fine slurry is fixed), meanwhile, aggregation of large particles is accelerated through high-speed centrifugation, uniform dispersed slurry and large particles are effectively separated, and invalid catalyst slurry is recycled.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell manufacturing technology, specifically relating to a method for the recovery and utilization of fuel cell catalyst slurry. Background Technology

[0002] Catalyst slurry (also known as catalyst ink) is a crucial raw material for fuel cell membrane electrode assembly (MEA) production, and its dispersion uniformity significantly impacts the final battery performance. The catalyst slurry consists of carbon-supported nanoscale platinum catalyst (tens of nanometers in size), perfluorosulfonic acid resin (as a proton conductor), and a water-alcohol solvent. The platinum catalyst and perfluorosulfonic acid resin form aggregated particles, typically with a particle size controlled within a moderate range (1-5 μm) to ensure adequate flowability and a uniformly covered catalyst layer structure, thereby achieving optimal microstructure for electron conduction and gas transport. However, the catalyst slurry is thermodynamically unstable, and over time, these aggregated particles easily agglomerate, growing into larger particles. Excessively large aggregated particle sizes (>10 μm) can easily lead to clogging of the spray nozzle or die, uneven coating distribution, and decreased electrode performance. Even larger, more significant agglomerations can result in a decrease in the active surface area of ​​the fuel cell, localized excessive thickness, and high ohmic losses. In the laboratory preparation and continuous production of membrane electrode slurries, catalyst slurries are often not used up at once. If left for too long, the particles will aggregate and fail, resulting in the waste of a large amount of expensive catalyst slurry. The disposal of the remaining slurry has become a thorny problem.

[0003] Existing platinum catalyst slurry recovery technologies mostly employ high-temperature roasting or chemical dissolution methods to regenerate platinum catalysts, which not only wastes raw materials but also incurs high environmental costs.

[0004] Patent CN101382489A describes a method for determining the stability of a platinum catalyst slurry by centrifuging it at a certain speed for a period of time. However, during centrifugation, the high-speed rotation causes some particles to gradually grow larger, significantly impacting the slurry's stability and making it impossible to accurately assess its stability.

[0005] Patent CN119715271A provides a method for determining the state of fuel cell catalyst slurry using graded centrifugation, which uses the measurement of viscosity, conductivity and transmittance to understand and analyze the dispersion state of the slurry.

[0006] Patent CN118547163A uses an eluent to separate platinum-carbon catalysts, which introduces impurities. Furthermore, the eluent contains inorganic reducing agents, decomposing agents, and dissolving agents, which can cause serious environmental pollution.

[0007] This invention first uses low-temperature centrifugation to separate large aggregated particles, and then evaluates the state of the catalyst slurry by changes in viscosity and solid content to determine whether the stored catalyst slurry can be recycled. The operation is simple and easy to implement, does not require the addition of other chemical reagents, greatly improves the utilization rate of the slurry, reduces catalyst waste, and lowers production costs.

[0008] Compared to patent application CN119715271A, which determines the dispersion state of slurry by measuring viscosity, conductivity, and transmittance, this invention determines whether the slurry can be recycled by observing changes in viscosity and solid content. In terms of process method, this invention employs low-temperature centrifugation, which effectively inhibits particle aggregation and growth during centrifugation, thereby achieving: 1) finer separation of large aggregates; 2) reduced formation of new agglomerates during separation; and 3) improved separation efficiency.

[0009] The core of this invention lies in controlling and reducing the aggregation of new particles while separating larger aggregated particles, thereby ensuring that the slurry after separation without large catalyst-resin aggregates can be used for CCM production. Specifically, a lower temperature is controlled to reduce catalyst particle agglomeration during centrifugation (i.e., to fix the dispersion state of the fine slurry), while high-speed centrifugation is used to accelerate the aggregation of large particles, achieving effective separation of uniformly dispersed slurry from coarse particles, and realizing the recycling of "dead" catalyst slurry.

[0010] Currently, the main methods for evaluating the quality of catalyst slurries include rheological curve testing, conductivity testing, cryo-electron microscopy, solid content testing, and laser particle size analysis. However, these devices are expensive and cannot reflect the complete dispersion state. Therefore, this invention uses low-temperature centrifugation and slurry rheological property testing to evaluate whether spent catalyst slurries can be used after being left to stand for a period of time. This achieves the recycling and efficient application of spent catalyst slurries in a simple, easy-to-implement, and convenient manner. Summary of the Invention

[0011] The purpose of this invention is to address the problems existing in the prior art by providing a method for the recovery and utilization of fuel cell catalyst slurry.

[0012] This invention utilizes low-temperature centrifugation and rheological testing to dynamically adjust the properties of spent catalyst slurry, evaluating its usability after a period of storage and achieving efficient recycling and application of spent catalyst slurry. First, unused remaining slurry is collected and stored at low temperature. Then, it undergoes low-temperature centrifugation, followed by filtration to remove large particle agglomerates. The filtrate is directly recovered to prepare new catalyst slurry, while the large particle agglomerates are recycled as platinum. Compared to existing technologies, this invention features a simple and easy-to-implement process, high slurry utilization, reduced production costs, and minimized environmental pollution. This method is suitable for the resource-based reuse of platinum-based catalysts.

[0013] The objective of this invention can be achieved through the following methods: This invention provides a method for recycling and utilizing fuel cell catalyst slurry, comprising the following steps: The catalyst slurry to be recovered is sheared and dispersed, and then filtered for the first time to obtain a primary filter cake and a primary filtrate. The primary filtrate is centrifuged at low temperature and then filtered for the second time to obtain a secondary filter cake and a secondary filtrate. If the obtained secondary filtrate passes the test, it is the recovered catalyst slurry. The temperature for low-temperature centrifugation is 5-15℃, the rotation speed is 1000-3000 rpm, and the time is 10-30 min.

[0014] As an embodiment of the present invention, the catalyst slurry to be recycled is the slurry remaining after the use of fresh catalyst slurry and left for a long time; the fresh catalyst slurry is the newly prepared catalyst slurry to be used.

[0015] As an embodiment of the present invention, the preferred time for low-temperature centrifugation is 10-20 min.

[0016] As an embodiment of the present invention, the solid content (platinum carbon catalyst, perfluorosulfonic acid resin) of the fresh catalyst slurry is 2-10%, and the viscosity is 4-40 mPa·s.

[0017] As an embodiment of the present invention, the fresh catalyst slurry comprises the following components: 1-10 parts by mass of catalyst, 1-15 parts by mass of perfluorosulfonic acid resin solution, and the remainder being a water-alcohol solvent.

[0018] The catalyst includes one of the following: platinum-carbon catalyst and oxidative catalyst. The platinum content of the platinum-carbon catalyst is 20-60%; the mass fraction of the perfluorosulfonic acid resin solution is 5-20%.

[0019] The materials are dispersed and mixed to prepare a catalyst slurry. The dispersion method includes one of high-speed shearing, ultrasonication, and ball milling.

[0020] The mass ratio of ionomer resin in the catalyst slurry to carbon support in the catalyst (referred to as I / C ratio) is 0.7-1.0.

[0021] The solvent includes one or more of deionized water and alcohols. The alcohols include one of n-propanol, isopropanol, and ethanol, preferably a combination of deionized water and alcohol, with a water-to-alcohol mass ratio of 1:5 to 5:1.

[0022] As an embodiment of the present invention, the shearing and dispersion time is 5-30 min.

[0023] As an embodiment of the present invention, the first filtration is through a coarse filter with a mesh size between 100 and 200 mesh.

[0024] As an embodiment of the present invention, the second filtration is performed through a fine filter with a mesh size between 300 and 400 mesh.

[0025] As an embodiment of the present invention, the filter screens used for the first filtration and the second filtration are either PTFE filter membranes or nylon mesh.

[0026] As an embodiment of the present invention, filtration can ensure that there are no large-scale aggregated solid particles in the separated slurry. The judgment methods mainly include several aspects: First, place the solution in a well-lit area and observe it after a period of time. If no suspended particles or sediment are visible to the naked eye, it indicates that there are no large-scale aggregated solid particles in the separated slurry. Second, if there is no obvious residual solid matter on the filter screen after filtration, it indicates that there are no large-scale aggregated solid particles in the separated slurry. Third, observe with an optical microscope or electron microscope. Take a small amount of solution and drop it onto a glass slide to make a temporary slide for observation. If no obvious large particles are found, it indicates that there are no large-scale aggregated solid particles in the separated slurry.

[0027] The recycling and utilization method of the present invention can be used for catalyst slurry that has been stored for a long time (such as 1-5 days) and the recovered catalyst slurry can be obtained through the low temperature centrifugation treatment of the present invention.

[0028] As an embodiment of the present invention, the viscosity of the recovered catalyst slurry changes by a rate of no more than 10-40% compared to the viscosity of the fresh catalyst slurry, and the solid content of the recovered catalyst slurry changes by a rate of no more than 20-60% compared to the solid content of the fresh catalyst slurry.

[0029] Determining whether something can be recycled by analyzing changes in viscosity and solids content is a matter of technical feasibility and economic rationality. For example, if the solids content and viscosity are too low, it means that the content of valuable platinum catalysts and ionomer resins in the slurry is low, and the I / C ratio may also change significantly. Treating such slurries faces the dilemma of "input exceeding output".

[0030] This invention provides a method for determining the recovery of fuel cell catalyst slurry, comprising the following steps: (1) After shearing and dispersing the catalyst slurry to be recovered, the first filtration is performed to obtain a primary filter cake and a primary filtrate; the primary filtrate is subjected to low-temperature centrifugation and then filtered a second time to obtain a secondary filter cake and a secondary filtrate. The temperature for low-temperature centrifugation is 5-15℃, the rotation speed is 1000-3000 rpm, and the time is 10-30 min.

[0031] (2) Judgment is made based on the recovery standards for viscosity and solid content: If the viscosity and solid content meet the recycling standards, the remaining catalyst slurry to be recycled will be treated and recycled using these parameters, and the resulting secondary filtrate will be the catalyst slurry to be directly recycled. If the viscosity and solid content do not meet the recycling standards, the catalyst slurry to be recycled cannot be reused and will be recycled as platinum resources. The standards for viscosity and solid content recovery are as follows: the viscosity of the recovered catalyst slurry should not differ from that of the fresh catalyst slurry by more than 10-40%, and the solid content of the recovered catalyst slurry should not differ from that of the fresh catalyst slurry by more than 20-60%.

[0032] The rate of change in the recovery standard is calculated as follows: Viscosity change rate = (Viscosity of fresh catalyst slurry - Viscosity of secondary filtrate) / Viscosity of fresh catalyst slurry * 100% Solid content change rate = (Solid content of fresh catalyst slurry - Solid content of secondary filtrate) / Solid content of fresh catalyst slurry * 100% This invention refines the low-temperature centrifugation parameters and uses orthogonal experimental design within the aforementioned parameter range to determine the optimal centrifugation parameters. During centrifugation, lower temperatures, slower rotation speeds, and shorter times make it more difficult to separate catalyst aggregates, but result in higher slurry recovery rates.

[0033] As an embodiment of the present invention, the catalyst slurry to be recycled is the slurry remaining after the use of fresh catalyst slurry and left for 1-5 days; the fresh catalyst slurry is the newly prepared catalyst slurry to be used.

[0034] As an embodiment of the present invention, the catalyst in the catalyst slurry includes one of a platinum-carbon catalyst and an oxide catalyst.

[0035] As an embodiment of the present invention, the slurry to be recovered is stirred before centrifugation; the stirring time is 10-30 minutes.

[0036] In one embodiment of the present invention, filtration involves first passing the slurry through a coarse filter (100-200 mesh) and then through a fine filter (300-400 mesh). The mesh size is determined according to the dispersion requirements of different slurry systems, such as selecting 100 mesh, 200 mesh, 300 mesh, or 400 mesh. PTFE filter membranes, nylon mesh, or other filter materials are used. Filtration ensures that the separated slurry is free of large-scale aggregated solid particles.

[0037] The recycling standard is based on tests conducted under specific experimental conditions. If the slurry ratio is significantly adjusted, the optimal parameter values ​​need to be re-evaluated. The viscosity and solids content of the slurry directly determine its rheological properties, which are the primary factors affecting the success of the coating process and the formation of the catalyst layer's microstructure. The catalyst layer is the site of the electrochemical reaction; defects in the catalyst layer directly impact the performance of the fuel cell unit. Its microstructure must simultaneously ensure the smooth transport of reactant gases, protons, electrons, and generated water, requiring a suitable porous structure.

[0038] Excessive viscosity and solids content: The slurry resembles a thick syrup with poor fluidity. During coating, it is difficult to spread evenly, resulting in uneven catalyst layer thickness. During drying, poor solvent evaporation can easily lead to internal stress and cracking. More importantly, excessive viscosity makes it difficult for the catalyst and ionomers in the slurry to form an ideal micro-network structure, resulting in low porosity and an undesirable pore size distribution in the dried catalyst layer. This severely hinders the transport of reactant gases and water.

[0039] Insufficient viscosity and solid content: The slurry, resembling clear water, while exhibiting good fluidity, is prone to sedimentation and separation of solids, resulting in poor dispersibility and potential re-agglomeration of catalyst particles. During coating, an excessively thin slurry will flow excessively before drying, making it difficult to control the consistency of areal density (catalyst loading per unit area). Simultaneously, the drying process becomes difficult and may cause coating cracking. The resulting catalyst layer may lack structural strength, and the ionomer coating of catalyst particles may be uneven, reducing the effective three-phase reaction interface and directly impacting the battery's chemical reaction efficiency.

[0040] In existing technologies, filtration methods are used, which are suitable for freshly prepared slurries. However, older slurries, after being left for a period of time, become ineffective due to catalyst particle agglomeration, making it difficult to filter out the effective components. Sedimentation is more suitable for treating waste slurries, allowing for the collection and recovery of bottom catalyst deposits after removing the supernatant. Conventional centrifugation can achieve rapid separation, but high-speed rotation generates a large amount of heat, accelerating the agglomeration of both agglomerated and unagglomerated catalyst particles, resulting in significant catalyst waste. The core idea of ​​this invention is to control a lower temperature to reduce catalyst particle agglomeration during centrifugation (i.e., fix the dispersion state of the fine slurry), while simultaneously using high-speed centrifugation to accelerate the aggregation of large particles, achieving effective separation of uniformly dispersed slurry from coarse particles.

[0041] Compared with the prior art, the present invention has the following beneficial effects: (1) Low temperature centrifugation synergistic technology: By fixing the dispersion state of catalyst particles at low temperature and combining it with low temperature centrifugation, the recovery rate of precious metals and the purity of regenerated slurry can be significantly improved.

[0042] (2) Low-cost regeneration process: improves slurry recovery rate, reduces fuel cell cost, eliminates the need for complex chemical elution steps, reduces the use of strong acid and alkali reagents, and reduces environmental pollution and treatment costs.

[0043] (3) Industrialization prospects: It is compatible with existing coating processes and is suitable for large-scale production.

[0044] (4) By adopting the method of the present invention, the utilization rate of catalyst slurry is improved, the problem of the inability to recycle and process waste catalyst slurry is solved, and the production cost is reduced. Recycling waste materials to prepare new qualified catalyst slurry can ensure the consistency and high performance of CCM quality, and is a method for improving the usability of catalyst slurry. Attached Figure Description

[0045] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the recycling and utilization method of the present invention. Detailed Implementation

[0046] The present invention will now be described in detail with reference to specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0047] This invention provides a method for the recovery and utilization of fuel cell catalyst slurry, such as... Figure 1 As shown, the specific steps are as follows: Step 1: Prepare fresh catalyst slurry: Add catalyst with a platinum content of 20-60%, deionized water, n-propanol, and perfluorosulfonic acid resin with a mass fraction of 5-20% to a flat-bottomed test tube and disperse for 0.5-2 hours to obtain a mixed slurry. Step 2: Test the rheological properties of the fresh catalyst slurry, with a viscosity range of 4-40 mPa·s; Step 3: Stir and disperse the slurry that has been left for a long time (e.g., after several days) for 30 minutes, then centrifuge it under certain conditions: a centrifugation temperature range of 5-15℃, a centrifugation time of 10-30 minutes, and a rotation speed of 1000-3000 rpm. Conduct an orthogonal experimental design based on the above parameter range to select the optimal experimental conditions. Step 4: After centrifugation, filter the solution and test the rheological curve of the filtrate. Weigh the solid filter cake. Dry the filter cake sediment to recover platinum metal. Step 5: Analyze the filtrate after centrifugation to determine whether it meets the recycling requirements based on the viscosity of the rheological curve. Specifically, the viscosity of the recovered catalyst slurry should not differ from that of the fresh catalyst slurry by more than 10-40%, and the solid content of the recovered catalyst slurry should not differ from that of the fresh catalyst slurry by more than 20-60%.

[0048] Step 7: Use the recycled liquid to prepare fresh mixed slurry again, and after testing the viscosity and finding that it meets the requirements, proceed with production again.

[0049] Preparation of fresh catalyst slurry used in the examples: A mixture of 60% platinum-carbon catalyst, deionized water, n-propanol, and 20% perfluorosulfonic acid resin solution was prepared. The solid content (platinum-carbon catalyst and perfluorosulfonic acid resin) of the slurry was 5%, the I / C ratio was 0.8, and the water-to-alcohol volume ratio was 1:1. The mixture was sheared and dispersed for 1.5 hours using a high-speed disperser to obtain a uniformly dispersed and stable slurry. Viscosity analysis was performed, and the slurry viscosity was found to be 12.5 mPa·s. The slurry was divided into 9 portions and stored at a low temperature (5℃) for 3 days for subsequent use.

[0050] Example 1 Take a portion of the catalyst slurry that has been stored at low temperature (5℃) for 3 days, shear and disperse it for 10 minutes, filter it through a 300-mesh filter (coarse filter), and obtain the primary filter cake (weight W). 1-1 (1.62 g), first filtrate (weight W) 1-2 (8.52 g); The primary filtrate was centrifuged at 5000 rpm for 20 minutes at 5°C and filtered through a 400-mesh filter to obtain the secondary filtrate (mass W). 1-3 (7.95g), secondary filter cake (weight W) 1-4 The sample was 0.82 g. The viscosity μ1 of the secondary filtrate was measured to be 7.3 mPa·s, and the solid content of the secondary filtrate was 1.5%.

[0051] The viscosity change rate of the secondary filtrate was 42%, the sum of the two filter cakes was 2.44g, the solid content change rate was 70%, and the secondary filtrate had no recycling value.

[0052] Example 2 Take a portion of the catalyst slurry that has been stored at low temperature (5℃) for 3 days, shear and disperse it for 10 minutes, filter it through a 300-mesh filter (coarse filter), and obtain the primary filter cake (weight W). 2-1 (1.65 g), first filtrate (weight W) 2-2 (8.55 g); The primary filtrate was centrifuged at 5000 rpm for 20 minutes at 15°C and filtered through a 400-mesh filter to obtain the secondary filtrate (mass W). 2-3(8.00g), secondary filter cake (weight W) 2-4 The sample was 0.85 g. The viscosity of the secondary filtrate (μ2) was measured to be 5.36 mPa·s, and the solid content of the secondary filtrate was 1.4%.

[0053] The viscosity change rate of the secondary filtrate was 57%, the sum of the two filter cakes was 2.50g, the solid content change rate was 72%, and the secondary filtrate had no recycling value.

[0054] Example 3 Take a portion of the catalyst slurry that has been stored at low temperature (5℃) for 3 days, shear and disperse it for 10 minutes, filter it through a 300-mesh filter (coarse filter), and obtain the primary filter cake (weight W). 3-1 (1.69 g), first filtrate (weight W) 3-2 (8.32 g); The primary filtrate was centrifuged at 5000 rpm for 20 minutes at 30°C and filtered through a 400-mesh filter to obtain the secondary filtrate (mass W). 3-3 (8.00g), secondary filter cake (weight W) 3-4 The sample was 0.75 g. The viscosity of the secondary filtrate (μ3) was measured to be 5.05 mPa·s, and the solid content of the secondary filtrate was 1.0%.

[0055] The viscosity change rate of the secondary filtrate was 60%, the sum of the two filter cakes was 2.44g, the solid content change rate was 80%, and the secondary filtrate had no recycling value.

[0056] Example 4 Take a portion of the catalyst slurry that has been stored at low temperature (5℃) for 3 days, shear and disperse it for 10 minutes, filter it through a 300-mesh filter (coarse filter), and obtain the primary filter cake (weight W). 4-1 (1.60 g), first filtrate (weight W) 4-2 (8.50 g); The primary filtrate was centrifuged at 1000 rpm for 20 minutes at 5°C and filtered through a 400-mesh filter to obtain the secondary filtrate (mass W). 4-3 (7.80g), secondary filter cake (weight W) 4-4 The sample was 0.89 g. The viscosity of the secondary filtrate (μ4) was measured to be 8.2 mPa·s, and the solid content of the secondary filtrate was 2.3%.

[0057] The viscosity change rate of the secondary filtrate was 34%, the sum of the two filter cakes was 2.49g, the solid content change rate was 54%, and the secondary filtrate has recycling value.

[0058] Example 5 Take a portion of the catalyst slurry that has been stored at low temperature (5℃) for 3 days, shear and disperse it for 10 minutes, filter it through a 300-mesh filter (coarse filter), and obtain the primary filter cake (weight W).5-1 (1.56 g), first filtrate (weight W) 5-2 (8.70 g); The primary filtrate was centrifuged at 3000 rpm for 20 minutes at 5°C and filtered through a 400-mesh filter to obtain the secondary filtrate (mass W). 5-3 (7.90g), secondary filter cake (weight W) 5-4 The sample was 0.69 g. The viscosity of the secondary filtrate (μ5) was measured to be 8.0 mPa·s, and the solid content of the secondary filtrate was 2.0%.

[0059] The viscosity change rate of the secondary filtrate was 36.0%, the sum of the two filter cakes was 2.25g, the solid content change rate was 60%, and the secondary filtrate has recycling value.

[0060] Example 6 Take a portion of the catalyst slurry that has been stored at low temperature (5℃) for 3 days, shear and disperse it for 10 minutes, filter it through a 300-mesh filter (coarse filter), and obtain the primary filter cake (weight W). 6-1 (1.58 g), first filtrate (weight W) 6-2 (8.26 g); The primary filtrate was centrifuged at 3000 rpm for 10 minutes at 5°C and filtered through a 400-mesh filter to obtain the secondary filtrate (mass W). 6-3 (8.10g), secondary filter cake (weight W) 6-4 The sample was 0.72 g. The viscosity of the secondary filtrate (μ6) was measured to be 10.16 mPa·s, and the solid content of the secondary filtrate was 3.5%.

[0061] The viscosity change rate of the secondary filtrate was 19%, the sum of the two filter cakes was 2.30g, the solid content change rate was 30%, and the secondary filtrate has recycling value.

[0062] Example 7 Take a portion of the catalyst slurry that has been stored at low temperature (5℃) for 3 days, shear and disperse it for 10 minutes, filter it through a 300-mesh filter (coarse filter), and obtain the primary filter cake (weight W). 7-1 (1.56 g), first filtrate (weight W) 7-2 (8.70 g); The primary filtrate was centrifuged at 3000 rpm for 30 minutes at 5°C and filtered through a 400-mesh filter to obtain the secondary filtrate (mass W). 7-3 (7.90g), secondary filter cake (weight W) 7-4 The sample weight was 0.69 g. The viscosity of the secondary filtrate (μ7) was measured to be 7.56 mPa·s, and the solid content of the secondary filtrate was 1.8%.

[0063] The viscosity change rate of the secondary filtrate was 40%, the sum of the two filter cakes was 2.25g, the solid content change rate was 64%, and the secondary filtrate had no recycling value.

[0064] Example 8 Take a portion of the catalyst slurry that has been stored at low temperature (5℃) for 3 days, shear and disperse it for 10 minutes, filter it through a 300-mesh filter (coarse filter), and obtain the primary filter cake (weight W). 8-1 (1.56 g), first filtrate (weight W) 8-2 (8.72 g); The primary filtrate was centrifuged at 1000 rpm for 10 minutes at 5°C and filtered through a 400-mesh filter to obtain the secondary filtrate (mass W). 8-3 (7.95g), secondary filter cake (weight W) 8-4 The sample was 0.62 g. The viscosity of the secondary filtrate (μ8) was measured to be 10.82 mPa·s, and the solid content of the secondary filtrate was 3.8%.

[0065] The viscosity change rate of the secondary filtrate was 13%, the sum of the two filter cakes was 2.18g, the solid content change rate was 24%, and the secondary filtrate has recycling value.

[0066] Example 9 Take a portion of the catalyst slurry that has been stored at low temperature (5℃) for 3 days, shear and disperse it for 10 minutes, filter it through a 300-mesh filter (coarse filter), and obtain the primary filter cake (weight W). 9-1 (1.63 g), first filtrate (weight W) 9-2 (8.75 g); The primary filtrate was centrifuged at 2000 rpm for 10 minutes at 5°C and filtered through a 400-mesh filter to obtain the secondary filtrate (mass W). 9-3 (7.95g), secondary filter cake (weight W) 9-4 The sample was 0.68 g. The viscosity of the secondary filtrate (μ9) was measured to be 10.35 mPa·s, and the solid content of the secondary filtrate was 3.65%.

[0067] The viscosity change rate of the secondary filtrate was 17%, the sum of the two filter cakes was 2.31g, the solid content change rate was 27%, and the secondary filtrate has recycling value.

[0068] Example 10 The secondary filtrates obtained in Examples 4, 5, and 6 were supplemented with solid material (based on an I / C ratio of 0.8, with the solid content consisting of supplemental ionomer solution and platinum-carbon catalyst) weighing the sum of the two filter cakes. The mixture was sheared and dispersed using a high-speed disperser for 2 hours to obtain a uniformly dispersed new catalyst slurry. Viscosity analysis was performed, and the slurry viscosities were 11.81, 12.55, and 12.56 mPa·s, respectively, which were basically the same as those of the fresh slurry. This was considered to meet the usage requirements, thus confirming that the secondary filtrate could be recycled.

[0069] The parameters and test results of the embodiments are shown in Table 1: Table 1

[0070] Therefore, according to the solution provided by this invention, if the viscosity of the recovered slurry changes by no more than 10-40% compared to the test results of the fresh slurry, and there are no large-scale aggregated solid particles in the separated slurry, and the solid content does not exceed 20-60% of the solid content of the fresh slurry, then the filtered slurry can be recycled as a catalyst slurry. Otherwise, if the above range is not met, the filtered slurry cannot be used and should be directly recycled as waste platinum. During centrifugation, the lower the temperature, the lower the rotation speed, and the shorter the time, the more difficult it is to separate catalyst aggregates, but the slurry recovery rate is high. The fresh slurry prepared using the recovered liquid meets the required viscosity range and can be used in production applications. In addition, this invention, by combining centrifugation and viscosity analysis, shortens the previously time-consuming catalyst slurry evaluation process to about 1 hour, solving the industry pain points of low quality inspection efficiency and ambiguous standards in fuel cells, and is suitable for batch quality control in large-scale production.

[0071] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for recovering and utilizing fuel cell catalyst slurry, characterized in that, Includes the following steps: The catalyst slurry to be recovered is sheared and dispersed, and then filtered for the first time to obtain a primary filter cake and a primary filtrate. The primary filtrate is centrifuged at low temperature and then filtered for the second time to obtain a secondary filter cake and a secondary filtrate. If the obtained secondary filtrate passes the test, it is the recovered catalyst slurry. The temperature for low-temperature centrifugation is 5-15℃, the rotation speed is 1000-3000 rpm, and the time is 10-30 min.

2. The recycling and utilization method according to claim 1, characterized in that, The catalyst slurry to be recycled is the slurry remaining after the use of fresh catalyst slurry and left for a long time; the fresh catalyst slurry is the newly prepared catalyst slurry to be used. The solid content of the fresh catalyst slurry ranges from 2-10%, and the viscosity ranges from 4-40 mPa·s.

3. The recycling and utilization method according to claim 2, characterized in that, The fresh catalyst slurry comprises the following components: 1-10 parts by mass of catalyst, 1-15 parts by mass of perfluorosulfonic acid resin solution, and the balance being a water-alcohol solvent.

4. The recycling and utilization method according to claim 1, characterized in that, The first filtration is through a coarse filter with a mesh size between 100 and 200.

5. The recycling and utilization method according to claim 1, characterized in that, The second filtration is through a fine filter with a mesh size between 300 and 400.

6. The recycling and utilization method according to claim 1, characterized in that, The viscosity of the recovered catalyst slurry should not differ from that of the fresh catalyst slurry by more than 10-40%, and the solid content of the recovered catalyst slurry should not differ from that of the fresh catalyst slurry by more than 20-60%. The specific parameters should be determined based on the slurry system and process requirements.

7. A method for recovering long-stored fuel cell catalyst slurry, characterized in that, Includes the following steps: (1) After shearing and dispersing the catalyst slurry to be recovered, the first filtration is performed to obtain a primary filter cake and a primary filtrate; the primary filtrate is subjected to low-temperature centrifugation and then filtered a second time to obtain a secondary filter cake and a secondary filtrate. The temperature for low-temperature centrifugation is 5-15℃, the rotation speed is 1000-3000 rpm, and the time is 10-30 min; (2) Process according to the viscosity and solid content recovery standards of claim 6: If the viscosity and solid content meet the recycling standards, the remaining catalyst slurry to be recycled is treated and recycled using these parameters, and the resulting secondary filtrate is the directly recycled process catalyst slurry; if it does not meet the recycling standards, the catalyst slurry to be recycled cannot be recycled in the process, but is instead recycled as a platinum resource. The standards for viscosity and solid content recovery are as follows: the viscosity of the recovered catalyst slurry should not differ from that of the fresh catalyst slurry by more than 10-40%, and the solid content of the recovered catalyst slurry should not differ from that of the fresh catalyst slurry by more than 20-60%.

8. The recycling and utilization method according to claim 7, characterized in that, The catalyst slurry to be recycled is the slurry remaining after the use of fresh process catalyst slurry and left for 1-5 days; the fresh catalyst slurry is the newly prepared process catalyst slurry to be used.

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