Carbon fiber paper and its preparation method and application

Abstract

The present invention belongs to the technical field of fuel cell gas diffusion layer. The present invention provides a carbon fiber paper and a preparation method thereof. Acrylonitrile-N-4-pyridyl-2-acrylamide copolymer and N,N-dimethylformamide are mixed to obtain an electrostatic spinning solution; the electrostatic spinning solution is electrostatically spun to obtain a polyacrylonitrile-based non-woven felt; the polyacrylonitrile-based non-woven felt is pre-oxidized to obtain a polyacrylonitrile-based pre-oxidized felt; the polyacrylonitrile-based pre-oxidized felt is impregnated in a resin solution and then dried, hot-pressed, carbonized, and graphitized to obtain carbon fiber paper. The present invention also provides the application of carbon fiber paper in the gas diffusion layer of a proton exchange membrane fuel cell. The present invention adopts electrostatic spinning technology to prepare polyacrylonitrile-based non-woven felts of different thicknesses, realizes ultra-thin and controllable preparation of the thickness of carbon fiber paper, and the carbon fiber paper of the present invention has excellent conductivity, so that it has a good effect in a proton exchange membrane fuel cell.

Description

Technical Field

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

[0002] Fuel cells are a type of electrochemical reaction device that converts chemical energy stored in fuel directly into electrical energy. They are not limited by the Carnot cycle effect and therefore have high efficiency. In addition, fuel cells use fuel and oxygen as raw materials and emit very few harmful gases. Among them, proton exchange membrane fuel cells (PEMFC) have the advantages of high energy density, fast response speed, clean and environmentally friendly, and are widely used in aerospace, mobile power generation, new energy vehicles and other fields. The main components of PEMFC are bipolar plates, gas diffusion layers, catalyst layers, and proton exchange membranes.

[0003] The gas diffusion layer plays a key role in supporting the catalyst layer, conducting current, and providing drainage channels and gas channels for electrode reactions. It is an important component that restricts the performance of fuel cells. Carbon paper has excellent conductivity, air permeability, corrosion resistance and mechanical strength, and is a commonly used gas diffusion layer substrate material.

[0004] The preparation process of carbon paper is complex and has high requirements. At present, most high-performance carbon paper in China is imported products, usually made of carbon fiber as raw material, and prepared by wet papermaking technology. However, carbon fiber is different from plant fiber. The surface of carbon fiber contains only a small amount of groups. It can only produce a cutting effect during the pulping process, and cannot produce a fibrillation phenomenon. It will not produce hydrogen bonds after the paper sheet is formed. The carbon fiber is difficult to disperse during the papermaking process, and the paper strength is low, which requires high forming. In addition, the diameter of the carbon fiber filament is large (≥7μm), and the thickness of the obtained carbon fiber paper is large (≥0.18mm), which is not conducive to electronic conduction. Therefore, how to simplify the process and solve the poor dispersion of fibers to prepare carbon paper with ultra-thin controllable thickness and excellent conductivity is the key to realizing the mass production and independent preparation of domestic high-performance carbon paper.

[0005] Therefore, the research on obtaining a carbon paper with ultra-thin controllable thickness, good conductivity, low molding requirements, simple process and low cost has important economic benefits and social significance. Summary of the invention

[0006] The purpose of the present invention is to provide a carbon fiber paper and a preparation method and application thereof in order to overcome the deficiencies of the prior art. The carbon fiber paper of the present invention has good electrical conductivity and ultra-thin thickness.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing carbon fiber paper, comprising the following steps:

[0009] 1) mixing acrylonitrile-N-4-pyridyl-2-acrylamide copolymer and N,N-dimethylformamide to obtain an electrospinning solution; electrospinning the electrospinning solution to obtain a polyacrylonitrile-based nonwoven felt;

[0010] 2) pre-oxidizing the polyacrylonitrile-based non-woven felt to obtain a polyacrylonitrile-based pre-oxidized felt;

[0011] 3) The polyacrylonitrile-based pre-oxidized felt is impregnated in a resin solution and then dried, hot-pressed, carbonized, and graphitized to obtain carbon fiber paper.

[0012] Preferably, in step 1), the mass ratio of the acrylonitrile-N-4-pyridyl-2-acrylamide copolymer to N,N-dimethylformamide is 1-2:8-9.

[0013] Preferably, the electrospinning flow rate in step 1) is 0.6-0.8 mL / h, and the thickness of the polyacrylonitrile-based nonwoven felt is 0.10-0.24 mm.

[0014] Preferably, the pre-oxidation treatment in step 2) is to pre-oxidize the polyacrylonitrile-based non-woven felt at 180-220° C. for 5-15 min, 270-300° C. for 30-90 min, and 310-340° C. for 20-40 min in sequence;

[0015] The heating rate from room temperature to 180-220°C is 2-8°C / min, the heating rate from 180-220°C to 270-300°C is 0.2-2°C / min, and the heating rate from 270-300°C to 310-340°C is 2-8°C / min.

[0016] Preferably, in step 3), the mass concentration of the resin solution is 8-20%, in which the resin is boron phenolic resin and the solvent is methanol and / or ethanol; and the immersion time is 10-40 minutes.

[0017] Preferably, in step 3), the drying temperature is 60-100° C., and the drying time is 20-60 min; the hot pressing curing temperature is 140-170° C., the hot pressing curing pressure is 5-10 MPa, and the hot pressing curing time is 10-40 min.

[0018] Preferably, in step 3), the carbonization temperature is 1000-1600° C., and the carbonization time is 3-15 min; the graphitization temperature is 1900-2800° C., and the graphitization time is 15-30 min;

[0019] The heating rate from room temperature to carbonization temperature and the heating rate from carbonization temperature to graphitization temperature are independently 2-8°C / min; the carbonization and graphitization are carried out in high-purity nitrogen.

[0020] The present invention also provides carbon fiber paper prepared by the preparation method, wherein the thickness of the carbon fiber paper is 0.05-0.10 mm, and the resistivity of the carbon fiber paper is 4-9 mΩ·cm.

[0021] The invention also provides application of the carbon fiber paper in a gas diffusion layer of a proton exchange membrane fuel cell.

[0022] The beneficial effects of the present invention include the following:

[0023] 1) The present invention adopts electrostatic spinning technology to prepare polyacrylonitrile-based non-woven felts of different thicknesses, and prepares carbon fiber papers of different thicknesses through pre-oxidation, resin impregnation, hot pressing curing, one-step carbonization and graphitization and other process flows, thereby achieving ultra-thin and controllable preparation of carbon fiber paper. The carbon fiber paper of the present invention has excellent conductivity, so that it has a good effect in proton exchange membrane fuel cells.

[0024] 2) The method of the present invention solves the problem of fiber dispersibility, and does not require dispersants and matching fibers and secondary carbonization and graphitization. It has low molding requirements, simple processes, low costs, and can achieve large-scale mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a microstructure diagram of the carbon fiber paper of Example 1;

[0026] Figure 2 This is the microstructure diagram of the carbon fiber paper of Comparative Example 1. DETAILED DESCRIPTION

[0027] The present invention provides a method for preparing carbon fiber paper, comprising the following steps:

[0028] 1) mixing acrylonitrile-N-4-pyridyl-2-acrylamide copolymer and N,N-dimethylformamide to obtain an electrospinning solution; electrospinning the electrospinning solution to obtain a polyacrylonitrile-based nonwoven felt;

[0029] 2) pre-oxidizing the polyacrylonitrile-based non-woven felt to obtain a polyacrylonitrile-based pre-oxidized felt;

[0030] 3) The polyacrylonitrile-based pre-oxidized felt is impregnated in a resin solution and then dried, hot-pressed, carbonized, and graphitized to obtain carbon fiber paper.

[0031] In the present invention, the preparation process of acrylonitrile-N-4-pyridyl-2-acrylamide copolymer is as follows: acrylonitrile, N-4-pyridyl-2-acrylamide, azobisisobutyronitrile and solvent are mixed to obtain a mixture, and the mixture is reacted under a nitrogen atmosphere and mechanical stirring; in the mixture, the total monomer concentration [M] is 20wt%, the concentration of azobisisobutyronitrile is 1.0wt%, and the mass ratio of acrylonitrile to N-4-pyridyl-2-acrylamide is 98:2; the reaction temperature is 57-63°C, the reaction time is 22-26h; the stirring rate is 100-140r / min; the reaction product is diluted with dimethyl sulfoxide, precipitated with methanol, filtered, washed and dried in sequence, and the mass ratio of the reaction product to dimethyl sulfoxide during dilution is 4-6:1; the washing reagent is deionized water; and the drying temperature is 60°C.

[0032] In the present invention, the mass ratio of the acrylonitrile-N-4-pyridyl-2-acrylamide copolymer and N,N-dimethylformamide in step 1) is preferably 1-2:8-9, more preferably 1.2-1.8:8.2-8.8, and more preferably 1.4-1.5:8.5-8.6.

[0033] In the present invention, the electrospinning flow rate of step 1) is preferably 0.6-0.8 mL / h, more preferably 0.65-0.75 mL / h, and more preferably 0.7 mL / h; the thickness of the polyacrylonitrile-based non-woven felt is preferably 0.10-0.24 mm, more preferably 0.12-0.22 mm, and more preferably 0.15-0.20 mm.

[0034] In the present invention, electrostatic spinning liquid is sprayed onto a roller to form fiber filaments, which are collected to obtain polyacrylonitrile-based nonwoven felt. The electrostatic spinning method of the present invention for preparing polyacrylonitrile-based nonwoven felt has low molding requirements, a simple process flow, does not require any auxiliary agent, does not generate waste liquid, has high fiber connection strength, has ultra-thin and controllable thickness, has low cost, and consumes little energy.

[0035] The spinning solution of the invention is sprayed out from the spinneret according to the set spinning flow rate, and the fiber filaments are sprayed on the roller rotating at a uniform speed, so that the spinning uniformity is ensured and the carbon fiber paper with uniform thickness is obtained.

[0036] In the present invention, the specific process of the pre-oxidation treatment in step 2) is preferably a first pre-oxidation, a second pre-oxidation, and a third pre-oxidation of the polyacrylonitrile-based non-woven felt in sequence, and the temperature of the first pre-oxidation is preferably 180-220°C, more preferably 190-210°C, and more preferably 195-205°C; the time of the first pre-oxidation is preferably 5-15min, more preferably 7-13min, and more preferably 9-11min; the temperature of the second pre-oxidation is preferably 270-300°C, more preferably 275-295°C, and more preferably 280-290°C; the time of the second pre-oxidation is preferably 30-90min, more preferably 40-80min, and more preferably 50-70min; the temperature of the third pre-oxidation is preferably 310-340°C, more preferably 315-330°C, and more preferably 320-325°C; the time of the third pre-oxidation is preferably 20-40min, more preferably 25-35min, and more preferably 28-32min.

[0037] In step 2) of the present invention, the heating rate from room temperature to 180-220°C is preferably 2-8°C / min, more preferably 3-7°C / min, and more preferably 4-6°C / min; the heating rate from 180-220°C to 270-300°C is preferably 0.2-2°C / min, more preferably 0.5-1.5°C / min, and more preferably 0.8-1.2°C / min; the heating rate from 270-300°C to 310-340°C is preferably 2-8°C / min, more preferably 3-7°C / min, and more preferably 4-6°C / min.

[0038] The pre-oxidation treatment of the present invention is carried out under air atmosphere.

[0039] In step 3) of the present invention, the mass concentration of the resin solution is preferably 8-20%, more preferably 9-15%, and more preferably 10-12%; in the resin solution, the resin is preferably boron phenolic resin, and the solvent is preferably methanol and / or ethanol; the immersion time is preferably 10-40 min, more preferably 15-35 min, and more preferably 20-30 min.

[0040] In the present invention, the resin solution is impregnated by vacuum impregnation or atmospheric pressure impregnation, preferably vacuum impregnation; the vacuum degree of vacuum impregnation is preferably 120-140Pa, more preferably 125-135Pa, and more preferably 130Pa.

[0041] The boron phenolic resin of the present invention is a boron phenolic resin prepared by a method known in the art; the boron phenolic resin can increase the connectivity between fibers and obtain a carbon fiber paper with good mechanical properties and conductive properties.

[0042] In the present invention, the drying temperature in step 3) is preferably 60-100°C, more preferably 70-90°C, and more preferably 75-85°C; the drying time is preferably 20-60 min, more preferably 30-50 min, and more preferably 35-45 min.

[0043] In the present invention, the temperature of the hot pressing curing in step 3) is preferably 140-170°C, more preferably 145-165°C, more preferably 150-160°C, the pressure of the hot pressing curing is preferably 5-10MPa, more preferably 6-9MPa, more preferably 7-8MPa; the time of the hot pressing curing is preferably 10-40min, more preferably 15-35min, more preferably 20-30min; the hot pressing curing is preferably carried out using a flat vulcanizing press.

[0044] In the present invention, the carbonization temperature in step 3) is preferably 1000-1600°C, more preferably 1200-1500°C, and more preferably 1300-1400°C; the carbonization time is preferably 3-15min, more preferably 5-12min, and more preferably 8-10min; the graphitization temperature is preferably 1900-2800°C, more preferably 2200-2600°C, and more preferably 2400-2500°C; the graphitization time is preferably 15-30min, more preferably 18-25min, and more preferably 20-22min.

[0045] In step 3) of the present invention, the heating rate from room temperature to the carbonization temperature and the heating rate from the carbonization temperature to the graphitization temperature are independently preferably 2 to 8°C / min, more preferably 3 to 7°C / min, and more preferably 4 to 6°C / min; the carbonization and graphitization are preferably carried out in high-purity nitrogen.

[0046] The carbonization and graphitization in step 3) of the present invention are preferably carried out in a multi-stage distributed program-controlled temperature tubular furnace for one-step carbonization and graphitization.

[0047] The invention also provides carbon fiber paper prepared by the preparation method.

[0048] The thickness of the carbon fiber paper of the present invention is 0.05-0.10 mm, preferably 0.06-0.09 mm, more preferably 0.07-0.08 mm; the resistivity of the carbon fiber paper is 4-9 mΩ·cm, preferably 5-8 mΩ·cm, more preferably 5.5-7 mΩ·cm.

[0049] The carbon fiber paper of the present invention is composed of a fiber network that is interlaced and randomly arranged, and a large number of pores are generated between the fibers, so that it has good air permeability; the carbonized resin filled between the fiber filaments plays a role in bonding the fibers to form a conductive path, so that it has good conductivity and mechanical strength.

[0050] The invention also provides application of the carbon fiber paper in a gas diffusion layer of a proton exchange membrane fuel cell.

[0051] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0052] The model of the multi-stage step-by-step program temperature-controlled tube furnace used in the embodiments and comparative examples is KSL-1700X-GS.

[0053] In the embodiment, the preparation process of acrylonitrile-N-4-pyridyl-2-acrylamide copolymer is as follows: acrylonitrile, N-4-pyridyl-2-acrylamide, azobisisobutyronitrile and a solvent are mixed to obtain a mixture, wherein acrylonitrile and N-4-pyridyl-2-acrylamide account for 20% of the mass of the mixture, azobisisobutyronitrile accounts for 1% of the mass of the mixture, and the mass ratio of acrylonitrile to N-4-pyridyl-2-acrylamide is 98:2; the mixture is reacted under a nitrogen atmosphere and mechanical stirring (stirring rate is 120r / min, reaction temperature is 60°C, reaction time is 24h); the reaction product is diluted with dimethyl sulfoxide in sequence (the mass ratio of the reaction product to dimethyl sulfoxide is 5:1), precipitated with methanol, filtered, washed, and dried at 60°C.

[0054] Example 1

[0055] 15g of acrylonitrile-N-4-pyridyl-2-acrylamide copolymer was dissolved in 85g of N,N-dimethylformamide to prepare an electrospinning solution with an acrylonitrile-N-4-pyridyl-2-acrylamide copolymer content of 15wt%. The electrospinning solution was sprayed onto a roller at a flow rate of 0.75mL / h to form fiber filaments, which were collected to obtain a polyacrylonitrile-based nonwoven felt with a thickness of 0.16mm.

[0056] The polyacrylonitrile-based non-woven felt was placed in a multi-stage step-by-step program temperature-controlled tubular furnace, and air was introduced at a flow rate of 0.5 L / min. The temperature was increased from room temperature to 200°C at a heating rate of 5°C / min, and kept warm for 10 minutes; then the temperature was increased from 200°C to 290°C at a heating rate of 1°C / min, and kept warm for 60 minutes; then the temperature was increased from 290°C to 320°C at a heating rate of 5°C / min, and kept warm for 30 minutes to obtain the polyacrylonitrile-based pre-oxidized felt.

[0057] The polyacrylonitrile-based preoxidized felt was placed in a methanol solution of boron phenolic resin (the mass fraction of boron phenolic resin in the solution was 10%) and impregnated for 30 minutes. The impregnation method was vacuum impregnation at 130Pa. After the impregnation of the polyacrylonitrile-based preoxidized felt, it was dried at 80°C in a blast drying oven for 30 minutes. Then, it was hot-pressed and cured using a flat vulcanizer. The hot-pressing curing temperature was 160°C, the time was 30 minutes, and the pressure was 7MPa. The hot-pressed polyacrylonitrile-based preoxidized felt was obtained. The hot-pressed polyacrylonitrile-based preoxidized felt was placed in a multi-stage step-by-step program temperature-controlled tubular furnace for one-step carbonization and graphitization treatment. The one-step carbonization and graphitization treatment process was as follows: in high-purity nitrogen, the temperature was raised from room temperature to 1300°C at a heating rate of 5°C / min and kept for 5 minutes for carbonization treatment; then the temperature was raised from 1300°C to 2500°C at a heating rate of 5°C / min and kept for 20 minutes for graphitization treatment to prepare carbon fiber paper.

[0058] The carbon fiber paper of this embodiment has a thickness of 0.08 mm and a resistivity of 6.8 mΩ·cm.

[0059] The microstructure of the carbon fiber paper of this embodiment is as follows Figure 1 As shown by Figure 1 It can be seen that the fibers inside the carbon fiber paper are intertwined and connected with each other, the fibers are tightly bonded together by resin carbon, the interface compatibility with resin carbon is good, and the pore structure is complete.

[0060] Example 2

[0061] The vacuum impregnation in Example 1 was changed to normal pressure impregnation, and the other conditions were the same as in Example 1.

[0062] The thickness of the carbon fiber paper in this embodiment is 0.08 mm, and the resistivity is 8.5 mΩ·cm.

[0063] Example 3

[0064] 12g of acrylonitrile-N-4-pyridyl-2-acrylamide copolymer was dissolved in 88g of N,N-dimethylformamide to prepare an electrospinning solution with an acrylonitrile-N-4-pyridyl-2-acrylamide copolymer content of 12wt%. The electrospinning solution was sprayed onto a roller at a flow rate of 0.65mL / h to form fiber filaments, which were collected to obtain a polyacrylonitrile-based nonwoven felt with a thickness of 0.2mm.

[0065] The polyacrylonitrile-based non-woven felt was placed in a multi-stage step-by-step program temperature-controlled tubular furnace, and air was introduced at a flow rate of 0.4 L / min. The temperature was increased from room temperature to 190°C at a heating rate of 3°C / min, and kept warm for 8 minutes; then the temperature was increased from 190°C to 280°C at a heating rate of 0.5°C / min, and kept warm for 40 minutes; then the temperature was increased from 280°C to 315°C at a heating rate of 3°C / min, and kept warm for 25 minutes to obtain the polyacrylonitrile-based pre-oxidized felt.

[0066] The polyacrylonitrile-based preoxidized felt is placed in an anhydrous ethanol solution of boron phenolic resin (the mass fraction of boron phenolic resin in the solution is 12%) and impregnated for 20 minutes. The impregnation method is vacuum impregnation under 125Pa. After the impregnation of the polyacrylonitrile-based preoxidized felt, it is dried at 60°C in a blast drying oven for 40 minutes. Then, it is hot-pressed and cured by a flat vulcanizer. The temperature of the hot-pressing curing is 150°C, the time is 35 minutes, and the pressure is 6MPa. The polyacrylonitrile-based preoxidized felt after hot-pressing curing is obtained. The hot-pressed polyacrylonitrile-based preoxidized felt is placed in a multi-stage step-by-step program temperature-controlled tubular furnace for one-step carbonization and graphitization treatment. The process of one-step carbonization and graphitization treatment is: in high-purity nitrogen, the temperature is increased from room temperature to 1200°C at a heating rate of 3°C / min and the temperature is kept for 10 minutes for carbonization treatment; then the temperature is increased from 1200°C to 2200°C at a heating rate of 3°C / min and the temperature is kept for 25 minutes for graphitization treatment to prepare carbon fiber paper.

[0067] The carbon fiber paper of this embodiment has a thickness of 0.07 mm and a resistivity of 7.2 mΩ·cm.

[0068] Example 4

[0069] 18g of acrylonitrile-N-4-pyridyl-2-acrylamide copolymer was dissolved in 82g of N,N-dimethylformamide to prepare an electrospinning solution with an acrylonitrile-N-4-pyridyl-2-acrylamide copolymer content of 18wt%. The electrospinning solution was sprayed onto a roller at a flow rate of 0.7mL / h to form fiber filaments, which were collected to obtain a polyacrylonitrile-based nonwoven felt with a thickness of 0.14mm.

[0070] The polyacrylonitrile-based non-woven felt was placed in a multi-stage step-by-step program temperature-controlled tubular furnace, and air was introduced at a flow rate of 0.6 L / min. The temperature was increased from room temperature to 210°C at a heating rate of 6°C / min, and kept warm for 12 minutes; then the temperature was increased from 210°C to 295°C at a heating rate of 1.5°C / min, and kept warm for 70 minutes; then the temperature was increased from 295°C to 330°C at a heating rate of 7°C / min, and kept warm for 35 minutes to obtain the polyacrylonitrile-based pre-oxidized felt.

[0071] The polyacrylonitrile-based preoxidized felt was placed in a methanol solution of boron phenolic resin (the mass fraction of boron phenolic resin in the solution was 15%) and impregnated for 35 minutes. The impregnation method was vacuum impregnation at 135Pa. After the impregnation of the polyacrylonitrile-based preoxidized felt, it was dried at 70°C in a blast drying oven for 35 minutes. Then, it was hot-pressed and cured using a flat vulcanizer. The hot-pressing curing temperature was 165°C, the time was 20 minutes, and the pressure was 8MPa. The hot-pressed polyacrylonitrile-based preoxidized felt was obtained. The hot-pressed polyacrylonitrile-based preoxidized felt was placed in a multi-stage step-by-step program temperature-controlled tubular furnace for one-step carbonization and graphitization treatment. The one-step carbonization and graphitization treatment process was: in high-purity nitrogen, the temperature was raised from room temperature to 1500°C at a heating rate of 6°C / min and kept for 4 minutes for carbonization treatment; then the temperature was raised from 1500°C to 2600°C at a heating rate of 7°C / min and kept for 15 minutes for graphitization treatment to prepare carbon fiber paper.

[0072] The carbon fiber paper of this embodiment has a thickness of 0.06 mm and a resistivity of 6.1 mΩ·cm.

[0073] Comparative Example 1

[0074] The carbon fiber paper was prepared by the traditional wet forming process. Commercial short-cut polyacrylonitrile-based carbon fiber (model T-700, length 6 mm) was added to the fiber disintegrator, and then the dispersant polyethylene oxide aqueous solution was added (the mass concentration of the polyethylene oxide aqueous solution was 0.2%). The mass ratio of the dispersant to the short-cut polyacrylonitrile-based carbon fiber was 8:1. The carbon fiber was dispersed at a stirring rate of 500 r / min for 3 minutes to obtain a carbon fiber dispersion.

[0075] The carbon fiber dispersion was transferred to a paper sheet former using wet forming technology and dehydrated for 60 seconds under a vacuum condition of 0.05 MPa to allow the carbon fiber dispersion to pass through a stainless steel filter to form a carbon fiber base paper with a thickness of 0.15 mm on the filter surface.

[0076] The carbon fiber base paper is impregnated in a methanol solution of boron phenolic resin (the mass fraction of boron phenolic resin in the solution is 10%) for 30 minutes, and the impregnation method is vacuum impregnation under 130Pa. After the impregnation of the polyacrylonitrile-based pre-oxidized felt, it is dried at 80°C in a blast drying oven for 30 minutes, and then it is hot-pressed and cured by a flat vulcanizer. The temperature of the hot-pressing curing is 160°C, the time is 30 minutes, and the pressure is 7MPa, so as to obtain the hot-pressed and cured polyacrylonitrile-based pre-oxidized felt. The hot-pressed and cured polyacrylonitrile-based pre-oxidized felt is placed in a multi-stage step-by-step program temperature-controlled tubular furnace for one-step carbonization and graphitization treatment. The one-step carbonization and graphitization treatment process is: in high-purity nitrogen, the temperature is increased from room temperature to 1300°C at a heating rate of 5°C / min and the temperature is kept for 5 minutes for carbonization treatment; then the temperature is increased from 1300°C to 2500°C at a heating rate of 5°C / min and the temperature is kept for 20 minutes for graphitization treatment, so as to prepare the carbon fiber paper.

[0077] The carbon fiber paper of this comparative example has a thickness of 0.18 mm and a resistivity of 12 mΩ·cm.

[0078] The microstructure of the carbon fiber paper of this comparative example is as follows: Figure 2 As shown by Figure 2 It can be seen that the interior of the carbon fiber paper is composed of cut short fibers, the carbon fiber diameter is large, and the distribution uniformity is poor.

[0079] It can be seen from the embodiments and comparative examples that the preparation method of the present invention can prepare carbon fiber paper with ultra-thin controllable thickness while ensuring the excellent conductivity of the carbon fiber paper, and has low molding requirements, providing a new design idea for the large-scale production of low-cost, high-performance carbon fiber paper.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing carbon fiber paper, characterized in that: The following steps are included: 1) mixing acrylonitrile-N-4-pyridyl-2-acrylamide copolymer and N,N-dimethylformamide to obtain an electrospinning solution; electrospinning the electrospinning solution to obtain a polyacrylonitrile-based nonwoven felt; 2) pre-oxidizing the polyacrylonitrile-based non-woven felt to obtain a polyacrylonitrile-based pre-oxidized felt; 3) impregnating the polyacrylonitrile-based pre-oxidized felt in a resin solution and then drying, hot pressing and curing, carbonizing, and graphitizing in sequence to obtain carbon fiber paper; Step 1) the mass ratio of the acrylonitrile-N-4-pyridyl-2-acrylamide copolymer to N,N-dimethylformamide is 1-2:8-9; In step 3), in the resin solution, the resin is boron phenolic resin and the solvent is methanol and / or ethanol.

2. The preparation method according to claim 1, characterized in that: Step 1) The electrospinning flow rate is 0.6-0.8 mL / h, and the thickness of the polyacrylonitrile-based nonwoven felt is 0.10-0.24 mm.

3. The preparation method according to claim 2, characterized in that: Step 2) The pre-oxidation treatment is to pre-oxidize the polyacrylonitrile-based non-woven felt at 180-220° C. for 5-15 min, 270-300° C. for 30-90 min, and 310-340° C. for 20-40 min in sequence; The heating rate from room temperature to 180-220°C is 2-8°C / min, the heating rate from 180-220°C to 270-300°C is 0.2-2°C / min, and the heating rate from 270-300°C to 310-340°C is 2-8°C / min.

4. The preparation method according to claim 3, characterized in that: Step 3) The mass concentration of the resin solution is 8-20%, and the impregnation time is 10-40 minutes.

5. The preparation method according to claim 3, characterized in that: Step 3) The drying temperature is 60-100° C., and the drying time is 20-60 min; the hot pressing curing temperature is 140-170° C., the hot pressing curing pressure is 5-10 MPa, and the hot pressing curing time is 10-40 min.

6. The preparation method according to claim 4 or 5, characterized in that: Step 3) the carbonization temperature is 1000-1600°C, and the carbonization time is 3-15 minutes; the graphitization temperature is 1900-2800°C, and the graphitization time is 15-30 minutes; The heating rate from room temperature to carbonization temperature and the heating rate from carbonization temperature to graphitization temperature are independently 2-8°C / min; the carbonization and graphitization are carried out in high-purity nitrogen.

7. The carbon fiber paper prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The thickness of the carbon fiber paper is 0.05-0.10 mm, and the resistivity of the carbon fiber paper is 4-9 mΩ·cm.

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

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