A method for preparing carbon paper with improved internal pore structure distribution

Abstract

The present invention discloses a carbon paper preparation method for promoting internal pore structure distribution, comprising the following steps: step 1, carbon fiber is dispersed into NaOH solution, stirred and allowed to stand to remove the grease impurities on carbon fiber surface; step 2: the carbon fiber in step 1 is added to dopamine hydrochloride solution, stirred at room temperature, and dopamine hydrochloride modified carbon fiber is obtained; step 3, dopamine hydrochloride modified carbon fiber is added to APAM solution, and PVA fiber is added to continue to disperse, and after dispersion, wet paper is put into papermaking machine and prepares carbon paper base paper; step 4, configuration impregnation solution, the impregnation solution includes 10 15 parts of phenolic resin, 80 100 parts of anhydrous ethanol, 1 2 parts of urea, 1 2 parts of camphor by mass; step 5, carbon paper base paper is impregnated in impregnation solution for 15 25 minutes, then hot-pressed and carbonized after drying to obtain carbon paper finished product. The present invention can promote the pore structure distribution inside carbon paper so that it can have good air permeability under the premise of ensuring mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon paper, and in particular to a method for preparing carbon paper with improved internal pore structure distribution. Background Art

[0002] As a key base material for gas diffusion layers, carbon paper should provide gas and water transport pathways, allowing the reactant gases to enter the reaction zone smoothly and stably, and the generated water to drain smoothly without blocking the gas channels. It should also possess high strength, a certain degree of water permeability, a suitable pore size range, low resistivity, and a certain degree of thermal conductivity. Carbon fibers lack hydrogen bonding, resulting in very low interfiber strength. The mechanical properties of carbon paper are crucial to the proper ratio of carbon fibers to reinforcing fibers, while an appropriate pore size distribution contributes to its air permeability. Therefore, ensuring a good pore structure while maintaining mechanical properties is key to carbon paper preparation. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing carbon paper with improved internal pore structure distribution. The present invention can improve the internal pore structure distribution of carbon paper, so that it can have good air permeability while ensuring mechanical properties.

[0004] The technical solution of the present invention is a method for preparing carbon paper with improved internal pore structure distribution, comprising the following steps:

[0005] Step 1: Select carbon fibers with a length of 3-8 mm and disperse them in a NaOH solution. Stir and let stand to remove grease and impurities on the surface of the carbon fibers.

[0006] Step 2: Take 1-3 g / L dopamine hydrochloride solution, add the carbon fiber in step 1 to the dopamine hydrochloride solution, stir at room temperature, and react for 20-28 hours to obtain dopamine hydrochloride modified carbon fiber;

[0007] Step 3: Add dopamine hydrochloride modified carbon fiber to the APAM solution, use a fiber deflater to disperse it, then add PVA fiber and continue to disperse it. After dispersion, put the wet paper into a papermaking machine to prepare carbon paper base paper;

[0008] Step 4, preparing an impregnation solution, wherein the impregnation solution comprises 10-15 parts of phenolic resin, 80-100 parts of anhydrous ethanol, 1-2 parts of urea, and 1-2 parts of camphor in parts by mass;

[0009] Step 5: Immerse the carbon paper base in the impregnation solution for 15-25 minutes, then dry and hot-press carbonize to obtain a finished carbon paper.

[0010] In the above-mentioned method for preparing carbon paper with improved internal pore structure distribution, in step 1, the length of the carbon fibers is 4 mm, and the concentration of the NaOH solution is 1 mol / L.

[0011] In the aforementioned method for preparing carbon paper with improved internal pore structure distribution, in step 2, the concentration of the dopamine hydrochloride solution is 2.5 g / L, and the reaction time is 24 h.

[0012] In the aforementioned method for preparing carbon paper with improved internal pore structure distribution, in step 3, the wet paper is sandwiched between silicone oil paper without undergoing a pressing process, and hot pressed for 1200 seconds at 0.5 MPa using a flat vulcanizer, and then stored in a constant temperature and humidity room. The paper basis weight of the prepared carbon paper base is 57±2 g / m 2 .

[0013] In the aforementioned method for preparing carbon paper with improved internal pore structure distribution, in step 3, the ratio of the dopamine hydrochloride modified carbon fiber to the PVA fiber is 90:10, and the mass concentration of the APAM solution is 0.10%-0.16%.

[0014] In the aforementioned method for preparing carbon paper with improved internal pore structure distribution, in step 4, the impregnation solution comprises, by mass, 12 parts of phenolic resin, 90 parts of anhydrous ethanol, 1.5 parts of urea, and 1.5 parts of camphor.

[0015] In the aforementioned method for preparing carbon paper with improved internal pore structure distribution, in step 5, the carbon paper base is immersed in the impregnation liquid for 20 minutes.

[0016] The aforementioned method for preparing carbon paper to improve the internal pore structure distribution is as follows: the impregnated carbon paper base is placed in an 80°C oven and dried for 60 minutes; after drying, the sample is placed in a flat vulcanizer with an upper and lower temperature of 150°C and 3MPa and hot pressed for 60 minutes; finally, the molded sample is carbonized to 1000°C at 20°C / h and further graphitized to 2350°C at 150°C / h to obtain the final carbon paper.

[0017] Compared with the prior art, the present invention first utilizes dopamine hydrochloride to modify carbon fibers, thereby improving the wettability and dispersibility of carbon fibers and enabling good dispersion in an aqueous phase. Then, an impregnation liquid is configured. Under the impregnation liquid, the formation of pores in the carbon paper matrix region is quite obvious, forming an efficient porous network, thereby achieving an overall balance in porosity, permeability, conductivity, strength and electrochemical properties of the prepared carbon paper, thereby achieving excellent fuel cell performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 : Scanning electron microscope images of the carbon paper in Examples 1-4. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to the accompanying drawings and examples, but they are not intended to limit the present invention.

[0020] Example 1: A method for preparing carbon paper with improved internal pore structure distribution, characterized by comprising the following steps:

[0021] Step 1: Select carbon fibers with a length of 3 mm and disperse them in a 1 mol / L NaOH solution. Stir and let stand to remove grease and impurities on the surface of the carbon fibers.

[0022] Step 2: Take 1 g / L dopamine hydrochloride solution, add the carbon fiber in step 1 to the dopamine hydrochloride solution, stir at room temperature, and react for 20 hours to obtain dopamine hydrochloride modified carbon fiber;

[0023] Step 3: Add dopamine hydrochloride modified carbon fiber to APAM solution, use a fiber detangler to disperse it, then add PVA fiber to continue to disperse to obtain wet paper, after dispersion, without pressing process, sandwich the wet paper into silicone oil paper, use a flat vulcanizer to hot press 1200s under 0.5MPa conditions, and then store it in a constant temperature and humidity room. The prepared carbon paper base paper has a paper basis weight of 57.6g / m 2 The ratio of the dopamine hydrochloride modified carbon fiber to the PVA fiber is 90:10, and the mass concentration of the APAM solution is 0.12%.

[0024] Step 4: preparing an impregnation solution, wherein the impregnation solution comprises, by mass, 10 g of phenolic resin, 85 g of anhydrous ethanol, 1 g of urea, and 1 g of camphor;

[0025] Step 5: Immerse the carbon paper in the impregnation solution for 15 minutes. The impregnated carbon paper is then placed in an 80°C oven and dried for 60 minutes. The dried sample is then hot-pressed on a flat-plate vulcanizer at 150°C and 3 MPa for 60 minutes. Finally, the molded sample is carbonized to 1000°C at 20°C / h and further graphitized to 2350°C at 150°C / h to obtain the final carbon paper.

[0026] Example 2: A method for preparing carbon paper with improved internal pore structure distribution, characterized by comprising the following steps:

[0027] Step 1: Select carbon fibers with a length of 5 mm and disperse them in a 1 mol / L NaOH solution. Stir and let stand to remove grease and impurities on the surface of the carbon fibers.

[0028] Step 2: Take 3 g / L dopamine hydrochloride solution, add the carbon fiber in step 1 to the dopamine hydrochloride solution, stir at room temperature, and react for 24 hours to obtain dopamine hydrochloride modified carbon fiber;

[0029] Step 3: Add dopamine hydrochloride modified carbon fiber to APAM solution, use a fiber detangler to disperse it, then add PVA fiber to continue to disperse to obtain wet paper, after dispersion, without pressing process, sandwich the wet paper into silicone oil paper, use a flat vulcanizer to hot press 1200s under 0.5MPa conditions, and then store it in a constant temperature and humidity room. The prepared carbon paper base paper has a paper basis weight of 55.1g / m 2 The ratio of the dopamine hydrochloride modified carbon fiber to the PVA fiber is 90:10, and the mass concentration of the APAM solution is 0.15%.

[0030] Step 4: preparing an impregnation solution, wherein the impregnation solution comprises, by mass, 15 g of phenolic resin, 90 g of anhydrous ethanol, 2 g of urea, and 1 g of camphor;

[0031] Step 5: Immerse the carbon paper in the impregnation solution for 25 minutes. The impregnated carbon paper is then placed in an 80°C oven and dried for 60 minutes. The dried sample is then hot-pressed on a flat-plate vulcanizer at 150°C and 3 MPa for 60 minutes. Finally, the molded sample is carbonized to 1000°C at 20°C / h and further graphitized to 2350°C at 150°C / h to obtain the final carbon paper.

[0032] Example 3: A method for preparing carbon paper with improved internal pore structure distribution, characterized by comprising the following steps:

[0033] Step 1: Select carbon fibers with a length of 8 mm and disperse them in a 1 mol / L NaOH solution. Stir and let stand to remove grease and impurities on the surface of the carbon fibers.

[0034] Step 2: Take 2 g / L dopamine hydrochloride solution, add the carbon fiber in step 1 to the dopamine hydrochloride solution, stir at room temperature, and react for 24 hours to obtain dopamine hydrochloride modified carbon fiber;

[0035] Step 3: Add dopamine hydrochloride modified carbon fiber to APAM solution, use a fiber detangler to disperse it, then add PVA fiber to continue to disperse to obtain wet paper, after dispersion, without pressing process, sandwich the wet paper into silicone oil paper, use a flat vulcanizer to hot press 1200s under 0.5MPa conditions, and then store it in a constant temperature and humidity room. The prepared carbon paper base paper has a paper basis weight of 58.5g / m 2 The ratio of the dopamine hydrochloride modified carbon fiber to the PVA fiber is 90:10, and the mass concentration of the APAM solution is 0.16%.

[0036] Step 4: preparing an impregnation solution, wherein the impregnation solution comprises, by mass, 13 g of phenolic resin, 100 g of anhydrous ethanol, 1 g of urea, and 2 g of camphor;

[0037] Step 5: Immerse the carbon paper in the impregnation solution for 25 minutes. The impregnated carbon paper is then placed in an 80°C oven and dried for 60 minutes. The dried sample is then hot-pressed on a flat-plate vulcanizer at 150°C and 3 MPa for 60 minutes. Finally, the molded sample is carbonized to 1000°C at 20°C / h and further graphitized to 2350°C at 150°C / h to obtain the final carbon paper.

[0038] Example 4: A method for preparing carbon paper with improved internal pore structure distribution, characterized by comprising the following steps:

[0039] Step 1: Select carbon fibers with a length of 4 mm and disperse them in a 1 mol / L NaOH solution. Stir and let stand to remove grease and impurities on the surface of the carbon fibers.

[0040] Step 2: Take 2.5 g / L dopamine hydrochloride solution, add the carbon fiber in step 1 to the dopamine hydrochloride solution, stir at room temperature, and react for 24 hours to obtain dopamine hydrochloride modified carbon fiber;

[0041] Step 3: Add dopamine hydrochloride modified carbon fiber to APAM solution, use a fiber detangler to disperse it, then add PVA fiber to continue to disperse to obtain wet paper, after dispersion, without pressing, sandwich the wet paper between silicone oil paper, use a flat vulcanizer to hot press 1200s under 0.5MPa conditions, and then store it in a constant temperature and humidity room. The prepared carbon paper has a paper basis weight of 57g / m 2 The ratio of the dopamine hydrochloride modified carbon fiber to the PVA fiber is 90:10, and the mass concentration of the APAM solution is 0.14%.

[0042] Step 4: preparing an impregnation solution, wherein the impregnation solution comprises, by mass, 12 g of phenolic resin, 90 g of anhydrous ethanol, 1.5 g of urea, and 1.5 g of camphor;

[0043] Step 5: Immerse the carbon paper in the impregnation solution for 20 minutes. The impregnated carbon paper is then placed in an 80°C oven and dried for 60 minutes. The dried sample is then hot-pressed on a flat-plate vulcanizer at 150°C and 3 MPa for 60 minutes. Finally, the molded sample is carbonized to 1000°C at 20°C / h and further graphitized to 2350°C at 150°C / h to obtain the final carbon paper.

[0044] Comparative Example 1: This comparative example adopts the same process as Example 4, but differs from Example 4 in that the carbon fiber is not modified by the dopamine hydrochloride solution, and the impregnation solution is composed only of phenolic resin and anhydrous ethanol, and does not include urea and camphor.

[0045] Comparative Example 2: This comparative example adopts the same process as Example 4, but differs from Example 4 in that the carbon fibers are not modified by the dopamine hydrochloride solution.

[0046] Comparative Example 3: This comparative example adopts the same process as Example 4, but is different from Example 4 in that the impregnation liquid is composed only of phenolic resin and anhydrous ethanol, and does not include urea and camphor.

[0047] The applicant conducted performance tests on the carbon papers prepared in Examples 1-4 and Comparative Examples 1-3. The performance tests included:

[0048] 1. Tensile strength;

[0049] The tensile strength test of carbon paper base paper is based on the national standard "Determination of tensile strength of paper and board" (GB / T12914-2008). A strip of approximately 15×100 mm is cut from each sheet of paper and tested using a tensile strength tester.

[0050] 2. Breathability;

[0051] The prepared carbon paper was tested for air permeability using a TEXTEST FX30000 air permeability tester with a pressure of 200 Pa and an area of ​​20 cm per measurement. 2 , take 10 samples at different positions on each carbon paper base and take the average air permeability.

[0052] 3. Porosity;

[0053] The porosity of carbon paper is determined using the wet-dry method. After drying the carbon paper at 80°C for 24 hours, its mass is measured on an electronic balance, recorded as W1. The carbon paper is then soaked in anhydrous ethanol for 1 minute and its mass is measured, recorded as W2. The porosity of the carbon paper is calculated using formula (3.1).

[0054] A k =(W2-W1) / [ρW2+(ρ1-ρ2)W1];

[0055] Where: A k is the porosity, %; ρ2 is the density of anhydrous ethanol, g·cm -3 ; ρ1 is the average density of carbon paper, g·cm -3 .

[0056] 4. Resistivity;

[0057] The resistivity of the carbon paper was tested using a four-probe test method. The carbon paper was cut into a circle with a diameter of 11 cm. Ten points at different positions on the sample were measured separately. The plane resistivity values ​​of the ten points were recorded, and the average value was taken as the plane resistivity of the carbon paper.

[0058] The structure of the performance test is shown in Table 1:

[0059] sample Tensile strength KN / m Air permeability mm / s Porosity% Resistivity mΩ.cm Example 1 5.3 1375 95.6 95 Example 2 5.5 1450 96.5 87 Example 3 5.2 1355 95.8 98 Example 4 5.9 1560 97.9 81 Comparative Example 1 2.8 1190 92.1 135 Comparative Example 2 3.3 1065 91.3 142 Comparative Example 3 3.6 1120 93.6 121

[0060] Table 1

[0061] As can be seen from Table 1, the present invention improves the tensile strength, air permeability, and porosity of carbon paper, while reducing resistivity and correspondingly improving conductivity. Table 1 clearly shows that the porosity of the sample in Example 4 reaches nearly 98% after impregnation with the impregnation solution. This increased porosity improves the surface air permeability of the carbon paper. Meanwhile, various properties of the comparative examples are lower than those of the examples.

[0062] Furthermore, the pore size of the carbon papers in Examples 1-4 and Comparative Example 1 was calculated.

[0063] As shown in Table 2, (unit: um).

[0064]

[0065]

[0066] Table 2

[0067] The structure in Table 2 shows that the samples of Comparative Example 1 account for about 55% of the pore size between 20 and 50 μm, while the samples of the present invention have a significantly higher proportion of pore size between 20 and 50 μm, especially the samples of Example 4.

[0068] Furthermore, the carbon paper prepared in Examples 1-4 was cut into 1×1 cm squares, attached to double-sided carbon conductive tape, sprayed with gold, and the surface was scanned using a scanning electron microscope (Hita-chi, SU-1510) with an acceleration voltage of 15 kV.

[0069] Figure 1 The surface morphology of fractured carbon paper samples from Examples 1-4 was analyzed under a scanning electron microscope. Figures A, C, E, and G are schematic diagrams of the samples from Examples 1-4, while Figures B, D, F, and H are further magnified views. The images clearly show that the matrix regions of the samples from Examples 1-4 exhibit significant pore formation, forming a highly efficient porous network.

[0070] In summary, the present invention first utilizes dopamine hydrochloride to modify carbon fibers, thereby improving the wettability and dispersibility of carbon fibers and enabling good dispersion in an aqueous phase. Then, an impregnation liquid is configured. Under the impregnation liquid, the formation of pores in the carbon paper matrix region is quite obvious, forming an efficient porous network, thereby achieving an overall balance in porosity, permeability, conductivity, strength and electrochemical properties of the prepared carbon paper, thereby achieving excellent fuel cell performance.

Claims

1. A method for preparing carbon paper with improved internal pore structure distribution, characterized by: The steps include: Step 1: Select carbon fibers with a length of 3-8 mm and disperse them into a NaOH solution. Stir and let stand to remove grease and impurities on the surface of the carbon fibers. Step 2: Take 1-3 g / L dopamine hydrochloride solution, add the carbon fiber in step 1 to the dopamine hydrochloride solution, stir at room temperature, and react for 20-28 hours to obtain dopamine hydrochloride modified carbon fiber; Step 3: Add dopamine hydrochloride modified carbon fiber to the APAM solution, use a fiber deflater to disperse it, then add PVA fiber and continue to disperse it. After dispersion, put the wet paper into a papermaking machine to prepare carbon paper base paper; Step 4, preparing an impregnation solution, wherein the impregnation solution comprises 10-15 parts of phenolic resin, 80-100 parts of anhydrous ethanol, 1-2 parts of urea, and 1-2 parts of camphor in parts by mass; Step 5: Immerse the carbon paper base in the impregnation solution for 15-25 minutes, then dry and hot-press carbonize to obtain a finished carbon paper.

2. The method for preparing carbon paper with improved internal pore structure distribution according to claim 1, characterized in that: In step 1, the length of the carbon fiber is 4 mm, and the concentration of the NaOH solution is 1 mol / L.

3. The method for preparing carbon paper with improved internal pore structure distribution according to claim 1, characterized in that: In step 2, the concentration of the dopamine hydrochloride solution is 2.5 g / L, and the reaction time is 24 h.

4. The method for preparing carbon paper with improved internal pore structure distribution according to claim 1, characterized in that: In step 3, the wet paper was sandwiched between silicone oil paper without the pressing process, and hot pressed for 1200s at 0.5MPa using a flat vulcanizer, and then stored in a constant temperature and humidity room. The basis weight of the prepared carbon paper was 57±2g / m 2 .

5. The method for preparing carbon paper with improved internal pore structure distribution according to claim 4, characterized in that: In step 3, the ratio of the dopamine hydrochloride modified carbon fiber to the PVA fiber is 90:10, and the mass concentration of the APAM solution is 0.10%-0.16%.

6. The method for preparing carbon paper with improved internal pore structure distribution according to claim 1, characterized in that: In step 4, the impregnation solution includes 12 parts of phenolic resin, 90 parts of anhydrous ethanol, 1.5 parts of urea, and 1.5 parts of camphor in parts by mass.

7. The method for preparing carbon paper with improved internal pore structure distribution according to claim 1, characterized in that: In step 5, the carbon paper base is immersed in the impregnation liquid for 20 minutes.

8. The method for preparing carbon paper with improved internal pore structure distribution according to claim 7, characterized in that: The impregnated carbon paper base was placed in an 80°C oven and dried for 60 minutes. After drying, the sample was placed in a flat vulcanizer with an upper and lower temperature of 150°C and a pressure of 3 MPa and hot pressed for 60 minutes. Finally, the molded sample was carbonized to 1000°C at 20°C / h and further graphitized to 2350°C at 150°C / h to obtain the final carbon paper.

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