CN115172767A - Preparation method of carbon paper for gas diffusion layer of fuel cell - Google Patents

Preparation method of carbon paper for gas diffusion layer of fuel cell Download PDF

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Publication number
CN115172767A
CN115172767A CN202210876559.5A CN202210876559A CN115172767A CN 115172767 A CN115172767 A CN 115172767A CN 202210876559 A CN202210876559 A CN 202210876559A CN 115172767 A CN115172767 A CN 115172767A
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carbon paper
expanded graphite
fuel cell
gas diffusion
diffusion layer
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黄善聪
夏新兴
叶瑾
苏德凤
刘畅
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Zhejiang Sci Tech University ZSTU
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Zhejiang Sci Tech University ZSTU
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8605—Porous electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8647—Inert electrodes with catalytic activity, e.g. for fuel cells consisting of more than one material, e.g. consisting of composites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H01M4/8803—Supports for the deposition of the catalytic active composition
    • H01M4/8807—Gas diffusion layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/96—Carbon-based electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Composite Materials (AREA)
  • Paper (AREA)
  • Fuel Cell (AREA)

Abstract

The invention relates to a preparation method of carbon paper for a gas diffusion layer of a fuel cell. The invention firstly prepares the acrylic fiber pulp into slurry, reacts with the modified liquid under certain conditions, and is washed and dried by weak acid and clear water after the reaction is finished, thus obtaining the modified acrylic fiber pulp. Thereafter, an expanded graphite floating liquid was prepared and cut by a high-speed disperser to obtain fine expanded graphite. Oxidizing under subcritical condition, washing and filtering to obtain the modified micronized expanded graphite. Preparing the modified acrylic pulp and the carbon fiber into mixed slurry, and adding the modified micronized expanded graphite, the polyethylene oxide, the aluminum sulfate and the latex to obtain the stabilized mixed slurry. And (4) making the mixed slurry into paper, molding and drying to obtain the carbon paper precursor. And then, dipping the carbon paper precursor into a phenolic resin ethanol solution, drying, and finally, carrying out hot pressing and carbonization to obtain the carbon paper. The carbon paper prepared by the invention has the advantages of ultrahigh strength, excellent conductivity, uniform pore structure and the like, and the preparation method is rapid and stable.

Description

Preparation method of carbon paper for gas diffusion layer of fuel cell
Technical Field
The invention belongs to the technical field of fuel cell preparation, and particularly relates to a preparation method of carbon paper for a gas diffusion layer of a fuel cell.
Background
A fuel cell is a device for converting chemical energy of fuel into clean electrical energy through an electrochemical reaction. The energy storage device is different from the traditional battery type, cannot achieve the energy storage effect, is similar to a generator principle, enables the chemical energy of fuel to be converted into electric energy, and is an energy conversion device. Fuel cells have numerous advantages such as higher energy conversion efficiency, lower pollution and noise, higher operational reliability, and greater fuel availability.
The proton exchange membrane fuel cell is one of the fuel cells, has the advantages of small volume and weight, high energy density, high starting speed, safe and reliable operation and the like, and is the most promising class of fuel cells. It is composed of bipolar plate, gasket, gas diffusion layer, catalytic layer and proton exchange membrane. The gas diffusion layer is generally composed of a porous conductive material, and functions to transport reaction gas, remove product water, support a catalyst layer, collect current, and the like, and to achieve redistribution of the product water and the reaction gas. At present, common gas diffusion layers include carbon cloth, carbon paper, carbon black paper and the like, and particularly, carbon paper is common as a gas diffusion layer.
The carbon paper needs to have the following properties in a proton exchange membrane fuel cell: (1) certain strength. It is desirable to have high mechanical strength and suitable flexibility to provide structural support for the fuel cell. (2) suitable pore size structure. The device is used for gas delivery in the operation process of the fuel cell and water discharge after electrochemical reaction, and ensures that the electrochemical reaction is smoothly carried out. (3) low resistivity. The carbon paper is beneficial to electron transmission in the carbon paper, the contact resistance between the carbon paper and other parts is reduced, and the output power of the fuel cell is ensured. And (4) proper thickness and apparent density. The capability of the carbon paper for transmitting gas and moisture is improved. And (5) the surface is smooth. The contact resistance between the gas diffusion layer and the catalytic layer is reduced, and the stable output power of the proton exchange membrane fuel cell is ensured.
Chinese patent CN1185736C describes a method for preparing carbon paper, the raw material is pure carbon fiber, and then it is dispersed in water phase by using dispersant, and then directly formed into paper. Although the method can greatly reserve the content of the carbon fiber, the strength of the formed carbon paper is extremely low, and the method cannot be practically applied at all. According to patent CN110512459B, the raw materials used are viscose, cellulose nanofibrils and carbon fibers, and the strength of the carbon paper precursor can be improved by matching with other auxiliaries such as a surfactant, polyethylene oxide and a polyvinyl alcohol solution, but the strength of the carbon paper is not obviously improved due to the low residual carbon rate of the viscose and the cellulose nanofibrils, and the porosity of the carbon paper is not easy to adjust. Although the chinese patent CN113066996B proposes a method for preparing porous carbon paper, and the porosity and mechanical properties of the carbon paper are adjusted, the introduction of natural inorganic mineral fibers greatly improves the resistivity of the carbon paper, and reduces the electron transmission efficiency in the carbon paper and the output power of the fuel cell.
Therefore, the development of a method for manufacturing carbon paper for a gas diffusion layer of a fuel cell, which has high strength, high conductivity, good air permeability, stable quality and simple process, is a critical problem that needs to be solved urgently.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: aiming at the problems that the existing carbon paper for the gas diffusion layer of the fuel cell has large brittleness, low strength, difficult regulation and control of gaps and the like, the preparation method of the carbon paper for the gas diffusion layer of the fuel cell is provided.
The technical scheme adopted by the invention for solving the technical problem is as follows:
(1) Adding the acrylic fiber pulp into water to prepare slurry with the concentration of 2-20%, pulping to prepare slurry with the beating degree of 30-80 DEG SR, and dehydrating for later use. Preparing 2-12% alkali liquor, and then adding 10-30% absolute ethyl alcohol relative to the mass of the alkali liquor to prepare the modified liquid. Adding the pulped acrylic pulp into the prepared modified liquid, and reacting for 5-20min in a high-pressure reaction kettle with the pressure of 50-200kPa and the temperature of 50-80 ℃. Finally, washing and drying with weak acid and clear water to prepare the modified acrylic pulp.
(2) Mixing expanded graphite with water to prepare an expanded graphite floating liquid with the mass ratio of 1-5%, and cutting the expanded graphite floating liquid by using a high-speed dispersion machine to obtain the micronized expanded graphite. And then adding concentrated sulfuric acid and oxide which are 15-25 times and 1-5 times of the mass of the expanded graphite into the expanded graphite floating liquid, and reacting for 10-30min under subcritical conditions to obtain an expanded graphite suspension. Finally, washing and filtering the mixture by using hydrogen peroxide, sodium hydroxide and water to prepare the modified micronized expanded graphite.
(3) Adding the modified acrylic fiber pulp and the carbon fiber into water to prepare mixed slurry with the concentration of 0.05-0.2%. Then adding 2-10% of modified micronized expanded graphite relative to the mass of the carbon fiber, 0.1-0.2% of polyoxyethylene relative to the mass of the total fiber, 3-15% of aluminum sulfate and 5-25% of latex. Stirring evenly to obtain the stabilized mixed slurry. And (4) making the mixed slurry into paper, molding and drying to obtain the carbon paper precursor. And then soaking the carbon paper precursor in a phenolic resin ethanol solution, drying, and finally carrying out hot pressing and carbonization to obtain the carbon paper for the fuel cell.
Further, the alkali liquor in the step (1) is one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide.
Further, the weak acid in step (1) is one or more of formic acid, acetic acid and citric acid.
Further, the expanded graphite of the step (2) is prepared from 200-2000 mesh expandable graphite.
Furthermore, the size of the micronized expanded graphite in the step (2) is 500 nanometers to 70 micrometers.
Further, the oxide in the step (2) is one or more of potassium permanganate and potassium dichromate.
Furthermore, the subcritical condition in the step (2) is 493-593K and the pressure is 5-15MPa.
Further, the carbon fiber in the step (3) is one or more of polyacrylonitrile-based carbon fiber, pitch-based carbon fiber and viscose-based carbon fiber.
Furthermore, the diameter of the carbon fiber in the step (3) is 3-15 μm, and the length is 1-7mm.
Furthermore, the proportion of the modified acrylic fiber pulp and the carbon fiber in the step (3) is 1-20.
Further, the latex in the step (3) is one or more of styrene-butadiene latex, butyronitrile latex and natural latex.
Furthermore, the hot-pressing treatment temperature in the step (3) is 120-180 ℃, the pressure is 2-15MPa, and the time is 5-25min.
Furthermore, the carbonization condition in the step (3) is under inert atmosphere, the carbonization temperature is 800-1600 ℃, and the carbonization time is 20-200min.
Further, the carbonization condition in the step (3) is one or more of nitrogen and argon.
Further, the carbon paper quantitative amount in the step (3) is 30-150g/m 2 。
The invention has the beneficial effects that:
(1) The reinforcing fiber used in the invention is acrylic fiber pulp, and the modified acrylic fiber pulp is prepared by hydrophilic modification on the surface of the acrylic fiber pulp. The modified acrylic pulp overcomes the hydrophobic property of the original fiber, enhances the water wettability, improves the suspension stability of the pulp in water and also improves the bonding strength between fibers.
(2) The modified micronized expanded graphite is prepared by the subcritical liquid phase oxidation technology, and the preparation method is simple and efficient. Not only retains the molecular structure of natural graphite and the porous characteristic of expanded graphite, but also improves the water-wet dispersibility of the expanded graphite.
(3) The invention utilizes the branching structure and the bending characteristic of the acrylic pulp to form an interweaving and interconnecting state among carbon fibers, and the lock catch binding sites are added among the fibers by matching with the modified micronized expanded graphite, so that the strength of the carbon paper is obviously increased.
(4) According to the invention, the modified micronized expanded graphite is introduced, so that pore channels among the carbon papers are increased, and the carbon paper pore structure and the water and gas management capability are easy to regulate and control.
(5) The invention adsorbs the modified expanded graphite on the acrylic pulp, greatly reduces the surface resistance and the contact resistance of the carbon paper after carbonization, and greatly improves the conductivity.
(6) According to the invention, through the self-sliding characteristic between the expanded graphite layers and the introduction of latex, the flexibility of the carbon paper is obviously improved, so that the carbon paper is not easy to bend and damage in preparation and transportation.
(7) The carbon paper has the advantages of ultrahigh strength, excellent conductivity, uniform pore structure and the like, and the preparation method is rapid and stable and has good practical application value.
Detailed Description
The technical scheme of the invention is as follows:
(1) Adding the acrylic pulp into water to prepare a slurry with the concentration of 2-20%, then pulping to prepare a slurry with the beating degree of 30-80 DEG SR, and dehydrating for later use. Preparing 2-12% alkali solution (sodium hydroxide, potassium hydroxide and lithium hydroxide), and adding 10-30% absolute ethyl alcohol relative to the mass of the alkali solution to obtain the modified solution. Adding the pulped acrylic pulp into the prepared modified liquid, and reacting for 5-20min in a high-pressure reaction kettle with the pressure of 50-200kPa and the temperature of 50-80 ℃. Finally, washing with weak acid (formic acid, acetic acid and citric acid) and clear water and drying to prepare the modified acrylic pulp.
(2) Mixing expanded graphite with water to prepare 1-5% of expanded graphite floating liquid, and cutting the expanded graphite floating liquid by using a high-speed dispersion machine to obtain the micronized expanded graphite with the size of 500 nanometers-70 micrometers. Then adding concentrated sulfuric acid 15-25 times and oxide (potassium permanganate and potassium dichromate) 1-5 times of the mass of the expanded graphite into the expanded graphite floating liquid, and reacting for 10-30min under the subcritical conditions of temperature 493-593K and pressure 5-15MPa to obtain an expanded graphite suspension. Finally, washing and filtering the mixture by using hydrogen peroxide, sodium hydroxide and water to prepare the modified micronized expanded graphite.
(3) Adding the modified acrylic pulp and carbon fiber (polyacrylonitrile-based carbon fiber, pitch-based carbon fiber and viscose-based carbon fiber) with the diameter of 3-15 μm and the length of 1-7mm into water according to the proportion of 1-20 to prepare mixed slurry with the concentration of 0.05-0.2%. Then adding 2-10% of modified micronized expanded graphite relative to the mass of the carbon fiber. Then adding 0.1-0.2% of polyethylene oxide, 3-15% of aluminum sulfate and 5-25% of latex (styrene-butadiene latex, butyronitrile latex and natural latex) by mass relative to the total fibers (modified acrylic fiber pulp and carbon fibers). Stirring evenly to obtain the stabilized mixed slurry. Making the mixed slurry into paper, molding and drying to obtain the carbon paper precursor. Then dipping the carbon paper precursor into phenolic resin ethanol solution and drying, finally carrying out hot pressing at the temperature of 120-180 ℃, the pressure of 2-15MPa and the time of 5-25min and carbonization at the temperature of 800-1600 ℃ and the time of 20-200min to obtain the carbon paper precursor with the quantitative of 30-150g/m 2 A carbon paper for a fuel cell.
The principle of the method of the invention is as follows:
the acrylic pulp is formed by taking acrylonitrile as a main comonomer, has a highly fibrillated structure and a high proportion of branched structures, and contains a large amount of cyano (-CN) on the surface, so the acrylic pulp is a hydrophobic fiber. The invention converts hydrophobic group cyano into hydrophilic group carboxyl (-COH), amide (-CONH) by hydrophilic modification of acrylic pulp 2 ) And the like, endowing the acrylic pulp with hydrophilic property. The specific surface area of the fiber is increased through the surface etching effect, the hydrophilicity is improved, and the dispersion stability in water is further enhanced.
The expanded graphite and graphite have the same constituent elements and are carbon atoms, and the structure is that six carbon atoms form a regular hexagon in the same plane and stretch into a sheet layer. Because the surface of graphite has high degree of mineralization, it is neither hydrophilic nor oleophilic, so that the expanded graphite is not easy to disperse and agglomerate in water. The invention adopts a subcritical liquid phase oxidation technology to promote an oxidant to attack an oxidation active site influenced by steric hindrance between the surface of the expanded graphite and a sheet layer, so that the expanded graphite is endowed with hydrophilic groups such as hydroxyl groups, carboxyl groups and the like in an all-around 360-degree manner. The hydrophilic groups are added on the surface of the expanded graphite, so that the expanded graphite is easier to be wetted by water, and the water dispersibility of the expanded graphite is further enhanced.
The traditional carbon paper takes carbon fiber as a main body and adopts single phenolic resin as an adhesive, so that the strength is poor, the carbon paper is brittle, and gaps are not easy to adjust. The invention utilizes the extremely high carbon storage rate and the morphological characteristics of the acrylic pulp, namely fiber extending tree-shaped and cluster villous tiny fibers, and combines the hydrophilic modification process to interweave the acrylic pulp and the carbon fibers to form a hook-shaped structure, thereby firmly locking the carbon fibers. Therefore, the mechanical meshing action between the carbon fibers and between the carbon fibers and the resin is improved, the interface performance between the carbon fibers and the resin is enhanced, and the strength of the carbon fiber paper is improved.
The modified micronized expanded graphite and the acrylic pulp are combined through hydrogen bonds and intermolecular force, and serve as a 'lock catch' effect in a 'hook-shaped' structure, so that the strength of the carbon paper is further enhanced. In addition, the modified micronized expanded graphite also keeps the microstructure of the expanded graphite, namely loose porosity. The void structure of the carbon paper can be adjusted by adjusting the proportion of the modified micronized expanded graphite in the carbon paper.
The brittleness of the carbon paper is improved by adding latex into the sizing agent, and the latex is greatly lost due to the fact that the surfaces of the conventional carbon fiber, acrylic pulp and expanded graphite are not provided with hydrophilic groups. Active groups are introduced into the modified acrylic pulp and the expanded graphite, and latex is retained in the carbon paper through electrostatic adsorption and flocculation by combining with aluminum sulfate, so that the toughness of the carbon paper is further improved. In addition, the expanded graphite has a graphite sheet structure, and sliding surfaces are formed among sheets, so that the carbon paper is not easy to break in the bending process. Therefore, the modified micronized expanded graphite can not only enhance the hydrophilicity of the graphite, but also enhance the strength of the carbon paper, regulate and control the pores, improve the conductivity and improve the brittleness. Compared with the traditional carbon paper, the carbon paper has the advantages that the strength of the carbon paper is improved, the brittleness of the carbon paper is improved, and the pores of the carbon paper are regulated and controlled.
Example 1
The first step is as follows: adding the acrylic pulp into water to prepare a slurry with the concentration of 2%, then pulping to prepare a slurry with the beating degree of 30 DEG SR, and dehydrating for later use. Preparing sodium hydroxide with the concentration of 2%, and then adding absolute ethyl alcohol with the mass of 10% relative to the mass of the sodium hydroxide to prepare the modified liquid. Adding the pulped acrylic fiber pulp into the prepared modified liquid, and reacting for 5min in a high-pressure reaction kettle with the pressure of 50kPa and the temperature of 50 ℃. Finally, washing with formic acid and clear water and drying to prepare the modified acrylic pulp.
The second step: expanded graphite was mixed with water to prepare a 1% expanded graphite floating liquid, which was cut with a high-speed disperser to obtain fine expanded graphite having a size of 500 nm. And then adding concentrated sulfuric acid 15 times and potassium permanganate 1 time the mass of the expanded graphite into the expanded graphite floating liquid, and reacting for 10min under the subcritical conditions that the temperature is 493K and the pressure is 5MPa to obtain an expanded graphite suspension. Finally, washing and filtering the mixture by using hydrogen peroxide, sodium hydroxide and water to prepare the modified micronized expanded graphite.
The third step: adding the modified acrylic pulp and polyacrylonitrile-based carbon fiber with the diameter of 3mm and the length of 1mm into water according to the proportion of 1. Then, 2% by mass of the modified fine expanded graphite with respect to the mass of the carbon fibers was added. Then 0.1% of polyethylene oxide, 3% of aluminium sulphate and 5% of styrene-butadiene latex relative to the total fibre mass are added. Stirring evenly to obtain the stabilized mixed slurry. And manufacturing, molding and drying the mixed slurry to obtain the carbon paper precursor. Then dipping the carbon paper precursor into phenolic resin ethanol solution and drying, finally hot pressing at 120 ℃, 2MPa and 5min and carbonizing at 800 ℃ and 20min to obtain the carbon paper precursor with the quantitative of 30g/m 2 A carbon paper for a fuel cell.
Example 2
The first step is as follows: adding the acrylic pulp into water to prepare a slurry with the concentration of 20%, then pulping to prepare the slurry with the beating degree of 80 DEG SR, and dehydrating for later use. Preparing 12% potassium hydroxide, and adding 30% of absolute ethyl alcohol relative to the mass of the potassium hydroxide to prepare the modified solution. Adding the pulped acrylic pulp into the prepared modified liquid, and reacting for 20min in a high-pressure reaction kettle with the pressure of 200kPa and the temperature of 80 ℃. Finally, washing with acetic acid and clear water and drying to prepare the modified acrylic pulp.
The second step: expanded graphite was mixed with water to prepare a 5% expanded graphite floating solution, which was cut with a high-speed disperser to obtain micronized expanded graphite having a size of 70 μm. Then adding concentrated sulfuric acid with the mass of 25 times and potassium dichromate with the mass of 5 times of that of the expanded graphite into the expanded graphite floating liquid, and reacting for 30min under the subcritical conditions of 593K temperature and 15MPa pressure to obtain an expanded graphite suspension. Finally, washing and filtering the mixture by using hydrogen peroxide, sodium hydroxide and water to prepare the modified micronized expanded graphite.
The third step: mixing modified acrylic pulp with diameter of 15 μm and length of 7mmThe cyan-based carbon fiber was added to water at a ratio of 1. Then, 10% by mass of the modified finely expanded graphite with respect to the mass of the carbon fibers was added. Then 0.2% of polyethylene oxide, 15% of aluminium sulphate and 25% of nitrile latex relative to the total fibre mass are added. Stirring evenly to obtain the stabilized mixed slurry. And (4) making the mixed slurry into paper, molding and drying to obtain the carbon paper precursor. Then dipping the carbon paper precursor into phenolic resin ethanol solution and drying, finally hot pressing at 180 ℃, 15MPa and 25min and carbonizing at 1600 ℃ and 200min to obtain the carbon paper precursor with the quantitative of 150g/m 2 A carbon paper for a fuel cell.
Example 3
The first step is as follows: adding the acrylic pulp into water to prepare slurry with the concentration of 10%, then pulping to prepare slurry with the beating degree of 50 DEG SR, and dehydrating for later use. Preparing lithium hydroxide with the concentration of 8%, and then adding absolute ethyl alcohol with the mass of 20% of that of the lithium hydroxide to prepare a modified solution. Adding the pulped acrylic pulp into the prepared modified liquid, and reacting for 10min in a high-pressure reaction kettle with the pressure of 100kPa and the temperature of 60 ℃. And finally, washing with citric acid and clear water and drying to prepare the modified acrylic pulp.
The second step is that: expanded graphite was mixed with water to prepare a 3% floating solution of expanded graphite, and the floating solution was cut with a high-speed disperser to obtain fine expanded graphite having a size of 5 μm. And then adding concentrated sulfuric acid which is 20 times of the mass of the expanded graphite and potassium permanganate which is 3 times of the mass of the expanded graphite into the expanded graphite floating liquid, and reacting for 20min under subcritical conditions of temperature 553K and pressure 10MPa to obtain an expanded graphite suspension. Finally, washing and filtering the mixture by using hydrogen peroxide, sodium hydroxide and water to prepare the modified micronized expanded graphite.
The third step: the modified acrylic pulp and the viscose-based carbon fiber with the diameter of 10 mu m and the length of 3mm are added into water according to the proportion of 1. Then, 8% by mass of the modified fine expanded graphite with respect to the mass of the carbon fibers was added. Then 0.15% of polyethylene oxide, 6% of aluminium sulphate and 15% of natural latex relative to the total fibre mass are added. Stirring evenly to obtain the stabilized mixed slurry. And (4) making the mixed slurry into paper, molding and drying to obtain the carbon paper precursor. Then dipping the carbon paper precursor into a phenolic resin ethanol solution, drying, and finally carrying out hot pressing at the temperature of 150 ℃, the pressure of 8MPa and the time of 15min and carbonization at the temperature of 1200 ℃ and the time of 60min to obtain the carbon paper precursor with the quantitative of 60g/m 2 A carbon paper for a fuel cell.
Comparative example 1
The first step is as follows: adding the acrylic pulp into water to prepare slurry with the concentration of 10%, then pulping to prepare slurry with the beating degree of 50 DEG SR, and dehydrating for later use. Preparing lithium hydroxide with the concentration of 8%, and then adding absolute ethyl alcohol with the mass of 20% of that of the lithium hydroxide to prepare a modified solution. Adding the pulped acrylic pulp into the prepared modified liquid, and reacting for 10min in a high-pressure reaction kettle with the pressure of 100kPa and the temperature of 60 ℃. And finally, washing with citric acid and clear water and drying to prepare the modified acrylic pulp.
The second step is that: the modified acrylic pulp and the viscose-based carbon fiber with the diameter of 10 mu m and the length of 3mm are added into water according to the proportion of 1. Then 0.15% of polyethylene oxide, 6% of aluminium sulphate and 15% of natural latex relative to the total fibre mass are added. Stirring evenly to obtain the stabilized mixed slurry. And manufacturing, molding and drying the mixed slurry to obtain the carbon paper precursor. Then dipping the carbon paper precursor into a phenolic resin ethanol solution, drying, and finally carrying out hot pressing at the temperature of 150 ℃, the pressure of 8MPa and the time of 15min and carbonization at the temperature of 1200 ℃ and the time of 60min to obtain the carbon paper precursor with the quantitative of 60g/m 2 A carbon paper for a fuel cell.
Comparative example 2
The first step is as follows: expanded graphite was mixed with water to prepare a 3% floating solution of expanded graphite, and the floating solution was cut with a high-speed disperser to obtain fine expanded graphite having a size of 5 μm. And then adding concentrated sulfuric acid which is 20 times of the mass of the expanded graphite and potassium permanganate which is 3 times of the mass of the expanded graphite into the expanded graphite floating liquid, and reacting for 20min under subcritical conditions of the temperature of 553K and the pressure of 10MPa to obtain an expanded graphite suspension. Finally, washing and filtering the mixture by using hydrogen peroxide, sodium hydroxide and water to prepare the modified micronized expanded graphite.
The second step is that: viscose-based carbon fibers having a diameter of 10 μm and a length of 3mm were added to water to prepare a slurry having a concentration of 0.1%. Then, 8% by mass of the modified fine expanded graphite with respect to the mass of the carbon fibers was added. Then 0.15% of polyethylene oxide, 6% of aluminium sulphate and 15% of natural latex relative to the total fibre mass are added. Stirring evenly to obtain the stabilized mixed slurry. And manufacturing, molding and drying the mixed slurry to obtain the carbon paper precursor. Then dipping the carbon paper precursor into a phenolic resin ethanol solution, drying, and finally carrying out hot pressing at the temperature of 150 ℃, the pressure of 8MPa and the time of 15min and carbonization at the temperature of 1200 ℃ and the time of 60min to obtain the carbon paper precursor with the quantitative of 60g/m 2 A carbon paper for a fuel cell.
Comparative example 3
Viscose-based carbon fibers having a diameter of 10 μm and a length of 3mm were added to water to prepare a slurry having a concentration of 0.1%. Then 0.15% of polyethylene oxide, 6% of aluminium sulphate and 15% of natural latex relative to the total fibre mass are added. Stirring evenly to obtain the stabilized mixed slurry. And manufacturing, molding and drying the mixed slurry to obtain the carbon paper precursor. Then dipping the carbon paper precursor into phenolic resin ethanol solution and drying, finally hot pressing at 150 ℃, 8MPa and 15min and carbonizing at 1200 ℃ and 60min to obtain the carbon paper precursor with the quantitative of 60g/m 2 A carbon paper for a fuel cell.
Testing the performance of the carbon paper of the gas diffusion layer:
the carbon papers prepared in the above examples and comparative examples were respectively subjected to tensile strength, porosity, resistivity, air permeability, bending stiffness and other performance tests. The measurement results are shown in table 1.
Table 1 comparison of properties of carbon papers for gas diffusion layers
Figure BDA0003762595220000101
From comparative examples 2 and 3 in table 1, it can be seen that the addition of the modified expanded graphite can significantly increase the porosity and air permeability of the carbon paper and increase the tensile strength and bendability. From comparative examples 1 and 3, the modified acrylic pulp can significantly improve the tensile strength of the carbon paper, but the porosity and air permeability are reduced. As seen from examples 1-3 and comparative examples 1-3, the tensile strength and resistivity of the carbon paper can be significantly improved and the porosity and air permeability can be kept good by introducing the modified acrylic pulp and the modified expanded graphite on the carbon paper, and besides, the bending deformation resistance of the carbon paper is improved. In conclusion, the carbon paper disclosed by the invention is excellent in comprehensive performance, has the advantages of high strength, excellent conductivity, uniform gap structure and the like, is improved in bending deformation capability and toughness, and has a good practical application value.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in other forms, and any person skilled in the art may modify or change the technical content disclosed above into an equivalent embodiment with equivalent changes, but all those simple modifications, equivalent changes and modifications made on the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the present invention.

Claims (10)

1. A preparation method of carbon paper for a gas diffusion layer of a fuel cell is characterized by comprising the following steps:
(1) Adding the acrylic pulp into water to prepare a slurry with the concentration of 2-20%, then pulping to prepare a slurry with the beating degree of 30-80 DEG SR, and dehydrating for later use;
preparing 2-12% alkali liquor, and adding 10-30% absolute ethyl alcohol relative to the mass of the alkali liquor to prepare modified liquid;
adding the pulped acrylic pulp into the prepared modified liquid, and reacting for 5-20min in a high-pressure reaction kettle with the pressure of 50-200kPa and the temperature of 50-80 ℃;
washing with weak acid and clear water and drying to obtain modified acrylic pulp;
(2) Mixing expanded graphite with water to prepare an expanded graphite floating liquid with the mass ratio of 1-5%, and cutting the expanded graphite floating liquid by using a high-speed dispersion machine to obtain micronized expanded graphite;
adding concentrated sulfuric acid and oxide in an amount which is 15-25 times of the weight of the expanded graphite and 1-5 times of the weight of the expanded graphite into the expanded graphite floating liquid, and reacting for 10-30min under a subcritical condition to obtain an expanded graphite suspension;
washing and filtering with hydrogen peroxide, sodium hydroxide and water to prepare modified micronized expanded graphite;
(3) Adding the modified acrylic fiber pulp and the carbon fiber into water to prepare mixed slurry with the concentration of 0.05-0.2%;
adding 2-10% of modified micronized expanded graphite relative to the mass of the carbon fiber, and adding 0.1-0.2% of polyethylene oxide, 3-15% of aluminum sulfate and 5-25% of latex relative to the mass of the total fiber; stirring uniformly to obtain stabilized mixed slurry; making the mixed slurry into paper, molding and drying to obtain a carbon paper precursor; and then, dipping the carbon paper precursor into a phenolic resin ethanol solution, drying, and finally, carrying out hot pressing and carbonization to obtain the carbon paper of the gas diffusion layer of the fuel cell.
2. The method for preparing the carbon paper for the gas diffusion layer of the fuel cell according to claim 1, wherein the method comprises the following steps: the alkali liquor in the step (1) is one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; the weak acid is one or more of formic acid, acetic acid and citric acid.
3. The method for preparing the carbon paper for the gas diffusion layer of the fuel cell according to claim 1, wherein the method comprises the following steps: the expanded graphite in the step (2) is prepared from expandable graphite of 200-2000 meshes; the size of the micronized expanded graphite is 500 nanometers to 70 micrometers.
4. The method for preparing the carbon paper for the gas diffusion layer of the fuel cell according to claim 1, wherein the method comprises the following steps: the oxide in the step (2) is one or more of potassium permanganate and potassium dichromate.
5. The method for preparing the carbon paper for the gas diffusion layer of the fuel cell according to claim 1, wherein the method comprises the following steps: the subcritical condition in the step (2) is 493-593K, and the pressure is 5-15MPa.
6. The method for preparing the carbon paper for the gas diffusion layer of the fuel cell according to claim 1, wherein the method comprises the following steps: the carbon fiber in the step (3) is one or more of polyacrylonitrile-based carbon fiber, asphalt-based carbon fiber and viscose-based carbon fiber; the diameter of the carbon fiber is 3-15 μm, and the length is 1-7mm.
7. The method for preparing the carbon paper for the gas diffusion layer of the fuel cell according to claim 1, wherein the method comprises the following steps: the mass ratio of the modified acrylic fiber pulp to the carbon fiber in the step (3) is 1-20.
8. The method for preparing the carbon paper for the gas diffusion layer of the fuel cell according to claim 1, wherein the method comprises the following steps: the latex in the step (3) is one or more of styrene-butadiene latex, butyronitrile latex and natural latex.
9. The method for preparing the carbon paper for the gas diffusion layer of the fuel cell according to claim 1, wherein the method comprises the following steps: the hot-pressing treatment temperature in the step (3) is 120-180 ℃, the pressure is 2-15MPa, and the time is 5-25min; the carbonization condition is under inert atmosphere, the carbonization temperature is 800-1600 ℃, and the carbonization time is 20-200min.
10. The method for preparing the carbon paper for the gas diffusion layer of the fuel cell according to claim 1, wherein the method comprises the following steps: and (3) the carbonization condition is one or more of nitrogen and argon.
CN202210876559.5A 2022-07-25 2022-07-25 Preparation method of carbon paper for gas diffusion layer of fuel cell Pending CN115172767A (en)

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