A membrane electrode for a fuel cell and a method for manufacturing the same

Abstract

The application discloses a membrane electrode of a fuel cell and a preparation method thereof, and relates to the technical field of fuel cells. The membrane electrode of the fuel cell comprises a proton exchange membrane, catalytic layers on both sides of the proton exchange membrane, and diffusion layers covering the outer sides of the catalytic layers. The catalytic layer comprises a catalyst, and further comprises a proton conductor polymer and a nano-carbon layer coated cerium oxide compound. The mass ratio of the catalyst, the proton conductor polymer and the nano-carbon layer coated cerium oxide compound is 10:0.5-1.2:1-3. The mass fraction of carbon in the nano-carbon layer coated cerium oxide compound is 10%-20%. The membrane electrode prepared by the application can eliminate the degradation of free radicals to the proton exchange membrane and improve the durability of the membrane electrode due to the addition of the nano-carbon layer coated cerium oxide. The preparation method adopted by the application does not need special treatment, and is simple, fast and easy to realize batch production.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more specifically to a membrane electrode assembly (MEA) for a fuel cell and its preparation method. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are gaining increasing attention and recognition due to their advantages such as high energy conversion efficiency, zero pollution, and rapid start-up at low temperatures, and have wide applications in electric vehicles and small portable power generation devices. The membrane electrode assembly (MEA) is the core component of a PEMFC, and its performance directly determines the performance of the fuel cell. It mainly consists of a catalyst layer, a proton exchange membrane, and a gas diffusion layer; the durability of the fuel cell is closely related to the durability of these components.

[0003] Patent application CN202310392038.7 discloses a method for preparing a catalyst layer for a fuel cell, comprising the following steps: preparing a pore-forming agent solution, wherein the pore-forming agent solution contains a perfluorosulfonic acid resin, a first solvent and a pore-forming agent; spraying the pore-forming agent solution onto both sides of a proton exchange membrane in a mesh-like path to form a mesh-like protruding pore-forming agent layer; coating a catalyst slurry onto the pore-forming agent layer to form a catalyst layer; and drying the pore-forming agent layer first at 30-50°C and then at 100-150°C to obtain the catalyst layer for the fuel cell.

[0004] Patent application CN202210059749.8 discloses a fuel cell membrane electrode assembly (MEA), its fabrication method, and a fuel cell. The MEA includes an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane (PEM), a cathode catalyst layer, a cathode gas diffusion layer, and a sealing component. The anode catalyst layer includes a first anode catalyst layer and a second anode catalyst layer. The first anode catalyst layer and the cathode catalyst layer are respectively disposed on opposite sides of the PEM. The second anode catalyst layer is disposed between the first anode catalyst layer and the anode gas diffusion layer. The cathode gas diffusion layer is disposed on the side of the cathode catalyst layer away from the PEM. The sealing component is used to fix the first anode catalyst layer, the PEM, and the cathode catalyst layer.

[0005] Patent application CN202011555669.9 discloses a high-performance proton exchange membrane fuel cell membrane electrode structure and its preparation method for improving durability. The high-performance proton exchange membrane fuel cell membrane electrode structure of this invention includes: a fixed mass of an anode catalyst layer, a fixed mass of a cathode catalyst layer, a fixed mass of an ionomer, a first free radical scavenger added to the anode catalyst layer, and a second free radical scavenger added to the cathode catalyst layer. The first free radical scavenger accounts for 0.2%-5% of the total weight of the catalyst layer; the second free radical scavenger accounts for 0.1%-1% of the total weight of the catalyst layer.

[0006] The catalyst layer is where electrochemical reactions in a fuel cell occur. Hydrogenation occurs in the anode catalyst layer, and oxygen reduction occurs in the cathode catalyst layer. Typically, the catalyst layer is composed of a Pt / C catalyst and a certain amount of Nafion bonded together. Degradation of the Pt / C catalyst layer reduces the electrochemical active area of ​​the catalyst layer, thereby affecting the performance and durability of the battery. On the other hand, degradation of Nafion alters the structure of the catalyst layer, resulting in high fuel permeability and severe water loss under high temperature and low humidity conditions, which greatly reduces the performance of the catalyst layer. Summary of the Invention

[0007] CeO2, a free radical scavenger, effectively improves the chemical durability of fuel cell membranes, but CeO2 eluted from CeO2... 4+ Ions cause Pt / C degradation and a decrease in power performance. To address this adverse effect, this invention prepares a nano-carbon coating layer on CeO2 nanoparticles. Compared to pristine CeO2, the nano-carbon coating layer reduces CeO2 degradation. 4+ The high dissolution rate allows it to maintain its intrinsic activity while eliminating free radicals, which significantly improves the durability of membrane electrodes.

[0008] The present invention provides a membrane electrode assembly for a fuel cell, comprising a proton exchange membrane, a catalyst layer on both sides of the proton exchange membrane, and a diffusion layer covering the outside of the catalyst layer. The catalyst layer comprises a catalyst and further contains a proton conductor polymer and a cerium oxide compound coated with a nano-carbon layer.

[0009] The dry mass ratio of the catalyst, the proton conductor polymer, and the cerium oxide compound coated with a nano-carbon layer is 10:0.5-1.2:1-2.

[0010] The carbon mass fraction in the cerium oxide compound coated with the nano-carbon layer is 10% to 20%.

[0011] Specifically, the preparation method of the cerium oxide compound coated with the nano-carbon layer includes the following steps:

[0012] (1) Cerium oxide was added to a dispersant and dispersed evenly to obtain mixture 1;

[0013] (2) Dissolve the carbon source in water, mix it evenly, and then heat and mix it with the mixture 1 obtained in step (1). After separation and drying, mixture 2 is obtained.

[0014] (3) Heat-treat the mixture 2 in step (2) under an inert gas atmosphere to obtain the cerium oxide compound coated with the nano carbon layer.

[0015] Preferably, the mass ratio of carbon source to cerium oxide is 1:5 to 10.

[0016] The dispersant is deionized water and alcohol, and the mass ratio of CeO2 nanoparticles to deionized water and alcohol is 1:20-50:20-50.

[0017] In step (2), the carbon source is at least one of soluble starch, glucose, and fructose; the mass ratio of water added to soluble starch is 50-100:1, and the dissolution temperature is 70-95℃.

[0018] Vacuum drying temperature is 70-120℃; time is 3-6 hours;

[0019] The heating conditions are: mixing for 3-9 hours at a temperature of 110-150℃.

[0020] In step (3), the inert gas is argon; the heat treatment conditions are: heat treatment for 1-6 hours at a temperature of 200-500℃.

[0021] Specifically, the proton conductor polymer is an iron-platinum doped Nafion solution, obtained by an alkyl-thiol addition reaction of Nafion, vinylferrocene, and platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane.

[0022] The mass ratio of Nafion, vinyl ferrocene, and platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane is 10-20:2-5:0.06-0.5.

[0023] The specific steps for preparing the iron-platinum doped Nafion solution are as follows:

[0024] S1: Take 10-20 parts by weight of Nafion, dissolve it in 100-200 parts of dimethyl sulfoxide, and stir at 70-80℃ for 100-150 minutes;

[0025] S2: Add 2-5 parts of vinyl ferrocene, 0.06-0.5 parts of platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane, 3-6 parts of sodium 3-mercapto-1-propanesulfonate, and 3-6 parts of triethylamine to step S1, and stir at 70-80°C for 100-150 minutes to obtain the iron-platinum doped Nafion solution.

[0026] The catalyst is a platinum-carbon catalyst, which can be a commercial JM catalyst with a mass fraction of 60%.

[0027] The present invention also provides a method for preparing the membrane electrode of the fuel cell, comprising the following steps:

[0028] (I) The catalyst, proton conductor polymer, cerium oxide compound coated with nano-carbon layer and solvent are mixed and dispersed evenly to form catalyst ink;

[0029] (II) The catalyst ink obtained in step (I) is coated on both sides of the proton exchange membrane to form a cathode catalyst layer and an anode catalyst layer;

[0030] (III) The membrane electrode is obtained by hot pressing a diffusion layer onto the outside of the cathode catalyst layer and the anode catalyst layer.

[0031] The solvent is either isopropanol or n-butanol, and the ratio of its addition to the catalyst mass is 500-200:1.

[0032] In step (I), the dispersion is carried out by ultrasonic dispersion and magnetic stirring in sequence; wherein, the ultrasonic dispersion time is 30-60 min, the ultrasonic frequency is 10-40 kHz, and the magnetic stirring time is 20-60 min;

[0033] In step (II), the coating method is spraying, and the spraying process parameters are as follows: spraying flow rate 5-20 mL / min, suction cup heating temperature 90-150℃, and nozzle height distance from suction cup height 10-50 cm.

[0034] In step (III), the hot pressing temperature is 150-220℃, the hot pressing time is 30-300s, and the hot pressing pressure is 0.1MPa-4.5MPa.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) The membrane electrode prepared by the present invention can eliminate the degradation of the proton exchange membrane by free radicals and improve the durability of the membrane electrode by adding cerium oxide coated with nano carbon layer; the iron-platinum doped Nafion solution is obtained by mercapto-vinyl addition reaction to obtain ferrocene, and the platinum complex doped Nafion solution has good proton conductivity, which can improve the continuity of the hydrophilic phase of the proton exchange membrane and provide additional sites to increase the proton conductivity of the composite proton exchange membrane;

[0037] (2) It slowed down the degradation of Nafion and reduced fuel permeability;

[0038] (3) The preparation method used in this invention does not require special treatment, is simple and quick to operate, and is easy to achieve mass production. Attached Figure Description

[0039] Figure 1 The polarization curve test spectra are for single-cell tests in Examples 1-5;

[0040] Figure 2The polarization curve test spectra of single cells for Comparative Example 1 and Comparative Example 2 are shown.

[0041] Figure 3 The open-circuit voltage durability test results are for Example 3 and Comparative Examples 1 and 2. Detailed Implementation

[0042] In both the examples and comparative examples, the platinum loading of the cathode catalyst layer was 0.3 mg / cm³. 2 The platinum loading of the anode catalyst layer is 0.05 mg / cm³. 2 In order to facilitate comparison and testing.

[0043] The ability of a proton exchange membrane to conduct protons is characterized by its proton conductivity:

[0044] The method for detecting proton conductivity is as follows:

[0045] The sample was repeatedly soaked in dilute sulfuric acid and then in ultrapure water for more than 24 hours to reach equilibrium. Under low humidity and at 20°C, the AC impedance of the proton exchange membrane was measured using the four-electrode method. The conductivity can be calculated using the following formula:

[0046] Electrical conductivity = L / (R×D×h)

[0047] In the formula, L is the length of the membrane (em), R is the AC impedance of the membrane, d is the width of the membrane (em), h is the thickness of the proton exchange membrane (em), and the unit of conductivity is S / cm.

[0048] Example 1

[0049] Weigh 0.1g of commercial CeO2 (Zhejiang Yamei Nanotechnology Co., Ltd.) particles and place them in a sand mill jar. Add 3g of deionized water and 3g of alcohol, and disperse by sand milling at 3000rpm for 2 hours. Weigh 0.01g of soluble starch and place it in a beaker. Add 0.8g of deionized water and stir to dissolve at 90℃. Pour the dispersed CeO2 mixture into the beaker containing the dissolved soluble starch and stir at room temperature for 60min. Then transfer the mixture to a three-necked flask and stir at 130℃ for 5 hours in an oil bath, followed by natural cooling. Separate and wash the mixture. Then vacuum dry it at 100℃ for 4 hours in a vacuum drying oven. Place the dried solid in a tube furnace and heat treat it at 400℃ for 4 hours in an argon atmosphere to convert the starch into a nano-carbon coating layer, which coats the surface of the CeO2 nanoparticles and is labeled as 10%CL@CeO2.

[0050] The preparation method of iron-platinum doped Nafion solution is as follows:

[0051] S1: Dissolve 10g of Nafion in 100g of dimethyl sulfoxide and stir at 70℃ for 100-150 minutes.

[0052] S2: Add 2g vinyl ferrocene, 0.06g platinum(0)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane, 3g sodium 3-mercapto-1-propanesulfonate, and 3g triethylamine. Stir at 70°C for 100 minutes to obtain an iron-platinum doped Nafion solution.

[0053] Weigh 50 mg of 60% Pt / C (JM60) catalyst and add 5 mg of 10% CL@CeO2; transfer 3 g of deionized water to wet the catalyst and add 7 g of isopropanol. Disperse the mixture by sonication for 40 min, add iron-platinum doped Nafion solution, and continue sonication for 10 min; after completion, disperse the mixture by stirring for 30 min to obtain a uniformly mixed catalyst layer ink.

[0054] Wherein: the dry mass ratio of Pt / C catalyst; CL@CeO2; and iron-platinum doped Nafion is 10:0.5:1;

[0055] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 15 μm proton exchange membrane using a direct spraying method, forming thin anode and cathode catalytic layers on the membrane. A diffusion layer was then applied to the outside of the cathode and anode catalytic layers via hot pressing to obtain the membrane electrode assembly. The amount of Pt nanoparticles fed was controlled by weighing. The spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 100°C, spraying distance from the heating suction cup 30 cm; hot pressing temperature 150°C, hot pressing time 30 s, and hot pressing pressure 0.1 MPa. The conductivity of the proton exchange membrane was measured to be 0.092 S / cm.

[0056] Example 2

[0057] Weigh 0.1g of commercial CeO2 particles and place them in a sand mill jar. Add 3g of deionized water and 3g of alcohol, and disperse by sand milling at 3000 rpm for 2 hours. Weigh 0.01g of soluble starch and place it in a beaker. Add 0.8g of deionized water and stir to dissolve at 90℃. Pour the dispersed CeO2 mixture into the beaker containing the dissolved soluble starch and stir at room temperature for 60 minutes. Then transfer the mixture to a three-necked flask and stir at 130℃ for 5 hours in an oil bath, followed by natural cooling. Separate and wash the mixture. Then vacuum dry it at 100℃ for 4 hours in a vacuum drying oven. Place the dried solid in a tube furnace and heat treat it at 400℃ for 4 hours under an argon atmosphere to convert the starch into a nano-carbon coating layer, which is then coated on the surface of the CeO2 nanoparticles and labeled as 10% CL@CeO2.

[0058] The preparation method of iron-platinum doped Nafion solution is as follows:

[0059] S1: Dissolve 14g of Nafion in 120g of dimethyl sulfoxide and stir at 72℃ for 110 minutes.

[0060] S2: Add 3g vinyl ferrocene, 0.09g platinum(0)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane, 4g sodium 3-mercapto-1-propanesulfonate, and 4g triethylamine. Stir at 73°C for 110 minutes to obtain an iron-platinum doped Nafion solution.

[0061] Weigh 70 mg of 60% Pt / C (JM60) catalyst and add 10 mg of 10% CL@CeO2; transfer 5 g of deionized water to wet the catalyst, then add 10 g of isopropanol, sonicate the mixture for 40 min, add iron-platinum doped Nafion solution, and continue sonication for 10 min; after completion, disperse the mixture by stirring for 30 min to obtain a uniformly mixed catalyst layer ink.

[0062] The dry mass ratio of the catalyst, the proton conductor polymer, and the cerium oxide compound coated with a carbon nanolayer is 10:0.8:1.2.

[0063] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 15 μm proton exchange membrane using a direct spraying method, forming thin cathode and anodic catalytic layers on the membrane. A diffusion layer was then applied to the outside of the cathode and anodic catalytic layers via hot pressing to obtain the membrane electrode assembly. The amount of Pt nanoparticles fed was controlled by weighing. The spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 100°C, spraying distance from the heating suction cup 30 cm; hot pressing temperature 180°C, hot pressing time 100 s, and hot pressing pressure 2 MPa. The conductivity of the proton exchange membrane was measured to be 0.094 S / cm.

[0064] Example 3

[0065] Weigh 0.1g of commercial CeO2 particles and place them in a sand mill jar. Add 3g of deionized water and 3g of alcohol, and disperse by sand milling at 3000 rpm for 2 hours. Weigh 0.01g of soluble starch and place it in a beaker. Add 0.8g of deionized water and stir to dissolve at 90℃. Pour the dispersed CeO2 mixture into the beaker containing the dissolved soluble starch and stir at room temperature for 60 minutes. Then transfer the mixture to a three-necked flask and stir at 130℃ for 5 hours in an oil bath, followed by natural cooling. Separate and wash the mixture. Then vacuum dry it at 100℃ for 4 hours in a vacuum drying oven. Place the dried solid in a tube furnace and heat treat it at 400℃ for 4 hours under an argon atmosphere to convert the starch into a nano-carbon coating layer, which is then coated on the surface of the CeO2 nanoparticles and labeled as 10% CL@CeO2.

[0066] The preparation method of iron-platinum doped Nafion solution is as follows:

[0067] S1: Dissolve 16g of Nafion in 150g of dimethyl sulfoxide and stir at 75°C for 130 minutes.

[0068] S2: Add 4g vinyl ferrocene, 0.1g platinum(0)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane, 4g sodium 3-mercapto-1-propanesulfonate, and 4g triethylamine. Stir at 76°C for 135 minutes to obtain an iron-platinum doped Nafion solution.

[0069] Weigh 50 mg of 60% Pt / C (JM60) catalyst and add 15 mg of 10% CL@CeO2; transfer 8 g of deionized water to wet the catalyst, then add 12 g of isopropanol, sonicate the mixture for 40 min, add iron-platinum doped Nafion solution, and continue sonication for 10 min; after the end, disperse the mixture by stirring for 30 min to obtain a uniformly mixed catalyst layer ink.

[0070] The dry mass ratio of the catalyst, the proton conductor polymer, and the cerium oxide compound coated with a nano-carbon layer is 10:0.5 to 1:1.6.

[0071] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 15 μm proton exchange membrane using a direct spraying method, forming thin anode and cathode catalytic layers on the membrane. A diffusion layer was then applied to the outside of the cathode and anode catalytic layers via hot pressing to obtain the membrane electrode assembly. The amount of Pt nanoparticles fed was controlled by weighing. The spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 100°C, spraying distance from the heating suction cup 30 cm; hot pressing temperature 200°C, hot pressing time 200 s, and hot pressing pressure 3.5 MPa. The conductivity of the proton exchange membrane was measured to be 0.11 S / cm.

[0072] Example 4

[0073] Weigh 0.1g of commercial CeO2 particles into a sand mill jar, add 3g of deionized water and 3g of alcohol, and disperse by sand milling at 3000rpm for 2 hours; weigh 0.02g of soluble starch into a beaker, add 1.6g of deionized water, and stir to dissolve at 90℃; pour the dispersed CeO2 mixture into the beaker containing the dissolved soluble starch, stir at room temperature for 60min, then transfer the mixture to a three-necked flask, stir at 130℃ for 5 hours in an oil bath, and then allow to cool naturally; separate and wash the mixture; then vacuum dry at 100℃ for 4 hours in a vacuum drying oven; place the dried solid in a tube furnace and heat treat at 400℃ for 4 hours under an argon atmosphere to convert the starch into a nano-carbon coating layer, which coats the surface of the CeO2 nanoparticles and is labeled as 20%CL@CeO2;

[0074] The preparation method of iron-platinum doped Nafion solution is as follows:

[0075] S1: Take 18g of Nafion and add it to 170g of dimethyl sulfoxide. Stir at 77℃ for 140 minutes.

[0076] S2: Add 4g vinyl ferrocene, 0.3g platinum(0)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane, 5g sodium 3-mercapto-1-propanesulfonate, and 5g triethylamine. Stir at 78°C for 140 minutes to obtain an iron-platinum doped Nafion solution.

[0077] Weigh 50 mg of 60% Pt / C (JM60) catalyst and add 5 mg of 20% CL@CeO2; transfer 13 g of deionized water to wet the catalyst, then add 15 g of isopropanol, sonicate the mixture for 40 min, add iron-platinum doped Nafion solution, and continue sonication for 10 min; after completion, disperse the mixture by stirring for 30 min to obtain a uniformly mixed catalyst layer ink.

[0078] The dry mass ratio of the catalyst, the proton conductor polymer, and the cerium oxide compound coated with a nano-carbon layer is 10:1.1:2.3.

[0079] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 15 μm proton exchange membrane using a direct spraying method, forming thin anode and cathode catalytic layers on the membrane. A diffusion layer was then applied to the outside of the cathode and anode catalytic layers via hot pressing to obtain the membrane electrode assembly. The amount of Pt nanoparticles fed was controlled by weighing. The spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 100°C, spraying distance from the heating suction cup 30 cm; hot pressing temperature 210°C, hot pressing time 260 s, and hot pressing pressure 4 MPa. The conductivity of the proton exchange membrane was measured to be 0.12 S / cm.

[0080] Example 5

[0081] Weigh 0.1g of commercial CeO2 particles into a sand mill jar, add 3g of deionized water and 3g of alcohol, and disperse by sand milling at 3000rpm for 2 hours; weigh 0.02g of soluble starch into a beaker, add 1.6g of deionized water, and stir to dissolve at 90℃; pour the dispersed CeO2 mixture into the beaker containing the dissolved soluble starch, stir at room temperature for 60min, then transfer the mixture to a three-necked flask, stir at 130℃ for 5 hours in an oil bath, and then allow to cool naturally; separate and wash the mixture; then vacuum dry at 100℃ for 4 hours in a vacuum drying oven; place the dried solid in a tube furnace and heat treat at 400℃ for 4 hours under an argon atmosphere to convert the starch into a nano-carbon coating layer, which coats the surface of the CeO2 nanoparticles and is labeled as 20%CL@CeO2;

[0082] The method for preparing the iron-platinum doped Nafion solution is as follows:

[0083] S1: Take 20g of Nafion and add it to 200g of dimethyl sulfoxide. Stir at 80℃ for 150 minutes.

[0084] S2: Add 5g vinyl ferrocene, 0.5g platinum(0)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane, 6g sodium 3-mercapto-1-propanesulfonate, and 6g triethylamine. Stir at 80°C for 150 minutes to obtain an iron-platinum doped Nafion solution.

[0085] Weigh 50 mg of 60% Pt / C (JM60) catalyst and add 10 mg of 20% CL@CeO2; transfer 15 g of deionized water to wet the catalyst, then add 17 g of isopropanol, sonicate the mixture for 40 min, add 100 mg of iron-platinum doped Nafion solution, and continue sonication for 10 min; after the end, disperse the mixture by stirring for 30 min to obtain a uniformly mixed catalyst layer ink.

[0086] The dry mass ratio of the catalyst, the proton conductor polymer, and the cerium oxide compound coated with a carbon nanolayer is 10:1.2:3.

[0087] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 15 μm proton exchange membrane using a direct spraying method, forming thin cathode and anodic catalytic layers on the membrane. A diffusion layer was then applied to the outside of the cathode and anodic catalytic layers via hot pressing to obtain the membrane electrode assembly. The amount of Pt nanoparticles fed was controlled by weighing. The spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 100°C, spraying distance from the heating suction cup 30 cm; hot pressing temperature 220°C, hot pressing time 300 s, and hot pressing pressure 4.5 MPa. The conductivity of the proton exchange membrane was measured to be 0.14 S / cm.

[0088] Comparative Example 1

[0089] Weigh 50 mg of 60% Pt / C (JM60) catalyst and place it in a 50 mL beaker. Add 10 mg of commercial CeO2. Wet the catalyst with 3 g of deionized water and add 7 g of isopropanol. Disperse the mixture by sonication for 40 min. Add 100 mg of Nafion solution and continue sonication for 10 min. After the process, disperse the mixture by stirring for 30 min to obtain a uniformly mixed catalyst layer ink.

[0090] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 15 μm proton exchange membrane using a direct spraying method, forming thin anode and cathode catalytic layers on the membrane. A diffusion layer was then applied to the outside of the cathode and anode catalytic layers via hot pressing to obtain the membrane electrode assembly. The amount of Pt nanoparticles fed was controlled by weighing. The spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 100°C, spraying distance from the heating suction cup 30 cm; hot pressing temperature 200°C, hot pressing time 200 s, and hot pressing pressure 3.5 MPa. The conductivity of the proton exchange membrane was measured to be 0.055 S / cm.

[0091] Comparative Example 2

[0092] Weigh 50 mg of 60% Pt / C (JM60) catalyst and place it in a 50 mL beaker. Wet the catalyst with 3 g of deionized water and add 7 g of isopropanol. Disperse the mixture by sonication for 40 min. Add 100 mg of iron-platinum doped Nafion solution and continue sonication for 10 min. After the process, disperse the mixture by stirring for 30 min to obtain a uniformly mixed catalyst layer ink.

[0093] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 15 μm proton exchange membrane using a direct spraying method, forming thin cathode and anodic catalyst layers on the membrane. A diffusion layer was then applied to the outside of the cathode and anodic catalyst layers via hot pressing to obtain the membrane electrode assembly. The amount of Pt nanoparticles fed was controlled by weighing. The spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 100°C, spraying distance from the heating suction cup 30 cm; hot pressing temperature 200°C, hot pressing time 200 s, and hot pressing pressure 3.5 MPa. The conductivity of the proton exchange membrane was measured to be 0.063 S / cm.

[0094] Test Example 1

[0095] The fuel cell membrane electrode assemblies prepared in Examples 1-5 and Comparative Examples 1-2 were assembled into single cells, and iV polarization curve performance tests were conducted under the same conditions. The test conditions were as follows: single cell temperature 80 degrees Celsius, anode and cathode reaction gases Air / H2 with a stoichiometric ratio of 2 / 2; inlet air humidity 50% / 50%; and gas inlet pressures 150 kPa / 150 kPa, respectively. The results are as follows. Figure 1 and Figure 2 As shown.

[0096] Depend on Figure 1 It can be seen that, for Examples 1-5, the membrane electrode exhibits similar performance under high pressure and high humidity test conditions; at 2A / cm 2 At the given current density, the voltages corresponding to Examples 1-5 are 0.639V, 0.644V, 0.654V, 0.639V, and 0.637V, respectively; 3A / cm 2 At the current density, the voltages were 0.562V, 0.550V, 0.574V, 0.561V and 0.559V, respectively. The test results show that the addition of a certain amount of nano-carbon coated cerium oxide has little effect on the initial performance of the membrane electrode and can be used as a certain functional reagent for the catalytic layer of the membrane electrode.

[0097] Depend on Figure 2 It can be seen that the performance of the membrane electrode is not significantly different whether CeO2 is added or not; at 2A / cm 2 At the current density, the membrane electrode voltages were 0.633V and 0.638V, respectively, further verifying that the appropriate amount of CeO2 addition has no effect on the membrane electrode performance;

[0098] Test Example 2

[0099] Single-cell open-circuit voltage experiments were conducted on Examples 3 and Comparative Examples 1 and 2. The specific implementation methods were as follows: single cells were assembled as required, activated, and then subjected to open-circuit voltage durability testing. The test conditions were: single-cell temperature 80℃, relative humidity of cathode / anode 30% / 30%, pressure 150 kPa / kPa, hydrogen / air flow rate 350 / 850 ml / min, and test time 5 hours. The open-circuit voltage change curve over time was calculated. The results are as follows: Figure 3 As shown.

[0100] During operation, membrane electrode assemblies (MEAs) generate a large number of free radicals, which attack the ends of the main chain and the ether bonds of the side chains of the perfluorosulfonic acid membrane. This causes the main molecular chain or branches of the membrane to be gradually corroded and degraded, resulting in thinning of the proton exchange membrane. Continuous attack can lead to pinholes in the membrane, resulting in performance degradation. Figure 3 Tests show that the membrane electrodes with added CL@CeO2 and CeO2, in Example 3 and Comparative Example 1, exhibit significantly better open-circuit voltage durability than Comparative Example 2. After a period of time, the open-circuit voltage drop rate in Comparative Example 1 is significantly greater than that of the membrane electrode with nano-carbon layer-coated cerium oxide. This is because pure CeO2 readily undergoes CeO2 oxidation during membrane electrode operation. 4+ The dissolution of Ce weakens its functionality, while in Example 3, the CL@CeO2 coated with a nano-carbon layer effectively slows down the dissolution of Ce. 4+ The degradation of the open circuit voltage further improves the durability of the open circuit voltage.

Claims

1. A membrane electrode assembly for a fuel cell, comprising a proton exchange membrane, catalyst layers on both sides of the proton exchange membrane, and a diffusion layer covering the outer side of the catalyst layers, wherein the catalyst layers comprise a catalyst, characterized in that, The catalyst layer also contains a proton conductor polymer and a cerium oxide compound coated with a nano-carbon layer; The mass ratio of the catalyst, the proton conductor polymer, and the cerium oxide compound coated with a nano-carbon layer is 10:0.5~1.2:1~3. The carbon mass fraction in the cerium oxide compound coated with the nano-carbon layer is 10%~20%; The proton conductor polymer is an iron-platinum doped Nafion solution, obtained by an alkyl-thiol addition reaction of Nafion, vinylferrocene, and platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane. The mass ratio of Nafion, vinyl ferrocene, and platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane is 10-20:2-5:0.06-0.

5. The specific steps for preparing the iron-platinum doped Nafion solution are as follows: S1: Take 10-20 parts by weight of Nafion, dissolve it in 100-200 parts of dimethyl sulfoxide, and stir at 70-80℃ for 100-150 minutes; S2: Add 2-5 parts of vinyl ferrocene, 0.06-0.5 parts of platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane, 3-6 parts of sodium 3-mercapto-1-propanesulfonate, and 3-6 parts of triethylamine to step S1, and stir at 70-80°C for 100-150 minutes to obtain the iron-platinum doped Nafion solution.

2. The membrane electrode assembly of the fuel cell according to claim 1, characterized in that, The method for preparing the cerium oxide compound coated with the nano-carbon layer includes the following steps: (1) Cerium oxide is added to a dispersant and dispersed evenly to obtain mixture 1; (2) Dissolve the carbon source in water, mix it evenly, and then heat and mix it with the mixture 1 obtained in step (1). After separation and drying, mixture 2 is obtained. (3) Heat-treat the mixture 2 in step (2) under an inert gas atmosphere to obtain the cerium oxide compound coated with the nano carbon layer.

3. The membrane electrode assembly of the fuel cell according to claim 2, characterized in that, The mass ratio of carbon source to cerium oxide is 1:5~10.

4. The membrane electrode assembly of the fuel cell according to claim 2, characterized in that, In step (2), the carbon source is at least one of soluble starch, glucose, and fructose; The heating conditions are: mixing for 3-9 hours at a temperature of 110-150℃.

5. The membrane electrode assembly of the fuel cell according to claim 2, characterized in that, In step (3), the inert gas is argon; the heat treatment conditions are: heat treatment for 1-6 hours at a temperature of 200-500℃.

6. The method for preparing the membrane electrode assembly of the fuel cell according to any one of claims 1 to 5, characterized in that, Includes the following steps: (I) The catalyst, proton conductor polymer, cerium oxide compound coated with nano-carbon layer and solvent are mixed and dispersed evenly to form catalyst ink; (II) The catalyst ink obtained in step (I) is coated on both sides of the proton exchange membrane to form a cathode catalyst layer and an anode catalyst layer; (III) The membrane electrode is obtained by hot pressing a diffusion layer onto the outside of the cathode catalyst layer and the anode catalyst layer.

7. The preparation method according to claim 6, characterized in that, In step (I), the dispersion is carried out by ultrasonic dispersion and magnetic stirring in sequence; wherein, the ultrasonic dispersion time is 30-60 min, the ultrasonic frequency is 10-40 kHz, and the magnetic stirring time is 20-60 min; In step (II), the coating method is spraying, and the spraying process parameters are as follows: spraying flow rate 5~20mL / min, suction cup heating temperature 90~150℃, and the distance between the nozzle height and the suction cup height is 10~50cm. In step (III), the hot pressing temperature is 150~220℃, the hot pressing time is 30~300s, and the hot pressing pressure is 0.1MPa~4.5MPa.

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