CN114361469A

CN114361469A - Fuel cell catalyst layer and fuel cell

Info

Publication number: CN114361469A
Application number: CN202111662202.9A
Authority: CN
Inventors: 王博; 冯霄; 张庆暖
Original assignee: Beijing Institute of Technology BIT; Advanced Technology Research Institute of Beijing Institute of Technology
Current assignee: Beijing Institute of Technology BIT; Advanced Technology Research Institute of Beijing Institute of Technology
Priority date: 2021-12-31
Filing date: 2021-12-31
Publication date: 2022-04-15
Anticipated expiration: 2041-12-31
Also published as: CN114361469B

Abstract

The invention relates to a fuel cell catalyst layer and a fuel cell, and belongs to the technical field of fuel cells. The catalytic layer is composed of an electrocatalyst and an ionomer. The ionomer is a mixture of perfluorosulfonic acid ionomer and COFs ionomer, the COFs ionomer can be prepared by a solvothermal-post-modification method, a one-step solvothermal method or a wet ball milling method, and is a porous powder material with a sulfonic side chain and a two-dimensional nanosheet structure, and the ion exchange capacity can exceed 1.85meq g^–1Proton conductivity can be as high as 94.3mS cm^–1. A fuel cell is a proton exchange membrane fuel cell or a solid oxide fuel cell, wherein a catalytic layer of the fuel cell is the catalytic layer of the fuel cell, the power density of the fuel cell is about 1.5 times that of a proton exchange membrane fuel cell which is singly added with Nafion and has the same platinum loading capacity, and the electrochemical surface area and the mass activity of a catalyst are improved by 1.6 times.

Description

Fuel cell catalyst layer and fuel cell

Technical Field

The invention relates to a fuel cell catalyst layer and a fuel cell, and belongs to the technical field of fuel cells.

Background

The proton exchange membrane fuel cell is mainly composed of a proton exchange membrane, and a catalyst layer, a diffusion layer and a bipolar plate which are sequentially and symmetrically distributed on two sides of the proton exchange membrane from inside to outside. The catalytic layer is typically comprised of a catalyst and an ionomer. The catalyst generally used at present is a platinum-carbon-based catalyst. The problems of proton transmission, gas transmission, electron transfer and the like in the catalyst layer greatly influence the activity and the utilization rate of the catalyst. The proton conduction and gas transport problems in the catalytic layer are more important at high current densities, particularly for high power density fuel cells, and are related to ionomers. Ionomers are also known as ionomers, and refer to polymers that contain small amounts of pendant acid/base groups on the macromolecular backbone, and that play important roles in catalytic layer binding and proton conduction. The most widely used commercial ionomer at present is the commercialized ionomer from DuPont in Perfluorosulfonic acid ionomer (PFSA)

But PFSA also has the obvious disadvantages of high price, complex production process, large gas mass transfer resistance, poor high-temperature stability and the like. Researchers have been devoted to research on the substitution of PFSA with novel ionomers, but the ionomers currently used in fuel cells are all chain-like polymers, and the problems of excessive wrapping and occupation of active sites of platinum on the catalyst still exist. Japanese Toyota Central R&The HOPI ionomer reported by the laboratory in 2021 can increase the dissolved oxygen and improve the power density of the fuel cell by 1.04 times, but the HOPI is still a chain-shaped polymer and does not obviously improve the oxygen accessibility of the platinum catalytic site. Therefore, the development of novel porous ionomer used for the catalytic layer of the proton exchange membrane fuel cell has very positive promotion effect on improving the power density and reducing the price of the fuel cell.

Covalent Organic Framework (COFs) materials are a novel Organic porous material with crystallinity, and the porous material can carry out long-range ordered arrangement on Organic structural units in a two-dimensional or three-dimensional direction. The COFs have wide application scenes due to the characteristics of fine regulation and control of pore structures, easiness in modification and the like. COFs have the following advantages: (1) the structural units are connected and expanded in two-dimensional or three-dimensional directions through covalent bonds, so that rich pore channel structures can be formed, and the gas diffusion capacity is good; (2) the structure of the structural unit can be accurately controlled, the environment in the pores can be further regulated, and the ion exchange capacity of the ionomer can be improved. The COFs ionomer can be obtained by introducing a structural unit with an ion group, and is researched as a candidate material of a proton exchange membrane at present, but the porous structure of the COFs ionomer is easy to cause gas diffusion, so that whether the COFs ionomer is suitable as a proton exchange membrane material or not is still left to be commercialized , and no report is made on adding the COFs ionomer to a catalytic layer of a proton exchange membrane fuel cell to optimize the microstructure of the catalytic layer.

Disclosure of Invention

To overcome the drawbacks of the prior art, it is an object of the present invention to provide a catalyst layer for a fuel cell.

It is another object of the present invention to provide a fuel cell.

In order to achieve the purpose of the invention, the following technical scheme is provided.

A fuel cell catalytic layer comprised of an electrocatalyst and an ionomer.

Wherein the electrocatalyst is a conventional catalyst in fuel cells, preferably a platinum-carbon catalyst (Pt/C), a platinum-cobalt catalyst (PtCo/C) or a platinum-carbon catalyst (Pt/KB) with Ketjen black as a carbon support.

The ionomer is a mixture of perfluorosulfonic acid ionomers and COFs ionomers, wherein the mass ratio of the COFs ionomers to the perfluorosulfonic acid ionomers is 0.5: 1-1.5: 1; preferred mass ratios of COFs ionomer to perfluorosulfonic acid ionomer are 1:1. preferably, the perfluorosulfonic acid ionomer is Nafion manufactured by DuPont.

The COFs ionomer is synthesized by adopting a first method or a second method according to different reactant types.

The first method is a solvothermal-post-modification method, and comprises the following specific steps:

(1) uniformly dispersing amino aromatic compounds and aromatic aldehyde compounds in a solvent A, adding a catalyst, deoxidizing, carrying out solvothermal reaction, carrying out centrifugal separation to obtain a solid, washing, and carrying out vacuum drying to obtain the COFs framework.

The amino aromatic compound is 1,3, 5-triaminobenzene, 1,3, 5-tri (4-aminophenyl) benzene (TAB), 5,10,15, 20-tetra (4-amino) phenyl porphyrin, 2,7,9, 14-tetra-amino pyrene or p-phenylenediamine; preferably, the amino aromatic compound is 1,3, 5-tri (4-aminophenyl) benzene or 5,10,15, 20-tetra (4-amino) phenylporphyrin.

The aromatic aldehyde compounds are 2, 5-dihydroxy terephthalaldehyde (DHA), 2, 5-dimethoxy terephthalaldehyde, 2, 5-dibutoxy terephthalaldehyde, 1, 4-di (4-aldehyde phenyl) benzene, 4 '-biphenyldicarbaldehyde, 3' -terphthalaldehyde or 9, 10-anthracene dicarboxaldehyde; preferably, the aromatic aldehyde group compound is 2, 5-dihydroxy terephthalaldehyde.

The catalyst is scandium trifluoromethanesulfonate or acetic acid aqueous solution; preferably, the catalyst is 6mol/L acetic acid aqueous solution.

Preferably, the molar ratio of the amino aromatic compound to the aromatic aldehyde group compound is 2: 3.

Preferably, the temperature of the solvothermal reaction is 100-140 ℃ and the time is 1-5 days.

The solvent A is at least one of n-butyl alcohol and dichlorobenzene; preferably, the solvent A is a mixed solvent of n-butanol and dichlorobenzene, and the volume ratio of the n-butanol to the dichlorobenzene is 1:1.

(2) Uniformly mixing the COFs skeleton powder obtained in the step (1) and a reducing agent in an anhydrous tetrahydrofuran solvent, slowly dropwise adding glacial acetic acid serving as a catalyst, and stirring at room temperature for more than 48 hours to obtain a suspension; and (4) centrifugally separating, washing and drying the suspension in vacuum to obtain the reduced COFs framework.

The reducing agent is at least one of cyano sodium borohydride and sodium borohydride.

Preferably, the mass ratio of the COFs framework powder to the reducing agent is 1: 3-1: 10.

(3) Uniformly mixing the reduced COFs framework powder obtained in the step (2) and a reaction reagent in a solvent B, refluxing, stirring and reacting for more than 48 hours, and filtering with a sodium filter membrane after washing; then soaking the membrane in strong acid aqueous solution with hydrogen ion concentration of 1mol/L except sulfuric acid for more than 24 hours for ion exchange, and filtering the membrane by using a nanofiltration membrane; and (3) drying in vacuum to obtain the COFs ionomer.

Wherein the reaction reagent is catalyst sodium hydroxide and a grafting agent, or the reaction reagent is catalyst potassium iodide, a carrier and a grafting agent.

The grafting agent is 3-bromopropyl sodium sulfonate, 2-bromoethyl sodium sulfonate, 4-bromo-1-butanesulfonic acid sodium sulfonate, 9-bromo-1-nonanesulfonic acid or 5-bromo-1-pentanesulfonic acid salt.

When the catalyst is sodium hydroxide, the solvent B is deionized water, and the reaction temperature is 80 ℃.

When the catalyst is potassium iodide, the solvent B is dimethyl sulfoxide, potassium carbonate or sodium carbonate is added as a carrier, and the reaction temperature is 120 ℃.

The molar weight of the grafting agent is 5-10 times of the number of carbon-nitrogen single bonds in the reduced COFs skeleton obtained in the step (2).

The molar weight of the catalyst is equal to the number of carbon-nitrogen single bonds in the reduced COFs skeleton obtained in the step (2).

Preferably, the washing mode in the step (3) is to sequentially wash with tetrahydrofuran, ethanol and deionized water.

Preferably, the strong acid aqueous solution is sodium perchlorate aqueous solution with hydrogen ion concentration of 1 mol/L.

Preferably, the temperature of vacuum drying is 40-80 ℃, and the vacuum drying time is more than 12 h.

The second method is a one-step solvothermal method or a wet ball milling method, and reactants of the one-step solvothermal method and the wet ball milling method are both an amino aromatic compound with a sulfonic side chain and Trialdehyde Phloroglucinol (TP), so that the types of the COFs ionomers prepared by the two preparation methods are the same.

The amino aromatic compound with a sulfonic side chain is 2, 5-diamino-1, 4-Benzene Disulfonic Acid (BDA), 2-amino-1, 4-benzene disulfonic acid, 1, 4-p-phenylenediamine-2, 5-disulfonic acid, 2, 5-diaminophenyl-1, 3-disulfonic acid, 2, 5-diaminobenzene sulfonic acid, 4, 8-diamino-2, 6-naphthalene disulfonic acid, 4 '-diamino [1,1' -biphenyl ] -3-sulfonic acid, 4 '-diamino- [1,1' -biphenyl ] -3,3 '-disulfonic acid, 3' -dimethyl-4, 4 '-diaminobiphenyl-5-sulfonic acid, 4' -diamino-5, 5 '-dimethyl (1,1' -biphenyl) -3,3 '-disulfonic acid, 4' -diamino-2 ', 6-dimethyl [1,1' -biphenyl ] -3-sulfonic acid or 4,4 '-diamino-3, 3' -dimethylbiphenyl-5-sulfonic acid; preferably, the amino aromatic compound having a sulfonate side chain is 2, 5-diamino-1, 4-benzenedisulfonic acid (BDA) or 2-amino-1, 4-benzenedisulfonic acid.

Preferably, the molar ratio of the amino aromatic compound with the sulfonic side chain to the trialdehyde phloroglucinol is 3: 2.

The one-step solvothermal method comprises the following specific steps:

uniformly dispersing amino aromatic compounds with sulfonic side chains and Trialdehyde Phloroglucinol (TP) in an organic solvent, adding a catalyst, removing oxygen, carrying out solvothermal reaction, carrying out centrifugal separation to obtain a solid, washing, and drying in vacuum to obtain the COFs ionomer.

The organic solvent is at least one of mesitylene and dioxane; preferably, the organic solvent is a mixed solvent of mesitylene and dioxane, and the volume ratio of mesitylene to dioxane is 4: 1.

Preferably, the washing mode is that the washing is sequentially carried out by using N, N-Dimethylformamide (DMF), tetrahydrofuran and deionized water.

The wet ball milling method comprises the following specific steps:

the COFs ionomer is obtained by directly carrying out wet ball milling on an amino aromatic compound with a sulfonic side chain and Trialdehyde Phloroglucinol (TP) for more than 1 hour, and then washing, separating and vacuum drying.

The solvent of the wet ball milling is at least one of mesitylene and dioxane; preferably, the solvent for wet ball milling is a mixed solution of mesitylene and dioxane, and the volume ratio of mesitylene to dioxane is 1:1.

preferably, the ball milling frequency is 50HZ, and the ball milling time is 1 h-2.5 h. Preferably, the washing mode is that the washing is sequentially carried out by using N, N-Dimethylformamide (DMF), tetrahydrofuran and deionized water, and each solvent is soaked and washed for 2-3 times.

Preferably, the separation method is centrifugation or filtration with a nanofiltration membrane.

A fuel cell is a proton exchange membrane fuel cell or a solid oxide fuel cell, wherein a catalytic layer is the fuel cell catalytic layer.

Advantageous effects

1. The invention provides a fuel cell catalyst layer, wherein COFs ionomer is added in the catalyst layer, the COFs ionomer is a porous two-dimensional nanosheet powder material which can be highly dispersed in aqueous solution, has high proton conductivity, and has a proton reaching rate of 94.3mS cm at 80 DEG C^–1And good thermal and chemical stability.

2. The invention provides a catalyst layer of a fuel cell, wherein COFs ionomer is added in the catalyst layer, and the COFs ionomer can be prepared by a solvothermal-post-modification method of a first method or a solvothermal method and a wet ball milling method in a second method according to different reactant types. The method has the advantages of low cost and price of raw materials, more designability of the COFs skeleton synthesized by the method I, more selectable monomer types, simple operation of the method II and easiness in large-scale production.

3. The invention provides a fuel cell, which is a proton exchange membrane fuel cell or a solid oxide fuel cell, wherein a catalytic layer is the catalytic layer of the fuel cell. The catalyst layer has good proton conductivity, thermal stability and chemical stability, the porous structure of the catalyst layer is beneficial to the diffusion of gas in the catalyst layer, the rigid structure avoids the direct contact of sulfonic acid groups and catalysts, the utilization rate of the electro-catalysts can be improved, the power density of the proton exchange membrane fuel cell is improved, and the power generation cost is reduced; the porous framework structure of the COFs ionomer in the catalytic layer enables the catalyst layer to solve the poisoning effect of excessive wrapping and platinum active sites occupation on the catalyst. The power density of the fuel cell is obviously improved, the power density is about 1.5 times that of a proton exchange membrane fuel cell which is singly added with Nafion and has the same platinum loading capacity, the electrochemical surface area is improved by 1.6 times, the mass activity of the catalyst is improved by 1.6 times, and the fuel cell has a very positive effect on improving the overall performance of the fuel cell.

Drawings

FIG. 1 is a solid NMR spectrum of DhaTab-COF, RDT-COF and SDT-COF prepared in example 1.

FIG. 2 is a comparison of IR spectra of DhaTab-COF, RDT-COF and SDT-COF prepared in example 1. FIG. a is a full spectrum, and FIG. b is an enlarged view of a low wavenumber region.

FIG. 3 is a graph comparing the IR spectra of NUS-10 prepared in example 5 and NUS-9 prepared in example 6.

FIG. 4 is a graph comparing the IR spectra of NUS-10 prepared in example 7 and NUS-9 prepared in example 8.

FIG. 5 is a comparison of the X-ray powder diffraction patterns of DhaTab-COF, RDT-COF and SDT-COF prepared in example 1.

Fig. 6 is a graph comparing the diffraction patterns of X-ray powder samples of NUS-10 prepared in example 5 and NUS-9 prepared in example 6.

Fig. 7 is a graph comparing the diffraction patterns of X-ray powder samples of NUS-10 prepared in example 7 and NUS-9 prepared in example 8.

FIG. 8 is a scanning electron microscope photograph of DhaTab-COF, RDT-COF and SDT-COF prepared in example 1.

FIG. 9 is a TEM image of DhaTab-COF, RDT-COF and SDT-COF prepared in example 1.

Fig. 10 is a transmission electron microscope image of NUS-10 (fig. b) prepared in example 5 and NUS-9 (fig. a) prepared in example 6.

FIG. 11 is a graphic representation of the DhaTab-COF, RDT-COF and SDT-COF vs. N prepared in example 1₂Comparing the gas adsorption and desorption curves; wherein, solid is an adsorption curve, and hollow is a desorption curve.

FIG. 12 shows NUS-10 prepared in example 5 and NUS-9 prepared in example 6 vs. N₂Comparing the gas adsorption and desorption curves; wherein, solid is an adsorption curve, and hollow is a desorption curve.

FIG. 13 is a full spectrum plot of the X-ray photoelectron spectra of DhaTab-COF, RDT-COF and SDT-COF prepared in example 1.

FIG. 14 is an oxygen (panel A) and nitrogen (panel B) spectra of X-ray photoelectron spectra of DhaTab-COF, RDT-COF and SDT-COF prepared in example 1.

FIG. 15 is a thermogravimetric plot of DhaTab-COF, RDT-COF and SDT-COF prepared in example 1.

FIG. 16 is a Nyquist plot of the impedance at different temperatures after compression of the SDT-COF prepared in example 1.

FIG. 17 is a graph showing proton conductivity (panel a) and activation energy (panel b) with temperature after compression of the SDT-COF prepared in example 1.

FIG. 18 is a Nyquist plot (plot a) for SDT-COF prepared in example 1 at various relative humidities after tableting, and a plot of proton conductivity of SDT-COF as a function of relative humidity (plot b).

Fig. 19 is an atomic force microscope picture (panel a) and a thickness analysis curve (panel b) of SDT-COF prepared in example 1.

Fig. 20 is an electron microscopic mirror scan of the catalytic layer prepared in example 1.

Fig. 21 is an electron microscopic cross-sectional scan view of the catalytic layer prepared in example 1.

Fig. 22 is a polarization curve and a power density curve of the proton exchange membrane fuel cells prepared in example 11 and comparative example 1. Graph a shows the hydrogen-oxygen condition and graph b shows the hydrogen-air condition.

Fig. 23 is a polarization curve and a power density curve of the proton exchange membrane fuel cells prepared in example 13 and comparative example 3. Graph a shows the hydrogen-oxygen condition and graph b shows the hydrogen-air condition.

Fig. 24 is a polarization curve and a power density curve of the proton exchange membrane fuel cells prepared in example 12 and comparative example 2. Graph a shows the hydrogen-oxygen condition and graph b shows the hydrogen-air condition.

Figure 25 cyclic voltammograms of the proton exchange membrane fuel cells prepared in example 11 and comparative example 1.

Fig. 26 is a cyclic voltammogram of the proton exchange membrane fuel cells prepared in example 13 and comparative example 3.

Fig. 27 is a cyclic voltammogram of the proton exchange membrane fuel cells prepared in example 12 and comparative example 2.

Fig. 28 is a Nyquist plot for the proton exchange membrane fuel cells prepared in example 1 and comparative example 1. Graph a shows the hydrogen-oxygen condition and graph b shows the hydrogen-air condition.

Fig. 29 is a Nyquist plot for the proton exchange membrane fuel cells prepared in example 13 and comparative example 3. Graph a shows the hydrogen-oxygen condition and graph b shows the hydrogen-air condition.

Fig. 30 is a Nyquist plot for the proton exchange membrane fuel cells prepared in example 12 and comparative example 2. Graph a shows the hydrogen-oxygen condition and graph b shows the hydrogen-air condition.

Fig. 31 is a graph showing polarization curves and power density curves during an accelerated stress test of 30000 cycles for a pem fuel cell prepared in example 11. Graph a is a voltage-current density curve and graph b is a power density-current density curve.

Fig. 32 is a graph showing the change in mass activity during the accelerated stress test of 30000 cycles for a pem fuel cell prepared in example 11.

Detailed Description

The invention is further illustrated by the following figures and detailed description, wherein the process is conventional unless otherwise specified, and the starting materials are commercially available from a public disclosure without further specification.

In the following examples:

platinum carbon catalyst (Pt/C): the Pt/Vulcan catalyst manufactured by Johnson Matthey corporation, with a platinum loading of 40%.

Platinum cobalt catalyst (PtCo/C): PtCo/Vulcan XC-72 catalyst from Premetek company with a platinum loading of 40%.

Platinum-carbon catalyst with ketjen black as carbon carrier (Pt/KB): premetek Pt/Ketjenblack EC-300J catalyst, with a platinum loading of 40%.

Nafion: manufactured by DuPont corporation

DE2020 solution, wherein the mass fraction of Nafion is 20%.

Proton exchange membrane: manufactured by DuPont corporation

N211。

Planetary ball mill: the instrument is produced by equipment factories of large instruments in south China of Jiangsu, and the model of the instrument is QM-3B.

The conditions relating to the test apparatus are as follows: nuclear magnetic resonance spectrometer: the measured nuclear magnetic property was a solid nuclear magnetic property, model Agilent DD 2400 MHz NMR, Agilent corporation, usa.

An infrared spectrometer: model Bruker ALPHA, wavelength range 400cm^-1～4000cm^-1Bruker, USA.

X-ray powder diffractometer: model Bruker Foucus D8, Bruker corporation, usa; wherein the powder sample has a scanning temperature of 298K, a pressure of 40kV and a current of 50mA, and the X-ray radiation source is Cu-K_α。

Atomic force microscope: the instrument model used was manufactured by Bruker, Germany, and the instrument model was Dimension Edge.

X-ray photoelectron spectroscopy: an ESCALB 250Xi instrument, brand name Thermo Fisher Scientific, was used.

Scanning electron microscope: model JEOL S-4800, Hitachi, Japan; wherein, the sample is dipped on the conductive adhesive of the cross section sample stage, the test voltage is 5kV, and the test current is 10 muA.

Transmission electron microscope: the JEOL brand model is JEM-2100 equipment, and the accelerating voltage is 200 kV.

A gas adsorption instrument: model Quantachrome (ASiQMH 002-5), Quantachrome Inc., USA; the specific surface areas of the prepared COFs powder material and the catalytic layer added with the COFs ionomer are tested under the standard atmospheric pressure (101kPa), and the purity of the gas used in the test is 99.999%.

Thermogravimetric analyzer: the instrument model used was Q600 SDT from Thermal Analysis Corporation, USA.

Analysis of organic elements: the apparatus used was manufactured by Thermo Fisher under the model FlashSmart.

Electrochemical workstation, instrument model CHI 760E, instrument manufacturer: shanghai Putian. The method is used for testing the proton conductivity of COFs powder materials.

Fuel cell test system: the instrument used was 850e available from Scribner Associates, usa. The fuel cell testing method comprises the following steps:

first, the fuel cell membrane electrode was activated by constant pressure at 0.6V for 5 hours. The test conditions were all 80 ℃ and 100% relative humidity.

The voltage-current density curve was tested, sweeping from open circuit voltage to 0.2V, and holding each voltage point for 1 minute. Under the hydrogen-oxygen condition, the hydrogen flow rate is controlled at 300mL/min, the oxygen flow rate is controlled at 300mL/min, the back pressure is 50kPa, and the absolute pressure is 150 kPa. Under the hydrogen-air condition, the hydrogen flow rate is controlled at 500mL/min, the oxygen flow rate is controlled at 1500mL/min, the back pressure is 50kPa, and the absolute pressure is 150 kPa.

The impedance is tested under the same conditions as the voltage-current density curve.

Conditions for testing mass activity: the hydrogen flow rate was controlled at 1000mL/min, the oxygen flow rate at 2000 mL/min, the back pressure at 150kPa, and the absolute pressure at 250 kPa.

Test conditions of cyclic voltammograms: the flow rate of hydrogen was 200mL/min, the flow rate of nitrogen was 75 mL/min, the back pressure was 50kPa, and the absolute pressure was 150 kPa.

Example 1

A fuel cell catalytic layer consisting of a Pt/C catalyst, Nafion, and COF ionomer.

The mass ratio of the COF ionomer to Nafion is 1.5: 1.

the COF ionomer is prepared by a solvothermal-post-modification method, and comprises the following specific steps:

(1) 28.1mg of TAB, 19.9mg of DHA and 2mL of a mixed solution were added to a 10mL ampoule, wherein the molar ratio of TAB to DHA was 2:3, and the mixed solution was uniformly dispersed by ultrasonic treatment, wherein the mixed solution was composed of n-butanol and dichlorobenzene, and the volume ratio of n-butanol to dichlorobenzene was 1: 1; then adding 0.2mL of 6mol/L acetic acid aqueous solution, removing oxygen by a liquid nitrogen freezing thawing pump circulation method, calcining, melting and sealing a flask opening with a flame gun, placing the flask opening in an oven, carrying out solvothermal reaction at 120 ℃ for 3 days, cooling to room temperature, carrying out centrifugal separation on the obtained material to obtain a solid, washing the solid with DMF (dimethyl formamide), acetone and vacuum drying at 60 ℃ to obtain an orange powdery material which is a COF framework (hereinafter referred to as DhaTab-COF) consisting of DHA and TAB, wherein the theoretical yield is 48mg, the actual yield is 45.6mg and the yield is 95%. (2) mixing 10mg of DhaTab-COF, 66mg of sodium cyanoborohydride and 20mL of anhydrous tetrahydrofuran in a round-bottom flask, uniformly stirring by using magnetons, slowly dropwise adding 35 mu L of glacial acetic acid, and stirring at room temperature for 48 hours to obtain a suspension; and then, centrifugally separating the suspension, washing with tetrahydrofuran, centrifuging, washing with deionized water, filtering, and drying in vacuum at 60 ℃ to obtain a light yellow solid which is a reduced COF skeleton (hereinafter abbreviated as RDT-COF).

(3) 100mg of RDT-COF, 75.8mg of potassium iodide, 1.263g of potassium carbonate, 1.125g of sodium 3-bromopropylsulfonate and 40mL of dimethyl sulfoxide were mixed in a round-bottomed flask, and the mixture was stirred under reflux at 120 ℃ for 48 hours. Washing with tetrahydrofuran, ethanol and deionized water successively, and filtering with nanofiltration membrane. Then, the solution was immersed in a perchloric acid aqueous solution having a hydrogen ion concentration of 1mol/L for 24 hours to perform ion exchange, and the solution was filtered with a nanofiltration membrane. And (3) drying at 60 ℃ in vacuum for 12h to obtain a bright red powdery material, namely a COF ionomer (hereinafter referred to as SDT-COF), wherein the catalytic layer is marked as Pt/C @ SDT-Nafion.

The molar amount of the sodium 3-bromopropylsulfonate is 10 times of the number of carbon-nitrogen single bonds in the reduced COF material solid powder obtained in the step (2).

The potassium iodide is equal to the number of carbon-nitrogen single bonds in the reduced COF material solid powder obtained in the step (2). The SDT-COF prepared in the embodiment is analyzed for organic elements, the content of sulfur elements is calculated, and the grafting rate of sulfonic acid groups in the SDT-COF is 60% through analysis.

Example 2

Example 2 on the basis of example 1, only 66mg of sodium cyanoborohydride in the step (2) was replaced with 39mg of sodium borohydride, and the mass ratio of COF skeleton powder to reducing agent was 1: 3.9, the SDT-COF with the sulfonic group grafting rate of 60 percent can be obtained without changing other steps and conditions.

Example 3

Example 3 on the basis of example 1, dimethyl sulfoxide in step (3) was replaced with deionized water, 75.8mg of potassium iodide and 1.263g of potassium carbonate in step (3) were replaced with 18.3mg of sodium hydroxide, and the reaction temperature in step (3) was replaced from 120 ℃ to 80 ℃, and other steps and conditions were not changed, to obtain SDT-COF having a sulfonic acid group grafting rate of 30%.

Example 4

Example 4 on the basis of example 1, 28.1mg of TAB in step (1) was replaced with 54.0mg of 5,10,15, 20-tetrakis (4-amino) phenylporphyrin, 19.9mg of DHA was replaced with 34.4mg of 1, 4-bis (4-formylphenyl) benzene, and other steps and conditions were not changed to obtain a porphyrin-type COF ionomer consisting of 5,10,15, 20-tetrakis (4-amino) phenylporphyrin and 1, 4-bis (4-formylphenyl) benzene.

The porphyrin-based COF ionomer prepared in this example was analyzed for organic elements, the content of sulfur elements was calculated, and the grafting ratio of sulfonic acid groups in the porphyrin-based COF ionomer was about 60%.

Example 5

The mass ratio of the COF ionomer to Nafion was 0.5: 1.

The COF ionomer is prepared by a one-step solvothermal method, and the preparation method comprises the following specific steps: 38.2mg of 2, 5-diamino-1, 4-benzenedisulfonic acid (BDA, 0.142mmol), 20mg of trialdehyde phloroglucinol (TP, 0.095mmol), 2.4mL of mesitylene, and 0.6mL of dioxane were charged into a 10mL ampoule, ultrasonic dispersing, then adding 0.6mL of acetic acid aqueous solution with the concentration of 6mol/L, deoxidizing by circulating method of liquid nitrogen freezing-thawing pump, calcining, thawing, sealing the opening of the ampoule by flame gun, thermal reaction in 120 deg.C solvent in oven for 3 days, cooling to room temperature, and centrifuging the obtained material to obtain a solid, washing the solid with DMF and tetrahydrofuran, then washing the solid with deionized water, and drying in vacuum at 60 ℃ to obtain a dark red powdery material which is a COF ionomer (NUS-10 for short) consisting of BDA and TP, wherein the catalytic layer is marked as Pt/C @ NUS 10-Nafion.

Example 6

Example 6 based on example 5, 38.2mg BDA in step (1) was modified to 21mg 2-amino-1, 4-benzenedisulfonic acid, the molar ratio of amino aromatic compound of the sulfonic side chain and trialdehyde phloroglucinol was 2.3: and 2, keeping other steps and conditions unchanged to obtain the COF ionomer (NUS-9) consisting of 2-amino-1, 4-benzene disulfonic acid and TP, wherein the catalytic layer is marked as Pt/C @ NUS 9-Nafion.

Example 7

A fuel cell catalyst layer consisting of a Pt/C catalyst, Nafion and COF ionomer.

The mass ratio of the COF ionomer to Nafion is 0.5: 1. the COF ionomer is prepared by a wet ball milling method, and the specific steps are as follows:

38.2mg of BDA (0.142mmol), 20mg of TP (0.095mmol) and 0.1mL of mesitylene and 0.1mL of dioxane were charged into a 50mL Teflon ball mill pot, 10 agate beads having a diameter of 3mm were added as ball-milled beads 1.125g, and then placed in a planetary ball mill and ball-milled at a frequency of 50Hz for 2.5 hours. Washing the obtained material with DMF and tetrahydrofuran, then washing with deionized water, soaking and washing in each solvent for 3 times, filtering and separating with a nanofiltration membrane, and vacuum drying at 60 ℃ for 12h to obtain a COF ionomer (NUS-10 for short) consisting of BDA and TP.

Example 8

Example 8 based on example 7, only 38.2mg of BDA was replaced with 21mg of 2-amino-1, 4-benzenedisulfonic acid, and other steps and conditions were not changed to obtain a COF ionomer consisting of 2-amino-1, 4-benzenedisulfonic acid and TP (abbreviated as NUS-9).

Example 9

Example 9 on the basis of example 1, only the electrocatalysts in the catalytic layers were replaced by "PtCo/C" catalysts from "Pt/C catalysts", SDT-COF and Nafion mass ratios were replaced by "1: 1" from "1: 1.5", the catalytic layers were denoted as PtCo/C @ SDT-Nafion, and other steps and conditions were not changed.

Example 10

Example 10 on the basis of example 1, only the electrocatalysts in the catalytic layers were replaced by "Pt/C catalyst" and "Pt/KB" catalyst, the mass ratio of SDT-COF and Nafion was replaced by "1: 1" from "1: 1.5", the catalytic layers were marked as Pt/KB @ SDT-Nafion, and other steps and conditions were not changed.

Example 11

A proton exchange membrane fuel cell, wherein the catalytic layer of the fuel cell is the Pt/C @ SDT-Nafion catalytic layer described in example 1.

120mg of Pt/C catalyst, 144mg

DE2020 solution, 28.8mg SDT-COF in a glass bottle, adding 50mL isopropanol, ultrasonic dispersing in ice water bath for 2 hours to obtain catalyst slurry, spraying the catalyst slurry onto the glass bottle by spraying

And (4) obtaining a catalytic layer on two sides of the N211 proton exchange membrane.

The platinum loading of the catalyst layer on the cathode surface and the anode surface of the membrane electrode of the proton exchange membrane fuel cell is controlled to be 0.1mg/cm²The SDT-COF mass is equal to the carbon in the Pt/C catalystThe mass ratio of the carrier is controlled to be 0.8, the catalyst layer and the carbon fiber paper with the filling layer as the gas diffusion layer are hot-pressed for 3 minutes under the pressure of 4.0MPa for molding to obtain the membrane electrode of the proton exchange membrane fuel cell, and the membrane electrode is placed into a clamp to obtain the proton exchange membrane fuel cell.

Example 12

Example 12 based on example 11, only the catalytic layer was replaced with "Pt/C @ SDT-Nafion catalytic layer as described in example 1" instead of "PtCo/C @ SDT-Nafion catalytic layer as described in example 9", and other steps and conditions were not changed.

Example 13

Example 13 based on example 11, only the catalytic layer was replaced with "Pt/KB @ SDT-Nafion catalytic layer as described in example 10" from "Pt/C @ SDT-Nafion catalytic layer as described in example 1", and other steps and conditions were not changed.

Example 14

Example 14 based on example 11, only the catalytic layer was replaced with "Pt/C @ NUS10-Nafion catalytic layer" described in example 5 from "Pt/C @ SDT-Nafion catalytic layer" described in example 1, and other steps and conditions were not changed.

Example 15

Example 15 on the basis of example 11, only the catalytic layer was replaced with "Pt/C @ NUS9-Nafion catalytic layer" described in example 6 from "Pt/C @ SDT-Nafion catalytic layer" described in example 1, and other steps and conditions were not changed.

Comparative example 1

Comparative example 1 on the basis of example 11, only the ionomer "consisting of Nafion and SDT-COF" in the catalytic layer was replaced by Nafion ", the catalytic layer was denoted as Pt/C @ Nafion, and other steps and conditions were not changed.

Comparative example 2

Comparative example 2 on the basis of example 12, only the ionomer "consisting of Nafion and SDT-COF" in the catalytic layer was replaced by Nafion ", the catalytic layer was denoted PtCo/C @ Nafion, and other steps and conditions were not changed.

Comparative example 3

Comparative example 3 based on example 13, only the ionomer "consisting of Nafion and SDT-COF" in the catalytic layer was replaced by Nafion ", the catalytic layer was denoted Pt/KB @ Nafion, and other steps and conditions were not changed.

The test results of the above examples and comparative examples are as follows:

(1) test results of nuclear magnetic resonance spectrometer

The results of nuclear magnetic resonance spectroscopy tests on the DhaTab-COF, RDT-COF and SDT-COF prepared in example 1 are shown in fig. 1, and the chemical shift value at 152ppm in the spectrogram is attributed to the carbon (-C ═ N) on the imine bond of the DhaTab-COF, which indicates that DHA and TAB generate DhaTab-COF through solvothermal reaction, and the peak corresponding to the imine bond in the RDT-COF pattern disappears after reduction reaction, and the carbon (-C-N-) peak around 60ppm appears. After the graft reaction, the carbon (-CH-) around 60ppm became sharper, and carbon (-CH-) with a chemical shift around 30ppm appeared₂-) peaks, demonstrating the progress of the reduction and grafting reactions.

Examples 2 and 3 the test results were similar to example 1.

(2) Test results of infrared spectrometer

Infrared spectroscopic measurement of the SDT-COF prepared in example 1 was carried out, and the results are shown in FIG. 2, 1182cm in FIG. 2^-1、1044cm^-1And 526cm^-1The stretching vibration peak attributed to the sulfonic acid group confirmed the formation of a COF ionomer with sulfonic acid group side chains, i.e., SDT-COF.

FIG. 3 is an infrared spectrum of NUS-10 prepared by a one-step solvothermal method in example 5 and NUS-9 prepared by a one-step solvothermal method in example 6, FIG. 4 is an infrared spectrum of NUS-10 prepared by a wet ball-milling method in example 7 and NUS-9 prepared by a wet ball-milling method in example 8, and FIG. 3 is substantially the same as FIG. 4 at 1438cm^-1、1080cm^-1And 1026cm^-1The peak is assigned to the stretching vibration peak of grafted sulfonic acid group, 1578cm^-1And 820cm^-1The peak is shown as a peak on the COF skeleton, and it was confirmed that NUS-9 and NUS-10 obtained by the one-step solvothermal method and the wet ball milling method were the same as those of the COF ionomer described in this example, and NUS-9 and NUS-10 obtained by both methods were the same. Thus, NUS in example 5-10 exemplary embodiment, and embodiment 6 is the NUS-9 exemplary embodiment.

(3) Test results of X-ray powder diffractometer

X-ray powder diffraction tests were carried out on the DhaTab-COF, RDT-COF and SDT-COF prepared in example 1, and the results are shown in FIG. 5, in which 2.7 DEG, 4.7 DEG and 5.5 DEG peaks are respectively assigned to d of the DhaTab-COF₍₁₀₀₎、 d₍₁₁₀₎And d₍₂₀₀₎Crystal planes, indicating the synthesis of a topologically structured COF backbone.

XRD measurements were performed on NUS-10 prepared by the one-step solvothermal method in example 5 and NUS-9 prepared by the one-step solvothermal method in example 6, and the results are shown in fig. 6. The peaks at 4.8 °, 9.9 ° and 26.6 ° in FIG. 6 are assigned d of NUS-9 and NUS-10, respectively₍₁₀₀₎、d₍₂₀₀₎And d₍₀₀₁₎Crystal planes, indicating the synthesis of a topologically structured COF backbone.

XRD measurements were performed on NUS-10 prepared using the wet ball milling method of example 7 and NUS-9 prepared using the wet ball milling method of example 8, and the results are shown in FIG. 7. The crystallization peak of fig. 7 disappeared, indicating that the COF backbone was synthesized and that the COF ionomer prepared by the ball milling method was in an amorphous state.

In example 5 and example 6, or in example 7 and example 8, because the skeleton structures of NUS-9 and NUS-10 are the same and the difference is only one sulfonate side chain, the XRD spectrums of NUS-9 and NUS-10 are consistent.

(4) Test results of scanning electron microscope and transmission electron microscope

Scanning electron microscopy and transmission electron microscopy tests were performed on DhaTab-COF, RDT-COF and SDT-COF prepared in example 1, and the results are shown in FIGS. 8 and 9, respectively, and it can be seen that: DhaTab-COF, RDT-COF and SDT-COF are all two-dimensional nanosheet layer structures. The test results of example 2 and example 3 were similar to the results of example 1.

FIG. 10 is a TEM image of example 5 and example 6, which shows that NUS-10 and NUS-9 prepared by one-step solvothermal method are two-dimensional nanosheet structure, and example 7 and example 8 are similar to FIG. 10 in TEM image of NUS-10 and NUS-9 prepared by wet ball milling method.

Fig. 20 and 21 are electron microscope mirror scanning images and electron microscope cross-sectional scanning images of the catalytic layer of the proton exchange membrane fuel cell prepared in example 1, and it can be seen from the images that the catalytic layer is uniformly distributed and the thickness of the catalytic layer is 6 μm. The test results of example 2 and example 3 were similar to example 1.

(5) Atomic force microscope test results

The test result of the atomic force microscope performed on the SDT-COF prepared in example 1 is shown in fig. 19, in which a is an atomic force microscope image and b is a thickness analysis curve, and it can be seen that the layer thickness of the SDT-COF is 0.8 nm; atomic force microscopy was performed on NUS-10 and NUS-9 prepared in examples 5 and 6, and the results showed that NUS-10 lamellae were 2nm thick and NUS-9 lamellae were 3nm thick.

(6) Results of thermogravimetric testing

The thermal gravimetric test of the SDT-COF prepared in example 1 shows that the thermal decomposition temperature of the SDT-COF is 200 ℃ far higher than the general operation temperature (80 ℃) of a proton exchange membrane fuel cell, and the SDT-COF has good thermal stability as shown in FIG. 15. The test results of example 2 and example 3 were similar to the results of example 1.

The NUS-10 and NUS-9 samples prepared in examples 5 and 6 have thermal decomposition temperatures of 120 ℃ and 150 ℃ respectively, which are higher than the operating temperature of a proton exchange membrane fuel cell by 80 ℃, and can meet the requirement of the thermal stability of the ionomer during the operation of the fuel cell.

(7) Results of gas adsorption test

In order to study the porosity of the prepared COFs ionomers, a Quantachrome gas adsorption instrument is selected for characterization. N was carried out at 77K on SDT-COF obtained in example 1, NUS-10 obtained in example 5 and NUS-9 obtained in example 6₂The adsorption test of (A) is shown in FIG. 11 and FIG. 12, and the BET specific surface areas of the COF ionomers SDT-COF, NUS-10 and NUS-9 prepared in examples 1, 5 and 6 were calculated to be 60m in order using the delocalized density functional theory model (NLDFT)² g^-1、209m² g^-1And 175m² g^-1。

(8) Test results of X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy characterization of RDT-COF and SDT-COF prepared in example 1 revealed that characteristic peaks of tertiary amine appeared on the fine spectrum of nitrogen element and no peak corresponding to ether appeared on the fine spectrum of oxygen element as shown in fig. 13 and 14, confirming that grafting reaction occurred on the COF backbone and that grafting reaction occurred on nitrogen on the COF backbone rather than on the phenolic hydroxyl group.

The X-ray photoelectron spectroscopy test results of example 2 and example 3 were similar to example 1.

(9) Test results for proton conductivity of COFs ionomers as a function of temperature and relative humidity

The proton conductivity of the SDT-COF prepared in example 1 was measured according to the change of temperature and relative humidity, and it can be seen from the results of the measurements in FIG. 16 and FIG. 17 that the proton conductivity of the SDT-COF prepared in example 1 increases with the increase of temperature, and the proton conductivity after tabletting at 80 ℃ can be as high as 94.3 mS/cm. The test results of fig. 18 show that the proton conductivity of the SDT-COF prepared in example 1 decreases with decreasing relative humidity. The test results of example 2 and example 3 were similar to example 1.

Proton conductivity after tabletting of NUS-10 and NUS-9 prepared in example 5 and example 6 was 20.8 mS/cm and 45.5 mS/cm. Proton conductivity of NUS-10 and NUS-9 prepared by wet ball milling in examples 7 and 8 after tableting was similar to that of examples 5 and 6.

(10) Results of fuel cell performance improvement with addition of COFs ionomers to catalytic layers

The proton exchange membrane fuel cells prepared in examples 11 to 15 and comparative examples 1 to 3 were subjected to polarization curve and power density tests, cyclic voltammetry curve and Nyquist curve tests, and it can be seen from the test results in fig. 22 to 30 that after SDT-COF was added to catalyst layers containing different catalysts, the maximum power density and the maximum current density of the fuel cell were found to be significantly increased by testing the voltage-current density curve as compared with the case where the SDT-COF was not added; the specific electrochemical surface area of the fuel cell is obviously increased by testing cyclic voltammetry curves compared with that before the cyclic voltammetry curves are added; nyquist plot testing showed a significant decrease in impedance.

The acceleration stress test results of fig. 31-32 show that the mass activity of the catalyst is only reduced by 38% after 30000 cycles of test, which indicates that the SDT-COF has excellent electrochemical stability and the effect of maintaining the catalytic layer structure stable.

The maximum power density, the maximum current density, the mass activity and the electrochemical specific surface area of the proton exchange membrane fuel cells obtained in examples 11 to 15 and comparative examples 1 to 3 were measured, and the results are shown in table 1:

TABLE 1 comparison of electrochemical performance indexes of PEMFC obtained in examples 11-15 and comparative examples 1-3

Test results show that the fuel cell catalyst layer provided by the invention is applied to a proton exchange membrane fuel cell under the same experimental conditions, the power density of the fuel cell catalyst layer can be improved to about 1.5 times that of a proton exchange membrane fuel cell with the same platinum loading capacity by only using Nafion as an ionomer under the hydrogen-air condition, the maximum current density is improved by 1.5 times, the electrochemical surface area is improved by 1.6 times, the mass activity of the catalyst is improved by 1.6 times, and the fuel cell catalyst layer has a very positive effect on improving the overall performance of the fuel cell.

Claims

1. A fuel cell catalyst layer comprised of an electrocatalyst and an ionomer, wherein: the ionomer is a mixture of perfluorosulfonic acid ionomers and COFs ionomers;

the mass ratio of the COFs ionomer to the perfluorosulfonic acid ionomer is 0.5: 1-1.5: 1;

the COFs ionomer is synthesized by adopting a first method or a second method according to different reactant types;

(1) uniformly dispersing amino aromatic compounds and aromatic aldehyde compounds in a solvent A, adding a catalyst, deoxidizing, carrying out solvothermal reaction, carrying out centrifugal separation to obtain a solid, washing, and carrying out vacuum drying to obtain a COFs framework;

the amino aromatic compound is 1,3, 5-triaminobenzene, 1,3, 5-tri (4-aminophenyl) benzene, 5,10,15, 20-tetra (4-amino) phenyl porphyrin, 2,7,9, 14-tetra-aminopyrene or p-phenylenediamine;

the aromatic aldehyde compounds are 2, 5-dihydroxy terephthalaldehyde, 2, 5-dimethoxy terephthalaldehyde, 2, 5-dibutoxy terephthalaldehyde, 1, 4-di (4-aldehyde phenyl) benzene, 4 '-biphenyldicarboxaldehyde, 3' -terphthalaldehyde or 9, 10-anthracene dicarboxaldehyde;

the catalyst is scandium trifluoromethanesulfonate or acetic acid aqueous solution;

the solvent A is at least one of n-butyl alcohol and dichlorobenzene;

(2) uniformly mixing COFs framework powder and a reducing agent in an anhydrous tetrahydrofuran solvent, dropwise adding glacial acetic acid serving as a catalyst, and stirring at room temperature for more than 48 hours to obtain a suspension; centrifugally separating, washing and vacuum drying the suspension to obtain a reduced COFs framework;

the reducing agent is at least one of sodium cyanoborohydride and sodium borohydride;

(3) uniformly mixing the reduced COFs framework powder and a reaction reagent in a solvent B, refluxing, stirring and reacting for more than 48 hours, washing and filtering by using a sodium filter membrane; then soaking the membrane in strong acid aqueous solution with hydrogen ion concentration of 1mol/L except sulfuric acid for more than 24 hours for ion exchange, and filtering the membrane by using a nanofiltration membrane; vacuum drying to obtain COFs ionomer;

wherein the reaction reagent is catalyst sodium hydroxide and a grafting agent, or the reaction reagent is catalyst potassium iodide, a carrier and a grafting agent;

the grafting agent is 3-bromopropyl sodium sulfonate, 2-bromoethyl sodium sulfonate, 4-bromo-1-butanesulfonic acid sodium sulfonate, 9-bromo-1-nonanesulfonic acid or 5-bromo-1-pentanesulfonic acid salt;

when the catalyst is sodium hydroxide, the solvent B is deionized water, and the reaction temperature is 80 ℃;

when the catalyst is potassium iodide, the solvent B is dimethyl sulfoxide, potassium carbonate or sodium carbonate is added as a carrier, and the reaction temperature is 120 ℃;

the molar weight of the grafting agent is 5-10 times of the number of carbon-nitrogen single bonds in the reduced COFs skeleton;

the molar weight of the catalyst is equal to the number of carbon-nitrogen single bonds in the reduced COFs framework;

the second method is a one-step solvothermal method or a wet ball milling method, and reactants of the one-step solvothermal method and the wet ball milling method are both an amino aromatic compound with a sulfonic side chain and trialdehyde phloroglucinol;

the amino aromatic compound with a sulfonic side chain is 2, 5-diamino-1, 4-benzene disulfonic acid, 2-amino-1, 4-benzene disulfonic acid, 1, 4-p-phenylenediamine-2, 5-disulfonic acid, 2, 5-diaminophenyl-1, 3-disulfonic acid, 2, 5-diaminobenzene sulfonic acid, 4, 8-diamino-2, 6-naphthalene disulfonic acid, 4 '-diamino [1,1' -biphenyl ] -3-sulfonic acid, 4 '-diamino- [1,1' -biphenyl ] -3,3 '-disulfonic acid, 3' -dimethyl-4, 4 '-diaminobiphenyl-5-sulfonic acid, 4' -diamino-5, 5 '-dimethyl (1,1' -biphenyl) -3,3 '-disulfonic acid, 4' -diamino-2 ', 6-dimethyl [1,1' -biphenyl ] -3-sulfonic acid or 4,4 '-diamino-3, 3' -dimethylbiphenyl-5-sulfonic acid;

the one-step solvothermal method comprises the following specific steps:

uniformly dispersing amino aromatic compounds with sulfonic side chains and trialdehyde phloroglucinol in an organic solvent, adding a catalyst, deoxidizing, carrying out solvothermal reaction, carrying out centrifugal separation to obtain a solid, washing, and carrying out vacuum drying to obtain a COFs ionomer;

the organic solvent is at least one of mesitylene and dioxane;

the wet ball milling method comprises the following specific steps:

carrying out wet ball milling on an amino aromatic compound with a sulfonic side chain and trialdehyde phloroglucinol for more than 1 hour directly, and then washing, separating and drying in vacuum to obtain a COFs ionomer;

the solvent of the wet ball milling is at least one of mesitylene and dioxane.

2. A fuel cell catalyst layer according to claim 1, wherein: the mass ratio of the COFs ionomer to the perfluorosulfonic acid ionomer is 1:1.

3. a fuel cell catalyst layer according to claim 1, wherein: the electrocatalyst is a platinum-carbon catalyst, a platinum-cobalt catalyst or a platinum-carbon catalyst taking Ketjen black as a carbon carrier; the perfluorosulfonic acid ionomer is Nafion manufactured by DuPont.

4. The fuel cell catalyst layer according to claims 1 to 3, characterized in that: the molar ratio of the amino aromatic compound to the aromatic aldehyde group compound is 2: 3.

5. A fuel cell catalyst layer according to claim 4, wherein: the amino aromatic compound is 1,3, 5-tri (4-aminophenyl) benzene or 5,10,15, 20-tetra (4-amino) phenyl porphyrin; the aromatic aldehyde compound is 2, 5-dihydroxy terephthalaldehyde.

6. A fuel cell catalyst layer according to claim 4, wherein: the catalyst in the solvothermal-post-modification method is 6mol/L acetic acid aqueous solution; the temperature of the solvothermal reaction in the solvothermal-post-modification method is 100-140 ℃, and the time is 1-5 days; the solvent A is a mixed solvent of n-butyl alcohol and dichlorobenzene, and the volume ratio of the n-butyl alcohol to the dichlorobenzene is 1:1.

7. A fuel cell catalyst layer according to claim 4, wherein: the mass ratio of the COFs framework powder to the reducing agent is 1: 3-1: 10.

8. A fuel cell catalyst layer according to claim 4, wherein: the washing mode of the step (3) in the solvent thermal-post modification method is to wash with tetrahydrofuran, ethanol and deionized water in sequence; the strong acid aqueous solution is a sodium perchlorate aqueous solution with the hydrogen ion concentration of 1 mol/L; the temperature of the vacuum drying is 40-80 ℃, and the vacuum drying time is more than 12 h.

9. The fuel cell catalyst layer according to claims 1 to 3, characterized in that: the molar ratio of the amino aromatic compound with the sulfonic side chain to the trialdehyde phloroglucinol is 3: 2.

10. A fuel cell catalyst layer according to claim 9, wherein: the amino aromatic compound with the sulfonic side chain is 2, 5-diamino-1, 4-benzene disulfonic acid or 2-amino-1, 4-benzene disulfonic acid.

11. A fuel cell catalyst layer according to claim 10, wherein: the catalyst in the one-step solvothermal method is 6mol/L acetic acid aqueous solution; the organic solvent is a mixed solvent of mesitylene and dioxane, and the volume ratio of mesitylene to dioxane is 4: 1; the temperature of the solvothermal reaction in the one-step solvothermal method is 100-140 ℃, and the time is 1-5 days; the washing mode in the one-step solvothermal method is to wash by using N, N-dimethylformamide, tetrahydrofuran and deionized water in sequence.

12. A fuel cell catalyst layer according to claim 10, wherein: the solvent for wet ball milling is a mixed solution of mesitylene and dioxane, and the volume ratio of mesitylene to dioxane is 1: 1; the ball milling frequency is 50HZ, and the ball milling time is 1 h-2.5 h.

13. A fuel cell catalyst layer according to claim 12, wherein: the washing mode in the wet ball milling method is that the raw materials are sequentially washed by N, N-dimethylformamide, tetrahydrofuran and deionized water, and each solvent is soaked and washed for 2-3 times; the separation mode is centrifugation or filtration by a nanofiltration membrane; the temperature of vacuum drying is 40-80 ℃, and the vacuum drying time is more than 12 h.

14. A fuel cell, the fuel cell being a proton exchange membrane fuel cell or a solid oxide fuel cell, characterized in that: the catalyst layer of the fuel cell is the catalyst layer of the fuel cell according to any one of claims 1 to 13.