Cathode catalytic membrane and preparation method thereof, membrane electrode, fuel cell

Abstract

The application relates to a cathode catalytic membrane and a preparation method thereof, a membrane electrode and a fuel cell. The cathode catalytic membrane comprises a first catalytic layer, a second catalytic layer and a third catalytic layer which are stacked in sequence, the components of the first catalytic layer, the second catalytic layer and the third catalytic layer all comprise ion polymers and carbon-supported catalysts, and all have porous structures; the carbon-supported catalysts comprise carbon carriers and catalysts supported on the carbon carriers; the mass ratio of the ion polymer to the carbon carrier in the first catalytic layer is > the mass ratio of the ion polymer to the carbon carrier in the second catalytic layer > the mass ratio of the ion polymer to the carbon carrier in the third catalytic layer; the average pore diameter of the porous structure in the first catalytic layer and the third catalytic layer is larger than the average pore diameter of the porous structure in the second catalytic layer. The catalytic membrane can improve the activity of the membrane electrode, and further improve the efficiency of the fuel cell.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, and in particular to a cathode catalytic membrane and its preparation method, a membrane electrode, and a fuel cell. Background Technology

[0002] A fuel cell is a device that directly converts the chemical energy of fuel into electrical energy. It boasts high energy density and energy conversion efficiency, low pollution, and is considered an ideal power source for the future. A membrane fuel cell mainly consists of a proton exchange membrane, cathode / anode catalyst layers, cathode / anode gas diffusion layers, and cathode / anode frames. The proton exchange membrane, cathode / anode catalyst layers, and gas diffusion layers form the membrane electrode assembly (MEA). The MEA is the site where chemical reactions occur and electrical energy is generated, playing a major role in the performance and lifespan of the fuel cell. The catalyst layer is the core of the electrochemical reaction and plays a crucial role in the conversion of chemical energy into electrical energy.

[0003] Traditional fuel cell catalyst layers typically consist of Pt / C catalyst particles, Nafion ionomers, and numerous irregular porous structures. These pores are formed by the solidification of solvents in the catalyst slurry after evaporation. During fuel cell operation, the porous structure of the catalyst layer determines the efficiency of gas transport and water transfer within the layer. With increasing current density during fuel cell operation, problems such as water blockage and membrane flooding, as well as insufficient gas flow, frequently occur, affecting the activity of the membrane electrode assembly (MEA) and consequently negatively impacting fuel cell efficiency. Furthermore, traditional MEAs have limited drainage and gas transport capabilities, reducing their activity and efficiency, and failing to meet the increasingly stringent performance requirements of proton exchange membrane fuel cells.

[0004] Therefore, traditional technologies still need improvement. Summary of the Invention

[0005] Based on this, the present invention provides a cathode catalytic membrane and its preparation method, a membrane electrode, and a fuel cell. The catalytic membrane can improve the activity of the membrane electrode, thereby improving the efficiency of the fuel cell.

[0006] In one aspect, this application provides a cathode catalytic membrane comprising a first catalytic layer, a second catalytic layer, and a third catalytic layer stacked sequentially. The components of the first catalytic layer, the second catalytic layer, and the third catalytic layer all include ionomers and carbon-supported catalysts, and all have porous structures. The carbon-supported catalyst includes a carbon support and a catalyst supported on the carbon support.

[0007] The mass ratio of the ionic polymer to the carbon support in the first catalyst layer is greater than the mass ratio of the ionic polymer to the carbon support in the second catalyst layer, which is greater than the mass ratio of the ionic polymer to the carbon support in the third catalyst layer.

[0008] The average pore size of the porous structures in the first catalyst layer and the third catalyst layer is greater than the average pore size of the porous structures in the second catalyst layer.

[0009] The aforementioned cathode catalytic membrane comprises a first catalytic layer, a second catalytic layer, and a third catalytic layer stacked sequentially. The mass ratio of ionomer to carbon support (I / C ratio) is controlled to decrease in each of the three catalytic layers, thereby controlling the specific distribution trend of porous structures in each layer. Simultaneously, the pore sizes of the porous structures in the first and third catalytic layers are controlled to be larger than those in the second catalytic layer, forming a unique macropore-micropore-macropore pore distribution structure. When applied to the fabrication of membrane electrode assemblies (MEAs) and subsequently fuel cells, on the one hand, the specific porous structure distribution trend and unique pore size structure in the cathode catalytic membrane allow the MEA to absorb moisture from the micropores even in low-humidity environments, ensuring effective proton transport. On the other hand, under high current density, the generated moisture can effectively diffuse through the micropores of the second catalytic layer to the macropores of the third catalytic layer, or rapidly diffuse to the anode through concentration gradient.

[0010] In some embodiments, the average pore size of the porous structure in the first catalyst layer is 50 nm to 200 nm; and / or

[0011] The average pore size of the porous structure in the second catalyst layer is 5 nm to 30 nm; and / or

[0012] The average pore size of the porous structure in the third catalyst layer is 20 nm to 100 nm.

[0013] In some embodiments, the mass ratio of the ionic polymer to the carbon support in the first catalyst layer is (1.1–1.4):1; and / or

[0014] In the second catalyst layer, the mass ratio of the ionomer to the carbon support is (0.8–1.2):1; and / or

[0015] In the third catalyst layer, the mass ratio of the ion polymer to the carbon support is (0.5–0.9):1.

[0016] In some embodiments, the carbon-supported catalyst includes a carbon support and a metal catalyst supported on the carbon support;

[0017] The loading of the metal catalyst in the first catalyst layer is K1 mg / cm³. 2The loading of the metal catalyst in the second catalyst layer is K2 mg / cm³. 2 The loading of the metal catalyst in the third catalyst layer is K3 mg / cm³. 2 ;

[0018] K1 < K3 < K2.

[0019] In some embodiments, the ratio of K1, K2 and K3 is 1:(1.8 to 3):(1.2 to 1.8).

[0020] In another aspect, the present invention provides a method for preparing the above-described cathode catalytic membrane, comprising the following steps:

[0021] A first catalytic slurry, a second catalytic slurry, and a third catalytic slurry are provided. The components of the first catalytic slurry, the second catalytic slurry, and the third catalytic slurry all include ionomers and carbon-supported catalysts. The carbon-supported catalysts include a carbon support and a catalyst supported on the carbon support. The components of the first catalytic slurry also include a pore-forming agent.

[0022] Wherein, the mass ratio of the ionic polymer to the carbon support in the first catalytic slurry is greater than the mass ratio of the ionic polymer to the carbon support in the second catalytic slurry, which is greater than the mass ratio of the ionic polymer to the carbon support in the third catalytic slurry;

[0023] The cathode catalytic membrane is obtained by sequentially using the first catalytic slurry, the second catalytic slurry, and the third catalytic slurry to form a first catalytic layer, a second catalytic layer, and a third catalytic layer on a substrate.

[0024] In some embodiments, the components of the first catalytic slurry, the second catalytic slurry, and the third catalytic slurry all include a dispersant and a solvent, and the mass ratio of the dispersant to the solvent in the first catalytic slurry, the second catalytic slurry, and the third catalytic slurry is (1-10):1, (1-10):1, and (1-10):1, respectively; and / or

[0025] In the first catalytic slurry, the mass ratio of the pore-forming agent to the carbon-supported catalyst is (0.35~2.85):1.

[0026] In another aspect, the present invention provides a membrane electrode comprising a proton exchange membrane, an anodic catalytic membrane and a cathode catalytic membrane as described above, wherein the anodic catalytic membrane and the cathode catalytic membrane are respectively located on opposite sides of the proton exchange membrane, and the first catalytic layer in the cathode catalytic membrane is closer to the proton exchange membrane than the third catalytic layer.

[0027] The aforementioned membrane electrode includes a proton exchange membrane, an anode catalytic membrane, and a cathode catalytic membrane as described above. The anode and cathode catalytic membranes are located on opposite sides of the proton exchange membrane, and the first catalytic layer in the cathode catalytic membrane is close to the proton exchange membrane. Thus, the specific porous structure distribution trend and special pore size structure in the cathode catalytic membrane enable the membrane electrode to absorb water from the small pores even in low humidity environments, ensuring effective proton transport. On the other hand, under high current density, the generated water can effectively diffuse through the small pore structure of the second catalytic layer in the cathode catalytic membrane to the large pore structure in the third catalytic layer. During drainage, even if more water accumulates, the pores still meet the requirements for water drainage and gas transport, thereby improving the activity of the membrane electrode.

[0028] In some embodiments, the anodic catalyst membrane includes a first anodic catalyst layer and a second anodic catalyst layer stacked sequentially, wherein the first anodic catalyst layer is closer to the proton exchange membrane than the second anodic catalyst layer;

[0029] The first anode catalyst layer and the second anode catalyst layer are both composed of ion polymers and carbon-supported catalysts, and both have porous structures. The carbon-supported catalyst includes a carbon support and a catalyst supported on the carbon support.

[0030] The mass ratio of the ionic polymer to the carbon support in the first anode catalyst layer is greater than the mass ratio of the ionic polymer to the carbon support in the second anode catalyst layer;

[0031] The average pore size of the porous structure in the first anode catalyst layer is smaller than the average pore size of the porous structure in the second anode catalyst layer.

[0032] Thus, a reaction gradient catalytic layer with three cathode sections and two anode sections is formed in the membrane electrode, improving the utilization rate of the catalyst. In the first and second anode catalytic layers, the mass ratio of ion polymer to carbon support decreases. At the same time, the pore size of the porous structure in the first anode catalytic layer is controlled to be smaller than that in the second anode catalytic layer. Under high current density, the water generated in the membrane electrode can diffuse effectively from the small pore structure of the second catalytic layer in the cathode catalytic membrane to the macropore structure in the third catalytic layer, or it can diffuse rapidly from the small pore structure of the first anode catalytic layer in the anode catalytic membrane through the concentration gradient, and then be discharged through the macropore structure of the second anode catalytic layer, further avoiding "flooding" and improving the activity of the membrane electrode.

[0033] In some embodiments, the mass ratio of the ionomer to the carbon support in the first anode catalyst layer is (0.7–1.3):1, and / or

[0034] In the first anode catalyst layer, the mass ratio of the ion polymer to the carbon support is (0.5-10):1.

[0035] In some embodiments, the carbon-supported catalyst in the first anode catalyst layer and the second anode catalyst layer includes a carbon support and a metal catalyst supported on the carbon support;

[0036] The loading of the metal catalyst in the first anode catalyst layer is T1 mg / cm³. 2 The loading of the metal catalyst in the second anode catalyst layer is T2 mg / cm³. 2 T1 > T2.

[0037] In some embodiments, the ratio of T1 to T2 is 1:(0.4 to 0.8).

[0038] In another aspect, the present invention provides a fuel cell comprising a membrane electrode assembly as described above.

[0039] The aforementioned fuel cells have high activity and high efficiency. Attached Figure Description

[0040] Figure 1 This is a structural diagram of a membrane electrode in one embodiment.

[0041] Explanation of reference numerals in the attached figures:

[0042] 1. Fuel cell; 10. Proton exchange membrane; 20. Cathode catalyst membrane; 21. First catalyst layer; 22. Second catalyst layer; 23. Third catalyst layer; 30. Anode catalyst membrane; 31. First anode catalyst layer; 32. Second anode catalyst layer. Detailed Implementation

[0043] To facilitate understanding of the present invention, a more comprehensive description will be provided below. Preferred embodiments of the invention are given in specific examples. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0045] As described in the background section, traditional membrane electrodes have limited drainage and gas transport capabilities. In order to improve the drainage and gas transport capabilities of membrane electrodes, conventional techniques often control the hydrophobicity or porosity of the cathode catalytic layer in the cathode catalytic membrane to make it have an increasing or decreasing trend. Functional additives are often required, such as hydrophobic agents, to improve hydrophobicity. However, in order to maintain the high catalytic efficiency and activity of the cathode catalytic layer itself, the amount of functional additives such as hydrophobic agents can be limited, resulting in a limited ability to improve the hydrophobicity of the cathode catalytic layer.

[0046] Through extensive practical production and research, the technicians of this invention have discovered that the single-gradient design used in traditional technologies has poor water retention in the membrane electrode assembly (MEA), thus affecting the energy conversion of the fuel cell. After numerous experimental investigations, the technicians of this application have obtained the cathode catalytic membrane described in this application, which improves the activity of the MEA and thereby enhances the efficiency of the fuel cell. The specific technical solution is as follows.

[0047] One embodiment of the present invention provides a cathode catalytic membrane, which includes a first catalytic layer, a second catalytic layer and a third catalytic layer stacked sequentially. The components of the first catalytic layer, the second catalytic layer and the third catalytic layer all include ionomers and carbon-supported catalysts, and all have a porous structure. The carbon-supported catalyst includes a carbon support and a catalyst supported on the carbon support.

[0048] The mass ratio of ionic polymer to carbon support in the first catalyst layer is greater than that in the second catalyst layer, which is greater than that in the third catalyst layer.

[0049] The average pore size of the porous structures in the first and third catalyst layers is greater than that in the second catalyst layer.

[0050] It should be noted that, as long as the average pore size of the porous structure in the first catalyst layer is greater than that in the second catalyst layer, and the average pore size of the porous structure in the third catalyst layer is greater than that in the second catalyst layer, there are no particular restrictions on the relative size of the average pore size of the porous structure in the first catalyst layer and the average pore size of the porous structure in the third catalyst layer.

[0051] The aforementioned cathode catalytic membrane comprises a first catalytic layer, a second catalytic layer, and a third catalytic layer stacked sequentially. The mass ratio of ionomer to carbon support (I / C ratio) is controlled to decrease in each of the three catalytic layers, thereby controlling the specific distribution trend of porous structures in each layer. This improves the conductivity within the cathode catalytic membrane and near its interface. Simultaneously, the average pore size of the porous structures in the first and third catalytic layers is controlled to be larger than that in the second catalytic layer, forming a unique macropore-micropore-macropore pore distribution structure. When applied to the fabrication of membrane electrode assemblies (MEAs) and subsequently fuel cells, on the one hand, the specific porous structure distribution trend and unique pore size structure in the cathode catalytic membrane allow the MEA to absorb moisture from the micropores, ensuring effective proton transport even in low-humidity environments. On the other hand, under high current densities, the generated moisture can effectively diffuse through the micropores of the second catalytic layer to the macropores of the third catalytic layer, or rapidly diffuse to the anode due to concentration gradient.

[0052] In practical applications, in the aforementioned cathode catalytic membrane, the third catalytic layer has a large-pore structure with a small I / C ratio, located near the gas diffusion layer, which provides better electron conduction performance and the ability to transport gas and moisture. The middle second catalytic layer has a small-pore structure with an I / C ratio between the first and second catalytic layers, and has a capillary-like effect. The water generated in the second catalytic layer can flow into the first catalytic layer with the gas, thereby wetting the proton exchange membrane. At the same time, the water generated in the first catalytic layer can be quickly discharged to avoid flooding.

[0053] In some embodiments, the average pore size of the porous structure in the first catalyst layer is 50 nm to 200 nm.

[0054] In some embodiments, the average pore size of the porous structure in the second catalyst layer is 5 nm to 30 nm.

[0055] In some embodiments, the average pore size of the porous structure in the third catalyst layer is 20 nm to 100 nm.

[0056] In some embodiments, the mass ratio of ionomer to carbon support in the first catalyst layer is (1.1–1.4):1.

[0057] In some embodiments, the mass ratio of ionomer to carbon support in the second catalyst layer is (0.8–1.2):1.

[0058] In some embodiments, the mass ratio of ionomer to carbon support in the third catalyst layer is (0.5–0.9):1.

[0059] In some embodiments, the carbon-supported catalyst includes a carbon support and a metal catalyst supported on the carbon support; the loading of the metal catalyst in the first catalyst layer is K1 mg / cm³. 2 The loading of the metal catalyst in the second catalyst layer is K2 mg / cm³. 2 The loading of the metal catalyst in the third catalyst layer is K3 mg / cm³. 2 .

[0060] K1 < K3 < K2.

[0061] It is understandable that the loading of metal catalyst in the first catalyst layer, the third catalyst layer, and the second catalyst layer shows an increasing trend. That is, among the three catalyst layers of the cathode catalytic membrane, the second catalyst layer contains the largest loading of metal catalyst.

[0062] By controlling the variation trend of the loading of metal catalysts in each of the first, third, and second catalyst layers, the utilization efficiency of the catalyst is improved, and the catalytic activity of the membrane electrode is further enhanced.

[0063] In some embodiments, the ratio of K1, K2 and K3 is 1:(1.8 to 3):(1.2 to 1.8).

[0064] In some embodiments, K1 is selected from any value of (0.02 to 0.05), K2 is selected from any value of (0.1 to 0.2), and K3 is selected from any value of (0.04 to 0.08).

[0065] In some embodiments, the carbon support is made of carbon black, including but not limited to: Vulcan XC-72R and / or Ketjen carbon black.

[0066] In some embodiments, the metal catalysts include, but are not limited to, Pt and Co. Specific carbon-supported catalysts include, but are not limited to, Pt / C catalysts or Pt-Co / C catalysts.

[0067] In some embodiments, the mass percentage of the metal catalyst in the carbon-supported catalyst is 30 wt% to 60 wt%.

[0068] One embodiment of this application also provides a method for preparing the above-mentioned cathode catalytic membrane, including the following steps S10 to S20.

[0069] Step S10: Provide a first catalytic slurry, a second catalytic slurry, and a third catalytic slurry. The components of the first catalytic slurry, the second catalytic slurry, and the third catalytic slurry all include ionomers and carbon-supported catalysts. The carbon-supported catalyst includes a carbon support and a catalyst supported on the carbon support. The components of the first catalytic slurry also include a pore-forming agent.

[0070] Among them, the mass ratio of ionic polymer to carbon support in the first catalytic slurry is greater than that in the second catalytic slurry, which is greater than that in the third catalytic slurry.

[0071] Step S20: The first catalytic layer, the second catalytic layer, and the third catalytic layer are sequentially formed on the substrate using the first catalytic slurry, the second catalytic slurry, and the third catalytic slurry to obtain a cathode catalytic membrane.

[0072] By controlling the mass ratio of ionic polymer to carbon support to decrease in the first, second, and third catalytic slurries, on the one hand, the mass ratio of ionic polymer to carbon support decreases in each of the three catalytic layers, and on the other hand, a porous structure is initially formed. Generally, the smaller the I / C ratio, the larger the pore size of the formed porous structure. Furthermore, by adding a pore-forming agent to the first catalytic layer slurry, the pore size of the formed porous structure can be increased, so that the pore size of the porous structure in the first and third catalytic layers is larger than that in the second catalytic layer.

[0073] In some embodiments, the pore-forming agent material includes at least one of ammonium salts such as ammonium bicarbonate, ammonium carbonate, ammonium acetate, and ammonium chloride.

[0074] The aforementioned pore-forming agent undergoes thermal decomposition during heating, thereby forming pores.

[0075] In some embodiments, the mass ratio of pore-forming agent to carbon-supported catalyst in the first catalytic slurry is (0.35–2.85):1.

[0076] In some embodiments, the components of the first catalytic slurry, the second catalytic slurry and the third catalytic slurry all include a dispersant and a solvent, and the mass ratios of the dispersant and the solvent in the first catalytic slurry, the second catalytic slurry and the third catalytic slurry are (1-10):1, (1-10):1 and (1-10):1, respectively.

[0077] In some of these embodiments, the solvent is water.

[0078] In some embodiments, the dispersant includes at least one of ethanol, isopropanol, and n-propanol.

[0079] In some embodiments, the ionomer is added in the form of an aqueous solution, and the mass concentration of the resulting ionomer solution is 5 wt% to 30 wt%.

[0080] In some embodiments, the solid content of the first catalytic slurry is 1 wt% to 5 wt%.

[0081] In some embodiments, the solid content of the second catalyst slurry is 0.8 wt% to 4.2 wt%.

[0082] In some embodiments, the solid content of the first catalytic slurry is 0.4 wt% to 3.6 wt%.

[0083] In some embodiments, the ionomer is a perfluorosulfonic acid resin.

[0084] Please refer to Figure 1 According to one embodiment of this application, a membrane electrode 1 is provided, which includes a proton exchange membrane 10, an anodic catalytic membrane 30 and a cathode catalytic membrane 20 as described above, wherein the anodic catalytic membrane 30 and the cathode catalytic membrane 20 are respectively located on both sides of the proton exchange membrane 10.

[0085] Specifically, the cathode catalytic membrane 20 includes a first catalytic layer 21, a second catalytic layer 22 and a third catalytic layer 23 stacked sequentially, and the first catalytic layer 21 in the cathode catalytic membrane 20 is closer to the proton exchange membrane 10 than the third catalytic layer 23.

[0086] In the aforementioned membrane electrode 10, the specific porous structure distribution trend and special pore size structure in the cathode catalytic membrane 20 enable the membrane electrode to absorb water from the small pores even in low humidity environments, ensuring effective proton transport. On the other hand, under high current density, the generated water can effectively diffuse through the small pore structure of the second catalytic layer in the cathode catalytic membrane to the macropore structure in the third catalytic layer. During the drainage process, even if more water accumulates, the pores still meet the requirements for water drainage and gas transport, thereby improving the activity of the membrane electrode.

[0087] Please continue to refer to this. Figure 1 In some embodiments, the anodic catalyst membrane 30 includes a first anodic catalyst layer 31 and a second anodic catalyst layer 32 stacked sequentially, wherein the first anodic catalyst layer 31 is closer to the proton exchange membrane 10 than the second anodic catalyst layer 32.

[0088] The first anode catalyst layer 31 and the second anode catalyst layer 32 are both composed of ion polymers and carbon-supported catalysts, and both have porous structures. The carbon-supported catalyst includes a carbon support and a catalyst supported on the carbon support.

[0089] The mass ratio of ion polymer to carbon support in the first anode catalyst layer 31 is greater than that in the second anode catalyst layer 32.

[0090] Furthermore, the average pore size of the porous structure in the first anode catalyst layer 31 is smaller than the average pore size of the porous structure in the second anode catalyst layer 32.

[0091] Thus, a reaction gradient catalytic layer with three cathode sections and two anode sections is formed in the membrane electrode 1, improving the utilization rate of the catalyst. In the first anode catalytic layer 31 and the second anode catalytic layer 32, the mass ratio of ion polymer and carbon support decreases. At the same time, the average pore size of the porous structure in the first anode catalytic layer 31 is controlled to be smaller than that in the second anode catalytic layer 32. Under high current density, the water generated in the membrane electrode 1 can be effectively diffused through the small pore structure of the second catalytic layer 22 in the cathode catalytic membrane 21 to the macroporous structure in the third catalytic layer 23, or it can be rapidly diffused through the concentration gradient to the small pore structure of the first anode catalytic layer 31 in the anode catalytic membrane 30, and then discharged through the macroporous structure of the second anode catalytic layer 32, further avoiding "flooding" and improving the activity of the membrane electrode.

[0092] The first anode catalyst layer 31, which is close to the proton exchange membrane 10, is a microporous catalyst layer with a small pore size and a high I / C ratio, providing a relatively high proton conductivity and promoting the diffusion of water generated at the cathode to the anode. The second anode catalyst layer 32 is a macroporous catalyst layer with a large pore size and a low I / C ratio, which further promotes the discharge of water that has diffused to the anode.

[0093] The main function of the proton exchange membrane 10 is to separate the oxidant from the reducing agent and conduct ions. Commonly used proton exchange membranes in the art can be used. Specific examples include commercially available proton exchange membranes such as Nafion 211, Nafion 212, HP, XL100, NC700, and Gore.

[0094] In some embodiments, the average pore size of the porous structure in the first anode catalyst layer 31 is 5–30 nm.

[0095] In some embodiments, the average pore size of the porous structure in the second anode catalyst layer 32 is 20–100 nm.

[0096] In some embodiments, the mass ratio of the ion polymer to the carbon support in the first anode catalyst layer 31 is (0.7 to 1.3):1.

[0097] In some embodiments, the mass ratio of the ion polymer to the carbon support in the first anode catalyst layer 32 is (0.5–10):1.

[0098] In some embodiments, the carbon-supported catalysts in the first anode catalyst layer 31 and the second anode catalyst layer 32 include a carbon support and a metal catalyst supported on the carbon support.

[0099] The loading of the metal catalyst in the first anode catalyst layer 31 is T1 mg / cm³. 2 The loading of the metal catalyst in the second anode catalyst layer is T2 mg / cm³. 2 T1 > T2. T1 is selected from any value between 0.03 and 0.06, and T2 is selected from any value between 0.01 and 0.02.

[0100] In some embodiments, the ratio of T1 to T2 is 1:(0.4 to 0.8).

[0101] In some embodiments, the carbon-supported catalysts in the cathode catalytic membrane 20 and the anode catalytic membrane 30 include a carbon support and a metal catalyst supported on the carbon support.

[0102] In the cathode catalytic membrane 20, the loading of the metal catalyst is 0.18 mg / cm³. 2 ~0.24mg / cm 2 In the anodic catalytic membrane 30, the loading of the metal catalyst is 0.04 mg / cm³. 2 ~0.06mg / cm 2 .

[0103] In a specific example, the metal catalyst is Pt.

[0104] In some embodiments, the membrane electrode 10 further includes a cathode diffusion layer ( Figure 1 (not shown in the image) and the anode diffusion layer ( Figure 1 (Not shown in the image), the cathode diffusion layer is located on the side of the cathode catalytic membrane 20 away from the proton exchange membrane 10, and the anode diffusion layer is located on the side of the anode catalytic membrane 30 away from the proton exchange membrane 10, and is used for gas diffusion.

[0105] In another embodiment of the present invention, a fuel cell is provided, the fuel cell including the membrane electrode as described above.

[0106] The aforementioned fuel cell also includes an electrode frame.

[0107] The aforementioned fuel cells have high activity and high efficiency.

[0108] The present invention will now be described with reference to specific embodiments. However, the present invention is not limited to the embodiments described below. It should be understood that the appended claims summarize the scope of the present invention. Under the guidance of the inventive concept, those skilled in the art should realize that any changes made to the various embodiments of the present invention will be covered by the spirit and scope of the claims of the present invention.

[0109] The following are specific examples.

[0110] Example 1

[0111] (1) Preparation of cathode catalyst slurry:

[0112] Preparation of the first catalyst layer slurry: Weigh 0.1g of platinum carbon catalyst with a platinum content of 40wt%, add 5g of deionized water, and then add dropwise an ionomer solution containing 84mg of ionomer (concentration of 10wt%) to make the I / C ratio 1.4:1. Then add 32mg of ammonium bicarbonate solid, disperse evenly by ultrasonication in an ice bath, and then add 9g of isopropanol dropwise. Mix evenly by ultrasonication in an ice bath, and then use a high-speed emulsifying shear machine to strongly disperse for 30min at a dispersion speed of 20000r / min to obtain the first catalyst layer slurry to be sprayed.

[0113] Preparation of the second catalyst layer slurry: Weigh 0.1g of platinum-carbon catalyst with a platinum content of 50wt%, add 5g of deionized water, and then add dropwise an ionomer solution containing 55mg of ionomer (concentration of 10wt%) to make the I / C ratio 1.1:1. After uniformly dispersing by ultrasonication in an ice bath, add 13g of isopropanol dropwise and mix evenly by ultrasonication in an ice bath. Perform strong dispersion for 30min using a high-speed emulsifying shear machine at a dispersion speed of 20000r / min to obtain the second catalyst layer slurry to be sprayed.

[0114] Preparation of the third catalyst layer slurry: Weigh 0.1g of platinum-carbon catalyst with a platinum content of 40wt%, add 5g of deionized water, and then add dropwise an ionomer solution containing 48mg of ionomer (concentration of 10wt%) to make the I / C ratio 0.8:1. After uniformly dispersing by ultrasonication in an ice bath, add 20g of isopropanol dropwise and mix evenly by ultrasonication in an ice bath. Perform strong dispersion for 30min using a high-speed emulsifying shear machine at a dispersion speed of 20000r / min to obtain the third catalyst layer slurry to be sprayed.

[0115] (2) Preparation of anode catalyst slurry:

[0116] Preparation of the first anode catalyst layer slurry: Weigh 0.1g of platinum-carbon catalyst with a platinum content of 50wt%, add 5g of deionized water, and then add dropwise an ionomer solution containing 60mg of ionomer (concentration of 10%) to make the I / C ratio 1.2:1. After uniformly dispersing by ultrasonication in an ice bath, add 13g of isopropanol dropwise and mix evenly by ultrasonication in an ice bath. Then, perform strong dispersion for 30min using a high-speed emulsifying shear machine at a dispersion speed of 20000r / min to obtain the first anode catalyst layer slurry to be sprayed.

[0117] Preparation of the second anode catalyst slurry: Weigh 0.1g of platinum carbon catalyst with a platinum content of 40wt%, add 5g of deionized water, and then add dropwise an ionomer solution containing 48mg of ionomer (concentration of 10wt%) to make the I / C ratio 0.8:1. After uniformly dispersing by ultrasonication in an ice bath, add 20g of isopropanol dropwise and mix evenly by ultrasonication in an ice bath. Then, perform strong dispersion for 30min using a high-speed emulsifying shear machine at a dispersion speed of 20000r / min to obtain the second anode catalyst slurry to be sprayed.

[0118] (3) Fabrication of membrane electrodes:

[0119] The first catalyst slurry prepared above was sprayed onto one side of the proton exchange membrane using an ultrasonic spraying machine, dried at 80°C to form the first catalyst layer, and the pore size of the first catalyst layer was tested, specifically referring to: GB / T20042.4-2009 Proton Exchange Membrane Fuel Cells Part 4: Electrocatalyst Test Methods, using the BET test method.

[0120] The second catalyst slurry was sprayed onto the first catalyst layer and dried at 80°C to form the second catalyst layer. The pore size of the second catalyst layer was tested, and the specific results are shown in Table 1.

[0121] The third catalyst slurry was sprayed onto the second catalyst layer and dried at 80°C to form the third catalyst layer, thereby forming a cathode catalytic membrane and obtaining a semi-prefabricated membrane electrode. The pore size of the third catalyst layer was tested, and the specific results are shown in Table 1.

[0122] A first anode catalyst slurry was sprayed onto the other side of the proton exchange membrane on the pre-fabricated membrane electrode and dried at 80°C to form a first anode catalyst layer. The pore size of the first anode catalyst layer was tested, and the specific results are shown in Table 1. Then, a second layer of anode catalyst slurry was sprayed onto the first anode catalyst layer and dried at 80°C to form a second anode catalyst layer, thereby forming an anode catalyst membrane. The pore size of the second anode catalyst layer was tested, and the specific results are shown in Table 1, thus obtaining the pre-fabricated membrane electrode.

[0123] The total platinum loading on the cathode catalytic membrane was 0.24 mg / cm³. 2 The platinum loading in the first catalyst layer is 0.04 mg / cm³. 2 The platinum loading of the second catalyst layer is 0.13 mg / cm³. 2 The platinum loading of the third catalyst layer is 0.07 mg / cm³. 2 The total platinum loading on the anodic catalyst membrane was 0.06 mg / cm³. 2 The platinum loading of the first anode catalyst layer is 0.04 mg / cm³. 2 The platinum loading of the second anode catalyst layer is 0.02 mg / cm³. 2 .

[0124] (4) Place carbon paper on both sides of the pre-fabricated electrode and assemble it into a single cell with an activation area of ​​25 cm². 2 Power generation tests were conducted under the following conditions: battery operating temperature 80℃, gas excess coefficient H2 / Air = 1.5 / 2.5, humidity 50%, and no back pressure. The voltage at different current densities was recorded. See Table 1 for specific results.

[0125] Example 2

[0126] (1) The cathode catalyst slurry is prepared as follows:

[0127] Preparation of the first catalyst layer slurry: Weigh 0.1g of platinum-carbon catalyst with a platinum content of 40wt%, add 5g of deionized water, and then add dropwise an ionomer solution containing 78mg of ionomer (concentration of 10wt%) to make the I / C ratio 1.3:1. Then add 28mg of ammonium bicarbonate solid, disperse evenly by ultrasonication in an ice bath, and then add 8.5g of isopropanol dropwise. Mix evenly by ultrasonication in an ice bath, and then use a high-speed emulsifying shear machine to strongly disperse for 30min at a dispersion speed of 18000r / min to obtain the first catalyst layer slurry to be sprayed.

[0128] The remaining steps in step (1) are the same as those in step (1) of Example 1.

[0129] Step (2) is the same as step (2) in Example 1.

[0130] Step (3) is basically the same as step (3) in Example 1, except that the temperature used for forming the first catalyst layer, the second catalyst layer, and the third catalyst layer is 100°C, while the other conditions are the same as in step (3) of Example 1. The total platinum loading on the obtained cathode catalyst film is 0.22 mg / cm³. 2 The platinum loading in the first catalyst layer is 0.03 mg / cm³. 2 The platinum loading of the second catalyst layer is 0.11 mg / cm³. 2 The platinum loading of the third catalyst layer is 0.08 mg / cm³. 2 The total platinum loading on the anodic catalyst membrane was 0.06 mg / cm³. 2 The platinum loading of the first anode catalyst layer is 0.04 mg / cm³. 2 The platinum loading of the second anode catalyst layer is 0.02 mg / cm³. 2 .

[0131] Step (4) is the same as step (4) in Example 1. See Table 1 for specific results.

[0132] Example 3

[0133] (1) The cathode catalyst slurry is prepared as follows:

[0134] Preparation of the first catalyst layer slurry: Weigh 0.1g of platinum-carbon catalyst with a platinum content of 40wt%, add 5g of deionized water, and then add dropwise an ionomer solution containing 84mg of ionomer (concentration of 10wt%) to make the I / C ratio 1.4:1. Then add 25mg of ammonium acetate solid, disperse evenly by ultrasonication in an ice bath, and then add 8.3g of ethanol dropwise. Mix evenly by ultrasonication in an ice bath, and then use a high-speed emulsifying shear machine to strongly disperse for 30min at a dispersion speed of 18000r / min to obtain the first catalyst layer slurry to be sprayed.

[0135] Preparation of the second catalyst layer slurry: Weigh 0.1g of platinum-carbon catalyst with a platinum content of 50wt%, add 5g of deionized water, and then add dropwise an ionomer solution containing 50mg of ionomer (concentration of 10wt%) to make the I / C ratio 1:1. After uniform dispersion by ultrasonication in an ice bath, add 13g of isopropanol dropwise and mix uniformly by ultrasonication in an ice bath. Use a high-speed emulsifying shear machine for strong dispersion for 30min at a dispersion speed of 20000r / min to obtain the second catalyst layer slurry to be sprayed.

[0136] Preparation of the third catalyst layer slurry: Weigh 0.1g of platinum-carbon catalyst with a platinum content of 40wt%, add 5g of deionized water, and then add dropwise an ionomer solution containing 36mg of ionomer (concentration of 10wt%) to make the I / C ratio 0.6:1. After uniformly dispersing by ultrasonication in an ice bath, add 19g of ethanol dropwise and mix thoroughly by ultrasonication in an ice bath. Perform strong dispersion for 30min using a high-speed emulsifying shear machine at a dispersion speed of 20000r / min to obtain the third catalyst layer slurry to be sprayed.

[0137] (2) Preparation of anode catalyst slurry:

[0138] Preparation of the first anode catalyst layer slurry: Weigh 0.1g of platinum carbon catalyst with a platinum content of 50wt%, add 5g of deionized water, and then add dropwise an ionomer solution containing 50mg of ionomer (concentration of 10%) to make the I / C ratio 1:1. After uniformly dispersing by ultrasonication in an ice bath, add 13g of ethanol dropwise and mix evenly by ultrasonication in an ice bath. Then, use a high-speed emulsifying shear machine to strongly disperse for 30min at a dispersion speed of 20000r / min to obtain the first anode catalyst layer slurry to be sprayed.

[0139] Preparation of the second anode catalyst slurry: Weigh 0.1g of platinum carbon catalyst with a platinum content of 40wt%, add 5g of deionized water, and then add dropwise an ionomer solution containing 36mg of ionomer (concentration of 20wt%) to make the I / C ratio 0.6:1. After uniformly dispersing by ultrasonication in an ice bath, add 19g of ethanol dropwise and mix uniformly by ultrasonication in an ice bath. Use a high-speed emulsifying shear machine for strong dispersion for 30min at a dispersion speed of 20000r / min to obtain the second anode catalyst slurry to be sprayed.

[0140] Step (3) is basically the same as step (3) in Example 1, except that the temperature used for forming the first catalyst layer, the second catalyst layer, and the third catalyst layer is 110°C, while the other conditions are the same as in step (3) of Example 1. The total platinum loading on the obtained cathode catalyst film is 0.20 mg / cm³. 2 The platinum loading in the first catalyst layer is 0.04 mg / cm³. 2 The platinum loading of the second catalyst layer is 0.11 mg / cm³. 2 The platinum loading of the third catalyst layer is 0.05 mg / cm³. 2 The total platinum loading on the anodic catalyst membrane was 0.05 mg / cm³. 2 The platinum loading of the first anode catalyst layer is 0.03 mg / cm³. 2 The platinum loading of the second anode catalyst layer is 0.02 mg / cm³. 2 .

[0141] Step (4) is the same as step (4) in Example 1. See Table 1 for specific results.

[0142] Example 4

[0143] Example 4 is basically the same as Example 1, except that the steps for preparing the anodic catalytic membrane in step (3) of membrane electrode preparation are as follows:

[0144] The first anode catalyst slurry prepared is sprayed onto the other side of the proton exchange membrane on the pre-fabricated membrane electrode and dried at 80°C to form the first anode catalyst layer. The above spraying step is repeated once to form the second anode catalyst layer, thereby forming the anode catalyst membrane. The thickness of the anode catalyst membrane is the same as that of the anode catalyst membrane prepared in Example 1, and the pre-fabricated membrane electrode is obtained.

[0145] The preparation of the cathode catalytic membrane was the same as in Example 1, and the other steps were also the same as in Example 1.

[0146] Comparative Example 1

[0147] Comparative Example 1 is basically the same as Example 1, except that in step (3) of Comparative Example 1, the preparation of the membrane electrode is carried out by using only the second layer of catalyst slurry for both the cathode catalytic membrane and the anode catalytic membrane. Specifically, the second layer of catalyst slurry prepared above is sprayed onto one side of the proton exchange membrane using an ultrasonic spraying machine and dried at 80°C to form a cathode catalytic membrane. Then, the second layer of catalyst slurry prepared above is sprayed onto the other side of the proton exchange membrane using an ultrasonic spraying machine and dried to form an anode catalytic membrane. The platinum loading on the cathode catalytic membrane and the anode catalytic membrane is the same.

[0148] The remaining steps are the same as in Example 1. For specific results, please see Table 1.

[0149] Comparative Example 2

[0150] Comparative Example 2 is basically the same as Example 1, except that ammonium bicarbonate is not added when preparing the first catalyst layer slurry in step (1) of Comparative Example 2.

[0151] The remaining steps are the same as in Example 1. For specific results, please see Table 1.

[0152] The physical properties and performance test results of each embodiment and comparative example are shown in Table 1. F1, F2, F3, F4, and F5 represent the average pore size of the porous structures on the first catalyst layer, second catalyst layer, third catalyst layer, first anode catalyst layer, and second anode catalyst layer, respectively.

[0153] Table 1

[0154]

[0155] Note that " / " indicates that it does not exist.

[0156] As can be seen from Table 1, the fuel cell membrane electrode assembly obtained using the scheme of this application in Examples 1-3 achieves a performance of 200 mA / cm². 2 The voltage at the given current density can reach over 0.826V, at 1200mA / cm 2 The voltage at the given current density can reach 0.779V, at 2000mA / cm 2 The voltage at the current density can reach over 0.640V, resulting in high power generation efficiency. Further comparison with Example 1, Comparative Examples 1 and 2 shows that the present invention employs a special gradient design for the cathode catalyst layer structure, controlling the I / C ratio and pore size of each layer. This effectively reduces the interface effect of the membrane electrode, improves proton conduction and mass transfer efficiency, increases the gas transport channels within the membrane electrode catalyst layer, and forms a three-segment cathode and two-segment anode reaction gradient catalyst layer. This improves platinum utilization, reduces platinum usage, and significantly increases the battery voltage.

[0157] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0158] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A cathode catalytic membrane, characterized by, The cathode catalytic film comprises a first catalytic layer, a second catalytic layer and a third catalytic layer which are stacked in sequence, components of the first catalytic layer, the second catalytic layer and the third catalytic layer all comprise an ionic polymer and a carbon-supported catalyst, and all have a porous structure, the carbon-supported catalyst comprises a carbon carrier and a catalyst supported on the carbon carrier; The mass ratio of the ionic polymer to the carbon carrier in the first catalytic layer is > the mass ratio of the ionic polymer to the carbon carrier in the second catalytic layer > the mass ratio of the ionic polymer to the carbon carrier in the third catalytic layer; The average pore diameter of the porous structure in the first catalytic layer and the third catalytic layer is both larger than the average pore diameter of the porous structure in the second catalytic layer; The first catalytic layer in the cathode catalytic film is closer to the proton exchange membrane of the fuel cell membrane electrode than the third catalytic layer. The average pore diameter of the porous structure in the first catalytic layer is 50 nm to 200 nm; and / or 2. The cathode catalytic film of claim 1, wherein, The average pore diameter of the porous structure in the second catalytic layer is 5 nm to 30 nm; and / or The average pore diameter of the porous structure in the third catalytic layer is 20 nm to 100 nm. In the first catalytic layer, the mass ratio of the ionic polymer to the carbon carrier is (1.1-1.4):1; and / or 3. The cathode catalytic film according to any one of claims 1 to 2, wherein In the second catalytic layer, the mass ratio of the ionic polymer to the carbon carrier is (0.8-1.2):1; and / or In the third catalytic layer, the mass ratio of the ionic polymer to the carbon carrier is (0.5-0.9):

1. The carbon-supported catalyst comprises a carbon carrier and a metal catalyst supported on the carbon carrier; 4. The cathode catalytic film according to any one of claims 1 to 2, wherein K1 < K3 < K2. the loading of the metal catalyst in the first catalytic layer is K1 mg / cm 2 , the loading of the metal catalyst in the second catalytic layer is K2 mg / cm 2 , the loading of the metal catalyst in the third catalytic layer is K3 mg / cm 2 ; The ratio of K1, K2 and K3 is 1:(1.8-3):(1.2-1.8).

5. The cathode catalytic film of claim 4, wherein, The method comprises the following steps:

6. The method for preparing the cathode catalytic membrane according to any one of claims 1 to 5, characterized in that, The first catalytic slurry, the second catalytic slurry and the third catalytic slurry all comprise an ionic polymer and a carbon-supported catalyst, the carbon-supported catalyst comprises a carbon carrier and a catalyst supported on the carbon carrier, and the components of the first catalytic slurry further comprise a pore-forming agent; The mass ratio of the ionic polymer to the carbon carrier in the first catalytic slurry is > the mass ratio of the ionic polymer to the carbon carrier in the second catalytic slurry > the mass ratio of the ionic polymer to the carbon carrier in the third catalytic slurry; The first catalytic slurry, the second catalytic slurry and the third catalytic slurry are sequentially used to form a first catalytic layer, a second catalytic layer and a third catalytic layer on a substrate to obtain the cathode catalytic film. The components of the first catalytic slurry, the second catalytic slurry and the third catalytic slurry all comprise a dispersant and a solvent, and the mass ratio of the dispersant to the solvent in the first catalytic slurry, the second catalytic slurry and the third catalytic slurry is (1-10):1, (1-10):1 and (1-10):1, respectively; and / or 7. The method for preparing the cathode catalytic membrane as described in claim 6, characterized in that, ​ The mass ratio of the pore-forming agent to the carbon-supported catalyst in the first catalytic slurry is (0.35-2.85):

1.

8. A membrane electrode characterized by, The membrane electrode comprises a proton exchange membrane, an anode catalytic membrane and a cathode catalytic membrane as claimed in any one of claims 1-5, the anode catalytic membrane and the cathode catalytic membrane being respectively located on two sides of the proton exchange membrane, and the first catalytic layer in the cathode catalytic membrane is closer to the proton exchange membrane than the third catalytic layer.

9. The membrane electrode of claim 8, wherein, The anode catalytic membrane comprises a first anode catalytic layer and a second anode catalytic layer stacked in sequence, the first anode catalytic layer being closer to the proton exchange membrane than the second anode catalytic layer; The components of the first anode catalytic layer and the second anode catalytic layer both comprise an ionic polymer and a carbon-supported catalyst, and both have a porous structure, the carbon-supported catalyst comprising a carbon carrier and a catalyst supported on the carbon carrier; The mass ratio of the ionic polymer to the carbon carrier in the first anode catalytic layer is greater than the mass ratio of the ionic polymer to the carbon carrier in the second anode catalytic layer; The average pore size of the porous structure in the first anode catalytic layer is smaller than the average pore size of the porous structure in the second anode catalytic layer.

10. The membrane electrode of claim 9, wherein, The mass ratio of the ionic polymer to the carbon carrier in the first anode catalytic layer is (0.7-1.3):1, and / or The mass ratio of the ionic polymer to the carbon carrier in the second anode catalytic layer is (0.5-10):

1.

11. The membrane electrode according to any one of claims 9 to 10, wherein The carbon-supported catalyst in the first anode catalytic layer and the second anode catalytic layer comprises a carbon carrier and a metal catalyst supported on the carbon carrier; the loading amount of the metal catalyst in the first anode catalytic layer is T1 mg / cm 2 the loading amount of the metal catalyst in the second anode catalytic layer is T2 mg / cm 2 ; T1 > T2.

12. The membrane electrode of claim 11, wherein, The ratio of T1 to T2 is 1:(0.4-0.8).

13. A fuel cell characterized by comprising: The fuel cell comprises a membrane electrode as claimed in any one of claims 8-12.

Images