A pressurized carbonization process for improving the performance of carbon paper for gas diffusion layer and carbon paper thereof

Abstract

The present invention relates to the technical field of carbon paper, and in particular to a pressurized carbonization process for improving the performance of carbon paper for gas diffusion layer. The present application discloses a pressurized carbonization process for improving the performance of carbon paper for gas diffusion layer, comprising the following steps: pressurizing hot pressed paper under preset pressure conditions; carbonizing the hot pressed paper under pressure treatment; after the carbonization treatment is completed, carbon paper is obtained; the preset pressure condition is 300-5000pa. The pressurized carbonization process described in the present application optimizes the pore structure and physical properties of carbon paper by precisely controlling the temperature and pressure conditions during the carbonization process, thereby meeting the high performance requirements of the fuel cell for the gas diffusion layer.

Description

Technical Field

[0001] The invention relates to the technical field of carbon paper, and in particular to a pressurized carbonization process for improving the performance of carbon paper for a gas diffusion layer. Background Art

[0002] In the field of fuel cell technology, the gas diffusion layer (GDL), as one of the key components, plays a vital role in the performance of the battery. The gas diffusion layer is usually made of carbon paper, which not only needs to have excellent air permeability and conductivity, but also needs to have sufficient mechanical strength and chemical stability to withstand various complex environments during the operation of the fuel cell. However, the existing carbon paper often has problems such as uneven performance and unreasonable pore structure during the preparation process, which limits its application effect in fuel cells.

[0003] With the continuous development of fuel cell technology, the performance requirements for carbon paper used in gas diffusion layers are becoming higher and higher. In order to improve the performance of carbon paper, researchers have tried various carbonization processes, including atmospheric pressure carbonization, high temperature carbonization, etc. However, these traditional carbonization processes have certain limitations in improving the performance of carbon paper. For example, atmospheric pressure carbonization processes often find it difficult to effectively control the pore structure during the carbonization process, resulting in the difficulty in simultaneously meeting the requirements for the air permeability and conductivity of carbon paper; and although the high-temperature carbonization process can form a better pore structure, it has high energy consumption and is prone to oxidation of the carbon paper surface, affecting its service life.

[0004] There are some solutions to the above problems in the prior art. For example, the performance of carbon paper can be improved by optimizing carbonization process parameters (such as temperature, time, etc.); or special additives can be used to regulate the pore structure during the carbonization process. However, these solutions still have certain defects in practical applications. On the one hand, the optimization of process parameters is often limited by equipment conditions and operating levels, making it difficult to achieve consistency control in large-scale production; on the other hand, the introduction of special additives may increase production costs and may affect the chemical stability and environmental friendliness of carbon paper.

[0005] Therefore, it is particularly important to develop a carbonization process that can significantly improve the performance of carbon paper for gas diffusion layer, has a simple process, is easy to control and has low cost. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the present invention provides a pressurized carbonization process for improving the performance of carbon paper for gas diffusion layer. By precisely controlling the temperature and pressure conditions during the carbonization process, the pore structure and physical properties of the carbon paper are optimized, thereby meeting the high performance requirements of the gas diffusion layer of the fuel cell.

[0007] The technical solution adopted by this application to solve its technical problem is:

[0008] On the one hand, the present application provides a pressurized carbonization process for improving the performance of carbon paper for gas diffusion layer, comprising the following steps:

[0009] Pressurizing the hot pressing paper under a preset pressure condition;

[0010] The hot pressed paper under pressure is subjected to carbonization treatment;

[0011] After the carbonization treatment is completed, carbon paper is obtained;

[0012] The preset pressure condition is 300-5000pa.

[0013] In some embodiments, the target temperature of the carbonization treatment is 1800-2000° C., the time of the carbonization treatment is 3-4 hours, and the temperature is lowered after the insulation is completed, and the cooling process is natural cooling.

[0014] In some embodiments, the preparation process of the hot pressed paper is to prepare carbon fiber base paper by wet molding of short chopped carbon fibers, and then impregnate the fiber base paper with phenolic resin, and then mold and cure it to prepare hot pressed paper.

[0015] In some embodiments, the pressurization treatment is performed in a pressurization device.

[0016] In some embodiments, the carbonization process is performed in a vacuum heating device.

[0017] In some embodiments, the carbonization treatment is performed in an inert gas protective atmosphere.

[0018] In some embodiments, the pressurizing device includes a base plate and a plurality of graphite sheets disposed on the base plate; during the pressurizing process, the hot pressing paper is laid flat on the base plate, and the hot pressing paper is fixedly pressed using a plurality of graphite sheets, so that a preset pressure is generated on the hot pressing paper.

[0019] In some embodiments, the pressurizing device for pressurizing is placed in a vacuum heating device for carbonization treatment.

[0020] In some embodiments, during the carbonization treatment, the temperature is increased to the target temperature at a rate of 25 to 50° C. / min.

[0021] On the other hand, the present application provides carbon paper, including the carbon paper prepared by the pressurized carbonization process described above.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The pressurized carbonization process described in this application is simple to operate, easy to realize industrial production, and has high application value.

[0024] 2. The pressurized carbonization process described in the present application reduces the cracking of resin carbon and improves the bending strength and tensile strength of carbon paper by applying pressure. Under the action of pressure, the discharge of pyrolysis small molecule gases is controlled, reducing the generation of cracks, making the surface of carbon paper smoother, and improving the interface bonding strength between carbon fiber and resin carbon, making the overall performance of carbon paper more stable and reliable.

[0025] 3. The pressurized carbonization process described in the present application can obtain a carbon paper with a dense structure, which makes the electron transmission channel smoother, reduces the plane resistivity, and improves the conductive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0027] Figure 1 This is an electron microscope image of the carbon paper prepared in Example 1;

[0028] Figure 2 This is an electron microscope image of the carbon paper prepared in Example 2;

[0029] Figure 3 This is an electron microscope image of the carbon paper prepared in Example 3;

[0030] Figure 4 This is a schematic diagram of applying pressure to hot-pressed paper during the carbonization process in Example 1;

[0031] Figure 5 A schematic diagram of applying pressure to hot-pressed paper during carbonization in Example 2;

[0032] Figure 6 A schematic diagram of applying pressure to hot pressed paper during carbonization in Example 3;

[0033] Figure 7 It is a schematic diagram of the structure of the pressurizing device;

[0034] Figure 8 This is an electron microscope image of the carbon paper prepared in Comparative Example 1;

[0035] Among them: 1. Pressed paper; 2. Bottom plate; 3. Graphite sheet; 4. Screws. DETAILED DESCRIPTION

[0036] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments, and the contents mentioned in the implementation modes are not intended to limit the present invention.

[0037] As used herein, "and / or" includes the term of all combinations of any one or more associated listed items. The terms used herein are only used to describe specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "a", "an", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It is further understood that "including", when used in this specification, specifies the stated features, integers, steps, operations, elements and / or compositions, but does not exclude the existence or addition of one or more other features, integers, steps, operations, elements, compositions and / or combinations thereof.

[0038] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. It is further understood that terms, such as defined in commonly used dictionaries, are interpreted in accordance with their meanings in the context of the relevant art and are not in an idealized or overly formal sense unless explicitly so defined herein.

[0039] The exemplary invention described herein may appropriately lack any one or more element limitations that are not specifically disclosed herein. Therefore, the terms "comprise", "include", "contain", etc. should be understood broadly and non-restrictively. In addition, the terminology used herein is used as a description, not a limitation, and it is unintentional to use these terminology expressions that do not include any equivalent characteristics, but only describe some of their characteristics, but various modifications are possible within the scope of the present invention according to the rights. Therefore, although the present invention has been specifically disclosed by preferred embodiments and optional features, the modifications disclosed herein to embody the changes of the present invention may be recorded by those skilled in the art, and such modifications and changes will be considered to be within the scope of the present invention.

[0040] Terminology explanation:

[0041] Hot-pressed paper usually refers to a composite material made by hot pressing, which contains carbon fiber and other components (such as phenolic resin). During the hot pressing process, the resin is heated and softened, and then tightly combined with the carbon fiber under pressure to form a composite sheet with certain strength and rigidity.

[0042] Carbonization usually refers to the process of pyrolyzing organic matter at high temperature to convert it into carbonaceous materials. In the preparation of hot-pressed paper, carbonization is mainly used to pyrolyze phenolic resin and convert it into resin carbon, while promoting the bonding between carbon fiber and resin carbon.

[0043] Vacuum heating device is a device that can heat materials under vacuum or inert gas protection. It usually includes heating system, vacuum system, inert gas supply system and control system, etc., which are used to create a non-oxidizing heating environment to prevent the material from being oxidized at high temperature.

[0044] Medium frequency induction furnace is a device that uses the magnetic field generated by medium frequency current to generate eddy current inside the metal to heat the metal. In the carbonization treatment of hot press paper, the medium frequency induction furnace can be used as a heating source to transfer heat to the hot press paper and pressurizing device in the furnace through the principle of electromagnetic induction.

[0045] Inert gas refers to a gas with very stable chemical properties that is not easy to react chemically with other elements or compounds. Common inert gases include nitrogen (N2), argon (Ar), helium (He), etc. In the process of material processing and heat treatment, inert gas is often used as a protective gas to prevent the material from being oxidized at high temperature.

[0046] The present application provides a pressurized carbonization process for improving the performance of carbon paper for a gas diffusion layer, comprising the following steps:

[0047] Pressurizing the hot pressing paper under a preset pressure condition;

[0048] The hot pressed paper under pressure is subjected to carbonization treatment;

[0049] After the carbonization treatment is completed, carbon paper is obtained;

[0050] The preset pressure condition is 300-5000pa.

[0051] Therefore, when the preset pressure condition is 300-5000Pa, the carbonization treatment is carried out. By applying pressure during the carbonization process, the discharge rate of the pyrolysis small molecule gas is reduced, and the cracking degree of the resin carbon is reduced, thereby inhibiting the generation of cracks and improving the mechanical strength and conductive properties of the carbon paper. At the same time, the effect of pressure makes the interface between the carbon fiber and the resin carbon more tightly bonded and the structure more dense.

[0052] In some embodiments, the preparation process of the hot pressed paper is to prepare carbon fiber base paper by wet molding of short chopped carbon fibers, and then impregnate the fiber base paper with phenolic resin, and then mold and cure it to prepare hot pressed paper.

[0053] It can be understood that the hot-pressed paper of the present application can be commercially available hot-pressed paper prepared according to the above process, or hot-pressed paper conventionally prepared by a person skilled in the art according to the above process.

[0054] Specifically, in the preparation process of hot-pressed paper, the wet forming technology can ensure the uniform distribution and good formability of carbon fibers, providing a good foundation for the subsequent impregnation and carbonization processes. The wet forming technology utilizes the suspension and dispersibility of fibers in aqueous media, and through mechanical stirring and forming equipment, the carbon fibers are evenly distributed and form a fiber layer of a certain thickness, and then the carbon fiber base paper is obtained through dehydration, drying and other processes;

[0055] Specifically, phenolic resin, as a binder, penetrates into the carbon fiber base paper through the impregnation process, enhancing the bonding between the carbon fibers and providing the necessary material basis for the subsequent carbonization process; phenolic resin has good wettability and bonding properties, and can react with the active groups on the surface of the carbon fibers to form chemical bonds, thereby enhancing the bonding between the carbon fibers. During the impregnation process, the resin penetrates into the pores and between the fibers of the carbon fibers through capillary action, forming a uniform resin distribution.

[0056] The molding and curing process makes the impregnated carbon fiber base paper form a dense hot-pressed paper, further improving the bonding strength between the carbon fibers and the stability of the overall structure. At the same time, the resin undergoes a curing reaction at high temperature to form a strong bonding interface with the carbon fibers, improving the overall strength and stability of the carbon paper.

[0057] In some embodiments, the target temperature of the carbonization treatment is 1800-2000°C, and the temperature is kept at 1800-2000°C for 0.5-1h. After the temperature is kept, the temperature is cooled, and the cooling process is natural cooling.

[0058] Specifically, the target temperature of the carbonization treatment is 1800-2000°C, which is to ensure that the phenolic resin can be fully pyrolyzed and converted into resin carbon, while promoting the chemical bonding and interface bonding between the carbon fiber and the resin carbon, and optimizing the physical and chemical properties of the carbon paper; 1800-2000°C can promote the complete carbonization of the resin, reduce the content of residues, and improve the purity and density of the carbon paper.

[0059] More specifically, during the carbonization treatment, the temperature is raised to 1800-2000°C by controlling the heating rate at 25-50°C / min, and then kept at 1800-2000°C. The holding time is preferably 0.5-1h. After the holding is completed, the temperature is lowered, and the cooling process is natural. Within the selected temperature range, the holding time of the carbonization treatment is controlled in order to balance the completeness of the carbonization process and the production efficiency. A shorter time may result in incomplete carbonization, while too long a time may increase production costs and may cause excessive changes in the properties of the carbon paper. Therefore, the holding time is controlled within 0.5-1h to achieve the best efficiency and quality of the carbonization process.

[0060] In this application, high-temperature carbonization is performed. At high temperatures, the phenolic resin undergoes a series of pyrolysis reactions, including dehydration, polycondensation, cracking, etc., and finally forms resin carbon. In this process, the chemical composition and physical structure of the resin change significantly, and the bonding interface with the carbon fiber also changes, from the resin-fiber interface to the resin carbon-fiber interface. High temperature promotes the formation of resin carbon and enhances the interaction between carbon fiber and resin carbon, including chemical bonding and physical adsorption, thereby improving the overall performance and stability of carbon paper.

[0061] In some embodiments, the pressurization treatment is performed in a pressurization device. Figure 5 The pressurizing device shown includes a base plate 2 and a plurality of graphite sheets 3 arranged on the base plate 2; when performing the pressurizing treatment, the hot pressing paper 1 is laid flat on the base plate, and the hot pressing paper is fixedly pressed using a plurality of graphite sheets 3, so that a preset pressure is generated on the hot pressing paper.

[0062] It can be understood that in the carbonization process, a pressure device is provided in the present application to apply pressure to the hot pressing paper; the device is designed to achieve uniform application of pressure and can control the amount of applied pressure by adjusting the number of graphite sheets.

[0063] Specifically, the graphite sheets, as pressure transmission media, have good thermal conductivity and stability, and can maintain stable pressure output in high temperature environments; when external force is applied to the graphite sheets (such as through mechanical devices or manual operations), they will evenly transfer this pressure to the hot pressing paper below, forming a preset pressure distribution; during the heating process, the heat generated by the heat source (such as an electric heating element) is transferred to the graphite sheet through the bottom plate. Due to the high thermal conductivity of graphite, the heat can be quickly and evenly transferred to the hot pressing paper, promoting the hot pressing reaction.

[0064] Specifically, when using the pressurizing device, lay the hot press paper flat on the bottom plate as required to ensure that the surface is flat and wrinkle-free; check whether the graphite sheet is clean and undamaged, and adjust its position as needed to ensure that it can evenly cover the hot press paper. During the pressurization process, the pressure gauge reading can be observed to ensure that the pressure value is within the preset range, and then the graphite sheet is fixed to the bottom plate by the graphite screw 4. If the pressure needs to be adjusted, it can be adjusted by adjusting the number of graphite sheets, etc.

[0065] In some embodiments, the carbonization treatment is performed in a vacuum heating device; the carbonization treatment is performed in an inert gas protective atmosphere.

[0066] It can be understood that the main purpose of setting the carbonization process in a vacuum heating device is to create a non-oxidizing gas environment to prevent the hot pressed paper from being oxidized by oxygen in the air during the carbonization process, thereby ensuring the quality of the carbonization process and the stability of product performance; specifically, the vacuum environment can effectively exclude oxygen in the furnace, reduce the occurrence of oxidation reactions, and is beneficial to the pyrolysis conversion of phenolic resin and the combination of carbon fiber and resin carbon.

[0067] Moreover, in the vacuum heating device, an inert gas (such as nitrogen) is usually introduced to replace the air\oxygen in the vacuum heating device and maintain the stability of the atmosphere in the vacuum heating device. The inert gas does not chemically react with the carbon paper material, which plays a role in further preventing oxidation.

[0068] Specifically, the pressurizing device for pressurizing treatment is placed in a vacuum heating device (for example, in a medium frequency induction furnace) for carbonization treatment; during the carbonization treatment, the temperature is raised to the target temperature at a rate of 25 to 50° C. / min.

[0069] It is understandable that during the carbonization process, setting the heating rate within the range of 25-50℃ / min can ensure a smooth carbonization process, while avoiding the problem of thermal stress concentration and cracking caused by too fast heating, which helps the resin carbon to form a good bonding interface with the carbon fiber during the carbonization process. Too fast heating may cause the resin carbon to harden quickly and be difficult to bond tightly with the carbon fiber; too slow heating may prolong the carbonization time and increase energy consumption.

[0070] The pressurized carbonization process described in the present application is further described through the following examples and comparative examples.

[0071] Example 1

[0072] A pressurized carbonization process for improving the performance of carbon paper for a gas diffusion layer comprises the following steps:

[0073] a. preparing carbon fiber base paper by wet forming of chopped carbon fibers, and then impregnating the base paper with phenolic resin, and then molding and curing to prepare hot pressed paper;

[0074] b. Place the hot pressed paper in a pressure device and fix it, covering a piece of graphite sheet to generate a pressure of 300Pa;

[0075] c. Place the pressure device prepared in step b and the hot pressing paper in the medium frequency induction furnace, evacuate the furnace and pass N2, repeat 3 times to form a non-oxidizing gas atmosphere in the furnace, and complete the preparation of carbonization reaction conditions.

[0076] d. Using the medium frequency induction furnace prepared in step c for the carbonization reaction conditions, the hot pressed paper was heated (heating rate of 50°C / min) to 1800°C and kept warm for 0.5h, and then cooled naturally after the end of the insulation; Figure 4 This is a schematic diagram of applying pressure to hot-pressed paper during the carbonization process in Example 1;

[0077] e. Remove the pressure from the carbon paper that has been carbonized in step d to obtain a finished product.

[0078] Test analysis:

[0079] The carbon paper product prepared in this embodiment was used as a sample to test electrical properties and mechanical properties. The obtained plane resistivity was 12.42 mΩ·cm, the bending strength was 18.85 MPa, the tensile strength was 17.03 MPa, Figure 1 This is an electron microscope picture of the sample after carbonization in this embodiment. This embodiment prepares a carbon paper product with good conductivity and high mechanical strength. During the carbonization process in this embodiment, a certain pressure is applied to reduce the generation of surface cracks, which is beneficial to improve the direct interface bonding strength between carbon fiber and resin carbon, making the structure more compact.

[0080] Example 2

[0081] A pressurized carbonization process for improving the performance of carbon paper for a gas diffusion layer comprises the following steps:

[0082] a. preparing carbon fiber base paper by wet forming of chopped carbon fibers, and then impregnating the base paper with phenolic resin, and then molding and curing to prepare hot pressed paper;

[0083] b. Place the hot pressed paper in a pressure device and fix it, covering 8 graphite sheets, generating a total pressure of 5000Pa;

[0084] c. Place the pressure device with hot pressing paper prepared in step b into a medium frequency induction furnace, evacuate the furnace, pass N2, repeat 3 times, form a non-oxidizing gas atmosphere in the furnace, and complete the preparation of carbonization reaction conditions.

[0085] d. Using the medium frequency induction furnace prepared in step c for the carbonization reaction conditions, the hot pressed paper was heated (heating rate of 25°C / min) to 2000°C and kept warm for 1h, and then cooled naturally after the end of the insulation; Figure 5 A schematic diagram of applying pressure to hot-pressed paper during carbonization in Example 2;

[0086] e. Remove the pressure from the carbon paper that has been carbonized in step d to obtain a finished product.

[0087] Test analysis:

[0088] The carbon paper product prepared in this embodiment was used as a sample to test the electrical and mechanical properties. The obtained plane resistivity was 10.56 mΩ·cm, the bending strength was 20.63 MPa, the tensile strength was 19.36 MPa, Figure 2 This is an electron microscope picture of the sample after carbonization in this embodiment. This embodiment prepares a carbon paper product with good conductivity and high mechanical strength. In this embodiment, a certain pressure is applied during the carbonization process to reduce the generation of surface cracks, which is beneficial to improve the direct interface bonding strength between carbon fiber and resin carbon, making the structure more compact.

[0089] Example 3

[0090] A pressurized carbonization process for improving the performance of carbon paper for a gas diffusion layer comprises the following steps:

[0091] a. preparing carbon fiber base paper by wet forming of chopped carbon fibers, and then impregnating the base paper with phenolic resin, and then molding and curing to prepare hot pressed paper;

[0092] b. Place the hot pressing paper in a pressure device and fix it, covering 3 graphite sheets, and generating a total pressure of 1800Pa; c. Place the pressure device with the hot pressing paper prepared in step b into a medium frequency induction furnace, evacuate the inside of the furnace, pass N2, repeat 3 times, so that a non-oxidizing gas atmosphere is formed in the furnace, and the preparation of carbonization reaction conditions is completed.

[0093] d. Using the medium frequency induction furnace prepared in step c for the carbonization reaction conditions, the hot pressed paper was heated (heating rate of 35°C / min) to 1900°C and kept warm for 45min, and then cooled naturally after the end of the insulation; Figure 6 A schematic diagram of applying pressure to hot pressed paper during carbonization in Example 3;

[0094] e. Remove the pressure from the carbon paper that has been carbonized in step d to obtain a finished product.

[0095] Test analysis:

[0096] The carbon paper product prepared in this embodiment was used as a sample to test the electrical and mechanical properties. The obtained plane resistivity was 12.01 mΩ·cm, the bending strength was 18.97 MPa, the tensile strength was 18.01 MPa, Figure 3 This is an electron microscope picture of the sample after carbonization in this embodiment. This embodiment prepares a carbon paper product with good conductivity and high mechanical strength. In this embodiment, a certain pressure is applied during the carbonization process to reduce the generation of surface cracks, which is beneficial to improve the direct interface bonding strength between carbon fiber and resin carbon, making the structure more compact.

[0097] Comparative Example 1

[0098] A carbonization process of carbon paper comprises the following steps:

[0099] a. preparing carbon fiber base paper by wet forming of chopped carbon fibers, and then impregnating the base paper with phenolic resin, and then molding and curing to prepare hot pressed paper;

[0100] b. The hot pressed paper prepared in step a is placed directly into a medium frequency induction furnace, the furnace is evacuated, N2 is passed, and repeated 3 times to form a non-oxidizing gas atmosphere in the furnace to complete the carbonization reaction conditions;

[0101] c. Using the medium frequency induction furnace prepared in step b for the carbonization reaction conditions, the hot pressed paper was heated (heating rate of 25°C / min) to 1800°C and kept warm for 0.5h, and then cooled naturally after the end of the insulation;

[0102] d. Take out the carbon paper that has completed the carbonization treatment in step c to obtain a finished product.

[0103] Test analysis:

[0104] The carbon paper product prepared in this comparative example was used as a sample to test electrical properties and mechanical properties. The obtained plane resistivity was 13.04 mΩ·cm, the bending strength was 16.92 MPa, and the tensile strength was 16.01 MPa. Figure 8 As shown, there are more cracks.

[0105] Comparative Example 2

[0106] A pressurized carbonization process for improving the performance of carbon paper for a gas diffusion layer comprises the following steps:

[0107] In step d, no heat preservation is performed, and the remaining steps are the same as those in Example 1.

[0108] The carbon paper product prepared in this comparative example was used as a sample to test electrical properties, mechanical properties, etc., and the obtained plane resistivity was 12.93 mΩ·cm, the bending strength was 17.52 MPa, and the tensile strength was 17.22 MPa.

[0109] Comparative Example 3

[0110] A pressurized carbonization process for improving the performance of carbon paper for a gas diffusion layer comprises the following steps:

[0111] In step d, the heating rate is 100° C. / min, and the remaining steps are consistent with Example 1.

[0112] The carbon paper product prepared in this comparative example was used as a sample to test electrical properties, mechanical properties, etc., and the obtained plane resistivity was 12.03 mΩ·cm, the bending strength was 19.05 MPa, and the tensile strength was 16.49 MPa.

[0113] Comparative Example 4

[0114] A pressurized carbonization process for improving the performance of carbon paper for a gas diffusion layer comprises the following steps:

[0115] In step d, the temperature is increased to 1500° C. at a heating rate of 25° C. / min, and the remaining steps are consistent with those in Example 1.

[0116] The finished carbon paper prepared in this comparative example was used as a sample to conduct tests on electrical properties, mechanical properties, etc. The plane resistivity was 20.21mΩ·cm, the flexural strength was 11.48MPa, and the tensile strength was 12.44MPa. In summary, the carbonization process of the present application, during the high-temperature carbonization process, effectively slows down the discharge of pyrolysis small molecule gases and reduces the cracking of resin carbon by applying a certain pressure to the hot-pressed paper, which is beneficial to improving the bonding strength of the interface between carbon fiber and resin carbon, making the structure more compact, thereby improving the electrical conductivity and mechanical properties of carbon paper. The carbon paper prepared under this process has excellent mechanical properties, good electrical conductivity, and is easy to prepare.

[0117] The above tests are based on GB / T20042.7-2014 Proton Exchange Membrane Fuel Cell Part 7: Carbon Paper Characteristics Test Method. Among them: the plane resistivity test instrument adopts a four-probe resistivity tester (HPS2661); the bending strength test instrument adopts a bending strength tester (RH-T300); the tensile strength test instrument adopts a tensile testing machine (RH-KZY (100N).

[0118] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A pressurized carbonization process for improving the performance of carbon paper for gas diffusion layer, characterized in that: The following steps are involved: Pressurizing the hot pressing paper under a preset pressure condition; The hot pressed paper under pressure is subjected to carbonization treatment; After the carbonization treatment is completed, carbon paper is obtained; The preset pressure condition is 300-5000pa; The target temperature of the carbonization treatment is 1800-2000°C, the carbonization treatment time is 3-4h, and the temperature is lowered after the heat preservation, and the cooling process is natural cooling; The preparation process of the hot pressed paper is to prepare carbon fiber base paper by wet molding of short chopped carbon fibers, and then impregnate the fiber base paper with phenolic resin, and then mold and cure to prepare the hot pressed paper.

2. The pressurized carbonization process according to claim 1, characterized in that: The pressurization treatment is performed in a pressurizing device.

3. The pressurized carbonization process according to claim 1, characterized in that: The carbonization treatment is carried out in a vacuum heating device.

4. The pressurized carbonization process according to claim 1, characterized in that: The carbonization treatment is carried out in an inert gas protective atmosphere.

5. The pressurized carbonization process according to claim 2, characterized in that: The pressurizing device comprises a bottom plate and a plurality of graphite sheets arranged on the bottom plate; During the pressurization process, the hot press paper is laid flat on the bottom plate, and a plurality of graphite sheets are used to fix and press the hot press paper, so that a preset pressure is generated on the hot press paper.

6. The pressurized carbonization process according to claim 5, characterized in that: The pressurizing device for pressurizing treatment is placed in a vacuum heating device for carbonization treatment.

7. The pressurized carbonization process according to claim 5, characterized in that: During the carbonization treatment, the temperature is raised to the target temperature at a rate of 25 to 50°C / min.

8. Carbon paper, characterized in that The carbon paper is prepared by the pressurized carbonization process according to any one of claims 1 to 7.

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