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. The membrane electrode of the fuel cell comprises a proton exchange membrane, a cathode catalytic layer and an anode catalytic layer on both sides of the proton exchange membrane, and diffusion layers covering the outer sides of the cathode catalytic layer and the anode catalytic layer, the cathode catalytic layer comprises a catalyst and a perfluorosulfonic acid type polymer, and the cathode catalytic layer further comprises a plasma amino-modified hydrophobic agent and graphitized carbon black; the mass ratio of the catalyst, the plasma amino-modified hydrophobic agent and the graphitized carbon black is 45-65:5-22.5:5-10. The catalytic layer prepared by the application has the advantages that the addition of the plasma amino-modified hydrophobic modifier and the conductive agent increases the dispersity of the perfluorosulfonic acid resin, reduces the obstruction of the perfluorosulfonic acid resin film to oxygen transmission, and improves the performance of the membrane electrode. The preparation method has the advantages of no special treatment, simple and fast operation, and easy 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), as an energy conversion device, can directly convert the chemical energy in fuels such as hydrogen and methanol into electrical energy. They feature high energy density, high efficiency, and environmental friendliness, making them an ideal power source for electric vehicles and a hot topic in research and development. The membrane electrode assembly (MEA) is the core component of a PEMFC, mainly consisting of five parts: the proton exchange membrane, the cathode catalyst layer, the anode catalyst layer, the cathode gas diffusion layer, and the anode gas diffusion layer. The catalyst layer in the MEA is where the electrochemical reaction occurs, converting chemical energy into electrical energy. The performance of the catalyst layer depends not only on the activity of the catalyst itself but also on the proportions of its components, the porosity of the catalyst layer structure, and its pore size distribution.

[0003] For example, patent application CN202310586077.0 discloses a self-humidifying fuel cell membrane electrode and its preparation method, belonging to the field of fuel cell technology. The preparation method includes the following steps: S1, mixing platinum-carbon catalyst, distilled water, and isopropanol, stirring and dispersing, and then adding a perfluorosulfonic acid resin solution to obtain a slurry; S2, placing a proton exchange membrane on a heating plate, pouring the above slurry into a spray gun and slowly spraying it onto the proton exchange membrane to obtain an anode catalyst film, and spraying the slurry onto the other side of the proton exchange membrane to obtain a cathode catalyst film; S3, depositing a hydrophilic oxide film on the anode surface of the catalyst film using a reaction source to obtain a hydrophilic anode catalyst film; S4, placing a gas diffusion layer on both sides of the above catalyst film and hot-pressing it. This invention uniformly incorporates hydrophilic oxides into the catalyst and perfluorosulfonic acid resin, improving the hydrophilicity of the anode surface of the membrane electrode and maintaining the uniform dispersion of hydrophilic substances.

[0004] For example, patent application CN 202210735413.9 provides a fuel cell membrane electrode and its preparation method. The membrane electrode sequentially comprises an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer, and a cathode gas diffusion layer. A first free radical quencher is disposed between the anode gas diffusion layer and the anode catalyst layer, and the first free radical quencher contains uniformly distributed carbon-supported cerium oxide. This invention adds a free radical quencher to the anode diffusion layer, reducing the harm of free radicals generated by gas permeation through the membrane and significantly improving the service life of the membrane electrode. During preparation, the cathode catalyst layer uses a CCM (carbon-coated membrane) and the anode catalyst layer uses a GDE (glucose-coated membrane), avoiding the expansion and contraction deformation of the proton exchange membrane during catalyst layer preparation, which is beneficial for the preparation and production of the thin-film membrane electrode.

[0005] Currently, the preparation and design of cathode catalyst layers face more difficulties and challenges than those of anode catalyst layers. This is because cathodes are prone to flooding, which leads to a decrease in the activity of the cathode catalyst and blockage of the gas diffusion layer pores. In addition, oxygen reduction in the cathode catalyst layer is relatively difficult, resulting in low catalyst utilization. To obtain high-performance oxygen reduction catalysts, hydrophilic carbon black with a high specific surface area is usually used as the cathode catalyst support. This results in an overly hydrophilic cathode catalyst layer, which in turn makes it more susceptible to flooding. Therefore, while ensuring the high oxygen reduction performance of the cathode catalyst layer, accelerating the drainage efficiency on the cathode side to a certain extent and mitigating the occurrence of flooding is an important means to improve the performance of membrane electrode assemblies. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a membrane electrode assembly (MEA) for a fuel cell and its preparation method. By adding a certain amount of fluorine-containing compound as a hydrophobic modifier to the cathode catalyst layer and improving its conductivity through plasma modification, the water flooding of the cathode catalyst layer is improved, thereby reducing the obstruction of oxygen transport by the perfluorosulfonic acid resin membrane and enhancing the MEA performance.

[0007] The specific technical solution of the present invention is as follows:

[0008] A membrane electrode assembly for a fuel cell includes a proton exchange membrane, a cathode catalyst layer and an anode catalyst layer on both sides of the proton exchange membrane, and a diffusion layer covering the outside of the cathode catalyst layer and the anode catalyst layer. The cathode catalyst layer includes a catalyst and a perfluorosulfonic acid type polymer, and the cathode catalyst layer also contains a plasma-aminated modified hydrophobic agent and graphitized carbon black.

[0009] The mass ratio of catalyst: plasma-aminated modified hydrophobic agent: graphitized carbon black is 45-65: 5-22.5: 5-10.

[0010] Preferably, the hydrophobic agent is at least one of PTFE, FEP and PFA, with a mass fraction of 5-15 wt%.

[0011] The graphitized carbon black is at least one of Super P Li, ENSACO 350G, and KS-6;

[0012] The catalyst is a platinum-carbon catalyst with a platinum loading of 40%-50%. The platinum-carbon catalyst can be TKK10E50E or Jiuling PT, etc.

[0013] To avoid reducing the conductivity of the catalyst layer due to the addition of hydrophobic agents, a certain amount of graphitized carbon black is added to the cathode catalyst layer to enhance its conductivity.

[0014] Preferably, the preparation method of the plasma-aminated modified hydrophobic agent includes the following steps:

[0015] The hydrophobic agent was modified using a plasma surface treatment instrument in a mixed gas atmosphere of hydrogen, nitrogen, and trimethylchlorosilane to obtain the plasma-aminated hydrophobic agent.

[0016] The flow rate of the mixed gas is 10-30 ml / min.

[0017] The plasma equipment uses hydrogen, nitrogen, and trimethylchlorosilane in a volume ratio of 10-30:50-70:0.2-0.5.

[0018] The plasma surface treatment instrument is set with a power of 150-200W and a processing time of 15-30 minutes.

[0019] The cathode-side hydrophobic modifier is modified by plasma amination to improve its adhesion to the proton exchange membrane surface and enhance its conductivity.

[0020] The perfluorosulfonic acid polymer is a Nafion aqueous solution with a mass fraction of 5-10 wt%, and the mass ratio of the perfluorosulfonic acid polymer to the catalyst is 25-60:100.

[0021] Preferably, the platinum loading of the cathode catalyst layer is 0.3-0.6 mg / cm³. 2 The platinum loading of the anode catalyst layer is 0.05-0.1 mg / cm³. 2 This range of parameters can balance performance and cost, improving the power density of the membrane electrode and thus reducing costs.

[0022] The present invention also provides a method for preparing the membrane electrode of the fuel cell, comprising the following steps:

[0023] (1) The catalyst, proton conductor polymer, carbon black, hydrophobic agent and solvent are mixed and dispersed evenly to form catalyst ink;

[0024] The hydrophobic agent is modified by plasma amination;

[0025] (2) Coat the catalyst ink obtained in step (1) on both sides of the proton exchange membrane to form a cathode catalyst layer and an anode catalyst layer;

[0026] (3) The membrane electrode is obtained by hot pressing a diffusion layer onto the outside of the cathode catalyst layer and the anode catalyst layer.

[0027] Preferably, in step (1), the method for plasma amination modification of the hydrophobic agent includes the following steps:

[0028] The hydrophobic agent was modified using a plasma surface treatment instrument in a mixed gas atmosphere of hydrogen, nitrogen, and trimethylchlorosilane to obtain the plasma-aminated hydrophobic agent.

[0029] The flow rate of the mixed gas is 10-30 ml / min.

[0030] The plasma equipment uses hydrogen, nitrogen, and trimethylchlorosilane in a volume ratio of 10-30:50-70:0.2-0.5.

[0031] The plasma surface treatment instrument is set with a power of 150-200W and a processing time of 15-30 minutes.

[0032] The cathode-side hydrophobic modifier is modified by plasma amination to improve its adhesion to the proton exchange membrane surface and enhance its conductivity.

[0033] Specifically, in step (1), the solvent is at least one of ethanol, isopropanol and n-butanol, and the mass ratio of solvent to catalyst is 100-200:1;

[0034] Water was also added in step (1), with a mass ratio of water to catalyst of 50-100:1;

[0035] The dispersion is carried out by ultrasonic dispersion and magnetic stirring in sequence; wherein the ultrasonic dispersion time is 10-30 min, the ultrasonic frequency is 20-40 kHz, and the magnetic stirring time is 10-30 min.

[0036] The specific steps of step (1) are as follows:

[0037] Weigh out 45-65 × 10⁻⁶ parts by weight of Pt / C catalyst. -3 Parts, 5-15wt% hydrophobic agent suspension aqueous emulsion 50-150×10 -3 Place the sample in a mixing vessel and add 5-10 × 10⁻⁶ units of graphite carbon. -3 Take 3 parts of deionized water to wet the catalyst, then add 7-15 parts of isopropanol, 400-500×10 -3 A 5-10 wt% Nafion aqueous solution was prepared, and the mixture was ultrasonically dispersed and magnetically stirred. The ultrasonic dispersion time was 10-30 min, the ultrasonic frequency was 20-40 kHz, and the magnetic stirring time was 10-30 min to obtain a uniformly mixed catalytic layer ink.

[0038] In step (2), the coating method is spraying.

[0039] The process parameters for the spraying method are as follows: spraying flow rate is 6-15 mL / min, suction cup heating temperature is 80-130℃, and the distance between the nozzle and the suction cup is 20-40 cm.

[0040] In step (3), the hot pressing temperature is 120-200℃, the hot pressing time is 10-300s, and the hot pressing pressure is 0.2MPa-5MPa.

[0041] Further, in step (3), the hot pressing temperature is 150-180℃, the hot pressing time is 100-200s, and the hot pressing pressure is 1MPa-3MPa.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] (1) The catalyst layer prepared in this invention has increased the dispersion of perfluorosulfonic acid resin due to the addition of plasma amination modified hydrophobic regulator and conductive agent, which reduces the obstruction of perfluorosulfonic acid resin film to oxygen transport and improves the performance of membrane electrode.

[0044] (2) The preparation method used in this invention is free from special processing, simple and quick to operate, and easy to achieve mass production. Attached Figure Description

[0045] Figure 1 The polarization curve test spectra of single cells in Examples 1-5 are shown.

[0046] Figure 2 The polarization curve test spectra are for Comparative Example 1 and Comparative Example 2. Detailed Implementation

[0047] Example 1

[0048] The modified PTFE was modified by plasma amination, and the modification method is as follows:

[0049] S1: PTFE was plasma modified in a plasma device under a mixed gas atmosphere of hydrogen, nitrogen, and trimethylchlorosilane at a gas flow rate of 10 ml / min to obtain an amino-containing cathode-side hydrophobic modifier.

[0050] The plasma device uses a mixture of hydrogen, nitrogen, and trimethylchlorosilane in a volume ratio of 10:70:0.2.

[0051] Set the power of the plasma surface treatment instrument to 150W and the processing time to 15min.

[0052] Weigh 55 mg of 40Pt / C (Jiuling PT40%) catalyst and 50 mg of 5wt% modified PTFE suspension emulsion, place them in a stirred tank, add 5 mg of graphite carbon Super P Li, then transfer 3 g of deionized water to wet the catalyst, and add 7 g of isopropanol and 400 mg of 5wt% Nafion aqueous solution. Disperse the mixture using ultrasound and magnetic stirring; the ultrasound dispersion time is 10 min, the ultrasound frequency is 20 kHz, and the magnetic stirring time is 10 min, to obtain a uniformly mixed catalyst layer ink.

[0053] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 12 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 spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 80°C, spraying distance from the heating suction cup 20 cm; hot pressing temperature 150°C, hot pressing time 100 s, and hot pressing pressure 1 MPa. 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 .

[0054] Example 2

[0055] Modified PTFE is modified by plasma amination, and the modification method is as follows:

[0056] S1: PTFE was plasma modified in a plasma device under a mixed gas atmosphere of hydrogen, nitrogen, and trimethylchlorosilane at a gas flow rate of 15 ml / min to obtain an amino-containing cathode-side hydrophobic modifier.

[0057] The plasma equipment uses a mixture of hydrogen, nitrogen, and trimethylchlorosilane in a volume ratio of 30:50:0.5.

[0058] The power of the plasma surface treatment instrument was set to 170W and the processing time to 20min.

[0059] Weigh 50 mg of 50% Pt / C (TEE 10E50E) catalyst and 100 mg of 8 wt% modified PTFE suspension emulsion, place them in a stirred tank, add 5 mg of graphite carbon Super P Li, then transfer 3 g of deionized water to wet the catalyst, and add 9 g of isopropanol and 420 mg of 7 wt% Nafion aqueous solution. The mixture is then dispersed by ultrasonication and stirred magnetically. The ultrasonic dispersion time is 15 min, the ultrasonic frequency is 27 kHz, and the magnetic stirring time is 15 min, resulting in a uniformly mixed catalyst layer ink.

[0060] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 12 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 spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 80°C, spraying distance from the heating suction cup 25 cm; hot pressing temperature 160°C, hot pressing time 120 s, and hot pressing pressure 1.3 MPa. The platinum loading of the cathode catalyst layer was 0.45 mg / cm³. 2 The platinum loading of the anode catalyst layer is 0.65 mg / cm³. 2 .

[0061] Example 3

[0062] Modified PTFE is modified by plasma amination, and the modification method is as follows:

[0063] S1: PTFE was plasma modified in a plasma device under a mixed gas atmosphere of hydrogen, nitrogen, and trimethylchlorosilane at a gas flow rate of 18 ml / min to obtain an amino-containing cathode-side hydrophobic modifier.

[0064] The plasma equipment uses a mixture of hydrogen, nitrogen, and trimethylchlorosilane in a volume ratio of 15:55:0.3.

[0065] The power of the plasma surface treatment instrument was set to 170W and the processing time to 22min.

[0066] Weigh 45 mg of 50% Pt / C (TEE10E50E) catalyst and 150 mg of 15 wt% modified PTFE suspension emulsion, place them in a stirred tank, add 5 mg of graphite carbon Super P Li, then transfer 3 g of deionized water to wet the catalyst, and add 10 g of isopropanol and 400 mg of 8 wt% Nafion aqueous solution. Disperse the mixture using ultrasound and magnetic stirring; the ultrasound dispersion time is 22 min, the ultrasound frequency is 30 kHz, and the magnetic stirring time is 25 min, to obtain a uniformly mixed catalyst layer ink.

[0067] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 12 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 spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 80°C, spraying distance from the heating suction cup 30 cm; hot pressing temperature 160°C, hot pressing time 150 s, and hot pressing pressure 1.6 MPa. The platinum loading of the cathode catalyst layer was 0.5 mg / cm³. 2The platinum loading of the anode catalyst layer is 0.08 mg / cm³. 2 .

[0068] Example 4

[0069] Modified FEP is modified by plasma amination, and the modification method is as follows:

[0070] S1: FEP was plasma modified in a plasma device under a mixed gas atmosphere of hydrogen, nitrogen and trimethylchlorosilane at a gas flow rate of 25 ml / min to obtain FEP with amino groups.

[0071] The plasma equipment uses a mixture of hydrogen, nitrogen, and trimethylchlorosilane in a volume ratio of 25:60:0.4.

[0072] The power of the plasma surface treatment instrument was set to 190W and the processing time to 25min.

[0073] Weigh 60 mg of 50% Pt / C (TEE10E50E) catalyst and 100 mg of 5 wt% modified FEP suspension emulsion, place them in a stirred tank, add 7.5 mg of graphite carbon SuperP Li, then transfer 3 g of deionized water to wet the catalyst, and add 12 g of isopropanol and 460 mg of 9 wt% Nafion aqueous solution. The mixture is then dispersed by ultrasonication and magnetic stirring. The ultrasonic dispersion time is 30 min, the ultrasonic frequency is 40 kHz, and the magnetic stirring time is 30 min, resulting in a uniformly mixed catalyst layer ink.

[0074] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 12 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 spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 80°C, spraying distance from the heating suction cup 35 cm; hot pressing temperature 170°C, hot pressing time 180 s, and hot pressing pressure 2 MPa. The platinum loading of the cathode catalyst layer was 0.6 mg / cm³. 2 The platinum loading of the anode catalyst layer is 0.1 mg / cm³. 2 .

[0075] Example 5

[0076] Modified PFA is obtained by plasma amination modification, and the modification method is as follows:

[0077] S1: PFA is plasma modified in a plasma device under a mixed gas atmosphere of hydrogen, nitrogen, and trimethylchlorosilane at a gas flow rate of 30 ml / min to obtain amino-containing PFA.

[0078] The plasma equipment uses a mixture of hydrogen, nitrogen, and trimethylchlorosilane in a volume ratio of 30:70:0.5.

[0079] Set the power of the plasma surface treatment instrument to 200W and the processing time to 30min.

[0080] Weigh 65 mg of 50% Pt / C (TEE10E50E) catalyst and 100 mg of 5 wt% modified PFA suspension emulsion, place them in a stirred tank, add 10 mg of graphite carbon Super P Li, then transfer 3 g of deionized water to wet the catalyst, add 15 g of isopropanol, add 500 mg of 10 wt% Nafion aqueous solution, and disperse the mixture using ultrasonic dispersion and magnetic stirring; wherein, the ultrasonic dispersion time is 30 min, the ultrasonic frequency is 40 kHz, and the magnetic stirring time is 30 min, to obtain a uniformly mixed catalyst layer ink.

[0081] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 12 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 spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 80°C, spraying distance from the heating suction cup 40 cm; hot pressing temperature 180°C, hot pressing time 200 s, and hot pressing pressure 3 MPa. 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 .

[0082] Comparative Example 1

[0083] Weigh 50 mg of 50% Pt / C (TEE10E50E) catalyst and 100 mg of 15 wt% PFA aqueous suspension emulsion, place them in a stirred tank, then transfer 3 g of deionized water to wet the catalyst, add 7 g of isopropanol, add 400 mg of 5 wt% Nafion aqueous solution, and disperse the mixture using ultrasonic dispersion and magnetic stirring; wherein, the ultrasonic dispersion time is 10 min, the ultrasonic frequency is 20 kHz, and the magnetic stirring time is 10 min, to obtain a uniformly mixed catalyst layer ink.

[0084] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 12 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 spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 80°C, spraying distance from the heating suction cup 40 cm; hot pressing temperature 120°C, hot pressing time 300 s, and hot pressing pressure 0.2 MPa. 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 .

[0085] Comparative Example 2

[0086] Weigh 50 mg of 50% Pt / C (TEE10E50E) catalyst and place it in a stirred tank. Then, transfer 3 g of deionized water to wet the catalyst, add 7 g of isopropanol, and add 400 mg of 5 wt% Nafion aqueous solution. Disperse the mixture using ultrasound and stir magnetically. The ultrasound dispersion time is 10 min, the ultrasound frequency is 20 kHz, and the magnetic stirring time is 10 min to obtain a uniformly mixed catalyst layer ink.

[0087] The uniformly dispersed catalyst slurry was directly sprayed onto the surface of a 12 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 spraying process parameters were set as follows: nozzle flow rate 10 mL / min, suction cup heating temperature 80°C, spraying distance from the heating suction cup 40 cm; hot pressing temperature 200°C, hot pressing time 10 s, and hot pressing pressure 5 MPa. 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 .

[0088] Test Example 1

[0089] The fuel cell membrane electrodes prepared in Examples 1-5 and Comparative Examples 1-2 were assembled into single cells, and their iV polarization curve performance was tested under the same conditions. The results are as follows: Figure 1 , Figure 2 As shown, the test conditions are as follows: single cell temperature 80 degrees Celsius, anode and cathode reaction gas Air / H2, metering ratio 2 / 1.5; inlet air humidity 40% / 50%, gas inlet pressure 150 kPa / 150 kPa respectively.

[0090] The test spectra show that, for Comparative Examples 1 and 2, the membrane electrode exhibits poor performance at high current densities (2 A / cm²) for those without added hydrophobic agents or with only added hydrophobic agents but no added conductive agents. 2 At that time, the voltage was about 0.55V and 0.53V, which was much lower than the data measured in Examples 1-5. For Examples 1-5, the amount of hydrophobic agent and graphitized carbon black added also had a certain impact on the membrane electrode performance. This is because the hydrophobic agent is a non-conductive material. If too much is added, it will increase the resistance of the catalyst layer, thereby affecting the ohmic polarization in the polarization curve. In addition, too much hydrophobic agent will also cover the active sites of the catalyst, resulting in a weakening of the catalyst performance, which in turn affects the membrane electrode performance. On the other hand, the excessive addition of graphitized carbon black will increase the thickness of the catalyst layer to a certain extent, which will hinder the mass transfer of oxygen to a certain extent and affect the membrane electrode performance. Therefore, these two substances need to be added in appropriate amounts to improve the membrane electrode performance.

Claims

1. A membrane electrode assembly for a fuel cell, comprising a proton exchange membrane, a cathode catalyst layer and an anode catalyst layer on opposite sides of the proton exchange membrane, and a diffusion layer covering the outer sides of the cathode catalyst layer and the anode catalyst layer, wherein the cathode catalyst layer comprises a catalyst and a perfluorosulfonic acid type polymer, characterized in that, The cathode catalyst layer also contains a plasma-aminated modified hydrophobic agent and graphitized carbon black. The mass ratio of catalyst: plasma-aminated modified hydrophobic agent: graphitized carbon black is 45-65: 5-22.5: 5-10.

2. The membrane electrode assembly of the fuel cell according to claim 1, characterized in that, The hydrophobic agent is at least one of PTFE, FEP and PFA, with a mass fraction of 5-15 wt%. The graphitized carbon black is at least one of Super P Li, ENSACO 350G, and KS-6; The catalyst is a platinum-carbon catalyst with a platinum loading of 40%-50%.

3. The membrane electrode assembly of the fuel cell according to claim 1 or 2, characterized in that, The preparation method of plasma-aminated modified hydrophobic agents includes the following steps: The hydrophobic agent was modified using a plasma surface treatment instrument in a mixed gas atmosphere of hydrogen, nitrogen, and trimethylchlorosilane to obtain the plasma-aminated hydrophobic agent. The flow rate of the mixed gas is 10-30 ml / min. The volume ratio of hydrogen, nitrogen, and trimethylchlorosilane is 10⁻³⁰∶50⁻⁷⁰∶0.2⁻⁰.⁵. The plasma surface treatment instrument is set to a power of 150-200W.

4. The membrane electrode assembly of the fuel cell according to claim 1, characterized in that, The perfluorosulfonic acid polymer is a Nafion aqueous solution with a mass fraction of 5-10 wt%, and the mass ratio of the perfluorosulfonic acid polymer to the catalyst is 25-60:

100.

5. The membrane electrode assembly of the fuel cell according to claim 1, characterized in that, The platinum loading of the cathode catalyst layer is 0.3-0.6 mg / cm³. 2 The platinum loading of the anode catalyst layer is 0.05-0.1 mg / cm³. 2 .

6. A method for preparing the membrane electrode assembly of the fuel cell according to any one of claims 1-5, characterized in that, Includes the following steps: (1) The catalyst, perfluorosulfonic acid polymer, graphitized carbon black, hydrophobic agent and solvent are mixed and dispersed evenly to form a catalyst ink; The hydrophobic agent is modified by plasma amination; (2) The catalyst ink obtained in step (1) is coated on both sides of the proton exchange membrane to form a cathode catalyst layer and an anode catalyst layer; (3) 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 method for preparing the membrane electrode assembly of a fuel cell according to claim 6, characterized in that, In step (1), the method for plasma amination modification of the hydrophobic agent includes the following steps: The hydrophobic agent was modified using a plasma surface treatment instrument in a mixed gas atmosphere of hydrogen, nitrogen, and trimethylchlorosilane to obtain the plasma-aminated hydrophobic agent. The flow rate of the mixed gas is 10-30 ml / min. The volume ratio of hydrogen, nitrogen, and trimethylchlorosilane is 10⁻³⁰∶50⁻⁷⁰∶0.2⁻⁰.⁵. The plasma surface treatment instrument is set to a power of 150-200W.

8. The method for preparing the membrane electrode assembly of a fuel cell according to claim 6, characterized in that, In step (1), the solvent is at least one of ethanol, isopropanol and n-butanol, and the mass ratio of solvent to catalyst is 100-200:1; Water was also added in step (1), with a mass ratio of water to catalyst of 50-100:1; The dispersion is carried out by ultrasonic dispersion and magnetic stirring in sequence; wherein the ultrasonic dispersion time is 10-30 min, the ultrasonic frequency is 20-40 kHz, and the magnetic stirring time is 10-30 min.

9. The method for preparing the membrane electrode assembly of a fuel cell according to claim 6, characterized in that, In step (2), the coating method is spraying. The spraying process parameters are as follows: spraying flow rate is 6~15mL / min, suction cup heating temperature is 80~130℃, and the distance between the nozzle and the suction cup is 20~40cm.

10. The method for preparing the membrane electrode assembly of a fuel cell according to claim 6, characterized in that, In step (3), the hot pressing temperature is 120~200℃, the hot pressing time is 10~300s, and the hot pressing pressure is 0.2MPa~5MPa.

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