Preparation method of carbon paper, carbon paper and fuel cell

Abstract

The invention discloses a preparation method of carbon paper, which comprises the following steps: obtaining a nanoparticle / polyacrylonitrile composite nanofiber membrane with a rough surface by adopting a synchronous electrostatic spinning / electrostatic spraying method, and then preparing a carbon paper precursor material through hot pressing, pre-oxidation and carbonization treatment in sequence; and carrying out low-temperature oxygen plasma hydrophilic modification on a part of the carbon paper precursor material. According to the method, a rough structure is conveniently obtained through electrostatic spinning and electrostatic spraying, the hydrophilic and hydrophobic performance is adjusted, the carbon paper structure is stable, a fluorine-containing water repellent agent is avoided, the green and sustainable development trend is met, and the problem of hydrophilic and hydrophobic imbalance caused by uneven distribution of the water repellent agent in traditional fluorine-containing treatment is solved; meanwhile, the carbon paper optimized by hot pressing, pre-oxidation and carbonization processes has excellent mechanical strength and electron transmission performance, and provides high-performance material support for scenes such as a proton exchange membrane fuel cell gas diffusion layer and the like. The invention also discloses carbon paper and a fuel cell.

Description

Technical Field

[0001] This invention relates to the field of carbon paper preparation technology, specifically to a method for preparing carbon paper, carbon paper, and fuel cells. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are clean and efficient power devices that use hydrogen and air (oxygen) as reactants to convert chemical energy into electrical energy through electrochemical reactions. Their high efficiency, high power density, and ease of scalability make them a strong candidate for next-generation power sources for transportation vehicles, stationary applications, and portable devices. The gas diffusion layer is one of the core components of the PEMFC membrane electrode assembly, primarily serving to support the battery structure and transport electrons, reactants, products, and heat. Carbon paper is a commonly used material for the gas diffusion layer.

[0003] Commercial carbon paper typically employs a conventional wet papermaking process, which includes steps such as wet papermaking, resin impregnation, hot pressing and curing, heat treatment, and surface treatment. The main purpose of surface treatment is to optimize the surface properties and pore structure of the base layer carbon paper. The carbon paper material used in the gas diffusion layer needs to possess both hydrophilic and hydrophobic properties to better control gas-liquid transfer in fuel cells. Currently, fluorinated hydrophobic agents are mainly used to adjust these properties. For example, patent ZL202210057234.4 discloses a high-performance gas diffusion layer for hydrogen fuel cells, comprising a porous support layer, a first microporous layer, and a second microporous layer. First, the porous support layer is immersed in a hydrophobic slurry for a certain period, then removed and dried to obtain a hydrophobically treated porous support layer. Next, carbon powder, fluorocarbon material, carbon-based aerogel, fluorinated binder, and film-forming material are prepared and mixed uniformly in a specific ratio. The mixture is then hot-pressed into a film-like sheet to obtain the first microporous layer. The first microporous layer is then hot-pressed onto the surface of the porous support layer to obtain a first microporous layer-porous support layer composite material. Then, carbon powder, fluorinated binder, dispersant, and water are prepared and mixed uniformly in a specific ratio to obtain a second microporous layer slurry. The second microporous layer slurry is sprayed or coated onto the surface of the first microporous layer of the first microporous layer-porous support layer composite material. Finally, the pretreated gas diffusion layer is dried and sintered to obtain the high-performance gas diffusion layer for hydrogen fuel cells. Patent ZL202310954612.3 discloses a method for preparing a gas diffusion layer for fuel cells. Untreated carbon paper is impregnated with a hydrophobic agent such as polytetrafluoroethylene solution, dried, and sintered at 350-400°C. After coating with a microporous layer, it is sintered again at 350-400°C to obtain the gas diffusion layer.

[0004] However, fluorinated hydrophobic agents are difficult to disperse uniformly within the carbon paper, resulting in limited performance of the gas diffusion layer. During fuel cell operation, the gas diffusion layer requires precise moisture control. Uneven distribution of the hydrophobic agent can lead to localized hydrophilic-hydrophobic imbalances—some areas become overly hydrophobic, hindering water drainage and causing "flooding"; others become hydrophilic, failing to effectively prevent water immersion and affecting gas transport. This inhomogeneity severely limits the power density and stability of fuel cells. Furthermore, fluorinated compounds, especially long-chain PFAS (per- and polyfluoroalkyl substances), are subject to increasingly stringent global regulations and restrictions due to their persistent degradation, bioaccumulation, and potential toxicity, which contradicts the future trend of sustainable industrial development. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a method for preparing carbon paper, comprising the following steps:

[0006] Mixed solvent one and mixed solvent two were prepared separately. The conductive agent was added to mixed solvent one and dispersed evenly. Then, polyacrylonitrile powder was added and stirred to form a uniform dispersion liquid one. The nanoparticles were added to mixed solvent two and dispersed evenly. Then, silane coupling agent and polyacrylonitrile powder were added and stirred to form a uniform dispersion liquid two.

[0007] The uniformly dispersed liquid one is electrospun, and the uniformly dispersed liquid two is electrospun in the electrospinning area to obtain a polyacrylonitrile fiber membrane with a rough surface.

[0008] The polyacrylonitrile fiber membrane is subjected to hot pressing, followed by pre-oxidation and carbonization to prepare carbon paper precursor material.

[0009] The carbon paper precursor material is partially hydrophilically modified to obtain the carbon paper.

[0010] Furthermore, the compositions of the first mixed solvent and the second mixed solvent are the same or different, and each of the first mixed solvent and the second mixed solvent includes a component one and a component two, wherein the first component is selected from one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone, and the second component is selected from one of acetone, ethanol and ethyl acetate, and the volume ratio of the first component to the second component is 1:1 to 5:1.

[0011] Furthermore, the conductive agent is one or more of carbon nanotubes, carbon black, and graphene, and the content of the conductive agent in the uniform dispersion liquid is 0.5wt% to 5wt%.

[0012] Furthermore, the polyacrylonitrile content in the uniform dispersion is 10wt% to 20wt%.

[0013] Furthermore, the nanoparticles are one of nano-silica, titanium dioxide and zirconium dioxide, the diameter of the nanoparticles is 20-500 nm, and the content of the nanoparticles in the uniform dispersion liquid is 0.5 wt%-5 wt%.

[0014] Furthermore, the silane coupling agent is one of KH550, KH560 and KH570, and the content of the silane coupling agent in the uniform dispersion liquid II is 0.5wt% to 5wt%.

[0015] Furthermore, the polyacrylonitrile content in the uniform dispersion II is 2wt% to 5wt%.

[0016] Furthermore, during the electrospinning process, the positive voltage applied to the needle is 10-20kV, the negative voltage applied to the receiver is -1 to -5kV, and the distance between the needle and the receiver is 10-20cm.

[0017] Furthermore, the electrostatic spraying and the electrospinning use the same roller receiver, and during the electrostatic spraying process, the positive voltage applied to the needle is 10-20kV, and the distance between the needle and the receiver is 10-20cm.

[0018] Furthermore, in the hot pressing process, the hot pressing temperature is 100℃~160℃, and the hot pressing time is 10~30min.

[0019] Furthermore, in the pre-oxidation treatment, the pre-oxidation temperature is 200-300℃, the pre-oxidation time is 0.5-4h, and the pre-oxidation treatment is carried out in an air atmosphere.

[0020] Furthermore, in the carbonization process, the carbonization temperature is 800–1500°C, the carbonization time is 2–8 h, and the carbonization process is carried out in an inert gas atmosphere.

[0021] Furthermore, in the hydrophilic modification, the carbon paper precursor material is shielded using a mold with a specific hollow pattern, and then the carbon paper precursor material is subjected to low-temperature oxygen plasma hydrophilic modification treatment. The specific hollow pattern is one or more of the following: circular array, square array, parallel DC channel, and serpentine channel.

[0022] Furthermore, in the low-temperature oxygen plasma hydrophilic modification treatment, the plasma radio frequency power is 20-100W, and the treatment time is 1-10min.

[0023] According to another specific embodiment of the present invention, an embodiment of the present invention discloses a carbon paper, which is prepared by the above-described carbon paper preparation method.

[0024] According to another specific embodiment of the present invention, an embodiment of the present invention discloses a fuel cell comprising the above-described carbon paper.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] (1) In this invention, polyacrylonitrile fibers with a rough surface are obtained by electrospinning / electrospraying, and then carbon paper materials are prepared by hot pressing, pre-oxidation and carbonization in sequence. The carbon fibers also have a rough surface and have a three-dimensional hydrophobic effect. The hydrophobic properties are uniform and do not require subsequent treatment with fluorine-containing hydrophobic agents.

[0027] (2) The present invention modifies a portion of the carbon paper material to be hydrophilic, thereby obtaining carbon paper with both hydrophilic and hydrophobic structures, which is beneficial to improving the performance of the gas diffusion layer and thus beneficial to improving the performance of fuel cells. Detailed Implementation

[0028] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention is presented in conjunction with preferred embodiments, this does not mean that the features of the invention are limited to these embodiments. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of the present invention. To provide a deep understanding of the invention, many specific details will be included in the following description. The invention may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of the invention, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0029] The terms “first”, “second”, etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below.

[0031] The first aspect of this invention discloses a method for preparing carbon paper, which has both hydrophilic and hydrophobic structures. The method for preparing carbon paper includes the following steps:

[0032] (1) Prepare mixed solvent one and mixed solvent two respectively. Add the conductive agent to mixed solvent one, disperse it evenly, add polyacrylonitrile powder, and stir to form a uniform dispersion liquid one; add the nanoparticles to mixed solvent two, disperse it evenly, add silane coupling agent and polyacrylonitrile powder, and stir to form a uniform dispersion liquid two.

[0033] (2) Electrospinning the uniformly dispersed liquid one, and electrospinning the uniformly dispersed liquid two into the electrospinning area to obtain a polyacrylonitrile fiber membrane with a rough surface.

[0034] (3) The polyacrylonitrile fiber membrane is subjected to hot pressing, followed by pre-oxidation and carbonization to prepare carbon paper precursor material;

[0035] (4) Part of the carbon paper precursor material is hydrophilicized to obtain carbon paper with hydrophilic and hydrophobic structures.

[0036] Electrospinning is a technique that uses high-voltage electrostatics to stretch melts or solutions into nano- or submicron fibers. It can very effectively prepare high-porosity nanofiber membranes, and the morphology and structure of the membrane can be controlled and modified for hydrophilicity / hydrophobicity by changing the membrane-forming conditions. Electrospraying is a simple method that uses high-voltage electrostatics to charge polymer droplets ejected from a needle, and then prepares polymer micro / nanoparticles through solvent evaporation from the droplets. Electrospraying and electrospinning are two forms of electrostatic jet technology, with similar principles and apparatus, but the resulting material morphology and structure differ. In electrospinning, a high-voltage electric field is used to form an extremely fine fiber stream from a uniformly dispersed liquid (liquid one). Under the influence of the electric field, these fibers gradually deposit and solidify on a receiving device, forming the basic framework of the fiber membrane. Simultaneously, a second uniformly dispersed liquid (liquid two) is electrostatically sprayed onto the forming fiber membrane, producing tiny droplets containing nanoparticles, silane coupling agents, and polyacrylonitrile. Because this process occurs simultaneously, the particles formed by the spraying of the second uniformly dispersed liquid are evenly distributed on the surface and inside the fiber membrane, ensuring the balanced and stable performance of the subsequent carbon paper. Furthermore, these tiny droplets dry rapidly on the fiber membrane surface, allowing nanoparticles and polyacrylonitrile to adhere to the fibers, thus roughening the membrane surface. This roughened surface significantly increases the specific surface area of ​​the carbon paper, creating favorable conditions for subsequent performance improvements. When applied to fields such as battery electrodes, it allows for more complete electrochemical reactions, improving battery charge-discharge performance and efficiency. Simultaneously, the roughened surface enhances the interfacial bonding between the carbon paper and other materials, making the synergistic effect between components more significant in composite material systems, thereby improving the overall stability and reliability of the material.

[0037] Furthermore, hot pressing, pre-oxidation, and carbonization further enhance the performance of the fiber membrane. Hot pressing is a preliminary densification and shaping process for the polyacrylonitrile fiber membrane. Under specific temperature and pressure conditions, the bonds between fibers become tighter, reducing gaps and improving the mechanical strength of the membrane, allowing it to maintain its integrity during subsequent processing. Simultaneously, hot pressing can also cause a certain degree of orientation alignment in the molecular chains of the fiber membrane, laying the foundation for subsequent performance optimization. In pre-oxidation, the polyacrylonitrile molecular chains undergo a series of complex chemical reactions such as cyclization, dehydrogenation, and oxidation under specific temperature and oxygen atmosphere, significantly improving the fiber's heat resistance and enabling it to withstand the high temperatures of subsequent carbonization without decomposition or deformation. Moreover, the pre-oxidation process alters the chemical properties of the fiber, increasing the active groups on the fiber surface, which facilitates reactions with other atoms or groups during carbonization, further optimizing the structure and performance of the carbon paper. Carbonization completely converts polyacrylonitrile into carbon material. During this process, non-carbon elements are gradually removed, and the carbon content continuously increases, resulting in carbon paper with high conductivity and good chemical stability. The carbonization process further optimizes the microstructure of the carbon paper, making the carbon atoms more orderly arranged and forming a carbon structure with a high degree of graphitization, thereby improving the conductivity and mechanical strength of the carbon paper. After a series of treatments including hot pressing, pre-oxidation, and carbonization, the overall performance of the carbon paper is comprehensively improved, meeting its application requirements in many high-end fields.

[0038] In the subsequent preparation of hydrophilic modification, some areas of the carbon paper precursor material are treated to introduce hydrophilic groups, such as hydroxyl (-OH) and carboxyl (-COOH), onto its surface, resulting in carbon paper with a hydrophilic-hydrophobic structure.

[0039] The preparation method of this invention can easily increase the roughness of the fiber surface and adjust the hydrophilic and hydrophobic properties by combining electrospinning and electrospraying processes. The carbon paper structure is stable and avoids the use of fluorinated hydrophobic agents. This avoids the environmental residue and bioaccumulation risks caused by fluorinated compounds, which is in line with the trend of green and sustainable development. It also solves the problem of hydrophilic and hydrophobic imbalance caused by uneven distribution of hydrophobic agents in traditional fluorinated treatment. At the same time, the carbon paper optimized by hot pressing, pre-oxidation and carbonization processes can also form a continuous conductive network with conductive agents, taking into account both excellent mechanical strength and electron transport performance, and providing high-performance material support for scenarios such as the gas diffusion layer of proton exchange membrane fuel cells.

[0040] In an embodiment of the present invention, in step (1), the compositions of mixed solvent one and mixed solvent two are the same or different, and each of mixed solvent one and mixed solvent two includes component one and component two, wherein component one is selected from one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone, and component two is selected from one of acetone, ethanol and ethyl acetate. Further, in mixed solvent one and mixed solvent two, the volume ratio of component one to component two is 1:1 to 5:1. The synergistic effect of the two solvent components can optimize the solvent evaporation rate, avoid the problems of fiber adhesion or uneven formation of sprayed particles, and at the same time, the volume ratio design can effectively correspond to the viscosity required by electrospinning and electrospraying, ensuring the effective execution of each process and obtaining the required polyacrylonitrile fiber membrane.

[0041] In the embodiments of the present invention, in step (1), the conductive agent is one or more of carbon nanotubes, carbon black and graphene. Furthermore, the content of the conductive agent in the uniform dispersion liquid is 0.5wt% to 5wt%, which can ensure both the basic conductive path and the uniform dispersion of the conductive agent.

[0042] In an embodiment of the present invention, in step (1), the polyacrylonitrile content in the uniform dispersion is 10wt% to 20wt%. At this content, the polyacrylonitrile can be fully dissolved in the mixed solvent and form a uniform system, ensuring that the solution has stable fluidity and stretchability during spinning, and can efficiently form a continuous and uniform fiber structure, providing a regular basic morphology for the construction of carbon paper skeleton. Furthermore, this content is matched with 0.5wt% to 5wt% of conductive agent, so that the conductive agent and polyacrylonitrile form a sufficient synergistic effect.

[0043] In the embodiments of the present invention, in step (1), the nanoparticles are one of nano-silica, titanium dioxide, and zirconium dioxide, with a diameter of 20–500 nm, and the content of the nanoparticles in the uniform dispersion liquid II is 0.5 wt%–5 wt%. The particle size range of 20–500 nm facilitates uniform spraying and adhesion to the fiber surface and interior, providing an ideal microstructure basis for subsequent hydrophobic properties. At the same time, the content of 0.5 wt%–5 wt% ensures that the particles are uniformly suspended in the dispersion liquid II, forming moderately dense rough units that work synergistically with the silane coupling agent to construct a stable hydrophobic interface after carbonization. In addition, nanoparticles such as silica and titanium dioxide have excellent thermal stability and can withstand the high-temperature environment of pre-oxidation and carbonization. During the carbonization process, they form a strong bond with carbon fibers, ensuring the long-term stability of the rough structure and ultimately providing durable and efficient hydrophobic performance support for the carbon paper.

[0044] In the embodiments of the present invention, in step (1), the silane coupling agent is one of KH550, KH560 and KH570, and the content of the silane coupling agent in the uniform dispersion liquid II is 0.5wt% to 5wt%. KH550, KH560 and KH570 can uniformly fix the nanoparticles in the polymer matrix, effectively improving the bonding strength between the particles and the fiber. The content of 0.5wt% to 5wt% can ensure sufficient coating and modification of the nanoparticles, avoid particle detachment during spraying and subsequent treatment, and adjust the interfacial tension of the dispersion liquid II through intermolecular forces, optimize the formation and adhesion effect of the spray droplets, and make the nanoparticles form a uniformly distributed rough structure on the fiber surface.

[0045] In the embodiments of the present invention, in step (1), the polyacrylonitrile content in the uniform dispersion liquid II is 2wt% to 5wt%, forming a uniform dispersion system with the silane coupling agent and nanoparticles, thereby enhancing the spraying effect and ensuring the stability of the rough structure.

[0046] In an embodiment of the present invention, in step (2), during the electrospinning process, the positive voltage applied to the needle is 10 to 20 kV, the negative voltage applied to the receiver is -1 to -5 kV, and the distance between the needle and the receiver is 10 to 20 cm.

[0047] In an embodiment of the present invention, in step (2), the same roller receiver is used for electrostatic spraying and electrostatic spinning, and during the electrostatic spraying process, the positive voltage applied to the needle is 10-20kV, and the distance between the needle and the receiver is 10-20cm.

[0048] In the embodiments of the present invention, the hot pressing temperature is 100℃~160℃ and the hot pressing time is 10~30min, which can fully enhance the overall mechanical strength of the fiber membrane and provide a structurally stable substrate for subsequent high-temperature treatment.

[0049] In an embodiment of the present invention, in step (3), the pre-oxidation temperature is 200-300°C, the pre-oxidation time is 0.5-4 h, and the pre-oxidation is carried out in an air atmosphere.

[0050] In an embodiment of the present invention, in step (3), the carbonization temperature is 800–1500°C, the carbonization time is 2–8 h, and the carbonization process is carried out in an inert gas atmosphere. The inert gas is, for example, argon or nitrogen, to ensure that the carbon elements are fully reorganized to form a continuous network, ultimately giving the carbon paper excellent electrical conductivity, high temperature resistance, and a stable structure, thus meeting the dual requirements of the gas diffusion layer for electron transport and mass transfer.

[0051] In an embodiment of the present invention, in the hydrophilic modification, a mold with a specific hollow pattern is used to cover the carbon paper precursor material, and then the carbon paper precursor material is subjected to low-temperature oxygen plasma hydrophilic modification treatment. The specific hollow pattern is one or more of the following: circular array, square array, parallel DC channel and serpentine channel.

[0052] The second aspect of the present invention discloses a carbon paper, which is prepared by the carbon paper preparation method with hydrophilic and hydrophobic structure in the above embodiments. It has a uniform and stable hydrophobic structure and also has hydrophilic function, which can be adapted to the use requirements of gas diffusion layer and provide stable and reliable mass transport function and structural support for fuel cell.

[0053] A third aspect of the present invention discloses a fuel cell comprising the carbon paper of the above embodiments. The carbon paper has a uniform hydrophobic and hydrophilic structure, which facilitates the diffusion of substances within the fuel cell, thereby improving the power density, operational stability, and service life of the fuel cell. Specifically, the fuel cell is a proton exchange membrane fuel cell.

[0054] The following will describe the implementation methods in more detail.

[0055] Example 1

[0056] The present invention prepares carbon paper with hydrophilic and hydrophobic structures, mainly comprising the following steps:

[0057] (1) Mix N,N-dimethylformamide and acetone in a volume ratio of 1:1 to prepare two identical mixed solvents, namely mixed solvent one and mixed solvent two. Add 5 wt% carbon nanotubes to mixed solvent one and disperse them evenly by ultrasonication. Then add 10 wt% polyacrylonitrile powder and stir thoroughly to form a uniform dispersion liquid one. Add 4 wt% nano silica (diameter 20 nm) to mixed solvent two and disperse them evenly by ultrasonication. Then add 5 wt% polyacrylonitrile powder and 4 wt% KH550 silane coupling agent and stir thoroughly to form a uniform dispersion liquid two.

[0058] (2) Electrospinning was performed using uniform dispersion liquid one, under the following conditions: the positive voltage applied by the needle was +10kV, the negative voltage applied by the receiver was -1kV, and the distance between the needle and the receiver was 10cm; at the same time, electrospinning was performed using uniform dispersion liquid two to the electrospinning area, the positive voltage applied by the needle during the electrospinning process was +10kV, and the distance between the needle and the receiver was 10cm; a polyacrylonitrile fiber membrane with a rough surface was obtained.

[0059] (3) The polyacrylonitrile fiber membrane is processed by hot pressing at 100°C for 30 min; then it is pre-oxidized at 200°C for 4 h in air atmosphere, and then carbonized at 800°C for 4 h in argon atmosphere to obtain carbon paper precursor material.

[0060] (4) The carbon paper precursor material is shielded by a mold with a uniformly distributed circular array, and the material is modified by low-temperature oxygen plasma hydrophilication using a low-temperature plasma treatment instrument. Oxygen is introduced, the plasma radio frequency power is 100W, and the treatment time is 1min to obtain carbon paper.

[0061] Example 2

[0062] The present invention prepares carbon paper with hydrophilic and hydrophobic structures, mainly comprising the following steps:

[0063] (1) Mix N,N-dimethylformamide and acetone at a volume ratio of 2:1 to prepare two identical mixed solvents, namely mixed solvent one and mixed solvent two. Add 0.5wt% carbon nanotubes and 0.5wt% carbon black to mixed solvent one and disperse it evenly by ultrasonication. Then add 15wt% polyacrylonitrile powder and stir thoroughly to form a uniform dispersion liquid one. Add 5wt% nano titanium dioxide (30nm in diameter) to mixed solvent two and disperse it evenly by ultrasonication. Then add 2wt% polyacrylonitrile powder and 5wt% KH560 silane coupling agent and stir thoroughly to form a uniform dispersion liquid two.

[0064] (2) Electrospinning was performed using a uniformly dispersed liquid one, under the following conditions: the positive voltage applied by the needle was +15kV, the negative voltage applied by the receiver was -2kV, and the distance between the needle and the receiver was 15cm; at the same time, electrospinning was performed using a uniformly dispersed liquid two to the electrospinning area, the positive voltage applied by the needle during the electrospinning process was +15kV, and the distance between the needle and the receiver was 15cm; a polyacrylonitrile fiber membrane with a rough surface was obtained.

[0065] (3) The polyacrylonitrile fiber membrane is processed by hot pressing at 120°C for 20 min; then it is pre-oxidized at 300°C for 2 h in air atmosphere, and then carbonized at 1000°C for 4 h in argon atmosphere to obtain carbon paper precursor material.

[0066] (4) The carbon paper precursor material is shielded by a mold with a uniformly distributed circular array, and the material is modified by low-temperature oxygen plasma hydrophilication using a low-temperature plasma treatment instrument. Oxygen is introduced, the plasma radio frequency power is 80W, and the treatment time is 1min to obtain carbon paper.

[0067] Example 3

[0068] The present invention prepares carbon paper with hydrophilic and hydrophobic structures, mainly comprising the following steps:

[0069] (1) Mix N,N-dimethylacetamide and ethyl acetate at a volume ratio of 5:1 to prepare two identical mixed solvents, namely mixed solvent one and mixed solvent two. Add 0.5wt% carbon nanotubes and 0.5wt% graphene to mixed solvent one and disperse them evenly by ultrasonication. Then add 15wt% polyacrylonitrile powder and stir thoroughly to form a uniform dispersion liquid one. Add 2wt% nano-zirconia (100nm in diameter) to mixed solvent two and disperse them evenly by ultrasonication. Then add 5wt% polyacrylonitrile powder and 2wt% KH570 silane coupling agent and stir thoroughly to form a uniform dispersion liquid two.

[0070] (2) Electrospinning was performed using a uniformly dispersed liquid one, under the following conditions: the positive voltage applied by the needle was +15kV, the negative voltage applied by the receiver was -2kV, and the distance between the needle and the receiver was 20cm; at the same time, electrospinning was performed using a uniformly dispersed liquid two to the electrospinning area, the positive voltage applied by the needle during the electrospinning process was +15kV, and the distance between the needle and the receiver was 20cm; a polyacrylonitrile fiber membrane with a rough surface was obtained.

[0071] (3) The polyacrylonitrile fiber membrane is processed by hot pressing at 100°C for 20 min; then it is pre-oxidized at 300°C for 2 h in air atmosphere, and then carbonized at 1000°C for 4 h in argon atmosphere to obtain carbon paper precursor material.

[0072] (4) The carbon paper precursor material is shielded by a mold with a uniformly distributed circular array, and the material is modified by low-temperature oxygen plasma hydrophilication using a low-temperature plasma treatment instrument. Oxygen is introduced, the plasma radio frequency power is 60W, and the treatment time is 2min to obtain carbon paper.

[0073] Example 4

[0074] The present invention prepares carbon paper with hydrophilic and hydrophobic structures, mainly comprising the following steps:

[0075] (1) Mix dimethyl sulfoxide and acetone at a volume ratio of 5:1 to prepare two identical mixed solvents, namely mixed solvent one and mixed solvent two. Add 2 wt% carbon nanotubes and 0.2 wt% carbon black to mixed solvent one and disperse it evenly by ultrasonication. Then add 20 wt% polyacrylonitrile powder and stir thoroughly to form a uniform dispersion liquid one. Add 5 wt% nano silica (30 nm in diameter) to mixed solvent two and disperse it evenly by ultrasonication. Then add 5 wt% polyacrylonitrile powder and 5 wt% KH550 silane coupling agent and stir thoroughly to form a uniform dispersion liquid two.

[0076] (2) Electrospinning was performed using a uniformly dispersed liquid one, under the following conditions: the positive voltage applied by the needle was +20kV, the negative voltage applied by the receiver was -5kV, and the distance between the needle and the receiver was 15cm; at the same time, electrospinning was performed using a uniformly dispersed liquid two to the electrospinning area, the positive voltage applied by the needle during the electrospinning process was +15kV, and the distance between the needle and the receiver was 15cm; a polyacrylonitrile fiber membrane with a rough surface was obtained.

[0077] (3) The polyacrylonitrile fiber membrane is processed by hot pressing at a temperature of 150°C for 10 min; then it is pre-oxidized at 250°C for 4 h in air atmosphere, and then carbonized at 1500°C for 2 h in argon atmosphere to obtain carbon paper precursor material.

[0078] (4) The carbon paper precursor material is shielded by a mold with a uniformly distributed circular array, and the material is modified by low-temperature oxygen plasma hydrophilication using a low-temperature plasma treatment instrument. Oxygen is introduced, the plasma radio frequency power is 20W, and the treatment time is 10min to obtain carbon paper.

[0079] Example 5

[0080] The present invention prepares carbon paper with hydrophilic and hydrophobic structures, mainly comprising the following steps:

[0081] (1) Mix N,N-dimethylacetamide and acetone at a volume ratio of 2:1 to prepare two identical mixed solvents, namely mixed solvent one and mixed solvent two. Add 3 wt% carbon nanotubes to mixed solvent one and disperse them evenly by ultrasonication. Then add 18 wt% polyacrylonitrile powder and stir thoroughly to form a uniform dispersion liquid one. Add 2 wt% nano silica (500 nm in diameter) to mixed solvent two and disperse them evenly by ultrasonication. Then add 2 wt% polyacrylonitrile powder and 0.5 wt% KH550 silane coupling agent and stir thoroughly to form a uniform dispersion liquid two.

[0082] (2) Electrospinning was performed using a uniformly dispersed liquid one, under the following conditions: the positive voltage applied by the needle was +20kV, the negative voltage applied by the receiver was -5kV, and the distance between the needle and the receiver was 20cm; at the same time, electrospinning was performed using a uniformly dispersed liquid two to the electrospinning area, the positive voltage applied by the needle during the electrospinning process was +20kV, and the distance between the needle and the receiver was 20cm; a polyacrylonitrile fiber membrane with a rough surface was obtained.

[0083] (3) The polyacrylonitrile fiber membrane is processed by hot pressing at a temperature of 160°C for 10 min; then it is pre-oxidized at 300°C for 2 h in air atmosphere, and then carbonized at 800°C for 4 h in argon atmosphere to obtain carbon paper precursor material.

[0084] (4) The carbon paper precursor material is shielded by a mold with a uniformly distributed circular array, and the material is modified by low-temperature oxygen plasma hydrophilication using a low-temperature plasma treatment instrument. Oxygen is introduced, the plasma radio frequency power is 80W, and the treatment time is 1min to obtain carbon paper.

[0085] Comparative Example 1

[0086] The process is basically the same as that in Example 1, except that in step (2), the electrostatic spraying method is not used to obtain a nanofiber membrane with a rough surface, but only electrospinning is performed.

[0087] Comparative Example 2

[0088] The process is basically the same as that in Example 1, except that the low-temperature oxygen plasma modification treatment in step (4) is not performed.

[0089] In the initial state after preparation and after soaking in H2SO4 solution for 7 days, the contact angle of the untreated portions of the carbon paper in Examples 1-5 and Comparative Examples 1-2 was measured. Specifically, the hydrophobic portions of Examples 1-5 and Comparative Example 2, and the untreated portion of Comparative Example 1 were measured. Furthermore, the carbon paper from each example and comparative example was used to prepare fuel cells, and the limiting power density of the cells was tested. The test results are shown in Table 1 below.

[0090] Table 1

[0091]

[0092] As can be seen from Table 1, compared with Comparative Example 1 and Comparative Example 2, the carbon paper with hydrophilic and hydrophobic structure prepared in Examples 1-5 showed significantly improved stability after accelerated acid degradation experiments. The fuel cells prepared using the carbon paper of the examples also showed good electrical performance, and the stability of the cells was improved, which is beneficial to the reliability of the cells in application.

[0093] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing carbon paper, characterized in that, Includes the following steps: Mixed solvent one and mixed solvent two were prepared separately. The conductive agent was added to mixed solvent one and dispersed evenly. Then, polyacrylonitrile powder was added and stirred to form a uniform dispersion liquid one. The nanoparticles were added to mixed solvent two and dispersed evenly. Then, silane coupling agent and polyacrylonitrile powder were added and stirred to form a uniform dispersion liquid two. The uniformly dispersed liquid one is electrospun, and the uniformly dispersed liquid two is electrospun in the electrospinning area to obtain a polyacrylonitrile fiber membrane with a rough surface. The polyacrylonitrile fiber membrane is subjected to hot pressing, followed by pre-oxidation and carbonization to prepare carbon paper precursor material. The carbon paper precursor material is partially hydrophilically modified to obtain the carbon paper.

2. The method for preparing carbon paper according to claim 1, characterized in that, The mixed solvent one and the mixed solvent two have the same or different compositions, and each of the mixed solvent one and the mixed solvent two includes component one and component two, wherein component one is selected from N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone, and component two is selected from acetone, ethanol and ethyl acetate, and the volume ratio of component one to component two is 1:1 to 5:

1.

3. The method for preparing carbon paper according to claim 1, characterized in that, The conductive agent is one or more of carbon nanotubes, carbon black and graphene, and the content of the conductive agent in the uniform dispersion liquid is 0.5wt% to 5wt%.

4. The method for preparing carbon paper according to claim 1, characterized in that, The polyacrylonitrile content in the uniform dispersion is 10wt% to 20wt%.

5. The method for preparing carbon paper according to claim 1, characterized in that, The nanoparticles are one of nano-silica, titanium dioxide and zirconium dioxide, the diameter of the nanoparticles is 20 to 500 nm, and the content of the nanoparticles in the uniform dispersion liquid is 0.5 wt% to 5 wt%.

6. The method for preparing carbon paper according to claim 1, characterized in that, The silane coupling agent is one of KH550, KH560 and KH570, and the content of the silane coupling agent in the uniform dispersion liquid II is 0.5wt% to 5wt%.

7. The method for preparing carbon paper according to claim 1, characterized in that, The polyacrylonitrile content in the uniform dispersion II is 2wt% to 5wt%.

8. The method for preparing carbon paper according to claim 1, characterized in that, During the electrospinning process, the positive voltage applied by the needle is 10-20kV, the negative voltage applied by the receiver is -1 to -5kV, and the distance between the needle and the receiver is 10-20cm.

9. The method for preparing carbon paper according to claim 1, characterized in that, The electrostatic spraying and electrospinning use the same roller receiver, and during the electrostatic spraying process, the positive voltage applied to the needle is 10-20kV, and the distance between the needle and the receiver is 10-20cm.

10. The method for preparing carbon paper according to claim 1, characterized in that, In the hot pressing process, the hot pressing temperature is 100℃~160℃ and the hot pressing time is 10~30min.

11. The method for preparing carbon paper according to claim 1, characterized in that, In the pre-oxidation treatment, the pre-oxidation temperature is 200-300℃, the pre-oxidation time is 0.5-4 h, and the pre-oxidation treatment is carried out in an air atmosphere.

12. The method for preparing carbon paper according to claim 1, characterized in that, In the carbonization process, the carbonization temperature is 800–1500℃, the carbonization time is 2–8 h, and the carbonization process is carried out under an inert gas atmosphere.

13. The method for preparing carbon paper according to claim 1, characterized in that, In the hydrophilic modification, the carbon paper precursor material is shielded using a mold with a specific hollow pattern, and then the carbon paper precursor material is subjected to low-temperature oxygen plasma hydrophilic modification treatment. The specific hollow pattern is one or more of the following: circular array, square array, parallel DC channel, and serpentine channel.

14. The method for preparing carbon paper according to claim 13, characterized in that, In the low-temperature oxygen plasma hydrophilic modification treatment, the plasma radio frequency power is 20-100W and the treatment time is 1-10min.

15. A type of charcoal paper, characterized in that, The carbon paper is prepared by the method described in any one of claims 1-14.

16. A fuel cell, characterized in that, Includes the carbon paper as described in claim 15.

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