A high-conductive carbon paper with uniform conductivity and its preparation method and application

Abstract

A highly conductive carbon paper with uniform conductivity, and its preparation method and application. The present invention belongs to the technical field of carbon fiber paper. The purpose of the present invention is to solve the technical problems of uneven overall conductivity and low porosity of carbon paper. The present invention adopts a bio-based dispersant sodium alginate, and utilizes its polyhydroxyl group and strong hydrophilicity to solve the problems of uneven dispersion of carbon fibers and low porosity after wet papermaking, thereby improving the air permeability. Using PDA as a medium, more nickel ions are adsorbed, thereby growing more nickel hydroxide, and then reduced to more metallic nickel elements, which significantly improves the conductivity of carbon paper, and nickel balls can increase the surface roughness of carbon paper, which well solves the problem of uneven overall conductivity of carbon paper. At the same time, during the sintering and reduction process, PDA, due to its carbon-rich system, can contain more carbon in the system after sintering, without introducing other impurities and damaging the original properties. It is widely used in the field of proton exchange membrane fuel cells.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon fiber paper, and in particular relates to a highly conductive carbon paper with uniform conductivity, a preparation method thereof, and an application thereof. Background Art

[0002] Carbon fiber paper (CFP) has been extensively studied as a gas diffusion layer in high-performance fuel cells. Proton exchange membrane fuel cells (PEMFCs) are considered the next generation of power generation equipment due to their high efficiency, high power density, high energy conversion rate, and lightweight properties. They are used in automotive power supplies, household energy sources, submarines, and aircraft. The gas diffusion layer (GDL), a key component of PEMFCs, supports the catalyst layer and provides important mass transfer pathways for reactant gas, water management, and electrical transport. Currently, the substrate for GDLs is carbon fiber paper (CFP). This is primarily manufactured using a wet cloth process on conventional papermaking equipment, mixing carbon fibers (CF) with a binder. The process then involves resin impregnation, hot pressing, curing, carbonization, and graphitization.

[0003] CF is a fiber material with a carbon content greater than 95%, mainly composed of CC bonds. Carbon fiber is different from plant fiber. The surface of carbon fiber contains only a small amount of groups and is not easily wetted by water. During the pulping process, it can only produce a cutting effect, and cannot produce a fibrillation phenomenon. No hydrogen bonds will be generated between the fibers after the paper sheet is formed. Moreover, due to the electrostatic adsorption of short-cut carbon fibers, they are easy to aggregate in the solution. These characteristics will lead to poor and uneven fiber distribution, affecting the pore size distribution of CFP, reducing the mechanical strength of CFP, and forming low porosity after wet papermaking and poor conductivity of carbon paper after papermaking, which significantly affects the performance of PEMFC. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problems of uneven overall conductivity and low porosity of carbon paper, and to provide a highly conductive carbon paper with uniform conductivity, a preparation method and application thereof.

[0005] The purpose of the present invention is to achieve through the following technical solutions:

[0006] One of the purposes of the present invention is to provide a method for preparing highly conductive carbon paper with uniform conductivity, the preparation method being carried out according to the following steps:

[0007] S1: Sodium alginate was dissolved in deionized water and magnetically stirred in an oil bath. Short-cut carbon fibers and Tween 80 were then added and stirred continuously to obtain a dispersion.

[0008] S2: adding the dispersion to the polyacrylamide aqueous solution, adding the binder after magnetic stirring, heating and stirring until completely dissolved, and then wet-making paper to obtain a carbon fiber blank;

[0009] S3: impregnating the carbon fiber blank with a thermosetting resin solution by suction filtration, hot pressing, and then carbonizing at high temperature to obtain carbon paper;

[0010] S4: Immerse the carbon paper in a dopamine aqueous solution and a tris(hydroxymethyl)aminomethane aqueous solution until the solution turns brown, take it out, hydrothermally treat it with nickel salt, urea and water, and finally calcine it to obtain a highly conductive carbon paper with uniform conductivity.

[0011] Preferably, the chopped carbon fibers in S1 have a diameter of 3-15 μm and a length of 5-20 mm.

[0012] More preferably, the length is 6 mm.

[0013] Preferably, the mass ratio of sodium alginate to chopped carbon fibers in S1 is (1.5-2.5):1.

[0014] Preferably, the amount of Tween 80 added in S1 is 0.01% of the total mass of the dispersion.

[0015] Preferably, the mass ratio of polyacrylamide in the S2 polyacrylamide aqueous solution to sodium alginate in the S1 dispersion is 1:(8-12).

[0016] Preferably, the binder in S2 includes pulp, polyester, and polyvinyl alcohol.

[0017] Preferably, the amount of the binder in S2 is 8-12% of the mass of the chopped carbon fibers.

[0018] Preferably, the thermosetting resin in S3 is phenolic resin or furan.

[0019] Preferably, the mass ratio of the thermosetting resin to the chopped carbon fibers in the thermosetting resin solution in S3 is (15-25): 1. Preferably, the hot pressing temperature in S3 is 140-160° C., the pressure is 4.7 MPa, and the time is ≥20 min.

[0020] Preferably, the high temperature carbonization temperature in S3 is 2000-2400° C., and the time is 1-3 hours.

[0021] Preferably, the concentration of the dopamine aqueous solution in S4 is 1.8-2 g / L, and the concentration of the tris(hydroxymethyl)aminomethane aqueous solution is 0.8-1 g / L.

[0022] Preferably, the immersion time in S4 is 6-24 hours.

[0023] Preferably, the nickel salt in S4 is nickel sulfate, and the ratio of nickel salt to urea and water is (10-15) g: (10-15) g: 1 L.

[0024] Preferably, the mass ratio of nickel salt to chopped carbon fiber in S4 is (20-30):1.

[0025] Preferably, the hydrothermal treatment temperature in S4 is 80-100° C. and the time is 2-4 h.

[0026] Preferably, the calcination temperature in S4 is 600-700° C. and the calcination time is 1-3 h.

[0027] A second object of the present invention is to provide a hydrophobic carbon paper based on the above-mentioned highly conductive carbon paper with uniform conductivity.

[0028] A third object of the present invention is to provide a method for preparing hydrophobic carbon paper based on the above-mentioned highly conductive carbon paper with uniform conductivity, wherein the preparation method comprises: immersing the above-mentioned highly conductive carbon paper with uniform conductivity in a PTFE solution.

[0029] Preferably, the viscosity of the PTFE solution is 0.015-0.020 Pa.s.

[0030] A fourth object of the present invention is to provide an application of the hydrophobic carbon paper prepared by the above method in a fuel cell.

[0031] A fifth object of the present invention is to provide a proton exchange membrane fuel cell, wherein the proton exchange membrane fuel cell uses the hydrophobic carbon paper prepared according to the above method as a gas diffusion layer.

[0032] Compared with the prior art, the present invention has the following significant effects:

[0033] (1) The present invention adopts a bio-based dispersant sodium alginate, which takes advantage of its polyhydroxyl group, strong hydrophilicity, and easy solubility in water to solve the problems of uneven dispersion of carbon fibers and low porosity after wet papermaking, thereby improving the air permeability.

[0034] (2) The present invention uses PDA as a medium to adsorb more nickel ions, thereby growing more nickel hydroxide, which is then reduced to more metallic nickel, significantly improving the conductivity of carbon paper. In addition, the Ni balls can increase the surface roughness of the carbon paper, effectively solving the problem of uneven conductivity of the carbon paper as a whole. At the same time, during the sintering and reduction process, PDA, due to its carbon-rich system, can contain more carbon in the system after sintering without introducing other impurities and damaging the original properties. This makes it widely used in the field of proton exchange membrane fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is an electron microscope image of the carbon fiber blank in step (2) of Example 1;

[0036] Figure 2 is a TGA curve of the thermal stability of the carbon paper in step (3) of Example 1;

[0037] Figure 3is an electron microscope image of the carbon paper in step (4) of Example 1;

[0038] Figure 4 : is a comparison chart of the thin layer conductivity of untreated commercial carbon paper and the carbon paper in step (4) of Example 1;

[0039] Figure 5 This is a photo of the highly conductive hydrophobic carbon paper with uniform conductivity obtained in Example 1. DETAILED DESCRIPTION

[0040] A specific embodiment of the present invention is to provide a method for preparing highly conductive hydrophobic carbon paper with uniform conductivity, the preparation method being carried out according to the following steps:

[0041] (1) Sodium alginate was dissolved in deionized water, placed in an oil bath at 70°C, and magnetically stirred at 1200-1300 rpm for 20 min. Short-cut carbon fibers and Tween 80 were then added and stirred for 90 min to obtain a dispersion.

[0042] The chopped carbon fibers have a diameter of 3-15 μm and a length of 5-20 mm, preferably 6 mm. The mass ratio of sodium alginate to chopped carbon fibers is (1.5-2.5):1. The concentration of sodium alginate in deionized water is 1 g / L. Tween 80 is added in an amount of 0.01% of the total mass of the dispersion.

[0043] (2) First, polyacrylamide is dissolved in deionized water, placed in an oil bath at 40°C, and magnetically stirred at 1200-1300 rpm for 30 minutes until completely dissolved to obtain a polyacrylamide aqueous solution; then, a dispersion liquid is added to the polyacrylamide aqueous solution, magnetically stirred at 1200-1300 rpm for 90 minutes, a binder is added, and heated and stirred at 100°C for 30 minutes until completely dissolved, and then the solution is poured into a papermaking machine for wet papermaking and drying to obtain a carbon fiber blank;

[0044] The concentration of the polyacrylamide aqueous solution is 0.5 g / L. The mass ratio of sodium alginate in the dispersion to polyacrylamide in the polyacrylamide aqueous solution is (8-12):1. The binder includes pulp, polyester, and polyvinyl alcohol. The binder is used in an amount of 8-12% of the mass of the chopped carbon fibers.

[0045] (3) First, phenolic resin is dissolved in anhydrous ethanol to obtain a thermosetting resin solution; then, the carbon fiber blank is impregnated with the thermosetting resin solution by suction filtration, hot-pressed at 140-160°C and 4.7 MPa for ≥20 min, and then heated to 2000-2400°C at a rate of 4-6°C / min and kept warm for 1-3 h for high-temperature carbonization to obtain carbon paper;

[0046] The phenolic resin concentration in the thermosetting resin solution is 40-60 g / L. The thermosetting resin solution is an acetone solution of furan, modified phenolic, or phenolic epoxy resin, with phenolic resin being the most preferred. The mass ratio of the thermosetting resin to the chopped carbon fibers in the thermosetting resin solution is (15-25):1.

[0047] (4) Immersing the carbon paper in a 1.8-2 g / L dopamine aqueous solution and a 0.8-1 g / L tris(hydroxymethyl)aminomethane aqueous solution for 6-24 h until the solution turns brown, taking it out and hydrothermally treating it with nickel sulfate, urea and water at 80-100° C. for 2-4 h, and finally calcining it at 600-700° C. for 1-3 h to obtain a highly conductive carbon paper with uniform conductivity;

[0048] The ratio of nickel sulfate to urea and water is (10-15) g: (10-15) g: 1 L. The mass ratio of nickel sulfate to chopped carbon fiber is (20-30): 1.

[0049] (5) Immersing the highly conductive carbon paper with uniform conductivity obtained in step (4) in a PTFE solution with a viscosity of 0.015-0.020 Pa.s to obtain highly conductive hydrophobic carbon paper with uniform conductivity.

[0050] In this embodiment, a bio-based dispersant, sodium alginate, is used. By utilizing its polyhydroxyl group, strong hydrophilicity, and easy solubility in water, the problems of uneven dispersion of carbon fibers and low porosity after wet papermaking are solved, thereby improving the air permeability.

[0051] In this embodiment, PDA is used as a medium to adsorb more nickel ions, thereby growing more nickel hydroxide, which is then reduced to more metallic nickel. This significantly improves the conductivity of the carbon paper. The Ni balls can also increase the surface roughness of the carbon paper, effectively solving the problem of uneven conductivity of the carbon paper. At the same time, during the sintering and reduction process, PDA, due to its carbon-rich system, can increase the carbon content in the system after sintering without introducing other impurities and damaging the original properties. This makes it widely used in the field of proton exchange membrane fuel cells.

[0052] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0053] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are conventional in the art and can be obtained commercially by those skilled in the art unless otherwise specified.

[0054] As used in the following examples, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0055] When amount, concentration or other value or parameter are represented with the range of scope, preferred range or a series of upper preferred value and lower preferred value limit, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value and any range lower limit or preferred value, and no matter whether this scope is disclosed separately.For example, when disclosing scope "1 to 5", described scope should be interpreted as including scope "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc.When numerical range is described in this article, unless otherwise stated, otherwise this scope is intended to include its end value and all integers and fractions within the scope.In this application specification and claims, range limitation can be combined and / or interchanged, and if these ranges are not otherwise stated, include all subranges contained therein.

[0056] The indefinite articles "a" and "an" before the elements or components of the present invention do not limit the quantity requirement (i.e. the number of times they appear). Therefore, "a" or "an" should be interpreted as including one or at least one, and elements or components in the singular also include plural forms, unless the quantity clearly refers to only the singular form.

[0057] The term "one embodiment" or "embodiment" of the present invention refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it necessarily refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0058] The endpoints of the ranges and any values ​​disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0059] Example 1

[0060] The preparation method of the highly conductive hydrophobic carbon paper with uniform conductivity of this embodiment is carried out by the following steps:

[0061] (1) 0.5 g of sodium alginate was dissolved in 500 mL of deionized water in an oil bath at 70°C and magnetically stirred at 1200 rpm for 20 min. Subsequently, 0.25 g of chopped carbon fibers (6 mm in length and 3-15 μm in diameter) and Tween 80 were added and stirred for 90 min to obtain a dispersion. The amount of Tween 80 added was 0.01% of the total mass of the dispersion.

[0062] (2) First, 0.05 g of polyacrylamide was dissolved in 100 mL of deionized water, placed in an oil bath at 40 ° C, and magnetically stirred at 1200 rpm for 30 min until completely dissolved to obtain a polyacrylamide aqueous solution; then, the dispersion was added to the polyacrylamide aqueous solution, magnetically stirred at 1200 for 90 min, and polyvinyl alcohol (10% by weight of the chopped carbon fiber) was added, heated and stirred at 100 ° C for 30 min until completely dissolved, and then the solution was poured into a papermaking machine for wet papermaking and dried to obtain a carbon fiber blank; Figure 1 This is an electron microscope image of the carbon fiber blank. It can be seen that the short fibers have good dispersion and good air permeability.

[0063] (3) First, 5 g of phenolic resin was dissolved in 100 mL of anhydrous ethanol to obtain a phenolic resin solution; then, the carbon fiber blank was impregnated with the phenolic resin solution by suction filtration, hot-pressed at 150 °C and 4.7 MPa for 1 h, and then heated to 2000 °C at a rate of 5 °C / min and kept warm for 2 h for high-temperature carbonization to obtain carbon paper; Figure 2 This is a TGA curve diagram of the thermal stability of carbon paper after hot pressing (molding) and carbon paper after high-temperature carbonization. The figure shows that the thermal stability of carbon paper after carbonization is more stable.

[0064] (4) The carbon paper was immersed in a 2 g / L dopamine aqueous solution and a 1 g / L tris(hydroxymethyl)aminomethane aqueous solution for 6 h until the solution turned brown. After being taken out, it was hydrothermally treated with 6.325 g nickel sulfate, 6 g urea and 500 mL water at 90 °C for 3 h, and finally calcined at 650 °C for 2 h to obtain a highly conductive carbon paper with uniform conductivity. Figure 3 The electron microscope image of the growth of metal Ni balls on carbon fiber paper shows that Ni balls grow in large quantities and are evenly distributed under the adsorption of PDA. The untreated commercial carbon paper is used as a blank control. The comparison of the thin layer conductivity of the untreated commercial carbon paper and the thin layer conductivity of the carbon paper containing Ni balls is shown in the figure. Figure 4 As shown in the figure, it can be seen that the carbon paper containing Ni balls has lower resistivity and better conductivity.

[0065] (5) The carbon paper prepared in step (4) was immersed in a PTFE solution with a viscosity of 0.020 Pa.s for a total of 15 minutes, divided into three immersions to obtain highly conductive hydrophobic carbon paper with uniform conductivity. Figure 5This is a real photo of the obtained highly conductive hydrophobic carbon paper with uniform conductivity. It can be seen that its surface is smooth and flat and its overall performance is excellent.

[0066] In this embodiment, due to the appropriate temperature and content of sodium alginate and polyacrylamide, the obtained carbon paper staple fibers are evenly dispersed and the phenolic resin content is appropriate; the PDA content is appropriate, the adsorbed nickel balls grow in large quantities and are evenly dispersed, the hydrothermal time is appropriate, and the pore size of the obtained carbon paper containing nickel balls is appropriate and does not affect the air permeability.

[0067] Comparative Example 1: This comparative example differs from Example 1 in that the amount of sodium alginate in step (1) is changed from 0.5 g to 0.25 g. Other parameters and steps are the same as those in Example 1.

[0068] In this embodiment, the staple fibers are unevenly dispersed due to the low content of the dispersant.

[0069] Comparative Example 2: This comparative example differs from Example 1 in that the amount of phenolic resin in step (3) is changed from 5 g to 2.5 g. Other parameters and steps are the same as those in Example 1.

[0070] In this embodiment, due to the low content of phenolic resin and the short impregnation time, the bonding force between the short fibers is relatively small, and the obtained carbon paper is damaged.

[0071] Comparative Example 3: This comparative example differs from Example 1 in that the hot pressing temperature in step (3) is changed to 130° C. Other parameters and steps are the same as those in Example 1.

[0072] In this embodiment, since the temperature of the carbon paper during molding and curing was relatively low, the phenolic resin was not completely cured, and the obtained carbon paper was adhered to the molding plate and was incomplete.

[0073] The foregoing are merely preferred embodiments of the present invention. These embodiments are all different implementations based on the overall concept of the present invention. The scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing highly conductive carbon paper with uniform conductivity, characterized in that: Follow these steps: S1: Sodium alginate was dissolved in deionized water and magnetically stirred in an oil bath. Short-cut carbon fibers and Tween 80 were then added and stirred continuously to obtain a dispersion. The mass ratio of sodium alginate to short-cut carbon fibers was (1.5-2.5):

1. S2: adding the dispersion to the polyacrylamide aqueous solution, adding the binder after magnetic stirring, heating and stirring until completely dissolved, and then wet-making paper to obtain a carbon fiber blank; S3: impregnating the carbon fiber blank with a thermosetting resin solution by suction filtration, hot pressing, and then carbonizing at high temperature to obtain carbon paper; S4: immersing the carbon paper in a dopamine aqueous solution and a tris(hydroxymethyl)aminomethane aqueous solution until the solution turns brown, taking it out and hydrothermally treating it with nickel salt, urea and water, and finally calcining it at a temperature of 600-700° C. for 1-3 hours to obtain a highly conductive carbon paper with uniform conductivity; The mass ratio of polyacrylamide in the polyacrylamide aqueous solution in S2 to sodium alginate in the dispersion in S1 is 1:(8-12), the binder in S2 is polyvinyl alcohol, and the amount of the binder is 8-12% of the mass of the chopped carbon fibers; The thermosetting resin in S3 is phenolic resin, and the mass ratio of thermosetting resin to chopped carbon fiber in the thermosetting resin solution is (15-25):

1. The hot pressing temperature is 140-160°C, the pressure is 4.7 MPa, the time is ≥20 min, and the high-temperature carbonization temperature is 2000-2400°C, and the time is 1-3 h. The nickel salt is nickel sulfate, the ratio of nickel salt to urea and water is (10-15) g: (10-15) g: 1 L, the mass ratio of nickel salt to chopped carbon fiber is (20-30): 1, the hydrothermal treatment temperature is 80-100° C., and the time is 2-4 hours.

2. The method according to claim 1, characterized in that The concentration of the dopamine aqueous solution in S4 is 1.8-2 g / L, the concentration of the tris(hydroxymethyl)aminomethane aqueous solution is 0.8-1 g / L, and the immersion time is 6-24 h.

3. Hydrophobic carbon paper with uniform conductivity and high conductivity prepared by the method according to any one of claims 1 to 2.

4. The method for preparing the hydrophobic carbon paper according to claim 3, wherein: The highly conductive carbon paper with uniform conductivity prepared by the method according to any one of claims 1 to 2 is immersed in a PTFE solution.

5. The method according to claim 4, characterized in that The viscosity of PTFE solution is 0.015-0.020 Pa.s.

6. Use of the hydrophobic carbon paper prepared by the method according to claim 4 or 5 in a fuel cell.

7. A proton exchange membrane fuel cell, characterized in that: The proton exchange membrane fuel cell uses the hydrophobic carbon paper prepared by the method according to claim 4 or 5 as a gas diffusion layer.

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