Membrane electrode activation method

Abstract

The invention relates to the technical field of fuel cells, in particular to a membrane electrode activation method. Comprising the following steps: soaking a membrane electrode in deionized water for the first time; immersing the membrane electrode into the activating solution for secondary soaking; and finally, cleaning the membrane electrode by using deionized water, and drying. The activation time can be shortened through an activation solution compounded by acid and an oxidizing agent, and meanwhile, the electrochemical active area of the membrane electrode is increased; the concentration of sulfuric acid in the activating solution is limited to be 0.2-0.8 mol / L, and the concentration of hydrogen peroxide is limited to be 0.05-0.4 mol / L, so that the attenuation of the active area after circulation can be reduced while the electrochemical active area of the membrane electrode is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a membrane electrode activation method. Background Art

[0002] Fuel cells, as highly efficient energy conversion devices, hold enormous potential for future applications in clean energy and new energy vehicles. The membrane electrode assembly (MEA), a core component of fuel cells, directly determines the efficiency and lifespan of the cell. However, current MEA fabrication technology faces several challenges. First, the MEA fabrication process often involves complex steps, including high-temperature treatment and catalyst coating. These steps are not only time-consuming but can also adversely affect MEA performance. Second, due to the complexity of MEA materials, their preparation and activation processes require precise control to ensure optimal performance after activation. Existing MEA activation methods present significant challenges. These typically require long, constant-current discharges, which not only consume significant energy but can also damage the MEA during activation, thereby reducing its electrochemical performance and durability. Furthermore, prolonged activation can introduce impurities, disrupting the MEA structure and further impacting its performance. Therefore, developing an efficient and stable MEA activation test method is crucial.

[0003] Chinese invention patent application CN116435560A discloses a batch preparation process for polymer electrolyte ordered large-area membrane electrodes. This method can mass-produce polymer electrolyte ordered large-area membrane electrodes for use in fuel cells or electrolytic cells, greatly improving the production efficiency of ordered membrane electrodes and ensuring their consistency. Furthermore, the batch preparation of ordered membrane electrodes can reduce the production cost of membrane electrodes, but the MEA activation step is not specified. Summary of the Invention

[0004] The present invention provides a membrane electrode activation method, comprising the following steps: first soaking the membrane electrode in deionized water; then soaking the membrane electrode in activation solution for a second time; and finally washing the membrane electrode with deionized water and drying it.

[0005] Optionally, the activation solution includes acid, oxidant and water.

[0006] Optionally, the acid includes sulfuric acid, and the oxidant includes hydrogen peroxide.

[0007] The concentration of sulfuric acid in the activation solution is 0.2-0.8 mol / L.

[0008] Optionally, the concentration of sulfuric acid in the activation solution is 0.3-0.7 mol / L.

[0009] The concentration of hydrogen peroxide in the activation solution is 0.05-0.4 mol / L.

[0010] Optionally, the concentration of hydrogen peroxide in the activation solution is 0.05-0.2 mol / L.

[0011] The inventors have found that a composite activation solution composed of an acid and an oxidant can shorten the activation time and simultaneously increase the electrochemically active area of the membrane electrode. While the acid and oxidant dissolve inorganic pollutants on the electrode surface and clean the electrode surface, the acid can also regulate the charge distribution on the electrode surface and enhance the exposure of the catalyst active sites. At the same time, the acid and the oxidant synergistically form a strong oxidizing environment, accelerating the removal of the passivation layer on the electrode surface and shortening the activation time. The inventors have further found that the concentration of sulfuric acid in the activation solution is 0.2-0.8 mol / L and the concentration of hydrogen peroxide is 0.05-0.4 mol / L, which can increase the electrochemically active area of the membrane electrode while reducing the attenuation of the active area after cycling. The specific concentration can effectively clean the surface while avoiding excessive corrosion, achieving a balance between improving the activation effect and protecting the material. At the same time, the composite activation solution with a specific concentration significantly increases the electrochemically active area by removing surface impurities and reconstructing the catalyst microstructure, thereby reducing the loss of active sites after recycling and inhibiting the attenuation of the active area.

[0012] The secondary soaking is performed at a temperature of 40-80° C. and for a time of 1-3 hours.

[0013] Optionally, the temperature of the secondary soaking is 40-60° C., and the time is 1-2 hours.

[0014] The drying temperature is 60-100° C. and the drying time is 1-2 hours.

[0015] Optionally, the drying temperature is 70-90°C.

[0016] Beneficial effects

[0017] 1. The activation solution composed of acid and oxidant can shorten the activation time and increase the electrochemical active area of the membrane electrode.

[0018] 2. By limiting the concentration of sulfuric acid in the activation solution to 0.2-0.8 mol / L and the concentration of hydrogen peroxide to 0.05-0.4 mol / L, the electrochemical active area of the membrane electrode can be increased while reducing the attenuation of the active area after cycling.

[0019] 3. By limiting the secondary immersion temperature to 40-80℃ and the time to 1-3h, the electrochemical active surface area of the membrane electrode can reach 120m 2 / g, and the attenuation rate can be controlled at 15% after 5000 cycles.

[0020] 4. By limiting the drying temperature to 60-100°C and the drying time to 1-2 hours, the contact angle of the activated membrane electrode can be reduced and the proton conductivity can be improved.

[0021] 5. The membrane electrode activation method provided by the present invention is simple to operate, does not involve high-temperature treatment, and is suitable for large-scale production. DETAILED DESCRIPTION

[0022] Example 1

[0023] A membrane electrode activation method comprises the following steps: firstly, soaking the membrane electrode in deionized water for 30 minutes; then soaking the membrane electrode in activation solution for a second time; and finally, washing the membrane electrode with deionized water and drying it.

[0024] The activation solution is an aqueous solution of an acid and an oxidant; the acid is sulfuric acid, and the oxidant is hydrogen peroxide.

[0025] The concentration of sulfuric acid in the activation solution is 0.5 mol / L; the concentration of hydrogen peroxide in the activation solution is 0.1 mol / L.

[0026] The secondary immersion was carried out at a temperature of 60° C. and for 2 hours.

[0027] The drying temperature is 80° C. and the drying time is 1 hour.

[0028] Comparative Example 1

[0029] A membrane electrode activation method comprises the following steps: first, soaking the membrane electrode in deionized water for 30 minutes; soaking it in a 1 mol / L nitric acid solution for 1 hour, and then treating it with a 0.5 mol / L sulfuric acid solution; and finally, washing the membrane electrode with deionized water and drying it.

[0030] Comparative Example 2

[0031] The specific implementation is the same as that of Example 1; the difference is that the acid is hydrochloric acid.

[0032] Comparative Example 3

[0033] The specific implementation is the same as that of Example 1; the difference is that the acid is nitric acid.

[0034] Comparative Example 4

[0035] The specific implementation is the same as that of Example 1; the difference is that the acid is phosphoric acid.

[0036] Comparative Example 5

[0037] The specific implementation is the same as that of Example 1; the difference is that the oxidant is potassium permanganate, and the concentration of potassium permanganate in the activation solution is 0.05 mol / L.

[0038] Comparative Example 6

[0039] The specific implementation is the same as that of Example 1; the difference is that the oxidant is ammonium disulfate.

[0040] Comparative Example 7

[0041] The specific implementation is the same as that of Example 1; the difference is that the oxidant is ozone, and the concentration of ozone in the activation solution is 10 ppm.

[0042] Comparative Example 8

[0043] The specific implementation is the same as that of Example 1; the difference is that the concentration of sulfuric acid in the activation solution is 0.1 mol / L.

[0044] Comparative Example 9

[0045] The specific implementation is the same as that of Example 1; the difference is that the concentration of sulfuric acid in the activation solution is 1 mol / L.

[0046] Comparative Example 10

[0047] The specific implementation is the same as that of Example 1; the difference is that the concentration of hydrogen peroxide in the activation solution is 0.01 mol / L.

[0048] Comparative Example 11

[0049] The specific implementation is the same as that of Example 1; the difference is that the concentration of hydrogen peroxide in the activation solution is 0.5 mol / L.

[0050] Comparative Example 12

[0051] The specific implementation is the same as that of Example 1; the difference is that the temperature of the secondary soaking is 60°C.

[0052] Comparative Example 13

[0053] The specific implementation is the same as that of Example 1; the difference is that the temperature of the secondary soaking is 60°C.

[0054] Comparative Example 14

[0055] The specific implementation is the same as that of Example 1; the difference is that the secondary immersion time is 0.5 h.

[0056] Comparative Example 15

[0057] The specific implementation is the same as that of Example 1; the difference is that the secondary immersion time is 4 hours.

[0058] Comparative Example 16

[0059] The specific implementation is the same as that of Example 1; the difference is that the drying temperature is 50°C.

[0060] Comparative Example 17

[0061] The specific implementation is the same as that of Example 1; the difference is that the drying temperature is 120°C.

[0062] Comparative Example 18

[0063] The specific implementation is the same as that of Example 1; the difference is that the drying time is 0.5 h.

[0064] Comparative Example 19

[0065] The specific implementation is the same as that of Example 1; the difference is that the drying time is 2 hours.

[0066] Performance testing methods

[0067] The activation methods of the embodiment and the comparative example were used to activate the same type of membrane electrode (size: 5 cm 2 , Pt loading 0.3 mg / cm 2 ) was activated and the following tests were performed. The test data are listed in Table 1, where “ / ” indicates no test.

[0068] Testing equipment: Electrochemical workstation (Gamry Interface 5000); three-electrode system: working electrode (membrane electrode), reference electrode (Ag / AgCl), counter electrode (Pt sheet); constant temperature and humidity test chamber (controlled at 30°C and 80% relative humidity); fuel cell test bench (for polarization curve and durability testing);

[0069] A control group was set up: no activation was performed.

[0070] 1. Electrochemically active area (ECSA) test

[0071] Test method: Cyclic voltammetry (CV)

[0072] Test conditions: voltage range: -0.2V~1.0V; scan rate: 50mV / s; electrolyte: 0.1M HClO4 (nitrogen saturated).

[0073] Test steps: 1. Fix the membrane electrode in the electrode holder and immerse it in the electrolyte; 2. Flow nitrogen for 20 minutes to remove dissolved oxygen; scan continuously for 10 cycles until the curve is stable, and take the data of the last cycle.

[0074] 2. Durability test

[0075] Accelerated decay test: potential cycle range: 0.6V~1.0V, scan rate: 50mV / s, electrolyte: H2 / O2, number of cycles: 5000 times (simulating fuel cell start-stop conditions), calculate the reduction rate (decay rate) of the ECSA of the membrane electrode after durability compared to before durability.

[0076] 3. Contact angle test: GB / T 20042.5-2024 "Proton exchange membrane fuel cell part 5: membrane electrode test method"

[0077] 4. Proton conductivity test: National standard: GB / T 20042.3-2022 "Proton exchange membrane fuel cell part 3: proton exchange membrane test method"

[0078] Performance test data

[0079] Table 1

[0080]

[0081]

Claims

1. A membrane electrode activation method, characterized in that: The following steps are involved: First, the membrane electrode is immersed in deionized water for a first soak; then the membrane electrode is immersed in activation solution for a second soak; finally, the membrane electrode is cleaned with deionized water and dried; the activation solution includes acid, oxidant and water.

2. The membrane electrode activation method according to claim 1, characterized in that: The acid includes sulfuric acid, and the oxidant includes hydrogen peroxide.

3. The membrane electrode activation method according to claim 2, characterized in that: The concentration of sulfuric acid in the activation solution is 0.2-0.8 mol / L.

4. The membrane electrode activation method according to claim 3, characterized in that: The concentration of sulfuric acid in the activation solution is 0.3-0.7 mol / L.

5. The membrane electrode activation method according to claim 2, characterized in that: The concentration of hydrogen peroxide in the activation solution is 0.05-0.4 mol / L.

6. The membrane electrode activation method according to claim 5, characterized in that: The concentration of hydrogen peroxide in the activation solution is 0.05-0.2 mol / L.

7. The membrane electrode activation method according to claim 2, characterized in that: The secondary soaking is performed at a temperature of 40-80° C. and for a time of 1-3 hours.

8. The membrane electrode activation method according to claim 7, characterized in that: The secondary soaking is performed at a temperature of 40-60° C. and for a time of 1-2 hours.

9. The membrane electrode activation method according to claim 2, characterized in that: The drying temperature is 60-100° C. and the drying time is 1-2 hours.

10. The membrane electrode activation method according to claim 9, characterized in that: The drying temperature is 70-90°C.

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