Preparation method of membrane electrode based on independent microporous layer

Abstract

The invention provides a preparation method of a membrane electrode based on an independent microporous layer, which comprises the following steps: S1, preparing microporous layer slurry, coating a bottom plate with the microporous layer slurry, and sintering to form a microporous layer; s2, preparing catalyst layer slurry, and respectively coating the catalyst layer slurry on the microporous layer to obtain an anode catalyst layer assembly and a cathode catalyst layer assembly; s3, stripping the micropore layer and the catalyst layer of the cathode and catalyst layer assembly from the bottom plate to form a cathode assembly, and stripping the micropore layer and the catalyst layer of the anode and catalyst layer assembly from the bottom plate to form an anode assembly; and S4, carrying out hot pressing on the cathode assembly, the proton exchange membrane and the anode assembly to obtain the membrane electrode. According to the preparation method of the membrane electrode based on the independent microporous layer, the problem of membrane swelling caused by direct contact between the catalyst layer slurry and the proton exchange membrane is avoided in the preparation process, transfer printing of a matrix is not needed in the preparation process, and the manufacturing cost of the membrane electrode is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane electrodes, and particularly relates to a method for preparing a membrane electrode based on an independent microporous layer. Background Art

[0002] In the context of the continuous development of the global economy today, fossil energy is over-consumed, and the resulting environmental pollution problems are becoming increasingly serious, which has caused great concern among people. In this situation, people urgently expect to find green energy and new high-efficiency energy conversion devices; hydrogen energy has the advantages of low pollution and high energy conversion efficiency, and is a green new energy with development potential in the 21st century. As the core component of a fuel cell, the membrane electrode plays an important role in the energy conversion process.

[0003] At present, the preparation methods of traditional membrane electrodes are divided into the following several types: (1) The transfer printing method, in which the catalyst slurry is coated on a transfer substrate, and then the slurry on the transfer substrate with the catalyst is transferred to the proton exchange membrane. The process flow is relatively complex, the transfer substrate is expensive, and there may be a situation where the transfer is not complete during the transfer process, resulting in low membrane utilization; (2) The direct coating method, in which the catalyst is directly coated on both sides of the proton exchange membrane to obtain a membrane electrode. During the direct coating process, the solvent in the catalyst slurry will cause the proton exchange membrane to swell, making the surface of the prepared membrane electrode uneven and the uniformity poor, affecting the performance of the membrane electrode. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a membrane electrode based on an independent microporous layer. The independent microporous layer exists independently of the base layer. The catalytic layer is coated on the independent microporous layer, and then the combination is hot-pressed onto the proton exchange membrane to obtain a membrane electrode. This avoids the swelling of the proton exchange membrane caused by the direct coating method, removes the expensive transfer substrate of the transfer printing method, and the independent microporous layer avoids the problem of increased gas transport resistance caused by the infiltration of the microporous layer into the carbon paper, thus avoiding the problem of battery flooding.

[0005] The technical solution adopted by the present invention is as follows: A method for preparing a membrane electrode based on an independent microporous layer, which includes the following steps: Step S1. Prepare a microporous layer slurry, then coat the microporous layer slurry on a bottom plate and sinter it to form a microporous layer by forming a film of the microporous layer slurry; Step S2. Prepare a catalytic layer slurry, then coat the catalytic layer slurry on the microporous layer to form an anode catalytic layer and a cathode catalytic layer respectively, and obtain an anode catalytic layer combination and a cathode catalytic layer combination correspondingly; Step S3. Peel off the microporous layer and the catalytic layer of the cathode catalyst layer assembly and the anode catalyst layer assembly from the bottom plate to form a cathode assembly and an anode assembly; Step S4. Thermally press the cathode assembly, the proton exchange membrane and the anode assembly to obtain a membrane electrode.

[0006] Preferably, in the method for preparing a membrane electrode based on an independent microporous layer, by weight, the microporous layer slurry in Step S1 comprises 5 - 40 parts of a conductive carbon material, 5 - 40 parts of a linear carbon material, 20 - 40 parts of a surfactant, 20 - 80 parts of a hydrophobic agent, 10 - 30 parts of a binder, and 5 - 100 parts of a solvent.

[0007] Preferably, in the method for preparing a membrane electrode based on an independent microporous layer, the conductive carbon material is selected from one or more of acetylene black, XC - 72R, and BP2000, and the linear carbon material is selected from one or two of carbon nanotubes and carbon nanofibers.

[0008] Preferably, in the method for preparing a membrane electrode based on an independent microporous layer, the surfactant is selected from one of Triton X - 100 and Tween 80; the hydrophobic agent is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, and polypropylene.

[0009] Preferably, in the method for preparing a membrane electrode based on an independent microporous layer, the binder is selected from one or two of polyvinyl alcohol and polyvinylpyrrolidone; the solvent is selected from one or more of ethanol, n - propanol, isopropanol, and deionized water.

[0010] Preferably, in the method for preparing a membrane electrode based on an independent microporous layer, the mass of the microporous layer in Step S1 is 1 - 10 mg / cm 2 ; the bottom plate is selected from one of a glass plate and a high - temperature resistant film.

[0011] Preferably, in the method for preparing a membrane electrode based on an independent microporous layer, the coating method of the catalytic layer slurry in Step S1 is selected from one of spraying, slot coating, and doctor blading; the sintering temperature in Step S1 is 320 - 380 °C, and the sintering time is 5 min - 120 min.

[0012] Preferably, in the method for preparing a membrane electrode based on an independent microporous layer, the catalytic layer slurry in Step S2 comprises 5 - 20 parts of a noble metal catalyst, 2 - 10 parts of a surfactant, 5 - 20 parts of a cation exchange resin, and 50 - 100 parts of a solvent.

[0013] Preferably, in the method for preparing the membrane electrode based on an independent microporous layer, the noble metal catalyst is selected from one of platinum-carbon catalyst, platinum-cobalt catalyst, and platinum-cobalt-manganese catalyst; the surfactant is selected from one of Triton X-100 and Tween; the cation exchange resin is perfluorosulfonic acid resin; and the solvent is selected from one of n-propanol, isopropanol, ethanol, and deionized water.

[0014] Preferably, in the method for preparing the membrane electrode based on an independent microporous layer, the coating method of the catalytic layer slurry in step S2 is selected from one of spraying, slot coating, and blade coating; the hot pressing temperature in step S4 is 120 - 150 °C, the hot pressing pressure is 0.5 - 5 MPa, and the hot pressing time is 10 - 120 min; the masses of the anode catalytic layer and the cathode catalyst in step S2 are both 0.05 - 0.6 mg / cm 2 。

[0015] Advantages of the present invention: (1) In the method for preparing the membrane electrode based on an independent microporous layer of the present invention, during the preparation process, the catalytic layer is coated on the independent microporous layer instead of directly on the proton exchange membrane, thus avoiding the problem of swelling of the proton exchange membrane caused by direct contact between the catalytic layer slurry and the proton exchange membrane, and there is no need for a transfer matrix during the preparation process, reducing the manufacturing cost of the membrane electrode.

[0016] (2) In the method for preparing the membrane electrode based on an independent microporous layer of the present invention, the microporous layer exists independently of the carbon paper and does not need to be coated on the carbon paper, thus avoiding the problem of increased gas transport resistance caused by the infiltration of the microporous layer into the carbon paper, and there is a wider range of choices for the carbon paper base layer, and the carbon paper base layer can be selected from carbon cloth, carbon felt, nickel foam, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a single cell polarization curve graph of Examples 1 - 2 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be further described below in conjunction with specific embodiments.

[0019] The platinum-carbon catalyst used in the examples is 60% platinum-carbon catalyst, the manufacturer is Johnson Matthey, and the model is Hispec9100.

[0020] Example 1 A method for preparing a membrane electrode based on an independent microporous layer, comprising the following steps: Step S1. Dissolve 20 g of Triton X-100 in 20 g of water, then add 20 g of 60% PTFE emulsion, 10 g of XC-72R, 40 g of carbon fiber, and 10 g of polyvinyl alcohol. Stir with a paddle at a speed of 1000 rpm for 30 min to obtain the microporous layer slurry. Then coat the microporous layer slurry on the bottom plate by slit coating and sinter it to form a microporous layer by film formation. The sintering temperature is 350 °C and the sintering time is 0.5 h. The loading of the microporous layer slurry is 6 mg / cm 2 , and the cathode microporous layer is the same as the anode microporous layer; Step S2. Add 5 g of 60% platinum-carbon catalyst, 5 g of Nafion perfluorosulfonic acid resin, and 2 g of Triton X-100 to 100 g of n-propanol solvent. Stir with a paddle at a speed of 1000 rpm for 30 min to obtain the catalyst layer slurry. Then spray 80% of the catalyst layer slurry on the microporous layer to form a cathode catalyst layer assembly, and coat 20% of the catalyst layer slurry on the microporous layer to form an anode catalyst layer assembly; the platinum loading of the cathode catalyst layer is 0.4 mg / cm 2 , and the platinum loading of the anode catalyst layer is 0.1 mg / cm 2 ; Step S3. Peel the microporous layer and the catalyst layer of the cathode catalyst layer assembly from the bottom plate to form a cathode assembly, and peel the microporous layer and the catalyst layer of the anode catalyst layer assembly from the bottom plate to form an anode assembly; Step S4. Thermally press the cathode assembly, the perfluorosulfonic acid proton exchange membrane, and the anode assembly at a temperature of 120 °C, a pressure of 1 MPa, and a time of 30 min to obtain the membrane electrode.

[0021] Example 2 The difference between Example 2 and Example 1 is that the thermal pressing temperature in Step S4 is 150 °C, the thermal pressing pressure is 5 MPa, and the thermal pressing time is 30 min.

[0022] Comparative Example 1 A method for preparing a membrane electrode based on an independent microporous layer, comprising the following steps: Step S1. Dissolve 20 g of Triton X-100 in 20 g of water, then add 20 g of 60% PTFE emulsion, 10 g of XC-72R, 40 g of carbon fiber, and 10 g of polyvinyl alcohol. Stir with a paddle at a speed of 1000 rpm for 30 min to obtain the microporous layer slurry. Then coat the microporous layer slurry on the carbon paper by slit coating and sinter it to form a gas diffusion layer by film formation. The sintering temperature is 350 °C and the sintering time is 0.5 h. The loading of the microporous layer slurry is 6 mg / cm 2 ; Step S2. Add 5 g of 60% platinum-carbon catalyst, 5 g of Nafion perfluorosulfonic acid resin, and 2 g of Triton X-100 into 100 g of n-propanol solvent, and stir with a paddle at a speed of 1000 rpm for 30 min to obtain a catalytic layer slurry. Then spray the catalytic layer slurry on both sides of the perfluorosulfonic acid proton exchange membrane to obtain a catalytic layer coated membrane. The catalytic layer slurry is sprayed on one side of the perfluorosulfonic acid proton exchange membrane to form a cathode catalytic layer, and the platinum loading of the cathode catalytic layer is 0.4 mg / cm 2 , and the catalytic layer slurry is sprayed on the other side of the perfluorosulfonic acid proton exchange membrane to form an anode catalytic layer, and the platinum loading of the anode catalytic layer is 0.1 mg / cm 2 ; Step S3. Stack gas diffusion layers on both sides of the catalytic layer coated membrane, and thermally press the gas diffusion layer and the catalytic layer coated membrane. The thermal pressing temperature is 120 °C, the thermal pressing pressure is 1 MPa, and the thermal pressing time is 30 min to obtain a membrane electrode.

[0023] Perform single-cell tests on the membrane electrodes obtained in Example 1, Example 2, and Comparative Example 1. The single-cell test conditions are as follows: the single-cell area is 25 cm 2 , the anode and cathode stoichiometric ratios are 1.5:2.5, the anode dew point is set at 64 °C, the cathode dew point is 64 °C, the anode inlet stack pressure is 1.1 bar, the cathode inlet stack pressure is 1.0 bar, and the cell test temperature is 80 °C.

[0024] The test results are as Figure 1 shown. It can be seen from Figure 1 that the performances of Example 1 and Example 2 are both higher than that of Comparative Example 1. Water flooding occurs in the large current region of Comparative Example 1, indicating that the independent microporous layer avoids the problem of increased gas transport resistance caused by the infiltration of the microporous layer into the carbon paper, solves the problem of large current water flooding, and in addition, the use of a transfer matrix is omitted in the preparation process, saving costs. Moreover, there is no direct contact between the catalytic layer slurry and the membrane, avoiding the swelling problem of the perfluorosulfonic acid proton exchange membrane.

[0025] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a membrane electrode based on an independent microporous layer, characterized in that: The following steps are involved: Step S1. preparing a microporous layer slurry, and then coating the microporous layer slurry on a base plate and sintering to form a microporous layer; Step S2. preparing a catalyst layer slurry, and then coating the catalyst layer slurry on the microporous layer to form an anode catalyst layer and a cathode catalyst layer, respectively, and obtaining an anode catalyst layer assembly and a cathode catalyst layer assembly respectively; Step S3. The microporous layer and the catalytic layer of the cathode catalyst layer assembly and the anode catalyst layer assembly are peeled off from the bottom plate to form a cathode assembly and an anode assembly; Step S4: hot-pressing the cathode assembly, the proton exchange membrane and the anode assembly to obtain a membrane electrode.

2. The method for preparing a membrane electrode based on an independent microporous layer according to claim 1, characterized in that: In parts by weight, the microporous layer slurry of step S1 includes 5-40 parts of conductive carbon material, 5-40 parts of linear carbon material, 20-40 parts of surfactant, 20-80 parts of hydrophobic agent, 10-30 parts of binder, and 5-100 parts of solvent.

3. The method for preparing a membrane electrode based on an independent microporous layer according to claim 2, characterized in that: The conductive carbon material is selected from one or more of acetylene black, XC-72R, and BP2000; the linear carbon material is selected from one or two of carbon nanotubes and carbon nanofibers.

4. The method for preparing a membrane electrode based on an independent microporous layer according to claim 2, characterized in that: The surfactant is selected from one of Triton X-100 and Tween 80; the hydrophobic agent is selected from one of polytetrafluoroethylene, polyvinylidene fluoride and polypropylene.

5. The method for preparing a membrane electrode based on an independent microporous layer according to claim 2, characterized in that: The binder is selected from one of polyvinyl alcohol and polyvinyl pyrrolidone; the solvent is selected from one or more of ethanol, n-propanol, isopropanol and deionized water.

6. The method for preparing a membrane electrode based on an independent microporous layer according to claim 1, characterized in that: The mass of the microporous layer in step S1 is 1-10 mg / cm 2 ; The bottom plate is selected from one of a glass plate and a high temperature resistant film.

7. The method for preparing a membrane electrode based on an independent microporous layer according to claim 1, characterized in that: The microporous layer slurry coating method in step S1 is selected from one of spraying, slit coating and blade coating; the sintering temperature is 320-380° C., and the sintering time is 5 min-120 min.

8. The method for preparing a membrane electrode based on an independent microporous layer according to claim 1, characterized in that: The catalyst layer slurry of step S2 includes 5-20 parts of a noble metal catalyst, 2-10 parts of a surfactant, 5-20 parts of a cation exchange resin and 50-100 parts of a solvent.

9. The method for preparing a membrane electrode based on an independent microporous layer according to claim 8, characterized in that: The noble metal catalyst is selected from one of platinum-carbon catalyst, platinum-cobalt catalyst and platinum-cobalt-manganese catalyst; the surfactant is selected from one of Triton X-100 and Tween; the cation exchange resin is perfluorosulfonic acid resin; the solvent is selected from one or more of n-propanol, isopropanol, ethanol and deionized water.

10. The method for preparing a membrane electrode based on an independent microporous layer according to claim 1, characterized in that: The catalytic layer slurry coating method of step S2 is selected from one of spraying, slit coating and scraping; the hot pressing temperature of step S4 is 120-150°C, the hot pressing pressure is 0.5-5MPa, and the hot pressing time is 10-120min; the mass of the anode catalyst layer and the cathode catalyst layer of step S2 is 0.05-0.6mg / cm 2 .

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