WO2022027944A1 - 一种燃料电池气体扩散层结构及其加工方法 - Google Patents

一种燃料电池气体扩散层结构及其加工方法 Download PDF

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WO2022027944A1
WO2022027944A1 PCT/CN2021/075284 CN2021075284W WO2022027944A1 WO 2022027944 A1 WO2022027944 A1 WO 2022027944A1 CN 2021075284 W CN2021075284 W CN 2021075284W WO 2022027944 A1 WO2022027944 A1 WO 2022027944A1
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diffusion layer
gas diffusion
texture
fuel cell
micro
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PCT/CN2021/075284
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English (en)
French (fr)
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董非
尹必峰
贾和坤
许晟
解玄
陈鑫
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江苏大学
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Priority claimed from CN202010783407.1A external-priority patent/CN112072119B/zh
Priority claimed from CN202010783392.9A external-priority patent/CN112117465B/zh
Application filed by 江苏大学 filed Critical 江苏大学
Publication of WO2022027944A1 publication Critical patent/WO2022027944A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the invention relates to the technical field of fuel cells, in particular to a fuel cell gas diffusion layer structure and a processing method thereof.
  • the base material of the gas diffusion layer is generally carbon fiber.
  • the material is beneficial to improve the performance of the electrode and needs to meet the following requirements, including uniform porous structure, good air permeability, strong electrical conductivity, compact structure and smooth surface, balance of hydrophilicity and hydrophobicity, and good thermal stability. This poses a greater challenge to the preparation process of the gas diffusion layer, that is, the traditional hot pressing method.
  • the use of laser machining technology in the surface processing of gas diffusion layers has the advantages of accurate precision, good thermal effect and easy implementation, and can basically replace the traditional hot pressing preparation process.
  • the gas diffusion layer is located between the catalyst layer and the bipolar plate, and is one of the most important parts of the PEM fuel cell.
  • the catalyst layer, gas diffusion layer, and membrane electrode are sandwiched between flow field plates.
  • the gas diffusion layer is the outermost layer of the membrane electrode, providing electrical contact between the electrode and the bipolar plate, and evenly distributing the reactants to the catalyst Floor.
  • the gas diffusion layer facilitates water management in PEM fuel cells because the gas diffusion layer retains an appropriate amount of water to wet the membrane electrode, and the gas diffusion layer helps the product water to leave the cathode, eliminating electrode flooding.
  • the surface of the cathode will continuously generate water. In the case of high power, the rate of water generation is getting faster and faster. If the product water cannot be discharged in time, it will cause flooding. This leads to blockage of gas channels, reduces the amount of product delivered, and reduces the performance of the battery.
  • the Chinese patent discloses a preparation method of a fuel cell gas diffusion layer with hydrophobicity. It is proposed to perform hydrophobic treatment on the base layer material and heat treatment in combination with the prepared microporous layer slurry to obtain a fuel cell gas with hydrophobicity. diffusion layer. From a structural point of view: the Chinese patent discloses that by using doped diamond to form pores on the surface of the gas diffusion layer, it is not easy to form water flooding, and a method of sequentially expanding the pores is designed to prevent liquid water from forming a water film in the pores and improve the stability of the battery. .
  • the above patents help to improve the flooding of the gas diffusion layer of fuel cells, but the processing technology is too cumbersome and time-consuming, which is not conducive to large-scale commercialization.
  • the present invention provides a fuel cell gas diffusion layer structure and a processing method thereof.
  • By processing groove texture on the surface of the gas diffusion layer base layer it helps to promote water to leave the cathode to help eliminate The phenomenon of electrode flooding, while allowing only the right amount of water to contact the membrane electrode to keep the membrane wet.
  • the present invention adopts the method of laser processing, which is easy to implement, has long service life, stable working state, and does not need to change the material of the gas diffusion layer. From the perspective of improving the structure, a fuel cell with high efficiency and anti-flooding performance is developed. gas diffusion layer.
  • the present invention achieves the above technical purpose through the following technical means.
  • the gas diffusion layer is a base layer on one side of the bipolar plate, and the surface of the gas diffusion layer is provided with several micro-textures for eliminating the flooding phenomenon of liquid reaction products.
  • micro-texture is a groove texture
  • the surface of the gas diffusion layer is provided with a plurality of groove textures that are interlaced and communicated with each other.
  • the area of several of the groove textures accounts for 20%-50% of the surface area of the gas diffusion layer.
  • cross section of the groove texture is rectangular, trapezoidal or arc-shaped.
  • any edge of the groove texture is provided with an outwardly inclined chamfer, so as to improve the water resistance of the gas diffusion layer.
  • cross-sectional areas of the groove textures along the flow direction among the plurality of groove textures that are interlaced and communicated with each other first expand and then decrease with the flow direction.
  • the cross-sectional area at both ends of the groove texture along the flow direction is gradual, and the cross-sectional area in the middle of the groove texture along the flow direction remains unchanged; the cross-sectional area in the middle of the groove texture is the 1.5 to 3 times the minimum cross-sectional area.
  • micro-texture is a micro-pit texture, and several micro-pit textures are uniformly distributed on the surface of the gas diffusion layer.
  • micro-pit texture is a spherical cap
  • micro-pit texture depth H 3-100 ⁇ m.
  • the ratio of several of the micro-pit textures to the total area of the surface of the gas diffusion layer is 10%-45%.
  • a method for processing a gas diffusion layer structure of a fuel cell comprising the steps of:
  • the intertwined and connected groove texture is processed on the surface of the gas diffusion layer by ultrafast laser;
  • the impurities remaining on the surface of the gas diffusion layer are removed by ultrasonic cleaning.
  • the pulse width of the ultrafast laser is ⁇ 10ps
  • the processing speed of the ultrafast laser is 0-2000mm/s
  • the laser power of the ultrafast laser is 0-100W
  • the repetition frequency of the ultrafast laser is 0-2000mm/s. 1MHz
  • the scanning times of the ultrafast laser is 1-20 times.
  • a method for processing a gas diffusion layer structure of a fuel cell comprising the steps of:
  • the surface of the gas diffusion layer close to the bipolar plate is processed multiple times at the same point interval by laser to obtain a gas diffusion layer with a texture of uniformly distributed micro-pits;
  • At least 4 action points are selected around any micro-pit texture for laser micro-machining, and the laser and the machined surface of the gas diffusion layer are inclined at an angle of ⁇ , so that the edge of the micro-pit texture produces an outwardly inclined chamfer.
  • the laser parameters for processing the micro-pit texture are: laser power 0.1W-50W, repetition frequency 0-100kHz, pulse width 0-100ns; laser parameters for the laser micro-processing are: laser power 0.1W- 5W, repetition rate is 0-500kHz, pulse width is 0-10ps.
  • the minimum distance between the action point and the micro-pit texture boundary is 1-40 ⁇ m, and the interval between adjacent action points is 30-250 ⁇ m.
  • deburring treatment is also included, and ultrasonic cleaning, glow cleaning and sputtering cleaning are used to sequentially deburr the gas diffusion layer after laser micromachining.
  • the fuel cell gas diffusion layer structure of the present invention through surface processing groove texture, can make the water after the reaction gather in the groove, help to promote the product water to leave the cathode to help eliminate the phenomenon of flooding of the cathode , while allowing only the right amount of water to contact the membrane electrode to keep the membrane wet.
  • the groove texture can increase the specific surface area of the gas diffusion layer, help the wetting of the reactant gas flow, improve the stability of the reaction, and also help the oxidant gas in the channel.
  • the internal flow is uniform and the oxygen supply from the gas diffusion layer to the membrane electrode is enhanced.
  • the fuel cell gas diffusion layer structure of the present invention has improved water resistance and durability compared with the traditional gas diffusion layer, and has a longer service life. life.
  • the method for processing the gas diffusion layer structure of the fuel cell according to the present invention only needs to form an orderly groove structure on the surface of the base layer of the gas diffusion layer.
  • the fuel cell gas diffusion layer structure of the present invention through the cross-sectional area of the groove texture along the flow direction, first gradually expands and then gradually shrinks with the flow direction, which helps to reduce the amount of product water at the inlet, Reducing the local "flooding" phenomenon at the inlet helps to increase the distribution uniformity of the product water on the surface of the gas diffusion layer, and is more conducive to the wetting of the reactant gas flow.
  • the fuel cell gas diffusion layer structure of the present invention has a micro-pit texture with a certain angle around it through laser micro-processing, which can make the fuel cell cathode reaction water more easily dented on the surface of the gas diffusion layer on the side of the bipolar plate. Aggregation at the pit improves the reaction water tolerance of the fuel cell.
  • FIG. 1 is a schematic diagram of the structure of the gas diffusion layer of the fuel cell according to the present invention.
  • FIG. 2 is a partial enlarged view of the arc-shaped groove texture in Example 1.
  • FIG. 3 is a partial enlarged view of a rectangular groove texture in Example 2.
  • FIG. 4 is a partial enlarged view of the trapezoidal groove texture in Example 3.
  • FIG. 4 is a partial enlarged view of the trapezoidal groove texture in Example 3.
  • FIG. 5 is a partial enlarged plan view of the groove texture of the graded trapezoid structure in Example 3.
  • FIG. 5 is a partial enlarged plan view of the groove texture of the graded trapezoid structure in Example 3.
  • FIG. 6 is a comparison diagram of the drag reduction rate of the gas diffusion layers with different cross-sectional shapes in the embodiment and the prior art.
  • FIG. 7 is a schematic diagram of Embodiment 4 of the fuel cell gas diffusion layer structure according to the present invention.
  • FIG. 8 is a cross-sectional view of the micropit texture of Example 4.
  • FIG. 9 is a schematic diagram of the action point according to the present invention.
  • FIG. 10 is a graph comparing droplet flow behavior on Example 4 and a conventional gas diffusion layer.
  • FIG. 11 is a comparison diagram of polarization curves of Example 1 and Example 3 and a conventional gas diffusion layer.
  • FIG. 12 is a graph comparing the pressure drop of Example 1 and Example 3 with a conventional gas diffusion layer.
  • FIG. 13 is a graph of the drag reduction rate of Example 1 and Example 3.
  • FIG. 13 is a graph of the drag reduction rate of Example 1 and Example 3.
  • 1-gas diffusion layer 2-groove texture; 3-action point; 4-laser micromachining region; 5-micro-pit texture.
  • the gas diffusion layer 1 is the base layer on the side close to the bipolar plate, and the surface of the gas diffusion layer 1 is provided with a number of grooves that are interlaced and communicated with each other.
  • Groove texture 2 a plurality of groove textures 2 which are interlaced and communicated with each other divide the surface of the gas diffusion layer 1 into a grid shape, which is used to eliminate the phenomenon of electrode flooding.
  • the plurality of groove textures 2 that are interlaced and communicated with each other include groove textures parallel or nearly parallel to the flow direction and groove textures perpendicular to the flow direction.
  • the cross-sectional area of the groove texture parallel to the flow direction and the groove texture perpendicular to the flow direction in Example 1 were the same.
  • the base layer material of the gas diffusion layer 1 is carbon black paper, and the specific dimensions are: length 20mm, width 20mm, and thickness 0.5mm.
  • the angle ⁇ 30° exists around the edge of the groove texture 2 .
  • Example 1 several groove textures 2 are crisscrossed to divide the surface of the gas diffusion layer 1 into a square grid, which may also be a rhombus, a parallelogram, or a polygon.
  • Several groove textures 2 account for 42.39% of the surface area of the entire GDL base layer.
  • the surface of the base layer of the gas diffusion layer has an orderly groove structure, which allows the liquid water to leave the cathode and eliminates the phenomenon of flooding. Part of the water can accumulate in the groove to keep the membrane wet; this structure can increase the specific surface area and enhance the gas diffusion.
  • the oxygen supply from the layer to the membrane electrode improves the stability of the reaction and improves the performance of the fuel cell.
  • Example 1 the groove texture 2 is processed on the surface of the base layer of the gas diffusion layer by the method of laser processing.
  • the laser parameters corresponding to the laser processing are selected: the laser power is 50W, the speed is 1000mm/s, the repetition frequency is 0.5MHz, and the scanning 10 times; ultrasonic cleaning was used for 15min to remove surface impurities.
  • the gas diffusion layer 1 base layer material is carbon fiber
  • the cross-sectional shape of the groove texture 2 is a rectangle; the specific dimensions are: length 30mm, width 30mm , 1mm thick.
  • the groove texture 2 accounts for 47.98% of the surface area of the entire base layer of the gas diffusion layer.
  • the groove structure on the surface of the gas diffusion layer increases the surface area, can better eliminate the flooding phenomenon, and enhance the supply of reactants.
  • Example 2 the groove structure is processed on the surface of the base layer of the gas diffusion layer by the method of laser processing.
  • the laser parameters corresponding to the laser processing are selected: the laser power is 50W, the speed is 800mm/s, the repetition frequency is 1MHz, and the number of scans is 5 times. ; using ultrasonic cleaning for 15min to remove surface impurities.
  • the base layer material of the gas diffusion layer 1 is carbon fiber
  • the cross-sectional shape of the groove texture 2 is a trapezoid
  • the specific size of the gas diffusion layer 1 is: : Length 50mm, width 50mm, thickness 1.5mm.
  • the cross-sectional area of the grooved texture 2 along the flow direction first expands and then contracts with the flow direction.
  • the cross-sectional area at both ends of the groove texture 2 along the flow direction is gradual, and the cross-sectional area in the middle of the groove texture 2 along the flow direction remains unchanged; the cross-sectional area in the middle of the groove texture 2 along the flow direction The area is 1.5 to 3 times the smallest cross-sectional area at both ends.
  • the inlet end of the groove texture 2 along the flow direction is a gradually expanding section, and the gradually expanding section is 1/3 of the total length of the groove texture 2 along the flow direction.
  • the outlet end of the groove texture 2 in the flow direction is a tapered section, and the tapered section is 1/3 of the total length of the groove texture 2 along the flow direction, and the middle 1/3 length of the groove texture 2
  • the cross-sectional area remains the same.
  • the cross-sectional area in the middle of the groove texture 2 along the flow direction is twice the smallest cross-sectional area at both ends.
  • Several groove textures 2 account for 34.4% of the surface area of the entire GDL base layer.
  • the groove structure on the surface of the gas diffusion layer increases the surface area, which can better eliminate the flooding phenomenon and enhance the supply of reactants.
  • the groove texture 2 is processed on the surface of the base layer of the gas diffusion layer by the method of laser processing and forming, and the laser parameters corresponding to the laser processing are selected: the laser power is 50W, the speed is 800mm/s, the repetition frequency is 1MHz, and the number of scans is 1MHz. 5 times; ultrasonic cleaning was used for 15 minutes to remove surface impurities.
  • FIG. 6 is a comparison diagram of the drag reduction rate of the gas diffusion layers with different cross-sectional shapes of the present invention and the prior art.
  • the drag reduction rate is calculated by the following formula:
  • P m (Pa) is the inventive gas diffusion pressure drop and P c (Pa) is the conventional gas diffusion pressure drop.
  • the x-axis is the time step
  • the Y-axis is the drag reduction rate.
  • the squares, circles and triangular curves in the figure represent the drag reduction rates of the gas diffusion layers with semicircular, trapezoidal and rectangular cross-sections, respectively. It can be seen that the gas diffusion layers of the three cross-sectional shapes have a larger drag reduction rate.
  • the gas diffusion layer with a trapezoidal cross-sectional shape has a larger drag reduction rate than other shapes of the gas diffusion layer, indicating a better drag reduction effect.
  • the square and inverted triangular curve in the figure represent the drag reduction rate of the gas diffusion layer with trapezoidal and graded trapezoidal cross-sections, respectively. It can be seen from this that the gas diffusion layer with a gradient-trapezoidal cross-sectional shape has a larger drag reduction rate than the gas diffusion layer with a trapezoidal cross-section and no gradient, indicating a better drag reduction effect.
  • a plurality of micro-pit textures 5 are evenly distributed on the surface of the gas diffusion layer 1 near the bipolar plate to prevent the clogging of the reaction water.
  • the material of the gas diffusion layer 1 is carbon paper, and the micro-pit texture 5 is processed by ultra-fast laser, and then the edge of the micro-pit texture 5 has an outwardly inclined chamfer through laser micro-processing to improve the micro-pit texture. 5 has water storage capacity.
  • the fuel cell reaction water can be more easily gathered at the micro-dimple texture 5, and the reaction gas can pass through the unprocessed surface area, thereby improving the water resistance of the bulk diffusion layer and preventing the occurrence of "" Water flooding phenomenon, improve the working performance and stability of the fuel cell.
  • the actual working area of the gas diffusion layer 1 is increased, which is beneficial to increase the concentration of oxidant in the system, improve the reaction efficiency of the fuel cell, and improve its working performance.
  • the gas diffusion layer is a gas diffusion layer of a proton exchange membrane fuel cell PEMFC, and its material is carbon fiber.
  • the ratio of several of the micro-pit textures 5 to the total surface area of the gas diffusion layer 1 is 10%-45%.
  • the method for processing the gas diffusion layer structure of the fuel cell according to the present invention includes the following steps: processing the surface of the gas diffusion layer 1 near the bipolar plate for multiple times at the same point and spacing by means of a laser to obtain a texture 5 with uniformly distributed micro-pits. As shown in FIG.
  • At least 4 action points are selected around any micro-pit texture 5 for laser micro-machining, and the laser is inclined with the machined surface of the gas diffusion layer 1 by an angle of ⁇ , so that the micro-pit texture 5 is
  • the edge of texture 5 produces an outwardly inclined chamfer, which can improve the water resistance of the gas diffusion layer and prevent the "water-flooding" phenomenon of the fuel cell; ultrasonic cleaning, glow cleaning and sputtering cleaning are used to sequentially clean the gas after laser microprocessing.
  • the diffusion layer 1 is deburred.
  • the raised parts around the micro-pit texture 5 are essentially the burrs generated by the laser-processed micro-pit texture 5 on the periphery, and the peripheral area with burrs is defined as the laser micro-machining area 4, and these burr points are used in at least uniformly distributed areas.
  • the four action points 3 are laser micro-machined to produce chamfers. This processing method can reduce the workload of deburring in the later stage.
  • the laser parameters for processing the micro-pit texture 5 are laser power of 0.1W-50W, repetition frequency of 0-100kHz, and pulse width of 0-100ns.
  • the laser parameters used in the laser micromachining are laser power 0.1W-5W, repetition frequency 0-500kHz, and pulse width 0-10ps.
  • the invention improves the microstructure of the fuel cell cathode gas diffusion layer on the side surface of the bipolar plate, uses an ultrafast laser to process evenly distributed micro-pit texture 5, and then uses laser micro-processing to protrude around the micro-pit Part of the four action points are selected for reprocessing to obtain a micro-pit texture 5 with a certain angle around it, which can improve the water resistance of the gas diffusion layer, prevent the "water flooding” phenomenon of the fuel cell, and improve the performance of the fuel cell.
  • the gas diffusion layer of the fuel cell has the advantages of microstructure processing and high processing precision; it can be directly processed on the basis of existing products, and the method is simple; it is easy to realize, no need to redesign the bipolar plate structure, and the operation is simple and convenient , high stability;
  • the gas diffusion layer 1 is made of carbon paper, with a length of 40 mm, a width of 20 mm, and a thickness of 0.3 mm.
  • the 4 action points 3 are 1 ⁇ m away from the boundary of the micro-pit, and the interval between two adjacent points is 36.7 ⁇ m; the deburring treatment methods used are: ultrasonic cleaning, sputtering cleaning, and glow cleaning for 1 min each.
  • the micro-pit texture 5 is processed by ultrafast laser on the surface of the fuel cell cathode gas diffusion layer on the side of the bipolar plate, and at least 4 action points are selected around any micro-pit texture 5 for laser
  • the laser is inclined at an angle of ⁇ to the processed surface of the gas diffusion layer 1 , so that the edge of the micropit texture 5 produces an outwardly inclined chamfer.
  • the specific parameters of the ultrafast laser are: a pulse width of 10ps, a power of 5W, and a repetition rate of 1kHz; the laser parameters of the laser micromachining are: a power of 0.1W, a repetition rate of 1kHz, and a pulse width of 5ps.
  • FIG. 10 is a comparison diagram of droplet flow behavior on the embodiment 4 of the present invention and a conventional gas diffusion layer.
  • the first row and the second row are the droplet flow behaviors of the conventional gas diffusion layer and the gas diffusion layer of Example 4 of the present invention, respectively.
  • the first to fourth columns are the droplet flow behavior at each time step, respectively. It can be seen from this that after 1.0 ms, the fourth embodiment of the present invention can greatly speed up the flow rate of droplets and greatly reduce the probability of "flooding". At the same time, the invention greatly reduces the area of the droplet contacting the bipolar plate, and reduces the anti-corrosion requirement of the bipolar plate.
  • FIG. 11 is a comparison diagram of polarization curves of Example 1 and Example 3 of the present invention and a conventional gas diffusion layer. It can be seen from the figure that Example 1 and Example 3 of the present invention are obtained under the same voltage as the conventional gas diffusion layer. The current density is higher, it can be seen that the fuel cell gas diffusion layer of the present invention is indeed effective for improving the performance of the fuel cell.
  • FIG. 12 is a comparison chart of the pressure drop between Example 1, Example 3 and the traditional gas diffusion layer. It can be seen from the figure that the pressure drop of the two microstructure gas diffusion layers of the present invention is higher than that of the traditional gas diffusion layer. , which makes the droplets more easily deformed, and it is not easy to form larger droplets to block the flow channel, which is conducive to drainage, so that the flooding phenomenon can be effectively suppressed.
  • FIG. 13 is a graph showing the drag reduction ratio between the present invention and the conventional gas diffusion layer.
  • the drag reduction rate is calculated by the following formula:
  • P m (Pa) is the gas diffusion pressure drop of the present invention
  • P c (Pa) is the conventional gas diffusion pressure drop.
  • the x-axis is the time step
  • the Y-axis is the drag reduction rate. It can be seen from the above that the drag reduction rate of the gas diffusion layer in Examples 1 and 3 of the present invention is relatively large, which shows that they can greatly reduce the flow resistance of droplets, thereby effectively removing water and improving the performance of the fuel cell.

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Abstract

本发明提供了一种燃料电池气体扩散层结构及其加工方法，气体扩散层为靠近双极板一侧的基底层，所述气体扩散层表面设有若干微织构，用于消除液体反应产物水淹现象。所述微织构为沟槽织构，所述气体扩散层表面设有若干相互交错连通的沟槽织构。若干相互交错连通的沟槽织构中沿流向的所述沟槽织构的横截面面积随流向先渐扩再后渐缩。沿流向的所述沟槽织构两端的横截面面积渐变，沿流向的所述沟槽织构中间的横截面面积保持不变。本发明微织构可使液态水离开阴极，消除电极水淹现象允许适量的水润湿气流，保持膜电极的湿润。

Description

一种燃料电池气体扩散层结构及其加工方法 技术领域
本发明涉及燃料电池技术领域，特别涉及一种燃料电池气体扩散层结构及其加工方法。
背景技术
近几十年，以煤炭、石油为主的传统能源被大量使用，造成严重的环境污染和自然资源的日益枯竭。因此我们急切渴望一种高效节能，具有低污染、低排放的清洁新能源。随着现代技术的日益成熟，人们把研究重心和精力投入到对燃料电池的研究，燃料电池作为一种能量转换装置具有很高的转换效率，被誉为未来理想的电能来源。质子交换膜燃料电池是燃料电池中最常见、应用最多的类型，以工作温度低、功率密度高、启动快、动态响应快等优点，近年来备受关注。
气体扩散层基底材料一般为碳纤维。该材料有利于改善电极的性能，需满足以下要求，包括均匀的多孔质结构、透气性好、导电能力强、结构紧密且表面平整、亲水和疏水性平衡、热稳定行好。这对气体扩散层的制备工艺即传统的热压法提出更大挑战。随着激光精密加工技术越来越获得市场上的认可，利用激光加工技术应用于气体扩散层表面加工，具有精度准、热效应好，易实现的优势，基本可取代传统的热压制备工艺。
气体扩散层位于催化剂层和双极板之间，是PEM燃料电池最为重要的零部件之一。在PEM燃料电池中，催化剂层、气体扩散层和膜电极夹在流场板之间，气体扩散层是膜电极最外层，为电极和双极板提供电接触，将反应物平均分配到催化剂层。气体扩散层有助于在PEM燃料电池中进行水管理，因为气体扩散层可以保留适量的水润湿膜电极，另外气体扩散层有助于生成物水的离开阴极，消除电极水淹现象。
燃料电池在运行过程中，阴极表面会持续不断地生成水，在高功率情况下，生成水的速率越来越快，若生成物水无法及时排出，将会引起水淹现象。导致气体通道堵塞，减少生成物的输送量，降低电池的性能。
现阶段有很多专利考虑到气体扩散层水淹现象。从材料角度：中国专利公开了一种具有疏水性的燃料电池气体扩散层的制备方法提出将基底层材料进行疏水处理，结合配制的微孔层浆料进行热处理，得到具有疏水性的燃料电池气体扩散层。从结构角度：中国专利公开了通过利用掺杂金刚石在气体扩散层表面形成孔隙不易形成水淹，设计一种孔隙依次扩大的方法，使液态水在孔隙中无法形成水膜，提高电池的稳定性。以上专利有助于改善燃料电池气体扩散层水淹现象，但加工工艺过于繁琐，耗时较长，不利于大规模商业化推广。
发明内容
针对现有技术中存在的不足，本发明提供了一种燃料电池气体扩散层结构及其加工方法，通过在气体扩散层基底层表面加工沟槽织构，有助于促进水离开阴极以帮助消除电极水淹现象，同时仅允许适量的水接触膜电极来保持膜的湿润。本发明采用激光加工的方法，该方法易于实现，使用寿命长，工作状态稳定，无需改变气体扩散层材料，从改进结构的角度出发，开发了一种具有高效防“水淹”性能的燃料电池气体扩散层。
本发明是通过以下技术手段实现上述技术目的的。
一种燃料电池气体扩散层结构，气体扩散层为靠近双极板一侧的基底层，所述气体扩散层表面设有若干微织构，用于消除液体反应产物水淹现象。
进一步，所述微织构为沟槽织构，所述气体扩散层表面设有若干相互交错连通的沟槽织构。
进一步，所述沟槽织构的宽度D＝50-200μm，所述沟槽织构的深度H＝10-30μm，所述沟槽织构的间距S＝200-700μm。
进一步，若干所述沟槽织构的面积占所述气体扩散层表面积的20％-50％。
进一步，所述沟槽织构的横截面为长方形、梯形或圆弧形。
进一步，当所述沟槽织构的横截面为长方形或圆弧形时，任一所述沟槽织构边缘设有向外倾斜的倒角，用于提升气体扩散层的耐水性能。
进一步，外倾斜的所述倒角θ＝10°-30°。
进一步，若干相互交错连通的沟槽织构中沿流向的所述沟槽织构的横截面面积随流向先渐扩再后渐缩。
进一步，沿流向的所述沟槽织构两端的横截面面积渐变，沿流向的所述沟槽织构中间的横截面面积保持不变；所述沟槽织构中间的横截面面积为两端的最小横截面面积的1.5～3倍。
进一步，所述微织构为微凹坑织构，所述气体扩散层表面均布若干微凹坑织构。
进一步，所述微凹坑织构为球冠，所述微凹坑织构球径D＝50-300μm，所述微凹坑织构深度H＝3-100μm。
进一步，所述微凹坑织构等距分布在气体扩散层表面，相邻所述微凹坑织构之间的中心距S＝150-1000μm。
进一步，若干所述微凹坑织构占所述气体扩散层表面的总面积之比为10％-45％。
进一步，任一所述微凹坑织构的边缘设有向外倾斜的倒角，用于提升气体扩散层的耐水性能；外倾斜的所述倒角θ＝5°-20°。
一种燃料电池气体扩散层结构的加工方法，包括如下步骤：
通过超快激光在气体扩散层表面加工相互交错连通的沟槽织构；
利用超声清洗去除气体扩散层表面残留的杂质。
进一步，所述超快激光的脉宽≤10ps，所述超快激光的加工速度0-2000mm/s，所述超快激光的激光功率为0-100W，所述超快激光的重复频率0-1MHz，所述超快激光的扫描次数1-20次。
一种燃料电池气体扩散层结构的加工方法，包括如下步骤：
通过激光对气体扩散层靠近双极板一侧表面进行同点间隔多次加工，得到具有均布微凹坑织构的气体扩散层；
在任一微凹坑织构周围选取至少4个作用点进行激光微加工，所述激光与气体扩散层的加工表面倾斜θ角，使得微凹坑织构边缘产生向外倾斜的倒角。
进一步，加工所述微凹坑织构的激光参数为：激光功率0.1W-50W，重复频率为0-100kHz，脉宽0-100ns；所述激光微加工的激光参数为：激光功率0.1W-5W，重复频率为0-500kHz,脉宽0-10ps。
进一步，所述作用点距微凹坑织构边界的最小距离为1-40μm，相邻所述作用点之间的间隔为30-250μm。
进一步，还包括去毛刺处理，利用超声清洗、辉光清洗和溅射清洗依次对激光微加工后的气体扩散层进行去毛刺处理。
本发明的有益效果在于：
1.本发明所述的燃料电池气体扩散层结构，通过表面加工沟槽织构，可以使反应后的水聚集在沟槽中，有助于促进生成物水离开阴极以帮助消除阴极水淹现象，同时仅允许适量的水接触膜电极来保持膜的湿润。
2.本发明所述的燃料电池气体扩散层结构，沟槽织构可以增加气体扩散层的比表面积，有助于反应物气流润湿，提高反应的稳定性，还有助于氧化剂气体在通道内流通均匀，增强气体扩散层到膜电极的氧供应。
3.本发明所述的燃料电池气体扩散层结构，经过微凹坑织构改造的燃料电池气体扩散层，其耐水性及耐久性相对于传统气体扩散层均有所提升，具有较长的使用寿命。
4.本发明所述的燃料电池气体扩散层结构的加工方法，仅需在气体扩散层基底层表面开设有序地沟槽结构。
5.本发明所述的燃料电池气体扩散层结构，通过沿流向的所述沟槽织构的横截面面积随流向先渐扩再后渐缩，有助于降低进口处生成物水的水量，减少进口处局部“水淹”现象，有助于增加生成物水在气体扩散层表面的分布均匀性，更有利于反应物气流润湿。
6.本发明所述的燃料电池气体扩散层结构，经过激光微加工四周存在一定角度的微凹坑织构，能够使燃料电池阴极反应水更易在气体扩散层靠双极板一侧表面微凹坑处聚集，提升了燃料电池的反应水耐受性能。
附图说明
图1为本发明所述的燃料电池气体扩散层结构的示意图。
图2为实施例1圆弧形的沟槽织构局部放大图。
图3为实施例2长方形的沟槽织构局部放大图。
图4为实施例3梯形的沟槽织构局部放大图。
图5为实施例3渐变梯形结构的沟槽织构局部放大俯视图。
图6为实施例中不同截面形状气体扩散层与现有技术的减阻率比较图。
图7为本发明所述的燃料电池气体扩散层结构的实施例4示意图。
图8为实施例4的微凹坑织构截面图。
图9为本发明所述的作用点的示意图。
图10为实施例4与传统气体扩散层上液滴流动行为比较图。
图11为实施例1和实施例3与传统气体扩散层极化曲线对比图。
图12为实施例1和实施例3与传统气体扩散层的压降比较图。
图13为实施例1和实施例3的减阻率图。
图中：
1-气体扩散层；2-沟槽织构；3-作用点；4-激光微加工作用区域；5-微凹坑织构。
具体实施方式
下面结合附图以及具体实施例对本发明作进一步的说明，但本发明的保护范围并不限于此。
实施例1：
如图1和2所示，本发明所述的燃料电池气体扩散层结构，气体扩散层1为靠近双极板一侧的基底层，所述气体扩散层1表面设有若干相互交错连通的沟槽织构2，若干相互交错连通的沟槽织构2将气体扩散层1表面划分成网格状，用于消除电极水淹现象。若干相互交错连通的沟槽织构2包括与流向平行或接近平行的沟槽织构、与流向垂直的沟槽织构。实施例1中与流向平行的沟槽织构和与流向垂直的沟槽织构的横截面面积相同。气体扩散层1的基底层材料为炭黑纸，具体尺寸为：长20mm，宽20mm，厚0.5mm。沟槽织构2截面形状为圆弧；沟槽织构2加工具体尺寸为：沟槽织构2宽度D＝200μm，沟槽织构2深度H＝10μm，相邻横向沟槽织构2间距S＝700μm。沟槽织构2边缘一周存在的角度θ＝30°。实施例1中若 干沟槽织构2纵横交错将气体扩散层1表面划分成方形网格，也可以是菱形或者平行四边形或者多边形。若干沟槽织构2占整个气体扩散层基底层表面积的42.39％。气体扩散层基底层表面具有有序地沟槽结构，该结构使液态水离开阴极，消除水淹现象，部分水可以聚集在沟槽中来保持膜的湿润；该结构可以增加比表面积，增强气体扩散层到膜电极的氧供应，提高反应的稳定性，提升燃料电池的性能。
本实施例1通过激光加工成形的方法在气体扩散层基底层表面加工沟槽织构2，选用激光加工对应的激光参数：激光功率为50W，速度为1000mm/s，重复频率为0.5MHz，扫描次数10次；采用超声清洗15min去除表面杂质。
实施例2：
如图1和3所示，本发明所述的燃料电池气体扩散层结构，该气体扩散层1基底层材料为碳纤维，沟槽织构2截面形状为长方形；具体尺寸为：长30mm，宽30mm，厚1mm。沟槽织构2具体尺寸为：沟槽织构2深度H＝20μm，相邻沟槽织构2间距S＝500μm，与流向平行的沟槽织构的横截面面积大于与流向垂直的沟槽织构的横截面面积，与流向垂直的沟槽织构的宽度D＝100μm，与流向平行的沟槽织构的宽度为1.5D。该沟槽织构2占整个气体扩散层基底层表面积的47.98％。该气体扩散层表面沟槽结构增加表面积，可以更好地消除水淹现象，增强反应物供应。
本实施例2通过激光加工成形的方法在气体扩散层基底层表面加工沟槽结构，选用激光加工对应的激光参数：激光功率为50W，速度为800mm/s，重复频率为1MHz，扫描次数5次；采用超声清洗15min去除表面杂质。
实施例3：
如图1、4和5所示，本发明所述的燃料电池气体扩散层结构，该气体扩散层1基底层材料为碳纤维，沟槽织构2截面形状为梯形；气体扩散层1具体尺寸为：长50mm，宽50mm，厚1.5mm。梯形沟槽织构2具体尺寸为：梯形沟槽织构2宽度D 上底＝50μm、D 下底＝30μm，沟槽织构2深度H＝30μm，相邻沟槽织构2间距S＝250μm。沿流向的所述沟槽织构2的横截面面积随流向先渐扩再后渐缩。沿流向的所述沟槽织构2两端的横截面面积渐变，沿流向的所述沟槽织构2中间的横截面面积保持不变；沿流向的所述沟槽织构2中间的横截面面积为两端最小的横截面面积的1.5～3倍。如图5所示，实施例3中沿流向的所述沟槽织构2进口端为渐扩段，所述渐扩段为沿流向的所述沟槽织构2总长的1/3，沿流向的所述沟槽织构2出口端为渐缩段，所述渐缩段为沿流向的所述沟槽织构2总长的1/3，中间1/3长度的所述沟槽织构2横截面面积保持不变。沿流向的所述沟槽织构2中间的横截面面积为两端的最小横截面面积的2倍。若干沟槽织构2占整个气体扩散层基底层表面积的34.4％。该气体扩散层表面 沟槽结构增加表面积，可以更好地消除水淹现象，增强反应物供应。
本实施例3通过激光加工成形的方法在气体扩散层基底层表面加工沟槽织构2，选用激光加工对应的激光参数：激光功率为50W，速度为800mm/s，重复频率为1MHz，扫描次数5次；采用超声清洗15min去除表面杂质。
图6为本发明不同截面形状气体扩散层与现有技术的减阻率比较图。减阻率通过如下公式计算得到：
Figure PCTCN2021075284-appb-000001
P m(Pa)是本发明气体扩散层压降，P c(Pa)是传统气体扩散层压降。图中x轴为时间步，Y轴为减阻率。图中方块、圆和三角曲线分别代表截面为半圆形、梯形和长方形的气体扩散层减阻率。从中可以看出，三种截面形状的气体扩散层均有较大的减阻率。截面形状为梯形的气体扩散层相比于其他形状的气体扩散层有较大的减阻率，说明有较好的减阻效果。图中方块和倒三角曲线分别代表截面为梯形和渐变梯形的气体扩散层减阻率。从中可以看出，截面形状为渐变梯形的气体扩散层相比于截面为梯形且不渐变的气体扩散层有较大的减阻率，说明有较好的减阻效果。
实施例4
如图7和图8所示，本发明所述的燃料电池气体扩散层结构，所述气体扩散层1靠近双极板一侧表面均布若干微凹坑织构5，用于防止反应水堵塞气体扩散层间隙。气体扩散层1的材料为碳纸，经过超快激光加工的微凹坑织构5，再经过激光微加工使得微凹坑织构5边缘产生向外倾斜的倒角，提高微凹坑织构5具有储水能力。经过微凹坑织构5能够使燃料电池反应水更易聚集在微凹坑织构5处，反应气体可从未加工的表面区域通过，从而提升了体扩散层的耐水性能，防止燃料电池发生“水淹”现象，提升燃料电池的工作性能及稳定性。另外，在实际应用的过程中，由于微凹坑织构5的存在，气体扩散层1实际工作面积增加，有利于增加系统内氧化剂浓度，改善了燃料电池反应效率，提升其工作性能。
所述气体扩散层为质子交换膜燃料电池PEMFC的气体扩散层，其材料为碳纤维。所述气体扩散层1具体尺寸参数为：长40-60mm，宽20-50mm，厚0.3-1.1mm；所述微凹坑织构5为球冠，所述微凹坑织构5直径D＝50-300μm，所述微凹坑织构5深度H＝3-100μm。所述微凹坑织构5等距分布在气体扩散层1表面，相邻所述微凹坑织构5之间的中心距S＝150-1000μm。若干所述微凹坑织构5占所述气体扩散层1表面的总面积之比为10％-45％。任一所述微凹坑织构5的边缘设有向外倾斜的倒角，用于提升气体扩散层1的耐水性能。外倾斜的所述倒角θ＝5°-20°。
本发明所述的燃料电池气体扩散层结构的加工方法，包括如下步骤：通过激光对气体扩散层1靠近双极板一侧表面进行同点间隔多次加工，得到具有均布微凹坑织构5的气体扩散层；如图9所示，在任一微凹坑织构5周围选取至少4个作用点进行激光微加工，所述激光与气体扩散层1的加工表面倾斜θ角，使得微凹坑织构5边缘产生向外倾斜的倒角，能够提升气体扩散层的耐水性能，防止燃料电池发生“水淹”现象；利用超声清洗、辉光清洗和溅射清洗依次对激光微加工后的气体扩散层1进行去毛刺处理。微凹坑织构5周围凸起部分实质是激光加工微凹坑织构5在周边产生的毛刺，而具有毛刺的周边区域定义为激光微加工作用区域4，利用这些毛刺点在至少均布的四个作用点3进行激光微加工，产生倒角。这样加工方法可以减小后期去除毛刺的工作量。所述加工微凹坑织构5的激光参数为激光功率0.1W-50W，重复频率为0-100kHz，脉宽0-100ns。所述激光微加工所用的激光参数为激光功率0.1W-5W，重复频率为0-500kHz，脉宽0-10ps。
本发明对燃料电池阴极气体扩散层靠双极板侧表面进行微观结构性改进，利用超快激光加工出均匀分布的微凹坑织构5，再利用激光微加工，在微凹坑周围凸起部分选取四个作用点进行再加工，得到四周具有一定角度的微凹坑织构5，能够提升气体扩散层的耐水性能，防止燃料电池发生“水淹”现象，改善燃料电池的性能。
本发明所涉及的经过微观结构改造的燃料电池气体扩散层，其强度及耐久性相对于传统双极板流道均有所提升，具有较长的使用寿命；本发明所涉及的经过微观结构改造的燃料电池气体扩散层，其加工制造方法能进行微结构加工，加工精度高；可以直接在现有产品基础上进行加工，方法简便；易于实现，无需对双极板结构进行再设计，操作简便，稳定性高；
以质子交换膜燃料电池(PEMFC)的气体扩散层1为例，实施一下实例作具体说明：
如图7-9所示，所述气体扩散层1的材料为碳纸，长度为40mm，宽度为20mm，厚度为0.3mm。所述微凹坑织构5为球冠，微凹坑织构5的球径D＝50μm，深度H＝50μm；微凹坑织构5边缘一周存在的角度θ＝5°；激光微加工选取的4个作用点3距微凹坑边界1μm，相邻两点间隔36.7μm；所用去毛刺处理方法为：超声清洗、溅射清洗、辉光清洗各1min。本实施例4中通过超快激光在燃料电池阴极气体扩散层靠双极板一侧表面加工出的微凹坑织构5，在任一微凹坑织构5周围选取至少4个作用点进行激光微加工，所述激光与气体扩散层1的加工表面倾斜θ角，使得微凹坑织构5边缘产生向外倾斜的倒角。所述超快激光具体参数为：脉宽10ps，功率5W，重复频率为1kHz；所述激光微加工的激光参数为：功率0.1W，重复频率为1kHz，脉宽5ps。
图10为本发明实施例4与传统气体扩散层上液滴流动行为比较图。第一行和第二行分别为传统气体扩散层和本发明实施例4气体扩散层的液滴流动行为。第一列至第四列分别为各 个时间步的液滴流动行为。从中可以看出在1.0ms以后，本发明实施例4能够极大地加快液滴流动速度，大大降低出现“水淹”的概率。同时，本发明大大减小了液滴接触双极板的面积，降低了双极板的防腐要求。
图11为本发明实施例1、实施例3与传统气体扩散层的极化曲线对比图，从图可看出，本发明实施例1和实施例3比传统气体扩散层在同样电压下所获得的电流密度更高，由此可看出，本发明所述的燃料电池气体扩散层对于提高燃料电池性能确实是有效的。
图12为实施例1、实施例3与传统气体扩散层的压降对比图，从图中可以看出，本发明所述两种微结构气体扩散层的压降均要高于传统气体扩散层，这使得液滴更容易变形，不易形成较大的液滴从而堵塞流道，有利于排水，从而能够有效抑制水淹现象。
图13为本发明与传统气体扩散层减阻率图。减阻率通过如下公式计算得到：
Figure PCTCN2021075284-appb-000002
式中，P m(Pa)是本发明气体扩散层压降，P c(Pa)是传统气体扩散层压降。图中x轴为时间步，Y轴为减阻率。从中可以看出，本发明实施例1和实施例3气体扩散层减阻率较大，这说明其能够大大降低液滴流动阻力，从而有效去除水，提高燃料电池性能。
所述实施例为本发明的优选的实施方式，但本发明并不限于上述实施方式，在不背离本发明的实质内容的情况下，本领域技术人员能够做出的任何显而易见的改进、替换或变型均属于本发明的保护范围。

Claims (20)

  1. 一种燃料电池气体扩散层结构，气体扩散层(1)为靠近双极板一侧的基底层，其特征在于，所述气体扩散层(1)表面设有若干微织构，用于消除液体反应产物水淹现象。
  2. 根据权利要求1所述的燃料电池气体扩散层结构，其特征在于，所述微织构为沟槽织构(2)，所述气体扩散层(1)表面设有若干相互交错连通的沟槽织构(2)。
  3. 根据权利要求2所述的燃料电池气体扩散层结构，其特征在于，所述沟槽织构(2)的宽度D＝50-200μm，所述沟槽织构(2)的深度H＝10-30μm，所述沟槽织构(2)的间距S＝200-700μm。
  4. 根据权利要求2所述的燃料电池气体扩散层结构，其特征在于，若干所述沟槽织构(2)的面积占所述气体扩散层(1)表面积的20％-50％。
  5. 根据权利要求2所述的燃料电池气体扩散层结构，其特征在于，所述沟槽织构(2)的横截面为长方形、梯形或圆弧形。
  6. 根据权利要求5所述的燃料电池气体扩散层结构，其特征在于，当所述沟槽织构(2)的横截面为长方形或圆弧形时，任一所述沟槽织构(2)边缘设有向外倾斜的倒角，用于提升气体扩散层(1)的耐水性能。
  7. 根据权利要求6所述的燃料电池气体扩散层结构，其特征在于，外倾斜的所述倒角θ＝10°-30°。
  8. 根据权利要求1-7任一项所述的燃料电池气体扩散层结构，其特征在于，若干相互交错连通的沟槽织构(2)中沿流向的所述沟槽织构(2)的横截面面积随流向先渐扩再后渐缩。
  9. 根据权利要求8所述的燃料电池气体扩散层结构，其特征在于，沿流向的所述沟槽织构(2)两端的横截面面积渐变，沿流向的所述沟槽织构(2)中间的横截面面积保持不变；所述沟槽织构(2)中间的横截面面积为两端的最小横截面面积的1.5～3倍。
  10. 根据权利要求1所述的燃料电池气体扩散层结构，其特征在于，所述微织构为微凹坑织构(5)，所述气体扩散层(1)表面均布若干微凹坑织构(5)。
  11. 根据权利要求10所述的燃料电池气体扩散层结构，其特征在于，所述微凹坑织构(5)为球冠，所述微凹坑织构(5)球径D＝50-300μm，所述微凹坑织构(5)深度H＝3-100μm。
  12. 根据权利要求10所述的燃料电池气体扩散层结构，其特征在于，所述微凹坑织构(5)等距分布在气体扩散层(1)表面，相邻所述微凹坑织构(5)之间的中心距S＝150-1000μm。
  13. 根据权利要求10所述的燃料电池气体扩散层结构，其特征在于，若干所述微凹坑织构(5)占所述气体扩散层(1)表面的总面积之比为10％-45％。
  14. 根据权利要求10-13任一项所述的燃料电池气体扩散层结构，其特征在于，任一所述微凹坑织构(5)的边缘设有向外倾斜的倒角，用于提升气体扩散层(1)的耐水性能；外 倾斜的所述倒角θ＝5°-20°。
  15. 一种根据权利要求2-9任一项所述的燃料电池气体扩散层结构的加工方法，其特征在于，包括如下步骤：
    通过超快激光在气体扩散层(1)表面加工相互交错连通的沟槽织构(2)；
    利用超声清洗去除气体扩散层(1)表面残留的杂质。
  16. 根据权利要求15所述的燃料电池气体扩散层结构的加工方法，其特征在于，所述超快激光的脉宽≤10ps，所述超快激光的加工速度0-2000mm/s，所述超快激光的激光功率为0-100W，所述超快激光的重复频率0-1MHz，所述超快激光的扫描次数1-20次。
  17. 一种根据权利要求14所述的燃料电池气体扩散层结构的加工方法，其特征在于，包括如下步骤：
    通过激光对气体扩散层(1)靠近双极板一侧表面进行同点间隔多次加工，得到具有均布微凹坑织构(5)的气体扩散层；
    在任一微凹坑织构(5)周围选取至少4个作用点进行激光微加工，所述激光与气体扩散层(1)的加工表面倾斜θ角，使得微凹坑织构(5)边缘产生向外倾斜的倒角。
  18. 根据权利要求17所述的燃料电池气体扩散层结构的加工方法，其特征在于，加工所述微凹坑织构(5)的激光参数为：激光功率0.1W-50W，重复频率为0-100kHz，脉宽0-100ns；所述激光微加工的激光参数为：激光功率0.1W-5W，重复频率为0-500kHz,脉宽0-10ps。
  19. 根据权利要求17所述的燃料电池气体扩散层结构的加工方法，其特征在于，所述作用点距微凹坑织构(5)边界的最小距离为1-40μm，相邻所述作用点之间的间隔为30-250μm。
  20. 根据权利要求17所述的燃料电池气体扩散层结构的加工方法，其特征在于，还包括去毛刺处理，利用超声清洗、辉光清洗和溅射清洗依次对激光微加工后的气体扩散层(1)进行去毛刺处理。
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