Carbon paper for gas diffusion layer and its preparation method and application

Abstract

The present invention discloses a carbon paper for gas diffusion layer and its preparation method and application, which belongs to the technical field of carbon paper preparation. The preparation method provided by the present invention comprises the following steps: ultrasonically etching the nascent carbon fiber paper after wet papermaking with hydrogen peroxide, and then synthesizing polydopamine in situ to obtain polydopamine-modified nascent carbon fiber paper; dispersing graphene oxide modified by silane coupling agent in ethanol, and then adding phenolic resin and ultrasonically dispersing to obtain an impregnation solution; ultrasonically impregnating the polydopamine-modified nascent carbon fiber paper in the impregnation solution, drying, and then subjecting it to hot pressing curing and high-temperature carbonization to obtain the obtained carbon paper. The preparation method of the present invention is simple, and the preparation process is environmentally friendly and safe. The carbon paper material prepared by the present invention has an excellent interface, and has high electrical conductivity and high mechanical strength while maintaining high air permeability.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon paper preparation, and in particular to carbon paper for a gas diffusion layer, a preparation method and an application thereof. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Proton exchange membrane fuel cells are a clean, efficient and sustainable energy storage device that can directly convert chemical energy into electrical energy. They are widely used in promoting large-scale energy storage such as hydrogen fuel cell vehicles. The gas diffusion layer is one of the most important components affecting the performance and stability of proton exchange membrane fuel cells. At present, there are many materials used for gas diffusion layers, mainly including carbon fiber paper (carbon paper), carbon cloth or non-woven fabric, metal materials, etc. Compared with other substrate materials, carbon fiber paper has become an ideal material for gas diffusion layer substrates due to its advantages such as high conductivity, uniform porous structure, corrosion resistance, low cost, good mechanical properties and dimensional stability.

[0004] Carbon paper is a structural and functional integrated material composed of chopped carbon fibers and resin. Traditional carbon paper is mainly prepared from chopped carbon fibers as raw materials, and is produced through processes such as wet papermaking, impregnation densification, and high-temperature carbonization. The difficulties in preparing high-performance carbon paper mainly focus on the impregnation densification process. The core key technology of impregnation densification is the interface bonding between nascent carbon fiber paper (paper obtained after wet papermaking) and the resin, which has a direct impact on the flatness, air permeability, electrical conductivity, and mechanical strength of the final carbon paper. At present, thermosetting phenolic resin is the main precursor for impregnation densification of carbon fiber paper because of its low cost, easy availability of raw materials, high carbon residue rate, and good heat resistance and chemical stability. However, since a layer of cured acrylic resin binder is attached to the surface of the carbon fibers in the nascent carbon fiber paper, the carbon fibers have fewer surface active functional groups and are chemically inert. The wettability with the phenolic resin is poor, and the resin adhesion is uneven, resulting in problems such as uneven paper thickness and low interfacial bonding strength. At the same time, the resin carbon converted from a single phenolic resin after carbonization is a hard carbon phase with poor crystallinity, which increases the difficulty of graphitization treatment and cannot effectively reduce the resistivity.

[0005] The current impregnation process uses a mixture of conductive carbon filler or modified conductive carbon filler, thermosetting phenolic resin, and an organic solvent as the carbon paper impregnant. The virgin carbon fiber paper is then impregnated with this impregnant, and after curing and carbonization, the carbon paper for the gas diffusion layer is obtained. However, this method does not improve the interfacial bonding between the carbon fiber and the phenolic resin, and the production process requires the use of concentrated nitric acid or hydrochloric acid, which is highly hazardous, and the residual solution has an impact on the environment.

[0006] Therefore, how to provide a safe and environmentally friendly method for preparing carbon paper for gas diffusion layer, so as to simultaneously improve the interface bonding between carbon fiber and phenolic resin and increase the graphitization degree of the resin matrix. Summary of the Invention

[0007] In view of this, the present invention provides a carbon paper for gas diffusion layer and its preparation method and application, which solves the problems in the prior art that it is difficult to simultaneously improve the interface bonding between carbon fiber and phenolic resin and increase the graphitization degree of the resin matrix, and the preparation process is relatively dangerous and environmentally unfriendly.

[0008] In a first aspect, the present invention provides a method for preparing carbon paper for a gas diffusion layer, comprising the following steps:

[0009] The nascent carbon fiber paper after wet papermaking is ultrasonically etched with hydrogen peroxide, and then polydopamine is synthesized in situ to obtain polydopamine-modified nascent carbon fiber paper;

[0010] Silane coupling agent-modified graphene oxide is dispersed in ethanol, and then phenolic resin is added and ultrasonically dispersed to obtain an impregnation solution;

[0011] The polydopamine modified nascent carbon fiber paper is ultrasonically impregnated in the impregnation solution, dried, hot-pressed solidified, and carbonized at high temperature to obtain the paper.

[0012] Preferably, the concentration of the hydrogen peroxide is 5 to 30 wt %, the ultrasonic etching time is 2 to 10 min, and the ultrasonic frequency is 30 to 100 kHz.

[0013] Preferably, the step of in situ synthesis of polydopamine is: ultrasonically reacting the as-received carbon fiber paper after ultrasonic etching in a dopamine aqueous solution with a pH of 8.5 to 9.5 for 0.5 to 2 hours, and then drying at 80 to 100° C.; the concentration of the dopamine aqueous solution is 1 to 5 g / L.

[0014] Preferably, the preparation method of the silane coupling agent modified graphene oxide is: heating and hydrolyzing the silane coupling agent in an aqueous solution, then adding graphene oxide, soaking at a constant temperature for 1 to 10 minutes, and centrifugally drying to obtain the graphene oxide.

[0015] Furthermore, the silane coupling agent is selected from aniline methyl triethoxysilane, KH550, KH560 or KH590; the concentration of the silane coupling agent is 0.5-2wt%, the heating hydrolysis temperature is 30-50°C, and the heating hydrolysis time is 20-60min; the concentration of the graphene oxide is 0.1-1wt%; and the aqueous solution is water or ethanol aqueous solution.

[0016] Preferably, in the impregnation solution, the dispersion concentration of the silane coupling agent-modified graphene oxide in ethanol is 0.1-1 wt%, and the concentration of the phenolic resin is 5-15 wt%; and the ultrasonic dispersion time is 20-40 min.

[0017] Preferably, the usage ratio of the polydopamine-modified virgin carbon fiber paper to the impregnation solution is (0.5-5) g:100 g; and the ultrasonic impregnation time is 8-20 min.

[0018] Preferably, in the steps of hot pressing curing and high-temperature carbonization after drying, the drying temperature is 60-90°C, the hot pressing curing temperature is 160-190°C, the hot pressing curing pressure is 2-5 MPa, and the hot pressing curing time is 20-50 min; the high-temperature carbonization temperature is 1400-1600°C, and the high-temperature carbonization time is 0.5-2 h.

[0019] In a second aspect, the present invention provides carbon paper for a gas diffusion layer prepared by the above preparation method.

[0020] In a third aspect, the present invention provides the use of the carbon paper for gas diffusion layer in a proton exchange membrane fuel cell.

[0021] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0022] (1) The present invention uses a hydrogen peroxide solution to etch the nascent carbon fiber paper after wet papermaking, and then uses polydopamine to modify the etched carbon fiber paper to obtain a modified nascent carbon fiber paper rich in hydroxyl and amino groups and well impregnated with a phenolic resin. The modified carbon fiber paper is then impregnated with a phenolic resin solution containing silane coupling agent-modified graphene oxide. After hot pressing and carbonization, a carbon fiber paper with excellent interface, high air permeability and low resistivity is obtained. The preparation method is simple and easy to achieve low-cost continuous or batch production; and the preparation process is environmentally friendly and safe.

[0023] (2) The carbon paper material prepared by the present invention is a porous carbon / carbon composite material with excellent interface prepared by loading polydopamine and graphene oxide. The carbon paper material has an excellent interface and has high conductivity and high mechanical strength while maintaining high air permeability. The resistivity is lower than 15mΩ·cm and the tensile strength is higher than 10MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute undue limitations thereon. It is obvious that one of ordinary skill in the art could derive other drawings based on these drawings without inventive effort.

[0025] Figure 1 is a scanning electron microscope image of the carbon paper prepared in Example 1 of the present invention;

[0026] Figure 2 : This is a high-resolution XPS image of the nascent carbon fiber paper before and after polydopamine modification prepared in Example 2 of the present invention, wherein CFP-PDA is the nascent carbon fiber paper after polydopamine modification, and CFP-H2O2 is the nascent carbon fiber paper before polydopamine modification;

[0027] Figure 3 is a scanning electron microscope image of the carbon paper prepared in Example 2 of the present invention;

[0028] Figure 4 is a scanning electron microscope image of the carbon paper prepared in Example 3 of the present invention;

[0029] Figure 5 is a scanning electron microscope image of the carbon paper prepared in Comparative Example 1 of the present invention;

[0030] Figure 6 3 is a scanning electron microscope image of the carbon paper prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0031] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0032] The present invention provides a method for preparing carbon paper for a gas diffusion layer, comprising the following steps:

[0033] The nascent carbon fiber paper after wet papermaking is ultrasonically etched with hydrogen peroxide, and then polydopamine is synthesized in situ to obtain polydopamine-modified nascent carbon fiber paper;

[0034] Silane coupling agent-modified graphene oxide is dispersed in ethanol, and then phenolic resin is added and ultrasonically dispersed to obtain an impregnation solution;

[0035] The polydopamine modified nascent carbon fiber paper is ultrasonically impregnated in the impregnation solution, dried, hot-pressed solidified, and carbonized at high temperature to obtain the paper.

[0036] The present invention first performs hydrogen peroxide etching activation on the virgin carbon fiber paper prepared by wet papermaking to remove the binder attached to the surface of the virgin carbon fiber paper. Then, polydopamine is synthesized in situ on the etched surface of the virgin carbon fiber paper to introduce polar groups such as amino groups and hydroxyl groups, thereby achieving good wettability with the phenolic resin and improving the interfacial bonding strength. There are reports in the prior art on the modification of carbon fibers using polydopamine. However, if the carbon fibers are first modified with polydopamine and then wet papermaking is performed, the binder will be coated on the carbon fiber surface, covering up the polydopamine. At the same time, the functional groups of the polydopamine react with the functional groups of the binder, consuming the polydopamine, making it unable to play a role in improving the interface during the resin impregnation process. The present invention adopts the above technical solution to significantly improve the wettability between the virgin carbon fiber paper and the phenolic resin.

[0037] The impregnation solution of the present invention contains graphene oxide modified with a silane coupling agent. The surface of the graphene oxide modified with the silane coupling agent has more polar groups, which can increase the activity of the impregnation solution, thereby further enhancing the wettability between the raw carbon fiber paper and the phenolic resin. Furthermore, the introduction of the silane coupling agent-modified graphene oxide can also increase the degree of graphitization of the phenolic resin after carbonization, thereby improving the conductivity of the carbon paper.

[0038] In the present invention, the hydrogen peroxide concentration is 5 to 30 wt%, more preferably 5 to 15 wt%, and even more preferably 8 to 12 wt%. The ultrasonic etching time is 2 to 10 minutes, more preferably 2 to 5 minutes, and the ultrasonic frequency is 30 to 100 kHz, more preferably 40 to 80 kHz. The strong oxidizing effect of hydrogen peroxide removes the resin adhesive attached to the surface of the virgin carbon fiber paper. The etching time should not be too long, otherwise it may damage the bonding area of ​​the virgin carbon fiber paper, affecting the mechanical strength of the carbon fiber paper.

[0039] In the present invention, the step of in situ synthesis of polydopamine is: ultrasonically reacting the nascent carbon fiber paper after ultrasonic etching in a dopamine aqueous solution with a pH of 8.5 to 9.5 for 0.5 to 2 hours, and then drying at 80 to 100°C; the concentration of the dopamine aqueous solution is 1 to 5 g / L. Dopamine can undergo self-polymerization under alkaline conditions, and the surface of the modified nascent carbon fiber paper has polar groups such as amino groups and hydroxyl groups. The present invention does not impose any special restrictions on the alkaline control method, and the alkaline control method commonly used by those skilled in the art can be adopted. The present invention also does not impose any special restrictions on the drying time, as long as it is dried to constant weight.

[0040] In the present invention, the preparation method of the silane coupling agent-modified graphene oxide comprises: heating and hydrolyzing the silane coupling agent in an aqueous solution, then adding the graphene oxide and soaking the mixture at a constant temperature for 1 to 10 minutes, more preferably 2 to 5 minutes; and finally centrifugation and drying. Upon heating and hydrolysis, the silane coupling agent produces silanol groups, which can form hydrogen bonds with hydroxyl groups on the surface of the graphene oxide. Upon heating, Si-OC groups are formed, thereby grafting the silane coupling agent onto the graphene oxide. The present invention imposes no particular restrictions on the centrifugal drying process; commonly used centrifugal drying methods in the art can be used.

[0041] In the present invention, the silane coupling agent is selected from aniline methyl triethoxysilane, KH550, KH560, or KH590, more preferably aniline methyl triethoxysilane; the concentration of the silane coupling agent is 0.5 to 2 wt%, more preferably 0.5 to 1 wt%; the heating and hydrolysis temperature is 30 to 50°C, more preferably 35 to 45°C; the heating and hydrolysis time is 20 to 60 minutes, more preferably 20 to 40 minutes. The concentration of the graphene oxide is 0.1 to 1 wt%. The aqueous solution is water or ethanol aqueous solution. The specific solvent can be adjusted according to the solubility of the selected silane coupling agent, and the present invention does not impose any special restrictions on this.

[0042] In the impregnation solution of the present invention, the dispersion concentration of the silane coupling agent modified graphene oxide in ethanol is 0.1-1 wt%, and the concentration of the phenolic resin is 5-15 wt%. The ultrasonic dispersion time is 20-40 minutes.

[0043] In the present invention, the ratio of the polydopamine modified virgin carbon fiber paper to the impregnation solution is (0.5-5) g:100 g, more preferably (0.5-2) g:100 g; the ultrasonic impregnation time is 8-20 min, more preferably 8-15 min.

[0044] In the present invention, in the steps of hot pressing and high-temperature carbonization after drying, the drying temperature is 60-90°C, the hot pressing and curing temperature is 160-190°C, more preferably 160-180°C, the hot pressing and curing pressure is 2-5 MPa, and the hot pressing and curing time is 20-50 min, more preferably 20-40 min; the high-temperature carbonization temperature is 1400-1600°C, more preferably 1450-1550°C, and the high-temperature carbonization time is 0.5-2 h. The impregnation solution of the present invention contains silane coupling agent-modified graphene oxide, which can make the phenolic resin have a higher degree of graphitization at a lower graphitization temperature. The higher the degree of graphitization, the lower the contact resistance between the carbon fiber and the phenolic resin, and thus the higher the conductivity.

[0045] The present invention also provides carbon paper for gas diffusion layer prepared by the above preparation method. The carbon paper for gas diffusion layer of the present invention has both low resistivity and high mechanical strength while maintaining high air permeability. The resistivity is lower than 15mΩ·cm and the tensile strength is higher than 10MPa.

[0046] The present invention also provides an application of the carbon paper for gas diffusion layer in a proton exchange membrane fuel cell. Specifically, the carbon paper for gas diffusion layer is used as the gas diffusion layer of the proton exchange membrane fuel cell to transport gas and conduct electrons.

[0047] The technical solution of the present invention is further described below with reference to specific embodiments.

[0048] Example 1

[0049] This embodiment provides a method for preparing carbon paper.

[0050] Step 1: soak the wet-made raw carbon fiber paper in a 10 wt% hydrogen peroxide solution and perform ultrasonic etching for 5 minutes at an ultrasonic frequency of 40 kHz.

[0051] Step 2: The carbon fiber paper material treated in step 1 is ultrasonically immersed in a 2 g / L dopamine aqueous solution with a pH of 8.5 for 60 minutes, and then dried at 100° C. to obtain polydopamine-modified nascent carbon fiber paper.

[0052] Step 3: Prepare a 0.5 wt% anilinemethyltriethoxysilane (AMT) ethanol aqueous solution (ethanol: water = 92:8, v / v); the solution is magnetically stirred at 40°C for 30 minutes to ensure the hydrolysis of AMT, and then a single layer of graphene oxide (GO) is added, and the mixture is kept at 40°C for 2 minutes, followed by centrifugal drying to obtain AMT-modified GO.

[0053] Step 4: Disperse the AMT-modified GO in step 3 in ethanol, control the concentration of AMT-modified GO to 0.1 wt %, directly add 10 wt % phenolic resin powder (PF) after ultrasonication for 30 min, and continue ultrasonic dispersion for 30 min to obtain a uniformly dispersed GO-PF impregnation solution.

[0054] Step 5: 0.7 g of the polydopamine-modified virgin carbon fiber paper obtained in step 2 was impregnated into 100 g of the GO-PF impregnation solution obtained in step 4, ultrasonicated for 10 min, and then dried at 80°C.

[0055] Step 6: The material dried in step 5 is hot-pressed and cured at 170° C. and 3 MPa for 30 minutes.

[0056] Step 7: Carbonize the material after hot pressing and curing in step 6 at 1500° C. for 1 hour to obtain the product.

[0057] Figure 1 The surface morphology of the carbon paper prepared in this example shows that the carbon fibers are closely overlapped, the structure is compact, and the pore structure is uniform.

[0058] Example 2

[0059] This embodiment provides a method for preparing carbon paper.

[0060] Step 1: soak the fresh carbon fiber paper after wet papermaking in a 10 wt% hydrogen peroxide solution and ultrasonically etch it for 5 minutes at an ultrasonic frequency of 80 kHz.

[0061] Step 2: ultrasonically immersing the carbon fiber paper material treated in step 1 in a 2 g / L dopamine aqueous solution with a pH of 8.5 for 60 minutes, and then drying at 100° C. to obtain polydopamine-modified nascent carbon fiber paper;

[0062] Step 3: Prepare a 0.5 wt% anilinemethyltriethoxysilane (AMT) ethanol aqueous solution (ethanol: water = 92:8, v / v); the solution is magnetically stirred at 40°C for 30 minutes to ensure the hydrolysis of AMT, and then a single layer of graphene oxide (GO) is added, and the mixture is kept at a constant temperature of 40°C for 5 minutes, followed by centrifugal drying to obtain AMT-modified GO.

[0063] Step 4: Disperse the AMT-modified GO in step 3 in ethanol, control the concentration of AMT-modified GO to 0.5 wt %, directly add 10 wt % phenolic resin powder (PF) after ultrasonication for 30 min, and continue ultrasonic dispersion for 30 min to obtain a uniformly dispersed GO-PF impregnation solution.

[0064] Step 5: 0.7 g of the polydopamine-modified virgin carbon fiber paper obtained in step 2 was impregnated into 100 g of the GO-PF impregnation solution obtained in step 4, ultrasonicated for 10 min, and then dried at 80°C.

[0065] Step 6: The material dried in step 5 is hot-pressed and cured at 170° C. and 3 MPa for 30 minutes.

[0066] Step 7: Carbonize the material after hot pressing and curing in step 6 at 1500° C. for 1 hour to obtain the product.

[0067] Figure 2 This is the high-resolution XPS graph (X-ray photoelectron spectroscopy) of the nascent carbon fiber paper before and after polydopamine modification in this example. It can be seen that the successful modification of polydopamine increases the N and O contents of the nascent carbon paper, thereby enhancing the activity of the nascent carbon fiber paper. Figure 3This is a surface morphology of the carbon paper prepared in this example. It can be seen from the figure that the amount of resin impregnated on the carbon fiber surface increases, and the phenolic resin is fully carbonized and tightly bonded to the carbon fiber without cracks.

[0068] Example 3

[0069] This embodiment provides a method for preparing carbon paper.

[0070] Step 1: soak the fresh carbon fiber paper after wet papermaking in a 10 wt% hydrogen peroxide solution and ultrasonically etch for 2 minutes at an ultrasonic frequency of 60 kHz.

[0071] Step 2: The carbon fiber paper material treated in step 1 is ultrasonically immersed in a 2 g / L dopamine aqueous solution with a pH of 8.5 for 60 minutes, and then dried at 100° C. to obtain polydopamine-modified nascent carbon fiber paper.

[0072] Step 3: Prepare a 0.75 wt% anilinemethyltriethoxysilane (AMT) ethanol aqueous solution (ethanol: water = 92:8, v / v); the solution is magnetically stirred at 40°C for 30 min to ensure hydrolysis of AMT, and then multilayer GO is added and soaked at a constant temperature of 40°C for 2 min, followed by centrifugal drying to obtain AMT-modified GO.

[0073] Step 4: Disperse the AMT-modified GO in step 3 in ethanol, control the concentration of AMT-modified GO to 0.75 wt %. After ultrasonication for 30 min, directly add 5 wt % of phenolic resin powder (PF), and continue ultrasonic dispersion for 30 min to obtain a uniformly dispersed GO-PF impregnation solution.

[0074] Step 5: Impregnate 0.7 g of the polydopamine-modified virgin carbon fiber paper obtained in step 2 into 100 g of the impregnation solution obtained in step 4, ultrasonicate for 10 min, and then dry at 80°C.

[0075] Step 6: The material dried in step 5 is hot-pressed and cured at 170° C. and 3 MPa for 30 minutes.

[0076] Step 7: Carbonize the material after hot pressing and curing in step 6 at 1500° C. for 1 hour to obtain the product.

[0077] Figure 4 This is the surface morphology of the carbon paper prepared in this example. It can be seen that the resin bonding area at the carbon fiber overlap is reduced, and the resin is more attached to the fiber surface. The carbon paper structure is uniform and flat, so it has better tensile strength and better air permeability.

[0078] Comparative Example 1

[0079] This comparative example differs from Example 1 in that the impregnation solution in this comparative example does not contain AMT-modified GO. The specific steps are as follows:

[0080] Step 1: soak the wet-made raw carbon fiber paper in a 10 wt% hydrogen peroxide solution and perform ultrasonic etching for 5 minutes at an ultrasonic frequency of 40 kHz.

[0081] Step 2: The carbon fiber paper material treated in step 1 is ultrasonically immersed in a 2 g / L dopamine aqueous solution with a pH of 8.5 for 60 minutes, and then dried at 100° C. to obtain polydopamine-modified nascent carbon fiber paper.

[0082] Step 3: Immerse the polydopamine-modified virgin carbon fiber paper prepared in step 2 in a 10 wt% phenolic resin ethanol solution, ultrasonicate for 10 minutes, and then dry at 80°C.

[0083] Step 4: The material dried in step 3 was hot-pressed and cured at 170° C. and 3 MPa for 30 minutes.

[0084] Step 5: Carbonize the material after hot pressing and curing in step 4 at 1500° C. for 1 hour to obtain the product.

[0085] The overall performance test data results of the final product carbon paper are shown in Table 1.

[0086] Figure 5 The surface morphology of the carbon paper prepared for this comparative example shows that the phenolic resin is unevenly impregnated and there is resin agglomeration. Although the unilateral modification of carbon fiber by polydopamine improves the polarity of carbon fiber, the phenolic resin still has the problem of poor activity. Therefore, when impregnated, agglomeration occurs at the overlap of carbon fiber paper. The presence of graphene oxide can both enhance the activity of phenolic resin and improve the interfacial strength of carbon paper and reduce the resistivity of carbon paper after carbonization. This comparative example only adds polydopamine and does not use graphene oxide, so the tensile strength is lower than the embodiment and the resistivity is higher.

[0087] Comparative Example 2

[0088] The difference between this comparative example and Example 1 is that this comparative example does not use polydopamine for modification. The specific steps are as follows:

[0089] Step 1: Soak the raw carbon fiber paper in a 10 wt% hydrogen peroxide solution and perform ultrasonic etching for 5 minutes at an ultrasonic frequency of 40 kHz.

[0090] Step 2: Prepare a 0.5 wt% anilinemethyltriethoxysilane (AMT) ethanol aqueous solution (ethanol: water = 92:8, v / v); the solution is magnetically stirred at 40°C for 30 minutes to ensure the hydrolysis of AMT, and then a single layer of graphene oxide (GO) is added, and the mixture is kept at 40°C for 2 minutes, followed by centrifugal drying to obtain AMT-modified GO.

[0091] Step 3: Disperse the AMT-modified GO in step 2 in ethanol, control the concentration of AMT-modified GO to 0.1 wt%, directly add 10 wt% of phenolic resin powder (PF) after ultrasonication for 30 min, and continue ultrasonic dispersion for 30 min to obtain a uniformly dispersed GO-PF impregnation solution.

[0092] Step 4: 0.7 g of the material treated in step 1 was immersed in 100 g of the GO-PF impregnation solution obtained in step 4, ultrasonicated for 10 min, and then dried at 80°C.

[0093] Step 5: The material dried in step 4 was hot-pressed and cured at 170° C. and 3 MPa for 30 minutes.

[0094] Step 6: Carbonize the material after hot pressing and curing in step 5 at 1500° C. for 1 hour to obtain the product.

[0095] Figure 6 This is the surface morphology of the carbon paper prepared in this comparative example; it can be seen from the figure that resin carbon aggregation and cracking occur on the surface of the carbon paper. Because graphene is added in this comparative example, the viscosity of the impregnating resin is further increased, but the fiber surface is not modified, the resin wettability is poor, and more resin adheres to the fiber overlap. After compression molding, a larger resin film is formed at the overlap. After high-temperature carbonization, the resin carbon film cracks. The resin carbon cannot fully play a connecting and fixing role, so the mechanical properties are poor. At the same time, because the graphene oxide is converted into graphene with good conductivity after carbonization, the resistivity of the carbon paper is slightly lower, but due to the poor interface, the resistivity is still higher than that of Example 1.

[0096] Test example

[0097] The carbon papers prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests. Air permeability was measured using an air permeability meter. The pressure was increased to 50 Pa, and the system automatically monitored the air flow through the carbon paper. Tensile properties were measured using a universal tensile testing machine, with the length and width of the tensile specimens measuring 70 mm by 10 mm. Resistivity was measured using a four-probe resistivity meter.

[0098] The test results are shown in Table 1.

[0099] Table 1 Carbon paper performance test data results

[0100]

[0101]

[0102] As can be seen in Table 1, Comparative Example 1 does not modify the phenolic resin, and the degree of graphitization of the phenolic resin after carbonization is low. Therefore, the resistivity is much lower than that of the carbon paper after adding GO, indicating that graphene oxide has a significant effect on improving the conductivity of the carbon paper. Comparative Example 2, in which virgin carbon fiber paper is simply etched with hydrogen peroxide and then impregnated with a phenolic resin impregnation solution doped with modified graphene oxide, produces carbon paper with a tensile strength far lower than that of the carbon paper prepared in Example 1. This shows that surface polydopamine has a significant effect on repairing the etching effects caused by hydrogen peroxide, improving the interface, and enhancing mechanical strength.

[0103] The test results of Examples 1 to 3 show that the carbon fiber paper material prepared by the present invention has a well-connected interface and a uniform pore structure. The prepared carbon paper has the advantages of high mechanical strength, high conductivity and high permeability, and can be used as a gas diffusion layer of a proton exchange membrane fuel cell to transport gas and conduct electrons.

[0104] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing carbon paper for a gas diffusion layer, characterized in that: The steps include: The nascent carbon fiber paper after wet papermaking is ultrasonically etched with hydrogen peroxide, and then polydopamine is synthesized in situ to obtain polydopamine-modified nascent carbon fiber paper; the in situ polydopamine synthesis step comprises: ultrasonically reacting the nascent carbon fiber paper after ultrasonic etching in a dopamine aqueous solution with a pH of 8.5-9.5 for 0.5-2 hours, and then drying at 80-100° C.; the concentration of the dopamine aqueous solution is 1-5 g / L Dispersing graphene oxide modified with a silane coupling agent in ethanol, then adding phenolic resin and performing ultrasonic dispersion to obtain an impregnation solution; in the impregnation solution, the dispersion concentration of the graphene oxide modified with a silane coupling agent in ethanol is 0.1-1 wt %, and the concentration of the phenolic resin is 5-15 wt %; and the ultrasonic dispersion time is 20-40 min; The polydopamine-modified virgin carbon fiber paper is ultrasonically impregnated in the impregnation solution, wherein the amount ratio of the polydopamine-modified virgin carbon fiber paper to the impregnation solution is (0.5-5) g:100 g; the ultrasonic impregnation time is 8-20 min; after drying, hot pressing and curing, and high-temperature carbonization are performed to obtain the product; The temperature of the hot pressing curing is 160-190° C., the pressure of the hot pressing curing is 2-5 MPa, and the time of the hot pressing curing is 20-50 min.

2. The preparation method according to claim 1, wherein The concentration of the hydrogen peroxide is 5-30 wt %, the ultrasonic etching time is 2-10 min, and the ultrasonic frequency is 30-100 kHz.

3. The preparation method according to claim 1, wherein The preparation method of the silane coupling agent modified graphene oxide comprises the following steps: heating and hydrolyzing the silane coupling agent in an aqueous solution, then adding the graphene oxide, soaking the graphene oxide at a constant temperature for 1 to 10 minutes, and centrifugally drying the graphene oxide.

4. The preparation method according to claim 3, wherein The silane coupling agent is selected from aniline methyl triethoxysilane, KH550, KH560 or KH590; the concentration of the silane coupling agent in water is 0.5-2wt%, the temperature of the heating hydrolysis is 30-50°C, and the time of the heating hydrolysis is 20-60 minutes; the concentration of the graphene oxide is 0.1-1wt%; and the aqueous solution is water or ethanol aqueous solution.

5. The preparation method according to claim 1, wherein In the steps of hot pressing curing and high-temperature carbonization after drying, the drying temperature is 60-90° C.; the high-temperature carbonization temperature is 1400-1600° C., and the high-temperature carbonization time is 0.5-2 hours.

6. Carbon paper for gas diffusion layer prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the carbon paper for gas diffusion layer according to claim 6 in a proton exchange membrane fuel cell.

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