A modified graphene fiber nonwoven fabric and its application in proton exchange membrane fuel cells

Abstract

The present invention relates to a modified graphene fiber nonwoven fabric and its application in a proton exchange membrane fuel cell. The modified graphene fiber nonwoven fabric is modified using a phenolic resin as a sizing agent for interfiber junction bonding to obtain the modified graphene fiber nonwoven fabric. The application of the modified graphene fiber nonwoven fabric in a proton exchange membrane fuel cell addresses the problems of traditional commercial carbon paper exhibiting brittleness, fragility, and poor conductivity. Furthermore, after a single cell operates for a long time, conditions such as an increasingly acidic water environment and stress relaxation can damage the carbon fiber structure of the gas diffusion layer, thereby reducing the gas diffusion layer's mass transfer and gas conduction properties, thereby reducing the output power density and service life of the fuel cell.

Description

Technical Field

[0001] The present invention relates to the fields of graphene fiber nonwoven fabrics and proton exchange membrane fuel cell membrane electrodes, and in particular to modified graphene fiber nonwoven fabrics and applications thereof in proton exchange membrane fuel cells. Background Art

[0002] A fuel cell is an energy conversion and storage device that converts the chemical energy of fuel and oxidant into electrical energy through an electrochemical reaction. Unconstrained by the Carnot cycle, it boasts a high energy conversion efficiency (40%-60%). By fully utilizing waste heat, the efficiency can reach 90%. Furthermore, it offers advantages such as high power density, light weight, simple construction, high reliability, rapid startup, low-temperature resistance, and low noise levels. For example, a proton exchange membrane fuel cell uses hydrogen or hydrogen-rich gas as fuel. It boasts advantages unmatched by lithium batteries, such as large capacity, low cost, and long storage cycles. The reaction product, H2O, is crucial for addressing the two major global challenges of energy shortage and environmental pollution, making it an ideal choice for portable applications, power stations, and high-power vehicles.

[0003] In 2004, the research group of Professor AK Geim of the University of Manchester in the UK successfully prepared graphene using a mechanical exfoliation method. Structurally, graphene is a sp2 hybridized single-layer carbon atom crystal tightly packed into a two-dimensional honeycomb lattice structure. The carbon atoms within the layer are connected by covalent bonds and have ultra-high strength (120GPa). Therefore, using graphene as a source material to construct carbon-based materials with specific structures, thereby achieving the design and controllable and large-scale preparation of carbonaceous functional material nanostructures, has gradually attracted the attention of scientists around the world. Compared with traditional carbon fibers, graphene fibers have a larger sheet diameter and oriented graphite whisker structure in structure, and have higher strength, high modulus, high electrical conductivity, high thermal conductivity and other characteristics, which has attracted widespread attention from scholars at home and abroad.

[0004] The proton exchange membrane fuel cell is mainly composed of a membrane electrode and a bipolar plate, and the membrane electrode is mainly composed of three parts: a gas diffusion layer, a catalyst layer, and a proton exchange membrane. The electrochemical reaction of the fuel cell occurs in the membrane electrode, specifically: (1) The externally supplied fuel passes through the anode current collector and the anode gas diffusion layer to the anode catalyst layer, and is oxidized under the action of the catalyst. The fuel molecules are decomposed into positively charged ions and release negatively charged electrons, completing the anode reaction; (2) The ions pass through the proton exchange membrane to reach the cathode, and the electrons form a current in the external circuit, which can output electrical energy to the load through appropriate connection; (3) At the other end of the battery, oxygen passes through the cathode current collector and the cathode gas diffusion layer to the cathode catalyst layer, reacts with the ions and electrons that pass through the membrane to form products such as water and generate heat, completing the cathode reaction; (4) Most of the water generated by the reaction on the cathode side is discharged with the air, and a small part diffuses through the membrane to the anode under the action of the pressure difference. The functions of the gas diffusion layer are: (1) as a buffer and diffusion layer before the fuel gas enters the catalyst layer; (2) to provide a transport channel for electrons and water generated by the reaction; (3) as a supporting skeleton of the membrane electrode to provide physical support for the proton exchange membrane and catalyst. Therefore, this also requires that the ideal gas diffusion layer material meets the following conditions: (1) good hydrophobicity; (2) excellent air permeability; (3) good electrical conductivity; (4) high porosity; (5) certain mechanical strength and flexibility; (6) excellent electrochemical stability; (7) good thermal conductivity. The gas diffusion layer is the main place for gas and water transmission, and its performance degradation is one of the major factors affecting the service life of the proton exchange membrane fuel cell.

[0005] Currently, commercial gas diffusion layers are made of carbon fiber paper, carbon fiber woven cloth, and carbon black paper, with carbon paper being the most predominant. Traditional commercial carbon paper, such as Japan's TorayTM060, has excellent hydrophobicity, mechanical properties, and high porosity. However, due to its network structure of physically bonded polyacrylonitrile-based carbon fibers, the overall carbon paper exhibits brittleness, easy breakage, and poor electrical conductivity. Furthermore, after prolonged operation of a single cell, the increasingly acidic water environment and stress relaxation conditions can damage the carbon fiber structure of the gas diffusion layer, reducing its mass transfer and gas conduction properties. This, in turn, reduces the output power density and service life of the fuel cell.

[0006] Therefore, there is a need for a modified graphene fiber nonwoven fabric and its application in proton exchange membrane fuel cells. Summary of the Invention

[0007] A modified graphene fiber nonwoven fabric is obtained by modifying the graphene fiber nonwoven fabric by using phenolic resin as a sizing agent for overlapping the fiber nodes of the graphene fiber nonwoven fabric.

[0008] Furthermore, a modified graphene fiber nonwoven fabric is used in a proton exchange membrane fuel cell, characterized by comprising the following steps:

[0009] (1) The modified graphene fiber non-woven fabric is hot-pressed to obtain a graphene fiber non-woven fabric composite;

[0010] (2) graphitizing the graphene fiber non-woven fabric composite at 2800°C to obtain graphene fiber carbon paper;

[0011] (3) impregnating the graphene fiber non-woven fabric composite in polytetrafluoroethylene emulsion to attach a polytetrafluoroethylene hydrophobic layer to the surface of the graphene fiber, and then sintering the composite through heat treatment to remove the surfactant to obtain super-hydrophobic graphene fiber carbon paper;

[0012] (4) Super hydrophobic graphene fiber carbon paper as the graphene fiber carbon paper gas diffusion layer of the membrane electrode;

[0013] (5) Graphene fiber carbon paper gas diffusion layer as proton exchange membrane fuel cell membrane electrode.

[0014] Furthermore, the sizing treatment uses phenolic resin as a sizing agent with a mass fraction of 10%-30%, and the impregnation temperature and time are 50°C and 12h; the hot press uses 200°C and 1MPa hot pressing for 5min to obtain the graphene fiber non-woven fabric composite.

[0015] Furthermore, the graphene fiber non-woven fabric composite is graphitized at 2800° C. to obtain graphene fiber carbon paper.

[0016] Furthermore, the graphene fiber non-woven fabric composite is impregnated in polytetrafluoroethylene emulsion so that a polytetrafluoroethylene hydrophobic layer is attached to the surface of the graphene fiber, and then heat-treated and sintered to remove the surfactant to obtain super-hydrophobic graphene fiber carbon paper.

[0017] Furthermore, conductive carbon black and polytetrafluoroethylene emulsion with a mass ratio of 1:1, dispersants of water and isopropyl alcohol, and a volume ratio of 2-5:1 are ultrasonically dispersed to obtain a slurry, and the slurry is then evenly loaded on the surface of superhydrophobic graphene fiber carbon paper by spraying to prepare a microporous layer with a thickness of 10-40 μm. The layer is then sintered at 350°C for 30 minutes to obtain a graphene fiber carbon paper gas diffusion layer for proton exchange membrane fuel cells.

[0018] Furthermore, a CCM (catalyst coated membrane) containing a graphene fiber carbon paper gas diffusion layer loaded with a catalyst is hot-pressed and composited to obtain a proton exchange membrane fuel cell membrane electrode.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. Intrinsic performance advantages: Graphene fiber composite non-woven carbon paper with fusion fiber network structure has high conductivity (52000S / m), high porosity (above 0.85), high density (0.4g / cm 3 Above), high strength and other advantages;

[0021] 2. Installation performance advantages: In fuel cell single cell testing applications, under the same conditions, compared with commercial carbon paper, it has the performance advantages of low ohmic polarization, high hydrophobicity, high specific surface area, high cycle stability, high corrosion resistance, self-support, and low cost;

[0022] 3. Cost advantage: This carbon paper is prepared through a one-step high-temperature process, which not only surpasses traditional GDL carbon paper materials in performance, but also shortens the high-cost technical route of repeated high-temperature treatment of traditional GDL.

[0023] 4. The present invention uses direct solution impregnation of graphene fibers, which does not require a very high concentration.

[0024] 5. Fusion of fiber + sizing agent promotes overlap, and overlap between three-dimensional random fiber networks; during the graphitization process, due to the two-dimensional topological seed graphitization effect, graphene fibers can induce the graphitization of the sizing agent phenolic resin, and then a more regular graphite structure can be obtained, thereby improving the conductivity of the overall carbon paper fiber conductive network. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the appearance of the super-hydrophobic graphene fiber carbon paper of the present invention;

[0026] Figure 2 This is a resistance comparison diagram of the volt-ampere characteristic curve test of the super-hydrophobic graphene fiber carbon paper of Example 1 of the present invention and commercial carbon paper;

[0027] Figure 3 This is a performance diagram of the IV cycle test of a super-hydrophobic graphene fiber carbon paper single cell according to Example 1 of the present invention;

[0028] Figure 4 This is a performance diagram of the IV cycle test of a super-hydrophobic graphene fiber carbon paper single cell according to Example 2 of the present invention;

[0029] Figure 5 This is a performance diagram of the IV cycle test of a super-hydrophobic graphene fiber carbon paper single cell according to Example 3 of the present invention;

[0030] Figure 6 This is a performance diagram of the IV cycle test of a super-hydrophobic graphene fiber carbon paper single cell according to Example 4 of the present invention;

[0031] Figure 7 This is a performance diagram of the IV cycle test of a super-hydrophobic graphene fiber carbon paper single cell according to Example 5 of the present invention;

[0032] Figure 8 This is a performance diagram of the IV cycle test of a super-hydrophobic graphene fiber carbon paper single cell according to Example 6 of the present invention;

[0033] Figure 9 This is a performance diagram of the IV cycle test of a super-hydrophobic graphene fiber carbon paper single cell according to Example 7 of the present invention;

[0034] Figure 10 SEM image of the super-hydrophobic graphene fiber carbon paper of Example 1 of the present invention;

[0035] Figure 11 SEM image of the super-hydrophobic graphene fiber carbon paper according to Example 2 of the present invention;

[0036] Figure 12 SEM image of the super-hydrophobic graphene fiber carbon paper of Example 3 of the present invention;

[0037] Figure 13 SEM image of the super-hydrophobic graphene fiber carbon paper of Example 4 of the present invention;

[0038] Figure 14 SEM image of the super-hydrophobic graphene fiber carbon paper of Example 5 of the present invention;

[0039] Figure 15 SEM image of the super-hydrophobic graphene fiber carbon paper of Example 6 of the present invention;

[0040] Figure 16 SEM image of the super-hydrophobic graphene fiber carbon paper of Example 7 of the present invention;

[0041] Figure 17 SEM image of commercial carbon paper of the comparative example of the present invention;

[0042] Figure 18 Graph showing the hydrophobicity of the graphene fiber carbon paper of the present invention (Example 1). DETAILED DESCRIPTION

[0043] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0044] According to the design scheme of the present invention, the modified graphene fiber nonwoven fabric and its application in a proton exchange membrane fuel cell include the following steps:

[0045] Step 1: The graphene fiber non-woven fabric is sizing with phenolic resin. Different phenolic resin solution concentration gradients, as well as immersion time and temperature, are set to control the lap strength and air permeability of the graphene fiber non-woven fabric to obtain a modified graphene fiber non-woven fabric, which is then hot-pressed to obtain a graphene fiber non-woven fabric composite. Specifically, the mass fraction of phenolic resin as a sizing agent is 20%, the immersion temperature and time are 50°C for 12 hours, and then the graphene fiber non-woven fabric composite is obtained by hot pressing at 200°C and 1MPa for 5 minutes. Graphitization treatment at 2800°C is then performed to obtain graphene fiber carbon paper.

[0046] Step 2: Impregnate graphene fiber carbon paper in polytetrafluoroethylene emulsion to adhere a polytetrafluoroethylene hydrophobic layer to the surface of the graphene fiber, then sinter through heat treatment to remove the surfactant to obtain super-hydrophobic graphene fiber carbon paper. Specifically, conductive carbon black and polytetrafluoroethylene emulsion are mixed in a mass ratio of 1:1, the dispersant is water and isopropyl alcohol, the volume ratio of water to isopropyl alcohol is 2-5:1, and the dispersion is carried out by ultrasound. The slurry is then evenly loaded on the surface of the super-hydrophobic carbon paper by spraying to prepare a microporous layer with a thickness of 10-40 μm. The surfactant is then removed by sintering to obtain a super-hydrophobic graphene fiber carbon paper for the gas diffusion layer of a proton exchange membrane fuel cell.

[0047] Step 3: Hot-press the super-hydrophobic graphene fiber carbon paper and a commercial proton exchange membrane (CCM) loaded with a catalyst to form a proton exchange membrane fuel cell membrane electrode. Specifically, the temperature is 150°C, the pressure is 0.2 MPa, and the time is 90 seconds.

[0048] Example 1

[0049] (1) The graphene fiber non-woven fabric was placed in a vacuum oven and heated to 70 ° C and immersed in a 30% by mass phenolic resin solution for 2 h. After the phenolic resin was fully sized on the fiber nodes, the modified graphene fiber non-woven fabric was obtained. A hot press was used to fully cure the graphene fiber non-woven fabric composite at a temperature of 200 ° C and a pressure of 0.5 MPa. The graphite treatment was then performed at 2800 ° C to obtain graphene fiber carbon paper with a porosity of 0.83. Figure 1 As shown in Figure 2, the in-plane conductivity can reach 52000S / m. The resistance comparison between graphene fiber carbon paper and commercial carbon paper under the same conditions is obtained through the volt-ampere characteristic curve test. Figure 2 As shown, the resistance of commercial carbon paper is 1.53Ω, while the resistance of graphene fiber carbon paper is only 0.79Ω;

[0050] (2) The graphene fiber carbon paper is subjected to hydrophobic treatment. The graphene fiber carbon paper is impregnated with a polytetrafluoroethylene emulsion having a mass fraction of 10%. After the fiber surface is covered with a polytetrafluoroethylene hydrophobic layer and the mass of the hydrophobic agent accounts for 10% of the mass of the original carbon paper, the surface active agent is removed by thermal sintering at 350°C. Thus, super-hydrophobic graphene fiber carbon paper is obtained. The water contact angle is as follows: Figure 18 As shown in Figure 3, the water contact angle can reach 145°, which is in the superhydrophobic range.

[0051] (3) A microporous layer is attached to the surface of superhydrophobic graphene fiber carbon paper. First, a microporous layer slurry is prepared. Conductive carbon black and polytetrafluoroethylene emulsion are dispersed in a dispersion of water and isopropyl alcohol at a mass ratio of 1:1, and the volume ratio of water to isopropyl alcohol is 2:1. The slurry is evenly dispersed by ultrasound and then coated on the carbon paper surface. The thickness is controlled at 20 μm. The residual slurry is then removed by sintering at 350°C to obtain a graphene fiber carbon paper gas diffusion layer.

[0052] (4) The prepared graphene fiber carbon paper gas diffusion layer was hot pressed with the commercial catalyst-loaded proton exchange membrane at a temperature of 150°C, a pressure of 0.2 MPa, and a time of 90 s to prepare a complete new high-performance proton exchange membrane fuel cell membrane electrode. The complete membrane electrode was loaded into the test fixture and a single cell test was performed on the fuel cell test platform, 850E. The volt-ampere characteristic curve (IV Curve) was tested under conditions of 200 ccm air flow rate, 80°C operating temperature, etc. (such as Figure 3 As shown, the output power density is as high as 1100mW·cm -2 ), and compared with commercial carbon paper TGP-H-060 under the same conditions, the output power prepared in this embodiment is more than 30% higher.

[0053] Example 2

[0054] (1) The graphene fiber non-woven fabric is placed in a vacuum oven and heated to 70°C and immersed in a 20% by mass phenolic resin solution for 2 hours. After the phenolic resin is fully sized on the fiber nodes, a modified graphene fiber non-woven fabric can be obtained. A hot press is used to fully cure the graphene fiber non-woven fabric composite at a temperature of 200°C and a pressure of 0.5 MPa. The graphite treatment at 2800°C is then performed to obtain a graphene fiber carbon paper with a porosity of 0.85 and an in-plane conductivity of 51000 S / m.

[0055] (2) The graphene fiber carbon paper is subjected to a hydrophobic treatment. The graphene fiber is immersed in a 10% by mass polytetrafluoroethylene emulsion. After ensuring that the fiber surface is covered with a polytetrafluoroethylene hydrophobic layer and the mass of the hydrophobic agent accounts for 10% of the mass of the original carbon paper, it is sintered at 350°C to remove the surfactant, thereby obtaining superhydrophobic graphene fiber carbon paper.

[0056] (3) A microporous layer is attached to the surface of superhydrophobic graphene fiber carbon paper. First, a microporous layer slurry is prepared. Conductive carbon black and polytetrafluoroethylene emulsion are dispersed in a dispersion of water and isopropyl alcohol at a mass ratio of 1:1, and the volume ratio of water to isopropyl alcohol is 2:1. The slurry is evenly dispersed by ultrasound and then coated on the carbon paper surface. The thickness is controlled at 20 μm. The residual slurry is then removed by sintering at 350°C to obtain a graphene fiber carbon paper gas diffusion layer.

[0057] (4) The prepared graphene fiber carbon paper gas diffusion layer was hot pressed with the commercial catalyst-loaded proton exchange membrane at a temperature of 150°C, a pressure of 0.2 MPa, and a time of 90 seconds to prepare a complete new high-performance proton exchange membrane fuel cell membrane electrode. The complete membrane electrode was loaded into the test fixture and a single cell test was performed on the fuel cell test platform, 850E. The volt-ampere characteristic curve (IV Curve) was tested under conditions such as a 200ccm air flow rate and a working temperature of 80°C (such as Figure 4 As shown, the output power density is as high as 1098mW·cm -2 ), and compared with commercial carbon paper TGP-H-060 under the same conditions, the output power prepared in this embodiment is more than 30% higher.

[0058] Example 3

[0059] (1) The graphene fiber non-woven fabric is placed in a vacuum oven and heated at 70°C and immersed in a 10% by mass phenolic resin solution for 2 hours. After the phenolic resin is fully sized on the fiber nodes, a modified graphene fiber non-woven fabric can be obtained. A hot press is used to fully cure the graphene fiber non-woven fabric composite at a temperature of 200°C and a pressure of 0.5 MPa. The graphite treatment at 2800°C is then performed to obtain a graphene fiber carbon paper with a porosity of 0.89 and an in-plane conductivity of 49500 S / m.

[0060] (2) The graphene fiber carbon paper is subjected to a hydrophobic treatment. The graphene fiber carbon paper is impregnated with a polytetrafluoroethylene emulsion having a mass fraction of 10%. After ensuring that the fiber surface is covered with a polytetrafluoroethylene hydrophobic layer and the mass of the hydrophobic agent accounts for 10% of the mass of the original carbon paper, the surface active agent is removed by thermal sintering at 350°C, thereby obtaining super-hydrophobic graphene fiber carbon paper.

[0061] (3) A microporous layer is attached to the surface of superhydrophobic graphene fiber carbon paper. First, a microporous layer slurry is prepared. Conductive carbon black and polytetrafluoroethylene emulsion are dispersed in a dispersion of water and isopropyl alcohol at a mass ratio of 1:1, and the volume ratio of water to isopropyl alcohol is 2:1. The slurry is evenly dispersed by ultrasound and then coated on the carbon paper surface. The thickness is controlled at 20 μm. The residual slurry is then removed by sintering at 350°C to obtain a graphene fiber carbon paper gas diffusion layer.

[0062] (4) The prepared super-hydrophobic graphene fiber carbon paper sample was hot pressed with a commercial catalyst-loaded proton exchange membrane at a temperature of 150°C, a pressure of 0.2 MPa, and a time of 90 s to prepare a complete new high-performance proton exchange membrane fuel cell membrane electrode. The complete membrane electrode was loaded into a test fixture and a single cell test was performed on a fuel cell test platform, 850E. The volt-ampere characteristic curve (IV Curve) was tested under conditions of an air flow rate of 200 ccm and an operating temperature of 80°C (such as Figure 5 As shown, the output power density is as high as 1099mW·cm -2 ) and compared with commercial carbon paper TGP-H-060 under the same conditions, the output power of this embodiment is more than 30% higher.

[0063] Example 4

[0064] (1) The graphene fiber non-woven fabric was placed in a vacuum oven and heated to 70°C and immersed in a 30% by mass phenolic resin solution for 2 hours. After the phenolic resin was fully sized on the fiber nodes, a modified graphene fiber non-woven fabric was obtained. A hot press was used to fully cure the graphene fiber non-woven fabric composite at a temperature of 200°C and a pressure of 0.5 MPa. The carbon paper sample was then graphitized at 2800°C. The porosity reached 0.83 and the in-plane conductivity could reach 52000 S / m.

[0065] (2) The graphene fiber carbon paper is subjected to a hydrophobic treatment. The graphene fiber carbon paper is impregnated with a polytetrafluoroethylene emulsion having a mass fraction of 5%. After ensuring that the fiber surface is covered with a polytetrafluoroethylene hydrophobic layer and the mass of the hydrophobic agent accounts for 5% of the mass of the original carbon paper, the surface active agent is removed by thermal sintering at 350°C, thereby obtaining a graphene fiber super-hydrophobic graphene fiber carbon paper having super-hydrophobic properties.

[0066] (3) A microporous layer is attached to the surface of superhydrophobic graphene fiber carbon paper. First, a microporous layer slurry is prepared. Conductive carbon black and polytetrafluoroethylene emulsion are dispersed in a dispersion of water and isopropyl alcohol at a mass ratio of 1:1, and the volume ratio of water to isopropyl alcohol is 2:1. The slurry is evenly dispersed by ultrasound and then coated on the carbon paper surface. The thickness is controlled at 20 μm. The residual slurry is then removed by sintering at 350°C to obtain a graphene fiber carbon paper gas diffusion layer.

[0067] (4) The prepared graphene fiber carbon paper gas diffusion layer was hot pressed with the commercial catalyst-loaded proton exchange membrane at a temperature of 150°C, a pressure of 0.2 MPa, and a time of 90 seconds to prepare a complete new high-performance proton exchange membrane fuel cell membrane electrode. The complete membrane electrode was loaded into the test fixture and a single cell test was performed on the fuel cell test platform, 850E. The volt-ampere characteristic curve (IV Curve) was tested under conditions such as a 200ccm air flow rate and a working temperature of 80°C (such as Figure 6As shown, the output power density is as high as 1095mW·cm -2 ), and compared with commercial carbon paper TGP-H-060 under the same conditions, the output power prepared in this embodiment is more than 30% higher.

[0068] Example 5

[0069] (1) The graphene fiber non-woven fabric is placed in a vacuum oven and heated to 70°C and immersed in a 30% by mass phenolic resin solution for 2 hours. After the phenolic resin is fully sized on the fiber nodes, a modified graphene fiber non-woven fabric can be obtained. A hot press is used to fully cure the graphene fiber non-woven fabric composite at a temperature of 200°C and a pressure of 0.5 MPa. The graphite treatment is then performed at 2800°C to obtain a graphene fiber carbon paper with a porosity of 0.83 and an in-plane conductivity of 52000 S / m.

[0070] (2) The graphene fiber carbon paper is subjected to a hydrophobic treatment. The graphene fiber carbon paper is impregnated with a polytetrafluoroethylene emulsion having a mass fraction of 1%. After ensuring that the fiber surface is covered with a polytetrafluoroethylene hydrophobic layer and the mass of the hydrophobic agent accounts for 1% of the mass of the original carbon paper, the surface active agent is removed by thermal sintering at 350°C, thereby obtaining super-hydrophobic graphene fiber carbon paper.

[0071] (3) A microporous layer is attached to the surface of superhydrophobic graphene fiber carbon paper. First, a microporous layer slurry is prepared. Conductive carbon black and polytetrafluoroethylene emulsion are dispersed in a dispersion of water and isopropyl alcohol at a mass ratio of 1:1, and the volume ratio of water to isopropyl alcohol is 2:1. The slurry is evenly dispersed by ultrasound and then coated on the carbon paper surface. The thickness is controlled at 20 μm. The residual slurry is then removed by sintering at 350°C to obtain a graphene fiber carbon paper gas diffusion layer.

[0072] (3) The prepared graphene fiber carbon paper gas diffusion layer and the commercial catalyst-loaded proton exchange membrane were hot pressed at a temperature of 150°C, a pressure of 0.2 MPa, and a time of 90 seconds to prepare a complete new high-performance proton exchange membrane fuel cell membrane electrode. The complete membrane electrode was loaded into the test fixture and a single cell test was performed on the fuel cell test platform, 850E. The volt-ampere characteristic curve (IV Curve) was tested under conditions such as a 200ccm air flow rate and a working temperature of 80°C (such as Figure 7 As shown, the output power density is as high as 1094mW·cm -2 ), and compared with commercial carbon paper TGP-H-060 under the same conditions, the output power prepared in this embodiment is more than 30% higher.

[0073] Example 6

[0074] (1) The graphene fiber non-woven fabric is placed in a vacuum oven and heated to 70°C and immersed in a 30% by mass phenolic resin solution for 2 hours. After the phenolic resin is fully sized on the fiber nodes, a modified graphene fiber non-woven fabric can be obtained. A hot press is used to fully cure the graphene fiber non-woven fabric composite at a temperature of 200°C and a pressure of 0.5 MPa. The graphite treatment is then performed at 2800°C to obtain a graphene fiber carbon paper with a porosity of 0.83 and an in-plane conductivity of 52000 S / m.

[0075] (2) The graphene fiber carbon paper is subjected to a hydrophobic treatment. The graphene fiber carbon paper is impregnated with a polytetrafluoroethylene emulsion having a mass fraction of 1%. After ensuring that the fiber surface is covered with a polytetrafluoroethylene hydrophobic layer and the mass of the hydrophobic agent accounts for 1% of the mass of the original carbon paper, the surface active agent is removed by thermal sintering at 350°C, thereby obtaining super-hydrophobic graphene fiber carbon paper.

[0076] (3) A microporous layer is attached to the surface of superhydrophobic graphene fiber carbon paper. First, a microporous layer slurry is prepared. Conductive carbon black and polytetrafluoroethylene emulsion are dispersed in a dispersion of water and isopropyl alcohol at a mass ratio of 1:1, and the volume ratio of water to isopropyl alcohol is 3:1. The slurry is evenly dispersed by ultrasound and then coated on the carbon paper surface. The thickness is controlled to be 20 μm. The residual slurry is then removed by sintering at 350°C to obtain a graphene fiber carbon paper gas diffusion layer.

[0077] (3) The prepared graphene fiber carbon paper gas diffusion layer and the commercial catalyst-loaded proton exchange membrane were hot pressed at a temperature of 150°C, a pressure of 0.2 MPa, and a time of 90 seconds to prepare a complete new high-performance proton exchange membrane fuel cell membrane electrode. The complete membrane electrode was loaded into the test fixture and a single cell test was performed on the fuel cell test platform, 850E. The volt-ampere characteristic curve (IV Curve) was tested under conditions such as a 200ccm air flow rate and a working temperature of 80°C (such as Figure 8 As shown, the output power density is as high as 1093mW·cm -2 ), and compared with commercial carbon paper TGP-H-060 under the same conditions, the output power prepared in this embodiment is more than 30% higher.

[0078] Example 7

[0079] (1) The graphene fiber non-woven fabric is placed in a vacuum oven and heated to 70°C and immersed in a 30% by mass phenolic resin solution for 2 hours. After the phenolic resin is fully sized on the fiber nodes, a modified graphene fiber non-woven fabric can be obtained. A hot press is used to fully cure the graphene fiber non-woven fabric composite at a temperature of 200°C and a pressure of 0.5 MPa. The graphite treatment is then performed at 2800°C to obtain a graphene fiber carbon paper with a porosity of 0.83 and an in-plane conductivity of 52000 S / m.

[0080] (2) The graphene fiber carbon paper is subjected to a hydrophobic treatment. The graphene fiber carbon paper is impregnated with a polytetrafluoroethylene emulsion having a mass fraction of 1%. After ensuring that the fiber surface is covered with a polytetrafluoroethylene hydrophobic layer and the mass of the hydrophobic agent accounts for 1% of the mass of the original carbon paper, the surface active agent is removed by thermal sintering at 350°C, thereby obtaining super-hydrophobic graphene fiber carbon paper.

[0081] (3) A microporous layer is attached to the surface of superhydrophobic graphene fiber carbon paper. First, a microporous layer slurry is prepared. Conductive carbon black and polytetrafluoroethylene emulsion are dispersed in a dispersion of water and isopropyl alcohol at a mass ratio of 1:1, and the volume ratio of water to isopropyl alcohol is 5:1. The slurry is evenly dispersed by ultrasound and then coated on the carbon paper surface with a thickness of 20 μm. The residual slurry is then removed by sintering at 350°C to obtain a graphene fiber carbon paper gas diffusion layer.

[0082] (4) The prepared graphene fiber carbon paper gas diffusion layer was hot pressed with the commercial catalyst-loaded proton exchange membrane at a temperature of 150°C, a pressure of 0.2 MPa, and a time of 90 seconds to prepare a complete new high-performance proton exchange membrane fuel cell membrane electrode. The complete membrane electrode was loaded into the test fixture and a single cell test was performed on the fuel cell test platform, 850E. The volt-ampere characteristic curve (IV Curve) was tested under conditions such as a 200ccm air flow rate and a working temperature of 80°C (such as Figure 9 As shown, the output power density is as high as 1092mW·cm -2 ), and compared with commercial carbon paper TGP-H-060 under the same conditions, the output power prepared in this embodiment is more than 30% higher.

[0083] Comparative Example

[0084] like Figure 10-16 The SEM images shown in Figure 1 show the fused graphene fiber network structure of the graphene fiber carbon paper of Examples 1-7, and Figure 17 Comparative Example: Commercial Carbon Paper Polyacrylonitrile-Based Carbon Fiber Network. The comparative example is a purely physical overlap structure formed by bonding fibers with a sizing agent, while the embodiment of the present invention is a conductive fiber network formed by interactively fusing graphene fibers with a phenolic resin. Graphene fibers have larger-scale graphite domains than polyacrylonitrile-based carbon fibers, and their electrical conductivity and other properties are greatly improved. Furthermore, the rough, wrinkled surface of the graphene fibers has a larger surface area, significantly improving catalyst loading and load stability compared to the smoother surface of commercial carbon paper polyacrylonitrile-based carbon fibers. Furthermore, during the graphitization process, due to the two-dimensional topological seed graphitization effect, graphene can induce graphitization of the sizing agent phenolic resin, thereby improving the conductivity of the overall carbon paper fiber conductive network.

[0085] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. Application of a modified graphene fiber nonwoven fabric in a proton exchange membrane fuel cell, wherein the modified graphene fiber nonwoven fabric is modified by using phenolic resin as a sizing agent for overlapping the fiber nodes of the graphene fiber nonwoven fabric, characterized in that: The mass fraction of phenolic resin used as a sizing agent is 10%-30%. The application includes the following steps: (1) The modified graphene fiber non-woven fabric is hot-pressed by a hot press to obtain a graphene fiber non-woven fabric composite; the hot press adopts 200°C and 0.5 MPa hot pressing to obtain the graphene fiber non-woven fabric composite; (2) The graphene fiber non-woven fabric composite is graphitized at 2800°C to obtain graphene fiber carbon paper; (3) impregnating the graphene fiber non-woven fabric composite in polytetrafluoroethylene emulsion to attach a polytetrafluoroethylene hydrophobic layer to the surface of the graphene fiber, and then sintering it through heat treatment to remove the surfactant to obtain super-hydrophobic graphene fiber carbon paper; (4) Conductive carbon black and polytetrafluoroethylene emulsion with a mass ratio of 1:1 and a dispersant of water and isopropyl alcohol with a volume ratio of 2-5:1 are dispersed by ultrasonication to obtain a slurry, and the slurry is then evenly loaded on the surface of superhydrophobic graphene fiber carbon paper by spraying to prepare a microporous layer with a thickness of 10-40 μm, and then sintered at 350 ° C to obtain a graphene fiber carbon paper gas diffusion layer for proton exchange membrane fuel cells; (5) The graphene fiber carbon paper gas diffusion layer and the catalyst-loaded CCM (catalyst coated membrane) are hot-pressed to obtain a proton exchange membrane fuel cell membrane electrode.

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