A method for preparing a membrane electrode including an anode catalyst layer that induces water distribution.

Abstract

This invention relates to the field of fuel cell technology, specifically a method for preparing a membrane electrode including an anode catalyst layer that induces water distribution. The method includes the following steps: a water-isopropanol mixture is mixed as a solvent, and a hydrophobically treated platinum-based catalyst and ion exchange resin are added and pre-dispersed to obtain an intermediate slurry; a hydrophilic carbon fiber (CF)-supported anti-reverse electrode agent, IrO2 / CF, is added to the pre-ground slurry for secondary dispersion to obtain a final slurry; the final slurry is coated onto a PTFE substrate and dried to obtain an anode catalyst layer; a commercial catalyst and ion exchange resin are mixed in a water-alcohol solvent, dispersed to obtain a cathode slurry, coated onto a PTFE substrate, and dried to obtain a cathode catalyst layer; the catalyst layer is transferred to both sides of a proton exchange membrane to obtain a membrane electrode. This invention can drive liquid water away from the platinum active region and distribute it in a large-pore hydrophilic region with excellent mass transfer conditions formed by IrO2 / CF, providing liquid water not only for anti-reverse electrode but also preventing damage to the Pt / C electrochemical active region from low-temperature freezing.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, specifically a method for preparing a membrane electrode including an anode catalyst layer that induces water distribution. Background Technology

[0002] During fuel cell operation, a significant amount of water participates in the physicochemical processes of the battery system. The state of water affects the battery in multiple ways; for example, at low temperatures, the phase change of water can affect battery performance; and during the reverse electrode process, water dissociation can influence the corrosion process of the carbon support. Therefore, controlling water distribution is of great importance in the design of the battery catalyst layer.

[0003] Under reverse polarity conditions, the anti-reverse polarity aid catalyzes the water electrolysis reaction, delaying the corrosion process of the carbon support. If the water content at the anode is too low, the effect of the anti-reverse polarity aid is limited, and the carbon support will corrode more rapidly. Currently, the main method for optimizing the anti-reverse polarity effect is to design novel anti-reverse polarity aids and their supports, making it difficult to enhance the anti-reverse polarity effect from the perspective of catalyst layer structure design. Under low-temperature conditions, water inside the membrane electrode freezes, which can block the mass transfer path of the membrane electrode, freeze proton channels, and change the stress distribution, negatively impacting the membrane electrode performance. Currently, methods for solving low-temperature start-up and operation are mainly based on control strategies for the system and operating conditions, including internal heating, external heating, and shutdown purging. However, these methods are all passive solutions to the freezing problem and fail to directly intervene in the ice formation process at the membrane electrode level to enhance the low-temperature adaptability of the membrane electrode. Therefore, in view of the above situation, there is an urgent need to develop a method for preparing a membrane electrode that includes an anode catalyst layer that induces water distribution to overcome the shortcomings in current practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a membrane electrode including an anode catalyst layer that induces water distribution, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing a membrane electrode including an anode catalyst layer that induces water distribution includes the following steps:

[0007] Step 1: Water and isopropanol are mixed as solvents, and hydrophobic platinum-based catalyst and ion exchange resin are added and pre-milled to obtain an intermediate slurry. The hydrophobic platinum-based catalyst is obtained by loading nano-platinum-based particles onto a hydrophobic carbon support.

[0008] Step 2: Add the hydrophilic anti-reverse polarization additive IrO2 / CF to the intermediate slurry and perform secondary ball milling to obtain the final slurry;

[0009] Step 3: The final slurry is coated onto the PTFE substrate and dried to obtain the anode catalyst layer;

[0010] Step 4: Mix the commercial catalyst with the ion exchange resin in an aqueous alcohol solvent, ball mill to obtain a cathode slurry, coat it on a PTFE substrate, and dry it to obtain a cathode catalyst layer;

[0011] Step 5: Transfer the catalytic layer onto both sides of the proton exchange membrane to obtain the membrane electrode.

[0012] As a further aspect of the present invention: the nano-platinum-based particles include one or more of Pt particles and Pt alloy particles, and the particle size of the nano-platinum-based particles is between 2-7 nm.

[0013] As a further aspect of the present invention, the preparation of the hydrophobic carbon support includes the following steps: taking 10g of carbon material and calcining it at 500°C for 3 hours under a hydrogen atmosphere to obtain a hydrophobic carbon support; the carbon support includes one or more of XC-72, graphene, acetylene black, and high specific surface area carbon.

[0014] As a further aspect of the present invention: in step three, the preparation of the hydrophilic anti-reverse polarization agent IrO2 / CF includes the following steps: loading nano-iridium oxide onto hydrophilic carbon fibers.

[0015] As a further embodiment of the present invention, the preparation of the hydrophilic carbon fiber includes the following steps: take 10g of carbon fiber with a diameter in the range of 50-100nm, add 30ml of 30% hydrogen peroxide and mix and stir for 2 hours; heat treat at 150℃ for 3 hours in air atmosphere, mix the treated carbon fiber with nitric acid-sulfuric acid mixture at a ratio of 3:1, and reflux at 90℃ for 60 hours; finally wash and filter the carbon fiber to obtain hydrophilic carbon fiber.

[0016] As a further aspect of the present invention: the platinum content in the hydrophobically treated platinum-based catalyst is between 40% and 50%, and the iridium oxide content in the hydrophilic anti-reverse polarization aid IrO2 / CF accounts for 10% to 15% of the total mass of the aid.

[0017] As a further aspect of the present invention: in the pre-ground slurry, the I / C value is between 0.3 and 0.8, wherein I / C = mass of ion exchange resin / mass of carbon in catalyst, and the solid content is between 4 and 5%.

[0018] As a further aspect of the present invention: in the final anode slurry, the mass of IrO2 / CF is approximately 1 / 3 to 1 / 4 of that of Pt / C.

[0019] As a further aspect of the present invention: the cathode slurry uses a commercial catalyst with an I / C ratio between 0.4 and 1 and a solid content between 4 and 10%.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention designs a catalyst layer structure for inducing water distribution and its manufacturing method. For a uniform catalyst layer, different carbon materials are used to create micro-regions with varying hydrophilicity. The hydrophobic carbon particles used for platinum loading can repel liquid water from the platinum active region and instead concentrate it in the macroporous hydrophilic region with superior mass transfer conditions, preventing water from affecting the gas mass transfer process. The hydrophilic carbon fibers used for loading anti-reverse polarity additives can absorb moisture, providing the necessary liquid water for the anti-reverse polarity reaction. Thus, liquid water solidifies in the hydrophilic region without platinum catalyst, reducing the impact of icing on battery performance. Thirdly, the hydrophilic region, with its macroporous structure of overlapping carbon fibers, can accommodate more ice, improving the battery's low-temperature lifespan. Attached Figure Description

[0022] Figure 1 The graph shows the reverse polarity test results of Examples 1-4 and Comparative Example 1.

[0023] Figure 2 The graph shows the results of low-temperature cycling tests for Examples 1-4 and Comparative Example 1. Detailed Implementation

[0024] The technical solution of this patent will be further described in detail below with reference to specific embodiments.

[0025] The embodiments of this patent are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this patent, and should not be construed as limiting this patent.

[0026] Example 1

[0027] A method for preparing a membrane electrode including an anode catalyst layer that induces water distribution includes the following steps:

[0028] Step 1: Add IrO2 / CF without hydrophilic treatment of carbon fiber to intermediate slurry containing platinum-based catalyst and ball mill to obtain final slurry, but the XC-72 carbon support of platinum-based catalyst used is not hydrophobic treated.

[0029] Step 2: The final slurry is coated onto a PTFE substrate and dried to obtain the anode catalyst layer;

[0030] Step 3: Mix the commercial catalyst and ion exchange resin in an alcoholic solvent, ball mill to obtain a cathode slurry, coat it on a PTFE substrate, and dry it to obtain a cathode catalyst layer;

[0031] Step 4: Transfer the catalytic layer onto both sides of the proton exchange membrane to obtain the membrane electrode.

[0032] The platinum loading at the anode of the membrane electrode is 0.01-0.07 mg / cm³. 2 The cathode platinum loading is 0.1-0.4 mg / cm³. 2 .

[0033] Example 2

[0034] A method for preparing a membrane electrode including an anode catalyst layer that induces water distribution includes the following steps:

[0035] Step 1: Add the hydrophilically treated IrO2 / CF to the intermediate slurry containing the platinum-based catalyst and ball mill it to obtain the final slurry, but the XC-72 carbon support of the platinum-based catalyst used is not hydrophobically treated.

[0036] Step 2: The final slurry is coated onto a PTFE substrate and dried to obtain the anode catalyst layer;

[0037] Step 3: Mix the commercial catalyst and ion exchange resin in an alcoholic solvent, ball mill to obtain a cathode slurry, coat it on a PTFE substrate, and dry it to obtain a cathode catalyst layer;

[0038] Step 4: Transfer the catalytic layer onto both sides of the proton exchange membrane to obtain the membrane electrode.

[0039] The platinum loading at the anode of the membrane electrode is 0.01-0.07 mg / cm³. 2 The cathode platinum loading is 0.05-0.4 mg / cm³. 2 .

[0040] Example 3

[0041] A method for preparing a membrane electrode including an anode catalyst layer that induces water distribution includes the following steps:

[0042] Step 1: Mix water and isopropanol as a solvent, add hydrophobically treated platinum-based catalyst and ion exchange resin, and then pre-mill to obtain an intermediate slurry;

[0043] Step 2: Add the untreated IrO2 / CF to the pre-ground slurry for secondary ball milling to obtain the final slurry;

[0044] Step 3: The final slurry is coated onto the PTFE substrate and dried to obtain the anode catalyst layer;

[0045] Step 4: Mix the commercial catalyst with the ion exchange resin in an aqueous alcohol solvent, ball mill to obtain a cathode slurry, coat it on a PTFE substrate, and dry it to obtain a cathode catalyst layer;

[0046] Step 5: Transfer the catalytic layer onto both sides of the proton exchange membrane to obtain the membrane electrode.

[0047] The platinum loading at the anode of the membrane electrode is 0.01-0.07 mg / cm³. 2 The cathode platinum loading is 0.05-0.4 mg / cm³. 2 .

[0048] Example 4

[0049] A method for preparing a membrane electrode including an anode catalyst layer that induces water distribution includes the following steps:

[0050] Step 1: Mix water and isopropanol as a solvent, add hydrophobically treated platinum-based catalyst and ion exchange resin, and then pre-mill to obtain an intermediate slurry;

[0051] Step 2: Add the hydrophilically treated IrO2 / CF to the pre-ground slurry for secondary ball milling to obtain the final slurry;

[0052] Step 3: The final slurry is coated onto the PTFE substrate and dried to obtain the anode catalyst layer;

[0053] Step 4: Mix the commercial catalyst with the ion exchange resin in an aqueous alcohol solvent, ball mill to obtain a cathode slurry, coat it on a PTFE substrate, and dry it to obtain a cathode catalyst layer;

[0054] Step 5: Transfer the catalytic layer onto both sides of the proton exchange membrane to obtain the membrane electrode.

[0055] The platinum loading at the anode of the membrane electrode is 0.01-0.07 mg / cm³. 2 The cathode platinum loading is 0.05-0.4 mg / cm³. 2 .

[0056] Comparative Example 1

[0057] Step 1: The platinum-based catalyst and ion exchange resin are mixed in an aqueous alcohol solvent, ball-milled to obtain an anode slurry, which is then coated onto a PTFE substrate and dried to obtain an anode catalyst layer. The carbon support of the platinum-based catalyst used is not treated in any way.

[0058] Step 2: The commercial catalyst and ion exchange resin are mixed in an alcoholic solvent, ball-milled to obtain a cathode slurry, which is then coated onto a PTFE substrate and dried to obtain a cathode catalyst layer.

[0059] Step 3: Transfer the catalytic layer onto both sides of the proton exchange membrane to obtain the membrane electrode.

[0060] The platinum loading at the anode of the membrane electrode is 0.01-0.07 mg / cm³. 2 The cathode platinum loading is 0.05-0.4 mg / cm³. 2 .

[0061] The membrane electrodes prepared in Examples 1 to 4 and Comparative Example 1 were subjected to reverse polarity tests, and the test results are as follows: Figure 1 As shown:

[0062] The reverse polarity test involves supplying a reverse current to the battery using an external power source to verify its corrosion resistance under a gas-deficient state. In this test, the reverse current density was 200 mA / cm², and the test was conducted under constant current conditions. During the test, the battery temperature was 75°C, nitrogen gas was introduced at a flow rate of 1 SLPM at the anode, humidity was 100%, and back pressure was 60 kPa; air was introduced at a flow rate of 2 SLPM at the cathode, humidity was 120%, and back pressure was 50 kPa. The test stopped when the battery voltage dropped to -1.5V. The battery's reverse polarity resistance is positively correlated with the time it takes to reach -1.5V.

[0063] The comparison between Examples 1-4 and Comparative Example 1 shows that the addition of iridium oxide improves the anti-reverse polarity performance. Examples 3 and 4 show a significant improvement over Examples 1 and 2, indicating that the hydrophobic treatment of the catalyst carbon support forces water to diffuse into the iridium oxide region, which is beneficial to enhancing the anti-reverse polarity effect. Example 2 is better than Example 1, and Example 4 is better than Example 3, indicating that after hydrophilic treatment, sufficient water is provided to participate in the water electrolysis reaction under the reverse polarity state, which enhances the effect of iridium oxide.

[0064] Using hydrophilic IrO2 / CF results in a lower voltage, which can increase water accumulation in the catalyst layer to some extent and reduce battery performance. However, by combining it with a hydrophobic catalyst, the accumulated water can be effectively driven to the iridium oxide region, significantly improving battery performance and mitigating the mass transfer loss caused by hydrophilic materials.

[0065] Low-temperature cycling tests were conducted on the membrane electrodes prepared in Examples 1-4 and Comparative Example 1, and the test results are as follows: Figure 2 As shown:

[0066] The voltage of the membrane electrode at 1500 mA / cm² was measured and recorded as VBOL. The battery was then purged with nitrogen for 5 minutes and placed in a high-low temperature cycling chamber. The conditions were set as follows: 4 hours at 20°C and 50% humidity. The temperature was then lowered to -40°C and 50% humidity at a rate of 5°C / min and maintained for 4 hours. The temperature was then increased to 20°C and 50% humidity at a rate of 5°C / min and maintained for 4 hours. This completed one cycle. The cycle was repeated 100 or 200 times according to the set requirements. After 100 cycles, the electrode was activated, and the voltage at 1500 mA / cm² was measured and recorded as V100. Similarly, after 200 cycles, the voltage was recorded as V200. This was used to evaluate the degradation of the membrane electrode during low-temperature cycling.

[0067] Examples 1-4, compared with Comparative Example 1, demonstrate that the hydrophobic catalyst carbon support combined with the hydrophilic anti-reverse polarization agent IrO2 / CF can effectively reduce the total degradation value of the battery in the reverse polarization test and low temperature test, and significantly improve the battery performance.

[0068] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for preparing a membrane electrode including an anode catalyst layer that induces water distribution. Its features are, Includes the following steps: Step 1: Mix water and isopropanol as solvents, add hydrophobically treated platinum-based catalyst and ion exchange resin, and pre-mill to obtain an intermediate slurry. The hydrophobically treated platinum-based catalyst is obtained by loading nano-platinum-based particles onto a hydrophobic carbon support. Step 2: Add the hydrophilic treated carbon fiber loaded with anti-reverse polarization agent IrO2 / CF to the intermediate slurry and perform secondary ball milling to obtain the final slurry; Step 3: The final slurry is coated onto the PTFE substrate and dried to obtain the anode catalyst layer; Step 4: Mix the commercial platinum-based catalyst with the ion exchange resin in an alcoholic solvent, ball mill to obtain a cathode slurry, coat it on a PTFE substrate, and dry it to obtain a cathode catalyst layer; Step 5: Transfer the anode and cathode catalytic layers onto both sides of the proton exchange membrane to obtain the membrane electrode.

2. The preparation method according to claim 1, characterized in that, The nano-platinum-based particles include one or more of Pt particles and Pt alloy particles, and the particle size of the nano-platinum-based particles is between 2-7 nm.

3. The preparation method according to claim 2, characterized in that, The preparation of the hydrophobic carbon support includes the following steps: Take 10g of carbon material and calcine it at 500℃ for 3 hours under a hydrogen atmosphere to obtain a hydrophobic carbon support; the carbon support includes one or more of XC-72, graphene, and acetylene black.

4. The preparation method according to claim 1, characterized in that, In step three, the preparation of the hydrophilic anti-reverse polarization agent IrO2 / CF includes the following steps: loading nano-iridium oxide onto hydrophilic carbon fibers.

5. The preparation method according to claim 4, characterized in that, The preparation of the hydrophilic carbon fiber includes the following steps: take 10g of carbon fiber with a diameter in the range of 50-100nm, add 30ml of 30% hydrogen peroxide and mix and stir for 2 hours; heat treat at 150℃ for 3 hours in air atmosphere, mix the treated carbon fiber with nitric acid-sulfuric acid mixture at 3:1, and reflux at 90℃ for 60 hours; finally wash and filter the carbon fiber to obtain hydrophilic carbon fiber.

6. The preparation method according to claim 1, characterized in that, The platinum content in the hydrophobically treated platinum-based catalyst is between 40% and 50%, and the iridium oxide content in the hydrophilic anti-reverse polarization promoter IrO2 / CF accounts for 10% to 15% of the total mass of the promoter.

7. The preparation method according to claim 1, characterized in that, In the pre-ground slurry, the I / C value is between 0.4 and 0.6, where I / C = mass of ion exchange resin / mass of carbon in catalyst, and the solid content is between 4% and 5%.

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