Modified catalyst of fuel cell, membrane electrode and preparation method and application of modified catalyst

Abstract

The invention relates to a modified catalyst of a fuel cell, a membrane electrode and a preparation method and application thereof, and belongs to the technical field of fuel cells. The catalyst is treated by using the treating agent under a low-temperature heating condition, so that the treating agent can fully infiltrate a pore channel of the catalyst, and a small amount of hydrophilic functional groups can be modified on the catalyst or a carrier due to the oxidability of the treating agent; by combining heat treatment, the surface of the catalyst carrier can be further moderately oxidized, so that the hydrophilicity of the carrier is improved, the water content in a pore channel of a catalyst layer prepared from the catalyst under a dry working condition is optimized, and the proton transmission in the pore channel is improved; meanwhile, the pore size distribution of the catalyst can be adjusted, the accessibility of protons in a catalyst layer prepared from the catalyst is improved, the transmission of reaction substances is improved, and the mass transfer limitation of reaction gas under medium-high current density is optimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fuel cell technology, in particular to a modified catalyst for fuel cell, membrane electrode assembly and preparation method and application thereof. BACKGROUND

[0002] Proton exchange membrane fuel cell (PEMFC) is one of the most promising power sources for electric vehicles, which is composed of multiple single fuel cells in series, and the single fuel cell is mainly composed of membrane electrode assembly (MEA) and bipolar plate. The membrane electrode assembly (MEA) provides micro-channels for multi-phase mass transfer and electrochemical reaction sites for PEMFC, which is mainly composed of catalyst layer, proton exchange membrane and gas diffusion layer. The catalyst layer is the most core component of MEA, which is the electrochemical reaction site and the transfer channel for gas, water, electrons and protons.

[0003] The catalyst is the key material of the catalyst layer, and the current commercial catalyst is mainly active metal nanoparticles supported on carbon black to increase the mass specific surface area of the active metal and provide a channel for oxygen to reach the surface of the active metal. When the catalyst is mixed with ionomer to prepare slurry, the active metal is covered by the ionomer and is easily poisoned by the sulfonate groups on it, resulting in reduced catalyst activity and increased mass transfer resistance. Porous carbon is the main catalyst carrier at present, and part of the active metal nanoparticles existing in the pores does not contact with the ionomer, thereby reducing the loss of kinetic activity caused by the adsorption of sulfonic groups of the ionomer. In the pores where the ionomer cannot enter, liquid water is mainly responsible for transporting protons to the metal reaction sites. Therefore, when the fuel cell operates in a relatively dry condition, part of the carbon carrier pores lack water molecules as proton carriers, and the transport of protons is further limited, resulting in reduced performance of the fuel cell. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provide a modified catalyst for fuel cell, membrane electrode assembly and preparation method and application thereof, which regulates the pore size distribution of carbon carrier and improves the hydrophilicity to improve the proton accessibility in the catalyst layer and improve the transport of reactants.

[0005] The present application finds that by low-temperature heating, the catalyst is sufficiently infiltrated by the treatment agent with oxidizing oxidant or decomposable into oxidant, so that the treatment agent is sufficiently distributed in the catalyst; then by the way of local oxidation through heat treatment, the catalyst which has been deposited is in-situ surface treated, which can effectively and moderately improve the hydrophilicity of the catalyst; in the heat treatment process, the method of rapid heating is adopted to make the water in the fully wet catalyst rapidly and massively gasified, so that some loose pore channels are further opened, which can appropriately increase the pore volume of the 5-10nm pore diameter mesopore of the carbon carrier, thereby further improving the proton accessibility in the catalytic layer prepared by the catalyst and improving the gas mass transfer, so as to effectively improve the water mass transfer limitation of the catalytic layer under dry working conditions and medium-high current density, thereby improving the performance of the fuel cell under dry working conditions and medium-high current density.

[0006] To achieve the above object, the technical scheme adopted by the present application is: In a first aspect, the present application provides a preparation method of a modified catalyst for fuel cells, comprising the following steps: S1, mixing the carbon-supported metal catalyst with the treatment agent to obtain a treatment agent mixture; heating the obtained treatment agent mixture to reflux reaction, and cooling to room temperature to obtain a reaction product; washing and filtering the obtained reaction product to obtain a catalyst filter cake; the heating temperature is 40-80℃; the treatment agent is an aqueous solution of oxidant; the ratio of oxidant to carbon-supported metal catalyst in the catalyst filter cake is (0.02-0.12) mol:1g; S2, drying the catalyst filter cake obtained in step S1 to obtain a dry catalyst filter cake and grinding to obtain a catalyst powder; the water content of the dry catalyst filter cake is 20%-60%; S3, heat treating the catalyst powder obtained in step S2, and cooling to room temperature after the heat treatment is completed to obtain a modified catalyst; the heat treatment atmosphere is a mixture of protective gas and oxygen; the volume flow ratio of the protective gas to oxygen is (6-9):(1-4), the heating rate of the heat treatment is greater than 30℃ / min, and the heat treatment temperature is lower than 400℃.

[0007] The present application can make the treating agent fully infiltrate the catalyst pores by treating the catalyst under low-temperature heating conditions, and the oxidizing property of the treating agent can modify a small amount of hydrophilic functional groups on the catalyst or carrier. When the catalyst powder containing a small amount of oxidizing agent and a large amount of water is heat-treated, the temperature is rapidly increased from room temperature to the heat-treatment temperature in a short time, on the one hand, the oxidizing agent is in-situ decomposed into a gas with oxidizing property at high temperature in the catalyst, and the catalyst carrier surface is further oxidized to improve the hydrophilicity of the carrier, optimize the water content in the pores of the catalyst layer prepared by the catalyst in dry working conditions, and further improve the proton transport in the pores; on the other hand, the rapid heating in a short time can make a large amount of water vapor volatilize and escape rapidly, resulting in the further opening of part of the loose carbon pore structure in the carbon carrier, which is beneficial to adjusting the catalyst pore size distribution, improving the proton accessibility in the catalyst layer prepared by the catalyst, and improving the transport of reactants, and optimizing the mass transfer limitation of reaction gas under medium and high current density.

[0008] The present application successfully improves the hydrophilicity of the catalyst and the pore volume of the catalyst macropore (5-10nm pore size) mesopore by modifying the carbon carrier surface through treating the carbon-supported metal catalyst with a treating agent and heat treatment, and the modified catalyst applied to the catalyst layer of the fuel cell can improve the proton accessibility in the catalyst layer, improve the gas mass transfer, and thus improve the performance of the fuel cell under dry working conditions and medium and high current density.

[0009] The modification of the carbon-supported metal catalyst needs to meet specific modification conditions, for example, the ratio of the oxidizing agent to the catalyst in the catalyst filter cake obtained after treatment with the treating agent cannot be too high or too low, and too high or too low will reduce the hydrophilicity of the modified catalyst. For example, the oxygen content in the heat treatment atmosphere cannot be too high or too low, the heating rate of the heat treatment cannot be too slow, and the temperature of the heat treatment cannot be too high.

[0010] As a preferred embodiment of the preparation method of the modified catalyst according to the present application, in step S1, the carbon-supported metal catalyst includes a platinum-carbon catalyst, a platinum-cobalt alloy catalyst and other fuel cell catalysts with active metal particles supported on a carbon carrier.

[0011] As a preferred embodiment of the preparation method of the modified catalyst according to the present application, in step S1, the sufficient reflux reaction time is 60-300min.

[0012] As a preferred embodiment of the preparation method of the modified catalyst according to the present application, in step S1, the heating temperature is 60℃, and the sufficient reflux reaction time is 180min.

[0013] As a preferred embodiment of the preparation method of the modified catalyst, in step S1, the ratio of the carbon-supported metal catalyst to the treating agent is 10-80 g:1 L; the concentration of the oxidizing agent in the treating agent is 1-5 mol / L.

[0014] As a preferred embodiment of the preparation method of the modified catalyst, in step S1, the ratio of the carbon-supported metal catalyst to the treating agent is 40 g:1 L; the concentration of the oxidizing agent in the treating agent is 3 mol / L.

[0015] As a preferred embodiment of the preparation method of the modified catalyst, in step S1, the oxidizing agent comprises at least one of hydrogen peroxide, peroxy acid salt, nitrate or nitric acid.

[0016] As a preferred embodiment of the preparation method of the modified catalyst, in step S1, the peroxy acid salt is ammonium persulfate, and the nitrate is ammonium nitrate.

[0017] As a preferred embodiment of the preparation method of the modified catalyst, in step S1, the ratio of the oxidizing agent to the carbon-supported metal catalyst in the catalyst filter cake is (0.07-0.12) mol:1 g. In this range, the prepared modified catalyst has better hydrophilicity.

[0018] As a preferred embodiment of the preparation method of the modified catalyst, in step S1, the ratio of the oxidizing agent to the carbon-supported metal catalyst in the catalyst filter cake is 0.07 mol:1 g.

[0019] As a preferred embodiment of the preparation method of the modified catalyst, in step S2, the water content of the dry catalyst filter cake is 40%-60%. In this range, the prepared modified catalyst has better hydrophilicity.

[0020] As a preferred embodiment of the preparation method of the modified catalyst, in step S2, the water content of the dry catalyst filter cake is 40%.

[0021] As a preferred embodiment of the preparation method of the modified catalyst, in step S3, the heat treatment time is 120-720 min.

[0022] As a preferred embodiment of the preparation method of the modified catalyst, in step S3, the protective gas comprises at least one of nitrogen, helium, neon, argon, krypton or xenon.

[0023] As a preferred embodiment of the preparation method of the modified catalyst, in step S3, the heat treatment has a temperature rising rate of 50-150 ℃ / min and a temperature of 200-300 ℃.

[0024] As a preferred embodiment of the preparation method of the modified catalyst, in step S3, the volume flow ratio of the protective gas to oxygen is (6-7):(3-4), the heating rate of the heat treatment is 100-150℃ / min, and the temperature of the heat treatment is 250-300℃. In this range, the hydrophilicity of the prepared modified catalyst is better.

[0025] As a preferred embodiment of the preparation method of the modified catalyst, in step S3, the volume flow ratio of the protective gas to oxygen is 7:3, the heating rate of the heat treatment is 100℃ / min, the temperature of the heat treatment is 250℃, and the time of the heat treatment is 240min.

[0026] In a second aspect, the application provides a modified catalyst prepared by the above preparation method.

[0027] In a third aspect, the application provides the use of the above modified catalyst in the preparation of a catalytic layer and / or a membrane electrode of a fuel cell.

[0028] In a fourth aspect, the application provides a membrane electrode, wherein the catalytic layer of the membrane electrode is prepared by using the above modified catalyst.

[0029] In a fifth aspect, the application provides a preparation method of a membrane electrode, comprising the following steps: S1, dispersing the above modified catalyst in water, then adding a resin and an organic solvent, mixing uniformly to obtain a modified catalyst slurry; S2, coating the modified catalyst slurry obtained in step S1 on one side of a proton exchange membrane, drying to form a cathode catalytic layer, and coating an anode catalyst slurry on the other side of the proton exchange membrane, drying to obtain a catalyst-coated membrane (CCM), assembling a frame and a gas diffusion layer to the obtained catalyst-coated membrane to obtain a membrane electrode.

[0030] Compared with the prior art, the application has the following beneficial effects: In the application, the catalyst is treated by using a treating agent under low-temperature heating conditions, so that the treating agent can fully infiltrate the pores of the catalyst, the oxidizability of the treating agent can modify a small amount of hydrophilic functional groups on the catalyst or the carrier, and then combined with heat treatment, the surface of the catalyst carrier can be further moderately oxidized to improve the hydrophilicity of the carrier, the water content in the pores of the catalytic layer prepared by the catalyst can be optimized, and the proton transmission in the pores can be improved; at the same time, the pore size distribution of the catalyst can be adjusted, the proton accessibility in the catalytic layer prepared by the catalyst can be improved, the transmission of the reactant can be improved, and the mass transfer limitation of the reaction gas under medium and high current densities can be optimized. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1The pore volume statistics results of different pore sizes of the catalysts of Examples 1-3 and Comparative Examples 1-2, 5-6, 9 in Test Example 1 of the present application are shown in Table 1. Figure 2 The single cell polarization performance curves of membrane electrode 1-3 and comparative membrane electrode 1-11 in Test Example 3 of the present application are shown in Figure 1. Figure 3 The single cell polarization performance curves of membrane electrode 4 and comparative membrane electrodes 12-13 in Test Example 3 of the present application are shown in Figure 2. Figure 4 The single cell polarization performance curves of membrane electrode 1 and comparative membrane electrode 1 before and after corrosion of the carbon carrier in Test Example 5 of the present application are shown in Figure 3, wherein BOL represents the initial performance before corrosion and EOL represents the end performance after corrosion. DETAILED DESCRIPTION

[0032] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in combination with specific examples.

[0033] Other materials, reagents, etc. used in the examples can be obtained from commercial channels unless otherwise specified.

[0034] Catalyst TEC10E50E-HT (Pt / C catalyst with 50% platinum content) and catalyst TEC10EA30e (Pt / C catalyst with 30% platinum content) are produced by TKK (Japan).

[0035] D2020 resin is a perfluorosulfonic acid resin dispersion liquid with a resin solid content of 20 wt%, produced by DuPont.

[0036] Example 1 A modified catalyst for a fuel cell, and a preparation method thereof, comprising the following steps: (1) adding catalyst TEC10E50E-HT into a 3.0M aqueous ammonium nitrate solution to obtain a treatment agent mixture, wherein the content of the catalyst in the aqueous ammonium nitrate solution is 40 g / L (i.e. the ratio of the catalyst to the aqueous ammonium nitrate solution is 40 g: 1 L); the obtained treatment agent mixture is stirred and heated to 60°C, and refluxed for 180 min, and then cooled to room temperature to obtain a reaction product; the obtained reaction product is repeatedly washed and filtered with ultrapure water until the ratio of ammonium nitrate to catalyst in the filter cake is 0.07 mol: 1 g, to obtain a catalyst filter cake; (2) drying the catalyst filter cake obtained in step (1) in a fume hood to obtain a dry catalyst filter cake, wherein the water content of the obtained dry catalyst filter cake is 40% (the water content test temperature is 60°C); and grinding the obtained dry catalyst filter cake to obtain a catalyst powder; (3) The catalyst powder obtained in step (2) is placed in a muffle furnace for heat treatment, the heat treatment atmosphere is a mixed gas of argon and oxygen with a volume flow ratio of 7:3, the heat treatment temperature is 250℃, the heat treatment time is 240 min, and the heat treatment ends after cooling to room temperature to obtain a modified catalyst.

[0037] Example 2 A modified catalyst for a fuel cell, the preparation method comprising the following steps: (1) Catalyst TEC10E50E-HT is added to a 5.0M hydrogen peroxide aqueous solution to obtain a treatment agent mixture, wherein the content of the catalyst in the hydrogen peroxide aqueous solution is 80g / L; the obtained treatment agent mixture is heated to 40℃ under stirring and refluxed for 300 min, and then cooled to room temperature to obtain a reaction product; the obtained reaction product is repeatedly washed and filtered with ultrapure water until the ratio of hydrogen peroxide to catalyst in the filter cake is 0.12mol:1g to obtain a catalyst filter cake; (2) The catalyst filter cake obtained in step (1) is dried in a fume hood to obtain a dried catalyst filter cake, the water content of the obtained dried catalyst filter cake is 60% (the water content test temperature is 60℃), and the obtained dried catalyst filter cake is ground to obtain a catalyst powder; (3) The catalyst powder obtained in step (2) is placed in a muffle furnace for heat treatment, the heat treatment atmosphere is a mixed gas of argon and oxygen with a volume flow ratio of 7:3, the heat treatment temperature is 250℃, the heat treatment time is 240 min, and the heat treatment ends after cooling to room temperature to obtain a modified catalyst.

[0038] Example 3 A modified catalyst for a fuel cell, the preparation method comprising the following steps: (1) Catalyst TEC10E50E-HT is added to a 5.0M hydrogen peroxide aqueous solution to obtain a treatment agent mixture, wherein the content of the catalyst in the hydrogen peroxide aqueous solution is 80g / L; the obtained treatment agent mixture is heated to 40℃ under stirring and refluxed for 300 min, and then cooled to room temperature to obtain a reaction product; the obtained reaction product is repeatedly washed and filtered with ultrapure water until the ratio of hydrogen peroxide to catalyst in the filter cake is 0.12mol:1g to obtain a catalyst filter cake; (2) The catalyst filter cake obtained in step (1) is dried in a fume hood to obtain a dried catalyst filter cake, the water content of the obtained dried catalyst filter cake is 60% (the water content test temperature is 60℃), and the obtained dried catalyst filter cake is ground to obtain a catalyst powder; (3) The catalyst powder obtained in step (2) is placed in a muffle furnace for heat treatment, the heat treatment atmosphere is a mixture of argon and oxygen with a volume flow ratio of 6:4, the heating rate of heat treatment is 50℃ / min, the heat treatment temperature is 200℃, the heat treatment time is 720min, and after the heat treatment is completed, it is cooled to room temperature to obtain a modified catalyst.

[0039] Example 4 A modified catalyst for a fuel cell, the difference between the modified catalyst of the present example and that of Example 1 is only that the catalyst raw material before modification is different, and the catalyst of the present example is a self-made Pt / C catalyst adjusted from the catalyst TEC10E50E-HT of Example 1.

[0040] The preparation method of the modified catalyst of the present example includes the following steps: (1) Take Ketjen black in a round-bottom flask, add ethylene glycol and ultrapure water, the mass ratio of Ketjen black, ethylene glycol and water is 1:100:100, ultrasonic treatment for 1h to obtain a Ketjen black mixed solution; dilute the chloroplatinic acid aqueous solution with a concentration of 50g / L to 10g / L with ethylene glycol to obtain a chloroplatinic acid mixed solution; take the chloroplatinic acid mixed solution with a mass ratio of chloroplatinic acid to Ketjen black of 1:1 and drop it into the Ketjen black mixed solution drop by drop, stir for 1h, then use 1mol / L NaOH solution to adjust the pH value of the mixed solution to 12, then heat in an oil bath at 160℃ for 3h, cool to room temperature after the reaction is completed, then use 1mol / L nitric acid solution to adjust the pH value of the mixed solution to 2, then stir at 40℃ for 20h to obtain a reaction product; filter wash the obtained reaction product with ultrapure water until the filtrate is neutral, dry and grind the obtained solid to obtain a Pt / C catalyst; (2) Compared with Example 1, the catalyst TEC10E50E-HT of step (1) of Example 1 is adjusted to the Pt / C catalyst of step (1) of the present example; (3) The same as step (2) of Example 1; (4) The same as step (3) of Example 1 to obtain a modified catalyst.

[0041] Comparative Example 1 A catalyst for a fuel cell, the difference between the catalyst of the present comparative example and that of Example 1 is only that it is not treated with a treatment agent and is not subjected to a heat treatment modification process. The catalyst of the present comparative example is the catalyst TEC10E50E-HT.

[0042] Comparative Example 2 A modified catalyst for a fuel cell, the difference between the modified catalyst of the present comparative example and that of Example 1 is only that it is only treated with a treatment agent and is not subjected to a heat treatment. The preparation method of the modified catalyst of the present comparative example includes the following steps: (1) The same as Example 1; (2) The catalyst filter cake obtained in step (1) was dried completely in a fume hood, ground, and a modified catalyst was obtained.

[0043] Comparative Example 3 A modified catalyst for a fuel cell, the modified catalyst of this comparative example differs from Example 1 only in the ratio of treating agent to catalyst in the catalyst filter cake.

[0044] The modified catalyst of this comparative example differs from Example 1 in that the ratio of ammonium nitrate to catalyst in the filter cake of step (1) of Example 1 was changed from 0.07 mol: 1 g to 0.01 mol: 1 g.

[0045] Comparative Example 4 A modified catalyst for a fuel cell, the modified catalyst of this comparative example differs from Example 1 only in the ratio of treating agent to catalyst in the catalyst filter cake.

[0046] The modified catalyst of this comparative example differs from Example 1 in that the ratio of ammonium nitrate to catalyst in the filter cake of step (1) of Example 1 was changed from 0.07 mol: 1 g to 0.15 mol: 1 g.

[0047] Comparative Example 5 A modified catalyst for a fuel cell, the modified catalyst of this comparative example differs from Example 1 only in the water content of the dried catalyst filter cake.

[0048] The modified catalyst of this comparative example differs from Example 1 in that the water content of the dried catalyst filter cake of step (2) of Example 1 was changed from 40% to 5%.

[0049] Comparative Example 6 A modified catalyst for a fuel cell, the modified catalyst of this comparative example differs from Example 1 only in the water content of the dried catalyst filter cake and the atmosphere of the heat treatment.

[0050] The modified catalyst of this comparative example differs from Example 1 in that the water content of the dried catalyst filter cake of step (2) of Example 1 was changed from 40% to 5% and the mixed gas of step (3) of Example 1 was changed to saturated water vapor.

[0051] Comparative Example 7 A modified catalyst for a fuel cell, the modified catalyst of this comparative example differs from Example 1 only in the ratio of protective gas to oxygen in the mixed gas of the heat treatment atmosphere.

[0052] The modified catalyst of this comparative example differs from Example 1 in that the ratio of argon to oxygen in the volume flow rate of step (3) of Example 1 was changed from 7:3 to 5:5.

[0053] Comparative Example 8 A modified catalyst for a fuel cell, the comparative example modified catalyst differs from example 1 only in the ratio of the protective gas to oxygen in the mixed gas of the heat treatment atmosphere.

[0054] The comparative example modified catalyst differs from example 1 only in the ratio of the protective gas to oxygen in the mixed gas of the heat treatment atmosphere.

[0055] Comparative example 9 A modified catalyst for a fuel cell, the comparative example modified catalyst differs from example 1 only in the temperature of the heat treatment.

[0056] The comparative example modified catalyst differs from example 1 only in the temperature of the heat treatment.

[0057] Comparative example 10 A modified catalyst for a fuel cell, the comparative example modified catalyst differs from example 1 only in the temperature of the heat treatment.

[0058] The comparative example modified catalyst differs from example 1 only in the temperature of the heat treatment.

[0059] Comparative example 11 A modified catalyst for a fuel cell, the comparative example modified catalyst differs from example 1 only in the temperature of the heat treatment.

[0060] The comparative example modified catalyst differs from example 1 only in the temperature of the heat treatment.

[0061] Comparative example 12 A catalyst for a fuel cell, the comparative example catalyst differs from example 4 only in that the treatment agent treatment and the heat treatment modification treatment are not performed. The comparative example catalyst is the Pt / C catalyst prepared in example 4 step (1).

[0062] Comparative example 13 A modified catalyst for a fuel cell, the comparative example modified catalyst differs from example 4 only in the preparation process of the Pt / C catalyst. The modified catalyst of the comparative example first treats the carbon support and then deposits Pt. The specific preparation method includes the following steps: (1) adding Ketjen black into 3.0M aqueous ammonium nitrate solution to obtain a treatment agent mixture, wherein the content of Ketjen black in the aqueous ammonium nitrate solution is 40g / L; the obtained treatment agent mixture is heated to 60℃ under stirring and refluxed for 180min, and then cooled to room temperature to obtain a reaction product; the obtained reaction product is repeatedly washed and filtered with ultrapure water until the ratio of ammonium nitrate to Ketjen black in the filter cake is 0.07mol:1g, to obtain a Ketjen black filter cake; (2) drying the Ketjen black filter cake obtained in step (1) in a fume hood to obtain a dried Ketjen black filter cake, wherein the water content of the obtained dried Ketjen black filter cake is 40%(the water content test temperature is 60℃), and the obtained dried Ketjen black filter cake is ground to obtain a Ketjen black powder; (3) placing the Ketjen black powder obtained in step (2) in a muffle furnace for heat treatment, wherein the heat treatment atmosphere is a mixed gas with a volume flow ratio of argon to oxygen of 7:3, the heat treatment temperature is 250℃, the heat treatment time is 240min, and the cooling rate after heat treatment is room temperature, to obtain a modified Ketjen black; (4) adding ethylene glycol and ultrapure water to the modified Ketjen black obtained in step (3), wherein the mass ratio of the modified Ketjen black, ethylene glycol and water is 1:100:100, and the mixture is ultrasonically treated for 1h to obtain a modified Ketjen black mixed solution; diluting a 50g / L chloroplatinic acid aqueous solution to 10g / L with ethylene glycol to obtain a chloroplatinic acid mixed solution; adding the chloroplatinic acid mixed solution dropwise into the modified Ketjen black mixed solution, wherein the mass ratio of chloroplatinic acid to modified Ketjen black is 1:1, stirring for 1h, then adjusting the pH value of the mixture to 12 with a 1mol / L NaOH solution, and then heating in an oil bath at 160℃ for 3h, cooling to room temperature after the reaction is completed, then adjusting the pH value of the mixture to 2 with a 1mol / L nitric acid solution, and then stirring at 40℃ for 20h to obtain a reaction product; the obtained reaction product is filtered and washed with ultrapure water until the filtrate is neutral, and the obtained solid is dried and ground to obtain a modified catalyst.

[0063] Application Example The modified catalyst is applied to the preparation of a membrane electrode of a fuel cell.

[0064] A membrane electrode of a fuel cell, the preparation method comprising the following steps: (1) dispersing the modified catalyst into water, then adding a perfluorosulfonic acid resin dispersion liquid (D2020 resin) with a resin solid content of 20wt%, and ethanol, mixing uniformly to obtain an initial slurry with a solid content of 10wt%, wherein the I / C ratio of the obtained initial slurry is 0.7, and the weight ratio of the ethanol and water is 1:1; ball-milling and dispersing the obtained initial slurry to obtain a cathode slurry, wherein the dispersion time is 4h; (2) dispersing the catalyst TEC10EA30e into water, then adding a dispersion liquid of perfluorosulfonic acid resin (D2020 resin) with a resin solid content of 20 wt%, ethanol, mixing to obtain an initial slurry with a solid content of 10 wt%, the I / C ratio of the obtained initial slurry being 1.0, the weight ratio of the ethanol and water being 1:4; ball-milling the obtained initial slurry to obtain an anode slurry, the dispersion time being 4 h; (3) coating the cathode slurry obtained in step (1) on one side of a proton exchange membrane and drying to obtain a cathode catalyst layer, the platinum loading being 0.25 mg / cm 2 ; coating the anode slurry obtained in step (2) on the other side of the proton exchange membrane, the platinum loading being 0.05 mg / cm 2 , and drying to obtain a catalyst-coated membrane (CCM); assembling a frame and a gas diffusion layer to the fuel cell chip (CCM) to obtain a membrane electrode.

[0065] Membrane electrodes 1-4 and comparative membrane electrode 1-13 were prepared according to the above-mentioned membrane electrode preparation method using the catalysts of Examples 1-4 and Comparative Examples 1-13, respectively. The information of the catalysts corresponding to the membrane electrodes 1-4 and comparative membrane electrode 1-13 is shown in Table 1, and Table 1 Catalyst Catalyst Membrane electrode 1 Example 1 Comparative membrane electrode 6 Comparative example 6 Membrane electrode 2 Example 2 Comparative membrane electrode 7 Comparative example 7 Membrane electrode 3 Example 3 Comparative membrane electrode 8 Comparative example 8 Membrane electrode 4 Example 4 Comparative membrane electrode 9 Comparative example 9 Comparative membrane electrode 1 Comparative example 1 Comparative membrane electrode 10 Comparative example 10 Comparative membrane electrode 2 Comparative example 2 Comparative membrane electrode 11 Comparative example 11 Comparative membrane electrode 3 Comparative example 3 Comparative membrane electrode 12 Comparative example 12 Comparative membrane electrode 4 Comparative example 4 Comparative membrane electrode 13 Comparative example 13 Comparative membrane electrode 5 Comparative example 5 / / Test Example 1 The catalysts of Examples 1-3 and Comparative Examples 1-2, 5-6, 9 were used as samples, and a full-automatic specific surface area analyzer was used to test the pore volume of the catalyst samples, and the pore volume data was counted.

[0066] The pore volume counting results corresponding to different pore diameters of the catalysts of Examples 1-3 and Comparative Examples 1-2, 5-6, 9 are shown in Table 2. Figure 1 The results show that, compared with Comparative Example 1 without any modification treatment, Comparative Example 2 treated only with the treating agent, and Comparative Example 5 completely dried before heat treatment, the pore volume of the modified catalyst of Example 1-3 in the pore diameter range of 5-10 nm is significantly increased, indicating that the treating agent of the application combined with heat treatment can increase the pore volume of the catalyst in the pore diameter range of 5-10 nm; the heat treatment of the catalyst containing appropriate moisture at a short time and rapid heating (rapid gasification of moisture) can increase the pore volume of the catalyst in the pore diameter range of 5-10 nm to a certain extent, appropriately increase the pore volume of the carbon carrier in the large pore diameter range, thereby improving the accessibility of protons and reaction gases and improving the performance of the membrane electrode.

[0067] In Comparative Example 6, the modified catalyst was completely dried after being treated with the treating agent, and water vapor was only introduced during heat treatment, which was not generated in situ from the inside of the catalyst, and had basically no significant effect on the distribution regulation of the small-diameter pores of the catalyst; it is indicated that the modified catalyst of the application needs to control a specific moisture content before heat treatment.

[0068] The heating rate of the heat treatment of Comparative Example 9 is too slow, and the residual water in the pores of the catalyst slowly evaporates during the heating process. Although the pore volume in the range of 5-10 nm of Comparative Example 9 is slightly larger than that of Comparative Example 1, the increase in the pore volume of the catalyst with a large pore diameter is not as good as that of Example 1, indicating that the heat treatment of the modified catalyst of the present application needs to control a specific heating rate.

[0069] Test Example 2 The catalysts of Examples 1-3 and Comparative Examples 1-11 were used as samples, and the samples were placed in a high humidity environment to measure the water absorption weight gain rate of the samples, thereby reflecting the surface hydrophilicity of the samples. The specific test method is as follows: After the catalyst samples were completely dried at 60°C under vacuum for 48 h, they were placed in a 25°C, 95% RH environment box for 48 h, and the mass change of the catalyst samples was measured to calculate the weight gain rate of each catalyst sample.

[0070] The weight gain rates of the catalysts of Examples 1-3 and Comparative Examples 1-11 are shown in Table 2 below, Table 2 Sample Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Weight gain rate (%) 8.9 8.2 7.8 6.1 6.4 6.2 6.8 Sample Comparative example 5 Comparative example 6 Comparative example 7 Comparative example 8 Comparative example 9 Comparative example 10 Comparative example 11 Weight gain rate (%) 7.6 7.8 10.2 7.2 7.7 10.8 9.6 The results in Table 2 show that the water absorption weight gain rates of the catalyst samples of Examples 1-3 in a high humidity environment are significantly increased compared to Comparative Example 1, indicating that the surface hydrophilicity of the modified catalyst treated by the treatment agent and heat treatment of the present application is significantly improved, which can effectively improve the performance of the battery under dry working conditions.

[0071] Comparative Example 2 treated only by the treatment agent and Comparative Example 3 with less residual treatment agent in the catalyst have no significant change in surface hydrophilicity. Comparative Example 4 with more residual treatment agent in the catalyst has a slight improvement in surface hydrophilicity, but is poorer than Examples 1-3; indicating that the residual amount of the treatment agent after treatment has an effect on the surface hydrophilicity of the modified catalyst, and a residual amount within a specific range can obtain a modified catalyst with better surface hydrophilicity.

[0072] The oxygen content in the heat treatment (in-situ oxidation process) of Comparative Example 8 is too low, which affects the overall oxidation effect, and the catalyst hydrophilicity is slightly poorer than Examples 1-3. This indicates that the oxygen content in the heat treatment of the modified catalyst of the present application cannot be lower than the range of Examples.

[0073] Test Example 3 The membrane electrode samples of Application Examples 1-4 and Comparative Membrane Electrodes 1-13 were used as membrane electrode samples to test the membrane electrode single cell polarization performance.

[0074] The membrane electrode samples were tested for membrane electrode single cell polarization performance curves using an 850e fuel cell test system, and the test conditions were 68°C and 20% RH.

[0075] The single cell polarization performance curves of Membrane Electrodes 1-3 and Comparative Membrane Electrodes 1-11 are shown in FIG. 2.Figure 2 The current density is 1.5 A / cm2 2 The corresponding single cell voltage E (V) is shown in Table 3 below, Table 3 Sample E (V) Sample E (V) Membrane electrode 1 0.729 Comparative membrane electrode 5 0.714 Membrane electrode 2 0.725 Comparative membrane electrode 6 0.711 Membrane electrode 3 0.724 Comparative membrane electrode 7 0.682 Comparative membrane electrode 1 0.709 Comparative membrane electrode 8 0.713 Comparative membrane electrode 2 0.708 Comparative membrane electrode 9 0.715 Comparative membrane electrode 3 0.707 Comparative membrane electrode 10 0.678 Comparative membrane electrode 4 0.712 Comparative membrane electrode 11 0.691 The results show that the single cell voltage of the membrane electrode 1-3 is higher than that of the comparative membrane electrode 1-11, indicating that the preparation conditions of the modified catalyst prepared in the examples can better improve the performance of the membrane electrode.

[0076] The single cell voltage E of the comparative membrane electrode 1 is basically the same as that of the comparative membrane electrode 2 and the comparative membrane electrode 3, indicating that compared with the catalyst comparative example 1 without any treatment, the catalyst comparative example 2 treated only by the treatment agent and the catalyst comparative example 3 treated by the treatment agent with a too low residual content of the treatment agent have no significant effect on the improvement of the polarization performance of the membrane electrode and no significant improvement on the performance under dry conditions.

[0077] The single cell voltage E of the comparative membrane electrode 4 is slightly higher than that of the comparative membrane electrode 1, but lower than that of the membrane electrode 1-3, indicating that compared with the comparative example 1, the catalyst comparative example 4 treated by the treatment agent with a too high residual content of the treatment agent has an improvement on the polarization performance of the membrane electrode, but the improvement effect is limited.

[0078] The single cell voltage E of the comparative membrane electrode 5 is slightly higher than that of the comparative membrane electrode 1, but lower than that of the membrane electrode 1-3, indicating that compared with the comparative example 1, the catalyst comparative example 5 treated by the treatment agent and dried to a too low water content has an improvement on the performance of the membrane electrode, but the improvement effect is limited.

[0079] The results of the comparative membrane electrode 6 show that during the heat treatment, even if there is a large amount of water vapor in the external atmosphere, however, since it is not generated from the inside of the catalyst due to rapid gasification, it has no significant effect on the control of the pore volume of the catalyst, resulting in no significant improvement in the polarization performance compared with the comparative membrane electrode 5. The results of the comparative membrane electrode 9 show that during the heat treatment, the heating rate is too slow, and the control of the pore volume of the catalyst is not significant, resulting in no significant improvement in the polarization performance compared with the membrane electrode 1-3.

[0080] The polarization performance of the comparative membrane electrode 7 and 10 is significantly reduced compared with the comparative membrane electrode 1, indicating that during the heat treatment, the oxygen content cannot be too high, and the heat treatment temperature cannot be too high.

[0081] The results of the comparative membrane electrode 8 show that the oxygen content in the heat treatment atmosphere is too low, which has an effect on the overall oxidation, and the improvement effect on the performance of the membrane electrode is not obvious compared with the membrane electrode 1-3.

[0082] The results of the comparative membrane electrode 11 show that the temperature of the treatment agent treatment cannot be too high, and the high treatment temperature in the relatively thick treatment agent may cause excessive oxidation of the catalyst, and the polarization performance is significantly reduced compared with the membrane electrode 1.

[0083] The single cell polarization performance curves of the membrane electrode 4 and the comparative membrane electrodes 12-13 are shown in FIG. 4, and the results show that the single cell voltage of the membrane electrode 4 is higher than that of the comparative membrane electrodes 12-13, indicating that the preparation conditions of the modified catalyst in the embodiment can better improve the performance of the membrane electrode. Figure 3

[0084] When the current density is 1.5 A / cm 2 , the single cell voltage of the membrane electrode 4 is 0.722 V, the single cell voltage of the comparative membrane electrode 12 is 0.701 V, and the single cell voltage of the comparative membrane electrode 13 is 0.710 V. It can be seen that after the platinum particles are deposited on the carbon carrier, the catalyst of the embodiment 4 is treated by the treatment agent and heat treated, and the performance of the prepared membrane electrode is significantly improved compared with the catalyst of the comparative example 12 without any treatment; the catalyst of the comparative membrane electrode 13 (comparative example 13) is first treated by the treatment agent of the application on the carbon carrier and then loaded with platinum particles, and although its performance is slightly improved compared with the comparative membrane electrode 12 (the catalyst is comparative example 12), the improvement effect is not as significant as that of the membrane electrode 4, which may be due to the influence of the early carbon carrier treatment on the subsequent platinum particle deposition.

[0085] Test Example 4 The platinum content of the catalysts of the embodiments 1-3 and the comparative examples 1-11 was tested by using a thermogravimetric analyzer.

[0086] The test results of the platinum content of the catalysts of the embodiments 1-3 and the comparative examples 1-11 are shown in Table 4 below, Table 4 Sample Pt content (%) Sample Pt content (%) Example 1 49.38 Comparative example 5 49.19 Example 2 49.30 Comparative example 6 49.25 Example 3 49.20 Comparative example 7 62.24 Comparative example 1 49.26 Comparative example 8 49.21 Comparative example 2 49.14 Comparative example 9 49.33 Comparative example 3 49.28 Comparative example 10 65.12 Comparative example 4 49.45 Comparative example 11 49.28 The results in Table 4 show that the platinum content of the comparative example 1, which is the untreated catalyst, is 49.26%, and the platinum contents of the embodiments 1-3, the comparative examples 2-6, the comparative examples 8-9 and the comparative example 11 do not change significantly. However, the platinum content of the comparative example 7 is significantly increased to 62.24% due to the high oxygen content in the heat treatment atmosphere, which may cause the decomposition of part of the carbon carrier in the catalyst; and the platinum content of the comparative example 10 is increased to 65.12% due to the high heat treatment temperature, which may also cause the decomposition of part of the carbon carrier in the catalyst.

[0087] Test Example 5 The polarization performance of the membrane electrode before and after the corrosion of the carbon carrier was tested by using the membrane electrode 1 and the comparative membrane electrode 1 as the membrane electrode samples.

[0088] The carbon carrier of the membrane electrode sample was tested by using the 850e fuel cell test system to test the corrosion of the carbon carrier of the membrane electrode.

[0089] The single cell polarization performance curves of the membrane electrode 1 and the comparative membrane electrode 1 before and after the corrosion of the carbon carrier are shown in FIG. 5, and the results show that the single cell voltage of the membrane electrode 1 is higher than that of the comparative membrane electrode 1, indicating that the carbon carrier treatment in the application can better improve the performance of the membrane electrode. Figure 4 ​BOL represents initial performance before corrosion, and EOL represents end performance after corrosion.

[0090] The results show that the voltage attenuation of the comparative membrane electrode 1 is 25 mV, and the voltage attenuation of the membrane electrode 1 is 22 mV, which has no significant difference, indicating that the method for modifying the catalyst can effectively improve the performance of the fuel cell under dry working conditions and medium and high current densities, and has no significant effect on the stability of the carbon carrier of the catalyst, and does not affect the service life of the membrane electrode. 2 Next, the voltage attenuation of the comparative membrane electrode 1 is 25 mV, and the voltage attenuation of the membrane electrode 1 is 22 mV, which has no significant difference, indicating that the method for modifying the catalyst can effectively improve the performance of the fuel cell under dry working conditions and medium and high current densities, and has no significant effect on the stability of the carbon carrier of the catalyst, and does not affect the service life of the membrane electrode.

[0091] Finally, it should be explained that the above examples are only used to illustrate the technical solutions of the present application, but not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for preparing a modified catalyst for a fuel cell, characterized in that: The following steps are involved: S1. Mixing the carbon-supported metal catalyst and the treating agent to obtain a treating agent mixture; heating the obtained treating agent mixture to fully reflux for reaction, and cooling to room temperature to obtain a reactant; washing and filtering the obtained reactant to obtain a catalyst filter cake; The heating temperature is 40-80° C.; the treating agent is an aqueous solution of an oxidant; the ratio of the oxidant to the carbon-supported metal catalyst in the catalyst filter cake is (0.02-0.12) mol:1 g; S2, drying the catalyst filter cake obtained in step S1 to obtain a dry catalyst filter cake and grinding the dried catalyst filter cake to obtain a catalyst powder; the moisture content of the dried catalyst filter cake is 20% to 60%; S3, heat-treating the catalyst powder obtained in step S2, and cooling it to room temperature after the heat treatment to obtain a modified catalyst; The atmosphere of the heat treatment is a mixture of protective gas and oxygen; the volume flow ratio of the protective gas to oxygen is (6-9):(1-4), the heating rate of the heat treatment is greater than 30°C / min, and the heat treatment temperature is lower than 400°C.

2. The preparation method according to claim 1, wherein In step S1, the time for the sufficient reflux reaction is 60 to 300 minutes.

3. The preparation method according to claim 1, wherein In step S1, the ratio of the carbon-supported metal catalyst to the treating agent is 10-80 g:1 L; And / or, the concentration of the oxidant in the treatment agent is 1 to 5 mol / L.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step S1, the oxidant includes at least one of hydrogen peroxide, peroxide salt, nitrate or nitric acid.

5. The preparation method according to claim 1, wherein In step S3, the heating rate of the heat treatment is 50-150°C / min; And / or, the heat treatment temperature is 200-300°C.

6. The preparation method according to claim 1, wherein In step S3, the heat treatment time is 120 to 720 minutes; and / or the protective gas includes at least one of nitrogen, helium, neon, argon, krypton or xenon.

7. A modified catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the modified catalyst according to claim 7 in preparing a catalyst layer and / or membrane electrode of a fuel cell.

9. A membrane electrode, characterized in that The catalytic layer of the membrane electrode is prepared using the modified catalyst according to claim 7.

10. The method for preparing the membrane electrode according to claim 9, characterized in that: The following steps are involved: S1. Dispersing the modified catalyst according to claim 7 in water, then adding resin and organic solvent, and mixing to obtain modified catalyst slurry; S2. The modified catalyst slurry obtained in step S1 is coated on one side of the proton exchange membrane, and after drying, a cathode catalyst layer is formed. The anode catalyst slurry is coated on the other side of the proton exchange membrane, and after drying, a catalyst-coated membrane is obtained. The obtained catalyst-coated membrane is assembled with a frame and a gas diffusion layer to obtain a membrane electrode.

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