A membrane electrode and a method for manufacturing the same

Abstract

The application discloses a membrane electrode and a preparation method thereof, and belongs to the technical field of fuel cells. The membrane electrode comprises a proton exchange membrane, an anode catalytic layer and a cathode catalytic layer. The cathode catalytic layer comprises a hydrophilic strengthening area, a main reaction area and a hydrophobic homogeneous area arranged in sequence according to an area ratio of 15%-20%:60%-70%:15%-20%. The hydrophilic strengthening area is coated with a composite catalytic layer A which is jointly formed by a catalyst A, an ionomer A, a hydrophilic material A, a one-dimensional structure reinforcing material and a two-dimensional structure reinforcing material. The main reaction area is coated with a composite catalytic layer B which is jointly formed by a catalyst B, an ionomer B and a hydrophilic material B. The hydrophobic homogeneous area is coated with a composite catalytic layer C which is jointly formed by a catalyst C, an ionomer C, a hydrophobic material C and a structure reinforcing material. The application has the advantages of strong self-adaptive water management capability, good durability, high structural stability and the like.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and specifically to a membrane electrode and its preparation method. Background Technology

[0002] The performance, efficiency, and durability of a proton exchange membrane fuel cell depend primarily on its membrane electrode assembly (MEA). The cathode catalytic layer is a complex coupling site for oxygen reduction, water generation, proton conduction, electron conduction, and multiphase mass transport. The internal balance of water-gas-mass transport is the physical basis for maintaining efficient and stable operation.

[0003] Currently, commercially available and mainstream catalyst layer structures are typically near-homogeneous composites consisting of catalysts, ionomers, and pores. However, their pore structure lacks proactive and targeted control design in the three-dimensional structure of the membrane electrode assembly (MEA). While conventional homogeneous structures perform reasonably well under ideal and stable fuel cell operating conditions, their inherent defects become apparent under the dynamic and wide-range operating conditions of actual vehicles, especially with frequent switching between "high power-high humidity" and "idle-low humidity," creating an irreconcilable "water management contradiction." Under high current density or high humidity conditions, the cathode generates water at an extremely high rate, and liquid water tends to accumulate excessively in the lower region of the catalyst layer. This severely hinders oxygen transport to the active sites near the proton exchange membrane, causing "flooding," which leads to a sharp drop in output voltage due to concentration polarization and unstable power output. Conversely, the upper part of the catalyst layer is prone to water depletion due to gas flow, gravity, and other factors, especially under low humidity, high temperature, or low current conditions. This results in a decline in the ionomer's electron conductivity, known as "membrane dryness," and a significant increase in ohmic losses, also leading to performance degradation.

[0004] Existing technologies mostly focus on macroscopic hydrophobic treatment of the gas diffusion layer or water management design of the flow channel plate. These are passive or indirect adjustments to the external environment of the catalyst layer, failing to address the core region where the reaction occurs—the microscopic pores inside the catalyst layer. Therefore, the key to overcoming the current performance and durability bottlenecks of automotive fuel cells lies in innovating from the source of the catalyst layer's structural design to construct an adaptive micro / nano pore system that can actively and intelligently optimize the transport paths of water, oxygen, and protons based on the internal water, gas, and electrochemical states, thereby achieving optimal "water balance" under a wide range of humidity, current, and pressure conditions. Summary of the Invention

[0005] The purpose of this invention is to provide a membrane electrode and its preparation method to solve the problems of water shortage and drying on the upper side and excessive water accumulation on the lower side in existing membrane electrodes during the reaction process, so as to achieve adaptive control of water field distribution, reduce the risk of water blockage and reverse polarity, and improve the stability of its own reaction.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a membrane electrode comprising a proton exchange membrane, an anode catalyst layer, and a cathode catalyst layer, wherein the cathode catalyst layer comprises a hydrophilic enhancement region, a main reaction region, and a hydrophobic homogeneous region arranged in a ratio of 15%~20%:60%~70%:15%~20% in sequence. The hydrophilic reinforcement region is coated with a composite catalytic layer A, which is composed of catalyst A, ionomer A, hydrophilic material A, one-dimensional structure reinforcement material and two-dimensional structure reinforcement material; The main reaction zone is coated with a composite catalytic layer B, which is composed of catalyst B, ionomer B, and hydrophilic material B. The hydrophobic homogeneous region is coated with a composite catalytic layer C, which is composed of catalyst C, ionomer C, hydrophobic material C, and structural reinforcement material.

[0007] Furthermore, the porosity of the hydrophilic enhancement zone is 30%~40%, the porosity of the main reaction zone is 40%~45%, and the porosity of the hydrophobic homogeneous zone is 45%~60%.

[0008] Furthermore, catalyst A is at least one of platinum-carbon catalyst and transition metal composite platinum-carbon catalyst; Ionomer A is at least one of perfluorosulfonic acid polymer, sulfonated polyether ether ketone, sulfonated polyarylether sulfone, sulfonated polyimide, and phosphate-doped polybenzimidazole; Hydrophilic material A is at least one of sulfonated SiO2, hydrophilic fumed silica, and sulfonated carbon nanotubes; The one-dimensional structural reinforcement material is at least one of perfluorosulfonic acid / PVDF composite electrospinning and carbon nanofibers; The two-dimensional reinforcing material is a single layer of graphene.

[0009] Furthermore, catalyst B is at least one of platinum-carbon catalyst, transition metal composite platinum-carbon catalyst, and transition metal catalyst; Ionomer B is at least one of perfluorosulfonic acid polymer, sulfonated polyether ether ketone, sulfonated polyarylether sulfone, sulfonated polyimide, and phosphate-doped polybenzimidazole; The hydrophilic material B is at least one of sulfonated SiO2 and sulfonated carbon nanotubes.

[0010] Furthermore, catalyst C is at least one of platinum-carbon catalyst and transition metal composite platinum-carbon catalyst; Ionomer C is at least one of perfluorosulfonic acid polymer, sulfonated polyether ether ketone, sulfonated polyarylether sulfone, sulfonated polyimide, and phosphate-doped polybenzimidazole; The hydrophobic material C is at least one of fluorinated polymer nanoparticles and surface-fluorinated carbon black. The structural reinforcement material is nano-silica modified with a silane coupling agent.

[0011] Furthermore, the platinum loading ratio of the hydrophilic enhancement region, the main reaction region, and the hydrophobic homogeneous region is 0.6~0.8:1:0.6~0.8; the membrane electrode also includes a plastic encapsulation frame encapsulated on the surface of the membrane electrode.

[0012] A second aspect of the present invention provides a method for preparing the above-mentioned membrane electrode, comprising the following steps: S1. Prepare slurry for the anode catalyst, hydrophilic enhancement zone, main reaction zone, and hydrophobic homogenization zone respectively; S2. The anode catalyst slurry is coated on one side of the proton exchange membrane to form an anode catalyst layer; S3. On the other side of the proton exchange membrane, the hydrophilic reinforcement zone slurry, the main reaction zone slurry, and the hydrophobic homogeneous zone slurry are sequentially coated according to the area ratio of hydrophilic reinforcement zone, main reaction zone, and hydrophobic homogeneous zone of 15%~20%: 60%~70%: 15%~20% to form composite catalyst layer A, composite catalyst layer B, and composite catalyst layer C, respectively.

[0013] Furthermore, the anode catalyst slurry comprises: platinum-carbon catalyst, ionomer solution, deionized water, small molecule alcohol, and pore-forming agent; The hydrophilic reinforcement slurry contains: catalyst A, ionomer solution A, hydrophilic material A, one-dimensional structure reinforcement material, two-dimensional structure reinforcement material, deionized water, small molecule alcohol and pore-forming agent; The slurry in the main reaction zone contains: catalyst B, ionomer solution B, hydrophilic material B, deionized water, small molecule alcohol, and pore-forming agent; The hydrophobic homogeneous slurry contains: catalyst C, ionomer solution C, hydrophobic material C, structural reinforcement material, deionized water, small molecule alcohol, and pore-forming agent.

[0014] Furthermore, in the anode catalyst slurry: the mass of the ionomer in the ionomer solution is 25%-85% of the mass of carbon in the platinum-carbon catalyst, the mass ratio of water to small molecule alcohol is 1:1~2, the content of pore-forming agent is 0.5%-2% of the mass of platinum-carbon catalyst, and the solid content of the slurry is 2%-10%; In the hydrophilic reinforcement zone slurry: the mass of ionomer A in ionomer solution A is 25%-85% of the mass of carbon in catalyst A; the mass ratio of water to small molecule alcohol is 1:1-3; the pore-forming agent content is 1%-2% of the mass of catalyst A; the hydrophilic material A is 1%-3% of the mass of catalyst A; the one-dimensional reinforcing material is 2%-5% of the mass of catalyst A; the two-dimensional reinforcing material is 1%-3% of the mass of catalyst A; the slurry solid content is 2%-10%; and the platinum loading is 0.03-0.25 mg / cm³. 2 ; In the slurry of the main reaction zone, the mass of ionomer B in ionomer solution B is 25%-85% of the mass of carbon in catalyst B, the mass ratio of water to small molecule alcohol is 1:1~4, the content of pore-forming agent is 2%-3% of the mass of catalyst B, and the solid content of slurry is 2%-10%. In the hydrophobic homogeneous slurry, the mass of ionomer C in the ionomer solution C is 25%-85% of the mass of carbon in the catalyst C, the mass ratio of water to small molecule alcohol is 1:1~3, the content of pore-forming agent is 3%-6% of the mass of catalyst C, the hydrophobic material C is 1.5%-2.5% of the mass of catalyst C, the structural reinforcement material is 0.5%-3% of the mass of catalyst C, and the solid content of the slurry is 2%-10%.

[0015] Furthermore, in S2 and S3, the coating can be any one of spraying, screen printing, casting, or transfer printing.

[0016] This invention achieves the following synergistic effect by sequentially arranging a hydrophilic enhancement zone, a main reaction zone, and a hydrophobic homogeneous zone in the cathode catalyst layer from the side closest to the proton exchange membrane to the side furthest from the proton exchange membrane, and by synergistically controlling the area ratio (15%~20%: 60%~70%: 15%~20%), porosity (30%~40%, 40%~45%, 45%~60%), and the composition and platinum loading ratio (0.6~0.8: 1: 0.6~0.8) of the three zones: The hydrophilic enhancement zone is located at the highest air intake position, where moisture on the membrane layer evaporates more easily, leading to proton conduction efficiency reduction, membrane degradation and perforation, and platinum particle migration and aggregation. This invention reduces the porosity of this region (30%~40%) to decrease moisture evaporation and utilizes the capillary effect generated by the small pore size to induce capillary condensation, simultaneously inhibiting the outward discharge or excessive evaporation of liquid water. This maintains a certain water saturation level inside the catalyst layer, preventing it from drying out. Furthermore, the hydrophilic properties of the materials (sulfonated SiO2, hydrophilic fumed silica, sulfonated carbon nanotubes) further lock in moisture, ensuring proton conduction efficiency. Simultaneously, the platinum loading is reduced to accommodate the lower reaction efficiency in this region, avoiding platinum waste. In addition, one-dimensional structural reinforcement materials (perfluorosulfonic acid / PVDF composite electrospinning, carbon nanofibers) are added to form physical cross-linking points in the catalyst layer, effectively inhibiting crack propagation and preventing the catalyst layer from cracking due to drying. Two-dimensional structural reinforcement materials (monolayer graphene) are added to enhance the cohesion of the catalyst layer and improve dimensional stability by utilizing its high aspect ratio.

[0017] The main reaction zone is the area of ​​most vigorous reaction, producing a large amount of water. It needs to be drained as quickly as possible to avoid localized water blockage and reduced reaction efficiency. This invention increases the porosity of this zone to 40%~45%, utilizing gravity and gas flow to rapidly remove water vapor, preventing water accumulation and achieving a dynamic balance between water production and drainage.

[0018] Due to the low gravity and gas pressure, the hydrophobic homogeneous region cannot drain water in time, easily leading to flooding. This can result in the loss of the three-phase interface, gas inability to contact the catalyst, reduced reaction activity, and even reverse polarity, inducing oxidation and corrosion of ionomers and carbon carriers. Flooding can also cause platinum particles to dissolve and agglomerate, the film to swell excessively, and even perforate, resulting in a permanent reduction in reaction activity. This invention increases the porosity of this region to 45%–60% and adds hydrophobic materials (fluorinated polymer nanoparticles and surface-fluorinated carbon black) to rapidly drain water vapor under gas flow conditions, reducing condensation and mitigating flooding. Simultaneously, a structural reinforcing material (silane coupling agent-modified nano-silica) is added as a physical crosslinking point. In this material, inorganic nanoparticles form hydrogen bonds with the sulfonic acid groups in the ionomer, and organic functional groups interact with the ionomer backbone, achieving chemical anchoring, inhibiting ionomer dissolution, and significantly improving mechanical strength.

[0019] The three zones work together to form a gradient water management framework of "water protection at the top, buffering in the middle, and drainage at the bottom," enabling the cathode catalytic layer to automatically optimize the transport paths of water, oxygen, and protons based on the internal water, gas, and electrochemical states, fundamentally solving the water management contradiction of "dryness at the top and flooding at the bottom" in existing technologies.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. Through the synergistic design of three zones with different porosities and hydrophilic / hydrophobic materials, the hydrophilic enhancement zone is guaranteed to retain water (less water production), the main reaction zone is hydrophobic (high reaction efficiency, rapid hydrophobicity), and the hydrophobic homogeneous zone is strongly hydrophobic (more condensate). This ensures that the water and gas states are automatically optimized for transport paths, effectively alleviates the contradiction between flooding and drying, reduces concentration polarization, significantly improves performance under high current density, broadens the working window of the membrane electrode, and increases the limiting current density and power density.

[0021] 2. The one-dimensional / two-dimensional reinforcing material in the hydrophilic reinforcement region forms a physical cross-linking network, which effectively inhibits crack propagation and prevents the catalyst layer from cracking due to drying; the silane coupling agent modified nano-silica in the hydrophobic homogeneous region inhibits the swelling of ionomers through chemical anchoring, reduces the mechanical stress caused by dry and wet cycles, avoids membrane perforation, and extends the service life of the membrane electrode.

[0022] 3. The one-dimensional structure of the hydrophilic reinforcement region forms physical cross-linking points to inhibit crack propagation, the high aspect ratio of the two-dimensional structure of the reinforcement material enhances cohesion, and the silane coupling agent-modified nano-silica in the hydrophobic homogeneous region achieves chemical anchoring through hydrogen bonding and main chain interaction. All three together improve the mechanical strength and dimensional stability of the catalyst layer.

[0023] 4. The platinum loading in the hydrophilic enhancement zone and the hydrophobic homogeneous zone is adjusted to 0.6 to 0.8 times that in the main reaction zone. This reduces the amount of precious metal platinum while ensuring overall reaction efficiency, thus avoiding waste of platinum and loss due to platinum particle dissolution and agglomeration caused by water flooding.

[0024] 5. This invention effectively alleviates the contradiction between flooding and drying, reduces concentration polarization, significantly improves performance under high current density, increases the limiting current density and power density of the membrane electrode, and at the same time reduces the mechanical stress of the catalyst layer caused by wet-dry cycles, thus extending its service life. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the present invention.

[0026] The names corresponding to the reference numerals in the attached figures are as follows: 1-Hydrophilic enhancement zone, 2-Main reaction zone, 3-Hydrophobic homogenization zone, 4-Sealing frame. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] In the description of this invention, it should be noted that the terms "A", "B", "C", etc. are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] like Figure 1 As shown, this invention provides a membrane electrode, namely a catalyst-coated membrane (CCM), comprising a proton exchange membrane, an anode catalytic layer, and a cathode catalytic layer. The cathode catalytic layer of this invention is not a traditional homogeneous structure, but rather sequentially designed with three functional regions along the gas flow and drainage directions: a hydrophilic reinforcement region, a main reaction region, and a hydrophobic homogeneous region, with area proportions of 15%~20%, 60%~70%, and 15%~20%, respectively. Specifically, the hydrophilic reinforcement region, the main reaction region, and the hydrophobic homogeneous region are arranged in a planar manner along the extension direction of the proton exchange membrane (i.e., from the proton exchange membrane side to the gas diffusion layer side). The hydrophilic reinforcement region is located close to the proton exchange membrane, the hydrophobic homogeneous region is located away from the proton exchange membrane, and the main reaction region is located between the hydrophilic reinforcement region and the hydrophobic homogeneous region. This invention constructs a micro / nano-channel system capable of adaptively adjusting the internal "water-gas-mass" state by synergistically controlling the micro-composition, porosity, and platinum loading of each region.

[0030] The hydrophilic reinforcement region is located near the proton exchange membrane side. This region is upstream of the gas inlet and close to the membrane side, where moisture is easily volatilized, leading to increased proton conduction resistance and a high risk of membrane degradation. This region is coated with a composite catalyst layer A, consisting of catalyst A, ionomer A, hydrophilic material A, one-dimensional reinforcing material, and two-dimensional reinforcing material.

[0031] In specific implementation, catalyst A is at least one of platinum-carbon catalyst and transition metal composite platinum-carbon catalyst; ionomer A is at least one of perfluorosulfonic acid polymer, sulfonated polyether ether ketone, sulfonated polyarylene ether sulfone, sulfonated polyimide, and phosphoric acid-doped polybenzimidazole; hydrophilic material A is at least one of sulfonated SiO2, hydrophilic fumed silica, and sulfonated carbon nanotubes; one-dimensional structure reinforcing material is at least one of perfluorosulfonic acid / PVDF composite electrospinning and carbon nanofibers; and two-dimensional structure reinforcing material is monolayer graphene.

[0032] The hydrophilic reinforcement region, through the addition of hydrophilic materials, enhances the region's ability to bind trace amounts of water, preferentially locking in the water generated during the reaction, effectively alleviating membrane-side dryness, maintaining polymer humidity, and ensuring unobstructed proton conduction pathways. Furthermore, the introduction of one-dimensional (fibrous) and two-dimensional (sheet-like) reinforcing materials forms a physical cross-linked network and high aspect ratio anchors within the catalyst layer, significantly suppressing crack propagation caused by wet-dry cycles and improving the cohesion and dimensional stability of the catalyst layer.

[0033] This invention also controls the platinum loading in this region to be 0.6 to 0.8 times that of the main reaction region (absolute loading 0.24-0.56 mg / cm³). 2 The reactor was designed with a low porosity (30%~40%) to balance the reaction activity and water retention requirements, thus avoiding a vicious cycle of "water shortage" caused by low reaction efficiency.

[0034] The main reaction zone is the central core area, where the electrochemical reactions are most intense, resulting in extremely high water production rates. Failure to drain water promptly will directly cause "flooding," hindering oxygen transport and causing significant concentration polarization losses. This zone is coated with a composite catalyst layer B composed of catalyst B, ionomer B, and hydrophilic material B. The highest platinum loading is achieved (0.4-0.7 mg / cm³). 2 The porosity is designed to be moderate, ranging from 40% to 45%.

[0035] In specific implementations, catalyst B is at least one of platinum-carbon catalyst, transition metal composite platinum-carbon catalyst, and transition metal catalyst; ionomer B is at least one of perfluorosulfonic acid polymer, sulfonated polyether ether ketone, sulfonated polyarylene ether sulfone, sulfonated polyimide, and phosphoric acid-doped polybenzimidazole; hydrophilic material B is at least one of sulfonated SiO2 and sulfonated carbon nanotubes. If it is a mixture, the mass ratio of sulfonated SiO2 to sulfonated carbon nanotubes is 0.2:0.8.

[0036] This region exhibits the most vigorous reaction, producing a significant amount of water. Its porosity (40%–45%) falls between that of the hydrophilic enhancement region and the hydrophobic homogeneous region. By increasing the porosity of the catalyst layer in this region, water vapor is rapidly removed using gravity and gas flow, preventing water accumulation and achieving rapid hydrophobicity. Simultaneously, this region maintains a moderate platinum loading (0.4–0.7 mg / cm³). 2 (and higher than the hydrophilic enhancement region and the hydrophobic homogeneous region), ensuring high power output capability. The generated liquid water can be quickly guided to the hydrophobic homogeneous region for discharge, while retaining a certain degree of wetness to maintain proton conduction, avoiding local water blockage that reduces reaction efficiency, which is the core of alleviating the "flooding" problem.

[0037] The hydrophobic homogeneous region, located away from the proton exchange membrane and downstream of the gas flow channel, experiences lower gas pressure and is affected by gravity. Condensate from the main reaction zone easily accumulates here, forming "bubbles" that clog the three-phase reaction interface, leading to catalyst deactivation or even reaction failure. This region is coated with a composite catalyst layer C, consisting of catalyst C, ionomer C, hydrophobic material C, and structural reinforcement material.

[0038] In specific implementation, catalyst C is at least one of platinum-carbon catalyst and transition metal composite platinum-carbon catalyst; ionomer C is at least one of perfluorosulfonic acid polymer, sulfonated polyether ether ketone, sulfonated polyarylene ether sulfone, sulfonated polyimide, and phosphoric acid-doped polybenzimidazole; hydrophobic material C is at least one of fluorinated polymer nanoparticles and surface-fluorinated carbon black, possessing high hydrophobic properties, and the composition of the material matrix and the membrane electrode is similar. The structural reinforcement material is silane coupling agent-modified nano-silica.

[0039] This invention increases the porosity of the hydrophobic homogeneous region (45%~60%) and adds hydrophobic materials (fluorinated polymer nanoparticles, surface-fluorinated carbon black) to rapidly expel water vapor under gas flow conditions, reducing condensate and mitigating flooding. Simultaneously, the invention controls the platinum loading in the hydrophobic homogeneous region to be 0.6~0.8 times that of the main reaction region (absolute loading 0.24-0.56 mg / cm²). Since this region is prone to flooding, a high platinum loading not only fails to function effectively but also causes repeated dissolution and adsorption of platinum particles due to flooding, accelerating the dissolution, aggregation, and loss of platinum particles, resulting in a permanent decrease in reactivity. Appropriately reducing the platinum loading can reduce platinum waste and loss while maintaining basic reactivity. Furthermore, this invention adds a structural reinforcing material—silane coupling agent-modified nano-silica—as a physical crosslinking point. In this nano-silica, inorganic nanoparticles form hydrogen bonds with the sulfonic acid groups in the ionomer, and organic functional groups interact with the ionomer backbone to achieve chemical anchoring, inhibiting ionomer dissolution and significantly improving mechanical strength.

[0040] In a preferred embodiment, the membrane electrode of the present invention further includes a molding frame encapsulated on the surface of the membrane electrode. Two molding frames are symmetrically arranged. Each molding frame has a two-layer structure: one layer is PET (polyester film), and the other layer is EVA (ethylene-vinyl acetate copolymer) hot-melt material. In use, the CCM (i.e., the proton exchange membrane and the catalyst layers on both sides) is sandwiched between the two molding frames, so that the two sides of the CCM are respectively bonded to the EVA layers of the two molding frames, and then the CCM is fixed between the two molding frames by thermoforming.

[0041] The present invention also provides a reliable preparation method for the above-mentioned membrane electrode, comprising the following steps: S1. Zoned Slurry Preparation: Four functional slurries were prepared separately: an anode catalyst slurry, a hydrophilic enhancement zone slurry, a main reaction zone slurry, and a hydrophobic homogenizing zone slurry. Each slurry was based on the corresponding catalyst, deionized water, the corresponding ionomer solution, a small molecule alcohol, and a pore-forming agent, with specific functional materials precisely added according to its functional zone. The differentiated design of the pore-forming agent dosage in each zone was key to achieving different porosities: 2%-3% of the corresponding catalyst mass in the main reaction zone, 3%-6% in the hydrophobic homogenizing zone, and 1%-2% in the hydrophilic enhancement zone (in conjunction with a low porosity design). The solid content of each zone's slurry was controlled between 2% and 10%.

[0042] S2. Anode Preparation: The anode catalyst slurry is uniformly coated onto one side of the proton exchange membrane using methods such as spraying, screen printing, casting, or transfer printing, controlling the platinum loading to be 0.03-0.25 mg / cm³. 2 .

[0043] S3. Preparation of the three-zone cathode: On the other side of the proton exchange membrane, according to the area ratio (15%~20% : 60%~70% : 15%~20%), from the side closer to the proton exchange membrane to the side farther away from the proton exchange membrane, the hydrophilic reinforcement zone slurry, the main reaction zone slurry, and the hydrophobic homogeneous zone slurry are uniformly coated by spraying, screen printing, casting, or transfer printing (spraying is preferred).

[0044] The catalyst, ionomer solution, deionized water, small molecule alcohol, and pore-forming agent in the anode catalyst slurry are commonly used materials in this field. The ionomer in the ionomer solution is at least one of perfluorosulfonic acid polymer, sulfonated polyether ether ketone, sulfonated polyarylether sulfone, sulfonated polyimide, and phosphoric acid-doped polybenzimidazole. The small molecule alcohol and pore-forming agent used in the anode catalyst slurry, hydrophilic reinforcement zone slurry, main reaction zone slurry, and hydrophobic homogenizing zone slurry are the same. The small molecule alcohol is at least one of isopropanol, n-propanol, and ethanol; the pore-forming agent is a thermally decomposable ammonium salt, such as at least one of ammonium carbonate, ammonium bicarbonate, ammonium oxalate, and ammonium citrate.

[0045] In practice, the hydrophilic reinforcement zone, main reaction zone, and hydrophobic homogeneous zone are connected by sequential coating. The connections between these zones can partially overlap or be adjacent without overlap. When overlapping is used, the connections between adjacent zones have a 2-5 mm overlap area. This overlap area contains the slurry components from both adjacent zones, forming a component transition zone. This helps alleviate interfacial stress caused by abrupt component changes and improves the overall structural stability of the catalyst layer.

[0046] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A membrane electrode comprising a proton exchange membrane, an anode catalyst layer, and a cathode catalyst layer, characterized in that, The cathode catalyst layer comprises a hydrophilic enhancement region (1), a main reaction region (2), and a hydrophobic homogeneous region (3) arranged in an area ratio of 15%~20%: 60%~70%: 15%~20%. The hydrophilic reinforcement region (1) is coated with a composite catalytic layer A composed of catalyst A, ionomer A, hydrophilic material A, one-dimensional structure reinforcement material and two-dimensional structure reinforcement material; The main reaction zone (2) is coated with a composite catalyst layer B composed of catalyst B, ionomer B, and hydrophilic material B; The hydrophobic homogeneous region (3) is coated with a composite catalytic layer C composed of catalyst C, ionomer C, hydrophobic material C, and structural reinforcement material.

2. The membrane electrode according to claim 1, characterized in that, The porosity of the hydrophilic enhancement zone (1) is 30%~40%, the porosity of the main reaction zone (2) is 40%~45%, and the porosity of the hydrophobic homogeneous zone (3) is 45%~60%.

3. The membrane electrode according to claim 1, characterized in that, Catalyst A is at least one of platinum-carbon catalyst and transition metal composite platinum-carbon catalyst; Ionomer A is at least one of perfluorosulfonic acid polymer, sulfonated polyether ether ketone, sulfonated polyarylether sulfone, sulfonated polyimide, and phosphate-doped polybenzimidazole; Hydrophilic material A is at least one of sulfonated SiO2, hydrophilic fumed silica, and sulfonated carbon nanotubes; The one-dimensional structural reinforcement material is at least one of perfluorosulfonic acid / PVDF composite electrospinning and carbon nanofibers; The two-dimensional reinforcing material is a single layer of graphene.

4. The membrane electrode according to claim 1, characterized in that, Catalyst B is at least one of platinum-carbon catalyst, transition metal composite platinum-carbon catalyst, and transition metal catalyst; Ionomer B is at least one of perfluorosulfonic acid polymer, sulfonated polyether ether ketone, sulfonated polyarylether sulfone, sulfonated polyimide, and phosphate-doped polybenzimidazole; The hydrophilic material B is at least one of sulfonated SiO2 and sulfonated carbon nanotubes.

5. The membrane electrode according to claim 1, characterized in that, Catalyst C is at least one of platinum-carbon catalyst and transition metal composite platinum-carbon catalyst; Ionomer C is at least one of perfluorosulfonic acid polymer, sulfonated polyether ether ketone, sulfonated polyarylether sulfone, sulfonated polyimide, and phosphate-doped polybenzimidazole; The hydrophobic material C is at least one of fluorinated polymer nanoparticles and surface-fluorinated carbon black. The structural reinforcement material is nano-silica modified with a silane coupling agent.

6. The membrane electrode according to claim 1, characterized in that, The platinum loading ratio of the hydrophilic enhancement region (1), the main reaction region (2), and the hydrophobic homogeneous region (3) is 0.6~0.8:1:0.6~0.8; the membrane electrode also includes a plastic encapsulation frame (4) encapsulated on the surface of the membrane electrode.

7. A method for preparing the membrane electrode according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Prepare slurry for the anode catalyst, hydrophilic enhancement zone, main reaction zone, and hydrophobic homogenization zone respectively; S2. The anode catalyst slurry is coated on one side of the proton exchange membrane to form an anode catalyst layer; S3. On the other side of the proton exchange membrane, the hydrophilic reinforcement zone slurry, the main reaction zone slurry, and the hydrophobic homogeneous zone slurry are sequentially coated according to the area ratio of hydrophilic reinforcement zone, main reaction zone, and hydrophobic homogeneous zone of 15%~20%: 60%~70%: 15%~20% to form composite catalyst layer A, composite catalyst layer B, and composite catalyst layer C, respectively.

8. A preparation method according to claim 7, characterized in that, The anode catalyst slurry comprises: platinum-carbon catalyst, ionomer solution, deionized water, small molecule alcohol, and pore-forming agent; The hydrophilic reinforcement slurry contains: catalyst A, ionomer solution A, hydrophilic material A, one-dimensional structure reinforcement material, two-dimensional structure reinforcement material, deionized water, small molecule alcohol and pore-forming agent; The slurry in the main reaction zone contains: catalyst B, ionomer solution B, hydrophilic material B, deionized water, small molecule alcohol, and pore-forming agent; The hydrophobic homogeneous slurry contains: catalyst C, ionomer solution C, hydrophobic material C, structural reinforcement material, deionized water, small molecule alcohol, and pore-forming agent.

9. A preparation method according to claim 8, characterized in that, In the anode catalyst slurry: the mass of the ionomer in the ionomer solution is 25%-85% of the mass of carbon in the platinum-carbon catalyst, the mass ratio of water to small molecule alcohol is 1:1~2, the content of pore-forming agent is 0.5%-2% of the mass of platinum-carbon catalyst, and the solid content of the slurry is 2%-10%; In the hydrophilic reinforcement zone slurry: the mass of ionomer A in ionomer solution A is 25%-85% of the mass of carbon in catalyst A; the mass ratio of water to small molecule alcohol is 1:1-3; the pore-forming agent content is 1%-2% of the mass of catalyst A; the hydrophilic material A is 1%-3% of the mass of catalyst A; the one-dimensional reinforcing material is 2%-5% of the mass of catalyst A; the two-dimensional reinforcing material is 1%-3% of the mass of catalyst A; the slurry solid content is 2%-10%; and the platinum loading is 0.03-0.25 mg / cm³. 2 ; In the slurry of the main reaction zone, the mass of ionomer B in ionomer solution B is 25%-85% of the mass of carbon in catalyst B, the mass ratio of water to small molecule alcohol is 1:1~4, the content of pore-forming agent is 2%-3% of the mass of catalyst B, and the solid content of slurry is 2%-10%. In the hydrophobic homogeneous slurry, the mass of ionomer C in the ionomer solution C is 25%-85% of the mass of carbon in the catalyst C, the mass ratio of water to small molecule alcohol is 1:1~3, the content of pore-forming agent is 3%-6% of the mass of catalyst C, the hydrophobic material C is 1.5%-2.5% of the mass of catalyst C, the structural reinforcement material is 0.5%-3% of the mass of catalyst C, and the solid content of the slurry is 2%-10%.

10. A preparation method according to claim 7, characterized in that, In S2 and S3, the coating can be any one of spraying, screen printing, casting, or transfer printing.

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