Membrane Electrode and Fuel Cell

Abstract

A membrane electrode and a fuel cell, belonging to the field of fuel cells. The membrane electrode for a fuel cell includes a cathode diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode diffusion layer stacked in sequence. The membrane electrode has a first region and a second region arranged in sequence along the hydrogen flow direction. The contact angle of the cathode catalyst layer in the second region is greater than its contact angle in the first region; the contact angle of the cathode catalyst layer in the second region is greater than the contact angle of the cathode diffusion layer, and the contact angle of the cathode catalyst layer in the first region is less than the contact angle of the cathode diffusion layer. Through the above arrangement, not only can the water drainage of the cathode catalyst layer in the second region be improved, the diffusion of cathode water in the second region to the anode catalyst layer be reduced, and the anode catalyst layer located in the second region be prevented from being flooded, but also the water retention of the cathode catalyst layer in the first region can be increased, realizing the uniformity of the water distribution in the entire cathode catalyst layer and anode catalyst layer.

Description

Technical Field

[0001] This application relates to the field of fuel cells, and more particularly, to a membrane electrode and a fuel cell. Background Art

[0002] A polymer electrolyte membrane fuel cell (PEMFC) generally consists of a proton exchange membrane sandwiched between two catalyst layers, two porous gas diffusion layers, and two bipolar plates with flow channels. Protons and electrons generated by the hydrogen oxidation reaction in the anode catalyst layer flow through the proton exchange membrane and the external circuit respectively, and participate in the oxygen reduction reaction in the cathode catalyst layer, generating water and waste heat.

[0003] Although considerable progress has been made in overall cell performance, key performance and durability limitations focus on the water management of PEMFCs, namely the transport of product water (liquid and vapor) and the resulting drying and / or flooding of the component parts. Too little water can cause the membrane electrode to dry out, which increases ionic resistance and exacerbates the voltage drop due to ohmic losses. Too much water can cause flooding overflow, clogging the pores of the catalyst layer and gas diffusion layer, thus reducing the transport rate of reaction gases to the catalyst sites. Inappropriate humidity conditions not only reduce the performance and efficiency of fuel cells, but may even lead to irreversible degradation of internal components such as catalysts or membranes. For example, under drier conditions, the proton membrane is more vulnerable to attack by free radicals, resulting in damage due to chemical corrosion. Under wetter conditions, the Pt catalyst is prone to problems such as migration and loss, and issues such as Pt band are likely to occur. At the same time, the over-wet state is also likely to cause problems such as local under-gassing and reversal at the anode, seriously affecting the long-term durability of the stack. Therefore, water management is a key issue for proton exchange membrane fuel cells. Summary of the Invention

[0004] This application provides a membrane electrode and a fuel cell, which can alleviate the problem of overall or local under-gassing, and improve the sensitivity, lifespan and safety of fuel cells under different humidities.

[0005] The embodiments of this application are implemented as follows:

[0006] In a first aspect, an embodiment of this application provides a membrane electrode for a fuel cell. The fuel cell has a hydrogen outlet and a hydrogen inlet. The membrane electrode includes a cathode diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode diffusion layer stacked in sequence. The membrane electrode has a first region and a second region arranged in sequence along the hydrogen flow direction. The first region corresponds to the hydrogen inlet, and the second region corresponds to the hydrogen outlet;

[0007] The contact angle of the cathode catalyst layer in the second region is greater than its contact angle in the first region;

[0008] The contact angle of the cathode catalyst layer in the second region is greater than that of the cathode diffusion layer, and the contact angle of the cathode catalyst layer in the first region is less than that of the cathode diffusion layer.

[0009] For the membrane electrode provided in this application, since the contact angle of the cathode catalyst layer in the second region is greater than that in the first region, it is beneficial for water to transfer from the second region to the first region of the cathode catalyst. At this time, by controlling the contact angle of the cathode catalyst layer in the second region to be greater than that of the cathode diffusion layer, the drainage of the cathode catalyst layer in the second region can be improved, the diffusion of cathode water in the second region to the anode catalyst layer can be reduced, and the anode catalyst layer located in the second region can be prevented from being flooded. At the same time, by controlling the contact angle of the cathode catalyst layer in the first region to be less than that of the cathode diffusion layer, the water retention capacity of the cathode catalyst layer in the first region can be increased. Thus, through the combined effect, the uniformity of the water distribution in the entire cathode catalyst layer and anode catalyst layer can be achieved, the sensitivity of the fuel cell to different humidities can be improved, the overall or local under-aeration problem caused by flooding can be alleviated, and the life and safety of the fuel cell can be enhanced.

[0010] In some alternative embodiments, taking the area of the cathode catalyst layer as the area of the catalytic active region of the membrane electrode, the area ratio of the first region in the catalytic active region area is 40%-60%, and the area ratio of the second region in the catalytic active region area is 40%-60%.

[0011] In some alternative embodiments, the contact angle of the anode catalyst layer in the second region is greater than that of the anode diffusion layer, and the contact angle of the anode catalyst layer in the first region is less than that of the anode diffusion layer.

[0012] In some alternative embodiments, the difference between the contact angle of the cathode catalyst layer in the second region and the contact angle of the cathode diffusion layer is 5°-10°.

[0013] In some alternative embodiments, the difference between the contact angle of the cathode catalyst layer in the first region and the contact angle of the cathode diffusion layer is 5°-10°.

[0014] In some alternative embodiments, the contact angle of the cathode catalyst layer in the second region is less than the contact angle of the anode catalyst layer in the second region.

[0015] In some alternative embodiments, the contact angle of the cathode catalyst layer in the first region is greater than the contact angle of the anode catalyst layer in the first region.

[0016] In some alternative embodiments, the contact angle of the cathode catalyst layer in the second region is 140°-150°, and the contact angle of the cathode catalyst layer in the first region is 120°-130°.

[0017] In some optional embodiments, the contact angle of the anode catalyst layer in the second region is 140°-150°, and the contact angle of the anode catalyst layer in the first region is 120°-130°.

[0018] In some optional embodiments, the contact angles of the cathode diffusion layer and / or the anode diffusion layer are 130°-140° respectively;

[0019] Optionally, the cathode diffusion layer and the anode diffusion layer are carbon paper layers respectively.

[0020] In a second aspect, the present application provides a fuel cell, which includes at least one membrane electrode provided in the first aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 Schematic diagram of the structure of the membrane electrode provided in Embodiment 1 of the present application;

[0023] Figure 2 SEM images of the cathode catalyst layer at the hydrogen outlet position and the proton exchange membrane near the cathode after long-term operation of the membrane electrode provided in Embodiment 1 of the present application;

[0024] Figure 3 SEM images of the cathode catalyst layer at the hydrogen outlet position and the proton exchange membrane near the cathode after long-term operation of the membrane electrode provided in Comparative Example 1 of the present application.

[0025] Reference numerals: 10 - membrane electrode; 11 - hydrogen inlet; 12 - hydrogen outlet; 13 - oxygen inlet; 14 - oxygen outlet; 15 - first region; 16 - second region. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following will describe the implementation solutions of the present application in detail with reference to the embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0027] Overall or partial hydrogen deficiency has always been a problem challenging fuel cell design and component response under variable load conditions in vehicles, especially the problem of local hydrogen deficiency at the anode. Along with the reverse current mechanism, local hydrogen deficiency at the anode can form a high cathode potential, and then the carbon carrier corrodes. Under the common hydrogen-air countercurrent intake structure, anode water management has attracted much attention. As the electrochemical reaction proceeds, the hydrogen partial pressure gradually decreases from the inlet to the outlet of the anode active area, and the water vapor partial pressure increases. The risk of "flooding" in the outlet area is relatively high, and local hydrogen deficiency may occur at any time. At the cathode inlet, due to the lower temperature, the membrane is prone to drying, resulting in too large a humidity difference between the inlet and outlet of the membrane electrode.

[0028] In view of this, the present application is hereby proposed.

[0029] The following specifically describes the membrane electrode and fuel cell of the embodiments of the present application:

[0030] In a first aspect, the present application provides a membrane electrode for a fuel cell. The fuel cell has a hydrogen outlet and a hydrogen inlet. The membrane electrode includes a cathode diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode diffusion layer stacked in sequence. The membrane electrode has a first region and a second region arranged in sequence along the hydrogen flow direction. The first region corresponds to the hydrogen inlet, and the second region corresponds to the hydrogen outlet;

[0031] The contact angle of the cathode catalyst layer in the second region is greater than its contact angle in the first region;

[0032] The contact angle of the cathode catalyst layer in the second region is greater than the contact angle of the cathode diffusion layer, and the contact angle of the cathode catalyst layer in the first region is less than the contact angle of the cathode diffusion layer.

[0033] Wherein, the cathode catalyst layer contains a cathode catalyst, and the anode catalyst layer contains an anode catalyst.

[0034] The contact angle of the cathode catalyst layer refers to the contact angle of the surface of the catalyst layer facing the corresponding cathode diffusion layer. The contact angle of the cathode diffusion layer refers to the contact angle of the surface of the diffusion layer facing the cathode catalyst layer.

[0035] The test method for the contact angle of the cathode / anode catalyst layer is: placing the cathode / anode catalyst layer on the platform of a contact angle measuring instrument to perform contact angle tests in the first region and the second region.

[0036] The test method for the contact angle of the cathode / anode diffusion layer is: placing the cathode / anode diffusion layer on the platform of a contact angle measuring instrument to perform contact angle tests.

[0037] It can be understood that the larger the contact angle, the higher the hydrophobicity, and water is likely to transfer from the side with high hydrophobicity to the side with low hydrophobicity. The contact angle of the cathode catalyst layer in the second region is greater than its contact angle in the first region, that is, the hydrophobicity of the cathode catalyst layer in the second region is greater than its hydrophobicity in the first region, which is conducive to the transfer of moisture in the second region of the cathode catalyst to the first region, that is, it is conducive to the transfer of moisture on the side of the cathode catalyst corresponding to the hydrogen outlet to the side corresponding to the hydrogen inlet.

[0038] For the membrane electrode provided in this application, since the contact angle of the cathode catalyst layer in the second region is greater than its contact angle in the first region, it is conducive to the transfer of moisture in the second region of the cathode catalyst to the first region. At this time, by controlling the contact angle of the cathode catalyst layer in the second region to be greater than the contact angle of the cathode diffusion layer, the drainage of the cathode catalyst layer in the second region can be improved, the diffusion of cathode water in the second region to the anode catalyst layer can be reduced, and the anode catalyst layer located in the second region can be prevented from being flooded. At the same time, by controlling the contact angle of the cathode catalyst layer in the first region to be less than the contact angle of the cathode diffusion layer, the water retention capacity of the cathode catalyst layer in the first region can be increased. Thus, through the combined action, the uniformity of the water distribution in the entire cathode catalyst layer and anode catalyst layer can be achieved, the sensitivity of the fuel cell to different humidities can be improved, the overall or local gas shortage problem caused by flooding can be alleviated, and the service life and safety of the fuel cell can be enhanced.

[0039] In some optional embodiments, taking the area of the cathode catalyst layer as the area of the catalytic active region of the membrane electrode, the area ratio of the first region in the catalytic active region area is 40%-60%, and the area ratio of the second region in the catalytic active region area is 40%-60%.

[0040] That is, the area of the first region accounts for 40%-60% of the area of the catalytic active region of the entire membrane electrode (calculated based on the area of the cathode catalyst layer). The area of the second region accounts for 40%-60% of the area of the catalytic active region of the entire membrane electrode (calculated based on the area of the cathode catalyst layer).

[0041] Exemplarily, the area of the first region or the second region accounts for any value of 40%, 45%, 50%, 55%, and 60% or any value between any two values of the area of the catalytic active region of the entire membrane electrode (calculated based on the area of the cathode catalyst layer).

[0042] In some optional embodiments, the contact angle of the anode catalyst layer in the second region is greater than the contact angle of the anode diffusion layer, and the contact angle of the anode catalyst layer in the first region is less than the contact angle of the anode diffusion layer.

[0043] The contact angle of the anode catalyst layer refers to the contact angle of the surface of the catalyst layer facing the corresponding anode diffusion layer. The contact angle of the anode diffusion layer refers to the contact angle of the surface of the diffusion layer facing the anode catalyst layer.

[0044] By making the contact angle of the anode catalyst layer in the second region greater than that of the anode diffusion layer, the diffusion of water from the anode catalyst layer in the second region to the anode diffusion layer is promoted, which is beneficial to improving the drainage of the anode catalyst layer in the second region and avoiding flooding of the anode catalyst layer in the second region. By making the contact angle of the anode catalyst layer in the first region less than that of the anode diffusion layer, it is beneficial to improve the water retention of the anode catalyst layer in the first region and to achieve uniformity in the water distribution of the entire anode catalyst layer.

[0045] In some alternative embodiments, the difference between the contact angle of the cathode catalyst layer in the second region and the contact angle of the cathode diffusion layer is 5° - 10°.

[0046] It can be understood that the contact angle of the cathode catalyst layer in the second region is greater than that of the cathode diffusion layer. That is, the difference in contact angle here refers to the contact angle of the cathode catalyst layer in the second region minus the contact angle of the cathode diffusion layer.

[0047] Controlling the difference in their contact angles within the above range is beneficial to improving the drainage of the cathode catalyst layer in the second region, reducing the diffusion of cathode water in the second region to the anode catalyst layer, and avoiding flooding of the anode catalyst layer in the second region.

[0048] Exemplarily, the difference between the contact angle of the cathode catalyst layer in the second region and the contact angle of the cathode diffusion layer is any value among 5°, 6°, 7°, 8°, 9°, 10° or between any two of them.

[0049] In some alternative embodiments, the difference between the contact angle of the cathode catalyst layer in the first region and the contact angle of the cathode diffusion layer is 5° - 10°.

[0050] It can be understood that the contact angle of the cathode catalyst layer in the first region is less than that of the cathode diffusion layer. That is, the difference in contact angle here refers to the contact angle of the cathode diffusion layer minus the contact angle of the cathode catalyst layer in the second region.

[0051] Controlling the difference in their contact angles within the above range is beneficial to increasing the water retention of the cathode catalyst layer in the first region.

[0052] Exemplarily, the difference between the contact angle of the cathode catalyst layer in the first region and the contact angle of the cathode diffusion layer is any value among 5°, 6°, 7°, 8°, 9°, 10° or between any two of them.

[0053] In some alternative embodiments, the contact angle of the cathode catalyst layer in the second region is less than the contact angle of the anode catalyst layer in the second region.

[0054] Through the above settings, it is beneficial for the water in the anode catalyst layer to transfer from the second region to the second region of the cathode catalyst layer, which is beneficial to jointly act with the above-mentioned cathode catalyst layer and cathode diffusion layer to achieve the uniformity of the water distribution in the entire cathode catalyst layer and anode catalyst layer.

[0055] In some alternative embodiments, the contact angle of the cathode catalyst layer in the first region is greater than that of the anode catalyst layer in the first region.

[0056] Through the above settings, it is beneficial to achieve the uniformity of the water distribution in the entire cathode catalyst layer and anode catalyst layer.

[0057] In some alternative embodiments, the contact angle of the cathode catalyst layer in the second region is 140° - 150°, and the contact angle of the cathode catalyst layer in the first region is 120° - 130°.

[0058] Exemplarily, the contact angle of the cathode catalyst layer in the second region is any value among 140°, 142°, 145°, 147°, 150° or between any two values.

[0059] Exemplarily, the contact angle of the cathode catalyst layer in the first region is any value among 120°, 121°, 123°, 125°, 127°, 130° or between any two values.

[0060] In some alternative embodiments, the contact angle of the anode catalyst layer in the second region is 140° - 150°, and the contact angle of the anode catalyst layer in the first region is 120° - 130°.

[0061] Exemplarily, the contact angle of the anode catalyst layer in the second region is any value among 140°, 142°, 145°, 147°, 150° or between any two values.

[0062] Exemplarily, the contact angle of the anode catalyst layer in the first region is any value among 120°, 121°, 123°, 125°, 127°, 130° or between any two values.

[0063] In some alternative embodiments, the contact angles of the cathode diffusion layer and / or the anode diffusion layer are 130° - 140° respectively.

[0064] Exemplarily, the contact angles of the cathode diffusion layer and / or the anode diffusion layer are any value among 130°, 132°, 135°, 137°, 140° or between any two values respectively.

[0065] Controlling the contact angles of the above-mentioned cathode catalyst layer, anode catalyst layer, and cathode diffusion layer and / or anode diffusion layer within the above ranges is beneficial for the combined effect, achieving the uniformity of water distribution in the entire cathode catalyst layer and anode catalyst layer, and improving the sensitivity, safety, and lifespan of the fuel cell under different humidities.

[0066] Optionally, the cathode diffusion layer and the anode diffusion layer are each a carbon paper layer.

[0067] It should be noted that the first region and the second region of each of the above-mentioned cathode / anode catalyst layers can be subjected to hydrophilic treatment and hydrophobic treatment according to actual contact angle requirements. Among them, the hydrophilic treatment includes, but is not limited to, adding, for example, water-retaining components in the cathode / anode catalyst layer of the corresponding region, or directly using hydrophilic catalysts, hydrophilic ion conductors, etc. The water-retaining components include, but are not limited to, at least one of SiO2, TiO2, or polyvinyl alcohol; the hydrophobic treatment includes, but is not limited to, adding hydrophobic components, using hydrophobic catalysts, hydrophobic ion conductors, etc.

[0068] Among them, the cathode / anode diffusion layer can also be selected according to the actual contact angle or adjusted for hydrophilicity and hydrophobicity through PTFE or the like.

[0069] The second aspect of the present application provides a fuel cell, which includes at least one membrane electrode provided in the first aspect of the present application.

[0070] The membrane electrode and fuel cell of the present application will be further described in detail below in conjunction with embodiments.

[0071] Embodiment 1

[0072] Please refer to Figure 1 , the fuel cell has a hydrogen outlet 11, a hydrogen inlet 12, an oxygen outlet 13, and an oxygen inlet 14. Among them, the hydrogen outlet 11 and the hydrogen inlet 12 are arranged diagonally along the membrane electrode, and the oxygen outlet 13 and the oxygen inlet 14 are arranged diagonally along the membrane electrode.

[0073] The membrane electrode includes, in the thickness direction, a cathode diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode diffusion layer stacked in sequence. The membrane electrode has a first region 15 and a second region 16 arranged in sequence along the hydrogen flow direction. Among them, the first region 15 corresponds to the hydrogen inlet 11, and the second region 16 corresponds to the hydrogen outlet 12. Among them, the first region 15 and the second region 16 are arranged diagonally along the membrane electrode as Figure 1 shown.

[0074] 1. Preparation of catalyst coated membrane (CCM):

[0075] First Region Cathode Catalyst Layer: Weigh 1.5 g of 60 wt% Pt / C cathode catalyst, 3 g of Nafion D2020 ionomer solution, and 0.1 g of PVA hydrophilic component. Add 20 g of water and 60 g of ethanol and mix them for dispersion to obtain the first region cathode catalyst layer slurry. Spray this slurry on one side of the proton exchange membrane and dry it to form the first region cathode catalyst layer, making the first region cathode catalyst layer account for one - half of the entire cathode catalyst layer area. The contact angle of the first region cathode catalyst layer is measured to be 120°.

[0076] First Region Anode Catalyst Layer: Weigh 1.5 g of 60 wt% Pt / C anode catalyst, 3 g of Nafion D2020 ionomer solution, and 0.1 g of PVA hydrophilic component. Add 20 g of water and 60 g of ethanol and mix them for dispersion to obtain the first region anode catalyst layer slurry. Spray this slurry on the other side of the proton exchange membrane and dry it to form the first region anode catalyst layer, making the first region anode catalyst layer account for one - half of the entire anode catalyst layer area. The contact angle of the first region anode catalyst layer is measured to be 120°.

[0077] Second Region Cathode Catalyst Layer: Weigh 1.5 g of 60 wt% Pt / C cathode catalyst, 3 g of Nafion D2020 ionomer solution, and 0.1 g of PTFE hydrophobic component. Add 20 g of water and 60 g of ethanol and mix them for dispersion to obtain the second region cathode catalyst layer slurry. Spray this slurry on one side of the proton exchange membrane and dry it to form the second region cathode catalyst layer, making the second region cathode catalyst layer account for one - half of the entire cathode catalyst layer area. The contact angle of the second region cathode catalyst layer is measured to be 140°.

[0078] Second Region Anode Catalyst Layer: Weigh 1.5 g of 60 wt% Pt / C anode catalyst, 3 g of Nafion D2020 ionomer solution, and 0.1 g of PTFE hydrophobic component. Add 20 g of water and 60 g of ethanol and mix them for dispersion to obtain the second region anode catalyst layer slurry. Spray this slurry on the other side of the proton exchange membrane and dry it to form the second region anode catalyst layer, making the second region anode catalyst layer account for one - half of the entire anode catalyst layer area. The contact angle of the second region anode catalyst layer is measured to be 140°.

[0079] 2. Preparation of Membrane - Electrode Assembly (MEA):

[0080] Select anodic carbon paper and cathodic carbon paper with a contact angle of 130° each, and use a frame to encapsulate the anodic carbon paper, CCM, and cathodic carbon paper to form an MEA.

[0081] Comparative Example 1

[0082] 1. Preparation of Catalyst Coated Membrane (CCM):

[0083] Cathode catalyst layer: Weigh 1.5 g of 60 wt% Pt / C cathode catalyst and 3 g of Nafion D2020 ionomer solution, add 20 g of water and 60 g of ethanol, and mix and disperse them to obtain the cathode catalyst layer slurry. Spray the slurry on one side of the proton exchange membrane, and after drying, form the cathode catalyst layer. The measured contact angle is 130°.

[0084] Anode catalyst layer: Weigh 1.5 g of 60 wt% Pt / C anode catalyst and 3 g of Nafion D2020 ionomer solution, add 20 g of water and 60 g of ethanol, and mix and disperse them to obtain the anode catalyst layer slurry. Spray the slurry on the other side of the proton exchange membrane, and after drying, form the anode catalyst layer. The measured contact angle is 130°.

[0085] 2. Preparation of membrane electrode assembly (MEA):

[0086] Select the anode carbon paper and cathode carbon paper with a contact angle of 130°, and use a frame to encapsulate the anode carbon paper, CCM, and cathode carbon paper to form the MEA.

[0087] Comparative Example 2

[0088] 1. Preparation of catalyst coated membrane (CCM):

[0089] Cathode catalyst layer: Weigh 1.5 g of 60 wt% Pt / C cathode catalyst, 3 g of Nafion D2020 ionomer solution and 0.1 g of PVA hydrophilic component, add 20 g of water and 60 g of ethanol, and mix and disperse them to obtain the cathode catalyst layer slurry. Spray the slurry on one side of the proton exchange membrane, and after drying, form the cathode catalyst layer. The measured contact angle is 120°.

[0090] Anode catalyst layer: Weigh 1.5 g of 60 wt% Pt / C anode catalyst, 3 g of Nafion D2020 ionomer solution and 0.1 g of PVA hydrophilic component, add 20 g of water and 60 g of ethanol, and mix and disperse them to obtain the anode catalyst layer slurry. Spray the slurry on the other side of the proton exchange membrane, and after drying, form the anode catalyst layer. The measured contact angle is 120°.

[0091] 2. Preparation of membrane electrode assembly (MEA):

[0092] Select the anode carbon paper and cathode carbon paper with a contact angle of 130°, and use a frame to encapsulate the anode carbon paper, CCM, and cathode carbon paper to form the MEA.

[0093] Comparative Example 3

[0094] 1. Preparation of catalyst coated membrane (CCM):

[0095] Cathode catalyst layer: Weigh 1.5 g of 60 wt% Pt / C cathode catalyst, 3 g of Nafion D2020 ionomer solution and 0.1 g of PTFE hydrophobic component, add 20 g of water and 60 g of ethanol, mix and disperse to obtain the cathode catalyst layer slurry. Spray the slurry on one side of the proton exchange membrane, and after drying, form the cathode catalyst layer. The measured contact angle is 140°.

[0096] Anode catalyst layer: Weigh 1.5 g of 60 wt% Pt / C anode catalyst, 3 g of Nafion D2020 ionomer solution and 0.1 g of PTFE hydrophobic component, add 20 g of water and 60 g of ethanol, mix and disperse to obtain the anode catalyst layer slurry. Spray the slurry on the other side of the proton exchange membrane, and after drying, form the anode catalyst layer. The measured contact angle is 140°.

[0097] 2. Preparation of membrane electrode assembly (MEA):

[0098] Select anode carbon paper and cathode carbon paper with a contact angle of 130°, and use a frame to encapsulate the anode carbon paper, CCM and cathode carbon paper to form MEA.

[0099] Test Example 1

[0100] Measure the voltage values of the MEAs of Example 1 and Comparative Examples 1 - 3 at different humidities respectively. The measurement methods include:

[0101] Polarization curve test: Set the fuel cell test temperature to 85 °C, pass hydrogen through the anode and air through the cathode, with the anode - cathode gas stoichiometric ratio of 1.5:2. Set the anode humidity and cathode humidity according to requirements, and record the voltage values with the change of current. The results are shown in Table 1.

[0102] Table 1 Test Results

[0103]

[0104]

[0105] As can be seen from Table 1, the overall performance of the MEA of Example 1 is improved compared with that of Comparative Examples 1 - 3, and at the same time, the sensitivity in the dry state and wet state is improved.

[0106] Test the changes in the catalyst layer after long - term operation of the membrane electrode assemblies provided in Example 1 and Comparative Example 1. According to Figure 2 It can be seen that after long - term operation of Example 1, the change in the thickness of the overall catalyst layer is small, and the influence of the "Pt band" formed by Pt particles in the proton exchange membrane is small; according to Figure 3 It can be seen that after long - term operation of Comparative Example 1, the thickness of the cathode catalyst layer significantly thins, indicating that the carbon corrosion of the cathode is relatively serious. At the same time, the "Pt band" phenomenon is very obvious, indicating that the Pt loss phenomenon is very serious.

[0107] By comparison, it is shown that the MEA provided by this application can effectively improve the service life and safety of fuel cells.

[0108] The above are only specific embodiments of this application and are not intended to limit this application. For those skilled in the art, various changes and modifications can be made to this application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A membrane electrode for a fuel cell, the fuel cell having a hydrogen outlet and a hydrogen inlet, the membrane electrode comprising a cathode diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode diffusion layer stacked in sequence, characterized in that, The membrane electrode has a first region and a second region arranged in sequence along the hydrogen flow direction, the first region corresponding to the hydrogen inlet and the second region corresponding to the hydrogen outlet; The contact angle of the cathode catalyst layer in the second region is greater than its contact angle in the first region; The contact angle of the cathode catalyst layer in the second region is greater than the contact angle of the cathode diffusion layer, and the contact angle of the cathode catalyst layer in the first region is less than the contact angle of the cathode diffusion layer; The contact angle of the anode catalyst layer in the second region is greater than the contact angle of the anode diffusion layer, and the contact angle of the anode catalyst layer in the first region is less than the contact angle of the anode diffusion layer; The contact angle of the cathode catalyst layer in the second region is 140°-150°, and the contact angle of the cathode catalyst layer in the first region is 120°-130°; The difference between the contact angle of the cathode catalyst layer in the second region and the contact angle of the cathode diffusion layer is 5°-10°; and / or, the difference between the contact angle of the cathode catalyst layer in the first region and the contact angle of the cathode diffusion layer is 5°-10°.

2. The membrane electrode according to claim 1, wherein Taking the area of the cathode catalyst layer as the area of the catalytic active region of the membrane electrode, the area ratio of the first region in the area of the catalytic active region is 40%-60%, and the area ratio of the second region in the area of the catalytic active region is 40%-60%.

3. The membrane electrode according to any one of claims 1-2, characterized in that, The contact angle of the cathode catalyst layer in the second region is less than the contact angle of the anode catalyst layer in the second region.

4. The membrane electrode according to any one of claims 1-2, wherein The contact angle of the cathode catalyst layer in the first region is greater than the contact angle of the anode catalyst layer in the first region.

5. The membrane electrode according to any one of claims 1-2, characterized in that, The contact angle of the anode catalyst layer in the second region is 140°-150°, and the contact angle of the anode catalyst layer in the first region is 120°-130°.

6. The membrane electrode according to any one of claims 1-2, characterized in that, The contact angles of the cathode diffusion layer and / or the anode diffusion layer are 130°-140° respectively.

7. The membrane electrode according to any one of claims 1-2, characterized in that, The cathode diffusion layer and the anode diffusion layer are carbon paper layers respectively.

8. A fuel cell, characterized in that, The fuel cell includes at least one membrane electrode as described in any one of claims 1-7.

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