Variable contact angle non-noble metal-based film electrode and preparation method and application thereof

Abstract

The present application relates to the field of fuel cell. In particular, it relates to a membrane electrode assembly with a variable contact angle non-noble metal catalyst layer and a preparation method thereof. By using a variable contact angle cathode catalyst layer, the ionomer content is low and the contact angle is large on the side close to the gas diffusion layer, which is conducive to the gas entering the membrane electrode for reaction and the liquid discharging; the ionomer content is high and the contact angle is small on the side close to the proton exchange membrane, which is still hydrophobic, on the one hand, it is conducive to the increase of the ionomer water content and the reduction of the proton transmission resistance, on the other hand, the hydrophobicity improves the liquid transmission capacity, avoids the decrease of the mass transfer capacity of the thick non-noble metal-based catalyst layer, thereby optimizing the interface between the cathode side gas diffusion layer and the thick non-noble metal catalyst layer, further reducing the gas-liquid transmission resistance, and improving the performance of the membrane electrode. Therefore, the membrane electrode is used for preparing a fuel cell, which can effectively improve the power density of the fuel cell.

Description

A variable contact angle non-noble metal-based film electrode, its preparation method and application Technical Field

[0001] This invention relates to the field of fuel cells. In particular, it relates to a variable contact angle non-noble metal-based membrane electrode, its preparation method, and its application. Background Technology

[0002] The environmental pollution and energy security problems caused by the use of traditional energy sources such as fossil fuels hinder the high-quality development of countries. Developing clean energy has become a consensus among all humankind. Hydrogen energy, as a zero-carbon energy source, is an ideal energy storage medium and energy carrier. Fuel cells are the core of efficient hydrogen energy utilization, and membrane electrode assemblies (MEAs) are key components of fuel cells. The catalyst in a MEA accounts for approximately 41% of its cost, and precious metal Pt-based catalysts are commonly used (Journal of Power Sources, 2018, 399:304-313). In particular, the slow oxygen reduction reaction on the cathode side typically requires a high loading of precious metal catalysts. The high cost of catalysts hinders the commercialization of proton exchange membrane fuel cells. In recent years, non-precious metal oxygen reduction catalysts have made significant progress and show a trend towards commercialization (Journal of Power Sources, 2023, 586:233534). Therefore, developing stable and lower-cost non-precious metal-based MEAs is a major direction for promoting the development of fuel cells.

[0003] However, due to their lower intrinsic kinetic activity, non-precious metal oxygen reduction catalysts typically have higher loadings on the cathode side than precious metal catalysts. This results in a non-precious metal-based catalyst layer being approximately 2-3 times thicker than the Pt-based catalyst layer, causing severe gas mass transfer resistance, hindering the transport of water generated in the reaction, and reducing fuel cell performance. In precious metal Pt-based cathode catalyst layers, hydrophobicity is often used to optimize the catalyst layer. For example, CN1167832C demonstrates a thin-layer hydrophobic catalyst electrode where the addition of polytetrafluoroethylene (PTFE) increases the catalyst layer contact angle to greater than 90°, facilitating the removal of water generated in the reaction and improving the membrane electrode's flood resistance. CN106961838B demonstrates a membrane electrode with a composite catalyst layer, consisting of a hydrophilic layer and a hydrophobic layer. The hydrophilic layer is closer to the proton exchange membrane, while the hydrophobic layer uses PTFE additives. The hydrophilic catalyst layer forms a tight bond with the proton exchange membrane, preventing it from easily detaching.

[0004] Adding hydrophobic agents reduces the conductivity of the cathode catalyst layer. Furthermore, CN1167832C mentions that added hydrophobic agents also increase the catalyst layer thickness to some extent. Clearly, current hydrophobication strategies are not suitable for non-noble metal-based catalyst layers with a thickness much greater than that of noble metal catalyst layers. Developing a high-performance non-noble metal-based film electrode that improves gas-liquid transport capabilities is therefore essential. Summary of the Invention

[0005] Based on the above objectives, the purpose of this application is to provide a variable contact angle non-noble metal-based film electrode, its preparation method, and its application. To this end, the first technical solution of this application discloses a variable contact angle non-noble metal-based film electrode, comprising a cathode gas diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode gas diffusion layer;

[0006] The cathode catalyst layer is a non-precious metal catalyst and comprises three sublayers: an outer sublayer, a middle sublayer, and an inner sublayer. The outer sublayer is connected to the cathode gas diffusion layer, the inner sublayer is connected to the proton exchange membrane, and the middle sublayer is located between the outer and inner sublayers. The contact angles of the three sublayers decrease sequentially from the outer to the inner sublayer.

[0007] Furthermore, the amount of non-precious metal catalyst added to the three sub-layers of the cathode catalyst layer is equal, and the change in its contact angle is adjusted by adding different masses of ionomer.

[0008] Furthermore, by mass ratio, the mass ratio of ionomer to non-precious metal catalyst in the sublayer of the cathode catalyst layer is 0.8. The amount of ionomer added decreases sequentially from the inner sublayer of the cathode catalyst layer to the outer sublayer of the cathode catalyst layer, and the mass ratio between two adjacent sublayers decreases by 0.02 to 0.6.

[0009] Furthermore, the non-precious metal element in the non-precious metal catalyst is any one or any combination of Fe, Co, Ni, Mn, Cu, and Zn.

[0010] Furthermore, the ionomer is a proton exchange resin, including any one or any combination of long-chain perfluorosulfonic acid, short-chain perfluorosulfonic acid, or a mixture of long and short-chain perfluorosulfonic acid.

[0011] The second technical solution of this application discloses a method for preparing the above-mentioned variable contact angle non-noble metal-based film electrode, including the following steps:

[0012] Preparation of cathode catalyst layer: Non-precious metal catalyst, ionomer, deionized water and organic solvent are mixed and dispersed in an ultrasonic water bath to obtain a catalyst slurry with three sub-layers. The amount of ionomer added decreases from the inner sub-layer of the cathode catalyst layer to the outer sub-layer of the cathode catalyst layer, and the mass ratio between two adjacent sub-layers decreases by 0.02 to 0.6.

[0013] Preparation of the anode catalyst layer: The noble metal catalyst, ionomer, deionized water and organic solvent are mixed and dispersed in an ultrasonic water bath to obtain a catalyst slurry;

[0014] Electrode preparation: The cathode gas diffusion electrode and the anode gas diffusion electrode were prepared by the GDE method;

[0015] Fabrication of membrane electrode: The cathode gas diffusion electrode, proton exchange membrane and anode gas diffusion electrode are combined by hot pressing to form a non-noble metal-based membrane electrode with variable contact angle.

[0016] Furthermore, in preparing the cathode gas diffusion electrode, the catalyst slurry of the outer sublayer of the cathode catalyst layer is ultrasonically sprayed onto the micropore side of the gas diffusion layer, then the catalyst slurry of the middle sublayer of the cathode catalyst layer is ultrasonically sprayed onto the outer sublayer of the cathode catalyst layer, and finally the catalyst slurry of the inner sublayer of the cathode catalyst layer is ultrasonically sprayed onto the middle sublayer of the cathode catalyst layer; in preparing the anode gas diffusion electrode, the anode catalyst slurry is ultrasonically sprayed onto the micropore side of the gas diffusion layer to form the anode catalyst layer.

[0017] Furthermore, the catalyst loading of the three sublayers in the cathode catalyst layer is equal, wherein the total non-precious metal catalyst loading is 0.5–5 mg cm⁻¹. -2 The loading of the noble metal catalyst in the anode catalyst layer is 0.05–0.4 mg. Pt cm -2 .

[0018] Furthermore, the variable contact angle non-noble metal-based membrane electrode obtained according to the above preparation method and its application in the preparation of fuel cells.

[0019] Beneficial effects: The present invention employs a variable contact angle cathode catalyst layer. On the side near the gas diffusion layer, the ionomer content is low and the contact angle is large, which is conducive to the gas entering the membrane electrode for reaction and the liquid discharge. On the side near the proton exchange membrane, the ionomer content is high and the contact angle is small while still maintaining hydrophobicity. On the one hand, this is conducive to increasing the water content of the ionomer and reducing the proton transport resistance. On the other hand, the hydrophobicity improves the liquid transport capacity and avoids the decline in the mass transfer capacity of the thicker non-precious metal-based catalyst layer, thereby improving the membrane electrode performance.

[0020] The mass ratio of ionomer to catalyst used in this invention is much larger than that in ordinary noble metal-based catalyst layers (the mass ratio of ionomer to catalyst in noble metal-based catalyst layers is usually around 0.25), resulting in a wider range of contact angle variation in the formed catalyst layer, which effectively improves the water management capability of the membrane electrode. Furthermore, in terms of catalyst layer composition, no additional hydrophobic agent is added, thus avoiding an increase in the electron transport impedance of the membrane electrode.

[0021] This invention uses a non-precious metal catalyst as the cathode oxygen reduction catalyst, which has low preparation cost, simple operating conditions, and is conducive to mass production and large-scale application.

[0022] This invention uses the GDE method to prepare membrane electrodes, aiming to optimize the interface between the cathode-side gas diffusion layer and the thicker non-precious metal catalyst layer, further reduce gas-liquid transport resistance, and improve the power density of fuel cells. Attached Figure Description

[0023] Figure 1 is a schematic diagram of a non-noble metal-based film electrode structure with variable contact angle;

[0024] Figure 2 shows the material transport principle of a variable contact angle non-noble metal base film electrode and a conventional non-noble metal base film electrode;

[0025] Figure 3 shows the relationship between different ionomer to catalyst mass ratios and the contact angle of the catalyst layer;

[0026] Figure 4 is a comparison of the polarization curves of the variable contact angle non-noble metal film electrodes prepared in Examples 1, 2, and 3 with the ordinary non-noble metal film electrode in Comparative Example 4. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments. This embodiment is implemented based on the technology of the present invention, and detailed implementation methods and specific operating procedures are given to illustrate the inventiveness of the present invention. However, the scope of protection of the present invention is not limited to the following embodiments.

[0028] The first embodiment of this application provides a variable contact angle non-noble metal-based film electrode, as shown in Figure 1: it includes a cathode gas diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode gas diffusion layer; wherein, the cathode catalyst layer is a non-noble metal catalyst, comprising three sublayers, namely an outer sublayer, a middle sublayer, and an inner sublayer; the outer sublayer is connected to the cathode gas diffusion layer, the inner sublayer is connected to the proton exchange membrane, and the middle sublayer is located between the outer and inner sublayers; wherein, the contact angles of the three sublayers decrease sequentially from the outer sublayer to the inner sublayer.

[0029] In this embodiment, the amount of non-precious metal catalyst added to the three sub-layers of the cathode catalyst layer is equal, and the change in contact angle is adjusted by adding different masses of ionomer. It should be noted that in the prior art, adding ionomer to the catalyst layer is generally used to adhere the catalyst, form highly active three-phase points, and play a role in proton conduction. However, in this embodiment, the addition of ionomer also serves to adjust the contact angle of the catalyst layer, achieving the purpose of a variable contact angle cathode catalyst layer.

[0030] In a further embodiment, to achieve the purpose of a non-precious metal-based film electrode with variable contact angle, the contact angle of the three sublayers is adjusted by regulating the mass ratio of ionomer to non-precious metal catalyst, while maintaining a constant non-precious metal catalyst content. As shown in Figure 1, the mass ratio of ionomer to non-precious metal catalyst decreases sequentially from the inner sublayer of the cathode catalyst layer to the outer sublayer, with a mass ratio of 0.8 for the middle sublayer of the cathode catalyst layer. The inner sublayer of the cathode catalyst layer has the highest mass ratio, i.e., the highest ionomer content, and its catalyst layer contact angle is the smallest. The ionomer content gradually decreases from the inner sublayer of the cathode catalyst layer to the outer sublayer, with the mass ratio difference between two adjacent sublayers ranging from 0.02 to 0.6, meaning the outermost catalyst layer has the lowest ionomer content and the largest contact angle.

[0031] It should be noted that even in the inner sublayer of the cathode catalyst layer, where the contact angle is smallest, it still needs to be controlled to be greater than 90° to maintain hydrophobic properties. Therefore, the mass ratio of ionomer to non-precious metal catalyst needs to be controlled within the range of 0.2 to 1.4. The resulting cathode catalyst layer is shown in Figure 2. As can be seen from Figure 2, in the variable contact angle membrane electrode, the contact angle gradually increases from the inner sublayer to the outer sublayer, generating a driving force for outward drainage. Water is transported from the inner sublayer to the gas diffusion layer, and liquid water is smoothly discharged from the membrane electrode, which is beneficial for the continuous entry of reactant gases into the catalyst layer for reaction and avoids water flooding and other factors that reduce the performance of the membrane electrode. In the ordinary membrane electrode, compared with the variable contact angle membrane electrode, there is no additional drainage driving force provided by the change in contact angle, and the non-precious metal catalyst layer is thicker, making it easier for water to accumulate in the non-precious metal catalyst layer. This affects the entry of reactant gases into the catalyst layer for reaction, leading to a decrease in membrane electrode performance and causing reverse polarity in the fuel cell stack.

[0032] It should be noted that the cathode catalyst layer also includes organic solvent and deionized water. Their basic functions and addition methods are consistent with existing technologies, and will not be specifically described in this embodiment. Preferably, the mass ratio of organic solvent to catalyst is 150-800. However, it is understood that the catalyst loading of the three sublayers in the cathode catalyst layer is equal, and the addition amounts of organic solvent and deionized water are also equal. The contact angle is changed only by varying the amount of ionomer added. The total non-precious metal catalyst loading is 0.5–5 mg cm⁻¹. -2 .

[0033] In a further embodiment, the non-precious metal element in the non-precious metal catalyst is any one or any combination of Fe, Co, Ni, Mn, Cu, and Zn. The support for the non-precious metal catalyst is carbon nanotubes, graphene, porous carbon, carbon black, etc., and the metal element is dispersed in the form of single atoms, diatomic particles, clusters, nanoparticles, etc. The ionomer is a proton exchange resin, including any one or any combination of long-chain perfluorosulfonic acid, short-chain perfluorosulfonic acid, or a mixture of long and short-chain perfluorosulfonic acid, such as Nafion, Aquivion, 3M PFSA, etc.

[0034] It should be noted that, in this embodiment, the cathode gas diffusion layer, proton exchange membrane, anode catalyst layer and anode gas diffusion layer are conventionally known in the art, and this application does not make any special description, but only provides preferred embodiments.

[0035] In some preferred embodiments, the proton exchange membrane is a commercially available proton exchange membrane such as Nafion 211, Nafion 212, NC 700, Gore M765.08, Gore M788.12, Gore M820.15, or Gore M735.18.

[0036] In some preferred embodiments, the anode catalyst layer comprises a noble metal catalyst, deionized water, an organic solvent, and an ionomer. The noble metal catalyst may contain one or any combination of the following metals: Pt, PtRu, PtPd, PtPb, PtFe, PtCo, PtNi, PtMn, and PtCu. The noble metal catalyst may use a catalyst support such as carbon nanotubes, graphene, porous carbon, or carbon black. The dispersion form of the metal elements includes, but is not limited to, single atoms, diatomic particles, clusters, and nanoparticles. The mass ratio of Pt in the noble metal catalyst is 0%–70%. The loading of the noble metal catalyst in the anode catalyst layer is 0.05–0.4 mg. Pt cm -2 The mass ratio of organic solvent to catalyst in the anode catalyst slurry is 50–300.

[0037] The organic solvents in the catalyst slurries of the cathode and anode mainly serve a dispersing function, including one or any combination of n-propanol, isopropanol, n-butanol, ethanol, and propylene glycol.

[0038] The second embodiment of this application provides a second technical solution that discloses a method for preparing the above-mentioned variable contact angle non-noble metal-based film electrode, including the following steps:

[0039] Preparation of cathode catalyst layer: Non-precious metal catalyst, ionomer, deionized water and organic solvent are mixed and dispersed in an ultrasonic water bath to obtain a catalyst slurry with three sub-layers. The amount of ionomer added decreases from the inner sub-layer of the cathode catalyst layer to the outer sub-layer of the cathode catalyst layer, and the mass ratio between two adjacent sub-layers decreases by 0.02 to 0.6.

[0040] Preparation of the anode catalyst layer: The noble metal catalyst, ionomer, deionized water and organic solvent are mixed and dispersed in an ultrasonic water bath to obtain a catalyst slurry;

[0041] Electrode preparation: The cathode gas diffusion electrode and the anode gas diffusion electrode were prepared by the GDE method;

[0042] Fabrication of membrane electrode: The cathode gas diffusion electrode, proton exchange membrane and anode gas diffusion electrode are combined by hot pressing to form a non-noble metal-based membrane electrode with variable contact angle.

[0043] In this embodiment, after the components of the catalyst slurry are mixed according to the mass ratio, they need to be dispersed in an ultrasonic water bath at a temperature of 0 to 10°C for a dispersion time of 0.5 to 10 hours.

[0044] In this embodiment, the components of the membrane electrode are assembled by hot pressing. The temperature range of the hot pressing operation is 90–140°C; the pressure of the hot pressing operation is set to 50–1200 psi; and the hot pressing operation time is set to 1–10 min.

[0045] In a further embodiment, when preparing the cathode gas diffusion electrode, the catalyst slurry of the outer sublayer of the cathode catalyst layer is ultrasonically sprayed onto the micropore side of the gas diffusion layer, then the catalyst slurry of the middle sublayer of the cathode catalyst layer is ultrasonically sprayed onto the outer sublayer of the cathode catalyst layer, and finally the catalyst slurry of the inner sublayer of the cathode catalyst layer is ultrasonically sprayed onto the middle sublayer of the cathode catalyst layer; when preparing the anode gas diffusion electrode, the anode catalyst slurry is ultrasonically sprayed onto the micropore side of the gas diffusion layer to form the anode catalyst layer. The ultrasonic power during ultrasonic spraying is 0.5–3.5 W, and the spraying liquid flow rate is 0.02–2 mL / min. -1 The operating temperature is 25–80℃.

[0046] In a further embodiment, the catalyst loading of the three sublayers in the cathode catalyst layer is equal, wherein the total non-precious metal catalyst loading is 0.5–5 mg / cm³. -2 The loading of the noble metal catalyst in the anode catalyst layer is 0.05–0.4 mg. Pt cm -2 .

[0047] The third embodiment of this application discloses a variable contact angle non-noble metal-based membrane electrode obtained according to the above preparation method and its application in the preparation of fuel cells.

[0048] In this embodiment, by employing a variable contact angle cathode catalyst layer, the ionomer content is low and the contact angle is large on the side near the gas diffusion layer, which facilitates gas entry into the membrane electrode assembly (MEA) for reaction and liquid discharge. On the side near the proton exchange membrane, the ionomer content is high and the contact angle is small while maintaining hydrophobicity. This not only increases the water content of the ionomer, reducing proton transport resistance, but also enhances liquid transport capacity, preventing a decrease in mass transfer capacity of the thicker non-precious metal-based catalyst layer. This optimizes the interface between the cathode-side gas diffusion layer and the thicker non-precious metal catalyst layer, further reducing gas-liquid transport resistance and improving MEA performance. Therefore, using this MEA in fuel cell fabrication can effectively improve fuel cell power density.

[0049] To facilitate understanding of the present invention, specific embodiments are provided below for further explanation. It should be noted that these embodiments are for illustrative purposes only and should not be construed as limiting the invention in any way.

[0050] Example 1: Preparation of a non-noble metal-based film electrode with variable contact angle

[0051] 1. Preparation of catalyst slurry for the anode catalyst layer: Take 6 mg of 60% Pt / C catalyst, add 260 μL of deionized water to wet the catalyst, then add 560 μL of isopropanol, add Nafion-D521 to make the ionomer account for 25% of the dry weight of the slurry, place it in a water bath and sonicate for 0.5 h to make the ionomer adhere evenly to the catalyst particles, then add 1159 μL of isopropanol, and continue to sonicate in the water bath for 3 h to obtain the catalyst slurry for the anode catalyst layer.

[0052] 2. Preparation of the anode electrode: Using a 1.8W ultrasonic nozzle, the anode catalyst slurry is sprayed onto a 5cm surface. 2 The square commercial gas diffusion layer with micropores allows for an anode Pt loading of 0.3 mg / cm². -2 .

[0053] 3. Preparation of the catalyst slurry for the cathode catalyst layer: Take 10 mg of non-precious metal-based FeSNC catalyst, add 650 μL of deionized water to wet the catalyst, then add 935 μL of isopropanol, and add Nafion-D521 ionomer. The mass ratio of ionomer to catalyst in the outer sublayer of the cathode catalyst layer is 0.7 (7 mg), the mass ratio of ionomer to catalyst in the middle sublayer of the cathode catalyst layer is 0.8 (8 mg), and the mass ratio of ionomer to catalyst in the inner sublayer of the cathode catalyst layer is 0.9 (9 mg); that is, the difference in the mass ratio of ionomer to catalyst between adjacent catalyst sublayers is 0.1. The mass of ionomer is determined based on the mass ratio of ionomer to catalyst in each sublayer. The catalyst slurry is placed in a water bath and sonicated for 0.5 h to ensure that the ionomer adheres uniformly to the catalyst particles. Then, 1832 μL of isopropanol is added, and sonication in the water bath continues for 3 h.

[0054] 4. Preparation of the cathode electrode: Using a 1.8W ultrasonic nozzle, the catalyst slurry of the outer sublayer of the cathode catalyst layer is sprayed onto a 5cm layer. 2 The square commercial gas diffusion layer with micropores allows for a catalyst loading of 1 mg / cm² on the outer sublayer of the cathode catalyst layer. -2 Subsequently, the catalyst slurry from the nucleus layer of the cathode catalyst layer was sprayed onto the outer nucleus layer of the cathode catalyst layer, so that the catalyst loading of the nucleus layer of the cathode catalyst layer was 1 mg cm⁻¹. -2 Finally, the catalyst slurry of the inner sublayer of the cathode catalyst layer is sprayed onto the sublayer of the cathode catalyst layer, so that the catalyst loading of the inner sublayer of the cathode catalyst layer is 1 mg cm⁻¹. -2 .

[0055] 5. Preparation of membrane electrode: The cathode electrode and anode electrode are symmetrically placed on both sides of the commercial proton exchange membrane N211 with the catalytic layer as the opposite side. After hot pressing in a hot press at a temperature of 125°C, a pressure of 500 psi, and a time of 5 min, the membrane electrode is obtained.

[0056] Example 2: Preparation of a non-noble metal-based film electrode with variable contact angle

[0057] The preparation method is the same as in Example 1, except that in step 3 of Example 2, the amount of ionomer added is such that the mass ratio of ionomer to catalyst in the outer sublayer of the cathode catalyst layer is 0.65 (6.5 mg), the mass ratio of ionomer to catalyst in the middle sublayer of the cathode catalyst layer is 0.8 (8 mg), and the mass ratio of ionomer to catalyst in the inner sublayer of the cathode catalyst layer is 0.95 (9.5 mg); that is, the difference in the mass ratio of ionomer to catalyst in adjacent catalyst sublayers is 0.15.

[0058] Example 3: Preparation of a non-noble metal-based film electrode with variable contact angle

[0059] The preparation method is the same as in Example 1, except that in step 3 of Example 3, the amount of ionomer added is such that the mass ratio of ionomer to catalyst in the outer sublayer of the cathode catalyst layer is 0.6 (6 mg), the mass ratio of ionomer to catalyst in the middle sublayer of the cathode catalyst layer is 0.8 (8 mg), and the mass ratio of ionomer to catalyst in the inner sublayer of the cathode catalyst layer is 1.0 (10 mg).

[0060] That is, the difference in the mass ratio of ionomer to catalyst in adjacent catalytic sublayers is 0.2.

[0061] Comparative Example 1: Preparation of Non-Noble Metal-Based Film Electrodes

[0062] The preparation method is the same as in Example 1, except that in step 3 of Comparative Example 1, the amount of ionomer added is such that the mass ratio of ionomer to catalyst in the outer sublayer, middle sublayer, and inner sublayer of the cathode catalyst layer is 0.8 (8 mg), that is, the ionomer gradient of Comparative Example 1 is 0, which is a cathode catalyst layer with uniform Nafion content.

[0063] In the membrane electrodes of Examples 1, 2, and 3 above, the cathode catalyst layer has an ionomer gradient, wherein the mass ratio of ionomer to catalyst in the outer sublayer, middle sublayer, and inner sublayer of the cathode catalyst layer are as follows: Example 1 (0.7 / 0.8 / 0.9), Example 2 (0.65 / 0.8 / 0.95), and Example 3 (0.6 / 0.8 / 1.0), respectively, and the contact angle gradually decreases in the catalyst layer. In contrast, the cathode catalyst layer in Comparative Example 1 does not have an ionomer gradient, the mass ratio of ionomer to catalyst is 0.8, and the contact angle remains unchanged in the catalyst layer. The catalyst mass on the cathode side of the comparative example membrane electrode and the membrane electrodes of the examples is kept consistent, both being 3 mg / cm³. -2 .

[0064] Test Example 1: Proton Exchange Membrane Fuel Cell Testing

[0065] The membrane electrodes prepared in Examples 1-3 and Comparative Example 1 were tested in a proton exchange membrane fuel cell. The test conditions were: hydrogen as the anode gas and a flow rate of 0.3 L / min. -1 The cathode gas is oxygen, and the flow rate is 0.4 L / min. -1 Battery temperature 80℃, fully humidified; back pressure 1 bar; battery clamp active area 5 cm². 2 .

[0066] The test results are shown in Figures 3-4. Figure 3 shows the contact angle of the catalyst layer with different mass ratios of ionomer to catalyst. When the mass ratio is 0.6, the contact angle is 138.60±0.65°. As the mass ratio increases, the contact angle decreases. For example, when the mass ratio is 1.4, the contact angle is 95.10±1.45°, which is about 43.5° lower, and can significantly adjust the contact angle of the catalyst layer.

[0067] As shown in Figure 4, the peak power densities of Examples 1, 2, 3 and Comparative Example 1 are 925 mW / cm². -2 950mW cm -2 886mW cm -2 and 846mW cm -2 The peak power densities of the embodiments were all higher than those of Comparative Example 1, indicating that the use of a variable contact angle ionomer catalyst layer on the cathode side can significantly improve the performance of the membrane electrode. Among them, when the mass ratio of ionomer to catalyst in each sublayer differed by 0.15, the membrane electrode of Example 2 exhibited the highest power density, representing a 12.29% performance improvement compared to the membrane electrode of Comparative Example 1. The limiting current densities of Examples 1, 2, 3, and Comparative Example 1 were 4265 mA / cm². -2 4603mAcm -2 4031mAcm -2 and 3942mAcm -2 The limiting current density of the embodiments is higher than that of Comparative Example 1, indicating that the use of a variable contact angle catalyst layer on the cathode side can significantly improve the operating current density range of the membrane electrode, which means that the membrane electrode has an enhanced ability to discharge liquid water under high current density, thus improving the gas-liquid transport capability of the membrane electrode.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A variable contact angle non-noble metal-based film electrode, characterized in that, The system comprises a cathode gas diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode gas diffusion layer. The cathode catalyst layer is a non-precious metal catalyst and consists of three sublayers: an outer sublayer, a middle sublayer, and an inner sublayer. The outer sublayer is connected to the cathode gas diffusion layer, the inner sublayer is connected to the proton exchange membrane, and the middle sublayer is located between the outer and inner sublayers. The contact angle of the three sublayers decreases sequentially from the outer to the inner sublayer. The amount of non-precious metal catalyst added to each of the three sublayers is equal, and the change in contact angle is adjusted by adding different masses of ionomer. By mass ratio, the mass ratio of ionomer to non-precious metal catalyst in the middle sublayer is 0.8, and the amount of ionomer added decreases sequentially from the inner to the outer sublayer, with the mass ratio between two adjacent sublayers decreasing by 0.02 to 0.

6.

2. The variable contact angle non-noble metal-based film electrode according to claim 1, characterized in that, The non-precious metal element in the non-precious metal catalyst is any one or any combination of Fe, Co, Ni, Mn, Cu, and Zn.

3. The variable contact angle non-noble metal-based film electrode according to claim 1, characterized in that, The ionomer is a proton exchange resin, including any one or any combination of long-chain perfluorosulfonic acid, short-chain perfluorosulfonic acid, or a mixture of long and short-chain perfluorosulfonic acid.

4. The method for preparing a variable contact angle non-noble metal-based film electrode as described in any one of claims 1-3, characterized in that, The process includes the following steps: Preparing the cathode catalyst layer: a non-precious metal catalyst, ionomer, deionized water, and organic solvent are mixed and dispersed in an ultrasonic water bath to obtain a catalyst slurry with three sublayers. The amount of ionomer added decreases sequentially from the inner sublayer to the outer sublayer of the cathode catalyst layer, and the mass ratio between two adjacent sublayers decreases by 0.02~0.

6. Preparing the anode catalyst layer: a precious metal catalyst, ionomer, deionized water, and organic solvent are mixed and dispersed in an ultrasonic water bath to obtain a catalyst slurry. Preparing the electrodes: a cathode gas diffusion electrode and an anode gas diffusion electrode are prepared using the GDE method. Preparing the membrane electrode: the cathode gas diffusion electrode, proton exchange membrane, and anode gas diffusion electrode are combined by hot pressing to form a variable contact angle non-precious metal-based membrane electrode.

5. The preparation method according to claim 4, characterized in that, When preparing the cathode gas diffusion electrode, the catalyst slurry of the outer sublayer of the cathode catalyst layer is ultrasonically sprayed onto the micropore side of the gas diffusion layer, then the catalyst slurry of the middle sublayer of the cathode catalyst layer is ultrasonically sprayed onto the outer sublayer of the cathode catalyst layer, and finally the catalyst slurry of the inner sublayer of the cathode catalyst layer is ultrasonically sprayed onto the middle sublayer of the cathode catalyst layer; when preparing the anode gas diffusion electrode, the anode catalyst slurry is ultrasonically sprayed onto the micropore side of the gas diffusion layer to form the anode catalyst layer.

6. The preparation method according to claim 4, characterized in that, The catalyst loading in the three sublayers of the cathode catalyst layer is equal, with the total non-precious metal catalyst loading being 0.5~5 mg cm⁻¹. -2 The loading of the noble metal catalyst in the anode catalyst layer is 0.05~0.4 mg. Pt cm -2 .

7. A variable contact angle non-noble metal-based film electrode obtained by any of the preparation methods described in claims 4-6.

8. The application of the variable contact angle non-noble metal-based membrane electrode as described in any one of claims 1-3 and 7 in the preparation of fuel cells.

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