Resin crosslinking and setting carbon fiber conductive base paper for hydrogen fuel cell and preparation process thereof

Abstract

This invention relates to the interdisciplinary fields of carbon fiber and specialty papermaking, and particularly to a resin-crosslinked conductive carbon fiber base paper for hydrogen fuel cells and its preparation process. The preparation method first involves soaking aramid pulp A in deionized water; then, pitch-based carbon fiber B and aramid pulp are wet-formed to obtain carbon fiber paper; next, the pitch-based carbon fiber paper is impregnated with phenolic resin, dried, and finished to obtain pitch-based carbon fiber base paper; finally, the pitch-based carbon fiber base paper is placed in a tube furnace for heating and heat preservation to obtain carbon fiber conductive paper. This method solves the problem of simultaneously achieving high conductivity and high air permeability. It is a new method for preparing carbon fiber conductive paper using pitch-based carbon fiber as the skeleton, aramid pulp as the auxiliary forming fiber, and low-concentration phenolic resin impregnation and high-temperature carbonization for reinforcement.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of special papermaking and carbon fiber material preparation, specifically a resin cross-linked shaped carbon fiber conductive base paper for hydrogen fuel cells and its preparation process. Background Technology

[0002] Hydrogen fuel cells, as a highly efficient and clean energy conversion technology, directly convert the chemical energy of hydrogen and oxygen into electrical energy through an electrochemical reaction. They offer significant advantages such as high energy conversion efficiency, zero pollution, and quiet operation. Their working principle is based on the reverse reaction of water electrolysis. At the anode, hydrogen is oxidized into hydrogen ions and electrons; at the cathode, oxygen reacts with hydrogen ions and electrons to produce water, completing the electrical energy conversion. Hydrogen fuel cells have broad application prospects in transportation, distributed power generation, and energy storage. For example, hydrogen fuel cell vehicles are becoming an important direction for future automotive development due to their rapid refueling and long driving range. Key components include a proton exchange membrane, catalyst, gas diffusion layer, and bipolar plates. The gas diffusion layer plays a crucial role in supporting the catalyst layer, conducting gas, and removing reaction products, while also serving as an important carrier for current collection. However, due to the chemical corrosion of the working environment and high performance requirements, there are not many materials suitable for the gas diffusion layer of fuel cells. Carbon paper, however, has been successfully commercialized by international companies such as Toray Industries of Japan and SGL Carbon of Germany, possessing extremely high commercial potential and value.

[0003] Carbon paper is made from carbon fiber base paper through processes such as carbonization, graphitization, and hydrophobic treatment. The structure and properties of the carbon fiber base paper determine the quality of the final carbon paper. However, carbon fiber itself has the characteristics of strong interfacial inertness and high brittleness, making it difficult to prepare carbon fiber base paper with high conductivity and high air permeability.

[0004] To obtain carbon fiber base paper with high air permeability, researchers have successively used polyvinyl alcohol, phenolic resin, and other adhesives to bond carbon fibers, followed by high-temperature curing to obtain carbon fiber base paper. For example, US20180069245 successfully prepared flexible carbon fiber paper by using 15% polyvinyl alcohol to bond carbon fibers. CN202411510294.2 prepared carbon fiber paper for fuel cell gas diffusion layers through resin impregnation, hot pressing, and graphitization. US2006214320 obtained carbon paper with a deflection of 1.5–4.8 mm by mixing with cellulose and impregnating with phenolic resin. In addition, CN102465475A successfully prepared industrial high-temperature carbon fiber electric heating paper by mixing polyacrylonitrile-based carbon fibers with serpentine asbestos fibers and using a wet papermaking process. However, these methods still have problems with insufficient air permeability or the introduction of impurities. Summary of the Invention

[0005] To address the problem that the resin reinforcement process of traditional carbon fiber base paper is difficult to control precisely, resulting in a trade-off between air permeability and conductivity, this invention provides a resin cross-linked and shaped carbon fiber conductive base paper for hydrogen fuel cells and its preparation process. The paper uses pitch-based carbon fiber as the skeleton and aramid pulp as the auxiliary forming fiber. It is reinforced by impregnation with low-concentration phenolic resin and high-temperature carbonization to prepare carbon fiber conductive paper, thereby resolving the contradiction between conductivity and air permeability in carbon fiber paper.

[0006] This invention is achieved through the following technical solution:

[0007] A process for preparing resin-crosslinked shaped carbon fiber conductive base paper for hydrogen fuel cells includes the following steps:

[0008] S1, aramid pulp is shredded and soaked in deionized water to obtain aramid pulp soaking solution A, then PEO dispersant is added to disperse and obtain mixed system B;

[0009] S2, carbon fiber is added to the mixed system B for further decomposition, and carbon fiber paper E is obtained by wet forming;

[0010] S3, carbon fiber paper E is impregnated in phenolic resin dispersion F, and then dried and hot-pressed to obtain carbon fiber paper H;

[0011] S4. Carbon fiber paper H is carbonized under oxygen-free conditions to obtain carbon fiber conductive base paper.

[0012] Preferably, the requirements for aramid pulp are as follows: length 3–8 mm, diameter 7–8 μm, resistivity 1.5–2.0 μΩ·m, tensile strength 2.2–2.4 GPa, and elongation at break 0.25%–0.26%;

[0013] The concentration of the PEO dispersion is 5~6 g / L; the conductivity of the deionized water is (0.08~0.1) μS / cm.

[0014] Preferably, in S1, the ratio of aramid pulp B to water is 1.0-1.2g: 2L, and the soaking time of the aramid pulp is (6-8) hours or more;

[0015] The amount of PEO dispersant used is (1.5~2.0) wt% of the total oven-dry mass of carbon fiber and aramid pulp, and the rotation speed during disintegration is (10000~20000) rpm.

[0016] Preferably, the preparation method of carbon fiber paper E is as follows:

[0017] S21, add pitch-based carbon fiber to the mixed system B, mix evenly, and then disperse again to obtain mixed fiber slurry C;

[0018] S22, homogenize and dewater the mixed fiber pulp C to obtain a wet paper web D;

[0019] S23, wet paper web D is vacuum dried to obtain carbon fiber paper E.

[0020] Preferably, in S21, the ratio of the added pitch-based carbon fiber to the oven-dry mass of aramid pulp is (5~6):4, and the delamination speed is (5000~8000) rpm.

[0021] Preferably, in S23, during vacuum drying, the temperature is (95~120)℃, the time is (15~20)min, and the vacuum degree is (0.096-0.098)MPa.

[0022] Preferably, in S3, the phenolic resin dispersion F is prepared by dissolving phenolic resin powder in ethanol, wherein the solid content of the phenolic resin powder is (1~1.5)wt%;

[0023] During impregnation, the carbon fiber paper E is completely immersed in the phenolic resin dispersion F for (5~10) min;

[0024] During drying, the temperature is (95~110)℃ and the time is (1~1.5)h;

[0025] During hot pressing, the temperature is (140~160)℃, the pressure is (9~10)MPa, and the time is (5~8)min.

[0026] Preferably, in S4, during the carbonization process, the protective gas is argon or nitrogen, the heating rate is (8~10)℃ / min, the holding temperature is (700~1000)℃, and the holding time is (1~1.5)h.

[0027] A carbon fiber conductive base paper obtained by the aforementioned process for preparing cross-linked and shaped carbon fiber conductive base paper for hydrogen fuel cells, wherein the carbon fiber conductive base paper has an air permeability of 7635-8251 mL / min and a sheet resistance of less than 5Ω / □.

[0028] A hydrogen fuel cell that uses the aforementioned carbon fiber conductive paper as a gas diffusion layer.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] This invention discloses a process for preparing resin-crosslinked shaped carbon fiber conductive base paper for hydrogen fuel cells. The process uses pitch-based carbon fiber as the skeleton, aramid pulp as the auxiliary forming fiber, low-concentration phenolic resin impregnation, and high-temperature carbonization as reinforcement methods to prepare carbon fiber conductive paper with high air permeability, thus resolving the contradiction between conductivity and air permeability in carbon fiber paper.

[0031] Compared to publicly available process schemes, the raw material composition has been optimized first: on the one hand, aramid pulp fibers are introduced, and the good dispersibility of the aramid pulp after fibrillation improves the uniformity of the carbon fiber base paper and promotes fiber interweaving; on the other hand, a low-concentration phenolic resin is used for impregnation and bonding to avoid pore blockage. In this structure, the introduced aramid pulp raw material is composed of alternating benzene rings and amide bonds, with a high carbon content in its molecular structure. The introduced phenolic resin mainly consists of phenol and formaldehyde, with a high carbon content in its molecular structure. After carbonization, the carbon content is further increased, forming a richer conductive network between the original fiber interweaving network, which is conducive to obtaining paper with higher conductivity and improving the overall conductivity of the paper.

[0032] Meanwhile, the introduced aramid pulp, with its excellent flexibility and adhesion, can improve the flexibility and strength of the paper, effectively alleviating the brittleness and interfacial inertia of carbon fibers. It can also form a rich conductive network during carbonization, thus significantly improving the overall conductivity of the paper and successfully resolving the contradiction between the strength, toughness, and conductivity of carbon fibers. Furthermore, the ratio of aramid pulp was determined through long-term process optimization. If the aramid pulp content is too low, the improvement in paper uniformity will be insignificant, and the flexibility will be insufficient; if the content is too high, it will hinder resin impregnation and easily block the paper's pore structure.

[0033] Furthermore, this invention, by introducing aramid pulp as an aid, achieves bonding and reinforcement of the interlacing points between carbon fibers, between carbon fibers and aramid pulp, and between aramid pulp through impregnation with ultra-low concentration phenolic resin. The lower concentration of phenolic resin not only ensures sufficient fiber contact at points where it is insufficient, facilitating the construction of the conductive network after subsequent carbonization, but also avoids clogging the pores of the paper, ensuring its high air permeability. Simultaneously, it enables stress transfer during stretching, improving mechanical strength and ensuring the achievement of the paper's performance.

[0034] Furthermore, the preferred aramid pulp terminal groups in this invention contain abundant amino groups, which have good compatibility and self-bonding ability with phenolic resin, ensuring high efficiency at low concentrations. The principle is that the aramid pulp terminal groups and the resin can form extensive hydrogen bond bonds, and the curing of phenolic resin can crosslink the aramid pulp filaments. Therefore, the two achieve a high-strength bond through a combination of chemical and physical processes.

[0035] Furthermore, this invention incorporates a high-temperature carbonization process. This is because, where the raw material fibers have insufficient contact, the penetrated, bonded, and cured phenolic resin forms a dense network. High-temperature carbonization allows for the construction of a richer conductive network, thereby improving the overall conductivity of the carbon fiber paper. The heating rate is limited because excessively rapid heating causes the O and N groups of the phenolic resin to volatilize quickly, carrying away some C atoms and reducing the residual carbon content, which is detrimental to the construction of conductive pathways. The holding temperature is limited to ensure the conductivity of the finished paper. Excessively high temperatures are not energy-efficient, while excessively low temperatures result in insufficient carbonization, making it difficult to form a carbon element conductive network and thus hindering the efficient improvement of the carbon fiber paper's conductivity.

[0036] This invention discloses a carbon fiber conductive base paper suitable for the gas diffusion layer of hydrogen fuel cells. Its main functions include charge collection, aeration, and water conduction. In terms of charge collection, its excellent conductivity and low contact resistance efficiently transfer electrons generated by the electrode reaction to the external circuit, thereby reducing the battery's internal resistance and improving its energy conversion efficiency. Regarding aeration, its porous structure provides an efficient transport channel for the reactant gases, ensuring that hydrogen and oxygen can reach the catalyst layer uniformly and rapidly, promoting the smooth progress of the electrochemical reaction. The water conduction function allows for the timely drainage of water generated by the electrochemical reaction, preventing flooding, avoiding obstruction of gas diffusion and electrode reactions, and ensuring stable battery operation. The combined effect of these functions contributes to improving the performance and lifespan of the hydrogen fuel cell. Attached Figure Description

[0037] Figure 1 This is a flowchart of a process for preparing resin-crosslinked shaped carbon fiber conductive base paper for hydrogen fuel cells according to the present invention.

[0038] Figure 2 This is a surface SEM image of the carbon fiber base paper in Example 2.

[0039] Figure 3 This is a SEM image of the surface of the resin-impregnated carbon fiber paper in Example 3.

[0040] Figure 4 This is a SEM image of the surface of the carbonized carbon fiber conductive paper in Example 4. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0042] This invention discloses a resin-crosslinked shaped carbon fiber conductive base paper for hydrogen fuel cells and its preparation process, referring to... Figure 1 This includes the following steps:

[0043] S1. Select aramid pulp with a length of 3–8 mm, a diameter of 7–8 μm, a resistivity of 1.5–2.0 μΩ·m, a tensile strength of 2.2–2.4 GPa, and an elongation at break of 0.25%–0.26%. Soak the pulp in deionized water for 6–8 hours to obtain aramid pulp soaking solution A. The conductivity of the deionized water is (0.08–0.1) μS / cm, and the ratio of aramid pulp B to water is 1.0–1.2 g: 2 L.

[0044] Then, 8-10 mL of PEO dispersion with a concentration of 5-6 g / L was added to the aramid pulp soaking solution A, and the mixture was decomposed using a fiber dissociator at 10,000-20,000 rpm to obtain mixed system B.

[0045] S2, carbon fibers are added to the mixed system B for further decomposition, and carbon fiber paper E is obtained through wet forming. Specifically:

[0046] S21. Select pitch-based carbon fibers with a length of 7 mm, a diameter of 13 μm, a resistivity of 2.0 μΩ·m, a tensile strength of 2.3 GPa, and an elongation at break of 0.25%. Add pitch-based carbon fibers to aramid pulp at an oven-dry mass ratio of 5~6:4. Add the mixture to the aramid pulp suspension and disperse it evenly at 5000~8000 rpm to obtain mixed fiber pulp C.

[0047] S22, the mixed fiber pulp C is poured into the paper forming machine to form a wet paper web D.

[0048] S23, wet paper web D is vacuum dried to obtain carbon fiber paper E. Specifically, wool felt is laid on both sides to absorb moisture, and then vacuum dried in a paper dryer at 95~120℃ for 15~20 minutes to obtain carbon fiber paper E.

[0049] S3, carbon fiber paper E is impregnated in phenolic resin dispersion F, and then dried and hot-pressed to obtain carbon fiber paper H.

[0050] In this process, 5g of phenolic resin powder is dissolved in 500-600ml of anhydrous ethanol to obtain phenolic resin dispersion F.

[0051] Carbon fiber paper E is impregnated in phenolic resin dispersion F for 5-10 min, and then dried in an oven at 95-110℃ for 1-1.5 h to obtain phenolic resin impregnated carbon fiber paper G; then the prepared resin impregnated carbon fiber paper G is hot-pressed on a flat vulcanizing machine at 140-160℃ and 9-10MPa for 5-8 min to obtain carbon fiber paper H.

[0052] S4. Carbon fiber paper H is carbonized under oxygen-free conditions to obtain carbon fiber conductive base paper. Specifically, carbon fiber paper H is cut into small squares with a side length of 2~5cm, and argon or nitrogen gas is introduced into a tube furnace. The heating rate is controlled at 8~10℃ / min, and the temperature is raised to 700~1000℃ and held for 1~1.5h to obtain carbon fiber conductive paper.

[0053] This invention discloses a process for preparing resin-crosslinked carbon fiber conductive base paper for hydrogen fuel cells. This process involves soaking aramid pulp in deionized water, wet forming of mixed pulp, resin impregnation and strengthening, hot pressing finishing, and high-temperature carbonization to prepare carbon fiber conductive paper with high air permeability. By using aramid pulp to assist in interlacing, low-concentration resin strengthening, and high-temperature carbonization, the problem of simultaneously achieving high conductivity and high air permeability is solved.

[0054] The process scheme of this invention uses conventional equipment such as a descaling machine, paper forming device, dryer, hot press, and tube furnace. The solvents are tap water and ethanol, making the process environmentally friendly. This lays a solid foundation for the industrialization and large-scale production of this technology and gives it a high competitive advantage in the market. The descaling speed of the pulp, the fiber addition sequence, the drying temperature, the hot pressing finishing temperature, the hot pressing finishing pressure, and the holding temperature during the carbonization process are all the result of process optimization. For example, the pulp descaling speed ensures no breakage under high dispersion, the drying temperature ensures energy savings under high efficiency, the finishing temperature ensures no rheological blockage during phenolic resin curing, and the holding temperature during the carbonization process ensures the construction of the conductive network. These are all the result of long-term process optimization, and the technical effect is improved paper quality and energy savings.

[0055] The present invention also discloses a carbon fiber conductive paper obtained by cross-linking carbon fiber conductive base paper for hydrogen fuel cells and its preparation process. The carbon fiber conductive base paper has an air permeability of 7635-8251 mL / min and a sheet resistance of less than 5Ω / □.

[0056] The present invention also discloses a hydrogen fuel cell that uses carbon fiber conductive paper as a gas diffusion layer.

[0057] Example 1

[0058] S1, Tear the aramid pulp into pieces, add deionized water to soak, and obtain aramid pulp soaking solution A. Disperse the soaking solution, add 10 mL of PEO dispersion with a concentration of 5 g / L, and dissolve to obtain mixed system B.

[0059] S2, select pitch-based carbon fiber with a length of 7 mm, a diameter of 13 μm, a resistivity of 2.0 μΩ·m, a tensile strength of 2.3 GPa, and an elongation at break of 0.25%, add pitch-based carbon fiber to aramid pulp at an oven-dry mass ratio of 6:4, add it to the aramid pulp suspension and disperse it evenly at 5000 rpm to obtain mixed fiber pulp C;

[0060] The mixed fiber pulp C is poured into a paper forming machine to form a wet paper web D.

[0061] Wool felt is laid on both sides to absorb moisture, and then vacuum dried at 120°C for 20 minutes in a paper dryer to obtain carbon fiber paper E.

[0062] S3, Dissolve 5g of phenolic resin powder in 600ml of anhydrous ethanol to obtain phenolic resin dispersion F;

[0063] The prepared carbon fiber paper E was impregnated in phenolic resin dispersion F for 10 min, and then placed in an oven to dry at 105℃ for 1 h to obtain phenolic resin impregnated carbon fiber paper G.

[0064] The prepared resin-impregnated carbon fiber paper G was hot-pressed at 150°C and 10MPa for 5 minutes on a flat vulcanizing machine to obtain carbon fiber paper H.

[0065] S4. Cut the carbon fiber paper H into small squares with a side length of 3cm, put them into a tube furnace, introduce argon gas for protection, control the heating rate at 10℃ / min, heat to 700℃ and hold for 1h to obtain carbon fiber conductive paper.

[0066] The carbon fiber conductive paper prepared in this embodiment has a basis weight of 90 g / m³. 2 It has a thickness of 0.156 mm, an air permeability of 7635 mL / min, and a sheet resistance of 15.19 Ω / □, exhibiting high air permeability and high conductivity.

[0067] Example 2

[0068] S1, Tear the aramid pulp into pieces, add deionized water to soak, and obtain aramid pulp soaking solution A. Disperse the soaking solution, add 10 mL of PEO dispersion with a concentration of 5 g / L, and dissolve to obtain mixed system B.

[0069] S2, select pitch-based carbon fiber with a length of 7 mm, a diameter of 13 μm, a resistivity of 2.0 μΩ·m, a tensile strength of 2.3 GPa, and an elongation at break of 0.25%, add pitch-based carbon fiber to aramid pulp at an oven-dry mass ratio of 6:4, add it to the aramid pulp suspension and disperse it evenly at 5000 rpm to obtain mixed fiber pulp C;

[0070] The mixed fiber pulp C is poured into a paper forming machine to form a wet paper web D.

[0071] Wool felt is laid on both sides to absorb moisture, and then vacuum dried at 120°C for 20 minutes in a paper dryer to obtain carbon fiber paper E.

[0072] S3, Dissolve 5g of phenolic resin powder in 600ml of anhydrous ethanol to obtain phenolic resin dispersion F;

[0073] The prepared carbon fiber paper E was impregnated in phenolic resin dispersion F for 10 min, and then placed in an oven to dry at 105℃ for 1 h to obtain phenolic resin impregnated carbon fiber paper G.

[0074] The prepared resin-impregnated carbon fiber paper G was hot-pressed at 150°C and 10MPa for 5 minutes on a flat vulcanizing machine to obtain carbon fiber paper H.

[0075] S4. Cut the carbon fiber paper H into small squares with a side length of 3cm, put them into a tube furnace, introduce argon gas for protection, control the heating rate to be 10℃ / min, heat to 800℃ and hold for 1h to obtain carbon fiber conductive paper.

[0076] The carbon fiber conductive paper prepared in this embodiment has a basis weight of 90 g / m³. 2 With a thickness of 0.149 mm, an air permeability of 8003 mL / min, and a sheet resistance of 4.91 Ω / □, it exhibits high air permeability and high electrical conductivity; (Refer to...) Figure 2 The carbon fiber and aramid pulp are interwoven and have abundant pores.

[0077] Example 3

[0078] S1, Tear the aramid pulp into pieces, add deionized water to soak, and obtain aramid pulp soaking solution A. Disperse the soaking solution, add 10 mL of PEO dispersion with a concentration of 5 g / L, and dissolve to obtain mixed system B.

[0079] S2, select pitch-based carbon fiber with a length of 7 mm, a diameter of 13 μm, a resistivity of 2.0 μΩ·m, a tensile strength of 2.3 GPa, and an elongation at break of 0.25%, add pitch-based carbon fiber to aramid pulp at an oven-dry mass ratio of 6:4, add it to the aramid pulp suspension and disperse it evenly at 5000 rpm to obtain mixed fiber pulp C;

[0080] The mixed fiber pulp C is poured into a paper forming machine to form a wet paper web D.

[0081] Wool felt is laid on both sides to absorb moisture, and then vacuum dried at 120°C for 20 minutes in a paper dryer to obtain carbon fiber paper E.

[0082] S3, Dissolve 5g of phenolic resin powder in 600ml of anhydrous ethanol to obtain phenolic resin dispersion F;

[0083] The prepared carbon fiber paper E was impregnated in phenolic resin dispersion F for 10 min, and then placed in an oven to dry at 105℃ for 1 h to obtain phenolic resin impregnated carbon fiber paper G.

[0084] The prepared resin-impregnated carbon fiber paper G was hot-pressed at 150°C and 10MPa for 5 minutes on a flat vulcanizing machine to obtain carbon fiber paper H.

[0085] S4. Cut the carbon fiber paper H into small squares with a side length of 3cm, put them into a tube furnace, introduce argon gas for protection, control the heating rate to be 10℃ / min, heat to 900℃ and hold for 1h to obtain carbon fiber conductive paper.

[0086] The carbon fiber conductive paper prepared in this embodiment has a basis weight of 90 g / m³. 2 It has a thickness of 0.155 mm, an air permeability of 8251 mL / min, and a sheet resistance of 3.11 Ω / □, exhibiting high air permeability and high conductivity. (Reference) Figure 3 The carbon fiber and aramid pulp form an interwoven network with gas channels in the middle, which explains the high air permeability.

[0087] Example 4

[0088] S1, Tear the aramid pulp into pieces, add deionized water to soak, and obtain aramid pulp soaking solution A. Disperse the soaking solution, add 10 mL of PEO dispersion with a concentration of 5 g / L, and dissolve to obtain mixed system B.

[0089] S2, select pitch-based carbon fiber with a length of 7 mm, a diameter of 13 μm, a resistivity of 2.0 μΩ·m, a tensile strength of 2.3 GPa, and an elongation at break of 0.25%, add pitch-based carbon fiber to aramid pulp at an oven-dry mass ratio of 6:4, add it to the aramid pulp suspension and disperse it evenly at 5000 rpm to obtain mixed fiber pulp C;

[0090] The mixed fiber pulp C is poured into a paper forming machine to form a wet paper web D.

[0091] Wool felt is laid on both sides to absorb moisture, and then vacuum dried at 120°C for 20 minutes in a paper dryer to obtain carbon fiber paper E.

[0092] S3, Dissolve 5g of phenolic resin powder in 600ml of anhydrous ethanol to obtain phenolic resin dispersion F;

[0093] The prepared carbon fiber paper E was impregnated in phenolic resin dispersion F for 10 min, and then placed in an oven to dry at 105℃ for 1 h to obtain phenolic resin impregnated carbon fiber paper G.

[0094] The prepared resin-impregnated carbon fiber paper G was hot-pressed at 150°C and 10MPa for 5 minutes on a flat vulcanizing machine to obtain carbon fiber paper H.

[0095] S4. Cut the carbon fiber paper H into small squares with a side length of 3cm, put them into a tube furnace, introduce argon gas for protection, control the heating rate at 10℃ / min, heat to 1000℃ and hold for 1h to obtain carbon fiber conductive paper.

[0096] The carbon fiber conductive paper prepared in this embodiment has a basis weight of 90 g / m³. 2 It has a thickness of 0.151 mm, an air permeability of 7856 mL / min, and a sheet resistance of 2.38 Ω / □, exhibiting high air permeability and high electrical conductivity. (Reference) Figure 4 After the phenolic resin is carbonized, a richer conductive network is formed between the original interwoven fiber network, making the conductive path richer and the conductivity higher, which explains the reason why the prepared carbon fiber conductive paper has a low sheet resistance.

[0097] Example 5

[0098] S1, Tear the aramid pulp into pieces, add deionized water to soak, and obtain aramid pulp soaking solution A. Disperse the soaking solution, add 10 mL of PEO dispersion with a concentration of 5 g / L, and dissolve to obtain mixed system B.

[0099] S2, select pitch-based carbon fiber with a length of 7 mm, a diameter of 13 μm, a resistivity of 2.0 μΩ·m, a tensile strength of 2.3 GPa, and an elongation at break of 0.25%, add pitch-based carbon fiber to aramid pulp at an oven-dry mass ratio of 6:4, add it to the aramid pulp suspension and disperse it evenly at 5000 rpm to obtain mixed fiber pulp C;

[0100] The mixed fiber pulp C is poured into a paper forming machine to form a wet paper web D.

[0101] Wool felt is laid on both sides to absorb moisture, and then vacuum dried at 120°C for 20 minutes in a paper dryer to obtain carbon fiber paper E.

[0102] S3, Dissolve 5g of phenolic resin powder in 600ml of anhydrous ethanol to obtain phenolic resin dispersion F;

[0103] The prepared carbon fiber paper E was impregnated in phenolic resin dispersion F for 10 min, and then placed in an oven to dry at 105℃ for 1 h to obtain phenolic resin impregnated carbon fiber paper G.

[0104] The prepared resin-impregnated carbon fiber paper G was hot-pressed at 150°C and 10MPa for 5 minutes on a flat vulcanizing machine to obtain carbon fiber paper H.

[0105] S4. Cut the carbon fiber paper H into small squares with a side length of 3cm, put them into a tube furnace, introduce argon gas for protection, control the heating rate to be 10℃ / min, heat to 1100℃ and hold for 1h to obtain carbon fiber conductive paper.

[0106] The carbon fiber conductive paper prepared in this embodiment has a basis weight of 90 g / m³. 2 It has a thickness of 0.153 mm, an air permeability of 8159 mL / min, and a sheet resistance of 1.86 Ω / □, exhibiting high air permeability and high conductivity.

[0107] Table 1 Technical parameters of carbon fiber base paper prepared in Examples 1-4

[0108]

[0109] Table 1 shows the technical parameters of the carbon fiber base paper prepared in the examples. Data analysis shows that the air permeability of the carbon fiber base paper prepared by the process route provided by the present invention can reach the range of 7635-8251 mL / min, which is a relatively high level. This is because the pitch-based carbon fiber and aramid pulp are fully interwoven, but the high porosity is retained. The sheet resistance of the carbon fiber conductive paper obtained by carbonization in Examples 2-5 is less than 5Ω / □, which achieves high conductivity. This is because the high temperature carbonizes the aramid pulp and phenolic resin, forming a rich conductive network on the basis of the base paper, which enhances the conductivity of the carbon fiber paper.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A process for preparing resin-crosslinked shaped carbon fiber conductive base paper for hydrogen fuel cells, characterized in that, Includes the following steps: S1, aramid pulp is shredded and soaked in deionized water to obtain aramid pulp soaking solution A, then PEO dispersant is added to disperse and obtain mixed system B; The relevant requirements for aramid pulp are as follows: length 3–8 mm, diameter 7–8 μm, resistivity 1.5–2.0 μΩ·m, tensile strength 2.2–2.4 GPa, and elongation at break 0.25%–0.26%; The concentration of the PEO dispersion is 5~6 g / L; the conductivity of the deionized water is (0.08~0.1) μS / cm; S2, carbon fiber is added to the mixed system B for further decomposition, and carbon fiber paper E is obtained by wet forming; The preparation method of carbon fiber paper E is as follows: S21, add pitch-based carbon fiber to the mixed system B, mix evenly and then disperse again to obtain mixed fiber slurry C; the ratio of the added pitch-based carbon fiber to the oven-dry mass of aramid slurry is (5~6):

4. S22, homogenize and dewater the mixed fiber pulp C to obtain a wet paper web D; S23, wet paper web D is vacuum dried to obtain carbon fiber paper E; S3, carbon fiber paper E is impregnated in phenolic resin dispersion F, and then dried and hot-pressed to obtain carbon fiber paper H; phenolic resin dispersion F is prepared by dissolving phenolic resin powder in ethanol, wherein the solid content of phenolic resin powder is (1~1.5)wt% S4. Carbon fiber paper H is carbonized under oxygen-free conditions to obtain carbon fiber conductive base paper with a sheet resistance of less than 5Ω / □.

2. The process for preparing resin-crosslinked shaped carbon fiber conductive base paper for hydrogen fuel cells according to claim 1, characterized in that, In S1, the ratio of aramid pulp B to water is 1.0-1.2g: 2L, and the soaking time of the aramid pulp is (6-8) hours or more; The amount of PEO dispersant used is (1.5~2.0) wt% of the total oven-dry mass of carbon fiber and aramid pulp, and the rotation speed during disintegration is (10000~20000) rpm.

3. The process for preparing resin-crosslinked shaped carbon fiber conductive base paper for hydrogen fuel cells according to claim 1, characterized in that, In S21, the dewatering speed is (5000~8000) rpm.

4. The process for preparing resin-crosslinked shaped carbon fiber conductive base paper for hydrogen fuel cells according to claim 1, characterized in that, In S23, during vacuum drying, the temperature is (95~120)℃, the time is (15~20)min, and the vacuum degree is (0.096-0.098)MPa.

5. The process for preparing resin-crosslinked shaped carbon fiber conductive base paper for hydrogen fuel cells according to claim 1, characterized in that, In S3, during impregnation, the carbon fiber paper E is completely immersed in the phenolic resin dispersion F for (5~10) min. During drying, the temperature is (95~110)℃ and the time is (1~1.5)h; During hot pressing, the temperature is (140~160)℃, the pressure is (9~10)MPa, and the time is (5~8)min.

6. The process for preparing resin-crosslinked shaped carbon fiber conductive base paper for hydrogen fuel cells according to claim 1, characterized in that, In S4, during carbonization, the protective gas is argon or nitrogen, the heating rate is (8~10)℃ / min, the holding temperature is (700~1000)℃, and the holding time is (1~1.5)h.

7. A carbon fiber conductive base paper obtained by the resin crosslinking and shaping carbon fiber conductive base paper preparation process for hydrogen fuel cells according to any one of claims 1 to 6, characterized in that, The air permeability of this carbon fiber conductive base paper is 7635–8251 mL / min.

8. A hydrogen fuel cell, characterized in that, The hydrogen fuel cell uses the carbon fiber conductive paper described in claim 7 as the gas diffusion layer.

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