Membrane electrode of fuel cell and preparation method for membrane electrode

Abstract

A membrane electrode of a fuel cell. The membrane electrode comprises a proton exchange membrane, a cathode catalyst layer and an anode catalyst layer, each of which is on one side of the proton exchange membrane, and diffusion layers 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, and also contains a plasma amination modified hydrophobic agent and graphitized carbon black. The mass ratio of the catalyst to the plasma amination modified hydrophobic agent to the graphitized carbon black is 45-65: 5-22.5: 5-10. Since a plasma amination modified hydrophobic regulator and an electrically conductive agent are added into the catalyst layers, the dispersity of a perfluorosulfonic acid resin is increased, thereby reducing the impediment of oxygen transport by a perfluorosulfonic acid resin thin film and improving the performance of a membrane electrode. The preparation method used is simple and quick in terms of operation and makes it easy to achieve batch production.

Description

Membrane electrode for fuel cell and preparation method thereof Technical Field

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

[0002] As an energy conversion device, the proton exchange membrane fuel cell (PEMFC) can directly convert the chemical energy in fuels such as hydrogen and methanol into electrical energy. With its high energy density, high efficiency, and environmental friendliness, it is an ideal power source for electric vehicles and has long been a hot topic of research and development. The membrane electrode assembly (MEA) is the core component of the PEMFC and primarily consists of five parts: the proton exchange membrane, cathode catalyst layer, anode catalyst layer, cathode gas diffusion layer, and anode gas diffusion layer. The catalytic layer within the MEA is where the electrochemical reaction occurs throughout the PEMFC, converting chemical energy into electrical energy. The performance of the catalytic layer depends not only on the activity of the catalyst itself but also on the ratio of its components, the porosity of the catalytic layer structure, and the pore size distribution.

[0003] For example, the patent application with application number CN202310586077.0 discloses a self-humidifying fuel cell membrane electrode and its preparation method, which belongs to the field of fuel cell technology. The preparation method includes the following steps: S1, mixing a platinum carbon catalyst, distilled water and isopropyl alcohol, 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 on the proton exchange membrane to obtain an anode surface catalyst membrane, and spraying the slurry on the other side of the proton exchange membrane to obtain a cathode surface catalyst membrane; S3, the reaction source deposits a hydrophilic oxide film on the anode surface of the catalyst membrane to obtain an anode hydrophilic catalyst membrane; S4, placing a gas diffusion layer on both sides of the above catalyst membrane and hot pressing it into shape. This invention uniformly dopes the hydrophilic oxide into the catalyst and perfluorosulfonic acid resin, improves the hydrophilicity of the anode surface of the membrane electrode, and keeps the hydrophilic substance uniformly dispersed.

[0004] For another example, the patent application with application number CN 202210735413.9 provides a fuel cell membrane electrode and its preparation method, wherein the membrane electrode comprises an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer and a cathode gas diffusion layer in sequence, and a first free radical quencher is provided between the anode gas diffusion layer and the anode catalyst layer, and carbon-supported cerium oxide is evenly distributed in the first free radical quencher. This invention adds a free radical quencher to the anode diffusion layer, which reduces the free radical hazards generated by thin film gas permeation and greatly improves the service life of the membrane electrode. During the preparation of this invention, CCM is used for the cathode catalyst layer and GDE is used for the anode catalyst layer, which avoids the expansion and contraction deformation of the proton exchange membrane during the preparation of the catalyst layer, and is beneficial to the preparation and production of thin film membrane electrodes.

[0005] At present, the preparation and design of the cathode catalyst layer face more difficulties and challenges than the anode catalyst layer. This is because the cathode is prone to water flooding, which leads to a decrease in the activity of the cathode catalyst and the blockage of the gas diffusion layer pores. In addition, the reduction of oxygen in the cathode catalyst layer is relatively difficult and the catalyst utilization rate is low. In order to obtain high-performance oxygen reduction catalysts, high-specific-surface-area hydrophilic carbon black is usually used as the cathode catalyst carrier. The result is that the cathode catalyst layer is overly hydrophilic, and thus more prone to water flooding. Therefore, under the premise of ensuring the high-activity oxygen reduction performance of the cathode catalyst layer, accelerating the drainage efficiency on the cathode side and slowing down the occurrence of water flooding to a certain extent are important means to improve the performance of the membrane electrode.

[0006] Summary of the Invention

[0007] Based on the deficiencies in the prior art, the present invention provides a membrane electrode for a fuel cell and a method for preparing the same. By adding a certain amount of fluorine-containing compound as a hydrophobic regulator 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 the perfluorosulfonic acid resin film to oxygen transmission and improving the performance of the membrane electrode.

[0008] The specific technical solutions of the present invention are as follows:

[0009] A fuel cell membrane electrode comprises 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, wherein the cathode catalyst layer comprises a catalyst and a perfluorosulfonic acid polymer, and further comprises a plasma amination-modified hydrophobic agent and graphitized carbon black;

[0010] The mass ratio of the catalyst: the plasma amination modified hydrophobic agent: the graphitized carbon black is 45-65: 5-22.5: 5-10.

[0011] Preferably, the hydrophobic agent is at least one of PTFE, FEP and PFA, with a mass fraction of 5-15wt%;

[0012] The graphitized carbon black is at least one of Super P Li, ENSACO 350G, and KS-6;

[0013] The catalyst is a platinum-carbon catalyst with a platinum loading of 40%-50%. The platinum-carbon catalyst may be TKK10E50E or Jiuling PT.

[0014] In order to avoid the reduction of the conductivity of the catalytic layer due to the addition of the hydrophobic agent, a certain amount of graphitized carbon black is added to the cathode catalytic layer to enhance its conductivity.

[0015] Preferably, the preparation method of the plasma amination modified hydrophobic agent comprises the following steps:

[0016] The hydrophobic agent is plasma modified in a mixed gas atmosphere of hydrogen, nitrogen and trimethylchlorosilane using a plasma surface treatment instrument to obtain the plasma amination modified hydrophobic agent.

[0017] The mixed gas flow rate is 10-30ml / min.

[0018] The plasma equipment uses hydrogen, nitrogen, and trimethylchlorosilane in a volume ratio of 10-30:50-70:0.2-0.5.

[0019] The plasma surface treatment instrument was set to have a power of 150-200 W and a treatment time of 1530 min.

[0020] The cathode side hydrophobic regulator is modified by plasma amination to improve the adhesion of the hydrophobic regulator on the surface of the proton exchange membrane and improve the conductivity of the cathode side hydrophobic regulator.

[0021] 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.

[0022] Preferably, the platinum loading of the cathode catalyst layer is 0.3-0.6 mg / cm 2 The platinum loading of the anode catalyst layer is 0.05-0.1 mg / cm 2 Parameters within this range can take into account both performance and cost, and can improve the performance of membrane electrode power density and thus reduce costs.

[0023] The present invention also provides a method for preparing the membrane electrode of the fuel cell, comprising the following steps:

[0024] (1) mixing and uniformly dispersing a catalyst, a proton conductor polymer, carbon black, a hydrophobic agent, and a solvent to form a catalyst ink;

[0025] The hydrophobic agent is plasma amination modified;

[0026] (2) coating 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;

[0027] (3) Covering the cathode catalyst layer and the anode catalyst layer with a diffusion layer by hot pressing to obtain the membrane electrode.

[0028] Preferably, in step (1), the method for plasma amination modification of the hydrophobic agent comprises the following steps:

[0029] The hydrophobic agent is plasma modified in a mixed gas atmosphere of hydrogen, nitrogen and trimethylchlorosilane using a plasma surface treatment instrument to obtain the plasma amination modified hydrophobic agent.

[0030] The mixed gas flow rate is 10-30ml / min.

[0031] The plasma equipment uses hydrogen, nitrogen, and trimethylchlorosilane in a volume ratio of 10-30:50-70:0.2-0.5.

[0032] The plasma surface treatment instrument is set to a power of 150-200W and a treatment time of 15-30min.

[0033] The cathode side hydrophobic regulator is modified by plasma amination to improve the adhesion of the hydrophobic regulator on the surface of the proton exchange membrane and improve the conductivity of the cathode side hydrophobic regulator.

[0034] Specifically, in step (1), the solvent is at least one of ethanol, isopropanol and n-butanol, and the mass ratio of the solvent to the catalyst is 100-200:1;

[0035] Water is also added in step (1), and the mass ratio of water to catalyst is 50-100:1;

[0036] The dispersion is carried out by ultrasonic dispersion and magnetic stirring in sequence; wherein, the ultrasonic dispersion time is 10-30 minutes, the ultrasonic frequency is 20-40KHz, and the magnetic stirring time is 10-30 minutes.

[0037] The specific steps of step (1) are:

[0038] According to weight, weigh 45-65×10 -3 5-15wt% hydrophobic agent suspension water emulsion 50-150×10 -3 parts, placed in a stirring kettle, and added 5-10×10 -3 Then, 3 parts of deionized water were taken to wet the catalyst, and 7-15 parts of isopropanol were added, 400-500×10 -3 A 5-10 wt% Nafion aqueous solution is prepared, and the mixture is subjected to ultrasonic dispersion and magnetic stirring; 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 to obtain a uniformly mixed catalytic layer ink.

[0039] In step (2), the coating method is spraying,

[0040] The process parameters of the spraying method are as follows: the spraying flow rate is 6 to 15 mL / min, the suction cup heating temperature is 80 to 130° C., and the height of the nozzle from the suction cup is 20 to 40 cm.

[0041] In step (3), the hot pressing temperature is 120-200° C., the hot pressing time is 10-300 s, and the hot pressing pressure is 0.2 MPa-5 MPa.

[0042] Furthermore, in step (3), the hot pressing temperature is 150-180° C., the hot pressing time is 100-200 s, and the hot pressing pressure is 1 MPa-3 MPa.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) The catalyst layer prepared by the present invention increases the dispersion of the perfluorosulfonic acid resin due to the addition of a plasma amination-modified hydrophobic regulator and a conductive agent, thereby reducing the obstruction of the perfluorosulfonic acid resin film to oxygen transmission and improving the membrane electrode performance;

[0045] (2) The preparation method adopted by the present invention does not require special treatment, is simple and quick to operate, and is easy to achieve batch production. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] FIG1 is a graph showing polarization curves of single cells of Examples 1-5;

[0047] FIG2 is a graph showing the polarization curves of Comparative Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0048] Example 1

[0049] Modified PTFE is modified by plasma amination, and the modification method is as follows:

[0050] S1: PTFE is plasma modified in a plasma equipment in a mixed gas atmosphere of hydrogen, nitrogen and trimethylchlorosilane at a gas flow rate of 10 ml / min to obtain a cathode-side hydrophobic regulator with amino groups.

[0051] The gas used in the plasma equipment is a mixed gas of hydrogen, nitrogen and trimethylchlorosilane, with a volume ratio of 10:70:0.2.

[0052] The power of the plasma surface treatment instrument was set to 150 W and the treatment time was set to 15 min.

[0053] Weigh 55 mg of 40% Pt / C (Jiuling PT40%) catalyst and 50 mg of 5wt% modified PTFE suspension aqueous emulsion, place them in a stirring tank, add 5 mg of graphite carbon Super P Li, then transfer 3 g of deionized water to wet the catalyst, and then add 7 g of isopropanol and 400 mg of 5wt% Nafion aqueous solution, and use ultrasonic dispersion and magnetic stirring to obtain a uniformly mixed catalytic layer ink; wherein, the ultrasonic dispersion time is 10 min, the ultrasonic frequency is 20 kHz, and the magnetic stirring time is 10 min.

[0054] By direct spraying, the above-mentioned evenly dispersed catalyst slurry is directly sprayed onto the surface of a 12μm proton exchange membrane to form a thin layer of cathode and anode catalyst layers on the membrane. The diffusion layer is covered on the outside of the cathode catalyst layer and the anode catalyst layer by hot pressing to obtain the membrane electrode. The spraying process parameters are set as follows: nozzle flow rate 10mL / min, suction cup heating temperature 80 degrees Celsius, spraying height from the heating suction cup 20cm; the hot pressing temperature is 150℃, hot pressing time is 100s, and hot pressing pressure is 1MPa. The platinum loading of the cathode catalyst layer is 0.3mg / cm 2 , the platinum loading of the anode catalyst layer is 0.05 mg / cm 2 .

[0055] Example 2

[0056] Modified PTFE is modified by plasma amination, and the modification method is as follows:

[0057] S1: PTFE is plasma modified in a plasma equipment in a mixed gas atmosphere of hydrogen, nitrogen and trimethylchlorosilane at a gas flow rate of 15 ml / min to obtain a cathode-side hydrophobic regulator with amino groups.

[0058] The gas used in the plasma equipment is a mixture of hydrogen, nitrogen and trimethylchlorosilane in a volume ratio of 30:50:0.5.

[0059] The power of the plasma surface treatment instrument was set to 170 W and the treatment time was set to 20 min.

[0060] Weigh 50 mg of 50% Pt / C (TEE10E50E) catalyst and 100 mg of 8 wt% modified PTFE suspension aqueous emulsion, place them in a stirring tank, add 5 mg of graphite carbon Super P Li, then transfer 3 g of deionized water to wet the catalyst, then add 9 g of isopropanol and 420 mg of 7 wt% Nafion aqueous solution, and use ultrasonic dispersion and magnetic stirring to obtain a uniformly mixed catalytic layer ink; wherein, the ultrasonic dispersion time is 15 min, the ultrasonic frequency is 27 kHz, and the magnetic stirring time is 15 min.

[0061] The above-mentioned evenly dispersed catalyst slurry is directly sprayed onto the surface of a 12μm proton exchange membrane by direct spraying to form a thin layer of cathode and anode catalyst layers on the membrane. The diffusion layer is covered on the outside of the cathode catalyst layer and the anode catalyst layer by hot pressing to obtain the membrane electrode. The spraying process parameters are set as follows: nozzle flow rate 10mL / min, suction cup heating temperature 80 degrees Celsius, spraying height from the heating suction cup is 25cm; the hot pressing temperature is 160℃, hot pressing time is 120s, and hot pressing pressure is 1.3MPa. The platinum loading of the cathode catalyst layer is 0.45mg / cm 2 , the platinum loading of the anode catalyst layer is 0.65 mg / cm 2 .

[0062] Example 3

[0063] Modified PTFE is modified by plasma amination, and the modification method is as follows:

[0064] S1: PTFE is plasma modified in a plasma equipment in a mixed gas atmosphere of hydrogen, nitrogen and trimethylchlorosilane at a gas flow rate of 18 ml / min to obtain a cathode-side hydrophobic regulator with amino groups.

[0065] The gas used in the plasma equipment is a mixture of hydrogen, nitrogen and trimethylchlorosilane in a volume ratio of 15:55:0.3.

[0066] The power of the plasma surface treatment instrument was set to 170 W, and the treatment time was set to 22 min.

[0067] Weigh 45 mg of 50% Pt / C (TEE10E50E) catalyst and 150 mg of 15 wt% modified PTFE suspension aqueous emulsion, place them in a stirring tank, add 5 mg of graphite carbon Super P Li, then transfer 3 g of deionized water to wet the catalyst, then add 10 g of isopropanol and 400 mg of 8 wt% Nafion aqueous solution, and use ultrasonic dispersion and magnetic stirring to obtain a uniformly mixed catalytic layer ink; wherein, the ultrasonic dispersion time is 22 min, the ultrasonic frequency is 30 kHz, and the magnetic stirring time is 25 min.

[0068] The above-mentioned evenly dispersed catalyst slurry is directly sprayed onto the surface of a 12μm proton exchange membrane by direct spraying to form a thin layer of cathode and anode catalyst layers on the membrane. The diffusion layer is covered on the outside of the cathode catalyst layer and the anode catalyst layer by hot pressing to obtain the membrane electrode. The spraying process parameters are set as follows: nozzle flow rate 10mL / min, suction cup heating temperature 80 degrees Celsius, spraying height from the heating suction cup 30cm; the hot pressing temperature is 160℃, hot pressing time is 150s, and hot pressing pressure is 1.6MPa. The platinum loading of the cathode catalyst layer is 0.5mg / cm2 , the platinum loading of the anode catalyst layer is 0.08 mg / cm 2 .

[0069] Example 4

[0070] The modified FEP is modified by plasma amination, and the modification method is as follows:

[0071] S1: FEP was plasma modified in a plasma equipment in a mixed gas atmosphere of hydrogen, nitrogen and trimethylchlorosilane at a gas flow rate of 25 ml / min to obtain FEP with amino groups.

[0072] The gas used in the plasma equipment is a mixture of hydrogen, nitrogen and trimethylchlorosilane in a volume ratio of 25:60:0.4.

[0073] The power of the plasma surface treatment instrument was set to 190 W and the treatment time was set to 25 min.

[0074] 60 mg of 50% Pt / C (TEE10E50E) catalyst and 100 mg of 5 wt% modified FEP suspension aqueous emulsion were weighed and placed in a stirring tank. 7.5 mg of graphite carbon Super P Li was added, and then 3 g of deionized water was transferred to wet the catalyst. 12 g of isopropanol and 460 mg of 9 wt% Nafion aqueous solution were added. The mixture was ultrasonically dispersed and magnetically stirred; the ultrasonic dispersion time was 30 min, the ultrasonic frequency was 40 kHz, and the magnetic stirring time was 30 min to obtain a uniformly mixed catalytic layer ink.

[0075] The above-mentioned evenly dispersed catalyst slurry is directly sprayed onto the surface of a 12μm proton exchange membrane by direct spraying to form a thin layer of cathode and anode catalyst layers on the membrane. The diffusion layer is covered on the outside of the cathode catalyst layer and the anode catalyst layer by hot pressing to obtain the membrane electrode. The spraying process parameters are set as follows: nozzle flow rate 10mL / min, suction cup heating temperature 80 degrees Celsius, spraying height from the heating suction cup 35cm; the hot pressing temperature is 170℃, hot pressing time is 180s, and hot pressing pressure is 2MPa. The platinum loading of the cathode catalyst layer is 0.6mg / cm 2 , the platinum loading of the anode catalyst layer is 0.1 mg / cm 2 .

[0076] Example 5

[0077] The modified PFA is modified by plasma amination, and the modification method is as follows:

[0078] S1: PFA was plasma modified in a plasma equipment in a mixed gas atmosphere of hydrogen, nitrogen and trimethylchlorosilane at a gas flow rate of 30 ml / min to obtain PFA with amino groups.

[0079] The gas used in the plasma equipment is a mixture of hydrogen, nitrogen and trimethylchlorosilane in a volume ratio of 30:70:0.5.

[0080] The power of the plasma surface treatment instrument was set to 200 W and the treatment time was set to 30 min.

[0081] Weigh 65 mg of 50% Pt / C (TEE10E50E) catalyst and 100 mg of 5 wt% modified PFA suspension emulsion, place them in a stirring 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 use ultrasonic dispersion and magnetic stirring to obtain a uniformly mixed catalytic layer ink; wherein, the ultrasonic dispersion time is 30 min, the ultrasonic frequency is 40 kHz, and the magnetic stirring time is 30 min.

[0082] The above-mentioned evenly dispersed catalyst slurry is directly sprayed onto the surface of a 12μm proton exchange membrane by direct spraying to form a thin layer of cathode and anode catalyst layers on the membrane. The diffusion layer is covered on the outside of the cathode catalyst layer and the anode catalyst layer by hot pressing to obtain the membrane electrode. The spraying process parameters are set as follows: nozzle flow rate 10mL / min, suction cup heating temperature 80 degrees Celsius, spraying height from the heating suction cup 40cm; the hot pressing temperature is 180℃, hot pressing time is 200s, and hot pressing pressure is 3MPa. The platinum loading of the cathode catalyst layer is 0.3mg / cm 2 , the platinum loading of the anode catalyst layer is 0.05 mg / cm 2 .

[0083] Comparative Example 1

[0084] Weigh 50 mg of 50% Pt / C (TEE10E50E) catalyst and 100 mg of 15 wt% PFA aqueous suspension emulsion and place them in a stirring 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. The mixture is ultrasonically dispersed and magnetically stirred; 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 catalytic layer ink.

[0085] The above-mentioned evenly dispersed catalyst slurry is directly sprayed onto the surface of a 12μm proton exchange membrane by direct spraying to form a thin cathode and anode catalyst layer covering the membrane. The diffusion layer is covered on the outside of the cathode catalyst layer and the anode catalyst layer by hot pressing to obtain the membrane electrode. The spraying process parameters are set as follows: nozzle flow rate 10mL / min, suction cup heating temperature 80 degrees Celsius, spraying height from the heating suction cup 40cm; the hot pressing temperature is 120℃, hot pressing time is 300s, and hot pressing pressure is 0.2MPa. The platinum loading of the cathode catalyst layer is 0.3mg / cm 2 , the platinum loading of the anode catalyst layer is 0.05 mg / cm 2 .

[0086] Comparative Example 2

[0087] 50 mg of 50% Pt / C (TEE10E50E) catalyst was weighed and placed in a stirring vessel. Then, 3 g of deionized water was transferred to wet the catalyst, and 7 g of isopropanol was added. 400 mg of a 5 wt% Nafion aqueous solution was added, and the mixture was ultrasonically dispersed and magnetically stirred. The ultrasonic dispersion time was 10 min, the ultrasonic frequency was 20 kHz, and the magnetic stirring time was 10 min to obtain a uniformly mixed catalytic layer ink.

[0088] The above-mentioned evenly dispersed catalyst slurry is directly sprayed onto the surface of a 12μm proton exchange membrane by direct spraying to form a thin layer of cathode and anode catalyst layers on the membrane. The diffusion layer is covered on the outside of the cathode catalyst layer and the anode catalyst layer by hot pressing to obtain the membrane electrode. The spraying process parameters are set as follows: nozzle flow rate 10mL / min, suction cup heating temperature 80 degrees Celsius, spraying height from the heating suction cup 40cm; the hot pressing temperature is 200℃, hot pressing time is 10s, and hot pressing pressure is 5MPa. The platinum loading of the cathode catalyst layer is 0.3mg / cm 2 , the platinum loading of the anode catalyst layer is 0.05 mg / cm 2 .

[0089] Test Example 1

[0090] The fuel cell membrane electrode prepared in Examples 1-5 and Comparative Examples 1-2 was assembled into a single cell, and the IV polarization curve performance test was carried out under the same conditions. The results are shown in Figures 1 and 2. The test conditions are as follows: the single cell temperature is 80 degrees Celsius, the anode and cathode reaction gases are Air / H2, and the stoichiometric ratio is 2 / 1.5; the inlet humidity is 40% / 50%, and the gas inlet pressures are 150KPa / 150KPa respectively.

[0091] From the test spectrum, it can be seen that for Comparative Examples 1 and 2, when no hydrophobic agent is added or only hydrophobic agent is added without conductive agent, the performance of the membrane electrode at a large current density is poor, 2A / cm 2 When the voltage is about 0.55V and 0.53V, it is much lower than the data measured in Examples 1-5. For Examples 1-5, the amount of hydrophobic agent added and the amount of graphitized carbon black added also have a certain influence on the membrane electrode performance. This is because the hydrophobic agent is a non-conductive substance. If it is added too much, it will increase the resistance of the catalytic 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 weakened catalyst performance, thereby affecting the membrane electrode performance. Excessive addition of graphitized carbon black will increase the thickness of the catalytic layer to a certain extent, 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 for a fuel cell, comprising 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, 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 amination-modified hydrophobic agent and graphitized carbon black; The mass ratio of catalyst: plasma amination modified hydrophobic agent: graphitized carbon black is 45-65: 5-22.5: 5-10.

2. The membrane electrode for a 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 5-15wt%; The graphitized carbon black is at least one of Super P Li, ENSACO 350G, and KS-6; The catalyst is a platinum-carbon catalyst, and the platinum loading is 40%-50%.

3. The membrane electrode for a fuel cell according to claim 1 or 2, characterized in that: The preparation method of the plasma amination modified hydrophobic agent comprises the following steps: The hydrophobic agent is plasma modified in a mixed gas atmosphere of hydrogen, nitrogen and trimethylchlorosilane using a plasma surface treatment apparatus to obtain the plasma amination-modified hydrophobic agent. The mixed gas flow rate is 10-30ml / min. The gas used in the plasma equipment is hydrogen, nitrogen, and trimethylchlorosilane in a volume ratio of 10-30:50-70:0.2-0.

5. The plasma surface treatment instrument is set to have a power of 150-200 W and a treatment time of 15 30min.

4. The membrane electrode 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 5-10wt%, and the mass ratio of the perfluorosulfonic acid polymer to the catalyst is 25-60:

100.

5. The membrane electrode 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 / cm 2 The platinum loading of the anode catalyst layer is 0.05-0.1 mg / cm 2 .

6. The method for preparing a membrane electrode for a fuel cell according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) mixing and uniformly dispersing a catalyst, a perfluorosulfonic acid polymer, graphitized carbon black, a hydrophobic agent, and a solvent to form a catalyst ink; The hydrophobic agent is plasma amination modified; (2) coating 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; (3) Covering the cathode catalyst layer and the anode catalyst layer with a diffusion layer by hot pressing to obtain the membrane electrode.

7. The method for preparing a membrane electrode for a fuel cell according to claim 6, characterized in that: In step (1), the method for plasma amination modification of the hydrophobic agent comprises the following steps: The hydrophobic agent is plasma modified in a mixed gas atmosphere of hydrogen, nitrogen and trimethylchlorosilane using a plasma surface treatment apparatus to obtain the plasma amination-modified hydrophobic agent. The mixed gas flow rate is 10-30ml / min. The gas used in the plasma equipment is hydrogen, nitrogen, and trimethylchlorosilane in a volume ratio of 10-30:50-70:0.2-0.

5. The plasma surface treatment instrument is set to have a power of 150-200 W and a treatment time of 15 30min.

8. The method for preparing a membrane electrode for 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 the solvent to the catalyst is 100-200:1; Water is also added in step (1), and the mass ratio of water to catalyst is 50-100:1; The dispersion is carried out by ultrasonic dispersion and magnetic stirring in sequence; wherein the ultrasonic dispersion time is 10-30 minutes, the ultrasonic frequency is 20-40KHz, and the magnetic stirring time is 10-30 minutes.

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

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

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