Green preparation method of carbon fiber paper for gas diffusion layer of fuel cell and carbon fiber paper

Abstract

The invention discloses a green preparation method of carbon fiber paper for a gas diffusion layer of a fuel cell. The green preparation method comprises the following steps: placing carbon fiber body paper with certain gram weight in an overlapping manner according to a preset total gram; impregnating the carbon fiber raw paper in a mixed resin aqueous solution, taking out the carbon fiber raw paper, and precuring to obtain carbon fiber preformed paper; performing hot-pressing curing treatment on the carbon fiber preformed paper at high temperature to obtain carbon fiber hot-pressed paper; and carbonizing and graphitizing the carbon fiber hot-pressed paper at a preset temperature in a protective atmosphere for a preset time to obtain the carbon fiber paper. According to the green preparation method provided by the invention, water is taken as a solvent, water-soluble phenolic resin which is more environment-friendly than alcohol-soluble phenolic resin is taken as a resin matrix, and the performance of the carbon paper is improved by adding different types of water-soluble resin. The invention further discloses the corresponding carbon fiber paper.

Description

Technical Field

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

[0002] As a greener, lower-carbon, and clean energy with diverse application scenarios, hydrogen energy is gradually becoming one of the important media for the world's energy transformation and development. my country's "Medium- and Long-Term Plan for the Development of the Hydrogen Energy Industry from 2021 to 2035" clearly states that hydrogen energy is planned to be an important part of the future national new energy system and an important carrier for achieving green and low-carbon transformation. The hydrogen energy industry is also planned as a strategic emerging industry and a key development direction for future industries, which fully highlights the important position of hydrogen energy in my country's future energy transformation.

[0003] As an important field of hydrogen energy application, proton exchange membrane fuel cell (PEMFC) has received widespread attention from the public. Gas diffusion layer (GDL) is one of the core components of PEMFC, which is mainly composed of microporous layer and substrate layer. So far, carbon fiber paper is the most widely used GDL substrate material due to its mature preparation process, stable product performance, relatively low cost, and convenient post-processing.

[0004] Carbon fiber paper is a typical carbon / carbon composite material made of chopped carbon fiber as the main raw material through preforming, impregnation, hot pressing, carbonization and graphitization. Thermosetting phenolic resin is a commonly used impregnation material for carbon fiber paper because of its mature production process technology, good mechanical and heat resistance after curing, and high residual carbon content after carbonization. The fluidity and wettability of phenolic resin on carbon fiber play a decisive role in the impregnation effect, and a good impregnation effect can improve the pore filling efficiency of the resin in the carbon fiber network structure. Therefore, the viscosity of the resin solution required for impregnation is relatively low, and the concentration of phenolic resin used to prepare carbon fiber paper on the market is generally high. Therefore, thermosetting phenolic resin needs to be diluted with a large amount of organic solvents (ethanol, etc.) when used. These organic solvents will cause serious harm to the environment and human health, and are also flammable and explosive.

[0005] Environmental protection and energy conservation are two major driving forces that have greatly promoted the research and development of hydrogen fuel cells. As a key component of hydrogen fuel cells, the supply and demand of carbon fiber paper in the gas diffusion layer has formed an oligopolistic market. The current development status of carbon fiber paper in my country can no longer meet the supply demand of carbon fiber paper required for the development of domestic fuel cells. Therefore, it is an urgent task to realize the localization of high-performance, low-cost and environmentally friendly carbon fiber paper.

[0006] Water-soluble phenolic resin uses water as a diluent, which is safe and environmentally friendly. However, compared with ordinary alcohol-soluble phenolic resin, water-soluble phenolic resin-based carbon fiber paper is not tough enough, and it needs to be improved in order to better achieve the task of localizing high-performance, low-cost, green and environmentally friendly carbon fiber paper. Summary of the invention

[0007] Based on the above situation of the prior art, the present invention is committed to using water-soluble phenolic resin, which is more environmentally friendly than alcohol-soluble phenolic resin, and adjusting the resin properties by adding other different types of resins to improve the brittleness of carbon paper, thereby obtaining carbon paper with wider adaptability.

[0008] In order to achieve the above technical objectives, some embodiments of the present invention propose a green preparation method for carbon fiber paper for fuel cell gas diffusion layer, which includes the steps of: placing carbon fiber base paper of predetermined gram weight in overlapping layers according to predetermined total gram weight; immersing the carbon fiber base paper in a mixed resin aqueous solution, taking it out and pre-curing it in an oven for a predetermined time to obtain resin-attached carbon fiber preformed paper; placing the resin-attached carbon fiber preformed paper in a customized mold, performing hot pressing and curing treatment on a flat vulcanizer to obtain carbon fiber hot-pressed paper; carbonizing and graphitizing the carbon fiber hot-pressed paper at a predetermined temperature and protective atmosphere for a predetermined time to obtain the carbon fiber paper.

[0009] In some embodiments, the weight of the carbon fiber base paper ranges from 10 to 60 g / m 2 The total weight of the carbon fiber base paper is between 40 and 60 g / m 2 between.

[0010] In some embodiments, the mixed resin aqueous solution is a mixture of a water-soluble phenolic resin with a solid content of more than 70% and a water-soluble epoxy resin with a solid content of more than 50%; the concentration of the resin in the resin solution is 10% to 20%.

[0011] In some embodiments, the immersion time is 0.5 to 3 hours; the pre-curing temperature is 60 to 90° C., the time is 10 to 60 minutes, and the pre-curing method is hanging drying.

[0012] In some embodiments, the hot pressing curing process parameters are 5-11 MPa, temperature is 140-160° C., and hot pressing time is 1-2 h.

[0013] In some embodiments, the carbonization is carried out under the protection of an inert atmosphere at a temperature of 900-1200° C., a heating rate of 5-10° C. / min, and a heat preservation period of 2-4 hours.

[0014] In some embodiments, the graphitization is carried out under the protection of an inert atmosphere, with a heating rate of 5-10°C / min, a maximum temperature of 2000-2500°C, and a heat preservation time of 2-6h.

[0015] The present invention also provides a carbon fiber paper prepared by one of the above-mentioned preparation methods, wherein the gas permeability of the carbon fiber paper is 32000-42000 ml·mm / (cm 2 ·h·mmHg); the graphitization degree reaches 40~70%, the porosity is 60~81%, and the TP resistance value under 1MPa pressure is only 10~20mΩ·cm 2 , tensile strength is 3~15MPa, and elastic modulus is 800~1500MPa.

[0016] The beneficial effects of the present invention are as follows: the green preparation method provided by the present invention uses water as a solvent and a water-soluble phenolic resin that is more environmentally friendly than an alcohol-soluble phenolic resin as a resin matrix, and improves the performance of carbon paper by adding different types of water-soluble resins. Compared with the impregnation solution prepared by the alcohol-soluble phenolic resin, the water-based phenolic resin uses water as a diluent to reduce the amount of organic solvent used, thereby reducing the pollution to the environment and the harm to the health of production personnel during the production process of carbon fiber paper, which is in line with the current world's environmental protection and economic concepts; compared with the impregnation solution prepared only by the water-soluble phenolic resin, the addition of other types of water-soluble resins enables the prepared carbon fiber paper to have better performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a flow chart of a green preparation method of carbon fiber paper for a fuel cell gas diffusion layer according to the present application. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below through preferred embodiments. The following embodiments can enable those skilled in the art to understand the present invention more comprehensively, but do not limit the present invention in any way.

[0019] Unless otherwise defined, the unit symbols used in this document are g for gram, °C for degree Celsius, h for hour, kV for kilovolt, cm for centimeter, mL / min for milliliter per minute, and g / m 2 Indicates grams per square meter; cm 2 represents square centimeters; wt% represents weight percentage; ℃ / min represents degrees Celsius per minute; μm represents micrometers; MPa represents megapascals; mΩ·cm 2 It represents milliohm-cm2.

[0020] Gram weight, also known as surface density, is expressed in g / m 2 Therefore, the gram weight of the carbon fiber base paper is also called the surface density of the carbon fiber base paper, and the total gram weight of the laminate is also called the total surface density of the laminate.

[0021] The present invention proposes an environmentally friendly preparation method of carbon fiber paper for fuel cell gas diffusion layer, such as Figure 1 As shown, it includes the following steps: step S1: cutting carbon fiber base paper of a certain gram weight into suitable sizes and placing them in overlapping layers according to a certain total gram weight; step S2: immersing the carbon fiber base paper in a mixed resin aqueous solution, taking it out and pre-curing it in an oven for a period of time to obtain a preformed carbon fiber paper with resin attached; step S3: placing the preformed carbon fiber paper with resin attached in a customized mold, performing hot pressing curing treatment on a flat vulcanizer, and obtaining a carbon fiber hot-pressed paper; step S4: carbonizing and graphitizing the carbon fiber hot-pressed paper at a certain temperature and in a protective atmosphere for a period of time to obtain a carbon fiber paper.

[0022] The carbon fiber base paper has a gram weight range of 10-30 g / m 2 The total weight of the carbon fiber base paper is between 40 and 60 g / m 2 The mixed resin aqueous solution is a mixture of water-soluble phenolic resin (solid content is more than 70%) and water-soluble epoxy resin (solid content is more than 50%); the concentration of the resin in the resin solution is 10%~20%. The impregnation time is 10~60min; the pre-curing temperature is 60~90℃, the time is 10~60min, and the pre-curing method is hanging drying. The hot pressing curing process parameters are 5~11MPa, temperature is 140~160℃, and hot pressing time is 1~2h. The carbonization process is under the protection of an inert atmosphere with a temperature of 900~1200℃, a heating rate of 5~10℃ / min, and a heat preservation of 2~4h. The graphitization process is under the protection of an inert atmosphere with a heating rate of 5~10℃ / min, a maximum temperature of 2000~2500℃, and a heat preservation of 2~6h.

[0023] The present invention also provides carbon fiber paper prepared by the above-mentioned preparation method, wherein the gas permeability of the carbon fiber paper is 32000-42000 ml·mm / (cm 2 ·h·mmHg); the graphitization degree reaches 40~70%, the porosity is 60~81%, and the TP resistance value under 1MPa pressure is only 10~20mΩ·cm 2 , tensile strength is 3~15MPa, and elastic modulus is 800~1500MPa.

[0024] Example 1: Take 10g / m 2 The total weight of carbon fiber base paper is 40g / m 2The layers are stacked to obtain multi-layer carbon fiber base paper; water-soluble phenolic resin and water-soluble epoxy resin are prepared with deionized water to prepare a mixed solution with a total concentration of 12.5wt%; the multi-layer carbon fiber base paper is immersed in the resin solution for 0.5h, and after taking it out, it is pre-cured at 60℃ for 60min to obtain carbon fiber pre-cured paper; the carbon fiber pre-cured paper is pressed at a temperature of 160℃ and a pressure of 5MPa for 2h to obtain carbon fiber hot-pressed paper by the stacking hot pressing method; the carbon fiber hot-pressed paper is carbonized at a temperature of 900℃, a heating rate of 5℃ / min, and a heat preservation of 4h under the protection of an inert atmosphere to obtain carbon fiber carbonized paper; then the carbon fiber carbonized paper is graphitized under the protection of an inert atmosphere, a heating rate of 5℃ / min, a maximum temperature of 2000℃, and a heat preservation of 6h to obtain carbon fiber paper. The performance parameters of the carbon fiber paper obtained in Example 1 are 37832ml·mm / (cm 2 ·h·mmHg); the graphitization degree reached 56.51%, the porosity was 80.39%, and the TP resistance value under 1MPa pressure was only 18.2mΩ·cm 2 , tensile strength is 3.5MPa and elastic modulus is 879MPa.

[0025] Example 2: Take 10g / m 2 and 20g / m 2 The total weight of carbon fiber base paper is 40g / m 2 The layers are stacked to obtain multi-layer carbon fiber base paper; water-soluble phenolic resin and water-soluble epoxy resin are prepared with deionized water to form a mixed solution with a total concentration of 12.5wt%; the multi-layer carbon fiber base paper is immersed in the resin solution for 1 hour, and then pre-cured at 60°C for 60 minutes to obtain carbon fiber pre-cured paper; the carbon fiber pre-cured paper is pressed at a temperature of 160°C and a pressure of 6MPa for 2 hours by a stacking hot pressing method to obtain carbon fiber hot pressing paper; the carbon fiber hot pressing paper is carbonized at a temperature of 950°C, a heating rate of 5°C / min, and a heat preservation of 3.5 hours under the protection of an inert atmosphere to obtain carbon fiber carbonized paper; then the carbon fiber carbonized paper is placed under the protection of an inert atmosphere, the heating rate is 5°C / min, the maximum temperature is 2000°C, and the heat preservation is 5 hours, and graphitization treatment is performed to obtain carbon fiber paper. The performance parameters of the carbon fiber paper obtained in Example 2 are 37329ml·mm / (cm 2 ·h·mmHg); the graphitization degree reached 58.19%, the porosity was 74.51%, and the TP resistance value under 1MPa pressure was only 16.5mΩ·cm 2 , tensile strength is 5.6MPa and elastic modulus is 975MPa.

[0026] Example 3: Take 10g / m 2 and 30g / m 2 The total weight of carbon fiber base paper is 50g / m2 The layers are stacked to obtain multi-layer carbon fiber base paper; water-soluble phenolic resin and water-soluble epoxy resin are prepared with deionized water to prepare a mixed solution with a total concentration of 15wt%; the multi-layer carbon fiber base paper is immersed in the resin solution for 1.5 hours, and then pre-cured at 70°C for 30 minutes to obtain carbon fiber pre-cured paper; the carbon fiber pre-cured paper is pressed at a temperature of 150°C and a pressure of 7MPa for 1.5 hours by a stacking hot pressing method to obtain carbon fiber hot pressing paper; the carbon fiber hot pressing paper is carbonized at a temperature of 1000°C, a heating rate of 8°C / min, and a heat preservation of 3 hours under the protection of an inert atmosphere to obtain carbon fiber carbonized paper; then the carbon fiber carbonized paper is graphitized under the protection of an inert atmosphere, a heating rate of 8°C / min, a maximum temperature of 2500°C, and a heat preservation of 4 hours to obtain carbon fiber paper. The performance parameters of the carbon fiber paper obtained in Example 3 are 32134ml·mm / (cm 2 ·h·mmHg); the graphitization degree reached 57.43%, the porosity was 76.10%, and the TP resistance value under 1MPa pressure was only 13.5mΩ·cm 2 , tensile strength is 8.6MPa and elastic modulus is 1130MPa.

[0027] Example 4: Take 30g / m 2 The total weight of carbon fiber base paper is 60g / m 2 The layers are stacked to obtain multi-layer carbon fiber base paper; water-soluble phenolic resin and water-soluble epoxy resin are prepared with deionized water to prepare a mixed solution with a total concentration of 17.5wt%; the multi-layer carbon fiber base paper is immersed in the resin solution for 2 hours, and then pre-cured at 80°C for 20 minutes to obtain carbon fiber pre-cured paper; the carbon fiber pre-cured paper is pressed at a temperature of 140°C and a pressure of 9MPa for 1 hour by a stacking hot pressing method to obtain carbon fiber hot pressing paper; the carbon fiber hot pressing paper is carbonized at a temperature of 1100°C, a heating rate of 10°C / min, and a heat preservation of 2.5 hours under the protection of an inert atmosphere to obtain carbon fiber carbonized paper; then the carbon fiber carbonized paper is graphitized under the protection of an inert atmosphere, a heating rate of 10°C / min, a maximum temperature of 2500°C, and a heat preservation of 3 hours to obtain carbon fiber paper. The performance parameters of the carbon fiber paper obtained in Example 4 are 36412ml·mm / (cm 2 ·h·mmHg); the graphitization degree reached 59.53%, the porosity was 68.49%, and the TP resistance value under 1MPa pressure was only 15.8mΩ·cm 2 , tensile strength is 8.9MPa and elastic modulus is 1238MPa.

[0028] Example 5: Take 60g / m 2The carbon fiber base paper is made of 100 grams of weight; water-soluble phenolic resin and water-soluble epoxy resin are prepared into a mixed solution with a total concentration of 20wt% with deionized water; the carbon fiber base paper is immersed in the resin solution for 3 hours, and after taking it out, it is pre-cured at 90°C for 10 minutes to obtain carbon fiber pre-cured paper; the carbon fiber pre-cured paper is pressed at a temperature of 140°C and a pressure of 11MPa for 1 hour by a laminated hot pressing method to obtain carbon fiber hot pressing paper; the carbon fiber hot pressing paper is carbonized at a temperature of 1200°C, a heating rate of 10°C / min, and a heat preservation of 2 hours under the protection of an inert atmosphere to obtain carbon fiber carbonized paper; then the carbon fiber carbonized paper is graphitized under the protection of an inert atmosphere, a heating rate of 10°C / min, a maximum temperature of 2500°C, and a heat preservation of 2 hours to obtain carbon fiber paper. The performance parameters of the carbon fiber paper obtained in Example 5 are 41321ml·mm / (cm 2 ·h·mmHg); the graphitization degree reached 61.50%, the porosity was 74.31%, and the TP resistance value under 1MPa pressure was only 11.5mΩ·cm 2 , tensile strength is 12.4MPa, and elastic modulus is 1321MPa.

[0029] The above examples are summarized in Table 1: Table 1 Parameter (unit) Example 1 Example 2 Example 3 Example 4 Example 5 <![CDATA[The basis weight of the carbon fiber original paper (g / m 2 )]]> 10 10，20 10，30 30 60 Total surface density of laminate (g / m²) 40 40 50 60 60 Total concentration of resin solution (wt%) 10 12.5 15 17.5 20 Immersion time (h) 0.5 1 1.5 2 3 Pre-curing temperature (℃) 60 60 70 80 90 Pre-curing time (min) 60 60 30 20 10 Hot pressing pressure (MPa) 5 6 7 9 11 Hot pressing temperature (℃) 160 160 150 140 140 Hot pressing time (h) 2 2 1.5 1 1 Carbonization temperature (℃) 900 950 1000 1100 1200 Carbonization heating rate (℃ / min) 5 5 8 10 10 Carbonization holding time (h) 4 3.5 3 2.5 2 Graphitization heating rate (℃ / min) 5 5 8 10 10 Maximum graphitization temperature (℃) 2000 2000 2500 2500 2500 Graphitization holding time (h) 6 5 4 3 2 Air permeability [ml·mm / (cm²·h·mmHg)] 37832 37329 32134 36412 41321 Graphitization degree (%) 56.51 58.19 57.43 59.53 61.50 Porosity (%) 80.39 74.51 76.10 68.49 74.31 TP resistance value at 1MPa (mΩ·cm²) 18.2 16.5 13.5 15.8 11.5 Tensile strength (MPa) 3.5 5.6 8.6 8.9 12.4 Elastic modulus (MPa) 879 975 1130 1238 1321 Although the preferred embodiments of the present invention are described above, the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms of specific changes without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the scope of protection of the present invention.

Claims

1. A green preparation method of carbon fiber paper for fuel cell gas diffusion layer, characterized in that: Includes steps: Placing carbon fiber base paper of a certain gram weight in overlapping layers according to a predetermined total gram weight; The carbon fiber base paper is immersed in the mixed resin aqueous solution, and then taken out and pre-cured to obtain the carbon fiber preformed paper; The carbon fiber preformed paper is subjected to a hot pressing curing treatment at a high temperature to obtain a carbon fiber hot pressing paper; The carbon fiber hot-pressed paper is carbonized and graphitized for a predetermined time under a preset temperature and a protective atmosphere to obtain the carbon fiber paper.

2. The preparation method according to claim 1, characterized in that: The carbon fiber base paper has a gram weight range of 10-60 g / m 2 The total weight of the laminate is between 40 and 60 g / m 2 between.

3. The preparation method according to claim 1, characterized in that: The mixed resin aqueous solution is a mixed solution of a water-soluble epoxy resin with a solid content of more than 50% and a water-soluble phenolic resin with a solid content of more than 70%, and the concentration of the resin in the resin aqueous solution is 10% to 20%.

4. The preparation method according to claim 1, characterized in that: The immersion time is 0.5 to 3 hours; the pre-curing temperature is 60 to 90° C., the time is 10 to 60 minutes, and the pre-curing method is hanging drying.

5. The preparation method according to claim 1, characterized in that: The process parameters of the hot pressing curing treatment are 5-11 MPa, temperature 140-160° C., and hot pressing time 1-2 h.

6. The preparation method according to claim 1, characterized in that: The carbonization is carried out under the protection of an inert atmosphere at a temperature of 900-1200° C., a heating rate of 5-10° C. / min, and a heat preservation period of 2-4 hours.

7. The preparation method according to claim 1, characterized in that: The graphitization is carried out under the protection of an inert atmosphere, with a heating rate of 5-10°C / min, a maximum temperature of 2000-2500°C, and a heat preservation time of 2-6h.

8. The carbon fiber paper obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The gas permeability of the carbon fiber paper is 32000~42000ml·mm / (cm 2 ·h·mmHg); the graphitization degree reaches 40~70%, the porosity is 60~81%, and the TP resistance value under 1MPa pressure is 10~20mΩ·cm 2 , tensile strength is 3~15MPa, and elastic modulus is 800~1500MPa.

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