Membrane electrode with multi-layer gradient structure, and preparation method and application of membrane electrode catalyst layer

Abstract

The invention relates to the technical field of fuel cells, in particular to a multilayer gradient structure membrane electrode and 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 / is of a multi-layer structure and comprise an inner catalyst layer connected with the proton exchange membrane and an outer catalyst layer connected with the gas diffusion layer; the mass ratio I / C of the ionomer of the inner catalyst layer to the carbon support 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 high-efficiency proton transmission, and the low ionomer content in the outer layer ensures high-efficiency gas / product mass transfer, thereby fundamentally solving the problem of balancing conduction and mass transfer in a 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, the repeatability is good, and the method is suitable for large-scale production. And finally, determining the application of the membrane electrode in the hydrogen-oxygen / hydrogen-air fuel cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cells, in particular to a structure design and preparation method of a membrane electrode assembly (MEA), and more particularly to a multi-layer gradient structure membrane electrode, a preparation method and application of a catalyst layer of the membrane electrode. BACKGROUND

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

[0003] Commercial catalysts, such as the TEC series of TANAKA KIKINZOKU KOGYO (TKK) (e.g., TKK 60 series platinum-carbon catalyst), are widely used due to their high activity and stability. In the catalyst slurry, platinum-carbon catalyst and ionomer form agglomerate particles of appropriate size, and ionomer is distributed on the surface of the agglomerate or inserted into the agglomerate to stabilize the agglomerate structure. In the catalyst layer, the role of ionomer (such as Nafion) is to bond catalyst particles, provide proton conduction channels, and form a three-phase reaction interface. The content of ionomer significantly affects the performance of the catalyst layer: 1. Too low ionomer content: insufficient proton conduction channels, low catalyst utilization, leading to increased activation polarization.

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

[0005] Currently, most studies use a single ionomer content catalyst layer, and this homogeneous structure is difficult to optimize proton conduction and gas transmission at the same time, especially at high current density, mass transfer limitation becomes a performance bottleneck.

[0006] Therefore, it is necessary to improve and optimize the existing membrane electrode and preparation method to better meet user needs. SUMMARY

[0007] The primary purpose of the present application is to overcome the contradiction between mass transfer and gas transmission of the single ionomer content catalyst layer in the prior art, and to provide a membrane electrode with significantly improved performance. Secondly, a preparation method of the catalyst layer of the membrane electrode is provided, which has controllable process and good repeatability, and is suitable for large-scale production. Finally, the application of the membrane electrode in hydrogen-oxygen / hydrogen-air fuel cells is clarified.

[0008] To achieve the above-mentioned purposes, the embodiment of the present application firstly provides a multi-layer gradient structure membrane electrode, which comprises 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 ionomer and catalyst; the cathode catalyst layer and / or the anode catalyst layer is a multi-layer structure, which comprises 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 carrier in the catalyst of the inner catalyst layer is higher than that of the outer catalyst layer.

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

[0010] Further preferably, the cathode catalyst layer and / or the anode catalyst layer further comprises an intermediate catalyst layer arranged between the outer catalyst layer and the inner catalyst layer, and the mass ratio I / C of the ionomer to the carbon carrier in the catalyst of the inner catalyst layer, the intermediate catalyst layer and the outer catalyst layer decreases in turn.

[0011] Further preferably, the mass ratio I / C of the ionomer to the carbon carrier in the catalyst of the intermediate catalyst layer is 0.6-0.8.

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

[0013] In addition, the embodiment of the present application further provides a preparation method of a membrane electrode catalyst layer, which comprises the following steps: Preparation of a plurality of catalyst layer slurries: each slurry is obtained by uniformly mixing catalyst, ionomer, short-chain monoalcohol and deionized water; and the mass ratio I / C of the ionomer to the carbon carrier in the catalyst of the slurries decreases in turn; Layered coating: the prepared slurries are sequentially coated on one side of the proton exchange membrane by using a transfer method, a direct spraying method or a GDL method, and the coating order satisfies that the mass ratio I / C of the ionomer to the carbon carrier in the catalyst of the slurry closest to the proton membrane is the highest, and decreases with the increase of the coating order.

[0014] Further preferably, the number of the prepared catalyst layer slurries is two, and the mass ratio I / C of the ionomer to the carbon carrier in the catalyst of the two slurries is 0.8-1.2 and 0.4-0.6 respectively.

[0015] Further preferably, the number of the prepared catalyst layer slurries is three, and the mass ratio I / C of the ionomer to the carbon carrier in the catalyst of the three slurries is 0.8-1.2, 0.6-0.8 and 0.4-0.6 respectively.

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

[0017] In addition, the present application also provides a use of the multi-layer gradient structure membrane electrode in a fuel cell.

[0018] It should be understood that the present application aims to change the single-layer catalytic layer of the membrane electrode into a multi-layer catalytic layer with gradient distribution of ionomers, without involving adjustment of the catalyst. Therefore, the catalyst of the above-mentioned catalytic layer slurry or the catalytic layer of the membrane electrode is a conventional catalyst composition.

[0019] Therefore, the catalyst of the catalytic layer of the membrane electrode before and after the application date of the present application can be obtained by the process of the present application to obtain a multi-layer catalytic layer with gradient distribution of ionomers, and the membrane electrode obtained by the preparation method of the present application and the corresponding preparation method all fall within the protection scope of the present application.

[0020] Compared with the prior art, the present application has the following beneficial technical effects: Synergistic optimization: high ionomer content in the inner layer ensures efficient proton transmission, and low ionomer content in the outer layer ensures efficient gas / product mass transfer, which fundamentally solves the trade-off problem between conduction and mass transfer in the uniform catalytic layer.

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

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

[0023] Flexible method: the preparation method has strong selectivity and good compatibility with the existing MEA preparation process, and is easy to realize technical transformation and large-scale production. BRIEF DESCRIPTION OF DRAWINGS

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

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

[0026] Figure 2 is a schematic diagram of a membrane electrode with a traditional single-layer catalytic layer structure provided by Comparative Example 1 of the present application.

[0027] Figure 3 Figure 1 is a polarization curve diagram of the membrane electrode of the present application embodiment 1-7 and comparative examples 1-2 in a fuel cell. DETAILED DESCRIPTION

[0028] The present application will be described in greater detail by explaining specific working examples. It will be obvious to a person skilled in the art that the working examples described are only a part of all possible embodiments of the present application, and are not to be construed as limiting the scope of the present application. Based on the working examples of the present application, all other working examples obtained by a person skilled in the art without creative work fall within the scope of the present application.

[0029] The technical solutions of the present application will be described in detail below in combination with the drawings and working examples, but the present application is not limited in the scope of the described working examples. The process parameters not mentioned in the working examples can be performed according to conventional methods, and the raw materials used can be obtained through commercial channels.

[0030] Example 1: Preparation and testing of double-layer gradient MEA fuel cell membrane electrode Preparation of slurry: Inner layer slurry: Take 200 mg of TKK TEC10V60E catalyst (the mass ratio of carbon in the catalyst is 40%, and the mass ratio of platinum is 60%), and mix with 1.28 g of Nafion ionomer solution (5 wt%), 8.0 g of isopropyl alcohol, and 8.0 g of deionized water. In the above slurry, the mass ratio of ionomer to carbon carrier in the catalyst I / C = (1.28 g of Nafion solution mass x 5%) / (0.2 g of TKK TEC10V60E catalyst mass x 40%) = 0.064 / 0.08 = 0.8. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0031] Outer layer slurry: Take 200 mg of TKK TEC10V60E catalyst (mass ratio of carbon 40%), and mix with 0.96 g of Nafion ionomer solution (5 wt%), 7.7 g of isopropyl alcohol, and 7.7 g of deionized water. I / C = (0.96 g x 5%) / (0.2 g x 40%) = 0.048 / 0.08 = 0.6. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0032] Preparation of MEA (transfer method): The outer layer slurry is uniformly coated on the PTFE release film by ultrasonic spraying, and the loading amount is controlled at 0.15 mg Pt / cm 2 , and dried at 80°C to a semi-dry state. The inner layer slurry is sprayed on the above semi-dry inner layer, and the loading amount is controlled at 0.3 mg Pt / cm2 Then, dry at 80°C to form a cathode.

[0033] The outer layer slurry was uniformly coated on the PTFE release film by ultrasonic spraying, with a loading of 0.05 mg Pt / cm 2 , and dried at 80°C to a semi-dry state. The inner layer slurry was sprayed on the semi-dry inner layer, with a loading of 0.1 mg Pt / cm 2 , and then completely dried at 80°C to form an anode.

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

[0035] The PTFE film with the double-layer catalytic layer was aligned with the treated proton exchange membrane, and hot-pressed at 135°C and 5 MPa pressure for 90 seconds. After cooling, the PTFE film was carefully removed, and the catalytic layer was transferred to the membrane.

[0036] Example 2: Preparation and testing of double-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, the calculation method of this example 2 and subsequent examples and comparative examples is the same as example 1), 8.4 g of isopropanol, and 8.4 g of deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0037] Outer layer slurry: Take 200 mg of TKK TEC10V60E catalyst, mix 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, high-speed shearing at 5000 rpm for 0.5 h.

[0038] MEA preparation (transfer method): The outer layer slurry was uniformly coated on the PTFE release film by ultrasonic spraying, with a loading of 0.15 mg Pt / cm 2 , and dried at 80°C to a semi-dry state. The inner layer slurry was sprayed on the semi-dry inner layer, with a loading of 0.3 mg Pt / cm 2 , and then completely dried at 80°C to form a cathode.

[0039] The outer layer slurry was uniformly coated on the PTFE release film by ultrasonic spraying, with a loading of 0.05 mg Pt / cm 2, 80°C to semi-dry state. The inner layer slurry was sprayed on the above semi-dry inner layer, loading controlled at 0.1 mg Pt / cm 2 , then fully dried at 80°C to form the cathode.

[0040] Nafion 211 proton exchange membrane was subjected to standard pre-treatment (H2O2, sulfuric acid boil).

[0041] The PTFE membrane with double layer catalyst layer above was aligned with the treated proton exchange membrane, hot-pressed at 135°C, 5 MPa pressure for 90 seconds. After cooling, the PTFE membrane was carefully removed, and the catalyst layer was transferred to the membrane.

[0042] Example 3: Double layer gradient MEA fuel cell membrane electrode preparation and testing Slurry preparation: Inner layer slurry: 200 mg TKK TEC10V60E catalyst was mixed with 1.6 g Nafion ionomer solution (5 wt%, equivalent to I / C = 1.0), 8.4 g isopropyl alcohol, 8.4 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0043] Outer layer slurry: 200 mg TKK TEC10V60E catalyst was mixed with 0.8 g Nafion ionomer solution (5 wt%, equivalent to I / C = 0.5), 7.5 g isopropyl alcohol, 7.5 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0044] MEA preparation (direct spraying method): Nafion 211 proton exchange membrane was subjected to standard pre-treatment (H2O2, sulfuric acid boil).

[0045] The inner layer slurry was uniformly coated on the proton exchange membrane by ultrasonic spraying, loading controlled at 0.15 mg Pt / cm 2 , 80°C to semi-dry state. The outer layer slurry was sprayed on the above semi-dry inner layer, loading controlled at 0.3 mg Pt / cm 2 , then fully dried at 80°C to form the cathode.

[0046] The inner layer slurry was uniformly coated on the other side of the proton exchange membrane by ultrasonic spraying, loading controlled at 0.05 mg Pt / cm 2 , 80°C to semi-dry state. The outer layer slurry was sprayed on the above semi-dry inner layer, loading controlled at 0.1 mg Pt / cm 2 , then fully dried at 80°C to form the anode.

[0047] Example 4: Double-layer gradient MEA fuel cell membrane electrode preparation and testing Slurry preparation: Inner layer slurry: Take 200 mg TKK TEC10V60E catalyst, mix with 1.92 g Nafion ionomer solution (5 wt%, equivalent to I / C = 1.2), 8.8 g isopropyl alcohol, 8.8 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0048] Outer layer slurry: Take 200 mg TKK TEC10V60E catalyst, mix with 0.64 g Nafion ionomer solution (5 wt%, equivalent to I / C = 0.4), 7.3 g isopropyl alcohol, 7.3 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

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

[0050] The inner layer slurry was uniformly coated on the proton exchange membrane by ultrasonic spraying, and the loading amount was controlled at 0.15 mg Pt / cm 2 , dried at 80°C to semi-dry state. The outer layer slurry was sprayed on the above semi-dry inner layer, and the loading amount was controlled at 0.3 mg Pt / cm 2 , and then completely dried at 80°C to form the cathode.

[0051] The inner layer slurry was uniformly coated on the other side of the proton exchange membrane by ultrasonic spraying, and the loading amount was controlled at 0.05 mg Pt / cm 2 , dried at 80°C to semi-dry state. The outer layer slurry was sprayed on the above semi-dry inner layer, and the loading amount was controlled at 0.1 mg Pt / cm 2 , and then completely dried at 80°C to form the anode.

[0052] Example 5: Three-layer gradient MEA fuel cell membrane electrode preparation and testing Slurry preparation: Inner layer slurry: Take 200 mg TKK TEC10V60E catalyst, mix with 1.6 g Nafion ionomer solution (5 wt%, equivalent to I / C = 1.0), 8.4 g isopropyl alcohol, 8.4 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0053] Middle layer slurry: 200 mg TKK TEC10V60E catalyst was mixed with 1.12 g Nafion ionomer solution (5 wt%, equivalent to I / C = 0.7), 8.8 g isopropyl alcohol, 8.8 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0054] Outer layer slurry: 200 mg TKK TEC10V60E catalyst was mixed with 0.8 g Nafion ionomer solution (5 wt%, equivalent to I / C = 0.5), 7.5 g isopropyl alcohol, 7.5 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

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

[0056] The inner layer slurry was uniformly coated on the proton exchange membrane by ultrasonic spraying, and the loading amount was controlled at 0.1 mg Pt / cm 2 . The middle layer slurry was sprayed on the above semi-dry inner layer, and the loading amount was controlled at 0.2 mg Pt / cm 2 . The outer layer slurry was sprayed on the above semi-dry double-layer catalyst layer, and the loading amount was controlled at 0.3 mg Pt / cm 2 , and then completely dried at 80°C to form the cathode.

[0057] The inner layer slurry was uniformly coated on the other side of the proton exchange membrane by ultrasonic spraying, and the loading amount was controlled at 0.03 mg Pt / cm 2 . The middle layer slurry was sprayed on the above semi-dry inner layer, and the loading amount was controlled at 0.07 mg Pt / cm 2 . The outer layer slurry was sprayed on the above semi-dry double-layer catalyst layer, and the loading amount was controlled at 0.1 mg Pt / cm 2 , and then completely dried at 80°C to form the anode.

[0058] Example 6: Three-layer gradient MEA fuel cell membrane electrode preparation and test Slurry preparation: Inner layer slurry: 200 mg TKK TEC10V60E catalyst was mixed with 1.92 g Nafion ionomer solution (5 wt%, equivalent to I / C = 1.2), 8.8 g isopropyl alcohol, 8.8 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0059] Middle layer slurry: 200 mg TKK TEC10V60E catalyst was mixed with 1.28 g Nafion ionomer solution (5 wt%, equivalent to I / C = 0.8), 8.0 g isopropyl alcohol, 8.0 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0060] Outer layer slurry: 200 mg TKK TEC10V60E catalyst was mixed with 0.64 g Nafion ionomer solution (5 wt%, equivalent to I / C = 0.4), 7.3 g isopropyl alcohol, 7.3 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

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

[0062] The inner layer slurry was uniformly coated on the proton exchange membrane by ultrasonic spraying, and the loading amount was controlled at 0.1 mg Pt / cm 2 , and dried at 80°C to a semi-dry state. The middle layer slurry was sprayed on the above semi-dry inner layer, and the loading amount was controlled at 0.2 mg Pt / cm 2 . The outer layer slurry was sprayed on the above semi-dry double-layer catalyst layer, and the loading amount was controlled at 0.3 mg Pt / cm 2 , and then completely dried at 80°C to form the cathode.

[0063] The inner layer slurry was uniformly coated on the other side of the proton exchange membrane by ultrasonic spraying, and the loading amount was controlled at 0.03 mg Pt / cm 2 , and dried at 80°C to a semi-dry state. The middle layer slurry was sprayed on the above semi-dry inner layer, and the loading amount was controlled at 0.07 mg Pt / cm 2 . The outer layer slurry was sprayed on the above semi-dry double-layer catalyst layer, and the loading amount was controlled at 0.1 mg Pt / cm 2 , and then completely dried at 80°C to form the anode.

[0064] Example 7: Three-layer gradient MEA fuel cell membrane electrode preparation and test Slurry preparation: Inner layer slurry: 200 mg TKK TEC10V60E catalyst was mixed with 1.92 g Nafion ionomer solution (5 wt%, equivalent to I / C = 1.2), 8.8 g isopropyl alcohol, 8.8 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0065] Middle layer slurry: 200 mg TKK TEC10V60E catalyst was mixed with 0.96 g Nafion ionomer solution (5 wt%, equivalent to I / C = 0.6), 7.7 g isopropyl alcohol, 7.7 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0066] Outer layer slurry: 200 mg TKK TEC10V60E catalyst was mixed with 0.64 g Nafion ionomer solution (5 wt%, equivalent to I / C = 0.4), 7.3 g isopropyl alcohol, 7.3 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

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

[0068] The inner layer slurry was uniformly coated on the proton exchange membrane by ultrasonic spraying, with a loading of 0.1 mg Pt / cm 2 , and dried at 80°C to a semi-dry state. The middle layer slurry was sprayed on the above semi-dry inner layer, with a loading of 0.2 mg Pt / cm 2 . The outer layer slurry was sprayed on the above semi-dry double-layer catalyst layer, with a loading of 0.3 mg Pt / cm 2 , and then completely dried at 80°C to form the cathode.

[0069] The inner layer slurry was uniformly coated on the other side of the proton exchange membrane by ultrasonic spraying, with a loading of 0.03 mg Pt / cm 2 , and dried at 80°C to a semi-dry state. The middle layer slurry was sprayed on the above semi-dry inner layer, with a loading of 0.07 mg Pt / cm 2 . The outer layer slurry was sprayed on the above semi-dry double-layer catalyst layer, with a loading of 0.1 mg Pt / cm 2 , and then completely dried at 80°C to form the anode.

[0070] Comparative Example 1: Single catalyst layer MEA fuel cell membrane electrode preparation and testing A single catalyst layer MEA was prepared, with a structure as shown in Figure 2 . The I / C ratio was the average of the I / C ratios of the inner and outer layers of Example 1, 0.7. The slurry was prepared: Take 400 mg TKK TEC10V60E catalyst, mix with 2.24 g Nafion ionomer solution (5 wt%, equivalent to I / C = 0.7), 15.7 g isopropyl alcohol, 15.7 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0071] MEA preparation (transfer method): The slurry is uniformly coated on the PTFE release film by ultrasonic spraying, and the loading amount is controlled at 0.3 mg Pt / cm 2 , and completely dried at 80°C to form the cathode.

[0072] The slurry is uniformly coated on the PTFE release film by ultrasonic spraying, and the loading amount is controlled at 0.1 mg Pt / cm 2 , and completely dried at 80°C to form the anode.

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

[0074] The above PTFE film with double-layer catalyst layer is aligned with the treated proton exchange film, and hot-pressed at 135°C and 5 MPa pressure for 90 seconds. After cooling, the PTFE film is carefully removed, and the catalyst layer is transferred to the film.

[0075] Comparative Example 2: Preparation and testing of double-layer gradient MEA fuel cell membrane electrode Slurry preparation: Inner layer slurry: Take 200 mg TKK TEC10V60E catalyst, mix with 2.24 g Nafion ionomer solution (5 wt%, equivalent to I / C = 1.4), 9.2 g isopropyl alcohol, 9.2 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0076] Outer layer slurry: Take 200 mg TKK TEC10V60E catalyst, mix with 0.48 g Nafion ionomer solution (5 wt%, equivalent to I / C = 0.3), 7.1 g isopropyl alcohol, 7.1 g deionized water. After ultrasonic dispersion for 30 minutes, high-speed shearing at 5000 rpm for 0.5 h.

[0077] MEA preparation (transfer method): The slurry is uniformly coated on the PTFE release film by ultrasonic spraying, and the loading amount is controlled at 0.3 mg Pt / cm 2 , and completely dried at 80°C to form the cathode.

[0078] The slurry was uniformly coated on PTFE release film by ultrasonic spraying, and the loading was controlled at 0.1 mg Pt / cm 2 The anode was completely dried at 80°C.

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

[0080] The PTFE film with the double-layer catalytic layer was aligned with the treated proton exchange membrane, and hot-pressed at 135°C and 5 MPa for 90 seconds. After cooling, the PTFE film was carefully removed, and the catalytic layer was transferred to the membrane.

[0081] Fuel cell membrane electrode performance test: The commercial GDL was arranged on both sides of the membrane electrode of Example 1-7 and Comparative Example 1-2, and a single cell was assembled. The performance of the membrane electrode fuel cell was tested under the conditions of 80°C, H2 / O2, and 100% RH, and the output voltage of the membrane electrode was 0.8 A / cm 2 and 2 A / cm 2 The results are shown in Table 1.

[0082] Table 1 Voltage @ 0.8 A / cm 2 ]] Voltage @ 2A / cm 2 ]] 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 , the voltage of the MEA of Example 1 of the present application was 0.604 V at a current density of 2 A / cm 2 , while that of Comparative Example 1 was only 0.574 V. By changing the single-layer membrane electrode to a membrane electrode with a gradient distribution of ionomers, the output voltage at high current density was significantly improved. By further optimizing the I / C ratio of the multi-layer membrane electrode or using more layers of ionomer gradient, the performance of the membrane electrode in the fuel cell can be further improved by about 10%. Different coating methods of the membrane electrode have little effect on this method, indicating that this method is widely adaptable to coating methods and is conducive to subsequent large-scale production. However, with the further expansion of the I / C ratio gradient, the outer three-phase reaction interface is too small, and the inner catalytic layer pores are blocked, making it difficult for the reaction gas to enter, resulting in a decrease in the overall performance of the membrane electrode. It is necessary to control the ionomer gradient within a suitable range.

[0083] The above embodiments are used to illustrate the inventive intent and embodiments of the present application, but those skilled in the art of the present application can understand that the above embodiments of the present application are only one of the preferred embodiments of the present application, and due to the limitation of the length, all embodiments cannot be listed one by one, any embodiment that can embody the technical solution of the claims of the present application is within the protection scope of the present application.

[0084] It should be noted that the above content is a further detailed description of the present application in combination with specific embodiments, and cannot be considered as limiting the specific embodiments of the present application. Under the guidance of the above examples, those skilled in the art can make various improvements and modifications on the basis of the above examples, and these improvements or modifications fall within the protection scope of the present application.

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: The cathode catalyst layer and / or anode catalyst layer have a multilayer structure, 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 in the inner catalyst layer to the carbon support in the catalyst is higher than that in the outer catalyst layer.

2. The multilayer gradient structure film electrode according to claim 1, characterized in that: 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; 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.

3. The multilayer gradient structure film electrode according to claim 2, 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.

4. The multilayer gradient structure film electrode according to claim 3, 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.

5. A multilayer gradient structure film electrode according to claim 1, characterized in that: The catalyst is a TKK 60 series platinum-carbon catalyst; the ionomer is a perfluorosulfonic acid resin.

6. A method for preparing a membrane electrode catalytic layer, characterized in that... Includes 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.

7. The method for preparing a membrane electrode catalytic layer according to claim 6, characterized in that: Two types of catalyst layer slurries were prepared, and the mass ratio (I / C) of the ionomer to the carbon support in the catalyst for these two slurries were 0.8 ~ 1.2 and 0.4 ~ 0.6, respectively.

8. The method for preparing a membrane electrode catalytic layer according to claim 6, 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.

9. The method for preparing a membrane electrode catalytic layer according to claim 6, characterized in that: 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.

10. The application of a multilayer gradient structure membrane electrode as described in any one of claims 1-5 in a fuel cell.

Images