A gas diffusion layer, its preparation method and application

Abstract

The application discloses a kind of gas diffusion layer and its preparation method and application, it is related to fuel cell technical field.The gas diffusion layer includes conductive substrate layer and hydrophobic filling layer, multiple channels are opened in conductive substrate layer and pass through its thickness, multiple channels include first channel and second channel different in aperture, and the pore wall surface of channel has hydrophilicity, hydrophobic filling layer is filled in channel and covers the surface of one side of conductive substrate layer, and hydrophobic filling layer has hydrophobicity, wherein, the inner wall surface of channel and the gap between hydrophobic filling layer filled in channel are formed.The present application utilizes the wettability gradient formed by hydrophilic pore wall and hydrophobic filling layer, combines interface gap and multi-level pore array structure, realizes the spatial complementation of liquid water directional discharge and reaction gas efficient permeation, can solve the performance attenuation problem caused by fuel cell cathode waterlogging under high current density, is conducive to improving water management capability and battery output performance.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, specifically to a gas diffusion layer, its preparation method, and its application. Background Technology

[0002] As a highly efficient energy conversion device, the performance of a proton exchange membrane fuel cell (PEMFC) largely depends on the quality of its key component, water management. Especially under high current density operating conditions, if the large amount of liquid water generated by the cathode reaction cannot be drained in time, flooding can easily occur. Once liquid water accumulates, it not only blocks the bipolar plate channels but also fills the microporous transport path between the gas diffusion layer (GDL) and the catalyst layer (CL), severely limiting the effective transport of oxygen (O2), leading to a continuous decrease in battery voltage and even irreversible performance damage.

[0003] In existing technologies, gas diffusion layers typically use carbon fiber paper or carbon cloth as a substrate and are modified by impregnation with hydrophobic agents such as polytetrafluoroethylene (PTFE) to improve drainage performance. However, this traditional homogeneous structure has significant limitations in practical applications. On the one hand, there is a constraint between hydrophobicity and gas permeability: simply increasing the PTFE content can enhance hydrophobicity, but it will fill the fiber gaps and reduce gas permeability; conversely, reducing the PTFE content leads to insufficient capillary drainage capacity. On the other hand, traditional GDLs have a relatively uniform pore size distribution and exhibit overall hydrophobic characteristics, lacking differentiated transport channel designs for liquid water and reactive gases, and also lacking the ability to regulate hydrophilic-hydrophobic wettability gradients. In environments where water and gas coexist, a single-pore structure is difficult to achieve water-gas separation and transport, often resulting in a contradiction between poor drainage and obstructed gas supply.

[0004] Therefore, how to overcome the limitations of traditional homogeneous structures and construct a new channel that can achieve water-gas separation and transmission by modifying the structure of the gas diffusion layer, so as to effectively prevent water flooding under high current density and at the same time ensure the appropriate wettability of the membrane, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention provides a gas diffusion layer, its preparation method, and its application, aiming to solve the problem of performance degradation caused by cathode flooding in existing fuel cells under high current density.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a gas diffusion layer, the gas diffusion layer comprising: A conductive substrate layer, wherein a plurality of channels penetrating its thickness are formed on the conductive substrate layer, the plurality of channels including a first channel and a second channel with different diameters, and the surface of the pore wall of the channels is hydrophilic. A hydrophobic filling layer, wherein the hydrophobic filling layer fills the pores and covers one side surface of the conductive substrate layer, and the hydrophobic filling layer is hydrophobic; A gap is formed between the inner wall surface of the pore and the hydrophobic filling layer that fills the pore.

[0007] In some embodiments, the first channel and the second channel are arranged alternately, and the diameter of the second channel is 1 / 3 to 1 / 2 of the diameter of the first channel.

[0008] In some embodiments, both the first and second channels are tapered orifices, and the cross-sectional dimension on the side facing the gas flow channel is larger than the cross-sectional dimension on the side near the membrane electrode.

[0009] In some embodiments, the first channel has a cross-sectional dimension of 120-190 μm on the side facing the gas flow channel and a cross-sectional dimension of 60-120 μm on the side near the membrane electrode.

[0010] In some embodiments, the cross-sectional dimension of the second channel is 50-80 μm on the side facing the gas flow channel and 25-40 μm on the side near the membrane electrode.

[0011] In some embodiments, the width of the gap is 1-5 μm.

[0012] In some embodiments, the water contact angle of the pore wall surface is less than 50°, and the water contact angle of the hydrophobic filling layer is greater than 140°.

[0013] In some embodiments, the conductive substrate layer comprises multi-walled carbon nanotubes and polytetrafluoroethylene.

[0014] In some embodiments, the hydrophobic filler layer comprises conductive carbon black and polytetrafluoroethylene.

[0015] Secondly, the present invention provides a method for preparing the gas diffusion layer, comprising the following steps: Provide a conductive composite film as a conductive substrate layer; Multiple channels are formed on the conductive substrate layer by using a laser, and the surface of the channel wall is made hydrophilic. The multiple channels include a first channel and a second channel with different diameters. A hydrophobic slurry is filled into the pores to form a hydrophobic filling layer; The filled conductive substrate is heat-treated to form a gap between the hydrophobic filling layer and the pore surface.

[0016] Thirdly, the present invention provides a membrane electrode assembly, the membrane electrode assembly including the gas diffusion layer.

[0017] Fourthly, the present invention provides a fuel cell, the fuel cell including the membrane electrode assembly described above.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention achieves functional separation of water-gas transport channels by constructing a wettability gradient between the hydrophilic pore walls and the hydrophobic filling layer, combined with interfacial gaps. Liquid water is directionally discharged along the hydrophilic pore walls, while reactant gases are transported through the hydrophobic filling layer, effectively solving the flooding problem caused by water-gas competition for channels in traditional homogeneous structures. Experimental data show that the breakthrough pressure of liquid water is reduced by approximately 85% compared to traditional GDL, significantly improving water management capabilities.

[0019] 2. A multi-level pore array design, employing alternating first (large) and second (small) channels, achieves spatial complementarity between drainage and gas supply channels. Large pores provide a low-resistance drainage path, while small pores ensure gas permeation, optimizing gas distribution on the electrode surface. This structure reduces the cathode charge transfer resistance from 29.0 mΩ to 21.0 mΩ and the mass transfer resistance from 25.9 mΩ to 19.5 mΩ, improving electrode reaction kinetics.

[0020] 3. Thanks to the synergistic optimization of water vapor transport efficiency, the gas diffusion layer of this application can significantly improve the output performance of fuel cells. Under a relative humidity of 50%, the peak power density reaches 1.18 W / cm², which is about 24% higher than that of conventional GDL and superior to single-pore design, confirming the performance advantages of multi-level pore arrays at high current densities.

[0021] 4. The preparation method boasts high process integration, utilizing laser thermal effects to further achieve pore formation and hydrophilication of the pore walls. Heat treatment induces slurry shrinkage, naturally forming interfacial gaps without requiring additional complex processes. The conical pore structure effectively prevents filler detachment, ensuring the structural stability and long-term operational reliability of the gas diffusion layer. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0023] This invention provides a gas diffusion layer, its preparation method, and its application, aiming to solve the problem of performance degradation caused by cathode flooding in existing fuel cells under high current density.

[0024] In a first aspect, the present invention provides a gas diffusion layer, wherein, according to an embodiment of the present invention, the gas diffusion layer comprises: A conductive substrate layer, wherein a plurality of channels penetrating its thickness are formed on the conductive substrate layer, the plurality of channels including a first channel and a second channel with different diameters, and the surface of the pore wall of the channels is hydrophilic. A hydrophobic filling layer, wherein the hydrophobic filling layer fills the pores and covers one side surface of the conductive substrate layer, and the hydrophobic filling layer is hydrophobic; A gap is formed between the inner wall surface of the pore and the hydrophobic filling layer that fills the pore.

[0025] The gas diffusion layer provided by this invention achieves functional separation of water-gas transport channels by constructing a multi-level pore array with hydrophilic pore walls and a hydrophobic filling layer, forming an interfacial gap between them. The wettability gradient formed by the hydrophilic pore walls and the hydrophobic filling layer drives liquid water to be directionally discharged along the pore walls and interfacial gap, while the reactant gas is smoothly transported through the internal pores of the hydrophobic filling layer, effectively solving the flooding problem caused by water-gas competition for channels in traditional homogeneous structures. The interfacial gap, as an additional low-resistance drainage channel, works in conjunction with the spatial distribution of the multi-level pore array to reduce the liquid water breakthrough pressure and cathode mass transfer resistance, thereby improving the peak power density and operational stability of the fuel cell at high current densities.

[0026] In some embodiments of the present invention, the first and second channels are arranged alternately, and the diameter of the second channel is 1 / 3 to 1 / 2 of the diameter of the first channel. This alternating arrangement of the first and second channels, with the second channel diameter being 1 / 3 to 1 / 2 of the first channel diameter, achieves spatial complementarity between the drainage channel and the gas permeation path. The alternating distribution of the first channel (large pore) and the second channel (small pore) creates a local pressure gradient and capillary force difference, prompting the large pores to prioritize drainage while the small pores maintain gas flow, thereby reducing the overall water breakthrough pressure and preventing flooding. Furthermore, this size ratio ensures that the second channel, while guaranteeing sufficient gas permeability, possesses appropriate capillary force, avoiding the problems of excessively small pores leading to a surge in mass transfer resistance or excessively large pores reducing the differentiation of drainage function. Therefore, this structure overcomes the constraints of drainage and gas supply in single-pore designs, improving the battery's water and gas management capabilities under high current density.

[0027] It should be noted that the present invention does not impose any particular limitation on the specific alternating arrangement of the first and second channels, and those skilled in the art can flexibly choose according to actual water and air management needs. As an exemplary embodiment, in some embodiments of the present invention, the first and second channels are arranged in a checkerboard pattern, with a center-to-center distance of 200 μm between adjacent channels.

[0028] In some embodiments of the present invention, both the first and second channels are tapered holes, and the cross-sectional dimension on the side near the gas flow channel is larger than the cross-sectional dimension on the side near the membrane electrode. Utilizing a top-wide, bottom-narrow geometry, the hydrophobic filling layer filled within the channels is mechanically secured. This structure effectively prevents the filled hydrophobic filling layer columns from sliding out towards the membrane electrode side under gravity or operating pressure, avoiding the risk of catalyst layer contamination, while simultaneously ensuring the structural stability of the gas diffusion layer during long-term operation.

[0029] In some embodiments of the present invention, the cross-sectional dimension of the first channel is 120-190 μm on the side facing the gas flow channel and 60-120 μm on the side near the membrane electrode. By controlling the dimension of the first channel on the side facing the gas flow channel (corresponding to the inlet dimension) within the range of 120-190 μm and the dimension on the side near the membrane electrode (corresponding to the outlet dimension) within the range of 60-120 μm, a drainage main channel with a suitable taper can be formed. The larger inlet dimension ensures sufficient liquid water collection area, effectively reducing water breakthrough pressure; the outlet dimension matches the membrane electrode interface, avoiding poor drainage due to the channel being too small or a decrease in structural strength due to the channel being too large. This size range forms a significant pore size gradient with the second channel, guiding liquid water to preferentially enter the larger pores for discharge, thereby achieving efficient directional drainage.

[0030] It should be noted that the "cross-sectional dimension" mentioned in this application refers to the geometric measurement of a cross-section perpendicular to the extension direction of the channel. Specifically, when the cross-section of the channel is circular, the cross-sectional dimension is the diameter; when the cross-section of the channel is non-circular, such as elliptical or rectangular, the cross-sectional dimension may refer to its equivalent diameter, or it may refer to the major axis and minor axis dimensions of the cross-section. The numerical range defined in this embodiment is measured based on the above definition to ensure the consistency of the channel's function.

[0031] In some embodiments of the present invention, the cross-sectional dimension of the second channel is 50-80 μm on the side facing the gas flow channel and 25-40 μm on the side near the membrane electrode. The inlet size of the second channel is 50-80 μm and the outlet size is 25-40 μm, which is 1 / 3-1 / 2 of the size of the first channel. This size allows the pore to have suitable capillary force, which, according to the Young-Laplace equation, can effectively prevent liquid water from entering while ensuring the smooth passage of the reactant gas. Together with the first channel, a multi-level pore array is constructed to achieve a spatial functional division of drainage and gas supply, avoiding the contradiction between drainage and gas supply in a single-aperture design.

[0032] In some embodiments of the present invention, the width of the gap is 1-5 μm. Controlling the gap width within the above range can synergize with the wettability gradient of the hydrophilic pore wall and the hydrophobic filling layer to directionally guide the separation and transport of water and air.

[0033] In some embodiments of the present invention, the water contact angle of the pore wall surface is less than 50°, and the water contact angle of the hydrophobic filling layer is greater than 140°. A water contact angle of less than 50° on the pore wall surface imparts strong hydrophilicity, driving liquid water to spread and drain rapidly along the pore wall and interfacial gaps; a water contact angle of greater than 140° on the hydrophobic filling layer presents a superhydrophobic state, effectively blocking liquid water from intruding into the gas transport path.

[0034] In this application, a contact angle measuring instrument was used to measure the static water contact angle of the laser-modified hole wall surface and the cured hydrophobic filling layer surface to characterize their wettability differences.

[0035] In some embodiments of the present invention, the conductive substrate layer comprises multi-walled carbon nanotubes (MWCNTs) and polytetrafluoroethylene (PTFE). MWCNTs can construct efficient electron transport networks, endowing the substrate layer with excellent conductivity; PTFE, as a binder, can enhance the mechanical strength and film-forming properties of the film. This composite material system not only ensures the structural stability of the substrate but also utilizes the characteristic of PTFE to introduce polar groups through laser thermal decomposition, combined with the absorption of laser energy by MWCNTs, to synergistically achieve a hydrophilic transformation of the pore wall surface, which is beneficial for constructing stable water-gas separation and transport channels.

[0036] In some embodiments of the present invention, the hydrophobic filling layer comprises conductive carbon black (CB) and polytetrafluoroethylene (PTFE). Conductive carbon black can construct an efficient electron conduction network, ensuring the timely collection and transport of reaction electrons; PTFE not only acts as a binder to maintain structural integrity but also imparts superhydrophobic properties to the hydrophobic filling layer, preventing liquid water from obstructing the gas transport path. Furthermore, this material system exhibits shrinkage behavior during heat treatment, which, in synergy with the laser-modified rigid pore walls, promotes the natural formation of interfacial gaps, thereby enhancing water-gas separation while ensuring efficient gas permeation.

[0037] Secondly, the present invention provides a method for preparing the aforementioned gas diffusion layer. According to an embodiment of this application, the preparation method includes the following steps: S100: Provides a conductive composite film as a conductive substrate layer.

[0038] This step aims to obtain a substrate layer with excellent conductivity and mechanical support. Specifically, multi-walled carbon nanotubes (MWCNTs) and polytetrafluoroethylene (PTFE) are used as raw materials to prepare MWCNT / PTFE nanocomposite films via vacuum filtration. During this process, the ratio of MWCNTs to PTFE is optimized. MWCNTs are used to construct an efficient electron transport network, while PTFE provides bonding and reinforcement, resulting in a substrate layer with both good conductivity and mechanical strength. This provides a stable structural support for subsequent laser perforation and filling processes.

[0039] S200: Multiple channels are formed on the conductive substrate layer using a laser, and the surface of the channel walls is made hydrophilic. The multiple channels include a first channel and a second channel with different diameters.

[0040] This step utilizes laser processing to form a multi-level pore array with alternating first and second channels on the substrate layer, simultaneously achieving hydrophilic modification of the pore wall surface. The laser thermal effect causes the PTFE on the pore wall surface to decompose, introducing oxygen- and nitrogen-containing polar groups such as -COOH and -OH, increasing the oxygen atom ratio from 6.72% to 15.75% and the nitrogen atom ratio from 0.38% to 4.08%. At the same time, a micro-nano-scale rough structure is formed on the pore wall surface. The synergistic effect of chemical modification and physical morphological changes enhances surface energy, reducing the pore wall contact angle to approximately 42.5°, achieving a transformation from hydrophobic to hydrophilic. By combining the first and second channels with different pore sizes, a spatially complementary network for drainage and gas supply is constructed. Large pores provide low-resistance drainage channels, while small pores ensure gas permeation, resolving the contradiction between drainage and gas supply in single-pore-size designs and improving the water and gas management efficiency of the battery under high current density.

[0041] S300: A hydrophobic slurry is filled into the pores to form a hydrophobic filling layer.

[0042] This step involves filling the channels of a multi-level pore array with a hydrophobic slurry to form a hydrophobic filling layer. Specifically, a carbon black / PTFE slurry with superhydrophobic properties is prepared, and a multi-stage coating or screen printing process is used to ensure that the slurry fully fills the interior of the tapered channels to form a hydrophobic filling layer, and a continuous microporous layer is formed on the film surface.

[0043] S400: The filled base layer is heat-treated to form a gap between the hydrophobic filling layer and the pore surface.

[0044] This step induces the slurry to solidify and shrink through heat treatment. Utilizing the shrinkage difference between this shrinkage and the rigid, rough pore walls formed by laser carbonization, combined with insufficient interfacial bonding and the geometric constraints of the tapered pores, a micron-level gap naturally forms between the filling layer and the pore surface. This gap, in conjunction with the wettability gradient of the hydrophilic pore walls and the hydrophobic filler, provides an additional low-resistance transport path for liquid water, directionally guiding water-air separation, effectively reducing water breakthrough pressure and improving transport efficiency.

[0045] According to embodiments of this application, laser thermal effects are used to achieve pore formation and hydrophilic modification of the pore walls in one step, eliminating the need for additional chemical grafting steps and simplifying the process. The difference between the slurry shrinkage induced by heat treatment and the rigid pore walls formed by laser modification naturally creates micron-level interfacial gaps, avoiding complex precision masking or etching processes and reducing production costs. The gas diffusion layer structure prepared by this method is stable, with a clear hydrophilic-hydrophobic interface, effectively achieving water-gas separation and transport, which is beneficial for improving the performance of fuel cells at high current densities.

[0046] Thirdly, the present invention provides a membrane electrode assembly, wherein, according to an embodiment of the present application, the membrane electrode assembly includes the gas diffusion layer.

[0047] The membrane electrode assembly provided by this invention possesses excellent water vapor management capabilities due to the aforementioned gas diffusion layer. The synergistic effect of the multi-level pore array, the wettability gradient formed by the hydrophilic pore walls and the hydrophobic filling layer, and the interfacial gaps achieves spatial complementarity between directional liquid water discharge and efficient permeation of reactive gases. This structure effectively reduces the cathode water breakthrough pressure and mass transfer resistance, avoiding flooding under high current densities, thereby significantly improving the peak power density and long-term operational stability of the membrane electrode assembly.

[0048] Fourthly, the present invention provides a fuel cell, wherein, according to an embodiment of the present application, the fuel cell includes the membrane electrode assembly described above.

[0049] The fuel cell provided by this invention improves the water-gas transport efficiency within the system by integrating the aforementioned membrane electrode assembly. The water-gas separation channel constructed by the gas diffusion layer reduces the cathode water breakthrough pressure and mass transfer resistance, avoiding flooding during high current density operation. This allows the fuel cell to achieve a higher peak power density while maintaining a more stable voltage output, extending the battery's lifespan under high load conditions, making it suitable for applications with high power density requirements.

[0050] The technical solution provided by the present invention will be described in detail below with reference to the embodiments.

[0051] Unless otherwise specified, the raw materials used in the examples and comparative examples are commercially available analytical grade materials.

[0052] Example 1 This embodiment provides a gas diffusion layer and a fuel cell, the preparation steps of which are as follows: (1) Preparation of conductive composite film: Multi-walled carbon nanotubes (MWCNTs) and polytetrafluoroethylene (PTFE) emulsion were mixed at a mass ratio of 50:50, and deionized water and 0.1 wt.% Triton™ TMN-10 dispersant were added. After ultrasonic treatment for 1 hour, the mixture was vacuum filtered onto a 0.22 μm filter membrane. The filter membrane was dried at 100°C for 1 hour, and then hot-pressed and sintered at 350°C and 5 MPa for 1 hour to prepare a MWCNT / PTFE conductive composite film with a thickness of approximately 140 μm.

[0053] (2) Laser processing of multi-level hole array: A nanosecond pulse laser with a wavelength of 355 nm is used to periodically punch holes in the above thin film.

[0054] Laser processing creates tapered channels of two sizes: First channel (large aperture): The incident surface cross-sectional dimensions are 120 μm × 190 μm, and the bottom surface cross-sectional dimensions are 60 μm × 120 μm; Second channel (small hole): The incident surface cross-sectional dimensions are 50 μm × 80 μm, and the bottom surface cross-sectional dimensions are 25 μm × 40 μm.

[0055] The channels are arranged in a checkerboard pattern, with a center-to-center spacing of 200 μm between adjacent channels. The laser thermal effect simultaneously modifies the surface of the channel walls to be hydrophilic (contact angle approximately 42.5°, surface tension 57.1 mN / m).

[0056] (3) Preparation of hydrophobic filler slurry: Carbon black (Super P®) and PTFE emulsion were mixed at a mass ratio of 4:1. Isopropanol and deionized water (volume ratio of 1:1) were added as a mixing solvent, and 0.2 wt.% of nonionic surfactant was added. The mixture was ultrasonically dispersed for 30 minutes and then milled three times with a three-roll mill to obtain a uniform hydrophobic slurry with a solid content of about 12 wt.% (contact angle >140°).

[0057] (4) Slurry coating and filling: The slurry obtained in step 3 is coated onto the surface of the laser-processed film using a doctor blade. The doctor blade gap is set to 50 μm, and the coating is repeated 3 times. After each coating, the film is placed in a 100°C oven for 10 minutes to dry, so that the slurry can fully fill the pores and form a surface coating layer.

[0058] (5) Heat treatment sintering: The filled sample was placed under a nitrogen atmosphere and kept at 350°C for 1 hour, and then naturally cooled to room temperature. During this process, the solidification shrinkage of the slurry and the rigid surface of the pore wall produced a difference, forming a micron-level gap (about 3 μm wide) between the filling layer and the pore surface, thus obtaining a multi-level porous gas diffusion layer sample.

[0059] (6) Fabrication of fuel cells: The gas diffusion layer prepared above is used as the cathode gas diffusion layer, and together with the anode gas diffusion layer (such as commercial carbon paper), proton exchange membrane (such as Nafion 212), and catalyst layer (cathode Pt loading 0.4 mg / cm², anode 0.1 mg / cm²), it is assembled into a membrane electrode assembly (MEA). The MEA is then assembled with bipolar plates, current collectors, end plates, and other components to form a single cell. The battery assembly pressure is controlled at 1.0-1.5 MPa, and the active area is 25 cm².

[0060] Example 2 This embodiment provides a gas diffusion layer and a fuel cell, similar to Embodiment 1, except that: laser processing forms two sizes of tapered channels, with the same dimensional parameters as Embodiment 1. The channels are arranged in a hexagonal close-packed manner, that is, each first channel (large hole) is surrounded by 6 second channels (small holes), the spacing between the first channels is controlled at 400 μm, and the spacing between the second channels is approximately 200 μm. Hydrophilic modification of the hole wall surface is simultaneously achieved during laser processing.

[0061] Example 3 This embodiment provides a gas diffusion layer and a fuel cell, similar to Embodiment 1, except that laser processing forms two sizes of tapered channels with the same dimensional parameters as Embodiment 1. The channels are arranged in a cluster distribution pattern, with six first channels (large holes) evenly distributed around each second channel (small hole), forming a locally high-density gas channel. The spacing between the first channels is controlled at 400 μm, and the spacing between the second channels is approximately 200 μm. Hydrophilic modification of the hole wall surface is simultaneously achieved during laser processing.

[0062] Example 4 This embodiment provides a gas diffusion layer and a fuel cell, similar to Embodiment 1, except that: laser processing forms two sizes of tapered channels. First channel (large aperture): the incident surface cross-sectional dimension is 150μm, and the bottom surface cross-sectional dimension is 90μm; Second channel (small hole): The incident surface cross-sectional dimension is 60μm, and the bottom surface cross-sectional dimension is 30μm.

[0063] Example 5 This embodiment provides a gas diffusion layer and a fuel cell, similar to Embodiment 1, except that the gap width is controlled to be 1 μm by adjusting the heat treatment temperature and the PTFE content in the slurry.

[0064] Example 6 This embodiment provides a gas diffusion layer and a fuel cell, similar to Embodiment 1, except that the gap width is 5μm.

[0065] Comparative Example 1 This comparative example provides a gas diffusion layer and a fuel cell, similar to Example 1, except that: the laser processing only creates a first channel (large hole) of a single size, with an incident surface cross-section of 120 μm × 190 μm and a bottom surface cross-section of 60 μm × 120 μm. The channels are uniformly arrayed, with a center-to-center distance of 200 μm between adjacent holes. The laser thermal effect simultaneously causes hydrophilic modification of the hole wall surface.

[0066] Comparative Example 2 This comparative example provides a gas diffusion layer and a fuel cell, similar to Example 1, except that: instead of laser drilling the conductive composite film, the hydrophobic filling layer slurry is directly coated onto the surface of the complete film.

[0067] Comparative Example 3 This comparative example provides a gas diffusion layer and a fuel cell, similar to Example 1, except that: a doctor blade is used to coat the material only once, and the doctor blade gap is set to 20 μm, so that the slurry only covers the surface of the film and fails to fully fill the deep interior of the pores.

[0068] Comparative Example 4 This comparative example provides a gas diffusion layer and a fuel cell, similar to Example 1, except that: the laser processing only creates a second channel (orifice) of a single size, with an incident surface cross-section of 50 μm × 80 μm and a bottom surface cross-section of 25 μm × 40 μm. The channels are uniformly arrayed, with a center-to-center spacing of 200 μm between adjacent channels. Hydrophilic modification of the orifice wall surface is simultaneously achieved during laser processing.

[0069] Performance testing Electrochemical performance tests were conducted on the gas diffusion layers and fuel cells of Examples 1-6 and Comparative Examples 1-4. The test process included: 1. Liquid Water Breakthrough Pressure Test: The maximum pressure required for liquid water to penetrate the gas diffusion layer is measured using a capillary flow porosimeter. Specifically, using a capillary flow porosimeter, the sample is cut into a circular disc with a diameter of 47 mm, wetted with a low surface tension liquid (such as Galwick, surface tension 15.9 mN / m), and the gas pressure is gradually increased. The maximum pressure value corresponding to the liquid being expelled is recorded. The test is repeated 3 times and the average value is taken.

[0070] 2. Electrochemical Impedance Spectroscopy (EIS) Testing: Electrochemical impedance spectroscopy (EIS) testing was performed under specific operating conditions of the fuel cell. The cathode charge transfer resistance (R_Cct) and mass transfer resistance (R_mt) were obtained through equivalent circuit fitting. Specifically, the test was conducted on a single-cell test platform. The set operating conditions included: cell temperature 80°C, cathode relative humidity 100%, back pressure 150 kPa, and current density 1.0 A / cm². A 10 mV AC sinusoidal perturbation signal was applied, with a frequency range of 0.1 Hz to 10 kHz, and 10 points per decade. Equivalent circuit fitting was performed using ZView software (circuit model: L-Rohm-(R_Cct / / CPE)-R_mt), and the R_Cct and R_mt values ​​were extracted.

[0071] 3. Single-cell performance testing: Test conditions are as follows: battery operating temperature is 80℃, relative humidity of hydrogen at the anode and air at the cathode is 50% (simulating low humidity conditions); stoichiometry of hydrogen at the anode is 1.5, and stoichiometry of air at the cathode is 2.0; battery back pressure is ambient pressure. The test uses a constant voltage scanning mode, scanning from the open-circuit voltage (OCV) to 0.3 V, with a scan step size of 0.05 V. After each voltage point stabilizes for 3 minutes, the corresponding current density value is recorded. Power density is calculated based on the product of voltage and current density, and the peak power density is the maximum power density obtained during the test.

[0072] The test results are shown in Table 1: Table 1 Performance Test Results

[0073] As shown in Table 1, the gas diffusion layer provided by this invention exhibits excellent water management performance. Thanks to the construction of a multi-level pore array hydrophilic-superhydrophobic columnar interface, liquid water can be rapidly discharged along the hydrophilic pore walls of the large pores. Specifically, the breakthrough pressure of liquid water is reduced by approximately 85% compared to the conventional gas diffusion layer in Comparative Example 4, and is superior to the single-pore design in Comparative Example 1. Simultaneously, the multi-level pore array structure optimizes gas distribution, effectively reducing mass transfer resistance and charge transfer resistance. Specifically, the cathode charge transfer resistance (R_Cct) decreases from 29.0 mΩ to 21.0 mΩ, and the mass transfer resistance (R_mt) decreases from 25.9 mΩ to 19.5 mΩ. This, in turn, improves the output performance of the fuel cell. Under 50% relative humidity, the peak power density reaches 1.18 W / cm², an increase of approximately 24% compared to the conventional gas diffusion layer in Comparative Example 4 (0.95 W / cm²), and also superior to the single-pore design in Comparative Example 1 (1.13 W / cm²).

[0074] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0075] It should be noted that in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, technology, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, technology, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, technology, article, or apparatus that includes said element. In this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified.

[0076] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A gas diffusion layer, characterized in that, include: A conductive substrate layer, wherein a plurality of channels penetrating its thickness are formed on the conductive substrate layer, the plurality of channels including a first channel and a second channel with different diameters, and the surface of the pore wall of the channels is hydrophilic. A hydrophobic filling layer, wherein the hydrophobic filling layer fills the pores and covers one side surface of the conductive substrate layer, and the hydrophobic filling layer is hydrophobic; A gap is formed between the inner wall surface of the pore and the hydrophobic filling layer that fills the pore.

2. The gas diffusion layer as described in claim 1, characterized in that, The first channel and the second channel are arranged alternately, and the diameter of the second channel is 1 / 3 to 1 / 2 of the diameter of the first channel.

3. The gas diffusion layer as described in claim 1, characterized in that, Both the first and second channels are tapered holes, and the cross-sectional dimension of the side facing the gas flow channel is larger than the cross-sectional dimension of the side near the membrane electrode.

4. The gas diffusion layer as described in claim 3, characterized in that, The first pore has a cross-sectional dimension of 120-190 μm on the side facing the gas flow channel and a cross-sectional dimension of 60-120 μm on the side near the membrane electrode; and / or, The second channel has a cross-sectional dimension of 50-80 μm on the side facing the gas flow channel and a cross-sectional dimension of 25-40 μm on the side near the membrane electrode.

5. The gas diffusion layer as described in claim 1, characterized in that, The width of the gap is 1-5 μm.

6. The gas diffusion layer as described in claim 1, characterized in that, The water contact angle of the pore wall surface is less than 50°, and the water contact angle of the hydrophobic filling layer is greater than 140°.

7. The gas diffusion layer as described in claim 1, characterized in that, The conductive substrate layer comprises multi-walled carbon nanotubes and polytetrafluoroethylene; and / or, The hydrophobic filler layer comprises conductive carbon black and polytetrafluoroethylene.

8. A method for preparing a gas diffusion layer as described in any one of claims 1-7, characterized in that, Includes the following steps: Provide a conductive composite film as a conductive substrate layer; Multiple channels are formed on the conductive substrate layer by using a laser, and the surface of the channel wall is made hydrophilic. The multiple channels include a first channel and a second channel with different diameters. A hydrophobic slurry is filled into the pores to form a hydrophobic filling layer; The filled conductive substrate is heat-treated to form a gap between the hydrophobic filling layer and the pore surface.

9. A membrane electrode assembly, characterized in that, The membrane electrode assembly includes a gas diffusion layer as described in any one of claims 1-7.

10. A proton exchange membrane fuel cell, characterized in that, Includes the membrane electrode assembly as described in claim 9.

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