Method for improving membrane electrode catalyst layer of proton exchange membrane fuel cell by sulfonyl modified carbon material

Abstract

The invention relates to the field of fuel cell catalysts, and discloses a method for improving a membrane electrode catalyst layer of a proton exchange membrane fuel cell by using a sulfonic acid group modified carbon material, which comprises the following steps: adding a carbon material into an acid solution, carrying out reflux reaction, washing and drying to obtain a carbon material with an oxygen-containing functional group; adding the carbon material containing the oxygen functional group into an organic solvent for dispersion, adding an organic matter containing a sulfonic acid group after reaction, and performing condensation reaction to obtain a sulfonic acid group modified carbon material; and adding the sulfonic acid group modified carbon material into the proton exchange membrane fuel cell slurry to prepare the sulfonic acid group modified material improved proton exchange membrane fuel cell membrane electrode. A sulfonic acid group and water molecules form a hydrogen bond under a low-humidity working condition, so that the water retention capacity of the catalyst layer is improved, and the proton conduction capacity is improved; under the high-humidity condition, due to the ionization charge repulsion effect of sulfonic acid groups and ionomers, the adsorption of the ionomers on the surface of the carbon material is reduced, the porosity of the catalyst layer is improved, the discharge of redundant water is facilitated, and the gas transmission rate is increased.

Description

Technical Field

[0001] This invention relates to the field of fuel cell catalysts, specifically a method for improving the catalyst layer of a proton exchange membrane fuel cell membrane electrode using sulfonic acid-modified carbon materials. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are beneficial for achieving my country's "dual carbon" goals due to their high efficiency and pollution-free characteristics. However, the performance of PEMFCs depends to a considerable extent on the three-phase interface of the membrane electrode catalytic layer. Improving the three-phase interface is of great significance for enhancing the performance and operating conditions of PEMFCs.

[0003] In the three-phase interface of a proton exchange membrane fuel cell, water in the liquid phase is one of the key components. A proper distribution of water within the membrane electrode catalytic layer is an important characteristic of an excellent three-phase interface.

[0004] Existing catalyst layers lack water retention under low humidity conditions, making it difficult to maintain sufficient water content to ensure high proton conductivity. Under high humidity conditions, excess water cannot be drained in time, making it difficult to avoid water flooding within the catalyst layer and resulting in low oxygen transport efficiency. Therefore, it is necessary to design a method to improve the catalyst layer of the membrane electrode of a proton exchange membrane fuel cell using sulfonic acid-modified carbon materials. Summary of the Invention

[0005] The purpose of this invention is to provide a method for improving the catalyst layer of the membrane electrode of a proton exchange membrane fuel cell using sulfonic acid-modified carbon materials, in order to solve the problems in the prior art.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for improving the catalyst layer of a proton exchange membrane fuel cell membrane electrode using sulfonic acid-modified carbon materials includes the following steps:

[0008] S1: Add carbon material to an acid solution, reflux the reaction, wash and dry to obtain carbon material with oxygen-containing functional groups;

[0009] S2: Add carbon materials containing oxygen functional groups to an organic solvent for dispersion, react for a period of time, and then add organic materials containing sulfonic acid groups to carry out a condensation reaction to obtain carbon materials modified with sulfonic acid groups.

[0010] S3: Sulfonic acid group-modified carbon material is added to the proton exchange membrane fuel cell slurry and then prepared into a membrane electrode to obtain a sulfonic acid group-modified material improved proton exchange membrane fuel cell membrane electrode.

[0011] Furthermore, the acid solution in S1 is an acidic solution containing an oxidizing agent, wherein the oxidizing agent is one or more of nitric acid and hydrogen peroxide solution.

[0012] Furthermore, the carbon material in S1 is one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, Katjen Black EC300J, Katjen Black ECP, Katjen Black EC600JD, and Katjen Black ECP600JD.

[0013] Furthermore, the oxidizing acid solution in S1 is a mixed solution composed of sulfuric acid and one or more of nitric acid, hydrogen peroxide, and potassium permanganate.

[0014] Furthermore, the temperature range of the reflux reaction in S1 is 50–80°C, and the time range is 30–300 minutes.

[0015] Furthermore, the organic solvent in S2 is one of the following: an ethanol, isopropanol, n-propanol, or n-butanol solution of N,N'-dicyclohexylcarbodiimide.

[0016] Furthermore, the carbon material rich in oxygen-containing functional groups in S2 is added to an organic solvent for ultrasonic dispersion, and the reaction is carried out for a period of time at 50°C for 20 to 60 minutes.

[0017] Furthermore, the organic compounds containing sulfonic acid groups in S2 are p-aminobenzenesulfonic acid and aminosulfonic acid.

[0018] Furthermore, the condensation reaction in S2 is carried out at a temperature of 50°C for 24 hours.

[0019] Further, in step S3, the membrane electrode preparation process involves mixing sulfonic acid-modified carbon materials, catalyst, water, alcohol, and ionomer to prepare a catalyst slurry. This slurry is then coated onto a proton exchange membrane using ultrasonic spraying. Finally, it is assembled with a gas diffusion layer to form a membrane electrode with an effective area of ​​5 cm². 2 ;

[0020] The amount of carbon material modified with sulfonic acid groups added is 5% to 10% of the mass of the catalyst support.

[0021] The beneficial effects of this invention are:

[0022] 1. The sulfonic acid group-modified carbon material prepared in this invention mainly achieves the water retention function of the carbon material by grafting sulfonic acid groups. By adding this material, under low humidity conditions, the sulfonic acid groups form hydrogen bonds with water molecules, which increases the water retention capacity of the catalyst layer and improves the proton conduction capacity under low humidity conditions. Under high humidity conditions, due to the repulsive effect of the ionized charge between the sulfonic acid groups and the ionomers, the adsorption of ionomers on the surface of the sulfonic acid group-modified carbon material is greatly reduced, which increases the porosity of the catalyst layer, helps to drain excess water, and increases the gas transport rate.

[0023] 2. The sulfonic acid group-modified carbon material prepared in this invention is mainly a high-conductivity carbon material with a porous structure. Low-conductivity water-retaining materials such as fumed silica, nano-titanium dioxide, and covalent organic frameworks, after optimizing the three-phase interface of the catalyst layer, lead to an increase in ohmic polarization resistance due to the low conductivity of the material. In contrast, this invention selects a high-conductivity carbon material with a porous structure. After sulfonic acid group modification, the hydrophilicity of the material is improved, and the water retention capacity of the catalyst layer is improved. After being added to the catalyst layer, it will not cause a decrease in conductivity. Attached Figure Description

[0024] The invention will now be further described with reference to the accompanying drawings.

[0025] Figure 1 This is a schematic diagram of the principle of part S1 of the technical solution of the present invention;

[0026] Figure 2 This is a schematic diagram of the principle of part S2 of the technical solution of the present invention;

[0027] Figure 3 These are the high humidity and high back pressure membrane electrode IV curves of the first implementation case and the comparative case of the technical solution of this invention;

[0028] Figure 4 These are the membrane electrode IV curves under low humidity and low back pressure conditions in Implementation Case 1 and the comparative case of the technical solution of this invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] A method for improving the catalyst layer of a proton exchange membrane fuel cell membrane electrode using sulfonic acid-modified carbon materials includes the following steps:

[0031] S1: Weigh the carbon material and add it to an oxidizing acid solution, reflux the reaction, then wash and dry it to obtain a carbon material with oxygen-containing functional groups.

[0032] S2: Then, carbon materials rich in oxygen-containing functional groups are added to an organic solvent for dispersion. After reacting for a period of time, organic matter containing sulfonic acid groups is added to carry out a condensation reaction to obtain carbon materials modified with sulfonic acid groups.

[0033] S3: Sulfonic acid group-modified carbon material is added to the proton exchange membrane fuel cell slurry and then sprayed to form a membrane electrode, thus obtaining a sulfonic acid group-modified material to improve the proton exchange membrane fuel cell membrane electrode.

[0034] In step S1, the acid solution is an acidic solution containing an oxidizing agent, wherein the oxidizing agent is one or more of nitric acid and hydrogen peroxide solution.

[0035] In step S1, the carbon material used is one or more of the following: single-walled carbon nanotubes, multi-walled carbon nanotubes, Katjen Black EC300J, Katjen Black ECP, Katjen Black EC600JD, and Katjen Black ECP600JD.

[0036] In step S1, the oxidizing acid solution used is a mixed solution, which is a mixture of sulfuric acid and one or more of nitric acid, hydrogen peroxide, and potassium permanganate.

[0037] In step S1, the temperature range for the reflux reaction is 50–80°C, and the time range is 30–300 minutes.

[0038] In step S2, the organic solvent used is one of the following: an ethanol, isopropanol, n-propanol, or n-butanol solution of N,N'-dicyclohexylcarbodiimide.

[0039] In step S2, carbon materials rich in oxygen-containing functional groups are added to an organic solvent and ultrasonically dispersed for a period of time at 50°C for 20–60 minutes.

[0040] In step S2, the organic compounds containing sulfonic acid groups used are p-aminobenzenesulfonic acid and aminosulfonic acid.

[0041] In step S2, the condensation reaction is carried out at a temperature of 50°C for 24 hours.

[0042] In step S3, the amount of carbon material modified with sulfonic acid groups added is 5% to 10% of the mass of the catalyst support.

[0043] This invention provides a nitrogen-functionalized carbon support prepared by the above method.

[0044] In the following specific embodiments, all operations not specified are performed under conventional conditions or manufacturer's recommendations, and all raw materials not specified by manufacturer and specifications are conventional products that can be obtained commercially.

[0045] The membrane electrode was prepared by ultrasonic spraying: a catalyst slurry was prepared by mixing the catalyst with water, alcohol, and ionomer in a certain proportion. The catalyst slurry was then coated onto a proton exchange membrane (Gore M765.08, 8 μm) by ultrasonic spraying. The membrane electrode was then assembled with a gas diffusion layer to form a membrane electrode with an effective area of ​​5 cm². 2 Membrane electrode testing was performed using a Scribner 850e test bench. The cell temperature was 80°C, the dew point temperature was 80°C, and the back pressure was 250 kPa. abs .

[0046] Example 1:

[0047] Take 5g of short multi-walled carbon nanotubes and place them in 250ml of concentrated H2SO4. Place them in an ice bath at 2℃ and slowly add 15g of KMnO4 after cooling (the temperature needs to be controlled). After reacting in an ice-water bath for 1 hour, raise the reaction temperature to 50℃ and react for 5 hours. Then wash with 5% hydrochloric acid (volume fraction) and ultrapure water to neutralize the solution and dry it for later use.

[0048] Short multi-walled carbon nanotubes treated with acid oxidation were dispersed in anhydrous ethanol, and N,N'-dicyclohexylcarbodiimide was added. The mixture was reacted at 50°C for 30 minutes, followed by the addition of an aqueous solution of p-aminobenzenesulfonic acid. The reaction was carried out for 24 hours, and the nanotubes were washed and dried for later use.

[0049] 5% (by mass) of sulfonic acid-modified short multi-walled carbon nanotubes were mixed with the catalyst support, and water, n-propanol, and ionomer were added. After ultrasonic treatment in a water bath, a slurry was prepared and ultrasonically sprayed onto a Gore M765.08 proton exchange membrane to prepare a 25 cm² membrane. 2 Membrane electrode.

[0050] The membrane electrode assembly (MEA) was tested using a Scribner 850e, and the gas diffusion layer for the MEA was Toray TGL-R-055 with a compression ratio of 25%. The test temperature was set to 80°C, the dew point temperature to 80°C, and the back pressure to 250 kPa. abs The battery was activated after stabilizing at 0.4V for 3 hours, and then polarization curves were recorded, requiring every 0.1A cm⁻¹. 2 Maintain for 3 minutes and record the voltage in the last second.

[0051] Example 2:

[0052] Unlike Implementation Case 1, the acid oxidation treatment was replaced with a mixed solution of concentrated H2SO4 and concentrated HNO3 (volume ratio 1:1). The specific implementation steps are as follows: Take 5g of short multi-walled carbon nanotubes into 125ml of concentrated H2SO4, slowly add 125ml of concentrated HNO3, reflux at 70℃ for 5 hours, wash until neutral, and then dry for later use.

[0053] Example 3:

[0054] Unlike Implementation Case 1, the short multi-walled carbon nanotubes are replaced with short single-walled carbon nanotubes.

[0055] Example 4:

[0056] Unlike Implementation Case 1, the short multi-walled carbon nanotubes were replaced with Katjen Black EC600JD, and the acid oxidation treatment was replaced with a mixed solution of 10wt% HNO3 and 30wt% H2O2 (volume ratio 2:1). The specific implementation steps are as follows: Take 5g of Katjen Black EC600JD into 250ml of a mixed solution of 10wt% HNO3 and 30wt% H2O2 (volume ratio 2:1), reflux at 70℃ for 5 hours, wash until neutral, and then dry for later use.

[0057] Example 5:

[0058] Unlike Implementation Case 1, the short multi-walled carbon nanotubes were replaced with Katjen Black EC 600JD, and the acid oxidation treatment was replaced with concentrated HNO3 treatment. The specific implementation steps are as follows: Take 5g of KatjenBlack EC 600JD into 250ml of concentrated HNO3, reflux at 70℃ for 3 hours, wash until neutral, and then dry for later use.

[0059] Example 6:

[0060] Unlike Implementation Case 4, the Katjen Black EC 600JD is replaced with the Katjen Black EC 300J.

[0061] Example 7:

[0062] Unlike Implementation Case 1, N,N'-dicyclohexylcarbodiimide is replaced with N,N'-diisopropylcarbodiimide.

[0063] Example 8:

[0064] Unlike Implementation Case 1, N,N'-dicyclohexylcarbodiimide is replaced with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

[0065] Example 9:

[0066] Unlike Implementation Case 1, sulfonic acid group-modified short multi-walled carbon nanotubes were mixed with the catalyst at 10% of the catalyst support mass, and then mixed with water, n-propanol and ionomer to form a slurry after ultrasonic treatment in a water bath.

[0067] Comparative Cases:

[0068] A carbon material without any sulfonic acid group modification was prepared by mixing a catalyst, water, n-propanol, and ionomer, followed by ultrasonic treatment in a water bath to form a slurry. This slurry was then ultrasonically sprayed onto a Gore M765.08 proton exchange membrane to prepare a 25cm thick membrane. 2 Membrane electrode.

[0069] Comparing Example 1 with the comparative case, such as Figure 3 , Figure 4 As shown, the comparative case under high humidity and high back pressure conditions has a lower membrane electrode IV curve than Example 1.

[0070] Under low humidity and low back pressure conditions, the membrane electrode IV curve of the comparative case was significantly lower than that of Example 1.

[0071] The sulfonic acid group-modified carbon material prepared in this technical solution mainly achieves its water-retention function by grafting sulfonic acid groups. By adding this material, under low humidity conditions, the formation of hydrogen bonds between the sulfonic acid groups and water molecules increases the water retention capacity of the catalyst layer and improves proton conductivity under low humidity conditions. Under high humidity conditions, the repulsive effect of the ionized charges of the sulfonic acid groups and the ionomers significantly reduces the adsorption of ionomers on the surface of the sulfonic acid group-modified carbon material, increasing the porosity of the catalyst layer, facilitating the removal of excess water, and increasing the gas transport rate.

[0072] The sulfonic acid-modified carbon material prepared in this technical solution is primarily a high-conductivity carbon material with a porous structure. Low-conductivity water-retaining materials such as fumed silica, nano-titanium dioxide, and covalent-organic frameworks (COFs), after optimization of the three-phase interface of the catalyst layer, actually lead to an increase in ohmic polarization resistance due to their low conductivity. In contrast, this invention selects a high-conductivity carbon material with a porous structure, which, after sulfonic acid modification, improves its hydrophilicity and enhances the water-retaining capacity of the catalyst layer. Its addition to the catalyst layer does not cause a decrease in conductivity.

[0073] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for improving the catalyst layer of a proton exchange membrane fuel cell membrane electrode using sulfonic acid-modified carbon materials, characterized in that, Includes the following steps: S1: Add carbon material to an acid solution, reflux the reaction, wash and dry to obtain carbon material with oxygen-containing functional groups; S2: Add carbon materials containing oxygen functional groups to an organic solvent for dispersion, react for a period of time, and then add organic materials containing sulfonic acid groups to carry out a condensation reaction to obtain carbon materials modified with sulfonic acid groups. S3: Sulfonic acid group-modified carbon material is added to the proton exchange membrane fuel cell slurry and then prepared into a membrane electrode to obtain a sulfonic acid group-modified material improved proton exchange membrane fuel cell membrane electrode.

2. The method for improving the membrane electrode catalytic layer of a proton exchange membrane fuel cell using sulfonic acid-modified carbon materials according to claim 1, characterized in that, The acid solution in S1 is an acidic solution containing an oxidizing agent, wherein the oxidizing agent is one or more of nitric acid and hydrogen peroxide solution.

3. The method for improving the membrane electrode catalytic layer of a proton exchange membrane fuel cell using sulfonic acid-modified carbon materials according to claim 2, characterized in that, The carbon material in S1 is one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, Katjen Black EC300J, Katjen Black ECP, Katjen Black EC600JD, and Katjen Black ECP600JD.

4. The method for improving the membrane electrode catalytic layer of a proton exchange membrane fuel cell using sulfonic acid-modified carbon materials according to claim 3, characterized in that, The oxidizing acid solution in S1 is a mixed solution composed of sulfuric acid and one or more of nitric acid, hydrogen peroxide, and potassium permanganate.

5. The method for improving the membrane electrode catalytic layer of a proton exchange membrane fuel cell using sulfonic acid-modified carbon materials according to claim 4, characterized in that, The temperature range of the reflux reaction in S1 is 50–80°C, and the time range is 30–300 minutes.

6. The method for improving the membrane electrode catalytic layer of a proton exchange membrane fuel cell using sulfonic acid-modified carbon materials according to any one of claims 1-5, characterized in that, The organic solvent in S2 is one of the following: an ethanol, isopropanol, n-propanol, or n-butanol solution of N,N'-dicyclohexylcarbodiimide.

7. The method for improving the membrane electrode catalytic layer of a proton exchange membrane fuel cell using sulfonic acid-modified carbon materials according to claim 6, characterized in that, The oxygen-rich carbon material in S2 is added to an organic solvent and ultrasonically dispersed for a period of time at 50°C for 20–60 minutes.

8. The method for improving the membrane electrode catalytic layer of a proton exchange membrane fuel cell using sulfonic acid-modified carbon materials according to claim 6, characterized in that, The organic compounds containing sulfonic acid groups in S2 are p-aminobenzenesulfonic acid and aminosulfonic acid.

9. The method for improving the membrane electrode catalytic layer of a proton exchange membrane fuel cell using sulfonic acid-modified carbon materials according to claim 6, characterized in that, The condensation reaction in S2 is carried out at a temperature of 50°C for 24 hours.

10. The method for improving the membrane electrode catalytic layer of a proton exchange membrane fuel cell using sulfonic acid-modified carbon materials according to claim 1, characterized in that, The membrane electrode preparation process in S3 involves mixing sulfonic acid-modified carbon materials, catalyst, water, alcohol, and ionomer to prepare a catalyst slurry. This slurry is then ultrasonically sprayed onto a proton exchange membrane, and finally assembled with a gas diffusion layer to form a membrane electrode. The effective area of ​​the membrane electrode is 5 cm². 2 ; The amount of carbon material modified with sulfonic acid groups added is 5% to 10% of the mass of the catalyst support.

Images