A surface textured proton exchange membrane, method of making and use thereof

Abstract

This invention discloses a surface-textured proton exchange membrane, its preparation method, and its applications, relating to the field of key materials technology for fuel cells. Using etched glass with a three-dimensional microscopic rough texture as a template, this invention employs a wet-coating integrated molding process. While the resin underlayer is not yet dry, an expanded porous film is composited to reinforce the framework. After surface coating and two-step heat treatment, the membrane is peeled off, resulting in an enhanced proton exchange membrane with a crater-like three-dimensional texture on one side. The fabricated membrane significantly improves dimensional stability without degrading mechanical strength and can form a 3D interlocking interface with the catalyst layer to expand the three-phase reaction interface and improve catalyst utilization. This invention features a simple process, low cost, and reusable templates, making it suitable for large-scale production and high-efficiency applications in fuel cells.

Description

Technical Field

[0001] This invention relates to the field of key materials technology for fuel cells, specifically to a surface-textured proton exchange membrane, its preparation method and its application, and particularly to a method for preparing a surface-textured proton exchange membrane based on an etching template method and its application in proton exchange membrane fuel cells. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are considered ideal devices for clean energy conversion due to their high energy conversion efficiency and zero emissions. In PEMFCs, the interface between the proton exchange membrane (PEM) and the catalyst layer (CL) is the key core region that determines electrochemical kinetics and overall efficiency.

[0003] Currently, commercially available composite proton exchange membranes (such as ePTFE-enhanced membranes) are typically prepared on a flat substrate using a casting method. A conventional two-dimensional (2D) planar contact is formed between PEM and CL. The three-phase reaction interface (TPB) of this 2D planar interface is limited, which restricts the utilization rate of the catalyst and the charge transfer rate.

[0004] To improve interfacial contact, existing technologies have attempted surface modification through methods such as imprinting. However, these physical methods often damage the inherent mechanical integrity of the composite film (e.g., decreased tensile strength, increased swelling ratio), making it difficult to meet the practical application requirements of fuel cells. Furthermore, conventional micro / nano fabrication is costly and not economically viable for large-scale production. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a surface-textured proton exchange membrane, its preparation method, and its application. This method is a simple, scalable, and cost-effective "etched glass template method" for preparing an enhanced surface-textured proton exchange membrane with fine three-dimensional surface morphology and excellent mechanical properties.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] <First Aspect> A method for preparing a surface-textured proton exchange membrane includes the following steps: S1. Substrate preparation: Select a template with a three-dimensional micro-rough texture on the surface as the substrate. S2. Underlayer coating: The resin dispersion is uniformly coated onto the textured surface of the substrate using a coating method to form a wet underlayer film. S3, Reinforcing layer composite: While the bottom wet film is still wet, the expanded porous film is laid flat on the bottom wet film, so that the resin dispersion is impregnated into the skeleton network of the expanded porous film. S4. Surface coating: A resin dispersion is uniformly coated on the wetted, expanded porous film surface to form a surface coating and obtain a composite wet film. S5. Heat treatment and peeling: The composite wet membrane is heat-treated, then cooled and peeled off from the substrate to obtain a proton exchange membrane with a three-dimensional textured surface on one side.

[0008] As one implementation scheme, the parameters of the three-dimensional micro-rough texture are: average roughness Sa = 500~2000 nm, unfolded area ratio S dr =1.05~1.8.

[0009] In some embodiments, the parameters of the three-dimensional micro-rough texture are: average roughness Sa = 800~1300 nm, unfolded area ratio S dr =1.1~1.3.

[0010] As one implementation, the parameters of the three-dimensional micro-rough texture are: average roughness Sa = 800~830nm.

[0011] As one implementation, the parameters of the three-dimensional micro-rough texture are: average roughness Sa = 1200~1280nm.

[0012] As one implementation scheme, the parameters of the three-dimensional micro-rough texture are: unfolded area ratio S dr =1.19~1.21.

[0013] As one implementation, the template has micro-protrusion structures distributed on a partial or all area of ​​one surface.

[0014] As one implementation, the substrate material is any one of glass, sapphire, etched metal, ceramic, or organic board.

[0015] In some embodiments, the substrate material is glass.

[0016] In some embodiments, the substrate is an anti-glare (AG) etched glass that has undergone chemical etching or physical etching treatment.

[0017] As one embodiment, the resin dispersion is one or more of perfluorosulfonic acid resin dispersion, sulfonated polyether ether ketone dispersion, and sulfonated polyimide dispersion.

[0018] As one embodiment, the expanded porous film is one or more of expanded polytetrafluoroethylene porous film, polyvinylidene fluoride porous film, and polyimide porous film.

[0019] As one implementation, the thickness of the underlying wet film is 50~120 μm.

[0020] As one implementation, the thickness of the surface coating is 50~120 μm.

[0021] As one implementation, the thickness of the underlying wet film is 70~90μm.

[0022] As one implementation, the thickness of the surface coating is 70~90 μm.

[0023] As one implementation method, the heat treatment method is as follows: first, pre-dry at 60~100 ℃ for 2~4 h, then raise the temperature to 130~180 ℃ and hold for 15~30 min.

[0024] <Second aspect> A surface-textured proton exchange membrane is prepared using the method described above.

[0025] As one embodiment, the proton exchange membrane includes a central reinforcing framework composed of an expanded porous film, and resin layers filling and covering both sides of the reinforcing framework, wherein one side surface of the proton exchange membrane has a rough three-dimensional textured surface.

[0026] As one embodiment, one side of the proton exchange membrane has a rough three-dimensional textured surface, while the other side has a smooth surface.

[0027] As one implementation, the rough three-dimensional texture of the proton exchange membrane is characterized by "crater-like" pitted texture.

[0028] As one implementation, the average roughness of the three-dimensional texture is Sa = 500~2000 nm, and the unfolded area ratio is S dr =1.05~1.8.

[0029] In some embodiments, the average roughness of the three-dimensional texture is Sa = 800~1300 nm, and the unfolded area ratio S dr =1.1~1.3.

[0030] In some embodiments, the average roughness of the three-dimensional texture is 800~830 nm.

[0031] As one implementation, the average roughness of the three-dimensional texture is 830~1300 nm.

[0032] In some embodiments, the average roughness of the three-dimensional texture is 1200~1280 nm.

[0033] In some embodiments, the unfolded area ratio of the three-dimensional texture is S dr =1.19~1.21.

[0034] <Third aspect> A membrane electrode comprising the aforementioned surface-textured proton exchange membrane.

[0035] As one implementation, when the proton exchange membrane has a three-dimensional texture on only one side, the side with the three-dimensional texture contacts the cathode catalyst.

[0036] As one embodiment, the catalyst loading at the anode and cathode of the membrane electrode is 0.1 mg / cm³, respectively. 2 and 0.4 mg / cm 2 .

[0037] As one embodiment, the catalyst layer is formed by spraying a slurry composed of a Pt / C catalyst, isopropanol, deionized water, and PFSA resin dispersion.

[0038] As one embodiment, the mass ratio of Pt / C catalyst, isopropanol, deionized water and PFSA resin dispersion in the slurry is 1:3:1:2.4.

[0039] <Fourth Aspect> A fuel cell includes the membrane electrode assembly described above.

[0040] As one implementation, the fuel cell is subjected to a back pressure of 0~0.1MPa gauge pressure during operation.

[0041] As one implementation, when the average roughness of the three-dimensional textured side of the proton exchange membrane is 800~830 nm and the unfolded area ratio is 1.1~1.3, the prepared fuel cell operates under normal pressure.

[0042] In some embodiments, when the average roughness of the three-dimensional textured side of the proton exchange membrane is 800~830nm and the unfolded area ratio is 1.19~1.21, the prepared fuel cell operates under atmospheric pressure.

[0043] As one implementation, when the average roughness of the three-dimensional textured side of the proton exchange membrane is 830~1280 nm and the unfolded area ratio is 1.1~1.3, the prepared fuel cell operates under a back pressure not higher than 0.1 MPa gauge pressure.

[0044] In some embodiments, when the average roughness of one side of the three-dimensional texture of the proton exchange membrane is 1200~1280 nm and the unfolded area ratio is 1.19~1.21, the prepared fuel cell operates under a back pressure of 0.1 MPa gauge pressure.

[0045] Compared with the prior art, the present invention has the following beneficial effects: (1) Green sustainability and extremely low manufacturing costs This invention utilizes etched glass from a large-scale industrial production line as a film-forming template, eliminating the need for expensive micro-nano etching equipment. It can reproduce crater-like surface textures with high fidelity, resulting in a proton exchange membrane with a textured surface of controllable depth on one side and a smooth surface on the other. Furthermore, this etched film template can be completely reused after peeling off the film and cleaning, significantly reducing the manufacturing cost of PEMs and possessing extremely high feasibility for industrial mass production. This enables green, low-cost, and scalable proton exchange membrane fabrication.

[0046] (2) Perfectly balances microscopic morphology and macroscopic robustness This invention employs a solution coating integrated molding method, directly laminating an ePTFE porous membrane while the underlying perfluorosulfonic acid (PFSA) resin dispersion is in a "wet" state, achieving complete resin wetting of the ePTFE framework. Comprehensive morphological, mechanical, and swelling analyses confirm that this method imparts a three-dimensional microstructure to the membrane without degrading or even enhancing its mechanical strength, while reducing the area swelling rate and improving dimensional stability. This achieves synergistic optimization of mechanical properties and durability, ensuring robustness in actual service.

[0047] (3) Formation of 3D interlocking interface, significantly improving electrochemical performance This invention precisely transfers the three-dimensional micro-rough texture on the etched glass template to the surface of the proton exchange membrane. When assembled into a membrane electrode assembly (MEA), the surface textured membrane can form a 3D interlocking interface with the catalyst layer, significantly expanding the three-phase reaction interface, improving catalyst accessibility and utilization, enhancing oxygen reduction reaction kinetics, and increasing the electrochemical active area (ECSA) and peak power density of the fuel cell.

[0048] (4) The synergistic mechanism between morphology and operating conditions was revealed. This invention reveals the deep synergy between microstructure and fuel cell operating conditions, and clarifies that moderate texturing (such as in Example 1) can significantly improve performance under normal pressure; films with greater roughness (such as in Example 2) can effectively alleviate the mass transfer limitation under normal pressure by applying back pressure, unlocking performance potential and greatly expanding the application scenarios and operating limits of textured films.

[0049] (5) Good texture replication effect, wide process window and strong stability Compared with conventional hot-press replication methods, the solution coating integrated molding method of this invention achieves deeper texture replication, higher fidelity, and more uniform structure. It can achieve precise control of crater texture at a specific depth, and the textured film can maintain an intact crater texture without tearing or deformation under different film thicknesses and different annealing processes. It has a wide process window and strong morphological stability, making it suitable for stable industrial production. Attached Figure Description

[0050] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 The image shows the microstructure of the proton exchange membrane prepared according to the present invention. Figure 1 a is P-PEM, Figure 1 b is T1-PEM, Figure 1 c represents T2-PEM.

[0051] Figure 2 The three-dimensional surface morphology of P-PEM, T1-PEM and T2-PEM at magnifications of 20x (a,b,c) and 50x (d,e,f), respectively; (i) the roughness (S) of the film. a ) and unfolded area ratio (S) dr ) value, where, Figure 2 a represents the three-dimensional surface morphology of P-PEM at 20x magnification, with an XY plane scanning range of 708.509 μm × 531.209 μm and color marks corresponding to -0.277 μm to 0.423 μm; Figure 2 b represents the three-dimensional surface morphology of T1-PEM at a magnification of 20x, with an XY plane scanning range of 708.509 μm × 531.209 μm and a color mark corresponding to -6.424 μm to 2.883 μm; Figure 2 c represents the three-dimensional surface morphology of T2-PEM at 20x magnification, with an XY plane scanning range of 708.509 μm × 531.209 μm and a color mark corresponding to -10.914 μm to 4.479 μm; Figure 2 d represents the three-dimensional surface morphology of P-PEM at 50x magnification, with an XY plane scanning range of 289.381 μm × 216.965 μm and color marks corresponding to -0.466 μm to 0.419 μm; Figure 2 e represents the three-dimensional surface morphology of T1-PEM at 50x magnification, with an XY plane scanning range of 289.381 μm × 216.965 μm and a color scale corresponding to -2.291 μm to 2.805 μm; Figure 2 f represents the three-dimensional surface morphology of T2-PEM at 50x magnification, with an XY plane scanning range of 289.381 μm × 216.965 μm and a color scale corresponding to -3.545 μm to 4.125 μm. Detailed Implementation

[0052] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0053] To facilitate understanding, the abbreviations or nouns mentioned below will be explained first: Average roughness; The unfolded area ratio S dr The percentage increase in actual surface area relative to projected area reflects the extent of improvement in effective interface; a higher value indicates a greater surface expansion. PFSA resin dispersion: Perfluorosulfonic acid resin dispersion, manufactured by Chemours, model D2020 resin solution, polymer content 20 wt.%; ePTFE porous membrane: expanded polytetrafluoroethylene porous membrane, manufactured by Yumingtai Chemical, model with a porosity of 78% and a thickness of 10 micrometers.

[0054] This invention uses a commercially available etched glass plate with microstructure as a film-forming template. The template used in this invention is characterized by its surface being covered with micro-protrusions.

[0055] As an example, this invention describes a method for preparing surface-textured proton exchange membranes using templates with two different roughnesses, specifically: Low-roughness template (labeled T1): Its average surface roughness (Sa) is approximately 815 nm (typically between 800 and 830 nm due to machining tolerances); its unfolded area ratio (S dr The value is approximately 1.193. High-roughness template (labeled T2): Its surface has a deeper microstructure, and the average surface roughness (S) is higher. a Its unfolded area ratio (S) is approximately 1243 nm (typically between 1200 and 1280 nm); dr It is approximately 1.204.

[0056] As an example, the template used in this invention is a 5mm thick etched glass plate.

[0057] Those skilled in the art can determine the roughness (S) based on the above. a ) and unfolded area ratio (S) dr The parameters are used to select or customize a glass plate with an equivalent three-dimensional microstructure from commercially available anti-glare (AG) etched glass as the implementation template of this invention.

[0058] The following is an introduction to the preparation of surface-textured proton exchange membranes using a solution coating integrated molding method. The surface of the prepared proton exchange membrane has a "crater-like" pit texture, which is complementary to the micro-protrusion structure of the glass template used.

[0059] Example 1 Etched glass T1 was used as a template.

[0060] A doctor blade coater was used to uniformly coat the perfluorosulfonic acid (PFSA) resin dispersion onto the template surface to form a bottom PFSA wet film, wherein the doctor blade gap was set to 80 μm. While the underlying PFSA wet film is still wet, immediately lay the expanded polytetrafluoroethylene (ePTFE) porous membrane flat on its surface and wait for the PFSA resin to completely impregnate the ePTFE skeleton network. On the fully wetted ePTFE membrane surface, PFSA resin dispersion is uniformly coated again with an 80 μm doctor blade gap to form a surface coating. The obtained composite wet film was subjected to two-step heat treatment: the first step was to pre-dry at 80 ℃ for 3 h, and the second step was to heat to 150 ℃ for 20 min for high-temperature annealing. After cooling to room temperature, the membrane is peeled off from the template surface to obtain an enhanced proton exchange membrane with a three-dimensional textured surface on one side, referred to as textured membrane T1-PEM.

[0061] The template can be reused after cleaning.

[0062] The microstructure of the template T1 surface was transferred from the template to the T1-PEM membrane surface, resulting in a "crater-like" texture on one side of the proton exchange membrane prepared in this embodiment. The texture is relatively shallow (Sa=815 nm), while the other side of the T1-PEM membrane is a smooth surface.

[0063] Example 2 Etched glass T2 was used as a template.

[0064] The preparation steps in this embodiment are the same as in Example 1, and the resulting textured membrane is named T2-PEM.

[0065] The microstructure of the template T2 surface was transferred from the template to the T2-PEM membrane surface, resulting in a "crater-like" texture with deep texture (Sa=1243 nm) on one side of the proton exchange membrane prepared in this embodiment, while the other side of the T2-PEM membrane is a smooth surface.

[0066] Example 3 Etched glass T1 was used as a template.

[0067] A doctor blade coater was used to uniformly coat the perfluorosulfonic acid (PFSA) resin dispersion onto the template surface to form a bottom PFSA wet film, wherein the doctor blade gap was set to 50 μm. While the underlying PFSA wet film is still wet, immediately lay the expanded polytetrafluoroethylene (ePTFE) porous membrane on its surface to promote the complete entry of PFSA resin into the ePTFE skeleton network. On the fully wetted ePTFE membrane surface, PFSA resin dispersion is uniformly coated again with a 50μm doctor blade gap to form a surface coating. The obtained composite wet film was subjected to two-step heat treatment: the first step was to pre-dry at 80 ℃ for 3 h, and the second step was to heat to 150 ℃ for 20 min for high-temperature annealing. After cooling to room temperature, the textured film T1-PEM-thin is peeled off from the template surface to obtain the textured film.

[0068] The template can be reused after cleaning.

[0069] The microstructure of the template T1 surface was stably transferred to the thinner composite membrane surface. The proton exchange membrane prepared in this embodiment has a complete "crater-like" texture on one side (Sa=812 nm). This indicates that reducing the film thickness did not affect the resin's filling and replication of the template's microstructure under a small coating gap.

[0070] Example 4 Etched glass T1 was used as a template.

[0071] A doctor blade coater was used to uniformly coat the perfluorosulfonic acid (PFSA) resin dispersion onto the template surface to form a bottom PFSA wet film, wherein the doctor blade gap was set to 120 μm. While the underlying PFSA wet film is still wet, immediately lay the expanded polytetrafluoroethylene (ePTFE) porous membrane on its surface to promote the complete entry of PFSA resin into the ePTFE skeleton network. On the fully wetted ePTFE membrane surface, PFSA resin dispersion is uniformly coated again with a 120μm doctor blade gap to form a surface coating. The obtained composite wet film was subjected to two-step heat treatment: the first step was to pre-dry at 80 ℃ for 3 h, and the second step was to heat to 150 ℃ for 20 min for high-temperature annealing. After cooling to room temperature, the textured film T1-PEM-thickness is obtained by peeling it off from the template surface.

[0072] The template can be reused after cleaning.

[0073] The proton exchange membrane prepared in this embodiment has a complete "crater-like" texture on one side (Sa=818 nm). This indicates that with a large coating gap, the increase in membrane thickness did not cause texture tearing or deformation during demolding, achieving high-fidelity morphology transfer at large thicknesses.

[0074] Example 5 Etched glass T2 was used as a template.

[0075] A doctor blade coater was used to uniformly coat the perfluorosulfonic acid (PFSA) resin dispersion onto the template surface to form a bottom PFSA wet film, wherein the doctor blade gap was set to 80 μm. While the underlying PFSA wet film is still wet, immediately lay the expanded polytetrafluoroethylene (ePTFE) porous membrane on its surface to promote the complete entry of PFSA resin into the ePTFE skeleton network. On the fully wetted ePTFE membrane surface, PFSA resin dispersion is uniformly coated again with an 80 μm doctor blade gap to form a surface coating. The obtained composite wet film was subjected to two-step heat treatment: the first step was to pre-dry at 90 ℃ for 2 h, and the second step was to heat to 180 ℃ and hold for 15 min for high-temperature annealing. After cooling to room temperature, the textured membrane T2-PEM-HT was peeled off from the template surface.

[0076] The template can be reused after cleaning.

[0077] The proton exchange membrane prepared in this embodiment has a deep "crater-like" texture on one side (Sa=1240 nm). This indicates that increasing the annealing temperature and adjusting the holding time can still ensure high-fidelity transfer of the deep texture, and the resin does not undergo thermal degradation, resulting in smooth demolding.

[0078] Comparative Example 1 A flat glass plate is used as a template, and the glass is marked with P.

[0079] The preparation steps of this comparative example are the same as those of Example 1, and the resulting film is a conventional planar film, named P-PEM.

[0080] Comparative Example 2 Comparative Example 2: The P-PEM prepared in Comparative Example 1 was directly hot-pressed onto the etched glass template T1 at 150℃ and 5MPa. The resulting film was named P-T1-PEM.

[0081] Detection and Analysis The proton exchange membranes prepared in the examples or comparative examples were tested using a scanning electron microscope, a confocal microscope, a universal testing machine, a fuel cell test bench, and an electrochemical workstation. The test results are listed in Table 1.

[0082] (1) Microscopic morphology and surface structure analysis The surface morphology of the prepared film was observed using a scanning electron microscope, such as... Figure 1 As shown.

[0083] Figure 1 In a, P-PEM exhibits a featureless, flat morphology, a characteristic of films cast on a smooth glass substrate.

[0084] Figure 1 b and Figure 1 In c, the film prepared using an etched glass template exhibits a distinct surface texture, indicating effective transfer of the template pattern. A comparison reveals that T1-PEM and T2-PEM possess different degrees of crater-like structures. Visually, the craters on T1-PEM are more densely packed, while those on T2-PEM are larger but sparser in distribution.

[0085] Furthermore, confocal microscopy is used for detection. For example... Figure 2 As shown, the textured surface of the T1-PEM film exhibits an average roughness Sa = 815 nm and an unfolded area ratio S dr =1.193. The textured surface of the T2-PEM film exhibits an average roughness Sa = 1243 nm, and an unfolded area ratio S dr =1.204. The P-PEM film surface exhibits a surface roughness Sa = 38 nm and an unfolded area ratio Sdr = 0.001. It can be observed that although the surface areas of T1-PEM and T2-PEM are significantly higher than those of P-PEM in terms of unfolded area ratio, the difference between T1-PEM and T2-PEM is negligible. This indicates that although T2-PEM has a deeper feature density (highest Sa), its lower texture density limits its overall gain in specific surface area, making its surface area essentially equivalent to that of T1-PEM, which has a higher feature density but is shallower. In other words, the average roughness (Sa) alone does not determine the expansion of surface area; texture feature density is equally crucial.

[0086] Although the hot pressing method in Comparative Example 2 can form a certain texture on the film surface, the crater texture is relatively shallow (Sa=230 nm, significantly lower than in Example 1) due to the large rheological resistance of the polymer chains flowing into the glass micropits in the solid state. This indicates that, for the high-fidelity crater texture of the specific depth sought in this invention, the solution coating integrated molding method is a better choice, achieving better microstructure control.

[0087] (2) Mechanical strength and swelling test In terms of mechanical properties, the tensile strength of T1-PEM is basically equivalent to that of P-PEM, while the tensile strength of T2-PEM is about 6.35% higher than that of P-PEM. This indicates that the preparation method provided by the present invention will not degrade the mechanical properties of the proton exchange membrane, and can even effectively improve the mechanical strength, thus ensuring the structural stability of the membrane.

[0088] In terms of swelling performance, the area swelling ratios of both T1-PEM and T2-PEM are lower than those of P-PEM, significantly improving planar dimensional stability. The mechanical durability of proton exchange membranes is mainly determined by the area swelling ratio; the smaller the area swelling ratio, the lower the fatigue stress and the higher the mechanical durability. The proton exchange membranes T1-PEM and T2-PEM prepared in this invention exhibit obvious low area swelling characteristics, achieving synergistic optimization of the mechanical properties and dimensional stability of the membrane material, and meeting the service requirements of proton exchange membranes.

[0089] The P-T1-PEM film prepared in Comparative Example 2 exhibits localized inhomogeneity in its overall mechanical properties.

[0090] Mechanical and swelling properties show that the "wet impregnation + two-step heat treatment" template method of this invention can achieve surface modification without sacrificing intrinsic tensile strength and dimensional stability. That is, T1-PEM and T2-PEM maintain the same film robustness as conventional P-PEM, ensuring the feasibility of its practical application.

[0091] Table 1

[0092] (3) Analysis of electrochemical performance and mass transfer mechanism The proton exchange membrane was assembled into a membrane electrode assembly (MEA), with catalyst loadings of 0.1 mg / cm³ at the anode and cathode, respectively. 2 and 0.4 mg / cm 2 In PEMFCs, the cathode is the rate-limiting electrode; therefore, for surface-textured proton exchange membranes, the cathode catalyst is deposited on the textured surface. The specific assembly method is as follows: A catalyst slurry was prepared by mixing a Pt / C catalyst (40 wt.%), isopropanol, deionized water, and PFSA resin dispersion, wherein the mass ratio of each component was Pt / C catalyst (40 wt.%): isopropanol: deionized water: PFSA resin dispersion = 1:3:1:2.4. The slurry was uniformly sprayed onto both sides of a proton exchange membrane using an air spray gun (IWATA HP-CH, Japan) to form a catalyst layer. After drying, a catalyst-coated membrane (CCM) was obtained. The CCM was then sandwiched between two gas diffusion layers (GDL) to assemble a membrane assembly (MEA).

[0093] The test conditions were: single-cell temperature 80 °C, 100% relative humidity. The test was conducted at a rate of 0.3 L / min. - ¹ Hydrogen gas is supplied at a flow rate of 0.6 L / min (anode). - ¹ Air is supplied at a flow rate (cathode). Polarization characteristics (IV and IP curves) are measured at atmospheric pressure and back pressure of 0.1 MPa gauge pressure.

[0094] For ease of explanation, the MEAs prepared using P-PEM, T1-PEM, and T2-PEM are named P-MEA, T1-MEA, and T2-MEA, respectively.

[0095] Table 2 lists the electrochemical performance data of the membrane electrodes of the proton exchange membranes prepared in each example and comparative example. It can be seen that, compared with P-MEA, T1-MEA significantly improves ECSA (approximately 35.6%) and peak power density at ambient pressure by approximately 29%. The textured proton exchange membrane, through its crater-like surface microstructure, forms a three-dimensional interlocked interface with the catalyst layer, significantly expanding the three-phase reaction interface and thus improving catalyst utilization. Among them, the fine, high-texture-density texture of T1-PEM maximizes the interfacial area; therefore, the improvement in ECSA and peak power density at ambient pressure is much greater than that of T2-PEM with its lower texture-density. Although T2-PEM has a greater texture depth, its lower texture-density results in limited interfacial gain, achieving only a slight improvement.

[0096] While surface texturing offers clear benefits, high surface roughness, such as in T2-PEM, can lead to mass transfer limitations (increased mass transfer resistance) at ambient pressure. Applying a back pressure of 0.1 MPa gauge pressure during fuel cell operation improved the output performance of both T1-MEA and T2-MEA. In particular, applying back pressure effectively alleviated the mass transfer limitation caused by high roughness in T2-MEA, resulting in a more significant increase in peak power density, reaching 1172 mW / cm². 2 Approaching 1180 mW / cm² of T1-MEA 2 .

[0097] Table 2

[0098] This invention discovers that the micro-texture parameters (average roughness Sa and unfolded area ratio Sdr) of the etched glass template have a decisive influence on the interfacial contact state of the final proton exchange membrane (PEM) and the electrical / mass transfer performance of the fuel cell. Based on this discovery, this invention defines the parameters of the micro-roughness texture, and its technical rationale and necessity are as follows: (1) When the parameter is below the lower limit (e.g., Sa < 500 nm or Sdr <1.05): Within this parameter range, the glass template exhibits extremely low roughness characteristics, meaning that the texture density or depth is too small, approaching the surface state of a conventional planar membrane (P-PEM). This results in the formation of extremely shallow or sparsely distributed "crater" structures on the membrane surface.

[0099] The aforementioned structure leads to negative problems: it cannot effectively increase the geometric contact area between the membrane (PEM) and the catalyst layer (CL), and cannot achieve a mechanical interlocking effect. Therefore, in electrochemical reactions, the interfacial ohmic resistance (high-frequency impedance) is difficult to reduce significantly, and under the stress caused by wet-dry cycling, the catalyst layer is still prone to microscopic peeling, thus negating the significance of texturing the membrane surface.

[0100] (2) When the parameter is higher than the upper limit (e.g., Sa>2000 nm or S) dr >1.8): Within this parameter range, the glass template exhibits extremely high roughness characteristics, meaning it has extremely high texture depth or extremely high unfolded area ratio. The specific negative issues arising from this are as follows: a. Molding defect risk: When the micro-pits in the template are too deep (deeper than 2 μm), the polymer resin solution is very likely to trap air during the casting process, resulting in unfilled micro-pores; at the same time, the excessively deep micro-pits will generate a large mechanical embedding force during demolding, which can easily break the polymer molecular chains, causing the "volcano" structure on the film surface to tear and collapse, affecting the molding quality of the film.

[0101] b. Severe flooding and mass transfer limitations (mass transfer crisis): If an extremely deep "crater" array is replicated, although the interfacial contact area increases, the extremely deep pits will become "miniature reservoirs" for water generated by electrochemical reactions. During fuel cell operation, under the action of capillary forces, liquid water is difficult to drain from the bottom of the extremely deep crater, leading to severe electrode flooding. This drastically increases the mass transfer resistance of oxygen, causing the polarization curve to decay rapidly in the high current density region.

[0102] It should be noted that, for deeper textures (such as in Example 2), the present invention has creatively proposed to overcome the problem of liquid water accumulation in deep pits by applying cathode / anode back pressure, thereby breaking the mass transfer limitation under normal pressure; however, if Sa exceeds 2000 nm, even if a back pressure of conventional strength is applied, it is difficult to achieve effective drainage, and the extremely thin proton exchange membrane is also prone to the risk of gas cross-leakage in deep pits.

[0103] Therefore, the parameter range defined in this invention, namely Sa=500~2000 nm, Sdr=1.05~1.8, and the preferred Sa=800~1300 nm, Sdr=1.1~1.3, is not an arbitrary choice from conventional experiments in the field, but rather the optimal microstructure range obtained through research and verification after overcoming the dual technical biases of "shallow textures have no gain" and "extremely deep textures are prone to water flooding and difficult to demold".

[0104] In summary, this invention provides a coating method based on etched glass substrates, which is a scalable and cost-effective PEM preparation strategy. This invention provides a practical and reliable technical solution for designing high-performance fuel cells with optimized 3D interfaces.

[0105] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a surface-textured proton exchange membrane, characterized in that, Includes the following steps: S1. Substrate preparation: Select a template with a three-dimensional micro-rough texture as the substrate. The parameters of the three-dimensional micro-rough texture are: average roughness Sa = 500~2000 nm, unfolded area ratio S dr =1.05~1.8; S2. Underlayer coating: The resin dispersion is uniformly coated onto the textured surface of the substrate using a coating method to form a wet underlayer film. S3, Reinforcing layer composite: While the bottom wet film is still wet, the expanded porous film is laid flat on the bottom wet film, so that the resin dispersion is impregnated into the skeleton network of the expanded porous film. S4. Surface coating: A resin dispersion is uniformly coated on the wetted, expanded porous film surface to form a surface coating and obtain a composite wet film. S5. Heat treatment and peeling: The composite wet membrane is heat-treated, then cooled and peeled off from the substrate to obtain a proton exchange membrane with a three-dimensional textured surface on one side.

2. The method according to claim 1, characterized in that, The preferred surface characteristic parameters of the substrate are: average roughness Sa of 800~1300 nm, and unfolded area ratio S. dr It is 1.1~1.

3.

3. The method according to claim 1, characterized in that, The substrate material is any one of glass, sapphire, etched metal, ceramic, or organic board.

4. The method according to claim 1, characterized in that, It also includes any of the following technical features: A1. The resin in the resin dispersion is one or more of perfluorosulfonic acid resin, sulfonated polyether ether ketone resin, and sulfonated polyimide resin; B1. The expanded porous film is one or more of expanded polytetrafluoroethylene porous film, polyvinylidene fluoride porous film, and polyimide porous film.

5. The method according to claim 1, characterized in that, The heat treatment method is as follows: first, pre-dry at 60~100 ℃ for 2~4 h, then raise the temperature to 130~180 ℃ and hold for 15~30 min.

6. The surface-textured proton exchange membrane prepared according to any one of claims 1 to 5, characterized in that, The proton exchange membrane includes a central reinforcing framework composed of an expanded porous film, and resin layers filling and covering both sides of the reinforcing framework. One side surface of the proton exchange membrane has a rough three-dimensional texture.

7. The proton exchange membrane according to claim 6, characterized in that, The average roughness of the three-dimensional texture is Sa = 500~2000 nm, and the unfolded area ratio is S dr =1.05~1.

8.

8. A membrane electrode, characterized in that, Includes the proton exchange membrane as described in claim 7 or 8.

9. The fuel cell according to claim 8, characterized in that, The proton exchange membrane has a three-dimensional textured surface on one side in contact with the cathode catalyst.

10. A fuel cell, characterized in that, Includes the membrane electrode as described in claim 8 or 9.

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