Process for improving preparation efficiency of air-cooled membrane electrode

Abstract

The invention relates to a process for improving the preparation efficiency of an air-cooled membrane electrode, and belongs to the technical field of hydrogen fuel cells. The process adopts a manner of combining coating, transfer printing and spraying, and comprises the following steps: firstly, forming a compact inner catalyst layer on the cathode side of a proton exchange membrane by coating, and adopting a mesoporous or high-activation polarized catalyst with the loading capacity of 0.16-0.25 mg / cm; a catalyst layer with the loading capacity of 0.10-0.15 mg / cm is formed on the anode side through transfer printing; and finally, a loose outer catalyst layer is formed on the cathode inner layer through spraying, a common platinum-carbon catalyst is adopted, and the loading capacity is 0.15-0.20 mg / cm. The slurry used in the three processes adopts the same resin and the same solvent so as to ensure the interface compatibility. According to the invention, a gradient structure with dense inside and sparse outside is constructed, the contradiction that high performance, low cost and high efficiency production of the air-cooled membrane electrode are difficult to realize at the same time is solved, and the output performance and durability of the battery are improved at the same time.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of hydrogen fuel cells, in particular to a process for improving the preparation efficiency of air-cooled membrane electrodes. BACKGROUND

[0002] Air-cooled hydrogen fuel cells are widely used in the fields of backup power supply, portable power generation devices and unmanned aerial vehicles due to their compact structure, simple system and fast start-up speed. The performance of the membrane electrode, as the core component of the air-cooled hydrogen fuel cell, directly determines the energy density, efficiency and service life of the fuel cell.

[0003] The working environment of the air-cooled membrane electrode is usually low-humidity or self-humidification, which poses a great challenge to the water thermal management on the cathode side: on the one hand, it is necessary to ensure that the proton exchange membrane has sufficient humidity to maintain high proton conductivity; on the other hand, it is necessary to timely remove the water generated by the reaction to prevent the "waterlogging" from hindering the oxygen transmission to the catalytically active sites.

[0004] In order to improve the performance, the prior art tends to use new catalysts with high specific surface area and intrinsic activity, such as mesoporous catalysts or highly activated polarization catalysts. However, these materials have inherent defects: the mesoporous structure is prone to water loss in a low-humidity environment, resulting in a sharp increase in proton conduction resistance; and some highly activated polarization catalysts have poor long-term chemical stability and fast service life decay. In addition, the preparation process of these catalysts is complex and costly, making it difficult to be used in large-scale full-catalytic layers.

[0005] To solve the above problems, the industry has proposed a technical idea of constructing a layered or gradient catalyst layer, that is, a small amount of high-performance catalyst is placed on the inner side close to the proton exchange membrane to utilize its high activity, and a conventional platinum-carbon (Pt / C) catalyst with low cost and good stability is used on the outer side to ensure mass transfer and mechanical durability. However, there are great process challenges in realizing such a fine gradient structure. At present, only the spraying process can accurately control the deposition position and thickness of the catalyst. However, the spraying method has extremely low production efficiency, low utilization rate of catalyst slurry, and waste caused by overspraying. Moreover, for large-scale preparation, its production rhythm is difficult to meet the market demand, which becomes one of the key factors for the high cost and production bottleneck of air-cooled membrane electrodes.

[0006] Therefore, it is necessary to develop a process that can accurately construct a gradient catalyst layer structure with high efficiency and low cost, and has high performance and high production efficiency. SUMMARY

[0007] The technical problem to be solved by the application is to provide a process for improving the preparation efficiency of air-cooled membrane electrodes, which solves the technical problems of low production efficiency, low utilization rate of catalyst slurry, waste caused by overspraying, and difficulty in meeting the market demand in terms of production rhythm for large-scale preparation. At the same time, the problem of too dense catalyst layer in the air-cooled membrane electrode prepared by the coating process is solved.

[0008] To achieve the above object, the present application provides the following technical solutions: A process for improving the preparation efficiency of air-cooled membrane electrode, comprising the following steps: Using a coating process, mesoporous catalyst or high-activation polarization catalyst slurry is coated on the cathode side of the proton exchange membrane to form a dense inner cathode catalyst layer after drying; Using a transfer printing process, a catalyst layer prepared from platinum-carbon catalyst slurry is transferred to the anode side of the proton exchange membrane to form an anode catalyst layer; Using a spraying process, ordinary platinum-carbon catalyst slurry is sprayed on the inner cathode catalyst layer to form a loose and porous outer cathode catalyst layer after drying; Wherein, the resin binder used in the inner cathode catalyst layer, the anode catalyst layer, and the outer cathode catalyst layer is of the same type, and the organic solvent used is of the same type.

[0009] Further, the dry thickness of the inner cathode catalyst layer is 4-8 microns, and the platinum loading is 0.16-0.25 mg / cm²; the platinum loading of the anode catalyst layer is 0.10-0.15 mg / cm²; the platinum loading of the outer cathode catalyst layer is 0.15-0.20 mg / cm².

[0010] Further, the mesoporous catalyst or high-activation polarization catalyst slurry consists of the following components by mass percentage: 12%-18% mesoporous or high-activation polarization catalyst, 30%-35% pure water, 35%-40% methanol or isopropyl alcohol, and 8%-10% resin solution.

[0011] Further, the platinum-carbon catalyst slurry used for anode transfer printing consists of the following components by mass percentage: 10%-15% ordinary platinum-carbon catalyst, 35%-40% pure water, 35%-40% methanol or isopropyl alcohol, and 5%-8% resin solution.

[0012] Further, the ordinary platinum-carbon catalyst slurry used for outer cathode spraying consists of the following components by mass percentage: 1.5%-2.0% ordinary platinum-carbon catalyst, 14%-16% pure water, 70%-80% ethanol or isopropyl alcohol, and 2%-4% resin solution.

[0013] Further, the slurry used in the coating process and the transfer printing process is mixed and ground using a planetary ball mill; the slurry used in the spraying process is dispersed using a high-speed shearing disperser.

[0014] Further, the resin binder is perfluorosulfonic acid resin.

[0015] Further, the organic solvent is isopropanol.

[0016] A membrane electrode prepared by the process of any one of the above, the cathode catalytic layer of the membrane electrode has a gradient structure composed of a dense inner layer and a loose outer layer.

[0017] A hydrogen fuel cell comprising the membrane electrode as described above.

[0018] In summary, the present application includes at least one of the following processes and methods for improving the efficiency of air-cooled membrane electrode preparation: The present application combines the three processes of coating, transfer printing and spraying, fully utilizes the high efficiency advantages of coating and transfer printing, and uses low efficiency spraying only for the outermost thin layer. This process combination makes the overall production efficiency improve by more than 200% compared with the full spraying process, significantly reduces the waste of expensive catalyst overspray, effectively reduces the production cost, and solves the preparation efficiency bottleneck problem raised in the background art; Through the "dense inside and loose outside" gradient structure of the cathode catalytic layer. The dense inner layer formed by coating can accurately position the high-activity catalyst at the reaction interface, which is beneficial to proton conduction and water retention; the loose outer layer formed by spraying improves the gas transmission and drainage capacity; By using the same resin and the same organic solvent for the three slurries, the compatibility of the process combination is improved, ensuring good bonding strength between the catalyst layers and continuous proton and electron conduction channels, thereby greatly improving the stability of the production process and the consistency of the performance of the final product, meeting the quality requirements of large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The process flowchart provided by the present application is mainly provided. DETAILED DESCRIPTION

[0020] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application will be further described below in conjunction with specific embodiments.

[0021] The following will be described in conjunction with the accompanying Figure 1 The present application will be further described in detail.

[0022] The present application discloses a process for improving the efficiency of air-cooled membrane electrode preparation.

[0023] Embodiment 1 Slurry preparation: Cathode coating slurry: accurately weigh 12g of mesoporous Pt catalyst, 30g of deionized water, 40g of isopropanol, and 8g of 5wt% Nafion resin solution. Put it in a planetary ball mill and ball mill for 6 hours.

[0024] Anode transfer paste: 10 g of normal Pt / C catalyst (40% Pt), 40 g of deionized water, 35 g of isopropyl alcohol, 5 g of Nafion solution with a concentration of 5 wt% were accurately weighed. Put in the planetary ball mill for 4 hours of ball milling.

[0025] Cathode spray paste: 1.5 g of normal Pt / C catalyst (40% Pt), 16 g of deionized water, 80 g of ethanol, 2.5 g of Nafion solution with a concentration of 5 wt% were accurately weighed. A high-speed shear disperser was used to shear and disperse for 30 minutes at 10,000 rpm.

[0026] Cathode inner layer preparation: The cathode coating paste prepared by S101 was coated on the cathode side of the Gore 8 micron membrane using a coating machine. Drying at 80°C, forming a dense inner layer with a thickness of about 4 μm and a platinum loading of 0.16 mg / cm².

[0027] Anode layer preparation: The anode transfer paste prepared by S101 was blade-coated on the transfer film, and after drying, it was transferred to the film anode side by a hot roller (125°C, 0.8 MPa), forming an anode catalyst layer with a platinum loading of 0.10 mg / cm².

[0028] Cathode outer layer preparation: The CCM semi-finished product was fixed on the spray platform (75°C), and the cathode spray paste prepared by S101 was sprayed using a spray gun, finally forming a loose outer layer with a platinum loading of 0.2 mg / cm².

[0029] Post-processing: 100°C vacuum heat treatment for 1 hour.

[0030] Effect: This example successfully constructed an effective gradient structure. Tests show that its performance is significantly better than that of a conventional uniform catalyst layer MEA with the same total loading, especially in the voltage stability under low humidity conditions, which reflects the advantages of the present application.

[0031] Example 2 Preparation of slurry: Cathode coating paste: 15 g of high-activation polarization catalyst, 32 g of deionized water, 37 g of isopropyl alcohol, and 9 g of Nafion resin solution with a concentration of 5 wt% were accurately weighed. Put in the planetary ball mill for 6 hours of ball milling.

[0032] Anode transfer paste: 12 g of normal Pt / C catalyst (40% Pt), 37 g of deionized water, 37 g of isopropyl alcohol, and 6.5 g of Nafion solution with a concentration of 5 wt% were accurately weighed. Put in the planetary ball mill for 4 hours of ball milling.

[0033] Cathode spraying slurry: Accurately weigh 1.8g of ordinary Pt / C catalyst (40% Pt), 15g of deionized water, 75g of isopropanol, and 3.2g of 5wt% Nafion solution. Disperse using a high-speed shear disperser for 30 minutes.

[0034] Cathode inner layer preparation: The slurry was coated using a slit coating device. It was dried at 80°C to form a dense inner layer with a thickness of approximately 6 μm and a platinum loading of 0.20 mg / cm².

[0035] Anode layer preparation: A transfer printing process was used to transfer the anodic catalyst layer with a platinum loading of 0.12 mg / cm² at 130°C and 1 MPa.

[0036] Cathode outer layer preparation: Ultrasonic spraying equipment was used to spray the outer layer, resulting in a loose outer layer with a platinum loading of 0.18 mg / cm².

[0037] Post-treatment: Vacuum heat treatment at 100°C for 1 hour.

[0038] Results: The MEA prepared in this embodiment exhibits excellent overall performance in peak power, rated power efficiency, and long-term stability tests. The water management advantages of the gradient structure are fully utilized, demonstrating the effectiveness and reliability of the invention.

[0039] Example 3 Slurry preparation: Cathode coating slurry: Accurately weigh 18g of mesoporous Pt catalyst, 35g of deionized water, 35g of methanol, and 10g of 5wt% Aquivion® resin solution. Place in a planetary ball mill and ball mill for 6 hours.

[0040] Anodic transfer paste: Accurately weigh 15g of ordinary Pt / C catalyst (40% Pt), 35g of deionized water, 40g of methanol, and 8g of 5wt% Aquivion® solution. Place in a planetary ball mill and ball mill for 4 hours.

[0041] Cathode spraying slurry: Accurately weigh 2.0g of ordinary Pt / C catalyst (40% Pt), 14g of deionized water, 78g of isopropanol, and 4.0g of 5wt% Aquivion® solution. Disperse using a high-speed shear disperser for 30 minutes.

[0042] Note: Methanol and Aquivion resin are used in this example to demonstrate the substitutability of materials under the principle of using the same solvent and resin.

[0043] Cathode inner layer preparation: A slurry was coated using a precision coating device. It was then dried at 85°C to form a dense inner layer with a thickness of approximately 8 μm and a platinum loading of 0.25 mg / cm².

[0044] Anode layer preparation: A transfer printing process was used to form an anode catalyst layer with a platinum loading of 0.15 mg / cm² at 135°C and 1.2 MPa.

[0045] Cathode outer layer preparation: Spraying is performed to finally form a loose outer layer with a platinum loading of 0.20 mg / cm².

[0046] Post-treatment: Vacuum heat treatment at 100°C for 1 hour.

[0047] Results: The MEA prepared in this example exhibits high output power, demonstrating its potential in high power density applications. It also proves that the solvent (methanol / isopropanol) and resin (Nafion / Aquivion) ​​are interchangeable under similar conditions, and that the process is stable and reliable.

[0048] Comparative example: The CCM was prepared using a full spray coating process. The total cathode loading was the same as in Example 2 (0.38 mg / cm²), and it also had a two-layer structure, but both the inner and outer layers were spray coated. The anode was also spray coated.

[0049] Test results show that the MEAs prepared using the process of this invention exhibit significantly better performance than the comparative samples prepared using the traditional full-spray coating process. Example 2 demonstrates excellent overall performance and production efficiency. All examples successfully constructed effective gradient structures, proving the feasibility and superiority of this invention throughout the entire range of requirements.

[0050] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A process for improving the fabrication efficiency of air-cooled film electrodes, characterized in that, Includes the following steps: A coating process is used to coat a mesoporous catalyst or a highly activated polarized catalyst slurry onto the cathode side of a proton exchange membrane, and then dry it to form a dense inner cathode catalyst layer. A transfer printing process is used to transfer the catalyst layer prepared from platinum-carbon catalyst slurry to the anode side of the proton exchange membrane to form an anode catalyst layer; A spraying process is used to spray ordinary platinum-carbon catalyst slurry onto the inner catalytic layer of the cathode, and then dry it to form a loose and porous outer catalytic layer of the cathode. The resin binders used in the inner cathode catalyst layer, the anode catalyst layer, and the outer cathode catalyst layer are all of the same type, and the organic solvents used are all of the same type.

2. The process for improving the fabrication efficiency of air-cooled film electrodes according to claim 1, characterized in that, The dry state thickness of the inner cathode catalyst layer is 4-8 micrometers, and the platinum loading is 0.16-0.25 mg / cm²; the platinum loading of the anode catalyst layer is 0.10-0.15 mg / cm²; and the platinum loading of the outer cathode catalyst layer is 0.15-0.20 mg / cm².

3. The process for improving the fabrication efficiency of air-cooled film electrodes according to claim 1, characterized in that, The mesoporous catalyst or highly activated polarized catalyst slurry is composed of the following components by mass percentage: 12%-18% mesoporous or highly activated polarized catalyst, 30%-35% pure water, 35%-40% methanol or isopropanol, and 8%-10% resin solution.

4. The process for improving the fabrication efficiency of air-cooled film electrodes according to claim 1, characterized in that, The platinum-carbon catalyst slurry used for anodic transfer comprises, by weight percentage, the following components: 10%-15% ordinary platinum-carbon catalyst, 35%-40% pure water, 35%-40% methanol or isopropanol, and 5%-8% resin solution.

5. The process for improving the fabrication efficiency of air-cooled film electrodes according to claim 1, characterized in that, The ordinary platinum-carbon catalyst slurry used for cathode outer layer spraying consists of the following components by mass percentage: 1.5%-2.0% ordinary platinum-carbon catalyst, 14%-16% pure water, 70%-80% ethanol or isopropanol, and 2%-4% resin solution.

6. The process for improving the fabrication efficiency of air-cooled film electrodes according to claim 1, characterized in that, The slurry used in the coating process and the transfer process is mixed and ground using a planetary ball mill; the slurry used in the spraying process is dispersed using a high-speed shear disperser.

7. The process for improving the fabrication efficiency of air-cooled film electrodes according to claim 1, characterized in that, The resin binder is a perfluorosulfonic acid resin.

8. The process for improving the fabrication efficiency of air-cooled film electrodes according to claim 1, characterized in that, The organic solvent is isopropanol.

9. A membrane electrode, characterized in that, Prepared by the process described in any one of claims 1-8, the cathode catalytic layer of the membrane electrode has a gradient structure consisting of a dense inner layer and a loose outer layer.

10. A hydrogen fuel cell, characterized in that, It includes the membrane electrode as described in claim 9.

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