Multilayer gradient structure membrane electrode, preparation method of membrane electrode catalytic layer and application

Abstract

The application relates to the technical field of fuel cells, in particular to a multilayer gradient structure membrane electrode, a preparation method and application of a membrane electrode catalyst layer. The membrane electrode comprises a proton exchange membrane, a cathode catalyst layer, an anode catalyst layer and a gas diffusion layer; the cathode catalyst layer and / or the anode catalyst layer are in a multilayer structure, comprising an inner catalyst layer in contact with the proton exchange membrane and an outer catalyst layer in contact with the gas diffusion layer; the mass ratio I / C of ionomer in the inner catalyst layer to the carbon carrier in the catalyst is higher than that of the outer catalyst layer. The high ionomer content in the inner layer of the membrane electrode ensures efficient proton transmission, and the low ionomer content in the outer layer ensures efficient gas / product mass transfer, fundamentally solving the trade-off problem between conduction and mass transfer in the uniform catalyst layer. In addition, the preparation method of the membrane electrode catalyst layer adopts a transfer printing method, a direct spraying method or a GDL method, the process is controllable and has good repeatability, and is suitable for large-scale production. Finally, the application of the membrane electrode in a hydrogen-oxygen / hydrogen-air fuel cell is clarified.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, specifically to a method for the structural design and fabrication of a membrane electrode assembly (MEA), particularly a method for fabricating a multilayer gradient structure MEA, a method for fabricating the MEA catalyst layer, and its application. Background Technology

[0002] The membrane electrode assembly (MEA) is a core component of a fuel cell device, and its performance directly determines the energy conversion efficiency. A traditional MEA typically consists of a proton exchange membrane, a cathode catalyst layer, an anode catalyst layer, and a gas diffusion layer. Among these, the structure and composition of the catalyst layer are crucial for proton conduction and electron transfer in the fuel cell reaction.

[0003] Commercial catalysts, such as the TANAKA KIKINZOKU KOGYO (TKK) TEC series (e.g., TKK 60 series platinum-carbon catalysts), are widely used due to their high activity and stability. In the catalyst slurry, the platinum-carbon catalyst and ionomers form appropriately sized agglomerates. The ionomers are distributed on the surface of the agglomerates or interspersed within them, thus stabilizing the agglomerate structure. In the catalyst layer, the role of ionomers (such as Nafion) is to bind catalyst particles, provide proton conduction channels, and form a three-phase reaction interface. The content of ionomers significantly affects the performance of the catalyst layer. 1. Low ionomer content: Insufficient proton conduction channels, low catalyst utilization, leading to increased activation polarization.

[0004] 2. Excessive ionomer content: It will block the pores of the catalyst layer, hinder the transport of reactant gases (such as H2, O2) or products (such as O2, H2), cause concentration polarization, and may form an excessively thick catalyst layer, increasing mass transfer resistance.

[0005] Currently, most studies use catalyst layers with a single ionomer content. This homogeneous structure makes it difficult to simultaneously optimize proton conduction and gas transport, especially at high current densities, where mass transfer limitation becomes a performance bottleneck.

[0006] Therefore, it is necessary to improve and optimize existing membrane electrodes and their preparation methods to better meet user needs. Summary of the Invention

[0007] The primary objective of this invention is to overcome the contradiction between mass transfer and gas transport in existing catalyst layers with a single ionomer content, and to provide a membrane electrode assembly (MEA) with significantly improved performance. Secondly, it provides a method for preparing the catalyst layer of this MEA, which is process-controllable, highly reproducible, and suitable for large-scale production. Finally, it clarifies the application of this MEA in hydrogen-oxygen / hydrogen-air fuel cells.

[0008] To achieve the aforementioned objectives, this invention first proposes a multilayer gradient structure membrane electrode, comprising a proton exchange membrane, a cathode catalyst layer, an anode catalyst layer, and a gas diffusion layer. The cathode catalyst layer and the anode catalyst layer comprise ionomers and catalysts. The cathode catalyst layer and / or the anode catalyst layer are multilayer structures, including an inner catalyst layer in contact with the proton exchange membrane and an outer catalyst layer in contact with the gas diffusion layer. The mass ratio (I / C) of the ionomer to the carbon support in the catalyst in the inner catalyst layer is higher than that in the outer catalyst layer.

[0009] More preferably, the mass ratio (I / C) of the ionomer in the inner catalyst layer to the carbon support in the catalyst is 0.8 to 1.2; and the mass ratio (I / C) of the ionomer in the outer catalyst layer to the carbon support in the catalyst is 0.4 to 0.6.

[0010] More preferably, the cathode catalyst layer and / or anode catalyst layer further includes an intermediate catalyst layer disposed between the outer catalyst layer and the inner catalyst layer, wherein the mass ratio (I / C) of the ionomer in the inner catalyst layer, the intermediate catalyst layer and the outer catalyst layer decreases sequentially.

[0011] More preferably, the mass ratio (I / C) of the ionomer in the intermediate catalyst layer to the carbon support in the catalyst is 0.6 to 0.8.

[0012] More preferably, the catalyst is a TKK 60 series platinum-carbon catalyst; and the ionomer is a perfluorosulfonic acid resin.

[0013] In addition, this invention also proposes a method for preparing a membrane electrode catalytic layer, comprising the following steps: Preparation of various catalyst layer slurries: Each slurry is obtained by uniformly mixing catalyst, ionomer, short-chain monool, and deionized water; and the mass ratio (I / C) of the ionomer to the carbon support in the catalyst decreases sequentially in these slurries. Layered coating: The prepared slurry is sequentially coated onto one side of the proton exchange membrane using a transfer printing method, direct spraying method, or GDL method. The coating order satisfies the following: the mass ratio (I / C) of the ionomer to the carbon support in the catalyst is highest in the slurry that is in close contact with the proton exchange membrane, and decreases as the coating order increases.

[0014] More preferably, the prepared catalyst layer slurry consists of two types, and the mass ratio (I / C) of the ionomer to the carbon support in the catalyst for these two types of slurries is 0.8 ~ 1.2 and 0.4 ~ 0.6, respectively.

[0015] More preferably, the number of catalyst layer slurries prepared is three, and the mass ratio (I / C) of the ionomer to the carbon support in the catalyst of these three slurries is 0.8 ~ 1.2, 0.6 ~ 0.8 and 0.4 ~ 0.6, respectively.

[0016] More preferably, in the above preparation method, the catalyst is a TKK 60 series platinum-carbon catalyst; the ionomer is a perfluorosulfonic acid resin; and the short-chain monool includes one or more of n-propanol, isopropanol, and ethanol.

[0017] In addition, this invention also proposes an application of a multilayer gradient structure membrane electrode as described above in a fuel cell.

[0018] It should be understood that the present invention aims to change the monolayer catalyst layer of the membrane electrode into a multilayer catalyst layer with an ionomer gradient distribution, without involving any adjustment to the catalyst. Therefore, the catalyst in the above-mentioned catalyst slurry or the catalyst layer of the membrane electrode is a conventional catalyst composition.

[0019] Therefore, both membrane electrode catalysts before and after the filing date of this invention can be used to obtain multilayer catalysts with ionomer gradient distributions through the process of this invention. The membrane electrodes obtained by these formulations through the preparation method of this invention, as well as the corresponding preparation methods, all fall within the protection scope of this invention.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects: Synergistic optimization: The high ionomer content in the inner layer ensures efficient proton transport, while the low ionomer content in the outer layer ensures efficient gas / product mass transfer, fundamentally solving the trade-off between conduction and mass transfer in a homogeneous catalyst layer.

[0021] Performance improvement: In fuel cell mode, especially in the high current density region, the voltage of this membrane electrode structure is significantly higher than that of traditional homogeneous membrane electrodes, and the power density is significantly improved.

[0022] Interface stability: The higher ionomer content in the inner layer helps to form a tighter interface with the proton exchange membrane, reducing contact resistance and improving mechanical stability.

[0023] Flexible methods: The preparation methods are highly selective, have good compatibility with existing MEA preparation processes, and are easy to realize technology transfer and large-scale production. Attached Figure Description

[0024] The above features and advantages of the present invention will become clearer and more readily understood from the following description of exemplary embodiments thereof in conjunction with the accompanying drawings.

[0025] Figure 1 This is a schematic diagram of a membrane electrode with a double-layer gradient structure provided in Embodiment 1 of the present invention.

[0026] Figure 2 This is a schematic diagram of a membrane electrode with a conventional single catalytic layer structure provided in Comparative Example 1 of the present invention.

[0027] Figure 3 These are polarization curves of the membrane electrodes of Examples 1-7 and Comparative Examples 1-2 in fuel cells. Detailed Implementation

[0028] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but this does not limit the present invention to the scope of the described embodiments. Process parameters not specified in the embodiments of this application can be performed according to conventional methods, and all raw materials used can be obtained through commercial channels.

[0030] Example 1: Fabrication and Testing of Bilayer Gradient MEA Fuel Cell Membrane Electrode Slurry preparation: Inner slurry: 200 mg of TKK TEC10V60E catalyst (containing 40% carbon and 60% platinum by mass) was mixed with 1.28 g of Nafion ionomer solution (5 wt%), 8.0 g of isopropanol, and 8.0 g of deionized water. In the above slurry, the mass ratio of ionomer to carbon support in the catalyst, I / C = (1.28 g Nafion solution mass × 5%) / (0.2 g TKKTEC10V60E catalyst mass × 40%) = 0.064 / 0.08 = 0.8. After ultrasonic dispersion for 30 minutes, the mixture was sheared at 5000 rpm for 0.5 hours.

[0031] Outer slurry: 200 mg of TKK TEC10V60E catalyst (40% carbon by mass) was mixed with 0.96 g of Nafion ionomer solution (5 wt%), 7.7 g of isopropanol, and 7.7 g of deionized water. I / C = (0.96 g × 5%) / (0.2 g × 40%) = 0.048 / 0.08 = 0.6. After ultrasonic dispersion for 30 minutes, the mixture was sheared at 5000 rpm for 0.5 hours.

[0032] MEA preparation (transfer method): The outer slurry was uniformly coated onto the PTFE release film using ultrasonic spraying, with the loading rate controlled at 0.15 mg Pt / cm³. 2 Dry at 80℃ until semi-dry. Spray the inner layer slurry onto the semi-dry inner layer, controlling the loading at 0.3 mg Pt / cm³.2 Then, it is completely dried at 80°C to form a cathode.

[0033] The outer slurry was uniformly coated onto the PTFE release film using ultrasonic spraying, with the loading rate controlled at 0.05 mg Pt / cm³. 2 Dry at 80℃ until semi-dry. Spray the inner layer slurry onto the semi-dry inner layer, controlling the loading at 0.1 mg Pt / cm³. 2 Then, it is completely dried at 80°C to form the anode.

[0034] The Nafion 211 proton exchange membrane was subjected to standard pretreatment (H2O2, sulfuric acid boiling).

[0035] Align the PTFE membrane with the bilayer catalyst layer with the treated proton exchange membrane and hot-press it at 135°C and 5 MPa for 90 seconds. After cooling, carefully peel off the PTFE membrane, and the catalyst layer is transferred onto the membrane.

[0036] Example 2: Fabrication and Testing of Bilayer Gradient MEA Fuel Cell Membrane Electrode Slurry preparation: Inner layer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix with 1.6 g of Nafion ionomer solution (5 wt%, equivalent to I / C = 1.0, the calculation method in Example 2 and subsequent examples and comparative examples is the same as in Example 1), 8.4 g of isopropanol, and 8.4 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0037] Outer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix it with 0.8 g of Nafion ionomer solution (5 wt%, equivalent to I / C=0.5), 7.5 g of isopropanol, and 7.5 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0038] MEA preparation (transfer method): The outer slurry was uniformly coated onto the PTFE release film using ultrasonic spraying, with the loading rate controlled at 0.15 mg Pt / cm³. 2 Dry at 80℃ until semi-dry. Spray the inner layer slurry onto the semi-dry inner layer, controlling the loading at 0.3 mg Pt / cm³. 2 Then, it is completely dried at 80°C to form a cathode.

[0039] The outer slurry was uniformly coated onto the PTFE release film using ultrasonic spraying, with the loading rate controlled at 0.05 mg Pt / cm³. 2Dry at 80℃ until semi-dry. Spray the inner layer slurry onto the semi-dry inner layer, controlling the loading at 0.1 mg Pt / cm³. 2 Then, it is completely dried at 80°C to form the anode.

[0040] The Nafion 211 proton exchange membrane was subjected to standard pretreatment (H2O2, sulfuric acid boiling).

[0041] Align the PTFE membrane with the bilayer catalyst layer with the treated proton exchange membrane and hot-press it at 135°C and 5 MPa for 90 seconds. After cooling, carefully peel off the PTFE membrane, and the catalyst layer is transferred onto the membrane.

[0042] Example 3: Fabrication and Testing of Bilayer Gradient MEA Fuel Cell Membrane Electrode Slurry preparation: Inner layer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix with 1.6 g of Nafion ionomer solution (5 wt%, equivalent to I / C=1.0), 8.4 g of isopropanol, and 8.4 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0043] Outer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix it with 0.8 g of Nafion ionomer solution (5 wt%, equivalent to I / C=0.5), 7.5 g of isopropanol, and 7.5 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0044] MEA preparation (direct spraying method): The Nafion 211 proton exchange membrane was subjected to standard pretreatment (H2O2, sulfuric acid boiling).

[0045] The inner layer slurry was uniformly coated onto the proton exchange membrane using ultrasonic spraying, with the loading rate controlled at 0.15 mg Pt / cm³. 2 Dry at 80℃ until semi-dry. Spray the outer layer slurry onto the semi-dry inner layer, controlling the loading at 0.3 mg Pt / cm³. 2 Then, it is completely dried at 80°C to form a cathode.

[0046] The inner layer slurry was uniformly coated onto the other side of the proton exchange membrane using ultrasonic spraying, with the loading rate controlled at 0.05 mg Pt / cm². 2 Dry at 80℃ until semi-dry. Spray the outer layer slurry onto the semi-dry inner layer, controlling the loading at 0.1 mg Pt / cm³. 2 Then, it is completely dried at 80°C to form the anode.

[0047] Example 4: Fabrication and Testing of Bilayer Gradient MEA Fuel Cell Membrane Electrode Slurry preparation: Inner layer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix with 1.92 g of Nafion ionomer solution (5 wt%, equivalent to I / C=1.2), 8.8 g of isopropanol, and 8.8 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0048] Outer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix it with 0.64 g of Nafion ionomer solution (5 wt%, equivalent to I / C=0.4), 7.3 g of isopropanol, and 7.3 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0049] MEA preparation (direct spraying method): The Nafion 211 proton exchange membrane was subjected to standard pretreatment (H2O2, sulfuric acid boiling).

[0050] The inner layer slurry was uniformly coated onto the proton exchange membrane using ultrasonic spraying, with the loading rate controlled at 0.15 mg Pt / cm³. 2 Dry at 80℃ until semi-dry. Spray the outer layer slurry onto the semi-dry inner layer, controlling the loading at 0.3 mg Pt / cm³. 2 Then, it is completely dried at 80°C to form a cathode.

[0051] The inner layer slurry was uniformly coated onto the other side of the proton exchange membrane using ultrasonic spraying, with the loading rate controlled at 0.05 mg Pt / cm². 2 Dry at 80℃ until semi-dry. Spray the outer layer slurry onto the semi-dry inner layer, controlling the loading at 0.1 mg Pt / cm³. 2 Then, it is completely dried at 80°C to form the anode.

[0052] Example 5: Fabrication and Testing of Three-Layer Gradient MEA Fuel Cell Membrane Electrode Slurry preparation: Inner layer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix with 1.6 g of Nafion ionomer solution (5 wt%, equivalent to I / C=1.0), 8.4 g of isopropanol, and 8.4 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0053] Intermediate layer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix with 1.12 g of Nafion ionomer solution (5 wt%, equivalent to I / C=0.7), 8.8 g of isopropanol, and 8.8 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0054] Outer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix it with 0.8 g of Nafion ionomer solution (5 wt%, equivalent to I / C=0.5), 7.5 g of isopropanol, and 7.5 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0055] MEA preparation (direct spraying method): The Nafion 211 proton exchange membrane was subjected to standard pretreatment (H2O2, sulfuric acid boiling).

[0056] The inner layer slurry was uniformly coated onto the proton exchange membrane using ultrasonic spraying, with the loading rate controlled at 0.1 mg Pt / cm³. 2 Dry at 80℃ until semi-dry. Spray the intermediate layer slurry onto the semi-dry inner layer, controlling the loading at 0.2 mg Pt / cm³. 2 The outer slurry was sprayed onto the semi-dry bilayer catalyst layer, with the loading controlled at 0.3 mg Pt / cm³. 2 Then, it is completely dried at 80°C to form a cathode.

[0057] The inner layer slurry was uniformly coated onto the other side of the proton exchange membrane using ultrasonic spraying, with the loading rate controlled at 0.03 mg Pt / cm². 2 Dry at 80℃ until semi-dry. Spray the intermediate layer slurry onto the semi-dry inner layer, controlling the loading at 0.07 mg Pt / cm³. 2 The outer slurry was sprayed onto the semi-dry bilayer catalyst layer, with the loading controlled at 0.1 mgPt / cm³. 2 Then, it is completely dried at 80°C to form the anode.

[0058] Example 6: Fabrication and Testing of Three-Layer Gradient MEA Fuel Cell Membrane Electrode Slurry preparation: Inner layer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix with 1.92 g of Nafion ionomer solution (5 wt%, equivalent to I / C=1.2), 8.8 g of isopropanol, and 8.8 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0059] Intermediate layer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix with 1.28 g of Nafion ionomer solution (5 wt%, equivalent to I / C=0.8), 8.0 g of isopropanol, and 8.0 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0060] Outer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix it with 0.64 g of Nafion ionomer solution (5 wt%, equivalent to I / C=0.4), 7.3 g of isopropanol, and 7.3 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0061] MEA preparation (direct spraying method): The Nafion 211 proton exchange membrane was subjected to standard pretreatment (H2O2, sulfuric acid boiling).

[0062] The inner layer slurry was uniformly coated onto the proton exchange membrane using ultrasonic spraying, with the loading rate controlled at 0.1 mg Pt / cm³. 2 Dry at 80℃ until semi-dry. Spray the intermediate layer slurry onto the semi-dry inner layer, controlling the loading at 0.2 mg Pt / cm³. 2 The outer slurry was sprayed onto the semi-dry bilayer catalyst layer, with the loading controlled at 0.3 mg Pt / cm³. 2 Then, it is completely dried at 80°C to form a cathode.

[0063] The inner layer slurry was uniformly coated onto the other side of the proton exchange membrane using ultrasonic spraying, with the loading rate controlled at 0.03 mg Pt / cm². 2 Dry at 80℃ until semi-dry. Spray the intermediate layer slurry onto the semi-dry inner layer, controlling the loading at 0.07 mg Pt / cm³. 2 The outer slurry was sprayed onto the semi-dry bilayer catalyst layer, with the loading controlled at 0.1 mgPt / cm³. 2 Then, it is completely dried at 80°C to form the anode.

[0064] Example 7: Fabrication and Testing of Three-Layer Gradient MEA Fuel Cell Membrane Electrode Slurry preparation: Inner layer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix with 1.92 g of Nafion ionomer solution (5 wt%, equivalent to I / C=1.2), 8.8 g of isopropanol, and 8.8 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0065] Intermediate layer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix with 0.96 g of Nafion ionomer solution (5 wt%, equivalent to I / C = 0.6), 7.7 g of isopropanol, and 7.7 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0066] Outer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix it with 0.64 g of Nafion ionomer solution (5 wt%, equivalent to I / C=0.4), 7.3 g of isopropanol, and 7.3 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0067] MEA preparation (direct spraying method): The Nafion 211 proton exchange membrane was subjected to standard pretreatment (H2O2, sulfuric acid boiling).

[0068] The inner layer slurry was uniformly coated onto the proton exchange membrane using ultrasonic spraying, with the loading rate controlled at 0.1 mg Pt / cm³. 2 Dry at 80℃ until semi-dry. Spray the intermediate layer slurry onto the semi-dry inner layer, controlling the loading at 0.2 mg Pt / cm³. 2 The outer slurry was sprayed onto the semi-dry bilayer catalyst layer, with the loading controlled at 0.3 mg Pt / cm³. 2 Then, it is completely dried at 80°C to form a cathode.

[0069] The inner layer slurry was uniformly coated onto the other side of the proton exchange membrane using ultrasonic spraying, with the loading rate controlled at 0.03 mg Pt / cm². 2 Dry at 80℃ until semi-dry. Spray the intermediate layer slurry onto the semi-dry inner layer, controlling the loading at 0.07 mg Pt / cm³. 2 The outer slurry was sprayed onto the semi-dry bilayer catalyst layer, with the loading controlled at 0.1 mgPt / cm³. 2 Then, it is completely dried at 80°C to form the anode.

[0070] Comparative Example 1: Fabrication and Testing of Membrane Electrode in a Single-Catalyst-Layer MEA Fuel Cell Prepare a single-layer catalytic MEA with the following structure: Figure 2 As shown. The I / C ratio is taken as the average of the I / C ratios of the inner and outer layers in Example 1, which is 0.7. Slurry preparation: Take 400 mg of TKK TEC10V60E catalyst and mix it with 2.24 g of Nafion ionomer solution (5 wt%, equivalent to I / C = 0.7), 15.7 g of isopropanol, and 15.7 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0071] MEA preparation (transfer method): The slurry was uniformly coated onto the PTFE release film using ultrasonic spraying, with the loading rate controlled at 0.3 mg Pt / cm². 2 The cathode is completely dried at 80°C.

[0072] The slurry was uniformly coated onto the PTFE release film using ultrasonic spraying, with the loading rate controlled at 0.1 mg Pt / cm². 2 It is completely dried at 80°C to form the anode.

[0073] The Nafion 211 proton exchange membrane was subjected to standard pretreatment (H2O2, sulfuric acid boiling).

[0074] Align the PTFE membrane with the bilayer catalyst layer with the treated proton exchange membrane and hot-press it at 135°C and 5 MPa for 90 seconds. After cooling, carefully peel off the PTFE membrane, and the catalyst layer is transferred onto the membrane.

[0075] Comparative Example 2: Fabrication and Testing of Bilayer Gradient MEA Fuel Cell Membrane Electrode Slurry preparation: Inner layer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix with 2.24 g of Nafion ionomer solution (5 wt%, equivalent to I / C=1.4), 9.2 g of isopropanol, and 9.2 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0076] Outer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix it with 0.48 g of Nafion ionomer solution (5 wt%, equivalent to I / C=0.3), 7.1 g of isopropanol, and 7.1 g of deionized water. After ultrasonic dispersion for 30 minutes, shear at 5000 rpm for 0.5 h.

[0077] MEA preparation (transfer method): The slurry was uniformly coated onto the PTFE release film using ultrasonic spraying, with the loading rate controlled at 0.3 mg Pt / cm². 2 The cathode is completely dried at 80°C.

[0078] The slurry was uniformly coated onto the PTFE release film using ultrasonic spraying, with the loading rate controlled at 0.1 mg Pt / cm². 2 It is completely dried at 80°C to form the anode.

[0079] The Nafion 211 proton exchange membrane was subjected to standard pretreatment (H2O2, sulfuric acid boiling).

[0080] Align the PTFE membrane with the bilayer catalyst layer with the treated proton exchange membrane and hot-press it at 135°C and 5 MPa for 90 seconds. After cooling, carefully peel off the PTFE membrane, and the catalyst layer is transferred onto the membrane.

[0081] Fuel cell membrane electrode performance testing: Commercial GDL was added to both sides of Examples 1-7 and Comparative Examples 1-2 to assemble them into single cells. The membrane electrode fuel cell performance was tested under conditions of 80°C, H2 / O2, and 100% RH, with the membrane electrode reaching 0.8 A / cm. 2 and 2A / cm 2 The output voltage results are shown in Table 1.

[0082] Table 1 Example 1 0.726V 0.604V Example 2 0.735V 0.626V Example 3 0.734V 0.620V Example 4 0.728V 0.600V Example 5 0.732V 0.630V Example 6 0.735V 0.620V Example 7 0.732V 0.612V Comparative Example 1 0.728V 0.574V Comparative Example 2 0.726V 0.564V Results: As shown in Table 1 and Figure 3 As shown, the MEA of Embodiment 1 of the present invention is 2 A / cm 2 The voltage at the current density was 0.604V, while in Comparative Example 1 it was only 0.574V. Changing the single-layer membrane electrode to a membrane electrode with an ionomer gradient distribution significantly improved the output voltage at high current density. Further optimization of the I / C ratio of the multilayer membrane electrode or the use of more layers of ionomer gradient can further improve the performance of the membrane electrode in fuel cells by approximately 10%. Different membrane electrode coating methods have little impact on this method, indicating its broad adaptability to coating methods and its suitability for subsequent large-scale production. However, with further expansion of the I / C ratio gradient, the outer three-phase reaction interface becomes insufficient, while the pores of the inner catalyst layer become clogged, hindering the entry of reactant gases and leading to a decrease in the overall performance of the membrane electrode. Therefore, it is necessary to control the ionomer gradient within an appropriate range.

[0083] The foregoing embodiments have provided a detailed description of the inventive intent and implementation of the present invention. However, those skilled in the art will understand that the above embodiments are merely preferred embodiments of the present invention. Due to space limitations, not all embodiments can be listed here. Any implementation that embodies the technical solution of the claims of the present invention is within the protection scope of the present invention.

[0084] It should be noted that the above content is a further detailed description of the present invention in conjunction with specific embodiments, and it should not be considered that the specific embodiments of the present invention are limited to this. Under the guidance of the above embodiments, those skilled in the art can make various improvements and modifications based on the above embodiments, and these improvements or modifications fall within the protection scope of the present invention.

Claims

1. A multilayer gradient structure membrane electrode, comprising a proton exchange membrane, a cathode catalytic layer, an anode catalytic layer, and a gas diffusion layer, wherein the cathode catalytic layer and the anode catalytic layer comprise an ionomer and a catalyst; characterized in that: Both the cathode catalyst layer and the anode catalyst layer have a multilayer structure. Both the cathode catalyst layer and the anode catalyst layer include an inner catalyst layer that is in contact with the proton exchange membrane and an outer catalyst layer that is in contact with the gas diffusion layer. The mass ratio (I / C) of the ionomer in the inner catalyst layer to the carbon support in the catalyst is 0.8 to 1.2, and the mass ratio (I / C) of the ionomer in the outer catalyst layer to the carbon support in the catalyst is 0.4 to 0.

6. The catalyst is a TKK 60 series platinum-carbon catalyst; the ionomer is a perfluorosulfonic acid resin.

2. The multilayer gradient structure film electrode according to claim 1, characterized in that: The cathode catalyst layer and / or anode catalyst layer further include an intermediate catalyst layer disposed between the outer catalyst layer and the inner catalyst layer, wherein the mass ratio (I / C) of the ionomer in the inner catalyst layer, the intermediate catalyst layer and the outer catalyst layer decreases sequentially.

3. The multilayer gradient structure film electrode according to claim 2, characterized in that: The mass ratio (I / C) of the ionomer in the intermediate catalyst layer to the carbon support in the catalyst is 0.6 to 0.

8.

4. A method for preparing the catalytic layer of the multilayer gradient structure film electrode according to claim 1, characterized in that... Includes the following steps: Preparation of various catalyst layer slurries: Each slurry is obtained by uniformly mixing TKK 60 series platinum-carbon catalyst, perfluorosulfonic acid resin, short-chain monool, and deionized water; and the mass ratio (I / C) of the ionomer to the carbon support in the catalyst of these slurries decreases sequentially; wherein, these slurries include at least slurries with an I / C of 0.8~1.2 and slurries with an I / C of 0.4~0.6, and the short-chain monool is selected from one or more of n-propanol, isopropanol, and ethanol; Layered coating: Through a layered coating process, the various catalyst layer slurries are sequentially formed on both sides of the proton exchange membrane in descending order of the mass ratio (I / C) of the ionomer to the carbon support in the catalyst. This results in the catalyst layer that is in close contact with the proton exchange membrane being formed by the slurry with the highest I / C, and the I / C of the slurry corresponding to each catalyst layer decreases layer by layer away from the proton exchange membrane. The layered coating process is selected from one of the following: direct spraying, transfer printing, or GDL method.

5. The method for preparing a membrane electrode catalytic layer according to claim 4, characterized in that, Three types of catalyst slurries were prepared, and the mass ratios (I / C) of the ionomers to the carbon support in the catalyst for these three slurries were 0.8 ~ 1.2, 0.6 ~ 0.8, and 0.4 ~ 0.6, respectively.

6. The application of a multilayer gradient structure membrane electrode as described in any one of claims 1-3 in a fuel cell.

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