Catalyst-coated membrane, method for producing the same, and use thereof

Abstract

The application discloses a catalyst-coated membrane and a preparation method and application thereof, and relates to the field of fuel cells. According to the application, the viscosity of the catalyst slurry used by each layer of the second catalytic layer is controlled to be less than 150 cP, and the dielectric constant of the solvent is in the range of 50-75, so that a complete and smooth-surfaced second catalytic layer can be coated on the first catalytic layer, and there is no obvious gap or pore between the first catalytic layer and the second catalytic layer and between each layer of the second catalytic layer, and the interface resistance is low. In addition, the first catalytic layer and the second catalytic layer are prepared by adopting a slot coating method, the coating speed is high, the efficiency is high, the membrane electrode can be prepared on a large scale, the limitation on the properties of the slurry is small, and the ideal catalytic layer structure can be prepared according to the design.

Description

Technical Field

[0001] The present invention relates to the field of fuel cells, and in particular to a catalyst coating membrane and a preparation method and application thereof. Background Art

[0002] The membrane electrode is the core component of the fuel cell, and its durability and other performance properties largely depend on the structure of the catalyst layer in the CCM (catalyst coated membrane), especially the structure of the cathode catalyst layer. The membrane electrode catalyst layer, especially the cathode catalyst layer, is designed in a layered structure or a gradient material design to optimize the mass transfer process and proton transfer process therein, such as patents CN108063267A, CN103367768A, CN103165915A, CN1612381A, etc. The catalyst layer of the double-layer or more-layer structure is usually prepared by directly spraying on the proton exchange membrane, or spraying two or more layers on PTFE (polytetrafluoroethylene) and then transferring them to the proton exchange membrane. However, spray coating technology has a slow production speed and low efficiency, making it unsuitable for large-scale production applications. In addition, it has high requirements for the particle size, viscosity, and solid content of the slurry. For example, the catalyst particle size is generally small, and the viscosity and solid content are low for effective spraying. The properties of the slurry have a decisive effect on the structure of the catalytic layer formed. Therefore, the use of spray coating technology has significant limitations on the structural design of the catalytic layer. In addition, the use of a continuous spraying method usually causes the structure of the previous layer to affect the structure of the next layer, which is not conducive to the design of independent catalytic layers with two or more layers. There is also an existing technology that prepares a two-layer catalytic layer by coating a first catalytic layer on a proton exchange membrane, coating a second catalytic layer on PTFE, and then transferring the second catalytic layer to the first catalytic layer. Although this method can achieve large-scale industrial production, because the surfaces of the two catalytic layers must face each other during the transfer process, and the catalytic layer surfaces are generally uneven, large pores are easily formed between the transferred second layer and the first layer, resulting in increased interfacial impedance and weak bonding between the first and second layers. At the same time, the preparation process is quite cumbersome and the preparation efficiency is low.

[0003] The slit coating method for preparing the catalyst layer has the advantages of fast coating speed, precise control, good coating effect, and the ability to achieve continuous production. It has been widely used in the field of lithium batteries and has gradually been applied in the field of fuel cells in recent years. At present, in the field of lithium batteries, it is common to use slit coating to prepare electrodes with two or more layers, but in the field of fuel cells, slit coating has not been used to prepare catalytic layers with two or more layers. It should be pointed out that although the preparation of the multi-layer structure of the membrane electrode catalyst layer of the fuel cell is similar in form to the preparation of the composite structure of the lithium battery electrode, the actual difficulties to be overcome are completely different. First, the substrate for the fuel cell membrane electrode coating is a perfluorosulfonic acid resin exchange membrane. This polymer membrane will undergo significant swelling after absorbing water and alcohol (that is, it will undergo dimensional changes in thickness, length and width); the current collector of the lithium battery is usually made of metal foil, such as aluminum foil, which is relatively stable and does not swell. Secondly, the adhesive used in the fuel cell catalyst layer is perfluorosulfonic acid resin, which will also undergo significant deformation when exposed to alcohol and water. The slurry used in lithium batteries uses PVDF as a binder, which is insoluble in alcohol and water and is generally unaffected by these two substances. Therefore, when preparing a fuel cell membrane electrode structure with two or more catalyst layers, one cannot simply apply the first layer first, dry it, and then apply the second layer. This is because applying the second catalyst layer will cause the proton exchange membrane to swell, the perfluorosulfonic acid resin in the first catalyst layer to swell, and the substances in the first catalyst layer to be re-dispersed by the solvent in the second coating slurry. This will cause the original first catalyst layer to deform and fall off, preventing the formation of a good double-layer structure. Summary of the Invention

[0004] Based on the defects of the existing technology, the purpose of the present invention is to provide a catalyst coating membrane and its preparation method and application, aiming to design an independent double-layer or more-layer catalytic layer, and the resulting double-layer or more-layer catalytic layer has a good structure, a smooth surface, no obvious gaps or pores between layers, low interface resistance, a simple preparation method, high efficiency, and low requirements for the slurry used.

[0005] To achieve the above object, the present invention provides a catalyst-coated membrane, comprising a proton exchange membrane, wherein the proton exchange membrane comprises a first surface and a second surface, wherein a first catalytic layer and a second catalytic layer are sequentially disposed on the first surface of the proton exchange membrane, and the second catalytic layer comprises at least one layer;

[0006] The first catalytic layer and the second catalytic layer are both prepared by applying the catalyst slurry in a slot coating manner and then drying;

[0007] The viscosity of the catalyst slurry used to prepare each layer of the second catalytic layer is less than 150 cP, and the dielectric constant of the solvent is 50-75;

[0008] A third catalytic layer is provided on the second surface of the proton exchange membrane, and the third catalytic layer includes at least one layer.

[0009] The inventors found in the course of research that the key to the success of slit direct coating to construct a double-layer or more-layered catalytic layer is the viscosity of the catalyst slurry used in each layer of the second catalytic layer and the dielectric constant of the solvent used in the catalyst slurry. When the viscosity of the catalyst slurry used in each layer of the second catalytic layer is too large, it is easy to produce the adverse effect of uneven coating, and may also produce wire drawing. The dielectric constant of the solvent used in each layer of the second catalytic layer mainly affects the morphology of the ionomer and the interaction between the ionomer and the catalyst, and then affects the interaction between the layers of the second catalytic layer and the first catalytic layer. There are documents showing that the dielectric constant of the solvent affects the morphology of the ionomer. When the dielectric constant is high, the dispersed state of the ionomer is solution-like; when the dielectric constant is low, the ionomer is easy to precipitate and is not easy to disperse; when the dielectric constant is moderate, the ionomer tends to form a colloid (M.Uchida, J.Electrochem.Soc.1995,142,463). The inventors found that when the solvent dielectric constant of the catalyst slurry used in each layer of the second catalytic layer is in the range of 50-75, and the viscosity of the catalyst slurry used in each layer of the second catalytic layer is less than 150cP, a complete and smooth second catalytic layer can be formed by coating on the first catalytic layer, and there are no obvious gaps or pores between the first catalytic layer and the second catalytic layer, and between the layers of the second catalytic layer, and the interface resistance is low.

[0010] Compared with constructing a single-layer catalytic layer through slit direct coating on the first surface, constructing a double-layer or more-layer catalytic layer through slit direct coating can significantly improve the performance of the membrane electrode. Because the reactants are not evenly distributed in the catalytic layer, the design of a multi-layer catalytic layer structure can adjust the properties and content of the catalyst and perfluorosulfonic acid resin in different layers according to the distribution of the reactants, thereby improving the utilization rate of the material and making the distribution of electricity and heat in the entire membrane electrode uniform, preventing local overheating, and helping to improve the stability of the membrane electrode.

[0011] When the solvent of the catalyst slurry used in each layer of the second catalytic layer is a mixed solvent, the solvent dielectric constant of the slurry is calculated according to the following formula:

[0012] ε 混 1 / 3 =∑ i C i ε i 1 / 3 ;

[0013] Among them, C i is the volume fraction of component i, ε i is the dielectric constant of component i, ε 混 is the dielectric constant of the slurry.

[0014] The test method for the viscosity of the catalyst slurry used in each layer of the second catalytic layer is as follows: a rheometer is used to perform viscosity testing, a suitable rotor model is selected according to the slurry conditions, the rotor speed is set to 250RPM, the temperature is controlled at 25°C, the acquisition time is set to 30s, and the torque during the test is 10-90% and the data is considered valid.

[0015] In consideration of rapid large-scale coating control and to avoid poor coating uniformity of the second catalytic layer slurry, preferably, the viscosity of the catalyst slurry used to prepare each layer of the second catalytic layer is 5-85 cP.

[0016] The catalyst slurry used to prepare each layer of the third catalytic layer can be the catalyst slurry used in the first catalytic layer and / or the catalyst slurry used in each layer of the second catalytic layer, or other different slurries can be selected.

[0017] Preferably, the first catalytic layer and the second catalytic layer are cathode catalytic layers of a PEM (proton exchange membrane) fuel cell.

[0018] Preferably, the material of the proton exchange membrane includes perfluorosulfonic acid resin.

[0019] The present invention has no special requirements for the formulation of the catalyst material and slurry used to prepare the first catalytic layer. Any anode catalyst layer material and slurry or cathode catalyst layer material and slurry in the art can be used, as long as these materials and slurries can be applied to the proton exchange membrane through slit coating to obtain a uniformly distributed crack-free coating structure. The key to the present invention is to control the properties of the catalyst slurry used in each layer of the second catalytic layer, so as to obtain a uniformly distributed crack-free multi-layer catalytic layer structure. The viscosity of the catalyst slurry used in each layer of the second catalytic layer should be less than 150 cP, and the dielectric constant of the mixed solvent used should be between 50-75. There are no special requirements for the formulation of its materials and slurry.

[0020] Optionally, the catalyst slurry used to prepare the first catalytic layer and the catalyst slurry used to prepare each layer of the second catalytic layer both include a catalyst, a perfluorosulfonic acid resin and a solvent, and the solvent includes an organic solvent and water.

[0021] Optionally, the catalyst in the catalyst slurry used to prepare the first catalytic layer and the catalyst slurry used to prepare each layer of the second catalytic layer includes at least one of Pt / C and PtM / C, wherein M in PtM / C is at least one of Co, Ni, Cu, Au, Ag, Ir, Ru, Cr, and Fe.

[0022] In some specific embodiments, at least one of the conditions (a)-(b) is satisfied:

[0023] (a) preparing the first catalytic layer using a catalyst slurry comprising the following components in weight percentage: 2.4-10% catalyst, 0.8-8% perfluorosulfonic acid resin, 0.5-40% alcohol solvent, and the remainder water; wherein the dry weight ratio of perfluorosulfonic acid resin to catalyst in the catalyst slurry used in the first catalytic layer is 1:1-0.2:1;

[0024] (b) The catalyst slurry used to prepare the second catalytic layer includes the following components in percentage by weight: 3-8% catalyst, 0.8-6% perfluorosulfonic acid resin, 0.5-40% alcohol solvent, and the remainder water; wherein the dry weight ratio of perfluorosulfonic acid resin to catalyst in the catalyst slurry used to prepare the second catalytic layer is less than or equal to 1.6 times the dry weight ratio of perfluorosulfonic acid resin to catalyst in the first catalyst slurry. In these embodiments, the multi-layer catalytic layer formed by the first catalytic layer and the second catalytic layer has a good structure, a smooth surface, and no obvious gaps or pores between the layers. The alcohol solvent in the catalyst slurry used to prepare the first catalytic layer and the catalyst slurry used to prepare each layer of the second catalytic layer can be selected from at least one of ethanol, n-butanol, tert-butanol, n-propanol, isopropanol, and ethylene glycol, but is not limited thereto.

[0025] Preferably, the thickness of each layer of the second catalytic layer and the first catalytic layer is 0.1 to 30 μm, and the platinum loading is 10 to 500 μg / cm 2 .

[0026] Optionally, the third catalytic layer is coated by at least one of ultrasonic spraying, electrostatic spraying, doctor blade coating, slit coating, and screen printing.

[0027] The first catalytic layer and the second catalytic layer have adjacent layers with at least one of different pore structures, ionomer types, ionomer content, catalyst types, catalyst content, surfactant types, surfactant content, additive types, additive content, platinum loading, layer thickness, layer roughness, and layer surface hydrophobicity.

[0028] The first catalyst layer and the second catalyst layer are each formed by coating in one step.

[0029] In a second aspect, the present invention provides a method for preparing the catalyst coating membrane, comprising the following steps:

[0030] (1) preparing a catalyst slurry for preparing the first catalytic layer and a catalyst slurry for preparing each layer of the second catalytic layer;

[0031] (2) coating and drying the catalyst slurry used to prepare the first catalytic layer and the catalyst slurry used to prepare each layer of the second catalytic layer on the first surface of the proton exchange membrane to form the first catalytic layer and the second catalytic layer;

[0032] (3) coating at least one catalytic layer on the second surface of the proton exchange membrane to obtain a catalyst-coated membrane;

[0033] Among them, the coating method in step (2) is a slit coating method.

[0034] When preparing the first and second catalytic layers, the catalyst slurry can be applied and dried first before applying the next layer of catalyst slurry, or each layer of catalyst slurry can be applied and dried simultaneously, or both methods can be used. When applying each layer of catalyst slurry simultaneously, a multi-channel coating die can be used.

[0035] Preferably, the specific process of step (2) is as follows: the catalyst slurry used to prepare the first catalytic layer is coated on the first surface of the proton exchange membrane and dried to form the first catalytic layer, and then the catalyst slurries used to prepare the second catalytic layer are coated and dried in sequence to form the second catalytic layer.

[0036] Preferably, the drying temperature in step (2) is controlled at 60-150°C.

[0037] In a third aspect, the present invention provides a membrane electrode or fuel cell comprising the above-mentioned catalyst-coated membrane.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The present invention controls the viscosity of the catalyst slurry used in each layer of the second catalytic layer to be less than 150 cP, and the dielectric constant of the solvent is 50-75, thereby ensuring that a complete and smooth second catalytic layer can be formed on the first catalytic layer, and there are no obvious gaps or pores between the first catalytic layer and the second catalytic layer, and between the layers of the second catalytic layer, and the interface resistance is low.

[0040] (2) The present invention adopts a slit coating method to prepare the first catalytic layer and the second catalytic layer. The coating speed is fast and the efficiency is high, which is conducive to the large-scale preparation of membrane electrodes. In addition, the slit coating has few restrictions on the properties of the slurry and can prepare the ideal catalytic layer structure according to the design. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The SEM images of the interface between the first catalytic layer and the second catalytic layer in Example 1 and Comparative Example 2;

[0042] Figure 2 is the high-frequency resistance of the membrane electrode of Example 1 and Comparative Example 2;

[0043] Figure 3 Polarization curves of membrane electrodes of Example 1 and Comparative Examples 1-2;

[0044] Figure 4Microscope photos of the surface of the second catalytic layer (top) and the interface between the first catalytic layer and the second catalytic layer (bottom) of Example 1, Example 2 and Comparative Example 3;

[0045] Figure 5 These are microscope photos of the surface of the second catalytic layer of Example 1, Comparative Example 4 and Comparative Example 5. DETAILED DESCRIPTION

[0046] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments and comparative examples. Its purpose is to understand the content of the present invention in detail, rather than to limit the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the protection scope of the present invention. The experimental reagents and instruments involved in the implementation of the present invention are all commonly used ordinary reagents and instruments unless otherwise specified.

[0047] Example 1

[0048] S1: Weigh 5.1 g of Tec10E50e 50 wt% Pt / C catalyst (TKK, Japan), 12.8 g of 20 wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the stirred water and stir for 5 minutes. Then add the perfluorosulfonic acid resin dispersion D2020 and stir for 2 minutes. Then add ethanol and continue stirring for 2 minutes to complete the pre-dispersion of the slurry. Disperse the slurry using a Beads mill at a speed of 3000 rpm for 30 minutes. Then collect the dispersed catalyst slurry and degas it to obtain the first catalytic slurry.

[0049] 5.1 g of Tec10E50e-HT 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) of Japan), 14.0 g of 20 wt% perfluorosulfonic acid resin dispersion, 11.0 g of n-butanol, and 48.8 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the stirred water and stirred for 5 minutes. The perfluorosulfonic acid resin dispersion D2020 was then added and stirred for 2 minutes. The n-butanol was then added and stirred for another 2 minutes to complete the pre-dispersion of the slurry. The slurry was dispersed in a Beads mill at 3000 rpm for 30 minutes. The dispersed catalyst slurry was then collected and degassed to obtain a second catalytic slurry with a viscosity of 85 cP and a dielectric constant of ~54.6.

[0050] S2: The first catalytic slurry prepared in S1 is coated on one side of the proton exchange membrane by slot coating, and then baked at 80°C until it becomes non-flowable to obtain a semi-CCM containing the first cathode catalytic layer, wherein the Pt loading of the first catalytic layer is 150 μg / cm 2 , thickness is ∼5 μm;

[0051] S3: The second catalytic slurry prepared in S1 is coated on the first catalytic layer by the slot coating method and dried at 80°C until it becomes non-flowable to form the second catalytic layer. A semi-CCM containing a cathode double-layer catalytic layer is obtained. The Pt loading of the second catalytic layer is 150 μg / cm 2 , thickness is ∼4.5 μm;

[0052] S4: The anode catalyst slurry was coated on the side of the proton exchange membrane without the catalytic layer by a slot coating method. The anode catalyst slurry had the same formulation and preparation method as the first catalytic slurry in step S1, except that the Pt / C catalyst used was Elyst Pt50 0380 from Umicore. The coating loading was 100 μg / cm 2 , forming CCM, which is further assembled to form membrane electrode and fuel cell.

[0053] When the method of this embodiment is used for continuous roll-to-roll rapid coating production (coating line speed ≥ 3 m / min), there is no obvious gap or pore between the first catalytic layer and the second catalytic layer in the obtained semi-CCM containing the cathode double-layer catalytic layer, and the two are well combined.

[0054] Example 2

[0055] S1: Weigh 5.1 g of Tec10E50e 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) Co., Ltd.), 12.8 g of 20 wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the stirred water and stir for 5 minutes. Then, add the perfluorosulfonic acid resin dispersion D2020 and stir for 2 minutes. Then, add ethanol and continue stirring for 2 minutes to pre-disperse the slurry. Disperse the slurry using a Beads mill at 3000 rpm for 30 minutes. Collect the dispersed catalyst slurry and degas to obtain the first catalytic slurry.

[0056] 5.1 g of Tec10E50e-HT 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) of Japan), 16.8 g of a 20 wt% perfluorosulfonic acid resin dispersion, 9.3 g of tert-butyl alcohol, and 46.7 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the stirred water and stirred for 5 minutes. The perfluorosulfonic acid resin dispersion was then added and stirred for 2 minutes. The tert-butyl alcohol was then added and stirred for another 2 minutes to complete the pre-dispersion of the slurry. The slurry was dispersed in a Beads mill at 3000 rpm for 30 minutes. The dispersed catalyst slurry was then collected and deaerated to obtain a second catalytic slurry with a viscosity of 47 cP and a dielectric constant of 50.3.

[0057] S2: The first catalytic slurry prepared in S1 is coated on one side of the proton exchange membrane by slot coating, and then baked at 80°C until it becomes non-flowable to obtain a semi-CCM containing the first cathode catalytic layer, wherein the Pt loading of the first catalytic layer is 100 μg / cm 2 , thickness is ∼3.5 μm;

[0058] S3: The second catalytic slurry prepared in S1 is coated on the first catalytic layer by the slot coating method and dried at 80°C until it is non-flowable to form the second catalytic layer. A semi-CCM containing a cathode double-layer catalytic layer is obtained. The Pt loading of the second catalytic layer is 200 μg / cm 2 , thickness is ~6.0μm.

[0059] S4: The anode catalyst slurry is coated on the side of the proton exchange membrane without the catalytic layer by a slit coating method. The anode catalyst slurry and its preparation method are the same as those in Example 1, and the loading is 100 μg / cm 2 , forming CCM, which is further assembled to form membrane electrode and fuel cell.

[0060] When the method of this embodiment is used for continuous roll-to-roll rapid coating production (coating line speed ≥ 3 m / min), there is no obvious gap or pore between the first catalytic layer and the second catalytic layer in the obtained semi-CCM containing the cathode double-layer catalytic layer, and the two are well combined.

[0061] Example 3

[0062] S1: Weigh 5.1 g of Tec10E50e 50 wt% Pt / C catalyst (TKK, Japan), 12.8 g of 20 wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the stirred water and stir for 5 minutes. Then add the perfluorosulfonic acid resin dispersion D2020 and stir for 2 minutes. Then add ethanol and continue stirring for 2 minutes to complete the pre-dispersion of the slurry. Disperse the slurry using a Beads mill at a speed of 3000 rpm for 30 minutes. Then collect the dispersed catalyst slurry and degas it to obtain the first catalytic slurry.

[0063] 5.2 g of Tec10E50e-HT wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) of Japan), 14.0 g of 20 wt% perfluorosulfonic acid resin dispersion, 11.7 g of ethanol, and 69.1 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the stirred water and stirred for 5 minutes. The perfluorosulfonic acid resin dispersion D2020 was then added and stirred for 2 minutes. Ethanol was then added and stirred for another 2 minutes to complete the pre-dispersion of the slurry. The slurry was dispersed in a Beads mill at 3000 rpm for 30 minutes. The dispersed catalyst slurry was then collected and degassed to obtain a second catalytic slurry with a viscosity of 5.7 cP and a dielectric constant of ~63.9.

[0064] S2-S4: Same as Example 1.

[0065] When the method of this embodiment is used for continuous roll-to-roll rapid coating production (coating line speed ≥ 3 m / min), there is no obvious gap or pore between the first catalytic layer and the second catalytic layer in the obtained semi-CCM containing the cathode double-layer catalytic layer, and the two are well combined.

[0066] Example 4

[0067] S1: Weigh 5.1 g of Tec10E50e 50 wt% Pt / C catalyst (TKK, Japan), 12.8 g of 20 wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the stirred water and stir for 5 minutes. Then add the perfluorosulfonic acid resin dispersion D2020 and stir for 2 minutes. Then add ethanol and continue stirring for 2 minutes to complete the pre-dispersion of the slurry. Disperse the slurry using a Beads mill at a speed of 3000 rpm for 30 minutes. Then collect the dispersed catalyst slurry and degas it to obtain the first catalytic slurry.

[0068] 8.0 g of Tec10E50e-HT 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) of Japan), 20.0 g of 20 wt% perfluorosulfonic acid resin dispersion, 12.4 g of n-propanol, and 59.6 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the stirred water and stirred for 5 minutes. The perfluorosulfonic acid resin dispersion D2020 was then added and stirred for 2 minutes. The n-propanol was then added and stirred for another 2 minutes to complete the pre-dispersion of the slurry. The slurry was dispersed in a Beads mill at 3000 rpm for 30 minutes. The dispersed catalyst slurry was then collected and deaerated to obtain a second catalytic slurry with a viscosity of 146 cP and a dielectric constant of 60.0.

[0069] S2-S4: Same as Example 1.

[0070] When the sample is coated under static conditions (the proton exchange membrane is fixed on the substrate and does not move before drying is completed) using the method of this embodiment, there is no obvious gap or pore between the first catalytic layer and the second catalytic layer in the obtained semi-CCM containing the cathode double-layer catalytic layer, the two are well combined, and the second catalytic layer is easy to coat evenly; however, when the method of this embodiment is used for continuous roll-to-roll rapid coating (coating line speed ≥ 3 meters / minute), although there is no obvious gap or pore between the first catalytic layer and the second catalytic layer, the second catalytic layer is prone to uneven coating. This is because the viscosity of the second layer slurry is too high, resulting in unstable pressure on the coating die head during large-scale production, resulting in inconsistent slurry discharge volume, thereby affecting coating unevenness.

[0071] Example 5

[0072] S1: Weigh 5.1 g of Tec10E50e 50 wt% Pt / C catalyst (TKK, Japan), 12.8 g of 20 wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the stirred water and stir for 5 minutes. Then add the perfluorosulfonic acid resin dispersion D2020 and stir for 2 minutes. Then add ethanol and continue stirring for 2 minutes to complete the pre-dispersion of the slurry. Disperse the slurry using a Beads mill at a speed of 3000 rpm for 30 minutes. Then collect the dispersed catalyst slurry and degas it to obtain the first catalytic slurry.

[0073] Weigh 1.0 g of Tec10E50e-HT 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) of Japan), 4.0 g of 20 wt% perfluorosulfonic acid resin dispersion, 12.4 g of n-propanol, and 59.6 g of ultrapure water. The Pt / C catalyst was slowly added to the stirred water and stirred for 5 minutes. The perfluorosulfonic acid resin dispersion D2020 was then added and stirred for 2 minutes. The n-propanol was then added and stirred for another 2 minutes to complete the pre-dispersion of the slurry. The slurry was dispersed in a Beads mill at 3000 rpm for 30 minutes. The dispersed catalyst slurry was then collected and degassed to obtain a second catalytic slurry with a viscosity of ~2 cP and a dielectric constant of ~60.0.

[0074] S2-S4: Same as Example 1.

[0075] When the method of this embodiment is used to prepare static samples, there is no obvious gap or pore between the first catalytic layer and the second catalytic layer in the obtained semi-CCM containing a double-layer cathode catalytic layer, the two are well combined, and the second catalytic layer is easy to coat evenly; when the method of this embodiment is used for continuous roll-to-roll rapid coating production (coating line speed ≥ 3 meters / minute), although there is no obvious gap or pore between the first catalytic layer and the second catalytic layer, the second catalytic layer is prone to uneven coating. This is because the viscosity of the second layer slurry is too low and it is easy to flow. In the roll-to-roll continuous large-scale coating process, the proton membrane is moving, and the airflow of the drying gas is large, which easily causes the slurry to flow disorderly during the drying process, resulting in uneven coating.

[0076] Example 6

[0077] S1: Weigh 5.1 g of Tec10E50e 50 wt% Pt / C catalyst (TKK, Japan), 12.8 g of 20 wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the stirred water and stir for 5 minutes. Then add the perfluorosulfonic acid resin dispersion D2020 and stir for 2 minutes. Then add ethanol and continue stirring for 2 minutes to complete the pre-dispersion of the slurry. Disperse the slurry using a Beads mill at a speed of 3000 rpm for 30 minutes. Then collect the dispersed catalyst slurry and degas it to obtain the first catalytic slurry.

[0078] 3.9 g of Tec10E50e-HT 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) of Japan), 10.5 g of 20 wt% perfluorosulfonic acid resin dispersion, 0.6 g of ethanol, and 85.0 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the stirred water and stirred for 5 minutes. The perfluorosulfonic acid resin dispersion D2020 was then added and stirred for 2 minutes. Ethanol was then added and stirred for another 2 minutes to complete the pre-dispersion of the slurry. The slurry was dispersed in a Beads mill at 3000 rpm for 30 minutes. The dispersed catalyst slurry was then collected and degassed to obtain a second catalytic slurry with a viscosity of 14.2 cP and a dielectric constant of ~74.8.

[0079] S2-S4: Same as Example 1.

[0080] When the method of this embodiment is used for continuous roll-to-roll rapid coating production (coating line speed ≥ 3 m / min), there is no obvious gap or pore between the first catalytic layer and the second catalytic layer in the obtained semi-CCM containing the cathode double-layer catalytic layer, and the two are well combined.

[0081] Example 7

[0082] S1: Weigh 10.0 g of Tec10E50e 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) of Japan), 40 g of 20 wt% perfluorosulfonic acid resin dispersion, 19.2 g of ethanol, and 40.8 g of ultrapure water. Slowly add the Pt / C catalyst to the stirred water and stir for 5 minutes. Then add the perfluorosulfonic acid resin dispersion D2020 and stir for 2 minutes. Then, add ethanol and continue stirring for 2 minutes to complete the pre-dispersion of the slurry. Disperse the slurry using a Beads mill at a speed of 3000 rpm for 30 minutes. Then, collect the dispersed catalyst slurry and degas it to obtain the first catalytic slurry.

[0083] 8.0 g of Tec10E50e-HT 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) of Japan), 30 g of 20 wt% perfluorosulfonic acid resin dispersion, 14.4 g of n-butanol, and 47.6 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the stirred water and stirred for 5 minutes. The perfluorosulfonic acid resin dispersion D2020 was then added and stirred for 2 minutes. The n-butanol was then added and stirred for another 2 minutes to complete the pre-dispersion of the slurry. The slurry was dispersed in a Beads mill at 3000 rpm for 30 minutes. The dispersed catalyst slurry was then collected and degassed to obtain a second catalytic slurry with a viscosity of ~75 cP and a dielectric constant of ~51.0.

[0084] S2-S4: Same as Example 1.

[0085] When static intermittent coating is performed using the method of this embodiment, there is no obvious gap or pore between the first catalytic layer and the second catalytic layer in the obtained half CCM containing the cathode double-layer catalytic layer. The two are well combined, and the second catalytic layer is easy to coat evenly.

[0086] Example 8

[0087] S1: Weigh 2.4 g of Tec10E50e 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) of Japan), 4 g of 20 wt% perfluorosulfonic acid resin dispersion, 0.5 g of ethanol, and 93.1 g of ultrapure water. Slowly add the Pt / C catalyst to the stirred water and stir for 5 minutes. Then add the perfluorosulfonic acid resin dispersion D2020 and stir for 2 minutes. Then, add ethanol and continue stirring for 2 minutes to complete the pre-dispersion of the slurry. Disperse the slurry using a Beads mill at a speed of 3000 rpm for 30 minutes. Then, collect the dispersed catalyst slurry and degas it to obtain the first catalytic slurry.

[0088] 3g of Tec10E50e-HT 50wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) of Japan), 4g of 20wt% perfluorosulfonic acid resin dispersion, 2.4g of n-butanol, and 67.6g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the stirred water and stirred for 5 minutes. The perfluorosulfonic acid resin dispersion D2020 was then added and stirred for 2 minutes. The n-butanol was then added and stirred for another 2 minutes to complete the pre-dispersion of the slurry. The slurry was dispersed in a Beads mill at 3000 rpm for 30 minutes. The dispersed catalyst slurry was then collected and deaerated to obtain a second catalytic slurry with a viscosity of ~70 cP and a dielectric constant of ~54.6.

[0089] S2-S4: Same as Example 1.

[0090] When the static gap coating of the sample is performed using the method of this embodiment, there is no obvious gap or pore between the first catalytic layer and the second catalytic layer in the obtained half CCM containing the cathode double-layer catalytic layer. The two are well combined, and the second catalytic layer is easy to coat evenly.

[0091] Comparative Example 1

[0092] S1: Weigh 5.1 g of Tec10E50e 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) of Japan), 12.8 g of 20 wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the stirred water and stir for 5 minutes. Then add the perfluorosulfonic acid resin dispersion and stir for 2 minutes. Then, add ethanol and continue stirring for 2 minutes to complete the pre-dispersion of the slurry. Disperse the slurry using a Beads mill at a speed of 3000 rpm for 30 minutes. Then, collect the dispersed catalyst slurry and degas it to obtain the first catalytic slurry.

[0093] S2: The first catalytic slurry prepared in S1 is coated on one side of the proton exchange membrane by slot coating, and then baked at 80°C until it becomes non-flowable to obtain a semi-CCM containing the first cathode catalytic layer, wherein the Pt loading of the first catalytic layer is 300 μg / cm 2 , thickness is ∼10 μm;

[0094] S3: The anode catalyst slurry is coated on the side of the proton exchange membrane without the catalytic layer by a slit coating method. The anode catalyst slurry and its preparation method are the same as those in Example 1, with a loading of 100 μg / cm 2 , forming CCM, which is further assembled to form membrane electrode and fuel cell.

[0095] Comparative Example 2

[0096] S1: Weigh 5.1 g of Tec10E50e 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) of Japan), 12.8 g of 20 wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the stirred water and stir for 5 minutes. Then add the perfluorosulfonic acid resin dispersion and stir for 2 minutes. Then, add ethanol and continue stirring for 2 minutes to complete the pre-dispersion of the slurry. Disperse the slurry using a Beads mill at a speed of 3000 rpm for 30 minutes. Then, collect the dispersed catalyst slurry and degas it to obtain the first catalytic slurry.

[0097] 5.1 g of Tec10E50e-HT 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) of Japan), 14.0 g of 20 wt% perfluorosulfonic acid resin dispersion, 11.0 g of n-butanol, and 48.8 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the stirred water and stirred for 5 minutes. The perfluorosulfonic acid resin dispersion D2020 was then added and stirred for 2 minutes. The n-butanol was then added and stirred for another 2 minutes to complete the pre-dispersion of the slurry. The slurry was dispersed in a Beads mill at 3000 rpm for 30 minutes. The dispersed catalyst slurry was then collected and degassed to obtain a second catalytic slurry with a viscosity of 85 cP and a dielectric constant of ~54.6. S2: The first catalytic slurry prepared in S1 is coated on one side of the proton exchange membrane by slot coating, and then baked at 80°C until it becomes non-flowable to obtain a semi-CCM containing the first cathode catalytic layer, wherein the Pt loading of the first catalytic layer is 150 μg / cm 2 , with a thickness of 5μm; the second catalytic slurry was coated on the PTFE membrane by slit coating and dried at 80°C to form a second catalytic layer. The Pt loading of the catalytic layer was 150μg / cm 2 , with a thickness of 4.5μm.

[0098] S3: The catalytic layer on the PTFE is transferred to the first catalytic layer by a hot pressing transfer method to obtain a double-layer catalytic layer.

[0099] S4: The anode catalyst slurry is coated on the side of the proton exchange membrane without the catalytic layer by a slit coating method. The anode catalyst slurry and its preparation method are the same as those in Example 1. The coating loading is 100 μg / cm 2 , forming CCM, which is further assembled to form membrane electrode and fuel cell.

[0100] Comparative Example 3

[0101] S1: The preparation method of the first catalytic slurry is the same as that of Example 1;

[0102] 6.1 g of Tec10E50e-HT 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) Co., Ltd.), 16.8 g of a 20 wt% perfluorosulfonic acid resin dispersion, 19.7 g of tert-butyl alcohol, and 36.3 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the stirred water and stirred for 5 minutes. The perfluorosulfonic acid resin dispersion was then added and stirred for 2 minutes. The tert-butyl alcohol was then added and stirred for another 2 minutes to complete the pre-dispersion of the slurry. The slurry was dispersed in a Beads mill at 3000 rpm for 30 minutes. The dispersed catalyst slurry was then collected and degassed to obtain a second catalytic slurry with a viscosity of 26.0 cP and a dielectric constant of ~38.4.

[0103] S2: The first catalytic slurry prepared in S1 is coated on one side of the proton exchange membrane by slot coating, and then baked at 80°C until it becomes non-flowable to obtain a semi-CCM containing the first cathode catalytic layer, wherein the Pt loading of the first catalytic layer is 150 μg / cm 2 , thickness is ∼5 μm;

[0104] S3: The second catalytic slurry prepared in S1 is coated on the first catalytic layer by the slot coating method and dried at 80°C until it becomes non-flowable to form the second catalytic layer. A semi-CCM containing a cathode double-layer catalytic layer is obtained. The Pt loading of the second catalytic layer is 150 μg / cm 2 , thickness is ∼4.5 μm;

[0105] S4: The anode catalyst slurry is coated on the side of the proton exchange membrane without the catalytic layer by a slit coating method. The anode catalyst slurry and its preparation method are the same as those in Example 1, and the loading is 100 μg / cm 2 , forming CCM, which is further assembled to form membrane electrode and fuel cell.

[0106] Comparative Example 4

[0107] S1: The preparation method of the first catalytic slurry is the same as that of Example 1;

[0108] 6.1 g of Tec10E50e-HT 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) Co., Ltd.), 16.8 g of a 20 wt% perfluorosulfonic acid resin dispersion, 12.8 g of n-propanol, and 43.2 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the stirred water and stirred for 5 minutes. The perfluorosulfonic acid resin dispersion was then added and stirred for 2 minutes. The n-propanol was then added and stirred for another 2 minutes to complete the pre-dispersion of the slurry. The slurry was dispersed in a Beads mill at 3000 rpm for 30 minutes. The dispersed catalyst slurry was then collected and deaerated to obtain a second catalytic slurry with a viscosity of 196.2 cP and a dielectric constant of ~52.3.

[0109] S2: The first catalytic slurry prepared in S1 is coated on one side of the proton exchange membrane by slot coating, and then baked at 80°C until it becomes non-flowable to obtain a semi-CCM containing the first cathode catalytic layer, wherein the Pt loading of the first catalytic layer is 150 μg / cm 2 , thickness is ∼5 μm;

[0110] S3: The second catalytic slurry prepared in S1 is coated on the first catalytic layer by the slot coating method and dried at 80°C until it becomes non-flowable to form the second catalytic layer. A semi-CCM containing a cathode double-layer catalytic layer is obtained. The Pt loading of the second catalytic layer is 150 μg / cm 2 , thickness is ∼4.5 μm;

[0111] S4: The anode catalyst slurry is coated on the side of the proton exchange membrane without the catalytic layer by a slit coating method. The anode catalyst slurry and its preparation method are the same as those in Example 1, and the loading is 100 μg / cm 2 , forming CCM, which is further assembled to form membrane electrode and fuel cell.

[0112] Comparative Example 5

[0113] S1: The preparation method of the first catalytic slurry is the same as that of Example 1;

[0114] 3.2 g of Tec10E50e-HT 50 wt% Pt / C catalyst (produced by Tanaka Kikinzoku (TKK) Co., Ltd.), 8.7 g of a 20 wt% perfluorosulfonic acid resin dispersion, 1.5 g of ethylene glycol, and 86.5 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the stirred water and stirred for 5 minutes. The perfluorosulfonic acid resin dispersion was then added and stirred for 2 minutes. The ethylene glycol was then added and stirred for another 2 minutes to complete the pre-dispersion of the slurry. The slurry was dispersed in a Beads mill at 3000 rpm for 30 minutes. The dispersed catalyst slurry was then collected and deaerated to obtain a second catalytic slurry with a viscosity of 16.0 cP and a dielectric constant of ~78.3.

[0115] S2: The first catalytic slurry prepared in S1 is coated on one side of the proton exchange membrane by slot coating, and then baked at 80°C until it becomes non-flowable to obtain a semi-CCM containing the first cathode catalytic layer, wherein the Pt loading of the first catalytic layer is 150 μg / cm 2 , thickness is ∼5 μm;

[0116] S3: The second catalytic slurry prepared in S1 is coated on the first catalytic layer by the slot coating method and dried at 80°C until it becomes non-flowable to form the second catalytic layer. A semi-CCM containing a cathode double-layer catalytic layer is obtained. The Pt loading of the second catalytic layer is 150 μg / cm 2 , thickness is ∼4.5 μm;

[0117] S4: The anode catalyst slurry is coated on the side of the proton exchange membrane without the catalytic layer by a slit coating method. The anode catalyst slurry and its preparation method are the same as those in Example 1, and the loading is 100 μg / cm 2 , forming CCM, which is further assembled to form membrane electrode and fuel cell.

[0118] Effect Examples

[0119] The cathode double-layer catalyst layer or fuel cell obtained in each example and comparative example was subjected to performance testing. The high-frequency resistance and polarization curve testing methods were as follows: Power density (polarization curve test) was determined in accordance with Section 11.2 of GB / T 28817-2012. Test procedure: The sample was formed into an MEA of appropriate size and placed in a cell fixture, which was then connected to a test bench. Nitrogen was introduced to both sides of the cell for purge, and the cell temperature was raised to 68°C. After reaching the set temperature, hydrogen (2 L / min) and air (5 L / min) were introduced to the anode and cathode of the cell, respectively, at a humidity An / Ca = 71% / 97% RH and a back pressure An / Ca = 190 / 150 kPa. The cell was activated at 2.4 A / cm² for 5 hours. The IV characteristic curve was measured at a constant gas flow rate. Each current point was maintained for 10 minutes, and the data for the last minute were averaged. The test equipment simultaneously automatically recorded the high-frequency impedance.

[0120] Some of the test results can be found in Figures 1 to 5 .

[0121] from Figure 1 From the cross-sectional SEM images of the double-layer catalytic layer structures prepared by different methods, it can be seen that there is no obvious gap or large pore between the two catalytic layers formed by stacked direct coating, and the two catalytic layers are well bonded; while in the two-layer catalytic layer structure formed by the first layer direct coating and the second layer transfer method, there are obvious pores between the first layer and the second layer. The existence of these pores easily increases the overall impedance of the catalytic layer and easily becomes a flooded area when the fuel cell is running.

[0122] from Figure 2 The measured high-frequency resistance of dual-layer catalytic membrane electrodes prepared by different methods shows that the resistance of the dual-layer catalytic membrane electrode formed by direct coating the first layer and transferring the second layer is greater than that of the dual-layer catalytic membrane electrode formed by direct coating. This further demonstrates that the dual-layer catalytic membrane electrode formed by direct coating has a better bond between the two catalytic layers.

[0123] from Figure 3 It can be seen from the polarization curves of the embodiments and comparative examples that, compared with the membrane electrode with only one layer structure (Comparative Example 1), the use of a double-layer structure can significantly improve the performance of the membrane electrode; comparing the different implementation methods of the double-layer structure, the membrane electrode with a double-layer catalytic layer structure prepared by two stacked direct coating methods has obvious performance advantages over the membrane electrode prepared by directly coating one layer and transferring the other layer.

[0124] from Figure 4It can be seen that when the dielectric constant of the catalyst slurry solvent used for the second layer coating is between 50-75, a two-layer direct coating process can be used to directly prepare a membrane electrode with a two-layer catalytic layer structure; when the dielectric constant of the second layer catalyst slurry is less than 50 (Comparative Example 3), coating the second layer will cause the catalytic layer to crack and the catalytic layer to separate from the proton membrane. Figure 5 It can be seen that when the dielectric constant of the second catalyst slurry is greater than 75 (Comparative Example 5), the second layer coating will result in uneven coating.

[0125] Further, from Figure 5 It can be seen that when the viscosity of the catalyst slurry used for the second layer coating is 196 cP (the dielectric constant of the slurry solvent is 52.3), although the coated second layer slurry can form a second catalytic layer on the first catalytic layer, the second catalytic layer is very uneven.

[0126] This shows that when a continuous double-layer direct coating process is used to prepare a membrane electrode with a double-layer catalytic layer structure, it is necessary to control the viscosity of the second layer catalyst slurry and the dielectric constant of the slurry solvent.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a catalyst coating membrane, characterized in that: The following steps are involved: preparing a catalyst slurry for preparing the first catalytic layer, a catalyst slurry for preparing each layer of the second catalytic layer, and a catalyst slurry for preparing each layer of the third catalytic layer; The catalyst slurry used to prepare the first catalytic layer is coated on the first surface of the proton exchange membrane and dried to form the first catalytic layer. Then, each catalyst slurry used to prepare the second catalytic layer is sequentially coated and dried to form the second catalytic layer, wherein the coating method is a slit coating method, the first catalytic layer is located on the first surface of the proton exchange membrane, and the second catalytic layer is located on the surface of the first catalytic layer away from the proton exchange membrane, and the second catalytic layer comprises at least one layer; Coating at least one catalytic layer on the second surface of the proton exchange membrane to form a third catalytic layer, wherein the third catalytic layer comprises at least one layer; The viscosity of the catalyst slurry used to prepare each layer of the second catalytic layer is less than 150 cP, and the dielectric constant of the solvent is 50-75 to obtain a catalyst coating film.

2. The method for preparing a catalyst coating membrane according to claim 1, wherein: The viscosity of the catalyst slurry used to prepare each layer of the second catalytic layer is 5-85 cP.

3. The method for preparing a catalyst coating membrane according to claim 1, wherein: The first catalytic layer and the second catalytic layer belong to the cathode catalytic layer of the PEM fuel cell.

4. The method for preparing a catalyst coating membrane according to claim 1, wherein: The material of the proton exchange membrane includes perfluorosulfonic acid resin.

5. The method for preparing a catalyst coating membrane according to claim 1, wherein: The catalyst slurry used to prepare the first catalytic layer and the catalyst slurry used to prepare each layer of the second catalytic layer both include a catalyst, a perfluorosulfonic acid resin and a solvent, and the solvent includes an organic solvent and water.

6. The method for preparing a catalyst coating membrane according to claim 5, wherein: The catalyst in the catalyst slurry used to prepare the first catalytic layer and the catalyst slurry used to prepare each layer of the second catalytic layer includes at least one of Pt / C and PtM / C, wherein M in PtM / C is at least one of Co, Ni, Cu, Au, Ag, Ir, Ru, Cr, and Fe.

7. The method for preparing a catalyst coating membrane according to claim 1, wherein: At least one of the conditions (a)-(b) is met: (a) preparing the first catalytic layer using a catalyst slurry comprising the following components in percentage by weight: 2.4-10% catalyst, 0.8-8% perfluorosulfonic acid resin, 0.5-40% alcohol solvent, and the remainder being water; wherein the dry weight ratio of perfluorosulfonic acid resin to catalyst in the catalyst slurry used in the first catalytic layer is 1:1-0.2:1; (b) The catalyst slurry used to prepare the second catalytic layer comprises the following components in percentage by weight: 3-8% catalyst, 0.8-6% perfluorosulfonic acid resin, 0.5-40% alcohol solvent, and the remainder water; wherein the dry weight ratio of the perfluorosulfonic acid resin to the catalyst in the catalyst slurry used to prepare the second catalytic layer is less than or equal to 1.6 times the dry weight ratio of the perfluorosulfonic acid resin to the catalyst in the first catalyst slurry.

8. The method for preparing a catalyst coating membrane according to claim 1, wherein: The thickness of each layer of the second catalytic layer and the first catalytic layer is 0.1 to 30 μm, and the platinum loading is 10 to 500 μg / cm2.

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