Carbon paper for proton exchange membrane fuel cell cathode gas diffusion layer and method of making same

Abstract

The application discloses a kind of proton exchange membrane fuel cell cathode gas diffusion layer carbon paper and preparation method thereof, to substrate carbon paper layer is sequentially treated and heat treated, i.e. the carbon paper can be obtained.The carbon paper is accurately regulated in the case of guaranteeing that cathode gas diffusion layer pore structure is not obviously influenced to its in-plane hydrophobic characteristics, and process is simple, realizes gas-water separation and efficient transmission in fuel cell reaction process, and has good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of green and clean new energy, and relates to a carbon paper for the cathode gas diffusion layer of a proton exchange membrane fuel cell and its preparation method. Background Technology

[0002] The gas diffusion layer is a crucial component of a proton exchange membrane fuel cell (PEMFC), primarily serving to support the catalyst layer, transport reactant gases and generated water, and facilitate charge and heat transfer during the electrochemical reaction. Ultra-high power density is the mainstream trend for the future development of PEMFCs, requiring safe and stable operation under high current density conditions. During high current density operation, the internal electrochemical reaction rate of a PEMFC accelerates, necessitating faster transport of reactant gases and rapid drainage of generated water. This operational process places higher demands on the battery's internal water management capabilities, particularly its drainage performance. In the cathode-side catalyst layer, protons and oxygen undergo a hydration reaction under the influence of the catalyst and electrons. The generated water flows through the gas diffusion layer into the cathode-side flow field and is discharged from the battery along with the circulating reactant gases.

[0003] In the aforementioned process, the porous structure of the cathode-side gas diffusion layer, while transporting oxygen required for the reaction to the cathode-side catalyst layer, simultaneously discharges the water generated during the reaction to the cathode flow field. During this process, the generated water easily becomes trapped in the pores of the gas diffusion layer, blocking the transport channels of the reactant gases and causing a gas shortage phenomenon in the electrochemical reaction of the cathode-side catalyst layer. Furthermore, the random distribution of pores in the gas diffusion layer leads to random transport of liquid water within it, which in turn forces random changes in the oxygen transport channels, severely affecting the stability and sustainability of the electrochemical reaction under high current density conditions. Therefore, to improve the stability of hydrogen fuel cells under high current density conditions, it is necessary to improve the stability and orderliness of mass transfer in the gas diffusion layer, requiring optimized design and control of the gas diffusion layer structure.

[0004] Therefore, constructing a liquid water directional transport structure by controlling the local wettability characteristics of the carbon paper in the gas diffusion layer, and realizing the separation and directional transport of liquid water and reactant gas in the gas diffusion layer, is of great significance for improving the power density of fuel cells. Summary of the Invention

[0005] To overcome the aforementioned problems, the inventors conducted intensive research and developed a carbon paper for the cathode gas diffusion layer of a proton exchange membrane fuel cell and its preparation method. The carbon paper is obtained by sequentially subjecting a substrate carbon paper layer to hydrophobic treatment and heat treatment. The carbon paper precisely controls its in-plane hydrophobic characteristics while ensuring that the pore structure of the cathode gas diffusion layer is not significantly affected, achieving a "sub-hydrophobic-hydrophobic" periodic arrangement structure within the plane. This provides a directional transport channel for liquid water, realizing gas-water separation and efficient transport during the fuel cell reaction process. Furthermore, the process is simple, achieving gas-water separation and efficient transport during the fuel cell reaction process, and has excellent application prospects, thus completing this invention.

[0006] Specifically, the object of the present invention is to provide the following aspects:

[0007] In a first aspect, a carbon paper for the cathode gas diffusion layer of a proton exchange membrane fuel cell is provided, characterized in that the carbon paper includes a hydrophobic region and a subhydrophobic region, wherein the contact angle between the hydrophobic region and water is 120-160°, and the contact angle between the subhydrophobic region and water is 90-119°.

[0008] In a second aspect, a method for preparing carbon paper for the cathode gas diffusion layer of a proton exchange membrane fuel cell is provided, the method comprising:

[0009] Step 1: Perform hydrophobic treatment on the substrate carbon paper layer to obtain the pre-fabricated carbon paper layer;

[0010] Step 2: Heat-treat the pre-made carbon paper layer to obtain the carbon paper.

[0011] Thirdly, a fuel cell is provided, the cell comprising the carbon paper described in the first aspect.

[0012] The beneficial effects of this invention include:

[0013] (1) The carbon paper provided by the present invention can precisely control the hydrophobic characteristics of its surface while ensuring that the pore structure of the cathode gas diffusion layer is not significantly affected, so as to realize the construction of a "sub-hydrophobic-hydrophobic" periodic arrangement structure in the surface, provide a directional transport channel for liquid water, and realize gas-water separation and efficient transport in the fuel cell reaction process.

[0014] (2) The carbon paper provided by the present invention has a high-efficiency mass transfer electrode structure. As a cathode of a hydrogen fuel cell, it has a high mass transfer efficiency and can effectively reduce the mass transfer loss inside the battery under high current density conditions, so as to improve the electrochemical reaction efficiency and battery performance.

[0015] (3) The carbon paper structure control method provided by the present invention has a simple process and precise control over the distribution of hydrophobic and subhydrophobic regions, and has a good application prospect. Attached Figure Description

[0016] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0017] In the attached diagram:

[0018] Figure 1 A schematic diagram of the structure of a clamp according to a preferred embodiment of the present invention is shown;

[0019] Figure 2 (a) SEM characterization of the carbon paper prepared in Example 1 is shown;

[0020] Figure 2 (b) shows Figure 2 (a) Enlarged view of a portion of the bright area;

[0021] Figure 2 (c) shows Figure 2 (a) Enlarged view of a dark area in the middle;

[0022] Figure 3 The image shows the contact angle characterization diagrams of the bright and dark areas of the carbon paper prepared in Example 1 when in contact with water.

[0023] Figure 4 The capillary resistance change process of liquid water transport in carbon paper is shown;

[0024] Figure 4 (a) shows the capillary resistance over time during the transport of liquid water on carbon paper prepared in Example 1 and untreated carbon paper, respectively;

[0025] Figure 4 (b) shows the water breakthrough sites of liquid water on untreated carbon paper;

[0026] Figure 4 (c) Shows the water breakthrough site of liquid water on the carbon paper prepared in Example 1;

[0027] Explanation of icon numbers:

[0028] 1-Upper clamp;

[0029] 2- Pre-fabricated carbon paper layer to be processed;

[0030] 3-Lower clamp;

[0031] 4-Screw;

[0032] 5-Clamp end plate;

[0033] 6-Electrically and thermally conductive materials;

[0034] 7-Insulating materials. Detailed Implementation

[0035] Specific embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0036] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0037] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship in the working state of this invention, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0038] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0039] On one hand, according to the present invention, a carbon paper for the cathode gas diffusion layer of a proton exchange membrane fuel cell includes a hydrophobic region and a subhydrophobic region. The contact angle between the hydrophobic region and water is 120° to 160°, and the contact angle between the subhydrophobic region and water is 90° to 119°. In one embodiment, the contact angle between the hydrophobic region and water is approximately 126°, and the contact angle between the subhydrophobic region and water is approximately 114°.

[0040] According to the present invention, the hydrophobic region and the secondary hydrophobic region form a periodic arrangement structure of "secondary hydrophobic-hydrophobic" on the surface of the carbon paper, that is, hydrophobic region, secondary hydrophobic region, hydrophobic region, secondary hydrophobic region... or, in other words, the adjacent hydrophobic regions are separated by secondary hydrophobic regions.

[0041] Furthermore, both the hydrophobic region and the subhydrophobic region contain a hydrophobic medium, and the division between the hydrophobic region and the subhydrophobic region is achieved by controlling the content of the hydrophobic medium.

[0042] The total amount of the hydrophobic medium is 10-30 wt% of the carbon paper mass, preferably 15-25 wt%, and more preferably 25 wt%. Within this range, gas-water separation and efficient transport can be achieved during the fuel cell reaction process. In particular, when the total amount of the hydrophobic medium is 25 wt% of the carbon paper mass, the gas-water separation and efficient transport effect is most significant.

[0043] According to the present invention, the hydrophobic medium is one or more of polytetrafluoroethylene, polydimethylsiloxane, and polyvinylidene fluoride, preferably polytetrafluoroethylene.

[0044] Among them, polytetrafluoroethylene, polydimethylsiloxane and polyvinylidene fluoride are all stable hydrophobic substances, especially polytetrafluoroethylene, which has superior stability.

[0045] Furthermore, since hydrophobic media typically have high viscosity, diluting them before hydrophobic treatment is more effective. The concentration of the hydrophobic media is 5–20 wt%, for example, 10 wt%.

[0046] In this invention, the distribution characteristics of the hydrophobic region and the subhydrophobic region are mainly determined by the flow field structure. The shapes of the hydrophobic region and the subhydrophobic region can be regular shapes, such as rectangles and squares, or they can be irregular shapes, such as wavy, elliptical, or gradually changing width shapes. The hydrophobic region corresponds to the ridge part of the flow field, and the subhydrophobic region corresponds to the flow channel part of the flow field. They are distributed in other areas besides the hydrophobic region.

[0047] In a preferred embodiment, both the hydrophobic region and the secondary hydrophobic region are rectangular. The width of the hydrophobic region is 0.5–5 mm, and the width of the secondary hydrophobic region is 0.2–1 mm. The total width of the hydrophobic region and the secondary hydrophobic region is consistent with the flow field length, which is 2–100 mm. The length of the hydrophobic region and the length of the secondary hydrophobic region are consistent with the flow field width, which is 2–300 mm.

[0048] In a further preferred embodiment, both the hydrophobic region and the secondary hydrophobic region are rectangular. The width of the hydrophobic region is 1 mm, the width of the secondary hydrophobic region is 1 mm, the total width of the hydrophobic region and the secondary hydrophobic region is the same as the flow field length, which is 23 mm, and the length of the hydrophobic region and the length of the secondary hydrophobic region are the same as the flow field width, which is 60 mm.

[0049] According to the present invention, the areas of the hydrophobic region and the subhydrophobic region are respectively consistent with the ratio of the area of ​​the ridge to the area of ​​the channel in the ridge flow field. Typically, the area of ​​the hydrophobic region is 10-50% of the total area of ​​the carbon paper, and the remainder is the subhydrophobic region.

[0050] According to the present invention, the substrate carbon paper layer used to prepare carbon paper containing hydrophobic and subhydrophobic regions is not limited to any commercially available substrate carbon paper layer, but preferably a substrate carbon paper layer with a porosity of about 75% and a thickness of 150 to 200 micrometers, more preferably a substrate carbon paper layer with a porosity of 75% and a thickness of 190 micrometers, such as Toray carbon paper or SGL carbon paper.

[0051] Theoretically, the thinner the carbon paper substrate, the shorter the distance electrons travel from the catalyst layer to the bipolar plate, resulting in lower resistance and improved battery output performance. However, excessive thinness leads to insufficient support strength, so the substrate thickness should be minimized while maintaining adequate support characteristics. Regarding porosity, higher porosity results in better air permeability and lower mass transfer resistance; however, excessively high porosity reduces electron transport paths and increases resistance. Commercially available carbon paper substrates with a porosity of around 75% and a thickness of 150–200 micrometers typically achieve good performance.

[0052] In a second aspect, a method for preparing the carbon paper described in the first aspect is provided, the method comprising:

[0053] Step 1: Perform hydrophobic treatment on the substrate carbon paper layer to obtain the pre-fabricated carbon paper layer;

[0054] Step 2: Heat-treat the pre-made carbon paper layer to obtain the carbon paper.

[0055] Specifically:

[0056] Step 1: Perform hydrophobic treatment on the substrate carbon paper layer.

[0057] In step 1, a hydrophobic medium is used to hydrophobically treat the substrate carbon paper layer. This hydrophobic treatment can be achieved through methods such as impregnation, hydrothermal deposition, chemical vapor deposition, or physical vapor deposition. The distribution of hydrophobic and sub-hydrophobic regions is achieved by adjusting the content of the hydrophobic medium. Hydrothermal deposition, chemical vapor deposition, or physical vapor deposition methods for hydrophobically treating the substrate carbon paper layer are relatively complex and require very high precision. Preferably, the substrate carbon paper layer is hydrophobically treated using the extremely simple impregnation method.

[0058] In step 1, the hydrophobic medium content in each region of the prefabricated carbon paper layer obtained by hydrophobic treatment of the substrate carbon paper layer is consistent. Therefore, during the heat treatment in step 2, the temperature of the fixture and different regions of the hydrophobic layer on the prefabricated carbon paper layer can be adjusted to achieve different hydrophobic medium contents in different regions, thereby realizing the distribution of hydrophobic and subhydrophobic regions.

[0059] According to the present invention, the impregnation method includes: immersing the substrate carbon paper layer in a hydrophobic medium for 0.1 to 1 hour, followed by drying at 50 to 200°C, for example, immersing the substrate carbon paper layer in a hydrophobic medium for 0.5 hours, followed by drying at 150°C. During this process, a hydrophobic layer is formed on the surface of the pre-made carbon paper layer. The hydrophobicity of the hydrophobic layer on the surface of the pre-made carbon paper layer is then tested. When the contact angle between the hydrophobic layer on the surface of the pre-made carbon paper layer and water reaches 150 to 160°, the next step is performed; otherwise, the pre-made carbon paper layer containing the hydrophobic layer undergoes a second hydrophobic treatment, or even a third, fourth, or more hydrophobic treatments, until the contact angle between the hydrophobic layer on the surface of the pre-made carbon paper layer and water reaches 150 to 160°. Preferably, the process continues until the contact angle between the hydrophobic layer on the surface of the pre-made carbon paper layer and water reaches 150°.

[0060] At this point, the contact angle between the hydrophobic layer and water reaches 150-160°, which helps to allow sufficient time for subsequent heat treatment to reduce the hydrophobicity of the pre-made carbon paper layer.

[0061] Step 2: Heat-treat the pre-made carbon paper layer to obtain the carbon paper.

[0062] In step 2, the heat treatment includes: heating from room temperature to 500-1200°C at a heating rate of 10-50°C / min, holding at that temperature for 2-10 minutes, and then naturally cooling to room temperature.

[0063] In a further preferred embodiment, the heat treatment includes: heating from room temperature to 700-900°C at a heating rate of 20-40°C / min, holding at that temperature for 1-3 minutes, and then naturally cooling to room temperature.

[0064] In a further preferred embodiment, the heat treatment includes: heating from room temperature to 800°C at a heating rate of 30°C / min, holding at that temperature for 2 minutes, and then naturally cooling to room temperature.

[0065] The "normal temperature" refers to room temperature, which is typically 0–40°C, such as 25°C.

[0066] According to the present invention, during the heat treatment process, the power is adjusted to 2 to 25 kW, preferably 10 to 20 kW, and more preferably 15 kW.

[0067] According to the present invention, the heat treatment is carried out in a vacuum environment or in a protective atmosphere, which helps to avoid the oxidative decomposition of the carbon paper in the pre-made carbon paper layer.

[0068] The vacuum level of the vacuum environment is less than 1 Pa; the protective atmosphere can be a reducing atmosphere such as an argon-hydrogen mixture, or an inert gas such as argon, helium, or nitrogen, and the protective atmosphere is preferably an argon-hydrogen mixture.

[0069] In this invention, the heat treatment method used includes, but is not limited to, induction heating, plasma sintering or resistance heating, with induction heating being preferred, which can achieve rapid heating and cooling.

[0070] According to the present invention, the induction heating employs, as follows: Figure 1 The fixture shown includes an upper fixture 1 and a lower fixture 3. The upper fixture 1 and the lower fixture 3 have the same structure and are symmetrically distributed on both sides of the pre-made carbon paper layer 2 to be processed. It can also be understood that the upper fixture 1 and the lower fixture 3 are used to clamp the pre-made carbon paper layer 2 to be processed.

[0071] Furthermore, the upper clamp 1 has clamp end plates 5 on both sides, and the clamp end plates 5 are provided with screws 4 for fixing the clamp end plates 5. The part of the clamp 1 that contacts the pre-made carbon paper layer is a clamp made of conductive and thermally conductive material 6 and insulating material 7. The clamp can realize the adjustment of the contact angle between the hydrophobic layer and water.

[0072] According to the preferred embodiment, such as Figure 1 As shown, the clamping element is a periodic arrangement of conductive and thermally conductive material 6 and insulating material 7. The conductive and thermally conductive material is preferably a metal material, and the insulating material is preferably a ceramic material. That is, the clamping element is a periodic arrangement of metal material and ceramic material, so as to achieve different temperatures in different areas of the clamping element and the hydrophobic layer on the pre-made carbon paper layer, thereby realizing the distribution of hydrophobic area and sub-hydrophobic area.

[0073] Furthermore, by utilizing the significant difference in thermal response between metallic and ceramic materials, different heating effects are achieved in different regions of the pre-fabricated carbon paper layer 2 to be treated. The regions covered by ceramic materials do not have a significant heating effect, while the regions covered by metallic materials produce a significant heating effect. This leads to varying degrees of changes in the physicochemical properties and surface roughness of the carbon fiber surface in the corresponding regions, thereby achieving the regulation of the hydrophobic characteristics of the carbon paper. In other words, the hydrophobic characteristics of adjacent regions of carbon paper show significant differences, providing a driving force for the directional transport of liquid water.

[0074] According to the present invention, the area covered by the metal material is a secondary hydrophobic region. During the heat treatment process, the hydrophobic medium is decomposed by heat, which reduces the hydrophobic characteristics of this region. The area covered by the ceramic material is a hydrophobic region. During the heat treatment process, no obvious thermal decomposition effect is produced, and it still retains a high degree of hydrophobicity. Finally, a "secondary hydrophobic-hydrophobic" periodic arrangement structure is formed on the carbon paper plane.

[0075] According to the present invention, the subhydrophobic region is beneficial for guiding the directional transport of liquid water, and the hydrophobic region provides a stable area and channel for the transport of reactant gases.

[0076] According to the present invention, the shapes of the ceramic material and the metal material are designed according to the flow field structure. The area covered by the ceramic material is a hydrophobic region, corresponding to the ridge portion of the flow field; the area covered by the metal material is a secondary hydrophobic region, corresponding to the flow channel portion of the flow field.

[0077] According to the present invention, the metallic material may be a metal or alloy such as copper or tungsten, preferably a metal, and more preferably copper; the ceramic material may be alumina ceramic, zirconia ceramic or high-temperature resistant quartz material, preferably zirconia.

[0078] According to the present invention, due to the different thermal conductivity of metallic and ceramic materials, during heat treatment, the temperature of the area covered by the metallic material is 800–1000°C, and the temperature of the area covered by the ceramic material is 400–600°C. In one embodiment, during heat treatment, the temperature of the area covered by the metallic material is 800°C, and the temperature of the area covered by the ceramic material is 500°C.

[0079] According to the present invention, the carbon paper with a "sub-hydrophobic-hydrophobic" periodic arrangement has a high-efficiency mass transfer electrode structure. As a cathode of a hydrogen fuel cell, it has a high mass transfer efficiency, which can effectively reduce the mass transfer loss inside the battery under high current density conditions, thereby improving the electrochemical reaction efficiency and battery performance.

[0080] Thirdly, the application of the carbon paper described in the first aspect in fuel cells is provided.

[0081] Example

[0082] The present invention is further described below through specific examples; however, these examples are merely exemplary and do not constitute any limitation on the scope of protection of the present invention.

[0083] Example 1

[0084] Toray carbon paper with a thickness of 190 micrometers and a porosity of 75% was placed in polytetrafluoroethylene with a concentration of 10 wt% for 0.5 h, and then dried at 150 °C to obtain a pre-made carbon paper layer. The contact angle between the hydrophobic layer on the surface of the pre-made carbon paper layer and water was measured to be 120°. The above hydrophobic treatment was repeated 3 times, and the contact angle between the hydrophobic layer and water was measured to be 150°.

[0085] Next, place the aforementioned pre-made carbon paper layer in a position such as... Figure 1The final carbon paper can be obtained by heat treatment in the fixture shown in the following manner: In an argon-hydrogen mixture, the temperature is raised from room temperature to 800°C at a heating rate of 30°C / min, held for 2 minutes, and then allowed to cool naturally to room temperature. During the heat treatment process, the power is adjusted to 15kW. At the above heat treatment temperature, the temperature of the area covered by the metal material reaches 800°C, and the temperature of the area covered by the ceramic material reaches 500°C. Figure 1 In the process, the metal material is copper, the ceramic material is zirconium oxide, the width of the metal material region is 1 mm, the width of the ceramic material region is 1 mm, and the length of the metal material region and the length of the ceramic material region are the same as the width of the flow field, which is 60 mm.

[0086] The total amount of hydrophobic medium on the carbon paper is 25 wt% of the carbon paper mass. The width of the hydrophobic region is 1 mm, the width of the secondary hydrophobic region is 1 mm, and the total width of the hydrophobic region and the secondary hydrophobic region is consistent with the flow field length, which is 23 mm. The length of the hydrophobic region and the length of the secondary hydrophobic region are consistent with the flow field width.

[0087] Figure 2 (a) shows the SEM characterization of the prepared carbon paper. It can be seen that the carbon paper has a periodically arranged "sub-hydrophobic-hydrophobic" structure with regular alternating bright and dark areas. ① is the bright area, and ② is the sub-hydrophobic area. The magnified local image is shown below. Figure 2 As shown in (b), ② is the dark area and the hydrophobic area, and its enlarged local view is shown below. Figure 2 As shown in (c), it can be seen that the carbon paper with "sub-hydrophobic-hydrophobic" characteristics has significant differences in thermal effect during induction heating, which leads to different degrees of changes in the physicochemical properties and surface roughness of the carbon fiber surface in the corresponding region. Ultimately, this results in significant differences in the hydrophobic characteristics of the carbon paper in adjacent regions, providing a driving force for the directional transport of liquid water.

[0088] Figure 3 The diagram shows the contact angles of the bright and dark areas of the prepared carbon paper in contact with water. It can be seen that the wettability of different regions of the carbon paper exhibits a "sub-hydrophobic-hydrophobic" characteristic. The static contact angle of the droplet in the bright area of ​​the carbon paper surface shows a hydrophobic characteristic (~114°), while the static contact angle in the dark area shows a more significant hydrophobic characteristic (~126°). The gradient difference in the hydrophobic characteristics of the carbon paper in the in-plane direction is conducive to guiding the directional transport of liquid water in the sub-hydrophobic region, and provides a stable region and channel for the transport of reactive gases in the hydrophobic region.

[0089] Figure 4 This illustrates the change in capillary resistance during the transport of liquid water in carbon paper. Figure 4 (a) shows the capillary resistance over time during the transport of liquid water in carbon paper prepared in Example 1 and untreated carbon paper (Toray carbon paper, with the same dimensions as the Toray carbon paper used in Example 1). Figure 4(b) shows the water breakthrough sites of liquid water on untreated carbon paper. Figure 4 (c) shows the water breakthrough sites of liquid water on the carbon paper prepared in Example 1. It can be seen that the breakthrough pressure of liquid water in the carbon paper with the "sub-hydrophobic-hydrophobic" periodic arrangement characteristics prepared in Example 1 is significantly lower than that in the untreated carbon paper, indicating that the carbon paper of Example 1 is beneficial for internal drainage of fuel cells under high current density conditions. At the same time, there is only one breakthrough site of liquid water in the carbon paper with the "sub-hydrophobic-hydrophobic" periodic arrangement characteristics prepared in Example 1, while there are four breakthrough sites of liquid water in the untreated carbon paper. This indicates that the liquid water transport path in the untreated carbon paper is randomly distributed, while the liquid water transport in the carbon paper prepared in Example 1 is a single path, showing better directional transport characteristics.

[0090] The present invention has been described in detail above with reference to preferred embodiments and exemplary examples. However, it should be noted that these specific embodiments are merely illustrative explanations of the invention and do not constitute any limitation on the scope of protection of the invention. Various improvements, equivalent substitutions, or modifications can be made to the technical content and embodiments of the present invention without departing from the spirit and scope of protection of the invention, and all such modifications fall within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing carbon paper for the cathode gas diffusion layer of a proton exchange membrane fuel cell, characterized in that, The method includes: Step 1: The substrate carbon paper layer is hydrophobically treated with a hydrophobic medium to obtain a pre-fabricated carbon paper layer. Step 2: Heat-treat the pre-made carbon paper layer to obtain the carbon paper; The heat treatment method is induction heating, which is achieved by a fixture. The fixture includes an upper fixture (1) and a lower fixture (3). The upper fixture (1) and the lower fixture (3) have the same structure and are symmetrically distributed on both sides of the pre-made carbon paper layer (2) to be treated. The part of the fixture that contacts the pre-made carbon paper layer is a clamp made of conductive and thermally conductive material (6) and insulating material (7). The clamp is made of conductive and thermally conductive material (6) and insulating material (7) arranged periodically to achieve different temperatures between the fixture and different areas of the hydrophobic layer on the pre-made carbon paper layer, thereby achieving the distribution of hydrophobic and subhydrophobic areas.

2. The method according to claim 1, characterized in that, The hydrophobic medium is one or more of polytetrafluoroethylene emulsion, polydimethylsiloxane, and polyvinylidene fluoride.

3. The method according to claim 1, characterized in that, In step 1, the contact angle between the hydrophobic layer on the surface of the pre-made carbon paper layer and water is 150~160°.

4. The method according to claim 1, characterized in that, During heat treatment in step 2, the temperature of different areas of the fixture and the hydrophobic layer on the pre-made carbon paper is adjusted to achieve different contents of hydrophobic medium in different areas, thus realizing the distribution of hydrophobic and subhydrophobic areas.

5. A carbon paper for the cathode gas diffusion layer of a proton exchange membrane fuel cell prepared by the method described in claim 1, characterized in that, The carbon paper includes a hydrophobic region and a subhydrophobic region. The contact angle between the hydrophobic region and water is 120° to 160°, and the contact angle between the subhydrophobic region and water is 90° to 119°.

6. The carbon paper according to claim 5, characterized in that, The hydrophobic region and the subhydrophobic region form a periodic arrangement of "subhydrophobic-hydrophobic" on the surface of the carbon paper.

7. The carbon paper according to claim 5 or 6, characterized in that, Both the hydrophobic region and the subhydrophobic region contain hydrophobic media, and the total amount of hydrophobic media is 10~30wt% of the carbon paper mass.

8. The carbon paper according to claim 5, characterized in that, The hydrophobic medium is one or more of polytetrafluoroethylene emulsion, polydimethylsiloxane, and polyvinylidene fluoride.

9. A fuel cell, characterized in that, The battery comprises the carbon paper as described in any one of claims 5 to 8.

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