Cathode catalyst layer, preparation method thereof and fuel cell

Abstract

The invention relates to a cathode catalyst layer, a preparation method thereof and a fuel cell. The cathode catalyst layer comprises a cobalt-based MOFs material, a catalyst and an ionomer, the cobalt-based MOFs material comprises any one of Co-MOF-74, ZIF-67 or Co3 (BTC) 2 or a combination of at least two of the Co-MOF-74, the ZIF-67 and the Co3 (BTC) 2. The cobalt-based MOFs with oxygen adsorption capacity are added into the cathode catalyst layer, and the cobalt-based MOFs have an annular structure of which the molecular diameter is close to that of oxygen, so that the adsorption capacity of the cathode catalyst layer in the membrane electrode to the oxygen can be enhanced, the oxygen can reach catalytic active sites more easily through a flow channel and a gas diffusion layer, and the performance is improved; on the other hand, Co < 2 + > / Co < 3 + > in the cobalt-based MOFs has certain oxidation-reduction capacity, and the power density of the membrane electrode is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a cathode catalyst layer, a preparation method thereof, and a fuel cell. Background Art

[0002] The efficient transport of hydrogen, oxygen, electrons, protons, and water within a proton exchange membrane fuel cell (PEMFC) is crucial for the power generation performance of the catalyst layer. The transport of these substances is primarily influenced by the microstructure of the catalyst layer, such as the pore structure for gas diffusion, the structure of carbon particles for electron conduction, and the ion channels in the ionomer for proton conduction. The fuel cell membrane electrode (MEA) is the core component of the fuel cell. The catalytic layer in the MEA is the site for chemical reactions that generate electrical energy, and its performance is directly affected by oxygen concentration. As a cathode reactant, changes in oxygen concentration significantly affect the electrochemical reaction rate, mass transfer, and overall fuel cell efficiency.

[0003] CN119627123A discloses a carboxylporphyrin-containing catalyst slurry, its preparation method, and application, relating to the field of proton exchange membrane fuel cells. The carboxylporphyrin-containing catalyst slurry comprises a carboxylporphyrin compound, a platinum-based catalyst, a perfluorosulfonic acid electrolyte, water, and an alcohol. The carboxylporphyrin compound exhibits a dual-effect synergistic effect of oxygen adsorption and proton transfer in the platinum-based catalyst, enhancing fuel cell activity. This invention introduces carboxyl-containing porphyrins, which have a modest improvement in fuel cell performance. However, the carboxyl structure of the carboxylporphyrin further exacerbates the acidity of the catalyst layer environment, impacting membrane electrode durability.

[0004] CN115449834A discloses a catalyst with an amorphous shell, comprising a crystalline matrix and an amorphous shell coated on the surface of the crystalline matrix; the thickness of the amorphous shell is 0.5 nm to 5 nm. This invention belongs to the field of catalyst preparation technology. The crystalline matrix in the catalyst can maintain the structural stability of the catalyst at high oxidation potentials, and the disordered atomic arrangement in the amorphous shell can enhance catalytic activity. However, this catalyst is primarily used in electrolytic cell anodes and fuel cell anti-reverse electrodes, and the structure of the amorphous shell may affect the catalytic effect in the fuel cell catalyst layer.

[0005] The cathode in proton exchange membrane fuel cells requires a large amount of platinum-based catalysts. The use of a large amount of platinum-based catalysts leads to high costs of fuel cells. In order to reduce the cost of catalysts and at the same time improve the electrochemical reaction rate and fuel cell performance, it is necessary to develop a new membrane electrode catalyst layer.

[0006] The electrochemical reaction rate in the catalyst layer of the fuel cell membrane electrode is closely related to the oxygen concentration in the catalyst layer. Therefore, how to increase the oxygen concentration in the membrane electrode catalyst layer to improve fuel cell performance has become an urgent problem to be solved. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention aims to provide a cathode catalyst layer, a preparation method thereof and a fuel cell. The cathode catalyst layer of the present invention enhances the adsorption of oxygen by the membrane electrode cathode catalyst layer by adding cobalt-based MOFs with oxygen adsorption capacity, so that oxygen can more easily reach the catalytic active sites through the flow channel and the gas diffusion layer, thereby improving performance. On the other hand, the Co in the cobalt-based MOFs 2+ / Co 3+ It has a certain redox ability, which helps to further improve the performance of the cathode catalyst layer and membrane electrode.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a cathode catalyst layer, which includes a cobalt-based MOFs material, a catalyst and an ionomer; the cobalt-based MOFs material includes any one of Co-MOF-74, ZIF-67 or Co3(BTC)2 or a combination of at least two of them.

[0010] The cathode catalyst layer provided by the present invention is added with cobalt-based MOFs having oxygen adsorption capacity. On the one hand, the diameter of the ring structure of the cobalt-based MOFs selected by the present invention is about 0.34nm, which is close to the molecular diameter of oxygen 0.341nm, and has oxygen adsorption function, which can enhance the oxygen adsorption capacity of the cathode catalyst layer in the membrane electrode, making it easier for oxygen to reach the catalytic active sites through the flow channel and the gas diffusion layer, thereby improving performance. On the other hand, the Co in the cobalt-based MOFs 2+ / Co 3+ It has a certain redox ability, which helps to further improve the performance of membrane electrode.

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0012] Preferably, the mass ratio of the carbon support to the cobalt-based MOFs material in the catalyst is 1:(0.05-0.15), for example, it can be 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14 or 1:0.15, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0013] The present invention further controls the mass ratio of the carbon support to the cobalt-based MOFs material in the catalyst to be 1:(0.05-0.15). This mass ratio affects both the catalyst's ability to adsorb oxygen and the transmission of oxygen to the surface of the catalytic active sites. If too much cobalt-based MOFs material is added, it will adhere to the catalyst surface, covering the active sites, reducing the catalytic efficiency and affecting the performance; if too little cobalt-based MOFs material is added, it will not play a role in improving the oxygen adsorption capacity.

[0014] Preferably, the cobalt-based MOFs material accounts for 1wt%-5wt% of the total mass of the cathode catalyst layer, for example, it can be 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0015] Preferably, the ionomer accounts for 20wt%-30wt% of the total mass of the cathode catalyst layer, for example, it can be 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt% or 30wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] Preferably, the carbon support accounts for 30wt%-40wt% of the total mass of the cathode catalyst layer, for example, it can be 30wt%, 32wt%, 34wt%, 35wt%, 36wt%, 38wt% or 40wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, the average particle size of the cobalt-based MOFs is 50 nm-500 nm, for example, 50 nm, 80 nm, 90 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or 500 nm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0018] The present invention further controls the average particle size of cobalt-based MOFs to be 50nm-500nm. If the average particle size of cobalt-based MOFs is too large, it will cause instability of the catalytic layer. During the membrane electrode preparation process, it will collapse under hot pressure and affect the gas channel. If the average particle size of cobalt-based MOFs is too small, cobalt-based MOFs will be filled between the catalyst carbon support particles to form a relatively dense cathode catalyst layer membrane structure, blocking the micropores and mesopores in the catalyst layer, and also affecting the transmission of oxygen from the gas diffusion layer to the catalytic layer and the active sites, thereby reducing performance.

[0019] Preferably, the catalyst comprises a Pt / C catalyst or a Pt alloy catalyst, wherein platinum accounts for 50 wt% to 70 wt% of the total mass of the catalyst.

[0020] Preferably, the platinum accounts for 30wt%-40wt% of the total mass of the cathode catalyst layer, for example, it can be 30wt%, 32wt%, 34wt%, 35wt%, 36wt%, 38wt% or 40wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] Preferably, the Pt loading in the cathode catalyst layer is 0.2 mg / cm 2 -0.4mg / cm 2 , for example, it can be 0.2 mg / cm 2 , 0.25mg / cm 2 , 0.3mg / cm 2 , 0.35mg / cm 2 or 0.4 mg / cm 2 , but not limited to the listed values, other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, the ionomer comprises any one or a combination of at least two of perfluorosulfonic acid ionomer (such as Nafion), metal-doped ionomer (such as PtRu-doped Nafion) or composite ionomer (such as Nafion-PANI, Nafion-Silica, Nafion-PSA). Typical but non-limiting combinations include a combination of perfluorosulfonic acid ionomer and metal-doped ionomer, a combination of metal-doped ionomer and composite ionomer, a combination of perfluorosulfonic acid ionomer and composite ionomer, and a combination of perfluorosulfonic acid ionomer, metal-doped ionomer and composite ionomer.

[0023] In a second aspect, the present invention provides a method for preparing a cathode catalyst layer as described in the first aspect, the method comprising the following steps:

[0024] Cobalt-based MOFs material, catalyst, ionomer solution and solvent are mixed to obtain cathode catalyst layer slurry; the cathode catalyst layer slurry is coated on a substrate to obtain a cathode catalyst layer.

[0025] The preparation method of the present invention is simple and efficient, matches the existing production process, and is suitable for large-scale production.

[0026] Preferably, the mass fraction of the ionomer solution is 20 wt%-50 wt%, for example, it can be 20 wt%, 22 wt%, 25 wt%, 28 wt%, 30 wt%, 32 wt%, 35 wt%, 38 wt%, 40 wt%, 42 wt%, 45 wt%, 48 wt% or 50 wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0027] Preferably, the mass ratio of the solvent to water is 1:(3-6), for example, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5 or 1:6, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] Preferably, the solvent comprises any one of water, n-propanol or isopropanol, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of water and n-propanol, a combination of n-propanol and isopropanol, a combination of water and isopropanol, and a combination of water, n-propanol and isopropanol.

[0029] Preferably, the solid content of the cathode catalyst layer slurry is 0.5%-5%, for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] Preferably, the mixing method includes ultrasound.

[0031] Preferably, the substrate comprises a proton exchange membrane.

[0032] Preferably, the temperature of the ultrasound is 2°C-10°C, for example, it can be 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C or 10°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, the ultrasonic time is 0.5h-3h, for example, 0.5h, 1h, 1.5h, 2h, 2.5h or 3h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, the coating method includes ultrasonic spraying.

[0035] Preferably, the cathode catalyst layer slurry is coated on a substrate, and drying is further performed before obtaining the cathode catalyst layer.

[0036] Preferably, the drying temperature is 40°C-80°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, the drying time is 5 min-30 min, for example, 5 min, 10 min, 15 min, 20 min, 25 min or 30 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises the following steps:

[0039] (1) mixing a cobalt-based MOFs material, a catalyst, an ionomer solution, and a solvent, and ultrasonically mixing the mixture at 2° C. to 10° C. for 0.5 h to 3 h to obtain a cathode catalyst layer slurry having a solid content of 1% to 50%, wherein the mass ratio of the carbon support in the catalyst to the cobalt-based MOFs material is 1:(0.05-0.15);

[0040] (2) Ultrasonic spraying the cathode catalyst layer slurry obtained in step (1) onto the proton exchange membrane, and drying at 40° C.-80° C. for 5 min-30 min to obtain the cathode catalyst layer.

[0041] In a third aspect, the present invention provides a fuel cell membrane electrode, which comprises the cathode catalyst layer described in the first aspect or the cathode catalyst layer prepared by the preparation method described in the second aspect.

[0042] The fuel cell membrane electrode provided by the present invention has a strong oxygen adsorption capacity and a high battery power density. The other structural membrane layers in the fuel cell membrane electrode provided by the present invention are prepared using raw materials and methods known in the art. For example, the structure may include a seven-layer structure comprising a gas diffusion layer, a PEN frame, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, a PEN frame, and a gas diffusion layer, stacked in sequence.

[0043] In a fourth aspect, the present invention provides a fuel cell comprising the fuel cell membrane electrode according to the third aspect.

[0044] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0045] Compared with the prior art, the present invention has at least the following beneficial effects:

[0046] (1) The present invention can enhance the oxygen adsorption capacity of the cathode catalyst layer in the membrane electrode by adding cobalt-based MOFs with oxygen adsorption capacity to the cathode catalyst layer, thereby increasing the oxygen adsorption power inside the cathode catalyst layer, making it easier for oxygen to reach the catalytic active sites through the flow channel and the gas diffusion layer, thereby improving performance; on the other hand, the Co in the cobalt-based MOFs 2+ / Co 3+ It has a certain redox ability, and the power density of the membrane electrode is further improved.

[0047] (2) The fuel cell membrane electrode provided by the present invention has a strong oxygen adsorption capacity and a high battery power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a polarization curve diagram of the membrane electrode prepared in Example 1 of the present invention;

[0049] Figure 2 is a polarization curve diagram of the membrane electrode prepared in Example 4 of the present invention;

[0050] Figure 3 is a polarization curve diagram of the membrane electrode prepared in Example 5 of the present invention;

[0051] Figure 4 This is a polarization curve diagram of the membrane electrode prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0052] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0053] In the following examples and comparative examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the field. Unless otherwise specified, the experimental methods and technical means used were conventional methods and means in the field. The gas diffusion layer used was the commercial JNTG brand, the catalyst was the commercial JM9100 60 wt% Pt content Pt / C catalyst, the Nafion ionomer was a DuPont product, and the proton membrane was the commercial Nafion 112 proton membrane. Other chemical reagents, such as isopropyl alcohol, were sourced from Sinopharm Chemical Reagent Co., Ltd. and Aladdin Chemical Reagent Co., Ltd.

[0054] Example 1

[0055] The present embodiment provides a cathode catalyst layer, which includes ZIF-67 with an average particle size of 200 nm, a Pt / C catalyst, and a Nafion D520 ionomer. The mass ratio of the carbon support to the ZIF-67 in the Pt / C catalyst is 1:0.1; the ZIF-67 accounts for 3 wt% of the total mass of the cathode catalyst layer, and the ionomer accounts for 25 wt% of the total mass of the cathode catalyst layer; the Pt loading of the cathode catalyst layer is 0.3 mg / cm 2 .

[0056] The method for preparing the cathode catalyst layer provided in this embodiment comprises the following steps:

[0057] (1) ZIF-67, Pt / C catalyst, 5 wt% Nafion D520 solution, isopropanol, and water were mixed and ultrasonically mixed at 10°C for 2 h to obtain a cathode catalyst layer slurry with a solid content of 2%;

[0058] (2) Ultrasonic spraying of the cathode catalyst layer slurry obtained in step (1) onto the proton exchange membrane, and drying at 60° C. for 10 min to obtain a cathode catalyst layer.

[0059] Example 2

[0060] The present embodiment provides a cathode catalyst layer, wherein the cathode catalyst layer includes Co-MOF-74 with an average particle size of 100 nm, a Pt / C catalyst, and a Nafion D520 ionomer, wherein the mass ratio of the carbon support to the Co-MOF-74 in the Pt / C catalyst is 1:0.06; the Co-MOF-74 accounts for 2 wt% of the total mass of the cathode catalyst layer, and the ionomer accounts for 20 wt% of the total mass of the cathode catalyst layer; the Pt loading of the cathode catalyst layer is 0.2 mg / cm 2 .

[0061] The method for preparing the cathode catalyst layer provided in this embodiment comprises the following steps:

[0062] (1) Co-MOF-74, Pt / C catalyst, 5 wt% Nafion D520 solution, n-propanol, and water were mixed and ultrasonically mixed at 5°C for 1 h to obtain a cathode catalyst layer slurry with a solid content of 1%;

[0063] (2) Ultrasonic spraying of the cathode catalyst layer slurry obtained in step (1) onto the proton exchange membrane, and drying at 50° C. for 30 min to obtain a cathode catalyst layer.

[0064] Example 3

[0065] The present embodiment provides a cathode catalyst layer, which includes Co3(BTC)2 with an average particle size of 480 nm, a Pt / C catalyst, and a Nafion NR212 ionomer. The mass ratio of the carbon support to Co3(BTC)2 in the Pt / C catalyst is 1:0.15; Co3(BTC)2 accounts for 4 wt% of the total mass of the cathode catalyst layer, and the ionomer accounts for 30 wt% of the total mass of the cathode catalyst layer; the Pt loading of the cathode catalyst layer is 0.4 mg / cm 2 .

[0066] The method for preparing the cathode catalyst layer provided in this embodiment comprises the following steps:

[0067] (1) Co3(BTC)2, Pt / C catalyst, 5 wt% Nafion NR212 solution, isopropanol, and water were mixed and ultrasonically mixed at 2°C for 3 h to obtain a cathode catalyst layer slurry with a solid content of 4%;

[0068] (2) Ultrasonic spraying the cathode catalyst layer slurry obtained in step (1) onto the proton exchange membrane, and drying at 80° C. for 5 minutes to obtain a cathode catalyst layer.

[0069] Example 4

[0070] This embodiment provides a cathode catalyst layer, which is different from Example 1 only in that the mass ratio of the carbon support to the cobalt-based MOFs material in the catalyst is 1:0.2.

[0071] Example 5

[0072] This embodiment provides a cathode catalyst layer, which is different from Example 1 only in that the mass ratio of the carbon support to the cobalt-based MOFs material in the catalyst is 1:0.01.

[0073] Example 6

[0074] This embodiment provides a cathode catalyst layer, which is different from the embodiment 1 only in that the average particle size of the cobalt-based MOFs is 1 μm.

[0075] Example 7

[0076] This embodiment provides a cathode catalyst layer, which differs from the embodiment 1 only in that the average particle size of the cobalt-based MOFs is 30 nm.

[0077] Comparative Example 1

[0078] This comparative example provides a cathode catalyst layer, which differs from Example 1 only in that, when preparing the cathode catalyst layer, no cobalt-based MOFs material is added in step (1).

[0079] Comparative Example 2

[0080] This comparative example provides a cathode catalyst layer, which differs from Example 1 only in that, when preparing the cathode catalyst layer, step (1) is replaced by an equal amount of cerium-based MOFs material (Ce-MOF-74).

[0081] Comparative Example 3

[0082] This comparative example provides a cathode catalyst layer, which differs from Example 1 only in that, when preparing the cathode catalyst layer, step (1) is replaced by an equal amount of iron-based MOFs material (Fe-MIL-88B).

[0083] Application Example 1

[0084] This application example provides a fuel cell membrane electrode, which includes a seven-layer structure of a gas diffusion layer, a PEN frame, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, a PEN frame and a gas diffusion layer stacked in sequence.

[0085] The method for preparing the fuel cell membrane electrode comprises the following steps:

[0086] (3) Preparation of anode catalyst layer slurry: The raw materials used in the preparation differ from those used in the cathode catalyst layer slurry in Example 1 only in that no cobalt-based MOFs material is added. The remaining preparation methods are the same as in Example 1. After ultrasonic spraying and drying, the anode catalyst layer is obtained.

[0087] (4) using a PEN frame to seal and bond the three-layer membrane electrode obtained in (3) to form a five-layer membrane electrode;

[0088] (5) A JNTG gas diffusion layer is bonded to the five-layer membrane electrode obtained in (4) to obtain a fuel cell membrane electrode.

[0089] The polarization curve of the membrane electrode of the cathode catalyst layer prepared in Application Example 1 is as follows: Figure 1 As shown, from Figure 1 It can be seen that the membrane electrode exhibits a high power density (1.3W / cm 2 ).

[0090] Application Example 2-Application Example 7

[0091] Application Examples 2 to 7 respectively provide a fuel cell membrane electrode. The difference between the fuel cell membrane electrode and Application Example 1 is that the cathode catalyst layer in the above-mentioned Examples 2 to 7 is respectively adopted, and the corresponding anode catalyst layer is adjusted accordingly according to the composition and preparation method of the cathode catalyst layer.

[0092] The polarization curve of the membrane electrode of the cathode catalyst layer prepared in Application Example 4-Application 5 is as follows: Figure 2-Figure 3 As shown, from Figure 2 and Figure 3 It can be seen that the power density of the membrane electrode is 1.25W / cm 2 and 1.2W / cm 2 , which is lower than that of Example 1.

[0093] Comparative Application Example 1-Comparative Application Example 3

[0094] Comparative Application Examples 1 to 3 respectively provide a fuel cell membrane electrode. The difference between the fuel cell membrane electrode and Application Example 1 is that the cathode catalyst layer in the above-mentioned Comparative Examples 1 to 3 is respectively adopted, and the corresponding anode catalyst layer is adjusted accordingly according to the composition and preparation method of the cathode catalyst layer.

[0095] The polarization curve of the membrane electrode of the cathode catalyst layer prepared in comparative application example 1 is shown in FIG. Figure 4 As shown, from Figure 4 It can be seen that the power density of the membrane electrode is 1.18W / cm 2 , which are all decreased compared with the embodiment.

[0096] Test method: The fuel cell membrane electrode prepared in the corresponding use case and comparative application example was tested. The test results are shown in Table 1 below.

[0097] Table 1

[0098]

[0099]

[0100] The test results show that:

[0101] (1) It can be seen from Examples 1 to 3 that the present invention can enhance the oxygen adsorption capacity of the cathode catalyst layer in the membrane electrode by adding cobalt-based MOFs with oxygen adsorption capacity to the cathode catalyst layer, thereby increasing the oxygen adsorption power inside the cathode catalyst layer, making it easier for oxygen to reach the catalytic active sites through the flow channel and the gas diffusion layer, thereby improving performance; on the other hand, the Co in the cobalt-based MOFs 2+ / Co 3+ It has a certain redox ability, and the power density of the membrane electrode is further improved.

[0102] (2) By comparing Example 1 with Example 4-Example 5, it can be seen that the present invention further controls the mass ratio of the carbon support to the cobalt-based MOFs material in the catalyst to be 1:(0.05-0.15). This mass ratio affects both the adsorption capacity of oxygen and the transmission of oxygen to the surface of the catalytic active sites. If the amount of cobalt-based MOFs material added is too much, it will adhere to the catalyst surface, cover the active sites, reduce the catalytic efficiency, and affect the performance; if the amount of cobalt-based MOFs material added is too little, it cannot play a role in improving the oxygen adsorption capacity.

[0103] (3) By comparing Example 1 with Example 6-Example 7, it can be seen that the present invention further controls the average particle size of cobalt-based MOFs to 50nm-500nm. If the average particle size of cobalt-based MOFs is too large, it will cause instability of the catalytic layer. During the membrane electrode preparation process, it will collapse under hot pressure and affect the gas channel; if the average particle size of cobalt-based MOFs is too small, cobalt-based MOFs will be filled between the catalyst carbon support particles to form a relatively dense cathode catalyst layer membrane structure, blocking the micropores and mesopores in the catalyst layer, and also affecting the transmission of oxygen from the gas diffusion layer to the catalyst layer and the active sites, thereby reducing performance.

[0104] (4) It can be seen from Example 1 and Comparative Example 1 that if cobalt-based MOFs are not added to the cathode catalyst layer, the power density of the fuel cell will decrease and the performance will be inferior to that of the example.

[0105] (5) It can be seen from Example 1 and Comparative Examples 2-3 that when other metal-based MOFs are used, the power density is greatly reduced. This is because the cerium-based or iron-based MOFs materials not only do not have additional redox couples, but also further inhibit the catalytic activity of the Pt catalyst. On the other hand, iron ions are prone to Fenton effect in the catalytic layer, destroying the proton membrane and the ionomers in the catalytic layer, while destroying the carbon carrier, reducing the transmission of protons and electrons, and failing to achieve further improvement in the membrane electrode performance.

[0106] In summary, the present invention can enhance the oxygen adsorption capacity of the cathode catalyst layer in the membrane electrode by adding cobalt-based MOFs with oxygen adsorption capacity to the cathode catalyst layer, thereby increasing the oxygen adsorption power inside the cathode catalyst layer, making it easier for oxygen to reach the catalytic active sites through the flow channel and the gas diffusion layer, thereby improving performance; on the other hand, the Co in the cobalt-based MOFs 2+ / Co 3+ It has a certain redox ability, and the power density of the membrane electrode is further improved.

[0107] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A cathode catalyst layer, characterized in that: The cathode catalyst layer includes a cobalt-based MOFs material, a catalyst and an ionomer; The cobalt-based MOFs material includes any one of Co-MOF-74, ZIF-67 or Co3(BTC)2 or a combination of at least two thereof.

2. The cathode catalyst layer according to claim 1, characterized in that The mass ratio of the carbon support to the cobalt-based MOFs material in the catalyst is 1:(0.05-0.15); Preferably, the cobalt-based MOFs material accounts for 1wt%-5wt% of the total mass of the cathode catalyst layer; Preferably, the ionomer accounts for 20 wt% to 30 wt% of the total mass of the cathode catalyst layer.

3. The cathode catalyst layer according to claim 1 or 2, characterized in that: The average particle size of the cobalt-based MOFs is 50 nm to 500 nm.

4. The cathode catalyst layer according to claim 1, characterized in that The catalyst includes a Pt / C catalyst or a Pt alloy catalyst; Preferably, the ionomer includes any one of perfluorosulfonic acid ionomer, metal-doped ionomer or composite ionomer, or a combination of at least two thereof.

5. A method for preparing a cathode catalyst layer according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: Cobalt-based MOFs material, catalyst, ionomer solution and solvent are mixed to obtain cathode catalyst layer slurry; the cathode catalyst layer slurry is coated on a substrate to obtain a cathode catalyst layer.

6. The preparation method according to claim 5, characterized in that The mass fraction of the ionomer solution is 20wt%-50wt%; Preferably, the solvent includes any one of water, n-propanol or isopropanol, or a combination of at least two of them.

7. The preparation method according to claim 5 or 6, characterized in that: The solid content of the cathode catalyst layer slurry is 0.5%-5%; Preferably, the substrate comprises a proton exchange membrane.

8. The preparation method according to any one of claims 5 to 7, characterized in that The cathode catalyst layer slurry is coated on a substrate, and drying is also included before obtaining the cathode catalyst layer.

9. A fuel cell membrane electrode, characterized in that: The fuel cell membrane electrode comprises the cathode catalyst layer according to any one of claims 1 to 4 or the cathode catalyst layer prepared by the preparation method according to any one of claims 5 to 8.

10. A fuel cell, characterized in that: The fuel cell comprises the fuel cell membrane electrode according to claim 9.

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