CN114335570A

CN114335570A - Gas diffusion layer for fuel cell and preparation method and application thereof

Info

Publication number: CN114335570A
Application number: CN202111581040.6A
Authority: CN
Inventors: 杨瑞枝; 顾天颐; 张乾
Original assignee: Suzhou University
Current assignee: Suzhou University
Priority date: 2021-12-22
Filing date: 2021-12-22
Publication date: 2022-04-12
Anticipated expiration: 2041-12-22
Also published as: CN114335570B; WO2023116893A1

Abstract

The invention provides a gas diffusion layer for a fuel cell and a preparation method and application thereof, in particular to a microporous layer in the gas diffusion layer for a membrane electrode with high power density and preparation thereof. The fuel cell gas diffusion layer is composed of two parts, namely a substrate and a microporous layer. In the invention, firstly, a hydrophobic agent is grafted on the surface of hydrophilic conductive carbon by a chemical grafting method to prepare super-hydrophobic conductive carbon, and then the conductive carbon subjected to hydrophobic treatment is sprayed on a carbon paper substrate to form a microporous layer in a gas diffusion layer. The gas diffusion layer prepared by the method has super-hydrophobicity, the combination of the conductive carbon and the hydrophobic agent is uniform and stable, and particularly, the method effectively promotes the water-gas transmission of a three-phase interface and improves the output power of the fuel cell.

Description

Gas diffusion layer for fuel cell and preparation method and application thereof

Technical Field

The invention relates to a preparation method of a microporous layer in a gas diffusion layer of a proton exchange membrane fuel cell, belonging to the technical field of directly converting chemical energy into electric energy.

Background

The membrane electrode is the core component of a fuel cell, which consists of a Proton Exchange Membrane (PEM), a Catalyst Layer (CL) and a Gas Diffusion Layer (GDL) with a microporous layer (MPL), ensuring the transport of reactant gases, product water, protons and reaction heat. The gas diffusion layer is located between the catalytic layer and the flow field and functions to distribute the reactant gases over the catalyst layer and to expel the resulting product (liquid water) out of the cell. GDLs typically select carbon paper or carbon cloth as a substrate to serve as gas distribution, mechanical support, and electrical conductivity. The most common technique at present is to form a layer of MPL composed of carbon black and Polytetrafluoroethylene (PTFE) on the surface of GDL, which helps to remove water generated by electrochemical reaction in time, thereby reducing mass transfer polarization. The hydrophobic treatment process is a key factor for determining the transmission of reaction gas to the catalyst layer and the discharge of product water during the operation of the GDL on the fuel cell and preventing the membrane electrode from being flooded with water. In the traditional MPL preparation process, the battery performance needs to be improved due to poor synergistic effect of a conductive agent and a hydrophobic agent, particularly the peak output power is low, PTFE needs to be melted by heat treatment at the temperature of more than 350 ℃ when PTFE is used, the treatment temperature is high, the treatment time is long, and the production cost of the MPL of the microporous layer is increased; in addition, the existing MPL layer has the problem of poor water resistance, and the increase of the washing time of liquid water on GDL can cause the loss of hydrophobic substances, thereby increasing the resistance and easily causing 'flooding' (Energy & Fuels, 2008, 22(4): 2533-. Therefore, the method has very important significance for long-time heavy current work of the fuel cell, research and development of a new preparation process of the microporous layer and improvement of the combination stability of the hydrophobic material.

Disclosure of Invention

In order to improve the hydrophobic stability of the microporous layer of the proton exchange membrane fuel cell under a large-current working environment and further improve the output power and the durability of the fuel cell, the invention provides a novel preparation method of the diffusion layer, which obtains the uniform distribution of a hydrophobic agent on a molecular level so as to construct a preparation method of a high-performance microporous layer.

The invention adopts the following technical scheme:

a gas diffusion layer for a fuel cell comprises a conductive substrate, silane modified carbon powder and a binder, wherein the silane modified carbon powder and the binder are positioned on the conductive substrate; preferably, the gas diffusion layer for the fuel cell is composed of a conductive substrate, and silane modified carbon powder and a binder which are positioned on the conductive substrate. In the invention, the carbon-based elements are not agglomerated and are not separated, the distribution uniformity is good, the flooding of the electrode is avoided, and in addition, the water washing resistance is strong.

The invention discloses a preparation method of the gas diffusion layer for the fuel cell, which comprises the following steps of mixing carbon powder with a solvent and silane after surface hydroxylation treatment, and then heating and stirring to obtain silane modified carbon powder; then mixing the silane modified carbon powder, an adhesive and a dispersant to obtain microporous layer slurry; and then compounding the microporous layer slurry with a conductive substrate, and drying to obtain the gas diffusion layer for the fuel cell.

In the invention, the carbon powder is one or a mixture of several of various carbon blacks, synthetic carbon, graphite, graphene and carbon nanotubes; the conductive substrate is one of carbon paper and carbon cloth; the adhesive is an adhesive for a conventional battery.

In the invention, the silane is one or more of vinyl silane, chlorohydrocarbon silane, amino hydrocarbon silane, epoxy hydrocarbon silane, methacryloxyalkyl silane, sulfur-containing hydrocarbon silane, pseudohalogen silane and alkane silane, wherein the vinyl silane is one or more of vinyltrichlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltriacetoxysilane, vinylmethyldichlorosilane and the like; chlorohydrocarbon-based silanes such as gamma-chloropropyltrichlorosilane, gamma-chloropropyltrimethoxysilane, chloromethyltriethoxysilane, etc.; aminoalkyl silanes such as gamma-aminopropyltriethoxysilane, gamma-ureidopropyltrimethoxysilane, anilinomethyltrimethoxysilane and the like, epoxyalkyl silanes such as gamma- (2, 3-glycidoxy) propyltrimethoxysilane, gamma- (2, 3-glycidoxy) propyltriethoxysilane and the like; methacryloxyalkyl-type silanes such as gamma-methacryloxypropyl trichlorosilane, gamma-methacryloxypropyl trimethoxysilane (KH 570), polymethylsiloxane, etc.; sulfur-containing hydrocarbon silanes such as gamma-mercaptopropyltrimethoxysilane, gamma-mercaptopropyltriethoxysilane, bis- (3-triethoxysilylpropyl) tetrasulfide, and the like; pseudohalogen silanes such as beta-cyanoethyltrichlorosilane, beta-cyanoethylmethyldichlorosilane, beta-cyanoethyltriethoxysilane, etc.; alkane silanes such as hexadecyl trimethoxy silane, octadecyl trichlorosilane, dodecyl triethoxy silane, etc.

In the invention, the solvent is a mixed solution of small molecular alcohol and water, the small molecule can be ethanol, methanol or ethylene glycol, and preferably, the mass ratio of the small molecular alcohol to the water is 1: 0.2-9; the dispersant is one or more of isopropanol, alcohol and glycol.

In the invention, the carbon powder is treated by ferric salt and hydrogen peroxide to obtain surface hydroxylation treated carbon powder, preferably, the using amount ratio of the carbon powder, the ferric salt and the hydrogen peroxide is 1g to (4-5) g to (200-300) mL; or treating the carbon powder with a strong oxidant to obtain the surface hydroxylation treated carbon powder, wherein the strong oxidant is acid and potassium permanganate acid, such as nitric acid or sulfuric acid, preferably, the using amount ratio of the carbon powder to the acid is 1g to (150-300) mL, and the using amount ratio of the carbon powder to the potassium permanganate is 1g to (0.05-0.07) mol. For example, 1g of the carbon powder is mixed with 200 mL of 65wt% concentrated nitric acid or 200 mL of 0.3M KMnO₄And refluxing the solution at 80-100 ℃ for 4-12 h, and then fully washing and drying to obtain the carbon powder with the hydroxylated surface.

According to the method, carbon powder is subjected to surface hydroxylation treatment and then mixed with a solvent, the pH value of a system is adjusted to 2-6 by using an acid, then silane is added and mixed, then heating and stirring are carried out, and silane modified carbon powder is obtained after filtering, washing and drying; wherein the acid is acetic acid, hydrochloric acid, etc.

In the invention, the mass ratio of the carbon powder to the silane is 2: 1.25-25; the dosage ratio of the silane modified carbon powder, the adhesive and the dispersant is (0.03-0.1) g to (0.05-0.2) g to 10 mL.

In the invention, the heating and stirring temperature is 60-150 ℃ and the time is 1-8 hours.

In the invention, the microporous layer slurry is compounded with the conductive substrate and dried to obtain the gas diffusion layer for the fuel cell.

Compared with the prior art, the invention has the following advantages:

the preparation method of the microporous layer provided by the invention avoids a high-temperature heat treatment process; the uniform dispersion degree of the hydrophobic conductive carbon powder in the microporous layer is improved; the stability of the combination of the hydrophobic conductive carbon powder in the microporous layer is improved; the working current and voltage of the fuel cell are improved, and the output power of the fuel cell under high current density is improved.

Drawings

FIG. 1 is a graph comparing FTIR before and after modification of conductive carbon black of example 1 of the present invention.

Fig. 2 is a contact angle of a microporous layer obtained in example 1 of the present invention.

Fig. 3 is a graph comparing performance curves of a cathode gas diffusion layer-assembled fuel cell prepared in example 1 of the present invention with a cathode gas diffusion layer-assembled fuel cell prepared using Polytetrafluoroethylene (PTFE) as a water repellent agent, using a conventional physical mixing and coating method, and heat treatment at 350 ℃ (comparative example 1) and a commercial gas diffusion layer (dongli TGP-060) as a cathode gas diffusion layer.

Fig. 4 is a graph comparing performance curves of a cathode gas diffusion layer-assembled fuel cell prepared in example 2 of the present invention and a cathode gas diffusion layer-assembled fuel cell prepared by using Polytetrafluoroethylene (PTFE) as a water repellent agent, using a conventional physical mixing and coating method, and performing a heat treatment at 350 ℃ (comparative example 2).

Fig. 5 is a graph comparing performance curves of a cathode gas diffusion layer-assembled fuel cell prepared in example 3 of the present invention and a cathode gas diffusion layer-assembled fuel cell prepared by using Polytetrafluoroethylene (PTFE) as a water repellent agent, using a conventional physical mixing and coating method, and performing a heat treatment at 350 ℃ (comparative example 3).

Fig. 6 is a graph comparing performance curves of a cathode gas diffusion layer-assembled fuel cell prepared in example 4 of the present invention and a cathode gas diffusion layer-assembled fuel cell prepared by using Polytetrafluoroethylene (PTFE) as a water repellent agent, using a conventional physical mixing and coating method, and performing a heat treatment at 350 ℃ (comparative example 4).

Fig. 7 is a graph comparing performance curves of a cathode gas diffusion layer-assembled fuel cell prepared in example 5 of the present invention and a cathode gas diffusion layer-assembled fuel cell prepared by using Polytetrafluoroethylene (PTFE) as a water repellent agent, using a conventional physical mixing and coating method, and performing a heat treatment at 350 ℃ (comparative example 5).

Fig. 8 is a graph comparing performance curves of a cathode gas diffusion layer-assembled fuel cell prepared in example 6 of the present invention and a cathode gas diffusion layer-assembled fuel cell prepared by using Polytetrafluoroethylene (PTFE) as a water repellent agent, using a conventional physical mixing and coating method, and performing a heat treatment at 350 ℃ (comparative example 6).

FIG. 9 shows water contact angles at different reaction temperatures.

Detailed Description

In addition to providing a water drain function, the gas diffusion layer of the pem fuel cell also has an effect on maintaining the water discharge from the catalyst layer and the ability of the gas to diffuse into the catalyst layer, which may cause a problem of decreased cell performance at high current densities. The method comprises the steps of mixing carbon powder subjected to surface hydroxylation with a solvent and silane, and then heating and stirring to obtain silane modified carbon powder; then mixing the silane modified carbon powder, an adhesive and a dispersant to obtain microporous layer slurry; then compounding the microporous layer slurry with a conductive substrate, and drying to obtain a gas diffusion layer for a fuel cell; the catalyst has excellent hydrophobic property and good drainage property, and particularly, the diffusion of gas to a catalyst reaction layer is improved, so that higher current density and voltage can be realized, and the output power of the fuel cell under high current density is improved.

As an example, the method for preparing the gas diffusion layer for a fuel cell disclosed in the present invention is as follows:

1) carrying out surface hydroxylation treatment on the conductive carbon powder to enable the surface to have oxygen-containing functional groups such as-OH and the like, adding the conductive carbon powder into a mixed solution of deionized water and ethanol or methanol or ethylene glycol, wherein the ratio of water to alcohol is 0.2-9: 1, and carrying out conventional ultrasonic dispersion for 10-60 minutes to form a uniform dispersion liquid;

2) adding acetic acid or hydrochloric acid water solution to adjust the pH of the solution to 2-6;

3) adding silane into the solution, wherein the mass ratio of carbon powder to silane is 2: 1.25-25, heating to 60-150 ℃, stirring for 1-8 hours by a conventional machine, after the reaction of the silane and the carbon powder is finished, carrying out centrifugal cleaning or suction filtration cleaning on the solution, repeatedly washing with water and ethanol in sequence, and drying the cleaned material in a 60 ℃ oven for later use;

4) adding the dried modified carbon powder into one or more of mixed solution of isopropanol, alcohol and glycol, adding a binding agent Nafion solution, wherein the Nafion content is 1-50 wt%, and performing ultrasonic dispersion for 1-8 h to form microporous layer slurry;

5) spraying the microporous layer slurry on a carbon paper substrate, drying, weighing, and repeating the steps until the loading amount of the conductive carbon powder reaches 0.5-3.0 mg/cm²And obtaining the gas diffusion layer for the fuel cell.

The test method comprises the following steps: the prepared gas diffusion layer was used as a cathode gas diffusion layer, and a membrane electrode prepared with a commercial catalyst of Pt/C (Pt content 48.5 wt%) and a commercial anode gas diffusion layer were assembled to a fuel cell and then tested. After activation treatment, steady state test is carried out, and finally polarization curve and power density test are carried out at 80 ℃, 40% relative humidity and H₂And an air stoichiometric ratio of 1.5:2, a front pressure of 102/71 (Kpa), a back pressure of 100/40 (Kpa), a test area of 25cm². The test used the U.S. fuel cell test system (Scribner Associates, Inc, 890 e).

In order to facilitate understanding of the present invention, the present invention will be described below by way of examples. It should be understood by those skilled in the art that the examples are only for the purpose of facilitating understanding of the present invention and do not limit the present invention to the scope of the examples. The raw materials involved in the invention are all conventional products for batteries, and the specific preparation operation and the test method are all conventional methods.

All cells in the following examples and comparative examples had the same composition except for the cathode gas diffusion layer.

Example 1

1g of carbon black (Super P, particle size of 50 nm) and 4.5g of FeCl₂•4H₂O, 250 mL of aqueous Hydrogen peroxide solution (H)₂O₂:H₂O = 1:3, volume ratio) was stirred for 1 hour, and then the reaction product was filtered and washed using 0.1M hydrochloric acid solution to remove residues in the productFinally, fully washing and drying the iron ions to obtain the carbon black with hydroxylated surface; weighing 0.2g of carbon black with hydroxylated surface, treating, adding into a mixed solution of 45mL of ethanol and 5mL of deionized water, and carrying out ultrasonic dispersion for 30 minutes;

adjusting pH to 2 with acetic acid solution (0.1M), adding 1mL of gamma-mercaptopropyltrimethoxysilane, stirring in a 60 ℃ water bath for 4h, then centrifugally cleaning the solution, washing with water and ethanol in sequence, placing the cleaned material in a 60 ℃ oven for drying, and obtaining the Fourier infrared spectroscopy (FTIR) result of the silane-modified conductive carbon black shown in figure 1, wherein the silane-modified conductive carbon black can be seen in 1141cm^-1And 1201cm^-1Peak at 1018 cm is a fluorine-containing functional group^-1And 1072 cm^-1The peaks at (A) are Si-O-C, and Si-O-Si bonds, respectively, which demonstrate the grafting of the silane onto the conductive carbon black;

weighing 0.05g of the modified carbon black, adding 0.1g of a binding agent Nafion solution (5 wt.%) and 10 mL of an isopropanol solution, and performing ultrasonic dispersion for 5 hours to obtain microporous layer slurry;

spraying the microporous layer slurry on a carbon paper substrate, and drying at 75 ℃ for 2h to obtain the gas diffusion layer, wherein the Super P-type carbon black loading is 1.5 mg cm^-2The water contact angle of the resulting gas diffusion layer was 151.0 ° as shown in fig. 2, and hydrophobicity was achieved.

Comparative example 1

Using the carbon black super P of example 1 and Polytetrafluoroethylene (PTFE) as a hydrophobic agent, 0.1g of carbon black and 0.033g of a 60% PTFE dispersion were weighed and dissolved in 16mL of isopropanol, and the mixture was sprayed on a carbon paper substrate with a carbon black loading of 1.5 mg cm for 1 hour using ultrasonication^-2. And finally, placing the sprayed carbon paper into a 350 ℃ muffle furnace for sintering for 1h, preparing a cathode gas diffusion layer (water contact angle is 149 degrees), assembling the cathode gas diffusion layer into a battery, and performing a polarization curve and power density test by using a fuel cell test system under the same test conditions as those of the embodiment 1.

Comparative example 1 ″

A commercial cathode gas diffusion layer (Dongli TGP-060, which belongs to the existing industrialized high-performance commodity, the water contact angle is 145.6 degrees) is adopted to assemble a battery, and a fuel cell test system is adopted to carry out polarization curve and power density tests, wherein the test conditions are the same as those of the example 1.

The gas diffusion layers prepared in example 1, comparative example 1 and comparative example 1' above were used as cathode diffusion layers of fuel cells, respectively, and assembled into cells for a single cell test, and the cell performance curve is shown in FIG. 3, and the peak output power of the resulting cell is 1212 mW cm for the gas diffusion layer of example 1^-2(ii) a The cell obtained with the gas diffusion layer of comparative example 1 had a peak output of 1060 mW cm^-2(ii) a The peak output of the cell obtained with the gas diffusion layer of comparative example 1' was 1103 mW cm^-2. The results show that the fuel cell assembled by using the cathode gas diffusion layer prepared according to the present invention can achieve higher current density and voltage and improve the output power of the fuel cell at high current density, compared to the cathode gas diffusion layer prepared by using PTFE as a water repellent, using a conventional physical mixing and coating method and heat-treating at 350 c, and the cathode gas diffusion layer of a commercial microporous layer.

Example 2

1g of carbon black (Vulcan-XC 72, particle size of 30 nm) and 4.5g of FeCl₂•4H₂O, 250 mL of aqueous Hydrogen peroxide solution (H)₂O₂:H₂O = 1:3, volume ratio) for 1 hour, then filtering and washing the reaction product with 0.1M hydrochloric acid solution to remove residual iron ions in the product, and finally fully washing and drying to obtain carbon black with hydroxylated surface; weighing 0.2g of carbon black with hydroxylated surface, adding the carbon black into a mixed solution of 45mL of methanol and 5mL of deionized water, and carrying out ultrasonic dispersion for 30 minutes;

adjusting the pH value to 3 by using an acetic acid solution (0.1M), adding 1mL of vinyltriethoxysilane, stirring in a water bath at 80 ℃ for 6 hours, after the reaction is finished, carrying out suction filtration and cleaning on the solution, repeatedly washing the solution by using water and ethanol in sequence, and drying the cleaned material in a 60 ℃ oven;

weighing 0.1g of modified carbon black (Vulcan-XC 72), adding 0.2g of a binding agent Nafion solution (5 wt.%) and 20mL of an ethylene glycol solution, and performing ultrasonic dispersion for 4 hours to obtain microporous layer slurry;

spraying microporous layer slurry on carbon paper baseDrying at 70 ℃ for 2h to obtain the gas diffusion layer (water contact angle is 150.1 ℃), wherein the loading amount of Vulcan-XC72 type carbon black is 2.0 mg cm^-2。

Comparative example 2

Using the carbon black (Vulcan-XC 72) of example 2 and Polytetrafluoroethylene (PTFE) as a water repellent, 0.2g of the carbon black and 0.066g of a 60% PTFE dispersion were weighed out and dissolved in 32mL of isopropanol, and the slurry was sprayed on a carbon paper substrate with a carbon black loading of 2.0 mg cm for 4h under ultrasound^-2. Finally, the carbon paper after spraying is placed into a muffle furnace at 350 ℃ to be sintered for 1h, and the cathode gas diffusion layer (the water contact angle is 149.4 degrees) is prepared.

The cell was assembled by using the gas diffusion layers prepared in example 2 and comparative example 2 as cathode diffusion layers of a fuel cell, respectively, and a single cell test was performed, as shown in FIG. 4, and the peak output of the cell obtained in example 2 was 1219 mW cm^-2(ii) a The peak output of the battery obtained in comparative example 2 was 1043.2 mW cm^-2. The result shows that the fuel cell assembled by the gas diffusion layer prepared by the invention can realize higher current density and voltage, and the output power of the fuel cell under high current density is improved.

Example 3

1g of carbon black (Ketjen black, particle size 40-50 nm) and 4.5g of FeCl₂•4H₂O, 250 mL of aqueous Hydrogen peroxide solution (H)₂O₂:H₂O = 1:3, volume ratio) for 1 hour, then filtering and washing the reaction product with 0.1M hydrochloric acid solution to remove residual iron ions in the product, and finally fully washing and drying to obtain carbon black with hydroxylated surface; weighing 0.2g of carbon black with hydroxylated surface, adding the carbon black into a mixed solution of 45mL of ethanol and 5mL of deionized water, and carrying out ultrasonic dispersion for 40 minutes;

adjusting the pH value to 3 by using a hydrochloric acid solution (0.1M), adding 2mL of gamma-methacryloxypropyltrimethoxysilane, stirring for 4 hours at a temperature of 120 ℃ in an oil bath, centrifugally cleaning the solution after the reaction is finished, repeatedly washing the solution by using water and ethanol in sequence, and drying the cleaned material in a 60 ℃ oven;

weighing 0.1g of modified Ketjen black, adding 0.2g of Nafion solution (5 wt.%) as a binder and 20ml of ethanol solution, and performing ultrasonic dispersion for 5 hours to obtain microporous layer slurry;

spraying the microporous layer slurry on a carbon paper substrate, and drying at 80 ℃ for 2h to obtain the gas diffusion layer, wherein the etjen black type carbon black loading is 2.0 mg cm^-2。

Comparative example 3

Using the carbon black (Ketjen black) of example 3 and Polytetrafluoroethylene (PTFE) as a water repellent, 0.2g of the carbon black and 0.066g of a 60% PTFE dispersion were weighed out in 32mL of isopropanol and ultrasonically treated for 5 hours to spray the slurry onto a carbon paper substrate with a carbon black loading of 2.0 mg cm^-2. And finally, putting the carbon paper subjected to spraying into a muffle furnace at 350 ℃ for sintering for 1h to prepare the cathode gas diffusion layer.

The gas diffusion layer prepared as described above was used as a cathode diffusion layer of a fuel cell to assemble a cell, a single cell test was performed, a polarization curve and a power curve are shown in FIG. 5, and the peak output power of the cell obtained in example 3 was 1215 mW cm^-2(ii) a The peak output of the battery obtained in comparative example 3 was 1063.5 mW cm^-2. The result shows that the fuel cell assembled by the gas diffusion layer prepared by the invention can realize higher current density and voltage, and the output power of the fuel cell under high current density is improved.

Example 4

With 1g of multilayer graphene and 4.5g of FeCl₂•4H₂O, 250 mL of aqueous Hydrogen peroxide solution (H)₂O₂:H₂O = 1:3, volume ratio) for 1 hour, then filtering and washing the reaction product with 0.1M hydrochloric acid solution to remove residual iron ions in the product, and finally fully washing and drying to obtain surface hydroxylated multilayer graphene; weighing 0.3g of multilayer graphene subjected to surface hydroxylation treatment, adding the multilayer graphene into a mixed solution of 50 mL of ethanol and 6mL of deionized water, and performing ultrasonic dispersion for 40 minutes;

adjusting the pH value to 6 by using a hydrochloric acid solution (0.1M), adding 3 mL of gamma- (2, 3-epoxypropoxy) propyltriethoxysilane, stirring for 4 hours in an oil bath at 100 ℃, after the reaction is finished, centrifugally cleaning the solution, repeatedly washing the solution by using water and ethanol in sequence, and drying the cleaned material in a 60 ℃ oven;

weighing 0.2g of modified graphene, adding 0.4g of a binding agent Nafion solution (5 wt.%) and 40ml of an ethanol solution, and performing ultrasonic dispersion for 5 hours to obtain microporous layer slurry;

spraying the microporous layer slurry on a carbon paper substrate, and drying at 80 ℃ for 2h to obtain the gas diffusion layer, wherein the graphene loading capacity is 2.5mg cm^-2。

Comparative example 4

Using the multi-layer graphene in example 4 and Polytetrafluoroethylene (PTFE) as a hydrophobic agent, 0.3g of the multi-layer graphene and 0.1g of a 60% PTFE dispersion were weighed and dissolved in 50 mL of isopropanol, sonicated for 1 hour, and the slurry was sprayed onto a carbon paper substrate with a multi-layer graphene loading of 2.5mg cm^-2. And finally, putting the carbon paper subjected to spraying into a muffle furnace at 350 ℃ for sintering for 1h to prepare the cathode gas diffusion layer.

The gas diffusion layer prepared as described above was used as a cathode diffusion layer of a fuel cell to assemble a cell, a single cell test was performed, a polarization curve and a power curve were as shown in fig. 6, and the peak output power of the cell obtained in example 4 was 1128 mW cm^-2(ii) a The peak output of the battery obtained in comparative example 4 was 930.7 mW cm^-2. The result shows that the fuel cell assembled by the gas diffusion layer prepared by the invention can realize higher current density and voltage, and the output power of the fuel cell under high current density is improved.

Example 5

With 1g of multi-walled carbon nanotubes and 4.5g of FeCl₂•4H₂O, 250 mL of aqueous Hydrogen peroxide solution (H)₂O₂:H₂O = 1:3, volume ratio) for 1 hour, then filtering and washing the reaction product with 0.1M hydrochloric acid solution to remove residual iron ions in the product, and finally fully washing and drying to obtain the multi-walled carbon nanotube with hydroxylated surface; weighing 0.3g of multi-walled carbon nano-tube subjected to surface hydroxylation treatment, adding the multi-walled carbon nano-tube into a mixed solution of 50 mL of ethanol and 6mL of deionized water, and carrying out ultrasonic dispersion for 40 minutes;

adjusting the pH value to 4 by using a hydrochloric acid solution (0.1M), adding 3 mL of gamma-aminopropyltriethoxysilane, stirring in a 90 ℃ water bath for 4 hours, after the reaction is finished, carrying out suction filtration and cleaning on the solution, repeatedly washing the solution by using water and ethanol in sequence, and drying the cleaned material in a 60 ℃ drying oven;

weighing 0.2g of modified multi-walled carbon nano-tube, adding 0.4g of a binding agent Nafion solution (5 wt.%) and 40ml of an ethanol solution, and performing ultrasonic dispersion for 5 hours to obtain microporous layer slurry;

spraying the microporous layer slurry on a carbon paper substrate, and drying at 80 ℃ for 2h to obtain the gas diffusion layer, wherein the loading capacity of the carbon nano tube is 2.5mg cm^-2。

Comparative example 5

The multi-walled carbon nanotubes in example 5 were used, Polytetrafluoroethylene (PTFE) was used as a hydrophobic agent, 0.3g of the multi-walled carbon nanotubes and 0.1g of a 60% PTFE dispersion were weighed and dissolved in 50 mL of isopropanol, and the mixture was ultrasonically treated for 1 hour, and the slurry was sprayed on a carbon paper substrate with a carbon black loading of 2.5mg cm^-2. And finally, putting the carbon paper subjected to spraying into a muffle furnace at 350 ℃ for sintering for 1h to prepare the cathode gas diffusion layer.

The gas diffusion layer prepared as described above was used as a cathode diffusion layer of a fuel cell to assemble a cell, a single cell test was performed, a polarization curve and a power curve were shown in FIG. 7, and the peak output power of the cell obtained in example 5 was 1320 mW cm^-2(ii) a The peak output of the battery obtained in comparative example 5 was 963.6 mW cm^-2. The result shows that the fuel cell assembled by the gas diffusion layer prepared by the invention can realize higher current density and voltage, and the output power of the fuel cell under high current density is improved.

Example 6

1g of activated carbon (particle size: 50-250 nm) and 4.5g of FeCl₂•4H₂O, 250 mL of aqueous Hydrogen peroxide solution (H)₂O₂:H₂O = 1:3, volume ratio) for 1 hour, then filtering and washing the reaction product with 0.1M hydrochloric acid solution to remove residual iron ions in the product, and finally fully washing and drying to obtain surface hydroxylated activated carbon; weighing 0.4g of activated carbon subjected to surface hydroxylation treatment, adding the activated carbon into a mixed solution of 60mL of ethanol and 6mL of deionized water, and performing ultrasonic dispersion for 40 minutes;

adjusting the pH value to 5 by using a hydrochloric acid solution (0.1M), adding 4 mL of chloromethyltriethoxysilane, stirring for 5 hours at 130 ℃ in an oil bath, after the reaction is finished, centrifugally cleaning the solution, repeatedly washing the solution by using water and ethanol in sequence, and drying the cleaned material in a 60 ℃ oven;

weighing 0.3g of modified activated carbon, adding 0.5g of a binding agent Nafion solution (5 wt.%) and 60ml of an ethanol solution, and performing ultrasonic dispersion for 5 hours to obtain microporous layer slurry;

spraying the microporous layer slurry on a carbon paper substrate, and drying at 80 ℃ for 2h to obtain the gas diffusion layer with the activated carbon loading of 3.0 mg cm^-2。

Comparative example 6

Using the activated carbon of example 6 and Polytetrafluoroethylene (PTFE) as the water repellent, 0.4g of the activated carbon and 0.0132g of a 60% PTFE dispersion were weighed out and dissolved in 65 mL of isopropanol, and the slurry was sprayed on a carbon paper substrate with an activated carbon loading of 3.0 mg cm by sonication for 1h^-2. And finally, putting the carbon paper subjected to spraying into a muffle furnace at 350 ℃ for sintering for 1h to prepare the cathode gas diffusion layer.

The gas diffusion layer prepared as described above was used as a cathode diffusion layer of a fuel cell to assemble a cell, a single cell test was performed, a polarization curve and a power curve are shown in fig. 8, and the peak output power of the cell obtained in example 6 was 1327 mW cm^-2(ii) a The peak output of the battery obtained in comparative example 6 was 860.8 mW cm^-2. The result shows that the fuel cell assembled by the gas diffusion layer prepared by the invention can realize higher current density and voltage, and the output power of the fuel cell under high current density is improved.

Example 7

Mixing 0.3g of surface-hydroxylated activated carbon (from example 6), 3 mL of chloromethyltriethoxysilane, 0.5g of a binding agent Nafion solution (5 wt.%), and 60mL of an ethanol solution, ultrasonically dispersing for 5 hours to obtain a microporous layer slurry, spraying the microporous layer slurry onto a carbon paper substrate, and drying at 80 ℃ for 2 hours to obtain a gas diffusion layer, wherein the loading amount of the activated carbon is 3.0 mg cm^-2. Using the test method of example 6, the peak output power of the obtained battery was 442 mW cm^-2. Gas diffusion layer prepared in this example, usingThe fuel cell assembled by the gas diffusion layer prepared by the invention obviously improves the output power of the fuel cell.

Example 8

Performing ultrasonic dispersion on 0.1g of carbon black subjected to surface hydroxylation treatment (taken from example 2), 0.5 mL of vinyl triethoxysilane, 0.2g of a Nafion binder solution (5 wt.%) and 20mL of a glycol solution for 4 hours to obtain microporous layer slurry, spraying the microporous layer slurry on a carbon paper substrate, and drying at 70 ℃ for 2 hours to obtain the gas diffusion layer, wherein the carbon black loading capacity of a Vulcan-XC72 type is 2.0 mg cm^-2. The peak output power of the obtained cell was 547 mW cm using the test method of example 2^-2. The gas diffusion layer prepared in the example is adopted to assemble the fuel cell, and the output power of the fuel cell is obviously improved.

Example 9

Multilayer graphene is used for replacing carbon black in example 3, modified graphene and corresponding microporous layer slurry and gas diffusion layer are prepared by the same silane and the same process, and the prepared gas diffusion layer (graphene loading is 2.0 mg cm)^-2) The cathode diffusion layer used as a fuel cell is assembled into a cell, a single cell test is carried out, and the peak output power of the obtained cell is 1132 mW cm^-2(ii) a In example 3, carbon black (Ketjen black) was used as a carbon element of the microporous layer, and the peak output power of the obtained battery was 1215 mW cm^-2. It can be seen that the same silane, but different carbon materials in density or structure, have a significant impact on fuel cell performance.

Comparison of carbon Material bond stability to substrate

Using the gas diffusion layers prepared in example 1, sonication was performed in deionized water for 30, 60, 90 and 120 min, respectively, and weighed after drying at 100 ℃, and the weight loss was calculated, which was referred to as an experimental group.

0.05g of hydroxylated carbon black (Super P), 0.25mL of gamma-mercaptopropyltrimethoxysilane, 0.1g of Nafion solution (5 wt.%) as a binder, and 10 mL of isopropanol solution from example 1 were mixed, dispersed ultrasonically for 5 hours to obtain a microporous layer slurry, and the slurry was sprayed on carbonPaper substrate, and drying at 75 ℃ for 2h to obtain the gas diffusion layer, wherein the loading of Super P-type carbon black is 1.5 mg cm^-2The gas diffusion layers were sonicated in deionized water for 30, 60, 90 and 120 min, respectively, dried at 100 ℃ and then weighed, and the weight lost was calculated, called the control group.

A commercial cathode gas diffusion layer (dongli TGP-060, which is an existing industrial high-performance commodity) was used, sonicated in deionized water for 30, 60, 90 and 120 min, respectively, dried at 100 ℃ and then weighed, and the weight loss was calculated and designated as a control.

The results are shown in table 1, and it can be seen that the weight loss of the gas diffusion layer prepared by the invention after 30, 60, 90 and 120 min of ultrasound is very small, and is between 0.0001g and 0.0004g, which indicates that the bonding stability of the carbon material and the substrate is very good, wherein the ultrasound power is 300W, and the ultrasound solvent is ultrapure water.

Table 1 comparison of the amount of loss of different gas diffusion layers after different times of sonication

Relationship between parameters and properties of silane and carbon powder reaction

1g of carbon black (Ketjen black, particle size 40-50 nm) and 4.5g of FeCl₂•4H₂O, 250 mL of aqueous Hydrogen peroxide solution (H)₂O₂:H₂O = 1:3, volume ratio) for 1 hour, then filtering and washing the reaction product with 0.1M hydrochloric acid solution to remove residual iron ions in the product, and finally fully washing and drying to obtain carbon black with hydroxylated surface; weighing 0.2g of carbon black with hydroxylated surface, adding the carbon black into a mixed solution of 45mL of ethanol and 5mL of deionized water, and carrying out ultrasonic dispersion for 40 minutes; adjusting the pH value to 3 by using a hydrochloric acid solution (0.1M), adding 2mL of gamma-methacryloxypropyltrimethoxysilane, stirring for 4 hours by using oil baths at 75,100, 125 and 150 ℃, after the reaction of silane and carbon powder is finished, carrying out centrifugal cleaning or suction filtration cleaning on the solution, repeatedly washing by using water and ethanol in sequence, and drying at 60 ℃; 0.1g of the total weight of the powder is weighedAdding 0.2g of Nafion solution (5 wt.%) as a binder and 20ml of ethanol solution into the Ketjen black after sexual intercourse, and performing ultrasonic dispersion for 5 hours to obtain microporous layer slurry; spraying the microporous layer slurry on a carbon paper substrate, and drying at 80 ℃ for 2h to obtain the gas diffusion layer, wherein the etjen black type carbon black loading is 2.0 mg cm^-2. And (3) performing a water contact angle test on the prepared four gas diffusion layers, wherein the contact angle is 149.1-150.7 degrees, as shown in figure 9.

The invention belongs to the technical field of fuel cells, and particularly discloses a preparation method of a microporous layer in a gas diffusion layer and application of the microporous layer in a proton exchange membrane fuel cell. Grafting a hydrophobic agent on the surface of hydrophilic conductive carbon powder by a chemical grafting method, preparing the silane modified conductive carbon powder into slurry, and spraying the slurry on a carbon paper substrate to form a microporous layer in a gas diffusion layer. The fuel cell gas diffusion layer disclosed by the invention has the advantages that: silane is bonded to the surface of the carbon-based element by adopting a chemical grafting method, and the hydrophobic conductive agent is uniformly distributed on a molecular level, so that a stable microporous layer is constructed, particularly, the gas diffusion layer prepared by adopting the method has super-hydrophobicity, effectively promotes the water-gas transmission of a three-phase interface, improves the output power of the fuel cell, and opens up a promising path for enhancing the water/gas transmission characteristic of the gas diffusion layer of the fuel cell and improving the performance of the fuel cell.

While specific embodiments of the present invention have been described above, it will be understood that the above examples are given for clarity of illustration only and are not limiting. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions for each raw material of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims

1. The gas diffusion layer for the fuel cell is characterized by comprising a conductive substrate, silane modified carbon powder and a binder, wherein the silane modified carbon powder and the binder are positioned on the conductive substrate.

2. The gas diffusion layer for a fuel cell according to claim 1, wherein the silane is modified the carbon powder by a chemical grafting method.

3. The gas diffusion layer for the fuel cell according to claim 1, wherein the carbon powder is one or a mixture of carbon black, synthetic carbon, graphite, graphene and carbon nanotubes; the conductive substrate is one of carbon paper and carbon cloth.

4. The gas diffusion layer for a fuel cell according to claim 1, wherein the silane is one or more selected from the group consisting of vinyl silanes, chlorohydrocarbon silanes, amino hydrocarbon silanes, epoxy hydrocarbon silanes, methacryloxyalkyl silanes, sulfur-containing hydrocarbon silanes, pseudohalogen silanes, and alkane silanes.

5. The method for preparing a gas diffusion layer for a fuel cell according to claim 1, comprising the steps of subjecting carbon powder to surface hydroxylation, mixing the carbon powder with a solvent and silane, and heating and stirring the mixture to obtain silane-modified carbon powder; then mixing the silane modified carbon powder, an adhesive and a dispersant to obtain microporous layer slurry; and then compounding the microporous layer slurry with a conductive substrate, and drying to obtain the gas diffusion layer for the fuel cell.

6. The method of manufacturing a gas diffusion layer for a fuel cell according to claim 5, wherein the solvent is a mixed solution of a small molecule alcohol and water; the mass ratio of the carbon powder to the silane is 2: 1.25-25.

7. The method for manufacturing a gas diffusion layer for a fuel cell according to claim 5, wherein the dispersant is one or more of isopropyl alcohol, alcohol and ethylene glycol; the dosage ratio of the silane modified carbon powder, the adhesive and the dispersant is (0.03-0.1) g to (0.05-0.2) g to 10 mL.

8. The preparation method of the gas diffusion layer for the fuel cell according to claim 5, wherein the carbon powder is subjected to surface hydroxylation treatment and then mixed with a solvent, the pH value of the system is adjusted to 2-6 by using an acid, then silane is added and mixed, then the mixture is heated and stirred for 1-8 hours at the temperature of 60-200 ℃, and then the silane modified carbon powder is obtained after filtering, washing and drying of a filter cake.

9. The method of manufacturing a gas diffusion layer for a fuel cell according to claim 5, wherein a carbon powder loading amount in the gas diffusion layer for a fuel cell is 0.5 to 3.0 mg/cm²。

10. Use of the gas diffusion layer for a fuel cell according to claim 1 for the preparation of a membrane electrode for a fuel cell.