Anode catalyst layer for fuel cell as well as preparation method and application of anode catalyst layer

Abstract

The invention belongs to the technical field of hydrogen fuel cells, and particularly relates to an anode catalyst layer applied to a fuel cell and a preparation method and application of the anode catalyst layer. The anode catalyst layer for the fuel cell comprises a water electrolysis layer and a hydroxide layer which are overlapped, and the hydroxide layer is in contact with a proton exchange membrane of the fuel cell; the water electrolysis layer comprises a water electrolysis catalyst, carbon powder and first perfluorinated sulfonic acid resin; the hydroxide layer comprises a hydroxide reaction catalyst and second perfluorinated sulfonic acid resin; the ion exchange equivalent EW1 of the first perfluorinated sulfonic acid resin is less than or equal to the ion exchange equivalent EW2 of the second perfluorinated sulfonic acid resin. The anode catalyst layer for the fuel cell has the beneficial effects that through the gradient design of the hydrophilic and hydrophobic properties of the water electrolysis layer and the hydroxide layer, the antipole resistance of the anode catalyst layer is remarkably improved, the performance attenuation degree after antipole is reduced, and the service life of the fuel cell is prolonged.

Description

Technical Field

[0001] This application belongs to the field of hydrogen fuel cell technology, specifically relating to an anode catalyst layer for use in fuel cells, its preparation method, and its application. Background Technology

[0002] Hydrogen fuel cells, as a clean and efficient energy conversion device, have broad application prospects in transportation and stationary power generation. However, the durability and cost of hydrogen fuel cells severely restrict their commercialization process and are currently the most critical issues that need to be addressed.

[0003] Factors affecting the durability of hydrogen fuel cells include start-stop, load cycling, idling, high load, and reverse polarity. Reverse polarity accidents can cause severe and irreversible damage to the catalyst layer in a very short time. During reverse polarity in a hydrogen fuel cell, the anode catalyst layer undergoes water electrolysis and carbon corrosion reactions, providing protons and electrons to the cathode to maintain charge balance between the anode and cathode. The water electrolysis reaction uses only water as a reactant, and the reaction process does not damage the catalyst layer structure. However, the carbon corrosion reaction includes both water and carbon. Carbon corrosion causes the catalyst layer structure to collapse, Pt nanoparticles to detach, and the electrochemical active area to decrease, severely affecting the performance and durability of the hydrogen fuel cell. Therefore, developing an anode catalyst layer with anti-reverse polarity capabilities is of great significance for improving the durability of hydrogen fuel cells.

[0004] The key to improving the anti-reverse polarity of the anode catalyst layer lies in promoting the water electrolysis reaction while inhibiting carbon corrosion. Currently, the most widely used method to improve anti-reverse polarity is to add a water electrolysis catalyst to the anode catalyst layer. However, the high cost of water electrolysis catalysts further increases the cost of fuel cells. Therefore, improving the utilization efficiency of water electrolysis catalysts and reducing their usage is one of the most pressing issues in anti-reverse polarity research. For example, existing technology discloses a membrane electrode structure and preparation method to improve anti-reverse polarity. By adding carbon materials to the anti-reverse polarity slurry, the uniformity of the anti-reverse polarity catalyst distribution and the accuracy of its loading are improved. Simultaneously, a hydrophilic layer, an anode catalyst layer, an anti-reverse polarity functional layer, and an anode diffusion layer are sequentially designed on the anode side of the proton exchange membrane to construct channels conducive to water transport and promote the water electrolysis reaction. Compared with traditional methods, this extends the anti-reverse polarity time by 2-10 times with the same amount of anti-reverse polarity catalyst. Existing technologies also disclose anode catalyst layers with high reverse polarity resistance. These layers are designed as an inner catalyst layer near the proton exchange membrane and an outer catalyst layer near the gas diffusion layer. Hydrophilic substances are added to the inner catalyst layer, significantly improving the reverse polarity resistance time. Both of these approaches significantly improve the reverse polarity resistance time by increasing the hydrophilicity of the anode catalyst layer. However, since water is one of the reactants in the carbon corrosion reaction, increasing the hydrophilicity of the anode catalyst layer, while promoting water electrolysis, also promotes carbon corrosion, leading to corrosion of the anode Pt / C catalyst and consequently a significant decrease in membrane electrode performance and durability. Therefore, in optimizing the reverse polarity resistance design of the anode catalyst layer, both hydrophilicity and hydrophobicity need to be considered simultaneously to improve the reverse polarity resistance time while minimizing performance degradation after reverse polarity. Summary of the Invention

[0005] This application provides an anode catalyst layer for fuel cells, its preparation method, and its application, aiming to solve the problems of poor anti-reverse polarity performance of anode catalyst layers for fuel cells, severe performance degradation after reverse polarity, and high cost due to the large amount of precious metal catalysts used.

[0006] The first aspect of this application provides an anode catalyst layer for a fuel cell, comprising an overlapping water electrolysis layer and a hydroxide layer, wherein the hydroxide layer is in contact with the proton exchange membrane of the fuel cell;

[0007] The water electrolysis layer includes a water electrolysis catalyst, carbon powder, and a first perfluorosulfonic acid resin; the hydroxide layer includes a hydroxide reaction catalyst and a second perfluorosulfonic acid resin. The ion exchange equivalent EW1 of the first perfluorosulfonic acid resin is less than or equal to the ion exchange equivalent EW2 of the second perfluorosulfonic acid resin.

[0008] According to some embodiments of the anode catalyst layer for fuel cells described in this application, the water electrolysis catalyst includes IrO2@ATO; preferably, the mass content of the active component IrO2 in the IrO2@ATO is 40%-60%.

[0009] According to some embodiments of the anode catalyst layer for fuel cells described in this application, the carbon powder includes carbon nanofibers.

[0010] According to some embodiments of the anode catalyst layer for fuel cells described in this application, the ion exchange equivalent EW1 of the first perfluorosulfonic acid resin is 700-900 g / mol.

[0011] According to some embodiments of the anode catalyst layer for fuel cells described in this application, the loading of IrO2, the active component of the water electrolysis catalyst IrO2@ATO in the water electrolysis layer, is 2-10 μg / cm³. 2 .

[0012] According to some embodiments of the anode catalyst layer for fuel cells described in this application, the mass ratio of water electrolysis catalyst to carbon powder in the water electrolysis layer is 1:(2-20).

[0013] According to some embodiments of the anode catalyst layer for fuel cells described in this application, the mass ratio of carbon powder to the first perfluorosulfonic acid resin C1 / I1 in the water electrolysis layer is 1:(0.9-1.2).

[0014] According to some embodiments of the anode catalyst layer for fuel cells described in this application, the hydroxide reaction catalyst comprises Pt / C; preferably, the mass content of the active component Pt in the Pt / C is 20%-40%; preferably, the graphite crystallite size Lc of the carbon support in the Pt / C is ≥4nm.

[0015] According to some embodiments of the anode catalyst layer for fuel cells described in this application, the ion exchange equivalent EW2 of the second perfluorosulfonic acid resin is 800-1000 g / mol.

[0016] According to some embodiments of the anode catalyst layer for fuel cells described in this application, the loading of Pt, the active component of the hydroxide reaction catalyst in the hydroxide layer, is 20-40 μg / cm³. 2 .

[0017] According to some embodiments of the anode catalyst layer for fuel cells described in this application, the mass ratio of the carbon support for the hydroxide reaction catalyst to the second perfluorosulfonic acid resin in the hydroxide layer, C2 / I2, is 1:(0.8-1.1).

[0018] According to some embodiments of the anode catalyst layer for fuel cells described in this application, the mass ratio C1 / I1 of carbon powder to the first perfluorosulfonic acid resin in the water electrolysis layer is less than or equal to the mass ratio C2 / I2 of the carbon support of the hydroxide reaction catalyst to the second perfluorosulfonic acid resin in the hydroxide layer.

[0019] According to some embodiments of the anode catalyst layer for fuel cells described in this application, the thickness of the water electrolysis layer is 3-6 μm, and the thickness of the hydroxide layer is 1-3 μm.

[0020] This application also provides a method for preparing the anode catalyst layer for a fuel cell as described in the first aspect of this application, including the following steps: (1) The water electrolysis catalyst, carbon powder, first perfluorosulfonic acid resin and first solvent are mixed to obtain water electrolysis layer slurry; (2) The water electrolysis layer slurry is coated onto the surface of the base film and dried to obtain the water electrolysis layer; (3) The hydroxide reaction catalyst, the second perfluorosulfonic acid resin and the second solvent are mixed to obtain the hydroxide layer slurry; (4) Coat the surface of the water electrolysis layer with the hydroxide layer slurry and dry it to obtain the hydroxide layer.

[0021] According to some embodiments of the method for preparing an anode catalyst layer for a fuel cell described in this application, the first solvent and the second solvent each independently comprise water and alcohol; preferably, the volume ratio of water to alcohol in the first solvent and the second solvent is each independently 1:(0.3-3).

[0022] According to some embodiments of the method for preparing the anode catalyst layer for fuel cells described in this application, in steps (2) and (4), the drying temperature is independently 50-80°C.

[0023] A third aspect of this application provides a membrane electrode for use in fuel cells, comprising the anode catalyst layer for fuel cells described in the first aspect of this application or the anode catalyst layer for fuel cells prepared by the method described in the second aspect of this application.

[0024] The beneficial effects of this application include: the anode catalyst layer for fuel cells described in this application includes a water electrolysis layer and a hydroxide layer. By adjusting the formulation of the water electrolysis layer and the hydroxide layer, and controlling the key parameters C1 / I1≤C2 / I2 of the water electrolysis layer and the hydroxide layer, the hydrophilicity of the water electrolysis layer is better than that of the hydroxide layer, which is conducive to the contact between water and the water electrolysis reaction catalyst and promotes the water electrolysis reaction under reverse polarity conditions. At the same time, it effectively avoids the contact between water and the carbon support of the hydroxide reaction catalyst and inhibits the occurrence of carbon corrosion reaction under reverse polarity conditions.

[0025] The anode catalyst layer for fuel cells described in this application achieves superior hydrophilicity of the water electrolysis layer compared to the hydroxide layer by controlling the ion exchange equivalent EW1≤EW2 of the perfluorosulfonic acid resin contained in the water electrolysis layer and the hydroxide layer. On the other hand, by using a carbon support graphite microcrystal size ≥4nm for the catalyst contained in the hydroxide layer, the hydrophobicity of the hydroxide layer and the corrosion resistance of the carbon support itself are improved. This synergistically enhances the anti-reverse polarity performance of the anode catalyst layer and reduces the loading of noble metal catalysts IrO2 and Pt, thereby lowering the cost of the fuel cell.

[0026] The anode catalyst layer for fuel cells described in this application significantly improves the anti-reverse polarity of the anode catalyst layer through the hydrophilicity-hydrophobicity gradient design of the water electrolysis layer and the hydroxide layer, reduces the degree of performance degradation after reverse polarity, and extends the service life of the fuel cell. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the working principle of the anode catalyst layer for fuel cells described in this application.

[0028] Figure 2 This is a reverse polarity time curve of the membrane electrode prepared by the anode catalyst layer for fuel cells described in Examples 1-7 of this application.

[0029] Figure 3 The graphs show the initial performance of the membrane electrode prepared from the anode catalyst layer for fuel cells described in Examples 1-7.

[0030] Figure 4 This is a performance curve of the membrane electrode prepared by the anode catalyst layer for fuel cells described in Examples 1-7 after 30 minutes of reverse polarity. Detailed Implementation

[0031] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0032] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0033] This application provides an anode catalyst layer for a fuel cell, comprising an overlapping water electrolysis layer and a hydroxide layer, wherein the hydroxide layer is in contact with the proton exchange membrane of the fuel cell; The water electrolysis layer includes a water electrolysis catalyst, carbon powder, and a first perfluorosulfonic acid resin; the hydroxide layer includes a hydroxide reaction catalyst and a second perfluorosulfonic acid resin. The ion exchange equivalent (EW1) of the first perfluorosulfonic acid resin is less than or equal to the ion exchange equivalent (EW2) of the second perfluorosulfonic acid resin. The smaller the ion exchange equivalent of the perfluorosulfonic acid resin, the stronger its hydrophilicity. That is, when EW1 ≤ EW2, the water electrolysis layer is more hydrophilic, which is beneficial for the contact between water and the water electrolysis catalyst, promoting the water electrolysis reaction and increasing the anti-reverse electrode time. The hydroxide layer is more hydrophobic, which helps to inhibit the contact between water and the carbon support of the Pt / C catalyst, inhibiting carbon corrosion and preventing irreversible damage to the catalyst layer structure, thus reducing performance degradation after reverse electrode reaction. The anode catalyst layer for fuel cells described in this application, through the hydrophilicity / hydrophobicity gradient design of the water electrolysis layer and the hydroxide layer, significantly improves the anti-reverse electrode capability of the anode catalyst layer, reduces the degree of performance degradation after reverse electrode reaction, and extends the electrode's service life.

[0034] In some embodiments of this application, the water electrolysis catalyst comprises IrO2@ATO; preferably, the mass content of the active component IrO2 in the IrO2@ATO is 40%-60%; for example, 40%, 45%, 48%, 50%, 55%, 60%, etc. If the proportion of IrO2 in the catalyst IrO2@ATO is too low, the number of active sites per unit area will be significantly reduced, affecting the catalytic efficiency of the water electrolysis reaction; if the proportion of IrO2 is too high, the cost will be high, and the highly loaded IrO2 may fall off due to thermal stress or electrochemical cycling, reducing the durability of the catalyst. ATO in IrO2@ATO refers to antimony tin oxide, and its structure is a core-shell structure of IrO2 coating ATO.

[0035] In some embodiments of this application, the carbon powder includes carbon nanofibers; compared with carbon nanoparticles, carbon nanofibers can form a richer pore structure, which is beneficial to water transport and improves the anti-reverse polarity time.

[0036] In some embodiments of this application, the ion exchange equivalent (EW1) of the first perfluorosulfonic acid resin is 700-900 g / mol, such as 700 g / mol, 800 g / mol, 850 g / mol, 900 g / mol, etc. If the ion exchange equivalent of the first perfluorosulfonic acid resin is too low, it will result in a high water absorption and swelling rate, poor mechanical stability, and reduced durability; if the ion exchange equivalent is too high, it will result in reduced hydrophilicity of the water electrolysis layer and a shortened anti-reverse polarity time.

[0037] In some embodiments of this application, the loading of IrO2, the active component of the water electrolysis catalyst IrO2@ATO, in the water electrolysis layer is 2-10 μg / cm³. 2 For example, 2μg / cm 2 3μg / cm 2 5μg / cm 2 8μg / cm 2 10μg / cm 2 If the loading of IrO2, the active component of the water electrolysis catalyst IrO2@ATO, is too low in the water electrolysis layer, it will result in poor anti-reverse polarity performance; if the loading of the active component is too high, it will result in increased cost.

[0038] In some embodiments of this application, the mass ratio of water electrolysis catalyst to carbon powder in the water electrolysis layer is 1:(2-20); for example, 1:2, 1:5, 1:10, 1:20, etc. A mass ratio that is too low will result in a low density of the water electrolysis catalyst in the water electrolysis layer, leading to a decrease in anti-reverse polarity performance; a mass ratio that is too high will result in higher costs.

[0039] In some embodiments of this application, the mass ratio C1 / I1 of the carbon powder to the first perfluorosulfonic acid resin in the water electrolysis layer is 1:(0.9-1.2). For example, 1:0.9, 1:1.0, 1:1.2, etc. A mass ratio that is too low can easily cause the water electrolysis catalyst to be over-coated by the first perfluorosulfonic acid resin, affecting mass transfer and hindering the improvement of anti-reverse polarity. A mass ratio that is too high can restrict proton transport channels and reduce the hydrophilicity of the water electrolysis layer, which is detrimental to improving the anti-reverse polarity time.

[0040] In some embodiments of this application, the hydrogenation catalyst comprises Pt / C; preferably, the mass content of the active component Pt in the Pt / C is 20%-40%; for example, 20%, 30%, 40%, etc. If the mass content of Pt is too low, the number of active sites per unit area will be significantly reduced, making it impossible to effectively catalyze the hydrogenation reaction; if the mass content of Pt is too high, the dispersibility of Pt nanoparticles will be poor, making them prone to agglomeration into large particles, leading to a decrease in catalytic activity. It will also result in a higher Pt loading, increasing the cost of the fuel cell. Pt / C refers to a catalyst formed by Pt nanoparticles supported on a carbon support.

[0041] In some embodiments of this application, the graphite crystallite size Lc of the carbon support in the Pt / C is ≥4nm; for example, 4nm, 5nm, 6nm, etc. If the graphite crystallite size is too small, the graphitization degree of the carbon support is low, the corrosion resistance is poor, and carbon corrosion is prone to occur, leading to Pt shedding and fuel cell performance degradation.

[0042] In some embodiments of this application, the ion exchange equivalent (EW2) of the second perfluorosulfonic acid resin is 800-1000 g / mol, such as 800 g / mol, 800 g / mol, 900 g / mol, 1000 g / mol, etc. If the ion exchange equivalent (EW2) of the second perfluorosulfonic acid resin is too low, it will result in a high water absorption and swelling rate, poor mechanical stability, and reduced durability; if it is too high, it will result in low proton conductivity and decreased fuel cell performance.

[0043] In some embodiments of this application, the loading of Pt, the active component of the hydroxide reaction catalyst, in the hydroxide layer is 20-40 μg / cm³. 2 For example, 20 μg / cm 2 30μg / cm 2 40μg / cm 2 Etc. Insufficient loading of active components is detrimental to the catalytic oxidation reaction, while excessive loading of active components will lead to increased costs.

[0044] In some embodiments of this application, the mass ratio (C2 / I2) of the carbon support for the hydroxide reaction catalyst in the hydroxide layer to the second perfluorosulfonic acid resin is 1:(0.8-1.1). For example, 1:0.8, 1:1.0, 1:1.1, etc. A mass ratio that is too low can easily reduce the hydrophobicity of the hydroxide layer, which is not conducive to suppressing the carbon corrosion reaction; a mass ratio that is too high can lead to limited proton transport channels, resulting in a decrease in fuel cell performance.

[0045] In some embodiments of this application, the mass ratio C1 / I1 of carbon powder to the first perfluorosulfonic acid resin in the water electrolysis layer is less than or equal to the mass ratio C2 / I2 of the carbon support of the hydroxide reaction catalyst to the second perfluorosulfonic acid resin in the hydroxide layer. If C1 / I1 > C2 / I2, that is, the water electrolysis layer is more hydrophobic, which is not conducive to promoting the water electrolysis reaction; at the same time, the hydroxide layer is more hydrophilic, which is not conducive to inhibiting the carbon corrosion reaction. The anode catalyst layer for fuel cells described in this application includes a water electrolysis layer and a hydroxide layer. By adjusting the formulation of the water electrolysis layer and the hydroxide layer, and controlling the key parameter C1 / I1 ≤ C2 / I2 of the water electrolysis layer and the hydroxide layer, the hydrophilicity of the water electrolysis layer is better than that of the hydroxide layer, which is conducive to the contact between water and the water electrolysis reaction catalyst and promotes the water electrolysis reaction under the reverse electrode condition; at the same time, it effectively avoids the contact between water and the carbon support of the hydroxide reaction catalyst and inhibits the occurrence of the carbon corrosion reaction under the reverse electrode condition.

[0046] In some embodiments of this application, the thickness of the water electrolysis layer is 3-6 μm, and the thickness of the hydroxide layer is 1-3 μm.

[0047] This application also provides a method for preparing the anode catalyst layer for a fuel cell as described in the first aspect of this application, including the following steps: (1) The water electrolysis catalyst, carbon powder, first perfluorosulfonic acid resin and first solvent are mixed to obtain water electrolysis layer slurry; (2) The water electrolysis layer slurry is coated onto the surface of the base film and dried to obtain the water electrolysis layer; (3) The hydroxide reaction catalyst, the second perfluorosulfonic acid resin and the second solvent are mixed to obtain the hydroxide layer slurry; (4) Coat the surface of the water electrolysis layer with the hydroxide layer slurry and dry it to obtain the hydroxide layer.

[0048] The method for preparing the anode catalyst layer for fuel cells described in this application can be achieved through conventional slurry preparation and coating processes, and is simple to operate.

[0049] As a preferred embodiment, the coating method may include blade coating, slot coating, or ultrasonic spraying. The base film may include a polytetrafluoroethylene (PTFE) film or a polyimide (PI) film.

[0050] In some embodiments of this application, the first solvent and the second solvent each independently comprise water and an alcohol; preferably, the volume ratio of water to alcohol in the first solvent and the second solvent is each independently 1:(0.3-3), for example 1:0.3, 1:0.5, 1:1, 1:1.5, 1:3, etc. As a preferred embodiment, the alcohol comprises n-propanol or isopropanol.

[0051] In some embodiments of this application, the drying temperature in steps (2) and (4) is independently 50-80°C, for example 50°C, 60°C, 70°C, 80°C, etc.

[0052] This application also provides a membrane electrode for use in fuel cells, including the anode catalyst layer for fuel cells described in the first aspect of this application or the anode catalyst layer for fuel cells prepared by the preparation method described in the second aspect of this application.

[0053] The technical solution of this application will be further described below with reference to specific embodiments.

[0054] Example 1 A method for preparing an anode catalyst layer for a fuel cell includes the following steps: Step (1): Preparation of water electrolysis layer slurry: Take 0.5g IrO2@ATO and 3g carbon nanofibers and add them to a ball mill jar. Add 20g of ultrapure water to the ball mill jar and fully wet the slurry under magnetic stirring. Then add 30g isopropanol and 9.6g of a 25% mass concentration first perfluorosulfonic acid resin solution (the C1 / I1 value in this example is 1:0.8). Stir evenly and then add ball milling beads. Ball mill at 450 rpm for 5 hours to obtain a uniformly dispersed water electrolysis layer slurry. The mass fraction of IrO2 in IrO2@ATO is 40%. The ion exchange equivalent of the first perfluorosulfonic acid resin in the first perfluorosulfonic acid resin solution is 700g / mol. Step (2): Preparation of the water electrolysis layer: The water electrolysis layer slurry obtained in step (1) is coated onto the PTFE base film and dried at 80℃ to obtain a water electrolysis layer with a thickness of 4μm; the IrO2 loading in the water electrolysis layer is 8μg / cm³. 2 .

[0055] Step (3): Preparation of hydroxide layer slurry: Take 1g of Pt / C catalyst and add it to a ball mill jar. Add 10g of ultrapure water to the ball mill jar and fully wet it under magnetic stirring. Then add 15g of isopropanol and 3.36g of a second perfluorosulfonic acid resin solution with a mass concentration of 25% (the C2 / I2 value in this example is 1:1.2). Stir evenly, add ball milling beads, and ball mill at 450rpm for 5h to obtain a uniformly dispersed hydroxide layer slurry. The mass fraction of Pt in the Pt / C catalyst is 30%, and the graphite crystallite size Lc of the carbon support in the Pt / C catalyst is 5.5nm. The ion exchange equivalent EW2 of the second perfluorosulfonic acid resin is 800g / mol. Step (4): Preparation of the hydroxide layer: The hydroxide layer slurry prepared in step (3) is coated onto the water electrolysis layer in step (2), and dried at 80°C to obtain a hydroxide layer with a thickness of 2 μm; the Pt loading in the hydroxide layer is 40 μg / cm³. 2 .

[0056] Example 2 The only difference between the preparation method of the anode catalyst layer for fuel cells in Example 2 and that in Example 1 is that the ion exchange equivalent EW1 of the first perfluorosulfonic acid resin used in the preparation of the water electrolysis layer slurry during the preparation of the anode catalyst layer for fuel cells in Example 2 is 700 g / mol; and the ion exchange equivalent EW2 of the second perfluorosulfonic acid resin used in the preparation of the hydroxide layer slurry is 700 g / mol.

[0057] Example 3 The only difference between the preparation method of the anode catalyst layer for fuel cells in Example 3 and Example 1 is that the ion exchange equivalent EW1 of the first perfluorosulfonic acid resin used in the preparation of the water electrolysis layer slurry during the preparation of the anode catalyst layer for fuel cells in Example 3 is 800 g / mol; and the ion exchange equivalent EW2 of the second perfluorosulfonic acid resin used in the preparation of the hydroxide layer slurry is 700 g / mol.

[0058] Example 4 The only difference between the preparation method of the anode catalyst layer for fuel cells in Example 4 and that in Example 1 is that, in the preparation process of the anode catalyst layer for fuel cells in Example 4, the mass ratio of carbon powder to the first perfluorosulfonic acid resin C1 / I1 in the water electrolysis layer is 1:1.2; and the mass ratio of the carbon support for the hydroxide reaction catalyst to the second perfluorosulfonic acid resin C2 / I2 in the hydroxide layer is 1:1.2.

[0059] The specific operating steps include: Step (1): Preparation of water electrolysis layer slurry: Take 0.5g IrO2@ATO and 3g carbon nanofibers and add them to a ball mill jar. Add 16.4g of ultrapure water to the ball mill jar and fully wet the slurry under magnetic stirring. Then add 30g isopropanol and 14.4g of a 25% mass concentration first perfluorosulfonic acid resin solution (the C1 / I1 value in this example is 1:1.2). Stir evenly and then add ball milling beads. Ball mill at 450 rpm for 5 hours to obtain a uniformly dispersed water electrolysis layer slurry. The mass fraction of IrO2 in IrO2@ATO is 40%. The ion exchange equivalent of the first perfluorosulfonic acid resin in the first perfluorosulfonic acid resin solution is 700g / mol. Step (2): Preparation of the water electrolysis layer: The water electrolysis layer slurry obtained in step (1) is coated onto the PTFE base film and dried at 80℃ to obtain a water electrolysis layer with a thickness of 4μm; the IrO2 loading in the water electrolysis layer is 8μg / cm³. 2 .

[0060] Step (3): Preparation of hydroxide layer slurry: Take 1g of Pt / C catalyst and add it to a ball mill jar. Add 10g of ultrapure water to the ball mill jar and fully wet it under magnetic stirring. Then add 15g of isopropanol and 3.36g of a second perfluorosulfonic acid resin solution with a mass concentration of 25% (the C2 / I2 value in this example is 1:1.2). Stir evenly, add ball milling beads, and ball mill at 450rpm for 5h to obtain a uniformly dispersed hydroxide layer slurry. The mass fraction of Pt in the Pt / C catalyst is 30%, and the graphite crystallite size Lc of the carbon support in the Pt / C catalyst is 5.5nm. The ion exchange equivalent EW2 of the second perfluorosulfonic acid resin is 800g / mol. Step (4): Preparation of the hydroxide layer: The hydroxide layer slurry prepared in step (3) is coated onto the water electrolysis layer in step (2), and dried at 80°C to obtain a hydroxide layer with a thickness of 2 μm; the Pt loading in the hydroxide layer is 40 μg / cm³. 2 .

[0061] Example 5 The only difference between the preparation method of the anode catalyst layer for fuel cells in Example 5 and that in Example 1 is that, in the preparation process of the anode catalyst layer for fuel cells in Example 5, the mass ratio of carbon powder to the first perfluorosulfonic acid resin C1 / I1 in the water electrolysis layer is 1:1.2; and the mass ratio of the carbon support for the hydroxide reaction catalyst to the second perfluorosulfonic acid resin C2 / I2 in the hydroxide layer is 1:0.8.

[0062] The specific operating steps include: Step (1): Preparation of water electrolysis layer slurry: Take 0.5g IrO2@ATO and 3g carbon nanofibers and add them to a ball mill jar. Add 16.4g of ultrapure water to the ball mill jar and fully wet the slurry under magnetic stirring. Then add 30g isopropanol and 14.4g of a 25% mass concentration first perfluorosulfonic acid resin solution (the C1 / I1 value in this example is 1:1.2). Stir evenly and then add ball milling beads. Ball mill at 450 rpm for 5 hours to obtain a uniformly dispersed water electrolysis layer slurry. The mass fraction of IrO2 in IrO2@ATO is 40%. The ion exchange equivalent of the first perfluorosulfonic acid resin in the first perfluorosulfonic acid resin solution is 700g / mol. Step (2): Preparation of the water electrolysis layer: The water electrolysis layer slurry obtained in step (1) is coated onto the PTFE base film and dried at 80℃ to obtain a water electrolysis layer with a thickness of 4μm; the IrO2 loading in the water electrolysis layer is 8μg / cm³. 2 .

[0063] Step (3): Preparation of hydroxide layer slurry: 1g of Pt / C catalyst was added to a ball mill jar, and 10.84g of ultrapure water was added to the ball mill jar. The mixture was fully wetted under magnetic stirring. Then, 15g of isopropanol and 2.24g of the second perfluorosulfonic acid resin solution (the C2 / I2 value in this example is 1:0.8) were added and stirred evenly. The ball milling beads were added and the mixture was ball milled at 450 rpm for 5 hours to obtain a uniformly dispersed hydroxide layer slurry. The mass fraction of Pt in the Pt / C catalyst was 30%, and the graphite crystallite size Lc of the carbon support in the Pt / C catalyst was 5.5nm. The ion exchange equivalent EW2 of the second perfluorosulfonic acid resin was 800g / mol, and the mass concentration was 25%. Step (4): Preparation of the hydroxide layer: The hydroxide layer slurry prepared in step (3) is coated onto the water electrolysis layer in step (2), and dried at 80°C to obtain a hydroxide layer with a thickness of 2 μm; the Pt loading in the hydroxide layer is 40 μg / cm³. 2 .

[0064] Example 6 The only difference between the preparation method of the anode catalyst layer for fuel cells in Example 6 and Example 1 is that the graphite crystallite size Lc of the carbon support in the Pt / C catalyst for the hydrogenation reaction is 4 nm in the preparation process of the anode catalyst layer for fuel cells in Example 6.

[0065] Example 7 The only difference between the preparation method of the anode catalyst layer for fuel cells in Example 7 and that in Example 1 is that the graphite crystallite size Lc of the carbon support in the Pt / C catalyst for the hydrogenation reaction is 2.1 nm during the preparation of the anode catalyst layer for fuel cells in Example 7.

[0066] Performance study of the anode catalyst layer for fuel cells described in Examples 1-7 of this application The anode catalyst layer for fuel cells described in Examples 1-7 of this application was hot-pressed with the proton exchange membrane and the cathode catalyst layer, respectively, and then the frame and gas diffusion layer were hot-pressed to prepare a membrane electrode. The performance and anti-reverse polarity performance of the membrane electrode were tested, and the results are shown in Table 1.

[0067] Table 1

[0068] As can be seen from Table 1: Comparing the anodic catalyst layer parameters and test results of Examples 1-3, EW1 < EW2 in Example 1, EW1 = EW2 in Example 2, and EW1 > EW2 in Example 3. Test results show that the reverse electrode times of Examples 1 and 2 are 183 min and 175 min, respectively, significantly better than the 109 min of Example 3. Simultaneously, the reverse electrode decay rates of Examples 1 and 2 are 0.58% and 1.32%, respectively, lower than the 2.67% of Example 3. This indicates that when the anodic catalyst layer EW1 ≤ EW2, the membrane electrode exhibits a longer reverse electrode resistance time and lower reverse electrode decay. The main reason is that a smaller EW value indicates stronger hydrophilicity; when EW1 ≤ EW, the water electrolysis layer is more hydrophilic, which is conducive to the water electrolysis reaction; the hydroxide layer is more hydrophobic, which is beneficial for inhibiting carbon corrosion.

[0069] Comparing the anodic catalyst layer parameters and test results of Examples 1 and 4-5, the C1 / I1 ratio in Example 1 is greater than the C2 / I2 ratio, the C1 / I1 ratio in Example 4 is equal to the C2 / I2 ratio, and the C1 / I1 ratio in Example 5 is less than the C2 / I2 ratio. The test results show that the reverse electrode times in Examples 4 and 5 are 194 min and 196 min, respectively, which are better than the 183 min in Example 1. Simultaneously, the reverse electrode decay in Examples 4 and 5 is 0.15% and 0%, respectively, which is less than the 0.58% in Example 1. This indicates that when the anodic catalyst layer C1 / I1 ≤ C2 / I2, the membrane electrode reverse electrode time is longer and the reverse electrode decay is smaller. The main reason is that the smaller the C / I value, the stronger the hydrophilicity. When C1 / I1 ≤ C2 / I2, the water electrolysis layer is more hydrophilic, which is conducive to the water electrolysis reaction; the hydroxide layer is more hydrophobic, which is conducive to inhibiting the carbon corrosion reaction. Furthermore, the data from Examples 1-5 show that the EW value has a greater impact on the reverse electrode time and reverse electrode decay than the C / I value.

[0070] Comparing the anodic catalyst layer parameters and test results of Examples 1 and 6-7, the carbon support graphite crystallite size of the Pt / C hydroxide catalyst in Example 1 was 5.5 nm, in Example 6 it was 4 nm, and in Example 7 it was 2.1 nm. Test results showed that the reverse electrode times of Examples 1 and 6 were 183 min and 171 min, respectively, significantly better than the 131 min of Example 7. Simultaneously, the reverse electrode decay of Examples 1 and 6 was 0.58% and 1.03%, respectively, significantly lower than the 7.96% of Example 7. This indicates that when the graphite crystallite size Lc ≥ 4 nm, the membrane electrode exhibits a longer reverse electrode resistance time and lower reverse electrode decay. The main reason is that the larger the graphite crystallite size, the stronger the corrosion resistance of the carbon support itself, and the higher the hydrophobicity, which can reduce the contact between water and the carbon support, inhibiting the occurrence of carbon corrosion reaction.

[0071] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. An anode catalyst layer for a fuel cell, characterized in that, It includes an overlapping water electrolysis layer and a hydroxide layer, wherein the hydroxide layer is in contact with the proton exchange membrane of the fuel cell; The water electrolysis layer includes a water electrolysis catalyst, carbon powder, and a first perfluorosulfonic acid resin; the hydroxide layer includes a hydroxide reaction catalyst and a second perfluorosulfonic acid resin. The ion exchange equivalent EW1 of the first perfluorosulfonic acid resin is less than or equal to the ion exchange equivalent EW2 of the second perfluorosulfonic acid resin.

2. The anode catalyst layer for a fuel cell according to claim 1, characterized in that, The water electrolysis catalyst comprises IrO2@ATO; preferably, the mass content of the active component IrO2 in the IrO2@ATO is 40%-60%; And / or, the carbon powder includes carbon nanofibers; And / or, the ion exchange equivalent EW1 of the first perfluorosulfonic acid resin is 700-900 g / mol.

3. The anode catalyst layer for fuel cells according to claim 2, characterized in that, The loading of IrO2, the active component of the water electrolysis catalyst IrO2@ATO in the water electrolysis layer, is 2-10 μg / cm³. 2 ; And / or, the mass ratio of water electrolysis catalyst to carbon powder in the water electrolysis layer is 1:(2-20); And / or, the mass ratio of carbon powder to the first perfluorosulfonic acid resin C1 / I1 in the water electrolysis layer is 1:(0.9-1.2).

4. The anode catalyst layer for a fuel cell according to claim 3, characterized in that, The hydrogenation catalyst comprises Pt / C; preferably, the mass content of the active component Pt in the Pt / C is 20%-40%; preferably, the graphite crystallite size Lc of the carbon support in the Pt / C is ≥4nm; And / or, the ion exchange equivalent EW2 of the second perfluorosulfonic acid resin is 800-1000 g / mol.

5. The anode catalyst layer for a fuel cell according to claim 4, characterized in that, The loading of Pt, the active component of the hydroxide reaction catalyst, in the hydroxide layer is 20-40 μg / cm³. 2 ; And / or, the mass ratio of the carbon support for the hydroxide reaction catalyst in the hydroxide layer to the second perfluorosulfonic acid resin, C2 / I2, is 1:(0.8-1.1).

6. The anode catalyst layer for a fuel cell according to claim 5, characterized in that, The mass ratio of carbon powder to the first perfluorosulfonic acid resin in the water electrolysis layer, C1 / I1, is less than or equal to the mass ratio of the carbon support for the hydroxide reaction catalyst to the second perfluorosulfonic acid resin in the hydroxide layer, C2 / I2.

7. The anode catalyst layer for a fuel cell according to claim 1, characterized in that, The thickness of the water electrolysis layer is 3-6 μm, and the thickness of the hydroxide layer is 1-3 μm.

8. The method for preparing the anode catalyst layer for a fuel cell according to any one of claims 1-7, characterized in that, Includes the following steps: (1) The water electrolysis catalyst, carbon powder, first perfluorosulfonic acid resin and first solvent are mixed to obtain water electrolysis layer slurry; (2) The water electrolysis layer slurry is coated onto the surface of the base film and dried to obtain the water electrolysis layer; (3) The hydroxide reaction catalyst, the second perfluorosulfonic acid resin and the second solvent are mixed to obtain the hydroxide layer slurry; (4) Coat the surface of the water electrolysis layer with the hydroxide layer slurry and dry it to obtain the hydroxide layer.

9. The method for preparing the anode catalyst layer for a fuel cell according to claim 8, characterized in that, The first solvent and the second solvent each independently comprise water and alcohol; preferably, the volume ratio of water to alcohol in the first solvent and the second solvent is each independently 1:(0.3-3). And / or, in steps (2) and (4), the drying temperature is independently 50-80°C.

10. A membrane electrode assembly for use in a fuel cell, characterized in that, Includes the anode catalyst layer for fuel cells according to any one of claims 1-7 or the anode catalyst layer for fuel cells obtained by the preparation method according to any one of claims 8-9.

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