CN117393785B

CN117393785B - Catalytic layer coating film and preparation method thereof

Info

Publication number: CN117393785B
Application number: CN202311612724.7A
Authority: CN
Inventors: 俞庆阳; 胡桂林; 王朝云; 秦森杰; 汤飞
Original assignee: Shanghai Tomorrow Guandi Hydrogen Energy Technology Co ltd
Current assignee: Shanghai Tomorrow Guandi Hydrogen Energy Technology Co ltd
Priority date: 2023-11-29
Filing date: 2023-11-29
Publication date: 2024-08-06
Anticipated expiration: 2043-11-29
Also published as: CN117393785A

Abstract

The invention discloses a catalytic layer coating film and a preparation method thereof, and relates to the technical field of fuel cells, wherein the coating film comprises an anode catalytic layer, a proton exchange film and a cathode catalytic layer, the anode catalytic layer and the cathode catalytic layer are respectively arranged at two sides of the proton exchange film, and a catalyst used by the anode catalytic layer and the cathode catalytic layer is Pt/NPC _G,N; the preparation method adopted by the invention can control the primary particle size, the pore volume ratio, the pore size distribution, the pore structure with communicated inside, the graphitization degree, the nitrogen group modification, the Pt nano particle size, the ionomer assembly form and the avoidance of harmful anions of the NPC _G,N carrier; proper pore size, pore size distribution and internal communication structure not only allow mass transport, but also prevent ionomer impregnation; the specific pore size can realize the spatial separation of the Pt nano particles and the ionomer, and relieve the poisoning effect of the ionomer on the Pt nano particles.

Description

Catalytic layer coating film and preparation method thereof

Technical Field

The invention relates to the technical field of fuel cells, in particular to a catalytic layer coating film and a preparation method thereof.

Background

Proton exchange membrane fuel cells are an electrochemical energy conversion device that utilizes renewable energy sources. The stack in a proton exchange membrane fuel cell is a key core component that makes up the fuel cell. According to the electrical application requirements of voltage, current, power and the like, a plurality of membrane electrodes and bipolar plates are alternately stacked in series to form a galvanic pile. The membrane electrode determines the stack performance, lifetime and cost. The catalytic layer coating membrane, CCM for short, is the most central component of the membrane electrode, and the whole electrochemical reaction is completed on the CCM, which is called a chip of the fuel cell.

The CCM is composed of an anode catalytic layer, a proton exchange membrane, a cathode catalytic layer and the like, wherein the anode catalytic layer and the cathode catalytic layer are respectively coated on two sides of the proton exchange membrane. To ensure efficient conduction of protons in the catalytic layer, perfluorosulfonic acid ionomers have been widely used in the catalytic layer of CCMs. Perfluorosulfonic acid type ionomers have been widely used in automotive fuel cell catalytic layers to ensure proton conduction of the catalytic layers; in a conventional fuel cell automotive catalytic layer, pt and ionomer on the catalyst are in contact coexistence.

However, conventional catalytic layers suffer from the following disadvantages:

First, the side chains of perfluorosulfonic acid ionomers contain several ether linkages. The ether bond has a strong adsorption effect on Pt on the catalyst, and the adsorption effect can drive sulfonic groups at the tail ends of the side chains to be adsorbed on Pt nano particles; adsorption of sulfonic acid groups on Pt nanoparticles results in a decrease in platinum catalytic activity, and this adsorption poisoning phenomenon has a greater impact on the oxygen reduction reaction of the fuel cell cathode catalytic layer. Resulting in a decrease in cathode Pt catalytic activity and utilization, further resulting in an increase in Pt loading and cost.

Secondly, when the voltage fluctuation range is wider, pt on smaller-sized particles is dissolved due to the surface energy difference between adjacent Pt nanoparticles, and is deposited on nearby larger-sized particles in the form of atoms or ions, the electrochemical active area is reduced due to the increase of the particle size, and the performance of the fuel cell is reduced; the so-called Ostwald ripening mechanism.

Third, when the voltage is frequently changed, pt is dissolved into an ionic form, and may diffuse and migrate from a high Pt ion concentration region to a low ion concentration region in a proton exchange membrane phase, and hydrogen permeated from an anode is reduced, which may cause Pt to precipitate in the proton exchange membrane and form Pt bands, and may significantly reduce proton conductivity and reliability of the proton exchange membrane.

Fourth, during operation of the proton exchange membrane fuel cell, due to improper gas supply, severe load change and start-stop conditions, the carbon carrier is easily corroded, and Pt nanoparticles are caused to fall off from the carrier.

The above disadvantages eventually lead to a decrease in the output power of the fuel cell stack.

Disclosure of Invention

The invention aims to provide a catalytic layer coating film and a preparation method thereof, which solve the following technical problems:

1. Adsorption of the ionomer on Pt in the catalytic layer inhibits its catalytic activity;

coarsening of pt nanoparticles causes a decrease in electrochemically active area;

pt is deposited in the proton exchange membrane, which reduces the conductivity and reliability of the proton exchange membrane;

4. Corrosion of the carbon support, the Pt nanoparticles shed from the carbon support, causing a decrease in the electrochemically active area.

The aim of the invention can be achieved by the following technical scheme:

The invention discloses a catalytic layer coating film, which comprises an anode catalytic layer, a proton exchange film and a cathode catalytic layer, wherein the anode catalytic layer and the cathode catalytic layer are respectively arranged at two sides of the proton exchange film, and the anode catalytic layer and the cathode catalytic layer comprise catalyst slurry respectively sprayed at two sides of the proton exchange film.

The preparation raw materials of the catalyst slurry comprise dimethylacetamide, N-methylformamide, pt/NPC _G,N catalyst and NafionD2020 ionomer, wherein the dimethylacetamide, the N-methylformamide and the NafionD2020 ionomer are all existing products, the dimethylacetamide and the N-methylformamide are both directly purchased from the market, and the NafionD2020 ionomer is purchased from Chemours company; the mass fraction of the platinum content in the Pt/NPC _G,N catalyst is 50%, and the Pt/NPC _G,N catalyst with 50% platinum content needs to be prepared by itself.

The preparation of a Pt/NPC _G,N catalyst with 50% platinum content needs to be divided into the following four processes:

(one) preparing a carbon carrier;

graphitizing the carbon carrier;

(III) carrying out nitrogen group modification on the graphitized carbon carrier;

And (IV) synthesizing the Pt/NPC _G,N catalyst with 50% platinum content by using the carbon carrier modified by the nitrogen group.

The four processes for preparing the Pt/NPC _G,N catalyst having a platinum content of 50% described above will be described in detail, respectively, as follows.

In a first aspect, a carbon support is prepared, comprising the steps of:

S1, placing a silver nitrate solution with the mass fraction of 5% in a flask, then adding a sodium hydroxide solution with the mass fraction of 10% into the flask, and shaking uniformly while dripping, wherein the volume ratio of the sodium hydroxide solution to the silver nitrate solution is 6:1; and then dropwise adding 2% ammonia water solution into the flask, and shaking uniformly while dropwise adding until the generated precipitate is just dissolved, thus obtaining the clarified silver nitrate ammonia water solution.

S2: washing H ₂C₂ gas by using sodium hypochlorite solution, and then washing gas by using saturated copper sulfate solution to obtain pure H ₂C₂ gas; the sodium hypochlorite solution has strong oxidizing property and strong alkalinity, impurities in H ₂C₂ gas can be thoroughly removed, and a small amount of residual impurities can be removed by the saturated copper sulfate solution, so that the interference of the impurities contained in H ₂C₂ on the reaction is avoided;

Pure H ₂C₂ gas is introduced into a flask of silver nitrate ammonia water solution at the speed of 30ml/min, and the flask is placed in an ultrasonic vibration tank with the ultrasonic frequency of 20kHz, so that H ₂C₂ reacts with the silver nitrate ammonia water solution to generate yellow precipitate, and the yellow precipitate is gradually converted into white precipitate with a little silver gray color, namely Ag ₂C₂, along with the progress of the reaction.

S3: after the reaction is completed, the mixture containing Ag ₂C₂ in the flask is transferred into a cloth funnel, and suction filtration, water washing and suction drying are carried out to obtain Ag ₂C₂ precipitate.

S4: transferring the Ag ₂C₂ precipitate into a PTFE reaction kettle, and placing the reaction kettle into a vacuum drying oven, wherein the absolute pressure of the vacuum drying oven is less than or equal to 2Pa, and the temperature is 55 ℃; immediately after 13 hours of drying, the vacuum oven was set to 210 ℃; during the drying stage of 13 hours, the silver particles in Ag ₂C₂ tend to be encapsulated by carbon particles, and the drying can remove the hydrated water molecules contained in Ag ₂C₂;

When the temperature of the drying oven rises to about 150 ℃, an instant explosion sound can be heard; when the Ag ₂C₂ explodes, the wrapped silver particles are ejected, so that the surface and the inside of the carbon can generate pore structures;

The resulting powder was collected immediately after the explosion sound and dissolved in a diluted nitric acid at a volume ratio of 9:50 to silver nitrate solution and stirred at room temperature (20 ℃ C. -25 ℃ C.) for 1.5 hours to remove silver powder, silver particles remaining on carbon and unstable Ag ₂C₂.

S5: repeatedly washing the powder dissolved in dilute nitric acid for 3-5 times in a suction filtration mode until silver ions in the powder are removed; after washing, checking whether the washing filtrate contains silver ions or not by using an ammonium chloride reagent until white AgCl does not appear in the washing filtrate, and indicating that the silver ions in the powder are washed; the washed powder was dried in vacuo at 60℃to give nanoporous carbon (Nano Porous Carbon, denoted NPC), the NPC support.

The method optimizes the synthesis steps to prepare quite pure Ag ₂C₂ intermediate; on one hand, the sodium hypochlorite solution and the saturated copper sulfate solution are used for washing the acetylene, so that the interference of trace impurities in the acetylene on a synthesis experiment is eliminated; on the other hand, 2% ammonia water solution is used as a solvent system for the reaction, so that the generation of by-product precipitation Ag ₂C₂·AgNO₃ is avoided; meanwhile, the silver content of Ag ₂C₂ precipitate is measured by adopting an iron ammonium alum indicator method, the measured result is 89.90 percent, the theoretical content of the Ag ₂C₂ precipitate is very close to 89.98 percent, and the precipitate generated by the reaction of H ₂C₂ and silver nitrate ammonia water solution is quite pure Ag ₂C₂, which also proves that the mass fraction and the proportion of each component adopted by the invention are all optimal values from the side.

The invention also controls the particle size of Ag ₂C₂ sediment by changing the ventilation time of pure acetylene gas, and the particle size of Ag ₂C₂ sediment determines the primary average particle size of the subsequent nano porous carbon; the preferable aeration flow and aeration time are 30ml/min and 50min respectively, the average particle diameter of Ag ₂C₂ is observed by a scanning electron microscope, 100 Ag ₂C₂ particles are randomly selected, the particle diameters are measured, and the average value is calculated, so that the result shows that the average particle diameter of Ag ₂C₂ is 50nm; characterizing the average primary particle diameter of the nano porous carbon by using a scanning electron microscope, randomly selecting primary particles of 100 nano porous carbon, measuring the particle diameter and calculating the average value; the results showed that the average primary particle size of the nanoporous carbon was about 50nm, consistent with the average particle size of Ag ₂C₂.

Because Ag ₂C₂ can spray out the silver particles wrapped at about 150 ℃, the size of the silver particles determines the pore size, pore size distribution and pore size proportion of the nano porous carbon; the segregation degree of silver particles is controlled by changing the vacuum drying temperature and the vacuum drying time of Ag ₂C₂, so that the main pore size, the pore size distribution and the main pore size proportion of the nano porous carbon are controlled; the invention preferably carries out nitrogen isothermal adsorption and desorption curves on the nano porous carbon at 55 ℃ and 13h respectively to represent the pore size, pore size distribution and pore size proportion, and the adsorption curve has a protruding peak at 2.8nm in a mesoporous region, which indicates that the main pore diameter of the nano porous carbon is 2.8nm; the adsorption peaks of the adsorption curve are continuously distributed to 10nm, which means that the pore size distribution of the nano porous carbon is relatively uniform, the maximum pore size is only 10nm, further calculation shows that the cumulative pore volume ratio of 2.8-10nm of the nano porous carbon is 80%, the cumulative pore volume ratio of 2.8nm pore size is 72%, and literature data shows that too small pore size can cause difficult Pt particle loading, reaction gas transmission, proton conduction, liquid water discharge and the like; too large pore sizes can cause ionomer impregnation, pt nanoparticle poisoning, and pore sizes of 2.5nm-5.0nm can balance many of the above factors.

Further analyzing the isothermal adsorption and desorption curve of nitrogen, wherein the specific surface area of the nano porous carbon is 1610m ²/g, which is favorable for highly dispersing Pt in the form of nano particles; carrying out transmission electron microscope characterization on the nano-porous carbon, and finding that the interior of the nano-porous carbon has a communicated pore structure; on one hand, the communicated pores inside the nano porous carbon are beneficial to the formation of hydrogen bonds between protons and water molecules, and the transmission of protons inside the nano porous carbon is realized through a proton solvent conjugation mechanism; on the other hand, the communication pores inside the nano porous carbon are beneficial to the transmission of reaction gas and the discharge of liquid water; compared with a spherical carbon carrier, pt particles on the nano porous carbon are positioned in the nano porous carbon, and the steric effect of the nano porous carbon relieves the deposition growth problem of the Pt particles caused by an Ostwald curing mechanism to a certain extent;

The nano porous carbon prepared by the invention is a uniform pore structure with communicated inside, and particularly, the pore structure is characterized in that the size of the pore structure is usually between 2.8nm and 10nm, and the difference of pore sizes is also smaller; these channels can be used to disperse Pt nanoparticles, which have less chance to migrate to other locations when Pt nanoparticles are dispersed in these channels, which helps to improve the dimensional stability of the Pt nanoparticles; due to the existence of these pores, the nanoporous carbon generally has a higher specific surface area, which can provide more attachment sites, reduce interactions between Pt nanoparticles, and thus reduce the possibility of migration thereof.

In a second aspect, graphitizing the nanoporous carbon (NPC support) comprises the steps of:

and (3) placing the nano porous carbon in an argon atmosphere, and protecting for 2 hours at 1700 ℃. Graphitized (GRAPHITING) nanoporous carbon (noted NPC _G support) was obtained.

Firstly, the imperfect structure in the nano porous carbon can be removed by improving the graphitization degree of the nano porous carbon, and the electron conductivity of the nano porous carbon is improved, so that the ohmic polarization loss of the fuel cell during operation is reduced; secondly, the nano-porous carbon is usually required to bear high-temperature and high-pressure environments, and the graphitization treatment can increase the mechanical strength and stability of the nano-porous carbon, so that the nano-porous carbon can resist the extreme environments more, and the service life of the catalyst is prolonged; finally, when the fuel cell is operated at high power, more liquid water is generated, if the liquid water is not discharged in time, the liquid water can cover active sites of the catalyst, so that the transmission resistance of oxygen in the catalytic layer is greatly increased, the concentration polarization loss is increased during the high power operation, the performance of the fuel cell is greatly attenuated during the high power operation, and the graphitization treatment can increase the hydrophobicity of the catalytic layer, especially the liquid water generated during the high power operation of the fuel cell is discharged in time.

According to the dynamic working condition operation requirement of the vehicle-mounted fuel cell, if the graphitization degree of the nano porous carbon is too high, the hydrophobicity of the catalytic layer is too strong, and when the fuel cell operates at low power, less water is produced, as proton conduction is carried out in the form of hydrated protons, the proton transmission resistance is relatively high due to the too small water content of the catalytic layer, and the ohmic polarization loss is increased when the fuel cell operates at low power; meanwhile, if the graphitization degree is too high, the pore structure of the nano porous carbon can be severely collapsed in a large area, the internal communication structure is destroyed, and the pore size can be greatly changed.

In order to control the graphitization degree of the nano porous carbon, the working temperature and the relative humidity of the low-power operation of the fuel cell are taken as parameters; the operating temperature of the fuel cell for low power operation is preferably 25 ℃, and the saturated vapor pressure of the water vapor at 25 ℃ is 3.169kpa; the relative humidity of the fuel cell for low power operation is preferably 10%; the real area of the nano porous carbon is taken as a denominator, the water vapor adsorption volume of the nano porous carbon for adsorbing 10% RH air is taken as a molecule, and the adsorption quantity alpha is defined; the more hydrophobic the material is when the alpha value is closer to 0.375ml/m2, the more suitable the fuel cell is for operating conditions; through repeated experiments, the graphitization condition is finally determined as 1700 ℃ and 2h under the protection of argon atmosphere in the steps.

In a third aspect, the modification of nitrogen groups on graphitized nanoporous carbon (NPC _G support) mainly comprises the following steps:

S1, preparing a nitric acid solution with the mass fraction of 65%, injecting the nitric acid solution into an oil bath flask, and adding graphitized nano-porous carbon into the oil bath flask, wherein 4g of graphitized nano-porous carbon is added into each 100ml of nitric acid solution.

S2: methyl silicone oil is injected into the oil bath pot, so that the volume of the methyl silicone oil reaches 80 percent of the full volume of the oil bath pot; placing the oil bath flask into an oil bath pot, and adjusting the height of a fixed bracket of the oil bath flask to ensure that the liquid level in the oil bath flask is slightly lower than the liquid level of methyl silicone oil and can be lower than 1-5mm; simultaneously starting a magnetic stirrer to enable the rotating speed of a tetrafluoro magnetic rotor in the oil bath flask to be 200RPM; starting the heating function of the oil bath pan, quickly heating the methyl silicone oil to 70 ℃ and preserving heat for 2 hours;

S3: taking out the oil bath flask after heat preservation, slowly adding ultrapure water with the resistivity of about 18.2MΩ & cm at normal temperature (20-25 ℃) while shaking the oil bath flask to avoid uneven cooling, transferring the materials in the oil bath flask into a beaker, and filtering and cleaning the materials in the beaker for more than 3 times by using a vacuum suction filtration device to obtain an NPC _G (alpha) carrier; because of the modification of NPC _G (α) by nitric acid, NPC _G (α) has a small amount of oxygen-containing functional groups such as hydroxyl groups and carboxyl groups.

S4: and (3) putting the NPC _G (alpha) into a tube furnace for heat treatment, wherein the gas flow rate of the heat treatment is 0.5L/min for ammonia gas and 0.2L/min for argon gas, the temperature is 200 ℃, the time is 2h, and the nitrogen-containing functional groups are used for replacing the oxygen-containing functional groups, so that the NPC _G (alpha) is subjected to nitrogen group modification (Nitrogen Modification), and further the NPC _G,N carrier is obtained, namely the nitrogen modification of the graphitized nano-porous carbon carrier is completed.

The interface of the fuel cell catalytic layer is mainly an ionomer-carbon carrier interface, an ionomer-platinum interface and a platinum-carbon carrier interface, the graphitized nano-porous carbon carrier is subjected to nitrogen group modification, and as the nitrogen group is positively charged and the sulfonic acid group is negatively charged, the bonding effect of the ionomer and the carbon carrier can be enhanced due to the existence of coulomb attraction, so that the bonding effect of the ionomer-platinum is inhibited, and the adsorption effect of the sulfonic acid group on the ionomer side chain on platinum nano particles is relieved.

Proper degree of nitrogen modification can enhance the ionomer-carbon support interaction, inhibit the ionomer from strongly contacting the platinum in the catalytic layer, and facilitate the improvement of the catalytic activity of Pt/C in the catalytic layer.

In a fourth aspect, a Pt/NPC _G,N catalyst having a platinum content of 50% was synthesized using a nitrogen group modified support, i.e., NPC _G,N support; the process uses sodium hexahydroxy platinate as a precursor of Pt, adopts an ethylene glycol microwave-assisted reduction method for synthesis, and mainly comprises the following steps:

S1: the volume ratio is 3:1, mixing ethylene glycol and isopropanol in a round-bottom flask to obtain an ethylene glycol-isopropanol mixed solvent, and then adding an NPC _G,N carrier into the mixed solvent, wherein 1g of the NPC _G,N carrier is added into each 1L of the mixed solvent; dispersing for 7 hours in a constant-temperature ultrasonic cleaner to form NPC _G,N carbon powder slurry which is uniformly dispersed, wherein the temperature in the ultrasonic dispersing process is controlled at 20+/-1 ℃;

S2: adding sodium hexahydroxy platinate crystal into NPC _G,N carbon powder slurry while stirring, wherein the weight ratio of the sodium hexahydroxy platinate crystal to the NPC _G,N carrier is 40:71; simultaneously fixing the round-bottom flask on a magnetic stirrer, setting the rotating speed of a tetrafluoro magnetic rotor to 300RPM, and continuously stirring for 12 hours;

S3: transferring the Pt-containing NPC _G,N carbon powder slurry to a polytetrafluoroethylene container, and dropwise adding NaOH solution while stirring until the pH value is=12 to obtain alkaline carbon powder slurry.

S4: placing alkaline carbon powder slurry into a microwave oven, and respectively adjusting the output power and the duration of microwave energy to 800W and 1min; after the reaction is finished, taking out the tetrafluoroethylene container, and waiting for the tetrafluoroethylene container to be naturally cooled to 20-25 ℃; then adding HNO ₃ with the concentration of 1M dropwise into the carbon powder slurry with the pH value of 3-4;

s5: immediately after the obtained slurry was filtered, the filter residue was repeatedly washed several times with 100 ℃ boiling ultrapure water until the pH of the 100 ℃ boiling ultrapure water used for washing was raised to 7, thereby removing impurities that may affect the catalyst performance;

S6: after the cleaning is finished, placing the slurry into a vacuum drying oven for drying, wherein the vacuum degree is less than or equal to 2Pa, the temperature is 80 ℃ and the time is 12 hours; and after the vacuum drying is finished, the catalyst is prevented from being oxidized or burnt violently, and the Pt/NPC _G,N catalyst with 50 percent of platinum content is obtained.

S7: after the drying is finished, filling inert gas argon into a vacuum drying box to prevent the newly prepared catalyst from suddenly contacting with air; when the pressure in the drying box reaches 1 atmosphere, an air outlet at the lower part of the drying box is opened, and meanwhile, standard air is introduced from an air inlet at the upper part of the drying box at a speed of 5ml/min, so that the ratio of argon to air in the drying box is gradually adjusted, and the ventilation time of the air is maintained for 4 hours. This is the operational step of catalyst deactivation.

In the prior literature, platinum sulfate and chloroplatinic acid are mostly adopted as precursors for synthesis, wherein sulfate ions (SO ₄ ^2-) and chloride ions (Cl ^-) are adsorbed on the surface of platinum, SO that active sites on the surface of platinum are competitively occupied, the probability of adsorption of oxygen molecules on the active sites on the surface of platinum is reduced, and the catalytic efficiency of platinum on oxygen reduction reaction is reduced; compared with platinum sulfate and chloroplatinic acid, the sodium hexahydroxyplatinate precursor does not contain SO ₄ ^2- and Cl ^-, and SO ₄ ^2-、Cl^- and other impurity ions are not introduced in the synthesis process, SO that the catalytic activity of platinum on the oxygen reduction reaction can be prevented from being influenced.

Meanwhile, the microwave-assisted reduction method has the advantages of short heating time, simultaneous heating of the inside and the outside of the reaction liquid and the like, is favorable for more uniform nucleation and faster crystallization, and can rapidly synthesize uniform platinum nanoparticles with small particle diameters, such as particle diameters of 2-4 nm. The whole reaction system is in a liquid phase, and the platinum precursor is uniformly adsorbed on the NPC _G,N carrier, so that the highly dispersed Pt/NPC _G,N catalyst is synthesized, wherein the Pt content is 50%.

After Pt/NPC _G,N (50%) is prepared by the method, all raw materials of the CCM catalyst can be obtained; next, a catalyst slurry is prepared, which comprises the following main steps:

S1: mixing dimethylacetamide and N-methyl formamide in a volume ratio of 3:1 to obtain a dispersing agent, wherein the mass ratio is 0.45:1 and Pt/NPC _G,N (50%) to obtain a dispersoid, adding the dispersoid to the dispersing agent, and mixing to obtain a catalyst formulation, namely "the catalyst formulation is composed of the dispersoid and the dispersing agent", wherein the mass fraction of the dispersoid in the catalyst formulation is 1.7%.

S2: adding the catalyst preparation into a pulping machine for pulping and dispersing;

the dispersing function of the pulping machine is completed by a rotary stirring blade, a rod type ultrasonic dispersing machine and a high-speed shearing machine; the function of the rotary stirring blade is mechanical stirring, and the rotating speed of the rotary stirring blade is set to be 50r/min; the rod type ultrasonic dispersion machine has the functions of ultrasonic dispersion, the dispersion power is set to 1000W, and the dispersion frequency is set to 20kHz; the high-speed shearing machine has the functions of shearing and dispersing, and the rotating speed is 18000r/min; the temperature control module consists of a temperature sensor and a water cooling unit, so that the temperature is kept at 15 ℃ during pulping dispersion, and the overheating of the pulp in the operation steps of pulping dispersion is avoided; the whole pulping time was set to 20min. And after the step of pulping and dispersing is completed, pulping slurry is obtained.

S3: transferring the pulping slurry to a grinder for grinding at 15 ℃ to obtain grinding slurry;

Transferring the pulping slurry to a tank of a mill; preferably 0.02mm diameter zirconium dioxide grinding beads, the linear velocity of the grinding rod is set to 3m/s; the temperature control module consists of cooling water and a water cooler in the interlayer so as to ensure that the temperature during grinding is constant at 15 ℃ and avoid overheating of slurry in the grinding operation step; the entire grinding time was set to 20min. After the polishing step is completed, a polishing slurry is obtained.

S4: transferring the grinding slurry to a groove type ultrasonic oscillator for ultrasonic dispersion to obtain catalyst slurry;

Transferring the grinding slurry into a groove type ultrasonic oscillator for ultrasonic dispersion; the dispersion power was set at 800W and the dispersion frequency was set at 20kHz; the temperature control module consists of a temperature sensor and a water cooling unit, so that the temperature in ultrasonic dispersion is ensured to be constant at 15 ℃, and the slurry is prevented from being overheated in the operation step of ultrasonic dispersion. The total ultrasonic dispersion time was set to 30min. After the step of ultrasonic dispersion is completed, a catalyst slurry is obtained.

S5: and detecting the particle size of the catalyst slurry, and preparing the CCM after the catalyst slurry is qualified.

The method comprises the steps of detecting the particle size of catalyst slurry by using a laser nanometer particle size analyzer, and if the particle size of the catalyst slurry meets the technical requirements, preparing CCM, wherein the particle size detection standard of the catalyst slurry is as follows: when the cumulative particle count of the catalyst slurry is D ₁₀、D₅₀、D₉₀、D₉₉, the corresponding particle size requirements are 0.2um, 1.0um, 2.0um, 3.0um.

The catalyst slurry consisted of a dispersoid, which was Pt/NPC _G,N (50%) catalyst prepared according to the present invention and NafionD2020 ionomer from Chemours company, and a dispersant, which was a mixed solvent of dimethylacetamide and N-methylformamide.

Molecular interactions of the dispersant with NafionD2020 ionomers are a major factor in ionomer assembly, further affecting the final mesostructure of the catalytic layer; the prior literature shows that the solubility parameter delta and relative permittivity epsilon of the dispersant are two major factors regulating this interaction, the NafionD2020 ionomer backbone and side chains have delta values of 9.7 (cal/cm ³)^0.5 and 17.3 (cal/cm ³)^0.5; the greater the difference in delta values of the dispersant and ionomer, the worse their compatibility and the greater the ionomer agglomerate size), respectively.

Since NafionD2020 ionomer is composed of a hydrophobic perfluorocarbon main chain and hydrophilic sulfonic acid group side chains, the dispersion requirement cannot be met by means of a single solvent, and therefore, the dimethylacetamide-N-methyl formamide mixed solvent is selected as a dispersing agent of catalyst slurry.

For the backbone of NafionD2020 ionomer, dimethylacetamide is preferred as the solvent of the backbone, the delta value is (cal/cm ³)^0.5, the delta value of dimethylacetamide is closer to the delta value of NafionD backbone than the solvents such as ultrapure water, ethanol and isopropanol, the compatibility with the backbone is better, the backbone of the ionomer can be exposed to dimethylacetamide solvent, and the agglomeration degree of the ionomer backbone is low.

For the side chains of NafionD2020 ionomers, N-methylformamide is preferred as the solvent for the side chains; on the one hand, compared with solvents such as ultrapure water, ethanol, isopropanol and the like, the polarity of N-methyl formamide is stronger, and the relative dielectric constant is up to 182.4; in N-methyl formamide solvents, polar sulfonic acid groups are highly dissociated, which can lead to high electronegativity of the side chains, which electrostatic repulsion of the side chains is beneficial to reduce the size of ionomer agglomerates; on the other hand, the solubility parameter delta value of N-methyl formamide is 16.1 (cal/cm ³)^0.5, which is very close to the delta value of an ionomer side chain of NafionD). Therefore, the invention adopts the mixed solvent prepared by the ratio of V (dimethylacetamide): V (N-methyl formamide) =3:1 as a dispersing agent to realize low-degree agglomeration of a perfluorocarbon skeleton main chain and a sulfonic acid group side chain of an ionomer molecule, and the NafionD2020 ionomer molecule has a curled structure with low molecular agglomeration in the mixed solvent, and the molecular conformation of the main chain can induce the agglomeration degree of the side chain to be reduced.

Based on the disclosed catalytic layer coating film, the invention also discloses a preparation method of the catalytic layer coating film, which comprises the following steps:

Spraying catalyst slurry on one side of a cathode catalytic layer and one side of an anode catalytic layer of the proton exchange membrane in a progressive scanning mode by using a spraying machine to form the cathode catalytic layer and the anode catalytic layer; the catalyst slurry is sprayed onto the proton exchange membrane in an atomized form.

The proton exchange membrane adopts a GORE company M788.12 type proton exchange membrane; the characteristic parameters of the M788.12 type proton exchange membrane are as follows: proton conductivity is less than or equal to 120mΩ cm ² @80 ℃, RH is 30%, thickness is 12 μm, and swelling rate is less than or equal to 5%; the swelling ratio was measured under the conditions of "100℃for 10min in ultrapure water" and "23℃for 50% RH".

An ultrasonic vibration piece is arranged in the middle of a spray head of the spraying machine and is used for atomizing the catalyst slurry; a heating platform is arranged right below the spray head and used for evaporating the dispersing agent in the catalyst slurry; one side, e.g., the left side, of the spray head is also provided with a nozzle for providing high pressure nitrogen gas, and the other side, e.g., the right side, of the spray head is provided with a nozzle for providing catalyst slurry for spraying atomized catalyst slurry onto the proton exchange membrane. The heating platform consists of microporous ceramic, the microporous ceramic is connected with a vacuum pump, and negative pressure is generated by the vacuum pump to inhibit the size deformation of the proton exchange membrane generated when the mixed solvent is evaporated.

The platinum loading of the cathode catalytic layer is 0.3mg/cm ²; the platinum loading of the anode catalytic layer was 0.05mg/cm ².

When the cathode catalytic layer is sprayed, the flow rate of the catalyst slurry is 5.8ml/min; the nitrogen pressure is 200kpa (A), the moving speed of a spray head is 300mm/s, the height of the spray head is 25mm, the spacing between rows is 5mm, the spraying times are 4 times, the heating temperature is 110 ℃, and the adsorption pressure of a vacuum pump is 60kpa (A).

When the anode catalytic layer is sprayed, the flow rate of the catalyst slurry is 2.4ml/min; the nitrogen pressure is 200kpa (A), the moving speed of a spray head is 370mm/s, the height of the spray head is 25mm, the spacing between rows is 5mm, the spraying times are 2 times, the heating temperature is 110 ℃, and the adsorption pressure of a vacuum pump is 60kpa (A).

The invention has the beneficial effects that:

(1) In the invention, ag ₂C₂ is used as an intermediate in the preparation of the catalyst carbon carrier, and experimental conditions are adjusted to control the primary particle size, the size of the main pore diameter, the volume ratio of the main pore diameter and the volume ratio of mesopores of the synthetic carbon carrier; the primary particle size affects the specific surface area of the carbon carrier, and the larger specific surface area is beneficial to the high dispersion of Pt in the form of nano particles; in the internal pores of the carbon carrier, protons can form hydrogen bonds with water molecules in the pores, and the protons can be transferred from one water molecule to the other water molecule through proton-water molecule conjugation, so that the protons can be transferred in the internal pores of the carbon carrier; the carbon carrier for the fuel cell is generally a porous material, if the pore diameter is smaller, the reaction gas, protons and liquid water are difficult to transport, and if the pore diameter is larger, the ionomer can be immersed into the pores to poison the Pt nano particles; the preparation method adopted by the invention can control the pore size and the pore size proportion, and the pore size of the size can not only allow the material to be transported, but also prevent the ionomer from being immersed; the specific pore size can realize the spatial separation of the Pt nano particles and the ionomer, and relieve the poisoning effect of the ionomer on the Pt nano particles.

(2) The internal pores of the synthesized carbon material are communicated; on one hand, the steric hindrance effect generated by the connection of the pores is larger than that of a spherical surface, so that the dissolution and redeposition of Pt nano particles can be relieved, and the degradation rate of the catalyst is reduced; on the other hand, the carbon carrier material is the pore diameter with specific size, so that the migration and diffusion of Pt nano can be limited, and the possibility of forming a Pt band in a proton exchange membrane is reduced;

(3) Proper graphitization treatment is carried out on the carbon carrier, so that the conductivity, the hydrophobicity and the stability of the carbon carrier are improved, and the collapse of a large area of pore structures is avoided;

(4) Moderately modifying the surface of the carbon carrier with nitrogen groups, wherein the sulfonic acid groups of the side chains of the ionomer are negatively charged, so that coulombic attraction exists between the sulfonic acid groups and the positively charged nitrogen groups on the surface of the carbon carrier, and the interaction promotes the carbon surface to be in close contact with the ionomer, so that poisoning effect of the ionomer on Pt on the carbon surface is inhibited;

(5) Sodium hexahydroxy platinate is used as a precursor of Pt; the sodium hexahydroxyplatinate does not contain anions such as sulfate ions, chloride ions, bromide ions, iodide ions and the like, so that the anions are prevented from being introduced into the synthesis step of the catalyst from the source, and the influence on the catalytic activity of the catalyst is avoided;

(6) The carbon-supported platinum catalyst is prepared by adopting a glycol microwave reduction method, and the reaction system can be heated in a short time by microwave radiation, so that the production efficiency is high; the microwave radiation can uniformly heat the reaction system inside and outside simultaneously, pt nano particles with uniform particle size can be obtained, the power and time of the microwave radiation can be adjusted, and the nucleation particle size of the Pt nano particles can be controlled accurately;

(7) The invention adopts a dimethylacetamide-N-methylformamide mixed solvent; the solubility parameter value of the dimethylacetamide is very close to the main chain value of the ionomer, which is favorable for the main chain of the ionomer to form a single-chain coiled structure, the relative dielectric constant of the N-methylformamide is large, the side chain dissociation of the ionomer is favorable, and the aggregation of the ionomer is avoided due to the electrostatic repulsion of the side chain.

Drawings

The invention is further described below with reference to the accompanying drawings.

FIG. 1 is a transmission electron microscope image of an NPC _G,N carbon support prepared in accordance with the present invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

The method comprises the steps of firstly synthesizing a pure Ag ₂C₂ intermediate, regulating the particle size of the pure Ag ₂C₂ intermediate, then vacuum drying Ag ₂C₂ to enable silver particles to have segregation phenomenon similar to alloy cooling so as to regulate proper pore diameter, and preparing nano porous carbon (Nano Porous Carbon) with proper pore diameter and internal communicating pore channel structure by assistance of explosion and ejection of the silver particles, wherein the nano porous carbon is called NPC; and synthesizing the Pt/NPC catalyst with 50% of platinum content by using chloroplatinic acid as a precursor of Pt and adopting a glycol microwave-assisted reduction method.

After the synthesis of the Pt/NPC catalyst with the platinum content of 50 percent is completed, carrying out transmission electron microscope characterization to measure the particle size of the Pt nano particles; the catalyst slurry was then formulated, consisting of a dispersion of 50% platinum Pt/NPC catalyst and NafionD2020 ionomer, and a dispersant, where m (Pt/NPC catalyst): m (NafionD 2020 ionomer) =1: 0.45; the dispersants are isopropanol and ethanol, wherein V (isopropanol): v (ethanol) =1: 1, a step of; the mass fraction of dispersoid in the dispersing agent is 1.7%; the catalyst formulation is dispersed according to the steps of pulping dispersion, grinding and ultrasonic dispersion. The preparation method and the spraying parameters of the catalytic layer coating film (CCM) provided by the invention are used for preparing the catalytic layer coating film, and a SIGRACET BC type gas diffusion layer of Siegesbec company is adopted for preparing the membrane electrode.

Comparative example 1

The method is characterized in that the characteristics of specific surface area, pore size distribution, main pore diameter proportion and the like are measured by taking the commercial activated carbon of the Kanto chemical company of Japan as a carbon carrier and firstly carrying out nitrogen isothermal adsorption and desorption curve characterization. Carrying out scanning electron microscope characterization on the porous material to measure the average primary particle diameter of the porous material, and finally carrying out transmission electron microscope characterization on the porous material to explore whether an internal communication pore canal exists or not; after the various characterization of the commercial activated carbon is completed, chloroplatinic acid is used as a precursor of Pt, and a glycol microwave-assisted reduction method is adopted to synthesize a Pt/C catalyst with 50% of platinum content, wherein the method is the same as that in the example 1;

After the synthesis of the Pt/C catalyst with the platinum content of 50 percent is completed, the catalyst is subjected to transmission electron microscope characterization to measure the particle size of the Pt nano particles; then preparing catalyst slurry, wherein the catalyst slurry consists of dispersoids and dispersing agents; the dispersoids are a Pt/C catalyst with a platinum content of 50% and NafionD2020 ionomer, where m (Pt/C catalyst with a platinum content of 50%): m (NafionD 2020 ionomer) =1: 0.45; the dispersants are isopropanol and ethanol, wherein V (isopropanol): v (ethanol) =1: 1, a step of; the mass fraction of dispersoids was 1.7%; the catalyst formulation is dispersed according to the steps of pulping dispersion, grinding and ultrasonic dispersion. According to the preparation method and the spraying parameters of the catalytic layer coating film, the catalytic layer coating film is prepared, and the membrane electrode is prepared by adopting the SIGRACET BC type gas diffusion layer of the Siegesbec company.

To characterize the stability of the 50% platinum Pt/NPC catalyst prepared in example 1 of the present invention, the membrane electrode samples prepared in example 1 and comparative example 1 were assembled into a single cell and mounted on a fuel cell test bench.

The test conditions were: the cathode was 100% humidified with nitrogen, the anode was 100% humidified with hydrogen, the gas flows were all 0.5SLPM, the gas inlet pressures were all 150kpa (a), and the cell temperature was 80 ℃.

The testing method comprises the following steps: connecting the positive electrode of the electrochemical potentiostat with the cathode of the battery, connecting the negative electrode of the electrochemical potentiostat with the anode of the battery, setting the potentiostat to perform square wave circulation between 0.6V and 0.9V, and enabling the potential switching time to be less than 0.5s; wherein 0.6V lasts 3s,0.95V lasts 3s, 6s per cycle; after the 6000 th cycle is completed, the catalyst durability test is completed; taking out a membrane electrode sample, stripping the gas diffusion layer, randomly selecting a small amount of catalyst layer samples on the catalyst layer coating film, and observing the particle size of Pt nano particles in the catalyst layer samples by using a transmission electron microscope; the ethanol solvent is used for stripping and dissolving the catalytic layers on two sides of the catalytic layer coating film, and an X-ray fluorescence spectrum analyzer and an electron spectrum analyzer are used for measuring the platinum content and platinum band distribution in the proton exchange film.

The results of various characterizations of the nanoporous carbon support of example 1 and the commercial activated carbon support of comparative example 1 are listed in table 4, table 4 as follows:

TABLE 4 Table 4

As can be seen from table 4, although the average primary particle size of the commercial activated carbon is 11.1% smaller than that of the nanoporous carbon, the specific surface area of the nanoporous carbon is 20.5% larger than that of the commercial activated carbon, which benefits from the nanoporous carbon having an internally connected pore structure and a larger pore size; although the pore size distribution of the nanoporous carbon is wider than that of the commercial activated carbon, the pore size of the nanoporous carbon is very uniform, with a pore volume of 2.8nm up to 72%, which benefits from segregation of silver particles.

The platinum particle size, the platinum content inside the proton exchange membrane, and the platinum band distribution inside the proton exchange membrane of the Pt/C catalyst having 50% platinum content in example 1 and comparative example 1 before and after the catalyst durability test are shown in table 5, and table 5 is as follows:

TABLE 5

As can be seen from table 5, since the nanoporous carbon has an internally connected pore structure and the main pore size is 2.8nm, the volume of the main pore size is up to 72%, which is favorable for the nucleation of platinum ions into platinum nanoparticles in the carbon support, and about 75% of Pt nanoparticles are supported in the nanoporous carbon; while commercial activated carbon has no internally connected pores, about 98% of the platinum nanoparticles are supported on the surface of the commercial activated carbon; the Pt/NPC catalyst of example 1 has a Pt primary particle diameter very close to that of the Pt/C catalyst of comparative example 1, indicating that the nanoporous carbon having a main pore diameter of 2.8nm can well support platinum nanoparticles.

After 6000 square wave potential cycles on the membrane electrode, the Pt particle size increase rate of the Pt/NPC catalyst in example 1 is less than 5%, while the Pt particle size increase rate of the Pt/NPC catalyst in comparative example 1 is about 61%; the membrane electrode using the 50% platinum content Pt/NPC catalyst of example 1 had only about 103PPM of platinum content in the proton exchange membrane, no significant platinum bands were detected; while the membrane electrode using the Pt/C catalyst of comparative example 1, which had a platinum content of 50%, contained about 773PPM of platinum in the proton exchange membrane, a significant platinum band was detected.

In the Pt/NPC catalyst with 50% platinum content in example 1, most of the platinum nanoparticles are positioned in the inner pore canal of the nano porous carbon carrier, the pore size is mainly 2.8nm, and the pore size of 2.8nm and the communicating pore canal have steric hindrance effect, so that the dissolution and growth of the platinum nanoparticles can be relieved; due to the limitation of pore channel structure and pore size of the carbon carrier, the platinum nano particles inside the carbon carrier are not easy to migrate to the outside, thereby relieving the loss of platinum and avoiding the formation of platinum bands in the proton exchange membrane.

To characterize the catalytic activity of the 50% platinum content Pt/NPC catalyst prepared in example 1 of the present invention and the TKK platinum carbon catalyst TEC10E50E (50%) for oxygen reduction reactions, electrochemical tests were performed on the specific mass activity of Pt/NPC and TEC10E50E (50%), respectively.

Electrochemical test conditions: adopting a three-electrode electrochemical test system, and taking a rotary disc electrode as a working electrode, wherein the geometric area of the working electrode is 0.19625cm ²; the graphite electrode is used as a counter electrode, the reversible hydrogen electrode is used as a reference electrode, and the electrolyte of the reference electrode is 0.1M perchloric acid solution;

Electrochemical testing method: taking an oxygen saturated perchloric acid solution as an electrolyte, and continuously introducing oxygen in the electrochemical test process to ensure the concentration of dissolved oxygen in the electrolyte; the electrochemical experiment technology selects a linear sweep voltammetry, the potential sweep rate is set to 10mV/s, the potential sweep range is 0.2V-1.1V (relative to a reversible hydrogen electrode), and the rotating disk electrode system is set at a rotating speed of 1600 rpm; the ambient temperature of the entire test system was maintained at 25 ℃.

The catalyst is uniformly coated on the geometric area of the working electrode in the form of ink, the ink consists of solute and solvent, the catalyst is solute, ultrapure water, absolute ethyl alcohol and NafionD2020 ionomer emulsion (5%) are solvent, and the specific proportion of 1ml solvent is 0.5ml of ultrapure water, 0.5ml of absolute ethyl alcohol and 0.05ml of nafion emulsion (5%); the ink is prepared according to 1mg (solute)/ml (solvent) and the ink is uniformly dispersed by ultrasonic; accurately measuring the volume of the ink by a liquid-transferring gun and titrating the ink on a working electrode to ensure that the surface density of the catalyst on the working electrode is 20mg/cm ²; and then drying the ink on the working electrode by using an infrared lamp irradiation and nitrogen micro-flow purging mode to uniformly and completely cover the geometric area of the working electrode.

Even platinum-based catalysts still achieve current at a potential of less than 1V; therefore, the current density at 0.9V is usually taken in the study of the oxygen reduction reaction to replace the exchange current density, the kinetic current i _K is calculated by combining Koutecky-Levich equation, and the specific mass activity is further calculated. And the results are listed in table 6, table 6 below:

TABLE 6

	Specific mass activity
		Pt/NPC catalyst with 50% platinum content	0.111A/mg
TEC10E50E (50%) from AKK company	0.095A/mg

It can be seen from Table 6 that the Pt/NPC catalyst prepared in example 1, which had a 50% platinum content, had a specific mass activity 14.4% greater than TEC10E 50E. This is because most Pt nanoparticles are located in the pore structure where the NPC is internally connected, have a main pore diameter of 2.8nm, and are continuously distributed to 10nm. These specific size pore sizes can limit the impregnation of the ionomer, achieve spatial separation of the Pt nanoparticles from the ionomer, and mitigate poisoning of the Pt nanoparticles by sulfonic acid groups of the ionomer side chains.

Example 2:

The synthesis method of the invention firstly synthesizes pure Ag ₂C₂ intermediate and adjusts the grain size, then carries out vacuum drying on Ag ₂C₂ to enable silver particles to generate segregation phenomenon similar to alloy cooling so as to adjust the proper pore diameter, and then prepares NPC with proper pore diameter and internal communicating pore canal structure by assistance of explosion ejection of silver particles.

After NPC synthesis is completed, the NPC is sufficiently cleaned and dried in vacuum to remove impurities and moisture in the NPC; the NPC after treatment is put into a graphite boat and is put into a high temperature furnace; the high-temperature furnace is subjected to gas replacement by argon, and the operation is repeated for 3 times, so that the interference of air on experiments is avoided; heating the temperature of the high-temperature furnace to 1700 ℃ at a speed of 5 ℃/min, preserving heat at 1700 ℃ for 2 hours, and naturally cooling to room temperature after finishing; after the natural cooling is completed, taking out a sample in the graphite boat, which is called NPC _G below; the continuous flow of argon is ensured in the processes of heating, heat preservation and natural cooling.

And synthesizing the Pt/NPC _G catalyst with 50% of platinum content by using chloroplatinic acid as a precursor of Pt and adopting a glycol microwave-assisted reduction method.

After the synthesis of the Pt/NPC _G catalyst with 50% platinum content was completed, a transmission electron microscope was first used to image to characterize the internal pore structure, then a nitrogen isothermal adsorption-desorption curve test was performed to characterize the main pore size, pore size distribution and specific surface area, and finally a water vapor adsorption experiment at 25 ℃ and 10% relative humidity was performed to characterize the graphitization degree, i.e., hydrophobicity, of NPC _G.

The catalyst slurry was then formulated, consisting of a dispersion of 50% platinum Pt/NPC _G catalyst and NafionD2020 ionomer, with a dispersant, where m (Pt/NPC _G catalyst): m (NafionD 2020 ionomer) =1: 0.45; the dispersants are isopropanol and ethanol, wherein V (isopropanol): v (ethanol) =1: 1, a step of; the mass fraction of the dispersoid was 1.7%. The catalyst formulation is dispersed according to the steps of pulping dispersion, grinding and ultrasonic dispersion. According to the preparation method and the spraying parameters of the catalytic layer coating film, the catalytic layer coating film is prepared, and the membrane electrode is prepared by adopting the SIGRACET BC type gas diffusion layer of the Siegesbec company.

Carrying out a carrier durability test on a Pt/NPC _G catalyst with 50% platinum content to judge the graphitization effect of the nano porous carbon; a second membrane electrode was also prepared as in example 1 and subjected to a carrier durability test on a fuel cell test bench.

The durability test procedure for the Pt/NPC _G catalyst support was:

assembling the membrane electrode sample into a single cell, and mounting the single cell on a fuel cell testing machine;

Single cell activation is carried out firstly to enhance the catalyst activity, electron conductivity and proton conductivity in the membrane electrode and improve the performance of the cell; the reaction gases are standard hydrogen and standard air; standard hydrogen is 99.999% high purity hydrogen and standard air is 99.999% purity (standard air consists of high purity nitrogen and high purity oxygen, with 21% oxygen content); the activation conditions of the membrane electrode are as follows: the reaction temperature of the battery is 75 ℃; the relative humidity of the reaction gas was 100%; the stoichiometric ratio of standard hydrogen is 1.2; the stoichiometric ratio of standard air is 2.5; the back pressure of the outlet of the single cell is 0.1MPa; the current density of the battery in stable operation is more than or equal to 0.5A/cm ²; the time of the stable operation of the battery is more than or equal to 4 hours;

Then, carrying out a polarization curve test of the 0 th cycle; the polarization test conditions of the membrane electrode are as follows: the reaction temperature of the battery is 75 ℃; the relative humidity of the reaction gas was 100%; the stoichiometric ratio of standard hydrogen is 1.2; the stoichiometric ratio of standard air is 2.5; the back pressure of the outlet of the single cell is 0.2MPa;

Then, a carrier durability test was performed under the following conditions: 100% humidified nitrogen at the cathode and 100% humidified hydrogen at the anode, the gas flows are all 0.5SLPM; the gas stacking pressure is 150kpa (A), and the temperature of a single cell is 80 ℃; connecting an anode of an electrochemical potentiostat with a cathode of a battery, connecting a cathode of the battery, setting the potentiostat to perform triangular wave circulation between 1.0V and 1.5V, and scanning at a rate of 0.5V/s for 2s in each cycle; finally, the polarization curve of the cell is measured at the 1000 th cycle of the integration.

The BOL test of the fuel cell is referred to as the "Beginning of Life" test, and the carrier durability BOL test results are set forth in Table 7, table 7 below:

TABLE 7

As can be seen from Table 7, when the current density is less than or equal to 0.7A/cm2, the voltage value of the membrane electrode prepared by the Pt/NPC _G is slightly higher than that of the membrane electrode prepared by the Pt/NPC, the difference between the two is less than or equal to 5mV, which indicates that proper graphitization treatment can be compatible with the low-power operation condition of the fuel cell, and larger proton conduction impedance is avoided; proper graphitization treatment can basically keep relatively smaller pore diameter on NPC _G, and make relatively larger pore diameter collapse properly, so that pore diameter distribution is closer to an optimal range value of 2.5nm-5.0nm, and poisoning phenomenon of sulfonic acid groups of ionomer side chains on Pt nano particles is reduced.

When the current density of the membrane electrode is gradually carried to 1.5A/cm ², the difference between the membrane electrode and the membrane electrode is gradually enlarged to 11mV, because in an ohmic polarization control area and a concentration polarization control area, the electron conductivity of the NPC _G carrier is improved and the ohmic polarization loss is reduced due to graphitization treatment; meanwhile, the graphitization treatment increases the hydrophobicity of the NPC _G, so that the generated liquid water can be timely discharged under the high-power operation working condition of the fuel cell, and meanwhile, the channel structure communicated with the inside of the NPC _G is beneficial to the transmission of reaction gas, proton conduction and liquid water discharge.

The EOL test of the fuel cell is referred to as the "End of Life" test, and the results of the carrier durability EOL test are shown in table 8, table 8 below:

TABLE 8

As can be seen from the data in tables 7 and 8, the voltage of the membrane electrode prepared from Pt/NPC _G was hardly attenuated by 1000 cycles of carrier durability, and the voltage attenuation amplitude was less than or equal to 5mV; the voltage attenuation amplitude of the membrane electrode prepared by Pt/NPC is larger, and the voltage attenuation amplitude is about 15 mV-20 mV under the high-power operation condition; this is because the graphitization treatment can improve the crystal structure stability and mechanical strength of the carbon carrier, can better withstand the high-temperature and high-pressure operation environment of the fuel cell, and prolongs the service life of the membrane electrode.

The result of the isothermal adsorption and desorption curve of nitrogen shows that for NPC _G, the adsorption peak of 2.8nm still stands out, and the maximum pore diameter is reduced from 10nm to 6nm; proper graphitization of NPC can retain relatively small pore size, while relatively large pore size collapses into relatively small pore size; the specific surface area of NPC after graphitization is reduced to 1100m ²/g; through measurement and calculation, the adsorption quantity alpha=0.35 ml/m ² is very close to the theoretical value of the literature, and the high-power operation condition and the low-power operation condition of the fuel cell are considered.

Therefore, the invention carries out proper degree graphitization on the nano porous carbon, and the graphitization is not only beneficial to improving the electronic conductivity and reducing the ohmic polarization loss of the fuel cell and increasing the mechanical strength and the stability of the carbon carrier, but also beneficial to discharging liquid water and reducing the coverage of the active site of the catalyst and reducing the concentration polarization loss; and graphitization to a proper degree can avoid the collapse of the internal pore canal structure of the carbon carrier, the communication structure is destroyed, and the pore size is also changed greatly.

Example 3:

The synthesis method of the invention firstly synthesizes pure Ag ₂C₂ intermediate and adjusts the grain size, then carries out vacuum drying on Ag ₂C₂ to enable silver particles to generate segregation phenomenon similar to alloy cooling so as to adjust the proper pore diameter, and then prepares nano porous carbon with proper pore diameter and internal communicated pore channel structure, namely NPC by assistance of explosion ejection of silver particles.

After NPC synthesis is completed, the NPC is sufficiently cleaned and dried in vacuum to remove impurities and moisture in the NPC; the NPC after treatment is put into a graphite boat and is put into a high temperature furnace; the high-temperature furnace is subjected to gas replacement by argon, and the operation is repeated for 3 times, so that the interference of air on experiments is avoided; heating the temperature of the high-temperature furnace to 1700 ℃ at a speed of 5 ℃/min, preserving heat at 1700 ℃ for 2 hours, and naturally cooling to room temperature after finishing. After the natural cooling is finished, taking out a sample NPC _G in the graphite boat; the continuous flow of argon is ensured in the processes of heating, heat preservation and natural cooling.

After the synthesis of NPC _G is completed, carrying out nitrogen group modification on the NPC _G carrier; preparing 500ml of 65% nitric acid solution and injecting the solution into a spherical oil bath flask, and adding 20 g of NPC _G carrier into the oil bath flask; placing the oil bath flask into an oil bath pot; simultaneously, the magnetic stirrer was turned on, and the rotational speed of the tetrafluoro magnetic rotor was set to 200RPM. Rapidly heating the oil bath to 70 ℃ and preserving heat for 2 hours; taking out after heat preservation, slowly adding the ultra-pure water at normal temperature, shaking to avoid uneven cooling, and transferring the materials in the oil bath flask into a beaker; filtering and cleaning the materials in the beaker by using a vacuum suction filtration device; the filtering and cleaning operation steps are repeated three times to remove the residual nitric acid solution, thus obtaining NPC _G (alpha) carrier; the NPC _G (alpha) carrier is put into a tube furnace for heat treatment, the gas flow is 'ammonia gas 0.5L/min, argon gas 0.2L/min', the heat treatment temperature is set to 200 ℃, and the heat treatment time is 2 hours, so as to prepare the nitrogen modified carbon carrier, which is marked as the NPC _G,N carrier.

And synthesizing the Pt/NPC _G,N catalyst with 50% of platinum content by using chloroplatinic acid as a precursor of Pt and adopting a glycol microwave-assisted reduction method.

Meanwhile, a Pt/NPC catalyst and a Pt/NPC _G catalyst were prepared as in example 1 and example 2, respectively; the electrochemical tests of specific mass activities were performed on the "Pt/NPC _G,N catalyst", "Pt/NPC _G catalyst" and "Pt/NPC catalyst", respectively, and compared with "TEC10E50E catalyst".

The conditions and method of electrochemical testing were the same as in example 1.

Even though the platinum-based catalyst still achieved a current at a potential of less than 1V, it is common to take a current density of 0.9V instead of the exchange current density in the study of the oxygen reduction reaction, calculate the kinetic current i _K in combination with the equation Koutecky-Levich, and further calculate the specific mass activity, and the results are shown in table 9, table 9 below:

TABLE 9

Catalyst species	Specific mass activity
		Pt/NPC_G,N	0.130A/mg
Pt/NPC_G	0.121A/mg
		Pt/NPC	0.111A/mg
TEC10E50E	0.095A/mg

As can be seen from Table 9, the specific mass activity was gradually increased in the order of "TEC10E50E catalyst, pt/NPC _G catalyst, pt/NPC _G,N catalyst", and the specific mass activity was closely related to the intrinsic activity of the catalyst.

Firstly, because of the space limitation of NPC on the ionomer in the catalytic layer on the working electrode, the ionomer cannot be completely immersed into the NPC, and the poisoning of Pt nanometer in the NPC by the ionomer sulfonic acid group is relieved; then proper graphitization treatment changes the pore size distribution of NPC, further prevents the ionomer from immersing NPC _G, and further relieves the poisoning of Pt nanometer in NPC by ionomer sulfonic acid groups; finally, the nitrogen group modifies the NPC _G, which enhances the interaction of the carbon support-ionomer due to the presence of coulomb attraction, and alleviates the poisoning of Pt nanoparticles on the surface of NPC _G,N by the ionomer sulfonic acid group.

To sum up: NPC, NPC proper graphite treatment and NPC _G nitrogen group modification promote the specific mass activity of the catalyst in two dimensions of preventing the sulfonic acid group from being immersed into the inside of the carbon carrier and enhancing the interaction between the sulfonic acid group and the surface of the carbon carrier.

Example 4

NPC _G,N vector was prepared as described in example 3.

The catalyst Pt/NPC _G,N with 50% platinum content is synthesized by adopting a glycol microwave-assisted reduction method by taking sodium hexahydroxy platinate as a precursor of Pt, and is named as Pt/NPC _G,N (0).

Meanwhile, a Pt/NPC _G,N catalyst, designated "Pt/NPC _G,N (1)", was prepared as in example 3, and electrochemical tests of specific mass activity were performed on the Pt/NPC _G,N (0) catalyst and the Pt/NPC _G,N (1) catalyst. Wherein, (0) represents a precursor of Pt using sodium hexahydroxyplatinate, and (1) represents a precursor of Pt using chloroplatinic acid.

Even though the platinum-based catalyst still achieved a current at a potential of less than 1V, it is common to take a current density of 0.9V instead of the exchange current density in the study of the oxygen reduction reaction, calculate the kinetic current i _K in combination with the equation Koutecky-Levich, and further calculate the specific mass activity, and list the results in table 10 as follows:

Table 10

	Specific mass activity
		Pt/NPC_G,N(0)	0.137A/mg
Pt/NPC_G,N(1)	0.130A/mg

As can be seen from Table 10, the specific mass activity of the Pt/NPC _G,N (0) catalyst was increased by 0.007A/mg due to the use of sodium hexahydroxy platinate precursor; the chloroplatinic acid precursor contains chloride ions, the chloride ions can be adsorbed on the surface of platinum and compete with oxygen for the active sites of the Pt nano particles, so that the possibility of oxygen molecular adsorption is reduced, and the catalytic activity of the Pt nano particles on oxygen reduction reaction is reduced; sodium hexahydroxyplatinate does not directly contain chloride ions, and sodium hexahydroxyplatinate does not directly contain sulfate ions, bromide ions, iodide ions, and the like, which are harmful to the oxygen reduction reaction.

Example 5

NPC _G,N vector was prepared as described in example 3.

The method comprises the steps of using sodium hexahydroxy platinate as a precursor of Pt, and adopting a ball milling impregnation reduction method to synthesize a Pt/NPC _G,N catalyst with 50% of platinum content, which is marked as Pt/NPC _G,N (3) "; the main synthesis steps of the ball milling dipping reduction method are as follows:

Firstly, putting a Pt precursor, an NPC _G,N carrier, ultrapure water and ball-milling beads into a ball-milling tank according to a certain proportion; then, assembling a ball milling tank on a ball mill for ball milling so as to fully impregnate the Pt precursor on the NPC _G,N carrier to obtain a paste; then putting the paste into an ultralow temperature refrigerator with the temperature of less than-40 ℃ to quickly freeze to obtain frozen paste; finally, putting the frozen paste into a vacuum dryer for gradual and sectional sublimation to perform in-situ drying to obtain Pt precursor/NPC _G,N powder; placing Pt precursor/NPC _G,N powder into a tube furnace for reduction to obtain Pt/NPC _G,N powder, namely Pt/NPC _G,N (3) catalyst; wherein, (3) represents reduction synthesis in a tube furnace.

In this example, a 50% platinum content Pt/NPC _G,N (0) catalyst was synthesized according to example 4, wherein Pt/NPC _G,N (0) was synthesized using microwave assisted reduction of ethylene glycol.

Pt/NPC _G,N (0) and Pt/NPC _G,N (3) were imaged with a transmission electron microscope, respectively, to characterize the platinum particle size of the catalyst, and the results are listed in table 11, table 11 below:

TABLE 11

	Size of Pt particle diameter
		Pt/NPC _G,N (3) catalysts	4.5nm
Pt/NPC _G,N (0) catalysts	3.0nm

As can be seen from Table 11, the Pt/NPC _G,N (0) catalyst synthesized by microwave-assisted reduction of ethylene glycol has a platinum particle size of 3.0nm, and smaller platinum particle sizes have higher catalytic activity; the platinum nano particles with small particle size have higher specific surface area; smaller platinum nanoparticles can provide more active surface, and can provide more active sites available for oxygen reduction reactions, given the platinum mass.

On one hand, the microwave heating time is short, the reduction time is generally 1-3 min, the reduction synthesis process is very rapid, and the Pt nucleation time is controllable; in contrast, the reduction time of the ball milling impregnation method is generally 1-2 hours, so that the production efficiency of the catalyst can be greatly improved by adopting microwave heating.

On the other hand, because the microwave is heated inside and outside simultaneously, the temperature of the reaction system is relatively uniform, the temperature gradient of the solvent system is reduced, the aggregation phenomenon of particles in the system is reduced, and the reduction process is also very uniform; in contrast, the heating uniformity of the tube furnace is lower than the microwave heating uniformity.

Finally, when the ethylene glycol microwave-assisted reduction method is adopted, the ethylene glycol can provide proper reducibility in synthesis, so that the growth of platinum nano particles can be effectively limited.

Considering the service life of platinum nanoparticles, the platinum nanoparticles being too small, i.e. a particle size of less than 2nm, may cause some negative effects; because the particle size of the particles is too small, the particle size has relatively high surface energy, and the surface energy drives the dissolution and aggregation growth of the too small particles. The catalytic activity and the service life of the platinum nano particles are comprehensively considered, and the size of the platinum nano particles is further optimized by adjusting the conditions of reaction time, system temperature, reactant concentration and the like, so that the controllable synthesis of the platinum nano particles with the size of 3nm is realized.

Example 6

A Pt/NPC _G,N (0) catalyst with a 50% platinum content was prepared as in example 4 and a transmission electron microscope image was taken of the Pt/NPC _G,N (0) catalyst to characterize its morphology.

First, a catalyst slurry was prepared for Pt/NPC _G,N (0), denoted as "slurry ①". Slurry ① consists of dispersoids and dispersants; the dispersoids are Pt/NPC _G,N (0) catalyst and NafionD2020 ionomer, where m [ Pt/NPC _G,N (0) ]: m [ NafionD2020 ionomer ] =1: 0.45; the dispersants are dimethylacetamide and N-methylformamide, wherein V (dimethylacetamide): v (N methylformamide) =3: 1, a step of; the mass fraction of the dispersoid was 1.7%.

Meanwhile, the Pt/NPC _G,N (0) was subjected to catalyst slurry preparation, which was designated as "slurry ②". Slurry ② consists of dispersoids and dispersants; the dispersoids are Pt/NPC _G,N (0) catalyst and NafionD2020 ionomer, where m (Pt/NPC _G,N (0)): m (NafionD 2020 ionomer) =1: 0.45; the dispersants are isopropanol and ethanol, wherein V (isopropanol): v (ethanol) =1: 1, a step of; the mass fraction of the dispersoid was 1.7%.

Dispersing the slurry ① and the slurry ② according to the operation steps of pulping dispersion, grinding and ultrasonic dispersion; after the dispersion is completed, zeta potential measurement is carried out on the slurry ① and the slurry ② by using a Zeta potential analyzer of Malvern company so as to represent the stability of the catalyst slurry; and the results are listed in table 12, table 12 below:

Table 12

	Zeta potential
		Sizing agent ②	-41mV
Sizing agent ①	-46mV

As can be seen from table 12, the Zeta potential of the slurry ① is more negative and the slurry particle surface is more negatively charged, in which case the slurry particles repel each other and the slurry ① has higher stability; on the one hand, because the slurry ① contains N-methylformamide, the relative dielectric constant of the N-methylformamide is relatively large, the dissociation of the side chain of the ionomer is facilitated, electrostatic repulsion is generated after the side chain is dissociated, and the aggregation of slurry particles is relieved; on the other hand, the solubility parameter delta value of N-methyl formamide is close to the delta value of ionomer side chains, and the ionomer side chains can be stretched more, so that the agglomeration of slurry particles is relieved.

Then preparing a catalytic layer coating film according to the method and the spraying parameters provided by the invention; CCM prepared from slurry ① was designated CCM1. CCM prepared from slurry ② was designated CCM2. Preparing a membrane electrode by using a Saigril SIGRACET BC type gas diffusion layer; the membrane electrode prepared from CCM1 is designated MEA1. The membrane electrode prepared from CCM2 material was designated MEA2.

Assembling the membrane electrode sample into a single cell, and mounting the single cell on a fuel cell testing machine; single cell activation is carried out firstly to enhance the catalyst activity, electron conductivity and proton conductivity in the membrane electrode and improve the performance of the cell; the reaction gases are standard hydrogen and standard air; standard hydrogen is 99.999% high purity hydrogen. Standard air is high purity nitrogen and high purity oxygen of 99.999% purity, with an oxygen content of 21%. The activation conditions of the membrane electrode are as follows: the reaction temperature of the battery is 75 ℃; the relative humidity of the reaction gas was 100%; the stoichiometric ratio of standard hydrogen is 1.2; the stoichiometric ratio of standard air is 2.5; the back pressure of the outlet of the single cell is 0.1MPa; the current density of the battery in stable operation is more than or equal to 0.5A/cm < 2 >; the time of the stable operation of the battery is more than or equal to 4 hours.

Then carrying out a polarization curve test; the polarization test conditions of the membrane electrode are as follows: the reaction temperature of the battery is 75 ℃; the relative humidity of the reaction gas was 100%; the stoichiometric ratio of standard hydrogen is 1.2; the stoichiometric ratio of standard air is 2.5; the back pressure of the outlet of the single cell is 0.2MPa; and the polarization curve test results of MEA1 and MEA2 are listed in table 13, table 13 below:

TABLE 13

As can be seen from Table 13, when the current density is less than or equal to 0.7A/cm ², the voltages of MEA1 and MEA2 are not much different, and the difference is within 5 mV; when the current density is 0.8-1.5A/cm ², the performance of the MEA1 is slightly excellent, and the difference between the two is 5-10mV; this is because a "dimethylacetamide-N-methylformamide" mixed solvent is used in preparing the slurry ①; the delta value of the dimethylacetamide is closer to the delta value of the main chain of the ionomer, and the dimethylacetamide is more compatible with the main chain of the ionomer; n-methyl formamide can enable ionomer side chains to be dissociated to a greater extent, so that electrostatic repulsion between ionomers is enhanced; on the one hand, when the main chain and the side chain of the ionomer are well dispersed, the sulfonic acid groups of the side chain of the ionomer can be more effectively contacted with water molecules and interact, so that the migration rate of protons is improved, and the ohmic polarization loss of the catalytic layer is reduced; on the other hand, when the main chain and the side chain of the ionomer are well dispersed, the film covered on the catalyst by the ionomer is more uniform, the diffusion resistance of oxygen molecules in the film is smaller, the concentration of oxygen at the three-phase interface is increased, the concentration polarization loss of the catalyst is reduced, and the efficiency of electrochemical reaction is improved.

The transmission electron microscope image of the NPC _G,N carrier prepared by the invention is shown in figure 1; it can be seen that a communicating pore canal structure exists inside the NPC _G,N carrier; according to the previous measurement result, the main pore diameter is 2.8nm, and the pore diameter distribution range is 2.8-6nm; in the catalytic layer, the pore diameter of 2.8-6nm can prevent the ionomer from immersing into the carbon carrier, so that the poisoning effect of the ionomer on the catalyst is relieved; graphitizing the carbon carrier improves the service life and hydrophobicity of the catalyst; the nitrogen group modification enhances the interaction of the carbon carrier and the ionomer, thereby further relieving the poisoning effect of the ionomer on the catalyst; the precursor of sodium hexahydroxy platinate is adopted, so that impurity ions such as Cl ^-、SO₄ ^2- and the like are prevented from being introduced in the catalyst synthesis process; the synthesis conditions of the microwave-assisted glycol reduction method are optimized, and the growth rate of Pt nano particles can be regulated and controlled; optimizing the dispersion solvent of the catalyst slurry can reduce the degree of agglomeration of the ionomer in the slurry.

In the description of the present invention, it should be understood that the terms "upper," "lower," "left," "right," and the like indicate an orientation or a positional relationship based on that shown in the drawings, and are merely for convenience of description and for simplifying the description, and do not indicate or imply that the apparatus or element in question must have a specific orientation, as well as a specific orientation configuration and operation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

The foregoing describes one embodiment of the present invention in detail, but the description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. All equivalent changes and modifications within the scope of the present invention are intended to be covered by the present invention.

Claims

1. The utility model provides a catalysis layer coating membrane, includes positive pole catalysis layer, proton exchange membrane and negative pole catalysis layer, positive pole catalysis layer and negative pole catalysis layer locate the both sides of proton exchange membrane respectively, its characterized in that, positive pole catalysis layer and negative pole catalysis layer include the catalyst thick liquids that respectively spray in proton exchange membrane both sides, the preparation method of catalyst thick liquids is:

s1: mixing dimethylacetamide and N-methyl formamide in a volume ratio of 3:1 to obtain a dispersing agent, wherein the mass ratio is 1:0.45 Pt/NPC _G,N catalyst and NafionD2020 ionomer were mixed to obtain a dispersoid; adding dispersoids into a dispersing agent, and mixing to obtain a catalyst preparation, wherein the mass fraction of the dispersoids in the dispersing agent is 1.7%;

s2: adding the catalyst preparation material into a pulping machine for pulping and dispersing to obtain pulping slurry;

S4: transferring the grinding slurry into a groove type ultrasonic vibration machine, dispersing at 15 ℃ to obtain catalyst slurry, detecting the particle size of the catalyst slurry, and preparing a catalyst coating film after the catalyst slurry is qualified;

In step S1, the Pt/NPC _G,N catalyst is a Pt/NPC _G,N catalyst with a platinum content of 50%, and the preparation method of the Pt/NPC _G,N catalyst with a platinum content of 50% is as follows:

① : the volume ratio is 3:1, mixing ethylene glycol with isopropanol to obtain an ethylene glycol-isopropanol mixed solvent, and then adding an NPC _G,N carrier into the mixed solvent, wherein 1g of the NPC _G,N carrier is added into each 1L of the mixed solvent; forming NPC _G,N carbon powder slurry with uniform dispersion after ultrasonic dispersion;

② : adding sodium hexahydroxy platinate crystal into NPC _G,N carbon powder slurry while stirring, and uniformly stirring, wherein the weight ratio of the sodium hexahydroxy platinate crystal to the NPC _G,N carrier is 40:71;

③ : adjusting the NPC _G,N carbon powder slurry containing Pt to pH=12 to obtain alkaline carbon powder slurry;

④ : naturally cooling the alkaline carbon powder slurry after the heating reaction is finished; then adjusting the slurry to ph=3-4;

⑤ : after the obtained slurry was filtered, the filter residue was repeatedly washed several times with boiling ultrapure water immediately until the pH of the boiling ultrapure water used for washing was raised to 7;

⑥ : after the cleaning is finished, the slurry is put into a vacuum drying oven for drying, and is slowly exposed to the air after the drying is finished to complete passivation, so that the Pt/NPC _G,N catalyst with 50 percent of platinum content is obtained;

The preparation method of the NPC _G,N carrier comprises the following steps:

(a) Adding NPC _G carrier into 65% nitric acid solution, adding 4g NPC _G carrier into each 100ml nitric acid solution;

(b) : heating the nitric acid solution containing the NPC _G carrier in an oil bath at 70 ℃ for 2 hours and stirring;

(c) : after the oil bath is finished, slowly adding ultra-pure water at normal temperature, shaking the container, transferring the materials in the oil container into a beaker, and repeatedly filtering and cleaning to obtain an NPC _G (alpha) carrier;

(d) : carrying out heat treatment on the NPC _G (alpha) carrier to obtain an NPC _G,N carrier;

The preparation method of the NPC _G carrier comprises the following steps: the NPC carrier is placed in argon atmosphere and is protected for 2 hours at 1700 ℃;

the preparation method of the NPC carrier comprises the following steps:

Adding 10% sodium hydroxide solution into 5% silver nitrate solution, and shaking uniformly while dripping, wherein the volume ratio of the sodium hydroxide solution to the silver nitrate solution is 6:1; dropwise adding 2% ammonia water solution while shaking until the generated precipitate is just dissolved, thus obtaining clarified silver nitrate ammonia water solution;

II: washing H ₂C₂ gas by using sodium hypochlorite solution, and then washing gas by using saturated copper sulfate solution to obtain pure H ₂C₂ gas; introducing pure H ₂C₂ gas into silver nitrate ammonia water solution at the rate of 30ml/min, and simultaneously placing the flask in an ultrasonic vibration tank to enable H ₂C₂ and the silver nitrate ammonia water solution to react to generate yellow precipitate, and gradually converting the yellow precipitate into white precipitate Ag ₂C₂ with a little silver color along with the progress of the reaction;

III: after the reaction is finished, filtering the mixture containing Ag ₂C₂ to obtain Ag ₂C₂ precipitate;

IV: vacuum drying Ag ₂C₂ precipitate to 210 deg.c, collecting the resultant powder, dissolving the powder in dilute nitric acid in the volume ratio of 9 to 50, and stirring at room temperature for 1.5 hr;

v: and (3) washing the powder dissolved in the dilute nitric acid in a suction filtration mode, and placing the washed powder in a 60 ℃ environment for vacuum drying to finally obtain the nano porous carbon, namely the NPC carrier.

2. The catalytic layer coating film according to claim 1, wherein in step iv, the Ag ₂C₂ precipitate is vacuum dried to about 210 ℃, comprising: placing the Ag ₂C₂ precipitate in a vacuum drying oven for vacuum drying, wherein the absolute pressure of the vacuum drying oven is less than or equal to 2Pa, and the temperature is 55 ℃; immediately after 13 hours of drying, the vacuum oven was warmed to about 210 ℃.

3. The catalytic layer coating film according to claim 1, wherein in step S4, the catalyst slurry has a particle size detection qualification standard of: when the cumulative particle count of the catalyst slurry is D ₁₀、D₅₀、D₉₀、D₉₉, the corresponding particle size requirements are 0.2um, 1.0um, 2.0um, 3.0um.

4. A method for producing the catalytic layer coating film according to any one of claims 1 to 3, comprising the steps of: spraying catalyst slurry on one side of a cathode catalytic layer and one side of an anode catalytic layer of the proton exchange membrane in a progressive scanning mode by using a spraying machine to form the cathode catalytic layer and the anode catalytic layer; the catalyst slurry is sprayed onto the proton exchange membrane in an atomized form.

5. The method for preparing a catalytic layer coating film according to claim 4, wherein an ultrasonic vibration plate is mounted on a nozzle of the spray coater for atomizing a catalyst; a heating platform is arranged right below the spray head and used for evaporating the dispersing agent in the catalyst slurry; one side of the spray head is also provided with a nozzle for supplying high-pressure nitrogen.

6. The method for producing a catalytic layer coated film according to claim 4, wherein the platinum loading of the cathode catalytic layer is 0.3mg/cm ²; the platinum loading of the anode catalytic layer was 0.05mg/cm ².